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| FRAGILE SITE MENTAL RETARDATION 1 GENE; FMR1
#### Alternative titles; symbols FRAGILE X MENTAL RETARDATION PROTEIN; FMRP FRAGILE X SYNDROME, INCLUDED FRAGILE X MENTAL RETARDATION SYNDROME, INCLUDED MENTAL RETARDATION, X-LINKED, ASSOCIATED WITH marXq28, INCLUDED X-LINKED MENTAL RETARDATION AND MACROORCHIDISM, INCLUDED MARKER X SYNDROME, INCLUDED MARTIN-BELL SYNDROME, INCLUDED FRAGILE SITE, FOLIC ACID TYPE, RARE, FRA(X)(q27.3), INCLUDED; FRAXA, INCLUDED FRAGILE X TREMOR/ATAXIA SYNDROME, INCLUDED; FXTAS, INCLUDED ### TABLE OF CONTENTS #### DESCRIPTION NOMENCLATURE CLINICAL FEATURES INHERITANCE CYTOGENETICS MAPPING MOLECULAR GENETICS GENOTYPE/PHENOTYPE CORRELATIONS PATHOGENESIS GENE FUNCTION DIAGNOSIS POPULATION GENETICS ANIMAL MODEL HISTORY ALLELIC VARIANTS View List SEE ALSO REFERENCES CONTRIBUTORS CREATION DATE EDIT HISTORY Clinical Synopsis Gene map locus Xq27.3 ### TEXT #### DESCRIPTION X-linked mental retardation associated with marXq28, or fragile X syndrome, is characterized by moderate to severe mental retardation, macroorchidism, large ears, prominent jaw, and high-pitched jocular speech. Expression is variable, with mental retardation being the most common feature. This phenotype is associated with mutations in the FMR1 gene. McCabe et al. (1999) summarized the proceedings of a workshop on the fragile X syndrome held in December 1998. #### NOMENCLATURE Hecht et al. (1989) suggested a new system of gene symbols for fragile sites. Their suggestion for the fragile site discussed here was FRAXQ27*RFA, where R means 'rare' and FA indicates that it is of the 'folic acid type.' The gene encoded in this region of the X chromosome which is associated with mental retardation is also called fragile X mental retardation 1 (FMR1). #### CLINICAL FEATURES The phenotype of the fragile X syndrome (as it came to be most often known) includes moderate to severe mental retardation, macroorchidism, large ears, prominent jaw, and high-pitched, jocular speech. Expression is variable, with mental retardation the most common feature; however, Jacobs (1982) encountered a man and Daker et al. (1981) reported 2 brothers with marXq28 and average intelligence. Fryns and Van Den Berghe (1982) presented a kindred in which the fragile X chromosome was transmitted by at least 3 normal males. These men died at ages 68, 72, and 76 and had a normal phenotype including normal intelligence; one was an administrator and 2 were officers. Johnson et al. (1991) described a large kindred with 10 mentally retarded, fragile-X-positive males, and 2 normal transmitting males. Pellissier et al. (1991) also described a kindred with 2 normal transmitter brothers. Patients have a prominent symphysis of the mandible rather than true prognathism. Many of the fragile X males have relative macrocephaly (as gauged by the ratio of head circumference to height). Testis volume, calculated as pi/6 x length x width(2), is increased in most postpubertal men and occasionally in boys. Histopathologic examination is unremarkable except for edema. The question of whether ovarian size is increased in females with the fragile X was addressed by Goodman et al. (1987). Stigmata of connective tissue abnormality include finger joint hypermobility, instability of other joints (Opitz et al., 1984; Hagerman et al., 1984), and mitral valve prolapse (Pyeritz et al., 1982). Hagerman and Synhorst (1984) not only confirmed mitral valve prolapse but also demonstrated mild dilatation of the ascending aorta. Lubs et al. (1984) restudied the black family in which Lubs (1969) first described the marker X; they confirmed large testes. Meryash et al. (1984) studied 18 males, aged 18 to 69 years. Of 15 subjects, 13 had macroorchidism. Average height was less than published standards. Of the 18 subjects, 17 had absolute or relative macrocephaly and 12 were dolichocephalic. In a multicenter study in Sweden, Blomquist et al. (1985) found the fragile X in 13 of 83 boys (16%) with infantile autism but in none of 19 girls with infantile autism. Klauck et al. (1997) concluded from molecular genetic studies of 141 patients from 105 simplex and 18 multiplex families that an association of autism with fragile X is nonexistent and that the Xq27.3 region is not a candidate for autism. Rodewald et al. (1987) described ganglioglioma of the cauda equina in a 17-year-old male with familial Martin-Bell syndrome. Because of the association of neoplasms with autosomal chromosome abnormalities, Rodewald et al. (1987) suggested that this may be more than coincidence. They found, however, no reports of tumors associated with Martin-Bell syndrome. Fryns (1993) pointed out that periorbital hyperpigmentation and scrotal hyperpigmentation about the time of puberty are frequent features. Hyperkinetic behavior and a problem with concentration are present in most affected males. Longitudinal observations indicate a deterioration of IQ with age; mental retardation may, for example, be moderate at age 12 and severe at age 25. Loesch and Hay (1988) presented the clinical findings on 113 fragile X female heterozygotes from 44 families. In 85% of a subsample of 92 adult females, the nonverbal IQ score was 85 or less. Verbal ability deficits were much less common. Typical facial characteristics, irregular teeth, and hypermobility of finger joints occurred in approximately 40% of adult females, but facial abnormalities were less common in children. Although the frequency of miscarriages was increased, a moderate increase in the number of children was found in female carriers with borderline intellectual impairment. Thode et al. (1988) were unable to corroborate the existence of a form of the Martin-Bell syndrome with no detectable fragile X. They identified 32 men with the phenotype who were fragile X negative but concluded that they did not fit the full criteria. Voelckel et al. (1988) reported the findings of 3 brothers with the fragile X, only 2 of whom were mentally retarded. The intellectually normal brother was phenotypically normal in other ways also. A Prader-Willi-like subphenotype of the fragile X syndrome was described by de Vries et al. (1993). The features were extreme obesity with a full, round face, small, broad hands and feet, and regional skin hyperpigmentation. Unlike the Prader-Willi syndrome (176270), the patients lacked the neonatal hypotonia and feeding problems during infancy followed by hyperphagia during toddlerhood. In a group of 26 patients with suspected Prader-Willi syndrome but without detectable molecular abnormalities of chromosome 15, one fragile X patient was found. Schrander-Stumpel et al. (1994) found the FMR1 mutation in a 3-year-old boy with unexplained extreme obesity and delayed motor and speech development. They compared the clinical features with those in 9 reported patients with the fragile X syndrome and extreme obesity. They suggested that behavioral characteristics such as hyperkinesis, autistic-like behavior, and apparent speech and language deficits may help point toward the diagnosis of the fragile X syndrome. Davids et al. (1990) found that of 150 male patients with the fragile X syndrome, 75 had flat feet, 85 had excessive laxity of joints, and 10 had scoliosis. In 29 of the patients, flat feet had been evaluated or treated by an orthopedic surgeon before the diagnosis of fragile X syndrome had been made. This condition accounts for about one-half of X-linked mental retardation and is the second most common 'chromosomal' cause of mental impairment after trisomy 21. In Sweden, Blomquist et al. (1982) confirmed the latter finding; in an unselected series of 96 boys with IQ less than 50 born between 1959 and 1970, 6 had fraXq28. Reiss et al. (1994) showed that the volume of the hippocampus was enlarged in fragile X patients compared to controls. Furthermore, there was an age-related increase in the volume of the hippocampus and an age-related decrease in the volume of the superior temporal gyrus. In another study, Reiss et al. (1991) showed that fragile X males showed a significantly decreased size of the posterior cerebellar vermis and increased size of the fourth ventricle, when compared with age- and sex-matched groups of fragile-X-negative, developmentally disabled subjects and individuals with normal IQ. Reiss et al. (1991) showed that young fragile X females likewise had decreased size of the posterior cerebellar vermis and increased size of the fourth ventricle, when compared with normal age-, sex-, and IQ-matched females. The findings were intermediate between those of the fragile X males and the nonfragile X control groups. Rousseau et al. (1991) observed an age-dependent phenomenon: the 'full' fragile X mutation was found preferentially on the inactive X in leukocytes in adult females but not in younger ones. This phenomenon was not observed in female carriers of a 'premutation,' who have little phenotypic expression. Preliminary data suggested that young females who show preferential presence of a full mutation on the active X in leukocytes may be at increased risk for mental retardation. There is a known decrease with age of the expression of the fragile site. General overgrowth was described in 4 fragile X patients, all of whom came from families with other affected relatives who showed the classic Martin-Bell phenotype (de Vries et al., 1995). Lachiewicz et al. (2000) compared physical characteristics of young boys with fragile X with those of a control group. After adjustment for multiple comparisons, only 4 of 42 characteristics studied differed significantly in their distributions between the 2 groups. These included adverse response to touch on the skin, difficulty touching the tongue to the lips, soft skin over the dorsum of the hand, and hallucal crease. Ten other characteristics were identified that may also have predictive value for fragile X syndrome. Backes et al. (2000) evaluated a group of boys with fragile X syndrome, ascertained by molecular genetic methods, to determine a cognitive and behavioral profile. The cognitive phenotype revealed a general intelligence corresponding to mild to moderately severe mental retardation. Psychiatric comorbidity was high, and attention deficit hyperactivity disorder, oppositional defiant disorder, enuresis, and encopresis predominated. No significant correlation between the specific features of the phenotype and genotype were found. Limprasert et al. (2000) described unilateral macroorchidism in a boy with fragile X syndrome and discussed the possible explanations. Gould et al. (2000) compared sleep patterns and endogenous melatonin profiles in 13 boys with fragile X to 8 age-matched normal controls. Results showed greater variability in total sleep time, difficulty in sleep maintenance, and significantly greater nocturnal melatonin production in the boys with fragile X. #### Female Premutation Carriers Murray et al. (1998) screened 147 women with idiopathic premature ovarian failure and found a significant association with premutations in the FMR1 gene, with 6 women having premutations, including 4 familial and 2 sporadic cases, but no women with full mutations in the FMR1 gene. There were no pre- or full mutations of the FMR2 gene, but there was an excess of small alleles with fewer than 11 repeats at this locus. Murray et al. (1998) concluded that premutations of FMR1 can affect ovarian development or function, or both. Steyaert et al. (2003) stated that premature ovarian failure and underlying hormonal changes are recognized as a distinct phenotype in female fragile X premutation carriers, but neurocognitive deficits had not been equally established. They used the Sonneville Visual Attentions Task (SVAT) method to assess reaction time on different tasks in 3 groups of female subjects: premutation carriers, full mutation carriers, and control subjects. Their findings supported earlier findings that the fragile X premutation may affect neurocognitive function, in particular aspects of attention. Hundscheid et al. (2003) investigated whether premutation carriers have an increased risk for other diseases. Of 306 women from 84 fragile X families, 264 (86.3%) participated in the study. They first evaluated the occurrence of diseases that are commonly associated with menopause in the women with premature ovarian failure and compared this to that in women with either a normal FMR1 gene or a full mutation. They found no statistically significant differences in the occurrence of diseases known to be associated with menopause, such as cardiovascular diseases and osteoporosis; however, lower bone mineral density was observed only in premutation carriers (designated PC). Other medical problems were not more common in PC than in non-PC from the same families. Once a premutation carrier experiences premature ovarian failure, she is at risk for early estrogen deprivation which, if not treated, may lead to premature decrease in bone density. #### Fragile X Tremor/Ataxia Syndrome (FXTAS) Hagerman et al. (2001) reported 5 men with the fragile X premutation, ranging from 78 to 98 repeats, who presented in the sixth decade with progressive intention tremor, parkinsonism, cognitive decline, generalized atrophy on MRI, and impotence. Levels of FMR1 mRNA were 2 to 4 times higher than normal, which the authors suggested resulted in a pathogenic gain-of-function effect. Leehey et al. (2003) reported 2 unrelated men who presented with essential tremor at ages 58 and 49 years and were later found to carry the fragile X premutation (90 and 160 repeats, respectively). Besides the disabling intention tremor, both patients had tandem gait difficulties, generalized brain atrophy, and elevated FMR1 mRNA. Comparing 21 fragile X premutation carriers (7 male and 14 female) to 16 noncarriers, Berry-Kravis et al. (2003) found that the male premutation carriers had significantly increased postural and kinetic tremor and limb ataxia, as measured by standard scale scoring. The female carrier and control groups did not differ on any measure. The authors noted that the premutation is associated with increased levels of CGG repeat-containing FMR1 mRNA, which may interfere with nuclear function and lead to neurodegenerative symptoms. Late-onset tremor, gait unsteadiness, and dementia can be associated with brain atrophy in males of normal intelligence who are premutation carriers of the fragile X syndrome. By means of a telephone survey, Rogers et al. (2003) showed that this association is probably causal rather than coincidental. The premutation males were grandfathers ascertained through one of their daughter's sons having had the fragile X syndrome. The controlled subjects were the corresponding grandfathers on the paternal side of the family. Jacquemont et al. (2003) demonstrated that carriers of the fragile X premutation can be affected by a multisystem, progressive neurologic disorder, which they termed the 'fragile X tremor/ataxia syndrome.' They presented a series of 26 patients, all more than 50 years of age, who were carriers of the fragile X premutation and affected by a neurologic disorder with 2 main clinical features, cerebellar ataxia and/or intention tremor. Other documented symptoms were short-term memory loss, executive function deficits, cognitive decline, parkinsonism, peripheral neuropathy, lower limb proximal muscle weakness, and autonomic dysfunction. Symmetric regions of increased T2 signal intensity in the middle cerebellar peduncles and adjacent cerebellar white matter were considered to be highly sensitive for this neurologic condition, and their presence was the radiologic inclusion criterion for this series of cases. Molecular findings included elevated mRNA and low-normal or mildly decreased levels of FMR1 protein. The clinical presentation of these patients, coupled with a specific lesion visible on MRI and with neuropathologic findings, afforded a more complete delineation of this fragile X premutation-associated tremor/ataxia syndrome and distinguished it from other movement disorders. Macpherson et al. (2003) presented further evidence that premutations of the FMR1 gene may have clinical effects. They analyzed a cohort of patients with neurodegenerative disorders referred for genetic analysis of spinocerebellar ataxia genes and found that 3 of 59 males carried the premutation. Hagerman et al. (2004) described 5 female carriers of the FMR1 premutation who presented with symptoms of tremor and ataxia and received a diagnosis of FXTAS. Unlike their male counterparts with FXTAS, none of the women had dementia. Females had not been reported in previous studies of FXTAS, suggesting that they may be relatively protected from this disorder. Brain tissue was available from 1 of the 5 patients, who died at age 85 years; microscopic examination revealed intranuclear neuronal and astrocytic inclusions, in accord with the previously reported findings in males with FXTAS. #### INHERITANCE All mothers of males with the fragile X have been found to be carriers; the mutation must occur either at a low rate or only in males. In 4 of 27 large fragile X pedigrees, Fryns (1984) found strong evidence of transmission by normal males. Froster-Iskenius et al. (1984) raised the possibility of an autosomal suppressor system to account for the transmission of the marker X syndrome by unaffected males. Pembrey et al. (1985) advanced a premutation hypothesis to explain unusual characteristics of the genetics of this disorder: transmission occurs through normal males; the heterozygous daughters of such males are never mentally retarded and have few or no fragile sites, and by contrast in the next generation, a third of heterozygous females are mentally subnormal with an average of 29% fragile sites (Sherman et al., 1985). This came to be called the Sherman paradox (Fu et al., 1991). Sherman et al. (1985) suggested that a premutation exists which generates a definitive mutation only when transmitted by a female and that there is a submicroscopic rearrangement at Xq27.3 which per se causes no trouble but generates a significant genetic imbalance when involved in a recombinational event with the other X chromosome. Winter and Pembrey (1986) put the hypothesis of Pembrey et al. (1985) to test by analyzing linkage relationships of flanking genetic markers in daughters of 'normal transmitting males.' A significant reduction in recombination was found in meioses giving rise to affected grandsons of normal transmitting males (NTMs), as compared to families with no apparent normal transmitting males. One interpretation offered was interference related to a recombinational event leading to the full fragile X mutation. Weaver and Sherman (1987) gave guidelines for counseling families with the Martin-Bell syndrome. Because of the peculiarities of the pedigrees, it is necessary to give different estimates for the risk among the sons and daughters of normal carrier mothers, mentally impaired carrier mothers, and normal transmitting males. Among the sons, the probability for mental impairment is 0.38, 0.5, and 0, respectively, and the chance of a son being a mentally normal carrier is 0.12, 0, and 0, respectively. Among the daughters, the risk of being a mentally impaired carrier is 0.16, 0.28, and 0, respectively, and the chance of being a mentally normal carrier is about 0.34, 0.22, and 1.0, respectively. Given a sporadic case in a male with no fragile X demonstrable in the mother, the estimates for occurrence in a brother of the proband vary from 9 to 27%, depending on the theoretical model used; the estimated risk in first cousins varies from 0.01 to 0.05. See review by Nussbaum and Ledbetter (1986). Having excluded a mutation rate in male germ cells of the magnitude required by an exclusive mutation hypothesis to explain the high incidence of the fragile X syndrome, Vogel et al. (1990) proceeded to demonstrate an increased fitness of heterozygous females by a comparison with the reproductive performance of 'adequate' controls (mothers and grandparents of Down syndrome patients). Estimates ranged between 1.11 and 1.36. A higher incidence of dizygotic twinning suggested a biologic component for this increased fertility. On the other hand, the fragile X families had a significantly lower social status than the controls. This suggested a sociopsychologic component of their higher fertility. #### Imprinting Laird et al. (1990) concluded from an analysis of data on fragile X that 2 progenitor cells for human oogonia may be present at the time of the initial event that leads to chromosome imprinting. The estimate was based on the fact that one-half of the female's primary oocytes would, on the average, be expected to show imprinting if X-chromosome inactivation is the initial step. Laird (1987) proposed that the fragile X syndrome is caused by abnormal chromosome imprinting. According to this model, the fragile X mutation leads to an imprint, i.e., a stable inactivation of a gene or genes at the fragile X site, because the mutation prevents complete reactivation, before oogenesis, of a mutant fragile X chromosome that had been inactivated in a female for dosage compensation. The basis of this localized block to complete reactivation of a fragile X chromosome was proposed to be late replication of DNA at the fragile site (Laird et al., 1987). The population genetic predictions of the 'X-inactivation imprinting' model indicate that the fraction of carrier males who are nonpenetrant (nonimprinted) would be about 0.5 at equilibrium (Sved and Laird, 1990). Sved and Laird (1988) suggested that this predicted fraction is higher than the reported fraction of 0.2 (Sherman et al., 1985) because of an unusual ascertainment bias. Laird (1991) explained the cytogenetic disappearance of the fragile X site in the few daughters of affected males that have been reported as a consequence of erasure of the imprint when it is passed through males. (Erasure of chromosome imprinting often occurs when the imprinted chromosome is passed through the parental gender opposite from the gender that established the imprint.) Reimprinting apparently can occur, however, in primary oocytes of these daughters (Laird, 1991). According to the X-inactivation imprinting model, proposed as accounting for the unusual pattern of inheritance and expression in the fragile X syndrome, the fragile X mutation causes a local block to the attempted reactivation of the mutant X chromosome prior to oogenesis. This local block results in an imprinted fragile X chromosome that is deleterious in males and in females in whom that chromosome is predominantly the active one. Follette and Laird (1992) examined the stability of the imprinted state, defining stability as 100% penetrance of the syndrome in sons who receive an imprinted chromosome from the mother. In a preliminary estimate, they concluded that the fragile X imprint was stable in 46 of 48 female meioses, giving a tentative estimate of about 96% for the stability of the imprint. Kirkilionis et al. (1992) presented the pedigree of a large family that illustrated dramatically the Sherman paradox and was compatible with the predictions of the Laird X-inactivation imprinting model. Zeesman et al. (2004) reported a family in which a fragile X mosaic male, with both premutation and full mutation alleles in his peripheral blood leukocytes, had a daughter with both premutation and partially methylated full mutation alleles and a significant developmental disability. The sperm cells in the father contained only alleles in the premutation range; because the daughter had both premutation and full mutation alleles, the expansion to full mutation must have occurred postzygotically. The authors believed this to be the first report of a paternally derived full mutation expressed in a female. #### CYTOGENETICS Lubs (1969) first described a marker X chromosome in mentally retarded males; a secondary constriction on the distal long arm gave the appearance of large satellites. Lubs (1969) suggested that either the anomalous region itself or a closely linked recessive gene might account for X-linked retardation. This observation went unconfirmed for years until cytogeneticists reverted to a folate-deficient medium for tissue culture such as Lubs (1969) employed. Appearance of this secondary constriction (widely referred to as a fragile site) was shown to be dependent on folate deficiency in the culture medium (which leads to deficiency of thymidine monophosphate), localized to the interface between Xq27 and q28, and associated with mental retardation and macroorchidism in males (Giraud et al., 1976; Harvey et al., 1977; Sutherland, 1977). Sutherland was in Melbourne when he made his initial observations on the fragile X. When he went to Adelaide, he upgraded his laboratory, changing from 199 to F10 culture medium to give better chromosomes for banding. The failure to find the fragile X with the new medium led to his discovery of the critical role of folate (Gerald, 1983). Turner et al. (1978) suggested labeling the marker secondary constriction Xq27; however, convention requires that 'a break suspected at an interface between two bands is identified arbitrarily by the higher of the two band numbers' (ISCN, 1978; section 2.4.4.2). Brookwell and Turner (1983) again concluded that the fragile site is in band Xq27, close to the 27-28 interface. The marker X is not preferentially inactivated in heterozygotes (Lubs, 1969; Martin et al., 1980). #### MAPPING Filippi et al. (1983) studied linkage with G6PD and colorblindness in 18 Sardinian pedigrees. In 6 informative pedigrees the fragile X syndrome showed close linkage with G6PD deficiency and deutan colorblindness. The maximum likelihood estimate of recombination was 6% with 90% fiducial limits between 2.5 and 19.5% and odds favoring linkage of 428:1. No hint of linkage of G6PD and the Renpenning form of X-linked mental retardation (309500) or other unspecified type of X-linked mental retardation was found. Patients with the Renpenning form not only lack the facial features and macroorchidism typical of the fragile X syndrome but also have microcephaly. Szabo et al. (1984) postulated that the fragile X mutation occurs in a region (Xq27.3) that is a 'hotspot' for meiotic recombination; that the microscopically detectable change is probably a minute chromosomal aberration resulting from an inaccurate recombination event; and that recombination is suppressed at the Xq27.3 region in females heterozygous for the fragile X. The hypothesis was based on the finding that the factor IX locus (306900) and the G6PD locus (305900) are closely linked to the fragile X 'locus' but factor IX segregates independently of the hemophilia A, deutan and protan colorblindness loci which are in the G6PD cluster. Warren et al. (1985) reported a family in which 2 brothers with fragile X mental retardation had different factor IX RFLPs, indicating that a recombinational event occurred between the 2 loci and that the 2 loci may not be as tightly linked as previously published data suggested. Camerino et al. (1983) found no recombination out of 17 opportunities for meiotic recombination in 2 families. The combined data gave a peak of 4.02 at a theta of 0.05. Brown et al. (1985) found that pedigrees with nonpenetrant males have tight linkage to factor IX, whereas the linkage is loose in those pedigrees with full penetrance in males. Giannelli et al. (1987) studied linkage between the Martin-Bell syndrome and the factor IX gene as well as with the anonymous probe 52A. Heterogeneity was found in their own 9 families and in those reported in the literature. One group of families showed tight linkage of fragile X to factor IX while the other showed loose linkage. In the combined collection of families, the 2 groups represented 0.3 and 0.7 of the total, respectively, and showed recombination fractions of 0.0-0.15 and 0.25-0.5, respectively. Families with nonpenetrant carrier males showed tighter linkage to factor IX than did the others. By contrast, no significant difference was found in the recombination between 52A and factor IX in the 2 groups of fragile X families or in these families vs those with Hunter syndrome (309900) examined in the same laboratory. Giannelli et al. (1987) favored the possibility that this indicates the existence of 2 fragile X loci. Brown et al. (1988) performed a multilocus linkage analysis of the fragile X syndrome in 147 families using 4 flanking markers. As previously observed by Giannelli et al. (1987), significant variation in the recombination distance between F9 and FRAXA was found also in this group of families. Heterogeneity testing showed that 20% of the families had tight F9-FRAXA linkage, whereas 80% demonstrated loose linkage, with an average recombination distance of 0.35. On average, the multipoint distances found were DXS51-F9, 6.9%; F9-FRAXA, 22.4%; FRAXA-DXS52, 12.7%; and DXS52-DXS15, 2.2%. Thibodeau et al. (1988) also reported on linkage data between the fragile X locus and 4 polymorphic markers: DXS51, F9, DXS98, and DXS52. The markers were studied in 14 families with fragile X and 9 normal pedigrees from the CEPH collection. In this set of families, as has been previously observed, there was evidence for genetic heterogeneity between the fragile X locus and the F9 site. The observed recombination frequencies were as follows: DXS51-F9, 0%; F9-DXS52, 45%; DXS51-FRAXA, 15%; F9-FRAXA, 18%; DXS98-FRAXA, 36%; and DXS52-FRAXA, 15%. The authors proposed the following relative order for the 5 loci, based on multipoint linkage analysis: (DXS51, F9, DXS98)--FRAXA--DXS52. Poustka et al. (1991) described a physical map of the end of Xq encompassing the region from Xq27.2 to the telomere, inclusive of band Xq28. The map covered a total of 12 Mb of DNA and extended from the telomere to a location 3 Mb proximal to the most likely position of the fragile X mutation. The map determined order and position of loci throughout the Xq28 region and localized cell line breakpoints marking the fragile X region to an interval of 300-700 kb between 8 and 8.7 Mb proximal to the Xq telomere. #### MOLECULAR GENETICS The presence of a trinucleotide repeat sequence, designated p(CCG)n, as the basis of the unstable DNA that characterizes the fragile X genotype was first demonstrated by Kremer et al. (1991). They showed that normal X chromosomes have about 40 +/- 25 copies of p(CCG)n and that within these limits the sequence is a stable DNA polymorphism. The fragile X genotype was characterized by an increased amount of unstable DNA that maps to the repeat. Note on nomenclature for trinucleotide repeats: The repeat involved in the fragile X syndrome is variously referred to here as (CGG)n or (CCG)n. Furthermore, the identical repeat found in the cloned FRAXE gene (309548) was referred to as (GCC)n by Knight et al. (1993). There are only 10 different trinucleotide repeats; however, each can be written in a number of ways. Sutherland (1993) favored the convention that lists the motif in alphabetical order in the 5-prime to 3-prime direction. Consistent with this, he uses the (CCG)n designation. He preferred, furthermore, the designation (AGC)n for the other clinically significant dinucleotide repeat found in myotonic dystrophy, Huntington disease, Kennedy disease, and SCA1; (CAG)n is the designation most often used. Sutherland (1993) suggested that the same convention can apply to dinucleotides. He wrote: 'It must be very confusing for newcomers to the literature to find (AC)n, (CA)n, (GT)n, and (TG)n repeats, when the cognoscenti know these are synonyms.' Using the G6PD Mediterranean variant as a marker, Rocchi et al. (1990) investigated the number of somatic cells (fibroblasts or red cells) with an active fragile X chromosome. They found a significant inverse correlation between IQ level in heterozygotes and the percentage of fibroblasts with the fragile X as the active chromosome. In contrast, no significant correlation was found between IQ and the red cell data, suggesting somatic selection against hematopoietic stem cells with an active fragile X. Using a 275-kb fragment of human DNA isolated in a yeast artificial chromosome (YAC) and thought to span the fragile site, Yu et al. (1991) derived 2 probes that spanned the fragile site as demonstrated by in situ hybridization. Mapping delineated further the sequences that appeared to span the fragile site to about 15 kb. A 5-kb EcoRI fragment was found to contain fragile site breakpoints. When this fragment was used as a probe on the chromosomal DNA of normal and fragile X individuals, alterations in the mobility of the sequences were found only in fragile X DNA. These sequences were of an increased size and varied within families, indicating that the region was unstable. The results were consistent with those of Oberle et al. (1991). Wohrle et al. (2001) transferred hypermethylated and unmethylated full expansions of human fragile X chromosomes from murine A9 hybrids into murine embryocarcinoma cells, a model system of pluripotent embryonic cells. Full-expansion alleles that were fully methylated and stable in the donors' fibroblasts and in A9 became demethylated, reactivated, and destabilized in the undifferentiated embryocarcinoma hybrids. When destabilized expansions were reintroduced from embryocarcinoma cells into A9, instability was reversed to stability. Khalifa et al. (1990) found no evidence that DNA methylation in the vicinity of the fragile X site influences the phenotype of the syndrome. In studies of peripheral lymphocytes, Webb and Jacobs (1990) found that the number of active fra(X) chromosomes was consistently higher in retarded heterozygous females than in mentally normal heterozygous females. A review of the findings in the literature showed the same result. By using microdissected markers close to the fragile site, Bell et al. (1991) demonstrated that the fragile X syndrome is not associated with large structural rearrangements in Xq27.3 but is associated with methylation of DNA sequences distal to the fragile site. Significant differences were observed in the pulsed field gel electrophoresis pattern observed after BssHII digestion of DNA from fragile X-positive, mentally retarded individuals compared with normal male controls. A 600-kb band was either absent or of reduced intensity in affected males. The pattern was normal in normal, fragile X-negative transmitting males, whereas their mentally retarded, fragile X-positive grandsons lacked the fragment. These observations suggested that the absence of the band is the result of methylation of the BssHII site. The findings were considered consistent with Laird's hypothesis of imprinting at this locus and with a 2-step process for the expression of the disease (Laird et al., 1987). The methylation probably occurs in a CpG island. The lack of expression of a gene associated with this island could result in the disease phenotype. Oberle et al. (1991) found that probes adjacent to a single CpG island that was mapped at or very near the fragile site detected very localized DNA rearrangements that constitute the fragile X mutations. These rearrangements occurred in a 550-bp GC-rich fragment. Phenotypically normal, transmitting males had a 150-bp to 400-bp insertion that was inherited by their daughters either unchanged or with little change in size. Fragile-X-positive persons in the next generation had much larger fragments that differed among sibs and showed a generally heterogeneous pattern indicating somatic mutation. The mutated allele appeared unmethylated in normal transmitting males, methylated only on the inactive X chromosome in their daughters, and totally methylated in most fragile X males. However, some males had a mosaic pattern. Expression of the fragile X syndrome thus appears to result from a 2-step mutation as well as highly localized methylation. Rousseau et al. (1992) reviewed the 'unstable and methylatable mutations causing the fragile X syndrome.' They pointed out that the CGG repeat is in phase with the following protein coding sequence and, if translated, would code for a stretch of 6 to 54 arginines. The predicted sequence of the FMR1 protein has no strong homology with any other known protein; Verkerk et al. (1991) demonstrated that it contains a nuclear translocation signal. The premutation is meiotically unstable but generally mitotically stable. The full mutation is both meiotically and mitotically unstable; as a result, a heterogeneous pattern of bands of the CGG repeats is seen on Southern blots, e.g., for leukocyte DNA, reflecting mosaicism. Devys et al. (1992) demonstrated that the pattern of mosaicism was strictly identical in 3 pairs of monozygotic twins, indicating that the somatic heterogeneity and abnormal methylation are established early in development. FMR1 mRNA is absent in those with the full mutation, with the exception of mosaics. Warren et al. (1987) presented evidence that physical breakage occurs at the fragile X site. They demonstrated translocations in somatic cell hybrids that join the fragile site to heterologous DNA; these might be useful in the molecular cloning of the fragile X sequence (268,266:Warren et al., 1988, 1990). Indeed, such proved to be the case. Verkerk et al. (1991) used the symbol FMR1 (for fragile-site mental retardation-1) for the gene they identified in the breakpoint cluster region in the fragile X syndrome. They found the gene, which expresses a 4.8-kb message in human brain, within a 4-cosmid contig of YAC DNA. Within a 7.4-kb EcoRI fragment, containing FMR1 exonic sequences distal to a CpG island previously shown to be hypermethylated in fragile X patients, they demonstrated a fragile X site-induced breakpoint cluster region that exhibits length variation in fragile X chromosomes. This fragment contained a lengthy CGG repeat that is 250 bp distal of the CpG island and maps within an FMR1 exon. Localization of the brain-expressed FMR1 gene to this EcoRI fragment suggested the involvement of this gene in the phenotypic expression of the fragile X syndrome. As cited earlier, Wohrle et al. (1992) described partial deletion of the FMR1 gene in a patient with the fragile X syndrome. Gedeon et al. (1992) described a patient with typical clinical features of the fragile X syndrome but without cytogenetic expression of the fragile X and without an amplified CCG trinucleotide repeat fragment. The patient had a previously uncharacterized submicroscopic deletion encompassing the CCG repeat, the entire FMR1 gene, and about 2.5 megabases of flanking sequences. Random X inactivation was found in the patient's mother, who was shown to be a carrier of the deletion. Tarleton et al. (1993) described a de novo deletion. Kirchgessner et al. (1995) studied the expression of the FMR1 gene from inactive X chromosomes by RT-PCR, both in somatic cell hybrids that contained an active or inactive human X chromosome and in a female patient with a large deletion surrounding the FMR gene. In both analyses, the data indicated that FMR1 is normally subject to X inactivation. The authors stated that this finding is consistent with the results of previous studies of DNA methylation of FMR1 on active and inactive X chromosomes and supports the involvement in the variable phenotype of females for with full mutations of the FMR1 gene. Sun and Baumer (1999) studied a fibroblast culture from a 20-week female fetus who was diagnosed as a full mutation heterozygote. Higher passage cells showed a complete absence of cells in which the normal X chromosome would be inactivated. Studies of a control fibroblast culture derived from a female fetus with normal FMR1 alleles showed no selection. The authors concluded that cloning and serial cultivation of fetal fibroblasts indicated the possibility of a selection process that is dependent on the activation status of the X chromosome carrying an FMR1 full mutation. Morton and Macpherson (1992) proposed a model in which the fragile X mutation is postulated to occur as a multistep process. This attractive model provides a framework in which the seemingly contradictory observations of a mutation old enough to establish a founder effect and an apparently high new mutation rate are united. Morton and Macpherson (1992) suggested that 4 types of alleles occur in the fragile X syndrome (see table in the review by Chakravarti, 1992). The 4 types of alleles are as follows: N = normal, with a frequency of 0.9751; S = stable insert with a frequency of 0.0225 and a mean age of about 90 generations; Z = unstable insert with a frequency of 0.0014 and a mean age of 2 generations; and L = mutation with a frequency of 0.0010 and a mean age of 1.4 generations. Thus myotonic dystrophy (160900) and fragile X appear to share both the phenomenon of anticipation and the phenomenon of founder effect. Richards and Sutherland (1992) referred to the amplification mutation involving (CCG)n in the fragile X syndrome and the (AGC)n repeat in myotonic dystrophy and Kennedy disease (313200) as 'dynamic mutations.' In studies using 2 polymorphic CA repeats located close to the 'mutation target' for the fragile X syndrome, Oudet et al. (1993) observed significant differences in allelic and haplotypic distributions between normal and fragile X chromosomes, indicating that a limited number of primary events may have been at the origin of most present-day fragile X chromosomes in Caucasian populations. They proposed a putative scheme with 6 founder chromosomes from which most of the observed fragile X-linked haplotypes can be derived directly or by a single event at one of the marker loci. Such founder chromosomes may have carried a number of CGG repeats in an upper-normal range, from which recurrent multistep expansion mutations have arisen. The diversity of haplotypes at the fragile X locus may reflect genetic heterogeneity but may also be explained by mutations in the markers themselves. Smits et al. (1993) stated that they had been unable to demonstrate any new mutation in 84 probands referred to them to date. Interestingly, they also demonstrated the same FMR1 gene mutation in 5 fragile X probands with common ancestors married in 1747. Very few mutations in FMR1 other than expanded stretches of CGG repeats in the 5-prime noncoding region have been described as a cause of the fragile X syndrome. The ile367-to-asn mutation (309550.0001) is one of the rare exceptions. This and other such cases involved isolated instances. Meijer et al. (1994), however, reported a family in which 11 individuals had a 1.6-kb deletion proximal to the CGG repeat of the FMR1 gene as the cause of the fragile X syndrome. Although fragile X chromosomes were not cytologically detectable, all 4 affected males and 2 of the carrier females showed the characteristic clinical phenotype. Using RT-PCR, Meijer et al. (1994) demonstrated that FMR1 was not expressed in the affected males, strongly suggesting that the FMR1 promoter sequences 5-prime to the CGG repeat were missing. The deletion patients had approximately 45 CGG repeats in the FMR1 gene; these were not interspersed by AGG triplets that are usually present in both normal and expanded repeats, however. Meijer et al. (1994) hypothesized that prior to the occurrence of the deletion an expansion of the repeat occurred and that the deletion removed the 5-prime part of the CGG repeat containing the AGG triplets. Transmission of the deletion through the family could be traced back to the deceased grandfather of the affected males, which supported the hypothesis that the FMR1 gene product is not required for spermatogenesis. Eichler et al. (1993) showed by exon-exon PCR and restriction analysis that the FMR1 gene consists of 17 exons spanning 38 kb. From sequencing of intron-exon boundaries, they concluded that the splice donors and acceptors located in the 5-prime portion of the gene demonstrated greater adherence to consensus than did those in the 3-prime end, providing a possible explanation for the finding of alternative splicing in FMR1. Ashley et al. (1993) isolated and characterized cDNA clones encoding the murine homolog, Fmr-1, which exhibited marked sequence identity with the human gene, including the conservation of the CGG repeat. A conserved ATG downstream of the CGG repeat in both human and mouse and an in-frame stop codon in other human 5-prime cDNA sequences demarcate the FMR1 coding region and confine the CGG repeat to the 5-prime untranslated region. Ashley et al. (1993) also presented evidence for alternative splicing of the FMR1 gene in mouse and human brain and showed that one of these splicing events alters the FMR1 reading frame, predicting isoforms with novel carboxy termini. Ashley et al. (1993) identified ribonucleoprotein particle domains within the FMR protein, and RNA was shown to bind in stoichiometric ratios, which suggested that there are 2 RNA binding sites per FMR protein molecule. The protein was able to bind to its own message with high affinity and interacted with approximately 4% of human fetal brain messages. The absence of the normal interaction of the FMR protein with a subset of RNA molecules might result in the pleiotropic phenotype associated with the fragile X syndrome. The K homology (KH) domain, originally described in the pre-mRNA-binding heterogeneous nuclear ribonucleoprotein (hnRNP) K protein, contains approximately 50 amino acids and is found in a diverse group of proteins of which many, if not all, are RNA-binding proteins. The sequence motif has been evolutionarily conserved. The importance of the KH domain is underscored by the observation that a single point mutation in a conserved residue of a KH domain in the protein product of the FMR1 gene leads to severe fragile X syndrome (309550.0001). To assess the role of KH domains in RNA binding, Siomi et al. (1994) used mutagenesis of KH domains in hnRNP K and FMR1. Conserved residues of all 3 KH domains of hnRNP K are required for its wildtype RNA binding. Furthermore, Siomi et al. (1994) stated that the FMR1 protein containing the ile304-to-asn mutation of De Boulle et al. (1993) showed severe impairment of binding to RNA. (De Boulle et al. (1993) referred to the mutation as ile367-to-asn.) The results demonstrated an essential role for KH domains in RNA binding and strengthened the connection between the fragile X syndrome and loss of RNA-binding activity of FMR1. Lewis et al. (2000) determined the structure of the KH3 domain of NOVA2 (601991) interacting with single-stranded RNA at 2.4-angstrom resolution. The structure of the KH3 domain bound to a stem loop RNA resembled a molecular vise, with 5-prime-UCAC-3-prime pinioned between an invariant gly-X-X-gly motif and the variable loop. Tetranucleotide recognition was supported by an aliphatic alpha-helix/beta-sheet RNA-binding platform, which mimicked 5-prime-UG-3-prime by making Watson-Crick-like hydrogen bonds with 5-prime-CA-3-prime. Sequence conservation suggested to the authors that fragile X mental retardation results from perturbation of RNA binding by the KH2 domain of the FMR1 protein. Verheij et al. (1993) investigated the nature and function of the protein encoded by the FMR1 gene using polyclonal antibodies raised against the predicted amino acid sequences. Four different protein products, possibly resulting from alternative splicing, were identified by immunoblotting in lymphoblastoid cell lines of healthy persons. All these proteins were missing in cell lines from patients not expressing FMR1 mRNA. The intracellular localization of the FMR1 gene products as demonstrated by transient expression in COS-1 cells was cytoplasmic. In the fragile X syndrome, the amplification of the CGG repeat blocks transcription of the FMR1 gene; this results in the absence of FMR protein with consequent mental retardation. Siomi et al. (1993) demonstrated that the protein product of the FMR1 gene contains 2 types of sequence motifs characteristic of RNA-binding proteins: an RGG box and 2 heterogeneous nuclear RNP K homology domains. They also demonstrated that FMR1 binds RNA in vitro. Using antibodies to FMR1, they detected its expression in cells of unaffected humans but little or no FMR1 in fragile-X-affected patients. It is noteworthy that the point mutation described by de Boulle et al. (1993), ile367-to-asn, is in one of the most highly conserved residues of one of these RNA-binding domains. FMR1 protein and the fragile X-related proteins 1 (FXR1; 600819) and 2 (FXR2; 605339) form a family with functional similarities, such as RNA binding, polyribosomal association, and nucleocytoplasmic shuttling. Tamanini et al. (1999) found that FMR1 and FXR1 proteins shuttle between cytoplasm and nucleoplasm, while FXR2 protein shuttles between cytoplasm and nucleolus. Using several FMR1 deletion mutants in coimmunoprecipitation experiments, Siomi et al. (1996) identified amino acids 359 to 472, which are encoded by exons 13 and 14, as the 60S ribosomal subunit-binding region. They found that amino acids 171 to 211 are sufficient for FMR1 interaction with FXR2 and that FMR1 is not required for the association of FXR1 or FXR2 with the 60S ribosomal subunit. FXR1 and FXR2 associated with 60S ribosomal subunits in cells lacking FMR1 and in cells derived from a fragile X syndrome patient. Oostra and Chiurazzi (2001) reviewed the FMR1 gene and FMR1 protein function, including information on animal models for fragile X syndrome. In a daughter of a female carrier of the fragile X mutation, van den Ouweland et al. (1994) found a haplotype using flanking markers that predicted she had inherited the fragile X premutation chromosome. However, the CGG repeat sequence and the intragenic polymorphic marker FMRb showed the normal maternal alleles, while 2 other intragenic markers, FMRa and FRAXAC2, and other more distant markers, showed the risk haplotype. These observations were interpreted as indicating gene conversion and might represent back mutation at the FMR1 locus. It had been suggested that expansion of the CGG repeat in the FMR1 gene is a postzygotic event with the germline protected. From an analysis of intact ovaries of full-mutation fetuses, Malter et al. (1997) showed that only full-expansion alleles could be detected in oocyte (but in the unmethylated state). Similarly, the testis of a 13-week full-mutation fetus showed no evidence of premutations, while a 17-week full mutation fetus exhibited some germ cells with attributes of premutations. These data discounted the hypothesis that the germline is protected from full expansion and suggested that full-mutation contraction occurs in the immature testis. Thus, full expansion may already exist in the maternal oocyte or postzygotic expansion, if it occurs, arises quite early in development prior to germline segregation. Kunst et al. (1997) studied the influence of AGG interruptions on CGG repeat stability. Kunst et al. (1997) analyzed the sorted sperm of 2 donors, each with 39 total repeats but distinct AGG interruption patterns. There was approximately 15% variation in repeat length in each case. However, the male with 29 perfect repeats showed 3% expansion changes while the male with 19 perfect repeats had none. Kunst et al. (1997) also noted that all variant sperm showed expansion or contraction of the 3-prime end of the repeat array. Kunst et al. (1997) concluded that these data are consistent with the hypothesis that perfect repeat tracts influence repeat stability and that changes of the FMR1 repeat exhibit polarity. Instability of the fragile X CGG repeat involves both maternally-derived expansions and deletions in the gametes of full-mutation males. Using an SV40 primate replication system, Edamura et al. (2005) investigated the effect of CGG tract length, DNA replication direction, location of replication initiation, and CpG methylation upon CGG stability. Replication-dependent deletions with 53 CGG repeats were observed when replication was initiated proximal to the repeat, with CGG as the lagging-strand template. When they initiated replication further from the repeat, while maintaining CGG as the lagging-strand template or using CCG as the lagging-strand template, significant instability was not observed. CpG methylation of the unstable template stabilized the repeat, decreasing both the frequency and the magnitude of deletion events. Furthermore, CpG methylation slowed the efficiency of replication for all templates. Interestingly, replication forks displayed no evidence of a block at the CGG repeat tract, regardless of replication direction or CpG methylation status. Templates with 20 CGG repeats were stable under all circumstances. These results showed that CGG deletions occur during replication and are sensitive to replication-fork dynamics, tract length, and CpG methylation. Chiurazzi et al. (1998) investigated whether FMR1 activity could be restored in vitro by inducing DNA demethylation with 5-azadeoxycytidine (5-azadC) in fragile X patients' lymphoblastoid cells. The authors reported that treatment with 5-azadC causes reactivation of fully mutated FMR1 genes with 300 to 800 repeats, as shown by the restoration of specific mRNA and protein production. This effect correlated with the extent of promoter demethylation, determined by restriction analysis with methylation-sensitive enzymes. Chiurazzi et al. (1999) investigated the role of histone acetylation in regulating FMR1 expression by treating lymphoblastoid cell lines of nonmosaic full mutation patients with 3 drugs capable of inducing histone hyperacetylation. They observed a consistent, although modest, reactivation of the FMR1 gene with 4-phenylbutyrate, sodium butyrate, and the cytotoxic drug trichostatin A, as shown by RT-PCR. Combining these drugs with 5-azadC resulted in a 2- to 5-fold increase in FMR1 mRNA levels obtained with 5-azadC alone, thus showing a synergistic effect of histone hyperacetylation and DNA demethylation in the reactivation of FMR1 full mutations. Crawford et al. (2000) performed small pool (SP)-PCR on sperm and blood DNA from 7 unaffected males whose repeat sizes ranged from 20 to 33. Regression analyses suggested that components of the repeat structure, such as the number of interruptions and purity of the 3-prime end of the repeat, are important determinants of germline repeat instability. In contrast, elements other than repeat structure, such as haplotype background, seemed to have an impact on somatic repeat instability. The factors identified for either cell type, however, explained only a small portion of the variance, suggesting to the authors that other factors may be involved in this process. Jin and Warren (2000) reviewed the molecular mechanism of CGG repeat expansion and physiologic functions of the FMR1 protein. Laggerbauer et al. (2001) showed that FMR1 strongly inhibited translation of various mRNAs at nanomolar concentrations in both rabbit reticulocyte lysate and microinjected Xenopus laevis oocytes. The effect was specific for FMR1, since other proteins with similar RNA-binding domains, including the autosomal homologs of FMR1, FXR1, and FXR2, failed to suppress translation in the same concentration range. Initial studies addressing the underlying mechanism of inhibition suggested that FMR1 may inhibit the assembly of 80S ribosomes on the target mRNAs. A disease-causing substitution, ile304 to asn (I304N; 309550.0001), rendered FMR1 incapable of interfering with translation in both test systems, and severely impaired homooligomerization of FMR1. The failure of FMR1 I304N to suppress translation was not due to its reduced affinity for mRNA or its interacting proteins FXR1 and FXR2. The authors hypothesized that inhibition of translation may be a function of FMR1 in vivo, and that failure of mutant FMR1 protein to oligomerize may contribute to the pathophysiologic events leading to fragile X syndrome. Using recombinant rat Fmrp in an in vitro translation system, Li et al. (2001) found dose-dependent inhibition of rat brain mRNA translation without accelerated mRNA degradation. Translation suppression by Fmrp was reversed in a trans-acting manner by the 3-prime untranslated portion of the Fmr1 message, which contains an Fmrp-binding element. Fmrp did not suppress translation of the beta-globin transcript, which does not bind Fmrp. Similarly, removal of the Fmrp-binding site on a translation template abolished the inhibitory effect of Fmrp, supporting the hypothesis that FMRP inhibits translation by direct interaction with template mRNA. In a boy with speech and developmental delay and low normal IQ measures, Tarleton et al. (2002) identified a G-to-C point mutation within the CGG repeat region of FMR1. The patient had a 31-repeat segment, within the normal range, but was originally thought to have a deletion in the FMR1 gene. Peripheral blood analysis showed a 24% reduction in the FMR protein. Tarleton et al. (2002) suggested that the mild phenotype resulted from the mild change in FMRP expression. Terracciano et al. (2004) reported a family in which unstable transmission of an intermediate 44 CGG fragile X allele from the maternal grandfather occurred, with expansion first to a premutated allele of 61 CGGs in a daughter and then to a fully mutated allele in her child, representing a rare progression from intermediate to full mutation in just 2 generations. #### GENOTYPE/PHENOTYPE CORRELATIONS In a survey of retarded females who had no obvious physical abnormalities, 7% expressed marXq28 in lymphocytes (Turner et al., 1980). Among obligate heterozygotes, the likelihood of detecting marXq28 correlates with severity of retardation (Howard-Peebles and Stoddard, 1980; Jacobs et al., 1980). In 2 heterozygous sisters who were slow learners, Uchida and Joyce (1982) found that the fragile X was the active one in 100 of 129 cells (77.5%) and 85 of 120 cells (70.8%), whereas 2 heterozygous relatives of normal intelligence had the fragile X active in 40 of 78 cells (51.3%) and 10 of 32 cells (31.3%). An earlier suggestion that the proportion of cells exhibiting marXq28 decreases with increasing heterozygote age (Sutherland, 1979; Jacobs et al., 1980; Turner et al., 1980) is probably an artifact due to ascertaining fewer retarded women in older age groups (Jacobs, 1982). Snyder et al. (1984) showed that culture conditions that promote expression of the fragile X site do not affect expression of lymphocyte HPRT but do cause a marked reduction in G6PD activity. Langenbeck et al. (1984) found that mean corpuscular hemoglobin is increased in this disorder and asked whether this is a reflection of a defect in folate metabolism. Why the marker site is related to retardation is unknown. At least 12 other heritable secondary constrictions ('fragile sites') on other chromosomes were proved by the early 1980s (Sutherland, 1981; Hecht et al., 1982), but none had an association with a particular phenotype. In all pedigrees of marXq28 studied, no crossing-over between the marker and mental retardation had occurred. This suggested that the marker, rather than being closely linked to a gene causing mental retardation, is a direct cytologic indicator of the genetic mutation causing this phenotype (Kaiser-McCaw et al., 1980). As stated earlier, the designation Sherman paradox came to be applied to the following phenomenon: 20% of males who carry a fragile X chromosome are phenotypically normal; their daughters, to whom they transmit the fragile X chromosome, are likewise normal, but their grandsons are often affected. The brothers of the clinically normal, transmitting males have a low risk, while grandsons and great-grandsons have much higher risks. Fu et al. (1991) demonstrated that the Sherman paradox is related to the particular structure of the (CGG)n repeat found in the coding sequence of the FMR1 gene. (The CGG triplet codes for arginine.) In normal individuals the range of allele sizes varied from a low of 6 to a high of 54 repeats. Premutations showing no phenotypic effect in fragile X families ranged in size from 52 to more than 200 repeats. All alleles with greater than 52 repeats, including those identified in a normal family, were meiotically unstable, with a mutation frequency of 1, while 75 meioses of alleles of 46 repeats and below showed no mutation. Demonstration of mosaicism may indicate that premutation alleles are also mitotically unstable. Fu et al. (1991) showed that the risk of expansion during oogenesis to the full mutation increased with the number of repeats, thus explaining the Sherman paradox, which might be viewed as an example of the phenomenon of anticipation. Remarkably, the premutation expands to a full mutation only when it is transmitted by a female; consequently, daughters of normal transmitting males have only the premutation and never the full mutation, and never show mental retardation or cytogenetic expression of the fragile X syndrome. Furthermore, daughters of affected males do not express the fragile X syndrome at either the clinical or the cytogenetic level. In a study of the sperm in 4 male fragile X patients, Reyniers et al. (1993) found that only the premutation was present, although the full mutation was present in peripheral lymphocytes. This led them to conclude that expansion of the premutation to the full mutation in this disorder does not occur in meiosis but in a postzygotic stage. The same conclusion was supported by the finding of Kruyer et al. (1994) in 2 affected monozygotic brothers who differed in the number of CGG repeats. In another family with 2 monozygotic twin sisters with the same number of repeats, only 1 was mentally retarded. When the methylation status of the FMR1 CpG island was studied, Kruyer et al. (1994) found that the majority of the normal chromosomes had been inactivated in the affected twin. Using monoclonal antibodies specific for the FMR-1 protein, Devys et al. (1993) found that they could detect 4 or 5 protein bands that appeared identical in cells of normal males and of males carrying a premutation but were absent in affected males with a full mutation. Immunohistochemistry showed a cytoplasmic localization of the FMR1 protein. The highest levels were observed in neurons, while glial cells contained very low levels. In epithelial tissues, levels of FMR1 were higher in dividing layers. In adult testes, FMR1 was detected only in spermatogonia. To study the involvement of the FMR1 gene in the fragile X syndrome, Pieretti et al. (1991) studied its expression in lymphoblastoid cell lines and leukocytes derived from patients and normal controls. FMR1 mRNA was absent in most male fragile X patients. Normal persons and carriers all showed expression. The work of Wohrle et al. (1992) supported the suggestion that a gene designated FMR1 is involved in the phenotype of the fragile X syndrome. One exon of this gene is carried on a 5.1-kb EcoRI fragment that exhibits length variation in fragile X patients because of amplification of or insertion into a CGG-repeat sequence which probably represents the cytogenetically identified fragile site. The EcoRI fragment also includes an HTF island that is hypermethylated in fragile X patients showing absence of FMR1 mRNA. In a fragile X-negative mentally retarded male who presented with the clinical phenotype of the fragile X syndrome, Wohrle et al. (1992) found a deletion that included the HTF island and exons of the FMR1 gene. Less than 250 kb of genomic DNA, including DXS548 and at least 5 exons of the FMR1 gene, was deleted. The data supported the hypothesis that loss of function of the FMR1 gene is responsible for the clinical phenotype of the fragile X syndrome. This opens the possibility that pathogenetic mechanisms other than amplification of the CGG repeat can have the same phenotypic consequences. Wohrle et al. (1992) indicated that they had started a systematic screening of sporadic cases of the fragile X syndrome who are cytogenetically negative. McConkie-Rosell et al. (1993) performed fragile X chromosome studies, physical examinations, and psychological testing on 6 brothers, 3 of whom were affected with fragile X to varying degrees, 2 of whom were nonpenetrant carriers, and 1 of whom was unaffected. Two of the affected brothers and the 2 'nonpenetrant' brothers were found to be methylation mosaics. A correlation was seen between the degree of methylation and the phenotypic expression identified in the 3 affected males. The 2 males initially classified as nonpenetrant were found to have mild phenotypic expression which consisted of minor cognitive deficits and a partial physical phenotype. These two, who were negative on fragile X chromosome studies, were found on DNA analysis to have large, broad smears, with approximately 97% of the DNA unmethylated; they were mosaic for hypermethylation of an expansion of the CGG repeat in the premutation range (100-600 bp). These results indicated that some 'nonpenetrant' carrier males may have varying amounts of methylation of the FMR1 regions, which can result in mild expression of the fragile X syndrome. Expression of the syndrome may not be confined to males with large, hypermethylated expansions (full mutation), but may instead have a gradient effect with a threshold for the full expression of the phenotype. Abitbol et al. (1993) used in situ hybridization to demonstrate that FMR1 mRNAs are expressed from an early stage in proliferating and migrating cells of the nervous system and retina as well as several non-nervous tissues. In the brain of 25-week old fetuses, it was produced in highest levels in cholinergic neurons of the nucleus basalis magnocellularis and in pyramidal neurons of the hippocampus. The early transcription of the gene and the distribution of mRNAs in human fetuses suggest that alterations of FMR1 gene expression contributes to the pathogenesis of the fragile X syndrome and especially the mental retardation. Bachner et al. (1993) presented evidence suggesting that, in addition to a 'housekeeping' function, which is necessary in every cell, bears no correlation with proliferation or morphogenetic processes, and is reflected by a low level of ubiquitous expression, the FMR1 gene serves a second function in the mature testis, reflected by high expression in spermatogonia and not in Sertoli cells. They suggested further that FMR1 expression in spermatogonia is necessary for germ cell proliferation. Zhong et al. (1993) described a second mutable sequence within the FMR1 gene. Richards et al. (1991) had described 2 polymorphic markers, designated AC1 and AC2, located within FMR1 and flanking the unstable (CGG)n repeat by approximately 10 kb. Zhong et al. (1993) confirmed linkage disequilibrium of the (CGG)n repeat with AC1 but found linkage equilibrium with AC2, which they also found was highly mutable. A mutation rate of 3.3% was observed but only among fragile X maternally-derived meioses. The finding of a second mutable locus within FMR1 suggested that the target for tandem repeat instability may not be confined to the (CGG)n repeat alone but may also involve microsatellites. Zhong et al. (1993) cited evidence that the AC sequence is located within intron 2 of the FMR1 gene and is adjacent to an Alu element. A 14-center collaborative study of genotype-phenotype correlations in the fragile X syndrome involved 318 affected families comprising 2,253 individuals, 1,344 of whom carried a fragile X mutation and 693 of whom had a typical full fragile X mutation (Rousseau et al., 1994). There was a significantly higher prevalence of 'mosaic' cases among males who carry a full mutation (12%) than among females who carry a full mutation (6%); the mosaic males had a larger expansion than did the mosaic females. ('Mosaics' are individuals carrying the full mutation who also have some premutations in some of their cells.) The mental status of premutated individuals did not differ from that of those with a normal genotype. Both the abnormal methylation of the FMR1-EagI site and the size of the expansion were highly correlated with cytogenetics, facial dysmorphism, macroorchidism, and mental retardation. Among female carriers of a full mutation, those with mental retardation had significantly larger expansion than did those without MR. Among 164 independent couples, 3 unrelated husbands carried a premutation that suggests that the prevalence of fragile X premutations in the general population is approximately 0.9% of the X chromosomes. The data validated the use of direct DNA testing for fragile X diagnosis and carrier identification. Quan et al. (1995) described a phenotypically atypical case of fragile X syndrome caused by a deletion that included the entire FMR1 gene and at least 9.0 Mb of flanking DNA. The proband was a 6-year-old mentally retarded male with obesity and anal atresia. The diagnosis of fragile X syndrome was established by the failure of the proband's DNA to hybridize to a restriction fragment specific for the 5-prime end of the FMR1 gene. The analysis of flanking markers in the interval Xq26.3-q28 indicated a deletion extending from between 160- to 500-kb distal, and 9.0-Mb proximal, to the FMR1 gene. High-resolution chromosome banding confirmed a deletion with breakpoints in Xq26.3 and Xq27.3. This deletion was maternally transmitted and arose as a new mutation on the grandpaternal X chromosome. The maternal transmission of the deletion was confirmed by fluorescence in situ hybridization using a 34-kb cosmid containing most of the FMR1 gene. The patient's unusual clinical presentation may indicate the presence of genes located in the deleted interval proximal to the FMR1 locus that are able to modify the fragile X syndrome phenotype. Quan et al. (1995) described a patient with mosaicism for expansion and deletion of the FMR1 CGG repeat. In addition to mental retardation, the affected male had cherubism (118400). Mosaicism had been described previously by Hirst et al. (1995), among others. The work of Reyniers et al. (1993) and Wohrle et al. (1993) suggested that the expansion of an FMR1 premutation to a full mutation occurs mitotically during a postzygotic stage. In this model of fragile X expansion, carriers of fully expanded FMR1 alleles transmit only premutation-sized alleles. The expansion of the maternally derived allele then occurs mitotically during early embryonic development. The failure to observe the expanded FMR1 alleles in the germline suggest that the expansion event occurs between days 5 and 20 of development, after the separation of the germline but before the divergence of tissue types. The findings of Quan et al. (1995) of mosaicism for expansion and deletion were consistent with this model of fragile X expansion. The detection of premutation-sized alleles in the proband was consistent with the transmission of a maternal premutation-sized FMR1 allele and postzygotic expansion. An unmethylated CpG island upstream of the FMR1 deletion indicated that the expansion and deletion of the CGG repeat occurred before FMR1 methylation. Cherubism was presumably an unrelated phenomenon. Verheij et al. (1995) demonstrated that the ile367-to-asn substitution in the FMR1 protein did not alter the translation, processing, or localization of FMR1 proteins in lymphoblastoid cells from a patient carrying this mutation. All the high molecular weight FMR1 proteins isolated from normal lymphoblastoid cells and cells from the patient with this substitution were able to bind RNA. However, the FMR1 proteins of the patient had reduced affinity for RNA binding at high salt concentrations. The FMR protein is cytoplasmic and contains 2 conserved RNA-binding domains, suggesting a possible involvement in RNA metabolism. Khandjian et al. (1996) observed that the FMR protein cosediments with polyribosomes after centrifugation in sucrose density gradients. Specifically, it is associated with the ribosomal 60S subunit and possesses the characteristics of a nonintegral ribosomal protein. Immunofluorescent studies showed a tight colocalization of FMRP with cytoplasmic ribosomes in NIH 3T3 and HeLa cells and in primary cultures of neurons. Thus, the authors concluded that fragile X mental retardation may result from defects in the translational machinery due to absence of FMRP. By immunofluorescence studies, Sittler et al. (1996) found that splice variants of FMR1 that exclude exon 14 sequences (and have alternate C-terminal regions) are nuclear. Analysis of various deletion mutants suggested the presence of a cytoplasmic retention domain encoded in exon 14 and of a nuclear association domain encoded within the first 8 exons that appear, however, to lack a typical nuclear localization signal. In 2 clinically normal brothers, Smeets et al. (1995) found expanded CGG repeats in cytogenetically visible fragile sites. The FMR1 promoter was unmethylated and both RNA and protein could be detected. This indicated to the authors that inactivation of the FMR1 gene and not repeat expansion itself resulted in the fragile X phenotype. Smeets et al. (1995) concluded that repeat expansion does not necessarily induce methylation and that methylation is no absolute requirement for the induction of fragile sites. This fragile X family was ascertained through a mentally retarded boy who was the grandson of 1 of the 2 brothers through a daughter. Subramanian et al. (1996) extended studies of the previously demonstrated replication timing delay of the FMR1 locus and proximal flanking sequences when involved in the full expansion of the repeat element. In this assay, relative times of replication of specific loci were inferred from the ratios of singlet and doublet fluorescence in situ hybridization signals in interphase nuclei. In all individuals with a full expansion of the trinucleotide repeat, a large region of delayed timing was observed; the apparent timing of the earlier-replicating allele in female cells in this region was intermediate between normal and affected alleles in male cells, a finding in accordance with expectations of a mixed population of cells resulting from random X inactivation. Expansion of the nearby FRAXE locus also was found to correlate with replication timing delay, although the extent of the altered region was somewhat less. Trinucleotide repeat expansion thus may be acting in the Xq27.3-q28 region to alter long-range chromatin structure that could influence transcription of gene sequences within the affected domain. Yeshaya et al. (1998) studied replication timing of the fragile X locus relative to the nontranscribed late replicating alpha-satellite region of chromosome X in lymphocytes and amniocytes from normal males, males with fragile X, and males who were premutation carriers. Three distinct populations were identified among the various samples. The first population had a high frequency of cells showing a doublet FMR1; this pattern, indicating early replication of FMR1, characterized cell populations of normal males. The second population had a high frequency of cells showing a singlet FMR1; this pattern, indicating very late replication of FMR1, characterized the population of fragile X patients. The third population had about one-half of the cells showing a singlet FMR1 and the other half with a doublet FMR1, indicating somatic variation in the replication timing of FMR1. This was the pattern seen in the population of premutation carriers. Nolin et al. (1996) examined transmission of the FMR1 CGGn repeat in 191 families with fragile X and in the general population. They reported that when fathers have (CGG)n expansions in the premutation range (greater than 80 repeats) the daughters frequently inherited smaller repeat expansions. A similar repeat number was inherited more often than expected by chance among a sibship segregating fragile X. They concluded that this familial clustering, observed in the offspring of both males and females with a premutation, implies that there may be an additional factor, independent of parental repeat size, that influences (CGG)n repeat instability. Nolin et al. (1996) found that gray-zone alleles (40 to 60 repeats) in families with no previous history of fragile X syndrome varied in their stability but that there was no repeat expansion to the full fragile X mutation in 1 generation. Jakala et al. (1997) found that males with the full fragile X (fM) mutation showed worse cognitive performance than did males with the premutation (pM); deficits in females with the fM were qualitatively similar but less severe than in males with the fM. In a visual memory test, both fM groups were impaired. Hippocampal volumes normalized for intracranial or brain area did not significantly differ between fM and pM groups. Minor abnormalities in temporal lobe structures were found by MRI in fM subjects. Patients with hereditary nonpolyposis colon cancer resulting from mutation in a mismatch repair gene such as MLH1 (120436) show instability of repeat sequences. Fulchignoni-Lataud et al. (1997) found that peripheral blood leukocytes from HNPCC patients showed roughly twice as great allele variation of the FMR1 CGG repeat as did controls, especially when patients carried mutations in MLH1. The findings suggested that instability within nonneoplastic cells of a subset of HNPCC patients might be a mechanism for transition from normal to the premutation range of the FMR1 CGG repeat. In a survey of 222 unrelated mentally retarded individuals attending Spanish special schools, Mila et al. (1997) found 11 boys with full mutations in the FMR1 gene and 1 boy with a CCG repeat expansion in the FMR2 gene. Feng et al. (1997) demonstrated that normal FMRP associates with elongating polyribosomes via large mRNP particles. Using a highly sensitive quantification assay, Kenneson et al. (2001) demonstrated significantly diminished FMRP levels in carriers, negatively correlated with repeat number. Despite reduced FMRP, these carrier alleles overexpressed FMR1, resulting in a positive correlation between repeat number and FMR1 message level. These biochemical deviations were associated with intermediate and premutation FMR1 alleles, which are found in approximately 4% of the population. The authors suggested that the phenotypic spectrum of fragile X syndrome may need to be redefined on a biochemical level. Primerano et al. (2002) noted that lymphoblastoid cells from patients with the full fragile X mutation (greater than 200 CGG repeats) have essentially absent levels of FMR1 mRNA and FMR1 protein, consistent with hypermethylation of the FMR1 gene and complete transcriptional silencing of the gene. In cells from 3 patients with premutation alleles (97, 170, and 195 CGG repeats), Primerano et al. (2002) found significantly increased levels of FMR1 mRNA compared with normal controls, and the level of mRNA increased with longer CGG repeats in the premutation range. However, overexpression of the mRNA from the premutation expanded alleles was not associated with increased levels of FMRP protein, suggesting a defect in translation. An analysis of polysomes and mRNA showed that the association of mRNA with polysomes progressively decreased with increasing allele expansion. Thus, in cases with premutation, impaired FMR1 translation leads to lower FMRP levels and clinical involvement. Hagerman and Hagerman (2004) pointed out that carriers of premutation alleles (55 to 200 CGG repeats) of the FMR1 gene can present with 1 or more of 3 distinct clinical disorders: mild cognitive and/or behavioral deficits on the fragile X spectrum; premature ovarian failure; and fragile X tremor/ataxia syndrome (FXTAS), a neurodegenerative disorder of older adult carriers. #### PATHOGENESIS Darnell et al. (2001) used RNA selection to demonstrate that the FMRP RGG box binds intramolecular G quartets. These data allowed them to identify mRNAs encoding proteins involved in synaptic or developmental neurobiology that harbor FMRP-binding elements. The majority of these mRNAs had an altered polysome association in fragile X patient cells. These data demonstrated that G quartets serve as physiologically relevant targets for FMRP and identified mRNAs whose dysregulation may underlie human mental retardation. Brown et al. (2001) coimmunoprecipitated mRNA with the FMRP ribonucleoprotein complex and used it to interrogate microarrays. They identified 432 associated mRNAs from mouse brain. Quantitative RT-PCR confirmed some to be more than 60-fold enriched in the immunoprecipitant. In parallel studies, mRNAs from polyribosomes of fragile X cells were used to probe microarrays. Despite equivalent cytoplasmic abundance, 251 mRNAs had an abnormal polyribosome profile in the absence of FMRP. Although this represented less than 2% of the total messages, 50% of the coimmunoprecipitated mRNAs with expressed human orthologs were found in this group. Nearly 70% of those transcripts found in both studies contained a G quartet structure, demonstrated as an in vitro FMRP target. Brown et al. (2001) concluded that translational dysregulation of mRNAs normally associated with FMRP may be the proximal cause of fragile X syndrome, and they identified candidate genes relevant to this phenotype. #### GENE FUNCTION In Drosophila, Ishizuka et al. (2002) found that Fmr1 is a component of a large protein complex known as the RNA-induced silencing complex (RISC), which is a sequence-specific nuclease complex that mediates RNA interference (RNAi). Fmr1 was found to associate with argonaute-2 (Ago2; 606229) and dicer (606241), 2 proteins normally present in the RISC. The findings suggested that defects in an RNAi-related machinery may underlie human disease. Mazroui et al. (2002) established an immortal murine embryonic STEK Fmr1 knockout cell line, and showed by transfection assays with Fmr1-expressing vectors that newly synthesized Fmrp accumulated into cytoplasmic granules. These structures contained mRNAs and several other RNA-binding proteins. The formation of the cytoplasmic granules was dependent on determinants located in the RGG domain. The authors also presented evidence that FMRP acts as a translation repressor following cotransfection with reporter genes. The FMRP-containing mRNPs are dynamic structures that oscillate between polyribosomes and cytoplasmic granules reminiscent of the stress granules that contain repressed mRNAs. Mazroui et al. (2002) suggested that, in neurons, FMRP may play a role as an mRNA repressor in incompetent mRNP granules that have to be translocated from the cell body to distal locations such as dendritic spines and synaptosomes. FMRP is a selective RNA-binding protein that forms a messenger ribonucleoprotein complex that associates with polyribosomes and can suppress protein translation in vitro. MicroRNAs (miRNAs) are a class of noncoding RNAs that are believed to control translation of specific target mRNAs. In vitro, Jin et al. (2004) showed that mammalian FMRP interacts with AGO1 (606228), a downstream component of the miRNA pathway, and that AGO1 is required for the biologic functions of Fmr1 in vivo in Drosophila. The results suggested a mechanism by which FMR1 regulates translational suppression. In Drosophila, Lgl (600966) encodes a cytoskeletal protein involved in cellular polarity and cytoplasmic transport. Zarnescu et al. (2005) found that mouse Lgl was expressed at low levels in the cytoplasm along with Fmr1. Overexpression of fluorescence-tagged Fmr1 directed the assembly of endogenous Lgl into perinuclear and cytoplasmic granules. In a mouse catecholaminergic cell line, Fmr1 overexpression resulted in reorganization of endogenous Lgl into Fmr1-containing granules in the perinuclear region and within developing neurites. #### DIAGNOSIS Jenkins et al. (1984) described prenatal diagnosis. The testes of 2 fragile-X-positive fetuses appeared large for gestational age. Antibiotics such as Bactrim (Roche) and Septra (Burroughs Wellcome) contain trimethoprim, which can lower folate levels by inhibition of dihydrofolate reductase. Hecht and Glover (1983) urged avoidance of trimethoprim and other folate antagonists in pregnant women who are at risk for having a child with the fragile X syndrome. Lejeune et al. (1982) described severe clinical regression of psychomotor development in a 2-year-old boy with the fragile X syndrome while on trimethoprim. Jacky and Dill (1980) achieved marXq28 expression in cultured fibroblasts and Jenkins et al. (1982) detected the marker in cultured amniocytes, enabling successful prenatal diagnosis. Thymidine deficiency induced by BUdR or FUdR appeared necessary for expression in cells other than lymphocytes (Glover, 1981; Tommerup et al., 1981). Until reliable expression was possible, however, absence of the marX in amniocytes of male or female fetuses had to be interpreted with caution (see later for prenatal diagnosis using molecular markers). Jacobs et al. (1982) showed that the marX can be demonstrated on lymphoblastoid cell lines and that it is reliably and repeatedly demonstrable after the addition of FUdR to cultures. This simple technique provides a useful in vitro experimental test system. Sutherland (1989) indicated that there is a fragile site (FRAXD) located at Xq27.2, separate from the classic fragile site at Xq27.3 which is responsible for mental retardation. Obviously, this is a point of diagnostic importance. The FRAXD is inducible by high doses of aphidicolin. Ramos et al. (1992) concluded that the fragile site at Xq27.2 can be demonstrated in normal persons under the conditions of thymidylate stress routinely used for cytogenetic diagnosis of the fragile X syndrome. Furthermore, this fragile site is present at low levels (1-2%) in all persons who express it and, therefore, its expression is unlikely to cause false-positive diagnoses of the syndrome. Lesions at Xq26 are also seen at low levels in lymphocytes of persons without the syndrome. Oberle et al. (1991) identified carriers of the fragile X mutation regardless of sex or phenotypic expression. Rare apparent false negatives were considered to be the result of genetic heterogeneity or misdiagnosis. Rousseau et al. (1991) concluded that direct DNA diagnosis of the fragile X syndrome is efficient and reliable. Southern analysis of EcoRI and EagI digests of DNA distinguished clearly in a single test between the normal genotype, the premutation, and the full mutation. Fifteen percent of those with full mutations had some cells carrying only the premutation. All of the mothers of affected children were carriers of either a premutation or a full mutation. Because of the certainty of DNA diagnosis, this method replaces cytogenetic detection of the fragile X chromosome, which carries a rate of misdiagnosis of about 5% for both false positives and the more frequent false negative conclusion, and diagnosis by the linkage principle, which gives a probabilistic result rather than an absolute one. As pointed out by Jacobs (1991), in spite of the advances in the molecular understanding of fragile X, the cytogenetic marker still has an honorable role to play in its diagnosis. As the cytogenetic test is reliable for virtually all males and for the great majority, but not all, of affected females, the most efficient and cost effective methodology for diagnostic specimens still seemed to her to be cytogenetic analysis, followed by molecular studies only when the fra(X) is seen or suspected. Sutherland et al. (1991) illustrated the use of direct DNA diagnosis in establishing the carrier status of a cytogenetically normal woman in a family with the fragile X syndrome and in diagnosing the mutation in her male fetus by detecting the unstable sequence in DNA obtained by chorionic villus sampling. They used a probe referred to as pfxa3. The carrier mother had a normal 1.0-kb band and an abnormal 1.2-kb band. In the villus sample the normal 1.0-kb band was replaced by a 2.3-kb band, a size seen in affected males. Normal carrier males usually have a fragile X band that is between 1.1 and 1.6 kb. Richards et al. (1991) described 2 polymorphic microsatellite AC repeat markers, FRAXAC1 and FRAXAC2, physically located within 10 kb and on either side of the (CCG)n repeat responsible for the fragile site. The two show strong linkage disequilibrium and have heterozygosity of 44 and 71%, respectively. No recombination was observed either between these markers in 40 CEPH pedigrees or with FMR1 in affected pedigrees. These markers provide the means for accurate diagnosis of the fragile X genotype in families by polymerase chain reaction (PCR) analysis. Richards et al. (1991) used them to position FMR1 within the multipoint map of the X chromosome to a position 3.7 cM distal to DXS297 and 1.2 cM proximal to DXS296. Griffiths and Strachan (1991) described a technique, based on a culture system reported by Wheater and Roberts (1987), that enables the cytogeneticist to do fra(X) screening and prometaphase banding on the same specimen. Yu et al. (1992) found that all persons of the fragile X genotype (where testing was possible) had a parent with amplified p(CCG)n repeat, indicating that few, if any, cases of fragile X syndrome are not familial. Mandel et al. (1992) reported on the Fifth International Workshop on the Fragile X and X-Linked Mental Retardation held near Strasbourg, France, in August 1991. In addition to their summary, over 50 papers on the fragile X syndrome and 18 papers related to other X-linked mental retardation syndromes presented at the conference were published in the American Journal of Medical Genetics. All aspects of the fragile X syndrome (clinical, cytogenetic, molecular and linkage, and population) were covered in great detail. Mandel et al. (1992) reviewed the hypothesis of Patricia Jacobs which postulates 3 mutations: a change from a normal insert (N) to a small insert that is at low risk of converting to a large insert (S); a change from that type of small insert to a small insert at high risk of converting to a large insert (S*); and a change from the high risk small insert to a large insert (L) which is associated with clinical abnormality. Cytogenetic screening of the mentally handicapped for the fra(X) is equivalent to testing for individuals with a large insert (L) as there is no evidence that a small insert (S) has a deleterious effect on the phenotype. The consensus was that in diagnostic laboratories cytogenetics is still the method of choice, with subsequent molecular investigation of those patients found or suspected of being fra(X) positive; no consensus was reached on the relative merits of cytogenetics and molecular techniques for screening. Mulley et al. (1992) reported a high success rate with the direct molecular diagnosis of fragile X using the pfxa3 probe which detects amplification of an unstable DNA element consisting of variable length CCG repeats. Diagnosis was definitive in all males with only one X chromosome. Prenatal diagnosis of the fragile X syndrome on the basis of the cytogenetic alteration in amniocytes (Jenkins et al., 1984) was insecure because of technical uncertainties. Yamauchi et al. (1993) used the diagnostic DNA probe pPCRfx1 to confirm that an at-risk fetus was a heterozygous female carrier. Dreesen et al. (1995) approached preimplantation testing for the fragile X syndrome by genotyping the polymorphic DXS548 AC-repeat locus, which is closely linked to the FMR1 gene, in unfertilized oocytes and extruded polar bodies. They concluded that a PCR procedure could be performed within 16 hours after blastomere biopsy and that for carrier females heterozygous at the DXS548 locus, preimplantation testing with DXS548 is a possible alternative to prenatal testing. Willemsen et al. (1995, 1997) developed a diagnostic method that allows detection of the fragile X syndrome from a blood smear. The test made use of mouse monoclonal antibodies against the FMR1 protein. This noninvasive test requires only 1 or 2 drops of blood and can be used for screening large groups of mentally retarded persons and neonates for the fragile X syndrome. Willemsen et al. (1999) modified the 'antibody test' for application to hair roots. The advantages of this modification of the test were considered to be (1) plucking of hair follicles does no appreciable harm to mentally retarded patients, (2) hair can be sent in a simple envelope to a diagnostic center, and (3) the result of the test is available within 5 hours of plucking. Mentally retarded female patients with a full mutation showed FMR protein expression in only some of their hair roots (less than 55%), and no overlap with normal female controls was observed. Willemsen et al. (2003) undertook to determine whether there is a correlation between FMRP expression in hair roots and cognitive function in female fragile X carriers. In 34 female full mutation carriers and unaffected female control relatives, the expression of FMRP in hair roots was studied using a specific antibody test; the percentage of hair follicles that expressed FMRP was determined. In addition, participants completed tests to measure their basic cognitive functioning. In the female carriers, a highly significant relationship was found between the centile score on the cognitive testing and the percentage of hair roots that expressed FMRP. Cognitive function in the female carriers was much more strongly determined by the absence of FMRP than by genetic background. Turner et al. (1996) suggested that the clinical definition of this disorder be redefined in the male as mental handicap associated with absolute or relative deficiency of the FMR1 protein. In the absence of a readily available protein test, analysis of the FMR1 trinucleotide repeat size had been used for diagnosis (Snow et al., 1993). They stated that increase in the size of the repeat in the FMR gene over a particular value initiates methylation of the FMR gene promoter site, resulting in the switching off of the FMR1 gene transcription. Turner et al. (1996) noted that this method of testing also defines individuals who lack FMR1 protein as a consequence of deletion of the gene but will not identify those individuals whose FMR1 protein is defective through mutation. Storm et al. (1998) noted that incomplete EcoRI digestion may lead to false diagnosis of fragile X syndrome and suggested that HindIII digest be used instead of EcoRI to identify premutation vs normal fragment length in genomic DNA. The FMR protein is highly expressed in neurons of the normal mammalian brain and absent or in low levels in leukocytes from individuals with fragile X-associated mental impairment. It is inferred from these findings that the FMR protein has a critical role in the development and functioning of the brain, and that leukocyte-derived molecular assessments provide a good indicator of FMR1 expression in the brain. Abrams et al. (1999) studied blood to brain correspondence in fragile X patients directly in living individuals with the FMR1 mutation by biopsy of olfactory neuroblasts (ON) in 2 mentally retarded, autistic brothers with expansion mutations in their leukocytes. Olfactory neurons were chosen for study because they are accessible neurons that undergo regeneration and are closely linked to the brain. In both subjects, the ON genotype was highly, but not perfectly, consistent with that observed in leukocytes. These results augmented the limited amount of direct evidence, which indicated that FMR1 mutation patterns in leukocytes are a good, albeit potentially fallible, reflection of such patterns in the brain. This report further demonstrated the feasibility of using ON samples to evaluate FMR1 mutations in humans in vivo. Stoll (2001) presented 11 children under the age of 8 years and the difficulties in diagnosis of fragile X syndrome at this age. The author concluded that this study emphasized the importance of fragile X DNA testing in all children with mental retardation, autism, or significant developmental delay without a clear etiology. To evaluate the effectiveness of a fragile X carrier screening program, Toledano-Alhadef et al. (2001) tested 14,334 Israeli women of childbearing age for fragile X carrier status between 1992 and 2000. These women were either preconceptional or pregnant and had no family history of mental retardation. All those found to be carriers of premutation or full-mutation alleles were offered genetic counseling and also prenatal diagnosis, if applicable. They identified 207 carriers of an allele with more than 50 repeats, representing a prevalence of 1:69. There were 127 carriers with more than 54 repeats, representing a prevalence of 1:113. Three asymptomatic women carried the full-mutation allele. Among the premutation and full-mutation carriers, 177 prenatal diagnoses were performed. Expansion occurred in 30 fetuses, 5 of which had an expansion to the full mutation. On the basis of these results, the expected number of prevented affected offspring of women identified as carriers, the cost of the test in this study, and the estimated cost of lifetime care for a mentally retarded person, the authors considered the screening to be cost effective and recommended wide-scale screening to identify female carriers. #### POPULATION GENETICS Jacobs (1982) indicated that a reasonable estimate of frequency is 0.5 per 1000 males. Many of the cases first ascertained were of northern European descent; subsequently, however, affected males have been found in most ethnic groups. Webb et al. (1986) performed a population study of school children in the city of Coventry, England, and, using cytogenetic studies, gave an overall prevalence for fragile X syndrome in males and females of 1:952. Morton et al. (1997) reevaluated the 29 children diagnosed with fragile X syndrome by Webb et al. (1986) and confirmed the presence of the FMR1 gene expansion in only 7 of the children, giving a revised prevalence of 1:2720 to 1:5714 (depending on whether the 4 children lost to follow-up are included). Turner et al. (1996) reported that on the basis of molecular genetic analysis, a prevalence figure of 1:4,000 or 2.4:10,000 was more realistic than the 1:1000 reported by Webb et al. (1986). Filippi et al. (1991) reported findings in a very large Sardinian kindred spanning 6 generations and including 13 patients with Martin-Bell syndrome, several instances of normal transmitting males or females, and the G6PD Mediterranean (305900.0006) mutant segregating in some of its branches. All the fragile X patients and the 15 obligate heterozygous women could be traced through their X-chromosome lineage to a woman in the first generation who must have been heterozygous for a silent premutation at the FRAX locus. Filippi et al. (1991) concluded that this premutation had been converted into a true FRAX mutation at least 9 times during the gametogenesis of this ancestor's X-related descendants, of whom 4 were males. See 309530 for a general discussion of X-linked mental retardation. Richards et al. (1992) presented haplotype evidence for a founder effect in the fragile X mutation. They found clear evidence of linkage disequilibrium between fragile X and 2 polymorphic microsatellite markers that flank FMR1 and are within 10 kb of the (CCG)n repeat. These markers have 5 to 7 alleles, show no recombination with each other, and define 15 haplotypes. In an analysis of 134 fragile X chromosomes from unrelated affected individuals in Australia and the United States, they found that 58% of the fragile X mutations occurred on the 3 backgrounds that account for 18% of normal chromosomes. Correspondingly, the single most common normal haplotype, which has a frequency of 50%, carries only 18% of fragile X mutations. The data argue for the expected occurrence of multiple, independent mutations but also indicate the unexpectedly long history of some of these fragile X mutations. Using the FRAXAC1 polymorphic marker in the study of a large number of patients, Hirst et al. (1993) found its allele distribution to be strikingly different on fragile X chromosomes, confirming earlier observations and giving further support to the suggestion of a fragile X founder effect (Richards et al., 1992). In Israel, in a study of 122 families affected with the fragile X syndrome, diagnosed in 7 genetic centers, Dar et al. (1995) found that Tunisian Jews, who comprise only 4% of the general population, accounted for 21% of the fragile X families, suggesting founder effect. The CGG repeat, which is normally polymorphic in length, is frequently interrupted by AGG triplets, which are believed to stabilize the repeat. The absence of AGG triplets, leading to long tracts of perfect CGG repeats, may give rise to predisposed alleles. Kunst et al. (1996) determined the repeat length of 345 chromosomes from 9 populations from various parts of the world and used automated DNA sequencing to assess 14 of them. They found that the FMR1 alleles were very heterogeneous, although the level of variation correlated with the age and/or genetic history of a particular population. Native American alleles, interrupted by 3 AGG repeats, exhibited marked stability over 7,000 years. However, in older African populations, parsimony analysis predicted the occasional loss of an AGG, leading to more perfect CGG repeats. Russo et al. (1998) described a female who was a compound heterozygote, having a full FMR1 mutation on one X chromosome and a premutation on the other X chromosome. The parents came from the same small village. Russo et al. (1998) found reports of 2 previous instances of compound heterozygous females (Mila et al., 1996; Linden et al., 1999). The proband's mother and aunt reported that they had undergone premature ovarian failure at 35 years of age. Linden et al. (1999) reported a second case of compound heterozygosity, in a 15-year-old woman with fragile X syndrome who had a full mutation of 363 repeats on one X chromosome and a premutation of 103 repeats on the other X chromosome. As predicted, testing demonstrated that her father carried a premutation (98 repeats) as did her mother (146 repeats). Cognitively, this woman was functioning in the mid range of involvement for fragile X females. She attended regular classes and received supplemental assistance for her learning disabilities. She experienced behavioral characteristics typical of females with fragile X syndrome including severe shyness, anxiety, panic episodes, mood swings, and attention deficits. She responded well to appropriate treatment including fluoxetine for anxiety, methylphenidate for attention problems, and educational therapy. Allingham-Hawkins et al. (1999) reported preliminary results from an international collaborative study examining premature menopause in fragile X carriers. A total of 760 women from fragile X families were surveyed concerning fragile X carrier status and their menstrual and reproductive histories. Among the subjects, 395 carried a premutation, 128 carried a full mutation, and 237 were noncarriers. In 63 (16%) of the premutation carriers, menopause occurred before the age of 40, compared with none of the full-mutation carriers and 1 (0.4%) of the controls. Thus, premutation carrier status and premature menopause have a significant association. Fragile X premutations appear to be a risk factor for premature ovarian failure (POF), defined as menopause at age less than 40 years. Since premutations may be inherited from either the mother or the father, Hundscheid et al. (2000) evaluated the influence of the inheritance pattern on the duration of reproductive life in female carriers. The occurrence of POF and age at menopause in women with a paternally inherited fragile X premutation (PIP) were compared to those in women with a maternally inherited fragile X premutation (MIP). The authors identified 148 women in whom the paternal origin of the premutation could be determined. In 109 of these, POF had occurred: 82 women had a PIP, and 27 had a MIP. Twenty-three of the women (28%) with a PIP had POF, compared with only 1 (3.7%) with a MIP (P = 0.007 with 2-tailed Fisher exact test). Kaplan-Meier analysis of all 148 premutations showed that the age at menopause was significantly lower in the women with a PIP than in the women with a MIP (P = 0.003 with Breslow test in Kaplan-Meier analysis). Hundscheid et al. (2000) hypothesized that the paternal effect in POF in fragile X premutation carriers can be explained by paternal genomic imprinting. Expression of the FMR1 gene and other X-linked genes is nonfunctional during normal spermatogenesis, when the X chromosome becomes condensed and transcriptionally inactive. Most genes are reactivated during the first few cell divisions after fertilization, whereas 2 X chromosomes are active in the female morula. However, when a PIP is imprinted, there may be a delay in reactivation of the inactive paternal X chromosome during early embryonic development; thus, only the maternal allele would be expressed at this critical developmental stage. Although there was no direct evidence that abnormal FMR1 protein production in oocytes leads to a smaller oocyte pool, it was considered possible that FMR1 protein plays a role in oogenesis, because FMR1 is highly expressed when oogenesis occurs. Murray et al. (2000) and Vianna-Morgante and Costa (2000) were unable to confirm a parent-of-origin effect on premature ovarian failure in fragile X premutation carriers. The reason for the discrepancy with the findings of Hundscheid et al. (2000) was discussed by Hundscheid et al. (2000) and Sherman (2000). Machado-Ferreira et al. (2004) studied 58 women from 24 fragile X syndrome families. Using Southern blotting for direct DNA analysis, they identified 19 normal individuals, 33 premutation carriers, and 6 fully mutated individuals; the results included 4 cases of somatic mosaicism showing premutated and fully mutated alleles. Among the premutated women, 11 (including 1 case of somatic mosaicism) experienced menopause before the age of 40 (by definition POF), while none of the normal women identified in these families experienced POF. The data corroborated the notion that females carrying alleles in the premutation range are at high risk of experiencing POF. Crawford et al. (1999) found that the prevalence of the FRAXA full mutation in African American males was approximately the same as that in Caucasian American males. Goldman et al. (1997) reported that the prevalence of FRAXA syndrome among institutionalized South African blacks was similar to that reported in the literature for institutionalized white populations. Several population-based studies in Caucasians of mostly northern European descent established that the prevalence of the fragile X syndrome is probably between 1 in 6,000 and 1 in 4,000 males. Crawford et al. (2002) presented the final results of a 4-year study in the metropolitan area of Atlanta, Georgia, establishing the prevalence of the fragile X syndrome and the frequency of CGG repeat variants in a large Caucasian and African-American population. They found that one-quarter to one-third of the children identified with the fragile X syndrome attending Atlanta public schools were not diagnosed before the age of 10 years. Also, a revised prevalence for the syndrome revealed a higher point estimate for African-American males (1/2,545; 95% CI 1/5,208-1/1,289) than reported previously, although confidence intervals included the prevalence estimated for Caucasians from this and other studies (1/3,717; 95% CI 1/7,692-1/1,869). Mingroni-Netto et al. (2002) studied the distribution of CGG repeats and DXS548/FRAXAC1 haplotypes in normal South American populations of different ethnic backgrounds. They found that some rare alleles that seem nearly absent in Europe occurred in higher frequencies among African Brazilians, which suggested a general trend for higher genetic diversity among Africans. Thus, the rarer alleles could be African in origin and would have been lost or possibly not present in the groups that gave rise to Europeans. Studies of (CGG)n repeat structures of selected human populations showed a high degree of conservation of the canonical (CGG)9AGG interruption pattern in different populations and confirmed the proposed stabilizing effect of AGG interruptions (Eichler and Nelson, 1996). In the native population of Greenland, Larsen et al. (1999) found a narrow distribution of (CGG)n allele sizes, similar to that reported for Asian populations. DNA sequencing of alleles with 36 CGG repeats revealed an AGG(CGG)6 insertion previously reported exclusively in Asian populations and a high frequency of 2 other sequence patterns. The data confirmed the Asian origin of the Greenlandic (Eskimo) population and indicated that some (CGG)n alleles have remained stable for 15,000 to 30,000 years, since the population of the New World arrived from Asia via the Bering Strait. The findings added new evidence for the 'out of Asia' theory of the colonization of the New World (Cavalli-Sforza et al., 1994). Studies in Native Americans (Amerinds) had not shown the (CGG)6AGG insertion. This may be due to the relatively small sample sizes in these studies, but may also be caused either by a later migration of the Eskimo population compared with the Amerind and the Na-dene populations (as proposed in the '3 migrations theory' Greenberg et al., 1986 or by genetic bottlenecks during the population of the New World (Wallace and Torroni, 1992)). Larsen et al. (2001) analyzed the AGG interspersion pattern of the (CGG)n repeat and the haplotype distribution of 2 closely located microsatellite markers in 3 circumarctic populations: Norwegians, Saami, and Nenets. The data indicated the existence of chromosomes of Asian origin in the Saami and Nenets populations. Haplotype analysis of Norwegian fragile X males compared to other populations showed that the fragile X founder haplotypes may vary between populations and that the CGG expansion associated with fragile X syndrome may originate from subpopulations of unstable alleles within the normal population. Beresford et al. (2000) reported molecular analysis of 177 males with mental handicap and 1,226 random alleles from Guthrie newborn screening samples in Nova Scotia. No FMR1 premutations or mutations were found. Beresford et al. (2000) also noted that only 1 case of fragile X had been reported in this region since 1980, in an individual who had moved from elsewhere in Canada. Beresford et al. (2000) concluded that the fragile X syndrome was rare in Nova Scotia, a phenomenon they found remarkable given the high prevalence of other rare heritable disorders in the region and that the population has tens of thousands of founders from multiple founding groups. Dombrowski et al. (2002) screened 10,572 independent French-Canadian males for premutation-size FMR1 alleles and identified 13 who carried alleles of more than 54 repeats, which corresponded to a population frequency of 1 in 813. (Rousseau et al. (1995) reported a population frequency of 1 in 259 for female carriers of an allele of more than 54 repeats.) Haplotype analysis of the 13 identified male carriers revealed that the prevalence of the major fragile X mutation-associated haplotype was increased among FMR1 alleles of 40 to 54 repeats. Although sequencing of highly unstable premutation alleles from fragile X families revealed only pure CGG tracts, 48 of 49 males from the general population with 40 or more triplets had 1 to 2 AGG interruptions. This suggests that the loss of an AGG interruption in the triplet repeat array may not be necessary for expansion of normal alleles of 29 to 30 triplets to intermediate size. The authors concluded that loss of AGG interruptions appears to be a late event that may lead to greatly increased instability and may be related to the haplotype background of specific FMR1 alleles. Biancalana et al. (2004) reported the molecular diagnosis of fragile X syndrome in France during the 5-year period from 1997 to 2001: 477 families were diagnosed with fragile X syndrome, representing 2.8% of tested male probands and 1% of tested female probands. #### ANIMAL MODEL Faust et al. (1992) and Laval et al. (1992) determined the location of the corresponding gene on the mouse X chromosome by use of human cDNA clones in an interspecific backcross. Both groups found preservation of the order of loci, although no fragile site had been detected microscopically in that region of the mouse X chromosome. The Dutch-Belgian Fragile X Consortium (1994) created a knockout model for the fragile X syndrome in mice. The knockout mice lacked normal FMR1 protein and showed macroorchidism, learning deficits, and hyperactivity. Magnetic resonance imaging (MRI) of the brain of fragile X patients has revealed abnormalities in the size of specific brain structures, including the cerebellar vermis, the hippocampus, and the ventricular system. Kooy et al. (1999) tested for parallel changes in the fragile X knockout mouse model. They did not find evidence for size alterations in various brain regions of the fragile X mouse model, but the method described may find a wide application in the study of mutant mouse models with neurologic involvement. By mRNA in situ hybridization studies, Hinds et al. (1993) demonstrated that expression of the Fmr-1 gene was localized to several areas of the brain and the tubules of the testes in the adult mouse, whereas universal and very strong expression was observed in early mouse embryos. To identify transcribed sequences rapidly and efficiently, Hanzlik et al. (1993) developed a recombination-based assay to screen bacteriophage lambda-libraries for sequences that share homology with a given probe. This strategy determines whether a given probe is transcribed in a given tissue at a given time of development and may also be used to isolate the transcribed sequence free of the screening probe. Hanzlik et al. (1993) used the technique to demonstrate that the fragile X sequence is transcribed ubiquitously in an 11-week fetus, in a variety of 20-week fetal tissues including brain, spinal cord, eye, liver, kidney, and skeletal muscle, and in adult jejunum. Eberhart et al. (1996) performed immunolocalization studies to gain insight into the function of the protein FMRP which is encoded by the FMR1 gene. Their studies revealed a nuclear localization signal in the amino terminus and a nuclear export signal encoded by exon 14. Eberhart et al. (1996) further demonstrated that FMRP is found in ribonucleoprotein (RNP) particles. They reported that their data are consistent with nascent FMRP entering the nucleus to assemble into RNP particles prior to export back into the cytoplasm. Peier et al. (2000) generated yeast artificial chromosome (YAC) transgenic mice order to determine whether the Fmr1 knockout mouse phenotype could be rescued. The YAC transgene supported production of the human FMRP protein at levels 10 to 15 times that of endogenous protein; the protein was expressed in a cell- and tissue-specific manner. Macroorchidism was absent in knockout mice carrying the YAC transgene, indicating functional rescue by the human protein. While the knockout mice displayed reduced anxiety-related responses and increased exploratory behavior, the FMR1 YAC transgenic mice displayed opposing behavioral responses and other abnormal behaviors, presumably due to overexpression of FMRP. The authors suggested that overexpression of FMRP may harbor its own behavioral phenotype. Human-murine homology at the FMR1 locus extends to the repeat region and promoter. The murine repeat region contains triplets ranging from 8 to 12 repeats. Bontekoe et al. (2001) generated a knockin mouse Fmr1 gene in which the murine (CGG)8 repeat was exchanged with a human (CGG)98 repeat. Unlike other CGG transgenic models, this model showed moderate CGG repeat instability (2 contractions and 13 expansions among 155 transmissions) in both maternal and paternal transmission. An abnormal phenotype was not described. Zhang et al. (2001) developed a Drosophila model of fragile X syndrome using loss-of-function mutants and overexpression of the FMR1 homolog, Dfxr (Drosophila fragile X-related gene). Dfxr nulls displayed enlarged synaptic terminals, whereas neuronal overexpression resulted in fewer and larger synaptic boutons. Synaptic structural defects were accompanied by altered neurotransmission, with synapse type-specific regulation in central and peripheral synapses. These phenotypes mimicked those observed in mutants of Futsch, a microtubule-associated protein with homology to mammalian MAP1B (157129). Immunoprecipitation of Dfxr showed association with Futsch mRNA, and Western blot analyses demonstrated that Dfxr inversely regulates Futsch expression. Dfxr-Futsch double mutants restored normal synaptic structure and function. Zhang et al. (2001) proposed that Dfxr acts as a translational repressor of Futsch to regulate microtubule-dependent synaptic growth and function. Using wildtype Drosophila and Drosophila mutant in Dfxr, Morales et al. (2002) showed that the DFXR protein is constitutively expressed in brain neuronal cell bodies and excluded from glia. The protein was found to be required for normal neurite extension, guidance, and branching, although different neuronal cell types appeared to be regulated differently, indicating diverse targets in the brain. Overexpression of the protein resulted in similar abnormalities, suggesting that the dose of DFXR is strictly regulated and critical for normal function. Dfxr mutants exhibited abnormal circadian behavior and eclosion. Protein synthesis occurs in neuronal dendrites, often near synapses. Polyribosomal aggregates often appear in dendritic spines, particularly during development. Some protein synthesis appears to be regulated directly by synaptic activity. Greenough et al. (2001) found that FMRP is one of the proteins that is synthesized in a preparation called synaptoneurosomes when stimulated with glutamate or group I metabotropic glutamate receptor agonists (e.g., 604473). They also found that agonist-activated protein synthesis in synaptoneurosomes was dramatically reduced in a knockout mouse model of fragile X syndrome. Studies of autopsy samples from patients with fragile X syndrome indicated that dendritic spines may fail to assume a normal mature size and shape and that there are more spines per unit of dendrite length in the patient samples. Similar findings on spine size and shape had come from studies of the knockout mouse. Normal dendritic regression was also impaired in the knockout mouse. These findings suggested that FMRP may be required for the normal processes of maturation and elimination to occur in cerebral cortical development. Irwin et al. (2002) compared the dendritic spines on layer V pyramidal cells of visual cortices of wildtype and fragile-X knockout mice. The knockout mice had significantly more long dendritic spines, significantly fewer short dendritic spines, significantly more dendritic spines with an immature-like morphology, and significantly fewer dendritic spines with a more mature morphology. However, unlike the human patients, the knockout mice did not exhibit statistically significant dendritic spine density differences from controls. Fragile-X mice also did not demonstrate any significant differences from controls in dendritic tree complexity or dendritic arbor. In behavioral studies of Mfr1 knockout mice, Qin et al. (2002) observed hyperactivity and a higher rate of entrance into the center of an open field compared with controls, suggesting decreased levels of anxiety. Impaired performance of the knockout mice on a passive avoidance task suggested a deficit in learning and memory. To learn what brain regions are involved in the behavioral abnormalities of fragile X mental retardation, Qin et al. (2002) applied the carbon-labeled deoxyglucose method for determining regional cerebral metabolic rates of glucose. They found higher values in all 38 regions tested, as compared to control wildtype littermates; in 26 of the regions, differences were statistically significant. The greatest increases occurred in regions of the limbic system and primary sensory and posterior parietal cortical areas. The regions most affected were consistent with behavioral deficiencies and regions in which Fmrp expression is highest. Qin et al. (2002) suggested that the higher cerebral glucose metabolism in fragile X mice may be a function of abnormalities found in dendritic spines. Willemsen et al. (2003) described neurohistologic, biochemical, and molecular studies of the brains of transgenic mice with an expanded CGG repeat (102 to 110 repeats) in human FMR1, and reported elevated Fmr1 mRNA levels and intranuclear inclusions with ubiquitin, Hsp40 (see 604572), and the 20S catalytic core complex of the proteasome as constituents. An increase was observed in both the number and the size of the inclusions during the course of life, which correlated with the progressive character of the cerebellar tremor/ataxia syndrome in humans. Willemsen et al. (2003) concluded that the observations in expanded-repeat mice supported a direct role of the Fmr1 gene, by either CGG expansion per se or by mRNA level, in the formation of the inclusions and suggested a correlation between the presence of intranuclear inclusions in distinct regions of the brain and the clinical features in symptomatic premutation carriers. Miyashiro et al. (2003) determined that the RNA cargoes associated with Fmr1-mRNP complexes were altered in Fmr1 null mice. Some of these cargoes, as well as the proteins encoded by them, showed discrete changes in their abundance and/or subcellular distribution. Weiler et al. (2004) studied neurotransmitter-activated synaptic protein synthesis in Fmr1 knockout mice. Synaptoneurosomes from knockout mice did not manifest accelerated polyribosome assembly or protein synthesis as it occurs in wildtype mice upon stimulation of group I metabotropic glutamate receptors. Direct activation of protein kinase C (see 176960) did not compensate in the knockout mice, indicating that the FMRP-dependent step is further along the signaling pathway. Visual cortices of young knockout mice exhibited a lower proportion of dendritic spine synapses containing polyribosomes than did the cortices of wildtype mice, corroborating this finding in vivo. This deficit in rapid neurotransmitter-controlled local translation of specific proteins may contribute to the morphologic and functional abnormalities observed in patients with fragile X syndrome. #### HISTORY In retrospect, it was concluded that the X-linked mental retardation reported by Martin and Bell (1943) was the fragile X syndrome. Thus, the Martin-Bell syndrome is a synonym for the fragile X syndrome. According to Opitz and Sutherland (1984), Escalante, a graduate student with Frota-Pessoa in Sao Paulo, Brazil, and Drs. Bryan and Gillian Turner in Sydney, Australia, independently noted macroorchidism in X-linked mental retardation in the late 1960s. Escalante et al. (1971) published their findings (which they had reported in 1969 at the Warsaw Congress of the International Association for the Scientific Study of Mental Deficiency) in the Journal de Genetique Humaine. When I visited the Doctors Turner in Sydney in March 1970, they showed me several mentally retarded patients with macroorchidism. Opitz et al. (1984) referred to this disorder as the Martin-Bell syndrome on the assumption that the family reported from the Queen Square Hospital in London by J. Purdon Martin and Julia Bell (Martin and Bell, 1943) had that disorder. Although macroorchidism was not mentioned by Martin and Bell (1943), one of the patients was described as having a 'big face and jaw'; furthermore, at least 9 of the affected males were maternal grandsons of 2 unaffected brothers. All but 1 of the mothers of affected males were daughters of these 2 brothers, the other being their sister. Martin and Bell (1943) hypothesized that some controlling factor caused suppression of the disease in the 2 grandfathers without affecting their liability to transmit it. For a superb biography of Julia Bell (1879-1979), see Bundey (1996). Richards et al. (1981) followed up on the Martin-Bell kindred, demonstrating that it was indeed the fragile X syndrome. The original index patient was then aged 56. All 4 affected males who had adequate karyotyping showed the fragile X syndrome in 17 to 50% of their cells. The other major contribution of Julia Bell was in the defining of many hereditary disorders, such as the forms of brachydactyly, on the basis of massive collections of pedigrees in the famous Treasury of Human Inheritance. She also collaborated with J. B. S. Haldane in the first estimation of linkage in the human, that of colorblindness and hemophilia (Bell and Haldane, 1937). ### ALLELIC VARIANTS (selected examples) #### .0001 FRAGILE X MENTAL RETARDATION SYNDROME [FMR1, ILE304ASN] De Boulle et al. (1993) described a patient with typical features of the fragile X mental retardation syndrome: coarse acromegaloid facial features, large forehead, asymmetric long face, large ears, thick lips, mandibular prognathism, macroorchidism, etc. A study of the chromosomes grown in folate-deprived culture conditions showed no evidence of the fragile X. Mutation analysis showed a T-to-A transversion converting codon 367 from ATT (ile) to AAT (asn). The mutation was not found in the mother, brother, or nephews who had normal intellectual abilities and no stigmata of fragile X syndrome. De Boulle et al. (1993) referred to this mutation as ILE367ASN. The ile304-to-asn (I304N) mutation results in an unusually severe phenotype. Feng et al. (1997) demonstrated that normal FMRP associates with elongating polyribosomes via large mRNP particles. Despite normal expression and cytoplasmic mRNA association, the I304N FMRP is incorporated into abnormal mRNP particles that are not associated with polyribosomes. These data indicated that association of FMRP with polyribosomes must be functionally important and implied that the mechanism of the severe phenotype in the I304N patient lies in the sequestration of bound mRNAs in nontranslatable mRNP particles. In the absence of FMRP, these same mRNAs may be partially translated via alternate mRNPs, although perhaps abnormally localized or regulated, resulting in typical fragile X syndrome. #### .0002 FRAGILE X MENTAL RETARDATION SYNDROME [FMR1, 1-BP DEL, ACT125CT, FS159TER] The fragile X syndrome is postulated to be due to a loss of function of the FMR1 gene product: methylation of the expanded repeats correlates with downregulation of transcription of FMR1. However, the nature of the mutation offers a possibility of methylation spreading to adjacent genes with consequent loss of expression and contribution to the phenotype. None of the deletions of FMR1 that have been reported in patients with phenotypes consistent with the diagnosis of fragile X syndrome is strictly intragenic. Lugenbeel et al. (1995) identified 2 different intragenic loss-of-function mutations in FMR1: a single de novo nucleotide deletion in a young patient and an inherited 2-bp change in an adult male (see 309550.0003), each with classic features of fragile X syndrome. The young patient was seen at the age of 3 years because of developmental delay. On physical examination, he 'presented as a remote child with poor eye contact and increased activity.' Features indicative of fragile X syndrome included wide prominent ears, long face with 'coarse' features, epicanthal folds, and hypermobile joints. He had reduced balance, poor motor skills, and infantile speech. DNA analysis indicated 29 CGG repeats. Genitalia were normal. Mutation detection electrophoresis (MDE) revealed 1 heteroduplex band in the exon 5 amplification product. Sequence analysis of the subcloned exon 5 fragment revealed the absence of an adenosine residue at position 373 (in codon thr125) of the FMR1 mRNA, resulting in a frameshift and predicting a premature translation stop 66 amino acids 3-prime to the deletion and 159 residues from the initiating codon. Mutation was absent in the patient's mother. Although an RNA transcript was detected by reverse transcriptase PCR, repeated protein studies by Western blot could not identify a protein product of the size expected from the truncated open reading frame. These patients provided strong evidence that absence of FMRP leads directly to fragile X syndrome. Lugenbeel et al. (1995) stated that the possibility of downregulation of other nearby genes that contribute to the phenotype in these cases is remote. #### .0003 FRAGILE X MENTAL RETARDATION SYNDROME [FMR1, IVS1, G-T, -1 AND G-A, +1] Lugenbeel et al. (1995) described an adult patient who showed the classic clinical phenotype of a postpubescent fragile X male, including macroorchidism. The sequence of exon 2 demonstrated a 2-bp change in the splice acceptor site (GG to TA) at position 23714-23715 in the genomic sequence (GSDB Accession No. L69074). RT-PCR detected 2 products of reduced size from the 5-prime region of the FMR1 transcript. Sequence analysis demonstrated that the larger product resulted from splicing out exon 2, while the smaller product was created by splicing out exons 2 and 3. Loss of exon 2 resulted in a frameshift and premature termination 4 amino acids into exon 3; loss of exons 2 and 3 removed 49 amino acids of the FMR protein but did not alter the reading frame; thus a protein of reduced size would be generated. No such protein was recognized by Western blot, however. The same mutation was identified in the mother, who was described as mildly retarded. Other members of the family were either noncarriers or not available for study. See also 309550.0002; these patients provided strong evidence that absence of FMRP leads directly to fragile X syndrome. Lugenbeel et al. (1995) stated that the possibility of downregulation of other nearby genes that contribute to the phenotype in these cases is remote. #### .0004 FRAGILE X MENTAL RETARDATION SYNDROME [FMR1, (CGG)n EXPANSION] The usual cause of the fragile X syndrome is an expanded (CGG)n repeat in the 5-prime noncoding region of the FMR1 gene. #### .0005 FMR1 POLYMORPHISM [FMR1, IVS10, C-T, +14] In 3 unrelated fragile X patients, Wang et al. (1997) reported a C-to-T transition at nucleotide 14 in intron 10 of the FMR1 gene. The (CGG)n repeat of FMR1 was not expanded in these patients. To determine the effect of this mutation on the FMR1 transcripts of these patients, total RNA from peripheral blood cells was reverse transcribed and amplified by polymerase chain reaction (RT-PCR). Direct and subcloned sequencing of the RT-PCR products revealed that the transcripts from the allele with the C-to-T mutation skipped exon 10 entirely, resulting in the joining of exons 9 and 11. Deletion of exon 10 resulted in frameshift and premature termination of translation, which removed the highly conserved region that encodes the KH2 and RGG box domains of the FMR protein. The 3 patients with this mutation were found among 406 mentally retarded patients investigated at the cytogenetic and molecular levels; 27 patients with the fragile X syndrome phenotype were found to have no karyotypic abnormalities, no (CGG)n expansion of FMR1, and no deletion of the FMR1 promoter. One of the 3 patients with the intronic mutation, the only male, also had a G-to-A substitution in exon 15. Vincent and Gurling (1998) suggested that IVS10+14C-T is in fact a polymorphism and not a disorder-related mutation. Wang and Li (1998) confirmed that this was the case by studying additional controls. ### SEE ALSO Ashley et al. (1993); Bowen et al. (1978); Bundey (1996); Cantu et al. (1978); Cantu et al. (1976); Carmi et al. (1984); Choo et al. (1984); Cremers et al. (1987); Davies et al. (1985); Gerald (1980); Haataja et al. (1994); Hirst et al. (1993); Hofker et al. (1987); Kinnell (1982); Krawczun et al. (1985); Lubs et al. (1984); Mattei et al. (1981); Mulligan et al. (1985); Park et al. (1994); Parrish et al. (1994); Purrello et al. (1985); Reiss et al. (1991); Rousseau et al. (1991); Ruvalcaba et al. (1977); Soysa et al. (1982); Steinbach (1986); Sutherland and Ashford (1979); Sutherland and Baker (1992); Turner et al. (1980); Turner et al. (1975); Van Roy et al. (1983); Zoll et al. (1985) ### REFERENCES 1. Abitbol, M.; Menini, C.; Delezoide, A.-L.; Rhyner, T.; Vekemans, M.; Mallet, J. : Nucleus basalis magnocellularis and hippocampus are the major sites of FMR-1 expression in the human fetal brain. Nature Genet. 4: 147-153, 1993. PubMed ID : 8348153 2. Abrams, M. T.; Kaufmann, W. E.; Rousseau, F.; Oostra, B. A.; Wolozin, B.; Taylor, C. V.; Lishaa, N.; Morel, M.-L.; Hoogeveen, A.; Reiss, A. L. : FMR1 gene expression in olfactory neuroblasts from two males with fragile X syndrome. Am. J. Med. Genet. 82: 25-30, 1999. PubMed ID : 9916838 3. Allingham-Hawkins, D. J.; Babul-Hirji, R.; Chitayat, D.; Holden, J. J. A.; Yang, K. T.; Lee, C.; Hudson, R.; Gorwill, H.; Nolin, S. L.; Glicksman, A.; Jenkins, E. C.; Brown, W. T.; and 27 others : Fragile X premutation is a significant risk factor for premature ovarian failure: the international collaborative POF in fragile X study--preliminary data. Am. J. Med. Genet. 83: 322-325, 1999. PubMed ID : 10208170 4. Ashley, C. T.; Sutcliffe, J. S.; Kunst, C. B.; Leiner, H. A.; Eichler, E. E.; Nelson, D. L.; Warren, S. T. : Human and murine FMR-1: alternative splicing and translational initiation downstream of the CGG-repeat. Nature Genet. 4: 244-251, 1993. PubMed ID : 8358432 5. Ashley, C. T., Jr.; Wilkinson, K. D.; Reines, D.; Warren, S. T. : FMR1 protein: conserved RNP family domains and selective RNA binding. Science 262: 563-566, 1993. PubMed ID : 7692601 6. Bachner, D.; Steinbach, P.; Wohrle, D.; Just, W.; Vogel, W.; Hameister, H.; Manca, A.; Poustka, A. : Enhanced Fmr-1 expression in testis. (Letter) Nature Genet. 4: 115-116, 1993. PubMed ID : 8348147 7. Backes, M.; Genc, B.; Schreck, J.; Doerfler, W.; Lehmkuhl, G.; von Gontard, A. : Cognitive and behavioral profile of fragile X boys: correlations to molecular data. Am. J. Med. Genet. 95: 150-156, 2000. PubMed ID : 11078566 8. Bell, J.; Haldane, J. B. S. : The linkage between the genes for colour-blindness and haemophilia in man. Proc. Roy. Soc. London 123B: 119-150, 1937. 9. Bell, M. V.; Hirst, M. C.; Nakahori, Y.; MacKinnon, R. N.; Roche, A.; Flint, T. J.; Jacobs, P. A.; Tommerup, N.; Tranebjaerg, L.; Froster-Iskenius, U.; Kerr, B.; Turner, G.; Lindenbaum, R. H.; Winter, R.; Pembrey, M.; Thibodeau, S.; Davies, K. E. : Physical mapping across the fragile X: hypermethylation and clinical expression of the fragile X syndrome. Cell 64: 861-866, 1991. PubMed ID : 1997211 10. Beresford, R. G.; Tatlidil, C.; Riddell, D. C.; Welch, J. P.; Ludman, M. D.; Neumann, P. E.; Greer, W. L. : Absence of fragile X syndrome in Nova Scotia. J. Med. Genet. 37: 77-79, 2000. PubMed ID : 10691418 11. Berry-Kravis, E.; Lewin, F.; Wuu, J.; Leehey, M.; Hagerman, R.; Hagerman, P.; Goetz, C. G. : Tremor and ataxia in fragile X premutation carriers: blinded videotape study. Ann. Neurol. 53: 616-623, 2003. PubMed ID : 12730995 12. Biancalana, V.; Beldjord, C.; Taillandier, A.; Szpiro-Tapia, S.; Cusin, V.; Gerson, F.; Philippe, C.; Mandel, J.-L.; French National Working Group on Fragile X Syndrome : Five years of molecular diagnosis of fragile X syndrome (1997-2001): a collaborative study reporting 95% of the activity in France. Am. J. Med. Genet. 129A: 218-224, 2004. 13. Blomquist, H. K.; Bohman, M.; Edvinsson, S. O.; Gillberg, C.; Gustavson, K.-H.; Holmgren, G.; Wahlstrom, J. : Frequency of the fragile X syndrome in infantile autism: a Swedish multicenter study. Clin. Genet. 27: 113-117, 1985. PubMed ID : 3978844 14. Blomquist, H. K.; Gustavson, K.-H.; Holmgren, G.; Nordenson, I.; Sweins, A. : Fragile site X chromosomes and X-linked mental retardation in severely retarded boys in a northern Swedish county: a prevalence study. Clin. Genet. 21: 209-214, 1982. PubMed ID : 7201364 15. Bontekoe, C. J. M.; Bakker, C. E.; Nieuwenhuizen, I. M.; van der Linde, H.; Lans, H.; de Lange, D.; Hirst, M. C.; Oostra, B. A. : Instability of a (CGG)98 repeat in the Fmr1 promoter. Hum. Molec. Genet. 10: 1693-1699, 2001. PubMed ID : 11487573 16. Bowen, P.; Biederman, B.; Swallow, K. A. : The X-linked syndrome of macro-orchidism and mental retardation: further observations. Am. J. Med. Genet. 2: 409-414, 1978. PubMed ID : 263449 17. Brookwell, R.; Turner, G. : High resolution banding and the locus of the Xq fragile site. Hum. Genet. 63: 77, 1983. PubMed ID : 6682088 18. Brown, V.; Jin, P.; Ceman, S.; Darnell, J. C.; O'Donnell, W. T.; Tenenbaum, S. A.; Jin, X.; Feng, Y.; Wilkinson, K. D.; Keene, J. D.; Darnell, R. B.; Warren, S. T. : Microarray identification of FMRP-associated brain mRNAs and altered mRNA translational profiles in fragile X syndrome. Cell 107: 477-487, 2001. PubMed ID : 11719188 19. Brown, W. T.; Gross, A.; Chan, C.; Jenkins, E. C.; Mandel, J. L.; Oberle, I.; Arveiler, B.; Novelli, G.; Thibodeau, S.; Hagerman, R.; and 18 others : Multilocus analysis of the fragile X syndrome. Hum. Genet. 78: 201-205, 1988. PubMed ID : 3162224 20. Brown, W. T.; Gross, A. C.; Chan, C. B.; Jenkins, E. C. : Genetic linkage heterogeneity in the fragile X syndrome. Hum. Genet. 71: 11-18, 1985. PubMed ID : 2993154 21. Bundey, S. : Julia Bell, MRCS LRCP FRCP (1879-1979): Steamboat lady, statistician and geneticist. J. Med. Bio. 4: 8-13, 1996. 22. Camerino, G.; Mattei, M. G.; Mattei, J. F.; Jaye, M.; Mandel, J. L. : Close linkage of fragile X-linked mental retardation syndrome to haemophilia B and transmission through a normal male. Nature 306: 701-707, 1983. PubMed ID : 6689201 23. Cantu, J. M.; Scaglia, H. E.; Gonzalez-Diddi, M.; Hernandez-Jauregui, P.; Morato, T.; Moreno, M. E.; Giner, J.; Alcantar, A.; Herrera, D.; Perez-Palacios, G. : Inherited congenital normofunctional testicular hyperplasia and mental deficiency. Hum. Genet. 41: 331-339, 1978. PubMed ID : 649159 24. Cantu, J. M.; Scaglia, H. E.; Medina, M.; Gonzalez-Diddi, M.; Morato, T.; Moreno, M. E.; Perez-Palacios, G. : Inherited congenital normofunctional testicular hyperplasia and mental deficiency. Hum. Genet. 33: 23-33, 1976. PubMed ID : 939556 25. Carmi, R.; Meryash, D. L.; Wood, J.; Gerald, P. S. : Fragile-X syndrome ascertained by the presence of macro-orchidism in a 5-month-old infant. Pediatrics 74: 883-886, 1984. PubMed ID : 6493884 26. Cavalli-Sforza, L.; Menozzi, P.; Piazza, A. : The History and Geography of Human Genes. Princeton: Princeton Univ. Press , 1994. 27. Chakravarti, A. : Fragile X founder effect? Nature Genet. 1: 237-238, 1992. PubMed ID : 1302018 28. Chiurazzi, P.; Pomponi, M. G.; Pietrobono, R.; Bakker, C. E.; Neri, G.; Oostra, B. A. : Synergistic effect of histone hyperacetylation and DNA demethylation in the reactivation of the FMR1 gene. Hum. Molec. Genet. 8: 2317-2323, 1999. PubMed ID : 10545613 29. Chiurazzi, P.; Pomponi, M. G.; Willemsen, R.; Oostra, B. A.; Neri, G. : In vitro reactivation of the FMR1 gene involved in fragile X syndrome. Hum. Molec. Genet. 7: 109-113, 1998. PubMed ID : 9384610 30. Choo, K. H.; George, D.; Fillby, G.; Halliday, J. L.; Leversha, M.; Webb, G.; Danks, D. M. : Linkage analysis of X-linked mental retardation with and without fragile-X using factor IX gene probe. (Letter) Lancet II: 349, 1984. 31. Crawford, D. C.; Meadows, K. L.; Newman, J. L.; Taft, L. F.; Pettay, D. L.; Gold, L. B.; Hersey, S. J.; Hinkle, E. F.; Stanfield, M. L.; Holmgreen, P.; Yeargin-Allsopp, M.; Boyle, C.; Sherman, S. L. : Prevalence and phenotype consequence of FRAXA and FRAXE alleles in a large, ethnically diverse, special education-needs population. Am. J. Hum. Genet. 64: 495-507, 1999. PubMed ID : 9973286 32. Crawford, D. C.; Meadows, K. L.; Newman, J. L.; Taft, L. F.; Scott, E.; Leslie, M.; Shubek, L.; Holmgreen, P.; Yeargin-Allsopp, M.; Boyle, C.; Sherman, S. L. : Prevalence of the fragile X syndrome in African-Americans. Am. J. Med. Genet. 110: 226-233, 2002. PubMed ID : 12116230 33. Crawford, D. C.; Wilson, B.; Sherman, S. L. : Factors involved in the initial mutation of the fragile X CGG repeat as determined by sperm small pool PCR. Hum. Molec. Genet. 9: 2909-2918, 2000. PubMed ID : 11092767 34. Cremers, F. P. M.; Pfeiffer, R. A.; van de Pol, T. J. R.; Hofker, M. H.; Kruse, T. A.; Wieringa, B.; Ropers, H. H. : An interstitial duplication of the X chromosome in a male allows physical fine mapping of probes from the Xq13-q22 region. Hum. Genet. 77: 23-27, 1987. PubMed ID : 3476455 35. Daker, M. G.; Chidiac, P.; Fear, C. N.; Berry, A. L. : Fragile X in a normal male: a cautionary tale. Lancet I: 780, 1981. 36. Dar, H.; Schaap, T.; Bait-Or, H.; Borochowitz, Z.; Gelman-Kohan, Z.; Chemke, T.; Chaki, R.; Cohen, H.; Falik-Borenstein, Z.; Chemke, J. : Ethnic distribution of the fragile X syndrome in Israel: evidence of founder chromosomes(?). Israel J. Med. Sci. 31: 323-325, 1995. PubMed ID : 7759228 37. Darnell, J. C.; Jensen, K. B.; Jin, P.; Brown, V.; Warren, S. T.; Darnell, R. B. : Fragile X mental retardation protein targets G quartet mRNAs important for neuronal function. Cell 107: 489-499, 2001. PubMed ID : 11719189 38. Davids, J. R.; Hagerman, R. J.; Eilert, R. E. : Orthopaedic aspects of fragile-X syndrome. J. Bone Joint Surg. 72A: 889-896, 1990. 39. Davies, K. E.; Mattei, M. G.; Mattei, J. F.; Veenema, H.; McGlade, S.; Harper, K.; Tommerup, N.; Nielsen, K. B.; Mikkelsen, M.; Beighton, P.; Drayna, D.; White, R.; Pembrey, M. E. : Linkage studies of X-linked mental retardation: high frequency of recombination in the telomeric region of the human X chromosome (fragile site/linkage/recombination/X chromosome). Hum. Genet. 70: 249-255, 1985. PubMed ID : 2991115 40. De Boulle, K.; Verkerk, A. J. M. H.; Reyniers, E.; Vits, L.; Hendrickx, J.; Van Roy, B.; Van Den Bos, F.; de Graaff, E.; Oostra, B. A.; Willems, P. J. : A point mutation in the FMR-1 gene associated with fragile X mental retardation. Nature Genet. 3: 31-35, 1993. PubMed ID : 8490650 41. de Vries, B. B. A.; Fryns, J.-P.; Butler, M. G.; Canziani, F.; Wesby-van Swaay, E.; van Hemel, J. O.; Oostra, B. A.; Halley, D. J. J.; Niermeijer, M. F. : Clinical and molecular studies in fragile X patients with a Prader-Willi-like phenotype. J. Med. Genet. 30: 761-766, 1993. PubMed ID : 8411072 42. de Vries, B. B. A.; Robinson, H.; Stolte-Dijkstra, I.; Tjon Pian Gi, C. V.; Dijkstra, P. F.; van Doorn, J.; Halley, D. J. J.; Oostra, B. A.; Turner, G.; Niermeijer, M. F. : General overgrowth in the fragile X syndrome: variability in the phenotypic expression of the FMR1 gene mutation. J. Med. Genet. 32: 764-769, 1995. PubMed ID : 8558551 43. Devys, D.; Biancalana, V.; Rousseau, F.; Boue, J.; Mandel, J. L.; Oberle, I. : Analysis of full fragile X mutations in fetal tissues and monozygotic twins indicate that abnormal methylation and somatic heterogeneity are established early in development. Am. J. Med. Genet. 43: 208-216, 1992. PubMed ID : 1605193 44. Devys, D.; Lutz, Y.; Rouyer, N.; Bellocq, J.-P.; Mandel, J.-L. : The FMR-1 protein is cytoplasmic, most abundant in neurons and appears normal in carriers of a fragile X premutation. Nature Genet. 4: 335-340, 1993. PubMed ID : 8401578 45. Dombrowski, C.; Levesque, S.; Morel, M. L.; Rouillard, P.; Morgan, K.; Rousseau, F. : Premutation and intermediate-size FMR1 alleles in 10 572 males from the general population: loss of an AGG interruption is a late event in the generation of fragile X syndrome alleles. Hum. Molec. Genet. 11: 371-378, 2002. PubMed ID : 11854169 46. Dreesen, J. C. F. M.; Geraedts, J. P. M.; Dumoulin, J. C. M.; Evers, J. L. H.; Pieters, M. H. E. C. : RS46 (DXS548) genotyping of reproductive cells: approaching preimplantation testing of the fragile-X syndrome. Hum. Genet. 96: 323-329, 1995. PubMed ID : 7649550 47. Dutch-Belgian Fragile X Consortium : Fmr1 knockout mice: a model to study fragile X mental retardation. Cell 78: 23-33, 1994. PubMed ID : 8033209 48. Eberhart, D. E.; Malter, H. E.; Feng, Y.; Warren, S. T. : The fragile X mental retardation protein is a ribonucleoprotein containing both nuclear localization and nuclear export signals. Hum. Molec. Genet. 5: 1083-1091, 1996. PubMed ID : 8842725 49. Edamura, K. N.; Leonard, M. R.; Pearson, C. E. : Role of replication and CpG methylation in fragile X syndrome CGG deletions in primate cells. Am. J. Hum. Genet. 76: 302-311, 2005. PubMed ID : 15625623 50. Eichler, E. E.; Nelson, D. L. : Genetic variation and evolutionary stability of the FMR1 CGG repeat in six closed human populations. Am. J. Med. Genet. 64: 220-225, 1996. PubMed ID : 8826480 51. Eichler, E. E.; Richards, S.; Gibbs, R. A.; Nelson, D. L. : Fine structure of the human FMR1 gene. Hum. Molec. Genet. 2: 1147-1153, 1993. PubMed ID : 8401496 52. Escalante, J. A.; Grunspun, H.; Frota-Pessoa, O. : Severe sex-linked mental retardation. J. Genet. Hum. 19: 137-140, 1971. 53. Faust, C. J.; Verkerk, A. J. M. H.; Wilson, P. J.; Morris, C. P.; Hopwood, J. J.; Oostra, B. A.; Herman, G. E. : Genetic mapping on the mouse X chromosome of human cDNA clones for the fragile X and Hunter syndromes. Genomics 12: 814-817, 1992. PubMed ID : 1572654 54. Feng, Y.; Absher, D.; Eberhart, D. E.; Brown, V.; Malter, H. E.; Warren, S. T. : FMRP associates with polyribosomes as an mRNP, and the I304N mutation of severe fragile X syndrome abolishes this association. Molec. Cell 1: 109-118, 1997. PubMed ID : 9659908 55. Filippi, G.; Arslanian, A.; Dagna-Bricarelli, F.; Pierluigi, M.; Grasso, M.; Rinaldi, A.; Rocchi, M.; Siniscalco, M. : Premutation for the Martin-Bell syndrome analyzed in a large pedigree segregating also for G6PD-deficiency. I. A working hypothesis on the nature of the FRAX-mutations. Am. J. Med. Genet. 40: 387-394, 1991. PubMed ID : 1746598 56. Filippi, G.; Rinaldi, A.; Archidiacono, N.; Rocchi, M.; Balazs, I.; Siniscalco, M. : Linkage between G6PD and fragile-X syndrome. Am. J. Med. Genet. 15: 113-119, 1983. PubMed ID : 6602550 57. Follette, P. J.; Laird, C. D. : Estimating the stability of the proposed imprinted state of the fragile-X mutation when transmitted by females. Hum. Genet. 88: 335-343, 1992. PubMed ID : 1346387 58. Froster-Iskenius, U.; Schulze, A.; Schwinger, E. : Transmission of the marker X syndrome trait by unaffected males: conclusions from studies of large families. Hum. Genet. 67: 419-427, 1984. PubMed ID : 6593289 59. Fryns, J. P. : The fragile X syndrome: a study of 83 families. Clin. Genet. 26: 497-528, 1984. PubMed ID : 6499265 60. Fryns, J. P. : Personal Communication. Leuven, Belgium, 5/28/1993. 61. Fryns, J. P.; Van Den Berghe, H. : Transmission of fragile(X)(q27) from normal male(s). Hum. Genet. 61: 262-263, 1982. PubMed ID : 7173872 62. Fu, Y.-H.; Kuhl, D. P. A.; Pizzuti, A.; Pieretti, M.; Sutcliffe, J. S.; Richards, S.; Verkerk, A. J. M. H.; Holden, J. J. A.; Fenwick, R. G., Jr.; Warren, S. T.; Oostra, B. A.; Nelson, D. L.; Caskey, C. T. : Variation of the CGG repeat at the fragile X site results in genetic instability: resolution of the Sherman paradox. Cell 67: 1047-1058, 1991. PubMed ID : 1760838 63. Fulchignoni-Lataud, M. C.; Olchwang, S.; Serre, J. L. : The fragile X CGG repeat shows a marked level of instability in hereditary non-polyposis colorectal cancer patients. Europ. J. Hum. Genet. 5: 89-93, 1997. PubMed ID : 9195158 64. Gedeon, A. K.; Baker, E.; Robinson, H.; Partington, M. W.; Gross, B.; Manca, A.; Korn, B.; Poustka, A.; Yu, S.; Sutherland, G. R.; Mulley, J. C. : Fragile X syndrome without CCG amplification has an FMR1 deletion. Nature Genet. 1: 341-344, 1992. PubMed ID : 1302032 65. Gerald, P. S. : Personal Communication. Boston, Mass., 8/12/1983. 66. Gerald, P. S. : X-linked mental retardation and an X-chromosome marker. (Editorial) New Eng. J. Med. 303: 696-697, 1980. PubMed ID : 6931287 67. Giannelli, F.; Morris, A. H.; Garrett, C.; Daker, M.; Thurston, C.; Smith, C. A. B. : Genetic heterogeneity of X-linked mental retardation with fragile X: association of tight linkage to factor IX and incomplete penetrance in males. Ann. Hum. Genet. 51: 107-124, 1987. PubMed ID : 3674751 68. Giraud, F.; Ayme, S.; Mattei, J. F.; Mattei, M. G. : Constitutional chromosomal breakage. Hum. Genet. 34: 125-136, 1976. PubMed ID : 1033912 69. Glover, T. W. : FUdR induction of the X-chromosome fragile site: evidence for the mechanism of folic acid and thymidine inhibition. Am. J. Hum. Genet. 33: 234-242, 1981. PubMed ID : 6452060 70. Goldman, A.; Krause, A.; Jenkins, T. : Fragile X syndrome occurs in the South African black population. (Editorial) S. Afr. Med. J. 87: 418-420, 1997. PubMed ID : 9254780 71. Goodman, R. M.; Strauss, S.; Friedman, E.; Chaki, R. : Ovarian size in the fragile X mental retardation syndrome. Am. J. Med. Genet. 26: 17-18, 1987. PubMed ID : 3812558 72. Gould, E. L.; Loesch, D. Z.; Martin, M. J.; Hagerman, R. J.; Armstrong, S. M.; Huggins, R. M. : Melatonin profiles and sleep characteristics in boys with fragile X syndrome: a preliminary study. Am. J. Med. Genet. 95: 307-315, 2000. PubMed ID : 11186882 73. Greenberg, J. H.; Turner, C. G., II; Zegura, S. L. : The settlement of the Americas: a comparison of the linguistic, dental, and genetic evidence. Curr. Anthrop. 27: 477-497, 1986. 74. Greenough, W. T.; Klintsova, A. Y.; Irwin, S. A.; Galvez, R.; Bates, K. E.; Weiler, I. J. : Synaptic regulation of protein synthesis and the fragile X protein. Proc. Nat. Acad. Sci. 98: 7101-7106, 2001. PubMed ID : 11416194 75. Griffiths, M. J.; Strachan, M. C. : A single lymphocyte culture for fragile X induction and prometaphase chromosome analysis. J. Med. Genet. 28: 837-839, 1991. PubMed ID : 1757959 76. Haataja, R.; Vaisanen, M.-L.; Li, M.; Ryynanen, M.; Leisti, J. : The fragile X syndrome in Finland: demonstration of a founder effect by analysis of microsatellite haplotypes. Hum. Genet. 94: 479-483, 1994. PubMed ID : 7959680 77. Hagerman, P. J.; Hagerman, R. J. : The fragile-X premutation: a maturing perspective. Am. J. Hum. Genet. 74: 805-816, 2004. Note: Erratum: Am. J. Hum. Genet. 75: 352 only, 2004. PubMed ID : 15052536 78. Hagerman, R. J.; Leavitt, B. R.; Farzin, F.; Jacquemont, S.; Greco, C. M.; Brunberg, J. A.; Tassone, F.; Hessl, D.; Harris, S. W.; Zhang, L.; Jardini, T.; Gane, L. W.; Ferranti, J.; Ruiz, L.; Leehey, M. A.; Grigsby, J.; Hagerman, P. J. : Fragile-X-associated tremor/ataxia syndrome (FXTAS) in females with the FMR1 premutation. Am. J. Hum. Genet. 74: 1051-1056, 2004. PubMed ID : 15065016 79. Hagerman, R. J.; Leehey, M.; Heinrichs, W.; Tassone, F.; Wilson, R.; Hills, J.; Grigsby, J.; Gage, B.; Hagerman, P. J. : Intention tremor, parkinsonism, and generalized brain atrophy in male carriers of fragile X. Neurology 57: 127-130, 2001. PubMed ID : 11445641 80. Hagerman, R. J.; Synhorst, D. P. : Mitral valve prolapse and aortic dilatation in the fragile X syndrome. Am. J. Med. Genet. 17: 123-131, 1984. PubMed ID : 6711591 81. Hagerman, R. J.; Van Housen, K.; Smith, A. C. M.; McGavran, L. : Consideration of connective tissue dysfunction in the fragile X syndrome. Am. J. Med. Genet. 17: 111-121, 1984. PubMed ID : 6711590 82. Hanzlik, A. J.; Osemlak-Hanzlik, M. M.; Hauser, M. A.; Kurnit, D. M. : A recombination-based assay demonstrates that the fragile X sequence is transcribed widely during development. Nature Genet. 3: 44-48, 1993. PubMed ID : 8490653 83. Harvey, J.; Judge, C.; Wiener, S. : Familial X-linked mental retardation with an X chromosome abnormality. J. Med. Genet. 14: 46-50, 1977. PubMed ID : 839500 84. Hecht, F.; Cannizzaro, L. A.; Hecht, B. K. : Gene symbols for fragile sites: a proposal. (Letter) Hum. Genet. 82: 394, 1989. PubMed ID : 2737673 85. Hecht, F.; Glover, T. W. : Antibiotics containing trimethoprim and the fragile X chromosome. (Letter) New Eng. J. Med. 308: 285-286, 1983. PubMed ID : 6848950 86. Hecht, F.; Jacky, P. B.; Sutherland, G. R. : The fragile X chromosome: current methods. Am. J. Med. Genet. 11: 489-495, 1982. PubMed ID : 6211983 87. Hinds, H. L.; Ashley, C. T.; Sutcliffe, J. S.; Nelson, D. L.; Warren, S. T.; Housman, D. E.; Schalling, M. : Tissue specific expression of FMR-1 provides evidence for a functional role in fragile X syndrome. Nature Genet. 3: 36-43, 1993. PubMed ID : 8490651 88. Hirst, M.; Grewal, P.; Flannery, A.; Slatter, R.; Maher, E.; Barton, D.; Fryns, J.-P.; Davies, K. : Two new cases of FMR1 deletion associated with mental impairment. Am. J. Hum. Genet. 56: 67-74, 1995. PubMed ID : 7825604 89. Hirst, M. C.; Barnicoat, A.; Flynn, G.; Wang, Q.; Daker, M.; Buckle, V. J.; Davies, K. E.; Bobrow, M. : The identification of a third fragile site, FRAXF, in Xq27-q28 distal to both FRAXA and FRAXE. Hum. Molec. Genet. 2: 197-200, 1993. PubMed ID : 8499907 90. Hirst, M. C.; Knight, S. J. L.; Christodoulou, Z.; Grewal, P. K.; Fryns, J. P.; Davies, K. E. : Origins of the fragile X syndrome mutation. J. Med. Genet. 30: 647-650, 1993. PubMed ID : 8411050 91. Hofker, M. H.; Bergen, A. A. B.; Skraastad, M. I.; Carpenter, N. J.; Veenema, H.; Connor, J. M.; Bakker, E.; van Ommen, G. J. B.; Pearson, P. L. : Efficient isolation of X chromosome-specific single copy probes from a cosmid library of a human X/hamster hybrid-cell line: mapping of new probes close to the locus for X-linked mental retardation. Am. J. Hum. Genet. 40: 312-328, 1987. PubMed ID : 2883888 92. Howard-Peebles, P. N.; Stoddard, G. R. : Familial X-linked mental retardation with a marker X chromosome and its relationship to macroorchidism. Clin. Genet. 17: 125-128, 1980. PubMed ID : 6928810 93. Hundscheid, R. D. L.; Sistermans, E. A.; Thomas, C. M. G.; Braat, D. D. M.; Straatman, H.; Kiemeney, L. A. L. M.; Oostra, B. A.; Smits, A. P. T. : Imprinting effect in premature ovarian failure confined to paternally inherited fragile X premutations. Am. J. Hum. Genet. 66: 413-418, 2000. PubMed ID : 10677300 94. Hundscheid, R. D. L.; Smits, A. P. T.; Thomas, C. M. G.; Kiemeney, L. A. L. M.; Braat, D. D. M. : Female carriers of fragile X premutations have no increased risk for additional diseases other than premature ovarian failure. Am. J. Med. Genet. 117A: 6-9, 2003. 95. Hundscheid, R. D. L.; Thomas, C. M. G.; Braat, D. D. M.; Oostra, B. A.; Smits, A. P. T. : Reply to the letters from Murray et al. and Vianna-Morgante and Costa. (Letter) Am. J. Hum. Genet. 67: 256-258, 2000. PubMed ID : 10848497 96. Irwin, S. A.; Idupulapati, M.; Gilberg, M. E.; Harris, J. B.; Chakravarti, A. B.; Rogers, E. J.; Crisostomo, R. A.; Larsen, B. P.; Mehta, A.; Alcantara, C. J.; Patel, B.; Swain, R. A.; Weiler, I. J.; Oostra, B. A.; Greenough, W. T. : Dendritic spine and dendritic field characteristics of layer V pyramidal neurons in the visual cortex of fragile-X knockout mice. Am. J. Med. Genet. 111: 140-146, 2002. PubMed ID : 12210340 97. ISCN : An International System for Human Cytogenetic Nomenclature (1978). Cytogenet. Cell Genet. 21: 309-404, 1978. PubMed ID : 747930 98. Ishizuka, A.; Siomi, M. C.; Siomi, H. : A Drosophila fragile X protein interacts with components of RNAi and ribosomal proteins. Genes Dev. 16: 2497-2508, 2002. PubMed ID : 12368261 99. Jacky, P. B.; Dill, F. J. : Expression in fibroblast culture of the satellited-X chromosome associated with familial sex-linked mental retardation. Hum. Genet. 53: 267-269, 1980. PubMed ID : 6928413 100. Jacobs, P. A. : The fragile X syndrome. (Editorial) J. Med. Genet. 28: 809-810, 1991. PubMed ID : 1757953 101. Jacobs, P. A. : Personal Communication. Honolulu, Hawaii, 1982. 102. Jacobs, P. A.; Glover, T. W.; Mayer, M.; Fox, P.; Gerrard, J. W.; Dunn, H. G.; Herbst, D. S. : X-linked mental retardation: a study of 7 families. Am. J. Med. Genet. 7: 471-479, 1980. PubMed ID : 7211957 103. Jacobs, P. A.; Hunt, P. A.; Mayer, M.; Wang, J.-C.; Boss, G. R.; Erbe, R. W. : Expression of the marker(X)(q28) in lymphoblastoid cell lines. Am. J. Hum. Genet. 34: 552-557, 1982. PubMed ID : 6213152 104. Jacquemont, S.; Hagerman, R. J.; Leehey, M.; Grigsby, J.; Zhang, L.; Brunberg, J. A.; Greco, C.; Des Portes, V.; Jardini, T.; Levine, R.; Berry-Kravis, E.; Brown, W. T.; Schaeffer, S.; Kissel, J.; Tassone, F.; Hagerman, P. J. : Fragile X premutation tremor/ataxia syndrome: molecular, clinical, and neuroimaging correlates. Am. J. Hum. Genet. 72: 869-878, 2003. PubMed ID : 12638084 105. Jakala, P.; Hanninen, T.; Ryynanen, M.; Laakso, M.; Partanen, K.; Mannermaa, A.; Soininen, H. : Fragile-X: neuropsychological test performance, CGG triplet repeat lengths, and hippocampal volumes. J. Clin. Invest. 100: 331-338, 1997. PubMed ID : 9218509 106. Jenkins, E. C.; Brown, W. T.; Brooks, J.; Duncan, C. J.; Rudelli, R. D.; Wisniewski, H. M. : Experience with prenatal fragile X detection. Am. J. Med. Genet. 17: 215-239, 1984. PubMed ID : 6711597 107. Jenkins, E. C.; Brown, W. T.; Duncan, C. J.; Brooks, J. : Demonstration of the fragile X chromosome in amniotic fluid cells. (Abstract) Clin. Res. 30: 292A, 1982. 108. Jin, P.; Warren, S. T. : Understanding the molecular basis of fragile X syndrome. Hum. Molec. Genet. 9: 901-908, 2000. PubMed ID : 10767313 109. Jin, P.; Zarnescu, D. C.; Ceman, S.; Nakamoto, M.; Mowrey, J.; Jongens, T. A.; Nelson, D. L.; Moses, K.; Warren, S. T. : Biochemical and genetic interaction between the fragile X mental retardation protein and the microRNA pathway. Nature Neurosci. 7: 113-117, 2004. PubMed ID : 14703574 110. Johnson, V. P.; Carpenter, N. J.; Skorey, P. A. : Martin-Bell syndrome segregating in a large kindred with normal transmitting males: clinical, cytogenetic, and linkage study. Am. J. Med. Genet. 38: 275-282, 1991. PubMed ID : 1673299 111. Kaiser-McCaw, B.; Hecht, F.; Cadien, J. D.; Moore, B. C. : Fragile X-linked mental retardation. Am. J. Hum. Genet. 7: 503-505, 1980. 112. Kenneson, A.; Zhang, F.; Hagedorn, C.. H.; Warren, S. T. : Reduced FMRP and increased FMR1 transcription is proportionally associated with CGG repeat number in intermediate-length and premutation carriers. Hum. Molec. Genet. 10: 1449-1454, 2001. PubMed ID : 11448936 113. Khalifa, M. M.; Reiss, A. L.; Migeon, B. R. : Methylation status of genes flanking the fragile site in males with the fragile-X syndrome: a test of the imprinting hypothesis. Am. J. Hum. Genet. 46: 744-753, 1990. PubMed ID : 2316521 114. Khandjian, E. W.; Corbin, F.; Woerly, S.; Rousseau, F. : The fragile X mental retardation protein is associated with ribosomes. Nature Genet. 12: 91-93, 1996. PubMed ID : 8528261 115. Kinnell, H. G. : Fragile-X disorder associated with antisocial personality. (Letter) Lancet II: 1104, 1982. 116. Kirchgessner, C. U.; Warren, S. T.; Willard, H. F. : X inactivation if the FMR1 fragile X mental retardation gene. J. Med. Genet. 32: 925-929, 1995. PubMed ID : 8825916 117. Kirkilionis, A. J.; Chudley, A. E.; Greenberg, C. R.; Yan, D. L.; McGillivray, B.; Hamerton, J. L. : Transmission of the fra(X) haplotype from three nonpenetrant brothers to their affected grandsons. Am. J. Med. Genet. 43: 588-591, 1992. PubMed ID : 1605253 118. Klauck, S. M.; Munstermann, E.; Bieber-Martig, B.; Ruhl, D.; Lisch, S.; Schmotzer, G.; Poustka, A.; Poustka, F. : Molecular genetic analysis of the FMR-1 gene in a large collection of autistic patients. Hum. Genet. 100: 224-229, 1997. PubMed ID : 9254854 119. Knight, S. J. L.; Flannery, A. V.; Hirst, M. C.; Campbell, L.; Christodoulou, Z.; Phelps, S. R.; Pointon, J.; Middleton-Price, H. R.; Barnicoat, A.; Pembrey, M. E.; Holland, J.; Oostra, B. A.; Bobrow, M.; Davies, K. E. : Trinucleotide repeat amplification and hypermethylation of a CpG island in FRAXE mental retardation. Cell 74: 127-134, 1993. PubMed ID : 8334699 120. Kooy, R. F.; Reyniers, E.; Verhoye, M.; Sijbers, J.; Bakker, C. E.; Oostra, B. A.; Willems, P. J.; Van Der Linden, A. : Neuroanatomy of the fragile X knockout mouse brain studied using in vivo high resolution magnetic resonance imaging. Europ. J. Hum. Genet. 7: 526-532, 1999. PubMed ID : 10439957 121. Krawczun, M. S.; Jenkins, E. C.; Brown, W. T. : Analysis of the fragile-X chromosome: localization and detection of the fragile site in high resolution preparations. Hum. Genet. 69: 209-211, 1985. PubMed ID : 4038969 122. Kremer, E. J.; Pritchard, M.; Lynch, M.; Yu, S.; Holman, K.; Baker, E.; Warren, S. T.; Schlessinger, D.; Sutherland, G. R.; Richards, R. I. : Mapping of DNA instability at the fragile X to a trinucleotide repeat sequence p(CCG)n. Science 252: 1711-1714, 1991. PubMed ID : 1675488 123. Kruyer, H.; Mila, M.; Glover, G.; Carbonell, P.; Ballesta, F.; Estivill, X. : Fragile X syndrome and the (CGG)n mutation: two families with discordant MZ twins. Am. J. Hum. Genet. 54: 437-442, 1994. PubMed ID : 8116613 124. Kunst, C. B.; Leeflang, E. P.; Iber, J. C.; Arnheim, N.; Warren, S. T. : The effect of FMR1 CGG repeat interruptions on mutation frequency as measured by sperm typing. J. Med. Genet. 34: 627-631, 1997. PubMed ID : 9279752 125. Kunst, C. B.; Zerylnick, C.; Karickhoff, L.; Eichler, E.; Bullard, J.; Chalifoux, M.; Holden, J. J. A.; Torroni, A.; Nelson, D. L.; Warren, S. T. : FMR1 in global populations. Am. J. Hum. Genet. 58: 513-522, 1996. PubMed ID : 8644711 126. Lachiewicz, A. M.; Dawson, D. V.; Spiridigliozzi, G. A. : Physical characteristics of young boys with fragile X syndrome: reasons for difficulties in making a diagnosis in young males. Am. J. Med. Genet. 92: 229-236, 2000. PubMed ID : 10842286 127. Laggerbauer, B.; Ostareck, D.; Keidel, E.-M.; Ostareck-Lederer, A.; Fischer, U. : Evidence that fragile X mental retardation protein is a negative regulator of translation. Hum. Molec. Genet. 10: 329-338, 2001. PubMed ID : 11157796 128. Laird, C. D. : Proposed mechanism of inheritance and expression of the human fragile X syndrome of mental retardation. Genetics 117: 587-599, 1987. PubMed ID : 3692144 129. Laird, C. D. : Possible erasure of the imprint on a fragile X chromosome when transmitted by a male. Am. J. Med. Genet. 38: 391-395, 1991. PubMed ID : 2018078 130. Laird, C. D.; Jaffe, E.; Karpen, G.; Lamb, M.; Nelson, R. : Fragile sites in human chromosomes as regions of late-replicating DNA. Trends Genet. 3: 274-281, 1987. 131. Laird, C. D.; Lamb, M. M.; Thorne, J. L. : Two progenitor cells for human oogonia inferred from pedigree data and the X-inactivation imprinting model of the fragile-X syndrome. Am. J. Hum. Genet. 46: 696-719, 1990. PubMed ID : 1969225 132. Langenbeck, U.; Schmidtke, J.; Bartels, I.; Hansmann, I.; Knuppel, H. : Mean corpuscular hemoglobin is increased in Martin-Bell syndrome. Hum. Genet. 66: 365-366, 1984. PubMed ID : 6724586 133. Larsen, L. A.; Armstrong, J. S. M.; Gronskov, K.; Hjalgrim, H.; Brondum-Nielsen, K.; Hasholt, L.; Norgaard-Pedersen, B.; Vuust, J. : Analysis of FMR1 (CGG)n alleles and FRAXA microsatellite haplotypes in the population of Greenland: implications for the population of the New World from Asia. Europ. J. Hum. Genet. 7: 771-777, 1999. PubMed ID : 10573009 134. Larsen, L. A.; Vuust, J.; Nystad, M.; Evseeva, I.; Van Ghelue, M.; Tranebjaerg, L. : Analysis of FMR1 (CGG)n alleles and DXS548-FRAXAC1 haplotypes in three European circumpolar populations: traces of genetic relationship with Asia. Europ. J. Hum. Genet. 9: 724-727, 2001. PubMed ID : 11571563 135. Laval, S. H.; Blair, H. J.; Hirst, M. C.; Davies, K. E.; Boyd, Y. : Mapping of FMR1, the gene implicated in fragile X-linked mental retardation, on the mouse X chromosome. Genomics 12: 818-821, 1992. PubMed ID : 1572655 136. Leehey, M. A.; Munhoz, R. P.; Lang, A. E.; Brunberg, J. A.; Grigsby, J.; Greco, C.; Jacquemont, S.; Tassone, F.; Lozano, A. M.; Hagerman, P. J.; Hagerman, R. J. : The fragile X premutation presenting as essential tremor. Arch. Neurol. 60: 117-121, 2003. PubMed ID : 12533098 137. Lejeune, J.; Legrand, N.; Lafourcade, J.; Rethore, M.-O.; Raoul, O.; Maunoury, C. : Fragilite du chromosome X et effets de la trimethoprime. Ann. Genet. 25: 149-151, 1982. PubMed ID : 6982662 138. Lewis, H. A.; Musunuru, K.; Jensen, K. B.; Edo, C.; Chen, H.; Darnell, R. B.; Burley, S. K. : Sequence-specific RNA binding by a Nova KH domain: implications for paraneoplastic disease and the fragile X syndrome. Cell 100: 323-332, 2000. PubMed ID : 10676814 139. Li, Z.; Zhang, Y.; Ku, L.; Wilkinson, K. D.; Warren, S. T.; Feng, Y. : The fragile X mental retardation protein inhibits translation via interacting with mRNA. Nucleic Acids Res. 29: 2276-2283, 2001. PubMed ID : 11376146 140. Limprasert, P.; Jaruratanasirikul, S.; Vasiknanonte, P. : Unilateral macroorchidism in fragile X syndrome. (Letter) Am. J. Med. Genet. 95: 516-517, 2000. PubMed ID : 11146477 141. Linden, M. G.; Tassone, F.; Gane, L. W.; Hills, J. L.; Hagerman, R. J.; Taylor, A. K. : Compound heterozygous female with fragile X syndrome. Am. J. Med. Genet. 83: 318-321, 1999. PubMed ID : 10208169 142. Loesch, D. Z.; Hay, D. A. : Clinical features and reproductive patterns in fragile X female heterozygotes. J. Med. Genet. 25: 407-414, 1988. PubMed ID : 3398009 143. Lubs, H.; Travers, H.; Lujan, E.; Carroll, A. : A large kindred with X-linked mental retardation, marker X and macroorchidism. Am. J. Med. Genet. 17: 145-157, 1984. PubMed ID : 6585140 144. Lubs, H. A.; Watson, M.; Breg, R.; Lujan, E. : Restudy of the original marker X family. Am. J. Med. Genet. 17: 133-144, 1984. PubMed ID : 6711592 145. Lubs, H. A., Jr. : A marker X chromosome. Am. J. Hum. Genet. 21: 231-244, 1969. PubMed ID : 5794013 146. Lugenbeel, K. A.; Peier, A. M.; Carson, N. L.; Chudley, A. E.; Nelson, D. L. : Intragenic loss of function mutations demonstrate the primary role of FMR1 in fragile X syndrome. Nature Genet. 10: 483-485, 1995. PubMed ID : 7670500 147. Machado-Ferreira, M. C.; Costa-Lima, M. A.; Boy, R. T.; Esteves, G. S.; Pimentel, M. M. G. : Premature ovarian failure and FRAXA premutation: positive correlation in a Brazilian survey. Am. J. Med. Genet. 126A: 237-240, 2004. 148. Macpherson, J.; Waghorn, A.; Hammans, S.; Jacobs, P. : Observation of an excess of fragile-X premutations in a population of males referred with spinocerebellar ataxia. (Letter) Hum. Genet. 112: 619-620, 2003. PubMed ID : 12612802 149. Malter, H. E.; Iber, J. C.; Willemsen, R.; de Graaff, E.; Tarleton, J. C.; Leisti, J.; Warren, S. T.; Oostra, B. A. : Characterization of the full fragile X syndrome mutation in fetal gametes. Nature Genet. 15: 165-169, 1997. PubMed ID : 9020841 150. Mandel, J.-L.; Hagerman, R.; Froster, U.; Brown, W. T.; Jenkins, E. C.; Jacobs, P.; Turner, G.; Lubs, H.; Neri, G. : Fifth International Workshop on the Fragile X and X-Linked Mental Retardation. Am. J. Med. Genet. 43: 5-27, 1992. PubMed ID : 1605233 151. Martin, J. P.; Bell, J. : A pedigree of mental defect showing sex-linkage. J. Neurol. Psychiat. 6: 154-157, 1943. 152. Martin, R. H.; Lin, C. C.; Mathies, B. J.; Lowry, R. B. : X-linked mental retardation with macro-orchidism and marker-X chromosomes. Am. J. Med. Genet. 7: 433-441, 1980. PubMed ID : 6938132 153. Mattei, J. F.; Mattei, M. G.; Aumeras, C.; Auger, M.; Giraud, F. : X-linked mental retardation with the fragile X: a study of 15 families. Hum. Genet. 59: 281-289, 1981. PubMed ID : 7333582 154. Mazroui, R.; Huot, M.-E.; Tremblay, S.; Filion, C.; Labelle, Y.; Khandjian, E. W. : Trapping of messenger RNA by fragile X mental retardation protein into cytoplasmic granules induces translation repression. Hum. Molec. Genet. 11: 3007-3017, 2002. PubMed ID : 12417522 155. McCabe, E. R. B.; de la Cruz, F.; Clapp, K. : Workshop on Fragile X: future research directions. Am. J. Med. Genet. 85: 317-322, 1999. PubMed ID : 10398250 156. McConkie-Rosell, A.; Lachiewicz, A. M.; Spiridigliozzi, G. A.; Tarleton, J.; Schoenwald, S.; Phelan, M. C.; Goonewardena, P.; Ding, X.; Brown, W. T. : Evidence that methylation of the FMR-1 locus is responsible for variable phenotypic expression of the fragile X syndrome. Am. J. Hum. Genet. 53: 800-809, 1993. PubMed ID : 8213810 157. Meijer, H.; de Graaff, E.; Merckx, D. M. L.; Jongbloed, R. J. E.; de Die-Smulders, C. E. M.; Engelen, J. J. M.; Fryns, J.-P.; Curfs, P. M. G.; Oostra, B. A. : A deletion of 1.6 kb proximal to the CGG repeat of the FMR1 gene causes the clinical phenotype of the fragile X syndrome. Hum. Molec. Genet. 3: 615-620, 1994. PubMed ID : 8069307 158. Meryash, D. L.; Cronk, C. E.; Sachs, B.; Gerald, P. S. : An anthropometric study of males with the fragile-X syndrome. Am. J. Med. Genet. 17: 159-174, 1984. PubMed ID : 6711593 159. Mila, M.; Castellvi-Bel, S.; Gine, R.; Vazquez, C.; Badenas, C.; Sanchez, A.; Estivill, X. : A female compound heterozygote (pre- and full mutation) for the CGG FMR1 expansion. Hum. Genet. 98: 419-421, 1996. PubMed ID : 8792815 160. Mila, M.; Sanchez, A.; Badenas, C.; Brun, C.; Jimenez, D.; Villa, M. P.; Castellvi-Bel, S.; Estivill, X. : Screening for FMR1 and FMR2 mutations in 222 individuals from Spanish special schools: identification of a case of FRAXE-associated mental retardation. Hum. Genet. 100: 503-507, 1997. PubMed ID : 9341861 161. Mingroni-Netto, R. C.; Angeli, C. B.; Auricchio, M. T. B. M.; Leal-Mesquita, E. R.; Ribeiro-dos-Santos, A. K. C.; Ferrari, I.; Hutz, M. H.; Salzano, F. M.; Hill, K.; Hurtado, A. M.; Vianna-Morgante, A. M. : Distribution of CGG repeats and FRAXAC1/DXS548 alleles in South American populations. Am. J. Med. Genet. 111: 243-252, 2002. PubMed ID : 12210320 162. Miyashiro, K. Y.; Beckel-Mitchener, A.; Purk, T. P.; Becker, K. G.; Barret, T.; Liu, L.; Carbonetto, S.; Weiler, I. J.; Greenough, W. T.; Eberwine, J. : RNA cargoes associating with FMRP reveal deficits in cellular functioning in Fmr1 null mice. Neuron 37: 417-431, 2003. PubMed ID : 12575950 163. Morales, J.; Hiesinger, P. R.; Schroeder, A. J.; Kume, K.; Verstreken, P.; Jackson, F. R.; Nelson, D. L.; Hassan, B. A. : Drosophila fragile X protein, DFXR, regulates neuronal morphology and function in the brain. Neuron 34: 961-972, 2002. PubMed ID : 12086643 164. Morton, J. E.; Bundey, S.; Webb, T. P.; MacDonald, F.; Rindl, P. M.; Bullock, S. : Fragile X syndrome is less common than previously estimated. J. Med. Genet. 34: 1-5, 1997. PubMed ID : 9032640 165. Morton, N. E.; Macpherson, J. N. : Population genetics of the fragile-X syndrome: multiallelic model for the FMR1 locus. Proc. Nat. Acad. Sci. 89: 4215-4217, 1992. PubMed ID : 1570349 166. Mulley, J. C.; Yu, S.; Gedeon, A. K.; Donnelly, A.; Turner, G.; Loesch, D.; Chapman, C. J.; Gardner, R. J. M.; Richards, R. I.; Sutherland, G. R. : Experience with direct molecular diagnosis of fragile X. J. Med. Genet. 29: 368-374, 1992. PubMed ID : 1619631 167. Mulligan, L. M.; Phillips, M. A.; Forster-Gibson, C. J.; Beckett, J.; Partington, M. W.; Simpson, N. E.; Holden, J. J. A.; White, B. N. : Genetic mapping of DNA segments relative to the locus for the fragile-X syndrome at Xq27.3. Am. J. Hum. Genet. 37: 463-472, 1985. PubMed ID : 2988332 168. Murray, A.; Ennis, S.; Morton, N. : No evidence for parent of origin influencing premature ovarian failure in fragile X premutation carriers. (Letter) Am. J. Hum. Genet. 67: 253-254, 2000. PubMed ID : 10848495 169. Murray, A.; Webb, J.; Grimley, S.; Conway, G.; Jacobs, P. : Studies of FRAXA and FRAXE in women with premature ovarian failure. J. Med. Genet. 35: 637-640, 1998. PubMed ID : 9719368 170. Nolin, S. L.; Lewis, F. A., III; Ye, L. L.; Houck, G. E., Jr.; Glicksman, A. E.; Limprasert, P.; Li, S. Y.; Zhong, N.; Ashley, A. E.; Feingold, E.; Sherman, S. L.; Brown, W. T. : Familial transmission of the FMR1 GCC repeat. Am. J. Hum. Genet. 59: 1252-1261, 1996. PubMed ID : 8940270 171. Nussbaum, R. L.; Ledbetter, D. H. : Fragile X syndrome: a unique mutation in man. Annu. Rev. Genet. 20: 109-145, 1986. PubMed ID : 3545058 172. Oberle, I.; Rousseau, F.; Heitz, D.; Kretz, C.; Devys, D.; Hanauer, A.; Boue, J.; Bertheas, M. F.; Mandel, J. L. : Instability of a 550-base pair DNA segment and abnormal methylation in fragile X syndrome. Science 252: 1097-1102, 1991. PubMed ID : 2031184 173. Oostra, B. A.; Chiurazzi, P. : The fragile X gene and its function. Clin. Genet. 60: 399-408, 2001. PubMed ID : 11846731 174. Opitz, J. M.; Sutherland, G. R. : International workshop on the fragile X and X-linked mental retardation. Am. J. Med. Genet. 17: 5-94, 1984. PubMed ID : 6369987 175. Opitz, J. M.; Westphal, J. M.; Daniel, A. : Discovery of a connective tissue dysplasia in the Martin-Bell syndrome. Am. J. Med. Genet. 17: 101-109, 1984. PubMed ID : 6711589 176. Oudet, C.; Mornet, E.; Serre, J. L.; Thomas, F.; Lentes-Zengerling, S.; Kretz, C.; Deluchat, C.; Tejada, I.; Boue, J.; Boue, A.; Mandel, J. L. : Linkage disequilibrium between the fragile X mutation and two closely linked CA repeats suggests that fragile X chromosomes are derived from a small number of founder chromosomes. Am. J. Hum. Genet. 52: 297-304, 1993. PubMed ID : 8094266 177. Park, V.; Howard-Peebles, P.; Sherman, S.; Taylor, A.; Wulfsberg, E. : Policy statement: American College of Medical Genetics. Fragile X syndrome: diagnostic and carrier testing. Am. J. Med. Genet. 53: 380-381, 1994. PubMed ID : 7864050 178. Parrish, J. E.; Oostra, B. A.; Verkerk, A. J. M. H.; Richards, C. S.; Reynolds, J.; Spikes, A. S.; Shaffer, L. G.; Nelson, D. L. : Isolation of a GCC repeat showing expansion in FRAXF, a fragile site distal to FRAXA and FRAXE. Nature Genet. 8: 229-235, 1994. PubMed ID : 7874164 179. Peier, A. M.; McIlwain, K. L.; Kenneson, A.; Warren, S. T.; Paylor, R.; Nelson, D. L. : (Over)correction of FMR1 deficiency with YAC transgenics: behavioral and physical features. Hum. Molec. Genet. 9: 1145-1159, 2000. PubMed ID : 10767339 180. Pellissier, M.-C.; Voelckel, M.-A.; Piquet, C.; Mattei, M.-G.; Mattei, J.-F. : Transmission of mental retardation with fragile X site by two normal transmitter brothers. Am. J. Med. Genet. 38: 367-369, 1991. PubMed ID : 1673312 181. Pembrey, M. E.; Winter, R. M.; Davies, K. E. : A premutation that generates a defect at crossing over explains the inheritance of fragile X mental retardation. Am. J. Med. Genet. 21: 709-717, 1985. PubMed ID : 4040705 182. Pieretti, M.; Zhang, F.; Fu, Y.-H.; Warren, S. T.; Oostra, B. A.; Caskey, C. T.; Nelson, D. L. : Absence of expression of the FMR-1 gene in fragile X syndrome. Cell 66: 817-822, 1991. PubMed ID : 1878973 183. Poustka, A.; Dietrich, A.; Langenstein, G.; Toniolo, D.; Warren, S. T.; Lehrach, H. : Physical map of human Xq27-qter: localizing the region of the fragile X mutation. Proc. Nat. Acad. Sci. 88: 8302-8306, 1991. PubMed ID : 1924290 184. Primerano, B.; Tassone, F.; Hagerman, R. J.; Hagerman, P.; Amaldi, F.; Bagni, C. : Reduced FMR1 mRNA translation efficiency in fragile X patients with premutations. RNA 8: 1482-1488, 2002. PubMed ID : 12515381 185. Purrello, M.; Alhadeff, B.; Esposito, D.; Szabo, P.; Rocchi, M.; Truett, M.; Masiarz, F.; Siniscalco, M. : The human genes for hemophilia A and hemophilia B flank the X chromosome fragile site at Xq27.3. EMBO J. 4: 725-729, 1985. PubMed ID : 3924593 186. Pyeritz, R. E.; Stamberg, J.; Thomas, G. H.; Bell, B. B.; Zahka, K. G.; Bernhardt, B. A. : The marker Xq28 syndrome (fragile X syndrome) in a retarded man with mitral valve prolapse. Johns Hopkins Med. J. 151: 231-237, 1982. PubMed ID : 6958915 187. Qin, M.; Kang, J.; Smith, C. B. : Increased rates of cerebral glucose metabolism in a mouse model of fragile X mental retardation. Proc. Nat. Acad. Sci. 99: 15758-15763, 2002. PubMed ID : 12427968 188. Quan, F.; Grompe, M.; Jakobs, P.; Popovich, B. W. : Spontaneous deletion in the FMR1 gene in a patient with fragile X syndrome and cherubism. Hum. Molec. Genet. 4: 1681-1684, 1995. PubMed ID : 8541863 189. Quan, F.; Zonana, J.; Gunter, K.; Peterson, K. L.; Magenis, R. E.; Popovich, B. W. : An atypical case of fragile X syndrome caused by a deletion that includes the FMR1 gene. Am. J. Hum. Genet. 56: 1042-1051, 1995. PubMed ID : 7726157 190. Ramos, F. J.; Emanuel, B. S.; Spinner, N. B. : Frequency of the common fragile site at Xq27.2 under conditions of thymidylate stress: implications for cytogenetic diagnosis of the fragile-X syndrome. Am. J. Med. Genet. 42: 835-838, 1992. PubMed ID : 1532475 191. Reiss, A. L.; Aylward, E.; Freund, L. S.; Joshi, P. K.; Bryan, R. N. : Neuroanatomy of fragile X syndrome: the posterior fossa. Ann. Neurol. 29: 26-32, 1991. PubMed ID : 1996876 192. Reiss, A. L.; Freund, L.; Tseng, J. E.; Joshi, P. K. : Neuroanatomy in fragile X females: the posterior fossa. Am. J. Hum. Genet. 49: 279-288, 1991. PubMed ID : 1867191 193. Reiss, A. L.; Lee, J.; Freund, L. : Neuroanatomy of fragile X syndrome: the temporal lobe. Neurology 44: 1317-1324, 1994. PubMed ID : 8035938 194. Reyniers, E.; Vits, L.; De Boulle, K.; Van Roy, B.; Van Velzen, D.; de Graaff, E.; Verkerk, A. J. M. H.; Jorens, H. Z. J.; Darby, J. K.; Oostra, B.; Willems, P. J. : The full mutation in the FMR-1 gene of male fragile X patients is absent in their sperm. Nature Genet. 4: 143-148, 1993. PubMed ID : 8348152 195. Richards, B. W.; Sylvester, P. E.; Brooker, C. : Fragile X-linked mental retardation: the Martin-Bell syndrome. J. Ment. Defic. Res. 25: 253-256, 1981. PubMed ID : 7328634 196. Richards, R. I.; Holman, K.; Friend, K.; Kremer, E.; Hillen, D.; Staples, A.; Brown, W. T.; Goonewardena, P.; Tarleton, J.; Schwartz, C.; Sutherland, G. R. : Evidence of founder chromosomes in fragile X syndrome. Nature Genet. 1: 257-260, 1992. PubMed ID : 1302021 197. Richards, R. I.; Holman, K.; Kozman, H.; Kremer, E.; Lynch, M.; Pritchard, M.; Yu, S.; Mulley, J.; Sutherland, G. R. : Fragile X syndrome: genetic localisation by linkage mapping of two microsatellite repeats FRAXAC1 and FRAXAC2 which immediately flank the fragile site. J. Med. Genet. 28: 818-823, 1991. PubMed ID : 1757956 198. Richards, R. I.; Holman, K.; Kozman, H.; Kremer, E.; Lynch, M.; Pritchard, M.; Yu, S.; Mulley, J.; Sutherland, G. R. : Fragile X syndrome: genetic localisation by linkage mapping of two microsatellite repeats FRAXAC1 and FRAXAC2 which immediately flank the fragile site. J. Med. Genet. 28: 818-823, 1991. PubMed ID : 1757956 199. Richards, R. I.; Sutherland, G. R. : Dynamic mutations: a new class of mutations causing human disease. Cell 70: 709-712, 1992. PubMed ID : 1516128 200. Rocchi, M.; Archidiacono, N.; Rinaldi, A.; Filippi, G.; Bartolucci, G.; Fancello, G. S.; Siniscalco, M. : Mental retardation in heterozygotes for the fragile-X mutation: evidence in favor of an X inactivation-dependent effect. Am. J. Hum. Genet. 46: 738-743, 1990. PubMed ID : 2316520 201. Rodewald, L.; Miller, D. C.; Sciorra, L.; Barabas, G.; Lee, M.-L. : Central nervous system neoplasm in a young man with Martin-Bell syndrome--fra(X)-XLMR. Am. J. Med. Genet. 26: 7-12, 1987. PubMed ID : 3812581 202. Rogers, C.; Partington, M. W.; Turner, G. M. : Tremor, ataxia and dementia in older men may indicate a carrier of the fragile X syndrome. Clin. Genet. 64: 54-56, 2003. PubMed ID : 12791039 203. Rousseau, F.; Heitz, D.; Biancalana, V.; Blumenfeld, S.; Kretz, C.; Boue, J.; Tommerup, N.; Van Der Hagen, C.; DeLozier-Blanchet, C.; Croquette, M.-F.; Gilgenkrantz, S.; Jalbert, P.; Voelckel, M.-A.; Oberle, I.; Mandel, J.-L. : Direct diagnosis by DNA analysis of the fragile X syndrome of mental retardation. New Eng. J. Med. 325: 1673-1681, 1991. PubMed ID : 1944467 204. Rousseau, F.; Heitz, D.; Mandel, J.-L. : The unstable and methylatable mutations causing the fragile X syndrome. Hum. Mutat. 1: 91-96, 1992. PubMed ID : 1301206 205. Rousseau, F.; Heitz, D.; Oberle, I.; Mandel, J.-L. : Selection in blood cells from female carriers of the fragile X syndrome: inverse correlation between age and proportion of active X chromosomes carrying the full mutation. J. Med. Genet. 28: 830-836, 1991. PubMed ID : 1757958 206. Rousseau, F.; Heitz, D.; Tarleton, J.; MacPherson, J.; Malmgren, H.; Dahl, N.; Barnicoat, A.; Mathew, C.; Mornet, E.; Tejada, I.; Maddalena, A.; Spiegel, R.; Schinzel, A.; Marcos, J. A. G.; Schorderet, D. F.; Schaap, T.; Maccioni, L.; Russo, S.; Jacobs, P. A.; Schwartz, C.; Mandel, J. L. : A multicenter study on genotype-phenotype correlations in the fragile X syndrome, using direct diagnosis with probe StB12.3: the first 2,253 cases. Am. J. Hum. Genet. 55: 225-237, 1994. PubMed ID : 8037202 207. Rousseau, F.; Rouillard, P.; Morel, M.-L.; Khandjian, E. W.; Morgan, K. : Prevalence of carriers of premutation-size alleles of the FMR1 gene--and implications for the population genetics of the fragile X syndrome. Am. J. Hum. Genet. 57: 1006-1018, 1995. PubMed ID : 7485149 208. Russo, S.; Briscioli, V.; Cogliati, F.; Macchi, M.; Lalatta, F.; Larizza, L. : An unusual fragile X sibship: female compound heterozygote and male with a partially methylated full mutation. Clin. Genet. 54: 309-314, 1998. PubMed ID : 9831342 209. Ruvalcaba, R. H. A.; Myhre, S. A.; Roosen-Runge, E. C.; Beckwith, J. B. : X-linked mental deficiency megalotestes syndrome. J.A.M.A. 238: 1646-1650, 1977. PubMed ID : 578251 210. Schrander-Stumpel, C.; Gerver, W.-J.; Meyer, H.; Engelen, J.; Mulder, H.; Fryns, J.-P. : Prader-Willi-like phenotype in fragile X syndrome. Clin. Genet. 45: 175-180, 1994. PubMed ID : 8062434 211. Sherman, S. L. : Premature ovarian failure among fragile X premutation carriers: parent-of-origin effect? (Editorial) Am. J. Hum. Genet. 67: 11-13, 2000. PubMed ID : 10848491 212. Sherman, S. L.; Jacobs, P. A.; Morton, N. E.; Froster-Iskenius, U.; Howard-Peebles, P. N.; Nielsen, K. B.; Partington, M. W.; Sutherland, G. R.; Turner, G.; Watson, M. : Further segregation analysis of the fragile X syndrome with special reference to transmitting males. Hum. Genet. 69: 289-299, 1985. PubMed ID : 3838733 213. Siomi, H.; Choi, M.; Siomi, M. C.; Nussbaum, R. L.; Dreyfuss, G. : Essential role for KH domains in RNA binding: impaired RNA binding by a mutation in the KH domain of FMR1 that causes fragile X syndrome. Cell 77: 33-39, 1994. PubMed ID : 8156595 214. Siomi, H.; Siomi, M. C.; Nussbaum, R. L.; Dreyfuss, G. : The protein product of the fragile X gene, FMR1, has characteristics of an RNA-binding protein. Cell 74: 291-298, 1993. PubMed ID : 7688265 215. Siomi, M. C.; Zhang, Y.; Siomi, H.; Dreyfuss, G. : Specific sequences in the fragile X syndrome protein FMR1 and the FXR proteins mediate their binding to 60S ribosomal subunits and the interactions among them. Molec. Cell. Biol. 16: 3825-3832, 1996. PubMed ID : 8668200 216. Sittler, A.; Devys, D.; Weber, C.; Mandel, J.-L. : Alternative splicing of exon 14 determines nuclear or cytoplasmic localisation of fmr1 protein isoforms. Hum. Molec. Genet. 5: 95-102, 1996. PubMed ID : 8789445 217. Smeets, H. J. M.; Smits, A. P. T.; Verheij, C. E.; Theelen, J. P. G.; Willemsen, R.; van de Burgt, I.; Hoogeveen, A. T.; Oosterwijk, J. C.; Oostra, B. A. : Normal phenotype in two brothers with a full FMR1 mutation. Hum. Molec. Genet. 4: 2103-2108, 1995. PubMed ID : 8589687 218. Smits, A. P. T.; Dreesen, J. C. F. M.; Post, J. G.; Smeets, D. F. C. M.; de Die-Smulders, C.; Spaans-van der Bijl, T.; Govaerts, L. C. P.; Warren, S. T.; Oostra, B. A.; van Oost, B. A. : The fragile X syndrome: no evidence for any recent mutations. J. Med. Genet. 30: 94-96, 1993. PubMed ID : 8445628 219. Snow, K.; Doud, L. K.; Hagerman, R.; Pergolizzi, R. G.; Erster, S. H.; Thibodeau, S. N. : Analysis of a CGG sequence at the FMR-1 locus in fragile X families and in the general population. Am. J. Hum. Genet. 53: 1217-1228, 1993. PubMed ID : 7902673 220. Snyder, F. F.; Lin, C. C.; Harasym, C. A.; Jamro, H. K.; Kushnig, M. L.; Lowe, J. K.; O'Brien, S. I. : Evidence for close association between the fragile X(q27-28) chromosome site and glucose-6-phosphate dehydrogenase (G6PD) but not with hypoxanthine-guanine phosphoribosyltransferase (HPRT). (Abstract) Cytogenet. Cell Genet. 37: 587, 1984. 221. Soysa, P.; Senanayahe, M.; Mikkelsen, M.; Poulsen, H. : Martin-Bell syndrome fra(X)(q28) in a Sri Lankan family. J. Ment. Defic. Res. 26: 251-257, 1982. PubMed ID : 7169632 222. Steinbach, P. : Mental impairment in Martin-Bell syndrome is probably determined by interaction of several genes: simple explanation of phenotypic differences between unaffected and affected males with the same X chromosome. Hum. Genet. 72: 248-252, 1986. PubMed ID : 3957348 223. Steyaert, J.; Legius, E.; Borghgraef, M.; Fryns, J.-P. : A distinct neurocognitive phenotype in female fragile-X premutation carriers assessed with visual attention tasks. Am. J. Med. Genet. 116A: 44-51, 2003. 224. Stoll, C. : Problems in the diagnosis of fragile X syndrome in young children are still present. Am. J. Med. Genet. 100: 110-115, 2001. PubMed ID : 11298371 225. Storm, K.; Handig, I.; Reyniers, E.; Oostra, B. A.; Kooy, R. F.; Willems, P. J. : Incomplete EcoRI digestion may lead to false diagnosis of fragile X syndrome. Hum. Genet. 102: 54-56, 1998. PubMed ID : 9490298 226. Subramanian, P. S.; Nelson, D. L.; Chinault, A. C. : Large domains of apparent delayed replication timing associated with triplet repeat expansion at FRAXA and FRAXE. Am. J. Hum. Genet. 59: 407-416, 1996. PubMed ID : 8755928 227. Sun, Y. J.; Baumer, A. : Nonrandom X inactivation and selection of fragile X full mutation in fetal fibroblasts. Am. J. Med. Genet. 86: 162-164, 1999. PubMed ID : 10449653 228. Sutherland, G. R. : Personal Communication. Adelaide, Australia, 6/1989. 229. Sutherland, G. R. : Heritable sites on human chromosomes. VII. Children homozygous for the BrdU-requiring fra10q25 are phenotypically normal. Am. J. Hum. Genet. 33: 946-949, 1981. PubMed ID : 7325157 230. Sutherland, G. R. : Personal Communication. Adelaide, Australia, 11/3/1993. 231. Sutherland, G. R. : Fragile sites on human chromosomes: demonstration of their dependence on the type of tissue culture medium. Science 197: 265-266, 1977. PubMed ID : 877551 232. Sutherland, G. R. : Heritable fragile sites on human chromosomes. II. Distribution, phenotypic effects, and cytogenetics. Am. J. Hum. Genet. 31: 136-148, 1979. PubMed ID : 453198 233. Sutherland, G. R.; Ashford, P. L. C. : X-linked mental retardation with macro-orchidism and the fragile site at Xq27 or 28. Hum. Genet. 48: 117-120, 1979. PubMed ID : 572332 234. Sutherland, G. R.; Baker, E. : Characterisation of a new rare fragile site easily confused with the fragile X. Hum. Molec. Genet. 1: 111-113, 1992. PubMed ID : 1301146 235. Sutherland, G. R.; Gedeon, A.; Kornman, L.; Donnelly, A.; Byard, R. W.; Mulley, J. C.; Kremer, E.; Lynch, M.; Pritchard, M.; Yu, S.; Richards, R. I. : Prenatal diagnosis of fragile X syndrome by direct detection of the unstable DNA sequence. New Eng. J. Med. 325: 1720-1722, 1991. PubMed ID : 1944473 236. Sved, J. A.; Laird, C. D. : The X-inactivation imprinting model can explain the incidence of the fragile-X syndrome of mental retardation in mother-offspring pairs. Brain Dysfunction 1: 245-254, 1988. 237. Sved, J. A.; Laird, C. D. : Population genetic consequences of the fragile X syndrome, based on the X-inactivation imprinting model. Am. J. Hum. Genet. 46: 443-451, 1990. PubMed ID : 2309697 238. Szabo, P.; Purrello, M.; Rocchi, M.; Archidiacono, N.; Alhadeff, B.; Filippi, G.; Toniolo, D.; Martini, G.; Luzzatto, L.; Siniscalco, M. : Cytological mapping of the human glucose-6-phosphate dehydrogenase gene distal to the fragile-X site suggests a high rate of meiotic recombination across this site. Proc. Nat. Acad. Sci. 81: 7855-7859, 1984. PubMed ID : 6595664 239. Tamanini, F.; Bontekoe, C.; Bakker, C. E.; van Unen, L.; Anar, B.; Willemsen, R.; Yoshida, M.; Galjaard, H.; Oostra, B. A.; Hoogeveen, A. T. : Different targets for the fragile X-related proteins revealed by their distinct nuclear localizations. Hum. Molec. Genet. 8: 863-869, 1999. PubMed ID : 10196376 240. Tarleton, J.; Kenneson, A.; Taylor, A. K.; Crandall, K.; Fletcher, R.; Casey, R.; Hart, P. S.; Hatton, D.; Fisch, G.; Warren, S. T. : A single base alteration in the CGG repeat region of FMR1: possible effects on gene expression and phenotype. J. Med. Genet. 39: 196-200, 2002. PubMed ID : 11897823 241. Tarleton, J.; Richie, R.; Schwartz, C.; Rao, K.; Aylsworth, A. S.; Lachiewicz, A. : An extensive de novo deletion removing FMR1 in a patient with mental retardation and the fragile X syndrome phenotype. Hum. Molec. Genet. 2: 1973-1974, 1993. PubMed ID : 8281165 242. Terracciano, A.; Pomponi, M. G.; Marino, G. M. E.; Chiurazzi, P.; Rinaldi, M. M.; Dobosz, M.; Neri, G. : Expansion to a full mutation of a FMR1 intermediate allele over two generations. Europ. J. Hum. Genet. 12: 333-336, 2004. PubMed ID : 14735162 243. Thibodeau, S. N.; Dorkins, H. R.; Faulk, K. R.; Berry, R.; Smith, A. C. M.; Hagerman, R.; King, A.; Davies, K. E. : Linkage analysis using multiple DNA polymorphic markers in normal families and in families with fragile X syndrome. Hum. Genet. 79: 219-227, 1988. PubMed ID : 3402993 244. Thode, A.; Laing, S.; Partington, M. W.; Turner, G. : Is there a fragile(X) negative Martin-Bell syndrome?. Am. J. Med. Genet. 30: 459-471, 1988. PubMed ID : 3052069 245. Toledano-Alhadef, H.; Basel-Vanagaite, L.; Magal, N.; Davidov, B.; Ehrlich, S.; Drasinover, V.; Taub, E.; Halpern, G. J.; Ginott, N.; Shohat, M. : Fragile X carrier screening and the prevalence of premutation and full-mutation carriers in Israel. Am. J. Hum. Genet. 69: 351-360, 2001. PubMed ID : 11443541 246. Tommerup, N.; Poulsen, H.; Brondum-Nielsen, K. : 5-Fluoro-2-prime-deoxyuridine induction of the fragile site on Xq28 associated with X-linked mental retardation. J. Med. Genet. 33: 234-242, 1981. 247. Turner, G.; Brookwell, R.; Daniel, A.; Selikowitz, M.; Zilibowitz, M. : Heterozygous expression of X-linked mental retardation and X-chromosome marker fra(X)(q27). New Eng. J. Med. 303: 662-664, 1980. PubMed ID : 6931286 248. Turner, G.; Daniel, A.; Frost, M. : X-linked mental retardation, macro-orchidism, and the Xq27 fragile site. J. Pediat. 96: 837-841, 1980. PubMed ID : 7189210 249. Turner, G.; Eastman, C.; Casey, J.; McLeay, A.; Procopis, P.; Turner, B. : X-linked mental retardation associated with macro-orchidism. J. Med. Genet. 12: 367-371, 1975. PubMed ID : 1240971 250. Turner, G.; Till, R.; Daniel, A. : Marker X chromosomes, mental retardation and macro-orchidism. (Letter) New Eng. J. Med. 299: 1472, 1978. PubMed ID : 714140 251. Turner, G.; Webb, T.; Wake, S.; Robinson, H. : Prevalence of fragile X syndrome. Am. J. Med. Genet. 64: 196-197, 1996. PubMed ID : 8826475 252. Uchida, I. A.; Joyce, E. M. : Activity of the fragile X in heterozygous carriers. Am. J. Hum. Genet. 34: 286-293, 1982. PubMed ID : 6176123 253. van den Ouweland, A. M. W.; Deelen, W. H.; Kunst, C. B.; Uzielli, M.-L. G.; Nelson, D. L.; Warren, S. T.; Oostra, B. A.; Halley, D. J. J. : Loss of mutation at the FMR1 locus through multiple exchanges between maternal X chromosomes. Hum. Molec. Genet. 3: 1823-1827, 1994. PubMed ID : 7849707 254. Van Roy, B. C.; De Smedt, M. C.; Raes, R. A.; Dumon, J. E.; Leroy, J. G. : Fragile X trait in a large kindred: transmission also through normal males. J. Med. Genet. 20: 286-289, 1983. PubMed ID : 6620329 255. Verheij, C.; Bakker, C. E.; de Graaff, E.; Keulemans, J.; Willemsen, R.; Verkerk, A. J. M. H.; Galjaard, H.; Reuser, A. J. J.; Hoogeveen, A. T.; Oostra, B. A. : Characterization and localization of the FMR-1 gene product associated with fragile X syndrome. Nature 363: 722-724, 1993. PubMed ID : 8515814 256. Verheij, C.; de Graaff, E.; Bakker, C. E.; Willemsen, R.; Willems, P. J.; Meijer, N.; Galjaard, H.; Reuser, A. J. J.; Oostra, B. A.; Hoogeveen, A. T. : Characterization of FMR1 proteins isolated from different tissues. Hum. Molec. Genet. 4: 895-901, 1995. PubMed ID : 7633450 257. Verkerk, A. J. M. H.; Pieretti, M.; Sutcliffe, J. S.; Fu, Y.-H.; Kuhl, D. P. A.; Pizzuti, A.; Reiner, O.; Richards, S.; Victoria, M. F.; Zhang, F.; Eussen, B. E.; van Ommen, G.-J. B.; Blonden, L. A. J.; Riggins, G. J.; Chastain, J. L.; Kunst, C. B.; Galjaard, H.; Caskey, C. T.; Nelson, D. L.; Oostra, B. A.; Warren, S. T. : Identification of a gene (FMR-1) containing a CGG repeat coincident with a breakpoint cluster region exhibiting length variation in fragile X syndrome. Cell 65: 905-914, 1991. PubMed ID : 1710175 258. Vianna-Morgante, A. M.; Costa, S. S. : Premature ovarian failure is associated with maternally and paternally inherited premutation in Brazilian families with fragile X. (Letter) Am. J. Hum. Genet. 67: 254-255, 2000. PubMed ID : 10848496 259. Vincent, J. B.; Gurling, H. M. D. : Point mutation in intron 10 of FMR1 is unlikely to be a cause of fragile X syndrome. (Letter) Hum. Mutat. 12: 431 only, 1998. PubMed ID : 9829913 260. Voelckel, M. A.; Mattei, M. G.; N'Guyen, C.; Philip, N.; Birg, F.; Mattei, J. F. : Dissociation between mental retardation and fragile site expression in a family with fragile X-linked mental retardation. Hum. Genet. 80: 375-378, 1988. PubMed ID : 2904402 261. Vogel, F.; Crusio, W. E.; Kovac, C.; Fryns, J.-P.; Freund, M. : Selective advantage of fra (X) heterozygotes. Hum. Genet. 86: 25-32, 1990. PubMed ID : 2147668 262. Wallace, D. C.; Torroni, A. : American Indian prehistory as written in the mitochondrial DNA: a review. Hum. Biol. 64: 403-416, 1992. PubMed ID : 1351474 263. Wang, Y.-C.; Li, S.-Y. : Response to Vincent and Gurling. (Letter) Hum. Mutat. 12: 432 only, 1998. 264. Wang, Y.-C.; Lin, M.-L.; Lin, S. J.; Li, Y.-C.; Li, S.-Y. : Novel point mutation within intron 10 of FMR-1 gene causing fragile X syndrome. Hum. Mutat. 10: 393-399, 1997. PubMed ID : 9375856 265. Warren, S. T.; Glover, T. W.; Davidson, R. L.; Jagadeeswaran, P. : Linkage and recombination between fragile X-linked mental retardation and the factor IX gene. (Letter) Hum. Genet. 69: 44-46, 1985. PubMed ID : 3967889 266. Warren, S. T.; Knight, S. J. L.; Peters, J. F.; Stayton, C. L.; Consalez, G. G.; Zhang, F. P. : Isolation of the human chromosomal band Xq28 within somatic cell hybrids by fragile X site breakage. Proc. Nat. Acad. Sci. 87: 3856-3860, 1990. PubMed ID : 2339126 267. Warren, S. T.; Zhang, F.; Licameli, G. R.; Peters, J. F. : The fragile X site in somatic cell hybrids: an approach for molecular cloning of fragile sites. Science 237: 420-423, 1987. PubMed ID : 3603029 268. Warren, S. T.; Zhang, F. P.; Sutcliffe, J. S.; Peters, J. F. : Strategy for molecular cloning of the fragile X site DNA. Am. J. Med. Genet. 30: 613-623, 1988. PubMed ID : 3177473 269. Weaver, D. D.; Sherman, S. L. : A counseling guide to the Martin-Bell syndrome. (Letter) Am. J. Med. Genet. 26: 39-44, 1987. PubMed ID : 3812576 270. Webb, T.; Jacobs, P. A. : Fragile Xq27.3 in female heterozygotes for the Martin-Bell syndrome. J. Med. Genet. 27: 627-631, 1990. PubMed ID : 2246771 271. Webb, T. P.; Bundey, S.; Thake, A.; Todd, J. : The frequency of the fragile X chromosome among schoolchildren in Coventry. J. Med. Genet. 23: 396-399, 1986. PubMed ID : 3783615 272. Weiler, I. J.; Spangler, C. C.; Klintsova, A. Y.; Grossman, A. W.; Kim, S. H.; Bertaina-Anglade, V.; Khaliq, H.; de Vries, F. E.; Lambers, F. A. E.; Hatia, F.; Base, C. K.; Greenough, W. T. : Fragile X mental retardation protein is necessary for neurotransmitter-activated protein translation at synapses. Proc. Nat. Acad. Sci. 101: 17504-17509, 2004. PubMed ID : 15548614 273. Wheater, R. F.; Roberts, S. H. : An improved lymphocyte culture technique: deoxycytidine release of a thymidine block and use of a constant humidity chamber for slide making. J. Med. Genet. 24: 113-115, 1987. PubMed ID : 3560169 274. Willemsen, R.; Anar, B.; De Diego Otero, Y.; de Vries, B. B. A.; Hilhorst-Hofstee, Y.; Smits, A.; van Looveren, E.; Willems, P. J.; Galjaard, H.; Oostra, B. A. : Noninvasive test for fragile X syndrome, using hair root analysis. Am. J. Hum. Genet. 65: 98-103, 1999. PubMed ID : 10364521 275. Willemsen, R.; Hoogeveen-Westerveld, M.; Reis, S.; Holstege, J.; Severijnen, L.-A. W. F. M.; Nieuwenhuizen, I. M.; Schrier, M.; van Unen, L.; Tassone, F.; Hoogeveen, A. T.; Hagerman, P. J.; Mientjes, E. J.; Oostra, B. A. : The FMR1 CGG repeat mouse displays ubiquitin-positive intranuclear neuronal inclusions; implications for the cerebellar tremor/ataxia syndrome. Hum. Molec. Genet. 12: 949-959, 2003. PubMed ID : 12700164 276. Willemsen, R.; Mohkamsing, S.; De Vries, B.; Devys, D.; van den Ouweland, A.; Mandel, J. L.; Galjaard, H.; Oostra, B. : Rapid antibody test for fragile X syndrome. Lancet 345: 1147-1148, 1995. PubMed ID : 7723547 277. Willemsen, R.; Smits, A.; Mohkamsing, S.; van Beerendonk, H.; de Haan, A.; de Vries, B.; van den Ouweland, A.; Sistermans, A.; Galjaard, H.; Oostra, B. A. : Rapid antibody test for diagnosing fragile X syndrome: a validation of the technique. Hum. Genet. 99: 308-311, 1997. PubMed ID : 9050914 278. Willemsen, R.; Smits, A.; Severijnen, L.-A.; Jansen, M.; Jacobs, A.; De Bruyn, E.; Oostra, B. : Predictive testing for cognitive functioning in female carriers of the fragile X syndrome using hair root analysis. J. Med. Genet. 40: 377-379, 2003. PubMed ID : 12746404 279. Winter, R. M.; Pembrey, M. E. : Analysis of linkage relationships between genetic markers around the fragile X locus with special reference to the daughters of normal transmitting males. Hum. Genet. 74: 93-97, 1986. PubMed ID : 3463533 280. Wohrle, D.; Hennig, I.; Vogel, W.; Steinbach, P. : Mitotic stability of fragile X mutations in differentiated cells indicates early post-conceptional trinucleotide repeat expansion. Nature Genet. 4: 140-142, 1993. PubMed ID : 8348151 281. Wohrle, D.; Kotzot, D.; Hirst, M. C.; Manca, A.; Korn, B.; Schmidt, A.; Barbi, G.; Rott, H.-D.; Poustka, A.; Davies, K. E.; Steinbach, P. : A microdeletion of less than 250 kb, including the proximal part of the FMR-1 gene and the fragile-X site, in a male with the clinical phenotype of fragile-X syndrome. Am. J. Hum. Genet. 51: 299-306, 1992. PubMed ID : 1642231 282. Wohrle, D.; Salat, U.; Hameister, H.; Vogel, W.; Steinbach, P. : Demethylation, reactivation, and destabilization of human fragile X full-mutation alleles in mouse embryocarcinoma cells. Am. J. Hum. Genet. 69: 504-515, 2001. PubMed ID : 11462172 283. Yamauchi, M.; Nagata, S.; Seki, N.; Toyama, Y.; Harada, N.; Niikawa, N.; Masuno, I.; Kajii, T.; Hori, T. : Prenatal diagnosis of fragile X syndrome by direct detection of the dynamic mutation due to an unstable DNA sequence. Clin. Genet. 44: 169-172, 1993. PubMed ID : 8261644 284. Yeshaya, J.; Shalgi, R.; Shohat, M.; Avivi, L. : Replication timing of the various FMR1 alleles detected by FISH: inferences regarding their transcriptional status. Hum. Genet. 102: 6-14, 1998. PubMed ID : 9490300 285. Yu, S.; Mulley, J.; Loesch, D.; Turner, G.; Donnelly, A.; Gedeon, A.; Hillen, D.; Kremer, E.; Lynch, M.; Pritchard, M.; Sutherland, G. R.; Richards, R. I. : Fragile-X syndrome: unique genetics of the heritable unstable element. Am. J. Hum. Genet. 50: 968-980, 1992. PubMed ID : 1570846 286. Yu, S.; Pritchard, M.; Kremer, E.; Lynch, M.; Nancarrow, J.; Baker, E.; Holman, K.; Mulley, J. C.; Warren, S. T.; Schlessinger, D.; Sutherland, G. R.; Richards, R. I. : Fragile X genotype characterized by an unstable region of DNA. Science 252: 1179-1181, 1991. PubMed ID : 2031189 287. Zarnescu, D. C.; Jin, P.; Betschinger, J.; Nakamoto, M.; Wang, Y.; Dockendorff, T. C.; Feng, Y.; Jongens, T. A.; Sisson, J. C.; Knoblich, J. A.; Warren, S. T.; Moses, K. : Fragile X protein functions with lgl and the PAR complex in flies and mice. Dev. Cell 8: 43-52, 2005. PubMed ID : 15621528 288. Zeesman, S.; Zwaigenbaum, L.; Whelan, D. T.; Hagerman, R. J.; Tassone, F.; Taylor, S. A. M. : Paternal transmission of fragile X syndrome. Am. J. Med. Genet. 129A: 184-189, 2004. 289. Zhang, Y. Q.; Bailey, A. M.; Matthies, H. J. G.; Renden, R. B.; Smith, M. A.; Speese, S. D.; Rubin, G. M.; Broadie, K. : Drosophila fragile X-related gene regulates the MAP1B homolog Futsch to control synaptic structure and function. Cell 107: 591-603, 2001. PubMed ID : 11733059 290. Zhong, N.; Dobkin, C.; Brown, W. T. : A complex mutable polymorphism located within the fragile X gene. Nature Genet. 5: 248-253, 1993. PubMed ID : 8275089 291. Zoll, B.; Arnemann, J.; Krawczak, M.; Cooper, D. N.; Pescia, G.; Wahli, W.; Steinbach, P.; Schmidtke, J. : Evidence against close linkage of the loci for fraXq of Martin-Bell syndrome and for factor IX. Hum. Genet. 71: 122-126, 1985. PubMed ID : 2995232 ### CONTRIBUTORS Victor A. McKusick - updated : 4/19/2005 Patricia A. Hartz - updated : 2/23/2005 Victor A. McKusick - updated : 1/27/2005 George E. Tiller - updated : 12/17/2004 Marla J. F. O'Neill - updated : 10/7/2004 Victor A. McKusick - updated : 9/22/2004 Marla J. F. O'Neill - updated : 5/19/2004 Victor A. McKusick - updated : 4/23/2004 Victor A. McKusick - updated : 4/14/2004 Cassandra L. Kniffin - updated : 3/1/2004 Cassandra L. Kniffin - updated : 1/22/2004 Victor A. McKusick - updated : 11/6/2003 Cassandra L. Kniffin - updated : 10/31/2003 Cassandra L. Kniffin - updated : 9/25/2003 Victor A. McKusick - updated : 8/1/2003 Victor A. McKusick - updated : 8/1/2003 Victor A. McKusick - updated : 7/18/2003 Patricia A. Hartz - updated : 7/8/2003 Cassandra L. Kniffin - updated : 5/28/2003 Victor A. McKusick - updated : 5/8/2003 Victor A. McKusick - updated : 4/11/2003 Victor A. McKusick - updated : 3/6/2003 Cassandra L. Kniffin - updated : 3/4/2003 Victor A. McKusick - updated : 1/31/2003 Victor A. McKusick - updated : 1/14/2003 Deborah L. Stone - updated : 11/15/2002 Patricia A. Hartz - updated : 11/11/2002 Cassandra L. Kniffin - updated : 10/15/2002 George E. Tiller - updated : 9/25/2002 Victor A. McKusick - updated : 9/19/2002 Victor A. McKusick - updated : 7/2/2002 Michael B. Petersen - updated : 2/28/2002 Victor A. McKusick - updated : 2/12/2002 Stylianos E. Antonarakis - updated : 1/10/2002 George E. Tiller - updated : 12/26/2001 George E. Tiller - updated : 12/6/2001 Stylianos E. Antonarakis - updated : 11/20/2001 Victor A. McKusick - updated : 9/20/2001 Deborah L. Stone - updated : 9/12/2001 Victor A. McKusick - updated : 8/30/2001 Victor A. McKusick - updated : 8/1/2001 George E. Tiller - updated : 4/25/2001 Sonja A. Rasmussen - updated : 4/23/2001 George E. Tiller - update : 2/5/2001 Michael J. Wright - updated : 1/12/2001 Sonja A. Rasmussen - updated : 1/8/2001 Victor A. McKusick - updated : 12/19/2000 Sonja A. Rasmussen - updated : 12/12/2000 George E. Tiller - updated : 10/16/2000 Ada Hamosh - updated : 9/25/2000 Victor A. McKusick - updated : 9/11/2000 Sonja A. Rasmussen - updated : 7/13/2000 George E. Tiller - updated : 6/7/2000 George E. Tiller - updated : 5/2/2000 Stylianos E. Antonarakis - updated : 4/17/2000 Victor A. McKusick - updated : 3/31/2000 George E. Tiller - updated : 3/23/2000 Victor A. McKusick - updated : 11/24/1999 Sonja A. Rasmussen - updated : 11/16/1999 Sonja A. Rasmussen - updated : 10/5/1999 Victor A. McKusick - updated : 9/8/1999 Victor A. McKusick - updated : 6/30/1999 Victor A. McKusick - updated : 4/12/1999 Victor A. McKusick - updated : 2/18/1999 Victor A. McKusick - updated : 1/25/1999 Victor A. McKusick - updated : 1/12/1999 Michael J. Wright - updated : 11/16/1998 Victor A. McKusick - updated : 10/5/1998 Ada Hamosh - updated : 4/30/1998 Michael J. Wright - updated : 2/10/1998 Victor A. McKusick - updated : 11/26/1997 Victor A. McKusick - updated : 10/14/1997 Victor A. McKusick - updated : 9/2/1997 Victor A. McKusick - updated : 2/3/1997 Moyra Smith - updated : 1/31/1997 Moyra Smith - updated : 9/6/1996 Moyra Smith - updated : 8/27/1996 Mark H. Paalman - updated : 7/25/1996 Moyra Smith - updated : 3/26/1996 ### CREATION DATE Victor A. McKusick : 6/4/1986 ### EDIT HISTORY alopez : 4/19/2005 mgross : 2/23/2005 wwang : 2/11/2005 wwang : 2/10/2005 wwang : 2/7/2005 terry : 1/27/2005 tkritzer : 12/17/2004 carol : 10/22/2004 carol : 10/8/2004 terry : 10/7/2004 tkritzer : 9/23/2004 terry : 9/22/2004 tkritzer : 8/26/2004 tkritzer : 8/24/2004 carol : 6/30/2004 carol : 5/19/2004 terry : 5/19/2004 tkritzer : 4/27/2004 terry : 4/23/2004 alopez : 4/16/2004 terry : 4/14/2004 joanna : 3/16/2004 tkritzer : 3/3/2004 ckniffin : 3/1/2004 tkritzer : 2/10/2004 ckniffin : 1/22/2004 tkritzer : 11/10/2003 terry : 11/6/2003 tkritzer : 10/31/2003 ckniffin : 10/31/2003 carol : 9/25/2003 ckniffin : 9/17/2003 terry : 8/20/2003 carol : 8/1/2003 terry : 8/1/2003 cwells : 7/29/2003 terry : 7/28/2003 terry : 7/28/2003 terry : 7/18/2003 mgross : 7/8/2003 tkritzer : 6/9/2003 ckniffin : 5/28/2003 tkritzer : 5/9/2003 terry : 5/8/2003 tkritzer : 4/17/2003 terry : 4/11/2003 carol : 3/7/2003 terry : 3/6/2003 carol : 3/6/2003 ckniffin : 3/4/2003 tkritzer : 2/4/2003 tkritzer : 2/3/2003 terry : 1/31/2003 carol : 1/23/2003 tkritzer : 1/17/2003 terry : 1/14/2003 carol : 11/15/2002 mgross : 11/11/2002 mgross : 11/11/2002 alopez : 10/21/2002 mgross : 10/18/2002 carol : 10/18/2002 ckniffin : 10/15/2002 cwells : 9/25/2002 tkritzer : 9/19/2002 tkritzer : 9/19/2002 carol : 9/11/2002 cwells : 7/17/2002 cwells : 7/15/2002 terry : 7/2/2002 mgross : 4/8/2002 cwells : 3/6/2002 cwells : 2/28/2002 terry : 2/12/2002 mgross : 1/10/2002 mgross : 1/10/2002 cwells : 1/4/2002 cwells : 12/26/2001 cwells : 12/18/2001 cwells : 12/6/2001 mgross : 11/21/2001 mgross : 11/20/2001 mcapotos : 10/8/2001 mcapotos : 10/1/2001 terry : 9/20/2001 carol : 9/12/2001 terry : 8/30/2001 terry : 8/30/2001 mcapotos : 8/16/2001 mcapotos : 8/2/2001 terry : 8/2/2001 terry : 8/1/2001 cwells : 5/9/2001 cwells : 5/1/2001 cwells : 4/25/2001 mcapotos : 4/23/2001 cwells : 2/5/2001 cwells : 1/30/2001 mcapotos : 1/29/2001 alopez : 1/12/2001 mcapotos : 1/8/2001 terry : 12/19/2000 mcapotos : 12/12/2000 alopez : 10/16/2000 alopez : 10/3/2000 terry : 9/25/2000 carol : 9/13/2000 terry : 9/11/2000 mcapotos : 7/14/2000 mcapotos : 7/13/2000 mcapotos : 7/13/2000 alopez : 6/7/2000 alopez : 5/2/2000 mgross : 4/17/2000 mgross : 4/11/2000 terry : 3/31/2000 alopez : 3/23/2000 alopez : 12/7/1999 carol : 11/29/1999 terry : 11/24/1999 mgross : 11/16/1999 carol : 10/5/1999 jlewis : 9/16/1999 terry : 9/8/1999 jlewis : 7/15/1999 terry : 6/30/1999 carol : 5/24/1999 terry : 5/20/1999 carol : 4/14/1999 terry : 4/12/1999 mgross : 3/10/1999 carol : 2/18/1999 terry : 2/18/1999 carol : 1/25/1999 carol : 1/19/1999 terry : 1/15/1999 terry : 1/12/1999 alopez : 12/7/1998 terry : 11/16/1998 carol : 10/8/1998 terry : 10/5/1998 terry : 6/4/1998 alopez : 5/21/1998 alopez : 5/11/1998 dholmes : 5/11/1998 dholmes : 4/30/1998 alopez : 2/18/1998 terry : 2/10/1998 alopez : 12/5/1997 alopez : 12/3/1997 alopez : 12/3/1997 dholmes : 12/1/1997 mark : 10/14/1997 terry : 9/12/1997 terry : 9/10/1997 jenny : 9/10/1997 terry : 9/2/1997 terry : 8/5/1997 alopez : 7/29/1997 alopez : 7/29/1997 mark : 7/16/1997 alopez : 7/10/1997 alopez : 7/8/1997 joanna : 7/7/1997 joanna : 6/24/1997 terry : 5/5/1997 jenny : 3/31/1997 mark : 2/3/1997 mark : 2/3/1997 mark : 1/31/1997 jamie : 1/16/1997 mark : 10/19/1996 terry : 9/20/1996 mark : 9/6/1996 terry : 9/3/1996 terry : 8/27/1996 mark : 7/25/1996 mark : 3/26/1996 terry : 3/19/1996 mark : 3/14/1996 terry : 3/14/1996 mark : 3/10/1996 terry : 3/5/1996 mark : 2/14/1996 terry : 2/9/1996 mark : 1/20/1996 mark : 1/19/1996 mark : 1/4/1996 terry : 12/29/1995 terry : 12/29/1995 terry : 11/16/1995 mark : 11/6/1995 pfoster : 7/6/1995 jason : 7/18/1994 mimadm : 5/17/1994 warfield : 4/20/1994 Copyright © 1966-2005 Johns Hopkins University
2: | %209850 | GeneTests, Links
| AUTISM
#### Alternative titles; symbols AUTISTIC DISORDER AUTISM, SUSCEPTIBILITY TO, 4, INCLUDED AUTS4, INCLUDED ### TABLE OF CONTENTS #### DESCRIPTION CLINICAL FEATURES INHERITANCE MAPPING POPULATION GENETICS PATHOGENESIS MOLECULAR GENETICS HISTORY REFERENCES CONTRIBUTORS CREATION DATE EDIT HISTORY Clinical Synopsis Gene map locus 15q11-q13, 6p21.3-p21.2 ### TEXT #### DESCRIPTION Autism, the prototypical pervasive developmental disorder (PDD), is usually apparent by 3 years of age. It is characterized by a triad of limited or absent verbal communication, a lack of reciprocal social interaction or responsiveness, and restricted, stereotypical, and ritualized patterns of interests and behavior (Bailey et al., 1996; Risch et al., 1999). One form of autism (AUTS4) has been mapped to chromosome 15q. Other loci for autism have been mapped to chromosome 7q (AUTS1; 608636), 3q25-q27 (AUTS2; 607373), 13q14 (AUTS3; 608049), and 2q (AUTS5; 606053). Three X-linked forms of autism (AUTSX1; 300425; AUTSX2; 300495; AUTSX3; 300496) are caused by mutations in the NLGN3 (300336), NLGN4 (300427), and MECP2 (300005) genes, respectively. #### CLINICAL FEATURES The DSM-IV (American Psychiatric Association, 1994) specifies several diagnostic criteria for autism. In general, patients with autism exhibit qualitative impairment in social interaction, as manifest by impairment in the use of nonverbal behaviors such as eye-to-eye gaze, facial expression, body postures, and gestures, failure to develop appropriate peer relationships, and lack of social sharing or reciprocity. Patients have impairments in communication, such as a delay in, or total lack of, the development of spoken language. In patients who do develop adequate speech, there remains a marked impairment in the ability to initiate or sustain a conversation, as well as stereotyped or idiosyncratic use of language. Patients also exhibit restricted, repetitive and stereotyped patterns of behavior, interests, and activities, including abnormal preoccupation with certain activities and inflexible adherence to routines or rituals. In his pioneer description of infantile autism, Kanner (1943) defined the disorder as 'an innate inability to form the usual, biologically provided affective contact with people.' Kanner (1943) noted that in most cases the child's behavior was abnormal from early infancy, and he suggested the presence of an inborn, presumably genetic, defect. In a review, Smalley (1997) stated that mental retardation is said to be present in approximately 75% of cases of autism, seizures in 15 to 30% of cases, and electroencephalographic abnormalities in 20 to 50% of cases. In addition, approximately 15 to 37% of cases of autism have a comorbid medical condition, including 5 to 14% with a known genetic disorder or chromosomal anomaly. The 4 most common associations include fragile X syndrome (309550), tuberous sclerosis (191100), 15q duplications, and untreated phenylketonuria (261600). Significant associations at a phenotypic level may reflect disruptions in a common neurobiologic pathway, common susceptibility genes, or genes in linkage disequilibrium. Lainhart et al. (2002) stated that approximately 20% of children with autism appear to have relatively normal development during the first 12 to 24 months of life. This period of relative normalcy gradually or suddenly ends and is followed by a period of regression, characterized most prominently by a significant loss of language skills, after which the full autism syndrome becomes evident. Rarely, children with autism may exhibit hyperlexia, or precocious reading (238350). Among a group of 66 children with pervasive developmental disorder, Burd et al. (1985) identified 4 with hyperlexia. #### INHERITANCE Folstein and Rutter (1977) reported that there had been no recorded cases of an autistic child having an overtly autistic parent; however, they noted that autistic persons rarely marry and rarely give birth. Folstein and Rutter (1977) stated that about 2% of sibs are affected, and that speech delay is common in the sibships containing autistic children. In a study of 21 same-sex twins pairs, 11 monozygotic (MZ) and 10 dizygotic (DZ), in which at least 1 had infantile autism, Folstein and Rutter (1977) found 36% concordance among the MZ twins and no concordance among the DZ twins. The concordance for cognitive abnormalities was 82% for MZ pairs and 10% for DZ pairs. In 12 of the 17 pairs discordant for autism, a biologic hazard liable to cause brain damage was identified. The authors concluded that brain injury in infancy may lead to autism on its own or in combination with a genetic predisposition. An inheritance pattern was not suggested. In 40 pairs of twins, Ritvo et al. (1985) found a concordance rate for autism of 23.5% in dizygotic twins (4 of 17 pairs) and 95.7% in monozygotic twins (22 of 23 pairs). Ritvo et al. (1985) ascertained 46 families with 2 (n = 41) or 3 (n = 5) sibs with autism. Classic segregation analysis yielded a maximum likelihood estimate of the segregation ratio of 0.19 +/- 0.07, a value significantly different from 0.50 expected of an autosomal dominant trait and not significantly different from 0.25 expected of a recessive trait. The authors rejected a polygenic threshold model and suggested autosomal recessive inheritance. Using the Utah Genealogical Database, Jorde et al. (1990) determined kinship for all possible pairs of autistic subjects. The average kinship coefficient for autistic subjects and controls showed a strong tendency for autism to cluster in families. However, the familial aggregation was confined exclusively to sib pairs and did not extend to more distant relatives. The authors concluded that the findings excluded recessive inheritance, since the autosomal recessive hypothesis would predict several first-cousin pairs, of which none were found. The rapid fall off in risk to relatives, as well as the sib risk of 4.5%, was consistent with multifactorial causation. By analysis of 99 autistic probands and their families, Bolton et al. (1994) found an increased familial risk for both autism and more broadly defined pervasive developmental disorders (PPDs) in sibs, 2.9% and 2.9%, respectively, which is about 75 times higher than the risk in the general population. In 27 same-sex pairs of monozygotic twins and 20 dizygotic twins, Bailey et al. (1995) found that 60% of monozygotic pairs were concordant for autism compared to 0% of dizygotic pairs. When they considered a broader spectrum of related cognitive or social abnormalities, 92% of monozygotic pairs were concordant compared to 10% of dizygotic pairs. The high concordance in monozygotes indicated a high degree of genetic control, and the rapid fall off of concordance in dizygotics suggested to Bailey et al. (1995) a multilocus, epistatic model. In the nonconcordant monozygotic pairs, there was a significantly higher incidence of obstetric complications, which the authors attributed to prenatal developmental anomalies, as evidenced by the very high incidence of minor congenital anomalies in the affected twins. They also reported an association of autism with increased head circumference. In a sample of families selected because each had exactly 2 affected sibs, Greenberg et al. (2001) observed a remarkably high proportion of affected twin pairs, both MZ and DZ. Of 166 affected sib pairs, 30 (12 MZ, 17 DZ, and 1 of unknown zygosity) were twin pairs. Deviation from expected values was statistically significant; in a similarly ascertained sample of individuals with type I diabetes (222100), there was no deviation from expected values. Greenberg et al. (2001) noted that to ascribe the excess of twins with autism solely to ascertainment bias would require very large ascertainment factors; e.g., affected twin pairs would need to be approximately 10 times more likely to be ascertained than affected nontwin sib pairs. In the extreme situation of 'complete stoppage', a form of ascertainment bias in which parents stop having children after the birth of their first affected child, the only families to have an affected sib pair would be those with an affected twin pair, or affected triplets. The authors suggested that risk factors related to twinning or to fetal development or other factors, genetic or nongenetic, in the parents may contribute to autism. Hallmayer et al. (2002) presented information refuting the suggestion that the twinning process itself is an important risk factor in the development of autism. Silverman et al. (2002) analyzed 3 autistic symptom domains, social interaction, communication, and repetitive behaviors, and variability in the presence and emergence of useful phrase speech in 212 multiply affected sibships with autism. They found that the variance within sibships was reduced for the repetitive behavior domain and for delays in and the presence of useful phrase speech. These features and the nonverbal communication subdomain provided evidence of familiality when only the diagnosis of autism was considered for defining multiply affected sibships. #### MAPPING #### Linkage to Chromosome 15 Baker et al. (1994) reported 2 patients with autism who had duplication of chromosome 15q11-q13. Flejter et al. (1996) reported 2 patients with autism, mental retardation, seizures, and mild hypotonia who both had supernumerary inv dup(15)(pter-q13::q13-pter) chromosomes. In both cases, the abnormal chromosome appeared to be derived from the mother. Cook et al. (1997) reported a family in which 2 children with autism, 1 of whom had a milder form, had maternal inheritance of a 15q11-q13 duplication. Microsatellite and methylation analysis showed that the unaffected mother inherited the 15q11-q13 duplication from her father. A third unaffected child did not inherit the duplication. Cook et al. (1997) noted that the findings in this family emphasized the significance of parental origin for duplications of 15q11-q13; paternal inheritance led to a normal phenotype, whereas maternal inheritance led to autism or atypical autism. The authors suggested that the percentage of autistic patients who have large, cytologically detectable abnormalities in the critical 15q11-q13 region is likely to be small (less than 3% of cases in their clinic). Nonetheless, among those remaining autistic cases it is possible that a larger percentage have mutations of an autism susceptibility gene(s) within this region. In 4 of 100 patients with autism, Schroer et al. (1998) identified abnormalities in proximal 15q: 1 patient had 4 copies of proximal 15q, 2 patients had 3 copies, and 1 patient had 1 copy. All of the chromosome 15 abnormalities were inherited from the mother. Philippe et al. (1999) presented evidence suggesting a potential autism susceptibility region that overlapped with a 15q11-q13 region identified in previous candidate gene studies (Pericak-Vance et al., 1997). Wolpert et al. (2000) reported 3 unrelated autistic patients with isodicentric chromosomes that encompassed the proximal region of 15q11.2. All 3 abnormal chromosomes were of maternal origin. In reviewing previous reports of individuals with autism and abnormalities of proximal 15q, Wolpert et al. (2000) suggested that there may be additional specific findings in these patients, including hypotonia, seizures, delayed motor milestones, and mental retardation. Filipek et al. (2003) reported 2 autistic children who had a 15q11-q13 inverted duplication. Both had uneventful perinatal courses, normal electroencephalogram and MRI scans, moderate motor delay, lethargy, severe hypotonia, and modest lactic acidosis. Both children also had muscle mitochondrial enzyme assays that showed a pronounced mitochondrial hyperproliferation and a partial respiratory chain block most parsimoniously placed at the level of complex III, suggesting that candidate gene loci for autism within the critical region on chromosome 15 may affect pathways influencing mitochondrial function. Shao et al. (2003) used a novel statistical method, ordered subset analysis, to identify a homogeneous subset of families that contribute to overall linkage at chromosome 15. Data from 221 patients with autism was used as a covariate, yielding evidence for linkage to 15q11-q13 with an increase in the lod score from 1.45 to 4.71. The authors noted that the candidate region includes the gamma-aminobutyric acid receptor beta-3 gene (GABRB3; 137192). Bonati et al. (2005) presented evidence pointing to a more distal region of 15q having a role in autism. They reported the case of a male child with autistic disorder, postnatal overgrowth, and a minor brain malformation. Karyotyping and FISH analysis showed the presence of an extra copy of the distal portion of 15q (15q25.2-qter) transposed to 15p, leading to 15q25.2-qter pure trisomy. This karyotype-phenotype study further supported the evidence for a specific phenotype related to trisomy 15q25 or 15q26-qter and suggested that distal 15q may be implicated in specific behavioral phenotypes. #### Genetic Heterogeneity Using findings from a family study of autism and a similar study of twins, Pickles et al. (1995) concluded that autism has a multiple locus mode of inheritance involving 3 loci. Risch et al. (1999) performed a 2-stage genomewide screen of 2 groups of families with autism: 90 families comprising 97 affected sib pairs (ASPs) and 49 families with 50 affected sib pairs. Unaffected sibs, which provided 51 discordant sib pairs (DSPs) for the initial screen and 29 for the follow-up, were included as controls. There was a slightly increased identity by descent (IBD) in the ASPs (sharing of 51.6%) compared with the DSPs (sharing of 50.8%). The results were considered most compatible with a model specifying a large number of loci, perhaps 15 or more, and less compatible with models specifying 10 or fewer loci. The largest lod scores obtained were for a marker on 1p yielding a maximum multipoint lod score of 2.15, and on 17p, yielding a maximum lod score of 1.21. Lopreiato and Wulfsberg (1992) described a complex chromosomal rearrangement in a 6.5-year-old boy with autism who was otherwise normal except for minimal dysmorphism. The rearrangement seen in every cell examined involved chromosomes 1, 7 and 21: 46, XY, -1, -7, -21, t(1;7;21)(1qter-p22.1::21q22.3-qter; 7pter-q11.23::7q36.-7qter; 21pter-q22.3::7q36.1-q11.23::1p22.1-pter). In 51 multiplex families with autism, Philippe et al. (1999) used nonparametric linkage analysis to perform a genomewide screen with 264 microsatellite markers. By 2-point and multipoint affected sib-pair analyses, 11 regions gave nominal P values of 0.05 or lower. Philippe et al. (1999) observed overlap of 4 of these regions with regions on 2q, 7q, 6p, and 19p that had been identified by the earlier genomewide scan of autism conducted by the International Molecular Genetic Study of Autism Consortium (1998). The most significant multipoint linkage was close to marker D6S283 (maximum lod score = 2.23, P = 0.0013). Smalley (1997) reported on the status of linkage studies in autism. Lamb et al. (2000) reviewed chromosomal aberrations, candidate gene studies, and linkage studies of autism. Folstein and Rosen-Sheidley (2001) reviewed the genetics of autism. In 12 of 105 families with 2 or more sibs affected with autism, Yu et al. (2002) identified deletions ranging from 5 to more than 260 kb. One family had complex deletions at marker D7S630 on 7q, 3 families had different deletions at D7S517 on 7p, and another 3 families had different deletions at D8S264 on 8p. A 192-kb deletion at a fourth marker, D8S272, was found in 5 families. However, the deletion at D8S272 was also found in multiple control populations without autism, indicating a polymorphism. For the other 3 sites, no additional deletions were identified in any of the groups without autism, suggesting that these 3 deletions may be specific to autism kindreds and harbor potential autism susceptibility alleles. Yu et al. (2002) suggested that autism susceptibility alleles may cause the deletions by inducing errors during meiosis. Liu et al. (2001) genotyped 335 microsatellite markers in 110 multiplex families with autism. All families included at least 2 affected sibs, at least 1 of whom had autism; the remaining affected sibs carried diagnoses of either Asperger syndrome or pervasive developmental disorder. Affected sib-pair analysis yielded multipoint maximum lod scores that reached the accepted threshold for suggestive linkage on chromosomes 5, X, and 19. Further analysis yielded impressive evidence for linkage of autism and autism-spectrum disorders to markers on chromosomes 5 and 8, with suggestive linkage to a marker on chromosome 19. Yonan et al. (2003) followed up on previously reported genomewide screens for autism performed by Liu et al. (2001) and Alarcon et al. (2002) showing suggestive evidence for linkage of autism spectrum disorders on chromosomes 5, 8, 16, 19, and X, and nominal evidence on several additional chromosomes. In their analysis, Yonan et al. (2003) increased the sample size 3-fold. Multipoint maximum lod scores obtained from affected sib-pair analysis of all 345 families yielded suggestive evidence for linkage on chromosomes 17, 5, 11, 4, and 8 (listed in order of MLS). The most significant findings were an MLS of 2.83 on 17q, near the serotonin transporter (SLC6A4; 182138), and an MLS of 2.54 on 5p. Bartlett et al. (2005) applied the posterior probability of linkage (PPL) method to a collection of families with autism. The results indicated a 'substantial' probability of linkage to chromosome 1 (1q23-q24), which had been previously overlooked; the findings also provided further characterization of the possible parent-of-origin effect (imprinting) at the 17q11 locus that was previously described by Yonan et al. (2003). The autism spectrum disorder shows a striking sex bias, with a male:female ratio of idiopathic autism estimated at 4-10:1, and with an increase in this ratio as the intelligence of the affected individuals increases (Folstein and Rosen-Sheidley, 2001). Stone et al. (2004) investigated the genetic aspects of this large sex bias by monitoring changes in linkage when the family set for an affected sib pair genome scan was subdivided on the basis of sex of affected children. This produced a significant excess in the total number of linkage peaks and identified a major male-specific linkage peak at chromosome 17q11 (p less than 0.01). These results suggested that sexual dichotomy is an important factor in the genetics of autism. It is well established that male and female brains develop, are structured, and function differently. A large body of research shows not only that males and females process input in different ways, but also that this sexual dichotomy extends to the macroscopic structures of the brain. #### Exclusion Studies In a multicenter study in Sweden, Blomquist et al. (1985) found the fragile X (309550) in 13 of 83 boys (16%) with infantile autism, but in none of 19 girls with infantile autism. Using the UCLA Registry for Genetic Studies of Autism, Spence et al. (1985) studied 46 families with at least 2 affected children. Linkage studies in 34 families showed no evidence of linkage with HLA (142800), and close linkage with 19 other autosomal markers was excluded. The highest lod score, 1.04, was found with haptoglobin (140100) on chromosome 16q22 at recombination fractions of 10% in males and 50% in females. There was no association of the disorder with fragile X. Using data from 38 multiplex families with autism to perform a multipoint linkage analysis with markers on the X chromosome, Hallmayer et al. (1996) excluded a moderate to strong gene effect causing autism on the X chromosome. Using the Autism Diagnostic Instrument-Revised (ADI-R), the Autism Diagnostic Observation Scale (ADOS), and psychometric tests, Klauck et al. (1997) identified 141 autistic patients from 105 simplex and 18 multiplex families; 131 patients met all 4 ADI-R algorithm criteria for autism and 10 patients showed a broader phenotype of autism. Using amplification of the CCG repeat at the fragile X locus, hybridization to the complete FMR1 cDNA probe, and hybridization to additional probes from the neighborhood of the FMR1 gene, the authors found no significant changes in 139 patients (99%) from 122 families. One multiplex family with 3 children showing no dysmorphic features of the fragile X syndrome (1 male meeting 3 of 4 ADI-algorithm criteria, 1 normal male with slight learning disability but negative ADI-R testing, and 1 fully autistic female), the FRAXA full-mutation-specific CCG-repeat expansion in the genotype was not correlated with the autism phenotype. Further analysis revealed a mosaic pattern of methylation at the FMR1 gene locus in the 2 sons of the family, indicating at least a partly functional gene. Klauck et al. (1997) concluded that the association of autism with fragile X at Xq27.3 is nonexistent and excluded this location as a candidate gene for autism. #### POPULATION GENETICS Smalley (1997) reported that autism has a population prevalence of approximately 4 to 5 in 10,000 with a male to female ratio of 4 to 1. In a review of 20 studies on autism published between 1966 and 1997, Gillberg and Wing (1999) determined that autism is considerably more common than previously believed. The early studies yielded prevalence rates of under 0.5 per 1,000 children, whereas the later studies showed a mean rate of about 1 in 1,000. Children born after 1970 had a much higher rate than those born after 1970. Bertrand et al. (2001) performed a prevalence study of autism spectrum disorders in Brick Township, New Jersey. There were 6.7 cases per 1,000 children, aged 3 to 10 years, in 1998. The prevalence for children whose condition met full diagnostic criteria for autistic disorder was 4.0 cases per 1,000 children, and the prevalence for PDD-not otherwise specified (NOS) and Asperger syndrome was 2.7 cases per 1,000 children. #### PATHOGENESIS Schain and Freedman (1961) reported elevated levels of serotonin (5-HT; see 182138) in patients with autism. Abramson et al. (1989) reported elevated blood serotonin in autistic probands and in their first-degree relatives. Piven et al. (1989, 1991) found that serotonin levels were significantly higher in autistic individuals with a sib with autism or PDD than in those without a sib with these disorders, and that autistic patients without an affected sib had serotonin levels that were significantly higher than controls. A biologic basis of autism was suggested by the finding of developmental hypoplasia in lobules VI and VII of the cerebellar vermis (Courchesne et al., 1988). The ontogenetically, developmentally, and anatomically distinct vermal lobules I to V were found to be of normal size. However, Schaefer et al. (1996) disputed the relationship of cerebellar vermal atrophy to infantile autism. They found that the average relative size of lobules VI and VII of the cerebellar vermis was no different in their 13 patients with infantile autism when compared to that of 125 normal individuals. They found relative hypoplasia of lobules VI and VII in patients with Rett syndrome (312750) and Sotos cerebral gigantism (117550), 2 disorders characterized by autistic behaviors. No relative vermian atrophy was seen in other disorders associated with autistic behavior: fragile X, Angelman (AS; 105830), adult phenylketonuria (261600), and Sanfilippo (252900). Furthermore, they found a relative atrophy of lobules VI and VII in several patients with primary cerebellar hypoplasia and Usher syndrome type II (276901), syndromes not associated with autistic behavior. Regressive autism, characterized most prominently by a loss of language skills, has been attributed to environmental factors, particularly adverse reactions to vaccines; epidemiologic evidence, however, shows no association between vaccination and the rate of autism as reviewed by the Institute of Medicine Immunization Safety Reviews (2001); see also Taylor et al. (2002). Lainhart et al. (2002) noted that twin and family studies showed that the liability to autism extends beyond the full autism syndrome and includes qualitatively similar, albeit milder, deficits, referred to as the broader autism phenotype (BAP). If regressive autism is solely caused by environmental events, such as adverse reactions to vaccines, rates of the BAP in the relatives of children with regressive autism should be no greater than in the general population. If environmental events do not independently cause regressive autism, or if they act as 'second-hit' phenomena in children who already have a genetic liability to autism, rates of the BAP should be similar in relatives of autistic children with and without regression. Lainhart et al. (2002) found that the rate of the BAP was significantly higher in parents of children with regressive and nonregressive autism than in parents of nonautistic children. They concluded that environmental events are unlikely to be the sole cause of regressive autism, although environmental events may act in an additive or 'second-hit' fashion in individuals with a genetic vulnerability to autism. #### MOLECULAR GENETICS Noting that elevations in serotonin had been found in patients with autism (Abramson et al., 1989; Piven et al., 1991), Klauck et al. (1997) used the transmission/disequilibrium test (TDT) to analyze a common polymorphism (5-HTTLPR; long/short promoter polymorphism) in the upstream regulatory region of the serotonin transporter gene (SLC6A4; 182183.0001) and a VNTR in intron 2 of the same gene in a total of 117 autistic trios. They found a higher frequency and preferential transmission of the 5-HTTLPR long allele in the patients with autism. In contrast, Cook et al. (1997) found preferential transmission of the short 5-HTTLPR allele in autism, but no association between autism and the VNTR in intron 2. Kim et al. (2002) studied 115 trios consisting of a proband with autism and both parents. Ninety-eight probands were male and 17 were female, and the sample included 94 Caucasians, 7 African Americans, 8 Asian Americans, and 6 Hispanics. Seven SNP and 4 SSR markers in and around the serotonin transporter gene on chromosome 17q11 showed nominally significant evidence of transmission disequilibrium. In 81 trios, there was replication of a previous finding of transmission equilibrium between a haplotype consisting of the 5-HTTLPR polymorphism and a VNTR in intron 2, but there was no preferential transmission of 5-HTTLPR as an independent marker. No mutations were detected in the SLC6A4 gene. Maestrini et al. (1999) found no association or linkage to the 5-HTT gene or to the GABRB3 gene in 94 families comprising 174 individuals with autism. Zhong et al. (1999) and Persico et al. (2000) found no linkage or association between the 5-HTTLR gene alleles and autism. Conroy et al. (2004) investigated the role of the serotonin transporter in autism in the genetically homogeneous Irish population by genotyping 84 families for 5 polymorphisms in the SLC6A4 gene. Analysis of allele transmissions using the TDT revealed preferential transmission of the short promoter allele (p = 0.0334). A number of haplotypes, especially those involving and surrounding a T-to-C transition in promoter IB, designated SNP10, showed evidence of association. Odds ratios (ORs) ranged from 1.2 to 2.4. A haplotype defined by SNP10, a 12-repeat allele in the VNTR in intron 2, and a G-to-A transition in intron 2 (designated SNP18) was the most significant haplotype associated with transmission to affected probands (OR, 1.8; chi squared, 7.3023; p = 0.0069). #### HISTORY Eisenberg (1994) provided a biographic sketch of Leo Kanner (1894-1981), the pioneer pediatric psychiatrist who first described and named infantile autism (Kanner, 1943). ### REFERENCES 1. Abramson, R. K.; Wright, H. H.; Carpenter, R.; Brennan, W.; Lumpuy, O.; Cole, E.; Young, S. R. : Elevated blood serotonin in autistic probands and their first-degree relatives. J. Autism Dev. Disord. 19: 397-407, 1989. PubMed ID : 2793785 2. Alarcon, M.; Cantor, R. M.; Liu, J.; Gilliam, T. C.; Autism Genetic Resource Exchange Consortium; Geschwind, D. H. : Evidence for a language quantitative trait locus on chromosome 7q in multiplex autism families. Am. J. Hum. Genet. 70: 60-71, 2002. PubMed ID : 11741194 3. American Psychiatric Association : Diagnostic and Statistical Manual of Mental Disorders. (4th ed.) Washington, D.C.: American Psychiatric Association , 1994. 4. Bailey, A.; Le Couteur, A.; Gottesman, I.; Bolton, P.; Simonoff, E.; Yuzda, E.; Rutter, M. : Autism as a strongly genetic disorder: evidence from a British twin study. Psychol. Med. 25: 63-77, 1995. PubMed ID : 7792363 5. Bailey, A.; Phillips, W.; Rutter, M. : Autism: towards an integration of clinical, genetic, neuropsychological, and neurobiological perspectives. J. Child Psychol. Psychiat. 37: 89-126, 1996. PubMed ID : 8655659 6. Baker, P.; Piven, J.; Schwartz, S.; Patil, S. : Duplication of chromosome 15q11-13 in two individuals with autistic disorder. J. Autism Dev. Disord. 24: 529-535, 1994. PubMed ID : 7961335 7. Bartlett, C. W.; Goedken, R.; Vieland, V. J. : Effects of updating linkage evidence across subsets of data: reanalysis of the Autism Genetic Resource Exchange data set. Am. J. Hum. Genet. 76: 688-695, 2005. PubMed ID : 15729670 8. Bertrand, J.; Mars, A.; Boyle, C.; Bove, F.; Yeargin-Allsopp, M.; Decoufle, P. : Prevalence of autism in a United States population: the Brick Township, New Jersey, investigation. Pediatrics 108: 1155-1161, 2001. PubMed ID : 11694696 9. Blomquist, H. K.; Bohman, M.; Edvinsson, S. O.; Gillberg, C.; Gustavson, K.-H.; Holmgren, G.; Wahlstrom, J. : Frequency of the fragile X syndrome in infantile autism: a Swedish multicenter study. Clin. Genet. 27: 113-117, 1985. PubMed ID : 3978844 10. Bolton, P.; Macdonald, H.; Pickles, A.; Rios, P.; Goode, S.; Crowson, M.; Bailey, A.; Rutter, M. : A case-control family history study of autism. J. Child Psychol. Psychiat. 35: 877-900, 1994. PubMed ID : 7962246 11. Bonati, M. T.; Finelli, P.; Giardino, D.; Gottardi, G.; Roberts, W.; Larizza, L. : Trisomy 15q25.2-qter in an autistic child: genotype-phenotype correlations. Am. J. Med. Genet. 133A: 184-188, 2005. 12. Burd, L.; Kerbeshian, J.; Fisher, W. : Inquiry into the incidence of hyperlexia in a statewide population of children with pervasive developmental disorder. Psychol. Rep. 57: 236-238, 1985. PubMed ID : 4048337 13. Conroy, J.; Meally, E.; Kearney, G.; Fitzgerald, M.; Gill, M.; Gallagher, L. : Serotonin transporter gene and autism: a haplotype analysis in an Irish autistic population. Molec. Psychiat. 9: 587-593, 2004. 14. Cook, E. H., Jr.; Courchesne, R.; Lord, C.; Cox, N. J.; Yan, S.; Lincoln, A.; Haas, R.; Courchesne, E.; Leventhal, B. L. : Evidence of linkage between the serotonin transporter and autistic disorder. Molec. Psychiat. 2: 247-250, 1997. 15. Cook, E. H., Jr.; Lindgren, V.; Leventhal, B. L.; Courchesne, R.; Lincoln, A.; Shulman, C.; Lord, C.; Courchesne, E. : Autism or atypical autism in maternally but not paternally derived proximal 15q duplication. Am. J. Hum. Genet. 60: 928-934, 1997. PubMed ID : 9106540 16. Courchesne, E.; Yeung-Courchesne, R.; Press, G. A.; Hesselink, J. R.; Jernigan, T. L. : Hypoplasia of cerebellar vermal lobules VI and VII in autism. New Eng. J. Med. 318: 1349-1354, 1988. PubMed ID : 3367935 17. Eisenberg, L. : Images in psychiatry: Leo Kanner (1894-1981). Am. J. Psychiat. 151: 751, 1994. PubMed ID : 8166319 18. Filipek, P. A.; Juranek, J.; Smith, M.; Mays, L. Z.; Ramos, E. R.; Bocian, M.; Masser-Frye, D.; Laulhere, T. M.; Modahl, C.; Spence, M. A.; Gargus, J. J. : Mitochondrial dysfunction in autistic patients with 15q inverted duplication. Ann. Neurol. 53: 801-804, 2003. PubMed ID : 12783428 19. Flejter, W. L.; Bennett-Baker, P. E.; Ghaziuddin, M.; McDonald, M.; Sheldon, S.; Gorski, J. L. : Cytogenetic and molecular analysis of inv dup(15) chromosomes observed in two patients with autistic disorder and mental retardation. Am. J. Med. Genet. 61: 182-187, 1996. PubMed ID : 8669450 20. Folstein, S.; Rutter, M. : Infantile autism: a genetic study of 21 twin pairs. J. Child Psychol. Psychiat. 18: 297-321, 1977. PubMed ID : 562353 21. Folstein, S.; Rutter, M. : Genetic influences and infantile autism. Nature 265: 726-728, 1977. PubMed ID : 558516 22. Folstein, S. E.; Rosen-Sheidley, B. : Genetics of autism: complex aetiology for a heterogeneous disorder. Nature Rev. Genet. 2: 943-955, 2001. 23. Gillberg, C.; Wing, L. : Autism: not an extremely rare disorder. Acta Psychiat. Scand. 99: 399-406, 1999. PubMed ID : 10408260 24. Greenberg, D. A.; Hodge, S. E.; Sowinski, J.; Nicoll, D. : Excess of twins among affected sibling pairs with autism: implications for the etiology of autism. Am. J. Hum. Genet. 69: 1062-1067, 2001. PubMed ID : 11590546 25. Hallmayer, J.; Glasson, E. J.; Bower, C.; Petterson, B.; Croen, L.; Grether, J.; Risch, N. : On the twin risk in autism. Am. J. Hum. Genet. 71: 941-946, 2002. PubMed ID : 12297988 26. Hallmayer, J.; Hebert, J. M.; Spiker, D.; Lotspeich, L.; McMahon, W. M.; Petersen, P. B.; Nicholas, P.; Pingree, C.; Lin, A. A.; Cavalli-Sforza, L. L.; Risch, N.; Ciaranello, R. D. : Autism and the X chromosome: multipoint sib-pair analysis. Arch. Gen. Psychiat. 53: 985-989, 1996. PubMed ID : 8911221 27. Institute of Medicine Immunization Safety Reviews : Measles-mumps-rubella vaccine and autism. Washington, D.C.: National Academy Press , 2001. Pp. 13-69. 28. International Molecular Genetic Study of Autism Consortium : A full genome screen for autism with evidence for linkage to a region on chromosome 7q. Hum. Molec. Genet. 7: 571-578, 1998. PubMed ID : 9546821 29. Jorde, L. B.; Mason-Brothers, A.; Waldmann, R.; Ritvo, E. R.; Freeman, B. J.; Pingree, C.; McMahon, W. M.; Petersen, B.; Jenson, W. R.; Mo, A. : The UCLA--University of Utah epidemiologic survey of autism: genealogical analysis of familial aggregation. Am. J. Med. Genet. 36: 85-88, 1990. PubMed ID : 2333911 30. Kanner, L. : Autistic disturbances of affective contact. Nerv. Child 2: 217-250, 1943. 31. Kim, S. J.; Cox, N.; Courchesne, R.; Lord, C.; Corsello, C.; Akshoomoff, N.; Guter, S.; Leventhal, B. L.; Courchesne, E.; Cook, E. H., Jr. : Transmission disequilibrium mapping at the serotonin transporter gene (SLC6A4) region in autistic disorder. Molec. Psychiat. 7: 278-288, 2002. 32. Klauck, S. M.; Munstermann, E.; Bieber-Martig, B.; Ruhl, D.; Lisch, S.; Schmotzer, G.; Poustka, A.; Poustka, F. : Molecular genetic analysis of the FRM-1 gene in a large collection of autistic patients. Hum. Genet. 100: 224-229, 1997. PubMed ID : 9254854 33. Klauck, S. M.; Poustka, F.; Benner, A.; Lesch, K.-P.; Poustka, A. : Serotonin transporter (5-HTT) gene variants associated with autism? Hum. Molec. Genet. 6: 2233-2238, 1997. PubMed ID : 9361027 34. Lainhart, J. E.; Ozonoff, S.; Coon, H.; Krasny, L.; Dinh, E.; Nice, J.; McMahon, W. : Autism, regression, and the broader autism phenotype. Am. J. Med. Genet. 113: 231-237, 2002. PubMed ID : 12439889 35. Lamb, J. A.; Moore, J.; Bailey, A.; Monaco, A. P. : Autism: recent molecular genetic advances. Hum. Molec. Genet. 9: 861-868, 2000. PubMed ID : 10767308 36. Liu, J.; Nyholt, D. R.; Magnussen, P.; Parano, E.; Pavone, P.; Geschwind, D.; Lord, C.; Iversen, P.; Hoh, J.; Autism Genetic Resource Exchange Consortium; Ott, J.; Gilliam, T. C. : A genomewide screen for autism susceptibility loci. Am. J. Hum. Genet. 69: 327-340, 2001. Note: Erratum: Am. J. Hum. Genet. 69: 672 only, 2001. PubMed ID : 11452361 37. Lopreiato, J. O.; Wulfsberg, E. A. : A complex chromosome rearrangement in a boy with autism. J. Dev. Behav. Pediat. 13: 281-283, 1992. 38. Maestrini, E.; Lai, C.; Marlow, A.; Matthews, N.; Wallace, S.; Bailey, A.; Cook, E. H.; Weeks, D. E.; Monaco, A. P.; International Molecular Genetic Study of Autism (IMGSA) Consortium : Serotonin transporter (5-HTT) and gamma-aminobutyric acid receptor subunit beta-3 (GABRB3) gene polymorphisms are not associated with autism in the IMGSA families. Am. J. Med. Genet. (Neuropsychiat. Genet.) 88: 492-496, 1999. 39. Pericak-Vance, M. A.; Wolpert, C. M.; Menold, M. M.; Bass, M. P.; DeLong, G. R.; Beaty, L. M.; Zimmerman, A.; Potter, N.; Gilbert, J. R.; Vance, J. M.; Wright, H. H.; Abramson, R. K.; Cuccaro, M. L. : Linkage evidence supports the involvement of chromosome 15 in autistic disorder (AUT). (Abstract) Am. J. Hum. Genet. 61 (suppl.): A40 only, 1997. 40. Persico, A. M.; Militerni, R.; Bravaccio, C.; Schneider, C.; Melmed, R.; Conciatori, M.; Damiani, V.; Baldi, A.; Keller, F. : Lack of association between serotonin transporter gene promoter variants and autistic disorder in two ethnically distinct samples. Am. J. Med. Genet. 96: 123-127, 2000. PubMed ID : 10686565 41. Philippe, A.; Martinez, M.; Guilloud-Bataille, M.; Gillberg, C.; Rastam, M.; Sponheim, E.; Coleman, M.; Zappella, M.; Aschauer, H.; van Malldergerme, L.; Penet, C.; Feingold, J.; Brice, A.; Leboyer, M.; Paris Autism Research International Sibpair Study : Genome-wide scan for autism susceptibility genes. Hum. Molec. Genet. 8: 805-812, 1999. PubMed ID : 10196369 42. Pickles, A.; Bolton, P.; Macdonald, H.; Bailey, A.; Le Couteur, A.; Sim, C.-H.; Rutter, M. : Latent-class analysis of recurrence risks for complex phenotypes with selection and measurement error: a twin and family history study of autism. Am. J. Hum. Genet. 57: 717-726, 1995. PubMed ID : 7668301 43. Piven, J.; Tsai, G.; Nehme, E.; Coyle, J.; Chase, G.; Folstein, S. : Platelet serotonin, a possible marker for familial autism. (Abstract) Am. J. Hum. Genet. 45 (suppl.): A58, 1989. 44. Piven, J.; Tsai, G. C.; Nehme, E.; Coyle, J. T.; Chase, G. A.; Folstein, S. E. : Platelet serotonin, a possible marker for familial autism. J. Autism Dev. Disord. 21: 51-59, 1991. PubMed ID : 2037549 45. Risch, N.; Spiker, D.; Lotspeich, L.; Nouri, N.; Hinds, D.; Hallmayer, J.; Kalaydjieva, L.; McCague, P.; Dimiceli, S.; Pitts, T.; Nguyen, L.; Yang, J.; and 19 others : A genomic screen of autism: evidence for a multilocus etiology. Am. J. Hum. Genet. 65: 493-507, 1999. PubMed ID : 10417292 46. Ritvo, E. R.; Freeman, B. J.; Mason-Brothers, A. M.; Mo, A.; Ritvo, A. M. : Concordance for the syndrome of autism in 40 pairs of affected twins. Am. J. Psychiat. 142: 74-77, 1985. PubMed ID : 4038442 47. Ritvo, E. R.; Spence, M. A.; Freeman, B. J.; Mason-Brothers, A.; Mo, A.; Marazita, M. L. : Evidence for an autosomal recessive type of autism in 46 multiple incidence families. Am. J. Psychiat. 142: 187-192, 1985. PubMed ID : 4038589 48. Schaefer, G. B.; Thompson, J. N., Jr.; Bodensteiner, J. B.; McConnell, J. M.; Kimberling, W. J.; Gay, C. T.; Dutton, W. D.; Hutchings, D. C.; Gray, S. B. : Hypoplasia of the cerebellar vermis in neurogenic syndromes. Ann. Neurol. 39: 382-385, 1996. PubMed ID : 8602758 49. Schain, R. J.; Freedman, D. X. : Studies on 5-hydroxyindole metabolism in autistic and other mentally retarded children. J. Pediat. 58: 315-320, 1961. PubMed ID : 13747230 50. Schroer, R. J.; Phelan, M. C.; Michaelis, R. C.; Crawford, E. C.; Skinner, S. A.; Cuccaro, M.; Simensen, R. J.; Bishop, J.; Skinner, C.; Fender, D.; Stevenson, R. E. : Autism and maternally derived aberrations of chromosome 15q. Am. J. Med. Genet. 76: 327-336, 1998. PubMed ID : 9545097 51. Shao, Y.; Cuccaro, M. L.; Hauser, E. R.; Raiford, K. L.; Menold, M. M.; Wolpert, C. M.; Ravan, S. A.; Elston, L.; Decena, K.; Donnelly, S. L.; Abramson, R. K.; Wright, H. H.; DeLong, G. R.; Gilbert, J. R.; Pericak-Vance, M. A. : Fine mapping of autistic disorder to chromosome 15q11-q13 by use of phenotypic subtypes. Am. J. Hum. Genet. 72: 539-548, 2003. PubMed ID : 12567325 52. Silverman, J. M.; Smith, C. J.; Schmeidler, J.; Hollander, E.; Lawlor, B. A.; Fitzgerald, M.; Buxbaum, J. D.; Delaney, K.; Galvin, P.; Autism Genetic Research Exchange Consortium : Symptom domains in autism and related conditions: evidence for familiality. Am. J. Med. Genet. (Neuropsychiat. Genet.) 114: 64-73, 2002. 53. Smalley, S. L. : Genetic influences in childhood-onset psychiatric disorders: autism and attention-deficit/hyperactivity disorder. Am. J. Hum. Genet. 60: 1276-1282, 1997. PubMed ID : 9199546 54. Spence, M. A.; Ritvo, E. R.; Marazita, M. L.; Funderburk, S. J.; Sparkes, R. S.; Freeman, B. J. : Gene mapping studies with the syndrome of autism. Behav. Genet. 15: 1-13, 1985. PubMed ID : 3985910 55. Stone, J. L.; Merriman, B.; Cantor, R. M.; Yonan, A. L.; Gilliam, T. C.; Geschwind, D. H.; Nelson, S. F. : Evidence for sex-specific risk alleles in autism spectrum disorder. Am. J. Hum. Genet. 75: 1117-1123, 2004. PubMed ID : 15467983 56. Taylor, B.; Miller, E.; Lingam, R.; Andrews, N.; Simmons, A.; Stowe, J. : Measles, mumps, and rubella vaccination and bowel problems or developmental regression in children with autism: population study. Brit. Med. J. 324: 393-396, 2002. PubMed ID : 11850369 57. Wolpert, C. M.; Menold, M. M.; Bass, M. P.; Qumsiyeh, M. B.; Donnelly, S. L.; Ravan, S. A.; Vance, J. M.; Gilbert, J. R.; Abramson, R. K.; Wright, H. H.; Cuccaro, M. L.; Pericak-Vance, M. A. : Three probands with autistic disorder and isodicentric chromosome 15. Am. J. Med. Genet. (Neuropsychiat. Genet.) 96: 365-372, 2000. 58. Yonan, A. L.; Alarcon, M.; Cheng, R.; Magnusson, P. K. E.; Spence, S. J.; Palmer, A. A.; Grunn, A.; Juo, S.-H. H.; Terwilliger, J. D.; Liu, J.; Cantor, R. M.; Geschwind, D. H.; Gilliam, T. C. : A genomewide screen of 345 families for autism-susceptibility loci. Am. J. Hum. Genet. 73: 886-897, 2003. PubMed ID : 13680528 59. Yu, C.-E.; Dawson, G.; Munson, J.; D'Souza, I.; Osterling, J.; Estes, A.; Leutenegger, A.-L.; Flodman, P.; Smith, M.; Raskind, W. H.; Spence, M. A.; McMahon, W.; Wijsman, E. M.; Schellenberg, G. D. : Presence of large deletions in kindreds with autism. Am. J. Hum. Genet. 71: 100-115, 2002. PubMed ID : 12058345 60. Zhong, N.; Ye, L.; Ju, W.; Brown, W. T.; Tsiouris, J.; Cohen, I. : 5-HTTLPR variants not associated with autistic spectrum disorders. Neurogenetics 2: 129-131, 1999. PubMed ID : 10369890 ### CONTRIBUTORS Victor A. McKusick - updated : 3/23/2005 Victor A. McKusick - updated : 3/11/2005 John Logan Black, III - updated : 3/1/2005 Victor A. McKusick - updated : 11/12/2004 Cassandra L. Kniffin - updated : 5/24/2004 Cassandra L. Kniffin - reorganized : 5/17/2004 Cassandra L. Kniffin - updated : 5/6/2004 John Logan Black, III - updated : 3/11/2004 Victor A. McKusick - updated : 12/1/2003 Victor A. McKusick - updated : 8/15/2003 Victor A. McKusick - updated : 2/28/2003 Victor A. McKusick - updated : 11/27/2002 Victor A. McKusick - updated : 11/14/2002 John Logan Black, III - updated : 8/14/2002 Victor A. McKusick - updated : 8/2/2002 Victor A. McKusick - updated : 4/12/2002 Victor A. McKusick - updated : 2/21/2002 Victor A. McKusick - updated : 2/14/2002 Victor A. McKusick - updated : 2/4/2002 Ada Hamosh - updated : 1/30/2002 Victor A. McKusick - updated : 1/22/2002 Michael B. Petersen - updated : 12/5/2001 Victor A. McKusick - updated : 11/27/2001 Victor A. McKusick - updated : 10/25/2001 George E. Tiller - update : 10/2/2001 Victor A. McKusick - updated : 9/7/2001 Victor A. McKusick - updated : 10/3/2000 George E. Tiller - updated : 5/1/2000 Victor A. McKusick - updated : 1/11/2000 Victor A. McKusick - updated : 5/17/1999 Orest Hurko - updated : 3/24/1999 Victor A. McKusick - updated : 4/24/1998 Victor A. McKusick - updated : 9/12/1997 Victor A. McKusick - updated : 6/17/1997 Orest Hurko - updated : 5/6/1996 Orest Hurko - updated : 8/2/1995 ### CREATION DATE Victor A. McKusick : 6/3/1986 ### EDIT HISTORY tkritzer : 3/25/2005 ckniffin : 3/24/2005 ckniffin : 3/24/2005 terry : 3/23/2005 wwang : 3/15/2005 terry : 3/11/2005 carol : 3/10/2005 tkritzer : 3/1/2005 alopez : 11/18/2004 terry : 11/12/2004 tkritzer : 5/28/2004 ckniffin : 5/24/2004 ckniffin : 5/19/2004 carol : 5/18/2004 ckniffin : 5/18/2004 carol : 5/17/2004 ckniffin : 5/17/2004 ckniffin : 5/6/2004 carol : 3/23/2004 joanna : 3/17/2004 terry : 3/11/2004 tkritzer : 12/8/2003 terry : 12/1/2003 alopez : 8/19/2003 terry : 8/15/2003 terry : 8/15/2003 joanna : 5/12/2003 ckniffin : 4/1/2003 ckniffin : 4/1/2003 carol : 3/31/2003 tkritzer : 3/6/2003 terry : 2/28/2003 tkritzer : 12/5/2002 tkritzer : 12/2/2002 terry : 11/27/2002 carol : 11/20/2002 carol : 11/20/2002 terry : 11/14/2002 terry : 11/14/2002 carol : 8/14/2002 tkritzer : 8/7/2002 tkritzer : 8/7/2002 tkritzer : 8/5/2002 terry : 8/2/2002 alopez : 4/26/2002 cwells : 4/19/2002 terry : 4/12/2002 mgross : 2/25/2002 mgross : 2/25/2002 terry : 2/21/2002 carol : 2/21/2002 cwells : 2/21/2002 cwells : 2/15/2002 terry : 2/14/2002 carol : 2/11/2002 terry : 2/4/2002 alopez : 2/4/2002 terry : 1/30/2002 carol : 1/30/2002 terry : 1/22/2002 cwells : 12/5/2001 alopez : 11/30/2001 terry : 11/27/2001 carol : 10/25/2001 terry : 10/25/2001 cwells : 10/10/2001 cwells : 10/2/2001 cwells : 9/20/2001 cwells : 9/13/2001 alopez : 9/7/2001 alopez : 9/7/2001 carol : 5/3/2001 terry : 10/5/2000 terry : 10/3/2000 alopez : 5/1/2000 mgross : 2/7/2000 terry : 1/11/2000 mgross : 6/4/1999 mgross : 6/4/1999 mgross : 5/25/1999 terry : 5/17/1999 carol : 3/24/1999 dholmes : 5/12/1998 dholmes : 5/11/1998 carol : 4/24/1998 terry : 4/14/1998 mark : 9/19/1997 terry : 9/12/1997 terry : 9/10/1997 terry : 9/10/1997 mark : 6/18/1997 terry : 6/17/1997 terry : 6/12/1997 terry : 6/12/1997 mark : 5/6/1996 mark : 5/6/1996 terry : 4/30/1996 mark : 9/10/1995 terry : 4/19/1995 jason : 6/22/1994 supermim : 3/16/1992 carol : 3/7/1992 Copyright © 1966-2005 Johns Hopkins University
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| MENTAL RETARDATION WITH PSYCHOSIS, PYRAMIDAL SIGNS, AND MACROORCHIDISM
#### Alternative titles; symbols PPMX ### TABLE OF CONTENTS #### TEXT CLINICAL FEATURES MAPPING MOLECULAR GENETICS REFERENCES CONTRIBUTORS CREATION DATE EDIT HISTORY Clinical Synopsis Gene map locus Xq28 ### TEXT A number sign (#) is used with this entry because of evidence that the disorder is caused by mutation in the MECP2 gene (300005), which is also the site of mutations causing Rett syndrome (312750). #### CLINICAL FEATURES Lindsay et al. (1996) described an X-linked mental retardation syndrome linked to Xq28. This syndrome was identified in a 3-generation family in which 4 of 6 moderately retarded males had episodes of manic depressive psychosis. Lindsay et al. (1996) contended that despite the known high psychiatric morbidity in individuals with learning difficulties and the specific association between mental retardation and atypical manic depressive illness, the frequency and severity of the psychiatric illness in this family and its consistent association with mental retardation suggested a syndromic basis for the disorder. Affected males also exhibited neurologic signs including tremor, shuffling gait, and increased tone and tendon reflexes. Lindsay et al. (1996) noted, however, that it is difficult to be sure that the neurologic features were not secondary to treatment with neuroleptic drugs. Affected males exhibited macroorchidism. #### MAPPING The highest lod score observed in the family described by Lindsay et al. (1996) was 3.311 at theta = 0 with marker DXS1123. The marker DXS1691 defined the proximal boundary of the approximately 8-Mb region that contains the putative PPMX gene. On cytogenetic analysis no fragile sites were detected, and no CGG repeat expansions were detected at the FRAXA (309550), FRAXE (309548,) or FRAXF (300031) loci. #### MOLECULAR GENETICS In the family originally reported by Lindsay et al. (1996), Klauck et al. (2002) found an A140V (300005.0015) missense mutation in the MECP2 gene. The A140V mutation had been previously described in 2 patients with familial mental retardation and 2 patients with sporadic mental retardation. ### REFERENCES 1. Klauck, S. M.; Lindsay, S.; Beyer, K. S.; Splitt, M.; Burn, J.; Poustka, A. : A mutation hot spot for nonspecific X-linked mental retardation in the MECP2 gene causes the PPM-X syndrome. Am. J. Hum. Genet. 70: 1034-1037, 2002. PubMed ID : 11885030 2. Lindsay, S.; Splitt, M.; Edney, S.; Berney, T. P.; Knight, S. J. L.; Davies, K. E.; O'Brien, O.; Gale, M.; Burn, J. : PPM-X: A new X-linked mental retardation syndrome with psychosis, pyramidal signs, and macroorchidism maps to Xq28. Am. J. Hum. Genet. 58: 1120-1126, 1996. PubMed ID : 8651288 ### CONTRIBUTORS Victor A. McKusick - updated : 4/12/2002 ### CREATION DATE Moyra Smith : 6/13/1996 ### EDIT HISTORY alopez : 4/26/2002 cwells : 4/19/2002 terry : 4/12/2002 carol : 6/19/1996 Copyright © 1966-2005 Johns Hopkins University
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| AUTISM, SUSCEPTIBILITY TO, 1
#### Alternative titles; symbols AUTS1 ### TABLE OF CONTENTS #### TEXT MAPPING MOLECULAR GENETICS REFERENCES CONTRIBUTORS CREATION DATE EDIT HISTORY Clinical Synopsis ### TEXT For a phenotypic description and a discussion of genetic heterogeneity of autism, see 209850. #### MAPPING The International Molecular Genetic Study of Autism Consortium (1998) conducted a 2-stage genome search for susceptibility loci for autism, using 87 affected sib pairs and 12 non-sib affected relative-pairs from a total of 99 families. Regions on 6 chromosomes were identified that generated a multipoint maximum lod score of greater than 1. A region on 7q was the most significant, with a maximum lod score of 3.55 near markers D7S530 and D7S684 in the subset of 56 U.K. affected sib-pair families, and a maximum lod score of 2.53 in all 87 affected sib-pair families. An area on 16p near the telomere was the next most significant, with an maximum lod score of 1.97 in the U.K. families and 1.51 in all families. Vincent et al. (2000) identified an autistic individual carrying a translocation, t(7;13)(q31.3;q21), with the chromosome 7 breakpoint located in the region of 7q in which a susceptibility locus for autism had been postulated. They found that a novel gene, called RAY1 (605318), was interrupted by the translocation breakpoint. Mutation screening of the entire coding region in a set of 27 unrelated autistic individuals failed to identify phenotype-specific variants, suggesting that coding mutations in the RAY1 gene are unlikely to be involved in the etiology of autism. By analyzing 125 autistic sib pairs, the International Molecular Genetic Study of Autism Consortium (2001) found a maximum multipoint lod score of 2.15 at marker D7S477, whereas analysis of 153 sib pairs generated a maximum multipoint lod score of 3.37. Linkage disequilibrium mapping identified 2 regions of association: 1 was under the peak of linkage, the other was 27 cM distal. In another study, the International Molecular Genetic Study of Autism Consortium (2001) found a multipoint maximum lod score of 3.20 at marker D7S477. They also detected a multipoint maximum lod score of 4.80 at marker D2S188 on chromosome 2q. Lamb et al. (2005) analyzed 219 affected sib pairs with autism and found evidence for 2 susceptibility loci on chromosome 7q, at D7S477 and the interval D7S530 to D7S640. A 2-locus model program generated a maximum lod score of 3.34; however, a single-locus model generated maximum lod scores of 1.94 at D7S477 and 2.51 for D7S530 to D7S640. Linkage to the latter region increased when only the male sibs were considered, suggesting that genomic imprinting may play a role. Gutknecht (2001) reviewed published full-genome scans and found that a region of approximately 50 cM on 7q appeared to play a role in the etiology of autistic disorder. She noted, however, that the finding must be considered with caution because lod score values did not reach the threshold for significant linkage. Folstein and Mankoski (2000) suggested a relationship between autism and specific language impairment (SLI; see 602081) because genetic studies in each disorder point to a locus on 7q31. To study the genetics of autism, Alarcon et al. (2002) divided the syndrome into component autism-related traits (endophenotypes), hypothesizing that quantitative trait loci (QTLs) related to one or more of these traits might underlie putative or significant regions of autism linkage. They performed nonparametric linkage analyses in 152 families segregating autism, focusing on 3 traits derived from the Autism Diagnostic Interview: 'age at first word,' 'age at first phrase,' and a composite measure of 'repetitive and stereotyped behaviors.' Using nonparametric multipoint linkage analysis, they found the strongest QTL evidence for the age at first word on 7q, and subsequent linkage analyses of additional markers and association analyses of the same region supported the initial result. Moreover, the peak fine-mapping result for repetitive behaviors localized to a region overlapping this language QTL. The authors suggested that a putative autism susceptibility locus on chromosome 7 may be the result of separate QTLs for the language and repetitive or stereotyped behavior deficits that are associated with the disorder. In 12 of 105 families with 2 or more sibs affected with autism, Yu et al. (2002) identified deletions ranging from 5 to more than 260 kb. One family had complex deletions at marker D7S630 on 7q, 3 families had different deletions at D7S517 on 7p, and another 3 families had different deletions at D8S264 on 8p. A 192-kb deletion at a fourth marker, D8S272, was found in 5 families. However, the deletion at D8S272 was also found in multiple control populations without autism, indicating a polymorphism. For the other 3 sites, no additional deletions were identified in any of the groups without autism, suggesting that these 3 deletions may be specific to autism kindreds and harbor potential autism susceptibility alleles. Yu et al. (2002) suggested that autism susceptibility alleles may cause the deletions by inducing errors during meiosis. #### MOLECULAR GENETICS Petit et al. (1995) tested 2 markers of the homeogene engrailed-2 (131310) on chromosome 7q36 in separate populations of 100 autistic and 100 control children. The gene is involved in cerebellar development. With a probe showing a PvuII polymorphism, the investigators found significant differences in the allele frequencies between the 2 populations. With a second probe showing an SstI polymorphism, no difference was apparent. Wassink et al. (2001) examined WNT2 (147870) as a candidate gene for autism for several reasons: the WNT family of genes influences the development of numerous organs and systems, including the central nervous system; WNT2 is located in the 7q31-q33 region linked to autism and is adjacent to a chromosomal breakpoint in an individual with autism; and a mouse knockout of the dishevelled-1 (DVL1; 601365) gene, a member of a gene family essential for the function of the WNT pathway, exhibits a behavioral phenotype characterized primarily by diminished social interaction (Lijam et al., 1997). Wassink et al. (2001) found 2 families containing nonconservative coding sequence variants that segregated with autism. They also identified linkage disequilibrium between a WNT2 3-prime untranslated region single-nucleotide polymorphism (SNP) and their sample of autism-affected sib-pair families and trios (2 parents and 1 affected child). Linkage disequilibrium occurred almost exclusively in a subgroup of affected sib-pair families defined by the presence of severe language abnormalities and was also found to be associated with evidence for linkage to 7q. ### REFERENCES 1. Alarcon, M.; Cantor, R. M.; Liu, J.; Gilliam, T. C.; Autism Genetic Resource Exchange Consortium; Geschwind, D. H. : Evidence for a language quantitative trait locus on chromosome 7q in multiplex autism families. Am. J. Hum. Genet. 70: 60-71, 2002. PubMed ID : 11741194 2. Folstein, S. E.; Mankoski, R. E. : Chromosome 7q: where autism meets language disorder? (Editorial) Am. J. Hum. Genet. 67: 278-281, 2000. PubMed ID : 10889044 3. Gutknecht, L. : Full-genome scans with autistic disorder: a review. Behav. Genet. 31: 113-123, 2001. PubMed ID : 11529268 4. International Molecular Genetic Study of Autism Consortium : A genomewide screen for autism: strong evidence for linkage to chromosomes 2q, 7q, and 16p. Am. J. Hum. Genet. 69: 570-581, 2001. PubMed ID : 11481586 5. International Molecular Genetic Study of Autism Consortium : A full genome screen for autism with evidence for linkage to a region on chromosome 7q. Hum. Molec. Genet. 7: 571-578, 1998. PubMed ID : 9546821 6. International Molecular Genetic Study of Autism Consortium : Further characterization of the autism susceptibility locus AUTS1 on chromosome 7q. Hum. Molec. Genet. 10: 973-982, 2001. PubMed ID : 11392322 7. Lamb, J. A.; Barnby, G.; Bonora, E.; Sykes, N.; Bacchelli, E.; Blasi, F.; Maestrini, E.; Broxholme, J.; Tzenova, J.; Weeks, D.; Bailey, A. J.; Monaco, A. P.; International Molecular Genetic Study of Autism Consortium : Analysis of IMGSAC autism susceptibility loci: evidence for sex limited and parent of origin specific effects. J. Med. Genet. 42: 132-137, 2005. PubMed ID : 15689451 8. Lijam, N.; Paylor, R.; McDonald, M. P.; Crawley, J. N.; Deng, C.-X.; Herrup, K.; Stevens, K. E.; Maccaferri, G.; McBain, C. J.; Sussman, D. J.; Wynshaw-Boris, A. : Social interaction and sensorimotor gating abnormalities in mice lacking Dvl1. Cell 90: 895-905, 1997. PubMed ID : 9298901 9. Petit, E.; Herault, J.; Martineau, J.; Perrot, A.; Barthelemy, C.; Hameury, L.; Sauvage, D.; Lelord, G.; Muh, J. P. : Association study with two markers of a human homeogene in infantile autism. J. Med. Genet. 32: 269-274, 1995. PubMed ID : 7643354 10. Vincent, J. B.; Herbrick, J.-A.; Gurling, H. M. D.; Bolton, P. F.; Roberts, W.; Scherer, S. W. : Identification of a novel gene on chromosome 7q31 that is interrupted by a translocation breakpoint in an autistic individual. Am. J. Hum. Genet. 67: 510-514, 2000. PubMed ID : 10889047 11. Wassink, T. H.; Piven, J.; Vieland, V. J.; Huang, J.; Swiderski, R. E.; Pietila, J.; Braun, T.; Beck, G.; Folstein, S. E.; Haines, J. L.; Sheffield, V. C. : Evidence supporting WNT2 as an autism susceptibility gene. Am. J. Med. Genet. 105: 406-413, 2001. PubMed ID : 11449391 12. Yu, C.-E.; Dawson, G.; Munson, J.; D'Souza, I.; Osterling, J.; Estes, A.; Leutenegger, A.-L.; Flodman, P.; Smith, M.; Raskind, W. H.; Spence, M. A.; McMahon, W.; Wijsman, E. M.; Schellenberg, G. D. : Presence of large deletions in kindreds with autism. Am. J. Hum. Genet. 71: 100-115, 2002. PubMed ID : 12058345 ### CONTRIBUTORS Cassandra L. Kniffin - updated : 3/18/2005 ### CREATION DATE Cassandra L. Kniffin : 5/4/2004 ### EDIT HISTORY ckniffin : 3/18/2005 tkritzer : 12/9/2004 carol : 5/17/2004 ckniffin : 5/17/2004 ckniffin : 5/17/2004 ckniffin : 5/6/2004 Copyright © 1966-2005 Johns Hopkins University
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| AUTISM, SUSCEPTIBILITY TO, 3
#### Alternative titles; symbols AUTS3 ### TABLE OF CONTENTS #### TEXT REFERENCES CREATION DATE EDIT HISTORY Clinical Synopsis Gene map locus 13q14.2-q14.1 ### TEXT For a phenotypic description and a discussion of genetic heterogeneity of autism, see 209850. Ritvo et al. (1988) reported on the simultaneous occurrence of autism and retinoblastoma in a patient with a deletion that extended from 13q12 to 13q14. Steele et al. (2001) described a case of autism with a de novo deletion of 13q14-q22. Bradford et al. (2001) analyzed the effect of incorporating language information and parental structural language phenotypes into the genome screening for autism. Their results revealed 2 distinct peaks of linkage on 13q. In a sporadic case of autism and language deficit due to auditory processing defects, Smith et al. (2002) demonstrated an interstitial deletion in chromosome 13q. The breakpoints of the deletion were estimated to be 13q13.2 and 13q14.1. Chromosome analysis on peripheral blood from the parents revealed normal karyotypes. Smith et al. (2002) determined that the deletion occurred on the paternally derived chromosome 13. Molecular genetic studies indicated that the deletion mapped between the 2 chromosome 13 linkage peaks described by Bradford et al. (2001) in studies of subjects with autism and language deficits. The 9-Mb region contains at least 4 genes that are expressed in brain and that play a role in brain development: neurobeachin (NBEA; 604889); MAB21L1 (601280), which maps within NBEA; DCAMKL1 (604742); and MADH9 (603295). ### REFERENCES 1. Bradford, Y.; Haines, J.; Hutcheson, H.; Gardiner, M.; Braun, T.; Sheffield, V.; Cassavant, T.; Huang, W.; Wang, K.; Vieland, V.; Folstein, S.; Santangelo, S.; Piven, J. : Incorporating language phenotypes strengthens evidence of linkage to autism. Am. J. Med. Genet. 105: 539-547, 2001. PubMed ID : 11496372 2. Ritvo, E. R.; Mason-Brothers, A.; Menkes, J. H.; Sparkes, R. S. : Association of autism, retinoblastoma, and reduced esterase D activity. Arch. Gen. Psychiat. 45: 600 only, 1988. PubMed ID : 3377648 3. Smith, M.; Woodroffe, A.; Smith, R.; Holguin, S.; Martinez, J.; Filipek, P. A.; Modahl, C.; Moore, B.; Bocian, M. E.; Mays, L.; Laulhere, T.; Flodman, P.; Spence, M. A. : Molecular genetic delineation of a deletion of chromosome 13q12-q13 in a patient with autism and auditory processing deficits. Cytogenet. Genome Res. 98: 233-239, 2002. PubMed ID : 12826745 4. Steele, M. M.; Al-Adeimi, M.; Siu, V. M.; Fan, Y.-S. : Brief report: a case of autism with interstitial deletion of chromosome 13. J. Autism Dev. Disord. 31: 231-234, 2001. PubMed ID : 11450821 ### CREATION DATE Victor A. McKusick : 8/18/2003 ### EDIT HISTORY carol : 5/17/2004 ckniffin : 5/17/2004 ckniffin : 5/6/2004 carol : 3/18/2004 tkritzer : 10/1/2003 alopez : 9/3/2003 alopez : 8/18/2003 Copyright © 1966-2005 Johns Hopkins University
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| AUTISM, SUSCEPTIBILITY TO, 2
#### Alternative titles; symbols AUTS2 ### TABLE OF CONTENTS #### TEXT NOMENCLATURE REFERENCES CREATION DATE EDIT HISTORY Clinical Synopsis Gene map locus 3q25-q27 ### TEXT For a phenotypic description and discussion of genetic heterogeneity of autism, see (209850). In a group of 38 Finnish families in which a proband had autism, Auranen et al. (2002) found that approximately one-third of the probands had a first-degree relative with Asperger syndrome or developmental dysphagia. The authors defined this group as having 'autism spectrum disorders.' In 19 families with autism alone, the most significant evidence for linkage was found on 3q25-q27, with a maximum 2-point lod score of 3.16 with marker D3S3037. In another 18 families with autism and Asperger syndrome (see 608638), Auranen et al. (2002) found an increased lod score of 4.31 at the same marker (D3S3037). #### NOMENCLATURE Auranen et al. (2002) referred to the locus for autism susceptibility on 3q25-q27 as AUTS2. This symbol has also been approved for a gene on chromosome 7 (607270). ### REFERENCES 1. Auranen, M.; Vanhala, R.; Varilo, T.; Ayers, K.; Kempas, E.; Ylisaukko-oja, T.; Sinsheimer, J. S.; Peltonen, L.; Jarvela, I. : A genomewide screen for autism-spectrum disorders: evidence for a major susceptibility locus on chromosome 3q25-27. Am. J. Hum. Genet. 71: 777-790, 2002. PubMed ID : 12192642 ### CREATION DATE Victor A. McKusick : 11/20/2002 ### EDIT HISTORY carol : 5/17/2004 ckniffin : 5/17/2004 ckniffin : 5/6/2004 ckniffin : 5/6/2004 carol : 3/18/2004 carol : 11/20/2002 carol : 11/20/2002 Copyright © 1966-2005 Johns Hopkins University
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| MUCOPOLYSACCHARIDOSIS TYPE II
#### Alternative titles; symbols MPS II; MPS2 HUNTER SYNDROME IDURONATE 2-SULFATASE DEFICIENCY IDS DEFICIENCY SULFOIDURONATE SULFATASE DEFICIENCY SIDS DEFICIENCY IDURONATE 2-SULFATASE, INCLUDED; IDS, INCLUDED ### TABLE OF CONTENTS #### DESCRIPTION CLINICAL FEATURES INHERITANCE CYTOGENETICS MAPPING MOLECULAR GENETICS GENOTYPE/PHENOTYPE CORRELATIONS DIAGNOSIS CLINICAL MANAGEMENT POPULATION GENETICS ANIMAL MODEL ALLELIC VARIANTS View List SEE ALSO REFERENCES CONTRIBUTORS CREATION DATE EDIT HISTORY Clinical Synopsis Gene map locus Xq28 ### TEXT #### DESCRIPTION Mucopolysaccharidosis II arises from iduronate sulfatase deficiency, which results in tissue deposits of mucopolysaccharides and urinary excretion of large amounts of chondroitin sulfate B and heparitin sulfate. #### CLINICAL FEATURES Sex-linked mucopolysaccharidosis differs from the autosomal type (MPS I; see 607014) in being on the average less severe and in not showing clouding of the cornea. Features are dysostosis with dwarfism, grotesque facies, hepatosplenomegaly from mucopolysaccharide deposits, cardiovascular disorders from mucopolysaccharide deposits in the intima, deafness, and excretion of large amounts of chondroitin sulfate B and heparitin sulfate in the urine. Danes and Bearn (1965) found that fibroblasts from patients with this disorder show metachromatic cytoplasmic inclusions and that about half the fibroblasts of heterozygotes show such inclusions. Two forms of MPS II are distinguishable clinically. A severe form (called MPS IIA in my nomenclature) has progressive mental retardation and physical disability and death before age 15 years in most cases. A mild form (called MPS IIB) is compatible with survival to adulthood, and reproduction is known to have occurred (DiFerrante and Nichols, 1972). Intellect is impaired minimally, if at all. There are probably more than 2 allelic forms of the Hunter syndrome and differentiation between the 2 forms even within families is often not sharp. Hobolth and Pedersen (1978) described a kindred with 6 cases of mild Hunter syndrome additionally remarkable for survival to ages 65 and 87 in 2 of the cases and for progeny from 3 affected males. Tsuzaki et al. (1987) described an unusually mild form of the Hunter syndrome. At 14 years of age, their patient had normal growth and development. He had mild dysostosis radiologically, coarse facial features, flexion contractures of the elbows and shoulder joints, and moderate hepatosplenomegaly. At age 8 he had the murmur of aortic regurgitation, and at age 12 angiocardiography was said to have shown grade 4 aortic regurgitation. The mother was a healthy carrier. Ballenger et al. (1980) described spastic quadriplegia in a 24-year-old man due to impingement of the thickened meninges on the cervical spinal cord. Tracheal narrowing required tracheostomy. Schiro et al. (1996) described grouped papules on the extensor surface of the upper portions of the arms and legs as an initial presenting feature in a 5-year-old boy with Hurler-Scheie syndrome. Other physical findings included progressive flexion contractures and mild developmental delay. Sapadin and Friedman (1998) noted extensive Mongolian spots in a 4.5-year-old African American boy with Hunter syndrome. These patches were present at birth over the buttocks and lumbar sacral area. Other patches continued to appear over the paraspinal area of the entire back, and smaller lesions occurred on the anterior trunk. 'Pebbly' skin first appeared on the proximal arms, soon after became visible on the scapulas and thighs, and later in the pectoral areas. The other features were typical of Hunter syndrome, which was confirmed by enzyme assay. Ochiai et al. (2003) investigated the occurrence of Mongolian spots in 7 Japanese infants with Hunter syndrome before and after hematopoietic stem cell transplantation (HSCT). Pre-HSCT observation revealed that all the patients had extensive Mongolian spots that were present at birth and showed no signs of resolution during the post-HSCT period. Electron microscopic findings showed that pigment-bearing dermal melanocytes contained many free melanosomes in stage IV. These were surrounded by extracellular sheaths and encircled by elastic fibers. The results of Ochiai et al. (2003) indicated a strong clinical correlation between extensive Mongolian spots and Hunter syndrome, and ultrastructural findings suggested that the hyperpigmentation is a long-lasting symptom. Ochiai et al. (2003) concluded that recognition of extensive Mongolian spots is essential as it may lead to early diagnosis in patients with mild forms of Hunter syndrome. #### INHERITANCE Neufeld et al. (1977) described 2 families, each with a girl clinically affected with the Hunter syndrome and with profound deficiency of iduronate 2-sulfatase (EC 3.1.6.13). The patients were karyotypically normal and had normal fathers. Cloning of the mothers' fibroblasts did not show the mosaicism expected of the X-linked disease. Homozygosity for a previously unsuspected autosomal recessive gene for iduronate sulfatase was considered the most likely explanation, although heterozygosity for the X-linked gene and subsequent selection could not be completely excluded. Studies of the enzyme at the molecular level and of complementation in somatic cell hybrids are required to distinguish between these possibilities. The mutation in the 2 families was presumably different (although perhaps allelic) because it took the severe form in one family and the mild form in the other. Strong support for autosomal recessive inheritance came from the fact that the parents were first cousins in one family and had ancestors from the same ethnic group and same small town in the other family. Possibly these cases are instances of multiple sulfatase deficiency in which the deficiency of iduronate sulfatase is particularly striking (Neufeld, 1981). In 1 of the families, however, this did not appear to be the explanation. Sukegawa et al. (1998) reported a brother/sister pair with Hunter syndrome. Both had normal karyotypes. The sister was heterozygous for the R468L mutation in genomic DNA, but homozygous for the allele in fibroblasts and lymphoblasts, resulting in relatively severe manifestations of the disease. Analysis of methylation patterns of the androgen receptor gene showed skewed X-chromosome inactivation of the paternal allele. #### CYTOGENETICS Broadhead et al. (1986) described a 2.5-year-old girl with typical full expression of MPS II. Chromosome studies showed partial deletion of the long arm of one X chromosome; band Xq25 was thought to be missing. Studies using BrdU indicated that the deleted X chromosome was consistently late replicating and, as a result, the Hunter gene presumed to be present on the other X chromosome was fully expressed. There were no other cases of Hunter syndrome known in the family; however, the mother had a partial deficiency (43%) of serum iduronate-2-sulfate sulfatase. The father's serum enzyme activity was in the control range. Hence, caution must obviously be exercised in interpreting the findings of X/autosome translocations as indication of an X-linked trait at the site of the breakpoint on the X chromosome, when there is no way to identify carrier status in the mother. In such instances, the full expression of the disorder in a female may be merely the result of nonrandom inactivation of the abnormal X chromosome uncovering the mutant gene on the other X chromosome. Winchester et al. (1992) reported the occurrence of Hunter syndrome in a karyotypically normal girl who was 1 of identical twins. Molecular studies showed nonrandom X inactivation in both her fibroblasts and her lymphocytes, while her normal twin showed equal usage of the 2 X chromosomes. In view of previous reports of 7 pairs of identical female twins in which 1 had Duchenne muscular dystrophy, Winchester et al. (1992) suggested that twinning may be strongly associated with nonrandom X inactivation. In some cases of twins discordant for DMD symmetric nonrandom X inactivation was found with each twin showing a nonrandom pattern but in opposite directions. In at least one case (Lupski et al., 1991), however, 1 girl showed an apparently random pattern and the affected girl a nonrandom pattern. The patient with Hunter syndrome reported by Winchester et al. (1992) was of the latter type. Goldenfum et al. (1996) demonstrated that both twins reported by Winchester et al. (1992) were heterozygous for a 1-bp deletion of cytosine at position 123 of their cDNA. The asymptomatic cotwin showed random X inactivation. #### MAPPING Mossman et al. (1983) described a 3-year-old girl with typical Hunter syndrome. She had an apparently balanced reciprocal translocation between chromosomes X and 5 with the break in the former being between q26 and q27. The parents' karyotypes were normal. Pedigree analysis and normal enzyme levels in the mother's fibroblasts, serum, and hair roots indicated that the child was a new mutation. Location of the Hunter gene in the q26-q27 region and disruption of this gene in the origination of the translocation in this girl was proposed. The principle here is the same as that used to assign regionally the DMD locus (300377) and several others; the translocation chromosome is presumably the active one. Roberts et al. (1987, 1988, 1989) reexamined the case of Mossman et al. (1983) cytogenetically and concluded that the breakpoint was in Xq28 rather than being more proximal, as previously suggested. This finding is more in keeping with the linkage studies with DNA markers, which suggest location of the locus at Xq28. Furthermore, replication studies indicated that the normal X in this patient was preferentially inactivated. Berg et al. (1968) concluded that the Hunter locus and the Xm locus (314900) are within measurable distance of each other, the best estimate of the recombination fraction being 0.09. Mochi et al. (1985) found no evidence of linkage with the factor IX gene (deficiency of which causes hemophilia B), which is located at Xq27. Chase et al. (1986) concluded that the Hunter locus is distal to the factor IX locus inasmuch as the maximum lod score for the linkage of these loci was 0.424 at theta = 0.25, whereas that for the linkage of the Hunter syndrome and DX13 was 3.01 at theta = 0.1. DX13 maps to Xq28. From studies with DNA probes, Upadhyaya et al. (1985, 1986) suggested that the Hunter locus may be close to that for the fragile site at Xq27. Le Guern et al. (1990) did a family linkage study using 4 polymorphic markers from the Xq27-q28 region. A maximum lod score of 6.57 at theta = 0.0 was obtained with DXS304. Furthermore, they showed, consistent with the finding of others, that the breakpoint of the translocation described by Mossman et al. (1983) is distal to DXS98 and proximal to DXS304. Thomas et al. (1989) extended studies of the X;5 translocation by study of cell hybrids containing the derivative X as their only human X chromosomal material. By study of DNA markers and of a hybrid clone that apparently had undergone a secondary DNA rearrangement, they concluded that the 'IDS and FRAXA are probably located in the same subregion around Xq27.3.' Couillin et al. (1990) described a method for isolating the 2 X;5 translocated derivative chromosomes in separate rodent-human cell hybrids. The method was based mainly on immunofluorescent screening using MIC2 (313470) and MIC5 (308840) antigenic markers. The MIC5 gene was found to be between IDS and G6PD (305900). Couillin et al. (1990) concluded that the fragile X site is proximal to IDS. Wilson et al. (1991) used an IDS cDNA clone to localize the gene to Xq28, distal to the fragile X site. The cDNA clone was also shown to span the X chromosome breakpoint in a female Hunter syndrome patient with an X;autosome translocation (Suthers et al., 1989). See section on Animal Models for mapping studies in the mouse relating to the FMR1 (309550), F9 (306900), and GABRA3 (305660) genes. #### MOLECULAR GENETICS Clarke et al. (1992) reported molecular characterization of the mutation associated with marked unbalanced expression of the mutant X chromosome in a karyotypically normal girl with Hunter syndrome. Southern analysis of DNA extracted from somatic cell hybrids containing only the mutant X chromosome showed deletion of several Xq27.3-q28 loci including FRAXA (309550) and the 3-prime end of the IDS gene. Three flanking loci, including DXS52, were intact. On the basis of these results, Clarke et al. (1992) concluded that the mutation was a simple deletion extending a maximum of 3-5 cM to the centromeric side of the IDS gene. Their studies indicated that the telomeric terminus of the deletion was located near the middle of the coding sequence of the gene. The patient was the one previously reported by Clarke et al. (1990, 1991). Birot et al. (1996) described a family with a cytogenetically evident deletion in Xq27.2-q28 that removed the IDS and FMR1 genes. This was said to be the largest deletion in this region of the X chromosome identified in a male patient, indicating that there is no gene in this region, the absence of which would be lethal. Wilson et al. (1990) isolated and sequenced a 2.3-kb cDNA clone coding for the entire sequence of human IDS. Analysis of the deduced 550-amino acid precursor indicated that IDS has a 25-amino acid amino-terminal signal sequence, followed by 8 amino acids that are removed from the proprotein. A strong sequence homology was found with human arylsulfatases A, B, and C, and human glucosamine-6-sulfatase. The IDS cDNA detected structural alterations or gross deletions of the IDS gene in many of the clinically severe Hunter syndrome patients studied. Palmieri et al. (1992) isolated a 1.2-Mb YAC contig spanning the IDS gene. Several putative CpG islands were identified in the region, suggesting the presence of other genes. Southern analysis of DNA from 25 unrelated Italian MPS II patients uncovered 4 with deletions or rearrangements in the IDS gene. DNA from a patient with a translocation breakpoint in the gene permitted orientation of the contig in relation to the centromere. Wilson et al. (1991) had found a deletion or gene rearrangement in 7 of 23 Hunter patients of Australian and British origin. In 2 of 14 unrelated German MPS II patients, structural alteration of the IDS gene was found by Southern analysis using an IDS cDNA clone as a probe. In one of these patients, a severely affected male, no Southern fragments were detected. In 12 patients, Bunge et al. (1992) used single-strand conformation polymorphism analysis for mutation analysis. Missense or nonsense mutations and deletions or insertions of a small number of basepairs were found in most; probably only about 20% of Hunter patients have complete deletion or gross structural alteration of the IDS gene. The broad clinical variability among Hunter patients is apparently a reflection of extensive genetic heterogeneity. Flomen et al. (1993) reported the structure of the IDS gene which contains 9 exons (designated A to I) and 8 introns (designated 1 to 8). They characterized the intron sequences surrounding the 9 exons. They found that the IDS gene bears no relationship to the exon organization of steroid sulfatase (308100), despite the homology between these 2 proteins. This suggested that the division of the sulfatases into 2 subgroups on the basis of substrate specificity is also reflected at the level of gene structure. Wilson et al. (1993) provided the complete sequence of the IDS gene which spans approximately 24 kb. The potential promoter for IDS lacks a TATA box but contains GC box consensus sequences, consistent with its role as a housekeeping gene. The methylation pattern of CpG sites of a housekeeping gene correlates with the likelihood of mutation. More than 35% of the separate point mutations in the IDS gene causing MPS II are found in CpG sites as transitional events. To gain insight into the relationship between methylation status and CpG hotspot mutations, Tomatsu et al. (2004) investigated patterns of cytosine methylation in the entire IDS gene, except for introns 4-8. Bisulfite genomic sequencing was performed on the normal leukocyte DNA. The data showed that: (1) cytosine methylation at the CpG sites was extensive, except for those present from the promoter region to a portion of intron 3; (2) a sharp boundary of methylated-nonmethylated regions was observed at the 5-prime flanking region, whereas a gradual change in methylation was observed in the 2.0-kb segment in the 3-prime flanking region; (3) the boundary of the 5-prime flanking region contained multiple SP1 (189906) sites and the TATA box; (4) the CpG sites in exons 1 and 2 were hypomethylated and were associated only with rare transitional mutations, and although the CpG sites in exon 3 were also hypomethylated, they were associated with a high rate of transitional mutations; (5) there was no striking sex difference in the methylation patterns in active alleles; and, (6) the methylation in both strands was symmetrical, except at the boundary of methylated-unmethylated regions. #### GENOTYPE/PHENOTYPE CORRELATIONS Neufeld (1987) suggested that for the sake of simplicity the enzyme deficient in this disorder be termed iduronate sulfatase. Complementation of the X-linked and 'autosomal' forms of MPS II by cell fusion has not been reported. Indeed, it seems likely that all cases of presumed autosomal Hunter syndrome (iduronate sulfatase deficiency) in fact represent cases of multiple sulfatase deficiency (Burk et al., 1981). In analyzing 5 samples of families with MPS II, with a total of 158 cases, Machill et al. (1991) found that the mutant allele segregated in agreement with mendelian expectations for an X-linked recessive disorder, but the proportion of sporadic cases was significantly lower than expected under mutation-selection equilibrium. Heterogeneity among the samples was evident but was caused entirely by a sample of Ashkenazi families, in which the segregation pattern had previously been interpreted as suggesting prenatal selection in favor of the pathologic allele. In their analysis of the 5 samples by a maximum likelihood approach, Machill et al. (1991) found no suggestion of segregation distortion. The apparent deficiency of sporadic cases might be due to ascertainment bias. In Ashkenazi Jews in Israel, Zlotogora et al. (1985) found no new mutations among the mothers of probands. Furthermore, they found a striking deviation in segregation of the Hunter and normal alleles in heterozygous females, with favoring of the former. In non-Ashkenazi populations, the rate of new mutations and the segregation ratio have been close to those expected (Archer et al., 1983; Tonnesen, 1984). Zlotogora et al. (1991) reported that 10 of the 12 Jewish families with Hunter syndrome in Israel were of Ashkenazi or Moroccan origin. They provided further evidence that in these families there is a paucity of new mutations and they confirmed the significant deviation of the segregation ratio between the Hunter gene and the normal allele among the offspring of heterozygous mothers and among the sibs of affected children. Selection in favor of the X chromosome carrying the Hunter allele was suggested. It has apparently not been observed in other ethnic groups. The explanation may lie in another closely linked gene such that the phenomenon is particular to the Jewish population. Another possibility is that the mutation itself gives an advantage to that chromosome. In 2 unrelated patients with complete deletion of the IDS gene, Wraith et al. (1991) reported that the phenotype was that of very severe Hunter syndrome. In addition, both had features not commonly seen in MPS II, namely, early onset of seizures in one patient and ptosis in the other. Clarke et al. (1990) described clinically and biochemically typical Hunter syndrome in a karyotypically normal girl. Cross-correction with fibroblasts of a classic male patient did not occur. In a second report, Clarke et al. (1990) presented evidence they interpreted as indicating that in this patient the maternal X chromosome was selectively inactivated, whereas presumably the paternal X chromosome carried a mutation for this disorder. The critical evidence was provided by somatic cell hybrid clones produced by fusion of the patient's fibroblasts with HPRT-negative hamster fibroblasts and grown in HAT-ouabain medium to select for hybrids containing at least one active human X chromosome. Clarke et al. (1991) presented further evidence in support of this hypothesis. As reviewed below, a number of point mutations have been found in the IDS gene in patients with the Hunter syndrome. Froissart et al. (1993) described 2 patients who appeared to have complete deletion of the IDS gene. It appeared that these patients had a more severe form of Hunter syndrome. From a study of a total of 26 cases, Bunge et al. (1993) found that about 20% of patients have deletions of the whole IDS gene or other major structural alterations. In about 23% of cases, deletion of 1, 2, or 3 basepairs was found, while the remaining patients, about 57%, carried point mutations predicting amino acid replacement, premature termination of translation, or aberrant splicing. Hopwood et al. (1993) reviewed mutations in the IDS gene in Hunter syndrome. From the group of 319 patients thus far studied by Southern analysis, 14 had full deletion of the gene and 48 had partial deletion or other gross rearrangements. All patients with full deletions or gross rearrangements had severe clinical presentations. In a total of 32 patients, 29 different 'small' mutations had been characterized: 4 nonsense and 13 missense mutations, 7 different small deletions from 1 to 3 bp, with most leading to a frameshift and premature chain termination, and 5 different splice site mutations also leading to small insertions or deletions in the mRNA. A 60-bp deletion that resulted from the creation of a new donor splice site was observed in 5 unrelated patients with relatively mild clinical phenotypes. As a means of molecular diagnosis, Jonsson et al. (1995) developed a rapid method to sequence the entire iduronate 2-sulfatase coding region: PCR amplicons representing the IDS cDNA were sequenced with an automatic machine, and output was analyzed by computer-assisted interpretation of tracings. Mutations were found in 10 of 11 patients studied. Unique missense mutations were identified in 5 patients. Bondeson et al. (1995) identified a second IDS locus (designated IDS2 by them) located within 90 kb telomeric of the IDS gene. They showed that this region is involved in a recombination event with the primary IDS gene in about 13% of patients with the Hunter syndrome. Analysis of the resulting rearrangement at the molecular level showed that these patients had suffered a recombination event that resulted in a disruption of the IDS gene in intron 7 with an inversion of the intervening DNA. All 6 patients with a similar type of rearrangement showed recombination between intron 7 of the IDS gene and sequences close to exon 3 of the IDS2 locus, implying that these regions are hotspots for recombination. Nucleotide sequencing showed that the inversion is caused by recombination between homologous sequences present in the IDS gene and the IDS2 locus. No detectable deletions or insertions were observed as a consequence of the recombination. The IDS2 gene, presumably a pseudogene, contains sequences that are related to exons 2 and 3 as well as introns 2, 3, and 7 of the IDS gene. The only example of a similar inversion caused by homologous recombination may be that involving intron 22 of the factor VIII gene causing severe hemophilia A (306700). In the case of the F8 gene, the inversions occur almost exclusively in the male germ cells. It has therefore been hypothesized that mispairing leading to inversion is inhibited by pairing of the X chromosomes in the female germ cells. Interestingly, both the F8 gene and the IDS gene are located in Xq28, a distal part of the X chromosome that is generally unpaired in males. Bondeson et al. (1995) provided additional information concerning the IDS2 gene. Birot et al. (1996) described a patient with Hunter syndrome in whom an exchange between the IDS gene and pseudogene through interchromosomal recombination had apparently caused internal deletion of exons 4, 5, 6, and 7. In the rearranged gene, the junction intron contained pseudogene intron 3- and intron 7-related sequences. Malmgren et al. (1995) was able to identify, in addition to the previously reported 2.3-kb cDNA clone that contains the entire coding sequence of IDS, a 1.4-kb transcript that may encode an IDS-like enzyme. The predicted protein is identical to the previously described enzyme, except for the absence of a 207-amino acid COOH-terminal domain, which is replaced by 7 amino acids. They suggested that an additional form of the IDS enzyme may exist in humans and may have implications for the pathogenesis of the Hunter syndrome and the observed clinical heterogeneity. Sukegawa et al. (1995) described 8 new examples of point mutations in the IDS gene in Japanese Hunter syndrome patients exhibiting various degrees of severity. Rathmann et al. (1996) identified IDS mutations in 31 families/patients with MPS II. Twenty mutations were novel and unique and another was novel but was found in 3 unrelated patients. One of the mutations detected was of special interest as it is an A-to-G substitution in an intron far from the coding region that is deleterious because it creates a new 5-prime splice donor site that results in the inclusion of a 78-bp intronic sequence (309900.0014). The authors analyzed a total of 101 point mutations in the coding region and found that they tended to be more frequent in exons III, VIII, and IX. CpG dinucleotides were involved in 47% of the point mutations, of which G:C-to-A:T transitions constituted nearly 80%. Almost all recurrent point mutations involved CpG sites. Analysis of a collection of 50 families studied by this group revealed that mutations occurred more frequently in male meioses; they estimated the male-to-female ratio to be between 3.76 and 6.3. Steen-Bondeson et al. (1992) investigated the occurrence of rearrangements and deletions of the IDS gene in a Southern analysis of 46 unrelated MPS2 patients of different ethnic origins using a cDNA clone containing the entire IDS gene as a probe. Structural alterations were found in DNA from 9 patients, 2 of whom showed large deletions including all coding sequences of the gene. The distal and proximal breakpoints of these deletions were determined by hybridization of markers flanking the IDS gene. Seven of the observed alterations constituted major rearrangements of the gene. Six of these rearrangements showed similar or identical patterns by Southern analysis, suggestive of a region prone to structural alterations within the IDS gene. Steen-Bondeson et al. (1992) also demonstrated the potential use of the IDS probe for carrier detection in families with a rearranged IDS gene. They also described a contiguous gene deletion syndrome characterized by Hunter syndrome and epilepsy. The patient showed classic severe phenotype of Hunter syndrome and in addition suffered from epileptic seizures. Epilepsy had been described in 2 patients reported by Wilson et al. (1991) and Wraith et al. (1991), with a complete deletion of the gene. Froissart et al. (1997) found evidence of germline and somatic mosaicism in the mother of a boy with the arg443-to-ter mutation (309900.0001). The mutation was found in a varying proportion of tissues tested (7% in leukocytes, lymphocytes and lymphoblastoid cells, and 22% in fibroblasts). The proband's sister carried the 'at risk' allele (as determined by haplotype analysis), but not the mutation. In sporadic cases of X-linked diseases, germline mosaicism of the proband's mother is difficult to exclude and should be considered in genetic counseling. Patients with complete deletion of the IDS locus often have atypical phenotypes, including ptosis, obstructive sleep apnea, and seizures (Wraith et al., 1991; Froissart et al., 1993). In approximately 13% of patients with Hunter syndrome, the mutation consists of a homologous recombination event between the IDS gene and an adjacent unexpressed IDS pseudogene, resulting in disruption of the IDS gene in intron 7 and an inversion of the intervening DNA (Bondeson et al., 1995). These individuals have a severe MPS-II phenotype with no variant symptoms. Timms et al. (1997) used genomic DNA sequencing to identify several new genes in the IDS region. DNA deletion patients with atypical symptoms were analyzed to determine whether these atypical symptoms could be due to involvement of these other loci. The occurrence of seizures in 2 individuals correlated with a deletion extending proximal to IDS, up to and including part of the FMR2 locus (309548). Other (nonseizure) symptoms were associated with distal deletions. In addition, a group of patients with no variant symptoms, and a characteristic rearrangement involving a recombination between the IDS gene and an adjacent IDS pseudogene, showed normal expression of loci distal to IDS. Timms et al. (1997) concluded that together, these results identified FMR2 as a candidate gene for seizures, when mutated along with IDS. Karsten et al. (1997) noted that the region of the IDS gene, in addition to the IDS2 gene that harbors sequences homologous to exons 2 and 3 and introns 2, 3, and 7, contains several novel genes (e.g., genes W, X, and Y). In addition, a neighboring region has undergone a duplication and exists in an inverted version on the telomeric side of IDS. Karsten et al. (1997) identified 2 distinct deletions separated by 30 kb in a patient with Hunter syndrome. One deletion included exons 5 and 6 of the IDS gene; the second deletion included exons 3 and 4 of the W gene, located telomeric of the IDS gene. Both deletions were the result of nonhomologous (illegitimate) recombination events between short direct repeats at the deletion breakpoints. Lagerstedt et al. (2000) analyzed a 43.6-kb deletion in a patient with Hunter syndrome and found a fusion transcript including sequences from the gene W and the IDS gene. Surprisingly, a similar but longer fusion transcript containing exons 2-4 of gene W and exons 4-9 of the IDS gene could be detected in RNA of normal cell lines originating from various tissues. Timms et al. (1998) described a patient with features of moderate to severe Hunter syndrome and a 178-bp deletion upstream of IDS exon 1 spanning a predicted promoter element. Sequencing of all 9 IDS exons failed to show any additional mutations within the coding region or in intron/exon boundaries. The 178-bp deletion was flanked by 2 13-bp direct repeats and potential DNA topoisomerase II recognition sites. These findings suggested to Timms et al. (1998) nonhomologous recombination as a possible mechanism for the deletion. Expression studies detected no IDS transcripts. Froissart et al. (1998) studied 70 unrelated Hunter patients and found a mutation in each. There was striking molecular heterogeneity. Large gene rearrangements were identified in 14 patients. In the 56 other patients, 43 different mutations were identified, and 31 had not previously been described. Since only a few mutations were present in several patients, genotype/phenotype correlations were difficult. The mother was not found to be a carrier in 5 among 44 sporadic cases. Haplotype analysis demonstrated a high frequency of mutations in male meiosis. Isogai et al. (1998) characterized 25 different small mutations in the IDS gene in a series of 43 Japanese patients with Hunter disease. As in other series, 3 different mutations in codon 468 of exon 9 were found: arg468 to trp (309900.0012), arg468 to gln (309900.0013), arg468 to leu (309900.0015). All 3 mutations were associated with a severe phenotype. In a study of 31 Spanish families with Hunter disease, Gort et al. (1998) found 22 novel small mutations (7 reported previously by the same group) and 4 large deletions or rearrangements. This brought the number of separate IDS mutations that had been reported to that time to nearly 150. Li et al. (1999) provided yet more evidence of the molecular heterogeneity of this condition by identifying 17 mutations in 18 unrelated patients with MPS2. The mutations included 7 missense mutations, 5 small deletions, 2 insertions, 2 splice site mutations, and an intragenic deletion of exons 4, 5, 6, and 7. Nine of the small mutations were novel. In 36 Russian patients with Hunter syndrome, Karsten et al. (1998) found 25 different mutations, of which 15 were novel. Most of the missense mutations resulted in intermediate or severe phenotypes. #### DIAGNOSIS Tonnesen et al. (1983) found that cross-correction between the 2 cell populations of the Hunter syndrome heterozygote is inhibited by fructose 1-phosphate or mannose 6-phosphate. Intercellular uptake of lysosomal enzymes in cultured fibroblasts is prevented by addition of either mannose-6-phosphate or fructose-1-phosphate to the culture medium. They studied 25 obligatory carriers to determine the usefulness of fructose 1-phosphate as a means of carrier detection. In 23 carriers, (35)S-sulfate incorporation was significantly increased. In 1 carrier, incorporation was already increased before addition of fructose and in 1 carrier it was normal both before and after fructose. Tonnesen (1984) identified Hunter carriers by studying (35)S-sulfate accumulation in the presence and absence of fructose-1-phosphate. Petruschka et al. (1983) tested the Tonnesen technique by studying various mixtures of normal and Hunter cells in culture as well as obligatory carriers. They concluded that the method 'seems to be suitable for carrier detection.' Archer et al. (1983) concluded that carrier detection was best when hair-root analysis and serum enzyme levels were taken together. Daniele and Di Natale (1987) demonstrated crossreacting material in the serum and fibroblasts of Hunter patients. Zlotogora and Bach (1986) proposed that prenatal diagnosis of Hunter syndrome may be possible by measurement of iduronate sulfatase in the mother's serum. The level of IDS consistently rises in the serum of pregnant women. In pregnancies with Hunter-affected male fetuses, serum enzyme levels did not change. The normal increase occurs usually by the 6th to 12th week. Bakker et al. (1991) found that the IDS cDNA probe was partially deleted in 3 of 12 Dutch patients with Hunter syndrome. In 2 of the 3 patients, Southern blots showed the presence of a deletion junction fragment which could be used for highly reliable direct carrier detection in their families. Schroder et al. (1993) used different carrier detection tests, i.e., IDS activity in serum, sulfate incorporation in cultured skin fibroblasts, and RFLP analysis, in 13 unrelated families with 16 patients and 36 females at risk for MPS II. Twenty-nine females were confirmed as carriers, and in 5 women, the heterozygous state was excluded. The use of the intragenic IDS cDNA probes and flanking probes provided accuracy in carrier detection that was equal to or better than biochemical methods. Structural alterations were found in the DNA of 2 patients: one showed a major deletion including the whole coding sequence of the IDS gene; an aberrant Southern fragment occurred in the HindIII/pc2S15 blot of the other patient, suggesting a new HindIII restriction site by point mutation in an IDS gene intron. Ben Simon-Schiff et al. (1993) confirmed the reliability of the serum assay of IDS activity in the identification of heterozygotes; the serum test correctly detected 11 of 12 of the first-degree relatives tested by the serum assay, 6 of 7 carriers, and 5 of 5 noncarriers. The only case with an apparent false negative result in the serum test was thought to represent an instance of germinal mosaicism. In a family in which there was no surviving affected individual, Timms et al. (1998) described carrier testing using direct dye primer sequencing of PCR products to identify mixed bases in an obligate carrier. Two mixed bases were observed within exon 8 of the IDS gene. These resulted in a missense mutation and a nonsense mutation. Four additional female family members were screened for the same mutations, and none were found in any of these additional subjects, including in 1 who had been identified previously as a carrier by skin biopsy. Timms et al. (1998) concluded that this approach can be used to provide unambiguous information about a subject's carrier status, even in families in which the disorder is mild. #### CLINICAL MANAGEMENT Braun et al. (1993) tested in vitro the correction of the enzyme defect in the Hunter syndrome, using an amphotropic retroviral vector containing the human IDS coding sequence. Lymphoblastoid cell lines from patients with Hunter syndrome were transduced with the vector and expressed high levels of IDS enzyme activity, 10- to 70-fold higher than normal human peripheral blood leukocytes or lymphoblastoid cell lines. The transduced cells failed to show accumulation of (35)SO4 into glycosaminoglycan, indicating that recombinant IDS enzyme participated in glycosaminoglycan metabolism. Vellodi et al. (1999) reported the results of bone marrow transplantation performed in 10 patients with Hunter disease. The donor was an HLA-identical sib in 2 cases, an HLA-nonidentical relative in 6 cases, and a volunteer unrelated donor in 1 case. Details were not available in the last case. Only 3 patients had survived for more than 7 years post bone marrow transplant; of those, 1 died 11 years after bone marrow transplant. The authors suggested that this high mortality probably resulted from poor donor selection. In 2 who had survived long-term, there had been a steady progression of physical disability and mental handicap. One patient had maintained normal intellectual development, with only mild physical disability. #### POPULATION GENETICS Schaap and Bach (1980) reported a frequency of approximately 1 in 34,000 males born in Israel between 1967 and 1975. In a questionnaire study in the United Kingdom, Young and Harper (1982) estimated the frequency of the Hunter syndrome as about 1 in 132,000 male births. The severe form was 3.38 times more frequent than the mild form. No increased incidence in Jews was noted. In British Columbia, 6 cases of the Hunter syndrome were born between 1952 and 1986, giving a frequency of 1 in 110,950 live male births (Lowry et al., 1990). Chakravarti and Bale (1983) concluded that the high frequency of Hunter disease in Israeli Jews (Goodman, 1979) is compatible with genetic drift. Using multiple ascertainment sources, Nelson et al. (2003) estimated the incidence rate for mucopolysaccharidoses in western Australia for the period 1969 to 1996. An incidence of approximately 1 in 320,000 live births (1 in 165,000 male live births) was obtained for Hunter syndrome. #### ANIMAL MODEL Faust et al. (1992) and Daniele et al. (1993) demonstrated that the homologous Ids gene in the mouse occupies the same position on the X chromosome in relation to the FMR1 (309550), F9 (306900), and GABRA3 (305660) genes. Wilkerson et al. (1998) described Hunter syndrome in a Labrador retriever. The findings included coarse facial features, macrodactyly, unilateral corneal dystrophy (an atypical feature for type II mucopolysaccharidosis), generalized osteopenia, progressive neurologic deterioration, and a positive urine spot test for acid mucopolysaccharides. Deficiency in iduronate-2-sulfatase was demonstrated in cultured dermal fibroblasts. Hair root analysis for IDS showed that the dam (mother) was a carrier and that a phenotypically normal male littermate was normal. ### ALLELIC VARIANTS (selected examples) #### .0001 MUCOPOLYSACCHARIDOSIS TYPE II, INTERMEDIATE FORM [IDS, ARG443TER] In a 12-year-old Japanese boy with Hunter syndrome of intermediate severity, Sukegawa et al. (1992) found a C-to-T transition of nucleotide 1327 which resulted in substitution of a termination codon for the normal arginine at position 443 of the peptide sequence. Although the truncated enzyme protein was synthesized, it was unstable. Bunge et al. (1992) found the same mutation in a 3-year-old male (their H20). The patient had skeletal deformities but normal psychomotor development. Froissart et al. (1993) found the same mutation in 2 patients. #### .0002 MUCOPOLYSACCHARIDOSIS TYPE II [IDS, SER333LEU] Using PCR and chemical mismatch detection of amplified cDNA in the study of 6 patients with Hunter syndrome, Flomen et al. (1992) identified one patient with a complete deletion of the IDS gene, a second patient with a nonsense mutation, a third patient with a point mutation that created a novel splice site, and 3 missense mutations. Their patient 4 had a C-to-T transition at nucleotide 1122 resulting in substitution of leucine for serine-333 which is a conserved residue within a region of homology among sulfatases. #### .0003 MUCOPOLYSACCHARIDOSIS TYPE II [IDS, TRP502SER] In their patient 5, Flomen et al. (1992) found a G-to-C transversion at nucleotide 1629 which resulted in the substitution of serine for tryptophan-502 and the introduction of a small polar side chain in a hydrophobic domain. #### .0004 MUCOPOLYSACCHARIDOSIS TYPE II [IDS, PRO160ARG] In their patient 6, Flomen et al. (1992) found a C-to-G transversion in nucleotide 603 which resulted in substitution of arginine for proline-160. #### .0005 MUCOPOLYSACCHARIDOSIS TYPE II [IDS, ARG172TER] In their patient 2, Flomen et al. (1992) identified, by the chemical mismatch detection method, a C-to-T transition at nucleotide 638, converting arginine 172 to a stop codon. #### .0006 MUCOPOLYSACCHARIDOSIS TYPE II [IDS, 60-BP DEL] In their patient 3, Flomen et al. (1992) found in genomic DNA a C-to-T transition at nucleotide 1246, which produced no change in the sense of the codon, i.e., was silent, but created a cryptic donor splice site leading to partial loss of an exon. Sixty basepairs were lost from the cDNA, from G1244 to G1305. #### .0007 MUCOPOLYSACCHARIDOSIS TYPE II [IDS, DEL] In an 8.5-year-old boy with such severe Hunter syndrome that bladder and bowel control was never achieved, chronic diarrhea was a major problem, and speech was limited and delayed in development, Beck et al. (1992) demonstrated complete lack of the IDS coding sequences and the simultaneous deletion of both DXS466 and DXS304, 2 loci mapped probably not more than 900 kb from the IDS locus. By following the segregation of an RFLP at the IDS locus, Beck et al. (1992) found that the deletion probably occurred in the germ cells of the patient's maternal grandfather. The 2 patients with IDS deletion reported by Wraith et al. (1991) likewise had severe expression of the disease with epileptic seizures and profound mental retardation; they never attained speech. Ptosis was present in 1 of the 2 patients of Wraith et al. (1991) but was not present in the second patient or in the patient reported by Beck et al. (1992) with deletion of IDS. In an addendum, Beck et al. (1992) cited their results suggesting that DXS466 lies within an intron in the 5-prime half of the IDS gene. #### .0008 MUCOPOLYSACCHARIDOSIS TYPE II [IDS, CYS422GLY] In an 8-year-old patient with very mild manifestations of Hunter syndrome and normal intelligence, Bunge et al. (1992) identified a TGC-to-GGC transversion of codon 422 resulting in the substitution of glycine for cysteine. #### .0009 MUCOPOLYSACCHARIDOSIS TYPE II [IDS, LYS135ARG] In a 5-year-old patient with typical features of Hunter syndrome and decline in ability to speak, Bunge et al. (1992) identified an AAA-to-AGA transition in codon 135 resulting in substitution of arginine for lysine. In addition, a silent ACC-to-ACT change was found at codon 146. #### .0010 MUCOPOLYSACCHARIDOSIS TYPE II [IDS, TRP475TER] In a 20-year-old patient with typical features of MPS II and 'still able to talk,' Bunge et al. (1992) identified a TGG-to-TGA change in codon 475 converting the trp codon to a stop codon. #### .0011 MUCOPOLYSACCHARIDOSIS TYPE II [IDS, 2-BP DEL, CODON 170] In an 8-year-old patient with typical features of Hunter syndrome and attendance at a special school, Bunge et al. (1992) identified a deletion of 2 bp (CA) from codon 170 (ACA). The deletion resulted in a frameshift with 27 altered amino acids and a premature chain termination. #### .0012 MUCOPOLYSACCHARIDOSIS TYPE II, MILD FORM [IDS, ARG468TRP] By direct sequencing of RT-PCR products, Crotty et al. (1992) identified a C-to-T transition at nucleotide 1402 leading to a replacement of arginine-468 by tryptophan (R468W). The mutation abolished an MspI restriction site, thus allowing confirmation of the mutant sequence and analysis in family members. The mother was shown to be heterozygous; her serum IDS enzyme activity had previously been shown to be in the heterozygote range. The proband had mild Hunter syndrome. The diagnosis was first suggested at the age of 2.3 years and confirmed by measurement of elevated urinary glycosaminoglycan excretion and absence of serum IDS enzyme activity. At age 2.9 years, the child's IQ was 115; the patient was 5 years old at the time of the report. #### .0013 MUCOPOLYSACCHARIDOSIS TYPE II, SEVERE FORM [IDS, ARG468GLN] Although the arg468-to-trp mutation (309900.0012) was associated with a mild form of MPS II, Whitley et al. (1993) found very severe manifestations in a boy who was found to have a mutation in the same codon: a G-to-A transition in nucleotide 1403 resulted in substitution of glutamine for arginine-468. In a note added in proof, it was reported that fibroblast cultures showed a large acrocentric supernumerary marker chromosome which presumably was responsible for the quantitatively and qualitatively atypical features of the proband's face. The proband died at the age of 23 months. Sukegawa et al. (1997) described the findings in a girl with Hunter syndrome of severe type. She had a normal karyotype but a marked deficiency of iduronate-2-sulfatase activity in lymphocytes and cultured fibroblasts. The common R468Q mutation was identified in the IDS gene. RT-PCR showed her cDNA to represent only the R468Q allele, although at the genomic level she was heterozygous, with one normal allele. The brother had the R468Q mutation, and her mother was a carrier of this mutation. In genomic DNA from the patient's fibroblasts, only the paternal allele of the androgen receptor gene, a gene subjected to differential methylation of the inactive X chromosome, was methylated. These findings were interpreted as indicating that the severe form of Hunter disease in this girl was the result of selective expression of the maternal allele carrying the missense mutation R468Q, which in turn resulted from skewed X inactivation of the paternal nonmutant X chromosome. #### .0014 MUCOPOLYSACCHARIDOSIS TYPE II, MILD FORM [IDS, 78-BP INS] Rathmann et al. (1996) detected a splice site mutation in a 6-year-old boy presenting with a mild course of mucopolysaccharidosis type II. Screening for mutations by amplification of single exons and SSCP did not reveal any aberration; however, analysis of the 3-prime half of the IDS mRNA by agarose gel electrophoresis detected bands of 3 different sizes. The most abundant transcript was approximately 80 to 100 bp larger than the mRNA of an unaffected control. Furthermore, there was an apparently normal-sized fragment and a third abnormally small fragment of approximately 90 to 110 bp. Direct sequencing of the corresponding PCR-amplified cDNA fragments revealed that the largest message contained a 78-bp insertion between exons VII and VIII. The same 78-bp sequence was found in the smaller transcript, although in that case it was flanked by exons VII and IX of the IDS gene (i.e., exon VIII was skipped during splicing). The DNA fragment running a roughly equivalent distance as the normal-sized message in the agarose gel electrophoresis was considered most likely a heteroduplex formed by the 2 mRNA/cDNA species just mentioned, because only the larger and smaller fragments were detected. The presumed 3-prime acceptor splice consensus sequence (aggt) at the beginning of the 78-bp sequence was found to be unaltered, whereas an A-to-G transition was identified at the fifth nucleotide following the last base of the included sequence. This substitution created a new 5-prime splice donor site (aagtgaa-to-AAgtgag) and resulted in the inclusion of a 78-bp intronic sequence. Rathmann et al. (1996) suggested that neither translation product derived from the 2 alternative splice transcripts had IDS activity because each encoded a largely truncated IDS protein due to an early termination signal in the 78-bp inclusion. #### .0015 MUCOPOLYSACCHARIDOSIS TYPE II, SEVERE FORM [IDS, ARG468LEU ] Mutations at codon 468 (R468) have been noted in subjects of various ethnic origins (Crotty et al., 1992; Hopwood et al., 1993; Whitley et al., 1993). In a patient with a severe MPS II phenotype, Isogai et al. (1998) found a G-to-T transversion at nucleotide 1403, resulting in an arg468-to-leu amino acid substitution. In their series of Japanese patients, 5 (29%) of 17 patients with missense mutations had a change in codon R468. They demonstrated that the CpG dinucleotide at this site was methylated, suggesting that this R468 codon is a mutational hotspot. #### .0016 MUCOPOLYSACCHARIDOSIS TYPE II [IDS, 3-BP DEL, 473TCC] In a Japanese patient with a severe form of mucopolysaccharidosis type II, Sukegawa et al. (1995) described an in-frame deletion of 3 nucleotides, 473delTCC, in exon 3 of the IDS gene, resulting in the loss serine-117. Bonuccelli et al. (2001) studied the effects of this mutation by transient expression of the mutation in COS-7 cells. No significant IDS activity was identified. #### .0017 MUCOPOLYSACCHARIDOSIS TYPE II [IDS, MET488ILE, GLY489ALA ] Ricci et al. (2003) stated that more than 200 different mutations in the IDS gene had been reported. They described an Italian patient with Hunter syndrome who had 2 missense changes involving adjacent amino acids, met488 to ile (M488I) and gly489 to ala (G489A). In vitro expression by COS-7 cells confirmed the G489A mutation as causative. The M488I mutation was associated with residual activity. Although a cumulative effect of the 2 mutations could be excluded 'in vitro,' Ricci et al. (2003) were cautious about drawing a conclusion with regard to the possible role that the 2 mutations could have played 'in vivo' in modulating the phenotype of the patient. At the age of 23 years, the patient showed clinical manifestations of intermediate severity. ### SEE ALSO Bach et al. (1973); Booth and Nadler (1974); Brown et al. (1982); Cantz et al. (1970); Clarke et al. (1990); Danes and Bearn (1967); Dean et al. (1979); Gerich (1969); Kleijer et al. (1979); McKusick (1972); Nwokoro and Neufeld (1979); Ockerman and Kohlin (1968); Schachern et al. (1984); Tonnesen et al. (1982); Upadhyaya et al. (1985); Van Pelt (1960); Wehnert et al. (1992); Wiesmann et al. (1980); Yatziv et al. (1977); Young and Harper (1979); Yutaka et al. (1978); Zlotogora and Bach (1984) ### REFERENCES 1. Archer, I. M.; Young, I. D.; Rees, D. W.; Oladimeji, A.; Wusteman, F. S.; Harper, P. S. : Carrier detection in Hunter syndrome. Am. J. Med. Genet. 16: 61-69, 1983. PubMed ID : 6227239 2. Bach, G.; Eisenberg, F., Jr.; Cantz, M.; Neufeld, E. F. : The defect in the Hunter syndrome: deficiency of sulfoiduronate sulfatase. Proc. Nat. Acad. Sci. 70: 2134-2138, 1973. PubMed ID : 4269173 3. Bakker, E.; Kneppers, A.; Deutz-Terlouw, P.; Goor, J.; Poorthuis, B.; Kleyer, W.; Niermeijer, M.; Kamp, J.; Hopwood, J.; Ommen, G. : Partial gene deletions in 3 out of 12 Dutch Hunter patients: direct and indirect carrier detection by DNA-analysis. (Abstract) Cytogenet. Cell Genet. 58: 2055-2056, 1991. 4. Ballenger, C. E.; Swift, T. R.; Leshner, R. T.; El Gammal, T. A.; McDonald, T. F. : Myelopathy in mucopolysaccharidosis type II (Hunter syndrome). Ann. Neurol. 7: 382-385, 1980. PubMed ID : 6769383 5. Beck, M.; Steglich, C.; Zabel, B.; Dahl, N.; Schwinger, E.; Hopwood, J. J.; Gal, A. : Deletion of the Hunter gene and both DXS466 and DXS304 in a patient with mucopolysaccharidosis type II. Am. J. Med. Genet. 44: 100-103, 1992. PubMed ID : 1355630 6. Ben Simon-Schiff, E.; Bach, G.; Zlotogora, J.; Abeliovich, D. : Combined enzymatic and linkage analysis for heterozygote detection in Hunter syndrome: identification of an apparent case of germinal mosaicism. Am. J. Med. Genet. 47: 837-842, 1993. PubMed ID : 7904121 7. Berg, K.; Danes, B. S.; Bearn, A. G. : The linkage relation of the loci for the Xm serum system and the X-linked form of Hurler's syndrome (Hunter's syndrome). Am. J. Hum. Genet. 20: 398-401, 1968. PubMed ID : 4969416 8. Birot, A.-M.; Bouton, O.; Froissart, R.; Maire, I.; Bozon, D. : IDS gene-pseudogene exchange responsible for an intragenic deletion in a Hunter patient. Hum. Mutat. 8: 44-50, 1996. PubMed ID : 8807335 9. Birot, A. M.; Delobel, B.; Gronnier, P.; Bonnet, V.; Maire, I.; Bozon, D. : A 5-megabase familial deletion removes the IDS and FMR-1 genes in a male Hunter patient. Hum. Mutat. 7: 266-268, 1996. PubMed ID : 8829661 10. Bondeson, M.-L.; Dahl, N.; Malmgren, H.; Kleijer, W. J.; Tonnesen, T.; Carlberg, B.-M.; Pettersson, U. : Inversion of the IDS gene resulting from recombination with IDS-related sequences is a common cause of the Hunter syndrome. Hum. Molec. Genet. 4: 615-621, 1995. PubMed ID : 7633410 11. Bondeson, M.-L.; Malmgren, H.; Dahl, N.; Carlberg, B.-M.; Pettersson, U. : Presence of an IDS-related locus (IDS2) in Xq28 complicates the mutational analysis of Hunter syndrome. Europ. J. Hum. Genet. 3: 219-227, 1995. PubMed ID : 8528670 12. Bonuccelli, G.; Di Natale, P.; Corsolini, F.; Villani, G.; Regis, S.; Filocamo, M. : The effect of four mutations on the expression of iduronate-2-sulfatase in mucopolysaccharidosis type II. Biochim. et Biophys. Acta 1537: 233-238, 2001. 13. Booth, C. W.; Nadler, H. L. : Demonstration of the heterozygous state in Hunter's syndrome. Pediatrics 53: 396-399, 1974. PubMed ID : 4273646 14. Braun, S. E.; Aronovich, E. L.; Anderson, R. A.; Crotty, P. L.; McIvor, R. S.; Whitley, C. B. : Metabolic correction and cross-correction of mucopolysaccharidosis type II (Hunter syndrome) by retroviral-mediated gene transfer and expression of human iduronate-2-sulfatase. Proc. Nat. Acad. Sci. 90: 11830-11834, 1993. PubMed ID : 8265633 15. Broadhead, D. M.; Kirk, J. M.; Burt, A. J.; Gupta, V.; Ellis, P. M.; Besley, G. T. N. : Full expression of Hunter's disease in a female with an X-chromosome deletion leading to non-random inactivation. Clin. Genet. 30: 392-398, 1986. PubMed ID : 3100113 16. Brown, F. R., III; Hall, C. W.; Neufeld, E. F.; Munoz, L. L.; Braine, H.; Andrzejewski, S.; Camargo, E. E.; Mark, S. A.; Richard, J. M.; Moser, H. W. : Administration of iduronate sulfatase by plasma exchange to patients with the Hunter syndrome: a clinical study. Am. J. Med. Genet. 13: 309-318, 1982. PubMed ID : 6817638 17. Bunge, S.; Steglich, C.; Beck, M.; Rosenkranz, W.; Schwinger, E.; Hopwood, J. J.; Gal, A. : Mutation analysis of the iduronate-2-sulfatase gene in patients with mucopolysaccharidosis type II (Hunter syndrome). Hum. Molec. Genet. 1: 335-339, 1992. PubMed ID : 1303211 18. Bunge, S.; Steglich, C.; Zuther, C.; Beck, M.; Morris, C. P.; Schwinger, E.; Schinzel, A.; Hopwood, J. J.; Gal, A. : Iduronate-2-sulfatase gene mutations in 16 patients with mucopolysaccharidosis type II (Hunter syndrome). Hum. Molec. Genet. 2: 1871-1875, 1993. PubMed ID : 8281149 19. Burk, R.; Valle, D.; Thomas, G.; Moser, A.; Moser, H.; Rosenbaum, K.; Schmid, K. : Multiple sulfatase deficiency (MSD): clinical and biochemical studies in two patients. (Abstract) Am. J. Hum. Genet. 33: 73A only, 1981. 20. Cantz, M.; Chrambach, A.; Neufeld, E. F. : Characterization of the factor deficient in the Hunter syndrome by polyacrylamide gel electrophoresis. Biochem. Biophys. Res. Commun. 39: 936-942, 1970. PubMed ID : 4987382 21. Chakravarti, A.; Bale, S. J. : Differences in the frequency of X-linked deleterious genes in human populations. Am. J. Hum. Genet. 35: 1252-1257, 1983. PubMed ID : 6418001 22. Chase, D. S.; Morris, A. H.; Ballabio, A.; Pepper, S.; Giannelli, F.; Adinolfi, M. : Genetics of Hunter syndrome: carrier detection, new mutations, segregation and linkage analysis. Ann. Hum. Genet. 50: 349-360, 1986. PubMed ID : 3126700 23. Clarke, J. T. R.; Greer, W. L.; Strasberg, P. M.; Pearce, R. D.; Skomorowski, M. A.; Ray, P. N. : Hunter disease (mucopolysaccharidosis type II) associated with unbalanced inactivation of the X chromosomes in a karyotypically normal girl. Am. J. Hum. Genet. 49: 289-297, 1991. PubMed ID : 1678247 24. Clarke, J. T. R.; Pearce, R. D.; Greer, W. L.; Strasberg, P.; Ray, P. N. : Hunter disease (MPS, type II) in a karyotypically normal girl associated with selective X-chromosome inactivation. (Abstract) Am. J. Hum. Genet. 47 (suppl.): A52 only, 1990. 25. Clarke, J. T. R.; Willard, H. F.; Teshima, I.; Chang, P. L.; Skomorowski, M. A. : Hunter disease (mucopolysaccharidosis type II) in a karyotypically normal girl. Clin. Genet. 37: 355-362, 1990. PubMed ID : 2112988 26. Clarke, J. T. R.; Wilson, P. J.; Morris, C. P.; Hopwood, J. J.; Richards, R. I.; Sutherland, G. R.; Ray, P. N. : Characterization of a deletion at Xq27-q28 associated with unbalanced inactivation of the nonmutant X chromosome. Am. J. Hum. Genet. 51: 316-322, 1992. PubMed ID : 1642233 27. Couillin, P.; Le Guern, E.; Ravise, N.; Grisard, M.-C.; Oostra, B. A.; Boue, A. : Strategy for constructing somatic hybrids isolating the two derivative chromosomes in X;autosome translocations: application to a female patient t(X;5) with Hunter syndrome. Ann. Genet. 33: 196-207, 1990. PubMed ID : 2128908 28. Crotty, P. L.; Braun, S. E.; Anderson, R. A.; Whitley, C. B. : Mutation R468W of the iduronate-2-sulfatase gene in mild Hunter syndrome (mucopolysaccharidosis type II) confirmed by in vitro mutagenesis and expression. Hum. Molec. Genet. 1: 755-757, 1992. PubMed ID : 1284597 29. Danes, B. S.; Bearn, A. G. : Hurler's syndrome: a genetic study of clones in cell culture with particular reference to the Lyon hypothesis. J. Exp. Med. 126: 509-522, 1967. PubMed ID : 4962269 30. Danes, B. S.; Bearn, A. G. : Hurler's syndrome: demonstration of an inherited disorder of connective tissue in cell culture. Science 149: 987-989, 1965. PubMed ID : 4953285 31. Daniele, A.; Di Natale, P. : Hunter syndrome: presence of material cross-reacting with antibodies against iduronate sulfatase. Hum. Genet. 75: 234-238, 1987. PubMed ID : 3104200 32. Daniele, A.; Faust, C. J.; Herman, G. E.; Di Natale, P.; Ballabio, A. : Cloning and characterization of the cDNA for the murine iduronate sulfatase gene. Genomics 16: 755-757, 1993. PubMed ID : 8325651 33. Dean, M. F.; Stevens, R. L.; Muir, H.; Benson, P. F.; Button, L. A.; Anderson, R. L.; Boylston, A.; Mowbray, J. : Enzyme replacement therapy by fibroblast transplantation: long term biochemical study in three cases of Hunter's syndrome. J. Clin. Invest. 63: 138-145, 1979. PubMed ID : 105013 34. DiFerrante, N. M.; Nichols, B. L., Jr. : A case of the Hunter syndrome with progeny. Johns Hopkins Med. J. 130: 325-328, 1972. PubMed ID : 4622960 35. Faust, C. J.; Verkerk, A. J. M. H.; Wilson, P. J.; Morris, C. P.; Hopwood, J. J.; Oostra, B. A.; Herman, G. E. : Genetic mapping on the mouse X chromosome of human cDNA clones for the fragile X and Hunter syndromes. Genomics 12: 814-817, 1992. PubMed ID : 1572654 36. Flomen, R. H.; Green, E. P.; Green, P. M.; Bentley, D. R.; Giannelli, F. : Determination of the organisation of coding sequences within the iduronate sulphate sulphatase (IDS) gene. Hum. Molec. Genet. 2: 5-10, 1993. PubMed ID : 8490623 37. Flomen, R. H.; Green, P. M.; Bentley, D. R.; Giannelli, F.; Green, E. P. : Detection of point mutations and a gross deletion in six Hunter syndrome patients. Genomics 13: 543-550, 1992. PubMed ID : 1639384 38. Froissart, R.; Blond, J.-L.; Maire, I.; Guibaud, P.; Hopwood, J. J.; Mathieu, M.; Bozon, D. : Hunter syndrome: gene deletions and rearrangements. Hum. Mutat. 2: 138-140, 1993. PubMed ID : 8318991 39. Froissart, R.; Maire, I.; Bonnet, V.; Levade, T.; Bozon, D. : Germline and somatic mosaicism in a female carrier of Hunter disease. J. Med. Genet. 34: 137-140, 1997. PubMed ID : 9039991 40. Froissart, R.; Maire, I.; Millat, G.; Cudry, S.; Birot, A.-M.; Bonnet, V.; Bouton, O.; Bozon, D. : Identification of iduronate sulfatase gene alterations in 70 unrelated Hunter patients. Clin. Genet. 53: 362-368, 1998. PubMed ID : 9660053 41. Gerich, J. E. : Hunter's syndrome: beta-galactosidase deficiency in skin. New Eng. J. Med. 280: 799-802, 1969. PubMed ID : 4975290 42. Goldenfum, S. L.; Young, E.; Michelakakis, H.; Tsagarakis, S.; Winchester, B. : Mutation analysis in 20 patients with Hunter disease. Hum. Mutat. 7: 76-78, 1996. PubMed ID : 8664909 43. Goodman, R. M. : Genetic Disorders among the Jewish People. Baltimore: Johns Hopkins Univ. Press (pub.) 1979. Pp. 458-470. 44. Gort, L.; Chabas, A.; Coll, M. J. : Hunter disease in the Spanish population: molecular analysis in 31 families. J. Inherit. Metab. Dis. 21: 655-661, 1998. PubMed ID : 9762601 45. Hobolth, N.; Pedersen, C. : Six cases of a mild form of the Hunter syndrome in five generations: three affected males with progeny. (Abstract) Clin. Genet. 13: 121 only, 1978. 46. Hopwood, J. J.; Bunge, S.; Morris, C. P.; Wilson, P. J.; Steglich, C.; Beck, M.; Schwinger, E.; Gal, A. : Molecular basis of mucopolysaccharidosis type II: mutations in the iduronate-2-sulphatase gene. Hum. Mutat. 2: 435-442, 1993. PubMed ID : 8111411 47. Isogai, K.; Sukegawa, K.; Tomatsu, S.; Fukao, T.; Song, X.-Q.; Yamada, Y.; Fukuda, S.; Orii, T.; Kondo, N. : Mutation analysis in the iduronate-2-sulphatase gene in 43 Japanese patients with mucopolysaccharidosis type II (Hunter disease). J. Inherit. Metab. Dis. 21: 60-70, 1998. PubMed ID : 9501270 48. Jonsson, J. J.; Aronovich, E. L.; Braun, S. E.; Whitley, C. B. : Molecular diagnosis of mucopolysaccharidosis type II (Hunter syndrome) by automated sequencing and computer-assisted interpretation: toward mutation mapping of the iduronate-2-sulfatase gene. Am. J. Hum. Genet. 56: 597-607, 1995. PubMed ID : 7887413 49. Karsten, S.; Voskoboeva, E.; Tishkanina, S.; Pettersson, U.; Krasnopolskaja, X.; Bondeson, M.-L. : Mutational spectrum of the iduronate-2-sulfatase (IDS) gene in 36 unrelated Russian MPS II patients. Hum. Genet. 103: 732-735, 1998. PubMed ID : 9921913 50. Karsten, S. L.; Lagerstedt, K.; Carlberg, B.-M.; Kleijer, W. J.; Zaremba, J.; Van Diggelen, O. P.; Czartoryska, B.; Pettersson, U.; Bondeson, M.-L. : Two distinct deletions in the IDS gene and the gene W: a novel type of mutation associated with the Hunter syndrome. Genomics 43: 123-129, 1997. PubMed ID : 9244428 51. Kleijer, W. J.; Mooy, P. D.; Liebaers, I.; van de Kamp, J. J. P.; Niermeijer, M. F. : Prenatal monitoring for the Hunter syndrome: the heterozygous female fetus. Clin. Genet. 15: 113-117, 1979. PubMed ID : 153809 52. Lagerstedt, K.; Carlberg, B.-M.; Karimi-Nejad, R.; Kleijer, W. J.; Bondeson, M.-L. : Analysis of a 43.6 kb deletion in a patient with Hunter syndrome (MPSII): identification of a fusion transcript including sequences from the gene W and the IDS gene. Hum. Mutat. 15: 324-331, 2000. PubMed ID : 10737977 53. Le Guern, E.; Couillin, P.; Oberle, I.; Ravise, N.; Boue, J. : More precise localization of the gene for Hunter syndrome. Genomics 7: 358-362, 1990. PubMed ID : 2114352 54. Li, P.; Bellows, A. B.; Thompson, J. N. : Molecular basis of iduronate-2-sulphatase gene mutations in patients with mucopolysaccharidosis type II (Hunter syndrome). J. Med. Genet. 36: 21-27, 1999. PubMed ID : 9950361 55. Lowry, R. B.; Applegarth, D. A.; Toone, J. R.; MacDonald, E.; Thunem, N. Y. : An update on the frequency of mucopolysaccharide syndromes in British Columbia. Hum. Genet. 85: 389-390, 1990. PubMed ID : 2118475 56. Lupski, J. R.; Garcia, C. A.; Zoghbi, H. Y.; Hoffman, E. P.; Fenwick, R. G. : Discordance of muscular dystrophy in monozygotic female twins: evidence supporting asymmetric splitting of the inner cell mass in a manifesting carrier of Duchenne dystrophy. Am. J. Med. Genet. 40: 354-364, 1991. PubMed ID : 1683155 57. Machill, G.; Barbujani, G.; Danieli, G. A.; Herrmann, F. H. : Segregation and sporadic cases in families with Hunter's syndrome. J. Med. Genet. 28: 398-401, 1991. PubMed ID : 1908009 58. Malmgren, H.; Carlberg, B.-M.; Pettersson, U.; Bondeson, M.-L. : Identification of an alternative transcript from the human iduronate-2-sulfatase (IDS) gene. Genomics 29: 291-293, 1995. PubMed ID : 8530090 59. McKusick, V. A. : Heritable Disorders of Connective Tissue. St. Louis: C. V. Mosby (pub.) (4th ed.) 1972. 60. Mochi, M.; Fadda, S.; Prosperi, L.; Sbarra, D.; Di Natale, P.; Ballabio, A.; Rocchi, M.; Romeo, G. : Linkage studies in Hunter families using X-linked DNA polymorphisms. (Abstract) Cytogenet. Cell Genet. 40: 700 only, 1985. 61. Mossman, J.; Blunt, S.; Stephens, R.; Jones, E. E.; Pembrey, M. : Hunter's disease in a girl: association with X:5 chromosomal translocation disrupting the Hunter gene. Arch. Dis. Child. 58: 911-915, 1983. PubMed ID : 6418082 62. Nelson, J.; Crowhurst, J.; Carey, B.; Greed, L. : Incidence of the mucopolysaccharidoses in western Australia. Am. J. Med. Genet. 123A: 310-313, 2003. 63. Neufeld, E. F. : Personal Communication. Bethesda, Md., 3/8/1981. 64. Neufeld, E. F. : Personal Communication. Los Angeles, Calif., 7/24/1987. 65. Neufeld, E. F.; Liebaers, I.; Epstein, C. J.; Yatsiv, S.; Milunsky, A.; Migeon, B. R. : The Hunter syndrome in females: is there an autosomal recessive form of iduronate sulfatase deficiency? Am. J. Hum. Genet. 29: 455-461, 1977. PubMed ID : 409284 66. Nwokoro, N.; Neufeld, E. F. : Detection of Hunter heterozygotes by enzymatic analysis of hair roots. Am. J. Hum. Genet. 31: 42-49, 1979. PubMed ID : 107796 67. Ochiai, T.; Ito, K.; Okada, T.; Chin, M.; Shichino, H.; Mugishima, H. : Significance of extensive Mongolian spots in Hunter's syndrome. Brit. J. Derm. 148: 1173-1178, 2003. PubMed ID : 12828746 68. Ockerman, P. A.; Kohlin, P. : Glycosidases in skin and plasma in Hunter's syndrome. Abnormality of a beta-galactosidase in skin. Acta Paediat. Scand. 57: 281-284, 1968. PubMed ID : 4236601 69. Palmieri, G.; Capra, V.; Romano, G.; D'Urso, M.; Johnson, S.; Schlessinger, D.; Morris, P.; Hopwood, J.; Di Natale, P.; Gatti, R.; Ballabio, A. : The iduronate sulfatase gene: isolation of a 1.2-Mb YAC contig spanning the entire gene and identification of heterogeneous deletions in patients with Hunter syndrome. Genomics 12: 52-57, 1992. PubMed ID : 1733863 70. Petruschka, L.; Machill, G.; Wehnert, M.; Seidlitz, G.; Knapp, A. : Reliability of the Tonnesen technique for the identification of Hunter carriers. Hum. Genet. 64: 404-406, 1983. PubMed ID : 6413387 71. Rathmann, M.; Bunge, S.; Beck, M.; Kresse, H.; Tylki-Szymanska, A.; Gal, A. : Mucopolysaccharidosis type II (Hunter syndrome): mutation 'hot spots' in the iduronate-2-sulfatase gene. Am. J. Hum. Genet. 59: 1202-1209, 1996. PubMed ID : 8940265 72. Ricci, V.; Filocamo, M.; Regis, S.; Corsolini, F.; Stroppiano, M.; Di Duca, M.; Gatti, R. : Expression studies of two novel in CIS-mutations identified in an intermediate case of Hunter syndrome. Am. J. Med. Genet. 120A: 84-87, 2003. 73. Roberts, S. H.; Upadhyaya, M.; Sarfarazi, M.; Harper, P. S. : Further evidence localizing the gene for Hunter syndrome to the most distal band of the X chromosome long arm. (Abstract) Cytogenet. Cell Genet. 46: 682 only, 1987. 74. Roberts, S. H.; Upadhyaya, M.; Sarfarazi, M.; Harper, P. S. : Further evidence localising the gene for Hunter's syndrome to the distal region of the X chromosome long arm. J. Med. Genet. 26: 309-313, 1989. PubMed ID : 2499679 75. Roberts, S. H.; Upadhyaya, M.; Sarfarazi, M.; Harper, P. S. : Further evidence localising the gene for Hunter syndrome to Xq28. (Abstract) J. Med. Genet. 25: 280 only, 1988. 76. Sapadin, A. N.; Friedman, I. S. : Extensive Mongolian spots associated with Hunter syndrome. J. Am. Acad. Derm. 39: 1013-1015, 1998. PubMed ID : 9843019 77. Schaap, T.; Bach, G. : Incidence of mucopolysaccharidoses in Israel: is Hunter disease a 'Jewish disease'? Hum. Genet. 56: 221-223, 1980. PubMed ID : 6821579 78. Schachern, P. A.; Shea, D. A.; Paparella, M. M. : Mucopolysaccharidosis I-H (Hurler's syndrome) and human temporal bone histopathology. Ann. Otol. Rhinol. Laryng. 93: 65-69, 1984. PubMed ID : 6422830 79. Schiro, J. A.; Mallory, S. B.; Demmer, L.; Dowton, S. B.; Luke, M. C. : Grouped papules in Hurler-Scheie syndrome. J. Am. Acad. Derm. 35: 868-870, 1996. PubMed ID : 8912609 80. Schroder, W.; Petruschka, L.; Wehnert, M.; Zschiesche, M.; Seidlitz, G.; Hopwood, J. J.; Herrmann, F. H. : Carrier detection of Hunter syndrome (MPS II) by biochemical and DNA techniques in families at risk. J. Med. Genet. 30: 210-213, 1993. PubMed ID : 8097259 81. Steen-Bondeson, M.-L.; Dahl, N.; Tonnesen, T.; Kleijer, W. J.; Seidlitz, G.; Gustavson, K.-H.; Wilson, P. J.; Morris, C. P.; Hopwood, J. J.; Pettersson, U. : Molecular analysis of patients with Hunter syndrome: implication of a region prone to structural alterations within the IDS gene. Hum. Molec. Genet. 1: 195-198, 1992. PubMed ID : 1303177 82. Sukegawa, K.; Matsuzaki, T.; Fukuda, S.; Masuno, M.; Fukao, T.; Kokuryu, M.; Iwata, S.; Tomatsu, S.; Orii, T.; Kondo, N. : Brother/sister siblings affected with Hunter disease: evidence for skewed X chromosome inactivation. Clin. Genet. 52: 96-101, 1998. 83. Sukegawa, K.; Song, X.-Q.; Masuno, M.; Fukao, T.; Shimozawa, N.; Fukuda, S.; Isogai, K.; Nishio, H.; Matsuo, M.; Tomatsu, S.; Kondo, N.; Orii, T. : Hunter disease in a girl caused by R468Q mutation in the iduronate-2-sulfatase gene and skewed inactivation of the X chromosome carrying the normal allele. Hum. Mutat. 10: 361-367, 1997. PubMed ID : 9375851 84. Sukegawa, K.; Tomatsu, S.; Fukao, T.; Iwata, H.; Song, X.-Q.; Yamada, Y.; Fukuda, S.; Isogai, K.; Orii, T. : Mucopolysaccharidosis type II (Hunter disease): identification and characterization of eight point mutations in the iduronate-2-sulfatase gene in Japanese patients. Hum. Mutat. 6: 136-143, 1995. PubMed ID : 7581397 85. Sukegawa, K.; Tomatsu, S.; Tamai, K.; Ikeda, M.; Sasaki, T.; Masue, M.; Fukuda, S.; Yamada, Y.; Orii, T. : Intermediate form of mucopolysaccharidosis type II (Hunter disease): a C-1327 to T substitution in the iduronate sulfatase gene. Biochem. Biophys. Res. Commun. 183: 809-813, 1992. PubMed ID : 1550586 86. Suthers, G. K.; Callen, D. F.; Hyland, V. J.; Kozman, H. M.; Baker, E.; Eyre, H.; Harper, P. S.; Roberts, S. H.; Hors-Cayla, M. C.; Davies, K. E.; Bell, M. V.; Sutherland, G. R. : A new DNA marker tightly linked to the fragile X locus (FRAXA). Science 246: 1298-1300, 1989. PubMed ID : 2573953 87. Thomas, N. S. T.; Roberts, S. H.; Upadhyaya, M.; Knight, S.; Harper, P. S. : Physical localization of the X;autosomal translocation breakpoint from a girl expressing Hunter syndrome using Xq27-q28 DNA markers. (Abstract) Cytogenet. Cell Genet. 51: 1090 only, 1989. 88. Timms, K. M.; Bondeson, M.-L.; Ansari-Lari, M. A.; Lagerstedt, K.; Muzny, D. M.; Dugan-Rocha, S. P.; Nelson, D. L.; Pettersson, U.; Gibbs, R. A. : Molecular and phenotypic variation in patients with severe Hunter syndrome. Hum. Molec. Genet. 6: 479-486, 1997. PubMed ID : 9147653 89. Timms, K. M.; Edwards, F. J.; Belmont, J. W.; Yates, J. R. W.; Gibbs, R. A. : Reassessment of biochemically determined Hunter syndrome carrier status by DNA testing. J. Med. Genet. 35: 646-649, 1998. PubMed ID : 9719370 90. Timms, K. M.; Huckett, L. E.; Belmont, J. W.; Shapira, S. K.; Gibbs, R. A. : DNA deletion confined to the iduronate-2-sulfatase promoter abolishes IDS gene expression. Hum. Mutat. 11: 121-126, 1998. PubMed ID : 9482575 91. Tomatsu, S.; Orii, K. O.; Bi, Y.; Gutierrez, M. A.; Nishioka, T.; Yamaguchi, S.; Kondo, N.; Orii, T.; Noguchi, A.; Sly, W. S. : General implications for CpG hot spot mutations: methylation patterns of the human iduronate-2-sulfatase gene locus. Hum. Mutat. 23: 590-598, 2004. PubMed ID : 15146464 92. Tonnesen, T. : The use of fructose 1-phosphate to detect Hunter heterozygotes in fibroblast cultures from high-risk carriers. Hum. Genet. 66: 212-216, 1984. PubMed ID : 6425196 93. Tonnesen, T.; Guttler, F.; Lykkelund, C. : Reliability of the use of fructose 1-phosphate to detect Hunter cells in fibroblast-cultures of obligate carriers of the Hunter syndrome. Hum. Genet. 64: 371-375, 1983. PubMed ID : 6225723 94. Tonnesen, T.; Lykkelund, C.; Guttler, F. : Diagnosis of Hunter's syndrome carriers; radioactive sulphate incorporation into fibroblasts in the presence of fructose 1-phosphate. Hum. Genet. 60: 167-171, 1982. PubMed ID : 6210620 95. Tsuzaki, S.; Matsuo, N.; Nagai, T.; Osano, M.; Orii, T. : An unusually mild variant of Hunter's syndrome in a 14-year-old boy: normal growth and development. Acta Paediat. Scand. 76: 844-846, 1987. PubMed ID : 3116824 96. Upadhyaya, M.; Bamforth, S.; Harper, P. S.; Sarfarazi, M.; Thomas, N. S. T.; Shaw, D. J.; Meredith, A. L.; Rees, D.; Davies, K.; Young, I. D. : Localization of Hunter syndrome gene by genetic linkage analysis. (Abstract) Cytogenet. Cell Genet. 40: 765 only, 1985. 97. Upadhyaya, M.; Bamforth, S.; Young, I.; Thomas, N.; Sarfarazi, M.; Davies, K.; Harper, P. S. : Hunter's syndrome: evidence supporting a location on the distal part of the X chromosome long arm. (Abstract) J. Med. Genet. 22: 394-395, 1985. 98. Upadhyaya, M.; Sarfarazi, M.; Bamforth, J. S.; Thomas, N. S. T.; Oberle, I.; Young, I.; Harper, P. S. : Localisation of the gene for Hunter syndrome on the long arm of X chromosome. Hum. Genet. 74: 391-398, 1986. PubMed ID : 2878868 99. Van Pelt, J. F. : Gargoylism. Thesis: Nijmegen (pub.) 1960. 100. Vellodi, A.; Young, E.; Cooper, A.; Lidchi, V.; Winchester, B.; Wraith, J. E. : Long-term follow-up following bone marrow transplantation for Hunter disease. J. Inherit. Metab. Dis. 22: 638-648, 1999. PubMed ID : 10399096 101. Wehnert, M.; Hopwood, J. J.; Schroder, W.; Herrmann, F. H. : Structural gene aberrations in mucopolysaccharidosis II (Hunter). Hum. Genet. 89: 430-432, 1992. PubMed ID : 1352274 102. Whitley, C. B.; Anderson, R. A.; Aronovich, E. L.; Crotty, P. L.; Anyane-Yeboa, K.; Russo, D.; Warburton, D. : Caveat to genotype-phenotype correlation in mucopolysaccharidosis type II: discordant clinical severity of R468W and R468Q mutations of the iduronate-2-sulfatase gene. Hum. Mutat. 2: 235-237, 1993. PubMed ID : 8364592 103. Wiesmann, U. N.; Spycher, M. A.; Meier, C.; Liebaers, I.; Herschkowitz, N. : Prenatal mucopolysaccharidosis II (Hunter): a pathogenetic study. Pediat. Res. 14: 749-756, 1980. PubMed ID : 6770331 104. Wilkerson, M. J.; Lewis, D. C.; Marks, S. L.; Prieur, D. J. : Clinical and morphologic features of mucopolysaccharidosis type II in a dog: naturally occurring model of Hunter syndrome. Vet. Path. 35: 230-233, 1998. 105. Wilson, P. J.; Meaney, C. A.; Hopwood, J. J.; Morris, C. P. : Sequence of the human iduronate 2-sulfatase (IDS) gene. Genomics 17: 773-775, 1993. PubMed ID : 8244397 106. Wilson, P. J.; Morris, C. P.; Anson, D. S.; Occhiodoro, T.; Bielicki, J.; Clements, P. R.; Hopwood, J. J. : Hunter syndrome: isolation of an iduronate-2-sulfatase cDNA clone and analysis of patient DNA. Proc. Nat. Acad. Sci. 87: 8531-8535, 1990. PubMed ID : 2122463 107. Wilson, P. J.; Suthers, G. K.; Callen, D. F.; Baker, E.; Nelson, P. V.; Cooper, A.; Wraith, J. E.; Sutherland, G. R.; Morris, C. P.; Hopwood, J. J. : Frequent deletions at Xq28 indicate genetic heterogeneity in Hunter syndrome. Hum. Genet. 86: 505-508, 1991. PubMed ID : 1901826 108. Winchester, B.; Young, E.; Geddes, S.; Genet, S.; Hurst, J.; Middleton-Price, H.; Williams, N.; Webb, M.; Habel, A.; Malcolm, S. : Female twin with Hunter disease due to nonrandom inactivation of the X-chromosome: a consequence of twinning. Am. J. Med. Genet. 44: 834-838, 1992. PubMed ID : 1481858 109. Wraith, J. E.; Cooper, A.; Thornley, M.; Wilson, P. J.; Nelson, P. V.; Morris, C. P.; Hopwood, J. J. : The clinical phenotype of two patients with a complete deletion of the iduronate-2-sulphatase gene (mucopolysaccharidosis II--Hunter syndrome). Hum. Genet. 87: 205-206, 1991. PubMed ID : 1906048 110. Yatziv, S.; Erickson, R. P.; Epstein, C. J. : Mild and severe Hunter syndrome (MPS II) within the same sibships. Clin. Genet. 11: 319-326, 1977. PubMed ID : 140775 111. Young, I. D.; Harper, P. S. : Long-term complications in Hunter's syndrome. Clin. Genet. 16: 125-132, 1979. PubMed ID : 113150 112. Young, I. D.; Harper, P. S. : Incidence of Hunter's syndrome. (Letter) Hum. Genet. 60: 391-392, 1982. PubMed ID : 6809596 113. Yutaka, T.; Fulharty, A. L.; Stevens, R. L.; Kihara, H. : Iduronate sulfatase analysis of hair roots for identification of Hunter syndrome heterozygotes. Am. J. Hum. Genet. 30: 575-582, 1978. PubMed ID : 106723 114. Zlotogora, J.; Bach, G. : Heterozygote detection in Hunter syndrome. Am. J. Med. Genet. 17: 661-665, 1984. PubMed ID : 6424473 115. Zlotogora, J.; Bach, G. : Hunter syndrome: prenatal diagnosis in maternal serum. Am. J. Hum. Genet. 38: 253-260, 1986. PubMed ID : 3080875 116. Zlotogora, J.; Schaap, T.; Zeigler, M.; Bach, G. : Hunter syndrome among Ashkenazi Jews in Israel; evidence for prenatal selection favoring the Hunter allele. Hum. Genet. 71: 329-332, 1985. PubMed ID : 3935563 117. Zlotogora, J.; Schaap, T.; Zeigler, M.; Bach, G. : Hunter syndrome in Jews in Israel: further evidence for prenatal selection favoring the Hunter allele. Hum. Genet. 86: 531-533, 1991. PubMed ID : 1901828 ### CONTRIBUTORS Victor A. McKusick - updated : 6/15/2004 Victor A. McKusick - updated : 1/5/2004 Gary A. Bellus - updated : 9/4/2003 Victor A. McKusick - updated : 6/23/2003 Victor A. McKusick - updated : 1/14/2002 Victor A. McKusick - updated : 4/19/2000 Ada Hamosh - updated : 7/15/1999 Victor A. McKusick - updated : 6/17/1999 Michael J. Wright - updated : 2/12/1999 Victor A. McKusick - updated : 1/21/1999 Michael J. Wright - updated : 11/16/1998 Victor A. McKusick - updated : 10/13/1998 Victor A. McKusick - updated : 9/15/1998 Ada Hamosh - updated : 8/13/1998 Victor A. McKusick - updated : 6/12/1998 Victor A. McKusick - updated : 3/26/1998 Victor A. McKusick - updated : 11/26/1997 Victor A. McKusick - updated : 8/26/1997 Victor A. McKusick - updated : 4/15/1997 Victor A. McKusick - updated : 3/6/1997 Victor A. McKusick - updated : 2/18/1997 Victor A. McKusick - updated : 2/7/1997 ### CREATION DATE Victor A. McKusick : 6/4/1986 ### EDIT HISTORY tkritzer : 6/23/2004 terry : 6/15/2004 alopez : 3/17/2004 carol : 1/14/2004 cwells : 1/5/2004 carol : 10/17/2003 alopez : 9/4/2003 cwells : 6/27/2003 terry : 6/23/2003 mgross : 4/8/2002 carol : 3/13/2002 carol : 1/17/2002 carol : 1/17/2002 mcapotos : 1/14/2002 mcapotos : 1/14/2002 terry : 4/19/2000 alopez : 7/23/1999 terry : 7/15/1999 jlewis : 6/23/1999 terry : 6/17/1999 carol : 5/24/1999 alopez : 5/11/1999 carol : 3/22/1999 mgross : 3/1/1999 terry : 2/12/1999 carol : 2/1/1999 terry : 1/21/1999 alopez : 12/8/1998 terry : 11/16/1998 carol : 10/19/1998 terry : 10/13/1998 carol : 10/5/1998 carol : 9/18/1998 terry : 9/15/1998 carol : 8/13/1998 carol : 6/15/1998 terry : 6/15/1998 terry : 6/12/1998 alopez : 5/21/1998 alopez : 3/26/1998 terry : 3/20/1998 alopez : 12/5/1997 alopez : 12/3/1997 alopez : 12/3/1997 dholmes : 12/1/1997 mark : 9/11/1997 jenny : 9/5/1997 terry : 8/26/1997 alopez : 7/29/1997 alopez : 7/8/1997 jenny : 4/15/1997 terry : 4/9/1997 mark : 3/6/1997 terry : 3/4/1997 jenny : 2/18/1997 terry : 2/12/1997 terry : 2/7/1997 terry : 2/3/1997 terry : 1/17/1997 terry : 1/16/1997 jamie : 1/15/1997 terry : 1/7/1997 terry : 8/22/1996 mark : 7/22/1996 terry : 7/2/1996 terry : 6/27/1996 mark : 1/31/1996 terry : 1/25/1996 mark : 1/23/1996 mark : 1/22/1996 mark : 10/2/1995 pfoster : 7/6/1995 davew : 8/22/1994 warfield : 4/20/1994 mimadm : 4/18/1994 carol : 3/12/1994 Copyright © 1966-2005 Johns Hopkins University
8: | +309548 | GeneTests, Links
| FRAGILE SITE, FOLIC ACID TYPE, RARE, FRA(X)(q28); FRAXE
#### Alternative titles; symbols MENTAL RETARDATION, X-LINKED, ASSOCIATED WITH FRAGILE SITE FRAXE FRAGILE SITE MENTAL RETARDATION 2 GENE, INCLUDED; FMR2, INCLUDED ### TABLE OF CONTENTS #### TEXT SEE ALSO REFERENCES CONTRIBUTORS CREATION DATE EDIT HISTORY Clinical Synopsis Gene map locus Xq28 ### TEXT In patients who have the cytogenetic changes of fragile X syndrome but lack the molecular changes characteristic of that disorder (i.e., are FMR1-mutation negative; see FMR1, 309550), Sutherland and Baker (1992) identified a second site of fragility, symbolized FRAXE. It was found to lie approximately 150 to 600 kb distal to the FRAXA site and to be folate sensitive. It was thought not to be associated with mental retardation. However, several families originally described as having the fragile X syndrome on the basis of mental impairment and cytogenetic analysis were shown by fluorescence in situ hybridization (FISH) to express FRAXE. Sutherland (1993) expressed reservations about the relationship of the FRAXE site to mental retardation because of the likelihood of bias of ascertainment. Mulley et al. (1995), however, provided data suggesting that an etiologic relationship may exist between FRAXE and nonspecific X-linked mental impairment. Using a physical mapping strategy, Knight et al. (1993, 1994) cloned FRAXE and demonstrated that persons expressing this site possess amplification of a GCC repeat adjacent to a CpG island in Xq28. PCR analysis across the region showed that normal individuals had 6 to 25 copies of the GCC repeat, whereas mentally retarded, FRAXE-positive persons had more than 200 copies and were methylated at the CpG island. Sequences adjacent to the repeat are highly conserved across animal species and showed mRNA transcripts on Northern blot hybridization. FRAXE and FRAXF (600226) cannot be distinguished microscopically, although they can be distinguished by molecular methods (see Hirst et al., 1993). Both lie distal to FRAXA in Xq28. A fourth fragile site on the long arm, FRAXD, lies proximal to FRAXA. It is obviously important to distinguish FRAXA from the other fragile sites. Mulley et al. (1995) reported mental impairment and instability of the CCG repeat at FRAXE in 6 kindreds. In one of these, cosegregation of FRAXA (309550) and FRAXE was found. Cytogenetic expression of FRAXE was shown to skip a generation when associated with the reduction in size of the CCG expansion when transmitted through a male; however, in general, transmission occurred through females and copy number increased from one generation to the next. In these respects, the behavior of FRAXE paralleled that of FRAXA. After removal of index cases, Mulley et al. (1995) found that these families had more mentally impaired male and female carriers than could reasonably be expected by chance, suggesting an etiologic relationship between FRAXE and nonspecific mental impairment. Allingham-Hawkins and Ray (1995) examined 300 developmentally delayed males, referred for fragile X testing but negative for the FMR1 gene trinucleotide expansion, for the FRAXE expansion. The group had a wide range of intellectual or behavioral problems and included 19 who had low-level fragile site expression detected cytogenetically at Xq27-q28. None of the patients tested positive for the FRAXE expansion. These results suggested that FRAXE is not a common etiologic factor in this group of patients. The data supported the hypothesis that FRAXE is either very rare or is a benign fragile site that is not associated with any clinical phenotype, similar to the FRAXF and FRA16A (136580) sites. Chakrabarti et al. (1996), who referred to the repeat unit in FRAXE as GCC, stated that normal individuals have 6 to 35 copies of the repeat, whereas cytogenetically positive, developmentally delayed males have more than 200 copies and show methylation of the associated CpG island. Through the use of conserved sequences adjacent to the FRAXE GCC repeat, they isolated a 1,495-bp cDNA that began 331 bp distal to the FRAXE site and extended to a region more than 170 kb distal in Xq28. The cDNA sequence possessed both a putative start of translation and a poly(A) tail. The predicted protein had amino acid motifs that shared significant homology with the human AF-4 gene (159557) which encodes a putative transcription factor. On Northern analysis, the cDNA detected a 9.5-kb transcript in human brain, placenta, and lung. This transcript was present in multiple human brain tissues, but was more abundant in the hippocampus and the amygdala, thus providing possible functional insights. RT-PCR of normal adult brain RNA provided evidence for the existence of the 1,495-bp transcript represented by the isolated cDNA. Knight et al. (1996) described the results of a UK survey designed to assess the frequency of FRAXE in a population of individuals referred for fragile X syndrome testing and found to be negative for expansion events at the FRAXA locus. No FRAXE expansion events were found in 362 cytogenetically negative males studied, and 1 expansion event was identified in a sample of 534 males for whom cytogenetic analyses were either unrecorded or not performed. Further, FRAXE expansion events were detected in 2 related females known to be cytogenetically positive for a fragile site in Xq27.3-q28. Knight et al. (1996) provided clinical details of the 1 FRAXE male identified plus 3 other FRAXE individuals identified through previous referrals for fragile X syndrome testing. The first male had shown developmental delay and microcephaly. At the age of 10 years he showed short stature and an 'engaging' personality, which suggested William syndrome. No abnormality at the elastin locus (130160) characteristic of William syndrome was found, however. At the age of 11 years, educational psychologic assessment showed word recognition at 6.4 years and base number skills at 6.1 years. The other 3 cases, although showing developmental delay, were either of normal stature or unusually tall without microcephaly. Knight et al. (1996) concluded that FRAXE is a relatively rare but significant form of mental retardation for which genetic diagnosis would be appropriate. Brown (1996) concluded that for various reasons routine FRAXE screening is not warranted. Holinski-Feder et al. (1996) concurred that routine testing for FRAXE is not indicated; follow-up testing may be useful in selected FRAXA-negative subjects. Gu et al. (1996) identified a large gene they called FMR2 which is transcribed distally from the CpG island at FRAXE and is downregulated by repeat expansion and methylation. The novel gene is expressed in adult brain and placenta and shows similarity in its protein product with MLLT2 (159557), a protein encoded by a gene at 4q21 that is involved in translocations found in acute lymphoblastic leukemia cells. The FMR2 gene was also reported by Gecz et al. (1996), who showed by RT-PCR that loss of FMR2 expression was correlated with FRAXE expansion. Gecz et al. (1997) found that the FMR2 gene is expressed as an 8.7-kb transcript in placenta and adult brain. A fetal-specific FMR2 of approximately 12 kb was detected in fetal brain and at a lower level in fetal lung and kidney. The gene is composed of 22 exons spanning at least 500 kb. Alternative splicing involving exons 2, 3, 5, 7, and 21 was not tissue specific as tested on mRNA from human fetal and infant brain. FMR2 is translated into a 1,311-amino acid nuclear protein with putative transcription transactivation potential. Subcellular localization with green fluorescent protein as a reporter showed that both nuclear addresses found in the FMR2 sequence are functional and direct the FMR2 protein into the nucleus. FMR2, together with AF4 (159557) and LAF4 (601464), forms a new family of nuclear proteins with DNA-binding capacity and transcription transactivation potential. BLAST searches of the dbEST database revealed at least 2 other groups of nonoverlapping ESTs showing high similarity to the FMR2-related family of proteins. One of them mapped to 5q31. This family of nuclear proteins is involved in mental retardation (FMR2), cancer (AF4), and lymphocyte differentiation (LAF4), as well as unknown functions for the EST-identified members. Gecz et al. (1997) concluded that OX19, which is an alternative transcript from the FRAXE-associated CpG island, is a truncated isoform of the FMR2 gene with an alternative 3-prime end. The 2 isoforms show a similar pattern of expression, with the OX19 isoform expressed at a much lower level. Gecz et al. (1997) stated that although molecular tools to study FRAXE-related mental retardation are available, further psychometric and molecular studies are needed to characterize the effect of the FRAXE full mutation for the purpose of genetic counseling. Barnicoat et al. (1997) found that 4 of 42 families with a distal Xq fragile site did not have a FRAXA mutation. FISH and molecular analyses in 3 of these families demonstrated expansion of the CCG repeat at FRAXE and 1 at FRAXF. All the males who expressed FRAXE had a large methylated CCG repeat at FRAXE. All males with the mutation had some degree of mental handicap. In a survey of 222 unrelated mentally retarded individuals attending Spanish special schools, Mila et al. (1997) found 11 boys with full mutations in the FMR1 gene and 1 boy with a CCG repeat expansion in the FMR2 gene. This boy showed mild mental retardation with psychotic behavior and no remarkable physical traits. Molecular studies revealed mosaicism for methylation in the FMR2 gene. Russo et al. (1998) reported molecular characterization in FRAXE-positive subjects with mental retardation in 2 unrelated Italian families. In 1 family, 13 subjects over 3 generations were investigated with the identification of 3 FRAXE-positive males, 1 with a fully mutated allele and 1 with a mosaic genotype. Only the propositus was investigated in family 2. All the affected individuals lacked a definite phenotype and showed different degrees of mental retardation. Slight mental retardation was evident in the mosaic male. Murray et al. (1999) screened a cohort of 209 women with premature ovarian failure (POF; 311360) for FRAXA and FRAXE premutations, and found an excess of FRAXE alleles with fewer than 11 repeats. Sequence analysis of these alleles showed that the excess was caused by 3 individuals carrying cryptic deletions in FMR2. Murray et al. (1999) proposed that microdeletions in FMR2 may be a significant cause of POF, being found in 1.5% of the population with POF, but in only 0.04% of the general population. The fragile X triplet repeat expansion at Xq27.3 (FMR1; 309550) is associated with mutation or instability 600 kb distal at the FMR2 repeat locus. Ennis et al. (2001) proposed concatenated mutation as a possible explanation. Concatenated mutation is defined as the association between a mutation at one locus and a mutation, recombination, deletion, or transposition at another locus, regardless of the cause or temporal sequence of these events. By examining evidence from a sample of over 7,000 independent haplotypes from the FRAX region and using cladistic groups to define more thoroughly the properties of these haplotypes, they isolated one group of haplotypes that may be predisposed to the phenomenon of concatenated mutation. They found that distinguishing concatenated mutation from founder effects was difficult within a single population, but presented evidence for and against concatenated mutation. Obsessive-compulsive disorder (OCD; 164230) is a chronic psychiatric disease characterized by recurrent obsessions, compulsions, or both. Wang et al. (2003) performed cytogenetic analysis of 26 patients with OCD and, in 1 male patient, identified a fragile X chromosome with 21% of cells demonstrating a fragile site at chromosome Xq27-q28. PCR and Southern blot analysis showed that the molecular basis of the fragile X chromosome was expansion of the CCG repeat at FRAXE. The number of expanded repeats was estimated to be more than 300 copies, qualifying it as a full FRAXE mutation. Another member of the family was found to have a full FRAXE mutation (630 to 1,200 copies of the CCG repeat), with speech impairment as the clinical phenotype; 2 other members of the family with normal phenotypes had no FRAXE expansion. The 2 FRAXE expansions led to complete methylation at the CCG repeat. These findings expanded the spectrum of clinical phenotypes associated with FRAXE mutations. ### SEE ALSO Knight et al. (1993) ### REFERENCES 1. Allingham-Hawkins, D. J.; Ray, P. N. : FRAXE expansion is not a common etiological factor among developmentally delayed males. Am. J. Hum. Genet. 57: 72-76, 1995. PubMed ID : 7541938 2. Barnicoat, A. J.; Wang, Q.; Turk, J.; Green, E.; Mathew, C. G.; Flynn, G.; Buckle, V.; Hirst, M.; Davies, K.; Bobrow, M. : Clinical, cytogenetic, and molecular analysis of three families with FRAXE. J. Med. Genet. 34: 13-17, 1997. PubMed ID : 9032643 3. Brown, W. T. : The FRAXE syndrome: is it time for routine screening? (Editorial) Am. J. Hum. Genet. 58: 903-905, 1996. PubMed ID : 8651273 4. Chakrabarti, L.; Knight, S. J. L.; Flannery, A. V.; Davies, K. E. : A candidate gene for mild mental handicap at the FRAXE fragile site. Hum. Molec. Genet. 5: 275-282, 1996. PubMed ID : 8824884 5. Ennis, S.; Murray, A.; Morton, N. E. : Haplotypic determinants of instability in the FRAX region: concatenated mutation or founder effect? Hum. Mutat. 18: 61-69, 2001. PubMed ID : 11438994 6. Gecz, J.; Bielby, S.; Sutherland, G. R.; Mulley, J. C. : Gene structure and subcellular localization of FMR2, a member of a new family of putative transcription activators. Genomics 44: 201-213, 1997. PubMed ID : 9299237 7. Gecz, J.; Gedeon, A. K.; Sutherland, G. R.; Mulley, J. C. : Identification of the gene FMR2, associated with FRAXE mental retardation. Nature Genet. 13: 105-108, 1996. PubMed ID : 8673085 8. Gecz, J.; Oostra, B. A.; Hockey, A.; Carbonell, P.; Turner, G.; Haan, E. A.; Sutherland, G. R.; Mulley, J. C. : FMR2 expression in families with FRAXE mental retardation. Hum. Molec. Genet. 6: 435-441, 1997. PubMed ID : 9147647 9. Gu, Y.; Shen, Y.; Gibbs, R. A.; Nelson, D. L. : Identification of FMR2, a novel gene associated with the FRAXE CCG repeat and CpG island. Nature Genet. 13: 109-113, 1996. PubMed ID : 8673086 10. Hirst, M. C.; Barnicoat, A.; Flynn, G.; Wang, Q.; Daker, M.; Buckle, V. J.; Davies, K. E.; Bobrow, M. : The identification of a third fragile site, FRAXF, in Xq27-q28 distal to both FRAXA and FRAXE. Hum. Molec. Genet. 2: 197-200, 1993. PubMed ID : 8499907 11. Holinski-Feder, E.; Chahrokh-Zadeh, S.; Jedele, K. B.; Meindl, A.; Steinbach, P.; Wohrle, D. : FRAXE testing. (Letter) Am. J. Hum. Genet. 59: 1168-1169, 1996. PubMed ID : 8900249 12. Knight, S. J. L.; Flannery, A. V.; Hirst, M. C.; Campbell, L.; Christodoulou, Z.; Phelps, S. R.; Middleton-Price, H. R.; Bamicoat, A.; Pembrey, M. E.; Holland, J.; Bobrow, M.; Oostra, B. A.; Davies, K. E. : FRAXE mental retardation associated with trinucleotide repeat expansion and hypermethylation of a CpG island in Xq28. (Abstract) Am. J. Hum. Genet. 53 (suppl.): A79, 1993. 13. Knight, S. J. L.; Flannery, A. V.; Hirst, M. C.; Campbell, L.; Christodoulou, Z.; Phelps, S. R.; Pointon, J.; Middleton-Price, H. R.; Barnicoat, A.; Pembrey, M. E.; Holland, J.; Oostra, B. A.; Bobrow, M.; Davies, K. E. : Trinucleotide repeat amplification and hypermethylation of a CpG island in FRAXE mental retardation. Cell 74: 127-134, 1993. PubMed ID : 8334699 14. Knight, S. J. L.; Ritchie, R. J.; Chakrabarti, L.; Cross, G.; Taylor, G. R.; Mueller, R. F.; Hurst, J.; Paterson, J.; Yates, J. R. W.; Dow, D. J.; Davies, K. E. : A study of FRAXE in mentally retarded individuals referred for fragile X syndrome (FRAXA) testing in the United Kingdom. Am. J. Hum. Genet. 58: 906-913, 1996. PubMed ID : 8651274 15. Knight, S. J. L.; Voelckel, M. A.; Hirst, M. C.; Flannery, A. V.; Moncla, A.; Davies, K. E. : Triplet repeat expansion at the FRAXE locus and X-linked mild mental handicap. Am. J. Hum. Genet. 55: 81-86, 1994. PubMed ID : 8023854 16. Mila, M.; Sanchez, A.; Badenas, C.; Brun, C.; Jimenez, D.; Villa, M. P.; Castellvi-Bel, S.; Estivill, X. : Screening for FMR1 and FMR2 mutations in 222 individuals from Spanish special schools: identification of a case of FRAXE-associated mental retardation. Hum. Genet. 100: 503-507, 1997. PubMed ID : 9341861 17. Mulley, J. C.; Yu, S.; Loesch, D. Z.; Hay, D. A.; Donnelly, A.; Gedeon, A. K.; Carbonell, P.; Lopez, I.; Glover, G.; Gabarron, I.; Yu, P. W. L.; Baker, E.; Haan, E. A.; Hockey, A.; Knight, S. J. L.; Davies, K. E.; Richards, R. I.; Sutherland, G. R. : FRAXE and mental retardation. J. Med. Genet. 32: 162-169, 1995. PubMed ID : 7783162 18. Mulley, J. C.; Yu, S.; Loesch, D. Z.; Hay, D. A.; Donnelly, A.; Gedeon, A. K.; Carbonell, P.; Lopez, I.; Glover, G.; Gabarron, I.; Yu, P. W. L.; Baker, E.; Haan, E. A.; Hockey, A.; Knight, S. J. L.; Davies, K. E.; Richards, R. I.; Sutherland, G. R. : FRAXE and mental retardation. J. Med. Genet. 32: 162-169, 1995. PubMed ID : 7783162 19. Murray, A.; Webb, J.; Dennis, N.; Conway, G.; Morton, N. : Microdeletions in FMR2 may be a significant cause of premature ovarian failure. J. Med. Genet. 36: 767-770, 1999. PubMed ID : 10528856 20. Russo, S.; Selicorni, A.; Bedeschi, M. F.; Natacci, F.; Viziello, P.; Fortuna, R.; Pagani, G.; Dalpra, L.; Larizza, L. : Molecular characterization of FRAXE-positive subjects with mental impairment in two unrelated Italian families. Am. J. Med. Genet. 75: 304-308, 1998. PubMed ID : 9475603 21. Sutherland, G. R. : Personal Communication. Adelaide, Australia, 11/17/1993. 22. Sutherland, G. R.; Baker, E. : Characterisation of a new rare fragile site easily confused with the fragile X. Hum. Molec. Genet. 1: 111-113, 1992. PubMed ID : 1301146 23. Wang, Q.; Gu, Y.; Ferguson, J. M.; Chen, Q.; Boatwright, S.; Gardiner, J.; Below, C.; Espinosa, J.; Nelson, D. L.; Shaffer, L. G. : Cytogenetic analysis of obsessive-compulsive disorder (OCD): identification of a FRAXE fragile site. Am. J. Med. Genet. 118A: 25-28, 2003. ### CONTRIBUTORS Victor A. McKusick - updated : 4/16/2003 Victor A. McKusick - updated : 10/7/2002 Victor A. McKusick - updated : 7/24/2001 Michael J. Wright - updated : 1/18/2000 Victor A. McKusick - updated : 4/28/1998 Victor A. McKusick - updated : 3/3/1998 Victor A. McKusick - updated : 10/7/1997 Victor A. McKusick - updated : 3/28/1997 Alan F. Scott - updated : 8/23/1996 ### CREATION DATE Victor A. McKusick : 9/28/1993 ### EDIT HISTORY alopez : 3/17/2004 tkritzer : 4/28/2003 terry : 4/16/2003 mgross : 11/11/2002 tkritzer : 10/9/2002 terry : 10/7/2002 carol : 8/7/2001 mcapotos : 7/31/2001 terry : 7/24/2001 alopez : 1/18/2000 carol : 2/11/1999 terry : 9/4/1998 alopez : 4/29/1998 terry : 4/28/1998 alopez : 3/23/1998 terry : 3/3/1998 mark : 10/14/1997 terry : 10/7/1997 terry : 3/28/1997 terry : 3/20/1997 terry : 12/20/1996 joanna : 8/23/1996 terry : 5/14/1996 terry : 5/6/1996 terry : 5/3/1996 terry : 4/29/1996 mark : 3/26/1996 mark : 3/26/1996 terry : 3/19/1996 mark : 3/15/1996 terry : 3/12/1996 mark : 6/29/1995 terry : 1/27/1995 carol : 12/7/1994 mimadm : 2/27/1994 carol : 12/9/1993 carol : 11/24/1993 Copyright © 1966-2005 Johns Hopkins University
9: | #600651 | Links
| FRAGILE SITE 11B; FRA11B
### TABLE OF CONTENTS #### TEXT REFERENCES CREATION DATE EDIT HISTORY ### TEXT A number sign (#) is used with this entry because like other fragile sites it does not represent a gene or a specific phenotype. As indicated below, the fragile site is associated with the CBL2 gene (165360) and is probably related to a specific deletion clinical syndrome. Folate-sensitive fragile sites are inherited chromosomal aberrations that appear as poorly condensed regions of metaphase chromosomes and are susceptible to breakage under certain experimental conditions. Until the work of Jones et al. (1995), reviewed later, there had been no direct evidence of chromosomal breakage occurring in vivo in carriers of fragile sites. Two folate-sensitive fragile sites, characterized at the molecular level, had been associated with a clinical phenotype: FRAXA with the fragile X syndrome (309550), the second most common cause of mental retardation after Down syndrome, and FRAXE (309548), which is associated with a rare form of mild mental retardation. The molecular basis of FRAXA is the extensive expansion of a CCG-trinucleotide repeat in the 5-prime untranslated region of the FMR1 gene (see 309550) and associated methylation of an adjacent CpG island. In most cases, the clinical presentation of fragile X syndrome is caused by a reduction in transcription of FMR1 as a result of this FRAXA-induced methylation. Other folate-sensitive fragile sites have been found to be associated with p(CCG)n repeat expansion and changes in regional methylation status. Database searches identified numerous human genes with p(CCG)n repeats located in their 5-prime untranslated regions, but only one of these, CBL2 (165360), was located in the vicinity of a rare folate-sensitive fragile site, FRA11B. Jones et al. (1995) reported the localization of FRA11B to the CBL2 p(CCG)n repeat and demonstrated an association with the chromosome deletion characteristic of Jacobsen (11q-minus) syndrome (147791). Given the very low frequency of both FRA11B and Jacobsen syndrome, an association between them is very unlikely to be due to chance. Hence, the finding of the association was the first demonstration of a direct link between a fragile site and chromosome breakage in vivo. This example is a demonstration of the impact of genetic background in the development of a chromosomal rearrangement. ### REFERENCES 1. Jones, C.; Penny, L.; Mattina, T.; Yu, S.; Baker, E.; Voullaire, L.; Langdon, W. Y.; Sutherland, G. R.; Richards, R. I.; Tunnacliffe, A. : Association of a chromosome deletion syndrome with a fragile site within the proto-oncogene CBL2. Nature 376: 145-149, 1995. PubMed ID : 7603564 ### CREATION DATE Victor A. McKusick : 8/18/1995 ### EDIT HISTORY dkim : 12/16/1998 terry : 5/14/1996 terry : 5/6/1996 mimadm : 11/3/1995 mark : 8/18/1995 Copyright © 1966-2005 Johns Hopkins University
10: | +306900 | GeneTests, Links
| HEMOPHILIA B; HEMB
#### Alternative titles; symbols CHRISTMAS DISEASE FACTOR IX DEFICIENCY PLASMA THROMBOPLASTIN COMPONENT; PTC COAGULATION FACTOR IX, INCLUDED; F9, INCLUDED FACTOR IX, INCLUDED ### TABLE OF CONTENTS #### TEXT ANIMAL MODEL ALLELIC VARIANTS View List SEE ALSO REFERENCES CONTRIBUTORS CREATION DATE EDIT HISTORY Clinical Synopsis Gene map locus Xq27.1-q27.2 ### TEXT Aggeler et al. (1952) described a 16-year-old white male with a hemophilia-like disorder in which there appeared to be a deficiency of a previously undescribed coagulation factor, which the authors named plasma thromboplastin component (PTC). They cited reports indicating that blood from some cases of 'hemophilia' is capable of correcting the coagulation defect in other cases of hemophilia in vitro. They interpreted this as meaning that the cases were a mixture of PTC deficiency and true hemophilia. They stated further that 'it is not known whether PTC deficiency is hereditary...' The question had not long to await an answer because Biggs et al. (1952) in the December 27 (Christmas) issue of the British Medical Journal reported a 5-year-old boy by the name of Christmas who had this disorder, as well as other patients, some of whom came from families showing a typical X-linked pedigree pattern for the disorder. Biggs et al. (1952) defended the familial eponym in the following way: 'The naming of clinical disorders after patients was introduced by Sir Jonathan Hutchinson and is now familiar from serological research; it has the advantage that no hypothetical implication is attached to such a name.' Giangrande (2003) provided historical information concerning the patient Stephen Christmas (1947-1993), whose mutation in the F9 gene (306900.0109) was reported by Taylor et al. (1992) and his physicians. Christmas disease is the result of a hereditary defect in factor IX (plasma thromboplastic component). Linkage studies in the early 1960s suggested that the genes responsible for hemophilias A and B were not allelic; hemophilia A was found to be tightly linked to colorblindness (see later), whereas hemophilia B apparently was not linked to colorblindness. Blackburn et al. (1962) described 2 unrelated girls with Christmas disease (PTC deficiency) and a 'primary' vascular abnormality. In both instances all other members of the family were normal. This may be a situation comparable to the combination of AHG and vascular defects in Willebrand disease. The combination of factor IX with factor VII deficiency in an X-linked pattern of inheritance was described by several workers (e.g., Nour-Eldin and Wilkinson, 1959). However, Verstraete et al. (1962) found factor VII deficiency in all affected males of 4 families with Christmas disease and suggested that it is a consistent secondary phenomenon. By the latter view, no separate mutation for the combined defect need be postulated. Hougie and Twomey (1967) defined a variant of hemophilia B that differs from the usual form by the presence of a prolonged prothrombin time. They presented evidence that a structurally abnormal and inactive form of factor IX, formed in these cases, acts as an inhibitor of the normal reaction between factor VII and animal brain. They called the variant hemophilia B(M), after the initial of the family surname. Only a minority of hemophilia B cases are of this type. Roberts et al. (1968) also demonstrated heterogeneity in hemophilia B. About 90% of patients showed reduced PTC-inhibitor-neutralizing activity proportional to the reduction in PTC clotting activity. These were interpreted as CRM-negative mutants. About 10% of patients showed fully effective PTC-inhibitor-neutralizing activity. These were interpreted as CRM-positive mutants. Lascari et al. (1969) described a daughter of an affected male who had an XX karyotype, factor IX level of 5%, and hemarthrosis. The factor IX level in the mother was 100%. The girl was thought to be a manifesting heterozygote. Unfortunate lyonization was postulated. Denson et al. (1968) demonstrated what was probably the same biologically ineffective molecule by immunologic means. Unfortunate lyonization was postulated in an affected girl probably heterozygous for the Christmas disease gene. George et al. (1971) reported a family in which 3 of 4 members with Christmas disease developed an inhibitor to factor IX. The inhibitor was an IgG antibody directed against the activated form of factor IX (IXA). There was no immunologically detectable factor IX-like material in the affected family members without an inhibitor. This is consistent with the previous postulates that inhibitors to factor IX develop only in patients with Christmas disease who lack the factor IX antigen. The fourth member of the family, who had no factor IX antigen, was transfused several times, but failed to develop antibodies to factor IX. Inhibitors to factor IX develop infrequently compared to factor VIII. This suggested that there may be a predisposition, and studies in this family suggest a familial predisposition although others have not noted an increased familial incidence. Axelrod et al. (1990) demonstrated that primary skin fibroblasts from hemophilic dogs, transduced by recombinant retrovirus containing a canine factor IX cDNA, secreted high levels of biologically active canine factor IX into the medium. Brinkhous et al. (1973) showed that in the dog the loci for hemophilias A and B are probably 50 map units or more apart. The genetic distance between the 2 loci is probably 50 map units in man as well. Both factor IX and factor X consist of two polypeptide chains referred to as the L (light) and H (heavy) chains. Thus, two nonallelic forms of hemophilia B or factor IX deficiency may exist. The H chain bears a structural resemblance to the polypeptide chain of pancreatic trypsin. The L chain is covalently linked to the H chain by a single disulfide bond (Fujikawa et al., 1974). Spinelli et al. (1976) observed deletion of the short arm of one X chromosome in a female with hemophilia B. Family investigations were negative. Hashimi et al. (1978) reported a girl with Christmas disease. Her father was affected and her parents were first cousins (offspring of sisters). They referred to a similar instance of plausible homozygosity. Wadelius et al. (1993) reported the case of a female with hemophilia B whose father had severe hemophilia B and who herself had a factor IX activity of about 1%. No chromosomal abnormality could be detected and DNA analysis gave no indication of deletions or mutations of TaqI cleavage sites in the F9 gene. Analysis of the methylation pattern of locus DXS255 indicated that the expression of hemophilia B in this patient was caused by nonrandom X inactivation. Bertina and Veltkamp (1978) found 14 cases of hemophilia B+ among 33 hemophilia B patients (in 11 independent pedigrees). Using a variety of criteria, they concluded that at least 7 different factor IX variants were present in the 11 families. In an editorial on variants of vitamin K-dependent coagulation factors, Bertina et al. (1979) stated that 9 defective variants of factor II, 5 variants of factor X, and many variants (about 180 pedigrees) of factor IX have been identified. At least one variant of factor VII (Padua) is also known. The availability of a factor IX gene clone (Kurachi and Davie, 1982) provides the tool for mapping by in situ hybridization. Giannelli et al. (1983) demonstrated deletions of the factor IX gene in cases of Christmas disease with development of antibodies. In the United Kingdom, antibodies develop in about 1% of all cases and about 2.5% of severe cases. They predicted that deletion would be found in more cases of classic hemophilia because the disorder is more frequent than Christmas disease, and antibodies develop with replacement therapy in a higher proportion of classic hemophilia cases. They stated that 798 cases of Christmas disease were known in the U.K., corresponding to a frequency of 1 in 30,000 males. Peake et al. (1984) studied the DNA of a patient with severe factor IX deficiency with 4 genomic gene probes specific for various parts of the factor IX gene. All gave a negative result, indicating at least partial gene deletion. Gene deletion was described also by Chen et al. (1985). Camerino et al. (1983) used a factor IX gene probe to demonstrate close linkage to the fragile X/mental retardation syndrome (309550) (17 nonrecombinants, 0 recombinants; lod = 5.12 at theta = 0.0). Chance et al. (1983) used a cloned cDNA probe for human factor IX to assign the F9 gene to Xq27-qter in rodent-man somatic cell hybrids and in metaphase preparations (by in situ hybridization). F9 was in a fragment of the X chromosome, Xq27-Xqter, that was associated with no HPRT activity in the hybrid cell, suggesting that F9 is distal to HPRT. On sum, the evidence seems to indicate that F9 is in the Xq27 band. Giannelli et al. (1984) used a genomic probe containing a TaqI polymorphism in the study of 3 families with Christmas disease. They concluded that the polymorphism should be useful in both genetic counseling and prenatal diagnosis. The mother was identified as the first mutant and a sister as a carrier. In eukaryotic DNA, a high proportion of CpG dinucleotides are methylated at the cytosine residue to give 5-methylcytosine. In common with many restriction enzymes that include CpG within their recognition sequence, HhaI will not cleave at those sites where the cytosine residue is methylated. The PCR technique overcomes this limitation by allowing the production of large amounts of newly synthesized unmethylated DNA from a small amount of starting template. Winship et al. (1989) used PCR to detect a polymorphic HhaI site located 8 kb 3-prime to the F9 gene and estimated that almost half of female subjects can be expected to be heterozygous at this site. Use of this marker increases the proportion of persons in whom the carrier state of hemophilia B can be diagnosed. (Gray (1989) pointed out that the dinucleoside monophosphate moiety CpG should properly be referred to as a cytidylylguanosine. He brought this to attention because of the title of the paper by Winship et al. (1989) which referred to these as cytosine phosphoguanidine dinucleotides. Furthermore, in the title, summary, and introduction of the article, phosphoguanidine was spelled 'phosphoguanadine.' It appears from the letter in reply by Winship (1989) that the errors were made by the editorial staff of the journal inasmuch as the authors had used the standard abbreviation CpG throughout the manuscript in its original form. The editor indicated that the title of the paper should have read: 'Detection of polymorphisms at deoxy(cytidylyl-3-prime,5-prime-guanosine)dinucleotides (CpG) and diagnosis of haemophilia B carriers.') Chen et al. (1991) found that of the 51 substitutions found in their series of patients with hemophilia B, 23 (45%) occurred as C-to-T or G-to-A transitions at 11 sites within CpG dinucleotides. More than one family had identical defects for 6 of the CpG mutations. At 4 of these sites, most patients had different haplotypes compatible with distinct mutations. Non-CpG mutations occurred throughout the coding regions with only 1 mutation in more than one family. The one exception was an ile397-to-thr mutation that was found in 7 families which all shared a rare haplotype, suggesting a common ancestor. (See 306900.0069.) Using a cDNA probe in the study of human-mouse hybrid cells, Camerino et al. (1984) mapped HEMB to Xq26-q27. Furthermore, they identified a TaqI polymorphism with allelic frequencies of about 0.71 and 0.29. In mapping the human X with RFLPs, Drayna et al. (1984) concluded that the genetic distance from Xp22 to Xqter is at least 215 recombination units. Factor IX is about 15 recombination units distal to HPRT. By in situ hybridization and by study of rodent-human somatic cell hybrids with various aberrations of the human X, Boyd et al. (1984) assigned the factor IX locus to Xq26-qter. Cloned DNA sequences of the gene were used in these studies. Based on the peptide sequence of bovine factor IX, Jagadeeswaran et al. (1984) synthesized a 17-basepair oligonucleotide probe to screen a human liver cDNA library. They identified a recombinant clone with a 917-nucleotide insert whose sequence corresponded to 70% of the coding region of human factor IX. This F9 cDNA was used to probe restriction endonuclease digested polymorphism, as well as to verify that the haploid genome contains a single copy of the gene. The cDNA was also used to map F9 to the Xq26-qter region. By in situ hybridization, Purrello et al. (1985) showed that the loci for hemophilia A and hemophilia B flank the X chromosome fragile site. The authors believed that this finding, combined with the knowledge that hemophilia B recombines freely with at least 2 loci of the G6PD cluster, supports the Siniscalco hypothesis that the chromosomal segment in which the fragile X site occurs is normally a region of high meiotic recombination (Szabo et al., 1984). Using intragenic RFLPs of factor IX in the study of 3 families with the fragile X syndrome (309550), Forster-Gibson et al. (1985) found a minimum of 4 recombinations in 9 meioses. A maximum lod score of 2.75 at theta 0.20 was estimated. Factor IX circulates as an inactive zymogen until proteolytic release of its 'activation peptide' allows it to assume the conformation of an active serine protease (Davie and Fujikawa, 1975). Its role in the blood coagulation cascade is to activate factor X through interactions with calcium, membrane phospholipids, and factor VIII. Factor IX(Chapel Hill), a CRM+ variant of hemophilia B, results from an arg-to-his change at residue 145, which prevents cleavage at one of the activation sites (Noyes et al., 1983). A change affecting the other cleavage site is thought to be involved in the variant factor IX(Deventer) (Bertina and van der Linden, 1982). Barrai et al. (1985) analyzed 1,485 families with hemophilia A, hemophilia B, or hemophilia of unknown type. The proportion of sporadic cases was estimated to be 0.166 and 0.078, respectively, for the 2 types of hemophilia. The age of maternal grandfathers at birth of the mother of hemophilia B cases was higher than that of appropriate controls. They could not find a difference in mutation rate in sperm and eggs for hemophilia A. In a study of the families of 45 hemophilia B patients in Malmo, Sweden, Kling et al. (1992) found that 24 had only a single affected member; in 13 of these 24 cases, ascendant relatives were available for study. Detection of the gene defect showed the mutation to be de novo in the proband in 3 of these 13 cases and inherited from a carrier mother in the remaining 10. All 10 carrier mothers were shown to have de novo mutation, as the patients' grandfathers were phenotypically and/or hematologically normal and the grandmothers were noncarriers. In 6 of the 10 cases, RFLP patterns were informative as to the origin of the mutant X chromosome and in all cases the mutation was of paternal origin. The average age of the father at the birth of the new carrier female was 41.5 years. Thus the data support a paternal age effect in the HEMB mutation and a higher mutation rate in males than in females. Ketterling et al. (1993) analyzed germline origin of the mutation in 43 families; in 25 it occurred in the female germline and in 18 it occurred in the male germline. The excess of germline origins in females does not imply an overall excess mutation rate per basepair in the female germline because when the mother and maternal grandparents are analyzed the excess of X chromosomes in females, 4:1, skews the data in favor of female origins. Bayesian analysis corrects for this bias and indicates that the 25:18 ratio actually represents a predominance of mutations in males. Transitions at the dinucleotide CpG, estimated to account for 36% of mutations in the F9 gene (Koeberl et al., 1990), showed the most striking male predominance of mutation, 11:1. This finding is comparable with previous data suggesting that methylation at CpG dinucleotides is reduced or absent in the female germline (Driscoll and Migeon, 1990). This, rather than the increased number of replications in the male germ cells, probably accounts for the male excess. (For example, by age 28 years, the average age of conception in the Ketterling et al. (1993) study, male germ cells have undergone 15-fold more divisions than female germ cells, according to Vogel and Motulsky (1986).) Methylation of CpG dinucleotides constitutes an endogenous mechanism of mutation, which results from insufficient repair of the deamination product to 5-methyl cytosine. In a severely affected, antigen-negative (CRM-negative) patient, Rees et al. (1985) found a point mutation changing the obligatory GT to a TT within the donor splice junction of exon f. This is comparable to point mutations in splice junctions that lead to beta-zero-thalassemia. Connor et al. (1985), by total ascertainment, found 28 families with hemophilia B in the west of Scotland (prevalence = 1/26,870 males). Of 26 living obligate carriers, 42% were heterozygous for a TaqI polymorphism recognized by the factor IX genomic probe. Linkage disequilibrium was apparent for this RFLP and hemophilia B in the west of Scotland. This surprising finding suggested that some of these families might be related. Vianna-Morgante et al. (1986) observed de novo t(X;1)(q27;q23) in a girl with hemophilia B who had no affected relatives. In a full description of the case, Krepischi-Santos et al. (2001) stated that the translocated X was preferentially active and that methylation analysis of the DXS255 locus confirmed the skewed X inactivation with the paternal allele being the active one. Molecular analysis showed deletion of at least part of the F9 gene. Nisen et al. (1986) described hemophilia B in a girl with the karyotype 46,X,del(X)q27. They showed that the X chromosome with the deletion was inactivated in all cells. The mother's identical twin sister had a son with severe hemophilia B. The proband was lacking the paternal factor VIII gene, indicating that the deletion had occurred in the paternal X chromosome and had included the factor VIII locus. However, both the maternal and the paternal factor IX loci were present. The interpretation applied by Nisen et al. (1986) was that inactivation of the deleted, paternally derived X chromosome in all cells had provided the opportunity for expression of the hemophilia B gene which the proband had inherited from her mother. Matthews et al. (1987) did Southern blot analyses in 9 hemophilia B patients, including 2 brothers, who produced anti-factor IX antibodies. Two were shown to have total deletion of the factor IX gene. The brothers were shown to have a presumably identical complex rearrangement of HEMB involving 2 separate deletions. Five other patients had a structurally intact factor IX gene. Matthews et al. (1987) concluded that whereas large structural HEMB defects predispose the patients to the development of antibody, the phenomenon can be associated with other defects of the gene. In a patient with severe factor IX deficiency who had developed an inhibitor in high titer, Hassan et al. (1985) observed a deletion of about 33 kb of the F9 locus. Vidaud et al. (1986) also identified an intragenic lesion of the F9 gene. They referred to the gene as F-IX(Strasbourg). In 5 kindreds studied in detail, Poon et al. (1987) were able to determine the carrier status of all 11 females at risk; prenatal diagnosis could be offered to the offspring of each of the 6 carriers identified. Green et al. (1988) analyzed the F9 gene in a male and his hemophilic uncle, who developed inhibitors to factor IX, and in the mother of the proband. A partial deletion was described as the basis for the change in this mutation which was called London-1. The findings suggested that the deletion had arisen by illegitimate (nonhomologous) recombination. Taylor et al. (1988) described a complete deletion of the factor IX gene, which extended at least 80 kb 3-prime of the gene. The phenotype in this family was that of severe factor IX deficiency, with no detectable factor IX protein in the circulation. The patient did not have antibodies to factor IX, despite total deletion of the gene. A new TaqI variant polymorphism 5-prime to exon 4 was also described in this family. Moreover, linkage analysis between the factor IX locus and the DXS99 anonymous segment demonstrated the first recorded recombination event between the 2 loci. Matthews et al. (1988) discussed the family originally reported by Peake et al. (1984) as having an X-chromosome deletion of minimum size 114 kb that included the entire F9 gene. By isolation of further 3-prime flanking probes, they located the 3-prime breakpoint of the deletion to a position 145 kb 3-prime to the start of the F9 gene. Abnormal junction fragments detected at the breakpoint were used in the detection of carriers. Siguret et al. (1988) demonstrated a CGA (arginine) to UGA (stop) mutation in the catalytic domain (exon h) of the F9 gene, using PCR amplified DNA for sequencing. Wadelius et al. (1988) found total deletion of the F9 gene in 3 affected males in 1 family. They did not have antibodies against native factor IX. Two of the patients, who were cousins, had inherited the same maternal HLA haplotype, suggesting that immune gene(s) located at the MHC locus may be important for the development of antibodies against factor IX. Mandalaki et al. (1986) reported an extensive family in Greece that was thought to have hemophilia B Leyden. Factor IX(Kawachinagano) is a mutant factor IX protein initially recognized in a patient with severe hemophilia B who had 46% of normal factor IX antigen but no detectable clotting activity. This mutant factor IX is not activated by factor XIa in the presence of calcium ions. Koeberl et al. (1989) used the method of genome amplification with transcript sequencing to perform direct genomic sequencing on 8 regions of the factor IX gene from 22 hemophiliacs. They found a high rate of mutation at the dinucleotide CpG. Transitions of CpG accounted for 31% (5 out of 16) of the distinct mutations and for 38% (5 out of 13) of the single base changes. Cooper and Krawczak (1990) made an extensive survey of the single basepair substitutions that cause human genetic disease and found that 32% were CG-to-TG or CG-to-CA transitions--a 12-fold increase over the frequency predicted from random expectation. They presented a computer model (MUTPRED) designed to predict the location of mutations within gene coding regions causing human genetic disease. The model predicted successfully the rank order of disease prevalence and/or mutation rates associated with various human autosomal dominant and X-linked recessive conditions. The mutational spectrum predicted for the F9 gene resembled closely that observed for point mutations causing hemophilia B. Cooper and Krawczak (1990) quoted from Edmund Spenser's 'The Faerie Queene' (c. 1609): '...mutability in them doth play her cruell cruell sports, to many men's decay.' By use of PCR followed by sequencing, Bottema et al. (1989) were able to identify the mutation in all 14 hemophilia B cases studied. Analysis for heterozygosity in at-risk female relatives was then done, either by sequencing the appropriate region or by detection of an altered restriction site. They estimated that the mutation will be associated with an altered restriction site in about one-half of the families. Koeberl et al. (1990) compared RFLP-based carrier detection with a direct method involving genomic amplification with transcript sequencing (GAWTS). They pointed out that the RFLP approach 'suffers from multiple levels of uncertainty.' They found that 22 at-risk females were diagnosed by direct testing, whereas only 11 females could be diagnosed by standard RFLP analysis. To study the nature of spontaneous mutation, Koeberl et al. (1990) sequenced 8 regions (a total of 2.46 kb) of likely functional significance in the F9 gene in 60 consecutive, unrelated hemophiliacs. From the pattern of mutations causing disease and from a knowledge of evolutionarily conserved amino acids, they reconstructed the underlying pattern of mutation and calculated the mutation rates per basepair per generation for transitions (G-A or C-T changes) as 27 x 10(-10), transversions (A-T, A-C, G-T, or G-C changes) as 4.1 x 10(-10), and deletions as 0.9 x 10(-10), for a total mutation rate of 32 x 10(-10). No insertions were observed in this sample. The proportion of transitions at non-CpG nucleotides was raised 7-fold over that expected if one base substitution were as likely as another; at the dinucleotide CpG, transitions were found to be increased 24-fold relative to transitions at other sites. The pattern of spontaneous mutations resembled that observed in E. coli when the data were corrected for ascertainment bias. Mutations putatively affecting splicing accounted for at least 13% of mutations, indicating that the division of the gene into 8 exons represents a significant genetic cost to the organism. All the missense mutations occurred at evolutionarily conserved amino acids. Bottema et al. (1990) found that in Asians (mostly Koreans), as in Caucasians, transitions dominate among factor IX mutations, followed by transversions and microdeletions/insertions. The missense mutations occur at evolutionarily conserved amino acids. On the basis of their data combined with previous data, they concluded that more than two-thirds of the missense mutations that can occur at nonconserved amino acids do not cause hemophilia B. Bottema et al. (1991) identified 95 independent missense mutations in the F9 gene resulting in hemophilia B; 94 of these occurred at amino acids that are evolutionarily conserved in mammalian factor IX sequences. They pointed out that the likelihood of a missense mutation causing hemophilia B depends on whether the residue is also conserved in the factor IX-related proteases: factor VII, factor X, and protein C. They found that most of the possible missense mutations in residues conserved in factor IX in all the related proteases will cause disease, whereas missense mutations not conserved in the related proteases are 6-fold less likely to cause disease. Missense mutations at nonconserved residues are 33-fold less likely to cause disease. They concluded that many of the residues in factor IX are spacers; that is, the main chains are presumably necessary to keep other amino acid interactions in register, but the nature of the side chain is unimportant. Bottema et al. (1991) found that transversions at CpG dinucleotides are elevated an estimated 7.7-fold relative to other transversions. On the other hand, the mutation rates at non-CpG dinucleotides are relatively uniform. They suggested that the high rate of CpG transversions accounts for the fact that the F9 gene has a G+C content of approximately 40%. Bottema et al. (1993) gave an updated estimate on mutations at CpG dinucleotides in the F9 gene. Of the independent transitions they had delineated in a consecutive sample of 290 families with hemophilia B, 42% occurred at CpG sites. Overall, CpG mutations represented 36% of the point mutations and 30% of all mutations in their sample. An observed 20-fold enhancement for mutation at CpG sites with frequent mutations reflected, they suggested, the situation at fully or mostly methylated sites. In studies of the patterns of independent mutation resulting in hemophilia B in 127 Caucasian and 44 non-Caucasian patients, Gostout et al. (1993) could find no differences, suggesting either predominance of endogenous processes or common mutagen exposure rather than mutagen exposure specifically associated with non-Caucasian status or non-Western life style. Of 727 independent mutations (0.28%) of the F9 gene in patients with hemophilia B, Li et al. (2001) observed only 2 germline retrotransposition mutations: a 279-bp insertion in exon h originating from an Alu family of short interspersed elements not previously known to be active, and a 463-bp insertion in exon e of a LINE-1 element originating in a maternal grandmother. The authors stated that if the rates of recent germline mutation in F9 are typical of the genome, a retrotransposition event is estimated to occur somewhere in the genome of about 1 in every 17 children born. Analysis of other estimates for retrotransposition frequency and overall mutation rates suggested that the actual rate of retrotransposition is likely to be in the range of 1 in every 2.4 to 1 in every 28 live births. Kazazian (1999) analyzed the frequency of retrotransposition events involving 860 genes. These included retrotranspositions identified in X-linked and severe autosomal dominant disorders (which are likely to have occurred within the last 150 years) and autosomal recessive disorders in which the mutations may have occurred 10,000 or more years ago. Ljung et al. (2001) surveyed a series comprising all 77 known families with hemophilia B in Sweden. The disorder was severe in 38, moderate in 10, and mild in 29. A total of 51 different mutations were found. Ten of the mutations, all C-to-T or G-to-A transitions, recurred in 1 to 6 additional families. Using haplotype analysis of 7 polymorphisms in the F9 gene, Ljung et al. (2001) found that the 77 families carried 65 unique, independent mutations. Of the 48 families with severe or moderate hemophilia, 23 (48%) had a sporadic case compared with 31 families of 78 (40%) in the whole series. Five of those 23 sporadic cases carried de novo mutations; 11 of 23 of the mothers were proven carriers; and in the remaining 7 families, it was not possible to determine carriership. Among 48 patients with severe hemophilia B, 11 (23%) developed inhibitors and all of them had deletions or nonsense mutations. Thus, 11 of 37 (30%) patients with severe hemophilia B as a result of deletion/nonsense mutations developed inhibitors compared with none of 11 patients with missense mutations. Ljung et al. (2001) found that the ratio of male to female mutation rates was 5:3 and that the overall mutation rate per gamete per generation was 5.4 x 10(-6). Green et al. (1991) suggested a strategy for facilitating carrier and prenatal diagnosis by identification of all hemophilia B mutations in a given population so that only the relevant parts of the molecule can be focused on when performing the amplification mismatch detection (AMD) as developed by Montandon et al. (1989). In the population of families with hemophilia B at the Malmo Haemophilia Centre, Montandon et al. (1992) estimated that the overall mutation rate was 4.1 x 10(-6) and that the ratio of male to female specific mutation rates was 11. Three of 13 isolated cases had a new mutation, whereas the other 10 had mothers who carried a new mutation. Yao et al. (1991) infected rat capillary endothelial cells (CECs) with a Moloney murine leukemia virus-derived retrovirus vector that contained human factor IX cDNA. They found that a single RNA transcript of 4.4 kb, predicted by the construct, and a recombinant factor IX of 68 kD identical to purified plasma factor IX were formed. The recombinant factor IX that was produced showed full clotting activity, demonstrating that CECs have an efficient mechanism for posttranslational modifications, including gamma-carboxylation, essential for its biologic activity. These results, in addition to other properties of the endothelium, including large numbers of cells, accessibility, and direct contact with the circulating blood, suggest that CECs can serve as an efficient drug delivery vehicle producing factor IX for somatic gene therapy of hemophilia B. Little et al. (1992) generated overlapping yeast artificial chromosomes (YACs) resulting in a contig of 8 Mb that included most of band Xq26 and represented 10 to 15 cM of the genetic map. The contig included probes for HPRT (308000) and for F9. Giannelli et al. (1992) used hemophilia B as a model of a genetic disease with marked mutational heterogeneity to lay out an overall strategy for genetic counseling. They started with the construction of a national database which could be used for diagnosis and genetic counseling on the basis of DNA abnormality. In the U.K. there were just over 1,000 patients with hemophilia B and these were probably derived from 500 to 600 families. They characterized the mutation in a group of unrelated patients and in only 1 of 170 patients examined from the Swedish and British series did they fail to find a mutation in the essential regions of the gene. Thus the screening procedures used were capable of detecting all types of mutations. By phenotype/genotype correlations they generated information of prognostic value concerning each of those mutations. Green et al. (1991) provided a list of point mutations that cause hemophilia B. Sommer et al. (1992) estimated that missense mutations cause only 59% of moderate and severe hemophilia B and that these mutations are almost always (95%) of independent origin (i.e., de novo mutations). In contrast, missense mutations were found in virtually all (97%) families with mild disease and only a minority of these (41%) were of independent origin. Giannelli et al. (1993) reported on the findings in a database of 806 patients with hemophilia B in whom the defect in factor IX had been identified at the molecular level. A total of 379 independent mutations were described. The list included 234 different amino acid substitutions. There were 13 promoter mutations, 18 mutations in donor splice sites, 15 mutations in acceptor splice sites, and 4 mutations creating cryptic splice sites (probably new splice sites within exons). In analyses of DNA from 290 families with hemophilia B (203 independent mutations), Ketterling et al. (1994) found 12 deletions more than 20 bp in length. Eleven of these were more than 2 kb long and one was 1.1 kb. Gerrard et al. (1993) introduced a recombinant human F9 cDNA into cultured primary human keratinocytes by means of a defective retroviral vector. In tissue culture, transduced keratinocytes were found to secrete biologically active factor IX and after transplantation of these cells into nude mice, human factor IX was detected in the bloodstream in small quantities for 1 week. The implications of this for design of therapy in the patients was discussed. Busby et al. (1985) transfected baby hamster kidney (BHK) cells with a plasmid containing a gene for factor IX and a plasmid containing a selectable marker. The cells secreted material that these authors believed to be authentic factor IX. The therapeutic advantages of factor IX produced by cultured cells (because of freedom from infection) were discussed. Preclinical studies in mice and hemophilic dogs have shown that introduction of an adeno-associated viral (AAV) vector encoding blood coagulation factor IX into skeletal muscle results in sustained expression of factor IX at levels sufficient to correct the hemophilic phenotype (Herzog et al., 1997; Herzog et al., 1999). On the basis of these data and additional preclinical studies demonstrating an absence of vector-related toxicity, Kay et al. (2000) initiated a clinical study of intramuscular injection of an AAV vector expressing human factor IX in adults with severe hemophilia B. The study had a dose-escalation design. Assessment in the first 3 patients of safety and gene transfer and expression showed no evidence of germline transmission of vector sequences or formation of inhibitory antibodies against factor IX. By PCR and Southern blot analyses of muscle biopsies, Kay et al. (2000) found that the vector sequences were present in muscle, and demonstrated expression of factor IX by immunohistochemistry. They observed modest changes in clinical endpoints, including circulating levels of factor IX and frequency of factor IX protein infusion. The evidence of gene expression at low doses of vector suggested that dose calculations based on animal data may have overestimated the amount of vector required to achieve therapeutic levels in humans, and that the approach offers the possibility of converting severe hemophilia B to a milder form of the disease. Manno et al. (2003) investigated the safety of intramuscular injection of a recombinant AAV (rAAV) vector expressing factor IX in patients with hemophilia B. Muscle biopsies of injection sites performed 2 to 10 months after vector administration confirmed gene transfer as evidenced by Southern blot and transgene expression as evidenced by immunohistochemical staining. However, circulating levels of factor IX were less than 2% in all cases and less than 1% in most. Manno et al. (2003) concluded that the results demonstrated the safety of intramuscular rAAV administration in humans in a manner similar to that used in mice and hemophilic dogs (103,104:Herzog et al., 1997, 1999). Based particularly on his extensive experience with mutation analysis in hemophilia B, Sommer (1994) proposed an ingenious hypothesis concerning the role of cancer in mediating evolutionary selection for a constant rate of germline mutation. The hypothesis was based on data suggesting that most germline mutations are due to endogenous processes such as methylation of DNA at CpG dinucleotides. Furthermore, despite differences in environment, diet, lifestyle, and occupational exposure, the pattern of factor IX mutations is remarkably similar in populations all over the world. Also despite the many differences in the environment of modern day humans, the biases in the dinucleotide mutation rates during the past 150 years are compatible with the ancient pattern that fashioned the G+C content of 40%. Assuming that somatic mutation leading to early-onset cancer occurs at rates similar to the germline mutation rate, then these cancers that interfere with reproduction might cap the germline mutation rate. Some have pointed out that cancer is a sensitive mediator of negative selection because the multiple mutations required for carcinogenesis can amplify the effects of small increases in the mutation rate. A certain rate of mutation is required to generate sufficient variation for adaptation during evolutionary time. Sexual reproduction and recombination serves to enhance variation, but ultimately new germline mutation is required to replenish variant alleles lost secondary to negative selection, genetic drift, and population bottlenecks. Unfortunately, the requisite mutation rate carries a terrible price, since for each advantageous mutation, there are many disadvantageous ones. Consequently, the optimal mutation rate should be at a level just sufficient to maintain the variation needed for adaptation. Mechanisms for negative selection are needed to keep the mutation rate in check. Cancer may serve that role. Giannelli et al. (1996) described the sixth edition of their hemophilia B database of point mutations and short (less than 30 bp) additions and deletions. The 1,380 patient entries were ordered by the nucleotide number of their mutation. References to published mutations were given and the laboratories generating the data were indicated. The database was compiled by the central coordinators (Giannelli and Green) from lists updating the previous year's lists prepared by coordinators for the different countries. They announced that the database, including all repeated mutations, would be available from individual country coordinators on floppy discs. Giannelli et al. (1997) described the seventh edition of their database; 1,535 patient entries were ordered by the nucleotide number of their mutation. When known, details were given on factor IX activity, factor IX antigen in the circulation, presence of inhibitor, and origin of mutation. Soucie et al. (1998) studied the frequency of hemophilia A and hemophilia B in 6 U.S. states: Colorado, Georgia, Louisiana, Massachusetts, New York, and Oklahoma. The age-adjusted prevalence of hemophilia in all 6 states in 1994 was 13.4 cases per 100,000 males (10.5 hemophilia A and 2.9 hemophilia B). The prevalence by race/ethnicity was 13.2 cases per 100,000 white, 11.0% among African American, and 11.5% among Hispanic males. Application of age-specific prevalence rates from the 6 surveillance states to the U.S. population resulted in an estimated national population of 13,320 cases of hemophilia A and 3,640 cases of hemophilia B. For the 10-year period 1982 to 1991, the average incidence of hemophilia A and B in the 6 surveillance states was estimated to be 1 in 5,032 live male births. Green et al. (1999) conducted a population-based study of hemophilia B mutations in the United Kingdom in order to construct a national confidential database of mutations and pedigrees to be used for the provision of carrier and prenatal diagnoses based on mutation detection. This allowed the direct estimate of overall mutation rate, male mutation rate, and female mutation rate for hemophilia B. The values obtained per gamete per generation and the 95% confidence intervals were 7.73 (6.29-9.12) x 10(-6) for overall mutation rate; 18.8 (14.5-22.9) x 10(-6) for male mutation rate; and 2.18 (1.44-3.16) x 10(-6) for female mutation rate. The ratio of male-to-female mutation rates was 8.64 (95% CI, 5.46-14.5). The higher male rate was not caused by a much higher rate of transition at CpG sites in the male. Attempts to detect evidence of gonadal mosaicism for hemophilia B mutation in suitable families did not detect any instances of ovarian mosaicism in 47 available opportunities. This suggested that the risk of a noncarrier mother manifesting as a gonadal mosaic by transmitting the mutation to a second child should be less than 0.062. Giannelli et al. (1999) also estimated the rates per base per generation of specific types of mutations, using their direct estimate of the overall mutation rate for hemophilia B and information on the mutations present in the U.K. population as well as those reported year by year in the hemophilia B world database. These rates were as follows: transitions at CpG sites, 9.7 x 10(-8); other transitions, 7.3 x 10(-9); transversions at CpG sites, 5.4 x 10(-9); other transversions, 6.9 x 10(-9); and small deletions/insertions causing frameshifts, 3.2 x 10(-10). Ketterling et al. (1999) estimated the male:female ratio of mutations in the F9 gene by Bayesian analysis of 59 families. The overall ratio was estimated at 3.75. It varied with the type of mutation, from 6.65 and 6.10 for transitions at CpG and A:T to G:C transitions at non-CpG dinucleotides, respectively, to 0.57 and 0.42 for microdeletions/microinsertions and large deletions (more than 1 kb), respectively. The value for the 2 subsets of non-CpG transitions differed (6.10 for A:T to G:C vs 0.80 for G:C to A:T). Somatic mosaicism was detected in 11% of the 45 'origin individuals' for whom the causative mutation was visualized directly by genomic sequencing of leukocyte DNA (estimated sensitivity of approximately 1 part in 20). Four of the 5 defined somatic mosaics had G:C to A:T transitions at non-CpG dinucleotides, hinting that this mutation subtype may occur commonly early in embryogenesis. The age at conception was analyzed for 41 U.S. Caucasian families in which the age of the origin parent and the year of conception for the first carrier/hemophiliac were available. No evidence for a paternal age effect was seen; however, an advanced maternal age effect was observed (P = 0.03) and was particularly prominent in transversions. This suggested that an increased maternal age results in a higher rate of transmitted mutations, whereas the increased number of mitotic replications associated with advanced paternal age has little, if any, effect on the rate of transmitted mutation. By sequencing the complete factor IX gene in 2 sisters with hemophilia B with different phenotypes and no family history of hemorrhagic diathesis, Costa et al. (2000) found a common 5-prime splice site mutation in intron 3 (306900.0107) and an additional missense mutation (I344T; 306900.0108) in 1 sister. The presence of dysfunctional antigen in the latter strongly suggested that these mutations were in trans. Neither mutation was found in leukocyte DNA from the asymptomatic parents, but the mother was a somatic mosaic for the shared splice site mutation. The somatic mosaicism in the mother for the splice site mutation was demonstrated by studies of buccal and uroepithelial cells. The missense mutation must have resulted from a de novo mutation in the father's gametes. The compound heterozygous proband was a 14-year-old girl with moderate hemophilia B, manifest by hematomas, hemarthrosis, and epistaxis. A sister suffered only from rare hematomas. Liu et al. (2000) found that the pattern of germline mutations in 66 hemophilia B patients from mainland China was similar to that in U.S. Caucasians, blacks, and Mexican Hispanics. The existence of a ubiquitous mutagen or the possibility that multiple mutagens could produce the same pattern of mutation was considered unlikely; the findings were compatible with the inference that endogenous processes predominate in germline mutations. Rusconi et al. (2002) demonstrated that protein-binding oligonucleotides (aptamers) against coagulation factor IXa are potent anticoagulants. They also showed that oligonucleotides complementary to these aptamers could act as antidotes capable of efficiently reversing the activity of these new anticoagulants in plasma from healthy volunteers and from patients who cannot tolerate heparin. Rusconi et al. (2002) concluded that their strategy was generalizable for rationally designing a drug-antidote pair, thus opening the way for developing safer regulatable therapeutics. Cutler et al. (2004) described a family in which the usual pattern of X-linked inheritance of hemophilia B was complicated by mosaicism in the proband's maternal grandfather. The proband was an infant with severe factor IX deficiency who was initially thought to be a sporadic case. Testing of other family members identified his mother as a carrier and his asymptomatic maternal grandfather as having very mild factor IX deficiency. The causative mutation was identified as a 2-bp deletion (AG within codons 134-135) in the F9 gene (306900.0110). #### ANIMAL MODEL Choo et al. (1987) introduced into transgenic mice a full-length human factor IX cDNA containing all the natural mRNA sequences plus some flanking intron sequences combined with a metallothionein promoter. This DNA clone was microinjected into the pronuclei of fertilized eggs. The transgenic mice expressed high levels of mRNA, gamma-carboxylated and glycosylated protein, and biologic clotting activity that were indistinguishable from normal human plasma factor IX. The study demonstrated the feasibility of expressing highly complex heterologous proteins in transgenic mice. It provided the groundwork for the production of human factor IX in large quantities in transgenic livestock for therapeutic use and also for the investigation of alternative genetic therapies for hemophilia B. Armentano et al. (1990) used a recombinant retroviral factor to transfer the factor IX gene into hepatocytes from 3-week old New Zealand white rabbits. The infected cells produced human factor IX that was indistinguishable from the enzyme derived from normal human plasma. Kay et al. (1993) developed a method for hepatic gene transfer in vivo by the direct infusion of recombinant retroviral vectors into the portal vasculature and showed that the method resulted in the persistent expression of exogenous genes. To determine the applicability to the treatment of hemophilia B, efficacy studies were done in a hemophilia B dog model. When the canine factor IX cDNA was transduced directly into hepatocytes of affected dogs in vivo, the animals constitutively expressed low levels of canine factor IX for more than 5 months. Persistent expression of the clotting factor resulted in reduction of whole blood clotting time and partial thromboplastin time of the treated animals. Wang et al. (1997) generated a mouse in which the gene encoding factor IX was disrupted by homologous recombination. The nullizygous mice were devoid of factor IX antigen in plasma. Consistent with the bleeding disorder, the factor IX coagulant activities for wildtype, heterozygous, and homozygous mice were 92, 53, and less than 5%, respectively, in activated partial thromboplastin time assays. Plasma factor IX activity in the deficient mice -/- was restored by introducing wildtype murine factor IX gene via adenoviral vectors. Thus, these factor IX-deficient mice provided a useful animal model for gene therapy studies of hemophilia B. The factor IX-deficient mice showed extensive bleeding after clipping a portion of the tail and bled to death unless the wound was cauterized. Additionally, in contrast to the normal mice, they showed swollen extremities and extensive hemorrhagic lesions after trauma. Female homozygous -/- mice gave birth without complications. Schnieke et al. (1997) produced transgenic sheep carrying the human factor IX gene by nuclear transfer. Ovine primary fetal fibroblasts were cotransfected with a neomycin-resistance marker gene (neo) and a human coagulation factor IX genomic construct designed for expression of the encoded protein in sheep milk. Nuclear transfer to enucleated oocytes was performed using either cloned transfectant fibroblasts or a population of neomycin-resistant cells as donors. Six transgenic lambs were liveborn: 3 produced from cloned transfectant cells contained factor IX and neo transgenes, whereas 3 produced from the uncloned population contained the marker gene only. A murine model of factor IX deficiency was generated by Kundu et al. (1998) as a basis for developing gene therapy strategies for hemophilia B. Knockout mice using embryonic stem cells resulted in an apparently faithful model of hemophilia B. Blood coagulation capacity increases with age in healthy individuals. Through extensive longitudinal analyses of human factor IX gene expression in transgenic mice, Kurachi et al. (1999) identified 2 essential age regulatory elements that they termed AE5-prime and AE3-prime. These elements are required and together are sufficient for normal age regulation of factor IX expression. AE5-prime, located between nucleotides -770 through -802, is a PEA3-related element present in the 5-prime upstream region of the gene encoding factor IX and is responsible for age-stable expression of the gene. AE3-prime, located in the middle of the 3-prime untranslated region, is responsible for age-associated elevation in mRNA levels. In a concerted manner, AE5-prime and AE3-prime recapitulate natural patterns of the advancing age-associated increase in factor IX gene expression. In 2 distinct dog breeds, Gu et al. (1999) found factor IX deficiency. In one breed, they identified a large deletion mutation, spanning the entire 5-prime region of the F9 gene extending to exon 6. In the second breed, an insertion of approximately 5 kb disrupted exon 8. The insertion was associated with alternative splicing between a donor site 5-prime and acceptor site 3-prime to the normal exon 8 splice junction, with introduction of a new stop codon. Yant et al. (2000) described the successful use of transposon technology for the nonhomologous insertion of foreign genes into the genomes of adult mammals using naked DNA. Yant et al. (2000) showed that the 'Sleeping beauty' transposase, the product of a synthetic transposable element, can efficiently insert transposon DNA into the mouse genome in approximately 5 to 6% of transfected mouse liver cells. Chromosomal transposition resulted in long-term expression (greater than 5 months) of human blood coagulation factor IX at levels that were therapeutic in a mouse model of hemophilia B. Brooks et al. (2003) found that mild hemophilia B in a large pedigree of German wirehaired pointers was caused by a line-1 insertion in the factor IX gene. The insert could be traced through at least 5 generations and segregated with the hemophilia B phenotype. ### ALLELIC VARIANTS (selected examples) #### .0001 HEMOPHILIA B (LEYDEN) [F9, T-A, -20] Veltkamp et al. (1970) first described this variant (called factor IX Leyden), which is characterized by disappearance of the bleeding diathesis as the patient ages. In these patients, plasma factor IX levels are less than 1% of normal before puberty, but after puberty factor IX activity and antigen levels rise steadily in a 1:1 ratio to a maximum of 50 to 60%. Briet et al. (1982) described a variant of hemophilia B which took a severe form early in life but remitted after puberty, with increase in IX:C levels from below 1% of normal to about 50% of normal when studied at about age 80 years. In 3 pedigrees, all traced to a small village in the east of the Netherlands, the authors identified 27 affected males. In 2 probably related Dutch pedigrees, Reitsma et al. (1988) found that patients had a single point mutation (T-to-A) at position -20 of the F9 gene. This led to the hypothesis that hemophilia B Leyden results from a promoter mutation. The findings suggested that a point mutation can lead to a switch from constitutive to steroid hormone-dependent gene expression. Reijnen et al. (1992) demonstrated that the -20 promoter mutation disrupts the binding of hepatocyte nuclear factor 4 (HNF-4), a member of the steroid hormone receptor superfamily of transcription factors. Studies also demonstrated that the G-to-C mutation at -26 (306900.0097) also disrupts the binding of HNF-4. Whereas HNF-4 transactivated the wildtype promoter sequence in liver and nonliver (e.g., HeLa) cell types, it transactivated the -20 mutated promoter to only a limited extent and the -26 mutated promoter not at all. The data suggested that HNF-4 is a major factor controlling factor IX expression in the normal individual. Furthermore, the severity of the hemophilia phenotype appeared to be related directly to the degree of disruption of HNF-4 binding and transactivation; the -26 G-to-C mutation was accompanied by a bleeding tendency which did not ameliorate after puberty. #### .0002 HEMOPHILIA B (LEYDEN) [F9, G-A, -6] Fahner et al. (1988) found a G-to-A change in nucleotide -6 as the cause of hemophilia B of the Leyden characteristic, i.e., severe bleeding disorder in childhood which becomes mild after puberty. Hirosawa et al. (1990) pointed out that all 5 families with factor IX Leyden genes analyzed to date have mutations in a region about 40 bp in length, which they referred to as the Leyden-specific, or LS, region. Base changes at nucleotide -20 as well as at nucleotide -6 and deletions of the 3-prime half of the LS region reduced expression of the factor IX gene to about 15-31% that of normal controls, as assessed in a cultured cell (HepG2) expression system. Androgen significantly increased the transcriptional activities of both mutant and normal factor IX genes in a concentration-dependent manner. Crossley et al. (1990) also identified a G-to-A change at position -6 as the cause of hemophilia B Leyden. #### .0003 HEMOPHILIA B (LEYDEN) [F9, G-C, -6] Attree et al. (1989) found a G-to-C change in nucleotide -6. Vidaud et al. (1993) cited evidence indicating that the G-C transversion at position -6 produces a much milder disorder than does the G-A transition at the same position (306900.0002). #### .0004 HEMOPHILIA B (LEYDEN) [F9, DEL A, +13] Reitsma et al. (1989) studied the F9 gene in a Greek patient and an American patient of Armenian descent with hemophilia B Leyden. In one they found deletion of A at position +13 of the factor IX gene and in the other an A-to-G mutation at the same position, 32 bp downstream of the point mutation in the Dutch kindred (Reitsma et al., 1988). See also Crossley et al. (1989). Crossley and Brownlee (1990) identified a binding site for the CCAAT/enhancer binding protein (C/EBP) extending from +1 to +18. They showed that the A-to-G mutation at +13 prevents the binding of C/EBP to this site. Furthermore, they showed that C/EBP is capable of transactivating a cotransfected normal factor IX promoter but not the mutant promoter. #### .0005 FACTOR IX, NORMAL VARIANT [F9, ILE-40PHE] Koeberl et al. (1989) described a normal variant, isoleucine or phenylalanine, at position -40 in exon 1. #### .0006 FACTOR IX POLYMORPHISM [F9, IVS1, A192G] Tanimoto et al. (1988) found a normal polymorphism, A to G, at nucleotide 192 in IVS1 of the F9 gene. #### .0007 HEMOPHILIA B [F9, ARG14TRP] In a case (designated Ox3) of severe hemophilia B of the CRM-positive type, Bentley et al. (1986) of Oxford University found mutation of arginine to glutamine at position -4, leading to defective cleavage of the N-terminal propeptide. The type of mutation in this mutant factor IX is similar to that in the procollagen molecule (either the alpha-1 or alpha-2 chain of type I collagen) in cases of type VII Ehlers-Danlos syndrome. Two proteolytic cleavages normally occur to remove the prepeptide and the propeptide regions. The mutant F-IX had 18 additional amino acids on the N-terminal portion. Normally the signal peptidase cleaves the peptide bond between residues -18 and -19. Further cleavage to mature F-IX depends on the arginine residue at -4. Arginine at -4 shows evolutionary conservation in factor X, prothrombin, C3, C4, C5, and tissue type plasminogen activator--all proteins that, like F-IX, are processed by site-specific trypsin-like enzymes. In addition to the CRM-positive and CRM-negative forms, there is a CRM-reduced class. Sugimoto et al. (1989) demonstrated by amino acid sequence that the mutant factor IX retained the propeptide region of 18 amino acids due to a substitution of arginine at position -4 by glutamine. They assumed that this attached propeptide region of the molecule directly interferes with the adjacent NH(2)-terminus and prevents the metal-induced conformational changes that are essential for biologic activity of normal factor IX. #### .0008 HEMOPHILIA B [F9, ARG(-4)GLN] FACTOR IX SAN DIMAS Ware et al. (1989) studied the intragenic defect in factor IX(San Dimas) which was derived from a patient with moderately severe hemophilia B who had 98% factor IX antigen but very low factor IX clotting activity. They found a point mutation in exon 2. A guanine-to-adenine transition caused the substitution of a glutamine codon for an arginine codon at -4 in the propeptide of factor IX. The variant protein circulated in the plasma as profactor IX with a mutant 18-amino acid propeptide still attached. Factor IX(San Dimas) shows similarities to factor IX(Cambridge), which has a substitution of serine for arginine at -1 (306900.0009). #### .0009 HEMOPHILIA B [F9, ARG(-1)SER] FACTOR IX CAMBRIDGE Diuguid et al. (1986) found that mutant factor IX(Cambridge), isolated from a patient with severe hemophilia B, has an 18-residue propeptide attached to its NH2-end. A point mutation at residue -1, from arginine to serine, precluded cleavage of the propeptide by the processing protease and interfered also with gamma-carboxylation of the mutant factor IX. The last effect indicates the importance of the leader sequence in substrate recognition by the vitamin K-dependent carboxylase. #### .0010 HEMOPHILIA B [F9, GLU7ASP] See Winship (1989). #### .0011 HEMOPHILIA B [F9, GLN11TER] See Winship (1989); the patient studied had a severe form of hemophilia B. #### .0012 HEMOPHILIA B [F9, CYS18ARG] Information was provided by Bertina (1989); the patient studied had a severe form of hemophilia B. #### .0013 HEMOPHILIA B [F9, GLU27LYS] FACTOR IX SEATTLE 3 Chen et al. (1989) studied 5 patients with severe hemophilia B and detectable factor IX antigen that showed altered reactivity to a specific polyclonal antibody fraction or monoclonal anti-factor IX antibody. By the PCR technique, they identified a single base transition in each of the 5 families. Three different mutations were identified: factor IX(Seattle-3) showed a G-to-A transition in exon 2, changing the codon for glu27 to lys; factor IX(Durham) showed a G-to-A transition in exon 4, changing the codon for gly60 to ser; and factor IX(Seattle-4) showed a G-to-A transition in exon 8, changing arg248 to gln in exon 8. #### .0014 HEMOPHILIA B [F9, GLU27VAL] FACTOR IX CHONGQING Wang et al. (1990) studied a Chinese patient with sporadic hemophilia B of severe form. A defect in the factor IX Gla domain was suspected because of low antigen on an assay using a calcium-dependent antibody fraction. Since the Gla domain is coded mainly by exon 2, Wang et al. (1990) amplified and sequenced the exon and found an A-to-T substitution at nucleotide 6455. The transversion changed glutamic acid-27 to valine. In leukocyte DNA from the patient's mother, the nucleotide sequence of exon 2 was entirely normal. #### .0015 HEMOPHILIA B [F9, ARG29TER] See Green et al. (1989). This mutation, which is due to a transition at a CpG dinucleotide, was found by Koeberl et al. (1990) in 2 cases of severe hemophilia B. Koeberl et al. (1990) estimated that approximately 1 in 4 individuals with hemophilia B can be expected to have a mutation at arginine and concluded that nonsense mutations at 1 of the 6 arginine residues are common causes of severe hemophilia. #### .0016 HEMOPHILIA B [F9, ARG29GLN] See Koeberl et al. (1989) and Zhang et al. (1989). The hemophilia was clinically mild. #### .0017 HEMOPHILIA B [F9, GLU33ASP] See Koeberl et al. (1989). #### .0018 HEMOPHILIA B [F9, 5-IVS355] Brownlee (1988) described a GT-to-GG donor splice site mutation in IVS3 in association with severe hemophilia B. #### .0019 HEMOPHILIA B [F9, ASP47GLY] FACTOR IX ALABAMA Davis et al. (1984, 1987) found that factor IX(Alabama), a CRM+ mutation responsible for a clinically moderate form of hemophilia B, has an adenine to guanine transition in the first nucleotide of exon d, causing substitution of glycine for aspartic acid (GAT to GGT) at residue 47. The structural defect in factor IX(Alabama) results in a molecule with 10% of normal coagulant activity. McCord et al. (1990) concluded that the asp47-to-gly mutation, which occurs in a calcium-binding site, results in a loss of a stable calcium-mediated conformational change, leading to improper interaction with factor VIIIa and factor X. #### .0020 HEMOPHILIA B [F9, GLN50PRO] See Lozier et al. (1989). The hemophilia was clinically severe. #### .0021 HEMOPHILIA B [F9, PRO55ALA] FACTOR IX HOLLYWOOD See Green et al. (1989) and Spitzer et al. (1989). The hemophilia was clinically mild. #### .0022 HEMOPHILIA B [F9, GLY60SER] FACTOR IX DURHAM In 2 men with mild hemophilia B (Durham), Denton et al. (1988) found that the highly conserved gly60 residue had been changed to ser. The mutation was accompanied by defective epitope expression in the 2 patients, suggesting that a change in the tertiary structure of the EGF-like domain is the cause of the mild hemophilia B. See Chen et al. (1989). Poort et al. (1989) found the same mutation in a Dutch family. A G-to-A change at position 10430 in exon 4 was responsible. The presence of the same mutation in 3 patients from distinct geographic areas confirmed the notion that CG dinucleotides are 'hotspots' for mutation. #### .0023 HEMOPHILIA B [F9, ASP64GLY] See Green et al. (1989). The hemophilia was clinically mild. #### .0024 HEMOPHILIA B [F9, GLY114ALA] See Winship et al. (1989). The hemophilia was clinically severe. #### .0025 HEMOPHILIA B [F9, ASN120TYR] See Green et al. (1989). The hemophilia was clinically severe. #### .0026 HEMOPHILIA B [F9, ARG145CYS] FACTOR IX CARDIFF Liddell et al. (1989) described a molecular defect in factor IX Cardiff, a variant that showed faulty activation with the production of a stable reaction product with a molecular weight compatible with that of a putative light chain-activation intermediate. A single C-to-T transition was discovered that changed the arg residue at position 145 (the first residue of the first bond in the activation peptide) to a cys. The hemophilia was clinically moderate to severe. #### .0027 HEMOPHILIA B [F9, ARG145HIS] FACTOR IX CHAPEL HILL FACTOR IX NAGOYA 3 Factor IX(Chapel Hill), a CRM+ variant of mild hemophilia B, results from an arg-to-his change at residue 145, which prevents cleavage at one of the activation sites (Noyes et al., 1983). See Koeberl et al. (1989). Suehiro et al. (1990) concluded that the arg145-to-his substitution impairs the cleavage between the light chain and the activation peptide by factor XIa/calcium ions. #### .0028 FACTOR IX MALMO [F9, THR148ALA] McGraw et al. (1985) demonstrated that there is a common polymorphism at the third amino acid residue of the activation peptide: threonine (coded by ACT) or alanine (coded by GCT). Winship and Brownlee (1986) defined a polymorphism in the coding portion of the F9 gene by means of two 19-bp oligonucleotide probes. The polymorphism, an A-to-G transition at nucleotide 20,422, resulting in either alanine or threonine at amino acid 148 of the activated peptide, gave rise to an MnlI RFLP. Technical problems, however, made it difficult to detect the polymorphic fragments by conventional Southern blotting. The polymorphism as identified by the oligonucleotide probes was used for linkage studies in a 3-generation family. Graham et al. (1988) showed that the polymorphism demonstrable immunologically in factor IX in normal persons is due to a dimorphism of amino acids threonine and alanine at position 148 of the protein. Factor IX protein with threonine reacted to the mouse monoclonal antibody, whereas that with alanine at that position did not. The polymorphism is referred to as the Malmo polymorphism; positive reactors are designated Malmo A, and negative reactors are designated Malmo B. Strong linkage disequilibrium was found with 2 other intragenic RFLPs. #### .0029 HEMOPHILIA B [F9, GLN173TER] See Koeberl et al. (1989). The hemophilia was clinically severe. #### .0030 HEMOPHILIA B [F9, ARG180TRP] FACTOR IX B-M NAGOYA FACTOR IX DEVENTER Suehiro et al. (1989) demonstrated substitution of tryptophan for arginine at position 180 in the factor IX protein of a patient with severe hemophilia B. Bertina et al. (1990) found the same mutation. #### .0031 HEMOPHILIA B [F9, ARG180GLN] FACTOR IX HILO FACTOR IX NOVARA Huang et al. (1989) demonstrated a point mutation in a hemophilia B(m) variant, factor IX(Hilo). Glutamine (CAG) was substituted for arginine (CGG) at amino acid 180 in exon 6 (G-to-A at nucleotide 20519). Bertina et al. (1990) found the same mutation. The hemophilia was clinically severe. #### .0032 HEMOPHILIA B [F9, VAL181PHE] FACTOR IX MILANO See Bertina et al. (1989, 1990). #### .0033 HEMOPHILIA B [F9, VAL182PHE] FACTOR IX KASHIHARA Sakai et al. (1989) found that the defect in hemophilia B Kashihara, a severe hemorrhagic disorder in which a factor IX antigen is present in normal amounts but factor IX biological activity is markedly reduced, has a defect in valine-182 (equivalent to valine-17 in the chymotrypsin numbering system), which is replaced by phenylalanine. The change appears to hinder sterically the cleavage of arg180-val181 required for the activation of this zymogen. #### .0034 HEMOPHILIA B(m) [F9, VAL182LEU] FACTOR IX CARDIFF II See Taylor et al. (1989). One of the variant forms of hemophilia B in which normal levels of a dysfunctional factor IX protein is found is referred to as hemophilia B(m) (Hougie and Twomey, 1967; Kasper et al., 1977). The abnormal factor IX results in prolongation of the prothrombin time performed with ox brain thromboplastin. In 1 such patient, Taylor et al. (1990) found a G-to-C transversion at nucleotide 20,524, changing the amino acid encoded at residue 182 from valine to leucine. The abnormal factor IX protein showed a normal molecular weight and normal calcium-binding properties. Activation of the mutant factor IX with factor XIa showed normal proteolytic cleavage. Hemophilia was clinically mild in these patients. #### .0035 HEMOPHILIA B [F9, GLN191TER] See Matsushita et al. (1989). The hemophilia was clinically severe. #### .0036 HEMOPHILIA B [F9, GLN191LEU] Information was provided by Chen and Thompson (1989). The hemophilia was clinically severe. #### .0037 HEMOPHILIA B [F9, TRP194TER] See Green et al. (1989). The hemophilia was clinically severe. #### .0038 HEMOPHILIA B [F9, 5-IVS6SS] See Rees et al. (1985). The hemophilia was clinically severe. #### .0039 HEMOPHILIA B [F9, TRP215TER] Information was provided by Chen and Thompson (1989). The hemophilia was clinically severe. #### .0040 HEMOPHILIA B [F9, CYS222TRP] See Koeberl et al. (1989). The hemophilia was clinically moderate in severity. #### .0041 FACTOR IX, DNA POLYMORPHISM [F9, VAL227VAL] A T-to-C substitution in codon 227 produced no change in amino acid (Koeberl et al., 1989). #### .0042 HEMOPHILIA B [F9, ALA233THR] See Koeberl et al. (1989). The hemophilia was clinically mild. #### .0043 HEMOPHILIA B [F9, 3-IVS7SS] Matsushita et al. (1989) found a G-to-A substitution in the last nucleotide in the 3-prime acceptor splice site of IVS7. The hemophilia was severe and was associated with a serum inhibitor. #### .0044 HEMOPHILIA B [F9, ARG248TER] See Green et al. (1989). #### .0045 HEMOPHILIA B [F9, ARG248GLN] FACTOR IX SEATTLE 4 FACTOR IX DREIHACKEN See Chen et al. (1989). In a patient with hemophilia B, Ludwig et al. (1992) identified a G-to-A transition at nucleotide 30864 of the F9 gene, resulting in replacement of arg248 by gln in the mature factor IX protein. #### .0046 HEMOPHILIA B [F9, ARG252TER] FACTOR IX PORTLAND In male sibs with severe hemophilia B, Chen et al. (1989) demonstrated a C-to-T change at nucleotide 30875 resulting in a nonsense mutation (TGA) and termination of protein synthesis at amino acid residue 252. The change involved a CpG dinucleotide. The protein was designated factor IX(Portland). #### .0047 HEMOPHILIA B [F9, ASN260SER] See Koeberl et al. (1989). The hemophilia was clinically mild. #### .0048 HEMOPHILIA B [F9, PRO287LEU] Information was provided by Chen and Thompson (1989). The hemophilia was clinically severe. #### .0049 HEMOPHILIA B [F9, ALA291PRO] See Winship et al. (1989). #### .0050 HEMOPHILIA B [F9, THR296MET] See Koeberl et al. (1989). Hemophilia B is an X-linked disorder relatively frequent among the Amish, particularly those living in Ohio (Wall et al., 1967). Ketterling et al. (1991) demonstrated that the Amish mutation is thr296-to-met. Among 64 families of European descent with hemophilia B, Ketterling et al. (1991) found that 6 (9%) had a C-to-T transition at base 31008 leading to the thr296-to-met mutation in the catalytic domain of factor IX. Five of the patients had the same haplotype and were known to be from the Amish group or were presumed to be. All 6 patients had clinically mild disease. #### .0051 HEMOPHILIA B [F9, VAL307ALA] See Bottema et al. (1989). The hemophilia was clinically mild. #### .0052 HEMOPHILIA B [F9, GLY309VAL] See Thompson et al. (1989). The hemophilia was clinically severe. #### .0053 HEMOPHILIA B [F9, TRP310TER] See Wang et al. (1990). The hemophilia was clinically severe. #### .0054 HEMOPHILIA B [F9, GLY311ARG] See Koeberl et al. (1989). #### .0055 HEMOPHILIA B [F9, ARG333TER] See Zhang et al. (1989). This mutation, due to a transition at a CpG dinucleotide, was found by Koeberl et al. (1990) in 2 patients with severe hemophilia B. #### .0056 HEMOPHILIA B [F9, ARG333GLN] FACTOR IX LONDON Tsang et al. (1988) characterized the mutation in factor IX (London 2), which caused a severe CRM+ hemophilia B. Tsang et al. (1988) found a G-to-A transition at position 31119. The mutation resulted in substitution of glutamine for arginine at position 333. This arginine residue is conserved in the catalytic domain of normal human and bovine factor IX, factor X, and prothrombin. This mutation pinpoints a functionally critical feature of factor IX which may be involved in substrate or cofactor binding. #### .0057 HEMOPHILIA B [F9, CYS336ARG] See Green et al. (1989). The hemophilia was clinically of moderate severity. #### .0058 HEMOPHILIA B [F9, ARG338TER] FACTOR IX BONN 1 Ludwig et al. (1989) demonstrated a C-to-T transition at amino acid 338, converting the CGA codon for arginine to a TGA stop codon. The factor IX was known as Bonn-1. The hemophilia was clinically severe. #### .0059 HEMOPHILIA B [F9, ARG338GLN] See Zhang et al. (1989). The hemophilia was clinically of moderate severity. #### .0060 HEMOPHILIA B [F9, MET348VAL] Information was provided by Chen and Thompson (1989). The hemophilia was clinically of moderate severity. #### .0061 HEMOPHILIA B [F9, SER360LEU] Information was provided by Chen and Thompson (1989). The hemophilia was clinically of moderate severity. #### .0062 HEMOPHILIA B [F9, GLY363VAL] See Spitzer et al. (1988). The hemophilia was clinically of moderate severity. #### .0063 HEMOPHILIA B [F9, GLY367ARG] Information was provided by Chen and Thompson (1989). The hemophilia was clinically severe. #### .0064 HEMOPHILIA B [F9, PRO368THR] See Bertina et al. (1989, 1990). #### .0065 HEMOPHILIA B [F9, PHE378LEU] Information was provided by Chen and Thompson (1989). The hemophilia was clinically severe. #### .0066 HEMOPHILIA B [F9, ALA390GLU] Information was provided by Thompson (1989). The hemophilia was clinically of moderate severity. #### .0067 HEMOPHILIA B [F9, ALA390VAL] FACTOR IX NIIGATA FACTOR IX LAKE ELSINORE Spitzer et al. (1988) found substitution of valine for alanine at position 390, resulting from a single base substitution (C-to-T) in exon 8. Sugimoto et al. (1988) demonstrated substitution of valine for alanine at position 390 in the catalytic domain as the molecular defect in factor IX Niigata. The patient had a moderately severe form of hemophilia B with a normal level of factor IX antigen but very low clotting activity. Bertina et al. (1990) referred to this mutation as 'Lake Elsinore.' #### .0068 HEMOPHILIA B [F9, GLY396ARG] FACTOR IX ANGERS Attree et al. (1989) designed a strategy allowing rapid analysis of the critical serine protease catalytic domain of activated factor IX, encoded by exons VII and VIII of the gene. The method involved enzymatic amplification of genomic DNA, analysis of the amplification products by denaturing gradient gel electrophoresis, and direct sequencing of the fragments displaying an altered melting behavior. They used this procedure to characterize 2 'new' mutations: factor IX(Angers), a G-to-A substitution generating an arg in place of a gly at amino acid 396 of the mature factor IX protein; and factor IX(Bordeaux), an A-to-T substitution introducing a nonsense codon in place of the normal codon for lys at position 411. The hemophilia was clinically severe. #### .0069 HEMOPHILIA B [F9, ILE397THR] FACTOR IX LONG BEACH FACTOR IX VANCOUVER FACTOR IX LOS ANGELES Ware et al. (1988) demonstrated that the defect in factor IX(Long Beach) is a result of a thymine-to-cytosine transition leading to the substitution of a threonine codon (ACA) for an isoleucine codon (ATA) in exon 8 of the F9 gene. In a case of hemophilia B of moderate severity, Geddes et al. (1989) found a mutation in the protease domain of factor IX that changed the codon for isoleucine-397 (ATA) to a threonine codon (ACA). The resulting abnormal protein had been named factor IX(Vancouver) (Geddes et al., 1987). Thus, factor IX(Long Beach), factor IX(Vancouver), and factor IX(Los Angeles) have the same defect. In 11 of 65 consecutive males with hemophilia B (17%), Bottema et al. (1990) found this mutation, a T-to-C transition at base 31311, which substitutes threonine for isoleucine-397. The 11 patients were of western European descent and had the same haplotype. Judging from the frequency of this haplotype, the probability of the same mutation occurring independently 11 times in this haplotype was considered to be minuscule. Despite the lack of overlapping pedigrees, a common ancestor for these patients was suspected. The clinical symptoms were considerably moderate/mild. Sarkar et al. (1991) found this mutation in 2 females with hemophilia B. Both were heterozygous, coming from unrelated families. Nonrandom X inactivation was proposed, although other possibilities included a second undetected intronic or promoter mutation. Chen et al. (1991) found this mutation in 7 families which all shared a rare haplotype, suggesting a common ancestor. #### .0070 HEMOPHILIA B [F9, TRP407ARG] See Koeberl et al. (1989). #### .0071 HEMOPHILIA B [F9, LYS411TER] FACTOR IX BORDEAUX See Attree et al. (1989). The hemophilia was clinically severe. #### .0072 HEMOPHILIA B [F9, EX1-8DEL] Deletions of various sizes deleting exons 1-8 were reported by Giannelli et al. (1983), Anson et al. (1988), Taylor et al. (1988), Matthews et al. (1987), Ludwig et al. (1989), Wadelius et al. (1988), Bernardi et al. (1985), Mikami et al. (1987), Tanimoto et al. (1988), Koeberl et al. (1989), and Hassan et al. (1985). Some of the deletions were associated with development of inhibitors and others of comparable size were not. The hemophilia was clinically severe. #### .0073 HEMOPHILIA B [F9, EX1DEL] Ludwig et al. (1989) described deletion of exon 1 in a case of severe hemophilia B. #### .0074 HEMOPHILIA B [F9, EX1-3DEL] See Ludwig et al. (1989). The hemophilia was severe and was associated with serum inhibitors. #### .0075 HEMOPHILIA B [F9, EX2-8DEL] Information was provided by Chen and Thompson (1989). The hemophilia was severe and was associated with serum inhibitors. #### .0076 HEMOPHILIA B [F9, EX4-5DEL] See Ludwig et al. (1989). The hemophilia was clinically severe. #### .0077 HEMOPHILIA B [F9, EX4DEL] See Vidaud et al. (1986). The hemophilia was clinically severe. #### .0078 HEMOPHILIA B [F9, EX4INS] FACTOR IX EL SALVADOR In a patient with moderate to severe hemophilia B, Chen et al. (1988) found a large insertion in the F9 gene, which appeared to have originated from outside the gene rather than to represent an internal duplication. The abnormal gene was dubbed El Salvador for the birthplace of the patient. #### .0079 HEMOPHILIA B [F9, EX5-8DEL] See Matthews et al. (1987) and Peake et al. (1989). The hemophilia was severe and was associated with serum inhibitors. #### .0080 HEMOPHILIA B [F9, EX51INS] See Vidaud et al. (1989). The hemophilia was clinically severe. #### .0081 HEMOPHILIA B [F9, EX7DEL] See Ludwig et al. (1989). The hemophilia was clinically severe. #### .0082 HEMOPHILIA B [F9, ASP85FS] FACTOR IX SEATTLE 2 In a case of severe hemophilia B, Schach et al. (1987) found deletion of a single adenine nucleotide in exon 5. This resulted in a frameshift that converted an aspartic acid at position 85 in the protein to a valine and the formation of a stop signal at position 86. #### .0083 HEMOPHILIA B OXFORD h5 [F9, VAL328PHE] Winship (1990) found a substitution of valine by phenylalanine at residue 328 in exon h of factor IX in a patient with hemophilia B referred to as hemophilia B Oxford h5 (Oxh5). The substitution was caused by a G-to-T transversion at nucleotide 31103. Arg327-val328 is the major thrombin cleavage site in factor IX. Winship (1990) suggested that the mutant protein may have increased susceptibility to thrombin cleavage with resulting in vivo instability of the mutant protein. #### .0084 HEMOPHILIA B [F9, ARG116TER] In a 4-year-old boy with severe hemophilia B, an isolated case in his family, Montandon et al. (1990) identified a C-to-T transition at residue 17762 resulting in a translation stop at codon arginine-116. A second mutation in this patient at residue 30890 resulted in a his257-to-tyr substitution (306900.0085); this mutation was subsequently shown to be neutral by the fact that its origin preceded the maternal grandfather and it produced no reduction in factor IX coagulant and antigen level in the grandfather. On the other hand, analysis of other family members showed that the mutation for arg116-to-ter had occurred at gametogenesis in the paternal grandfather. The patient was referred to as Malmo 7. #### .0085 FACTOR IX POLYMORPHISM [F9, HIS257TYR] See 306900.0084. #### .0086 HEMOPHILIA B [F9, CYS350SER] Taylor et al. (1991) described a male patient in whom they documented somatic mosaicism for a cysteine-to-serine alteration at codon 350 in the catalytic domain of factor IX. The mutation resulted from a guanine-to-cytosine transversion at nucleotide 31170. Using a combination of allele-specific oligonucleotide hybridization and differential termination of primer extension, Taylor et al. (1991) showed that hepatic, renal, smooth muscle, and hematopoietic cells possessed both normal and mutant factor IX sequences. An additional unusual phenomenon in this pedigree was the presence of 2 females in successive generations with moderately severe factor IX deficiency. These females were the daughter and granddaughter of the proband. No evidence of X chromosome or autosome cytogenetic abnormalities was found, no additional sequence alterations were identified in the factor IX gene in either woman and no gross changes were observed on Southern analysis of the regulatory regions in the 5-prime and 3-prime ends of the gene. The normal X chromosomes of the 2 women were shown to have different haplotypes at the factor IX locus. Taylor et al. (1991) speculated that the X chromosome bearing the normal factor IX gene has been exclusively inactivated in both affected women, possibly secondary to a second genetic change affecting the primary inactivation center on the mutant X chromosome and resulting in a failure of inactivation of the mutant factor IX sequences. #### .0087 HEMOPHILIA B [F9, ASP64ASN] Winship and Dragon (1991) described a G-to-A transition of nucleotide 10442, resulting in substitution of asparagine for aspartic acid-64. The change resulted in a functionally defective factor IX molecule that altered calcium-binding properties. #### .0088 HEMOPHILIA B (LEYDEN) [F9, T-C, +8] In an Anglo-Irish family living in New Zealand, Royle et al. (1991) identified a T-to-C transition at position +8 in the promoter region as the cause of hemophilia B (Leyden). This mutation is situated within the repeat consensus sequence in the transcribed but untranslated portion of the gene. The mutation had arisen de novo in the proband. #### .0089 HEMOPHILIA B (LEYDEN) [F9, A-T, -5] In a 3-year-old boy, Picketts et al. (1992) described an A-to-T transversion at position -5 of the factor IX promoter. Picketts et al. (1993) identified 5 transcription factor binding sites within the F9 promoter and showed that the Leyden mutation at nucleotide -5 interfered with the binding of proteins to 1 of 3 newly identified sites. The correlation between the postpubertal recovery of these mutants and the induction of the transcription factor DBP (D-site binding protein; 124097) led Picketts et al. (1993) to the discovery of a synergistic interaction between DBP and C/EBP (CCAAT/enhancer binding protein; 116897). #### .0090 HEMOPHILIA B (LEYDEN) [F9, A-G, +13] As indicated in 306900.0004, Reitsma et al. (1989) found an A-to-G mutation at position +13 of the factor IX gene in an American patient of Armenian descent with hemophilia B Leyden. #### .0091 HEMOPHILIA B [F9, GLY311GLU] FACTOR IX AMAGASAKI In a patient with hemophilia B, Miyata et al. (1991) identified a G-to-A substitution in exon 8 resulting in replacement of glycine-311, a highly conserved amino acid residue among serine proteases, by glutamic acid. The mutation resulted in complete loss of both coagulant activity and esterase activity. #### .0092 HEMOPHILIA B [F9, IVS4, 4442-BP DEL] FACTOR IX MADRID 2 In a 17-year-old male with severe hemophilia B, Solera et al. (1992) found a 4,442-bp deletion, which removed both the donor splice site located at the 5-prime end of intron d and the last 2 coding nucleotides located at the 3-prime end of exon 4. This fragment had been replaced by a 47-bp sequence from the normal factor IX gene, inserted in inverted orientation. They identified 2 homologous sequences at the ends of the deleted DNA fragment. #### .0093 HEMOPHILIA B [F9, SER365ILE] FACTOR IX SCHMALLENBERG Ludwig et al. (1992) described the molecular basis of hemophilia B in 5 patients who had neither deletions nor rearrangements of the F9 gene. By enzymatic amplification and sequencing of all exons and promoter regions, a causative mutation in the protease domain was identified in each patient. The first was a G-to-T transversion in nucleotide 31215, leading to substitution of isoleucine for serine-365. #### .0094 HEMOPHILIA B [F9, SER365GLY] FACTOR IX VAREL Ludwig et al. (1992) demonstrated an A-to-G transition at nucleotide 31214 resulting in replacement of serine-365 by glycine. This mutation was in the same codon as that involved in factor IX Schmallenberg (306900.0093). This patient also had a silent mutation (GAT to GAC) at asp364. Thus, this patient had a double basepair substitution of TA to CG at nucleotides 31213 and 31214 but only a single amino acid change of ser365-to-gly. This patient also developed an antibody to factor IX during replacement therapy, which suggested that deletion of the factor IX gene is not necessary for development of antibody. #### .0095 HEMOPHILIA B [F9, ASP364HIS] FACTOR IX MECHTAL In a patient with hemophilia B, Ludwig et al. (1992) identified a G-to-C transversion at nucleotide 31211, resulting in substitution of his for asp364. #### .0096 HEMOPHILIA B [F9, GLU245VAL] FACTOR IX MONSCHAU In a patient with hemophilia B, Ludwig et al. (1992) identified an A-to-T transversion at nucleotide 30855, resulting in substitution of valine for glutamic acid-245. #### .0097 HEMOPHILIA B BRANDENBURG [F9, G-C, -26] Unlike other F9 promoter mutations which result in hemophilia B Leyden (e.g., 306900.0001), this promoter mutation, a G-to-C change at -26, is accompanied by a bleeding tendency that is not ameliorated after puberty (Reijnen et al., 1992). Reijnen et al. (1992) demonstrated that this mutation disrupted the binding of hepatocyte nuclear factor IV (HNF-4), a member of the steroid hormone receptor superfamily of transcription factors, which normally binds at nucleotides -34 to -10. Whereas HNF-4 transactivated the wildtype promoter sequence in liver and nonliver (e.g., HeLa) cell types, it did not at all transactivate the -26 mutated promoter. Crossley et al. (1992) provided an explanation for why the -20 promoter mutation shows recovery at puberty and the -26 Brandenburg mutation does not. Both mutations impair transcription by disrupting the binding site for the liver-enriched transcription factor LF-A1/HNF4. The -26 but not the -20 mutation also disrupts an androgen-responsive element, which overlaps the LF-A1/HNF4 site. This explains the failure of improvement in -26 patients. #### .0098 HEMOPHILIA B DUE TO ALU INSERTION [F9, ALU INSERTION, EX5] In a patient with severe hemophilia B, Vidaud et al. (1993) discovered a de novo insertion of a human-specific Alu repeat element within exon 5 of the F9 gene. The element interrupted the reading frame of the mature factor IX at glutamic acid 96 resulting in a stop codon within the inserted sequence. The Alu repeat was 322 bp long and was thought to have been inserted through retroposition. Insertional mutagenesis involving an Alu element has been reported in type I neurofibromatosis (162200.0001) and in gyrate atrophy (258870.0023). The involvement of Alu elements in gene deletion through homologous recombination and unequal crossing-over has been demonstrated in familial hypercholesterolemia (e.g., 143890.0029) and ADA deficiency (102700.0008). #### .0099 HEMOPHILIA B [HEMB, ILE-30ASN] Among the many mutations of the F9 gene described in hemophilia B (Giannelli et al., 1992), the density of amino acid substitutions in the domains coded by the different exons is similar, except for exon 'a' where it is much lower. Exon 'a' codes for the predomain of the signal peptide that is necessary for the transport of factor IX to the endoplasmic reticulum and for its secretion. Comparison of the signal peptide of secreted proteins shows lack of conservation of the primary amino acid sequence, and the only constant features are the presence of a charged residue at the amino end and a core of 8-12 hydrophobic residues. In a patient with severe, antigen-negative hemophilia B, Green et al. (1993) found an A-to-T transversion causing substitution of isoleucine by asparagine at position -30. This change disrupted the hydrophobic core of the prepeptide, a feature required for secretion. Thus, hemophilia in this patient was caused by failure to secrete factor IX from the hepatocytes. Only one other amino acid substitution had been reported in the prepeptide of factor IX; a cys-to-arg mutation at position -19 affecting the cleavage site between the pre- and propeptide (cys-19/thr-18) caused mild hemophilia (Bottema et al., 1991) (306900.0100). #### .0100 HEMOPHILIA B [HEMB, CYS-19ARG] See 306900.0099. #### .0101 HEMOPHILIA B [F9, VAL373GLU] Aguilar-Martinez et al. (1994) identified a val373-to-glu mutation in a 40-year-old man in whom the diagnosis of hemophilia was made at the age of 4 and who had been suffering hemarthrosis since the age of 13. A first cousin was affected. The mutation was located in the serine protease catalytic domain of the F9 gene. #### .0102 WARFARIN SENSITIVITY [F9, ALA-10THR] The propeptide sequences of the vitamin K-dependent clotting factors serve as a recognition site for the enzyme gamma-glutamyl carboxylase (137167), which catalyzes the carboxylation of glutamic acid residues in the amino terminus of the mature protein. Chu et al. (1996) described a mutation in the propeptide of factor IX that resulted in warfarin sensitivity because of reduced affinity of the carboxylase for the factor IX precursor. The patient studied in this report was a 49-year-old Caucasian male who was referred for evaluation of bleeding complications that developed during anticoagulation with warfarin. The patient had a congenital bicuspid aortic valve with accompanying aortic stenosis and regurgitation. An artificial valve was inserted when he was 49 years old. Bleeding complications occurred when he was given warfarin for anticoagulation after surgery. The patient's family history was negative for bleeding diatheses. The patient had mild Charcot-Marie-Tooth disease and several members of his family in several generations were also affected. The proband had a factor IX activity level of more than 100% when not receiving warfarin and less than 1% when receiving warfarin, at a point where other vitamin K-dependent factors were at 30 to 40% activity levels. Direct sequence analysis of amplified genomic DNA from all 8 exons and exon-intron junctions showed a G-to-A transition at nucleotide 6346 resulting in an alanine-to-threonine change at residue -10 in the propeptide. To define the mechanism by which the mutation resulted in warfarin sensitivity, they analyzed wildtype and mutant recombinant peptides in an in vitro carboxylation reaction. The peptides that were analyzed included the wildtype sequence of F9, the ala-10thr sequence, and the ala-10gly substitution which reflects the sequence in bone gamma-carboxyglutamic acid protein (112260). Measurement of carbon dioxide incorporation at a range of peptide concentrations demonstrated about twice normal V(max) values for both A-10T and A-10G, whereas K(m) values showed a 33-fold difference between wildtype and the variants. These studies delineated a novel mechanism for warfarin sensitivity and explained the observation that bone gamma-carboxyglutamic acid protein is more sensitive to warfarin than the coagulation proteins. #### .0103 WARFARIN SENSITIVITY [F9, ALA-10VAL ] Oldenburg et al. (1997) reported 3 patients in whom mutations in the factor IX propeptide was found to cause severe bleeding during coumarin therapy. Strikingly, the bleeding occurred within the therapeutic ranges of the prothrombin time (PT) and international normalized ratio (INR). In all 3 patients, coumarin therapy caused an unusually selective decrease of factor IX activity to levels below 1 to 3%. Upon withdrawal of coumarin, factor IX levels increased to subnormal or normal values of 55, 85 and 125%, respectively. In 1 patient the ala-10-to-thr mutation (306900.0102) was found; in 2 patients the missense mutation affecting the ala-10 residue was ala (GCC) to val (GTC). The mutation in the propeptide at a position that is essential for the carboxylase recognition site causes a reduced affinity of the carboxylase enzyme to the propeptide. This effect leads to an impaired carboxylase epoxidase reaction that is decisively triggered by the vitamin K concentration. #### .0104 HEMOPHILIA B [F9, ALA351PRO ] Chan et al. (1998) observed a 20-year-old female student with mild hemophilia B. She was found to be heterozygous for a mutation in codon 351 of the F9 gene: GCT (ala) was converted to CCT (pro). She had inherited the mutation from her carrier mother. Analysis of the methyl-sensitive HpaII sites at the 5-prime end of the hypoxanthine phosphoribosyltransferase gene (HPRT; 308000) showed that skewed inactivation of the X chromosome carrying her normal F9 gene accounted for the hemophilia phenotype. #### .0105 HEMOPHILIA B [F9, 17747G-A] Drost et al. (2000) demonstrated that nucleotide 17747 of the F9 gene is a mutation hotspot in all Latin American population samples but not in other populations. Two substitutions were observed, G-A and G-C (306900.0106). The authors suggested that this was the first evidence of population-specific effects on germline mutation that causes human genetic disease. #### .0106 HEMOPHILIA B [F9, 17747G-C] See (306900.0105) and Drost et al. (2000). #### .0107 HEMOPHILIA B [F9, IVS3DS, T-C, +2 ] In a woman with moderately severe hemophilia B, Costa et al. (2000) found a T-to-C transition at position +2 in the 5-prime splice site of intron 3 (6704T-C) and an ile344-to-thr missense mutation (360900.0108). The splice site mutation came from the mother who was a somatic mosaic; the missense mutation appeared to be a de novo mutation from the father. #### .0108 HEMOPHILIA B [F9, ILE344THR ] See 306900.0107 and Costa et al. (2000). #### .0109 HEMOPHILIA B [F9, CYS206SER ] Taylor et al. (1992) found that the causative mutation in the first reported patient with Christmas disease (Biggs et al., 1952) was a cys206-to-ser change in the F9 gene. The patient died at the age of 46 years from acquired immunodeficiency syndrome, contracted through treatment with blood products (Giangrande, 2003). #### .0110 HEMOPHILIA B [F9, 2-BP DEL ] Cutler et al. (2004) described a family in which the maternal grandfather of a severely affected infant with hemophilia B was a somatic and germline mosaic and had very mild factor IX deficiency. The maternal grandfather was apparently a somatic and germline mosaic for the family mutation, a 2-bp deletion (AG within codons 134-135) in the F9 gene causing a frameshift mutation and the creation of a premature termination sequence in exon 6 at codon 141. One daughter, the mother of the proband, was a carrier of the mutation; the other daughter, was not a carrier. ### SEE ALSO Anson et al. (1985); Attree et al. (1989); Bottema et al. (1991); Bottema et al. (1990); Bottema et al. (1989); Braunstein et al. (1981); Bray and Thompson (1986); Brown et al. (1970); Camerino et al. (1985); Chan et al. (1989); Chen et al. (1989); Choo et al. (1982); Connor et al. (1986); Didisheim and Vandervoort (1962); Giannelli et al. (1992); Girolami et al. (1980); Goldsmith et al. (1979); Graham et al. (1962); Green et al. (1991); Grunebaum et al. (1984); Hay et al. (1986); Holmberg et al. (1980); Kitchens et al. (1976); Koeberl et al. (1990); Koeberl et al. (1990); Liebman et al. (1985); Lillicrap et al. (1986); Mattei et al. (1985); Neal et al. (1973); Neuschatz and Necheles (1973); Orstavik et al. (1985); Orstavik et al. (1979); Smith (1985); Spitzer et al. (1988); Thompson (1987); Usharani et al. (1985); Vidaud et al. (1993); Whittaker et al. (1962); Winship (1989); Yoshioka et al. (1986) ### REFERENCES 1. Aggeler, P. M.; White, S. G.; Glendening, M. B.; Page, E. W.; Leake, T. B.; Bates, G. : Plasma thromboplastin component (PTC) deficiency: a new disease resembling hemophilia. Proc. Soc. Exp. Biol. Med. 79: 692-694, 1952. PubMed ID : 14920537 2. Aguilar-Martinez, P.; Romey, M.-C.; Gris, J.-C.; Schved, J.-F.; Demaille, J.; Claustres, M. : A novel mutation (val373-to-glu) in the catalytic domain of factor IX, resulting in moderately/severe hemophilia B in a southern French patient. Hum. Mutat. 3: 156-158, 1994. PubMed ID : 8199596 3. Anson, D. S.; Austen, D. E. G.; Brownlee, G. G. : Expression of active human clotting factor IX from recombinant DNA clones in mammalian cells. Nature 315: 683-685, 1985. PubMed ID : 2989700 4. Anson, D. S.; Blake, D. J.; Winship, P. R.; Birnbaum, D.; Brownlee, G. G. : Nullisomic deletion of the mcf.2 transforming gene in two haemophilia B patients. EMBO J. 7: 2795-2799, 1988. PubMed ID : 2846283 5. Armentano, D.; Thompson, A. R.; Darlington, G.; Woo, S. L. C. : Expression of human factor IX in rabbit hepatocytes by retrovirus-mediated gene transfer: potential for gene therapy of hemophilia B. Proc. Nat. Acad. Sci. 87: 6141-6145, 1990. PubMed ID : 2385589 6. Attree, O.; Vidaud, D.; Vidaud, M.; Amselem, S.; Lavergne, J.-M.; Goossens, M. : Mutations in the catalytic domain of human coagulation factor IX: rapid characterization by direct genomic sequencing of DNA fragments displaying an altered melting behavior. Genomics 4: 266-272, 1989. PubMed ID : 2714791 7. Attree, O.; Vidaud, M.; Vidaud, D.; Lavergne, J. M.; Goossens, M. : New strategies for rapid detection and characterization of mutations in hemophilia B. (Abstract) Thromb. Haemost. 62: 8, 1989. 8. Axelrod, J. H.; Read, M. S.; Brinkhous, K. M.; Verma, I. M. : Phenotypic correction of factor IX deficiency in skin fibroblasts of hemophilic dogs. Proc. Nat. Acad. Sci. 87: 5173-5177, 1990. PubMed ID : 2367529 9. Barrai, I.; Cann, H. M.; Cavalli-Sforza, L. L.; Barbujani, G.; De Nicola, P. : Segregation analysis of hemophilia A and B. Am. J. Hum. Genet. 37: 680-699, 1985. PubMed ID : 9556658 10. Bentley, A. K.; Rees, D. J. G.; Rizza, C.; Brownlee, G. G. : Defective propeptide processing of blood clotting factor IX caused by mutation of arginine to glutamine at position -4. Cell 45: 343-348, 1986. PubMed ID : 3009023 11. Bernardi, F.; Del Senno, L.; Barbieri, R.; Buzzoni, D.; Gambari, R.; Marchetti, G.; Conconi, F.; Panicucci, F.; Positano, M.; Pitruzzello, S. : Gene deletion in an Italian haemophilia B subject. J. Med. Genet. 22: 305-307, 1985. PubMed ID : 4045960 12. Bertina, R. M. : Personal Communication. Leiden, The Netherlands, 1989. 13. Bertina, R. M.; Briet, E.; Veltkamp, J. J. : Variants of vitamin K dependent coagulation factors. (Editorial) Acta Haemat. 62: 1-3, 1979. 14. Bertina, R. M.; van der Linden, I. K. : Factor IX Deventer--evidence for the heterogeneity of hemophilia B(M). Thromb. Haemost. 47: 136-140, 1982. PubMed ID : 7101232 15. Bertina, R. M.; van der Linden, I. K.; Mannucci, P. M.; Reinalda-Poot, H. H.; Cupers, R.; Poort, S. R.; Reitsma, P. H. : Mutations in haemophilia B-M occur at the 180arg-to-val activation site or in the catalytic domain. (Abstract) Thromb. Haemost. 62: 203, 1989. 16. Bertina, R. M.; van der Linden, I. K.; Mannucci, P. M.; Reinalda-Poot, H. H.; Cupers, R.; Poort, S. R.; Reitsma, P. H. : Mutations in hemophilia B(m) occur at the arg(180)-to-val activation site or in the catalytic domain of factor IX. J. Biol. Chem. 265: 10876-10883, 1990. PubMed ID : 2162822 17. Bertina, R. M.; Veltkamp, J. J. : The abnormal factor IX of hemophilia B+ variants. Thromb. Haemost. 40: 335-349, 1978. PubMed ID : 734633 18. Biggs, R.; Douglas, A. S.; Macfarlane, R. G.; Dacie, J. V.; Pitney, W. R.; Merskey, C.; O'Brien, J. R. : Christmas disease: a condition previously mistaken for haemophilia. Brit. Med. J. 2: 1378-1382, 1952. PubMed ID : 12997790 19. Blackburn, E. K.; Monaghan, J. H.; Lederer, H.; MacFie, J. M. : Christmas disease associated with primary capillary abnormalities. Brit. Med. J. 1: 154-156, 1962. 20. Bottema, C. D. K.; Bottema, M. J.; Ketterling, R. P.; Yoon, H.-S.; Janco, R. L.; Phillips, J. A., III; Sommer, S. S. : Why does the human factor IX gene have a G+C content of 40%?. Am. J. Hum. Genet. 49: 839-850, 1991. PubMed ID : 1897528 21. Bottema, C. D. K.; Ketterling, R. P.; Ii, S.; Yoon, H.-S.; Phillips, J. A., III; Sommer, S. S. : Missense mutations and evolutionary conservation of amino acids: evidence that many of the amino acids in factor IX function as 'spacer' elements. Am. J. Hum. Genet. 49: 820-838, 1991. PubMed ID : 1680287 22. Bottema, C. D. K.; Ketterling, R. P.; Vielhaber, E.; Yoon, H.-S.; Gostout, B.; Jacobson, D. P.; Shapiro, A.; Sommer, S. S. : The pattern of spontaneous germ-line mutation: relative rates of mutation at or near CpG dinucleotides in the factor IX gene. Hum. Genet. 91: 496-503, 1993. PubMed ID : 8314564 23. Bottema, C. D. K.; Ketterling, R. P.; Yoon, H.-S.; Sommer, S. S. : The pattern of factor IX germ-line mutation in Asians is similar to that of Caucasians. Am. J. Hum. Genet. 47: 835-841, 1990. PubMed ID : 2220823 24. Bottema, C. D. K.; Koeberl, D. D.; Ketterling, R. P.; Bowie, E. J. W.; Taylor, S. A. M.; Lillicrap, D.; Shapiro, A.; Gilchrist, G.; Sommer, S. S. : A past mutation at isoleucine-397 is now a common cause of moderate/mild haemophilia B. Brit. J. Haemat. 75: 212-216, 1990. PubMed ID : 2372508 25. Bottema, C. D. K.; Koeberl, D. D.; Ketterling, R. P.; Lillicrap, D. P.; Bridges, P.; Sommer, S. S. : The molecular pathology of hemophilia B is a mirror of the pattern of recent germline mutations in humans. (Abstract) Blood 74: 252A, 1989. 26. Bottema, C. D. K.; Koeberl, D. D.; Sommer, S. S. : Direct carrier testing in 14 families with haemophilia B. Lancet II: 526-529, 1989. 27. Boyd, Y.; Buckle, V. J.; Munro, E. A.; Choo, K. H.; Migeon, B. R.; Craig, I. W. : Assignment of the haemophilia B (factor IX) locus to the q26-qter region of the X chromosome. Ann. Hum. Genet. 48: 145-152, 1984. PubMed ID : 6331274 28. Braunstein, K. M.; Noyes, C. M.; Griffith, M. J.; Lundblad, R. L.; Roberts, H. R. : Characterization of the defect in activation of factor IX(Chapel Hill) by human factor XIa. J. Clin. Invest. 68: 1404-1410, 1981. PubMed ID : 6947980 29. Bray, G. L.; Thompson, A. R. : Partial factor IX protein in a pedigree with hemophilia B due to a partial gene deletion. J. Clin. Invest. 77: 1194-1200, 1986. PubMed ID : 3514676 30. Briet, E.; Bertina, R. M.; van Tilburg, N. H.; Veltkamp, J. J. : Hemophilia B Leyden: a sex-linked hereditary disorder that improves after puberty. New Eng. J. Med. 306: 788-790, 1982. PubMed ID : 7062952 31. Brinkhous, K. M.; Davis, P. D.; Graham, J. B.; Dodds, W. J. : Expression and linkage of genes for X-linked hemophilias A and B in the dog. Blood 41: 577-585, 1973. PubMed ID : 4688873 32. Brooks, M. B.; Gu, W.; Barnas, J. L.; Ray, J.; Ray, K. : A line 1 insertion in the factor IX gene segregates with mild hemophilia B in dogs. Mammalian Genome 14: 788-795, 2003. PubMed ID : 14722728 33. Brown, P. E.; Hougie, C.; Roberts, H. R. : The genetic heterogeneity of hemophilia B. New Eng. J. Med. 283: 61-64, 1970. PubMed ID : 5420360 34. Brownlee, G. G. : Haemophilia B: a review of patient defects, diagnosis with gene probes and prospects for gene therapy. Recent Adv. Haemat. 5: 251-265, 1988. 35. Busby, S.; Kumar, A.; Joseph, M.; Halfpap, L.; Insley, M.; Berkner, K.; Kurachi, K.; Woodbury, R. : Expression of active human factor IX in transfected cells. Nature 316: 271-273, 1985. PubMed ID : 3894976 36. Camerino, G.; Grzeschik, K. H.; Jaye, M.; de la Salle, H.; Tolstoshev, P.; Lecocq, J. P.; Heilig, R.; Mandel, J. L. : Regional localization on the human X chromosome and polymorphism of the coagulation factor IX gene (hemophilia B locus). Proc. Nat. Acad. Sci. 81: 498-502, 1984. PubMed ID : 6320191 37. Camerino, G.; Mattei, M. G.; Mattei, J. F.; Jaye, M.; Mandel, J. L. : Genetics of the fragile X-mental retardation syndrome: close linkage to hemophilia B and transmission through a normal male. Nature 306: 701-704, 1983. PubMed ID : 6689201 38. Camerino, G.; Oberle, I.; Drayna, D.; Mandel, J. L. : A new MspI restriction fragment length polymorphism in the hemophilia B locus. Hum. Genet. 71: 79-81, 1985. PubMed ID : 2411652 39. Chan, V.; Chan, T. K.; Tong, T. M. F.; Todd, D. : A novel missense mutation in exon 4 of the factor VIII:C gene resulting in moderately severe hemophilia A. Blood 74: 2688-2691, 1989. PubMed ID : 2510835 40. Chan, V.; Chan, V. W. Y.; Yip, B.; Chim, C. S.; Chan, T. K. : Hemophilia B in a female carrier due to skewed inactivation of the normal X-chromosome. Am. J. Hemat. 58: 72-76, 1998. PubMed ID : 9590153 41. Chance, P. F.; Dyer, K. A.; Kurachi, K.; Yoshitake, S.; Ropers, H.-H.; Wieacker, P.; Gartler, S. M. : Regional localization of the human factor IX gene by molecular hybridization. Hum. Genet. 65: 207-208, 1983. PubMed ID : 6686210 42. Chen, S.-H.; Scott, C. R.; Edson, J. R.; Kurachi, K. : An insertion within the factor IX gene: hemophilia B(El Salvador). Am. J. Hum. Genet. 42: 581-584, 1988. PubMed ID : 2831715 43. Chen, S.-H.; Scott, C. R.; Schoof, J.; Lovrien, E. W.; Kurachi, K. : Factor IX(Portland): a nonsense mutation (CGA to TGA) resulting in hemophilia B. Am. J. Hum. Genet. 44: 567-569, 1989. PubMed ID : 2929599 44. Chen, S.-H.; Thompson, A. R. : Personal Communication. Seattle, Wash., 11/1989. 45. Chen, S.-H.; Thompson, A. R.; Zhang, M.; Scott, C. R. : Three point mutations in the factor IX genes of five hemophilia B patients: identification strategy using localization by altered epitopes in their hemophilic proteins. J. Clin. Invest. 84: 113-118, 1989. PubMed ID : 2472424 46. Chen, S.-H.; Yoshitake, S.; Chance, P. F.; Bray, G. L.; Thompson, A. R.; Scott, C. R.; Kurachi, K. : An intragenic deletion of the factor IX gene in a family with hemophilia B. J. Clin. Invest. 76: 2161-2164, 1985. PubMed ID : 3001143 47. Chen, S.-H.; Zhang, M.; Lovrien, E. W.; Scott, C. R.; Thompson, A. R. : CG dinucleotide transitions in the factor IX gene account for about half of the point mutations in hemophilia B patients: a Seattle series. Hum. Genet. 87: 177-182, 1991. PubMed ID : 2066105 48. Choo, K. H.; Gould, K. G.; Rees, D. J. G.; Brownlee, G. G. : Molecular cloning of the gene for human anti-haemophilic factor IX. Nature 299: 178-180, 1982. PubMed ID : 6287289 49. Choo, K. H.; Raphael, K.; McAdam, W.; Peterson, M. G. : Expression of active human blood clotting factor IX in transgenic mice: use of a cDNA with complete mRNA sequence. Nucleic Acids Res. 15: 871-884, 1987. PubMed ID : 3029708 50. Chu, K.; Wu, S.-M.; Stanley, T.; Stafford, D. W.; High, K. A. : A mutation in the propeptide of factor IX leads to warfarin sensitivity by a novel mechanism. J. Clin. Invest. 98: 1619-1625, 1996. PubMed ID : 8833911 51. Connor, J. M.; Pettigrew, A. F.; Hann, I. M.; Forbes, C. D.; Lowe, G. D. O.; Affara, N. A. : Application of an intragenic genomic probe to genetic counselling for haemophilia B in the west of Scotland. J. Med. Genet. 22: 441-446, 1985. PubMed ID : 4078877 52. Connor, J. M.; Pettigrew, A. F.; Shiach, C.; Hann, I. M.; Lowe, G. D. O.; Forbes, C. D. : Application of three intragenic DNA polymorphisms for carrier detection in haemophilia B. J. Med. Genet. 23: 300-309, 1986. PubMed ID : 3018248 53. Cooper, D. N.; Krawczak, M. : The mutational spectrum of single base-pair substitutions causing human genetic disease: patterns and predictions. Hum. Genet. 85: 55-74, 1990. PubMed ID : 2192981 54. Costa, J.-M.; Vidaud, D.; Laurendeau, I.; Vidaud, M.; Fressinaud, E.; Moisan, J.-P.; David, A.; Meyer, D.; Lavergne, J.-M. : Somatic mosaicism and compound heterozygosity in female hemophilia B. Blood 96: 1585-1587, 2000. PubMed ID : 10942410 55. Crossley, M.; Brownlee, G. G. : Disruption of a C/EBP binding site in the factor IX promoter is associated with haemophilia B. Nature 345: 444-446, 1990. PubMed ID : 2342576 56. Crossley, M.; Ludwig, M.; Stowell, K. M.; De Vos, P.; Olek, K.; Brownlee, G. G. : Recovery from hemophilia B Leyden: an androgen-responsive element in the factor IX promoter. Science 257: 377-379, 1992. PubMed ID : 1631558 57. Crossley, M.; Winship, P. R.; Austen, D. E. G.; Rizza, C. R.; Brownlee, G. G. : A less severe form of haemophilia B Leyden. Nucleic Acids Res. 18: 4633, 1990. PubMed ID : 2388855 58. Crossley, P. M.; Winship, P. R.; Black, A.; Rizza, C. R.; Brownlee, G. G. : Unusual case of haemophilia B. (Letter) Lancet I: 960, 1989. 59. Cutler, J. A.; Mitchell, M. J.; Smith, M. P.; Savidge, G. F. : Germline mosaicism resulting in the transmission of severe hemophilia B from a grandfather with a mild deficiency. Am. J. Med. Genet. 129A: 13-15, 2004. 60. Davie, E. W.; Fujikawa, K. : Basic mechanisms in blood coagulation. Ann. Rev. Biochem. 44: 799-829, 1975. PubMed ID : 237463 61. Davis, L. M.; McGraw, R. A.; Graham, J. B.; Roberts, H. R.; Stafford, D. W. : Identification of the genetic defect in factor IX (Alabama): DNA sequence analysis reveals a gly substitution for asp(46). (Abstract) Blood 64 (suppl.): 262a, 1984. 62. Davis, L. M.; McGraw, R. A.; Ware, J. L.; Roberts, H. R.; Stafford, D. W. : Factor IX (Alabama): a point mutation in a clotting protein results in hemophilia B. Blood 69: 140-143, 1987. PubMed ID : 3790720 63. Denson, K. W.; Biggs, P.; Mannucci, P. M. : An investigation of three patients with Christmas disease due to an abnormal type of factor IX. J. Clin. Path. 21: 160-165, 1968. PubMed ID : 4972271 64. Denton, P. H.; Fowlkes, D. M.; Lord, S. T.; Reisner, H. M. : Hemophilia B Durham: a mutation in the first EGF-like domain of factor IX that is characterized by polymerase chain reaction. Blood 72: 1407-1411, 1988. PubMed ID : 3262389 65. Didisheim, P.; Vandervoort, R. L. E. : Detection of carriers for factor IX (PTC) deficiency. Blood 20: 150-155, 1962. PubMed ID : 13886232 66. Diuguid, D. L.; Rabiet, M. J.; Furie, B. C.; Liebman, H. A.; Furie, B. : Molecular basis of hemophilia B: a defective enzyme due to an unprocessed propeptide is caused by a point mutation in the factor IX precursor. Proc. Nat. Acad. Sci. 83: 5803-5807, 1986. PubMed ID : 3461460 67. Drayna, D.; Davies, K.; Hartley, D.; Mandel, J.-L.; Camerino, G.; Williamson, R.; White, R. : Genetic mapping of the human X chromosome by using restriction fragment length polymorphisms. Proc. Nat. Acad. Sci. 81: 2836-2839, 1984. PubMed ID : 6326147 68. Driscoll, D. J.; Migeon, B. R. : Sex difference in methylation of single-copy genes in human meiotic germ cells: implications for X chromosome inactivation, parental imprinting, and origin of CpG mutations. Somat. Cell Molec. Genet. 16: 267-282, 1990. PubMed ID : 1694309 69. Drost, J. B.; Scaringe, W. A.; Jaloma-Cruz, A. R.; Li, X.; Ossa, D. F.; Kasper, C. K.; Sommer, S. S. : Novel hotspot detector software reveals a non-CpG hotspot of germline mutation in the factor IX gene (F9) in Latin Americans. Hum. Mutat. 16: 203-210, 2000. PubMed ID : 10980527 70. Fahner, J. B.; Salier, J. P.; Landa, L.; Hirosawa, S.; Lovrien, E. W.; Kurachi, K. : Defective promoter structure in a human factor IX-Leyden. (Abstract) Blood 72: 295A, 1988. 71. Forster-Gibson, C. J.; Mulligan, L. M.; Partington, M. W.; Simpson, N. E.; Holden, J. J. A.; White, B. N. : The genetic distance between the coagulation factor IX gene and the locus for the fragile X syndrome: clinical implications. J. Neurogenet. 2: 231-237, 1985. PubMed ID : 3860635 72. Fujikawa, K.; Coan, M. H.; Enfield, D. L.; Titani, K.; Ericsson, L. H.; Davie, E. W. : A comparison of bovine prothrombin, factor IX (Christmas factor), and factor X (Stuart factor). Proc. Nat. Acad. Sci. 71: 427-430, 1974. PubMed ID : 4205592 73. Geddes, V. A.; Le Bonniec, B. F.; Louie, G. V.; Brayer, G. D.; Thompson, A. R.; MacGillivray, R. T. A. : A moderate form of hemophilia B is caused by a novel mutation in the protease domain of factor IX(Vancouver). J. Biol. Chem. 264: 4689-4697, 1989. PubMed ID : 2494175 74. Geddes, V. A.; Louie, G. V.; Brayer, G. D.; MacGillivray, R. T. A. : Molecular basis of hemophilia B: identification of the defect in factor IX Vancouver. (Abstract) Thromb. Haemost. 58 (suppl.): 294, 1987. 75. George, J. N.; Miller, G. M.; Breckenridge, R. T. : Studies on Christmas disease: investigation and treatment of a familial acquired inhibitor of factor IX. Brit. J. Haemat. 21: 333-342, 1971. PubMed ID : 4998792 76. Gerrard, A. J.; Hudson, D. L.; Brownlee, G. G.; Watt, F. M. : Towards gene therapy for haemophilia B using primary human keratinocytes. Nature Genet. 3: 180-183, 1993. PubMed ID : 8499952 77. Giangrande, P. L. F. : Historical review: six characters in search of an author: the history of the nomenclature of coagulation factors. Brit. J. Haemat. 121: 703-712, 2003. PubMed ID : 12780784 78. Giannelli, F.; Anagnostopoulos, T.; Green, P. M. : Mutation rates in humans. II. Sporadic mutation-specific rates and rate of detrimental human mutations inferred from hemophilia B. Am. J. Hum. Genet. 65: 1580-1587, 1999. PubMed ID : 10577911 79. Giannelli, F.; Anson, D. S.; Choo, K. H.; Rees, D. J. G.; Winship, P. R.; Ferrari, N.; Rizza, C. R.; Brownlee, G. G. : Characterisation and use of an intragenic polymorphic marker for detection of carriers of haemophilia B (factor IX deficiency). Lancet I: 239-241, 1984. 80. Giannelli, F.; Choo, K. H.; Rees, D. J. G.; Boyd, Y.; Rizza, C. R.; Brownlee, G. G. : Gene deletions in patients with haemophilia B and anti-factor IX antibodies. Nature 303: 181-182, 1983. PubMed ID : 6843667 81. Giannelli, F.; Green, P. M.; High, K. A.; Sommer, S.; Lillicrap, D. P.; Ludwig, M.; Olek, K.; Reitsma, P. H.; Goossens, M.; Yoshioka, A.; Brownlee, G. G. : Haemophilia B: database of point mutations and short additions and deletions--third edition, 1992. Nucleic Acids Res. 20: 2027-2063, 1992. PubMed ID : 1598234 82. Giannelli, F.; Green, P. M.; High, K. A.; Sommer, S.; Poon, M.-C.; Ludwig, M.; Schwaab, R.; Reitsma, P. H.; Goossens, M.; Yoshioka, A.; Brownlee, G. G. : Haemophilia B: database of point mutations and short additions and deletions--fourth edition, 1993. Nucleic Acids Res. 21: 3075-3087, 1993. PubMed ID : 8392713 83. Giannelli, F.; Green, P. M.; Sommer, S. S.; Poon, M.-C.; Ludwig, M.; Schwaab, R.; Reitsma, P. H.; Goossens, M.; Yoshioka, A.; Brownlee, G. G. : Haemophilia B (sixth edition): a database of point mutations and short additions and deletions. Nucleic Acids Res. 24: 103-118, 1996. PubMed ID : 8594556 84. Giannelli, F.; Green, P. M.; Sommer, S. S.; Poon, M.-C.; Ludwig, M.; Schwaab, R.; Reitsma, P. H.; Goossens, M.; Yoshioka, A.; Figueiredo, M. S.; Brownlee, G. G. : Haemophilia B: database of point mutations and short additions and deletions, 7th edition. Nucleic Acids Res. 25: 133-135, 1997. PubMed ID : 9016521 85. Giannelli, F.; Saad, S.; Montandon, A. J.; Bentley, D. R.; Green, P. M. : A new strategy for the genetic counselling of diseases of marked mutational heterogeneity: haemophilia B as a model. J. Med. Genet. 29: 602-607, 1992. PubMed ID : 1404290 86. Girolami, A.; Dal Bo Zanon, R.; De Marco, L.; Cappellato, G. : Hemophilia B with associated factor VII deficiency: a distinct variant of hemophilia B with low factor VII activity and normal factor VII antigen. Blut 40: 267-273, 1980. PubMed ID : 7370439 87. Goldsmith, J. C.; Roer, M. E. S.; Orringer, E. P. : A new treatment strategy for hemophilia B: incorporation of factor IX into red cell ghosts. Am. J. Hemat. 7: 119-125, 1979. PubMed ID : 539589 88. Gostout, B.; Vielhaber, E.; Ketterling, R. P.; Yoon, H.-S.; Bottema, C. D. K.; Kasper, C. K.; Koerper, M. A.; Sommer, S. S. : Germline mutations in the factor IX gene: a comparison of the pattern in Caucasians and non-Caucasians. Hum. Molec. Genet. 2: 293-298, 1993. PubMed ID : 8499919 89. Graham, J. B.; Lubahn, D. B.; Lord, S. T.; Kirshtein, J.; Nilsson, I. M.; Wallmark, A.; Ljung, R.; Frazier, L. D.; Ware, J. L.; Lin, S. W.; Stafford, D. W.; Bosco, J. : The Malmo polymorphism of coagulation factor IX, an immunologic polymorphism due to dimorphism of residue 148 that is in linkage disequilibrium with two other F.IX polymorphisms. Am. J. Hum. Genet. 42: 573-580, 1988. PubMed ID : 2450455 90. Graham, J. B.; Tarleton, H. L.; Race, R. R.; Sanger, R. : A human double cross-over. Nature 195: 834, 1962. PubMed ID : 13901025 91. Gray, M. W. : CpG polymorphisms and haemophilia B. (Letter) Lancet II: 502-503, 1989. 92. Green, P. M.; Bentley, D. R.; Mibashan, R. S.; Giannelli, F. : Partial deletion by illegitimate recombination of the factor IX gene in a haemophilia B family with two inhibitor patients. Molec. Biol. Med. 5: 95-106, 1988. PubMed ID : 3398774 93. Green, P. M.; Bentley, D. R.; Mibashan, R. S.; Nilsson, I. M.; Giannelli, F. : Molecular pathology of haemophilia B. EMBO J. 8: 1067-1072, 1989. PubMed ID : 2743975 94. Green, P. M.; Mitchell, V. E.; McGraw, A.; Goldman, E.; Giannelli, F. : Haemophilia B caused by a missense mutation in the prepeptide sequence of factor IX. Hum. Mutat. 2: 103-107, 1993. PubMed ID : 8318985 95. Green, P. M.; Montandon, A. J.; Bentley, D. R.; Giannelli, F. : Genetics and molecular biology of haemophilias A and B. Blood Coagul. Fibrinolysis 2: 539-565, 1991. PubMed ID : 1768766 96. Green, P. M.; Montandon, A. J.; Ljung, R.; Bentley, D. R.; Nilsson, I.-M.; Kling, S.; Giannelli, F. : Haemophilia B mutations in a complete Swedish population sample: a test of new strategy for the genetic counselling of diseases with high mutational heterogeneity. Brit. J. Haemat. 78: 390-397, 1991. PubMed ID : 1873221 97. Green, P. M.; Saad, S.; Lewis, C. M.; Giannelli, F. : Mutation rates in humans. I. Overall and sex-specific rates obtained from a population study of hemophilia B. Am. J. Hum. Genet. 65: 1572-1579, 1999. PubMed ID : 10577910 98. Grunebaum, L.; Cazenave, J.-P.; Camerino, G.; Kloepfer, C.; Mandel, J. L.; Tolstoshev, P.; Jaye, M.; de la Salle, H.; Lecocq, J. P. : Carrier detection of haemophilia B by using a restriction site polymorphism associated with the coagulation factor IX gene. J. Clin. Invest. 73: 1491-1495, 1984. PubMed ID : 6325506 99. Gu, W.; Brooks, M.; Catalfamo, J.; Ray, J.; Ray, K. : Two distinct mutations cause severe hemophilia B in two unrelated canine pedigrees. Thromb. Haemost. 82: 1270-1275, 1999. PubMed ID : 10544912 100. Hashimi, K. Z.; MacIver, J. E.; Delamore, I. W. : Christmas disease in a female. Lancet II: 965-966, 1978. 101. Hassan, H. J.; Leonardi, A.; Guerriero, R.; Chelucci, C.; Cianetti, L.; Ciavarella, N.; Ranieri, P.; Pilolli, D.; Peschle, C. : Hemophilia B with inhibitor: molecular analysis of the subtotal deletion of the factor IX gene. Blood 66: 728-730, 1985. PubMed ID : 2992643 102. Hay, C. W.; Robertson, K. A.; Yong, S.-L.; Thompson, A. R.; Growe, G. H.; MacGillivray, R. T. A. : Use of a BamHI polymorphism in the factor IX gene for the determination of hemophilia B carrier status. Blood 67: 1508-1511, 1986. PubMed ID : 3008893 103. Herzog, R. W.; et al; et al : Stable gene transfer and expression of human blood coagulation factor IX after intramuscular injection of recombinant adeno-associated virus. Proc. Nat. Acad. Sci. 94: 5804-5809, 1997. PubMed ID : 9159155 104. Herzog, R. W.; Yang, E. Y.; Couto, L. B.; Hagstrom, J. N.; Elwell, D.; Fields, P. A.; Burton, M.; Bellinger, D. A.; Read, M. S.; Brinkhous, K. M.; Podsakoff, G. M.; Nichols, T. C.; Kurtzman, G. J.; High, K. A. : Long-term correction of canine hemophilia B by gene transfer of blood coagulation factor IX mediated by adeno-associated viral vector. Nature Med. 5: 56-63, 1999. PubMed ID : 9883840 105. Hirosawa, S.; Fahner, J. B.; Salier, J.-P.; Wu, C.-T.; Lovrien, E. W.; Kurachi, K. : Structural and functional basis of the developmental regulation of human coagulation factor IX gene: factor IX Leyden. Proc. Nat. Acad. Sci. 87: 4421-4425, 1990. PubMed ID : 2352926 106. Holmberg, L.; Gustavii, B.; Cordesius, E.; Kristoffersson, A.-C.; Ljung, R.; Lofberg, L.; Stromberg, P.; Nilsson, I. M. : Prenatal diagnosis of hemophilia B by an immunoradiometric assay of factor IX. Blood 56: 397-401, 1980. PubMed ID : 7407407 107. Hougie, C.; Twomey, J. J. : Hemophilia B(M): a new type of factor-IX deficiency. Lancet I: 698-700, 1967. 108. Huang, M.-N.; Kasper, C. K.; Roberts, H. R.; Stafford, D. W.; High, K. A. : Molecular defect in factor IX(Hilo), a hemophilia B(m) variant: arg-to-gln at the carboxyterminal cleavage site of the activation peptide. Blood 73: 718-721, 1989. PubMed ID : 2563663 109. Jagadeeswaran, P.; Lavelle, D. E.; Kaul, R.; Mohandas, T.; Warren, S. T. : Isolation and characterization of human factor IX cDNA: identification of Taq I polymorphism and regional assignment. Somat. Cell Molec. Genet. 10: 465-473, 1984. PubMed ID : 6089357 110. Kasper, C. K.; Osterud, B.; Minami, J. Y.; Schonick, W.; Rapaport, S. I. : Hemophilia B--characterization of genetic variants and detection of carriers. Blood 50: 351-366, 1977. PubMed ID : 884315 111. Kay, M. A.; Manno, C. S.; Ragni, M. V.; Larson, P. J.; Couto, L. B.; McClelland, A.; Glader, B.; Chew, A. J.; Tai, S. J.; Herzog, R. W.; Arruda, V.; Johnson, F.; Scallan, C.; Skarsgard, E.; Flake, A. W.; High, K. A. : Evidence for gene transfer and expression of factor IX in haemophilia B patients treated with an AAV vector. Nature Genet. 24: 257-261, 2000. PubMed ID : 10700178 112. Kay, M. A.; Rothenberg, S.; Landen, C. N.; Bellinger, D. A.; Leland, F.; Toman, C.; Finegold, M.; Thompson, A. R.; Read, M. S.; Brinkhous, K. M.; Woo, S. L. C. : In vivo gene therapy of hemophilia B: sustained partial correction in factor IX-deficient dogs. Science 262: 117-119, 1993. PubMed ID : 8211118 113. Kazazian, H. H., Jr. : An estimated frequency of endogenous insertional mutations in humans. Nature Genet. 22: 130 only, 1999. PubMed ID : 10369250 114. Ketterling, R. P.; Bottema, C. D. K.; Koeberl, D. D.; Ii, S.; Sommer, S. S. : T-296-to-M, a common mutation causing mild hemophilia B in the Amish and others: founder effect, variability in factor IX activity assays, and rapid carrier detection. Hum. Genet. 87: 333-337, 1991. PubMed ID : 1864609 115. Ketterling, R. P.; Vielhaber, E.; Bottema, C. D. K.; Schaid, D. J.; Cohen, M. P.; Sexauer, C. L.; Sommer, S. S. : Germ-line origins of mutation in families with hemophilia B: the sex ratio varies with the type of mutation. Am. J. Hum. Genet. 52: 152-166, 1993. PubMed ID : 8434583 116. Ketterling, R. P.; Vielhaber, E.; Li, X.; Drost, J.; Schaid, D. J.; Kasper, C. K.; Phillips, J. A., III; Koerper, M. A.; Kim, H.; Sexauer, C.; Gruppo, R.; Ambriz, R.; Paredes, R.; Sommer, S. S. : Germline origins in the human F9 gene: frequent G:C-to-A:T mosaicism and increased mutations with advanced maternal age. Hum. Genet. 105: 629-640, 1999. PubMed ID : 10647899 117. Ketterling, R. P.; Vielhaber, E. L.; Lind, T. J.; Thorland, E. C.; Sommer, S. S. : The rates and patterns of deletions in the human factor IX gene. Am. J. Hum. Genet. 54: 201-213, 1994. PubMed ID : 8304338 118. Kitchens, C. S.; Levin, J.; Smith, W. K. : Hemorrhagic diathesis in a carrier of hemophilia B. Am. J. Med. 60: 138-143, 1976. PubMed ID : 1082713 119. Kling, S.; Ljung, R.; Sjorin, E.; Montandon, J.; Green, P.; Giannelli, F.; Nilsson, I. M. : Origin of mutation in sporadic cases of haemophilia-B. Europ. J. Haemat. 48: 142-145, 1992. 120. Koeberl, D. D.; Bottema, C. D. K.; Buerstedde, J.-M.; Sommer, S. S. : Functionally important regions of the factor IX gene have a low rate of polymorphism and a high rate of mutation in the dinucleotide CpG. Am. J. Hum. Genet. 45: 448-457, 1989. PubMed ID : 2773937 121. Koeberl, D. D.; Bottema, C. D. K.; Ketterling, R. P.; Bridge, P. J.; Lillicrap, D. P.; Sommer, S. S. : Mutations causing hemophilia B: direct estimate of the underlying rates of spontaneous germ-line transitions, transversions, and deletions in a human gene. Am. J. Hum. Genet. 47: 202-217, 1990. PubMed ID : 2198809 122. Koeberl, D. D.; Bottema, C. D. K.; Sarkar, G.; Ketterling, R. P.; Chen, S.-H.; Sommer, S. S. : Recurrent nonsense mutations at arginine residues cause severe hemophilia B in unrelated hemophiliacs. Hum. Genet. 84: 387-390, 1990. PubMed ID : 1969838 123. Koeberl, D. D.; Bottema, C. D. K.; Sommer, S. S. : Comparison of direct and indirect methods of carrier detection in an X-linked disease. Am. J. Med. Genet. 35: 600-608, 1990. PubMed ID : 1970704 124. Krepischi-Santos, A. C. V.; Carneiro, J. D. A.; Svartman, M.; Bendit, I.; Odone-Filho, V.; Vianna-Morgante, A. M. : Deletion of the factor IX gene as a result of translocation t(X;1) in a girl affected by haemophilia B. Brit. J. Haemat. 113: 616-620, 2001. PubMed ID : 11380446 125. Kundu, R. K.; Sangiorgi, F.; Wu, L.-Y.; Kurachi, K.; Anderson, W. F.; Maxson, R.; Gordon, E. M. : Targeted inactivation of the coagulation factor IX gene causes hemophilia B in mice. Blood 92: 168-174, 1998. PubMed ID : 9639513 126. Kurachi, K.; Davie, E. W. : Isolation and characterization of a cDNA coding for human factor IX. Proc. Nat. Acad. Sci. 79: 6461-6464, 1982. PubMed ID : 6959130 127. Kurachi, S.; Deyashiki, Y.; Takeshita, J.; Kurachi, K. : Genetic mechanisms of age regulation of human blood coagulation factor IX. Science 285: 739-743, 1999. PubMed ID : 10426997 128. Lascari, A. D.; Hoak, J. C.; Taylor, J. C. : Christmas disease in a girl. Am. J. Dis. Child. 117: 585-588, 1969. PubMed ID : 5781711 129. Li, X.; Scaringe, W. A.; Hill, K. A.; Roberts, S.; Mengos, A.; Careri, D.; Pinto, M. T.; Kasper, C. K.; Sommer, S. S. : Frequency of recent retrotransposition events in the human factor IX gene. Hum. Mutat. 17: 511-519, 2001. PubMed ID : 11385709 130. Liddell, M. B.; Peake, I. R.; Taylor, S. A. M.; Lillicrap, D. P.; Giddings, J. C.; Bloom, A. L. : Factor IX Cardiff: a variant factor IX protein that shows abnormal activation is caused by an arginine to cysteine substitution at position 145. Brit. J. Haemat. 72: 556-560, 1989. PubMed ID : 2775660 131. Liebman, H. A.; Limentani, S. A.; Furie, B. C.; Furie, B. : Immunoaffinity purification of factor IX (Christmas factor) by using conformation-specific antibodies directed against the factor IX-metal complex. Proc. Nat. Acad. Sci. 82: 3879-3883, 1985. PubMed ID : 2408269 132. Lillicrap, D. P.; Liddell, M. B.; Matthews, R. J.; Peake, I. R.; Bloom, A. L. : Comparison of phenotypic assessment and the use of two restriction fragment length polymorphisms in the diagnosis of the carrier state in haemophilia B. Brit. J. Haemat. 62: 557-565, 1986. PubMed ID : 3006741 133. Little, R. D.; Pilia, G.; Johnson, S.; D'Urso, M.; Schlessinger, D. : Yeast artificial chromosomes spanning 8 megabases and 10-15 centimorgans of human cytogenetic band Xq26. Proc. Nat. Acad. Sci. 89: 177-181, 1992. PubMed ID : 1729687 134. Liu, J.-Z.; Li, X.; Drost, J.; Thorland, E. C.; Liu, Q.; Lind, T.; Roberts, S.; Wang, H. Y.; Sommer, S. S. : The human factor IX gene as germline mutagen test: samples from mainland China have the putatively endogenous pattern of mutation. Hum. Mutat. 16: 31-36, 2000. PubMed ID : 10874302 135. Ljung, R.; Petrini, P.; Tengborn, L.; Sjorin, E. : Haemophilia B mutations in Sweden: a population-based study of mutational heterogeneity. Brit. J. Haemat. 113: 81-86, 2001. PubMed ID : 11328285 136. Lozier, B. N.; Stanfield-Oakley, S. A.; High, K. A. : Factor IX New London: a point mutation causing hemophilia B. (Abstract) Thromb. Haemost. 62: 162, 1989. 137. Ludwig, M.; Sabharwal, A. K.; Brackmann, H. H.; Olek, K.; Smith, K. J.; Birktoft, J. J.; Bajaj, S. P. : Hemophilia B caused by five different nondeletion mutations in the protease domain of factor IX. Blood 79: 1225-1232, 1992. PubMed ID : 1346975 138. Ludwig, M.; Schwaab, R.; Eigel, A.; Horst, J.; Egli, H.; Brackmann, H.-H.; Olek, K. : Identification of a single nucleotide C-to-T transition and five different deletions in patients with severe hemophilia B. Am. J. Hum. Genet. 45: 115-122, 1989. PubMed ID : 2741941 139. Mandalaki, T.; Louizou, C.; Dimitriadou, C.; Briet, E. : Haemophilia B Leyden in Greece. Thromb. Haemost. 56: 340-342, 1986. PubMed ID : 3563965 140. Manno, C. S.; Chew, A. J.; Hutchison, S.; Larson, P. J.; Herzog, R. W.; Arruda, V. R.; Tai, S. J.; Ragni, M. V.; Thompson, A.; Ozelo, M.; Couto, L. B.; Leonard, D. G. B.; Johnson, F. A.; McClelland, A.; Scallan, C.; Skarsgard, E.; Flake, A. W.; Kay, M. A.; High, K. A.; Glader, B. : AAV-mediated factor IX gene transfer to skeletal muscle in patients with severe hemophilia B. Blood 101: 2963-2972, 2003. PubMed ID : 12515715 141. Matsushita, T.; Tanimoto, M.; Yamamoto, K.; Sugiura, I.; Hamaguchi, M.; Takamatsu, J.; Saito, H. : Nucleotide sequence analysis of hemophilia B with the inhibitor phenotype. (Abstract) Blood 74: 251A, 1989. 142. Mattei, M. G.; Baeteman, M. A.; Heilig, R.; Oberle, I.; Davies, K.; Mandel, J. L.; Mattei, J. F. : Localization by in situ hybridization of the coagulation factor IX gene and of two polymorphic DNA probes with respect to the fragile X site. Hum. Genet. 69: 327-331, 1985. PubMed ID : 2985491 143. Matthews, R. J.; Anson, D. S.; Peake, I. R.; Bloom, A. L. : Heterogeneity of the factor IX locus in nine hemophilia B inhibitor patients. J. Clin. Invest. 79: 746-753, 1987. PubMed ID : 3029178 144. Matthews, R. J.; Peake, I. R.; Bloom, A. L.; Anson, D. S. : Carrier detection through the use of abnormal deletion junction fragments in a case of haemophilia B involving complete deletion of the factor IX gene. J. Med. Genet. 25: 779-780, 1988. PubMed ID : 2907054 145. McCord, D. M.; Monroe, D. M.; Smith, K. J.; Roberts, H. R. : Characterization of the functional defect in factor IX Alabama: evidence for a conformational change due to high affinity calcium binding in the first epidermal growth factor domain. J. Biol. Chem. 265: 10250-10254, 1990. PubMed ID : 2355000 146. McGraw, R. A.; Davis, L. M.; Noyes, C. M.; Lundblad, R. L.; Roberts, H. R.; Graham, J. B.; Stafford, D. W. : Evidence for a prevalent dimorphism in the activation peptide of human coagulation factor IX. Proc. Nat. Acad. Sci. 82: 2847-2851, 1985. PubMed ID : 3857619 147. Mikami, S.; Nishino, M.; Nishimura, T.; Fukui, H. : RFLPs of factor IX gene in Japanese haemophilia B families and gene deletion in two high-responder-inhibitor patients. Jpn. J. Hum. Genet. 32: 21-31, 1987. 148. Miyata, T.; Sakai, T.; Sugimoto, M.; Naka, H.; Yamamoto, K.; Yoshioka, A.; Fukui, H.; Mitsui, K.; Kamiya, K.; Umeyama, H.; Iwanaga, S. : Factor IX Amagasaki: a new mutation in the catalytic domain resulting in the loss of both coagulant and esterase activities. Biochemistry 30: 11286-11291, 1991. PubMed ID : 1958666 149. Montandon, A. J.; Green, P. M.; Bentley, D. R.; Ljung, R.; Kling, S.; Nilsson, I. M.; Giannelli, F. : Direct estimate of the haemophilia B (factor IX deficiency) mutation rate and of the ratio of the sex-specific mutation rates in Sweden. Hum. Genet. 89: 319-322, 1992. PubMed ID : 1601423 150. Montandon, A. J.; Green, P. M.; Bentley, D. R.; Ljung, R.; Nilsson, I. M.; Giannelli, F. : Two factor IX mutations in the family of an isolated haemophilia B patient: direct carrier diagnosis by amplification mismatch detection (AMD). Hum. Genet. 85: 200-204, 1990. PubMed ID : 2370049 151. Montandon, A. J.; Green, P. M.; Giannelli, F.; Bentley, D. R. : Direct detection of point mutations by mismatch analysis: application to haemophilia B. Nucleic Acids Res. 17: 3347-3358, 1989. PubMed ID : 2726481 152. Neal, W. R.; Tayloe, D. T., Jr.; Cederbaum, A. I.; Roberts, H. R. : Detection of genetic variants of haemophilia B with an immunosorbent technique. Brit. J. Haemat. 25: 63-68, 1973. PubMed ID : 4793126 153. Neuschatz, J.; Necheles, T. F. : Hemophilia B in a phenotypically normal girl with XX (ring): XO mosaicism. Acta Haemat. 49: 108-113, 1973. PubMed ID : 4196476 154. Nisen, P.; Stamberg, J.; Ehrenpreis, R.; Velasco, S.; Shende, A.; Engelberg, J.; Karayalcin, G.; Waber, L. : The molecular basis of severe hemophilia B in a girl. New Eng. J. Med. 315: 1139-1142, 1986. PubMed ID : 3093864 155. Nour-Eldin, F.; Wilkinson, J. F. : Factor-VII deficiency with Christmas disease in one family. Lancet I: 1173-1176, 1959. 156. Noyes, C. M.; Griffith, M. J.; Roberts, H. R.; Lundblad, R. L. : Identification of the molecular defect in factor IX(Chapel Hill): substitution of histidine for arginine at position 145. Proc. Nat. Acad. Sci. 80: 4200-4202, 1983. PubMed ID : 6603618 157. Oldenburg, J.; Quenzel, E.-M.; Harbrecht, U.; Fregin, A.; Kress, W.; Muller, C. R.; Hertefelder, H.-J.; Schwaab, R.; Brackmann, H.-H.; Hanfland, P. : Missense mutations at ala-10 in the factor IX propeptide: an insignificant variant in normal life but a decisive cause of bleeding during oral anticoagulant therapy. Brit. J. Haemat. 98: 240-244, 1997. PubMed ID : 9233593 158. Orstavik, K. H.; Stormorken, H.; Sparr, T. : Hemophilia B(M) in a female. Thromb. Res. 37: 561-566, 1985. PubMed ID : 3983911 159. Orstavik, K. H.; Veltkamp, J. J.; Bertina, R. M.; Hermans, J. : Detection of carriers of haemophilia B. Brit. J. Haemat. 42: 295-301, 1979. 160. Peake, I. R.; Furlong, B. L.; Bloom, A. L. : Carrier detection by direct gene analysis in a family with haemophilia B (factor IX deficiency). Lancet I: 242-243, 1984. 161. Peake, I. R.; Matthews, R. J.; Bloom, A. L. : Haemophilia B Chicago: severe haemophilia B caused by two deletions and an inversion within the factor IX gene. Brit. J. Haemat. 71 (suppl. 1): 1, 1989. 162. Picketts, D. J.; D'Souza, C.; Bridge, P. J.; Lillicrap, D. : An A to T transversion at position -5 of the factor IX promoter results in hemophilia B. Genomics 12: 161-163, 1992. PubMed ID : 1733855 163. Picketts, D. J.; Lillicrap, D. P.; Mueller, C. R. : Synergy between transcription factors DBP and C/EBP compensates for a haemophilia B Leyden factor IX mutation. Nature Genet. 3: 175-179, 1993. PubMed ID : 8499951 164. Poon, M.-C.; Chui, D. H. K.; Patterson, M.; Starozik, D. M.; Dimnik, L. S.; Hoar, D. I. : Hemophilia B (Christmas disease) variants and carrier detection analyzed by DNA probes. J. Clin. Invest. 79: 1204-1209, 1987. PubMed ID : 2881949 165. Poort, S. R.; Briet, E.; Bertina, R. M.; Reitsma, P. H. : A Dutch pedigree with mild hemophilia B with a missense mutation in the first EGF domain [factor IX(Oud en Nieuw Gastel)]. Nucleic Acids Res. 17: 5869, 1989. PubMed ID : 2762170 166. Purrello, M.; Alhadeff, B.; Esposito, D.; Szabo, P.; Rocchi, M.; Truett, M.; Masiarz, F.; Siniscalco, M. : The human genes for hemophilia A and hemophilia B flank the X chromosome fragile site at Xq27.3. EMBO J. 4: 725-729, 1985. PubMed ID : 3924593 167. Rees, D. J. G.; Rizza, C. R.; Brownlee, G. G. : Haemophilia B caused by a point mutation in a donor splice junction of the human factor IX gene. Nature 316: 643-645, 1985. PubMed ID : 4033760 168. Reijnen, M. J.; Sladek, F. M.; Bertina, R. M.; Reitsma, P. H. : Disruption of a binding site for hepatocyte nuclear factor 4 results in hemophilia B Leyden. Proc. Nat. Acad. Sci. 89: 6300-6303, 1992. PubMed ID : 1631121 169. Reitsma, P. H.; Bertina, R. M.; Ploos van Amstel, J. K.; Riemens, A.; Briet, E. : The putative factor IX gene promoter in hemophilia B Leyden. Blood 72: 1074, 1988. PubMed ID : 3416069 170. Reitsma, P. H.; Mandalaki, T.; Kasper, C. K.; Bertina, R. M.; Briet, E. : Two novel point mutations correlate with an altered developmental expression of blood coagulation factor IX (hemophilia B Leyden phenotype). Blood 73: 743-746, 1989. PubMed ID : 2917196 171. Roberts, H. R.; Grizzle, J. E.; McLester, W. D.; Penick, G. D. : Genetic variants of hemophilia B: detection by means of a specific PTC inhibitor. J. Clin. Invest. 47: 360-365, 1968. PubMed ID : 12066779 172. Royle, G.; Van de Water, N. S.; Berry, E.; Ockelford, P. A.; Browett, P. J. : Haemophilia B Leyden arising de novo by point mutation in the putative factor IX promoter region. Brit. J. Haemat. 77: 191-194, 1991. PubMed ID : 2004020 173. Rusconi, C. P.; Scardino, E.; Layzer, J.; Pitoc, G. A.; Ortel, T. L.; Monroe, D.; Sullenger, B. A. : RNA aptamers as reversible antagonists of coagulation factor IXa. Nature 419: 90-94, 2002. PubMed ID : 12214238 174. Sakai, T.; Yoshioka, A.; Yamamoto, K.; Niinomi, K.; Fujimura, Y.; Fukui, H.; Miyata, T.; Iwanaga, S. : Blood clotting factor IX Kashihara: amino acid substitution of valine-182 by phenylalanine. J. Biochem. 105: 756-759, 1989. PubMed ID : 2753873 175. Sarkar, G.; Cassady, J. D.; Pyeritz, R. E.; Gilchrist, G. S.; Sommer, S. S. : Isoleucine-397 is changed to threonine in two females with hemophilia B. Nucleic Acids Res. 19: 1165, 1991. PubMed ID : 1902289 176. Schach, B. G.; Yoshitake, S.; Davie, E. W. : Hemophilia B (factor IX-Seattle 2) due to a single nucleotide deletion in the gene for factor IX. J. Clin. Invest. 80: 1023-1028, 1987. PubMed ID : 2821070 177. Schnieke, A. E.; Kind, A. J.; Ritchie, W. A.; Mycock, K.; Scott, A. R.; Ritchie, M.; Wilmut, I.; Colman, A.; Campbell, K. H. S. : Human factor IX transgenic sheep produced by transfer of nuclei from transfected fetal fibroblasts. Science 278: 2130-2133, 1997. PubMed ID : 9405350 178. Siguret, V.; Amselem, S.; Vidaud, M.; Assouline, Z.; Kerbiriou-Nabias, D.; Pietu, G.; Goossens, M.; Larrieu, M. J.; Bahnak, B.; Meyer, D.; Lavergne, J. M. : Identification of a CpG mutation in the coagulation factor-IX gene by analysis of amplified DNA sequences. Brit. J. Haemat. 70: 411-416, 1988. PubMed ID : 3219291 179. Smith, K. J. : Monoclonal antibodies to coagulation factor IX define a high-frequency polymorphism by immunoassays. Am. J. Hum. Genet. 37: 668-679, 1985. PubMed ID : 9556657 180. Solera, J.; Magallon, M.; Martin-Villar, J.; Coloma, A. : Factor IX(Madrid 2): a deletion/insertion in factor IX gene which abolishes the sequence of the donor junction at the exon IV-intron d splice site. Am. J. Hum. Genet. 50: 434-437, 1992. PubMed ID : 1346483 181. Sommer, S. S. : Does cancer kill the individual and save the species? (Letter) Hum. Mutat. 3: 166-169, 1994. PubMed ID : 8199598 182. Sommer, S. S.; Bowie, E. J. W.; Ketterling, R. P.; Bottema, C. D. K. : Missense mutations and the magnitude of functional deficit: the example of factor IX. Hum. Genet. 89: 295-297, 1992. PubMed ID : 1601420 183. Soucie, J. M.; Evatt, B.; Jackson, D.; Hemophilia Surveillance System Project Investigators : Occurrence of hemophilia in the United States. Am. J. Hemat. 59: 288-294, 1998. PubMed ID : 9840909 184. Spinelli, A.; Schmid, W.; Straub, P. W. : Christmas disease (haemophilia B) in a girl with deletion of the short arm of one X-chromosome (functional Turner syndrome). Brit. J. Haemat. 34: 129-135, 1976. PubMed ID : 952762 185. Spitzer, S.; Katzman, D.; Kasper, C.; Bajaj, S. P. : Factor IX Hollywood: substitution of 55 pro-to-ala in the first EGF domain. (Abstract) Thromb. Haemost. 62: 203, 1989. 186. Spitzer, S. G.; Pendurthi, U. R.; Kasper, C. K.; Bajaj, S. P. : Molecular defect in factor IX (Bm Lake Elsinore): substitution of ala390 by val in the catalytic domain. J. Biol. Chem. 263: 10545-10548, 1988. PubMed ID : 3392024 187. Spitzer, S. G.; Warn-Cramer, B. J.; Kasper, C. C.; Pendurthi, U. R.; Bajaj, S. P. : Mutations in the catalytic domain of factor IXa which prevent macromolecular catalysis. (Abstract) Circulation 78 (suppl. II): 118, 1988. 188. Suehiro, K.; Kawabata, S.; Miyata, T.; Takeya, H.; Takamatsu, J.; Ogata, K.; Kamiya, T.; Saito, H.; Niho, Y.; Iwanaga, S. : Blood clotting factor IX B(M) Nagoya: substitution of arginine 180 by tryptophan and its activation by alpha-chymotrypsin and rat mast cell chymase. J. Biol. Chem. 264: 21257-21265, 1989. PubMed ID : 2592373 189. Suehiro, K.; Miyata, T.; Takeya, H.; Takamatsu, J.; Saito, H.; Murakawa, M.; Okamura, T.; Niho, Y.; Iwanaga, S. : Blood clotting factor IX Nagoya 3: the molecular defect of zymogen activation caused by an arginine-145 to histidine substitution. Thromb. Res. 60: 311-320, 1990. PubMed ID : 2087690 190. Sugimoto, M.; Miyata, T.; Kawabata, S.; Yoshioka, A.; Fukui, H.; Iwanaga, S. : Factor IX Kawachinagano: impaired function of the Gla-domain caused by attached propeptide region due to substitution of arginine by glutamine at position -4. Brit. J. Haemat. 72: 216-221, 1989. PubMed ID : 2757966 191. Sugimoto, M.; Miyata, T.; Kawabata, S.; Yoshioka, A.; Fukui, H.; Takahashi, H.; Iwanaga, S. : Blood clotting factor IX Niigata: substitution of alanine-390 by valine in the catalytic domain. J. Biochem. 104: 878-880, 1988. PubMed ID : 3243764 192. Szabo, P.; Purrello, M.; Rocchi, M.; Archidiacono, N.; Alhadeff, B.; Filippi, G.; Toniolo, D.; Martini, G.; Luzzatto, L.; Siniscalco, M. : Cytological mapping of the human glucose-6-phosphate dehydrogenase gene distal to the fragile-X site suggests a high rate of meiotic recombination across this site. Proc. Nat. Acad. Sci. 81: 7855-7859, 1984. PubMed ID : 6595664 193. Tanimoto, M.; Kojima, T.; Kamiya, T.; Takamatsu, J.; Ogata, K.; Obata, Y.; Inagaki, M.; Iizuka, A.; Nagao, T.; Kurachi, K.; Saito, H. : DNA analysis of seven patients with hemophilia B who have anti-factor IX antibodies: relationship to clinical manifestations and evidence that the abnormal gene was inherited. J. Lab. Clin. Med. 112: 307-313, 1988. PubMed ID : 3411192 194. Taylor, S. A. M.; Deugau, K. V.; Lillicrap, D. P. : Somatic mosaicism and female-to-female transmission in a kindred with hemophilia B (factor IX deficiency). Proc. Nat. Acad. Sci. 88: 39-42, 1991. PubMed ID : 1986380 195. Taylor, S. A. M.; Duffin, J.; Cameron, C.; Teitel, J.; Garvey, B.; Lillicrap, D. P. : Characterization of the original Christmas disease mutation (cysteine 206serine): from clinical recognition to molecular pathogenesis. Thromb. Haemost. 67: 63-65, 1992. PubMed ID : 1615485 196. Taylor, S. A. M.; Liddell, M. B.; Peake, I. R.; Bloom, A. L.; Lillicrap, D. P. : A mutation adjacent to the beta cleavage site of factor IX (valine 182 to leucine) results in mild haemophilia B(m). Brit. J. Haemat. 75: 217-221, 1990. PubMed ID : 2372509 197. Taylor, S. A. M.; Liddell, M. B.; Peake, I. R.; Lillicrap, D. P. : Mutations affecting cleavage of the activation peptide of factor IX as a cause of hemophilia B. (Abstract) Am. J. Hum. Genet. 45: A223, 1989. 198. Taylor, S. A. M.; Lillicrap, D. P.; Blanchette, V.; Giles, A. R.; Holden, J. J. A.; White, B. N. : A complete deletion of the factor IX gene and new TaqI variant in a hemophilia B kindred. Hum. Genet. 79: 273-276, 1988. PubMed ID : 2841226 199. Thompson, A. R. : Personal Communication. Seattle, Wash., 11/1989. 200. Thompson, A. R. : Alloantibodies in hemophilia B binding to multiple factor IX epitopes. Thromb. Res. 46: 169-174, 1987. PubMed ID : 2438804 201. Thompson, A. R.; Chen, S.-H.; Brayer, G. D. : Severe hemophilia B due to a G to T transversion changing gly 309 to val and inhibiting active protease conformation by preventing ion pair formation. (Abstract) Blood 74: 134A, 1989. 202. Tsang, T. C.; Bentley, D. R.; Mibashan, R. S.; Giannelli, F. : A factor IX mutation, verified by direct genomic sequencing, causing haemophilia B by a novel mechanism. EMBO J. 7: 3009-3015, 1988. PubMed ID : 3181127 203. Usharani, P.; Warn-Cramer, B. J.; Kasper, C. K.; Bajaj, S. P. : Characterization of three abnormal factor IX variants (Bm Lake Elsinore, Long Beach, and Los Angeles) of hemophilia-B: evidence for defects affecting the latent catalytic site. J. Clin. Invest. 75: 76-83, 1985. PubMed ID : 3965513 204. Veltkamp, J. J.; Meilof, J.; Remmelts, H. G.; Van der Vlerk, D.; Loeliger, E. A. : Another genetic variant of haemophilia B: haemophilia B Leyden. Scand. J. Haemat. 7: 82-90, 1970. PubMed ID : 5450691 205. Verstraete, M.; Vermylen, C.; Vandenbroucke, J. : Hemophilia B associated with a decreased factor VII activity. Am. J. Med. Sci. 243: 20-26, 1962. PubMed ID : 13925578 206. Vianna-Morgante, A. M.; Batista, D. A. S.; Levisky, R. B.; Zatz, M. : X;autosome translocations in females with X-linked recessive diseases. (Abstract) 7th Int. Cong. Hum. Genet., Berlin 97, 1986. 207. Vidaud, D.; Tartary, M.; Costa, J.-M.; Bahnak, B. R.; Gispert-Sanchez, S.; Fressinaud, E.; Gazengel, C.; Meyer, D.; Goossens, M.; Lavergne, J.-M.; Vidaud, M. : Nucleotide substitutions at the -6 position in the promoter region of the factor IX gene result in different severity of hemophilia B Leyden: consequences for genetic counseling. Hum. Genet. 91: 241-244, 1993. PubMed ID : 8478007 208. Vidaud, D.; Vidaud, M.; Bahnak, B. R.; Siguret, V.; Sanchez, S. G.; Laurian, Y.; Meyer, D.; Goossens, M.; Lavergne, J. M. : Haemophilia B due to a de novo insertion of a human-specific Alu subfamily member within the coding region of the factor IX gene. Europ. J. Hum. Genet. 1: 30-36, 1993. PubMed ID : 8069649 209. Vidaud, M.; Chabret, C.; Gazengel, C.; Grunebaum, L.; Cazenave, J. P.; Goossens, M. : A de novo intragenic deletion of the potential EGF domain of the factor IX gene in a family with severe hemophilia B. Blood 68: 961-963, 1986. PubMed ID : 2875754 210. Vidaud, M.; Vidaud, D.; Siguret, V.; Lavergne, J. M.; Goossens, M. : Mutational insertion of an Alu sequence causes hemophilia B. (Abstract) Am. J. Hum. Genet. 45: A226, 1989. 211. Vogel, F.; Motulsky, A. G. : Population genetics.In: Vogel, F.; Motulsky, A. G. : Human Genetics. Berlin: Springer (pub.) 1986. Pp. 433-511. 212. Wadelius, C.; Blomback, M.; Pettersson, U. : Molecular studies of haemophilia B in Sweden: identification of patients with total deletion of the factor IX gene and without inhibitory antibodies. Hum. Genet. 81: 13-17, 1988. PubMed ID : 2848757 213. Wadelius, C.; Lindstedt, M.; Pigg, M.; Egberg, N.; Pettersson, U.; Anvret, M. : Hemophilia B in a 46,XX female probably caused by non-random X inactivation. Clin. Genet. 43: 1-4, 1993. PubMed ID : 8096443 214. Wall, R. L.; McConnell, J.; Moore, D.; Macpherson, C. R.; Marson, A. : Christmas disease, color-blindness and blood group Xg(a). Am. J. Med. 43: 214-226, 1967. PubMed ID : 5298508 215. Wang, L.; Zoppe, M.; Hackeng, T. M.; Griffin, J. H.; Lee, K.-F.; Verma, I. M. : A factor IX-deficient mouse model for hemophilia B gene therapy. Proc. Nat. Acad. Sci. 94: 11563-11566, 1997. PubMed ID : 9326649 216. Wang, N. S.; Zhang, M.; Thompson, A. R.; Chen, S.-H. : Factor IX(Chongqing): a new mutation in the calcium-binding domain of factor IX resulting in severe hemophilia B. Thromb. Haemost. 63: 24-26, 1990. PubMed ID : 2339358 217. Ware, J.; Davis, L.; Frazier, D.; Bajaj, S. P.; Stafford, D. W. : Genetic defect responsible for the dysfunctional protein: factor IX (Long Beach). Blood 72: 820-822, 1988. PubMed ID : 3401602 218. Ware, J.; Diuguid, D. L.; Liebman, H. A.; Rabiet, M.-J.; Kasper, C. K.; Furie, B. C.; Furie, B.; Stafford, D. W. : Factor IX San Dimas: substitution of glutamine for arg(-4) in the propeptide leads to incomplete gamma-carboxylation and altered phospholipid binding properties. J. Biol. Chem. 264: 11401-11406, 1989. PubMed ID : 2738071 219. Whittaker, D. L.; Copeland, D. L.; Graham, J. B. : Linkage of color blindness with hemophilias A and B. Am. J. Hum. Genet. 14: 149-158, 1962. PubMed ID : 14006651 220. Winship, P. R. : Haemophilia B caused by mutation of a potential thrombin cleavage site in factor IX. Nucleic Acids Res. 18: 1310, 1990. PubMed ID : 2320433 221. Winship, P. R. : Characterisation of the molecular defect in haemophilia B patients using the polymerase chain reaction procedure. (Abstract) Thromb. Haemost. 62: 465, 1989. 222. Winship, P. R. : CpG polymorphisms and haemophilia B. (Letter) Lancet II: 503, 1989. 223. Winship, P. R.; Brownlee, G. G. : Diagnosis of haemophilia B carriers using intragenic oligonucleotide probes. (Letter) Lancet II: 218-219, 1986. 224. Winship, P. R.; Dragon, A. C. : Identification of haemophilia B patients with mutations in the two calcium binding domains of factor IX: importance of a beta-OH asp64-to-asn change. Brit. J. Haemat. 77: 102-109, 1991. PubMed ID : 1998585 225. Winship, P. R.; Rees, D. J. G.; Alkan, M. : Detection of polymorphisms at cytosine phosphoguanidine dinucleotides and diagnosis of haemophilia B carriers. Lancet I: 631-634, 1989. 226. Yant, S. R.; Meuse, L.; Chiu, W.; Ivics, Z.; Izsvak, Z.; Kay, M. A. : Somatic integration and long-term transgene expression in normal and haemophilic mice using a DNA transposon system. Nature Genet. 25: 35-41, 2000. PubMed ID : 10802653 227. Yao, S.-N.; Wilson, J. M.; Nabel, E. G.; Kurachi, S.; Hachiya, H. L.; Kurachi, K. : Expression of human factor IX in rat capillary endothelial cells: toward somatic gene therapy for hemophilia B. Proc. Nat. Acad. Sci. 88: 8101-8105, 1991. PubMed ID : 1896457 228. Yoshioka, A.; Ohkubo, Y.; Nishimura, T.; Tanaka, I.; Fukui, H.; Ogata, K.; Kamiya, T.; Takahashi, H. : Heterogeneity of factor IX BM: difference in cleavage sites by factor XIa and Ca(2+) in factor IX Kashihara, factor IX Nagoya and factor IX Niigata. Thromb. Res. 42: 595-604, 1986. PubMed ID : 3487139 229. Zhang, M.; Chen, S.-H.; Thompson, A. R.; Lovrien, E.; Scott, C. R. : CG dinucleotides are 'hot spots' in the factor IX gene for point mutations: evidence from the study of 25 families with defined mutations causing hemophilia B. (Abstract) Am. J. Hum. Genet. 45: A231, 1989. ### CONTRIBUTORS Victor A. McKusick - updated : 1/11/2005 Victor A. McKusick - updated : 4/22/2004 Victor A. McKusick - updated : 9/4/2003 Victor A. McKusick - updated : 7/18/2003 Ada Hamosh - updated : 9/12/2002 Victor A. McKusick - updated : 9/20/2001 Victor A. McKusick - updated : 6/26/2001 Victor A. McKusick - updated : 6/22/2001 Victor A. McKusick - updated : 1/10/2001 Victor A. McKusick - updated : 9/22/2000 Victor A. McKusick - updated : 8/17/2000 Ada Hamosh - updated : 4/28/2000 Victor A. McKusick - updated : 3/1/2000 Victor A. McKusick - updated : 1/14/2000 Victor A. McKusick - updated : 1/13/2000 Victor A. McKusick - updated : 12/20/1999 Ada Hamosh - updated : 7/28/1999 Victor A. McKusick - updated : 2/14/1999 Victor A. McKusick - updated : 8/17/1998 Victor A. McKusick - updated : 7/13/1998 Victor A. McKusick - updated : 12/18/1997 Victor A. McKusick - updated : 11/6/1997 Victor A. McKusick - updated : 9/16/1997 Victor A. McKusick - updated : 3/21/1997 ### CREATION DATE Victor A. McKusick : 6/4/1986 ### EDIT HISTORY wwang : 1/14/2005 wwang : 1/12/2005 terry : 1/11/2005 terry : 4/22/2004 alopez : 4/7/2004 carol : 3/17/2004 cwells : 9/30/2003 terry : 9/4/2003 tkritzer : 7/29/2003 terry : 7/18/2003 carol : 7/7/2003 alopez : 9/12/2002 cwells : 9/12/2002 mcapotos : 1/2/2002 mcapotos : 9/27/2001 terry : 9/20/2001 mcapotos : 7/5/2001 mcapotos : 7/5/2001 mcapotos : 6/26/2001 terry : 6/26/2001 terry : 6/22/2001 mcapotos : 3/27/2001 cwells : 1/17/2001 terry : 1/10/2001 mcapotos : 10/3/2000 mcapotos : 9/22/2000 carol : 8/18/2000 terry : 8/17/2000 alopez : 5/1/2000 terry : 4/28/2000 alopez : 3/1/2000 terry : 3/1/2000 mgross : 2/21/2000 terry : 1/14/2000 terry : 1/13/2000 carol : 12/27/1999 terry : 12/20/1999 terry : 9/21/1999 alopez : 7/30/1999 carol : 7/28/1999 kayiaros : 7/8/1999 kayiaros : 7/8/1999 carol : 2/14/1999 carol : 2/5/1999 psherman : 1/8/1999 dkim : 12/15/1998 dkim : 12/10/1998 dkim : 9/22/1998 dkim : 9/22/1998 carol : 8/18/1998 terry : 8/17/1998 dkim : 7/21/1998 carol : 7/16/1998 terry : 7/13/1998 alopez : 5/21/1998 mark : 12/18/1997 terry : 12/16/1997 terry : 11/13/1997 terry : 11/6/1997 mark : 9/22/1997 terry : 9/16/1997 terry : 9/16/1997 alopez : 7/29/1997 alopez : 7/8/1997 terry : 5/28/1997 terry : 3/21/1997 terry : 3/17/1997 mark : 11/12/1996 terry : 10/24/1996 mark : 7/22/1996 mark : 7/9/1996 mark : 3/30/1996 terry : 3/12/1996 mark : 12/20/1995 jason : 7/19/1994 carol : 5/23/1994 terry : 4/26/1994 warfield : 4/20/1994 mimadm : 4/15/1994 pfoster : 4/5/1994 Copyright © 1966-2005 Johns Hopkins University
11: | *609356 | Links
| FMRP-INTERACTING PROTEIN, 82-KD
#### Alternative titles; symbols 82-@FIP KIAA1321 PROLIFERATION-INDUCING GENE 1; PIG1 ### TABLE OF CONTENTS #### CLONING GENE FUNCTION MAPPING REFERENCES CREATION DATE EDIT HISTORY ### TEXT #### CLONING Using yeast 2-hybrid analysis to identify proteins that interact with the RNA-binding protein FMRP (309550), Bardoni et al. (2003) isolated an 82-kD protein, which they designated 82-FIP (82-kD FMRP-interacting protein). The 82-FIP cDNA had previously been identified by Nagase et al. (2000), and named KIAA1321, by sequencing clones obtained from an adult brain cDNA library. The deduced 82-FIP protein contains 695 amino acids and shares 95% sequence identity with the mouse protein. The protein is highly evolutionarily conserved. #### GENE FUNCTION Bardoni et al. (2003) determined that FMRP interacts with 82-FIP through a motif in its N terminus between residues 66 and 134 which it also uses to interact with NUFIP1 (604354). Bardoni et al. (2003) demonstrated that both FMRP and 82-FIP interact in vitro and in vivo and both localize in FMRP-containing mRNP complexes associated with polyribosomes. Using immunohistochemistry on adult mouse brain sections, Bardoni et al. (2003) localized 82-FIP in both nucleus and cytoplasm in most neurons, with a distribution matching that of FMRP. In the cortex, it was distributed in a diffuse way in the nucleus and in the cytoplasm. The protein was only localized in the cytoplasm in neurons of the dentate gyrus in the olfactory bulb, in the ependymal epithelium, and in the granular layer of the cerebellum. In Purkinje cells, 82-Fip was distributed in both cell compartments and was localized in nuclear dots adjacent to the nucleolus. Subcellular distribution of 82-FIP was cell cycle-dependent in cultured cells, being cytoplasmic in the G2/M phase and accumulating in nucleus during the G1 phase, which suggested that the composition of some FMRP-containing RNP complexes may be cell cycle-modulated. #### MAPPING By radiation hybrid analysis, Nagase et al. (2000) mapped the KIAA1321 gene to chromosome 17. ### REFERENCES 1. Bardoni, B.; Castets, M.; Huot, M.-E.; Schenck, A; Adinolfi, S.; Corbin, F.; Pastore, A.; Khandjian, E. W.; Mandel, J.-L. : 82-FIP, a novel FMRP (fragile X mental retardation protein) interacting protein, shows a cell cycle-dependent intracellular localization. Hum. Molec. Genet. 12: 1689-1698, 2003. PubMed ID : 12837692 2. Nagase, T.; Kikuno, R.; Ishikawa, K.; Hirosawa, M.; Ohara, O. : Prediction of the coding sequences of unidentified human genes. XVI. The complete sequences of 150 new cDNA clones from brain which code for large proteins in vitro. DNA Res. 7: 65-73, 2000. PubMed ID : 10718198 ### CREATION DATE George E. Tiller : 5/5/2005 ### EDIT HISTORY tkritzer : 5/19/2005 Copyright © 1966-2005 Johns Hopkins University
12: | #606438 | GeneTests, Links
| HUNTINGTON DISEASE-LIKE 2; HDL2
### TABLE OF CONTENTS #### TEXT CLINICAL FEATURES MOLECULAR GENETICS POPULATION GENETICS NOMENCLATURE REFERENCES CONTRIBUTORS CREATION DATE EDIT HISTORY Clinical Synopsis Gene map locus 16q24.3 ### TEXT A number sign (#) is used with this entry because of evidence that Huntington disease-like-2 can be caused by an expanded CAG/CTG repeat in the junctophilin-3 gene (JPH3; 605268). #### CLINICAL FEATURES Margolis et al. (2001) described a large kindred with an autosomal dominant disorder that is clinically similar to Huntington disease (143100) but arose from a CAG expansion in a different gene. The disorder is characterized by onset in the fourth decade, involuntary movements and abnormalities of voluntary movements, psychiatric symptoms, weight loss, dementia, and relentless course with death about 20 years after disease onset. Brain magnetic resonance imaging scans and an autopsy revealed marked striatal atrophy and moderate cortical atrophy, with striatal neurodegeneration in a dorsal-to-ventral gradient and occasional intranuclear inclusions. This family was of African-American ethnicity, and the parents of the first known affected individual were from a semirural region of the southeastern United States. The disorder in this family, designated family W, fell well within the spectrum of HD. Other than a lower frequency of eye movement findings and the absence of seizures, the disease was similar to juvenile-onset HD (van Dijk et al., 1986) and the 'Westphal' variant of HD observed in some adult cases. Unlike the HD-like disorder linked to 20p (603218), seizures did not occur in affected members of pedigree W. However, in both pedigrees, rigidity was more prominent than chorea. Walker et al. (2002) reported a family in which 3 individuals were affected with what the authors thought was an autosomal dominant form of chorea-acanthocytosis (200150), but which was later found by Walker et al. (2003) to be HDL2. The proband was a 56-year-old man who had initially been diagnosed with Huntington disease. At age 34 years, he developed a slowly progressive deterioration in memory and personality, with involuntary movements of the face and hands. By age 54 years, he was unable to stand, had no spontaneous speech, and showed continuous choreiform movements. Postmortem examination of the brain showed severe, diffuse cortical atrophy and severe atrophy of the caudate and putamen, as well as ubiquitinated intranuclear inclusions with immunoreactivity for expanded polyglutamine repeats throughout the brain. His son, who had fragile X syndrome (309550), developed gait abnormalities, chorea, and dystonia in his late twenties. Head CT scan showed generalized cerebral and caudate atrophy. Walker et al. (2002) suspected that the fragile X was unrelated to the neurologic disorder. The third patient, the nephew of the proband, developed personality changes, primitive reflexes, hyperreflexia, and mild parkinsonism beginning at age 28 years. All 3 patients had 30 to 35% acanthocytosis on peripheral blood smear. #### MOLECULAR GENETICS Margolis et al., (2001) found that in family W all tested affected individuals, and no tested unaffected individuals, had a CAG/CTG trinucleotide repeat expansion of 50 to 60 triplets, as determined by the repeat expansion detection assay. Tests for the HD expansion, for all other then-known CAG expansion mutations, and for linkage to chromosomes 20p and 4p were negative, indicating that this mutation was novel. Holmes et al. (2001) demonstrated that the expanded CAG/CTG repeat in the original pedigree was located in an alternatively spliced exon of the JPH3 gene (605268.0001). This exon has multiple splice acceptor sites. They found the same mutation in the JPH3 gene in other African-American patients with a Huntington disease-like neurologic disorder. Among 74 patients with an HD-like phenotype but without CAG repeat expansions in the IT15 gene (143100.0001), Stevanin et al. (2002) identified 1 patient with a pure uninterrupted 50 CAG/CTG repeat in the JPH3 gene. The patient was a 44-year-old Moroccan woman with subcortical dementia, mild choreic movements, and atrophy of the cerebral cortex. In the study by Stevanin et al. (2002), the HDL2 locus accounted for only 2% of typical HD cases not caused by expansion in the IT15 gene, suggesting further genetic heterogeneity. In the family reported by Walker et al. (2002) as having choreoacanthocytosis, Walker et al. (2003) identified trinucleotide repeat expansions of 51, 58, and 57 triplets in the junctophilin-3 gene, confirming Huntington disease-like-2. Walker et al. (2003) also reported a Mexican family with HDL2, characterized by dementia, depression, chorea, and parkinsonism, in which affected members had 46, 49, and 46 triplet repeats. One of the patients also had acanthocytosis. Another unrelated affected African-American patient, who did not have acanthocytosis, had 44 triplet repeats. The findings indicated that some, but not all, patients with the HDL2 mutation may develop acanthocytosis, and Walker et al. (2003) suggested that there may be reduced penetrance of this feature or that the acanthocytosis may vary over the course of the disease. #### POPULATION GENETICS In 9 independent series of patients referred for HD testing in North America (538 patients) or Japan (44 patients), Margolis et al. (2004) found an HDL2 frequency of approximately 1% in North America and 0% in Japan. HDL2 was identified predominantly in patients of African ancestry. One affected Mexican pedigree originated from a region of Mexico colonized by Africans. Repeat expansions in the junctophilin-3 gene ranged from 44 to 57 triplets, and a younger age at onset was correlated with a longer repeat length. #### NOMENCLATURE Margolis et al. (2001) stated that consistent with the recommendation of the Nomenclature Committee of HUGO, the disorder that maps to 20p is designated Huntington disease-like-1 (HDL1; 603218). They concluded that the family from Saudi Arabia that had been described as 'HD-like-3' is sufficiently distinct, based primarily on autosomal recessive inheritance and in part on presentation (onset age 3 to 4 years, prominent seizures, rapid course), to be classified separately. Since about 1% of all cases of clinically or pathologically defined HD do not carry the HD mutation, it was considered likely that the basis for other rare 'HD-like' disorders will be identified. ### REFERENCES 1. Holmes, S. E.; O'Hearn, E.; Rosenblatt, A.; Callahan, C.; Hwang, H. S.; Ingersoll-Ashworth, R. G.; Fleisher, A.; Stevanin, G.; Brice, A.; Potter, N. T.; Ross, C. A.; Margolis, R. L. : A repeat expansion in the gene encoding junctophilin-3 is associated with Huntington disease-like 2. Nature Genet. 29: 377-378, 2001. PubMed ID : 11694876 2. Margolis, R. L.; Holmes, S. E.; Rosenblatt, A.; Gourley, L.; O'Hearn, E.; Ross, C. A.; Seltzer, W. K.; Walker, R. H.; Ashizawa, T.; Rasmussen, A.; Hayden, M.; Almqvist, E. W.; and 13 others : Huntington's disease-like 2 (HDL2) in North America and Japan. Ann. Neurol. 56: 670-674, 2004. Note: Erratum: Ann. Neurol. 56: 911 only, 2004. PubMed ID : 15468075 3. Margolis, R. L.; O'Hearn, E.; Rosenblatt, A.; Willour, V.; Holmes, S. E.; Franz, M. L.; Callahan, C.; Hwang, H. S.; Troncoso, J. C.; Ross, C. A. : A disorder similar to Huntington's disease is associated with a novel CAG repeat expansion. Ann. Neurol. 50: 373-380, 2001. 4. Stevanin, G.; Camuzat, A.; Holmes, S. E.; Julien, C.; Sahloul, R.; Dode, C.; Hahn-Barma, V.; Ross, C. A.; Margolis, R. L.; Durr, A.; Brice, A. : CAG/CTG repeat expansions at the Huntington's disease-like 2 locus are rare in Huntington's disease patients. Neurology 58: 965-967, 2002. PubMed ID : 11914418 5. Van Dijk, J. G.; Van de Velde, E. A.; Roos, R. A. C.; Bruyn, G. W. : Juvenile Huntington disease. Hum. Genet. 73: 235-239, 1986. PubMed ID : 2942452 6. Walker, R. H.; Morgello, S.; Davidoff-Feldman, B.; Melnick, A.; Walsh, M. J.; Shashidharan, P.; Brin, M. F. : Autosomal dominant chorea-acanthocytosis with polyglutamine-containing neuronal inclusions. Neurology 58: 1031-1037, 2002. PubMed ID : 11940688 7. Walker, R. H.; Rasmussen, A.; Rudnicki, D.; Holmes, S. E.; Alonso, E.; Matsuura, T.; Ashizawa, T.; Davidoff-Feldman, B.; Margolis, R. L. : Huntington's disease-like 2 can present as chorea-acanthocytosis. Neurology 61: 1002-1004, 2003. PubMed ID : 14557581 ### CONTRIBUTORS Cassandra L. Kniffin - updated : 1/28/2004 Victor A. McKusick - updated : 11/5/2001 ### CREATION DATE Victor A. McKusick : 11/1/2001 ### EDIT HISTORY ckniffin : 3/11/2005 carol : 3/2/2004 carol : 2/25/2004 ckniffin : 2/25/2004 ckniffin : 1/28/2004 carol : 12/16/2002 tkritzer : 12/12/2002 tkritzer : 12/12/2002 ckniffin : 12/9/2002 alopez : 11/20/2001 alopez : 11/5/2001 terry : 11/5/2001 alopez : 11/1/2001 joanna : 11/1/2001 Copyright © 1966-2005 Johns Hopkins University
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| CYTOPLASMIC FMRP-INTERACTING PROTEIN 2; CYFIP2
#### Alternative titles; symbols p53-INDUCIBLE PROTEIN; PIR121 ### TABLE OF CONTENTS #### CLONING MAPPING REFERENCES CREATION DATE EDIT HISTORY Gene map locus Chr.5 ### TEXT #### CLONING To identify novel proteins that interact with the fragile X mental retardation protein (FMRP), encoded by the FMR1 gene (309550), Schenck et al. (2001) used yeast 2-hybrid screening with the FMRP N terminus as bait. They identified 2 proteins as FMRP interactors, which they called cytoplasmic FMRP interacting proteins 1 (CYFIP1; 606322) and 2 (CYFIP2). CYFIP2 contains 1,252 amino acids and shares 88% sequence identity with CYFIP1. CYFIP1/2 are members of a highly conserved protein family and share approximately 99% sequence identity with their mouse orthologs. CYFIP1 interacts exclusively with FMRP, whereas CYFIP2 also interacts with the FMRP-related proteins FXR1P (600819) and FXR2P (605339). The interaction of FMRP and CYFIP involves the domain of FMRP that also mediates homo- and heteromerization, suggesting a competition between interaction among the FXR proteins and interaction with CYFIP. Schenck et al. (2001) determined that CYFIP1/2 are distributed in an identical pattern in the cytoplasm, showing colocalization with FMRP and ribosomes. Consistent with FMRP and RAC1 localization in dendritic fine structures, CYFIP1/2 are present in synaptosomal extracts. #### MAPPING The International Radiation Hybrid Mapping Consortium mapped the CYFIP2 gene to chromosome 5 (stSG9917). ### REFERENCES 1. Schenck, A.; Bardoni, B.; Moro, A.; Bagni, C.; Mandel, J. L. : A highly conserved protein family interacting with the fragile X mental retardation protein (FMRP) and displaying selective interactions with FMRP-related proteins FXR1P and FXR2P. Proc. Nat. Acad. Sci. 98: 8844-8849, 2001. PubMed ID : 11438699 ### CREATION DATE Victor A. McKusick : 9/28/2001 ### EDIT HISTORY alopez : 3/19/2004 joanna : 8/12/2002 carol : 9/28/2001 Copyright © 1966-2005 Johns Hopkins University
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| CYTOPLASMIC FMRP INTERACTING PROTEIN 1; CYFIP1
#### Alternative titles; symbols KIAA0068 ### TABLE OF CONTENTS #### CLONING GENE STRUCTURE MAPPING MOLECULAR GENETICS REFERENCES CONTRIBUTORS CREATION DATE EDIT HISTORY Gene map locus Chr.15 ### TEXT #### CLONING To identify novel proteins that interact with the fragile X mental retardation protein (FMRP), encoded by the FMR1 gene (309550), Schenck et al. (2001) used yeast 2-hybrid screening with the FMRP N terminus as bait. They identified 2 proteins as FMRP interactors, which they called cytoplasmic FMRP interacting proteins 1 (CYFIP1) and 2 (CYFIP2; 606323). CYFIP1 contains 1,253 amino acids and shares 88% sequence identity with CYFIP2. CYFIP1/2 are members of a highly conserved protein family and share approximately 99% sequence identity with their mouse orthologs. CYFIP1 interacts exclusively with FMRP, whereas CYFIP2 also interacts with the FMRP-related proteins FXR1P (600819) and FXR2P (605339). The interaction of FMRP and CYFIP involves the domain of FMRP that also mediates homo- and heteromerization, suggesting a competition between interaction among the FXR proteins and interaction with CYFIP. Schenck et al. (2001) determined that CYFIP1/2 are distributed in an identical pattern in the cytoplasm, showing colocalization with FMRP and ribosomes. CYFIP1 has been shown to interact with the small GTPase RAC1 (602048), which is implicated in development and maintenance of neuronal structures (Kobayashi et al., 1998). Consistent with FMRP and RAC1 localization in dendritic fine structures, CYFIP1/2 are present in synaptosomal extracts. By genomic sequence analysis to identify novel genes adjacent to the imprinted domain in the Prader-Willi syndrome (PWS; 176270)/Angelman (AS; 105830) syndrome deletion region of chromosome 15, Chai et al. (2003) identified CYFIP1. Northern blot analysis detected a 4.4-kb transcript in all human and mouse tissues examined, with highest expression in placenta. #### GENE STRUCTURE Chai et al. (2003) determined that the CYFIP1 gene contains 31 exons and spans 111.4 kb. The 5-prime end is associated with a strong CpG island. The mouse Cyfip1 gene has a similar 31-exon structure. #### MAPPING By analysis of a panel of human-rodent hybrid cell lines, Nomura et al. (1994) mapped the CYFIP1 gene, which they called KIAA0068, to chromosome 15. By genomic sequence analysis, Chai et al. (2003) mapped the CYFIP1 gene to chromosome 15q11.2, within a region deleted in some cases of PWS and AS. CYFIP1 lies within a gene cluster distal to breakpoint hot spot 1 (BP1) and proximal to BP2. The order of genes within this cluster is cen-NIPA1 (608145)-NIPA2 (608146)-CYFIP1-GCP5 (608147)-BP2-tel. Chai et al. (2003) mapped the mouse Cyfip1 gene to a region of chromosome 7C that contains the same gene cluster and shows homology of synteny to human chromosome 15q11-q13. #### MOLECULAR GENETICS Deletions associated with AS and PWS are either class I, with the deletion extending from BP1 (15q11.2) to BP3 (15q13), or class II, with a more telomeric deletion extending from BP2 (15q11.2) to BP3. Chai et al. (2003) determined that a BAC clone containing exons 7 through 31 of the CYFIP1 gene, which is located between BP1 and BP2, could be used as probe in FISH to distinguish between class I and class II deletions in a panel of cell lines from patients with AS deletions. By replication-timing studies, Chai et al. (2003) determined that replication of the mouse genomic region spanning Nipa1-Nipa2-Cyfip1 showed a pattern of asynchrony, but the asynchrony was not due to parent-of-origin influences. PCR of mouse brain cDNA from transgenic PWS and AS mouse models indicated that the Nipa1, Nipa2, Cyfip1, and Gcp5 genes are nonimprinted. RT-PCR detected expression of the human NIPA1, NIPA2, CYFIP1, and GCP5 genes in lymphocytes from a normal individual and from PWS and AS imprinting mutation patients. CYFIP1 was expressed from both the maternal and paternal chromosome 15 in somatic cell hybrids, further indicating that these 4 genes are nonimprinted. ### REFERENCES 1. Chai, J.-H.; Locke, D. P.; Greally, J. M.; Knoll, J. H. M.; Ohta, T.; Dunai, J.; Yavor, A.; Eichler, E. E.; Nicholls, R. D. : Identification of four highly conserved genes between breakpoint hotspots BP1 and BP2 of the Prader-Willi/Angelman syndromes deletion region that have undergone evolutionary transposition mediated by flanking duplicons. Am. J. Hum. Genet. 73: 898-925, 2003. PubMed ID : 14508708 2. Kobayashi, K.; Kuroda, S.; Fukata, M.; Nakamura, T.; Nagase, T.; Nomura, N.; Matsuura, Y.; Yoshida-Kubomura, N.; Iwamatsu, A.; Kaibuchi, K. : p140Sra-1 (specifically Rac1-associated protein) is a novel specific target for Rac1 small GTPase. J. Biol. Chem. 273: 291-295, 1998. PubMed ID : 9417078 3. Nomura, N.; Nagase, T.; Miyajima, N.; Sazuka, T.; Tanaka, A.; Sato, S.; Seki, N.; Kawarabayasi, Y.; Ishikawa, K.; Tabata, S. : Prediction of the coding sequences of unidentified human genes. II. The coding sequences of 40 new genes (KIAA0041-KIAA0080) deduced by analysis of cDNA clones from human cell line KG-1. DNA Res. 1: 223-229, 1994. PubMed ID : 7584044 4. Schenck, A.; Bardoni, B.; Moro, A.; Bagni, C.; Mandel, J. L. : A highly conserved protein family interacting with the fragile X mental retardation protein (FMRP) and displaying selective interactions with FMRP-related proteins FXR1P and FXR2P. Proc. Nat. Acad. Sci. 98: 8844-8849, 2001. PubMed ID : 11438699 ### CONTRIBUTORS Patricia A. Hartz - updated : 10/2/2003 ### CREATION DATE Victor A. McKusick : 9/28/2001 ### EDIT HISTORY alopez : 3/19/2004 mgross : 10/2/2003 mcapotos : 12/26/2001 carol : 9/28/2001 Copyright © 1966-2005 Johns Hopkins University
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| BRAIN CYTOPLASMIC RNA 1; BCYRN1
#### Alternative titles; symbols BC200 RNA; BC200 BC200-ALPHA ### TABLE OF CONTENTS #### DESCRIPTION CLONING GENE FUNCTION MAPPING ANIMAL MODEL REFERENCES CONTRIBUTORS CREATION DATE EDIT HISTORY ### TEXT #### DESCRIPTION Alu repeat elements make up a large portion of usually nontranscribed short interspersed repetitive elements. BC200 RNA, which contains domains homologous to Alu sequences, is a small cytoplasmic RNA expressed in a highly defined neural and subcellular distribution in primate brain and in cell lines. #### CLONING Bc1 (brain cytoplasmic-1) RNA is a small, stable RNA species, prevalently expressed in rat neurons, in which it is one of the few RNAs that are transported into dendritic processes (Tiedge et al., 1991). By screening total or polyadenylated brain RNA with rat Bc1 RNA, Tiedge et al. (1993) obtained cDNAs encoding human BCYRN1, which they termed BC200 RNA. Sequence analysis predicted that the RNA is subdivided into 3 major structural domains: a 5-prime domain derived from Alu elements that contains consensus elements A and B of the split RNA polymerase III promoter and signal recognition particle motifs; a central A-rich region; and a unique 3-prime sequence containing 42 nucleotides. RNA blot analysis detected transcripts in brain, with low levels in testis. In situ hybridization analysis showed expression in retinal ganglion cells, inner plexiform, and the innermost layer of the inner nuclear layers, but little or no expression was found in the photoreceptor cell layer. Expression was also observed in hippocampus and the neocortex, particularly in dendritic locations. By screening a human genomic library with the 3-prime end of BC200 RNA as the probe, Martignetti and Brosius (1993) cloned the full-length BC200 RNA, which they called BC200-alpha, and 2 pseudogenes, which they called BC200-beta and BC200-gamma. Mapping studies and Southern blot analysis indicated that all are single-copy genes. Sequence analysis demonstrated that BC200 RNA is the product of a monomeric Alu sequence rather than an Alu dimer. Martignetti and Brosius (1993) proposed that BC200 RNA was retropositionally generated and recruited, or 'exapted,' into a function regulating dendritic protein biosynthesis. #### GENE FUNCTION Using a mouse Fmr1 (309550) knockout model, Zalfa et al. (2003) showed that Fmrp acts as a translational repressor of specific mRNAs at synapses. Fmrp associated not only with these target mRNAs, but also with the dendritic, nontranslatable RNA Bc1. Blocking of Bc1 inhibited the interaction of Fmrp with its target mRNAs. Furthermore, Bc1 bound directly to Fmrp and could also associate, in the absence of any protein, with the mRNAs regulated by Fmrp. To determine whether BC200 RNA, a potential analog of Bc1, associated with human FMRP, Zalfa et al. (2003) immunoprecipitated the FMRP-RNP particle from human neuroblastoma, glioma, and lymphoblast cell line extracts. BC200 was detected by RT-PCR in extracts from glioma and neuronal cell lines, but not in extracts from lymphoblast cell lines. The authors concluded that Bc1 and BC200 likely have the same functional significance. These results suggested a mechanism where Bc1 could determine the specificity of Fmrp function by linking the regulated mRNAs and Fmrp. Thus, when FMRP is not present in humans, loss of translational repression of specific mRNAs at synapses could result in the synaptic dysfunction phenotype of fragile X patients. Lukiw et al. (1992) measured the abundance of BC200 RNA in total RNA isolated from temporal neocortices of brains with no pathology and those affected with neurodegenerative disease. BC200 levels were comparable between brains with no pathology and those affected with non-Alzheimer dementia, but there was a 70% reduction of BC200 in brains with Alzheimer disease (104300). #### MAPPING By linkage analysis and radiation hybrid analysis, Basile et al. (1998) mapped the BCYRN1 gene to chromosome 2p16. Taylor et al. (1997) mapped the mouse Bc1 gene, a potential functional analog of BCYRN1, to the distal end of chromosome 7. #### ANIMAL MODEL Lewejohann et al. (2004) found that Bc1 knockout mice were healthy, with normal brain morphology and no apparent neurologic defects. In a series of tests for exploration and spatial memory, the mutant mice showed reduced exploration and increased anxiety compared with controls, but spatial memory was not affected. In an outdoor pen, the survival rates of Bc1 mutant mice were lower than those of controls. ### REFERENCES 1. Basile, V.; Vicente, A.; Martignetti, J. A.; Skryabin, B. V.; Brosius, J.; Kennedy, J. L. : Assignment of the human BC200 RNA gene (BCYRN1) to chromosome 2p16 by radiation hybrid mapping. Cytogenet. Cell Genet. 82: 271-272, 1998. PubMed ID : 9858834 2. Lewejohann, L.; Skryabin, B. V.; Sachser, N.; Prehn, C.; Heiduschka, P.; Thanos, S.; Jordan, U.; Dell'Omo, G.; Vyssotski, A. L.; Pleskacheva, M. G.; Lipp, H.-P.; Tiedge, H.; Brosius, J.; Prior, H. : Role of a neuronal small non-messenger RNA: behavioural alterations in BC1 RNA-deleted mice. Behav. Brain Res. 154: 273-289, 2004. PubMed ID : 15302134 3. Lukiw, W. J.; Handley, P.; Wong, L.; McLachlan, D. R. C. : BC200 RNA in normal human neocortex, non-Alzheimer dementia (NAD), and senile dementia of the Alzheimer type (AD). Neurochem. Res. 17: 591-597, 1992. PubMed ID : 1603265 4. Martignetti, J. A.; Brosius, J. : BC200 RNA: a neural RNA polymerase III product encoded by a monomeric Alu element. Proc. Nat. Acad. Sci. 90: 11563-11567, 1993. PubMed ID : 8265590 5. Taylor, B. A.; Navin, A.; Skryabin, B. V.; Brosius, J. : Localization of the mouse gene (Bc1) encoding neural BC1 RNA near the fibroblast growth factor 3 locus (Fgf3) on distal chromosome 7. Genomics 44: 153-154, 1997. PubMed ID : 9286715 6. Tiedge, H.; Chen, W.; Brosius, J. : Primary structure, neural-specific expression, and dendritic location of human BC200 RNA. J. Neurosci. 13: 2382-2390, 1993. PubMed ID : 7684772 7. Tiedge, H.; Fremeau, R. T., Jr.; Weinstock, P. H.; Arancio, O.; Brosius, J. : Dendritic location of neural BC1 RNA. Proc. Nat. Acad. Sci. 88: 2093-2097, 1991. PubMed ID : 1706516 8. Zalfa, F.; Giorgi, M.; Primerano, B.; Moro, A.; Di Penta, A.; Reis, S.; Oostra, B.; Bagni, C. : The fragile X syndrome protein FMRP associates with BC1 RNA and regulates the translation of specific mRNAs at synapses. Cell 112: 317-327, 2003. PubMed ID : 12581522 ### CONTRIBUTORS Patricia A. Hartz - updated : 2/21/2005 Stylianos E. Antonarakis - updated : 4/15/2003 ### CREATION DATE Paul J. Converse : 7/9/2001 ### EDIT HISTORY mgross : 2/21/2005 mgross : 4/15/2003 mgross : 4/15/2003 mgross : 7/9/2001 mgross : 7/9/2001 Copyright © 1966-2005 Johns Hopkins University
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| FRAGILE X MENTAL RETARDATION, AUTOSOMAL HOMOLOG 2; FXR2
### TABLE OF CONTENTS #### DESCRIPTION CLONING GENE FUNCTION GENE STRUCTURE MAPPING ANIMAL MODEL SEE ALSO REFERENCES CONTRIBUTORS CREATION DATE EDIT HISTORY Gene map locus 17p13.1 ### TEXT #### DESCRIPTION Fragile X mental retardation is directly associated with the FMR1 gene at Xq27.3 (309550). FMR1 is an RNA-binding protein, and mutations in the gene are believed to result in the absence or reduced expression of the protein or a functionally impaired mutant protein. FMR1 protein and the fragile X-related proteins 1 and 2 (FXR1, 600819, and FXR2) form a family with functional similarities, such as RNA binding, polyribosomal association, and nucleocytoplasmic shuttling. #### CLONING Using a yeast 2-hybrid screen of a brain cDNA library with FMR1 as bait, followed by screening of a fetal brain library, Zhang et al. (1995) isolated a cDNA encoding FXR2. Sequence analysis predicted that the 673-amino acid protein, with high N-terminal homology to FMR1 and FXR1 and approximately 60% identity overall, contains 2 ribonucleoprotein K homology (KH) domains, which are involved in RNA binding. Northern blot analysis indicated that FXR2 is expressed as a 3.0-kb transcript in Hela cells and in mouse brain. Immunoblot analysis showed that FXR2 is expressed as a 95-kD protein, although the predicted molecular weight was 74 kD. Immunofluorescence microscopy revealed that FXR2, like FMR1 and FXR1, is expressed in the cytoplasm. Using immunohistochemistry, Tamanini et al. (1997) observed high expression of FMR1, FXR1, and FXR2 in adult cerebellar neurons, especially in Purkinje cell cytoplasm, and in cortical and brainstem neuron cytoplasm and proximal dendrites. In contrast, FMR1, but not FXR1 or FXR2, expression was absent in the brain of a fragile X patient. Examination of 18-week normal and fragile X fetal brains showed an expression pattern of the proteins in neurons that paralleled the adult pattern. In testis, FMR1 is expressed in spermatogonia cytoplasm; FXR1 is expressed in spermatogonia and also in cells inside the seminiferous tubules corresponding to maturing spermatogenic cells; and FXR2, at low intensity, is expressed throughout the seminiferous tubules. The expression pattern was unchanged in the testis of a fragile X patient. In fetal testis, FMR1 and FXR1 are expressed in all normal primordial germ cells, but FMR1 is present in only some fragile X germ cells. FXR2 is strongly expressed in interstitial cells of both fragile X and control testis. Kirkpatrick et al. (2001) identified several motifs that are shared between FXR1, FXR2, and FRM1, including a nuclear localization signal, a nuclear export signal, a KH domain, and an arginine/glycine-rich (RGG) box. In addition, FXR1 and FXR2 contain 2 unique nucleolar targeting sequences (NoSs). #### GENE FUNCTION Protein binding analysis by Zhang et al. (1995) demonstrated that full-length or N-terminal FXR2 binds to FMR1 or FXR1 and to itself. Each of these 3 proteins can form heteromers with the others, and each can also form homomers. Immunoprecipitation analysis established that FMR1 and FXR2 also form complexes in HeLa cells. Tamanini et al. (1999) found that FMR1 and FXR1 proteins shuttle between cytoplasm and nucleoplasm, while FXR2 protein shuttles between cytoplasm and nucleolus. In additional studies, Tamanini et al. (2000) showed that FXR2 protein contains in its C-terminal part a stretch of basic amino acids 'RPQRRNRSRRRRFR' that resembles the NoS of the viral protein Rev. This particular sequence is also present within exon 15 of the FXR1 gene, which undergoes alternative splicing. Cells which were transfected with constructs of FXR1 protein and FXR2 protein isoforms with the potential NoS and also treated with the nuclear export inhibitor leptomycin B showed a nucleolar localization; expressed constructs lacking the NoS showed signal in the nucleoplasm outside the nucleoli. The authors hypothesized that the intranuclear distribution of FXR2 protein and FXR1 protein isoforms is likely to be mediated by a similar NoS localized in their C-terminal regions. This domain is absent in some FXR1 protein isoforms as well as in all FMR1 protein isoforms, suggesting functional differences for this family of proteins, possibly related to RNA metabolism in different tissues. #### GENE STRUCTURE Kirkpatrick et al. (2001) determined that the FXR2 gene contains 17 exons and spans 14 to 38 kb. The 5-prime untranslated region of the FXR2 gene overlaps the CG-rich promoter region of the SHBG gene (182205) and is transcribed in the opposite orientation. #### MAPPING By PCR analysis of a hybrid cell line and by FISH, Zhang et al. (1995) mapped the FXR2 gene to chromosome 17p13.1. Kirkpatrick et al. (2001) mapped the mouse Fxr2 gene to chromosome 11. #### ANIMAL MODEL Bontekoe et al. (2002) generated an Fxr2 knockout mouse model. No pathologic differences between knockout and wildtype mice were found in brain or testis; however, their behaviors were distinctive. Fxr2 knockout mice were hyperactive (i.e., traveled a greater distance, spent more time moving, and moved faster) in the open-field test, were impaired on the rotarod test, had reduced levels of prepulse inhibition, displayed less contextual conditioned fear, were impaired at locating the hidden platform in the Morris water task, and were less sensitive to a heat stimulus. The authors implicated a role for Fxr2 in central nervous system function. ### SEE ALSO Siomi et al. (1996) ### REFERENCES 1. Bontekoe, C. J. M.; McIlwain, K. L.; Nieuwenhuizen, I. M.; Yuva-Paylor, L. A.; Nellis, A.; Willemsen, R.; Fang, Z.; Kirkpatrick, L.; Bakker, C. E.; McAninch, R.; Cheng, N. C.; Merriweather, M.; Hoogeveen, A. T.; Nelson, D.; Paylor, R.; Oostra, B. A. : Knockout mouse model for Fxr2: a model for mental retardation. Hum. Molec. Genet. 11: 487-498, 2002. PubMed ID : 11875043 2. Kirkpatrick, L. L.; McIlwain, K. A.; Nelson, D. L. : Comparative genomic sequence analysis of the FXR gene family: FMR1, FXR1, and FXR2. Genomics 78: 169-177, 2001. PubMed ID : 11735223 3. Siomi, M. C.; Zhang, Y.; Siomi, H.; Dreyfuss, G. : Specific sequences in the fragile X syndrome protein FMR1 and the FXR proteins mediate their binding to 60S ribosomal subunits and the interactions among them. Molec. Cell. Biol. 16: 3825-3832, 1996. PubMed ID : 8668200 4. Tamanini, F.; Bontekoe, C.; Bakker, C. E.; van Unen, L.; Anar, B.; Willemsen, R.; Yoshida, M.; Galjaard, H.; Oostra, B. A.; Hoogeveen, A. T. : Different targets for the fragile X-related proteins revealed by their distinct nuclear localizations. Hum. Molec. Genet. 8: 863-869, 1999. PubMed ID : 10196376 5. Tamanini, F.; Kirkpatrick, L. L.; Schonkeren, J.; van Unen, L.; Bontekoe, C.; Bakker, C.; Nelson, D. L.; Galjaard, H.; Oostra, B. A.; Hoogeveen, A. T. : The fragile X-related proteins FXR1P and FXR2P contain a functional nucleolar-targeting signal equivalent to the HIV-1 regulatory proteins. Hum. Molec. Genet. 9: 1487-1493, 2000. PubMed ID : 10888599 6. Tamanini, F.; Willemsen, R.; van Unen, L.; Bontekoe, C.; Galjaard, H.; Oostra, B. A.; Hoogeveen, A. T. : Differential expression of FMR1, FXR1 and FXR2 proteins in human brain and testis. Hum. Molec. Genet. 6: 1315-1322, 1997. PubMed ID : 9259278 7. Zhang, Y.; O'Connor, J. P.; Siomi, M. C.; Srinivasan, S.; Dutra, A.; Nussbaum, R. L.; Dreyfuss, G. : The fragile X mental retardation syndrome protein interacts with novel homologs FXR1 and FXR2. EMBO J. 14: 5358-5366, 1995. PubMed ID : 7489725 ### CONTRIBUTORS Patricia A. Hartz - updated : 11/11/2002 George E. Tiller - updated : 10/2/2002 ### CREATION DATE George E. Tiller : 10/16/2000 ### EDIT HISTORY terry : 3/3/2005 tkritzer : 2/26/2003 mgross : 11/11/2002 mgross : 11/11/2002 cwells : 10/2/2002 terry : 12/11/2000 alopez : 10/24/2000 alopez : 10/16/2000 alopez : 10/16/2000 alopez : 10/16/2000 Copyright © 1966-2005 Johns Hopkins University
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| NUCLEAR FRAGILE X MENTAL RETARDATION PROTEIN-INTERACTING PROTEIN 1; NUFIP1
#### Alternative titles; symbols NUCLEAR FMRP-INTERACTING PROTEIN; NUFIP ### TABLE OF CONTENTS #### TEXT REFERENCES CONTRIBUTORS CREATION DATE EDIT HISTORY Gene map locus 13q14 ### TEXT Silenced expression of the FMR1 gene (309550) is responsible for fragile X syndrome. The FMR1 gene encodes an RNA-binding protein (FMRP) that can shuttle between the nucleus and the cytoplasm and is found associated with polysomes in the cytoplasm. Using a yeast 2-hybrid assay, Bardoni et al. (1999) identified a novel protein interacting with FMRP, and they designated the protein NUFIP (nuclear FMRP-interacting protein). NUFIP mRNA expression was found to be strikingly similar to that of the FMR1 gene in neurons of cortex, hippocampus, and cerebellum. At the subcellular level, NUFIP colocalized with nuclear isoforms of FMRP in a dot-like pattern. NUFIP contains a C2H2 zinc finger motif and a nuclear localization signal. In vitro, NUFIP showed RNA-binding activity. NUFIP did not interact with the FMRP homologs encoded by the FXR1 (600819) and FXR2 (605339) genes. These results indicated a specific nuclear role for FMRP. By somatic cell hybrid analysis and fluorescence in situ hybridization, Bardoni et al. (2000) mapped the NUFIP1 gene to chromosome 13q14 and an NUFIP1 pseudogene to chromosome 6q12. ### REFERENCES 1. Bardoni, B.; Giglio, S.; Schenck, A.; Rocchi, M.; Mandel, J. L. : Assignment of NUFIP1 (nuclear FMRP interacting protein 1) gene to chromosome 13q14 and assignment of a pseudogene to chromosome 6q12. Cytogenet. Cell Genet. 89: 11-13, 2000. PubMed ID : 10894927 2. Bardoni, B.; Schenck, A.; Mandel, J. L. : A novel RNA-binding nuclear protein that interacts with the fragile X mental retardation (FMR1) protein. Hum. Molec. Genet. 8: 2557-2566, 1999. PubMed ID : 10556305 ### CONTRIBUTORS Carol A. Bocchini - updated : 1/8/2001 ### CREATION DATE Victor A. McKusick : 12/21/1999 ### EDIT HISTORY cwells : 1/9/2001 carol : 1/8/2001 mgross : 12/21/1999 Copyright © 1966-2005 Johns Hopkins University
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| CHUDLEY-MCCULLOUGH SYNDROME
#### Alternative titles; symbols DEAFNESS, SENSORINEURAL, WITH PARTIAL AGENESIS OF THE CORPUS CALLOSUM AND ARACHNOID CYSTS DEAFNESS, BILATERAL SENSORINEURAL, AND HYDROCEPHALUS DUE TO FORAMEN OF MONRO OBSTRUCTION ### TABLE OF CONTENTS #### TEXT REFERENCES CONTRIBUTORS CREATION DATE EDIT HISTORY ### TEXT Chudley et al. (1997) reported a Canadian Mennonite family in which a brother and sister had hydrocephalus due to obstruction at the foramen of Monro and profound bilateral sensorineural deafness. The parents were second cousins. Autosomal recessive inheritance was proposed on the basis of consanguinity, affected sibs of both sexes, and no evidence of intrauterine infections or other adverse perinatal events. Hendriks et al. (1999) reported 2 sisters with congenital sensorineural hearing loss, partial agenesis of the corpus callosum, arachnoid cysts, and hydrocephalus. Both girls had normal psychomotor development and absence of any distinctive physical features. The parents had normal hearing and no abnormalities on brain MRI. They were nonconsanguineous but from the same small isolated village. The authors suggested that this combination probably represents a new autosomal recessive condition; however, the overlap with disorder in the families reported by Chudley et al. (1997) suggests otherwise. Lemire and Stoeber (2000) presented 2 sisters of Mennonite descent with hydrocephalus and profound bilateral sensorineural deafness. The parents were nonconsanguineous. One sister had hydrocephalus due to obstruction of the foramen of Monro. This sister also had a full mutation in the FMR1 (309550) gene, presumed to be an incidental finding. The other sister had no evidence of a foramen of Monro obstruction but had other brain abnormalities, including callosal dysgenesis, gray matter heterotopia, cortical dysplasia, and cerebellar dysgenesis. The authors suggested the eponym Chudley-McCullough syndrome for this condition. They proposed that neuroimaging of the brain be considered in all individuals with profound sensorineural hearing loss, especially those of Mennonite background. Welch et al. (2003) described a family in which 2 brothers and a sister had Chudley-McCullough syndrome. Each had profound sensorineural deafness that was either congenital or rapidly progressive in infancy, together with asymmetric dilatation of the lateral ventricle secondary to obstruction of the foramen of Monro. Other brain abnormalities included arachnoid cyst, partial agenesis of the corpus callosum, and abnormalities in the migration of cerebellar cells. Welch et al. (2003) recommended an audiologic assessment of all children with hydrocephalus, especially those with obstruction of the foramen of Monro. ### REFERENCES 1. Chudley, A. E.; McCullough, C.; McCullough, D. W. : Bilateral sensorineural deafness and hydrocephalus due to foramen of Monro obstruction in sibs: a newly described autosomal recessive disorder. Am. J. Med. Genet. 68: 350-356, 1997. PubMed ID : 9024571 2. Hendriks, Y. M. C.; Laan, L. A. E. M.; Vielvoye, G. J.; van Haeringen, A. : Bilateral sensorineural deafness, partial agenesis of the corpus callosum, and arachnoid cysts in two sisters. Am. J. Med. Genet. 86: 183-186, 1999. PubMed ID : 10449658 3. Lemire, E. G.; Stoeber, G. P. : Chudley-McCullough syndrome: bilateral sensorineural deafness, hydrocephalus, and other structural brain abnormalities. Am. J. Med. Genet. 90: 127-130, 2000. PubMed ID : 10607951 4. Welch, K. O.; Tekin, M.; Nance, W. E.; Blanton, S. H.; Arnos, K. S.; Pandya, A. : Chudley-McCullough syndrome: expanded phenotype and review of the literature. Am. J. Med. Genet. 119A: 71-76, 2003. ### CONTRIBUTORS Victor A. McKusick - updated : 5/15/2003 Sonja A. Rasmussen - updated : 6/13/2000 ### CREATION DATE Sonja A. Rasmussen : 10/5/1999 ### EDIT HISTORY mgross : 3/17/2004 tkritzer : 5/20/2003 terry : 5/15/2003 carol : 6/13/2000 carol : 10/6/1999 carol : 10/5/1999 Copyright © 1966-2005 Johns Hopkins University
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| CGG-BINDING PROTEIN 1; CGGBP1
#### Alternative titles; symbols CGG-BINDING PROTEIN, 20-KD p20CGGBP ### TABLE OF CONTENTS #### DESCRIPTION CLONING GENE FUNCTION GENE STRUCTURE MAPPING REFERENCES CONTRIBUTORS CREATION DATE EDIT HISTORY Gene map locus 3p12-p11.1 ### TEXT #### DESCRIPTION CGGBP1 influences expression of the fragile X mental retardation gene, FMR1 (309550), by specifically interacting with the 5-prime (CGG)n-3-prime repeat in its 5-prime UTR. #### CLONING Autonomous expansions of trinucleotide repeats with the general structure (CGG)n are associated with several human genetic disorders. Expansion of the (CGG)n repeat in the 5-prime UTR of FMR1 is accompanied by extensive methylation of the CG dinucleotides in the repeat and is associated with transcriptional silencing of the FMR1 gene. Deissler et al. (1996) identified a 20-kD HeLa cell nuclear protein, p20-CGGBP (CGG-binding protein), that specifically bound the double-stranded CGG repeat. p20-CGGBP binding was severely inhibited by complete or partial methylation of the binding motif. By searching an EST database with the partial protein sequence of p20-CGGBP, Deissler et al. (1997) identified a cDNA containing the entire p20-CGGBP coding region. The predicted 166-amino acid protein contains a putative nuclear localization signal. Northern blot analysis revealed that p20-CGGBP is expressed as a 1.2-kb transcript in HeLa cells. Dot blot hybridization indicated that this mRNA is expressed in a number of human tissues. Using Southern blots, Deissler et al. (1997) found that the p20-CGGBP gene is conserved among mammals. Naumann et al. (2004) identified an exon 3 splice variant of CGGBP1 as well as several alternate polyadenylation signals. Northern blot analysis detected transcripts of 4.5- and 1.2-kb expressed in varying ratios in all adult and fetal tissues examined. Highest expression was in adult skeletal muscle, thymus, and pancreas. Mouse Cggbp1 was expressed in embryonic stem cells and throughout mouse embryonic development. #### GENE FUNCTION Naumann et al. (2004) determined that the promoter region of CGGBP1 is unmethylated in human cells, and in vitro methylation inactivated the promoter in a reporter assay. They found that CGGBP1 bound to 5-prime-(CGG)n-3-prime repeats in vitro with n equal to or greater than 5. It also bound interrupted repeats. #### GENE STRUCTURE Naumann et al. (2004) determined that the CGGBP gene contains 4 exons, with the entire open reading frame located within exon 4. The promoter region contains CAAT boxes and several Sp1 (189906)-binding sites. #### MAPPING By analysis of a somatic cell hybrid panel, Deissler et al. (1997) mapped the p20-CGGBP protein to human chromosome 3. Using FISH, Naumann et al. (2004) mapped the CGGBP gene near the centromere on chromosome 3p. ### REFERENCES 1. Deissler, H.; Behn-Krappa, A.; Doerfler, W. : Purification of nuclear proteins from human HeLa cells that bind specifically to the unstable tandem repeat (CGG)n in the human FMR1 gene. J. Biol. Chem. 271: 4327-4334, 1996. PubMed ID : 8626781 2. Deissler, H.; Wilm, M.; Genc, B.; Schmitz, B.; Ternes, T.; Naumann, F.; Mann, M.; Doerfler, W. : Rapid protein sequencing by tandem mass spectrometry and cDNA cloning of p20-CGGBP: a novel protein that binds to the unstable triplet repeat 5-prime-d(CGG)n-3-prime in the human FMR1 gene. J. Biol. Chem. 272: 16761-16768, 1997. PubMed ID : 9201980 3. Naumann, F.; Remus, R.; Schmitz, B.; Doerfler, W. : Gene structure and expression of the 5-prime-(CGG)n-3-prime-binding protein (CGGBP1). Genomics 83: 106-118, 2004. PubMed ID : 14667814 ### CONTRIBUTORS Patricia A. Hartz - updated : 2/6/2004 ### CREATION DATE Rebekah S. Rasooly : 12/16/1998 ### EDIT HISTORY mgross : 2/6/2004 mgross : 2/6/2004 alopez : 1/4/1999 alopez : 12/17/1998 Copyright © 1966-2005 Johns Hopkins University
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| POLY(rC)-BINDING PROTEIN 2; PCBP2
#### Alternative titles; symbols HETEROGENEOUS NUCLEAR RIBONUCLEOPROTEIN E2; HNRPE2 ### TABLE OF CONTENTS #### DESCRIPTION CLONING GENE FUNCTION MAPPING GENE STRUCTURE REFERENCES CONTRIBUTORS CREATION DATE EDIT HISTORY Gene map locus 12q13.12-q13.13 ### TEXT #### DESCRIPTION Heterogeneous nuclear riboprotein E2 is a poly(rC)-binding protein with translational regulatory functions (Ostareck-Lederer et al., 1998). #### CLONING Leffers et al. (1995) described the cloning and characterization of 2 cDNAs for poly(rC)-binding proteins, called PCBP1 (601209) and PCBP2 by them. The authors analyzed an EST database for sequences that were predicted to encode a protein with K-homologous (KH) domains. The 60- to 70-amino acid KH motifs are found in several putative nucleic acid binding proteins such as FMR1 (309550) and HNRNPK (600712) and are thought to be involved in RNA binding. Using primers from 1 EST the authors produced a probe that was used to screen a cDNA library of transformed human amnion cells. The cDNA they isolated for PCBP1 encodes a putative 356-amino acid protein that contains 3 KH domains. It is 83% identical to PCBP2 at the DNA level and 90% homologous at the amino acid level. The PCBP2 protein is about 99% similar to the mouse hnRNP-X/mCTBP protein (Hahm et al., 1993) and is a probable homolog. Chkheidze and Liebhaber (2003) determined that endogenous HeLa cell PCBP2 localized to the nucleus in a particulate and diffuse staining pattern that differed from the speckled pattern observed with PCBP1. They identified 2 nuclear localization signals within PCBP2, within a 9-amino acid segment between KH2 and KH3, and within a 12-amino acid segment of KH3. Mutation analysis revealed that both signals were required for nuclear localization. A splice variant of PCBP2 that contains a 31-amino acid segment between KH2 and KH3 showed both nuclear and cytoplasmic distribution. #### GENE FUNCTION When expressed with a vaccinia virus system in transformed amnion cells, Leffers et al. (1995) found that both PCBP1 and PCBP2 bound poly(rC) when not phosphorylated; phosphorylated protein bound with much lower affinity. Transcripts of both PCBPs were detected in all the human tissues analyzed. Studying the arrest of differentiation, which is a feature of chronic myelogenous leukemia cells with the fusion BCR-ABL gene (151410), Perrotti et al. (2002) found that BCR-ABL regulates the expression of C/EBP-alpha (CEBPA; 116897), the principal regulator of granulocytic differentiation, inducing HNRNPE2, which inhibits the translation of CEBPA mRNA. #### MAPPING Tommerup and Leffers (1996) mapped PCBP2 distal to FRA12A (136630) at 12q13.12-q13.13 by fluorescence in situ hybridization. Makeyev and Liebhaber (2000) identified 2 processed PCBP2 pseudogenes that mapped to chromosome 21q22.3 and chromosome 8q21-q22. #### GENE STRUCTURE Makeyev and Liebhaber (2000) determined that the human and mouse PCBP2 genes contain 15 exons and span more than 19 kb. ### REFERENCES 1. Chkheidze, A. N.; Liebhaber, S. A. : A novel set of nuclear localization signals determine distributions of the alpha-CP RNA-binding proteins. Molec. Cell. Biol. 23: 8405-8415, 2003. PubMed ID : 14612387 2. Hahm, K.; Kim, G.; Turck, C.; Smale, S. T. : Isolation of a murine gene encoding a nucleic acid-binding protein with homology to hnRNP K. Nucleic Acids Res. 21: 21-26, 1993. PubMed ID : 8441616 3. Leffers, H.; Dejgaard, K.; Celis, J. E. : Characterisation of two major cellular poly(rC)-binding human proteins, each containing three K-homologous (KH) domains. Europ. J. Biochem. 230: 447-453, 1995. PubMed ID : 7607214 4. Makeyev, A. V.; Liebhaber, S. A. : Identification of two novel mammalian genes establishes a subfamily of KH-domain RNA-binding proteins. Genomics 67: 301-316, 2000. PubMed ID : 10936052 5. Ostareck-Lederer, A.; Ostareck, D. H.; Hentze, M. W. : Cytoplasmic regulatory functions of the KH-domain proteins hnRNPs K and E1/E2. Trends Biochem. Sci. 23: 409-411, 1998. PubMed ID : 9852755 6. Perrotti, D.; Cesi, V.; Trotta, R.; Guerzoni, C.; Santilli, G.; Campbell, K.; Iervolino, A.; Condorelli, F.; Gambacorti-Passerini, C.; Caligiuri, M. A.; Calabretta, B. : BCR-ABL suppresses C/EBP-alpha expression through inhibitory action of hnRNP E2. Nature Genet. 30: 48-58, 2002. PubMed ID : 11753385 7. Tommerup, N.; Leffers, H. : Assignment of human KH-box-containing genes by in situ hybridization: HNRNPK maps to 9q21.32-q21.33, PCBP1 to 2p12-p13, and PCBP2 to 12q13.12-q13.13, distal to FRA12A. Genomics 32: 297-298, 1996. PubMed ID : 8833161 ### CONTRIBUTORS Patricia A. Hartz - updated : 2/11/2004 Victor A. McKusick - updated : 1/14/2002 ### CREATION DATE Alan F. Scott : 4/17/1996 ### EDIT HISTORY cwells : 3/2/2004 terry : 2/11/2004 terry : 3/6/2002 alopez : 1/14/2002 mark : 6/7/1996 terry : 5/2/1996 mark : 4/17/1996 terry : 4/17/1996 mark : 4/17/1996 Copyright © 1966-2005 Johns Hopkins University
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