Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0025362 (mental retardation)
 15,878 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The fragile X mental retardation gene (FMR1) contains a CGG repeat sequence in its 5' untranslated region that can become unstable and expand in length from generation to generation. Alleles with expanded repeats in the range of approximately 55-199, termed premutation alleles, are associated with an increased risk for fragile-X-associated primary ovarian insufficiency (FXPOI). However, not all women who carry the premutation develop FXPOI. To determine if additional genes could explain variability in onset and severity, we used a random-effects Cox proportional hazards model to analyze age at menopause on 680 women from 225 families who have a history of fragile X syndrome and 321 women from 219 families from the general population. We tested for the presence of a residual additive genetic effect after adjustment for FMR1 repeat length, race, smoking, body mass index, and method of ascertainment. Results showed significant familial aggregation of age at menopause with an estimated additive genetic variance of 0.55-0.96 depending on the parameterization of FMR1 repeat size and definition of age at menopause (P-values ranging between 0.0002 and 0.0027). This is the first study to analyze familial aggregation of FXPOI. This result is important for proper counseling of women who carry FMR1 premutation alleles and for guidance of future studies to identify additional genes that influence ovarian insufficiency.
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PMID:Fragile X-associated primary ovarian insufficiency: evidence for additional genetic contributions to severity. 1835 16

The fragile X mental retardation 1 (FMR1) gene, located on the X chromosome, is characterized by a dynamic CGG repeat expansion in the 5' untranslated region. It has long been known that female carriers of the FMR1 premutation allele (55-199 CGG) are at risk for passing the FMR1 full mutation (> or =200 repeats) to their offspring, which results in a common form of mental retardation known as fragile X syndrome. The FMR1 premutation allele, however, also places female carriers at significantly increased risk for prematurely diminished ovarian function, which we refer to as fragile X-associated primary ovarian insufficiency (FXPOI). Although of particular concern for younger women, to date, studies of FXPOI have been restricted to women > or =18 years of age and have not specifically addressed ovarian reserve and menstrual cycle characteristics among adolescent carriers. We discuss the expected reproductive phenotype among FMR1 premutation carriers during adolescence, the associated health considerations based on our current understanding of FXPOI, and the directions for future studies.
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PMID:Reproductive health of adolescent girls who carry the FMR1 premutation: expected phenotype based on current knowledge of fragile x-associated primary ovarian insufficiency. 1857 14

A ring X chromosome is found in about 6% of patients with Turner syndrome (TS), often with mosaicism for a 45,X cell line. Patients with this karyotype are reported to have a higher incidence of a more severe phenotype including mental retardation. In fact, some studies have shown a correlation between this severity and the presence or absence of an intact and functional X inactivation center (XIST). However, the phenotype of the individuals with r(X) cannot be entirely defined in terms of their X-inactivation patterns. Nevertheless, a small group of these patients have been described to manifest clinical features reminiscent of the Kabuki syndrome. Here we present a female patient with clinical features resembling Kabuki syndrome and a mos 45,X/46,X,r(X) karyotype. Methylation analyses of polymorphic alleles of the androgen receptor gene showed that both alleles were unmethylated suggesting an active ring chromosome. A specific X chromosome array CGH was performed estimating the size of the ring to be 17 Mb, lacking the XIST gene, and including some genes with possible implications in the phenotype of the patient.
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PMID:A small and active ring X chromosome in a female with features of Kabuki syndrome. 1892 62

The 5' untranslated region of the fragile X mental retardation gene, FMR1, contains a polymorphic CGG repeat. Expansions of this repeat are associated with a spectrum of disorders. Full mutation alleles, repeats >or= 200, are associated with fragile X syndrome. Premutation alleles, repeats of approximately 55-199, are associated with a tremor-ataxia syndrome most commonly in older males and primary ovarian insufficiency in females. However, the neuropsychological impact of carrying a premutation allele is presently unclear in younger adults. In this study, we analyzed neuropsychological scores for 138 males and 506 females ascertained from the general population and from families with a history of fragile X syndrome. Subjects were age 18-50 years and had varying repeat lengths. Neuropsychological scores were obtained from measures of general intelligence, memory, and executive functioning, including attention. Principal component analysis followed by varimax rotation was used to create independent factors for analysis. These factors were modeled for males and females separately via a general linear model that accounted for correlation among related subjects. All models were adjusted for potential confounders, including age at testing, ethnicity, and household income. Among males, no repeat length associations were detected for any factor. Among females, only a significant association with repeat length and self-report attention (p < 0.01) was detected, with premutation carriers self-reporting significantly more attention-related problems compared to noncarriers. No significant interactions between repeat length and age were detected. Overall, these results indicate the lack of a global neuropsychological impact of carrying a premutation allele among adults under the age of 50.
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PMID:No evidence for a difference in neuropsychological profile among carriers and noncarriers of the FMR1 premutation in adults under the age of 50. 1902 94

The CGG-repeat present in the 5'UTR of the FMR1 gene is unstable upon transmission to the next generation. The repeat is up to 55 CGGs long in the normal population. In fragile X patients, a repeat length exceeding 200 CGGs (full mutation: FM) generally leads to methylation of the repeat and the promoter region, which is accompanied by silencing of the FMR1 gene. The gene product FMRP is involved in regulation of transport and translation of certain mRNA in the dendrite, thereby affecting synaptic plasticity. This is central to learning and memory processes. The absence of FMRP seen in FM is the cause of the mental retardation seen in fragile X patients. The premutation (PM) is defined as 55-200 CGGs. Female PM carriers are at risk of developing primary ovarian insufficiency. Recently it was discovered that elderly PM carriers might develop a progressive neurodegenerative disorder called fragile X-associated tremor/ataxia syndrome. Although arising from the mutations in the same gene, distinct mechanisms lead to fragile X syndrome (absence of FMRP) and FXTAS (toxic RNA gain of function). The pathogenic mechanisms thought to underlie these disorders are discussed, with a specific emphasis on FXTAS. This review gives insight on the implications of all possible repeat length categories seen in fragile X families.
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PMID:The FMR1 gene and fragile X-associated tremor/ataxia syndrome. 1910 4

Turner syndrome is a common disorder with a prevalence of 1:2,500 live female births. Although not associated with mental retardation, there is an increased risk of learning difficulties in this population. In particular, mathematical learning difficulties among girls with Turner syndrome are prevalent, significant, and persistent. As such, the study of mathematical performance in girls with Turner syndrome presents opportunities to advance our knowledge of mathematics ability, disability, and disability subtypes. Moreover, the Turner syndrome phenotype illustrates the challenges faced when defining mathematical learning disability (MLD) and characterizing MLD subtypes because the cognitive phenotype is aligned with several proposed MLD subtypes. There is some evidence linking MLD in Turner syndrome with spatial deficits, with executive dysfunction, and with deficient numerosity skills. Yet there is also conflicting evidence as to whether any of these explanations underlies MLD in Turner syndrome. Most mathematical difficulties in girls with Turner syndrome, as a group, occur on timed tests or on complex problems. On untimed tests, achievement test scores may be age appropriate. Therefore, the inclusion of MLD in the Turner syndrome cognitive phenotype reminds us that we cannot rule out MLD solely on the basis of performance on an untimed calculations subtest, and it poses a challenge to the widespread practice in which many researchers engage, that is, defining MLD on the basis of broad mathematics achievement test outcomes.
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PMID:Mathematical learning disability in girls with Turner syndrome: a challenge to defining MLD and its subtypes. 1921 15

The fragile X mutation is an expansion of a CGG triplet repeat in the 5' untranslated region of the FMR1 gene. Expansion to >200 repeats (the "full mutation") silences FMR1 transcription and leads to the fragile X mental retardation syndrome in males and in some females. It also affects the structure of the mitotic chromosome as evidenced by a folate sensitive fragile site. Isolated cases of 45,X/46,XX (mosaic Turner syndrome) in full mutation females have been reported but an increased prevalence was not apparent from these reports. PCR and Southern analysis of the CGG repeat in 423 prenatal female samples identified 106 full mutation cases. Surprisingly five of these had 45,X/4,6XX mosaicism while none of the other 317 female fetuses did. In two of the five cases >or=50% of the cells were reported to be 45,X and in the other three, <or=14%. We investigated the association of the full mutation and mosaic Turner syndrome using polymorphisms and single cell cloning to identify the X chromosome that was lost. Our analysis indicates that at least four of the five full mutation mosaicism cases were due to loss of the maternal, full mutation chromosome. These data indicate that 45,X/46,XX mosaicism is much more common than expected in fragile X full mutation females. Moreover, they suggest that the presence of the fragile X full mutation on a chromosome may predispose it to loss during mitosis, possibly due to the altered structure of the metaphase fragile X chromosome.
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PMID:Fragile X prenatal analyses show full mutation females at high risk for mosaic Turner syndrome: fragile X leads to chromosome loss. 2058 58

Women with fragile X mental retardation (FMR1) gene premutations (55-200 CGG repeats) were until recently believed to be unaffected. It is now known that up to 8% of older female FMR1 premutation carriers develop fragile X-associated tremor/ataxia syndrome (FXTAS). Female carriers may also develop primary ovarian insufficiency, thyroid disease, hypertension, seizures, peripheral neuropathy, and fibromyalgia. We present a 60-year-old woman with FMR1 premutation who had depression, anxiety, and conversion disorder with seizures. The FMR1 premutation with its associated mRNA toxicity is postulated as an underlying neurobiological mechanism of conversion symptoms, through functional and structural neural dysconnectivity.
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PMID:Conversion disorder in women with the FMR1 premutation. 1984 97

Following the discovery of two disorders associated with premutation alleles of the fragile X mental retardation gene (FMR1), primary ovarian insufficiency [fragile X-associated primary ovarian insufficiency (FXPOI)] and a tremor/ataxia syndrome [fragile X-associated tremor/ataxia disorder (FXTAS)], numerous studies have examined other potential co-morbid conditions, including neuropsychological deficits. Here, the frequency of self-reported diagnoses obtained through medical history interviews from FMR1 premutation carriers and non-carriers aged 18-50 were analyzed. Study subjects included 537 women, 334 of whom carry the premutation and 151 men, 37 of whom carry the premutation. Men with the premutation did not report any medical conditions at higher rates compared with non-carriers, controlling for age, ethnicity/race, and household income. Women with the premutation reported mental health disorders [i.e. attention deficit hyperactivity disorder (ADHD), anxiety, depression] significantly more often than non-carriers. However, after adjusting for covariates, these increased rates were not statistically significant. Additional follow-up analyses examined the consequence of ovarian dysfunction as a cause of co-occurring conditions. Women with an indication of ovarian insufficiency (i.e. irregular cycles) reported higher rates of thyroid problems and depression/anxiety. Because only women, not men, reported these conditions more often, the relationship between FXPOI and hormone irregularities in women should be explored for a potential link with the increase in the reported medical conditions.
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PMID:Co-occurring diagnoses among FMR1 premutation allele carriers. 2005 84

Abnormalities of sex chromosomes are associated with various forms of neuropsychiatric disorders, such as schizophrenia. Turner syndrome occurs approximately threefold more frequently in female schizophrenics compared to the general female population. A single case is reported. We report on a case of a 41-year-old woman with Turner syndrome, schizophrenia, mental retardation, and hypothyroidism. A polymorphism of the HOPA gene within Xq13 termed HOPA(12bp) is associated with schizophrenia, mental retardation, and hypothyroidism. Interestingly, Xq13 is the X-chromosome region that contains the X-inactivation center and a gene escaping X-inactivation whose gene product may be involved in the X-inactivation process as well as in the pathogenesis of sex chromosome anomalies such as Turner syndrome. These genes that escape X-inactivation may produce their gene products in excess, influencing normal brain growth and differentiation. Our case gives a further hint for an involvement of the X-chromosome in the pathogenesis of schizophrenia.
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PMID:Turner syndrome and schizophrenia: a further hint for the role of the X-chromosome in the pathogenesis of schizophrenic disorders. 2021 87


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