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)

Human genital skin fibroblasts (GSF) make a relatively abundant 56/58 kDa protein that binds androgens. The protein shares many properties with the approximately 100 kDa androgen receptor that is encoded by a locus in the q12 region of the X chromosome. It does not appear to be androgen-induced, yet is absent in GSF of most patients with complete androgen insensitivity (CAI). A precursor-product relation with the androgen receptor (AR) protein has been largely excluded; that it may be an unorthodox product of the AR gene has not. The 56/58 kDa protein is made by the GSF of a mentally retarded subject who has CAI because of a complete deletion of the coding portion of the AR gene. Hence, the strong constitutional and statistical correlations that have been demonstrated between the two proteins cannot arise because they share the same gene. The subject's genomic DNA hybridizes normally with 11 single-copy probes from Xq11-Xq13. Therefore, we cannot attribute her mental retardation to a contiguous gene syndrome.
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PMID:The 56/58 kDa androgen-binding protein in male genital skin fibroblasts with a deleted androgen receptor gene. 205 Feb 65

We evaluated testicular function in 15 men with the Martin-Bell (fragile-X) mental retardation syndrome. Macro-orchidism was present in all subjects. Their mean serum LH and FSH levels and plasma testosterone and dihydrotestosterone levels were normal. The mean plasma levels of androstenedione, 17-hydroxyprogesterone, and progesterone were slightly elevated above the normal range, whereas the plasma levels of dehydroepiandrosterone and dehydroepiandrosterone-sulfate were normal. The response in the levels of plasma testosterone following a 5 day period of hCG stimulation was normal in 8 subjects and there was no abnormal accumulation of androgen precursors. The level of 5 alpha-reductase activity and androgen receptor binding was normal in genital skin fibroblasts derived from 3 of these patients. The response of gonadotropin secretion to GnRH stimulation was normal in the 8 men who were tested. Therefore, our data are consistent with the hypothesis that testicular enlargement in men with the Martin-Bell syndrome is not mediated by hormonal factors.
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PMID:Gonadal function in men with the Martin-Bell (fragile-X) syndrome. 308 5

A young girl with a clinically moderate form of myotubular myopathy was found to carry a cytogenetically detectable deletion in Xq27-q28. The deletion had occurred de novo on the paternal X chromosome. It encompasses the fragile X (FRAXA) and Hunter syndrome (IDS) loci, and the DXS304 and DXS455 markers, in Xq27.3 and proximal Xq28. Other loci from the proximal half of Xq28 (DXS49, DXS256, DXS258, DXS305, and DXS497) were found intact. As the X-linked myotubular myopathy locus (MTM1) was previously mapped to Xq28 by linkage analysis, the present observation suggested that MTM1 is included in the deletion. However, a significant clinical phenotype is unexpected in a female MTM1 carrier. Analysis of inactive X-specific methylation at the androgen receptor gene showed that the deleted X chromosome was active in approximately 80% of leukocytes. Such unbalanced inactivation may account for the moderate MTM1 phenotype and for the mental retardation that later developed in the patient. This observation is discussed in relation to the hypothesis that a locus modulating X inactivation may lie in the region. Comparison of this deletion with that carried by a male patient with a severe Hunter syndrome phenotype but no myotubular myopathy, in light of recent linkage data on recombinant MTM1 families, led to a considerable refinement of the position of the MTM1 locus, to a region of approximately 600 kb, between DXS304 and DXS497.
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PMID:Myotubular myopathy in a girl with a deletion at Xq27-q28 and unbalanced X inactivation assigns the MTM1 gene to a 600-kb region. 772 66

Extensive linkage analyses in three families with non-specific X-linked mental retardation (MRX) have localized the gene in each family to the pericentromeric region of the chromosome. The MRX17 gene is localized with a peak lod of 2.41 (theta = 0.0) with the trinucleotide repeat polymorphism at the androgen receptor (AR) gene locus. This gene lies in the interval between the markers DXS255 and DXS990, as defined by recombinants. The MRX18 gene maps to the interval between the markers DXS538 and DXS1126, with a peak lod score of 2.01 (theta = 0.0) at the PFC gene locus. In the third family (Family E) with insufficient informative meioses for assignment of an MRX acronym, the maximum lod score is 1.8 at a recombination fraction of zero for several marker loci between DXS207 and DXS426. Exclusions from the regions of marker loci spanning Xq support the localization of the MRX gene in Family E to the pericentromeric region. Localizations of these and other MRX genes have determined that MRX2 and MRX19 map to distal Xp, MRX3, and MRX6 map to distal Xq, whilst the majority cluster in the pericentromeric region. In addition, we confirm that there are at least two distinct MRX genes near the centromere as delineated by the non-overlapping regional localizations of MRX17 and MRX18. Determination of these non-overlapping localizations is currently the only means of classifying non-syndromal forms of mental retardation and determining the minimum number of MRX loci.
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PMID:Pericentromeric genes for non-specific X-linked mental retardation (MRX). 794 39

We present data to suggest the existence of a mental retardation (MR) locus at Xq11.2-q12 between DXS1 and DXS905, identified in two subjects with complete androgen insensitivity syndrome (CAIS) and MR. Androgen insensitivity syndrome is a disorder of male sexual differentiation caused by a defect in the androgen receptor (AR) gene (Xq11-q12). Two subjects with CAIS resulting from a complete deletion of the AR gene have previously been reported, one of whom also has MR. We have identified another mentally retarded person with a complete deletion of the AR gene. The deletion in the two patients with CAIS and MR extends past the AR gene and includes several marker loci both proximal and distal to the AR gene, the limits of the deletions being DXS1 and DXS905. The deletions in the CAIS patients who do not have MR do not include any of the markers outside the AR gene itself. These data suggest that located close to the AR gene is a gene which is implicated in non-specific MR.
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PMID:Androgen insensitivity with mental retardation: a contiguous gene syndrome? 903 95

The rat androgen-binding protein/sex hormone-binding globulin (ABP/SHBG) gene is regulated by promoters P1 and PA. P1 regulates the mRNA encoding secreted ABP/SHBG, whereas PA regulates an alternate mRNA which encodes a modified protein that is targeted to the nucleus. Promoter PA is GC rich, consisting of 70-80% GC residues. During routine BLAST sequence analysis it was discovered that this GC-rich region is highly related to the human fragile X-related protein 2 (FXR-2) 5'-untranslated RNA sequence. Furthermore, the nucleotide coding sequence of the initial 14 FXR-2 amino acid residues was identical in the ABP/SHBG gene. The 5'-untranslated FXR-2 sequence contains triplet (CGG) repeats, which are also present in the rat ABP/SHBG gene. The meiotic instability of CGG repeats in the human fragile X (FMR1) gene causes the fragile X mental retardation syndrome. The data presented here suggest that the ABP/SHBG and FXR-2 genes overlap with each gene transcribed in the opposite direction. In support of this structure, the human ABP/SHBG and the FXR-2 genes map to the same site on chromosome 17. Thus, the ABP/SHBG gene contains triplet repeats in the alternate promoter PA. It will be of particular interest to determine if triplet instability affects ABP/SHBG gene expression. A triplet instability in the X-linked androgen receptor gene causes spinal and bulbar muscular atrophy.
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PMID:The rat androgen-binding protein (ABP/SHBG) gene contains triplet repeats similar to unstable triplets: evidence that the ABP/SHBG and the fragile X-related 2 genes overlap. 943 88

We describe two female patients mosaic for a cell line with an extra marker X chromosome in addition to a normal 46,XX cell line. To our knowledge, these cases are the first reports of females who had a cell line with a supernumerary marker X chromosome in addition to a normal cell line. They also had strikingly similar manifestations, including small hands and feet, minor facial anomalies, obesity, and mental retardation. The DNA content of the mar(X) chromosomes was investigated by fluorescent in situ hybridization using pericentromeric probes. The XIST gene, which is necessary for initiation of X-inactivation, was deleted from both marker chromosomes, suggesting that these chromosomes were not subject to inactivation. The short arm breakpoints of the mar(X)s were between the DNA markers DXS423E on Xp11.21 and UBE1 on Xp11.23. In Patient 1, mar(X) contained the androgen receptor gene and the DNA marker DXS1, both mapping to Xq11.2, whereas in Patient 2 the chromosome breakpoint was proximal to these markers. We suggest that the similar phenotypes of these patients may be due to the overexpression of genes in the common pericentromeric region of the X chromosome.
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PMID:Characterization of a supernumerary small marker X chromosome in two females with similar phenotypes. 984 58

X inactivation is the process by which mammalian females achieve dosage compensation by transcriptionally silencing one X chromosome. In chromosomally normal females, this process is random. However, most females with one abnormal X chromosome demonstrate complete skewing of X inactivation, presumably as the result of cell selection. We present a mentally retarded girl with a 46,X,t(X;9)(q28;q12) karyotype. Analysis of this patient's lymphocytes, using late replication banding and methylation assays for the androgen receptor (AR) and fragile X mental retardation (FMR1) genes, did not show the predicted nonrandom X inactivation pattern. Thus, this patient is functionally disomic for Xq28-qter in a proportion of her cells, most likely resulting in her abnormal phenotype. This case demonstrates the utility of correlating X inactivation patterns with phenotype in females with one structurally abnormal X chromosome, and suggests that both cytogenetic and molecular X inactivation studies should be included in the routine study of these individuals.
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PMID:Random X inactivation in a girl with a balanced t(X;9) and an abnormal phenotype. 963 70

We analysed parental origin and X inactivation status of X derived marker (mar(X)) or ring X (r(X)) chromosomes in six Turner syndrome patients. Two of these patients had mental retardation of unknown cause in addition to the usual Turner syndrome phenotype. By FISH analysis, the mar(X)/r(X) chromosomes of all patients retained the X centromere and the XIST locus at Xq13.2. By polymorphic marker analysis, both patients with mental retardation were shown to have uniparental X disomy while the others had both a maternal and paternal contribution of X chromosomes. By RT-PCR analysis and the androgen receptor assay, it was shown that in one of these mentally retarded patients, the XIST on the mar(X) was not transcribed and consequently the mar(X) was not inactivated, leading to functional disomy X. In the other patient, the XIST was transcribed but the r(X) appeared to be active by the androgen receptor assay. Our results suggest that uniparental disomy X may not be uncommon in mentally retarded patients with Turner syndrome. Functional disomy X seems to be the cause of mental retardation in these patients, although the underlying molecular basis could be diverse. In addition, even without unusual dysmorphic features, Turner syndrome patients with unexplained mental retardation need to be investigated for possible mosaicism including these mar(X)/r(X) chromosomes.
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PMID:Uniparental and functional X disomy in Turner syndrome patients with unexplained mental retardation and X derived marker chromosomes. 967 97

We report on three brothers with mental retardation and a contracted CAG repeat in the androgen receptor (AR) gene. It is known that expansion of the CAG repeat in this gene leads to spinal and bulbar muscular atrophy (SBMA or Kennedy disease); however, contracted repeats have not yet been implicated in disease. As the range of the length of CAG repeats in the AR gene, like those of other genes associated with dynamic mutations, follows a normal distribution, the theoretical possibility of disease at both ends of the distribution should be considered.
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PMID:CAG repeat contraction in the androgen receptor gene in three brothers with mental retardation. 1039 29


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