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Query: UMLS:C0025362 (mental retardation)
 15,878 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We report on a mother and child with a paracentric inversion of the long arm of chromosome 18: 46,XX,inv(18)(q21.1q23). The child had findings in common with those seen in 18q- syndrome including: microcephaly, epicanthal folds, midface hypoplasia, and abnormally modeled ears, dermatoglyphic whorls on fingertips, clubfeet, hearing loss, and developmental delay. The mother and several maternal relatives had mild mental retardation and hearing loss. Magnetic resonance imaging of the child's brain showed abnormal myelination. Molecular studies including PCR-based markers for the MBP locus and fluorescent in situ hybridization with a P1 genomic clone on mother and child demonstrated only one copy of the MBP locus (18q23) with the deletion extending beyond the MBP locus. Therefore, the deletion in the MBP region may account for the abnormal myelination seen in the patient. The other clinical findings, including mental retardation and hearing loss in this family, may reflect disruption of distal or proximal genes within the deleted MBP region or at the more proximal breakpoint 18q21.1, and may represent a contiguous gene syndrome. Further study of this family may help define those genes functioning in the MBP region that contribute to the phenotype of 18q- syndrome.
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PMID:Chromosome 18q paracentric inversion in a family with mental retardation and hearing loss. 955 94

Genetic loci for several diseases, including X-linked nonspecific mental retardation and short stature, have been mapped to Xp22.1. In spite of the recent publications of two draft sequences for the human genome, this region seems to be largely unmapped and unsequenced. Here we report an integrated physical and transcript map of approximately 2-Mb from DXS8004 to DXS365. Using sequence tagged site (STS)-content mapping and chromosome walking, we assembled a genomic clone contig of 54 BACs and one cosmid with an estimated 4.5-fold coverage of this region. The minimum tiling path consists of 23 BACs and one cosmid. Onto this contig, we mapped 30 new STSs derived from the unique end-sequences of the BACs, three expressed sequence tags, five genes, and seven CpG islands. This integrated map provides a unique resource for the positional cloning of candidate disease genes mapping to Xp22.1 and is therefore of value for the completion of the genomic sequence of this region.
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PMID:Physical and transcript map of a 2-Mb region in Xp22.1 containing candidate genes for X-linked mental retardation and short stature. 1186 56

A female patient with non-syndromic mental retardation was shown by high resolution GTL banding to have inherited an apparently balanced translocation, 46,X,t(X;8)(q28;q12)mat. Replication studies in the mother and daughter showed a skewed X inactivation pattern in lymphocytes, with the normal X chromosome preferentially inactivated. The mother also had significant intellectual disability. To investigate the possibility that a novel candidate gene for XLMR was disrupted at the X chromosome translocation breakpoint, we mapped the breakpoint using fluorescence in situ hybridisation (FISH). This showed that the four known genes involved in non-syndromic mental retardation in Xq28, FMR2, SLC6A8, MECP2, and GDI1, were not involved in the translocation. Intriguingly, we found that the X chromosome breakpoint in the daughter could not be defined by a single breakpoint spanning genomic clone and further analysis showed a 650 kb submicroscopic duplication between DXS7067 and DXS7060 on either side of the X chromosome translocation breakpoint. This duplicated region contains 11 characterised genes, of which nine are expressed in brain. Duplication of one or several of the genes within the 650 kb interval is likely to be responsible for the mental retardation phenotype seen in our patient. Xq28 appears to be an unstable region of the human genome and genomic rearrangements are recognised as major causes of two single gene defects, haemophilia A and incontinentia pigmenti, which map within Xq28. This patient therefore provides further evidence for the instability of this genomic region.
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PMID:Identification of a 650 kb duplication at the X chromosome breakpoint in a patient with 46,X,t(X;8)(q28;q12) and non-syndromic mental retardation. 1262 34