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

X-linked ichthyosis (XLI) is often associated with a recurrent microdeletion at Xp22.31 due to non-allelic homologous recombination between the CRI-S232 low-copy repeat regions flanking the STS gene. The clinical features of these patients may include mental retardation (MR) and the VCX-A gene has been proposed as the candidate MR gene. Analysis of DNA from four XLI patients with MR by array-comparative genomic hybridization (array-CGH) on a 150 kb resolution X chromosome-specific array revealed a 1.5 Mb interstitial microdeletion with breakpoints in the CRI-S232 repeat sequences, each of which harbors a VCX gene. We demonstrate that the recombination sites in all four cases are situated in the 1 kb repeat unit 2 region present at the 3' ends of the VCX-A and VCX-B genes thereby deleting VCX-A and VCX-B1 but not VCX-B and VCX-C. Array-CGH with DNA of an XLI patient with MR and an inherited t(X;Y)(p22.31;q11.2) showed an Xpter deletion of 8.0 Mb resulting in the deletion of all four VCX genes and duplication of both VCY homologs. These data confirm the role of VCX-A in the occurrence of MR in XLI patients. Moreover, we propose a VCX/Y teamwork-dependent mechanism for the incidence of mental impairment in XLI patients.
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PMID:Deletion of VCX-A due to NAHR plays a major role in the occurrence of mental retardation in patients with X-linked ichthyosis. 1588 81

We describe a familial interstitial deletion of 7.7-Mb involving Xp22.2-22.3. The deletion was transmitted from an asymptomatic mother to her two children with severe developmental delay, no speech development and autistic behavior. Assessment of the deletion boundaries by FISH and PCR analyses indicated that the deletions encompasses 27 genes. Several of these genes are associated with known disorders, like KAL1 (Kallmann syndrome), steroid sulfatase (STS) (X-linked ichtyosis), and arylsulfatase E (ARSE) (chondrodysplasia punctata). The deletion also includes all four VCX genes (VCX-A, VCX-B1, VCX-B, and VCX-C) and the neuroligin 4 (NLGN4) gene. VCX-A deficiency has been shown previously to be associated with mental retardation and NLGN4 mutations lead to mental retardation in conjunction with autism. Functional deficiency of both MRX genes, VCX-A and NLGN4, are most likely associated with the impaired cognitive development of the patients described here. The phenotype associated with the Xp deletion was highly variable in female carriers and might be attributed to unfavorable X inactivation. However, all the 27 genes included in the deleted interval escape X inactivation and are expressed at variable levels from the normal X chromosome. Thus, the overall X inactivation pattern and inter-individual expression variability of the genes in distal Xp might be determinants of the phenotype associated with the deletion.
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PMID:Molecular cytogenetic analysis of a familial interstitial deletion Xp22.2-22.3 with a highly variable phenotype in female carriers. 1647 Jul 42

Xp22.3 deletion in males can be associated with short stature (SHOX), chondrodysplasia punctata (ARSE), mental retardation (MRX49 locus), ichthyosis (STS), Kallmann syndrome (KAL1) and ocular albinism (OA1), according to the size of the deletion. Studies of terminal and interstitial deletions in male patients with a partial nullisomy of the X chromosome have led to the identification of the VCX-3A gene at the MRX49 locus on Xp22.3. The NLGN4X gene has then been identified less than 350 kb away from VCX-3A. Nonsense mutations in NLGN4X have been associated with autism and/or moderate mental retardation in males. We report a 17-year old male patient presenting with severe ichthyosis and Kallmann syndrome related to a 3.7 Mb interstitial Xp22.3 deletion, encompassing STS and KAL1 genes, respectively. However, despite the deletion of NLGN4X and all VCX genes, including VCX-3A, our patient did not manifest any learning disabilities or behavioural problems. Therefore, our case argues against a major role of NLGN4X and the VCX genes alone in cognitive development and/or communication processes.
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PMID:Normal intelligence and social interactions in a male patient despite the deletion of NLGN4X and the VCX genes. 1819 80

Posttranscriptional regulation is an important control mechanism governing gene expression in neurons. We recently demonstrated that VCX-A, a protein implicated in X-linked mental retardation, is an RNA-binding protein that specifically binds the 5' end of capped mRNAs to prevent their decapping and decay. Previously, expression of VCX-A was reported to be testes restricted. Consistent with a role in cognitive function, we demonstrate that VCX-A is ubiquitously expressed in human tissues including the brain. Moreover, retinoic acid-induced differentiation of human SH-SY5Y neuroblastoma cells promoted the accumulation of VCX-A in distinct cytoplasmic foci within neurites that colocalize with staufen1-containing RNA granules, suggesting a role in translational suppression and/or mRNA transport. Exogenous expression of VCX-A in rat primary hippocampal neurons, which normally do not express the primate-restricted VCX proteins, promoted neurite arborization, and shRNA-directed knockdown of the VCX genes in SH-SY5Y cells resulted in a reduction of both primary and secondary neurite projections upon differentiation. We propose that the cap-binding property of VCX-A reflects a role of this protein in mRNA translational regulation. In support of this hypothesized role, we demonstrate that VCX-A can specifically bind a subset of mRNAs involved in neuritogenesis and is also capable of promoting translational silencing. Thus, VCX-A contains the capacity to modulate the stability and translation of a subset of target mRNAs involved in neuronal differentiation and arborization. It is plausible that defects of these functions in the absence of the VCX genes could contribute to a mental retardation phenotype.
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PMID:Modulation of neuritogenesis by a protein implicated in X-linked mental retardation. 1981 18

X-linked ichthyosis is a genetic disorder affecting the skin and caused by a deficit in the steroid sulfatase enzyme (STS), often associated with a recurrent microdeletion at Xp22.31. Most of the STS deleted patients have X-linked ichthyosis as the only clinical feature and it is believed that patients with more complex disorders including mental retardation could be present as a result of contiguous gene deletion. In fact, VCX3A gene, a member of the VCX (variable charge, X chromosome) gene family, was previously proposed as the candidate gene for X-linked non-specific mental retardation in patients with X-linked ichthyosis. We report on a boy with familial ichthyosis, dysmorphic features and moderate mental retardation with approximately 2 Mb interstitial deletion on Xp22.3 involving VCX3A and STS genes.
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PMID:Xp22.3 interstitial deletion: a recognizable chromosomal abnormality encompassing VCX3A and STS genes in a patient with X-linked ichthyosis and mental retardation. 2379 52