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)

Mental retardation (MR) is a nonprogressive condition characterized by a significant impairment of intellectual capabilities with deficit of cognitive and adaptive functioning and onset before 18 years. Mental retardation occurs in about 2 to 3% of the general population and it is estimated that 25 to 35% of the cases may be due to genetic causes. Among these "genetic" MR, 25 to 30% are probably due to mutations in a gene on the X chromosome (X-linked mental retardation, XLMR). Given the genetic heterogeneity of XLMR, the availability of a considerable number of patients with accurate phenotypic classification is a crucial factor for research. The X-linked Mental Retardation Italian Network, which has been active since 2003, has collected detailed clinical information and biological samples from a vast number of MR patients. Collected samples and clinical information are inserted within the XLMR bank, a comprehensive molecular and clinical web-based database available at the address http://xlmr.unisi.it. The database is organized in three distinct parts. Part I and II contain several electronic schedules to register information on the family, the phenotypic description, the photographs, and a 20 sec movie of the patient. Part III allows the registration of molecular analyses performed on each case; samples and clinical data are usable via password-restricted access. Clinical and molecular centers interested in joining the network may request a password by simply contacting the Medical Genetics of the University of Siena. The XLMR bank is an innovative biological database that allows the collection of molecular and clinical data, combines descriptive and iconographic resources, and represents a fundamental tool for researchers in the field of mental retardation.
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PMID:The Italian XLMR bank: a clinical and molecular database. 1698 48

Mutations in X-linked genes are likely to account for the observation that more males than females are affected with mental retardation. Causative mutations have been identified in both syndromic XLMR and in the genetically heterogeneous non-syndromic forms of XLMR, without a clear clinical phenotype other than cognitive deficit. Progress in genome analysis and the establishment of large collaborations between clinical and molecular research teams, especially the European XLMR consortium, have led to the identification of 20 non-syndromic XLMR genes and 25 syndromic XLMR genes. Given the extensive heterogeneity of non syndromic XLMR, different strategies are used for the identification of new genes: linkage analysis, studies of balanced chromosomal rearrangements (X-autosome translocations, microdeletions) and candidate genes strategies by mutation screening in regions of the X chromosome known to be involved in neuronal development and function. Delineating the monogenic causes of XLMR and their molecular and cellular consequences will provide insight into the mechanisms that are required for normal development of cognitive function in humans. Non syndromic XLMR proteins include 5 distinct classes: transmembrane receptors, small GTPases effectors or regulators, enzymes and translational regulators.
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PMID:[Update on the genetics of X-linked mental retardation]. 1702 63

X-linked mental retardation has been traditionally divided into syndromic (S-XLMR) and non-syndromic forms (NS-XLMR), although the borderlines between these phenotypes begin to vanish and mutations in a single gene, for example PQBP1, can cause S-XLMR as well as NS-XLMR. Here, we report two maternal cousins with an apparently X-linked phenotype of mental retardation (MR), microphthalmia, choroid coloboma, microcephaly, renal hypoplasia, and spastic paraplegia. By multipoint linkage analysis with markers spanning the entire X-chromosome we mapped the disease locus to a 28-Mb interval between Xp11.4 and Xq12, including the BCOR gene. A missense mutation in BCOR was described in a family with Lenz microphthalmia syndrome, a phenotype showing substantial overlapping features with that described in the two cousins. However, no mutation in the BCOR gene was found in both patients. Subsequent mutation analysis of PQBP1, located within the delineated linkage interval in Xp11.23, revealed a 2-bp deletion, c.461_462delAG, that cosegregated with the disease. Notably, the same mutation is associated with the Hamel cerebropalatocardiac syndrome, another form of S-XLMR. Haplotype analysis suggests a germline mosaicism of the 2-bp deletion in the maternal grandmother of both affected individuals. In summary, our findings demonstrate for the first time that mutations in PQBP1 are associated with an S-XLMR phenotype including microphthalmia, thereby further extending the clinical spectrum of phenotypes associated with PQBP1 mutations.
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PMID:A two base pair deletion in the PQBP1 gene is associated with microphthalmia, microcephaly, and mental retardation. 1703 86

Understanding the mechanisms whereby information encoded within patterns of action potentials is deciphered by neurons is central to cognitive psychology. The multiprotein complexes formed by NMDA receptors linked to synaptic membrane-associated guanylate kinase (MAGUK) proteins including synapse-associated protein 102 (SAP102) and other associated proteins are instrumental in these processes. Although humans with mutations in SAP102 show mental retardation, the physiological and biochemical mechanisms involved are unknown. Using SAP102 knock-out mice, we found specific impairments in synaptic plasticity induced by selective frequencies of stimulation that also required extracellular signal-regulated kinase signaling. This was paralleled by inflexibility and impairment in spatial learning. Improvement in spatial learning performance occurred with extra training despite continued use of a suboptimal search strategy, and, in a separate nonspatial task, the mutants again deployed a different strategy. Double-mutant analysis of postsynaptic density-95 and SAP102 mutants indicate overlapping and specific functions of the two MAGUKs. These in vivo data support the model that specific MAGUK proteins couple the NMDA receptor to distinct downstream signaling pathways. This provides a mechanism for discriminating patterns of synaptic activity that lead to long-lasting changes in synaptic strength as well as distinct aspects of cognition in the mammalian nervous system.
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PMID:Synapse-associated protein 102/dlgh3 couples the NMDA receptor to specific plasticity pathways and learning strategies. 1734 5

Mental retardation (MR) is a common trait, affecting approximately 2-3% of individuals in the general population. Although the etiology of MR remains largely unknown, genetics apparently play a major role. Recent molecular studies of X-linked form of MR in European and North American countries have revealed 24 nonsyndromic X-linked mental retardation (NS-XLMR) genes including FTSJ1, a human homolog of the Escherichia coli 2'-O-rRNA methyltransferase FtsJ/RrmJ gene. Here we identified a novel FTSJ1 mutation in an XLMR family through mutation screening of a cohort of 73 unrelated Japanese male probands with MR. Sequence analysis of the proband and his mother revealed a G > A substitution at the consensus for the donor splicing site in intron 8 (c.571 + 1G > A) of FTSJ1. This mutation prevented the removal intron 8 from the pre-mRNA, thereby leading to a frameshift in the mutant FTSJ1 mRNA and resulting in a premature termination in exon 9. Quantitative RT-PCR showed a significant reduction of mutant FTSJ1 mRNA in the patient's lymphoblast cells, which was restored by treatment with cycloheximide, a potent inhibitor of nonsense-mediated mRNA decay (NMD). Therefore, mRNAs carrying this mutation are likely subject to degradation by NMD. Together, loss-of-function of FTSJ1 may be a mechanism for the cognitive dysfunction observed in this family. Our study also suggested that the FTSJ1 mutation probably accounts for XLMR in Japanese at a similar frequency (1-2%) as in Europeans.
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PMID:A loss-of-function mutation in the FTSJ1 gene causes nonsyndromic X-linked mental retardation in a Japanese family. 1808 Oct 26

To investigate the possible genetic association of nonsyndromic X-linked mental retardation (NS-XLMR) with FTSJ1 gene polymorphisms, a case-control association study was performed focusing on the Chinese Han population in the Qinba mountain region. Three common single nucleotide polymorphisms (SNPs) (rs2268954, rs2070991, rs5905692) in the gene were selected and genotyped using the polymerase chain reaction single-strand confirmation polymorphism (PCR-SSCP) method. Pairwise linkage disequilibrium (LD) analysis showed that the three SNPs were in strong LD (all D' > 0.8). There were significant differences between cases and controls in allele frequency distribution of rs2268954 (P = 0.036), rs2070991 (P = 0.043), and rs5905692 (P = 0.014) and in the distributions of common haplotypes combined by these SNPs (global P = 0.01236) in male subjects. In female subjects, however, no positive results were found. Our results suggest a positive association between the genetic variants of the FTSJ1 gene and NS-XLMR in young male subjects in the Chinese Han population in the Qinba region.
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PMID:Positive association of the FTSJ1 gene polymorphisms with nonsyndromic X-linked mental retardation in young Chinese male subjects. 1840 46

Mental retardation is a serious medical and social problem. The prevalence of mental retardation is estimated at 2-3%. Establishing the cause of mental retardation is extremely important for prognosis, management, and genetic counseling. It is postulated that 25-35% of mental retardation cases may be of genetic background. Among the genetic causes 25-30% are probably result of mutations located in the X chromosome (X-linked mental retardation--XLMR). X-linked mental retardation is a heterogeneous set of conditions responsible for a large proportion of inherited mental retardation. More than 200 XLMR conditions and 45 cloned genes are listed in catalogue available on the Internet. Traditionally, based on clinical presentation, XLMR conditions were divided into specific and nonspecific forms or syndromic and nonsyndromic. The distinction between specific and non-specific forms of XLMR is gradually becoming less clear and spectrum of phenotypic variability is very large as both syndromic and nonsyndromic forms have been described for several of the XLMR genes. Mutations in patients suffering from X-linked mental retardation genes have been found only in a relatively limited number of cases. Up to 50% of the patients from XLMR families might have mutations in one of the known genes implicated in XLMR so far. However, current methods are generally too expensive or too unreliable to justify mutation screening of all known XLMR genes in diagnostic testing. Thus it is necessary to use empirical data of recurrence risk in genetic counseling of the family with mental retardation.
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PMID:[X-linked mental retardation--treatment scheme]. 1893 66

Mental retardation is a serious medical and social problem. The prevalence of mental retardation in Western countries is estimated to be between 2 and 3%. Establishing the cause of mental retardation is essential for prognosis, management, and genetic counseling. It is estimated that 25-35% of mental retardation might have a genetic background. Of these genetic causes, 25-30% are probably due to mutations on the X chromosome (X-linked mental retardation, XLMR). XLMR is a heterogeneous set of conditions involved in a large proportion of inherited mental retardation. More than 200 XLMR conditions have been reported and 76 genes has been linked to them. XLMR conditions are commonly subdivided into syndromic and nonsyndromic forms on the basis of clinical presentation. The distinction between these forms of XLMR is gradually becoming less clear as phenotypes are described for several of the genes. The spectrum of phenotypic variability in XLMR is so large that mutations in several XLMR genes have been found in both syndromic and nonsyndromic (XLMR) pedigrees. About 42% of patients from families with an XLMR history might have mutations in one of the known genes implicated in XLMR. However, in genetic counseling we have to use empiric recurrence risk.
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PMID:X-linked mental retardation. 1897 87

Mental retardation is a serious social problem. It affects 2-3% of the population. It is estimated that mutations in the ARX gene can be found in 1 in 12,000 live male births. This is the second most common cause of X-linked mental retardation after fragile X syndrome. The ARX gene belongs to transcription factors involved in differentiation of specific neuronal cells in the central nervous system. The most common mutation in the ARX gene is c. 428_451dup24, duplication of 24 bp in exon 2 of the gene, causing elongation of the second alanine tract (polyA12_II). Described disorders caused by mutations in the ARX gene include: hydrocephaly with abnormal genitalia (HYD-AG), lissencephaly with abnormal genitalia (XLAG), agenesis of corpus callosum with abnormal genitalia (ACC-AG), Partington syndrome (PRTS), X-linked infantile spasms (ISSX), myoclonic epilepsy with spasticity and mental retardation (XMESID), and nonspecific mental retardation (NS-XLMR).
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PMID:[ARX--one gene--many phenotypes]. 1897 39

The high concordance for autism symptoms in monozygotic twin-pairs compared to di-zygotic twins and/or non-twin sib-ships suggests a high genetic determinism in autism. Those results have hypothesized multi-factorial determinism in accordance with family studies and mathematical models. However, linkage and association or candidate gene strategies have failed to-date to identify clearly involved mechanisms. Mental retardation (MR) is known as frequently associated to autism. Multiplex XLMR pedigrees have been reported with only one mutated patient having autism and MR: different X-located MR genes have been shown to be involved (NLGN4, MECP2, OPHN1, ZNF674 and FRAXA) which does not suggest that they could be "autism genes". Tuberous sclerosis studies and report of numerous autosomal domains shown deleted in MR-autistic subjects suggest that several autosomal dominant (AD) genes could be also involved in MR with autism. Whereas multiplex AD-MR families are rare, AD de novo mutations could explain numerous sporadic situations of non-specific MR and of autism with MR, in accordance with twin studies. Finally, we hypothesize that in those autistic subjects with mendelian MR, the XL-MR or AD-MR gene (G1) would pave the way for a second Mendelian factor (G2) responsible for autism symptoms.
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PMID:Could autism with mental retardation result from digenism and frequent de novo mutations? 1916 Jan 28


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