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

Mutations in ARHGEF6, encoding a guanine nucleotide exchange factor for Rho GTPases, have been shown to cause X-chromosomal non-specific mental retardation (MRX) in human. Here we report the identification and characterization of the orthologous mouse gene, Arhgef6. The gene transcript of approximately 4.4 kb is present in various mouse tissues indicating ubiquitous expression as found for human ARHGEF6. The open reading frame encodes a polypeptide of 771 amino acids with high homology to human ARHGEF6. The structural motifs of both proteins are conserved including an N-terminal CH domain, followed by an SH3 domain, and a tandem organization of the DH and PH domains. Analysis of the temporal expression pattern revealed that Arhgef6 is strongly expressed in the very early embryo and somewhat less in later stages. A genomic cosmid clone containing Arhgef6 exons 1 and 2 has been isolated and used for mapping the gene on the mouse X chromosome.
 ...
PMID:The mouse Arhgef6 gene: cDNA sequence, expression analysis, and chromosome assignment. 1206

Although MECP2 was initially identified as the causative gene in classic Rett syndrome (RTT), the gene has now been implicated in several phenotypes that extend well beyond the clinically defined disorder. MECP2 mutations have been found in people with various disorders, including neonatal onset encephalopathy, X-linked recessive mental retardation (MRX), classic and atypical RTT, autism, and Angelman syndrome, as well as mildly affected females and normal carrier females. To make matters more complex, in approximately 20% of classic sporadic RTT cases and more than 50% of affected sister pairs, no mutation in MECP2 has been found. X-chromosome inactivation patterns can clearly affect the phenotypic expression in females, while the effect of the type and position of the mutation is more apparent in the broader phenotype than in RTT. Both males and females are at risk, although an excess of paternally derived mutations are found in most cases of classic RTT. Thus, because of the range of disparate phenotypes, the gene may account for a relatively large portion of mental retardation in the population.
 ...
PMID:The phenotypic consequences of MECP2 mutations extend beyond Rett syndrome. 1211 34

Nonspecific X-linked mental retardation (MRX) patients are characterized by mental retardation, without additional distinguishing features. Consequently, MRX families can only be distinguished by mapping studies; yet, due to imprecise mapping studies performed in the past, the number of genes causing MRX is debatable, and a more precise localization for families is necessary to estimate this number. MRX 9 has been mapped to the pericentromeric region Xp21-q13. We refined the mapping of the MRX9 family to Xp11.22-Xp11.4. A sequencing analysis of three likely candidate genes in Xp11, SREB3, synapsin I, and TM4SF2, revealed no mutations.
 ...
PMID:Family MRX9 revisited: further evidence for locus heterogeneity in MRX. 1223 14

The TM4SF2 gene (localized at Xp11.4 between the loci DXS564 and DXS556) has been found to be mutated in one MRX family. In order to define the corresponding behavioral phenotype, global IQ and specific cognitive skills were assessed in seven males and three females of this family, independent of subject status. Mental retardation (MR) was mild in three patients and moderate in three others. Despite the broad variability of severity of MR, a cognitive profile specific to the MR in this family was documented. It was characterized by language disorder that was more marked in the articulatory component and spatial/verbal short-term memory dissociation with larger mnemonic span for spatial than for verbal cues. Linkage analysis was then performed on the basis of the cognitively determined status. Recombinations were observed with the loci DXS556 at Xp11.4 and DXS441 at Xq13.2 (maximum LOD score = 2.23 at theta = 0 for ALAS2). This localization region does not include the TM4SF2 gene that has been found mutated in both patients with MR and in one non-MR male subject of this family. The present results suggest two main hypotheses. First, TM4SF2 gene mutation could be involved in MR in this family, therefore representing accentuated intra familial phenotypic variability. Second, the structural particularity detected in the TM4SF2 gene might reflect a rare polymorphism rather than a pathogenic mutation, with the gene responsible for MR in this family being therefore more likely to be searched for in the pericentromeric region of the X chromosome.
 ...
PMID:TM4SF2 gene involvement reconsidered in an XLMR family after neuropsychological assessment. 1237 45

This review covers the history and nosology of X-linked mental retardation (XLMR) in which the following, largely clinically based, subclassification was used: fragile X syndrome (FRAXA), syndromic forms (MRXS) and non-specific forms (MRX). After the discovery of the FMR2 gene at the FRAXE site, 10 MRX genes have been identified in the last 6 years. A short description is given of the strategies used to identify the genes that cause mental retardation (MR). Furthermore, their potential functions and the association with MR will be discussed. It is emphasized that mutations in several of these MR genes can result in non-specific, as well as in syndromic forms of XLMR. Present findings stress the importance of accurate clinical evaluation. Most considerably, genotype-phenotype correlation studies of affected individuals in XLMR families with MRX gene mutations are necessary to define the criteria of MRX vs MRXS subclassification.
 ...
PMID:X-linked mental retardation: vanishing boundaries between non-specific (MRX) and syndromic (MRXS) forms. 1248 86

X-linked nonspecific mental retardation (MRX) accounts for approximately 25% of mental retardation in males. A number of MRX loci have been mapped on the X chromosome, reflecting the complexity of gene action in central nervous system (CNS) specification and function. Eleven MRX genes have been identified, but many other causative loci remain to be refined to the single gene level. In 21 MRX families, the causative gene is located in the pericentromeric region; and we report here the identification by linkage analysis of a further such locus, MRX81. The new MRX locus was identified by two- and multi-point parametric analysis carried out on a large Italian family. Tight linkage of MRX81 to DNA markers ALAS2, DXS991, and DXS7132 was observed with a maximum LOD score of 3.43. Haplotype construction delineates an MRX81 critical region of 8 cM, the smallest MRX pericentromeric interval so far described, between DXS1039 and DXS1216, and placing it in Xp11.2-Xq12. So far, automated sequencing of two candidates in the region, the MRX gene oligophrenin (OPHN1) and the brain-specific ephrinB1 (EFNB1) gene, in DNA from affected males excluded their candidacy for MRX81, suggesting a novel disease gene.
 ...
PMID:Mapping of MRX81 in Xp11.2-Xq12 suggests the presence of a new gene involved in nonspecific X-linked mental retardation. 1267 50

The ribosomal S6 kinase family members RSK2 (RPS6KA3) and RSK4 (RPS6KA6) belong to the group of X chromosomal genes, in which defects cause unspecific mental retardation (MRX) in humans. In this study, we investigated the spatiotemporal expression pattern of these genes during mouse development with emphasis to midgestation stages. Additionally, we analyzed the expression of the phosphoinositide-dependent protein kinase-1 gene, Pdk1 (Pspk1), which is essential for the activation of Rsk family members and thus regulates their function. During midgestation we observed specifically enhanced expression of Rsk2 first in somites, later restricted to the dermatomyotome of the somites, then in the sensory ganglia of cranial nerves and in the dorsal root ganglia of the spinal nerves. High Rsk2 expression in the cranial nerve ganglia persists throughout development and is correlated with Pdk1 expression. In the brain of 2-day-old mice, Pdk1 is expressed in the cortical plate of the cerebral cortex and in the stratum pyramidale of the hippocampus, whereas Rsk2 expression is lower in these structures. For Rsk4 ubiquitous expression at lower levels was observed throughout development.
 ...
PMID:Expression pattern of the Rsk2, Rsk4 and Pdk1 genes during murine embryogenesis. 1271 46

Isolated mental retardation is clinically and genetically heterogenous and may be inherited in an autosomal dominant, autosomal recessive, or X-linked manner. We report here a linkage analysis in a large family including 15 members, 6 of whom presenting X-linked non-syndromic mental retardation (MRX). Two-point linkage analysis using 23 polymorphic markers covering the entire X chromosome demonstrated significant linkage between the causative gene and DXS8055 with a maximum LOD score of 2.98 at theta = 0.00. Haplotype analysis indicated location for the disease gene in a 23.1 cM interval between DXS1106 and DXS8067. This MRX localization overlaps with 7 XLMR loci (MRX23, MRX27, MRX30, MRX35, MRX47, MRX53, and MRX63). This interval contains two genes associated with non-syndromic mental retardation (NSMR), namely the PAK3 gene, encoding a p21-activated kinase (MRX30 and MRX47) and the FACL4 gene encoding a fatty acyl-CoA ligase (MRX63). As skewed X-inactivation, an apparently constant feature in FACL4 carrier females was not observed in an obligate carrier belonging to the MRX family presented here, the PAK3 gene should be considered as the strongest candidate for this MRX locus.
 ...
PMID:Localization of a non-syndromic X-linked mental retardation gene (MRX80) to Xq22-q24. 1294 69

Nonsyndromic X-linked mental retardation (MRX) is a highly heterogeneous condition in which mental retardation appears to be the only consistent manifestation. According to the most recent data, 77 MRX families with a lod score of >2 have been mapped and eight genes have been cloned. We hereby report on a linkage analysis performed on a Greek family with apparently nonsyndromic MRX. The affected males have moderate to severe mental retardation, severe speech problems, and aggressive behavior. Two-point linkage analysis with 26 polymorphic markers spanning the entire X chromosome was carried out. We could assign the causative gene to a 27 Mb interval in Xq12-Xq21.33. The maximum LOD score was found for markers DXS1225, DXS8114, and DXS990 at 2.36, 2.06, 2.06, respectively at theta = 0.00. Recombination was observed for DXS983 at the proximal side and DXS6799 at the distal side. Nineteen other MRX families have been described with a partial overlapping disease gene interval in proximal Xq. No mutations were found in the MRX77 family for three known or candidate MRX genes, from this region OPHN1, RSK4, and ATR-X. These data indicate that the Xq12-Xq21.33 interval contains at least one additional MRX gene.
 ...
PMID:A gene for nonsyndromic X-linked mental retardation (MRX77) maps to Xq12-Xq21.33. 1294 71

Non-syndromic X-linked mental retardation (MRX) is a frequent cause of inherited mental retardation. It is a heterogeneous condition in which the first 12 genes discovered to date explain no more than 15% of the MRX situations ascertained by recurrence in multiplex families. In Rett syndrome (RTT), an X-linked dominant condition mostly sporadic and usually lethal in males, most affected females have been shown to be mutated in the Methyl-CpG binding protein 2 gene (MECP2) that maps at Xq28. Some mentally retarded males related to RTT females carry the same mutation. Several MRX families mapping to Xq28 were subsequently tested for MECP2 and a causative mutation was discovered in three families, suggesting that it could be one of the main genes involved in MRX. We report here the corresponding phenotypes in these three families of increasing severity. In family 1, an in-frame deletion DeltaP387-M466 was found in the 3' region. The patients had severe to mild non-progressive MR, with better motor skills than verbal abilities. In family 2, an Arg to Trp substitution (R167W) was found between the transcription repression domain (TRD) and the methyl binding domain (MBD). The patients had brisk reflexes and essential tremor with mild and non-progressive MR, poor motor co-ordination and written language difficulties. In the third family (MRX16), a Glu to Gly substitution (E137G) was found in the MBD. The patients had manifestations similar to those of family 2, but MR was mild to moderate, speech articulation was poor and some had verbal stereotypies. Regression of language skills was suspected in three patients. Phenotype-genotype correlation could thus be suspected and is discussed in these three families.
 ...
PMID:MECP2 gene mutations in non-syndromic X-linked mental retardation: phenotype-genotype correlation. 1459 36


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>