Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Factors involved in the stability of trinucleotide repeats during transmission were studied in 139 families in which a full mutation, premutation or intermediate allele at either FRAXA or FRAXE was segregating. The transmission of alleles at FRAXA, FRAXE and four microsatellite loci were recorded for all individuals. Instability within the minimal and common ranges (0-40 repeats for FRAXA, 0-30 repeats for FRAXE) was extremely rare; only one example was observed, an increased in size at FRAXA from 29 to 39 repeats. Four FRAXA and three FRAXE alleles in the intermediate range (41-60) repeats for FRAXA, 31-60 for FRAXE) were unstably transmitted. Instability was more frequent for FRAXA intermediate alleles that had a tract of pure CGG greater than 37 although instability only occurred in two of 13 such transmissions: the changes observed were limited to only one or two repeats. Premutation FRAXA alleles over 100 repeats expanded to a full mutation during female transmission in 100% of cases, in agreement with other published series. There was no clear correlation between haplotype and probability of expansion of FRAXA premutations. Instability at FRAXA or FRAXE was more often observed in conjunction with a second instability at an independent locus suggesting genomic instability as a possible mechanism by which at least some FRAXA and FRAXE mutations arise.
Hum Mol Genet 1997 Feb
PMID:The role of size, sequence and haplotype in the stability of FRAXA and FRAXE alleles during transmission. 906 37

Fragile X syndrome is caused by the expansion and concomitant methylation of a CGG repeat in the 5' untranslated region of the FMR1 gene which results in the transcriptional silencing of the FMR1 gene, delayed replication of the FMR1 locus, and the formation of a folate sensitive fragile site (FRAXA) at Xq27.3. The mechanism by which repeat expansion and methylation causes these changes is unknown. An in vivo system in which cells were permeabilized with lysophosphatidylcholine followed by digestion with MspI endonuclease was utilized to assess the chromatin conformation at the fragile X locus. The FMR1 gene was inaccessible to MspI digestion in fragile X patients, but not in normal or carrier individuals, confirming that altered chromatin conformation results from the repeat expansion and methylation seen in fragile X syndrome.
Somat Cell Mol Genet 1996 Nov
PMID:Nuclease sensitivity of permeabilized cells confirms altered chromatin formation at the fragile X locus. 913 Oct 13

Normal individuals express the two alternative transcripts, FMR2 and Ox19, from the FRAXE-associated CpG island. Molecular analysis of the Ox19 transcript suggests that it is a truncated isoform of the FMR2 gene with an alternative 3' end. Both isoforms showed a similar pattern of expression, with the Ox19 isoform expressed at a much lower level. Fibroblasts, chorionic villi and hair roots showed the highest level of FMR2 expression, whole blood cells and amniocytes showed very low expression, and the transcript was not detected in lymphoblasts. Fibroblasts of 11 individuals from seven families segregating FRAXE were assayed for FMR2 expression and FRAXE CpG island methylation. A man with an unmethylated expansion of 0.6 kb expressed FMR2 and represents a pre-mutation carrier. All chromosomes with FRAXE CCG expansions of 0.8 kb or greater were fully methylated and did not express the FMR2 gene, analogous to the mechanism of silencing the FMR1 gene in carriers of the FRAXA full mutation. The boundary between FRAXE pre-mutation and FRAXE full mutation is between 0.7 and 0.8 kb. Two men with absence of FMR2 expression in fibroblasts were not mentally impaired, suggesting that IQ in some men with FRAXE full mutation may remain within the normal range. Although molecular tools to study FRAXE non-specific mental retardation are now available, further psychometric and molecular studies are needed to characterize the effect of the FRAXE full mutation for the purpose of genetic counselling.
Hum Mol Genet 1997 Mar
PMID:FMR2 expression in families with FRAXE mental retardation. 914 47

Fragile X syndrome is the most frequent cause of heritable mental retardation. Most patients have a mutation in the 5' untranslated region of the FMR1 gene, consisting of the amplification of a polymorphic (CGG)nrepeat sequence, and cytogenetically express the folate-sensitive fragile site FRAXA in Xq27.3. Fragile X patients harbour an expanded sequence with >200 CGG repeats (full mutation), accompanied by methylation of most cytosines of the sequence itself and of the upstream CpG island. This abnormal hypermethylation of the promoter suppresses gene transcription, resulting in the absence of the FMR1 protein. Rare individuals of normal intelligence were shown to carry a completely or partially unmethylated full mutation and to express the FMR1 protein. Given this observation and knowing that the open reading frame of the mutated FMR1 gene is intact, we decided to investigate whether its activity could be restored in vitro by inducing DNA demethylation with 5-azadeoxycytidine (5-azadC) in fragile X patients' lymphoblastoid cells. We report that treatment with 5-azadC causes reactivation of fully mutated FMR1 genes with 300-800 repeats, as shown by the restoration of specific mRNA and protein production. This effect correlates with the extent of promoter demethylation, determined by restriction analysis with methylation-sensitive enzymes. These results confirm the critical role of FMR1 promoter hypermethylation in the pathogenesis of the fragile X syndrome, provide an additional explanation for the normal IQ of the rare males with unmethylated full mutations and pave the way to future attempts at pharmacologically restoring mutant FMR1 gene activity in vivo.
Hum Mol Genet 1998 Jan
PMID:In vitro reactivation of the FMR1 gene involved in fragile X syndrome. 938 10

The FRA3B at 3p14.2 is the most highly expressed of the common fragile sites observed when DNA replication is perturbed by aphidicolin or folate stress. The molecular basis for chromosome fragility at FRA3B is unknown. In contrast to the rare fragile sites, including FRAXA, no repeat motifs, such as trinucleotide repeats, have been identified within FRA3B. Several lines of evidence suggest that fragile sites are regions of DNA whose replication is unusually sensitive to interference. We have used fluorescence in situ hybridization to determine the relative timing of replication of FRA3B sequences. Our studies revealed that FRA3B sequences are late replicating. Exposure to aphidicolin, an inhibitor of both DNA polymerase alpha and delta, results in a reproducible delay in the timing of replication, and some cells enter G2without having completed replication of FRA3B sequences. Our results support a model in which common fragile sites are sequences that initiate replication late in S phase or are slow to replicate, and the chromosomal breaks and gaps observed in metaphase cells are due to unreplicated DNA.
Hum Mol Genet 1998 Apr
PMID:Replication of a common fragile site, FRA3B, occurs late in S phase and is delayed further upon induction: implications for the mechanism of fragile site induction. 949 31

Non-specific X-linked mental retardation (MRX) is a very common disorder which affects approximately 1 in 600 males. Despite this high frequency, little is known about the molecular defects underlying this disorder, mainly because of the clinical and genetic heterogeneity which is evident from linkage studies. Recently, a collaborative study using the candidate gene approach demonstrated the presence of mutations in GDIalpha, a Rab GDP-dissociation inhibitor encoded by a gene localized in Xq28, associated with non-specific mental retardation. GDIalpha is mainly a brain-specific protein that plays a critical role in the recycling of Rab GTPases involved in membrane vesicular transport. The study presented here was designed to assess the prevalence of mutations in the GDIalpha in mentally retarded patients and to discuss the clinical phenotypes observed in affected individuals. Mutation screening of the whole coding region of the GDIalpha gene, using a combination of denaturing gradient gel electrophoresis and direct sequencing, was carried out in 164 patients found negative for expansions across the FRAXA GCC repeat. In addition to the nonsense mutation recently reported in MRX48, we have identified a novel missense mutation in exon 11 of the GDIalpha gene in one familial form of non-specific mental retardation. In this family (family R), all affected males show moderate to severe mental retardation, and the X-linked semidominant inheritance is strongly suggested by the severe phenotypes in males with respect to mildly affected females or unaffected obligatory carriers. This study showed that the prevalence of GDIalpha mutations in non-specific mental retardation could be estimated to be 0.5-1%, and molecular diagnosis and genetic counselling in some cases of non-specific mental handicap can now be provided.
Hum Mol Genet 1998 Aug
PMID:Non-specific X-linked semidominant mental retardation by mutations in a Rab GDP-dissociation inhibitor. 966 74

The folate-sensitive fragile site FRAXE is located in proximal Xq28 of the human X chromosome and lies approximately 600 kb distal to the fragile X syndrome (FRAXA) fragile site at Xq27.3. Although FRAXA and FRAXE are indistinguishable by means of conventional cytogenetics, they can now be delineated at the molecular level and provides the basis for a proper diagnosis. The screening for CGG amplifications in the FMR1 gene was based on standard protocols using EcoRI digests on Southern blots and hybridization with the StB12.3 probe. The FRAXE mutation was analyzed by digestion with HindIII and the filters were probed with OxE20. We present the results of 144 patients referred for fragile X testing but negative for the FMR1 gene trinucleotide expansion, that were also screened for the FMR2 expansion. For FRAXE mutation a molecular protocol for OxE18 probe was used, in the DNA samples digested with EcoRI on the same blots as those used for detection of FRAXA. None of the patients tested were positive for the FRAXE expansion. This technique was successfully established into our laboratory routine showing the practical use of testing for FRAXA and FRAXE in a large series of patients.
Int J Mol Med 2000 Jan
PMID:FRAXE mutation in mentally retarded patients using the OxE18 probe. 1060 77

Following the recent discovery that the methyl-CpG binding protein 2 (MECP2) gene located on Xq28 is involved in Rett syndrome (RTT), a wild spectrum of phenotypes, including mental handicap, has been shown to be associated with mutations in MECP2. These findings, with the compelling genetic evidence suggesting the presence in Xq28 of additional genes besides RabGDI1 and FMR2 involved in non-specific X-linked mental retardation (MRX), prompted us to investigate MECP2 in MRX families. Two novel mutations, not found in RTT, were identified. The first mutation, an E137G, was identified in the MRX16 family, and the second, R167W, was identified in a new mental retardation (MR) family shown to be linked to Xq28. In view of these data, we screened MECP2 in a cohort of 185 patients found negative for the expansions across the FRAXA CGG repeat and reported the identification of mutations in four sporadic cases of MR. One of the mutations, A140V, which we found in two patients, has been described previously, whereas the two others, P399L and R453Q, are novel mutations. In addition to the results demonstrating the involvement of MECP2 in MRX, this study shows that the frequency of mutations in MECP2 in the mentally retarded population screened for the fragile X syndrome is comparable to the frequency of the CGG expansions in FMR1. Therefore, implementation of systematic screening of MECP2 in MR patients should result in significant progress in the field of molecular diagnosis and genetic counseling of mental handicap.
Hum Mol Genet 2001 Apr 15
PMID:MECP2 is highly mutated in X-linked mental retardation. 1130 67

Myotonic dystrophy (DM), Huntington's disease (HD) and Fragile X syndrome (FRAXA) are three monogenic disease which are caused by so-called dynamic mutations. These mutations are caused by triplet repeats inside or in the vicinity of the gene which have the tendency to expand beyond the normal range thus disrupting the normal functioning of the gene. We describe here our experiences from 1995 to May 2000 with PGD for these three triplet repeat diseases.
Mol Cell Endocrinol 2001 Oct 22
PMID:PGD in the lab for triplet repeat diseases - myotonic dystrophy, Huntington's disease and Fragile-X syndrome. 1157 38

Microsatellites have been used extensively in gene mapping, linkage and association studies but with the near completion of the human genome project (HGP) single nucleotide polymorphisms (SNP) have become the marker of choice. However, for association studies to be useful large numbers of SNPs must be analysed. To make these studies cost effective a simple and non-labour intensive method for SNP genotyping is essential. This work describes a single-tube modification of the amplification refractory mutation system (Biallelic-ARMS). Control amplimers flanking the SNP were amplified in a single-tube multiplex PCR with two SNP specific primers that prime in opposite directions. The SNP allele was identified on the basis of PCR product size after gel electrophoresis. Biallelic-ARMS was used to analyse six SNPs within 300 kb of the FRAXA repeat, two from the HGP SNP Database (ATL1 and FMRb) and four novel SNPs (WEX1, WEX10, WEX17 and WEX28). The study population consisted of 649 males with a range of FRAXA (10 to >200) repeat sizes. Each SNP correlated with distinct haplogroups, as identified by DXS548, FRAXAC1 and FRAXAC2 flanking microsatellite repeat patterns and confirmed the initial choice of haplogroups for FRAXA repeat stability defined by Enniset al.
Mol Cell Probes 2002 Aug
PMID:SNP genotyping using a simple and rapid single-tube modification of ARMS illustrated by analysis of 6 SNPs in a population of males with FRAXA repeat expansions. 1227 Feb 71


<< Previous 1 2 3 Next >>