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

Fragile X syndrome is one of the most common reasons for human hereditary mental retardation. It is associated with the expansion of CGG repeats in the 5'-untranslated region of the FMR1 gene, which results in the suppression of its expression and the development of the disease. At present, methods based on PCR and Southern blot analysis are used for diagnostics of the fragile X syndrome. The presence of a fragile site FRAXA on the X chromosome is typical for patients with this pathology. We developed a method of visualizing this site in cell cultures obtained from patients using the fluorescent in situ hybridization (FISH) and the combination of two probes. The method allows one to detect five types of signals on the X chromosome, three of which are normal, while two are associated with the emergence of fragile site FRAXA. An analysis of the distribution of all signal types in cell lines from healthy individuals and patients with fragile X syndrome demonstrated that the method allows one to determine differences between lines with a high statistical significance and that it is applicable to detecting cells that are carriers of the syndrome.
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PMID:[Method for the Molecular Cytogenetic Visualization of Fragile Site FRAXA]. 2890 90

Chromosome fragile sites tend to form gap or break in chromosomes when the cells are exposed to replication stress. Folic acid deprivation in the culture medium induces folate-sensitive rare fragile sites, such as FRAXA which is responsible for the fragile X mental retardation syndrome. Chromosome instability at fragile sites can be evaluated by biomarkers of genomic instability such as frequency of micronuclei (MN). It was aimed to analyse the chromosome content of MN in Fragile X cells during folate deprivation by the MN-fluorescence in situ hybridization (FISH) method. Samples from five Fragile X syndrome patients, diagnosed using cytogenetic and molecular methods, as well as from their parents and five controls were included in the study. Blood samples were cultured in two different culture media (folate-deficient and normal). Results of MN-FISH test were analysed in terms of MN frequency and chromosome content of MN. An accumulation of MN in Fragile X patients, mainly containing T (+) or C (+) MN or T (+) plus C (+) MN in binucleated cells was found. Finally, MN-FISH analysis allowed confirming that the increase in MN frequency is due to a higher sensitivity to chromosome breakage along the X chromosome.
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PMID:Analysis of Xq27.3 Fragility Using the Micronucleus-Fluorescence In situ Hybridization Assay. 3311 Apr 86


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