Fragile X syndrome: search for phenotypic manifestations at loci for hypoxanthine phosphoribosyltransferase and glucose-6-phosphate dehydrogenase.
The subjects of this study were individuals with the form of X-linked mental retardation that is associated with the presence of a cytologically variant X chromosome having a secondary constriction or "fragile site" at Xq 27-28 (Fra X). Studies were carried out to test the hypothesis that deletions or modifications at neighboring loci occur as a consequence of events at the fragile site. Skin fibroblasts and peripheral blood lymphocytes from affected males were analyzed with respect to the expression of two X-lined enzymes: glucose-6-phosphate dehydrogenase (G6PD) and hypoxanthine phosphoribosyltransferase (HPRT); loci for these enzymes are known to be located in the region of the fragile site. Although the number of cells resistant to thioguanine (HPRT-deficient) obtained from some cultures from one Fra X male and blood cells of another was greater than expected, the frequency of these cells was not increased in cultures from other Fra X males. Furthermore, our results indicate that the G6PD activity and electrophoretic mobility in Fra X males is similar to that in normal cells, thus providing no evidence for the loss of the long-arm telomere in the fragile X syndrome.
D000328:Adult; D002478:Cells, Cultured; D002648:Child; D005260:Female; D005347:Fibroblasts / Q000201:enzymology; D006580:Genetic Carrier Screening; D005954:Glucosephosphate Dehydrogenase / Q000235:genetics*; D006801:Humans; D007041:Hypoxanthine Phosphoribosyltransferase / Q000235:genetics*; D008607:Intellectual Disability / Q000201:enzymology / Q000235:genetics*; D007527:Isoenzymes / Q000235:genetics; D008297:Male; D012729:Sex Chromosome Aberrations / Q000201:enzymology*; D012867:Skin / Q000201:enzymology; D013577:Syndrome; D014960:X Chromosome
D007527:Isoenzymes; D005954:Glucosephosphate Dehydrogenase; D007041:Hypoxanthine Phosphoribosyltransferase