Differential expression of fragile site Xq27 in cultured fibroblasts from hemizygotes and heterozygotes and its implications for prenatal diagnosis.
Expression of the fragile site Xq27 (fraXq27) was studied in metaphases derived from fibroblasts of 8 hemizygotes and 2 heterozygotes, cultured in 2 different media containing reduced concentrations of folic acid. The proportion of fra(X) (q27)-positive metaphases ranged from 1.0 to 14%, which is considerably lower than in lymphocyte cultures from the same individual, but differed with respect to the culture medium used. Four hemizygotes showed a higher proportion of fra(X)-positive cells in medium 199 than in methotrexate-exposed cultures. No fra(X)-negative cultures were observed when the folic acid inhibitor methotrexate was added to medium 199. Thus, in all 10 individuals carrying the fra(X), the fragile site could be detected in fibroblast cultures. We conclude that the expression of fra(X) (q27) in cultured fibroblasts should be studied using at least 2 types of culture conditions, because familial, i.e. genetic differences may influence the expression of this fragile site in fibroblasts. The implications for prenatal diagnosis are discussed on the basis of investigations in 15 pregnancies at risk for the trait.
D000293:Adolescent; D000328:Adult; D002478:Cells, Cultured; D002648:Child; D002675:Child, Preschool; D003470:Culture Media; D005260:Female; D005347:Fibroblasts / Q000648:ultrastructure*; D005600:Fragile X Syndrome / Q000175:diagnosis* / Q000235:genetics; D006579:Heterozygote; D006801:Humans; D008297:Male; D008727:Methotrexate / Q000494:pharmacology; D011247:Pregnancy; D011296:Prenatal Diagnosis; D012729:Sex Chromosome Aberrations / Q000175:diagnosis*
D003470:Culture Media; D008727:Methotrexate