title: X chromosome inactivation in fibroblasts of mentally retarded female carriers of the fragile site Xq27.3: application of the probe M27 beta to evaluate X inactivation status.
abstract: Over 30% of female carriers of the fragile X [fra(X)] syndrome are clinically affected. A nonrandom X chromosome inactivation in these cases could be a plausible explanation. A review of previous studies addressing this question showed inconclusive results; thus, we analysed the X inactivation pattern in fibroblasts of 4 unrelated, mentally retarded fra(X) carriers with a high expression of the fragile site Xq27.3. Using Southern analysis with a highly polymorphic probe M27 beta that recognizes methylation differences between the active and inactive X chromosome we found a 50/50 inactivation pattern in 2 cases and skewed patterns in the other 2. As biased patterns were also observed in control females we conclude that at present no evidence exists for a nonrandom X chromosome inactivation in the fra(X) syndrome in females.
authors.affiliation: Murdoch Institute, Royal Children's Hospital, Parkville, Melbourne, Australia.
authors.forename: M
authors.initials: M
authors.lastname: Schmidt
authors.forename: D
authors.initials: D
authors.lastname: Du Sart
authors.forename: P
authors.initials: P
authors.lastname: Kalitsis
authors.forename: N
authors.initials: N
authors.lastname: Fraser
authors.forename: M
authors.initials: M
authors.lastname: Leversha
authors.forename: L
authors.initials: L
authors.lastname: Voullaire
authors.forename: D
authors.initials: D
authors.lastname: Foster
authors.forename: J
authors.initials: J
authors.lastname: Davies
authors.forename: L
authors.initials: L
authors.lastname: Hills
authors.forename: V
authors.initials: V
authors.lastname: Petrovic
mesh_terms: D015139:Blotting, Southern; D002478:Cells, Cultured; D015342:DNA Probes; D004303:Dosage Compensation, Genetic; D005260:Female; D005347:Fibroblasts / Q000473:pathology*; D005600:Fragile X Syndrome / Q000235:genetics* / Q000473:pathology; D005819:Genetic Markers; D006579:Heterozygote; D006801:Humans; D008607:Intellectual Disability / Q000235:genetics* / Q000473:pathology; D008297:Male; D008745:Methylation; D008957:Models, Genetic; D012150:Polymorphism, Restriction Fragment Length
chemical_list: D015342:DNA Probes; D005819:Genetic Markers