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.
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.
Schmidt
M
M
Murdoch Institute, Royal Children's Hospital, Parkville, Melbourne, Australia.
Du Sart
D
D
Kalitsis
P
P
Fraser
N
N
Leversha
M
M
Voullaire
L
L
Foster
D
D
Davies
J
J
Hills
L
L
Petrovic
V
V
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
D015342:DNA Probes; D005819:Genetic Markers