The fragile X syndrome of mental retardation is related to the number of trinucleotide CGG repeats at the 5'-untranslated region of the FMRI gene located on the X-chromosome.
We have studied X-chromosomes from 649 unaffected Chinese subjects and 324 patients with mild mental retardation.
All study subjects were unrelated.
The CGG repeat number was analysed by electrophoresis of a polymerase chain reaction followed by gel transfer and hybridisation with a 32P-labeled (CCG) 5 probe.
The DNA samples having detectable CGG expansion were further analysed by Southern blot analysis with probe StB12.3 after restriction digestion by EcoR I and Eag I. For the unaffected Chinese subjects, a different distribution pattern of CGG allele size from Caucasians was observed.
It was a bimodal pattern and the CGG repeat number ranged from 19 to 54.
The most common CGG repeat allele was 29 compared with 30 in Caucasians.
The second mode appeared at 36 repeats.
There was mild statistical difference in the repeat patterns between the mentally retarded patients and unaffected subjects, although the essential features were similar.
Among the mentally retarded patients, one male had an unmethylated full mutation and one female had a full mutation.
The fragile X prevalence was 0.6%, which is lower than two previous studies in Chinese mentally retarded patients utilising cytogenetic analysis. (...)
Mots-clés Pascal : X fragile syndrome, Homme, Séquence répétée, Trinucléotide, Chinois, Prévalence, Hong Kong, Chine, Asie, Epidémiologie, Fragilité chromosomique
Mots-clés Pascal anglais : Fragile X syndrome, Human, Repeated sequence, Trinucleotide, Chinese, Prevalence, Hong Kong, China, Asia, Epidemiology, Chromosome fragility
Notice produite par :
Inist-CNRS - Institut de l'Information Scientifique et Technique
Cote : 99-0330119
Code Inist : 002B23C. Création : 16/11/1999.