On the frequency of the fragile X premutation in Thailand
- Institut fuer Humangenetik, Muenster (Germany); and others
Inactivation of the FMR1 gene is the molecular basis of the fraX syndrome, the most common heritable cause of neurodevelopemental disability; it occurs in around 1 in 1200 male and 1 in 2000 female births. Inactivation is caused by expansion of a CGG repeat in the 5{prime} untranslated portion of the FMR1 transcript. In regard to the CGG unstable triplets at the FMR1 locus, individuals can be divided into three groups according to the number of repeats: (i) about 6 to 50 are found in the general population, (ii) approximately 52 to 200 (= premutations) predispose female carriers to bearing children with fraX syndrome, (iii) sizes over 200 (full mutation) exceeding 1000 repeats in affected individuals. Prevalence figures for the FMR1 mutation in different populations are only rarely available, if at all. A few studies suggest frequencies for the premutation to be about 1 in 500 to 1000 X chromosomes. In the present investigation, 1075 X chromosomes from 644 genetically unrelated individuals from Thailand (431 females and 213 males) from families unselected for mental retardation or fragile X were analyzed by Southern blot analysis for the presence of FMR1 mutations. In addition, the size of small premutation allele was determined. In three females, triplet repeat numbers on their X chromosomes were 54/30, 30/130 and 24/120; two males were found with 54 and 52 repeats, respectively. Thus, among 1075 X chromosomes, two definitive premutations and three alleles with CGG repeat numbers of borderline premutation size have been detected.
- OSTI ID:
- 133960
- Report Number(s):
- CONF-941009-; ISSN 0002-9297; TRN: 95:005313-0694
- Journal Information:
- American Journal of Human Genetics, Vol. 55, Issue Suppl.3; Conference: 44. annual meeting of the American Society of Human Genetics, Montreal (Canada), 18-22 Oct 1994; Other Information: PBD: Sep 1994
- Country of Publication:
- United States
- Language:
- English
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