A point mutation in the FMR-1 gene associated with fragile X mental retardation.

Department of Medical Genetics, University of Antwerp-UIA, Belgium.
Nature Genetics (Impact Factor: 29.65). 02/1993; 3(1):31-5. DOI: 10.1038/ng0193-31
Source: PubMed

ABSTRACT The vast majority of patients with fragile X syndrome show a folate-sensitive fragile site at Xq27.3 (FRAXA) at the cytogenetic level, and both amplification of the (CGG)n repeat and hypermethylation of the CpG island in the 5' fragile X gene (FMR-1) at the molecular level. We have studied the FMR-1 gene of a patient with the fragile X phenotype but without cytogenetic expression of FRAXA, a (CGG)n repeat of normal length and an unmethylated CpG island. We find a single point mutation in FMR-1 resulting in an lle367Asn substitution. This de novo mutation is absent in the patient's family and in 130 control X chromosomes, suggesting that the mutation causes the clinical abnormalities. Our results suggest that mutations in FMR-1 are directly responsible for fragile X syndrome, irrespective of possible secondary effects caused by FRAXA.

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Aug 11, 2014