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Nat Genet. 1993 Jun;4(2):143-6.

The full mutation in the FMR-1 gene of male fragile X patients is absent in their sperm.

Author information

1
Department of Medical Genetics, University of Antwerp-ULA, Belgium.

Abstract

Fragile X syndrome is characterized at the molecular level by amplification of a (CGG)n repeat and hypermethylation of a CpG island preceeding the open reading frame of the fragile X gene (FMR-1) located in Xq27.3. Anticipation in this syndrome is associated with progressive amplification of the (CGG)n repeat from a premutation to a full mutation through consecutive generations. Remarkably, expansion of the premutation to the full mutation is strictly maternal. To clarify this parental influence we studied FMR-1 in sperm of four male fragile X patients. This showed that only the premutation was present in their sperm, although they had a full mutation in peripheral lymphocytes. This might suggest that expansion of the premutation to the full mutation in FMR-1 does not occur in meiosis but in a postzygotic stage.

PMID:
8348152
DOI:
10.1038/ng0693-143
[Indexed for MEDLINE]

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