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

Nature Genetics volume 4, pages 143146 (1993) | Download Citation

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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.

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Author information

Affiliations

  1. Department of Medical Genetics, University of Antwerp - UIA, Universiteitsplein 1, 2610, Antwerp, Belgium

    • Edwin Reyniers
    • , Lieve Vits
    • , Kristel De Boulle
    • , Bernadette Van Roy
    • , Desirée Van Velzen
    •  & Patrick J. Willems
  2. Department of Clinical Genetics, Erasmus University, Dr. Molewaterplein 50, 3153 DR Rotterdam, The Netherlands

    • Esther de Graaff
    • , Annemieke J.M.H. Verkerk
    •  & Ben Oostra
  3. Psychiatric Hospital Sint-Amadeus, Deurnestraat 252, 2640 Mortsel, Belgium

    • Hugo Z.J. Jorens
  4. Department of Psychiatry, County of San Mateo, 227 West 37th Avenue, California 94403, USA

    • John K. Darby

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DOI

https://doi.org/10.1038/ng0693-143

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