NORMAL PHENOTYPE IN 2 BROTHERS WITH A FULL FMR1 MUTATION

HJM SMEETS, APT SMITS, CE VERHEIJ, JPG THEELEN, R WILLEMSEN, [No Value] VANDEBURGT, AT HOOGEVEEN, JC Oosterwijk, BA OOSTRA

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Abstract

The fragile X syndrome is associated with an expanding CGG repeat in the 5' untranslated region of the first exon of the FMR1 gene. Subsequent methylation of the promoter region inhibits expression of the FMR1 gene. In two clinically normal brothers large, expanded CGG repeats and cytogenetically visible fragile sites were found. The FMR1 promoter was unmethylated and both RNA and protein could be detected. This indicates that inactivation of the FMR1 gene and not repeat expansion itself results in the fragile X phenotype. We conclude that repeat expansion does not necessarily induce methylation and that methylation is no absolute requirement for the induction of fragile sites.

Original languageEnglish
Pages (from-to)2103-2108
Number of pages6
JournalHuman Molecular Genetics
Volume4
Issue number11
Publication statusPublished - Nov-1995

Keywords

  • FRAGILE-X-SYNDROME
  • MYOTONIC-DYSTROPHY
  • MENTAL-RETARDATION
  • METHYLATION ANALYSIS
  • PRENATAL-DIAGNOSIS
  • MESSENGER-RNA
  • CPG ISLAND
  • GENE
  • REPEAT
  • PROTEIN

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