Isolation of a GCC repeat showing expansion in FRAXF, a fragile site distal to FRAXA and FRAXE

Julia E. Parrish, Ben A. Oostra, Annemieke J.M.H. Verkerk, C. Sue Richards, James Reynolds, Aimee S. Spikes, Lisa G. Shaffer, David L. Nelson

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152 Scopus citations


Three folate-sensitive fragile sites, termed FRAXA, FRAXE and FRAXF, have been identified on the distal end of chromosome Xq. The first two contain expanded, hypermethylated and unstable CGG (or GCC) repeats within CpG islands. We now report the isolation of similar sequences responsible for the third fragile site, FRAXF. A 5-kilobase EcoRI fragment derived from a cosmid coincident with the cytogenetic anomaly detects expanded, methylated and unstable sequences in five individuals who exhibit fragile sites in distal Xq; these individuals have normal repeat lengths at both FRAXA and FRAXE. By sequence analysis, the expanded region contains a GCC repeat. PCR and sequence analysis of chromosomes from the general population indicates that the repeat is polymorphic (6 to 29 triplets), and is stable upon transmission.

Original languageEnglish (US)
Pages (from-to)229-235
Number of pages7
JournalNature genetics
Issue number3
StatePublished - Nov 1994
Externally publishedYes

ASJC Scopus subject areas

  • Genetics


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