The protein encoded by this gene is predicted to be a transmembrane protein. This gene is best known for localizing to the CpG island of the fragile site FRAXF. The 5' untranslated region of this gene contains a CGG trinucleotide repeat sequence that normally consists of 7-40 tandem CGG repeats but which can expand to greater than 300 repeats. Methylation of the CpG island leads to transcriptional silencing of this gene, but neither the silencing nor an expanded repeat region appear to manifest itself in a clear phenotypic manner. Alternative splicing results in multiple transcript variants. A pseudogene of this gene has been defined on the X chromosome. [provided by RefSeq, Aug 2013],