Transmembrane Protein 185A (TMEM185A)

The FAM11A gene originates from the CpG island of the fragile site FRAXF and contains the FRAXF CGG repeat in its 5-prime untranslated region. Expansion of the FRAXF CGG repeat and consequent methylation of the CpG island results in transcriptional silencing of the FAM11A gene.

In 5 individuals who exhibited fragile sites in distal Xq, a 5-kb EcoRI fragment derived from a cosmid coincident with the cytogenetic anomaly detected expanded, methylated, and unstable sequences; these individuals had normal repeat lengths at both FRAXA and FRAXE. PCR and sequence analysis of chromosomes from the general population indicated that the repeat is polymorphic (6 to 29 triplets) and is stable upon transmission.