An autosomal homologue of the choroideremia gene colocalizes with the Usher syndrome type II locus on the distal part of chromosome 1q.

Employing the mouse homologue of the human choroideremia cDNA as a probe, we have identified a homologous human gene. The consensus cDNA of this gene, designated human choroideremia-like (hCHML) gene, encompasses an open reading frame of 1968 base pairs. The deduced polypeptide of hCHML displays several regions of homology to smg p25A GDI, a bovine protein known to regulate the GDP/GTP exchange of the GTP-binding protein smg p25A. hCHML is located at 1q31-qter, a chromosomal region which, by means of linkage analysis, was previously shown to carry a gene locus for Usher syndrome type II. The colocalization of hCHML and Usher syndrome type II, as well as the clinical similarities between choroideremia and Usher syndrome type II, make hCHML a candidate gene for this disorder.