Mapping of the choroideremia-like (CHML) gene at 1q42-qter and mutation analysis in patients with Usher syndrome type II.

The human choroideremia-like (CHML) gene and a locus for Usher syndrome type 2 (USH2) were recently mapped to the 1q31-qter region employing physical mapping and genetic linkage studies, respectively. Using a human-rodent hybrid cell line, we could refine the assignment of CHML in this study to 1q42-qter. USH2 was shown to map to the same chromosomal segment as evidenced by the fact that D1S58, a polymorphic marker previously shown to be located proximal to the USH2 locus, was also assigned in the 1q42-qter segment. To investigate a possible role of the CHML gene in the pathogenesis of USH2, we investigated 10 Dutch and 9 Danish USH2 patients for point mutations in the open reading frame of the CHML gene. Employing polymerase chain reaction-single-strand conformation polymorphism analysis and direct sequencing, we found no disease-specific mutations. These results suggest that CHML is not involved in the pathogenesis of USH2.