A carboxy-terminal truncation of 99 amino acids resulting from a novel mutation (Arg555-->stop) in the CHM gene leads to choroideremia

The gene content of the MHC class I telomerically adjacent region, in linkage disequilibrium with hereditary hemochromatosis, has not been well characterized yet. In the present work, we established three bacterial clone contigs, including mainly P1-derived artificial chromosomes. These contigs cover 89% of the 1.2-Mb 6p-subtelomeric region encompassing locus D6S105. Terminal exon trapping was applied to selected clones from these contigs. Forty-six independent terminal exons were identified and mapped within the region, 2 of which matched perfectly to expressed sequence tags. These 3' exons are all expressed in human fetal brain but differentially expressed in four tissues and two cell lines. The high number of exons identified indicates that the high gene density observed in the MHC class I region extends to this telomerically adjacent region.