Large-scale comparative mapping of the MHC class I region of predominant haplotypes in Japanese.

In order to further our understanding of major histocompatibility complex (MHC) class I gene organization, we began a comparative analysis of the large scale organization of the class I region in diverse haplotypes. For these studies, the MHC in healthy Japanese donors who have the predominant MHC haplotypes and/or HLA-A or -B alleles was examined by pulsed field gel electrophoresis and Southern analysis using probes spanning the class I region. Hybridization with probes from the HLA-A to HLA-G region revealed that individuals expressing HLA-A30, -A31, or -A33 have an approximately 70 kilobase (kb) insertion near the HLA-A gene as compared with haplotypes containing the HLA-A11 or -A26 allele. Conversely, HLA-A24-containing haplotypes appear to have an approximately 50 kb deletion from the same region. Further, it appears that chromosomes carrying closely related alleles are similar to each other in this region, consistent with their presumed evolutionary relationship. While little is known about the gene content between the HLA-A and HLA-G region, it will be interesting to examine the prospect that functional genes do in fact reside within the inserted or deleted portions, thereby raising the possibility that distinct functional differences are conferred by different haplotypes. Overall, the results reported here should contribute to furthering our understanding of the association between diseases and HLA as well as provide new insights into the evolution of the MHC.