Physical mapping and evolution of the centromeric class I gene-containing region of the rat MHC

Abstract

We physically mapped the centromeric part of the BN rat MHC (RT1(n) haplotype) in a contig of overlapping P1-derived artificial chromosome (PAC) clones encompassing about 300 kb. The following genes were identified and ordered as: (Syngap, Hset, Daxx, Bing1)-Tapbp-Rg12-Ke2-Bing4-B3galt4-Rps18-Sacm21-RT1-A1-RT1-A2-RT1-A3-Ring1-Ring2-Ke4-Rxrb-Col11a2-RT1-Hb-Ring3-RT1-DMb. Thus, in contrast to other RT1 haplotypes, RT1(n) contains three class I genes, RT1-A1, RT1-A2, and RT1-A3, mapping between the Sacm21 and Ring1 genes. Comparisons of the sequences flanking the Sacm21 and Ring1 genes in rat, human, and mouse suggest that the class I gene-containing region was inserted between these genes in rat and mouse at a similar position. Thus, this insertion is likely to have occurred in a common ancestor of these rodents, although the presence of a site particularly permissive for insertions cannot be excluded.