EXPANSION AND CONTRACTION OF RHESUS MACAQUE DRB REGIONS BY DUPLICATION AND DELETION

Previous sequence analysis of the rhesus macaque MHC (MhcMamu) class I I DRB region has allowed the detection of at least 34 alleles belongin g to different lineages. In this communication, 36 new Mamu-DRB allele s are reported. The gene content of the DRB region has been determined for several homozygous animals of consanguineous origin. As in other primates, the number of DRB genes present per haplotype is not constan t, varying from two to six genes in rhesus macaques. Six major groups of DRB haplotypes have been defined in our rhesus macaque colony. Two haplotype groups were found to carry, as well as other Mamu-DRB genes, two genes that cluster into distinct HLA-DRB1 lineages. In one of the se two groups, a haplotype harbors another two sets of DRB alleles tha t belong to the Mhc-DRB6 and -DRBW6 lineages, respectively. Such a ha plotype was probably generated by duplication, and our data suggest th at after this particular expansion of the DR region, one of the duplic ated Mamu-DRB6 alleles was the target of an Alu insertion. Although ce rtain transspecies allelic lineages are evolutionarily stable, and hav e been conserved for at least 36 million years, the rhesus macaque cla ss II haplotypes differ significantly from those found in humans, chim panzees, and gorillas. Mhc-DRB regions are therefore comparatively uns table over longer evolutionary time spans, with regard to both the num ber of genes and the gene content, and must have been subjected to exp ansion and contraction.