title: Co-duplication of olfactory receptor and MHC class I genes in the mouse major histocompatibility complex.
abstract: We report the 897 kb sequence of a cluster of olfactory receptor (OR) genes located at the distal end of the major histocompatibility complex (MHC) class I region on mouse chromosome 17 of strain 129/SvJ (H2bc). With additional information from the mouse genome draft sequence, we identified 59 OR loci (approximately 20% pseudogenes) in contrast to only 25 OR loci (approximately 50% pseudogenes) in the corresponding centromeric OR cluster that is part of the 'extended MHC class I region' on human chromosome 6. Comparative analysis leads to three major observations: (i) most of the OR subfamilies have evolved independently in the two species, expanding more in the mouse, and resulting in co-orthologs--subfamilies of highly similar paralogs that keep orthologous relationships with their human counterparts; (ii) three of the mouse OR subfamilies have no orthologs in humans; and (iii) MHC class I loci are interspersed in the OR cluster in mouse but not in human, and were subjected to co-duplication with OR genes. Screening of our sequence against the available sequences of other strains/haplotypes revealed that most of the OR loci are polymorphic and that the number of OR loci may vary among strains/haplotypes. Our findings that MHC-linked OR loci share duplication with MHC class I loci, have duplicated extensively and are polymorphic revives questions about potential reciprocal influences acting on the dynamics and evolution of the H2 region and the H2-linked OR loci.
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D002874:Chromosome Mapping; D002896:Chromosomes, Human, Pair 6; D033481:Chromosomes, Mammalian; D016384:Consensus Sequence; D019143:Evolution, Molecular; D020440:Gene Duplication; D005805:Genes, MHC Class I; D006239:Haplotypes; D000949:Histocompatibility Antigens Class II / Q000235:genetics; D006801:Humans; D008285:Major Histocompatibility Complex / Q000235:genetics*; D051379:Mice; D008815:Mice, Inbred Strains; D008969:Molecular Sequence Data; D009154:Mutation; D010802:Phylogeny; D011110:Polymorphism, Genetic; D017434:Protein Structure, Tertiary; D018035:Receptors, Odorant / Q000737:chemistry / Q000235:genetics*; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity
chemical_list: C416189:H2-M antigens; D000949:Histocompatibility Antigens Class II; D018035:Receptors, Odorant