title: Characterization and locus-specific typing of MHC class I genes in the red-billed gull (Larus scopulinus) provides evidence for major, minor, and nonclassical loci.
abstract: A major challenge facing studies of major histocompatibility complex (MHC) evolution in birds is the difficulty in genotyping alleles at individual loci, and the consequent inability to investigate sequence variation and selection pressures for each gene. In this study, four MHC class I loci were isolated from the red-billed gull (Larus scopulinus), representing both the first characterized MHCI genes within Charadriiformes (shorebirds, gulls, and allies) and the first full-length MHCI sequences described outside Galloanserae (gamebirds + waterfowl). Complete multilocus genotypes were obtained for 470 individuals using a combination of reference-strand conformation analysis and direct sequencing of gene-specific amplification products, and variation of peptide-binding region (PBR) exons was surveyed for all loci. Each gene is transcribed and has conserved sequence features characteristic of antigen-presenting MHCI molecules. However, higher allelic variation, a more even allele frequency distribution, and evidence of positive selection acting on a larger number of PBR residues suggest that only one locus (Lasc-UAA) functions as a major classical MHCI gene. Lasc-UBA, with more limited variation and PBR motifs that encompass a subset of Lasc-UAA diversity, was assigned a putative minor classical function, whereas the divergent and largely invariant binding-groove motifs of Lasc-UCA and -UDA are suggestive of nonclassical loci with specialized ligand-binding roles.
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, Canada. alison.cloutier@utoronto.ca
authors.forename: Alison
authors.initials: A
authors.lastname: Cloutier
authors.forename: James A
authors.initials: JA
authors.lastname: Mills
authors.forename: Allan J
authors.initials: AJ
authors.lastname: Baker
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D030161:Avian Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D046091:Charadriiformes / Q000235:genetics* / Q000276:immunology*; D017124:Conserved Sequence; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D019143:Evolution, Molecular; D005091:Exons; D005805:Genes, MHC Class I; D014644:Genetic Variation; D015395:Histocompatibility Antigens Class I / Q000737:chemistry / Q000235:genetics; D008285:Major Histocompatibility Complex; D008912:Minor Histocompatibility Loci; D008969:Molecular Sequence Data; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012641:Selection, Genetic; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid
chemical_list: D030161:Avian Proteins; D017931:DNA Primers; D018076:DNA, Complementary; D015395:Histocompatibility Antigens Class I