title: The MHC of the duck (Anas platyrhynchos) contains five differentially expressed class I genes.
abstract: MHC class I proteins mediate a variety of functions in antiviral defense. In humans and mice, three MHC class I loci each contribute one or two alleles and each can present a wide variety of peptide Ags. In contrast, many lower vertebrates appear to use a single MHC class I locus. Previously we showed that a single locus was predominantly expressed in the mallard duck (Anas platyrhynchos) and that locus was adjacent to the polymorphic transporter for the Ag-processing (TAP2) gene. Characterization of a genomic clone from the same duck now allows us to compare genes to account for their differential expression. The clone carried five MHC class I genes and the TAP genes in the following gene order: TAP1, TAP2, UAA, UBA, UCA, UDA, and UEA. We designated the predominantly expressed gene UAA. Transcripts corresponding to the UDA locus were expressed at a low level. No transcripts were found for three loci, UBA, UCA, and UEA. UBA had a deletion within the promoter sequences. UCA carried a stop codon in-frame. UEA did not have a polyadenylation signal sequence. All sequences differed primarily in peptide-binding pockets and otherwise had the hallmarks of classical MHC class I alleles. Despite the presence of additional genes in the genome, the duck expresses predominantly one MHC class I gene. The limitation to one expressed MHC class I gene may have functional consequences for the ability of ducks to eliminate viral pathogens, such as influenza.
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, Canada.
authors.forename: Debra A
authors.initials: DA
authors.lastname: Moon
authors.forename: Simona M
authors.initials: SM
authors.lastname: Veniamin
authors.forename: Julie A
authors.initials: JA
authors.lastname: Parks-Dely
authors.forename: Katharine E
authors.initials: KE
authors.lastname: Magor
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002645:Chickens; D017124:Conserved Sequence; D018076:DNA, Complementary / Q000235:genetics; D004372:Ducks / Q000235:genetics* / Q000276:immunology*; D019143:Evolution, Molecular; D020440:Gene Duplication; D015870:Gene Expression; D005805:Genes, MHC Class I; D014644:Genetic Variation; D015395:Histocompatibility Antigens Class I / Q000235:genetics; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D010802:Phylogeny; D011401:Promoter Regions, Genetic; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D013045:Species Specificity
chemical_list: D018076:DNA, Complementary; D015395:Histocompatibility Antigens Class I