title: Sequence variability at three MHC loci of finless porpoises (Neophocaena phocaenoides).
abstract: Major histocompatibility complex (MHC) class II DQB and DRA genes and class I gene of finless porpoises (Neophocaena phocaenoides) were investigated by single-strand conformation polymorphism and sequence analysis. The DRA, DQB, and MHC-I loci each contained 5, 14, and 34 unique sequences, respectively, and considerable sequence variation was found at the MHC-I and DQB loci. Gene duplication was manifested as three to five distinct sequences at each of the DQB and MHC-I loci from some individuals, and these sequences at each of the two loci separately clustered into four groups (cluster A, B, C, and D) based on the phylogenetic trees. Phylogenetic reconstruction revealed a trans-species pattern of evolution. Relatively high rates of non-synonymous (dN) vs synonymous (dS) substitution in the peptide-binding region (PBR) suggested balancing selection for maintaining polymorphisms at the MHC-I and DQB loci. In contrast, one single locus with little sequence variation was detected in the DRA gene, and no non-synonymous substitutions in the PBR indicated no balancing selection on this gene.
authors.affiliation: Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, 122 Ninghai Road, Nanjing 210097, China.
authors.forename: Shixia
authors.initials: S
authors.lastname: Xu
authors.forename: Peng
authors.initials: P
authors.lastname: Sun
authors.forename: Kaiya
authors.initials: K
authors.lastname: Zhou
authors.forename: Guang
authors.initials: G
authors.lastname: Yang
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D005819:Genetic Markers / Q000235:genetics / Q000276:immunology; D014644:Genetic Variation / Q000276:immunology*; D015395:Histocompatibility Antigens Class I / Q000235:genetics*; D000949:Histocompatibility Antigens Class II / Q000235:genetics*; D008969:Molecular Sequence Data; D010802:Phylogeny; D018807:Polymorphism, Single-Stranded Conformational; D019576:Porpoises / Q000235:genetics* / Q000276:immunology*
chemical_list: D005819:Genetic Markers; D015395:Histocompatibility Antigens Class I; D000949:Histocompatibility Antigens Class II