title: Genetic variation of the MHC DQB locus in the finless porpoise (Neophocaena phocaenoides).
abstract: The Major Histocompatibility Complex (MHC) is a large multigene coding for glycoproteins that play a key role in the initiation of immune responses in vertebrates. The exon 2 region of the MHC DQB locus was analyzed using 160 finless porpoises from 5 populations in Japanese waters. The 5 populations were based on a previous mitochondrial DNA control region analysis, which showed distinct geographical separation. Eight DQB alleles were detected, and the geographical distribution of the alleles indicated that most of them are shared among the populations. Heterozygosity of the DQB alleles in each population ranged from 0.55 to 0.78, and for all 5 populations was 0.78. Low MHC variability is not a common feature in marine mammals, but the finless porpoise populations inhabiting coastal waters had a relatively high MHC heterozygosity. Balancing selection in the MHC DQB alleles of the finless porpoise was indicated by the higher rate of nonsynonymous than synonymous substitutions for PBR; however, an excess of hetrozygotes compared to expectation was not observed. This suggests that the MHC DQB locus in the finless porpoise may have been under balancing selection for a long evolutionary time period, and is influenced by genetic drift beyond the effect of balancing selection for short time periods in small local populations.
authors.affiliation: Graduate School of Social and Cultural Studies, Kyushu University, Fukuoka, Japan.
authors.forename: Kosuke
authors.initials: K
authors.lastname: Hayashi
authors.forename: Hideyoshi
authors.initials: H
authors.lastname: Yoshida
authors.forename: Shin
authors.initials: S
authors.lastname: Nishida
authors.forename: Mutsuo
authors.initials: M
authors.lastname: Goto
authors.forename: Luis A
authors.initials: LA
authors.lastname: Pastene
authors.forename: Naohisa
authors.initials: N
authors.lastname: Kanda
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Baba
authors.forename: Hiroko
authors.initials: H
authors.lastname: Koike
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D004272:DNA, Mitochondrial / Q000235:genetics; D040961:Genetic Drift; D014644:Genetic Variation; D005828:Genetics, Population; D005843:Geography; D007564:Japan; D008285:Major Histocompatibility Complex / Q000235:genetics*; D008969:Molecular Sequence Data; D010802:Phylogeny; D019576:Porpoises / Q000145:classification* / Q000235:genetics*; D016415:Sequence Alignment
chemical_list: D004272:DNA, Mitochondrial