title: Genetic variation of the MHC class II DRB genes in the Japanese weasel, Mustela itatsi, endemic to Japan, compared with the Siberian weasel, Mustela sibirica.
abstract: Major histocompatibility complex (MHC) genes encode proteins that play a critical role in vertebrate immune system and are highly polymorphic. To further understand the molecular evolution of the MHC genes, we compared MHC class II DRB genes between the Japanese weasel (Mustela itatsi), a species endemic to Japan, and the Siberian weasel (Mustela sibirica), a closely related species on the continent. We sequenced a 242-bp region of DRB exon 2, which encodes antigen-binding sites (ABS), and found 24 alleles from 31 M. itatsi individuals and 17 alleles from 21 M. sibirica individuals, including broadly distributed, species-specific and/or geographically restricted alleles. Our results suggest that pathogen-driven balancing selection have acted to maintain the diversity in the DRB genes. For predicted ABS, nonsynonymous substitutions exceeded synonymous substitutions, also indicating positive selection, which was not seen at non-ABS. In a Bayesian phylogenetic tree, two M. sibirica DRB alleles were basal to the rest of the sequences from mustelid species and may represent ancestral alleles. Trans-species polymorphism was evident between many mustelid DRB alleles, especially between M. itatsi and M. sibirica. These two Mustela species divided about 1.7 million years ago, but still share many MHC alleles, indicative of their close phylogenetic relationship.
authors.affiliation: Department of Biological Sciences, Faculty of Science, Hokkaido University, Sapporo, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Nishita
authors.affiliation: Zoological Institute, Russian Academy of Sciences, Moscow, Russia.
authors.forename: A V
authors.initials: AV
authors.lastname: Abramov
authors.affiliation: Institute of Plant & Animal Ecology, Russian Academy of Sciences, Moscow, Russia.
authors.forename: P A
authors.initials: PA
authors.lastname: Kosintsev
authors.affiliation: Department of Life Science, Tunghai University, Taichung, Taiwan.
authors.forename: L-K
authors.initials: LK
authors.lastname: Lin
authors.affiliation: Seian University of Art and Design, Otsu, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Watanabe
authors.affiliation: Forest Ecology Laboratory, Department of Forest Science, Faculty of Regional Environmental Science, Tokyo University of Agriculture, Fuchu, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Yamazaki
authors.affiliation: Department of Ecoregion Science, Faculty of Agriculture, Tokyo University of Agriculture and Technology, Fuchu, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Kaneko
authors.affiliation: Department of Biological Sciences, Faculty of Science, Hokkaido University, Sapporo, Japan.
authors.forename: R
authors.initials: R
authors.lastname: Masuda
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D005091:Exons / Q000235:genetics; D005787:Gene Frequency; D005802:Genes, MHC Class II; D014644:Genetic Variation; D008969:Molecular Sequence Data; D045969:Mustelidae / Q000235:genetics* / Q000276:immunology; D010802:Phylogeny; D011544:Pseudogenes / Q000235:genetics; D012641:Selection, Genetic; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017385:Sequence Homology; D013045:Species Specificity
keywords: DRB gene; balancing selection; conservation; major histocompatibility complex; molecular evolution; mustelidae; trans-species polymorphism