title: Gene duplication and evidence for balancing selection acting on MHC class II DAA gene of the half-smooth tongue sole (Cynoglossus semilaevis).
abstract: Allelic polymorphism and evolution mechanism of major histocompatibility complex (MHC) genes has been investigated in many mammals, however, much less is known in teleost. In order to investigate the mechanisms creating and maintaining variability at the MHC class II DAA locus, we examined the polymorphism, gene duplication and balancing selection of MHC class II DAA gene of the half-smooth tongue sole (Cynoglossus semilaevis). We described 33 alleles in the C. semilaevis, recombination and gene duplication seems to play more important roles in the origin of new alleles. The rate of non-synonymous substitutions (d(N)) occurred at a significantly higher frequency than that of synonymous substitutions (d(S)) in peptide-binding region (PBR) and non-PBR, suggesting balancing selection for maintaining polymorphisms at the MHC II DAA locus. Many positive selection sites were found to act very intensively on antigen-binding sites. Our founding suggests a snapshot in an evolutionary process of MHC-DAA gene evolution of the C. semilaevis.
authors.affiliation: Laboratory for Marine Living Resources and Molecular Engineering, School of Marine Science, Zhejiang Ocean University, Zhoushan 316000, PR China.
authors.forename: Tian-jun
authors.initials: TJ
authors.lastname: Xu
authors.forename: Yue-na
authors.initials: YN
authors.lastname: Sun
authors.forename: Ri-xin
authors.initials: RX
authors.lastname: Wang
mesh_terms: D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D016000:Cluster Analysis; D017931:DNA Primers / Q000235:genetics; D019143:Evolution, Molecular; D005412:Flatfishes / Q000235:genetics*; D020440:Gene Duplication / Q000235:genetics*; D005802:Genes, MHC Class II / Q000235:genetics*; D008969:Molecular Sequence Data; D010802:Phylogeny; D011110:Polymorphism, Genetic; D012641:Selection, Genetic; D017422:Sequence Analysis, DNA
chemical_list: D017931:DNA Primers