Isolation and characterization of major histocompatibility complex class II B genes in cranes
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In this study, we isolated and characterized the major histocompatibility complex (MHC) class II B genes in cranes. Genomic sequences spanning exons 1 to 4 were amplified and determined in 13 crane species and three other species closely related to cranes. In all, 55 unique sequences were identified, and at least two polymorphic MHC class II B loci were found in most species. An analysis of sequence polymorphisms showed the signature of positive selection and recombination. A phylogenetic reconstruction based on exon 2 sequences indicated that trans-species polymorphism has persisted for at least 10 million years, whereas phylogenetic analyses of the sequences flanking exon 2 revealed a pattern of concerted evolution. These results suggest that both balancing selection and recombination play important roles in the crane MHC evolution.
KeywordsAves Concerted evolution Gruiformes MHC Trans-species polymorphism
We thank Tama Zoological Park, Hirakawa Zoological Park, Fukuoka Municipal Zoological and Botanical Gardens, Maruyama Zoo, Osaka Municipal Tennoji Zoological Gardens, Sayama Chikozan Park Children’s Zoo, Kushiro Zoo, Inokashira Park Zoo, Ueno Zoological Gardens, Nogeyama Zoological Gardens of Yokohama, and Chiba Zoological Park for providing samples, and Dr. Matthew Dick and Masahito T. Kimura for invaluable comments and English editing of the manuscript. This study was supported in part by a grant (D-1201) from the Environment Research and Technology Development Fund of the Ministry of the Environment, Japan, and a research grant from the Akiyama Life Science Foundation.
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