Akiyama Takuya, Kohyama Tetsuo I, Nishida Chizuko, Onuma Manabu, Momose Kunikazu, Masuda Ryuichi
Department of Natural History Sciences, Graduate School of Science, Hokkaido University, N10W8, Kita-ku, Sapporo, Hokkaido, 060-0810, Japan.
Department of Biological Sciences, Faculty of Science, Hokkaido University, N10W8, Kita-ku, Sapporo, Hokkaido, 060-0810, Japan.
Immunogenetics. 2017 Jul;69(7):451-462. doi: 10.1007/s00251-017-0994-6. Epub 2017 May 14.
Populations that have drastically decreased in the past often have low genetic variation, which may increase the risk of extinction. The genes of major histocompatibility complex (MHC) play an important role in the adaptive immune response of jawed vertebrates. Maintenance of adaptive genetic diversity such as that of MHC genes is important for wildlife conservation. Here, we determined genotypes of exon 3 of MHC class IA genes (MHCIA) and exon 2 of MHC class IIB genes (MHCIIB) to evaluate genetic variation of the endangered red-crowned crane population on Hokkaido Island, Japan, which experienced severe population decline in the past. We identified 16 and 6 alleles of MHCIA and MHCIIB, respectively, from 152 individuals. We found evidence of a positive selection at the antigen-binding sites in MHCIA exon 3 and MHCIIB exon 2. The phylogenetic analyses indicated evidence of trans-species polymorphism among the crane MHC genes. The genetic variability in both classes of MHC genes at the population level was low. No geographic structure was found based on the genetic diversity of microsatellite and MHC genes. Our study provides useful data for the optimal management of the red-crowned crane population in Hokkaido and can contribute to future studies on MHC genes of the continental populations of the red-crowned crane and other crane species.
过去数量急剧减少的种群通常遗传变异较低，这可能会增加灭绝风险。主要组织相容性复合体（MHC）的基因在有颌脊椎动物的适应性免疫反应中发挥着重要作用。维持诸如MHC基因这样的适应性遗传多样性对于野生动物保护至关重要。在此，我们测定了MHC I A类基因（MHCIA）外显子3和MHC II B类基因（MHCIIB）外显子2的基因型，以评估日本北海道岛濒危丹顶鹤种群的遗传变异，该种群在过去经历了严重的数量下降。我们从152个个体中分别鉴定出MHCIA和MHCIIB的16个和6个等位基因。我们发现MHCIA外显子3和MHCIIB外显子2的抗原结合位点存在正选择的证据。系统发育分析表明鹤类MHC基因间存在跨物种多态性的证据。种群水平上两类MHC基因的遗传变异性都很低。基于微卫星和MHC基因的遗传多样性未发现地理结构。我们的研究为北海道丹顶鹤种群的优化管理提供了有用数据，并可为未来关于丹顶鹤大陆种群及其他鹤类物种MHC基因的研究做出贡献。
