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首页> 外文期刊>Zoological Science >Loss of Genetic Diversity at an MHC Locus in the Endangered Tokyo Bitterling Tanakia tanago (Teleostei: Cyprinidae)
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Loss of Genetic Diversity at an MHC Locus in the Endangered Tokyo Bitterling Tanakia tanago (Teleostei: Cyprinidae)

机译：濒临灭绝的东京苦涩的Tanakia tanago（Teleostei：鲤科）的MHC基因座的遗传多样性丧失。

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摘要

Genetic diversity at a major histocompatibility complex (MHC) class II B gene was examined for two wild and three captive populations of the endangered Tokyo bitterling Tanakia tanago. A specific primer set was first developed to amplify the MHC II B exon 2 locus. Using single strand conformation polymorphism (SSCP) and sequencing analysis, 16 DAB3 alleles were detected with 56 nucleotide substitutions in the 276-bp region. In the putative antigen-binding sites of exon 2, the rate of nonsynonymous substitutions was significantly higher than that of synonymous substitutions (d(N)/d(S) = 2.79), indicating positive selection on the retention of polymorphism. The population from the Handa Natural Habitat Conservation Area and that from the Tone River system exhibited low variation (one and three alleles, respectively), whereas the captive population that originated from a mix of three distinct populations had the highest amounts of variation (14 alleles). The levels of heterozygosity at the MHC varied considerably among populations and showed significant correlations with those at putative neutral microsatellite markers, suggesting that genetic drift following a bottleneck has affected MHC variability in some populations. Comparisons between endangered and non-endangered fish species in previous reports and the present results indicate that the number of MHC alleles per population is on average 70% lower in endangered species than non-endangered species. Considering the functional consequence of this locus, attention should be paid to captive and wild endangered fish populations in terms of further loss of MHC alleles.
机译：研究了濒临灭绝的东京苦涩的东京七叶树（Tanakia tanago）的两个野生种群和三个圈养种群的主要组织相容性复合体（MHC）II B类基因的遗传多样性。首先开发了特异性引物组以扩增MHC II B外显子2基因座。使用单链构象多态性（SSCP）和测序分析，检测到16个DAB3等位基因，在276bp区域中有56个核苷酸取代。在外显子2的推定抗原结合位点中，非同义替换的比率显着高于同义替换的比率（d（N）/ d（S）= 2.79），表明在保留多态性方面有积极的选择。半田自然栖息地保护区和通河河系的种群变异较小（分别为一个和三个等位基因），而由三个不同种群混合而成的圈养种群变异量最大（14个等位基因） ）。在人群中，MHC的杂合度水平差异很大，并且与推定的中性微卫星标记的杂合度水平显着相关，这表明瓶颈后的遗传漂移影响了某些人群的MHC变异性。在以前的报告中，濒危鱼类和非濒危鱼类之间的比较和目前的结果表明，濒危物种中每个种群的MHC等位基因数量平均比非濒危物种低70％。考虑到该基因座的功能后果，应进一步关注MHC等位基因的进一步丧失，以应对圈养和野生濒危鱼类种群。

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