Genetic Diversity of the MHC Class-II DQA Gene in Brown Bears (Ursus arctos) on Hokkaido, Northern Japan
Genetic Diversity of the MHC Class-II DQA Gene in Brown Bears (Ursus arctos) on Hokkaido, Northern Japan
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DOI：
10.2108/zsj.26.530
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发表时间：
2009-08-01
影响因子：
0.9
通讯作者：
Masuda, Ryuichi
中科院分区：
文献类型：
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作者：
Goda, Naoki;Mano, Tsutomu;Masuda, Ryuichi
为了研究日本北部北海道棕熊(Ursus Arctos)群体中主要组织相容性复合体(MHC)基因的遗传多样性，对32只棕熊的MHC-II类DQA基因的外显子2和内含子2部分进行了克隆和测序。根据哺乳动物MHC命名委员会制定的严格的等位基因鉴定标准，共鉴定出4种DQA类型(Urar-DQA*01至Urar-DQA*04)。然而，在这四个基因中，Urar-DQA*04有一个12bp的缺失，在cDNA分析中没有检测到，这表明这是一个位于由基因复制产生的不同座位上的假基因。表达的其他3个DQA等位基因的核苷酸序列非常相似，表明北海道棕熊种群的DQA变异低于其他哺乳动物。我们将这种低遗传多样性归因于(1)可能的平衡选择的一些有限的影响；(2)北海道棕熊种群从欧亚大陆迁徙和隔离后的瓶颈和近亲繁殖；(3)在北海道棕熊种群中，DQA的进化速度比其他MHC基因慢得多。
To investigate genetic diversity of a major histocompatibility complex (MHC) gene in the brown bear (Ursus arctos) population on Hokkaido Island, northern Japan, we cloned and sequenced parts of exon 2 and intron 2 of the MHC class-II DQA gene from 32 brown bears. According to strict criteria for allele identification established by mammalian MHC nomenclature committees, four DQA types (Urar-DQA*01 to Urar-DQA*04) were identified. Of the four, however, Urar-DQA*04 had a 12-bp deletion not detected in a cDNA analysis, indicating that this is a pseudogene at a distinct locus generated by gene duplication. The nucleotide sequences of the other three DQA alleles, which were expressed (because detected from cDNA), were very similar, indicating lower DQA variation in the Hokkaido brown bear population than in other mammals. We attribute this low genetic diversity to (1) some limited effect of possible balancing selection; (2) bottlenecks and inbreeding after migration and isolation of the Hokkaido brown bear population from the Eurasian Continent; (3) a much slower evolutionary rate in DQA than in other MHC genes in the Hokkaido brown bear population.