An endemic frog harbors multiple expression loci with different patterns of variation in the MHC class II B gene.
An endemic frog harbors multiple expression loci with different patterns of variation in the MHC class II B gene.
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DOI：
10.1002/jez.b.22525
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发表时间：
2013-12
期刊：
影响因子：
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通讯作者：
Yilin Shu;Pei Hong;Yi‐Wen Yang;Hailong Wu
中科院分区：
文献类型：
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作者：
Yilin Shu;Pei Hong;Yi‐Wen Yang;Hailong Wu
中国凹耳蛙（Odorrana tormota）是第一个被证明能够产生和感知超声波频率的非哺乳类脊椎动物。由于人类活动造成的栖息地退化，目前该物种处于灭绝的边缘。在这项研究中，我们证明，该物种窝藏至少四个表达的主要组织相容性复合体（MHC）II类B位点。从基因组DNA中分离出四个不同的内含子2序列和三个内含子1序列。此外，从三个cDNA样品中回收了八个等位基因，其中五个可以分配到三个单独的基因座，而其余三个等位基因的基因座同一性无法确定。根据内含子序列，设计了Odto-A、Odto-B和Odto-C的基因座特异性引物。其中，Odto-B在黄山群体（n = 32）中呈单态分布，Odto-C在部分个体中仅获得3个相似序列，表现出低等位多态性。与此相反，Odto-A表现出较高的等位基因多样性与20个独特的等位基因从人口中恢复。未检测到等位基因间或等位基因内重组。然而，在推定的抗原结合位点（ABS）中检测到10个正选择的氨基酸残基和过量的非同义替换，这些结果结合跨物种进化表明，某种形式的平衡选择，保持较高的等位基因多态性的基因座。我们的研究结果表明，尽管受到人口严重减少的影响，O。与其他两栖动物相比，在MHC II类B基因座的等位基因数量和多样性方面，tormota表现出高多态性。
The Chinese concave-eared torrent frog (Odorrana tormota) was the first non-mammalian vertebrate demonstrated to both produce and perceive ultrasonic frequencies. Due to habitat degradation caused by human activity, currently, the species is at the edge of extinction. In this study, we demonstrated that the species harbors at least four expressed major histocompatibility complex (MHC) class II B loci. Four distinct intron 2 sequences and three intron 1 sequences were isolated from genomic DNA. Additionally, eight alleles were recovered from three cDNA samples, of which five could be assigned to three individual loci while the locus identity of the remaining three alleles could not be determined. Based on the intron sequences, locus-specific primers were designed for Odto-A, Odto-B, and Odto-C. Of these loci, Odto-B was monomorphic in Huangshan population (n = 32), and Odto-C displayed low allelic polymorphism with only three similar sequences obtained from partial individuals. In contrast, Odto-A showed high allelic diversity with 20 unique alleles recovered from the population. No inter- or intra-allele recombination was detected. However, 10 positive selected amino acid residues and an excess of non-synonymous substitutions were detected in the putative antigen binding sites (ABS), these results combined with trans-species evolution suggested some form of balancing selection that maintained higher allelic polymorphism for the locus. Our findings demonstrate that despite the effects of a severely shrinking population, O. tormota exhibits high polymorphism compared to other amphibians, both in terms of the allele number and diversity across the MHC class II B loci.