HLA class II linkage disequilibrium and haplotype evolution in the Cayapa Indians of Ecuador.
HLA class II linkage disequilibrium and haplotype evolution in the Cayapa Indians of Ecuador.
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DOI：
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发表时间：
1995-08
影响因子：
9.8
通讯作者：
Elizabeth A. Trachtenberg;Henry A. Erlich;Olga Rickards;G. Destefano;W. Klitz
中科院分区：
文献类型：
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作者：
Elizabeth A. Trachtenberg;Henry A. Erlich;Olga Rickards;G. Destefano;W. Klitz
对厄瓜多尔卡亚帕印第安人样本中的 HLA II 类基因座进行基于 DNA 的分型揭示了几条证据，表明选择作用维持了 II 类区域现有的多态性水平并使其多样化。正如在其他美洲原住民群体中所注意到的那样，DRB1、DQA1、DQB1 和 DPB1 基因座的总体多态性水平相对于其他人群中发现的水平有所降低。尽管如此，四个基因座中每个基因座的等位基因频率分布的相对均匀性表明平衡选择在维持多态性中的作用。特别是 DQA1 和 DQB1 基因座与中性模型的偏离接近最大，这表明在这些情况下平衡选择特别强。几种新的 DQA1-DQB1 单倍型和新 DRB1 等位基因的发现表明，有利于 II 类等位基因和单倍型多样化的进化趋势。在没有其他力量（例如选择）的情况下，着丝粒 DPB1 基因座和其他 II 类基因座之间的重组间隔将减少该区域的不平衡。然而，几乎所有常见等位基因都被发现是强烈不平衡的 DR-DP 单倍型的一部分，这与最近卡亚帕对这些单倍型的选择作用一致。
DNA-based typing of the HLA class II loci in a sample of the Cayapa Indians of Ecuador reveals several lines of evidence that selection has operated to maintain and to diversify the existing level of polymorphism in the class II region. As has been noticed for other Native American groups, the overall level of polymorphism at the DRB1, DQA1, DQB1, and DPB1 loci is reduced relative to that found in other human populations. Nonetheless, the relative evenness in the distribution of allele frequencies at each of the four loci points to the role of balancing selection in the maintenance of the polymorphism. The DQA1 and DQB1 loci, in particular, have near-maximum departures from the neutrality model, which suggests that balancing selection has been especially strong in these cases. Several novel DQA1-DQB1 haplotypes and the discovery of a new DRB1 allele demonstrate an evolutionary tendency favoring the diversification of class II alleles and haplotypes. The recombination interval between the centromeric DPB1 locus and the other class II loci will, in the absence of other forces such as selection, reduce disequilibrium across this region. However, nearly all common alleles were found to be part of DR-DP haplotypes in strong disequilibrium, consistent with the recent action of selection acting on these haplotypes in the Cayapa.