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首页> 外文期刊>Journal of genetics >Patterns of nucleotide sequence variation in ICAM1 and TNF genes in twelve ethnic groups of India: roles of demographic history and natural selection
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Patterns of nucleotide sequence variation in ICAM1 and TNF genes in twelve ethnic groups of India: roles of demographic history and natural selection

机译：印度的十二个种族的ICAM1和TNF基因的核苷酸序列变异模式：人口统计学和自然选择的作用

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We have studied DNA sequence variation in and around the genes ICAM1 and TNF, which play functional and correlated roles in inflammatory processes and immune cell responses, in 12 diverse ethnic groups of India, with a view to investigating the relative roles of demographic history and natural selection in shaping the observed patterns of variation. The total numbers of single nucleotide polymorphisms (SNPs) detected at the ICAM1 and TNF loci were 29 and 12, respectively. Haplotype and allele frequencies differed significantly across populations. The site frequency spectra at these loci were significantly different from those expected under neutrality, and showed an excess of intermediate-frequency variants consistent with balancing selection. However, as expected under balancing selection, there was no significant reduction of $F_{ST}$ values compared to neutral autosomal loci. Mismatch distributions were consistent with population expansion for both loci. On the other hand, the phylogenetic network among haplotypes for the TNF locus was similar to expectations under population expansion, while that for the ICAM1 was as expected under balancing selection. Nucleotide diversity at the ICAM1 locus was an order of magnitude lower in the promoter region, compared to the introns or exons, but no such difference was noted for the TNF gene. Thus, we conclude that the pattern of nucleotide variation in these genes has been modulated by both demographic history and selection. This is not surprising in view of the known allelic associations of several polymorphisms in these genes with various diseases, both infectious and noninfectious.
机译：我们已经研究了印度12个不同种族的ICAM1和TNF基因及其周围的DNA序列变异，这些基因在炎症过程和免疫细胞应答中发挥功能和相关作用，以调查人口统计学和自然史的相对作用选择以塑造观察到的变化模式。在ICAM1和TNF位点检测到的单核苷酸多态性（SNP）总数分别为29和12。不同人群的单倍型和等位基因频率差异显着。这些位点的站点频谱与中性条件下的预期频谱显着不同，并且显示出过多的中频变量与平衡选择一致。但是，正如在平衡选择下所预期的，与中性常染色体基因座相比，$ F_ {ST} $值没有显着降低。不匹配的分布与两个基因座的种群扩展一致。另一方面，TNF基因座的单倍型之间的系统发育网络与人口扩张下的预期相似，而ICAM1的单体型与平衡选择下的预期相似。与内含子或外显子相比，ICAM1基因座处的核苷酸多样性在启动子区域低一个数量级，但对于TNF基因却没有发现这种差异。因此，我们得出结论，这些基因中核苷酸变异的模式已受到人口统计学历史和选择的调节。考虑到这些基因中几种多态性与多种传染病和非传染病的已知等位基因关联，这并不奇怪。

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