一项新的对人类及黑猩猩进行的全基因组分析披露,这两个物种在数百万年中同时拥有着某些相同的会导致多态性—— 即在同一物种中有着不同的物理形式——的突变组合。在此之前,在人与猿之间只确认了2种共有的多态性:主要组织相容性复合体或MHC的变体,及作为不同血型基础的ABO血型系统中的多态性。Ellen Leffler及其同事对59个人及10个西非黑猩猩的全基因组序列进行了研究并确认了在这两个物种中有125个区域含有类似的突变——它们中的大多数出现在基因组的非编码区域。据研究人员披露,这些区域中有6个看来代表了自这两个世系分开后仍然持续存在于这两个物种中的多态性。这些新的发现提供了平衡选择的证据,在这种选择过程中,某些在一个物种中的非显性特质却仍然以高出显性特质的程度得到维持。这种现象常常会使某些多态性在进化的过程中得以保留。(生物谷Bioon.com)
DOI: 10.1126/science.1234070
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Multiple Instances of Ancient Balancing Selection Shared Between Humans and Chimpanzees
Ellen M. Leffler1,*,Ziyue Gao2,*, Susanne Pfeifer3,*, Laure Ségurel1,4,*, Adam Auton5, Oliver Venn5, Rory Bowden3,5, Ronald Bontrop6, Jeffrey D. Wall7, Guy Sella8,9, Peter Donnelly3,5, Gilean McVean3,5, Molly Przeworski1,4,9,
Instances in which natural selection maintains genetic variation in a population over millions of years are thought to be extremely rare. We conducted a genome-wide scan for long-lived balancing selection by looking for combinations of SNPs shared between humans and chimpanzees. In addition to the major histocompatibility complex (MHC), we identified 125 regions in which the same haplotypes are segregating in the two species, all but two of which are non-coding. In six cases, there is evidence for an ancestral polymorphism that persisted to the present in humans and chimpanzees. Regions with shared haplotypes are significantly enriched for membrane glycoproteins, and a similar trend is seen among shared coding polymorphisms. These findings indicate that ancient balancing selection has shaped human variation and point to genes involved in host-pathogen interactions as common targets.