Department of Human Genetics, University of Chicago, Chicago, IL 60637, USA.
Proc Natl Acad Sci U S A. 2012 Nov 6;109(45):18493-8. doi: 10.1073/pnas.1210603109. Epub 2012 Oct 22.
The ABO histo-blood group, the critical determinant of transfusion incompatibility, was the first genetic polymorphism discovered in humans. Remarkably, ABO antigens are also polymorphic in many other primates, with the same two amino acid changes responsible for A and B specificity in all species sequenced to date. Whether this recurrence of A and B antigens is the result of an ancient polymorphism maintained across species or due to numerous, more recent instances of convergent evolution has been debated for decades, with a current consensus in support of convergent evolution. We show instead that genetic variation data in humans and gibbons as well as in Old World monkeys are inconsistent with a model of convergent evolution and support the hypothesis of an ancient, multiallelic polymorphism of which some alleles are shared by descent among species. These results demonstrate that the A and B blood groups result from a trans-species polymorphism among distantly related species and has remained under balancing selection for tens of millions of years-to date, the only such example in hominoids and Old World monkeys outside of the major histocompatibility complex.
ABO 组织血型，输血不相容的关键决定因素，是人类发现的第一个遗传多态性。值得注意的是，ABO 抗原在许多其他灵长类动物中也存在多态性，迄今为止所有测序物种中负责 A 和 B 特异性的都是相同的两个氨基酸变化。A 和 B 抗原的这种重现是由于跨物种维持的古老多态性，还是由于许多更近的趋同进化实例，几十年来一直存在争议，目前的共识支持趋同进化。相反，我们表明，人类和长臂猿以及旧世界猴子中的遗传变异数据与趋同进化模型不一致，并支持古老的多等位基因多态性假说，其中一些等位基因在物种之间通过血统共享。这些结果表明，A 和 B 血型是由远缘物种之间的跨物种多态性产生的，并且自数千万年前以来一直受到平衡选择的影响——迄今为止，这是除了主要组织相容性复合体之外，在人科和旧世界猴中唯一的此类例子。
