Villanea Fernando A, Safi Kristin N, Busch Jeremiah W
School of Biological Sciences, Washington State University, PO Box 644236, Pullman, Washington, 99164, United States of America.
Department of Anthropology, Washington State University, PO Box 644910, Pullman, Washington, 99164, United States of America.
PLoS One. 2015 May 6;10(5):e0125003. doi: 10.1371/journal.pone.0125003. eCollection 2015.
The ABO locus in humans is characterized by elevated heterozygosity and very similar allele frequencies among populations scattered across the globe. Using knowledge of ABO protein function, we generated a simple model of asymmetric negative frequency dependent selection and genetic drift to explain the maintenance of ABO polymorphism and its loss in human populations. In our models, regardless of the strength of selection, models with large effective population sizes result in ABO allele frequencies that closely match those observed in most continental populations. Populations must be moderately small to fall out of equilibrium and lose either the A or B allele (N(e) ≤ 50) and much smaller (N(e) ≤ 25) for the complete loss of diversity, which nearly always involved the fixation of the O allele. A pattern of low heterozygosity at the ABO locus where loss of polymorphism occurs in our model is consistent with small populations, such as Native American populations. This study provides a general evolutionary model to explain the observed global patterns of polymorphism at the ABO locus and the pattern of allele loss in small populations. Moreover, these results inform the range of population sizes associated with the recent human colonization of the Americas.
人类的ABO基因座具有杂合性升高以及全球各地人群中等位基因频率非常相似的特点。利用ABO蛋白功能的相关知识，我们构建了一个不对称负频率依赖选择和遗传漂变的简单模型，以解释ABO多态性的维持及其在人类群体中的丧失。在我们的模型中，无论选择强度如何，有效群体规模大的模型所产生的ABO等位基因频率与大多数大陆群体中观察到的频率非常匹配。群体必须适度小才能偏离平衡并丢失A或B等位基因（有效群体大小Ne≤50），而要完全丧失多样性则需要更小（Ne≤25），这几乎总是涉及O等位基因的固定。在我们的模型中发生多态性丧失的ABO基因座处杂合性较低的模式与小群体一致，如美洲原住民群体。本研究提供了一个通用的进化模型，以解释在ABO基因座观察到的全球多态性模式以及小群体中等位基因丧失的模式。此外，这些结果为与近期人类美洲殖民化相关的群体规模范围提供了信息。
