Department of Evolutionary Biology, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, 752 36 Uppsala, Sweden; Master Bioscience, Department of Biology, École Normale Supérieure de Lyon, 46 Allée d'Italie, 69364 Lyon Cedex 07, France.
Department of Evolutionary Biology, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, 752 36 Uppsala, Sweden.
Curr Biol. 2014 Apr 14;24(8):852-8. doi: 10.1016/j.cub.2014.02.041. Epub 2014 Apr 3.
The ability to digest milk into adulthood, lactase persistence (LP), as well as specific genetic variants associated with LP, is heterogeneously distributed in global populations. These variants were most likely targets of selection when some populations converted from hunter-gatherer to pastoralist or farming lifestyles. Specific LP polymorphisms are associated with particular geographic regions and populations; however, they have not been extensively studied in southern Africa. We investigate the LP-regulatory region in 267 individuals from 13 southern African populations (including descendants of hunter-gatherers, pastoralists, and agropastoralists), providing the first comprehensive study of the LP-regulatory region in a large group of southern Africans. The "East African" LP single-nucleotide polymorphism (SNP) (14010G>C) was found at high frequency (>20%) in a strict pastoralist Khoe population, the Nama of Namibia, suggesting a connection to East Africa, whereas the "European" LP SNP (13910C>T) was found in populations of mixed ancestry. Using genome-wide data from various African populations, we identify admixture (13%) in the Nama, from an Afro-Asiatic group dating to >1,300 years ago, with the remaining fraction of their genomes being from San hunter-gatherers. We also find evidence of selection around the LCT gene among Khoe-speaking groups, and the substantial frequency of the 14010C variant among the Nama is best explained by adaptation to digesting milk. These genome-local and genome-wide results support a model in which an East African group brought pastoralist practices to southern Africa and admixed with local hunter-gatherers to form the ancestors of Khoe people.
成年人能够消化牛奶，乳糖持续存在（LP），以及与 LP 相关的特定遗传变异，在全球人群中分布不均。当一些人群从狩猎采集者转变为牧民或农耕生活方式时，这些变异很可能是选择的目标。特定的 LP 多态性与特定的地理区域和人群有关；然而，它们在南部非洲并没有得到广泛研究。我们调查了来自 13 个南部非洲人群（包括狩猎采集者、牧民和农牧民的后代）的 267 个人的 LP 调节区域，这是对南部非洲人中 LP 调节区域的首次全面研究。在一个严格的牧民科伊人（Nama）中，发现了“东非”LP 单核苷酸多态性（SNP）（14010G>C）的高频（>20%），这表明与东非有关，而“欧洲”LP SNP（13910C>T）则存在于混合血统的人群中。利用来自不同非洲人群的全基因组数据，我们发现纳米比亚的 Nama 人群中存在 13%的混合，这是一个可以追溯到 1300 多年前的 Afro-Asiatic 群体，他们的基因组其余部分来自 San 狩猎采集者。我们还在科伊语群体中发现了围绕 LCT 基因的选择证据，并且 Nama 中 14010C 变体的大量频率最好通过适应消化牛奶来解释。这些基因组局部和全基因组的结果支持了一个模型，即一个东非群体将牧民的做法带到了南部非洲，并与当地的狩猎采集者混合，形成了科伊人祖先。
