Department of Medical Genetics and Genomic Medicine, University of Campinas-UNICAMP, and the Brazilian Institute of Neuroscience and Neurotechnology (BRAINN), Campinas, SP, Brazil.
Departament de Ciències Experimentals i de la Salut, Institute of Evolutionary Biology (CSIC-UPF), Universitat Pompeu Fabra, Barcelona, Spain.
Sci Rep. 2019 Sep 25;9(1):13900. doi: 10.1038/s41598-019-50362-2.
Admixed American populations have different global proportions of European, Sub-Saharan African, and Native-American ancestry. However, individuals who display the same global ancestry could exhibit remarkable differences in the distribution of local ancestry blocks. We studied for the first time the distribution of local ancestry across the genome of 264 Brazilian admixed individuals, ascertained within the scope of the Brazilian Initiative on Precision Medicine. We found a decreased proportion of European ancestry together with an excess of Native-American ancestry on chromosome 8p23.1 and showed that this is due to haplotypes created by chromosomal inversion events. Furthermore, Brazilian non-inverted haplotypes were more similar to Native-American haplotypes than to European haplotypes, in contrast to what was found in other American admixed populations. We also identified signals of recent positive selection on chromosome 8p23.1, and one gene within this locus, PPP1R3B, is related to glycogenesis and has been associated with an increased risk of type 2 diabetes and obesity. These findings point to a selection event after admixture, which is still not entirely understood in recent admixture events.
混合人群的欧洲人、撒哈拉以南非洲人和美洲原住民祖先的全球比例不同。然而，表现出相同全球祖先的个体在局部祖先块的分布上可能存在显著差异。我们首次研究了 264 名巴西混合个体的基因组中局部祖先的分布，这些个体是在巴西精准医学倡议范围内确定的。我们发现染色体 8p23.1 上的欧洲祖先比例降低，同时美洲原住民祖先比例增加，这是由染色体倒位事件产生的单倍型造成的。此外，与其他美洲混合人群相比，巴西未发生倒位的单倍型与美洲原住民的单倍型更为相似，而与欧洲的单倍型则不相似。我们还在染色体 8p23.1 上发现了近期正选择的信号，该基因座内的 PPP1R3B 基因与糖生成有关，与 2 型糖尿病和肥胖的风险增加有关。这些发现指向了混合后的选择事件，这在最近的混合事件中还不完全清楚。
