Dinâmica da miscigenação em populações da América Latina

Abstract

Admixture is the product of gene flow between long-time isolated populations that form a new hybrid population. Admixture studies are important in anthropology, and in genetic epidemiology to avoid spurious statistical associations due to false positive. Our research group (LDGH UFMG) aims to study admixture aspects and genetic epidemiology of populations with high native American ancestry, that are normally neglected in population studies. This study aims, through a 83-SNP panel of ancestry informative markers (AIMs), estimate the individual and population admixture distribution of four populations of Latin America: Ecuadorian (EQU), Nicaraguan (NIC), Mexican (MEX) and Peruvian (LIM), product of admixture between European, African and Native American, and evaluate the efficiency of the panel used in this investigation, and to perform qualitative inferences of the dynamic of admixture in these populations. We performed classic population genetics analyses in order to assess intra-population and inter-population diversity indexes (F statistics, Hardy- Weinberg Equilibrium, Maximum likelihood estimations of admixture and Linkage Disequilibrium (LD) estimators). Principal Component Analysis (PCA) was also used to confirm and illustrate the population differentiation. Overall, these analyses produced consistent results, showing that most of our SNPs have low inter-continental and high intercontinental diversity, as expected for AIMs. None of the admixed populations presented high African ancestry, with the highest average population African contribution of 0,12 in Nicaragua. PCA analysis showed a continuum of individual European and Native American ancestry in the admixed populations, with the two first principal components statistics explaining 42,7% of the total variance contained in the genetic dataset. Individuals of African populations were the most differentiated between all populations studied. The analysis of LD and of the distribution of individual ancestry allowed us to qualitatively address the temporal dynamics of admixture in EQU, NIC, MEX and LIM. It suggested that NIC and MEX undergone most recent events of admixture, and relatively recent contributions of individuals with high European ancestry were low in EQU and LIM. In the near future, we will use more sophisticated conceptual tools to study the distribution of individual admixture and linkage disequilibrium to improve our inferences about the admixture dynamics in these populations.