Ancestry, diversity, and genetics of health-related traits in African-derived communities (quilombos) from Brazil.

Brazilian quilombos are communities formed by enslaved Africans and their descendants all over the country during slavery and shortly after its abolition. Quilombos harbor a great fraction of the largely unknown genetic diversity of the African diaspora in Brazil. Thus, genetic studies in quilombos have the potential to provide important insights not only into the African roots of the Brazilian population but also into the genetic bases of complex traits and human adaptation to diverse environments. This review summarizes the main results of genetic studies performed on quilombos so far. Here, we analyzed the patterns of African, Amerindian, European, and subcontinental ancestry (within Africa) of quilombos from the five different geographic regions of Brazil. In addition, uniparental markers (from the mtDNA and the Y chromosome) studies are analyzed together to reveal demographic processes and sex-biased admixture that occurred during the formation of these unique populations. Lastly, the prevalence of known malaria-adaptive African mutations and other African-specific variants discovered in quilombos, as well as the genetic bases of health-related traits, are discussed here, together with their implication for the health of populations of African descent.

Uniparental markers reveal new insights on subcontinental ancestry and sex-biased admixture in Brazil.

The Brazilian population is a product of asymmetric admixture among European men and Amerindian and African women. However, Brazilian subcontinental ancestry is scarcely documented, especially regarding its African roots. Here, we aimed to unveil the uniparental continental and subcontinental contributions from distinct Brazilian regions, including South (n = 43), Southeast (n = 71), the poorly genetically characterized Central-Western region (n = 323), and a subset of unique Brazilian Amerindians (n = 24), in the context of their genome-wide ancestral contributions. The overwhelming majority of European Y haplogroups (85%) contrast sharply with the predominant African and Amerindian mtDNA haplogroups (73.2%) in admixed populations, whereas in Amerindians, non-Native haplogroups could only be detected through the paternal line. Our in-depth investigation of uniparental markers showed signals of an Andean and Central-Brazilian Amerindian maternal contribution to Southeastern and Central-Western Brazil (83.1 ± 2.1% and 56.9 ± 0.2%, respectively), the last having the highest paternal Amerindian ancestry yet described for an admixed Brazilian region (9.7%) and contrasting with higher Southern-Brazilian Amerindian contribution to Southern Brazil (59.6 ± 1%). Unlike the higher African Bantu contribution previously reported for the South and Southeast, a relevant Western African non-Bantu contribution was detected in those regions (85.7 ± 5% and 71.8 ± 10.8% respectively). In contrast, a higher Bantu contribution was described for the first time in the Central-West (64.8 ± 1.3% maternal and 86.9 ± 9.6% paternal). We observed sex-biased signatures consistent with the historically recorded Brazilian colonization and added new insights in the subcontinental maternal ancestry of Brazilians from regions never studied at this level.