Revisiting the Genetic Ancestry of Brazilians Using Autosomal AIM-Indels

Abstract

There are many different studies that contribute to the global picture of the ethnic heterogeneity in Brazilian populations. These studies use different types of genetic markers and are focused on the comparison of populations at different levels. In some of them, each geographical region is treated as a single homogeneous population, whereas other studies create different subdivisions: political (e.g., pooling populations by State), demographic (e.g., urban and rural), or ethnic (e.g., culture, self-declaration, or skin colour). In this study, we performed an enhanced reassessment of the genetic ancestry of ~ 1,300 Brazilians characterised for 46 autosomal Ancestry Informative Markers (AIMs). In addition, 798 individuals from twelve Brazilian populations representing the five geographical macro-regions of Brazil were newly genotyped, including a Native American community and a rural Amazonian community. Following an increasing North to South gradient, European ancestry was the most prevalent in all urban populations (with values up to 74%). The populations in the North consisted of a significant proportion of Native American ancestry that was about two times higher than the African contribution. Conversely, in the Northeast, Center-West and Southeast, African ancestry was the second most prevalent. At an intrapopulation level, all urban populations were highly admixed, and most of the variation in ancestry proportions was observed between individuals within each population rather than among population. Nevertheless, individuals with a high proportion of Native American ancestry are only found in the samples from Terena and Santa Isabel. Our results allowed us to further refine the genetic landscape of Brazilians while establishing the basis for the effective application of an autosomal AIM panel in forensic casework and clinical association studies within the highly admixed Brazilian populations.

A minimum set of ancestry informative markers for determining admixture proportions in a mixed American population: the Brazilian set

“…Conversely, in the Northeast, Center-West, and Southeast, the African contribution is the second most important. 5,6 A study performed by Pena et al, 7 analyzing a group of 40 validated insertion-deletion DNA polymorphisms in 934 Brazilians resident in the four most populous Brazilian regions, unraveled a high level of individual admixture in Brazilians across all regions.…”

“…However, at least two main difficulties are imposed in applying these panels in a new study sample, (1) AIMs such as insertion-deletion [5][6][7] or microsatellite markers 13 are difficult to multiplex, need primer design by the developers and standardization of PCR conditions, hindering the access and reproduction in large samples. If the AIMs are SNPs, another difficulty (also present in the first case) is (2) the adequacy of reference ancestral populations used in AIMs selection and its effect on ancestry estimates for the specific population to be studied.…”

Distribution of forensic marker allelic frequencies in Pernambuco, Northestern Brazil

“…The presence of rare alleles or the characteristic substructure of Brazilian populations may account for this finding (Soloum et al, 2013). For all markers, H E values were very similar to H O values.…”

Anemia among pregnant women attending primary healthcare units in the municipality of São Paulo, Brazil: evaluations after the mandatory fortification of wheat and maize flours with iron

“…Although the race, ethnicity, and skin color classifications that are frequently employed in epidemiological studies may correlate with ancestry, they are usually nonspecific and inaccurate measures of underlying genetic factors in highly admixed populations [43][44][45]. Moreover, because ethnoracial self-classification is a social construct, it may be a proxy for diverse environmental exposures [46].…”