Assessment of the Relationship between Self-Declared Ethnicity, Mitochondrial Haplogroups and Genomic Ancestry in Brazilian Individuals

Abstract

In populations that have a high degree of admixture, such as in Brazil, the sole use of ethnicity self-declaration information is not a good method for classifying individuals regarding their ethnicity. Here, we evaluate the relationship of self-declared ethnicities with genomic ancestry and mitochondrial haplogroups in 492 individuals from southeastern Brazil. Mitochondrial haplogroups were obtained by analyzing the hypervariable regions of the mitochondrial DNA (mtDNA), and the genomic ancestry was obtained using 48 autosomal insertion-deletion ancestry informative markers (AIM). Of the 492 individuals, 74.6% self-declared as White, 13.8% as Brown and 10.4% as Black. Classification of the mtDNA haplogroups showed that 46.3% had African mtDNA, and the genomic ancestry analysis showed that the main contribution was European (57.4%). When we looked at the distribution of mtDNA and genomic ancestry according to the self-declared ethnicities from 367 individuals who self-declared as White, 37.6% showed African mtDNA, and they had a high contribution of European genomic ancestry (63.3%) but also a significant contribution of African ancestry (22.2%). Of the 68 individuals who self-declared as Brown, 25% showed Amerindian mtDNA and similar contribution of European and African genomic ancestries. Of the 51 subjects who self-declared as black, 80.4% had African mtDNA, and the main contribution of genomic ancestry was African (55.6%), but they also had a significant proportion of European ancestry (32.1%). The Brazilian population had a uniform degree of Amerindian genomic ancestry, and it was only with the use of genetic markers (autosomal or mitochondrial) that we were able to capture Amerindian ancestry information. Additionally, it was possible to observe a high degree of heterogeneity in the ancestry for both types of genetic markers, which shows the high genetic admixture that is present in the Brazilian population. We suggest that in epidemiological studies, the use of these methods could provide complementary information.

The correlation between ancestry and color in two cities of Northeast Brazil with contrasting ethnic compositions

“…4,5,7,[22][23][24] In contrast, this paper is only one of many showing that Brazil can exhibit marked population structure, and self-identified skin color is generally consistent with the dominant or relative ancestral contribution. 6,8,[25][26][27][28][29] In this study, for both cities, blacks were twice as African as others in the surrounding population and whites more European, whereas the browns were intermediate. However, within localities, the designation of skin color may be relative to the ancestral mixture of one's neighbors.…”

Self-Assessment of Color Categories and Its Relationship with HLA Profiling in Brazilian Bone Marrow Donors

“…Recently, a study of 1594 individuals from Brazil observed that individuals self-assessed as Blacks had around 40% of European genetic ancestry, whereas those selfassessed as mestizos (Brown or "Pardo") had around 70% of European genetic ancestry [29]. Other studies with ancestryinformative markers on different populations in Brazil have also shown a discrepancy between self-declared information and genetic ancestry [30][31][32][33].…”

Amerindian genetic ancestry is associated with higher survival rates compared to African and European ancestry in Brazilian patients with heart failure

“…The mtDNA analysis for the composition of haplotypes (sequences) and mt-haplogroup classification was realized in the control region of mtDNA [8].…”

“…The evaluation of genomic ancestry was conducted using 48 biallelic ancestry informative markers (AIMs) (16 markers of African ancestry, 16 of European ancestry, and 16 of Amerindian ancestry) type insertion-deletion (INDEL) from autosomal chromosomes [8][9].…”

“…This finding is particularly relevant since the information about the Amerindian genetic background is not usually retrieved by the standard self-referred questions about ethnicity [8]. In fact, for a mixed population, such as the Brazilian, genetic determination of autosomal ancestry may be the best technique to unveil this characteristic associated with better prognosis.…”