A continuum of admixture in the Western Hemisphere revealed by the African Diaspora genome

Abstract

The African Diaspora in the Western Hemisphere represents one of the largest forced migrations in history and had a profound impact on genetic diversity in modern populations. To date, the fine-scale population structure of descendants of the African Diaspora remains largely uncharacterized. Here we present genetic variation from deeply sequenced genomes of 642 individuals from North and South American, Caribbean and West African populations, substantially increasing the lexicon of human genomic variation and suggesting much variation remains to be discovered in African-admixed populations in the Americas. We summarize genetic variation in these populations, quantifying the postcolonial sex-biased European gene flow across multiple regions. Moreover, we refine estimates on the burden of deleterious variants carried across populations and how this varies with African ancestry. Our data are an important resource for empowering disease mapping studies in African-admixed individuals and will facilitate gene discovery for diseases disproportionately affecting individuals of African ancestry.

The Genetic Diversity of the Americas

“…These findings are consistent with historical information suggesting that approximately 68% and 32% of African slaves introduced to Brazil originated in westcentral/southeast and West Africa, respectively (84). Subsequent mtDNA and highdensity genotype analyses have confirmed and extended these results, highlighting areas of non-Bantu speakers in northwest and west-central Africa as major sources for the slaves brought to the Americas, with relatively smaller contributions from other regions, such as east African (Bantu-speaking) areas (18,48,57,63,98). Some regional variation has been reported for the relative importance of specific African source regions in the Americas; for instance, the non-Bantu component is more frequent in southern than northern Brazil, in agreement with historical information on the predominant origin of slaves introduced to different parts of this country (48).…”

Human Demographic History Impacts Genetic Risk Prediction across Diverse Populations

“…We focus on these populations as the demography has previously been modeled and this avoids the challenges of simulating the geographically heterogeneous 47 and sex-biased process of admixture in the Americas. 76 To imitate a GWAS with European sample bias and evaluate polygenic risk scores in other populations, we simulated 200,000 European, 200,000 East Asian, and 200,000 African individuals. Next, we assigned ''true'' causal effect sizes to m evenly spaced alleles.…”

Making progress toward understanding the genetic architecture of asthma in the most affected US ethnic group

“…Whereas some have called for genetic studies to no longer use racial categories (because many racial terms are inadequate, with origins that are often political in nature, rather than biologically based) [20], there are also concerns that if racial/ethnic categories are ignored, then current minority groups will not be adequately included in research and clinical studies [6]. As statistical methods to perform gene association studies in admixed populations continue to improve [9,21] and an expanded catalogue of variation in diverse populations grows (via efforts such as the 1000 Genomes Project and the Consortium on Asthma in African Ancestry Populations (CAAPA) [22,23]), the need to group subjects into specific racial/ethnic categories for genetic studies will decrease. This is of great importance both to Puerto Ricans and other recently admixed minority groups, as well as the growing number of individuals who are of mixed racial/ethnic backgrounds and are often not included in genetic studies.…”