The effect of population history on patterns of genetic diversity at the TAS2R bitter taste receptor genes in West Central and Central African populations

Michael Campbell

USC

Bitter taste perception is a highly variable trait in humans, and the ability to detect bitter compounds has been largely attributed to genetic variants in 25 bitter taste receptor (TAS2R) genes. Furthermore, bitter taste perception has been hypothesized to be a dietary adaptation in humans. However, few studies have characterized patterns of diversity and signatures of selection at the TAS2R genes in distinct African populations. Given the extensive genetic substructure and evidence for local adaptation in Africa, we hypothesized that Africans practicing diverse subsistence strategies could have distinct patterns of selection resulting from divergent diets. To test this hypothesis, we examined sequence variation at 22 bitter taste receptor genes in rainforest hunter-gatherers and Bantu-speaking agriculturalists from Cameroon. Here, we identified 353 single nucleotide polymorphisms (SNPs) across the TAS2R genes, 35 of which have never been previously described. We also observed striking signatures of positive selection, including unusually long haplotypes around alleles at the TAS2R genes. In addition, some of these signals of selection were shared between rainforest hunter-gatherers and Bantu-speaking agriculturalists. To better understand these results, we performed genomic genotyping in our African populations. Interestingly, we observed varying proportions of ancestry originating from Bantu-speakers in hunter-gatherers with the highest levels of admixture occurring in the Bakola population. These findings demonstrate that gene flow from neighboring agriculturalists has also shaped patterns of diversity in hunter-gatherers, including variation in the TAS2R genes. Overall, this research provides new insights into the evolution of biologically relevant bitter taste genes in highly understudied African populations.