Limited evidence for adaptive evolution and functional effect of allelic variation at rs702424 in the promoter of the TAS2R16 bitter taste receptor gene in Africa

Abstract

Bitter taste perception, mediated by receptors encoded by the TAS2R loci, plays important roles in human health and nutrition. Prior studies have demonstrated that nonsynonymous variation at site 516 in the coding exon of TAS2R16, a bitter taste receptor gene on chromosome 7, has been subject to positive selection and is strongly correlated with differences in sensitivity to salicin, a bitter anti-inflammatory compound, in human populations. However, a recent study suggested that the derived G-allele at rs702424 in the TAS2R16 promoter has also been the target of recent selection and may have an additional effect on levels of salicin bitter taste perception. Here, we examined alleles at rs702424 for signatures of selection using Extended Haplotype Homozygosity (EHH) and FST statistics in 44 diverse populations from West Central, Central and East Africa. We also performed a genotype-phenotype analysis of salicin sensitivity in a subset of 135 individuals from East Africa. Based on our data, we did not find evidence for positive selection at rs702424 in African populations, suggesting that site 516 is likely the variant under selection at TAS2R16. Additionally, we did not detect a significant association between rs702424 alleles and salicin bitter taste recognition, implying that this site does not contribute to salicin phenotypic variance. Overall, this study of African diversity provides further information regarding the genetic architecture and evolutionary history of a biologically-relevant trait in humans.

Demographic history was a formative mechanism of the genetic structure for the taste receptor TAS2R16 in human populations inhabiting Africa's Sahel/Savannah Belt

“…In contrast to the Fay and Wu's H test, the MFDM test, which is free of the confounding impacts of demography, was not significant for any population studied. These results thus rather support the notion that positive selection was not a major mechanism shaping the genetic structure of TAS2R16 either in Africa (Campbell et al, 2014a) or throughout the world (Dobon et al, 2019), even if several other taste or taste‐implicated genes might have undergone recent selection processes (Sjöstrand et al, 2021).…”

“…Interestingly, in West Central Africa, the ancestral allele has not been fully replaced, and no positive selection signal has been found (Campbell et al, 2014a). Why the allele for low sensitivity to toxic β-D-glucopyranosides has been retained here thus remains unknown, and might be a complex question to answer in view of the pleiotropic nature of TAS2R16 and other TAS2R genes (An & Liggett, 2018;Di Bona et al, 2020;Grassin-Delyle et al, 2019).…”

“…It is therefore possible that increased sensitivity to toxic β‐D‐glucopyranosides, which acts as protection against their ingestion, was the driving force of evolution behind the derived T‐516 allele (Soranzo et al, 2005). Interestingly, in West Central Africa, the ancestral allele has not been fully replaced, and no positive selection signal has been found (Campbell et al, 2014a). Why the allele for low sensitivity to toxic β‐D‐glucopyranosides has been retained here thus remains unknown, and might be a complex question to answer in view of the pleiotropic nature of TAS2R16 and other TAS2R genes (An & Liggett, 2018; Di Bona et al, 2020; Grassin‐Delyle et al, 2019).…”

Taste buds: cells, signals and synapses

“…Genetic analyses of human populations in Africa, Asia and Europe suggest that PTC-taster and non-taster alleles of TAS2R38 have been maintained by natural selection across more than 100,000 years of human evolution 180 . Similarly, an allele of the human gene TAS2R16 — which confers sensitivity to several β-glucopyranosides found in nature (for example, those in bitter almonds, bearberry and manioc) — has been subjected to positive selection pressure across human evolution 181, 182 .…”

Coevolution between Human's Anticancer Activities and Functional Foods from Crop Origin Center in the World

“…grasses, sedges, and succulents) represents a significant distinction between extant great apes and common ancestor (Wynn et al, 2013). Bitter taste perception for derived G-allele at rs702424 in the TAS2R16 promoter has important roles in human health and nutrition, African diversity provides information of a biologically-relevant trait in humans (Campbell et al, 2014).…”