Evolution of Functionally Diverse Alleles Associated with PTC Bitter Taste Sensitivity in Africa

Abstract

Although human bitter taste perception is hypothesized to be a dietary adaptation, little is known about genetic signatures of selection and patterns of bitter taste perception variability in ethnically diverse populations with different diets, particularly from Africa. To better understand the genetic basis and evolutionary history of bitter taste sensitivity, we sequenced a 2,975 bp region encompassing TAS2R38, a bitter taste receptor gene, in 611 Africans from 57 populations in West Central and East Africa with diverse subsistence patterns, as well as in a comparative sample of 132 non-Africans. We also examined the association between genetic variability at this locus and threshold levels of phenylthiocarbamide (PTC) bitterness in 463 Africans from the above populations to determine how variation influences bitter taste perception. Here, we report striking patterns of variation at TAS2R38, including a significant excess of novel rare nonsynonymous polymorphisms that recently arose only in Africa, high frequencies of haplotypes in Africa associated with intermediate bitter taste sensitivity, a remarkably similar frequency of common haplotypes across genetically and culturally distinct Africans, and an ancient coalescence time of common variation in global populations. Additionally, several of the rare nonsynonymous substitutions significantly modified levels of PTC bitter taste sensitivity in diverse Africans. While ancient balancing selection likely maintained common haplotype variation across global populations, we suggest that recent selection pressures may have also resulted in the unusually high level of rare nonsynonymous variants in Africa, implying a complex model of selection at the TAS2R38 locus in African populations. Furthermore, the distribution of common haplotypes in Africa is not correlated with diet, raising the possibility that common variation may be under selection due to their role in nondietary biological processes. In addition, our data indicate that novel rare mutations contribute to the phenotypic variance of PTC sensitivity, illustrating the influence of rare variation on a common trait, as well as the relatively recent evolution of functionally diverse alleles at this locus.

Variation in the Ability to Taste Bitter Thiourea Compounds: Implications for Food Acceptance, Dietary Intake, and Obesity Risk in Children

“…Three polymorphisms at amino acid 49 (proline or alanine), 262 (alanine or valine), and 296 (valine or isoleucine) combine to form the taster haplotype PAV and the nontaster haplotype AVI. Other more rare haplotypes (e.g., AAV, PVI) contribute to intermediate PROP/PTC sensitivity (26,80) and are more common in African Americans than in Caucasians (30,106). The AVI and PAV haplotypes completely explain the bimodal distribution in the ability to taste PTC and up to 85% of the variability in PTC thresholds (the lowest concentration of PTC that can be distinguished from water) (36), yet these single-nucleotide polymorphisms do not completely explain the PROP phenotype (81).…”

Was ist Geschmack?

“…Jahren vorhanden war, scheint besonders mit der Wahrnehmung von goitrogenen Substanzen in der Nahrung in Verbindung zu stehen (Campbell et al 2011). Träger dieser Mutation ver-…”

Geographic Distribution and Adaptive Significance of Genomic Structural Variants: An Anthropological Genetics Perspective

“…Some of the studies in this line identified genetic variants that are adaptively associated with taste perception (e.g., Campbell et al 2012), smell perception (reviewed in Hasin-Brumshtein et al 2009), skin color (e.g., Norton et al 2007), eye and hair color (e.g., Sulem et al 2007), various aspects of diet (e.g., Tishkoff et al 2007), high-altitude lifestyle (e.g., Bigham et al 2010), and immune response (reviewed in Karlsson et al 2014). These connections between genetic and phenotypic variation among healthy individuals are often considered within an adaptive framework, and more recently in the light of gene-culture coevolution (reviewed in Laland et al 2010).…”