UC Merced

Gustation, or taste, is a gatekeeper for substances ingested orally. It is hypothesized to have served our ancestors in detecting nutrients from potential food sources and in rejecting potentially toxic substances. Early human migrations following the dispersal from the African continent would have placed ancient populations in novel environments, suggesting the ability to detect nutrients and identify sources of toxins would have been critical to survival to our early ancestors. This role suggests that taste has been subject to selective pressures through the course of evolution. Such pressures contribute to diversity and variance in taste across contemporary populations, suggesting that large differences in taste perception traits are likely the result of holdovers from our evolutionary past. The potential contribution of taste to nutritional behaviors and a variety of diseases, including obesity and diabetes, places taste of interest in taste to health scientist and public health researchers. In chapter 2, I highlight past and recent research examining diversity and genotype-phenotype associations across taste genes. Additionally in this chapter, population genomic data are used to explore diversity and signatures of natural selection across the genes mediating taste. Health and taste researchers alike are interested in such analysis and findings as they describe the underpinnings of natural variability seen among alleles and human phenotypes, and can prioritize targets of future investigation. In chapter 3, I describe Inia, a framework and tool to reproduce such analysis with limited technical expertise. Inia serves as a wrapper around popular analytical tools, providing summaries and rich annotation of variation across local genomic regions. To demonstrate Inia, I examine the putative sour receptor gene OTOP1. In chapter 4, I examine the putative fat receptor gene CD36, whose transcript is superimposed on the g-protein subunit gene GNAT3. CD36 and GNAT3, both of which contribute to taste perception, harbor extensive variation along their locus and such variation may contribute to phenotypic differences. In this chapter I examine potentially functional variants across the region, and explore the extent to which such variation may contribute to phenotypic variance at the population level. This chapter provides an examination of diversity and signatures of selection across CD36 and GNAT3, and provides evidence of important regional trends. Finally, linkage structure across the region is explored given the close proximity of these genes and their dual contribution to taste perception. Together, this dissertation serves to provide insight into the extent and origin of diversity among human populations with regards to the taste genes and the potential contributions to human health and behaviors.