Population Genomic Insights into Natural Selection and Altitude Adaptation

Hosted by the Biochemistry and Molecular Biology department. Abstract Next generation sequencing data is transforming the field of population genetics by allowing the targets of natural selection to be studied at the genomic scale. I will describe three recent and ongoing projects that revolve around the quest to identify the genes and mutations that underlie adaptive evolution: I recently participated in the analysis of 50 sequenced exomes from ethnic Tibetans, with the goal of identifying genes involved in human adaptation to extreme altitude. By comparing variation in three populations, we identifiedgenes that showed unusually strong allele frequency changes in the Tibetan sample specifically. The strongest signal of natural selection came from EPAS1, a gene known to be involved in hypoxia response, but not previously studied with regard to altitude adaptation. One intronic EPAS1 SNP showed an 80% frequency difference between Tibetan and Han samples, and was significantly associated with erythrocyte abundance in a Tibetan sample. As a graduate student, I discovered melanic forms of Drosophila melanogaster that were associated with high altitude sites in the species' African ancestral range. I studied ebony as a candidate gene, and found that variation at this locus was strongly associated with pigmentation phenotypes and showed evidence for recent natural selection in a melanic population. More recently, I was involved in a collaborative study that identified five specific mutations in the ebony regulatory region that underlie melanic evolution. Intriguingly, the genetic basis of melanicpigmentation appears to vary among African mountain ranges. I am now initiating a project that will fuse quantitative genomic and population genomic approaches to reveal the genetic basis of parallel melanic evolution in multiple highland populations. I have contributed to a recent analysis of >40 D. melanogaster genomes. This data set has already led to many new insights regarding the targets of natural selection, including (A) a strong enrichment of 5' and 3' untranslated regions among putative targets of selection, (B) notable differences between the biological processes targeted by recent selection in an African versus a North American population, and (C) an overabundance of loci targeted by recent selection in both D. melanogaster and its relative D. simulans. I am now leading the analysis of ~100genomes from African populations of D. melanogaster. This data set will allow many new insights regarding local adaptation and the genomic influence of natural selection. Biography I gained a foundation in population genetics during my Ph.D. research with Chip Aquadro at Cornell University, where I studied the impact of natural selection and population history on genetic variation in Drosophila melanogaster As a postdoc, I focused on computational, statistical, and theoretical aspects of population genetics in my work with Rasmus Nielsen (UC Berkeley). I am now applying this background to the analysis of genomic resequencing data from human and Drosophila populations, while continuing my postdoctoral research with Chuck Langley (UC Davis)

Contact

Tamara S. Housel
txh9@psu.edu
814-865-3072