Talk by Choongwon Jeong

DAG Talk

  • Date: Mar 8, 2016
  • Time: 11:00 AM - 12:30 PM (Local Time Germany)
  • Speaker: Choongwon Jeong
  • The University of Chicago
  • Location: MPI SHH Jena
  • Room: Villa V14
  • Host: Abteilung Archäogenetik
  • Contact:
High altitude East Asians: genetic history and adaptations to altitude
High altitude environments confer challenging burdens to their inhabitants, driven by hypobaric hypoxia and other environmental factors. However, indigenous populations of the Tibetan plateau, the most prominent highland of the world, have thrived in such a harsh habitat for millennia. Distinct physiological traits of Tibetans and Sherpa, such as attenuated erythropoietic response to altitudinal increase, have long been suspected to be based on adaptive genetic changes. However, our understanding on their adaptations to the high altitude, as well as their origin and population structure, is far from a complete picture. In our lab, we have been studying population genetics of Tibetans and Sherpa by generating and analyzing array-based genotype data of 1,200 individuals and whole genome sequences of several dozen, including ancient samples. We found interesting features of Tibetans and Sherpa with regard to their genetic history and adaptation. First, contemporary Tibetans from the plateau harbor signatures of genetic admixture, best modeled by a mixture of two ancestral gene pools represented by modern day Sherpa and lowland East Asians. These two sources may have a deep split time, beginning at 20-40 thousand years ago. Second, sequencing of ancient samples from the high altitude corridors of the Himalayan arc revealed continuous occupation of Tibetan-like populations since the initial settlement, as well as in situ evolution of adaptive haplotypes in the EGLN1 and EPAS1 genes. Third, genomic scans of positive selection detected several interesting genes, such as EGLN1, EPAS1, SLCO1A2, XYLT1, EP300 and RUNX1. Last, we found several loci associated with key physiological and fertility phenotypes in our Nepalese Tibetan cohort, including a replication of association between lower hemoglobin level and the adaptive EPAS1 haplotype. Interestingly, a phenotype-phenotype association was also found between lower hemoglobin level and higher proportion of live births from pregnancies, suggesting beneficial effect of low hemoglobin level. To summarize, our study of high altitude East Asians show a role of high altitude environments as a major determinant of genetic adaptation and population structure of the inhabitants. Further study will help us understand details of the genetic history of Tibetans and their genetic basis of high altitude adaptations.
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