Variant Genome Region Associated with Cold Adaptation in Arctic Inuits May Be Traced Back to Ancient Denisovan Populations

In the Arctic, the Inuits have adapted to severe cold and a predominantly seafood diet. After the first population genomic analysis of the Greenland Inuits (Fumagalli, Moltke et al. 2015, Science doi:10.1126/science.aab2319), a region in the genome containing two genes (TBX15 and WARS2) has now been scrutinized by scientists. This region is thought to be central to cold adaptation by coding for the generation of heat from a specific type of body fat, and was earlier found to be a candidate for adaptation in the Inuits. Now, a team of scientists led by Fernando Racimo, Rasmus Nielsen, et al. has followed up on the first natural selection study in Inuits to trace back the origins of these adaptations. To perform the study, the scientists used the genomic data from nearly 200 Greenlandic Inuits and compared this to data from the 1000 Genomes Project and ancient hominid DNA from Neanderthals and Denisovans. The results, published in the advanced online edition of Molecular Biology and Evolution, provide convincing evidence that the Inuit variant of the TBX15/WARS2 region first came into modern humans from an archaic hominid population, likely related to the Denisovans. "The Inuit DNA sequence in this region matches very well with the Denisovan genome, and it is highly differentiated from other present-day human sequences, though we can't discard the possibility that the variant was introduced from another archaic group whose genomes we haven't sampled yet,” said Dr. Racimo, lead author of the study. The authors found that the variant is present at low-to-intermediate frequencies throughout Eurasia, and at especially high frequencies in the Inuits and Native American populations, but almost absent in Africa.
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