Nav: Home

Arctic Inuit, Native American cold adaptations may originate from extinct hominids

December 20, 2016

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 has now been scrutinized by scientists: TBX15 and WARS2. This region is thought to be central to cold adaptation by generating 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. have followed up on the first natural selection study in Inuits to trace back the origins of these adaptations.

To perform the study, they used the genomic data from nearly 200 Greenlandic Inuits and compared this to 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 Fernando 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. TBX15 is a gene known to affect the human body's response to cold, and is associated with a number of traits related to body fat distribution. The authors speculate that the archaic variant may have been beneficial to modern humans during their expansion throughout Siberia and across Beringia, into the Americas.

The research team also worked to understand the physiological role of the region, which may be of interest to scientists concerned with factors that help determine BMI index and fat metabolism. They found an association between the archaic region and the gene expression of TBX15 and WARS2 in various tissues, like fibroblasts and adipose tissue. They also observed that the methylation patterns in this region in the Denisovan genome are very different from those of Neanderthals and present-day humans. "All this suggests that the introduced variant may have altered the regulation of these genes, thought the exact mechanism by which this occurred remains elusive." - said Racimo, who was a graduate student in UC Berkeley at the time of the study, and now works at the New York Genome Center.

The evidence adds to the remarkable number of recent examples of ancient interbreeding that may have conferred unique adaptive traits to modern humans, either from Neanderthals or Denisovans. And it is the second major example ---the other being the EPAS1 genomic locus (found in the high altitude adaptation of Tibetans) to be passed on from archaic humans into the modern human gene pool.
-end-


Molecular Biology and Evolution (Oxford University Press)

Related Genome Articles:

A close look into the barley genome
An international consortium, with the participation of the Helmholtz Zentrum München, Plant Genome and Systems Biology Department (PGSB), has published methodologically significant data on the barley genome.
Barley genome sequenced
Looking for a better beer or single malt Scotch whiskey?
From Genome Research: Pathogen demonstrates genome flexibility in cystic fibrosis
Chronic lung infections can be devastating for patients with cystic fibrosis (CF), and infection by Burkholderia cenocepacia, one of the most common species found in cystic fibrosis patients, is often antibiotic resistant.
A three-dimensional map of the genome
Cells face a daunting task. They have to neatly pack a several meter-long thread of genetic material into a nucleus that measures only five micrometers across.
Rhino genome results
A study by San Diego Zoo Global reveals that the prospects for recovery of the critically endangered northern white rhinoceros -- of which only three individuals remain -- will reside with the genetic resources that have been banked at San Diego Zoo Global's Frozen Zoo®.
More Genome News and Genome Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Teaching For Better Humans
More than test scores or good grades — what do kids need to prepare them for the future? This hour, guest host Manoush Zomorodi and TED speakers explore how to help children grow into better humans, in and out of the classroom. Guests include educators Olympia Della Flora and Liz Kleinrock, psychologist Thomas Curran, and writer Jacqueline Woodson.
Now Playing: Science for the People

#534 Bacteria are Coming for Your OJ
What makes breakfast, breakfast? Well, according to every movie and TV show we've ever seen, a big glass of orange juice is basically required. But our morning grapefruit might be in danger. Why? Citrus greening, a bacteria carried by a bug, has infected 90% of the citrus groves in Florida. It's coming for your OJ. We'll talk with University of Maryland plant virologist Anne Simon about ways to stop the citrus killer, and with science writer and journalist Maryn McKenna about why throwing antibiotics at the problem is probably not the solution. Related links: A Review of the Citrus Greening...