Researchers have for the first time mapped the genome of the Himalayan marmot (Marmota himalayana), a hibernating mammal that inhabits the high-elevation regions of the Himalayan mountains. Published in the journal iScience, the results hint at the genetic mechanisms underlying high-altitude adaptation and hibernation.
The Himalayan marmot (Marmota himalayana). Image credit: Shauryankar Lingwal / CC BY-SA 4.0.
“As one of the highest-altitude-dwelling mammals, the Himalayan marmot is chronically exposed to cold temperature, hypoxia, and intense UV radiation,” said Dr. Enqi Liu, a researcher at Xi’an Jiaotong University Health Science Center, China.
“They also hibernate for more than six months during the wintertime.”
Those striking biological features led Dr. Liu and co-authors to consider the Himalayan marmot as an ideal animal model for studying the molecular mechanisms of adaptation to extreme environments.
To begin, the scientists sequenced and assembled a complete draft genome of a male Himalayan marmot.
They also re-sequenced 20 other Himalayan marmots, including individuals living at high and low altitudes, and four other marmot species.
Additionally, RNA sequencing was done to compare gene-expression differences between marmots in a state of torpor and awake marmots.
The study authors found that the Himalayan marmot diverged from the Mongolian marmot about two million years ago.
They identified two genes — Slc25a14 and ψAamp (a processed pseudogene) — that have been selected in different directions in marmots living at low versus high altitudes, suggesting they are related to survival in high-altitude populations under conditions of extremely low oxygen.
They further suggest that Slc25a14 may have an important neuroprotective role.
The shift in ψAamp affects the stability of RNA encoding the gene Aamp, which may be a protective strategy to prevent the excess growth of new blood vessels under extremely low-oxygen conditions.
The RNA sequencing data show that gene-expression changes occur in the liver and brain during hibernation.
These include genes in the fatty acid metabolism pathway as well as blood clotting and stem cell differentiation.
“Interestingly, a previous study suggested that because the hibernator’s brain is exposed to near-freezing temperatures and has decreased blood flow, there is an increased risk of blood clots,” Dr. Liu and colleagues said.
“Their brain stem cells may also be better prepared to repair injuries as an adaptation needed to survive extreme environmental stresses.”
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Liang Bai et al. Hypoxic and Cold Adaptation Insights from the Himalayan Marmot Genome. iScience, published online December 20, 2018; doi: 10.1016/j.isci.2018.11.034
