The Himalayan Marmot and a Genome for High-Altitude Life

The Himalayan marmot is a fascinating mammal because it often lives at high altitudes. It makes its home in the Himalayas and on the Tibetan Plateau. It apparently has no problem dealing with the very cold temperatures, low oxygen levels, and high intensity of ultraviolet light in much of its environment. In fact, it’s thought to have a large population. A new study has analyzed the animal’s genome and found genes that help it survive under the seemingly harsh conditions at high elevation, especially when it's hibernating in winter.

A Himalayan marmot in Bhutan

Christopher J. Fynn, via Wikimedia Commons, CC BY-SA 3.0 License

The Himalayan Marmot or Marmota himalayana

The Himalayan marmot has a wide range and can be found in Pakistan, India, Nepal, Bhutan, and China. Like other marmots, the animal has a stout body with short legs and a stubby tail. The back legs are longer than the front ones. Its coat is thick and is buff in colour with dark or black patches. One of the black patches is often on the nose and another is often on the forehead. A black line may travel down the face to connect the two areas.

Diet and Life

Himalayan marmots feed mainly on herbs and grasses but occasionally eat fruits and roots. They live in colonies, which vary in size, and spend their nights in burrows. They hibernate in groups. Winter burrows may be as deep as thirty metres. The depth enables the animals to survive the most severe environmental conditions. Nevertheless, they experience low temperatures and low oxygen concentrations during hibernation. The animal hibernates for the impressively-long time of more than six months—from late September to some time in April.

Gestation reportedly lasts for one month. Between two and eleven youngsters are said to be born in either late spring or early summer. This data needs to be confirmed, however. Reproduction is one aspect of the marmot’s biology that needs to be further studied.

Studying the Animal’s Genome

Some Chinese scientists have recently finished sequencing the genome of the Himalayan marmot. They’ve made some interesting discoveries with respect to genes that seem to be adapted to help the animal survive hypoxia (low oxygen) and cold temperatures.

The scientists compared genome activity in Himalayan marmots living at high altitude with the activity in animals living at a comparatively low altitude. The animals are found at elevations of around 1,900 to 5,000 metres. As part of their research, the scientists observing transcriptional changes in the animals.

Genes do their job by making proteins. Transcription is the process in which the instructions encoded in a gene in a DNA molecule are copied onto a messenger RNA (mRNA) molecule. The mRNA leaves the nucleus, where the DNA is located, and travels to a ribosome in the cell. Here the protein coded for by the DNA is made. The fact that transcriptional changes appeared in the scientists' study of the marmots meant that the activity of genes had changed.

The analysis of the marmot's genome is preliminary, but the researchers have already made some interesting discoveries. One is that the Himalayan marmot separated from the Mongolian marmot about 1.98 million years ago. Some other highlights of the research are described below.

Genome Discoveries

The scientists found that during hibernation there was an increased activity of genes involved in fatty acid breakdown and decreased activity of genes involved in fatty acid manufacture. The researchers also observed a decreased synthesis of amino acids, decreased breakdown of carbohydrates, and a decrease in activity of genes involved in the circadian rhythm. The circadian rhythm is a cycle of biological activity over an approximately twenty-four hour period.

The activity of a gene known as Slc25a14 and a pseudogene known as ψAamp was different in the high and low elevation marmots and may be involved in helping the animal survive under harsh conditions. A pseudogene is similar to a real gene in structure but doesn’t code for a protein. Researchers have discovered that some pseudogenes aren’t completely inactive and have a regulatory function. This appears to be the case for the ψAamp pseudogene.

In hibernating animals living at high elevation, Slc25a14 activity stimulates processes that help to protect the marmot from hypoxia. The pseudogene appears to decrease the activity of the Aamp gene, resulting in a decrease in angiogenesis, or new blood vessel formation. This may be beneficial during very hypoxic conditions during hibernation.

Previous research has shown that the brains of hibernating animals living at high altitude are exposed to temperatures near freezing and have decreased blood flow. This puts the animals at an increased risk for blood clots in the brain—or it would do, if their body didn’t respond appropriately. The new research has shown that the genes involved in blood clotting become less active. In addition, genes involved in regulating stem cells become more active. Stem cells are unspecialized but divide to form specialized ones. The activation of stem cells may enable brain cells damaged during hibernation to be replaced.

Clues for Further Research

As the researchers say, their discoveries should act as clues for other scientists. The researchers acknowledge that more research is needed, but the discoveries so far are very interesting. The Himalayan marmot is a common animal, but it seems that there is still a lot to learn about it.

References

Information about the Himalayan marmot from Wildscreen Arkive

Marmota himalayana entry from the IUCN Red List

Himalayan marmot genome offers clues to life at extremely high altitudes from the EurekAlert news service

Hypoxic and Cold Adaptation Insights from the Himalayan Marmot Genome from iScience, Cell Press