Tibetan locals - who live at an altitude of 4,300 meters - possess a gene mutation that allows them to thrive in such an environment.
Image credit: Dr. Tsewang Tashi
The research team, including senior study author Dr. Josef Prchal, professor of internal medicine at the University of Utah, recently published their findings in the journal Nature Genetics.
At areas of high altitude, air pressure is low, meaning there are fewer oxygen molecules available to breathe in.
In response to high altitudes, the body can produce too many cells in the blood - a condition known as polycythemia. This can occur when levels of hemoglobin - a protein in red blood cells that carries oxygen - increase in an attempt to boost the amount of oxygen carried through the body.
Polycythemia can cause the blood to become thicker, meaning the heart has to work harder to pump it around the body. This can lead to long-term health problems, such as heart failure.
However, Dr. Prchal and colleagues have identified a gene mutation in Tibetans that stops their hemoglobin levels increasing at high altitudes, adapting their body to such environments.
Mutation in EGLN1 gene helps Tibetans adapt to high altitudes
To reach their findings, the team needed to collect blood samples of Tibetans in order to extract and analyze their DNA. But this became a challenge.
Dr. Prchal says that, despite several trips to Asia and numerous meetings with Chinese officials - who represent exiled Tibetans in India - the Tibetans were wary of foreigners and refused to take part in the study.
Soon after Dr. Prchal returned to the US, Dr. Tsewang Tashi - a native of Tibet - joined the Huntsman Cancer Institute at the University of Utah. Dr. Prhcal asked for his help in rounding up volunteers for the study, and Dr. Tashi was more than willing.
In addition, Dr. Prchal managed to gain a letter of support from the Tibetan spiritual leader, the Dalai Lama. "The Dalai Lama felt that a better understanding of the adaptation would be helpful not only to the Tibetan community but also to humanity at large," explains Dr. Prchal
As a result, the team was able to recruit 90 Tibetan participants from the US and abroad.
Through closely analyzing an area of the participants' DNA known as the "GC-rich" region, the team discovered that approximately 88% of Tibetans who live in high altitudes possess a mutation in the EGLN1 gene, which appears to control hemoglobin levels in response to high altitudes.
Furthermore, this mutation can be traced back to more than 8,000 years ago, and it is not present in Asians closely related to the Tibetans who reside in lowland areas.
The researchers say their findings suggest that the EGLN1 gene plays a key role in protecting Tibetans from developing polycythemia at high altitudes, and that "further studies are warranted to determine whether these alleles also alter other pathological responses to high-altitude hypoxia, such as pulmonary hypertension."
Dr. Prchal adds:
"These findings help us understand the unique aspects of Tibetan adaptation to high altitudes, and to better understand human evolution."
In addition, the team says because oxygen has an important role in human physiology and illness, a better understanding of human adaptation to high altitudes could pave the way for new treatments for an array of diseases.
"A more complete understanding of the genetic basis for adaptation to high altitude may lead to new approaches for the treatment of common causes of mortality, such as ischemic cardiovascular disease, in which hypoxia has a major pathophysiological role," the researchers conclude.
Last year, Medical News Today reported on a study by researchers from the University of California-San Diego, which claimed to identify two genes that explain why some people are more prone to chronic mountain sickness at high altitudes.