Living with less
Survival secret of highlanders
A Tibetan father and son on a pilgrimage around China's Mount Kailas
Scientists have long wondered how the Tibetans are able to survive in the oxygen-thin high altitudes of the Tibetan highlands. The great Tibetan Plateau stands more than 13,000 feet (4000) meters above the sea level and usually at such heights most people are susceptible to hypoxia. That is when little or no oxygen reaches the body tissues which eventually lead to fatal lung or brain inflammation. A recent research has discovered that two new gene variants, which are linked to hemoglobin help Tibetans to use oxygen more efficiently than other people who live at low altitudes. Published on May 13th, in the journal Science, researchers from the University of Utah (U of U) School of Medicine and Qinghai University Medical School, China, reported that thousands of years ago, the Tibetan highlanders began to genetically adapt to prevent polycythemia, a process where the body produces too many red blood cells due to oxygen deprivations. This ancient yet distinct suit of physiological train also allowed the Tibetans to effectively deal with other health abnormalities like swelling of the lungs and brain as well as hypertension of the lung vessels leading to eventual respiratory failure. According to Dr. Lynn B. Jorde, professor and chair of U of U school of medicine and a senior author of the study, "For the first time, we have genes that help explain that adaptation". In a press release, Dr. Josef T. Prchal, study co-author and a hematologist and professor of internal medicine at U of U said, "What's unique about Tibetans is they don't develop high red blood cells counts. If we can understand this, we can develop therapies for human disease". As part of the research, the team of scientists analyzed samples of 31 Tibetan residents of a village located at 14,720 feet above the sea level. And after a rigorous process of comparing the villagers' DNA with samples taken from other people living in lower elevations nearby, the team of international scientists was able to isolate 10 specific genes that were exclusively found only among the high-elevation Tibetan subjects. And amongst these 10, there were two genes, EGLN1 and PPARA that the researchers found to be significantly associated with the decreased hemoglobin phenotype, which is unique to this particular part of the highland population. In other words, these two genes help the body fight high altitude sickness. Prof. Jorde explains, the Tibetans who have more copies of the gene variants (by inheriting a copy of each advantageous variant from both parents), had the least amount of oxygen in their blood system and used it more efficiently than people without either variant or only one copy from one parent. In his own words, "Tibetans with these genes appear to be much more efficient with the oxygen they have". According to the research report, the identification of these genes provides support for previously hypothesized mechanisms of high altitude adaptation and further explains the complexity of hypoxia response pathways in humans. The next step of the research is to do functional studies to see how these gene variants actually regulate oxygen level. The study team leader Tatum Simonson, a Doctoral student at the U of U's Eccles Institute of Human Genetics explains, the future of the research is aimed at teasing out more details about what exactly the altered genes do, which could help scientists find ways to "prevent people from getting sick" at high altitudes.
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