A group of top international scientists including geneticists from the Royal College of Surgeons in Ireland (RCSI) has made a breakthrough in understanding human adaptation to high altitude environments.
The new study identifies a gene in Tibetan highlanders, who live high in the Himalayas, which allows them to thrive at altitudes more than two miles above sea level which induce serious altitude sickness in other populations. The findings are published in the prestigious science journal Proceedings of the National Academy of Sciences (PNAS) this week.
The study also has implications to a wider understanding of human health and fitness. Low oxygen levels (hypoxia) is a common problem in patients both at home and in hospital. The new research is a step towards understanding how an indigenous population deals with hypoxia. By identifying genes that have helped Tibetans adapt to hypoxia we can potentially develop new approaches to dealing with low oxygen in for example, intensive care patients.
People who live or travel at high altitude respond to the lack of oxygen by making more haemoglobin, the oxygen-carrying component of human blood. Athletes often train at high altitude to increase haemoglobin concentration in order to process more oxygen when competing. However, high levels of haemoglobin at high altitude can cause altitude sickness. Tibetans have evolved physiologically to avoid altitude sickness by maintaining low haemoglobin concentrations.
To pinpoint the genetic variants underlying Tibetans' relatively low haemoglobin levels, the researchers collected blood samples from nearly 200 Tibetan villagers living in three regions high in the Himalayas.
A senior author of the study, Dr. Gianpiero Cavalleri, Biomedical Research Lecturer, RCSI, explains: "when we compared the DNA of the Tibetans to lowland Chinese we saw a genetic signature that was carried by almost all of the Tibetans but by very few of the Chinese. This same type is linked with low haemoglobin."
The study findings are particularly significant because they are the first to show evidence for natural selection (evolution) at high altitude for a specific genetic site. The research highlights the effect of having, or not having, this gene on individuals attempting to live or travel at high altitude. The implications also extend to cardiovascular health and fitness: "physiologists have known that high altitude populations in South America, Africa and the Himalaya have adapted in different ways to low oxygen environments. It seems nature has come up with different solutions to the same problem - there are probably many more genetic signals to be characterized and described", Dr. Cavalleri says.
The team's findings will be published the week of June 7th in the early online edition of Proceedings of the National Academy of Sciences.
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