Monday, 21 May 2012

Genetic Adaptation for Life at High Altitudes

Genetic Adaptation for Life at High Altitudes

Researchers from the University of California performed a study recently on the genetic adaptations to living in high altitudes. When most people reach altitudes higher than 4000m above sea level they experience a range of nasty symptoms, such as nausea, headaches and if they try to live up there, lower birth weights and higher infant mortality rates (Sanders, 2010). The researchers from the University of California studied the genomes of people living on the Tibetan Plateau. These Tibetans live at altitudes greater than 4000m but don’t experience any of the symptoms mentioned above.

The researchers collected the genomes from 50 unrelated Tibetans from 2 villages each at an elevation greater than 4000m. They then compared these genomes to a sample of 40 genomes collected from the Han Chinese. The Han Chinese were used as a control group because they don’t display any of the adaptations to high altitude that the Tibetans do, however they are close genetic relatives of the Tibetans (Megan J. Wilson, 2011). Indeed the analysis of the genomes suggested that the Tibetans and the Han Chinese split from each other less than 3000 years ago (a relatively short time in the history of human evolution) (Sanders, 2010). They analysed the genomes using a Genome Wide Allelic Differentiation Scan (GWADS), basically searching for variations in the two types of genomes. The variations they were looking for were called Single Nucleotide Polymorphisms (SNPs). What they found was that the two genomes were very similar, with variations occurring in only about 30 genes. Almost all of these 30 genes were related to how the body used oxygen (Sanders, 2010).

(Ishu, 2008)
The gene that had the most profound change was the EPAS1 gene, which in earlier studies had been dubbed the “super athlete gene”. This is because the EPAS1 gene regulates the body’s amount of haemoglobin in relation to the oxygen levels (Henderson J, 2005). What really surprised the researchers was the fact that people with 2 SNPs in this gene had lower than usual haemoglobin levels but were able to function just fine at high altitudes (Megan J. Wilson, 2011). This seems contradictory to what most people would assume about haemoglobin. Haemoglobin is the protein that allows oxygen to be carried in the blood so it was expected that having less of it would be a hindrance, especially in the low oxygen high altitude environments. However the research clearly showed that lower haemoglobin levels were present in the Tibetans who were well adapted to living at high altitude. Researchers are now struggling with the question of whether the ideal levels of haemoglobin differ at different altitudes.
Despite this the study has found about 30 genes that seem to be the key to living at high altitude. This information will have applications in the military, mountain climbing groups and even for farmers (who lose a large number of cattle each yeah when they graze in high altitude environments) (Smith-Thomas, 2010). This is substantial progress even if the answer does raise new questions.

Bibliography

U.S. National Library of Medicine. (2012). What are single nucleotide polymorphisms (SNPs)? Retrieved March 18, 2012, from http://ghr.nlm.nih.gov/handbook/genomicresearch/snp
Henderson J, W.-C. J. (2005, October 5). The EPAS1 gene influences the aerobic-anaerobic contribution in elite endurance athletes. Retrieved March 18, 2012, from National Centre For Biotechnology Information: http://www.ncbi.nlm.nih.gov/pubmed/16208515
Ishu. (2008, December 17). Single Nucleotide Polymorphism (SNP) Animation. Retrieved April 1, 2012, from Biotechnology Online: http://ishanwadibiotechnology.blogspot.com.au/2008/12/single-nucleotide-polymorphism-snp.html
Megan J. Wilson, P. C. (2011). Genomic Analysis of High Altitude Adaptation: Innovations and Implications. Retrieved March 17, 2012, from PubMed Central: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3097096/?tool=pubmed
Sanders, R. (2010, July 1). Tibetans adapted to high altitude in less than 3,000 years. Retrieved March 17, 2012, from University of California Berkeley: http://newscenter.berkeley.edu/2010/07/01/tibetan_genome/
Smith-Thomas, H. (2010). Brisket Disease. Retrieved April 1, 2012, from Western Cowman: http://www.westerncowman.com/september07/brisketdisease.html




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