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A gene variation commonly found in endurance athletes most likely evolved as humans moved out of warm, food-rich environments to colder and harsher conditions, new research shows.
The common genetic variation - which separates endurance athletes from sprinters - is due to natural selection, according to Professor Kathryn North from the University of Sydney.
In a paper published in Nature Genetics (published in the advance online publication 9 September 2007), Professor Kathryn North and colleagues based at the Children's Hospital at Westmead show that the variant form of the gene ACTN3, commonly found in endurance athletes, is also associated with more efficient muscle metabolism.
Those findings, added to data from DNA tests of individuals around the world, have led researchers to conclude that the gene (originally the "sprinters" gene) evolved a variant form over millions of years to help humans 'endure' changing and more hostile environments.
The results build on Professor North's groundbreaking study, published in 2003, which specifically linked two variations of the ACTN3 gene to athletic performance. Her discovery was that variations of the gene provided an important guide to whether an elite athlete has ability to be a power sprinter or an endurance performer.
The original sprinter gene is more common, accounting for about 80 per cent of the Australian population. In these individuals ACTN3 encodes for a protein called alpha-actinin-3. This is the protein which is found only in fast-twitch muscle fibres and is responsible for the explosive bursts of power necessary for successful sprinters or track cyclists. Among elite power athletes the alpha-actinin-3 protein is nearly always present.
Those with the endurance variation of the gene, about 20 per cent of Australians, do not make the alpha-actinin-3 protein. But results in mice show that they may have more efficient muscle metabolism than sprinters. Among elite endurance athletes - marathon runners and rowers - the variant form of the gene is more common.
To find out how and why this variation in the ACTN3 gene came about the study looked at DNA samples from 96 individuals around the world.
"Most Africans have alpha-actinin-3, it's the normal ancestral state. But as you move into European and Asian populations there is a marked increase in the number of people without the protein. In some Asian populations that number reaches 40 per cent, or even higher in some isolated populations," Professor North said.
She believes the switch to more efficient metabolism is likely to have occurred due to natural selection during the last Ice Age, when humans began moving out of the food-rich areas of Africa into colder, harsher environments.
"We can now explain how this common genetic variation influences athletic performance as well as why it has become so common in the general population. There is a fascinating link between factors that influence survival in ancient humans and the factors that contribute to athletic abilities in modern man," said Professor North.
Editor's Note: Original news release can be found here.
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