Identical twin brothers, Scott (right) and Mark Kelly. Source: NASA

Spending time in space increases the rate of DNA methylation across thousands of genes, NASA’s Twins Study has found. Preliminary results from the study indicate that the number of genes ‘switched off’ with methylation increases when a person travels to space and that the effect persists for a short while after returning to Earth.  

“Some of the most exciting things that we’ve seen from looking at gene expression in space is that we really see an explosion, like fireworks taking off, as soon as the human body gets into space,” said Chris Mason, Ph.D., Twins Study Principal Investigator and Associate Professor at Weill Cornell Medicine, in a statement. “With this study, we’ve seen thousands and thousands of genes change how they are turned on and turned off. This happens as soon as an astronaut gets into space, and some of the activity persists temporarily upon return to Earth.”

NASA’s Twins Study is an attempt to learn more about how space travel might affect us on a genetic level and, potentially, help us to plan for a manned mission to Mars in the future. Such a journey would require the astronauts to be in space for years at a time and NASA hope to be able to predict how such a task would impact their health. To that end, the study has been following any genetic changes of astronaut Scott Kelly during and after a year in space, and comparing them to his identical twin brother Mark, who is himself a retired astronaut.

While Mark remained on Earth, Scott spent 12 months aboard the International Space Station before returning in March last year. The year-long mission was completed alongside cosmonaut Mikhail Kornienko, who is part of a separate study investigating the biological effects of spaceflight. Since Scott returned, researchers at NASA have been investigating any changes to his DNA that occurred while he was away and comparing them to DNA alterations experienced by his brother. Earlier this year, preliminary results were released that revealed that Scott’s telomeres, the caps on the end of his chromosomes, had grown longer during his trip.

The most recent report reveals that Scott’s DNA displayed increased levels of methylation during his trip and that the effect continued for some time after returning home. DNA methylation allows for genes to be ‘switched off’, by attaching a methyl group to the DNA molecule that prevents the binding of transcription factors, silencing expression. Because silencing gene expression is one way that cells can alter their function and activity, these results may indicate that prolonged space travel, such as would be required to reach Mars, could results in ‘unprecedented cell function.’

The full results of NASA’s Twins Study are expected to be released next year.

“This study represents one of the most comprehensive views of human biology,” Mason said. “It really sets the bedrock for understanding molecular risks for space travel as well as ways to potentially protect and fix those genetic changes.”

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