March 22, 2018

Did astronaut Scott Kelly's DNA really change 7% while he was in space? Not really, says NASA.

Daily Briefing

    Media headlines last week claimed that space travel had altered 7% of astronaut Scott Kelly's DNA, meaning that his genes no longer matched those of his identical twin brother Mark—but NASA experts say that's not exactly true.

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    Background: Identical twin astronauts offer a rare research opportunity

    NASA has studied the effects of long-stays in space on astronauts for years, but in 2014, it launched a unique study: NASA planned to monitor astronaut Scott Kelly's genes during a year-long stay aboard the International Space Station, using as a baseline—Mark Kelly, Scott's identical twin and a retired astronaut, who would remain on Earth.

    Scott flew to the space station in 2015 and lived there for a U.S. record of 340 days. The NASA study examined Scott and Mark before, during, and after the mission.

    What NASA really found

    Several media outlets published stories indicating that 7% of Scott's DNA was changed in such a way that it no longer matched Mark's DNA. Scott also tweeted his shock at the news.

    But NASA on Thursday published a statement clarifying that Scott's DNA had not fundamentally changed. Rather, NASA said, "What researchers did observe are changes in gene expression, which is how your body reacts to your environment." The changes occurred across a number of genes, NASA said, but were "within the range for humans under stress, such as mountain climbing or SCUBA diving."

    So where did the 7% figure come from? Of all the genes that changed expression while Scott was in orbit, 7% continued to display the same changes months after he returned to earth. As The Atlantic noted, "If 7% of Scott's genetic code changed … he'd come back an entirely different species."

    A grain of truth?

    While the 7% figure was misrepresented, The Atlantic reports that Scott's DNA did undergo a slight change. Scott's telomeres, which are protective caps at the end of chromosomes in DNA, lengthened while he was in space.

    Typically, telomeres shrink with age and even more so with stress, so scientists believed that Scott's telomeres would shrink due to the stress of spaceflight. However, just the opposite occurred.

    According to Susan Bailey, a radiation cytogeneticist and a professor at Colorado State University who led the telomere research, "There was no doubt that [Scott experienced] telomere elongation in space, and they shortened dramatically when he came back," she said. However, "that is very separate from gene expression. It's not the same thing at all."

    John Greally, the director of the Center for Epigenomics at Albert Einstein College of Medicine, said that the news misrepresentation was an honest mistake. "The way that people have run with this and overinterpreted is human nature. You don't need to talk to a genomics person to get feedback on that," he said. "But I love the fact that people care. It would be so much worse if they didn't" (Koren, The Atlantic, 3/16; Victor, New York Times, 3/16; Schwartz, New York Times, 3/24/14).

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