Astronaut’s Gene Expression No Longer the Same as His Identical Twin, According to NASA

Preliminary results from NASA‘s Twins Study revealed that 7% of astronaut Scott Kelly’s genetic expression had not returned to baseline after his return to Earth two years ago. Experts at NASA are studying what happened to the astronaut before, during, and after he spent one year aboard the International Space Station. Scientists are conducting an extensive comparison of Kelly and his identical twin, Mark, who remained on Earth.

Kelly spent 340 days on the ISS from 2015 to 2016, along with Russian crewmate Mikhail Kornienko. Earlier reports said that Kelly’s DNA had changed, which makes him no longer identical with his twin. But the reports were an inaccurate description of what really happened.

Kelly’s DNA did not change; it is his gene expression that did.

Gene expression is how the genes function within cells. According to NASA, some of Scott’s genes changed their expression while he was in space. Seven percent of those genes did not return to baseline.

This means that Kelly’s DNA still has the same sequence as before, but what his cells get from the DNA has changed.

Kelly and his twin are still identical.

Kelly’s gene expression transformation, however, suggests long-term changes to at least five biological pathways and functions, according to CNN.

To study the changes in Kelly caused by his time in space, experts at NASA measured Kelly’s proteins, metabolites, and cytokines before, during, and after his mission. The scientists found that flying to space can cause oxygen-deprivation stress, increased inflammation, and dramatic nutrient shifts – all of which can have an effect in a human’s gene expression.

According to NASA, the 7% change in Kelly’s gene expression is minimal.

Although 93% of Kelly’s genetic expression returned to normal once he was back on Earth, scientists note that changes in the function of his cells may occur.