Early results of NASA study show the stress of space travel

Alan Martin February 1, 2017

Its taken 29 years, but the 1988 buddy movie Twins no longer depicts the most important research on genetic differences in twin brothers. NASA has taken that crown, releasing some startling early results from their year-long analysis of identical twins Scott and Mark Kelly – one of whom spent a year in space, while the other remained on Earth.

While Mark stayed on Earth, Scott spent a year on the International Space Station, with measurements taken before, during and after his stay. And boy, are there differences. “Almost everyone is reporting that we see differences,” said Christopher Mason, a geneticist from Weill Cornell Medical College in New York.

Before I get into the details of what’s different, though, a few points. First of all, this is early days in the analysis (“the data [is] so fresh that some of them are still coming off the sequencing machines,” as Mason pointed out), and peer-reviewed conclusions may not be with us for over a year. Second, we’re talking about just two people, and there are all kinds of reasons the results may not be conveniently generalised to the wider population of potential space travellers. Finally, due to genetic privacy concerns, it’s not clear how much of the research we’ll ultimately get to see.

But onto the juicy stuff. What differences are we suddenly seeing in the Kelly twins? First, the telomeres (protective caps on the end of DNA strands) were longer in Scott than in Mark. Telomeres shorten with age, and have been linked to the physical signs of ageing and even disease, and while Scott’s telomeres quickly returned to his previous length on returning to Earth, any kind of lengthening was hugely unexpected. “That is exactly the opposite of what we thought,” explained Susan Bailey, a radiation biologist at Colorado State University. NASA is now planning to examine telomere length in ten more astronauts, with results expected to be revealed as early as next year.

DNA methylation reduced in Scott, while it increased in Mark over the same period. That’s when a chemical marker is added to DNA, which impacts gene expression. They returned to similar levels on return to Earth, and nobody really knows what that means just yet.

Finally, there was a big shift in gene expression signatures between the twins. These things often happen on Earth, reacting to changes in lifestyle, but this was on a greater scale than you’d expect. It’s entirely possible that’s just the stress of space and miserable space meals having an impact but, again, the scientists don’t know for sure yet.

Although the results currently provide more questions than they do answers, this is a big step forward for our understanding of the long-term impacts of space travel. Being able to do genomics in zero-gravity is a relatively new development, only becoming possible at the end of 2015. There are plenty of worrying side effects noted in retired astronauts, and this kind of study will hopefully help us to get a grip on these, making that mission to Mars more likely to end in cheers, rather than tears.

Images: NASA