Results of Landmark NASA DNA Twin Study Are In

NASA twins Mark Kelly and Scott Kelly
Brothers Mark Kelly and Scott Kelly participated in the landmark NASA twins study. NASA

Have you ever wondered exactly what happens to the human body when it's suspended in space for an extended period of time? Based on Hollywood productions alone, men and women who navigate the galaxy always seem to be just fine by the time they land back on Earth, but are astronauts so lucky in reality? NASA made it its mission to find out, and the results may surprise you.

In a new landmark DNA study just published in the April 12, 2019 issue of the journal Science, researchers from John Hopkins, Stanford and other institutions reveal that after a year in space, astronaut Scott Kelly experienced no major, long-term differences to his epigenome (a.k.a. the record of chemical changes to DNA) compared to that of his twin brother, Arizona Senate candidate Mark Kelly, who stayed firmly planted on Earth. (Mark is the husband of former Congresswoman Gabby Giffords who was shot point blank during a constituent meeting held outdoors in Casas Adobes, Arizona.)


While the scientists behind the study say the implications of their work aren't entirely clear yet, it appears additional research on the genomes of astronauts in space could help predict what kinds of unique health issues they may be at risk for.

"The Twins Study has been an important step toward understanding epigenetics and gene expression in human spaceflight," J.D. Polk, DO, chief health and medical officer, NASA headquarters, said in a statement. "This has helped inform the need for personalized medicine and its role in keeping astronauts healthy during deep space exploration, as NASA goes forward to the Moon and journeys onward to Mars."


Bodies In Space

Here's the deal with putting your body in space: It exposes you to harmful ultraviolet rays, radiation, limited food and exercise, lower gravity, disrupted sleep cycles and an unknown number of other potential hazards. And while scientists have spent decades studying the effects of space travel on astronauts, most of these men and women have traveled on missions that max out at six months. In order to travel somewhere, like say, Mars, missions need to be much longer, and scientists say it's critical to understand the effects these super-extended missions have on the human body.

"This is the dawn of human genomics in space," Andrew Feinberg, M.D., the Bloomberg Distinguished Professor of Medicine, Biomedical Engineering and Mental Health at Johns Hopkins University said in a statement. "We developed the methods for doing these types of human genomic studies, and we should be doing more research to draw conclusions about what happens to humans in space."


When scientists talk about epigenetics changes, they're referring to chemical DNA tweaks. These tiny alterations may have a major impact on a person's health by influencing the way genes are expressed, but they don't affect the genetic code itself. Potential problems pop up when epigenetic changes happen at the wrong time or place and in turn cause certain genes to turn on or off at the inappropriate time and place.

A major advantage of this new research is the fact that it studies identical twins who naturally have identical genetic material. But while the study subjects offer a rare and unique glimpse into the potential for long-term genetic changes in space, the researchers are quick to admit the tiny sample size means more testing is essential. "Since we only have two people in our study, we can't say that these changes are due to space travel itself," Feinberg said. "We need more studies of astronauts to draw such conclusions."


Twins Study Methodology

The methodology for the study involved collecting blood samples, physiological data and cognitive measurements from each Kelly twin at various points over a 27-month period, before, during and after Scott's one-year space mission. If you're wondering how in the world (or universe) Scott's samples reached the scientists from space, they were transported via a rocket (yes, seriously).

In the future, scientists hope to process and store samples onboard the International Space Station itself, but for the purposes of this study, samples were rocketed back to Earth and processed within 48 hours. Then Feinberg and his team examined the brothers' genomes, looking for epigenetic changes, specifically focusing on two types of white blood cells and examining a process called methylation, which occurs when chemical changes called methyl groups are added onto the DNA.


Generally speaking, there were just about as many epigenetic changes in Scott as there were in his twin. The biggest difference was observed nine months into Scott's space mission when 79 percent of his DNA was methylated (when methyl is added to DNA), compared to 83 percent of Mark's DNA. The locations of methylation were different in both men; Scott's methylation appeared near genes in immune system response, which researchers believe correlates with additional data that found Scott had increased markers associated with inflammation.

"It was encouraging to see that there was no massive disruption of the epigenome in either Mark or Scott," former postdoctoral student/current senior scientist at the HudsonAlpha Institute for Biotechnology, Lindsay Rizzardi, said in a statement. "However, with only two people in the study, we're limited in the conclusions we can draw about the effect of space travel on the genome. But the findings give us clues to what we should examine more closely in future studies of astronauts."