Issue link: https://tmcpulse.uberflip.com/i/980339
t m c » p u l s e | m a y 2 0 1 8 36 That Puzzling 7 Percent A portion of astronaut Scott Kelly's gene expression has not returned to normal T wo years after returning from his record-breaking year on the International Space Station, parts of Scott Kelly's DNA remain altered. The revelation, which came from NASA in March, prompted Scott's twin, Mark, also a retired astronaut, to tweet: "I used to have an identical twin brother. Then this happened…." The research surrounding Scott Kelly's DNA is part of NASA's ongoing Twins Study, which analyzes Scott's genome, as well as other molecular profiles, against his twin brother and also against Scott himself, pre-flight. This multi-omic approach—which compares data sets related to the numerous layers that contribute to DNA function and includes genomics, epig- enomics, and several other "omic" disciplines—will allow scientists to understand the genetic and health-related effects of space travel as they work to answer a question critical for a mission to Mars: What happens to the human body in space? "Understanding how zero grav- ity and radiation exposure affect the multi-omic signature of the human body is critical because it tells us about both life on Earth and in space," said Brendan Lee, M.D., Ph.D., chair of the department of molecular and human genetics at Baylor College of Medicine. "If we are to go to Mars, these issues will be very important, because when you get to Mars, there's not going to be a Texas Medical Center to take care of you. At the same time, I think by understanding how the body responds to a completely different environment, we will learn about whether there are applications on Earth that may benefit from those observations." NASA's press release about Scott Kelly's DNA revealed that 7 percent of his gene expression still has not returned to normal since he landed back on Earth. This finding might point to long-term modifications in genes related to his immune system, DNA repair, bone formation networks, hypoxia (lack of oxygen within tissues) and hypercapnia, which is a condition associated with too much carbon dioxide in the bloodstream. NASA stressed that these variances are associated with gene expression and do not indicate an alteration of the genetic code itself. Changes in the actual DNA code, known as genetic mutations, do occur, and can contribute to harmful conditions or diseases, including cancer. But the study of changes in gene expression and of how this may relate to chemical modifica- tions of DNA and of the proteins that bind DNA—a field called epi- genetics—is more complex. "I think it's sometimes difficult to convey the concept that there are actually two genomes; that there's the part of the genome that's made up of our DNA, and then the part of what we call the epigenome, which is the programming, the software, that makes the genome work," explained Cheryl Walker, Ph.D., Credit: NASA I think it's sometimes difficult to convey the concept that there are actually two genomes; that there's the part of the genome that's made up of our DNA, and then the part of what we call the epigenome, which is the programming, the software that makes the genome work. — CHERYL WALKER, PH.D. Director of the Center for Precision Environmental Health at Baylor College of Medicine B y A l e x a n d r a B e c k e r Twin brothers and former NASA astronauts Mark (left) and Scott Kelly, are part of NASA's ongoing Twins Study. Credit: NASA