Floating in zero gravity in space for one year has changed the DNA of NASA astronaut Scott Kelly. He and his twin brother, Mark, also a NASA astronaut, are part of the space agency’s Twin Study.
After he set a world record by spending 340 consecutive days aboard the International Space Station, Scott’s DNA has changed and he grew two inches in height while he stayed in space between 2015 and 2016. More than becoming taller than Mark, the telomeres of Scott’s actually become significantly longer in space.
Space genes activated
CBS reported that hundreds of Scott’s space genes were activated by his year-long flight which reportedly changed the astronaut’s immune system, DNA repair, bone formation networks, hypoxia, and hypercapnia. But upon his return to Earth, Scott’s height and 93 percent of his DNA returned to normal.
Nevertheless, there was a seven percent change in his genes which may stay that way. The researchers explained that the change in his DNA could be caused by the stresses of space travel that can cause changes in the biological pathways in a cell and the ejection of DNA and RNA.
Also upon his return to Earth, Scott’s mental reflexes and accuracy went down significantly. NASA blamed it on his re-exposure and adjustment to the planet’s gravity.
Meanwhile, NASA said that the Twin Study propelled the space agency into the genomics era of space travel. It was a perfect nature versus nurture study with Scott staying at the ISS and Mark remaining on Earth.
Prior to the launch of the Twin Study, NASA had a grasp of what happens to the human body after astronauts spend six months at the ISS which is the standard duration. However, in the case of Scott, his one-year mission is a stepping stone to a three-year mission to Mars.
After the NASA team measured a large number of metabolites, cytokines, and proteins, the researchers learned that astronauts who go on a space flight go through oxygen deprivation stress, increased inflammation, and dramatic nutrient shifts which affect gene expression.
When the team presented the unexpected finding in 2017 that Scott’s telomeres became longer, the researchers verified the unexpected change with multiple assays and genomics testing. But the majority of the telomeres shortened two days after he returned to Earth.
The research team is integrating and summarizing the findings and is evaluating the possible impact of the findings on future space travel beyond low Earth orbit. The team is expected to publish later a paper on its findings, while a series of smaller papers grouped by related research areas will likewise be released.
CNN reported that the preliminary results from the study of Scott and Mikhail Kornienko, a Russian cosmonaut, were released last week at the yearly Investigator’s Workshop for NASA’s Human Research Program.
The team is made up of 10 groups of researchers who are looking at a wide variety of information about the health of the Kelly twins. It includes their immune response, bone formation, gut microbiome, and how their DNA might be affected by living in space.
After the researchers performed genome sequencing of the DNA and RNA from white blood cells of Scott and Mark, they found that the twins have hundreds of mutations unique to each man. There are over 200,000 RNA molecules that were presented differently.
The chemical modifications to Scott’s DNA decreased while he was in space. However, it returned to normal upon his return to the planet. The researchers said that the modifications only show how sensitive the genes are to changing environments, whether in space or on Earth.
The researchers explained Scott’s longer telomeres while in space to an increase in exercise and decrease in calorie intake while on the station. They said that Scott experienced declining bone formation, but most of the levels of his healing hormones that help with bone and muscle health increased. The scientists said it is likely because of all the exercises that astronauts perform in space daily to battle bone and muscle loss.
While Scott’s level of cortisol, the stress hormone, remained normal, he suffered from a spike in inflammation as soon as he landed on Earth. The researchers explained it to the stress of re-entering the atmosphere.
The twins had differences in the bacteria in their digestive system. It was expected because they were living in different environments and eating different foods. In the case of Scott, two of the main bacterial groups switched dominant positions in his microbiome between the astronaut’s time in space and on Earth.
In March, Scott and Kornienko went through a series of tests after they got back to Earth from their year in space. When their capsule landed upright on dry land, the two had to maneuver themselves halfway out of the capsule before they were assisted out. Scott is convinced that it would be easier to leave the capsule on Mars because of the lesser gravity on the red planet.
[researchpaper 리서치페이퍼= Vittorio Hernandez 기자]