Kelly twins are still twins

  • After years of study with two brothers to see how space affects DNA, NASA reveals that only the expression of some genes changes


  • A statement from NASA itself made it appear wrong that 7% of Scott’s DNA was not the same as before

In March 2015, Scott Kelly took off for the International Space Station (ISS) to begin a 340-day adventure, one of the longest space voyages to date. Before the launch, Kelly, and his brother, also astronaut Mark, proposed to NASA that, given their status as identical twins, the agency could study in them the genetic variations caused by prolonged stays in space. In this way, since their return in 2016, scientists have analyzed the data collected, trying to understand what are the differences in the DNA evolution of the two brothers and the origin of these changes.

Over the past week, a multitude of reports appeared claiming that the Kelly twins were no longer identical and that 7% of Scott’s DNA had not returned to normal, citing a NASA press release as a source. The preliminary findings of the study referred to in the news gave rise to headlines such as “Twins are no longer identical” or “After a trip into space, the DNA of an astronaut is no longer the same as that of his brother.”

The truth is that, although some variations were detected in the genetic material of Scott Kelly after his return, traveling to space did not alter his DNA.

“Mark and Scott Kelly are still identical twins, the DNA of Scott has not changed in the essential, ” NASA has explained in a statement to deny such information. “What researchers have observed are changes in gene expression, which is the way the body reacts to its environment.” The agency also explains that these modifications are within the range of normal in stress situations and that the results are analogous to those that can occur in mountaineers or divers.

To put it in perspective, the difference in the genetic sequences of humans and chimpanzees is less than 2% and those of two different people -without kinship– around 0.1%. One of the first surprised was Kelly himself, who joked about one of the articles in a tweet saying “this could be good news, I do not have to say that Mark is my identical twin brother”.

The way in which genes are expressed can be affected by changes in the DNA sequence through random mutations, in many cases irrelevant. Gene expression can also be influenced by environmental factors, such as stress or diet. As the US space agency recognizes, “we are beginning to understand how space travel affects the human body at the molecular level, and NASA and other researchers who collaborate in these studies, we hope to announce more complete results this summer.” In fact, the rapid dissemination of incorrect information about Scott and his DNA raises the question of whether NASA should have waited to publish the full and contrasted article, instead of offering preliminary results. “It would have been preferable if we could have had the full document before, but we’re trying to be very careful about this,” Bailey, a professor at the University of Colorado and one of the researchers responsible, acknowledged The Atlantic magazine. “And this is a good example of why.”

Studies with twins are a work tool of exceptional value for geneticists. Now, the question is to establish the origin of the changes that did occur in the endings of the chromosomes (the telomeres) and their possible long-term effects. As the people responsible for the study explained to Nature last January, it is normal for the levels to return to normal once the astronauts return to Earth, once they make rapid changes in the diet and sleep patterns that continue in the ISS.

“The beauty of this study is that when you integrate the data sets of physiological, neurobehavioral and molecular information, you can draw correlations and see patterns,” explains Dr. Tejaswini Mishra, a researcher at the Stanford University School of Medicine. responsible for creating and integrating the database into the study. “Until now, no one had ever analyzed human subjects so deeply and outlined them in this detail.”