It is the age of space travel. Astronauts spend days and months inside a space craft on missions to explore our celestial neighborhood. The near future of space travel looks like a scene from a sci-fi story. People gearing up to reach the neighboring red planet in hopes of more space to live in when things have become too packed on the blue planet. However, to the human body customized to dwell on Earth, living in zero gravity can cause big changes in the general way the body functions.
A team of scientists studied two individuals, a set of identical twins, over the period of two years. One of the twins was on the Earth during the study period, while the other spent an year in the space in the middle of the study period. Scientists noted that the activity of several genes changed in the space dwelling twin during his space-time but a majority of these genes resumed normal activity on return to Earth. Curiously, the Earth dwelling twin showed bigger epigenetic changes than his astronaut brother. Epigenetic changes are chemical modifications of the DNA molecule that change the gene expression levels (the DNA's speed of activity) but do not mutate the DNA or abolish its function altogether.
Another curious finding was the lengthening of telomeres, or the ends of the chromosome, in the space twin. Telomeres are repetitive structures that protect the physical ends of the DNA molecule from degradation. The telomere length of a normal person shortens with age and with stresses and environmental pollution. While the telomere length of the Earth twin remained the same during the study period, his space counterpart showed increased telomere length during his spacecraft stay. His telomeres returned to normal length when he got back to the Earth.
Andrew Feinberg, an author of the study and the Bloomberg Distinguished Professor of Medicine, Biomedical Engineering and Mental Health at The Johns Hopkins University said "this is the dawn of human genomics in space". But he cautioned that inferences should not be drawn from a single study involving just one pair of case (the study subject) and control (the counterpart individual that has or lives in normal circumstances) participants. "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", Lindsay Rizzardi, another author says.
In this landmark and multi-center study published on April 14, 2019 in Science, the space twin's biological samples were shipped back to the Earth immediately for analyses in labs. However, as a future direction, scientists working on this project aim to develop ways to process and store biological samples in the spacecraft.
Image source: Max Pixel