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Twins have been the subject of scientific testing for years. NASA is adding to the research with identical twin astronauts, who they are using to study genetics. However, this study of twins has a twist – one of the twins is not on Earth.
Scott Kelly is currently on the International Space Station (ISS) and will be there with a Russian cosmonaut to study medical science in space, while his twin, Mark Kelly, will be studied on the ground. This experiment is to help scientists better understand the affects of the microgravity of space on genetics. NASA’s chief scientist for the ISS, Julie Robinson, compares this study to that of personalized medicine, in which doctors have started testing the genes of their patients before deciding on a treatment plan.
What has been discovered is that not everyone’s body reacts the same way to being in space. This is important for NASA scientists to understand, as it will one day influence who will be able to go to Mars. It is possible that there are people who do not have the right genes to allow them to be exposed to all of the radiation which occurs that far into space.
An example of the different effects of space on individual people was noted four years ago, when astronauts were returning to Earth with permanent vision loss. The eyesight damage mainly affected men, in whom the return to Earth would cause the optic nerve to swell, compressing the eyeball in such a way that it was no longer round. In addition, fluids in the brains of some astronauts would cause swelling, leading to extra pressure in the brain.
Another issue with space travel is bone loss. However, NASA has been working on alleviating this problem. Astronauts have been using resistant, high-intensity exercise, along with an accurate amount of calories and Vitamin D. This regimen has been effective in preventing the loss of bone mass density.
Researchers working on the “twin study” are going to analyze performance and behavioral health. The results could lead to a better understanding of people, so that NASA could put together better crews for space missions, as well as to provide them with the right support. Being on a mission to Mars for three years with only a handful of people is a difficult situation, and if things get tense between some people or things go wrong in the mission, astronauts cannot just quit. The idea is to try and prevent that situation. Scott’s last mission was six months long. Four months into the mission, he was ready to be done, which is called the Third-Quarter Effect. NASA is also working to alleviate this feeling by pairing the right crews together, as Scott will be spending a year at the ISS.
Scott has successfully completed one month aboard the ISS. Zero-gravity affects the body in a variety of ways, but it is not so easy to understand what is a result of zero-gravity, and what would have happened anyway. However, having two test subjects with the same genes, fitness level and lifestyle makes that determination a whole lot easier, and the research is already in motion in space and on Earth with NASA researchers.
Telomeres, cuffs that cushion the edges of chromosomes, get shorter as people get older. As telomeres get shorter, the chromosomes come unraveled, resulting in the afflictions that come with age. One of the questions NASA will be testing is which twin’s telomeres will be shorter – Scott’s or Mark’s. During the year that Scott will be spending in space, he will be orbiting the Earth at 17,500 mph (28,000 k/h), which could possibly slow his body clock by a few milliseconds. However, his telomeres may more than make up for that, and he could return to Earth physically older than Mark, even though there are many life stresses associated with accelerated telomere loss.
Chromosome samples were taken from the astronaut twins and then banked before Scott left NASA, so scientists would have a telomere baseline for this genetic study. More samples will be taken throughout the year. Scott will have to draw his own blood from space and then spin it down and freeze it, until a returning ship comes through the space station. Also, for two years after Scott’s return to Earth, the twins will be followed to see if space-related telomere loss will slow, and if the brothers will synchronize.
The blood samples will be used to look for the condition of the twins’ epigenomes, chemical on-off switches on top of the genome which regulate which genes are asserted and which genes are muted. Environment is a big operator in epigenetic change, especially in space, because cells will adjust to the weightless state. Molecular maps can be created to show what the different cells are doing, and what is happening to them while in zero-gravity. Chris Mason, with Weill Cornell Medical Center in New York, is the geneticist who is leading this part of the research.
The twins will also also have their microbiomes watched. The cells that make up the human body are outnumbered 10 to one by bacteria, viruses, yeasts, and molds which live in the body. These are good for the body, and they keep the digestive tract running as it should. The bacteria in the gastrointestinal tract, however, does not colonize, according to Martha Vitaterna, research professor at Northwestern University, and the co-investigator of the microbiome research. The bacteria the body needs comes from fresh vegetables and fresh fruits, which will be missing from Scott’s diet while he is in space.
Microbiomes can also be affected by genes, as each person’s genetic make-up determines which microorganisms will flourish in the intestines. Mark and Scott’s microbiomes will be watched throughout the year through stool samples, which Scott will, again, have to ship to NASA researchers.
Scott’s bodily fluids are shifting in space. In zero-gravity, his fluids will drift toward his head, as well as other places, because there is not any gravity pulling them down and keeping them where they are needed. Vision can be damaged permanently due to pressure on the optic nerve, and the eyes, as there will also be fluid build-up in the brain. The cardiovascular system can also be damaged when Scott returns to Earth, and there will be a risk of atherosclerosis.
There are some changes that can be monitored by studying blood samples. Scientists can look for proteins which regulate water excretion. Vascular damage can be found using ultrasound scans. Scott had dots tattooed on his upper body to indicate the exact places for him to position the ultrasound probe. Other studies that the twins will endure include monitoring their sleep cycles, immune systems, psychological states and more.
NASA is planning to go to Mars at some point, and the twins’ sacrifice as astronauts will go a long way in the field of genetics. The trip to Mars will take two years however, and scientists do not know how the human body will handle that trip. This study will go far toward answering many questions.
By Jeanette Smith
Photo courtesy of NASA – Creativecommons Flickr License