Thursday , June 17 2021

U of T expert on how space travel affects gene expression



The researchers had a rare opportunity to see how the conditions of the International Space Station translate into changes in gene expression when comparing identical twin astronauts. One of the twins spent nearly a year in space while the other remained on Earth.

The space station environment induced changes in gene expression through a process called epigenetics.

NASA scientists already know that astronauts will be affected differently by the physical stresses they experience. Studies of the genetic origins of astronauts may explain why some are more susceptible to health problems when they return to Earth. These findings can translate into personalized preventive measures for vulnerable astronauts.

Surprisingly, it seems that these findings may also lead to the development of therapies for common syndromes that affect us on Earth.

NASA studies the consequences of space travel on the human body since the beginning of the space age. At a press conference held about a week after arriving at the International Space Station (ISS), Canadian astronaut David Saint-Jacques said he felt "a bit congested" and "had a big red face … like the sensation that you feel monkey bars. "The basis for this uncomfortable feeling is related to the redistribution of fluids from the lower part to the upper body.

NASA Glenn's Advanced Exercise Countermeasures Project Addresses How Microgravity Affects Astronauts' Health NASA)

Health after long space missions

The health effects that result from long missions in space are not well understood. In general, astronauts remain in excellent mental and physical health relative to the general population, even after returning from long-term missions. Moreover, the health consequences of such missions have been recognized, including cardiovascular deconditioning and vision problems, whose causes are being investigated.

NASA scientists are exploring how gene expression-the way DNA is converted into tissues-changes in response to the environment within the ISS. The field of epigenetics describes mechanisms by which environmental factors such as microgravity, relatively high levels of carbon dioxide, and possible radiation outbreaks alter the way DNA is read.

Researchers also want to know how the unique DNA of each astronaut will determine their response to the space station environment. Currently, of the 37 studies in progress at the space station, three specifically focus on genetic research.

Two of a Kind

Preliminary results from the exceptional study of identical twin astronauts support the idea that space travel can affect gene expression in different organs. From 2015 to 2016, astronaut Scott Kelly was aboard the ISS for 340 consecutive days. His twin brother Mark stayed on Earth. Scott's basic genetic code was not altered, but the space station's environment affected the way in which this code was converted into tissue.

According to one of the study's lead scientists, Christopher Mason, these changes occurred in important biological pathways relevant to bone formation and the immune system. The changes in gene expression were categorized in relation to the possible risk, "low, medium or high".

Low-risk changes to gene expression (approximately 93 percent of all changes) returned to normal when Scott returned to Earth. Possible changes from medium to high risk were not reversed after six months and "are changes we want to keep an eye on," according to Mason. For example, there are changes of expression that lead to the immune system being on "maximum alert," says Mason.

Although the study of identical twins provides the best assessment of the effects of space on gene expression, there are not many twin astronauts around.

The validation of the findings in the Kelly twins will involve, by necessity, studies in other astronauts. Currently, these validation studies are taking place on the International Space Station, such as liquid biopsies (cell free DNA and blood RNA samples) are collected for analysis. But the experiments with the twins really provided a "stepping stone to all of these subsequent studies," says Mason.

Vision changes after missions

Previous studies on eye health in a group of astronauts suggest that not all astronauts will respond in the same way to life on the space station. The astronaut ophthalmic syndrome is a condition that affects some astronauts. These eye changes are classified by NASA "as a significant risk to human space travelers," and include changes in the lens and eye shape.

Pre-flight images of normal optical disc. Post-flight right and left optic disc showing visual changes of long-duration space flight: grade 1 edema (upper and nasal) on the right optic disc (photos by NASA)

In some cases, astronauts with excellent vision before space flight "come back needing to wear glasses," says Scott Smith, NASA's chief nutritional biochemist.

"We saw chemical differences in blood samples (from astronauts) before the flight, so we started looking at genetics."

Seventy-two astronauts provided blood samples for this study. In the analysis, the results of the research suggest that each astronaut's genetic history plays a role in determining his eye's vulnerability, or epigenetic response, to harmful triggers at the space station.

Eyes of space and earth's wombs

This research means that certain astronauts may be warned of their personal risk of developing vision problems during long space missions. Better yet, personalized preventive measures or personalized medications can be discovered and implemented for those at greater risk of disease.

"Virtually all the work NASA does has implications for the general population," says Smith.

Astronaut ophthalmic syndrome is related to another much more common health problem here on Earth. It turns out that the same genetic variants and changes in serum factors that are associated with ocular problems in astronauts are also linked to polycystic ovary syndrome (PCOS), a form of infertility in women.

PCOS affects up to 10 percent of women. A genetic component for this syndrome was previously suspected.

Genetic and epigenetic studies in astronauts promise to provide astronauts personalized medical interventions while in space. And they could also provide those of us on Earth with potential therapies.The conversation

Christine Bear is a professor at the University of Toronto School of Medicine.

This article has been republished in The Conversation under a Creative Commons license. Read the original article.


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