Astronaut has no lingering, major epigenetic differences from earthbound twin brother

Astronaut has no lingering, major epigenetic differences from earthbound twin brother
Andrew Feinberg and Lindsay Rizzardi test procedures for purifying blood samples on NASA's microgravity plane called the 'Vomit Comet.' Credit: Johns Hopkins Medicine

In a landmark study, a group of U.S. scientists from Johns Hopkins, Stanford University and other institutions has found no long-lasting, major differences between the epigenomes of astronaut Scott Kelly, who spent a year in space aboard the International Space Station, and his twin brother, Mark, who remained on Earth.

What this study tells us about the perils of travel on a person's genome is not clear, say the scientists, but research on additional astronauts in space could eventually help scientists predict the types of medical risks they may face on long space journeys where people experience less gravity than on Earth, exposure to harmful ultraviolet rays and other risks to health.

"This is the dawn of human genomics in space," says Andrew Feinberg, M.D., the Bloomberg Distinguished Professor of Medicine, Biomedical Engineering and Mental Health at The Johns Hopkins University. "We developed the methods for doing these types of human genomic studies, and we should be doing more research to draw conclusions about what happens to humans in space."

Epigenetic changes involve chemical "tweaks" to DNA that can influence , but the changes don't affect the underlying genetic code itself. The changes affect when and how a gene is read, or expressed, for its protein-encoding instructions. When epigenetic changes occur at the wrong time or place, the process can turn genes on or off at the wrong time and place, too.

Scientists have long monitored and studied the physiological effects of space travel on astronauts. However, most of these astronauts travel on spaceflight missions of six months or less, not the longer missions required to travel to Mars or elsewhere. More research is needed to understand the impact of long spaceflight missions on the human body, where there is more exposure to radiation, restricted diet, less exercise, lower gravity and disrupted sleep cycles.

Feinberg notes that studying identical twins—who, by nature, have the same genetic material—was an important and rare opportunity to compare physiological and genomic changes when one twin went into space and the other remained on Earth. "However, since we only have two people in our study, we can't say that these changes are due to space travel itself," says Feinberg. "We need more studies of astronauts to draw such conclusions."

For the study, described in the April 12 issue of Science, scientists collected , physiological data and cognitive measurements from Scott and Mark Kelly at various time points over 27 months before, during and after Scott's one-year space mission. The samples from Scott during the flight were collected on the space station when shipments from Earth arrived on a Soyuz rocket and, that same day, shipped back to Earth on the rocket so that the samples could be processed within 48 hours.

Feinberg and former postdoctoral student Lindsay Rizzardi, now a senior scientist at the HudsonAlpha Institute for Biotechnology, focused on epigenetic changes to Scott and Mark's genomes.

Colorado State Professor Susan Bailey studies telomeres, or the protective ‘caps’ on the ends of chromosomes. Credit: Colorado State University

Specifically, Feinberg and his team examined two types of white blood cells (CD4+ and CD8+) isolated from Mark and Scott's blood. They focused on epigenetic marks consisting of chemical modifications called methyl groups that are added onto the DNA in a process called methylation.

Overall, they found that about just as many epigenetic changes occurred in earthbound Mark's DNA as in his space-flying twin. There was a less than 5 percent difference in overall methylation between the twins during the mission. The largest difference occurred nine months into the mission when 79 percent of Scott's DNA was methylated, compared with 83 percent of Mark's.

The locations of methylation changes in the genome were different for each twin. For example, the scientists found methylation changes near genes involved in immune system responses in Scott during his time in space, but not in Mark. This correlated with data from other researchers involved in the current study who found increases in certain biochemical markers associated with inflammation in Scott but not Mark.

"It was encouraging to see that there was no massive disruption of the epigenome in either Mark or Scott," says Rizzardi. "However, 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."

In the current study, Scott's biological samples were shipped back to Earth immediately, but in the future, astronauts may need to process and store samples on the spacecraft. Feinberg, Rizzardi and NASA scientist Brian Crucian developed detailed instructions for doing complicated experiments in microgravity. Feinberg and Rizzardi traveled for a week on the famed "Vomit Comet," a plane that simulates weightlessness, to test their protocols for overcoming the challenges of collecting, purifying and storing blood samples aboard the space station.

Of the studies led by scientists at Stanford University, Colorado State University, Cornell University and others, some of the notable results included Scott's in-flight lengthening of telomeres, the protective endcaps on chromosomes. The telomere lengthening, as previously reported, returned to normal when Scott returned to Earth.

In addition, more than 90 percent of genes that changed activity levels during Scott's flight returned to normal six months after the flight. Yet, Feinberg notes, these changes are not indicative of space flight alone, nor do they differ from what might occur normally.

The scientists also found that the shape of Scott's eyeball changed over the course of the flight, including a thicker retinal nerve and folds in the choroid layer that surrounds the eye. These changes typically affect visual acuity and, says Feinberg, have occurred in other male astronauts but not females. The scientists also observed cognitive changes and increased stress levels in Scott during the flight, which, again, may not be attributed to space flight alone.

Feinberg says this study lays the groundwork to make predictions about an astronaut's gene-related and physiological function during a long-term mission: "If we know what to expect, we can anticipate health problems astronauts may encounter and ensure that medicines and other remedies are at hand during a mission."

Explore further

Year in space put US astronaut's disease defenses on alert

More information: F.E. Garrett-Bakelman el al., "The NASA Twins Study: A multidimensional analysis of a year-long human spaceflight," Science (2019). … 1126/science.aau8650

M. Loebrich el al., "Hazards of human spaceflight," Science (2019). … 1126/science.aaw7086

Journal information: Science

Citation: Astronaut has no lingering, major epigenetic differences from earthbound twin brother (2019, April 11) retrieved 22 April 2019 from
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Apr 11, 2019
This is a very encouraging study for space flight potential. Well done.

Apr 12, 2019
We've been labouring under the mistaken idea that all radiation is bad or has a notable impact. Studies done in Chernobyl and this story prove that it's time for scientists to reassess and determine if some radiation is harmless, or maybe even mildly beneficial.

Apr 13, 2019
Gosh TB - a story involving the ISS, and your comment is missing your usual "ISS is a white elephant and complete waste of money" content. Are you prepared to admit that the ISS does serve some useful purpose after all?

Apr 14, 2019
Still unknown is what happens after a year of cosmic ray exposure in deep space?

The ISS in low earth orbit is subject to cosmic rays without the benefit of much atmosphere, but from the perspective of cosmic ray exposure, it's a lot closer to being a commercial airline pilot than being in deep space for a year.

In deep space, half the cosmic rays are not stopped by the physical presence of the earth.

In deep space, there is no earth's magnetic field to deflect much of the rest.

Apr 14, 2019
I would say conservatively that deep space is probably four times the cosmic ray exposure of low earth orbit.

Maybe only double the exposure for the really high energy stuff that makes it through the atmosphere and the magnetic field, but not the earth itself.

Maybe hundreds of times the exposure for the weaker energy stuff that is almost completely deflected by the earth's magnetic field anywhere but the poles.

Apr 14, 2019
Since the ISS is still well within the magentosphere of Earth ist is pretty well protected from charged particles. Solely the shielding effect of the atmosphere is missing.

On the ISS the astronauts are exposed to roughly 0.8mSv per day.

For comparison: A usual exposure is a bout 2 mSv per year (which can vary quite a bit depending on where you live). The level of radiation before an evacuation is called (at least over here in germany) is an exposure of 100mSv within 7 days.
So the ISS is well below any level where anyone should panic, but still well above what even somone working with radilogical materials is allowed to be exposed to (20mSv per year)

That said the unit Sievert helps to stochatically estimate the chances of contracting cancer (i.e. genetic problems).
The study referred to in the article is looking at EPIgenetic effects (differences in protein expression).

Apr 14, 2019
Why do they need identical twins?
Why not compare pre and post space travel samples, of the astronaut?

Apr 14, 2019

I realize that they were studying protein expression. I'm just saying the other unresolved long pole in the tent is cosmic rays.

"Solely the shielding effect of the atmosphere is missing."

No. The earth itself (the big rock under us) blocks half. . . and obviously wouldn't be present in "deep space."

So, it's conservatively double for the lack of rock and double for the lack of magnetic field, but probably much more. . .

Your Sievert analysis is flawed when dealing with particles (from electrons to iron nuclei) traveling at relativistic speeds that undergo spallation, like a frangible projectile, and essentially create through and through wound channels of ruptured cells. It has been estimated that 5% of brain cells could be lost in transit to Mars in this fashion, leaving a huge question about how the body can cope with requiring that type of renewal (never mind the more well studied cancer implications).

It's like comparing bullet wounds to lead exposure.

Apr 14, 2019
What is repugnant about the Sievert analysis is that the "science" behind it has been politicized and warped twice: once by the nuclear power industry over the last 50 years, and then again by NASA in the context of space exploration because they are not sure they will need to have or want to pay for adequate shielding, magnetic or physical.

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