Astronaut's genetic expression is different in space

NASA astronaut Scott Kelly (and his genes) made headlines last week. Several media outlets, including CNN and CBS reported the guy who spent ‘a year in space’ has genetically altered himself in the process. Some went further to proclaim he was no longer an identical twin of his brother Mark, a retired NASA astronaut of some repute himself. Any hopes of getting a real-life mutant or superman must however, be tempered with the exact knowledge of the changes and the scientific explanation.

What Scott experienced was a shift in ‘gene expression’, a measure of how certain genetic changes compensate for prolonged change in environment, and consequently some biological functions and pathways incur a permanent physiological shift. In Scott’s case, the change was to the tune of 7%, when measureg against his genetic copy, Mark. It offered NASA an unusual, and unique chance to treat Mark as the ‘control subject’, and determine that the changes in Scott’s genetic expression were permanent, and irreversible.

Astronaut’s DNA altered by 7% … NOT!

Call it lazy journalism, but this sort of genetic change is nowhere close to DNA alteration, as some of the over-zealous outlets proclaimed. DNA is the unique genetic code of a person’s body, and altering them would mean re-structuring, or re-arranging cells itself. In effect, some genes may swap places, or even edit, alter, or amend some genetic sequential code. It can happen owing to external factors. Exposure to strong UV radiation, prolonged nicotine vapors, or radiation can cause DNA mutations. However, Scott wasn’t exposed to any of these. In fact, just by virtue of being different individuals, both Scott and Mark would have thousands of unique genetic mutations in their genome.

But his DNA was floating in his blood?

Yes! And that’s really not that dramatic as it sounds. DNA isn’t like some bone-spur or a blood clot. Thanks to CSI, almost everyone knows that even by spitting, sneezing, or leaving a fingerprint you could be leaving behind your DNA. For Scott, the prolonged stress of space travel presumably caused some bits of his DNA to circulate freely in his blood stream. But NASA also claims it could be a combination of other factors like age-related mutation.

What really happened?

Basically, his 340-day long stay in space meant Scott was continuously exposed to oxygen-deprivation, some dramatic shift in nutrients, and high degree of inflammation. To compensate for these, cytokines (secreted by immune systems), metabolites (for essential life functions), amino-acids (protein workhorses of a cell) underwent some chemical changes. Most of these, nearly 93% all told, reverted to their normal self, but the rest of the changes didn’t even after two years back on earth.

Typical DNA sequences comprises of base pairs (A, C, T, and G), which combine to form a gene. Cells read these to create the proteins. But not all of these genes are active, and it relies on a complex endocrine and related signals.

NASA guesses, prolonged exposure to restricted calorie intake, oxygen deficiency, and radiations have possibly recalibrated some of those signals, causing the mutations. Additionally some changes in blood formation, clotting, gut bacteria, immune-system hyperactivity and ageing, and collagen levels were detected. Let’s be clear however, exposure to environment high in carbon-di-oxide content, isolation, or zero-gravity stress, even on the earth can cause similar mutations.

Famous last words?

Regardless of the tweets by Scott and Mark themselves, they remain identical twins! NASA themselves claim they’re at the beginning of understanding impact of space travel on molecular changes.

#astronaut #geneexpression #space