Source: StatNews (Extract)
Posted: March 3, 2023

You’d think an irradiated wasteland would be a poor place to make a home, but some animals beg to differ.

Since the Chernobyl nuclear meltdown 37 years ago, both wild animals and free-roaming domesticated dogs have, to the surprise and delight of environmentalists, flocked to and flourished in the evacuated,1,000 square mile zone surrounding the plant. It’s a revealing paradox of modern life: A place too corrosive for humans to live is the rare place animals can live undisturbed.

These animals, and the dogs in particular, might teach us something, researchers at the National Institutes of Health and the University of South Carolina proposed Friday. Thriving for decades under extreme radiation, they have become a singular experiment in life on the edge — what it means to live and reproduce in one of the most hostile environments imaginable.

Studying them could tell us about the long-term damage humans suffer working in similar environments. It could also reveal the ways these animals have adapted, selecting over generations for genes that confer resistance to radiation and the other stressors — cold, food scarcity — of the Chernobyl exclusion zone in Ukraine.

Scientists, in theory, could one day use that genetic information to build therapies or protective gear that mimic those adaptations, helping shield workers at nuclear plants, for example, or even protect astronauts on missions to the moon or Mars.

“It’s a nuclear armageddon, it’s kind of Orwellian in a lot of ways,” said Tim Mousseau, a biologist at the University of South Carolina and one of the senior authors on the Science Advances paper. “But it’s actually extremely useful to us.”

Mousseau has been studying the effects of radioactive fallout on animals living in the zone since 1999, but mostly through smaller critters: Birds, small rodents. The area abounds in larger animals, such as moose and even a population of the world’s last truly wild horses, both of which may be more translatable to humans, but it’s “almost impossible to do nondestructive work on them,” Mousseau said.

“You have to capture them,” he said. “And that’s just impossible.”

Then in 2017, Mousseau got a call from a colleague that the feral dog population was getting a touch out of control. These dogs had for years been something of a beloved mystery to the researchers and plant personnel. But with their count booming past 800, authorities were looking for vets to set up a spaying-and-neutering program.

No one’s quite sure where these dogs came from. The Soviets tried to put down residents’ dogs after the meltdown, to prevent them from spreading radiation. But it’s suspected that soldiers missed a few and ever since, you can find some semi-feral but nevertheless totally good boys hanging outside the Chernobyl cafeteria, waiting for scraps from the workers who still keep the plant in order.

Mousseau signed up for the veterinary program, purely to help out, but soon realized that in drawing blood and DNA from the dogs, he was collecting a treasure trove. Researchers could use this data to measure the effects of radiation exposure over generations in large mammals similar to humans.

“It was like holy jumping!” Mousseau said. He explained, “the dogs are just, you know, uniquely, ideally suited for this particular kind of study.”

It wasn’t just the dogs’ similarity to humans or the fact that they were more approachable than, say, moose. The 800 or so dogs were also spread over a large area of the exclusion zone, from the highly radioactive area directly around the plant to more ambiently radioactive areas miles and miles out. Comparing the dogs in the outer reaches to the ones at the disaster site could help researchers zero in on what genetic changes are truly caused by radiation exposure and what is pure happenstance.

To even start answering those questions, though, scientists would need to create a kind of genetic baseline. These dogs’ 2 billion letter-long genomes have been scarred not only by gamma rays but also by the more casual scars of ancestry: Who their parents were and where their grandparents hailed from and who those grandparents paired with. Researchers needed to understand those mundane scars — to start unraveling the mysterious origin of the Chernobyl dogs — before they could understand the kind of scars we imagine turn turtles into ninjas.

So Mousseau teamed with Elaine Ostrander, a pioneering dog geneticist who had spent two decades sequencing and analyzing canine genomes for what they might tell us about both man and man’s best friend.

“It’s a really easy experiment to do wrong, right?” she said. “It would have been very easy to say, ‘these dogs live in high radiation, these dogs live in low dose,’ go ahead and compare the genomes and get a whole lot of false positives because these have more Berger-Picard in them and these have more Rottweilers.”

That analysis is what Ostrander and Mousseau are now publishing. It offers no definitive answer for the layperson, although it does suggest that the dogs do indeed descend from pets left behind by townsfolk who fled in 1986. And it leaves a detailed map that Ostrander can begin using for the exciting work.

At the NIH, Ostrander is now sequencing the dogs’ entire genomes. When the complete sequencing is done, she’ll be able, with the background knowledge she now has, to compare dogs in high dose radiation areas to dogs in low dose radiation areas and figure out which individual base pair changes are actually from radiation exposure.

For some changes — the candidates for what Ostrander calls her “dream mutations” — they’ll run further tests, expressing the warped genes in cells in the lab to see precisely how they may have helped these dogs survive.

“I think that’s just really a golden opportunity for us to try and understand how a genome copes [with such extremity],” she said. “How does a genome figure stuff out and figure it out so fast?”

The work has been partially held up by Covid and the Russian invasion of Ukraine, Mousseau said. Russian soldiers briefly took over the area last winter but they soon retreated and his team was able to visit as recently as October. They plan to return in June to continue research and provide more treatment to the dogs.

Meanwhile, outside researchers are eagerly awaiting results to Ostrander’s questions and others. How different are these dogs actually? Can their genetic repair systems handle the damage? What are the health outcomes?

“It’s a cliffhanger! I love Elaine, but she has left us with a cliffhanger,” said Bridgett M. vonHoldt, an ecology and evolutionary biologist at Princeton University. “Everyone wants to know. We need to know more.”