In 1986, reactor number four at the Chernobyl nuclear power plant in Ukraine suffered a catastrophic meltdown. An onslaught of radioactive atoms erupted from the wreckage and spread across Europe, even reaching as far as North America. An ecological catastrophe began to unfold in the area around the power plant. The pine trees were shattered. Insect populations plummeted. The polluted soil withered the crops.
In the hours following the meltdown, residents of nearby neighborhoods were forced to up and leave with little notice while clean-ups – military personnel and other civilians – moved in to “clean up” the radioactive mess. Pets were not allowed to travel with the evacuees and had to be abandoned. A directive from Ukraine’s Ministry of Internal Affairs tasked military personnel with hunting down and executing pets, including the many dogs in the area within the Chernobyl Exclusion Zone.
But some of the pets avoided capture and killing by making a home in the CEZ. Scavengers often fed and housed the now strays, and the populations persisted.
Today, the doomed Chernobyl reactor is entombed inside a massive concrete structure known as a sarcophagus, but the effects of its collapse remain. The radioactive atoms – radionuclides – released in the 10 days after the disaster still seep into the soil, water and, yes, the animals that have made the CEZ their home, including Chernobyl’s dogs.
This unfortunate fate for canines has a somewhat grim silver lining. By studying the DNA of these dogs, researchers could better understand how chronic radiation exposure leaves long-lasting effects on physiology and health.
In a new study, published in the journal Science Advances on March 3, researchers set out to decode the genetics of the dog population around Chernobyl by characterizing the genes of 302 free-roaming dogs that now call the power plant and the surrounding area home. It is the first time a large mammal in the CEZ has been studied in this way.
“They offer an opportunity to see how the harsh environment, which includes exposure to high and low levels of radiation, can affect the DNA of animals that have lived and reproduced for 15 generations in this area,” said Elaine Ostrander, a geneticist at the National National Institutes of Health Human Genome Research Institute and study author.
By studying tiny changes in DNA known as SNPs, the team was able to measure genetic similarity in these populations. By comparing the Chernobyl dogs to purebred dogs from elsewhere in Europe, the team revealed that a group of dogs living near the Chernobyl nuclear power plant, which occupies Pripyat and the nearby railway station, is a genetically distinct and closed family.
This group differed, genetically, from the dogs living just 10 miles away in the city of Chernobyl, which appear to have migrated further and bred with local dogs.
“This sets the stage for future studies aimed at finding mutations in key genes that arise from the radioactive environment,” said Ostrander.
Important, the study It does not suit show that the radiation in the disaster zone has, in itself, caused changes or mutations in the dogs’ DNA. Inbreeding and isolation can cause the changes the group has seen in DNA.
“To find out if there were de novo mutations caused by radiation, the researchers would need to sequence the entire genome of the dogs and see if there were any unique variants in that population,” said Claire Wade, animal geneticist and computational biologist at the University of Sydney is unrelated to the study.
A de novo mutation is one that was not passed down genetically. By looking at an entire genome—all of an organism’s DNA—rather than just SNPs, researchers can extract more information, discovering mutations in genes that may have physiological effects. That’s exactly what the Chernobyl dog team plans to do.
With more than 400 DNA samples now collected, researchers can begin to interrogate how DNA variation in these Chernobyl populations might help dogs live in a highly radioactive environment. Perhaps, for example, there are certain genes that are turned on or off that provide a survival advantage to dogs closer to the plant. Comparing whole genome sequences will help reveal these relationships.
So far, a complete DNA sequence has been recovered for more than half of the 400 samples, noted Tim Mousseau, a biologist at the University of South Carolina who has long studied the organisms around Chernobyl after the disaster and author of work.
A myth insists that life returned and flourished in Chernobyl after the disaster, but this is not necessarily true. Although dogs are the first large mammal to be studied at Chernobyl, previous research has explored the effects of radiation on many different organisms at the site, from insects to birds.
For example, a 1997 paper showed that barn swallows exposed to radiation around Chernobyl had higher de novo mutations and were more likely to be part albino, and Mousseau’s studies showed that species abundance has declined in contaminated regions.
Other studies hint at the kind of revelations that can come from studying organisms in the CEZ. In 2020, scientists discovered a species of fungus with high levels of melanin, a pigment that can absorb radiation and convert it into energy. The production of high levels of melanin could provide a kind of protective sunscreen or “shield” for astronauts, where the threat of radiation is ever-present.
Will the genomes of Chernobyl dogs provide a similar level of insight? This is an open question that the team wants to answer.
“We really have what we need to address questions about the role of environment in survival in this environment,” Mousseau said.