In 1986, reactor number four in The Chernobyl nuclear power plant in Ukraine has suffered a catastrophic meltdown. An attack of radioactive atoms erupted from the debris and spread throughout Europe, even reaching North America. In the area around the power plant, an environmental catastrophe is unfolding. Pine trees collapsed. Insect numbers have declined. Contaminated soil withered crops.
In the hours after the collapse, residents of nearby neighborhoods were forced to get up and leave without warning while liquidators—military and other civilians—moved in to “clean up” the radioactive mess. Pets were not allowed to travel with evacuees and had to be abandoned. A directive from Ukraine’s Ministry of Internal Affairs ordered military personnel to be tasked with hunting down and culling domestic animals, including several area dogs within the Chernobyl Exclusion Zone.
But some pets evaded capture and murder, and made a home in the CEZ. The liquidators often fed and sheltered the now lost, and the inhabitants persevered.
Today, the defunct Chernobyl reactor is buried inside a massive concrete structure known as a sarcophagus, but traces of the meltdown remain. Radioactive atoms — radionuclides — released in the 10 days after the disaster still permeate soil, water, and, yes, the animals that made Central and Eastern Europe their home, including the dogs of Chernobyl.
This unfortunate fate of canines has a somewhat grim silver lining. By studying the DNA of these dogs, researchers can better understand how chronic exposure to radiation has long-term effects on physiology and health.
In a new study, Published in Science Advances on March 3, the researchers set out to decode the genes of the dogs around Chernobyl, describing the genes of the 302 free-roaming dogs that now call the power station and the area around home. It is the first time that a large mammal of the CEZ has been studied in this way.
“It provides 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 thrived for 15 generations in this region,” said Eileen Ostrander, a geneticist at the center. National Human Genome Research Institute of the National Institutes of Health and author of the study.
By studying subtle changes in the DNA known as SNPs, the team was able to measure genetic similarity in these populations. By comparing Chernobyl dogs with purebred canines from elsewhere in Europe, the team revealed that one group of dogs that live near the Chernobyl nuclear power plant, occupying Pripyat and the adjacent train station, is a genetically distinct, closed family.
This group differed, genetically, from the dogs living only 10 miles away, in the city of Chernobyl, who seem to have migrated further and bred with the local dogs.
“This sets the stage for future studies aimed at finding mutations in key genes that result from the radioactive environment,” Ostrander said.
Importantly, the study does not show that radiation in the disaster area itself caused changes or mutations in the dogs’ DNA. Inbreeding and isolation can cause the kind of changes the team saw in their DNA.
said Claire Wade, an animal geneticist and computational biologist at the University of Sydney not associated with the study.
A de novo mutation is a mutation that has not been passed down genetically. By looking at an entire genome — all of an organism’s DNA — rather than just polymorphisms, researchers can elicit more information, discovering mutations in genes that may have physiological effects. This is 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 the Chernobyl clusters might help these dogs survive in a highly radioactive environment. Perhaps, for example, there are certain genes that are turned on or off that confer a survival advantage in the dogs closest to the plant. Comparison of whole genome sequences will help reveal these relationships.
Currently, the complete DNA sequences of more than half of the 400 samples have been recovered, noted Tim Musso, a University of South Carolina biologist who studied organisms around Chernobyl after the disaster and an author on the paper.
The legend persists that life returned and flourished in Chernobyl after the disaster, however This is not necessarily the case. Although dogs are the first large mammal to be studied at Chernobyl, previous research has explored the effects of radiation on many different organisms in the area, from insects to birds.
For example, A 1997 paper showed that swallows are exposed to radiation Around Chernobyl it had higher de novo mutations and was more likely to be partially albino, and Moso studies have shown that the abundance of the species has decreased in contaminated areas.
Other studies hint at this kind of revelation that may come from the study of biota in the CEZ. In 2020, scientists discovered a type of fungus that contains high levels of melanin, a pigment that can absorb radiation and convert it into energy. Producing high levels of melanin could provide a kind of sunscreen or “shield” for astronauts, where the radiation risk is ever present.
Will the genomes of Chernobyl dogs provide a similar level of insight? This is an open question that the team is eager to answer.
“We really have what we need to address questions about the environment’s role in survival in this environment,” Musso said.
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