Mutant dogs from the Chernobyl zone hide a surprising genetic secret

© Paul Bill/Pexels

The 1986 Chernobyl nuclear disaster left huge scars in the region. Large areas of land in Ukraine, Belarus and Russia have been contaminated with radionuclides, making soil and water unfit for consumption and agriculture in the long term. Exposure to harsh radiation has led to a drastic increase in thyroid cancer cases, especially in children, and other health problems, such as cardiovascular and immune diseases, have also been observed in the population.

The fauna and flora of the region have been severely affected by radioactivity, with genetic mutations and a reduction in biodiversity. Stray dogs in the Chernobyl Exclusion Zone have developed specific genetic mutations, linked to their chronic exposure to radiation. At least that's what was thought until now. A study published on December 27 in PLOS One, from the University of North Carolina and the Mailman School of Public Health at Columbia University has just challenged this theory.

A dog Chernobyl, photographed in 2017. © Jorge Franganillo/Wikipedia

The imprint of time rather than that of radiation

If the Two dog populations, separated by barely 16 km, present marked genetic divergences, their origin defies initial intuition. The long-favored hypothesis of radiation-induced mutations collapses in the face of genomic data.

DNA analysis of dogs living near the plant reveals a surprising absence mutations characteristic of radiation exposure. Professor Matthew Breen and his colleagues have nevertheless deployed an impressive methodological arsenal, analyzing nearly 400 genomic regions (specific segments of DNA) where the two populations diverge. They have not detected any trace of the alterations typical of prolonged exposure to ionizing radiation.

The researchers have therefore established that the dogs from the city of Chernobyl share their genetic heritage with their congeners from Russia and Poland, thus constituting an ideal control population. This reference allows us to understand that the observed differences result from another mechanism: a lightning natural selection in the early days of the catastrophe.

Megan Dillon, the study's lead author, offers an alternative explanation: The first dogs to survive the disaster likely already had genetic traits that made them resilient. This intense selective pressure would have created a distinct population near the plant, kept isolated from their urban cousins ​​for more than 30 generations. They are therefore not mutant dogs strictly speaking, that is to say individuals carrying genetic mutations directly induced by radiation, but are in reality the representatives of a distinct evolutionary lineage.

• A recent study found that the genetic differences between Chernobyl dogs and those from the city were not caused by radiation.
• The researchers found no evidence of genetic mutations linked to radiation exposure in dogs from the exclusion zone.
• The genetic differences are instead explained by intense natural selection at the start of the disaster, creating a distinct canine lineage.

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