DNA Mutations Discovered in The Children of Chernobyl Workers : ScienceAlert

The DNA damage from ionizing radiation (IR) erupting from the Chernobyl nuclear disaster of 1986 is showing up in the children of those originally exposed, researchers have found – the first time such a transgenerational link has been clearly established.

Previous studies have been inconclusive about whether this genetic damage could be passed from parent to child, but here the researchers – led by a team from the University of Bonn in Germany – looked for something slightly different.

Rather than picking out new DNA mutations in the next generation, they looked for what are known as clustered de novo mutations (cDNMs): two or more mutations in close proximity, found in the children but not the parents. These would be mutations resulting from breaks in the parental DNA caused by radiation exposure.

“We found a significant increase in the cDNM count in offspring of irradiated parents, and a potential association between the dose estimations and the number of cDNMs in the respective offspring,” write the researchers in their published paper.

“Despite uncertainty concerning the precise nature and quantity of the IR involved, the present study is the first to provide evidence for the existence of a transgenerational effect of prolonged paternal exposure to low-dose IR on the human genome.”

The findings are based on whole genome sequencing scans of 130 offspring of Chernobyl cleanup workers, 110 offspring of German military radar operators who were likely exposed to stray radiation, and 1,275 offspring of parents unexposed to radiation, used as controls.

On average, the researchers found 2.65 cDNMs per child in the Chernobyl group, 1.48 per child in the German radar group, and 0.88 per child in the control group. The researchers say those numbers are likely to be overestimates due to noise in the data, but even after making statistical adjustments, the difference was still significant.

What’s more, a higher radiation dose for the parent tended to mean a higher number of clusters in the child. This fits with the idea that radiation creates molecules known as reactive oxygen species, which are able to break DNA strands – breaks which can leave behind the clusters described in this study, if repaired imperfectly.

The good news is that the risk to health should be relatively small: children of exposed parents weren’t found to have any higher risk of disease. This is partly because a lot of the cDNMs likely fall in ‘non-coding’ DNA, rather than in genes that directly encode proteins.

“Given the low overall increase in cDNMs following paternal exposure to ionizing radiation and the low proportion of the genome that is protein coding, the likelihood that a disease occurring in the offspring of exposed parents is triggered by a cDNM is minimal,” the researchers write.

To put this in perspective, we know that older dads are more likely to pass on more DNA mutations to their children. The subsequent risk of disease associated with parental age at the time of conception is higher than the potential risks from radiation exposure examined here, the researchers report.

Related: Worms at Chernobyl Appear Mysteriously Unscathed by Radiation

There are some limitations to note. As the initial radiation exposure happened decades ago, the researchers had to estimate people’s exposure using historical records and decades-old devices.

Participation in the study was also voluntary, which may have introduced some bias, as those who suspected they’d been exposed to radiation may have been more likely to enrol.

Even with those limitations, we now know that with prolonged exposure, ionizing radiation can leave subtle traces in the DNA of the generations to come – emphasizing the need for safety precautions and careful monitoring for those at risk.

“The potential of transmission of radiation-induced genetic alterations to the next generation is of particular concern for parents who may have been exposed to higher doses of IR and potentially for longer periods of time than considered safe,” write the researchers.

The research has been published in Scientific Reports.