Paternal radiation exposure linked to DNA mutations in children

The children of men exposed to radiation following the Chernobyl nuclear reactor incident in 1986 show specific patterns of DNA mutations, providing evidence that radiation-induced changes in sperm can affect offspring.

The study, published in Scientific Reports, involved sequencing the genomes of more than 200 children of Chernobyl clean-up workers and German radar operators exposed to radiation, and comparing them to the genomes of more than 1200 children from unexposed families. The researchers found that children of exposed fathers had a higher frequency of clustered de novo mutations (cDNMs), with the number of mutations associated with the father's estimated radiation exposure. This seems to be an example of a parent's environment affecting their germline, with consequences for their children.

'Despite uncertainty concerning the precise nature and quantity of the ionising radiation involved, the present study is the first to provide evidence for the existence of a transgenerational effect of prolonged paternal exposure to low-dose ionising radiation on the human genome', said the researchers, who are based at the University of Bonn, Germany.

Environmental factors such as radiation are known to cause mutations in human cells, which are linked with increased risk of cancer. Since these mutations usually occur in somatic cells such as skin cells, they are not passed on to the next generation. However, this study suggests that radiation can also damage DNA in a man's sperm cells, and that this can result in mutations in his offspring.

The team found that children of Chernobyl workers had roughly three times as many cDNMs as children from unexposed families. Children of German radar operators, who were exposed to stray radiation, had nearly twice as many cDNMs as children from unexposed families.

Environmental factors can also cause epigenetic changes that can alter gene expression in offspring. However, these affect gene regulation rather than altering the DNA sequence itself.

Previous research has also shown that mutations in sperm increase with paternal age, including in disease-related genes, and that this can increase disease risk in the children of older fathers. However, most of the mutations found in this particular cohort occurred in non-coding regions of the genome.

'Given the low overall increase in cDNMs following paternal exposure to ionising 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', said the researchers.

The researchers also noted some limitations to their study, including voluntary participation – which may cause biases within their cohorts – and estimation of radiation exposure based on decades-old devices and historical records. Further research may explore other types of DNA changes, such as chromosomal translocations, which can be caused by radiation.