Scientists have shown that radiation irreversibly damages mature sperm and the disturbances are passed on to descendants. The findings are published in the journal Nature.

Researchers at the University of Cologne have found that radiation damage to mature sperm cannot be repaired but is transmitted to offspring. Female germ cells are completely restored and attempt to 'heal' sperm.

Scientists used Caenorhabditis elegans nematodes as a model to investigate the effects of radiation on genetic changes. The study showed that radiation damage to DNA does not interfere with sperm function, and eggs with similar damage either fully recover or become unviable if the damage cannot be repaired.

When an egg fuses with a damaged sperm, maternal repair proteins try to restore paternal DNA. But for this purpose, a mechanism is used that randomly combines torn DNA fragments. This leads to a large number of mutations, the researchers note.

The effect of radiation exposure on female (left) and male (right) germ cells on embryonic mortality in nematodes. When exposed to radiation on females, mortality is observed in the first generation (non-viable eggs), and in future generations, the born offspring fully recover to normal levels. Radiation exposure to males increases mortality slightly in the first generation, but it increases in future generations. Image by: Siyao Wang et al., Nature

The descendants resulting from this 'recovery' bear chromosomal damage that is not repaired by standard DNA repair mechanisms. The United genes are held together by specific histone proteins HIS-24 and HPL-1, which interfere with normal recovery.

To test whether a similar process works in humans, the researchers examined genetic data sets collected for the 1000 Genome Project and Islandic deCODE projects. Scientists have found the same structural DNA variants or randomly collected chromosomes in these sets. Like nematodes, chromosomal aberrations were specifically transmitted from fathers, not mothers.

Researchers note that such damage can potentially be caused, for example, during radiation or chemotherapy. Therefore, when planning a pregnancy after such treatment, it is necessary to take into account the possible risk that persists for the two months necessary to create new sperm instead of damaged ones.

 

Source: Nature