Stress alters the expression of small Ribonucleic acids (RNAs) in male mice and leads to depressive behaviours in later generations, a new research suggests.
"Trauma is insidious. It not only increases a person's risk for psychiatric disorders, but can also spill over into the next generation," researchers said.
The mice show depressive behaviours that persist in their progeny, which also show glitches in metabolism, they said.
In the study, Isabelle Mansuy, a neuroscientist at the University of Zurich, Switzerland, and her colleagues periodically separated mother mice from their young pups and exposed the mothers to stressful situations - either by placing them in cold water or physically restraining them.
These separations occurred every day but at erratic times, so that the mothers could not comfort their pups (termed the F1 generation) with extra cuddling before separation.
When raised this way, male offspring showed depressive behaviours and tended to underestimate risk, the study found.
Their sperm also showed abnormally high expression of five microRNAs. One of these, miR-375, has been linked to stress and regulation of metabolism.
The F1 males' offspring, the F2 generation, showed similar depressive behaviours, as well as abnormal sugar metabolism.
The F1 and F2 generations also had abnormal levels of the five microRNAs in their blood and in the hippocampus, a brain region involved in stress responses.
The study is notable for showing that sperm responds to the environment, said Stephen Krawetz, a geneticist at Wayne State University School of Medicine in Michigan, who was not involved in the study.
"Dad is having a much larger role in the whole process, rather than just delivering his genome and being done with it," he said.
The study was published in the journal Nature Neuroscience.