Sperm can pass trauma symptoms through generations, study finds

This article cites a study published in Nature Neuroscience and talks about how early life traumatic events can alter non-genetic mechanisms governing gene expression in the sperm cells of adult mice. The researchers at ETH Zurich University in Switzerland believe that this finding can explain why the offspring of traumatized mice exhibit some of the same symptoms that their parents do despite not being exposed to the trauma.

In this study, the researchers took a group of male mice and removed them periodically from their mothers for hours at a time to simulate trauma. Following these periods the mice exhibited altered behavior, including depressive like symptoms. The genetic explanation given by the researchers was that “the trauma that these mice experienced resulted in the over-expression of microRNAs in the brain and an abnormal dip the production of certain proteins.”

These traumatized mice then produced offspring and the symptoms that the parents exhibited were apparent in the pups despite never having experienced the trauma. These symptoms were even apparent in the third generation. Upon examination of the sperm in the traumatized mice it was found that the microRNAs were present in high concentrations. Theoretically the behaviors were passed down to the offspring. However, upon examination of the offspring’s sperm, there was no elevated amount of the microRNAs. Therefore, the researches decided to validate their findings indirectly by injecting sperm microRNAs from traumatized males into the oocytes of female mice. This allowed them to reproduce the same pattern of trauma symptoms in the resulting offspring that they had witnessed in the pups of the traumatized males.  In conclusion, I believe that microbiologist Eva Jablonka is on the right track when she says that "Epidemiological studies need to be re-thought," to try and find a way to ensure that the generations that follow are not exposed to the negative behavioral side effects due to the trauma of their parents and grandparents.