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.
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