Researchers in Switzerland are closer to understanding why extreme stress appears to have second-generation effects:
The researchers studied the number and kind of microRNAs expressed by adult mice exposed to traumatic conditions in early life and compared them with non-traumatized mice. They discovered that traumatic stress alters the amount of several microRNAs in the blood, brain and sperm – while some microRNAs were produced in excess, others were lower than in the corresponding tissues or cells of control animals. These alterations resulted in misregulation of cellular processes normally controlled by these microRNAs.
After traumatic experiences, the mice behaved markedly differently: they partly lost their natural aversion to open spaces and bright light and had depressive-like behaviors. These behavioral symptoms were also transferred to the next generation via sperm, even though the offspring were not exposed to any traumatic stress themselves.
Virginia Hughes adds:
The study is notable for showing that sperm responds to the environment, says Stephen Krawetz, a geneticist at Wayne State University School of Medicine in Detroit, Michigan, who studies microRNAs in human sperm. (He was not involved in the latest study.) “Dad is having a much larger role in the whole process, rather than just delivering his genome and being done with it,” he says.