April 25th, 2015
For the first time, researchers have found that stress can leave an epigenetic mark on sperm, which then alters the offspring’s hypothalamic-pituitary-adrenal (HPA) axis, a part of the brain that deals with responding to stress. The study was published in the Journal of Neuroscience.
The experiment was conducted with preadolescent and adult male mice, in which stress was induced – for example by confronting the mice with predator odor (fox urine) or foreign objects in their cages.
Their offspring, both male and female, turned out to have abnormally low reactivity to stress. Whenever the stress pathway is deregulated – this can be both an extreme high reactivity, as well as a very low activity – this means an organism cannot respond to changes in its environment. In people, this might cause stress-related mental disorders.
“It didn’t matter if dads were going through puberty or in adulthood when stressed before they mated. We’ve shown here for the first time that stress can produce long-term changes to sperm that reprogram the offspring HPA stress axis regulation,” said lead author Tracy Bale, associate professor of neuroscience. “These findings suggest one way in which paternal-stress exposure may be linked to such neuropsychiatric diseases.”
The scientists also examined the role of a series of microRNA (miRs) in the sperm – so-called non-coding RNA molecules that contribute to the expression of genes in the offspring, after fertilization. The results showed that in stressed male mice, there was a significant increase in expression of nine miRs. According to the researchers, this probably serves some evolutionary benefit: dads can “prepare” their offspring for certain environmental threats.
Next, we are examining the mechanism whereby these sperm miRs act at fertilization, and then we can think about using them as biomarkers in human diseases,” said Bale. “And then we can begin to predict who has been exposed to what, and to think about prevention or treatment down the road.”
Reference: Rodgers, A., Morgan, C., Bronson, S., Revello, S., & Bale, T. (2013). Paternal Stress Exposure Alters Sperm MicroRNA Content and Reprograms Offspring HPA Stress Axis Regulation Journal of Neuroscience, 33 (21), 9003-9012 DOI: 10.1523/JNEUROSCI.0914-13.2013
microrna biomarker,epigenetics inheritance, epigenetics sperm