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Stress Can Damage Sperm Quality, Leading To Stunted Brain Development Of Resulting Children, According To Mouse Study

father's stress affects children genetically
Researchers looked at the effects of stress on the sperm of male mice and found alterations in their own gene expression as well as their offspring's brain. Christian Guthier/Flickr Creat

Stress isn't good for anyone's health, and workplace stress has even been linked to severe health issues such as high blood pressure. But, the impact of stress can also carry through the generations by altering the expression of genes in sperm and causing inhibited brain development and stress responses in children, according to a recent research study by a group out of the University of Pennsylvania School of Medicine.

Scientists wanted to determine what effects a father's stress had on his children. They found the first instance of a stress-related disease being passed between generations by the father purely through DNA. Other studies have looked at the mother's exposure to drugs, altered diet, and stress and their impact on brain development and diseases in her children.

The scientists stressed out male mice before they were paired with a female mouse for breeding. They did this by suddenly moving them to a new cage, exposing them to chemicals that would be released by a predator, and introducing noises and foreign objects to their cages. Male mice play no role in raising babies, so any effects on the male would be purely from their contribution of sperm and genetic material.

The researchers found that the male mice's stress had changed the expression of genes in their sperm. Because the genes themselves are not altered by experience, the scientists looked into epigenetic causes — changes to the DNA that do not alter genes themselves, but change the DNA in a way that it affects if a gene will be expressed or not. They discovered that a certain group of microRNAs was increased in the sperm of the stress group, which can result in the suppression of the expression of some genes.

"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 Dr. Tracy Bale, Ph.D., associate professor of neuroscience in the Perelman School of Medicine Department of Psychiatry in a press statement. "These findings suggest one way in which paternal-stress exposure may be linked to such neuropsychiatric diseases."

In the children of stressed out mice, the research group found an amount of a stress hormone called corticosterone — a similar chemical to the stress hormone cortisol in humans. Without this hormone, the brain and body cannot properly deal with stress. The neural circuitry in the brains of children from stressed out male mice was also affected, increasing the expression of glucocorticoid-responsive genes in a specific brain region involved in stress regulation.

The study concluded that mild stress throughout a lifetime can change male sperm cells, and may contribute to neuropsychiatric diseases. "Next, we are examining the mechanism whereby these sperm [microRNA's] 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."

 

Source: Rodgers A, Morgan C, Bronson S, Revello S, Bale T. Paternal Stress Exposure Alters Sperm MicroRNA Content and Reprograms Offspring HPA Stress Axis Regulation. The Journal of Neuroscience. 2013.

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