Dealing with stress in your dad's DNA
Handling stress could make your children better at dealing with their own problems, research reveals.
Male mice subjected to unpredictable stressors produced offspring showing more flexible coping strategies when under pressure, a study in the journal Nature Communications found.
The secret might be hidden in a small change in how certain genes are regulated in the sperm of the father and the brains of their offspring.
Previous research on the effects of stress implicate a loop in the brain's limbic system, which mediates emotion and causes the release of the stress hormone cortisol. That chemical can amp up a feedback loop to the brain.
Much of this stress-related reaction in the brain is mediated, in part, by a mineralocorticoid receptor, or MR, in brain cells.
The latest study found small changes in regulatory DNA sequences near an MR gene in sperm cells of the stressed mice.
Changes in gene regulation in response to the environment are known as epigenetic processes. The study found epigenetic markers associated with six genes in the brain cells in the hippocampus of the offspring of stressed male mice.
Together, these changes offer a hint at a possible path for passing the effects of stress from one generation to the next.
Study co-author Isabelle Mansuy, a neuroscientist at the University of Zurich's Brain Research Institute, said soldiers could be prime examples.
"Many soldiers are people from lower socioeconomic environments and many of them have been exposed to violence, to broken families and to bad conditions when they were young," she said. " Many of these people are stress-resilient, and they also have some adaptive advantages when they are placed in a situation of danger or challenge.
"They have developed coping strategies perhaps that other people have not."
However Dr Mansuy added even the seemingly more resilient mice had many negative behaviours, including depression and anti-social tendencies.
"If we look at the whole behaviour of these animals, the benefit is really a very small proportion of the effects," she said. "Most other effects are fairly negative, because the animals are depressed, are anti-social and have cognitive impairment."
In the study, researchers tried to mimic the effects of erratic parenting and a stressful home environment by separating male mouse pups from their mothers for hours a day over the first two weeks of life. They were also restrained or forced to swim at unpredictable intervals.
The mice then matured in social groups of four or five unrelated mice of the same sex that had equally unpredictable childhoods. Then they were matched to females, producing pups of their own.
Once grown, the pups were subjected to mazes testing the ability to show goal-oriented and flexible behaviour under stress.
Compared with a control group, the offspring of stressed dads showed less hesitation in exploring a maze. And when offered the choice of a drink of water immediately or waiting for sugared water, the offspring of stressed males tended to wait for the greater reward.
They also were better at figuring out when certain rules or cues had been changed.