epigenetics: stressed dads == offspring with neuropsychiatric disorders

ars technica | Paternal stress given to offspring via RNA packed into sperm

The idea that parents can transmit environmentally acquired traits to their offspring has been intuitively attractive ever since Lamarck proposed it in 1801. It had to go underground as evidence continuously piled up supporting Darwin's theory of natural selection, but it seems to be enjoying a popular resurgence with the discovery of epigenetics. Epigenetics explains how information can be transmitted between generations without the involvement of DNA sequences.

A number of recent studies have suggested that stress levels and the nutritional status of parents (and even grandparents) can influence the health of their offspring. But these studies have been somewhat murky on the details on how this transmission could occur. Now scientists who had previously shown that paternal stress impacts the next generation of mice have zeroed in on how it happens: males pack their sperm with RNA that influences gene activity in their offspring.

Through the uterine environment, mothers can pass their environmental exposures on to the fetuses they are nurturing. Thus, studies looking at mechanisms of epigenetic inheritance tend to focus on fathers—pretty much all they give to the fetus is genetic material. And male mice don't need to help in rearing the young, so this genetic material can be their only contribution to the next generation.

In earlier work, these scientists exposed male mice to six weeks of alternating stressors like 36 hours of constant light, a 15-minute exposure to fox odor, exposure to a novel object (marbles) overnight, 15 minutes of restraint in a 50 mL conical tube, multiple cage changes, white noise all night long, or saturated bedding.

Poor little guys.

Then the scientists allowed the mice to breed. Adult offspring of these chronically stressed dads had reduced hypothalamic-pituitary-adrenal stress axis reactivity; when they themselves were restrained for 15 minutes, they did not make as much corticosterone as mice sired by relaxed dads. This is relevant, and problematic, because blunted stress responses in humans are associated with neuropsychiatric disorders like depression, schizophrenia, and autism.