Can Parental 'Memory' Be Inherited?

Are our personalities and behaviors shaped more by our genes or our circumstances? While this age-old “nature vs. nurture” question continues to fuel debates, a growing body of evidence suggests that parental environment can have a profound impact on future generations. In fact, a Dartmouth study published today in eLife examined how environmental stressors put on fruit flies influences the phenotypes of their offspring.

“While neuronally encoded behavior isn’t thought to be inherited across generations, we wanted to test the possibility that environmentally triggered modifications could allow ‘memory’ of parental experiences to be inherited,” explains first author Julianna Bozler.

When female flies are exposed to parasitoid wasps—which deposit their eggs into and kill their larvae—the flies shift their preference to food containing ethanol as an egg-laying substrate to protect their larvae from wasp infection. For the study, fruit flies were cohabitated with female wasps for four days before their eggs were collected. The embryos were separated into two cohorts: a wasp-exposed and a wasp-unexposed group. Both cohorts developed to maturity without any contact with adult flies or wasps.

“We found that the original wasp-exposed flies laid about 94% of their eggs on ethanol food, and that this behavior persisted in their offspring, even though they’d never had direct interaction with wasps,” Bozler says.

The ethanol preference was less potent in the first-generation offspring, with 73% of their eggs laid on ethanol food. “But remarkably, this inherited ethanol preference persisted for five generations, gradually reverting back to a pre-wasp exposed level,” she says. “This tells us that inheritance of ethanol preference is not a permanent germline change, but rather a reversible trait.”

Importantly, the research team determined that one of the critical factors driving ethanol preference behavior is the depression of Neuropeptide-F (NPF) that is imprinted in a specific region of the female fly’s brain. While this change, based in part on visual signals, was required to initiate transgenerational inheritance, both male and female progeny were able to pass on ethanol preference to their offspring.

Senior author Giovanni Bosco is excited about the results. “We hope that our findings may lead to greater insights into the role that parental experiences play across generations in diseases such as drug and alcohol disorders,” he says.