Aggression de-escalation gene identified in fruit flies: The gene, called nervy, prepares the nervous system to respond to socio-environmental signals to stop fighting

The brain mechanisms that cause aggressive behavior have been well studied. Far less understood are the processes that tell the body when it’s time to stop fighting. Now, a new study by Salk scientists identifies a gene and a group of cells in the brain that play a critical role in suppressing aggression in fruit flies.

The findings, published in Science Advances on September 7, 2022, have implications for disorders such as Parkinson’s disease, which can sometimes cause behavioral changes like increased aggression and combativeness.

“We’ve found an important mechanism in the brain that normally prevents us from expressing high levels of aggression,” says senior author Kenta Asahina, assistant professor in Salk’s Molecular Neurobiology Laboratory. “Although our findings are in fruit flies, the same mechanism may be at play in humans, at least at the molecular level, which could help better explain a host of psychiatric diseases.”

De-escalation, or the ability to decide when it’s time to stop fighting, is a vital behavior for survival because it allows animals to adjust their aggressiveness according to the costs and benefits of an encounter with a rival — at a certain point, continuing to fight is no longer worth it. Sensing when it’s time to de-escalate is complex because there isn’t an obvious trigger, such as the way fullness triggers an animal to stop eating.

For the study, scientists compared the behavior of normal fruit flies (Drosophilia) and fruit flies lacking various genes of interest. Specifically, they examined how frequently male flies lunged at other males, a typical aggressive behavior in this species. They found that flies missing a gene called nervy were significantly more aggressive than their normal counterparts.

The nervy gene isn’t actually involved in the animal’s moment-to-moment decision to stop fighting. Rather, it helps give the fly the ability to respond to environmental cues (likely the fly’s past experience with other individuals), the researchers say.

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