Forty years ago geneticist Barry Ganetzky accidentally knocked out a batch of laboratory fruit flies by snapping a vial against his hand. “All the flies were on the bottom of the vial, not walking, totally uncoordinated, just lying on their sides,” he recalls.
He did not give it much thought at the time, but as the devastating effects of head injuries in professional athletes have come to light, Ganetzky has realized that concussed Drosophila fruit flies might be scientifically useful. He and his colleagues at the University of Wisconsin–Madison have begun to explore how fruit flies could help uncover the cellular mechanisms behind traumatic brain injury (TBI) in humans.
Despite decades of study, TBI remains poorly understood. What is known is that injuries are caused by a rapid acceleration or deceleration—such as a car crash or a hard football hit—that sloshes the brain against the inner wall of the skull. The impact can trigger a cascade of cellular reactions that further damage the brain and neurons, potentially leading to long-term cognitive impairments.
Fruit flies may enable larger, more robust studies of TBI. Besides being inexpensive to maintain, Drosophila flies have short lives, which allows researchers to track health outcomes over an animal's entire life span. The insects have already found use in investigations of Alzheimer's and Parkinson's. “A neuron inside a fly head is, in principle, the same as a neuron inside a human head,” Ganetzky says. Similar to the human brain, the fly brain, which is about the size of a grain of sand, is encased in the hard shell of its exoskeleton and cushioned by a layer of fluid that allows the brain to slosh around on impact.
In a recent investigation, Ganetzky and his colleagues loaded fruit flies into a vial, then smacked the vial against a padded surface. The researchers later performed autopsies on the concussed insects. The results of the study, published last October in the Proceedings of the National Academy of Sciences USA, showed that the flies suffered brain damage and developed many of the same symptoms seen in humans with TBI, including loss of consciousness and coordination and an increased risk of death. As in humans, the ill effects of TBI appeared to depend on the severity of impact, as well as the individual's age and genetic makeup.
Ganetzky's team hopes that fly studies will one day lead to a test that diagnoses TBI via biomarkers in the blood and, potentially, a treatment that prevents the deterioration of brain cells.
“Flies are a simple, fast way of getting at the pathways that are involved in TBI,” says Leo Pallanck, who studies neurodegenerative diseases in fruit flies at the University of Washington. “We hope that will lead to treatments and preventive therapies.”