A protein famous for anchoring cells and helping them communicate is also crucial to the short-term memory of fruit flies. This surprising finding, reported in tomorrow's issue of Nature, suggests that the protein, an integrin, may help physically rearrange neurons as they rewire to form a memory.
Flies may seem forgetful--they often will fling themselves repeatedly at closed windows, for example--but they do have memory. Ronald Davis, a neurobiologist at Baylor College of Medicine in Houston, and his colleagues tested the ability of different fruit fly mutants to remember a painful experience. They gave each fly a whiff of an odor, then an electric shock. About 90% of the time, normal flies would hop away when they smelled the odor again, 3 to 4 minutes later. But one type of mutant fly seemed less able to connect the two stimuli even for a few minutes; they learned to avoid the odor half as often as normal flies.
By comparing the genetic sequences of the mutant and normal flies, the researchers found that the forgetful flies had an inactive copy of a gene that he and his Chilean collaborators dubbed Volado (Vol)--South American slang for absentminded. When the team inserted healthy copies of the gene into the forgetful flies, the mutants learned to avoid the odor. To Davis, this suggests that the neuronal connections are being rewired, at least in part, by the protein that Vol codes for, called Vol. This protein is an integrin, which helps cells adhere to others. Integrins are like "an on-off switch that allows a cell to talk more efficiently to its neighbors," says Davis, whose findings are the first to implicate a role for these proteins in memory.
"It's very nice work," says neurobiologist Eric Kandel of Columbia University's College of Physicians and Surgeons in New York. Because most animal species have integrins, Kandel thinks that experiments on fruit fly memory could lead to insights into human memory. Davis now plans to investigate the precise function of integrins in the fruit fly brain.