Scientists have discovered what appears to be an ancient link between feeding behavior in tiny worms and appetite control in people. The finding, reported in the 4 September issue of Cell, suggests that a surprisingly simple genetic control scheme may underlie some complex behaviors.
Many scientists suspect that it takes more than one gene to control a complicated behavior such as feeding, moving, or fighting. However, it's extremely hard to pinpoint genetic differences in organisms whose behavioral patterns vary, like a person who chooses to eat alone at a restaurant one day and with a group of friends the next. A team led by geneticist Cornelia Bargmann of the University of California, San Francisco, found an excellent animal model in which a complex behavior is clearly genetically programmed: Some populations of the tiny roundworm Caenorhabditis elegans hunt bacteria as a pack, while others forage on their own.
Bargmann and postdoc Mario de Bono examined how 17 social and solitary strains of the comma-sized worms foraged in a petri dish well stocked with bacteria. The loners spread out across the whole dish, while social individuals formed a writhing mass wherever bacteria were most abundant. The team transferred snippets of DNA from the solitary worms to the social worms; eventually they isolated a single gene that would make the formerly social worms hunt alone. "The discovery that a clearly defined trait is accounted for by one gene--and by one nucleotide within that gene--was a shocker," Bargmann says. Her team found that the gene resembles one that codes for a receptor for a signal molecule in the human brain, called neuropeptide Y, that may help control appetite.
Because the roundworm protein and the receptor for neuropeptide Y are closely related, the finding suggests that feeding behaviors arose earlier in evolution than scientists had thought. "It's remarkable that we see the same kind of molecule being used to relate feeding and behavior as we do in mammals," says geneticist Jonathan Hodgkin of the Medical Research Council Laboratory of Molecular Biology in Cambridge, U.K. "I am quite surprised that it boils down to this one protein."