De Bono then inserted the solitary worms' version of this gene into a social strain of wormsand the social worms suddenly became solitary. "That says this gene is sufficient for solitary behavior," Bargmann emphasizes. Next the team discovered that the protein encoded by this gene was remarkably similar to a protein found in human brains, a receptor for a substance called neuropeptide Y.
Biotech companies are extremely interested in neuropeptide Y because it is one of the strongest feeding stimulants found in rodents. Neuropeptide Y is also involved in obesity, anxiety, memory, blood pressure, and digestion. "By studying this protein in worms, we hope to understand how the same molecule functions in mammals," says de Bono. He would like to use the worm to predict how genes regulate blood pressure or eating behavior in humans.
Bargmann sees additional implications of this research. The fact that a sociability trait has now been linked to a gene is "empowering," she says. "We may in fact be finding that genetic influences on behavior are traceable."
Even more important, she believes, this work may open the way to greater knowledge about neuropeptides, "a class of molecules and pathways that we should be looking at more closely," she says, but that in recent years have been "the ugly stepchildren of the neuroscience world" in terms of their popularity and the number of people studying them.
The nervous system has two kinds of transmitters, she explains: the classical neurotransmitters, which send very rapid and precise all-or-none signals between neurons; and the neuropeptides, which modulate neurons over a longer period of time and either increase or decrease the likelihood that the neurons will respond to certain stimuli. Neuropeptides may prove very important in helping researchers understand the complicated genetics of human psychiatric disorders, Bargmann says.
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A snippet of DNA in a single gene determines whether a worm becomes a loner or prefers to eat in company. The protein produced by this gene, npr-1, glows green inside neurons of the worm's transparent head.
Image: Mario de Bono and Cornelia I. Bargmann, Cell, vol. 94, p. 684, fig. 4, September 1998 ©1998 by Cell Press