The molecule may be one of only a few "matchmaker" proteins that instruct one type of neuron to form a synapse with another type, essentially wiring up the body during embryological development, the researchers say. Such molecules have been sought for decades, but this is the first discovered in a living animal.
The matchmaker protein, known as SYG-1, was discovered in studies of egg-laying behavior in the roundworm C. elegans. It is a member of a large family of proteins known as the immunoglobulin superfamily, and is closely related to proteins in fruit flies, mice and humans. The related molecules are always found where two different types of cells form a close connection, and SYG-1 probably receives a signal to form a synapse from the animal's egg-laying tissue, the scientists report.
Discovery of matchmaker proteins in humans may help treat disorders such as chronic epilepsy and chronic pain in which synapse formation goes awry and neurons form the "wrong" connections, said Cornelia Bargmann, PhD, professor of anatomy and Howard Hughes Medical Institute investigator at UCSF. Knowing which proteins direct synapse formation may also help in treatment of peripheral nerve damage, which requires nerves to reconnect with precisely the right partner from among many in their immediate environment.
Scientists think that each neuron in a developing animal is destined to a particular behavioral task, and the synaptic connection allows it to achieve its destiny, connecting with the right partner from among many dozens of kinds of neurons it encounters.
"Like people, neurons can make good or bad choices about who they associate with," Bargmann said. "Molecules like the protein we discovered are needed to make the best choice."