James H. Thomas
Regulation of Behaviors in C. elegans
The nervous system is the most complex and sophisticated organ in all multicellular animals. Understanding how the nervous system develops and generates complex behaviors is one of the greatest challenges facing biologists. Dr. Thomas's laboratory uses genetic and molecular approaches to study the nervous system of the nematode C. elegans. This nervous system of C. elegans is simple and well described, with 302 neurons of precisely known structure. This simplicity and detailed knowledge of the nervous system provides a firm basis for analyzing how genes control its development and function.
Studies in the Thomas lab focus on various specific behaviors. The first is formation of a specialized larval stage called the dauer larva, which forms in response to environmental cues. A large number of genes that control dauer formation have been analyzed in the Thomas lab, and have been shown to function in specific orderly, though complex, pathways. These functional pathways correspond to the information processing that underlies dauer formation. The lab has found that an early step in the pathway is mediated by cGMP that is synthesized by a memberane guanylyl cyclase, in a process that is probably similar to visual transduction in the vertebrate photoreceptor. The other behaviors under study are egg laying and defecation. Even these lowly activities are surprisingly complex and interesting. Both are mediated by identified motor neurons and involve several neurotransmitters, including serotonin, GABA, acetylcholine, and dopamine. We are taking a genetic and molecular approach to understanding how these transmitter pathways converge to regulate these behaviors.