This project focuses on understanding the role of the hlh-3 protein in the differentiation and function of neurons with gender-specific roles in the nematode C. elegans. The long term goal is to determine whether HLH-3 is akin to a master regulator responsible for transcription of genes expressed in a dimorphic gender-specific neuronal circuitry, and as a result influences distinct behaviors in hermaphrodites and males. Hlh-3 is known to function in neurons of the egg-laying circuitry in hermaphrodites, and new evidence suggests it also functions in neurons of males which mediate detection of chemosensory and/or mechanosensory cues provided by the hermaphrodite. Not much is known about the gene networks expressed in males and females that are orchestrated to bring about gender-specific functions. This project utilizes molecular, genetic, and behavioral approaches to characterize the mechanism(s) by which neuronal function and animal behavior can be coordinated and regulated by a bHLH transcription factor. In the nematode, gender-specific behaviors are controlled by both gender-specific neurons as well as a shared neuronal circuitry. The principal investigator?s laboratory is a newcomer to this area of research, but this project will provide novel information that complements ongoing work in other laboratories in the nematode community. The project is the basis for the doctoral thesis of two graduate students and also provides research opportunities to undergraduate students. The undergraduates will be involved in further quantification of behavioral defects in males, creation of strains with cell-specific reporters, and in the characterization of the cells and gene expression patterns associated with phenotypes, if any. The data will be presented and discussed at regional and national meetings as well as submitted for publication in peer reviewed journals. Newly generated reagents will be available to the C. elegans community.