9630381 PI: Crews Appropriate neural control of muscle function requires that nerve cells form specific synaptic connections with muscles during embryogenesis. The reproducibility of these connections in both vertebrates and invertebrates implies the existence of precise recognition events between nerve cell and muscle. The Drosophila abrupt gene encodes a regulatory protein that directs nerve-muscle recognition during embryonic development, and this proposal represents a concerted effort to define a molecular pathway, centered around Abrupt, that controls this process. Genetic and molecular approaches will be utilized to define the cell type (nervous system or muscle) in which Abrupt functions, the identity and function of the genes that Abrupt regulates, and additional factors that interact with Abrupt to control nerve-muscle recognition.