We have little current understanding of the genetic and molecular mechanisms that link brain development and the proper regulation of sleep throughout life. Understanding these mechanisms is a longstanding challenge in sleep biology with great clinical relevance. Neurodevelopmental disorders including autism are prevalent and closely associated with sleep disturbances, but the underlying genetic and neuroanatomical mechanisms remain obscure. Our studies use the powerful Drosophila model system to characterize a conserved genetic pathway whose activity is required during neuronal development for the sleep regulation in adulthood. This pathway is composed of Insomniac (Inc), the Cullin-3 (Cul3) ubiquitin ligase, and their targets. Reduced activity of this pathway in the developing brain severely curtails the duration and consolidation of sleep in adulthood. Our findings suggest that this pathway has two distinct developmental functions that influence the structure and function of the mushroom body, a sleep regulatory center in the fly brain. In Aim 1 we will determine whether inc acts in neuroblasts to control the proliferation and number of sleep-regulatory neurons. We will also validate Inc substrates, including a target that may link Inc to asymmetric neuroblast division. In Aim 2, we will determine whether inc acts post-mitotically to regulate the structure and anatomy of sleep-regulatory neurons. In Aim 3, we will determine how inc affects the function of sleep-regulatory circuits. Because all of the genes under study are conserved and expressed in the mammalian brain, our studies may provide insight into mechanisms underlying normal sleep, sleep dysfunction, and various neurological disorders.