Project Summary Neurofibromatosis type 1 is one of the most common monogenic developmental disorders, affecting ~1 in 3,500 individuals worldwide. Some form of cognitive or neuropsychiatric dysfunction is present in approximately 50-80% of individuals with NF1, and these are considered to be major causes of lifetime morbidity. The neurofibromin protein (Nf1) directly inhibits Ras signaling, but also affects several other signaling cascades (possibly indirectly). The complexity of the signaling cascades implicated in neurofibromatosis 1, combined with the lack of drugs to target Nf1 directly, highlights the pressing need for new approaches to target NF1 phenotypes. Uncovering genetic modifiers of neurofibromatosis 1-related cellular dysfunction would provide potential new targets for treating this disorder. This project will focus on hyperactivity and repetitive behaviors in Drosophila loss of function Nf1 mutants. The large effect size of these behavioral deficits will enable their use it as a readout to unravel both the in vivo molecular and circuit functions of the neurofibromin protein in a powerful genetic model organism. Specific Aims will investigate the circuit mechanisms underlying hyperactivity in NF1 deficiency, dissect the molecular mechanisms of Nf1-regulated hyperactivity, and discover the roles of novel genes underlying the development of NF1 phenotypes.