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 often considered the 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 modifers 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 how Nf1 loss of function affects hyperactivity/repetitive behaviors, test the signaling and genetic interactions underlying Nf1 function, probe its role in a putative signaling complex with a novel lipid signaling interaction partner, and decipher the effects of loss of Nf1 on neuronal circuit excitability and function.