PROJECT SUMMARY/ABSTRACT Epilepsy is one of the most common neurological disorders. Approximately one third of patients are drug- resistant, underscoring the need for alternative therapies. One of the biggest challenges to developing disease- modifying therapies is the limited understanding of the underlying mechanisms behind the initiation and propagation of seizures. We propose to develop a novel, translational gene therapy that targets dentate gyrus (DG) granule cells, which have been shown to act as a seizure gate. We will make use of a promoter specific to DG granule cells, Prospero-related homeobox 1 (Prox-1), to selectively express the inhibitory DREADD, hM4D(Gi), in these cells. We hypothesize that this novel gene therapy with high translational potential will effectively suppress spontaneously recurring seizures in the intrahippocampal kainic acid (IHKA) mouse model of temporal lobe epilepsy. We will first develop and test the sensitivity and specificity of a truncated Prox-1 promoter and enhancers (Aim1). We then will examine the efficacy of a Prox-1::hM4D(Gi)-YFP viral vector in inhibiting DG granule cells and suppressing chronic seizures in the IHKA mouse model of epilepsy, while also testing memory effects (Aim 2). Development of an effective and highly translatable therapy can help us better understand the mechanisms at play during seizures, as well as improve treatment in patients with drug-resistant epilepsy. In addition to its utility in epilepsy, a Prox1-driven expression vector could have potential applications in Alzheimer’s disease and neuropsychiatric disorders as well as in lymphatic and cancer research.