PROJECT SUMMARY/ABSTRACT This proposal describes a five-year career development program that will lead the PI to a career as an independent physician-scientist, studying mechanisms and potential therapeutics of developmental and epileptic encephalopathies. Applicant: Dr. Ziobro holds M.D. and Ph.D. degrees and has completed specialty clinical training in both Child Neurology and Pediatric Epilepsy. She has previous experience in neuroscience research using rodent, neuronal cell culture, and organotypic hippocampal cell culture models of acquired epilepsy. This career development plan includes a period of mentored research designed to develop the applicant’s knowledge in advanced imaging techniques, viral vector design, brain slice electrophysiology, and interneuron development. These skills will complement her current skill-set and propel her development as an independent researcher. The concepts learned during this training period will be broadly applicable to multiple disease processes and allow for significant clinical translation in a clinically relevant field of study. Research Plan: PCDH19-clustering epilepsy (PCE) is one of the most common monogenic developmental and epileptic encephalopathies (DEEs), characterized by cognitive impairment and intractable seizure clusters starting in infancy. PCDH19 is and X-linked gene that encodes a transmembrane cell adhesion molecule, critical for cell interactions during brain development. PCE affects females and rare mosaic males, while males expressing only mutant PCDH19 do not develop epilepsy. A leading hypothesis to explain this phenomenon is that it occurs due to cellular interference associated with random X-inactivation (or mosaic mutations) in which cells expressing wild type and those expressing mutant PCDH19 fail to interact properly during brain development, which is supported by a preliminary data showing a unique cell segregation pattern of Pcdh19+ and Pcdh19- neurons in the cortex and hippocampus of the PCE mouse model. Our central hypothesis is that mosaic Pcdh19 expression alters interneuron development in the hippocampal CA1 region leading to aberrant network formation, hyperexcitability and increased seizure susceptibility. This proposal will characterize histologic (Aim 1) physiologic (Aim 2) and developmental (Aim 3) mechanisms of PCE. This study will provide significant insight into the mechanisms of PCE and guide potential therapeutic strategies that may be applicable to multiple genetic epilepsies.