PROJECT SUMMARY/ABSTRACT Neurodevelopmental disorders (NDDs) are a group of conditions that affect brain development and function often leading to lifelong impairments in motor, language, cognitive and/or social behaviors. Increasing evidence involve chromatin regulation in the pathogenic mechanism of neurodevelopmental disorders (NDDs), such as autism and intellectual disabilities. Importantly, chromatin regulators constitute an attractive group for pharmacological intervention given that most harbor enzymatic activities or well-defined binding domains that can be targeted. The overarching goal of this proposal is to identify and test the therapeutic potential of a novel class of chromatin regulator compounds. In particular our work will be focused on a NDD caused by EZH1 gain of function (GOF) mutations that we have recently identified. EZH1, and its paralogue EZH2, catalyze histone H3 Lysine 27 methylation, a chromatin modification that marks and maintains transcriptional repression. Based on our preliminary data we propose the hypothesis that the NDD in these patients is caused by dysregulation of H3K27 methylation leading to abnormal transcriptional repression of neuronal differentiation genes. Thus, we envision a unique opportunity for pharmacological treatment of this patients using EZH inhibitors. To test this hypothesis, we will dissect cellular and molecular mechanisms affected by EZH1 GOF mutations during neuronal differentiation (Aim 1) and identify EZH1 inhibitors with potential to restore neurodevelopmental defects caused by EZH1 GOF mutations (Aim 2). Results obtained here will serve as a proof of principle for the use of EZH inhibitors to treat NDDs caused by EZH1 GOF mutations and potentially extend their application to other NDDs with altered EZH1/2 and H3K27me3 mediated transcriptional repression.