Characterizing EZH1 Gain of function mutations to understand neurodevelopmental disease and inform EZH1-inhibitor innovation

PROJECT SUMMARY/ABSTRACT: Neurodevelopmental disorders (NDDs) represent a diverse array of conditions characterized by abnormal brain development and function which cause motor, cognitive, and communicative deficits that greatly impact a patient’s quality of life. However, many underlying disease mechanisms are still unknown, resulting in a dearth of effective treatments and an urgent need to better understand NDDs. One challenge of studying NDDs and developing effective treatments however is that many NDDs are multifactorial with both an individual’s genetics and environment playing key roles. Attributing a single disease mechanism to a patient phenotype can therefore be extremely difficult. Consequently, one approach to circumvent this is by focusing on NDDs with a singular and well-defined genetic cause. To this end, the Akizu lab recently identified a novel NDD caused by heterozygous missense mutations in Enhancer of Zeste Homologue 1 (EZH1) which is one of the two catalytic subunits within the Polycomb Repressive Complex 2 (PRC2) that is responsible for transcriptional repression through tri-methylation of the lysine at position 27 of histone H3 (H3K27me3). Initial mechanistic work identified several mutations that increase the catalytic activity of EZH1 and subsequent H3K27me3 levels, indicative of a gain-of-function (GOF) effect. Follow-up experiments further revealed that one GOF mutation p.A678G induces premature neuronal differentiation and enhanced maturation during the differentiation process along with a downregulation of glutamatergic synapse genes that together may potentially produce dysfunctional neurons. However, several unanswered questions remain such as whether the remaining 10 uncharacterized EZH1 missense mutations are GOF, if the previously characterized phenotype extends to other validated GOF mutations and also induces neuronal dysfunction, and whether EZH1-specific inhibitors can ameliorate these effects. This proposal therefore aims to answer these questions and gain further insight into the EZH1 GOF phenotype and relevant treatment strategies, advancing our understanding of NDD disease mechanisms and therapeutic approaches to help afflicted patients. The proposed research will also provide the applicant with intensive training in imaging and molecular methodologies; rigor and reproducibility; experimental design; and scientific communication. Furthermore, the applicant will be supported by a team of experts headed by the sponsor Dr. Naiara Akizu and also including Dr. Ethan Goldberg, Dr. Ana Cristancho, and Dr. George Burslem. Finally, the resources available at both the University of Pennsylvania and the Children’s Hospital of Philadelphia will ensure the successful completion of the proposed research and training of the applicant and will help fulfill their desire to become an independent research professor of neuroscience.