PROJECT SUMMARY Epilepsy is a common and costly cause of morbidity and mortality in children and adults. Developmental and epileptic encephalopathies (DEEs) are severe childhood epilepsies that require rapid diagnosis to initiate treatment that will control seizures and prevent or reverse the loss of neurologic function. However, these seizures often do not respond to medications. Most DEE patients are expected to have a known underlying genetic etiology, but they often lack a molecular diagnosis because the potential pathogenic variants are in genes that have not yet been associated with neurological dysfunction. We have identified de novo variants in the MAST4 gene in patients with developmental delay, DEE, vision abnormalities, and in some, structural brain abnormalities. MAST4 is a member of an understudied family of serine threonine kinases (MAST1-4 and MAST-like) that is among the IDG-eligible proteins with high potential to impact human health as a therapeutic target for epilepsy. In Aim 1, we will characterize MAST4 spatiotemporal expression in neurodevelopment and identify MAST4 interacting proteins in vivo using label-free mass spectrometry. In Aim 2, we will validate MAST4 interacting proteins and the impact of patient-specific mutations on these interactions in primary cultured neurons in vitro. The results from these experiments will provide both important functional data and tools to instruct the path to precision medicine for DEE patients with MAST4 mutations.

PROJECT NARRATIVE Developmental and epileptic encephalopathies are a variable group of severe childhood epilepsies that are suspected to be genetic, but causal genes are only beginning to emerge. MAST4 is a new DEE candidate gene and an IDG kinase with little known about its properties and functions. We will define the MAST4 interactome as a resource to investigate therapeutic targets for epilepsy.