Voltage-gated sodium channels (VGSCs) are critical regulators of neuronal excitability and are associated with severe neurologic and neuropsychiatric disorders including autism, cognitive and motor impairment, and epilepsy. Mutations in VGSCs, including SCN8A, are among the most common genetic causes of treatment- resistant epilepsy in children. Despite recent advances, epilepsy has remained a persistent problem that needs improved treatments, as approximately 40% of epileptic patients do not achieve sufficient seizure control with current therapeutic interventions. The applicant, Dr. Makinson, has a strong background in epilepsy research. He completed his PhD at Emory University under the mentorship of Dr. Andrew Escayg, where he performed detailed genetic, molecular, and behavioral analyses of mice carrying clinically-relevant mutations, including multiple studies on the VGSCs Scn1a and Scn8a. For the first part of his postdoctoral training Dr. Makinson worked with Dr. John Huguenard (Stanford University) to identify a novel mechanism for absence seizure generation involving reductions in Scn8a and concurrent impairment in recurrent inhibition in the thalamus. He also was instrumental in a collaboration with the laboratory of Dr. Sergiu Pasca (Stanford University) in which he characterized the electrophysiological properties of neurons derived from human induced pluripotent stem cells (hiPSCs) grown into a 3D cortex-like structure. Recently, Dr. Makinson showed that region-specific spheroids, including excitatory (pallial) and GABAergic (subpallial) types, can be assembled to produce functionally integrated neural networks. In this proposal, Dr. Makinson seeks to develop rodent and in vitro human models of SCN8A impairment and to use these models to interrogate the underlying pathogenic mechanisms of clinically-relevant mutations and to identify new therapeutic strategies to treat disease. These studies are designed to provide mechanistic insight into the earliest points of disease progression that ultimately lead to severe epileptic encephalopathies and cognitive impairment. Specifically, Dr. Makinson seeks to investigate the changes in neuronal excitability, network activity, and neuronal migration that occur in cerebral spheroids carrying mutations in SCN8A. Dr. Makinson will be supervised by Drs. Huguenard (primary mentor) and Pasca (co-mentor) as well as the advisory committee including Drs. Christopher Lee-Messer, Kimford Meador, Justin Du Bois, and Liqun Luo. Dr. Makinson will receive advanced instruction in neurodevelopment and expert training in the generation of 3D hiPSC-derived neuronal cultures carrying mutations in the SCN8A gene by Dr. Pasca. Dr. Huguenard will provide advanced training in electrophysiology, optogenetics, multiphoton imaging, computer programming, and in the analysis of complex biological data. Dr. Makinson, has the long-term goal of becoming an independent tenure-track investigator studying the neuronal and molecular mechanisms of epilepsy.
Mutations in the voltage-gated sodium channel gene SCN8A are associated with severe treatment resistant childhood epilepsies as well as cognitive and behavioral deficits. This project takes a novel approach - generation of 3D cellular structures - and an established approach - generation of mice carrying genetic mutations - to investigate the effects of mutations in the SCN8A gene. These complementary models of SCN8A pathology will be used to understand how mutations in SCN8A cause disease and to evaluate potential treatment strategies.
