Gene Therapy for GRIN2D-related Developmental and Epileptic Encephalopathy

Variants in subunits of the NMDA receptor have been shown to result in Developmental and Epileptic Encephalopathies (DEEs), characterized by intractable epilepsy, developmental delays, intellectual, motor, and behavioral impairments. Base editing (BE) is a genome editing approach based on CRISPR-Cas9 coupled to a cytosine or adenosine deaminase, that enables the direct, specific and irreversible conversion of a single DNA base without inducing dsDNA breaks. BE can thereby efficiently correct a variety of point mutations relevant to human disease. Focusing on the recurrent GRIN2D Val667Ile mutation, we aimed to utilize base editors, as therapy, first in cells and further in a mouse model. We have achieved successful A-to-G editing of the variant in a cellular model, as confirmed by sequencing and analyses, up to 42% editing. Following the proof-of-concept experiments, we designed viruses for a dual adeno-associated virus (AAV) approach to perform in vivo base editing to rescue the phenotype, as measured by behavioral assays, EEG and electrophysiology. We are currently conducting in vivo experiments, and initial results following intracerebroventricular injections at P0 have demonstrated successful viral expression in the brain, A-to-G editing, as well as improved survival and behavioral changes. Future work on this project may contribute to the ongoing efforts to improve the treatment options for patients with devastating DEEs, and the development of new personalized disease-modifying therapies.

​In collaboration with Prof. Moran Rubinstein