A NOVEL DUAL-MECHANISM GENE THERAPY APPROACH FOR GNB1-LINKED EPILEPSY AND NEURODEVELOPMENTAL DEFICITS

GNB1 Encephalopathy is a rare genetic neurodevelopmental disorder in which severe symptoms are met with no established therapeutic option. This ultra-rare condition arises from mutations in the GNB1 gene, encoding the Gβ1 subunit of the G-protein, a key component of G-protein-coupled receptors (GPCRs). Because different GNB1 mutations lead to distinct functional outcomes, current gene replacement or suppression strategies are unsuitable. In this context, we aim to generate a universal therapy for all patients by proposing a strategy to simultaneously silence and repair the mutated GNB1 gene using an adeno-associated viral (AAV) vector.
This study describes the development of this strategy, starting with the screening of silencing sequences and regulatory elements for the correct gene copy. Their efficacy, potency, and specificity were tested in vitro, and one construct was identified as suitable for therapeutic use and subsequently produced as an AAV-based therapy. To achieve efficient delivery to the central nervous system, a mouse neurotropic AAV vector was selected. Additionally, a new hybrid-background GNB1 I80T mouse model was generated and characterized, showing spike-and-wave discharges (SWDs) in females, myoclonic spikes in males, as well as cognitive deficits and anxiety-like behavior. After characterization, mice were injected at either postnatal day 10 or at 2 months of age with the AAV therapeutic vector, and phenotypic rescue is being assessed starting at 3 months of age. These findings provide insight into a potential lifelong treatment for this currently untreatable disorder.