Investigating developmental interneuron pathology and cell-based therapy in a translational rabbit model of dravet syndrome - dravet syndrome (DS) is a devastating developmental and epileptic…

Investigating developmental interneuron pathology and cell-based therapy in a translational rabbit model of dravet syndrome - dravet syndrome (DS) is a devastating developmental and epileptic encephalopathy (DEE), most often caused by loss-of-function variants in SCN1A, encoding the Α-subunit of the NAV1.1 voltage-gated sodium channel. The resulting NAV1.1 haploinsufficiency leads to drug-resistant seizures, cognitive and behavioral deficits, and a high risk of sudden unexpected death in epilepsy. Small-molecule therapies provide only partial symptom relief without addressing the underlying pathology. A body of literature supports the interneuron hypothesis of DS, proposing that NAV1.1 haploinsufficiency selectively disrupts the excitability of embryonic medial ganglionic eminence (MGE)-derived parvalbumin-positive (PV+) and somatostatin-positive (SST+) gabaergic interneurons, leading to disinhibition. Emerging data suggest that SCN1A may also regulate MGE progenitor cell proliferation and migration, in agreement with the designation of DS as a disease of brain development. Understanding whether MGE progenitor cells have altered proliferation or migration profiles in DS will increase basic knowledge of disease mechanisms and identify critical windows for early therapeutic intervention. Rodent studies have demonstrated the remarkable therapeutic potential of MGE progenitor transplantation in brain disease. These progenitors migrate extensively, mature into functional inhibitory interneurons, restore inhibitory tone, reduce seizures, and improve cognitive outcomes. Despite this success, key translational barriers remain: MGE transplantation has not been rigorously evaluated in large mammalian models of DS pathology. To address this GAP, we developed a novel transgenic SCN1A+/- rabbit model of DS. Rabbits more closely replicate human neuroanatomy and cardiorespiratory physiology than mice, making them an ideal translational model. Furthermore, unlike DS mice, which have a very narrow therapeutic window prior to disease onset, DS rabbits exhibit spontaneous seizures beginning around three months of age, providing a more clinically relevant therapeutic window. The objective of this project is to test the developmental MGE progenitor cell hypothesis in vivo and evaluate the therapeutic potential of MGE progenitor transplantation in our DS rabbit model. My central hypothesis is that SCN1A haploinsufficiency disrupts the embryonic developmental profile of MGE-derived interneurons, in addition to altering their excitability, and that transplantation of healthy wild-type (WT) MGE progenitors will restore inhibitory balance and rescue DS phenotypes. To test my hypothesis, I propose two specific aims: 1) determine whether SCN1A haploinsufficiency disrupts MGE-derived interneuron development. 2) evaluate therapeutic efficacy of MGE progenitor cell transplantation in DS rabbits. Successful completion of these aims will provide rigorous in vivo evidence that DS pathology fundamentally involves altered brain development and establish proof-of-concept for MGE transplantation in a translational large-animal DS model. This research will significantly advance understanding of DS pathogenesis, bridge critical translational gaps from rodents to humans, and strongly support clinical translation of cell-based therapies for DS and related epilepsies.