Brainstem metabolic changes in a mouse model of Dravet Syndrome

Dravet Syndrome (DS) is a severe genetic epileptic encephalopathy caused by mutations in the SCN1A gene that encodes the voltage-gated sodium channel (NaV1.1) subunit alpha. DS is characterized by intractable seizures, progressive developmental delay, cognitive impairment, and high mortality due to sudden unexpected death in epilepsy (SUDEP). Post-ictal apnea that precedes asystole has been observed to lead to SUDEP; however, the exact molecular underpinnings are unclear. Seizure-induced hippocampal metabolic alterations have been reported in DS mice. Whether such alterations occur in the brainstem, a master regulator of autonomic functions, thereby influencing morbidity, mortality/SUDEP, and seizure outcomes is unknown. We used Scn1aA1783V/WT DS mice and showed that there are temporal alterations in the brainstem metabolome which are distinct in comparison to the forebrain metabolome. Glycolytic, and pentose phosphate pathway intermediates were significantly elevated in the brainstem of DS mice during the period of enhanced susceptibility to mortality (post-natal day P20-30). Post P20-30, mitochondrial aconitate, and the antioxidant glutathione were significantly elevated. Single nuclei RNA sequencing (snRNA seq), and proteomic analyses revealed alterations in genes associated with neurotransmission, cellular respiration, protein translation, as well as systematic rewiring of protein kinase-mediated pathways that were specific to the brainstem. These findings suggest that there are widespread metabolic changes in the brainstem of DS mice that are associated with alterations in druggable molecular pathways. Overall design: The goal of this study was to evaluate baseline differences in the brainstem transcriptomes of a mouse with Dravet Syndrome (Scn1aA1783V/WT, carries a knock-in missense mutation in the gene SCN1A that encodes for a voltage-gated sodium channel subunit alpha) compared to a wildtype (WT) C57Bl6 mouse. Brainstem tissue was collected from mice during post-natal days P40-50. This is the developmental time period where Dravet mice have survived past the critical period of enhanced susceptibility to mortality (P20-30). This study will help us understand what the brainstem (critical region for regulation of autonomic functions) transcriptome looks like and whether transcriptomic alterations could play a role in influencing seizures, morbidity, and mortality outcomes in Dravet Syndrome mice.