Spreading Depolarization and Progression of Developmental Epileptic Encephalopathy

PROJECT SUMMARY Spreading depolarization (SD) is a wave of massive, near-complete cellular depolarization that slowly propagates across brain tissue. Recent decades of clinical studies have convincingly demonstrated that this prolonged depolarization wave occurs under certain conditions in the human brain and can contribute to deleterious acute and chronic neurological deficits. SD is distantly related to seizures, and their co-occurrence has been observed in numerous clinical and experimental settings. However, the majority of the findings are based on experimentally evoked SD, often in anesthetized animals. It remains an open question whether SD spontaneously emerges and contributes to neurological comorbidities in epilepsy patients. In order to address the neurological significance of spontaneous SD, we recently developed a chronic DC-band EEG recording and demonstrated that SD events indeed occur spontaneously in awake genetic and acquired epilepsy mouse models, each exhibiting distinct generation patterns and interactions with seizures unique to the respective models. With advanced multimodal electrophysiological and state-of-the-art behavioral analysis tools, we are now investigating both the neurological consequences and underlying regulatory mechanisms of these pathophysiological depolarizations in hyperexcitable neuronal circuitries. This project will investigate the contributions of SD to epilepsy comorbidities and disease progression in Dravet syndrome, a major example of developmental epileptic encephalopathy (DEE), using a well-established Scn1a deficient mouse model (Scn1a+/R1407X). Leveraging our expertise in acute and chronic electrophysiological monitoring in awake juvenile mice, we will thoroughly characterize the pathological significance of SD events in the developing juvenile Scn1a+/R1407X mice, in which the risk of premature mortality is high, neurobehavioral abnormalities begin to emerge, and spontaneous cortical and subcortical SD are present. Specifically, we will investigate 1) the correlation between SD and cardiorespiratory instability (AIM1), 2) acute and chronic neurobehavioral deficits associated with SD (AIM2), and 3) the contribution of hippocampal SD during early-life hyperthermic seizure to subsequent circuit dysfunctions (AIM3). These studies will investigate the understudied SD pathology in the well-established DS mouse model. These studies will examine the pathological significance of understudied SD phenomenon in the one of the one of the most studied mouse model of DEEs. The experimental methods established in this study will be directly applied to other epilepsy mouse models in our laboratory, further elucidating the general and disease-specific role of SD. The results obtained in this study may also provide insights into other SD-related pathologies such as stroke, traumatic brain injury, and migraine with aura.