Brain region-specific epileptogenesis in a conditional mouse model

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Despite the identification of a steadily increasing number of epilepsy genes and elucidation of molecular mechanisms of disease-causing mutations in heterologous expression systems, the exact mechanisms as to how epilepsy develops on the basis of a genetic defect is poorly understood. Functional studies in neurons and animal models offer interesting opportunities to understand the mechanisms underlying epileptogenesis and may pave the way for novel treatment options. Following the main hypothesis of this Research Unit (RU), epilepsy likely develops as a consequence of three interacting processes: the neurophysiological effect of the genetic mutation itself, an epileptogenic process triggered by the mutation, and developmentally regulated physiological changes of network properties within the brain. Therefore, we intend to understand the cascade caused by a molecular genetic dysfunction that triggers cellular changes of neuronal excitability and consecutively affects network function over time ending in epileptic seizures. We will use conditional mouse models in which we can switch on the genetic defect in a region- and time-specific manner to pursue the following aims: (i) to identify relevant brain regions and critical developmental time windows involved in the generation of certain seizure types using conditional region-specific expression of mutant genes; we will start with a conditional Scn1aA1783V mouse model in which we activate the mutation by local injection of viruses transducing Cre-recombinase; (ii) to explore in the same models the contribution and activity patterns of inhibitory and excitatory neurons and circuits in brain regions with an activated mutation using electrophysiology and Ca2+ imaging in vitro and in vivo; (iii) to understand transcriptional changes during epileptogenesis using cell-specific RNA-seq analyses before and after area- and time-specific activation of the mutation as a complementation of the neurophysiological studies of (i) and (ii). In addition, we will (iv) study interesting mutations that have been newly detected in projects P1-3 by studying their neurophysiological consequences using patch clamping and extracellular recordings either in transfected /transduced neuronal cell cultures or in brain slices from KI mouse models.