Abstracts

Rationale: Astrogliosis is commonly associated with epilepsy, but it has gone unexplored in Dravet syndrome. Dravet children experience their first seizure around 6 months old, and the disorder quickly advances to include multiple seizure types that put children at increased risk for SUDEP (Shmuely et al 2016). Dravet syndrome is highly resistant to current interventions, making the identification of novel cellular targets and therapeutics critical (Dravet & Oguni 2013). It is unknown if astrogliosis precedes the first epileptic episodes or what role glia play in the progression of the disorder.  Methods: To determine if astrogliosis precedes epileptic activity, we perfused pups from a Dravet mouse model with a knock-in mutation in the SCN1A gene (Ogiwara et al 2007) at postnatal day 11, 3 days before the onset of seizures. Immunocytochemistry and confocal microscopy were used to image the dentate gyrus, and GFAP integrated density was calculated for the hilus and granule layer regions. To determine if an A1R agonist could block the onset of astrogliosis, we treated Dravet mice with CPA from P11-P20 and analyzed the morphology of GFAP-positive cells in the dentate gyrus using FarSight (Kulkarni et al 2015), a unique toolkit developed at UH that reveals cellular 3D features. We then performed co-cluster analysis (Lu et al 2015) to assess the distribution of morphologically similar GFAP-positive cells.  Results: Astrogliosis was not detected in the dentate gyrus prior to the onset of seizures in SCN1A+/- mice when GFAP integrated density was compared to WT animals (n=10 animals/group with 2-5 slices/animal). Morphological co-cluster analysis of 120 features of GFAP-positive cells in adult mice 3-5 months old revealed that early postnatal activation of A1R with CPA had the long-term effect of blocking astrogliosis in Dravet mice and restored normal distribution of astrocyte morphological groups (n=8 animals/group with 2-3 slices/animal; p Conclusions: Our studies indicate that astrogliosis results after the onset of seizures in Dravet syndrome, and is unlikely to contribute to the first epileptic episodes. However, after initiated, astrogliosis in adult animals has the potential to contribute to the maintenance of an epileptogenic environment. We demonstrate that early postnatal treatment with A1R agonist is able to restructure the glial networks in the hippocampus of SCN1A+/- transgenic mice. These studies reveal astrocytes to be a novel cellular target in Dravet patients, however, further studies are necessary to determine if a strategy involving A1R agonists will yield beneficial outcomes. Funding: This research is supported by Dravet Syndrome Foundation (JŽ), University of Houston Biology of Behavior Institute (LM), Houston Livestock Show and Rodeo (LM), and University of Houston Biology and Biochemistry Imaging Core (LM and GM).