MD/PhD Student Boston University School of Medicine Boston, Massachusetts
Rationale: Temporal lobe epilepsy (TLE) often develops after a brain insult activates ongoing molecular cascades and neural circuit remodeling in the hippocampus resulting in increased susceptibility to spontaneous seizures and cognitive dysfunction. Targeting these cascades after a brain injury and/or in TLE patients could prevent or reverse their symptoms and have the potential to provide a viable disease-modifying treatment, especially for the over 30% of TLE patients who do not respond to currently available treatments. In recent years, the Janus Kinase/Signal Transducer and Activator of Transcription (JAK/STAT) pathway has been implicated in the pathogenesis of TLE. The JAK/STAT pathway is known to be involved in inflammation and immunity, and only more recently has been shown to be associated with neuronal functions such as synaptic plasticity. Our laboratories previously showed that a JAK inhibitor, WP1066, could greatly reduce the number of spontaneous seizures that animals went on to develop in the rat pilocarpine model of status epilepticus (SE). Methods: We investigated the mechanism of JAK/STAT-induced epileptogenic responses through the use of a new mouse transgenic line we developed where STAT3 knockout (KO) can be controlled by tamoxifen-induced CRE expression specifically in forebrain excitatory neurons via the Calcium/Calmodulin Dependent Protein Kinase II alpha (CamK2a) promoter. TLE was induced in STAT3KO and wild-type mice using unilateral intrahippocampal kainic acid injections (IHKA). Mice were continuously video-EEG monitored during and for four weeks after IHKA-induced SE, followed by memory assessment using Contextual Fear Conditioning. Deep RNA-sequencing was performed 24 hours after IHKA injection in hippocampal tissue ipsilateral and contralateral to the injection site. Results: Specific STAT3 knockout in neurons (nSTAT3KO) markedly reduces spontaneous seizure frequency in the IHKA model of TLE and ameliorates IHKA-induced memory deficits as measured by Contextual Fear Conditioning. Using deep RNA-sequencing, we recently discovered transcriptomic signatures 24 hours after intrahippocampal kainate (IHKA) injection (ipsilateral and contralateral to the injection site) that are in part reversed in nSTAT3KO. These include gene networks involved in inflammatory signaling (including those containing TFNFR1, IL6, TLR1, IRF7, NF-KB, CXCL2, ITGA5), glutamate receptor signaling (including GRM3/5/8, GRIN2C, HOMER3, SLC17A2/6/7), and ceramide signaling (RASD1/D2, S1PR2/3). Additional important gene targets whose levels decrease in response to IHKA, and are reversed by nSTAT3KO, are those coding for type 1 GABA receptor subunits (GABRA5, GABRG1/G2, GABRD). Single nuclei RNA-seq will determine how STAT3 knockout in neurons affects individual cells of the epileptic brain. Conclusions: The emerging transcriptome for STAT3 in the context of temporal lobe epilepsy suggests that it may be useful for identifying potential epileptogenic gene networks that were previously unknown and identifying potential new targets for the treatment of intractable epilepsies. Funding: Please list any funding that was received in support of this abstract.: R01 NS051710
