Molecular Pathways that Strengthen GABAergic Inhibition and Reduce Seizure Susceptibility - PROJECT SUMMARY The proposed project will fill an important knowledge gap in the field by providing a mechanistic understanding of how FLT3 signaling regulates neuronal function and circuit excitability in healthy and epileptic brains, and this work will advance the field by identifying new avenues for drug intervention to rescue impaired GABAergic inhibition that leads to brain disorders. GABAergic inhibition interacts with glutamatergic excitation to determine the level of neural activities in the nervous system. The neuronal chloride transporter KCC2 plays a pivotal role in regulating the polarity and efficacy of GABAergic signaling. Dysregulation of KCC2 is associated with impaired GABAergic inhibition present in various brain disorders including epilepsy, indicating KCC2 as a promising –yet to be explored– drug target for suppressing pathological brain hyperexcitability. Our published work discovered that small molecule compounds inhibiting the FLT3 kinase signaling are capable of enhancing the level of KCC2 protein expression in neurons to strengthen GABAergic inhibition. Although FLT3 has been historically studied in the context of blood cancer, our preliminary results show for the first time that in the brain FLT3 is specifically expressed in neurons, indicating that this kinase has functions in neurons yet to be explored. Leveraging a newly-developed neuron-specific Flt3 conditional knockout mouse line, we demonstrated that knocking out Flt3 gene from neurons, or treating mice with an FLT3 pathway inhibitor drug, substantially reduces seizure susceptibility. Specifically, we propose to further investigate the functional role of FLT3 in regulating the development of the GABAergic inhibition system in the mouse brain (Aim 1), and to examine to what extent the FLT3 signaling cascade regulates the onset and recurrence of epileptic seizures in mice (Aim 2). We will also elucidate the molecular and cellular mechanisms underlying FLT3 signaling in the brain (Aim 3).
