Tau loss attenuates neuronal network hyperexcitability in mouse and drosophila genetic models of epilepsy

Abstract

Neuronal network hyperexcitability underlies the pathogenesis of seizures and is a component of some degenerative neurological disorders such as Alzheimer's disease (AD). Recently, the microtubule-binding protein tau has been implicated in the regulation of network synchronization. Genetic removal of Mapt, the gene encoding tau, in AD models overexpressing amyloid-- (A-) decreases hyperexcitability and normalizes the excitation/inhibition imbalance. Whether this effect of tau removal is specific to A- mouse models remains to be determined. Here, we examined tau as an excitability modifier in the non-AD nervous system using genetic deletion of tau in mouse and Drosophila models of hyperexcitability. Kcna1-/- mice lack Kv1.1-delayed rectifier currents and exhibit severe spontaneous seizures, early lethality, and megencephaly. Young Kcna1-/-mice retained wild-type levels ofA-, tau, and tau phospho-Thr231. Decreasing tau in Kcna1-/-mice reduced hyperexcitability and alleviated seizure-related comorbidities. Tau reduction decreased Kcna1-/-video- EEG recorded seizure frequency and duration as well as normalized Kcna1-/- hippocampal network hyperexcitability in vitro. Additionally, tau reduction increased Kcna1-/-survival and prevented megencephaly and hippocampal hypertrophy, as determined by MRI. Bang-sensitive Drosophila mutants display paralysis and seizures in response to mechanical stimulation, providing a complementary excitability assay for epistatic interactions. We found that tau reduction significantly decreased seizure sensitivity in two independent bang-sensitive mutant models, kcc and eas. Our results indicate that tau plays a general role in regulating intrinsic neuronal network hyperexcitability independently of Aβ overexpression and suggest that reducing tau function could be a viable target for therapeutic intervention in seizure disorders and antiepileptogenesis. ©2013 the authors.