Assessing the contribution of altered PI3K signaling to breathing abnormalities and sudden death in epilepsy

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SUMMARY Sudden unexpected death in epilepsy (SUDEP) is the most frequent cause of mortality in epilepsy. There are no predictors and no cures. Previous research suggests that breathing abnormalities contribute to SUDEP, but the underlying molecular mechanisms or brain areas involved are not well understood. Moreover, there are no disease mechanism-based treatments. A better knowledge of the molecular, cellular and brain circuit defects that contribute to respiratory deficits in epilepsy and that could be pharmaceutically targeted to prevent or reduce SUDEP is therefore urgently needed. The proposed research will combine the synergistic expertise of two PIs in respiratory regulation (Crone) and epilepsy (Gross) to test the hypothesis that altered PI3K/mTOR signaling in the forebrain causes aberrant amygdala function, either directly through increased PI3K/mTOR activity in the amygdala or indirectly via altered brain circuits, which leads to breathing deficits that increase the risk for SUDEP. The hypothesis is supported by preliminary data showing that a mouse model with a deletion of PTEN, a negative regulator of the PI3K/mTOR pathway, in excitatory forebrain neurons has prominent breathing deficits, and that partial inhibition of PI3K activity reduces mortality in these mice. To further test this hypothesis, this grant proposal will take advantage of the two laboratories’ expertise in PI3K/mTOR signaling and their capability to perform continuous and synchronized diaphragm EMG/cortical EEG/video recording in mice, which provides a novel and powerful tool to simultaneously assess breathing and seizures for extended periods of time. Aim 1 will determine if breathing abnormalities in forebrain-specific Pten knockout mice are dependent on amygdala function and/or seizure activity. Breathing and EEG activity will be monitored over several weeks in presymptomatic and symptomatic mice to evaluate the timing and development of respiratory deficits and seizures. Viral approaches will be used to silence or ablate excitatory neurons in the amygdala to test if amygdala activity is necessary for breathing abnormalities and sudden death in this mouse model. Aim 2 will also use viral approaches and continuous monitoring of breathing and EEG to test if locally increasing PI3K/mTOR signaling in excitatiory neurons of the amygdala or the hippocampus is sufficient to cause respiratory deficits, seizures and/or SUDEP. This research will advance the knowledge about the functional consequences of defective PI3K/mTOR signaling in epilepsy, and will help reveal the brain circuits and molecular mechanisms involved in respiratory deficits causing SUDEP. Further, it will pave the way to develop novel treatment strategies for SUDEP targeting the underlying disease mechanisms.