Impact of Raptor and Rictor Deletion on Hippocampal Pathology Following Status Epilepticus

Area of Science:

• Neuroscience
• Cellular Biology
• Signaling Pathways

Background:

• Neuronal hyperactivation of the mechanistic target of rapamycin (mTOR) signaling pathway is implicated in the pathology following status epilepticus.
• Systemic mTOR inhibition offers limited insight into cell-type-specific roles due to mTOR's ubiquitous activity.

Purpose of the Study:

• To develop and utilize a viral/genetic strategy for cell-type-specific mTOR inhibition in excitatory hippocampal neurons post-status epilepticus.
• To investigate the impact of inhibiting mTORC1 (via Raptor deletion) or mTORC2 (via Rictor deletion) on neuronal pathology after induced seizures.

Main Methods:

• Developed a viral/genetic system to delete Raptor or Rictor in mouse hippocampal neurons after pilocarpine-induced status epilepticus.
• Achieved deletion in approximately 25% of hippocampal granule cells, with some impact on other neuron types.
• Assessed status epilepticus-induced changes including hilar neuron loss, mossy fiber sprouting, and c-Fos activation.

Main Results:

• Status epilepticus induced expected pathological changes, which were not prevented by gene deletion.
• Raptor deletion led to a relative decrease in c-Fos-positive granule cells compared to Rictor deletion groups.
• The genetic approach effectively modulated mTOR signaling, but deletion in a minority of cells did not alter key pathological measures.

Conclusions:

• The viral/genetic strategy is effective for modulating mTOR signaling in a cell-specific manner.
• Inhibiting mTORC1 or mTORC2 in a small fraction (25%) of excitatory hippocampal neurons is insufficient to mitigate major pathological outcomes of status epilepticus.
• Future studies could explore higher deletion rates or altered deletion timing for potentially different results.