Focal postnatal deletion of Tsc2 causes epilepsy

Carlie McCoy¹Mary Dusing²Lilian G Jerow³Grace C Winstel²Felix Zhan²Jason L Rogers⁴Madison Wesley²J Brian Otten²Steve C Danzer^2,3,5Candi Lynn LaSarge^2,3,5*

• ¹Division of Neurosurgery, Cincinnati Children's Hospital Medical Center, Cincinnati, OHIO, United States
• ²Department of Anesthesia, Cincinnati Children's Hospital Medical Center, Cincinnati, OHIO, United States
• ³Neuroscience Graduate Program, University of Cincinnati, Cincinnati, United States
• ⁴Noldus Information Technology Inc, Leesburg, United States
• ⁵Department of Anesthesiology, University of Cincinnati College of Medicine, Cincinnati, United States

Tuberous sclerosis complex (TSC) is a disorder caused by mutations in either the TSC1 or TSC2 genes. These mutations prevent the TSC1/TSC2 protein complex from forming, resulting in hyperactivation of the mechanistic target of rapamycin (mTOR) cell growth and protein synthesis pathway. Unfortunately, epilepsy is one of the most common neurological symptoms in TSC patients. Here, we created a novel TSC model to study this disorder by deleting Tsc2 from neurons in a focal area of the frontal cortex following neonatal bilateral AAV9-CaMKII-Cre-mCherry injections and show that these abnormal Tsc2 knockout cells are sufficient to cause epilepsy. Adult Tsc2fl/fl (fTSC2 KO) mice, and no Tsc2wt/wt (control) mice, had seizures during combined video-EEG monitoring. Histological analyses showed that virally infected cells in fTSC2 KO mice had enlarged somas and increased mTOR activation. These lesions led to secondary changes, including a decrease in surrounding parvalbumin and somatostatin cell densities. A separate group of control and fTSC2 KO mice, with low titer injections, were video recorded and tracked in a novel environment. fTSC2 KO mice displayed increased anxiety-like behavior, showing that focal Tsc2 knockout is sufficient to cause behavioral deficits. Altogether, this model is advantageous for delineating changes in the cortex of fTSC2 KO mice that support epilepsy and behavioral deficits and investigating possible targets for therapeutic intervention.