Abstracts

Rationale: The Rho/Rho kinase signaling pathway is an important regulator of neuronal skeletal structures. In previous study, kainic acid(KA) seizures cause acute activation of cofilin and collapse of dendritic spines. Rac1 is a crucial factor in Rho/Rho kinase signaling pathway. Thus, we generated the mice with conditional knockout (CKO) of the Rac1 gene to study the mechanism of Rho kinase in regulating epileptogenesis and comorbidity.  Methods: Mice were generated by Lox-P technology by cross-bred Rac1^flox/flox mice with Camk2a-CRE mice. The general appearance, growth and development were monitored. The change of Rho/Rho kinase signaling pathway of Rac1 CKO mice in native or after seizures status was analyzed by western blotting. Golgi staining was used to detect the neuronal morphology and dendritic spines. Spontaneous seizures were recorded by EEG-video. Morris water maze, Y-maze and open field test were used to study the behaviors of Rac1 CKO mice. Results: Rac1 CKO mice exhibited growth retardation as the control group. At postnatal 14 days, the body weight of Rac1 CKO mice was only 4.90 ± 0.57g, while that of control mice was 11.80±0.87g (p<0.05, n=20/group). The lifespan of Rac1 CKO mice was significantly decreased, with the average survival time of 23.85 ± 6.46 days (p<0.05, n=20/group). The approach-response test showed the score of Rac1 CKO mice was 3.25 ± 0.16 in Rac1 CKO mice, whereas the score was 1.86 ± 0.16 in the control mice (p<0.05, n =10). Additionally, the score of touch-response test was 3.38 ± 0.37 in Rac1 CKO mice, while that in control mice was 1.47 ± 0.23 (p<0.05, n=10), indicating the excitability in Rac1 CKO mice. Transient Vedeo-EEG recording showed that the Rac1 CKO developed seizures.  Conclusions: Knockout of the Rac1 gene in cortical excitatory neural cells results in the decrease of growth and lifespan, and increase of excitability. Rac1 may play an important role in epileptogenesis.  Funding: This work was supported by National Natural Science Foundation of China (81371429 to L. Z.), the Public Welfare Technology Application Research Project of Zhejiang Province (2016C33211 to F. Z.), Hangzhou Science and Technology Major Project for Innovation (20152013A02 to L. Z.), Hangzhou Science and Technology Project (20160533B73 to F.Z.).