Overexpression of human wtTDP-43 causes impairment in hippocampal plasticity and behavioral deficits in CAMKII-tTa transgenic mouse model

Aims: The current study utilizes the adeno-associated viral gene transfer system in the CAMKII alpha-tTA mouse model to overexpress human wild type TDP-43 (wtTDP-43) and alpha-synuclein (alpha-Syn) proteins. The co-existence of these proteins is evident in the pathology of neurodegenerative disorders such as frontotemporal lobar degeneration (FTLD), Parkinson disease (PD), and dementia with Lewy bodies (DLB). Methods: The novel bicistronic recombinant adeno-associated virus (rAAV) serotype 9 drives wtTDP-43 and alpha-Syn expression in the hippocampus via TetO CMV promoter. Behavior, electrophysiology, and biochemical and histological assays were used to validate neuropathology. Results: We report that overexpression of wtTDP-43 but not alpha-Syn contributes to hippocampal CA2-specific pyramidal neuronal loss and overall hippocampal atrophy. Further, we report a reduction of hippocampal long-term potentiation and decline in learning and memory performance of wtTDP-43 expressing mice. Elevated wtTDP-43 levels induced selective degeneration of Purkinje cell protein 4 (PCP-4) positive neurons while both wtTDP-43 and alpha-Syn expression reduced subsets of the glutamate receptor expression in the hippocampus. Conclusions: Overall, our findings suggest the significant vulnerability of hippocampal neurons toward elevated wtTDP-43 levels possibly via PCP-4 and GluR-dependent calcium signaling pathways. Further, we report that wtTDP-43 expression induced selective CA2 subfield degeneration, contributing to the deterioration of the hippocampal-dependent cognitive phenotype.