Robust tauopathy and memory deficits in a mouse model constitutively overexpressing human P301L MAPT

Mutations in the MAPT gene encoding tau protein can be causative for frontotemporal lobar degeneration, FTLD-tau. Preclinical mouse models expressing these disease-causing MAPT alleles have successfully modeled biochemical and neuropathological phenomena similar to those seen in human FTLD-tau. One such model, rTg4510, features P301L human tau primarily expressed in the forebrain under the control of a Tet-off system, using the CaMKII promoter to drive transgene expression. While this model allows temporal manipulation of the transgenic tau, many experiments do not require such manipulation, and the bigenic tet-off system adds to the costs of simple transgenics, introduces additional genetic variation, and increases animal usage. Here, we have generated and characterized mice that constitutively overexpress P301L human tau under the CaMKII promoter. The initial founder and offspring were produced in the FVB/N background where we identified a line of constitutive "cTau^P301L" mice that stably expresses the 0N4R isoform of P301L human tau at levels comparable to the rTg4510 mouse. The cTau^P301L line features a relatively small deletion at the transgene insertion site and demonstrates no overt motor phenotype. There was, however, unexpectedly high early lethality on the FVB background that was mitigated after just one crossing to C57BL/6 mice. In both backgrounds, Tau^P301L expression resulted in an age-dependent accumulation of tau and gliosis that occur prominently in the forebrain and hippocampus. In transgenic F1 B6/FVB mice, spatial memory deficits were detected by 6 months of age. Overall, this new cTau^P301L model recapitulates disease-associated pathology and memory deficits, with limited disruption of the murine genome and a lack of longevity-restricting motor phenotypes. The cTau^P301L mouse is a robust, new alternative to existing mouse models of tauopathy.