All shuttle AAV plasmids encoding each of the human tau variants were derived from the pAAV-PGK-MCS-WPRE backbone (modified from pAAV-CMV-MCS provided by Stratagene) following standard cloning procedures. The cDNA fragments encoding human 4R0N tau and the P301S mutant were kindly provided by Dr M.G. Spillantini (Centre for Brain Repair, Cambridge University). The human 2P mutant tau (2P tau) was generated by introducing missense mutations encoding the I277P and I308P amino acid substitutions in the 4R0N tau cDNA, using the QuikChange II Site-Directed Mutagenesis Kit (Agilent Technologies). The control vector is derived from the same backbone and encodes the maxFP fluorescent protein.