MAPT and Alzheimer disease: Heterozygous APP.PS1 transgenic (TG) and C57BL/6 wild-type (WT) animals (Fig. 1a) were injected with either AD-Tau seeds (i.e., TG-tau and WT-tau) or Buffer solution (i.e., TG-buffer and WT-buffer) via a cannula system (Fig. 1b).