Although several transgenic animal models of tauopathy, which overexpress wild-type or mutated human tau up to many folds of the endogenous murine tau, have been developed in the last two decades (Andorfer et al., 2003; Oddo et al., 2003; Santacruz et al., 2005; Yoshiyama et al., 2007; de Calignon et al., 2012; Rockenstein et al., 2015), filamentous tau pathology has not been observed in wild-type rodents expressing murine tau only (Ojo et al., 2016), suggesting that the level of tau expression may be critical for the development of tau pathology. This evidence concerns the gene MAPT and tauopathy.