MAPT and tauopathy: Regarding tauopathy in vitro by using mammalian HEK293 cells expressing pTRE3G-cherry-BI promoter-EGFP Tau P301L, NMN treatment offset the tau injury and resulted in a decrease in the expression of several phosphorylated-tau (p-tau) sites, including thr181, thr231, thr217, and ser396 (Fig. 2d, j–s, and Supplementary Fig. 1g).