To investigate whether the distribution pattern of tau was affected upon the addition of haSyn PFFs, we studied tau phosphorylated at residue Ser404 (pSer404-tau), which is one of the first sites to be hyperphosphorylated leading to the detachment of tau from microtubules, a phenomenon that is closely related to disease pathogenesis in tauopathies [1, 16, 36, 63]. Here, MAPT is linked to tauopathy.