MAPT and Alzheimer disease: Remarkably, since the presence of tau is not detectable in astrocytes under physiological conditions, the origin of this protein in astrocytes in AD-like conditions has been speculated, being proposed that during AD progression, tau translation might occur from mRNA present in astrocytes and astrocytic uptake of extracellular tau, released in the interstitial fluid by neurons, as well as intercellular propagation of tau through exosomes (see Richetin et al., 2020, and references within).