MAPT and Alzheimer disease: Endogenous and overexpressed tau have been detected in exosomes from immortal cell lines, rodent neuronal cultures, human iPSC neurons, mouse brain, and from CSF of AD patients (Saman et al., 2012; Dujardin et al., 2014; Tang et al., 2015; Polanco et al., 2016; Wang et al., 2017; Guix et al., 2018).