MAPT and Alzheimer disease: Increasing research evidence implicates defects in the endosomal-autophagic-lysosomal (EAL) system as a very early event in the genesis and progression of Alzheimer's disease (AD) pathology, including the buildup of amyloid-β (Aβ) and tau, and synaptic pathogenesis (Lie and Nixon, 2019; Nixon, 2017, 2020; Van Acker et al., 2019; van Weering and Scheper, 2019; Whyte et al., 2017).