MAPT and Alzheimer disease: Substantial progress has been made in understanding the basic mechanisms of AD and the prevailing hypothesis for AD pathogenesis is the amyloid cascade, in which secretion of amyloid β peptide (Aβ) gives rise to the extracellular deposition of amyloid plaques that in turn induce the aggregation of phosphorylated tau protein (O’Brien and Wong, 2011; Hampel et al., 2015).