MAPT and Alzheimer disease: The level of phosphorylated GSK‐3β is reduced in an AD mouse model, further leading to the excessive phosphorylation of Tau (Angelucci & Hort, 2017; Butterfield et al., 2006; Chen et al., 2015; Grison et al., 2011; Hall et al., 2011; Liao & Hung, 2010; P. J. Lu et al., 1999; S. L. Ma et al., 2012; Pastorino et al., 2006).