MAPT and Alzheimer disease: The development of AD manifested by Aβ accumulation forces tau hyper phosphorylation in sync with increased activity of glycogen synthase kinase-3β (GSK-3β) in the cortical neurons (Takashima et al., 1993, 1996; Tomidokoro et al., 2001; De Felice et al., 2008; Resende et al., 2008).