MAPT and Alzheimer disease: Mutant tau alone was demonstrated to be involved in neurofibrillary pathology, synaptic loss, and neurodegeneration (Dickstein et al., 2010; Kopeikina et al., 2013a), but abnormal tau protein is also linked to effects of Aβ as tau protein was shown to be essential to Aβ-induced neuronal degeneration in AD (Rapoport et al., 2002; Bennett et al., 2004; Revett et al., 2013).