MAPT and Alzheimer disease: In AD, Wnt signaling impairment accelerates the onset of the disease and provokes the development of three AD hallmarks: (i) the production and aggregation of β-amyloid; (ii) tau protein hyper-phosphorylation process that involves GSK3β and Dikkopf 1 (DKK1), and generates neurofibrillary tangles within neurons; (iii) hippocampal-dependent cognitive impairment [73,74,75].