Accumulation of misfolded or misprocessed variants of these four key neuronal proteins (tau, Aβ, α-syn, and TDP-43) is a common pathological feature underlying many neurodegenerative diseases in addition to AD (e.g., Amyotrophic lateral sclerosis (ALS), Parkinson’s disease (PD), Frontotemporal Lobular Degeneration (FTLD), and Dementia with Lewy Bodies (DLB)). This evidence concerns the gene MAPT and Alzheimer disease.