MAPT and Alzheimer disease: 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)).