MAPT and Alzheimer disease: Dysfunction, slow progressive loss of neurons in the central nervous system, impairment of synaptic plasticity, progressive muscle atrophy or wasting, and proteinopathies, such as misfolded amyloid-β (Aβ) and tau in Alzheimer's disease (AD), α-synuclein in Parkinson's disease (PD), are all characteristics of neurodegenerative diseases.