MAPT and Alzheimer disease: The most studied amyloids include amyloid beta (Aβ) and tau in Alzheimer’s disease (AD), α-synuclein in Parkinson’s disease, amylin in type II diabetes, and TDP-43 in amyotrophic lateral sclerosis.1–4 Amyloid is characterized by a cross-beta sheet quaternary structure,5–7 and it exists in soluble and insoluble forms in solutions and in tissues.8–10 Recent evidence suggests that the soluble and insoluble forms of amyloids have different toxicities,8–11 and they are the dominant species at different stages in the progression of the disease.