MAPT and Alzheimer disease: “Tauopathies” can be classified as either “primary”, where the tau lesion is upstream in the pathogenic cascade and tau is the predominant aggregated protein found in the brains of patients, these include progressive supranuclear palsy (PSP), corticobasal degeneration (CBD), Pick’s disease (PiD), and frontotemporal dementia with parkinsonism-17 (FTDP-17); or “secondary” tauopathies, where the tau lesion is downstream of a causative insult such as Aβ amyloid plaques in Alzheimer’s disease (AD)3,4.