Tau, a microtubule-associated protein, is the main component of the intracellular filamentous inclusions that are involved in neurodegenerative diseases known as tauopathies, including Alzheimer disease (AD), frontotemporal dementia with parkinsonism-17 (FTDP-17), Pick disease (PiD), progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD).