MAPT and Alzheimer disease: Tau is normally a highly soluble protein and mainly found in axons in adult neurons, however, intracellular inclusions of abnormally modified aggregated tau appear in neurons and glial cells in a range of neurodegenerative diseases collectively known as tauopathies, which include Alzheimer’s disease (AD), progressive supranuclear palsy (PSP), corticobasal degeneration, Pick’s disease.