MAPT and corticobasal degeneration disorder: Resulting tauopathies are classified in three groups according to the predominant species of tau that accumulate: 4R tauopathies (e.g., progressive supranuclear palsy, corticobasal degeneration), 3R tauopathies (e.g., Pick's disease), and 3R+4R tauopathies (e.g., AD) (6, 7); but in AD, the trigger of tau pathology is not genetic.