MAPT and progressive supranuclear palsy: To test the specificity of MD2.2 and MD3.1 for AD versus other tauopathies, we prepared soluble homogenates of frozen frontal cortex from corticobasal degeneration (CBD, 4R tau), progressive supranuclear palsy (PSP, 4R tau), and Pick disease (PiD, 3R tau) brains.