We and others have shown that [F-18]-AV-1451 has low affinity for tau aggregates that contain primarily 4R tau with straight filament ultrastructure that predominate in tauopathies such as progressive supranuclear palsy (PSP), corticobasal degeneration (CBD), and most cases of FTLD. The gene discussed is MAPT; the disease is Classical progressive supranuclear palsy.