Accumulation of 3R and 4R tau isoforms results in distinct clinical manifestations: tangles comprised of paired helical filaments in Alzheimer’s disease brain contain a mixture of 3R and 4R tau, whereas 4R isoforms predominate the inclusions in progressive supranuclear palsy and corticobasal degeneration brain (VandeVrede et al., 2020). Here, MAPT is linked to Classical progressive supranuclear palsy.