SCRN1 and progressive supranuclear palsy: However, a recent study that compared AD brain histopathology with other tauopathies demonstrated that secernin-1 is specific for tau isoforms in AD dementia and Down Syndrome as opposed to those in frontotemporal lobar degeneration dementia with Lewy bodies, progressive supranuclear palsy, and corticobasal degeneration [22].