MAPT and supranuclear palsy, progressive, 1: Genetic evidence supporting a causative role for 4R-Tau in PSP includes: clinical-pathologic PSP phenocopies caused by missense and splice site mutations of the MAPT gene8 encoding Tau; a locus inversion allele encompassing the MAPT gene that expresses less 4R-Tau9 and is protective against PSP10; rare instances of MAPT gene duplications in PSP11; and a strong association between PSP risk and non-coding SNPs near to MAPT12,13.