MAPT and supranuclear palsy, progressive, 1: Recently, in the peripheral nerves of skin, increased tau mRNA expression and total tau protein in the PSP cases has been reported,13 suggesting its potential as a biomarker.6,7 However, even in that study, immunostaining (immunofluorescence) did not demonstrate positivity for phosphorylated tau.13 This may have been due to a small number of peripheral nerve tissues and a few tau depositions in the skin.