MAPT and neurodegenerative disease: Tauopathies are neurodegenerative diseases caused by aggregation of the microtubule‐associated protein tau, encoded by the gene MAPT. Progressive supranuclear palsy (PSP) is a sporadic tauopathy, characterized by predominant involvement of tau isoforms with four microtubule‐binding repeats (4R tau; Chambers et al, 1999).