MAPT and frontotemporal dementia: Protofilament sizes of 94 residues (tau fibril in Pick’s disease, PDB 6gx531), 110 residues (tau fibril in progressive supranuclear palsy (PSP), PDB 7p6532) and 115 residues (tau fibril in argyrophilic grain disease (AGD), PDB 7p6d32) are only somewhat smaller than scrapie.