Amyloid beta (Aβ) peptide and tau protein in AD, tau protein in primary tauopathies (including progressive supranuclear palsy [PSP]) and α-synuclein in PD and other synucleinopathies, are some of the main proteins implicated in this aggregative mechanism at the origin of the neurodegenerative processes. The gene discussed is MAPT; the disease is progressive supranuclear palsy.