HTT and Parkinson disease: For example, accumulation of amyloid beta peptide and/or tau is associated with AD (Van Hoesen et al., 1991), α-synuclein (α-syn) with PD, Huntingtin (HTT) protein aggregates occur in HD and superoxide dismutase 1 protein aggregates (SOD1) with ALS (Sweeney et al., 2017).