HTT and Parkinson disease: However, mounting evidence suggests that the proteins implicated in other neurodegenerative diseases, including amyloid beta (Aβ) and tau in Alzheimer’s disease (AD), alpha synuclein (α-syn) in Parkinson’s disease (PD), TAR DNA binding protein (TDP-43) and superoxide dismutase (SOD1) in amyotrophic lateral sclerosis (ALS), and huntingtin (Htt) in Huntington’s disease (HD) spread via prion-like mechanisms [4,5,6,7,8,9,10,11,12].