Most neurodegenerative diseases are characterized by intracellular or extracellular aggregation of misfolded proteins, such as Aβ and tau in AD, α-synuclein in PD, huntingtin in HD and transactive response DNA-binding protein-43 (TDP-43) in amyotrophic lateral sclerosis (ALS) [111]. This evidence concerns the gene HTT and neurodegenerative disease.