HTT and Parkinson disease: Neurodegenerative disorders are characterized by formation of accumulated aggregates of misfolded or mutated proteins/peptides, such as amyloid-beta (Aβ) peptides in Alzheimer’s disease (AD), α-synuclein (αSyn) in Parkinson’s disease (PD), and mutated huntingtin (mHtt) in Huntington’s disease (HD); aggregate formation is associated with cognitive and physical deficit of dementia [142].