HTT and Parkinson disease: Many neurodegenerative diseases are characterized by formation of aggregates of misfolded or mutated proteins/peptides, such as Aβ peptides in Alzheimer’s disease (AD), α-synuclein (αSyn) in Parkinson’s disease (PD), and mutated huntingtin (mHtt) in Huntington’s disease (HD); however, calcium dysregulation is associated with all these diseases and in many cases precedes the detectable pathologies, such that a “calcium hypothesis of brain aging and AD” was proposed1,2.