HTT and multiple system atrophy: Historically, the aggregated proteins were assigned to defined clinical conditions: Aβ and Tau to AD [19, 37], α-synuclein to the synucleinopathies Parkinson’s disease (PD) [86, 110], dementia with Lewy bodies (DLB) [9, 110] and multiple system atrophy (MSA) [5, 116] and Huntingtin to Huntington’s disease (HD) [64, 102].