HTT and early-onset autosomal dominant Alzheimer disease: Some well-known hallmarks of these diseases include Amyloid β (Aβ) plaques and phosphorylated Tau (pTau)-containing tangles in Alzheimer's disease (AD) [4], α-synuclein-associated Lewy bodies in Parkinson's disease (PD) [5] and mutant huntingtin (Htt)-containing inclusion bodies in Huntington's disease (HD) [6].