APP and early-onset autosomal dominant Alzheimer disease: Examples of these proteins include amyloid precursor protein (APP) Aβ and C-terminal fragments (CTF) in Alzheimer’s disease (AD), mutant α-synuclein in Parkinson’s disease (PD), and polyglutamine (polyQ)-expanded mutant HTT (mHtt) in Huntington’s disease (HD) (Shademan et al., 2021; Chen et al., 2024; Deng et al., 2017; Menzies et al., 2017).