For example, amyloid plaque neurofibrillary tangles (NFTs) in the brains of patients with AD and beta-amyloid (Aβ) and tau proteins in cerebrospinal fluid (CSF) indicate AD pathology in the brain (Gaikwad et al. 2021; Horie et al. 2020), Lewy bodies formed via α-synuclein aggregation in the PD brain (Fares et al. 2021), and huntingtin proteins in HD (Layburn et al. 2022). Here, HTT is linked to Alzheimer disease.