MAPT and Alzheimer disease: Interestingly, accumulated α-synuclein was found in more than 50% of autopsied AD brain while tau protein could also be detected in one-third of PD cases, which may suggest overlapping mechanisms between AD and PD (Roberts et al., 2017; Zhang et al., 2018; Smith et al., 2019; Twohig and Nielsen, 2019; Visanji et al., 2019).