MAPT and early-onset autosomal dominant Alzheimer disease: It is worth noting that the N-terminal, but not C-terminal, fragments of tau including the 20–22 kDa NH2htau form(s), are mainly secreted from synaptosomes of Alzheimer’s disease brains (Sokolow et al., 2015) and detected both in CSF from Alzheimer’s disease patients (Johnson et al., 1997; Portelius et al., 2008; Meredith et al., 2013; Amadoro et al., 2014; Chen et al., 2019; Cicognola et al., 2019) and in conditioned media from patient-derived induced pluripotent stem cells cortical neurons (Bright et al., 2015; Kanmert et al., 2015; Sato et al., 2018).