MAPT and early-onset autosomal dominant Alzheimer disease: Recent in vitro and in vivo data have highlighted a crucial role of proteolytic fragments of tau protein, in particular those derived from truncation at its N-terminal domain, in the initiation/progression of Alzheimer’s disease and other related tauopathies, thus paving the way for their potential use as therapeutic targets or as biomarkers for diagnosing dementia and/or monitoring disease progression (Avila et al., 2016a; Quinn et al., 2018; Sebastián-Serrano et al., 2018).