The Ser422 phosphorylation site is prominent in early stages of Alzheimer’s disease and other tauopathies, thus making it relevant to tau pathology onset and progression (Guillozet-Bongaarts et al., 2006; Vana et al., 2011; Collin et al., 2014; Tiernan et al., 2016). Here, MAPT is linked to early-onset autosomal dominant Alzheimer disease.