Interestingly, tauopathies also differ in terms of the predominant isoform composing their tau inclusions (Table 1), with AD exhibiting a roughly 2:1 ratio of 4R to 3R tau (Goedert et al., 2012; Wagshal et al., 2015; Irwin, 2016; Custodio et al., 2017; Josephs, 2017; Ferrer, 2018). This evidence concerns the gene MAPT and Alzheimer disease.