MAPT and Alzheimer disease: For example, Trem2, a known AD risk gene expressed in microglia (Krasemann et al., 2017; Sims et al., 2017), is present in Signatures A and C. From this, we could conclude that Trem2 is responsive to tau across mouse strains and is correlated to tau seeding observed in wild-derived mice (Fig. 9 B).