In addition, single cell RNA sequencing of transplanted cells revealed a shift of microglial subclusters towards homeostatic, less reactive profiles in TREM2-KO microglia, which also failed to acquire a DAM signature when injected into AD mice, further supporting the notion that TREM2 knock out traps microglia into a homeostatic state (McQuade et al., 2020). Here, TREM2 is linked to Alzheimer disease.