TREM2 and Alzheimer disease: This cluster displays downregulation of microglia homeostatic genes (e.g., P2ry12, CX3CR1 and Tmem119) and major levels of known AD risk genes (e.g., ApoE, Tyrobp and Trem2; Keren-Shaul et al., 2017; Rothman et al., 2018; Wang et al., 2018; Marttinen et al., 2019; Hashemiaghdam and Mroczek, 2020; Table 1, GSE98969, GSE123467).