These microglial signatures are characterised by the downregulation of homeostatic genes (P2ry12, Tmem119, Sall1 and Cx3cr1) and upregulation of an inflammatory program (Trem2, Apoe, Axl, Lpl and Clec7a) (Table 5), several of which have been identified in genome-wide association studies linked to human AD. Here, APOE is linked to Alzheimer disease.