APOE and Alzheimer disease: In mouse AD models, single-cell RNA-seq defined disease-associated microglia (DAM) as a two-step response in which homeostatic/surveilling genes (e.g., P2ry12, Tmem119, Cx3cr1) decline while lipid handling and phagocytic modules rise; the mature, TREM2-dependent phase prominently induces genes such as Lpl, Itgax, Cst7, Apoe and related receptors (Keren-Shaul et al. 2017).