TREM2 and Alzheimer disease: The signature of DAM microglia is characterized by a reduction of the expression levels of microglia homeostatic genes (i.e., P2ry12/P2ry13, Cx3cr1, and Tmem119) and upregulation of many genes including known risk factors for AD (i.e., Apoe, Ctsd, Tyrobp, Lpl, and Trem2) (see reference [56] for full list of DAM genes).