These studies focused on investigating the pathological mechanisms of AD and the functions of microglia, including induction of neurotoxic astrocytes (A1 type) via secretion of inflammatory factors, identification of novel disease-associated microglia (DAM) and their role in Aβ clearance, synaptic pruning mediated by the complement pathway, and regulation of microglial phenotype transformation by the TREM2-APOE pathway. This evidence concerns the gene APOE and Alzheimer disease.