ABCA1 and Alzheimer disease: Previous researches suggest that astrocytes participate in synaptic pruning through different pathways under different physiological and pathological conditions: MEGF10 and MERTK pathways in developing and adult brain [6], type 2 inositol 1,4,5-trisphosphate receptor (IP3R2) pathways in developing brain [39], ATP-binding cassette transporter A1 (ABCA1) pathways during the later stage of ischemia [33] and MFG-E8 receptors in AD brain.