Recent reports in a model of AD show that, in the peri-amyloid plaque environment, the astrocytic signals mediated by CD44, Clusterin, and ApoE target the Triggering Receptor Expressed on Myeloid (TREM)2 signaling pathway in microglia by binding to TREM2 and its downstream partner DNAX Activation Protein of 12 kDa (Dap12), inducing microglia activation [101]. Here, TREM2 is linked to Alzheimer disease.