TREM2 and Alzheimer disease: For example, KO mice of triggering receptor expressed on myeloid cells 2 (TREM2), a receptor predominantly expressed in the microglia and whose mutations were associated with increased risk of AD, showed alterations in Cdc42, and Rac1 signaling and their activator partially ameliorated impaired microglial migration in response to Aβ treatment (Rong et al., 2020).