TREM2 and Alzheimer disease: As TREM2 is a strong risk factor for Alzheimer's disease (AD) in humans and was recently demonstrated to be a critical regulator of microglial activity in mouse models of AD (Guerreiro et al., 2013; Jonsson et al., 2013; Jay et al., 2015; Wang et al., 2015; Keren-Shaul et al., 2017; Ulland et al., 2017), many articles have reviewed the recent progress of TREM2/DAP12 research in AD (Ma et al., 2015; Colonna and Wang, 2016; Mecca et al., 2018).