TREM2 and Alzheimer disease: Also, TREM2KO mice showed reduced microglia proliferation during homeostasis and after injury (Cantoni et al., 2015; Poliani et al., 2015; Zheng et al., 2017), and impaired proliferation was observed in AD mouse models without TREM2 or harboring dysfunctional TREM2 variants (Jay et al., 2017a; Cheng-Hathaway et al., 2018; Meilandt et al., 2020).