APP and Alzheimer disease: We performed a gene expression meta-analysis of purified mouse microglia across a series of transgenic models of AD including genetic mutations in amyloid precursor protein (APP), presenilin (PS1; also known as PSEN1), microtubule-associated protein tau (MAPT) and triggering receptor expressed on myeloid cells 2 (TREM2) (Wang et al., 2015; Song et al., 2018; Orre et al., 2014; Srinivasan et al., 2016; Friedman et al., 2018).