PSEN1 and Alzheimer disease: Knocking out TREM1 in the brains of APP/PSEN1 mice has been shown to increase Aβ1–42 levels and total amyloid plaque burden, and selective overexpression or activation of TREM1 on microglia cells could improve Aβ neuropathology and rescue AD-related spatial cognitive impairments (Jiang et al., 2016).