PSEN1 and Alzheimer disease: As such Trem2 deficiency augments Aβ accumulation is due to dysfunctional responses of microglia: failing to form cluster around Aβ and becoming apoptotic rather than undergoing activation and proliferation.58 Disease-associated microglia (DAM) are localized with Aβ-containing plaques in 5XFAD mice that express human APP and PSEN1 transgenes with five known AD-linked mutations.