TREM2 and Alzheimer disease: A study using human microglia derived from induced pluripotent stem cells (iPSCs) revealed that TREM2 knockout reduced survival, phagocytosis and migration of microglia.204 However, since tau pathology happens much later than Aβ aggregation during the time course of AD, Gratuze et al. raised an objection to theory that loss of function of microglia carrying R47H variant is an inducement of tau pathology.