TREM2 and Alzheimer disease: This homeostatic phenotype also appears to be present in brain areas that are not as affected by the disease, such as the cerebellum [12]. Whereas in late AD, microglial cells defined as disease-associated microglia (DAM) [20] or microglia associated with neurodegenerative disease (MGnD) [21] have upregulated genes such as triggering receptor expressed on myeloid cells 2 (Trem2) and apolipoprotein E (ApoE).