TREM2 and Alzheimer disease: The findings of microglial-related pathway and DAM gene expression differences between the 5XFAD × TREM2−/− and 5XFAD × TREM2+/− mice, combined with differing microglial plaque-association but similar NP tau pathology after AD-tau injection, emphasize that TREM2 heterozygous and KO mice are distinct and that the former may better model the heterozygous TREM2 variants linked to AD risk.