TREM2 and Alzheimer disease: Since arginine 47 is located in the extracellular region of TREM2 and the R47H mutation changes the glycosylation status of the extracellular region of TREM2 (Figures 1–3), this base substitution can alter the binding of TREM2 to its ligands, its receptor function and its processing by proteases, all of which may underlie the molecular pathways by which this variant contributes to the pathogenesis of AD.