TREM2 and Alzheimer disease: Besides TREM2, G4 contains various other proteins that have been implicated in AD, including Apolipoprotein E (APOE)49, Neurogranin (NRGN)50,51, ADAM Metallopeptidase Domain 17 (ADAM17)52,53, and Nectin Cell Adhesion Molecule 2 (NECTIN2)54.