TREM2 and Alzheimer disease: Genome-wide association studies have identified some AD-related genes involved in lipid trafficking or metabolism, such as APOE, clusterin/apolipoprotein J, triggering receptor expressed on myeloid cells 2 (TREM2), PICALM, sterol regulatory-element binding protein 2 (SREBP2), and the ATP-binding cassette subfamily A (ABCA) [83].