In population studies, several genetic loci have been identified as risk factors for AD (e.g., CLU, CR1, APP, PICALM, BIN1, ABCA7, MS4A, MEF2C CD33, EPHA1, CD2AP, APOE, TRIP4, TREM2, SORL1), although the connection between genes in these loci and pathogenesis of AD has not been established (Ashford, 2004; Karch et al., 2012; Mäkelä et al., 2018). Here, TREM2 is linked to Alzheimer disease.