APOE and Alzheimer disease: Studies of common genetic variants have identified many gene loci that influence risk of late-onset Alzheimer disease (AD) in persons of European ancestry (EA), most notably the APOE ε2 and ε4 alleles which confer strong protective and deleterious effects, respectively (Saunders et al., 1993; Corder et al., 1994), as well as more than 20 modest effect loci (odds ratios between 1.1 and 1.3) including BIN1, CR1, ABCA7, CLU, PICALM, and the MS4A gene region (Lambert et al., 2013).