APOE and Alzheimer disease: Several preliminary studies have explored the influence of individual SNPs identified via AD GWAS such as loci within APOE, CLU, BIN1, or PICALM on brain structure and function, broadly suggesting that common variation within these genes are associated with AD and may influence brain structure and function decades before disease onset (Chauhan et al., 2015; Ferencz et al., 2014; Sperling et al., 2011; Trachtenberg et al., 2012; Yang et al., 2016; Zhang et al., 2015).