APOE and Alzheimer disease: Apolipoprotein E ε4 allele (APOE4) is the strongest risk gene for AD (Yamazaki et al., 2019) and affect the major pathway by which APOE4 increases the risk of AD by driving earlier and more abundant Aβ pathology in the brains of APOE4-positive older adults (Morris et al., 2010; Yamazaki et al., 2019).