APOE and Alzheimer disease: Furthermore, hub vulnerability manifests even in individuals at high risk for AD, such as patients with mild cognitive impairment (MCI) (Seo et al.2013; Sorg et al.2007; Wang et al.2013; Yao et al.2010), carriers of the Apolipoprotein E epsilon 4 allele (APOE ɛ4) (Brown et al.2011; Chen et al.2015; Wang et al.2015a), and cognitively healthy elderly with preclinical AD (Fischer et al.2015).