APOE and atherosclerosis: Genetic disruptions of lipoprotein metabolism through targeted knockout (KO) of the LDL receptor (LDLR) (Ishibashi et al., 1993) or of apolipoprotein E (ApoE) (Piedrahita et al., 1992), a major ligand for lipoprotein receptors, has given rise to the conventional mouse models of atherosclerosis that are widely used in basic atherosclerosis research today (Whitman, 2004).