APOE and atherosclerosis: A CETP ortholog is frustratingly absent in commonly used rodent models (Haa and Barter, 1982), rendering the study of atherosclerosis difficult: rodents are inherently resistant to atherosclerosis (Yin et al., 2012), and background manipulations such as targeted deletion of the Apoe or Ldlr genes are required to drive atherosclerosis.