APOE and atherosclerosis: Because several in vitro studies have demonstrated the direct involvement of the aSMase/ceramide pathway in promoting lipoprotein aggregation, retention, and foam cell formation, Devlin et al., developed an aSMase knockout mouse (Asm−/−) starting from the apolipoprotein E knockout mouse (ApoE−/−), the most common murine model for atherosclerosis.