To test the effect of CYP27A1 deficiency on the development of atherosclerosis, we previously crossed Cyp27a1 knockout (KO) mice with Apolipoprotein E (ApoE) KO mice, and fed the offspring with a Western diet (WD) for 3 and 6 months [9]. The gene discussed is CYP27A1; the disease is atherosclerosis.