PCSK9 and Hypercholesterolemia: Mice aged 6 weeks were treated with tamoxifen for five consecutive days to delete Jag1 from EC or to generate experimental controls and were then treated with adeno-associated viral proprotein convertase subtilisin/kexin type 9 (AAV-PCSK9) and exposed to a high-fat diet for 6 weeks to generate hypercholesterolemia and atherosclerotic lesions (Fig. 3A).