PCSK9 and familial hypercholesterolemia: Specifically, male C57BL/6J mice were injected i.p. with a single dose of an adeno-associated virus (AAV) vector expressing the mouse D377Y gain-of-function proprotein convertase subtilisin/kexin type 9 (PCSK9), which resulted in sustained hypercholesterolemia as described previously (28).