USF1 and familial hypercholesterolemia: In support of the suggestion that the higher foam cell susceptibility could be related to exacerbated hypercholesterolemia, plasma free cholesterol and cholesteryl ester levels were respectively 33% (P < 0.001) and 39% (P < 0.001) higher in USF1 knockout bone marrow recipients as compared to wild-type bone marrow recipients after 20 weeks of Western-type diet feeding (Figs. 6A).