In normal adult arteries, the core hedgehog proteins are expressed between the adventitial and medial layers39 and after injury in smooth muscle cells in the media and intima.40,41 Although our results suggest that smooth muscle is the primary site of HHIPL1 function, we cannot exclude a role for Hhipl1 in other atherosclerosis-relevant cell types, such as endothelial or inflammatory cells. The gene discussed is HHIPL1; the disease is atherosclerosis.