In keeping with our in vitro data, primary Osx p53Rb KO tumors and Osx p53RbSmo KO osteomas express SHH and display prominent primary cilia (Fig. 3c–e, Supplementary Fig. 7e–g), consistent with TP53 and RB1 inhibiting ligand responsiveness and primary cilia frequency. Here, RB1 is linked to osteoma.