Fig. 3. HH signaling to the cardiomyoblast and pericyte is essential for coronary development. (A,B) Whole-mount PECAM immunohistochemistry demonstrating that, compared with control (A), Smo^{mlc2v; dermo1} CKO heart (B) displays an arrest in coronary development. Bracket indicates atrial ventricular groove. (C) β-Galactosidase staining of an E12.5 Mlc2v-Cre/Rosa26R heart, demonstrating that Mlc2v-Cre does not efficiently target cardiomyoblasts located in the atrial ventricular grove (AVG, bracket). By contrast, Mlv2v-Cre efficiently targets the ventricular myocardium (area below bracket). (D,E) Cryosections of hearts stained with in situ probes for Ptch1 revealing that, compared with controls (D), Smo^{mlc2v; dermo1} CKO hearts (E) lack both myocardial (asterisk) and perivascular (arrow) sources of Ptch1 expression. (F-K) Immunofluorescent staining of cryosections for PECAM (red) and VEGF ligands (green) reveal that, compared with controls (F,H,J), Smo^{mlc2v; dermo1} CKO hearts (G,I,K) display diminished expression of VEGFA (F,G), VEGFB (H,I) and VEGFC (J,K). White arrowhead indicates (PECAM-positive) endocardial cells that appear unaffected in these conditional mutants. Red arrow in A,D denotes orientation of tissue sections in relation to whole-mount photographs (B, base; A, apex).