Fig. 2. Dermo1-Cre is active in the perivascular cell lineage. (A-C) lacZ staining of Dermo1-Cre/Rosa26-lacZ hearts showing that at E12.5 (A) Dermo1-Cre marks cells localized in patches of the epicardium that are undergoing EMT (bracket with asterisk, white arrowhead) and around intramyocardial blood vessels (arrow). (B) lacZ staining of postnatal day 10 (P10) hearts demonstrating that Dermo1-Cre-expressing cells give rise to perivascular interstitial cells (arrow), but not the vascular endothelium (arrowhead). (C, inset) Dermo1-Cre-positive cells also give rise to the interstitium of the valvular leaflets (asterisk). (D-F) Immunofluorescent staining of cryosections for lacZ (D, red) and PECAM (E, green) confirming that Dermo1-Cre marks cells positioned immediately adjacent to the intramyocardial blood vessels (arrow in D,E) and in patches of the epicardium (bracket with asterisk). Merge of D,E is shown in F. (G-L) Immunofluorescent staining for lacZ (G,J, green), cardiac actin (H, red) and smooth muscle actin (K, red) demonstrating that Dermo1-Cre marked cells (arrows) express smooth muscle actin and not cardiac actin. Bracket indicates position of the epicardium. (I,L) Merged images of G,H and J,K, respectively. (M-O) Immunofluorescent staining for VEGFA (M, green) and smooth muscle actin (N, red), revealing that smooth muscle cells located within the myocardial wall (arrows) express VEGFA. Asterisk denotes VEGFA-expressing myocardial cells. O, merged image of M,N.