Fig. 7. Expression of Jag1 and Notch2 proteins in hearts of E13.5 embryos. (A) Jag1 immunoreactivity is present in the pulmonary trunk and the aorta (arrows). Jag1 expression is also observed in cells surrounding the pulmonary trunk. (B) Notch2 protein is highly expressed around the aorta (arrow), in the ventricular myocardium, and at lower levels around the pulmonary trunk. (C) Jag1 immunoreactivity is observed in the pulmonary trunk (arrows) and in coronary vessels (arrowhead). (D) Notch2 is highly expressed in the atrial walls and in ventricular myocardium. All sections are from embryos at E13.5. la, left atrium; ao, aorta; lv, left ventricle; pt, pulmonary trunk; my, myocardium of the left ventricle.