Fig. 1

Defects in Pax9^–/– embryos on a congenic CD1 background. Embryos at E15.5 were imaged by MRI (A–H, I, L, O) and histology (J, K, M, N, P, Q). A–H Extracardiac defects in CD1-Pax9^–/– embryos. A normal palate (A, B), thymus (C) and hind limb digit (white arrow; D) are seen in control embryos. CD1-Pax9^–/– embryos display cleft palate (E, F), absent thymus (asterisk; G) and pre-axial digit duplication (red arrows; H). (I–Q) Cardiovascular defects in CD1-Pax9^–/– embryos. Control embryos have normal heart and aortic arch artery development (I–K). CD1-Pax9^–/– embryos have arch artery defects such as interrupted aortic arch type B (IAA-B), aberrant right subclavian artery (A-RSA), and absent common carotid arteries resulting in the internal and external left carotid arteries (iLC, eLC) arising directly from the aorta and dorsal aorta respectively (L, O). In the majority of CD1-Pax9^–/– embryos the outflow tract was unaffected (L–N) although double outlet right ventricle (DORV) with interventricular communication (IVC) was infrequently observed (O–Q). AD, arterial duct; Ao, aorta; BC, brachiocephalic artery; CP, cleft palate; LCC/RCC, left/right common carotid artery; LSA/RSA, left/right subclavian artery; LV/RV, left/right ventricle; P, palate; PT, pulmonary trunk; Th, thymus. Scale bars: 500 µm