Fig. 3

Msx1 haploinsufficiency modifies the Pax9^–/– cardiovascular phenotype. Embryos were imaged by µCT at E15.5 (A–D) and E12.5 (J–M), and following intracardiac ink injection at E10.5 (N–Q). A Control embryo with normal heart and aortic arch artery development. B CD1-Pax9^–/– embryos have defects such as interrupted aortic arch type B (IAA-B), retro-esophageal right subclavian artery (RE-RSA) and ventricular septal defect (VSD). A proportion of CD1-Pax9^–/–;Msx1^+/– embryos had cervical right subclavian artery (cRSA; C) or cervical aortic arch (cAo; D). E–I Defect frequencies seen in E15.5 embryos and neonates on C57Bl/6J (B6; data from [3]) and CD1 backgrounds are shown for Pax9^–/– (P9) and Pax9^–/–;Msx1^+/– (P9;M1) genotypes. CD1-Pax9^–/– mice have a significantly reduced penetrance of outflow tract defects such as DORV (E) although 4th PAA-derived defects are similar (F, G). IAA-B and RE-RSA are significantly reduced in CD1-Pax9^–/–;Msx1^+/– mice compared to CD1-Pax9^–/– mice (F, G) and cervical origins of the RSA (cRSA; H) and aorta (cAo; I) are increased. Fisher’s exact test for associations. ns, not significant; *p < 0.05, **p < 0.01, ***p < 0.001. J At E12.5 the aorta (Ao) and pulmonary trunk (PT) are septated and the right dorsal aorta (dAo) is regressing. K In CD1-Pax9^–/– embryos the PAA are abnormal with the 3rd and 4th PAA bilaterally absent, and the carotid duct (cd) persisting bilaterally. L, M In CD1-Pax9^–/–;Msx1^+/– embryos the 3rd and 4th PAAs often appear normal. N Control E10.5 embryo with PAAs patent to ink. The PAAs are abnormal in CD1-Pax9^–/– (O) and CD1-Pax9^–/–;Msx1^+/– (P, Q) embryos. Somite counts (s) are indicated. AD, arterial duct; LCC/RCC, left/right common carotid artery; LSA/RSA, left/right subclavian artery; LV/RV, left/right ventricle; PSC, primitive subclavian complex. Scale bars: 500 µm in A-D, 250 μm in J-M, 100 μm in N-Q