Fig. 1

Reduced Isl1 expression leads to defects in cardiac morphogenesis. a, b Wholemount and histological analysis of E12.5 hearts of control and Isl1 hypomorphs littermates showing impaired septation of the aorta (Ao) and pulmonary artery (PA) in Isl1 hypomorphs. Examples of Isl1 hypomorph showing partial septation of the aorta and the pulmonary artery with misaligned and hypoplastic aorta (a, middle panel, and b), and Isl1 hypomorph showing persistent truncus arteriosus (PTA, arrow). Cushion, c; Aorta, Ao; left ventricle, LV; right ventricle, RV. c Macroscopic appearance of E17.5 control and Isl1 hypomorphic heart with PTA (arrow). d Histological analysis of Isl1 hypomorphic hearts at E17.5 showing atrial septal defect (ASD, arrow), ventricular septal defect (VSD, arrow) and PTA compared to control hearts. At E17.5, a proportion of the mutant hearts are dilated. Atrial septum, AS. e, f MRI and 3D reconstruction of control and Isl1 hypomorphic hearts at E15.5 showing PTA, VSD and ASD (e) or other complex outflow tract phenotypes (f), e.g. right aortic arch (f, middle panel) and aortic vascular ring (AVR) (f, right panel). Aorta, Ao; aortic arch, AoA; pulmonary artery, PA; trachea, Tr; left ventricle, LV; right ventricle, RV; as, atrial septum; atrial septal defect (ASD), ventricular septal defect (VSD)