Figure 6

Cardiac malformations and thymus hypoplasia in Ptdsr^-/- embryos. (a–c) Transverse and oblique (through the plane of the ascending aorta) sections, and 3D reconstruction (left-ventral oblique view) of a heart of a wild-type embryo at 15.5 dpc. The left and right ventricles (lv, rv) are separated by the interventricular septum (ivs). The left and right atria (la, ra), and the trachea (tr) are also indicated. The ascending aorta (a-ao) arises from the left ventricular outflow tract (lvot), via the aortic valve (ao-v), and continues on as the aortic arch (ao-a), which joins the descending aorta (d-ao). The pulmonary artery (pa) arises from the right ventricular outflow tract (rvot), and continues as the arterial duct (ad), which joins the descending aorta. (d–f) Corresponding images of a Ptdsr^-/- embryo, showing a smaller heart with a ventricular septal defect (VSD). The aorta arises from the right ventricle. The pulmonary artery is small and its connection to the descending aorta (arterial duct) could not be identified. (g–i) Corresponding images of another Ptdsr^-/- embryo, showing a ventricular septal defect (VSD). The aorta overrides the VSD resulting in a double-outlet right ventricle. (j, k) Coronal sections of Ptdsr^+/+ and Ptdsr^-/- embryos, showing the two lobes of the thymus (th). The arterial duct of the pulmonary artery in the Ptdsr^-/- embryo is narrowed. (l) Correlation between embryo weight and volume. Scattergram of embryo weight versus embryo volume measured from multi-embryo MRI datasets for 16 embryos using Amira. The co-efficient of regression (r) is indicated. (m, n,) Absolute embryo and thymus volumes (μl) were measured from the MRI datasets from 5 wild-type (wt), 3 heterozygote (h), and 8 Ptdsr^-/- (m) embryos at 15.5 dpc. There was no significant difference in the wild-type and heterozygote data, which were therefore pooled together (wt/h). (o) Relative thymus volumes (% of embryo volume) were calculated as Ptdsr^-/- embryos were slightly smaller than littermate wild-type embryos. The data are represented as mean ± S.D. The probability of a type I error (P) is indicated. Scale bars = 317 μm; axes: r – right; l – left; d – dorsal; v – ventral; a – anterior, p – posterior. Individual embryos are indicated by number.