Fig. 4. Transposition of the great arteries and heart laterality defects in family 182. (A-D). A pup that died at birth showed thymic (T) hypoplasia (A) and an enlarged heart (A,B) with two thin outflows vessels positioned anterior-posterior (see arrowheads in C). For comparison, the chest cavity of a normal newborn mouse is shown in D. (E-J) Histological sections presented anterior to posterior (E-G) showed the aorta (Ao) positioned anteriorly (E), giving rise to the coronary arteries (F) and connecting to the RV (E). Lumen of the left coronary artery was enlarged (LCA). Panel G shows the pulmonary outflow (P) positioned posteriorly and a VSD. (H,I) Also observed is a primum ASD, single AV valve, canal type VSD (see canal in H), and bridging leaflet (arrow in H). Right atrial isomerism is indicated as the left-sided atrium (L-mRA) receives the left superior vena cava (LSVC) directly, while the right-sided atrium (R-mRA) receives the right superior vena cava (RSVC) in the normal fashion (I). (J) Ectopic pigment granules in the interventricular septum (arrows). (K-N) A fetal heart exhibited inverted ventricles together with right atrial isomerism. Apex of the heart is abnormally pointed to the right of the chest cavity (K,L). Arrow in K denotes the ductus arteriosus. The aortic (Ao) and pulmonary (PA) outflows are positioned anterior-posterior (L), with the anteriorly positioned aorta connected to the morphological right ventricle (mRV in M). A large coronary artery (CoA) drains into a sinusoidal fistula in the septum (see arrow in N). mLV, morphological left ventricle.