Fig. 8. Forelimb and heart defects in Family 166. (A-D) Forelimbs are abnormally flexed towards the chest, with clubbed front paws. Typically three digits are seen (B), but in some pups, there appears to be a fusion of the third and fourth digits (C,D). (F,G) Whole-mount view shows enlarged atria and an abnormal heart shape indicative of hypertrophy (F,G). An abnormal large peritruncal coronary vein is observed at the base of the outflows (white arrow, G). (E,H-M) Histology shows biventricular hypertrophy (H,J,L), and abnormal coronaries around the outflow vessels (E, white arrow in H). Also evident are muscular VSDs (see arrows in J-M), and disorganized myocardium (E,I,K,M), which frequently shows gaps between the myofiber bundles (see arrowhead in E). (N-P) The heart shown in (G) was processed for episcopic fluorescence image capture, and the image stacks obtained were re-sectioned at a different pitch to visualize the VSDs (see white arrows). Sections in E, H and I are from heterozygous, whereas the rest are from homozygous animals.