Fig 1.

s434 mutants possess an enlarged heart and lack endocardial cushions. (A and B) Overall morphology of s434 mutants (B) compared to wild-type siblings (A) at 48 hpf. Pericardial edema is evident by 48 hpf (arrow), although the rest of the body appears morphologically normal. (C and D) Higher magnification of the anterior region of the embryo demonstrates the enlarged heart of s434 mutants at 72 hpf (arrow). (E and F) s434 mutants lack atrioventricular (AVC) endocardial cushions (ECs) by 120 hpf, as shown by lack of kdrl:GFP expression. The arrowhead denotes the AVC. (G and H) Hematoxylin and eosin staining of transverse sections through the heart at 72 hpf. The mutant heart is dilated and surrounded by pericardial edema (asterisk). A, atrium; V, ventricle.