Fig. 4. Altered cardiac morphology in Tbx20 knockdown embryos. (A-C) Bright-field frontal views of E9.25 embryos. (A) Wild-type, (B) b12 knockdown and (C) a6 knockdown. Insets in B,C show the absence of EGFP signal in the embryo. (D-U) Rendered optical projection tomography of embryos stained for Actc and Mybpc3 to label cardiac myocytes. Embryo is rendered translucent white; heart is red (D-F,J-L,P-Q); chamber fill is yellow (G-I,M-O,S-U). Views are from the right (D,G,J,M,P,S), front (E,H,K,N,Q,T) or left (F,I,L,O,R,U) sides. (D-I) Wild-type embryo; (J-O) b12 knockdown embryo; (P-U) a6 knockdown embryo. a, atrium; lv, left ventricle; ot, outflow tract; rv, right ventricle. White arrowhead indicates unusual bulging of the rv.