Fig. 4

miR-143 is required and sufficient for CM growth and elongation. (A-I) At 48 hpf, WT, MO¹⁴³-injected and miR-143-overexpressing zebrafish embryos carrying a cmlc2::GFP transgene (green) were immunostained with anti-DM-GRASP antibodies (red) and imaged by confocal microscopy. Shown are flattened z-stacks (A,D,G) and individual sections (B,C,E,F,H,I) from each group. Dashed lines demarcate the approximate outer curvature/inner curvature (OC/IC) boundary based on proximity to the atrioventricular junction. (J,K) The circularities (J) and areas (K) of cells in the IC and OC of WT, MO¹⁴³ and miR-143-overexpressing (mimic) embryos. Asterisk indicates statistical significance compared with WT. (L,M) In situ hybridization for nppa expression in WT (L) and MO¹⁴³ (M) animals. The perimeters of the ventricles are highlighted with dashed yellow lines and the OC (nppa expressing) and IC (nppa non-expressing) populations are indicated. (N-R) Chimeric ventricles were derived by transplantation of WT (N,Q,R) or MO¹⁴³ (O,P,Q,R) blastula cells carrying the cmlc2::GFP transgene. (N-P) Mosaic hearts were immunostained with anti-DM-GRASP to outline cell borders. Representative images of WT (N) and MO¹⁴³ cells (O,P, green, ^*) in the OC. A morphant cell is shown projected from the ventricular wall (P, arrowhead). (Q,R) The average circularity and area for WT and MO¹⁴³ cells in the OC and IC.