Fig. 5

add3 is a physiologically relevant target of miR-143 repression. (A) The conserved miR-143 seed sequence (2-8) base pairing with its conserved target sequence in the add3 3′ UTR. (B,C) In situ hybridization for add3. Left, lateral views; right, high-magnification anterior views of the zebrafish heart. (D,E) Double-fluorescence in situ hybridization at 36 hpf (D) shows overlapping cmlc2 (green) and add3 (red) expression, which is also visible at 54 hpf (E). (F) The add3 target protector morpholino experimental strategy. (G,H) Tg(cmlc2::GFP) embryos were injected with MO^add3TP and imaged at 48 hpf under transmitted (G) and fluorescent light (H). Lateral views. As with MO¹⁴³ embryos, MO^add3TP animals exhibit ventricular collapse, atrial dilation and compromised function (see Movie 3 in the supplementary material). (I-K) Representative sections (J,K) and a flattened z-stack (I) of a 48 hpf MO^add3TP heart carrying the cmlc2::GFP transgene (green) immunostained with anti-DM-GRASP antibody (red). Dashed lines indicate the approximate OC/IC boundary based on the proximity of cells to the atrioventricular junction. (L) The average circularity and area of WT, MO¹⁴³, MO^add3TP, and MO¹⁴³ + MO^add3TP IC and OC myocytes. Asterisks indicate statistical significance compared with WT; error bars represent ± s.e.m.