(A) Zebrafish were injected with control, RBFox1 morpholino (MO) alone, or in combination with zebrafish rbfox1l mRNA. Embryos were analyzed at 48 hours after fertilization (hpf) (original magnification, ×1 [first column]; ×11 [second column]), and hearts were visualized under fluorescent microscope (original magnification, ×11) and recorded to facilitate cardiac function analysis (zebrafish M-mode echocardiography) based on software as described elsewhere (9). (B) Quantification of zebrafish cardiac ejection fraction in the 3 experimental groups (n = 30 per sample). (C) Summary of injection and the number of pericardial edema observed. **P < 0.01, multiway ANOVA (B) or Fisher’s exact test (C).