Fig. 2: ISO-mediated increase in ventricular contractility and strain activates myocardial snai1b.

a, b At 14 dpf, the expression of myocardial snai1b (dashed green outline) remained sparse in the ventricle, whereas Isoproterenol (ISO) treatment from 1 to 11 dpf revealed a persistent snai1b activation in the trabecular network. Anatomic labels: BA bulbus arteriosus, V ventricle, BV bulbus-ventricular annulus, Myo myocardium, Endo endocardium, Epi epicardium, Ery erythrocyte. c At 4 dpf, 4-D mapping of myocardial strain in a control and an ISO-treated heart. Two time points during diastole were displayed, and the ISO-treated heart experienced higher strain at the end-diastole time point than the control. Red dashed lines and squares mark the cross-section planes, and the red arrows indicate the viewing direction. Blue and green arrows indicate the direction of blood flow. Anatomic labels: V ventricle, AV atrioventricular canal, OFT outflow tract. d Average epicardial/endocardial ventricular strain within the sampling regions during one cardiac cycle. ISO treatment increased the myocardial strain across the endocardial surface during the end-diastolic and systolic phases. Source data are provided as a Source Data file. e Strain variations within the sampling regions, calculated as the standard deviation of strains at each time point (phase). ISO treatment induced greater myocardial strain variations compared with the control heart. Source data are provided as a Source Data file.