Fig. 3

mmp21 knockdown induced by SB-MO caused heart looping disorder in zebrafish embryos. A Relative mmp21 mRNA expression in zebrafish embryos injected with SB-MO and standard control MO at concentrations of 0.8 mM and 1.0 mM for 30 h was assessed by RT-qPCR. RT-qPCR results showed that microinjection of SB-MO (1.0 mM) significantly decreased the mmp21 mRNA expression in zebrafish embryos compared to the control MO group (data are shown as the mean ± SEM, one-way ANOVA with Tukey’s multiple comparisons test was used for statistical calculation, n = 3 independent experiments, ns: nonsignificant, ****p < 0.0001). B Whole-mount in situ hybridization using a cmlc2 antisense probe to detect cyclization of 48 hfp embryonic cardiac tubes after MO injection. a, b The WT and control MO groups showed normal heart looping (D-loop). c, d, e Zebrafish embryos in the SB-MO group formed an abnormal L-loop on the left side or manifested as ambiguous looping or no loop. f Some zebrafish embryos in the SB-MO group showed tail deformity, which may be caused by side effects of SB-MO. Scale bar, 200 μm