Fig. 3

Effects of CDK9 inhibition or knockdown on the structure and function of the developing zebrafish heart. For pharmacological inhibition (A), embryos were continuously exposed to vehicle (1% DMSO, clear bars) or flavopiridol (3µmol/l, dark bars) from 24 to 120hpf. For morpholino-mediated knockdown (B), embryo eggs at the one- to two-cell stage were injected with Cdk9 mismatch morpholino (clear bars) or Cdk9-targeting morpholino (SB, black bars). Ventricle ejection fraction (A,B, upper panels) and diastolic area (A,B, lower panels) were assessed sequentially in the same embryos at 72, 96 and 120hpf. Images in C show embryonic hearts following treatment with flavopiridol and Cdk9-Mo (SB). Left-hand panels are bright field images of the heart, and right-hand panels are histological sections through the heart stained with haematoxylin and eosin (H&E). n=3 experiments, >10 embryos per experiment, *P<0.05, **P<0.01, ***P<0.001. Two-way ANOVA test for repeated measures followed by Bonferroni′s post-hoc test. ‘A’, atrium; BA, bulbous arteriosus; V, ventricle. Means±s.e.m. are shown in upper and lower panels of A and B.