Expression of cell cycle-related genes and proteins in tbx5 knockdown and GH-treated zebrafish embryos at 30 h post-fertilization (hpf). Cell cycle-related genes, p27 (A) and cdk2 (B), were significantly induced in MO group embryos throughout the developmental stages but were similar among the WT, WTGH, and MOGH groups. (n = 3, 50 embryos/stage; relative expression = gene expression/β-actin expression). (C-R) Zebrafish embryos was stained with cell cycle-related (Cdk2 and P27) antibodies (red) and counterstained with DAPI (blue) for nuclear observation. In sagittal sections of the heart and transverse sections of the pectoral fins, expression patterns of Cdk2 and P27 were similar in all treatment groups in that they were significantly induced in tbx5-deficienct embryos (E, I, M, Q) and showed insignificant differences among the WT (C, G, K, O), WTGH (D, H, L, P), and MOGH (F, J, N, R) groups. (C-R) The anteriors of the embryos are to the left. WT, wild-type embryos; MO, tbx5 knockdown; MIS, mismatch tbx5-MO-treated embryos; WTGH, WT embryos treated with growth hormone (GH); MOGH, tbx5-MO- and GH-treated embryos. Data are presented as the mean ± S.D. *p < 0.05.