Phenotypes of tbx5 knockdown and GH-treated zebrafish embryos. The normal appearance of hearts in wild-type (WT) (A) and MIS (C) group embryos and string-like hearts occurring in MO (B) group embryos are depicted. In WTGH embryos (D), hearts are identical to those of the WT (A) group, and hearts of MOGH group embryos (E) showed improvements. No significant differences were observed in trunks of WT (F), MIS (H), and WTGH group embryos (I), in which trunks were straight and somites appeared “V-shaped.” On the other hand, trunks of embryos injected with tbx5-MO were severely bent (G) and had “U-shaped” somites, but these were partially restored in MOGH group embryos (J). In the MO group (L), truncated or undeveloped pectoral fins were demonstrated; nevertheless, WT (K) embryos micro-injected with mismatched tbx5-MO (M), WT (N) exogenous GH–treated embryos, and tbx5-deficient embryos exhibited normal appearances. Statistically, the normal morphogenetic rates of the heart (P), trunk (Q), and pectoral fins (R) were significantly lower in the MO group and partially improved in the MOGH group. Defective embryos were not found in the WT or MIS groups and almost all of the embryos in the WTGH group developed properly. Data are presented as mean ± S.D. *p < 0.05 vs. WT; #p < 0.05 MO + GH vs. MO. Black arrowhead, defect site; dashed line, shape of somite border; MO, tbx5 knockdown; MIS, mismatch tbx5-MO-treated embryos; WTGH, WT embryos treated with GH; MOGH, tbx5-MO- and GH-treated embryos.