Changes in the ADP/ATP ratio in tbx5 knockdown embryos. A: In wild-type (WT) embryos, the ATP level was higher than that in tbx5 deficiency embryos. B: The ADP/ATP ratio of tbx5 knockdown embryos was significantly higher, indicated that apoptosis had occurred (n = 10). Data are presented as the mean ± S.D. An asterisk indicates a significant difference (p < 0.05). MO, tbx5 knockdown embryos.