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Chamber maturation was affected in the Nkx2.7-knockdown zebrafish embryos. The expressions of tbx5 (A–F) and tbx20 (G–L) in hearts were compared between wild-type (WT) (A, D, G, J), Nkx2.7-MO- (B, E, H, K) and Nkx2.5/2.7-MO- injected embryos (C, F, I, L) at 48 (A–C, G–I) and 72 hpf (D–F, J–L). In WT embryos, tbx5 was expressed strongly in ventricle, but weakly in atrium at 48 hpf and beyond (A, D). However, in the Nkx2.7-MO (B, E) and Nkx2.5/2.7-MO (C, F) embryos, tbx5 retained its strong expression in the heart, although the expression pattern was gradually changed from ventricle-enriched expression to atrium-enriched expression from 48 hpf to 72 hpf (B and E; C and F). In WT embryos, tbx20 expression was similar to the expression gradient of tbx5 in the heart at 48 hpf, and the tbx20 expression was stronger than that of tbx5. In addition, tbx20 expression was also detected in outflow tract at 48 hpf (G), and tbx20 expression was restricted to outflow tract and inflow tract by 72 hpf (J). However, in Nkx2.7-MO (H, K) and Nkx2.5/2.7-MO (I, L) embryos, tbx20 was expressed strongly in the heart and outflow tract from 48 to 72 hpf. All images are ventral views, anterior to the top. v: ventricle; a: atrium. ot: outflow tract; i: inflow tract.
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