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Abnormal cardiac differentiation occurred in the Nkx2.7-knockdown zebrafish embryos. The expressions of bmp4 (A–F) and versican (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, bmp4 was expressed in the ventricle and inflow tract at 48 hpf (A), and then bmp4 was restricted in its expression at the AV boundary at 72 hpf (D). However, in the Nkx2.7-MO (B, E) and Nkx2.5/2.7-MO (C, F) embryos, bmp4 was still expressed predominantly in the ventricle and atrium from 48 to 72 hpf. Similarly, in WT embryos, the versican expression was more predominant in ventricle than in atrium, at about 31 to 33 hpf, and then versican was confined in its expression at the AV boundary after 33 hpf (G, J). In contrast, in the Nkx2.7-MO (H, K) and Nkx2.5/2.7-MO (I, L) embryos, the versican was significantly expressed in the atrium and ventricle. In addition, the versican expression pattern in otoliths remained unchanged (J, K, and L). All images are ventral views, anterior to the top. a: atrium; v: ventricle; i: inflow tract; av: atrioventricular boundary; ot: otoliths.
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