Nkx2.5 was overexpressed in the Nkx2.7-knockdown embryos.

<p>Nine nanograms of Nkx2.7-MO were injected into one-cell stage of embryos. <i>Nkx2.5</i> was expressed predominantly in ventricle (v) and weakly in atrium (a) of wild-type (WT) embryos at 48 hpf (A), but only minimally and weakly in ventricle at 72 hpf (C). However, the Nkx2.7-MO-injected embryos retained robust <i>Nkx2.5</i> expression in ventricle both at 48 and 72 hpf (B and D). The embryonic stages were as indicated, and embryos were observed ventrally. v: ventricle; a: atrium.