Transcriptional regulator that may be involved in heart developmental processes. At late neurula stage (stage 20), strongly expressed in the developing cement gland and in the bilateral heart primordia. Expression in the cement gland decreases from stage 25 onward, while expression continues to be strongly detected in the developing heart. In the heart-forming region at stage 25, expression seen in the heart field formed by fusion of the bilateral heart primordia and also seen in the hindbrain (rhombencephalon) at this stage, corresponding to the second and fourth rhombomeres. At stage 29/30, expression persists in these regions and also weakly detected in a more posterior region of the hindbrain. At stage 33, when heart looping is initiated, broadly expressed in the heart tube, ventricle, atrium and both branches of the sinus venosus. During heart looping (stage 36), expressed at a higher level in the atrium than in the ventricle.