Transcriptional repressor (By similarity). Downstream effector of Notch signaling which regulates cell fate choice in angioblasts. Represses the venous cell fate, thereby promoting the arterial cell fate and aorta formation. Expressed from the first somite stage. Expressed in lateral plate mesoderm before vessel formation, and thereafter in the aorta but not in the vein. At the 6-somite stage expression is seen in the lateral mesoderm of the head and trunk. While expression in the trunk lateral mesoderm is initially uniform, at the 16-somite stage, expression is restricted to angioblast precursors that have not yet migrated dorsally. At the 16-somite stage expression is also seen in the telencephalon, dorsal midbrain, neural crest and in the dorsal aorta and its vascular progenitors. By activation of the Notch signaling pathway. Belongs to the HEY family.