Probable transcription factor involved in the control of specification of mesoderm and endoderm. Acts in parallel with bonnie and clyde, faust and casanova in the Nodal signaling pathway. Restricted to the mesendoderm precursors during gastrulation. First detected at sphere stage (4 hours) in a small group of cells at the margin of the blastoderm. As epiboly starts, it extends over the whole circumference of the margin of the blastoderm, while it is not detected in the yolk syncytial layer. Expression domain extends over 6 rows of cells, that is over a region that includes the precursors of mesoderm and endoderm. At the shield stage, it is also expressed in the invaginating axial mesendoderm. After the shield stage, the abundance of transcripts declines abruptly and only a weak expression is detected in embryos at 60% epiboly and no expression at 70% epiboly or later. Not detected in 4 day old embryos or in adult fish. Regulated by the Nodal pathway. Belongs to the paired homeobox family.