May play a crucial role in specification of both the axial mesendoderm and the ventral nervous system. Expressed just before gastrulation in a narrow region on the dorsal side of the embryo. Expression can be detected in the involuted cells comprising the mesendoderm of the developing axis. At the end of gastrulation expression is turned on in the ventral neural plate in cells adjacent to the axial-expressing mesodermal cells. By mesoderm-inducing factor activin A.