Involved in specifying the paraxial, but not dorsal, mesoderm. May regulate the expression of T-box transcription factors required for mesoderm formation and differentiation (By similarity). Expressed in the presomitic mesoderm preceding the formation of somites. At stage 4 expressed in and around the primitive streak. During subsequent development, expression domain persists, and gradually retracts in parallel to the retracting Hensen's node towards the caudal end. Expression begins to accumulate in gastrulating mesoderm and is later restricted to paraxial mesoderm, prior to the onset of somite formation. No expression is seen within somites, nor in the tailbud mesoderm.