Transcription factor that play a central role in proper axial mesendoderm morphogenesis and endoderm formation. Required for efficient differentiation of cells from the primitive streak stage to blood, by acting early in the recruitment and/or expansion of mesodermal progenitors to the hemangioblastic and hematopoietic lineages. Also involved in the morphogenesis of the heart and the gut during embryogenesis. Acts as a negative regulator of brachyury expression (By similarity). Restricted to progenitors and secondary lymph tissues. In normal hematopoiesis, it is restricted to immature B- and T-lymphoid cells. Present in differentiating embryonic stem cells (at protein level). Phosphorylated at multiple sites. Belongs to the paired homeobox family.