Transcription factor which plays a regulatory role in the development of the embryo. Involved in the establishment of dorsal/ventral pattern in the early mesoderm. Activates the head organizer gene cer1 by acting synergistically with otx2 and siamois through the 5'-TAATCT-3' element of the cer1 promoter. Also binds as a complex with lhx1/lim1 and siamois to the 3x 5'-TAAT-3' element of the cer1 promoter. Expressed mostly in the presumptive endodermal cells of Xenopus embryos. By activin and TGF-beta1 (immediate early response gene). Belongs to the paired homeobox family.