Transcriptional activator. Activates ectoderm, in addition to inhibiting mesoderm and endoderm formation; required at the blastula stage for normal formation of both the central nervous system and epidermis, the two early derivatives of the ectoderm. In addition, also required to maintain the regional identity of the animal cells of the blastula, the cells that are precursors of ectodermal structures. Also plays a role in differential adhesion, which limits cell mixing as primary germ layers become specified. Expressed dynamically in a dorsal to ventral wave in the animal cap ectoderm in late blastula and gastrula stages. Expression is present in the cap in a salt and pepper arrangement which is maintained throughout early development. Expressed in lower levels in the mesoderm. At later stages, expression is lost from the developing nervous system, but epidermal expression persists through tailbud stages. Expression begins at stage 8.5, after the mid-blastula transition. Expression is highest at early gastrula stages and is maintained throughout neurula, tailbud and early tadpole stages. Inhibited by nodal signaling downstream of vegt, and by notch signaling downstream of dvr1/vg1. Neurula stage, but not early stage, expression is regulated by canonical wnt signaling.