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 (By similarity).