was cloned from a cDNA library constructed from isolated dorsal lip tissue of Xenopus laevis gastrula stage embryos. It encodes a homeodomain transcription factor with DNA binding specificity identical to that of the anterior morphogen 'bicoid' in Drosophila. 'Goosecoid' RNA expression in the dorsal lip of the frog embryo marks the Spemann organizer tissue, which in classic experiments was shown upon transplantation to the ventral side of a recipient embryo to induce formation of a secondary body axis. Injection of synthetic 'goosecoid' mRNA into early Xenopus embryos results in a similar phenotype. Genes homologous to 'goosecoid' have been isolated from mouse, zebrafish, and chick, in all of which the gene is expressed and plays an important role during the process of gastrulation in early embryonic development.