XENOPUS-GOOSECOID - A GENE EXPRESSED IN THE PRECHORDAL PLATE THAT HASDORSALIZING ACTIVITY

gsc is a homeobox gene expressed in the dorsal lip of the blastopore i n Xenopus. Its mRNA can mimic many aspects of Spemann's organizer acti vity when microinjected into the ventral side of the embryo. In the pr esent study we analyze gsc expression in late gastrula and neurula emb ryos of Xenopus. At these stages gsc is expressed in the prechordal pl ate, an anterior mesodermal structure underlying the forebrain. Furthe rmore, we studied the dorsalizing activity of gsc in animal caps and f ound that UV-sensitive cofactors in the marginal zone are required to induce dorso-anterior mesoderm in concert with gsc. FGF, an inducer of ventral mesoderm, cannot substitute for these factors.