DINO AND MERCEDES, 2 GENES REGULATING DORSAL DEVELOPMENT IN THE ZEBRAFISH EMBRYO

We describe two genes, dino and mercedes, which are required for the o rganization of the zebrafish body plan, In dine mutant embryos, the ta il is enlarged at the expense of the head and the anterior region of t he trunk, The altered expression patterns of various marker genes reve al that, with the exception of the dorsal most marginal zone, all regi ons of the early dine mutant embryo acquire more ventral fates, These alterations are already apparent before the onset of gastrulation, mer cedes mutant embryos show a similar but weaker phenotype, suggesting a role in the same patterning processes. The phenotypes suggests that d ine and mercedes are required for the establishment of dorsal fates in both the marginal and the animal zone of the early gastrula embryo, T heir function in the patterning of the ventrolateral mesoderm and the induction of the neuroectoderm is similar to the function of the Spema nn organizer in the amphibian embryo.