Functional interaction of vega2 and goosecoid homeobox genes in zebrafish

The gastrula organizer forms in the dorsal region of the zebrafish embryo, where the bozozok/ dharma homeobox gene downregulates expression of the veg a1 transcriptional repressor, Here, we describe a novel Vega family homeobo x gene, vega2, Expression of vega2 is initiated at the ventral blastoderm m argin during blastula stages, and by gastrulation becomes complementary to but partially overlapping with the dorsal expression domain of the homeobox gene goosecoid (gsc), This dorsal exclusion of vega2 expression is not obs erved in bozozok mutants in which organizer formation is impaired. Both veg a2 and vega1 can physically interact with Gsc, Zebrafish embryos injected w ith vega2 mRNA failed to express gsc and developed a headless phenotype, Co nversely, a putative dominant negative form of vega2, VP16-vega2, elicited the expansion of gsc expression and a dorsalized phenotype, We suggest that vega2, in cooperation with vega1, functions as a negative regulator of org anizer genes including gsc, and participates in the refinement of the gastr ula organizer domain. Published 2000 Wiley-Liss, Inc.(dagger)