Antivin, a novel and divergent member of the TGF beta superfamily, negatively regulates mesoderm induction

Mesoderm induction and patterning are mediated by members of the TGF beta s uperfamily, We have isolated a novel zebrafish member, antivin, that struct urally is highly related to mouse lefty. Overexpression of antivin complete ly abolishes mesoderm induction at blastula stage, yet resultant embryos de velop well-patterned epidermal and neural derivatives. The mesoderm-inhibit ing activity of antivin can be mimicked by lefty and is suppressed by incre asing levels of the mesodermal inducer Activin or its receptors, On the bas is of its expression and activity, we propose that Antivin normally functio ns as a competitive inhibitor of Activin to limit mesoderm induction in the early embryo.