Abstract

A recent paper by Watabe et al.(1) describes the identification, in the promoter region of the organizer‐specific gene goosecoid, of two distinct growth factor responsive elements that are required for the regulation of this gene both in vitro and in vivo. This is an important finding since it provides molecular evidence in support of the recently proposed model in which the production of dorsal type mesoderm is thought to require a synergistic interaction between a general mesoderm inducing factor and a dorsalizing competence modifier(2,6–8). Furthermore, the authors provide an elegant example of how a response element can become a useful tool to map the presence of a biologically available ligand within the embryo.