COMBINATORIAL SIGNALING IN DEVELOPMENT

Intercellular signaling plays a major role in the development of verte brate and invertebrate embryos. In several cases, including the induct ion of mesoderm and neural ectoderm induction in Xenopus and the induc tion of the vulva in C. elegans, multiple intercellular signals are ut ilized. This review examines a number of examples of signaling in deve lopment wherein two signals combine to affect the fate of a cell. The examples are placed in distinct categories, based on whether the signa ls synergize with or antagonize one another, and on the inductive pote ntial of the individual signals. These types of combinatorial signalin g events are suggested to be a general feature of embryonic developmen t.