The long term objective of this research program is to elucidate the mechanisms of cell interactions that control cell fates during early embryogenesis. Signaling between embryonic cells is a fundamental mechanism of cell fate specification in all multicellular animals. An understanding of cell-cell interactions in the early embryo will require not only an analysis of the molecular basis of the signaling, but also an understanding of the cellular context of such interactions within the embryo. With these goals in mind, the proposed research program involves an integration of cellular and molecular methodologies. The P.I. will apply these experimental strategies to the developing sea urchin embryo, a manipulable, optically transparent experimental system. He plans to focus on a key regulatory interaction that occurs between the two principal populations of mesodermal cells in the embryo, primary and secondary mesenchyme cells (PMCs and SMCs). PMCs transmit a signal during gastrulation that suppresses the skeletogenic potential of SMCs and directs these cells into an alternative developmental program. This interaction plays an important role in the specification of SMC fates and the process of skeletogenesis, and serves as a model system to study embryonic regulation and cell signalling in the early embryo. Three key aspects of the PMC-SMC interaction are to be addressed: (1) the development of new methods for studying the dynamics of cell fate-switching in living embryos; (2) the properties and molecular basis of PMC signaling; and (3) the properties of the responding SMCs. The proposed research will significantly advance our understanding of a central issue in developmental biology. In addition, this research program will continue to support the training and development of young developmental biologists at the undergraduate, graduate, and postdoctoral levels.
