The goal of the proposed research is to elucidate fundamental mechanisms involved in patterning metazoan embryos. Dr. Ettensohn seeks to define the precise roles of specific blastomere interactions in establishing territories of gene expression in the embryo and to elucidate molecular pathways that underlie such interactions. This work also addresses the problem of conditional fate specification- the allocation of cell fates by non-autonomous, context-dependent mechanisms- and the historical problem of embryonic regulation. The model system to be used is the sea urchin, which can be studied using a powerful set of cell and molecular biological tools.
Three specific objectives are to be pursued: 1) He will examine the role of Lv-ets, a member of the ets family of transcriptional regulators, in skeletogenic specification during normal development and when novel cell lineages are caused to express a skeletogenic fate by embryo manipulation. He will explore the possibility that Wnt/beta-catenin signaling, which has been shown to regulate skeletogenic specification, does so by altering Lv-ets protein expression and/or localization. 2) Signals from the vegetal region are known to regulate the fates of overlying cells. He will refine our understanding of the role of such signals in patterning through the use of new cell ablation methods, novel cell recombination experiments, and new molecular markers. He will directly test the model that a vegetal-to-animal cascade of signals patterns the early sea urchin embryo. 3) The Wnt/beta-catenin signaling pathway plays an important role in patterning in many organisms. Recent studies have provided strong evidence that components of this pathway are involved in the allocation of cell fates along the animal-vegetal axis of the sea urchin embryo. He will use overexpression of GSK3, C-cadherin, and mutant (activated) beta-catenin mRNAs in combination with embryo manipulation and molecular markers to clarify the role of this pathway in patterning. Dr. Ettensohn will use embryo dissociation studies to test the central question of whether the developmentally programmed pattern of nuclear localization of beta-catenin in the sea urchin (and possibly other metazoan embryos) is dependent on cell-cell signaling, or is regulated by a cell-autonomous mechanism. Finally, he will examine the mechanism by which suppression of the Wnt/beta-catenin pathway blocks skeletogenic specification.
