The overall goal of our research is to better understand the molecular forces that control pancreatic development and lineage selection. Understanding these forces may allow us to better treat such diseases as pancreatic cancer and diabetes. TGF-beta superfamily signaling has been strongly implicated in all aspects of pancreatic differentiation. For example, approximately 50 percent of pancreatic ductal cancers have mutations in smad4, a critical common mediator of TGF-beta superfamily intracellular signaling. Within the TGF-beta superfamily, the TGF-beta isoforms and their receptor, TGF-beta receptor type II (TBR-H), have been particularly implicated in pancreatic development. The central hypothesis of this grant proposal is that endogenous TGF-beta isoform signaling is specifically important in the induction of exocrine rather than endocrine lineage selection (primary exocrine lineage selection), and further in exocrine differentiation between ductal and acinar differentiation (secondary exocrine lineage selection). Our preliminary studies show a potential role for TGF-beta isoform signaling in pancreatic development, and we now wish to study the role of endogenous TGF-beta isoform signaling in exocrine primary and secondary lineage selection. These studies will be performed in normal embryos, transgenic embryos expressing a dominant-negative form of the TBR-II, and in a retinoid-induced embryonic pancreas, which shows enhanced exocrine differentiation, either acinar or ductal depending on the retinoid. The approach will first be to use various strategies to inhibit endogenous TGF-beta isoforms and/or TBR-II in normal embryonic pancreas in culture. Further, dominant-negative TBR-II transgenic mice will allow analysis of the role of TGF-beta isoform signaling, specifically in epithelial-mesenchymal interactions as they apply to our central hypothesis. The retinoid-induced system will allow us to specifically focus on the role of TGF-beta isoform signaling in secondary exocrine differentiation (ducts vs. acini). Given the overall importance of TGF-beta signaling in pancreatic differentiation, as well as the clinical relevance of TGF-beta signaling and pancreatic differentiation, the information gained from these experiments should enhance our understanding of pancreatic development toward a goal of better understanding the pathogenesis of pancreatic disease.