Dorsal Ventral Pancreatic Bud Comparison

During embryogenesis, the pancreas develops from separate dorsal and ventral buds, which fuse to form the mature pancreas. Little is known about the functional differences between these two buds or the relative contribution of cells derived from each portion to the pancreas after fusion. To follow the fate of dorsal or ventral bud derived cells in the pancreas after fusion, we produced chimeric Elas-GFP transgenic/wild type embryos in which either dorsal or ventral pancreatic bud cells expressed GFP. We found that ventral pancreatic cells migrate extensively into the dorsal pancreas after fusion, whereas the converse does not occur. Moreover, we found that annular pancreatic tissue is composed exclusively of ventral pancreas derived cells. To identify ventral pancreas specific genes that may play a role in pancreatic bud fusion, we isolated individual dorsal and ventral pancreatic buds, prior to fusion, from stage 38/39 Xenopus laevis tadpoles and compared their gene expression profiles. Morpholino-mediated knockdown of one of these ventral specific genes, transmembrane 4 superfamily member 3 (tm4sf3), inhibited dorsal-ventral pancreatic bud fusion as well as acinar cell differentiation. Conversely, overexpression of tm4sf3 promoted the development of annular pancreas. Our results are the first to define molecular and behavioral differences between the dorsal and ventral pancreas, and suggest an unexpected role for the ventral pancreas in pancreatic bud fusion. Keywords: Developmental genomics We analyzed two samples of dorsal and two samples of ventral pancreatic buds.