beta-Catenin expression during vascular development and degeneration of avian mesonephros.

beta-Catenin is a structural component of adherens junctions, a regulator of the Wnt signalling pathway and a transcriptional co-activator with a key role in vascular patterning. The avian mesonephros is a transitory embryonic kidney that is used in the study of vascular development and degeneration. Here we examine beta-catenin expression in this model during vascular development and degeneration. Quail embryos with developing or degenerating mesonephros were studied, on day 6 (30HH) or day 11 of incubation (40HH), respectively. QH1 whole mounts of developing mesonephros revealed numerous angioblast-like cells situated in the paramesonephric duct that seem to invade the mesonephros. Although these cells did not express beta-catenin, the surrounding periductal mesenchymal cells translocated high levels of beta-catenin into the nucleus. In contrast, degenerating mesonephros were devoid of angioblast-like cells and beta-catenin was lower than in the developing mesonephros. beta-Catenin was significantly reduced in the glomerular capillary tuffs, indicating that it was particularly down-regulated in the vascular system. No sex-related differences in beta-catenin expression were observed in degenerating mesonephros. Furthermore, two special populations of glomerular and peritubular endothelial cells were observed in degenerating mesonephros: one translocating beta-catenin into the nucleus and the other in apoptosis that did not translocate it. In conclusion, our results indicate that the paramesonephric duct is a potential new vasculogenetic pathway, and suggest that beta-catenin plays a role in the fate of mesonephric endothelial cells.