Fig. 1. Potential mediators of Wnt signaling in the developing pancreas. (A,B) In situ hybridization (purple) to E13.5 pancreatic primordia detects co-expression of Pdx1 (A) and the ß-catenin-binding transcription factor Tcf4 (B), while the related factor Lef1 is not expressed (data not shown). (C-D') To confirm the specificity of pan-specific (C,D) and dephospho-specific (C',D') anti-ß-catenin monoclonal antibodies, we immunostained (brown) near-adjacent sections of embryonic spinal cord and neonatal (P0) intestine. As expected, anti-dephospho-ß-catenin recognizes regions where Wnt signaling is known to be active, such as the ventricular zone of the spinal cord (arrow) and the intestinal crypts (arrowhead). (E-I') Pan-ß-catenin (E-I) and dephospho-ß-catenin (E'-I') staining was similarly performed on various stages of developing pancreas. Arrowheads and arrows indicate morphologically recognizable islet and acinar tissue, respectively. Dephospho-ß-catenin is specifically detected in the early pancreatic epithelium, and declines as the organ matures. me, pancreatic mesenchyme; ep, pancreatic epithelium.