Fig. 3. Stabilization of ß-catenin at E11.5, but not E13.5, results in pancreas hypoplasia. All images are from E18.5 embryos. (A-D) Whole-mount views of control (A) and PdxCre^ER ß-cat^active mutant (B-D) tamoxifen-injected embryos. (B) After injection at E11.5, mutants display a dramatic loss of pancreas mass. (C) When injected at E12.5, the dorsal and ventral pancreas appear moderately reduced in size in the majority of cases, but after E13.5 injection (D), gross pancreatic morphology appears normal. (E-H) Hematoxylin and Eosin-stained control (E) and mutant (F-H) pancreata after tamoxifen treatment. Mutants display the formation of large cysts (F, cysts indicated with black arrows) after injection at E11.5, but appear normal when injected at E12.5 (G) and E13.5 (H). (I-L) Pancreatic epithelia in control (I) and PdxCre^ER ß-cat^active mutant (J-L) tamoxifen-injected embryos. (J) Tamoxifen injection at E11.5 effectively targets a large number of cells within the PdxCre^ER ß-cat^active pancreatic epithelium, indicated by the accumulation of nuclear ß-catenin (compare with I). (K) After injection at E12.5, ß-catenin can be detected within the nuclei of a significant number of cells within the mutant pancreatic epithelium. (L) A large number of cells are present that exhibit nuclear ß-catenin within the pancreatic epithelium after injection at E13.5 (compare with morphology and histology in D and H). (M) The number of mutants seen at each tamoxifen injection time point, and the severity of the pancreas phenotype observed. Scale bars: 50 µm. s, stomach; sp, spleen; d, duodenum; dp, dorsal pancreas; vp, ventral pancreas.