Fig. 3. The size of the pancreatic epithelium in Fgf10^–/– embryos is greatly reduced. (A) Hnf3ß whole-mount in situ hybridisation to the epithelium of the foregut of wild-type E11.5 embryos. (B) Hnf3ß expression in the pancreatic region and posterior stomach was greatly reduced in the foregut of Fgf10 mutant embryos. (C) ISL1 was expressed predominantly in the dorsal mesenchyme and a few differentiating endocrine cells in the pancreatic epithelium from E10.5 wild-type embryos. The dorsal bud is oriented to the top. (D) Strong expression of ISL1 was observed in the dorsal mesenchyme of Fgf10^–/– embryos at E10.5, although very few scattered cells within the epithelium that expressed ISL1 were detected. (E) Sagittal sections of the dissected gut from wild-type embryo stained with carboxypeptidaseA (green) and glucagon (red). The branched morphology of both dorsal and ventral pancreatic buds is evident. (F) Sagittal section of dissected gut from an Fgf10^–/– embryo shows that the formation of both dorsal and ventral buds occurred, however, no branching of the epithelium is apparent. (G) Transverse sections of the dorsal bud of E13.5 wild-type embryo stained for the pan-epithelial markers cytokeratin (red) and glucagon (green). The dorsal pancreatic bud of a wild-type embryo shows a characteristic highly branched epithelium. (H) The dorsal bud of the Fgf10^–/– embryo has a small pancreatic epithelium and no branching of the epithelium is visible. Differentiation of early endocrine cells, as identified by glucagon staining, occurred in the mutant embryos and these cells are seen typically clustered together. db, dorsal pancreatic bud; vb, ventral pancreatic bud; ISL1, Islet1; CA, carboxypeptidaseA; du, duodenum.