Figure 3.

Pancreas morphogenesis in Pdx-1 null, Ptf1a null, and Pdx-1, Ptf1a double null embryos. A–H) Histological analysis of β-galactosidase expression from the Pdx-1^LacZko allele in Pdx-1 null (Pdx-1^{LacZko/LacZko}; Ptf1a^YFP/+), Ptf1a null (Pdx-1^LacZko/+; Ptf1a^YFP/YFP), and Pdx-1, Ptf1a double null (Pdx-1^{LacZko/LacZko}; Ptf1a^YFP/YFP) embryos at E12.5 and E15.5. A) In Pdx-1^LacZko/+; Ptf1a^YFP/+ E12.5 embryos, the dorsal pancreas is associated with the duodenum, the ventral pancreas is evaginating from the CBD epithelium and the two lobes have fused near the duodenum at their proximal ends. B) At E15.5 in Ptf1a^YFP/+; Pdx-1^LacZko/+ embryos, normal epithelial branching and lobulation indicates acinar development. X-gal staining also denotes Pdx-1 expression in the CBD, extrahepatic biliary ducts, cystic duct, and gall bladder. C) In Ptf1a null embryos at E12.5, the epithelium of the DPR is growth deficient and does not branch while the VPR is barely discernable. D) In Ptf1a null embryos at E15.5, LacZ expression is observed in the DPR which is minimally branched and extends from the duodenum towards the spleen. The absence of a VPR indicates assimilation of ventral pancreatic MPCs into the CBD and/or duodenum epithelium. E) Pdx-1 null embryos at E12.5 have a considerably smaller DPR than in Ptf1a null embryos at the same stage while they display a similar structure resembling a VPR contiguous with the CBD. F) By E15.5 the DPR of Pdx-1^{LacZko/LacZko}; Ptf1a^YFP/+ embryos undergoes limited branching and X-gal staining is more intense in the gall bladder and cystic duct, due to homozygosity of the Pdx-1^LacZko alleles, although no gross abnormalities are observed. As in Ptf1a null mice, there appears to be no VPR associated with the CBD in Pdx-1 null mice at E15.5 which suggests ventral pancreatic cells have contributed to the epithelium of the CBD and/or duodenum. G, H) The morphological phenotype of Pdx-1, Ptf1a double null embryos is identical to Pdx-1 null embryos. I–L) Whole mount fluorescence microscopy of YFP (Ptf1a^YFP) in Pdx-1 null and Pdx-1, Ptf1a double null embryos at E10.5 and E12.5. I, J) In Pdx-1 null embryos, YFP can be observed in the DPR from E10.5–12.5. YFP is not detectable at E13.5 which indicates a loss of dorsal pancreatic progenitor cells and that Ptf1a expression may be dependent on Pdx-1 after E12.5. K–L) YFP fluorescence in double null embryos indicates that neither Pdx-1 nor Ptf1a is necessary for dorsal expression of Ptf1a or epithelial budding. Scale bars = 50 µm. Duodenum (Duo), Stomach (Sto), Extrahepatic Biliary Ducts (EHBD), Common Bile Duct (CBD), Cystic Duct (CD), Gall Bladder (GB), Dorsal Pancreatic Remnant (DPR), Ventral Pancreatic Remnant (VPR).