Fig. 8. In situ hybridization analysis of Jag1 and Notch2 mRNAs in fetal and neonatal livers. In the wild-type liver, hepatoblasts very weakly express Jag1 and Notch2 mRNAs at 12.5 days (arrows; A,B,G,H), but epithelial cells of periportal biliary structures become positive for both mRNAs in later development (arrows; C-F,I,K,L). Epithelial cells of the extrahepatic bile duct are moderately positive for both mRNAs (A,G,J). Endothelial cells of the portal vein and hepatic artery (^*; E), and their connective tissue cells express Jag1 mRNA (A-F). Arrowheads indicate Jag1 mRNA-positive hemopoietic cells in the neonatal wild-type liver (F). In the 12.5-day knockout liver, although Jag1 mRNA expression in hepatoblasts is at a normal level (arrow; M), Notch2 mRNA is upregulated in hepatoblasts (arrow; Q). Hepatoblasts under the capsule (large arrowheads) are positive for Notch2 mRNA (R). In 15.5-day and neonatal knockout livers, Jag1 and Notch2 mRNAs are upregulated in pseudoglandular structures (star), but periportal epithelial cells are more strongly stained (small arrowheads; N-P,S,T). Jag1 mRNA expression is downregulated in endothelial cells of the portal vein (N), compared with that in the 17.5-day wild-type liver (C,D,E). ED, extrahepatic bile duct; PV, portal vein. Scale bars: 50 µm.