Fig. 3. Periportal cells of pseudoglandular structures in the 17.5-day knockout liver express biliary cell markers. PAS staining indicates that wild-type hepatocytes store abundant glycogen (A). Immunohistochemistry for cell type-specific markers and lectin histochemistry also show that wild-type hepatocytes express HNF4 in their nuclei (B), and that periportal biliary epithelial cells are negative for HNF4 (arrowhead; B), but are positive for bile duct-specific cytokeratin, laminin, DBA-binding sites and nidogen (C-F). The knockout liver develops many pseudoglandular structures, which are composed of hepatocyte-like cells poorly accumulating glycogen (G). Although most pseudoglandular structures are positive for bile duct-type cytokeratin (I), other bile duct markers are reactive only with periportal pseudoglandular structures (J-L). Staining pattern of HNF4 in the knockout liver resembles that of the wild-type liver; periportal biliary cells are negatively immunostained (arrows; H). HV, hepatic vein; PV, portal vein. Scale bars: 50 µm.