VKO mice display expanded pericentral hepatocyte gene expression. To assess hepatocyte zonation in VKO mice, expression of the pericentral hepatocyte marker glutamine synthetase (GS, purple) was assessed with immunohistochemistry. The lectin Dolichos biflorus agglutinin (DBA, brown, white arrows) was used to mark hilar intrahepatic bile ducts (IHBDs) next to hilar portal vein branches. In control mice at P15 (A) and P30 (C), the expression of GS is restricted to hepatocytes within a few cell diameters from a central vein. No GS expression is observed around portal veins. In VKO mice, however, a slight visual increase in the area of GS expression is observed at P15 (B). In P30 VKO mice, there is a large increase in the area of GS expression, with several large patches of hepatocytes displaying abnormal GS expression (D). Scale bar is 500 μm.