Stages of de novo biliary morphogenesis. Interpretative diagram and matched images showing five presumptive stages of intrahepatic biliary duct formation in the normal developing liver. (1) Single Sox9+ cells (green) with associated moesin/NHERF1+ punctum (red) and neighboring, obligately polarized future Sox9+ cells (green striped). (2) Sox9+ doublet with moesin/NHERF1+ apical surface in between. (3) Three or more consecutive ductal plate cells associated with moesin/NHERF1+ apical surface, Sox9 expression and some apical constriction. (4) Primitive ductal structure with open lumen, asymmetric distribution of Sox9+ cells and more uniform apical constriction. (5) Complete ductal structure with patent lumen surrounded completely by wedge-shaped Sox9+ cells. Asterisk, portal vein. H, hematopoietic cell. Scale bars: 10 µm.