Fig. 5. Lung epithelial cell differentiation marker gene expression in Wnt7b^lacZ–/– embryos. Sections from E18.5 wild-type and Wnt7b^lacZ–/– embryos were analyzed by in situ hybridization using probes for SP-C, CC10 and aquaporin 5. The pattern and expression levels of SP-C and CC10 were unchanged in Wnt7b^lacZ–/–, embryos while the level of aquaporin 5 gene expression was reduced in Wnt7b^lacZ–/– embryos (A-F). Transmission electron microscopy was performed to analyze the morphology of distal airway epithelial cells (G,H). Wild-type lungs tissue revealed both AEC-1 (G, arrow) and AEC-2 cells while Wnt7b^lacZ–/– lung tissue lacked well defined AEC-1 cells but instead contained only cuboidal AEC-2 cells (H, arrowheads). Both wild-type and Wnt7b^lacZ–/– lung tissue show an extensive capillary network surrounding the distal airways (G,H asterisks). Scale bars: 250 µm.