Fig. 3.

Mesenchymal β-Catenin is essential for embryonic lung development. (A–C) Anterior views of gross dissections of control (Dermo1-Cre, β-Catenin^f/+) and β-Catenin^Dermo1 lungs at E12.5 (A), E14.5 (B) and E18.5 (C). Note the decreased number of epithelial branches (numbers) but normal number and orientation of lobes at E12.5. tr, trachea; es, esophagus. (D–I) H&E stained histologic sections of lungs at the same stages shown in panels A–C. At E12.5 (E) and E14.5 (G), β-Catenin^Dermo1 lung tissue had fewer epithelial branches and decreased distal mesenchyme compared with controls (D, F). At E18.5 (I), β-Catenin^Dermo1 lung tissue contained small epithelial tubes surrounded by dense disorganized mesenchyme, whereas control lungs (H) had developed numerous primitive alveoli surrounded by blood vessels. (J) Cryo-section of a Dermo1-Cre, Rosa26R lung at E10.5 showing mesenchymal cell-specific β-Gal staining indicating Cre activity throughout embryonic mesenchyme and mesothelium, but not epithelium. (K–N) Immunohistochemistry detection of β-Catenin showing that β-Catenin^Dermo1 lungs have greatly reduced staining in lung mesenchyme as early as E12.5 (L) and complete absence of mesenchymal protein by E14.5 (N), compared with control lungs (K, M). Epithelial expression appeared unaffected at these stages of development. No counterstain was used in panels K and L. Panels M and N were counterstained with hematoxylin. Asterisk indicates mesenchyme; arrow indicates epithelium. Scale bars: panel A, 0.25 mm; panels B and C, 1 mm; panels D, F, H, 100 µm; panel J, 200 µm; panels K, M, 50 µm.