Fig. 1.

Mesothelial and epithelial FGF9 have unique functions in developing mouse lung. (A,B) lacZ staining for the Rosa26 reporter (R26R) targeted with Dermo1-Cre (A) and Shh-Cre (B) lungs at E10.5 showing mesenchymal/mesothelial and epithelial cell-specific β-gal staining, respectively. (C-E) Immunohistochemical detection of FGF9 in E12.5 lung showing expression in epithelium (arrows) and mesothelium and submesothelial mesenchyme (arrowheads) in control lungs (C). Fgf9^Dermo1 lungs (D) have greatly reduced staining in submesothelial mesenchyme (arrowheads) and Fgf9^Shh lungs (E) have reduced expression in epithelium (arrows). (F,G) Anterior views of gross dissections of control (Dermo1-Cre, Fgf9^f/+) and Fgf9^Dermo1 (F) and control (Shh-Cre, Fgf9^f/+) and Fgf9^Shh (G) lungs at E12.5. Note the decreased mesenchyme but normal epithelial branch number and orientation of lobes with the Fgf9^Dermo1 lung (F) and decreased number of epithelial branches and normal mesenchyme in Fgf9^Shh lung (G). (H-K) Hematoxylin and Eosin-stained histological sections of control (H,J), Fgf9^Dermo1 (I) and Fgf9^Shh (K) lungs at the same stages as shown in F,G. (L) Number of epithelial buds in the caudal and left lobes at E12.5. ^*P<0.001 (Student's t-test). Error bars represent s.d. Scale bars: 25 μm in A-E,H-L; 200 μm in F,G.