Figure 6. Cell proliferation is reduced in the epithelium of Yap-deficient lungs.
(A,B) Immunostaining of lung sections collected from wild-type and Yapf/f; ShhCre/+ mice injected with EdU at 14.5 dpc. Lung epithelial cells were distinguished by E-cadherin (E-cad) staining. (C) Quantification of cell proliferation rate in the epithelium (Epi) and mesenchyme (Mes) of control and Yapf/f; ShhCre/+ lungs at 11.5 and 14.5 dpc. The rate of epithelial cell proliferation was calculated as the ratio of the number of EdU+ epithelial cells (EdU+E-cad+) to the number of epithelial cells (E-cad+). An apparent reduction in the percentage of EdU+ cells was detected in the epithelium of Yapf/f; ShhCre/+ lungs compared to controls (n ≥ 8 for each group). By contrast, cell proliferation in the mesenchyme, where YAP was untouched by ShhCre, was indistinguishable between control and Yapf/f; ShhCre/+ lungs. The rate of mesenchymal cell proliferation was calculated as the ratio of the number of EdU+ mesenchymal cells (EdU+E-cad– DAPI+) to the number of mesenchymal cells (E-cad– DAPI+). All values are means ± SEM. (*) p<0.05; (**) p<0.01 (unpaired Student’s t-test). We found that most epithelial cells in control or Yap-deficient lungs at 11.5 dpc expressed Ki67. This is likely due to a short cell cycle at this stage, which makes Ki67 (as well as other commonly used markers) unsuitable for accurate detection of differences in cell proliferation.