Fig. 3. Fgf10-positive mesenchymal cells relocate around the bronchial epithelium. (A-D) ß-gal expression in the accessory lobe of unmanipulated Fgf10^LacZ/+ lung after 48 hours of culture. (D) Vibratome section of the accessory lobe shown in C (dotted box). Notice the presence of ß-galactosidase-positive cells around the proximal epithelium (double arrow). (E-H) Grafting of Fgf10^LacZ/+ mesenchyme (in blue) on wild-type lungs. (H) Vibratome section of the accessory lobe shown in G (dotted box). Note the presence of ß-galactosidase-positive cells around the proximal epithelium. The gray dotted line underlines the epithelium. (I-L) Ablation of the distal Fgf10^LacZ/+ accessory lobe mesenchyme and grafting of equivalent wild-type mesenchyme (green) results in a drastic decrease of ß-gal expression around the bronchi (K,L). (L) Vibratome section of the accessory lobe shown in K (dotted box). Notice the absence of ß-gal-positive cells around epithelium. The epithelium is outlined by the dotted line. (M-N) Time-lapse sequence of E12 accessory lobes after the auto-grafting of CMFDA labeled distal mesenchyme (which includes the mesothelium). (M) Twenty-five-hour time-lapse fluorescence showing that mesenchymal cells are not actively migrating along the epithelium. (N) Phase-contrast time-lapse sequence of M, showing the outgrowth and budding of the epithelium. acc, accessory lobe; Bright f, Bright Field. Scale bar: 190 µm in A,B,E,F,I,J; 165 µm in C,G,K; 45 µm in D,H,L; 60 µm in M,N.