Fig. 4. Hyperactivation of Tgfß signaling disrupts lung formation in the developing foregut. (A,B) Treatment of mouse foregut explants with recombinant TGFß1 results in lung agenesis (B, asterisk). (C,D) WMISH and immunostaining showing generalized induction of Tgfbi message (C) and protein (D), in TGFß1-treated foreguts. (E-H) PCNA staining showing abundant endodermal and mesodermal labeling in both control and TGFß1-treated foreguts (boxed regions in E,G are magnified in F,H). (I-L) WMISH showing Nkx2.1 and Sftpc in lung buds of controls (I,K, arrowheads), but not in the presumptive lung region of TGFß1-treated foreguts (J,L, asterisks). Ht, heart; Lu, lung; St, stomach; Th, thyroid; Ctr, control. Scale bar: 200 µm in E.