Figure 4.

Gene expression in renal tract explants. This panel depicts E10 explants after 48 h serum-free culture. All were wholemount-immunostained with antibody to Pax2 which labels MDs, UBs and both uninduced and induced MMs. (A), (F), (K) and (P) are wholemounts with Pax2 signal appearing black. (B)–(E), (G)–(J), (L)–(O), (Q)–(T) frames are histology sections of whole mounts; in (B), (G), (L) and (Q), the Pax2 signal is black, whereas the signal appears brown in remaining frames. (A)–(E) Wild types show UB penetration into condensing, induced MM expressing Itga8/red and Bcl2/blue, but lacking MM fibronectin/red (note that surrounding non-renal mesoderm does express fibronectin). (F)–(J) bl/bl explants show failure of both UB growth and MM induction with minimal expression of MM Itga8 (red) and Bcl2 (blue), but prominent fibronectin (red). Addition of hGDNF [(K)–(O)] or hGDF11 [(P)–(T)] to bl/bl explants allowed the formation of discrete metanephroi with penetrated UBs and aggregated and which expressed Itga8 (red) and Bcl2 (blue) but little fibronectin (red). In double-immunostained sections, nuclear signals for Pax2 are brown, and these signals are detected in both induced and uninduced MMs, and also in MDs and UBs. In (A), (F), (K) and (L), bars are 200 µm; in all other frames, bars are 75 µm.