Fig. 5. Nephrogenesis is delayed and disorganized in the Foxd1 null. (A) Wild type displayed Pax2 expression in condensed mesenchyme (cm) around the UB tips. The Foxd1 null (B) displayed much larger condensates. Wild type (C) and Foxd1 null (D) displayed Wnt4 expression in pre-tubular aggregates (pa) and both displayed expression of Sfrp2 in renal vesicles (rv) (E,F). Cell proliferation was determined by Ki-67 reactivity (G,H). Histochemistry with TRITC-PNA and FITC-lotus lectin revealed the presence of glomeruli (red spheres) and proximal tubules (green structures), respectively. At E15.5 and E16.5, wild-type kidneys (I,K) displayed glomeruli (gl) and proximal tubules (pt) in the juxtamedullary region, just below the nephrogenic zone. The Foxd1 null displayed no glomeruli or tubules at E15.5 (J), but did so at E16.5 (L), although there is no discrete nephrogenic zone. At E18.5, both the wild-type kidneys (M) and the Foxd1-null (N) display numerous glomeruli and proximal tubules, but they are poorly organized in the mutant. We counted 100 nephrons in M and 85 nephrons in N. Scale bar: 250 µm in A,B,D-F,I,J; 150 µm in G,H,K,L; 300 µm in M,N.