Fig. 6. Wnt7b signals to the adjacent interstitium through the canonical Wnt signaling pathway. (A) Hematoxylin and Eosin staining of E18.5 kidney sections following the removal of β-catenin activity from the renal interstitial mesenchyme. Mutant kidneys lack a renal medulla. Scale bar: 400 µm. (B) In situ hybridization (Axin2) and immunostaining (Lef1) on sections of E15.5 kidneys. A marked reduction was observed in Axin2 mRNA and Lef1 protein expression within the interstitial mesenchyme positioned adjacent to the nascent medullary collecting ducts (arrows) following removal of β-catenin activity from this cell population. By contrast, their expression was not altered in other renal tissues. Cyto, cytokeratin. Scale bars: 200 µm in top four panels; 100 µm in all other panels.