Fig. 3. Shh and Gli3 interact to control Pax2 and Sall1 expression during kidney development. (A-E) Pax2 mRNA expression in E11.5 mouse embryos. Pax2 mRNA was identified by whole-mount in situ hybridization using digoxigenin-labeled probes. In wild-type and Gli3^–/– embryos, Pax2 mRNA is expressed in the Wolffian duct (long arrow) and metanephros (short arrow). Pax2 mRNA was barely detectable in the Wolffian duct in 50% of Shh^–/– embryos (compare B with A). Pax2 mRNA was rescued to wild-type levels in all Shh^–/–;Gli3^–/– embryos examined. (F-J) Kidney histology in E14.5 embryos. Tissue sections (4 µm) were stained with Hematoxylin. Wild-type (F), Gli2^–/– (H) and Gli3^–/– (I) mice exhibit two normally positioned kidneys. A single, ectopic, dysplastic kidney was observed in Shh deficient mice (G). By contrast, kidney number and histology was rescued in Shh^–/–;Gli3^–/– mice (J). Scale bar: 200 µm. (K-O) Pax2 mRNA expression in E14.5 mouse kidneys. Pax2 mRNA was detected using a digoxigenin-labeled probe and in situ hybridization in 4 µm tissue sections. In wild-type (K), Gli2^–/– (M) and Gli3^–/– (N) kidneys, Pax2 mRNA was expressed in ureteric bud branches and metanephric-derived epithelial structures. In Shh^–/– mice (L), Pax2 mRNA expression was markedly diminished but was rescued in Shh^–/–;Gli3^–/– mice (O). Scale bar: 100 µm. (P-T) Sall1 mRNA expression in E14.5 mouse kidneys. Sall1 mRNA was detected using a digoxigenin-labeled probe and in situ hybridization in 4 µm tissue sections. In wild-type (P), Gli2^–/– (R), and Gli3^–/– (S) kidneys, Sall1 mRNA was expressed in metanephric-derived epithelial structures. In Shh^–/– mice (Q), Sall1 mRNA expression was markedly diminished but was rescued in Shh^–/–;Gli3^–/– mice (T). Scale bar: 100 µm.