Fig. 5. Wnt7b is essential for coordinated growth of the loop of Henle, a medullary localized component of the developing nephron. (A,B) The loop of Henle was visualized in E18.5 kidney vibratome sections by immunostaining for Uromodulin (Umod, red). Sections are counterstained with DBA (green) to visualize the ureteric bud epithelium. The loop of Henle was greatly reduced in mutant kidneys compared with in wild-type littermates. (C,D) Measurement of BrdU incorporation in the loop of Henle anlagen at E15.5. The loop of Henle was identified as a U-shaped tubule in serial sections within the deeper cortex beneath the outer cortex where S-shaped bodies were localized. Loops of Henle of similar lengths were compared in the wild-type and mutant. (E,F) Measurement of BrdU incorporation in the S-shaped body (white arrows) at E15.5. (G) Cell proliferation was greatly reduced in the loop of Henle anlagen of mutants (P<0.0026). By contrast, no difference was observed between mutant and wild-type littermates at the S-shaped body stage (P<0.3172). S-shaped bodies were identified by immunostaining as being positive for E-cadherin (E-cad) and Cadherin 6 (Cdh6), but negative for DBA. The loop of Henle was positive for Cdh6 but negative for DBA. Scale bars: in B, 400 µm for A and B; in F, 40 µm for C-E.