||Fig. 2: GDF6 is expressed in the infant kidney, during pronephros development in Xenopus laevis and murine urinary tract development.
a By immunohistochemical detection of GDF6 and the marker proteins aquaporin-1 (AQP1, straight and convoluted proximal tubule and thin descending limb of loop of Henle), aquaporin-2 (AQP2, collecting duct), and Tamm-Horsfall protein (THP, thick ascending limb of loop of Henle and distal tubule) in a normal human infant kidney section, GDF6 localized most prominently to proximal tubules. b By whole-mount RNA in situ hybridization in Xenopus laevis at stage 38, gdf6 was expressed in the tissue surrounding the pronephric tubule (arrow, enlarged image) as well as in the developing eye, branchial arches, notochord, and neural tube. c RNA in situ hybridization analysis on sagittal sections of the murine kidney and bladder from E11.5 to E18.5. Gdf6 expression was present in all compartments of the developing ureteric tree, including the ureteric tips (ut) and the ureter (u), at E11.5 to E14.5, dropped after onset of collecting duct differentiation, and was barely detectable at E18.5 (p pelvis, c cortex). In the lower urogenital tract, Gdf6 expression was found in the mesothelial lining (m) of the abdominal cavity at E11.5, in the undifferentiated urothelium of the urogenital sinus (us) and the bladder (bl) until E14.5, and in the nephric duct (nd) of male embryos at all analyzed stages (data partly not shown). Sections from three independent murine specimens were analyzed.