Figure 9.

Ureter Insertion depends on alignment of the new ureter orifice with the bladder, regression of the CND, fusion of the ureter with the urogenital sinus epithelium and expansion of the bladder. Left: Vibratome sections of E12, E13 and E14 wild type urogenital tracts stained with antibody directed against cytokeratin (red).Note the enormous growth of the bladder relative to the urethra during this 3-day period. Right: Top, vibratome section of a Hoxb7-Gfp embryo (green) stained with E-cadherin (red). Note a loop has formed that helps align the ureter with the position in the urothelium (red) where it will fuse. Right middle and bottom: Laminin (red) stained Hoxb7-Gfp (green) urinary tracts showing the relative positions of the CND, ureter and Wolffian duct. At E13 the ureter orifice is fused with the urogenital sinus epithelium, but remains close to the Wolffian duct. Note the cell debris at this stage between the ureter and Wolffian duct where the CND was previously. Right Bottom: Between E13 and E14, the ureter orifice, which is tethered to the urogenital sinus epithelium, moves anteriorly as the bladder undergoes dramatic expansion.