Fig. 3. Generation of branched ureteric systems from the `wrong end' of the ureters of more mature kidneys. (A) A cut ureteric stalk of an E12.5 kidney capped with E11.5 metanephric mesenchyme ramified through the mesenchyme to generate a branched collecting duct system (circled). (B) Branching morphogenesis of an E11.5 de-tipped stalk transferred to matrigel with GDNF, FGF1 and pleiotrophin, incubated for 144 hours and stained with FITC-phalloidin to reveal its anatomy. It is interesting to note that the phalloidin stain is particularly strong in the apical regions of cells at the branch tips, as described for normal ureteric buds developing in whole kidneys (Michael et al., 2005). (C,D) Tips formed from the `wrong end' of the ureter, as in A, induce the formation of nephrons in the surrounding mesenchyme. These are not detectable in the ureteric bud-specific anti-calbindin stain (C) but are visible in the anti-laminin stain (D, arrow).