Numerous nephron and normal nephron–UB connections are observed in double mutant kidneys.

<p>(A,B) Podocalyxin staining of nascent glomeruli in wild-type (A) and <i>Ret−/−;Spry1−/−</i> (B) kidneys at P0, showing numerous, cortically located nephrons in the double mutant, as in the wild-type. (C–H) Six optical sections at different Z-levels of a <i>Gdnf−/−</i>;<i>Spry1−/−</i> E15.5 kidney carrying <i>Hoxb7/myrVenus</i>. The sites where the UB connects to nephrons are visible as “holes” in the myrVenus-labeled UB, as the connecting tubule expresses little or no myrVenus. The connections of three nephrons (1, 2, 3) can be followed at different levels of the image stack. (I) Volume rendering of a wild-type kidney, with nephron connection sites indicated by the pink dots. (J) Volume rendering of double mutant kidneys shown in (C–H), showing normal number and positions of nephron connections per UB tip.