Abnormal branching of double mutant kidneys in organ culture.

<p>Kidneys of wild-type (A) and mutant genotypes (B–D), carrying <i>Hoxb7/myrVenus</i>, were excised at E12.5, cultured <i>in vitro</i>, and photographed at the indicated times. The <i>Ret−/−</i> Wolffian duct (B) failed to develop a ureter or kidney, while the <i>Spry1−/−</i> kidney (C) has multiple ureters (arrowheads), swollen UB tips and an enlarged common nephric duct (cnd). (D), in two examples of <i>Gdnf−/−</i>;<i>Spry1−/−</i> mutant kidneys, UB branching is retarded at E12.5, and subsequent branching in culture displays abnormal patterns (asterisks and arrowheads – see text) compared to wild-type.