Fig. 3. Recombinant GDNF induces epithelial overgrowth and excessive branching in both wild-type and Grem1-deficient mouse metanephric kidney primordia. Kidney primordia (E11.0, 40-42 somites) were cultured for 96 hours in medium supplemented with recombinant GDNF (100 ng/ml). (A) Wild type; note the formation of many epithelial buds along the Wolffian duct and overgrowth of the ureteric epithelium within 24 hours, which results in excessive branching. (B) Grem1-deficient kidney primordia; note the formation of many epithelial buds, overgrowth and excessive branching similar to the wild type (A).