Tight regulation of p53 activity by Mdm2 is required for ureteric bud growth and branching

► Mdm2 negatively regulates the stability and transcriptional activity of the tumor suppressor protein p53. ► This study demonstrates an absolute requirement for Mdm2 in the control of p53 activity during renal organogenesis. ► Conditional deletion of Mdm2 from the ureteric bud lineage induces severe defects on branching morphogenesis thus causing renal hypodysplasia and early postnatal death. ► The abnormal renal phenotype is caused by growth arrest and apoptosis of renal epithelia, both of which were rescued by concomitant p53 gene deletion.