Using anti-smooth muscle α actin antibody (a ureter smooth muscle marker), E-cadherin (a marker for ureter urothelium) and lectin Dolichos Biflorus (DBA, another marker for ureter urothelium), we found normal looking urothelium but disarrangement and reduced abundance of ureteral smooth muscle in three E14.5 Robo2del5/del5 homozygous embryos (Fig. 6M,N and Figure S8) before any ureteral dilatation or hydronephrosis. The gene discussed is CDH1; the disease is hydronephrosis.