Loss of ICAT gene function leads to arrest of ureteric bud branching and renal agenesis

ICAT, inhibitor of β-catenin and T cell factor, or Ctnnbip1, is a negative regulator of the Wnt signaling pathway that interferes with the interaction between β-catenin and T cell factor. Some ICAT-deficient (ICAT−/−) embryos exhibit unilateral or bilateral renal agenesis. In this study, we investigated developmental processes in the ICAT−/− kidney. ICAT was highly expressed in both the ureteric bud (UB) and the surrounding metanephric mesenchymal (MM) cells in the metanephros of embryonic day E11.5–E13.5 wild-type (ICAT+/+) mouse. In the E12.5-ICAT−/− metanephros, UB branching was delayed, and a T-shaped, bifurcated UB was frequently seen; this was never seen in the E12.5-ICAT+/+ metanephros. More apoptotic MM cells were detected in the ICAT−/− metanephros than in the ICAT+/+ metanephros. These results suggest that the loss of ICAT gene function causes the arrest of UB branching and the apoptotic death of MM cells, resulting in renal agenesis.