We showed that the suppression of the cystic phenotype produced by CTT expression in both the adult and neonatal models of ADPKD is dependent upon the availability of this interaction, since no significant rescue is observed when CTT-expressing Pkd1-KO mice are compared to Pkd1-KO mice in the NNT-deficient “J” background. Here, PKD1 is linked to autosomal dominant polycystic kidney disease.