To address the role of APOBEC3 enzymes in bladder cancer, we knocked in the cDNA encoding mouse Apobec3 (mA3) at the Rosa26 locus under control of a CAG promoter and a LoxP-STOP-LoxP cassette (Supplementary Fig. 1A) (hereafter called Rosa26LSL-Apobec3). This evidence concerns the gene MAP6 and urinary bladder carcinoma.