WT1 and Nephroblastoma: These animals were generated by breeding transgenic mice expressing Cre recombinase under the control of the Wilms Tumor one locus (Wt1-Cre) to animals carrying the floxed Zfp423 alleles (Zfp423loxP/loxP) (Figure 1A) (Zfp423loxP/loxP; Wt1-Cre animals, herein ‘Vis-KO’ mice).