To determine the presence of cooperating mutations in the diseased mice, we assessed the presence of the wild-type p53 allele and found that it was not lost in any of the mice at time of sacrifice (data not shown), and we also conducted whole exome sequencing on two mice (sick mice #3 and #4) and did not observe the acquisition of mutations in known leukemia-causing genes (Supplementary Table). This evidence concerns the gene TP53 and leukemia.