Recurrent variants were found in genes known to be relevant for human BCP-ALL including Trp53, Ebf1, Jak3, Ptpn11, and Ikzf1 (Figure 5B); a number of these mutations occurred at the murine homologue of known human “hot spot” amino acid residues that are associated with malignant transformation, including Pax5 P80R, Ptpn11 S506W, and Trp53 R270P (Figure 5C; supplemental Table 4). This evidence concerns the gene JAK3 and acute lymphoblastic leukemia.