While the Ptprc (CD45) gene was similarly expressed in the Pax5Jak2/+ and control B‐ALL tumors (Appendix Fig S2H), the increased expression of the repressed Pax5 target gene Hnrnpll (Fig 2E) may explain the decreased B220 expression on Pax5Jak2/+ B‐ALL cells, as the RNA‐binding protein hnRNPLL regulates the alternative splicing of exons 4–6 of the Ptprc (CD45) mRNA (Oberdoerffer et al, 2008) (Fig 2H and Appendix Fig S2I). The gene discussed is HNRNPLL; the disease is acute lymphoblastic leukemia.