A similar phenomenon was observed in Lin- mouse bone marrow cells transduced with the MA9 retrovirus (Supplementary Fig. 1E) MBNL1 was recently demonstrated to be a direct target of the MLL-AF4 fusion protein in patient-derived ALL cell lines as well as in an experimental retroviral model20,29. The gene discussed is MBNL1; the disease is acute lymphoblastic leukemia.