No immunophenotypic differences in leukaemia lineage between neonatal and adult recipients was seen upon primary transplantation of MLL-ENL-transduced HSPCs; however, serial transplantation of neonatal MLL-ENL leukaemia cells through neonatal recipients did drive a mixed-lineage leukaemia with a mature B-cell component. This evidence concerns the gene KMT2A and leukemia.