As a proof-of-principle, we here generated four novel R26 KI mice that enable conditional overexpression of 3 putative oncogenes (Jarid2, Runx2, MN1) and one dominant negative allele of a tumour suppressor (dnETV6), which all have been previously associated with the pathobiology of human leukemia7–12. This evidence concerns the gene MN1 and neoplasm.