MLL1, located on human chromosome 11, is disrupted in distinct recurrent chromosomal
translocations in several leukemia subsets. Studying the MLL1 gene and its oncogenic
variants has provided a paradigm for understanding cancer initiation and maintenance
through aberrant epigenetic gene regulation. Here we review the historical development of
model systems to recapitulate oncogenic MLL1-rearrangement (MLL-r) alleles encoding
mixed-lineage leukemia fusion proteins (MLL-FPs) or internal gene rearrangement products …