Given the unequivocal demonstration through transgenic mouse experiments that ectopic LMO1 expression in T-cells causes T-ALL,4 a detailed understanding of transcriptional control mechanisms operating at the LMO1 gene locus would appear vital to elucidate the mechanisms responsible for ectopic expression in T-ALL patients without LMO1 translocations. This evidence concerns the gene LMO1 and acute lymphoblastic leukemia.