Ectopic expression accompanied by the resolution of bivalent promoter marks into activating marks only is consistent with biallelic expression of LMO1 in nontranslocated T-ALL patients, in line with what has been shown before for LMO2. 40 Biallelic expression not only focuses attention on the alterations within the leukaemic transcriptional environment that may be responsible for ectopically activating LMO1, but also the regulatory sequences within the gene locus through which such ectopic activation may occur. This evidence concerns the gene LMO2 and acute lymphoblastic leukemia.