These T-ALL harbor chromosomal rearrangements, or alternatively noncoding sequence mutations, which cause the activation of members of the basic helix-loop-helix (bHLH) family of transcription factors (TAL1 and TAL2) and/or of the LIM-only domain (LMO1, LMO2, and LMO3) proteins [8,11,12,13]. Here, TAL1 is linked to acute lymphoblastic leukemia.