Chromosomal rearrangements are present in the majority of T-ALL patients, resulting in the ectopic expression of transcription factors, including T-cell acute lymphocytic leukemia protein 1 (TAL1), T-cell leukemia homeobox protein 1 and 3 (TLX1 and TLX3) and NK2 homeobox 1 (NKX2-1). The gene discussed is TLX1; the disease is acute lymphoblastic leukemia.