These expression profiles include the TAL/LMO, TLX1, TLX3, and HOXA clusters as well as the recently reported proliferative and immature T-ALL subtypes, which are mediated by the overexpression of NKX2-1, NKX2-2, and MEF2C. MEF2C functions as a transcriptional regulator, triggering an exhaustive transcriptional program characteristic of early T-cell progenitor (ETP) ALL. Here, MEF2C is linked to acute lymphoblastic leukemia.