Consistent with these heterogeneous phenotypes, mutations in, or altered expression of, genes encoding multiple transcription factors (cMYC, IKZF1, GATA3, TCF7, LEF1), epigenetic regulators (EZH2 and PHF6), cytokine receptors (IL7R and FLT3), cell cycle regulators (CDKN2A and CDKN2B), and signaling proteins (PTEN) have been identified in subsets of human T-ALL (5–7). Here, GATA3 is linked to acute lymphoblastic leukemia.