 The t(12;21) translocation, which generates the TEL-AML1 (ETV6-RUNX1) fusion gene, is the most common structural chromosome change in childhood cancer and is exclusively associated with the common B cell precursor subset of acute lymphoblastic leukemia (ALL).     ///    Modeling first-hit functions of the t(12;21) TEL-AML1 translocation in mice..     ///    TEL-AML1 expression was associated with an accumulation/expansion of primitive c-kit-positive multipotent progenitors and a modest increase in myeloid colony-forming cells.     ///    "TEL-AML1 expression was, however, permissive for myeloid differentiation. "    ///    The mechanism by which TEL-AML1 contributes to this early stage of leukemogenesis is unknown. 