 The TEL-JAK2 gene fusion, which has been identified in human leukemia, encodes a chimeric protein endowed with constitutive tyrosine kinase activity.     ///    This disease is similar to the bona fide TEL-JAK2 disease as assessed by phenotypic and gene profiling analyses.     ///    "Pre-TCR signaling synergizes with TEL-JAK2 to transform immature thymocytes and initiate leukemogenesis as shown by (1) the delayed leukemia onset in Rag2-, CD3epsilon- and pTalpha-deficient mice, (2) the occurrence of recurrent chromosomal alterations in pre-TCR-deficient leukemia, and (3) the correction of delayed leukemia onset in Rag2-deficient TEL-JAK2 mice by an H-Y TCRalphabeta transgene that mimics pre-TCR signaling. "    ///    "TEL-JAK2 transforms immature CD4(-)CD8(-) double-negative thymocytes, as demonstrated by the development of T-cell leukemia with full penetrance in a Rag2-deficient genetic background. "    ///    TEL-JAK2 transgenic expression in the mouse lymphoid lineage results in fatal and rapid T-cell leukemia/lymphoma.     ///    Pre-TCR expression cooperates with TEL-JAK2 to transform immature thymocytes and induce T-cell leukemia.. 