Interchromosomal translocations within T-cell neoplasms often involve their antigen receptor genes and another chromosome that provides a new transcription factor gene. Within T-cell acute lymphoblastic leukemia, translocations result in the aberrant expression of one of a series of putative transcription factors (Ttg-1, Ttg-2, Lyl-1, Sc1, tal-2, Hox11). Ttg-1 from chromosome segment 11p15 encodes a nuclear protein, which is predominantly expressed in neuronal cells, and belongs to a novel family of transcription factors possessing LIM domains. Transgenic mice that overexpress this candidate oncogene in early thymocytes develop immature, aggressive T-cell leukemia/lymphoma. A minority population of thymocytes representing an immature CD4 -8+ intermediate stage is preferentially affected. This model indicates that aberrant expression of putative transcription factors is of primary importance in the genesis of T-cell acute lymphoblastic leukemia/lymphoma.
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