HMGA1a transgenic/CDKN2A null leukemias presented a T-cell origin immunophenotype with the expression of Th y 1.2, CD3, CD8, and α β T-Cell Receptor (TCR); a markedly accelerated development; and disease recapitulating the salient clinical and pathologic features of human T-ALL. Here, HMGA1 is linked to acute lymphoblastic leukemia.