HMGA2 locus rearrangement in a case of acute lymphoblastic leukemia.

We report the first case of acute lymphoblastic leukemia associated with a t(9;12)(p22;q14) translocation within the HMGA2 locus. The breakpoint lies in the 5' region. Fluorescence in situ hybridization with a BAC clone covering the 5' region produced three signals versus two signals with a BAC clone covering the 3' region including intron 3 of HMGA2, which harbors most of the breakpoints described in benign mesenchymal tumors. HMGA2 locus rearrangement was associated with overexpression of an HMGA2 mRNA that lacked a carboxy-terminal tail. These results suggest that the HMGA2 gene rearrangement may contribute to the malignancy in leukemias harboring a 12q translocation.