Further characterization of complex chromosomal rearrangements in myeloid malignancies: spectral karyotyping adds precision in defining abnormalities associated with poor prognosis

Abstract

The mixed lineage leukemia gene (MLL, also known as HRX, ALL-1 and Htrx) located at 11q23 is involved in translocations with over 40 different chromosomal bands in a variety of leukemia subtypes. Here we report our analysis of a rare but recurring translocation, t(11;15)(q23;q14). This translocation has been described in a small subset of cases with both acute myeloblastic leukemia and ALL. Recent studies have shown that MLL is fused to AF15q14 in the t(11;15). Here we analyse a sample from another patient with this translocation and confirm the presence of an MLL-AF15q14 fusion. However, we have also identified and cloned another fusion transcript from the same patient sample. In this fusion transcript, MLL is fused to a novel gene, MLL partner containing FYVE domain (MPFYVE). Both MLL-AF15q14 and MLL-MPFYVE are in-frame fusion transcripts with the potential to code for novel fusion proteins. MPFYVE is also located on chromosome 15, approximately 170 kb telomeric to AF15q14. MPFYVE contains a highly conserved motif, the FYVE domain which, in other proteins, has been shown to bind to phosphotidyl-inositol-3 phosphate (PtdIns(3)P). The MLL-MPFYVE fusion may be functionally important in the leukemia process in at least some patients containing this translocation.