Fluorescence in situ hybridization studies using BAC clones of the EVI1 locus in hematological malignancies with 3q rearrangements

Chromosomal rearrangements involving 3q26 are a recurrent aberration in malignant myeloid disorders. Several of these rearrangements involve the EVI1 oncogene or its surrounding sequences and are associated with a poor prognosis. Fluorescence in situ hybridization (FISH) studies using bacterial artificial chromosome (BAC) clones were conducted to determine whether the EVI1 locus was rearranged in nine patients with hematological malignancies carrying 3q abnormalities. A dual-color probe was constructed with nine BACs; centromeric clones covering 1 Mb and including the EVI1 gene were labeled with a red fluorescent dye and telomeric clones covering 1 Mb were labeled with a green fluorescent dye. Two patients showed normal copies of the EVI1 locus, four patients showed one EVI1 locus rearranged (in all of them the breakpoint on 3q26 was telomeric to EVI1), one patient showed one copy of the EVI1 locus translocated to another chromosome, one patient showed one copy of the EVI1 locus rearranged and the other copy translocated, and one patient showed one extra copy of the EVI1 locus. In four cases, FISH studies using the EVI1 clones detected different 3q abnormalities not previously found by conventional cytogenetics. FISH analysis with BAC clones was a useful tool for identifying the chromosome breakpoints affecting the EVI1 locus in patients with 3q26 rearrangements.