Split-signal FISH for detection of chromosome aberrations

Chromosome aberrations are frequently observed in hematopoietic malignancies. These aberrations can deregulate expression of an oncogene, resulting in aberrant expression or overexpression, or they can form leukemia-specific chimeric fusion proteins. Detection of chromosome aberrations is an important tool for classification of the malignancy and for the definition of risk groups, which need different treatment protocols. We developed rapid and sensitive split-signal fluorescent in situ hybridization (FISH) assays for frequently occuring chromosome aberrations. The split-signal FISH approach uses two differentially labeled probes, located in one gene at opposite sites of the breakpoint region. In normal karyotypes, two co-localized green/red signals are visible, but a translocation results in a split of one of the co-localized signals. Split-signal FISH has three main advantages over the classical fusion-signal FISH approach, which uses of two labeled probes located in two genes. First, the detection of a chromosome aberration is independent of the involved partner gene. Second, split-signal FISH allows the identification of the partner gene or chromosome region if metaphase spreads are present, and finally it reduces false-positivity.