A novel approach for direct detection of the IGH::CRLF2 gene fusion by fluorescent in situ hybridization

BACKGROUND: High expression of the Cytokine Receptor-Like Factor 2 (CRLF2) gene has been observed in patients with acute lymphoblastic leukemia BCR-ABL1-like subtype. Currently, there is no commercial system available for the direct detection of the IGH::CRLF2 fusion by fluorescent in situ hybridization (FISH), as there are for many other leukemia-related gene fusions. In an effort to verify the IGH::CRLF2 fusion, some researchers prepare home-grown FISH probes from bacterial artificial chromosome clones flanking the IGH and CRLF2 genes, which is the best alternative to confirm the fusion, however difficult to reproduce in most cytogenetic laboratories. RESULTS: For the direct observation of the IGH::CRLF2 gene fusion we designed a methodological approach requiring the two commercially available IGH and CRLF2 break-apart probes. CONCLUSIONS: Our methodological approach allows direct visualization of the IGH::CRLF2 gene fusion and has the potential to be used for identification of other gene fusions.