Dohner H. Detection of chimeric BCR-ABL genes on bone marrow samples and blood smears in chronic myeloid and acute lymphoblastic leukemia by in situ hybridization

The presence of BCR-ABL fusion genes has important diag-nostic and prognostic implications in chronic myeloid leuke-mia (CML) and acute lymphoblastic leukemia (ALL). The CML-specific chimeric BCR-ABL gene with a break involving the major breakpoint cluster region (M-bcfi of the BCR-gene has been detected by means of fluorescence in situ hybrid-ization (FISH). In this study, we present a FISH protocol that allows the detection of breaks in both the major and the minor breakpoint cluster region (m-bcfi. Three hybridization signals of D107F9, a yeast artificial chromosome (YAC)-de-rived probe spanning the breakpoint regions of the BCR gene, were indicative of the translocation events. To in-crease the specificity further, this probe was combined with cos-ab1 8, a cosmid probe flanking the breakpoint within HE PHILADELPHIA chromosome (Phl) is the deriva