New concepts to improve resolution and sensitivity of molecular cytogenetic diagnostics by multicolor fluorescence in situ hybridization

Background: Routine application of multicolor fluorescence in situ hybridiz ation (M-FISH) technology for molecular cytogenetic diagnostics has been ha mpered by several technical limitations. First, when using chromosome-speci fic painting probes, there is a limit in cytogenetic resolution of approxim ately 2-3 Mb, which can mask hidden structural abnormalities that have a si gnificant clinical effect. Second, using whole chromosome painting probes, intrachromosomal rearrangements cannot be detected and the exact localizati on of breakpoints is often not possible. Methods: We suggest the use of multiplex-labeled region or locus- specific probes in combination with an optimal probe design to improve the sensitivi ty and resolution of the M-FISH technology. To allow the application of thi s assay in routine diagnostics, we developed a multipurpose image analysis system. Results: goldFISH was applied to the study of cryptic translocations in men tal retardation patients and to the study of high-resolution breakpoint map ping in non-small cell lung cancer patients. For an individual with mental retardation, who had an apparently normal karyotype by G-banding, m e detec ted an unbalanced translocation involving chromosomes 2 and 7. Conclusions: In combination with optimally designed probe kits, goldFISH ov ercomes most of the present limitations of the M-FISH technology and result s in virtually 100% reliability for detecting interchromosomal and intrachr omosomal rearrangements. Cytometry 44:7-15, 2001. (C) 2001 Wiley-Liss, Inc.