Multiplex-FISH for pre- and postnatal diagnostic applications

For >3 decades, Giemsa banding of metaphase chromosomes has been the standa rd karyotypic analysis for pre- and postnatal diagnostic applications. Howe ver, marker chromosomes or structural abnormalities are often encountered t hat cannot be deciphered by G-banding alone. Here we describe the use of mu ltiplex-FISH (M-FISH), which allows the visualization of the 22 human autos omes and the 2 sex chromosomes, in 24 different colors. By M-FISH, the euch romatin in marker chromosomes could be readily identified. In cases of stru ctural abnormalities, M-FISH identified translocations and insertions or de monstrated that the rearranged chromosome did not contain DNA material from another chromosome. In these cases, deleted or duplicated regions were dis cerned either by chromosome-specific multicolor bar codes or by comparative genomic hybridization. In addition, M-FISH was able to identify cryptic ab normalities in patients with a normal G-karyotype. In summary, M-FISH is a reliable tool for diagnostic applications, and results can be obtained in l ess than or equal to 24 h. When M-FISH is combined with G-banding analysis, maximum cytogenetic information is provided.