Fluorescence in situ hybridization (FISH) is a technique that allows specific DNA sequences to be detected on metaphase or interphase chromosomes in cell nuclei(1). The technique uses
DNA probes with unique sequences that hybridize to whole chromosomes or specific chromosomal regions, and serves as a powerful adjunct to classic cytogenetics. For instance, many earlier studies reported the frequent detection of increased
chromosome aberrations in
leukemia patients related with
benzene exposure,
benzene-
poisoning patients, and healthy workers exposed to
benzene, using classic cytogenetic analysis(2). Using FISH,
leukemia-specific chromosomal alterations have been observed to be elevated in apparently healthy workers exposed to benzene(3-6), indicating the critical roles of cytogentic changes in
benzene-induced leukemogenesis. Generally, a single FISH assay examines only one or a few whole chromosomes or specific loci per slide, so multiple hybridizations need to be conducted on multiple slides to cover all of the human chromosomes. Spectral karyotyping (SKY) allows visualization of the whole genome simultaneously, but the requirement for special software and equipment limits its application(7). Here, we describe a novel FISH assay, OctoChrome-FISH, which can be applied for Chromosomics, which we define here as the simultaneous analysis of all 24 human chromosomes on one slide in human studies, such as chromosome-wide
aneuploidy study (CWAS)(8). The basis of the method, marketed by Cytocell as the Chromoprobe Multiprobe System, is an OctoChrome device that is divided into 8 squares, each of which carries three different whole chromosome painting probes (Figure 1). Each of the three probes is directly labeled with a different colored fluorophore, green (
FITC), red (
Texas Red), and blue (
Coumarin). The arrangement of chromosome combinations on the OctoChrome device has been designed to facilitate the identification of the non-random structural chromosome alterations (translocations) found in the most common
leukemias and
lymphomas, for instance t(9;22), t(15;17), t(8;21), t(14;18)(9). Moreover, numerical changes (
aneuploidy) in chromosomes can be detected concurrently. The corresponding template slide is also divided into 8 squares onto which metaphase spreads are bound (Figure 2), and is positioned over the OctoChrome device. The probes and target
DNA are denatured at high-temperature and hybridized in a humid chamber, and then all 24 human chromosomes can be visualized simultaneously. OctoChrome FISH is a promising technique for the clinical diagnosis of
leukemia and
lymphoma and for detection of
aneuploidies in all chromosomes. We have applied this new Chromosomic approach in a CWAS study of
benzene-exposed Chinese workers(8,10).