Fluorescence in situ hybridization (FISH)

Abstract

Clinical observations and experimental studies point to the biological significance for the human population of spontaneous and induced chromosome aberrations, and to the need of their analysis and gaining better insight into the mechanisms of formation. Using conventional methods of assaying chromosome aberrations, only radiation-induced anomalies visualized as clearcut structural changes - dicentrics, centric rings and acentric fragment - are analyzed. Conventional methods fail to score aberrations with visibly unchanged morphological patterns of the metaphase chromosome, such as translocations and inversions. From the genetic risk viewpoint translocations are more important insofar as they are associated with genetic diseases and carcinogenesis. Over the last decade, the fluorescence in situ hybridization (FISH) technique became a powerful tool for cytogenetic analysis. Advances in molecular biology techniques generated a variety of DNA probes specific for different human genome regions, and for the genome of some laboratory, animals as well. In this regard the creation of DNA probes specific of whole chromosomes (chromosome libraries) plays a major role in the field of radiation cytogenetics. FISH using a DNA probe, specific of a given chromosome, stains with a characteristic fluorescence the entire chromosome the probe is derived from. The use of an appropriate counter-stain promotes visualization of the remaining unstained chromosomes in a different color so that chromosome aberrations among pained and unpauned chromosomes become apparently dichromatic. In this fashion all types of chromosome aberrations involving stained chromosomes lend themselves to visualization, whereas FISH affords a unique possibility to analyze translocations. This is a method contributing to prompt and accurate recording of chromosome translocations, both following in vitro irradiation of human lymphocytes, and in the event of radiation breakdown events. The generation of DNA probes specific of chromosomes for laboratory mammals commonly employed in practice enables both in vivo, and in vitro experimentation with these animals. Also discussed are some essential methodological aspects of the FISH technique.