Validation of Chromosome Painting. II. A Detailed Analysis of Aberrations Following High Doses of Ionizing Radiationin Vitro

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Abstract
Fluorescence in situ hybridization with chromosome-specific composite DNA probes (‘chromosome painting’) is useful for quantifying radiation-induced cytogenetic damage. Recently we showed that the frequency of aberrations observed with painting is similar to that seen with conventional cytogenetic methods, at least at doses of ⩽ 2 Gy. Above this dose, however, the agreement was not as good. We describe here the results of additional work designed to clarify our earlier findings, and provide a detailed analysis of the type and frequency of aberrations induced in human peripheral lymphocytes following acute exposure to 137Cs at doses of 0 (unexposed control), 1, 2, 3 and 4 Gy. The newly-developed nomenclature for chromosome aberrations detected by painting (Protocol for Aberration Identification and Nomenclature Terminology, ‘PAINT’) was used to classify all aberrations. Our results indicate that if the guidelines of the PAINT system are followed, chromosome painting can provide meaningful biodosimetry at high doses, and that the observation of complicated rearrangements not only does not interfere with dose estimation, but also the information provided by these exchanges can be easily broken down into the component aberrations and included in the dose estimate. We also show that the inequality between translocations and dicentrics that we previously observed can be explained by an excess of one class of translocated chromosomes, specifically those in which the centromere is from an unpainted chromosome. Translocated chromosomes in which the centromere is painted were found to occur at a frequency equal to dicentrics. These results should help clarify the use of painting for radiation biodosimetry by improving our understanding of the frequencies of various types of stable aberrations observed shortly after exposure. This will improve our ability to perform meaningful biodosimetry long after the frequencies of unstable aberrations have ceased to be informative.

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