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Simultaneous detection of chromosomal aberrations and sister-chromatid exchanges: experience with DNA intercalating
Abstract:
Micronuclei that arise from chromosomal fragments can be used as an index of cytogenetic damage in a number of mammalian cell-culture systems. Since sister-chromatid exchanges (SCE) can be scored at the second metaphase after treatment, micronuclei that have arisen from acentric fragments at the first mitosis should be present in the same preparations. When a series of 8 mutagens, most of them intercalating agents, was studied in Chinese hamster ovary (CHO) cells, increased frequencies of micronuclei were detected at all doses which induced increased frequencies of SCE. The time required to score the slides for micronuclei was about one tenth that required for SCE. Since it is clear that aberrations and SCE have different genetic consequences and that they arise by mechanisms that differ at least in part, we find it useful to be able to measure both on the same slides. In this way mutagenic agents such as X-rays and bleomycin that produce few, if any, SCE but much chromosomal breakage would not be missed, nor would any agent that produced SCE without aberrations.
Insights
Micronuclei detection in Chinese hamster ovary cells effectively indicates cytogenetic damage, correlating with sister-chromatid exchanges (SCE). This method offers a faster alternative for assessing mutagenicity compared to SCE analysis alone.
Area of Science:
- Cytogenetics
- Molecular Toxicology
- Cell Biology
Background:
- Micronuclei formation serves as a biomarker for chromosomal damage in mammalian cell systems.
- Sister-chromatid exchanges (SCE) are another indicator of genotoxic damage, scorable at the second metaphase post-treatment.
Purpose of the Study:
- To evaluate the utility of micronuclei as an index of cytogenetic damage in parallel with SCE analysis.
- To compare the scoring efficiency of micronuclei versus SCE in mutagenicity testing.
Main Methods:
- Treatment of Chinese hamster ovary (CHO) cells with eight different mutagens, primarily intercalating agents.
- Simultaneous scoring of micronuclei (arising from acentric fragments at first mitosis) and sister-chromatid exchanges (SCE) in the same cell preparations.
- Dose-response analysis for both micronuclei and SCE frequencies.
Main Results:
- Increased frequencies of micronuclei were observed at all doses that also induced increased frequencies of SCE.
- The time required for scoring micronuclei was approximately one-tenth of that needed for SCE scoring.
- A strong correlation was found between mutagenic agents inducing SCE and those inducing micronuclei.
Conclusions:
- Micronuclei analysis is a rapid and effective method for detecting cytogenetic damage induced by mutagens.
- Measuring both micronuclei and SCE provides a comprehensive assessment of different genotoxic mechanisms.
- This parallel approach ensures the detection of mutagens that may preferentially induce chromosomal aberrations or SCE.