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Is micronucleus induction by aneugens an early event leading to mutagenesis?
H Stopper1, I Eckert, D Schiffmann
1Institute of Pharmacology and Toxicology, University of Würzburg, Germany.
Abstract:
This study was designed to investigate a previously unidentified potential mechanism for mutation induction as well as to clarify a biological consequence of micronuclei with mutation induction as measured by trifluorothymidine (TFT) resistance in mouse L5178Y cells using four aneugens: colcemid, diethylstilbestrol, griseofulvin and vinblastine. All four compounds induced micronuclei which appeared in the first cell cycle after treatment. More than 85% of the micronuclei induced by each compound stained positive for the presence of kinetochores implying that the micronuclei contained whole chromosomes. However, these same compounds were unable to induce TFT resistance under three different treatment regimes. We concluded that these compounds, under conditions where they induce primarily kinetochore positive micronuclei, were not able to induce mutations. Thus, the induction of micronuclei containing whole chromosomes harboring a selectable gene is not an early event leading to mutations in these cells.
Insights
This study investigated micronuclei formation and mutation induction in mouse cells. Primarily kinetochore-positive micronuclei, indicating whole chromosomes, did not lead to trifluorothymidine resistance mutations.
Area of Science:
- Cell biology
- Genetics
- Toxicology
Background:
- Micronuclei are biomarkers of chromosomal damage.
- Their role in mutation induction requires further clarification.
- Understanding this link is crucial for genotoxicity assessment.
Purpose of the Study:
- To investigate the relationship between micronuclei formation and mutation induction.
- To determine if aneugen-induced micronuclei containing whole chromosomes cause mutations.
- To assess trifluorothymidine (TFT) resistance as a measure of mutation.
Main Methods:
- Mouse L5178Y cells were treated with four aneugens: colcemid, diethylstilbestrol, griseofulvin, and vinblastine.
- Micronuclei formation and kinetochore presence were analyzed.
- Trifluorothymidine (TFT) resistance was measured under various treatment conditions.
Main Results:
- All four aneugens induced micronuclei in the first cell cycle.
- Over 85% of induced micronuclei were kinetochore-positive, suggesting whole chromosome content.
- No significant induction of TFT resistance was observed, indicating a lack of mutation induction.
Conclusions:
- Aneugen treatment, resulting in kinetochore-positive micronuclei, did not induce mutations in mouse L5178Y cells.
- The formation of micronuclei containing whole chromosomes is not an early event leading to mutations.
- This suggests a complex relationship between micronuclei and mutagenesis.