Detection and characterization of micronuclei in a murine liver epithelial cell line, by application of the in vitro cytokinesis block MN assay and PRINS

The cytokinesis block micronucleus assay was applied to murine cell line C6, derived from fetal liver, after an optimal protocol had been designed. Micronucleus frequencies were assayed after exposure to three concentrations of colcemid or diepoxybutane. Two-colour primed in situ DNA synthesis (PRINS) was applied to simultaneously label telomeric and centromeric (minor satellite DNA) sequences. Both chemicals induced a highly significant increase in MN and the effect was dose dependent. Diepoxybutane did not appear to significantly increase the frequency of centromere-positive micronuclei. Colcemid, as expected, induced high frequencies of centromere-positive micronuclei at all concentrations tested; in addition a significant increase in centromere-negative micronuclei was observed at 10(-5) M. Many centromere-positive micronuclei carried three or four telomeres, thus indicating that a duplicated (non-disjoined) chromosome with two chromatids was contained in the micronucleus. This observation leads to the conclusion that micronuclei deriving from missegregation could be due to errors occurring before the onset of anaphase. The results obtained on C6 cells are in good agreement with those obtained on other cell systems, indicating that this cell line can be considered for in vitro aneuploidy evaluation.