Detection and characterization of micronuclei in a murine liver epithelialcell line, bg 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. Mi cronucleus frequencies were assayed after exposure to three concentrations of colcemid or diepoxybutane. Two-colour primed in situ DNA synthesis (PRIN S) was applied to simultaneously label telomeric and centromeric (minor sat ellite DNA) sequences, Both chemicals induced a highly significant increase in MN and the effect was dose dependent. Diepoxybutane did not appear to s ignificantly increase the frequency of centromere-positive micronuclei. Col cemid, as expected, induced high frequencies of centromere-positive micronu clei at all concentrations tested; in addition a significant increase in ce ntromere-negative micronuclei was observed at 10(-5) M. Many centromere-pos itive micronuclei carried three or four telomeres, thus indicating that a d uplicated (non-disjoined) chromosome with two chromatids was contained in t he micronucleus. This observation leads to the conclusion that micronuclei deriving from missegregation could be due to errors occurring before the on set of anaphase, The results obtained on C6 cells are in good agreement wit h those obtained on other cell systems, indicating that this cell line carl be considered for in vitro aneuploidy evaluation.