Division of Genetics and Mutagenesis, National Institute of Health Sciences, Tokyo 158-8501, Japan.
Mutat Res. 2010 Oct 13;692(1-2):12-8. doi: 10.1016/j.mrfmmm.2010.07.009. Epub 2010 Aug 5.
The micronucleus (MN) test is widely used to biomonitor humans exposed to clastogens and aneugens, but little is known about MN development. Here we used confocal time-lapse imaging and a fluorescent human lymphoblastoid cell line (T105GTCH), in which histone H3 and α-tubulin stained differentially, to record the emergence and behavior of micronuclei (MNi) in cells exposed to MN-inducing agents. In mitomycin C (MMC)-treated cells, MNi originated in early anaphase from lagging chromosome fragments just after chromosome segregation. In γ-ray-treated cells showing multipolar cell division, MN originated in late anaphase from lagging chromosome fragments generated by the abnormal cell division associated with supernumerary centrosomes. In vincristine(VC)-treated cells, MN formation was similar to that in MMC-treated cells, but MNi were also derived from whole chromosomes that did not align properly on the metaphase plate. Thus, the MN formation process induced by MMC, γ-rays, and VC, were strikingly different, suggesting that different mechanisms were involved. MN stability, however, was similar regardless of the treatment and unrelated to MN formation mechanisms. MNi were stable in daughter cells, and MN-harboring cells tended to die during cell cycle progression with greater frequency than cells without MN. Because of their persistence, MN may have significant impact on cells, causing genomic instability and abnormally transcribed genes.
微核（MN）试验被广泛用于监测人类暴露于断裂剂和非整倍体剂，但其发生机制尚不清楚。本研究应用共聚焦延时成像技术和荧光人淋巴母细胞系（T105GTCH），该细胞系中组蛋白 H3 和微管蛋白α被差异化染色，以记录细胞暴露于致 MN 剂后 MN 的发生和行为。在丝裂霉素 C（MMC）处理的细胞中，MN 起源于早后期，来自染色体分离后滞后的染色体片段。在表现出多极细胞分裂的γ射线处理的细胞中，MN 起源于后期，来自与过多中心体相关的异常细胞分裂产生的滞后染色体片段。在长春新碱（VC）处理的细胞中，MN 的形成与 MMC 处理的细胞相似，但 MN 也来自没有正确排列在中期板上的整条染色体。因此，MMC、γ射线和 VC 诱导的 MN 形成过程明显不同，提示涉及不同的机制。然而，MN 的稳定性与处理无关，与 MN 的形成机制无关。MN 稳定存在于子细胞中，并且携带 MN 的细胞在细胞周期进程中比没有 MN 的细胞更频繁地死亡。由于其持久性，MN 可能对细胞产生重大影响，导致基因组不稳定和异常转录基因。
