Abstract
It is believed that micronuclei (MN) originate from chromosome fragments or whole chromosomes that lag behind at anaphase during cell division. However, nobody looked its emergence in a living cell and nobody knows its consequence after cell division. Recently, a fluorescent microscope designed for live cell imaging enable to visualize cellular dynamics without cell killing by a direct detection of fluorescent-fused organelles and proteins. To understand the mechanism of MN formation derived by gamma-ray, we constructed dual-color fluorescent human lymphoblastoid TK6 cells in which histon H3 and tubulin-alpha were differentially expressed as fusion to mCherry (red) and EGFP (green) fluorescent proteins, respectively. Using a computer-controlled confocal microscope system, three-dimentional images of nuclei (chromosome) and microtubules were sequentially recorded by time-lapse during cell division (M phase) after exposure to gamma-ray. The moment of MN formation by gamma-ray was dynamically observed at anaphase. The MN emergence frequency in the live cell analysis was approximately consistent with that in conventional MN test. In addition, mitomycin C (MN-inducing agent) and vincristine (spindle poison agent) were also used in this study to compare with the style and phase of MN formation by gamma-ray. We will show some movies for the emergence of MN in the living cells exposed to gamma-ray, mitomycin C, and vincristine.
