Live-cell imaging study of mitochondrial morphology in mammalian cells exposed to X-rays

Noguchi, Miho; Kanari, Yukiko; Kaminaga, Kiichi; Sakamoto, Yuka; Narita, Ayumi; Fujii, Kentaro; Yokoya, Akinari

Recent reports suggest that extranuclear targets in cytoplasm may have a role in mediating radiation effects on mammalian cells exposed to ionizing radiation. Mitochondria, a kind of major organelles, are distributed throughout cytoplasm. They contain their own genome, and mediate essential cell functions, such as generation of ATP and regulation of cell death. Radiation effect on mitochondrial functions, however, remains to be fully elucidated. As the first step to understand the cytoplasmic effects of radiation, we have examined mitochondrial morphology in mammalian cells exposed to X-rays. Mitochondria are continuously fusing or dividing during mitosis, or in response to environmental condition changes. In this study, after irradiation of X-rays to mouse cells, we labeled mitochondria by Mitotracker Red and analyzed kinetics of mitochondrial morphology by a live-cell imaging technique using a fluorescence microscope. We demonstrated that X-irradiation causes mitochondrial fragmentation and the frequency of fragmentation increases with increasing X-ray dose. We report the radiation induced mitochondrial morphological change.