[Study of DNA damage and heterogeneity of cells by a gel microelectrophoresis method]

The influence of some cell parameters--cell size, cell DNA content, cell cycle phase--on migration of DNA from individual cell in constant electric field was studied on human peripheral lymphocytes and mouse lymphoblasts L5178Y by microelectrophoresis (neutral DNA-comet assay). It has been shown that the full comet length (l) did not depend on the cell parameters for intact and moderately irradiated cells (up to 25 Gy). It is proposed that migration capacity of DNA is related with damage to DNA. Then the heterogeneity of intact cells in the comet length can mirror the variation of background level of DNA lesions from cell to cell in the same population. Lymphoblasts of radiosensitive strain (LY-S cells) show higher average DNA-mobility and heterogeneity in DNA-comet length as compared to the cells of radioresistant strain (LY-R). This difference is suggested to be compatible with relatively higher background DNA-breakage in LY-S cells due to deficiency in repair of double-strand breaks in these cells. A subpopulation (about 20%) in LY-S cells with very migrating DNA was determined with neutral DNA-comet assay. It is reasonable to identify this subpopulation with cells of this line showing the lowest DNA repair rate. Thus neutral DNA-comet assay can be useful for evaluation of damage to and repair of DNA in individual cells and their heterogeneity.