Induction of The 4977‐bp “Common Deletion” In Mitochondrial DNY by Gamma Radiation in a Pearson's Syndrome Cell Line and Absolute Quantification by Real‐Time PCR

Mitochondrial DNA (mtDNA) has become an area of increasing interest in recent years. Mutations in this type of DNA have been correlated with aging and many other muscular and neurological conditions (Wallace et al., 1988). Here we show that a specific deletion of 4977 base pairs (known as the “common deletion”) can appear as a result of ionizing radiation damage. We grew lymphoblast cells derived from a patient with Pearson's Marrow/Pancreas syndrome (known to contain elevated levels of the common deletion) as well as the common MRC‐5 cancer fibroblast cell line and irradiated the cells with doses of 0.5–5 Gy of gamma radiation. Total (nuclear and mitochondrial) and mitochondrial DNA extracts were then analyzed for the presence and quantity of deleted mitochondrial genomes using real‐time PCR. Cloned plasmids containing the same mitochondrial DNA target sequences served as quantification controls. Results show that elevated amounts of total mitochondrial DNA can be found 72 hrs after irradiation and that the common deletion increases in these cells, but not in a dose‐dependent manner. More research is presently being done to elucidate the timeframe in which cells replicate their damaged mtDNA post irradiation.