G0 chromosomal radiosensitivity in ataxia telangiectasia lymphocytes

Contrary to an earlier report, peripheral lymphocytes from 4 AT patients were not found to exhibit higher yields of unequivocal chromosome type aberrations following irradiation in the G₀ phase of the cell cycle, providing that only first post-irradiation metaphases were included in the samples (ensured by 5-bromodeoxyuridine (BrdU) incorporation and differential fluorescence or Giemsa staining). We were able, however, to confirm the earlier-reported increase in chromatid-type aberrations in the G₀-irradiated cells. AT lymphocytes were found to experience more cell-cycle delay following G₀ irradiation than normal cells. These observations appear consistent with the damaged base excision DNA-repair defect reported for AT cells.