The effects of static magnetic fields and X-rays on instability of microsatellite repetitive sequences

To determine the genetic effect of static magnetic fields (SMF), which are not supposed to produce any significant DNA damage, we took advantage of DN A mismatch repair (MMR) deficient cells, in which all the errors produced d uring DNA replication are left uncorrected. We first established a simple a nd less labor-intensive method to analyze genetic changes in microsatellite repetitive sequences in the MMR-deficient cells. After exposure to a stron g SMF (6.34T) for 24h, both MMR deficient HCT116 cells and proficient HeLa S3 cells did not exhibit any significant effect on microsatellite changes. Moreover, when HCT 116 cells were synchronized at the G1/S boundary by aphi dicolin and exposed to SMF during the whole S-phase, no increase in microsa tellite changes was either observed. in contrast, irradiation by a low dose X-ray (2Gy) significantly increased microsatellite changes in HCT116 cells . This suggested that exposure to strong SMF may not induce any significant level of genetic changes in microsatellite sequences.