Journal Article

Two Major Factors Involved in the Reverse Dose-rate Effect for Somatic Mutation Induction are the Cell Cycle Position and LET Value

Hiroshi Tauchi, Hiroyuki Waku, Eigo Matsumoto, Sayaka Yara, Shino Okumura, Yoshiyuki Iwata, Kenshi Komatsu, Yoshiya Furusawa, Kiyomi Eguchi-Kasai and Akira Tachibana

in Journal of Radiation Research

Volume 50, issue 5, pages 441-448
Published in print September 2009 | ISSN: 0449-3060
Published online June 2009 | e-ISSN: 1349-9157 | DOI: https://dx.doi.org/10.1269/jrr.09033
Two Major Factors Involved in the Reverse Dose-rate Effect for Somatic Mutation Induction are the Cell Cycle Position and LET Value

More Like This

Show all results sharing these subjects:

  • Clinical Genetics
  • Molecular Biology and Genetics
  • Epidemiology
  • Radiology
  • Nuclear Chemistry, Photochemistry, and Radiation

GO

Show Summary Details

Preview

To study mechanisms which could be involved in the reverse dose rate effect observed during mutation induction after exposure to high LET radiation, synchronized mouse L5178Y cells were exposed to carbon 290 MeV/n beams with different LET values at the G2/M, G1, G1/S or S phases in the cell cycle. The frequency of Hprt-deficient (6-thioguanine-resistant) mutant induction was subsequently determined. The results showed that after exposure to high LET value radiation (50.8 and 76.5 keV/μm), maximum mutation frequencies were seen at the G2/M phase, but after exposure to lower LET radiation (13.3 keV/μm), the highest mutation frequencies were observed at the G1 phase. The higher LET beam always produced higher mutation frequencies in the G2/M phase than in the G1 phase, regardless of radiation dose. These results suggest that cells in the G2/M phase is hyper-sensitive for mutation induction from high LET radiation, but not to mutation induction from low LET radiation. Molecular analysis of mutation spectra showed that large deletions (which could include almost entire exons) of the mouse Hprt gene were most efficiently induced in G2/M cells irradiated with high LET radiation. These entire exon deletions were not as frequent in cells exposed to lower LET radiation. This suggests that inappropriate recombination repair might have occurred in response to condensed damage in condensed chromatin in the G2/M phase. In addition, by using a hyper-sensitive mutation detection system (GM06318-10 cells), a reverse dose-rate effect was clearly observed after exposure to carbon beams with higher LET values (66 keV/μm), but not after exposure to beams with lower LET values (13.3 keV/μm). Thus, G2/M sensitivity towards mutation induction, and the dependence on radiation LET values could both be major factors involved in the reverse dose rate effect produced by high LET radiation.

Keywords: Somatic mutation; Heavy ion beam; Cell cycle; LET; Hprt

Journal Article.  0 words. 

Subjects: Clinical Genetics ; Molecular Biology and Genetics ; Epidemiology ; Radiology ; Nuclear Chemistry, Photochemistry, and Radiation

Full text: subscription required

How to subscribe Recommend to my Librarian

Users without a subscription are not able to see the full content. Please, subscribe or login to access all content. subscribe or purchase to access all content.