Multiplex polymerase chain reaction-based deletion analysis of spontaneous, gamma ray- and alpha-induced hprt mutants of CHO-K1 cells.
Independent Chinese hamster ovary (CHO)-K1 cell mutants at the hypoxanthine-guanine phosphoribosyltransferase (hprt) locus were isolated from untreated, 60Co gamma ray- and 212Bi alpha-exposed cells and the genetic changes underlying the mutation determined by multiplex polymerase chain reaction (PCR)-based exon deletion analysis. In the 71 spontaneous mutants analyzed, 77.5% of the clones showed no change in exon number or size, 15.5% showed a loss of a single exon, 4.2% showed a loss of 2-8 exons, and 2.8% showed loss of all nine hprt exons (total gene deletion). Exposure to 6 Gy of gamma rays, which reduced survival levels to 10%, produced a significantly different deletion spectrum that was shifted toward deletions with 45% of the 20 mutants analyzed showing a loss of a single exon and 30% showing a loss of all nine exons. Exposure to 2 Gy alpha radiation from 212Bi, a 220Rn daughter, a dose which also reduced survival levels to about 10%, resulted in a deletion spectrum similar to the gamma-ray spectrum in that more than 75% of the 49 mutants analyzed were deletions. The alpha spectrum, however, was significantly different from both the spontaneous and gamma spectra with 55.1% of the alpha mutants showing a loss of all nine exons, 10.2% showing loss of a single exon, and 14.3% showing loss of 2-8 exons. Thus, alpha-radiation appears to produce larger intragenic deletions than gamma radiation. The results suggest that intragenic deletion size should be considered when low- and high linear energy transfer (LET) mutation spectra are compared.
Center for Mechanistic Biology and Biotechnology, Argonne National Laboratory, IL 60439-4833.
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Schwartz
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Rotmensch
J
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Sun
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An
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Xu
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Yu
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Hsie
D000512:Alpha Particles; D000818:Animals; D001483:Base Sequence; D001729:Bismuth; D016466:CHO Cells / Q000528:radiation effects*; D003037:Cobalt Radioisotopes; D006224:Cricetinae; D005091:Exons / Q000528:radiation effects; D005720:Gamma Rays; D005787:Gene Frequency; D007041:Hypoxanthine Phosphoribosyltransferase / Q000235:genetics* / Q000528:radiation effects*; D009154:Mutation; D016133:Polymerase Chain Reaction / Q000379:methods*; D011868:Radioisotopes; D017384:Sequence Deletion
D003037:Cobalt Radioisotopes; D011868:Radioisotopes; D007041:Hypoxanthine Phosphoribosyltransferase; D001729:Bismuth