Complex hprt deletion events are recovered after exposure of human lymphoblastoid cells to high-LET carbon and neon ion beams

Abstract

Hypoxanthine phosphoribosyltransferase gene (hprt) mutations were induced in human TK-6 lymphoblastoid cells by irradiation at a linear energy transfer (LET) of 250 or 310 keV/µm for carbon and neon ions, respectively. At such a high level of LET, ions will lose most of their total energy and stop shortly after passing through the cell. The hprt mutations were analyzed by multiplex PCR, long-PCR and DNA sequencing of both genomic and cDNA. Over half of the C ion-induced hprt mutations (10 of 19) were point mutations, in contrast to 15% of the mutations induced by Ne ions (three of 20). The remaining 47 and 85% of the C and Ne ion-induced mutants, respectively, are deletion events. The latter events include three complex losses of multiple non-contiguous exon regions in both ion irradiation collections. We note that mutations involving the exon 6 region are frequent in the Ne ion collection: all three of the complex events retained the exon 6 region with flanking deletion of sequence and three other mutants involved deletion of this region. It may be concluded that these high-LET C and Ne ion irradiations produce different mutational spectra.

Clustered DNA lesion repair in eukaryotes: Relevance to mutagenesis and cell survival

“…In most cellular systems examined but not all, high LET radiation is observed to generate larger deletions (over Mbp size). A high frequency of complex deletion events and complex rearrangements at deletion junctions have been observed with high LET radiation and have not been reported for low LET radiation [98–100]. An elevated mutation burden was maintained in kidney epithelium of mice exposed to high energy iron ion [101].…”

Heavy‐ion‐induced mutations in the gpt delta transgenic mouse: Effect of p53 gene knockout

“…We have extensively investigated the effects of exposure to heavy-ions, such as C-, Ne-, and Fe-ions accelerated by the RIKEN Ring Cyclotron, on cultured human cells [Suzuki et al, , 1997Kagawa et al, 1999]. Both the time-course of p53 induction and the cell-cycle progression pattern in the human lymphoblastoid cell line TK6 were measured after 135 MeV/u C-ion exposure and were found to be different from those after exposure to X-rays and 95 MeV/u Fe-ions [Morimoto et al, 2001].…”

X-Ray Induced Mutation Frequency at the <i>Hypoxanthine Phosphoribosyltransferase</i> Locus in Clinically Relevant Radioresistant Cells

“…All of the exonic regions of the HPRT locus excluding exon 1 were amplified by multiplex PCR. The PCR conditions and primer sequences were essentially as the same as the methods described by Kagawa et al [26]. Ex Taq DNA polymerase was used to amplify the genomic DNA (Takara Bio Inc., Shiga, Japan).…”