Nature of mutation in the human hprt gene following in vivo exposure to ionizing radiation of cesium-137.
The current study comprises the analysis of mutations in 10 individuals accidentally exposed to cesium-137 during the 1987 radiological accident in Goiânia, Brazil. Their exposures were among the highest experienced, ranging from 1 to 7 Gy. Peripheral T-lymphocyte samples were obtained 3.3 years after the original exposure and mutation was studied at the hprt locus using the 6-thioguanine-resistance selection assay. The mutational spectrum for the exposed population is comprised of 90 independent mutants. Based on T-cell receptor analysis, only 5% (5/95) were clonally related. Mutants were initially studied using RT-PCR and directly sequenced using an automated laser fluorescent DNA sequencer. Mutants that repeatedly failed to produce cDNAs were studied using a multiplex PCR assay with genomic DNA. Missense mutations were the most frequent event recovered, comprising 40% (23/57) of the spectral sample. An excess of events involving A:T base pairs was observed, exhibiting a significant difference (chi 2 = 12.7, P = 0.0004) when compared to the spontaneous spectrum. This finding may reflect the effect of ionizing radiation-induced damage, suggesting a potential similarity to radiation effects in prokaryotes. At the genomic level, 36.7% (33/90) of the mutants exhibited gross structural alterations, as detected by multiplex PCR. Deletion events were over-represented in our spectral sample, displaying a twofold increase when compared to the frequency observed in the spontaneous mutation database.
da Cruz
A D
AD
Department of Biology, University of Victoria, B.C., Canada.
Glickman
B W
BW
D000293:Adolescent; D000328:Adult; D001938:Brazil; D002588:Cesium Radioisotopes / Q000009:adverse effects*; D002648:Child; D002675:Child, Preschool; D004252:DNA Mutational Analysis; D005091:Exons / Q000235:genetics; D005260:Female; D016368:Frameshift Mutation; D017353:Gene Deletion; D006801:Humans; D007041:Hypoxanthine Phosphoribosyltransferase / Q000235:genetics / Q000528:radiation effects*; D008297:Male; D008875:Middle Aged; D016254:Mutagenesis, Insertional; D009154:Mutation; D017354:Point Mutation; D016133:Polymerase Chain Reaction / Q000379:methods; D018788:Radioactive Hazard Release; D011948:Receptors, Antigen, T-Cell / Q000235:genetics / Q000528:radiation effects; D017384:Sequence Deletion; D013601:T-Lymphocytes / Q000201:enzymology / Q000528:radiation effects*
D002588:Cesium Radioisotopes; D011948:Receptors, Antigen, T-Cell; D007041:Hypoxanthine Phosphoribosyltransferase