Nature of mutation in the humanhprt gene following in vivo exposure to ionizing radiation of cesium-137

Abstract

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 (χ2 = 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. Environ. Mol. Mutagen. 30:385–395, 1997 © 1997 Wiley‐Liss, Inc.

Genotoxicity of Therapeutic Intervention in Children with Acute Lymphocytic Leukemia

“…In addition, the HPRT gene is an excellent biomarker of effect because mutations at the HPRT locus have no direct clinical consequences and have been shown to reflect genome-wide mutational events (13,14). This approach for somatic mutation analysis in humans has been widely used to determine in vivo background as well as acquired somatic cell Mfs in pediatric and adult populations exposed to known and unknown environmental mutagens (15)(16)(17)(18)(19)(20)(21).…”

Homologous recombination between HERVs causes duplications in the AZFa region of men accidentally exposed to cesium-137 in Goiânia

“…Cellular exposure to ionizing radiation induces a genotoxicity stress in cells that could result in damage of their genetic material. A 3-year follow-up study of the population accidentally exposed to high doses of ionizing radiation found 40% of missense mutations involving A:T pairs (da Cruz and Glickman, 1997;. Recently, our group surveyed the genetic variation of 12 microsatellite loci in 10 families of exposed individuals and their offspring and the mutation rate was found to be higher in the exposed families compared to the control group (da Cruz et al, 2008).…”

7,12-dimethylbenz[a]anthracene-induced mutation in theTk gene ofTk+/? mice: Automated scoring of lymphocyte clones using a fluorescent viability indicator

“…The models using the endogenous X-linked hypoxanthine guanine phosphoribosyl transferase (hprt) gene of rodent lymphocytes as a target [Jones et al, 1985;Aidoo et al, 1997] theoretically can detect a wider range of mutations. In practice, most 6-thioguanine (6-TG)-resistant lymphocyte clones characterized at the molecular level contain only intragenic alterations in the hprt gene [Skopek et al, 1992;Mittelstaedt et al, 1995;Heflich et al, 1996;da Cruz and Glickman, 1997]. It is believed that there is a gene flanking the hprt gene that is necessary for cell survival, so that large deletions affecting this important gene cannot be recovered as hprt mutants.…”