Volume 2, Issue 1 , Pages 10-11, December 2009
Effect of low-dose radiation on mutation rates of STR loci commonly used in forensic casework
Article Outline
- Abstract
- 1. Introduction
- 2. Materials and methods
- 3. Results
- 4. Conclusion
- The role of the funding source
- Conflict of interest
- Acknowledgments
- References
- Copyright
Abstract
The possible effect of low-dose radiation on STR markers in people exposed to radiation during their professional activities was estimated in this study. We evaluated mutation rates in 17 forensic STR loci typed by the COrDIS-18 kit (CSF1PO, D10S1248, D12S391, D13S317, D16S539, D18S51, D21S11, D2S441, D3S1358, D5S818, D7S820, D8S1179, FGA, SE33, TH01, TPOX, and vWA) in 78 families (father–mother–child) with one parent exposed to low-dose radiation before fertilization. Five mutations were observed. In two cases, the new alleles were delivered from the non-exposed parent. The calculated mutation rate for the 17 studied STR loci in families appeared to be in good concordance with data published for normal populations. No evidence for an elevated mutation rate in STR markers after low-dose radiation was found.
Keywords: Short tandem repeat, Autosomal STR, Mutation rate, Allele frequencies
1. Introduction
Single-tube multiplex amplification of STRs has become a common approach in kinship analysis. Mutations are frequently observed when using a broad set of STR markers, but biostatistics can successfully handle these issues. Mutation rates of commonly used STR loci are well established for normal populations. However, there are a number of environmental risk factors and conditions that could potentially elevate germline mutation rates. Radiation is one such factor, previously reported as an inductor of minisatellite mutations [1]. We evaluated the mutation rates of 17 forensic STR loci in 78 families (father–mother–child) with one parent exposed to low-dose radiation.
2. Materials and methods
Blood samples were collected from 78 families, including 92 children (178 meioses). Two groups of families were included in the study. One group consisted of 55 families from Sarov City (Nizhni Novgorod region, Russia), with one member exposed to the chronic ß-radiation of tritium at a manufacturing site. The average time of exposure before fertilization was 7 years. The average radiation dose was below 20
cS per year. The other studied group included 23 families from the Ivanovo and Moscow regions with one member having worked within the 30-km control zone around the Chernobyl Nuclear Power Plant in 1986–1987, during and after the time of the disaster. The cumulative radiation dose in this group did not exceed 250cS.
DNA was extracted from blood samples using Diatom DNA prep (IsoGen Ltd., Russia). Single-tube multiplex amplification of 17 STR loci (plus Amelogenin) was performed using the recently developed 18-plex STR kit COrDIS-18 (GORDIZ Ltd./IsoGen Ltd., Russia), an “easy-to-handle”, ambient-temperature dry kit with all components provided in lyophilized form. COrDIS-18 combines the complete CODIS STR panel (CSF1PO, D13S317, D16S539, D18S51, D21S11, D3S1358, D5S818, D7S820, D8S1179, FGA, TH01, TPOX, and vWA) with four highly informative additional STR loci: D2S441, D10S1248, D12S391 and SE33. Allele identification was performed by capillary electrophoresis on an ABI 3130xl genetic analyzer (Fig. 1).
Fig. 1.
STR profile obtained with COrDIS-18 kit.
Identification of mutations was performed by a paternity calculation of obtained genotypes using GenoProof software version 1.3 (Qualitype, Germany). Inconsistencies in parent/child allelic transfers were interpreted as mutations. The parenthood was confirmed by a LR calculation, performed with inclusion of the mutation.
3. Results
The full profiles for 17 STR loci were obtained for the members of 78 families, including 150 parents and 92 children. This data set represents 178 meioses and 3204 parent/child allelic transfers. Five mutations were observed in four loci: D5S818, D7S820 and VWA, with one mutation per locus, and two mutations in the FGA locus. In all families with observed mutations, the parenthood was shown by a high probability >99.9% (calculated including the mutations). Three mutations had paternal origin, and two had maternal origin. Maternal mutations could not be linked to a low-dose effect since only the fathers were exposed to radiation.
The average mutation rate observed per locus was 0.17%, the same value as expected from the published data [2], [3]. The observed cumulative mutation rate for the 17 STR loci was 2.81% and did not exceed the expected value of 2.92% for the normal population based on the published data. Since published data on mutation rates for D10S1248 and D2S441 are not currently available, we used a value of 1.7×10−3, the average mutation rate of the remaining 15 loci, as the default rate in calculations for these loci.
4. Conclusion
No evidence was found for an elevated mutation rate in families with members exposed to low-dose radiation. In future studies, more loci should be included to obtain more statistically accurate results.
The role of the funding source
This wok was supported with Government funding.
Conflict of interest
None.
Acknowledgments
The authors thank ZAO SYNTOL for technical support. Part of this work was performed in the Center of Collective Use based at the All-Russia Research Institute of Agricultural Biotechnology (ARRIAB).
References
- . Elevated minisatellite mutation rate in the postchernobyl families from Ukraine. Am. J. Hum. Genet. 2002;71(October (4)):801–809
- . Mutation rate in human microsatellites: influence of the structure and length of the tandem repeat. Am. J. Hum. Genet. 1998;62(June (6)):1408–1415
- American Association of Blood Banks (AABB) (1992–2004). Annual Report Summary for Testing 1991–2003, AABB (typescripts), Bethesada MD.
PII: S1875-1768(09)00251-0
doi:10.1016/j.fsigss.2009.09.042
© 2009 Published by Elsevier Inc.
Volume 2, Issue 1 , Pages 10-11, December 2009
