PowerPlex® ESX and ESI Systems: A suite of new STR systems designed to meet the changing needs of the DNA-typing community
Received 13 August 2009; accepted 14 August 2009. published online 16 October 2009.
Abstract
With over 6 million profiles currently stored in European databases and the number expected to increase with cross-border data sharing, the likelihood of random matches will undoubtedly increase as well. To improve the overall power of discrimination as well as provide standardization across Europe, the ENFSI and EDNAP committees have made a recommendation to extend the current European Standard Set (ESS) for STR systems. The five-color PowerPlex® ESX and ESI Systems allow co-amplification and detection of the current commonly tested loci, plus the five new recommended loci. These kits will be offered in multiple formats, including one to detect SE33, to accommodate various requirements or preferences. Additionally, the kits have increased tolerance to common inhibitors and increased sensitivity to obtain full profiles from low-level DNA, and are robust enough to genotype degraded DNA samples through the use of mini STR loci. In this manuscript we present an overview of these systems and data on performance, including sensitivity and resistance to inhibitors. The PowerPlex® ESX and ESI Systems are useful tools in database sharing and standardization throughout Europe.
DNA database content and information sharing across European countries are expected to grow at a rapid pace, mainly in response to the Treaty of Prüm. To minimize random matches and add uniformity to submitted data, the ENFSI and EDNAP have made a recommendation to extend the loci included in the current European Standard Set. Since a large percentage of casework samples include minimal amounts of DNA or degraded DNA, the recommendation requires the inclusion of mini STR loci (i.e., amplicon sizes of 150bp or less).
The PowerPlex® ESX and ESI Systems were developed to align with these recommendations. They allow co-amplification and four-color detection of the following loci: D2S441, D10S1248, D22S1045, D12S391, D1S1656, D2S1338, D16S539, D3S1358, D18S51, D8S1179, D19S433, D21S11, TH01, vWA, FGA and Amelogenin, with or without SE33. The new Internal Lane Standard is labeled with a proprietary fifth dye. To meet varying customer and country requirements, multiple configurations are available (Fig. 1).
Fig. 1. Configuration of PowerPlex® ESX and ESI Systems with SE33 locus. The PowerPlex® ESX configuration includes the five new loci as mini STRs while the PowerPlex® ESI configuration includes the standard European loci as mini STRs.
2. Discussion
Samples collected for analysis come in a wide variety of types and quality. Hence it is important for an STR analysis kit to provide a robust and sensitive solution to generate the best possible results from these challenging samples. The PowerPlex® ESX and ESI Systems have been tested for sensitivity and robustness by amplifying DNA in the presence of increasing amounts of common inhibitors such as hematin, humic acid and tannic acid. The results show that at levels as low as 60pg of input DNA, a full profile can still be obtained with peak heights well above the 50 RFU cutoff (data not shown). The inhibitor study results are shown in Fig. 2.
Fig. 2. Performance in the presence of common inhibitors. Amplifications of 0.5ng of genomic DNA were performed using the PowerPlex® ESX 17 System in the presence of 300μM hematin (panel A), 60ng/μl humic acid (panel B) and 200ng/μl tannic acid (panel C).
Since different kits have been used to build databases, it is important to show concordance of the new kits with currently available kits. Concordance studies were performed at the National Institute for Standards and Technology and included 1461 samples. The kits compared were PowerPlex® ESX and ESI Systems, PowerPlex® ES, AmpFlSTR® Identifiler® (Applied BioSystems) and the NC01 panel (NIST). The results are summarized in Table 1. As the primer sequences in the Identifiler® System are identical to those used in AmpFlSTR® SGM+ and SEfiler™ Plus for the same loci, the concordance results can be extrapolated to these kits.
After addition of add-in primer to account for a G to T SNP in primer binding site at D22S1045 locus in PowerPlex® ESX configuration. This SNP was seen in four samples.
3. Conclusion
The PowerPlex® ESX and ESI Systems were developed to meet the latest recommendations by the ENFSI and EDNAP committees. To meet the different needs of European countries, the systems come in two different configurations, each configuration with and without the SE33 locus. The sensitivity, tolerance to inhibitors and use of mini STRs make these kits well-suited for challenging casework samples. Studies show concordance rates of greater than 99.5% with other commercially available kits.
Conflict of interest
None.
Funding
All research and development for these kits are funded by Promega Corporation. The authors of this paper are employees of Promega Corporation.
Acknowledgments
The authors would like to thank John Butler, Becky Hill and Margaret Kline from NIST for their help with the concordance studies.
Promega Corporation, 2800 Woods Hollow Rd., Madison, WI 53711, United States
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