Automated extraction of DNA and PCR setup using a Tecan Freedom EVO liquid handler

We have implemented and validated automated methods for DNA extraction and PCR setup developed for a Tecan Freedom EVO^® liquid handler mounted with a Te-MagS™ magnetic separation device. The DNA was extracted using the Qiagen MagAttract^® DNA Mini M48 kit. The DNA was amplified using AmpF?STR^® Identifiler^®, Y-filer^® (Applied Biosystems), GenePrint^® FFFL and PowerPlex^® Y (Promega). The methods were validated for fresh whole blood and blood from deceased according to EN/ISO 17025.     

Developmental validation of the PowerPlex ESX 16 and PowerPlex ESX 17 Systems

We describe the developmental validation study performed on the PowerPlex^® ESX 16 (European Standard Extended 16) and the PowerPlex^® ESX 17 Systems, part of a suite of four new DNA profiling kits developed by Promega in response to the ENFSI and EDNAP groups’ call for new STR multiplexes for Europe. The PowerPlex^® ESX 16 System combines the 11 loci compatible with the UK National DNA Database, contained within the AmpFlSTR^® SGM Plus^® PCR Amplification Kit, with five additional loci: D2S441, D10S1248, D22S1045, D1S1656 and D12S391. The multiplex was designed to incorporate these five new loci as mini- and midi-STRs while maintaining the loci found in the AmpFlSTR^® SGM Plus^® kit as standard size. The PowerPlex^® ESX 17 System amplifies the same loci as the PowerPlex^® ESX 16 System, but with the addition of a primer pair for the SE33 locus. Tests were designed to address the developmental validation guidelines issued by the Scientific Working Group on DNA Analysis Methods (SWGDAM), and those of the DNA Advisory Board (DAB). Samples processed include DNA mixtures, PCR reactions spiked with inhibitors, a sensitivity series, and 306 United Kingdom donor samples to determine concordance with data generated with the AmpFlSTR^® SGM Plus^® kit. Allele frequencies from 242 white Caucasian samples collected in the United Kingdom are also presented. The PowerPlex^® ESX 16 and ESX 17 Systems are robust and sensitive tools, suitable for the analysis of forensic DNA samples. Full profiles were routinely observed with 62.5 pg of a fully heterozygous single source DNA template. In mixture analysis, a range of 52-95% of unique minor contributor alleles was observed at 19:1 mixture ratios where only 25 pg of the minor component was present. Improved sensitivity combined with the robustness afforded by smaller amplicons has substantially improved the quantity of information obtained from degraded samples, and the improved chemistry confers exceptional tolerance to high levels of laboratory prepared inhibitors.     

Optimization and validation of a fast amplification protocol for AmpFlSTR Profiler Plus for rapid forensic human identification

The goal of this work was to optimize and validate a fast amplification protocol for the multiplex amplification of the STR loci included in AmpFlSTR^® Profiler Plus^® to expedite human DNA identification. By modifying the cycling conditions and by combining the use of a DNA polymerase optimized for high speed PCR (SpeedSTAR™ HS) and a more efficient thermal cycler instrument (Bio-RAD C1000™), we were able to reduce the amplification process from 4 h to 26 min. No modification to the commercial AmpFlSTR^® Profiler Plus^® primer mix was required. When compared to the current Royal Canadian Mounted Police (RCMP) amplification protocol, no differences with regards to specificity, sensitivity, heterozygote peak height ratios and overall profile balance were noted. Moreover, complete concordance was obtained with profiles previously generated with the standard amplification protocol and minor alleles in mixture samples were reliably typed. An increase in n − 4 stutter ratios (2.2% on average for all loci) was observed for profiles amplified with the fast protocol compared to the current procedure. Our results document the robustness of this rapid amplification protocol for STR profiling using the AmpFlSTR^® Profiler Plus^® primer set and demonstrate that comparable data can be obtained in substantially less time. This new approach could provide an alternative option to current multiplex STR typing amplification protocols in order to increase throughput or expedite time-sensitive cases.     

Evaluation of the Differex™ System

Differential extraction is an efficient method to separate sperm cells from epithelial cells. A manual Chelex^®-100 based method is used at the Swedish National Laboratory of Forensic Science, SKL. The Differex™ System (Promega) uses a Proteinase K digestion of epithelial cells followed by centrifugation and phase separation. The sperm- and epithelial fractions are further purified with DNA IQ™ System (Promega) or with phenol/chloroform. The Differex™ System in combination with DNA IQ™ System were evaluated and compared to the Chelex^®-100 method used routinely. After modifications, the Differex™ System gave comparable results to the Chelex^®-100 method. The modifications included additional Proteinase K and DTT, longer incubation time and additional steps when removing the solid support from the Digestion Solution. In the Chelex^®-100 based method microscopic examination is done on the sperm pellet in a total volume of 50 μl. It was not possible to do a microscopic examination in less than 100 μl using the Differex™ System. Additionally the sperms were in clusters of epithelial cell debris. Microscopic examination is an important part of the differential extraction at SKL. Therefore, the Differex™ System will not be implemented at our laboratory.     

A comparison of three automated DNA purification methods in Forensic casework

Manual Chelex^®-100 and organic extractions (phenol/chloroform) are used as routine methods at the Swedish National Laboratory of Forensic Science, SKL. The aim of this study was to find an automated DNA purification system to replace the organic method. The following methods were evaluated and compared to each other and to the organic method used routinely; BioRobot^® EZ1 with EZ1 DNA Investigator Kit and Card (Qiagen), iPrep™ Purification Instrument with iPrep™ ChargeSwitch^® Forensic Kit and Card (Invitrogen), Magnatrix™ 1200 Workstation with the Magnatrix™ gDNA Blood Kit Forensic and two different protocols; Forensic protocol A and B (Magnetic Biosolutions). Blood on fats, cotton swabs, moist snuff, paper towels and leather, post-mortem blood and muscle tissue were extracted with the different methods. DNA concentration and quality of the electropherograms were examined. Individual comparisons between the four extraction methods showed that iPrep™ and Magnatrix™ 1200 gave significantly lower mean quantities compared to BioRobot^® EZ1 and the organic extraction method (p < 0.05). There were no significant differences between the latter two. BioRobot^® EZ1 generated the best results and is in the process of being validated for routine analysis at SKL.     

Microgeographic variation of Y-chromosome haplotypes in Italy

Within an Italian collaborative exercise on the extended haplotype of the Y-chromosome, 1288 subjects were typed by the AmpFlSTR YFiler Amplification Kit (AB Applied Biosystems) and other 526 were typed by the PowerPlex Y^® System (Promega). The sampling scheme included either a “regional” or a “local” recruitment, the first referring to individuals born in the region of the participating lab, the second referring to individuals coming from small villages. Total sample sizes were N = 954 and 860, respectively. A significant decrease of haplotype diversity was found in the local samples. The results may be of interest in forensic applications of the Y-chromosome.     

Genetic characterization of a population from Cauca Department with 15 STRs markers

This study established allele frequencies and some parameters of forensic interest with 15 autosomal STRs markers in a sample of 172 unrelated individuals from the Department of Cauca – Colombia using the PowerPlex^® 16 BIO System (Promega CO) and Qiagen Multiplex PCR (Qiagen) kits. All markers analyzed showed more than 61% of heterozygosity. Penta E and Penta D were the only systems that are not in Hardy Weinberg equilibrium (p < 0.0033) after Bonferroni correction. The probabilities of paternity (W), the power of exclusion (PE) and of discrimination (PD) accumulated for all loci analyzed were 0.9999, 0.9999 and >0.9999, respectively. The parameters of forensic interest have values suitable for routine use in forensic genetics.     

PowerPlex 16 HS: Internal validation of a new tool for genetic analysis of forensic and parentage testing

Forensic human identification requires powerful and efficient tools to obtain useful results in a minimum timeframe. In this study several forensic and parentage samples that could not be analyzed with others kits were studied using the recently available PowerPlex^® 16 HS kit (Promega). DNA was extracted using four different methods, depending upon the particular sample, and the PCR products were run on an ABI 3130XL Sequencer. The resultant DNA profiles were analyzed using Gene Mapper ID v 3.2 Analysis Software (ABI). Of 30 samples processed with the PowerPlex^® 16 HS system, genetic analysis was successful in 18 (60%). The results obtained show that the PowerPlex^® 16 HS is a valuable tool for forensic identification and parentage testing that is particularly useful for difficult samples that have not yielded adequate results with other methods.     

Direct amplification of STRs from blood or buccal cell samples

Forensic databasing laboratories routinely analyze blood or buccal cell samples deposited on FTA^® paper. Prior to PCR amplification of the STRs, the FTA^® samples must undergo multi-step sample purification protocols to remove the PCR inhibitors present within the sample and from the FTA^® paper. The multi-step sample purification protocols are laborious, time-consuming and increase the potential for sample cross-contamination.To eliminate the need for DNA purification, we conducted studies to optimize the PCR buffer and thermal cycling parameters to allow for direct amplification of STRs from blood or buccal samples on FTA^® paper. We evaluated the effect of various factors on the DNA profile including: FTA^® disc size, blood sample load variation, and buffer formulation. The new STR assay enables the direct amplification of DNA from single source samples on FTA^® discs without sample purification. The new STR assay improves the workflow by eliminating tedious steps and minimizing sample handling. Furthermore, the new STR assay reduces cost by eliminating the need for purification reagents and expensive robots.     

Effect of blood stained soils and time period on DNA and allele drop out using Promega 16 Powerplex kit

Blood stained soils may be of great interest in forensic incidents. Amplification of DNA from soil is often inhibited by co-purified contaminants. Different soils types from Pakistan and Turkey were stained with blood and samples were collected systematically after specified intervals. Rapid, inexpensive, large-scale DNA extraction method involving minimal purification was developed. DNA was quantized using Spectrophotometer and Fluorometer and was confirmed by Agarose Gel Electrophoresis. DNA extracted from different soils in different periods showed a remarkable decrease in yield as well as degradation in every extraction. PCR amplification was performed using various DNA targets present in Promega 16 Powerplex^® System kit. Amplification could not carry out in all loci especially in degraded samples taken after 20 days. Allele n locus drop out was noticed which shows that DNA was degraded. For some loci more than 2 alleles were also noticed showing contamination while working with the blood stained soils.     

Analysis of forensic samples in Banco Nacional de Datos Genéticos

Analysis of forensic samples to evaluate the rate of success for molecular markers: autosomal STRs, Y chromosome, and mitochondrial DNA. Since 2006 to date a total of 390 forensic samples were analyzed: bones, teeth, hairs, swabs, stains and paraffin embedded tissue. Bones and teeth, were pulverized in a Freezer Mill, extracted by chloroform/phenol/isoamyl alcohol method, and then purified with Centricon 100 columns. DNA from paraffin was extracted with QIAmp DNA Mini kit (QIAGEN). Mitochondrial DNA Control Region sequences were determined for regions HV1/HV2. Sequencing was performed using the BigDye^® Terminator v 1.1 Kit and analyzed in ABIPRISM^® 3100 Genetic Analyzer (AB). STRs were amplified using Amp FlSTR Identifiler^®, Minifiler^® and YFiler^® Kit (AB) and analyzed in ABI PRISM^® 3100 Genetic Analyzer and ABI PRISM^® 3130xl Genetic Analyzer (AB). Among forensic samples, bones and teeth analyzed for autosomal STRs, we obtained successful results in all of them. Incomplete typing are represented by loci of higher molecular weight, which demonstrates the poor quality of the sample due to its state of degradation and obtained better results using mini STRs. Successful results in sequencing for mitochondrial HV1 region for all samples analyzed, but in few hair samples we obtained mixed sequences and that represented important difficulties for the analysis. Age of samples and conservation are factors related which affect DNA viability. Autosomal STRs solved all the samples analyzed in our study, but Y chromosome analysis and mitochondrial DNA sequencing are also important and necessary markers in some forensic cases.     

Evaluation of the PowerPlex Fusion System in a sample from East Timor

East Timor is a country located in Southeast Asia. In this study, we determined allele frequencies and forensic parameters for 24 STR autosomal loci included in the PowerPlex^® Fusion System. Autosomal STR data was collected from saliva samples of 100 individuals from East Timor. The amplification of the 24 autosomal STRs was performed using PowerPlex^® Fusion System (Promega Corporation) and the amplified products were analysed on 3500 Genetic Analyser using GeneMapper^® ID-X 1.2 Software (Applied Biosystems). All the analysed loci meet Hardy–Weinberg equilibrium after Bonferroni correction. In our samples, we found “off-ladder” alleles (D2S441, Penta E and FGA locus) confirmed by reamplification, amplification with others kits and sequenced when justified.     

Population genetics for Y-chromosomal STRs haplotypes of Chinese Tujia ethnic group

Allele and haplotype frequencies of 11 Y-chromosomal short tandem repeats (STRs) included in the PowerPlex^® Y Systems (Promega) were determined in a sample of 215 unrelated healthy male individuals of Chinese Tujia ethnic group living in Chongqing (Southwest of China). The gene diversity values of the Y-STRs loci ranged from 0.3757(DYS391) to 0.9170 (DYS385a/b). A total of 195 haplotypes were identified in the Y-STR loci, among which 180 were unique, 11 were found in two individuals, 3 were shared in three individuals and 1 was shared in four individuals. The observed haplotype diversity value and discrimination capacity were 0.9942 and 0.9070, respectively.     

Validation of the AmpF?STR SEfiler Plus™ PCR Amplification kit for forensic STR analysis

Validation of the AmpF?STR^® SEfiler Plus™ PCR Amplification kit with 29 and 30 PCR cycles for forensic STR analysis demonstrated that the kit had fewer artefacts than the AmpF?STR^® SGM Plus™ kit (28 PCR cycles). The SEfiler Plus kit was more sensitive and devoid of colour artefacts, but showed more stutters, drop-ins, drop-outs and allelic imbalances.     

The BodeChecks solution: A high throughput analysis software combining GeneMapper ID, FSS-i, LIMS, and artificial intelligence

Combining key attributes of GeneMapper^® ID and FSS-i³ software packages with our internally created LIMS and some additional analytical programming has permitted us to increase quality checks on DNA profile data review while eliminating analysis time.     

Developmental validation of the AmpF?STR SEfiler Plus™ PCR amplification kit: An improved multiplex with enhanced performance for inhibited samples

Since its introduction in 2002, the AmpF?STR^® SEfiler™ kit has provided a highly discriminating DNA profiling option to German forensic laboratories by combining the widely used SGM Plus^® Kit loci with the SE-33 locus required for the German DNA Database. Whilst proving successful on database samples, laboratories using the SEfiler™ kit have reported the need for chemistry better able to handle the ever-increasing number of casework samples.The new AmpF?STR^® SEfiler Plus™ kit contains the same loci and primer sequences as the SEfiler™ kit but uses improved synthesis and purification processes to minimize the presence of dye-labeled artifacts. Other improvements include modified PCR cycling conditions for enhanced sensitivity and a new buffer formulation that improves performance with inhibited samples when compared to the original SEfiler™ kit.Validation studies demonstrating the effectiveness of the multiplex are presented with emphasis on the models of inhibition and casework samples.     

An analysis of single and multi-copy methods for DNA quantitation by real-time polymerase chain reaction

The goal of this paper was to examine and compare two different commercially available approaches to the determination of the relative quantities of autosomal and Y chromosomal DNA using real-time PCR. One, Quantifiler^® Duo, utilizes a TaqMan^® assay with single copy probes for both autosomal human and Y quantification. The other method, Plexor HY^® utilizes a primer quenching assay with multi-copy probes for its quantification of autosomal human and Y chromosomal DNA. To test these approaches we have utilized the NIST Human DNA Quantitation Standard Reference Material 2372, a set of three different NIST human DNA quantification standards, to examine the precision, accuracy and sensitivity of the real-time PCR assays. We also examined data from both systems utilizing casework samples. The results show that both systems produced linear estimates for DNA quantity over a broad range of input DNA. However we did observe some apparent copy number effects when comparing the three different NIST standards which we attributed to issues with sequence variations in the different standards. Overall, the single copy approach provided better accuracy while the multi-copy approach produced better sensitivity. Thus the choice of which system to use should depend upon the goals of the user.     

Automated Quantifiler quantitative PCR setup, template normalization and PCR setup using HID EVOlution™ qPCR/STR setup on trace evidence samples

We have implemented and validated customized protocols for automated Quantifiler^® setup, template normalization and PCR setup using the Tecan HID EVOlution™ qPCR/STR setup. The protocols were validated for the Quantifiler^® human DNA quantification, AmpF?STR^® SGM Plus^® and SEfiler Plus™ PCR Amplification Kits (Applied Biosystems) according to EN/ISO 17025.     

Automated extraction of DNA from reference samples from various types of biological materials on the Qiagen BioRobot EZ1 Workstation

We have validated and implemented a protocol for DNA extraction from various types of biological materials using a Qiagen BioRobot EZ1 Workstation. The sample materials included whole blood, blood from deceased, buccal cells on Omni swabs and FTA Cards, blood on FTA Cards and cotton swabs, and muscle biopsies. The DNA extraction was validated according to EN/ISO 17025 for the STR kits AmpF?STR^® Identifiler^® and AmpF?STR^® Yfiler^® (Applied Biosystems). Of 298 samples extracted, 11 (4%) did not yield acceptable results. In conclusion, we have demonstrated that extraction of DNA from various types of biological material can be performed quickly and without the use of hazardous chemicals, and that the DNA may be successfully STR typed according to the requirements of forensic genetic investigations accredited according to EN/ISO 17025.