Unearthing who and Y at Harewood Cemetery and inference of George Washington's Y-chromosomal haplotype.

An excavation conducted at Harewood Cemetery to identify the unmarked grave of Samuel Washington resulted in the discovery of burials presumably belonging to George Washington's paternal grandnephews and their mother, Lucy Payne. To confirm their identities this study examined Y-chromosomal, mitochondrial, and autosomal DNA from the burials and a living Washington descendant. The burial's Y-STR profile was compared to FamilyTreeDNA's database, which resulted in a one-step difference from the living descendant and an exact match to another Washington. A more complete Y-STR and Y-SNP profile from the descendant was inferred to be the Washington Y profile. Kinship comparisons performed in relation to the descendant, who is a 4th and 5th degree relative of the putative individuals, resulted in >37,000 overlapping autosomal SNPs and strong statistical support with likelihood ratios exceeding one billion. This study highlights the benefits of a multi-marker approach for kinship prediction and DNA-assisted identification of historical remains.

Impact of SNP microarray analysis of compromised DNA on kinship classification success in the context of investigative genetic genealogy.

Single nucleotide polymorphism (SNP) data generated with microarray technologies have been used to solve murder cases via investigative leads obtained from identifying relatives of the unknown perpetrator included in accessible genomic databases, an approach referred to as investigative genetic genealogy (IGG). However, SNP microarrays were developed for relatively high input DNA quantity and quality, while DNA typically obtainable from crime scene stains is of low DNA quantity and quality, and SNP microarray data obtained from compromised DNA are largely missing. By applying the Illumina Global Screening Array (GSA) to 264 DNA samples with systematically altered quantity and quality, we empirically tested the impact of SNP microarray analysis of compromised DNA on kinship classification success, as relevant in IGG. Reference data from manufacturer-recommended input DNA quality and quantity were used to estimate genotype accuracy in the compromised DNA samples and for simulating data of different degree relatives. Although stepwise decrease of input DNA amount from 200 ng to 6.25 pg led to decreased SNP call rates and increased genotyping errors, kinship classification success did not decrease down to 250 pg for siblings and 1st cousins, 1 ng for 2nd cousins, while at 25 pg and below kinship classification success was zero. Stepwise decrease of input DNA quality via increased DNA fragmentation resulted in the decrease of genotyping accuracy as well as kinship classification success, which went down to zero at the average DNA fragment size of 150 base pairs. Combining decreased DNA quantity and quality in mock casework and skeletal samples further highlighted possibilities and limitations. Overall, GSA analysis achieved maximal kinship classification success from 800 to 200 times lower input DNA quantities than manufacturer-recommended, although DNA quality plays a key role too, while compromised DNA produced false negative kinship classifications rather than false positive ones.

Evidence for multi-copy Mega-NUMTs in the human genome.

The maternal mode of mitochondrial DNA (mtDNA) inheritance is central to human genetics. Recently, evidence for bi-parental inheritance of mtDNA was claimed for individuals of three pedigrees that suffered mitochondrial disorders. We sequenced mtDNA using both direct Sanger and Massively Parallel Sequencing in several tissues of eleven maternally related and other affiliated healthy individuals of a family pedigree and observed mixed mitotypes in eight individuals. Cells without nuclear DNA, i.e. thrombocytes and hair shafts, only showed the mitotype of haplogroup (hg) V. Skin biopsies were prepared to generate ρ° cells void of mtDNA, sequencing of which resulted in a hg U4c1 mitotype. The position of the Mega-NUMT sequence was determined by fluorescence in situ hybridization and two different quantitative PCR assays were used to determine the number of contributing mtDNA copies. Thus, evidence for the presence of repetitive, full mitogenome Mega-NUMTs matching haplogroup U4c1 in various tissues of eight maternally related individuals was provided. Multi-copy Mega-NUMTs mimic mixtures of mtDNA that cannot be experimentally avoided and thus may appear in diverse fields of mtDNA research and diagnostics. We demonstrate that hair shaft mtDNA sequencing provides a simple but reliable approach to exclude NUMTs as source of misleading results.

Challenges with co-amplification of microbial DNA in interpretation of STR profiles obtained from human skeletal remains.

STR-based DNA analysis is still the main tool for human DNA identification in most forensic DNA laboratories. DNA typing of aged human skeletal elements faces well-known interpretation challenges characteristic of degraded and low copy number DNA samples. Analyzing tens of thousands of human bone and teeth samples, we found that the occasional presence of artefactual peaks of presumed microbial origin adds another layer of complexity to the interpretation of STR profiles. In this paper, we present our approach and suggest guidelines for identifying and distinguishing non-human peaks, developed over the last 18 years. Additionally, we report a compendium of artefact peaks of presumed microbial origin recorded in human STR profiles obtained from bone and teeth samples, originating from Iraq, Chile, Maldives, Brazil and Western Balkans. Our experience has shown that these artefacts are not uncommon in bone STR testing, suggesting the possibility of occurrence in other forensic contexts, particularly trace DNA samples. Raising awareness among the forensic DNA community and accounting for this phenomenon is important for accurate STR interpretation.

Impact of DNA degradation on massively parallel sequencing-based autosomal STR, iiSNP, and mitochondrial DNA typing systems.

Biological samples, including skeletal remains exposed to environmental insults for extended periods of time, exhibit increasing levels of DNA damage and fragmentation. Human forensic identification methods typically use a combination of mitochondrial (mt) DNA sequencing and short tandem repeat (STR) analysis, which target segments of DNA ranging from 80 to 500 base pairs (bps). Larger templates are often unavailable as skeletal samples age and the associated DNA degrades. Single-nucleotide polymorphism (SNP) loci target shorter templates and may serve as a solution to the problem. Recently developed assays for STR and SNP analysis using a massively parallel sequencing approach, such as the ForenSeq kit (Verogen, San Diego, CA), offer a means for generating results from degraded samples as they target templates down to 60 to 170 bps. We performed a modeling study that demonstrates that SNPs can increase the significance of an identification when analyzing DNA down to an average size of 100 bps for input amounts between 0.375 and 1 ng of nuclear DNA. Observations from this study were then compared with human skeletal material results (n = 14, ninth to eighteenth centuries), which further demonstrated the utility of the ForenSeq kit for degraded samples. The robustness of the Promega PowerSeq™ Mito System was also tested with human skeletal remains (n = 70, ninth to eighteenth centuries), resulting in successful coverage of 99.29% of the mtDNA control region at 50× coverage or more. This was accompanied by modifications to a mainstream DNA extraction technique for skeletal remains that improved recovery of shorter templates.

Large scale DNA identification: The ICMP experience.

The International Commission on Missing Persons (ICMP) is a treaty-based international organization with a global mandate to address the issue of missing persons. It works with governments, civil society organizations, and others, and utilizes data systems and technical assistance in forensic science. ICMP's initial work focused on the ∼40,000 people missing in the Western Balkans from the conflicts of the 1990s. A "DNA-led" approach to large-scale DNA identification of the missing was developed, based on high-throughput autosomal STR testing of skeletal remains from mass graves and other sites, and the establishment of a regional database of DNA profiles from family members of the missing. Database pairwise and pedigree kinship searching is conducted using in-house DNA matching software, the Identification Data Management System (iDMS), providing high-certainty DNA matches that are integrated in a multi-disciplinary identification process. Anthropological guidelines for sampling skeletal remains for DNA testing are based on tens of thousands of tests from a wide range of skeletal elements, allowing for prioritization based on DNA preservation. Large-scale collection of family reference samples has been conducted, resulting in a database of more than 100,000 family reference DNA profiles across all projects and delivering family DNA match reports for more than 20,000 individuals. From the 1995 Srebrenica event, ICMP provided DNA matches for 6887 of the ∼8000 missing from that event. In assistance to justice, ICMP has provided extensive evidence and expert testimony in multiple war crimes trials, including those conducted at the ICTY. This article provides an overview of ICMP's technical involvement over the last 17 years in areas of DNA testing and database matching, and training and capacity building projects with partners. It also touches on the development of massively parallel sequencing (MPS) strategies specifically tailored to missing persons applications.

An economical and efficient method for postmortem DNA sampling in mass fatalities.

In mass fatality events, the need to identify large numbers of deceased persons using DNA can be a significant drain on already overburdened forensic practitioners, both in the field setting and the laboratory. The laboratory may be required to extract DNA from a variety of postmortem sample types, family or direct reference samples related to the missing, and perform matching of these results in a short period of time. While most forensic institutions are well equipped to handle both family and direct reference samples, postmortem samples such as bone or heterogeneous tissue samples can be difficult for labs to analyze. We have devised an easily deployable, efficient, and inexpensive method for collecting postmortem DNA samples on commercially available DNA preservation cards ("FTA®" cards). FTA® cards are already widely used in forensic labs and are convenient for shipping due to their small volume and stability at room temperature. We evaluated the suitability of a protocol involving swabbing of incisions made on cadavers and sample deposition onto FTA® cards over various postmortem intervals and under different environmental conditions. Each trial took place during a different point in the calendar year to evaluate the effects of seasonal weather patterns and temperature on decomposition, DNA yield, and rates of DNA degradation. To further account for the effects of seasonality (temperature and humidity), the progression of body decomposition was recorded following the Total Body Score (TBS) method [1]. DNA degradation was assessed either through STR amplification of 1.2 mm FTA punches or DNA extraction from 3.0 mm punches followed by real-time PCR quantification and STR amplification and genotyping. No consistent relationship was observed between postmortem interval and DNA degradation. Instead, the TBS score, which captures the stage of body decomposition, was shown to correlate well with DNA quantity. A TBS of 15 and below consistently yielded strong partial or full profiles (20 STR loci and Amelogenin using the PowerPlex 21 System) from all individuals from either 1.2 mm or 3.0 mm punches. Transfer of sample swabs to FTA cards is shown to be a simple and effective method for both field and laboratory operations over a range of conditions that can be evaluated by field forensic practitioners based on a body decomposition score. The approach could be beneficially integrated into mass fatality response plans.

Identification of Missing Norwegian World War II Soldiers, in Karelia Russia.

This article presents the multidisciplinary effort in trying to identify the skeletal remains of 100 Norwegian soldiers serving in the German army, killed in Karelia Russia in 1944, from the recovery of the remains through the final identification using DNA. Of the 150 bone samples sent for DNA testing, 93 DNA profiles were obtained relating to 57 unique individuals. The relatives could not be directly contacted as the soldiers were considered as traitors to Norway; therefore, only 45 reference samples, relating to 42 cases of the missing, were donated. DNA matches for 14 soldiers and 12 additional body part re-associations for these individuals were found. Another 24 bone samples were re-associated with 16 individuals, but no familial match was found. More than six decades after the end of WWII, DNA analysis can significantly contribute to the identification of the remains.

Characterization of mitochondrial DNA control region lineages in Iraq.

To evaluate the utility of mtDNA control region data for the purposes of forensic DNA testing in Iraq, a sample of 182 subjects (128 Arab Muslims, 15 Kurd Muslims, 22 Assyrian Christians and 17 Mandaean Arabs) was tested. High numbers of singleton haplotypes were observed among Arabs, Kurds and Assyrians, but fewer were found in Mandaeans. High molecular diversity and low random match probabilities confirmed the value of control region data in the investigation of maternal genetic lineages among the Iraqi population.

Characterization of a modified amplification approach for improved STR recovery from severely degraded skeletal elements.

Degraded skeletal remains generally contain limited quantities of genetic material and thus DNA-based identification efforts often target the mitochondrial DNA (mtDNA) control region due to the relative abundance of intact mtDNA as compared to nuclear DNA. In many missing person cases, however, the discriminatory power of mtDNA is inadequate to permit identification when associated anthropological, odontological, or contextual evidence is also limited, and/or the event involves a large number of individuals. In situations such as these, more aggressive amplification protocols which can permit recovery of STR data are badly needed as they may represent the last hope for conclusive identification. We have previously demonstrated the potential of a modified Promega PowerPlex 16 amplification strategy for the recovery of autosomal STR data from severely degraded skeletal elements. Here, we further characterize the results obtained under these modified parameters on a variety of sample types including pristine control DNA and representative case work specimens. Not only is the amplification approach evaluated here sensitive to extremely low authentic DNA input quantities (6 pg), but when the method was applied to thirty-one challenging casework specimens, nine or more alleles were reproducibly recovered from 69% of the samples tested. Moreover, when we independently considered bone samples extracted with a protocol that includes complete demineralization of the bone matrix, the percentage of samples yielding nine or more reproducible alleles increased to 95% with the modified amplification parameters. Overall, direct comparisons between the modified amplification protocol and the standard amplification protocol demonstrated that allele recovery was significantly greater using the aggressive parameters, with only a minimal associated increase in artifactual data.

Automatable full demineralization DNA extraction procedure from degraded skeletal remains.

During the 7 year period from 2002 to 2009 a high volume, silica-binding DNA extraction protocol for bone, based on modified QIAGEN's Blood Maxi Kit protocol was highly successful permitting the DNA matching of >14,500 missing persons from former Yugoslavia. This method, however, requires large amount of bone material and large volumes of reagents. The logical evolution was to develop a more efficient extraction protocol for bone samples that uses significantly less starting material while increasing the success in obtaining DNA results from smaller, more challenging samples. In this study we compared the performance of ICMP's original protocol against an automatable full demineralization approach. In order to provide reliable results and to simulate a wide variety of cases, we analyzed 40 bone samples in a comparative study based on DNA concentrations and quality of resulting STR profiles. The new protocol results in the dissolution of the entire bone powder sample, thus eliminating the possibility that DNA is left behind, locked in remaining solid bone matrix. For the majority of samples tested, the DNA concentrations obtained from half a gram of fully digested bone material were equivalent to or greater than the ones obtained from 2g of partially demineralized bone powder. Furthermore, the full demineralization process significantly increases the proportion of full profiles reflecting the correlation with better DNA quality. This method has been adapted for the QIAcube robotic platform. The performance of this automated full demineralization protocol is similar to the manual version and increases overall lab throughput. It also simplifies the process by eliminating quality control procedures that are advisable in manual procedures, and overall reduces the chance of human error. Finally we described a simple and efficient post-extraction clean-up method that can be applied to DNA extracts obtained from different protocols. This protocol has also been adjusted for the QIAcube platform.

Assessing a novel room temperature DNA storage medium for forensic biological samples.

The ability to properly collect, analyze and preserve biological stains is important to preserving the integrity of forensic evidence. Stabilization of intact biological evidence in cells and the DNA extracts from them is particularly important since testing is generally not performed immediately following collection. Furthermore, retesting of stored DNA samples may be needed in casework for replicate testing, confirmation of results, and to accommodate future testing with new technologies. A novel room temperature DNA storage medium, SampleMatrix™ (SM; Biomatrica, Inc., San Diego, CA), was evaluated for stabilizing and protecting samples. Human genomic DNA samples at varying amounts (0.0625-200 ng) were stored dry in SM for 1 day to 1 year under varying conditions that included a typical ambient laboratory environment and also through successive freeze-thaw cycles (3 cycles). In addition, spiking of 1-4 × SM into samples prior to analysis was performed to determine any inhibitory effects of SM. Quantification of recovered DNA following storage was determined by quantitative PCR or by agarose gel electrophoresis, and evaluation of quantitative peak height results from multiplex short tandem repeat (STR) analyses were performed to assess the efficacy of SM for preserving DNA. Results indicate no substantial differences between the quality of samples stored frozen in liquid and those samples maintained dry at ambient temperatures protected in SM. For long-term storage and the storage of low concentration samples, SM provided a significant advantage over freezer storage through higher DNA recovery. No detectable inhibition of amplification was observed at the recommended SM concentration and complete profiles were obtained from genomic DNA samples even in the presence of higher than recommended concentrations of the SM storage medium. The ability to stabilize and protect DNA from degradation at ambient temperatures for extended time periods could have tremendous impact in simplifying and improving sample storage conditions and requirements. The current work focuses on forensics analysis; however this technology is applicable to all endeavors requiring storage of DNA.

DNA extraction from aged skeletal samples for STR typing by capillary electrophoresis.

STR analysis of DNA extracted from skeletal samples can play an important role in the identification of missing persons. Here we present a method for the extraction of DNA from skeletal samples involving complete demineralization and digestion of the sample, followed by purification by silica binding. This method, together with the multiplex STR typing approach also presented, has proven highly successful in the recovery of DNA profiles from degraded, aged skeletal remains from a wide range of environmental contexts. The methodological steps presented include bone decontamination and grinding, DNA extraction, repurification in the case of highly inhibited samples, quantification, STR multiplex amplification, and profile reporting guidelines. However, the conditions applied for amplification and the criteria for allele calling and profile submission must be based on the results of each laboratory's internal validation experiments involving the type of samples relevant to the project at hand. The methods presented here have permitted large-scale DNA-based identification of persons missing from mass disasters and armed conflict.

The mtDNA composition of Uzbekistan: a microcosm of Central Asian patterns.

In order to better characterize and understand the mtDNA population genetics of Central Asia, the mtDNA control regions of over 1,500 individuals from Uzbekistan have been sequenced. Although all samples were obtained from individuals residing in Uzbekistan, individuals with direct ancestry from neighboring Central Asian countries are included. Individuals of Uzbek ancestry represent five distinct geographic regions of Uzbekistan: Fergana, Karakalpakstan, Khorezm, Qashkadarya, and Tashkent. Individuals with direct ancestry in nearby countries originate from Kazakhstan, Kyrgyzstan, Russia, Afghanistan, Turkmenistan, and Tajikistan. Our data reinforce the evidence of distinct clinal patterns that have been described among Central Asian populations with classical, mtDNA, and Y-chromosomal markers. Our data also reveal hallmarks of recent demographic events. Despite their current close geographic proximity, the populations with ancestry in neighboring countries show little sign of admixture and retain the primary mtDNA patterns of their source populations. The genetic distances and haplogroup distributions among the ethnic populations are more indicative of a broad east-west cline among their source populations than of their relatively small geographic distances from one another in Uzbekistan. Given the significant mtDNA heterogeneity detected, our results emphasize the need for heightened caution in the forensic interpretation of mtDNA data in regions as historically rich and genetically diverse as Central Asia.

Mitochondrial control region sequences from an African American population sample.

Entire mitochondrial control region data were generated for 248 African American individuals, which had been previously typed for 15 autosomal STRs [J.M. Butler, R. Schoske, P.M. Vallone, J.W. Redman, M.C. Kline, Allele frequencies for 15 autosomal STR loci on U.S. Caucasian, African American, and Hispanic populations, J. Forensic Sci. 48 (2003) 908-911].

Mitochondrial DNA control region variation in a population sample from Hong Kong, China.

Entire mitochondrial control region sequences were generated from 377 unrelated individuals from urban Hong Kong. In line with other control region datasets from China, the sample from Hong Kong exhibited significant genetic diversity that was reflected in a random match probability of 0.19% and a mean pairwise difference of 13.14. A total of 305 haplotypes were identified, of which 262 were unique. These sequences will be made publicly available to serve as forensic mtDNA reference data for China.

The use of mitochondrial DNA single nucleotide polymorphisms to assist in the resolution of three challenging forensic cases.

Mitochondrial DNA (mtDNA) single nucleotide polymorphisms (SNPs) in an 11-plex assay were typed in three missing person cases involving highly degraded human remains. Unlike the traditional forensic approach to analyzing mtDNA which focuses on sequencing portions of the noncoding Control Region, this assay targets discriminatory SNPs that reside principally in the coding region. In two of the cases, the SNP typing successfully excluded one of two reference families that could not be excluded on the basis of mtDNA hypervariable region sequencing alone, and resulted in the final resolution of both decades-old cases. In a third case, SNP typing confirmed the sorting and reassociation of multiple commingled skeletal elements. The application of a specific mtDNA SNP assay in these cases demonstrates its utility in distinguishing samples when the most common Caucasian hypervariable region type is encountered in forensic casework.

Investigation of heteroplasmy in the human mitochondrial DNA control region: a synthesis of observations from more than 5000 global population samples.

Instances of point and length heteroplasmy in the mitochondrial DNA control region were compiled and analyzed from over 5,000 global human population samples. These data represent observations from a large and broad population sample, representing nearly 20 global populations. As expected, length heteroplasmy was frequently observed in the HVI, HVII and HVIII C-stretches. Length heteroplasmy was also observed in the AC dinucleotide repeat region, as well as other locations. Point heteroplasmy was detected in approximately 6% of all samples, and while the vast majority of heteroplasmic samples comprised two molecules differing at a single position, samples exhibiting two and three mixed positions were also observed in this data set. In general, the sites at which heteroplasmy was most commonly observed correlated with reported control region mutational hotspots. However, for some sites, observations of heteroplasmy did not mirror established mutation rate data, suggesting the action of other mechanisms, both selective and neutral. Interestingly, these data indicate that the frequency of heteroplasmy differs between particular populations, perhaps reflecting variable mutation rates among different mtDNA lineages and/or artifacts of particular population groups. The results presented here contribute to our general understanding of mitochondrial DNA control region heteroplasmy and provide additional empirical information on the mechanisms contributing to mtDNA control region mutation and evolution.