Underlying Data for Sequencing the Mitochondrial Genome with the Massively Parallel Sequencing Platform Ion Torrent™ PGM™

Developmental validation of the ForenSeq MainstAY kit, MiSeq FGx sequencing system and ForenSeq Universal Analysis Software

For human identification purposes, forensic genetics has primarily relied upon a core set of autosomal (and to a lesser extent Y chromosome) short tandem repeat (STR) markers that are enriched by amplification using the polymerase chain reaction (PCR) that are subsequently separated and detected using capillary electrophoresis (CE). While STR typing conducted in this manner is well-developed and robust, advances in molecular biology that have occurred over the last 15 years, in particular massively parallel sequencing (MPS) [1-7], offer certain advantages as compared to CE-based typing. First and foremost is the high throughput capacity of MPS. Current bench top high throughput sequencers enable larger batteries of markers to be multiplexed and multiple samples to be sequenced simultaneously (e.g., millions to billions of nucleotides can be sequenced in one run). Second, compared to the length-based CE approach, sequencing STRs increases discrimination power, enhances sensitivity of detection, reduces noise due to instrumentation, and improves mixture interpretation [4,8-23]. Third, since detection of STRs is based on sequence and not fluorescence, amplicons can be designed that are shorter in length and of similar lengths among loci, where possible, which can improve amplification efficiency and analysis of degraded samples. Lastly, MPS offers a single format approach that can be applied to analysis of a wide variety of genetic markers of forensic interest (e.g., STRs, mitochondrial DNA, single nucleotide polymorphisms, insertion/deletions). These features make MPS a desirable technology for casework [14,15,24,25-48]. The developmental validation of the ForenSeq MainstAY library preparation kit with the MiSeq FGx Sequencing System and ForenSeq Universal Software is reported here to assist with validation of this MPS system for casework [49]. The results show that the system is sensitive, accurate and precise, specific, and performs well with mixtures and mock case-type samples.

Genomic Insights into the Population History of the Resande or Swedish Travelers

The Resande are a minority ethnic group in Sweden, who were characterized by an itinerant way of life, and they have been suggested to originate from the mixture between Swedish and Romani populations. Because the population history of the Resande has been scarcely studied, we analyzed genome-wide genotype array data from unrelated Resande individuals in order to shed light on their origins and demographic history for the first time from a genetic perspective. Our results confirm the Romani-related ancestry of this population and suggest an admixture event between a Romani-like population and a general Swedish-like population that occurred approximately between the mid-18th and mid-19th centuries, two centuries after the arrival of the first historically reported Romani families in Sweden. This inferred date suggests that the Romani group involved in the admixture is related to the pre-18th-century arrivals of Romani in Scandinavia. In addition, a reduction in the population size is detected previous to the admixture event, suggesting a subtle signal of isolation. The present work constitutes a step forward toward a better representation of ethnic minorities and underrepresented groups in population genetic analyses. In order to know in more detail the complete history of human populations, it is time to focus on studying populations that have not been previously considered for a general scenario and that can provide valuable information to fill in the gaps that still remain uncovered.

Genetic Diversity Analysis of the Chinese Daur Ethnic Group in Heilongjiang Province by Complete Mitochondrial Genome Sequencing

Mitochondrial DNA (mtDNA) has the characteristics of maternal inheritance, high mutation rate, high copy number, and no recombination. As the most powerful tool for studying the origin and evolution of modern humans, mtDNA has great significance in the research of population genetics and evolutionary genetics. Here, we provide new insights into the maternal genetic history of the Daur ethnic group by generating complete mitochondrial genomes from a total of 146 Daur individuals in China. We also collected the published complete mitochondrial genome sequences of 5,094 individuals from 56 worldwide populations as reference data to further explore the matrilineal genetic landscape of the Daur ethnic group. First, the haplotype diversity was 0.9943 ± 0.0019 and nucleotide diversity was 0.0428 ± 0.0210. The neutrality tests of the Daur group showed significant negative values and the mismatch distribution curve was obviously distributed in a unimodal pattern. The results showed that the Daur ethnic group has high genetic diversity and may have experienced recent population expansion. In addition, the main haplogroups of the Daur population were haplogroup D (31.51%), M* (20.55%), C (10.28%), F (7.53%), and B (6.85%), all of which were prevalent in northern China. It probably implies the northern Chinese origin of the Daur population. The PCA, F_ST, and phylogenetic analysis results indicated that the Daur group formed a cluster with East Asian populations, and had few genetic differences with the populations in northern China. More importantly, we found that disease-related mutation sites of the mitochondrial genome may be related to ethnic groups, which may have important implications for the prevention and occurrence of specific diseases. Overall, this study revealed the complexity and diversity of the matrilineal genetic background of the Daur ethnic group. Meanwhile, it provided meaningful data for the research on the diversity of the human genome.

The genetic scenario of Mercheros: an under-represented group within the Iberian Peninsula

BACKGROUND

The general picture of human genetic variation has been vastly depicted in the last years, yet many populations remain broadly understudied. In this work, we analyze for the first time the Merchero population, a Spanish minority ethnic group that has been scarcely studied and historically persecuted. Mercheros have been roughly characterised by an itinerant history, common traditional occupations, and the usage of their own language.

RESULTS

Here, we examine the demographic history and genetic scenario of Mercheros, by using genome-wide array data, whole mitochondrial sequences, and Y chromosome STR markers from 25 individuals. These samples have been complemented with a wide-range of present-day populations from Western Eurasia and North Africa. Our results show that the genetic diversity of Mercheros is explained within the context of the Iberian Peninsula, evidencing a modest signal of Roma admixture. In addition, Mercheros present low genetic isolation and intrapopulation heterogeneity.

CONCLUSIONS

This study represents the first genetic characterisation of the Merchero population, depicting their fine-scale ancestry components and genetic scenario within the Iberian Peninsula. Since ethnicity is not only influenced by genetic ancestry but also cultural factors, other studies from multiple disciplines are needed to further explore the Merchero population. As with Mercheros, there is a considerable gap of underrepresented populations and ethnic groups in publicly available genetic data. Thus, we encourage the consideration of more ethnically diverse population panels in human genetic studies, as an attempt to improve the representation of human populations and better reconstruct their fine-scale history.

Massively parallel sequencing of human skeletal remains in Vietnam using the precision ID mtDNA control region panel on the Ion S5™ system

Mitochondrial DNA (mtDNA) analysis using Sanger sequencing has been a routine practice for the identification of human skeletal remains. However, this process is usually challenging since DNA from the remains is highly degraded and at low concentration. Recently, the advent and implementation of massively parallel sequencing (MPS) have been offered the ability to improve mtDNA sequence data for forensic analysis. To assess the utility of the Ion S5™ system - an MPS platform for mtDNA analysis in challenging samples, we sequenced the mitochondrial control region of 52 age-old skeletal remains. Using the Precision ID mtDNA Control Region Panel, 50 full and two partial control region haplotypes at relatively high mean coverage of 2494 × were achieved for variant calling. Further variant analysis at 10% threshold for point heteroplasmy showed high degradation degree in terms of DNA damage in our bone samples. A higher point heteroplasmy threshold of 20% was required to diminish most of background noise caused by the damage. The results from this study indicated the potential application of the Ion S5™ system in sequencing degraded samples in Vietnam and provided valuable data sources for forensic analyses in the future.

Searching the undetected mtDNA variants in forensic MPS data

The efficiency of MPS in forensic mtDNA analysis has been thoroughly proven, although a reliable and well established data evaluation still remains a critical point. Numerous bioinformatics tools have been developed, but most of them require specific operating systems and high costs, while free open-source programs with user-friendly interfaces are few. In this study, 43 full mtGenomes were sequenced using the Ion Personal Genome Machine™ (PGM™) System and analyzed utilizing the plug-in Variant Caller (TVC) of the Ion Torrent Software Suite and the mtDNA-Server (mDS), a free web-based mitochondrial analysis tool for MPS data. The outcomes of these two different analysis tools were compared to variants noted after manual inspection of the aligned reads performed using Integrative Genomics Viewer (IGV). The comparison highlighted the presence of thirty-nine discordant variant calls, which were resolved by Sanger sequencing that confirmed the presence of all variants, except for 7 deletions. The combined adoption of IGV and Sanger type sequencing confirmatory steps, in addition of TVC and mDS analysis, resulted in a more accurate variants assignment with the detection of 32 additional true polymorphisms, which were noted in the final dataset. Regarding the heteroplasmy issue, out of a total of thirty heteroplasmic variants, twenty-eight were detected by the TVC, while the mDS detected twenty-two. Overall, none of the used bioinformatics tools were the perfect choice and a secondary analysis with an expert's opinion in complete mtGenome MPS data evaluation is still required in forensic genetic analysis.

The first GHEP-ISFG collaborative exercise on forensic applications of massively parallel sequencing

One of the main goals of the Spanish and Portuguese-Speaking Working Group of the International Society for Forensic Genetics (GHEP-ISFG) is to promote and contribute to the development and dissemination of scientific knowledge in the field of forensic genetics. The GHEP-ISFG supports several Working Commissions which develop different scientific activities. One of them, the Working Commission on "Massively Parallel Sequencing (MPS): Forensic Applications", organized its first collaborative exercise on forensic applications of MPS technology in 2019. The aim of this exercise was to assess the concordance between the MPS results and those obtained with conventional technologies (capillary electrophoresis and Sanger sequencing), as well as to compare the results obtained within the different MPS platforms and/or the different kits/panels and analysis software packages (commercial and open-access) available on the market. The seven participating laboratories analyzed some samples of the annual GHEP-ISFG proficiency test (EIADN No. 27 (2019)), using Ion Torrent™ or MiSeq FGx® platforms. Six of them sent autosomal STR sequence data, five laboratories performed MPS analysis of individual identification SNPs, four laboratories reported MPS data of Y-chromosomal STRs, and X-chromosomal STRs, three laboratories performed MPS analysis of ancestry informative SNPs and phenotype informative SNPs, two labs performed MPS analysis of the mitochondrial DNA control region, and only one lab produced MPS data of lineage informative SNPs. Autosomal STR sequencing results were highly concordant to the consensus obtained by capillary electrophoresis in the EIADN No. 27 (2019) exercise. Furthermore, in general, a high level of concordance was observed between the results of the participating laboratories, regardless of the platform used. The main discordances were due to errors during the analysis process or from sequence data obtained with low depth of coverage. In this paper we highlight some issues that still arise, such as standardization of the nomenclature for STRs analyzed by sequencing with MPS, the universal uptake of a nomenclature framework by the analysis software, and well established validation and accreditation of the new MPS platforms for use in routine forensic case-work.

Highly accurate mtGenome haplotypes from long-read SMRT sequencing can distinguish between monozygotic twins

Discriminating between monozygotic twins (MZ) remains a challenge in the field of forensics globally. It is very difficult to find sequence variants within MZ twins, despite using ultra-deep next generation sequencing (NGS) for nuclear DNA. However, mitochondrial DNA might be a potential marker owing to its higher mutation rate and easier sequencing via NGS. Here, we aimed to introduce a long-read single molecule real-time sequencing (SMRT) strategy, with better continuity and fewer alignment errors, to obtain more accurate mitochondrial genome (mtGenome) sequence on the Sequel platform. Compared to Ion Torrent Personal Genome Machine (PGM), the long-read SMRT sequencing strategy generated highly accurate and mapped circular consensus sequence (CCS) reads and exhibited robust performance in terms of reliable repeatability, consistent coverage pattern, and balanced strands in mtGenome recovery. Moreover, the long-read SMRT strategy exhibited superior ability to not only identify accurate haplotypes but also discover a total of 785 low-level variants within 16 MZ twin pairs with threshold of 2% and 20 CCS reads with Q30 quality. Taken together, our findings suggested the long-read SMRT technology as an appreciable strategy for obtaining accurate mitotypes and providing a promising solution for distinguishing between MZ twin pairs in forensic genetics.

Forensically relevant phylogeographic evaluation of mitogenome variation in the Basque Country

The Basque Country has been the focus of population (genetic) and evolutionary studies for decades, as it represents an interesting evolutionary feature: it is the only European country where a non-Indo-European language is still spoken today and, for which there are no known living or extinct relatives. Early studies that were based on anatomical and serological methods, along with subsequent molecular genetic investigations, contain controversial interpretations of their data. Additionally, the analysis of mitochondrial DNA, which is maternally inherited and thus suitable for the examination of the maternal phylogeny of the population, was the focus of some studies. Early mtDNA studies were however restricted to the information provided by the control region or its hypervariable segments only. These are known to harbour little phylogenetic information, particularly for haplogroup H that is dominant in Westeurasian populations including the Basques. Later studies analysed complete mitogenome sequences. Their information content is however limited, either because the number of samples was low, or because these studies only considered particular haplogroups. In this study we present the full mitogenome sequences of 178 autochthonous Basque individuals that were carefully selected based on their familial descent and discuss the observed phylogenetic signals in the light of earlier published findings. We confirm the presence of Basque-specific mtDNA lineages and extend the knowledge of these lineages by providing data on their distribution in comparison to other Basque and non-Basque populations. This dataset improves our understanding of the Basque mtDNA phylogeny and serves as a high-quality dataset that is provided via EMPOP for forensic genetic purposes.

Ion torrent high throughput mitochondrial genome sequencing (HTMGS)

The implementation and popularity of next generation sequencing (NGS) has led to the development of various rapid whole mitochondrial genome sequencing techniques. We summarise an efficient and cost-effective NGS approach for mitochondrial genomic DNA in humans using the Ion Torrent platform, and further discuss our bioinformatics pipeline for streamlined variant calling. Ion 316 chips were utilised with the Ion Torrent semi-conductor platform Personal Genome Machine (PGM) to perform tandem sequencing of mitochondrial genomes from the core pedigree (n = 315) of the Norfolk Island Health Study. Key improvements from commercial methods focus on the initial PCR step, which currently requires extensive optimisation to ensure the accurate and reproducible elongation of each section of the complete mitochondrial genome. Dual-platform barcodes were incorporated into our protocol thereby extending its potential application onto Illumina-based systems. Our bioinformatics pipeline consists of a modified version of GATK best practices tailored for mitochondrial genomic data. When compared with current commercial methods, our method, termed high throughput mitochondrial genome sequencing (HTMGS), allows high multiplexing of samples and the use of alternate library preparation reagents at a lower cost per sample (~1.7 times) when compared to current commercial methodologies. Our HTMGS methodology also provides robust mitochondrial sequencing data (>450X average coverage) that can be applied and modified to suit various study designs. On average, we were able to identify ~30 variants per sample with 572 variants observed across 315 samples. We have developed a high throughput sequencing and analysis method targeting complete mitochondrial genomes; with the potential to be platform agnostic with analysis options that adhere to current best practices.

Massively parallel sequencing-enabled mixture analysis of mitochondrial DNA samples

The mitochondrial genome has a number of characteristics that provide useful information to forensic investigations. Massively parallel sequencing (MPS) technologies offer improvements to the quantitative analysis of the mitochondrial genome, specifically the interpretation of mixed mitochondrial samples. Two-person mixtures with nuclear DNA ratios of 1:1, 5:1, 10:1, and 20:1 of individuals from different and similar phylogenetic backgrounds and three-person mixtures with nuclear DNA ratios of 1:1:1 and 5:1:1 were prepared using the Precision ID mtDNA Whole Genome Panel and Ion Chef, and sequenced on the Ion PGM or Ion S5 sequencer (Thermo Fisher Scientific, Waltham, MA, USA). These data were used to evaluate whether and to what degree MPS mixtures could be deconvolved. Analysis was effective in identifying the major contributor in each instance, while SNPs from the minor contributor's haplotype only were identified in the 1:1, 5:1, and 10:1 two-person mixtures. While the major contributor was identified from the 5:1:1 mixture, analysis of the three-person mixtures was more complex, and the mixed haplotypes could not be completely parsed. These results indicate that mixed mitochondrial DNA samples may be interpreted with the use of MPS technologies.

Performance of the Early Access AmpliSeq™ Mitochondrial Panel with degraded DNA samples using the Ion Torrent™ platform

The Early Access AmpliSeq™ Mitochondrial Panel amplifies whole mitochondrial genomes for phylogenetic and kinship identifications, using Ion Torrent™ technology. There is currently limited information on its performance with degraded DNA, a common occurrence in forensic samples. This study evaluated the performance of the Panel with DNA samples degraded in vitro, to mimic conditions commonly found in forensic investigations. Purified DNA from five individuals was heat-treated at five time points each (125°C for 0, 30, 60, 120, and 240 min; total n = 25). The quality of DNA was assessed via a real-time DNA assay of genomic DNA and prepared for massively parallel sequencing on the Ion Torrent™ platform. Mitochondrial sequences were obtained for all samples and had an amplicon coverage averaging between 66X to 2803X. Most amplicons (157/162) displayed high coverages (452 ± 333X), while reads with less than 100X coverage were recorded in five amplicons only (90 ± 5X). Amplicon coverage was decreased with prolonged heating. At 72% strand balance, reads were well balanced between forward and reverse strands. Using a coverage threshold of ten reads per SNP, complete sequences were recovered in all samples and resolved kinship and, haplogroup relations. Additionally, the HV1 and HV2 regions of the reference and 240-min heat-treated samples (n = 10) were Sanger-sequenced for concordance. Overall, this study demonstrates the efficacy of a novel forensic Panel that recovers high quality mitochondrial sequences from degraded DNA samples.

Mitochondrial genomes uncover the maternal history of the Pamir populations

The Pamirs, among the world's highest mountains in Central Asia, are one of homelands with the most extreme high altitude for several ethnic groups. The settlement history of modern humans on the Pamirs remains still opaque. Herein, we have sequenced the mitochondrial DNA (mtDNA) genomes of 382 individuals belonging to eight populations from the Pamirs and the surrounding lowlands in Central Asia. We construct the Central Asian (including both highlanders and lowlanders) mtDNA haplogroup tree at the highest resolution. All the matrilineal components are assigned into the defined mtDNA haplogroups in East and West Eurasians. No basal lineages that directly emanate from the Eurasian founder macrohaplogroups M, N, and R are found. Our data support the origin of Central Asian being the result of East-West Eurasian admixture. The coalescence ages for more than 93% mtDNA lineages in Central Asians are dated after the last glacial maximum (LGM). The post-LGM and/or later dispersals/admixtures play dominant roles in shaping the maternal gene pool of Central Asians. More importantly, our analyses reveal the mtDNA heterogeneity in the Pamir highlanders, not only between the Turkic Kyrgyz and the Indo-European Tajik groups, but also among three highland Tajiks. No evidence supports positive selection or relaxation of selective constraints in the mtDNAs of highlanders as compared to that of lowlanders. Our results suggest a complex history for the peopling of Pamirs by multiple waves of migrations from various genetic resources during different time scales.

Mitochondrial genomes of African pangolins and insights into evolutionary patterns and phylogeny of the family Manidae

BACKGROUND

This study used next generation sequencing to generate the mitogenomes of four African pangolin species; Temminck's ground pangolin (Smutsia temminckii), giant ground pangolin (S. gigantea), white-bellied pangolin (Phataginus tricuspis) and black-bellied pangolin (P. tetradactyla).

RESULTS

The results indicate that the mitogenomes of the African pangolins are 16,558 bp for S. temminckii, 16,540 bp for S. gigantea, 16,649 bp for P. tetradactyla and 16,565 bp for P. tricuspis. Phylogenetic comparisons of the African pangolins indicated two lineages with high posterior probabilities providing evidence to support the classification of two genera; Smutsia and Phataginus. The total GC content between African pangolins was observed to be similar between species (36.5% - 37.3%). The most frequent codon was found to be A or C at the 3rd codon position. Significant variations in GC-content and codon usage were observed for several regions between African and Asian pangolin species which may be attributed to mutation pressure and/or natural selection. Lastly, a total of two insertions of 80 bp and 28 bp in size respectively was observed in the control region of the black-bellied pangolin which were absent in the other African pangolin species.

CONCLUSIONS

The current study presents reference mitogenomes of all four African pangolin species and thus expands on the current set of reference genomes available for six of the eight extant pangolin species globally and represents the first phylogenetic analysis with six pangolin species using full mitochondrial genomes. Knowledge of full mitochondrial DNA genomes will assist in providing a better understanding on the evolution of pangolins which will be essential for conservation genetic studies.

Entire Mitochondrial DNA Sequencing on Massively Parallel Sequencing for the Korean Population

Mitochondrial DNA (mtDNA) genome analysis has been a potent tool in forensic practice as well as in the understanding of human phylogeny in the maternal lineage. The traditional mtDNA analysis is focused on the control region, but the introduction of massive parallel sequencing (MPS) has made the typing of the entire mtDNA genome (mtGenome) more accessible for routine analysis. The complete mtDNA information can provide large amounts of novel genetic data for diverse populations as well as improved discrimination power for identification. The genetic diversity of the mtDNA sequence in different ethnic populations has been revealed through MPS analysis, but the Korean population not only has limited MPS data for the entire mtGenome, the existing data is mainly focused on the control region. In this study, the complete mtGenome data for 186 Koreans, obtained using Ion Torrent Personal Genome Machine (PGM) technology and retrieved from rather common mtDNA haplogroups based on the control region sequence, are described. The results showed that 24 haplogroups, determined with hypervariable regions only, branched into 47 subhaplogroups, and point heteroplasmy was more frequent in the coding regions. In addition, sequence variations in the coding regions observed in this study were compared with those presented in other reports on different populations, and there were similar features observed in the sequence variants for the predominant haplogroups among East Asian populations, such as Haplogroup D and macrohaplogroups M9, G, and D. This study is expected to be the trigger for the development of Korean specific mtGenome data followed by numerous future studies.

STRait Razor v2s: Advancing sequence-based STR allele reporting and beyond to other marker systems

STRait Razor has provided the forensic community a free-to-use, open-source tool for short tandem repeat (STR) analysis of massively parallel sequencing (MPS) data. STRait Razor v2s (SRv2s) allows users to capture physically phased haplotypes within the full amplicon of both commercial (ForenSeq) and "early access" panels (PowerSeq, Mixture ID). STRait Razor v2s may be run in batch mode to facilitate population-level analysis and is supported by all Unix distributions (including MAC OS). Data are reported in tables in string (haplotype), length-based (e.g., vWA allele 14), and International Society of Forensic Genetics (ISFG)-recommended (vWA [CE 14]-GRCh38-chr12:5983950-5984049 (TAGA)₁₀ (CAGA)₃ TAGA) formats. STRait Razor v2s currently contains a database of ∼2500 unique sequences. This database is used by SRv2s to match strings to the appropriate allele in ISFG-recommended format. In addition to STRs, SRv2s has configuration files necessary to capture and report haplotypes from all marker types included in these multiplexes (e.g., SNPs, InDels, and microhaplotypes). To facilitate mixture interpretation, data may be displayed from all markers in a format similar to that of electropherograms displayed by traditional forensic software. The download package for SRv2s may be found at https://www.unthsc.edu/graduate-school-of-biomedical-sciences/molecular-and-medical-genetics/laboratory-faculty-and-staff/strait-razor.

A Comparison and Integration of MiSeq and MinION Platforms for Sequencing Single Source and Mixed Mitochondrial Genomes

Single source and multiple donor (mixed) samples of human mitochondrial DNA were analyzed and compared using the MinION and the MiSeq platforms. A generalized variant detection strategy was employed to provide a cursory framework for evaluating the reliability and accuracy of mitochondrial sequences produced by the MinION. The feasibility of long-read phasing was investigated to establish its efficacy in quantitatively distinguishing and deconvolving individuals in a mixture. Finally, a proof-of-concept was demonstrated by integrating both platforms in a hybrid assembly that leverages solely mixture data to accurately reconstruct full mitochondrial genomes.

MaGelLAn 1.0: a software to facilitate quantitative and population genetic analysis of maternal inheritance by combination of molecular and pedigree information

Background

Identification of genes or even nucleotides that are responsible for quantitative and adaptive trait variation is a difficult task due to the complex interdependence between a large number of genetic and environmental factors. The polymorphism of the mitogenome is one of the factors that can contribute to quantitative trait variation. However, the effects of the mitogenome have not been comprehensively studied, since large numbers of mitogenome sequences and recorded phenotypes are required to reach the adequate power of analysis. Current research in our group focuses on acquiring the necessary mitochondria sequence information and analysing its influence on the phenotype of a quantitative trait. To facilitate these tasks we have produced software for processing pedigrees that is optimised for maternal lineage analysis.

Results

We present MaGelLAn 1.0 (maternal genealogy lineage analyser), a suite of four Python scripts (modules) that is designed to facilitate the analysis of the impact of mitogenome polymorphism on quantitative trait variation by combining molecular and pedigree information. MaGelLAn 1.0 is primarily used to: (1) optimise the sampling strategy for molecular analyses; (2) identify and correct pedigree inconsistencies; and (3) identify maternal lineages and assign the corresponding mitogenome sequences to all individuals in the pedigree, this information being used as input to any of the standard software for quantitative genetic (association) analysis. In addition, MaGelLAn 1.0 allows computing the mitogenome (maternal) effective population sizes and probability of mitogenome (maternal) identity that are useful for conservation management of small populations.

Conclusions

MaGelLAn is the first tool for pedigree analysis that focuses on quantitative genetic analyses of mitogenome data. It is conceived with the purpose to significantly reduce the effort in handling and preparing large pedigrees for processing the information linked to maternal lines. The software source code, along with the manual and the example files can be downloaded at http://lissp.irb.hr/software/magellan-1-0/ and https://github.com/sristov/magellan.

Electronic supplementary material

The online version of this article (doi:10.1186/s12711-016-0242-9) contains supplementary material, which is available to authorized users.

Haplotype diversity in mitochondrial genome in a Chinese Han population

Investigations into the use of mitochondrial genome (mtGenome) typing by massively parallel sequencing technologies are well underway in many areas, including forensic genetics. Previous studies have demonstrated that mtGenome sequencing data generated from Ion torrent personal genome machine (PGM) system were highly viable and reliable in forensic research. In this study, 145 whole mtGenomes from unrelated Chinese Han population were sequenced using the Ion PGM system. Results showed that 145 distinct haplotypes were obtained at a relatively high coverage with limited strand bias. The distribution of variants across the entire mtGenomes was illustrated and 70.74% of the variants were observed outside of the control region. An overall increase in the number of unique haplotypes as well as haplotype diversity were observed by detection of mtGenome compared with hypervariable region I/II (HV I/II) and control region (CR). This study demonstrates the substantially higher degree of haplotype resolution with whole-mtGenome sequences in comparison to HV I/II or CR that historically targeted for forensic testing, which shows the potential value of mtGenome typing in forensic testing in the future.

Effects of the Ion PGM™ Hi-Q™ sequencing chemistry on sequence data quality

Massively parallel sequencing (MPS) offers substantial improvements over current forensic DNA typing methodologies such as increased resolution, scalability, and throughput. The Ion PGM™ is a promising MPS platform for analysis of forensic biological evidence. The system employs a sequencing-by-synthesis chemistry on a semiconductor chip that measures a pH change due to the release of hydrogen ions as nucleotides are incorporated into the growing DNA strands. However, implementation of MPS into forensic laboratories requires a robust chemistry. Ion Torrent's Hi-Q™ Sequencing Chemistry was evaluated to determine if it could improve on the quality of the generated sequence data in association with selected genetic marker targets. The whole mitochondrial genome and the HID-Ion STR 10-plex panel were sequenced on the Ion PGM™ system with the Ion PGM™ Sequencing 400 Kit and the Ion PGM™ Hi-Q™ Sequencing Kit. Concordance, coverage, strand balance, noise, and deletion ratios were assessed in evaluating the performance of the Ion PGM™ Hi-Q™ Sequencing Kit. The results indicate that reliable, accurate data are generated and that sequencing through homopolymeric regions can be improved with the use of Ion Torrent's Hi-Q™ Sequencing Chemistry. Overall, the quality of the generated sequencing data supports the potential for use of the Ion PGM™ in forensic genetic laboratories.

Blind study evaluation illustrates utility of the Ion PGM™ system for use in human identity DNA typing

Aim

To perform a blind study to assess the capability of the Ion Personal Genome Machine™ (PGM) system to sequence forensically relevant genetic marker panels and to characterize unknown individuals for ancestry and possible relatedness.

Methods

Twelve genomic samples were provided by a third party for blinded genetic analysis. For these 12 samples, the mitochondrial genome and three PGM™ panels containing human identity single nucleotide polymorphisms (SNPs), ancestry informative SNPs, and short tandem repeats (STRs) were sequenced on the PGM™ system and analyzed.

Results

All four genetic systems were run and analyzed on the PGM™ system in a reasonably quick time frame. Completeness of genetic profiles, depth of coverage, strand balance, and allele balance were informative metrics that illustrated the quality and reliability of the data produced. SNP genotypes allowed for identification of sex, paternal lineage, and population ancestry. STR genotypes were shown to be in complete concordance with genotypes generated by standard capillary electrophoresis-based technologies. Variants in the mitochondrial genome data provided information on population background and maternal relationships.

Conclusion

All results from analysis of the 12 genomic samples were consistent with sample information provided by the sample providers at the end of the blinded study. The relatively easy identification of intra-STR allele SNPs offered the potential for increased discrimination power. The promising nature of these results warrants full validation studies of this massively parallel sequencing technology and its further development for forensic data analysis.

Simultaneous Whole Mitochondrial Genome Sequencing with Short Overlapping Amplicons Suitable for Degraded DNA Using the Ion Torrent Personal Genome Machine

Whole mitochondrial (mt) genome analysis enables a considerable increase in analysis throughput, and improves the discriminatory power to the maximum possible phylogenetic resolution. Most established protocols on the different massively parallel sequencing (MPS) platforms, however, invariably involve the PCR amplification of large fragments, typically several kilobases in size, which may fail due to mtDNA fragmentation in the available degraded materials. We introduce a MPS tiling approach for simultaneous whole human mt genome sequencing using 161 short overlapping amplicons (average 200 bp) with the Ion Torrent Personal Genome Machine. We illustrate the performance of this new method by sequencing 20 DNA samples belonging to different worldwide mtDNA haplogroups. Additional quality control, particularly regarding the potential detection of nuclear insertions of mtDNA (NUMTs), was performed by comparative MPS analysis using the conventional long-range amplification method. Preliminary sensitivity testing revealed that detailed haplogroup inference was feasible with 100 pg genomic input DNA. Complete mt genome coverage was achieved from DNA samples experimentally degraded down to genomic fragment sizes of about 220 bp, and up to 90% coverage from naturally degraded samples. Overall, we introduce a new approach for whole mt genome MPS analysis from degraded and nondegraded materials relevant to resolve and infer maternal genetic ancestry at complete resolution in anthropological, evolutionary, medical, and forensic applications.

Whole mitochondrial genome genetic diversity in an Estonian population sample

Mitochondrial DNA is a useful marker for population studies, human identification, and forensic analysis. Commonly used hypervariable regions I and II (HVI/HVII) were reported to contain as little as 25% of mitochondrial DNA variants and therefore the majority of power of discrimination of mitochondrial DNA resides in the coding region. Massively parallel sequencing technology enables entire mitochondrial genome sequencing. In this study, buccal swabs were collected from 114 unrelated Estonians and whole mitochondrial genome sequences were generated using the Illumina MiSeq system. The results are concordant with previous mtDNA control region reports of high haplogroup HV and U frequencies (47.4 and 23.7% in this study, respectively) in the Estonian population. One sample with the Northern Asian haplogroup D was detected. The genetic diversity of the Estonian population sample was estimated to be 99.67 and 95.85%, for mtGenome and HVI/HVII data, respectively. The random match probability for mtGenome data was 1.20 versus 4.99% for HVI/HVII. The nucleotide mean pairwise difference was 27 ± 11 for mtGenome and 7 ± 3 for HVI/HVII data. These data describe the genetic diversity of the Estonian population sample and emphasize the power of discrimination of the entire mitochondrial genome over the hypervariable regions.

The past, present and future of mitochondrial genomics: have we sequenced enough mtDNAs?

The year 2014 saw more than a thousand new mitochondrial genome sequences deposited in GenBank—an almost 15% increase from the previous year. Hundreds of peer-reviewed articles accompanied these genomes, making mitochondrial DNAs (mtDNAs) the most sequenced and reported type of eukaryotic chromosome. These mtDNA data have advanced a wide range of scientific fields, from forensics to anthropology to medicine to molecular evolution. But for many biological lineages, mtDNAs are so well sampled that newly published genomes are arguably no longer contributing significantly to the progression of science, and in some cases they are tying up valuable resources, particularly journal editors and referees. Is it time to acknowledge that as a research community we have published enough mitochondrial genome papers? Here, I address this question, exploring the history, milestones and impacts of mitochondrial genomics, the benefits and drawbacks of continuing to publish mtDNAs at a high rate and what the future may hold for such an important and popular genetic marker. I highlight groups for which mtDNAs are still poorly sampled, thus meriting further investigation, and recommend that more energy be spent characterizing aspects of mitochondrial genomes apart from the DNA sequence, such as their chromosomal and transcriptional architectures. Ultimately, one should be mindful before writing a mitochondrial genome paper. Consider perhaps sending the sequence directly to GenBank instead, and be sure to annotate it correctly before submission.