mtDNA Genome Research Articles

Mitochondrial and nuclear disease panel (Mito-aND-Panel): Combined sequencing of mitochondrial and nuclear DNA by a cost-effective and sensitive NGS-based method.

BackgroundThe diagnosis of mitochondrial disorders is challenging because of the clinical variability and genetic heterogeneity of these conditions. Next‐Generation Sequencing (NGS) technology offers a robust high‐throughput platform for nuclear and mitochondrial DNA (mtDNA) analyses.MethodWe developed a custom Agilent SureSelect Mitochondrial and Nuclear Disease Panel (Mito‐aND‐Panel) capture kit that allows parallel enrichment for subsequent NGS‐based sequence analysis of nuclear mitochondrial disease‐related genes and the complete mtDNA genome. Sequencing of enriched mtDNA simultaneously with nuclear genes was compared with the separated sequencing of the mitochondrial genome and whole exome sequencing (WES).ResultsThe Mito‐aND‐Panel permits accurate detection of low‐level mtDNA heteroplasmy due to a very high sequencing depth compared to standard diagnostic procedures using Sanger sequencing/SNaPshot and WES which is crucial to identify maternally inherited mitochondrial disorders.ConclusionWe established a NGS‐based method with combined sequencing of the complete mtDNA and nuclear genes which enables a more sensitive heteroplasmy detection of mtDNA mutations compared to traditional methods. Because the method promotes the analysis of mtDNA variants in large cohorts, it is cost‐effective and simple to setup, we anticipate this is a highly relevant method for sequence‐based genetic diagnosis in clinical diagnostic applications.

Incomplete lineage sorting rather than hybridization explains the inconsistent phylogeny of the wisent

The wisent or European bison is the largest European herbivore and is completely cross-fertile with its American relative. However, mtDNA genome of wisent is similar to that of cattle, which suggests that wisent emerged as a hybrid of bison and an extinct cattle-like species. Here, we analyzed nuclear whole-genome sequences of the bovine species, and found only a minor and recent gene flow between wisent and cattle. Furthermore, we identified an appreciable heterogeneity of the nuclear gene tree topologies of the bovine species. The relative frequencies of various topologies, including the mtDNA topology, were consistent with frequencies of incomplete lineage sorting (ILS) as estimated by tree coalescence analysis. This indicates that ILS has occurred and may well account for the anomalous wisent mtDNA phylogeny as the outcome of a rare event. We propose that ILS is a possible explanation of phylogenomic anomalies among closely related species.

Genomic and life-history discontinuity reveals a precinctive lineage for a deep-water grouper with gene flow from tropical to temperate waters on the west coast of Australia

We address a critical knowledge gap for the Eightbar Grouper, Hyporthodus octofasciatus, one of the largest groupers targeted in mostly tropical, deep-water fisheries, using genetic analyses of mitochondrial DNA (mtDNA; N = 248) and age and growth information (N = 727) from specimens collected from the eastern Indian Ocean to the western central Pacific Ocean. We additionally used a genotype-by-sequencing approach on a subset of these samples (N = 94) to determine the extent of egg and larval dispersal between tropical and temperate regions along the west coast of Australia (WA). Discontinuity in mtDNA and nuclear genomes, and marked variation in growth trajectories and longevity revealed a distinct, non-interbreeding cryptic lineage in WA. The WA lineage appears to be geographically isolated from the oceanic Indo-West Pacific (IP) lineage and precinctive to a single continuous coastline from tropical to temperate waters (covering > 2200 km and ∼20° of latitude). The Hyporthodus phylogeny reveals a possible allopatric speciation scenario with sister lineages endemic to the east (i.e. H. ergastularius) and west (i.e. WA lineage of H. octofasciatus) coasts of Australia, each diverging from a broader IP distributed ancestor (i.e. IP lineage of H. octofasciatus) in the early Pleistocene Epoch. Sustainable management of these species therefore needs to consider their evolutionary distinction, in addition to aspects of their life-history strategies and limited geographic distribution that infers high vulnerability to fishing at relatively low levels of exploitation.

Genetic structure and sex-biased gene flow in the history of southern African populations.

ObjectivesWe investigated the genetic history of southern African populations with a special focus on their paternal history. We reexamined previous claims that the Y‐chromosome haplogroup E1b1b (E‐M293) was brought to southern Africa by pastoralists from eastern Africa, and investigated patterns of sex‐biased gene flow in southern Africa.Materials and methodsWe analyzed previously published complete mtDNA genome sequences and ∼900 kb of NRY sequences from 23 populations from Namibia, Botswana, and Zambia, as well as haplogroup frequencies from a large sample of southern African populations and 23 newly genotyped Y‐linked STR loci for samples assigned to haplogroup E1b1b.ResultsOur results support an eastern African origin for Y‐chromosome haplogroup E1b1b (E‐M293); however, its current distribution in southern Africa is not strongly associated with pastoralism, suggesting more complex demographic events and/or changes in subsistence practices in this region. The Bantu expansion in southern Africa had a notable genetic impact and was probably a rapid, male‐dominated expansion. Our finding of a significant increase in the intensity of the sex‐biased gene flow from north to south may reflect changes in the social dynamics between Khoisan and Bantu groups over time.ConclusionsOur study shows that the population history of southern Africa has been complex, with different immigrating groups mixing to different degrees with the autochthonous populations. The Bantu expansion led to heavily sex‐biased admixture as a result of interactions between Khoisan females and Bantu males, with a geographic gradient which may reflect changes in the social dynamics between Khoisan and Bantu groups over time.

Is mitochondrial DNA (MTDNA) quantification a potential biomarker for selection among euploid embryos?

Recently, there have been controversial publications about the clinical relevance of mtDNA quantification in human blastocysts. Previous studies have not found an association between this parameter and ploidy, maternal age or pregnancy outcome. However, some laboratories, based on their evidence, apply this quantification as an implantation potential biomarker between euploid embryos. Different methodologies have been used for mtDNA assessment, mainly next generation sequencing (NGS) platforms and real-time polymerase chain reaction (qPCR), with consistent results between them. The aim of this study was to evaluate if there was a relationship between human blastocyst mtDNA content and female age, embryo ploidy and clinical pregnancy. Retrospective cohort study. A cohort of 447 blastocysts obtained from 202 couples, with an average female age of 33.8 years old (21-46), undergoing preimplantation genetic testing for aneuploidies (PGT-A) were included. Data was collected between April 2016 and March 2018 from a single center. Mosaic embryos (between 20%-80%) were excluded from this analysis. Trophectoderm biopsies were assessed by NGS (Veriseq-Illumina). For each sample, reads were aligned to the human reference genome (hg19) and the mtDNA genome separately. The number of reads that mapped to the mtDNA were divided by the number of reads that mapped to the nuclear DNA in order to normalize technical variability. The resulting values were mathematically adjusted by correction factors for embryo ploidy (complete chromosomal monosomies or trisomies) and gender previously reported. T-test was performed for statistical analysis in order to analyze mtDNA scores regarding embryo aneuploidy, maternal age and clinical pregnancy. Regarding all blastocysts analyzed, 236 (53%) were euploid and 210 (47%) aneuploid. The amount of mtDNA was significantly higher in aneuploid embryos (P= 0.0002). However, the amount of mtDNA was not different between euploid embryos from younger (<38 years, n=187) and older women (≥38 years, n=49) (P=0.6870). During the period covered, 65 single embryo transfer were performed after thawing, resulting in 37 (57%) HCG-beta subunit positive and 26 (40%) ongoing pregnancies. The mtDNA score from euploid blastocysts that achieved a clinical pregnancy was no significantly different from those that did not result in an ongoing pregnancy (P=0.7589). This study contributes evidence that mtDNA quantification in euploid embryos have no clinical impact in pregnancy outcome. mtDNA score was only statistically associated with chromosomal aneuploidy suggesting that high levels of mtDNA may have a negative impact resulting in an inadequate chromosome segregation.

Comprehensive mitochondrial DNA analysis and IVF outcome.

STUDY QUESTIONDo mitochondrial DNA (mtDNA) copy number and heteroplasmy in human embryos affect the ongoing pregnancy rate?SUMMARY ANSWEROur study suggests that mtDNA copy number above a specific threshold is associated with the ongoing pregnancy rate.WHAT IS KNOWN ALREADYMitochondria play a vital role in cell function. Recently, there has been increasing research on mtDNA as a biomarker of embryo implantation. Although reports showed that high levels of mtDNA in the blastocyst are associated with low implantation potential, other publications were unable to confirm this. Confounding factors may influence the mtDNA copy number in euploid embryos. On the other hand it has been speculated that both mtDNA heteroplasmy and copy number contribute to mitochondrial function. Next generation sequencing (NGS) allows us to study in depth mtDNA heteroplasmy and copy number simultaneously.STUDY DESIGN, SIZE, DURATIONA prospective non-selection study was performed. We included 159 blastocyst biopsies from 142 couples who attended our clinic for preimplantation genetic testing for aneuploidies (PGT-A), from January 2017 to December 2017. All embryos were biopsied on Day 5 or Day 6. The aneuploid testing was performed by NGS. All blastocysts were diagnosed as euploid non-mosaic and were transferred. The mtDNA analysis was performed once the embryo diagnosis was known.PARTICIPANTS/MATERIALS, SETTING, METHODSSequencing reads mapping to the mtDNA genome were extracted from indexed bam files to identify copy number and heteroplasmy. The relative measure of mtDNA copy number was calculated by dividing the mtDNA reads by the nuclear DNA value to normalize for technical variants and the number of cells collected at the biopsy. All the results were subjected to a mathematical correction factor according to the embryo genome. Heteroplasmy was assigned by MitoSeek.MAIN RESULTS AND THE ROLE OF CHANCEThe mean average copy number and SD of mtDNA per genome was 0.0016 ± 0.0012. Regarding heteroplasmy, 40 embryos were heteroplasmy carriers (26.32%). MtDNA variants were detected in coding and non-coding regions and the highest number of variants in an embryo was eight. With respect to IVF outcome for mtDNA copy number analysis, we set a threshold of 0.003 for the following analysis. The vast majority of the embryos were below the threshold (142/159, 89.31%) and 17 embryos were classified as having higher mtDNA levels. We showed a reduction in ongoing pregnancy rate associated with elevated mtDNA copy number (42.96% versus 17.65%, P < 0.05). This result was independent of maternal age and day of the biopsy: these factors were included as confounding factors because mtDNA copy number was negatively correlated with female age (25 –30 y: 0.0017 ± 0.0011, 30 –35 y: 0.0012 ± 0.0007, 35 –40 y: 0.0016 ± 0.0009, over 40 y: 0.0024 + 0.0017, P < 0.05). Embryos biopsied on Day 5 were more likely to have higher quantities of mtDNA compared with those biopsied on Day 6 (0.0017 versus 0.0009, P < 0.001). According to IVF outcome and heteroplasmy, a lower ongoing pregnancy rate was reported for embryos that carried more than two variants. However, this did not reach statistical significance when we compared embryos with a number of variants lower or higher than two (39.15 versus 20.0, P = 0.188). Finally, a clear positive association between the mtDNA variants and copy number was reported when we compare embryos with or without heteroplasmy (0.0013 ± 0.0009 versus 0.0025 ± 0.0014, P < 0.001) and among different numbers of variants (0:0.0013 ± 0.0009, 1–2:0.0023 ± 0.0012, >2:0.0043 ± 0.0014, P < 0.05).LIMITATIONS, REASONS FOR CAUTIONA limitation may be the size of the sample and the high-throughput sequencing technology that might not have detected heteroplasmy levels below 2% which requires high sequence depth A clinical randomized trial comparing the clinical outcome after the transfer of embryos selected according to mtDNA levels or only by morphological evaluation will be necessary. More research into the impact of mtDNA heteroplasmy and copy number on IVF outcome is needed.WIDER IMPLICATIONS OF THE FINDINGSOur results demonstrate that embryos with elevated mtDNA copy number have a lower chance of producing an ongoing pregnancy. MtDNA copy number is higher in older women and is dependent upon the number of cell divisions that preceded biopsy. Moreover, our data suggest that mitochondrial activity could be a balance between functional capacity and relative mtDNA copy number.STUDY FUNDING/COMPETING INTEREST(S)There are no conflicts of interest or sources of funding to declare.Trial registration numberNot applicable.

Cultural Innovations Influence Patterns of Genetic Diversity in Northwestern Amazonia.

Human populations often exhibit contrasting patterns of genetic diversity in the mtDNA and the nonrecombining portion of the Y-chromosome (NRY), which reflect sex-specific cultural behaviors and population histories. Here, we sequenced 2.3 Mb of the NRY from 284 individuals representing more than 30 Native American groups from Northwestern Amazonia (NWA) and compared these data to previously generated mtDNA genomes from the same groups, to investigate the impact of cultural practices on genetic diversity and gain new insights about NWA population history. Relevant cultural practices in NWA include postmarital residential rules and linguistic exogamy, a marital practice in which men are required to marry women speaking a different language. We identified 2,969 SNPs in the NRY sequences, only 925 of which were previously described. The NRY and mtDNA data showed different sex-specific demographic histories: female effective population size has been larger than that of males through time, which might reflect larger variance in male reproductive success. Both markers show an increase in lineage diversification beginning ∼5,000 years ago, which may reflect the intensification of agriculture, technological innovations, and the expansion of regional trade networks documented in the archaeological evidence. Furthermore, we find similar excesses of NRY versus mtDNA between-population divergence at both the local and continental scale, suggesting long-term stability of female versus male migration. We also find evidence of the impact of sociocultural practices on diversity patterns. Finally, our study highlights the importance of analyzing high-resolution mtDNA and NRY sequences to reconstruct demographic history, since this can differ considerably between sexes.

Phylogeography, mitochondrial DNA diversity, and demographic history of geladas (Theropithecus gelada).

The large-bodied, terrestrial primates in the tribe Papionini are among the most intensely studied animals in the world, yet for some members of this tribe we know comparatively little about their evolutionary history and phylogeography. Geladas (Theropithecus gelada Rüppell, 1835), endemic primates of the Ethiopian highlands, are largely unstudied both in genetic diversity and intrageneric phylogeny. Currently, a northern and central subspecies and one isolated southern population are recognized, of which the central is classified as Least Concern, the northern as Vulnerable, and the southern is not yet assessed. The distribution and taxonomy of the subspecies remain poorly defined. Here, we estimate the mitochondrial DNA (mtDNA) diversity and phylogenetic relationships among gelada mtDNA lineages based on samples across the entire species range. We analysed 1.7 kb-long sequences of the mtDNA genome, spanning the cytochrome b gene and the hypervariable region I of the D-loop, derived from 162 faecal samples. We detected five major haplogroups or clades (south, central-1, central-2, north-1, north-2) which diverged between 0.67 and 0.43 million years ago, thus suggesting a rapid radiation, resulting in largely unresolved intrageneric phylogenetic relationships. Both, the northern and central demes contain two similarly valid haplogroups, each with little or no geographic segregation among respective haplogroups. Effective population sizes of the northern and central demes decreased during and after the last glacial maximum but remained stable for the southern deme, although on a very low level. The distribution of haplogroups within the geographic ranges of the putative gelada subspecies indicates that mtDNA sequence information does not allow reliable taxonomic inferences and thus is not sufficient for solving the taxonomic rank of the three demic populations, with the possible exception of the southern population. Nevertheless, due to the genetic differences all three populations deserve conservation efforts, in particular the smallest southern population.

Human mitochondrial DNA haplogroup M8a influences the penetrance of m.8684C>T in Han Chinese men with non-obstructive azoospermia.

What is the role of mitochondrial DNA (mtDNA) in the pathogenesis of non-obstructive azoospermia (NOA)? mtDNA genome sequencing followed by an independent population validation were performed in 628 NOA cases and 584 healthy controls. Antioxidant capacity of serum was evaluated in 54 randomly selected cases out of 536 and 49 out of 489 controls. In the screening stage, 13 mtDNA haplogroups (hg) were ascertained, and 10 susceptible variants were observed. In the validation stage, hg M8* in individuals was found to be associated with increased risk of NOA [odds ratio (OR) 2.61, 95% confidence interval (CI) 1.47-4.61] (P=0.001). Unexpectedly, the frequency of m.8684C>T, the defining marker for hg M8a, was also higher in NOA (OR 4.14, 95% CI 1.56-11.03) (P=0.002). Subsequently, the frequency distributions were compared among the sub-hg of hg M8* (including hg M8a, C and Z) and, intriguingly, no significance was found in hg C and Z. Additionally, the level of total antioxidant capacity was significantly decreased (P<0.05) compared with the control group. hg M8a background in general played an active role in the penetrance of 8684C>T in NOA, and mtDNA genetic variants (causing low antioxidant levels) might increase mtDNA damage and impair normal spermatogenesis.

Sequencing of mitochondrial genomes using the Precision ID mtDNA Whole Genome Panel.

Massively parallel sequencing offers a fast and cost-effective method for sequencing of the whole mtDNA genome. The Precision ID mtDNA Whole Genome Panel amplifies the entire mtDNA genome in two multiplex PCRs with 81 primer sets using the Ion AmpliSeq™ technology. In this study, the performance of the panel was evaluated by testing different amplification methods (two-in-one or conservative), the number of PCR cycles (21, 23, and 25), and different reaction volumes (recommended volume or half-volume). Furthermore, a dilution series, controlled mtDNA mixtures, and casework samples were also sequenced. The normalised read depths of the individual fragments were highly consistent irrespectively of the amplification methods or reaction volumes used. The sequencing output matched the mixture ratios of the controlled mtDNA mixtures indicating that the sequencing results were a loyal representation of the input DNA. Complete mtDNA profiles were generated from <10pg genomic DNA. Seven fragments with relatively low read depths and large variations in read depth were identified. One of these fragments covered part of the control region and the hypervariable region II.

Complete human mtDNA genome sequences from Vietnam and the phylogeography of Mainland Southeast Asia

Vietnam is an important crossroads within Mainland Southeast Asia (MSEA) and a gateway to Island Southeast Asia, and as such exhibits high levels of ethnolinguistic diversity. However, comparatively few studies have been undertaken of the genetic diversity of Vietnamese populations. In order to gain comprehensive insights into MSEA mtDNA phylogeography, we sequenced 609 complete mtDNA genomes from individuals belonging to five language families (Austroasiatic, Tai-Kadai, Hmong-Mien, Sino-Tibetan and Austronesian) and analyzed them in comparison with sequences from other MSEA countries and Taiwan. Within Vietnam, we identified 399 haplotypes belonging to 135 haplogroups; among the five language families, the sequences from Austronesian groups differ the most from the other groups. Phylogenetic analysis revealed 111 novel Vietnamese mtDNA lineages. Bayesian estimates of coalescence times and associated 95% HPD for these show a peak of mtDNA diversification around 2.5–3 kya, which coincides with the Dong Son culture, and thus may be associated with the agriculturally-driven expansion of this culture. Networks of major MSEA haplogroups emphasize the overall distinctiveness of sequences from Taiwan, in keeping with previous studies that suggested at most a minor impact of the Austronesian expansion from Taiwan on MSEA. We also see evidence for population expansions across MSEA geographic regions and language families.

Global demographic history of human populations inferred from whole mitochondrial genomes.

The Neolithic transition has led to marked increases in census population sizes across the world, as recorded by a rich archaeological record. However, previous attempts to detect such changes using genetic markers, especially mitochondrial DNA (mtDNA), have mostly been unsuccessful. We use complete mtDNA genomes from over 1700 individuals, from the 1000 Genomes Project Phase 3, to explore changes in populations sizes in five populations for each of four major geographical regions, using a sophisticated coalescent-based Bayesian method (extended Bayesian skyline plots) and mutation rates calibrated with ancient DNA. Despite the power and sophistication of our analysis, we fail to find size changes that correspond to the Neolithic transitions of the study populations. However, we do detect a number of size changes, which tend to be replicated in most populations within each region. These changes are mostly much older than the Neolithic transition and could reflect either population expansion or changes in population structure. Given the amount of migration and population mixing that occurred after these ancient signals were generated, we caution that modern populations will often carry ghost signals of demographic events that occurred far away from their current location.

The first complete mitochondrial genome of Limnadia lenticularis (Branchiopoda, Spinicaudata), with new insights on its phylogeography and on the taxonomy of the genus

We present the complete mitochondrial (mtDNA) genome of the branchiopod Limnadia lenticularis (Linnaeus, 1761). The circular genome is 15,151 bp in size and includes the standard complement of 37 genes (13 protein-coding genes, 22 tRNA genes and two rRNA genes) plus one non-coding region (control region). Genes were encoded on one or the other of both strands of the DNA, with a nucleotide composition of 35% GC. We perform the first phylogenetic reconstruction (Bayesian analysis) with eleven complete mtDNAs of branchiopods indicating that L. lenticularis is close to Daphnia species. This phylogeny and gene order showed two distinct groups: Anostraca (Artemia, Phallocryptus and Streptocephalus) and a second group formed by L. lenticularis, Daphnia and Triops. These results were also confirmed through a comparison of nucleotide identity for the 13 protein-coding genes and the two ribosomal RNA genes between these eleven mtDNAs. In addition to presenting the complete L. lenticularis mtDNA, we investigated the genetic diversity and relationships of different specimens from remote localities of this species using two partial markers: one nuclear (28S rRNA) and one mitochondrial (COX1). Our results suggest that Limnadia lenticularis is composed of three cryptic species (with allopatric distribution in Europe, East Asia and America).

Anti-replicative recombinant 5S rRNA molecules can modulate the mtDNA heteroplasmy in a glucose-dependent manner.

Mutations in mitochondrial DNA are an important source of severe and incurable human diseases. The vast majority of these mutations are heteroplasmic, meaning that mutant and wild-type genomes are present simultaneously in the same cell. Only a very high proportion of mutant mitochondrial DNA (heteroplasmy level) leads to pathological consequences. We previously demonstrated that mitochondrial targeting of small RNAs designed to anneal with mutant mtDNA can decrease the heteroplasmy level by specific inhibition of mutant mtDNA replication, thus representing a potential therapy. We have also shown that 5S ribosomal RNA, partially imported into human mitochondria, can be used as a vector to deliver anti-replicative oligoribonucleotides into human mitochondria. So far, the efficiency of cellular expression of recombinant 5S rRNA molecules bearing therapeutic insertions remained very low. In the present study, we designed new versions of anti-replicative recombinant 5S rRNA targeting a large deletion in mitochondrial DNA which causes the KSS syndrome, analyzed their specific annealing to KSS mitochondrial DNA and demonstrated their import into mitochondria of cultured human cells. To obtain an increased level of the recombinant 5S rRNA stable expression, we created transmitochondrial cybrid cell line bearing a site for Flp-recombinase and used this system for the recombinase-mediated integration of genes coding for the anti-replicative recombinant 5S rRNAs into nuclear genome. We demonstrated that stable expression of anti-replicative 5S rRNA versions in human transmitochondrial cybrid cells can induce a shift in heteroplasmy level of KSS mutation in mtDNA. This shift was directly dependent on the level of the recombinant 5S rRNA expression and the sequence of the anti-replicative insertion. Quantification of mtDNA copy number in transfected cells revealed the absence of a non-specific effect on wild type mtDNA replication, indicating that the decreased proportion between mutant and wild type mtDNA molecules is not a consequence of a random repopulation of depleted pool of mtDNA genomes. The heteroplasmy change could be also modulated by cell growth conditions, namely increased by cells culturing in a carbohydrate-free medium, thus forcing them to use oxidative phosphorylation and providing a selective advantage for cells with improved respiration capacities. We discuss the advantages and limitations of this approach and propose further development of the anti-replicative strategy based on the RNA import into human mitochondria.

Distribution and frequency of mitochondrial DNA polymorphisms in blue mussel (Mytilus edulis) populations of southwestern Nova Scotia (Canada)

The Atlantic blue mussel (Mytilus edulis Linnaeus, 1758) exhibits doubly uniparental inheritance of mitochondrial (mt) DNA. Females are usually homoplasmic for a female-transmitted mt genome (the F type) and males are heteroplasmic for an F type and a male-transmitted mt genome (the M type). F types can undergo “role-reversal” events, resulting in new male-transmitted mtDNA genomes known as recently masculinized (RM) types that co-occur in populations with evolutionarily older standard-male (SM) types. Phylogenetic analyses have shown that RM types periodically replace SM types. It has also been shown that sperm with RM mtDNA have greater swimming velocity and more efficient components of the electron transport chain compared to sperm with SM mtDNA, thus leading to the hypothesis that RM sperm may have a selective advantage over SM sperm. The present study examines the distribution of RM and SM mitotypes in male M. edulis (n = 225) from 13 localities in southwestern Nova Scotia (Canada). The SM type was more common in all populations, with the proportion of RM types ranging from 0% to 24.1%. The highest proportion of RM types was observed in an aquaculture operation. Analyses of additional populations are required to evaluate the selective pressures affecting the geographic distribution of RM and SM mitotypes in M. edulis.

Some maternal lineages of domestic horses may have origins in East Asia revealed with further evidence of mitochondrial genomes and HVR-1 sequences.

ObjectivesThere are large populations of indigenous horse (Equus caballus) in China and some other parts of East Asia. However, their matrilineal genetic diversity and origin remained poorly understood. Using a combination of mitochondrial DNA (mtDNA) and hypervariable region (HVR-1) sequences, we aim to investigate the origin of matrilineal inheritance in these domestic horses.MethodsTo investigate patterns of matrilineal inheritance in domestic horses, we conducted a phylogenetic study using 31 de novo mtDNA genomes together with 317 others from the GenBank. In terms of the updated phylogeny, a total of 5,180 horse mitochondrial HVR-1 sequences were analyzed.ResultsEightteen haplogroups (Aw-Rw) were uncovered from the analysis of the whole mitochondrial genomes. Most of which have a divergence time before the earliest domestication of wild horses (about 5,800 years ago) and during the Upper Paleolithic (35–10 KYA). The distribution of some haplogroups shows geographic patterns. The Lw haplogroup contained a significantly higher proportion of European horses than the horses from other regions, while haplogroups Jw, Rw, and some maternal lineages of Cw, have a higher frequency in the horses from East Asia. The 5,180 sequences of horse mitochondrial HVR-1 form nine major haplogroups (A-I). We revealed a corresponding relationship between the haplotypes of HVR-1 and those of whole mitochondrial DNA sequences. The data of the HVR-1 sequences also suggests that Jw, Rw, and some haplotypes of Cw may have originated in East Asia while Lw probably formed in Europe.ConclusionsOur study supports the hypothesis of the multiple origins of the maternal lineage of domestic horses and some maternal lineages of domestic horses may have originated from East Asia.

According to mitochondrial DNA evidence, Parascaris equorum and Parascaris univalens may represent the same species.

Parascarosis is caused mainly by parasitic infections with Parascaris equorum and Parascaris univalens, the most common ascarid nematodes, in the small intestine of equines. Parascarosis often causes severe illness and even death in foals and yearlings. In this study, we obtained the complete sequence of the P. equorum mitochondrial (mt) genome and compared its organization and structure with that of P. equorum Japan isolate (nearly complete), and the complete mtDNA sequences of P. univalens Switzerland and USA isolates. The complete mtDNA genome of P. equorum China isolate is 13,899 base pairs (bp), making it the smallest of the four genomes. All four Parascaris mt genomes are circular, and all genes are transcribed in the same direction. The P. equorum mtDNA genome consists of 12 protein-coding genes, two ribosomal RNA genes, 22 transfer (t) RNA genes and one non-coding region, which is consistent with P. equorum Japan isolate and P. univalens Switzerland isolate but distinct from P. univalens USA isolate, which has 20 tRNA genes. Differences in nucleotide sequences of the four entire mt genomes range from 0.1-0.9%, and differences in total amino acid sequences of protein-coding genes are 0.2-2.1%. Phylogenetic analyses showed that the four Parascaris species clustered in a clade, indicating that P. equorum and P. univalens are very closely related. These mt genome datasets provide genetic evidence that P. equorum and P. univalens may represent the same species, which will be of use in further studies of the taxonomy, systematics and population genetics of ascarids and other nematodes.

Ancient Roman mitochondrial genomes and isotopes reveal relationships and geographic origins at the local and pan-Mediterranean scales

Rome initiated several campaigns to expand, conquer, and enslave local Italic populations following the establishment of the republic in 504 BCE. However, the cultural and biological changes resulting from Roman subjugation across Italy remain a topic of intense historical debate. Although important, historic and archaeological lines of evidence fail to track the impact of forced enslavement and enculturation at individual and broader genetic scales and, more generally, offer fewer clues regarding the potential affinities of Roman period Italians to European, Near Eastern, western Asian and North African populations at this time.In this paper, we present the whole mitochondrial (mtDNA) genomes of 30 Roman period (1st–4th centuries CE) individuals buried in the Vagnari necropolis in southern Italy. We integrate the mtDNA data with previously published bioarchaeological and isotope (δ18O and 87Sr/86Sr) data for the Vagnari assemblage and compare Roman haplogroup composition to 15 newly sequenced mitochondrial genomes obtained from a pre-Roman Iron Age skeletal assemblage, located in close proximity to Vagnari. Additionally, we contrast our South Italian dataset with a further 332 complete ancient mtDNA genomes from the pan-Mediterranean region, Europe, western Asia and North African regions.Population pairwise ΦST values suggest that Roman Italians share closer genetic similarity to Neolithic, Bronze Age, and Armenian Iron Age populations from western and central Eurasia than with Iron Age Italians, Ptolemaic, and Roman period Egyptians. Vagnari individuals with δ18O, 87Sr/86Sr, and mtDNA data suggest a predominantly local demographic was employed at the site. However, two individuals belong to eastern Eurasian haplogroup D4b1c, indicating that the maternal ancestors of these two individuals migrated to South Italy prior to the 1st century CE. Additionally, we provide the first genetic evidence for possible maternal relatedness in a Roman period skeletal assemblage. Our research highlights the significance of integrating multiple lines of bioarchaeological data to inform interpretations about Roman colonial expansion and its impact on population structure.

Optimised detection of mitochondrial DNA strand breaks

Intrinsic and extrinsic factors that induce cellular oxidative stress damage tissue integrity and promote ageing, resulting in accumulative strand breaks to the mitochondrial DNA (mtDNA) genome. Limited repair mechanisms and close proximity to superoxide generation make mtDNA a prominent biomarker of oxidative damage. Using human DNA we describe an optimised long-range qPCR methodology that sensitively detects mtDNA strand breaks relative to a suite of short mitochondrial and nuclear DNA housekeeping amplicons, which control for any variation in mtDNA copy number. An application is demonstrated by detecting 16-36-fold mtDNA damage in human skin cells induced by hydrogen peroxide and solar simulated radiation.

Mitochondrial Genomics: A Complex Field Now Coming of Age

The groundwork for mitochondrial medicine was laid 30 years ago with identification of the first disease-causing mitochondrial DNA (mtDNA) mutations in 1988. Three decades later, mutations in nearly 300 genes involving every possible mode of inheritance within both nuclear and mitochondrial genomes are now recognized to collectively comprise the largest class of inherited metabolic disease affecting at least 1 in 4,300 individuals across all ages. Significant progress has been made in recent years to improve understanding of mitochondrial biology and disease pathophysiology. Markedly improved understanding of the highly diverse molecular etiologies of multi-systemic phenotypes in primary mitochondrial disease has resulted from massively parallel genomic sequencing technologies and improved bioinformatic resources that enable identification in individual patients of their disease's precise genetic etiology. Key informatics resources of particular utility to the mitochondrial disease genomics community have been developed, including: (1) Mitocarta 2.0 repository of 1200+ verified mitochondria-localized proteins, (2) MITOMAP Web resource of curated mtDNA genome variants, and (3) Mitochondrial Disease Sequence Data Resource (MSeqDR) that centralizes Web curation and annotation of mitochondrial disease genes and variants in both genomes, ontology-defined phenotypes, and access to many analytic tools to support genomic data mining and interpretation. Gene and mutation-based disease categorization has proven particularly useful to identify the full clinical spectrum of disease that may affect a given individual. Extensive genomic advances, both in technologic platforms and bioinformatics resources, have facilitated dramatic improvement in the accurate recognition and understanding of primary mitochondrial disease.