Fidelity and mutational spectrum of Pfu DNA polymerase on a human mitochondrial DNA sequence.

Science.gov (United States)

André, P; Kim, A; Khrapko, K; Thilly, W G

1997-08-01

The study of rare genetic changes in human tissues requires specialized techniques. Point mutations at fractions at or below 10(-6) must be observed to discover even the most prominent features of the point mutational spectrum. PCR permits the increase in number of mutant copies but does so at the expense of creating many additional mutations or "PCR noise". Thus, each DNA sequence studied must be characterized with regard to the DNA polymerase and conditions used to avoid interpreting a PCR-generated mutation as one arising in human tissue. The thermostable DNA polymerase derived from Pyrococcus furiosus designated Pfu has the highest fidelity of any DNA thermostable polymerase studied to date, and this property recommends it for analyses of tissue mutational spectra. Here, we apply constant denaturant capillary electrophoresis (CDCE) to separate and isolate the products of DNA amplification. This new strategy permitted direct enumeration and identification of point mutations created by Pfu DNA polymerase in a 96-bp low melting domain of a human mitochondrial sequence despite the very low mutant fractions generated in the PCR process. This sequence, containing part of the tRNA glycine and NADH dehydrogenase subunit 3 genes, is the target of our studies of mitochondrial mutagenesis in human cells and tissues. Incorrectly synthesized sequences were separated from the wild type as mutant/wild-type heteroduplexes by sequential enrichment on CDCE. An artificially constructed mutant was used as an internal standard to permit calculation of the mutant fraction. Our study found that the average error rate (mutations per base pair duplication) of Pfu was 6.5 x 10(-7), and five of its more frequent mutations (hot spots) consisted of three transversions (GC-->TA, AT-->TA, and AT-->CG), one transition (AT-->GC), and one 1-bp deletion (in an AAAAAA sequence). To achieve an even higher sensitivity, the amount of Pfu-induced mutants must be reduced.

Bridging two scholarly islands enriches both: COI DNA barcodes for species identification versus human mitochondrial variation for the study of migrations and pathologies.

Science.gov (United States)

Thaler, David S; Stoeckle, Mark Y

2016-10-01

DNA barcodes for species identification and the analysis of human mitochondrial variation have developed as independent fields even though both are based on sequences from animal mitochondria. This study finds questions within each field that can be addressed by reference to the other. DNA barcodes are based on a 648-bp segment of the mitochondrially encoded cytochrome oxidase I. From most species, this segment is the only sequence available. It is impossible to know whether it fairly represents overall mitochondrial variation. For modern humans, the entire mitochondrial genome is available from thousands of healthy individuals. SNPs in the human mitochondrial genome are evenly distributed across all protein-encoding regions arguing that COI DNA barcode is representative. Barcode variation among related species is largely based on synonymous codons. Data on human mitochondrial variation support the interpretation that most - possibly all - synonymous substitutions in mitochondria are selectively neutral. DNA barcodes confirm reports of a low variance in modern humans compared to nonhuman primates. In addition, DNA barcodes allow the comparison of modern human variance to many other extant animal species. Birds are a well-curated group in which DNA barcodes are coupled with census and geographic data. Putting modern human variation in the context of intraspecies variation among birds shows humans to be a single breeding population of average variance.

Roles of Mitochondrial DNA Mutations in Stem Cell Ageing

Directory of Open Access Journals (Sweden)

Tianhong Su

2018-03-01

Full Text Available Mitochondrial DNA (mtDNA mutations accumulate in somatic stem cells during ageing and cause mitochondrial dysfunction. In this review, we summarize the studies that link mtDNA mutations to stem cell ageing. We discuss the age-related behaviours of the somatic mtDNA mutations in stem cell populations and how they potentially contribute to stem cell ageing by altering mitochondrial properties in humans and in mtDNA-mutator mice. We also draw attention to the diverse fates of the mtDNA mutations with different origins during ageing, with potential selective pressures on the germline inherited but not the somatic mtDNA mutations.

Detection of mitochondrial DNA deletions in human cells induced by ionizing radiation

International Nuclear Information System (INIS)

Liu, Qing-Jie; Feng, Jiang-Bin; Lu, Xue; Li, Yu-Wen; Chen, De-Qing

2008-01-01

Full text: Purpose: To screen the novel mitochondrial DNA (mt DNA) deletions induced by ionizing radiation, and analyze the several kinds of mt DNA deletions, known as 3895 bp, 889 bp, 7436 bp or 4934 bp deletions. Methods: Long-range PCR with two pairs of primers, which could amplify the whole human mitochondrial genome, was used to analyze the lymphoblastoid cell line before and after exposed to 10 Gy 60 Co γ-rays. The limited condition PCR was used to certify the possible mt DNA deletion showed by long-range PCR. The PCR products were purified, cloned, sequenced and the sequence result were BLASTed. Regular PCR or nest-PCR were used to analyze the 3895 bp, 889 bp, 7436 bp or 4934 bp deletions before and after radiation exposure. The final PCR products were purified, sequenced and BALSTed on standard human mitochondrial genome sequence database. Results: (1) The predicted bands of mt DNA were observed on the control cell lines, and the possible mt DNA deletions were also detected on the irradiated cell lines. The deletions were certified by the limited condition PCR. The sequence BLAST results of the cloned PCR products showed that two kinds of deletions, 7455 bp deletion (nt 475-7929 in heavy strand) and 9225 bp deletion (nt 7714-369 in heavy strand), which were between two 8 bp direct repeats. Further bioinformatics analysis showed that the two deletions were novel deletions. (2) The 889 bp and 3895 bp deletion were not detected for the cell line samples not exposed to 60 Co γ-rays. The 889 bp and 3895 bp deletions were detected on samples exposed to 10 Gy 60 Co γ-rays. The BALST results showed that the 889 bp and 3895 deletions flanked nt 11688 bp-12576, nt 548 bp-4443, respectively. The 7436 bp deletion levels were not changed much before and after irradiation. (3) The 4934 bp deletions had the same pattern as 7436 bp deletion, but it could induced by radiation. Conclusions: Ionizing radiation could induce the human lymphoblastoid two novel mt DNA

RECQL4 localizes to mitochondria and preserves mitochondrial DNA integrity

DEFF Research Database (Denmark)

Croteau, Deborah L; Rossi, Marie L; Canugovi, Chandrika

2012-01-01

in premature aging. There is no information about whether any of the RecQ helicases play roles in mitochondrial biogenesis, which is strongly implicated in the aging process. Here, we used microscopy to visualize RECQL4 in mitochondria. Fractionation of human and mouse cells also showed that RECQL4 was present...... in mitochondria. Q-PCR amplification of mitochondrial DNA demonstrated that mtDNA damage accumulated in RECQL4-deficient cells. Microarray analysis suggested that mitochondrial bioenergetic pathways might be affected in RTS. Measurements of mitochondrial bioenergetics showed a reduction in the mitochondrial......Q helicase to be found in both human and mouse mitochondria, and the loss of RECQL4 alters mitochondrial integrity....

Mitochondrial DNA inheritance in the human fungal pathogen Cryptococcus gattii.

Science.gov (United States)

Wang, Zixuan; Wilson, Amanda; Xu, Jianping

2015-02-01

The inheritance of mitochondrial DNA (mtDNA) is predominantly uniparental in most sexual eukaryotes. In this study, we examined the mitochondrial inheritance pattern of Cryptococcus gattii, a basidiomycetous yeast responsible for the recent and ongoing outbreak of cryptococcal infections in the US Pacific Northwest and British Columbia (especially Vancouver Island) in Canada. Using molecular markers, we analyzed the inheritance of mtDNA in 14 crosses between strains within and between divergent lineages in C. gattii. Consistent with results from recent studies, our analyses identified significant variations in mtDNA inheritance patterns among strains and crosses, ranging from strictly uniparental to biparental. For two of the crosses that showed uniparental mitochondrial inheritance in standard laboratory conditions, we further investigated the effects of the following environmental variables on mtDNA inheritance: UV exposure, temperature, and treatments with the methylation inhibitor 5-aza-2'-deoxycytidine and with the ubiquitination inhibitor ammonium chloride. Interestingly, one of these crosses showed no response to these environmental variables while the other exhibited diverse patterns ranging from complete uniparental inheritance of the MATa parent mtDNA, to biparental inheritance, and to a significant bias toward inheritance of the MATα parental mtDNA. Our results indicate that mtDNA inheritance in C. gattii differs from that in its closely related species Cryptococcus neoformans. Copyright © 2015 Elsevier Inc. All rights reserved.

Characterization of Bombyx mori mitochondrial transcription factor A, a conserved regulator of mitochondrial DNA.

Science.gov (United States)

Sumitani, Megumi; Kondo, Mari; Kasashima, Katsumi; Endo, Hitoshi; Nakamura, Kaoru; Misawa, Toshihiko; Tanaka, Hiromitsu; Sezutsu, Hideki

2017-04-15

In the present study, we initially cloned and characterized a mitochondrial transcription factor A (Tfam) homologue in the silkworm, Bombyx mori. Bombyx mori TFAM (BmTFAM) localized to mitochondria in cultured silkworm and human cells, and co-localized with mtDNA nucleoids in human HeLa cells. In an immunoprecipitation analysis, BmTFAM was found to associate with human mtDNA in mitochondria, indicating its feature as a non-specific DNA-binding protein. In spite of the low identity between BmTFAM and human TFAM (26.5%), the expression of BmTFAM rescued mtDNA copy number reductions and enlarged mtDNA nucleoids in HeLa cells, which were induced by human Tfam knockdown. Thus, BmTFAM compensates for the function of human TFAM in HeLa cells, demonstrating that the mitochondrial function of TFAM is highly conserved between silkworms and humans. BmTfam mRNA was strongly expressed in early embryos. Through double-stranded RNA (dsRNA)-based RNA interference (RNAi) in silkworm embryos, we found that the knockdown of BmTFAM reduced the amount of mtDNA and induced growth retardation at the larval stage. Collectively, these results demonstrate that BmTFAM is a highly conserved mtDNA regulator and may be a good candidate for investigating and modulating mtDNA metabolism in this model organism. Copyright © 2017 Elsevier B.V. All rights reserved.

Mitochondrial DNA repair and aging

Energy Technology Data Exchange (ETDEWEB)

Mandavilli, Bhaskar S.; Santos, Janine H.; Van Houten, Bennett

2002-11-30

The mitochondrial electron transport chain plays an important role in energy production in aerobic organisms and is also a significant source of reactive oxygen species that damage DNA, RNA and proteins in the cell. Oxidative damage to the mitochondrial DNA is implicated in various degenerative diseases, cancer and aging. The importance of mitochondrial ROS in age-related degenerative diseases is further strengthened by studies using animal models, Caenorhabditis elegans, Drosophila and yeast. Research in the last several years shows that mitochondrial DNA is more susceptible to various carcinogens and ROS when compared to nuclear DNA. DNA damage in mammalian mitochondria is repaired by base excision repair (BER). Studies have shown that mitochondria contain all the enzymes required for BER. Mitochondrial DNA damage, if not repaired, leads to disruption of electron transport chain and production of more ROS. This vicious cycle of ROS production and mtDNA damage ultimately leads to energy depletion in the cell and apoptosis.

Mitochondrial DNA repair and aging

International Nuclear Information System (INIS)

Mandavilli, Bhaskar S.; Santos, Janine H.; Van Houten, Bennett

2002-01-01

The mitochondrial electron transport chain plays an important role in energy production in aerobic organisms and is also a significant source of reactive oxygen species that damage DNA, RNA and proteins in the cell. Oxidative damage to the mitochondrial DNA is implicated in various degenerative diseases, cancer and aging. The importance of mitochondrial ROS in age-related degenerative diseases is further strengthened by studies using animal models, Caenorhabditis elegans, Drosophila and yeast. Research in the last several years shows that mitochondrial DNA is more susceptible to various carcinogens and ROS when compared to nuclear DNA. DNA damage in mammalian mitochondria is repaired by base excision repair (BER). Studies have shown that mitochondria contain all the enzymes required for BER. Mitochondrial DNA damage, if not repaired, leads to disruption of electron transport chain and production of more ROS. This vicious cycle of ROS production and mtDNA damage ultimately leads to energy depletion in the cell and apoptosis

HmtDB 2016: data update, a better performing query system and human mitochondrial DNA haplogroup predictor.

Science.gov (United States)

Clima, Rosanna; Preste, Roberto; Calabrese, Claudia; Diroma, Maria Angela; Santorsola, Mariangela; Scioscia, Gaetano; Simone, Domenico; Shen, Lishuang; Gasparre, Giuseppe; Attimonelli, Marcella

2017-01-04

The HmtDB resource hosts a database of human mitochondrial genome sequences from individuals with healthy and disease phenotypes. The database is intended to support both population geneticists as well as clinicians undertaking the task to assess the pathogenicity of specific mtDNA mutations. The wide application of next-generation sequencing (NGS) has provided an enormous volume of high-resolution data at a low price, increasing the availability of human mitochondrial sequencing data, which called for a cogent and significant expansion of HmtDB data content that has more than tripled in the current release. We here describe additional novel features, including: (i) a complete, user-friendly restyling of the web interface, (ii) links to the command-line stand-alone and web versions of the MToolBox package, an up-to-date tool to reconstruct and analyze human mitochondrial DNA from NGS data and (iii) the implementation of the Reconstructed Sapiens Reference Sequence (RSRS) as mitochondrial reference sequence. The overall update renders HmtDB an even more handy and useful resource as it enables a more rapid data access, processing and analysis. HmtDB is accessible at http://www.hmtdb.uniba.it/. © The Author(s) 2016. Published by Oxford University Press on behalf of Nucleic Acids Research.

Signatures of Climatic Change In Human Mitochondrial Dna From Europe

Science.gov (United States)

Richards, M. B.; Macaulay, V. A.; Torroni, A.; Bandelt, H.-J.

Founder analysis is an approach to analysing non-recombining DNA sequence data, such as variation in the mitochondrial DNA (mtDNA), which aims at identifying and dating migrations into new territory. We applied the approach to about 4,000 human mtDNA sequences from Europe and the Near East, in order to estimate the proportion of modern lineages whose ancestors arrived at various times during the continent's past. We found that the major signal dates to about 15,000 years ago, at the time of rewarming following the Last Glacial Maximum (LGM). There is little or no archaeological evidence for immigration into Europe at this time, and the record indicates that at least parts of southern Europe remained populated during the LGM. Therefore, we interpret this signal as the trace of a bottleneck at the time of the LGM, as a result of the retreat from northern Europe during the peak of the glaciation, followed by a re-expansion from one or more refugial zones. Immigration episodes then figure at the beginning of the Early Upper Palaeolithic, during the Middle Upper Palaeolithic, and with the Neolithic. The impact of the latter on the composition of the European mtDNA pool was evidently rather minor. This result implies that climate is likely to have been a major force shaping human demographic history in Europe.

Age-related mitochondrial DNA depletion and the impact on pancreatic Beta cell function.

Science.gov (United States)

Nile, Donna L; Brown, Audrey E; Kumaheri, Meutia A; Blair, Helen R; Heggie, Alison; Miwa, Satomi; Cree, Lynsey M; Payne, Brendan; Chinnery, Patrick F; Brown, Louise; Gunn, David A; Walker, Mark

2014-01-01

Type 2 diabetes is characterised by an age-related decline in insulin secretion. We previously identified a 50% age-related decline in mitochondrial DNA (mtDNA) copy number in isolated human islets. The purpose of this study was to mimic this degree of mtDNA depletion in MIN6 cells to determine whether there is a direct impact on insulin secretion. Transcriptional silencing of mitochondrial transcription factor A, TFAM, decreased mtDNA levels by 40% in MIN6 cells. This level of mtDNA depletion significantly decreased mtDNA gene transcription and translation, resulting in reduced mitochondrial respiratory capacity and ATP production. Glucose-stimulated insulin secretion was impaired following partial mtDNA depletion, but was normalised following treatment with glibenclamide. This confirms that the deficit in the insulin secretory pathway precedes K+ channel closure, indicating that the impact of mtDNA depletion is at the level of mitochondrial respiration. In conclusion, partial mtDNA depletion to a degree comparable to that seen in aged human islets impaired mitochondrial function and directly decreased insulin secretion. Using our model of partial mtDNA depletion following targeted gene silencing of TFAM, we have managed to mimic the degree of mtDNA depletion observed in aged human islets, and have shown how this correlates with impaired insulin secretion. We therefore predict that the age-related mtDNA depletion in human islets is not simply a biomarker of the aging process, but will contribute to the age-related risk of type 2 diabetes.

A Spatio-Temporal Analysis of Mitochondrial DNA Haplogroup I

Directory of Open Access Journals (Sweden)

Revesz Peter Z.

2016-01-01

Full Text Available The recent recovery of ancient DNA from a growing number of human samples shows that mitochondrial DNA haplogroup I was introduced to Europe after the end of the Last Glacial Maximum. This paper provides a spatio-temporal analysis of the various subhaplogroups of mitochondrial DNA I. The study suggests that haplogroup I diversified into haplogroups I1, I2’3, I4 and I5 at specific regions in Eurasia and then spread southward to Crete and Egypt.

Slow mitochondrial repair of 5'-AMP renders mtDNA susceptible to damage in APTX deficient cells

DEFF Research Database (Denmark)

Akbari, Mansour; Sykora, Peter; Bohr, Vilhelm A

2015-01-01

deficient cells. Moreover, the removal of 5'-AMP from DNA was significantly slower in the mitochondrial extracts from human cell lines and mouse tissues compared with their corresponding nuclear extracts. These results suggest that, contrary to nuclear DNA repair, mitochondrial DNA repair is not able...... elucidated. Here, we monitored the repair of 5'-AMP DNA damage in nuclear and mitochondrial extracts from human APTX(+/+) and APTX(-/-) cells. The efficiency of repair of 5'-AMP DNA was much lower in mitochondrial than in nuclear protein extracts, and resulted in persistent DNA repair intermediates in APTX......Aborted DNA ligation events in eukaryotic cells can generate 5'-adenylated (5'-AMP) DNA termini that can be removed from DNA by aprataxin (APTX). Mutations in APTX cause an inherited human disease syndrome characterized by early-onset progressive ataxia with ocular motor apraxia (AOA1). APTX...

Mitochondrial DNA analysis suggests a Chibchan migration into Colombia

OpenAIRE

Noguera-Santamaría, Maria Claudia; Instituto de Genética Humana, Facultad de Medicina, Pontificia Universidad Javeriana. Grupo de Genética Humana, Facultad de Medicina, Universidad de La Sabana. Facultad de Ciencias de la Salud. Grupo Gisafaco. Corporación Universitaria Remington; Anderson, Carl Edlund; Department of Foreign Languages & Cultures, Universidad de La Sabana; Uricoechea, Daniel; Grupo de Genética Humana, Facultad de Medicina, Universidad de La Sabana; Durán, Clemencia; Instituto de Genética Humana, Facultad de Medicina, Pontificia Universidad Javeriana.; Briceño-Balcázar, Ignacio; Instituto de Genética Humana, Facultad de Medicina, Pontificia Universidad Javeriana Grupo de Genética Humana, Facultad de Medicina, Universidad de La Sabana; Bernal-Villegas, Jaime; Instituto de Genética Humana, Facultad de Medicina, Pontificia Universidad Javeriana Universidad Tecnológica de Bolívar

2015-01-01

The characterization of mitochondrial DNA (mtDNA) allows the establishment of genetic structures and phylogenetic relationships in human populations, tracing lineages far back in time. We analysed samples of mtDNA from twenty (20) Native American populations (700 individuals) dispersed throughout Colombian territory. Samples were collected during 1989-1993 in the context of the program Expedición Humana (“Human Expedition”) and stored in the Biological Repository of the Institute of Human Gen...

MitBASE : a comprehensive and integrated mitochondrial DNA database. The present status

NARCIS (Netherlands)

Attimonelli, M.; Altamura, N.; Benne, R.; Brennicke, A.; Cooper, J. M.; D'Elia, D.; Montalvo, A.; Pinto, B.; de Robertis, M.; Golik, P.; Knoop, V.; Lanave, C.; Lazowska, J.; Licciulli, F.; Malladi, B. S.; Memeo, F.; Monnerot, M.; Pasimeni, R.; Pilbout, S.; Schapira, A. H.; Sloof, P.; Saccone, C.

2000-01-01

MitBASE is an integrated and comprehensive database of mitochondrial DNA data which collects, under a single interface, databases for Plant, Vertebrate, Invertebrate, Human, Protist and Fungal mtDNA and a Pilot database on nuclear genes involved in mitochondrial biogenesis in Saccharomyces

Role of Mitochondrial DNA Mutations in Cellular Vulnerability to Mitochondria-Specific Environmental Toxins

National Research Council Canada - National Science Library

Hirsch, Etienne C

2005-01-01

In recent years, growing evidence has shown that mutations of mitochondrial DNA (mtDNA) are an important cause of mitochondrial disorders in humans, and have been associated with common neurodegenerative disorders, aging and cancers...

Transcription profiling suggests that mitochondrial topoisomerase IB acts as a topological barrier and regulator of mitochondrial DNA transcription.

Science.gov (United States)

Dalla Rosa, Ilaria; Zhang, Hongliang; Khiati, Salim; Wu, Xiaolin; Pommier, Yves

2017-12-08

Mitochondrial DNA (mtDNA) is essential for cell viability because it encodes subunits of the respiratory chain complexes. Mitochondrial topoisomerase IB (TOP1MT) facilitates mtDNA replication by removing DNA topological tensions produced during mtDNA transcription, but it appears to be dispensable. To test whether cells lacking TOP1MT have aberrant mtDNA transcription, we performed mitochondrial transcriptome profiling. To that end, we designed and implemented a customized tiling array, which enabled genome-wide, strand-specific, and simultaneous detection of all mitochondrial transcripts. Our technique revealed that Top1mt KO mouse cells process the mitochondrial transcripts normally but that protein-coding mitochondrial transcripts are elevated. Moreover, we found discrete long noncoding RNAs produced by H-strand transcription and encompassing the noncoding regulatory region of mtDNA in human and murine cells and tissues. Of note, these noncoding RNAs were strongly up-regulated in the absence of TOP1MT. In contrast, 7S DNA, produced by mtDNA replication, was reduced in the Top1mt KO cells. We propose that the long noncoding RNA species in the D-loop region are generated by the extension of H-strand transcripts beyond their canonical stop site and that TOP1MT acts as a topological barrier and regulator for mtDNA transcription and D-loop formation.

Mitochondrial oxidative stress in human hepatoma cells exposed to stavudine

International Nuclear Information System (INIS)

Velsor, Leonard W.; Kovacevic, Miro; Goldstein, Mark; Leitner, Heather M.; Lewis, William; Day, Brian J.

2004-01-01

The toxicity of nucleoside reverse transcriptase inhibitors (NRTIs) is linked to altered mitochondrial DNA (mtDNA) replication and subsequent disruption of cellular energetics. This manifests clinically as elevated concentrations of lactate in plasma. The mechanism(s) underlying how the changes in mtDNA replication lead to lactic acidosis remains unclear. It is hypothesized that mitochondrial oxidative stress links the changes in mtDNA replication to mitochondrial dysfunction and ensuing NRTIs toxicity. To test this hypothesis, changes in mitochondrial function, mtDNA amplification efficiency, and oxidative stress were assessed in HepG2-cultured human hepatoblasts treated with the NRTI stavudine (2',3'-didehydro-2',3'-deoxythymidine or d4T) for 48 h. d4T produced significant mitochondrial dysfunction with a 1.5-fold increase in cellular lactate to pyruvate ratios. In addition, d4T caused a dose-dependent decrease in mtDNA amplification and a correlative increase in abundance of markers of mitochondrial oxidative stress. Manganese (III) meso-tetrakis (4-benzoic acid) porphyrin, MnTBAP, a catalytic antioxidant, ameliorated or reversed d4T-induced changes in cell injury, energetics, mtDNA amplification, and mitochondrial oxidative stress. In conclusion, d4T treatment elevates mitochondrial reactive oxygen species (ROS), enhances mitochondrial oxidative stress, and contributes mechanistically to NRTI-induced toxicity. These deleterious events may be potentiated in acquired immunodeficiency syndrome (AIDS) by human immunodeficiency virus (HIV) infection itself, coinfection (e.g., viral hepatitis), aging, substance, and alcohol use

Radiosensitivity evaluation of Human tumor cell lines by detecting 4977bp deletion in mitochondrial DNA

International Nuclear Information System (INIS)

Zhang Yipei

2009-01-01

Objective: To explore the feasibility of determining radiosensitivity of human tumor cell lines in vitro using the assay of mtDNA4977bp deletion. Methods: Three human tumor cell lines were selected in this study, HepG 2 , EC-9706 and MCF-7. The surviving fraction(SF), the ratio of mtDNA4977bp deletion and DNA damage were detected by MTT assay and nested PCR technique respectively. Results: MTT assay: The SF of HepG 2 and EC-9706 after irradiated by 2, 4and 8Gy was lower significantly than that of MCF-7, which showed that the radiosensitivity of HepG 2 and EC-9706 was higher than that of MCF-7. But there was no statistical difference of SF between HepG 2 and EC-9706. PCR method:The differences on mtDNA 4977bp deletion in mitochondrial DNA among HepG 2 , EC-9706 and MCF-7 were not significant after 1Gy and 4Gy γ-ray irradiation. The ratio of 4977bp deletion in mitochondrial DNA of HepG 2 and EC-9706 increased while that of MCF-7 decreased after 8Gy irradiation. The ratio of mtDNA 4977bp deletion of HepG 2 and EC-9706 was higher significantly than that of MCF-7, which implies that the radiosensitivity of HepG 2 and EC-9706 was higher than that of MCF -7. Conclusion: As a new biological marker, mtDNA4977bp deletion may be hopeful to evaluate the radiosensitivity of tumor cells more objectively and exactly. (authors)

Endurance exercise rescues progeroid aging and induces systemic mitochondrial rejuvenation in mtDNA mutator mice

Science.gov (United States)

Safdar, Adeel; Bourgeois, Jacqueline M.; Ogborn, Daniel I.; Little, Jonathan P.; Hettinga, Bart P.; Akhtar, Mahmood; Thompson, James E.; Melov, Simon; Mocellin, Nicholas J.; Kujoth, Gregory C.; Prolla, Tomas A.; Tarnopolsky, Mark A.

2011-01-01

A causal role for mitochondrial DNA (mtDNA) mutagenesis in mammalian aging is supported by recent studies demonstrating that the mtDNA mutator mouse, harboring a defect in the proofreading-exonuclease activity of mitochondrial polymerase gamma, exhibits accelerated aging phenotypes characteristic of human aging, systemic mitochondrial dysfunction, multisystem pathology, and reduced lifespan. Epidemiologic studies in humans have demonstrated that endurance training reduces the risk of chronic diseases and extends life expectancy. Whether endurance exercise can attenuate the cumulative systemic decline observed in aging remains elusive. Here we show that 5 mo of endurance exercise induced systemic mitochondrial biogenesis, prevented mtDNA depletion and mutations, increased mitochondrial oxidative capacity and respiratory chain assembly, restored mitochondrial morphology, and blunted pathological levels of apoptosis in multiple tissues of mtDNA mutator mice. These adaptations conferred complete phenotypic protection, reduced multisystem pathology, and prevented premature mortality in these mice. The systemic mitochondrial rejuvenation through endurance exercise promises to be an effective therapeutic approach to mitigating mitochondrial dysfunction in aging and related comorbidities. PMID:21368114

The persistence of human DNA in soil following surface decomposition.

Science.gov (United States)

Emmons, Alexandra L; DeBruyn, Jennifer M; Mundorff, Amy Z; Cobaugh, Kelly L; Cabana, Graciela S

2017-09-01

Though recent decades have seen a marked increase in research concerning the impact of human decomposition on the grave soil environment, the fate of human DNA in grave soil has been relatively understudied. With the purpose of supplementing the growing body of literature in forensic soil taphonomy, this study assessed the relative persistence of human DNA in soil over the course of decomposition. Endpoint PCR was used to assess the presence or absence of human nuclear and mitochondrial DNA, while qPCR was used to evaluate the quantity of human DNA recovered from the soil beneath four cadavers at the University of Tennessee's Anthropology Research Facility (ARF). Human nuclear DNA from the soil was largely unrecoverable, while human mitochondrial DNA was detectable in the soil throughout all decomposition stages. Mitochondrial DNA copy abundances were not significantly different between decomposition stages and were not significantly correlated to soil edaphic parameters tested. There was, however, a significant positive correlation between mitochondrial DNA copy abundances and the human associated bacteria, Bacteroides, as estimated by 16S rRNA gene abundances. These results show that human mitochondrial DNA can persist in grave soil and be consistently detected throughout decomposition. Copyright © 2017 The Chartered Society of Forensic Sciences. Published by Elsevier B.V. All rights reserved.

Mitochondrial targeting of human O6-methylguanine DNA methyltransferase protects against cell killing by chemotherapeutic alkylating agents.

Science.gov (United States)

Cai, Shanbao; Xu, Yi; Cooper, Ryan J; Ferkowicz, Michael J; Hartwell, Jennifer R; Pollok, Karen E; Kelley, Mark R

2005-04-15

DNA repair capacity of eukaryotic cells has been studied extensively in recent years. Mammalian cells have been engineered to overexpress recombinant nuclear DNA repair proteins from ectopic genes to assess the impact of increased DNA repair capacity on genome stability. This approach has been used in this study to specifically target O(6)-methylguanine DNA methyltransferase (MGMT) to the mitochondria and examine its impact on cell survival after exposure to DNA alkylating agents. Survival of human hematopoietic cell lines and primary hematopoietic CD34(+) committed progenitor cells was monitored because the baseline repair capacity for alkylation-induced DNA damage is typically low due to insufficient expression of MGMT. Increased DNA repair capacity was observed when K562 cells were transfected with nuclear-targeted MGMT (nucl-MGMT) or mitochondrial-targeted MGMT (mito-MGMT). Furthermore, overexpression of mito-MGMT provided greater resistance to cell killing by 1,3-bis (2-chloroethyl)-1-nitrosourea (BCNU) than overexpression of nucl-MGMT. Simultaneous overexpression of mito-MGMT and nucl-MGMT did not enhance the resistance provided by mito-MGMT alone. Overexpression of either mito-MGMT or nucl-MGMT also conferred a similar level of resistance to methyl methanesulfonate (MMS) and temozolomide (TMZ) but simultaneous overexpression in both cellular compartments was neither additive nor synergistic. When human CD34(+) cells were infected with oncoretroviral vectors that targeted O(6)-benzylguanine (6BG)-resistant MGMT (MGMT(P140K)) to the nucleus or the mitochondria, committed progenitors derived from infected cells were resistant to 6BG/BCNU or 6BG/TMZ. These studies indicate that mitochondrial or nuclear targeting of MGMT protects hematopoietic cells against cell killing by BCNU, TMZ, and MMS, which is consistent with the possibility that mitochondrial DNA damage and nuclear DNA damage contribute equally to alkylating agent-induced cell killing during chemotherapy.

Mitochondrial DNA: A Blind Spot in Neuroepigenetics.

Science.gov (United States)

Manev, Hari; Dzitoyeva, Svetlana; Chen, Hu

2012-04-01

Neuroepigenetics, which includes nuclear DNA modifications such as 5-methylcytosine and 5-hydoxymethylcytosine and modifications of nuclear proteins such as histones, is emerging as the leading field in molecular neuroscience. Historically, a functional role for epigenetic mechanisms, including in neuroepigenetics, has been sought in the area of the regulation of nuclear transcription. However, one important compartment of mammalian cell DNA, different from nuclear but equally important for physiological and pathological processes (including in the brain), mitochondrial DNA has for the most part not had a systematic epigenetic characterization. The importance of mitochondria and mitochondrial DNA (particularly its mutations) in central nervous system physiology and pathology has long been recognized. Only recently have mechanisms of mitochondrial DNA methylation and hydroxymethylation, including the discovery of mitochondrial DNA-methyltransferases and the presence and the functionality of 5-methylcytosine and 5-hydroxymethylcytosine in mitochondrial DNA (e.g., in modifying the transcription of mitochondrial genome), been unequivocally recognized as a part of mammalian mitochondrial physiology. Here we summarize for the first time evidence supporting the existence of these mechanisms and we propose the term "mitochondrial epigenetics" to be used when referring to them. Currently, neuroepigenetics does not include mitochondrial epigenetics - a gap that we expect to close in the near future.

Fidelity and Mutational Spectrum of Pfu DNA Polymerase on a Human Mitochondrial DNA Sequence

Science.gov (United States)

André, Paulo; Kim, Andrea; Khrapko, Konstantin; Thilly, William G.

1997-01-01

The study of rare genetic changes in human tissues requires specialized techniques. Point mutations at fractions at or below 10−6 must be observed to discover even the most prominent features of the point mutational spectrum. PCR permits the increase in number of mutant copies but does so at the expense of creating many additional mutations or “PCR noise”. Thus, each DNA sequence studied must be characterized with regard to the DNA polymerase and conditions used to avoid interpreting a PCR-generated mutation as one arising in human tissue. The thermostable DNA polymerase derived from Pyrococcus furiosus designated Pfu has the highest fidelity of any DNA thermostable polymerase studied to date, and this property recommends it for analyses of tissue mutational spectra. Here, we apply constant denaturant capillary electrophoresis (CDCE) to separate and isolate the products of DNA amplification. This new strategy permitted direct enumeration and identification of point mutations created by Pfu DNA polymerase in a 96-bp low melting domain of a human mitochondrial sequence despite the very low mutant fractions generated in the PCR process. This sequence, containing part of the tRNA glycine and NADH dehydrogenase subunit 3 genes, is the target of our studies of mitochondrial mutagenesis in human cells and tissues. Incorrectly synthesized sequences were separated from the wild type as mutant/wild-type heteroduplexes by sequential enrichment on CDCE. An artificially constructed mutant was used as an internal standard to permit calculation of the mutant fraction. Our study found that the average error rate (mutations per base pair duplication) of Pfu was 6.5 × 10−7, and five of its more frequent mutations (hot spots) consisted of three transversions (GC → TA, AT → TA, and AT → CG), one transition (AT → GC), and one 1-bp deletion (in an AAAAAA sequence). To achieve an even higher sensitivity, the amount of Pfu-induced mutants must be

Solar radiation and mitochondrial DNA damage

International Nuclear Information System (INIS)

Hill, H.Z.; Locitzer, J.; Nassrin, E.; Ogbonnaya, A.; Hubbard, K.

2003-01-01

The 16.6 kB human mitochondrial DNA contains two homologous 13 base pair direct repeats separated by about 5 kB. During asynchronous mitochondrial DNA replication, the distant repeat sequences are thought to anneal, resulting in the looping out of a portion of the non-template strand which is subsequently deleted as a result of interaction with reactive oxygen species (ROS). A normal daughter and a deleted daughter mitochondrion result from such insults. This deletion has been termed the common deletion as it is the most frequent of the known mitochondrial DNA deletions. The common deletion is present in high frequency in several mitochondrial disorders, accumulates with age in slow turnover tissues and is increased in sun-exposed skin. Berneburg, et al. (Photochem. Photobiol. 66: 271, 1997) induced the common deletion in normal human fibroblasts after repeated exposures to UVA. In this study, the common deletion has been shown to be induced by repeated non-lethal exposures to FS20 sunlamp irradiation. Increases in the common deletion were demonstrated using nested PCR which produced a 303 bp product that was compared to a 324 bp product that required the presence of the undeleted 5 kB region. The cells were exposed to 10 repeated doses ranging from 0.5 (UVB) - 0.24 (UVA) J/sq m to 14.4 (UVB) - 5.8 J/sq m (UVA) measured using a UVX digital radiometer and UVB and UVA detectors respectively. Comparison with the earlier study by Berneberg, et al. suggests that this type of simulated solar damage is considerably more effective in fewer exposures than UVA radiation alone. The common deletion provides a cytoplasmic end-point for ROS damage produced by low dose chronic irradiations and other low level toxic exposures and should prove useful in evaluating cytoplasmic damage produced by ionizing radiation as well

Mitochondrial DNA diagnosis for taeniasis and cysticercosis.

Science.gov (United States)

Yamasaki, Hiroshi; Nakao, Minoru; Sako, Yasuhito; Nakaya, Kazuhiro; Sato, Marcello Otake; Ito, Akira

2006-01-01

Molecular diagnosis for taeniasis and cysticercosis in humans on the basis of mitochondrial DNA analysis was reviewed. Development and application of three different methods, including restriction fragment length polymorphism analysis, base excision sequence scanning thymine-base analysis and multiplex PCR, were described. Moreover, molecular diagnosis of cysticerci found in specimens submitted for histopathology and the molecular detection of taeniasis using copro-DNA were discussed.

Accurate quantification of mouse mitochondrial DNA without co-amplification of nuclear mitochondrial insertion sequences.

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Malik, Afshan N; Czajka, Anna; Cunningham, Phil

2016-07-01

Mitochondria contain an extra-nuclear genome in the form of mitochondrial DNA (MtDNA), damage to which can lead to inflammation and bioenergetic deficit. Changes in MtDNA levels are increasingly used as a biomarker of mitochondrial dysfunction. We previously reported that in humans, fragments in the nuclear genome known as nuclear mitochondrial insertion sequences (NumtS) affect accurate quantification of MtDNA. In the current paper our aim was to determine whether mouse NumtS affect the quantification of MtDNA and to establish a method designed to avoid this. The existence of NumtS in the mouse genome was confirmed using blast N, unique MtDNA regions were identified using FASTA, and MtDNA primers which do not co-amplify NumtS were designed and tested. MtDNA copy numbers were determined in a range of mouse tissues as the ratio of the mitochondrial and nuclear genome using real time qPCR and absolute quantification. Approximately 95% of mouse MtDNA was duplicated in the nuclear genome as NumtS which were located in 15 out of 21 chromosomes. A unique region was identified and primers flanking this region were used. MtDNA levels differed significantly in mouse tissues being the highest in the heart, with levels in descending order (highest to lowest) in kidney, liver, blood, brain, islets and lung. The presence of NumtS in the nuclear genome of mouse could lead to erroneous data when studying MtDNA content or mutation. The unique primers described here will allow accurate quantification of MtDNA content in mouse models without co-amplification of NumtS. Copyright © 2016 Elsevier B.V. and Mitochondria Research Society. All rights reserved.

Mitochondrial DNA and STR analyses for human DNA from maggots crop contents: a forensic entomology case from central-southern China.

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Li, X; Cai, J F; Guo, Y D; Xiong, F; Zhang, L; Feng, H; Meng, F M; Fu, Y; Li, J B; Chen, Y Q

2011-08-01

Insect larvae and adult insects found on human corpses can provide important forensic evidence however it is useful to be able to prove evidence of association. Without this, it could be claimed that the insect evidence was a contaminant or had been planted on the body. This paper describes how mitochondrial DNA (mtDNA) and STR analysis of the crop contents of larvae of the blowfly Aldrichina grahami collected from separated body parts was used to provide evidence of association.

Role of Mitochondrial DNA Copy Number Alteration in Human Renal Cell Carcinoma

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Chen-Sung Lin

2016-05-01

Full Text Available We investigated the role of mitochondrial DNA (mtDNA copy number alteration in human renal cell carcinoma (RCC. The mtDNA copy numbers of paired cancer and non-cancer parts from five resected RCC kidneys after radical nephrectomy were determined by quantitative polymerase chain reaction (Q-PCR. An RCC cell line, 786-O, was infected by lentiviral particles to knock down mitochondrial transcriptional factor A (TFAM. Null target (NT and TFAM-knockdown (TFAM-KD represented the control and knockdown 786-O clones, respectively. Protein or mRNA expression levels of TFAM; mtDNA-encoded NADH dehydrogenase subunit 1 (ND1, ND6 and cytochrome c oxidase subunit 2 (COX-2; nuclear DNA (nDNA-encoded succinate dehydrogenase subunit A (SDHA; v-akt murine thymoma viral oncogene homolog 1 gene (AKT-encoded AKT and v-myc myelocytomatosis viral oncogene homolog gene (c-MYC-encoded MYC; glycolytic enzymes including hexokinase II (HK-II, glucose 6-phosphate isomerase (GPI, phosphofructokinase (PFK, and lactate dehydrogenase subunit A (LDHA; and hypoxia-inducible factors the HIF-1α and HIF-2α, pyruvate dehydrogenase kinase 1 (PDK1, and pyruvate dehydrogenase E1 component α subunit (PDHA1 were analyzed by Western blot or Q-PCR. Bioenergetic parameters of cellular metabolism, basal mitochondrial oxygen consumption rate (mOCRB and basal extracellular acidification rate (ECARB, were measured by a Seahorse XFe-24 analyzer. Cell invasiveness was evaluated by a trans-well migration assay and vimentin expression. Doxorubicin was used as a chemotherapeutic agent. The results showed a decrease of mtDNA copy numbers in resected RCC tissues (p = 0.043. The TFAM-KD clone expressed lower mtDNA copy number (p = 0.034, lower mRNA levels of TFAM (p = 0.008, ND1 (p = 0.007, and ND6 (p = 0.017, and lower protein levels of TFAM and COX-2 than did the NT clone. By contrast, the protein levels of HIF-2α, HK-II, PFK, LDHA, AKT, MYC and vimentin; trans-well migration activity (p = 0

Mitochondrial DNA and Cancer Epidemiology Workshop

Science.gov (United States)

A workshop to review the state-of-the science in the mitochondrial DNA field and its use in cancer epidemiology, and to develop a concept for a research initiative on mitochondrial DNA and cancer epidemiology.

The effect of chronic alcohol consumption on mitochondrial DNA mutagenesis in human blood

Energy Technology Data Exchange (ETDEWEB)

Wurmb-Schwark, N. von [Institute of Legal Medicine, Christian Albrecht University of Kiel, Arnold-Heller-Str. 12, 24105 Kiel (Germany)], E-mail: nvonwurmb@rechtsmedizin.uni-kiel.de; Ringleb, A.; Schwark, T. [Institute of Legal Medicine, Christian Albrecht University of Kiel, Arnold-Heller-Str. 12, 24105 Kiel (Germany); Broese, T.; Weirich, S.; Schlaefke, D. [Clinic of Psychiatry and Psychotherapy, University of Rostock, Gehlsheimer Str. 20, Rostock (Germany); Wegener, R. [Institute of Legal Medicine, St-Georg-Str. 108, University of Rostock, 18055 Rostock (Germany); Oehmichen, M. [Institute of Legal Medicine, Christian Albrecht University of Kiel, Arnold-Heller-Str. 12, 24105 Kiel (Germany)

2008-01-01

The 4977 bp deletion of mitochondrial DNA (mtDNA) is known to accumulate with increasing age in post mitotic tissues. Recently, studies came out detecting this specific alteration also in fast replicating cells, e.g. in blood or skin tissue, often in correlation to specific diseases or - specifically in skin - external stressors such as UV radiation. In this study, we investigated mitochondrial mutagenesis in 69 patients with a chronic alcoholic disease and 46 age matched controls with a moderate drinking behavior. Two different fragments, specific for total and for deleted mtDNA (dmtDNA) were amplified in a duplex-PCR. A subsequent fragment analysis was performed and for relative quantification, the quotient of the peak areas of amplification products specific for deleted and total mtDNA was determined. Additionally, a real time PCR was performed to quantify mtDNA copy number. The relative amount of 4977 bp deleted mtDNA in alcoholics was significantly increased compared to controls. On the other hand, no difference regarding the mtDNA/nuclear DNA ratio in both investigated groups was detected. Additionally, no age dependence could be found nor in alcoholics, neither in the control group. These findings indicate that mtDNA mutagenesis in blood can be influenced by stressors such as alcohol. Ethanol seems to be a significant factor to alter mitochondrial DNA in blood and might be an additional contributor for the cellular aging process.

The effect of chronic alcohol consumption on mitochondrial DNA mutagenesis in human blood

International Nuclear Information System (INIS)

Wurmb-Schwark, N. von; Ringleb, A.; Schwark, T.; Broese, T.; Weirich, S.; Schlaefke, D.; Wegener, R.; Oehmichen, M.

2008-01-01

The 4977 bp deletion of mitochondrial DNA (mtDNA) is known to accumulate with increasing age in post mitotic tissues. Recently, studies came out detecting this specific alteration also in fast replicating cells, e.g. in blood or skin tissue, often in correlation to specific diseases or - specifically in skin - external stressors such as UV radiation. In this study, we investigated mitochondrial mutagenesis in 69 patients with a chronic alcoholic disease and 46 age matched controls with a moderate drinking behavior. Two different fragments, specific for total and for deleted mtDNA (dmtDNA) were amplified in a duplex-PCR. A subsequent fragment analysis was performed and for relative quantification, the quotient of the peak areas of amplification products specific for deleted and total mtDNA was determined. Additionally, a real time PCR was performed to quantify mtDNA copy number. The relative amount of 4977 bp deleted mtDNA in alcoholics was significantly increased compared to controls. On the other hand, no difference regarding the mtDNA/nuclear DNA ratio in both investigated groups was detected. Additionally, no age dependence could be found nor in alcoholics, neither in the control group. These findings indicate that mtDNA mutagenesis in blood can be influenced by stressors such as alcohol. Ethanol seems to be a significant factor to alter mitochondrial DNA in blood and might be an additional contributor for the cellular aging process

Changes in the human mitochondrial genome after treatment of malignant disease

International Nuclear Information System (INIS)

Wardell, Theresa M.; Ferguson, Elaine; Chinnery, Patrick F.; Borthwick, Gillian M.; Taylor, Robert W.; Jackson, Graham; Craft, Alan; Lightowlers, Robert N.; Howell, Neil; Turnbull, Douglass M.

2003-01-01

Mitochondrial DNA (mtDNA) is the only extrachromosomal DNA in human cells. The mitochondrial genome encodes essential information for the synthesis of the mitochondrial respiratory chain. Inherited defects of this genome are an important cause of human disease. In addition, the mitochondrial genome seems to be particularly prone to DNA damage and acquired mutations may have a role in ageing, cancer and neurodegeneration. We wished to determine if radiotherapy and chemotherapy used in the treatment of cancer could induce changes in the mitochondrial genome. Such changes would be an important genetic marker of DNA damage and may explain some of the adverse effects of treatment. We studied samples from patients who had received radiotherapy and chemotherapy for point mutations within the mtDNA control region, and for large-scale deletions. In blood samples from patients, we found a significantly increased number of point mutations compared to the control subjects. In muscle biopsies from 7 of 8 patients whom had received whole body irradiation as well as chemotherapy, the level of a specific mtDNA deletion was significantly greater than in control subjects. Our studies have shown that in patients who have been treated for cancer there is an increased level of mtDNA damage

Lack of mitochondrial MutS homolog 1 in Toxoplasma gondii disrupts maintenance and fidelity of mitochondrial DNA and reveals metabolic plasticity.

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Tamila Garbuz

Full Text Available The importance of maintaining the fidelity of the mitochondrial genome is underscored by the presence of various repair pathways within this organelle. Presumably, the repair of mitochondrial DNA would be of particular importance in organisms that possess only a single mitochondrion, like the human pathogens Plasmodium falciparum and Toxoplasma gondii. Understanding the machinery that maintains mitochondrial DNA in these parasites is of particular relevance, as mitochondrial function is a validated and effective target for anti-parasitic drugs. We previously determined that the Toxoplasma MutS homolog TgMSH1 localizes to the mitochondrion. MutS homologs are key components of the nuclear mismatch repair system in mammalian cells, and both yeast and plants possess MutS homologs that localize to the mitochondria where they regulate DNA stability. Here we show that the lack of TgMSH1 results in accumulation of single nucleotide variations in mitochondrial DNA and a reduction in mitochondrial DNA content. Additionally, parasites lacking TgMSH1 function can survive treatment with the cytochrome b inhibitor atovaquone. While the Tgmsh1 knockout strain has several missense mutations in cytochrome b, none affect amino acids known to be determinants of atovaquone sensitivity and atovaquone is still able to inhibit electron transport in the Tgmsh1 mutants. Furthermore, culture of Tgmsh1 mutant in the presence atovaquone leads to parasites with enhanced atovaquone resistance and complete shutdown of respiration. Thus, parasites lacking TgMSH1 overcome the disruption of mitochondrial DNA by adapting their physiology allowing them to forgo the need for oxidative phosphorylation. Consistent with this idea, the Tgmsh1 mutant is resistant to mitochondrial inhibitors with diverse targets and exhibits reduced ability to grow in the absence of glucose. This work shows TgMSH1 as critical for the maintenance and fidelity of the mitochondrial DNA in Toxoplasma

Nucleotide pools dictate the identity and frequency of ribonucleotide incorporation in mitochondrial DNA.

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Anna-Karin Berglund

2017-02-01

Full Text Available Previous work has demonstrated the presence of ribonucleotides in human mitochondrial DNA (mtDNA and in the present study we use a genome-wide approach to precisely map the location of these. We find that ribonucleotides are distributed evenly between the heavy- and light-strand of mtDNA. The relative levels of incorporated ribonucleotides reflect that DNA polymerase γ discriminates the four ribonucleotides differentially during DNA synthesis. The observed pattern is also dependent on the mitochondrial deoxyribonucleotide (dNTP pools and disease-causing mutations that change these pools alter both the absolute and relative levels of incorporated ribonucleotides. Our analyses strongly suggest that DNA polymerase γ-dependent incorporation is the main source of ribonucleotides in mtDNA and argues against the existence of a mitochondrial ribonucleotide excision repair pathway in human cells. Furthermore, we clearly demonstrate that when dNTP pools are limiting, ribonucleotides serve as a source of building blocks to maintain DNA replication. Increased levels of embedded ribonucleotides in patient cells with disturbed nucleotide pools may contribute to a pathogenic mechanism that affects mtDNA stability and impair new rounds of mtDNA replication.

Nucleotide pools dictate the identity and frequency of ribonucleotide incorporation in mitochondrial DNA.

Science.gov (United States)

Berglund, Anna-Karin; Navarrete, Clara; Engqvist, Martin K M; Hoberg, Emily; Szilagyi, Zsolt; Taylor, Robert W; Gustafsson, Claes M; Falkenberg, Maria; Clausen, Anders R

2017-02-01

Previous work has demonstrated the presence of ribonucleotides in human mitochondrial DNA (mtDNA) and in the present study we use a genome-wide approach to precisely map the location of these. We find that ribonucleotides are distributed evenly between the heavy- and light-strand of mtDNA. The relative levels of incorporated ribonucleotides reflect that DNA polymerase γ discriminates the four ribonucleotides differentially during DNA synthesis. The observed pattern is also dependent on the mitochondrial deoxyribonucleotide (dNTP) pools and disease-causing mutations that change these pools alter both the absolute and relative levels of incorporated ribonucleotides. Our analyses strongly suggest that DNA polymerase γ-dependent incorporation is the main source of ribonucleotides in mtDNA and argues against the existence of a mitochondrial ribonucleotide excision repair pathway in human cells. Furthermore, we clearly demonstrate that when dNTP pools are limiting, ribonucleotides serve as a source of building blocks to maintain DNA replication. Increased levels of embedded ribonucleotides in patient cells with disturbed nucleotide pools may contribute to a pathogenic mechanism that affects mtDNA stability and impair new rounds of mtDNA replication.

Nuclear mitochondrial DNA activates replication in Saccharomyces cerevisiae.

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Laurent Chatre

Full Text Available The nuclear genome of eukaryotes is colonized by DNA fragments of mitochondrial origin, called NUMTs. These insertions have been associated with a variety of germ-line diseases in humans. The significance of this uptake of potentially dangerous sequences into the nuclear genome is unclear. Here we provide functional evidence that sequences of mitochondrial origin promote nuclear DNA replication in Saccharomyces cerevisiae. We show that NUMTs are rich in key autonomously replicating sequence (ARS consensus motifs, whose mutation results in the reduction or loss of DNA replication activity. Furthermore, 2D-gel analysis of the mrc1 mutant exposed to hydroxyurea shows that several NUMTs function as late chromosomal origins. We also show that NUMTs located close to or within ARS provide key sequence elements for replication. Thus NUMTs can act as independent origins, when inserted in an appropriate genomic context or affect the efficiency of pre-existing origins. These findings show that migratory mitochondrial DNAs can impact on the replication of the nuclear region they are inserted in.

DNA methyltransferase 1 mutations and mitochondrial pathology: is mtDNA methylated?

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Alessandra eMaresca

2015-03-01

Full Text Available Autosomal dominant cerebellar ataxia, deafness and narcolepsy (ADCA-DN and Hereditary sensory neuropathy with dementia and hearing loss (HSN1E are two rare, overlapping neurodegenerative syndromes that have been recently linked to allelic dominant pathogenic mutations in the DNMT1 gene, coding for DNA (cytosine-5-methyltransferase 1. DNMT1 is the enzyme responsible for maintaining the nuclear genome methylation patterns during the DNA replication and repair, thus regulating gene expression. The mutations responsible for ADCA-DN and HSN1E affect the replication foci targeting sequence domain, which regulates DNMT1 binding to chromatin. DNMT1 dysfunction is anticipated to lead to a global alteration of the DNA methylation pattern with predictable downstream consequences on gene expression. Interestingly, ADCA-DN and HSN1E phenotypes share some clinical features typical of mitochondrial diseases, such as optic atrophy, peripheral neuropathy and deafness, and some biochemical evidence of mitochondrial dysfunction. The recent discovery of a mitochondrial isoform of DNMT1 and its proposed role in methylating mitochondrial DNA (mtDNA suggests that DNMT1 mutations may directly affect mtDNA and mitochondrial physiology. On the basis of this latter finding the link between DNMT1 abnormal activity and mitochondrial dysfunction in ADCA-DN and HSN1E appears intuitive, however mtDNA methylation remains highly debated. In the last years several groups demonstrated the presence of 5-methylcytosine in mtDNA by different approaches, but, on the other end, the opposite evidence that mtDNA is not methylated has also been published. Since over 1500 mitochondrial proteins are encoded by the nuclear genome, the altered methylation of these genes may well have a critical role in leading to the mitochondrial impairment observed in ADCA-DN and HSN1E. Thus, many open questions still remain unanswered, such as why mtDNA should be methylated, and how this process is

Butachlor induced dissipation of mitochondrial membrane potential, oxidative DNA damage and necrosis in human peripheral blood mononuclear cells

International Nuclear Information System (INIS)

Dwivedi, Sourabh; Saquib, Quaiser; Al-Khedhairy, Abdulaziz A.; Musarrat, Javed

2012-01-01

Highlights: ► Butachlor exhibited strong binding affinity with DNA and produced 8-oxodG adducts. ► Butachlor induced DNA strand breaks and micronuclei formation in PBMN cells. ► Butachlor induced ROS and dissipation of mitochondrial membrane potential in cells. ► Butachlor resulted in cell cycle arrest and eventually caused cellular necrosis. -- Abstract: Butachlor is a systemic herbicide widely applied on rice, tea, wheat, beans and other crops; however, it concurrently exerts toxic effects on beneficial organisms like earthworms, aquatic invertebrates and other non-target animals including humans. Owing to the associated risk to humans, this chloroacetanilide class of herbicide was investigated with the aim to assess its potential for the (i) interaction with DNA, (ii) mitochondria membrane damage and DNA strand breaks and (iii) cell cycle arrest and necrosis in butachlor treated human peripheral blood mononuclear (PBMN) cells. Fluorescence quenching data revealed the binding constant (Ka = 1.2 × 10 4 M −1 ) and binding capacity (n = 1.02) of butachlor with ctDNA. The oxidative potential of butachlor was ascertained based on its capacity of inducing reactive oxygen species (ROS) and substantial amounts of promutagenic 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodG) adducts in DNA. Also, the discernible butachlor dose-dependent reduction in fluorescence intensity of a cationic dye rhodamine (Rh-123) and increased fluorescence intensity of 2′,7′-dichlorodihydro fluorescein diacetate (DCFH-DA) in treated cells signifies decreased mitochondrial membrane potential (ΔΨm) due to intracellular ROS generation. The comet data revealed significantly greater Olive tail moment (OTM) values in butachlor treated PBMN cells vs untreated and DMSO controls. Treatment of cultured PBMN cells for 24 h resulted in significantly increased number of binucleated micronucleated (BNMN) cells with a dose dependent reduction in the nuclear division index (NDI). The flow

Deoxyribonucleoside kinases in mitochondrial DNA depletion.

Science.gov (United States)

Saada-Reisch, Ann

2004-10-01

Mitochondrial DNA (mtDNA) depletion syndromes (MDS) are a heterogeneous group of mitochondrial disorders, manifested by a decreased mtDNA copy number and respiratory chain dysfunction. Primary MDS are inherited autosomally and may affect a single organ or multiple tissues. Mutated mitochondrial deoxyribonucleoside kinases; deoxyguanosine kinase (dGK) and thymidine kinase 2 (TK2), were associated with the hepatocerebral and myopathic forms of MDS respectively. dGK and TK2 are key enzymes in the mitochondrial nucleotide salvage pathway, providing the mitochondria with deoxyribonucleotides (dNP) essential for mtDNA synthesis. Although the mitochondrial dNP pool is physically separated from the cytosolic one, dNP's may still be imported through specific transport. Non-replicating tissues, where cytosolic dNP supply is down regulated, are thus particularly vulnerable to dGK and TK2 deficiency. The overlapping substrate specificity of deoxycytidine kinase (dCK) may explain the relative sparing of muscle in dGK deficiency, while low basal TK2 activity render this tissue susceptible to TK2 deficiency. The precise pathophysiological mechanisms of mtDNA depletion due to dGK and TK2 deficiencies remain to be determined, though recent findings confirm that it is attributed to imbalanced dNTP pools.

Developing a biological dosimeter based on mitochondrial DNA

Energy Technology Data Exchange (ETDEWEB)

Adams, S; Carlisle, S M; Unrau, P; Deugau, K V [Atomic Energy of Canada Ltd., Chalk River, ON (Canada)

1996-12-31

Direct measurement of deoxyribonucleic acid (DNA) damage from ionizing radiation may be advantageous in determining radiation radiation exposures and assessing their effects on atomic radiation workers. The mitochondrial DNA molecule is one potential cellular DNA target which is: fully defined and sequenced; present in many copies per cell; not vital to cellular survival; and less subject to DNA repair than nuclear DNA. A method is described to isolate and analyse normal mitochondrial DNA. We describe the developments needed to determine DNA damage in mitochondrial DNA. The target is to make a biological dosimeter. (author). 6 refs., 3 figs.

Developing a biological dosimeter based on mitochondrial DNA

International Nuclear Information System (INIS)

Adams, S.; Carlisle, S.M.; Unrau, P.; Deugau, K.V.

1995-01-01

Direct measurement of deoxyribonucleic acid (DNA) damage from ionizing radiation may be advantageous in determining radiation radiation exposures and assessing their effects on atomic radiation workers. The mitochondrial DNA molecule is one potential cellular DNA target which is: fully defined and sequenced; present in many copies per cell; not vital to cellular survival; and less subject to DNA repair than nuclear DNA. A method is described to isolate and analyse normal mitochondrial DNA. We describe the developments needed to determine DNA damage in mitochondrial DNA. The target is to make a biological dosimeter. (author). 6 refs., 3 figs

Investigating the role of melanin in UVA/UVB- and hydrogen peroxide-induced cellular and mitochondrial ROS production and mitochondrial DNA damage in human melanoma cells.

Science.gov (United States)

Swalwell, Helen; Latimer, Jennifer; Haywood, Rachel M; Birch-Machin, Mark A

2012-02-01

Skin cancer incidence is dramatically increasing worldwide, with exposure to ultraviolet radiation (UVR) a predominant factor. The UVA component initiates oxidative stress in human skin, although its exact role in the initiation of skin cancer, particularly malignant melanoma, remains unclear and is controversial because there is evidence for a melanin-dependent mechanism in UVA-linked melanoma studies. Nonpigmented (CHL-1, A375), moderately pigmented (FM55, SKmel23), and highly pigmented (FM94, hyperpigmented FM55) human melanoma cell lines have been used to investigate UVA-induced production of reactive oxygen species using FACS analysis, at both the cellular (dihydrorhodamine-123) and the mitochondrial (MitoSOX) level, where most cellular stress is generated. For the first time, downstream mtDNA damage (utilizing a quantitative long-PCR assay) has been investigated. Using UVA, UVB, and H(2)O(2) as cellular stressors, we have explored the dual roles of melanin as a photoprotector and photosensitizer. The presence of melanin has no influence over cellular oxidative stress generation, whereas, in contrast, melanin protects against mitochondrial superoxide generation and mtDNA damage (one-way ANOVA with post hoc Tukey's analysis, Pmelanin binds directly to DNA, it acts as a direct photosensitizer of mtDNA damage during UVA irradiation (Pmelanin. Copyright © 2011 Elsevier Inc. All rights reserved.

Mitochondrial DNA deletion and impairment of mitochondrial biogenesis are mediated by reactive oxygen species in ionizing radiation-induced premature senescence

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Eom, Hyeon Soo; Jung, U Hee; Jo, Sung Kee [Radiation Biotechnology Research Division, Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Kim, Young Sang [College of Natural Sciences, Chungnam National University, Daejeon (Korea, Republic of)

2011-09-15

Mitochondrial DNA (mtDNA) deletion is a well-known marker for oxidative stress and aging, and contributes to harmful effects in cultured cells and animal tissues. mtDNA biogenesis genes (NRF-1, TFAM) are essential for the maintenance of mtDNA, as well as the transcription and replication of mitochondrial genomes. Considering that oxidative stress is known to affect mitochondrial biogenesis, we hypothesized that ionizing radiation (IR)-induced reactive oxygen species (ROS) causes mtDNA deletion by modulating the mitochondrial biogenesis, thereby leading to cellular senescence. Therefore, we examined the effects of IR on ROS levels, cellular senescence, mitochondrial biogenesis, and mtDNA deletion in IMR-90 human lung fibroblast cells. Young IMR-90 cells at population doubling (PD) 39 were irradiated at 4 or 8 Gy. Old cells at PD55, and H2O2-treated young cells at PD 39, were compared as a positive control. The IR increased the intracellular ROS level, senescence-associated {beta}-galactosidase (SA-{beta}-gal) activity, and mtDNA common deletion (4977 bp), and it decreased the mRNA expression of NRF-1 and TFAM in IMR-90 cells. Similar results were also observed in old cells (PD 55) and H{sub 2}O{sub 2}-treated young cells. To confirm that a increase in ROS level is essential for mtDNA deletion and changes of mitochondrial biogenesis in irradiated cells, the effects of N-acetylcysteine (NAC) were examined. In irradiated and H{sub 2}O{sub 2}-treated cells, 5 mM NAC significantly attenuated the increases of ROS, mtDNA deletion, and SA-{beta}-gal activity, and recovered from decreased expressions of NRF-1 and TFAM mRNA. These results suggest that ROS is a key cause of IR-induced mtDNA deletion, and the suppression of the mitochondrial biogenesis gene may mediate this process.

Mitochondrial DNA deletion and impairment of mitochondrial biogenesis are mediated by reactive oxygen species in ionizing radiation-induced premature senescence

International Nuclear Information System (INIS)

Eom, Hyeon Soo; Jung, U Hee; Jo, Sung Kee; Kim, Young Sang

2011-01-01

Mitochondrial DNA (mtDNA) deletion is a well-known marker for oxidative stress and aging, and contributes to harmful effects in cultured cells and animal tissues. mtDNA biogenesis genes (NRF-1, TFAM) are essential for the maintenance of mtDNA, as well as the transcription and replication of mitochondrial genomes. Considering that oxidative stress is known to affect mitochondrial biogenesis, we hypothesized that ionizing radiation (IR)-induced reactive oxygen species (ROS) causes mtDNA deletion by modulating the mitochondrial biogenesis, thereby leading to cellular senescence. Therefore, we examined the effects of IR on ROS levels, cellular senescence, mitochondrial biogenesis, and mtDNA deletion in IMR-90 human lung fibroblast cells. Young IMR-90 cells at population doubling (PD) 39 were irradiated at 4 or 8 Gy. Old cells at PD55, and H2O2-treated young cells at PD 39, were compared as a positive control. The IR increased the intracellular ROS level, senescence-associated β-galactosidase (SA-β-gal) activity, and mtDNA common deletion (4977 bp), and it decreased the mRNA expression of NRF-1 and TFAM in IMR-90 cells. Similar results were also observed in old cells (PD 55) and H 2 O 2 -treated young cells. To confirm that a increase in ROS level is essential for mtDNA deletion and changes of mitochondrial biogenesis in irradiated cells, the effects of N-acetylcysteine (NAC) were examined. In irradiated and H 2 O 2 -treated cells, 5 mM NAC significantly attenuated the increases of ROS, mtDNA deletion, and SA-β-gal activity, and recovered from decreased expressions of NRF-1 and TFAM mRNA. These results suggest that ROS is a key cause of IR-induced mtDNA deletion, and the suppression of the mitochondrial biogenesis gene may mediate this process.

Biomarkers of mitochondrial content in skeletal muscle of healthy young human subjects

DEFF Research Database (Denmark)

Larsen, Steen; Nielsen, Joachim; Hansen, Christina Neigaard

2012-01-01

Key points  Several biochemical measures of mitochondrial components are used as biomarkers of mitochondrial content and muscle oxidative capacity. However, no studies have validated these surrogates against a morphological measure of mitochondrial content in human subjects.  The most commonly used...... markers (citrate synthase activity, cardiolipin content, mitochondrial DNA content (mtDNA), complex I-V protein, and complex I-IV activity) were correlated with a measure of mitochondrial content (transmission electron microscopy) and muscle oxidative capacity (respiration in permeabilized fibres......).  Cardiolipin content followed by citrate synthase activity and complex I activity were the biomarkers showing the strongest association with mitochondrial content.  mtDNA was found to be a poor biomarker of mitochondrial content.  Complex IV activity was closely associated with mitochondrial oxidative...

Mitochondrial DNA triplication and punctual mutations in patients with mitochondrial neuromuscular disorders

Energy Technology Data Exchange (ETDEWEB)

Mkaouar-Rebai, Emna, E-mail: emna.mkaouar@gmail.com [Département des Sciences de la Vie, Faculté des Sciences de Sfax, Université de Sfax (Tunisia); Felhi, Rahma; Tabebi, Mouna [Laboratoire de Génétique Moléculaire Humaine, Faculté de Médecine de Sfax, Université de Sfax (Tunisia); Alila-Fersi, Olfa; Chamkha, Imen [Département des Sciences de la Vie, Faculté des Sciences de Sfax, Université de Sfax (Tunisia); Maalej, Marwa; Ammar, Marwa [Laboratoire de Génétique Moléculaire Humaine, Faculté de Médecine de Sfax, Université de Sfax (Tunisia); Kammoun, Fatma [Service de pédiatrie, C.H.U. Hedi Chaker de Sfax (Tunisia); Keskes, Leila [Laboratoire de Génétique Moléculaire Humaine, Faculté de Médecine de Sfax, Université de Sfax (Tunisia); Hachicha, Mongia [Service de pédiatrie, C.H.U. Hedi Chaker de Sfax (Tunisia); Fakhfakh, Faiza, E-mail: faiza.fakhfakh02@gmail.com [Département des Sciences de la Vie, Faculté des Sciences de Sfax, Université de Sfax (Tunisia)

2016-04-29

Mitochondrial diseases are a heterogeneous group of disorders caused by the impairment of the mitochondrial oxidative phosphorylation system which have been associated with various mutations of the mitochondrial DNA (mtDNA) and nuclear gene mutations. The clinical phenotypes are very diverse and the spectrum is still expanding. As brain and muscle are highly dependent on OXPHOS, consequently, neurological disorders and myopathy are common features of mtDNA mutations. Mutations in mtDNA can be classified into three categories: large-scale rearrangements, point mutations in tRNA or rRNA genes and point mutations in protein coding genes. In the present report, we screened mitochondrial genes of complex I, III, IV and V in 2 patients with mitochondrial neuromuscular disorders. The results showed the presence the pathogenic heteroplasmic m.9157G>A variation (A211T) in the MT-ATP6 gene in the first patient. We also reported the first case of triplication of 9 bp in the mitochondrial NC7 region in Africa and Tunisia, in association with the novel m.14924T>C in the MT-CYB gene in the second patient with mitochondrial neuromuscular disorder. - Highlights: • We reported 2 patients with mitochondrial neuromuscular disorders. • The heteroplasmic MT-ATP6 9157G>A variation was reported. • A triplication of 9 bp in the mitochondrial NC7 region was detected. • The m.14924T>C transition (S60P) in the MT-CYB gene was found.

Nuclear counterparts of the cytoplasmic mitochondrial 12S rRNA gene: a problem of ancient DNA and molecular phylogenies.

Science.gov (United States)

van der Kuyl, A C; Kuiken, C L; Dekker, J T; Perizonius, W R; Goudsmit, J

1995-06-01

Monkey mummy bones and teeth originating from the North Saqqara Baboon Galleries (Egypt), soft tissue from a mummified baboon in a museum collection, and nineteenth/twentieth-century skin fragments from mangabeys were used for DNA extraction and PCR amplification of part of the mitochondrial 12S rRNA gene. Sequences aligning with the 12S rRNA gene were recovered but were only distantly related to contemporary monkey mitochondrial 12S rRNA sequences. However, many of these sequences were identical or closely related to human nuclear DNA sequences resembling mitochondrial 12S rRNA (isolated from a cell line depleted in mitochondria) and therefore have to be considered contamination. Subsequently in a separate study we were able to recover genuine mitochondrial 12S rRNA sequences from many extant species of nonhuman Old World primates and sequences closely resembling the human nuclear integrations. Analysis of all sequences by the neighbor-joining (NJ) method indicated that mitochondrial DNA sequences and their nuclear counterparts can be divided into two distinct clusters. One cluster contained all temporary cytoplasmic mitochondrial DNA sequences and approximately half of the monkey nuclear mitochondriallike sequences. A second cluster contained most human nuclear sequences and the other half of monkey nuclear sequences with a separate branch leading to human and gorilla mitochondrial and nuclear sequences. Sequences recovered from ancient materials were equally divided between the two clusters. These results constitute a warning for when working with ancient DNA or performing phylogenetic analysis using mitochondrial DNA as a target sequence: Nuclear counterparts of mitochondrial genes may lead to faulty interpretation of results.

Introducing Human Population Biology through an Easy Laboratory Exercise on Mitochondrial DNA

Science.gov (United States)

Pardinas, Antonio F.; Dopico, Eduardo; Roca, Agustin; Garcia-Vazquez, Eva; Lopez, Belen

2010-01-01

This article describes an easy and cheap laboratory exercise for students to discover their own mitochondrial haplogroup. Students use buccal swabs to obtain mucosa cells as noninvasive tissue samples, extract DNA, and with a simple polymerase chain reaction-restriction fragment length polymorphism analysis they can obtain DNA fragments of…

Distinct patterns of mitochondrial genome diversity in bonobos (Pan paniscus and humans

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Zsurka Gábor

2010-09-01

Full Text Available Abstract Background We have analyzed the complete mitochondrial genomes of 22 Pan paniscus (bonobo, pygmy chimpanzee individuals to assess the detailed mitochondrial DNA (mtDNA phylogeny of this close relative of Homo sapiens. Results We identified three major clades among bonobos that separated approximately 540,000 years ago, as suggested by Bayesian analysis. Incidentally, we discovered that the current reference sequence for bonobo likely is a hybrid of the mitochondrial genomes of two distant individuals. When comparing spectra of polymorphic mtDNA sites in bonobos and humans, we observed two major differences: (i Of all 31 bonobo mtDNA homoplasies, i.e. nucleotide changes that occurred independently on separate branches of the phylogenetic tree, 13 were not homoplasic in humans. This indicates that at least a part of the unstable sites of the mitochondrial genome is species-specific and difficult to be explained on the basis of a mutational hotspot concept. (ii A comparison of the ratios of non-synonymous to synonymous changes (dN/dS among polymorphic positions in bonobos and in 4902 Homo sapiens mitochondrial genomes revealed a remarkable difference in the strength of purifying selection in the mitochondrial genes of the F0F1-ATPase complex. While in bonobos this complex showed a similar low value as complexes I and IV, human haplogroups displayed 2.2 to 7.6 times increased dN/dS ratios when compared to bonobos. Conclusions Some variants of mitochondrially encoded subunits of the ATPase complex in humans very likely decrease the efficiency of energy conversion leading to production of extra heat. Thus, we hypothesize that the species-specific release of evolutionary constraints for the mitochondrial genes of the proton-translocating ATPase is a consequence of altered heat homeostasis in modern humans.

Mitochondrial nucleoid clusters protect newly synthesized mtDNA during Doxorubicin- and Ethidium Bromide-induced mitochondrial stress

Energy Technology Data Exchange (ETDEWEB)

Alán, Lukáš, E-mail: lukas.alan@fgu.cas.cz; Špaček, Tomáš; Pajuelo Reguera, David; Jabůrek, Martin; Ježek, Petr

2016-07-01

Mitochondrial DNA (mtDNA) is compacted in ribonucleoprotein complexes called nucleoids, which can divide or move within the mitochondrial network. Mitochondrial nucleoids are able to aggregate into clusters upon reaction with intercalators such as the mtDNA depletion agent Ethidium Bromide (EB) or anticancer drug Doxorobicin (DXR). However, the exact mechanism of nucleoid clusters formation remains unknown. Resolving these processes may help to elucidate the mechanisms of DXR-induced cardiotoxicity. Therefore, we addressed the role of two key nucleoid proteins; mitochondrial transcription factor A (TFAM) and mitochondrial single-stranded binding protein (mtSSB); in the formation of mitochondrial nucleoid clusters during the action of intercalators. We found that both intercalators cause numerous aberrations due to perturbing their native status. By blocking mtDNA replication, both agents also prevented mtDNA association with TFAM, consequently causing nucleoid aggregation into large nucleoid clusters enriched with TFAM, co-existing with the normal nucleoid population. In the later stages of intercalation (> 48 h), TFAM levels were reduced to 25%. In contrast, mtSSB was released from mtDNA and freely distributed within the mitochondrial network. Nucleoid clusters mostly contained nucleoids with newly replicated mtDNA, however the nucleoid population which was not in replication mode remained outside the clusters. Moreover, the nucleoid clusters were enriched with p53, an anti-oncogenic gatekeeper. We suggest that mitochondrial nucleoid clustering is a mechanism for protecting nucleoids with newly replicated DNA against intercalators mediating genotoxic stress. These results provide new insight into the common mitochondrial response to mtDNA stress and can be implied also on DXR-induced mitochondrial cytotoxicity. - Highlights: • The mechanism for mitochondrial nucleoid clustering is proposed. • DNA intercalators (Doxorubicin or Ethidium Bromide) prevent TFAM

Performance of mitochondrial DNA mutations detecting early stage cancer

International Nuclear Information System (INIS)

Jakupciak, John P; Srivastava, Sudhir; Sidransky, David; O'Connell, Catherine D; Maragh, Samantha; Markowitz, Maura E; Greenberg, Alissa K; Hoque, Mohammad O; Maitra, Anirban; Barker, Peter E; Wagner, Paul D; Rom, William N

2008-01-01

Mutations in the mitochondrial genome (mtgenome) have been associated with cancer and many other disorders. These mutations can be point mutations or deletions, or admixtures (heteroplasmy). The detection of mtDNA mutations in body fluids using resequencing microarrays, which are more sensitive than other sequencing methods, could provide a strategy to measure mutation loads in remote anatomical sites. We determined the mtDNA mutation load in the entire mitochondrial genome of 26 individuals with different early stage cancers (lung, bladder, kidney) and 12 heavy smokers without cancer. MtDNA was sequenced from three matched specimens (blood, tumor and body fluid) from each cancer patient and two matched specimens (blood and sputum) from smokers without cancer. The inherited wildtype sequence in the blood was compared to the sequences present in the tumor and body fluid, detected using the Affymetrix Genechip ® Human Mitochondrial Resequencing Array 1.0 and supplemented by capillary sequencing for noncoding region. Using this high-throughput method, 75% of the tumors were found to contain mtDNA mutations, higher than in our previous studies, and 36% of the body fluids from these cancer patients contained mtDNA mutations. Most of the mutations detected were heteroplasmic. A statistically significantly higher heteroplasmy rate occurred in tumor specimens when compared to both body fluid of cancer patients and sputum of controls, and in patient blood compared to blood of controls. Only 2 of the 12 sputum specimens from heavy smokers without cancer (17%) contained mtDNA mutations. Although patient mutations were spread throughout the mtDNA genome in the lung, bladder and kidney series, a statistically significant elevation of tRNA and ND complex mutations was detected in tumors. Our findings indicate comprehensive mtDNA resequencing can be a high-throughput tool for detecting mutations in clinical samples with potential applications for cancer detection, but it is

Identification of the polypeptides encoded in the unassigned reading frames 2, 4, 4L, and 5 of human mitochondrial DNA

International Nuclear Information System (INIS)

Mariottini, P.; Chomyn, A.; Riley, M.; Cottrell, B.; Doolittle, R.F.; Attardi, G.

1986-01-01

In previous work, antibodies prepared against chemically synthesized peptides predicted from the DNA sequence were used to identify the polypeptides encoded in three of the eight unassigned reading frames (URFs) of human mitochondrial DNA (mtDNA). In the present study, this approach has been extended to other human mtDNA URFs. In particular, antibodies directed against the NH 2 -terminal octapeptide of the putative URF2 product specifically precipitated component 11 of the HeLa cell mitochondrial translation products, the reaction being inhibited by the specific peptide. Similarly, antibodies directed against the COOH-terminal nonapeptide of the putative URF4 product reacted specifically with components 4 and 5, and antibodies against a COOH-terminal heptapeptide of the presumptive URF4L product reacted specifically with component 26. Antibodies against the NH 2 -terminal heptapeptide of the putative product of URF5 reacted with component 1, but only to a marginal extent; however, the results of a trypsin fingerprinting analysis of component 1 point strongly to this component as being the authentic product of URF5. The polypeptide assignments to the mtDNA URFs analyzed here are supported by the relative electrophoretic mobilities of proteins 11, 4-5, 26, and 1, which are those expected for the molecular weights predicted from the DNA sequence for the products of URF2, URF4, URF4L, and URF5, respectively. With the present assignment, seven of the eight human mtDNA URFs have been shown to be expressed in HeLa cells

An Analysis of Enzyme Kinetics Data for Mitochondrial DNA Strand Termination by Nucleoside Reverse Transcription Inhibitors

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Wendelsdorf, Katherine V.; Song, Zhuo; Cao, Yang; Samuels, David C.

2009-01-01

Nucleoside analogs used in antiretroviral treatment have been associated with mitochondrial toxicity. The polymerase-γ hypothesis states that this toxicity stems from the analogs' inhibition of the mitochondrial DNA polymerase (polymerase-γ) leading to mitochondrial DNA (mtDNA) depletion. We have constructed a computational model of the interaction of polymerase-γ with activated nucleoside and nucleotide analog drugs, based on experimentally measured reaction rates and base excision rates, together with the mtDNA genome size, the human mtDNA sequence, and mitochondrial dNTP concentrations. The model predicts an approximately 1000-fold difference in the activated drug concentration required for a 50% probability of mtDNA strand termination between the activated di-deoxy analogs d4T, ddC, and ddI (activated to ddA) and the activated forms of the analogs 3TC, TDF, AZT, FTC, and ABC. These predictions are supported by experimental and clinical data showing significantly greater mtDNA depletion in cell culture and patient samples caused by the di-deoxy analog drugs. For zidovudine (AZT) we calculated a very low mtDNA replication termination probability, in contrast to its reported mitochondrial toxicity in vitro and clinically. Therefore AZT mitochondrial toxicity is likely due to a mechanism that does not involve strand termination of mtDNA replication. PMID:19132079

qPCR-based mitochondrial DNA quantification: Influence of template DNA fragmentation on accuracy

International Nuclear Information System (INIS)

Jackson, Christopher B.; Gallati, Sabina; Schaller, André

2012-01-01

Highlights: ► Serial qPCR accurately determines fragmentation state of any given DNA sample. ► Serial qPCR demonstrates different preservation of the nuclear and mitochondrial genome. ► Serial qPCR provides a diagnostic tool to validate the integrity of bioptic material. ► Serial qPCR excludes degradation-induced erroneous quantification. -- Abstract: Real-time PCR (qPCR) is the method of choice for quantification of mitochondrial DNA (mtDNA) by relative comparison of a nuclear to a mitochondrial locus. Quantitative abnormal mtDNA content is indicative of mitochondrial disorders and mostly confines in a tissue-specific manner. Thus handling of degradation-prone bioptic material is inevitable. We established a serial qPCR assay based on increasing amplicon size to measure degradation status of any DNA sample. Using this approach we can exclude erroneous mtDNA quantification due to degraded samples (e.g. long post-exicision time, autolytic processus, freeze–thaw cycles) and ensure abnormal DNA content measurements (e.g. depletion) in non-degraded patient material. By preparation of degraded DNA under controlled conditions using sonification and DNaseI digestion we show that erroneous quantification is due to the different preservation qualities of the nuclear and the mitochondrial genome. This disparate degradation of the two genomes results in over- or underestimation of mtDNA copy number in degraded samples. Moreover, as analysis of defined archival tissue would allow to precise the molecular pathomechanism of mitochondrial disorders presenting with abnormal mtDNA content, we compared fresh frozen (FF) with formalin-fixed paraffin-embedded (FFPE) skeletal muscle tissue of the same sample. By extrapolation of measured decay constants for nuclear DNA (λ nDNA ) and mtDNA (λ mtDNA ) we present an approach to possibly correct measurements in degraded samples in the future. To our knowledge this is the first time different degradation impact of the two

qPCR-based mitochondrial DNA quantification: Influence of template DNA fragmentation on accuracy

Energy Technology Data Exchange (ETDEWEB)

Jackson, Christopher B., E-mail: Christopher.jackson@insel.ch [Division of Human Genetics, Departements of Pediatrics and Clinical Research, Inselspital, University of Berne, Freiburgstrasse, CH-3010 Berne (Switzerland); Gallati, Sabina, E-mail: sabina.gallati@insel.ch [Division of Human Genetics, Departements of Pediatrics and Clinical Research, Inselspital, University of Berne, Freiburgstrasse, CH-3010 Berne (Switzerland); Schaller, Andre, E-mail: andre.schaller@insel.ch [Division of Human Genetics, Departements of Pediatrics and Clinical Research, Inselspital, University of Berne, Freiburgstrasse, CH-3010 Berne (Switzerland)

2012-07-06

Highlights: Black-Right-Pointing-Pointer Serial qPCR accurately determines fragmentation state of any given DNA sample. Black-Right-Pointing-Pointer Serial qPCR demonstrates different preservation of the nuclear and mitochondrial genome. Black-Right-Pointing-Pointer Serial qPCR provides a diagnostic tool to validate the integrity of bioptic material. Black-Right-Pointing-Pointer Serial qPCR excludes degradation-induced erroneous quantification. -- Abstract: Real-time PCR (qPCR) is the method of choice for quantification of mitochondrial DNA (mtDNA) by relative comparison of a nuclear to a mitochondrial locus. Quantitative abnormal mtDNA content is indicative of mitochondrial disorders and mostly confines in a tissue-specific manner. Thus handling of degradation-prone bioptic material is inevitable. We established a serial qPCR assay based on increasing amplicon size to measure degradation status of any DNA sample. Using this approach we can exclude erroneous mtDNA quantification due to degraded samples (e.g. long post-exicision time, autolytic processus, freeze-thaw cycles) and ensure abnormal DNA content measurements (e.g. depletion) in non-degraded patient material. By preparation of degraded DNA under controlled conditions using sonification and DNaseI digestion we show that erroneous quantification is due to the different preservation qualities of the nuclear and the mitochondrial genome. This disparate degradation of the two genomes results in over- or underestimation of mtDNA copy number in degraded samples. Moreover, as analysis of defined archival tissue would allow to precise the molecular pathomechanism of mitochondrial disorders presenting with abnormal mtDNA content, we compared fresh frozen (FF) with formalin-fixed paraffin-embedded (FFPE) skeletal muscle tissue of the same sample. By extrapolation of measured decay constants for nuclear DNA ({lambda}{sub nDNA}) and mtDNA ({lambda}{sub mtDNA}) we present an approach to possibly correct measurements in

Maternal age effect and severe germ-line bottleneck in the inheritance of human mitochondrial DNA

DEFF Research Database (Denmark)

Rebolledo-Jaramillo, Boris; Su, Marcia Shu-Wei; Stoler, Nicholas

2014-01-01

The manifestation of mitochondrial DNA (mtDNA) diseases depends on the frequency of heteroplasmy (the presence of several alleles in an individual), yet its transmission across generations cannot be readily predicted owing to a lack of data on the size of the mtDNA bottleneck during oogenesis......, an order of magnitude higher than for nuclear DNA. Notably, we found a positive association between the number of heteroplasmies in a child and maternal age at fertilization, likely attributable to oocyte aging. This study also took advantage of droplet digital PCR (ddPCR) to validate heteroplasmies...... and confirm a de novo mutation. Our results can be used to predict the transmission of disease-causing mtDNA variants and illuminate evolutionary dynamics of the mitochondrial genome....

Mitochondrial DNA Hypomethylation Is a Biomarker Associated with Induced Senescence in Human Fetal Heart Mesenchymal Stem Cells

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Dehai Yu

2017-01-01

Full Text Available Background. Fetal heart can regenerate to restore its normal anatomy and function in response to injury, but this regenerative capacity is lost within the first week of postnatal life. Although the specific molecular mechanisms remain to be defined, it is presumed that aging of cardiac stem or progenitor cells may contribute to the loss of regenerative potential. Methods. To study this aging-related dysfunction, we cultured mesenchymal stem cells (MSCs from human fetal heart tissues. Senescence was induced by exposing cells to chronic oxidative stress/low serum. Mitochondrial DNA methylation was examined during the period of senescence. Results. Senescent MSCs exhibited flattened and enlarged morphology and were positive for the senescence-associated beta-galactosidase (SA-β-Gal. By scanning the entire mitochondrial genome, we found that four CpG islands were hypomethylated in close association with senescence in MSCs. The mitochondrial COX1 gene, which encodes the main subunit of the cytochrome c oxidase complex and contains the differentially methylated CpG island 4, was upregulated in MSCs in parallel with the onset of senescence. Knockdown of DNA methyltransferases (DNMT1, DNMT3a, and DNMT3B also upregulated COX1 expression and induced cellular senescence in MSCs. Conclusions. This study demonstrates that mitochondrial CpG hypomethylation may serve as a critical biomarker associated with cellular senescence induced by chronic oxidative stress.

Thyrotropin-releasing hormone controls mitochondrial biology in human epidermis.

Science.gov (United States)

Knuever, Jana; Poeggeler, Burkhard; Gáspár, Erzsébet; Klinger, Matthias; Hellwig-Burgel, Thomas; Hardenbicker, Celine; Tóth, Balázs I; Bíró, Tamás; Paus, Ralf

2012-03-01

Mitochondrial capacity and metabolic potential are under the control of hormones, such as thyroid hormones. The most proximal regulator of the hypothalamic-pituitary-thyroid (HPT) axis, TRH, is the key hypothalamic integrator of energy metabolism via its impact on thyroid hormone secretion. Here, we asked whether TRH directly modulates mitochondrial functions in normal, TRH-receptor-positive human epidermis. Organ-cultured human skin was treated with TRH (5-100 ng/ml) for 12-48 h. TRH significantly increased epidermal immunoreactivity for the mitochondria-selective subunit I of respiratory chain complex IV (MTCO1). This resulted from an increased MTCO1 transcription and protein synthesis and a stimulation of mitochondrial biogenesis as demonstrated by transmission electron microscopy and TRH-enhanced mitochondrial DNA synthesis. TRH also significantly stimulated the transcription of several other mitochondrial key genes (TFAM, HSP60, and BMAL1), including the master regulator of mitochondrial biogenesis (PGC-1α). TRH significantly enhanced mitochondrial complex I and IV enzyme activity and enhanced the oxygen consumption of human skin samples, which shows that the stimulated mitochondria are fully vital because the main source for cellular oxygen consumption is mitochondrial endoxidation. These findings identify TRH as a potent, novel neuroendocrine stimulator of mitochondrial activity and biogenesis in human epidermal keratinocytes in situ. Thus, human epidermis offers an excellent model for dissecting neuroendocrine controls of human mitochondrial biology under physiologically relevant conditions and for exploring corresponding clinical applications.

Detection the human mitochondrial DNA 4977 bp deletion induced by 60Co γ-rays in vitro by nest-PCR

International Nuclear Information System (INIS)

Feng Jiangbing; Lu Xue; Chen Deqing; Liu Qingjie; Chen Xiaosui

2004-01-01

Objective: To establish a method for detecting the mitochondrial DNA 4977 bp deletion (mtDNA 4977) induced by different doses of ionizing radiation. Methods: A nest-PCR method was established with 3 primer pairs for detecting the human peripheral mtDNA 4977. The final PCR products were sequenced after purified and the sequence was BLASTed with the standard genome information of human mitochondrion. The mtDNA 4977 level induced by 0-5 Gy 60 Co γ-rays of 5 healthy individuals was analyzed with the established nest-PCR. Results: The mtDNA 4977 could be detected by the established nest-PCR method. The mtDNA 4977 was observed on samples after exposed to 1-5 Gy 60 Co γ-rays, but it was not observed before (0 Gy) exposure. Conclusion: The nest-PCR method established in this study could be used to detect the mtDNA 4977 induced by ionizing radiation. (authors)

Mitochondrial DNA as a non-invasive biomarker: Accurate quantification using real time quantitative PCR without co-amplification of pseudogenes and dilution bias

International Nuclear Information System (INIS)

Malik, Afshan N.; Shahni, Rojeen; Rodriguez-de-Ledesma, Ana; Laftah, Abas; Cunningham, Phil

2011-01-01

Highlights: → Mitochondrial dysfunction is central to many diseases of oxidative stress. → 95% of the mitochondrial genome is duplicated in the nuclear genome. → Dilution of untreated genomic DNA leads to dilution bias. → Unique primers and template pretreatment are needed to accurately measure mitochondrial DNA content. -- Abstract: Circulating mitochondrial DNA (MtDNA) is a potential non-invasive biomarker of cellular mitochondrial dysfunction, the latter known to be central to a wide range of human diseases. Changes in MtDNA are usually determined by quantification of MtDNA relative to nuclear DNA (Mt/N) using real time quantitative PCR. We propose that the methodology for measuring Mt/N needs to be improved and we have identified that current methods have at least one of the following three problems: (1) As much of the mitochondrial genome is duplicated in the nuclear genome, many commonly used MtDNA primers co-amplify homologous pseudogenes found in the nuclear genome; (2) use of regions from genes such as β-actin and 18S rRNA which are repetitive and/or highly variable for qPCR of the nuclear genome leads to errors; and (3) the size difference of mitochondrial and nuclear genomes cause a 'dilution bias' when template DNA is diluted. We describe a PCR-based method using unique regions in the human mitochondrial genome not duplicated in the nuclear genome; unique single copy region in the nuclear genome and template treatment to remove dilution bias, to accurately quantify MtDNA from human samples.

Quantitative analysis of gene-specific DNA damage in human spermatozoa

International Nuclear Information System (INIS)

Sawyer, Dennis E.; Mercer, Belinda G.; Wiklendt, Agnieszka M.; Aitken, R. John

2003-01-01

Recent studies have suggested that human spermatozoa are highly susceptible to DNA damage induced by oxidative stress. However, a detailed analysis of the precise nature of this damage and the extent to which it affects the mitochondrial and nuclear genomes has not been reported. To induce DNA damage, human spermatozoa were treated in vitro with hydrogen peroxide (H 2 O 2 ; 0-5 mM) or iron (as Fe(II)SO 4 , 0-500 μM). Quantitative PCR (QPCR) was used to measure DNA damage in individual nuclear genes (hprt, β-pol and β-globin) and mitochondrial DNA. Single strand breaks were also assessed by alkaline gel electrophoresis. H 2 O 2 was found to be genotoxic toward spermatozoa at concentrations as high as 1.25 mM, but DNA damage was not detected in these cells with lower concentrations of H 2 O 2 . The mitochondrial genome of human spermatozoa was significantly (P 2 O 2 -induced DNA damage than the nuclear genome. However, both nDNA and mtDNA in human spermatozoa were significantly (P<0.001) more resistant to damage than DNA from a variety of cell lines of germ cell and myoblastoid origin. Interestingly, significant DNA damage was also not detected in human spermatozoa treated with iron. These studies report, for the first time, quantitative measurements of DNA damage in specific genes of male germ cells, and challenge the commonly held belief that human spermatozoa are particularly vulnerable to DNA damage

Silencing of PINK1 expression affects mitochondrial DNA and oxidative phosphorylation in dopaminergic cells.

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Matthew E Gegg

Full Text Available Mitochondrial dysfunction has been implicated in the pathogenesis of Parkinson's disease (PD. Impairment of the mitochondrial electron transport chain (ETC and an increased frequency in deletions of mitochondrial DNA (mtDNA, which encodes some of the subunits of the ETC, have been reported in the substantia nigra of PD brains. The identification of mutations in the PINK1 gene, which cause an autosomal recessive form of PD, has supported mitochondrial involvement in PD. The PINK1 protein is a serine/threonine kinase localized in mitochondria and the cytosol. Its precise function is unknown, but it is involved in neuroprotection against a variety of stress signalling pathways.In this report we have investigated the effect of silencing PINK1 expression in human dopaminergic SH-SY5Y cells by siRNA on mtDNA synthesis and ETC function. Loss of PINK1 expression resulted in a decrease in mtDNA levels and mtDNA synthesis. We also report a concomitant loss of mitochondrial membrane potential and decreased mitochondrial ATP synthesis, with the activity of complex IV of the ETC most affected. This mitochondrial dysfunction resulted in increased markers of oxidative stress under basal conditions and increased cell death following treatment with the free radical generator paraquat.This report highlights a novel function of PINK1 in mitochondrial biogenesis and a role in maintaining mitochondrial ETC activity. Dysfunction of both has been implicated in sporadic forms of PD suggesting that these may be key pathways in the development of the disease.

Clinical case of Mitochondrial DNA Depletion

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A. V. Degtyareva

2017-01-01

Full Text Available The article reports clinical case of early neonatal manifestation of a rare genetic disease – mitochondrial DNA depletion syndrome, confirmed in laboratory in Russia. Mutations of FBXL4, which encodes an orphan mitochondrial F-box protein, involved in the maintenance of mitochondrial DNA (mtDNA, ultimately leading to disruption of mtDNA replication and decreased activity of mitochondrial respiratory chain complexes. It’s a reason of abnormalities in clinically affected tissues, most of all the muscular system and the brain. In our case hydronephrosis on the right, subependimal cysts of the brain, partial intestinal obstruction accompanied by polyhydramnios were diagnosed antenatal. Baby’s condition at birth was satisfactory and worsened dramatically towards the end of the first day of life. Clinical presentation includes sepsis-like symptom complex, neonatal depression, muscular hypotonia, persistent decompensated lactic acidosis, increase in the concentration of mitochondrial markers in blood plasma and urine, and changes in the basal ganglia of the brain. Imaging of the brain by magnetic resonance imaging (MRI demonstrated global volume loss particularly the subcortical and periventricular white matter with significant abnormal signal in bilateral basal ganglia and brainstem with associated delayed myelination. Differential diagnosis was carried out with hereditary diseases that occur as a «sepsis-like» symptom complex, accompanied by lactic acidosis: a group of metabolic disorders of amino acids, organic acids, β-oxidation defects of fatty acids, respiratory mitochondrial chain disorders and glycogen storage disease. The diagnosis was confirmed after sequencing analysis of 62 mytochondrial genes by NGS (Next Generation Sequencing. Reported disease has an unfavorable prognosis, however, accurate diagnosis is very important for genetic counseling and helps prevent the re-birth of a sick child in the family.

Major genomic mitochondrial lineages delineate early human expansions

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Flores Carlos

2001-08-01

Full Text Available Abstract Background The phylogeographic distribution of human mitochondrial DNA variations allows a genetic approach to the study of modern Homo sapiens dispersals throughout the world from a female perspective. As a new contribution to this study we have phylogenetically analysed complete mitochondrial DNA(mtDNA sequences from 42 human lineages, representing major clades with known geographic assignation. Results We show the relative relationships among the 42 lineages and present more accurate temporal calibrations than have been previously possible to give new perspectives as how modern humans spread in the Old World. Conclusions The first detectable expansion occurred around 59,000–69,000 years ago from Africa, independently colonizing western Asia and India and, following this southern route, swiftly reaching east Asia. Within Africa, this expansion did not replace but mixed with older lineages detectable today only in Africa. Around 39,000–52,000 years ago, the western Asian branch spread radially, bringing Caucasians to North Africa and Europe, also reaching India, and expanding to north and east Asia. More recent migrations have entangled but not completely erased these primitive footprints of modern human expansions.

The efficiency of mitochondrial DNA markers in constructing genetic ...

African Journals Online (AJOL)

The efficiency of mitochondrial DNA markers in constructing genetic relationship among Oryx species. ... These data were used to provide the genetic kinship among different Oryx species. The complete cytochrome b gene ... Key words: Conservation, endangered species, Oryx, mitochondrial DNA (mtDNA) markers.

[Relationship between mitochondrial DNA copy number, membrane potential of human embryo and embryo morphology].

Science.gov (United States)

Zhao, H; Teng, X M; Li, Y F

2017-11-25

Objective: To explore the relationship between the embryo with the different morphological types in the third day and its mitochondrial copy number, the membrane potential. Methods: Totally 117 embryos with poor development after normal fertilization and were not suitable transferred in the fresh cycle and 106 frozen embryos that were discarded voluntarily by infertility patients with in vitro fertilization-embryo transfer after successful pregnancy were selected. According to evaluation of international standard in embryos, all cleavage stage embryos were divided into class Ⅰ frozen embryo group ( n= 64), class Ⅱ frozen embryo group ( n= 42) and class Ⅲ fresh embryonic group (not transplanted embryos; n= 117). Real-time PCR and confocal microscopy methods were used to detect mitochondrial DNA (mtDNA) copy number and the mitochondrial membrane potential of a single embryo. The differences between embryo quality and mtDNA copy number and membrane potential of each group were compared. Results: The copy number of mtDNA and the mitochondrial membrane potential in class Ⅲ fresh embryonic group [(1.7±1.0)×10(5) copy/μl, 1.56±0.32] were significantly lower than those in class Ⅰ frozen embryo group [(3.4±1.7)×10(5) copy/μl, 2.66±0.21] and class Ⅱ frozen embryo group [(2.6±1.2)×10(5) copy/μl, 1.80±0.32; all Pembryo group were significantly higher than those in classⅡ frozen embryo group (both Pembryos of the better quality embryo are higher.

Mitochondrial DNA depletion by ethidium bromide decreases neuronal mitochondrial creatine kinase: Implications for striatal energy metabolism.

Science.gov (United States)

Warren, Emily Booth; Aicher, Aidan Edward; Fessel, Joshua Patrick; Konradi, Christine

2017-01-01

Mitochondrial DNA (mtDNA), the discrete genome which encodes subunits of the mitochondrial respiratory chain, is present at highly variable copy numbers across cell types. Though severe mtDNA depletion dramatically reduces mitochondrial function, the impact of tissue-specific mtDNA reduction remains debated. Previously, our lab identified reduced mtDNA quantity in the putamen of Parkinson's Disease (PD) patients who had developed L-DOPA Induced Dyskinesia (LID), compared to PD patients who had not developed LID and healthy subjects. Here, we present the consequences of mtDNA depletion by ethidium bromide (EtBr) treatment on the bioenergetic function of primary cultured neurons, astrocytes and neuron-enriched cocultures from rat striatum. We report that EtBr inhibition of mtDNA replication and transcription consistently reduces mitochondrial oxygen consumption, and that neurons are significantly more sensitive to EtBr than astrocytes. EtBr also increases glycolytic activity in astrocytes, whereas in neurons it reduces the expression of mitochondrial creatine kinase mRNA and levels of phosphocreatine. Further, we show that mitochondrial creatine kinase mRNA is similarly downregulated in dyskinetic PD patients, compared to both non-dyskinetic PD patients and healthy subjects. Our data support a hypothesis that reduced striatal mtDNA contributes to energetic dysregulation in the dyskinetic striatum by destabilizing the energy buffering system of the phosphocreatine/creatine shuttle.

Mitochondrial DNA depletion by ethidium bromide decreases neuronal mitochondrial creatine kinase: Implications for striatal energy metabolism.

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Emily Booth Warren

Full Text Available Mitochondrial DNA (mtDNA, the discrete genome which encodes subunits of the mitochondrial respiratory chain, is present at highly variable copy numbers across cell types. Though severe mtDNA depletion dramatically reduces mitochondrial function, the impact of tissue-specific mtDNA reduction remains debated. Previously, our lab identified reduced mtDNA quantity in the putamen of Parkinson's Disease (PD patients who had developed L-DOPA Induced Dyskinesia (LID, compared to PD patients who had not developed LID and healthy subjects. Here, we present the consequences of mtDNA depletion by ethidium bromide (EtBr treatment on the bioenergetic function of primary cultured neurons, astrocytes and neuron-enriched cocultures from rat striatum. We report that EtBr inhibition of mtDNA replication and transcription consistently reduces mitochondrial oxygen consumption, and that neurons are significantly more sensitive to EtBr than astrocytes. EtBr also increases glycolytic activity in astrocytes, whereas in neurons it reduces the expression of mitochondrial creatine kinase mRNA and levels of phosphocreatine. Further, we show that mitochondrial creatine kinase mRNA is similarly downregulated in dyskinetic PD patients, compared to both non-dyskinetic PD patients and healthy subjects. Our data support a hypothesis that reduced striatal mtDNA contributes to energetic dysregulation in the dyskinetic striatum by destabilizing the energy buffering system of the phosphocreatine/creatine shuttle.

Transcription profiles of mitochondrial genes correlate with mitochondrial DNA haplotypes in a natural population of Silene vulgaris

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Olson Matthew S

2010-01-01

Full Text Available Abstract Background Although rapid changes in copy number and gene order are common within plant mitochondrial genomes, associated patterns of gene transcription are underinvestigated. Previous studies have shown that the gynodioecious plant species Silene vulgaris exhibits high mitochondrial diversity and occasional paternal inheritance of mitochondrial markers. Here we address whether variation in DNA molecular markers is correlated with variation in transcription of mitochondrial genes in S. vulgaris collected from natural populations. Results We analyzed RFLP variation in two mitochondrial genes, cox1 and atp1, in offspring of ten plants from a natural population of S. vulgaris in Central Europe. We also investigated transcription profiles of the atp1 and cox1 genes. Most DNA haplotypes and transcription profiles were maternally inherited; for these, transcription profiles were associated with specific mitochondrial DNA haplotypes. One individual exhibited a pattern consistent with paternal inheritance of mitochondrial DNA; this individual exhibited a transcription profile suggestive of paternal but inconsistent with maternal inheritance. We found no associations between gender and transcript profiles. Conclusions Specific transcription profiles of mitochondrial genes were associated with specific mitochondrial DNA haplotypes in a natural population of a gynodioecious species S. vulgaris. Our findings suggest the potential for a causal association between rearrangements in the plant mt genome and transcription product variation.

Thimerosal-Derived Ethylmercury Is a Mitochondrial Toxin in Human Astrocytes: Possible Role of Fenton Chemistry in the Oxidation and Breakage of mtDNA

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Martyn A. Sharpe

2012-01-01

Full Text Available Thimerosal generates ethylmercury in aqueous solution and is widely used as preservative. We have investigated the toxicology of Thimerosal in normal human astrocytes, paying particular attention to mitochondrial function and the generation of specific oxidants. We find that ethylmercury not only inhibits mitochondrial respiration leading to a drop in the steady state membrane potential, but also concurrent with these phenomena increases the formation of superoxide, hydrogen peroxide, and Fenton/Haber-Weiss generated hydroxyl radical. These oxidants increase the levels of cellular aldehyde/ketones. Additionally, we find a five-fold increase in the levels of oxidant damaged mitochondrial DNA bases and increases in the levels of mtDNA nicks and blunt-ended breaks. Highly damaged mitochondria are characterized by having very low membrane potentials, increased superoxide/hydrogen peroxide production, and extensively damaged mtDNA and proteins. These mitochondria appear to have undergone a permeability transition, an observation supported by the five-fold increase in Caspase-3 activity observed after Thimerosal treatment.

Oxidative DNA damage causes mitochondrial genomic instability in Saccharomyces cerevisiae.

Science.gov (United States)

Doudican, Nicole A; Song, Binwei; Shadel, Gerald S; Doetsch, Paul W

2005-06-01

Mitochondria contain their own genome, the integrity of which is required for normal cellular energy metabolism. Reactive oxygen species (ROS) produced by normal mitochondrial respiration can damage cellular macromolecules, including mitochondrial DNA (mtDNA), and have been implicated in degenerative diseases, cancer, and aging. We developed strategies to elevate mitochondrial oxidative stress by exposure to antimycin and H(2)O(2) or utilizing mutants lacking mitochondrial superoxide dismutase (sod2Delta). Experiments were conducted with strains compromised in mitochondrial base excision repair (ntg1Delta) and oxidative damage resistance (pif1Delta) in order to delineate the relationship between these pathways. We observed enhanced ROS production, resulting in a direct increase in oxidative mtDNA damage and mutagenesis. Repair-deficient mutants exposed to oxidative stress conditions exhibited profound genomic instability. Elimination of Ntg1p and Pif1p resulted in a synergistic corruption of respiratory competency upon exposure to antimycin and H(2)O(2). Mitochondrial genomic integrity was substantially compromised in ntg1Delta pif1Delta sod2Delta strains, since these cells exhibit a total loss of mtDNA. A stable respiration-defective strain, possessing a normal complement of mtDNA damage resistance pathways, exhibited a complete loss of mtDNA upon exposure to antimycin and H(2)O(2). This loss was preventable by Sod2p overexpression. These results provide direct evidence that oxidative mtDNA damage can be a major contributor to mitochondrial genomic instability and demonstrate cooperation of Ntg1p and Pif1p to resist the introduction of lesions into the mitochondrial genome.

Induction of Mitochondrial DNA Deletion by Ionizing Radiation in Human Lung Fibroblast IMR-90 Cells

International Nuclear Information System (INIS)

Eom, Hyeon Soo; Jung, U Hee; Park, Hae Ran; Jo, Sung Kee

2009-01-01

Mitochondrial DNA (mtDNA) deletion is a well-known marker for oxidative stress and aging and also contributes to their unfavorable effects in cultured cells and animal tissues. This study was conducted to investigate the effect of ionizing radiation (IR) on mtDNA deletion and the involvement of reactive oxygen species (ROS) in this process in human lung fibroblast (IMR-90) cells. Young IMR-90 cells at population doubling (PD) 39 were irradiated with 137 Cs -rays and the intracellular ROS level was determined by 2',7'-dichlorofluorescein diacetate (DCFH-DA) and mtDNA common deletion (4977bp) was detected by nested PCR. Old cells at PD 55 and H 2 O 2 -treated young cells were compared as the positive control. IR increased the intracellular ROS level and mtDNA 4977 bp deletion in IMR-90 cells dose-dependently. The increases of ROS level and mtDNA deletion were also observed in old cells and H 2 O 2 -treated young cells. To confirm the increased ROS level is essential for mtDNA deletion in irradiated cells, the effects of N-acetylcysteine (NAC) on IRinduced ROS and mtDNA deletion were examined. 5 mM NAC significantly attenuated the IR-induced ROS increase and mtDNA deletion. These results suggest that IR induces the mtDNA deletion and this process is mediated by ROS in IMR-90 cells

Successful enrichment and recovery of whole mitochondrial genomes from ancient human dental calculus.

Science.gov (United States)

Ozga, Andrew T; Nieves-Colón, Maria A; Honap, Tanvi P; Sankaranarayanan, Krithivasan; Hofman, Courtney A; Milner, George R; Lewis, Cecil M; Stone, Anne C; Warinner, Christina

2016-06-01

Archaeological dental calculus is a rich source of host-associated biomolecules. Importantly, however, dental calculus is more accurately described as a calcified microbial biofilm than a host tissue. As such, concerns regarding destructive analysis of human remains may not apply as strongly to dental calculus, opening the possibility of obtaining human health and ancestry information from dental calculus in cases where destructive analysis of conventional skeletal remains is not permitted. Here we investigate the preservation of human mitochondrial DNA (mtDNA) in archaeological dental calculus and its potential for full mitochondrial genome (mitogenome) reconstruction in maternal lineage ancestry analysis. Extracted DNA from six individuals at the 700-year-old Norris Farms #36 cemetery in Illinois was enriched for mtDNA using in-solution capture techniques, followed by Illumina high-throughput sequencing. Full mitogenomes (7-34×) were successfully reconstructed from dental calculus for all six individuals, including three individuals who had previously tested negative for DNA preservation in bone using conventional PCR techniques. Mitochondrial haplogroup assignments were consistent with previously published findings, and additional comparative analysis of paired dental calculus and dentine from two individuals yielded equivalent haplotype results. All dental calculus samples exhibited damage patterns consistent with ancient DNA, and mitochondrial sequences were estimated to be 92-100% endogenous. DNA polymerase choice was found to impact error rates in downstream sequence analysis, but these effects can be mitigated by greater sequencing depth. Dental calculus is a viable alternative source of human DNA that can be used to reconstruct full mitogenomes from archaeological remains. Am J Phys Anthropol 160:220-228, 2016. © 2016 The Authors American Journal of Physical Anthropology Published by Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Sequence analysis of mitochondrial DNA hypervariable region III of ...

African Journals Online (AJOL)

The aims of this research were to study mitochondrial DNA hypervariable region III and establish the degree of variation characteristic of a fragment. The mitochondrial DNA (mtDNA) is a small circular genome located within the mitochondria in the cytoplasm of the cell and a smaller 1.2 kb pair fragment, called the control ...

[Genetic system for maintaining the mitochondrial human genome in yeast Yarrowia lipolytica].

Science.gov (United States)

Isakova, E P; Deryabina, Yu I; Velyakova, A V; Biryukova, J K; Teplova, V V; Shevelev, A B

2016-01-01

For the first time, the possibility of maintaining an intact human mitochondrial genome in a heterologous system in the mitochondria of yeast Yarrowia lipolytica is shown. A method for introducing directional changes into the structure of the mitochondrial human genome replicating in Y. lipolytica by an artificially induced ability of yeast mitochondria for homologous recombination is proposed. A method of introducing and using phenotypic selection markers for the presence or absence of defects in genes tRNA-Lys and tRNA-Leu of the mitochondrial genome is developed. The proposed system can be used to correct harmful mutations of the human mitochondrial genome associated with mitochondrial diseases and for preparative amplification of intact mitochondrial DNA with an adjusted sequence in yeast cells. The applicability of the new system for the correction of mutations in the genes of Lys- and Leu-specific tRNAs of the human mitochondrial genome associated with serious and widespread human mitochondrial diseases such as myoclonic epilepsy with lactic acidosis (MELAS) and myoclonic epilepsy with ragged-red fibers (MERRF) is shown.

MitoLSDB: a comprehensive resource to study genotype to phenotype correlations in human mitochondrial DNA variations.

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Shamnamole K

Full Text Available Human mitochondrial DNA (mtDNA encodes a set of 37 genes which are essential structural and functional components of the electron transport chain. Variations in these genes have been implicated in a broad spectrum of diseases and are extensively reported in literature and various databases. In this study, we describe MitoLSDB, an integrated platform to catalogue disease association studies on mtDNA (http://mitolsdb.igib.res.in. The main goal of MitoLSDB is to provide a central platform for direct submissions of novel variants that can be curated by the Mitochondrial Research Community. MitoLSDB provides access to standardized and annotated data from literature and databases encompassing information from 5231 individuals, 675 populations and 27 phenotypes. This platform is developed using the Leiden Open (source Variation Database (LOVD software. MitoLSDB houses information on all 37 genes in each population amounting to 132397 variants, 5147 unique variants. For each variant its genomic location as per the Revised Cambridge Reference Sequence, codon and amino acid change for variations in protein-coding regions, frequency, disease/phenotype, population, reference and remarks are also listed. MitoLSDB curators have also reported errors documented in literature which includes 94 phantom mutations, 10 NUMTs, six documentation errors and one artefactual recombination. MitoLSDB is the largest repository of mtDNA variants systematically standardized and presented using the LOVD platform. We believe that this is a good starting resource to curate mtDNA variants and will facilitate direct submissions enhancing data coverage, annotation in context of pathogenesis and quality control by ensuring non-redundancy in reporting novel disease associated variants.

Mitochondrial nucleoid interacting proteins support mitochondrial protein synthesis.

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He, J; Cooper, H M; Reyes, A; Di Re, M; Sembongi, H; Litwin, T R; Gao, J; Neuman, K C; Fearnley, I M; Spinazzola, A; Walker, J E; Holt, I J

2012-07-01

Mitochondrial ribosomes and translation factors co-purify with mitochondrial nucleoids of human cells, based on affinity protein purification of tagged mitochondrial DNA binding proteins. Among the most frequently identified proteins were ATAD3 and prohibitin, which have been identified previously as nucleoid components, using a variety of methods. Both proteins are demonstrated to be required for mitochondrial protein synthesis in human cultured cells, and the major binding partner of ATAD3 is the mitochondrial ribosome. Altered ATAD3 expression also perturbs mtDNA maintenance and replication. These findings suggest an intimate association between nucleoids and the machinery of protein synthesis in mitochondria. ATAD3 and prohibitin are tightly associated with the mitochondrial membranes and so we propose that they support nucleic acid complexes at the inner membrane of the mitochondrion.

Mitochondrial Fusion Proteins and Human Diseases

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Michela Ranieri

2013-01-01

Full Text Available Mitochondria are highly dynamic, complex organelles that continuously alter their shape, ranging between two opposite processes, fission and fusion, in response to several stimuli and the metabolic demands of the cell. Alterations in mitochondrial dynamics due to mutations in proteins involved in the fusion-fission machinery represent an important pathogenic mechanism of human diseases. The most relevant proteins involved in the mitochondrial fusion process are three GTPase dynamin-like proteins: mitofusin 1 (MFN1 and 2 (MFN2, located in the outer mitochondrial membrane, and optic atrophy protein 1 (OPA1, in the inner membrane. An expanding number of degenerative disorders are associated with mutations in the genes encoding MFN2 and OPA1, including Charcot-Marie-Tooth disease type 2A and autosomal dominant optic atrophy. While these disorders can still be considered rare, defective mitochondrial dynamics seem to play a significant role in the molecular and cellular pathogenesis of more common neurodegenerative diseases, for example, Alzheimer’s and Parkinson’s diseases. This review provides an overview of the basic molecular mechanisms involved in mitochondrial fusion and focuses on the alteration in mitochondrial DNA amount resulting from impairment of mitochondrial dynamics. We also review the literature describing the main disorders associated with the disruption of mitochondrial fusion.

Maternal inheritance and mitochondrial DNA variants in familial Parkinson's disease

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Pfeiffer Ronald F

2010-04-01

Full Text Available Abstract Background Mitochondrial function is impaired in Parkinson's disease (PD and may contribute to the pathogenesis of PD, but the causes of mitochondrial impairment in PD are unknown. Mitochondrial dysfunction is recapitulated in cell lines expressing mitochondrial DNA (mtDNA from PD patients, implicating mtDNA variants or mutations, though the role of mtDNA variants or mutations in PD risk remains unclear. We investigated the potential contribution of mtDNA variants or mutations to the risk of PD. Methods We examined the possibility of a maternal inheritance bias as well as the association between mitochondrial haplogroups and maternal inheritance and disease risk in a case-control study of 168 multiplex PD families in which the proband and one parent were diagnosed with PD. 2-tailed Fisher Exact Tests and McNemar's tests were used to compare allele frequencies, and a t-test to compare ages of onset. Results The frequency of affected mothers of the proband with PD (83/167, 49.4% was not significantly different from the frequency of affected females of the proband generation (115/259, 44.4% (Odds Ratio 1.22; 95%CI 0.83 - 1.81. After correcting for multiple tests, there were no significant differences in the frequencies of mitochondrial haplogroups or of the 10398G complex I gene polymorphism in PD patients compared to controls, and no significant associations with age of onset of PD. Mitochondrial haplogroup and 10398G polymorphism frequencies were similar in probands having an affected father as compared to probands having an affected mother. Conclusions These data fail to demonstrate a bias towards maternal inheritance in familial PD. Consistent with this, we find no association of common haplogroup-defining mtDNA variants or for the 10398G variant with the risk of PD. However, these data do not exclude a role for mtDNA variants in other populations, and it remains possible that other inherited mitochondrial DNA variants, or somatic mDNA

Atomistic Molecular Dynamics Simulations of Mitochondrial DNA Polymerase γ

DEFF Research Database (Denmark)

Euro, Liliya; Haapanen, Outi; Róg, Tomasz

2017-01-01

of replisomal interactions, and functional effects of patient mutations that do not affect direct catalysis have remained elusive. Here we report the first atomistic classical molecular dynamics simulations of the human Pol γ replicative complex. Our simulation data show that DNA binding triggers remarkable......DNA polymerase γ (Pol γ) is a key component of the mitochondrial DNA replisome and an important cause of neurological diseases. Despite the availability of its crystal structures, the molecular mechanism of DNA replication, the switch between polymerase and exonuclease activities, the site...... changes in the enzyme structure, including (1) completion of the DNA-binding channel via a dynamic subdomain, which in the apo form blocks the catalytic site, (2) stabilization of the structure through the distal accessory β-subunit, and (3) formation of a putative transient replisome-binding platform...

Blood cell mitochondrial DNA content and premature ovarian aging.

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Marco Bonomi

Full Text Available Primary ovarian insufficiency (POI is a critical fertility defect characterized by an anticipated and silent impairment of the follicular reserve, but its pathogenesis is largely unexplained. The frequent maternal inheritance of POI together with a remarkable dependence of ovarian folliculogenesis upon mitochondrial biogenesis and bioenergetics suggested the possible involvement of a generalized mitochondrial defect. Here, we verified the existence of a significant correlation between blood and ovarian mitochondrial DNA (mtDNA content in a group of women undergoing ovarian hyperstimulation (OH, and then aimed to verify whether mtDNA content was significantly altered in the blood cells of POI women. We recruited 101 women with an impaired ovarian reserve: 59 women with premature ovarian failure (POF and 42 poor responders (PR to OH. A Taqman copy number assay revealed a significant mtDNA depletion (P<0.001 in both POF and PR women in comparison with 43 women of similar age and intact ovarian reserve, or 53 very old women with a previous physiological menopause. No pathogenic variations in the mitochondrial DNA polymerase γ (POLG gene were detected in 57 POF or PR women with low blood mtDNA content. In conclusion, blood cell mtDNA depletion is a frequent finding among women with premature ovarian aging, suggesting that a still undetermined but generalized mitochondrial defect may frequently predispose to POI which could then be considered a form of anticipated aging in which the ovarian defect may represent the first manifestation. The determination of mtDNA content in blood may become an useful tool for the POI risk prediction.

SG-ADVISER mtDNA: a web server for mitochondrial DNA annotation with data from 200 samples of a healthy aging cohort.

Science.gov (United States)

Rueda, Manuel; Torkamani, Ali

2017-08-18

Whole genome and exome sequencing usually include reads containing mitochondrial DNA (mtDNA). Yet, state-of-the-art pipelines and services for human nuclear genome variant calling and annotation do not handle mitochondrial genome data appropriately. As a consequence, any researcher desiring to add mtDNA variant analysis to their investigations is forced to explore the literature for mtDNA pipelines, evaluate them, and implement their own instance of the desired tool. This task is far from trivial, and can be prohibitive for non-bioinformaticians. We have developed SG-ADVISER mtDNA, a web server to facilitate the analysis and interpretation of mtDNA genomic data coming from next generation sequencing (NGS) experiments. The server was built in the context of our SG-ADVISER framework and on top of the MtoolBox platform (Calabrese et al., Bioinformatics 30(21):3115-3117, 2014), and includes most of its functionalities (i.e., assembly of mitochondrial genomes, heteroplasmic fractions, haplogroup assignment, functional and prioritization analysis of mitochondrial variants) as well as a back-end and a front-end interface. The server has been tested with unpublished data from 200 individuals of a healthy aging cohort (Erikson et al., Cell 165(4):1002-1011, 2016) and their data is made publicly available here along with a preliminary analysis of the variants. We observed that individuals over ~90 years old carried low levels of heteroplasmic variants in their genomes. SG-ADVISER mtDNA is a fast and functional tool that allows for variant calling and annotation of human mtDNA data coming from NGS experiments. The server was built with simplicity in mind, and builds on our own experience in interpreting mtDNA variants in the context of sudden death and rare diseases. Our objective is to provide an interface for non-bioinformaticians aiming to acquire (or contrast) mtDNA annotations via MToolBox. SG-ADVISER web server is freely available to all users at https://genomics.scripps.edu/mtdna .

Advances in the understanding of mitochondrial DNA as a pathogenic factor in inflammatory diseases [version 1; referees: 3 approved

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Ray K. Boyapati

2017-02-01

Full Text Available Mitochondrial DNA (mtDNA has many similarities with bacterial DNA because of their shared common ancestry. Increasing evidence demonstrates mtDNA to be a potent danger signal that is recognised by the innate immune system and can directly modulate the inflammatory response. In humans, elevated circulating mtDNA is found in conditions with significant tissue injury such as trauma and sepsis and increasingly in chronic organ-specific and systemic illnesses such as steatohepatitis and systemic lupus erythematosus. In this review, we examine our current understanding of mtDNA-mediated inflammation and how the mechanisms regulating mitochondrial homeostasis and mtDNA release represent exciting and previously under-recognised important factors in many human inflammatory diseases, offering many new translational opportunities.

Induction of Mitochondrial DNA Deletion by Ionizing Radiation in Human Lung Fibroblast IMR-90 Cells

Energy Technology Data Exchange (ETDEWEB)

Eom, Hyeon Soo; Jung, U Hee; Park, Hae Ran; Jo, Sung Kee [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2009-06-15

Mitochondrial DNA (mtDNA) deletion is a well-known marker for oxidative stress and aging and also contributes to their unfavorable effects in cultured cells and animal tissues. This study was conducted to investigate the effect of ionizing radiation (IR) on mtDNA deletion and the involvement of reactive oxygen species (ROS) in this process in human lung fibroblast (IMR-90) cells. Young IMR-90 cells at population doubling (PD) 39 were irradiated with {sup 137}Cs -rays and the intracellular ROS level was determined by 2',7'-dichlorofluorescein diacetate (DCFH-DA) and mtDNA common deletion (4977bp) was detected by nested PCR. Old cells at PD 55 and H{sub 2}O{sub 2}-treated young cells were compared as the positive control. IR increased the intracellular ROS level and mtDNA 4977 bp deletion in IMR-90 cells dose-dependently. The increases of ROS level and mtDNA deletion were also observed in old cells and H{sub 2}O{sub 2}-treated young cells. To confirm the increased ROS level is essential for mtDNA deletion in irradiated cells, the effects of N-acetylcysteine (NAC) on IRinduced ROS and mtDNA deletion were examined. 5 mM NAC significantly attenuated the IR-induced ROS increase and mtDNA deletion. These results suggest that IR induces the mtDNA deletion and this process is mediated by ROS in IMR-90 cells.

The Mitochondrial DNA (mtDNA)-Associated Protein SWIB5 Influences mtDNA Architecture and Homologous Recombination

KAUST Repository

Blomme, Jonas

2017-04-19

In addition to the nucleus, mitochondria and chloroplasts in plant cells also contain genomes. Efficient DNA repair pathways are crucial in these organelles to fix damage resulting from endogenous and exogenous factors. Plant organellar genomes are complex compared with their animal counterparts, and although several plant-specific mediators of organelle DNA repair have been reported, many regulators remain to be identified. Here, we show that a mitochondrial SWI/SNF (nucleosome remodeling) complex B protein, SWIB5, is capable of associating with mitochondrial DNA (mtDNA) in Arabidopsis thaliana. Gainand loss-of-function mutants provided evidence for a role of SWIB5 in influencing mtDNA architecture and homologous recombination at specific intermediate-sized repeats both under normal and genotoxic conditions. SWIB5 interacts with other mitochondrial SWIB proteins. Gene expression and mutant phenotypic analysis of SWIB5 and SWIB family members suggests a link between organellar genome maintenance and cell proliferation. Taken together, our work presents a protein family that influences mtDNA architecture and homologous recombination in plants and suggests a link between organelle functioning and plant development.

Targeted impairment of thymidine kinase 2 expression in cells induces mitochondrial DNA depletion and reveals molecular mechanisms of compensation of mitochondrial respiratory activity

International Nuclear Information System (INIS)

Villarroya, Joan; Lara, Mari-Carmen; Dorado, Beatriz; Garrido, Marta; Garcia-Arumi, Elena; Meseguer, Anna; Hirano, Michio; Vila, Maya R.

2011-01-01

Highlights: → We impaired TK2 expression in Ost TK1 - cells via siRNA-mediated interference (TK2 - ). → TK2 impairment caused severe mitochondrial DNA (mtDNA) depletion in quiescent cells. → Despite mtDNA depletion, TK2 - cells show high cytochrome oxidase activity. → Depletion of mtDNA occurs without imbalance in the mitochondrial dNTP pool. → Nuclear-encoded ENT1, DNA-pol γ, TFAM and TP gene expression is lowered in TK2 - cells. -- Abstract: The mitochondrial DNA (mtDNA) depletion syndrome comprises a clinically heterogeneous group of diseases characterized by reductions of the mtDNA abundance, without associated point mutations or rearrangements. We have developed the first in vitro model to study of mtDNA depletion due to reduced mitochondrial thymidine kinase 2 gene (TK2) expression in order to understand the molecular mechanisms involved in mtDNA depletion syndrome due to TK2 mutations. Small interfering RNA targeting TK2 mRNA was used to decrease TK2 expression in Ost TK1 - cells, a cell line devoid of endogenous thymidine kinase 1 (TK1). Stable TK2-deficient cell lines showed a reduction of TK2 levels close to 80%. In quiescent conditions, TK2-deficient cells showed severe mtDNA depletion, also close to 80% the control levels. However, TK2-deficient clones showed increased cytochrome c oxidase activity, higher cytochrome c oxidase subunit I transcript levels and higher subunit II protein expression respect to control cells. No alterations of the deoxynucleotide pools were found, whereas a reduction in the expression of genes involved in nucleoside/nucleotide homeostasis (human equilibrative nucleoside transporter 1, thymidine phosphorylase) and mtDNA maintenance (DNA-polymerase γ, mitochondrial transcription factor A) was observed. Our findings highlight the importance of cellular compensatory mechanisms that enhance the expression of respiratory components to ensure respiratory activity despite profound depletion in mtDNA levels.

Mitochondrial regulation of epigenetics and its role in human diseases

DEFF Research Database (Denmark)

Minocherhomji, Sheroy; Tollefsbol, Trygve O; Singh, Keshav K

2012-01-01

as the sole pathogenic factor suggesting that additional mechanisms contribute to lack of genotype and clinical phenotype correlationship. An increasing number of studies have identified a possible effect on the epigenetic landscape of the nuclear genome as a consequence of mitochondrial dysfunction....... In particular, these studies demonstrate reversible or irreversible changes in genomic DNA methylation profiles of the nuclear genome. Here we review how mitochondria damage checkpoint (mitocheckpoint) induces epigenetic changes in the nucleus. Persistent pathogenic mutations in mtDNA may also lead...... to epigenetic changes causing genomic instability in the nuclear genome. We propose that "mitocheckpoint" mediated epigenetic and genetic changes may play key roles in phenotypic variation related to mitochondrial diseases or host of human diseases in which mitochondrial defect plays a primary role....

Mitochondrial depolarization in yeast zygotes inhibits clonal expansion of selfish mtDNA.

Science.gov (United States)

Karavaeva, Iuliia E; Golyshev, Sergey A; Smirnova, Ekaterina A; Sokolov, Svyatoslav S; Severin, Fedor F; Knorre, Dmitry A

2017-04-01

Non-identical copies of mitochondrial DNA (mtDNA) compete with each other within a cell and the ultimate variant of mtDNA present depends on their relative replication rates. Using yeast Saccharomyces cerevisiae cells as a model, we studied the effects of mitochondrial inhibitors on the competition between wild-type mtDNA and mutant selfish mtDNA in heteroplasmic zygotes. We found that decreasing mitochondrial transmembrane potential by adding uncouplers or valinomycin changes the competition outcomes in favor of the wild-type mtDNA. This effect was significantly lower in cells with disrupted mitochondria fission or repression of the autophagy-related genes ATG8 , ATG32 or ATG33 , implying that heteroplasmic zygotes activate mitochondrial degradation in response to the depolarization. Moreover, the rate of mitochondrially targeted GFP turnover was higher in zygotes treated with uncoupler than in haploid cells or untreated zygotes. Finally, we showed that vacuoles of zygotes with uncoupler-activated autophagy contained DNA. Taken together, our data demonstrate that mitochondrial depolarization inhibits clonal expansion of selfish mtDNA and this effect depends on mitochondrial fission and autophagy. These observations suggest an activation of mitochondria quality control mechanisms in heteroplasmic yeast zygotes. © 2017. Published by The Company of Biologists Ltd.

Genetics Home Reference: MPV17-related hepatocerebral mitochondrial DNA depletion syndrome

Science.gov (United States)

... DNA depletion syndrome MPV17-related hepatocerebral mitochondrial DNA depletion syndrome Printable PDF Open All Close All Enable ... collapse boxes. Description MPV17 -related hepatocerebral mitochondrial DNA depletion syndrome is an inherited disorder that can cause ...

Oxidative stress negatively affects human sperm mitochondrial respiration.

Science.gov (United States)

Ferramosca, Alessandra; Pinto Provenzano, Sara; Montagna, Daniela Domenica; Coppola, Lamberto; Zara, Vincenzo

2013-07-01

To correlate the level of oxidative stress in serum and seminal fluid and the level of sperm deoxyribonucleic acid (DNA) fragmentation with sperm mitochondrial respiratory efficiency. Sperm mitochondrial respiratory activity was evaluated with a polarographic assay of oxygen consumption carried out in hypotonically treated sperm cells. A possible relationship between sperm mitochondrial respiratory efficiency, the level of oxidative stress, and the level of sperm DNA fragmentation was investigated. Sperm motility was positively correlated with mitochondrial respiration but negatively correlated with oxidative stress and DNA fragmentation. Interestingly, sperm mitochondrial respiratory activity was negatively affected by oxidative stress and DNA fragmentation. Our data indicate that sperm mitochondrial respiration is decreased in patients with high levels of reactive oxygen species by an uncoupling between electron transport and adenosine triphosphate synthesis. This reduction in mitochondrial functionality might be 1 of the reasons responsible for the decrease in spermatozoa motility. Copyright © 2013 Elsevier Inc. All rights reserved.

Mitochondrial DNA: An Endogenous Trigger for Immune Paralysis.

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Schäfer, Simon T; Franken, Lars; Adamzik, Michael; Schumak, Beatrix; Scherag, André; Engler, Andrea; Schönborn, Niels; Walden, Jennifer; Koch, Susanne; Baba, Hideo A; Steinmann, Jörg; Westendorf, Astrid M; Fandrey, Joachim; Bieber, Thomas; Kurts, Christian; Frede, Stilla; Peters, Jürgen; Limmer, Andreas

2016-04-01

Critically ill patients are at high risk to suffer from sepsis, even in the absence of an initial infectious source, but the molecular mechanisms for their increased sepsis susceptibility, including a suppressed immune system, remain unclear. Although microbes and pathogen-associated molecular pattern are accepted inducers of sepsis and septic immunosuppression, the role of endogenous Toll-like receptor (TLR) ligands, such as mitochondrial DNA (mtDNA), in altering the immune response is unknown. Mitochondrial DNA serum concentrations of the mitochondrial genes D-Loop and adenosine triphosphatase 6 were determined (quantitative polymerase chain reaction) in 165 septic patients and 50 healthy volunteers. Furthermore, cytotoxic T-cell activity was analyzed in wild-type and TLR9 knockout mice, with/without previous mtDNA administration, followed by injection of an ovalbumin-expressing adenoviral vector. Mitochondrial DNA serum concentrations were increased in septic patients (adenosine triphosphatase 6, 123-fold; D-Loop, 76-fold, P < 0.0001) compared with volunteers. Furthermore, a single mtDNA injection caused profound, TLR9-dependent immunosuppression of adaptive T-cell cytotoxicity in wild-type but not in TLR9 knockout mice and evoked various immunosuppressive mechanisms including the destruction of the splenic microstructure, deletion of cross-presenting dendritic cells, and up-regulation of programmed cell death ligand 1 and indoleamine 2,3-dioxygenase. Several of these findings in mice were mirrored in septic patients, and mtDNA concentrations were associated with an increased 30-day mortality. The findings of this study imply that mtDNA, an endogenous danger associated molecular pattern, is a hitherto unknown inducer of septic immunoparalysis and one possible link between initial inflammation and subsequent immunosuppression in critically ill patients.

Proteomic Dissection of the Mitochondrial DNA Metabolism Apparatus in Arabidopsis

Energy Technology Data Exchange (ETDEWEB)

SAlly A. Mackenzie

2004-01-06

This study involves the investigation of nuclear genetic components that regulate mitochondrial genome behavior in higher plants. The approach utilizes the advanced plant model system of Arabidopsis thaliana to identify and functionally characterize multiple components of the mitochondrial DNA replication, recombination and mismatch repair system and their interaction partners. The rationale for the research stems from the central importance of mitochondria to overall cellular metabolism and the essential nature of the mitochondrial genome to mitochondrial function. Relatively little is understood about mitochondrial DNA maintenance and transmission in higher eukaryotes, and the higher plant mitochondrial genome displays unique properties and behavior. This investigation has revealed at least three important properties of plant mitochondrial DNA metabolism components. (1) Many are dual targeted to mitochondrial and chloroplasts by novel mechanisms, suggesting that the mitochondria a nd chloroplast share their genome maintenance apparatus. (2)The MSH1 gene, originating as a component of mismatch repair, has evolved uniquely in plants to participate in differential replication of the mitochondrial genome. (3) This mitochondrial differential replication process, termed substoichiometric shifting and also involving a RecA-related gene, appears to represent an adaptive mechanism to expand plant reproductive capacity and is likely present throughout the plant kingdom.

Phylogeography of mitochondrial DNA variation in brown bears and polar bears.

Science.gov (United States)

Shields, G F; Adams, D; Garner, G; Labelle, M; Pietsch, J; Ramsay, M; Schwartz, C; Titus, K; Williamson, S

2000-05-01

We analyzed 286 nucleotides of the middle portion of the mitochondrial cytochrome b gene of 61 brown bears from three locations in Alaska and 55 polar bears from Arctic Canada and Arctic Siberia to test our earlier observations of paraphyly between polar bears and brown bears as well as to test the extreme uniqueness of mitochondrial DNA types of brown bears on Admiralty, Baranof, and Chichagof (ABC) islands of southeastern Alaska. We also investigated the phylogeography of brown bears of Alaska's Kenai Peninsula in relation to other Alaskan brown bears because the former are being threatened by increased human development. We predicted that: (1) mtDNA paraphyly between brown bears and polar bears would be upheld, (2) the mtDNA uniqueness of brown bears of the ABC islands would be upheld, and (3) brown bears of the Kenai Peninsula would belong to either clade II or clade III of brown bears of our earlier studies of mtDNA. All of our predictions were upheld through the analysis of these additional samples. Copyright 2000 Academic Press.

Phylogeography of mitochondrial DNA variation in brown bears and polar bears

Science.gov (United States)

Shields, Gerald F.; Adams, Deborah; Garner, Gerald W.; Labelle, Martine; Pietsch, Jacy; Ramsay, Malcolm; Schwartz, Charles; Titus, Kimberly; Williamson, Scott

2000-01-01

We analyzed 286 nucleotides of the middle portion of the mitochondrial cytochrome b gene of 61 brown bears from three locations in Alaska and 55 polar bears from Arctic Canada and Arctic Siberia to test our earlier observations of paraphyly between polar bears and brown bears as well as to test the extreme uniqueness of mitochondrial DNA types of brown bears on Admiralty, Baranof, and Chichagof (ABC) islands of southeastern Alaska. We also investigated the phylogeography of brown bears of Alaska's Kenai Peninsula in relation to other Alaskan brown bears because the former are being threatened by increased human development. We predicted that: (1) mtDNA paraphyly between brown bears and polar bears would be upheld, (2) the mtDNA uniqueness of brown bears of the ABC islands would be upheld, and (3) brown bears of the Kenai Peninsula would belong to either clade II or clade III of brown bears of our earlier studies of mtDNA. All of our predictions were upheld through the analysis of these additional samples.

Distinct structural features of TFAM drive mitochondrial DNA packaging versus transcriptional activation.

Science.gov (United States)

Ngo, Huu B; Lovely, Geoffrey A; Phillips, Rob; Chan, David C

2014-01-01

TFAM (transcription factor A, mitochondrial) is a DNA-binding protein that activates transcription at the two major promoters of mitochondrial DNA (mtDNA)--the light strand promoter (LSP) and the heavy strand promoter 1 (HSP1). Equally important, it coats and packages the mitochondrial genome. TFAM has been shown to impose a U-turn on LSP DNA; however, whether this distortion is relevant at other sites is unknown. Here we present crystal structures of TFAM bound to HSP1 and to nonspecific DNA. In both, TFAM similarly distorts the DNA into a U-turn. Yet, TFAM binds to HSP1 in the opposite orientation from LSP explaining why transcription from LSP requires DNA bending, whereas transcription at HSP1 does not. Moreover, the crystal structures reveal dimerization of DNA-bound TFAM. This dimerization is dispensable for DNA bending and transcriptional activation but is important in DNA compaction. We propose that TFAM dimerization enhances mitochondrial DNA compaction by promoting looping of the DNA.

Defects of mtDNA Replication Impaired Mitochondrial Biogenesis During Trypanosoma cruzi Infection in Human Cardiomyocytes and Chagasic Patients: The Role of Nrf1/2 and Antioxidant Response

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Wan, Xianxiu; Gupta, Shivali; Zago, Maria P.; Davidson, Mercy M.; Dousset, Pierre; Amoroso, Alejandro; Garg, Nisha Jain

2012-01-01

Background Mitochondrial dysfunction is a key determinant in chagasic cardiomyopathy development in mice; however, its relevance in human Chagas disease is not known. We determined if defects in mitochondrial biogenesis and dysregulation of peroxisome proliferator-activated receptor gamma (PPARγ) coactivator-1 (PGC-1)–regulated transcriptional pathways constitute a mechanism or mechanisms underlying mitochondrial oxidative-phosphorylation (OXPHOS) deficiency in human Chagas disease. Methods and Results We utilized human cardiomyocytes and left-ventricular tissue from chagasic and other cardiomyopathy patients and healthy donors (n>6/group). We noted no change in citrate synthase activity, yet mRNA and/or protein levels of subunits of the respiratory complexes were significantly decreased in Trypanosoma cruzi–infected cardiomyocytes (0 to 24 hours) and chagasic hearts. We observed increased mRNA and decreased nuclear localization of PGC-1-coactivated transcription factors, yet the expression of genes for PPARγ-regulated fatty acid oxidation and nuclear respiratory factor (NRF1/2)–regulated mtDNA replication and transcription machinery was enhanced in infected cardiomyocytes and chagasic hearts. The D-loop formation was normal or higher, but mtDNA replication and mtDNA content were decreased by 83% and 40% to 65%, respectively. Subsequently, we noted that reactive oxygen species (ROS), oxidative stress, and mtDNA oxidation were significantly increased, yet NRF1/2-regulated antioxidant gene expression remained compromised in infected cardiomyocytes and chagasic hearts. Conclusions The replication of mtDNA was severely compromised, resulting in a significant loss of mtDNA and expression of OXPHOS genes in T cruzi–infected cardiomyocytes and chagasic hearts. Our data suggest increased ROS generation and selective functional incapacity of NRF2-mediated antioxidant gene expression played a role in the defects in mtDNA replication and unfitness of mtDNA for

Exploring the mitochondrial DNA variability of the Amazonian Yanomami.

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Varano, Sara; Scorrano, Gabriele; Martínez-Labarga, Cristina; Finocchio, Andrea; Rapone, Cesare; Berti, Andrea; Rickards, Olga

2016-11-01

The aim of this study was to explore the mitochondrial variability in the Yanomami population to reconstruct its demographic history and explore its genetic composition in relation to its cultural and linguistic features. A total of 174 human head hair shafts -collected in 1958- belonging to individuals from a Yanomami group living in Santa Isabel, Brazil, were analyzed. Automated extraction of the hairs was performed, and several methods were applied to optimize the analysis of the degraded DNA. The mtDNA hypervariable segments I-II, along with the 9-bp COII-tRNA Lys deletion, were investigated. Using published data from the Yanomami and other Amazonian populations, several statistical analyses were carried out to explore the genetic variability within the study population. Ninety eight percent of the mitochondrial DNA (mtDNA) sequences analyzed belonged to Native American haplogroups, while 2% belonged to African haplogroups. Compared with the Yanomami groups previously studied, the Santa Isabel sample seemed more genetically similar to other Amazonian populations. Among the Yanomami samples studied to date, the Santa Isabel Yanomami show a higher genetic heterogeneity. This could be due to gene flow with non-Yanomami populations, as well as to the introduction of new mitochondrial haplotypes by gold miners. In both cases, the geographic location of Santa Isabel might have made this Yanomami village less isolated than the others, suggesting that the Rio Negro played a central role in increasing its genetic variability. On the whole, the Yanomami were quite genetically diversified, probably mirroring their great linguistic heterogeneity. Am. J. Hum. Biol. 28:846-856, 2016. © 2016Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Fructose-Rich Diet Affects Mitochondrial DNA Damage and Repair in Rats.

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Cioffi, Federica; Senese, Rosalba; Lasala, Pasquale; Ziello, Angela; Mazzoli, Arianna; Crescenzo, Raffaella; Liverini, Giovanna; Lanni, Antonia; Goglia, Fernando; Iossa, Susanna

2017-03-24

Evidence indicates that many forms of fructose-induced metabolic disturbance are associated with oxidative stress and mitochondrial dysfunction. Mitochondria are prominent targets of oxidative damage; however, it is not clear whether mitochondrial DNA (mtDNA) damage and/or its lack of repair are events involved in metabolic disease resulting from a fructose-rich diet. In the present study, we evaluated the degree of oxidative damage to liver mtDNA and its repair, in addition to the state of oxidative stress and antioxidant defense in the liver of rats fed a high-fructose diet. We used male rats feeding on a high-fructose or control diet for eight weeks. Our results showed an increase in mtDNA damage in the liver of rats fed a high-fructose diet and this damage, as evaluated by the expression of DNA polymerase γ, was not repaired; in addition, the mtDNA copy number was found to be significantly reduced. A reduction in the mtDNA copy number is indicative of impaired mitochondrial biogenesis, as is the finding of a reduction in the expression of genes involved in mitochondrial biogenesis. In conclusion, a fructose-rich diet leads to mitochondrial and mtDNA damage, which consequently may have a role in liver dysfunction and metabolic diseases.

Oxidants and not alkylating agents induce rapid mtDNA loss and mitochondrial dysfunction

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Furda, Amy M.; Marrangoni, Adele M.; Lokshin, Anna; Van Houten, Bennett

2013-01-01

Mitochondrial DNA (mtDNA) is essential for proper mitochondrial function and encodes 22 tRNAs, 2 rRNAs and 13 polypeptides that make up subunits of complex I, III, IV, in the electron transport chain and complex V, the ATP synthase. Although mitochondrial dysfunction has been implicated in processes such as premature aging, neurodegeneration, and cancer, it has not been shown whether persistent mtDNA damage causes a loss of oxidative phosphorylation. We addressed this question by treating mouse embryonic fibroblasts with either hydrogen peroxide (H2O2) or the alkylating agent methyl methanesulfonate (MMS) and measuring several endpoints, including mtDNA damage and repair rates using QPCR, levels of mitochondrial- and nuclear-encoded proteins using antibody analysis, and a pharmacologic profile of mitochondria using the Seahorse Extracellular Flux Analyzer. We show that a 60 min treatment with H2O2 causes persistent mtDNA lesions, mtDNA loss, decreased levels of a nuclear-encoded mitochondrial subunit, a loss of ATP-linked oxidative phosphorylation and a loss of total reserve capacity. Conversely, a 60 min treatment with 2 mM MMS causes persistent mtDNA lesions but no mtDNA loss, no decrease in levels of a nuclear-encoded mitochondrial subunit, and no mitochondrial dysfunction. These results suggest that persistent mtDNA damage is not sufficient to cause mitochondrial dysfunction. PMID:22766155

Mitochondrial DNA Depletion Syndrome is Expressed in Amniotic Fluid Cell Cultures

OpenAIRE

Blake, Julian C.; Taanman, Jan-Willem; Morris, Andrew M. M.; Gray, R. George F.; Cooper, J. Mark; McKiernan, Patrick J.; Leonard, James V.; Schapira, Anthony H. V.

1999-01-01

Mitochondrial DNA depletion syndrome is an autosomal inherited disease associated with grossly reduced cellular levels of mitochondrial DNA in infancy. Most patients are born after a full and uncomplicated pregnancy, are normal at birth, but develop symptoms in the early neonatal period. These observations have led to the suggestion that the patients have a defect affecting the control of mitochondrial DNA copy number after birth. Using immunocytochemical techniques, we demonstrated that the ...

Mitochondrial DNA levels in Huntington disease leukocytes and dermal fibroblasts.

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Jędrak, Paulina; Krygier, Magdalena; Tońska, Katarzyna; Drozd, Małgorzata; Kaliszewska, Magdalena; Bartnik, Ewa; Sołtan, Witold; Sitek, Emilia J; Stanisławska-Sachadyn, Anna; Limon, Janusz; Sławek, Jarosław; Węgrzyn, Grzegorz; Barańska, Sylwia

2017-08-01

Huntington disease (HD) is an inherited neurodegenerative disorder caused by mutations in the huntingtin gene. Involvement of mitochondrial dysfunctions in, and especially influence of the level of mitochondrial DNA (mtDNA) on, development of this disease is unclear. Here, samples of blood from 84 HD patients and 79 controls, and dermal fibroblasts from 10 HD patients and 9 controls were analysed for mtDNA levels. Although the type of mitochondrial haplogroup had no influence on the mtDNA level, and there was no correlation between mtDNA level in leukocytes in HD patients and various parameters of HD severity, some considerable differences between HD patients and controls were identified. The average mtDNA/nDNA relative copy number was significantly higher in leukocytes, but lower in fibroblasts, of symptomatic HD patients relative to the control group. Moreover, HD women displayed higher mtDNA levels in leukocytes than HD men. Because this is the largest population analysed to date, these results might contribute to explanation of discrepancies between previously published studies concerning levels of mtDNA in cells of HD patients. We suggest that the size of the investigated population and type of cells from which DNA is isolated could significantly affect results of mtDNA copy number estimation in HD. Hence, these parameters should be taken into consideration in studies on mtDNA in HD, and perhaps also in other diseases where mitochondrial dysfunction occurs.

Mitochondrial DNA content in embryo culture medium is significantly associated with human embryo fragmentation.

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Stigliani, S; Anserini, P; Venturini, P L; Scaruffi, P

2013-10-01

Is the amount of cell-free DNA released by human embryos into culture medium correlated with embryo morphological features? The mitochondrial DNA (mtDNA) content of culture medium is significantly associated with the fragmentation rate on Days 2 and 3 of embryo development, whether the oocyte came from women ≤ 35 or >35 years old. Cellular fragmentation is often utilized as one of the morphological parameters for embryo quality assessment. The amount of cellular fragments is considered to be an important morphological parameter for embryo implantation potential. It has been hypothesized that fragments are apoptotic bodies or anuclear cytoplasmatic pieces of blastomeres, although no definitive conclusion has been drawn about their pathogenesis. Human fertilized oocytes were individually cultured from Day 1 to Days 2 and 3. A total of 800 samples (166 spent media from Day 2 and 634 from Day 3) were enrolled into the present study. Double-stranded DNA (dsDNA) was quantified in 800 spent embryo culture media by Pico Green dye fluorescence assay. After DNA purification, genomic DNA (gDNA) and mtDNA were profiled by specific quantitative PCR. Statistical analyses defined correlations among DNA contents, embryo morphology and maternal age. Different independent tests confirmed the presence of DNA into embryo culture medium and, for the first time, we demonstrate that both gDNA and mtDNA are detectable in the secretome. The amount of DNA is larger in embryos with bad quality cleavage compared with high-grade embryos, suggesting that the DNA profile of culture medium is an objective marker for embryo quality assessment. In particular, DNA profiles are significantly associated with fragmentation feature (total dsDNA: P = 0.0010; mtDNA; P = 0.0247) and advanced maternal age. It is necessary to establish whether DNA profiling of spent embryo culture medium is a robust onsite test that can improve the prediction of blastulation, implantation and/or pregnancy rate. The

Mitochondrial DNA copy number threshold in mtDNA depletion myopathy.

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Durham, S E; Bonilla, E; Samuels, D C; DiMauro, S; Chinnery, P F

2005-08-09

The authors measured the absolute amount of mitochondrial DNA (mtDNA) within single muscle fibers from two patients with thymidine kinase 2 (TK2) deficiency and two healthy controls. TK2 deficient fibers containing more than 0.01 mtDNA/microm3 had residual cytochrome c oxidase (COX) activity. This defines the minimum amount of wild-type mtDNA molecules required to maintain COX activity in skeletal muscle and provides an explanation for the mosaic histochemical pattern seen in patients with mtDNA depletion syndrome.

Import of desired nucleic acid sequences using addressing motif of mitochondrial ribosomal 5S-rRNA for fluorescent in vivo hybridization of mitochondrial DNA and RNA.

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Zelenka, Jaroslav; Alán, Lukáš; Jabůrek, Martin; Ježek, Petr

2014-04-01

Based on the matrix-addressing sequence of mitochondrial ribosomal 5S-rRNA (termed MAM), which is naturally imported into mitochondria, we have constructed an import system for in vivo targeting of mitochondrial DNA (mtDNA) or mt-mRNA, in order to provide fluorescence hybridization of the desired sequences. Thus DNA oligonucleotides were constructed, containing the 5'-flanked T7 RNA polymerase promoter. After in vitro transcription and fluorescent labeling with Alexa Fluor(®) 488 or 647 dye, we obtained the fluorescent "L-ND5 probe" containing MAM and exemplar cargo, i.e., annealing sequence to a short portion of ND5 mRNA and to the light-strand mtDNA complementary to the heavy strand nd5 mt gene (5'-end 21 base pair sequence). For mitochondrial in vivo fluorescent hybridization, HepG2 cells were treated with dequalinium micelles, containing the fluorescent probes, bringing the probes proximally to the mitochondrial outer membrane and to the natural import system. A verification of import into the mitochondrial matrix of cultured HepG2 cells was provided by confocal microscopy colocalizations. Transfections using lipofectamine or probes without 5S-rRNA addressing MAM sequence or with MAM only were ineffective. Alternatively, the same DNA oligonucleotides with 5'-CACC overhang (substituting T7 promoter) were transcribed from the tetracycline-inducible pENTRH1/TO vector in human embryonic kidney T-REx®-293 cells, while mitochondrial matrix localization after import of the resulting unlabeled RNA was detected by PCR. The MAM-containing probe was then enriched by three-order of magnitude over the natural ND5 mRNA in the mitochondrial matrix. In conclusion, we present a proof-of-principle for mitochondrial in vivo hybridization and mitochondrial nucleic acid import.

Mitochondrial DNA as an inflammatory mediator in cardiovascular diseases.

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Nakayama, Hiroyuki; Otsu, Kinya

2018-03-06

Mitochondria play a central role in multiple cellular functions, including energy production, calcium homeostasis, and cell death. Currently, growing evidence indicates the vital roles of mitochondria in triggering and maintaining inflammation. Chronic inflammation without microbial infection - termed sterile inflammation - is strongly involved in the development of heart failure. Sterile inflammation is triggered by the activation of pattern recognition receptors (PRRs) that sense endogenous ligands called damage-associated molecular patterns (DAMPs). Mitochondria release multiple DAMPs including mitochondrial DNA, peptides, and lipids, which induce inflammation via the stimulation of multiple PRRs. Among the mitochondrial DAMPs, mitochondrial DNA (mtDNA) is currently highlighted as the DAMP that mediates the activation of multiple PRRs, including Toll-like receptor 9, Nod-like receptors, and cyclic GMP-AMP synthetase/stimulator of interferon gene pathways. These PRR signalling pathways, in turn, lead to the activation of nuclear factor-κB and interferon regulatory factor, which enhances the transcriptional activity of inflammatory cytokines and interferons, and induces the recruitment of inflammatory cells. As the heart is an organ comprising abundant mitochondria for its ATP consumption (needed to maintain constant cyclic contraction and relaxation), the generation of massive amounts of mitochondrial radical oxygen species and mitochondrial DAMPs are predicted to occur and promote cardiac inflammation. Here, we will focus on the role of mtDNA in cardiac inflammation and review the mechanism and pathological significance of mtDNA-induced inflammatory responses in cardiac diseases. © 2018 The Author(s).

Mitochondrial DNA replication: a PrimPol perspective

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Bailey, Laura J.

2017-01-01

PrimPol, (primase–polymerase), the most recently identified eukaryotic polymerase, has roles in both nuclear and mitochondrial DNA maintenance. PrimPol is capable of acting as a DNA polymerase, with the ability to extend primers and also bypass a variety of oxidative and photolesions. In addition, PrimPol also functions as a primase, catalysing the preferential formation of DNA primers in a zinc finger-dependent manner. Although PrimPol's catalytic activities have been uncovered in vitro, we still know little about how and why it is targeted to the mitochondrion and what its key roles are in the maintenance of this multicopy DNA molecule. Unlike nuclear DNA, the mammalian mitochondrial genome is circular and the organelle has many unique proteins essential for its maintenance, presenting a differing environment within which PrimPol must function. Here, we discuss what is currently known about the mechanisms of DNA replication in the mitochondrion, the proteins that carry out these processes and how PrimPol is likely to be involved in assisting this vital cellular process. PMID:28408491

Mitochondrial cardiomyopathies

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Ayman W. El-Hattab

2016-07-01

Full Text Available Mitochondria are found in all nucleated human cells and perform a variety of essential functions, including the generation of cellular energy. Mitochondria are under dual genome control. Only a small fraction of their proteins are encoded by mitochondrial DNA (mtDNA while more than 99% of them are encoded by nuclear DNA (nDNA. Mutations in mtDNA or mitochondria-related nDNA genes result in mitochondrial dysfunction leading to insufficient energy production required to meet the needs of various organs, particularly those with high energy requirements, including the central nervous system, skeletal and cardiac muscles, kidneys, liver, and endocrine system. Because cardiac muscles are one of the high energy demanding tissues, cardiac involvement occurs in mitochondrial diseases with cardiomyopathies being one of the most frequent cardiac manifestations found in these disorders. Cardiomyopathy is estimated to occur in 20-40% of children with mitochondrial diseases. Mitochondrial cardiomyopathies can vary in severity from asymptomatic status to severe manifestations including heart failure, arrhythmias, and sudden cardiac death. Hypertrophic cardiomyopathy is the most common type; however, mitochondrial cardiomyopathies might also present as dilated, restrictive, left ventricular noncompaction, and histiocytoid cardiomyopathies. Cardiomyopathies are frequent manifestations of mitochondrial diseases associated with defects in electron transport chain (ETC complexes subunits and their assembly factors, mitochondrial tRNAs, rRNAs, ribosomal proteins, and translation factors, mtDNA maintenance, and coenzyme Q10 synthesis. Other mitochondrial diseases with cardiomyopathies include Barth syndrome, Sengers syndrome, TMEM70-related mitochondrial complex V deficiency, and Friedreich ataxia.

Mgm101p is a novel component of the mitochondrial nucleoid that binds DNA and is required for the repair of oxidatively damaged mitochondrial DNA

International Nuclear Information System (INIS)

Meeusen, S.; Tieu, Q.; Wong, E.; Weiss, E.; Schieltz, D.; Yates, J.R.; Nunnari, J.

1999-01-01

Maintenance of mitochondrial DNA (mtDNA) during cell division is required for progeny to be respiratory competent. Maintenance involves the replication, repair, assembly, segregation, and partitioning of the mitochondrial nucleoid. MGM101 has been identified as a gene essential for mtDNA maintenance in S. cerevisiae, but its role is unknown. Using liquid chromatography coupled with tandem mass spectrometry, we identified Mgm101p as a component of highly enriched nucleoids, suggesting that it plays a nucleoid-specific role in maintenance. Subcellular fractionation, indirect immunofluorescence and GFP tagging show that Mgm101p is exclusively associated with the mitochondrial nucleoid structure in cells. Furthermore, DNA affinity chromatography of nucleoid extracts indicates that Mgm101p binds to DNA, suggesting that its nucleoid localization is in part due to this activity. Phenotypic analysis of cells containing a temperature sensitive mgm101 allele suggests that Mgm101p is not involved in mtDNA packaging, segregation, partitioning or required for ongoing mtDNA replication. We examined Mgm101p's role in mtDNA repair. As compared with wild-type cells, mgm101 cells were more sensitive to mtDNA damage induced by UV irradiation and were hypersensitive to mtDNA damage induced by gamma rays and H2O2 treatment. Thus, we propose that Mgm101p performs an essential function in the repair of oxidatively damaged mtDNA that is required for the maintenance of the mitochondrial genome. (author)

"Stiff neonate" with mitochondrial DNA depletion and secondary neurotransmitter defects.

LENUS (Irish Health Repository)

Moran, Margaret M

2011-12-01

Mitochondrial disorders comprise a heterogenous group. A neonate who presented with episodes of severe truncal hypertonia and apnea progressed to a hypokinetic rigid syndrome characterized by hypokinesia, tremulousness, profound head lag, absent suck and gag reflexes, brisk deep tendon reflexes, ankle and jaw clonus, and evidence of autonomic dysfunction. Analysis of cerebrospinal fluid neurotransmitters from age 7 weeks demonstrated low levels of amine metabolites (homovanillic acid and 5-hydroxyindoleacetic acid), tetrahydrobiopterin, and pyridoxal phosphate. Mitochondrial DNA quantitative studies on muscle homogenate demonstrated a mitochondrial DNA depletion disorder. Respiratory chain enzymology demonstrated decreased complex IV activity. Screening for mitochondrial DNA rearrangement disorders and sequencing relevant mitochondrial genes produced negative results. No clinical or biochemical response to treatment with pyridoxal phosphate, tetrahydrobiopterin, or l-dopa occurred. The clinical course was progressive, and the patient died at age 19 months. Mitochondrial disorders causing secondary neurotransmitter diseases are usually severe, but are rarely reported. This diagnosis should be considered in neonates or infants who present with hypertonia, hypokinesia rigidity, and progressive neurodegeneration.

Modulation of Mitochondrial DNA Copy Number to Induce Hepatocytic Differentiation of Human Amniotic Epithelial Cells.

Science.gov (United States)

Vaghjiani, Vijesh; Cain, Jason E; Lee, William; Vaithilingam, Vijayaganapathy; Tuch, Bernard E; St John, Justin C

2017-10-15

Mitochondrial deoxyribonucleic acid (mtDNA) copy number is tightly regulated during pluripotency and differentiation. There is increased demand of cellular adenosine triphosphate (ATP) during differentiation for energy-intensive cell types such as hepatocytes and neurons to meet the cell's functional requirements. During hepatocyte differentiation, mtDNA copy number should be synchronously increased to generate sufficient ATP through oxidative phosphorylation. Unlike bone marrow mesenchymal cells, mtDNA copy number failed to increase by 28 days of differentiation of human amniotic epithelial cells (hAEC) into hepatocyte-like cells (HLC) despite their expression of some end-stage hepatic markers. This was due to higher levels of DNA methylation at exon 2 of POLGA, the mtDNA-specific replication factor. Treatment with a DNA demethylation agent, 5-azacytidine, resulted in increased mtDNA copy number, reduced DNA methylation at exon 2 of POLGA, and reduced hepatic gene expression. Depletion of mtDNA followed by subsequent differentiation did not increase mtDNA copy number, but reduced DNA methylation at exon 2 of POLGA and increased expression of hepatic and pluripotency genes. We encapsulated hAEC in barium alginate microcapsules and subsequently differentiated them into HLC. Encapsulation resulted in no net increase of mtDNA copy number but a significant reduction in DNA methylation of POLGA. RNAseq analysis showed that differentiated HLC express hepatocyte-specific genes but also increased expression of inflammatory interferon genes. Differentiation in encapsulated cells showed suppression of inflammatory genes as well as increased expression of genes associated with hepatocyte function pathways and networks. This study demonstrates that an increase in classical hepatic gene expression can be achieved in HLC through encapsulation, although they fail to effectively regulate mtDNA copy number.

Mutations in BALB mitochondrial DNA induce CCL20 up-regulation promoting tumorigenic phenotypes

Energy Technology Data Exchange (ETDEWEB)

Sligh, James [Department of Medicine—Dermatology Division, University of Arizona, Tucson, AZ 857 24 (United States); University of Arizona Cancer Center, Tucson, AZ 85724 (United States); Janda, Jaroslav [University of Arizona Cancer Center, Tucson, AZ 85724 (United States); Jandova, Jana, E-mail: jjandova@email.arizona.edu [Department of Medicine—Dermatology Division, University of Arizona, Tucson, AZ 857 24 (United States); University of Arizona Cancer Center, Tucson, AZ 85724 (United States)

2014-11-15

Highlights: • Alterations in mitochondrial DNA are commonly found in various human cancers. • Mutations in BALB mitochondrial DNA induce up-regulation of chemokine CCL20. • Increased growth and motility of mtBALB cells is associated with CCL20 levels. • mtDNA changes in BALB induce in vivo tumor growth through CCL20 up-regulation. • Mutations in mitochondrial DNA play important roles in keratinocyte neoplasia. - Abstract: mtDNA mutations are common in human cancers and are thought to contribute to the process of neoplasia. We examined the role of mtDNA mutations in skin cancer by generating fibroblast cybrids harboring a mutation in the gene encoding the mitochondrial tRNA for arginine. This somatic mutation (9821insA) was previously reported in UV-induced hyperkeratotic skin tumors in hairless mice and confers specific tumorigenic phenotypes to mutant cybrids. Microarray analysis revealed and RT-PCR along with Western blot analysis confirmed the up-regulation of CCL20 and its receptor CCR6 in mtBALB haplotype containing the mt-Tr 9821insA allele compared to wild type mtB6 haplotype. Based on reported role of CCL20 in cancer progression we examined whether the hyper-proliferation and enhanced motility of mtBALB haplotype would be associated with CCL20 levels. Treatment of both genotypes with recombinant CCL20 (rmCCL20) resulted in enhanced growth and motility of mtB6 cybrids. Furthermore, the acquired somatic alteration increased the in vivo tumor growth of mtBALB cybrids through the up-regulation of CCL20 since neutralizing antibody significantly decreased in vivo tumor growth of these cells; and tumors from anti-CCL20 treated mice injected with mtBALB cybrids showed significantly decreased CCL20 levels. When rmCCL20 or mtBALB cybrids were used as chemotactic stimuli, mtB6 cybrids showed increased motility while anti-CCL20 antibody decreased the migration and in vivo tumor growth of mtBALB cybrids. Moreover, the inhibitors of MAPK signaling and NF

Forensics and mitochondrial DNA: applications, debates, and foundations.

Science.gov (United States)

Budowle, Bruce; Allard, Marc W; Wilson, Mark R; Chakraborty, Ranajit

2003-01-01

Debate on the validity and reliability of scientific methods often arises in the courtroom. When the government (i.e., the prosecution) is the proponent of evidence, the defense is obliged to challenge its admissibility. Regardless, those who seek to use DNA typing methodologies to analyze forensic biological evidence have a responsibility to understand the technology and its applications so a proper foundation(s) for its use can be laid. Mitochondrial DNA (mtDNA), an extranuclear genome, has certain features that make it desirable for forensics, namely, high copy number, lack of recombination, and matrilineal inheritance. mtDNA typing has become routine in forensic biology and is used to analyze old bones, teeth, hair shafts, and other biological samples where nuclear DNA content is low. To evaluate results obtained by sequencing the two hypervariable regions of the control region of the human mtDNA genome, one must consider the genetically related issues of nomenclature, reference population databases, heteroplasmy, paternal leakage, recombination, and, of course, interpretation of results. We describe the approaches, the impact some issues may have on interpretation of mtDNA analyses, and some issues raised in the courtroom.

Differential Nuclear and Mitochondrial DNA Preservation in Post-Mortem Teeth with Implications for Forensic and Ancient DNA Studies

Science.gov (United States)

Higgins, Denice; Rohrlach, Adam B.; Kaidonis, John; Townsend, Grant; Austin, Jeremy J.

2015-01-01

Major advances in genetic analysis of skeletal remains have been made over the last decade, primarily due to improvements in post-DNA-extraction techniques. Despite this, a key challenge for DNA analysis of skeletal remains is the limited yield of DNA recovered from these poorly preserved samples. Enhanced DNA recovery by improved sampling and extraction techniques would allow further advancements. However, little is known about the post-mortem kinetics of DNA degradation and whether the rate of degradation varies between nuclear and mitochondrial DNA or across different skeletal tissues. This knowledge, along with information regarding ante-mortem DNA distribution within skeletal elements, would inform sampling protocols facilitating development of improved extraction processes. Here we present a combined genetic and histological examination of DNA content and rates of DNA degradation in the different tooth tissues of 150 human molars over short-medium post-mortem intervals. DNA was extracted from coronal dentine, root dentine, cementum and pulp of 114 teeth via a silica column method and the remaining 36 teeth were examined histologically. Real time quantification assays based on two nuclear DNA fragments (67 bp and 156 bp) and one mitochondrial DNA fragment (77 bp) showed nuclear and mitochondrial DNA degraded exponentially, but at different rates, depending on post-mortem interval and soil temperature. In contrast to previous studies, we identified differential survival of nuclear and mtDNA in different tooth tissues. Futhermore histological examination showed pulp and dentine were rapidly affected by loss of structural integrity, and pulp was completely destroyed in a relatively short time period. Conversely, cementum showed little structural change over the same time period. Finally, we confirm that targeted sampling of cementum from teeth buried for up to 16 months can provide a reliable source of nuclear DNA for STR-based genotyping using standard

Mitochondrial DNA maintenance is regulated in human hepatoma cells by glycogen synthase kinase 3β and p53 in response to tumor necrosis factor α.

Science.gov (United States)

Vadrot, Nathalie; Ghanem, Sarita; Braut, Françoise; Gavrilescu, Laura; Pilard, Nathalie; Mansouri, Abdellah; Moreau, Richard; Reyl-Desmars, Florence

2012-01-01

During chronic liver inflammation, up-regulated Tumor Necrosis Factor alpha (TNF-α) targets hepatocytes and induces abnormal reactive oxygen species (ROS) production responsible for mitochondrial DNA (mtDNA) alterations. The serine/threonine Glycogen Synthase Kinase 3 beta (GSK3β) plays a pivotal role during inflammation but its involvement in the maintenance of mtDNA remains unknown. The aim of this study was to investigate its involvement in TNF-α induced mtDNA depletion and its interrelationship with p53 a protein known to maintain mtDNA copy numbers. Using quantitative polymerase chain reaction (qPCR) we found that at 30 min in human hepatoma HepG2 cells TNF-α induced 0.55±0.10 mtDNA lesions per 10 Kb and a 52.4±2.8% decrease in mtDNA content dependent on TNF-R1 receptor and ROS production. Both lesions and depletion returned to baseline from 1 to 6 h after TNF-α exposure. Luminol-amplified chemiluminescence (LAC) was used to measure the rapid (10 min) and transient TNF-α induced increase in ROS production (168±15%). A transient 8-oxo-dG level of 1.4±0.3 ng/mg DNA and repair of abasic sites were also measured by ELISA assays. Translocation of p53 to mitochondria was observed by Western Blot and co-immunoprecipitations showed that TNF-α induced p53 binding to GSK3β and mitochondrial transcription factor A (TFAM). In addition, mitochondrial D-loop immunoprecipitation (mtDIP) revealed that TNF-α induced p53 binding to the regulatory D-loop region of mtDNA. The knockdown of p53 by siRNAs, inhibition by the phosphoSer(15)p53 antibody or transfection of human mutant active GSK3βS9A pcDNA3 plasmid inhibited recovery of mtDNA content while blockade of GSK3β activity by SB216763 inhibitor or knockdown by siRNAs suppressed mtDNA depletion. This study is the first to report the involvement of GSK3β in TNF-α induced mtDNA depletion. We suggest that p53 binding to GSK3β, TFAM and D-loop could induce recovery of mtDNA content through mtDNA repair.

Mitochondrial DNA maintenance is regulated in human hepatoma cells by glycogen synthase kinase 3β and p53 in response to tumor necrosis factor α.

Directory of Open Access Journals (Sweden)

Nathalie Vadrot

Full Text Available During chronic liver inflammation, up-regulated Tumor Necrosis Factor alpha (TNF-α targets hepatocytes and induces abnormal reactive oxygen species (ROS production responsible for mitochondrial DNA (mtDNA alterations. The serine/threonine Glycogen Synthase Kinase 3 beta (GSK3β plays a pivotal role during inflammation but its involvement in the maintenance of mtDNA remains unknown. The aim of this study was to investigate its involvement in TNF-α induced mtDNA depletion and its interrelationship with p53 a protein known to maintain mtDNA copy numbers. Using quantitative polymerase chain reaction (qPCR we found that at 30 min in human hepatoma HepG2 cells TNF-α induced 0.55±0.10 mtDNA lesions per 10 Kb and a 52.4±2.8% decrease in mtDNA content dependent on TNF-R1 receptor and ROS production. Both lesions and depletion returned to baseline from 1 to 6 h after TNF-α exposure. Luminol-amplified chemiluminescence (LAC was used to measure the rapid (10 min and transient TNF-α induced increase in ROS production (168±15%. A transient 8-oxo-dG level of 1.4±0.3 ng/mg DNA and repair of abasic sites were also measured by ELISA assays. Translocation of p53 to mitochondria was observed by Western Blot and co-immunoprecipitations showed that TNF-α induced p53 binding to GSK3β and mitochondrial transcription factor A (TFAM. In addition, mitochondrial D-loop immunoprecipitation (mtDIP revealed that TNF-α induced p53 binding to the regulatory D-loop region of mtDNA. The knockdown of p53 by siRNAs, inhibition by the phosphoSer(15p53 antibody or transfection of human mutant active GSK3βS9A pcDNA3 plasmid inhibited recovery of mtDNA content while blockade of GSK3β activity by SB216763 inhibitor or knockdown by siRNAs suppressed mtDNA depletion. This study is the first to report the involvement of GSK3β in TNF-α induced mtDNA depletion. We suggest that p53 binding to GSK3β, TFAM and D-loop could induce recovery of mtDNA content through mtDNA repair.

Mitochondrial DNA is a direct target of anti-cancer anthracycline drugs

International Nuclear Information System (INIS)

Ashley, Neil; Poulton, Joanna

2009-01-01

The anthracyclines, such as doxorubicin (DXR), are potent anti-cancer drugs but they are limited by their clinical toxicity. The mechanisms involved remain poorly understood partly because of the difficulty in determining sub-cellular drug localisation. Using a novel method utilising the fluorescent DNA dye PicoGreen, we found that anthracyclines intercalated not only into nuclear DNA but also mitochondrial DNA (mtDNA). Intercalation of mtDNA by anthracyclines may thus contribute to the marked mitochondrial toxicity associated with these drugs. By contrast, ethidium bromide intercalated exclusively into mtDNA, without interacting with nuclear DNA, thereby explaining why mtDNA is the main target for ethidium. By exploiting PicoGreen quenching we also developed a novel assay for quantification of mtDNA levels by flow-cytometry, an approach which should be useful for studies of mitochondrial dysfunction. In summary our PicoGreen assay should be useful to study drug/DNA interactions within live cells, and facilitate therapeutic drug monitoring and kinetic studies in cancer patients.

Stimulated human mast cells secrete mitochondrial components that have autocrine and paracrine inflammatory actions.

Directory of Open Access Journals (Sweden)

Bodi Zhang

Full Text Available Mast cells are hematopoietically-derived tissue immune cells that participate in acquired and innate immunity, as well as in inflammation through release of many chemokines and cytokines, especially in response to the pro-inflammatory peptide substance P (SP. Inflammation is critical in the pathogenesis of many diseases, but the trigger(s is often unknown. We investigated if mast cell stimulation leads to secretion of mitochondrial components and whether these could elicit autocrine and/or paracrine inflammatory effects. Here we show that human LAD2 mast cells stimulated by IgE/anti-IgE or by the SP led to secretion of mitochondrial particles, mitochondrial (mt mtDNA and ATP without cell death. Mitochondria purified from LAD2 cells and, when mitochondria added to mast cells trigger degranulation and release of histamine, PGD(2, IL-8, TNF, and IL-1β. This stimulatory effect is partially inhibited by an ATP receptor antagonist and by DNAse. These results suggest that the mitochondrial protein fraction may also contribute. Purified mitochondria also stimulate IL-8 and vascular endothelial growth factor (VEGF release from cultured human keratinocytes, and VEGF release from primary human microvascular endothelial cells. In order to investigate if mitochondrial components could be secreted in vivo, we injected rats intraperiotoneally (ip with compound 48/80, which mimicks the action of SP. Peritoneal mast cells degranulated and mitochondrial particles were documented by transimission electron microscopy outside the cells. We also wished to investigate if mitochondrial components secreted locally could reach the systemic circulation. Administration ip of mtDNA isolated from LAD2 cells in rats was detected in their serum within 4 hr, indicating that extravascular mtDNA could enter the systemic circulation. Secretion of mitochondrial components from stimulated live mast cells may act as "autopathogens" contributing to the pathogenesis of inflammatory

Mitochondrial-targeted DNA delivery using a DF-MITO-Porter, an innovative nano carrier with cytoplasmic and mitochondrial fusogenic envelopes

International Nuclear Information System (INIS)

Yamada, Yuma; Kawamura, Eriko; Harashima, Hideyoshi

2012-01-01

Mitochondrial gene therapy has the potential for curing a variety of diseases that are associated with mitochondrial DNA mutations and/or defects. To achieve this, it will be necessary to deliver therapeutic agents into the mitochondria in diseased cells. A number of mitochondrial drug delivery systems have been reported to date. However, reports of mitochondrial-targeted DNA delivery are limited. To achieve this, the therapeutic agent must be taken up by the cell (1), after which, the multi-processes associated with intracellular trafficking must be sophisticatedly regulated so as to release the agent from the endosome and deliver it to the cytosol (2) and to pass through the mitochondrial membrane (3). We report herein on the mitochondrial delivery of oligo DNA as a model therapeutic using a Dual Function (DF)-MITO-Porter, an innovative nano carrier designed for mitochondrial delivery. The critical structural elements of the DF-MITO-Porter include mitochondria-fusogenic inner envelopes and endosome-fusogenic outer envelopes, modified with octaarginine which greatly assists in cellular uptake. Inside the cell, the carrier passes through the endosomal and mitochondrial membranes via step-wise membrane fusion. When the oligo DNA was packaged in the DF-MITO-Porter, cellular uptake efficiency was strongly enhanced. Intracellular observation using confocal laser scanning microscopy showed that the DF-MITO-Porter was effectively released from endosomes. Moreover, the findings confirmed that the mitochondrial targeting activity of the DF-MITO-Porter was significantly higher than that of a carrier without outer endosome-fusogenic envelopes. These results support the conclusion that mitochondrial-targeted DNA delivery using a DF-MITO-Porter can be achieved when intracellular trafficking is optimally regulated.

Mitochondrial-targeted DNA delivery using a DF-MITO-Porter, an innovative nano carrier with cytoplasmic and mitochondrial fusogenic envelopes

Energy Technology Data Exchange (ETDEWEB)

Yamada, Yuma; Kawamura, Eriko; Harashima, Hideyoshi, E-mail: harasima@pharm.hokudai.ac.jp [Hokkaido University, Laboratory for Molecular Design of Pharmaceutics, Faculty of Pharmaceutical Sciences (Japan)

2012-08-15

Mitochondrial gene therapy has the potential for curing a variety of diseases that are associated with mitochondrial DNA mutations and/or defects. To achieve this, it will be necessary to deliver therapeutic agents into the mitochondria in diseased cells. A number of mitochondrial drug delivery systems have been reported to date. However, reports of mitochondrial-targeted DNA delivery are limited. To achieve this, the therapeutic agent must be taken up by the cell (1), after which, the multi-processes associated with intracellular trafficking must be sophisticatedly regulated so as to release the agent from the endosome and deliver it to the cytosol (2) and to pass through the mitochondrial membrane (3). We report herein on the mitochondrial delivery of oligo DNA as a model therapeutic using a Dual Function (DF)-MITO-Porter, an innovative nano carrier designed for mitochondrial delivery. The critical structural elements of the DF-MITO-Porter include mitochondria-fusogenic inner envelopes and endosome-fusogenic outer envelopes, modified with octaarginine which greatly assists in cellular uptake. Inside the cell, the carrier passes through the endosomal and mitochondrial membranes via step-wise membrane fusion. When the oligo DNA was packaged in the DF-MITO-Porter, cellular uptake efficiency was strongly enhanced. Intracellular observation using confocal laser scanning microscopy showed that the DF-MITO-Porter was effectively released from endosomes. Moreover, the findings confirmed that the mitochondrial targeting activity of the DF-MITO-Porter was significantly higher than that of a carrier without outer endosome-fusogenic envelopes. These results support the conclusion that mitochondrial-targeted DNA delivery using a DF-MITO-Porter can be achieved when intracellular trafficking is optimally regulated.

Mitochondrial DNA sequence evolution in shorebird populations

NARCIS (Netherlands)

Wenink, P.W.

1994-01-01

This thesis describes the global molecular population structure of two shorebird species, in particular of the dunlin, Calidris alpina, by means of comparative sequence analysis of the most variable part of the mitochondrial DNA (mtDNA) genome. There are several reasons

Mitochondrial DNA diversity of present-day Aboriginal Australians and implications for human evolution in Oceania.

Science.gov (United States)

Nagle, Nano; Ballantyne, Kaye N; van Oven, Mannis; Tyler-Smith, Chris; Xue, Yali; Wilcox, Stephen; Wilcox, Leah; Turkalov, Rust; van Oorschot, Roland A H; van Holst Pellekaan, Sheila; Schurr, Theodore G; McAllister, Peter; Williams, Lesley; Kayser, Manfred; Mitchell, R John

2017-03-01

Aboriginal Australians are one of the more poorly studied populations from the standpoint of human evolution and genetic diversity. Thus, to investigate their genetic diversity, the possible date of their ancestors' arrival and their relationships with neighboring populations, we analyzed mitochondrial DNA (mtDNA) diversity in a large sample of Aboriginal Australians. Selected mtDNA single-nucleotide polymorphisms and the hypervariable segment haplotypes were analyzed in 594 Aboriginal Australians drawn from locations across the continent, chiefly from regions not previously sampled. Most (~78%) samples could be assigned to mtDNA haplogroups indigenous to Australia. The indigenous haplogroups were all ancient (with estimated ages >40 000 years) and geographically widespread across the continent. The most common haplogroup was P (44%) followed by S (23%) and M42a (9%). There was some geographic structure at the haplotype level. The estimated ages of the indigenous haplogroups range from 39 000 to 55 000 years, dates that fit well with the estimated date of colonization of Australia based on archeological evidence (~47 000 years ago). The distribution of mtDNA haplogroups in Australia and New Guinea supports the hypothesis that the ancestors of Aboriginal Australians entered Sahul through at least two entry points. The mtDNA data give no support to the hypothesis of secondary gene flow into Australia during the Holocene, but instead suggest long-term isolation of the continent.

Quantification and presence of human ancient DNA in burial place ...

African Journals Online (AJOL)

Quantification and presence of human ancient DNA in burial place remains of Turkey using real time polymerase chain reaction. ... A published real-time PCR assay, which allows for the combined analysis of nuclear or ancient DNA and mitochondrial DNA, was modified. This approach can be used for recovering DNA from ...

Human C4orf14 interacts with the mitochondrial nucleoid and is involved in the biogenesis of the small mitochondrial ribosomal subunit.

Science.gov (United States)

He, J; Cooper, H M; Reyes, A; Di Re, M; Kazak, L; Wood, S R; Mao, C C; Fearnley, I M; Walker, J E; Holt, I J

2012-07-01

The bacterial homologue of C4orf14, YqeH, has been linked to assembly of the small ribosomal subunit. Here, recombinant C4orf14 isolated from human cells, co-purified with the small, 28S subunit of the mitochondrial ribosome and the endogenous protein co-fractionated with the 28S subunit in sucrose gradients. Gene silencing of C4orf14 specifically affected components of the small subunit, leading to decreased protein synthesis in the organelle. The GTPase of C4orf14 was critical to its interaction with the 28S subunit, as was GTP. Therefore, we propose that C4orf14, with bound GTP, binds to components of the 28S subunit facilitating its assembly, and GTP hydrolysis acts as the release mechanism. C4orf14 was also found to be associated with human mitochondrial nucleoids, and C4orf14 gene silencing caused mitochondrial DNA depletion. In vitro C4orf14 is capable of binding to DNA. The association of C4orf14 with mitochondrial translation factors and the mitochondrial nucleoid suggests that the 28S subunit is assembled at the mitochondrial nucleoid, enabling the direct transfer of messenger RNA from the nucleoid to the ribosome in the organelle.

The mitochondrial outer membrane protein MDI promotes local protein synthesis and mtDNA replication.

Science.gov (United States)

Zhang, Yi; Chen, Yong; Gucek, Marjan; Xu, Hong

2016-05-17

Early embryonic development features rapid nuclear DNA replication cycles, but lacks mtDNA replication. To meet the high-energy demands of embryogenesis, mature oocytes are furnished with vast amounts of mitochondria and mtDNA However, the cellular machinery driving massive mtDNA replication in ovaries remains unknown. Here, we describe a Drosophila AKAP protein, MDI that recruits a translation stimulator, La-related protein (Larp), to the mitochondrial outer membrane in ovaries. The MDI-Larp complex promotes the synthesis of a subset of nuclear-encoded mitochondrial proteins by cytosolic ribosomes on the mitochondrial surface. MDI-Larp's targets include mtDNA replication factors, mitochondrial ribosomal proteins, and electron-transport chain subunits. Lack of MDI abolishes mtDNA replication in ovaries, which leads to mtDNA deficiency in mature eggs. Targeting Larp to the mitochondrial outer membrane independently of MDI restores local protein synthesis and rescues the phenotypes of mdi mutant flies. Our work suggests that a selective translational boost by the MDI-Larp complex on the outer mitochondrial membrane might be essential for mtDNA replication and mitochondrial biogenesis during oogenesis. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.

Mitochondrial DNA Copy Number in Sleep Duration Discordant Monozygotic Twins.

Science.gov (United States)

Wrede, Joanna E; Mengel-From, Jonas; Buchwald, Dedra; Vitiello, Michael V; Bamshad, Michael; Noonan, Carolyn; Christiansen, Lene; Christensen, Kaare; Watson, Nathaniel F

2015-10-01

Mitochondrial DNA (mtDNA) copy number is an important component of mitochondrial function and varies with age, disease, and environmental factors. We aimed to determine whether mtDNA copy number varies with habitual differences in sleep duration within pairs of monozygotic twins. Academic clinical research center. 15 sleep duration discordant monozygotic twin pairs (30 twins, 80% female; mean age 42.1 years [SD 15.0]). Sleep duration was phenotyped with wrist actigraphy. Each twin pair included a "normal" (7-9 h/24) and "short" (sleeping twin. Fasting peripheral blood leukocyte DNA was assessed for mtDNA copy number via the n-fold difference between qPCR measured mtDNA and nuclear DNA creating an mtDNA measure without absolute units. We used generalized estimating equation linear regression models accounting for the correlated data structure to assess within-pair effects of sleep duration on mtDNA copy number. Mean within-pair sleep duration difference per 24 hours was 94.3 minutes (SD 62.6 min). We found reduced sleep duration (β = 0.06; 95% CI 0.004, 0.12; P sleep efficiency (β = 0.51; 95% CI 0.06, 0.95; P sleep duration was associated with a decrease in mtDNA copy number of 0.06. Likewise, a 1% decrease in actigraphy-defined sleep efficiency was associated with a decrease in mtDNA copy number of 0.51. Reduced sleep duration and sleep efficiency were associated with reduced mitochondrial DNA copy number in sleep duration discordant monozygotic twins offering a potential mechanism whereby short sleep impairs health and longevity through mitochondrial stress. © 2015 Associated Professional Sleep Societies, LLC.

A mitochondrial cytochrome b mutation causing severe respiratory chain enzyme deficiency in humans and yeast.

NARCIS (Netherlands)

Blakely, E.L.; Mitchell, A.L.; Fisher, N.; Meunier, B.; Nijtmans, L.G.J.; Schaefer, A.M.; Jackson, M.J.; Turnbull, D.M.; Taylor, R.W.

2005-01-01

Whereas the majority of disease-related mitochondrial DNA mutations exhibit significant biochemical and clinical heterogeneity, mutations within the mitochondrially encoded human cytochrome b gene (MTCYB) are almost exclusively associated with isolated complex III deficiency in muscle and a clinical

Transcutaneous application of carbon dioxide (CO2 induces mitochondrial apoptosis in human malignant fibrous histiocytoma in vivo.

Directory of Open Access Journals (Sweden)

Yasuo Onishi

Full Text Available Mitochondria play an essential role in cellular energy metabolism and apoptosis. Previous studies have demonstrated that decreased mitochondrial biogenesis is associated with cancer progression. In mitochondrial biogenesis, peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α regulates the activities of multiple nuclear receptors and transcription factors involved in mitochondrial proliferation. Previously, we showed that overexpression of PGC-1α leads to mitochondrial proliferation and induces apoptosis in human malignant fibrous histiocytoma (MFH cells in vitro. We also demonstrated that transcutaneous application of carbon dioxide (CO(2 to rat skeletal muscle induces PGC-1α expression and causes an increase in mitochondrial proliferation. In this study, we utilized a murine model of human MFH to determine the effect of transcutaneous CO(2 exposure on PGC-1α expression, mitochondrial proliferation and cellular apoptosis. PGC-1α expression was evaluated by quantitative real-time PCR, while mitochondrial proliferation was assessed by immunofluorescence staining and the relative copy number of mitochondrial DNA (mtDNA was assessed by real-time PCR. Immunofluorescence staining and DNA fragmentation assays were used to examine mitochondrial apoptosis. We also evaluated the expression of mitochondrial apoptosis related proteins, such as caspases, cytochorome c and Bax, by immunoblot analysis. We show that transcutaneous application of CO(2 induces PGC-1α expression, and increases mitochondrial proliferation and apoptosis of tumor cells, significantly reducing tumor volume. Proteins involved in the mitochondrial apoptotic cascade, including caspase 3 and caspase 9, were elevated in CO(2 treated tumors compared to control. We also observed an enrichment of cytochrome c in the cytoplasmic fraction and Bax protein in the mitochondrial fraction of CO(2 treated tumors, highlighting the involvement of mitochondria in apoptosis

Nuclear Expression of a Mitochondrial DNA Gene: Mitochondrial Targeting of Allotopically Expressed Mutant ATP6 in Transgenic Mice

Directory of Open Access Journals (Sweden)

David A. Dunn

2012-01-01

Full Text Available Nuclear encoding of mitochondrial DNA transgenes followed by mitochondrial targeting of the expressed proteins (allotopic expression; AE represents a potentially powerful strategy for creating animal models of mtDNA disease. Mice were created that allotopically express either a mutant (A6M or wildtype (A6W mt-Atp6 transgene. Compared to non-transgenic controls, A6M mice displayed neuromuscular and motor deficiencies (wire hang, pole, and balance beam analyses; P0.05. This study illustrates a mouse model capable of circumventing in vivo mitochondrial mutations. Moreover, it provides evidence supporting AE as a tool for mtDNA disease research with implications in development of DNA-based therapeutics.

Fluorescent in situ hybridization of mitochondrial DNA and RNA

Czech Academy of Sciences Publication Activity Database

Alán, Lukáš; Zelenka, Jaroslav; Ježek, Jan; Dlasková, Andrea; Ježek, Petr

2010-01-01

Roč. 57, č. 4 (2010), s. 403-408 ISSN 0001-527X R&D Projects: GA ČR GAP302/10/0346; GA ČR GPP304/10/P204; GA AV ČR KJB500110902 Institutional research plan: CEZ:AV0Z50110509 Keywords : mitochondrial DNA and RNA * nucleoids of mitochondrial DNA * molecular beacon fluorescent hybridization probes Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 1.234, year: 2010

Mitochondrial DNA Mutations in Epithelial Ovarian Tumor Progression

Science.gov (United States)

2007-12-01

Panici PL, Fazio VM: Mutations of D310 mitochondrial mononu- cleotide repeat in primary tumors and cytological speci- mens . Cancer Lett 2003, 190:73...BR: Detection of LOH and mitochondrial DNA alter- ations in ductal lavage and nipple aspirate fluids from high- risk patients. Breast Cancer Res

Selective Gene Delivery for Integrating Exogenous DNA into Plastid and Mitochondrial Genomes Using Peptide-DNA Complexes.

Science.gov (United States)

Yoshizumi, Takeshi; Oikawa, Kazusato; Chuah, Jo-Ann; Kodama, Yutaka; Numata, Keiji

2018-05-14

Selective gene delivery into organellar genomes (mitochondrial and plastid genomes) has been limited because of a lack of appropriate platform technology, even though these organelles are essential for metabolite and energy production. Techniques for selective organellar modification are needed to functionally improve organelles and produce transplastomic/transmitochondrial plants. However, no method for mitochondrial genome modification has yet been established for multicellular organisms including plants. Likewise, modification of plastid genomes has been limited to a few plant species and algae. In the present study, we developed ionic complexes of fusion peptides containing organellar targeting signal and plasmid DNA for selective delivery of exogenous DNA into the plastid and mitochondrial genomes of intact plants. This is the first report of exogenous DNA being integrated into the mitochondrial genomes of not only plants, but also multicellular organisms in general. This fusion peptide-mediated gene delivery system is a breakthrough platform for both plant organellar biotechnology and gene therapy for mitochondrial diseases in animals.

Replication stalling by catalytically impaired Twinkle induces mitochondrial DNA rearrangements in cultured cells

NARCIS (Netherlands)

Pohjoismaki, J.L.; Goffart, S.; Spelbrink, J.N.

2011-01-01

Pathological mitochondrial DNA (mtDNA) rearrangements have been proposed to result from repair of double-strand breaks caused by blockage of mitochondrial DNA (mtDNA) replication. As mtDNA deletions are seen only in post-mitotic tissues, it has been suggested that they are selected out in actively

Mitochondrial DNA damage and oxidative damage in HL-60 cells exposed to 900 MHz radiofrequency fields

Energy Technology Data Exchange (ETDEWEB)

Sun, Yulong; Zong, Lin; Gao, Zhen [School of Public Health, Soochow University, Suzhou, Jiangsu Province (China); Zhu, Shunxing [Laboratory Animal Center, Nantong University, Nantong, Jiangsu Province (China); Tong, Jian [School of Public Health, Soochow University, Suzhou, Jiangsu Province (China); Cao, Yi, E-mail: yicao@suda.edu.cn [School of Public Health, Soochow University, Suzhou, Jiangsu Province (China)

2017-03-15

Highlights: • Increased reactive oxygen species. • Decreased mitochondrial transcription Factor A and polymerase gamma. • Decreased mitochondrial transcripts (ND1 and 16S) and mtDNA copy number. • Increased 8-hydroxy-2′deoxyguanosine. • Decreased adenosine triphosphate. - Abstract: HL-60 cells, derived from human promyelocytic leukemia, were exposed to continuous wave 900 MHz radiofrequency fields (RF) at 120 μW/cm{sup 2} power intensity for 4 h/day for 5 consecutive days to examine whether such exposure is capable damaging the mitochondrial DNA (mtDNA) mediated through the production of reactive oxygen species (ROS). In addition, the effect of RF exposure was examined on 8-hydroxy-2′-dexoyguanosine (8-OHdG) which is a biomarker for oxidative damage and on the mitochondrial synthesis of adenosine triphosphate (ATP) which is the energy required for cellular functions. The results indicated a significant increase in ROS and significant decreases in mitochondrial transcription factor A, mtDNA polymerase gamma, mtDNA transcripts and mtDNA copy number in RF-exposed cells compared with those in sham-exposed control cells. In addition, there was a significant increase in 8-OHdG and a significant decrease in ATP in RF-exposed cells. The response in positive control cells exposed to gamma radiation (GR, which is also known to induce ROS) was similar to those in RF-exposed cells. Thus, the overall data indicated that RF exposure was capable of inducing mtDNA damage mediated through ROS pathway which also induced oxidative damage. Prior-treatment of RF- and GR-exposed the cells with melatonin, a well-known free radical scavenger, reversed the effects observed in RF-exposed cells.

A comprehensive characterization of rare mitochondrial DNA variants in neuroblastoma.

Science.gov (United States)

Calabrese, Francesco Maria; Clima, Rosanna; Pignataro, Piero; Lasorsa, Vito Alessandro; Hogarty, Michael D; Castellano, Aurora; Conte, Massimo; Tonini, Gian Paolo; Iolascon, Achille; Gasparre, Giuseppe; Capasso, Mario

2016-08-02

Neuroblastoma, a tumor of the developing sympathetic nervous system, is a common childhood neoplasm that is often lethal. Mitochondrial DNA (mtDNA) mutations have been found in most tumors including neuroblastoma. We extracted mtDNA data from a cohort of neuroblastoma samples that had undergone Whole Exome Sequencing (WES) and also used snap-frozen samples in which mtDNA was entirely sequenced by Sanger technology. We next undertook the challenge of determining those mutations that are relevant to, or arisen during tumor development. The bioinformatics pipeline used to extract mitochondrial variants from matched tumor/blood samples was enriched by a set of filters inclusive of heteroplasmic fraction, nucleotide variability, and in silico prediction of pathogenicity. Our in silico multistep workflow applied both on WES and Sanger-sequenced neuroblastoma samples, allowed us to identify a limited burden of somatic and germline mitochondrial mutations with a potential pathogenic impact. The few singleton germline and somatic mitochondrial mutations emerged, according to our in silico analysis, do not appear to impact on the development of neuroblastoma. Our findings are consistent with the hypothesis that most mitochondrial somatic mutations can be considered as 'passengers' and consequently have no discernible effect in this type of cancer.

Mitochondrial DNA plays an equal role in influencing female and male longevity in centenarians.

Science.gov (United States)

He, Yong-Han; Lu, Xiang; Tian, Jiao-Yang; Yan, Dong-Jing; Li, Yu-Chun; Lin, Rong; Perry, Benjamin; Chen, Xiao-Qiong; Yu, Qin; Cai, Wang-Wei; Kong, Qing-Peng

2016-10-01

The mitochondrion is a double membrane-bound organelle which plays important functional roles in aging and many other complex phenotypes. Transmission of the mitochondrial genome in the matrilineal line causes the evolutionary selection sieve only in females. Theoretically, beneficial or neutral variations are more likely to accumulate and be retained in the female mitochondrial genome during evolution, which may be an initial trigger of gender dimorphism in aging. The asymmetry of evolutionary processes between gender could lead to males and females aging in different ways. If so, gender specific variation loads could be an evolutionary result of maternal heritage of mitochondrial genomes, especially in centenarians who live to an extreme age and are considered as good models for healthy aging. Here, we tested whether the mitochondrial variation loads were associated with altered aging patterns by investigating the mtDNA haplogroup distribution and genetic diversity between female and male centenarians. We found no evidence of differences in aging patterns between genders in centenarians. Our results indicate that the evolutionary consequence of gender dimorphism in mitochondrial genomes is not a factor in the altered aging patterns in human, and that mitochondrial DNA contributes equally to longevity in males and females. Copyright © 2016 Elsevier Inc. All rights reserved.

Parental diabetes status reveals association of mitochondrial DNA haplogroup J1 with type 2 diabetes

Directory of Open Access Journals (Sweden)

Wainstein Julio

2009-06-01

Full Text Available Abstract Background Although mitochondrial dysfunction is consistently manifested in patients with Type 2 Diabetes mellitus (T2DM, the association of mitochondrial DNA (mtDNA sequence variants with T2DM varies among populations. These differences might stem from differing environmental influences among populations. However, other potentially important considerations emanate from the very nature of mitochondrial genetics, namely the notable high degree of partitioning in the distribution of human mtDNA variants among populations, as well as the interaction of mtDNA and nuclear DNA-encoded factors working in concert to govern mitochondrial function. We hypothesized that association of mtDNA genetic variants with T2DM could be revealed while controlling for the effect of additional inherited factors, reflected in family history information. Methods To test this hypothesis we set out to investigate whether mtDNA genetic variants will be differentially associated with T2DM depending on the diabetes status of the parents. To this end, association of mtDNA genetic backgrounds (haplogroups with T2DM was assessed in 1055 Jewish patients with and without T2DM parents ('DP' and 'HP', respectively. Results Haplogroup J1 was found to be 2.4 fold under-represented in the 'HP' patients (p = 0.0035. These results are consistent with a previous observation made in Finnish T2DM patients. Moreover, assessing the haplogroup distribution in 'DP' versus 'HP' patients having diabetic siblings revealed that haplogroup J1 was virtually absent in the 'HP' group. Conclusion These results imply the involvement of inherited factors, which modulate the susceptibility of haplogroup J1 to T2DM.

Identification of Forensic Samples via Mitochondrial DNA in the Undergraduate Biochemistry Laboratory

Science.gov (United States)

Millard, Julie T.; Pilon, André M.

2003-04-01

A recent forensic approach for identification of unknown biological samples is mitochondrial DNA (mtDNA) sequencing. We describe a laboratory exercise suitable for an undergraduate biochemistry course in which the polymerase chain reaction is used to amplify a 440 base pair hypervariable region of human mtDNA from a variety of "crime scene" samples (e.g., teeth, hair, nails, cigarettes, envelope flaps, toothbrushes, and chewing gum). Amplification is verified via agarose gel electrophoresis and then samples are subjected to cycle sequencing. Sequence alignments are made via the program CLUSTAL W, allowing students to compare samples and solve the "crime."

Pathological mechanisms underlying single large‐scale mitochondrial DNA deletions

Science.gov (United States)

Rocha, Mariana C.; Rosa, Hannah S.; Grady, John P.; Blakely, Emma L.; He, Langping; Romain, Nadine; Haller, Ronald G.; Newman, Jane; McFarland, Robert; Ng, Yi Shiau; Gorman, Grainne S.; Schaefer, Andrew M.; Tuppen, Helen A.; Taylor, Robert W.

2018-01-01

Objective Single, large‐scale deletions in mitochondrial DNA (mtDNA) are a common cause of mitochondrial disease. This study aimed to investigate the relationship between the genetic defect and molecular phenotype to improve understanding of pathogenic mechanisms associated with single, large‐scale mtDNA deletions in skeletal muscle. Methods We investigated 23 muscle biopsies taken from adult patients (6 males/17 females with a mean age of 43 years) with characterized single, large‐scale mtDNA deletions. Mitochondrial respiratory chain deficiency in skeletal muscle biopsies was quantified by immunoreactivity levels for complex I and complex IV proteins. Single muscle fibers with varying degrees of deficiency were selected from 6 patient biopsies for determination of mtDNA deletion level and copy number by quantitative polymerase chain reaction. Results We have defined 3 “classes” of single, large‐scale deletion with distinct patterns of mitochondrial deficiency, determined by the size and location of the deletion. Single fiber analyses showed that fibers with greater respiratory chain deficiency harbored higher levels of mtDNA deletion with an increase in total mtDNA copy number. For the first time, we have demonstrated that threshold levels for complex I and complex IV deficiency differ based on deletion class. Interpretation Combining genetic and immunofluorescent assays, we conclude that thresholds for complex I and complex IV deficiency are modulated by the deletion of complex‐specific protein‐encoding genes. Furthermore, removal of mt‐tRNA genes impacts specific complexes only at high deletion levels, when complex‐specific protein‐encoding genes remain. These novel findings provide valuable insight into the pathogenic mechanisms associated with these mutations. Ann Neurol 2018;83:115–130 PMID:29283441

Return of the mitochondrial DNA : Case study of mitochondrial genome evolution in the genus Fusarium

NARCIS (Netherlands)

Brankovics, Balázs

2018-01-01

Mitochondrial DNA played a prominent role in the fields of population genetics, systematics and evolutionary biology, due to its favorable characteristics, such as, uniparental inheritance, fast evolution and easy accessibility. However, the mitochondrial sequences have been mostly neglected in

Cellular aging of mitochondrial DNA-depleted cells

International Nuclear Information System (INIS)

Park, Sun Young; Choi, Bongkun; Cheon, Hwanju; Pak, Youngmi Kim; Kulawiec, Mariola; Singh, Keshav K.; Lee, Myung-Shik

2004-01-01

We have reported that mitochondrial DNA-depleted ρ 0 cells are resistant to cell death. Because aged cells have frequent mitochondrial DNA mutations, the resistance of ρ 0 cells against cell death might be related to the apoptosis resistance of aged cells and frequent development of cancers in aged individuals. We studied if ρ 0 cells have features simulating aged cells. SK-Hep1 hepatoma ρ 0 cells showed typical morphology associated with aging such as increased size and elongated appearance. They had increased senescence-associated β-Gal activity, lipofuscin pigment, and plasminogen activator inhibitor-1 expression. Consistent with their decreased proliferation, the expression of mitotic cyclins was decreased and that of cdk inhibitors was increased. Rb hypophosphorylation and decreased telomerase activity were also noted. Features simulating aged cells were also observed in MDA-MB-435 ρ 0 cells. These results support the mitochondrial theory of aging, and suggest that ρ 0 cells could serve as an in vitro model for aged cells

Sequence analysis of mitochondrial DNA hypervariable region III of ...

African Journals Online (AJOL)

Aghomotsegin

2015-07-01

Jul 1, 2015 ... population genetics research, studies based on mitochondrial DNA (mtDNA) and Y-chromosome DNA are an excellent way of illustrating population structure .... avoid landing investigators into serious situations of medical genetic privacy and ethnics, especially for. mtDNA coding area whose mutation often ...

Associations of mitochondrial haplogroups and mitochondrial DNA copy numbers with end-stage renal disease in a Han population.

Science.gov (United States)

Zhang, Yuheng; Zhao, Ying; Wen, Shuzhen; Yan, Rengna; Yang, Qinglan; Chen, Huimei

2017-09-01

Mitochondrial DNA (mtDNA) is closely related to mitochondrion function, and variations have been suggested to be involved in pathogenesis of complex diseases. The present study sought to elucidate mitochondrial haplogroups and mtDNA copy number in end-stage renal disease (ESRD) in a Han population. First, the mitochondrial haplogroups of 37 ESRD patients were clustered into several haplogroups, and haplogroup A & D were taken as the candidate risk haplogroups for ESRD. Second, the frequencies of A and D were assessed in 344 ESRD patients and 438 healthy controls, respectively. Haplogroup D was found to be risk maker for ESRD in young subjects (numbers were evaluated with quantitative-PCR. The ESRD patients exhibited greater cell-free mtDNA contents than the healthy controls but less intracellular mtDNA. Haplogroup D exhibited a further increase in cell-free mtDNA content and a decrease in intracellular mtDNA content among the ESRDs patients. Our findings suggest that mtNDA haplogroup D may contributes to pathogenesis of early-onset ESRD through alterations of mtDNA copy numbers.

Induced pluripotent stem cells with a pathological mitochondrial DNA deletion

Science.gov (United States)

Cherry, Anne B. C.; Gagne, Katelyn E.; McLoughlin, Erin M.; Baccei, Anna; Gorman, Bryan; Hartung, Odelya; Miller, Justine D.; Zhang, Jin; Zon, Rebecca L.; Ince, Tan A.; Neufeld, Ellis J.; Lerou, Paul H.; Fleming, Mark D.; Daley, George Q.; Agarwal, Suneet

2013-01-01

In congenital mitochondrial DNA (mtDNA) disorders, a mixture of normal and mutated mtDNA (termed heteroplasmy) exists at varying levels in different tissues, which determines the severity and phenotypic expression of disease. Pearson marrow pancreas syndrome (PS) is a congenital bone marrow failure disorder caused by heteroplasmic deletions in mtDNA. The cause of the hematopoietic failure in PS is unknown, and adequate cellular and animal models are lacking. Induced pluripotent stem (iPS) cells are particularly amenable for studying mtDNA disorders, as cytoplasmic genetic material is retained during direct reprogramming. Here we derive and characterize iPS cells from a patient with PS. Taking advantage of the tendency for heteroplasmy to change with cell passage, we isolated isogenic PS-iPS cells without detectable levels of deleted mtDNA. We found that PS-iPS cells carrying a high burden of deleted mtDNA displayed differences in growth, mitochondrial function, and hematopoietic phenotype when differentiated in vitro, compared to isogenic iPS cells without deleted mtDNA. Our results demonstrate that reprogramming somatic cells from patients with mtDNA disorders can yield pluripotent stem cells with varying burdens of heteroplasmy that might be useful in the study and treatment of mitochondrial diseases. PMID:23400930

Calorie restriction increases muscle mitochondrial biogenesis in healthy humans.

Directory of Open Access Journals (Sweden)

Anthony E Civitarese

2007-03-01

Full Text Available Caloric restriction without malnutrition extends life span in a range of organisms including insects and mammals and lowers free radical production by the mitochondria. However, the mechanism responsible for this adaptation are poorly understood.The current study was undertaken to examine muscle mitochondrial bioenergetics in response to caloric restriction alone or in combination with exercise in 36 young (36.8 +/- 1.0 y, overweight (body mass index, 27.8 +/- 0.7 kg/m(2 individuals randomized into one of three groups for a 6-mo intervention: Control, 100% of energy requirements; CR, 25% caloric restriction; and CREX, caloric restriction with exercise (CREX, 12.5% CR + 12.5% increased energy expenditure (EE. In the controls, 24-h EE was unchanged, but in CR and CREX it was significantly reduced from baseline even after adjustment for the loss of metabolic mass (CR, -135 +/- 42 kcal/d, p = 0.002 and CREX, -117 +/- 52 kcal/d, p = 0.008. Participants in the CR and CREX groups had increased expression of genes encoding proteins involved in mitochondrial function such as PPARGC1A, TFAM, eNOS, SIRT1, and PARL (all, p < 0.05. In parallel, mitochondrial DNA content increased by 35% +/- 5% in the CR group (p = 0.005 and 21% +/- 4% in the CREX group (p < 0.004, with no change in the control group (2% +/- 2%. However, the activity of key mitochondrial enzymes of the TCA (tricarboxylic acid cycle (citrate synthase, beta-oxidation (beta-hydroxyacyl-CoA dehydrogenase, and electron transport chain (cytochrome C oxidase II was unchanged. DNA damage was reduced from baseline in the CR (-0.56 +/- 0.11 arbitrary units, p = 0.003 and CREX (-0.45 +/- 0.12 arbitrary units, p = 0.011, but not in the controls. In primary cultures of human myotubes, a nitric oxide donor (mimicking eNOS signaling induced mitochondrial biogenesis but failed to induce SIRT1 protein expression, suggesting that additional factors may regulate SIRT1 content during CR.The observed increase in

Mitochondrial catalase overexpressed transgenic mice are protected against lung fibrosis in part via preventing alveolar epithelial cell mitochondrial DNA damage.

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Kim, Seok-Jo; Cheresh, Paul; Jablonski, Renea P; Morales-Nebreda, Luisa; Cheng, Yuan; Hogan, Erin; Yeldandi, Anjana; Chi, Monica; Piseaux, Raul; Ridge, Karen; Michael Hart, C; Chandel, Navdeep; Scott Budinger, G R; Kamp, David W

2016-12-01

Alveolar epithelial cell (AEC) injury and mitochondrial dysfunction are important in the development of lung fibrosis. Our group has shown that in the asbestos exposed lung, the generation of mitochondrial reactive oxygen species (ROS) in AEC mediate mitochondrial DNA (mtDNA) damage and apoptosis which are necessary for lung fibrosis. These data suggest that mitochondrial-targeted antioxidants should ameliorate asbestos-induced lung. To determine whether transgenic mice that express mitochondrial-targeted catalase (MCAT) have reduced lung fibrosis following exposure to asbestos or bleomycin and, if so, whether this occurs in association with reduced AEC mtDNA damage and apoptosis. Crocidolite asbestos (100µg/50µL), TiO 2 (negative control), bleomycin (0.025 units/50µL), or PBS was instilled intratracheally in 8-10 week-old wild-type (WT - C57Bl/6J) or MCAT mice. The lungs were harvested at 21d. Lung fibrosis was quantified by collagen levels (Sircol) and lung fibrosis scores. AEC apoptosis was assessed by cleaved caspase-3 (CC-3)/Surfactant protein C (SFTPC) immunohistochemistry (IHC) and semi-quantitative analysis. AEC (primary AT2 cells from WT and MCAT mice and MLE-12 cells) mtDNA damage was assessed by a quantitative PCR-based assay, apoptosis was assessed by DNA fragmentation, and ROS production was assessed by a Mito-Sox assay. Compared to WT, crocidolite-exposed MCAT mice exhibit reduced pulmonary fibrosis as measured by lung collagen levels and lung fibrosis score. The protective effects in MCAT mice were accompanied by reduced AEC mtDNA damage and apoptosis. Similar findings were noted following bleomycin exposure. Euk-134, a mitochondrial SOD/catalase mimetic, attenuated MLE-12 cell DNA damage and apoptosis. Finally, compared to WT, asbestos-induced MCAT AT2 cell ROS production was reduced. Our finding that MCAT mice have reduced pulmonary fibrosis, AEC mtDNA damage and apoptosis following exposure to asbestos or bleomycin suggests an important role

Double-stranded DNA-dependent ATPase Irc3p is directly involved in mitochondrial genome maintenance.

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Sedman, Tiina; Gaidutšik, Ilja; Villemson, Karin; Hou, YingJian; Sedman, Juhan

2014-12-01

Nucleic acid-dependent ATPases are involved in nearly all aspects of DNA and RNA metabolism. Previous studies have described a number of mitochondrial helicases. However, double-stranded DNA-dependent ATPases, including translocases or enzymes remodeling DNA-protein complexes, have not been identified in mitochondria of the yeast Saccharomyces cerevisae. Here, we demonstrate that Irc3p is a mitochondrial double-stranded DNA-dependent ATPase of the Superfamily II. In contrast to the other mitochondrial Superfamily II enzymes Mss116p, Suv3p and Mrh4p, which are RNA helicases, Irc3p has a direct role in mitochondrial DNA (mtDNA) maintenance. Specific Irc3p-dependent mtDNA metabolic intermediates can be detected, including high levels of double-stranded DNA breaks that accumulate in irc3Δ mutants. irc3Δ-related topology changes in rho- mtDNA can be reversed by the deletion of mitochondrial RNA polymerase RPO41, suggesting that Irc3p counterbalances adverse effects of transcription on mitochondrial genome stability. © The Author(s) 2014. Published by Oxford University Press on behalf of Nucleic Acids Research.

Mitochondrial DNA sequence characteristics modulate the size of the genetic bottleneck.

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Wilson, Ian J; Carling, Phillipa J; Alston, Charlotte L; Floros, Vasileios I; Pyle, Angela; Hudson, Gavin; Sallevelt, Suzanne C E H; Lamperti, Costanza; Carelli, Valerio; Bindoff, Laurence A; Samuels, David C; Wonnapinij, Passorn; Zeviani, Massimo; Taylor, Robert W; Smeets, Hubert J M; Horvath, Rita; Chinnery, Patrick F

2016-03-01

With a combined carrier frequency of 1:200, heteroplasmic mitochondrial DNA (mtDNA) mutations cause human disease in ∼1:5000 of the population. Rapid shifts in the level of heteroplasmy seen within a single generation contribute to the wide range in the severity of clinical phenotypes seen in families transmitting mtDNA disease, consistent with a genetic bottleneck during transmission. Although preliminary evidence from human pedigrees points towards a random drift process underlying the shifting heteroplasmy, some reports describe differences in segregation pattern between different mtDNA mutations. However, based on limited observations and with no direct comparisons, it is not clear whether these observations simply reflect pedigree ascertainment and publication bias. To address this issue, we studied 577 mother-child pairs transmitting the m.11778G>A, m.3460G>A, m.8344A>G, m.8993T>G/C and m.3243A>G mtDNA mutations. Our analysis controlled for inter-assay differences, inter-laboratory variation and ascertainment bias. We found no evidence of selection during transmission but show that different mtDNA mutations segregate at different rates in human pedigrees. m.8993T>G/C segregated significantly faster than m.11778G>A, m.8344A>G and m.3243A>G, consistent with a tighter mtDNA genetic bottleneck in m.8993T>G/C pedigrees. Our observations support the existence of different genetic bottlenecks primarily determined by the underlying mtDNA mutation, explaining the different inheritance patterns observed in human pedigrees transmitting pathogenic mtDNA mutations. © The Author 2016. Published by Oxford University Press.

Validation of the use of an artificial mitochondrial reporter DNA vector containing a Cytomegalovirus promoter for mitochondrial transgene expression.

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Yamada, Yuma; Ishikawa, Takuya; Harashima, Hideyoshi

2017-08-01

Mitochondria have their own gene expression system that is independent of the nuclear system, and control cellular functions in cooperation with the nucleus. While a number of useful technologies for achieving nuclear transgene expression have been reported, only a few have focused on mitochondria. In this study, we validated the utility of an artificial mitochondrial DNA vector with a virus promoter on mitochondrial transgene expression. We designed and constructed pCMV-mtLuc (CGG) that contains a CMV promotor derived from Cytomegalovirus and an artificial mitochondrial genome with a NanoLuc (Nluc) luciferase gene that records adjustments to the mitochondrial codon system. Nluc luciferase activity measurements showed that the pCMV-mtLuc (CGG) efficiently produced the Nluc luciferase protein in human HeLa cells. Moreover, we optimized the mitochondrial transfection of pCMV-mtLuc (CGG) using a MITO-Porter system, a liposome-based carrier for mitochondrial delivery via membrane fusion. As a result, we found that transfection of pCMV-mtLuc (CGG) by MITO-Porter modified with the KALA peptide (cationic amphipathic cell-penetrating peptide) showed a high mitochondrial transgene expression. The developed mitochondrial transgene expression system represents a potentially useful tool for the fields of nanoscience and nanotechnology for controlling the intracellular microenvironment via the regulation of mitochondrial function and promises to open additional innovative research fields of study. Copyright © 2017 Elsevier Ltd. All rights reserved.

Mitochondrial DNA haplogroup phylogeny of the dog: Proposal for a cladistic nomenclature.

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Fregel, Rosa; Suárez, Nicolás M; Betancor, Eva; González, Ana M; Cabrera, Vicente M; Pestano, José

2015-05-01

Canis lupus familiaris mitochondrial DNA analysis has increased in recent years, not only for the purpose of deciphering dog domestication but also for forensic genetic studies or breed characterization. The resultant accumulation of data has increased the need for a normalized and phylogenetic-based nomenclature like those provided for human maternal lineages. Although a standardized classification has been proposed, haplotype names within clades have been assigned gradually without considering the evolutionary history of dog mtDNA. Moreover, this classification is based only on the D-loop region, proven to be insufficient for phylogenetic purposes due to its high number of recurrent mutations and the lack of relevant information present in the coding region. In this study, we design 1) a refined mtDNA cladistic nomenclature from a phylogenetic tree based on complete sequences, classifying dog maternal lineages into haplogroups defined by specific diagnostic mutations, and 2) a coding region SNP analysis that allows a more accurate classification into haplogroups when combined with D-loop sequencing, thus improving the phylogenetic information obtained in dog mitochondrial DNA studies. Copyright © 2015 Elsevier B.V. All rights reserved.

Circulating mitochondrial DNA as biomarker linking environmental chemical exposure to early preclinical lesions elevation of mtDNA in human serum after exposure to carcinogenic halo-alkane-based pesticides.

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Lygia T Budnik

Full Text Available There is a need for a panel of suitable biomarkers for detection of environmental chemical exposure leading to the initiation or progression of degenerative diseases or potentially, to cancer. As the peripheral blood may contain increased levels of circulating cell-free DNA in diseased individuals, we aimed to evaluate this DNA as effect biomarker recognizing vulnerability after exposure to environmental chemicals. We recruited 164 individuals presumably exposed to halo-alkane-based pesticides. Exposure evaluation was based on human biomonitoring analysis; as biomarker of exposure parent halo-methanes, -ethanes and their metabolites, as well as the hemoglobin-adducts methyl valine and hydroxyl ethyl valine in blood were used, complemented by expert evaluation of exposure and clinical intoxication symptoms as well as a questionnaire. Assessment showed exposures to halo alkanes in the concentration range being higher than non-cancer reference doses (RfD but (mostly lower than the occupational exposure limits. We quantified circulating DNA in serum from 86 individuals with confirmed exposure to off-gassing halo-alkane pesticides (in storage facilities or in home environment and 30 non-exposed controls, and found that exposure was significantly associated with elevated serum levels of circulating mitochondrial DNA (in size of 79 bp, mtDNA-79, p = 0.0001. The decreased integrity of mtDNA (mtDNA-230/mtDNA-79 in exposed individuals implicates apoptotic processes (p = 0.015. The relative amounts of mtDNA-79 in serum were positively associated with the lag-time after intoxication to these chemicals (r = 0.99, p<0.0001. Several months of post-exposure the specificity of this biomarker increased from 30% to 97% in patients with intoxication symptoms. Our findings indicate that mitochondrial DNA has a potential to serve as a biomarker recognizing vulnerable risk groups after exposure to toxic/carcinogenic chemicals.

Development of a Model for the Teaching of Mitochondrial DNA

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A.P.S. Souza

2010-05-01

Full Text Available The Cellular Biology and Molecular Biology are fields of Science that use very abstract concepts, because they look into microscopic and molecular aspects of the nature. The process of teaching/learning of those disciplines requires didactic material, as an alternative approach for the students, to increase the chances of understanding these issues and to become an important tool in the synthesis of this knowledge. One of the methods that can be employed is the didactic models based on multimedia, because they allow an easy and fun interaction with these subjects. On this work was created a new educational model that represents the human mitochondrial DNA molecule, mtDNA, in its circular form, using the softwares Excel 2007 and PowerPoint 2007. The model was constructed in hypertext format, which allowed a quick and interactive access to the information contained in the genes found in the L and the H strands of mtDNA, and its function in the mitochondrial processes, like themechanism of energy production that occurs inside of the mitochondria by the coupling of electron transfer and ATP synthesis or still others uses like forensic identification.

Characterization of a Dairy Gyr herd with respect to its mitochondrial DNA (mt DNA origin

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Anibal Eugênio Vercesi Filho

2010-01-01

Full Text Available The Zebu breeds were introduced in Brazil mainly in the last century by imports from the Indian subcontinent. When the Zebu cattle arrived, the national herd suffered a significative change by backcrossing the national cows of taurine origin with Zebu sires. These processes created a polymorphism in the mitochondrial DNA (mtDNA in the Zebu animals with are in a major part derived from backcrossing and sharing mtDNA of taurine origin. To verify the maternal origin of cows belonging to the Dairy Gyr herd of APTA, Mococa 60 females were analyzed and 33 presented mtDNA from Bos taurus origin and 27 presented mtDNA from Bos indicus origin. None of these animals presented patterns of both mtDNA origins, indicating absence of heteroplasmy for these mitochondrial genotypes.

Mitochondrial DNA depletion, mitochondrial mutations and high TFAM expression in hepatocellular carcinoma

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Qiao, Lihua; Ru, Guoqing; Mao, Zhuochao; Wang, Chenghui; Nie, Zhipeng; Li, Qiang; Huang-yang, Yiyi; Zhu, Ling; Liang, Xiaoyang; Yu, Jialing; Jiang, Pingping

2017-01-01

We investigated the role of mitochondrial genetic alterations in hepatocellular carcinoma by directly comparing the mitochondrial genomes of 86 matched pairs of HCC and non-tumor liver samples. Substitutions in 637 mtDNA sites were detected, comprising 89.80% transitions and 6.60% transversions. Forty-six somatic variants, including 15 novel mutations, were identified in 40.70% of tumor tissues. Of those, 21 were located in the non-coding region and 25 in the protein-coding region. Twenty-two...

Alkyladenine DNA glycosylase (AAG) localizes to mitochondria and interacts with mitochondrial single-stranded binding protein (mtSSB).

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van Loon, Barbara; Samson, Leona D

2013-03-01

Due to a harsh environment mitochondrial genomes accumulate high levels of DNA damage, in particular oxidation, hydrolytic deamination, and alkylation adducts. While repair of alkylated bases in nuclear DNA has been explored in detail, much less is known about the repair of DNA alkylation damage in mitochondria. Alkyladenine DNA glycosylase (AAG) recognizes and removes numerous alkylated bases, but to date AAG has only been detected in the nucleus, even though mammalian mitochondria are known to repair DNA lesions that are specific substrates of AAG. Here we use immunofluorescence to show that AAG localizes to mitochondria, and we find that native AAG is present in purified human mitochondrial extracts, as well as that exposure to alkylating agent promotes AAG accumulation in the mitochondria. We identify mitochondrial single-stranded binding protein (mtSSB) as a novel interacting partner of AAG; interaction between mtSSB and AAG is direct and increases upon methyl methanesulfonate (MMS) treatment. The consequence of this interaction is specific inhibition of AAG glycosylase activity in the context of a single-stranded DNA (ssDNA), but not a double-stranded DNA (dsDNA) substrate. By inhibiting AAG-initiated processing of damaged bases, mtSSB potentially prevents formation of DNA breaks in ssDNA, ensuring that base removal primarily occurs in dsDNA. In summary, our findings suggest the existence of AAG-initiated BER in mitochondria and further support a role for mtSSB in DNA repair. Copyright © 2012. Published by Elsevier B.V.

Mechanism of Homologous Recombination and Implications for Aging-Related Deletions in Mitochondrial DNA

Science.gov (United States)

2013-01-01

SUMMARY Homologous recombination is a universal process, conserved from bacteriophage to human, which is important for the repair of double-strand DNA breaks. Recombination in mitochondrial DNA (mtDNA) was documented more than 4 decades ago, but the underlying molecular mechanism has remained elusive. Recent studies have revealed the presence of a Rad52-type recombination system of bacteriophage origin in mitochondria, which operates by a single-strand annealing mechanism independent of the canonical RecA/Rad51-type recombinases. Increasing evidence supports the notion that, like in bacteriophages, mtDNA inheritance is a coordinated interplay between recombination, repair, and replication. These findings could have profound implications for understanding the mechanism of mtDNA inheritance and the generation of mtDNA deletions in aging cells. PMID:24006472

Mitochondrial DNA Mutation Associated with Leber's Hereditary Optic Neuropathy

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Wallace, Douglas C.; Singh, Gurparkash; Lott, Marie T.; Hodge, Judy A.; Schurr, Theodore G.; Lezza, Angela M. S.; Elsas, Louis J.; Nikoskelainen, Eeva K.

1988-12-01

Leber's hereditary optic neuropathy is a maternally inherited disease resulting in optic nerve degeneration and cardiac dysrhythmia. A mitochondrial DNA replacement mutation was identified that correlated with this disease in multiple families. This mutation converted a highly conserved arginine to a histidine at codon 340 in the NADH dehydrogenase subunit 4 gene and eliminated an Sfa NI site, thus providing a simple diagnostic test. This finding demonstrated that a nucleotide change in a mitochondrial DNA energy production gene can result in a neurological disease.

Nuclear and mitochondrial DNA quantification of various forensic materials.

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Andréasson, H; Nilsson, M; Budowle, B; Lundberg, H; Allen, M

2006-12-01

Due to the different types and quality of forensic evidence materials, their DNA content can vary substantially, and particularly low quantities can impact the results in an identification analysis. In this study, the quantity of mitochondrial and nuclear DNA was determined in a variety of materials using a previously described real-time PCR method. DNA quantification in the roots and distal sections of plucked and shed head hairs revealed large variations in DNA content particularly between the root and the shaft of plucked hairs. Also large intra- and inter-individual variations were found among hairs. In addition, DNA content was estimated in samples collected from fingerprints and accessories. The quantification of DNA on various items also displayed large variations, with some materials containing large amounts of nuclear DNA while no detectable nuclear DNA and only limited amounts of mitochondrial DNA were seen in others. Using this sensitive real-time PCR quantification assay, a better understanding was obtained regarding DNA content and variation in commonly analysed forensic evidence materials and this may guide the forensic scientist as to the best molecular biology approach for analysing various forensic evidence materials.

Differential chromosomal and mitochondrial DNA synthesis in temperature-sensitive mutants of Ustilago maydis

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Unrau, P.

1977-01-01

The amount and type of residual DNA synthesis was determined in eight temperature-sensitive mutants of the smut fungus Ustilago maydis after incubation at the restrictive temperature (32/sup 0/C) for eight hours. Mutants ts-220, ts-207, ts-432 and ts-346 were found to have an overall reduction in the synthesis of both nuclear and mitochondrial DNA in comparison to the wild-type. In mutants ts-20, tsd 1-1, ts-84 and pol 1-1 nuclear DNA synthesis was depressed relative to mitochondrial synthesis. The DNA-polymerase mutant pol 1-1 had persistent nuclear synthesis at about 50% of the rate of synthesis of mitochondrial DNA and similar behavior was observed in a diploid homozygous strain. Mutant ts-84 had an initial burst of DNA synthesis which was reduced for nuclear but not mitochondrial synthesis after three hours preincubation at 32/sup 0/C. tsd 1-1 and ts-20 had nuclear residual synthesis amounting to about 25% of the relative rate of mitochondrial synthesis which correlates to increasing UV sensitivity of these strains on incubation at 32/sup 0/C. A pol 1-1 ts-84 double mutant had an additive loss of nuclear DNA synthesis which indicates that the steps of replication involved may be sequential.

Mitochondrial DNA Damage and Diseases [version 1; referees: 1 approved, 2 approved with reservations

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Gyanesh Singh

2015-07-01

Full Text Available Various endogenous and environmental factors can cause mitochondrial DNA (mtDNA damage.  One of the reasons for enhanced mtDNA damage could be its proximity to the source of oxidants, and lack of histone-like protective proteins. Moreover, mitochondria contain inadequate DNA repair pathways, and, diminished DNA repair capacity may be one of the factors responsible for high mutation frequency of the mtDNA. mtDNA damage might cause impaired mitochondrial function, and, unrepaired mtDNA damage has been frequently linked with several diseases. Exploration of mitochondrial perspective of diseases might lead to a better understanding of several diseases, and will certainly open new avenues for detection, cure, and prevention of ailments.

LORD-Q: a long-run real-time PCR-based DNA-damage quantification method for nuclear and mitochondrial genome analysis

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Lehle, Simon; Hildebrand, Dominic G.; Merz, Britta; Malak, Peter N.; Becker, Michael S.; Schmezer, Peter; Essmann, Frank; Schulze-Osthoff, Klaus; Rothfuss, Oliver

2014-01-01

DNA damage is tightly associated with various biological and pathological processes, such as aging and tumorigenesis. Although detection of DNA damage is attracting increasing attention, only a limited number of methods are available to quantify DNA lesions, and these techniques are tedious or only detect global DNA damage. In this study, we present a high-sensitivity long-run real-time PCR technique for DNA-damage quantification (LORD-Q) in both the mitochondrial and nuclear genome. While most conventional methods are of low-sensitivity or restricted to abundant mitochondrial DNA samples, we established a protocol that enables the accurate sequence-specific quantification of DNA damage in >3-kb probes for any mitochondrial or nuclear DNA sequence. In order to validate the sensitivity of this method, we compared LORD-Q with a previously published qPCR-based method and the standard single-cell gel electrophoresis assay, demonstrating a superior performance of LORD-Q. Exemplarily, we monitored induction of DNA damage and repair processes in human induced pluripotent stem cells and isogenic fibroblasts. Our results suggest that LORD-Q provides a sequence-specific and precise method to quantify DNA damage, thereby allowing the high-throughput assessment of DNA repair, genotoxicity screening and various other processes for a wide range of life science applications. PMID:24371283

Mitochondrial outer membrane permeabilization increases reactive oxygen species production and decreases mean sperm velocity but is not associated with DNA fragmentation in human sperm.

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Treulen, F; Uribe, P; Boguen, R; Villegas, J V

2016-02-01

Does induction of mitochondrial outer membrane permeabilization (MOMP) in vitro affect specific functional parameters of human spermatozoa? Our findings show that MOMP induction increases intracellular reactive oxygen species (ROS) and decreases mean sperm velocity but does not alter DNA integrity. MOMP in somatic cells is related to a variety of apoptotic traits, such as alteration of mitochondrial membrane potential (ΔΨm), and increase in ROS production and DNA fragmentation. Although the presence of these apoptotic features has been reported in spermatozoa, to date the effects of MOMP on sperm function and DNA integrity have not been analysed. The study included spermatozoa from fertile donors. Motile sperm were obtained using the swim-up method. The highly motile sperm were collected and diluted with human tubal fluid to a final cell concentration of 5 × 10(6) ml(-1). To induce MOMP, selected sperm were treated at 37°C for 4 h with a mimetic of a Bcl-2 pro-apoptotic protein, ABT-737. MOMP was evaluated by relocating of cytochrome c. In addition, the effect of ABT-737 on mitochondrial inner membrane permeabilization was assessed using the calcein-AM/cobalt chloride method. In turn, ΔΨm was evaluated with JC-1 staining, intracellular ROS production with dihydroethidium, sperm motility was analysed by computer-assisted sperm analysis and DNA fragmentation by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling (TUNEL) assay. Measurements were performed by flow cytometry. MOMP was associated with ΔΨm dissipation (P < 0.05), increased ROS production (P < 0.05) and decreased mean sperm velocity (P < 0.05), but it was not associated with DNA fragmentation. MOMP did not induce a large increase in ROS, which could explain the negligible effect of MOMP on sperm DNA fragmentation under our experimental conditions. The study was carried out in vitro using highly motile sperm, selected by swim-up, from healthy donors. The results obtained in this

Accurate measurement of mitochondrial DNA deletion level and copy number differences in human skeletal muscle.

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John P Grady

Full Text Available Accurate and reliable quantification of the abundance of mitochondrial DNA (mtDNA molecules, both wild-type and those harbouring pathogenic mutations, is important not only for understanding the progression of mtDNA disease but also for evaluating novel therapeutic approaches. A clear understanding of the sensitivity of mtDNA measurement assays under different experimental conditions is therefore critical, however it is routinely lacking for most published mtDNA quantification assays. Here, we comprehensively assess the variability of two quantitative Taqman real-time PCR assays, a widely-applied MT-ND1/MT-ND4 multiplex mtDNA deletion assay and a recently developed MT-ND1/B2M singleplex mtDNA copy number assay, across a range of DNA concentrations and mtDNA deletion/copy number levels. Uniquely, we provide a specific guide detailing necessary numbers of sample and real-time PCR plate replicates for accurately and consistently determining a given difference in mtDNA deletion levels and copy number in homogenate skeletal muscle DNA.

Primer retention owing to the absence of RNase H1 is catastrophic for mitochondrial DNA replication.

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Holmes, J Bradley; Akman, Gokhan; Wood, Stuart R; Sakhuja, Kiran; Cerritelli, Susana M; Moss, Chloe; Bowmaker, Mark R; Jacobs, Howard T; Crouch, Robert J; Holt, Ian J

2015-07-28

Encoding ribonuclease H1 (RNase H1) degrades RNA hybridized to DNA, and its function is essential for mitochondrial DNA maintenance in the developing mouse. Here we define the role of RNase H1 in mitochondrial DNA replication. Analysis of replicating mitochondrial DNA in embryonic fibroblasts lacking RNase H1 reveals retention of three primers in the major noncoding region (NCR) and one at the prominent lagging-strand initiation site termed Ori-L. Primer retention does not lead immediately to depletion, as the persistent RNA is fully incorporated in mitochondrial DNA. However, the retained primers present an obstacle to the mitochondrial DNA polymerase γ in subsequent rounds of replication and lead to the catastrophic generation of a double-strand break at the origin when the resulting gapped molecules are copied. Hence, the essential role of RNase H1 in mitochondrial DNA replication is the removal of primers at the origin of replication.

Mitochondrial DNA damage and vascular function in patients with diabetes mellitus and atherosclerotic cardiovascular disease.

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Fetterman, Jessica L; Holbrook, Monica; Westbrook, David G; Brown, Jamelle A; Feeley, Kyle P; Bretón-Romero, Rosa; Linder, Erika A; Berk, Brittany D; Weisbrod, Robert M; Widlansky, Michael E; Gokce, Noyan; Ballinger, Scott W; Hamburg, Naomi M

2016-03-31

Prior studies demonstrate mitochondrial dysfunction with increased reactive oxygen species generation in peripheral blood mononuclear cells in diabetes mellitus. Oxidative stress-mediated damage to mitochondrial DNA promotes atherosclerosis in animal models. Thus, we evaluated the relation of mitochondrial DNA damage in peripheral blood mononuclear cells s with vascular function in patients with diabetes mellitus and with atherosclerotic cardiovascular disease. We assessed non-invasive vascular function and mitochondrial DNA damage in 275 patients (age 57 ± 9 years, 60 % women) with atherosclerotic cardiovascular disease alone (N = 55), diabetes mellitus alone (N = 74), combined atherosclerotic cardiovascular disease and diabetes mellitus (N = 48), and controls age >45 without diabetes mellitus or atherosclerotic cardiovascular disease (N = 98). Mitochondrial DNA damage measured by quantitative PCR in peripheral blood mononuclear cells was higher with clinical atherosclerosis alone (0.55 ± 0.65), diabetes mellitus alone (0.65 ± 1.0), and combined clinical atherosclerosis and diabetes mellitus (0.89 ± 1.32) as compared to control subjects (0.23 ± 0.64, P < 0.0001). In multivariable models adjusting for age, sex, and relevant cardiovascular risk factors, clinical atherosclerosis and diabetes mellitus remained associated with higher mitochondrial DNA damage levels (β = 0.14 ± 0.13, P = 0.04 and β = 0.21 ± 0.13, P = 0.002, respectively). Higher mitochondrial DNA damage was associated with higher baseline pulse amplitude, a measure of arterial pulsatility, but not with flow-mediated dilation or hyperemic response, measures of vasodilator function. We found greater mitochondrial DNA damage in patients with diabetes mellitus and clinical atherosclerosis. The association of mitochondrial DNA damage and baseline pulse amplitude may suggest a link between mitochondrial dysfunction and excessive small artery pulsatility with potentially adverse microvascular impact.

Increased mitochondrial DNA deletions and copy number in transfusion-dependent thalassemia

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Calloway, Cassandra

2016-01-01

BACKGROUND. Iron overload is the primary cause of morbidity in transfusion-dependent thalassemia. Increase in iron causes mitochondrial dysfunction under experimental conditions, but the occurrence and significance of mitochondrial damage is not understood in patients with thalassemia. METHODS. Mitochondrial DNA (mtDNA) to nuclear DNA copy number (Mt/N) and frequency of the common 4977-bp mitochondrial deletion (ΔmtDNA4977) were quantified using a quantitative PCR assay on whole blood samples from 38 subjects with thalassemia who were receiving regular transfusions. RESULTS. Compared with healthy controls, Mt/N and ΔmtDNA4977 frequency were elevated in thalassemia (P = 0.038 and P 15 mg/g dry-weight or splenectomy, with the highest levels observed in subjects who had both risk factors (P = 0.003). Myocardial iron (MRI T2* 40/1 × 107 mtDNA, respectively (P = 0.025). Subjects with Mt/N values below the group median had significantly lower Matsuda insulin sensitivity index (5.76 ± 0.53) compared with the high Mt/N group (9.11 ± 0.95, P = 0.008). CONCLUSION. Individuals with transfusion-dependent thalassemia demonstrate age-related increase in mtDNA damage in leukocytes. These changes are markedly amplified by splenectomy and are associated with extrahepatic iron deposition. Elevated mtDNA damage in blood cells may predict the risk of iron-associated organ damage in thalassemia. FUNDING. This project was supported by Children’s Hospital & Research Center Oakland Institutional Research Award and by the National Center for Advancing Translational Sciences, NIH, through UCSF-CTSI grant UL1 TR000004. PMID:27583305

A mitochondrial DNA SNP multiplex assigning Caucasians into 36 haplo- and subhaplogroups

DEFF Research Database (Denmark)

Mikkelsen, Martin; Rockenbauer, Eszter; Sørensen, Erik

2008-01-01

Mitochondrial DNA (mtDNA) is maternally inherited without recombination events and has a high copy number, which makes mtDNA analysis feasible even when genomic DNA is sparse or degraded. Here, we present a SNP typing assay with 33 previously described mtDNA coding region SNPs for haplogroup...... previously typed by sequencing of the mitochondrial HV1 and HV2 regions. Haplogroup assignments based on mtDNA coding region SNPs and sequencing of HV1 and HV2 regions gave identical results for 27% of the samples, and except for one sample, differences in haplogroup assignments were at the subhaplogroup...

Minisequencing mitochondrial DNA pathogenic mutations

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Carracedo Ángel

2008-04-01

Full Text Available Abstract Background There are a number of well-known mutations responsible of common mitochondrial DNA (mtDNA diseases. In order to overcome technical problems related to the analysis of complete mtDNA genomes, a variety of different techniques have been proposed that allow the screening of coding region pathogenic mutations. Methods We here propose a minisequencing assay for the analysis of mtDNA mutations. In a single reaction, we interrogate a total of 25 pathogenic mutations distributed all around the whole mtDNA genome in a sample of patients suspected for mtDNA disease. Results We have detected 11 causal homoplasmic mutations in patients suspected for Leber disease, which were further confirmed by standard automatic sequencing. Mutations m.11778G>A and m.14484T>C occur at higher frequency than expected by change in the Galician (northwest Spain patients carrying haplogroup J lineages (Fisher's Exact test, P-value Conclusion We here developed a minisequencing genotyping method for the screening of the most common pathogenic mtDNA mutations which is simple, fast, and low-cost. The technique is robust and reproducible and can easily be implemented in standard clinical laboratories.

First description of a novel mitochondrial mutation in the MT-TI gene associated with multiple mitochondrial DNA deletion and depletion in family with severe dilated mitochondrial cardiomyopathy.

Science.gov (United States)

Alila-Fersi, Olfa; Tabebi, Mouna; Maalej, Marwa; Belguith, Neila; Keskes, Leila; Mkaouar-Rebai, Emna; Fakhfakh, Faiza

2018-03-18

Mitochondria are essential for early cardiac development and impaired mitochondrial function was described associated with heart diseases such as hypertrophic or dilated mitochondrial cardiomyopathy. In this study, we report a family including two individuals with severe dilated mitochondrial cardiomyopathy. The whole mitochondrial genome screening showed the presence of several variations and a novel homoplasmic mutation m.4318-4322delC in the MT-TI gene shared by the two patients and their mother and leading to a disruption of the tRNA Ile secondary structure. In addition, a mitochondrial depletion was present in blood leucocyte of the two affected brother whereas a de novo heteroplasmic multiple deletion in the major arc of mtDNA was present in blood leucocyte and mucosa of only one of them. These deletions in the major arc of the mtDNA resulted to the loss of several protein-encoding genes and also some tRNA genes. The mtDNA deletion and depletion could result to an impairment of the oxidative phosphorylation and energy metabolism in the respiratory chain in the studied patients. Our report is the first description of a family with severe lethal dilated mitochondrial cardiomyopathy and presenting several mtDNA abnormalities including punctual mutation, deletion and depletion. Copyright © 2018 Elsevier Inc. All rights reserved.

The Role of Mitochondrial DNA in Mediating Alveolar Epithelial Cell Apoptosis and Pulmonary Fibrosis

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Kim, Seok-Jo; Cheresh, Paul; Jablonski, Renea P.; Williams, David B.; Kamp, David W.

2015-01-01

Convincing evidence has emerged demonstrating that impairment of mitochondrial function is critically important in regulating alveolar epithelial cell (AEC) programmed cell death (apoptosis) that may contribute to aging-related lung diseases, such as idiopathic pulmonary fibrosis (IPF) and asbestosis (pulmonary fibrosis following asbestos exposure). The mammalian mitochondrial DNA (mtDNA) encodes for 13 proteins, including several essential for oxidative phosphorylation. We review the evidence implicating that oxidative stress-induced mtDNA damage promotes AEC apoptosis and pulmonary fibrosis. We focus on the emerging role for AEC mtDNA damage repair by 8-oxoguanine DNA glycosylase (OGG1) and mitochondrial aconitase (ACO-2) in maintaining mtDNA integrity which is important in preventing AEC apoptosis and asbestos-induced pulmonary fibrosis in a murine model. We then review recent studies linking the sirtuin (SIRT) family members, especially SIRT3, to mitochondrial integrity and mtDNA damage repair and aging. We present a conceptual model of how SIRTs modulate reactive oxygen species (ROS)-driven mitochondrial metabolism that may be important for their tumor suppressor function. The emerging insights into the pathobiology underlying AEC mtDNA damage and apoptosis is suggesting novel therapeutic targets that may prove useful for the management of age-related diseases, including pulmonary fibrosis and lung cancer. PMID:26370974

Mitochondrial and Nuclear DNA Damage and Repair in Age-Related Macular Degeneration

Directory of Open Access Journals (Sweden)

Janusz Blasiak

2013-01-01

Full Text Available Aging and oxidative stress seem to be the most important factors in the pathogenesis of age-related macular degeneration (AMD, a condition affecting many elderly people in the developed world. However, aging is associated with the accumulation of oxidative damage in many biomolecules, including DNA. Furthermore, mitochondria may be especially important in this process because the reactive oxygen species produced in their electron transport chain can damage cellular components. Therefore, the cellular response to DNA damage, expressed mainly through DNA repair, may play an important role in AMD etiology. In several studies the increase in mitochondrial DNA (mtDNA damage and mutations, and the decrease in the efficacy of DNA repair have been correlated with the occurrence and the stage of AMD. It has also been shown that mitochondrial DNA accumulates more DNA lesions than nuclear DNA in AMD. However, the DNA damage response in mitochondria is executed by nucleus-encoded proteins, and thus mutagenesis in nuclear DNA (nDNA may affect the ability to respond to mutagenesis in its mitochondrial counterpart. We reported that lymphocytes from AMD patients displayed a higher amount of total endogenous basal and oxidative DNA damage, exhibited a higher sensitivity to hydrogen peroxide and UV radiation, and repaired the lesions induced by these factors less effectively than did cells from control individuals. We postulate that poor efficacy of DNA repair (i.e., is impaired above average for a particular age when combined with the enhanced sensitivity of retinal pigment epithelium cells to environmental stress factors, contributes to the pathogenesis of AMD. Collectively, these data suggest that the cellular response to both mitochondrial and nuclear DNA damage may play an important role in AMD pathogenesis.

Mitochondrial DNA Copy Number in Sleep Duration Discordant Monozygotic Twins

DEFF Research Database (Denmark)

Wrede, Joanna E; Mengel-From, Jonas; Buchwald, Dedra

2015-01-01

STUDY OBJECTIVES: Mitochondrial DNA (mtDNA) copy number is an important component of mitochondrial function and varies with age, disease, and environmental factors. We aimed to determine whether mtDNA copy number varies with habitual differences in sleep duration within pairs of monozygotic twins...... structure to assess within-pair effects of sleep duration on mtDNA copy number. MEASUREMENTS AND RESULTS: Mean within-pair sleep duration difference per 24 hours was 94.3 minutes (SD 62.6 min). We found reduced sleep duration (β = 0.06; 95% CI 0.004, 0.12; P sleep efficiency (β = 0.51; 95% CI 0.......06, 0.95; P DNA copy number within twin pairs. Thus every 1-minute decrease in actigraphy-defined sleep duration was associated with a decrease in mtDNA copy number of 0.06. Likewise, a 1% decrease in actigraphy-defined sleep efficiency was associated...

mtDNA, Metastasis, and the Mitochondrial Unfolded Protein Response (UPRmt).

Science.gov (United States)

Kenny, Timothy C; Germain, Doris

2017-01-01

While several studies have confirmed a link between mitochondrial DNA (mtDNA) mutations and cancer cell metastasis, much debate remains regarding the nature of the alternations in mtDNA leading to this effect. Meanwhile, the mitochondrial unfolded protein response (UPR mt ) has gained much attention in recent years, with most studies of this pathway focusing on its role in aging. However, the UPR mt has also been studied in the context of cancer. More recent work suggests that rather than a single mutation or alternation, specific combinatorial mtDNA landscapes able to activate the UPR mt may be those that are selected by metastatic cells, while mtDNA landscapes unable to activate the UPR mt do not. This review aims at offering an overview of the confusing literature on mtDNA mutations and metastasis and the more recent work on the UPR mt in this setting.

The potential role for use of mitochondrial DNA copy number as predictive biomarker in presbycusis.

Science.gov (United States)

Falah, Masoumeh; Houshmand, Massoud; Najafi, Mohammad; Balali, Maryam; Mahmoudian, Saeid; Asghari, Alimohamad; Emamdjomeh, Hessamaldin; Farhadi, Mohammad

2016-01-01

Age-related hearing impairment, or presbycusis, is the most common communication disorder and neurodegenerative disease in the elderly. Its prevalence is expected to increase, due to the trend of growth of the elderly population. The current diagnostic test for detection of presbycusis is implemented after there has been a change in hearing sensitivity. Identification of a pre-diagnostic biomarker would raise the possibility of preserving hearing sensitivity before damage occurs. Mitochondrial dysfunction, including the production of reactive oxygen species and induction of expression of apoptotic genes, participates in the progression of presbycusis. Mitochondrial DNA sequence variation has a critical role in presbycusis. However, the nature of the relationship between mitochondrial DNA copy number, an important biomarker in many other diseases, and presbycusis is undetermined. Fifty-four subjects with presbycusis and 29 healthy controls were selected after ear, nose, throat examination and pure-tone audiometry. DNA was extracted from peripheral blood samples. The copy number of mitochondrial DNA relative to the nuclear genome was measured by quantitative real-time polymerase chain reaction. Subjects with presbycusis had a lower median mitochondrial DNA copy number than healthy subjects and the difference was statistically significant ( P =0.007). Mitochondrial DNA copy number was also significantly associated with degree of hearing impairment ( P =0.025) and audiogram configuration ( P =0.022). The findings of this study suggest that lower mitochondrial DNA copy number is responsible for presbycusis through alteration of mitochondrial function. Moreover, the significant association of mitochondrial DNA copy number in peripheral blood samples with the degree of hearing impairment and audiogram configuration has potential for use as a standard test for presbycusis, providing the possibility of the development of an easy-to-use biomarker for the early detection of

Compound mitochondrial DNA mutations in a neurological patient ...

Indian Academy of Sciences (India)

Compound mitochondrial DNA mutations in a neurological patient with ataxia, myoclonus and deafness. Ji Hoon Park, Bo Ram Yoon, Hye Jin Kim, Phil Hyu Lee, Byung-Ok Choi and Ki Wha Chung. J. Genet. 93, 173–177. Table 1. Variations from the whole mtDNA sequence in the AMDF patient. Mutation. Report. Locus/ ...

Increased levels of mitochondrial DNA copy number in patients with vitiligo.

Science.gov (United States)

Vaseghi, H; Houshmand, M; Jadali, Z

2017-10-01

Oxidative stress is known to be involved in the pathogenesis of autoimmune diseases such as vitiligo. Evidence suggests that the human mitochondrial DNA copy number (mtDNAcn) is vulnerable to damage mediated by oxidative stress. The purpose of this study was to examine and compare peripheral blood mtDNAcn and oxidative DNA damage byproducts (8-hydroxy-2-deoxyguanosine; 8-OHdG) in patients with vitiligo and healthy controls (HCs). The relative mtDNAcn and the oxidative damage (formation of 8-OHdG in mtDNA) of each sample were determined by real-time quantitative PCR. Blood samples were obtained from 56 patients with vitiligo and 46 HCs. The mean mtDNAcn and the degree of mtDNA damage were higher in patients with vitiligo than in HCs. These data suggest that increase in mtDNAcn and oxidative DNA damage may be involved in the pathogenesis of vitiligo. © 2017 British Association of Dermatologists.

DNA sequence evolution in fast evolving mitochondrial DNA nad1 exons in Geraniaceae and Plantaginaceae

NARCIS (Netherlands)

Bakker, F.T.; Breman, F.; Merckx, V.

2006-01-01

Previously, nucleotide substitution rates in mitochondrial DNA of Geraniaceae and Plantaginaceae have been shown to be exceptionally high compared with other angiosperm mtDNA lineages. It has also been shown that mtDNA introns were lost in Geraniaceae and Plantaginaceae. In this study we compile 127

A rolling circle replication mechanism produces multimeric lariats of mitochondrial DNA in Caenorhabditis elegans.

Directory of Open Access Journals (Sweden)

Samantha C Lewis

2015-02-01

Full Text Available Mitochondrial DNA (mtDNA encodes respiratory complex subunits essential to almost all eukaryotes; hence respiratory competence requires faithful duplication of this molecule. However, the mechanism(s of its synthesis remain hotly debated. Here we have developed Caenorhabditis elegans as a convenient animal model for the study of metazoan mtDNA synthesis. We demonstrate that C. elegans mtDNA replicates exclusively by a phage-like mechanism, in which multimeric molecules are synthesized from a circular template. In contrast to previous mammalian studies, we found that mtDNA synthesis in the C. elegans gonad produces branched-circular lariat structures with multimeric DNA tails; we were able to detect multimers up to four mtDNA genome unit lengths. Further, we did not detect elongation from a displacement-loop or analogue of 7S DNA, suggesting a clear difference from human mtDNA in regard to the site(s of replication initiation. We also identified cruciform mtDNA species that are sensitive to cleavage by the resolvase RusA; we suggest these four-way junctions may have a role in concatemer-to-monomer resolution. Overall these results indicate that mtDNA synthesis in C. elegans does not conform to any previously documented metazoan mtDNA replication mechanism, but instead are strongly suggestive of rolling circle replication, as employed by bacteriophages. As several components of the metazoan mitochondrial DNA replisome are likely phage-derived, these findings raise the possibility that the rolling circle mtDNA replication mechanism may be ancestral among metazoans.

Mitochondrial DNA Unwinding Enzyme Required for Liver Regeneration | Center for Cancer Research

Science.gov (United States)

The liver has an exceptional capacity to proliferate. This ability allows the liver to regenerate its mass after partial surgical removal or injury and is the key to successful partial liver transplants. Liver cells, called hepatocytes, are packed with mitochondria, and regulating mitochondrial DNA (mtDNA) copy number is crucial to mitochondrial function, including energy production, during proliferation. Yves Pommier, M.D., Ph.D., of CCR’s Developmental Therapeutics Branch, and his colleagues recently showed that the vertebrate mitochondrial topoisomerase, Top1mt, was critical in maintaining mitochondrial function in the heart after doxorubicin-induced damage. The group wondered whether Top1mt might play a similar role in liver regeneration.

Mitochondrial DNA mutations in preneoplastic lesions of the gastrointestinal tract: A biomarker for the early detection of cancer

Directory of Open Access Journals (Sweden)

Montgomery Elizabeth A

2006-12-01

Full Text Available Abstract Background Somatic mutations of mitochondrial DNA (mtDNA are common in many human cancers. We have described an oligonucleotide microarray ("MitoChip" for rapid sequencing of the entire mitochondrial genome (Zhou et al, J Mol Diagn 2006, facilitating the analysis of mtDNA mutations in preneoplastic lesions. We examined 14 precancerous lesions, including seven Barrett esophagus biopsies, with or without associated dysplasia; four colorectal adenomas; and three inflammatory colitis-associated dysplasia specimens. In all cases, matched normal tissues from the corresponding site were obtained as germline control. MitoChip analysis was performed on DNA obtained from cryostat-embedded specimens. Results A total of 513,639 bases of mtDNA were sequenced in the 14 samples, with 490,224 bases (95.4% bases assigned by the automated genotyping software. All preneoplastic lesions examined demonstrated at least one somatic mtDNA sequence alteration. Of the 100 somatic mtDNA alterations observed in the 14 cases, 27 were non-synonymous coding region mutations (i.e., resulting in an amino acid change, 36 were synonymous, and 37 involved non-coding mtDNA. Overall, somatic alterations most commonly involved the COI, ND4 and ND5 genes. Notably, somatic mtDNA alterations were observed in preneoplastic lesions of the gastrointestinal tract even in the absence of histopathologic evidence of dysplasia, suggesting that the mitochondrial genome is susceptible at the earliest stages of multistep cancer progression. Conclusion Our findings further substantiate the rationale for exploring the mitochondrial genome as a biomarker for the early diagnosis of cancer, and confirm the utility of a high-throughput array-based platform for this purpose from a clinical applicability standpoint.

Two potential Petunia hybrida mitochondrial DNA replication origins show structural and in vitro functional homology with the animal mitochondrial DNA heavy and light strand replication origins

NARCIS (Netherlands)

Haas, Jan M. de; Hille, Jacques; Kors, Frank; Meer, Bert van der; Kool, Ad J.; Folkerts, Otto; Nijkamp, H. John J.

1991-01-01

Four Petunia hybrida mitochondrial (mt) DNA fragments have been isolated, sequenced, localized on the physical map and analyzed for their ability to initiate specific DNA synthesis. When all four mtDNA fragments were tested as templates in an in vitro DNA synthesizing lysate system, developed from

A case study characterizing animal fecal sources in surface water using a mitochondrial DNA marker.

Science.gov (United States)

Bucci, John P; Shattuck, Michelle D; Aytur, Semra A; Carey, Richard; McDowell, William H

2017-08-01

Water quality impairment by fecal waste in coastal watersheds is a public health issue. The present study provided evidence for the use of a mitochondrial (mtDNA) marker to detect animal fecal sources in surface water. The accurate identification of fecal pollution is based on the notion that fecal microorganisms preferentially inhabit a host animal's gut environment. In contrast, mtDNA host-specific markers are inherent to eukaryotic host cells, which offers the advantage by detecting DNA from the host rather than its fecal bacteria. The present study focused on sampling water presumably from non-point sources (NPS), which can increase bacterial and nitrogen concentrations to receiving water bodies. Stream sampling sites located within the Piscataqua River Watershed (PRW), New Hampshire, USA, were sampled from a range of sites that experienced nitrogen inputs such as sewer and septic systems and suburban runoff. Three mitochondrial (mtDNA) gene marker assays (human, bovine, and canine) were tested from surface water. Nineteen sites were sampled during an 18-month period. Analyses of the combined single and multiplex assay results showed that the proportion of occurrence was highest for bovine (15.6%; n = 77) compared to canine (5.6%; n = 70) and human (5.7%; n = 107) mtDNA gene markers. For the human mtDNA marker, there was a statistically significant relationship between presence vs. absence and land use (Fisher's test p = 0.0031). This result was evident particularly for rural suburban septic, which showed the highest proportion of presence (19.2%) compared to the urban sewered (3.3%), suburban sewered (0%), and agricultural (0%) as well as forested septic (0%) sites. Although further testing across varied land use is needed, our study provides evidence for using the mtDNA marker in large watersheds.

The mitochondrial DNA 4,977-bp deletion and its implication in copy number alteration in colorectal cancer

Science.gov (United States)

2011-01-01

Background Qualitative and quantitative changes in human mitochondrial DNA (mtDNA) have been implicated in various cancer types. A 4,977 bp deletion in the major arch of the mitochondrial genome is one of the most common mutations associated with a variety of human diseases and aging. Methods We conducted a comprehensive study on clinical features and mtDNA of 104 colorectal cancer patients in the Wenzhou area of China. In particular, using a quantitative real time PCR method, we analyzed the 4,977 bp deletion and mtDNA content in tumor tissues and paired non-tumor areas from these patients. Results We found that the 4,977 bp deletion was more likely to be present in patients of younger age (≤65 years, p = 0.027). In patients with the 4,977 bp deletion, the deletion level decreased as the cancer stage advanced (p = 0.031). Moreover, mtDNA copy number in tumor tissues of patients with this deletion increased, both compared with that in adjacent non-tumor tissues and with in tumors of patients without the deletion. Such mtDNA content increase correlated with the levels of the 4,977 bp deletion and with cancer stage (p deletion may play a role in the early stage of colorectal cancer, and it is also implicated in alteration of mtDNA content in cancer cells. PMID:21232124

Additional mitochondrial DNA influences the interactions between the nuclear and mitochondrial genomes in a bovine embryo model of nuclear transfer.

Science.gov (United States)

Srirattana, Kanokwan; St John, Justin C

2018-05-08

We generated cattle embryos using mitochondrial supplementation and somatic cell nuclear transfer (SCNT), named miNT, to determine how additional mitochondrial DNA (mtDNA) modulates the nuclear genome. To eliminate any confounding effects from somatic cell mtDNA in intraspecies SCNT, donor cell mtDNA was depleted prior to embryo production. Additional oocyte mtDNA did not affect embryo development rates but increased mtDNA copy number in blastocyst stage embryos. Moreover, miNT-derived blastocysts had different gene expression profiles when compared with SCNT-derived blastocysts. Additional mtDNA increased expression levels of genes involved in oxidative phosphorylation, cell cycle and DNA repair. Supplementing the embryo culture media with a histone deacetylase inhibitor, Trichostatin A (TSA), had no beneficial effects on the development of miNT-derived embryos, unlike SCNT-derived embryos. When compared with SCNT-derived blastocysts cultured in the presence of TSA, additional mtDNA alone had beneficial effects as the activity of glycolysis may increase and embryonic cell death may decrease. However, these beneficial effects were not found with additional mtDNA and TSA together, suggesting that additional mtDNA alone enhances reprogramming. In conclusion, additional mtDNA increased mtDNA copy number and expression levels of genes involved in energy production and embryo development in blastocyst stage embryos emphasising the importance of nuclear-mitochondrial interactions.

In vitro-reconstituted nucleoids can block mitochondrial DNA replication and transcription.

Science.gov (United States)

Farge, Géraldine; Mehmedovic, Majda; Baclayon, Marian; van den Wildenberg, Siet M J L; Roos, Wouter H; Gustafsson, Claes M; Wuite, Gijs J L; Falkenberg, Maria

2014-07-10

The mechanisms regulating the number of active copies of mtDNA are still unclear. A mammalian cell typically contains 1,000-10,000 copies of mtDNA, which are packaged into nucleoprotein complexes termed nucleoids. The main protein component of these structures is mitochondrial transcription factor A (TFAM). Here, we reconstitute nucleoid-like particles in vitro and demonstrate that small changes in TFAM levels dramatically impact the fraction of DNA molecules available for transcription and DNA replication. Compaction by TFAM is highly cooperative, and at physiological ratios of TFAM to DNA, there are large variations in compaction, from fully compacted nucleoids to naked DNA. In compacted nucleoids, TFAM forms stable protein filaments on DNA that block melting and prevent progression of the replication and transcription machineries. Based on our observations, we suggest that small variations in the TFAM-to-mtDNA ratio may be used to regulate mitochondrial gene transcription and DNA replication. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.

Electronic cigarette aerosols and copper nanoparticles induce mitochondrial stress and promote DNA fragmentation in lung fibroblasts

Energy Technology Data Exchange (ETDEWEB)

Lerner, Chad A.; Rutagarama, Pierrot; Ahmad, Tanveer; Sundar, Isaac K.; Elder, Alison; Rahman, Irfan, E-mail: irfan_rahman@urmc.rochester.edu

2016-09-02

Oxidants or nanoparticles have recently been identified as constituents of aerosols released from various styles of electronic cigarettes (E-cigs). Cells in the lung may be directly exposed to these constituents and harbor reactive properties capable of incurring acute cell injury. Our results show mitochondria are sensitive to both E-cig aerosols and aerosol containing copper nanoparticles when exposed to human lung fibroblasts (HFL-1) using an Air-Liquid Interface culture system, evident by elevated levels of mitochondrial ROS (mtROS). Increased mtROS after aerosol exposure is associated with reduced stability of OxPhos electron transport chain (ETC) complex IV subunit and nuclear DNA fragmentation. Increased levels of IL-8 and IL-6 in HFL-1 conditioned media were also observed. These findings reveal both mitochondrial, genotoxic, and inflammatory stresses are features of direct cell exposure to E-cig aerosols which are ensued by inflammatory duress, raising a concern on deleterious effect of vaping. - Graphical abstract: Oxidants and possibly reactive properties of metal particles in E-cig aerosols impart mitochondrial oxidative stress and DNA damage. These biological effects accompany inflammatory response which may raise concern regarding long term E-cig use. Mitochondria may be particularly sensitive to reactive properties of E-cig aerosols in addition to the potential for them to induce genotoxic stress by generating increased ROS. - Highlights: • Mitochondria are sensitive to both E-cig aerosols and metal nanoparticles. • Increased mtROS by E-cig aerosol is associated with disrupted mitochondrial energy. • E-cig causes nuclear DNA fragmentation. • E-cig aerosols induce pro-inflammatory response in human fibroblasts.

Electronic cigarette aerosols and copper nanoparticles induce mitochondrial stress and promote DNA fragmentation in lung fibroblasts

International Nuclear Information System (INIS)

Lerner, Chad A.; Rutagarama, Pierrot; Ahmad, Tanveer; Sundar, Isaac K.; Elder, Alison; Rahman, Irfan

2016-01-01

Oxidants or nanoparticles have recently been identified as constituents of aerosols released from various styles of electronic cigarettes (E-cigs). Cells in the lung may be directly exposed to these constituents and harbor reactive properties capable of incurring acute cell injury. Our results show mitochondria are sensitive to both E-cig aerosols and aerosol containing copper nanoparticles when exposed to human lung fibroblasts (HFL-1) using an Air-Liquid Interface culture system, evident by elevated levels of mitochondrial ROS (mtROS). Increased mtROS after aerosol exposure is associated with reduced stability of OxPhos electron transport chain (ETC) complex IV subunit and nuclear DNA fragmentation. Increased levels of IL-8 and IL-6 in HFL-1 conditioned media were also observed. These findings reveal both mitochondrial, genotoxic, and inflammatory stresses are features of direct cell exposure to E-cig aerosols which are ensued by inflammatory duress, raising a concern on deleterious effect of vaping. - Graphical abstract: Oxidants and possibly reactive properties of metal particles in E-cig aerosols impart mitochondrial oxidative stress and DNA damage. These biological effects accompany inflammatory response which may raise concern regarding long term E-cig use. Mitochondria may be particularly sensitive to reactive properties of E-cig aerosols in addition to the potential for them to induce genotoxic stress by generating increased ROS. - Highlights: • Mitochondria are sensitive to both E-cig aerosols and metal nanoparticles. • Increased mtROS by E-cig aerosol is associated with disrupted mitochondrial energy. • E-cig causes nuclear DNA fragmentation. • E-cig aerosols induce pro-inflammatory response in human fibroblasts.

Adult mitochondrial DNA depletion syndrome with mild manifestations

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Josef Finsterer

2013-06-01

Full Text Available Mitochondrial DNA depletion syndrome (MDS is usually a severe disorder of infancy or childhood, due to a reduced copy number of mtDNA molecules. MDS with only mild, non-specific clinical manifestations and onset in adulthood has not been reported. A 47-year-old Caucasian female with short stature and a history of migraine, endometriosis, Crohn’s disease, C-cell carcinoma of the thyroid gland, and a family history positive for mitochondrial disorder (2 sisters, aunt, niece, developed day-time sleepiness, exercise intolerance, and myalgias in the lower-limb muscles since age 46y. She slept 9-10 hours during the night and 2 hours after lunch daily. Clinical exam revealed sore neck muscles, bilateral ptosis, and reduced Achilles tendon reflexes exclusively. Blood tests revealed hyperlipidemia exclusively. Nerve conduction studies, needle electromyography, and cerebral and spinal magnetic resonance imaging were non-informative. Muscle biopsy revealed detached lobulated fibers with subsarcolemmal accentuation of the NADH and SDH staining. Real-time polymerase chain reaction revealed depletion of the mtDNA down to 9% of normal. MDS may be associated with a mild phenotype in adults and may not significantly progress during the first year after onset. In an adult with hypersomnia, severe tiredness, exercise intolerance, and a family history positive for mitochondrial disorder, a MDS should be considered.

Adult cases of mitochondrial DNA depletion due to TK2 defect: an expanding spectrum.

Science.gov (United States)

Béhin, A; Jardel, C; Claeys, K G; Fagart, J; Louha, M; Romero, N B; Laforêt, P; Eymard, B; Lombès, A

2012-02-28

In this study we aim to demonstrate the occurrence of adult forms of TK2 mutations causing progressive mitochondrial myopathy with significant muscle mitochondrial DNA (mtDNA) depletion. Patients' investigations included serum creatine kinase, blood lactate, electromyographic, echocardiographic, and functional respiratory analyses as well as TK2 gene sequencing and TK2 activity measurement. Mitochondrial activities and mtDNA were analyzed in the patients' muscle biopsy. The 3 adult patients with TK2 mutations presented with slowly progressive myopathy compatible with a fairly normal life during decades. Apart from its much slower progression, these patients' phenotype closely resembled that of pediatric cases including early onset, absence of CNS symptoms, generalized muscle weakness predominating on axial and proximal muscles but affecting facial, ocular, and respiratory muscles, typical mitochondrial myopathy with a mosaic pattern of COX-negative and ragged-red fibers, combined mtDNA-dependent respiratory complexes deficiency and mtDNA depletion. In accordance with the disease's relatively slow progression, the residual mtDNA content was higher than that observed in pediatric cases. That difference was not explained by the type of the TK2 mutations or by the residual TK2 activity. TK2 mutations can cause mitochondrial myopathy with a slow progression. Comparison of patients with similar mutations but different disease progression might address potential mechanisms of mtDNA maintenance modulation.

Quantitative PCR analysis of diepoxybutane and epihalohydrin damage to nuclear versus mitochondrial DNA

Energy Technology Data Exchange (ETDEWEB)

LaRiviere, Frederick J. [Department of Chemistry, Washington and Lee University, Lexington, VA 24450 (United States); Newman, Adam G.; Watts, Megan L.; Bradley, Sharonda Q.; Juskewitch, Justin E. [Department of Chemistry, Colby College, 5757 Mayflower Hill Drive, Waterville, ME 04901 (United States); Greenwood, Paul G. [Department of Biology, Colby College, Waterville, ME 04901 (United States); Millard, Julie T., E-mail: jtmillar@colby.edu [Department of Chemistry, Colby College, 5757 Mayflower Hill Drive, Waterville, ME 04901 (United States)

2009-05-12

The bifunctional alkylating agents diepoxybutane (DEB) and epichlorohydrin (ECH) are linked to the elevated incidence of certain cancers among workers in the synthetic polymer industry. Both compounds form interstrand cross-links within duplex DNA, an activity suggested to contribute to their cytotoxicity. To assess the DNA targeting of these compounds in vivo, we assayed for damage within chicken erythro-progenitor cells at three different sites: one within mitochondrial DNA, one within expressed nuclear DNA, and one within unexpressed nuclear DNA. We determined the degree of damage at each site via a quantitative polymerase chain reaction, which compares amplification of control, untreated DNA to that from cells exposed to the agent in question. We found that ECH and the related compound epibromohydrin preferentially target nuclear DNA relative to mitochondrial DNA, whereas DEB reacts similarly with the two genomes. Decreased reactivity of the mitochondrial genome could contribute to the reduced apoptotic potential of ECH relative to DEB. Additionally, formation of lesions by all agents occurred at comparable levels for unexpressed and expressed nuclear loci, suggesting that alkylation is unaffected by the degree of chromatin condensation.

Quantitative PCR analysis of diepoxybutane and epihalohydrin damage to nuclear versus mitochondrial DNA

International Nuclear Information System (INIS)

LaRiviere, Frederick J.; Newman, Adam G.; Watts, Megan L.; Bradley, Sharonda Q.; Juskewitch, Justin E.; Greenwood, Paul G.; Millard, Julie T.

2009-01-01

The bifunctional alkylating agents diepoxybutane (DEB) and epichlorohydrin (ECH) are linked to the elevated incidence of certain cancers among workers in the synthetic polymer industry. Both compounds form interstrand cross-links within duplex DNA, an activity suggested to contribute to their cytotoxicity. To assess the DNA targeting of these compounds in vivo, we assayed for damage within chicken erythro-progenitor cells at three different sites: one within mitochondrial DNA, one within expressed nuclear DNA, and one within unexpressed nuclear DNA. We determined the degree of damage at each site via a quantitative polymerase chain reaction, which compares amplification of control, untreated DNA to that from cells exposed to the agent in question. We found that ECH and the related compound epibromohydrin preferentially target nuclear DNA relative to mitochondrial DNA, whereas DEB reacts similarly with the two genomes. Decreased reactivity of the mitochondrial genome could contribute to the reduced apoptotic potential of ECH relative to DEB. Additionally, formation of lesions by all agents occurred at comparable levels for unexpressed and expressed nuclear loci, suggesting that alkylation is unaffected by the degree of chromatin condensation.

Radiolabeled Cu-ATSM as a novel indicator of overreduced intracellular state due to mitochondrial dysfunction: studies with mitochondrial DNA-less ρ0 cells and cybrids carrying MELAS mitochondrial DNA mutation

International Nuclear Information System (INIS)

Yoshii, Yukie; Yoneda, Makoto; Ikawa, Masamichi; Furukawa, Takako; Kiyono, Yasushi; Mori, Tetsuya; Yoshii, Hiroshi; Oyama, Nobuyuki; Okazawa, Hidehiko; Saga, Tsuneo; Fujibayashi, Yasuhisa

2012-01-01

Objectives: Radiolabeled Cu-diacetyl-bis (N 4 -methylthiosemicarbazone) ( ⁎ Cu-ATSM), including 60/62/64 Cu-ATSM, is a potential imaging agent of hypoxic tumors for positron emission tomography (PET). We have reported that ⁎ Cu-ATSM is trapped in tumor cells under intracellular overreduced states, e.g., hypoxia. Here we evaluated ⁎ Cu-ATSM as an indicator of intracellular overreduced states in mitochondrial disorders using cell lines with mitochondrial dysfunction. Methods: Mitochondrial DNA-less ρ 0 206 cells; the parental 143B human osteosarcoma cells; the cybrids carrying mutated mitochondria from a patient of mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) (2SD); and that carrying wild-type one (2SA) were used. Cells were treated under normoxia or hypoxia, and 64 Cu-ATSM uptake was examined to compare it with levels of biological reductant NADH and NADPH. Results: ρ 0 206 cells showed higher 64 Cu-ATSM uptake than control 143B cells under normoxia, whereas 64 Cu-ATSM uptake was not significantly increased under hypoxia in ρ 0 206 cells. Additionally, 64 Cu-ATSM uptake showed correlate change to the NADH and NADPH levels, but not oxygenic conditions. 2SD cells showed increased 64 Cu-ATSM uptake under normoxia as compared with the control 2SA, and 64 Cu-ATSM uptake followed NADH and NADPH levels, but not oxygenic conditions. Conclusions: 64 Cu-ATSM accumulated in cells with overreduced states due to mitochondrial dysfunction, even under normoxia. We recently reported that 62 Cu-ATSM-PET can visualize stroke-like episodes maintaining oxygen supply in MELAS patients. Taken together, our data indicate that ⁎ Cu-ATSM uptake reflects overreduced intracellular states, despite oxygenic conditions; thus, ⁎ Cu-ATSM would be a promising marker of intracellular overreduced states for disorders with mitochondrial dysfunction, such as MELAS, Parkinson's disease and Alzheimer's disease.

Association between mitochondrial DNA variations and Alzheimer's Disease in the ADNI cohort

Science.gov (United States)

Lakatos, Anita; Derbeneva, Olga; Younes, Danny; Keator, David; Bakken, Trygve; Lvova, Maria; Brandon, Marty; Guffanti, Guia; Reglodi, Dora; Saykin, Andrew; Weiner, Michael; Macciardi, Fabio; Schork, Nicholas; Wallace, Douglas C.; Potkin, Steven G.

2010-01-01

Despite the central role of amyloid deposition in the development of Alzheimer's disease (AD), the pathogenesis of AD still remains elusive at the molecular level. Increasing evidence suggests that compromised mitochondrial function contributes to the aging process and thus may increase the risk of AD. Dysfunctional mitochondria contribute to reactive oxygen species (ROS) which can lead to extensive macromolecule oxidative damage and the progression of amyloid pathology. Oxidative stress and amyloid toxicity leave neurons chemically vulnerable. Because the brain relies on aerobic metabolism, it is apparent that mitochondria are critical for the cerebral function. Mitochondrial DNA sequence-changes could shift cell dynamics and facilitate neuronal vulnerability. Therefore we postulated that mitochondrial DNA sequence polymorphisms may increase the risk of AD. We evaluated the role of mitochondrial haplogroups derived from 138 mitochondrial polymorphisms in 358 Caucasian ADNI subjects. Our results indicate that the mitochondrial haplogroup UK may confer genetic susceptibility to AD independently of the APOE4 allele. PMID:20538375

Detection of novel polymorphisms in the mitochondrial DNA D-Loop ...

African Journals Online (AJOL)

aghomotsegin

2015-04-08

Apr 8, 2015 ... 1Department of Molecular Biology, Babylon University, Hilla City, Iraq. 2Babylon ... Mitochondrial DNA (mtDNA) is a useful genetic marker for answering .... to you for choosing the project, your enthusiasm for helping us ...

Packaging of single DNA molecules by the yeast mitochondrial protein Abf2p.

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Brewer, Laurence R; Friddle, Raymond; Noy, Aleksandr; Baldwin, Enoch; Martin, Shelley S; Corzett, Michele; Balhorn, Rod; Baskin, Ronald J

2003-10-01

Mitochondrial and nuclear DNA are packaged by proteins in a very different manner. Although protein-DNA complexes called "nucleoids" have been identified as the genetic units of mitochondrial inheritance in yeast and man, little is known about their physical structure. The yeast mitochondrial protein Abf2p was shown to be sufficient to compact linear dsDNA, without the benefit of supercoiling, using optical and atomic force microscopy single molecule techniques. The packaging of DNA by Abf2p was observed to be very weak as evidenced by a fast Abf2p off-rate (k(off) = 0.014 +/- 0.001 s(-1)) and the extremely small forces (<0.6 pN) stabilizing the condensed protein-DNA complex. Atomic force microscopy images of individual complexes showed the 190-nm structures are loosely packaged relative to nuclear chromatin. This organization may leave mtDNA accessible for transcription and replication, while making it more vulnerable to damage.

Therapeutic Targeting of the Mitochondria Initiates Excessive Superoxide Production and Mitochondrial Depolarization Causing Decreased mtDNA Integrity.

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Pokrzywinski, Kaytee L; Biel, Thomas G; Kryndushkin, Dmitry; Rao, V Ashutosh

2016-01-01

Mitochondrial dysregulation is closely associated with excessive reactive oxygen species (ROS) production. Altered redox homeostasis has been implicated in the onset of several diseases including cancer. Mitochondrial DNA (mtDNA) and proteins are particularly sensitive to ROS as they are in close proximity to the respiratory chain (RC). Mitoquinone (MitoQ), a mitochondria-targeted redox agent, selectively damages breast cancer cells possibly through damage induced via enhanced ROS production. However, the effects of MitoQ and other triphenylphosphonium (TPP+) conjugated agents on cancer mitochondrial homeostasis remain unknown. The primary objective of this study was to determine the impact of mitochondria-targeted agent [(MTAs) conjugated to TPP+: mitoTEMPOL, mitoquinone and mitochromanol-acetate] on mitochondrial physiology and mtDNA integrity in breast (MDA-MB-231) and lung (H23) cancer cells. The integrity of the mtDNA was assessed by quantifying the degree of mtDNA fragmentation and copy number, as well as by measuring mitochondrial proteins essential to mtDNA stability and maintenance (TFAM, SSBP1, TWINKLE, POLG and POLRMT). Mitochondrial status was evaluated by measuring superoxide production, mitochondrial membrane depolarization, oxygen consumption, extracellular acidification and mRNA or protein levels of the RC complexes along with TCA cycle activity. In this study, we demonstrated that all investigated MTAs impair mitochondrial health and decrease mtDNA integrity in MDA-MB-231 and H23 cells. However, differences in the degree of mitochondrial damage and mtDNA degradation suggest unique properties among each MTA that may be cell line, dose and time dependent. Collectively, our study indicates the potential for TPP+ conjugated molecules to impair breast and lung cancer cells by targeting mitochondrial homeostasis.

Genetic characteristics of mitochondrial DNA was associated with colorectal carcinogenesis and its prognosis.

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Jae-Ho Lee

Full Text Available Clinical value of mitochondrial DNA has been described in colorectal cancer (CRC. To clarify its role in colorectal carcinogenesis, mitochondrial microsatellite instability (mtMSI and other markers were investigated in CRCs and their precancerous lesions, as a multitier genetic study. DNA was isolated from paired normal and tumoral tissues in 78 tubular adenomas (TAs, 34 serrated polyps (SPs, and 100 CRCs. mtMSI, nucleus microsatellite instability (nMSI, KRAS mutation, and BRAF mutation were investigated in these tumors and their statistical analysis was performed. mtMSI was found in 30% of CRCs and 21.4% of precancerous lesions. Mitochondrial copy number was higher in SPs than TAs and it was associated with mtMSI in low grade TAs. KRAS and BRAF mutations were mutually exclusive in TAs and SPs. CRCs with mtMSI showed shorter overall survival times than the patients without mtMSI. In CRCs without nMSI or BRAF mutation, mtMSI was a more accurate marker for predicting prognosis. The genetic change of mitochondrial DNA is an early and independent event in colorectal precancerous lesions and mtMSI and mitochondrial contents are associated with the tubular adenoma-carcinoma sequence, resulting in poor prognosis. This result suggested that the genetic change in mitochondrial DNA appears to be a possible prognosis marker in CRC.

Oxidative damage of mitochondrial and nuclear DNA induced by ionizing radiation in human hepatoblastoma cells

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Morales, Albert; Miranda, Merce; Sanchez-Reyes, Alberto; Biete, Alberto; Fernandez-Checa, Jose C.

1998-01-01

Purpose: Since reactive oxygen species (ROS) act as mediators of radiation-induced cellular damage, the aim of our studies was to determine the effects of ionizing radiation on the regulation of hepatocellular reduced glutathione (GSH), survival and integrity of nuclear and mitochondrial DNA (mtDNA) in human hepatoblastoma cells (Hep G2) depleted of GSH prior to radiation. Methods and Materials: GSH, oxidized glutathione (GSSG), and generation of ROS were determined in irradiated (50-500 cGy) Hep G2 cells. Clonogenic survival, nuclear DNA fragmentation, and integrity of mtDNA were assessed in cells depleted of GSH prior to radiation. Results: Radiation of Hep G2 cells (50-400 cGy) resulted in a dose-dependent generation of ROS, an effect accompanied by a decrease of reduced GSH, ranging from a 15% decrease for 50 cGy to a 25% decrease for 400 cGy and decreased GSH/GSSG from a ratio of 17 to a ratio of 7 for controls and from 16 to 6 for diethyl maleate (DEM)-treated cells. Depletion of GSH prior to radiation accentuated the increase of ROS by 40-50%. The depletion of GSH by radiation was apparent in different subcellular sites, being particularly significant in mitochondria. Furthermore, depletion of nuclear GSH to 50-60% of initial values prior to irradiation (400 cGy) resulted in DNA fragmentation and apoptosis. Consequently, the survival of Hep G2 to radiation was reduced from 25% of cells not depleted of GSH to 10% of GSH-depleted cells. Fitting the survival rate of cells as a function of GSH using a theoretical model confirmed cellular GSH as a key factor in determining intrinsic sensitivity of Hep G2 cells to radiation. mtDNA displayed an increased susceptibility to the radiation-induced loss of integrity compared to nuclear DNA, an effect that was potentiated by GSH depletion in mitochondria (10-15% intact mtDNA in GSH-depleted cells vs. 25-30% of repleted cells). Conclusion: GSH plays a critical protective role in maintaining nuclear and mtDNA functional

Overexpression of mtDNA-associated AtWhy2 compromises mitochondrial function

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Abou-Rached Charbel

2008-04-01

Full Text Available Abstract Background StWhy1, a member of the plant-specific Whirly single-stranded DNA-binding protein family, was first characterized as a transcription factor involved in the activation of the nuclear PR-10a gene following defense-related stress in potato. In Arabidopsis thaliana, Whirlies have recently been shown to be primarily localized in organelles. Two representatives of the family, AtWhy1 and AtWhy3 are imported into plastids while AtWhy2 localizes to mitochondria. Their function in organelles is currently unknown. Results To understand the role of mitochondrial Whirlies in higher plants, we produced A. thaliana lines with altered expression of the atwhy2 gene. Organellar DNA immunoprecipitation experiments demonstrated that AtWhy2 binds to mitochondrial DNA. Overexpression of atwhy2 in plants perturbs mitochondrial function by causing a diminution in transcript levels and mtDNA content which translates into a low activity level of respiratory chain complexes containing mtDNA-encoded subunits. This lowered activity of mitochondria yielded plants that were reduced in size and had distorted leaves that exhibited accelerated senescence. Overexpression of atwhy2 also led to early accumulation of senescence marker transcripts in mature leaves. Inactivation of the atwhy2 gene did not affect plant development and had no detectable effect on mitochondrial morphology, activity of respiratory chain complexes, transcription or the amount of mtDNA present. This lack of phenotype upon abrogation of atwhy2 expression suggests the presence of functional homologues of the Whirlies or the activation of compensating mechanisms in mitochondria. Conclusion AtWhy2 is associated with mtDNA and its overexpression results in the production of dysfunctional mitochondria. This report constitutes the first evidence of a function for the Whirlies in organelles. We propose that they could play a role in the regulation of the gene expression machinery of organelles.

Mitochondrial DNA Depletion in Respiratory Chain–Deficient Parkinson Disease Neurons

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Rygiel, Karolina A.; Hepplewhite, Philippa D.; Morris, Christopher M.; Picard, Martin; Turnbull, Doug M.

2016-01-01

Objective To determine the extent of respiratory chain abnormalities and investigate the contribution of mtDNA to the loss of respiratory chain complexes (CI–IV) in the substantia nigra (SN) of idiopathic Parkinson disease (IPD) patients at the single‐neuron level. Methods Multiple‐label immunofluorescence was applied to postmortem sections of 10 IPD patients and 10 controls to quantify the abundance of CI–IV subunits (NDUFB8 or NDUFA13, SDHA, UQCRC2, and COXI) and mitochondrial transcription factors (TFAM and TFB2M) relative to mitochondrial mass (porin and GRP75) in dopaminergic neurons. To assess the involvement of mtDNA in respiratory chain deficiency in IPD, SN neurons, isolated with laser‐capture microdissection, were assayed for mtDNA deletions, copy number, and presence of transcription/replication‐associated 7S DNA employing a triplex real‐time polymerase chain reaction (PCR) assay. Results Whereas mitochondrial mass was unchanged in single SN neurons from IPD patients, we observed a significant reduction in the abundances of CI and II subunits. At the single‐cell level, CI and II deficiencies were correlated in patients. The CI deficiency concomitantly occurred with low abundances of the mtDNA transcription factors TFAM and TFB2M, which also initiate transcription‐primed mtDNA replication. Consistent with this, real‐time PCR analysis revealed fewer transcription/replication‐associated mtDNA molecules and an overall reduction in mtDNA copy number in patients. This effect was more pronounced in single IPD neurons with severe CI deficiency. Interpretation Respiratory chain dysfunction in IPD neurons not only involves CI, but also extends to CII. These deficiencies are possibly a consequence of the interplay between nDNA and mtDNA‐encoded factors mechanistically connected via TFAM. ANN NEUROL 2016;79:366–378 PMID:26605748

Somatic mitochondrial DNA mutations in cancer escape purifying selection and high pathogenicity mutations lead to the oncocytic phenotype: pathogenicity analysis of reported somatic mtDNA mutations in tumors

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Pereira, Luísa; Soares, Pedro; Máximo, Valdemar; Samuels, David C

2012-01-01

The presence of somatic mitochondrial DNA (mtDNA) mutations in cancer cells has been interpreted in controversial ways, ranging from random neutral accumulation of mutations, to positive selection for high pathogenicity, or conversely to purifying selection against high pathogenicity variants as occurs at the population level. Here we evaluated the predicted pathogenicity of somatic mtDNA mutations described in cancer and compare these to the distribution of variations observed in the global human population and all possible protein variations that could occur in human mtDNA. We focus on oncocytic tumors, which are clearly associated with mitochondrial dysfunction. The protein variant pathogenicity was predicted using two computational methods, MutPred and SNPs&GO. The pathogenicity score of the somatic mtDNA variants were significantly higher in oncocytic tumors compared to non-oncocytic tumors. Variations in subunits of Complex I of the electron transfer chain were significantly more common in tumors with the oncocytic phenotype, while variations in Complex V subunits were significantly more common in non-oncocytic tumors. Our results show that the somatic mtDNA mutations reported over all tumors are indistinguishable from a random selection from the set of all possible amino acid variations, and have therefore escaped the effects of purifying selection that act strongly at the population level. We show that the pathogenicity of somatic mtDNA mutations is a determining factor for the oncocytic phenotype. The opposite associations of the Complex I and Complex V variants with the oncocytic and non-oncocytic tumors implies that low mitochondrial membrane potential may play an important role in determining the oncocytic phenotype

Mitochondrial Respiration Is Reduced in Atherosclerosis, Promoting Necrotic Core Formation and Reducing Relative Fibrous Cap Thickness.

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Yu, Emma P K; Reinhold, Johannes; Yu, Haixiang; Starks, Lakshi; Uryga, Anna K; Foote, Kirsty; Finigan, Alison; Figg, Nichola; Pung, Yuh-Fen; Logan, Angela; Murphy, Michael P; Bennett, Martin

2017-12-01

Mitochondrial DNA (mtDNA) damage is present in murine and human atherosclerotic plaques. However, whether endogenous levels of mtDNA damage are sufficient to cause mitochondrial dysfunction and whether decreasing mtDNA damage and improving mitochondrial respiration affects plaque burden or composition are unclear. We examined mitochondrial respiration in human atherosclerotic plaques and whether augmenting mitochondrial respiration affects atherogenesis. Human atherosclerotic plaques showed marked mitochondrial dysfunction, manifested as reduced mtDNA copy number and oxygen consumption rate in fibrous cap and core regions. Vascular smooth muscle cells derived from plaques showed impaired mitochondrial respiration, reduced complex I expression, and increased mitophagy, which was induced by oxidized low-density lipoprotein. Apolipoprotein E-deficient (ApoE -/- ) mice showed decreased mtDNA integrity and mitochondrial respiration, associated with increased mitochondrial reactive oxygen species. To determine whether alleviating mtDNA damage and increasing mitochondrial respiration affects atherogenesis, we studied ApoE -/- mice overexpressing the mitochondrial helicase Twinkle (Tw + /ApoE -/- ). Tw + /ApoE -/- mice showed increased mtDNA integrity, copy number, respiratory complex abundance, and respiration. Tw + /ApoE -/- mice had decreased necrotic core and increased fibrous cap areas, and Tw + /ApoE -/- bone marrow transplantation also reduced core areas. Twinkle increased vascular smooth muscle cell mtDNA integrity and respiration. Twinkle also promoted vascular smooth muscle cell proliferation and protected both vascular smooth muscle cells and macrophages from oxidative stress-induced apoptosis. Endogenous mtDNA damage in mouse and human atherosclerosis is associated with significantly reduced mitochondrial respiration. Reducing mtDNA damage and increasing mitochondrial respiration decrease necrotic core and increase fibrous cap areas independently of changes in

Complete DNA sequence of the linear mitochondrial genome of the pathogenic yeast Candida parapsilosis

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Nosek, J.; Novotna, M.; Hlavatovicova, Z.

2004-01-01

The complete sequence of the mitochondrial DNA of the opportunistic yeast pathogen Candida parapsilosis was determined. The mitochondrial genome is represented by linear DNA molecules terminating with tandem repeats of a 738-bp unit. The number of repeats varies, thus generating a population...

Running on empty: does mitochondrial DNA mutation limit replicative lifespan in yeast?: Mutations that increase the division rate of cells lacking mitochondrial DNA also extend replicative lifespan in Saccharomyces cerevisiae.

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Dunn, Cory D

2011-10-01

Mitochondrial DNA (mtDNA) mutations escalate with increasing age in higher organisms. However, it has so far been difficult to experimentally determine whether mtDNA mutation merely correlates with age or directly limits lifespan. A recent study shows that budding yeast can also lose functional mtDNA late in life. Interestingly, independent studies of replicative lifespan (RLS) and of mtDNA-deficient cells show that the same mutations can increase both RLS and the division rate of yeast lacking the mitochondrial genome. These exciting, parallel findings imply a potential causal relationship between mtDNA mutation and replicative senescence. Furthermore, these results suggest more efficient methods for discovering genes that determine lifespan. Copyright © 2011 WILEY Periodicals, Inc.

Detection of mitochondrial DNA with the compact bead array sensor system (cBASS)

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Mulvaney, Shawn P.; Ibe, Carol N.; Caldwell, Jane M.; Levine, Jay F.; Whitman, Lloyd J.; Tamanaha, Cy R.

2009-02-01

Enteric pathogens are a significant contaminant in surface waters used for recreation, fish and shellfish harvesting, crop irrigation, and human consumption. The need for water monitoring becomes more pronounced when industrial, agricultural, and residential lands are found in close proximity. Fecal contamination is particularly problematic and identification of the pollution source essential to remediation efforts. Standard monitoring for fecal contamination relies on indicator organisms, but the technique is too broad to identify the source of contamination. Instead, real-time PCR of mitochondrial DNA (mtDNA) is an emerging method for identification of the contamination source. Presented herein, we evaluate an alternative technology, the compact Bead Array Sensor System (cBASS®) and its assay approach Fluidic Force Discrimination (FFD), for the detection of mtDNA. Previously, we achieved multiplexed, attomolar detection of toxins and femtomolar detection of nucleic acids in minutes with FFD assays. More importantly, FFD assays are compatible with a variety of complex matrices and therefore potentially applicable for samples where the matrix would interfere with PCR amplification. We have designed a triplex assay for the NADH gene found in human, swine, and bovine mtDNA and demonstrated the specific detection of human mtDNA spiked into a waste water sample.

As deficiências auditivas relacionadas às alterações do DNA mitocondrial. Hearing loss related to mitochondrial DNA changes

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Maria F. P. de Carvalho

2002-03-01

Full Text Available A deficiência auditiva é sintoma comum que pode apresentar várias etiologias, entre elas as causadas por alterações genéticas. As mutações genéticas podem ocorrer em genes nucleares e mitocondriais. A mitocôndria, uma organela intracelular, tem o seu próprio genoma (DNA, que é uma molécula circular e é transmitido exclusivamente pela mãe. As mutações do DNA mitocondrial são transmitidas pela linhagem materna, mas podem ocorrer mutações espontâneas. O fenótipo, ou expressão clínica, da mutação mitocondrial vai depender da quantidade de DNA mitocondrial mutante existente na célula, situação conhecida como heteroplasmia. A mitocôndria tem a função de disponibilizar energia para as células sob a forma de ATP (trifosfato de adenosina. Os órgãos que requerem grande quantidade de energia são mais comumente acometidos em casos de mutações do DNA mitocondrial, como células nervosas, musculares, endócrinas, ópticas e auditivas. Como a cóclea é grande consumidora de energia, uma mutação no DNA mitocondrial de células ciliadas causa deficiência auditiva do tipo neurossensorial, bilateral, simétrica e progressiva. As deficiências auditivas causadas por mutações no DNA mitocondrial correspondem a 0,5% a 1% de todas as deficiências auditivas de origem genética. Foi realizada uma extensa revisão bibliográfica, a fim de estudar as deficiências auditivas causadas por alterações no DNA mitocondrial. A deficiência auditiva pode se apresentar na forma isolada (forma não sindrômica, como nos casos de hiper-sensibilidade aos antibióticos aminoglicosídeos e presbiacusia, ou associada a outras doenças (forma sindrômica, como na síndrome de Kearns-Sayre e diabete e surdez de herança materna.Hearing loss is a common symptom that may be manifested by many etiologies and it is frequently associated to genetic problems. Genetic mutations may occur in nuclear or mitochondrial genes. Mitochondria are

Thymidine kinase 2 enzyme kinetics elucidate the mechanism of thymidine-induced mitochondrial DNA depletion.

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Sun, Ren; Wang, Liya

2014-10-07

Mitochondrial thymidine kinase 2 (TK2) is a nuclear gene-encoded protein, synthesized in the cytosol and subsequently translocated into the mitochondrial matrix, where it catalyzes the phosphorylation of thymidine (dT) and deoxycytidine (dC). The kinetics of dT phosphorylation exhibits negative cooperativity, but dC phosphorylation follows hyperbolic Michaelis-Menten kinetics. The two substrates compete with each other in that dT is a competitive inhibitor of dC phosphorylation, while dC acts as a noncompetitive inhibitor of dT phosphorylation. In addition, TK2 is feedback inhibited by dTTP and dCTP. TK2 also phosphorylates a number of pyrimidine nucleoside analogues used in antiviral and anticancer therapy and thus plays an important role in mitochondrial toxicities caused by nucleoside analogues. Deficiency in TK2 activity due to genetic alterations causes devastating mitochondrial diseases, which are characterized by mitochondrial DNA (mtDNA) depletion or multiple deletions in the affected tissues. Severe TK2 deficiency is associated with early-onset fatal mitochondrial DNA depletion syndrome, while less severe deficiencies result in late-onset phenotypes. In this review, studies of the enzyme kinetic behavior of TK2 enzyme variants are used to explain the mechanism of mtDNA depletion caused by TK2 mutations, thymidine overload due to thymidine phosphorylase deficiency, and mitochondrial toxicity caused by antiviral thymidine analogues.

Is There Still Any Role for Oxidative Stress in Mitochondrial DNA-Dependent Aging?

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Gábor Zsurka

2018-03-01

Full Text Available Recent deep sequencing data has provided compelling evidence that the spectrum of somatic point mutations in mitochondrial DNA (mtDNA in aging tissues lacks G > T transversion mutations. This fact cannot, however, be used as an argument for the missing contribution of reactive oxygen species (ROS to mitochondria-related aging because it is probably caused by the nucleotide selectivity of mitochondrial DNA polymerase γ (POLG. In contrast to point mutations, the age-dependent accumulation of mitochondrial DNA deletions is, in light of recent experimental data, still explainable by the segregation of mutant molecules generated by the direct mutagenic effects of ROS (in particular, of HO· radicals formed from H2O2 by a Fenton reaction. The source of ROS remains controversial, because the mitochondrial contribution to tissue ROS production is probably lower than previously thought. Importantly, in the discussion about the potential role of oxidative stress in mitochondria-dependent aging, ROS generated by inflammation-linked processes and the distribution of free iron also require careful consideration.

Influence of erythrocyte oxygenation and intravascular ATP on resting and exercising skeletal muscle blood flow in humans with mitochondrial myopathy

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Jeppesen, Tina D; Vissing, John; González-Alonso, José

2012-01-01

Oxygen (O(2)) extraction is impaired in exercising skeletal muscle of humans with mutations of mitochondrial DNA (mtDNA), but the muscle hemodynamic response to exercise has never been directly investigated. This study sought to examine the extent to which human skeletal muscle perfusion can incr...

TDP1 repairs nuclear and mitochondrial DNA damage induced by chain-terminating anticancer and antiviral nucleoside analogs

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Huang, Shar-yin N.; Murai, Junko; Dalla Rosa, Ilaria; Dexheimer, Thomas S.; Naumova, Alena; Gmeiner, William H.; Pommier, Yves

2013-01-01

Chain-terminating nucleoside analogs (CTNAs) that cause stalling or premature termination of DNA replication forks are widely used as anticancer and antiviral drugs. However, it is not well understood how cells repair the DNA damage induced by these drugs. Here, we reveal the importance of tyrosyl–DNA phosphodiesterase 1 (TDP1) in the repair of nuclear and mitochondrial DNA damage induced by CTNAs. On investigating the effects of four CTNAs—acyclovir (ACV), cytarabine (Ara-C), zidovudine (AZT) and zalcitabine (ddC)—we show that TDP1 is capable of removing the covalently linked corresponding CTNAs from DNA 3′-ends. We also show that Tdp1−/− cells are hypersensitive and accumulate more DNA damage when treated with ACV and Ara-C, implicating TDP1 in repairing CTNA-induced DNA damage. As AZT and ddC are known to cause mitochondrial dysfunction, we examined whether TDP1 repairs the mitochondrial DNA damage they induced. We find that AZT and ddC treatment leads to greater depletion of mitochondrial DNA in Tdp1−/− cells. Thus, TDP1 seems to be critical for repairing nuclear and mitochondrial DNA damage caused by CTNAs. PMID:23775789

Potential efficacy of mitochondrial genes for animal DNA barcoding: a case study using eutherian mammals.

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Luo, Arong; Zhang, Aibing; Ho, Simon Yw; Xu, Weijun; Zhang, Yanzhou; Shi, Weifeng; Cameron, Stephen L; Zhu, Chaodong

2011-01-28

A well-informed choice of genetic locus is central to the efficacy of DNA barcoding. Current DNA barcoding in animals involves the use of the 5' half of the mitochondrial cytochrome oxidase 1 gene (CO1) to diagnose and delimit species. However, there is no compelling a priori reason for the exclusive focus on this region, and it has been shown that it performs poorly for certain animal groups. To explore alternative mitochondrial barcoding regions, we compared the efficacy of the universal CO1 barcoding region with the other mitochondrial protein-coding genes in eutherian mammals. Four criteria were used for this comparison: the number of recovered species, sequence variability within and between species, resolution to taxonomic levels above that of species, and the degree of mutational saturation. Based on 1,179 mitochondrial genomes of eutherians, we found that the universal CO1 barcoding region is a good representative of mitochondrial genes as a whole because the high species-recovery rate (> 90%) was similar to that of other mitochondrial genes, and there were no significant differences in intra- or interspecific variability among genes. However, an overlap between intra- and interspecific variability was still problematic for all mitochondrial genes. Our results also demonstrated that any choice of mitochondrial gene for DNA barcoding failed to offer significant resolution at higher taxonomic levels. We suggest that the CO1 barcoding region, the universal DNA barcode, is preferred among the mitochondrial protein-coding genes as a molecular diagnostic at least for eutherian species identification. Nevertheless, DNA barcoding with this marker may still be problematic for certain eutherian taxa and our approach can be used to test potential barcoding loci for such groups.

Sequence polymorphism data of the hypervariable regions of mitochondrial DNA in the Yadav population of Haryana.

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Verma, Kapil; Sharma, Sapna; Sharma, Arun; Dalal, Jyoti; Bhardwaj, Tapeshwar

2018-06-01

Genetic variations among humans occur both within and among populations and range from single nucleotide changes to multiple-nucleotide variants. These multiple-nucleotide variants are useful for studying the relationships among individuals or various population groups. The study of human genetic variations can help scientists understand how different population groups are biologically related to one another. Sequence analysis of hypervariable regions of human mitochondrial DNA (mtDNA) has been successfully used for the genetic characterization of different population groups for forensic purposes. It is well established that different ethnic or population groups differ significantly in their mtDNA distributions. In the last decade, very little research has been conducted on mtDNA variations in the Indian population, although such data would be useful for elucidating the history of human population expansion across the world. Moreover, forensic studies on mtDNA variations in the Indian subcontinent are also scarce, particularly in the northern part of India. In this report, variations in the hypervariable regions of mtDNA were analyzed in the Yadav population of Haryana. Different molecular diversity indices were computed. Further, the obtained haplotypes were classified into different haplogroups and the phylogenetic relationship between different haplogroups was inferred.

Interspecies hybridization on DNA resequencing microarrays: efficiency of sequence recovery and accuracy of SNP detection in human, ape, and codfish mitochondrial DNA genomes sequenced on a human-specific MitoChip

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Carr Steven M

2007-09-01

Full Text Available Abstract Background Iterative DNA "resequencing" on oligonucleotide microarrays offers a high-throughput method to measure intraspecific biodiversity, one that is especially suited to SNP-dense gene regions such as vertebrate mitochondrial (mtDNA genomes. However, costs of single-species design and microarray fabrication are prohibitive. A cost-effective, multi-species strategy is to hybridize experimental DNAs from diverse species to a common microarray that is tiled with oligonucleotide sets from multiple, homologous reference genomes. Such a strategy requires that cross-hybridization between the experimental DNAs and reference oligos from the different species not interfere with the accurate recovery of species-specific data. To determine the pattern and limits of such interspecific hybridization, we compared the efficiency of sequence recovery and accuracy of SNP identification by a 15,452-base human-specific microarray challenged with human, chimpanzee, gorilla, and codfish mtDNA genomes. Results In the human genome, 99.67% of the sequence was recovered with 100.0% accuracy. Accuracy of SNP identification declines log-linearly with sequence divergence from the reference, from 0.067 to 0.247 errors per SNP in the chimpanzee and gorilla genomes, respectively. Efficiency of sequence recovery declines with the increase of the number of interspecific SNPs in the 25b interval tiled by the reference oligonucleotides. In the gorilla genome, which differs from the human reference by 10%, and in which 46% of these 25b regions contain 3 or more SNP differences from the reference, only 88% of the sequence is recoverable. In the codfish genome, which differs from the reference by > 30%, less than 4% of the sequence is recoverable, in short islands ≥ 12b that are conserved between primates and fish. Conclusion Experimental DNAs bind inefficiently to homologous reference oligonucleotide sets on a re-sequencing microarray when their sequences differ by

A comprehensive characterization of mitochondrial DNA mutations in glioblastoma multiforme.

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Vidone, Michele; Clima, Rosanna; Santorsola, Mariangela; Calabrese, Claudia; Girolimetti, Giulia; Kurelac, Ivana; Amato, Laura Benedetta; Iommarini, Luisa; Trevisan, Elisa; Leone, Marco; Soffietti, Riccardo; Morra, Isabella; Faccani, Giuliano; Attimonelli, Marcella; Porcelli, Anna Maria; Gasparre, Giuseppe

2015-06-01

Glioblastoma multiforme (GBM) is the most malignant brain cancer in adults, with a poor prognosis, whose molecular stratification still represents a challenge in pathology and clinics. On the other hand, mitochondrial DNA (mtDNA) mutations have been found in most tumors as modifiers of the bioenergetics state, albeit in GBM a characterization of the mtDNA status is lacking to date. Here, a characterization of the burden of mtDNA mutations in GBM samples was performed. First, investigation of tumor-specific vs. non tumor-specific mutations was carried out with the MToolBox bioinformatics pipeline by analyzing 45 matched tumor/blood samples, from whole genome or whole exome sequencing datasets obtained from The Cancer Genome Atlas (TCGA) consortium. Additionally, the entire mtDNA sequence was obtained in a dataset of 104 fresh-frozen GBM samples. Mitochondrial mutations with potential pathogenic interest were prioritized based on heteroplasmic fraction, nucleotide variability, and in silico prediction of pathogenicity. A preliminary biochemical analysis of the activity of mitochondrial respiratory complexes was also performed on fresh-frozen GBM samples. Although a high number of mutations was detected, we report that the large majority of them does not pass the prioritization filters. Therefore, a relatively limited burden of pathogenic mutations is indeed carried by GBM, which did not appear to determine a general impairment of the respiratory chain. This article is part of a Directed Issue entitled: Energy Metabolism Disorders and Therapies. Copyright © 2015 Elsevier Ltd. All rights reserved.

Mitochondrial Diseases: Clinical Features- Management of Patients

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Filiz Koc

2003-02-01

Full Text Available Mitochondria are unique organells which their own DNA in cells. Human mitochondrial DNA is circular, double-stranded molecule and small. Because all mitochondria are contributed by the ovum during the formation of the zygote, the mitochondrial genom is transmitted by maternal inheritance. Multisystem disorders such as deafness, cardiomyopathy, miyopathy can be seen in mitochondrial diseases. [Archives Medical Review Journal 2003; 12(0.100: 14-31

High-resolution mitochondrial DNA analysis sheds light on human diversity, cultural interactions, and population mobility in Northwestern Amazonia.

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Arias, Leonardo; Barbieri, Chiara; Barreto, Guillermo; Stoneking, Mark; Pakendorf, Brigitte

2018-02-01

Northwestern Amazonia (NWA) is a center of high linguistic and cultural diversity. Several language families and linguistic isolates occur in this region, as well as different subsistence patterns, with some groups being foragers and others agriculturalists. In addition, speakers of Eastern Tukanoan languages are known for practicing linguistic exogamy, a marriage system in which partners are taken from different language groups. In this study, we use high-resolution mitochondrial DNA sequencing to investigate the impact of this linguistic and cultural diversity on the genetic relationships and population structure of NWA groups. We collected saliva samples from individuals representing 40 different NWA ethnolinguistic groups and sequenced 439 complete mitochondrial genomes to an average coverage of 1,030×. The mtDNA data revealed that NWA populations have high genetic diversity with extensive sharing of haplotypes among groups. Moreover, groups who practice linguistic exogamy have higher genetic diversity, while the foraging Nukak have lower genetic diversity. We also find that rivers play a more important role than either geography or language affiliation in structuring the genetic relationships of populations. Contrary to the view of NWA as a pristine area inhabited by small human populations living in isolation, our data support a view of high diversity and contact among different ethnolinguistic groups, with movement along rivers probably facilitating this contact. Additionally, we provide evidence for the impact of cultural practices, such as linguistic exogamy, on patterns of genetic variation. Overall, this study provides new data and insights into a remote and little-studied region of the world. © 2017 Wiley Periodicals, Inc.

Mitochondrial Targeted Endonuclease III DNA Repair Enzyme Protects against Ventilator Induced Lung Injury in Mice

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Masahiro Hashizume

2014-08-01

Full Text Available The mitochondrial targeted DNA repair enzyme, 8-oxoguanine DNA glycosylase 1, was previously reported to protect against mitochondrial DNA (mtDNA damage and ventilator induced lung injury (VILI. In the present study we determined whether mitochondrial targeted endonuclease III (EndoIII which cleaves oxidized pyrimidines rather than purines from damaged DNA would also protect the lung. Minimal injury from 1 h ventilation at 40 cmH2O peak inflation pressure (PIP was reversed by EndoIII pretreatment. Moderate lung injury due to ventilation for 2 h at 40 cmH2O PIP produced a 25-fold increase in total extravascular albumin space, a 60% increase in W/D weight ratio, and marked increases in MIP-2 and IL-6. Oxidative mtDNA damage and decreases in the total tissue glutathione (GSH and the GSH/GSSH ratio also occurred. All of these indices of injury were attenuated by mitochondrial targeted EndoIII. Massive lung injury caused by 2 h ventilation at 50 cmH2O PIP was not attenuated by EndoIII pretreatment, but all untreated mice died prior to completing the two hour ventilation protocol, whereas all EndoIII-treated mice lived for the duration of ventilation. Thus, mitochondrial targeted DNA repair enzymes were protective against mild and moderate lung damage and they enhanced survival in the most severely injured group.

Using mitochondrial DNA to test the hypothesis of a European post-glacial human recolonization from the Franco-Cantabrian refuge.

Science.gov (United States)

García, O; Fregel, R; Larruga, J M; Álvarez, V; Yurrebaso, I; Cabrera, V M; González, A M

2011-01-01

It has been proposed that the distribution patterns and coalescence ages found in Europeans for mitochondrial DNA (mtDNA) haplogroups V, H1 and H3 are the result of a post-glacial expansion from a Franco-Cantabrian refuge that recolonized central and northern areas. In contrast, in this refined mtDNA study of the Cantabrian Cornice that contributes 413 partial and 9 complete new mtDNA sequences, including a large Basque sample and a sample of Asturians, no experimental evidence was found to support the human refuge-expansion theory. In fact, all measures of gene diversity point to the Cantabrian Cornice in general and the Basques in particular, as less polymorphic for V, H1 and H3 than other southern regions in Iberia or in Central Europe. Genetic distances show the Cantabrian Cornice is a very heterogeneous region with significant local differences. The analysis of several minor subhaplogroups, based on complete sequences, also suggests different focal expansions over a local and peninsular range that did not affect continental Europe. Furthermore, all detected clinal trends show stronger longitudinal than latitudinal profiles. In Northern Iberia, it seems that the highest diversity values for some haplogroups with Mesolithic coalescence ages are centred on the Mediterranean side, including Catalonia and South-eastern France.

The potential role for use of mitochondrial DNA copy number as predictive biomarker in presbycusis

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Falah M

2016-10-01

Full Text Available Masoumeh Falah,1,2 Massoud Houshmand,3 Mohammad Najafi,2 Maryam Balali,1 Saeid Mahmoudian,1 Alimohamad Asghari,4 Hessamaldin Emamdjomeh,1 Mohammad Farhadi1 1ENT and Head & Neck Research Center and Department, Iran University of Medical Sciences, Tehran, Iran; 2Cellular and Molecular Research Center, Biochemistry Department, Iran University of Medical Sciences, Tehran, Iran; 3Department of Medical Genetics, National Institute for Genetic Engineering and Biotechnology, Tehran, Iran; 4Skull base research center, Iran University of Medical Sciences, Tehran, Iran Objectives: Age-related hearing impairment, or presbycusis, is the most common communication disorder and neurodegenerative disease in the elderly. Its prevalence is expected to increase, due to the trend of growth of the elderly population. The current diagnostic test for detection of presbycusis is implemented after there has been a change in hearing sensitivity. Identification of a pre-diagnostic biomarker would raise the possibility of preserving hearing sensitivity before damage occurs. Mitochondrial dysfunction, including the production of reactive oxygen species and induction of expression of apoptotic genes, participates in the progression of presbycusis. Mitochondrial DNA sequence variation has a critical role in presbycusis. However, the nature of the relationship between mitochondrial DNA copy number, an important biomarker in many other diseases, and presbycusis is undetermined.Methods: Fifty-four subjects with presbycusis and 29 healthy controls were selected after ear, nose, throat examination and pure-tone audiometry. DNA was extracted from peripheral blood samples. The copy number of mitochondrial DNA relative to the nuclear genome was measured by quantitative real-time polymerase chain reaction.Results: Subjects with presbycusis had a lower median mitochondrial DNA copy number than healthy subjects and the difference was statistically significant (P=0.007. Mitochondrial DNA

Does aerobic exercises induce mtDNA mutation in human blood ...

African Journals Online (AJOL)

The aim of this study was to determine the effect of eight weeks aerobic training on mitochondrial DNA (mtDNA) mutation in human blood leucocytes. Twenty untrained healthy students (training group: n =10, age = 20.7±1.5 yrs, weight = 67.7±10 kg, BF% = 17.5±7.35 & control group: n =10, age = 21±1.3 yrs, weight ...

MitoBamAnnotator: A web-based tool for detecting and annotating heteroplasmy in human mitochondrial DNA sequences.

Science.gov (United States)

Zhidkov, Ilia; Nagar, Tal; Mishmar, Dan; Rubin, Eitan

2011-11-01

The use of Next-Generation Sequencing of mitochondrial DNA is becoming widespread in biological and clinical research. This, in turn, creates a need for a convenient tool that detects and analyzes heteroplasmy. Here we present MitoBamAnnotator, a user friendly web-based tool that allows maximum flexibility and control in heteroplasmy research. MitoBamAnnotator provides the user with a comprehensively annotated overview of mitochondrial genetic variation, allowing for an in-depth analysis with no prior knowledge in programming. Copyright © 2011 Elsevier B.V. and Mitochondria Research Society. All rights reserved. All rights reserved.

Mitochondrial DNA variation in brood stocks of the lake trout

International Nuclear Information System (INIS)

Grewe, P.M.; Hebert, P.D.N.

1986-01-01

Efforts are in progress to restore lake trout populations in the Great Lakes from hatchery stocks. In most cases, plantings include a variety of brood stocks that originated from different portions of the Great Lakes. Members of the various stocks can be differentially fin clipped to permit comparison of their survival success, but this does not allow assessment of their reproductive capability in the wild. Assessment of reproductive success requires the existence of genetic markers between brook stocks which will ideally persist over many generations. Efforts to identify allozyme differences between brood stocks have met with little success. The present investigation has employed an alternative technique to identify genetic markers--the restriction analysis of mitochondrial DNA. Mitochondiral DNA analysis of 7 lake trout brood stocks has revealed the existence of 10 mitochondrial clones falling into 3 major groups. The results indicate that mt-DNA markers have great potential for brood stock management. Genetic variability in the nuclear genome of each stock can be maintained by utilizing a large number of male parents, while restricting female parents to members of a single mitochondrial clone. Genetically marked fry could then be produced with only minor shifts in hatchery management

Mitochondrial DNA repair and association with aging- an update

DEFF Research Database (Denmark)

Diaz, Ricardo Gredilla; Bohr, Vilhelm; Stevnsner, Tinna V.

2010-01-01

in the aging process and to be particularly deleterious in post-mitotic cells. Thus, DNA repair is an important mechanism for maintenance of genomic integrity. Despite the importance of mitochondria in the aging process, it was thought for many years that mitochondria lacked an enzymatic DNA repair system...... proteins and novel DNA repair pathways, thought to be exclusively present in the nucleus, have recently been described also to be present in mitochondria. Here we review the main mitochondrial DNA repair pathways and their association with the aging process....

Decreased Mitochondrial DNA Content in Association with Exposure to Polycyclic Aromatic Hydrocarbons in House Dust during Wintertime: From a Population Enquiry to Cell Culture

Science.gov (United States)

Pieters, Nicky; Koppen, Gudrun; Smeets, Karen; Napierska, Dorota; Plusquin, Michelle; De Prins, Sofie; Van De Weghe, Hendrik; Nelen, Vera; Cox, Bianca; Cuypers, Ann; Hoet, Peter; Schoeters, Greet; Nawrot, Tim S.

2013-01-01

Polycyclic aromatic hydrocarbons (PAHs) are widespread environmental pollutants that are formed in combustion processes. At the cellular level, exposure to PAHs causes oxidative stress and/or some of it congeners bind to DNA, which may interact with mitochondrial function. However, the influence of these pollutants on mitochondrial DNA (mtDNA) content remains largely unknown. We determined whether indoor exposure to PAHs is associated with mitochondrial damage as represented by blood mtDNA content. Blood mtDNA content (ratio mitochondrial/nuclear DNA copy number) was determined by real-time qPCR in 46 persons, both in winter and summer. Indoor PAH exposure was estimated by measuring PAHs in sedimented house dust, including 6 volatile PAHs and 8 non-volatile PAHs. Biomarkers of oxidative stress at the level of DNA and lipid peroxidation were measured. In addition to the epidemiologic enquiry, we exposed human TK6 cells during 24 h at various concentrations (range: 0 to 500 µM) of benzo(a)pyrene and determined mtDNA content. Mean blood mtDNA content averaged (±SD) 0.95±0.185. The median PAH content amounted 554.1 ng/g dust (25th–75th percentile: 390.7–767.3) and 1385ng/g dust (25th–75th percentile: 1000–1980) in winter for volatile and non-volatile PAHs respectively. Independent for gender, age, BMI and the consumption of grilled meat or fish, blood mtDNA content decreased by 9.85% (95% CI: −15.16 to −4.2; p = 0.002) for each doubling of non-volatile PAH content in the house dust in winter. The corresponding estimate for volatile PAHs was −7.3% (95% CI: −13.71 to −0.42; p = 0.04). Measurements of oxidative stress were not correlated with PAH exposure. During summer months no association was found between mtDNA content and PAH concentration. The ability of benzo(a)pyrene (range 0 µM to 500 µM) to lower mtDNA content was confirmed in vitro in human TK6 cells. Based on these findings, mtDNA content can be a target of PAH toxicity in humans

Decreased mitochondrial DNA content in association with exposure to polycyclic aromatic hydrocarbons in house dust during wintertime: from a population enquiry to cell culture.

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Nicky Pieters

Full Text Available Polycyclic aromatic hydrocarbons (PAHs are widespread environmental pollutants that are formed in combustion processes. At the cellular level, exposure to PAHs causes oxidative stress and/or some of it congeners bind to DNA, which may interact with mitochondrial function. However, the influence of these pollutants on mitochondrial DNA (mtDNA content remains largely unknown. We determined whether indoor exposure to PAHs is associated with mitochondrial damage as represented by blood mtDNA content. Blood mtDNA content (ratio mitochondrial/nuclear DNA copy number was determined by real-time qPCR in 46 persons, both in winter and summer. Indoor PAH exposure was estimated by measuring PAHs in sedimented house dust, including 6 volatile PAHs and 8 non-volatile PAHs. Biomarkers of oxidative stress at the level of DNA and lipid peroxidation were measured. In addition to the epidemiologic enquiry, we exposed human TK6 cells during 24 h at various concentrations (range: 0 to 500 µM of benzo(apyrene and determined mtDNA content. Mean blood mtDNA content averaged (± SD 0.95 ± 0.185. The median PAH content amounted 554.1 ng/g dust (25(th-75(th percentile: 390.7-767.3 and 1385 ng/g dust (25(th-75(th percentile: 1000-1980 in winter for volatile and non-volatile PAHs respectively. Independent for gender, age, BMI and the consumption of grilled meat or fish, blood mtDNA content decreased by 9.85% (95% CI: -15.16 to -4.2; p = 0.002 for each doubling of non-volatile PAH content in the house dust in winter. The corresponding estimate for volatile PAHs was -7.3% (95% CI: -13.71 to -0.42; p = 0.04. Measurements of oxidative stress were not correlated with PAH exposure. During summer months no association was found between mtDNA content and PAH concentration. The ability of benzo(apyrene (range 0 µM to 500 µM to lower mtDNA content was confirmed in vitro in human TK6 cells. Based on these findings, mtDNA content can be a target of PAH toxicity in humans.

The interplay between SUCLA2, SUCLG2, and mitochondrial DNA depletion

DEFF Research Database (Denmark)

Miller, Chaya; Wang, Liya; Ostergaard, Elsebet

2011-01-01

SUCLA2-related mitochondrial DNA (mtDNA) depletion syndrome is a result of mutations in the β subunit of the ADP-dependent isoform of the Krebs cycle succinyl-CoA synthase (SCS). The mechanism of tissue specificity and mtDNA depletion is elusive but complementation by the GDP-dependent isoform en...

Mitochondrial nucleoid clusters protect newly synthesized mtDNA during Doxorubicin- and Ethidium Bromide-induced mitochondrial stress

Czech Academy of Sciences Publication Activity Database

Alán, Lukáš; Špaček, Tomáš; Pajuelo-Reguera, David; Jabůrek, Martin; Ježek, Petr

2016-01-01

Roč. 302, Jul 1 (2016), s. 31-40 ISSN 0041-008X R&D Projects: GA ČR(CZ) GAP305/12/1247; GA MŠk(CZ) LQ1604; GA MŠk(CZ) ED1.1.00/02.0109 Institutional support: RVO:67985823 Keywords : Doxorubicin * Ethidium Bromide * nucleoid clusters * mitochondrial DNA stress * mitochondrial transcription factor A Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 3.791, year: 2016

Periodic expression of nuclear and mitochondrial DNA replication genes during the trypanosomatid cell cycle.

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Pasion, S G; Brown, G W; Brown, L M; Ray, D S

1994-12-01

In trypanosomatids, DNA replication in the nucleus and in the single mitochondrion (or kinetoplast) initiates nearly simultaneously, suggesting that the DNA synthesis (S) phases of the nucleus and the mitochondrion are coordinately regulated. To investigate the basis for the temporal link between nuclear and mitochondrial DNA synthesis phases the expression of the genes encoding DNA ligase I, the 51 and 28 kDa subunits of replication protein A, dihydrofolate reductase and the mitochondrial type II topoisomerase were analyzed during the cell cycle progression of synchronous cultures of Crithidia fasciculata. These DNA replication genes were all expressed periodically, with peak mRNA levels occurring just prior to or at the peak of DNA synthesis in the synchronized cultures. A plasmid clone (pdN-1) in which TOP2, the gene encoding the mitochondrial topoisomerase, was disrupted by the insertion of a NEO drug-resistance cassette was found to express both a truncated TOP2 mRNA and a truncated topoisomerase polypeptide. The truncated mRNA was also expressed periodically coordinate with the expression of the endogenous TOP2 mRNA indicating that cis elements necessary for periodic expression are contained within cloned sequences. The expression of both TOP2 and nuclear DNA replication genes at the G1/S boundary suggests that regulated expression of these genes may play a role in coordinating nuclear and mitochondrial S phases in trypanosomatids.

Genetic evidence from mitochondrial DNA corroborates the origin of Tibetan chickens.

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Long Zhang

Full Text Available Chicken is the most common poultry species and is important to human societies. Tibetan chicken (Gallus gallus domesticus is a breed endemic to China that is distributed mainly on the Qinghai-Tibet Plateau. However, its origin has not been well characterized. In the present study, we sequenced partial mitochondrial DNA (mtDNA control region of 239 and 283 samples from Tibetan and Sichuan indigenous chickens, respectively. Incorporating 1091 published sequences, we constructed the matrilineal genealogy of Tibetan chickens to further document their domestication history. We found that the genetic structure of the mtDNA haplotypes of Tibetan chickens are dominated by seven major haplogroups (A-G. In addition, phylogenetic and network analyses showed that Tibetan chickens are not distinguishable from the indigenous chickens in surrounding areas. Furthermore, some clades of Tibetan chickens may have originated from game fowls. In summary, our results collectively indicated that Tibetan chickens may have diverged from indigenous chickens in the adjacent regions and hybridized with various chickens.

The pathophysiology of mitochondrial disease as modeled in the mouse.

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Wallace, Douglas C; Fan, Weiwei

2009-08-01

It is now clear that mitochondrial defects are associated with a plethora of clinical phenotypes in man and mouse. This is the result of the mitochondria's central role in energy production, reactive oxygen species (ROS) biology, and apoptosis, and because the mitochondrial genome consists of roughly 1500 genes distributed across the maternal mitochondrial DNA (mtDNA) and the Mendelian nuclear DNA (nDNA). While numerous pathogenic mutations in both mtDNA and nDNA mitochondrial genes have been identified in the past 21 years, the causal role of mitochondrial dysfunction in the common metabolic and degenerative diseases, cancer, and aging is still debated. However, the development of mice harboring mitochondrial gene mutations is permitting demonstration of the direct cause-and-effect relationship between mitochondrial dysfunction and disease. Mutations in nDNA-encoded mitochondrial genes involved in energy metabolism, antioxidant defenses, apoptosis via the mitochondrial permeability transition pore (mtPTP), mitochondrial fusion, and mtDNA biogenesis have already demonstrated the phenotypic importance of mitochondrial defects. These studies are being expanded by the recent development of procedures for introducing mtDNA mutations into the mouse. These studies are providing direct proof that mtDNA mutations are sufficient by themselves to generate major clinical phenotypes. As more different mtDNA types and mtDNA gene mutations are introduced into various mouse nDNA backgrounds, the potential functional role of mtDNA variation in permitting humans and mammals to adapt to different environments and in determining their predisposition to a wide array of diseases should be definitively demonstrated.

Deoxynucleoside salvage enzymes and tissue specific mitochondrial DNA depletion.

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Wang, L

2010-06-01

Adequate mitochondrial DNA (mtDNA) copies are required for normal mitochondria function and reductions in mtDNA copy number due to genetic alterations cause tissue-specific mtDNA depletion syndrome (MDS). There are eight nuclear genes, directly or indirectly involved in mtDNA replication and mtDNA precursor synthesis, which have been identified as the cause of MDS. However, the tissue specific pathology of these nuclear gene mutations is not well understood. Here, mtDNA synthesis, mtDNA copy number control, and mtDNA turnover, as well as the synthesis of mtDNA precursors in relation to the levels of salvage enzymes are discussed. The question why MDS caused by TK2 and p53R2 mutations are predominantly muscle specific while dGK deficiency affected mainly liver will be addressed.

What cost mitochondria? The maintenance of functional mitochondrial DNA within and across generations

NARCIS (Netherlands)

Aanen, D.K.; Spelbrink, J.N.; Beekman, M.

2014-01-01

The peculiar biology of mitochondrial DNA (mtDNA) potentially has detrimental consequences for organismal health and lifespan. Typically, eukaryotic cells contain multiple mitochondria, each with multiple mtDNA genomes. The high copy number of mtDNA implies that selection on mtDNA functionality is

Updating phylogeny of mitochondrial DNA macrohaplogroup m in India: dispersal of modern human in South Asian corridor.

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Adimoolam Chandrasekar

2009-10-01

Full Text Available To construct maternal phylogeny and prehistoric dispersals of modern human being in the Indian sub continent, a diverse subset of 641 complete mitochondrial DNA (mtDNA genomes belonging to macrohaplogroup M was chosen from a total collection of 2,783 control-region sequences, sampled from 26 selected tribal populations of India. On the basis of complete mtDNA sequencing, we identified 12 new haplogroups--M53 to M64; redefined/ascertained and characterized haplogroups M2, M3, M4, M5, M6, M8'C'Z, M9, M10, M11, M12-G, D, M18, M30, M33, M35, M37, M38, M39, M40, M41, M43, M45 and M49, which were previously described by control and/or coding-region polymorphisms. Our results indicate that the mtDNA lineages reported in the present study (except East Asian lineages M8'C'Z, M9, M10, M11, M12-G, D are restricted to Indian region.The deep rooted lineages of macrohaplogroup 'M' suggest in-situ origin of these haplogroups in India. Most of these deep rooting lineages are represented by multiple ethnic/linguist groups of India. Hierarchical analysis of molecular variation (AMOVA shows substantial subdivisions among the tribes of India (Fst = 0.16164. The current Indian mtDNA gene pool was shaped by the initial settlers and was galvanized by minor events of gene flow from the east and west to the restricted zones. Northeast Indian mtDNA pool harbors region specific lineages, other Indian lineages and East Asian lineages. We also suggest the establishment of an East Asian gene in North East India through admixture rather than replacement.

A role for recombination junctions in the segregation of mitochondrial DNA in yeast.

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Lockshon, D; Zweifel, S G; Freeman-Cook, L L; Lorimer, H E; Brewer, B J; Fangman, W L

1995-06-16

In S. cerevisiae, mitochondrial DNA (mtDNA) molecules, in spite of their high copy number, segregate as if there were a small number of heritable units. The rapid segregation of mitochondrial genomes can be analyzed using mtDNA deletion variants. These small, amplified genomes segregate preferentially from mixed zygotes relative to wild-type mtDNA. This segregation advantage is abolished by mutations in a gene, MGT1, that encodes a recombination junction-resolving enzyme. We show here that resolvase deficiency causes a larger proportion of molecules to be linked together by recombination junctions, resulting in the aggregation of mtDNA into a small number of cytological structures. This change in mtDNA structure can account for the increased mitotic loss of mtDNA and the altered pattern of mtDNA segregation from zygotes. We propose that the level of unresolved recombination junctions influences the number of heritable units of mtDNA.

Preventing the transmission of mitochondrial DNA disorders using prenatal or preimplantation genetic diagnosis.

Science.gov (United States)

Smeets, Hubert J M; Sallevelt, Suzanne C E H; Dreesen, Jos C F M; de Die-Smulders, Christine E M; de Coo, Irenaeus F M

2015-09-01

Mitochondrial disorders are among the most common inborn errors of metabolism; at least 15% are caused by mitochondrial DNA (mtDNA) mutations, which occur de novo or are maternally inherited. For familial heteroplasmic mtDNA mutations, the mitochondrial bottleneck defines the mtDNA mutation load in offspring, with an often high or unpredictable recurrence risk. Oocyte donation is a safe option to prevent the transmission of mtDNA disease, but the offspring resulting from oocyte donation are genetically related only to the father. Prenatal diagnosis (PND) is technically possible but usually not applicable because of limitations in predicting the phenotype. For de novo mtDNA point mutations, recurrence risks are low and PND can be offered to provide reassurance regarding fetal health. PND is also the best option for female carriers with low-level mutations demonstrating skewing to 0% or 100%. A fairly new option for preventing the transmission of mtDNA diseases is preimplantation genetic diagnosis (PGD), in which embryos with a mutant load below a mutation-specific or general expression threshold of 18% can be transferred. PGD is currently the best reproductive option for familial heteroplasmic mtDNA point mutations. Nuclear genome transfer and genome editing techniques are currently being investigated and might offer additional reproductive options for specific mtDNA disease cases. © 2015 New York Academy of Sciences.

Mitochondrial DNA (mtDNA) variants in the European haplogroups HV, JT, and U do not have a major role in schizophrenia.

Science.gov (United States)

Torrell, Helena; Salas, Antonio; Abasolo, Nerea; Morén, Constanza; Garrabou, Glòria; Valero, Joaquín; Alonso, Yolanda; Vilella, Elisabet; Costas, Javier; Martorell, Lourdes

2014-10-01

It has been reported that certain genetic factors involved in schizophrenia could be located in the mitochondrial DNA (mtDNA). Therefore, we hypothesized that mtDNA mutations and/or variants would be present in schizophrenia patients and may be related to schizophrenia characteristics and mitochondrial function. This study was performed in three steps: (1) identification of pathogenic mutations and variants in 14 schizophrenia patients with an apparent maternal inheritance of the disease by sequencing the entire mtDNA; (2) case-control association study of 23 variants identified in step 1 (16 missense, 3 rRNA, and 4 tRNA variants) in 495 patients and 615 controls, and (3) analyses of the associated variants according to the clinical, psychopathological, and neuropsychological characteristics and according to the oxidative and enzymatic activities of the mitochondrial respiratory chain. We did not identify pathogenic mtDNA mutations in the 14 sequenced patients. Two known variants were nominally associated with schizophrenia and were further studied. The MT-RNR2 1811A > G variant likely does not play a major role in schizophrenia, as it was not associated with clinical, psychopathological, or neuropsychological variables, and the MT-ATP6 9110T > C p.Ile195Thr variant did not result in differences in the oxidative and enzymatic functions of the mitochondrial respiratory chain. The patients with apparent maternal inheritance of schizophrenia did not exhibit any mutations in their mtDNA. The variants nominally associated with schizophrenia in the present study were not related either to phenotypic characteristics or to mitochondrial function. We did not find evidence pointing to a role for mtDNA sequence variation in schizophrenia. © 2014 Wiley Periodicals, Inc.

The current status of studies on mitochondrial DNA with tumor, radiation biological effects and aging

International Nuclear Information System (INIS)

Liu Qingjie; Sang Lu

2004-01-01

The mitochondrial plays a very important role in sustaining the normal physiological function, because it is the center of energy making and mitochondrial DNA (mtDNA) is the only genetic material outside the nuclear. The result of studies showed that many diseases have a close relationship with mtDNA mutation and deletion. This article reviewed the current status of research on mtDNA with tumor, radiation biological effects and aging, in order to initiate the application study of mtDNA in the circle of radiation medicine

RPO41-independent maintenance of [rho-] mitochondrial DNA in Saccharomyces cerevisiae.

Science.gov (United States)

Fangman, W L; Henly, J W; Brewer, B J

1990-01-01

A subset of promoters in the mitochondrial DNA (mtDNA) of the yeast Saccharomyces cerevisiae has been proposed to participate in replication initiation, giving rise to a primer through site-specific cleavage of an RNA transcript. To test whether transcription is essential for mtDNA maintenance, we examined two simple mtDNA deletion ([rho-]) genomes in yeast cells. One genome (HS3324) contains a consensus promoter (ATATAAGTA) for the mitochondrial RNA polymerase encoded by the nuclear gene RPO41, and the other genome (4a) does not. As anticipated, in RPO41 cells transcripts from the HS3324 genome were more abundant than were transcripts from the 4a genome. When the RPO41 gene was disrupted, both [rho-] genomes were efficiently maintained. The level of transcripts from HS3324 mtDNA was decreased greater than 400-fold in cells carrying the RPO41 disrupted gene; however, the low-level transcripts from 4a mtDNA were undiminished. These results indicate that replication of [rho-] genomes can be initiated in the absence of wild-type levels of the RPO41-encoded RNA polymerase.

Genetics Home Reference: RRM2B-related mitochondrial DNA depletion syndrome, encephalomyopathic form with renal ...

Science.gov (United States)

... Additional NIH Resources (1 link) National Institute of Neurological Disorders and Stroke: Mitochondrial Myopathy Information Page Educational Resources (7 links) Cincinnati Children's Hospital: Mitochondrial Diseases Disease InfoSearch: Mitochondrial DNA depletion ...

Alterations of mitochondrial DNA in CEM cells selected for resistance toward ddC toxicity.

Science.gov (United States)

Bjerke, M; Franco, M; Johansson, M; Balzarini, J; Karlsson, A

2006-01-01

2 ',3 '-dideoxycytidine (ddC) is a nucleoside analog that has been shown to produce a delayed toxicity which may be due to the depletion of mitochondrial DNA (mtDNA). In order to gain further understanding of the events involved in mitochondrial toxicity, two different CEM cell lines were selected for resistance to the delayed ddC toxicity.

No evidence of Neandertal mtDNA contribution to early modern humans.

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David Serre

2004-03-01

Full Text Available The retrieval of mitochondrial DNA (mtDNA sequences from four Neandertal fossils from Germany, Russia, and Croatia has demonstrated that these individuals carried closely related mtDNAs that are not found among current humans. However, these results do not definitively resolve the question of a possible Neandertal contribution to the gene pool of modern humans since such a contribution might have been erased by genetic drift or by the continuous influx of modern human DNA into the Neandertal gene pool. A further concern is that if some Neandertals carried mtDNA sequences similar to contemporaneous humans, such sequences may be erroneously regarded as modern contaminations when retrieved from fossils. Here we address these issues by the analysis of 24 Neandertal and 40 early modern human remains. The biomolecular preservation of four Neandertals and of five early modern humans was good enough to suggest the preservation of DNA. All four Neandertals yielded mtDNA sequences similar to those previously determined from Neandertal individuals, whereas none of the five early modern humans contained such mtDNA sequences. In combination with current mtDNA data, this excludes any large genetic contribution by Neandertals to early modern humans, but does not rule out the possibility of a smaller contribution.

Mitochondrial mosaics in the liver of 3 infants with mtDNA defects

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Scalais Emmanuel

2009-06-01

Full Text Available Abstract Background In muscle cytochrome oxidase (COX negative fibers (mitochondrial mosaics have often been visualized. Methods COX activity staining of liver for light and electron microscopy, muscle stains, blue native gel electrophoresis and activity assays of respiratory chain proteins, their immunolocalisation, mitochondrial and nuclear DNA analysis. Results Three unrelated infants showed a mitochondrial mosaic in the liver after staining for COX activity, i.e. hepatocytes with strongly reactive mitochondria were found adjacent to cells with many negative, or barely reactive, mitochondria. Deficiency was most severe in the patient diagnosed with Pearson syndrome. Ragged-red fibers were absent in muscle biopsies of all patients. Enzyme biochemistry was not diagnostic in muscle, fibroblasts and lymphocytes. Blue native gel electrophoresis of liver tissue, but not of muscle, demonstrated a decreased activity of complex IV; in both muscle and liver subcomplexes of complex V were seen. Immunocytochemistry of complex IV confirmed the mosaic pattern in two livers, but not in fibroblasts. MRI of the brain revealed severe white matter cavitation in the Pearson case, but only slight cortical atrophy in the Alpers-Huttenlocher patient, and a normal image in the 3rd. MtDNA in leucocytes showed a common deletion in 50% of the mtDNA molecules of the Pearson patient. In the patient diagnosed with Alpers-Huttenlocher syndrome, mtDNA was depleted for 60% in muscle. In the 3rd patient muscular and hepatic mtDNA was depleted for more than 70%. Mutations in the nuclear encoded gene of POLG were subsequently found in both the 2nd and 3rd patients. Conclusion Histoenzymatic COX staining of a liver biopsy is fast and yields crucial data about the pathogenesis; it indicates whether mtDNA should be assayed. Each time a mitochondrial disorder is suspected and muscle data are non-diagnostic, a liver biopsy should be recommended. Mosaics are probably more frequent

Hybrid male sterility is caused by mitochondrial DNA deletion.

Science.gov (United States)

Hayashida, Kenji; Kohno, Shigeru

2009-07-01

Although it is known that the hybrid male mouse is sterile just like any other animal's heterogametic sex, the reason why only the male germ cells are impaired has yet to be discovered. TdT-mediated dUTP nick end labeling assay using a confocal fluorescence microscope and DNA fragmentation assay of hybrid testis indicated destruction of the mitochondrial DNA (mtDNA) rather than the nuclear DNA. Previously we reported that maternal mtDNA inheritance is through selective sperm mtDNA elimination based on the sperm factor and two egg factors, and expression of these three factors was recognized in the hybrid testis. It was thereby assumed that mtDNA destruction caused by the expression of maternal mtDNA inheritance system in male germ cells is implicated in the hybrid male sterility of mice.

Tenofovir alafenamide (TAF) does not deplete mitochondrial DNA in human T-cell lines at intracellular concentrations exceeding clinically relevant drug exposures.

Science.gov (United States)

Stray, Kirsten M; Park, Yeojin; Babusis, Darius; Callebaut, Christian; Cihlar, Tomas; Ray, Adrian S; Perron, Michel

2017-04-01

HIV-infected patients treated with certain nucleoside reverse transcriptase inhibitors (NRTIs) have experienced adverse effects due to drug-related mitochondrial toxicity. Tenofovir alafenamide (TAF) is a novel prodrug of the NRTI tenofovir (TFV) with an improved safety profile compared to tenofovir disoproxil fumarate (TDF). Prior in vitro studies have demonstrated that the parent nucleotide TFV has no significant effects on mtDNA synthesis. This study investigated whether clinically relevant TAF and TDF exposures affect mtDNA content in human lymphocytes. First, activated or resting peripheral blood mononuclear cells (PBMCs), as well as MT-2 and Jurkat T-cell lines, were continuously treated with ddC for 10 days to establish their susceptibility to mtDNA depletion. PBMCs had low sensitivity to NRTI-mediated mtDNA depletion in vitro. In contrast, ddC treatment of rapidly dividing MT-2 and Jurkat cells resulted in a dose-dependent decrease in mtDNA. Therefore, these two T-cell lines were selected for evaluating TAF and TDF treatment effects. MT-2 and Jurkat cells were pulse-treated with TAF or TDF every 24 h for 10 days to mimic pharmacologically relevant drug exposures. Pulse treatment of cells with 3.3 μM TAF or 1.1 μM TDF for 10 days resulted in 2- to 7-fold greater steady-state intracellular TFV-diphosphate (TFV-DP) levels than those observed clinically in TAF- or TDF-treated patients. At these concentrations, no significant TAF- (106.7% and 84.1% of control; p = 0.77 and 0.12 for MT-2 and Jurkat, respectively) or TDF- (100.6% and 91.0% of control; p = 0.91 and 0.37, respectively) associated reduction in mtDNA content was observed compared with untreated control cells. This study demonstrates that, despite delivering higher intracellular levels of TFV-DP than TDF, TAF does not inhibit mtDNA synthesis in vitro at concentrations exceeding the clinically relevant intracellular drug exposures. Thus, TAF has a low potential for mitochondrial toxicity in

A unique DNA found in post-mitochondrial fraction from Ehrlich ascites tumor cells

International Nuclear Information System (INIS)

Guimaraes, R.C.; Bloch, D.P.

1982-01-01

A DNA found in post-mitochondrial fractions from Ehrlich ascites cells, comprising 0.2% of the total cellular DNA, is partially characterized. It appears in cytoplasmic homogenates as a 14.6 S molecule, and is eluted from hydroxyapatite with 0.24 M sodium phosphate buffer. Its Cs 2 SO 4 buoyant density is lower than Erlich ascites tumor nuclear DNA and it has low dG+dC content, as determined by chromatography of hydrolysates of 32 P-labelled DNA. It is enriched in sequences which reassociate rapidly in the presence of excess nuclear DNA. It can be used as promoter for DNA synthesis by an endogenous DNA-dependent DNA polymerase found in association with the post-mitochondrial preparations. It is found to be associated with newly incorporated radioactivity following incubation in vitro with labelled UTP. Its localization in situ has not yet been attempled. It is thought to represent viral A-type particle associated, or plasma membrane associated DNA. (author) [pt

Genome digging: insight into the mitochondrial genome of Homo.

Directory of Open Access Journals (Sweden)

Igor V Ovchinnikov

2010-12-01

Full Text Available A fraction of the Neanderthal mitochondrial genome sequence has a similarity with a 5,839-bp nuclear DNA sequence of mitochondrial origin (numt on the human chromosome 1. This fact has never been interpreted. Although this phenomenon may be attributed to contamination and mosaic assembly of Neanderthal mtDNA from short sequencing reads, we explain the mysterious similarity by integration of this numt (mtAncestor-1 into the nuclear genome of the common ancestor of Neanderthals and modern humans not long before their reproductive split.Exploiting bioinformatics, we uncovered an additional numt (mtAncestor-2 with a high similarity to the Neanderthal mtDNA and indicated that both numts represent almost identical replicas of the mtDNA sequences ancestral to the mitochondrial genomes of Neanderthals and modern humans. In the proteins, encoded by mtDNA, the majority of amino acids distinguishing chimpanzees from humans and Neanderthals were acquired by the ancestral hominins. The overall rate of nonsynonymous evolution in Neanderthal mitochondrial protein-coding genes is not higher than in other lineages. The model incorporating the ancestral hominin mtDNA sequences estimates the average divergence age of the mtDNAs of Neanderthals and modern humans to be 450,000-485,000 years. The mtAncestor-1 and mtAncestor-2 sequences were incorporated into the nuclear genome approximately 620,000 years and 2,885,000 years ago, respectively.This study provides the first insight into the evolution of the mitochondrial DNA in hominins ancestral to Neanderthals and humans. We hypothesize that mtAncestor-1 and mtAncestor-2 are likely to be molecular fossils of the mtDNAs of Homo heidelbergensis and a stem Homo lineage. The d(N/d(S dynamics suggests that the effective population size of extinct hominins was low. However, the hominin lineage ancestral to humans, Neanderthals and H. heidelbergensis, had a larger effective population size and possessed genetic diversity

Heterology of mitochondrial DNA from mammals detected by electron microscopic heteroduplex analyses

DEFF Research Database (Denmark)

Christiansen, Gunna; Christiansen, C

1983-01-01

Heteroduplex analysis of mitochondrial DNA (mtDNA) from evolutionary closely related mammals (rat vs. mouse, man vs. monkey) are analyzed and compared to heteroduplex analysis of mt-DNA from more distantly related mammals (rat vs. man, rat vs. monkey, mouse vs. man, mouse vs. monkey and man vs. c...

Mitochondrial DNA T4216C and A4917G variations in multiple sclerosis

DEFF Research Database (Denmark)

Andalib, Sasan; Talebi, Mahnaz; Sakhinia, Ebrahim

2015-01-01

DNA gene and A4917G variation in the mtDNA NADH Dehydrogenase 2 (ND2) gene are associated with MS in an Iranian population. MATERIAL AND METHODS: Blood samples were collected from 100 patients with MS and 100 unrelated healthy controls, and DNA extraction was performed by salting-out. By means.......637). Logistic regression analysis revealed an odds ratio (OR) of 1.2 with 95% CI of 0.4-3.5. CONCLUSION: The present study revealed no association between MS and T4216C variation in the ND1 mtDNA gene and A4917G variation in the mtDNA ND2 gene in the Iranian population....... focuses on the neurogenetics of the complex pathogenesis of MS in relation to factors such as mitochondrial DNA (mtDNA) variations. T4216C and A4917G are common mitochondrial gene variations associated with MS. The present study tested whether mtDNA T4216C variation in the NADH Dehydrogenase 1 (ND1) mt...

Thymidine kinase 2 (H126N) knockin mice show the essential role of balanced deoxynucleotide pools for mitochondrial DNA maintenance.

Science.gov (United States)

Akman, Hasan O; Dorado, Beatriz; López, Luis C; García-Cazorla, Angeles; Vilà, Maya R; Tanabe, Lauren M; Dauer, William T; Bonilla, Eduardo; Tanji, Kurenai; Hirano, Michio

2008-08-15

Mitochondrial DNA (mtDNA) depletion syndrome (MDS), an autosomal recessive condition, is characterized by variable organ involvement with decreased mtDNA copy number and activities of respiratory chain enzymes in affected tissues. MtDNA depletion has been associated with mutations in nine autosomal genes, including thymidine kinase (TK2), which encodes a ubiquitous mitochondrial protein. To study the pathogenesis of TK2-deficiency, we generated mice harboring an H126N Tk2 mutation. Homozygous Tk2 mutant (Tk2(-/-)) mice developed rapidly progressive weakness after age 10 days and died between ages 2 and 3 weeks. Tk2(-/-) animals showed Tk2 deficiency, unbalanced dNTP pools, mtDNA depletion and defects of respiratory chain enzymes containing mtDNA-encoded subunits that were most prominent in the central nervous system. Histopathology revealed an encephalomyelopathy with prominent vacuolar changes in the anterior horn of the spinal cord. The H126N TK2 mouse is the first knock-in animal model of human MDS and demonstrates that the severity of TK2 deficiency in tissues may determine the organ-specific phenotype.

Cells Lacking mtDNA Display Increased dNTP Pools upon DNA Damage

DEFF Research Database (Denmark)

Skovgaard, Tine; Rasmussen, Lene Juel; Munch-Petersen, Birgitte

Imbalanced dNTP pools are highly mutagenic due to a deleterious effect on DNA polymerase fidelity. Mitochondrial DNA defects, including mutations and deletions, are commonly found in a wide variety of different cancer types. In order to further study the interconnection between dNTP pools...... and mitochondrial function we have examined the effect of DNA damage on dNTP pools in cells deficient of mtDNA. We show that DNA damage induced by UV irradiation, in a dose corresponding to LD50, induces an S phase delay in different human osteosarcoma cell lines. The UV pulse also has a destabilizing effect...... shows that normal mitochondrial function is prerequisite for retaining stable dNTP pools upon DNA damage. Therefore it is likely that mitochondrial deficiency defects may cause an increase in DNA mutations by disrupting dNTP pool balance....

In vitro-reconstituted nucleoids can block mitochondrial DNA replication and transcription

NARCIS (Netherlands)

Farge, Géraldine; Mehmedovic, Majda; Baclayon, Marian; van den Wildenberg, Siet M J L; Roos, Wouter H; Gustafsson, Claes M; Wuite, Gijs J L; Falkenberg, Maria

2014-01-01

The mechanisms regulating the number of active copies of mtDNA are still unclear. A mammalian cell typically contains 1,000-10,000 copies of mtDNA, which are packaged into nucleoprotein complexes termed nucleoids. The main protein component of these structures is mitochondrial transcription factor A

mtDNA depletion myopathy: elucidation of the tissue specificity in the mitochondrial thymidine kinase (TK2) deficiency.

Science.gov (United States)

Saada, Ann; Shaag, Avraham; Elpeleg, Orly

2003-05-01

Decreased mitochondrial thymidine kinase (TK2) activity is associated with mitochondrial DNA (mtDNA) depletion and respiratory chain dysfunction and is manifested by isolated, fatal skeletal myopathy. Other tissues such as liver, brain, heart, and skin remain unaffected throughout the patients' life. In order to elucidate the mechanism of tissue specificity in the disease we have investigated the expression of the mitochondrial deoxynucleotide carrier, the mtDNA content and the activity of TK2 in mitochondria of various tissues. Our results suggest that low basal TK2 activity combined with a high requirement for mitochondrial encoded proteins in muscle predispose this tissue to the devastating effect of TK2 deficiency.

Overexpression of DNA ligase III in mitochondria protects cells against oxidative stress and improves mitochondrial DNA base excision repair

DEFF Research Database (Denmark)

Akbari, Mansour; Keijzers, Guido; Maynard, Scott

2014-01-01

slower than the preceding mitochondrial BER steps. Overexpression of DNA ligase III in mitochondria improved the rate of overall BER, increased cell survival after menadione induced oxidative stress and reduced autophagy following the inhibition of the mitochondrial electron transport chain complex I...

Mitochondrial DNA analysis of eneolithic trypillians from Ukraine reveals neolithic farming genetic roots.

Directory of Open Access Journals (Sweden)

Alexey G Nikitin

Full Text Available The agricultural revolution in Eastern Europe began in the Eneolithic with the Cucuteni-Trypillia culture complex. In Ukraine, the Trypillian culture (TC existed for over two millennia (ca. 5,400-2,700 BCE and left a wealth of artifacts. Yet, their burial rituals remain a mystery and to date almost nothing is known about the genetic composition of the TC population. One of the very few TC sites where human remains can be found is a cave called Verteba in western Ukraine. This report presents four partial and four complete mitochondrial genomes from nine TC individuals uncovered in the cave. The results of this analysis, combined with the data from previous reports, indicate that the Trypillian population at Verteba carried, for the most part, a typical Neolithic farmer package of mitochondrial DNA (mtDNA lineages traced to Anatolian farmers and Neolithic farming groups of central Europe. At the same time, the find of two specimens belonging to haplogroup U8b1 at Verteba can be viewed as a connection of TC with the Upper Paleolithic European populations. At the level of mtDNA haplogroup frequencies, the TC population from Verteba demonstrates a close genetic relationship with population groups of the Funnel Beaker/ Trichterbecker cultural complex from central and northern Europe (ca. 3,950-2,500 BCE.

Real-Time PCR Quantification of Heteroplasmy in a Mouse Model with Mitochondrial DNA of C57BL/6 and NZB/BINJ Strains

Science.gov (United States)

Sangalli, Juliano Rodrigues; Rodrigues, Thiago Bittencourt; Smith, Lawrence Charles; Meirelles, Flávio Vieira; Chiaratti, Marcos Roberto

2015-01-01

Mouse models are widely employed to study mitochondrial inheritance, which have implications to several human diseases caused by mutations in the mitochondrial genome (mtDNA). These mouse models take advantage of polymorphisms between the mtDNA of the NZB/BINJ and the mtDNA of common inbred laboratory (i.e., C57BL/6) strains to generate mice with two mtDNA haplotypes (heteroplasmy). Based on PCR followed by restriction fragment length polymorphism (PCR-RFLP), these studies determine the level of heteroplasmy across generations and in different cell types aiming to understand the mechanisms underlying mitochondrial inheritance. However, PCR-RFLP is a time-consuming method of low sensitivity and accuracy that dependents on the use of restriction enzyme digestions. A more robust method to measure heteroplasmy has been provided by the use of real-time quantitative PCR (qPCR) based on allelic refractory mutation detection system (ARMS-qPCR). Herein, we report an ARMS-qPCR assay for quantification of heteroplasmy using heteroplasmic mice with mtDNA of NZB/BINJ and C57BL/6 origin. Heteroplasmy and mtDNA copy number were estimated in germline and somatic tissues, providing evidence of the reliability of the approach. Furthermore, it enabled single-step quantification of heteroplasmy, with sensitivity to detect as low as 0.1% of either NZB/BINJ or C57BL/6 mtDNA. These findings are relevant as the ARMS-qPCR assay reported here is fully compatible with similar heteroplasmic mouse models used to study mitochondrial inheritance in mammals. PMID:26274500

Mitochondrial DNA variation in the Viking age population of Norway

OpenAIRE

Krzewińska, Maja; Bjørnstad, Gro; Skoglund, Pontus; Olason, Pall Isolfur; Bill, Jan; Götherström, Anders; Hagelberg, Erika

2015-01-01

The medieval Norsemen or Vikings had an important biological and cultural impact on many parts of Europe through raids, colonization and trade, from about AD 793 to 1066. To help understand the genetic affinities of the ancient Norsemen, and their genetic contribution to the gene pool of other Europeans, we analysed DNA markers in Late Iron Age skeletal remains from Norway. DNA was extracted from 80 individuals, and mitochondrial DNA polymorphisms were detected by next-generation sequencing. ...

Mitochondrial genome inheritance and replacement in the human germline.

Science.gov (United States)

Wolf, Don P; Hayama, Tomonari; Mitalipov, Shoukhrat

2017-08-01

Mitochondria, the ubiquitous power packs in nearly every eukaryotic cell, contain their own DNA, known as mtDNA, which is inherited exclusively from the mother. The number of mitochondrial genomes varies depending on the cell's energy needs. The mature oocyte contains the highest number of mitochondria of any cell type, although there is little if any mtDNA replication after fertilization until the embryo implants. This has potential repercussions for mitochondrial replacement therapy (MRT; see description of currently employed methods below) used to prevent the transmission of mtDNA-based disorders. If only a few mitochondria with defective mtDNA are left in the embryo and undergo extensive replication, it might therefore thwart the purpose of MRT In order to improve the safety and efficacy of this experimental therapy, we need a better understanding of how and which mtDNA is tagged for replication versus transcription after fertilization of the oocyte. © 2017 The Authors.

Global DNA methylation synergistically regulates the nuclear and mitochondrial genomes in glioblastoma cells.

Science.gov (United States)

Sun, Xin; Johnson, Jacqueline; St John, Justin C

2018-05-02

Replication of mitochondrial DNA is strictly regulated during differentiation and development allowing each cell type to acquire its required mtDNA copy number to meet its specific needs for energy. Undifferentiated cells establish the mtDNA set point, which provides low numbers of mtDNA copy but sufficient template for replication once cells commit to specific lineages. However, cancer cells, such as those from the human glioblastoma multiforme cell line, HSR-GBM1, cannot complete differentiation as they fail to enforce the mtDNA set point and are trapped in a 'pseudo-differentiated' state. Global DNA methylation is likely to be a major contributing factor, as DNA demethylation treatments promote differentiation of HSR-GBM1 cells. To determine the relationship between DNA methylation and mtDNA copy number in cancer cells, we applied whole genome MeDIP-Seq and RNA-Seq to HSR-GBM1 cells and following their treatment with the DNA demethylation agents 5-azacytidine and vitamin C. We identified key methylated regions modulated by the DNA demethylation agents that also induced synchronous changes to mtDNA copy number and nuclear gene expression. Our findings highlight the control exerted by DNA methylation on the expression of key genes, the regulation of mtDNA copy number and establishment of the mtDNA set point, which collectively contribute to tumorigenesis.

Mitochondrial tRNA cleavage by tRNA-targeting ribonuclease causes mitochondrial dysfunction observed in mitochondrial disease

Energy Technology Data Exchange (ETDEWEB)

Ogawa, Tetsuhiro, E-mail: atetsu@mail.ecc.u-tokyo.ac.jp; Shimizu, Ayano; Takahashi, Kazutoshi; Hidaka, Makoto; Masaki, Haruhiko, E-mail: amasaki@mail.ecc.u-tokyo.ac.jp

2014-08-15

Highlights: • MTS-tagged ribonuclease was translocated successfully to the mitochondrial matrix. • MTS-tagged ribonuclease cleaved mt tRNA and reduced COX activity. • Easy and reproducible method of inducing mt tRNA dysfunction. - Abstract: Mitochondrial DNA (mtDNA) is a genome possessed by mitochondria. Since reactive oxygen species (ROS) are generated during aerobic respiration in mitochondria, mtDNA is commonly exposed to the risk of DNA damage. Mitochondrial disease is caused by mitochondrial dysfunction, and mutations or deletions on mitochondrial tRNA (mt tRNA) genes are often observed in mtDNA of patients with the disease. Hence, the correlation between mt tRNA activity and mitochondrial dysfunction has been assessed. Then, cybrid cells, which are constructed by the fusion of an enucleated cell harboring altered mtDNA with a ρ{sup 0} cell, have long been used for the analysis due to difficulty in mtDNA manipulation. Here, we propose a new method that involves mt tRNA cleavage by a bacterial tRNA-specific ribonuclease. The ribonuclease tagged with a mitochondrial-targeting sequence (MTS) was successfully translocated to the mitochondrial matrix. Additionally, mt tRNA cleavage, which resulted in the decrease of cytochrome c oxidase (COX) activity, was observed.

Detection of irradiated fresh, chilled, and frozen foods by the mitochondrial DNA method

International Nuclear Information System (INIS)

Machioni, E.; Bergaentzle, M.; Todoriki, S.; Hasselmann, C.; Kuntz, F.

1996-01-01

DNA molecules are very sensitive to ionising radiation, even at low doses. Strand breaks are easy to detect despite the generally low DNA content of foods, but such ruptures are not specific to radiation processing. Preliminary experiments showed that cellular DNA in beef underwent strong enzymatic degradation during storage at +4 o C and thus radiation effects could not be isolated. In order to make DNA strand rupture more specific to radiation (other than by deep freezing) it appears necessary to isolate the irradiated DNA from cell enzymes. This is the case for mitochondrial DNA which is protected from enzymatic degradation by the mitochondrial walls but not from radiation. It can, therefore, be assumed that DNA strand breaks in mitochondria will be specific to ionising radiation. The aim of this work is to develop and validate the proposed test on different food samples (meat and fish products) which are already or may be industrially irradiated in the near future. (author)

Enzymatic removal of O6-ethylguanine from mitochondrial DNA in rat tissues exposed to N-ethyl-N-nitrosourea in vivo

International Nuclear Information System (INIS)

Satoh, M.S.; Huh, N.; Rajewsky, M.F.; Kuroki, T.

1988-01-01

DNA repair is essential for maintaining the integrity of the genetic material, and a number of DNA repair mechanisms have been fairly well characterized for the nuclear DNA of eukaryotic cells as well as prokaryotes. However, little is know about DNA repair in mitochondria. Using highly sensitive immunoanalytical methods to detect specific DNA alkylation products, the authors found active removal of O 6 -ethyl-2'-deoxyguanosine (O 6 -EtdGuo) from rat liver mitochondrial DNA after pulse-exposure to N-ethyl-N-nitrosourea in vivo. In the kidney, O 6 -EtdGuo was removed from mitochondrial DNA with moderate efficiency, but nearly no removal was observed from the DNA of brain mitochondria. Among the rat tissues examined, the kinetics of O 6 -EtdGuo elimination from mitochondrial DNA was very similar to the kinetics of removal from nuclear DNA. O 4 -Ethyl-2'-deoxythymidine, another premutagenic DNA ethylation product, was stable in both mitochondrial and nuclear DNA of rat liver

Mitochondrial Disease

OpenAIRE

Bulent Kurt; Turgut Topal

2013-01-01

Mitochondria are the major energy source of cells. Mitochondrial disease occurs due to a defect in mitochondrial energy production. A valuable energy production in mitochondria depend a healthy interconnection between nuclear and mitochondrial DNA. A mutation in nuclear or mitochondrial DNA may cause abnormalities in ATP production and single or multiple organ dysfunctions, secondarily. In this review, we summarize mitochondrial physiology, mitochondrial genetics, and clinical expression and ...

Mitochondrial Nucleoid: Shield and Switch of the Mitochondrial Genome

Science.gov (United States)

2017-01-01

Mitochondria preserve very complex and distinctively unique machinery to maintain and express the content of mitochondrial DNA (mtDNA). Similar to chromosomes, mtDNA is packaged into discrete mtDNA-protein complexes referred to as a nucleoid. In addition to its role as a mtDNA shield, over 50 nucleoid-associated proteins play roles in mtDNA maintenance and gene expression through either temporary or permanent association with mtDNA or other nucleoid-associated proteins. The number of mtDNA(s) contained within a single nucleoid is a fundamental question but remains a somewhat controversial issue. Disturbance in nucleoid components and mutations in mtDNA were identified as significant in various diseases, including carcinogenesis. Significant interest in the nucleoid structure and its regulation has been stimulated in relation to mitochondrial diseases, which encompass diseases in multicellular organisms and are associated with accumulation of numerous mutations in mtDNA. In this review, mitochondrial nucleoid structure, nucleoid-associated proteins, and their regulatory roles in mitochondrial metabolism are briefly addressed to provide an overview of the emerging research field involving mitochondrial biology. PMID:28680532

Molecular identification of Malaysian Chrysomya megacephala (Fabricius) and Chrysomya rufifacies (Macquart) using life stage specific mitochondrial DNA.

Science.gov (United States)

Kavitha, R; Tan, T C; Lee, H L; Nazni, W A; Sofian, A M

2013-06-01

DNA identification of blow fly species can be a very useful tool in forensic entomology. One of the potential benefits that mitochondrial DNA (mtDNA) has offered in the field of forensic entomology is species determination. Conventional identification methods have limitations for sibling and closely related species of blow fly and stage and quality of the specimen used. This could be overcome by DNA-based identification methods using mitochondrial DNA which does not demand intact or undamaged specimens. Mitochondrial DNA is usually isolated from whole blow fly and legs. Alternate sources for mitochondrial DNA isolation namely, egg, larva, puparium and empty puparium were explored in this study. The sequence of DNA obtained for each sample for every life cycle stage was 100% identical for a particular species, indicating that the egg, 1st instar, 2nd instar, 3rd instar, pupa, empty puparium and adult from the same species and obtained from same generation will exhibit similar DNA sequences. The present study also highlighted the usefulness of collecting all life cycle stages of blow fly during crime scene investigation with proper preservation and subsequent molecular analysis. Molecular identification provides a strong basis for species identification and will prove an invaluable contribution to forensic entomology as an investigative tool in Malaysia.

Postglacial species displacement in Triturus newts deduced from asymmetrically introgressed mitochondrial DNA and ecological niche models

Directory of Open Access Journals (Sweden)

Wielstra Ben

2012-08-01

Full Text Available Abstract Background If the geographical displacement of one species by another is accompanied by hybridization, mitochondrial DNA can introgress asymmetrically, from the outcompeted species into the invading species, over a large area. We explore this phenomenon using the two parapatric crested newt species, Triturus macedonicus and T. karelinii, distributed on the Balkan Peninsula in south-eastern Europe, as a model. Results We first delimit a ca. 54,000 km2 area in which T. macedonicus contains T. karelinii mitochondrial DNA. This introgression zone bisects the range of T. karelinii, cutting off a T. karelinii enclave. The high similarity of introgressed mitochondrial DNA haplotypes with those found in T. karelinii suggests a recent transfer across the species boundary. We then use ecological niche modeling to explore habitat suitability of the location of the present day introgression zone under current, mid-Holocene and Last Glacial Maximum conditions. This area was inhospitable during the Last Glacial Maximum for both species, but would have been habitable at the mid-Holocene. Since the mid-Holocene, habitat suitability generally increased for T. macedonicus, whereas it decreased for T. karelinii. Conclusion The presence of a T. karelinii enclave suggests that T. karelinii was the first to colonize the area where the present day introgression zone is positioned after the Last Glacial Maximum. Subsequently, we propose T. karelinii was outcompeted by T. macedonicus, which captured T. karelinii mitochondrial DNA via introgressive hybridization in the process. Ecological niche modeling suggests that this replacement was likely facilitated by a shift in climate since the mid-Holocene. We suggest that the northwestern part of the current introgression zone was probably never inhabited by T. karelinii itself, and that T. karelinii mitochondrial DNA spread there through T. macedonicus exclusively. Considering the spatial distribution of the

Nuclear transfer to prevent mitochondrial DNA disorders : revisiting the debate on reproductive cloning

NARCIS (Netherlands)

Bredenoord, A. L.; Dondorp, W.; Pennings, G.; De Wert, G.

Preclinical experiments are currently performed to examine the feasibility of several types of nuclear transfer to prevent mitochondrial DNA (mtDNA) disorders. Whereas the two most promising types of nuclear transfer to prevent mtDNA disorders, spindle transfer and pronuclear transfer, do not amount

Direct radiocarbon dating and DNA analysis of the Darra-i-Kur (Afghanistan) human temporal bone.

Science.gov (United States)

Douka, Katerina; Slon, Viviane; Stringer, Chris; Potts, Richard; Hübner, Alexander; Meyer, Matthias; Spoor, Fred; Pääbo, Svante; Higham, Tom

2017-06-01

The temporal bone discovered in the 1960s from the Darra-i-Kur cave in Afghanistan is often cited as one of the very few Pleistocene human fossils from Central Asia. Here we report the first direct radiocarbon date for the specimen and the genetic analyses of DNA extracted and sequenced from two areas of the bone. The new radiocarbon determination places the find to ∼4500 cal BP (∼2500 BCE) contradicting an assumed Palaeolithic age of ∼30,000 years, as originally suggested. The DNA retrieved from the specimen originates from a male individual who carried mitochondrial DNA of the modern human type. The petrous part yielded more endogenous ancient DNA molecules than the squamous part of the same bone. Molecular dating of the Darra-i-Kur mitochondrial DNA sequence corroborates the radiocarbon date and suggests that the specimen is younger than previously thought. Taken together, the results consolidate the fact that the human bone is not associated with the Pleistocene-age deposits of Darra-i-Kur; instead it is intrusive, possibly re-deposited from upper levels dating to much later periods (Neolithic). Despite its Holocene age, the Darra-i-Kur specimen is, so far, the first and only ancient human from Afghanistan whose DNA has been sequenced. Copyright © 2017 Elsevier Ltd. All rights reserved.

The Complete Mitochondrial DNA Sequence of Scenedesmus obliquus Reflects an Intermediate Stage in the Evolution of the Green Algal Mitochondrial Genome

Science.gov (United States)

Nedelcu, Aurora M.; Lee, Robert W.; Lemieux, Claude; Gray, Michael W.; Burger, Gertraud

2000-01-01

Two distinct mitochondrial genome types have been described among the green algal lineages investigated to date: a reduced–derived, Chlamydomonas-like type and an ancestral, Prototheca-like type. To determine if this unexpected dichotomy is real or is due to insufficient or biased sampling and to define trends in the evolution of the green algal mitochondrial genome, we sequenced and analyzed the mitochondrial DNA (mtDNA) of Scenedesmus obliquus. This genome is 42,919 bp in size and encodes 42 conserved genes (i.e., large and small subunit rRNA genes, 27 tRNA and 13 respiratory protein-coding genes), four additional free-standing open reading frames with no known homologs, and an intronic reading frame with endonuclease/maturase similarity. No 5S rRNA or ribosomal protein-coding genes have been identified in Scenedesmus mtDNA. The standard protein-coding genes feature a deviant genetic code characterized by the use of UAG (normally a stop codon) to specify leucine, and the unprecedented use of UCA (normally a serine codon) as a signal for termination of translation. The mitochondrial genome of Scenedesmus combines features of both green algal mitochondrial genome types: the presence of a more complex set of protein-coding and tRNA genes is shared with the ancestral type, whereas the lack of 5S rRNA and ribosomal protein-coding genes as well as the presence of fragmented and scrambled rRNA genes are shared with the reduced–derived type of mitochondrial genome organization. Furthermore, the gene content and the fragmentation pattern of the rRNA genes suggest that this genome represents an intermediate stage in the evolutionary process of mitochondrial genome streamlining in green algae. [The sequence data described in this paper have been submitted to the GenBank data library under accession no. AF204057.] PMID:10854413

Mitochondrial nicotinamide adenine dinucleotide reduced (NADH) oxidation links the tricarboxylic acid (TCA) cycle with methionine metabolism and nuclear DNA methylation.

Science.gov (United States)

Lozoya, Oswaldo A; Martinez-Reyes, Inmaculada; Wang, Tianyuan; Grenet, Dagoberto; Bushel, Pierre; Li, Jianying; Chandel, Navdeep; Woychik, Richard P; Santos, Janine H

2018-04-18

Mitochondrial function affects many aspects of cellular physiology, and, most recently, its role in epigenetics has been reported. Mechanistically, how mitochondrial function alters DNA methylation patterns in the nucleus remains ill defined. Using a cell culture model of induced mitochondrial DNA (mtDNA) depletion, in this study we show that progressive mitochondrial dysfunction leads to an early transcriptional and metabolic program centered on the metabolism of various amino acids, including those involved in the methionine cycle. We find that this program also increases DNA methylation, which occurs primarily in the genes that are differentially expressed. Maintenance of mitochondrial nicotinamide adenine dinucleotide reduced (NADH) oxidation in the context of mtDNA loss rescues methionine salvage and polyamine synthesis and prevents changes in DNA methylation and gene expression but does not affect serine/folate metabolism or transsulfuration. This work provides a novel mechanistic link between mitochondrial function and epigenetic regulation of gene expression that involves polyamine and methionine metabolism responding to changes in the tricarboxylic acid (TCA) cycle. Given the implications of these findings, future studies across different physiological contexts and in vivo are warranted.

Menadione-Induced DNA Damage Leads to Mitochondrial Dysfunction and Fragmentation During Rosette Formation in Fuchs Endothelial Corneal Dystrophy.

Science.gov (United States)

Halilovic, Adna; Schmedt, Thore; Benischke, Anne-Sophie; Hamill, Cecily; Chen, Yuming; Santos, Janine Hertzog; Jurkunas, Ula V

2016-06-20

Fuchs endothelial corneal dystrophy (FECD), a leading cause of age-related corneal edema requiring transplantation, is characterized by rosette formation of corneal endothelium with ensuing apoptosis. We sought to determine whether excess of mitochondrial reactive oxygen species leads to chronic accumulation of oxidative DNA damage and mitochondrial dysfunction, instigating cell death. We modeled the pathognomonic rosette formation of postmitotic corneal cells by increasing endogenous cellular oxidative stress with menadione (MN) and performed a temporal analysis of its effect in normal (HCEnC, HCECi) and FECD (FECDi) cells and ex vivo specimens. FECDi and FECD ex vivo specimens exhibited extensive mtDNA and nDNA damage as detected by quantitative PCR. Exposure to MN triggered an increase in mitochondrial superoxide levels and led to mtDNA and nDNA damage, while DNA amplification was restored with NAC pretreatment. Furthermore, MN exposure led to a decrease in ΔΨm and adenosine triphosphate levels in normal cells, while FECDi exhibited mitochondrial dysfunction at baseline. Mitochondrial fragmentation and cytochrome c release were detected in FECD tissue and after MN treatment of HCEnCs. Furthermore, cleavage of caspase-9 and caspase-3 followed MN-induced cytochrome c release in HCEnCs. This study provides the first line of evidence that accumulation of oxidative DNA damage leads to rosette formation, loss of functionally intact mitochondria via fragmentation, and subsequent cell death during postmitotic cell degeneration of ocular tissue. MN induced rosette formation, along with mtDNA and nDNA damage, mitochondrial dysfunction, and fragmentation, leading to activation of the intrinsic apoptosis via caspase cleavage and cytochrome c release. Antioxid. Redox Signal. 24, 1072-1083.

Mitochondrial DNA structure in the Arabian Peninsula

Directory of Open Access Journals (Sweden)

Cabrera Vicente M

2008-02-01

Full Text Available Abstract Background Two potential migratory routes followed by modern humans to colonize Eurasia from Africa have been proposed. These are the two natural passageways that connect both continents: the northern route through the Sinai Peninsula and the southern route across the Bab al Mandab strait. Recent archaeological and genetic evidence have favored a unique southern coastal route. Under this scenario, the study of the population genetic structure of the Arabian Peninsula, the first step out of Africa, to search for primary genetic links between Africa and Eurasia, is crucial. The haploid and maternally inherited mitochondrial DNA (mtDNA molecule has been the most used genetic marker to identify and to relate lineages with clear geographic origins, as the African Ls and the Eurasian M and N that have a common root with the Africans L3. Results To assess the role of the Arabian Peninsula in the southern route, we genetically analyzed 553 Saudi Arabs using partial (546 and complete mtDNA (7 sequencing, and compared the lineages obtained with those present in Africa, the Near East, central, east and southeast Asia and Australasia. The results showed that the Arabian Peninsula has received substantial gene flow from Africa (20%, detected by the presence of L, M1 and U6 lineages; that an 18% of the Arabian Peninsula lineages have a clear eastern provenance, mainly represented by U lineages; but also by Indian M lineages and rare M links with Central Asia, Indonesia and even Australia. However, the bulk (62% of the Arabian lineages has a Northern source. Conclusion Although there is evidence of Neolithic and more recent expansions in the Arabian Peninsula, mainly detected by (preHV1 and J1b lineages, the lack of primitive autochthonous M and N sequences, suggests that this area has been more a receptor of human migrations, including historic ones, from Africa, India, Indonesia and even Australia, than a demographic expansion center along the

Private mitochondrial DNA variants in danish patients with hypertrophic cardiomyopathy

DEFF Research Database (Denmark)

Hagen, Christian M; Aidt, Frederik H; Havndrup, Ole

2015-01-01

Hypertrophic cardiomyopathy (HCM) is a genetic cardiac disease primarily caused by mutations in genes coding for sarcomeric proteins. A molecular-genetic etiology can be established in ~60% of cases. Evolutionarily conserved mitochondrial DNA (mtDNA) haplogroups are susceptibility factors for HCM......>G, and MT-CYB: m.15024G>A, p.C93Y remained. A detailed analysis of these variants indicated that none of them are likely to cause HCM. In conclusion, private mtDNA mutations are frequent, but they are rarely, if ever, associated with HCM....

Human iPSC-Derived Neural Progenitors Are an Effective Drug Discovery Model for Neurological mtDNA Disorders.

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Lorenz, Carmen; Lesimple, Pierre; Bukowiecki, Raul; Zink, Annika; Inak, Gizem; Mlody, Barbara; Singh, Manvendra; Semtner, Marcus; Mah, Nancy; Auré, Karine; Leong, Megan; Zabiegalov, Oleksandr; Lyras, Ekaterini-Maria; Pfiffer, Vanessa; Fauler, Beatrix; Eichhorst, Jenny; Wiesner, Burkhard; Huebner, Norbert; Priller, Josef; Mielke, Thorsten; Meierhofer, David; Izsvák, Zsuzsanna; Meier, Jochen C; Bouillaud, Frédéric; Adjaye, James; Schuelke, Markus; Wanker, Erich E; Lombès, Anne; Prigione, Alessandro

2017-05-04

Mitochondrial DNA (mtDNA) mutations frequently cause neurological diseases. Modeling of these defects has been difficult because of the challenges associated with engineering mtDNA. We show here that neural progenitor cells (NPCs) derived from human induced pluripotent stem cells (iPSCs) retain the parental mtDNA profile and exhibit a metabolic switch toward oxidative phosphorylation. NPCs derived in this way from patients carrying a deleterious homoplasmic mutation in the mitochondrial gene MT-ATP6 (m.9185T>C) showed defective ATP production and abnormally high mitochondrial membrane potential (MMP), plus altered calcium homeostasis, which represents a potential cause of neural impairment. High-content screening of FDA-approved drugs using the MMP phenotype highlighted avanafil, which we found was able to partially rescue the calcium defect in patient NPCs and differentiated neurons. Overall, our results show that iPSC-derived NPCs provide an effective model for drug screening to target mtDNA disorders that affect the nervous system. Copyright © 2016 Elsevier Inc. All rights reserved.

A ketogenic diet accelerates neurodegeneration in mice with induced mitochondrial DNA toxicity in the forebrain.

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Lauritzen, Knut H; Hasan-Olive, Md Mahdi; Regnell, Christine E; Kleppa, Liv; Scheibye-Knudsen, Morten; Gjedde, Albert; Klungland, Arne; Bohr, Vilhelm A; Storm-Mathisen, Jon; Bergersen, Linda H

2016-12-01

Mitochondrial genome maintenance plays a central role in preserving brain health. We previously demonstrated accumulation of mitochondrial DNA damage and severe neurodegeneration in transgenic mice inducibly expressing a mutated mitochondrial DNA repair enzyme (mutUNG1) selectively in forebrain neurons. Here, we examine whether severe neurodegeneration in mutUNG1-expressing mice could be rescued by feeding the mice a ketogenic diet, which is known to have beneficial effects in several neurological disorders. The diet increased the levels of superoxide dismutase 2, and mitochondrial mass, enzymes, and regulators such as SIRT1 and FIS1, and appeared to downregulate N-methyl-D-aspartic acid (NMDA) receptor subunits NR2A/B and upregulate γ-aminobutyric acid A (GABA A ) receptor subunits α 1 . However, unexpectedly, the ketogenic diet aggravated neurodegeneration and mitochondrial deterioration. Electron microscopy showed structurally impaired mitochondria accumulating in neuronal perikarya. We propose that aggravation is caused by increased mitochondrial biogenesis of generally dysfunctional mitochondria. This study thereby questions the dogma that a ketogenic diet is unambiguously beneficial in mitochondrial disorders. Copyright © 2016 Elsevier Inc. All rights reserved.

Absence of correlation between serum CRP levels and mitochondrial D-loop DNA mutations in gastro-oesophageal adenocarcinoma

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Benjamin H. L. Tan

2014-01-01

Full Text Available Introduction: Both inflammation and mitochondrial DNA (mtDNA mutation are thought to play a role in the many human cancers. The aim of this study was to evaluate the relationship between inflammation and accumulation of mitochondrial DNA (mtDNA mutations in the D-loop region in carcinogenesis of gastro-oesophageal adenocarcinomas. Materials and Methods: Blood samples of 20 patients with gastro-oesophageal adenocarcinoma were taken for measurement of serum C-reactive protein (CRP concentration. Direct sequencing of mtDNA in the D-loop region was done in the 20 adenocarcinoma samples and their corresponding surrounding non-cancerous tissue. Sequences were compared with existing mtDNA databases to identify mutations. Results: mtDNA mutations in the D-loop region occur commonly with almost identical frequency in both non-cancerous tissue (3.0 ΁ 1.6 and adenocarcinoma (3.1 ΁ 1.9 (P = 0.916, paired t-test. CRP levels are not predictive of the number of D-loop mutations in both adenocarcinoma (β: -0.131; 95% CI: -2.354-1.364; P = 0.583 and non-cancerous tissue samples (β: 0.130; 95% CI: -1.125-1.933; P = 0.586. Five new mutations were identified that were not recorded previously in mtDNA databases. Conclusion: D-loop mtDNA mutations are common in both gastro-oesophageal adenocarcinoma and surrounding non-cancerous tissue. However, the accumulation of such mutations appears to occur independent of systemic inflammation. The frequency of D-loop mutations is likely not useful as a marker for carcinogenesis in gastro-oesophageal adenocarcinoma.

The mitochondrial and plastid genomes of Volvox carteri: bloated molecules rich in repetitive DNA

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Lee Robert W

2009-03-01

Full Text Available Abstract Background The magnitude of noncoding DNA in organelle genomes can vary significantly; it is argued that much of this variation is attributable to the dissemination of selfish DNA. The results of a previous study indicate that the mitochondrial DNA (mtDNA of the green alga Volvox carteri abounds with palindromic repeats, which appear to be selfish elements. We became interested in the evolution and distribution of these repeats when, during a cursory exploration of the V. carteri nuclear DNA (nucDNA and plastid DNA (ptDNA sequences, we found palindromic repeats with similar structural features to those of the mtDNA. Upon this discovery, we decided to investigate the diversity and evolutionary implications of these palindromic elements by sequencing and characterizing large portions of mtDNA and ptDNA and then comparing these data to the V. carteri draft nuclear genome sequence. Results We sequenced 30 and 420 kilobases (kb of the mitochondrial and plastid genomes of V. carteri, respectively – resulting in partial assemblies of these genomes. The mitochondrial genome is the most bloated green-algal mtDNA observed to date: ~61% of the sequence is noncoding, most of which is comprised of short palindromic repeats spread throughout the intergenic and intronic regions. The plastid genome is the largest (>420 kb and most expanded (>80% noncoding ptDNA sequence yet discovered, with a myriad of palindromic repeats in the noncoding regions, which have a similar size and secondary structure to those of the mtDNA. We found that 15 kb (~0.01% of the nuclear genome are homologous to the palindromic elements of the mtDNA, and 50 kb (~0.05% are homologous to those of the ptDNA. Conclusion Selfish elements in the form of short palindromic repeats have propagated in the V. carteri mtDNA and ptDNA, resulting in the distension of these genomes. Copies of these same repeats are also found in a small fraction of the nucDNA, but appear to be inert in this

Frequent occurrence of mitochondrial DNA mutations in Barrett's metaplasia without the presence of dysplasia.

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Soong Lee

Full Text Available BACKGROUND: Barrett's esophagus (BE is one of the most common premalignant lesions and can progress to esophageal adenocarcinoma (EA. The numerous molecular events may play a role in the neoplastic transformation of Barrett's mucosa such as the change of DNA ploidy, p53 mutation and alteration of adhesion molecules. However, the molecular mechanism of the progression of BE to EA remains unclear and most studies of mitochondrial DNA (mtDNA mutations in BE have performed on BE with the presence of dysplasia. METHODS/FINDINGS: Thus, the current study is to investigate new molecular events (Barrett's esophageal tissue-specific-mtDNA alterations/instabilities in mitochondrial genome and causative factors for their alterations using the corresponding adjacent normal mucosal tissue (NT and tissue (BT from 34 patients having Barrett's metaplasia without the presence of dysplasia. Eighteen patients (53% exhibited mtDNA mutations which were not found in adjacent NT. mtDNA copy number was about 3 times higher in BT than in adjacent NT. The activity of the mitochondrial respiratory chain enzyme complexes in tissues from Barrett's metaplasia without the presence of dysplasia was impaired. Reactive oxygen species (ROS level in BT was significantly higher than those in corresponding samples. CONCLUSION/SIGNIFICANCE: High ROS level in BT may contribute to the development of mtDNA mutations, which may play a crucial role in disease progression and tumorigenesis in BE.

Fly Diversity Revealed by PCR-RFLP of Mitochondrial DNA

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Asraoui, Jimmy F.; Sayar, Nancy P.; Knio, Khouzama M.; Smith, Colin A.

2008-01-01

In this article, we describe an inexpensive, two-session undergraduate laboratory activity that introduces important molecular biology methods in the context of biodiversity. In the first session, students bring tentatively identified flies (order Diptera, true flies) to the laboratory, extract DNA, and amplify a region of the mitochondrial gene…

A novel mutation in the mitochondrial DNA cytochrome b gene (MTCYB) in a patient with mitochondrial encephalomyopathy, lactic acidosis, and strokelike episodes syndrome.

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Emmanuele, Valentina; Sotiriou, Evangelia; Rios, Purificación Gutierrez; Ganesh, Jaya; Ichord, Rebecca; Foley, A Reghan; Akman, H Orhan; Dimauro, Salvatore

2013-02-01

Mutations in the mitochondrial DNA cytochrome b gene (MTCYB) have been commonly associated with isolated mitochondrial myopathy and exercise intolerance, rarely with multisystem disorders, and only once with a parkinsonism/mitochondrial encephalomyopathy, lactic acidosis, and strokelike episodes (MELAS) overlap syndrome. Here, we describe a novel mutation (m.14864 T>C) in MTCYB in a 15-year-old girl with a clinical history of migraines, epilepsy, sensorimotor neuropathy, and strokelike episodes, a clinical picture reminiscent of MELAS.  The mutation, which changes a highly conserved cysteine to arginine at amino acid position 40 of cytochrome b, was heteroplasmic in muscle, blood, fibroblasts, and urinary sediment from the patient but absent in accessible tissues from her asymptomatic mother. This case demonstrates that MTCYB must be included in the already long list of mitochondrial DNA genes that have been associated with the MELAS phenotype.

Mitochondrial myopathies.

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DiMauro, Salvatore

2006-11-01

Our understanding of mitochondrial diseases (defined restrictively as defects of the mitochondrial respiratory chain) is expanding rapidly. In this review, I will give the latest information on disorders affecting predominantly or exclusively skeletal muscle. The most recently described mitochondrial myopathies are due to defects in nuclear DNA, including coenzyme Q10 deficiency and mutations in genes controlling mitochondrial DNA abundance and structure, such as POLG, TK2, and MPV17. Barth syndrome, an X-linked recessive mitochondrial myopathy/cardiopathy, is associated with decreased amount and altered structure of cardiolipin, the main phospholipid of the inner mitochondrial membrane, but a secondary impairment of respiratory chain function is plausible. The role of mutations in protein-coding genes of mitochondrial DNA in causing isolated myopathies has been confirmed. Mutations in tRNA genes of mitochondrial DNA can also cause predominantly myopathic syndromes and--contrary to conventional wisdom--these mutations can be homoplasmic. Defects in the mitochondrial respiratory chain impair energy production and almost invariably involve skeletal muscle, causing exercise intolerance, cramps, recurrent myoglobinuria, or fixed weakness, which often affects extraocular muscles and results in droopy eyelids (ptosis) and progressive external ophthalmoplegia.

Mitochondrial DNA sequence variation in Finnish patients with matrilineal diabetes mellitus

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Soini Heidi K

2012-07-01

Full Text Available Abstract Background The genetic background of type 2 diabetes is complex involving contribution by both nuclear and mitochondrial genes. There is an excess of maternal inheritance in patients with type 2 diabetes and, furthermore, diabetes is a common symptom in patients with mutations in mitochondrial DNA (mtDNA. Polymorphisms in mtDNA have been reported to act as risk factors in several complex diseases. Findings We examined the nucleotide variation in complete mtDNA sequences of 64 Finnish patients with matrilineal diabetes. We used conformation sensitive gel electrophoresis and sequencing to detect sequence variation. We analysed the pathogenic potential of nonsynonymous variants detected in the sequences and examined the role of the m.16189 T>C variant. Controls consisted of non-diabetic subjects ascertained in the same population. The frequency of mtDNA haplogroup V was 3-fold higher in patients with diabetes. Patients harboured many nonsynonymous mtDNA substitutions that were predicted to be possibly or probably damaging. Furthermore, a novel m.13762 T>G in MTND5 leading to p.Ser476Ala and several rare mtDNA variants were found. Haplogroup H1b harbouring m.16189 T > C and m.3010 G > A was found to be more frequent in patients with diabetes than in controls. Conclusions Mildly deleterious nonsynonymous mtDNA variants and rare population-specific haplotypes constitute genetic risk factors for maternally inherited diabetes.

Nickel exposure induces oxidative damage to mitochondrial DNA in Neuro2a cells: the neuroprotective roles of melatonin.

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Xu, Shang-Cheng; He, Min-Di; Lu, Yong-Hui; Li, Li; Zhong, Min; Zhang, Yan-Wen; Wang, Yuan; Yu, Zheng-Ping; Zhou, Zhou

2011-11-01

Recent studies suggest that oxidative stress and mitochondrial dysfunction play important roles in the neurotoxicity of nickel. Because mitochondrial DNA (mtDNA) is highly vulnerable to oxidative stress and melatonin can efficiently protect mtDNA against oxidative damage in various pathological conditions, the aims of this study were to determine whether mtDNA oxidative damage was involved in the neurotoxicity of nickel and to assay the neuroprotective effects of melatonin in mtDNA. In this study, we exposed mouse neuroblastoma cell lines (Neuro2a) to different concentrations of nickel chloride (NiCl(2), 0.125, 0.25, and 0.5 mm) for 24 hr. We found that nickel significantly increased reactive oxygen species (ROS) production and mitochondrial superoxide levels. In addition, nickel exposure increased mitochondrial 8-hydroxyguanine (8-OHdG) content and reduced mtDNA content and mtDNA transcript levels. Consistent with this finding, nickel was found to destroy mtDNA nucleoid structure and decrease protein levels of Tfam, a key protein component for nucleoid organization. However, all the oxidative damage to mtDNA induced by nickel was efficiently attenuated by melatonin pretreatment. Our results suggest that oxidative damage to mtDNA may account for the neurotoxicity of nickel. Melatonin has great pharmacological potential in protecting mtDNA against the adverse effects of nickel in the nervous system. © 2011 John Wiley & Sons A/S.

An association analysis between mitochondrial DNA content, G10398A polymorphism, HPV infection, and the prognosis of cervical cancer in the Chinese Han population.

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Feng, Dali; Xu, Hui; Li, Xin; Wei, Yuehua; Jiang, Huangang; Xu, Hong; Luo, Aihua; Zhou, Fuxiang

2016-04-01

The aim was to analyze quantitative (mitochondrial DNA (mtDNA) content) and qualitative (G10398A polymorphism) mtDNA alterations as well as human papillomavirus (HPV) infection in cervical cancer prognosis. One hundred and twenty-two cases of formalin-fixed paraffin-embedded cervical carcinoma specimens were collected from the Yichang Tumor Hospital and Zhongnan Hospital of Wuhan University in the recent 10 years together with medical records. A quantitative real-time PCR (RT-PCR) was used to determine the copy number of the mitochondrial DNA and HPV expression levels. G10398A polymorphism was determined by PCR-RFLP assay. The overall survival of patients with higher mtDNA content was significantly reduced compared with lower mtDNA content patients (P = 0.029). But there was no difference of prognosis between the mtDNA 10398 A allele and G allele. However, the Kaplan-Meier survival curve illustrated a significantly reduced overall survival in the patients with 10398A plus high mtDNA copy number compared with the other groups (P content compared with 10398G (P content were positively related in the younger subgroup (≤45 years) (correlation coefficient = 0.456, P = 0.022). This study indicated that mtDNA content and HPV infection status are associated with cervical cancer prognosis. High mitochondrial DNA content plus 10398 A may be a marker of poor prognosis in cervical cancer. And mtDNA variation may potentially influence the predisposition to HPV infection and cervical carcinogenesis.

A cryptic mitochondrial DNA link between North European and West African dogs.

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Adeola, Adeniyi C; Ommeh, Sheila C; Song, Jiao-Jiao; Olaogun, S Charles; Sanke, Oscar J; Yin, Ting-Ting; Wang, Guo-Dong; Wu, Shi-Fang; Zhou, Zhong-Yin; Lichoti, Jacqueline K; Agwanda, Bernard R; Dawuda, Philip M; Murphy, Robert W; Peng, Min-Sheng; Zhang, Ya-Ping

2017-03-20

Domestic dogs have an ancient origin and a long history in Africa. Nevertheless, the timing and sources of their introduction into Africa remain enigmatic. Herein, we analyse variation in mitochondrial DNA (mtDNA) D-loop sequences from 345 Nigerian and 37 Kenyan village dogs plus 1530 published sequences of dogs from other parts of Africa, Europe and West Asia. All Kenyan dogs can be assigned to one of three haplogroups (matrilines; clades): A, B, and C, while Nigerian dogs can be assigned to one of four haplogroups A, B, C, and D. None of the African dogs exhibits a matrilineal contribution from the African wolf (Canis lupus lupaster). The genetic signal of a recent demographic expansion is detected in Nigerian dogs from West Africa. The analyses of mitochondrial genomes reveal a maternal genetic link between modern West African and North European dogs indicated by sub-haplogroup D1 (but not the entire haplogroup D) coalescing around 12,000 years ago. Incorporating molecular anthropological evidence, we propose that sub-haplogroup D1 in West African dogs could be traced back to the late-glacial dispersals, potentially associated with human hunter-gatherer migration from southwestern Europe. Copyright © 2016 Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, and Genetics Society of China. Published by Elsevier Ltd. All rights reserved.

Differential mitochondrial DNA and gene expression in inherited retinal dysplasia in miniature Schnauzer dogs.

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Appleyard, Greg D; Forsyth, George W; Kiehlbauch, Laura M; Sigfrid, Kristen N; Hanik, Heather L J; Quon, Anita; Loewen, Matthew E; Grahn, Bruce H

2006-05-01

To investigate the molecular basis of inherited retinal dysplasia in miniature Schnauzers. Retina and retinal pigment epithelial tissues were collected from canine subjects at the age of 3 weeks. Total RNA isolated from these tissues was reverse transcribed to make representative cDNA pools that were compared for differences in gene expression by using a subtractive hybridization technique referred to as representational difference analysis (RDA). Expression differences identified by RDA were confirmed and quantified by real-time reverse-transcription PCR. Mitochondrial morphology from leukocytes and skeletal muscle of normal and affected miniature Schnauzers was examined by transmission electron microscopy. RDA screening of retinal pigment epithelial cDNA identified differences in mRNA transcript coding for two mitochondrial (mt) proteins--cytochrome oxidase subunit 1 and NADH dehydrogenase subunit 6--in affected dogs. Contrary to expectations, these identified sequences did not contain mutations. Based on the implication of mt-DNA-encoded proteins by the RDA experiments we used real-time PCR to compare the relative amounts of mt-DNA template in white blood cells from normal and affected dogs. White blood cells of affected dogs contained less than 30% of the normal amount of two specific mtDNA sequences, compared with the content of the nuclear-encoded glyceraldehyde-3-phosphate dehydrogenase (GA-3-PDH) reference gene. Retina and RPE tissue from affected dogs had reduced mRNA transcript levels for the two mitochondrial genes detected in the RDA experiment. Transcript levels for another mtDNA-encoded gene as well as the nuclear-encoded mitochondrial Tfam transcription factor were reduced in these tissues in affected dogs. Mitochondria from affected dogs were reduced in number and size and were unusually electron dense. Reduced levels of nuclear and mitochondrial transcripts in the retina and RPE of miniature Schnauzers affected with retinal dysplasia suggest that

Norgal: extraction and de novo assembly of mitochondrial DNA from whole-genome sequencing data.

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Al-Nakeeb, Kosai; Petersen, Thomas Nordahl; Sicheritz-Pontén, Thomas

2017-11-21

Whole-genome sequencing (WGS) projects provide short read nucleotide sequences from nuclear and possibly organelle DNA depending on the source of origin. Mitochondrial DNA is present in animals and fungi, while plants contain DNA from both mitochondria and chloroplasts. Current techniques for separating organelle reads from nuclear reads in WGS data require full reference or partial seed sequences for assembling. Norgal (de Novo ORGAneLle extractor) avoids this requirement by identifying a high frequency subset of k-mers that are predominantly of mitochondrial origin and performing a de novo assembly on a subset of reads that contains these k-mers. The method was applied to WGS data from a panda, brown algae seaweed, butterfly and filamentous fungus. We were able to extract full circular mitochondrial genomes and obtained sequence identities to the reference sequences in the range from 98.5 to 99.5%. We also assembled the chloroplasts of grape vines and cucumbers using Norgal together with seed-based de novo assemblers. Norgal is a pipeline that can extract and assemble full or partial mitochondrial and chloroplast genomes from WGS short reads without prior knowledge. The program is available at: https://bitbucket.org/kosaidtu/norgal .

Repair of pyrimidine dimers in nuclear and mitochondrial DNA of yeast irradiated with low doses of ultraviolet light

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Prakash, L [Rochester Univ., N.Y. (USA). Dept. of Radiation Biology and Biophysics

1975-01-01

The repair of damage induced by ultraviolet light has been examined in both the nuclear and mitochondrial DNA of the yeast Saccharomyces cerevisiae. The sensitive assay used in this study is based on the capacity of the bacteriophage T4 u.v. endonuclease to produce single-strand breaks in DNA that contains pyrimidine dimers, thus permitting the use of low fluences (doses) of u.v. The results demonstrate that virtually all of the dimers induced in the nuclear DNA of a repair-proficient strain (RAD+) are removed following dark incubation for four hours in growth medium. In contrast, the dimers induced in mitochondrial DNA by the same u.v. fluence are retained under the same conditions. In the excision-deficient mutant, rad1-2, no evidence was obtained for removal of pyrimidine dimers from nuclear DNA. Photoreactivation of both RAD + and rad1-2 cultures resulted in decreases of dimers from both nuclear and mitochondrial DNA. It is concluded that an excision-repair mechanism operates on nuclear but not mitochondrial DNA in repair-proficient yeast, and that the rad1-2 mutant is defective in this process.

Exercise-Induced Neuroprotection of Hippocampus in APP/PS1 Transgenic Mice via Upregulation of Mitochondrial 8-Oxoguanine DNA Glycosylase

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Hai Bo

2014-01-01

Full Text Available Improving mitochondrial function has been proposed as a reasonable therapeutic strategy to reduce amyloid-β (Aβ load and to modify the progression of Alzheimer’s disease (AD. However, the relationship between mitochondrial adaptation and brain neuroprotection caused by physical exercise in AD is poorly understood. This study was undertaken to investigate the effects of long-term treadmill exercise on mitochondrial 8-oxoguanine DNA glycosylase-1 (OGG1 level, mtDNA oxidative damage, and mitochondrial function in the hippocampus of APP/PS1 transgenic mouse model of AD. In the present study, twenty weeks of treadmill training significantly improved the cognitive function and reduced the expression of Aβ-42 in APP/PS1 transgenic (Tg mice. Training also ameliorated mitochondrial respiratory function by increasing the complexes I, and IV and ATP synthase activities, whereas it attenuated ROS generation and mtDNA oxidative damage in Tg mice. Furthermore, the impaired mitochondrial antioxidant enzymes and mitochondrial OGG1 activities seen in Tg mice were restored with training. Acetylation level of mitochondrial OGG1 and MnSOD was markedly suppressed in Tg mice after exercise training, in parallel with increased level of SIRT3. These findings suggest that exercise training could increase mtDNA repair capacity in the mouse hippocampus, which in turn would result in protection against AD-related mitochondrial dysfunction and phenotypic deterioration.

A Phenotype-Driven Approach to Generate Mouse Models with Pathogenic mtDNA Mutations Causing Mitochondrial Disease

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Johanna H.K. Kauppila

2016-09-01

Full Text Available Mutations of mtDNA are an important cause of human disease, but few animal models exist. Because mammalian mitochondria cannot be transfected, the development of mice with pathogenic mtDNA mutations has been challenging, and the main strategy has therefore been to introduce mutations found in cell lines into mouse embryos. Here, we describe a phenotype-driven strategy that is based on detecting clonal expansion of pathogenic mtDNA mutations in colonic crypts of founder mice derived from heterozygous mtDNA mutator mice. As proof of concept, we report the generation of a mouse line transmitting a heteroplasmic pathogenic mutation in the alanine tRNA gene of mtDNA displaying typical characteristics of classic mitochondrial disease. In summary, we describe a straightforward and technically simple strategy based on mouse breeding and histology to generate animal models of mtDNA-mutation disease, which will be of great importance for studies of disease pathophysiology and preclinical treatment trials.

Molecular mechanisms of mitochondrial DNA depletion diseases caused by deficiencies in enzymes in purine and pyrimidine metabolism.

Science.gov (United States)

Eriksson, Staffan; Wang, Liya

2008-06-01

Mitochondrial DNA depletion syndrome (MDS), a reduction of mitochondrial DNA copy number, often affects muscle or liver. Mutations in enzymes of deoxyribonucleotide metabolism give MDS, for example, the mitochondrial thymidine kinase 2 (TK2) and deoxyguanosine kinase (dGK) genes. Sixteen TK2 and 22 dGK alterations are known. Their characteristics and symptoms are described. Levels of five key deoxynucleotide metabolizing enzymes in mouse tissues were measured. TK2 and dGK levels in muscles were 5- to 10-fold lower than other nonproliferating tissues and 100-fold lower compared to spleen. Each type of tissue apparently relies on de novo and salvage synthesis of DNA precursors to varying degrees.

Stock discrimination in Great Lakes Walleye using mitochondrial DNA restriction analysis

International Nuclear Information System (INIS)

Billington, N.; Hebert, P.D.N.

1986-01-01

Over the past two years it has become evident that because of its strict maternal inheritance and rapid rate of evolutionary differentiation, mitochondrial (mt) DNA diversity offers exceptional promise in the discrimination of fish stocks. The current project aims to determine the extent of mt DNA variation among stocks of walleye (Stizostedion vitreum) from the Great Lakes. At this point, mt DNA has been isolated from 68 walleye representing the Thames River stock and a reef breeding stock from western Lake Erie, as well as from individuals of S. canadense, a species which hybridizes with S. vitreum. Mitochondrial DNA was extracted from livers of these fish, purified by CsCl density gradient centrifugation and digested using 20 endonucleases. Polymorphisms were detected with 8 of the enzymes. There was a great deal of variation among fish from both spawning populations, so much so that individual fish could be identified by this technique. No single enzyme allowed discrimination of the two stocks, but restriction pattern variation following Dde I digestion permitted separation of 50% of Lake Erie fish from Thames River stock. Comparison of mt DNA restriction patterns of walleye and sauger showed that two species are easily separable, setting the stage for a more detailed study of hybridization between the taxa

Genetic portrait of Lisboa immigrant population from Angola with mitochondrial DNA.

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Simão, Filipa; Costa, Heloísa Afonso; da Silva, Claúdia Vieira; Ribeiro, Teresa; Porto, Maria João; Santos, Jorge Costa; Amorim, António

2015-03-01

Portugal has been considered a country of emigrants, nevertheless in the past decades the number of immigrants has grown throughout all the country. This migratory flux has contributed to a raise of heterogeneity at multiple levels. According to statistical data, at the end of 2012 the total number of Angolan immigrants in Portugal equalled about 20,000 individuals. A territorial predominance has been found for the metropolitan region of Lisboa. Angola is a country located in the Atlantic coast of Africa. The presence of Bantu people and the colonisation by Portuguese people on Angolan territory are considered to be the major modulators of the genetic patterns in Angola. Mitochondrial DNA is known for its features that enable an approach to the study of human origin and evolution, as well to the different migration pathways of populations. This genetic marker can also contribute to ascertaining the identity of individuals in forensic cases. The main aim of this study was to determine the genetic structure of the Angolan immigrant population living in Lisboa. Therefore, a total of 173 individuals, inhabitants in Lisboa, nonrelated and with Angolan ancestry were studied. Total control region of mitochondrial DNA was amplified from position 16,024 to position 576 using two pairs of primers - L15997/H016 and L16555/H639. The majority of the identified haplotypes belong to mtDNA lineages known to be specific of the sub-Saharan region. Our results show that this immigrant population inhabitant in Lisboa presents a genetic profile that is characteristic of African populations. This study also demonstrates the genetic diversity that this immigrant population introduces in Lisboa. This does not contradict the historical data concerning colonization of Angola, since this was made mainly by male European individuals, who did not contribute with their maternal information of mtDNA. Lisboa immigrant population from Angola can be accessed via EMPOP dataset with accession number

The mitochondrial ND1 m.3337G>A mutation associated to multiple mitochondrial DNA deletions in a patient with Wolfram syndrome and cardiomyopathy

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Mezghani, Najla [Laboratoire de Genetique Moleculaire Humaine, Faculte de Medecine de Sfax, Universite de Sfax (Tunisia); Mnif, Mouna [Service d' endocrinologie, C.H.U. Habib Bourguiba de Sfax (Tunisia); Mkaouar-Rebai, Emna, E-mail: emna_mkaouar@mail2world.com [Laboratoire de Genetique Moleculaire Humaine, Faculte de Medecine de Sfax, Universite de Sfax (Tunisia); Kallel, Nozha [Service d' endocrinologie, C.H.U. Habib Bourguiba de Sfax (Tunisia); Salem, Ikhlass Haj [Laboratoire de Genetique Moleculaire Humaine, Faculte de Medecine de Sfax, Universite de Sfax (Tunisia); Charfi, Nadia; Abid, Mohamed [Service d' endocrinologie, C.H.U. Habib Bourguiba de Sfax (Tunisia); Fakhfakh, Faiza [Laboratoire de Genetique Moleculaire Humaine, Faculte de Medecine de Sfax, Universite de Sfax (Tunisia)

2011-07-29

Highlights: {yields} We reported a patient with Wolfram syndrome and dilated cardiomyopathy. {yields} We detected the ND1 mitochondrial m.3337G>A mutation in 3 tested tissues (blood leukocytes, buccal mucosa and skeletal muscle). {yields} Long-range PCR amplification revealed the presence of multiple mitochondrial deletions in the skeletal muscle. {yields} The deletions remove several tRNA and protein-coding genes. -- Abstract: Wolfram syndrome (WFS) is a rare hereditary disorder also known as DIDMOAD (diabetes insipidus, diabetes mellitus, optic atrophy, and deafness). It is a heterogeneous disease and full characterization of all clinical and biological features of this disorder is difficult. The wide spectrum of clinical expression, affecting several organs and tissues, and the similarity in phenotype between patients with Wolfram syndrome and those with certain types of respiratory chain diseases suggests mitochondrial DNA (mtDNA) involvement in Wolfram syndrome patients. We report a Tunisian patient with clinical features of moderate Wolfram syndrome including diabetes, dilated cardiomyopathy and neurological complications. The results showed the presence of the mitochondrial ND1 m.3337G>A mutation in almost homoplasmic form in 3 tested tissues of the proband (blood leukocytes, buccal mucosa and skeletal muscle). In addition, the long-range PCR amplifications revealed the presence of multiple deletions of the mitochondrial DNA extracted from the patient's skeletal muscle removing several tRNA and protein-coding genes. Our study reported a Tunisian patient with clinical features of moderate Wolfram syndrome associated with cardiomyopathy, in whom we detected the ND1 m.3337G>A mutation with mitochondrial multiple deletions.

The mitochondrial ND1 m.3337G>A mutation associated to multiple mitochondrial DNA deletions in a patient with Wolfram syndrome and cardiomyopathy

International Nuclear Information System (INIS)

Mezghani, Najla; Mnif, Mouna; Mkaouar-Rebai, Emna; Kallel, Nozha; Salem, Ikhlass Haj; Charfi, Nadia; Abid, Mohamed; Fakhfakh, Faiza

2011-01-01

Highlights: → We reported a patient with Wolfram syndrome and dilated cardiomyopathy. → We detected the ND1 mitochondrial m.3337G>A mutation in 3 tested tissues (blood leukocytes, buccal mucosa and skeletal muscle). → Long-range PCR amplification revealed the presence of multiple mitochondrial deletions in the skeletal muscle. → The deletions remove several tRNA and protein-coding genes. -- Abstract: Wolfram syndrome (WFS) is a rare hereditary disorder also known as DIDMOAD (diabetes insipidus, diabetes mellitus, optic atrophy, and deafness). It is a heterogeneous disease and full characterization of all clinical and biological features of this disorder is difficult. The wide spectrum of clinical expression, affecting several organs and tissues, and the similarity in phenotype between patients with Wolfram syndrome and those with certain types of respiratory chain diseases suggests mitochondrial DNA (mtDNA) involvement in Wolfram syndrome patients. We report a Tunisian patient with clinical features of moderate Wolfram syndrome including diabetes, dilated cardiomyopathy and neurological complications. The results showed the presence of the mitochondrial ND1 m.3337G>A mutation in almost homoplasmic form in 3 tested tissues of the proband (blood leukocytes, buccal mucosa and skeletal muscle). In addition, the long-range PCR amplifications revealed the presence of multiple deletions of the mitochondrial DNA extracted from the patient's skeletal muscle removing several tRNA and protein-coding genes. Our study reported a Tunisian patient with clinical features of moderate Wolfram syndrome associated with cardiomyopathy, in whom we detected the ND1 m.3337G>A mutation with mitochondrial multiple deletions.

Mitochondrial DNA copy number in peripheral blood cells declines with age and is associated with general health among elderly

DEFF Research Database (Denmark)

Mengel-From, Jonas; Thinggaard, Mikael; Dalgård, Christine

2014-01-01

compared to nuclear DNA, i.e. the mitochondrial DNA copy number, was measured by PCR technology and used as a proxy for the content of mitochondria copies. In 1,067 Danish twins and singletons (18-93 years of age), with the majority being elderly individuals, the estimated mean mitochondrial DNA copy...

Mitochondrial DNA D-loop sequence variation among 5 maternal lines of the Zemaitukai horse breed

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E. Gus Cothran

2005-12-01

Full Text Available Genetic variation in Zemaitukai horses was investigated using mitochondrial DNA (mtDNA sequencing. The study was performed on 421 bp of the mitochondrial DNA control region, which is known to be more variable than other sections of the mitochondrial genome. Samples from each of the remaining maternal family lines of Zemaitukai horses and three random samples for other Lithuanian (Lithuanian Heavy Draught, Zemaitukai large type and ten European horse breeds were sequenced. Five distinct haplotypes were obtained for the five Zemaitukai maternal families supporting the pedigree data. The minimal difference between two different sequence haplotypes was 6 and the maximal 11 nucleotides in Zemaitukai horse breed. A total of 20 nucleotide differences compared to the reference sequence were found in Lithuanian horse breeds. Genetic cluster analysis did not shown any clear pattern of relationship among breeds of different type.

Mitochondrial dysfunction and human immunodeficiency virus ...

African Journals Online (AJOL)

Human immunodeficiency virus (HIV) infection and the pharmacological treatment thereof have both been shown to affect mitochondrial function in a number of tissues, and each may cause specific organ pathology through specific mitochondrial pathways. HIV has been shown to kill various tissue cells by activation of ...

A Novel 3670-Base Pair Mitochondrial DNA Deletion Resulting in Multi-systemic Manifestations in a Child

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Hsin-Ming Liu

2012-08-01

Full Text Available Mitochondrial DNA (mtDNA deletion is a rare occurrence that results in defects to oxidative phosphorylation. The common clinical presentations of mtDNA deletion vary but include mitochondrial myopathy, Pearson syndrome, Kearns-Sayre syndrome, and progressive external ophthalmoplegia. Here, we report the case of a 10-year-old boy who presented with progressive deterioration of his clinical status (which included hypoglycemia, short stature, sensorineural hearing loss, retinitis pigmentosa, and chronic gastrointestinal dysmotility that progressed to acute deterioration with pancreatitis, Fanconi syndrome, lactic acidosis, and acute encephalopathy. Following treatment, the patient was stabilized and his neurological condition improved. Through a combination of histological examinations and biochemical and molecular analyses, mitochondrial disease was confirmed. A novel 3670-base pair deletion (deletion of mtDNA nt 7,628-11,297 was identified in the muscle tissue. A direct repeat of CTACT at the breakpoints was also detected.

MPV17-related mitochondrial DNA maintenance defect: New cases and review of clinical, biochemical, and molecular aspects.

Science.gov (United States)

El-Hattab, Ayman W; Wang, Julia; Dai, Hongzheng; Almannai, Mohammed; Staufner, Christian; Alfadhel, Majid; Gambello, Michael J; Prasun, Pankaj; Raza, Saleem; Lyons, Hernando J; Afqi, Manal; Saleh, Mohammed A M; Faqeih, Eissa A; Alzaidan, Hamad I; Alshenqiti, Abduljabbar; Flore, Leigh Anne; Hertecant, Jozef; Sacharow, Stephanie; Barbouth, Deborah S; Murayama, Kei; Shah, Amit A; Lin, Henry C; Wong, Lee-Jun C

2018-04-01

Mitochondrial DNA (mtDNA) maintenance defects are a group of diseases caused by deficiency of proteins involved in mtDNA synthesis, mitochondrial nucleotide supply, or mitochondrial dynamics. One of the mtDNA maintenance proteins is MPV17, which is a mitochondrial inner membrane protein involved in importing deoxynucleotides into the mitochondria. In 2006, pathogenic variants in MPV17 were first reported to cause infantile-onset hepatocerebral mtDNA depletion syndrome and Navajo neurohepatopathy. To date, 75 individuals with MPV17-related mtDNA maintenance defect have been reported with 39 different MPV17 pathogenic variants. In this report, we present an additional 25 affected individuals with nine novel MPV17 pathogenic variants. We summarize the clinical features of all 100 affected individuals and review the total 48 MPV17 pathogenic variants. The vast majority of affected individuals presented with an early-onset encephalohepatopathic disease characterized by hepatic and neurological manifestations, failure to thrive, lactic acidemia, and mtDNA depletion detected mainly in liver tissue. Rarely, MPV17 deficiency can cause a late-onset neuromyopathic disease characterized by myopathy and peripheral neuropathy with no or minimal liver involvement. Approximately half of the MPV17 pathogenic variants are missense. A genotype with biallelic missense variants, in particular homozygous p.R50Q, p.P98L, and p.R41Q, can carry a relatively better prognosis. © 2017 Wiley Periodicals, Inc.

The efficiency of mitochondrial DNA markers in constructing genetic ...

African Journals Online (AJOL)

Administrator

2011-05-30

May 30, 2011 ... To date, only parts of mitochondrial DNA from cytochrome b, 12S rRNA, 16S rRNA and non-coding D- loop had been sequenced for different species of Oryx. Discrepancy in the genetic relationship among. Oryx species was previously revealed when combinations of these sequences were analyzed. In the.

Mitochondrial DNA phylogeography of least cisco Coregonus sardinella in Alaska.

Science.gov (United States)

Padula, V M; Causey, D; López, J A

2017-03-01

This study presents the first detailed analysis of the mitochondrial DNA diversity of least cisco Coregonus sardinella in Alaska using a 678 bp segment of the control region (D-loop) of the mitochondrial genome. Findings suggest that the history of C. sardinella in Alaska differs from that of other species of Coregonus present in the state and surrounding regions. The examined populations of C. sardinella are genetically diverse across Alaska. Sixty-eight distinct mitochondrial haplotypes were identified among 305 individuals sampled from nine locations. The haplotype minimum spanning network and phylogeny showed a modest level of geographic segregation among haplotypes, suggesting high levels of on-going or recent connectivity among distant populations. Observed Φ ST values and the results of homogeneity and AMOVAs indicate incipient genetic differentiation between aggregations in three broad regional groups. Sites north of the Brooks Range formed one group, sites in the Yukon and Selawik Rivers formed a second group and sites south of the Yukon drainage formed the third group. Overall, the sequence data showed that a large proportion of mtDNA genetic variation in C. sardinella is shared across Alaska, but this variation is not homogeneously distributed across all regions and for all haplotype groups. © 2017 The Fisheries Society of the British Isles.

Archeogenetika. Mitochondriální DNA a migrace Homo sapiens

Czech Academy of Sciences Publication Activity Database

Černý, Viktor

2010-01-01

Roč. 11, - (2010), s. 13-17 ISSN 1213-1628 R&D Projects: GA ČR GA206/08/1587; GA MŠk ME 917 Institutional research plan: CEZ:AV0Z80020508 Keywords : archaeogenetics * migrations * mitochondrial DNA Subject RIV: AC - Archeology, Anthropology, Ethnology

Prevalence of migraine in persons with the 3243A>G mutation in mitochondrial DNA

DEFF Research Database (Denmark)

Guo, S.; Esserlind, A-L; Andersson, Z

2016-01-01

% vs. 6%; P persons with the mDNA 3243A>G mutation was found. This finding suggests a clinical association between a monogenetically inherited disorder......BACKGROUND AND PURPOSE: Over the last three decades mitochondrial dysfunction has been postulated to be a potential mechanism in migraine pathogenesis. The lifetime prevalence of migraine in persons carrying the 3243A>G mutation in mitochondrial DNA was investigated. METHODS: In this cross......-sectional study, 57 mDNA 3243A>G mutation carriers between May 2012 and October 2014 were included. As a control group, a population-based cohort from our epidemiological studies on migraine in Danes was used. History of headache and migraine was obtained by telephone interview, based on a validated semi...

Mitochondrial DNA (mtDNA haplogroups in 1526 unrelated individuals from 11 Departments of Colombia

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Juan J. Yunis

2013-01-01

Full Text Available The frequencies of four mitochondrial Native American DNA haplogroups were determined in 1526 unrelated individuals from 11 Departments of Colombia and compared to the frequencies previously obtained for Amerindian and Afro-Colombian populations. Amerindian mtDNA haplogroups ranged from 74% to 97%. The lowest frequencies were found in Departments on the Caribbean coast and in the Pacific region, where the frequency of Afro-Colombians is higher, while the highest mtDNA Amerindian haplogroup frequencies were found in Departments that historically have a strong Amerindian heritage. Interestingly, all four mtDNA haplogroups were found in all Departments, in contrast to the complete absence of haplogroup D and high frequencies of haplogroup A in Amerindian populations in the Caribbean region of Colombia. Our results indicate that all four Native American mtDNA haplogroups were widely distributed in Colombia at the time of the Spanish conquest.

Thymidine kinase 2 deficiency-induced mitochondrial DNA depletion causes abnormal development of adipose tissues and adipokine levels in mice.

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Joan Villarroya

Full Text Available Mammal adipose tissues require mitochondrial activity for proper development and differentiation. The components of the mitochondrial respiratory chain/oxidative phosphorylation system (OXPHOS are encoded by both mitochondrial and nuclear genomes. The maintenance of mitochondrial DNA (mtDNA is a key element for a functional mitochondrial oxidative activity in mammalian cells. To ascertain the role of mtDNA levels in adipose tissue, we have analyzed the alterations in white (WAT and brown (BAT adipose tissues in thymidine kinase 2 (Tk2 H126N knockin mice, a model of TK2 deficiency-induced mtDNA depletion. We observed respectively severe and moderate mtDNA depletion in TK2-deficient BAT and WAT, showing both tissues moderate hypotrophy and reduced fat accumulation. Electron microscopy revealed altered mitochondrial morphology in brown but not in white adipocytes from TK2-deficient mice. Although significant reduction in mtDNA-encoded transcripts was observed both in WAT and BAT, protein levels from distinct OXPHOS complexes were significantly reduced only in TK2-deficient BAT. Accordingly, the activity of cytochrome c oxidase was significantly lowered only in BAT from TK2-deficient mice. The analysis of transcripts encoding up to fourteen components of specific adipose tissue functions revealed that, in both TK2-deficient WAT and BAT, there was a consistent reduction of thermogenesis related gene expression and a severe reduction in leptin mRNA. Reduced levels of resistin mRNA were found in BAT from TK2-deficient mice. Analysis of serum indicated a dramatic reduction in circulating levels of leptin and resistin. In summary, our present study establishes that mtDNA depletion leads to a moderate impairment in mitochondrial respiratory function, especially in BAT, causes substantial alterations in WAT and BAT development, and has a profound impact in the endocrine properties of adipose tissues.

Thymidine kinase 2 deficiency-induced mitochondrial DNA depletion causes abnormal development of adipose tissues and adipokine levels in mice.

Science.gov (United States)

Villarroya, Joan; Dorado, Beatriz; Vilà, Maya R; Garcia-Arumí, Elena; Domingo, Pere; Giralt, Marta; Hirano, Michio; Villarroya, Francesc

2011-01-01

Mammal adipose tissues require mitochondrial activity for proper development and differentiation. The components of the mitochondrial respiratory chain/oxidative phosphorylation system (OXPHOS) are encoded by both mitochondrial and nuclear genomes. The maintenance of mitochondrial DNA (mtDNA) is a key element for a functional mitochondrial oxidative activity in mammalian cells. To ascertain the role of mtDNA levels in adipose tissue, we have analyzed the alterations in white (WAT) and brown (BAT) adipose tissues in thymidine kinase 2 (Tk2) H126N knockin mice, a model of TK2 deficiency-induced mtDNA depletion. We observed respectively severe and moderate mtDNA depletion in TK2-deficient BAT and WAT, showing both tissues moderate hypotrophy and reduced fat accumulation. Electron microscopy revealed altered mitochondrial morphology in brown but not in white adipocytes from TK2-deficient mice. Although significant reduction in mtDNA-encoded transcripts was observed both in WAT and BAT, protein levels from distinct OXPHOS complexes were significantly reduced only in TK2-deficient BAT. Accordingly, the activity of cytochrome c oxidase was significantly lowered only in BAT from TK2-deficient mice. The analysis of transcripts encoding up to fourteen components of specific adipose tissue functions revealed that, in both TK2-deficient WAT and BAT, there was a consistent reduction of thermogenesis related gene expression and a severe reduction in leptin mRNA. Reduced levels of resistin mRNA were found in BAT from TK2-deficient mice. Analysis of serum indicated a dramatic reduction in circulating levels of leptin and resistin. In summary, our present study establishes that mtDNA depletion leads to a moderate impairment in mitochondrial respiratory function, especially in BAT, causes substantial alterations in WAT and BAT development, and has a profound impact in the endocrine properties of adipose tissues. © 2011 Villarroya et al.

Effect of Mucuna pruriens (Linn.) on mitochondrial dysfunction and DNA damage in epididymal sperm of streptozotocin induced diabetic rat.

Science.gov (United States)

Suresh, Sekar; Prithiviraj, Elumalai; Lakshmi, Nagella Venkata; Ganesh, Mohanraj Karthik; Ganesh, Lakshmanan; Prakash, Seppan

2013-01-09

Mucuna pruriens Linn. (M. pruriens) is a leguminous plant that has been recognized as an herbal medicine for improving fertility and related disorders in the Indian traditional system of medicine, however without proper scientific validations. To study the effect of ethanolic seed extract of M. pruriens on mitochondrial dysfunction and the DNA damage in hyperglycemic rat epididymal spermatozoa. Male Wistar albino rats were divided as control (Sham), diabetes induced [streptozotocin 60 mg/kg of body weight (b.w.) in 0.1M citrate buffer] (STZ), diabetic rats administered with 200mg/kg b.w. of extract (STZ+MP) and normal rats administered with 200mg/kg b.w. of extract (Sham+MP). M. pruriens was administered (gavage) once daily for a period of 60 days. On 60th day animals were sacrificed by cervical dislocation sperm were collected from epididymis and subjected various analysis like antioxidants, ROS, lipid peroxidation (LPO), DNA damage, chromosomal integrity and mitochondrial membrane potential (MMP). Significant reduction in the sperm count, motility, viability and significant increase in the number of abnormal sperm in STZ compared to sham was noticed. STZ rat sperm showed significant increase in LPO and DNA damage. Both the enzymic and non-enzymic were decreased; MMP and the mitochondrial functions were severely affected in STZ group. The diabetic rats supplemented with M. pruriens showed a remarkable recovery in antioxidant levels and reduced LPO with well preserved sperm DNA. MMP and mitochondrial function test were also preserved in STZ+MP rat sperm. The present study has clearly demonstrated the potency of M. pruriens to reduce the diabetic induced sperm damage induced by oxidative stress (OS). These observations are encouraging to perform similar studies in human. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Tissue specific distribution of pyrimidine deoxynucleoside salvage enzymes shed light on the mechanism of mitochondrial DNA depletion.