bims-midmar 2021-10-24 papers

bims-midmar

Biomed News

on Mitochondrial DNA maintenance and replication

Issue of 2021–10–24
twenty papers selected by
Flavia Söllner, Ludwig-Maximilians University

Human Mitochondrial DNA: Particularities and Diseases.
Research progress on the physiological function of mtDNA and its specific detection and therapy.
Mitochondrial Translation Occurs Preferentially in the Peri-Nuclear Mitochondrial Network of Cultured Human Cells.
Decreasing mitochondrial RNA polymerase activity reverses biased inheritance of hypersuppressive mtDNA.
An in vitro system to silence mitochondrial gene expression.
Interrogating Mitochondrial Biology and Disease Using CRISPR/Cas9 Gene Editing.
Human PrimPol Discrimination against Dideoxynucleotides during Primer Synthesis.
The Genetic Landscape of Mitochondrial Diseases in Spain: A Nationwide Call.
Mitochondrial DNA and Exercise: Implications for Health and Injuries in Sports.
Creating Cell Model 2.0 Using Patient Samples Carrying a Pathogenic Mitochondrial DNA Mutation: iPSC Approach for LHON.
Mitochondrial Strokes: Diagnostic Challenges and Chameleons.
Mitochondrial dynamics and its impact on human health and diseases: inside the DRP1 blackbox.
The crucial roles of mitochondria in supporting C4 photosynthesis.
Unravelling roles of error-prone DNA polymerases in shaping cancer genomes.
Mitochondrial and Oxidative Unbalance in Placentas from Mothers with SARS-CoV-2 Infection.
Multi-Omics Approach to Mitochondrial DNA Damage in Human Muscle Fibers.
Mitochondrial Contributions to Hematopoietic Stem Cell Aging.
Cell-Free Mitochondrial DNA as a Potential Biomarker for Astronauts' Health.
Mitochondrial Telomerase Reverse Transcriptase Protects from Myocardial Ischemia/reperfusion Injury by Improving Complex I Composition and Function.
Monitoring Mitochondrial Function in Aedes albopictus C6/36 Cell Line during Dengue Virus Infection.

Biomedicines. 2021 Oct 01. pii: 1364. [Epub ahead of print]9(10):

Human Mitochondrial DNA: Particularities and Diseases.

Mouna Habbane, Julio Montoya, Taha Rhouda, Yousra Sbaoui, Driss Radallah, Sonia Emperador.

  Mitochondria are the cell's power site, transforming energy into a form that the cell can employ for necessary metabolic reactions. These organelles present their own DNA. Although it codes for a small number of genes, mutations in mtDNA are common. Molecular genetics diagnosis allows the analysis of DNA in several areas such as infectiology, oncology, human genetics and personalized medicine. Knowing that the mitochondrial DNA is subject to several mutations which have a direct impact on the metabolism of the mitochondrion leading to many diseases, it is therefore necessary to detect these mutations in the patients involved. To date numerous mitochondrial mutations have been described in humans, permitting confirmation of clinical diagnosis, in addition to a better management of the patients. Therefore, different techniques are employed to study the presence or absence of mitochondrial mutations. However, new mutations are discovered, and to determine if they are the cause of disease, different functional mitochondrial studies are undertaken using transmitochondrial cybrid cells that are constructed by fusion of platelets of the patient that presents the mutation, with rho osteosarcoma cell line. Moreover, the contribution of next generation sequencing allows sequencing of the entire human genome within a single day and should be considered in the diagnosis of mitochondrial mutations.

Keywords:  mitochondrial diseases; molecular diagnosis; mtDNA; mutation

DOI:  https://doi.org/10.3390/biomedicines9101364
Chembiochem. 2021 Oct 18.

Research progress on the physiological function of mtDNA and its specific detection and therapy.

Congcong Zhang, Yufei Xue, Lan Wang, Qiong Wu, Bin Fang, Yu Shen, Hua Bai, Bo Peng, Naidi Yang, Lin Li.

  Mitochondrial DNA (mtDNA) is a mitochondrial genetic material, which is a circular double-stranded deoxyribonucleotide found in the mitochondria of cells. Despite the diminutive size of mitochondrial genome, mtDNA mutations are an important cause of mitochondrial diseases that are characterized by defects in oxidative phosphorylation. Mitochondrial diseases are involved in multiple systems, particularly in the organs that are highly dependent on aerobic metabolism. The diagnosis of mitochondrial disease is further complicated since mtDNA mutations can cause various clinical symptoms. To obtain more accurate diagnosis and treatment of mitochondrial diseases, the detection of mtDNA and the design of drugs acting on mtDNA are extremely important. Over the past few years, many probes and therapeutic drugs targeting mtDNA have been developed, making significant contributions to fundamental research including elucidation of the mechanisms of mitochondrial diseases at the genetic level. In this review, we summarize the structure, function, detection and their applications in mechanisms exploration and treatment of mtDNA mutation-related disorders. Noting that we specifically discuss how these probes and drugs for mtDNA are designed and developed. We hope that this review will provide readers with a comprehensive understanding of the importance of mtDNA, and promote the development of effective molecules for theragnosis of mtDNA mutation-related diseases.

Keywords:  DNA targeting; Fluorescent probes; Mitochondrial DNA; mitochondrial dysfunction; mitochondrial therapy

DOI:  https://doi.org/10.1002/cbic.202100474
Biology (Basel). 2021 Oct 15. pii: 1050. [Epub ahead of print]10(10):

Mitochondrial Translation Occurs Preferentially in the Peri-Nuclear Mitochondrial Network of Cultured Human Cells.

Christin A Albus, Rolando Berlinguer-Palmini, Caroline Hewison, Fiona McFarlane, Elisabeta-Ana Savu, Robert N Lightowlers, Zofia M Chrzanowska-Lightowlers, Matthew Zorkau.

  Human mitochondria are highly dynamic organelles, fusing and budding to maintain reticular networks throughout many cell types. Although extending to the extremities of the cell, the majority of the network is concentrated around the nucleus in most of the commonly cultured cell lines. This organelle harbours its own genome, mtDNA, with a different gene content to the nucleus, but the expression of which is critical for maintaining oxidative phosphorylation. Recent advances in click chemistry have allowed us to visualise sites of mitochondrial protein synthesis in intact cultured cells. We show that the majority of translation occurs in the peri-nuclear region of the network. Further analysis reveals that whilst there is a slight peri-nuclear enrichment in the levels of mitoribosomal protein and mitochondrial rRNA, it is not sufficient to explain this substantial heterogeneity in the distribution of translation. Finally, we also show that in contrast, a mitochondrial mRNA does not show such a distinct gradient in distribution. These data suggest that the relative lack of translation in the peripheral mitochondrial network is not due to an absence of mitoribosomes or an insufficient supply of the mt-mRNA transcripts.

Keywords:  co-localisation; heterogeneity; mammalian; mitochondria; peri-nuclear; peripheral; protein synthesis

DOI:  https://doi.org/10.3390/biology10101050
PLoS Genet. 2021 Oct 19. 17(10): e1009808

Decreasing mitochondrial RNA polymerase activity reverses biased inheritance of hypersuppressive mtDNA.

Daniel Corbi, Angelika Amon.

Faithful inheritance of mitochondrial DNA (mtDNA) is crucial for cellular respiration/oxidative phosphorylation and mitochondrial membrane potential. However, how mtDNA is transmitted to progeny is not fully understood. We utilized hypersuppressive mtDNA, a class of respiratory deficient Saccharomyces cerevisiae mtDNA that is preferentially inherited over wild-type mtDNA (rho+), to uncover the factors governing mtDNA inheritance. We found that some regions of rho+ mtDNA persisted while others were lost after a specific hypersuppressive takeover indicating that hypersuppressive preferential inheritance may partially be due to active destruction of rho+ mtDNA. From a multicopy suppression screen, we found that overexpression of putative mitochondrial RNA exonuclease PET127 reduced biased inheritance of a subset of hypersuppressive genomes. This suppression required PET127 binding to the mitochondrial RNA polymerase RPO41 but not PET127 exonuclease activity. A temperature-sensitive allele of RPO41 improved rho+ mtDNA inheritance over a specific hypersuppressive mtDNA at semi-permissive temperatures revealing a previously unknown role for rho+ transcription in promoting hypersuppressive mtDNA inheritance.

DOI: https://doi.org/10.1371/journal.pgen.1009808
Cell. 2021 Oct 11. pii: S0092-8674(21)01116-8. [Epub ahead of print]

An in vitro system to silence mitochondrial gene expression.

Luis Daniel Cruz-Zaragoza, Sven Dennerlein, Andreas Linden, Roya Yousefi, Elena Lavdovskaia, Abhishek Aich, Rebecca R Falk, Ridhima Gomkale, Thomas Schöndorf, Markus T Bohnsack, Ricarda Richter-Dennerlein, Henning Urlaub, Peter Rehling.

  The human mitochondrial genome encodes thirteen core subunits of the oxidative phosphorylation system, and defects in mitochondrial gene expression lead to severe neuromuscular disorders. However, the mechanisms of mitochondrial gene expression remain poorly understood due to a lack of experimental approaches to analyze these processes. Here, we present an in vitro system to silence translation in purified mitochondria. In vitro import of chemically synthesized precursor-morpholino hybrids allows us to target translation of individual mitochondrial mRNAs. By applying this approach, we conclude that the bicistronic, overlapping ATP8/ATP6 transcript is translated through a single ribosome/mRNA engagement. We show that recruitment of COX1 assembly factors to translating ribosomes depends on nascent chain formation. By defining mRNA-specific interactomes for COX1 and COX2, we reveal an unexpected function of the cytosolic oncofetal IGF2BP1, an RNA-binding protein, in mitochondrial translation. Our data provide insight into mitochondrial translation and innovative strategies to investigate mitochondrial gene expression.

Keywords:  IGF2BP1; antisense; mitochondria; mitochondrial ribosome; morpholino; oxidative phosphorylation; translation

DOI:  https://doi.org/10.1016/j.cell.2021.09.033
Genes (Basel). 2021 Oct 12. pii: 1604. [Epub ahead of print]12(10):

Interrogating Mitochondrial Biology and Disease Using CRISPR/Cas9 Gene Editing.

Jia-Xin Tang, Angela Pyle, Robert W Taylor, Monika Oláhová.

  Mitochondrial disease originates from genetic changes that impact human bodily functions by disrupting the mitochondrial oxidative phosphorylation system. MitoCarta is a curated and published inventory that sheds light on the mitochondrial proteome, but the function of some mitochondrially-localised proteins remains poorly characterised. Consequently, various gene editing systems have been employed to uncover the involvement of these proteins in mitochondrial biology and disease. CRISPR/Cas9 is an efficient, versatile, and highly accurate genome editing tool that was first introduced over a decade ago and has since become an indispensable tool for targeted genetic manipulation in biological research. The broad spectrum of CRISPR/Cas9 applications serves as an attractive and tractable system to study genes and pathways that are essential for the regulation and maintenance of mitochondrial health. It has opened possibilities of generating reliable cell and animal models of human disease, and with further exploitation of the technology, large-scale genomic screenings have uncovered a wealth of fundamental mechanistic insights. In this review, we describe the applications of CRISPR/Cas9 system as a genome editing tool to uncover new insights into pathomechanisms of mitochondrial diseases and/or biological processes involved in mitochondrial function.

Keywords:  CRISPR/Cas9; cell and animal models; genome editing; genome-wide CRISPR libraries screening; mitochondrial biology; mitochondrial disease

DOI:  https://doi.org/10.3390/genes12101604
Genes (Basel). 2021 Sep 24. pii: 1487. [Epub ahead of print]12(10):

Human PrimPol Discrimination against Dideoxynucleotides during Primer Synthesis.

Gustavo Carvalho, Alberto Díaz-Talavera, Patricia A Calvo, Luis Blanco, María I Martínez-Jiménez.

  PrimPol is required to re-prime DNA replication at both nucleus and mitochondria, thus facilitating fork progression during replicative stress. ddC is a chain-terminating nucleotide that has been widely used to block mitochondrial DNA replication because it is efficiently incorporated by the replicative polymerase Polγ. Here, we show that human PrimPol discriminates against dideoxynucleotides (ddNTP) when elongating a primer across 8oxoG lesions in the template, but also when starting de novo synthesis of DNA primers, and especially when selecting the 3'nucleotide of the initial dimer. PrimPol incorporates ddNTPs with a very low efficiency compared to dNTPs even in the presence of activating manganese ions, and only a 40-fold excess of ddNTP would significantly disturb PrimPol primase activity. This discrimination against ddNTPs prevents premature termination of the primers, warranting their use for elongation. The crystal structure of human PrimPol highlights Arg291 residue as responsible for the strong dNTP/ddNTP selectivity, since it interacts with the 3'-OH group of the incoming deoxynucleotide, absent in ddNTPs. Arg291, shown here to be critical for both primase and polymerase activities of human PrimPol, would contribute to the preferred binding of dNTPs versus ddNTPs at the 3'elongation site, thus avoiding synthesis of abortive primers.

Keywords:  CTNA; DNA primase; NRTIs; PrimPol; anti-retroviral; ddC; dideoxynucleotides; polymerase; zalcitabine

DOI:  https://doi.org/10.3390/genes12101487
Genes (Basel). 2021 Oct 09. pii: 1590. [Epub ahead of print]12(10):

The Genetic Landscape of Mitochondrial Diseases in Spain: A Nationwide Call.

Marcello Bellusci, Abraham J Paredes-Fuentes, Eduardo Ruiz-Pesini, Beatriz Gómez, Mitospain Working Group, Miguel A Martín, Julio Montoya, Rafael Artuch.

  The frequency of mitochondrial diseases (MD) has been scarcely documented, and only a few studies have reported data in certain specific geographical areas. In this study, we arranged a nationwide call in Spain to obtain a global estimate of the number of cases. A total of 3274 cases from 49 Spanish provinces were reported by 39 centres. Excluding duplicated and unsolved cases, 2761 patients harbouring pathogenic mutations in 140 genes were recruited between 1990 and 2020. A total of 508 patients exhibited mutations in nuclear DNA genes (75% paediatric patients) and 1105 in mitochondrial DNA genes (33% paediatric patients). A further 1148 cases harboured mutations in the MT-RNR1 gene (56% paediatric patients). The number of reported cases secondary to nuclear DNA mutations increased in 2014, owing to the implementation of next-generation sequencing technologies. Between 2014 and 2020, excepting MT-RNR1 cases, the incidence was 6.34 (95% CI: 5.71-6.97) cases per million inhabitants at the paediatric age and 1.36 (95% CI: 1.22-1.50) for adults. In conclusion, this is the first study to report nationwide epidemiological data for MD in Spain. The lack of identification of a remarkable number of mitochondrial genes necessitates the systematic application of high-throughput technologies in the routine diagnosis of MD.

Keywords:  Spanish registry; epidemiological data; incidence; mitochondrial DNA mutations; mitochondrial diseases; nuclear DNA mutations

DOI:  https://doi.org/10.3390/genes12101590
Cells. 2021 Sep 28. pii: 2575. [Epub ahead of print]10(10):

Mitochondrial DNA and Exercise: Implications for Health and Injuries in Sports.

Giada Zanini, Anna De Gaetano, Valentina Selleri, Gustavo Savino, Andrea Cossarizza, Marcello Pinti, Anna Vittoria Mattioli, Milena Nasi.

  Recently, several studies have highlighted the tight connection between mitochondria and physical activity. Mitochondrial functions are important in high-demanding metabolic activities, such as endurance sports. Moreover, regular training positively affects metabolic health by increasing mitochondrial oxidative capacity and regulating glucose metabolism. Exercise could have multiple effects, also on the mitochondrial DNA (mtDNA) and vice versa; some studies have investigated how mtDNA polymorphisms can affect the performance of general athletes and mtDNA haplogroups seem to be related to the performance of elite endurance athletes. Along with several stimuli, including pathogens, stress, trauma, and reactive oxygen species, acute and intense exercise also seem to be responsible for mtDNA release into the cytoplasm and extracellular space, leading to the activation of the innate immune response. In addition, several sports are characterized by a higher frequency of injuries, including cranial trauma, associated with neurological consequences. However, with regular exercise, circulating cell-free mtDNA levels are kept low, perhaps promoting cf-mtDNA removal, acting as a protective factor against inflammation.

Keywords:  NET; cf-mtDNA; exercise; sport; trauma

DOI:  https://doi.org/10.3390/cells10102575
Methods Mol Biol. 2021 Oct 21.

Creating Cell Model 2.0 Using Patient Samples Carrying a Pathogenic Mitochondrial DNA Mutation: iPSC Approach for LHON.

Pragya Singh, Tyler Bahr, Xiaoxu Zhao, Peiqing Hu, Marcel Daadi, TaoSheng Huang, Yidong Bai.

  Leber's Hereditary Optic Neuropathy is the most prevalent mitochondrial neurological disease caused by mutations in mitochondrial DNA encoded respiratory complex I subunits. Although the genetic origin for Leber's hereditary optic neuropathy was identified about 30 years ago, the underlying pathogenesis is still unclear primarily due to the lack of a relevant system or cell model. Current models are limited to lymphoblasts, fibroblasts, or cybrid cell lines. As the disease phenotype is limited to retinal ganglion cells, induced pluripotent stem cells will serve as an excellent model for studying this tissue-specific disease, elucidating its underlying molecular mechanisms, and identifying novel therapeutic targets. Here, we describe a detailed protocol for the generation of retinal ganglion cells, and also cardiomyocytes for proof of iPSC pluripotency.

Keywords:  Induced pluripotent stem cell; LHON; Retinal ganglion cells; mtDNA

DOI:  https://doi.org/10.1007/7651_2021_384
Genes (Basel). 2021 Oct 19. pii: 1643. [Epub ahead of print]12(10):

Mitochondrial Strokes: Diagnostic Challenges and Chameleons.

Chiara Pizzamiglio, Enrico Bugiardini, William L Macken, Cathy E Woodward, Michael G Hanna, Robert D S Pitceathly.

  Mitochondrial stroke-like episodes (SLEs) are a hallmark of mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS). They should be suspected in anyone with an acute/subacute onset of focal neurological symptoms at any age and are usually driven by seizures. Suggestive features of an underlying mitochondrial pathology include evolving MRI lesions, often originating within the posterior brain regions, the presence of multisystemic involvement, including diabetes, deafness, or cardiomyopathy, and a positive family history. The diagnosis of MELAS has important implications for those affected and their relatives, given it enables early initiation of appropriate treatment and genetic counselling. However, the diagnosis is frequently challenging, particularly during the acute phase of an event. We describe four cases of mitochondrial strokes to highlight the considerable overlap that exists with other neurological disorders, including viral and autoimmune encephalitis, ischemic stroke, and central nervous system (CNS) vasculitis, and discuss the clinical, laboratory, and imaging features that can help distinguish MELAS from these differential diagnoses.

Keywords:  MELAS; brain MRI; mitochondrial DNA; primary mitochondrial diseases; stroke-like episodes

DOI:  https://doi.org/10.3390/genes12101643
J Mol Med (Berl). 2021 Oct 16.

Mitochondrial dynamics and its impact on human health and diseases: inside the DRP1 blackbox.

Riddhi Banerjee, Agradeep Mukherjee, Shirisha Nagotu.

  Mitochondria are essential organelles that play a significant role in various cellular processes apart from providing energy in eukaryotic cells. An intricate link between mitochondrial structure and function is now unequivocally accepted. Several molecular players have been identified, which are important in maintaining the structure of the organelle. Dynamin-related protein 1 (DRP1) is one such conserved protein that is a vital regulator of mitochondrial dynamics. Multidisciplinary studies have helped elucidate the structure of the protein and its mechanism of action in great detail. Mutations in various domains of the protein have been identified that are associated with debilitating conditions in patients. The involvement of the protein in disease conditions such as neurodegeneration, cancer, and cardiovascular disorders is also gaining attention. The purpose of this review is to highlight recent findings on the role of DRP1 in human disease conditions and address its importance as a therapeutic target.

Keywords:  Cancer; Cardiovascular disease; DRP1; Mitochondria; Mutations; Neurodegeneration

DOI:  https://doi.org/10.1007/s00109-021-02150-7
New Phytol. 2021 Oct 20.

The crucial roles of mitochondria in supporting C4 photosynthesis.

Yuzhen Fan, Shinichi Asao, Robert T Furbank, Susanne von Caemmerer, David A Day, Guillaume Tcherkez, Tammy L Sage, Rowan F Sage, Owen K Atkin.

  C4 photosynthesis involves a series of biochemical and anatomical traits that significantly improve plant productivity under conditions that reduce the efficiency of C3 photosynthesis. We explore how evolution of the three classical biochemical types of C4 photosynthesis (NADP-ME, NAD-ME and PCK types) has affected the functions and properties of mitochondria. Mitochondria in C4 NAD-ME and PCK types play a direct role in decarboxylation of metabolites for C4 photosynthesis. Mitochondria in C4 PCK type also provide ATP for C4 metabolism, although this role for ATP provision is not seen in NAD-ME type. Such involvement has increased mitochondrial abundance/size and associated enzymatic capacity, and has altered mitochondrial location, ultrastructure and role in cellular carbon metabolism in the NAD-ME and PCK types. By contrast, these changes in mitochondrial properties are absent in the C4 NADP-ME type and C3 leaves, where mitochondria play no direct role in photosynthesis. From an eco-physiological perspective, rates of leaf respiration in darkness vary considerably among C4 species but does not differ systematically among the three C4 types. This review outlines further mitochondrial research in key areas central to the engineering of C4 pathway into C3 plants and to the understanding of variation in rates of C4 dark respiration.

Keywords:  C4 photosynthesis; C4 plants; leaf respiration; metabolic flexibility; mitochondria; mitochondrial anatomy; redox balancing

DOI:  https://doi.org/10.1111/nph.17818
Oncogene. 2021 Oct 18.

Unravelling roles of error-prone DNA polymerases in shaping cancer genomes.

Cyrus Vaziri, Igor B Rogozin, Qisheng Gu, Di Wu, Tovah A Day.

Mutagenesis is a key hallmark and enabling characteristic of cancer cells, yet the diverse underlying mutagenic mechanisms that shape cancer genomes are not understood. This review will consider the emerging challenge of determining how DNA damage response pathways-both tolerance and repair-act upon specific forms of DNA damage to generate mutations characteristic of tumors. DNA polymerases are typically the ultimate mutagenic effectors of DNA repair pathways. Therefore, understanding the contributions of DNA polymerases is critical to develop a more comprehensive picture of mutagenic mechanisms in tumors. Selection of an appropriate DNA polymerase-whether error-free or error-prone-for a particular DNA template is critical to the maintenance of genome stability. We review different modes of DNA polymerase dysregulation including mutation, polymorphism, and over-expression of the polymerases themselves or their associated activators. Based upon recent findings connecting DNA polymerases with specific mechanisms of mutagenesis, we propose that compensation for DNA repair defects by error-prone polymerases may be a general paradigm molding the mutational landscape of cancer cells. Notably, we demonstrate that correlation of error-prone polymerase expression with mutation burden in a subset of patient tumors from The Cancer Genome Atlas can identify mechanistic hypotheses for further testing. We contrast experimental approaches from broad, genome-wide strategies to approaches with a narrower focus on a few hundred base pairs of DNA. In addition, we consider recent developments in computational annotation of patient tumor data to identify patterns of mutagenesis. Finally, we discuss the innovations and future experiments that will develop a more comprehensive portrait of mutagenic mechanisms in human tumors.

DOI: https://doi.org/10.1038/s41388-021-02032-9
Antioxidants (Basel). 2021 Sep 24. pii: 1517. [Epub ahead of print]10(10):

Mitochondrial and Oxidative Unbalance in Placentas from Mothers with SARS-CoV-2 Infection.

Chiara Mandò, Valeria M Savasi, Gaia M Anelli, Silvia Corti, Anaïs Serati, Fabrizia Lisso, Chiara Tasca, Chiara Novielli, Irene Cetin.

  SARS-CoV-2 infection has been related to adverse pregnancy outcomes. A placental role in protecting the fetus from SARS-CoV-2 infection has been documented. Nevertheless, it is still unclear how the placenta is affected in SARS-CoV-2 infection. Here we assessed placental mitochondrial (mt) and oxidative features in COVID-19 and healthy mothers. mtDNA levels, DNA oxidative damage, expression levels of genes involved in antioxidant defenses, mitochondrial dynamics and respiratory chain subunits were investigated in placentas from singleton pregnancies of 30 women with SARS-CoV-2 infection during the third trimester (12 asymptomatic, 18 symptomatic) and 16 controls. mtDNA levels decreased in COVID-19 placentas vs. controls and inversely correlated with DNA oxidative damage, which increased in the symptomatic group. Antioxidant gene expressions decreased in SARS-CoV-2 mothers (CAT, GSS). Symptomatic cases also showed a lower expression of respiratory chain (NDUFA9, SDHA, COX4I1) and mt dynamics (DNM1L, FIS1) genes. Alterations in placental mitochondrial features and oxidative balance in COVID-19-affected mothers might be due to the impaired intrauterine environment, generated by systemic viral effects, leading to a negative vicious circle that worsens placental oxidative stress and mitochondrial efficiency. This likely causes cell homeostasis dysregulations, raising the potential of possible long-term effects.

Keywords:  COVID-19; SARS-CoV-2; mitochondria; oxidative stress; placenta; pregnancy

DOI:  https://doi.org/10.3390/antiox10101517
Int J Mol Sci. 2021 Oct 14. pii: 11080. [Epub ahead of print]22(20):

Multi-Omics Approach to Mitochondrial DNA Damage in Human Muscle Fibers.

Matthias Elstner, Konrad Olszewski, Holger Prokisch, Thomas Klopstock, Marta Murgia.

  Mitochondrial DNA deletions affect energy metabolism at tissue-specific and cell-specific threshold levels, but the pathophysiological mechanisms determining cell fate remain poorly understood. Chronic progressive external ophthalmoplegia (CPEO) is caused by mtDNA deletions and characterized by a mosaic distribution of muscle fibers with defective cytochrome oxidase (COX) activity, interspersed among fibers with retained functional respiratory chain. We used diagnostic histochemistry to distinguish COX-negative from COX-positive fibers in nine muscle biopsies from CPEO patients and performed laser capture microdissection (LCM) coupled to genome-wide gene expression analysis. To gain molecular insight into the pathogenesis, we applied network and pathway analysis to highlight molecular differences of the COX-positive and COX-negative fiber transcriptome. We then integrated our results with proteomics data that we previously obtained comparing COX-positive and COX-negative fiber sections from three other patients. By virtue of the combination of LCM and a multi-omics approach, we here provide a comprehensive resource to tackle the pathogenic changes leading to progressive respiratory chain deficiency and disease in mitochondrial deletion syndromes. Our data show that COX-negative fibers upregulate transcripts involved in translational elongation and protein synthesis. Furthermore, based on functional annotation analysis, we find that mitochondrial transcripts are the most enriched among those with significantly different expression between COX-positive and COX-negative fibers, indicating that our unbiased large-scale approach resolves the core of the pathogenic changes. Further enrichments include transcripts encoding LIM domain proteins, ubiquitin ligases, proteins involved in RNA turnover, and, interestingly, cell cycle arrest and cell death. These pathways may thus have a functional association to the molecular pathogenesis of the disease. Overall, the transcriptome and proteome show a low degree of correlation in CPEO patients, suggesting a relevant contribution of post-transcriptional mechanisms in shaping this disease phenotype.

Keywords:  disease models; mtDNA deletions; myopathy; proteomics; skeletal muscle; transcriptomics

DOI:  https://doi.org/10.3390/ijms222011080
Int J Mol Sci. 2021 Oct 15. pii: 11117. [Epub ahead of print]22(20):

Mitochondrial Contributions to Hematopoietic Stem Cell Aging.

Claudia Morganti, Keisuke Ito.

  Mitochondrial dysfunction and stem cell exhaustion are two hallmarks of aging. In the hematopoietic system, aging is linked to imbalanced immune response and reduced regenerative capacity in hematopoietic stem cells (HSCs), as well as an increased predisposition to a spectrum of diseases, including myelodysplastic syndrome and acute myeloid leukemia. Myeloid-biased differentiation and loss of polarity are distinct features of aged HSCs, which generally exhibit enhanced mitochondrial oxidative phosphorylation and increased production of reactive oxygen species (ROS), suggesting a direct role for mitochondria in the degenerative process. Here, we provide an overview of current knowledge of the mitochondrial mechanisms that contribute to age-related phenotypes in HSCs. These include mitochondrial ROS production, alteration/activation of mitochondrial metabolism, the quality control pathway of mitochondria, and inflammation. Greater understanding of the key machineries of HSC aging will allow us to identify new therapeutic targets for preventing, delaying, or even reversing aspects of this process.

Keywords:  ROS; aging; hematopoiesis; hematopoietic stem cell; inflammation; mitochondrial metabolism; stem cell exhaustion

DOI:  https://doi.org/10.3390/ijms222011117
J Am Heart Assoc. 2021 Oct 20. e022055

Cell-Free Mitochondrial DNA as a Potential Biomarker for Astronauts' Health.

Malik Bisserier, Santhanam Shanmughapriya, Amit Kumar Rai, Carolina Gonzalez, Agnieszka Brojakowska, Venkata Naga Srikanth Garikipati, Muniswamy Madesh, Paul J Mills, Kenneth Walsh, Arsen Arakelyan, Raj Kishore, Lahouaria Hadri, David A Goukassian.

  Background Space travel-associated stressors such as microgravity or radiation exposure have been reported in astronauts after short- and long-duration missions aboard the International Space Station. Despite risk mitigation strategies, adverse health effects remain a concern. Thus, there is a need to develop new diagnostic tools to facilitate early detection of physiological stress. Methods and Results We measured the levels of circulating cell-free mitochondrial DNA in blood plasma of 14 astronauts 10 days before launch, the day of landing, and 3 days after return. Our results revealed a significant increase of cell-free mitochondrial DNA in the plasma on the day of landing and 3 days after return with vast ~2 to 355-fold interastronaut variability. In addition, gene expression analysis of peripheral blood mononuclear cells revealed a significant increase in markers of inflammation, oxidative stress, and DNA damage. Conclusions Our study suggests that cell-free mitochondrial DNA abundance might be a biomarker of stress or immune response related to microgravity, radiation, and other environmental factors during space flight.

Keywords:  astronaut; biomarker; cell‐free DNA; space medicine

DOI:  https://doi.org/10.1161/JAHA.121.022055
Circulation. 2021 Oct 21.

Mitochondrial Telomerase Reverse Transcriptase Protects from Myocardial Ischemia/reperfusion Injury by Improving Complex I Composition and Function.

Niloofar Ale-Agha, Philipp Jakobs, Christine Goy, Mark Zurek, Julia Rosen, Nadine Dyballa-Rukes, Sabine Metzger, Jan Greulich, Florian von Ameln, Olaf Eckermann, Klaus Unfried, Fedor Brack, Maria Grandoch, Matthias Thielmann, Markus Kamler, Nilgün Gedik, Petra Kleinbongard, Andre Heinen, Gerd Heusch, Axel Gödecke, Joachim Altschmied, Judith Haendeler.

Background: The catalytic subunit of telomerase, Telomerase Reverse Transcriptase (TERT) has protective functions in the cardiovascular system. TERT is not only present in the nucleus, but also in mitochondria. However, it is unclear whether nuclear or mitochondrial TERT is responsible for the observed protection and appropriate tools are missing to dissect this. Methods: We generated new mouse models containing TERT exclusively in the mitochondria (mitoTERT mice) or the nucleus (nucTERT mice) to finally distinguish between the functions of nuclear and mitochondrial TERT. Outcome after ischemia/reperfusion, mitochondrial respiration in the heart as well as cellular functions of cardiomyocytes, fibroblasts, and endothelial cells were determined. Results: All mice were phenotypically normal. While respiration was reduced in cardiac mitochondria from TERT-deficient and nucTERT mice, it was increased in mitoTERT animals. The latter also had smaller infarcts than wildtype mice, whereas nucTERT animals had larger infarcts. The decrease in ejection fraction after one, two and four weeks of reperfusion was attenuated in mitoTERT mice. Scar size was also reduced and vascularization increased. Mitochondrial TERT protected a cardiomyocyte cell line from apoptosis. Myofibroblast differentiation, which depends on complex I activity, was abrogated in TERT-deficient and nucTERT cardiac fibroblasts and completely restored in mitoTERT cells. In endothelial cells, mitochondrial TERT enhanced migratory capacity and activation of endothelial NO synthase. Mechanistically, mitochondrial TERT improved the ratio between complex I matrix arm and membrane subunits explaining the enhanced complex I activity. In human right atrial appendages, TERT was localized in mitochondria and there increased by remote ischemic preconditioning. The Telomerase activator, TA-65 evoked a similar effect in endothelial cells, thereby increasing their migratory capacity, and enhanced myofibroblast differentiation. Conclusions: Mitochondrial, but not nuclear TERT, is critical for mitochondrial respiration and during ischemia/reperfusion injury. Mitochondrial TERT improves complex I subunit composition. TERT is present in human heart mitochondria, and remote ischemic preconditioning increases its level in those organelles. TA-65 has comparable effects ex vivo and improves migratory capacity of endothelial cells and myofibroblast differentiation. We conclude that mitochondrial TERT is responsible for cardioprotection and its increase could serve as a therapeutic strategy.

DOI: https://doi.org/10.1161/CIRCULATIONAHA.120.051923
Insects. 2021 Oct 14. pii: 934. [Epub ahead of print]12(10):

Monitoring Mitochondrial Function in Aedes albopictus C6/36 Cell Line during Dengue Virus Infection.

María E Santana-Román, Paola Maycotte, Salvador Uribe-Carvajal, Cristina Uribe-Alvarez, Nayeli Alvarado-Medina, Mohsin Khan, Aleem Siddiqui, Victoria Pando-Robles.

  Aedes aegypti and Aedes albopictus mosquitoes are responsible for dengue virus (DENV) transmission in tropical and subtropical areas worldwide, where an estimated 3 billion people live at risk of DENV exposure. DENV-infected individuals show symptoms ranging from sub-clinical or mild to hemorrhagic fever. Infected mosquitoes do not show detectable signs of disease, even though the virus maintains a lifelong persistent infection. The interactions between viruses and host mitochondria are crucial for virus replication and pathogenicity. DENV infection in vertebrate cells modulates mitochondrial function and dynamics to facilitate viral proliferation. Here, we describe that DENV also regulates mitochondrial function and morphology in infected C6/36 mosquito cells (derived from Aedes albopictus). Our results showed that DENV infection increased ROS (reactive oxygen species) production, modulated mitochondrial transmembrane potential and induced changes in mitochondrial respiration. Furthermore, we offer the first evidence that DENV causes translocation of mitofusins to mitochondria in the C6/36 mosquito cell line. Another protein Drp-1 (Dynamin-related protein 1) did not localize to mitochondria in DENV-infected cells. This observation therefore ruled out the possibility that the abovementioned alterations in mitochondrial function are associated with mitochondrial fission. In summary, this report provides some key insights into the virus-mitochondria crosstalk in DENV infected mosquito cells.

Keywords:  Aedes aegypti; dengue virus; mitochondria

DOI:  https://doi.org/10.3390/insects12100934