bims-algemi 2020-02-16 papers

bims-algemi

Biomed News

on Allotopic expression and gene therapy for mitochondrial disease

Issue of 2020–02–16
24 papers selected by
Atif Towheed, Columbia University Irving Medical Center

Pathogenic Mitochondria DNA Mutations: Current Detection Tools and Interventions.
How does protein degradation regulate TOM machinery-dependent mitochondrial import?
Advances in drug therapy for mitochondrial diseases.
Neuregulin-1 promotes mitochondrial biogenesis, attenuates mitochondrial dysfunction, and prevents hypoxia/reoxygenation injury in neonatal cardiomyocytes.
An inventory of interactors of the human HSP60/HSP10 chaperonin in the mitochondrial matrix space.
Mitochondrial respiratory chain complex I dysfunction induced by N-methyl carbamate ex vivo can be alleviated with a cell-permeable succinate prodrug Carbamate toxicity and treatment.
Yin and Yang of mitochondrial ROS in Drosophila.
Identification of Fis1 Interactors in Toxoplasma gondii Reveals a Novel Protein Required for Peripheral Distribution of the Mitochondrion.
Identification of mecciRNAs and their roles in the mitochondrial entry of proteins.
Viral Vector-Mediated Gene Transfer of Glutamic Acid Decarboxylase for Chronic Pain Treatment: A Literature Review.
The Mitochondrial Lon Protease: Novel Functions off the Beaten Track?
Targeting the Mitochondria in Heart Failure: A Translational Perspective.
Regulation of mRNA translation by a photoriboswitch.
Clinical Features of Chinese Sporadic Leber Hereditary Optic Neuropathy Caused by Rare Primary mtDNA Mutations.
Expanding the molecular and phenotypic spectrum of truncating MT-ATP6 mutations.
Codon and amino acid content are associated with mRNA stability in mammalian cells.
Mitochondria-Associated Membranes (MAMs): A Novel Therapeutic Target for Treating Metabolic Syndrome.
Mitochondrial DNA copy number is associated with all-cause mortality and cardiovascular events in patients with peripheral arterial disease.
Optogenetic control of mitochondrial protonmotive force to impact cellular stress resistance.
Reversible Mitochondrial Fragmentation in iPSC-Derived Cardiomyocytes From Children With DCMA, a Mitochondrial Cardiomyopathy.
Cellular stress responses and dysfunctional Mitochondrial-cellular senescence, and therapeutics in chronic respiratory diseases.
Long non-coding RNAs as novel diagnostic and therapeutic targets in kidney disease.
Suprachoroidal and Subretinal Injections of AAV Using Transscleral Microneedles for Retinal Gene Delivery in Nonhuman Primates.
Engineering adeno-associated virus vectors for gene therapy.

Genes (Basel). 2020 Feb 12. pii: E192. [Epub ahead of print]11(2):

Pathogenic Mitochondria DNA Mutations: Current Detection Tools and Interventions.

Mohd Fazirul Mustafa, Sharida Fakurazi, Maizaton Atmadini Abdullah, Sandra Maniam.

  Mitochondria are best known for their role in energy production, and they are the only mammalian organelles that contain their own genomes. The mitochondrial genome mutation rate is reported to be 10-17 times higher compared to nuclear genomes as a result of oxidative damage caused by reactive oxygen species during oxidative phosphorylation. Pathogenic mitochondrial DNA mutations result in mitochondrial DNA disorders, which are among the most common inherited human diseases. Interventions of mitochondrial DNA disorders involve either the transfer of viable isolated mitochondria to recipient cells or genetically modifying the mitochondrial genome to improve therapeutic outcome. This review outlines the common mitochondrial DNA disorders and the key advances in the past decade necessary to improve the current knowledge on mitochondrial disease intervention. Although it is now 31 years since the first description of patients with pathogenic mitochondrial DNA was reported, the treatment for mitochondrial disease is often inadequate and mostly palliative. Advancements in diagnostic technology improved the molecular diagnosis of previously unresolved cases, and they provide new insight into the pathogenesis and genetic changes in mitochondrial DNA diseases.

Keywords:  genetic intervention; mitochondria DNA mutations; mitochondria transfer; mitochondrial DNA; mitochondrial DNA diseases

DOI:  https://doi.org/10.3390/genes11020192
Curr Genet. 2020 Feb 14.

How does protein degradation regulate TOM machinery-dependent mitochondrial import?

Mohamed A Eldeeb, Mohamed A Ragheb, Mansoore Esmaili.

  Mitochondrial dysregulation is a pivotal hallmark of aging-related disorders. Although there is a considerable understanding of the molecular counteracting responses toward damaged mitochondria, the molecular underpinnings connecting the abnormal aggregation of mitochondrial precursor protein fragments and abrogation of mitochondrial import machinery are far from clear. Recently, proteasomal-dependent degradation was unveiled as a pivotal fine-tuner of TOM machinery-dependent mitochondrial import. Herein, the role of proteasomal-mediated degradation in regulating fidelity of TOM-dependent import is briefly discussed and analyzed. The insights obtained from the characterization of this process may be applied to targeting mitochondrial import dysfunction in some neurodegenerative disorders.

Keywords:  Mitochondrial import; Mitochondrial quality control; Mitophagy; Proteasome; Protein degradation; Protein quality control; TOM complex; Ubiquitin

DOI:  https://doi.org/10.1007/s00294-020-01056-0
Ann Transl Med. 2020 Jan;8(1): 17

Advances in drug therapy for mitochondrial diseases.

Lufei Zhang, Zhaoyong Zhang, Aisha Khan, Hui Zheng, Chao Yuan, Haishan Jiang.

  Mitochondrial diseases are a group of clinically and genetically heterogeneous disorders driven by oxidative phosphorylation dysfunction of the mitochondrial respiratory chain which due to pathogenic mutations of mitochondrial DNA (mtDNA) or nuclear DNA (nDNA). Recent progress in molecular genetics and biochemical methodologies has provided a better understanding of the etiology and pathogenesis of mitochondrial diseases, and this has expanded the clinical spectrum of this conditions. But the treatment of mitochondrial diseases is largely symptomatic and thus does not significantly change the course of the disease. Few clinical trials have led to the design of drugs aiming at enhancing mitochondrial function or reversing the consequences of mitochondrial dysfunction which are now used in the clinical treatment of mitochondrial diseases. Several other drugs are currently being evaluated for clinical management of patients with mitochondrial diseases. In this review, the current status of treatments for mitochondrial diseases is described systematically, and newer potential treatment strategies for mitochondrial diseases are also discussed.

Keywords:  Mitochondrial diseases; drug therapy; electron transfer chain; mitochondrial biogenesis; mitochondrial dynamics

DOI:  https://doi.org/10.21037/atm.2019.10.113
Cell Biochem Funct. 2020 Feb 10.

Neuregulin-1 promotes mitochondrial biogenesis, attenuates mitochondrial dysfunction, and prevents hypoxia/reoxygenation injury in neonatal cardiomyocytes.

Xiao-Xia Zhang, Xue-Si Wu, Shu-Hua Mi, Shan-Juan Fang, Sa Liu, Yi Xin, Quan-Ming Zhao.

  Neuregulin-1 (NRG-1)/erythroblastic leukaemia viral oncogene homologues (ErbB) pathway activation plays a crucial role in regulating the adaptation of the adult heart to physiological and pathological stress. In the present study, we investigate the effect of recombined human NRG-1 (rhNRG-1) on mitochondrial biogenesis, mitochondrial function, and cell survival in neonatal rat cardiac myocytes (NRCMs) exposed to hypoxia/reoxygenation (H/R). The results of this study showed that, in the H/R-exposed NRCMs, mitochondrial biogenesis was impaired, as manifested by the decrease of the expression of peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) and mitochondrial membrane proteins, the inner membrane (Tim23), mitofusin 1 (Mfn1), and mitofusin 2 (Mfn2). RhNRG-1 pretreatment effectively restored the expression of PGC-1α and these membrane proteins, upregulated the expression of the anti-apoptosis proteins Bcl-2 and Bcl-xL, preserved the mitochondrial membrane potential, and attenuated H/R-induced cell apoptosis. Blocking PGC-1 expression with siRNA abolished the beneficial role of rhNRG-1 on mitochondrial function and cell survival. The results of the present study strongly suggest that NRG-1/ErbB activation enhances the adaption of cardiomyocytes to H/R injury via promoted mitochondrial biogenesis and improved mitochondrial homeostasis. SIGNIFICANCE OF THE STUDY: The results of this research revealed for the first time the relationship between neuregulin-1 (NRG-1)/erythroblastic leukaemia viral oncogene homologues (ErbB) activation and mitochondrial biogenesis in neonatal cardiomyocytes and verified the significance of this promoted mitochondrial biogenesis in attenuating hypoxia/reoxygenation injury. This finding may open a new field to further understand the biological role of NRG-1/ErbB signalling pathway in cardiomyocyte.

Keywords:  apoptosis; cardiomyocytes; hypoxia/reoxygenation; mitochondrial biogenesis; neuregulin

DOI:  https://doi.org/10.1002/cbf.3503
Cell Stress Chaperones. 2020 Feb 14.

An inventory of interactors of the human HSP60/HSP10 chaperonin in the mitochondrial matrix space.

Anne Sigaard Bie, Cagla Cömert, Roman Körner, Thomas J Corydon, Johan Palmfeldt, Mark S Hipp, F Ulrich Hartl, Peter Bross.

  The HSP60/HSP10 chaperonin assists folding of proteins in the mitochondrial matrix space by enclosing them in its central cavity. The chaperonin forms part of the mitochondrial protein quality control system. It is essential for cellular survival and mutations in its subunits are associated with rare neurological disorders. Here we present the first survey of interactors of the human mitochondrial HSP60/HSP10 chaperonin. Using a protocol involving metabolic labeling of HEK293 cells, cross-linking, and immunoprecipitation of HSP60, we identified 323 interacting proteins. As expected, the vast majority of these proteins are localized to the mitochondrial matrix space. We find that approximately half of the proteins annotated as mitochondrial matrix proteins interact with the HSP60/HSP10 chaperonin. They cover a broad spectrum of functions and metabolic pathways including the mitochondrial protein synthesis apparatus, the respiratory chain, and mitochondrial protein quality control. Many of the genes encoding HSP60 interactors are annotated as disease genes. There is a correlation between relative cellular abundance and relative abundance in the HSP60 immunoprecipitates. Nineteen abundant matrix proteins occupy more than 60% of the HSP60/HSP10 chaperonin capacity. The reported inventory of interactors can form the basis for interrogating which proteins are especially dependent on the chaperonin.

Keywords:  Chaperonin; HSP10; HSP60; Mitochondrial protein quality control; Molecular chaperone; Protein folding

DOI:  https://doi.org/10.1007/s12192-020-01080-6
Toxicol In Vitro. 2020 Feb 11. pii: S0887-2333(19)30908-7. [Epub ahead of print] 104794

Mitochondrial respiratory chain complex I dysfunction induced by N-methyl carbamate ex vivo can be alleviated with a cell-permeable succinate prodrug Carbamate toxicity and treatment.

Joanna I Janowska, Sarah Piel, Nahima Saliba, Claire D Kim, David H Jang, Michael Karlsson, Todd J Kilbaugh, Johannes K Ehinger.

  Human exposure to carbamates and organophosphates poses a serious threat to society and current pharmacological treatment is solely targeting the compounds' inhibitory effect on acetylcholinesterase. This toxicological pathway, responsible for acute symptom presentation, can be counteracted with currently available therapies such as atropine and oximes. However, there is still significant long-term morbidity and mortality. We propose mitochondrial dysfunction as an additional cellular mechanism of carbamate toxicity and suggest pharmacological targeting of mitochondria to overcome acute metabolic decompensation. Here, we investigated the effects on mitochondrial respiratory function of N-succinimidyl N-methylcarbamate (NSNM), a surrogate for carbamate insecticides ex vivo in human platelets. Characterization of the mitochondrial toxicity of NSNM in platelets revealed a dose depended decrease in oxygen consumption linked to respiratory chain complex I while the pathway through complex II was unaffected. In intact platelets, an increase in lactate production was seen, due to a compensatory shift towards anaerobic metabolism. Treatment with a cell-permeable succinate prodrug restored the NSNM-induced (100 μM) decrease in oxygen consumption and normalized lactate production to the level of control. We have demonstrated that carbamate-induced mitochondrial complex I dysfunction can be alleviated with a mitochondrial targeted countermeasure: a cell-permeable prodrug of the mitochondrial complex II substrate succinate.

Keywords:  Carbamates; Cell-permeable succinate; Methyl isocyanate; Mitochondria; NSNM; Respirometry

DOI:  https://doi.org/10.1016/j.tiv.2020.104794
J Insect Physiol. 2020 Feb 08. pii: S0022-1910(19)30256-2. [Epub ahead of print] 104022

Yin and Yang of mitochondrial ROS in Drosophila.

Samuel G Towarnicki, Leanne M Kok, J William O Ballard.

  In this study, we test the hypothesis that Drosophila larvae producing mildly elevated levels of endogenous mitochondrial reactive oxygen species (ROS) benefit in stressful environmental conditions due to the priming of antioxidant responses. Reactive oxygen species (ROS) are produced as a by-product of oxidative phosphorylation and may be elevated when mutations decrease the efficiency of ATP production. In moderation, ROS are necessary for cell signaling and organismal health, but in excess can damage DNA, proteins, and lipids. We utilize two Drosophila melanogaster strains (Dahomey and Alstonville) that share the same nuclear genetic background but differ in their mitochondrial DNA haplotypes. Previously, we reported that Dahomey larvae harboring the V161L ND4 mtDNA mutation have reduced proton pumping and higher levels of mitochondrial ROS than Alstonville larvae when they are fed a 1:2 protein: carbohydrate (P:C) diet. Here, we explore the potential for mitochondrial ROS to provide resistance to dietary stressors by feeding larvae 1:2 P:C food supplemented with ethanol or hydrogen peroxide (H2O2). When fed a diet supplemented with ethanol or H2O2, Dahomey develop more quickly than Alstonville into larger pupae, while Alstonville developed faster on the control. Dahomey larvae displayed higher antioxidant capacity than Alstonville on all diets, with mitochondrial H2O2 levels unchanged after the addition of stressors. Addition of stressors to the diet did not affect the mitochondrial functions of Dahomey larvae as measured by mitochondrial membrane potential, respiratory control ratio, or larval survival after bacterial challenge. In contrast, Alstonville larvae developed slower, had lower pupal weight, higher cytosolic H2O2, and had reduced mitochondrial functions. Further, Alstonville larvae fed the ethanol treated diet had lower survival after bacterial infection than those fed the control diet. Surprisingly, they had greater survival when fed diet with H2O2 indicating a mitotype by stressor interaction that influences the immune response. Overall, these data suggest that elevated mitochondrial ROS in Dahomey can result in greater antioxidant capacity that prevents oxidative damage from exogenous stressors and may be a conserved response to high ethanol found in rotting fruit.

Keywords:  Beneficial mutation; Dietary stressors; Drosophila, mitochondrial DNA; Reactive oxygen species

DOI:  https://doi.org/10.1016/j.jinsphys.2020.104022
mBio. 2020 Feb 11. pii: e02732-19. [Epub ahead of print]11(1):

Identification of Fis1 Interactors in Toxoplasma gondii Reveals a Novel Protein Required for Peripheral Distribution of the Mitochondrion.

Kylie Jacobs, Robert Charvat, Gustavo Arrizabalaga.

  Toxoplasma gondii's single mitochondrion is very dynamic and undergoes morphological changes throughout the parasite's life cycle. During parasite division, the mitochondrion elongates, enters the daughter cells just prior to cytokinesis, and undergoes fission. Extensive morphological changes also occur as the parasite transitions from the intracellular environment to the extracellular environment. We show that treatment with the ionophore monensin causes reversible constriction of the mitochondrial outer membrane and that this effect depends on the function of the fission-related protein Fis1. We also observed that mislocalization of the endogenous Fis1 causes a dominant-negative effect that affects the morphology of the mitochondrion. As this suggests that Fis1 interacts with proteins critical for maintenance of mitochondrial structure, we performed various protein interaction trap screens. In this manner, we identified a novel outer mitochondrial membrane protein, LMF1, which is essential for positioning of the mitochondrion in intracellular parasites. Normally, while inside a host cell, the parasite mitochondrion is maintained in a lasso shape that stretches around the parasite periphery where it has regions of coupling with the parasite pellicle, suggesting the presence of membrane contact sites. In intracellular parasites lacking LMF1, the mitochondrion is retracted away from the pellicle and instead is collapsed, as normally seen only in extracellular parasites. We show that this phenotype is associated with defects in parasite fitness and mitochondrial segregation. Thus, LMF1 is necessary for mitochondrial association with the parasite pellicle during intracellular growth, and proper mitochondrial morphology is a prerequisite for mitochondrial division.IMPORTANCEToxoplasma gondii is an opportunistic pathogen that can cause devastating tissue damage in the immunocompromised and congenitally infected. Current therapies are not effective against all life stages of the parasite, and many cause toxic effects. The single mitochondrion of this parasite is a validated drug target, and it changes its shape throughout its life cycle. When the parasite is inside a cell, the mitochondrion adopts a lasso shape that lies in close proximity to the pellicle. The functional significance of this morphology is not understood and the proteins involved are currently not known. We have identified a protein that is required for proper mitochondrial positioning at the periphery and that likely plays a role in tethering this organelle. Loss of this protein results in dramatic changes to the mitochondrial morphology and significant parasite division and propagation defects. Our results give important insight into the molecular mechanisms regulating mitochondrial morphology.

Keywords:  Fis1; Toxoplasma ; membrane contact site; mitochondrion

DOI:  https://doi.org/10.1128/mBio.02732-19
Sci China Life Sci. 2020 Jan 21.

Identification of mecciRNAs and their roles in the mitochondrial entry of proteins.

Xu Liu, Xiaolin Wang, Jingxin Li, Shanshan Hu, Yuqi Deng, Hao Yin, Xichen Bao, Qiangfeng Cliff Zhang, Geng Wang, Baolong Wang, Qinghua Shi, Ge Shan.

  Mammalian mitochondria have small genomes encoding very limited numbers of proteins. Over one thousand proteins and noncoding RNAs encoded by the nuclear genome must be imported from the cytosol into the mitochondria. Here, we report the identification of hundreds of circular RNAs (mecciRNAs) encoded by the mitochondrial genome. We provide both in vitro and in vivo evidence to show that mecciRNAs facilitate the mitochondrial entry of nuclear-encoded proteins by serving as molecular chaperones in the folding of imported proteins. Known components involved in mitochondrial protein and RNA importation, such as TOM40 and PNPASE, interact with mecciRNAs and regulate protein entry. The expression of mecciRNAs is regulated, and these transcripts are critical for the adaption of mitochondria to physiological conditions and diseases such as stresses and cancers by modulating mitochondrial protein importation. mecciRNAs and their associated physiological roles add categories and functions to the known eukaryotic circular RNAs and shed novel light on the communication between mitochondria and the nucleus.

Keywords:  circRNA; mecciRNA; mitochondria; mitochondrial protein import

DOI:  https://doi.org/10.1007/s11427-020-1631-9
Hum Gene Ther. 2020 Feb 11.

Viral Vector-Mediated Gene Transfer of Glutamic Acid Decarboxylase for Chronic Pain Treatment: A Literature Review.

Megumi Kanao-Kanda, Hirotsugu Kanda, Shue Liu, Sabita Roy, Michal Toborek, Shuanglin Hao.

Chronic pain is long-lasting nociceptive state, impairing the patient's quality of life. Existing analgesics are generally not effective in the treatment of chronic pain, some of which such as opioids have the risk of tolerance/dependence, overdose death with higher daily opioid doses for increasing analgesic effect. Opioid use disorders have already reached an epidemic level in the United States, therefore, non-opioid analgesic approach and/or use of non-pharmacologic interventions will be employed with increasing frequency. Viral vector mediated gene therapy is promising in clinical trials in the nervous system diseases. Glutamic acid decarboxylase (GAD) enzyme, a key enzyme in biosynthesis of GABA, plays an important role in analgesic mechanism. In the literature review, we used PubMed and BioRxiv to search the studies, and the eligible criteria include (1) manuscript written in English, (2) use of viral vectors expressing GAD67 or GAD65, and (3) preclinical pain models. We identified 13 eligible original research papers, in which the pain models include nerve injury, HIV-related pain, painful diabetic neuropathy, and formalin test. GAD expressed by the viral vectors from all of the reports produced antinociceptive effects. Restoring GABA systems is a promising therapeutic strategy for chronic pain, which provides evidence for the clinical trial of gene therapy for pain in the near future.

DOI: https://doi.org/10.1089/hum.2019.359
Biomolecules. 2020 Feb 07. pii: E253. [Epub ahead of print]10(2):

The Mitochondrial Lon Protease: Novel Functions off the Beaten Track?

Wolfgang Voos, Karen Pollecker.

  To maintain organellar function, mitochondria contain an elaborate endogenous protein quality control system. As one of the two soluble energy-dependent proteolytic enzymes in the matrix compartment, the protease Lon is a major component of this system, responsible for the degradation of misfolded proteins, in particular under oxidative stress conditions. Lon defects have been shown to negatively affect energy production by oxidative phosphorylation but also mitochondrial gene expression. In this review, recent studies on the role of Lon in mammalian cells, in particular on its protective action under diverse stress conditions and its relationship to important human diseases are summarized and commented.

Keywords:  Lon protease; mitochondria; protein quality control

DOI:  https://doi.org/10.3390/biom10020253
JACC Basic Transl Sci. 2020 Jan;5(1): 88-106

Targeting the Mitochondria in Heart Failure: A Translational Perspective.

Hani N Sabbah.

  The burden of heart failure (HF) in terms of health care expenditures, hospitalizations, and mortality is substantial and growing. The failing heart has been described as "energy-deprived" and mitochondrial dysfunction is a driving force associated with this energy supply-demand imbalance. Existing HF therapies provide symptomatic and longevity benefit by reducing cardiac workload through heart rate reduction and reduction of preload and afterload but do not address the underlying causes of abnormal myocardial energetic nor directly target mitochondrial abnormalities. Numerous studies in animal models of HF as well as myocardial tissue from explanted failed human hearts have shown that the failing heart manifests abnormalities of mitochondrial structure, dynamics, and function that lead to a marked increase in the formation of damaging reactive oxygen species and a marked reduction in on demand adenosine triphosphate synthesis. Correcting mitochondrial dysfunction therefore offers considerable potential as a new therapeutic approach to improve overall cardiac function, quality of life, and survival for patients with HF.

Keywords:  ADP, adenosine diphosphate; ATP, adenosine triphosphate; CI (to V), complex I (to V); Drp, dynamin-related protein; ETC, electron transport chain; HF, heart failure; HFpEF, heart failure with preserved ejection fraction; HFrEF, heart failure with reduced ejection fraction; LV, left ventricular; MPTP, mitochondrial permeability transition pore; Mfn, mitofusin; OPA, optic atrophy; PGC, peroxisome proliferator-activated receptor coactivator; PINK, phosphatase and tensin homolog–inducible kinase; ROS, reactive oxygen species; TAZ, tafazzin; cardiolipin; heart failure; mitochondria; mtDNA, mitochondrial deoxyribonucleic acid; myocardial energetics; oxidative phosphorylation

DOI:  https://doi.org/10.1016/j.jacbts.2019.07.009
Elife. 2020 Feb 13. pii: e51737. [Epub ahead of print]9

Regulation of mRNA translation by a photoriboswitch.

Kelly A Rotstan, Michael M Abdelsayed, Luiz F M Passalacqua, Fabio Chizzolini, Kasireddy Sudarshan, A Richard Chamberlin, Jiří Míšek, Andrej Luptak.

  Optogenetic tools have revolutionized the study of receptor-mediated processes, but such tools are lacking for RNA-controlled systems. In particular, light-activated regulatory RNAs are needed for spatiotemporal control of gene expression. To fill this gap, we used in vitro selection to isolate a novel riboswitch that selectively binds the trans isoform of a stiff-stilbene (amino-tSS)-a rapidly and reversibly photoisomerizing small molecule. Structural probing revealed that the RNA binds amino-tSS about 100-times stronger than the cis photoisoform (amino-cSS). In vitro and in vivo functional analysis showed that the riboswitch, termed Werewolf-1 (Were-1), inhibits translation of a downstream open reading frame when bound to amino-tSS. Photoisomerization of the ligand with a sub-millisecond pulse of light induced the protein expression. In contrast, amino-cSS supported protein expression, which was inhibited upon photoisomerization to amino-tSS. Reversible photoregulation of gene expression using a genetically encoded RNA will likely facilitate high-resolution spatiotemporal analysis of complex RNA processes.

Keywords:  E. coli; biochemistry; chemical biology

DOI:  https://doi.org/10.7554/eLife.51737
J Neuroophthalmol. 2020 Mar;40(1): 30-36

Clinical Features of Chinese Sporadic Leber Hereditary Optic Neuropathy Caused by Rare Primary mtDNA Mutations.

Shilei Cui, Ling Yang, Hanqiu Jiang, Jingting Peng, Jun Shang, Jiawei Wang, Xiaojun Zhang.

OBJECTIVE: The primary aim of this study was to describe clinical features of Chinese sporadic Leber hereditary optic neuropathy (LHON) caused by rare primary mitochondrial DNA (mtDNA) mutations.
METHODS: We characterized a Chinese patient cohort with rare primary mtDNA mutations at Beijing Tongren Hospital between 2015 and 2018. The clinical features of these patients were retrospectively recorded and analyzed.
RESULTS: Sixteen patients with LHON who had the selected rare primary mutations, including m.4171C>A (3 patients), m.10197G>A (1 patient), m.14459G>A (4 patients), and m.14502T>C (8 patients), were evaluated. The mean age at disease onset was 15 ± 6 years, and the male to female ratio was 15:1. Of 32 eyes of all patients, 75% (24/32) had a worst Snellen best-corrected visual acuity ≤0.1 (worse than 20/200), while 67% (2/3) who were carrying the m.4171C>A mutation experienced significant visual improvement. In addition, 40% (2/5) of patients with LHON carrying only m.14502T>C mutation had only mild visual impairment. Isolated manifestations of LHON was present in 94% (15/16) of all patients; 1 patient with the m.14459G>A mutation had LHON plus dystonia. Brain MRI T2 short tau inversion recovery sequences demonstrated optic atrophy in 62.5% (10/16); increased T2 signal in the optic nerve was found in 38% (6/16) of patients. The patient with LHON plus dystonia demonstrated optic atrophy and increased T2 signal in basal ganglia.
CONCLUSION: Patients with LHON and rare primary mutations have diverse clinical phenotypes. Those with the m.4171C>A mutation are more likely to have a good visual prognosis, while the m.14502T>C mutation may play a synergistic role in disease onset. Increased signal in the optic nerve on MRI is not rare, and this feature should not exclude LHON as the potential cause for optic neuropathy.

DOI: https://doi.org/10.1097/WNO.0000000000000799
Neurol Genet. 2020 Feb;6(1): e381

Expanding the molecular and phenotypic spectrum of truncating MT-ATP6 mutations.

Enrico Bugiardini, Emanuela Bottani, Silvia Marchet, Olivia V Poole, Cristiane Beninca, Alejandro Horga, Cathy Woodward, Amanda Lam, Iain Hargreaves, Annapurna Chalasani, Alessandra Valerio, Eleonora Lamantea, Kerrie Venner, Janice L Holton, Massimo Zeviani, Henry Houlden, Rosaline Quinlivan, Costanza Lamperti, Michael G Hanna, Robert D S Pitceathly.

Objective: To describe the clinical and functional consequences of 1 novel and 1 previously reported truncating MT-ATP6 mutation.
Methods: Three unrelated probands with mitochondrial encephalomyopathy harboring truncating MT-ATP6 mutations are reported. Transmitochondrial cybrid cell studies were used to confirm pathogenicity of 1 novel variant, and the effects of all 3 mutations on ATPase 6 and complex V structure and function were investigated.
Results: Patient 1 presented with adult-onset cerebellar ataxia, chronic kidney disease, and diabetes, whereas patient 2 had myoclonic epilepsy and cerebellar ataxia; both harbored the novel m.8782G>A; p.(Gly86*) mutation. Patient 3 exhibited cognitive decline, with posterior white matter abnormalities on brain MRI, and severely impaired renal function requiring transplantation. The m.8618dup; p.(Thr33Hisfs*32) mutation, previously associated with neurogenic muscle weakness, ataxia, and retinitis pigmentosa, was identified. All 3 probands demonstrated a broad range of heteroplasmy across different tissue types. Blue-native gel electrophoresis of cultured fibroblasts and skeletal muscle tissue confirmed multiple bands, suggestive of impaired complex V assembly. Microscale oxygraphy showed reduced basal respiration and adenosine triphosphate synthesis, while reactive oxygen species generation was increased. Transmitochondrial cybrid cell lines studies confirmed the deleterious effects of the novel m.8782 G>A; p.(Gly86*) mutation.
Conclusions: We expand the clinical and molecular spectrum of MT-ATP6-related mitochondrial disorders to include leukodystrophy, renal disease, and myoclonic epilepsy with cerebellar ataxia. Truncating MT-ATP6 mutations may exhibit highly variable mutant levels across different tissue types, an important consideration during genetic counseling.

DOI: https://doi.org/10.1212/NXG.0000000000000381
PLoS One. 2020 ;15(2): e0228730

Codon and amino acid content are associated with mRNA stability in mammalian cells.

Megan E Forrest, Otis Pinkard, Sophie Martin, Thomas J Sweet, Gavin Hanson, Jeff Coller.

Messenger RNA (mRNA) degradation plays a critical role in regulating transcript levels in the cell and is a major control point for modulating gene expression. In yeast and other model organisms, codon identity is a powerful determinant of transcript stability, contributing broadly to impact half-lives. General principles governing mRNA stability are poorly understood in mammalian systems. Importantly, however, the degradation machinery is highly conserved, thus it seems logical that mammalian transcript half-lives would also be strongly influenced by coding determinants. Herein we characterize the contribution of coding sequence towards mRNA decay in human and Chinese Hamster Ovary cells. In agreement with previous studies, we observed that synonymous codon usage impacts mRNA stability in mammalian cells. Surprisingly, however, we also observe that the amino acid content of a gene is an additional determinant correlating with transcript stability. The impact of codon and amino acid identity on mRNA decay appears to be associated with underlying tRNA and intracellular amino acid concentrations. Accordingly, genes of similar physiological function appear to coordinate their mRNA stabilities in part through codon and amino acid content. Together, these results raise the possibility that intracellular tRNA and amino acid levels interplay to mediate coupling between translational elongation and mRNA degradation rate in mammals.

DOI: https://doi.org/10.1371/journal.pone.0228730
Curr Med Chem. 2020 Feb 11.

Mitochondria-Associated Membranes (MAMs): A Novel Therapeutic Target for Treating Metabolic Syndrome.

Ming Yang, Chenrui Li, Lin Sun.

  Mitochondria-associated endoplasmic reticulum (ER) membranes (MAMs) are the cellular structures that connect the ER and mitochondria and mediate communication between these two organelles. MAMs have been demonstrated to be involved in calcium signaling, lipid transfer, mitochondrial dynamic change, mitochondrial autophagy, and the ER stress response. In addition, MAMs are critical for metabolic regulation, and their dysfunction has been reported to be associated with metabolic syndrome, including the downregulation of insulin signaling and the accelerated progression of hyperlipidemia, obesity, and hypertension. This review covers the roles of MAMs in regulating insulin sensitivity and the molecular mechanism underlying MAM-regulated cellular metabolism and reveals the potential of MAMs as a therapeutic target in treating metabolic syndrome.

Keywords:  Diabetes; Endoplasmic reticulum; Insulin resistance; Metabolic syndrome; Mitochondria; Mitochondria-associated membrane (MAM)

DOI:  https://doi.org/10.2174/0929867327666200212100644
J Intern Med. 2020 Feb 09.

Mitochondrial DNA copy number is associated with all-cause mortality and cardiovascular events in patients with peripheral arterial disease.

A Koller, F Fazzini, C Lamina, B Rantner, B Kollerits, M Stadler, P Klein-Weigel, G Fraedrich, F Kronenberg.

   BACKGROUND: Dysfunctional mitochondria have an influence on inflammation and increased oxidative stress due to an excessive production of reactive oxygen species. The mitochondrial DNA copy number (mtDNA-CN) is a potential biomarker for mitochondrial dysfunction and has been associated with various diseases. However, results were partially contrasting which might have been caused by methodological difficulties to quantify mtDNA-CN.
OBJECTIVE: We aimed to investigate whether mtDNA-CN is associated with peripheral arterial disease (PAD) as well as all-cause mortality and cardiovascular events during seven years of follow-up.
METHODS: A total of 236 male patients with PAD from the Cardiovascular Disease in Intermittent Claudication (CAVASIC) study were compared with 249 age- and diabetes-matched controls. MtDNA-CN was measured with a well-standardized plasmid-normalized quantitative PCR-based assay determining the ratio between mtDNA-CN and nuclear DNA.
RESULTS: Individuals in the lowest quartile of mtDNA-CN had a twofold increased risk for PAD which, however, was no longer significant after adjusting for leukocytes and platelets. About 67 of the 236 patients had already experienced a cardiovascular event at baseline and those in the lowest mtDNA-CN quartile had a 2.34-fold increased risk for these events (95% CI 1.08-5.13). During follow-up, 37 PAD patients died and 66 patients experienced a cardiovascular event. Patients in the lowest mtDNA-CN quartile had hazard ratios of 2.66 (95% CI 1.27-5.58) for all-cause-mortality and 1.82 (95% CI 1.02-3.27) for cardiovascular events compared with the combined quartile 2-4 (adjusted for age, smoking, CRP, diabetes, prevalent cardiovascular disease, leukocytes and platelets).
CONCLUSION: This investigation supports the hypothesis of mitochondrial dysfunction in peripheral arterial disease and shows an association of low mtDNA-CNs with all-cause-mortality and prevalent and incident cardiovascular disease in PAD patients with intermittent claudication.

Keywords:  cardiovascular disease; mitochondrial copy number; mortality; peripheral arterial disease

DOI:  https://doi.org/10.1111/joim.13027
EMBO Rep. 2020 Feb 11. e49113

Optogenetic control of mitochondrial protonmotive force to impact cellular stress resistance.

Brandon J Berry, Adam J Trewin, Alexander S Milliken, Aksana Baldzizhar, Andrea M Amitrano, Yunki Lim, Minsoo Kim, Andrew P Wojtovich.

  Mitochondrial respiration generates an electrochemical proton gradient across the mitochondrial inner membrane called protonmotive force (PMF) to drive diverse functions and synthesize ATP. Current techniques to manipulate the PMF are limited to its dissipation; yet, there is no precise and reversible method to increase the PMF. To address this issue, we aimed to use an optogenetic approach and engineered a mitochondria-targeted light-activated proton pump that we name mitochondria-ON (mtON) to selectively increase the PMF in Caenorhabditis elegans. Here we show that mtON photoactivation increases the PMF in a dose-dependent manner, supports ATP synthesis, increases resistance to mitochondrial toxins, and modulates energy-sensing behavior. Moreover, transient mtON activation during hypoxic preconditioning prevents the well-characterized adaptive response of hypoxia resistance. Our results show that optogenetic manipulation of the PMF is a powerful tool to modulate metabolism and cell signaling.

Keywords:  anoxia; hypoxia; ischemia reperfusion; metabolism; uncoupling

DOI:  https://doi.org/10.15252/embr.201949113
Can J Cardiol. 2019 Oct 09. pii: S0828-282X(19)31286-3. [Epub ahead of print]

Reversible Mitochondrial Fragmentation in iPSC-Derived Cardiomyocytes From Children With DCMA, a Mitochondrial Cardiomyopathy.

Leili Rohani, Pranav Machiraju, Rasha Sabouny, Guoliang Meng, Shiying Liu, Tian Zhao, Fatima Iqbal, Xuemei Wang, Amir Ravandi, Joseph C Wu, Aneal Khan, Timothy Shutt, Derrick Rancourt, Steven C Greenway.

BACKGROUND: Dilated cardiomyopathy with ataxia syndrome (DCMA) is an understudied autosomal recessive disease caused by loss-of-function mutations in the poorly characterized gene DNAJC19. Clinically, DCMA is commonly associated with heart failure and early death in affected children through an unknown mechanism. DCMA has been linked to Barth syndrome, a rare but well-studied disorder caused by deficient maturation of cardiolipin (CL), a key mitochondrial membrane phospholipid.
METHODS: Peripheral blood mononuclear cells from 2 children with DCMA and severe cardiac dysfunction were reprogrammed into induced pluripotent stem cells (iPSCs). Patient and control iPSCs were differentiated into beating cardiomyocytes (iPSC-CMs) using a metabolic selection strategy. Mitochondrial structure and CL content before and after incubation with the mitochondrially targeted peptide SS-31 were quantified.
RESULTS: Patient iPSCs carry the causative DNAJC19 mutation (rs137854888) found in the Hutterite population, and the iPSC-CMs demonstrated highly fragmented and abnormally shaped mitochondria associated with an imbalanced isoform ratio of the mitochondrial protein OPA1, an important regulator of mitochondrial fusion. These abnormalities were reversible by incubation with SS-31 for 24 hours. Differentiation of iPSCs into iPSC-CMs increased the number of CL species observed, but consistent, significant differences in CL content were not seen between patients and control.
CONCLUSIONS: We describe a unique and novel cellular model that provides insight into the mitochondrial abnormalities present in DCMA and identifies SS-31 as a potential therapeutic for this devastating disease.

DOI: https://doi.org/10.1016/j.cjca.2019.09.021
Redox Biol. 2020 Jan 25. pii: S2213-2317(19)31423-5. [Epub ahead of print] 101443

Cellular stress responses and dysfunctional Mitochondrial-cellular senescence, and therapeutics in chronic respiratory diseases.

Marko Manevski, Thivanka Muthumalage, Dinesh Devadoss, Isaac K Sundar, Qixin Wang, Kameshwar P Singh, Hoshang J Unwalla, Hitendra S Chand, Irfan Rahman.

  The abnormal inflammatory responses due to the lung tissue damage and ineffective repair/resolution in response to the inhaled toxicants result in the pathological changes associated with chronic respiratory diseases. Investigation of such pathophysiological mechanisms provides the opportunity to develop the molecular phenotype-specific diagnostic assays and could help in designing the personalized medicine-based therapeutic approaches against these prevalent diseases. As the central hubs of cell metabolism and energetics, mitochondria integrate cellular responses and interorganellar signaling pathways to maintain cellular and extracellular redox status and the cellular senescence that dictate the lung tissue responses. Specifically, as observed in chronic obstructive pulmonary disease (COPD) and pulmonary fibrosis, the mitochondria-endoplasmic reticulum (ER) crosstalk is disrupted by the inhaled toxicants such as the combustible and emerging electronic nicotine-delivery system (ENDS) tobacco products. Thus, the recent research efforts have focused on understanding how the mitochondria-ER dysfunctions and oxidative stress responses can be targeted to improve inflammatory and cellular dysfunctions associated with these pathologic illnesses that are exacerbated by viral infections. The present review assesses the importance of these redox signaling and cellular senescence pathways that describe the role of mitochondria and ER on the development and function of lung epithelial responses, highlighting the cause and effect associations that reflect the disease pathogenesis and possible intervention strategies.

Keywords:  COPD; Cellular senescence; Cigarette smoke; DAMPs; Fibrosis; Mitochondrial dysfunction; ROS; UPR

DOI:  https://doi.org/10.1016/j.redox.2020.101443
Chronic Dis Transl Med. 2019 Dec;5(4): 252-257

Long non-coding RNAs as novel diagnostic and therapeutic targets in kidney disease.

Qin Zhou, Wei Chen, Xue-Qing Yu.

  Long non-coding RNAs (lncRNAs) have critical roles in the development of many diseases including kidney disease. An increasing number of studies have shown that lncRNAs are involved in kidney development and that their dysregulation can result in distinct disease processes, including acute kidney injury (AKI), chronic kidney disease (CKD), and renal cell carcinoma (RCC). Understanding the roles of lncRNAs in kidney disease may provide new diagnostic and therapeutic opportunities in the clinic. This review provides an overview of lncRNA characteristics, biological function and discusses specific studies that provide insight into the function and potential application of lncRNAs in kidney disease treatment.

Keywords:  Diabetic nephritis; Kidney disease; Long non-coding RNAs; Renal cell carcinoma; Renal fibrosis; Renal inflammation

DOI:  https://doi.org/10.1016/j.cdtm.2019.12.004
Mol Ther Methods Clin Dev. 2020 Mar 13. 16 179-191

Suprachoroidal and Subretinal Injections of AAV Using Transscleral Microneedles for Retinal Gene Delivery in Nonhuman Primates.

Glenn Yiu, Sook Hyun Chung, Iris N Mollhoff, Uyen Tu Nguyen, Sara M Thomasy, Jesse Yoo, Donna Taraborelli, Glenn Noronha.

  Retinal gene therapy using adeno-associated viruses (AAVs) is constrained by the mode of viral vector delivery. Intravitreal AAV injections are impeded by the internal limiting membrane barrier, while subretinal injections require invasive surgery and produce a limited region of therapeutic effect. In this study, we introduce a novel mode of ocular gene delivery in rhesus macaques using transscleral microneedles to inject AAV8 into the subretinal or suprachoroidal space, a potential space between the choroid and scleral wall of the eye. Using in vivo imaging, we found that suprachoroidal AAV8 produces diffuse, peripheral expression in retinal pigment epithelial (RPE) cells, but it elicited local infiltration of inflammatory cells. Transscleral subretinal injection of AAV8 using microneedles leads to focal gene expression with transduction of RPE and photoreceptors, and minimal intraocular inflammation. In comparison, intravitreal AAV8 shows minimal transduction of retinal cells, but elicits greater systemic humoral immune responses. Our study introduces a novel mode of transscleral viral delivery that can be performed without vitreoretinal surgery, with focal or diffuse transgene expression patterns suitable for different applications. The decoupling of local and systemic immune responses reveals important insights into the immunological consequences of AAV delivery to different ocular compartments surrounding the blood-retinal barrier.

Keywords:  AAV; gene therapy; microneedles; nonhuman primate; retina; retinal gene therapy; rhesus macaques; suprachoroidal; suprachoroidal delivery

DOI:  https://doi.org/10.1016/j.omtm.2020.01.002
Nat Rev Genet. 2020 Feb 10.

Engineering adeno-associated virus vectors for gene therapy.

Chengwen Li, R Jude Samulski.

Adeno-associated virus (AAV) vector-mediated gene delivery was recently approved for the treatment of inherited blindness and spinal muscular atrophy, and long-term therapeutic effects have been achieved for other rare diseases, including haemophilia and Duchenne muscular dystrophy. However, current research indicates that the genetic modification of AAV vectors may further facilitate the success of AAV gene therapy. Vector engineering can increase AAV transduction efficiency (by optimizing the transgene cassette), vector tropism (using capsid engineering) and the ability of the capsid and transgene to avoid the host immune response (by genetically modifying these components), as well as optimize the large-scale production of AAV.

DOI: https://doi.org/10.1038/s41576-019-0205-4