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Shahin S, Lu B, Zhou Y, Xu H, Chetsawang J, Baloh RH, Wang S. MFN1 augmentation prevents retinal degeneration in a Charcot-Marie-Tooth type 2A mouse model. iScience 2023; 26:106270. [PMID: 36936780 PMCID: PMC10014277 DOI: 10.1016/j.isci.2023.106270] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Revised: 12/30/2022] [Accepted: 02/20/2023] [Indexed: 03/12/2023] Open
Abstract
Charcot-Marie-Tooth disease type 2A (CMT2A), the most common inherited peripheral axonal neuropathy, is associated with more than 100 dominant mutations, including R94Q as the most abundant mutation in the Mitofusin2 (MFN2) gene. CMT2A is characterized by progressive motor and sensory loss, color-vision defects, and progressive loss of visual acuity. We used a well-established transgenic mouse model of CMT2A with R94Q mutation on MFN2 gene (MFN2 R94Q ) to investigate the functional and morphological changes in retina. We documented extensive vision loss due to photoreceptor degeneration, retinal ganglion cell and their axonal loss, retinal secondary neuronal and synaptic alternation, and Müller cell gliosis in the retina of MFN2 R94Q mice. Imbalanced MFN1/MFN2 ratio and dysregulated mitochondrial fusion/fission result in retinal degeneration via P62/LC3B-mediated mitophagy/autophagy in MFN2 R94Q mice. Finally, transgenic MFN1 augmentation (MFN2 R94Q :MFN1) rescued vision and retinal morphology to wild-type level via restoring homeostasis in mitochondrial MFN1/MFN2 ratio, fusion/fission cycle, and PINK1-dependent, Parkin-independent mitophagy.
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Affiliation(s)
- Saba Shahin
- Board of Governors Regenerative Medicine Institute, Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA
| | - Bin Lu
- Board of Governors Regenerative Medicine Institute, Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA
| | - Yueqin Zhou
- Board of Governors Regenerative Medicine Institute, Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA
| | - Hui Xu
- Board of Governors Regenerative Medicine Institute, Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA
| | - Jason Chetsawang
- Board of Governors Regenerative Medicine Institute, Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA
| | - Robert H. Baloh
- Board of Governors Regenerative Medicine Institute, Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA
| | - Shaomei Wang
- Board of Governors Regenerative Medicine Institute, Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA
- Corresponding author
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2
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Font-Porterias N, García-Fernández C, Aizpurua-Iraola J, Comas D, Torrents D, de Cid R, Calafell F. Sequence diversity of the uniparentally transmitted portions of the genome in the resident population of Catalonia. Forensic Sci Int Genet 2022; 61:102783. [DOI: 10.1016/j.fsigen.2022.102783] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2022] [Revised: 09/23/2022] [Accepted: 09/26/2022] [Indexed: 11/30/2022]
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3
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Zou W, Ji D, Zhang Z, Yang L, Cao Y. Players in Mitochondrial Dynamics and Female Reproduction. Front Mol Biosci 2021; 8:717328. [PMID: 34708072 PMCID: PMC8542886 DOI: 10.3389/fmolb.2021.717328] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Accepted: 09/07/2021] [Indexed: 01/16/2023] Open
Abstract
Mitochondrial dynamics (fission and fusion) are essential physiological processes for mitochondrial metabolic function, mitochondrial redistribution, and mitochondrial quality control. Various proteins are involved in regulating mitochondrial dynamics. Aberrant expression of these proteins interferes with mitochondrial dynamics and induces a range of diseases. Multiple therapeutic approaches have been developed to treat the related diseases in recent years, but their curative effects are limited. Meanwhile, the role of mitochondrial dynamics in female reproductive function has attracted progressively more attention, including oocyte development and maturation, fertilization, and embryonic development. Here, we reviewed the significance of mitochondrial dynamics, proteins involved in mitochondrial dynamics, and disorders resulting from primary mitochondrial dynamic dysfunction. We summarized the latest therapeutic approaches of hereditary mitochondrial fusion-fission abnormalities and reviewed the recent advances in female reproductive mitochondrial dynamics.
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Affiliation(s)
- Weiwei Zou
- Reproductive Medicine Center, Department of Obstetrics and Gynecology, The First Affiliated Hospital of Anhui Medical University, Hefei, China.,NHC Key Laboratory of Study on Abnormal Gametes and Reproductive Tract (Anhui Medical University), Hefei, China.,Key Laboratory of Population Health Across Life Cycle (Anhui Medical University), Ministry of Education of the People's Republic of China, Hefei, China
| | - Dongmei Ji
- Reproductive Medicine Center, Department of Obstetrics and Gynecology, The First Affiliated Hospital of Anhui Medical University, Hefei, China.,Anhui Province Key Laboratory of Reproductive Health and Genetics, Hefei, China.,Biopreservation and Artificial Organs, Anhui Provincial Engineering Research Center, Anhui Medical University, Hefei, China
| | - Zhiguo Zhang
- Reproductive Medicine Center, Department of Obstetrics and Gynecology, The First Affiliated Hospital of Anhui Medical University, Hefei, China.,Anhui Province Key Laboratory of Reproductive Health and Genetics, Hefei, China.,Biopreservation and Artificial Organs, Anhui Provincial Engineering Research Center, Anhui Medical University, Hefei, China
| | - Li Yang
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha, China
| | - Yunxia Cao
- Reproductive Medicine Center, Department of Obstetrics and Gynecology, The First Affiliated Hospital of Anhui Medical University, Hefei, China.,NHC Key Laboratory of Study on Abnormal Gametes and Reproductive Tract (Anhui Medical University), Hefei, China.,Key Laboratory of Population Health Across Life Cycle (Anhui Medical University), Ministry of Education of the People's Republic of China, Hefei, China
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Schiavon CR, Shadel GS, Manor U. Impaired Mitochondrial Mobility in Charcot-Marie-Tooth Disease. Front Cell Dev Biol 2021; 9:624823. [PMID: 33598463 PMCID: PMC7882694 DOI: 10.3389/fcell.2021.624823] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2020] [Accepted: 01/05/2021] [Indexed: 12/13/2022] Open
Abstract
Charcot-Marie-Tooth (CMT) disease is a progressive, peripheral neuropathy and the most commonly inherited neurological disorder. Clinical manifestations of CMT mutations are typically limited to peripheral neurons, the longest cells in the body. Currently, mutations in at least 80 different genes are associated with CMT and new mutations are regularly being discovered. A large portion of the proteins mutated in axonal CMT have documented roles in mitochondrial mobility, suggesting that organelle trafficking defects may be a common underlying disease mechanism. This review will focus on the potential role of altered mitochondrial mobility in the pathogenesis of axonal CMT, highlighting the conceptional challenges and potential experimental and therapeutic opportunities presented by this "impaired mobility" model of the disease.
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Affiliation(s)
- Cara R. Schiavon
- Waitt Advanced Biophotonics Center, Salk Institute for Biological Studies, La Jolla, CA, United States
- Molecular and Cell Biology Laboratory, Salk Institute for Biological Studies, La Jolla, CA, United States
| | - Gerald S. Shadel
- Molecular and Cell Biology Laboratory, Salk Institute for Biological Studies, La Jolla, CA, United States
| | - Uri Manor
- Waitt Advanced Biophotonics Center, Salk Institute for Biological Studies, La Jolla, CA, United States
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5
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Barreda Fierro R, Herrera Mora P, Zenteno JC, Villarroel Cortés CE. Clinical and molecular evidence of possible digenic inheritance for MFN2/GDAP1 genes in Charcot-Marie-Tooth disease. Neuromuscul Disord 2020; 30:986-990. [PMID: 33187793 DOI: 10.1016/j.nmd.2020.10.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Accepted: 10/14/2020] [Indexed: 10/23/2022]
Abstract
Charcot Marie Tooth disease (CMT) is a progressive motor and sensory polyneuropathy, it is characterized by a very heterogeneous molecular basis and phenotype. MFN2 and GDAP1 participate in mitochondrial energy metabolism and the rare coinheritance of its pathogenic variants has been associated with a cumulative effect in the observed phenotype. We describe a patient with a severe axonal CMT and inherited heterozygous MFN2 (p.Leu741Val) and GDAP1 (p.Gln163*) variants. In accordance with a possible digenic inheritance, none of the heterozygous carriers in his family were symptomatic or exhibited electrophysiological abnormalities. We also review all of the previously reported patients with coinheritance of variants in these two genes; similar to our patient, all exhibit a predominantly axonal severe CMT phenotype. Our findings expand the genotypic spectrum of CMT and further support that digenic inheritance should be considered for analyzing and counseling CMT patients.
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Affiliation(s)
- Renée Barreda Fierro
- Human Genetics Department, National Institute of Pediatrics, Mexico City, Mexico
| | | | - Juan Carlos Zenteno
- Genetics Department-Research Unit, Institute of Ophthalmology "Conde de Valenciana", Mexico City, Mexico; Biochemistry Department, Faculty of Medicine, UNAM, Mexico City, Mexico
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Escobar-Henriques M, Joaquim M. Mitofusins: Disease Gatekeepers and Hubs in Mitochondrial Quality Control by E3 Ligases. Front Physiol 2019; 10:517. [PMID: 31156446 PMCID: PMC6533591 DOI: 10.3389/fphys.2019.00517] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Accepted: 04/11/2019] [Indexed: 02/06/2023] Open
Abstract
Mitochondria are dynamic organelles engaged in quality control and aging processes. They constantly undergo fusion, fission, transport, and anchoring events, which empower mitochondria with a very interactive behavior. The membrane remodeling processes needed for fusion require conserved proteins named mitofusins, MFN1 and MFN2 in mammals and Fzo1 in yeast. They are the first determinants deciding on whether communication and content exchange between different mitochondrial populations should occur. Importantly, each cell possesses hundreds of mitochondria, with a different severity of mitochondrial mutations or dysfunctional proteins, which potentially spread damage to the entire network. Therefore, the degree of their merging capacity critically influences cellular fitness. In turn, the mitochondrial network rapidly and dramatically changes in response to metabolic and environmental cues. Notably, cancer or obesity conditions, and stress experienced by neurons and cardiomyocytes, for example, triggers the downregulation of mitofusins and thus fragmentation of mitochondria. This places mitofusins upfront in sensing and transmitting stress. In fact, mitofusins are almost entirely exposed to the cytoplasm, a topology suitable for a critical relay point in information exchange between mitochondria and their cellular environment. Consistent with their topology, mitofusins are either activated or repressed by cytosolic post-translational modifiers, mainly by ubiquitin. Ubiquitin is a ubiquitous small protein orchestrating multiple quality control pathways, which is covalently attached to lysine residues in its substrates, or in ubiquitin itself. Importantly, from a chain of events also mediated by E1 and E2 enzymes, E3 ligases perform the ultimate and determinant step in substrate choice. Here, we review the ubiquitin E3 ligases that modify mitofusins. Two mitochondrial E3 enzymes—March5 and MUL1—one ligase located to the ER—Gp78—and finally three cytosolic enzymes—MGRN1, HUWE1, and Parkin—were shown to ubiquitylate mitofusins, in response to a variety of cellular inputs. The respective outcomes on mitochondrial morphology, on contact sites to the endoplasmic reticulum and on destructive processes, like mitophagy or apoptosis, are presented. Ultimately, understanding the mechanisms by which E3 ligases and mitofusins sense and bi-directionally signal mitochondria-cytosolic dysfunctions could pave the way for therapeutic approaches in neurodegenerative, cardiovascular, and obesity-linked diseases.
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Affiliation(s)
- Mafalda Escobar-Henriques
- Center for Molecular Medicine Cologne (CMMC), Institute for Genetics, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Mariana Joaquim
- Center for Molecular Medicine Cologne (CMMC), Institute for Genetics, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
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7
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Mitochondrial quality control and neurodegenerative diseases. Neuronal Signal 2018; 2:NS20180062. [PMID: 32714594 PMCID: PMC7373240 DOI: 10.1042/ns20180062] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Revised: 10/03/2018] [Accepted: 10/19/2018] [Indexed: 12/17/2022] Open
Abstract
Mitochondria homeostasis is sustained by the mitochondrial quality control (MQC) system, which is crucial for cellular health, especially in the maintenance of functional mitochondria. A healthy mitochondria network is essential for life as it regulates cellular metabolism processes, particularly ATP production. Mitochondrial dynamics and mitophagy are two highly integrated processes in MQC system that determines whether damaged mitochondria will be repaired or degraded. Neurons are highly differentiated cells which demand high energy consumption. Therefore, compromised MQC processes and the accumulation of dysfunctional mitochondria may be the main cause of neuronal death and lead to neurodegeneration. Here, we focus on the inseparable relationship of mitochondria dynamics and mitophagy and how their dysfunction may lead to neurodegenerative diseases.
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8
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Herr DJ, Baarine M, Aune SE, Li X, Ball LE, Lemasters JJ, Beeson CC, Chou JC, Menick DR. HDAC1 localizes to the mitochondria of cardiac myocytes and contributes to early cardiac reperfusion injury. J Mol Cell Cardiol 2017; 114:309-319. [PMID: 29224834 DOI: 10.1016/j.yjmcc.2017.12.004] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Revised: 11/30/2017] [Accepted: 12/05/2017] [Indexed: 01/15/2023]
Abstract
RATIONALE Recent evidence indicates that histone deacetylase enzymes (HDACs) contribute to ischemia reperfusion (I/R) injury, and pan-HDAC inhibitors have been shown to be cardioprotective when administered either before an ischemic insult or during reperfusion. We have shown previously that selective inhibition of class I HDACs provides superior cardioprotection when compared to pan-HDAC inhibition in a pretreatment model, but selective class I HDAC inhibition has not been tested during reperfusion, and specific targets of class I HDACs in I/R injury have not been identified. OBJECTIVE We hypothesized that selective inhibition of class I HDACs with the drug MS-275 (entinostat) during reperfusion would improve recovery from I/R injury in the first hour of reperfusion. METHODS AND RESULTS Hearts from male Sprague-Dawley rats were subjected to ex vivo I/R injury±MS-275 class I HDAC inhibition during reperfusion alone. MS-275 significantly attenuated I/R injury, as indicated by improved LV function and tissue viability at the end of reperfusion. Unexpectedly, we observed that HDAC1 is present in the mitochondria of cardiac myocytes, but not fibroblasts or endothelial cells. We then designed mitochondria-restricted and mitochondria-excluded HDAC inhibitors, and tested both in our ex vivo I/R model. The selective inhibition of mitochondrial HDAC1 attenuated I/R injury to the same extent as MS-275, whereas the mitochondrial-excluded inhibitor did not. Further assays demonstrated that these effects are attributable to a decrease in SDHA activity and subsequent metabolic ROS production in reperfusion. CONCLUSIONS We demonstrate for the first time that HDAC1 is present within the mitochondria of cardiac myocytes, and mitochondrial HDAC1 contributes significantly to I/R injury within the first hour of reperfusion.
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Affiliation(s)
- Daniel J Herr
- Department of Medicine, Division of Cardiology, Medical University of South Carolina, Charleston, SC 29425, United States
| | - Mauhamad Baarine
- Department of Medicine, Division of Cardiology, Medical University of South Carolina, Charleston, SC 29425, United States
| | - Sverre E Aune
- Department of Medicine, Division of Cardiology, Medical University of South Carolina, Charleston, SC 29425, United States
| | - Xiaoyang Li
- Department of Drug Discovery and Biomedical Sciences, Medical University of South Carolina, Charleston, SC 29425, United States
| | - Lauren E Ball
- Department of Cell and Molecular Pharmacology, Medical University of South Carolina, Charleston, SC 29425, United States
| | - John J Lemasters
- Department of Drug Discovery and Biomedical Sciences, Medical University of South Carolina, Charleston, SC 29425, United States; Center for Cell Death, Injury & Regeneration, Medical University of South Carolina, Charleston, SC 29425, United States
| | - Craig C Beeson
- Department of Drug Discovery and Biomedical Sciences, Medical University of South Carolina, Charleston, SC 29425, United States
| | - James C Chou
- Department of Drug Discovery and Biomedical Sciences, Medical University of South Carolina, Charleston, SC 29425, United States
| | - Donald R Menick
- Department of Medicine, Division of Cardiology, Medical University of South Carolina, Charleston, SC 29425, United States; Ralph H. Johnson Veterans Affairs Medical Center, Charleston, SC 29425, United States.
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9
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Characterization of Charcot-Marie-Tooth optic neuropathy. J Neurol 2017; 264:2431-2435. [PMID: 29063243 DOI: 10.1007/s00415-017-8645-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Revised: 10/10/2017] [Accepted: 10/11/2017] [Indexed: 10/18/2022]
Abstract
Varying degrees of optic neuropathy can be seen in patients with Charcot-Marie-Tooth (CMT) disease. To define and characterize the extent of optic neuropathy in patients with CMT2A and CMT1A, two patients from both sub-classifications were evaluated. All patients underwent complete neuro-ophthalmic examinations, and optical coherence (OCT) measurements of the retinal nerve fiber layer (RNFL) and ganglion cell layer complex (GCC) were obtained, along with pattern visual evoked potential (VEP) and pattern electroretinogram (ERG) recordings. RNFL thickness measurements were decreased in both patients with CMT2A, and normal in both patients with CMT1A. GCC measurements were decreased in both patients with CMT2A, mildly decreased in one patient with CMT1A and normal in the second CMT1A patient. VEP latencies were delayed in one patient with CMT2A and one patient with CMT1A. VEP latencies were immeasurable in the other CMT2A patient and not obtained in the second CMT1A patient. Pattern ERG P50-N95 amplitudes were decreased in both patients with CMT2A and normal in one patient with CMT1A. The pattern ERG was immeasurable in the second patient with CMT1A. The pattern of RNFL and GCC thinning in CMT2A with optic neuropathy, a subset of HMSN VI, closely resembles that seen in other mitochondrial optic neuropathies.
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10
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Rizzo F, Ronchi D, Salani S, Nizzardo M, Fortunato F, Bordoni A, Stuppia G, Del Bo R, Piga D, Fato R, Bresolin N, Comi GP, Corti S. Selective mitochondrial depletion, apoptosis resistance, and increased mitophagy in human Charcot-Marie-Tooth 2A motor neurons. Hum Mol Genet 2016; 25:4266-4281. [PMID: 27506976 DOI: 10.1093/hmg/ddw258] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Revised: 07/21/2016] [Accepted: 07/21/2016] [Indexed: 01/10/2023] Open
Abstract
Charcot-Marie-Tooth 2A (CMT2A) is an inherited peripheral neuropathy caused by mutations in MFN2, which encodes a mitochondrial membrane protein involved in mitochondrial network homeostasis. Because MFN2 is expressed ubiquitously, the reason for selective motor neuron (MN) involvement in CMT2A is unclear. To address this question, we generated MNs from induced pluripotent stem cells (iPSCs) obtained from the patients with CMT2A as an in vitro disease model. CMT2A iPSC-derived MNs (CMT2A-MNs) exhibited a global reduction in mitochondrial content and altered mitochondrial positioning without significant differences in survival and axon elongation. RNA sequencing profiles and protein studies of key components of the apoptotic executioner program (i.e. p53, BAX, caspase 8, cleaved caspase 3, and the anti-apoptotic marker Bcl2) demonstrated that CMT2A-MNs are more resistant to apoptosis than wild-type MNs. Exploring the balance between mitochondrial biogenesis and the regulation of autophagy-lysosome transcription, we observed an increased autophagic flux in CMT2A-MNs that was associated with increased expression of PINK1, PARK2, BNIP3, and a splice variant of BECN1 that was recently demonstrated to be a trigger for mitochondrial autophagic removal. Taken together, these data suggest that the striking reduction in mitochondria in MNs expressing mutant MFN2 is not the result of impaired biogenesis, but more likely the consequence of enhanced mitophagy. Thus, these pathways represent possible novel molecular therapeutic targets for the development of an effective cure for this disease.
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Affiliation(s)
- Federica Rizzo
- Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan, Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Dario Ronchi
- Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan, Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Sabrina Salani
- Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan, Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Monica Nizzardo
- Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan, Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Francesco Fortunato
- Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan, Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Andreina Bordoni
- Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan, Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Giulia Stuppia
- Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan, Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Roberto Del Bo
- Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan, Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Daniela Piga
- Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan, Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Romana Fato
- Department of Pharmacy and Biotecnology (FaBiT), University of Bologna, Bologna, Italy
| | - Nereo Bresolin
- Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan, Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Giacomo P Comi
- Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan, Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Stefania Corti
- Dino Ferrari Centre, Neuroscience Section, Department of Pathophysiology and Transplantation (DEPT), University of Milan, Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
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Bioenergetic roles of mitochondrial fusion. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2016; 1857:1277-1283. [DOI: 10.1016/j.bbabio.2016.04.002] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Revised: 03/18/2016] [Accepted: 04/05/2016] [Indexed: 11/17/2022]
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Luz AL, Rooney JP, Kubik LL, Gonzalez CP, Song DH, Meyer JN. Mitochondrial Morphology and Fundamental Parameters of the Mitochondrial Respiratory Chain Are Altered in Caenorhabditis elegans Strains Deficient in Mitochondrial Dynamics and Homeostasis Processes. PLoS One 2015; 10:e0130940. [PMID: 26106885 PMCID: PMC4480853 DOI: 10.1371/journal.pone.0130940] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Accepted: 05/27/2015] [Indexed: 12/28/2022] Open
Abstract
Mitochondrial dysfunction has been linked to myriad human diseases and toxicant exposures, highlighting the need for assays capable of rapidly assessing mitochondrial health in vivo. Here, using the Seahorse XFe24 Analyzer and the pharmacological inhibitors dicyclohexylcarbodiimide and oligomycin (ATP-synthase inhibitors), carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazone (mitochondrial uncoupler) and sodium azide (cytochrome c oxidase inhibitor), we measured the fundamental parameters of mitochondrial respiratory chain function: basal oxygen consumption, ATP-linked respiration, maximal respiratory capacity, spare respiratory capacity and proton leak in the model organism Caenhorhabditis elegans. Since mutations in mitochondrial homeostasis genes cause mitochondrial dysfunction and have been linked to human disease, we measured mitochondrial respiratory function in mitochondrial fission (drp-1)-, fusion (fzo-1)-, mitophagy (pdr-1, pink-1)-, and electron transport chain complex III (isp-1)-deficient C. elegans. All showed altered function, but the nature of the alterations varied between the tested strains. We report increased basal oxygen consumption in drp-1; reduced maximal respiration in drp-1, fzo-1, and isp-1; reduced spare respiratory capacity in drp-1 and fzo-1; reduced proton leak in fzo-1 and isp-1; and increased proton leak in pink-1 nematodes. As mitochondrial morphology can play a role in mitochondrial energetics, we also quantified the mitochondrial aspect ratio for each mutant strain using a novel method, and for the first time report increased aspect ratios in pdr-1- and pink-1-deficient nematodes.
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Affiliation(s)
- Anthony L. Luz
- Nicholas School of the Environment, Duke University, Durham, North Carolina, United States of America
| | - John P. Rooney
- Nicholas School of the Environment, Duke University, Durham, North Carolina, United States of America
| | - Laura L. Kubik
- Nicholas School of the Environment, Duke University, Durham, North Carolina, United States of America
| | - Claudia P. Gonzalez
- Nicholas School of the Environment, Duke University, Durham, North Carolina, United States of America
| | - Dong Hoon Song
- Simulation Group, Samsung SDI, Suwon-si, Gyeonggi-do, Republic of Korea
| | - Joel N. Meyer
- Nicholas School of the Environment, Duke University, Durham, North Carolina, United States of America
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Strickland AV, Rebelo AP, Zhang F, Price J, Bolon B, Silva JP, Wen R, Züchner S. Characterization of the mitofusin 2 R94W mutation in a knock-in mouse model. J Peripher Nerv Syst 2015; 19:152-64. [PMID: 24862862 DOI: 10.1111/jns5.12066] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2014] [Revised: 02/25/2014] [Accepted: 03/19/2014] [Indexed: 11/29/2022]
Abstract
Charcot-Marie-Tooth disease (CMT) comprises a group of heterogeneous peripheral axonopathies affecting 1 in 2,500 individuals. As mutations in several genes cause axonal degeneration in CMT type 2, mutations in mitofusin 2 (MFN2) account for approximately 90% of the most severe cases, making it the most common cause of inherited peripheral axonal degeneration. MFN2 is an integral mitochondrial outer membrane protein that plays a major role in mitochondrial fusion and motility; yet the mechanism by which dominant mutations in this protein lead to neurodegeneration is still not fully understood. Furthermore, future pre-clinical drug trials will be in need of validated rodent models. We have generated a Mfn2 knock-in mouse model expressing Mfn2(R94W), which was originally identified in CMT patients. We have performed behavioral, morphological, and biochemical studies to investigate the consequences of this mutation. Homozygous inheritance leads to premature death at P1, as well as mitochondrial dysfunction, including increased mitochondrial fragmentation in mouse embryonic fibroblasts and decreased ATP levels in newborn brains. Mfn2(R94W) heterozygous mice show histopathology and age-dependent open-field test abnormalities, which support a mild peripheral neuropathy. Although behavior does not mimic the severity of the human disease phenotype, this mouse can provide useful tissues for studying molecular pathways associated with MFN2 point mutations.
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Affiliation(s)
- Alleene V Strickland
- Department of Human Genetics, Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami, FL, USA
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Mourier A, Motori E, Brandt T, Lagouge M, Atanassov I, Galinier A, Rappl G, Brodesser S, Hultenby K, Dieterich C, Larsson NG. Mitofusin 2 is required to maintain mitochondrial coenzyme Q levels. ACTA ACUST UNITED AC 2015; 208:429-42. [PMID: 25688136 PMCID: PMC4332246 DOI: 10.1083/jcb.201411100] [Citation(s) in RCA: 154] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Mitofusin 2 plays an unexpected role in maintaining the terpenoid biosynthesis pathway and is necessary for mitochondrial coenzyme Q biosynthesis. Mitochondria form a dynamic network within the cell as a result of balanced fusion and fission. Despite the established role of mitofusins (MFN1 and MFN2) in mitochondrial fusion, only MFN2 has been associated with metabolic and neurodegenerative diseases, which suggests that MFN2 is needed to maintain mitochondrial energy metabolism. The molecular basis for the mitochondrial dysfunction encountered in the absence of MFN2 is not understood. Here we show that loss of MFN2 leads to impaired mitochondrial respiration and reduced ATP production, and that this defective oxidative phosphorylation process unexpectedly originates from a depletion of the mitochondrial coenzyme Q pool. Our study unravels an unexpected and novel role for MFN2 in maintenance of the terpenoid biosynthesis pathway, which is necessary for mitochondrial coenzyme Q biosynthesis. The reduced respiratory chain function in cells lacking MFN2 can be partially rescued by coenzyme Q10 supplementation, which suggests a possible therapeutic strategy for patients with diseases caused by mutations in the Mfn2 gene.
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Affiliation(s)
- Arnaud Mourier
- Max Planck Institute for Biology of Ageing, 50931 Cologne, Germany
| | - Elisa Motori
- Max Planck Institute for Biology of Ageing, 50931 Cologne, Germany
| | - Tobias Brandt
- Max Planck Institute of Biophysics, 60438 Frankfurt, Germany
| | - Marie Lagouge
- Max Planck Institute for Biology of Ageing, 50931 Cologne, Germany
| | - Ilian Atanassov
- Max Planck Institute for Biology of Ageing, 50931 Cologne, Germany
| | - Anne Galinier
- STROMALab, UMR Université Paul Sabatier/Centre National de la Recherche Scientifique 5273, Institut National de la Santé et de la Recherche Médicale U1031, BP 84 225-F-31 432, Toulouse, France
| | - Gunter Rappl
- Department I of Internal Medicine, University Hospital Cologne, and Center for Molecular Medicine Cologne (CMMC), University of Cologne, 50931 Cologne, Germany Department I of Internal Medicine, University Hospital Cologne, and Center for Molecular Medicine Cologne (CMMC), University of Cologne, 50931 Cologne, Germany
| | - Susanne Brodesser
- CECAD Research Center, Lipidomics Facility, University of Cologne, 50931 Cologne, Germany
| | - Kjell Hultenby
- Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden
| | | | - Nils-Göran Larsson
- Max Planck Institute for Biology of Ageing, 50931 Cologne, Germany Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden
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15
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Baarine M, Beeson C, Singh A, Singh I. ABCD1 deletion-induced mitochondrial dysfunction is corrected by SAHA: implication for adrenoleukodystrophy. J Neurochem 2015; 133:380-96. [PMID: 25393703 DOI: 10.1111/jnc.12992] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2014] [Revised: 10/09/2014] [Accepted: 11/07/2014] [Indexed: 01/09/2023]
Abstract
X-linked Adrenoleukodystrophy (X-ALD), an inherited peroxisomal metabolic neurodegenerative disorder, is caused by mutations/deletions in the ATP-binding cassette transporter (ABCD1) gene encoding peroxisomal ABC transporter adrenoleukodystrophy protein (ALDP). Metabolic dysfunction in X-ALD is characterized by the accumulation of very long chain fatty acids ≥ C22:0) in the tissues and plasma of patients. Here, we investigated the mitochondrial status following deletion of ABCD1 in B12 oligodendrocytes and U87 astrocytes. This study provides evidence that silencing of peroxisomal protein ABCD1 produces structural and functional perturbations in mitochondria. Activities of electron transport chain-related enzymes and of citric acid cycle (TCA cycle) were reduced; mitochondrial redox status was dysregulated and the mitochondrial membrane potential was disrupted following ABCD1 silencing. A greater reduction in ATP levels and citrate synthase activities was observed in oligodendrocytes as compared to astrocytes. Furthermore, most of the mitochondrial perturbations induced by ABCD1 silencing were corrected by treating cells with suberoylanilide hydroxamic acid, an Histone deacetylase inhibitor. These observations indicate a novel relationship between peroxisomes and mitochondria in cellular homeostasis and the importance of intact peroxisomes in relation to mitochondrial integrity and function in the cell types that participate in the pathobiology of X-ALD. These observations suggest suberoylanilide hydroxamic acid as a potential therapy for X-ALD. Schematic description of the effects of loss of peroxisomal ATP-binding cassette transporter D1 (ABCD1) gene on cellular Redox and mitochondrial activities and their correction by suberoylanilide hydroxamic acid (SAHA) treatment. Pathogenomic accumulation of very long chain fatty acids (VLCFA) as a result of loss of ABCD1 leads to dysfunctions of mitochondrial biogenesis and its activities. Treatment with SAHA corrects mitochondrial dysfunctions. These studies describe unique cooperation between mitochondria and peroxisome for cellular activities.
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Affiliation(s)
- Mauhamad Baarine
- Department of Pediatrics, Darby Children's Research Institute, Medical University of South Carolina, Charleston, South Carolina, USA
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16
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Abstract
Beyond their contribution to basic metabolism, the major cellular organelles, in particular mitochondria, can determine whether cells respond to stress in an adaptive or suicidal manner. Thus, mitochondria can continuously adapt their shape to changing bioenergetic demands as they are subjected to quality control by autophagy, or they can undergo a lethal permeabilization process that initiates apoptosis. Along similar lines, multiple proteins involved in metabolic circuitries, including oxidative phosphorylation and transport of metabolites across membranes, may participate in the regulated or catastrophic dismantling of organelles. Many factors that were initially characterized as cell death regulators are now known to physically or functionally interact with metabolic enzymes. Thus, several metabolic cues regulate the propensity of cells to activate self-destructive programs, in part by acting on nutrient sensors. This suggests the existence of "metabolic checkpoints" that dictate cell fate in response to metabolic fluctuations. Here, we discuss recent insights into the intersection between metabolism and cell death regulation that have major implications for the comprehension and manipulation of unwarranted cell loss.
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Affiliation(s)
- Douglas R Green
- Department of Immunology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA.
| | - Lorenzo Galluzzi
- Equipe 11 labellisée par la Ligue Nationale contre le Cancer, Centre de Recherche des Cordeliers, F-75006 Paris, France. Université Paris Descartes/Paris V; Sorbonne Paris Cité; F-75005 Paris, France. INSERM, U1138, F-94805 Villejuif, France
| | - Guido Kroemer
- Equipe 11 labellisée par la Ligue Nationale contre le Cancer, Centre de Recherche des Cordeliers, F-75006 Paris, France. Université Paris Descartes/Paris V; Sorbonne Paris Cité; F-75005 Paris, France. INSERM, U1138, F-94805 Villejuif, France. Metabolomics and Cell Biology Platforms, Gustave Roussy, F-94805 Villejuif, France. Pôle de Biologie, Hôpital Européen Georges Pompidou, Assistance Publique-Hôpitaux de Paris, F-75015 Paris, France.
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17
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Abstract
SIGNIFICANCE Mitochondrial dynamics describes the continuous change in the position, size, and shape of mitochondria within cells. The morphological and functional complexity of neurons, the remarkable length of their processes, and the rapid changes in metabolic requirements arising from their intrinsic excitability render these cells particularly dependent on effective mitochondrial function and positioning. The rules that govern these changes and their functional significance are not fully understood, yet the dysfunction of mitochondrial dynamics has been implicated as a pathogenetic factor in a number of diseases, including disorders of the central and peripheral nervous systems. RECENT ADVANCES In recent years, a number of mutations of genes encoding proteins that play important roles in mitochondrial dynamics and function have been discovered in patients with Charcot-Marie-Tooth (CMT) disease, a hereditary peripheral neuropathy. These findings have directly linked mitochondrial pathology to the pathology of peripheral nerve and have identified certain aspects of mitochondrial dynamics as potential early events in the pathogenesis of CMT. In addition, mitochondrial dysfunction has now been implicated in the pathogenesis of noninherited neuropathies, including diabetic and inflammatory neuropathies. CRITICAL ISSUES The role of mitochondria in peripheral nerve diseases has been mostly examined in vitro, and less so in animal models. FUTURE DIRECTIONS This review examines available evidence for the role of mitochondrial dynamics in the pathogenesis of peripheral neuropathies, their relevance in human diseases, and future challenges for research in this field.
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Affiliation(s)
- Marija Sajic
- Department of Neuroinflammation, UCL Institute of Neurology , Queen Square, London, United Kingdom
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Clémençon B, Babot M, Trézéguet V. The mitochondrial ADP/ATP carrier (SLC25 family): pathological implications of its dysfunction. Mol Aspects Med 2013; 34:485-93. [PMID: 23506884 DOI: 10.1016/j.mam.2012.05.006] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2012] [Accepted: 02/10/2012] [Indexed: 02/04/2023]
Abstract
In aerobic eukaryotic cells, the high energy metabolite ATP is generated mainly within the mitochondria following the process of oxidative phosphorylation. The mitochondrial ATP is exported to the cytoplasm using a specialized transport protein, the ADP/ATP carrier, to provide energy to the cell. Any deficiency or dysfunction of this membrane protein leads to serious consequences on cell metabolism and can cause various diseases such as muscular dystrophy. Described as a decisive player in the programmed cell death, it was recently shown to play a role in cancer. The objective of this review is to summarize the current knowledge of the involvement of the ADP/ATP carrier, encoded by the SLC25A4, SLC25A5, SLC25A6 and SLC25A31 genes, in human diseases and of the efforts made at designing different model systems to study this carrier and the associated pathologies through biochemical, genetic, and structural approaches.
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Affiliation(s)
- Benjamin Clémençon
- Institute of Biochemistry and Molecular Medicine, NCCR TransCure, University of Bern, Bern, Switzerland.
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Kiebish MA, Yang K, Liu X, Mancuso DJ, Guan S, Zhao Z, Sims HF, Cerqua R, Cade WT, Han X, Gross RW. Dysfunctional cardiac mitochondrial bioenergetic, lipidomic, and signaling in a murine model of Barth syndrome. J Lipid Res 2013; 54:1312-25. [PMID: 23410936 DOI: 10.1194/jlr.m034728] [Citation(s) in RCA: 92] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Barth syndrome is a complex metabolic disorder caused by mutations in the mitochondrial transacylase tafazzin. Recently, an inducible tafazzin shRNA knockdown mouse model was generated to deconvolute the complex bioenergetic phenotype of this disease. To investigate the underlying cause of hemodynamic dysfunction in Barth syndrome, we interrogated the cardiac structural and signaling lipidome of this mouse model as well as its myocardial bioenergetic phenotype. A decrease in the distribution of cardiolipin molecular species and robust increases in monolysocardiolipin and dilysocardiolipin were demonstrated. Additionally, the contents of choline and ethanolamine glycerophospholipid molecular species containing precursors for lipid signaling at the sn-2 position were altered. Lipidomic analyses revealed specific dysregulation of HETEs and prostanoids, as well as oxidized linoleic and docosahexaenoic metabolites. Bioenergetic interrogation uncovered differential substrate utilization as well as decreases in Complex III and V activities. Transgenic expression of cardiolipin synthase or iPLA2γ ablation in tafazzin-deficient mice did not rescue the observed phenotype. These results underscore the complex nature of alterations in cardiolipin metabolism mediated by tafazzin loss of function. Collectively, we identified specific lipidomic, bioenergetic, and signaling alterations in a murine model that parallel those of Barth syndrome thereby providing novel insights into the pathophysiology of this debilitating disease.
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Affiliation(s)
- Michael A Kiebish
- Division of Bioorganic Chemistry and Molecular Pharmacology, Departments of Medicine, Washington University School of Medicine, St. Louis, MO 63110; and
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20
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Vielhaber S, Debska-Vielhaber G, Peeva V, Schoeler S, Kudin AP, Minin I, Schreiber S, Dengler R, Kollewe K, Zuschratter W, Kornblum C, Zsurka G, Kunz WS. Mitofusin 2 mutations affect mitochondrial function by mitochondrial DNA depletion. Acta Neuropathol 2013; 125:245-56. [PMID: 22926664 DOI: 10.1007/s00401-012-1036-y] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2012] [Revised: 07/13/2012] [Accepted: 08/18/2012] [Indexed: 12/01/2022]
Abstract
Charcot-Marie-Tooth neuropathy type 2A (CMT2A) is associated with heterozygous mutations in the mitochondrial protein mitofusin 2 (Mfn2) that is intimately involved with the outer mitochondrial membrane fusion machinery. The precise consequences of these mutations on oxidative phosphorylation are still a matter of dispute. Here, we investigate the functional effects of MFN2 mutations in skeletal muscle and cultured fibroblasts of four CMT2A patients applying high-resolution respirometry. While maximal activities of respiration of saponin-permeabilized muscle fibers and digitonin-permeabilized fibroblasts were only slightly affected by the MFN2 mutations, the sensitivity of active state oxygen consumption to azide, a cytochrome c oxidase (COX) inhibitor, was increased. The observed dysfunction of the mitochondrial respiratory chain can be explained by a twofold decrease in mitochondrial DNA (mtDNA) copy numbers. The only patient without detectable alterations of respiratory chain in skeletal muscle also had a normal mtDNA copy number. We detected higher levels of mtDNA deletions in CMT2A patients, which were more pronounced in the patient without mtDNA depletion. Detailed analysis of mtDNA deletion breakpoints showed that many deleted molecules were lacking essential parts of mtDNA required for replication. This is in line with the lack of clonal expansion for the majority of observed mtDNA deletions. In contrast to the copy number reduction, deletions are unlikely to contribute to the detected respiratory impairment because of their minor overall amounts in the patients. Taken together, our findings corroborate the hypothesis that MFN2 mutations alter mitochondrial oxidative phosphorylation by affecting mtDNA replication.
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Affiliation(s)
- Stefan Vielhaber
- Department of Neurology, University of Magdeburg, Leipziger Str. 44, 39120 Magdeburg, Germany
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21
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Eschenbacher WH, Song M, Chen Y, Bhandari P, Zhao P, Jowdy CC, Engelhard JT, Dorn GW. Two rare human mitofusin 2 mutations alter mitochondrial dynamics and induce retinal and cardiac pathology in Drosophila. PLoS One 2012; 7:e44296. [PMID: 22957060 PMCID: PMC3434137 DOI: 10.1371/journal.pone.0044296] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2012] [Accepted: 08/01/2012] [Indexed: 01/12/2023] Open
Abstract
Mitochondrial fusion is essential to organelle homeostasis and organ health. Inexplicably, loss of function mutations of mitofusin 2 (Mfn2) specifically affect neurological tissue, causing Charcot Marie Tooth syndrome (CMT) and atypical optic atrophy. As CMT-linked Mfn2 mutations are predominantly within the GTPase domain, we postulated that Mfn2 mutations in other functional domains might affect non-neurological tissues. Here, we defined in vitro and in vivo consequences of rare human mutations in the poorly characterized Mfn2 HR1 domain. Human exome sequencing data identified 4 rare non-synonymous Mfn2 HR1 domain mutations, two bioinformatically predicted as damaging. Recombinant expression of these (Mfn2 M393I and R400Q) in Mfn2-null murine embryonic fibroblasts (MEFs) revealed incomplete rescue of characteristic mitochondrial fragmentation, compared to wild-type human Mfn2 (hMfn2); Mfn2 400Q uniquely induced mitochondrial fragmentation in normal MEFs. To compare Mfn2 mutation effects in neurological and non-neurological tissues in vivo, hMfn2 and the two mutants were expressed in Drosophila eyes or heart tubes made deficient in endogenous fly mitofusin (dMfn) through organ-specific RNAi expression. The two mutants induced similar Drosophila eye phenotypes: small eyes and an inability to rescue the eye pathology induced by suppression of dMfn. In contrast, Mfn2 400Q induced more severe cardiomyocyte mitochondrial fragmentation and cardiac phenotypes than Mfn2 393I, including heart tube dilation, depressed fractional shortening, and progressively impaired negative geotaxis. These data reveal a central functional role for Mfn2 HR1 domains, describe organ-specific effects of two Mfn2 HR1 mutations, and strongly support prospective studies of Mfn2 400Q in heritable human heart disease of unknown genetic etiology.
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Affiliation(s)
- William H. Eschenbacher
- Center for Pharmacogenomics, Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Moshi Song
- Center for Pharmacogenomics, Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Yun Chen
- Center for Pharmacogenomics, Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Poonam Bhandari
- Center for Pharmacogenomics, Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Peter Zhao
- Center for Pharmacogenomics, Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Casey C. Jowdy
- Center for Pharmacogenomics, Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - John T. Engelhard
- Center for Pharmacogenomics, Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Gerald W. Dorn
- Center for Pharmacogenomics, Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri, United States of America
- * E-mail:
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Kiebish MA, Yang K, Sims HF, Jenkins CM, Liu X, Mancuso DJ, Zhao Z, Guan S, Abendschein DR, Han X, Gross RW. Myocardial regulation of lipidomic flux by cardiolipin synthase: setting the beat for bioenergetic efficiency. J Biol Chem 2012; 287:25086-97. [PMID: 22584571 DOI: 10.1074/jbc.m112.340521] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Lipidomic regulation of mitochondrial cardiolipin content and molecular species composition is a prominent regulator of bioenergetic efficiency. However, the mechanisms controlling cardiolipin metabolism during health or disease progression have remained elusive. Herein, we demonstrate that cardiac myocyte-specific transgenic expression of cardiolipin synthase results in accelerated cardiolipin lipidomic flux that impacts multiple aspects of mitochondrial bioenergetics and signaling. During the postnatal period, cardiolipin synthase transgene expression results in marked changes in the temporal maturation of cardiolipin molecular species during development. In adult myocardium, cardiolipin synthase transgene expression leads to a marked increase in symmetric tetra-18:2 molecular species without a change in total cardiolipin content. Mechanistic analysis demonstrated that these alterations result from increased cardiolipin remodeling by sequential phospholipase and transacylase/acyltransferase activities in conjunction with a decrease in phosphatidylglycerol content. Moreover, cardiolipin synthase transgene expression results in alterations in signaling metabolites, including a marked increase in the cardioprotective eicosanoid 14,15-epoxyeicosatrienoic acid. Examination of mitochondrial bioenergetic function by high resolution respirometry demonstrated that cardiolipin synthase transgene expression resulted in improved mitochondrial bioenergetic efficiency as evidenced by enhanced electron transport chain coupling using multiple substrates as well as by salutary changes in Complex III and IV activities. Furthermore, transgenic expression of cardiolipin synthase attenuated maladaptive cardiolipin remodeling and bioenergetic inefficiency in myocardium rendered diabetic by streptozotocin treatment. Collectively, these results demonstrate the unanticipated role of cardiolipin synthase in maintaining physiologic membrane structure and function even under metabolic stress, thereby identifying cardiolipin synthase as a novel therapeutic target to attenuate mitochondrial dysfunction in diabetic myocardium.
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Affiliation(s)
- Michael A Kiebish
- Division of Bioorganic Chemistry and Molecular Pharmacology, Department of Medicine, Washington University School of Medicine, St Louis, Missouri 63110, USA
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Mitochondrial dysfunction in glaucoma: Understanding genetic influences. Mitochondrion 2012; 12:202-12. [DOI: 10.1016/j.mito.2011.11.004] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2011] [Accepted: 11/11/2011] [Indexed: 12/27/2022]
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Abstract
BACKGROUND Charcot-Marie-Tooth disease (CMT) is the most common inherited disorder of the peripheral nervous system. The frequency of different CMT genotypes has been estimated in clinic populations, but prevalence data from the general population is lacking. Point mutations in the mitofusin 2 (MFN2) gene has been identified exclusively in Charcot-Marie-Tooth disease type 2 (CMT2), and in a single family with intermediate CMT. MFN2 point mutations are probably the most common cause of CMT2. The CMT phenotype caused by mutation in the myelin protein zero (MPZ) gene varies considerably, from early onset and severe forms to late onset and milder forms. The mechanism is not well understood. The myelin protein zero (P(0) ) mediates adhesion in the spiral wraps of the Schwann cell's myelin sheath. X-linked Charcot-Marie Tooth disease (CMTX) is caused by mutations in the connexin32 (cx32) gene that encodes a polypeptide which is arranged in hexameric array and form gap junctions. AIMS Estimate prevalence of CMT. Estimate frequency of Peripheral Myelin Protein 22 (PMP22) duplication and point mutations, insertions and deletions in Cx32, Early growth response 2 (EGR2), MFN2, MPZ, PMP22 and Small integral membrane protein of lysosome/late endosome (SIMPLE) genes. Description of novel mutations in Cx32, MFN2 and MPZ. Description of de novo mutations in MFN2. MATERIAL AND METHODS Our population based genetic epidemiological survey included persons with CMT residing in eastern Akershus County, Norway. The participants were interviewed and examined by one geneticist/neurologist, and classified clinically, neurophysiologically and genetically. Two-hundred and thirty-two consecutive unselected and unrelated CMT families with available DNA from all regions in Norway were included in the MFN2 study. We screened for point mutations in the MFN2 gene. We describe four novel mutations, two in the connexin32 gene and two in the MPZ gene. RESULTS A total of 245 affected from 116 CMT families from the general population of eastern Akershus county were included in the genetic epidemiological survey. In the general population 1 per 1214 persons (95% CI 1062-1366) has CMT. Charcot-Marie-Tooth disease type 1 (CMT1), CMT2 and intermediate CMT were found in 48.2%, 49.4% and 2.4% of the families, respectively. A mutation in the investigated genes was found in 27.2% of the CMT families and in 28.6% of the affected. The prevalence of the PMP22 duplication and mutations in the Cx32, MPZ and MFN2 genes was found in 13.6%, 6.2%, 1.2%, 6.2% of the families, and in 19.6%, 4.8%, 1.1%, 3.2% of the affected, respectively. None of the families had point mutations, insertions or deletions in the EGR2, PMP22 or SIMPLE genes. Four known and three novel mitofusin 2 (MFN2) point mutations in 8 unrelated Norwegian CMT families were identified. The novel point mutations were not found in 100 healthy controls. This corresponds to 3.4% (8/232) of CMT families having point mutations in MFN2. The phenotypes were compatible with CMT1 in two families, CMT2 in four families, intermediate CMT in one family and distal hereditary motor neuronopathy (dHMN) in one family. A point mutation in the MFN2 gene was found in 2.3% of CMT1, 5.5% of CMT2, 12.5% of intermediate CMT and 6.7% of dHMN families. Two novel missense mutations in the MPZ gene were identified. Family 1 had a c.368G>A (Gly123Asp) transition while family 2 and 3 had a c.103G>A (Asp35Asn) transition. The affected in family 1 had early onset and severe symptoms compatible with Dejerine-Sottas syndrome (DSS), while affected in family 2 and 3 had late onset, milder symptoms and axonal neuropathy compatible with CMT2. Two novel connexin32 mutations that cause early onset X-linked CMT were identified. Family 1 had a deletion c.225delG (R75fsX83) which causes a frameshift and premature stop codon at position 247 while family 2 had a c.536G>A (Cys179Tyr) transition which causes a change of the highly conserved cysteine residue, i.e. disruption of at least one of three disulfide bridges. The mean age at onset was in the first decade and the nerve conduction velocities were in the intermediate range. DISCUSSION Charcot-Marie-Tooth disease is the most common inherited neuropathy. At present 47 hereditary neuropathy genes are known, and an examination of all known genes would probably only identify mutations in approximately 50% of those with CMT. Thus, it is likely that at least 30-50 CMT genes are yet to be identified. The identified known and novel point mutations in the MFN2 gene expand the clinical spectrum from CMT2 and intermediate CMT to also include possibly CMT1 and the dHMN phenotypes. Thus, genetic analyses of the MFN2 gene should not be restricted to persons with CMT2. The phenotypic variation caused by different missense mutations in the MPZ gene is likely caused by different conformational changes of the MPZ protein which affects the functional tetramers. Severe changes of the MPZ protein cause dysfunctional tetramers and predominantly uncompacted myelin, i.e. the severe phenotypes congenital hypomyelinating neuropathy and DSS, while milder changes cause the phenotypes CMT1 and CMT2. The two novel mutations in the connexin32 gene are more severe than the majority of previously described mutations possibly due to the severe structural change of the gap junction they encode. CONCLUSION Charcot-Marie-Tooth disease is the most common inherited disorder of the peripheral nervous system with an estimated prevalence of 1 in 1214. CMT1 and CMT2 are equally frequent in the general population. The prevalence of PMP22 duplication and of mutations in Cx32, MPZ and MFN2 is 19.6%, 4.8%, 1.1% and 3.2%, respectively. The ratio of probable de novo mutations in CMT families was estimated to be 22.7%. Genotype- phenotype correlations for seven novel mutations in the genes Cx32 (2), MFN2 (3) and MPZ (2) are described. Two novel phenotypes were ascribed to the MFN2 gene, however further studies are needed to confirm that MFN2 mutations can cause CMT1 and dHMN.
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Affiliation(s)
- G J Braathen
- Head and Neck Research Group, Research Centre, Akershus University Hospital, Lørenskog, Norway.
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25
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Cassereau J, Chevrollier A, Gueguen N, Desquiret V, Verny C, Nicolas G, Dubas F, Amati-Bonneau P, Reynier P, Bonneau D, Procaccio V. Mitochondrial dysfunction and pathophysiology of Charcot–Marie–Tooth disease involving GDAP1 mutations. Exp Neurol 2011; 227:31-41. [DOI: 10.1016/j.expneurol.2010.09.006] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2010] [Revised: 09/02/2010] [Accepted: 09/04/2010] [Indexed: 11/29/2022]
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Johnson D, Nehrke K. Mitochondrial fragmentation leads to intracellular acidification in Caenorhabditis elegans and mammalian cells. Mol Biol Cell 2010; 21:2191-201. [PMID: 20444981 PMCID: PMC2893984 DOI: 10.1091/mbc.e09-10-0874] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
It is unclear how lesions in genes that regulate mitochondrial structural dynamics lead to disease. Here, tissue-specific biosensors expressed in the genetic model organism Caenorhabditis elegans are used to demonstrate that robust cellular acidification occurs when mitochondria are fragmented and may contribute to the etiology of morphology diseases in mammals. Mitochondrial structural dynamics are regulated through the opposing processes of membrane fission and fusion, which are conserved from yeast to man. The chronic inhibition of mitochondrial fusion as a result of genetic mutation is the cause of human autosomal dominant optic atrophy (ADOA) and Charcot-Marie-Tooth syndrome type 2A (CMT-2A). Here, we demonstrate that genetic fragmentation of the mitochondrial network in Caenorhabditis elegans induces cellular acidification in a broad range of tissues from the intestine, to body wall muscles, and neurons. Genetic epistasis analyses demonstrate that fragmentation itself, and not the loss of a particular protein, leads to acidosis, and the worm's fitness matches the extent of acidification. We suggest that fragmentation may cause acidification through two distinct processes: oxidative signaling after the loss of the ability of the mitochondrial inner membrane to undergo fusion and lactic acidosis after the loss of outer membrane fusion. Finally, experiments in cultured mammalian cells demonstrate a conserved link between mitochondrial morphology and cell pH homeostasis. Taken together these data reveal a potential role for acidosis in the differing etiology of diseases associated with mitochondrial morphology defects such as ADOA and CMT-2A.
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Affiliation(s)
- David Johnson
- Department of Biochemistry, Medicine, and Pharmacology and Physiology, University of Rochester Medical Center, Rochester, NY 14642, USA.
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Multi-site control and regulation of mitochondrial energy production. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2010; 1797:698-709. [PMID: 20226160 DOI: 10.1016/j.bbabio.2010.02.030] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2009] [Revised: 02/19/2010] [Accepted: 02/24/2010] [Indexed: 12/21/2022]
Abstract
With the extraordinary progress of mitochondrial science and cell biology, novel biochemical pathways have emerged as strategic points of bioenergetic regulation and control. They include mitochondrial fusion, fission and organellar motility along microtubules and microfilaments (mitochondrial dynamics), mitochondrial turnover (biogenesis and degradation), and mitochondrial phospholipids synthesis. Yet, much is still unknown about the mutual interaction between mitochondrial energy state, biogenesis, dynamics and degradation. Meanwhile, clinical research into metabolic abnormalities in tumors as diverse as renal carcinoma, glioblastomas, paragangliomas or skin leiomyomata, has designated new genes, oncogenes and oncometabolites involved in the regulation of cellular and mitochondrial energy production. Furthermore, the examination of rare neurological diseases such as Charcot-Marie Tooth type 2a, Autosomal Dominant Optic Atrophy, Lethal Defect of Mitochondrial and Peroxisomal Fission, or Spastic Paraplegia suggested involvement of MFN2, OPA1/3, DRP1 or Paraplegin, in the auxiliary control of mitochondrial energy production. Lastly, advances in the understanding of mitochondrial apoptosis have suggested a supplementary role for Bcl2 or Bax in the regulation of mitochondrial respiration and dynamics, which has fostered the investigation of alternative mechanisms of energy regulation. In this review, we discuss the regulatory mechanisms of cellular and mitochondrial energy production, and we emphasize the importance of the study of rare neurological diseases in addition to more common disorders such as cancer, for the fundamental understanding of cellular and mitochondrial energy production.
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