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Kimonis V, Al Dubaisi R, Maclean AE, Hall K, Weiss L, Stover AE, Schwartz PH, Berg B, Cheng C, Parikh S, Conner BR, Wu S, Hasso AN, Scott DA, Koenig MK, Karam R, Tang S, Smith M, Chao E, Balk J, Hatchwell E, Eis PS. NUBPL mitochondrial disease: new patients and review of the genetic and clinical spectrum. J Med Genet 2020; 58:314-325. [PMID: 32518176 DOI: 10.1136/jmedgenet-2020-106846] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2020] [Revised: 04/02/2020] [Accepted: 04/22/2020] [Indexed: 12/18/2022]
Abstract
BACKGROUND The nucleotide binding protein-like (NUBPL) gene was first reported as a cause of mitochondrial complex I deficiency (MIM 613621, 618242) in 2010. To date, only eight patients have been reported with this mitochondrial disorder. Five other patients were recently reported to have NUBPL disease but their clinical picture was different from the first eight patients. Here, we report clinical and genetic findings in five additional patients (four families). METHODS Whole exome sequencing was used to identify patients with compound heterozygous NUBPL variants. Functional studies included RNA-Seq transcript analyses, missense variant biochemical analyses in a yeast model (Yarrowia lipolytica) and mitochondrial respiration experiments on patient fibroblasts. RESULTS The previously reported c.815-27T>C branch-site mutation was found in all four families. In prior patients, c.166G>A [p.G56R] was always found in cis with c.815-27T>C, but only two of four families had both variants. The second variant found in trans with c.815-27T>C in each family was: c.311T>C [p.L104P] in three patients, c.693+1G>A in one patient and c.545T>C [p.V182A] in one patient. Complex I function in the yeast model was impacted by p.L104P but not p.V182A. Clinical features include onset of neurological symptoms at 3-18 months, global developmental delay, cerebellar dysfunction (including ataxia, dysarthria, nystagmus and tremor) and spasticity. Brain MRI showed cerebellar atrophy. Mitochondrial function studies on patient fibroblasts showed significantly reduced spare respiratory capacity. CONCLUSION We report on five new patients with NUBPL disease, adding to the number and phenotypic variability of patients diagnosed worldwide, and review prior reported patients with pathogenic NUBPL variants.
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Affiliation(s)
- Virginia Kimonis
- Division of Genetics and Metabolism, Department of Pediatrics, University of California Irvine, Irvine, California, USA
| | - Rehab Al Dubaisi
- Division of Genetics and Metabolism, Department of Pediatrics, University of California Irvine, Irvine, California, USA
| | - Andrew E Maclean
- Department of Biological Chemistry, John Innes Centre, Norwich, Norfolk, UK.,Wellcome Centre for Integrative Parasitology, University of Glasgow, Glasgow, Glasgow, UK
| | - Kathy Hall
- Division of Genetics and Metabolism, Department of Pediatrics, University of California Irvine, Irvine, California, USA
| | - Lan Weiss
- Division of Genetics and Metabolism, Department of Pediatrics, University of California Irvine, Irvine, California, USA
| | - Alexander E Stover
- CHOC National Human Neural Stem Cell Resource, Children's Hospital of Orange County Research Institute, Orange, California, USA
| | - Philip H Schwartz
- CHOC National Human Neural Stem Cell Resource, Children's Hospital of Orange County Research Institute, Orange, California, USA
| | - Bethany Berg
- Division of Genetics and Metabolism, Department of Pediatrics, University of California Irvine, Irvine, California, USA
| | - Cheng Cheng
- Division of Genetics and Metabolism, Department of Pediatrics, University of California Irvine, Irvine, California, USA
| | - Sumit Parikh
- Center for Pediatric Neurology, Cleveland Clinic, Cleveland, Ohio, USA
| | | | - Sitao Wu
- Ambry Genetics Corp, Aliso Viejo, California, USA
| | - Anton N Hasso
- Radiological Sciences, University of California Irvine School of Medicine, Irvine, California, USA
| | - Daryl A Scott
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA.,Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Texas, USA
| | - Mary Kay Koenig
- Department of Pediatrics, University of Texas McGovern Medical School, Houston, Texas, USA
| | - Rachid Karam
- Ambry Genetics Corp, Aliso Viejo, California, USA
| | - Sha Tang
- Ambry Genetics Corp, Aliso Viejo, California, USA
| | - Moyra Smith
- Division of Genetics and Metabolism, Department of Pediatrics, University of California Irvine, Irvine, California, USA
| | - Elizabeth Chao
- Division of Genetics and Metabolism, Department of Pediatrics, University of California Irvine, Irvine, California, USA.,Ambry Genetics Corp, Aliso Viejo, California, USA
| | - Janneke Balk
- Department of Biological Chemistry, John Innes Centre, Norwich, Norfolk, UK
| | | | - Peggy S Eis
- Population Bio, Inc, New York, New York, USA
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Zhang M, Jiang N, Chu Y, Postnikova O, Varghese R, Horvath A, Cheema AK, Golestaneh N. Dysregulated metabolic pathways in age-related macular degeneration. Sci Rep 2020; 10:2464. [PMID: 32051464 PMCID: PMC7016007 DOI: 10.1038/s41598-020-59244-4] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Accepted: 01/27/2020] [Indexed: 01/03/2023] Open
Abstract
Age-related macular degeneration is a major cause of vision impairment in the Western world among people of 55 years and older. Recently we have shown that autophagy is dysfunctional in the retinal pigment epithelium (RPE) of the AMD donor eyes (AMD RPE). We also showed increased reactive oxygen (ROS) production, increased cytoplasmic glycogen accumulation, mitochondrial dysfunction and disintegration, and enlarged and annular LAMP-1-positive organelles in AMD RPE. However, the underlying mechanisms inducing these abnormalities remain to be elucidated. Here, by performing a comprehensive study, we show increased PAPR2 expression, deceased NAD+, and SIRT1, increased PGC-1α acetylation (inactive form), lower AMPK activity, and overactive mTOR pathway in AMD RPE as compared to normal RPE. Metabolomics and lipidomics revealed dysregulated metabolites in AMD RPE as compared to normal RPE, including glycerophospholipid metabolism, involved in autophagy, lipid, and protein metabolisms, glutathione, guanosine, and L-glutamic acid, which are implicated in protection against oxidative stress and neurotoxicity, further supporting our observations. Our data show dysregulated metabolic pathways as important contributors to AMD pathophysiology, and facilitate the development of new treatment strategies for this debilitating disease of the visual system.
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Affiliation(s)
- Meng Zhang
- Department of Ophthalmology, Georgetown University Medical Center, Washington, DC, 20057, USA
| | - Nisi Jiang
- Department of Ophthalmology, Georgetown University Medical Center, Washington, DC, 20057, USA
| | - Yi Chu
- Department of Ophthalmology, Georgetown University Medical Center, Washington, DC, 20057, USA
| | - Olga Postnikova
- Laboratory of Retinal Cell & Molecular Biology (HNW28), NIH/NEI, Bethesda, MD, 20814, USA
| | - Rency Varghese
- Department of Oncology, Georgetown University Medical Center, Washington, DC, 20057, USA
| | - Anelia Horvath
- Department of Pharmacology and Physiology, Department of Biochemistry and Molecular Medicine, George Washington University, Washington, DC, 20037, USA
| | - Amrita K Cheema
- Department of Biochemistry and Molecular & Cellular Biology, Georgetown University Medical Center, Washington, DC, 20057, USA.,Department of Oncology, Georgetown University Medical Center, Washington, DC, 20057, USA
| | - Nady Golestaneh
- Department of Ophthalmology, Georgetown University Medical Center, Washington, DC, 20057, USA. .,Department of Neurology, Georgetown University Medical Center, Washington, DC, 20057, USA. .,Department of Biochemistry and Molecular & Cellular Biology, Georgetown University Medical Center, Washington, DC, 20057, USA.
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3
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Liu Y, Ren Y, Wang X, Liu X, Xu Y, He Y. Down regulation of UCP2 expression in retinal pigment epithelium cells under oxidative stress: an in vitro study. Int J Ophthalmol 2019; 12:1089-1094. [PMID: 31341797 DOI: 10.18240/ijo.2019.07.06] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Accepted: 05/06/2019] [Indexed: 11/23/2022] Open
Abstract
AIM To evaluate the expression of uncoupling protein 2 (UCP2) in a retinal pigment epithelium cell line (ARPE-19), under oxidative stress (OS). METHODS ARPE-19 cells were divided into groups treated with various concentrations of hydrogen peroxide (H2O2; 0, 150, 300, 500, 700, and 900 µmol/L) for 24h, to induce oxidative damage and cell viability was assessed by MTT assay. UCP2 mRNA expression in cells treated with H2O2 was investigated by reverse transcription-polymerase chain reaction (RT-PCR). UCP2 protein expression was assessed by Western blotting and ROS levels analyzed by flow cytometry (FCM). Further, UCP2-siRNA treated cultures were exposed to H2O2 (0, 75, 150, and 300 µmol/L) for 2h and cell viability determined by MTT assay. RESULTS Cells treated with higher concentrations of H2O2 appeared shrunken; their adhesion to adjacent cells was disrupted, and the number of dead cells increased. The results of cell viability assays demonstrated that the numbers of cells were decreased in a dose-dependent manner following treatment with H2O2. Compared with untreated controls, cell viability was significantly reduced after treatment with >300 µmol/L H2O2 (P<0.05). Cell metabolic activity was decreased with increased concentrations of H2O2 as detected by MTT assay. Levels of OS were further decreased in cells treated with UCP2-siRNA compared with those treated with H2O2 alone (P<0.05). The results of RT-PCR and Western blotting demonstrated that UCP2 expression was reduced in H2O2-treated groups compared with controls (P<0.05). FCM analysis showed that cell reactive oxygen species (ROS) levels were increased in H2O2-treated groups and further upregulated by UCP2-siRNA treatment (P<0.05). CONCLUSION Expression levels of UCP2 are decreased in ARPE-19 cells treated with H2O2. ROS levels are further increased in cells treated with UCP2-siRNA relative to those treated with H2O2 alone. UCP2 may have a protective role in ARPE-19 cells during oxidative injury.
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Affiliation(s)
- Ying Liu
- Department of Ophthalmology, the Second Affiliated Hospital of Xi'an Medical University; Ocular Immunology and Inflammation Institute, Shaanxi Provincial Clinical Research Center for Ophthalmology, Xi'an 710038, Shaanxi Province, China
| | - Yuan Ren
- Department of Ophthalmology, the Second Affiliated Hospital of Xi'an Medical University; Ocular Immunology and Inflammation Institute, Shaanxi Provincial Clinical Research Center for Ophthalmology, Xi'an 710038, Shaanxi Province, China
| | - Xia Wang
- Department of Ophthalmology, the Second Affiliated Hospital of Xi'an Medical University; Ocular Immunology and Inflammation Institute, Shaanxi Provincial Clinical Research Center for Ophthalmology, Xi'an 710038, Shaanxi Province, China
| | - Xu Liu
- Department of Ophthalmology, the Second Affiliated Hospital of Xi'an Medical University; Ocular Immunology and Inflammation Institute, Shaanxi Provincial Clinical Research Center for Ophthalmology, Xi'an 710038, Shaanxi Province, China
| | - Yun Xu
- Department of Ophthalmology, the Second Affiliated Hospital of Xi'an Medical University; Ocular Immunology and Inflammation Institute, Shaanxi Provincial Clinical Research Center for Ophthalmology, Xi'an 710038, Shaanxi Province, China
| | - Yuan He
- Department of Ophthalmology, the Second Affiliated Hospital of Xi'an Medical University; Ocular Immunology and Inflammation Institute, Shaanxi Provincial Clinical Research Center for Ophthalmology, Xi'an 710038, Shaanxi Province, China
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4
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Kavlick MF. Development of a triplex mtDNA qPCR assay to assess quantification, degradation, inhibition, and amplification target copy numbers. Mitochondrion 2018; 46:41-50. [PMID: 30261278 DOI: 10.1016/j.mito.2018.09.007] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Revised: 05/11/2018] [Accepted: 09/18/2018] [Indexed: 01/11/2023]
Abstract
A hybrid absolute/relative qPCR assay which provides information regarding the condition of mitochondrial DNA (mtDNA) in a DNA sample is described. MtDNA concentration (copy number/μL) is determined via absolute quantification using a standard curve of a synthetic duplex DNA previously described (Kavlick et al., 2011). The state of mtDNA degradation is determined via the relative quantification of a mtDNA target found within the 16 s rRNA gene which is 3× longer than that of the short target in the former duplex assay, using the delta, delta Ct (ΔΔCt) method. The presence or absence of PCR inhibitors in the sample is qualitatively determined using a custom internal positive control (IPC) system which targets a unique and non-naturally occurring duplex DNA sequence. This IPC effectively detected inhibition by humic acid, tannic acid, melanin, and EDTA. All three assay components utilize sensitive and specific hydrolysis probes. The utility of ΔΔCt method was demonstrated in a series of experiments involving laboratory-fragmented DNA. Also described is a method for estimating copy number of any mtDNA target longer than the two targets amplified. The described triplex assay works well for intact and for fragmented or degraded mtDNA and therefore may be useful in forensic and ancient DNA disciplines as well as in biomedical research or practice.
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Affiliation(s)
- Mark F Kavlick
- Counterterrorism and Forensic Science Research Unit, Laboratory Division, Federal Bureau of Investigation, 2501 Investigation Parkway, Quantico, VA 22135, United States.
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5
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Zhang M, Chu Y, Mowery J, Konkel B, Galli S, Theos AC, Golestaneh N. Pgc-1α repression and high-fat diet induce age-related macular degeneration-like phenotypes in mice. Dis Model Mech 2018; 11:dmm.032698. [PMID: 29925537 PMCID: PMC6176989 DOI: 10.1242/dmm.032698] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Accepted: 06/13/2018] [Indexed: 12/28/2022] Open
Abstract
Age-related macular degeneration (AMD) is the major cause of blindness in the elderly in developed countries and its prevalence is increasing with the aging population. AMD initially affects the retinal pigment epithelium (RPE) and gradually leads to secondary photoreceptor degeneration. Recent studies have associated mitochondrial damage with AMD, and we have observed mitochondrial and autophagic dysfunction and repressed peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α; also known as Ppargc1a) in native RPE from AMD donor eyes and their respective induced pluripotent stem cell-derived RPE. To further investigate the effect of PGC-1α repression, we have established a mouse model by feeding Pgc-1α+/− mice with a high-fat diet (HFD) and investigated RPE and retinal health. We show that when mice expressing lower levels of Pgc-1α are exposed to HFD, they present AMD-like abnormalities in RPE and retinal morphology and function. These abnormalities include basal laminar deposits, thickening of Bruch's membrane with drusen marker-containing deposits, RPE and photoreceptor degeneration, decreased mitochondrial activity, increased levels of reactive oxygen species, decreased autophagy dynamics/flux, and increased inflammatory response in the RPE and retina. Our study shows that Pgc-1α is important in outer retina biology and that Pgc-1α+/− mice fed with HFD provide a promising model to study AMD, opening doors for novel treatment strategies. Summary: A new mouse model has been established that exhibits characteristics of human age-related macular degeneration; the model will facilitate further studies of AMD disease mechanisms.
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Affiliation(s)
- Meng Zhang
- Department of Ophthalmology, Georgetown University Medical Center, Washington, DC 20057, USA
| | - Yi Chu
- Department of Ophthalmology, Georgetown University Medical Center, Washington, DC 20057, USA
| | - Joseph Mowery
- Electron and Confocal Microscopy Unit, USDA Agricultural Research Service, Beltsville, MD 20705, USA
| | - Brandon Konkel
- Department of Biochemistry and Molecular and Cellular Biology, Georgetown University Medical Center, Washington, DC 20057, USA
| | - Susana Galli
- Department of Biochemistry and Molecular and Cellular Biology, Georgetown University Medical Center, Washington, DC 20057, USA
| | - Alexander C Theos
- Department of Human Science, Georgetown University, Washington, DC 20057, USA
| | - Nady Golestaneh
- Department of Ophthalmology, Georgetown University Medical Center, Washington, DC 20057, USA .,Department of Biochemistry and Molecular and Cellular Biology, Georgetown University Medical Center, Washington, DC 20057, USA.,Department of Neurology, Georgetown University Medical Center, Washington, DC 20057, USA
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6
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Cellular Senescence in Age-Related Macular Degeneration: Can Autophagy and DNA Damage Response Play a Role? OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2017; 2017:5293258. [PMID: 29225722 PMCID: PMC5687149 DOI: 10.1155/2017/5293258] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Revised: 05/29/2017] [Accepted: 06/28/2017] [Indexed: 12/14/2022]
Abstract
Age-related macular degeneration (AMD) is the main reason of blindness in developed countries. Aging is the main AMD risk factor. Oxidative stress, inflammation and some genetic factors play a role in AMD pathogenesis. AMD is associated with the degradation of retinal pigment epithelium (RPE) cells, photoreceptors, and choriocapillaris. Lost RPE cells in the central retina can be replaced by their peripheral counterparts. However, if they are senescent, degenerated regions in the macula cannot be regenerated. Oxidative stress, a main factor of AMD pathogenesis, can induce DNA damage response (DDR), autophagy, and cell senescence. Moreover, cell senescence is involved in the pathogenesis of many age-related diseases. Cell senescence is the state of permanent cellular division arrest and concerns only mitotic cells. RPE cells, although quiescent in the retina, can proliferate in vitro. They can also undergo oxidative stress-induced senescence. Therefore, cellular senescence can be considered as an important molecular pathway of AMD pathology, resulting in an inability of the macula to regenerate after degeneration of RPE cells caused by a factor inducing DDR and autophagy. It is too early to speculate about the role of the mutual interplay between cell senescence, autophagy, and DDR, but this subject is worth further studies.
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7
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Nivison MP, Ericson NG, Green VM, Bielas JH, Campbell JS, Horner PJ. Age-related accumulation of phosphorylated mitofusin 2 protein in retinal ganglion cells correlates with glaucoma progression. Exp Neurol 2017; 296:49-61. [PMID: 28684211 PMCID: PMC6021128 DOI: 10.1016/j.expneurol.2017.07.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Revised: 06/26/2017] [Accepted: 07/02/2017] [Indexed: 01/19/2023]
Abstract
Dysregulation of axonal bioenergetics is likely a key mechanism in the initiation and progression of age-related neurodegenerative diseases. Glaucoma is a quintessential neurodegenerative disorder characterized by progressive deterioration of the optic nerve (ON) and eventual death of retinal ganglion cells (RGCs). Age and elevation of intraocular pressure are key risk factors in glaucoma, but the common early hallmarks of decreased axonal transport and increased bioenergetic vulnerability likely underlie disease initiation. We examined the correlation between bioenergetics and axonal transport with mitochondrial mutation frequency and post-translational modifications of mitofusin 2 (Mfn2) in RGCs during glaucoma progression. No increase in the frequency of mtDNA mutations was detected, but we observed significant shifts in mitochondrial protein species. Mfn2 is a fusion protein that functions in mitochondrial biogenesis, maintenance, and mitochondrial transport. We demonstrate that Mfn2 accumulates selectively in RGCs during glaucomatous degeneration, that two novel states of Mfn2 exist in retina and ON, and identify a phosphorylated form that selectively accumulates in RGCs, but is absent in ON. Phosphorylation of Mfn2 is correlated with higher ubiquitination, and failure of the protein to reach the ON. Together, these data suggest that post-translational modification of Mfn2 is associated with its dysregulation during a window of metabolic vulnerability that precedes glaucomatous degeneration. Future work to either manipulate expression of Mfn2 or to prevent its degradation could have therapeutic value in the treatment of neurodegenerative diseases where long-tract axons are vulnerable.
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Affiliation(s)
- Mary P Nivison
- Department of Pathology, University of Washington, Seattle, WA, USA
| | - Nolan G Ericson
- Translational Research Program, Public Health Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
| | - Virginia M Green
- Matrix Biology Program, Benaroya Research Institute, Seattle, WA, USA
| | - Jason H Bielas
- Department of Pathology, University of Washington, Seattle, WA, USA; Translational Research Program, Public Health Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA, USA; Human Biology Division, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
| | - Jean S Campbell
- Department of Pathology, University of Washington, Seattle, WA, USA
| | - Philip J Horner
- Department of Neurological Surgery, University of Washington, Seattle, WA, USA.
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8
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Golestaneh N, Chu Y, Cheng SK, Cao H, Poliakov E, Berinstein DM. Repressed SIRT1/PGC-1α pathway and mitochondrial disintegration in iPSC-derived RPE disease model of age-related macular degeneration. J Transl Med 2016; 14:344. [PMID: 27998274 PMCID: PMC5175395 DOI: 10.1186/s12967-016-1101-8] [Citation(s) in RCA: 79] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2016] [Accepted: 11/29/2016] [Indexed: 01/07/2023] Open
Abstract
BACKGROUND Study of age related macular degeneration (AMD) has been hampered by lack of human models that represent the complexity of the disease. Here we have developed a human in vitro disease model of AMD to investigate the underlying AMD disease mechanisms. METHODS Generation of iPSCs from retinal pigment epithelium (RPE) of AMD donors, age-matched normal donors, skin fibroblasts of a dry AMD patient, and differentiation of iPSCs into RPE (AMD RPE-iPSC-RPE, normal RPE-iPSC-RPE and AMD Skin-iPSC-RPE, respectively). Immunostaining, cell viability assay and reactive oxygen species (ROS) production under oxidative stress conditions, electron microscopy (EM) imaging, ATP production and glycogen concentration assays, quantitative real time PCR, western blot, karyotyping. RESULTS The AMD RPE-iPSC-RPE and AMD Skin-iPSC-RPE present functional impairment and exhibit distinct disease phenotypes compared to RPE-iPSC-RPE generated from normal donors (Normal RPE-iPSC-RPE). The AMD RPE-iPSC-RPE and AMD Skin-iPSC-RPE show increased susceptibility to oxidative stress and produced higher levels of reactive oxygen species (ROS) under stress in accordance with recent reports. The susceptibility to oxidative stress-induced cell death in AMD RPE-iPSC-RPE and Skin-iPSC-RPE was consistent with inability of the AMD RPE-iPSC-RPE and Skin-iPSC-RPE to increase SOD2 expression under oxidative stress. Phenotypic analysis revealed disintegrated mitochondria, accumulation of autophagosomes and lipid droplets in AMD RPE-iPSC-RPE and AMD Skin-iPSC-RPE. Mitochondrial activity was significantly lower in AMD RPE-iPSC-RPE and AMD Skin-iPSC-RPE compared to normal cells and glycogen concentration was significantly increased in the diseased cells. Furthermore, Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), a regulator of mitochondrial biogenesis and function was repressed, and lower expression levels of NAD-dependent deacetylase sirtuin1 (SIRT1) were found in AMD RPE-iPSC-RPE and AMD Skin-iPSC-RPE as compared to normal RPE-iPSC-RPE. CONCLUSIONS Our studies suggest SIRT1/PGC-1α as underlying pathways contributing to AMD pathophysiology, and open new avenues for development of targeted drugs for treatment of this devastating neurodegenerative disease of the visual system.
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Affiliation(s)
- Nady Golestaneh
- Department of Ophthalmology, Georgetown University Medical Center, 3900 Reservoir Road NW, Medical-Dental Building, Room NE203, Washington, DC 20057 USA
- Department of Neurology, Georgetown University Medical Center, Washington, DC USA
- Department of Biochemistry and Molecular & Cellular Biology, Georgetown University Medical Center, Washington, DC USA
| | - Yi Chu
- Department of Ophthalmology, Georgetown University Medical Center, 3900 Reservoir Road NW, Medical-Dental Building, Room NE203, Washington, DC 20057 USA
| | - Shuk Kei Cheng
- Department of Ophthalmology, Georgetown University Medical Center, 3900 Reservoir Road NW, Medical-Dental Building, Room NE203, Washington, DC 20057 USA
| | - Hong Cao
- Department of Ophthalmology, Georgetown University Medical Center, 3900 Reservoir Road NW, Medical-Dental Building, Room NE203, Washington, DC 20057 USA
| | - Eugenia Poliakov
- Retinal Cell and Molecular Biology (LRCMB), National Eye Institute, National Institutes of Health, Bethesda, MD USA
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9
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Nalbandian A, Llewellyn KJ, Gomez A, Walker N, Su H, Dunnigan A, Chwa M, Vesa J, Kenney MC, Kimonis VE. In vitro studies in VCP-associated multisystem proteinopathy suggest altered mitochondrial bioenergetics. Mitochondrion 2015; 22:1-8. [PMID: 25724235 DOI: 10.1016/j.mito.2015.02.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2014] [Revised: 02/13/2015] [Accepted: 02/17/2015] [Indexed: 01/01/2023]
Abstract
Mitochondrial dysfunction has recently been implicated as an underlying factor to several common neurodegenerative diseases, including Parkinson's disease, Alzheimer's and amyotrophic lateral sclerosis (ALS). Valosin containing protein (VCP)-associated multisystem proteinopathy is a new hereditary disorder associated with inclusion body myopathy, Paget disease of bone (PDB), frontotemporal dementia (FTD) and ALS. VCP has been implicated in several transduction pathways including autophagy, apoptosis and the PINK1/Parkin cascade of mitophagy. In this report, we characterized VCP patient and mouse fibroblasts/myoblasts to examine their mitochondrial dynamics and bioenergetics. Using the Seahorse XF-24 technology, we discovered decreased spare respiratory capacity (measurement of extra ATP that can be produced by oxidative phosphorylation in stressful conditions) and increased ECAR levels (measurement of glycolysis), and proton leak in VCP human fibroblasts compared with age- and sex-matched unaffected first degree relatives. We found decreased levels of ATP and membrane potential, but higher mitochondrial enzyme complexes II+III and complex IV activities in the patient VCP myoblasts when compared to the values of the control cell lines. These results suggest that mutations in VCP affect the mitochondria's ability to produce ATP, thereby resulting in a compensatory increase in the cells' mitochondrial complex activity levels. Thus, this novel in vitro model may be useful in understanding the pathophysiology and discovering new drug targets of mitochondrial dynamics and physiology to modify the clinical phenotype in VCP and related multisystem proteinopathies (MSP).
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Affiliation(s)
- Angèle Nalbandian
- Department of Pediatrics, Division of Genetics and Genomic Medicine, University of California-Irvine, Irvine, CA 92697, USA.
| | - Katrina J Llewellyn
- Department of Pediatrics, Division of Genetics and Genomic Medicine, University of California-Irvine, Irvine, CA 92697, USA
| | - Arianna Gomez
- Department of Pediatrics, Division of Genetics and Genomic Medicine, University of California-Irvine, Irvine, CA 92697, USA
| | - Naomi Walker
- Department of Pediatrics, Division of Genetics and Genomic Medicine, University of California-Irvine, Irvine, CA 92697, USA
| | - Hailing Su
- Department of Pediatrics, Division of Genetics and Genomic Medicine, University of California-Irvine, Irvine, CA 92697, USA
| | - Andrew Dunnigan
- Department of Pediatrics, Division of Genetics and Genomic Medicine, University of California-Irvine, Irvine, CA 92697, USA
| | - Marilyn Chwa
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California-Irvine, Irvine, CA 92697, USA
| | - Jouni Vesa
- Department of Pediatrics, Division of Genetics and Genomic Medicine, University of California-Irvine, Irvine, CA 92697, USA
| | - M C Kenney
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California-Irvine, Irvine, CA 92697, USA; Department of Pathology and Laboratory Medicine, University of California- Irvine, Irvine, CA 92697, USA
| | - Virginia E Kimonis
- Department of Pediatrics, Division of Genetics and Genomic Medicine, University of California-Irvine, Irvine, CA 92697, USA.
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10
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Abstract
Chronic hyperglycemia (HG)-associated reactive oxygen/nitrogen species (ROS/RNS) stress and low grade inflammation are considered to play critical roles in the development of diabetic retinopathy (DR). Excess glucose metabolic flux through the aldose reductase/polyol pathway, advanced glycation end product (AGE) formation, elevated hexosamine biosynthesis pathway (HBP), diacyl glycerol/PKC activation, and mitochondrial ROS generation are all implicated in DR. In addition, endoplasmic reticulum stress/unfolded protein response (er-UPR) and deregulation of mitochondrial quality control by autophagy/mitophagy are observed causing cellular bioenergetic deficiency and injury. Recently, a pro-oxidant and pro-apoptotic thioredoxin interacting protein (TXNIP) was shown to be highly upregulated in DR and by HG in retinal cells in culture. TXNIP binds to thioredoxin (Trx) inhibiting its oxidant scavenging and thiolreducing capacity. Hence, prolonged overexpression of TXNIP causes ROS/RNS stress, mitochondrial dysfunction, inflammation and premature cell death in DR. Initially, DR was considered as microvascular complications of endothelial dysfunction and pericyte loss characterized by capillary basement membrane thickening, pericyte ghost, blood retinal barrier leakage, acellular capillary and neovascularization. However, it is currently acknowledged that neuro-glia are also affected by HG in diabetes and that neuronal injury, glial activation, innate immunity/sterile inflammation, and ganglion apoptosis occur early in DR. In addition, retinal pigment epithelium (RPE) becomes dysfunctional in DR. Since TXNIP is induced by HG in most cells, its effects are not restricted to a particular cell type in DR. However, depending on the metabolic activity and anti-oxidant capacity, some cells may be affected earlier by TXNIP than others. Identification of TXNIP sensitive cells and elucidating the underlying mechanism(s) will be critical for preventing pre-mature cell death and progression of DR.
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Affiliation(s)
- Lalit P Singh
- Departments of Anatomy and Cell Biology and Ophthalmology, Wayne State University School of Medicine, Detroit, MI 48201, USA
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