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Lou X, Zhou Y, Liu Z, Xie Y, Zhang L, Zhao S, Gong S, Zhuo X, Wang J, Dai L, Ren X, Tong X, Jiang L, Fang H, Fang F, Lyu J. De novo frameshift variant in MT-ND1 causes a mitochondrial complex I deficiency associated with MELAS syndrome. Gene 2023; 860:147229. [PMID: 36717040 DOI: 10.1016/j.gene.2023.147229] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2022] [Revised: 01/04/2023] [Accepted: 01/24/2023] [Indexed: 01/29/2023]
Abstract
BACKGROUND The variant m.3571_3572insC/MT-ND1 thus far only reported in oncocytic tumors of different tissues. However, the role of m.3571_3572insC in inherited mitochondrial diseases has yet to be elucidated. METHODS A patient diagnosed with MELAS syndrome was recruited, and detailed medical records were collected and reviewed. The muscle was biopsied for mitochondrial respiratory chain enzyme activity. Series of fibroblast clones bearing different m.3571_3572insC variant loads were generated from patient-derived fibroblasts and subjected to functional assays. RESULTS Complex I deficiency was confirmed in the patient's muscle via mitochondrial respiratory chain enzyme activity assay. The m.3571_3572insC was filtered for the candidate variant of the patient according to the guidelines for mitochondrial mRNA variants interpretation. Three cell clones with different m.3571_3572insC variant loads were generated to evaluate mitochondrial function. Blue native PAGE analysis revealed that m.3571_3572insC caused a deficiency in the mitochondrial complex I. Oxygen consumption rate, ATP production, and lactate assays found an impairment of cellular bioenergetic capacity due to m.3571_3572insC. Mitochondrial membrane potential was decreased, and mitochondrial reactive oxygen species production was increased with the variant of m.3571_3572insC. According to the competitive cell growth assay, the mutant cells had impaired cell growth capacity compared to wild type. CONCLUSIONS A novel variant m.3571_3572insC was identified in a patient diagnosed with MELAS syndrome, and the variant impaired mitochondrial respiration by decreasing the activity of complex I. In conclusion, the genetic spectrum of mitochondrial diseases was expanded by including m.3571_3572insC/MT-ND1.
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Affiliation(s)
- Xiaoting Lou
- Center for Reproductive Medicine, Department of Genetic and Genomic Medicine, Zhejiang Provincial People's Hospital, Affiliated People's Hospital, Hangzhou Medical College, Hangzhou, Zhejiang 310014, China; Laboratory Medicine Center, Department of Clinical Laboratory, Zhejiang Provincial People's Hospital, Affiliated People's Hospital, Hangzhou Medical College, Hangzhou, Zhejiang 310014, China
| | - Yuwei Zhou
- Key Laboratory of Laboratory Medicine, Ministry of Education, Zhejiang Provincial Key Laboratory of Medical Genetics, College of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang 325035, China
| | - Zhimei Liu
- Department of Neurology, Beijing Children's Hospital, Capital Medical University, National Center for Children's Health, Beijing 100069, China
| | - Yaojun Xie
- Key Laboratory of Laboratory Medicine, Ministry of Education, Zhejiang Provincial Key Laboratory of Medical Genetics, College of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang 325035, China
| | - Luyi Zhang
- Key Laboratory of Laboratory Medicine, Ministry of Education, Zhejiang Provincial Key Laboratory of Medical Genetics, College of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang 325035, China
| | - Suzhou Zhao
- Fujungenetics Technologies Co., Ltd, Beijing 100176, China
| | - Shuai Gong
- Department of Neurology, Beijing Children's Hospital, Capital Medical University, National Center for Children's Health, Beijing 100069, China
| | - Xiuwei Zhuo
- Department of Neurology, Beijing Children's Hospital, Capital Medical University, National Center for Children's Health, Beijing 100069, China
| | - Junling Wang
- Department of Pediatrics, Third Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan 450052, China
| | - Lifang Dai
- Department of Neurology, Beijing Children's Hospital, Capital Medical University, National Center for Children's Health, Beijing 100069, China
| | - Xiaotun Ren
- Department of Neurology, Beijing Children's Hospital, Capital Medical University, National Center for Children's Health, Beijing 100069, China
| | - Xiao Tong
- Department of Neurology, Beijing Children's Hospital, Capital Medical University, National Center for Children's Health, Beijing 100069, China
| | - Liangliang Jiang
- Pediatric Neurology, Anhui Provincial Children's Hospital, Hefei, Anhui 230022, China
| | - Hezhi Fang
- Key Laboratory of Laboratory Medicine, Ministry of Education, Zhejiang Provincial Key Laboratory of Medical Genetics, College of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang 325035, China
| | - Fang Fang
- Department of Neurology, Beijing Children's Hospital, Capital Medical University, National Center for Children's Health, Beijing 100069, China.
| | - Jianxin Lyu
- Laboratory Medicine Center, Department of Clinical Laboratory, Zhejiang Provincial People's Hospital, Affiliated People's Hospital, Hangzhou Medical College, Hangzhou, Zhejiang 310014, China; Key Laboratory of Laboratory Medicine, Ministry of Education, Zhejiang Provincial Key Laboratory of Medical Genetics, College of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, Zhejiang 325035, China.
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Campbell T, Slone J, Huang T. Mitochondrial Genome Variants as a Cause of Mitochondrial Cardiomyopathy. Cells 2022; 11:cells11182835. [PMID: 36139411 PMCID: PMC9496904 DOI: 10.3390/cells11182835] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Revised: 09/05/2022] [Accepted: 09/07/2022] [Indexed: 11/16/2022] Open
Abstract
Mitochondria are small double-membraned organelles responsible for the generation of energy used in the body in the form of ATP. Mitochondria are unique in that they contain their own circular mitochondrial genome termed mtDNA. mtDNA codes for 37 genes, and together with the nuclear genome (nDNA), dictate mitochondrial structure and function. Not surprisingly, pathogenic variants in the mtDNA or nDNA can result in mitochondrial disease. Mitochondrial disease primarily impacts tissues with high energy demands, including the heart. Mitochondrial cardiomyopathy is characterized by the abnormal structure or function of the myocardium secondary to genetic defects in either the nDNA or mtDNA. Mitochondrial cardiomyopathy can be isolated or part of a syndromic mitochondrial disease. Common manifestations of mitochondrial cardiomyopathy are a phenocopy of hypertrophic cardiomyopathy, dilated cardiomyopathy, and cardiac conduction defects. The underlying pathophysiology of mitochondrial cardiomyopathy is complex and likely involves multiple abnormal processes in the cell, stemming from deficient oxidative phosphorylation and ATP depletion. Possible pathophysiology includes the activation of alternative metabolic pathways, the accumulation of reactive oxygen species, dysfunctional mitochondrial dynamics, abnormal calcium homeostasis, and mitochondrial iron overload. Here, we highlight the clinical assessment of mtDNA-related mitochondrial cardiomyopathy and offer a novel hypothesis of a possible integrated, multivariable pathophysiology of disease.
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Yang Z, Slone J, Huang T. Next-Generation Sequencing to Characterize Mitochondrial Genomic DNA Heteroplasmy. Curr Protoc 2022; 2:e412. [PMID: 35532282 DOI: 10.1002/cpz1.412] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Mitochondria play a very important role in many crucial cellular functions. Each eukaryotic cell contains hundreds of mitochondria with hundreds of mitochondrial genomes. Mutant and wild-type mitochondrial DNA (mtDNA) may co-exist as heteroplasmy and cause human disease. The purpose of the protocols in this article is to simultaneously determine the mtDNA sequence and quantify the heteroplasmy level using parallel sequencing. The protocols include mitochondrial genomic DNA PCR amplification of two full-length products using two distinct sets of PCR primers. The PCR products are mixed at an equimolar ratio, and the samples are then barcoded and sequenced with high-throughput next-generation sequencing technology. This technology is highly sensitive, specific, and accurate in determining mtDNA mutations and the degree/level of heteroplasmy. © 2022 Wiley Periodicals LLC. Basic Protocol 1: PCR amplification of mitochondrial DNA Basic Protocol 2: Analysis of next-generation sequencing of mitochondrial DNA Basic Protocol 3: Mutect2 pipeline for automated sample processing and large-scale data analysis.
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Affiliation(s)
- Zeyu Yang
- Department of Pediatrics, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York
| | - Jesse Slone
- Department of Pediatrics, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York
| | - Taosheng Huang
- Department of Pediatrics, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, New York
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Clinicopathological Features of Mitochondrial Nephropathy. Kidney Int Rep 2022; 7:580-590. [PMID: 35257070 PMCID: PMC8897298 DOI: 10.1016/j.ekir.2021.12.028] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2021] [Revised: 12/16/2021] [Accepted: 12/20/2021] [Indexed: 12/12/2022] Open
Abstract
Introduction The clinicopathologic characteristics of nephropathy associated with mitochondrial disease (MD) remain unknown. We retrospectively analyzed a cohort of patients with proteinuria, decreased glomerular filtration rate, or Fanconi syndrome who had a genetic mutation confirmed as the cause of MD, defined as mitochondrial nephropathy. Methods This nationwide survey included 757 nephrology sections throughout Japan, and consequently, data on 81 cases of mitochondrial nephropathy were collected. Results The most common renal manifestation observed during the disease course was proteinuria. Hearing loss was the most common comorbidity; a renal-limited phenotype was observed only in mitochondrial DNA (mtDNA) point mutation and COQ8B mutation cases. We found a median time delay of 6.0 years from onset of renal manifestations to diagnosis. Focal segmental glomerular sclerosis (FSGS) was the most common pathologic diagnosis. We then focused on 63 cases with the m.3243A>G mutation. The rate of cases with diabetes was significantly higher among adult-onset cases than among childhood-onset cases. Pathologic diagnoses were more variable in adult-onset cases, including diabetic nephropathy, nephrosclerosis, tubulointerstitial nephropathy, and minor glomerular abnormalities. During the median observation period of 11.0 years from the first onset of renal manifestations in patients with m.3243A>G, renal replacement therapy (RRT) was initiated in 50.8% of patients. Death occurred in 25.4% of the patients during the median observation period of 12.0 years. The median estimated glomerular filtration rate (eGFR) decline was 5.4 ml/min per 1.73 m2/yr in the cases, especially 8.3 ml/min per 1.73 m2/yr in FSGS cases, with m.3243A>G. Conclusion Here, we described the clinicopathologic features and prognosis of mitochondrial nephropathy using large-scale data.
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