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Cao Y, Zheng J, Wan H, Sun Y, Fu S, Liu S, He B, Cai G, Cao Y, Huang H, Li Q, Ma Y, Chen S, Wang F, Jiang H. A mitochondrial SCF-FBXL4 ubiquitin E3 ligase complex degrades BNIP3 and NIX to restrain mitophagy and prevent mitochondrial disease. EMBO J 2023; 42:e113033. [PMID: 36896912 PMCID: PMC10308365 DOI: 10.15252/embj.2022113033] [Citation(s) in RCA: 25] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Revised: 02/14/2023] [Accepted: 02/17/2023] [Indexed: 03/11/2023] Open
Abstract
Mitophagy is a fundamental quality control mechanism of mitochondria. Its regulatory mechanisms and pathological implications remain poorly understood. Here, via a mitochondria-targeted genetic screen, we found that knockout (KO) of FBXL4, a mitochondrial disease gene, hyperactivates mitophagy at basal conditions. Subsequent counter screen revealed that FBXL4-KO hyperactivates mitophagy via two mitophagy receptors BNIP3 and NIX. We determined that FBXL4 functions as an integral outer-membrane protein that forms an SCF-FBXL4 ubiquitin E3 ligase complex. SCF-FBXL4 ubiquitinates BNIP3 and NIX to target them for degradation. Pathogenic FBXL4 mutations disrupt SCF-FBXL4 assembly and impair substrate degradation. Fbxl4-/- mice exhibit elevated BNIP3 and NIX proteins, hyperactive mitophagy, and perinatal lethality. Importantly, knockout of either Bnip3 or Nix rescues metabolic derangements and viability of the Fbxl4-/- mice. Together, beyond identifying SCF-FBXL4 as a novel mitochondrial ubiquitin E3 ligase restraining basal mitophagy, our results reveal hyperactivated mitophagy as a cause of mitochondrial disease and suggest therapeutic strategies.
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Affiliation(s)
- Yu Cao
- College of Life SciencesBeijing Normal UniversityBeijingChina
- National Institute of Biological SciencesBeijingChina
- Beijing Key Laboratory of Cell Biology for Animal AgingBeijingChina
| | - Jing Zheng
- National Institute of Biological SciencesBeijingChina
- Beijing Key Laboratory of Cell Biology for Animal AgingBeijingChina
| | - Huayun Wan
- National Institute of Biological SciencesBeijingChina
- Beijing Key Laboratory of Cell Biology for Animal AgingBeijingChina
| | - Yuqiu Sun
- National Institute of Biological SciencesBeijingChina
- Beijing Key Laboratory of Cell Biology for Animal AgingBeijingChina
- Tsinghua Institute of Multidisciplinary Biomedical ResearchTsinghua UniversityBeijingChina
| | - Song Fu
- National Institute of Biological SciencesBeijingChina
- Beijing Key Laboratory of Cell Biology for Animal AgingBeijingChina
- Graduate School of Peking Union Medical CollegeBeijingChina
| | - Shanshan Liu
- National Institute of Biological SciencesBeijingChina
- Beijing Key Laboratory of Cell Biology for Animal AgingBeijingChina
| | - Baiyu He
- National Institute of Biological SciencesBeijingChina
- Beijing Key Laboratory of Cell Biology for Animal AgingBeijingChina
- College of Life SciencesChina Agriculture UniversityBeijingChina
| | - Gaihong Cai
- National Institute of Biological SciencesBeijingChina
| | - Yang Cao
- National Institute of Biological SciencesBeijingChina
| | - Huanwei Huang
- National Institute of Biological SciencesBeijingChina
| | - Qi Li
- National Institute of Biological SciencesBeijingChina
- Tsinghua Institute of Multidisciplinary Biomedical ResearchTsinghua UniversityBeijingChina
| | - Yan Ma
- National Institute of Biological SciencesBeijingChina
- Tsinghua Institute of Multidisciplinary Biomedical ResearchTsinghua UniversityBeijingChina
| | - She Chen
- National Institute of Biological SciencesBeijingChina
- Tsinghua Institute of Multidisciplinary Biomedical ResearchTsinghua UniversityBeijingChina
| | - Fengchao Wang
- National Institute of Biological SciencesBeijingChina
- Tsinghua Institute of Multidisciplinary Biomedical ResearchTsinghua UniversityBeijingChina
| | - Hui Jiang
- College of Life SciencesBeijing Normal UniversityBeijingChina
- National Institute of Biological SciencesBeijingChina
- Beijing Key Laboratory of Cell Biology for Animal AgingBeijingChina
- Tsinghua Institute of Multidisciplinary Biomedical ResearchTsinghua UniversityBeijingChina
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2
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Ma Y, Lei E, Xu Y, Feng Y. Prenatal diagnosis and molecular cytogenetic characterization of inherited chromosome 2q11.1q11.2 microduplication with fetal intrauterine growth retardation. Taiwan J Obstet Gynecol 2022; 61:726-727. [PMID: 35779931 DOI: 10.1016/j.tjog.2021.12.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/02/2021] [Indexed: 11/30/2022] Open
Affiliation(s)
- Yan Ma
- Transfusin Research Department, Wuhan Blood Center, Wuhan, Hubei, PR China
| | - E Lei
- Surgical Anesthesiology Department, Shiyan Maternal and Child Health Hospital, Shiyan, Hubei, PR China
| | - Yunfan Xu
- Department of Emergency, Wuhan Jihe Hospital, Wuhan, Hubei, PR China
| | - Yuexiang Feng
- Department of Endocrinology, Wuhan Hankou Hospital, Wuhan, Hubei, PR China.
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3
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Wang H, Han Y, Li S, Chen Y, Chen Y, Wang J, Zhang Y, Zhang Y, Wang J, Xia Y, Yuan J. Mitochondrial DNA Depletion Syndrome and Its Associated Cardiac Disease. Front Cardiovasc Med 2022; 8:808115. [PMID: 35237671 PMCID: PMC8882844 DOI: 10.3389/fcvm.2021.808115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2021] [Accepted: 12/23/2021] [Indexed: 12/06/2022] Open
Abstract
Mitochondria is a ubiquitous, energy-supplying (ATP-based) organelle found in nearly all eukaryotes. It acts as a “power plant” by producing ATP through oxidative phosphorylation, providing energy for the cell. The bioenergetic functions of mitochondria are regulated by nuclear genes (nDNA). Mitochondrial DNA (mtDNA) and respiratory enzymes lose normal structure and function when nuclear genes encoding the related mitochondrial factors are impaired, resulting in deficiency in energy production. Massive generation of reactive oxygen species and calcium overload are common causes of mitochondrial diseases. The mitochondrial depletion syndrome (MDS) is associated with the mutations of mitochondrial genes in the nucleus. It is a heterogeneous group of progressive disorders characterized by the low mtDNA copy number. TK2, FBXL4, TYPM, and AGK are genes known to be related to MDS. More recent studies identified new mutation loci associated with this disease. Herein, we first summarize the structure and function of mitochondria, and then discuss the characteristics of various types of MDS and its association with cardiac diseases.
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Affiliation(s)
- Haiying Wang
- Department of Physiology, Institute of Basic Medical College, Jining Medical University, Jining, China
| | - Yijun Han
- Clinical Medical College, Jining Medical University, Jining, China
| | - Shenwei Li
- Institute of Basic Medical College, Jining Medical University, Jining, China
| | - Yunan Chen
- Institute of Basic Medical College, Jining Medical University, Jining, China
| | - Yafen Chen
- Institute of Basic Medical College, Jining Medical University, Jining, China
| | - Jing Wang
- Dongying Fifth People's Hospital, Dongying, China
| | - Yuqing Zhang
- Institute of Basic Medical College, Jining Medical University, Jining, China
| | - Yawen Zhang
- Institute of Basic Medical College, Jining Medical University, Jining, China
| | - Jingsuo Wang
- Institute of Basic Medical College, Jining Medical University, Jining, China
| | - Yong Xia
- Key Laboratory of Precision Oncology of Shandong Higher Education, Institute of Precision Medicine, Jining Medical University, Jining, China
- Yong Xia
| | - Jinxiang Yuan
- The Collaborative Innovation Center, Jining Medical University, Jining, China
- *Correspondence: Jinxiang Yuan
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4
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Blood biomarkers for assessment of mitochondrial dysfunction: An expert review. Mitochondrion 2021; 62:187-204. [PMID: 34740866 DOI: 10.1016/j.mito.2021.10.008] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Revised: 09/28/2021] [Accepted: 10/28/2021] [Indexed: 12/20/2022]
Abstract
Although mitochondrial dysfunction is the known cause of primary mitochondrial disease, mitochondrial dysfunction is often difficult to measure and prove, especially when biopsies of affected tissue are not available. In order to identify blood biomarkers of mitochondrial dysfunction, we reviewed studies that measured blood biomarkers in genetically, clinically or biochemically confirmed primary mitochondrial disease patients. In this way, we were certain that there was an underlying mitochondrial dysfunction which could validate the biomarker. We found biomarkers of three classes: 1) functional markers measured in blood cells, 2) biochemical markers of serum/plasma and 3) DNA markers. While none of the reviewed single biomarkers may perfectly reveal all underlying mitochondrial dysfunction, combining biomarkers that cover different aspects of mitochondrial impairment probably is a good strategy. This biomarker panel may assist in the diagnosis of primary mitochondrial disease patients. As mitochondrial dysfunction may also play a significant role in the pathophysiology of multifactorial disorders such as Alzheimer's disease and glaucoma, the panel may serve to assess mitochondrial dysfunction in complex multifactorial diseases as well and enable selection of patients who could benefit from therapies targeting mitochondria.
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Oncul U, Kose E, Eminoglu FT. A Mild Phenotype of Mitochondrial DNA Depletion Syndrome Type 13 with a Novel FBXL4 Variant. Mol Syndromol 2021; 12:294-299. [PMID: 34602956 PMCID: PMC8436661 DOI: 10.1159/000515928] [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: 12/12/2020] [Accepted: 03/16/2021] [Indexed: 11/19/2022] Open
Abstract
Mitochondrial DNA depletion syndromes (MDDS) are a group of rare genetic disorders caused by defects in multiple genes involved in mitochondrial DNA maintenance. Among these, FBXL4 gene variants result in encephalomyopathic mtDNA depletion syndrome 13 (MTDPS13), which commonly presents as a combination of failure to thrive, neurodevelopmental delays, encephalopathy, hypotonia, a pattern of mild facial dysmorphisms, and persistent lactic acidosis. To date, 53 pathogenic FBXL4 variants and 100 cases have been described in the literature. In the present case report, we report on a 4.5-year-old boy with MTDPS13 and a novel variant. The patient had a history of antenatal hydrocephalus, severe developmental delay and mental motor retardation with psychomotor delay, severe hypotonia, mild left ventricular hypertrophic cardiomyopathy, mild facial dysmorphism, and elevated lactate levels. Symptoms suggested mitochondrial myopathy; subsequently, whole-exome sequencing was performed and a novel homozygous variant FBXL4 (NM_012160.4): c.486T>G (p.Tyr162Ter) was identified. While most of the patients with FBLX4 gene mutation have severe clinical manifestation and die at a very young age, clinical progress of our case was milder than previously reported. MDDS are very rare and can present with many different clinical signs and symptoms. In this report, we identified a novel pathogenic variant in the FBXL4 gene. This report shows that patients with FBLX4 gene mutations may present with a milder clinical phenotype than previously reported.
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Affiliation(s)
- Ummuhan Oncul
- Department of Pediatric Metabolism, Faculty of Medicine, Ankara University, Ankara, Turkey
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Di Nottia M, Verrigni D, Torraco A, Rizza T, Bertini E, Carrozzo R. Mitochondrial Dynamics: Molecular Mechanisms, Related Primary Mitochondrial Disorders and Therapeutic Approaches. Genes (Basel) 2021; 12:genes12020247. [PMID: 33578638 PMCID: PMC7916359 DOI: 10.3390/genes12020247] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Revised: 02/02/2021] [Accepted: 02/04/2021] [Indexed: 02/06/2023] Open
Abstract
Mitochondria do not exist as individual entities in the cell—conversely, they constitute an interconnected community governed by the constant and opposite process of fission and fusion. The mitochondrial fission leads to the formation of smaller mitochondria, promoting the biogenesis of new organelles. On the other hand, following the fusion process, mitochondria appear as longer and interconnected tubules, which enhance the communication with other organelles. Both fission and fusion are carried out by a small number of highly conserved guanosine triphosphatase proteins and their interactors. Disruption of this equilibrium has been associated with several pathological conditions, ranging from cancer to neurodegeneration, and mutations in genes involved in mitochondrial fission and fusion have been reported to be the cause of a subset of neurogenetic disorders.
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Wang S, Lin L, Wang Y, Wang A, Liu Z, Wu S, Lan X, Jia J, Zhang Y, Yuan F, Wang C, Luo X, Sun X, Avula SK, Tolaymat A, Liu C, Ren Y, Chen Y. Novel homozygous mutation in the FBXL4 gene is associated with mitochondria DNA depletion syndrome-13. J Neurol Sci 2020; 416:116948. [PMID: 32559514 DOI: 10.1016/j.jns.2020.116948] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Revised: 05/24/2020] [Accepted: 05/25/2020] [Indexed: 10/24/2022]
Abstract
BACKGROUND Mitochondrial DNA depletion syndrome-13 (MTDPS13) is caused by mutations in FBXL4 (F-box and leucine-rich repeat protein 4), a nuclear gene encoding an F-box protein that plays a role in maintaining mtDNA integrity and stability. METHODS We identified a novel homozygous FBXL4 gene mutation, c.993dupA (p.L332Tfs*3), in a 1-year-old girl of Han Chinese descent. We performed three-dimensional protein structural analysis and targeted mtDNA next-generation sequencing. We analysed FBXL4 expression and mitochondrial DNA level, and reviewed mutations reported in FBXL4-related literature. RESULTS This mutation resulted in premature termination of translation and loss of 288 amino acids from C-terminus. A three-dimensional structural analysis revealed that conserved LRR domains were lost in mutant FBXL4 protein, which likely affected its ability to form protein-protein interactions. There were no differences in FBXL4 mRNA expression levels between the patient and her parents. There were no mtDNA mutations in either the patient or her parents. However, ND1/GAPDH ratio in lymphocytes and urine, which represents mtDNA/nuclear DNA ratio, showed that the number of mitochondrial genomes was significantly lower in the patient than in her parents or wild-type subjects. CONCLUSION Homozygous FBXL4 gene mutation, c.993dupA, can cause mitochondrial dysfunction, and LRR region is especially important for FBXL4 protein function.
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Affiliation(s)
- Simei Wang
- Department of Neurology, Shanghai Children's Hospital, Shanghai JiaoTong University, Shanghai 200062, China; Division of Pediatric Neurology, Department of Pediatrics, University of Illinois and Children's Hospital of Illinois, Peoria, IL 61637, USA
| | - Longlong Lin
- Department of Neurology, Shanghai Children's Hospital, Shanghai JiaoTong University, Shanghai 200062, China
| | - Yilin Wang
- Department of Neurology, Shanghai Children's Hospital, Shanghai JiaoTong University, Shanghai 200062, China
| | - Anqi Wang
- Department of Neurology, Shanghai Children's Hospital, Shanghai JiaoTong University, Shanghai 200062, China
| | - Zhao Liu
- Division of Pediatric Neurology, Department of Pediatrics, University of Illinois and Children's Hospital of Illinois, Peoria, IL 61637, USA
| | - Shengnan Wu
- Department of Neurology, Shanghai Children's Hospital, Shanghai JiaoTong University, Shanghai 200062, China
| | - Xiaoping Lan
- Department of Neurology, Shanghai Children's Hospital, Shanghai JiaoTong University, Shanghai 200062, China
| | - Jia Jia
- Shanghai Center for Bioinformation Technology, Shanghai 201202, China
| | - Yuanfeng Zhang
- Department of Neurology, Shanghai Children's Hospital, Shanghai JiaoTong University, Shanghai 200062, China
| | - Fang Yuan
- Department of Neurology, Shanghai Children's Hospital, Shanghai JiaoTong University, Shanghai 200062, China
| | - Chunmei Wang
- Department of Neurology, Shanghai Children's Hospital, Shanghai JiaoTong University, Shanghai 200062, China
| | - Xiaona Luo
- Department of Neurology, Shanghai Children's Hospital, Shanghai JiaoTong University, Shanghai 200062, China
| | - Xiaomin Sun
- Department of Neurology, Shanghai Children's Hospital, Shanghai JiaoTong University, Shanghai 200062, China
| | - Sreenivas K Avula
- Division of Pediatric Neurology, Department of Pediatrics, University of Illinois and Children's Hospital of Illinois, Peoria, IL 61637, USA
| | - Abdullah Tolaymat
- Division of Pediatric Neurology, Department of Pediatrics, University of Illinois and Children's Hospital of Illinois, Peoria, IL 61637, USA
| | | | - Yun Ren
- Department of Neurology, Shanghai Children's Hospital, Shanghai JiaoTong University, Shanghai 200062, China
| | - Yucai Chen
- Department of Neurology, Shanghai Children's Hospital, Shanghai JiaoTong University, Shanghai 200062, China.
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8
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Chapman J, Ng YS, Nicholls TJ. The Maintenance of Mitochondrial DNA Integrity and Dynamics by Mitochondrial Membranes. Life (Basel) 2020; 10:life10090164. [PMID: 32858900 PMCID: PMC7555930 DOI: 10.3390/life10090164] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Revised: 08/20/2020] [Accepted: 08/23/2020] [Indexed: 12/18/2022] Open
Abstract
Mitochondria are complex organelles that harbour their own genome. Mitochondrial DNA (mtDNA) exists in the form of a circular double-stranded DNA molecule that must be replicated, segregated and distributed around the mitochondrial network. Human cells typically possess between a few hundred and several thousand copies of the mitochondrial genome, located within the mitochondrial matrix in close association with the cristae ultrastructure. The organisation of mtDNA around the mitochondrial network requires mitochondria to be dynamic and undergo both fission and fusion events in coordination with the modulation of cristae architecture. The dysregulation of these processes has profound effects upon mtDNA replication, manifesting as a loss of mtDNA integrity and copy number, and upon the subsequent distribution of mtDNA around the mitochondrial network. Mutations within genes involved in mitochondrial dynamics or cristae modulation cause a wide range of neurological disorders frequently associated with defects in mtDNA maintenance. This review aims to provide an understanding of the biological mechanisms that link mitochondrial dynamics and mtDNA integrity, as well as examine the interplay that occurs between mtDNA, mitochondrial dynamics and cristae structure.
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Affiliation(s)
- James Chapman
- Wellcome Centre for Mitochondrial Research, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, UK;
- Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
- Correspondence: (J.C.); (T.J.N.)
| | - Yi Shiau Ng
- Wellcome Centre for Mitochondrial Research, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, UK;
- Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Thomas J. Nicholls
- Wellcome Centre for Mitochondrial Research, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, UK;
- Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
- Correspondence: (J.C.); (T.J.N.)
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9
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Matsushima N, Takatsuka S, Miyashita H, Kretsinger RH. Leucine Rich Repeat Proteins: Sequences, Mutations, Structures and Diseases. Protein Pept Lett 2019; 26:108-131. [PMID: 30526451 DOI: 10.2174/0929866526666181208170027] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Revised: 11/26/2018] [Accepted: 11/26/2018] [Indexed: 12/18/2022]
Abstract
Mutations in the genes encoding Leucine Rich Repeat (LRR) containing proteins are associated with over sixty human diseases; these include high myopia, mitochondrial encephalomyopathy, and Crohn's disease. These mutations occur frequently within the LRR domains and within the regions that shield the hydrophobic core of the LRR domain. The amino acid sequences of fifty-five LRR proteins have been published. They include Nod-Like Receptors (NLRs) such as NLRP1, NLRP3, NLRP14, and Nod-2, Small Leucine Rich Repeat Proteoglycans (SLRPs) such as keratocan, lumican, fibromodulin, PRELP, biglycan, and nyctalopin, and F-box/LRR-repeat proteins such as FBXL2, FBXL4, and FBXL12. For example, 363 missense mutations have been identified. Replacement of arginine, proline, or cysteine by another amino acid, or the reverse, is frequently observed. The diverse effects of the mutations are discussed based on the known structures of LRR proteins. These mutations influence protein folding, aggregation, oligomerization, stability, protein-ligand interactions, disulfide bond formation, and glycosylation. Most of the mutations cause loss of function and a few, gain of function.
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Affiliation(s)
- Norio Matsushima
- Center for Medical Education, Sapporo Medical University, Sapporo 060-8556, Japan.,Institute of Tandem Repeats, Noboribetsu 059-0464, Japan
| | - Shintaro Takatsuka
- Center for Medical Education, Sapporo Medical University, Sapporo 060-8556, Japan
| | - Hiroki Miyashita
- Institute of Tandem Repeats, Noboribetsu 059-0464, Japan.,Hokubu Rinsho Co., Ltd, Sapporo 060-0061, Japan
| | - Robert H Kretsinger
- Department of Biology, University of Virginia, Charlottesville, VA 22904, United States
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10
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Sabouny R, Wong R, Lee-Glover L, Greenway SC, Sinasac DS, Khan A, Shutt TE. Characterization of the C584R variant in the mtDNA depletion syndrome gene FBXL4, reveals a novel role for FBXL4 as a regulator of mitochondrial fusion. Biochim Biophys Acta Mol Basis Dis 2019; 1865:165536. [PMID: 31442532 DOI: 10.1016/j.bbadis.2019.165536] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2019] [Revised: 07/16/2019] [Accepted: 08/18/2019] [Indexed: 12/16/2022]
Abstract
Mutations in FBXL4 (F-Box and Leucine rich repeat protein 4), a nuclear-encoded mitochondrial protein with an unknown function, cause mitochondrial DNA depletion syndrome. We report two siblings, from consanguineous parents, harbouring a previously uncharacterized homozygous variant in FBXL4 (c.1750 T > C; p.Cys584Arg). Both patients presented with encephalomyopathy, lactic acidosis and cardiac hypertrophy, which are reported features of FBXL4 impairment. Remarkably, dichloroacetate (DCA) administration to the younger sibling improved metabolic acidosis and reversed cardiac hypertrophy. Characterization of FBXL4 patient fibroblasts revealed severe bioenergetic defects, mtDNA depletion, fragmentation of mitochondrial networks, and abnormalities in mtDNA nucleoids. These phenotypes, observed with other pathogenic FBXL4 variants, confirm the pathogenicity of the p.Cys584Arg variant. Although treating FBXL4 fibroblasts with DCA improved extracellular acidification, in line with reduced lactate levels in patients, DCA treatment did not improve any of the other mitochondrial functions. Nonetheless, we highlight DCA as a potentially effective drug for the management of elevated lactate and cardiomyopathy in patients with pathogenic FBXL4 variants. Finally, as the exact mechanism through which FBXL4 mutations lead to mtDNA depletion was unknown, we tested the hypothesis that FBXL4 promotes mitochondrial fusion. Using a photo-activatable GFP fusion assay, we found reduced mitochondrial fusion rates in cells harbouring a pathogenic FBXL4 variant. Meanwhile, overexpression of wildtype FBXL4, but not the p.Cys584Arg variant, promoted mitochondrial hyperfusion. Thus, we have uncovered a novel function for FBXL4 in promoting mitochondrial fusion, providing important mechanistic insights into the pathogenic mechanism underlying FBXL4 dysfunction.
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Affiliation(s)
- Rasha Sabouny
- Department of Biochemistry & Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada; Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada.
| | - Rachel Wong
- Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada
| | - Laurie Lee-Glover
- Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada
| | - Steven C Greenway
- Department of Biochemistry & Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada; Department of Pediatrics, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada; Department of Cardiac Sciences, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada; Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada; Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada
| | - David S Sinasac
- Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada; Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada
| | | | - Aneal Khan
- Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada; Department of Pediatrics, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada; Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada
| | - Timothy E Shutt
- Department of Biochemistry & Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada; Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada; Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada; Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.
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11
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Ballout RA, Al Alam C, Bonnen PE, Huemer M, El-Hattab AW, Shbarou R. FBXL4-Related Mitochondrial DNA Depletion Syndrome 13 (MTDPS13): A Case Report With a Comprehensive Mutation Review. Front Genet 2019; 10:39. [PMID: 30804983 PMCID: PMC6370620 DOI: 10.3389/fgene.2019.00039] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Accepted: 01/18/2019] [Indexed: 01/28/2023] Open
Abstract
Mitochondrial DNA depletion syndromes (MTDPS) are a group of rare genetic disorders caused by defects in multiple genes involved in mitochondrial DNA (mtDNA) maintenance. Among those, FBXL4 mutations result in the encephalomyopathic mtDNA depletion syndrome 13 (MTDPS13; OMIM #615471), which commonly presents as a combination of failure to thrive, neurodevelopmental delays, encephalopathy, hypotonia, and persistent lactic acidosis. We report here the case of a Lebanese infant presenting to us with profound neurodevelopmental delays, generalized hypotonia, facial dysmorphic features, and extreme emaciation. Whole-exome sequencing (WES) showed the girl as having MTDPS13 with an underlying FBXL4 missense mutation that has been previously reported only twice in unrelated individuals (c.1303C > T). Comprehensive literature search marked our patient as being the 94th case of MTDPS13 reported to date worldwide, and the first from Lebanon. We include at the end of this report a comprehensive mutation review table of all the pathological FBXL4 mutations reported in the literature, using it to highlight, for the first time, a possible founder effect of Arab origins to the disorder, being most prevalent in patients of Arab descent as shown in our mutation table. Finally, we provide a direct comparison of the disorder's clinical manifestations across two unrelated patients harboring the same disease-causing mutation as our patient, emphasizing the remarkable variability in genotype-to-phenotype correlation characteristic of the disease.
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Affiliation(s)
- Rami A Ballout
- Faculty of Medicine, American University of Beirut, Beirut, Lebanon
| | - Chadi Al Alam
- Division of Pediatric Neurology, Department of Pediatrics, American University of Beirut Medical Center, Beirut, Lebanon
| | - Penelope E Bonnen
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, United States
| | - Martina Huemer
- Department of Pediatrics, Landeskrankenhaus Bregenz, Bregenz, Austria.,Division of Metabolism, University Children's Hospital Zürich, Zurich, Switzerland
| | - Ayman W El-Hattab
- Genetics Clinic, KidsHeart Medical Center, Dubai, United Arab Emirates
| | - Rolla Shbarou
- Division of Pediatric Neurology, Department of Pediatrics, American University of Beirut Medical Center, Beirut, Lebanon
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12
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El-Hattab AW, Dai H, Almannai M, Wang J, Faqeih EA, Al Asmari A, Saleh MAM, Elamin MAO, Alfadhel M, Alkuraya FS, Hashem M, Aldosary MS, Almass R, Almutairi FB, Alsagob M, Al-Owain M, Al-Sharfa S, Al-Hassnan ZN, Rahbeeni Z, Al-Muhaizea MA, Makhseed N, Foskett GK, Stevenson DA, Gomez-Ospina N, Lee C, Boles RG, Schrier Vergano SA, Wortmann SB, Sperl W, Opladen T, Hoffmann GF, Hempel M, Prokisch H, Alhaddad B, Mayr JA, Chan W, Kaya N, Wong LJC. Molecular and clinical spectra of FBXL4 deficiency. Hum Mutat 2017; 38:1649-1659. [DOI: 10.1002/humu.23341] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Revised: 09/05/2017] [Accepted: 09/08/2017] [Indexed: 11/07/2022]
Affiliation(s)
- Ayman W. El-Hattab
- Division of Clinical Genetics and Metabolic Disorders, Pediatric Department; Tawam Hospital; Al-Ain United Arab Emirates
| | - Hongzheng Dai
- Department of Molecular and Human Genetics; Baylor College of Medicine; Houston Texas
| | - Mohammed Almannai
- Department of Molecular and Human Genetics; Baylor College of Medicine; Houston Texas
| | - Julia Wang
- Medical Scientist Training Program and Program in Developmental Biology; Baylor College of Medicine; Houston Texas
| | - Eissa A. Faqeih
- Section of Medical Genetics, Children's Hospital; King Fahad Medical City; Riyadh Saudi Arabia
| | - Ali Al Asmari
- Section of Medical Genetics, Children's Hospital; King Fahad Medical City; Riyadh Saudi Arabia
| | - Mohammed A. M. Saleh
- Section of Medical Genetics, Children's Hospital; King Fahad Medical City; Riyadh Saudi Arabia
| | - Mohammed A. O. Elamin
- Section of Medical Genetics, Children's Hospital; King Fahad Medical City; Riyadh Saudi Arabia
| | - Majid Alfadhel
- King Abdullah International Medical Research Centre; King Saud bin Abdulaziz University for Health Sciences; Riyadh Saudi Arabia
- Division of Genetics, Department of Pediatrics; King Abdulaziz Medical City, Ministry of National Guard-Health Affairs (NGHA); Riyadh Saudi Arabia
| | - Fowzan S. Alkuraya
- Department of Genetics; King Faisal Specialist Hospital and Research Center; Riyadh Saudi Arabia
- Department of Anatomy and Cell Biology, College of Medicine; Alfaisal University; Riyadh Saudi Arabia
| | - Mais Hashem
- Department of Genetics; King Faisal Specialist Hospital and Research Center; Riyadh Saudi Arabia
| | - Mazhor S. Aldosary
- Department of Genetics; King Faisal Specialist Hospital and Research Center; Riyadh Saudi Arabia
| | - Rawan Almass
- Department of Genetics; King Faisal Specialist Hospital and Research Center; Riyadh Saudi Arabia
| | - Faten B. Almutairi
- Department of Genetics; King Faisal Specialist Hospital and Research Center; Riyadh Saudi Arabia
| | - Maysoon Alsagob
- Department of Genetics; King Faisal Specialist Hospital and Research Center; Riyadh Saudi Arabia
| | - Mohammed Al-Owain
- Department of Medical Genetics; King Faisal Specialist Hospital and Research Centre; Riyadh Saudi Arabia
| | - Shirin Al-Sharfa
- Department of Medical Genetics; King Faisal Specialist Hospital and Research Centre; Riyadh Saudi Arabia
| | - Zuhair N. Al-Hassnan
- Department of Medical Genetics; King Faisal Specialist Hospital and Research Centre; Riyadh Saudi Arabia
| | - Zuhair Rahbeeni
- Department of Medical Genetics; King Faisal Specialist Hospital and Research Centre; Riyadh Saudi Arabia
| | - Mohammed A. Al-Muhaizea
- Department of Anatomy and Cell Biology, College of Medicine; Alfaisal University; Riyadh Saudi Arabia
- Department of Neurosciences; King Faisal Specialist Hospital and Research Centre; Riyadh Saudi Arabia
| | - Nawal Makhseed
- Department of Pediatrics, Al-Jahra Hospital; Ministry of Health; Al-Jahra City Kuwait
| | - Gretchen K. Foskett
- Department of Pediatrics; Stanford University School of Medicine; Stanford California
| | - David A. Stevenson
- Department of Pediatrics; Stanford University School of Medicine; Stanford California
| | - Natalia Gomez-Ospina
- Department of Pediatrics; Stanford University School of Medicine; Stanford California
| | - Chung Lee
- Department of Pediatrics; Stanford University School of Medicine; Stanford California
| | | | | | - Saskia B. Wortmann
- Department of Pediatrics, Salzburger Landeskliniken; Paracelsus Medical University; Salzburg Austria
- Institute of Human Genetics; Technische Universität München; Munich Germany
- Institute of Human Genetics; Helmholtz Zentrum München; Neuherberg Germany
| | - Wolfgang Sperl
- Department of Pediatrics, Salzburger Landeskliniken; Paracelsus Medical University; Salzburg Austria
| | - Thomas Opladen
- Centre for Child and Adolescent Medicine, Divisions of General Pediatrics, Neuropediatrics, and Metabolic Medicine; University Hospital; Heidelberg Germany
| | - Georg F. Hoffmann
- Centre for Child and Adolescent Medicine, Divisions of General Pediatrics, Neuropediatrics, and Metabolic Medicine; University Hospital; Heidelberg Germany
| | - Maja Hempel
- Institute of Human Genetics; University Medical Center Hamburg-Eppendorf; Hamburg Germany
| | - Holger Prokisch
- Institute of Human Genetics; Technische Universität München; Munich Germany
- Institute of Human Genetics; Helmholtz Zentrum München; Neuherberg Germany
| | - Bader Alhaddad
- Institute of Human Genetics; Technische Universität München; Munich Germany
- Institute of Human Genetics; Helmholtz Zentrum München; Neuherberg Germany
| | - Johannes A. Mayr
- Department of Pediatrics; Paracelsus Medical University Salzburg; Salzburg Austria
| | - Wenyaw Chan
- Department of Biostatistics, School of Public Health; University of Texas-Health Science Center at Houston; Houston Texas
| | - Namik Kaya
- Department of Genetics; King Faisal Specialist Hospital and Research Center; Riyadh Saudi Arabia
| | - Lee-Jun C. Wong
- Department of Molecular and Human Genetics; Baylor College of Medicine; Houston Texas
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13
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El-Hattab AW, Craigen WJ, Scaglia F. Mitochondrial DNA maintenance defects. Biochim Biophys Acta Mol Basis Dis 2017; 1863:1539-1555. [PMID: 28215579 DOI: 10.1016/j.bbadis.2017.02.017] [Citation(s) in RCA: 166] [Impact Index Per Article: 23.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Revised: 01/31/2017] [Accepted: 02/14/2017] [Indexed: 01/12/2023]
Abstract
The maintenance of mitochondrial DNA (mtDNA) depends on a number of nuclear gene-encoded proteins including a battery of enzymes forming the replisome needed to synthesize mtDNA. These enzymes need to be in balanced quantities to function properly that is in part achieved by exchanging intramitochondrial contents through mitochondrial fusion. In addition, mtDNA synthesis requires a balanced supply of nucleotides that is achieved by nucleotide recycling inside the mitochondria and import from the cytosol. Mitochondrial DNA maintenance defects (MDMDs) are a group of diseases caused by pathogenic variants in the nuclear genes involved in mtDNA maintenance resulting in impaired mtDNA synthesis leading to quantitative (mtDNA depletion) and qualitative (multiple mtDNA deletions) defects in mtDNA. Defective mtDNA leads to organ dysfunction due to insufficient mtDNA-encoded protein synthesis, resulting in an inadequate energy production to meet the needs of affected organs. MDMDs are inherited as autosomal recessive or dominant traits, and are associated with a broad phenotypic spectrum ranging from mild adult-onset ophthalmoplegia to severe infantile fatal hepatic failure. To date, pathogenic variants in 20 nuclear genes known to be crucial for mtDNA maintenance have been linked to MDMDs, including genes encoding enzymes of mtDNA replication machinery (POLG, POLG2, TWNK, TFAM, RNASEH1, MGME1, and DNA2), genes encoding proteins that function in maintaining a balanced mitochondrial nucleotide pool (TK2, DGUOK, SUCLG1, SUCLA2, ABAT, RRM2B, TYMP, SLC25A4, AGK, and MPV17), and genes encoding proteins involved in mitochondrial fusion (OPA1, MFN2, and FBXL4).
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Affiliation(s)
- Ayman W El-Hattab
- Division of Clinical Genetics and Metabolic Disorders, Pediatrics Department, Tawam Hospital, Al-Ain, United Arab Emirates
| | - William J Craigen
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.
| | - Fernando Scaglia
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
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14
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Morton SU, Neilan EG, Peake RWA, Shi J, Schmitz-Abe K, Towne M, Markianos K, Prabhu SP, Agrawal PB. Hyperammonemia as a Presenting Feature in Two Siblings with FBXL4 Variants. JIMD Rep 2016; 35:7-15. [PMID: 27858371 DOI: 10.1007/8904_2016_17] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Revised: 10/03/2016] [Accepted: 10/05/2016] [Indexed: 01/13/2023] Open
Abstract
Early-onset mitochondrial encephalomyopathy is a rare disorder that presents in the neonatal period with lactic acidosis, hypotonia, and developmental delay. Sequence variants in the nuclear-encoded gene FBXL4 have been previously demonstrated to be a cause of early-onset mitochondrial encephalomyopathy in several unrelated families. We have identified a pair of siblings with mutations in FBXL4 who each presented in the neonatal period with hyperammonemia, low plasma levels of aspartate, low urine levels of tricarboxylic acid cycle intermediates suggesting a defect in anaplerosis, and cerebellar hypoplasia in addition to lactic acidosis and other classic signs of mitochondrial encephalomyopathy. After initial clinical stabilization, both subjects continued to have episodic exacerbations characterized by lactic acidosis and hyperammonemia. Previously reported cases of FBXL4 mutations are reviewed and compared with these affected siblings. These two new cases add to the spectrum of disease caused by mutations in FBLX4 and suggest possible benefit from anaplerotic therapies.
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Affiliation(s)
- Sarah U Morton
- Division of Newborn Medicine, Boston Children's Hospital and Harvard Medical School, 300 Longwood Ave, Hunnewell 4, Boston, MA, 02115, USA.,Gene Discovery Core, The Manton Center for Orphan Disease Research, Boston Children's Hospital and Harvard Medical School, Boston, MA, USA
| | - Edward G Neilan
- Division of Genetics and Genomics, Boston Children's Hospital and Harvard Medical School, Boston, MA, USA
| | - Roy W A Peake
- Department of Laboratory Medicine, Boston Children's Hospital and Harvard Medical School, Boston, MA, USA
| | - Jiahai Shi
- Department of Biomedical Sciences, City University of Hong Kong, Pok Fu Lam, Hong Kong
| | - Klaus Schmitz-Abe
- Division of Genetics and Genomics, Boston Children's Hospital and Harvard Medical School, Boston, MA, USA
| | - Meghan Towne
- Gene Discovery Core, The Manton Center for Orphan Disease Research, Boston Children's Hospital and Harvard Medical School, Boston, MA, USA.,Division of Genetics and Genomics, Boston Children's Hospital and Harvard Medical School, Boston, MA, USA
| | - Kyriacos Markianos
- Division of Newborn Medicine, Boston Children's Hospital and Harvard Medical School, 300 Longwood Ave, Hunnewell 4, Boston, MA, 02115, USA.,Gene Discovery Core, The Manton Center for Orphan Disease Research, Boston Children's Hospital and Harvard Medical School, Boston, MA, USA
| | - Sanjay P Prabhu
- Department of Radiology, Boston Children's Hospital and Harvard Medical School, Boston, MA, USA
| | - Pankaj B Agrawal
- Division of Newborn Medicine, Boston Children's Hospital and Harvard Medical School, 300 Longwood Ave, Hunnewell 4, Boston, MA, 02115, USA. .,Gene Discovery Core, The Manton Center for Orphan Disease Research, Boston Children's Hospital and Harvard Medical School, Boston, MA, USA. .,Division of Genetics and Genomics, Boston Children's Hospital and Harvard Medical School, Boston, MA, USA.
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