1
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Chung J, Park J, Lai ZW, Lambert TJ, Richards RC, Zhang J, Walther TC, Farese RV. The Troyer syndrome protein spartin mediates selective autophagy of lipid droplets. Nat Cell Biol 2023; 25:1101-1110. [PMID: 37443287 PMCID: PMC10415183 DOI: 10.1038/s41556-023-01178-w] [Citation(s) in RCA: 18] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Accepted: 05/30/2023] [Indexed: 07/15/2023]
Abstract
Lipid droplets (LDs) are crucial organelles for energy storage and lipid homeostasis. Autophagy of LDs is an important pathway for their catabolism, but the molecular mechanisms mediating LD degradation by selective autophagy (lipophagy) are unknown. Here we identify spartin as a receptor localizing to LDs and interacting with core autophagy machinery, and we show that spartin is required to deliver LDs to lysosomes for triglyceride mobilization. Mutations in SPART (encoding spartin) lead to Troyer syndrome, a form of complex hereditary spastic paraplegia1. Interfering with spartin function in cultured human neurons or murine brain neurons leads to LD and triglyceride accumulation. Our identification of spartin as a lipophagy receptor, thus, suggests that impaired LD turnover contributes to Troyer syndrome development.
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Affiliation(s)
- Jeeyun Chung
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
- Department of Molecular Metabolism, Harvard T. H. Chan School of Public Health, Boston, MA, USA
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, USA
| | - Joongkyu Park
- Department of Pharmacology, Department of Neurology, Wayne State University School of Medicine, Detroit, MI, USA
| | - Zon Weng Lai
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
- Department of Molecular Metabolism, Harvard T. H. Chan School of Public Health, Boston, MA, USA
| | - Talley J Lambert
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
- Department of Systems Biology, Harvard Medical School, Boston, MA, USA
| | - Ruth C Richards
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
- Department of Molecular Metabolism, Harvard T. H. Chan School of Public Health, Boston, MA, USA
| | - Jiuchun Zhang
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
| | - Tobias C Walther
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA.
- Department of Molecular Metabolism, Harvard T. H. Chan School of Public Health, Boston, MA, USA.
- Broad Institute of Harvard and MIT, Cambridge, MA, USA.
- Howard Hughes Medical Institute, Boston, MA, USA.
- Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY, USA.
| | - Robert V Farese
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA.
- Department of Molecular Metabolism, Harvard T. H. Chan School of Public Health, Boston, MA, USA.
- Broad Institute of Harvard and MIT, Cambridge, MA, USA.
- Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY, USA.
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2
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Khoshaeen A, Najafi M, Mahdavi MR, Jalali H, Mahdavi M. A novel missense mutation (c.1006C>T) of SPG20 gene associated with Troyer syndrome. J Genet 2020. [DOI: 10.1007/s12041-020-01210-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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3
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Dard L, Blanchard W, Hubert C, Lacombe D, Rossignol R. Mitochondrial functions and rare diseases. Mol Aspects Med 2020; 71:100842. [PMID: 32029308 DOI: 10.1016/j.mam.2019.100842] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2019] [Revised: 12/26/2019] [Accepted: 12/27/2019] [Indexed: 12/19/2022]
Abstract
Mitochondria are dynamic cellular organelles responsible for a large variety of biochemical processes as energy transduction, REDOX signaling, the biosynthesis of hormones and vitamins, inflammation or cell death execution. Cell biology studies established that 1158 human genes encode proteins localized to mitochondria, as registered in MITOCARTA. Clinical studies showed that a large number of these mitochondrial proteins can be altered in expression and function through genetic, epigenetic or biochemical mechanisms including the interaction with environmental toxics or iatrogenic medicine. As a result, pathogenic mitochondrial genetic and functional defects participate to the onset and the progression of a growing number of rare diseases. In this review we provide an exhaustive survey of the biochemical, genetic and clinical studies that demonstrated the implication of mitochondrial dysfunction in human rare diseases. We discuss the striking diversity of the symptoms caused by mitochondrial dysfunction and the strategies proposed for mitochondrial therapy, including a survey of ongoing clinical trials.
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Affiliation(s)
- L Dard
- Bordeaux University, 33000, Bordeaux, France; INSERM U1211, 33000, Bordeaux, France; CELLOMET, CGFB-146 Rue Léo Saignat, Bordeaux, France
| | - W Blanchard
- Bordeaux University, 33000, Bordeaux, France; INSERM U1211, 33000, Bordeaux, France; CELLOMET, CGFB-146 Rue Léo Saignat, Bordeaux, France
| | - C Hubert
- Bordeaux University, 33000, Bordeaux, France; INSERM U1211, 33000, Bordeaux, France
| | - D Lacombe
- Bordeaux University, 33000, Bordeaux, France; INSERM U1211, 33000, Bordeaux, France; CHU de Bordeaux, Service de Génétique Médicale, F-33076, Bordeaux, France
| | - R Rossignol
- Bordeaux University, 33000, Bordeaux, France; INSERM U1211, 33000, Bordeaux, France; CELLOMET, CGFB-146 Rue Léo Saignat, Bordeaux, France.
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4
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Liang H, Miao H, Yang H, Gong F, Chen S, Wang L, Zhu H, Pan H. Dwarfism in Troyer syndrome: a family with SPG20 compound heterozygous mutations and a literature review. Ann N Y Acad Sci 2019; 1462:118-127. [PMID: 31535723 DOI: 10.1111/nyas.14229] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Revised: 08/07/2019] [Accepted: 08/14/2019] [Indexed: 01/16/2023]
Abstract
Troyer syndrome is an autosomal recessive disease characterized by spastic paralysis, dysarthria, distal amyotrophy, and short stature. Recently, two siblings (an older brother and a younger sister) were admitted to our hospital for the chief complaints of "short stature and intellectual disability." Through whole exome sequencing of the sister, who is the proband, it was found that her SPG20 gene had compound heterozygous mutations: c.364_365delAT (p.Met122Valfs* 2) and c.892delA (p.Thr298Glnfs* 30). Target testing revealed that the brother had the same genotype as the sister, and the former mutation originated from the father, while the latter mutation originated from the mother. In summary, this is the first report of Troyer syndrome in a family caused by SPG20 compound heterozygous mutations. A novel SPG20 mutation was found, namely c.892delA (p.Thr298Glnfs* 30). In addition, we also summarize these Troyer syndrome patients' heights and their clinical characteristics, and provide a brief review of all known pathogenic mutations of SPG20.
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Affiliation(s)
- Hanting Liang
- Key Laboratory of Endocrinology of National Health Commission, Department of Endocrinology, Peking Union Medical College Hospital, Chinese Academy of Medical Science and Peking Union Medical College, Beijing, China
| | - Hui Miao
- Key Laboratory of Endocrinology of National Health Commission, Department of Endocrinology, Peking Union Medical College Hospital, Chinese Academy of Medical Science and Peking Union Medical College, Beijing, China
| | - Hongbo Yang
- Key Laboratory of Endocrinology of National Health Commission, Department of Endocrinology, Peking Union Medical College Hospital, Chinese Academy of Medical Science and Peking Union Medical College, Beijing, China
| | - Fengying Gong
- Key Laboratory of Endocrinology of National Health Commission, Department of Endocrinology, Peking Union Medical College Hospital, Chinese Academy of Medical Science and Peking Union Medical College, Beijing, China
| | - Shi Chen
- Key Laboratory of Endocrinology of National Health Commission, Department of Endocrinology, Peking Union Medical College Hospital, Chinese Academy of Medical Science and Peking Union Medical College, Beijing, China
| | - Linjie Wang
- Key Laboratory of Endocrinology of National Health Commission, Department of Endocrinology, Peking Union Medical College Hospital, Chinese Academy of Medical Science and Peking Union Medical College, Beijing, China
| | - Huijuan Zhu
- Key Laboratory of Endocrinology of National Health Commission, Department of Endocrinology, Peking Union Medical College Hospital, Chinese Academy of Medical Science and Peking Union Medical College, Beijing, China
| | - Hui Pan
- Key Laboratory of Endocrinology of National Health Commission, Department of Endocrinology, Peking Union Medical College Hospital, Chinese Academy of Medical Science and Peking Union Medical College, Beijing, China
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5
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Diquigiovanni C, Bergamini C, Diaz R, Liparulo I, Bianco F, Masin L, Baldassarro VA, Rizzardi N, Tranchina A, Buscherini F, Wischmeijer A, Pippucci T, Scarano E, Cordelli DM, Fato R, Seri M, Paracchini S, Bonora E. A novel mutation in SPART gene causes a severe neurodevelopmental delay due to mitochondrial dysfunction with complex I impairments and altered pyruvate metabolism. FASEB J 2019; 33:11284-11302. [PMID: 31314595 DOI: 10.1096/fj.201802722r] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Loss-of-function mutations in the SPART gene cause Troyer syndrome, a recessive form of spastic paraplegia resulting in muscle weakness, short stature, and cognitive defects. SPART encodes for Spartin, a protein linked to endosomal trafficking and mitochondrial membrane potential maintenance. Here, we identified with whole exome sequencing (WES) a novel frameshift mutation in the SPART gene in 2 brothers presenting an uncharacterized developmental delay and short stature. Functional characterization in an SH-SY5Y cell model shows that this mutation is associated with increased neurite outgrowth. These cells also show a marked decrease in mitochondrial complex I (NADH dehydrogenase) activity, coupled to decreased ATP synthesis and defective mitochondrial membrane potential. The cells also presented an increase in reactive oxygen species, extracellular pyruvate, and NADH levels, consistent with impaired complex I activity. In concordance with a severe mitochondrial failure, Spartin loss also led to an altered intracellular Ca2+ homeostasis that was restored after transient expression of wild-type Spartin. Our data provide for the first time a thorough assessment of Spartin loss effects, including impaired complex I activity coupled to increased extracellular pyruvate. In summary, through a WES study we assign a diagnosis of Troyer syndrome to otherwise undiagnosed patients, and by functional characterization we show that the novel mutation in SPART leads to a profound bioenergetic imbalance.-Diquigiovanni, C., Bergamini, C., Diaz, R., Liparulo, I., Bianco, F., Masin, L., Baldassarro, V. A., Rizzardi, N., Tranchina, A., Buscherini, F., Wischmeijer, A., Pippucci, T., Scarano, E., Cordelli, D. M., Fato, R., Seri, M., Paracchini, S., Bonora, E. A novel mutation in SPART gene causes a severe neurodevelopmental delay due to mitochondrial dysfunction with complex I impairments and altered pyruvate metabolism.
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Affiliation(s)
- Chiara Diquigiovanni
- Department of Medical and Surgical Sciences (DIMEC), St. Orsola-Malpighi Hospital, University of Bologna, Bologna, Italy
| | - Christian Bergamini
- Department of Pharmacy and Biotechnology (FaBit), University of Bologna, Bologna, Italy
| | - Rebeca Diaz
- School of Medicine, University of St. Andrews, St. Andrews, United Kingdom
| | - Irene Liparulo
- Department of Pharmacy and Biotechnology (FaBit), University of Bologna, Bologna, Italy
| | - Francesca Bianco
- Department of Medical and Surgical Sciences (DIMEC), St. Orsola-Malpighi Hospital, University of Bologna, Bologna, Italy
| | - Luca Masin
- Department of Pharmacy and Biotechnology (FaBit), University of Bologna, Bologna, Italy
| | | | - Nicola Rizzardi
- Department of Pharmacy and Biotechnology (FaBit), University of Bologna, Bologna, Italy
| | - Antonia Tranchina
- Department of Medical and Surgical Sciences (DIMEC), St. Orsola-Malpighi Hospital, University of Bologna, Bologna, Italy
| | - Francesco Buscherini
- Department of Medical and Surgical Sciences (DIMEC), St. Orsola-Malpighi Hospital, University of Bologna, Bologna, Italy
| | - Anita Wischmeijer
- Department of Pediatrics, Clinical Genetics Service, Regional Hospital of South Tyrol, Bolzano, Italy
| | - Tommaso Pippucci
- Department of Medical and Surgical Sciences (DIMEC), St. Orsola-Malpighi Hospital, University of Bologna, Bologna, Italy
| | - Emanuela Scarano
- Rare Disease Unit, Department of Pediatrics, St. Orsola-Malpighi Hospital, University of Bologna, Bologna, Italy
| | - Duccio Maria Cordelli
- Child Neurology and Psychiatry Unit, St. Orsola-Malpighi Hospital, University of Bologna, Bologna, Italy
| | - Romana Fato
- Department of Pharmacy and Biotechnology (FaBit), University of Bologna, Bologna, Italy
| | - Marco Seri
- Department of Medical and Surgical Sciences (DIMEC), St. Orsola-Malpighi Hospital, University of Bologna, Bologna, Italy
| | - Silvia Paracchini
- School of Medicine, University of St. Andrews, St. Andrews, United Kingdom
| | - Elena Bonora
- Department of Medical and Surgical Sciences (DIMEC), St. Orsola-Malpighi Hospital, University of Bologna, Bologna, Italy
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6
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Abstract
The hereditary spastic paraplegias (HSPs) are a heterogeneous group of neurologic disorders with the common feature of prominent lower-extremity spasticity, resulting from a length-dependent axonopathy of corticospinal upper motor neurons. The HSPs exist not only in "pure" forms but also in "complex" forms that are associated with additional neurologic and extraneurologic features. The HSPs are among the most genetically diverse neurologic disorders, with well over 70 distinct genetic loci, for which about 60 mutated genes have already been identified. Numerous studies elucidating the molecular pathogenesis underlying HSPs have highlighted the importance of basic cellular functions - especially membrane trafficking, mitochondrial function, organelle shaping and biogenesis, axon transport, and lipid/cholesterol metabolism - in axon development and maintenance. An encouragingly small number of converging cellular pathogenic themes have been identified for the most common HSPs, and some of these pathways present compelling targets for future therapies.
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Affiliation(s)
- Craig Blackstone
- Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, United States.
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7
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Bizzari S, Hamzeh AR, Nair P, Mohamed M, Saif F, Aithala G, Al-Ali MT, Bastaki F. Novel SPG20 mutation in an extended family with Troyer syndrome. Metab Brain Dis 2017; 32:2155-2159. [PMID: 28875386 DOI: 10.1007/s11011-017-0104-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/14/2017] [Accepted: 08/29/2017] [Indexed: 12/18/2022]
Abstract
Troyer Syndrome (TRS) is a rare autosomal recessive complicated spastic paraplegia disorder characterized by various neurological and musculoskeletal manifestations. Pathogenicity stems from mutations in SPG20 which encodes Spartin, a multifunctional protein that is thought to be essential for neuron viability. Here we report on the clinical and molecular characterization of TRS in five patients from an extended consanguineous family in the United Arab Emirates. Molecular analysis involved Whole Exome Sequencing and Sanger sequencing for identification and confirmation of the causative variant respectively. In silico tools including CADD and Polyphen-2 were used to assess pathogenicity of the variant. The clinical description of these patients included spastic paraparesis, motor and cognitive delay, gait abnormalities, musculoskeletal features, as well as white matter abnormalities and emotional liability. Molecular analysis revealed a novel homozygous missense mutation in SPG20 (c.1324G > C; p.Ala442Pro) occurring at an evolutionarily conserved residue in the Plant-Related Senescence domain of Spartin. The mutation segregated with the clinical phenotype in all patients. In silico algorithms predict the mutation to be disease causing, and the variant had not been previously reported in public or ethnic specific variant repositories.
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Affiliation(s)
- S Bizzari
- Centre for Arab Genomic Studies, P.O. Box 22252, Dubai, United Arab Emirates.
| | - A R Hamzeh
- Centre for Arab Genomic Studies, P.O. Box 22252, Dubai, United Arab Emirates
| | - P Nair
- Centre for Arab Genomic Studies, P.O. Box 22252, Dubai, United Arab Emirates
| | - M Mohamed
- Pediatric Department, Latifa Hospital, Dubai Health Authority, Dubai, United Arab Emirates
| | - F Saif
- Pediatric Department, Latifa Hospital, Dubai Health Authority, Dubai, United Arab Emirates
| | - G Aithala
- Pediatric Department, Latifa Hospital, Dubai Health Authority, Dubai, United Arab Emirates
| | - M T Al-Ali
- Centre for Arab Genomic Studies, P.O. Box 22252, Dubai, United Arab Emirates
| | - F Bastaki
- Pediatric Department, Latifa Hospital, Dubai Health Authority, Dubai, United Arab Emirates
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8
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Ring J, Rockenfeller P, Abraham C, Tadic J, Poglitsch M, Schimmel K, Westermayer J, Schauer S, Achleitner B, Schimpel C, Moitzi B, Rechberger GN, Sigrist SJ, Carmona-Gutierrez D, Kroemer G, Büttner S, Eisenberg T, Madeo F. Mitochondrial energy metabolism is required for lifespan extension by the spastic paraplegia-associated protein spartin. MICROBIAL CELL (GRAZ, AUSTRIA) 2017; 4:411-422. [PMID: 29234670 PMCID: PMC5722644 DOI: 10.15698/mic2017.12.603] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/21/2017] [Accepted: 11/20/2017] [Indexed: 01/11/2023]
Abstract
Hereditary spastic paraplegias, a group of neurodegenerative disorders, can be caused by loss-of-function mutations in the protein spartin. However, the physiological role of spartin remains largely elusive. Here we show that heterologous expression of human or Drosophila spartin extends chronological lifespan of yeast, reducing age-associated ROS production, apoptosis, and necrosis. We demonstrate that spartin localizes to the proximity of mitochondria and physically interacts with proteins related to mitochondrial and respiratory metabolism. Interestingly, Nde1, the mitochondrial external NADH dehydrogenase, and Pda1, the core enzyme of the pyruvate dehydrogenase complex, are required for spartin-mediated cytoprotection. Furthermore, spartin interacts with the glycolysis enhancer phospo-fructo-kinase-2,6 (Pfk26) and is sufficient to complement for PFK26-deficiency at least in early aging. We conclude that mitochondria-related energy metabolism is crucial for spartin's vital function during aging and uncover a network of specific interactors required for this function.
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Affiliation(s)
- Julia Ring
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, Graz, Austria
| | - Patrick Rockenfeller
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, Graz, Austria
- Kent Fungal Group, School of Biosciences, University of Kent, Canterbury, UK
| | - Claudia Abraham
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, Graz, Austria
| | - Jelena Tadic
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, Graz, Austria
| | - Michael Poglitsch
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, Graz, Austria
| | - Katherina Schimmel
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, Graz, Austria
- Institute of Molecular and Translational Therapeutic Strategies (IMTTS), IFB-Tx, Hannover Medical School, Hannover, Germany
| | - Julia Westermayer
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, Graz, Austria
| | - Simon Schauer
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, Graz, Austria
| | - Bettina Achleitner
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, Graz, Austria
| | - Christa Schimpel
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, Graz, Austria
- BioNanoNet Forschungsgesellschaft mbH, Graz, Austria
| | - Barbara Moitzi
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, Graz, Austria
| | - Gerald N. Rechberger
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, Graz, Austria
- Omics Center Graz, BioTechMed-Graz, Graz, Austria
| | - Stephan J. Sigrist
- Institute for Biology, Freie Universität Berlin, Berlin, Germany
- NeuroCure, Charité, Berlin, Germany
| | | | - Guido Kroemer
- BioTechMed Graz, Graz, Austria
- Cell Biology and Metabolomics Platforms, Gustave Roussy Comprehensive Cancer Center, Villejuif, France
- INSERM, U1138, Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, Paris, France
- Université Pierre et Marie Curie, Paris, France
- Pôle de Biologie, Hôpital Européen Georges Pompidou, Paris, France
- Karolinska Institute, Department of Women's and Children's Health, Karolinska University Hospital Stockholm, Sweden
| | - Sabrina Büttner
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, Graz, Austria
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
| | - Tobias Eisenberg
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, Graz, Austria
- BioTechMed Graz, Graz, Austria
| | - Frank Madeo
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, Graz, Austria
- BioTechMed Graz, Graz, Austria
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9
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Dardour L, Roelens F, Race V, Souche E, Holvoet M, Devriendt K. SPG20 mutation in three siblings with familial hereditary spastic paraplegia. Cold Spring Harb Mol Case Stud 2017; 3:mcs.a001537. [PMID: 28679690 PMCID: PMC5495031 DOI: 10.1101/mcs.a001537] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Accepted: 02/23/2017] [Indexed: 01/19/2023] Open
Abstract
Troyer syndrome (MIM#275900) is an autosomal recessive form of complicated hereditary spastic paraplegia. It is characterized by progressive lower extremity spasticity and weakness, dysarthria, distal amyotrophy, developmental delay, short stature, and subtle skeletal abnormalities. It is caused by deleterious mutations in the SPG20 gene, encoding spartin, on Chromosome 13q13. Until now, six unrelated families with a genetically confirmed diagnosis have been reported. Here we report the clinical findings in three brothers of a consanguineous Moroccan family, aged 24, 17, and 7 yr old, with spastic paraplegia, short stature, motor and cognitive delay, and severe intellectual disability. Targeted exon capture and sequencing showed a homozygous nonsense mutation in the SPG20 gene, c.1369C>T (p.Arg457*), in the three affected boys.
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Affiliation(s)
- Leila Dardour
- Center for Human Genetics, KU Leuven, 3000 Leuven, Belgium
| | | | - Valerie Race
- Center for Human Genetics, KU Leuven, 3000 Leuven, Belgium
| | - Erika Souche
- Center for Human Genetics, KU Leuven, 3000 Leuven, Belgium
| | | | - Koen Devriendt
- Center for Human Genetics, KU Leuven, 3000 Leuven, Belgium
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10
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Novel Homozygous Missense Mutation in SPG20 Gene Results in Troyer Syndrome Associated with Mitochondrial Cytochrome c Oxidase Deficiency. JIMD Rep 2016; 33:55-60. [PMID: 27539578 DOI: 10.1007/8904_2016_580] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/17/2016] [Revised: 07/14/2016] [Accepted: 07/18/2016] [Indexed: 12/13/2022] Open
Abstract
Troyer syndrome is an autosomal recessive form of hereditary spastic paraplegia (HSP) caused by deleterious mutations in the SPG20 gene. Although the disease is associated with a loss of function mechanism of spartin, the protein encoded by SPG20, the precise pathogenesis is yet to be elucidated. Recent data indicated an important role for spartin in both mitochondrial maintenance and function. Here we report a child presenting with progressive spastic paraparesis, generalized muscle weakness, dysarthria, impaired growth, and severe isolated decrease in muscle cytochrome c oxidase (COX) activity. Whole exome sequencing identified the homozygous c.988A>G variant in SPG20 gene (p.Met330Val) resulting in almost complete loss of spartin in skeletal muscle. Further analyses demonstrated significant tissue specific reduction of COX 4, a nuclear encoded subunit of COX, in muscle suggesting a role for spartin in proper mitochondrial respiratory chain function mediated by COX activity. Our findings need to be verified in other Troyer syndrome patients in order to classify it as a form of HSP caused by mitochondrial dysfunction.
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11
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Butler S, Helbig KL, Alcaraz W, Seaver LH, Hsieh DT, Rohena L. Three cases of Troyer syndrome in two families of Filipino descent. Am J Med Genet A 2016; 170:1780-5. [DOI: 10.1002/ajmg.a.37658] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Accepted: 03/25/2016] [Indexed: 11/10/2022]
Affiliation(s)
- Shauna Butler
- Department of Pediatrics; San Antonio Military Medical Center; JBSA Ft Sam Houston Texas
| | | | - Wendy Alcaraz
- Division of Clinical Genomics; Ambry Genetics; Aliso Viejo California
| | - Laurie H. Seaver
- Department of Pediatrics; University of Hawai‘i John A. Burns School of Medicine and Kapi'olani Medical Specialists; Honolulu Hawaii
| | - David T. Hsieh
- Department of Pediatrics; San Antonio Military Medical Center; JBSA Ft Sam Houston Texas
| | - Luis Rohena
- Department of Pediatrics; San Antonio Military Medical Center; JBSA Ft Sam Houston Texas
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12
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Melo US, Macedo-Souza LI, Figueiredo T, Muotri AR, Gleeson JG, Coux G, Armas P, Calcaterra NB, Kitajima JP, Amorim S, Olávio TR, Griesi-Oliveira K, Coatti GC, Rocha CRR, Martins-Pinheiro M, Menck CFM, Zaki MS, Kok F, Zatz M, Santos S. Overexpression of KLC2 due to a homozygous deletion in the non-coding region causes SPOAN syndrome. Hum Mol Genet 2015; 24:6877-85. [PMID: 26385635 DOI: 10.1093/hmg/ddv388] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2015] [Accepted: 09/14/2015] [Indexed: 02/06/2023] Open
Abstract
SPOAN syndrome is a neurodegenerative disorder mainly characterized by spastic paraplegia, optic atrophy and neuropathy (SPOAN). Affected patients are wheelchair bound after 15 years old, with progressive joint contractures and spine deformities. SPOAN patients also have sub normal vision secondary to apparently non-progressive congenital optic atrophy. A potential causative gene was mapped at 11q13 ten years ago. Here we performed next-generation sequencing in SPOAN-derived samples. While whole-exome sequencing failed to identify the causative mutation, whole-genome sequencing allowed to detect a homozygous 216-bp deletion (chr11.hg19:g.66,024,557_66,024,773del) located at the non-coding upstream region of the KLC2 gene. Expression assays performed with patient's fibroblasts and motor neurons derived from SPOAN patients showed KLC2 overexpression. Luciferase assay in constructs with 216-bp deletion confirmed the overexpression of gene reporter, varying from 48 to 74%, as compared with wild-type. Knockdown and overexpression of klc2 in Danio rerio revealed mild to severe curly-tail phenotype, which is suggestive of a neuromuscular disorder. Overexpression of a gene caused by a small deletion in the non-coding region is a novel mechanism, which to the best of our knowledge, was never reported before in a recessive condition. Although the molecular mechanism of KLC2 up-regulation still remains to be uncovered, such example adds to the importance of non-coding regions in human pathology.
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Affiliation(s)
- Uirá S Melo
- Human Genome and Stem Cell Research Center, Department of Genetics and Evolutionary Biology, Biosciences Institute, University of Sao Paulo (USP), Sao Paulo, SP 05508-090, Brazil
| | - Lucia I Macedo-Souza
- Human Genome and Stem Cell Research Center, Department of Genetics and Evolutionary Biology, Biosciences Institute, University of Sao Paulo (USP), Sao Paulo, SP 05508-090, Brazil
| | - Thalita Figueiredo
- Northeast Biotechnology Network (RENORBIO), Federal University of Paraiba (UFPB), Joao Pessoa, PB 58051-900, Brazil, Department of Biology, Paraiba State University (UEPB), Campina Grande, PB 58429-500, Brazil
| | - Alysson R Muotri
- Department of Pediatrics/Rady Children's Hospital San Diego, University of California San Diego, La Jolla, CA 92093, USA
| | - Joseph G Gleeson
- Laboratory for Pediatric Brain Disease, The Rockefeller University, New York, NY 10065, USA
| | - Gabriela Coux
- Instituto de Biología Molecular y Celular de Rosario (IBR), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) - Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario (UNR), Rosario, SF S2002LRK, Argentina
| | - Pablo Armas
- Instituto de Biología Molecular y Celular de Rosario (IBR), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) - Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario (UNR), Rosario, SF S2002LRK, Argentina
| | - Nora B Calcaterra
- Instituto de Biología Molecular y Celular de Rosario (IBR), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) - Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario (UNR), Rosario, SF S2002LRK, Argentina
| | | | - Simone Amorim
- Department of Neurology, School of Medicine, University of Sao Paulo (USP), São Paulo, SP 01246-903, Brazil
| | - Thiago R Olávio
- Human Genome and Stem Cell Research Center, Department of Genetics and Evolutionary Biology, Biosciences Institute, University of Sao Paulo (USP), Sao Paulo, SP 05508-090, Brazil
| | - Karina Griesi-Oliveira
- Human Genome and Stem Cell Research Center, Department of Genetics and Evolutionary Biology, Biosciences Institute, University of Sao Paulo (USP), Sao Paulo, SP 05508-090, Brazil
| | - Giuliana C Coatti
- Human Genome and Stem Cell Research Center, Department of Genetics and Evolutionary Biology, Biosciences Institute, University of Sao Paulo (USP), Sao Paulo, SP 05508-090, Brazil
| | - Clarissa R R Rocha
- Department of Microbiology, Institute of Biomedical Sciences, University of São Paulo (USP), São Paulo, SP 05508-900, Brazil and
| | - Marinalva Martins-Pinheiro
- Department of Microbiology, Institute of Biomedical Sciences, University of São Paulo (USP), São Paulo, SP 05508-900, Brazil and
| | - Carlos F M Menck
- Department of Microbiology, Institute of Biomedical Sciences, University of São Paulo (USP), São Paulo, SP 05508-900, Brazil and
| | - Maha S Zaki
- Department of Clinical Genetics, Human Genetics and Genome Research Division, National Research Center, Cairo 12311, Egypt
| | - Fernando Kok
- Human Genome and Stem Cell Research Center, Department of Genetics and Evolutionary Biology, Biosciences Institute, University of Sao Paulo (USP), Sao Paulo, SP 05508-090, Brazil, Mendelics Genomic Analysis, São Paulo, SP 04013-000, Brazil
| | - Mayana Zatz
- Human Genome and Stem Cell Research Center, Department of Genetics and Evolutionary Biology, Biosciences Institute, University of Sao Paulo (USP), Sao Paulo, SP 05508-090, Brazil,
| | - Silvana Santos
- Northeast Biotechnology Network (RENORBIO), Federal University of Paraiba (UFPB), Joao Pessoa, PB 58051-900, Brazil, Department of Biology, Paraiba State University (UEPB), Campina Grande, PB 58429-500, Brazil
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13
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Oxidative Stress in Caenorhabditis elegans: Protective Effects of Spartin. PLoS One 2015; 10:e0130455. [PMID: 26114733 PMCID: PMC4482654 DOI: 10.1371/journal.pone.0130455] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Accepted: 05/20/2015] [Indexed: 01/25/2023] Open
Abstract
Troyer syndrome is caused by a mutation in the SPG20 gene, which results in complete loss of expression of the protein spartin. We generated a genetic model of Troyer syndrome in worms to explore the locomotor consequences of a null mutation of the Caenorhabditis elegans SPG20 orthologue, F57B10.9, also known as spg-20. Spg-20 mutants showed decreased length, crawling speed, and thrashing frequency, and had a shorter lifespan than wild-type animals. These results suggest an age-dependent decline in motor function in mutant animals. The drug paraquat was used to induce oxidative stress for 4 days in the animals. We measured survival rate and examined locomotion by measuring crawling speed and thrashing frequency. After 4 days of paraquat exposure, 77% of wild-type animals survived, but only 38% of spg-20 mutant animals survived. Conversely, animals overexpressing spg-20 had a survival rate of 95%. We also tested lifespan after a 1 hour exposure to sodium azide. After a 24 hour recovery period, 87% of wild type animals survived, 57% of spg-20 mutant animals survived, and 82% of animals overexpressing spg-20 survived. In the behavioral assays, spg-20 mutant animals showed a significant decrease in both crawling speed and thrashing frequency compared with wild-type animals. Importantly, the locomotor phenotype for both crawling and thrashing was rescued in animals overexpressing spg-20. The animals overexpressing spg-20 had crawling speeds and thrashing frequencies similar to those of wild-type animals. These data suggest that the protein F57B10.9/SPG-20 might have a protective role against oxidative stress.
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Tawamie H, Wohlleber E, Uebe S, Schmäl C, Nöthen MM, Abou Jamra R. Recurrent null mutation in SPG20 leads to Troyer syndrome. Mol Cell Probes 2015; 29:315-8. [PMID: 26003402 DOI: 10.1016/j.mcp.2015.05.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Revised: 05/11/2015] [Accepted: 05/12/2015] [Indexed: 01/26/2023]
Abstract
Troyer syndrome is an autosomal recessive form of complex hereditary spastic paraplegia. To date, the disorder has only been described in the Amish and in kindred from Oman. In Amish, all affected individuals have a homozygous one nucleotide deletion; c.1110delA. In the Omani kindred, all affected have a homozygous two nucleotides deletion; c.364_365delTA (p.Met122ValfsTer2). Here we report the results of homozygosity mapping and whole exome sequencing in two siblings of a consanguineous Turkish family with mild intellectual disability, spastic paraplegia, and muscular dystrophy. We identified the same deletion that has been identified in the Omani kindred, but haplotype analysis suggests a recurrent event, and not a founder mutation. We summarize current knowledge of Troyer syndrome, and propose wider use of whole exome sequencing in routine diagnostics. This applies in particular to nonspecific phenotypes with high heterogeneity, such as spastic paraplegia, intellectual disability, and muscular dystrophy, since in such cases the assignment of a definite diagnosis is frequently delayed.
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Affiliation(s)
- Hasan Tawamie
- Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Eva Wohlleber
- Institute of Human Genetics, University of Bonn, Bonn, Germany; Humangenetik Freibrug, Freiburg, Germany
| | - Steffen Uebe
- Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | | | - Markus M Nöthen
- Institute of Human Genetics, University of Bonn, Bonn, Germany; Department of Genomics, Life and Brain Center, University Bonn, Bonn, Germany
| | - Rami Abou Jamra
- Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany; Centogene, Rostock, Germany.
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15
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Milewska M, Byrne PC. Different expression levels of spartin cause broad spectrum of cellular consequences in human neuroblastoma cells. Cell Biol Int 2015; 39:1007-15. [PMID: 25821002 DOI: 10.1002/cbin.10472] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Accepted: 03/19/2015] [Indexed: 11/11/2022]
Abstract
Hereditary spastic paraplegia describes a diverse group of neurodegenerative conditions characterised by progressive spasticity and weakness of the lower limbs. Mutations in the SPG20 gene encoding spartin cause an autosomal recessive hereditary spastic paraplegia known as Troyer syndrome. To evaluate the cellular consequences of sustained spartin depletion in neuronal cells, we established several clonal SH-SY5Y cell lines with different level of spartin knockdown. Here, we report that cells with modest spartin downregulation show signs of neuronal differentiation such as increased neuritogenesis and cytoskeleton rearrangement. Interestingly, we also indicate that permanent high level spartin depletion results in impaired cell growth and multiple mitochondrial aberrations, which we speculate, arise as a result of chronic oxidative stress. Our studies demonstrate that the scale of spartin downregulation is the major factor that determines the severity of cellular consequences observed and suggest that there is a critical level of spartin expression which must be maintained for proper cellular functions.
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Affiliation(s)
- Malgorzata Milewska
- School of Medicine and Medical Science, Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4, Ireland
| | - Paula Catherine Byrne
- School of Medicine and Medical Science, Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4, Ireland
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16
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Zhao J, Hedera P. Strumpellin and Spartin, Hereditary Spastic Paraplegia Proteins, are Binding Partners. J Exp Neurosci 2015; 9:15-25. [PMID: 25987849 PMCID: PMC4426939 DOI: 10.4137/jen.s22969] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Revised: 04/06/2015] [Accepted: 04/10/2015] [Indexed: 01/02/2023] Open
Abstract
Hereditary spastic paraplegia (HSP) is one of the most heterogeneous neurodegenerative diseases with more than 50 identified genes causing a relatively stereotypical phenotypic presentation. Recent studies of HSP pathogenesis have suggested the existence of shared biochemical pathways that are crucial for axonal maintenance and degeneration. We explored possible interactions of several proteins associated with this condition. Here we report interactions of endogenous and overexpressed strumpellin with another HSP-associated protein, spartin. This biochemical interaction does not appear to be a part of the Wiskott–Aldrich syndrome protein and Scar homologue (WASH) complex because spartin is not co-immunoprecipitated with WASH1 protein. The spartin–strumpellin association does not require the presence of the microtubule interacting and trafficking domain of spartin. Over-expression of mutant forms of strumpellin with the introduced HSP-causing mutations does not alter the colocalization of these two proteins. Knockdown of strumpellin in cultured cortical rat neurons interferes with development of neuronal branching and results in reduced expression of endogenous spartin. Proteosomal inhibition stabilized the levels of spartin and WASH1 proteins, supporting increased spartin degradation in the absence of strumpellin.
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Affiliation(s)
- Jiali Zhao
- Department of Neurology, Vanderbilt University, Nashville, TN, USA
| | - Peter Hedera
- Department of Neurology, Vanderbilt University, Nashville, TN, USA. ; Center for Molecular Neuroscience, Vanderbilt University, Nashville, TN, USA
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18
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Tokunaga M, Shiheido H, Hayakawa I, Utsumi A, Takashima H, Doi N, Horisawa K, Sakuma-Yonemura Y, Tabata N, Yanagawa H. Hereditary spastic paraplegia protein spartin is an FK506-binding protein identified by mRNA display. ACTA ACUST UNITED AC 2014; 20:935-42. [PMID: 23890011 DOI: 10.1016/j.chembiol.2013.05.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Revised: 05/22/2013] [Accepted: 05/24/2013] [Indexed: 11/15/2022]
Abstract
Here, we used mRNA display to search for proteins that bind to FK506, a potent immunosuppressant drug, and identified spartin, a hereditary spastic paraplegia protein, from a human brain cDNA library. We demonstrated that FK506 binds to the C-terminal region of spartin and thereby inhibits the interaction of spartin with TIP47, one of the lipid droplet-associated proteins. We further confirmed that FK506 inhibits localization of spartin and its binder, an E3 ubiquitin ligase AIP4, in lipid droplets and increases the protein level of ADRP (adipose differentiation-related protein), which is a regulator of lipid homeostasis. These results strongly suggest that FK506 suppresses the proteasomal degradation of ADRP, a substrate of AIP4, by inhibiting the spartin-TIP47 interaction and thereby blocking the localization of spartin and AIP4 in lipid droplets.
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Affiliation(s)
- Mayuko Tokunaga
- Department of Biosciences and Informatics, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan
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19
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Lo Giudice T, Lombardi F, Santorelli FM, Kawarai T, Orlacchio A. Hereditary spastic paraplegia: clinical-genetic characteristics and evolving molecular mechanisms. Exp Neurol 2014; 261:518-39. [PMID: 24954637 DOI: 10.1016/j.expneurol.2014.06.011] [Citation(s) in RCA: 244] [Impact Index Per Article: 24.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2014] [Revised: 06/07/2014] [Accepted: 06/12/2014] [Indexed: 12/12/2022]
Abstract
Hereditary spastic paraplegia (HSP) is a group of clinically and genetically heterogeneous neurological disorders characterized by pathophysiologic hallmark of length-dependent distal axonal degeneration of the corticospinal tracts. The prominent features of this pathological condition are progressive spasticity and weakness of the lower limbs. To date, 72 spastic gait disease-loci and 55 spastic paraplegia genes (SPGs) have been identified. All modes of inheritance (autosomal dominant, autosomal recessive, and X-linked) have been described. Recently, a late onset spastic gait disorder with maternal trait of inheritance has been reported, as well as mutations in genes not yet classified as spastic gait disease. Several cellular processes are involved in its pathogenesis, such as membrane and axonal transport, endoplasmic reticulum membrane modeling and shaping, mitochondrial function, DNA repair, autophagy, and abnormalities in lipid metabolism and myelination processes. Moreover, recent evidences have been found about the impairment of endosome membrane trafficking in vesicle formation and about the involvement of oxidative stress and mtDNA polymorphisms in the onset of the disease. Interactome networks have been postulated by bioinformatics and biological analyses of spastic paraplegia genes, which would contribute to the development of new therapeutic approaches.
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Affiliation(s)
- Temistocle Lo Giudice
- Laboratorio di Neurogenetica, Centro Europeo di Ricerca sul Cervello (CERC) - Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Santa Lucia, Rome, Italy; Dipartimento di Medicina dei Sistemi, Università di Roma "Tor Vergata", Rome, Italy
| | - Federica Lombardi
- Laboratorio di Neurogenetica, Centro Europeo di Ricerca sul Cervello (CERC) - Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Santa Lucia, Rome, Italy
| | - Filippo Maria Santorelli
- Unità Operativa Complessa di Medicina Molecolare, Neurogenetica e Malattie Neurodegenerative, IRCCS Stella Maris, Pisa, Italy
| | - Toshitaka Kawarai
- Department of Clinical Neuroscience, Institute of Health Biosciences, Graduate School of Medicine, University of Tokushima, Tokushima, Japan
| | - Antonio Orlacchio
- Laboratorio di Neurogenetica, Centro Europeo di Ricerca sul Cervello (CERC) - Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Santa Lucia, Rome, Italy; Dipartimento di Medicina dei Sistemi, Università di Roma "Tor Vergata", Rome, Italy.
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20
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Karlsson AB, Washington J, Dimitrova V, Hooper C, Shekhtman A, Bakowska JC. The role of spartin and its novel ubiquitin binding region in DALIS occurrence. Mol Biol Cell 2014; 25:1355-65. [PMID: 24523286 PMCID: PMC3982999 DOI: 10.1091/mbc.e13-11-0705] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Troyer syndrome is an autosomal recessive hereditary spastic paraplegia (HSP) caused by frameshift mutations in the SPG20 gene that results in a lack of expression of the truncated protein. Spartin is a multifunctional protein, yet only two conserved domains--a microtubule-interacting and trafficking domain and a plant-related senescence domain involved in cytokinesis and mitochondrial physiology, respectively--have been defined. We have shown that overexpressed spartin binds to the Ile44 hydrophobic pocket of ubiquitin, suggesting spartin might contain a ubiquitin-binding domain. In the present study, we demonstrate that spartin contributes to the formation of dendritic aggresome-like induced structures (DALIS) through a unique ubiquitin-binding region (UBR). Using short hairpin RNA, we knocked down spartin in RAW264.7 cells and found that DALIS frequency decreased; conversely, overexpression of spartin increased the percentage of cells containing DALIS. Using nuclear magnetic resonance spectroscopy, we characterized spartin's UBR and defined the UBR's amino acids that are key for ubiquitin binding. We also found that spartin, via the UBR, binds Lys-63-linked ubiquitin chains but does not bind Lys-48-linked ubiquitin chains. Finally, we demonstrate that spartin's role in DALIS formation depends on key residues within its UBR.
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Affiliation(s)
- Amelia B Karlsson
- Department of Molecular Pharmacology and Therapeutics, Loyola University Chicago, Maywood, IL 60153 Department of Chemistry, State University of New York at Albany, Albany, NY 12222 Department of Physiology, University of Pennsylvania, Philadelphia, PA 19104 Department of Oncology, University of Wisconsin-Madison, Madison, WI 53705
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21
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Renvoisé B, Stadler J, Singh R, Bakowska JC, Blackstone C. Spg20-/- mice reveal multimodal functions for Troyer syndrome protein spartin in lipid droplet maintenance, cytokinesis and BMP signaling. Hum Mol Genet 2012; 21:3604-18. [PMID: 22619377 DOI: 10.1093/hmg/dds191] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Hereditary spastic paraplegias (HSPs; SPG1-48) are inherited neurological disorders characterized by lower extremity spasticity and weakness. Loss-of-function mutations in the SPG20 gene encoding spartin cause autosomal recessive Troyer syndrome (SPG20), which has additional features of short stature, cognitive deficits and distal amyotrophy. To identify cellular impairments underlying Troyer syndrome, we generated Spg20-/- mice, which exhibit progressive gait defects. Although gross central nervous system pathology appeared largely normal, cerebral cortical neurons cultured from neonatal Spg20-/- mice exhibited increased axon branching, a phenotype suppressed by reintroducing spartin and which required its interaction with the endosomal sorting complex required for transport (ESCRT)-III protein IST1. Analysis of the bone morphogenetic protein (BMP) signaling pathway in Spg20-/- embryonic fibroblasts indicated that Smad1/5 phosphorylation is modestly elevated, possibly due to alterations in BMP receptor trafficking. Cytokinesis was impaired in embryonic fibroblasts cultured from Spg20-/- mice, and binucleated chondrocytes were prominent in epiphyseal growth plates of bones in Spg20-/- mice, perhaps explaining the short stature of patients. Finally, adipose tissue from Spg20-/- female mice exhibited increased lipid droplet (LD) numbers and alterations in perilipin levels, supporting a role for spartin in LD maintenance. Taken together, our results support multimodal functions for spartin that provide important insights into HSP pathogenesis.
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Affiliation(s)
- Benoît Renvoisé
- Cell Biology Section, Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
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22
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Finsterer J, Löscher W, Quasthoff S, Wanschitz J, Auer-Grumbach M, Stevanin G. Hereditary spastic paraplegias with autosomal dominant, recessive, X-linked, or maternal trait of inheritance. J Neurol Sci 2012; 318:1-18. [PMID: 22554690 DOI: 10.1016/j.jns.2012.03.025] [Citation(s) in RCA: 207] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2012] [Revised: 03/25/2012] [Accepted: 03/29/2012] [Indexed: 12/12/2022]
Abstract
Hereditary spastic paraplegia (SPG) is a clinically and genetically heterogeneous group of neurodegenerative disorders that are clinically characterised by progressive spasticity and weakness of the lower-limbs (pure SPG) and, majoritorian, additional more extensive neurological or non-neurological manifestations (complex or complicated SPG). Pure SPG is characterised by progressive spasticity and weakness of the lower-limbs, and occasionally sensory disturbances or bladder dysfunction. Complex SPGs additionally include cognitive impairment, dementia, epilepsy, extrapyramidal disturbances, cerebellar involvement, retinopathy, optic atrophy, deafness, polyneuropathy, or skin lesions in the absence of coexisting disorders. Nineteen SPGs follow an autosomal-dominant (AD-SPG), 27 an autosomal-recessive (AR-SPG), 5 X-linked (XL-SPG), and one a maternal trait of inheritance. SPGs are due to mutations in genes encoding for proteins involved in the maintenance of corticospinal tract neurons. Among the AD-SPGs, 40-45% of patients carry mutations in the SPAST-gene (SPG4) and 10% in the ATL1-gene (SPG3), while the other 9 genes are more rarely involved (NIPA1 (SPG6), KIAA0196 (SPG8), KIF5A (SPG10), RNT2 (SPG12), SPGD1 (SPG13), BSCL2 (SPG17), REEP1 (SPG31), ZFYVE27 (SPG33, debated), and SLC33A1 (SPG42, debated)). Among the AR-SPGs, ~20% of the patients carry mutations in the KIAA1840 (SPG11) gene whereas the 15 other genes are rarely mutated and account for SPGs in single families yet (CYP7B1 (SPG5), SPG7 (SPG7), ZFYVE26 (SPG15), ERLIN2 (SPG18), SPG20 (SPG20), ACP33 (SPG21), KIF1A (SPG30), FA2H (SPG35), NTE (SPG39), GJA12/GJC2 (SPG44), KIAA0415 (SPG48) and 4 genes encoding for the AP4-complex (SPG47)). Among the XL-SPGs, 3 causative genes have been identified (L1CAM (SPG1), PLP1 (SPG2), and SLC16A2 (SPG22)). The diagnosis of SPGs is based on clinical, instrumental and genetic investigations. Treatment is exclusively symptomatic.
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Abstract
Human voluntary movement is controlled by the pyramidal motor system, a long CNS pathway comprising corticospinal and lower motor neurons. Hereditary spastic paraplegias (HSPs) are a large, genetically diverse group of inherited neurologic disorders characterized by a length-dependent distal axonopathy of the corticospinal tracts, resulting in lower limb spasticity and weakness. A range of studies are converging on alterations in the shaping of organelles, particularly the endoplasmic reticulum, as well as intracellular membrane trafficking and distribution as primary defects underlying the HSPs, with clear relevance for other long axonopathies affecting peripheral nerves and lower motor neurons.
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Affiliation(s)
- Craig Blackstone
- Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA.
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24
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Lacroix B, Maddox AS. Cytokinesis, ploidy and aneuploidy. J Pathol 2011; 226:338-51. [DOI: 10.1002/path.3013] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2011] [Revised: 09/22/2011] [Accepted: 09/24/2011] [Indexed: 12/21/2022]
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Urbanczyk A, Enz R. Spartin recruits PKC-ζ via the PKC-ζ-interacting proteins ZIP1 and ZIP3 to lipid droplets. J Neurochem 2011; 118:737-48. [PMID: 21707618 DOI: 10.1111/j.1471-4159.2011.07367.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Protein kinase C-ζ interacting proteins (ZIP1-3) recruit the enzymatic activity of the atypical protein kinase C isoforms PKC-λ/ι or PKC-ζ to target proteins. In this study, we searched for binding partners of ZIP3 in the CNS and identified spartin, a multifunctional protein that is mutated in spastic paraplegia type 20. In transfected cells, spartin was present on the surface of lipid droplets (LD), whereas ZIP proteins appeared in intracellular speckles. In the presence of spartin, ZIP1 and ZIP3 were translocated to spartin-positive LD. This translocation was mediated by amino acids 196-393 of spartin that interacted with an N-terminal region of ZIP proteins. Furthermore, ZIP proteins interacted simultaneously with spartin and PKC-ζ, resulting in an enrichment of PKC-ζ on spartin/ZIP-labelled LD. Without spartin, neither ZIP proteins nor PKC-ζ were detected on LD. Interestingly, the presence of the spartin/ZIP/PKC-ζ complex increased LD size. This effect was most pronounced upon incorporation of the ZIP3 isoform into the trimer. Finally, we co-localized spartin, ZIP proteins and PKC-ζ in axon terminals of neurons in the mammalian retina. In summary, we describe spartin as new binding partner of the ZIP/PKC-ζ dimer that recruits PKC-ζ to LD and show that the expressed ZIP isoform regulates LD size.
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Affiliation(s)
- Andreas Urbanczyk
- Institut für Biochemie (Emil-Fischer-Zentrum), Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
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26
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Wang H, Xin B. Hypertrophic cardiomyopathy in the Amish community — What we may learn from it. PROGRESS IN PEDIATRIC CARDIOLOGY 2011. [DOI: 10.1016/j.ppedcard.2011.02.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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27
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Joshi DC, Bakowska JC. SPG20 protein spartin associates with cardiolipin via its plant-related senescence domain and regulates mitochondrial Ca2+ homeostasis. PLoS One 2011; 6:e19290. [PMID: 21559443 PMCID: PMC3084803 DOI: 10.1371/journal.pone.0019290] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2010] [Accepted: 04/01/2011] [Indexed: 12/15/2022] Open
Abstract
Hereditary spastic paraplegias (HSPs) are a group of neurological disorders characterized clinically by spasticity of lower limbs and pathologically by degeneration of the corticospinal tract. Troyer syndrome is an autosomal recessive HSP caused by a frameshift mutation in the spartin (SPG20) gene. Previously, we established that this mutation results in a lack of expression of the truncated mutant spartin protein. Spartin is involved in many cellular processes and associates with several intracellular organelles, including mitochondria. Spartin contains a conserved plant-related senescence domain at its C-terminus. However, neither the function of this domain nor the roles of spartin in mitochondrial physiology are currently known. In this study, we determined that the plant-related senescence domain of spartin interacts with cardiolipin but not with two other major mitochondrial phospholipids, phosphatidylcholine and phosphatidylethanolamine. We also found that knockdown of spartin by small interfering RNA in a human neuroblastoma cell line resulted in depolarization of the mitochondrial membrane. In addition, depletion of spartin resulted in a significant decrease in both mitochondrial calcium uptake and mitochondrial membrane potential in cells treated with thapsigargin. Our results suggest that impairment of mitochondrial calcium uptake might contribute to the neurodegeneration of long corticospinal axons and the pathophysiology of Troyer syndrome.
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Affiliation(s)
- Dinesh C. Joshi
- Department of Molecular Pharmacology and Therapeutics, Loyola University Chicago, Maywood, Illinois, United States of America
| | - Joanna C. Bakowska
- Department of Molecular Pharmacology and Therapeutics, Loyola University Chicago, Maywood, Illinois, United States of America
- * E-mail:
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28
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Lind GE, Raiborg C, Danielsen SA, Rognum TO, Thiis-Evensen E, Hoff G, Nesbakken A, Stenmark H, Lothe RA. SPG20, a novel biomarker for early detection of colorectal cancer, encodes a regulator of cytokinesis. Oncogene 2011; 30:3967-78. [PMID: 21499309 PMCID: PMC3174365 DOI: 10.1038/onc.2011.109] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Colorectal cancer is a common disease with high mortality. Suitable biomarkers for detection of tumors at an early curable stage would significantly improve patient survival. Here, we show that the SPG20 (spastic paraplegia-20) promoter, encoding the multifunctional Spartin protein, is hypermethylated in 89% of colorectal carcinomas, 78% of adenomas and only 1% of normal mucosa samples. SPG20 methylation was also present in a pilot series of stool samples and corresponding tumors from colorectal cancer patients. SPG20 promoter hypermethylation resulted in loss of mRNA expression in various cancer types and subsequent depletion of Spartin. We further showed that Spartin downregulation in cancer cells resulted in cytokinesis arrest, which was reversed when SPG20 methylation was inhibited. The present study identifies SPG20 promoter hypermethylation as a biomarker suitable for non-invasive detection of colorectal cancer, and a possible mechanism for cytokinesis arrest in colorectal tumorigenesis.
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Affiliation(s)
- G E Lind
- Department of Cancer Prevention, Institute for Cancer Research, Radiumhospitalet, Oslo University Hospital, Oslo, Norway
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29
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Renvoisé B, Parker RL, Yang D, Bakowska JC, Hurley JH, Blackstone C. SPG20 protein spartin is recruited to midbodies by ESCRT-III protein Ist1 and participates in cytokinesis. Mol Biol Cell 2010; 21:3293-303. [PMID: 20719964 PMCID: PMC2947466 DOI: 10.1091/mbc.e09-10-0879] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Hereditary spastic paraplegias (HSPs, SPG1-46) are inherited neurological disorders characterized by lower extremity spastic weakness. Loss-of-function SPG20 gene mutations cause an autosomal recessive HSP known as Troyer syndrome. The SPG20 protein spartin localizes to lipid droplets and endosomes, and it interacts with tail interacting protein 47 (TIP47) as well as the ubiquitin E3 ligases atrophin-1-interacting protein (AIP)4 and AIP5. Spartin harbors a domain contained within microtubule-interacting and trafficking molecules (MIT) at its N-terminus, and most proteins with MIT domains interact with specific ESCRT-III proteins. Using yeast two-hybrid and in vitro surface plasmon resonance assays, we demonstrate that the spartin MIT domain binds with micromolar affinity to the endosomal sorting complex required for transport (ESCRT)-III protein increased sodium tolerance (Ist)1 but not to ESCRT-III proteins charged multivesicular body proteins 1-7. Spartin colocalizes with Ist1 at the midbody, and depletion of Ist1 in cells by small interfering RNA significantly decreases the number of cells where spartin is present at midbodies. Depletion of spartin does not affect Ist1 localization to midbodies but markedly impairs cytokinesis. A structure-based amino acid substitution in the spartin MIT domain (F24D) blocks the spartin-Ist1 interaction. Spartin F24D does not localize to the midbody and acts in a dominant-negative manner to impair cytokinesis. These data suggest that Ist1 interaction is important for spartin recruitment to the midbody and that spartin participates in cytokinesis.
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Affiliation(s)
- Benoît Renvoisé
- Cellular Neurology Unit, Neurogenetics Branch, National Institute of Neurological Disorders and Stroke and Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
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30
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Hooper C, Puttamadappa SS, Loring Z, Shekhtman A, Bakowska JC. Spartin activates atrophin-1-interacting protein 4 (AIP4) E3 ubiquitin ligase and promotes ubiquitination of adipophilin on lipid droplets. BMC Biol 2010; 8:72. [PMID: 20504295 PMCID: PMC2887783 DOI: 10.1186/1741-7007-8-72] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2010] [Accepted: 05/26/2010] [Indexed: 01/01/2023] Open
Abstract
Background Spartin protein is involved in degradation of epidermal growth factor receptor and turnover of lipid droplets and a lack of expression of this protein is responsible for hereditary spastic paraplegia type 20 (SPG20). Spartin is a multifunctional protein that associates with many cellular organelles, including lipid droplets. Recent studies showed that spartin interacts with E3 ubiquitin ligases that belong to the neural precursor cell-expressed developmentally downregulated gene (Nedd4) family, including atrophin-1-interacting protein 4 (AIP4/ITCH). However, the biological importance of the spartin-AIP4 interaction remains unknown. Results In this study, we show that spartin is not a substrate for AIP4 activity and that spartin's binding to AIP4 significantly increases self-ubiquitination of this E3 ligase, indicating that spartin disrupts the AIP4 autoinhibitory intramolecular interaction. Correspondingly, spartin has a seven times higher binding affinity to the WW region of AIP4 than the binding of the WW region has to the catalytic homologues of the E6-associated protein C-terminus (HECT) domain, as measured by enzyme-linked immunosorbent assay. We also show that spartin recruits AIP4 to lipid droplets and promotes ubiquitination of lipid droplet-associated protein, adipophilin, which regulates turnover of lipid droplets. Conclusions Our findings demonstrate that spartin acts as an adaptor protein that activates and recruits AIP4 E3 ubiquitin ligase to lipid droplets and by this means regulates the level of ubiquitination of adipophilin and potentially other lipid-associated proteins. We propose that this is one of the mechanisms by which spartin regulates lipid droplet turnover and might contribute to the pathology of SPG20.
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Affiliation(s)
- Christopher Hooper
- Department of Molecular Pharmacology and Therapeutics, Loyola Chicago University, Maywood, IL, USA
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31
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Manzini MC, Rajab A, Maynard TM, Mochida GH, Tan WH, Nasir R, Hill RS, Gleason D, Al Saffar M, Partlow JN, Barry BJ, Vernon M, LaMantia AS, Walsh CA. Developmental and degenerative features in a complicated spastic paraplegia. Ann Neurol 2010; 67:516-25. [PMID: 20437587 PMCID: PMC3027847 DOI: 10.1002/ana.21923] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Objective We sought to explore the genetic and molecular causes of Troyer syndrome, one of several complicated hereditary spastic paraplegias (HSPs). Troyer syndrome had been thought to be restricted to the Amish; however, we identified 2 Omani families with HSP, short stature, dysarthria and developmental delay—core features of Troyer syndrome—and a novel mutation in the SPG20 gene, which is also mutated in the Amish. In addition, we analyzed SPG20 expression throughout development to infer how disruption of this gene might generate the constellation of developmental and degenerative Troyer syndrome phenotypes. Methods Clinical characterization of 2 non-Amish families with Troyer syndrome was followed by linkage and sequencing analysis. Quantitative polymerase chain reaction and in situ hybridization analysis of SPG20 expression were carried out in embryonic and adult human and mouse tissue. Results Two Omani families carrying a novel SPG20 mutation displayed clinical features remarkably similar to the Amish patients with Troyer syndrome. SPG20 mRNA is expressed broadly but at low relative levels in the adult brain; however, it is robustly and specifically expressed in the limbs, face, and brain during early morphogenesis. Interpretation Null mutations in SPG20 cause Troyer syndrome, a specific clinical entity with developmental and degenerative features. Maximal expression of SPG20 in the limb buds and forebrain during embryogenesis may explain the developmental origin of the skeletal and cognitive defects observed in this disorder. ANN NEUROL 2010;67:516–525
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Affiliation(s)
- M Chiara Manzini
- Department of Neurology, Howard Hughes Medical Institute, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02115, USA
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Meilleur KG, Traoré M, Sangaré M, Britton A, Landouré G, Coulibaly S, Niaré B, Mochel F, La Pean A, Rafferty I, Watts C, Shriner D, Littleton-Kearney MT, Blackstone C, Singleton A, Fischbeck KH. Hereditary spastic paraplegia and amyotrophy associated with a novel locus on chromosome 19. Neurogenetics 2009; 11:313-8. [PMID: 20039086 DOI: 10.1007/s10048-009-0230-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2009] [Accepted: 11/29/2009] [Indexed: 10/20/2022]
Abstract
We identified a family in Mali with two sisters affected by spastic paraplegia. In addition to spasticity and weakness of the lower limbs, the patients had marked atrophy of the distal upper extremities. Homozygosity mapping using single nucleotide polymorphism arrays showed that the sisters shared a region of extended homozygosity at chromosome 19p13.11-q12 that was not shared by controls. These findings indicate a clinically and genetically distinct form of hereditary spastic paraplegia with amyotrophy, designated SPG43.
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Affiliation(s)
- K G Meilleur
- Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA.
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Milewska M, McRedmond J, Byrne PC. Identification of novel spartin-interactors shows spartin is a multifunctional protein. J Neurochem 2009; 111:1022-30. [PMID: 19765186 DOI: 10.1111/j.1471-4159.2009.06382.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Hereditary spastic paraplegia describes a group of neurodegenerative diseases characterized by lower limb progressive weakness and spasticity. Troyer syndrome is an autosomal recessive form of hereditary spastic paraplegia caused by a frameshift mutation (1110delA) in the SPG20 gene encoding spartin protein, the cellular function of which remains unknown. Knowledge about spartin-interactors is also very limited. In this study, we apply a broad spectrum of proteomics techniques to identify novel spartin-binding proteins. We used a Tandem Affinity Purification technique followed by HPLC-mass spectrometry to characterize potential spartin-binding partners. Selected putative interactions were confirmed by co-immunoprecipitation experiments. We identified 94 potential spartin-binding proteins which were grouped into functional categories. We performed co-immunoprecipitation experiments to confirm that spartin interacts with GRP78, GRP75 and nucleolin proteins. Additionally, our mass spectrometry results confirmed previously published information about spartin interaction with ubiquitin and the E3 ubiquitin-protein ligases, AIP4/Itch and AIP5/WWP1. Our studies suggest that spartin is a multifunctional protein and for the first time we suggest a role for spartin in protein folding and turnover both in mitochondria and endoplasmic reticulum. We also show for the first time interaction between spartin and a nucleolar protein, nucleolin.
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Affiliation(s)
- Malgorzata Milewska
- School of Medicine and Medical Science, Conway Institute, University College Dublin, Ireland
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Endogenous spartin (SPG20) is recruited to endosomes and lipid droplets and interacts with the ubiquitin E3 ligases AIP4 and AIP5. Biochem J 2009; 423:31-9. [PMID: 19580544 PMCID: PMC2762690 DOI: 10.1042/bj20082398] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The HSPs (hereditary spastic paraplegias) are genetic conditions in which there is distal degeneration of the longest axons of the corticospinal tract, resulting in spastic paralysis of the legs. The gene encoding spartin is mutated in Troyer syndrome, an HSP in which paralysis is accompanied by additional clinical features. There has been controversy over the subcellular distribution of spartin. We show here that, at steady state, endogenous spartin exists in a cytosolic pool that can be recruited to endosomes and to lipid droplets. Cytosolic endogenous spartin is mono-ubiquitinated and we demonstrate that it interacts via a PPXY motif with the ubiquitin E3 ligases AIP4 [atrophin-interacting protein 4; WWP2 (WW domain-containing E3 ubiquitin protein ligase 2] and AIP5 (WWP1). Surprisingly, the PPXY motif, AIP4 and AIP5 are not required for spartin's ubiquitination, and so we propose that spartin acts as an adaptor for these proteins. Our results suggest that spartin is involved in diverse cellular functions, which may be of relevance to the complex phenotype seen in Troyer syndrome.
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Tsang HTH, Edwards TL, Wang X, Connell JW, Davies RJ, Durrington HJ, O'Kane CJ, Luzio JP, Reid E. The hereditary spastic paraplegia proteins NIPA1, spastin and spartin are inhibitors of mammalian BMP signalling. Hum Mol Genet 2009; 18:3805-21. [PMID: 19620182 PMCID: PMC2748891 DOI: 10.1093/hmg/ddp324] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The hereditary spastic paraplegias (HSPs) are genetic conditions characterized by distal axonopathy of the longest corticospinal tract axons, and so their study provides an important opportunity to understand mechanisms involved in axonal maintenance and degeneration. A group of HSP genes encode proteins that localize to endosomes. One of these is NIPA1 (non-imprinted in Prader-Willi/Angelman syndrome 1) and we have shown recently that its Drosophila homologue spichthyin inhibits bone morphogenic protein (BMP) signalling, although the relevance of this finding to the mammalian protein was not known. We show here that mammalian NIPA1 is also an inhibitor of BMP signalling. NIPA1 physically interacts with the type II BMP receptor (BMPRII) and we demonstrate that this interaction does not require the cytoplasmic tail of BMPRII. We show that the mechanism by which NIPA1 inhibits BMP signalling involves downregulation of BMP receptors by promoting their endocytosis and lysosomal degradation. Disease-associated mutant versions of NIPA1 alter the trafficking of BMPRII and are less efficient at promoting BMPRII degradation than wild-type NIPA1. In addition, we demonstrate that two other members of the endosomal group of HSP proteins, spastin and spartin, are inhibitors of BMP signalling. Since BMP signalling is important for distal axonal function, we propose that dysregulation of BMP signalling could be a unifying pathological component in this endosomal group of HSPs, and perhaps of importance in other conditions in which distal axonal degeneration is found.
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Affiliation(s)
- Hilda T H Tsang
- Cambridge Institute for Medical Research, Addenbrooke's Hospital, UK
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Eastman SW, Yassaee M, Bieniasz PD. A role for ubiquitin ligases and Spartin/SPG20 in lipid droplet turnover. ACTA ACUST UNITED AC 2009; 184:881-94. [PMID: 19307600 PMCID: PMC2699154 DOI: 10.1083/jcb.200808041] [Citation(s) in RCA: 105] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
HECT (homologous to the E6AP C terminus) ubiquitin ligases have diverse functions in eukaryotic cells. In screens for proteins that bind to the HECT ubiquitin ligase WWP1, we identified Spartin, which is also known as SPG20. This protein is truncated in a neurological disease, Troyer syndrome. In this study, we show that SPG20 associates with the surface of lipid droplets (LDs) and can regulate their size and number. SPG20 binds to another LD protein, TIP47, and both proteins compete with an additional LD protein, adipophilin/adipocyte differentiation-related protein, for occupancy of LDs. The mutant SPG20 present in Troyer syndrome does not possess these activities. Depletion of SPG20 using RNA interference increases the number and size of LDs when cells are fed with oleic acid. Binding of WWP1 to SPG20 and the consequent ubiquitin transfer remove SPG20 from LDs and reduce the levels of coexpressed SPG20. These experiments suggest functions for ubiquitin ligases and SPG20 in the regulation of LD turnover and potential pathological mechanisms in Troyer syndrome.
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Affiliation(s)
- Scott W Eastman
- Howard Hughes Medical Institute, The Rockefeller University, New York, NY 10065, USA
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