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Sharma G, Paganin M, Lauria F, Perenthaler E, Viero G. The SMN-ribosome interplay: a new opportunity for Spinal Muscular Atrophy therapies. Biochem Soc Trans 2024; 52:465-479. [PMID: 38391004 PMCID: PMC10903476 DOI: 10.1042/bst20231116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Revised: 02/12/2024] [Accepted: 02/13/2024] [Indexed: 02/24/2024]
Abstract
The underlying cause of Spinal Muscular Atrophy (SMA) is in the reduction of survival motor neuron (SMN) protein levels due to mutations in the SMN1 gene. The specific effects of SMN protein loss and the resulting pathological alterations are not fully understood. Given the crucial roles of the SMN protein in snRNP biogenesis and its interactions with ribosomes and translation-related proteins and mRNAs, a decrease in SMN levels below a specific threshold in SMA is expected to affect translational control of gene expression. This review covers both direct and indirect SMN interactions across various translation-related cellular compartments and processes, spanning from ribosome biogenesis to local translation and beyond. Additionally, it aims to outline deficiencies and alterations in translation observed in SMA models and patients, while also discussing the implications of the relationship between SMN protein and the translation machinery within the context of current and future therapies.
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2
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Custer SK, Gilson T, Astroski JW, Nanguneri SR, Iurillo AM, Androphy EJ. COPI coatomer subunit α-COP interacts with the RNA binding protein Nucleolin via a C-terminal dilysine motif. Hum Mol Genet 2023; 32:3263-3275. [PMID: 37658769 PMCID: PMC10656708 DOI: 10.1093/hmg/ddad140] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Revised: 08/07/2023] [Accepted: 08/30/2023] [Indexed: 09/05/2023] Open
Abstract
The COPI coatomer subunit α-COP has been shown to co-precipitate mRNA in multiple settings, but it was unclear whether the interaction with mRNA was direct or mediated by interaction with an adapter protein. The COPI complex often interacts with proteins via C-terminal dilysine domains. A search for candidate RNA binding proteins with C-terminal dilysine motifs yielded Nucleolin, which terminates in a KKxKxx sequence. This protein was an especially intriguing candidate as it has been identified as an interacting partner for Survival Motor Neuron protein (SMN). Loss of SMN causes the neurodegenerative disease Spinal Muscular Atrophy. We have previously shown that SMN and α-COP interact and co-migrate in axons, and that overexpression of α-COP reduced phenotypic severity in cell culture and animal models of SMA. We show here that in an mRNA independent manner, endogenous Nucleolin co-precipitates endogenous α-COP and ε-COP but not β-COP which may reflect an interaction with the so-called B-subcomplex rather a complete COPI heptamer. The ability of Nucleolin to bind to α-COP requires the presence of the C-terminal KKxKxx domain of Nucleolin. Furthermore, we have generated a point mutant in the WD40 domain of α-COP which eliminates its ability to co-precipitate Nucleolin but does not interfere with precipitation of partners mediated by non-KKxKxx motifs such as the kainate receptor subunit 2. We propose that via interaction between the C-terminal dilysine motif of Nucleolin and the WD40 domain of α-COP, Nucleolin acts an adaptor to allow α-COP to interact with a population of mRNA.
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Affiliation(s)
- Sara K Custer
- Dermatology, Indiana University School of Medicine, 545 Barnhill Drive, Emerson Hall 139, Indianapolis, IN 46202, United States
| | - Timra Gilson
- Dermatology, Indiana University School of Medicine, 545 Barnhill Drive, Emerson Hall 139, Indianapolis, IN 46202, United States
| | - Jacob W Astroski
- Dermatology, Indiana University School of Medicine, 545 Barnhill Drive, Emerson Hall 139, Indianapolis, IN 46202, United States
| | - Siddarth R Nanguneri
- Dermatology, Indiana University School of Medicine, 545 Barnhill Drive, Emerson Hall 139, Indianapolis, IN 46202, United States
| | - Alyssa M Iurillo
- Indiana University School of Medicine, 340 West 10 St, Indianapolis, IN 46202, United States
| | - Elliot J Androphy
- Dermatology, Indiana University School of Medicine, 545 Barnhill Drive, Emerson Hall 139, Indianapolis, IN 46202, United States
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3
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Maddison DC, Malik B, Amadio L, Bis-Brewer DM, Züchner S, Peters OM, Smith GA. COPI-regulated mitochondria-ER contact site formation maintains axonal integrity. Cell Rep 2023; 42:112883. [PMID: 37498742 PMCID: PMC10840514 DOI: 10.1016/j.celrep.2023.112883] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Revised: 06/05/2023] [Accepted: 07/12/2023] [Indexed: 07/29/2023] Open
Abstract
Coat protein complex I (COPI) is best known for its role in Golgi-endoplasmic reticulum (ER) trafficking, responsible for the retrograde transport of ER-resident proteins. The ER is crucial to neuronal function, regulating Ca2+ homeostasis and the distribution and function of other organelles such as endosomes, peroxisomes, and mitochondria via functional contact sites. Here we demonstrate that disruption of COPI results in mitochondrial dysfunction in Drosophila axons and human cells. The ER network is also disrupted, and the neurons undergo rapid degeneration. We demonstrate that mitochondria-ER contact sites (MERCS) are decreased in COPI-deficient axons, leading to Ca2+ dysregulation, heightened mitophagy, and a decrease in respiratory capacity. Reintroducing MERCS is sufficient to rescue not only mitochondrial distribution and Ca2+ uptake but also ER morphology, dramatically delaying neurodegeneration. This work demonstrates an important role for COPI-mediated trafficking in MERC formation, which is an essential process for maintaining axonal integrity.
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Affiliation(s)
- Daniel C Maddison
- UK Dementia Research Institute, School of Medicine, Cardiff University, Cardiff CF24 4HQ, UK
| | - Bilal Malik
- UK Dementia Research Institute, School of Biosciences, Cardiff University, Cardiff CF24 4HQ, UK
| | - Leonardo Amadio
- UK Dementia Research Institute, School of Medicine, Cardiff University, Cardiff CF24 4HQ, UK; UK Dementia Research Institute, School of Biosciences, Cardiff University, Cardiff CF24 4HQ, UK
| | - Dana M Bis-Brewer
- John P. Hussman Institute for Human Genomics, University of Miami, Miami, FL, USA; Dr. John T. Macdonald Foundation Department of Human Genetics, University of Miami, Miami, FL, USA
| | - Stephan Züchner
- John P. Hussman Institute for Human Genomics, University of Miami, Miami, FL, USA; Dr. John T. Macdonald Foundation Department of Human Genetics, University of Miami, Miami, FL, USA
| | - Owen M Peters
- UK Dementia Research Institute, School of Biosciences, Cardiff University, Cardiff CF24 4HQ, UK
| | - Gaynor A Smith
- UK Dementia Research Institute, School of Medicine, Cardiff University, Cardiff CF24 4HQ, UK.
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4
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Nakevska Z, Yokota T. Challenges and future perspective of antisense therapy for spinal muscular atrophy: A review. Eur J Cell Biol 2023; 102:151326. [PMID: 37295266 DOI: 10.1016/j.ejcb.2023.151326] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2022] [Revised: 05/18/2023] [Accepted: 05/20/2023] [Indexed: 06/12/2023] Open
Abstract
Spinal muscular atrophy (SMA), the most common genetic cause of infantile death, is caused by a mutation in the survival of motor neuron 1 gene (SMN1), leading to the death of motor neurons and progressive muscle weakness. SMN1 normally produces an essential protein called SMN. Although humans possess a paralogous gene called SMN2, ∼90% of the SMN it produces is non-functional. This is due to a mutation in SMN2 that causes the skipping of a required exon during splicing of the pre-mRNA. The first treatment for SMA, nusinersen (brand name Spinraza), was approved by the FDA in 2016 and by the EMU in 2017. Nusinersen is an antisense oligonucleotide-based therapy that alters the splicing of SMN2 to make functional full-length SMN protein. Despite the recent advancements in antisense oligonucleotide therapy and SMA treatment development, nusinersen is faced with a multitude of challenges, such as intracellular and systemic delivery. In recent years, the use of peptide-conjugated phosphorodiamidate morpholino oligomers (PPMOs) in antisense therapy has gained interest. These are antisense oligonucleotides conjugated to cell-penetrating peptides such as Pips and DG9, and they have the potential to address the challenges associated with delivery. This review focuses on the historic milestones, development, current challenges, and future perspectives of antisense therapy for SMA.
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Affiliation(s)
- Zorica Nakevska
- Department of Biological Sciences, Faculty of Science, University of Alberta, 116 St. and 85 Ave., Edmonton AB T6G 2E1, Canada.
| | - Toshifumi Yokota
- Neuroscience and Mental Health Institute, Faculty of Medicine and Dentistry, University of Alberta, 116 St. and 85 Ave., Edmonton AB T6G 2E1, Canada; Department of Medical Genetics, Faculty of Medicine and Dentistry, University of Alberta, 116 St. and 85 Ave., Edmonton AB T6G 2E1, Canada; The Friends of Garret Cumming Research and Muscular Dystrophy Canada HM Toupin Neurological Science Research Chair, 8812 112 St., Edmonton AB T6G 2H7, Canada.
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5
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Tonello F, Massimino ML, Peggion C. Nucleolin: a cell portal for viruses, bacteria, and toxins. Cell Mol Life Sci 2022; 79:271. [PMID: 35503380 PMCID: PMC9064852 DOI: 10.1007/s00018-022-04300-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Revised: 04/08/2022] [Accepted: 04/10/2022] [Indexed: 12/18/2022]
Abstract
The main localization of nucleolin is the nucleolus, but this protein is present in multiple subcellular sites, and it is unconventionally secreted. On the cell surface, nucleolin acts as a receptor for various viruses, some bacteria, and some toxins. Aim of this review is to discuss the characteristics that make nucleolin able to act as receptor or co-receptor of so many and different pathogens. The important features that emerge are its multivalence, and its role as a bridge between the cell surface and the nucleus. Multiple domains, short linear motifs and post-translational modifications confer and modulate nucleolin ability to interact with nucleic acids, with proteins, but also with carbohydrates and lipids. This modular multivalence allows nucleolin to participate in different types of biomolecular condensates and to move to various subcellular locations, where it can act as a kind of molecular glue. It moves from the nucleus to the cell surface and can accompany particles in the reverse direction, from the cell surface into the nucleus, which is the destination of several pathogens to manipulate the cell in their favour.
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Affiliation(s)
- Fiorella Tonello
- CNR of Italy, Neuroscience Institute, viale G. Colombo 3, 35131, Padua, Italy.
| | | | - Caterina Peggion
- Department of Biomedical Sciences, University of Padua, Via Ugo Bassi, 58/B, 35131, Padua, Italy
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6
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Varderidou-Minasian S, Verheijen BM, Harschnitz O, Kling S, Karst H, van der Pol WL, Pasterkamp RJ, Altelaar M. Spinal Muscular Atrophy Patient iPSC-Derived Motor Neurons Display Altered Proteomes at Early Stages of Differentiation. ACS OMEGA 2021; 6:35375-35388. [PMID: 34984269 PMCID: PMC8717385 DOI: 10.1021/acsomega.1c04688] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Accepted: 11/24/2021] [Indexed: 05/08/2023]
Abstract
Spinal muscular atrophy (SMA) is an autosomal recessive neurodegenerative disorder characterized by loss of motor neurons (MN) in the spinal cord leading to progressive muscle atrophy and weakness. SMA is caused by mutations in the survival motor neuron 1 (SMN1) gene, resulting in reduced levels of survival motor neuron (SMN) protein. The mechanisms that link SMN deficiency to selective motor neuron dysfunction in SMA remain largely unknown. We present here, for the first time, a comprehensive quantitative TMT-10plex proteomics analysis that covers the development of induced pluripotent stem cell-derived MNs from both healthy individuals and SMA patients. We show that the proteomes of SMA samples segregate from controls already at early stages of neuronal differentiation. The altered proteomic signature in SMA MNs is associated with mRNA splicing, ribonucleoprotein biogenesis, organelle organization, cellular biogenesis, and metabolic processes. We highlight several known SMN-binding partners and evaluate their expression changes during MN differentiation. In addition, we compared our study to human and mouse in vivo proteomic studies revealing distinct and similar signatures. Altogether, our work provides a comprehensive resource of molecular events during early stages of MN differentiation, containing potentially therapeutically interesting protein expression profiles for SMA.
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Affiliation(s)
- Suzy Varderidou-Minasian
- Biomolecular
Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular
Research and Utrecht Institute for Pharmaceutical Sciences, University of Utrecht, Padualaan 8, 3584
CH Utrecht, The Netherlands
- Netherlands
Proteomics Center, Padualaan
8, 3584 CH Utrecht, The Netherlands
| | - Bert M. Verheijen
- Department
of Translational Neuroscience, UMC Utrecht Brain Center, University
Medical Center Utrecht, Utrecht University, 3584 CG Utrecht, The Netherlands
- Department
of Neurology and Neurosurgery, UMC Utrecht Brain Center, University
Medical Center Utrecht, Utrecht University, 3584 CX Utrecht, The Netherlands
| | - Oliver Harschnitz
- Department
of Translational Neuroscience, UMC Utrecht Brain Center, University
Medical Center Utrecht, Utrecht University, 3584 CG Utrecht, The Netherlands
- Department
of Neurology and Neurosurgery, UMC Utrecht Brain Center, University
Medical Center Utrecht, Utrecht University, 3584 CX Utrecht, The Netherlands
| | - Sandra Kling
- Department
of Translational Neuroscience, UMC Utrecht Brain Center, University
Medical Center Utrecht, Utrecht University, 3584 CG Utrecht, The Netherlands
- Department
of Neurology and Neurosurgery, UMC Utrecht Brain Center, University
Medical Center Utrecht, Utrecht University, 3584 CX Utrecht, The Netherlands
| | - Henk Karst
- Department
of Translational Neuroscience, UMC Utrecht Brain Center, University
Medical Center Utrecht, Utrecht University, 3584 CG Utrecht, The Netherlands
| | - W. Ludo van der Pol
- Department
of Neurology and Neurosurgery, UMC Utrecht Brain Center, University
Medical Center Utrecht, Utrecht University, 3584 CX Utrecht, The Netherlands
| | - R. Jeroen Pasterkamp
- Department
of Translational Neuroscience, UMC Utrecht Brain Center, University
Medical Center Utrecht, Utrecht University, 3584 CG Utrecht, The Netherlands
| | - Maarten Altelaar
- Biomolecular
Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular
Research and Utrecht Institute for Pharmaceutical Sciences, University of Utrecht, Padualaan 8, 3584
CH Utrecht, The Netherlands
- Netherlands
Proteomics Center, Padualaan
8, 3584 CH Utrecht, The Netherlands
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7
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CaMKK2 facilitates Golgi-associated vesicle trafficking to sustain cancer cell proliferation. Cell Death Dis 2021; 12:1040. [PMID: 34725334 PMCID: PMC8560770 DOI: 10.1038/s41419-021-04335-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2021] [Revised: 10/13/2021] [Accepted: 10/19/2021] [Indexed: 12/19/2022]
Abstract
Calcium/calmodulin-dependent protein kinase kinase 2 (CaMKK2) regulates cell and whole-body metabolism and supports tumorigenesis. The cellular impacts of perturbing CAMKK2 expression are, however, not yet fully characterised. By knocking down CAMKK2 levels, we have identified a number of significant subcellular changes indicative of perturbations in vesicle trafficking within the endomembrane compartment. To determine how they might contribute to effects on cell proliferation, we have used proteomics to identify Gemin4 as a direct interactor, capable of binding CAMKK2 and COPI subunits. Prompted by this, we confirmed that CAMKK2 knockdown leads to concomitant and significant reductions in δ-COP protein. Using imaging, we show that CAMKK2 knockdown leads to Golgi expansion, the induction of ER stress, abortive autophagy and impaired lysosomal acidification. All are phenotypes of COPI depletion. Based on our findings, we hypothesise that CAMKK2 sustains cell proliferation in large part through effects on organelle integrity and membrane trafficking.
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8
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Sechi S, Karimpour-Ghahnavieh A, Frappaolo A, Di Francesco L, Piergentili R, Schininà E, D’Avino PP, Giansanti MG. Identification of GOLPH3 Partners in Drosophila Unveils Potential Novel Roles in Tumorigenesis and Neural Disorders. Cells 2021; 10:cells10092336. [PMID: 34571985 PMCID: PMC8468827 DOI: 10.3390/cells10092336] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Revised: 09/01/2021] [Accepted: 09/03/2021] [Indexed: 12/28/2022] Open
Abstract
Golgi phosphoprotein 3 (GOLPH3) is a highly conserved peripheral membrane protein localized to the Golgi apparatus and the cytosol. GOLPH3 binding to Golgi membranes depends on phosphatidylinositol 4-phosphate [PI(4)P] and regulates Golgi architecture and vesicle trafficking. GOLPH3 overexpression has been correlated with poor prognosis in several cancers, but the molecular mechanisms that link GOLPH3 to malignant transformation are poorly understood. We recently showed that PI(4)P-GOLPH3 couples membrane trafficking with contractile ring assembly during cytokinesis in dividing Drosophila spermatocytes. Here, we use affinity purification coupled with mass spectrometry (AP-MS) to identify the protein-protein interaction network (interactome) of Drosophila GOLPH3 in testes. Analysis of the GOLPH3 interactome revealed enrichment for proteins involved in vesicle-mediated trafficking, cell proliferation and cytoskeleton dynamics. In particular, we found that dGOLPH3 interacts with the Drosophila orthologs of Fragile X mental retardation protein and Ataxin-2, suggesting a potential role in the pathophysiology of disorders of the nervous system. Our findings suggest novel molecular targets associated with GOLPH3 that might be relevant for therapeutic intervention in cancers and other human diseases.
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Affiliation(s)
- Stefano Sechi
- Istituto di Biologia e Patologia Molecolari del CNR, c/o Dipartimento di Biologia e Biotecnologie, Sapienza Università di Roma, Piazzale A. Moro 5, 00185 Roma, Italy; (S.S.); (A.K.-G.); (A.F.); (R.P.)
| | - Angela Karimpour-Ghahnavieh
- Istituto di Biologia e Patologia Molecolari del CNR, c/o Dipartimento di Biologia e Biotecnologie, Sapienza Università di Roma, Piazzale A. Moro 5, 00185 Roma, Italy; (S.S.); (A.K.-G.); (A.F.); (R.P.)
| | - Anna Frappaolo
- Istituto di Biologia e Patologia Molecolari del CNR, c/o Dipartimento di Biologia e Biotecnologie, Sapienza Università di Roma, Piazzale A. Moro 5, 00185 Roma, Italy; (S.S.); (A.K.-G.); (A.F.); (R.P.)
| | - Laura Di Francesco
- Dipartimento di Scienze Biochimiche A. Rossi Fanelli, Sapienza Università di Roma, Piazzale A. Moro 5, 00185 Roma, Italy; (L.D.F.); (E.S.)
| | - Roberto Piergentili
- Istituto di Biologia e Patologia Molecolari del CNR, c/o Dipartimento di Biologia e Biotecnologie, Sapienza Università di Roma, Piazzale A. Moro 5, 00185 Roma, Italy; (S.S.); (A.K.-G.); (A.F.); (R.P.)
| | - Eugenia Schininà
- Dipartimento di Scienze Biochimiche A. Rossi Fanelli, Sapienza Università di Roma, Piazzale A. Moro 5, 00185 Roma, Italy; (L.D.F.); (E.S.)
| | - Pier Paolo D’Avino
- Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK;
| | - Maria Grazia Giansanti
- Istituto di Biologia e Patologia Molecolari del CNR, c/o Dipartimento di Biologia e Biotecnologie, Sapienza Università di Roma, Piazzale A. Moro 5, 00185 Roma, Italy; (S.S.); (A.K.-G.); (A.F.); (R.P.)
- Correspondence: ; Tel.: +39-064-991-2555
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9
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Blatnik AJ, McGovern VL, Burghes AHM. What Genetics Has Told Us and How It Can Inform Future Experiments for Spinal Muscular Atrophy, a Perspective. Int J Mol Sci 2021; 22:8494. [PMID: 34445199 PMCID: PMC8395208 DOI: 10.3390/ijms22168494] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Revised: 07/28/2021] [Accepted: 08/04/2021] [Indexed: 02/06/2023] Open
Abstract
Proximal spinal muscular atrophy (SMA) is an autosomal recessive neurodegenerative disorder characterized by motor neuron loss and subsequent atrophy of skeletal muscle. SMA is caused by deficiency of the essential survival motor neuron (SMN) protein, canonically responsible for the assembly of the spliceosomal small nuclear ribonucleoproteins (snRNPs). Therapeutics aimed at increasing SMN protein levels are efficacious in treating SMA. However, it remains unknown how deficiency of SMN results in motor neuron loss, resulting in many reported cellular functions of SMN and pathways affected in SMA. Herein is a perspective detailing what genetics and biochemistry have told us about SMA and SMN, from identifying the SMA determinant region of the genome, to the development of therapeutics. Furthermore, we will discuss how genetics and biochemistry have been used to understand SMN function and how we can determine which of these are critical to SMA moving forward.
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Affiliation(s)
| | | | - Arthur H. M. Burghes
- Department of Biological Chemistry & Pharmacology, The Ohio State University Wexner Medical Center, Rightmire Hall, Room 168, 1060 Carmack Road, Columbus, OH 43210, USA; (A.J.B.III); (V.L.M.)
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10
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Macken WL, Godwin A, Wheway G, Stals K, Nazlamova L, Ellard S, Alfares A, Aloraini T, AlSubaie L, Alfadhel M, Alajaji S, Wai HA, Self J, Douglas AGL, Kao AP, Guille M, Baralle D. Biallelic variants in COPB1 cause a novel, severe intellectual disability syndrome with cataracts and variable microcephaly. Genome Med 2021; 13:34. [PMID: 33632302 PMCID: PMC7908744 DOI: 10.1186/s13073-021-00850-w] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Accepted: 02/11/2021] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND Coat protein complex 1 (COPI) is integral in the sorting and retrograde trafficking of proteins and lipids from the Golgi apparatus to the endoplasmic reticulum (ER). In recent years, coat proteins have been implicated in human diseases known collectively as "coatopathies". METHODS Whole exome or genome sequencing of two families with a neuro-developmental syndrome, variable microcephaly and cataracts revealed biallelic variants in COPB1, which encodes the beta-subunit of COPI (β-COP). To investigate Family 1's splice donor site variant, we undertook patient blood RNA studies and CRISPR/Cas9 modelling of this variant in a homologous region of the Xenopus tropicalis genome. To investigate Family 2's missense variant, we studied cellular phenotypes of human retinal epithelium and embryonic kidney cell lines transfected with a COPB1 expression vector into which we had introduced Family 2's mutation. RESULTS We present a new recessive coatopathy typified by severe developmental delay and cataracts and variable microcephaly. A homozygous splice donor site variant in Family 1 results in two aberrant transcripts, one of which causes skipping of exon 8 in COPB1 pre-mRNA, and a 36 amino acid in-frame deletion, resulting in the loss of a motif at a small interaction interface between β-COP and β'-COP. Xenopus tropicalis animals with a homologous mutation, introduced by CRISPR/Cas9 genome editing, recapitulate features of the human syndrome including microcephaly and cataracts. In vitro modelling of the COPB1 c.1651T>G p.Phe551Val variant in Family 2 identifies defective Golgi to ER recycling of this mutant β-COP, with the mutant protein being retarded in the Golgi. CONCLUSIONS This adds to the growing body of evidence that COPI subunits are essential in brain development and human health and underlines the utility of exome and genome sequencing coupled with Xenopus tropicalis CRISPR/Cas modelling for the identification and characterisation of novel rare disease genes.
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Affiliation(s)
- William L Macken
- Wessex Clinical Genetics Service, Princess Anne Hospital, University Hospital Southampton NHS Foundation Trust, Coxford Rd, Southampton, SO165YA, UK
| | - Annie Godwin
- European Xenopus Resource Centre, University of Portsmouth School of Biological Sciences, King Henry Building, King Henry I Street, Portsmouth, PO1 2DY, UK
| | - Gabrielle Wheway
- Faculty of Medicine, University of Southampton, Duthie Building, Southampton General Hospital, Tremona Road, Southampton, SO16 6YD, UK
| | - Karen Stals
- Exeter Genomics Laboratory, Level 3 RILD building, Royal Devon & Exeter NHS Foundation Trust, Barrack Road, Exeter, EX2 5DW, UK
| | - Liliya Nazlamova
- Faculty of Medicine, University of Southampton, Duthie Building, Southampton General Hospital, Tremona Road, Southampton, SO16 6YD, UK
| | - Sian Ellard
- Exeter Genomics Laboratory, Level 3 RILD building, Royal Devon & Exeter NHS Foundation Trust, Barrack Road, Exeter, EX2 5DW, UK
- University of Exeter Medical School, RILD building, Royal Devon & Exeter NHS Foundation Trust, Barrack Road, Exeter, EX2 5DW, UK
| | - Ahmed Alfares
- Department of Pediatrics, College of Medicine, Qassim University, Qassim, Saudi Arabia
- Department of Pathology and Laboratory Medicine, King Abdulaziz Medical City, Riyadh, Saudi Arabia
| | - Taghrid Aloraini
- Department of Pathology and Laboratory Medicine, King Abdulaziz Medical City, Riyadh, Saudi Arabia
| | - Lamia AlSubaie
- Division of Genetics, Department of Pediatrics, King Abdullah Specialized Children Hospital, King Abdulaziz Medical City, Ministry of National Guard Health Affairs (MNGHA), Riyadh, Saudi Arabia
- King Abdullah International Medical Research Centre, Ministry of National Guard Health Affairs (MNGHA), Riyadh, Saudi Arabia
| | - Majid Alfadhel
- Division of Genetics, Department of Pediatrics, King Abdullah Specialized Children Hospital, King Abdulaziz Medical City, Ministry of National Guard Health Affairs (MNGHA), Riyadh, Saudi Arabia
- King Abdullah International Medical Research Centre, Ministry of National Guard Health Affairs (MNGHA), Riyadh, Saudi Arabia
- King Saud bin Abdulaziz University for Health Sciences, Ministry of National Guard Health Affairs (MNGHA), Riyadh, Saudi Arabia
| | - Sulaiman Alajaji
- King Saud bin Abdulaziz University for Health Sciences, Ministry of National Guard Health Affairs (MNGHA), Riyadh, Saudi Arabia
- Division of Allergy and Clinical Immunology, Department of Pediatrics, King Abdullah Specialized Children Hospital, King Abdulaziz Medical City, Ministry of National Guard Health Affairs (MNGHA), Riyadh, Saudi Arabia
| | - Htoo A Wai
- Faculty of Medicine, University of Southampton, Duthie Building, Southampton General Hospital, Tremona Road, Southampton, SO16 6YD, UK
| | - Jay Self
- Faculty of Medicine, University of Southampton, Duthie Building, Southampton General Hospital, Tremona Road, Southampton, SO16 6YD, UK
| | - Andrew G L Douglas
- Wessex Clinical Genetics Service, Princess Anne Hospital, University Hospital Southampton NHS Foundation Trust, Coxford Rd, Southampton, SO165YA, UK
- Faculty of Medicine, University of Southampton, Duthie Building, Southampton General Hospital, Tremona Road, Southampton, SO16 6YD, UK
| | - Alexander P Kao
- Zeiss Global Centre, School of Mechanical and Design Engineering, University of Portsmouth, Portsmouth, PO1 3DJ, UK
| | - Matthew Guille
- European Xenopus Resource Centre, University of Portsmouth School of Biological Sciences, King Henry Building, King Henry I Street, Portsmouth, PO1 2DY, UK.
| | - Diana Baralle
- Wessex Clinical Genetics Service, Princess Anne Hospital, University Hospital Southampton NHS Foundation Trust, Coxford Rd, Southampton, SO165YA, UK.
- Faculty of Medicine, University of Southampton, Duthie Building, Southampton General Hospital, Tremona Road, Southampton, SO16 6YD, UK.
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11
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Astroski JW, Akporyoe LK, Androphy EJ, Custer SK. Mutations in the COPI coatomer subunit α-COP induce release of Aβ-42 and amyloid precursor protein intracellular domain and increase tau oligomerization and release. Neurobiol Aging 2021; 101:57-69. [PMID: 33582567 DOI: 10.1016/j.neurobiolaging.2021.01.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Revised: 12/02/2020] [Accepted: 01/06/2021] [Indexed: 12/14/2022]
Abstract
Understanding the cellular processes that lead to Alzheimer's disease (AD) is critical, and one key lies in the genetics of families with histories of AD. Mutations a complex known as COPI were found in families with AD. The COPI complex is involved in protein processing and trafficking. Intriguingly, several recent publications have found components of the COPI complex can affect the metabolism of pathogenic AD proteins. We reduced levels of the COPI subunit α-COP, altering maturation and cleavage of amyloid precursor protein (APP), resulting in decreased release of Aβ-42 and decreased accumulation of the AICD. Depletion of α-COP reduced uptake of proteopathic Tau seeds and reduces intracellular Tau self-association. Expression of AD-associated mutant α-COP altered APP processing, resulting in increased release of Aβ-42 and increased intracellular Tau aggregation and release of Tau oligomers. These results show that COPI coatomer function modulates processing of both APP and Tau, and expression of AD-associated α-COP confers a toxic gain of function, resulting in potentially pathogenic changes in both APP and Tau.
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Affiliation(s)
- Jacob W Astroski
- Department of Dermatology, Indiana University School of Medicine, Indianapolis, IN, USA
| | | | - Elliot J Androphy
- Department of Dermatology, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Sara K Custer
- Department of Dermatology, Indiana University School of Medicine, Indianapolis, IN, USA.
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12
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Blatnik AJ, McGovern VL, Le TT, Iyer CC, Kaspar BK, Burghes AHM. Conditional deletion of SMN in cell culture identifies functional SMN alleles. Hum Mol Genet 2020; 29:3477-3492. [PMID: 33075805 DOI: 10.1093/hmg/ddaa229] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Revised: 10/01/2020] [Accepted: 10/12/2020] [Indexed: 12/31/2022] Open
Abstract
Spinal muscular atrophy (SMA) is caused by mutation or deletion of survival motor neuron 1 (SMN1) and retention of SMN2 leading to SMN protein deficiency. We developed an immortalized mouse embryonic fibroblast (iMEF) line in which full-length wild-type Smn (flwt-Smn) can be conditionally deleted using Cre recombinase. iMEFs lacking flwt-Smn are not viable. We tested the SMA patient SMN1 missense mutation alleles A2G, D44V, A111G, E134K and T274I in these cells to determine which human SMN (huSMN) mutant alleles can function in the absence of flwt-Smn. All missense mutant alleles failed to rescue survival in the conditionally deleted iMEFs. Thus, the function lost by these mutations is essential to cell survival. However, co-expression of two different huSMN missense mutants can rescue iMEF survival and small nuclear ribonucleoprotein (snRNP) assembly, demonstrating intragenic complementation of SMN alleles. In addition, we show that a Smn protein lacking exon 2B can rescue iMEF survival and snRNP assembly in the absence of flwt-Smn, indicating exon 2B is not required for the essential function of Smn. For the first time, using this novel cell line, we can assay the function of SMN alleles in the complete absence of flwt-Smn.
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Affiliation(s)
- Anton J Blatnik
- Ohio State Biochemistry Program.,Biological Chemistry & Pharmacology
| | | | | | | | - Brian K Kaspar
- Center for Gene Therapy, Nationwide Children's Hospital; Department of Pediatrics, College of Medicine and Public Health, The Ohio State University; and Department of Neuroscience, The Ohio State University, Columbus, OH 43210, USA
| | - Arthur H M Burghes
- Ohio State Biochemistry Program.,Biological Chemistry & Pharmacology.,Molecular Genetics.,Department of Neurology, The Ohio State University Wexner Medical Center, Columbus OH 43210 USA
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13
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Baron DM, Matheny T, Lin YC, Leszyk JD, Kenna K, Gall KV, Santos DP, Tischbein M, Funes S, Hayward LJ, Kiskinis E, Landers JE, Parker R, Shaffer SA, Bosco DA. Quantitative proteomics identifies proteins that resist translational repression and become dysregulated in ALS-FUS. Hum Mol Genet 2020; 28:2143-2160. [PMID: 30806671 DOI: 10.1093/hmg/ddz048] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2018] [Revised: 02/01/2019] [Accepted: 02/07/2019] [Indexed: 12/13/2022] Open
Abstract
Aberrant translational repression is a feature of multiple neurodegenerative diseases. The association between disease-linked proteins and stress granules further implicates impaired stress responses in neurodegeneration. However, our knowledge of the proteins that evade translational repression is incomplete. It is also unclear whether disease-linked proteins influence the proteome under conditions of translational repression. To address these questions, a quantitative proteomics approach was used to identify proteins that evade stress-induced translational repression in arsenite-treated cells expressing either wild-type or amyotrophic lateral sclerosis (ALS)-linked mutant FUS. This study revealed hundreds of proteins that are actively synthesized during stress-induced translational repression, irrespective of FUS genotype. In addition to proteins involved in RNA- and protein-processing, proteins associated with neurodegenerative diseases such as ALS were also actively synthesized during stress. Protein synthesis under stress was largely unperturbed by mutant FUS, although several proteins were found to be differentially expressed between mutant and control cells. One protein in particular, COPBI, was downregulated in mutant FUS-expressing cells under stress. COPBI is the beta subunit of the coat protein I (COPI), which is involved in Golgi to endoplasmic reticulum (ER) retrograde transport. Further investigation revealed reduced levels of other COPI subunit proteins and defects in COPBI-relatedprocesses in cells expressing mutant FUS. Even in the absence of stress, COPBI localization was altered in primary and human stem cell-derived neurons expressing ALS-linked FUS variants. Our results suggest that Golgi to ER retrograde transport may be important under conditions of stress and is perturbed upon the expression of disease-linked proteins such as FUS.
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Affiliation(s)
- Desiree M Baron
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Tyler Matheny
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO, USA
| | - Yen-Chen Lin
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA, USA
| | - John D Leszyk
- Department of Biochemistry and Molecular Pharmacology, Worcester, MA, USA.,Mass Spectrometry Facility, University of Massachusetts Medical School, Shrewsbury, MA, USA
| | - Kevin Kenna
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA, USA.,Department of Neurology, Brain Center Rudolf Magnus, University Medical Center Utrecht, University of Utrecht, Utrecht, The Netherlands
| | - Katherine V Gall
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA, USA
| | - David P Santos
- The Ken & Ruth Davee Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA.,Department of Physiology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Maeve Tischbein
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Salome Funes
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Lawrence J Hayward
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Evangelos Kiskinis
- The Ken & Ruth Davee Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA.,Department of Physiology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - John E Landers
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Roy Parker
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO, USA.,Howard Hughes Medical Institute, Chevy Chase, MD, USA
| | - Scott A Shaffer
- Department of Biochemistry and Molecular Pharmacology, Worcester, MA, USA.,Mass Spectrometry Facility, University of Massachusetts Medical School, Shrewsbury, MA, USA
| | - Daryl A Bosco
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA, USA.,Department of Biochemistry and Molecular Pharmacology, Worcester, MA, USA
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14
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Pushpalatha KV, Besse F. Local Translation in Axons: When Membraneless RNP Granules Meet Membrane-Bound Organelles. Front Mol Biosci 2019; 6:129. [PMID: 31824961 PMCID: PMC6882739 DOI: 10.3389/fmolb.2019.00129] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Accepted: 11/06/2019] [Indexed: 12/14/2022] Open
Abstract
Eukaryotic cell compartmentalization relies on long-known membrane-delimited organelles, as well as on more recently discovered membraneless macromolecular condensates. How these two types of organelles interact to regulate cellular functions is still largely unclear. In this review, we highlight how membraneless ribonucleoprotein (RNP) organelles, enriched in RNAs and associated regulatory proteins, cooperate with membrane-bound organelles for tight spatio-temporal control of gene expression in the axons of neuronal cells. Specifically, we present recent evidence that motile membrane-bound organelles are used as vehicles by RNP cargoes, promoting the long-range transport of mRNA molecules to distal axons. As demonstrated by recent work, membrane-bound organelles also promote local protein synthesis, by serving as platforms for the local translation of mRNAs recruited to their outer surface. Furthermore, dynamic and specific association between RNP cargoes and membrane-bound organelles is mediated by bi-partite adapter molecules that interact with both types of organelles selectively, in a regulated-manner. Maintaining such a dynamic interplay is critical, as alterations in this process are linked to neurodegenerative diseases. Together, emerging studies thus point to the coordination of membrane-bound and membraneless organelles as an organizing principle underlying local cellular responses.
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Affiliation(s)
| | - Florence Besse
- Université Côte d'Azur, CNRS, Inserm, Institut de Biology Valrose, Nice, France
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15
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Custer SK, Astroski JW, Li HX, Androphy EJ. Interaction between alpha-COP and SMN ameliorates disease phenotype in a mouse model of spinal muscular atrophy. Biochem Biophys Res Commun 2019; 514:530-537. [PMID: 31060774 DOI: 10.1016/j.bbrc.2019.04.176] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Accepted: 04/26/2019] [Indexed: 11/25/2022]
Abstract
We report that expression of the α-COP protein rescues disease phenotype in a severe mouse model of Spinal Muscular Atrophy (SMA). Lentiviral particles expressing α-COP were injected directly into the testes of genetically pure mouse strain of interest resulting in infection of the spermatagonial stem cells. α-COP was stably expressed in brain, skeletal muscle, and spinal cord without altering SMN protein levels. SMA mice transgenic for α-COP live significantly longer than their non-transgenic littermates, and showed increased body mass and normal muscle morphology at postnatal day 15. We previously reported that binding between SMN and α-COP is required for restoration of neurite outgrowth in cells lacking SMN, and we report similar finding here. Lentiviral-mediated transgenic expression of SMN where the dilysine domain in exon 2b was mutated was not able to rescue the SMA phenotype despite robust expression of the mutant SMN protein in brain, muscle and spinal cord. These results demonstrate that α-COP is a validated modifier of SMA disease phenotype in a mammalian, vertebrate model and is a potential target for development of future SMN-independent therapeutic interventions.
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Affiliation(s)
- Sara K Custer
- Indiana University School of Medicine, Dermatology, Indianapolis, IN, USA.
| | - Jacob W Astroski
- Indiana University School of Medicine, Dermatology, Indianapolis, IN, USA
| | - Hong Xia Li
- Indiana University School of Medicine, Dermatology, Indianapolis, IN, USA
| | - Elliot J Androphy
- Indiana University School of Medicine, Dermatology, Indianapolis, IN, USA
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16
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Šoltić D, Bowerman M, Stock J, Shorrock HK, Gillingwater TH, Fuller HR. Multi-Study Proteomic and Bioinformatic Identification of Molecular Overlap between Amyotrophic Lateral Sclerosis (ALS) and Spinal Muscular Atrophy (SMA). Brain Sci 2018; 8:brainsci8120212. [PMID: 30518112 PMCID: PMC6315439 DOI: 10.3390/brainsci8120212] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2018] [Revised: 11/28/2018] [Accepted: 11/30/2018] [Indexed: 12/24/2022] Open
Abstract
Unravelling the complex molecular pathways responsible for motor neuron degeneration in amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy (SMA) remains a persistent challenge. Interest is growing in the potential molecular similarities between these two diseases, with the hope of better understanding disease pathology for the guidance of therapeutic development. The aim of this study was to conduct a comparative analysis of published proteomic studies of ALS and SMA, seeking commonly dysregulated molecules to be prioritized as future therapeutic targets. Fifteen proteins were found to be differentially expressed in two or more proteomic studies of both ALS and SMA, and bioinformatics analysis identified over-representation of proteins known to associate in vesicles and molecular pathways, including metabolism of proteins and vesicle-mediated transport—both of which converge on endoplasmic reticulum (ER)-Golgi trafficking processes. Calreticulin, a calcium-binding chaperone found in the ER, was associated with both pathways and we independently confirm that its expression was decreased in spinal cords from SMA and increased in spinal cords from ALS mice. Together, these findings offer significant insights into potential common targets that may help to guide the development of new therapies for both diseases.
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Affiliation(s)
- Darija Šoltić
- School of Medicine, Keele University, Staffordshire ST5 5BG, UK; (D.S.); (M.B.)
- Institute for Science and Technology in Medicine, Keele University, Staffordshire ST5 5BG, UK
- Wolfson Centre for Inherited Neuromuscular Disease, RJAH Orthopaedic Hospital, Oswestry SY10 7AG, UK
| | - Melissa Bowerman
- School of Medicine, Keele University, Staffordshire ST5 5BG, UK; (D.S.); (M.B.)
- Institute for Science and Technology in Medicine, Keele University, Staffordshire ST5 5BG, UK
- Wolfson Centre for Inherited Neuromuscular Disease, RJAH Orthopaedic Hospital, Oswestry SY10 7AG, UK
| | - Joanne Stock
- School of Medicine, Keele University, Staffordshire ST5 5BG, UK; (D.S.); (M.B.)
- Institute for Science and Technology in Medicine, Keele University, Staffordshire ST5 5BG, UK
- Wolfson Centre for Inherited Neuromuscular Disease, RJAH Orthopaedic Hospital, Oswestry SY10 7AG, UK
| | - Hannah K. Shorrock
- Biomedical Sciences, Edinburgh Medical School, University of Edinburgh, Edinburgh EH8 9AG, UK; (H.K.S.); (T.H.G.)
- Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Edinburgh EH8 9AG, UK
| | - Thomas H. Gillingwater
- Biomedical Sciences, Edinburgh Medical School, University of Edinburgh, Edinburgh EH8 9AG, UK; (H.K.S.); (T.H.G.)
- Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Edinburgh EH8 9AG, UK
| | - Heidi R. Fuller
- School of Medicine, Keele University, Staffordshire ST5 5BG, UK; (D.S.); (M.B.)
- Institute for Science and Technology in Medicine, Keele University, Staffordshire ST5 5BG, UK
- Wolfson Centre for Inherited Neuromuscular Disease, RJAH Orthopaedic Hospital, Oswestry SY10 7AG, UK
- Correspondence: ; Tel.: +44-169-140-4693; Fax: +44-169-140-4065
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17
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Custer SK, Foster JN, Astroski JW, Androphy EJ. Abnormal Golgi morphology and decreased COPI function in cells with low levels of SMN. Brain Res 2018; 1706:135-146. [PMID: 30408476 DOI: 10.1016/j.brainres.2018.11.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Revised: 11/02/2018] [Accepted: 11/03/2018] [Indexed: 12/13/2022]
Abstract
We report here the finding of abnormal Golgi apparatus morphology in motor neuron like cells depleted of SMN as well as Golgi apparatus morphology in SMA patient fibroblasts. Rescue experiments demonstrate that this abnormality is dependent on SMN, but can also be rescued by expression of the COPI coatomer subunit alpha-COP. A motor neuron-like cell line containing an inducible alpha-COP shRNA was created to generate a parallel system to study knockdown of SMN or alpha-COP. Multiple assays of COPI-dependent intracellular trafficking in cells depleted of SMN demonstrate that alpha-COP function is suboptimal, including failed sequestration of plasma membrane proteins, altered binding of mRNA, and defective targeting and transport of Golgi-resident proteins.
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Affiliation(s)
- S K Custer
- Walther Hall, R3 C636, 980 West Walnut Street, Indianapolis, IN 46202, United States.
| | - J N Foster
- Walther Hall, R3 C636, 980 West Walnut Street, Indianapolis, IN 46202, United States.
| | - J W Astroski
- Walther Hall, R3 C636, 980 West Walnut Street, Indianapolis, IN 46202, United States.
| | - E J Androphy
- Walther Hall, R3 C636, 980 West Walnut Street, Indianapolis, IN 46202, United States.
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18
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Chaytow H, Huang YT, Gillingwater TH, Faller KME. The role of survival motor neuron protein (SMN) in protein homeostasis. Cell Mol Life Sci 2018; 75:3877-3894. [PMID: 29872871 PMCID: PMC6182345 DOI: 10.1007/s00018-018-2849-1] [Citation(s) in RCA: 111] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2018] [Revised: 05/30/2018] [Accepted: 05/31/2018] [Indexed: 12/11/2022]
Abstract
Ever since loss of survival motor neuron (SMN) protein was identified as the direct cause of the childhood inherited neurodegenerative disorder spinal muscular atrophy, significant efforts have been made to reveal the molecular functions of this ubiquitously expressed protein. Resulting research demonstrated that SMN plays important roles in multiple fundamental cellular homeostatic pathways, including a well-characterised role in the assembly of the spliceosome and biogenesis of ribonucleoproteins. More recent studies have shown that SMN is also involved in other housekeeping processes, including mRNA trafficking and local translation, cytoskeletal dynamics, endocytosis and autophagy. Moreover, SMN has been shown to influence mitochondria and bioenergetic pathways as well as regulate function of the ubiquitin-proteasome system. In this review, we summarise these diverse functions of SMN, confirming its key role in maintenance of the homeostatic environment of the cell.
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Affiliation(s)
- Helena Chaytow
- Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Edinburgh, UK
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh, UK
| | - Yu-Ting Huang
- Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Edinburgh, UK
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh, UK
| | - Thomas H Gillingwater
- Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Edinburgh, UK.
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh, UK.
| | - Kiterie M E Faller
- Euan MacDonald Centre for Motor Neurone Disease Research, University of Edinburgh, Edinburgh, UK
- Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh, UK
- Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh, UK
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19
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Suter B. RNA localization and transport. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2018; 1861:938-951. [PMID: 30496039 DOI: 10.1016/j.bbagrm.2018.08.004] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2018] [Revised: 08/23/2018] [Accepted: 08/23/2018] [Indexed: 12/30/2022]
Abstract
RNA localization serves numerous purposes from controlling development and differentiation to supporting the physiological activities of cells and organisms. After a brief introduction into the history of the study of mRNA localization I will focus on animal systems, describing in which cellular compartments and in which cell types mRNA localization was observed and studied. In recent years numerous novel localization patterns have been described, and countless mRNAs have been documented to accumulate in specific subcellular compartments. These fascinating revelations prompted speculations about the purpose of localizing all these mRNAs. In recent years experimental evidence for an unexpected variety of different functions has started to emerge. Aside from focusing on the functional aspects, I will discuss various ways of localizing mRNAs with a focus on the mechanism of active and directed transport on cytoskeletal tracks. Structural studies combined with imaging of transport and biochemical studies have contributed to the enormous recent progress, particularly in understanding how dynein/dynactin/BicD (DDB) dependent transport on microtubules works. This transport process actively localizes diverse cargo in similar ways to the minus end of microtubules and, at least in flies, also individual mRNA molecules. A sophisticated mechanism ensures that cargo loading licenses processive transport.
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Affiliation(s)
- Beat Suter
- Institute of Cell Biology, University of Bern, 3012 Bern, Switzerland.
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20
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Khalil B, Morderer D, Price PL, Liu F, Rossoll W. mRNP assembly, axonal transport, and local translation in neurodegenerative diseases. Brain Res 2018; 1693:75-91. [PMID: 29462608 PMCID: PMC5997521 DOI: 10.1016/j.brainres.2018.02.018] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Revised: 01/31/2018] [Accepted: 02/13/2018] [Indexed: 12/12/2022]
Abstract
The development, maturation, and maintenance of the mammalian nervous system rely on complex spatiotemporal patterns of gene expression. In neurons, this is achieved by the expression of differentially localized isoforms and specific sets of mRNA-binding proteins (mRBPs) that regulate RNA processing, mRNA trafficking, and local protein synthesis at remote sites within dendrites and axons. There is growing evidence that axons contain a specialized transcriptome and are endowed with the machinery that allows them to rapidly alter their local proteome via local translation and protein degradation. This enables axons to quickly respond to changes in their environment during development, and to facilitate axon regeneration and maintenance in adult organisms. Aside from providing autonomy to neuronal processes, local translation allows axons to send retrograde injury signals to the cell soma. In this review, we discuss evidence that disturbances in mRNP transport, granule assembly, axonal localization, and local translation contribute to pathology in various neurodegenerative diseases, including spinal muscular atrophy (SMA), amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD), and Alzheimer's disease (AD).
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Affiliation(s)
- Bilal Khalil
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL 32224 USA
| | - Dmytro Morderer
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL 32224 USA
| | - Phillip L Price
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL 32224 USA; Department of Cell Biology, Emory University, Atlanta, GA 30322 USA
| | - Feilin Liu
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL 32224 USA; Eye Center, The Second Hospital of Jilin University, Changchun, Jilin 130021, China
| | - Wilfried Rossoll
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL 32224 USA.
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21
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Thompson LW, Morrison KD, Shirran SL, Groen EJN, Gillingwater TH, Botting CH, Sleeman JE. Neurochondrin interacts with the SMN protein suggesting a novel mechanism for spinal muscular atrophy pathology. J Cell Sci 2018; 131:jcs.211482. [PMID: 29507115 PMCID: PMC5963842 DOI: 10.1242/jcs.211482] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Accepted: 02/16/2018] [Indexed: 12/15/2022] Open
Abstract
Spinal muscular atrophy (SMA) is an inherited neurodegenerative condition caused by a reduction in the amount of functional survival motor neuron (SMN) protein. SMN has been implicated in transport of mRNA in neural cells for local translation. We previously identified microtubule-dependent mobile vesicles rich in SMN and SNRPB, a member of the Sm family of small nuclear ribonucleoprotein (snRNP)-associated proteins, in neural cells. By comparing the interactomes of SNRPB and SNRPN, a neural-specific Sm protein, we now show that the essential neural protein neurochondrin (NCDN) interacts with Sm proteins and SMN in the context of mobile vesicles in neurites. NCDN has roles in protein localisation in neural cells and in maintenance of cell polarity. NCDN is required for the correct localisation of SMN, suggesting they may both be required for formation and transport of trafficking vesicles. NCDN may have potential as a therapeutic target for SMA together with, or in place of the targeting of SMN expression. This article has an associated First Person interview with the first author of the paper. Highlighted Article: The essential neural protein neurochondrin interacts with the spinal muscular atrophy (SMA) protein SMN in cell lines and in mice. This might be relevant to the molecular pathology of SMA.
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Affiliation(s)
- Luke W Thompson
- School of Biology, University of St Andrews, BSRC Complex, North Haugh St Andrews, KY16 9ST, UK
| | - Kim D Morrison
- School of Biology, University of St Andrews, BSRC Complex, North Haugh St Andrews, KY16 9ST, UK
| | - Sally L Shirran
- School of Biology, University of St Andrews, BSRC Complex, North Haugh St Andrews, KY16 9ST, UK
| | - Ewout J N Groen
- Edinburgh Medical School, Biomedical Sciences and Euan MacDonald Centre for Motor Neuron Disease Research, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, EH8 9XD, UK
| | - Thomas H Gillingwater
- Edinburgh Medical School, Biomedical Sciences and Euan MacDonald Centre for Motor Neuron Disease Research, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, EH8 9XD, UK
| | - Catherine H Botting
- School of Biology, University of St Andrews, BSRC Complex, North Haugh St Andrews, KY16 9ST, UK
| | - Judith E Sleeman
- School of Biology, University of St Andrews, BSRC Complex, North Haugh St Andrews, KY16 9ST, UK
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22
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Hosseinibarkooie S, Schneider S, Wirth B. Advances in understanding the role of disease-associated proteins in spinal muscular atrophy. Expert Rev Proteomics 2017. [PMID: 28635376 DOI: 10.1080/14789450.2017.1345631] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
INTRODUCTION Spinal muscular atrophy (SMA) is a neurodegenerative disorder characterized by alpha motor neuron loss in the spinal cord due to reduced survival motor neuron (SMN) protein level. While the genetic basis of SMA is well described, the specific molecular pathway underlying SMA is still not fully understood. Areas covered: This review discusses the recent advancements in understanding the molecular pathways in SMA using different omics approaches and genetic modifiers identified in both vertebrate and invertebrate systems. The findings that are summarized in this article were deduced from original articles and reviews with a particular focus on the latest advancements in the field. Expert commentary: The identification of genetic modifiers such as PLS3 and NCALD in humans or of SMA modulators such as Elavl4 (HuD), Copa, Uba1, Mapk10 (Jnk3), Nrxn2 and Tmem41b (Stasimon) in various SMA animal models improved our knowledge of impaired cellular pathways in SMA. Inspiration from modifier genes and their functions in motor neuron and neuromuscular junctions may open a new avenue for future SMA combinatorial therapies.
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Affiliation(s)
- Seyyedmohsen Hosseinibarkooie
- a Institute of Human Genetics , University of Cologne , Cologne , Germany.,b Center for Molecular Medicine Cologne , University of Cologne , Cologne , Germany.,c Institute for Genetics , University of Cologne , Cologne , Germany
| | - Svenja Schneider
- a Institute of Human Genetics , University of Cologne , Cologne , Germany.,b Center for Molecular Medicine Cologne , University of Cologne , Cologne , Germany.,c Institute for Genetics , University of Cologne , Cologne , Germany
| | - Brunhilde Wirth
- a Institute of Human Genetics , University of Cologne , Cologne , Germany.,b Center for Molecular Medicine Cologne , University of Cologne , Cologne , Germany.,c Institute for Genetics , University of Cologne , Cologne , Germany.,d Center for Rare Diseases Cologne , University Hospital of Cologne, University of Cologne , Cologne , Germany
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23
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Singh RN, Howell MD, Ottesen EW, Singh NN. Diverse role of survival motor neuron protein. BIOCHIMICA ET BIOPHYSICA ACTA. GENE REGULATORY MECHANISMS 2017; 1860:299-315. [PMID: 28095296 PMCID: PMC5325804 DOI: 10.1016/j.bbagrm.2016.12.008] [Citation(s) in RCA: 195] [Impact Index Per Article: 27.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2016] [Revised: 12/23/2016] [Accepted: 12/30/2016] [Indexed: 02/07/2023]
Abstract
The multifunctional Survival Motor Neuron (SMN) protein is required for the survival of all organisms of the animal kingdom. SMN impacts various aspects of RNA metabolism through the formation and/or interaction with ribonucleoprotein (RNP) complexes. SMN regulates biogenesis of small nuclear RNPs, small nucleolar RNPs, small Cajal body-associated RNPs, signal recognition particles and telomerase. SMN also plays an important role in DNA repair, transcription, pre-mRNA splicing, histone mRNA processing, translation, selenoprotein synthesis, macromolecular trafficking, stress granule formation, cell signaling and cytoskeleton maintenance. The tissue-specific requirement of SMN is dictated by the variety and the abundance of its interacting partners. Reduced expression of SMN causes spinal muscular atrophy (SMA), a leading genetic cause of infant mortality. SMA displays a broad spectrum ranging from embryonic lethality to an adult onset. Aberrant expression and/or localization of SMN has also been associated with male infertility, inclusion body myositis, amyotrophic lateral sclerosis and osteoarthritis. This review provides a summary of various SMN functions with implications to a better understanding of SMA and other pathological conditions.
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Affiliation(s)
- Ravindra N Singh
- Department of Biomedical Sciences, Iowa State University, Ames, IA 50011, United States.
| | - Matthew D Howell
- Department of Biomedical Sciences, Iowa State University, Ames, IA 50011, United States
| | - Eric W Ottesen
- Department of Biomedical Sciences, Iowa State University, Ames, IA 50011, United States
| | - Natalia N Singh
- Department of Biomedical Sciences, Iowa State University, Ames, IA 50011, United States
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24
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Tu WY, Simpson JE, Highley JR, Heath PR. Spinal muscular atrophy: Factors that modulate motor neurone vulnerability. Neurobiol Dis 2017; 102:11-20. [PMID: 28161391 DOI: 10.1016/j.nbd.2017.01.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Revised: 01/10/2017] [Accepted: 01/31/2017] [Indexed: 01/07/2023] Open
Abstract
Spinal muscular atrophy (SMA), a leading genetic cause of infant death, is a neurodegenerative disease characterised by the selective loss of particular groups of motor neurones in the anterior horn of the spinal cord with concomitant muscle weakness. To date, no effective treatment is available, however, there are ongoing clinical trials are in place which promise much for the future. However, there remains an ongoing problem in trying to link a single gene loss to motor neurone degeneration. Fortunately, given successful disease models that have been established and intensive studies on SMN functions in the past ten years, we are fast approaching the stage of identifying the underlying mechanisms of SMA pathogenesis Here we discuss potential disease modifying factors on motor neurone vulnerability, in the belief that these factors give insight into the pathological mechanisms of SMA and therefore possible therapeutic targets.
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Affiliation(s)
- Wen-Yo Tu
- Sheffield Institute for Translational Neuroscience, University of Sheffield, Sheffield, UK
| | - Julie E Simpson
- Sheffield Institute for Translational Neuroscience, University of Sheffield, Sheffield, UK
| | - J Robin Highley
- Sheffield Institute for Translational Neuroscience, University of Sheffield, Sheffield, UK
| | - Paul R Heath
- Sheffield Institute for Translational Neuroscience, University of Sheffield, Sheffield, UK.
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25
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Seo J, Singh NN, Ottesen EW, Lee BM, Singh RN. A novel human-specific splice isoform alters the critical C-terminus of Survival Motor Neuron protein. Sci Rep 2016; 6:30778. [PMID: 27481219 PMCID: PMC4969610 DOI: 10.1038/srep30778] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2016] [Accepted: 06/22/2016] [Indexed: 12/30/2022] Open
Abstract
Spinal muscular atrophy (SMA), a leading genetic disease of children and infants, is caused by mutations or deletions of Survival Motor Neuron 1 (SMN1) gene. SMN2, a nearly identical copy of SMN1, fails to compensate for the loss of SMN1 due to skipping of exon 7. SMN2 predominantly produces SMNΔ7, an unstable protein. Here we report exon 6B, a novel exon, generated by exonization of an intronic Alu-like sequence of SMN. We validate the expression of exon 6B-containing transcripts SMN6B and SMN6BΔ7 in human tissues and cell lines. We confirm generation of SMN6B transcripts from both SMN1 and SMN2. We detect expression of SMN6B protein using antibodies raised against a unique polypeptide encoded by exon 6B. We analyze RNA-Seq data to show that hnRNP C is a potential regulator of SMN6B expression and demonstrate that SMN6B is a substrate of nonsense-mediated decay. We show interaction of SMN6B with Gemin2, a critical SMN-interacting protein. We demonstrate that SMN6B is more stable than SMNΔ7 and localizes to both the nucleus and the cytoplasm. Our finding expands the diversity of transcripts generated from human SMN genes and reveals a novel protein isoform predicted to be stably expressed during conditions of stress.
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Affiliation(s)
- Joonbae Seo
- Department of Biomedical Sciences, Iowa State University, Ames, Iowa 50011, USA
| | - Natalia N. Singh
- Department of Biomedical Sciences, Iowa State University, Ames, Iowa 50011, USA
| | - Eric W. Ottesen
- Department of Biomedical Sciences, Iowa State University, Ames, Iowa 50011, USA
| | - Brian M. Lee
- Department of Biomedical Sciences, Iowa State University, Ames, Iowa 50011, USA
- Center for Advanced Host Defenses, Immunobiotics & Translational Comparative Medicine (CAHDIT), Iowa State University, Ames, IA 50011, USA
| | - Ravindra N. Singh
- Department of Biomedical Sciences, Iowa State University, Ames, Iowa 50011, USA
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26
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Garcia EL, Wen Y, Praveen K, Matera AG. Transcriptomic comparison of Drosophila snRNP biogenesis mutants reveals mutant-specific changes in pre-mRNA processing: implications for spinal muscular atrophy. RNA (NEW YORK, N.Y.) 2016; 22:1215-1227. [PMID: 27268418 PMCID: PMC4931114 DOI: 10.1261/rna.057208.116] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Accepted: 05/12/2016] [Indexed: 06/06/2023]
Abstract
Survival motor neuron (SMN) functions in the assembly of spliceosomal small nuclear ribonucleoproteins (snRNPs) that catalyze pre-mRNA splicing. Here, we used disruptions in Smn and two additional snRNP biogenesis genes, Phax and Ars2, to classify RNA processing differences as snRNP-dependent or gene-specific in Drosophila Phax and Smn mutants exhibited comparable reductions in snRNAs, and comparison of their transcriptomes uncovered shared sets of RNA processing changes. In contrast, Ars2 mutants displayed only small decreases in snRNA levels, and RNA processing changes in these mutants were generally distinct from those identified in Phax and Smn animals. Instead, RNA processing changes in Ars2 mutants support the known interaction of Ars2 protein with the cap-binding complex, as splicing changes showed a clear bias toward the first intron. Bypassing disruptions in snRNP biogenesis, direct knockdown of spliceosomal proteins caused similar changes in the splicing of snRNP-dependent events. However, these snRNP-dependent events were largely unaltered in three Smn mutants expressing missense mutations that were originally identified in human spinal muscular atrophy (SMA) patients. Hence, findings here clarify the contributions of Phax, Smn, and Ars2 to snRNP biogenesis in Drosophila, and loss-of-function mutants for these proteins reveal differences that help disentangle cause and effect in SMA model flies.
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Affiliation(s)
- Eric L Garcia
- Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Ying Wen
- Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Kavita Praveen
- Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - A Gregory Matera
- Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA Department of Genetics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA
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27
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Dimitriadi M, Derdowski A, Kalloo G, Maginnis MS, O'Hern P, Bliska B, Sorkaç A, Nguyen KCQ, Cook SJ, Poulogiannis G, Atwood WJ, Hall DH, Hart AC. Decreased function of survival motor neuron protein impairs endocytic pathways. Proc Natl Acad Sci U S A 2016; 113:E4377-86. [PMID: 27402754 PMCID: PMC4968725 DOI: 10.1073/pnas.1600015113] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Spinal muscular atrophy (SMA) is caused by depletion of the ubiquitously expressed survival motor neuron (SMN) protein, with 1 in 40 Caucasians being heterozygous for a disease allele. SMN is critical for the assembly of numerous ribonucleoprotein complexes, yet it is still unclear how reduced SMN levels affect motor neuron function. Here, we examined the impact of SMN depletion in Caenorhabditis elegans and found that decreased function of the SMN ortholog SMN-1 perturbed endocytic pathways at motor neuron synapses and in other tissues. Diminished SMN-1 levels caused defects in C. elegans neuromuscular function, and smn-1 genetic interactions were consistent with an endocytic defect. Changes were observed in synaptic endocytic proteins when SMN-1 levels decreased. At the ultrastructural level, defects were observed in endosomal compartments, including significantly fewer docked synaptic vesicles. Finally, endocytosis-dependent infection by JC polyomavirus (JCPyV) was reduced in human cells with decreased SMN levels. Collectively, these results demonstrate for the first time, to our knowledge, that SMN depletion causes defects in endosomal trafficking that impair synaptic function, even in the absence of motor neuron cell death.
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Affiliation(s)
- Maria Dimitriadi
- Department of Neuroscience, Brown University, Providence, RI 02912; Department of Biological and Environmental Sciences, University of Hertfordshire, Hatfield AL10 9AB, United Kingdom
| | - Aaron Derdowski
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI 02912
| | - Geetika Kalloo
- Department of Neuroscience, Brown University, Providence, RI 02912
| | - Melissa S Maginnis
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI 02912; Department of Molecular and Biomedical Sciences, University of Maine, Orono, ME 04469
| | - Patrick O'Hern
- Department of Neuroscience, Brown University, Providence, RI 02912
| | - Bryn Bliska
- Department of Neuroscience, Brown University, Providence, RI 02912
| | - Altar Sorkaç
- Department of Neuroscience, Brown University, Providence, RI 02912
| | - Ken C Q Nguyen
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461
| | - Steven J Cook
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461
| | - George Poulogiannis
- Chester Beatty Labs, The Institute of Cancer Research, London SW3 6JB, United Kingdom
| | - Walter J Atwood
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI 02912
| | - David H Hall
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461
| | - Anne C Hart
- Department of Neuroscience, Brown University, Providence, RI 02912;
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28
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Donlin-Asp PG, Bassell GJ, Rossoll W. A role for the survival of motor neuron protein in mRNP assembly and transport. Curr Opin Neurobiol 2016; 39:53-61. [PMID: 27131421 DOI: 10.1016/j.conb.2016.04.004] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Revised: 03/27/2016] [Accepted: 04/13/2016] [Indexed: 02/08/2023]
Abstract
Localization and local translation of mRNA plays a key role in neuronal development and function. While studies in various systems have provided insights into molecular mechanisms of mRNA transport and local protein synthesis, the factors that control the assembly of mRNAs and mRNA binding proteins into messenger ribonucleoprotein (mRNP) transport granules remain largely unknown. In this review we will discuss how insights on a motor neuron disease, spinal muscular atrophy (SMA), is advancing our understanding of regulated assembly of transport competent mRNPs and how defects in their assembly and delivery may contribute to the degeneration of motor neurons observed in SMA and other neurological disorders.
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Affiliation(s)
- Paul G Donlin-Asp
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, USA
| | - Gary J Bassell
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, USA; Department of Neurology, Emory University School of Medicine, Atlanta, GA, USA.
| | - Wilfried Rossoll
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, USA.
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29
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Han KJ, Foster D, Harhaj EW, Dzieciatkowska M, Hansen K, Liu CW. Monoubiquitination of survival motor neuron regulates its cellular localization and Cajal body integrity. Hum Mol Genet 2016; 25:1392-405. [PMID: 26908624 DOI: 10.1093/hmg/ddw021] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Accepted: 01/25/2016] [Indexed: 12/13/2022] Open
Abstract
Low levels of the survival motor neuron (SMN) protein cause spinal muscular atrophy, the leading genetic disorder for infant mortality. SMN is ubiquitously expressed in various cell types and localizes in both the cytoplasm and the nucleus, where it concentrates in two subnuclear structures termed Cajal body (CB) and gems. In addition, SMN can also be detected in the nucleolus of neurons. Mechanisms that control SMN sorting in the cell remain largely unknown. Here, we report that the ubiquitin (Ub) ligase Itch directly interacts with and monoubiquitinates SMN. Monoubiquitination of SMN has a mild effect on promoting proteasomal degradation of SMN. We generated two SMN mutants, SMN(K0), in which all lysines are mutated to arginines and thereby abolishing SMN ubiquitination, and Ub-SMN(K0), in which a single Ub moiety is fused at the N-terminus of SMN(K0) and thereby mimicking SMN monoubiquitination. Immunostaining assays showed that SMN(K0) mainly localizes in the nucleus, whereas Ub-SMN(K0) localizes in both the cytoplasm and the nucleolus in neuronal SH-SY5Y cells. Interestingly, canonical CB foci and coilin/small nuclear ribonucleoprotein (snRNP) co-localization are significantly impaired in SH-SY5Y cells stably expressing SMN(K0) or Ub-SMN(K0). Thus, our studies discover that Itch monoubiquitinates SMN and monoubiquitination of SMN plays an important role in regulating its cellular localization. Moreover, mislocalization of SMN disrupts CB integrity and likely impairs snRNP maturation.
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Affiliation(s)
- Ke-Jun Han
- Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora, CO 80015, USA and
| | - Daniel Foster
- Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora, CO 80015, USA and
| | - Edward W Harhaj
- Department of Oncology, Johns Hopkins School of Medicine, Baltimore, MD 21287, USA
| | - Monika Dzieciatkowska
- Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora, CO 80015, USA and
| | - Kirk Hansen
- Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora, CO 80015, USA and
| | - Chang-Wei Liu
- Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora, CO 80015, USA and
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30
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Gabanella F, Pisani C, Borreca A, Farioli-Vecchioli S, Ciotti MT, Ingegnere T, Onori A, Ammassari-Teule M, Corbi N, Canu N, Monaco L, Passananti C, Di Certo MG. SMN affects membrane remodelling and anchoring of the protein synthesis machinery. J Cell Sci 2016; 129:804-16. [PMID: 26743087 DOI: 10.1242/jcs.176750] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Accepted: 12/29/2015] [Indexed: 12/31/2022] Open
Abstract
Disconnection between membrane signalling and actin networks can have catastrophic effects depending on cell size and polarity. The survival motor neuron (SMN) protein is ubiquitously involved in assembly of spliceosomal small nuclear ribonucleoprotein particles. Other SMN functions could, however, affect cellular activities driving asymmetrical cell surface expansions. Genes able to mitigate SMN deficiency operate within pathways in which SMN can act, such as mRNA translation, actin network and endocytosis. Here, we found that SMN accumulates at membrane protrusions during the dynamic rearrangement of the actin filaments. In addition to localization data, we show that SMN interacts with caveolin-1, which mediates anchoring of translation machinery components. Importantly, SMN deficiency depletes the plasma membrane of ribosomes, and this correlates with the failure of fibroblasts to extend membrane protrusions. These findings strongly support a relationship between SMN and membrane dynamics. We propose that SMN could assembly translational platforms associated with and governed by the plasma membrane. This activity could be crucial in cells that have an exacerbated interdependence of membrane remodelling and local protein synthesis.
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Affiliation(s)
- Francesca Gabanella
- CNR-Institute of Cell Biology and Neurobiology, Rome 00143, Italy IRCCS Fondazione Santa Lucia, Rome 00143, Italy
| | - Cinzia Pisani
- CNR-IBPM, Department of Molecular Medicine, Sapienza University of Rome, Rome 00161, Italy
| | - Antonella Borreca
- CNR-Institute of Cell Biology and Neurobiology, Rome 00143, Italy IRCCS Fondazione Santa Lucia, Rome 00143, Italy
| | - Stefano Farioli-Vecchioli
- CNR-Institute of Cell Biology and Neurobiology, Rome 00143, Italy IRCCS Fondazione Santa Lucia, Rome 00143, Italy
| | - Maria Teresa Ciotti
- CNR-Institute of Cell Biology and Neurobiology, Rome 00143, Italy European Brain Research Institute (EBRI) Rita Levi-Montalcini, Rome 00143, Italy
| | - Tiziano Ingegnere
- Department of Ecological and Biological Sciences, Tuscia University, Viterbo 01100, Italy
| | - Annalisa Onori
- CNR-IBPM, Department of Molecular Medicine, Sapienza University of Rome, Rome 00161, Italy
| | - Martine Ammassari-Teule
- CNR-Institute of Cell Biology and Neurobiology, Rome 00143, Italy IRCCS Fondazione Santa Lucia, Rome 00143, Italy
| | - Nicoletta Corbi
- CNR-IBPM, Department of Molecular Medicine, Sapienza University of Rome, Rome 00161, Italy
| | - Nadia Canu
- CNR-Institute of Cell Biology and Neurobiology, Rome 00143, Italy Department of System Medicine, University of 'Tor Vergata', Rome 00137, Italy
| | - Lucia Monaco
- Department of Physiology and Pharmacology, Sapienza University of Rome, Rome 00185, Italy
| | - Claudio Passananti
- CNR-IBPM, Department of Molecular Medicine, Sapienza University of Rome, Rome 00161, Italy
| | - Maria Grazia Di Certo
- CNR-Institute of Cell Biology and Neurobiology, Rome 00143, Italy IRCCS Fondazione Santa Lucia, Rome 00143, Italy
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31
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Sanchez G, Bondy-Chorney E, Laframboise J, Paris G, Didillon A, Jasmin BJ, Côté J. A novel role for CARM1 in promoting nonsense-mediated mRNA decay: potential implications for spinal muscular atrophy. Nucleic Acids Res 2015; 44:2661-76. [PMID: 26656492 PMCID: PMC4824080 DOI: 10.1093/nar/gkv1334] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Accepted: 11/16/2015] [Indexed: 01/09/2023] Open
Abstract
Loss of ‘Survival of Motor Neurons’ (SMN) leads to spinal muscular atrophy (SMA), a disease characterized by degeneration of spinal cord alpha motor neurons, resulting in muscle weakness, paralysis and death during early childhood. SMN is required for assembly of the core splicing machinery, and splicing defects were documented in SMA. We previously uncovered that Coactivator-Associated Methyltransferase-1 (CARM1) is abnormally up-regulated in SMA, leading to mis-regulation of a number of transcriptional and alternative splicing events. We report here that CARM1 can promote decay of a premature terminating codon (PTC)-containing mRNA reporter, suggesting it can act as a mediator of nonsense-mediated mRNA decay (NMD). Interestingly, this pathway, while originally perceived as solely a surveillance mechanism preventing expression of potentially detrimental proteins, is now emerging as a highly regulated RNA decay pathway also acting on a subset of normal mRNAs. We further show that CARM1 associates with major NMD factor UPF1 and promotes its occupancy on PTC-containing transcripts. Finally, we identify a specific subset of NMD targets that are dependent on CARM1 for degradation and that are also misregulated in SMA, potentially adding exacerbated targeting of PTC-containing mRNAs to the already complex array of molecular defects associated with this disease.
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Affiliation(s)
- Gabriel Sanchez
- Centre for Neuromuscular Disease, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada
| | - Emma Bondy-Chorney
- Centre for Neuromuscular Disease, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada
| | - Janik Laframboise
- Centre for Neuromuscular Disease, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada
| | - Geneviève Paris
- Centre for Neuromuscular Disease, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada
| | - Andréanne Didillon
- Centre for Neuromuscular Disease, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada
| | - Bernard J Jasmin
- Centre for Neuromuscular Disease, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada
| | - Jocelyn Côté
- Centre for Neuromuscular Disease, Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada
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32
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Haase G, Rabouille C. Golgi Fragmentation in ALS Motor Neurons. New Mechanisms Targeting Microtubules, Tethers, and Transport Vesicles. Front Neurosci 2015; 9:448. [PMID: 26696811 PMCID: PMC4672084 DOI: 10.3389/fnins.2015.00448] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Accepted: 11/13/2015] [Indexed: 12/12/2022] Open
Abstract
Pathological alterations of the Golgi apparatus, such as its fragmentation represent an early pre-clinical feature of many neurodegenerative diseases and have been widely studied in the motor neuron disease amyotrophic lateral sclerosis (ALS). Yet, the underlying molecular mechanisms have remained cryptic. In principle, Golgi fragmentation may result from defects in three major classes of proteins: structural Golgi proteins, cytoskeletal proteins and molecular motors, as well as proteins mediating transport to and through the Golgi. Here, we present the different mechanisms that may underlie Golgi fragmentation in animal and cellular models of ALS linked to mutations in SOD1, TARDBP (TDP-43), VAPB, and C9Orf72 and we propose a novel one based on findings in progressive motor neuronopathy (pmn) mice. These mice are mutated in the TBCE gene encoding the cis-Golgi localized tubulin-binding cofactor E, one of five chaperones that assist in tubulin folding and microtubule polymerization. Loss of TBCE leads to alterations in Golgi microtubules, which in turn impedes on the maintenance of the Golgi architecture. This is due to down-regulation of COPI coat components, dispersion of Golgi tethers and strong accumulation of ER-Golgi SNAREs. These effects are partially rescued by the GTPase ARF1 through recruitment of TBCE to the Golgi. We hypothesize that defects in COPI vesicles, microtubules and their interaction may also underlie Golgi fragmentation in human ALS linked to other mutations, spinal muscular atrophy (SMA), and related motor neuron diseases. We also discuss the functional relevance of pathological Golgi alterations, in particular their potential causative, contributory, or compensatory role in the degeneration of motor neuron cell bodies, axons and synapses.
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Affiliation(s)
- Georg Haase
- Centre National de la Recherche Scientifique and Aix-Marseille Université UMR 7289, Institut de Neurosciences de la Timone Marseille, France
| | - Catherine Rabouille
- The Department of Cell Biology, Hubrecht Institute of the Royal Netherlands Academy of Arts and Sciences and University Medical Center Utrecht Utrecht, Netherlands
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33
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Huo Q, Kayikci M, Odermatt P, Meyer K, Michels O, Saxena S, Ule J, Schümperli D. Splicing changes in SMA mouse motoneurons and SMN-depleted neuroblastoma cells: evidence for involvement of splicing regulatory proteins. RNA Biol 2015; 11:1430-46. [PMID: 25692239 PMCID: PMC4601534 DOI: 10.1080/15476286.2014.996494] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Spinal Muscular Atrophy (SMA) is caused by deletions or mutations in the Survival Motor Neuron 1 (SMN1) gene. The second gene copy, SMN2, produces some, but not enough, functional SMN protein. SMN is essential to assemble small nuclear ribonucleoproteins (snRNPs) that form the spliceosome. However, it is not clear whether SMA is caused by defects in this function that could lead to splicing changes in all tissues, or by the impairment of an additional, less well characterized, but motoneuron-specific SMN function. We addressed the first possibility by exon junction microarray analysis of motoneurons (MNs) isolated by laser capture microdissection from a severe SMA mouse model. This revealed changes in multiple U2-dependent splicing events. Moreover, splicing appeared to be more strongly affected in MNs than in other cells. By testing mutiple genes in a model of progressive SMN depletion in NB2a neuroblastoma cells, we obtained evidence that U2-dependent splicing changes occur earlier than U12-dependent ones. As several of these changes affect genes coding for splicing regulators, this may acerbate the splicing response induced by low SMN levels and induce secondary waves of splicing alterations.
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Key Words
- ESE, exonic splicing enhancer
- FCS, fetal calf serum
- MN, motoneuron
- NMD, nonsense-mediated mRNA decay
- NMJ, neuromuscular junction, PCR
- RT, reverse transcription
- SMA, Spinal Muscular Atrophy
- SMN, Survival Motor Neuron
- Spinal Muscular Atrophy
- TcRβ, T-cell receptor β chain
- exon junction microarray
- hz, heterozygote, LCM
- laser capture microdissection
- major spliceosome
- minor spliceosome
- motoneurons
- neurodegerative disease
- polymerase chain reaction, qPCR
- real-time (quantitative) PCR
- sh, short hairpin
- snRNA, small nuclear ribonucleic acid
- snRNP assembly
- snRNP, small nuclear ribonucleoprotein
- splicing
- splicing regulators
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Affiliation(s)
- Qing Huo
- a Institute of Cell Biology ; University of Bern ; Bern , Switzerland
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34
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Li H, Custer SK, Gilson T, Hao LT, Beattie CE, Androphy EJ. α-COP binding to the survival motor neuron protein SMN is required for neuronal process outgrowth. Hum Mol Genet 2015; 24:7295-307. [PMID: 26464491 DOI: 10.1093/hmg/ddv428] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Accepted: 10/06/2015] [Indexed: 01/30/2023] Open
Abstract
Spinal muscular atrophy (SMA), a heritable neurodegenerative disease, results from insufficient levels of the survival motor neuron (SMN) protein. α-COP binds to SMN, linking the COPI vesicular transport pathway to SMA. Reduced levels of α-COP restricted development of neuronal processes in NSC-34 cells and primary cortical neurons. Remarkably, heterologous expression of human α-COP restored normal neurite length and morphology in SMN-depleted NSC-34 cells in vitro and zebrafish motor neurons in vivo. We identified single amino acid mutants of α-COP that selectively abrogate SMN binding, retain COPI-mediated Golgi-ER trafficking functionality, but were unable to support neurite outgrowth in cellular and zebrafish models of SMA. Taken together, these demonstrate the functional role of COPI association with the SMN protein in neuronal development.
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Affiliation(s)
- Hongxia Li
- Department of Dermatology, Indiana University School of Medicine, Indianapolis, IN 46202, USA and
| | - Sara K Custer
- Department of Dermatology, Indiana University School of Medicine, Indianapolis, IN 46202, USA and
| | - Timra Gilson
- Department of Dermatology, Indiana University School of Medicine, Indianapolis, IN 46202, USA and
| | - Le Thi Hao
- Department of Neuroscience, The Ohio State University, Columbus, OH 43210, USA
| | - Christine E Beattie
- Department of Neuroscience, The Ohio State University, Columbus, OH 43210, USA
| | - Elliot J Androphy
- Department of Dermatology, Indiana University School of Medicine, Indianapolis, IN 46202, USA and
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Wertz MH, Sahin M. Developing therapies for spinal muscular atrophy. Ann N Y Acad Sci 2015; 1366:5-19. [PMID: 26173388 DOI: 10.1111/nyas.12813] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Revised: 05/05/2015] [Accepted: 05/18/2015] [Indexed: 12/17/2022]
Abstract
Spinal muscular atrophy is an autosomal-recessive pediatric neurodegenerative disease characterized by loss of spinal motor neurons. It is caused by mutation in the gene survival of motor neuron 1 (SMN1), leading to loss of function of the full-length SMN protein. SMN has a number of functions in neurons, including RNA splicing and snRNP biogenesis in the nucleus, and RNA trafficking in neurites. The expression level of full-length SMN protein from the SMN2 locus modifies disease severity. Increasing full-length SMN protein by a small amount can lead to significant improvements in the neurological phenotype. Currently available interventions for spinal muscular atrophy patients are physical therapy and orthopedic, nutritional, and pulmonary interventions; these are palliative or supportive measures and do not address the etiology of the disease. In the past decade, there has been a push for developing therapeutics to improve motor phenotypes and increase life span of spinal muscular atrophy patients. These therapies are aimed primarily at restoration of full-length SMN protein levels, but other neuroprotective treatments have been investigated as well. Here, we discuss recent advances in basic and clinical studies toward finding safe and effective treatments of spinal muscular atrophy using gene therapy, antisense oligonucleotides, and other small molecule modulators of SMN expression.
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Affiliation(s)
- Mary H Wertz
- The F.M. Kirby Neurobiology Center, Department of Neurology, Children's Hospital Boston, Harvard Medical School, Boston, Massachusetts
| | - Mustafa Sahin
- The F.M. Kirby Neurobiology Center, Department of Neurology, Children's Hospital Boston, Harvard Medical School, Boston, Massachusetts
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Workman E, Kalda C, Patel A, Battle DJ. Gemin5 Binds to the Survival Motor Neuron mRNA to Regulate SMN Expression. J Biol Chem 2015; 290:15662-15669. [PMID: 25911097 PMCID: PMC4505476 DOI: 10.1074/jbc.m115.646257] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Revised: 04/22/2015] [Indexed: 12/21/2022] Open
Abstract
Reduced expression of SMN causes spinal muscular atrophy, a severe neurodegenerative disease. Despite the importance of maintaining SMN levels, relatively little is known about the mechanisms by which SMN levels are regulated. We show here that Gemin5, the snRNA-binding protein of the SMN complex, binds directly to the SMN mRNA and regulates SMN expression. Gemin5 binds with high specificity, both in vitro and in vivo, to sequence and structural elements in the SMN mRNA 3'-untranslated region that are reminiscent of the snRNP code to which Gemin5 binds on snRNAs. Reduction of Gemin5 redistributes the SMN mRNA from heavy polysomes to lighter polysomes and monosomes, suggesting that Gemin5 functions as an activator of SMN translation. SMN protein is not stoichiometrically present on the SMN mRNA with Gemin5, but the mRNA-binding activity of Gemin5 is dependent on SMN levels, providing a feedback mechanism for SMN to regulate its own expression via Gemin5. This work both reveals a new autoregulatory pathway governing SMN expression, and identifies a new mechanism through which SMN can modulate specific mRNA expression via Gemin5.
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Affiliation(s)
- Eileen Workman
- Department of Molecular and Cellular Biochemistry, The Ohio State University Wexner Medical Center, Columbus, Ohio 43210
| | - Caitlin Kalda
- Department of Molecular and Cellular Biochemistry, The Ohio State University Wexner Medical Center, Columbus, Ohio 43210
| | - Aalapi Patel
- Department of Molecular and Cellular Biochemistry, The Ohio State University Wexner Medical Center, Columbus, Ohio 43210
| | - Daniel J Battle
- Department of Molecular and Cellular Biochemistry, The Ohio State University Wexner Medical Center, Columbus, Ohio 43210; Department of Neurology, The Ohio State University Wexner Medical Center, Columbus, Ohio 43210.
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Dorshorst B, Henegar C, Liao X, Sällman Almén M, Rubin CJ, Ito S, Wakamatsu K, Stothard P, Van Doormaal B, Plastow G, Barsh GS, Andersson L. Dominant Red Coat Color in Holstein Cattle Is Associated with a Missense Mutation in the Coatomer Protein Complex, Subunit Alpha (COPA) Gene. PLoS One 2015; 10:e0128969. [PMID: 26042826 PMCID: PMC4456281 DOI: 10.1371/journal.pone.0128969] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Accepted: 05/01/2015] [Indexed: 12/31/2022] Open
Abstract
Coat color in Holstein dairy cattle is primarily controlled by the melanocortin 1 receptor (MC1R) gene, a central determinant of black (eumelanin) vs. red/brown pheomelanin synthesis across animal species. The major MC1R alleles in Holsteins are Dominant Black (MC1RD) and Recessive Red (MC1Re). A novel form of dominant red coat color was first observed in an animal born in 1980. The mutation underlying this phenotype was named Dominant Red and is epistatic to the constitutively activated MC1RD. Here we show that a missense mutation in the coatomer protein complex, subunit alpha (COPA), a gene with previously no known role in pigmentation synthesis, is completely associated with Dominant Red in Holstein dairy cattle. The mutation results in an arginine to cysteine substitution at an amino acid residue completely conserved across eukaryotes. Despite this high level of conservation we show that both heterozygotes and homozygotes are healthy and viable. Analysis of hair pigment composition shows that the Dominant Red phenotype is similar to the MC1R Recessive Red phenotype, although less effective at reducing eumelanin synthesis. RNA-seq data similarly show that Dominant Red animals achieve predominantly pheomelanin synthesis by downregulating genes normally required for eumelanin synthesis. COPA is a component of the coat protein I seven subunit complex that is involved with retrograde and cis-Golgi intracellular coated vesicle transport of both protein and RNA cargo. This suggests that Dominant Red may be caused by aberrant MC1R protein or mRNA trafficking within the highly compartmentalized melanocyte, mimicking the effect of the Recessive Red loss of function MC1R allele.
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Affiliation(s)
- Ben Dorshorst
- Science for Life Laboratory, Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
- Department of Animal and Poultry Sciences, Virginia Tech, Blacksburg, Virginia, United States of America
- * E-mail:
| | - Corneliu Henegar
- HudsonAlpha Institute for Biotechnology, Huntsville, Alabama, United States of America
| | - Xiaoping Liao
- Livestock Gentec, Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta, Canada
| | - Markus Sällman Almén
- Science for Life Laboratory, Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
| | - Carl-Johan Rubin
- Science for Life Laboratory, Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
| | - Shosuke Ito
- Department of Chemistry, Fujita Health University School of Health Sciences, Toyoake, Aichi, Japan
| | - Kazumasa Wakamatsu
- Department of Chemistry, Fujita Health University School of Health Sciences, Toyoake, Aichi, Japan
| | - Paul Stothard
- Livestock Gentec, Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta, Canada
| | | | - Graham Plastow
- Livestock Gentec, Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta, Canada
| | - Gregory S. Barsh
- HudsonAlpha Institute for Biotechnology, Huntsville, Alabama, United States of America
- Department of Genetics, Stanford University, Stanford, California, United States of America
| | - Leif Andersson
- Science for Life Laboratory, Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
- Science for Life Laboratory, Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, Uppsala, Sweden
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Cherry JJ, Kobayashi DT, Lynes MM, Naryshkin NN, Tiziano FD, Zaworski PG, Rubin LL, Jarecki J. Assays for the identification and prioritization of drug candidates for spinal muscular atrophy. Assay Drug Dev Technol 2015; 12:315-41. [PMID: 25147906 DOI: 10.1089/adt.2014.587] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Spinal muscular atrophy (SMA) is an autosomal recessive genetic disorder resulting in degeneration of α-motor neurons of the anterior horn and proximal muscle weakness. It is the leading cause of genetic mortality in children younger than 2 years. It affects ∼1 in 11,000 live births. In 95% of cases, SMA is caused by homozygous deletion of the SMN1 gene. In addition, all patients possess at least one copy of an almost identical gene called SMN2. A single point mutation in exon 7 of the SMN2 gene results in the production of low levels of full-length survival of motor neuron (SMN) protein at amounts insufficient to compensate for the loss of the SMN1 gene. Although no drug treatments are available for SMA, a number of drug discovery and development programs are ongoing, with several currently in clinical trials. This review describes the assays used to identify candidate drugs for SMA that modulate SMN2 gene expression by various means. Specifically, it discusses the use of high-throughput screening to identify candidate molecules from primary screens, as well as the technical aspects of a number of widely used secondary assays to assess SMN messenger ribonucleic acid (mRNA) and protein expression, localization, and function. Finally, it describes the process of iterative drug optimization utilized during preclinical SMA drug development to identify clinical candidates for testing in human clinical trials.
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Abstract
Spinal muscular atrophy (SMA) is a leading genetic cause of infant mortality. The disease originates from low levels of SMN protein due to deletion and/or mutations of SMN1 coupled with the inability of SMN2 to compensate for the loss of SMN1. While SMN1 and SMN2 are nearly identical, SMN2 predominantly generates a truncated protein (SMNΔ7) due to skipping of exon 7, the last coding exon. Several avenues for SMA therapy are being explored, including means to enhance SMN2 transcription, correct SMN2 exon 7 splicing, stabilize SMN/SMNΔ7 protein, manipulate SMN-regulated pathways and SMN1 gene delivery by viral vectors. This review focuses on the aspects of target discovery, validations and outcome measures for a promising therapy of SMA.
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Hao LT, Duy PQ, Jontes JD, Beattie CE. Motoneuron development influences dorsal root ganglia survival and Schwann cell development in a vertebrate model of spinal muscular atrophy. Hum Mol Genet 2014; 24:346-60. [PMID: 25180019 DOI: 10.1093/hmg/ddu447] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Low levels of the survival motor neuron protein (SMN) cause the disease spinal muscular atrophy. A primary characteristic of this disease is motoneuron dysfunction and paralysis. Understanding why motoneurons are affected by low levels of SMN will lend insight into this disease and to motoneuron biology in general. Motoneurons in zebrafish smn mutants develop abnormally; however, it is unclear where Smn is needed for motoneuron development since it is a ubiquitously expressed protein. We have addressed this issue by expressing human SMN in motoneurons in zebrafish maternal-zygotic (mz) smn mutants. First, we demonstrate that SMN is present in axons, but only during the period of robust motor axon outgrowth. We also conclusively demonstrate that SMN acts cell autonomously in motoneurons for proper motoneuron development. This includes the formation of both axonal and dendritic branches. Analysis of the peripheral nervous system revealed that Schwann cells and dorsal root ganglia (DRG) neurons developed abnormally in mz-smn mutants. Schwann cells did not wrap axons tightly and had expanded nodes of Ranvier. The majority of DRG neurons had abnormally short peripheral axons and later many of them failed to divide and died. Expressing SMN just in motoneurons rescued both of these cell types showing that their failure to develop was secondary to the developmental defects in motoneurons. Driving SMN just in motoneurons did not increase survival of the animal, suggesting that SMN is needed for motoneuron development and motor circuitry, but that SMN in other cells types factors into survival.
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Affiliation(s)
- Le Thi Hao
- Department of Neuroscience, The Ohio State University College of Medicine, 190 Rightmire Hall, 1060 Carmack Rd, Columbus, OH 43210, USA
| | - Phan Q Duy
- Department of Neuroscience, The Ohio State University College of Medicine, 190 Rightmire Hall, 1060 Carmack Rd, Columbus, OH 43210, USA
| | - James D Jontes
- Department of Neuroscience, The Ohio State University College of Medicine, 190 Rightmire Hall, 1060 Carmack Rd, Columbus, OH 43210, USA
| | - Christine E Beattie
- Department of Neuroscience, The Ohio State University College of Medicine, 190 Rightmire Hall, 1060 Carmack Rd, Columbus, OH 43210, USA
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Custer SK, Androphy EJ. Autophagy dysregulation in cell culture and animals models of spinal muscular atrophy. Mol Cell Neurosci 2014; 61:133-40. [PMID: 24983518 PMCID: PMC4135029 DOI: 10.1016/j.mcn.2014.06.006] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Revised: 06/20/2014] [Accepted: 06/27/2014] [Indexed: 10/25/2022] Open
Abstract
Abnormal autophagy has become a central thread linking neurodegenerative diseases, particularly of the motor neuron. One such disease is spinal muscular atrophy (SMA), a genetic neuromuscular disorder caused by mutations in the SMN1 gene resulting in low levels of Survival Motor Neuron (SMN) protein. Despite knowing the causal protein, the exact intracellular processes that are involved in the selective loss of motor neurons remain unclear. Autophagy induction can be helpful or harmful depending on the situation, and we sought to understand the state of the autophagic response in SMA. We show that cell culture and animal models demonstrate induction of autophagy accompanied by attenuated autophagic flux, resulting in the accumulation of autophagosomes and their associated cargo. Expression of the SMN-binding protein a-COP, a known modulator of autophagic flux, can ameliorate this autophagic traffic jam.
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Affiliation(s)
- Sara K Custer
- Indiana University School of Medicine, Department of Dermatology, Walther Hall, R3 C636, Indianapolis, IN 46202, United States
| | - Elliot J Androphy
- Indiana University School of Medicine, Department of Dermatology, Walther Hall, R3 C636, Indianapolis, IN 46202, United States.
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Bellouze S, Schäfer MK, Buttigieg D, Baillat G, Rabouille C, Haase G. Golgi fragmentation in pmn mice is due to a defective ARF1/TBCE cross-talk that coordinates COPI vesicle formation and tubulin polymerization. Hum Mol Genet 2014; 23:5961-75. [DOI: 10.1093/hmg/ddu320] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
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Bowerman M, Michalski JP, Beauvais A, Murray LM, DeRepentigny Y, Kothary R. Defects in pancreatic development and glucose metabolism in SMN-depleted mice independent of canonical spinal muscular atrophy neuromuscular pathology. Hum Mol Genet 2014; 23:3432-44. [PMID: 24497575 PMCID: PMC4049303 DOI: 10.1093/hmg/ddu052] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Spinal muscular atrophy (SMA) is characterized by motor neuron loss, caused by mutations or deletions in the ubiquitously expressed survival motor neuron 1 (SMN1) gene. We recently identified a novel role for Smn protein in glucose metabolism and pancreatic development in both an intermediate SMA mouse model (Smn(2B/-)) and type I SMA patients. In the present study, we sought to determine if the observed metabolic and pancreatic defects are SMA-dependent. We employed a line of heterozygous Smn-depleted mice (Smn(+/-)) that lack the hallmark SMA neuromuscular pathology and overt phenotype. At 1 month of age, pancreatic/metabolic function of Smn(+/-)mice is indistinguishable from wild type. However, when metabolically challenged with a high-fat diet, Smn(+/-)mice display abnormal localization of glucagon-producing α-cells within the pancreatic islets and increased hepatic insulin and glucagon sensitivity, through increased p-AKT and p-CREB, respectively. Further, aging results in weight gain, an increased number of insulin-producing β cells, hyperinsulinemia and increased hepatic glucagon sensitivity in Smn(+/-)mice. Our study uncovers and highlights an important function of Smn protein in pancreatic islet development and glucose metabolism, independent of canonical SMA pathology. These findings suggest that carriers of SMN1 mutations and/or deletions may be at an increased risk of developing pancreatic and glucose metabolism defects, as even small depletions in Smn protein may be a risk factor for diet- and age-dependent development of metabolic disorders.
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Affiliation(s)
- Melissa Bowerman
- Ottawa Hospital Research Institute, Ottawa, Ontario, Canada The Neuroscience Institute of Montpellier (INM), Inserm UMR1051, Saint Eloi Hospital, Montpellier, France
| | - John-Paul Michalski
- Ottawa Hospital Research Institute, Ottawa, Ontario, Canada Department of Cellular and Molecular Medicine and
| | | | | | | | - Rashmi Kothary
- Ottawa Hospital Research Institute, Ottawa, Ontario, Canada Department of Cellular and Molecular Medicine and Department of Medicine, University of Ottawa, Ottawa, Ontario, Canada
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Arnold WD, Burghes AHM. Spinal muscular atrophy: development and implementation of potential treatments. Ann Neurol 2013; 74:348-62. [PMID: 23939659 DOI: 10.1002/ana.23995] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2013] [Revised: 07/13/2013] [Accepted: 08/01/2013] [Indexed: 12/13/2022]
Abstract
In neurodegenerative disorders, effective treatments are urgently needed, along with methods to determine whether treatment worked. In this review, we discuss the rapid progress in the understanding of recessive proximal spinal muscular atrophy and how this is leading to exciting potential treatments of the disease. Spinal muscular atrophy is caused by loss of the survival motor neuron 1 (SMN1) gene and reduced levels of SMN protein. The critical downstream targets of SMN deficiency that result in motor neuron loss are not known. However, increasing SMN levels has a marked impact in mouse models, and these therapeutics are rapidly moving toward clinical trials. Promising preclinical therapies, the varying degree of impact on the mouse models, and potential measures of treatment effect are reviewed. One key issue discussed is the variable outcome of increasing SMN at different stages of disease progression.
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Affiliation(s)
- W David Arnold
- Neuromuscular Division, Department of Neurology, Wexner Medical Center, the Ohio State University, Columbus, OH; Department of Physical Medicine and Rehabilitation, Wexner Medical Center, the Ohio State University, Columbus, OH
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Small nuclear RNAs and mRNAs: linking RNA processing and transport to spinal muscular atrophy. Biochem Soc Trans 2013; 41:871-5. [PMID: 23863147 DOI: 10.1042/bst20120016] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The splicing of pre-mRNA by the spliceosome is a characteristic feature of eukaryotic cells, dependent on a group of snRNPs (small nuclear ribonucleoproteins). These splicing snRNPs have a complex assembly pathway involving multiple steps that take place in different regions of the cell, which is reflected in their complex subcellular distribution. Vital to the assembly of splicing snRNPs is the protein SMN (survival of motor neurons). In multicellular organisms, SMN acts in the cytoplasm, together with its associated protein complex to assemble a heptameric ring of proteins called the Sm proteins as an early stage in splicing snRNP assembly. A deficiency of the SMN protein results in the inherited neurodegenerative condition SMA (spinal muscular atrophy), a leading cause of infant mortality specifically affecting spinal motor neurons. It has long been a puzzle how lowered levels of a protein required for a process as fundamental as splicing snRNP assembly can result in a condition with such a definite cell-type-specificity. The present review highlights recent research that points to wider roles in RNA metabolism for both SMN itself and the Sm proteins with which it is linked.
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Seo J, Howell MD, Singh NN, Singh RN. Spinal muscular atrophy: an update on therapeutic progress. Biochim Biophys Acta Mol Basis Dis 2013; 1832:2180-90. [PMID: 23994186 DOI: 10.1016/j.bbadis.2013.08.005] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2013] [Revised: 07/27/2013] [Accepted: 08/14/2013] [Indexed: 12/24/2022]
Abstract
Humans have two nearly identical copies of survival motor neuron gene: SMN1 and SMN2. Deletion or mutation of SMN1 combined with the inability of SMN2 to compensate for the loss of SMN1 results in spinal muscular atrophy (SMA), a leading genetic cause of infant mortality. SMA affects 1 in ~6000 live births, a frequency much higher than in several genetic diseases. The major known defect of SMN2 is the predominant exon 7 skipping that leads to production of a truncated protein (SMNΔ7), which is unstable. Therefore, SMA has emerged as a model genetic disorder in which almost the entire disease population could be linked to the aberrant splicing of a single exon (i.e. SMN2 exon 7). Diverse treatment strategies aimed at improving the function of SMN2 have been envisioned. These strategies include, but are not limited to, manipulation of transcription, correction of aberrant splicing and stabilization of mRNA, SMN and SMNΔ7. This review summarizes up to date progress and promise of various in vivo studies reported for the treatment of SMA.
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Affiliation(s)
- Joonbae Seo
- Department of Biomedical Sciences, Iowa State University, Ames, IA 50011, USA
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Peeters K, Litvinenko I, Asselbergh B, Almeida-Souza L, Chamova T, Geuens T, Ydens E, Zimoń M, Irobi J, De Vriendt E, De Winter V, Ooms T, Timmerman V, Tournev I, Jordanova A. Molecular defects in the motor adaptor BICD2 cause proximal spinal muscular atrophy with autosomal-dominant inheritance. Am J Hum Genet 2013; 92:955-64. [PMID: 23664119 PMCID: PMC3675262 DOI: 10.1016/j.ajhg.2013.04.013] [Citation(s) in RCA: 103] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2013] [Revised: 04/16/2013] [Accepted: 04/16/2013] [Indexed: 12/14/2022] Open
Abstract
The most common form of spinal muscular atrophy (SMA) is a recessive disorder caused by deleterious SMN1 mutations in 5q13, whereas the genetic etiologies of non-5q SMA are very heterogeneous and largely remain to be elucidated. In a Bulgarian family affected by autosomal-dominant proximal SMA, we performed genome-wide linkage analysis and whole-exome sequencing and found a heterozygous de novo c.320C>T (p.Ser107Leu) mutation in bicaudal D homolog 2 (Drosophila) (BICD2). Further analysis of BICD2 in a cohort of 119 individuals with non-5q SMA identified a second de novo BICD2 mutation, c.2321A>G (p.Glu774Gly), in a simplex case. Detailed clinical and electrophysiological investigations revealed that both families are affected by a very similar disease course, characterized by early childhood onset, predominant involvement of lower extremities, and very slow disease progression. The amino acid substitutions are located in two interaction domains of BICD2, an adaptor protein linking the dynein molecular motor with its cargo. Our immunoprecipitation and localization experiments in HeLa and SH-SY5Y cells and affected individuals' lymphoblasts demonstrated that p.Ser107Leu causes increased dynein binding and thus leads to accumulation of BICD2 at the microtubule-organizing complex and Golgi fragmentation. In addition, the altered protein had a reduced colocalization with RAB6A, a regulator of vesicle trafficking between the Golgi and the endoplasmic reticulum. The interaction between p.Glu744Gly altered BICD2 and RAB6A was impaired, which also led to their reduced colocalization. Our study identifies BICD2 mutations as a cause of non-5q linked SMA and highlights the importance of dynein-mediated motility in motor neuron function in humans.
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Affiliation(s)
- Kristien Peeters
- Molecular Neurogenomics Group, Department of Molecular Genetics, VIB, Antwerp 2610, Belgium
- Neurogenetics Laboratory, Institute Born-Bunge, University of Antwerp, Antwerp 2610, Belgium
| | - Ivan Litvinenko
- Clinic of Child Neurology, Department of Pediatrics, Medical University-Sofia, Sofia 1000, Bulgaria
| | - Bob Asselbergh
- Neurogenetics Laboratory, Institute Born-Bunge, University of Antwerp, Antwerp 2610, Belgium
- Centralized Service Facility, Department of Molecular Genetics, VIB, Antwerp 2610, Belgium
| | - Leonardo Almeida-Souza
- Neurogenetics Laboratory, Institute Born-Bunge, University of Antwerp, Antwerp 2610, Belgium
- Peripheral Neuropathy Group, Department of Molecular Genetics, VIB, Antwerp 2610, Belgium
| | - Teodora Chamova
- Department of Neurology, Medical University-Sofia, Sofia 1000, Bulgaria
| | - Thomas Geuens
- Neurogenetics Laboratory, Institute Born-Bunge, University of Antwerp, Antwerp 2610, Belgium
- Peripheral Neuropathy Group, Department of Molecular Genetics, VIB, Antwerp 2610, Belgium
| | - Elke Ydens
- Neurogenetics Laboratory, Institute Born-Bunge, University of Antwerp, Antwerp 2610, Belgium
- Peripheral Neuropathy Group, Department of Molecular Genetics, VIB, Antwerp 2610, Belgium
| | - Magdalena Zimoń
- Molecular Neurogenomics Group, Department of Molecular Genetics, VIB, Antwerp 2610, Belgium
- Neurogenetics Laboratory, Institute Born-Bunge, University of Antwerp, Antwerp 2610, Belgium
| | - Joy Irobi
- Centralized Service Facility, Department of Molecular Genetics, VIB, Antwerp 2610, Belgium
| | - Els De Vriendt
- Molecular Neurogenomics Group, Department of Molecular Genetics, VIB, Antwerp 2610, Belgium
- Neurogenetics Laboratory, Institute Born-Bunge, University of Antwerp, Antwerp 2610, Belgium
| | - Vicky De Winter
- Neurogenetics Laboratory, Institute Born-Bunge, University of Antwerp, Antwerp 2610, Belgium
- Peripheral Neuropathy Group, Department of Molecular Genetics, VIB, Antwerp 2610, Belgium
| | - Tinne Ooms
- Molecular Neurogenomics Group, Department of Molecular Genetics, VIB, Antwerp 2610, Belgium
- Neurogenetics Laboratory, Institute Born-Bunge, University of Antwerp, Antwerp 2610, Belgium
| | - Vincent Timmerman
- Neurogenetics Laboratory, Institute Born-Bunge, University of Antwerp, Antwerp 2610, Belgium
- Peripheral Neuropathy Group, Department of Molecular Genetics, VIB, Antwerp 2610, Belgium
| | - Ivailo Tournev
- Department of Neurology, Medical University-Sofia, Sofia 1000, Bulgaria
- Department of Cognitive Science and Psychology, New Bulgarian University, Sofia 1618, Bulgaria
| | - Albena Jordanova
- Molecular Neurogenomics Group, Department of Molecular Genetics, VIB, Antwerp 2610, Belgium
- Neurogenetics Laboratory, Institute Born-Bunge, University of Antwerp, Antwerp 2610, Belgium
- Department of Medical Chemistry and Biochemistry, Molecular Medicine Center, Medical University-Sofia, Sofia 1431, Bulgaria
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Neveling K, Martinez-Carrera L, Hölker I, Heister A, Verrips A, Hosseini-Barkooie S, Gilissen C, Vermeer S, Pennings M, Meijer R, te Riele M, Frijns C, Suchowersky O, MacLaren L, Rudnik-Schöneborn S, Sinke R, Zerres K, Lowry R, Lemmink H, Garbes L, Veltman J, Schelhaas H, Scheffer H, Wirth B. Mutations in BICD2, which encodes a golgin and important motor adaptor, cause congenital autosomal-dominant spinal muscular atrophy. Am J Hum Genet 2013; 92:946-54. [PMID: 23664116 DOI: 10.1016/j.ajhg.2013.04.011] [Citation(s) in RCA: 124] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2013] [Revised: 04/15/2013] [Accepted: 04/15/2013] [Indexed: 12/13/2022] Open
Abstract
Spinal muscular atrophy (SMA) is a heterogeneous group of neuromuscular disorders caused by degeneration of lower motor neurons. Although functional loss of SMN1 is associated with autosomal-recessive childhood SMA, the genetic cause for most families affected by dominantly inherited SMA is unknown. Here, we identified pathogenic variants in bicaudal D homolog 2 (Drosophila) (BICD2) in three families afflicted with autosomal-dominant SMA. Affected individuals displayed congenital slowly progressive muscle weakness mainly of the lower limbs and congenital contractures. In a large Dutch family, linkage analysis identified a 9q22.3 locus in which exome sequencing uncovered c.320C>T (p.Ser107Leu) in BICD2. Sequencing of 23 additional families affected by dominant SMA led to the identification of pathogenic variants in one family from Canada (c.2108C>T [p.Thr703Met]) and one from the Netherlands (c.563A>C [p.Asn188Thr]). BICD2 is a golgin and motor-adaptor protein involved in Golgi dynamics and vesicular and mRNA transport. Transient transfection of HeLa cells with all three mutant BICD2 cDNAs caused massive Golgi fragmentation. This observation was even more prominent in primary fibroblasts from an individual harboring c.2108C>T (p.Thr703Met) (affecting the C-terminal coiled-coil domain) and slightly less evident in individuals with c.563A>C (p.Asn188Thr) (affecting the N-terminal coiled-coil domain). Furthermore, BICD2 levels were reduced in affected individuals and trapped within the fragmented Golgi. Previous studies have shown that Drosophila mutant BicD causes reduced larvae locomotion by impaired clathrin-mediated synaptic endocytosis in neuromuscular junctions. These data emphasize the relevance of BICD2 in synaptic-vesicle recycling and support the conclusion that BICD2 mutations cause congenital slowly progressive dominant SMA.
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Custer SK, Todd AG, Singh NN, Androphy EJ. Dilysine motifs in exon 2b of SMN protein mediate binding to the COPI vesicle protein α-COP and neurite outgrowth in a cell culture model of spinal muscular atrophy. Hum Mol Genet 2013; 22:4043-52. [PMID: 23727837 DOI: 10.1093/hmg/ddt254] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Spinal muscular atrophy (SMA) is a devastating neuromuscular disorder that stems from low levels of survival of motor neuron (SMN) protein. The processes that cause motor neurons and muscle cells to become dysfunctional are incompletely understood. We are interested in neuromuscular homeostasis and the stresses put upon that system by loss of SMN. We recently reported that α-COP, a member of the coatomer complex of coat protein I (COPI) vesicles, is an SMN-binding partner, implicating this protein complex in normal SMN function. To investigate the functional significance of the interaction between α-COP and SMN, we constructed an inducible NSC-34 cell culture system to model the consequences of SMN depletion and find that depletion of SMN protein results in shortened neurites. Heterologous expression of human SMN, and interestingly over-expression of α-COP, restores normal neurite length and morphology. Mutagenesis of the canonical COPI dilysine motifs in exon 2b results in failure to bind to α-COP and abrogates the ability of human SMN to restore neurite outgrowth in SMN-depleted motor neuron-like NSC-34 cells. We conclude that the interaction between SMN and α-COP serves an important function in the growth and maintenance of motor neuron processes and may play a significant role in the pathogenesis of SMA.
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