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Jacquier V, Prévot M, Gostan T, Bordonné R, Benkhelifa-Ziyyat S, Barkats M, Soret J. Splicing efficiency of minor introns in a mouse model of SMA predominantly depends on their branchpoint sequence and can involve the contribution of major spliceosome components. RNA (NEW YORK, N.Y.) 2022; 28:303-319. [PMID: 34893560 PMCID: PMC8848931 DOI: 10.1261/rna.078329.120] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Accepted: 11/22/2021] [Indexed: 06/14/2023]
Abstract
Spinal muscular atrophy (SMA) is a devastating neurodegenerative disease caused by reduced amounts of the ubiquitously expressed Survival of Motor Neuron (SMN) protein. In agreement with its crucial role in the biogenesis of spliceosomal snRNPs, SMN-deficiency is correlated to numerous splicing alterations in patient cells and various tissues of SMA mouse models. Among the snRNPs whose assembly is impacted by SMN-deficiency, those involved in the minor spliceosome are particularly affected. Importantly, splicing of several, but not all U12-dependent introns has been shown to be affected in different SMA models. Here, we have investigated the molecular determinants of this differential splicing in spinal cords from SMA mice. We show that the branchpoint sequence (BPS) is a key element controlling splicing efficiency of minor introns. Unexpectedly, splicing of several minor introns with suboptimal BPS is not affected in SMA mice. Using in vitro splicing experiments and oligonucleotides targeting minor or major snRNAs, we show for the first time that splicing of these introns involves both the minor and major machineries. Our results strongly suggest that splicing of a subset of minor introns is not affected in SMA mice because components of the major spliceosome compensate for the loss of minor splicing activity.
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Affiliation(s)
- Valentin Jacquier
- Institut de Génétique Moléculaire de Montpellier, Univ Montpellier, CNRS, Montpellier 34293, France
| | - Manon Prévot
- Institut de Génétique Moléculaire de Montpellier, Univ Montpellier, CNRS, Montpellier 34293, France
| | - Thierry Gostan
- Institut de Génétique Moléculaire de Montpellier, Univ Montpellier, CNRS, Montpellier 34293, France
| | - Rémy Bordonné
- Institut de Génétique Moléculaire de Montpellier, Univ Montpellier, CNRS, Montpellier 34293, France
| | - Sofia Benkhelifa-Ziyyat
- Centre de Recherche en Myologie (CRM), Institut de Myologie, Sorbonne Universités, UPMC Univ Paris 06, Inserm UMRS974, GH Pitié Salpêtrière, Paris 75013, France
| | - Martine Barkats
- Centre de Recherche en Myologie (CRM), Institut de Myologie, Sorbonne Universités, UPMC Univ Paris 06, Inserm UMRS974, GH Pitié Salpêtrière, Paris 75013, France
| | - Johann Soret
- Institut de Génétique Moléculaire de Montpellier, Univ Montpellier, CNRS, Montpellier 34293, France
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2
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Jablonka S, Hennlein L, Sendtner M. Therapy development for spinal muscular atrophy: perspectives for muscular dystrophies and neurodegenerative disorders. Neurol Res Pract 2022; 4:2. [PMID: 34983696 PMCID: PMC8725368 DOI: 10.1186/s42466-021-00162-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Accepted: 10/21/2021] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND Major efforts have been made in the last decade to develop and improve therapies for proximal spinal muscular atrophy (SMA). The introduction of Nusinersen/Spinraza™ as an antisense oligonucleotide therapy, Onasemnogene abeparvovec/Zolgensma™ as an AAV9-based gene therapy and Risdiplam/Evrysdi™ as a small molecule modifier of pre-mRNA splicing have set new standards for interference with neurodegeneration. MAIN BODY Therapies for SMA are designed to interfere with the cellular basis of the disease by modifying pre-mRNA splicing and enhancing expression of the Survival Motor Neuron (SMN) protein, which is only expressed at low levels in this disorder. The corresponding strategies also can be applied to other disease mechanisms caused by loss of function or toxic gain of function mutations. The development of therapies for SMA was based on the use of cell culture systems and mouse models, as well as innovative clinical trials that included readouts that had originally been introduced and optimized in preclinical studies. This is summarized in the first part of this review. The second part discusses current developments and perspectives for amyotrophic lateral sclerosis, muscular dystrophies, Parkinson's and Alzheimer's disease, as well as the obstacles that need to be overcome to introduce RNA-based therapies and gene therapies for these disorders. CONCLUSION RNA-based therapies offer chances for therapy development of complex neurodegenerative disorders such as amyotrophic lateral sclerosis, muscular dystrophies, Parkinson's and Alzheimer's disease. The experiences made with these new drugs for SMA, and also the experiences in AAV gene therapies could help to broaden the spectrum of current approaches to interfere with pathophysiological mechanisms in neurodegeneration.
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Affiliation(s)
- Sibylle Jablonka
- Institute of Clinical Neurobiology, University Hospital of Wuerzburg, Versbacher Str. 5, 97078, Wuerzburg, Germany.
| | - Luisa Hennlein
- Institute of Clinical Neurobiology, University Hospital of Wuerzburg, Versbacher Str. 5, 97078, Wuerzburg, Germany
| | - Michael Sendtner
- Institute of Clinical Neurobiology, University Hospital of Wuerzburg, Versbacher Str. 5, 97078, Wuerzburg, Germany.
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3
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Impairment of the neurotrophic signaling hub B-Raf contributes to motoneuron degeneration in spinal muscular atrophy. Proc Natl Acad Sci U S A 2021; 118:2007785118. [PMID: 33931501 DOI: 10.1073/pnas.2007785118] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Spinal muscular atrophy (SMA) is a motoneuron disease caused by deletions of the Survival of Motoneuron 1 gene (SMN1) and low SMN protein levels. SMN restoration is the concept behind a number of recently approved drugs which result in impressive yet limited effects. Since SMN has already been enhanced in treated patients, complementary SMN-independent approaches are needed. Previously, a number of altered signaling pathways which regulate motoneuron degeneration have been identified as candidate targets. However, signaling pathways form networks, and their connectivity is still unknown in SMA. Here, we used presymptomatic SMA mice to elucidate the network of altered signaling in SMA. The SMA network is structured in two clusters with AKT and 14-3-3 ζ/δ in their centers. Both clusters are connected by B-Raf as a major signaling hub. The direct interaction of B-Raf with 14-3-3 ζ/δ is important for an efficient neurotrophic activation of the MEK/ERK pathway and crucial for motoneuron survival. Further analyses in SMA mice revealed that both proteins were down-regulated in motoneurons and the spinal cord with B-Raf being reduced at presymptomatic stages. Primary fibroblasts and iPSC-derived motoneurons from SMA patients both showed the same pattern of down-regulation. This mechanism is conserved across species since a Caenorhabditis elegans SMA model showed less expression of the B-Raf homolog lin-45 Accordingly, motoneuron survival was rescued by a cell autonomous lin-45 expression in a C. elegans SMA model resulting in improved motor functions. This rescue was effective even after the onset of motoneuron degeneration and mediated by the MEK/ERK pathway.
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4
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Tiziano FD, Tizzano EF. 25 years of the SMN genes: the Copernican revolution of spinal muscular atrophy. ACTA MYOLOGICA : MYOPATHIES AND CARDIOMYOPATHIES : OFFICIAL JOURNAL OF THE MEDITERRANEAN SOCIETY OF MYOLOGY 2020; 39:336-344. [PMID: 33458589 PMCID: PMC7783429 DOI: 10.36185/2532-1900-037] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Accepted: 11/12/2020] [Indexed: 06/12/2023]
Abstract
The new era of advanced therapies has influenced and changed the views and perspectives of a neuromuscular disease such as spinal muscular atrophy (SMA). Being an autosomal recessive motor neuron disorder, characterized by different degrees of muscle weakness, after 25 years of the discovery of the determinant and modifier genes (SMN1 and SMN2, respectively) three SMN-dependent specific therapies are already approved by FDA (two by EMA), so that worldwide patients are currently under clinical investigation and treatment. This success was the combined effort mainly of patients and families, physician and researchers, advocacy groups and several Institutions together with the support of pharmaceutical companies. Progression trajectories, phenotypes, follow-up and care of the patients are continously evolving. Clinical investigations are currently demonstrating that early diagnosis and intervention are essential for better and more effective response to treatment, consistently improving prognosis. This scenario has created the need for awareness, early diagnosis and even implementation of of newborn screening programs. New views and perspectives of patient and family expectations, genetic counselling and multidisciplinary care: a truly Copernican revolution in neuromuscular and genetic diseases.
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Affiliation(s)
- Francesco Danilo Tiziano
- Section of Genomic Medicine, Department of Life Science and Public Health, Catholic University of Sacred Heart, Roma, Italy
| | - Eduardo F. Tizzano
- Department of Clinical and Molecular Genetics, Hospital Valle Hebron, Barcelona, Spain
- Medicine Genetics Group, Valle Hebron Research Institute (VHIR), Barcelona, Spain
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5
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Angelini DF, De Angelis F, Vacca V, Piras E, Parisi C, Nutini M, Spalloni A, Pagano F, Longone P, Battistini L, Pavone F, Marinelli S. Very Early Involvement of Innate Immunity in Peripheral Nerve Degeneration in SOD1-G93A Mice. Front Immunol 2020; 11:575792. [PMID: 33329541 PMCID: PMC7714949 DOI: 10.3389/fimmu.2020.575792] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Accepted: 10/19/2020] [Indexed: 12/13/2022] Open
Abstract
Recent preclinical and clinical evidence suggest that immune system has a role in the progression and prognosis of Amyotrophic Lateral Sclerosis (ALS), but the identification of a clear mechanism and immune players remains to be elucidated. Here, we have investigated, in 30 and 60 days (presymptomatic) and 120 days (symptomatic) old SOD1-G93A mice, systemic, peripheral, and central innate and adaptive immune and inflammatory response, correlating it with the progression of the neurodegeneration in neuromuscular junction, sciatic nerves, and spinal cord. Surprisingly, we found a very initial (45-60 days) presence of IgG in sciatic nerves together with a gradual enhancement of A20/TNFAIP3 (protein controlling NF-κB signalling) and a concomitantly significant increase and activation of circulating mast cells (MCs) as well as MCs and macrophages in sciatic nerve and an enhancement of IL-6 and IL-10. This immunological frame coincided with a myelin aggregation. The 30-60 days old SOD1-G93A mice didn't show real elements of neuroinflammation and neurodegeneration in spinal cord. In 120 days old mice macrophages and monocytes are widely diffused in sciatic nerves, peripheral neurodegeneration reaches the tip, high circulating levels of TNFα and IL-2 were found and spinal cord exhibits clear signs of neural damage and infiltrating immune cells. Our results underpin a clear immunological disorder at the origin of ALS axonopathy, in which MCs are involved in the initiation and sustaining of inflammatory events. These data cannot be considered a mere epiphenomenon of motor neuron degeneration and reveal new potential selective immune targets in ALS therapy.
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Affiliation(s)
| | - Federica De Angelis
- Neuroimmunology Unit, IRCCS Santa Lucia Foundation, Rome, Italy
- CNR—National Research Council, Institute of Biochemistry and Cell Biology, Rome, Italy
| | - Valentina Vacca
- CNR—National Research Council, Institute of Biochemistry and Cell Biology, Rome, Italy
| | - Eleonora Piras
- Neuroimmunology Unit, IRCCS Santa Lucia Foundation, Rome, Italy
| | - Chiara Parisi
- CNR—National Research Council, Institute of Biochemistry and Cell Biology, Rome, Italy
| | - Michele Nutini
- Neuroimmunology Unit, IRCCS Santa Lucia Foundation, Rome, Italy
| | - Alida Spalloni
- Neuroimmunology Unit, IRCCS Santa Lucia Foundation, Rome, Italy
| | - Francesca Pagano
- CNR—National Research Council, Institute of Biochemistry and Cell Biology, Rome, Italy
| | | | - Luca Battistini
- Neuroimmunology Unit, IRCCS Santa Lucia Foundation, Rome, Italy
| | - Flaminia Pavone
- CNR—National Research Council, Institute of Biochemistry and Cell Biology, Rome, Italy
| | - Sara Marinelli
- CNR—National Research Council, Institute of Biochemistry and Cell Biology, Rome, Italy
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6
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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: 44] [Impact Index Per Article: 7.3] [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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7
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Tejero R, Lopez-Manzaneda M, Arumugam S, Tabares L. Synaptotagmin-2, and -1, linked to neurotransmission impairment and vulnerability in Spinal Muscular Atrophy. Hum Mol Genet 2018; 25:4703-4716. [PMID: 28173138 DOI: 10.1093/hmg/ddw297] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2016] [Revised: 08/22/2016] [Accepted: 08/23/2016] [Indexed: 01/19/2023] Open
Abstract
Spinal muscular atrophy (SMA) is the most frequent genetic cause of infant mortality. The disease is characterized by progressive muscle weakness and paralysis of axial and proximal limb muscles. It is caused by homozygous loss or mutation of the SMN1 gene, which codes for the Survival Motor Neuron (SMN) protein. In mouse models of the disease, neurotransmitter release is greatly impaired, but the molecular mechanisms of the synaptic dysfunction and the basis of the selective muscle vulnerability are unknown. In the present study, we investigated these open questions by comparing the molecular and functional properties of nerve terminals in severely and mildly affected muscles in the SMNΔ7 mouse model. We discovered that synaptotagmin-1 (Syt1) was developmentally downregulated in nerve terminals of highly affected muscles but not in low vulnerable muscles. Additionally, the expression levels of synaptotagmin-2 (Syt2), and its interacting protein, synaptic vesicle protein 2 (SV2) B, were reduced in proportion to the degree of muscle vulnerability while other synaptic proteins, such as syntaxin-1B (Stx1B) and synaptotagmin-7 (Syt7), were not affected. Consistently with the extremely low levels of both Syt-isoforms, and SV2B, in most affected neuromuscular synapses, the functional analysis of neurotransmission revealed highly reduced evoked release, altered short-term plasticity, low release probability, and inability to modulate normally the number of functional release sites. Together, we propose that the strong reduction of Syt2 and SV2B are key factors of the functional synaptic alteration and that the physiological downregulation of Syt1 plays a determinant role in muscle vulnerability in SMA.
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Affiliation(s)
- Rocío Tejero
- Department of Medical Physiology and Biophysics, School of Medicine, University of Seville, Avda. Sánchez Pizjuán, 4. 41009 Seville, Spain
| | - Mario Lopez-Manzaneda
- Department of Medical Physiology and Biophysics, School of Medicine, University of Seville, Avda. Sánchez Pizjuán, 4. 41009 Seville, Spain
| | - Saravanan Arumugam
- Department of Medical Physiology and Biophysics, School of Medicine, University of Seville, Avda. Sánchez Pizjuán, 4. 41009 Seville, Spain
| | - Lucía Tabares
- Department of Medical Physiology and Biophysics, School of Medicine, University of Seville, Avda. Sánchez Pizjuán, 4. 41009 Seville, Spain
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8
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Boido M, De Amicis E, Valsecchi V, Trevisan M, Ala U, Ruegg MA, Hettwer S, Vercelli A. Increasing Agrin Function Antagonizes Muscle Atrophy and Motor Impairment in Spinal Muscular Atrophy. Front Cell Neurosci 2018; 12:17. [PMID: 29440993 PMCID: PMC5797594 DOI: 10.3389/fncel.2018.00017] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2017] [Accepted: 01/11/2018] [Indexed: 11/13/2022] Open
Abstract
Spinal muscular atrophy (SMA) is a pediatric genetic disease, characterized by motor neuron (MN) death, leading to progressive muscle weakness, respiratory failure, and, in the most severe cases, to death. Abnormalities at the neuromuscular junction (NMJ) have been reported in SMA, including neurofilament (NF) accumulation at presynaptic terminals, immature and smaller than normal endplates, reduced transmitter release, and, finally, muscle denervation. Here we have studied the role of agrin in SMAΔ7 mice, the experimental model of SMAII. We observed a 50% reduction in agrin expression levels in quadriceps of P10 SMA mice compared to age-matched WT controls. To counteract such condition, we treated SMA mice from birth onwards with therapeutic agrin biological NT-1654, an active splice variant of agrin retaining synaptogenic properties, which is also resistant to proteolytic cleavage by neurotrypsin. Mice were analyzed for behavior, muscle and NMJ histology, and survival. Motor behavior was significantly improved and survival was extended by treatment of SMA mice with NT-1654. At P10, H/E-stained sections of the quadriceps, a proximal muscle early involved in SMA, showed that NT-1654 treatment strongly prevented the size decrease of muscle fibers. Studies of NMJ morphology on whole-mount diaphragm preparations revealed that NT-1654-treated SMA mice had more mature NMJs and reduced NF accumulation, compared to vehicle-treated SMA mice. We conclude that increasing agrin function in SMA has beneficial outcomes on muscle fibers and NMJs as the agrin biological NT-1654 restores the crosstalk between muscle and MNs, delaying muscular atrophy, improving motor performance and extending survival.
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Affiliation(s)
- Marina Boido
- Department of Neuroscience Rita Levi Montalcini, Neuroscience Institute Cavalieri Ottolenghi, University of Turin, Turin, Italy
| | - Elena De Amicis
- Department of Neuroscience Rita Levi Montalcini, Neuroscience Institute Cavalieri Ottolenghi, University of Turin, Turin, Italy
| | - Valeria Valsecchi
- Department of Neuroscience Rita Levi Montalcini, Neuroscience Institute Cavalieri Ottolenghi, University of Turin, Turin, Italy
| | - Marco Trevisan
- Department of Neuroscience Rita Levi Montalcini, Neuroscience Institute Cavalieri Ottolenghi, University of Turin, Turin, Italy
| | - Ugo Ala
- Department of Molecular Biotechnology and Health Sciences, University of Turin, Turin, Italy
| | | | | | - Alessandro Vercelli
- Department of Neuroscience Rita Levi Montalcini, Neuroscience Institute Cavalieri Ottolenghi, University of Turin, Turin, Italy.,Department of Neuroscience Rita Levi Montalcini, National Institute of Neuroscience, Turin, Italy
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9
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Rietz A, Li H, Quist KM, Cherry JJ, Lorson CL, Burnett BG, Kern NL, Calder AN, Fritsche M, Lusic H, Boaler PJ, Choi S, Xing X, Glicksman MA, Cuny GD, Androphy EJ, Hodgetts KJ. Discovery of a Small Molecule Probe That Post-Translationally Stabilizes the Survival Motor Neuron Protein for the Treatment of Spinal Muscular Atrophy. J Med Chem 2017; 60:4594-4610. [PMID: 28481536 DOI: 10.1021/acs.jmedchem.6b01885] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Spinal muscular atrophy (SMA) is the leading genetic cause of infant death. We previously developed a high-throughput assay that employs an SMN2-luciferase reporter allowing identification of compounds that act transcriptionally, enhance exon recognition, or stabilize the SMN protein. We describe optimization and characterization of an analog suitable for in vivo testing. Initially, we identified analog 4m that had good in vitro properties but low plasma and brain exposure in a mouse PK experiment due to short plasma stability; this was overcome by reversing the amide bond and changing the heterocycle. Thiazole 27 showed excellent in vitro properties and a promising mouse PK profile, making it suitable for in vivo testing. This series post-translationally stabilizes the SMN protein, unrelated to global proteasome or autophagy inhibition, revealing a novel therapeutic mechanism that should complement other modalities for treatment of SMA.
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Affiliation(s)
- Anne Rietz
- Department of Dermatology, Indiana University School of Medicine , Indianapolis, Indiana 46202, United States
| | - Hongxia Li
- Department of Dermatology, Indiana University School of Medicine , Indianapolis, Indiana 46202, United States
| | - Kevin M Quist
- Department of Dermatology, Indiana University School of Medicine , Indianapolis, Indiana 46202, United States
| | - Jonathan J Cherry
- Department of Dermatology, Indiana University School of Medicine , Indianapolis, Indiana 46202, United States
| | - Christian L Lorson
- Department of Veterinary Pathobiology, Bond Life Sciences Center, University of Missouri , Columbia, Missouri 65201, United States
| | - Barrington G Burnett
- Department of Anatomy, Physiology and Genetics, F. Edward Hebert School of Medicine, Uniformed Services University of the Health Sciences , Bethesda, Maryland 20814, United States
| | - Nicholas L Kern
- Laboratory for Drug Discovery in Neurodegeneration, Brigham & Women's Hospital and Harvard Medical School , 65 Landsdowne Street, Cambridge, Massachusetts 02139, United States
| | - Alyssa N Calder
- Laboratory for Drug Discovery in Neurodegeneration, Brigham & Women's Hospital and Harvard Medical School , 65 Landsdowne Street, Cambridge, Massachusetts 02139, United States
| | - Melanie Fritsche
- Laboratory for Drug Discovery in Neurodegeneration, Brigham & Women's Hospital and Harvard Medical School , 65 Landsdowne Street, Cambridge, Massachusetts 02139, United States
| | - Hrvoje Lusic
- Laboratory for Drug Discovery in Neurodegeneration, Brigham & Women's Hospital and Harvard Medical School , 65 Landsdowne Street, Cambridge, Massachusetts 02139, United States
| | - Patrick J Boaler
- Laboratory for Drug Discovery in Neurodegeneration, Brigham & Women's Hospital and Harvard Medical School , 65 Landsdowne Street, Cambridge, Massachusetts 02139, United States
| | - Sungwoon Choi
- Laboratory for Drug Discovery in Neurodegeneration, Brigham & Women's Hospital and Harvard Medical School , 65 Landsdowne Street, Cambridge, Massachusetts 02139, United States
| | - Xuechao Xing
- Laboratory for Drug Discovery in Neurodegeneration, Brigham & Women's Hospital and Harvard Medical School , 65 Landsdowne Street, Cambridge, Massachusetts 02139, United States
| | - Marcie A Glicksman
- Laboratory for Drug Discovery in Neurodegeneration, Brigham & Women's Hospital and Harvard Medical School , 65 Landsdowne Street, Cambridge, Massachusetts 02139, United States
| | - Gregory D Cuny
- Laboratory for Drug Discovery in Neurodegeneration, Brigham & Women's Hospital and Harvard Medical School , 65 Landsdowne Street, Cambridge, Massachusetts 02139, United States
| | - Elliot J Androphy
- Department of Dermatology, Indiana University School of Medicine , Indianapolis, Indiana 46202, United States
| | - Kevin J Hodgetts
- Laboratory for Drug Discovery in Neurodegeneration, Brigham & Women's Hospital and Harvard Medical School , 65 Landsdowne Street, Cambridge, Massachusetts 02139, United States
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10
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Schoen M, Reichel JM, Demestre M, Putz S, Deshpande D, Proepper C, Liebau S, Schmeisser MJ, Ludolph AC, Michaelis J, Boeckers TM. Super-Resolution Microscopy Reveals Presynaptic Localization of the ALS/FTD Related Protein FUS in Hippocampal Neurons. Front Cell Neurosci 2016; 9:496. [PMID: 26834559 PMCID: PMC4709451 DOI: 10.3389/fncel.2015.00496] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2015] [Accepted: 12/09/2015] [Indexed: 12/12/2022] Open
Abstract
Fused in Sarcoma (FUS) is a multifunctional RNA-/DNA-binding protein, which is involved in the pathogenesis of the neurodegenerative disorders amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). A common hallmark of these disorders is the abnormal accumulation of mutated FUS protein in the cytoplasm. Under normal conditions FUS is confined to the nuclear compartment, in neurons, however, additional somatodendritic localization can be observed. In this study, we carefully analyzed the subcellular localization of endogenous FUS at synaptic sites of hippocampal neurons which are among the most affected cell types in FTD with FUS pathology. We could confirm a strong nuclear localization of FUS as well as its prominent and widespread neuronal expression throughout the adult and developing rat brain, particularly in the hippocampus, the cerebellum and the outer layers of the cortex. Intriguingly, FUS was also consistently observed at synaptic sites as detected by neuronal subcellular fractionation as well as by immunolabeling. To define a pre- and/or postsynaptic localization of FUS, we employed super-resolution fluorescence localization microscopy. FUS was found to be localized within the axon terminal in close proximity to the presynaptic vesicle protein Synaptophysin1 and adjacent to the active zone protein Bassoon, but well separated from the postsynaptic protein PSD-95. Having shown the presynaptic localization of FUS in the nervous system, a novel extranuclear role of FUS at neuronal contact sites has to be considered. Since there is growing evidence that local presynaptic translation might also be an important mechanism for plasticity, FUS - like the fragile X mental retardation protein FMRP - might act as one of the presynaptic RNA-binding proteins regulating this machinery. Our observation of presynaptic FUS should foster further investigations to determine its role in neurodegenerative diseases such as ALS and FTD.
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Affiliation(s)
- Michael Schoen
- Institute for Anatomy and Cell Biology, Ulm University Ulm, Germany
| | | | - Maria Demestre
- Institute for Anatomy and Cell Biology, Ulm University Ulm, Germany
| | - Stefan Putz
- Institute for Anatomy and Cell Biology, Ulm UniversityUlm, Germany; Department of Neurology, Ulm UniversityUlm, Germany
| | | | | | - Stefan Liebau
- Institute of Neuroanatomy, Eberhard Karls University Tübingen Tübingen, Germany
| | - Michael J Schmeisser
- Institute for Anatomy and Cell Biology, Ulm UniversityUlm, Germany; Department of Neurology, Ulm UniversityUlm, Germany
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11
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Xu CC, Denton KR, Wang ZB, Zhang X, Li XJ. Abnormal mitochondrial transport and morphology as early pathological changes in human models of spinal muscular atrophy. Dis Model Mech 2016; 9:39-49. [PMID: 26586529 PMCID: PMC4728333 DOI: 10.1242/dmm.021766] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Accepted: 10/28/2015] [Indexed: 12/14/2022] Open
Abstract
Spinal muscular atrophy (SMA), characterized by specific degeneration of spinal motor neurons, is caused by mutations in the survival of motor neuron 1, telomeric (SMN1) gene and subsequent decreased levels of functional SMN. How the deficiency of SMN, a ubiquitously expressed protein, leads to spinal motor neuron-specific degeneration in individuals affected by SMA remains unknown. In this study, we examined the role of SMN in mitochondrial axonal transport and morphology in human motor neurons by generating SMA type 1 patient-specific induced pluripotent stem cells (iPSCs) and differentiating these cells into spinal motor neurons. The initial specification of spinal motor neurons was not affected, but these SMA spinal motor neurons specifically degenerated following long-term culture. Moreover, at an early stage in SMA spinal motor neurons, but not in SMA forebrain neurons, the number of mitochondria, mitochondrial area and mitochondrial transport were significantly reduced in axons. Knocking down of SMN expression led to similar mitochondrial defects in spinal motor neurons derived from human embryonic stem cells, confirming that SMN deficiency results in impaired mitochondrial dynamics. Finally, the application of N-acetylcysteine (NAC) mitigated the impairment in mitochondrial transport and morphology and rescued motor neuron degeneration in SMA long-term cultures. Furthermore, NAC ameliorated the reduction in mitochondrial membrane potential in SMA spinal motor neurons, suggesting that NAC might rescue apoptosis and motor neuron degeneration by improving mitochondrial health. Overall, our data demonstrate that SMN deficiency results in abnormal mitochondrial transport and morphology and a subsequent reduction in mitochondrial health, which are implicated in the specific degeneration of spinal motor neurons in SMA.
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Affiliation(s)
- Chong-Chong Xu
- Department of Neuroscience, University of Connecticut Health Center, Farmington, CT 06030, USA
| | - Kyle R Denton
- Department of Neuroscience, University of Connecticut Health Center, Farmington, CT 06030, USA
| | - Zhi-Bo Wang
- Department of Neuroscience, University of Connecticut Health Center, Farmington, CT 06030, USA
| | - Xiaoqing Zhang
- Department of Regenerative Medicine, Tongji University School of Medicine, Shanghai 200092, China
| | - Xue-Jun Li
- Department of Neuroscience, University of Connecticut Health Center, Farmington, CT 06030, USA Stem Cell Institute, University of Connecticut, Farmington, CT 06030, USA
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12
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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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13
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PTEN depletion decreases disease severity and modestly prolongs survival in a mouse model of spinal muscular atrophy. Mol Ther 2014; 23:270-7. [PMID: 25369768 PMCID: PMC4445616 DOI: 10.1038/mt.2014.209] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2014] [Accepted: 10/21/2014] [Indexed: 12/13/2022] Open
Abstract
Spinal muscular atrophy (SMA) is the second most common genetic cause of death in childhood. However, no effective treatment is available to halt disease progression. SMA is caused by mutations in the survival motor neuron 1 (SMN1) gene. We previously reported that PTEN depletion leads to an increase in survival of SMN-deficient motor neurons. Here, we aimed to establish the impact of PTEN modulation in an SMA mouse model in vivo. Initial experiments using intramuscular delivery of adeno-associated vector serotype 6 (AAV6) expressing shRNA against PTEN in an established mouse model of severe SMA (SMNΔ7) demonstrated the ability to ameliorate the severity of neuromuscular junction pathology. Subsequently, we developed self-complementary AAV9 expressing siPTEN (scAAV9-siPTEN) to allow evaluation of the effect of systemic suppression of PTEN on the disease course of SMA in vivo. Treatment with a single injection of scAAV9-siPTEN at postnatal day 1 resulted in a modest threefold extension of the lifespan of SMNΔ7 mice, increasing mean survival to 30 days, compared to 10 days in untreated mice. Our data revealed that systemic PTEN depletion is an important disease modifier in SMNΔ7 mice, and therapies aimed at lowering PTEN expression may therefore offer a potential therapeutic strategy for SMA.
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14
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Krieger F, Metzger F, Jablonka S. Differentiation defects in primary motoneurons from a SMARD1 mouse model that are insensitive to treatment with low dose PEGylated IGF1. Rare Dis 2014; 2:e29415. [PMID: 25083343 PMCID: PMC4116388 DOI: 10.4161/rdis.29415] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2014] [Revised: 05/26/2014] [Accepted: 05/30/2014] [Indexed: 11/21/2022] Open
Abstract
Muscle atrophy and diaphragmatic palsy are the clinical characteristics of spinal muscular atrophy with respiratory distress type 1 (SMARD1), and are well represented in the neuromuscular degeneration (Nmd2J) mouse, modeling the juvenile form of SMARD1. Both in humans and mice mutations in the IGHMBP2 gene lead to motoneuron degeneration. We could previously demonstrate that treatment with a polyethylene glycol-coupled variant of IGF1 (PEG-IGF1) improves motor functions accompanied by reduced fiber degeneration in the gastrocnemius muscle and the diaphragm, but has no beneficial effect on motoneuron survival. These data raised the question which cell autonomous disease mechanisms contribute to dysfunction and loss of Ighmbp2-deficient motoneurons. An analysis of primary Ighmbp2-deficient motoneurons exhibited differentiation deficits such as reduced spontaneous Ca2+ transients and altered axon elongation, which was not compensated by PEG-IGF1. This points to an IGF1 independent mechanism of motoneuron degeneration that deserves treatment approaches in addition to IGF1.
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Affiliation(s)
- Frank Krieger
- Institute for Clinical Neurobiology; University of Wuerzburg; Wuerzburg, Germany
| | - Friedrich Metzger
- Roche Pharmaceutical Research and Early Development; Roche Innovation Center Basel; F. Hoffmann-La Roche Ltd.; Basel, Switzerland
| | - Sibylle Jablonka
- Institute for Clinical Neurobiology; University of Wuerzburg; Wuerzburg, Germany
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15
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Maximino JR, de Oliveira GP, Alves CJ, Chadi G. Deregulated expression of cytoskeleton related genes in the spinal cord and sciatic nerve of presymptomatic SOD1(G93A) Amyotrophic Lateral Sclerosis mouse model. Front Cell Neurosci 2014; 8:148. [PMID: 24904291 PMCID: PMC4033281 DOI: 10.3389/fncel.2014.00148] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2014] [Accepted: 05/08/2014] [Indexed: 12/11/2022] Open
Abstract
Early molecular events related to cytoskeleton are poorly described in Amyotrophic Lateral Sclerosis (ALS), especially in the Schwann cell (SC), which offers strong trophic support to motor neurons. Database for Annotation, Visualization and Integrated Discovery (DAVID) tool identified cytoskeleton-related genes by employing the Cellular Component Ontology (CCO) in a large gene profiling of lumbar spinal cord and sciatic nerve of presymptomatic SOD1(G93A) mice. One and five CCO terms related to cytoskeleton were described from the spinal cord deregulated genes of 40 days (actin cytoskeleton) and 80 days (microtubule cytoskeleton, cytoskeleton part, actin cytoskeleton, neurofilament cytoskeleton, and cytoskeleton) old transgene mice, respectively. Also, four terms were depicted from the deregulated genes of sciatic nerve of 60 days old transgenes (actin cytoskeleton, cytoskeleton part, microtubule cytoskeleton and cytoskeleton). Kif1b was the unique deregulated gene in more than one studied region or presymptomatic age. The expression of Kif1b [quantitative polymerase chain reaction (qPCR)] elevated in the lumbar spinal cord (40 days old) and decreased in the sciatic nerve (60 days old) of presymptomatic ALS mice, results that were in line to microarray findings. Upregulation (24.8 fold) of Kif1b was seen in laser microdissected enriched immunolabeled motor neurons from the spinal cord of 40 days old presymptomatic SOD1(G93A) mice. Furthermore, Kif1b was dowregulated in the sciatic nerve Schwann cells of presymptomatic ALS mice (60 days old) that were enriched by means of cell microdissection (6.35 fold), cell sorting (3.53 fold), and primary culture (2.70 fold) technologies. The gene regulation of cytoskeleton molecules is an important occurrence in motor neurons and Schwann cells in presymptomatic stages of ALS and may be relevant in the dying back mechanisms of neuronal death. Furthermore, a differential regulation of Kif1b in the spinal cord and sciatic nerve cells emerged as key event in ALS.
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Affiliation(s)
- Jessica R Maximino
- Department of Neurology, Neuroregeneration Research Center, University of São Paulo School of Medicine São Paulo, Brazil
| | - Gabriela P de Oliveira
- Department of Neurology, Neuroregeneration Research Center, University of São Paulo School of Medicine São Paulo, Brazil
| | - Chrystian J Alves
- Department of Neurology, Neuroregeneration Research Center, University of São Paulo School of Medicine São Paulo, Brazil
| | - Gerson Chadi
- Department of Neurology, Neuroregeneration Research Center, University of São Paulo School of Medicine São Paulo, Brazil
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16
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3' Splice site sequences of spinal muscular atrophy related SMN2 pre-mRNA include enhancers for nearby exons. ScientificWorldJournal 2014; 2014:617842. [PMID: 24616638 PMCID: PMC3925570 DOI: 10.1155/2014/617842] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2013] [Accepted: 12/19/2013] [Indexed: 11/18/2022] Open
Abstract
Spinal muscular atrophy (SMA) is a human genetic disease which occurs because of the deletion or mutation of SMN1 gene. SMN1 gene encodes the SMN protein which plays a key role in spliceosome assembly. Although human patients contain SMN2, a duplicate of SMN1, splicing of SMN2 produces predominantly exon 7 skipped isoform. In order to understand the functions of splice site sequences on exon 7 and 8, we analyzed the effects of conserved splice site sequences on exon 7 skipping of SMN2 and SMN1 pre-mRNA. We show here that conserved 5′ splice site sequence of exon 7 promoted splicing of nearby exons and subsequently reduced splicing of distant exons. However, to our surprise, conserved 3′ splice site sequence of exon 7 and 8 did not promote splicing of nearby exons. By contrast, the mutation inhibited splicing of nearby exons and subsequently promoted splicing of distant exons. Our study shows that 3′ splice sites of exon 7 and 8 contain enhancer for their splice site selection, in addition to providing cleavage sites.
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17
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Bonini SA, Ferrari-Toninelli G, Montinaro M, Memo M. Notch signalling in adult neurons: a potential target for microtubule stabilization. Ther Adv Neurol Disord 2013; 6:375-85. [PMID: 24228073 DOI: 10.1177/1756285613490051] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Cytoskeletal dysfunction has been proposed during the last decade as one of the main mechanisms involved in the aetiology of several neurodegenerative diseases. Microtubules are basic elements of the cytoskeleton and the dysregulation of microtubule stability has been demonstrated to be causative for axonal transport impairment, synaptic contact degeneration, impaired neuronal function leading finally to neuronal loss. Several pathways are implicated in the microtubule assembly/disassembly process. Emerging evidence is focusing on Notch as a microtubule dynamics regulator. We demonstrated that activation of Notch signalling results in increased microtubule stability and changes in axonal morphology and branching. By contrast, Notch inhibition leads to an increase in cytoskeleton plasticity with intense neurite remodelling. Until now, several microtubule-binding compounds have been tested and the results have provided proof of concept that microtubule-binding agents or compounds with the ability to stabilize microtubules may have therapeutic potential for the treatment of Alzheimer's disease and other neurodegenerative diseases. In this review, based on its key role in cytoskeletal dynamics modulation, we propose Notch as a new potential target for microtubule stabilization.
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Affiliation(s)
- Sara Anna Bonini
- Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy
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18
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Tiziano FD, Melki J, Simard LR. Solving the puzzle of spinal muscular atrophy: what are the missing pieces? Am J Med Genet A 2013; 161A:2836-45. [PMID: 24124019 DOI: 10.1002/ajmg.a.36251] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2013] [Accepted: 08/30/2013] [Indexed: 12/13/2022]
Abstract
Spinal muscular atrophy (SMA) is an autosomal recessive, lower motor neuron disease. Clinical heterogeneity is pervasive: three infantile (type I-III) and one adult-onset (type IV) forms are recognized. Type I SMA is the most common genetic cause of death in infancy and accounts for about 50% of all patients with SMA. Most forms of SMA are caused by mutations of the survival motor neuron (SMN1) gene. A second gene that is 99% identical to SMN1 (SMN2) is located in the same region. The only functionally relevant difference between the two genes identified to date is a C → T transition in exon 7 of SMN2, which determines an alternative spliced isoform that predominantly excludes exon 7. Thus, SMN2 genes do not produce sufficient full length SMN protein to prevent the onset of the disease. Since the identification of the causative mutation, biomedical research of SMA has progressed by leaps and bounds: from clues on the function of SMN protein, to the development of different models of the disease, to the identification of potential treatments, some of which are currently in human trials. The aim of this review is to elucidate the current state of knowledge, emphasizing how close we are to the solution of the puzzle that is SMA, and, more importantly, to highlight the missing pieces of this puzzle. Filling in these gaps in our knowledge will likely accelerate the development and delivery of efficient treatments for SMA patients and be a prerequisite towards achieving our final goal, the cure of SMA.
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19
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Vinsant S, Mansfield C, Jimenez-Moreno R, Del Gaizo Moore V, Yoshikawa M, Hampton TG, Prevette D, Caress J, Oppenheim RW, Milligan C. Characterization of early pathogenesis in the SOD1(G93A) mouse model of ALS: part II, results and discussion. Brain Behav 2013; 3:431-57. [PMID: 24381813 PMCID: PMC3869683 DOI: 10.1002/brb3.142] [Citation(s) in RCA: 121] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/18/2013] [Revised: 03/21/2013] [Accepted: 03/22/2013] [Indexed: 12/12/2022] Open
Abstract
Pathological events are well characterized in amyotrophic lateral sclerosis (ALS) mouse models, but review of the literature fails to identify a specific initiating event that precipitates disease pathology. There is now growing consensus in the field that axon and synapses are first cellular sites of degeneration, but controversy exists over whether axon and synapse loss is initiated autonomously at those sites or by pathology in the cell body, in nonneuronal cells or even in nonmotoneurons (MNs). Previous studies have identified pathological events in the mutant superoxide dismutase 1 (SOD1) models involving spinal cord, peripheral axons, neuromuscular junctions (NMJs), or muscle; however, few studies have systematically examined pathogenesis at multiple sites in the same study. We have performed ultrastructural examination of both central and peripheral components of the neuromuscular system in the SOD1(G93A) mouse model of ALS. Twenty percent of MNs undergo degeneration by P60, but NMJ innervation in fast fatigable muscles is reduced by 40% by P30. Gait alterations and muscle weakness were also found at P30. There was no change in axonal transport prior to initial NMJ denervation. Mitochondrial morphological changes are observed at P7 and become more prominent with disease progression. At P30 there was a significant decrease in excitatory axo-dendritic and axo-somatic synapses with an increase in C-type axo-somatic synapses. Our study examined early pathology in both peripheral and central neuromuscular system. The muscle denervation is associated with functional motor deficits and begins during the first postnatal month in SOD1(G93A) mice. Physiological dysfunction and pathology in the mitochondria of synapses and MN soma and dendrites occur, and disease onset in these animals begins more than 2 months earlier than originally thought. This information may be valuable for designing preclinical trials that are more likely to impact disease onset and progression.
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Affiliation(s)
- Sharon Vinsant
- Department of Neurobiology and Anatomy, The Neuroscience Program and The ALS Center, Wake Forest University School of Medicine Winston-Salem, North Carolina
| | - Carol Mansfield
- Department of Neurobiology and Anatomy, The Neuroscience Program and The ALS Center, Wake Forest University School of Medicine Winston-Salem, North Carolina
| | - Ramon Jimenez-Moreno
- Department of Neurobiology and Anatomy, The Neuroscience Program and The ALS Center, Wake Forest University School of Medicine Winston-Salem, North Carolina
| | | | - Masaaki Yoshikawa
- Department of Neurobiology and Anatomy, The Neuroscience Program and The ALS Center, Wake Forest University School of Medicine Winston-Salem, North Carolina
| | | | - David Prevette
- Department of Neurobiology and Anatomy, The Neuroscience Program and The ALS Center, Wake Forest University School of Medicine Winston-Salem, North Carolina
| | - James Caress
- Department of Neurology and the ALS Center, Wake Forest University School of Medicine Winston-Salem, North Carolina
| | - Ronald W Oppenheim
- Department of Neurobiology and Anatomy, The Neuroscience Program and The ALS Center, Wake Forest University School of Medicine Winston-Salem, North Carolina
| | - Carol Milligan
- Department of Neurobiology and Anatomy, The Neuroscience Program and The ALS Center, Wake Forest University School of Medicine Winston-Salem, North Carolina
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20
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Abstract
One of the major challenges facing the long term survival of neurons is their requirement to maintain efficient axonal transport over long distances. In humans as large, long-lived vertebrates, the machinery maintaining neuronal transport must remain efficient despite the slow accumulation of cell damage during aging. Mutations in genes encoding proteins which function in the transport system feature prominently in neurologic disorders. Genes known to cause such disorders and showing traditional Mendelian inheritance have been more readily identified. It has been more difficult, however, to isolate factors underlying the complex genetics contributing to the more common idiopathic forms of neurodegenerative disease. At the heart of neuronal transport is the rail network or scaffolding provided by neuron specific microtubules (MTs). The importance of MT dynamics and stability is underscored by the critical role tau protein plays in MT-associated stabilization versus the dysfunction seen in Alzheimer's disease, frontotemporal dementia and other tauopathies. Another example of the requirement for tight regulation of MT dynamics is the need to maintain balanced levels of post-translational modification of key MT building-blocks such as α-tubulin. Tubulins require extensive polyglutamylation at their carboxyl-terminus as part of a novel post-translational modification mechanism to signal MT growth versus destabilization. Dramatically, knock-out of a gene encoding a deglutamylation family member causes an extremely rapid cell death of Purkinje cells in the ataxic mouse model, pcd. This review will examine a range of neurodegenerative conditions where current molecular understanding points to defects in the stability of MTs and axonal transport to emphasize the central role of MTs in neuron survival.
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Affiliation(s)
- Fiona J Baird
- School of Pharmacy and Molecular Sciences, James Cook University, DB 21, James Cook Drive, Townsville, QLD 4811, Australia ; Centre of Biodiscovery and Molecular Therapeutics, James Cook University, DB 21, James Cook Drive, Townsville, QLD 4811, Australia
| | - Craig L Bennett
- School of Pharmacy and Molecular Sciences, James Cook University, DB 21, James Cook Drive, Townsville, QLD 4811, Australia ; Department of Pediatrics, University of California, San Diego, La Jolla, CA 92093, USA
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21
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Lorson MA, Lorson CL. SMN-inducing compounds for the treatment of spinal muscular atrophy. Future Med Chem 2012; 4:2067-84. [PMID: 23157239 PMCID: PMC3589915 DOI: 10.4155/fmc.12.131] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Spinal muscular atrophy (SMA) is a leading genetic cause of infant mortality. A neurodegenerative disease, it is caused by loss of SMN1, although low, but essential, levels of SMN protein are produced by the nearly identical gene SMN2. While no effective treatment or therapy currently exists, a new wave of therapeutics has rapidly progressed from cell-based and preclinical animal models to the point where clinical trials have initiated for SMA-specific compounds. There are several reasons why SMA has moved relatively rapidly towards novel therapeutics, including: SMA is monogenic; the molecular understanding of SMN gene regulation has been building for nearly 20 years; and all SMA patients retain one or more copies of SMN2 that produces low levels of full-length, fully functional SMN protein. This review primarily focuses upon the biology behind the disease and examines SMN1- and SMN2-targeted therapeutics.
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Affiliation(s)
- Monique A Lorson
- Department of Veterinary Pathobiology, Bond Life Sciences Center, Room 440C, University of Missouri, MO 65211 USA
| | - Christian L Lorson
- Department of Veterinary Pathobiology, Bond Life Sciences Center, Room 471G, University of Missouri, Columbia, MO 65211, USA
- Department of Molecular Microbiology & Immunology, University of Missouri, MO, USA
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22
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Tang X, Seyb KI, Huang M, Schuman ER, Shi P, Zhu H, Glicksman MA. A high-throughput screening method for small-molecule inhibitors of the aberrant mutant SOD1 and dynein complex interaction. ACTA ACUST UNITED AC 2011; 17:314-26. [PMID: 22140121 DOI: 10.1177/1087057111429595] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Aberrant protein-protein interactions are attractive drug targets in a variety of neurodegenerative diseases due to the common pathology of accumulation of protein aggregates. In amyotrophic lateral sclerosis, mutations in SOD1 cause the formation of aggregates and inclusions that may sequester other proteins and disrupt cellular processes. It has been demonstrated that mutant SOD1, but not wild-type SOD1, interacts with the axonal transport motor dynein and that this interaction contributes to motor neuron cell death, suggesting that disrupting this interaction may be a potential therapeutic target. However, it can be challenging to configure a high-throughput screening (HTS)-compatible assay to detect inhibitors of a protein-protein interaction. Here we describe the development and challenges of an HTS for small-molecule inhibitors of the mutant SOD1-dynein interaction. We demonstrate that the interaction can be formed by coexpressing the A4V mutant SOD1 and dynein intermediate complex in cells and that this interaction can be disrupted by compounds added to the cell lysates. Finally, we show that some of the compounds identified from a pilot screen to inhibit the protein-protein interaction with this method specifically disrupt the interaction between the dynein complex and mtSOD1 but not the dynein complex itself when applied to live cells.
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Affiliation(s)
- Xiaohu Tang
- Department of Molecular and Cellular Biochemistry, College of Medicine, University of Kentucky, Lexington, KY, USA
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23
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Torres-Benito L, Neher MF, Cano R, Ruiz R, Tabares L. SMN requirement for synaptic vesicle, active zone and microtubule postnatal organization in motor nerve terminals. PLoS One 2011; 6:e26164. [PMID: 22022549 PMCID: PMC3192162 DOI: 10.1371/journal.pone.0026164] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2011] [Accepted: 09/21/2011] [Indexed: 11/18/2022] Open
Abstract
Low levels of the Survival Motor Neuron (SMN) protein produce Spinal Muscular Atrophy (SMA), a severe monogenetic disease in infants characterized by muscle weakness and impaired synaptic transmission. We report here severe structural and functional alterations in the organization of the organelles and the cytoskeleton of motor nerve terminals in a mouse model of SMA. The decrease in SMN levels resulted in the clustering of synaptic vesicles (SVs) and Active Zones (AZs), reduction in the size of the readily releasable pool (RRP), and the recycling pool (RP) of synaptic vesicles, a decrease in active mitochondria and limiting of neurofilament and microtubule maturation. We propose that SMN is essential for the normal postnatal maturation of motor nerve terminals and that SMN deficiency disrupts the presynaptic organization leading to neurodegeneration.
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Affiliation(s)
- Laura Torres-Benito
- Department of Medical Physiology and Biophysics, School of Medicine, University of Seville, Seville, Spain
| | - Margret Feodora Neher
- Department of Medical Physiology and Biophysics, School of Medicine, University of Seville, Seville, Spain
| | - Raquel Cano
- Department of Medical Physiology and Biophysics, School of Medicine, University of Seville, Seville, Spain
| | - Rocio Ruiz
- Department of Medical Physiology and Biophysics, School of Medicine, University of Seville, Seville, Spain
| | - Lucia Tabares
- Department of Medical Physiology and Biophysics, School of Medicine, University of Seville, Seville, Spain
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Abstract
MNDs (motorneuron diseases) are neurodegenerative disorders in which motorneurons located in the motor cortex, in the brainstem and in the spinal cord are affected. These diseases in their inherited or sporadic forms are mainly characterized by motor dysfunctions, occasionally associated with cognitive and behavioural alterations. Although these diseases show high variability in onset, progression and clinical symptoms, they share common pathological features, and motorneuronal loss invariably leads to muscle weakness and atrophy. One of the most relevant aspect of these disorders is the occurrence of defects in axonal transport, which have been postulated to be either a direct cause, or a consequence, of motorneuron degeneration. In fact, due to their peculiar morphology and high energetic metabolism, motorneurons deeply rely on efficient axonal transport processes. Dysfunction of axonal transport is known to adversely affect motorneuronal metabolism, inducing progressive degeneration and cell death. In this regard, the understanding of the fine mechanisms at the basis of the axonal transport process and of their possible alterations may help shed light on MND pathological processes. In the present review, we will summarize what is currently known about the alterations of axonal transport found to be either causative or a consequence of MNDs.
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25
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Coady TH, Lorson CL. SMN in spinal muscular atrophy and snRNP biogenesis. WILEY INTERDISCIPLINARY REVIEWS-RNA 2011; 2:546-64. [PMID: 21957043 DOI: 10.1002/wrna.76] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Ribonucleoprotein (RNP) complexes function in nearly every facet of cellular activity. The spliceosome is an essential RNP that accurately identifies introns and catalytically removes the intervening sequences, providing exquisite control of spatial, temporal, and developmental gene expressions. U-snRNPs are the building blocks for the spliceosome. A significant amount of insight into the molecular assembly of these essential particles has recently come from a seemingly unexpected area of research: neurodegeneration. Survival motor neuron (SMN) performs an essential role in the maturation of snRNPs, while the homozygous loss of SMN1 results in the development of spinal muscular atrophy (SMA), a devastating neurodegenerative disease. In this review, the function of SMN is examined within the context of snRNP biogenesis and evidence is examined which suggests that the SMN functional defects in snRNP biogenesis may account for the motor neuron pathology observed in SMA.
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Affiliation(s)
- Tristan H Coady
- Department of Veterinary Pathobiology, Bond Life Sciences Center, University of Missouri, Columbia, MO, USA
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26
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Sun X, Fontaine JM, Hoppe AD, Carra S, DeGuzman C, Martin JL, Simon S, Vicart P, Welsh MJ, Landry J, Benndorf R. Abnormal interaction of motor neuropathy-associated mutant HspB8 (Hsp22) forms with the RNA helicase Ddx20 (gemin3). Cell Stress Chaperones 2010; 15:567-82. [PMID: 20157854 PMCID: PMC3006614 DOI: 10.1007/s12192-010-0169-y] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2009] [Revised: 01/07/2010] [Accepted: 01/08/2010] [Indexed: 01/16/2023] Open
Abstract
A number of missense mutations in the two related small heat shock proteins HspB8 (Hsp22) and HspB1 (Hsp27) have been associated with the inherited motor neuron diseases (MND) distal hereditary motor neuropathy and Charcot-Marie-Tooth disease. HspB8 and HspB1 interact with each other, suggesting that these two etiologic factors may act through a common biochemical mechanism. However, their role in neuron biology and in MND is not understood. In a yeast two-hybrid screen, we identified the DEAD box protein Ddx20 (gemin3, DP103) as interacting partner of HspB8. Using co-immunoprecipitation, chemical cross-linking, and in vivo quantitative fluorescence resonance energy transfer, we confirmed this interaction. We also show that the two disease-associated mutant HspB8 forms have abnormally increased binding to Ddx20. Ddx20 itself binds to the survival-of-motor-neurons protein (SMN protein), and mutations in the SMN1 gene cause spinal muscular atrophy, another MND and one of the most prevalent genetic causes of infant mortality. Thus, these protein interaction data have linked the three etiologic factors HspB8, HspB1, and SMN protein, and mutations in any of their genes cause the various forms of MND. Ddx20 and SMN protein are involved in spliceosome assembly and pre-mRNA processing. RNase treatment affected the interaction of the mutant HspB8 with Ddx20 suggesting RNA involvement in this interaction and a potential role of HspB8 in ribonucleoprotein processing.
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Affiliation(s)
- Xiankui Sun
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109 USA
| | - Jean-Marc Fontaine
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109 USA
| | - Adam D. Hoppe
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI 48109 USA
| | - Serena Carra
- Le Centre de recherche en cancérologie, l’Université Laval, L’Hôtel-Dieu de Québec, Laval, Québec Canada G1R 2J6
- Section for Radiation and Stress Cell Biology, Department of Cell Biology, University Medical Center Groningen, 9713 AV Groningen, The Netherlands
| | - Cheryl DeGuzman
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109 USA
| | - Jody L. Martin
- Department of Medicine, Cardiovascular Institute, Loyola University Medical Center, Maywood, IL 60153 USA
| | - Stephanie Simon
- Laboratory BFA, University Paris Diderot/CNRS, 75013 Paris, France
| | - Patrick Vicart
- Laboratory BFA, University Paris Diderot/CNRS, 75013 Paris, France
| | - Michael J. Welsh
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109 USA
| | - Jacques Landry
- Le Centre de recherche en cancérologie, l’Université Laval, L’Hôtel-Dieu de Québec, Laval, Québec Canada G1R 2J6
| | - Rainer Benndorf
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109 USA
- Department of Pediatrics, Ohio State University, Columbus, OH 43205 USA
- The Center for Clinical and Translational Research, The Research Institute at Nationwide Children’s Hospital, Research Building II, Room WA2109, 700 Children’s Drive, Columbus, OH 43205 USA
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Zhang H, Robinson N, Wu C, Wang W, Harrington MA. Electrophysiological properties of motor neurons in a mouse model of severe spinal muscular atrophy: in vitro versus in vivo development. PLoS One 2010; 5:e11696. [PMID: 20657731 PMCID: PMC2908141 DOI: 10.1371/journal.pone.0011696] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2010] [Accepted: 06/22/2010] [Indexed: 11/21/2022] Open
Abstract
We examined the electrophysiological activity of motor neurons from the mouse model of severe spinal muscular atrophy (SMA) using two different methods: whole cell patch clamp of neurons cultured from day 13 embryos; and multi-electrode recording of ventral horns in spinal cord slices from pups on post-natal days 5 and 6. We used the MED64 multi-electrode array to record electrophysiological activity from motor neurons in slices from the lumbar spinal cord of SMA pups and their unaffected littermates. Recording simultaneously from up to 32 sites across the ventral horn, we observed a significant decrease in the number of active neurons in 5-6 day-old SMA pups compared to littermates. Ventral horn activity in control pups is significantly activated by serotonin and depressed by GABA, while these agents had much less effect on SMA slices. In contrast to the large differences observed in spinal cord, neurons cultured from SMA embryos for up to 21 days showed no significant differences in electrophysiological activity compared to littermates. No differences were observed in membrane potential, frequency of spiking and synaptic activity in cells from SMA embryos compared to controls. In addition, we observed no difference in cell survival between cells from SMA embryos and their unaffected littermates. Our results represent the first report on the electrophysiology of SMN-deficient motor neurons, and suggest that motor neuron development in vitro follows a different path than in vivo development, a path in which loss of SMN expression has little effect on motor neuron function and survival.
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Affiliation(s)
- Hongmei Zhang
- Department of Biological Sciences, Delaware State University, Dover, Delaware, United States of America
| | - Natallia Robinson
- Department of Biological Sciences, Delaware State University, Dover, Delaware, United States of America
| | - Chiayen Wu
- Alfred I. DuPont Hospital for Children, Wilmington, Delaware, United States of America
| | - Wenlan Wang
- Alfred I. DuPont Hospital for Children, Wilmington, Delaware, United States of America
| | - Melissa A. Harrington
- Department of Biological Sciences, Delaware State University, Dover, Delaware, United States of America
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Nlend Nlend R, Meyer K, Schümperli D. Repair of pre-mRNA splicing: prospects for a therapy for spinal muscular atrophy. RNA Biol 2010; 7:430-40. [PMID: 20523126 DOI: 10.4161/rna.7.4.12206] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Recent analyses of complete genomes have revealed that alternative splicing became more prevalent and important during eukaryotic evolution. Alternative splicing augments the protein repertoire--particularly that of the human genome--and plays an important role in the development and function of differentiated cell types. However, splicing is also extremely vulnerable, and defects in the proper recognition of splicing signals can give rise to a variety of diseases. In this review, we discuss splicing correction therapies, by using the inherited disease Spinal Muscular Atrophy (SMA) as an example. This lethal early childhood disorder is caused by deletions or other severe mutations of SMN1, a gene coding for the essential survival of motoneurons protein. A second gene copy present in humans and few non-human primates, SMN2, can only partly compensate for the defect because of a single nucleotide change in exon 7 that causes this exon to be skipped in the majority of mRNAs. Thus SMN2 is a prime therapeutic target for SMA. In recent years, several strategies based on small molecule drugs, antisense oligonucleotides or in vivo expressed RNAs have been developed that allow a correction of SMN2 splicing. For some of these, a therapeutic benefit has been demonstrated in mouse models for SMA. This means that clinical trials of such splicing therapies for SMA may become possible in the near future.
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Ning K, Drepper C, Valori CF, Ahsan M, Wyles M, Higginbottom A, Herrmann T, Shaw P, Azzouz M, Sendtner M. PTEN depletion rescues axonal growth defect and improves survival in SMN-deficient motor neurons. Hum Mol Genet 2010; 19:3159-68. [PMID: 20525971 DOI: 10.1093/hmg/ddq226] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Phosphatase and tensin homolog (PTEN), a negative regulator of the mammalian target of rapamycin (mTOR) pathway, is widely involved in the regulation of protein synthesis. Here we show that the PTEN protein is enriched in cell bodies and axon terminals of purified motor neurons. We explored the role of the PTEN pathway by manipulating PTEN expression in healthy and diseased motor neurons. PTEN depletion led to an increase in growth cone size, promotion of axonal elongation and increased survival of these cells. These changes were associated with alterations of downstream signaling pathways for local protein synthesis as revealed by an increase in pAKT and p70S6. Most notably, this treatment also restores beta-actin protein levels in axonal growth cones of SMN-deficient motor neurons. Furthermore, we report here that a single injection of adeno-associated virus serotype 6 (AAV6) expressing siPTEN into hind limb muscles at postnatal day 1 in SMNDelta7 mice leads to a significant PTEN depletion and robust improvement in motor neuron survival. Taken together, these data indicate that PTEN-mediated regulation of protein synthesis in motor neurons could represent a target for therapy in spinal muscular atrophy.
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Affiliation(s)
- Ke Ning
- Academic Neurology Unit, Department of Neuroscience, School of Medicine and Biomedical Sciences, University of Sheffield, Sheffield S10 2RX, UK
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El-Kadi AM, Bros-Facer V, Deng W, Philpott A, Stoddart E, Banks G, Jackson GS, Fisher EMC, Duchen MR, Greensmith L, Moore AL, Hafezparast M. The legs at odd angles (Loa) mutation in cytoplasmic dynein ameliorates mitochondrial function in SOD1G93A mouse model for motor neuron disease. J Biol Chem 2010; 285:18627-39. [PMID: 20382740 PMCID: PMC2881788 DOI: 10.1074/jbc.m110.129320] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a debilitating and fatal late-onset neurodegenerative disease. Familial cases of ALS (FALS) constitute ∼10% of all ALS cases, and mutant superoxide dismutase 1 (SOD1) is found in 15–20% of FALS. SOD1 mutations confer a toxic gain of unknown function to the protein that specifically targets the motor neurons in the cortex and the spinal cord. We have previously shown that the autosomal dominant Legs at odd angles (Loa) mutation in cytoplasmic dynein heavy chain (Dync1h1) delays disease onset and extends the life span of transgenic mice harboring human mutant SOD1G93A. In this study we provide evidence that despite the lack of direct interactions between mutant SOD1 and either mutant or wild-type cytoplasmic dynein, the Loa mutation confers significant reductions in the amount of mutant SOD1 protein in the mitochondrial matrix. Moreover, we show that the Loa mutation ameliorates defects in mitochondrial respiration and membrane potential observed in SOD1G93A motor neuron mitochondria. These data suggest that the Loa mutation reduces the vulnerability of mitochondria to the toxic effects of mutant SOD1, leading to improved mitochondrial function in SOD1G93A motor neurons.
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Affiliation(s)
- Ali Morsi El-Kadi
- Biochemistry and Biomedical Science, School of Life Sciences, University of Sussex, Brighton BN1 9QG, United Kingdom
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31
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Dahlstrom AB. Fast intra-axonal transport: Beginning, development and post-genome advances. Prog Neurobiol 2010; 90:119-45. [DOI: 10.1016/j.pneurobio.2009.11.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2009] [Revised: 11/23/2009] [Accepted: 11/23/2009] [Indexed: 01/02/2023]
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Abstract
AbstractThe nematode Caenorhabditis elegans is a genetic model organism and the only animal with a complete nervous system wiring diagram. With only 302 neurons and 95 striated muscle cells, a rich array of mutants with defective locomotion and the facility for individual targeted gene knockdown by RNA interference, it lends itself to the exploration of gene function at nerve muscle junctions. With approximately 60% of human disease genes having a C. elegans homologue, there is growing interest in the deployment of lowcost, high-throughput, drug screens of nematode transgenic and mutant strains mimicking aspects of the pathology of devastating human neuromuscular disorders. Here we explore the contributions already made by C. elegans to our understanding of muscular dystrophies (Duchenne and Becker), spinal muscular atrophy, amyotrophic lateral sclerosis, Friedreich’s ataxia, inclusion body myositis and the prospects for contributions to other neuromuscular disorders. A bottleneck to low-cost, in vivo, large-scale chemical library screening for new candidate therapies has been rapid, automated, behavioural phenotyping. Recent progress in quantifying simple swimming (thrashing) movements is making such screening possible and is expediting the translation of drug candidates towards the clinic.
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Bäumer D, Lee S, Nicholson G, Davies JL, Parkinson NJ, Murray LM, Gillingwater TH, Ansorge O, Davies KE, Talbot K. Alternative splicing events are a late feature of pathology in a mouse model of spinal muscular atrophy. PLoS Genet 2009; 5:e1000773. [PMID: 20019802 PMCID: PMC2787017 DOI: 10.1371/journal.pgen.1000773] [Citation(s) in RCA: 195] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2009] [Accepted: 11/16/2009] [Indexed: 11/24/2022] Open
Abstract
Spinal muscular atrophy is a severe motor neuron disease caused by inactivating mutations in the SMN1 gene leading to reduced levels of full-length functional SMN protein. SMN is a critical mediator of spliceosomal protein assembly, and complete loss or drastic reduction in protein leads to loss of cell viability. However, the reason for selective motor neuron degeneration when SMN is reduced to levels which are tolerated by all other cell types is not currently understood. Widespread splicing abnormalities have recently been reported at end-stage in a mouse model of SMA, leading to the proposition that disruption of efficient splicing is the primary mechanism of motor neuron death. However, it remains unclear whether splicing abnormalities are present during early stages of the disease, which would be a requirement for a direct role in disease pathogenesis. We performed exon-array analysis of RNA from SMN deficient mouse spinal cord at 3 time points, pre-symptomatic (P1), early symptomatic (P7), and late-symptomatic (P13). Compared to littermate control mice, SMA mice showed a time-dependent increase in the number of exons showing differential expression, with minimal differences between genotypes at P1 and P7, but substantial variation in late-symptomatic (P13) mice. Gene ontology analysis revealed differences in pathways associated with neuronal development as well as cellular injury. Validation of selected targets by RT-PCR confirmed the array findings and was in keeping with a shift between physiologically occurring mRNA isoforms. We conclude that the majority of splicing changes occur late in SMA and may represent a secondary effect of cell injury, though we cannot rule out significant early changes in a small number of transcripts crucial to motor neuron survival.
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Affiliation(s)
- Dirk Bäumer
- MRC Functional Genomics Unit, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Sheena Lee
- MRC Functional Genomics Unit, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - George Nicholson
- Department of Statistics, University of Oxford, Oxford, United Kingdom
| | - Joanna L. Davies
- Department of Statistics, University of Oxford, Oxford, United Kingdom
| | - Nicholas J. Parkinson
- MRC Functional Genomics Unit, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Lyndsay M. Murray
- Centre for Integrative Physiology and Euan MacDonald Centre for Motor Neuron Disease Research, University of Edinburgh Medical School, Edinburgh, United Kingdom
| | - Thomas H. Gillingwater
- Centre for Integrative Physiology and Euan MacDonald Centre for Motor Neuron Disease Research, University of Edinburgh Medical School, Edinburgh, United Kingdom
| | - Olaf Ansorge
- Department of Neuropathology, John Radcliffe Hospital, Oxford, United Kingdom
| | - Kay E. Davies
- MRC Functional Genomics Unit, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Kevin Talbot
- MRC Functional Genomics Unit, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
- Department of Clinical Neurology, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
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Xu L, Guo YS, Liu YL, Wu SY, Yang C, Wu DX, Wu HR, Zhang YS, Li CY. Oxidative stress in immune-mediated motoneuron destruction. Brain Res 2009; 1302:225-32. [DOI: 10.1016/j.brainres.2009.07.093] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2009] [Revised: 07/24/2009] [Accepted: 07/25/2009] [Indexed: 10/20/2022]
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Volkenstein S, Brors D, Hansen S, Berend A, Mlynski R, Aletsee C, Dazert S. Auditory development in progressive motor neuronopathy mouse mutants. Neurosci Lett 2009; 465:45-9. [PMID: 19735697 DOI: 10.1016/j.neulet.2009.09.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2009] [Revised: 08/30/2009] [Accepted: 09/02/2009] [Indexed: 10/20/2022]
Abstract
The present study was performed to elucidate the hearing development in the progressive motor neuronopathy (pmn) mouse mutant. This mouse has been used as a model for human motoneuron disease. A missense mutation in the tubulin-specific chaperon E (Tbce) gene on mouse chromosome 13 was localized as the underlying genetic defect. The protein encoded by the Tbce gene is essential for the formation of primary tubulin complexes. Studies on motoneurons show disorganization in microtubules and disturbed axonal transport, followed by retrograde degeneration of the motoneurons. A similar pathomechanism is also possible for hearing disorders where disrupted microtubules could cause functional deficits in spiral ganglion neurons or in cochlear hair cells. Click auditory brainstem response (ABR) audiometry in homozygous pmn mutants showed a normal onset of hearing, but an increasing hearing threshold from postnatal day 26 (P26) on to death, compared to heterozygous mutants and wild-type mice. Histological sections of the cochlea at different ages showed a regular morphology. Additionally, spiral ganglion explants from mutant and wild-type mice were cultured. The neurite length from pmn mutants was shorter than in wild-type mice, and the neurite number/explant was significantly decreased in pmn mutants. We show that the pmn mouse mutant is a model for a progressive rapid hearing loss from P26 on, after initially normal hearing development. Heterozygous mice are not affected by this defect. With the knowledge of the well-known pathomechanism of this defect in motoneurons, a dysfunction of cellular mechanisms regulating tubulin assembling suggests that tubulin assembling plays an essential role in hearing function and maintenance.
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Affiliation(s)
- Stefan Volkenstein
- Department of Otorhinolaryngology-Head and Neck Surgery, Ruhr-University of Bochum, St. Elisabeth-Hospital, Bleichstr. 15, 44787 Bochum, Germany.
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Abstract
Serotonin (5-HT) has been intimately linked with global regulation of motor behavior, local control of motoneuron excitability, functional recovery of spinal motoneurons as well as neuronal maturation and aging. Selective degeneration of motoneurons is the pathological hallmark of amyotrophic lateral sclerosis (ALS). Motoneurons that are preferentially affected in ALS are also densely innervated by 5-HT neurons (e.g., trigeminal, facial, ambiguus, and hypoglossal brainstem nuclei as well as ventral horn and motor cortex). Conversely, motoneuron groups that appear more resistant to the process of neurodegeneration in ALS (e.g., oculomotor, trochlear, and abducens nuclei) as well as the cerebellum receive only sparse 5-HT input. The glutamate excitotoxicity theory maintains that in ALS degeneration of motoneurons is caused by excessive glutamate neurotransmission, which is neurotoxic. Because of its facilitatory effects on glutaminergic motoneuron excitation, 5-HT may be pivotal to the pathogenesis and therapy of ALS. 5-HT levels as well as the concentrations 5-hydroxyindole acetic acid (5-HIAA), the major metabolite of 5-HT, are reduced in postmortem spinal cord tissue of ALS patients indicating decreased 5-HT release. Furthermore, cerebrospinal fluid levels of tryptophan, a precursor of 5-HT, are decreased in patients with ALS and plasma concentrations of tryptophan are also decreased with the lowest levels found in the most severely affected patients. In ALS progressive degeneration of 5-HT neurons would result in a compensatory increase in glutamate excitation of motoneurons. Additionally, because 5-HT, acting through presynaptic 5-HT1B receptors, inhibits glutamatergic synaptic transmission, lowered 5-HT activity would lead to increased synaptic glutamate release. Furthermore, 5-HT is a precursor of melatonin, which inhibits glutamate release and glutamate-induced neurotoxicity. Thus, progressive degeneration of 5-HT neurons affecting motoneuron activity constitutes the prime mover of the disease and its progression and treatment of ALS needs to be focused primarily on boosting 5-HT functions (e.g., pharmacologically via its precursors, reuptake inhibitors, selective 5-HT1A receptor agonists/5-HT2 receptor antagonists, and electrically through transcranial administration of AC pulsed picotesla electromagnetic fields) to prevent excessive glutamate activity in the motoneurons. In fact, 5HT1A and 5HT2 receptor agonists have been shown to prevent glutamate-induced neurotoxicity in primary cortical cell cultures and the 5-HT precursor 5-hydroxytryptophan (5-HTP) improved locomotor function and survival of transgenic SOD1 G93A mice, an animal model of ALS.
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Affiliation(s)
- Reuven Sandyk
- The Carrick Institute for Clinical Ergonomics Rehabilitation, and Applied Neurosciences, School of Engineering Technologies State University of New York at Farmingdale, Farmingdale, New York 11735, USA.
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Lim A, Kraut R. The Drosophila BEACH family protein, blue cheese, links lysosomal axon transport with motor neuron degeneration. J Neurosci 2009; 29:951-63. [PMID: 19176804 PMCID: PMC3849423 DOI: 10.1523/jneurosci.2582-08.2009] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2008] [Revised: 11/12/2008] [Accepted: 12/07/2008] [Indexed: 01/29/2023] Open
Abstract
Impaired axon transport is one of the earliest pathological manifestations of several neurodegenerative diseases, and mutations in motor proteins can exacerbate or cause degeneration (Williamson and Cleveland, 1999; Gunawardena and Goldstein, 2004; Stokin and Goldstein, 2006). Compromised function in lysosomes and other degradative organelles that intersect with the lysosomal pathway are also strongly implicated in neurodegenerative disease pathology (Nixon and Cataldo, 2006; Rubinsztein, 2006). However, any functional link between these two phenomena has not as yet been recognized. Drosophila mutants in blue cheese (bchs) undergo progressive brain degeneration as adults and have shortened life span (Finley et al., 2003), but the cellular function of Bchs and the cause of degeneration have not been identified. A role in lysosomal trafficking is suggested by the homology of Bchs with the vesicle trafficking-associated BEACH (Beige and Chediak-Higashi) domain protein family (Wang et al., 2002; De Lozanne, 2003) and by its genetic interaction with a lysosomal transport pathway (Simonsen et al., 2007). Here, we describe the degeneration of a population of identified larval motor neurons in bchs mutants. We present evidence that Bchs is primarily lysosomal in those motor neurons in wild type and, using live fluorescence imaging of individual motor neurons in intact larvae, show that lysosomal vesicles fail to be transported toward motor neuron termini in bchs mutant and Bchs-overexpressing larvae. We suggest therefore that anterograde transport of lysosomes toward synaptic termini is a key factor in preventing motor neuron degeneration and that Bchs reveals a functional link between the lysosomal degradative pathway and transport.
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Affiliation(s)
- Angeline Lim
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, California 95064, and
| | - Rachel Kraut
- Institute of Bioengineering and Nanotechnology, Agency for Science, Technology, and Research, Singapore 138669
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Paladino P, Valentino F, Piccoli T, Piccoli F, La Bella V. Cerebrospinal fluid tau protein is not a biological marker in amyotrophic lateral sclerosis. Eur J Neurol 2008; 16:257-61. [PMID: 19138331 DOI: 10.1111/j.1468-1331.2008.02405.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
BACKGROUND Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder leading to progressive motor neuron cell death. Etiopathogenesis is still imperfectly known and much effort have been undertaken to find a biological marker that could help in the early diagnosis and in the monitoring of disease progression. Cerebrospinal fluid (CSF) concentrations of tau, an axonal microtubule-associated protein, have been measured in ALS with levels found increased in some studies and unchanged in others. METHODS Total CSF tau level was assayed in a population of ALS patients (n = 57) and controls (n = 110) using a specific ELISA method. RESULTS No significant differences in the median CSF tau levels between ALS cases and controls were found [ALS: 126 pg/ml (78-222); controls: 112 pg/ml (71-188), P = ns]. In the ALS group, the bulbar-onset patients showed increased CSF tau levels as compared with the spinal-onset cases. These differences might be related to the higher age of the bulbar-onset patients. Further, no correlations were found between CSF tau concentrations and the rate of progression of the disease. CONCLUSIONS These results do not support the hypothesis that total CSF tau protein is a reliable biological marker for ALS.
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Affiliation(s)
- P Paladino
- Department of Neurology and Psychiatry, ALS Clinical Research Center, AOUP-University of Palermo, Palermo, Italy
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Zhang Z, Lotti F, Dittmar K, Younis I, Wan L, Kasim M, Dreyfuss G. SMN deficiency causes tissue-specific perturbations in the repertoire of snRNAs and widespread defects in splicing. Cell 2008; 133:585-600. [PMID: 18485868 PMCID: PMC2446403 DOI: 10.1016/j.cell.2008.03.031] [Citation(s) in RCA: 484] [Impact Index Per Article: 30.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2007] [Revised: 01/04/2008] [Accepted: 03/24/2008] [Indexed: 11/16/2022]
Abstract
The survival of motor neurons (SMN) protein is essential for the biogenesis of small nuclear RNA (snRNA)-ribonucleoproteins (snRNPs), the major components of the pre-mRNA splicing machinery. Though it is ubiquitously expressed, SMN deficiency causes the motor neuron degenerative disease spinal muscular atrophy (SMA). We show here that SMN deficiency, similar to that which occurs in severe SMA, has unexpected cell type-specific effects on the repertoire of snRNAs and mRNAs. It alters the stoichiometry of snRNAs and causes widespread pre-mRNA splicing defects in numerous transcripts of diverse genes, preferentially those containing a large number of introns, in SMN-deficient mouse tissues. These findings reveal a key role for the SMN complex in RNA metabolism and in splicing regulation and indicate that SMA is a general splicing disease that is not restricted to motor neurons.
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Affiliation(s)
- Zhenxi Zhang
- Howard Hughes Medical Institute, Department of Biochemistry and Biophysics, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6148, USA
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40
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Sgobio C, Trabalza A, Spalloni A, Zona C, Carunchio I, Longone P, Ammassari-Teule M. Abnormal medial prefrontal cortex connectivity and defective fear extinction in the presymptomatic G93A SOD1 mouse model of ALS. GENES BRAIN AND BEHAVIOR 2008; 7:427-34. [DOI: 10.1111/j.1601-183x.2007.00367.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Abstract
Several recent studies have highlighted the role of axonal transport in the pathogenesis of motor neuron diseases. Mutations in genes that control microtubule regulation and dynamics have been shown to cause motor neuron degeneration in mice and in a form of human motor neuron disease. In addition, mutations in the molecular motors dynein and kinesins and several proteins associated with the membranes of intracellular vesicles that undergo transport cause motor neuron degeneration in humans and mice. Paradoxically, evidence from studies on the legs at odd angles (Loa) mouse and a transgenic mouse model for human motor neuron disease suggest that partial limitation of the function of dynein may in fact lead to improved axonal transport in the transgenic mouse, leading to delayed disease onset and increased life span.
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Affiliation(s)
- Ali Morsi El-Kadi
- Department of Biochemistry, School of Life Sciences, University of Sussex, Brighton, United Kingdom
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42
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Abstract
Spinal muscular atrophy, a common autosomal recessive motor neuron disorder, is caused by the loss of the survival motor neuron gene (SMN1). SMN2, a nearly identical copy gene, is present in all spinal muscular atrophy patients but differs by a critical nucleotide that alters exon 7 splicing efficiency. This results in low survival motor neuron protein levels, which are not enough to sustain motor neurons. SMN disruption has been undertaken in different organisms (yeast, nematode, fly, zebrafish, and mouse) in an attempt to model this disease and gain fundamental knowledge about the survival motor neuron protein. This review compares the various animal models generated to date and summarizes a research picture that reveals a pleiotropic role for survival motor neuron protein; this summary also points to unique requirements for survival motor neuron protein in motor neurons. It is hoped that these observations will aid in pointing towards complementary paths for therapeutic discovery research.
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Affiliation(s)
- Aloicia Schmid
- University of Utah, Eccles Institute of Human Genetics, Salt Lake City, Utah, USA
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Beattie CE, Carrel TL, McWhorter ML. Fishing for a mechanism: using zebrafish to understand spinal muscular atrophy. J Child Neurol 2007; 22:995-1003. [PMID: 17761655 DOI: 10.1177/0883073807305671] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Motoneuron diseases cause paralysis and death due to loss of motoneurons that innervate skeletal muscle. Spinal muscular atrophy is a human motoneuron disease that is genetically linked to the survival motor neuron gene (SMN). Although SMN was identified more than a decade ago, it remains unclear how decreased levels of the SMN protein cause spinal muscular atrophy. The use of animal models, however, offers a crucial tool in determining the function of SMN in this disease. In this review, we discuss our efforts to develop a zebrafish model of spinal muscular atrophy.
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Affiliation(s)
- Christine E Beattie
- Ohio State University Center for Molecular Neurobiology, Department of Neuroscience, Columbus, OH, USA.
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Jankelowitz SK, Howells J, Burke D. Plasticity of inwardly rectifying conductances following a corticospinal lesion in human subjects. J Physiol 2007; 581:927-40. [PMID: 17363389 PMCID: PMC2170828 DOI: 10.1113/jphysiol.2006.123661] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
This study investigated whether there are changes in the excitability of motor axons in peripheral nerves of patients with corticospinal lesions, reflecting plasticity of the motoneuron due to altered descending drives and/or changes in afferent feedback. The excitability of motor and sensory axons in peripheral nerves of the affected limb of 11 patients with unilateral hemiparesis due to stroke was compared with that for the unaffected limbs and with data for 12 age-matched controls. There was significantly less accommodation to hyperpolarizing currents in motor axons on the affected side. There were small differences between the data for the unaffected side and that of the control subjects but these were not statistically significant. Other findings indicate that there was no change in resting membrane potential. There was no comparable alteration in the excitability of sensory axons. The changes in response of motor axons to hyperpolarizing currents could be reproduced in a computer model of the human motor axon by reducing the hyperpolarization-activated conductance, IH, by 30% and the quantitatively small leak conductance by 77%. The data for the uninvolved side matched the data for control subjects best when IH was increased. These findings are consistent with modulation of IH by activity. They demonstrate a change in the biophysical properties of motor axons not directly affected by the pathology and synaptically remote from the lesion, and have implications for 'trans-synaptic' changes in central nervous system pathways. In human subjects studies of motor axon properties may allow insight into processes affecting the motoneuron.
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Affiliation(s)
- Stacey K Jankelowitz
- Medical Foundation Building - K25, The University of Sydney, NSW 2006, Australia.
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van Bergeijk J, Rydel-Könecke K, Grothe C, Claus P. The spinal muscular atrophy gene product regulates neurite outgrowth: importance of the C terminus. FASEB J 2007; 21:1492-502. [PMID: 17317728 DOI: 10.1096/fj.06-7136com] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Spinal muscular atrophy is a neurodegenerative disease accompanied by a loss of motoneurons. Either mutations or deletions in the survival of motoneuron (SMN) gene are responsible for this defect. SMN is an assembly protein for RNA-protein complexes in the nucleus and is also found in axons of neurons. However, it is unclear which dysfunctions of SMN are important for disease progression. In this study we analyzed the contributions of different SMN regions for localization and neuronal differentiation associated with outgrowth of neurites. Suppression of endogenous SMN protein levels significantly decreased the growth of neurites. Down-regulation of the interacting protein gemin2 had the opposite effect. Surprisingly, selective overexpression of the SMN C-terminal domain promoted neurite outgrowth similar to full-length protein and could rescue the SMN knock-down effects. The knock-down led to a significant change in the G-/F-actin ratio, indicating a role for SMN in actin dynamics. Therefore, our data suggest a functional role for SMN in microfilament metabolism in axons of motoneurons.
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Affiliation(s)
- Jeroen van Bergeijk
- Department of Neuroanatomy, Hannover Medical School, Carl-Neuberg-Str.1, 30625 Hannover, Germany
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Smith KDB, Kallhoff V, Zheng H, Pautler RG. In vivo axonal transport rates decrease in a mouse model of Alzheimer's disease. Neuroimage 2007; 35:1401-8. [PMID: 17369054 PMCID: PMC2063432 DOI: 10.1016/j.neuroimage.2007.01.046] [Citation(s) in RCA: 107] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2006] [Revised: 01/05/2007] [Accepted: 01/23/2007] [Indexed: 01/20/2023] Open
Abstract
Axonopathy is a pronounced attribute of many neurodegenerative diseases. In Alzheimer's disease (AD), axonal swellings and degeneration are prevalent and may contribute to the symptoms of AD senile dementia. Current limitations in identifying the contribution of axonal damage to AD include the inability to detect when this damage occurs in relation to other identifiers of AD because of the invasiveness of existing methods. To overcome this, we further developed the MRI methodology Manganese Enhanced MRI (MEMRI) to assess in vivo axonal transport rates. Prior to amyloid-beta (Abeta) deposition, the axonal transport rates in the Tg2576 mouse model of AD were normal. As Abeta levels increased and before plaque formation, we observed a significant decrease in axonal transport rates of the Tg2576 mice compared to controls. After plaque formation, the decline in the transport rate in the Tg2576 mice became even more pronounced. These data indicate that in vivo axonal transport rates decrease prior to plaque formation in the Tg2576 mouse model of AD.
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Affiliation(s)
| | - Verena Kallhoff
- Dept. Molecular and Human Genetics, One Baylor Plaza, Houston, TX 77030
| | - Hui Zheng
- Dept. Molecular and Human Genetics, One Baylor Plaza, Houston, TX 77030
- Huffington Center on Aging, One Baylor Plaza, Houston, TX 77030
- Dept. Neuroscience, One Baylor Plaza, Houston, TX 77030
- Dept. Molecular and Cellular Biology Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030
| | - Robia G. Pautler
- Dept. Molecular Physiology and Biophysics, One Baylor Plaza, Houston, TX 77030
- Dept. Radiology, One Baylor Plaza, Houston, TX 77030
- Dept. Neuroscience, One Baylor Plaza, Houston, TX 77030
- ** To whom correspondence should be addressed. Robia G. Pautler, Ph.D., One Baylor Plaza, BCM: 335, Houston, TX 77030, e-mail: , phone: 713–798–3892
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Abstract
The number of genes associated with motor neuron degeneration has increased considerably over the past few years. As more gene mutations are identified, the hope arises that certain common themes and/or pathways become clear. In this overview, we focus on recent discoveries related to amyotrophic lateral sclerosis (ALS), spinal muscular atrophies (SMA), and distal hereditary motor neuropathies (dHMN). It is striking that many of the mutated genes that were linked to these diseases encode proteins that are either directly or indirectly involved in axonal transport or play a role in RNA metabolism. We hypothesize that both phenomena are not only crucial for the normal functioning of motor neurons, but that they could also be interconnected. In analogy with the situation after acute stress, axonal mRNA translation followed by retrograde transport of the signal back to the nucleus could play an important role in chronic motor neuron diseases. We hope that information on the genetic causes of these diseases and the insight into the pathologic processes involved could ultimately lead to therapeutic strategies that prevent or at least slow this degenerative process.
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Affiliation(s)
- Ludo Van Den Bosch
- Neurobiology, Campus Gasthuisberg O&N2 PB1022,Herestraat 49, B-3000 Leuven, Belgium.
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Frebel K, Wiese S. Signalling molecules essential for neuronal survival and differentiation. Biochem Soc Trans 2006; 34:1287-90. [PMID: 17073803 DOI: 10.1042/bst0341287] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Motoneurons are made in excess throughout development. Initial analysis of the mechanisms that lead to apoptotic cell death during later stages of development and the early postnatal period led to the discovery of neurotrophic factors. These factors comprise different families acting through different tyrosine kinase receptors. Intracellular signalling cascades that lead to the survival of neurons are, on the one hand, the Ras/Raf (Ras-activated factor)/MAPK (mitogen-activated protein kinase) pathway and, on the other, the PI3K (phosphoinositide 3-kinase)/Akt (protein kinase B) pathway. The initial thought of these factors acting as single molecules in separate cascades has been converted into a model in which the dynamics of interaction of these pathways and the subcellular diverse functions of the key regulators have been taken into account. Bag1 (Bcl-2-associated athanogene 1), a molecule that was originally found to act as a co-chaperone of Hsp70 (heat-shock protein 70), also interacts with B-Raf, C-Raf and Akt to phosphorylate Bad (Bcl-2/Bcl-XL-antagonist, causing cell death), a pro-apoptotic member of the Bcl-2 family, and leads to specific subcellular distribution of phosphorylated Akt and B-Raf. These functions lead to survival of embryonic neural stem cells and therefore serve as a key event to regulate the viability of these cells.
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Affiliation(s)
- K Frebel
- Institute for Clinical Neurobiology, Julius-Maximilians University of Würzburg, Josef Schneider Strasse 11, D97080 Würzburg, Germany
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Briese M, Richter DU, Sattelle DB, Ulfig N. SMN, the product of the spinal muscular atrophy-determining gene, is expressed widely but selectively in the developing human forebrain. J Comp Neurol 2006; 497:808-16. [PMID: 16786553 DOI: 10.1002/cne.21010] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The expression pattern of the survival motor neuron (SMN) protein has been investigated immunohistochemically in the human fetal forebrain from 14 to 38 weeks of gestation. Mutations in the SMN gene cause spinal muscular atrophy (SMA), an autosomal recessive disease characterized by degeneration of lower motor neurons in the spinal cord leading to progressive muscle wasting. SMN is a multifunctional protein and has been implicated in diverse cytoplasmic and nuclear processes. The monoclonal murine SMN antibody used in this study recognized a major band at approximately 34 kDa. In spinal cord anterior horn motor neurons at 13 weeks of gestation, the soma, proximal neurites, and nucleus were immunostained. In the nucleus, SMN immunolabeling was observed at the nuclear membrane, at the nucleolus, and at dot-like structures in the nucleoplasm likely to be coiled bodies and gems. In the fetal forebrain, SMN was immunodetected as early as 14 weeks of gestation. From 14 to 24 weeks of gestation, intense immunostaining was observed in the basal nucleus of Meynert, a major source of cholinergic afferents to the cortex. Less intensely labeled cells at lower packing density were also observed in the thalamus, reticular and perireticular nucleus, globus pallidus, hippocampus, amygdala, and enthorinal cortex. Immunolabeled cells were still detectable at 38 gestational weeks, the latest time point investigated. These findings provide an anatomical basis for future investigations of SMN functions during brain development and for the neuropathological characterization of severe SMA cases.
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Affiliation(s)
- Michael Briese
- MRC Functional Genetics Unit, Department of Physiology, Anatomy and Genetics, Le Gros Clark Building, University of Oxford, Oxford OX1 3QX, United Kingdom
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Perrin FE, Boisset G, Lathuilière A, Kato AC. Cell death pathways differ in several mouse models with motoneurone disease: analysis of pure motoneurone populations at a presymptomatic age. J Neurochem 2006; 98:1959-72. [PMID: 16831193 DOI: 10.1111/j.1471-4159.2006.04024.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
To identify candidate genes that are responsible for motoneurone degeneration, we combined laser capture microdissection with microarray technology. We analysed gene expression in pure motoneurones from two mouse mutants that develop motoneurone degeneration, progressive motor neuronopathy and wobbler. At a presymptomatic age, there was a significant differential expression of a restricted number of genes (25 and 72 in progressive motor neuronopathy and wobbler respectively, of 22 600 transcripts screened). We compared these results to our previous analyses in the copper-zinc superoxide dismutase mutant mouse (SOD1(G93A)) in which we observed a de-regulation of 27 genes. Some of these genes were de-regulated uniquely in one mouse mutant and some have already been identified in cell death pathways implicated in amyotrophic lateral sclerosis and animal models of motoneurone degeneration (i.e. de-regulation of intermediate filaments, axonal transport, the ubiquitin-proteasome system and excitotoxicity). One gene, vimentin, was differentially up-regulated in all mouse mutants; this main candidate gene has been confirmed by in situ hybridization and immunohistochemistry to be expressed in motoneurones in all mouse mutants. Furthermore, vimentin expression correlated with the state of motoneurone degeneration. These results identify early molecular changes that may be involved in the pathogenesis of motoneurones leading to cell death and favour a complex multipathway induction of the disease; surprisingly, there was no important modification in cell death-associated genes. This is the first study to show a clear difference in the genes that are de-regulated at an early stage in three different mouse models of motoneurone disease.
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Affiliation(s)
- Florence E Perrin
- Department of Basic Neuroscience, Faculty of Medicine, Geneva, Switzerland
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