1
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Miller N, Xu Z, Quinlan KA, Ji A, McGivern JV, Feng Z, Shi H, Ko CP, Tsai LH, Heckman CJ, Ebert AD, Ma YC. Mitigating aberrant Cdk5 activation alleviates mitochondrial defects and motor neuron disease symptoms in spinal muscular atrophy. Proc Natl Acad Sci U S A 2023; 120:e2300308120. [PMID: 37976261 PMCID: PMC10666147 DOI: 10.1073/pnas.2300308120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2023] [Accepted: 07/31/2023] [Indexed: 11/19/2023] Open
Abstract
Spinal muscular atrophy (SMA), the top genetic cause of infant mortality, is characterized by motor neuron degeneration. Mechanisms underlying SMA pathogenesis remain largely unknown. Here, we report that the activity of cyclin-dependent kinase 5 (Cdk5) and the conversion of its activating subunit p35 to the more potent activator p25 are significantly up-regulated in mouse models and human induced pluripotent stem cell (iPSC) models of SMA. The increase of Cdk5 activity occurs before the onset of SMA phenotypes, suggesting that it may be an initiator of the disease. Importantly, aberrant Cdk5 activation causes mitochondrial defects and motor neuron degeneration, as the genetic knockout of p35 in an SMA mouse model rescues mitochondrial transport and fragmentation defects, and alleviates SMA phenotypes including motor neuron hyperexcitability, loss of excitatory synapses, neuromuscular junction denervation, and motor neuron degeneration. Inhibition of the Cdk5 signaling pathway reduces the degeneration of motor neurons derived from SMA mice and human SMA iPSCs. Altogether, our studies reveal a critical role for the aberrant activation of Cdk5 in SMA pathogenesis and suggest a potential target for therapeutic intervention.
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Affiliation(s)
- Nimrod Miller
- Department of Pediatrics, Northwestern University Feinberg School of Medicine, Chicago, IL60611
- Stanley Manne Children's Research Institute, Ann and Robert H. Lurie Children’s Hospital of Chicago, Chicago, IL60611
| | - Zhaofa Xu
- Department of Pediatrics, Northwestern University Feinberg School of Medicine, Chicago, IL60611
- Stanley Manne Children's Research Institute, Ann and Robert H. Lurie Children’s Hospital of Chicago, Chicago, IL60611
| | - Katharina A. Quinlan
- Department of Neuroscience, Northwestern University Feinberg School of Medicine, Chicago, IL60611
- Department of Physical Medicine and Rehabilitation, Northwestern University Feinberg School of Medicine, Chicago, IL60611
- Department of Physical Therapy and Human Movement Sciences, Northwestern University Feinberg School of Medicine, Chicago, IL60611
- Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, George and Anne Ryan Institute for Neuroscience, University of Rhode Island, Kingston, RI02881
| | - Amy Ji
- Department of Pediatrics, Northwestern University Feinberg School of Medicine, Chicago, IL60611
| | - Jered V. McGivern
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI53226
| | - Zhihua Feng
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, CA90089
| | - Han Shi
- Department of Pediatrics, Northwestern University Feinberg School of Medicine, Chicago, IL60611
- Stanley Manne Children's Research Institute, Ann and Robert H. Lurie Children’s Hospital of Chicago, Chicago, IL60611
| | - Chien-Ping Ko
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, CA90089
| | - Li-Huei Tsai
- Department of Brain and Cognitive Sciences, Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, MA02139
| | - Charles J. Heckman
- Department of Neuroscience, Northwestern University Feinberg School of Medicine, Chicago, IL60611
- Department of Physical Medicine and Rehabilitation, Northwestern University Feinberg School of Medicine, Chicago, IL60611
- Department of Physical Therapy and Human Movement Sciences, Northwestern University Feinberg School of Medicine, Chicago, IL60611
| | - Allison D. Ebert
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI53226
| | - Yongchao C. Ma
- Department of Pediatrics, Northwestern University Feinberg School of Medicine, Chicago, IL60611
- Stanley Manne Children's Research Institute, Ann and Robert H. Lurie Children’s Hospital of Chicago, Chicago, IL60611
- Department of Neuroscience, Northwestern University Feinberg School of Medicine, Chicago, IL60611
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2
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Kim JK, Jha NN, Awano T, Caine C, Gollapalli K, Welby E, Kim SS, Fuentes-Moliz A, Wang X, Feng Z, Sera F, Takeda T, Homma S, Ko CP, Tabares L, Ebert AD, Rich MM, Monani UR. A spinal muscular atrophy modifier implicates the SMN protein in SNARE complex assembly at neuromuscular synapses. Neuron 2023; 111:1423-1439.e4. [PMID: 36863345 PMCID: PMC10164130 DOI: 10.1016/j.neuron.2023.02.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Revised: 12/11/2022] [Accepted: 02/02/2023] [Indexed: 03/04/2023]
Abstract
Reduced survival motor neuron (SMN) protein triggers the motor neuron disease, spinal muscular atrophy (SMA). Restoring SMN prevents disease, but it is not known how neuromuscular function is preserved. We used model mice to map and identify an Hspa8G470R synaptic chaperone variant, which suppressed SMA. Expression of the variant in the severely affected mutant mice increased lifespan >10-fold, improved motor performance, and mitigated neuromuscular pathology. Mechanistically, Hspa8G470R altered SMN2 splicing and simultaneously stimulated formation of a tripartite chaperone complex, critical for synaptic homeostasis, by augmenting its interaction with other complex members. Concomitantly, synaptic vesicular SNARE complex formation, which relies on chaperone activity for sustained neuromuscular synaptic transmission, was found perturbed in SMA mice and patient-derived motor neurons and was restored in modified mutants. Identification of the Hspa8G470R SMA modifier implicates SMN in SNARE complex assembly and casts new light on how deficiency of the ubiquitous protein causes motor neuron disease.
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Affiliation(s)
- Jeong-Ki Kim
- Department of Neurology, New York, NY, USA; Center for Motor Neuron Biology & Disease, New York, NY, USA
| | - Narendra N Jha
- Department of Neurology, New York, NY, USA; Center for Motor Neuron Biology & Disease, New York, NY, USA
| | - Tomoyuki Awano
- Department of Neurology, New York, NY, USA; Center for Motor Neuron Biology & Disease, New York, NY, USA
| | - Charlotte Caine
- Department of Neurology, New York, NY, USA; Center for Motor Neuron Biology & Disease, New York, NY, USA
| | - Kishore Gollapalli
- Department of Neurology, New York, NY, USA; Center for Motor Neuron Biology & Disease, New York, NY, USA
| | - Emily Welby
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Seung-Soo Kim
- Department of Obstetrics and Gynecology, New York, NY, USA
| | - Andrea Fuentes-Moliz
- Department of Medical Physiology and Biophysics, University of Seville School of Medicine, 41009, Seville, Spain
| | - Xueyong Wang
- Department of Neuroscience, Cell Biology and Physiology, Wright State University, Dayton, OH 45435, USA
| | - Zhihua Feng
- Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA
| | - Fusako Sera
- Department of Medicine, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Taishi Takeda
- Department of Neurology, New York, NY, USA; Center for Motor Neuron Biology & Disease, New York, NY, USA
| | - Shunichi Homma
- Department of Medicine, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Chien-Ping Ko
- Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA
| | - Lucia Tabares
- Department of Medical Physiology and Biophysics, University of Seville School of Medicine, 41009, Seville, Spain
| | - Allison D Ebert
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Mark M Rich
- Department of Neuroscience, Cell Biology and Physiology, Wright State University, Dayton, OH 45435, USA
| | - Umrao R Monani
- Department of Neurology, New York, NY, USA; Department of Pathology & Cell Biology, New York, NY, USA; Center for Motor Neuron Biology & Disease, New York, NY, USA; Colleen Giblin Research Laboratory, Columbia University Irving Medical Center, New York, NY 10032, USA.
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3
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Zhao X, Feng Z, Risher N, Mollin A, Sheedy J, Ling KKY, Narasimhan J, Dakka A, Baird JD, Ratni H, Lutz C, Chen K, Naryshkin N, Ko CP, Welch E, Metzger F, Weetall M. SMN protein is required throughout life to prevent spinal muscular atrophy disease progression. Hum Mol Genet 2021; 31:82-96. [PMID: 34368854 DOI: 10.1093/hmg/ddab220] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Revised: 07/19/2021] [Accepted: 07/22/2021] [Indexed: 11/12/2022] Open
Abstract
Spinal muscular atrophy (SMA) is caused by the loss of the survival motor neuron 1 (SMN1) gene function. The related SMN2 gene partially compensates but produces insufficient levels of SMN protein due to alternative splicing of exon 7. Evrysdi™ (risdiplam), recently approved for the treatment of SMA, and related compounds promote exon 7 inclusion to generate full-length SMN2 mRNA and increase SMN protein levels. SMNΔ7 type I SMA mice survive without treatment for ~ 17 days. SMN2 mRNA splicing modulators increase survival of SMN∆7 mice with treatment initiated at postnatal day 3 (PND3). To define SMN requirements for adult mice, SMNΔ7 mice were dosed with a SMN2 mRNA splicing modifier from PND3 to PND40, then dosing was stopped. Mice not treated after PND40 showed progressive weight loss, necrosis, and muscle atrophy after ~ 20 days. Male mice presented a more severe phenotype than female mice. Mice dosed continuously did not show disease symptoms. The estimated half-life of SMN protein is 2 days indicating that the SMA phenotype reappeared after SMN protein levels returned to baseline. Although SMN protein levels decreased with age in mice and SMN protein levels were higher in brain than in muscle, our studies suggest that SMN protein is required throughout the life of the mouse and is especially essential in adult peripheral tissues including muscle. These studies indicate that drugs such as risdiplam will be optimally therapeutic when given as early as possible after diagnosis and potentially will be required for the life of an SMA patient.
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Affiliation(s)
- Xin Zhao
- PTC Therapeutics, Inc., South Plainfield, NJ 07080, USA
| | - Zhihua Feng
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA
| | - Nicole Risher
- PTC Therapeutics, Inc., South Plainfield, NJ 07080, USA
| | - Anna Mollin
- PTC Therapeutics, Inc., South Plainfield, NJ 07080, USA
| | | | - Karen K Y Ling
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA
| | | | - Amal Dakka
- PTC Therapeutics, Inc., South Plainfield, NJ 07080, USA
| | - John D Baird
- PTC Therapeutics, Inc., South Plainfield, NJ 07080, USA
| | - Hasane Ratni
- F. Hoffmann-La Roche, Pharmaceutical Research and Early Development, Roche Innovation Center Basel, Grenzacherstrasse 124, 4070 Basel, Switzerland
| | | | | | | | - Chien-Ping Ko
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA
| | - Ellen Welch
- PTC Therapeutics, Inc., South Plainfield, NJ 07080, USA
| | - Friedrich Metzger
- F. Hoffmann-La Roche, Pharmaceutical Research and Early Development, Roche Innovation Center Basel, Grenzacherstrasse 124, 4070 Basel, Switzerland
| | - Marla Weetall
- PTC Therapeutics, Inc., South Plainfield, NJ 07080, USA
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4
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Feng Z, Ling KKY, Zhao X, Zhou C, Karp G, Welch EM, Naryshkin N, Ratni H, Chen KS, Metzger F, Paushkin S, Weetall M, Ko CP. Corrigendum to: Pharmacologically-induced mouse model of adult spinal muscular atrophy to evaluate effectiveness of therapeutics after disease onset. Hum Mol Genet 2020; 30:843. [PMID: 33201218 DOI: 10.1093/hmg/ddaa247] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2020] [Revised: 02/29/2020] [Accepted: 03/30/2020] [Indexed: 11/14/2022] Open
Affiliation(s)
- Zhihua Feng
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089-2520, USA
| | - Karen K Y Ling
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089-2520, USA
| | - Xin Zhao
- PTC Therapeutics, Inc., South Plainfield, NJ 07080, USA
| | - Chunyi Zhou
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089-2520, USA
| | - Gary Karp
- PTC Therapeutics, Inc., South Plainfield, NJ 07080, USA
| | - Ellen M Welch
- PTC Therapeutics, Inc., South Plainfield, NJ 07080, USA
| | | | - Hasane Ratni
- F. Hoffmann-La Roche Ltd, Pharmaceutical Research and Early Development, Roche Innovation Center Basel, Grenzacherstrasse 124, 4070 Basel, Switzerland
| | - Karen S Chen
- SMA Foundation, 888 Seventh Avenue, Suite 400, New York, NY 10019, USA
| | - Friedrich Metzger
- F. Hoffmann-La Roche Ltd, Pharmaceutical Research and Early Development, Roche Innovation Center Basel, Grenzacherstrasse 124, 4070 Basel, Switzerland
| | - Sergey Paushkin
- SMA Foundation, 888 Seventh Avenue, Suite 400, New York, NY 10019, USA
| | - Marla Weetall
- PTC Therapeutics, Inc., South Plainfield, NJ 07080, USA
| | - Chien-Ping Ko
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089-2520, USA
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5
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Kim JK, Jha NN, Feng Z, Faleiro MR, Chiriboga CA, Wei-Lapierre L, Dirksen RT, Ko CP, Monani UR. Muscle-specific SMN reduction reveals motor neuron-independent disease in spinal muscular atrophy models. J Clin Invest 2020; 130:1271-1287. [PMID: 32039917 DOI: 10.1172/jci131989] [Citation(s) in RCA: 58] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Accepted: 11/26/2019] [Indexed: 12/12/2022] Open
Abstract
Paucity of the survival motor neuron (SMN) protein triggers the oft-fatal infantile-onset motor neuron disorder, spinal muscular atrophy (SMA). Augmenting the protein is one means of treating SMA and recently led to FDA approval of an intrathecally delivered SMN-enhancing oligonucleotide currently in use. Notwithstanding the advent of this and other therapies for SMA, it is unclear whether the paralysis associated with the disease derives solely from dysfunctional motor neurons that may be efficiently targeted by restricted delivery of SMN-enhancing agents to the nervous system, or stems from broader defects of the motor unit, arguing for systemic SMN repletion. We investigated the disease-contributing effects of low SMN in one relevant peripheral organ - skeletal muscle - by selectively depleting the protein in only this tissue. We found that muscle deprived of SMN was profoundly damaged. Although a disease phenotype was not immediately obvious, persistent low levels of the protein eventually resulted in muscle fiber defects, neuromuscular junction abnormalities, compromised motor performance, and premature death. Importantly, restoring SMN after the onset of muscle pathology reversed disease. Our results provide the most compelling evidence yet for a direct contributing role of muscle in SMA and argue that an optimal therapy for the disease must be designed to treat this aspect of the dysfunctional motor unit.
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Affiliation(s)
- Jeong-Ki Kim
- Department of Pathology and Cell Biology and.,Center for Motor Neuron Biology and Disease, Columbia University Medical Center, New York, New York, USA
| | - Narendra N Jha
- Department of Pathology and Cell Biology and.,Center for Motor Neuron Biology and Disease, Columbia University Medical Center, New York, New York, USA
| | - Zhihua Feng
- Department of Biological Sciences, University of Southern California, Los Angeles, California, USA
| | - Michelle R Faleiro
- Department of Pathology and Cell Biology and.,Center for Motor Neuron Biology and Disease, Columbia University Medical Center, New York, New York, USA
| | - Claudia A Chiriboga
- Department of Neurology and.,Department of Pediatrics, Columbia University Medical Center, New York, New York, USA
| | - Lan Wei-Lapierre
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, New York, USA
| | - Robert T Dirksen
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, New York, USA
| | - Chien-Ping Ko
- Department of Biological Sciences, University of Southern California, Los Angeles, California, USA
| | - Umrao R Monani
- Department of Pathology and Cell Biology and.,Center for Motor Neuron Biology and Disease, Columbia University Medical Center, New York, New York, USA.,Department of Neurology and
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6
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Abstract
Stem cell technology enables the production of three-dimensional organ-like structures, but engineering multi-tissue anatomy has proven difficult. In this issue of Cell Stem Cell, Martins et al. (2020) show that generating a common progenitor cell for posterior spinal cord and muscle enables the formation of functional neuromuscular junctions in single organoids.
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Affiliation(s)
- Justin K Ichida
- Department of Stem Cell Biology and Regenerative Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA; Eli and Edythe Broad CIRM Center for Regenerative Medicine and Stem Cell Research at USC, Los Angeles, CA 90033, USA; Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA.
| | - Chien-Ping Ko
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA
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7
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Osman EY, Van Alstyne M, Yen PF, Lotti F, Feng Z, Ling KK, Ko CP, Pellizzoni L, Lorson CL. Minor snRNA gene delivery improves the loss of proprioceptive synapses on SMA motor neurons. JCI Insight 2020; 5:130574. [PMID: 32516136 DOI: 10.1172/jci.insight.130574] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Accepted: 05/13/2020] [Indexed: 12/17/2022] Open
Abstract
Spinal muscular atrophy (SMA) is an inherited neuromuscular disorder caused by reduced expression of the survival motor neuron (SMN) protein. SMN has key functions in multiple RNA pathways, including the biogenesis of small nuclear ribonucleoproteins that are essential components of both major (U2-dependent) and minor (U12-dependent) spliceosomes. Here we investigated the specific contribution of U12 splicing dysfunction to SMA pathology through selective restoration of this RNA pathway in mouse models of varying phenotypic severity. We show that virus-mediated delivery of minor snRNA genes specifically improves select U12 splicing defects induced by SMN deficiency in cultured mammalian cells, as well as in the spinal cord and dorsal root ganglia of SMA mice without increasing SMN expression. This approach resulted in a moderate amelioration of several parameters of the disease phenotype in SMA mice, including survival, weight gain, and motor function. Importantly, minor snRNA gene delivery improved aberrant splicing of the U12 intron-containing gene Stasimon and rescued the severe loss of proprioceptive sensory synapses on SMA motor neurons, which are early signatures of motor circuit dysfunction in mouse models. Taken together, these findings establish the direct contribution of U12 splicing dysfunction to synaptic deafferentation and motor circuit pathology in SMA.
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Affiliation(s)
- Erkan Y Osman
- Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, Missouri, USA
| | - Meaghan Van Alstyne
- Center for Motor Neuron Biology and Disease, Department of Pathology and Cell Biology, Columbia University, New York, New York, USA
| | - Pei-Fen Yen
- Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, Missouri, USA
| | - Francesco Lotti
- Center for Motor Neuron Biology and Disease, Department of Pathology and Cell Biology, Columbia University, New York, New York, USA
| | - Zhihua Feng
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, California, USA
| | - Karen Ky Ling
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, California, USA
| | - Chien-Ping Ko
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, California, USA
| | - Livio Pellizzoni
- Center for Motor Neuron Biology and Disease, Department of Pathology and Cell Biology, Columbia University, New York, New York, USA
| | - Christian L Lorson
- Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, Missouri, USA
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8
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Ratni H, Ebeling M, Baird J, Bendels S, Bylund J, Chen KS, Denk N, Feng Z, Green L, Guerard M, Jablonski P, Jacobsen B, Khwaja O, Kletzl H, Ko CP, Kustermann S, Marquet A, Metzger F, Mueller B, Naryshkin NA, Paushkin SV, Pinard E, Poirier A, Reutlinger M, Weetall M, Zeller A, Zhao X, Mueller L. Discovery of Risdiplam, a Selective Survival of Motor Neuron-2 ( SMN2) Gene Splicing Modifier for the Treatment of Spinal Muscular Atrophy (SMA). J Med Chem 2018; 61:6501-6517. [PMID: 30044619 DOI: 10.1021/acs.jmedchem.8b00741] [Citation(s) in RCA: 269] [Impact Index Per Article: 44.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
SMA is an inherited disease that leads to loss of motor function and ambulation and a reduced life expectancy. We have been working to develop orally administrated, systemically distributed small molecules to increase levels of functional SMN protein. Compound 2 was the first SMN2 splicing modifier tested in clinical trials in healthy volunteers and SMA patients. It was safe and well tolerated and increased SMN protein levels up to 2-fold in patients. Nevertheless, its development was stopped as a precautionary measure because retinal toxicity was observed in cynomolgus monkeys after chronic daily oral dosing (39 weeks) at exposures in excess of those investigated in patients. Herein, we describe the discovery of 1 (risdiplam, RG7916, RO7034067) that focused on thorough pharmacology, DMPK and safety characterization and optimization. This compound is undergoing pivotal clinical trials and is a promising medicine for the treatment of patients in all ages and stages with SMA.
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Affiliation(s)
- Hasane Ratni
- F. Hoffmann-La Roche Ltd., pRED, Pharma Research & Early Development , Roche Innovation Center Basel , Grenzacherstrasse 124 , 4070 Basel , Switzerland
| | - Martin Ebeling
- F. Hoffmann-La Roche Ltd., pRED, Pharma Research & Early Development , Roche Innovation Center Basel , Grenzacherstrasse 124 , 4070 Basel , Switzerland
| | - John Baird
- PTC Therapeutics, Inc. , 100 Corporate Court , South Plainfield , New Jersey 07080 , United States
| | - Stefanie Bendels
- F. Hoffmann-La Roche Ltd., pRED, Pharma Research & Early Development , Roche Innovation Center Basel , Grenzacherstrasse 124 , 4070 Basel , Switzerland
| | - Johan Bylund
- F. Hoffmann-La Roche Ltd., pRED, Pharma Research & Early Development , Roche Innovation Center Basel , Grenzacherstrasse 124 , 4070 Basel , Switzerland
| | - Karen S Chen
- SMA Foundation , 888 Seventh Avenue, Suite 400 , New York , New York 10019 , United States
| | - Nora Denk
- F. Hoffmann-La Roche Ltd., pRED, Pharma Research & Early Development , Roche Innovation Center Basel , Grenzacherstrasse 124 , 4070 Basel , Switzerland
| | - Zhihua Feng
- Section of Neurobiology, Department of Biological Sciences , University of Southern California , Los Angeles , California 90089 , United States
| | - Luke Green
- F. Hoffmann-La Roche Ltd., pRED, Pharma Research & Early Development , Roche Innovation Center Basel , Grenzacherstrasse 124 , 4070 Basel , Switzerland
| | - Melanie Guerard
- F. Hoffmann-La Roche Ltd., pRED, Pharma Research & Early Development , Roche Innovation Center Basel , Grenzacherstrasse 124 , 4070 Basel , Switzerland
| | - Philippe Jablonski
- F. Hoffmann-La Roche Ltd., pRED, Pharma Research & Early Development , Roche Innovation Center Basel , Grenzacherstrasse 124 , 4070 Basel , Switzerland
| | - Bjoern Jacobsen
- F. Hoffmann-La Roche Ltd., pRED, Pharma Research & Early Development , Roche Innovation Center Basel , Grenzacherstrasse 124 , 4070 Basel , Switzerland
| | - Omar Khwaja
- F. Hoffmann-La Roche Ltd., pRED, Pharma Research & Early Development , Roche Innovation Center Basel , Grenzacherstrasse 124 , 4070 Basel , Switzerland
| | - Heidemarie Kletzl
- F. Hoffmann-La Roche Ltd., pRED, Pharma Research & Early Development , Roche Innovation Center Basel , Grenzacherstrasse 124 , 4070 Basel , Switzerland
| | - Chien-Ping Ko
- Section of Neurobiology, Department of Biological Sciences , University of Southern California , Los Angeles , California 90089 , United States
| | - Stefan Kustermann
- F. Hoffmann-La Roche Ltd., pRED, Pharma Research & Early Development , Roche Innovation Center Basel , Grenzacherstrasse 124 , 4070 Basel , Switzerland
| | - Anne Marquet
- F. Hoffmann-La Roche Ltd., pRED, Pharma Research & Early Development , Roche Innovation Center Basel , Grenzacherstrasse 124 , 4070 Basel , Switzerland
| | - Friedrich Metzger
- F. Hoffmann-La Roche Ltd., pRED, Pharma Research & Early Development , Roche Innovation Center Basel , Grenzacherstrasse 124 , 4070 Basel , Switzerland
| | - Barbara Mueller
- F. Hoffmann-La Roche Ltd., pRED, Pharma Research & Early Development , Roche Innovation Center Basel , Grenzacherstrasse 124 , 4070 Basel , Switzerland
| | - Nikolai A Naryshkin
- PTC Therapeutics, Inc. , 100 Corporate Court , South Plainfield , New Jersey 07080 , United States
| | - Sergey V Paushkin
- SMA Foundation , 888 Seventh Avenue, Suite 400 , New York , New York 10019 , United States
| | - Emmanuel Pinard
- F. Hoffmann-La Roche Ltd., pRED, Pharma Research & Early Development , Roche Innovation Center Basel , Grenzacherstrasse 124 , 4070 Basel , Switzerland
| | - Agnès Poirier
- F. Hoffmann-La Roche Ltd., pRED, Pharma Research & Early Development , Roche Innovation Center Basel , Grenzacherstrasse 124 , 4070 Basel , Switzerland
| | - Michael Reutlinger
- F. Hoffmann-La Roche Ltd., pRED, Pharma Research & Early Development , Roche Innovation Center Basel , Grenzacherstrasse 124 , 4070 Basel , Switzerland
| | - Marla Weetall
- PTC Therapeutics, Inc. , 100 Corporate Court , South Plainfield , New Jersey 07080 , United States
| | - Andreas Zeller
- F. Hoffmann-La Roche Ltd., pRED, Pharma Research & Early Development , Roche Innovation Center Basel , Grenzacherstrasse 124 , 4070 Basel , Switzerland
| | - Xin Zhao
- PTC Therapeutics, Inc. , 100 Corporate Court , South Plainfield , New Jersey 07080 , United States
| | - Lutz Mueller
- F. Hoffmann-La Roche Ltd., pRED, Pharma Research & Early Development , Roche Innovation Center Basel , Grenzacherstrasse 124 , 4070 Basel , Switzerland
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9
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Osman EY, Washington CW, Kaifer KA, Mazzasette C, Patitucci TN, Florea KM, Simon ME, Ko CP, Ebert AD, Lorson CL. Optimization of Morpholino Antisense Oligonucleotides Targeting the Intronic Repressor Element1 in Spinal Muscular Atrophy. Mol Ther 2016; 24:1592-601. [PMID: 27401142 DOI: 10.1038/mt.2016.145] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2016] [Accepted: 07/04/2016] [Indexed: 12/13/2022] Open
Abstract
Loss of Survival Motor Neuron-1 (SMN1) causes Spinal Muscular Atrophy, a devastating neurodegenerative disease. SMN2 is a nearly identical copy gene; however SMN2 cannot prevent disease development in the absence of SMN1 since the majority of SMN2-derived transcripts are alternatively spliced, encoding a truncated, unstable protein lacking exon 7. Nevertheless, SMN2 retains the ability to produce low levels of functional protein. Previously we have described a splice-switching Morpholino antisense oligonucleotide (ASO) sequence that targets a potent intronic repressor, Element1 (E1), located upstream of SMN2 exon 7. In this study, we have assessed a novel panel of Morpholino ASOs with the goal of optimizing E1 ASO activity. Screening for efficacy in the SMNΔ7 mouse model, a single ASO variant was more active in vivo compared with the original E1(MO)-ASO. Sequence variant eleven (E1(MOv11)) consistently showed greater efficacy by increasing the lifespan of severe Spinal Muscular Atrophy mice after a single intracerebroventricular injection in the central nervous system, exhibited a strong dose-response across an order of magnitude, and demonstrated excellent target engagement by partially reversing the pathogenic SMN2 splicing event. We conclude that Morpholino modified ASOs are effective in modifying SMN2 splicing and have the potential for future Spinal Muscular Atrophy clinical applications.
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Affiliation(s)
- Erkan Y Osman
- Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, Missouri, USA
| | - Charles W Washington
- Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, Missouri, USA
| | - Kevin A Kaifer
- Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, Missouri, USA.,Department of Molecular Microbiology and Immunology, School of Medicine, University of Missouri, Columbia, Missouri, USA
| | - Chiara Mazzasette
- Department of Biological Sciences, University of Southern California, Los Angeles, California, USA
| | - Teresa N Patitucci
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Kyra M Florea
- Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, Missouri, USA.,Department of Molecular Microbiology and Immunology, School of Medicine, University of Missouri, Columbia, Missouri, USA
| | - Madeline E Simon
- Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, Missouri, USA.,Department of Molecular Microbiology and Immunology, School of Medicine, University of Missouri, Columbia, Missouri, USA
| | - Chien-Ping Ko
- Department of Biological Sciences, University of Southern California, Los Angeles, California, USA
| | - Allison D Ebert
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Christian L Lorson
- Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, Missouri, USA.,Department of Molecular Microbiology and Immunology, School of Medicine, University of Missouri, Columbia, Missouri, USA
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10
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Zhao X, Feng Z, Ling KKY, Mollin A, Sheedy J, Yeh S, Petruska J, Narasimhan J, Dakka A, Welch EM, Karp G, Chen KS, Metzger F, Ratni H, Lotti F, Tisdale S, Naryshkin NA, Pellizzoni L, Paushkin S, Ko CP, Weetall M. Pharmacokinetics, pharmacodynamics, and efficacy of a small-molecule SMN2 splicing modifier in mouse models of spinal muscular atrophy. Hum Mol Genet 2016; 25:1885-1899. [PMID: 26931466 PMCID: PMC5062580 DOI: 10.1093/hmg/ddw062] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Accepted: 02/22/2016] [Indexed: 12/26/2022] Open
Abstract
Spinal muscular atrophy (SMA) is caused by the loss or mutation of both copies of the survival motor neuron 1 (SMN1) gene. The related SMN2 gene is retained, but due to alternative splicing of exon 7, produces insufficient levels of the SMN protein. Here, we systematically characterize the pharmacokinetic and pharmacodynamics properties of the SMN splicing modifier SMN-C1. SMN-C1 is a low-molecular weight compound that promotes the inclusion of exon 7 and increases production of SMN protein in human cells and in two transgenic mouse models of SMA. Furthermore, increases in SMN protein levels in peripheral blood mononuclear cells and skin correlate with those in the central nervous system (CNS), indicating that a change of these levels in blood or skin can be used as a non-invasive surrogate to monitor increases of SMN protein levels in the CNS. Consistent with restored SMN function, SMN-C1 treatment increases the levels of spliceosomal and U7 small-nuclear RNAs and corrects RNA processing defects induced by SMN deficiency in the spinal cord of SMNΔ7 SMA mice. A 100% or greater increase in SMN protein in the CNS of SMNΔ7 SMA mice robustly improves the phenotype. Importantly, a ∼50% increase in SMN leads to long-term survival, but the SMA phenotype is only partially corrected, indicating that certain SMA disease manifestations may respond to treatment at lower doses. Overall, we provide important insights for the translation of pre-clinical data to the clinic and further therapeutic development of this series of molecules for SMA treatment.
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Affiliation(s)
- Xin Zhao
- PTC Therapeutics, Inc., South Plainfield, NJ 07080, USA
| | - Zhihua Feng
- Department of Biological Sciences, Section of Neurobiology, University of Southern California, Los Angeles, CA 90089, USA
| | - Karen K Y Ling
- Department of Biological Sciences, Section of Neurobiology, University of Southern California, Los Angeles, CA 90089, USA
| | - Anna Mollin
- PTC Therapeutics, Inc., South Plainfield, NJ 07080, USA
| | | | - Shirley Yeh
- PTC Therapeutics, Inc., South Plainfield, NJ 07080, USA
| | | | | | - Amal Dakka
- PTC Therapeutics, Inc., South Plainfield, NJ 07080, USA
| | - Ellen M Welch
- PTC Therapeutics, Inc., South Plainfield, NJ 07080, USA
| | - Gary Karp
- PTC Therapeutics, Inc., South Plainfield, NJ 07080, USA
| | - Karen S Chen
- SMA Foundation, 888 Seventh Avenue, Suite 400, New York, NY 10019, USA
| | - Friedrich Metzger
- F. Hoffmann-La Roche, Pharmaceutical Research and Early Development, Roche Innovation Center Basel, Grenzacherstrasse 124, Basel 4070, Switzerland
| | - Hasane Ratni
- F. Hoffmann-La Roche, Pharmaceutical Research and Early Development, Roche Innovation Center Basel, Grenzacherstrasse 124, Basel 4070, Switzerland
| | - Francesco Lotti
- Department of Pathology and Cell Biology, Center for Motor Neuron Biology and Disease, Columbia University, New York, NY 10032, USA and
| | - Sarah Tisdale
- Department of Pathology and Cell Biology, Center for Motor Neuron Biology and Disease, Columbia University, New York, NY 10032, USA and
| | | | - Livio Pellizzoni
- Department of Pathology and Cell Biology, Center for Motor Neuron Biology and Disease, Columbia University, New York, NY 10032, USA and
| | - Sergey Paushkin
- SMA Foundation, 888 Seventh Avenue, Suite 400, New York, NY 10019, USA
| | - Chien-Ping Ko
- Department of Biological Sciences, Section of Neurobiology, University of Southern California, Los Angeles, CA 90089, USA,
| | - Marla Weetall
- PTC Therapeutics, Inc., South Plainfield, NJ 07080, USA,
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11
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Feng Z, Ling KKY, Zhao X, Zhou C, Karp G, Welch EM, Naryshkin N, Ratni H, Chen KS, Metzger F, Paushkin S, Weetall M, Ko CP. Pharmacologically induced mouse model of adult spinal muscular atrophy to evaluate effectiveness of therapeutics after disease onset. Hum Mol Genet 2016; 25:964-75. [PMID: 26758873 DOI: 10.1093/hmg/ddv629] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Accepted: 12/29/2015] [Indexed: 12/21/2022] Open
Abstract
Spinal muscular atrophy (SMA) is a genetic disease characterized by atrophy of muscle and loss of spinal motor neurons. SMA is caused by deletion or mutation of the survival motor neuron 1 (SMN1) gene, and the nearly identical SMN2 gene fails to generate adequate levels of functional SMN protein due to a splicing defect. Currently, several therapeutics targeted to increase SMN protein are in clinical trials. An outstanding issue in the field is whether initiating treatment in symptomatic older patients would confer a therapeutic benefit, an important consideration as the majority of patients with milder forms of SMA are diagnosed at an older age. An SMA mouse model that recapitulates the disease phenotype observed in adolescent and adult SMA patients is needed to address this important question. We demonstrate here that Δ7 mice, a model of severe SMA, treated with a suboptimal dose of an SMN2 splicing modifier show increased SMN protein, survive into adulthood and display SMA disease-relevant pathologies. Increasing the dose of the splicing modifier after the disease symptoms are apparent further mitigates SMA histopathological features in suboptimally dosed adult Δ7 mice. In addition, inhibiting myostatin using intramuscular injection of AAV1-follistatin ameliorates muscle atrophy in suboptimally dosed Δ7 mice. Taken together, we have developed a new murine model of symptomatic SMA in adolescents and adult mice that is induced pharmacologically from a more severe model and demonstrated efficacy of both SMN2 splicing modifiers and a myostatin inhibitor in mice at later disease stages.
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Affiliation(s)
- Zhihua Feng
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089-2520, USA
| | - Karen K Y Ling
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089-2520, USA
| | - Xin Zhao
- PTC Therapeutics, Inc., South Plainfield, NJ 07080, USA
| | - Chunyi Zhou
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089-2520, USA
| | - Gary Karp
- PTC Therapeutics, Inc., South Plainfield, NJ 07080, USA
| | - Ellen M Welch
- PTC Therapeutics, Inc., South Plainfield, NJ 07080, USA
| | | | - Hasane Ratni
- F. Hoffmann-La Roche Ltd, Pharmaceutical Research and Early Development, Roche Innovation Center Basel, Grenzacherstrasse 124, 4070 Basel, Switzerland and
| | - Karen S Chen
- SMA Foundation, 888 Seventh Avenue, Suite 400, New York, NY 10019, USA
| | - Friedrich Metzger
- F. Hoffmann-La Roche Ltd, Pharmaceutical Research and Early Development, Roche Innovation Center Basel, Grenzacherstrasse 124, 4070 Basel, Switzerland and
| | - Sergey Paushkin
- SMA Foundation, 888 Seventh Avenue, Suite 400, New York, NY 10019, USA
| | - Marla Weetall
- PTC Therapeutics, Inc., South Plainfield, NJ 07080, USA
| | - Chien-Ping Ko
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089-2520, USA,
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12
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Abstract
The neuromuscular junction (NMJ) is engineered to be a highly reliable synapse to carry the control of the motor commands of the nervous system over the muscles. Its development, organization, and synaptic properties are highly structured and regulated to support such reliability and efficacy. Yet, the NMJ is also highly plastic, able to react to injury and adapt to changes. This balance between structural stability and synaptic efficacy on one hand and structural plasticity and repair on another hand is made possible by the intricate regulation of perisynaptic Schwann cells, glial cells at this synapse. They regulate both the efficacy and structural plasticity of the NMJ in a dynamic, bidirectional manner owing to their ability to decode synaptic transmission and by their interactions via trophic-related factors.
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Affiliation(s)
- Chien-Ping Ko
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, California 90089-2520
| | - Richard Robitaille
- Département de Neurosciences, Université de Montréal, Montréal, Québec H3C 3J7, Canada Groupe de Recherche sur le Système Nerveux Central, Université de Montréal, Montréal, Québec H3C 3J7, Canada
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13
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Rindt H, Feng Z, Mazzasette C, Glascock JJ, Valdivia D, Pyles N, Crawford TO, Swoboda KJ, Patitucci TN, Ebert AD, Sumner CJ, Ko CP, Lorson CL. Astrocytes influence the severity of spinal muscular atrophy. Hum Mol Genet 2015; 24:4094-102. [PMID: 25911676 DOI: 10.1093/hmg/ddv148] [Citation(s) in RCA: 79] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2015] [Accepted: 04/20/2015] [Indexed: 02/02/2023] Open
Abstract
Systemically low levels of survival motor neuron-1 (SMN1) protein cause spinal muscular atrophy (SMA). α-Motor neurons of the spinal cord are considered particularly vulnerable in this genetic disorder and their dysfunction and loss cause progressive muscle weakness, paralysis and eventually premature death of afflicted individuals. Historically, SMA was therefore considered a motor neuron-autonomous disease. However, depletion of SMN in motor neurons of normal mice elicited only a very mild phenotype. Conversely, restoration of SMN to motor neurons in an SMA mouse model had only modest effects on the SMA phenotype and survival. Collectively, these results suggested that additional cell types contribute to the pathogenesis of SMA, and understanding the non-autonomous requirements is crucial for developing effective therapies. Astrocytes are critical for regulating synapse formation and function as well as metabolic support for neurons. We hypothesized that astrocyte functions are disrupted in SMA, exacerbating disease progression. Using viral-based restoration of SMN specifically to astrocytes, survival in severe and intermediate SMA mice was observed. In addition, neuromuscular circuitry was improved. Astrogliosis was prominent in end-stage SMA mice and in post-mortem patient spinal cords. Increased expression of proinflammatory cytokines was partially normalized in treated mice, suggesting that astrocytes contribute to the pathogenesis of SMA.
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Affiliation(s)
- Hansjörg Rindt
- Department of Veterinary Pathobiology and Department of Molecular Microbiology and Immunology, University of Missouri, Bond Life Sciences Center, Columbia, MO 65211, USA
| | - Zhihua Feng
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA
| | - Chiara Mazzasette
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA
| | - Jacqueline J Glascock
- Department of Veterinary Pathobiology and Department of Molecular Microbiology and Immunology, University of Missouri, Bond Life Sciences Center, Columbia, MO 65211, USA
| | - David Valdivia
- Departments of Neurology and Neuroscience, Johns Hopkins School of Medicine, Baltimore, MD 21205, USA
| | - Noah Pyles
- Departments of Neurology and Neuroscience, Johns Hopkins School of Medicine, Baltimore, MD 21205, USA
| | - Thomas O Crawford
- Departments of Neurology and Neuroscience, Johns Hopkins School of Medicine, Baltimore, MD 21205, USA
| | - Kathryn J Swoboda
- Department of Neurology, University of Utah School of Medicine, Salt Lake City, UT 84132, USA and
| | - Teresa N Patitucci
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Allison D Ebert
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Charlotte J Sumner
- Departments of Neurology and Neuroscience, Johns Hopkins School of Medicine, Baltimore, MD 21205, USA
| | - Chien-Ping Ko
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA
| | - Christian L Lorson
- Department of Veterinary Pathobiology and Department of Molecular Microbiology and Immunology, University of Missouri, Bond Life Sciences Center, Columbia, MO 65211, USA,
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14
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Miller N, Feng Z, Edens BM, Yang B, Shi H, Sze CC, Hong BT, Su SC, Cantu JA, Topczewski J, Crawford TO, Ko CP, Sumner CJ, Ma L, Ma YC. Non-aggregating tau phosphorylation by cyclin-dependent kinase 5 contributes to motor neuron degeneration in spinal muscular atrophy. J Neurosci 2015; 35:6038-50. [PMID: 25878277 PMCID: PMC4397602 DOI: 10.1523/jneurosci.3716-14.2015] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Revised: 02/25/2015] [Accepted: 03/03/2015] [Indexed: 01/27/2023] Open
Abstract
Mechanisms underlying motor neuron degeneration in spinal muscular atrophy (SMA), the leading inherited cause of infant mortality, remain largely unknown. Many studies have established the importance of hyperphosphorylation of the microtubule-associated protein tau in various neurodegenerative disorders, including Alzheimer's and Parkinson's diseases. However, tau phosphorylation in SMA pathogenesis has yet to be investigated. Here we show that tau phosphorylation on serine 202 (S202) and threonine 205 (T205) is increased significantly in SMA motor neurons using two SMA mouse models and human SMA patient spinal cord samples. Interestingly, phosphorylated tau does not form aggregates in motor neurons or neuromuscular junctions (NMJs), even at late stages of SMA disease, distinguishing it from other tauopathies. Hyperphosphorylation of tau on S202 and T205 is mediated by cyclin-dependent kinase 5 (Cdk5) in SMA disease condition, because tau phosphorylation at these sites is significantly reduced in Cdk5 knock-out mice; genetic knock-out of Cdk5 activating subunit p35 in an SMA mouse model also leads to reduced tau phosphorylation on S202 and T205 in the SMA;p35(-/-) compound mutant mice. In addition, expression of the phosphorylation-deficient tauS202A,T205A mutant alleviates motor neuron defects in a zebrafish SMA model in vivo and mouse motor neuron degeneration in culture, whereas expression of phosphorylation-mimetic tauS202E,T205E promotes motor neuron defects. More importantly, genetic knock-out of tau in SMA mice rescues synapse stripping on motor neurons, NMJ denervation, and motor neuron degeneration in vivo. Altogether, our findings suggest a novel mechanism for SMA pathogenesis in which hyperphosphorylation of non-aggregating tau by Cdk5 contributes to motor neuron degeneration.
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Affiliation(s)
- Nimrod Miller
- Departments of Pediatrics, Neurology, and Physiology, Northwestern University Feinberg School of Medicine, Lurie Children's Hospital of Chicago, Chicago, Illinois 60611
| | - Zhihua Feng
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, California 90089
| | - Brittany M Edens
- Departments of Pediatrics, Neurology, and Physiology, Northwestern University Feinberg School of Medicine, Lurie Children's Hospital of Chicago, Chicago, Illinois 60611
| | - Ben Yang
- Departments of Pediatrics, Neurology, and Physiology, Northwestern University Feinberg School of Medicine, Lurie Children's Hospital of Chicago, Chicago, Illinois 60611
| | - Han Shi
- Departments of Pediatrics, Neurology, and Physiology, Northwestern University Feinberg School of Medicine, Lurie Children's Hospital of Chicago, Chicago, Illinois 60611
| | - Christie C Sze
- Departments of Pediatrics, Neurology, and Physiology, Northwestern University Feinberg School of Medicine, Lurie Children's Hospital of Chicago, Chicago, Illinois 60611
| | - Benjamin Taige Hong
- Departments of Pediatrics, Neurology, and Physiology, Northwestern University Feinberg School of Medicine, Lurie Children's Hospital of Chicago, Chicago, Illinois 60611, State Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410078, China
| | - Susan C Su
- Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115, and
| | - Jorge A Cantu
- Departments of Pediatrics, Neurology, and Physiology, Northwestern University Feinberg School of Medicine, Lurie Children's Hospital of Chicago, Chicago, Illinois 60611
| | - Jacek Topczewski
- Departments of Pediatrics, Neurology, and Physiology, Northwestern University Feinberg School of Medicine, Lurie Children's Hospital of Chicago, Chicago, Illinois 60611
| | - Thomas O Crawford
- Departments of Neurology and Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Chien-Ping Ko
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, California 90089
| | - Charlotte J Sumner
- Departments of Neurology and Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Long Ma
- State Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410078, China
| | - Yong-Chao Ma
- Departments of Pediatrics, Neurology, and Physiology, Northwestern University Feinberg School of Medicine, Lurie Children's Hospital of Chicago, Chicago, Illinois 60611,
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15
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Naryshkin NA, Weetall M, Dakka A, Narasimhan J, Zhao X, Feng Z, Ling KKY, Karp GM, Qi H, Woll MG, Chen G, Zhang N, Gabbeta V, Vazirani P, Bhattacharyya A, Furia B, Risher N, Sheedy J, Kong R, Ma J, Turpoff A, Lee CS, Zhang X, Moon YC, Trifillis P, Welch EM, Colacino JM, Babiak J, Almstead NG, Peltz SW, Eng LA, Chen KS, Mull JL, Lynes MS, Rubin LL, Fontoura P, Santarelli L, Haehnke D, McCarthy KD, Schmucki R, Ebeling M, Sivaramakrishnan M, Ko CP, Paushkin SV, Ratni H, Gerlach I, Ghosh A, Metzger F. Motor neuron disease. SMN2 splicing modifiers improve motor function and longevity in mice with spinal muscular atrophy. Science 2014; 345:688-93. [PMID: 25104390 DOI: 10.1126/science.1250127] [Citation(s) in RCA: 346] [Impact Index Per Article: 34.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Spinal muscular atrophy (SMA) is a genetic disease caused by mutation or deletion of the survival of motor neuron 1 (SMN1) gene. A paralogous gene in humans, SMN2, produces low, insufficient levels of functional SMN protein due to alternative splicing that truncates the transcript. The decreased levels of SMN protein lead to progressive neuromuscular degeneration and high rates of mortality. Through chemical screening and optimization, we identified orally available small molecules that shift the balance of SMN2 splicing toward the production of full-length SMN2 messenger RNA with high selectivity. Administration of these compounds to Δ7 mice, a model of severe SMA, led to an increase in SMN protein levels, improvement of motor function, and protection of the neuromuscular circuit. These compounds also extended the life span of the mice. Selective SMN2 splicing modifiers may have therapeutic potential for patients with SMA.
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Affiliation(s)
| | - Marla Weetall
- PTC Therapeutics, 100 Corporate Court, South Plainfield, NJ 07080, USA
| | - Amal Dakka
- PTC Therapeutics, 100 Corporate Court, South Plainfield, NJ 07080, USA
| | - Jana Narasimhan
- PTC Therapeutics, 100 Corporate Court, South Plainfield, NJ 07080, USA
| | - Xin Zhao
- PTC Therapeutics, 100 Corporate Court, South Plainfield, NJ 07080, USA
| | - Zhihua Feng
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA
| | - Karen K Y Ling
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA
| | - Gary M Karp
- PTC Therapeutics, 100 Corporate Court, South Plainfield, NJ 07080, USA
| | - Hongyan Qi
- PTC Therapeutics, 100 Corporate Court, South Plainfield, NJ 07080, USA
| | - Matthew G Woll
- PTC Therapeutics, 100 Corporate Court, South Plainfield, NJ 07080, USA
| | - Guangming Chen
- PTC Therapeutics, 100 Corporate Court, South Plainfield, NJ 07080, USA
| | - Nanjing Zhang
- PTC Therapeutics, 100 Corporate Court, South Plainfield, NJ 07080, USA
| | | | - Priya Vazirani
- PTC Therapeutics, 100 Corporate Court, South Plainfield, NJ 07080, USA
| | | | - Bansri Furia
- PTC Therapeutics, 100 Corporate Court, South Plainfield, NJ 07080, USA
| | - Nicole Risher
- PTC Therapeutics, 100 Corporate Court, South Plainfield, NJ 07080, USA
| | - Josephine Sheedy
- PTC Therapeutics, 100 Corporate Court, South Plainfield, NJ 07080, USA
| | - Ronald Kong
- PTC Therapeutics, 100 Corporate Court, South Plainfield, NJ 07080, USA
| | - Jiyuan Ma
- PTC Therapeutics, 100 Corporate Court, South Plainfield, NJ 07080, USA
| | - Anthony Turpoff
- PTC Therapeutics, 100 Corporate Court, South Plainfield, NJ 07080, USA
| | - Chang-Sun Lee
- PTC Therapeutics, 100 Corporate Court, South Plainfield, NJ 07080, USA
| | - Xiaoyan Zhang
- PTC Therapeutics, 100 Corporate Court, South Plainfield, NJ 07080, USA
| | - Young-Choon Moon
- PTC Therapeutics, 100 Corporate Court, South Plainfield, NJ 07080, USA
| | | | - Ellen M Welch
- PTC Therapeutics, 100 Corporate Court, South Plainfield, NJ 07080, USA
| | - Joseph M Colacino
- PTC Therapeutics, 100 Corporate Court, South Plainfield, NJ 07080, USA
| | - John Babiak
- PTC Therapeutics, 100 Corporate Court, South Plainfield, NJ 07080, USA
| | - Neil G Almstead
- PTC Therapeutics, 100 Corporate Court, South Plainfield, NJ 07080, USA
| | - Stuart W Peltz
- PTC Therapeutics, 100 Corporate Court, South Plainfield, NJ 07080, USA.
| | - Loren A Eng
- SMA Foundation, 888 Seventh Avenue, Suite 400, New York, NY 10019, USA
| | - Karen S Chen
- SMA Foundation, 888 Seventh Avenue, Suite 400, New York, NY 10019, USA
| | - Jesse L Mull
- Department of Stem Cell and Regenerative Biology and the Harvard Stem Cell Institute, Harvard University, Cambridge, MA 02138, USA
| | - Maureen S Lynes
- Department of Stem Cell and Regenerative Biology and the Harvard Stem Cell Institute, Harvard University, Cambridge, MA 02138, USA
| | - Lee L Rubin
- Department of Stem Cell and Regenerative Biology and the Harvard Stem Cell Institute, Harvard University, Cambridge, MA 02138, USA
| | - Paulo Fontoura
- Roche Pharmaceutical Research and Early Development, Roche Innovation Center Basel, F. Hoffmann-La Roche, Grenzacherstrasse 124, 4070 Basel, Switzerland
| | - Luca Santarelli
- Roche Pharmaceutical Research and Early Development, Roche Innovation Center Basel, F. Hoffmann-La Roche, Grenzacherstrasse 124, 4070 Basel, Switzerland
| | - Daniel Haehnke
- Roche Pharmaceutical Research and Early Development, Roche Innovation Center Basel, F. Hoffmann-La Roche, Grenzacherstrasse 124, 4070 Basel, Switzerland
| | | | - Roland Schmucki
- Roche Pharmaceutical Research and Early Development, Roche Innovation Center Basel, F. Hoffmann-La Roche, Grenzacherstrasse 124, 4070 Basel, Switzerland
| | - Martin Ebeling
- Roche Pharmaceutical Research and Early Development, Roche Innovation Center Basel, F. Hoffmann-La Roche, Grenzacherstrasse 124, 4070 Basel, Switzerland
| | - Manaswini Sivaramakrishnan
- Roche Pharmaceutical Research and Early Development, Roche Innovation Center Basel, F. Hoffmann-La Roche, Grenzacherstrasse 124, 4070 Basel, Switzerland
| | - Chien-Ping Ko
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA
| | - Sergey V Paushkin
- SMA Foundation, 888 Seventh Avenue, Suite 400, New York, NY 10019, USA
| | - Hasane Ratni
- Roche Pharmaceutical Research and Early Development, Roche Innovation Center Basel, F. Hoffmann-La Roche, Grenzacherstrasse 124, 4070 Basel, Switzerland
| | - Irene Gerlach
- Roche Pharmaceutical Research and Early Development, Roche Innovation Center Basel, F. Hoffmann-La Roche, Grenzacherstrasse 124, 4070 Basel, Switzerland
| | - Anirvan Ghosh
- Roche Pharmaceutical Research and Early Development, Roche Innovation Center Basel, F. Hoffmann-La Roche, Grenzacherstrasse 124, 4070 Basel, Switzerland
| | - Friedrich Metzger
- Roche Pharmaceutical Research and Early Development, Roche Innovation Center Basel, F. Hoffmann-La Roche, Grenzacherstrasse 124, 4070 Basel, Switzerland.
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16
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Sahashi K, Ling KKY, Hua Y, Wilkinson JE, Nomakuchi T, Rigo F, Hung G, Xu D, Jiang YP, Lin RZ, Ko CP, Bennett CF, Krainer AR. Pathological impact of SMN2 mis-splicing in adult SMA mice. EMBO Mol Med 2013; 5:1586-601. [PMID: 24014320 PMCID: PMC3799581 DOI: 10.1002/emmm.201302567] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Revised: 08/06/2013] [Accepted: 08/09/2013] [Indexed: 12/18/2022] Open
Abstract
Loss-of-function mutations in SMN1 cause spinal muscular atrophy (SMA), a leading genetic cause of infant mortality. The related SMN2 gene expresses suboptimal levels of functional SMN protein, due to a splicing defect. Many SMA patients reach adulthood, and there is also adult-onset (type IV) SMA. There is currently no animal model for adult-onset SMA, and the tissue-specific pathogenesis of post-developmental SMN deficiency remains elusive. Here, we use an antisense oligonucleotide (ASO) to exacerbate SMN2 mis-splicing. Intracerebroventricular ASO injection in adult SMN2-transgenic mice phenocopies key aspects of adult-onset SMA, including delayed-onset motor dysfunction and relevant histopathological features. SMN2 mis-splicing increases during late-stage disease, likely accelerating disease progression. Systemic ASO injection in adult mice causes peripheral SMN2 mis-splicing and affects prognosis, eliciting marked liver and heart pathologies, with decreased IGF1 levels. ASO dose–response and time-course studies suggest that only moderate SMN levels are required in the adult central nervous system, and treatment with a splicing-correcting ASO shows a broad therapeutic time window. We describe distinctive pathological features of adult-onset and early-onset SMA.
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Van Meerbeke JP, Gibbs RM, Plasterer HL, Miao W, Feng Z, Lin MY, Rucki AA, Wee CD, Xia B, Sharma S, Jacques V, Li DK, Pellizzoni L, Rusche JR, Ko CP, Sumner CJ. The DcpS inhibitor RG3039 improves motor function in SMA mice. Hum Mol Genet 2013; 22:4074-83. [PMID: 23727836 DOI: 10.1093/hmg/ddt257] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Spinal muscular atrophy (SMA) is caused by mutations of the survival motor neuron 1 (SMN1) gene, retention of the survival motor neuron 2 (SMN2) gene and insufficient expression of full-length survival motor neuron (SMN) protein. Quinazolines increase SMN2 promoter activity and inhibit the ribonucleic acid scavenger enzyme DcpS. The quinazoline derivative RG3039 has advanced to early phase clinical trials. In preparation for efficacy studies in SMA patients, we investigated the effects of RG3039 in severe SMA mice. Here, we show that RG3039 distributed to central nervous system tissues where it robustly inhibited DcpS enzyme activity, but minimally activated SMN expression or the assembly of small nuclear ribonucleoproteins. Nonetheless, treated SMA mice showed a dose-dependent increase in survival, weight and motor function. This was associated with improved motor neuron somal and neuromuscular junction synaptic innervation and function and increased muscle size. RG3039 also enhanced survival of conditional SMA mice in which SMN had been genetically restored to motor neurons. As this systemically delivered drug may have therapeutic benefits that extend beyond motor neurons, it could act additively with SMN-restoring therapies delivered directly to the central nervous system such as antisense oligonucleotides or gene therapy.
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18
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Lin MY, Rohan JG, Cai H, Reim K, Ko CP, Chow RH. Complexin facilitates exocytosis and synchronizes vesicle release in two secretory model systems. J Physiol 2013; 591:2463-73. [PMID: 23401610 DOI: 10.1113/jphysiol.2012.244517] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Complexins (Cplxs) are small, SNARE-associated proteins believed to regulate fast, calcium-triggered exocytosis. However, studies have pointed to either an inhibitory and/or facilitatory role in exocytosis, and the role of Cplxs in synchronizing exocytosis is relatively unexplored. Here, we compare the function of two types of complexin, Cplx 1 and 2, in two model systems of calcium-dependent exocytosis. In mouse neuromuscular junctions (NMJs), we find that lack of Cplx 1 significantly reduces and desynchronizes calcium-triggered synaptic transmission; furthermore, high-frequency stimulation elicits synaptic facilitation, instead of normal synaptic depression, and the degree of facilitation is highly sensitive to the amount of cytoplasmic calcium buffering. In Cplx 2-null adrenal chromaffin cells, we also find decreased and desynchronized evoked release, and identify a significant reduction in the vesicle pool close to the calcium channels (immediately releasable pool, IRP). Viral transduction with either Cplx 1 or 2 rescues both the size of the evoked response and the synchronicity of release, and it restores the IRP size. Our findings in two model systems are mutually compatible and indicate a role of Cplx 1 and 2 in facilitating vesicle priming, and also lead to the new hypothesis that Cplxs may synchronize vesicle release by promoting coupling between secretory vesicles and calcium channels.
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Affiliation(s)
- Ming-Yi Lin
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089-2520, USA
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19
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Cobb MS, Rose FF, Rindt H, Glascock JJ, Shababi M, Miller MR, Osman EY, Yen PF, Garcia ML, Martin BR, Wetz MJ, Mazzasette C, Feng Z, Ko CP, Lorson CL. Development and characterization of an SMN2-based intermediate mouse model of Spinal Muscular Atrophy. Hum Mol Genet 2013; 22:1843-55. [PMID: 23390132 DOI: 10.1093/hmg/ddt037] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Spinal Muscular Atrophy (SMA) is due to the loss of the survival motor neuron gene 1 (SMN1), resulting in motor neuron (MN) degeneration, muscle atrophy and loss of motor function. While SMN2 encodes a protein identical to SMN1, a single nucleotide difference in exon 7 causes most of the SMN2-derived transcripts to be alternatively spliced resulting in a truncated and unstable protein (SMNΔ7). SMA patients retain at least one SMN2 copy, making it an important target for therapeutics. Many of the existing SMA models are very severe, with animals typically living less than 2 weeks. Here, we present a novel intermediate mouse model of SMA based upon the human genomic SMN2 gene. Genetically, this model is similar to the well-characterized SMNΔ7 model; however, we have manipulated the SMNΔ7 transgene to encode a modestly more functional protein referred to as SMN read-through (SMN(RT)). By introducing the SMN(RT) transgene onto the background of a severe mouse model of SMA (SMN2(+/+);Smn(-/-)), disease severity was significantly decreased based upon a battery of phenotypic parameters, including MN pathology and a significant extension in survival. Importantly, there is not a full phenotypic correction, allowing for the examination of a broad range of therapeutics, including SMN2-dependent and SMN-independent pathways. This novel animal model serves as an important biological and therapeutic model for less severe forms of SMA and provides an in vivo validation of the SMN(RT) protein.
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Affiliation(s)
- Melissa S Cobb
- Department of Veterinary Pathobiology, Life Sciences Center, University of Missouri, Columbia, MO 65211, USA
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20
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Sahashi K, Hua Y, Ling KKY, Hung G, Rigo F, Horev G, Katsuno M, Sobue G, Ko CP, Bennett CF, Krainer AR. TSUNAMI: an antisense method to phenocopy splicing-associated diseases in animals. Genes Dev 2012; 26:1874-84. [PMID: 22895255 DOI: 10.1101/gad.197418.112] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Antisense oligonucleotides (ASOs) are versatile molecules that can be designed to specifically alter splicing patterns of target pre-mRNAs. Here we exploit this feature to phenocopy a genetic disease. Spinal muscular atrophy (SMA) is a motor neuron disease caused by loss-of-function mutations in the SMN1 gene. The related SMN2 gene expresses suboptimal levels of functional SMN protein due to alternative splicing that skips exon 7; correcting this defect-e.g., with ASOs-is a promising therapeutic approach. We describe the use of ASOs that exacerbate SMN2 missplicing and phenocopy SMA in a dose-dependent manner when administered to transgenic Smn(-/-) mice. Intracerebroventricular ASO injection in neonatal mice recapitulates SMA-like progressive motor dysfunction, growth impairment, and shortened life span, with α-motor neuron loss and abnormal neuromuscular junctions. These SMA-like phenotypes are prevented by a therapeutic ASO that restores correct SMN2 splicing. We uncovered starvation-induced splicing changes, particularly in SMN2, which likely accelerate disease progression. These results constitute proof of principle that ASOs designed to cause sustained splicing defects can be used to induce pathogenesis and rapidly and accurately model splicing-associated diseases in animals. This approach allows the dissection of pathogenesis mechanisms, including spatial and temporal features of disease onset and progression, as well as testing of candidate therapeutics.
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Affiliation(s)
- Kentaro Sahashi
- Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA
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21
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Osborne M, Gomez D, Feng Z, McEwen C, Beltran J, Cirillo K, El-Khodor B, Lin MY, Li Y, Knowlton WM, McKemy DD, Bogdanik L, Butts-Dehm K, Martens K, Davis C, Doty R, Wardwell K, Ghavami A, Kobayashi D, Ko CP, Ramboz S, Lutz C. Characterization of behavioral and neuromuscular junction phenotypes in a novel allelic series of SMA mouse models. Hum Mol Genet 2012; 21:4431-47. [PMID: 22802075 DOI: 10.1093/hmg/dds285] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
A number of mouse models for spinal muscular atrophy (SMA) have been genetically engineered to recapitulate the severity of human SMA by using a targeted null mutation at the mouse Smn1 locus coupled with the transgenic addition of varying copy numbers of human SMN2 genes. Although this approach has been useful in modeling severe SMA and very mild SMA, a mouse model of the intermediate form of the disease would provide an additional research tool amenable for drug discovery. In addition, many of the previously engineered SMA strains are multi-allelic by design, containing a combination of transgenes and targeted mutations in the homozygous state, making further genetic manipulation difficult. A new genetic engineering approach was developed whereby variable numbers of SMN2 sequences were incorporated directly into the murine Smn1 locus. Using combinations of these alleles, we generated an allelic series of SMA mouse strains harboring no, one, two, three, four, five, six or eight copies of SMN2. We report here the characterization of SMA mutants in this series that displayed a range in disease severity from embryonic lethal to viable with mild neuromuscular deficits.
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Yoo YE, Ko CP. Dihydrotestosterone ameliorates degeneration in muscle, axons and motoneurons and improves motor function in amyotrophic lateral sclerosis model mice. PLoS One 2012; 7:e37258. [PMID: 22606355 PMCID: PMC3351454 DOI: 10.1371/journal.pone.0037258] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2012] [Accepted: 04/19/2012] [Indexed: 12/13/2022] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a lethal disease characterized by a progressive loss of motoneurons. The clinical symptoms include skeletal muscle weakness and atrophy, which impairs motor performance and eventually leads to respiratory failure. We tested whether dihydrotestosterone (DHT), which has both anabolic effects on muscle and neuroprotective effects on axons and motoneurons, can ameliorate clinical symptoms in ALS. A silastic tube containing DHT crystals was implanted subcutaneously in SOD1-G93A mice at early symptomatic age when decreases in body weight and grip-strength were observed as compared to wild-type mice. DHT-treated SOD1-G93A mice demonstrated ameliorated muscle atrophy and increased body weight, which was associated with stronger grip-strength. DHT treatment increased the expression of insulin-like growth factor-1 in muscle, which can exert myotrophic as well as neurotrophic effects through retrograde transport. DHT treatment attenuated neuromuscular junction denervation, and axonal and motoneuron loss. DHT-treated SOD1-G93A mice demonstrated improvement in motor behavior as assessed by rota-rod and gait analyses, and an increased lifespan. Application of DHT is a relatively simple and non-invasive procedure, which may be translated into therapy to improve the quality of life for ALS patients.
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Affiliation(s)
- Young-Eun Yoo
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, California, United States of America
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23
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Lin CW, Tseng SW, Yang SF, Ko CP, Lin CH, Wei LH, Chien MH, Hsieh YS. Role of lipocalin 2 and its complex with matrix metalloproteinase-9 in oral cancer. Oral Dis 2012; 18:734-40. [PMID: 22533572 DOI: 10.1111/j.1601-0825.2012.01938.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
OBJECTIVES Recent evidence demonstrated that lipocalin (LCN)2 is induced in many types of human cancer, while the detection of its complex with matrix metalloproteinase (MMP)-9 is correlated with the cancer disease status. We attempted to evaluate plasma expressions of LCN2, MMP-9, and their complex (LCN2/MMP-9) during the diagnostic work-up of patients with oral squamous cell carcinoma (OSCC) and investigated their correlations with disease progression. METHODS In total, 195 patients with OSCC and 81 healthy controls were recruited. Expression levels of LCN2, MMP-9, and LCN2/MMP-9 were determined with immunoenzymatic assays. RESULTS Patients with OSCC exhibited significantly higher levels of LCN2, MMP-9, and LCN2/MMP-9 compared with healthy controls (LCN2: P < 0.001; MMP-9: P < 0.001; LCN2/MMP-9: P < 0.01). Plasma levels of LCN2, MMP-9, and LCN2/MMP-9 in patients with OSCC were significantly correlated with each other and were associated with more-advanced clinical stages (P < 0.05) and/or a larger tumor size (P < 0.05), but were not associated with positive lymph-node metastasis or distal metastasis. CONCLUSION Our results suggest that plasma levels of LCN2 and the LCN2/MMP-9 complex may be useful in non-invasively monitoring OSCC progression, while supporting their potential role as biomarkers of oral cancer disease status.
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Affiliation(s)
- C W Lin
- Institute of Biochemistry and Biotechnology, Chung Shan Medical University, Taichung, Taiwan
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24
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Ling KKY, Gibbs RM, Feng Z, Ko CP. Severe neuromuscular denervation of clinically relevant muscles in a mouse model of spinal muscular atrophy. Hum Mol Genet 2011; 21:185-95. [PMID: 21968514 DOI: 10.1093/hmg/ddr453] [Citation(s) in RCA: 151] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Spinal muscular atrophy (SMA), a motoneuron disease caused by a deficiency of the survival of motor neuron (SMN) protein, is characterized by motoneuron loss and muscle weakness. It remains unclear whether widespread loss of neuromuscular junctions (NMJs) is involved in SMA pathogenesis. We undertook a systematic examination of NMJ innervation patterns in >20 muscles in the SMNΔ7 SMA mouse model. We found that severe denervation (<50% fully innervated endplates) occurs selectively in many vulnerable axial muscles and several appendicular muscles at the disease end stage. Since these vulnerable muscles were located throughout the body and were comprised of varying muscle fiber types, it is unlikely that muscle location or fiber type determines susceptibility to denervation. Furthermore, we found a similar extent of neurofilament accumulation at NMJs in both vulnerable and resistant muscles before the onset of denervation, suggesting that neurofilament accumulation does not predict subsequent NMJ denervation. Since vulnerable muscles were initially innervated, but later denervated, loss of innervation in SMA may be attributed to defects in synapse maintenance. Finally, we found that denervation was amendable by trichostatin A (TSA) treatment, which increased innervation in clinically relevant muscles in TSA-treated SMNΔ7 mice. Our findings suggest that neuromuscular denervation in vulnerable muscles is a widespread pathology in SMA, and can serve as a preparation for elucidating the biological basis of synapse loss, and for evaluating therapeutic efficacy.
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Affiliation(s)
- Karen K Y Ling
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089-2520, USA
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25
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Rohan JG, Lin SMY, Cho JH, Cai H, Reim K, Brose N, Ko CP, Chow RH. Complexin Facilitates Coupling of Secretory Vesicles and Voltage-Gated Calcium Channels. Biophys J 2011. [DOI: 10.1016/j.bpj.2010.12.374] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
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26
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Lin CM, Lin JW, Tsai JT, Ko CP, Hung KS, Hung CC, Su YK, Wei L, Chiu WT, Lee LM. Intracranial pressure fluctuation during hemodialysis in renal failure patients with intracranial hemorrhage. Acta Neurochir Suppl 2009; 101:141-4. [PMID: 18642649 DOI: 10.1007/978-3-211-78205-7_24] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Coagulopathy in renal failure patients often makes them vulnerable to intracranial hemorrhage. Emergency decompression to remove the hematoma and to stop bleeding is always indicated. After the surgery, hemodialysis (HD) should be arranged to maintain the BUN/Cr. level, and I/O balance. During HD, intracranial pressure in all of the patients in this study fluctuated. This phenomenon always resulted in neurological deterioration in acute or chronic renal failure. We present intracranial pressure (ICP) changes during HD in five acute or chronic renal failure patients with intracranial hemorrhage. They all underwent craniectomy or craniotomy with ICP monitors implantation. Different HD protocols were arranged for these patients and then we observed clinical results. ICP elevated during HD and resulted in severe brain swelling. This situation was one of the clinical presentations of dialysis disequilibrium syndrome (DDS). Four patients died because of this complication and one survived. ICP fluctuation seemed to be correlated with the fluid amount and frequency of HD. The prevalence and pathophysiology of DDS remain unclear. Renal failure patient with intracranial hemorrhage may be complicated with DDS when HD was performed. An attempt to reduce the fluid amount and to increase the frequency of HD might help these patients.
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Affiliation(s)
- C M Lin
- Department of Neurosurgery, Taipei Medical University-Wan Fang Hospital, Taipei, Taiwan
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27
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Affiliation(s)
- Chien-Ping Ko
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089-2520, USA.
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28
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29
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Lin JW, Tsai JT, Lee LM, Lin CM, Hung CC, Hung KS, Chen WY, Wei L, Ko CP, Su YK, Chiu WT. Effect of hyperbaric oxygen on patients with traumatic brain injury. Acta Neurochir Suppl 2008; 101:145-149. [PMID: 18642650 DOI: 10.1007/978-3-211-78205-7_25] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Hyperbaric oxygen therapy (HBOT) is the medical therapeutic use of oxygen at a higher atmospheric pressure. The United States Food and Drug Administration have approved several clinical applications for HBOT, but HBOT in traumatic brain injury (TBI) patients has still remained in controversial. The purpose of our study is to evaluate the benefit of HBOT on the prognosis of subacute TBI patients. We prospectively enrolled 44 patients with TBI from November 1, 2004 to October 31, 2005. The study group randomly included 22 patients who received HBOT after the patients' condition stabilization, and the other 22 corresponding condition patients were assigned into the matched control group who were not treated with HBOT. The clinical conditions of the patients were evaluated with the Glasgow Coma Scale (GCS) and Glasgow Outcome Scale (GOS) before and 3 to 6 months after HBOT. The GCS of the HBOT group was improved from 11.1 to 13.5 in average, and from 10.4 to 11.5 (p < 0.05) for control group. Among those patients with GOS = 4 before the HBOT, significant GOS improvement was observed in the HBOT group 6 months after HBOT. Based on this study, HBOT can provide some benefits for the subacute TBI patients with minimal adverse side effects.
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Affiliation(s)
- J W Lin
- Department of Neurosurgery, Taipei Medical University-Wan Fang Hospital, Taipei, Taiwan
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30
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Abstract
Glial cells are active participants in the function, formation, and maintenance of the chemical synapse. To investigate the molecular basis of neuron-glia interactions at the peripheral synapse, we examined whether and how Schwann cell-derived factors modulate synaptic function at developing neuromuscular junctions (NMJs). Schwann cell-conditioned medium (SC-CM) from Xenopus Schwann cell cultures was collected and applied to Xenopus nerve-muscle cocultures. We found that SC-CM increased the frequency of spontaneous synaptic currents (SSCs) within 3-15 min by an average of approximately 150-fold at developing neuromuscular synapses. The increase in SSC frequency by SC-CM is a presynaptic effect independent of neuronal excitability and requires the influx of Ca2+. In contrast to its potentiating effect on spontaneous transmitter release, SC-CM suppressed the evoked transmitter release. The SC-CM effect required the presence of motoneuron soma but not protein synthesis. Using molecular weight cutoff filters and dialysis membranes, we found that the molecular weight of functional factor(s) in SC-CM was within 500 and 5000 Da. The SC-CM effect was not attributable to currently known factors that modulate synaptic efficacy, including neurotrophins, glutamate, and ATP. SC-CM also enhanced spontaneous synaptic release at developing NMJs in Xenopus tadpoles in situ. Our results suggest that Schwann cells release small molecules that enhance spontaneous synaptic activities acutely and potently at developing neuromuscular synapses, and the glial cell-enhanced spontaneous neurotransmission may contribute to synaptogenesis.
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Affiliation(s)
- Guan Cao
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, California 90089-2520
| | - Chien-Ping Ko
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, California 90089-2520
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31
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Abstract
Emerging studies demonstrate that perisynaptic Schwann cells (PSCs), which are the glia cells juxtaposed to the motor nerve terminal, actively participate in multiple aspects of the neuromuscular junction. During development, PSCs guide and promote synaptic growth. In adult muscles, PSCs can sense nerve stimulation by increasing intracellular calcium and are also capable of modulating transmitter release. Although adult PSCs are not required for acute synaptic maintenance and function, they are indispensable for long-term synaptic maintenance. Furthermore, PSC sprouts lead nerve terminal extension during synaptic remodeling. After nerve injury, PSCs sprout profusely and PSC processes guide regenerating nerve terminals. Future challenges will be to identify the molecular mechanisms by which PSCs interact with the nerve terminal and the muscle fiber.
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Affiliation(s)
- Zhihua Feng
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089-2520, USA
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32
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Abstract
Glial cells are widely distributed throughout the nervous system, including at the chemical synapse. However, our knowledge of the role of glial cells at the synapse is rudimentary. Recent studies using a model synapse, the vertebrate neuromuscular junction (NMJ), have demonstrated that perisynaptic Schwann cells (PSCs), which are the glia juxtaposed to the nerve terminal at the NMJ, play active and essential roles in synaptic function, maintenance, and development. PSCs can respond to nerve activity by increasing intracellular calcium and are capable of modulating synaptic function in response to pharmacological manipulations. Studies using PSC ablation in vivo have shown that PSCs are essential for the long-term maintenance of synaptic structure and function at the adult NMJ. In vivo observations have also shown that PSCs guide presynaptic nerve terminal extension and dictate the pattern of innervation during synaptic regeneration and remodeling at adult NMJs. PSCs may also induce postsynaptic acetylcholine receptor aggregation. Furthermore, PSCs play an essential role in synaptic growth and maintenance during development of NMJs in vivo, and Schwann cell-derived factors can promote synaptogenesis and enhance synaptic transmission in tissue culture. These recent findings advance the emerging concept that glial cells help make bigger, stronger, and more stable synapses.
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Affiliation(s)
- Zhihua Feng
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, California 90089-2520, USA
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33
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Affiliation(s)
- Gabriel Corfas
- Division of Neuroscience, Children's Hospital, Boston, Massachusetts 02115, USA
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Abstract
The process by which excess axons are pruned during development has remained unclear. In this issue of Neuron, Bishop et al. use time-lapse imaging and serial electron microscopy of developing neuromuscular junctions to describe a novel cellular mechanism in which retracting axon branches shed fragments rich in normal synaptic organelles. These "axosomes" are engulfed by adjacent Schwann cells and may be assimilated into the glial cytoplasm. Shedding of axosomes and glial engulfment may represent a widespread mechanism of synapse elimination.
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Affiliation(s)
- Samir Koirala
- Division of Neuroscience, Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
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35
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Peng HB, Yang JF, Dai Z, Lee CW, Hung HW, Feng ZH, Ko CP. Differential effects of neurotrophins and schwann cell-derived signals on neuronal survival/growth and synaptogenesis. J Neurosci 2003; 23:5050-60. [PMID: 12832528 PMCID: PMC6741189] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/03/2023] Open
Abstract
Recent studies have shown that the survival of mammalian motoneurons in vitro is promoted by neurotrophins (NTs) and cAMP. There is also evidence that neurotrophins enhance transmitter release. We thus investigated whether these agents also promote synaptogenesis. Cultured Xenopus spinal cord neurons were treated with a mixture of BDNF, glia-derived neurotrophic factor, NT-3, and NT-4, in addition to forskolin and IBMX or the cell-permeant form of cAMP, to elevate the cAMP level. The outgrowth and survival of neurons were dramatically increased by this trophic stimulation. However, when these neurons were cocultured with muscle cells, the trophic agents resulted in a failure of synaptogenesis. Specifically, the induction of ACh receptor (AChR) clustering in cultured muscle cells was inhibited at nerve-muscle contacts, in sharp contrast to control, untreated cocultures. Because AChR clustering induced by agrin or growth factor-coated beads in muscle cells was unaffected by trophic stimulation, its effect on synaptogenesis is presynaptic in origin. In the control, agrin was deposited along the neurite and at nerve-muscle contacts. This was significantly downregulated in cultures treated with trophic stimuli. Reverse transcriptase-PCR analyses showed that this decrease in agrin deposition was caused by an inhibition of agrin synthesis by trophic stimuli. Both agrin synthesis and induction of AChR clustering were restored under trophic stimulation when Schwann cell-conditioned medium was introduced. These results suggest that trophic stimulation maintains spinal neurons in the growth state, and Schwann cell-derived factors allow them to switch to the synaptogenic state.
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Affiliation(s)
- H Benjamin Peng
- Department of Biology, Hong Kong University of Science and Technology, Kowloon, Hong Kong.
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36
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Abstract
Like other vertebrate synapses, the neuromuscular junction (NMJ) has glial cells that are closely associated with the pre- and post-synaptic components. These "perisynaptic Schwann cells" (PSCs) cover nerve terminals and are in close proximity to the synapse, yet their role at the NMJ has remained mysterious for decades. In this review we explore historical perspectives on PSCs and highlight key developments in recent years that have provided novel insight into PSC functions at the NMJ. First among these developments is the generation of specific antibody probes for PSCs. Using one such antibody and the principle of complement-mediated cell lysis, we have developed a novel technique to selectively ablate PSCs en masse from frog NMJs in vivo. Applying this approach, we have shown that PSCs are essential for the long-term maintenance of synaptic structure and function. In addition, PSCs are essential for the growth and maintenance of NMJs during development. Probes for PSCs also allow us to observe in vivo that processes extended by PSCs guide nerve terminals during synapse development, remodeling, and regeneration. PSCs may therefore dictate the pattern of innervation at the NMJ. Finally, PSCs may also induce postsynaptic acetylcholine receptor expression and aggregation. This wealth of recent findings about PSCs suggests that these synapse-associated glial cells are a more integral and essential component of the NMJ than previously appreciated. New approaches currently being applied at the NMJ may further support the emerging view that glial cells help make bigger, stronger, and more stable synapses.
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Affiliation(s)
- Samir Koirala
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089-2520, USA
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Brandon EP, Lin W, D'Amour KA, Pizzo DP, Dominguez B, Sugiura Y, Thode S, Ko CP, Thal LJ, Gage FH, Lee KF. Aberrant patterning of neuromuscular synapses in choline acetyltransferase-deficient mice. J Neurosci 2003; 23:539-49. [PMID: 12533614 PMCID: PMC6741871] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/28/2023] Open
Abstract
In this study we examined the developmental roles of acetylcholine (ACh) by establishing and analyzing mice lacking choline acetyltransferase (ChAT), the biosynthetic enzyme for ACh. As predicted, ChAT-deficient embryos lack both spontaneous and nerve-evoked postsynaptic potentials in muscle and die at birth. In mutant embryos, abnormally increased nerve branching occurs on contact with muscle, and hyperinnervation continues throughout subsequent prenatal development. Postsynaptically, ACh receptor clusters are markedly increased in number and occupy a broader muscle territory in the mutants. Concomitantly, the mutants have significantly more motor neurons than normal. At an ultrastructural level, nerve terminals are smaller in mutant neuromuscular junctions, and they make fewer synaptic contacts to the postsynaptic muscle membrane, although all of the typical synaptic components are present in the mutant. These results indicate that ChAT is uniquely essential for the patterning and formation of mammalian neuromuscular synapses.
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Affiliation(s)
- Eugene P Brandon
- Laboratory of Genetics and Peptide Biology Laboratories, The Salk Institute for Biological Studies, La Jolla, California 92037, USA
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Yang JF, Cao G, Koirala S, Reddy LV, Ko CP. Schwann cells express active agrin and enhance aggregation of acetylcholine receptors on muscle fibers. J Neurosci 2001; 21:9572-84. [PMID: 11739568 PMCID: PMC6763019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2001] [Revised: 09/19/2001] [Accepted: 10/01/2001] [Indexed: 02/22/2023] Open
Abstract
To explore novel roles of glial cells in synaptic function and formation, we examined the expression of agrin in frog Schwann cells and tested their role in the aggregation of acetylcholine receptors (AChRs). Using reverse transcription-PCR, we found that Schwann cells along nerve fibers in tadpoles expressed only the inactive agrin isoform B0 but began to also express active agrin isoforms B11 and B19 at approximately metamorphosis. During nerve regeneration in the adult, the expression of these active agrin isoforms in Schwann cells was upregulated, including the appearance of the most potent isoform, B8. This upregulation was induced by regenerating axons but not by nerve injury per se. In muscle cultures, the presence of adult Schwann cells enhanced the number and the total area of AChR aggregates 2.2- and 4.5-fold, respectively, and this enhancement was eliminated by heparin treatment. Furthermore, adult Schwann cells in culture expressed active agrin isoforms and produced agrin protein. Using a novel technique to selectively ablate perisynaptic Schwann cells (PSCs) at the neuromuscular junction, we found that PSCs also expressed active agrin isoforms B11 and B19, and these active isoforms were upregulated, including the appearance of B8, during reinnervation. Observation in vivo showed that extrajunctional AChR aggregates were associated with PSC sprouts after nerve injury and subsequent reinnervation. These results suggest that, contrary to the prevailing view that only neurons express active agrin, glial cells also express active agrin and play a role in the aggregation of AChRs both in vitro and in vivo.
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Affiliation(s)
- J F Yang
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, California 90089-2520, USA
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39
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Abstract
Fluorescence microscopy was used to study the behavior of perisynaptic Schwann cells (PSCs) in relation to motor nerve terminals and postsynaptic clusters of acetylcholine receptors, during the development of the neuromuscular junction (NMJ) in the frog Xenopus laevis. Pectoral (supracoracoideus) muscles were labeled with monoclonal antibody 2A12 for Schwann cells, the dye FM4-64 for nerve terminals (NTs), alpha-bungarotoxin for acetylcholine receptors (AChRs), and Hoechst 33258 for cellular nuclei, in animals from tadpole stage 57 to fully grown adults. When muscle fibers first appeared in stage 57, NMJs consisted of tightly apposed NTs and AChRs and were only partially covered with PSCs or their processes. Within a few stages, PSCs fully occupied and overgrew the NMJs, extending fine sprouts between a few micrometers and hundreds of micrometers beyond the borders of the junction. Sprouts of PSCs were most abundant during the time when secondary myogenesis, synaptogenesis, and synaptic growth occurred at their highest rates. PSCs were recruited to NMJs during synaptic growth, at rates between 1.3 PSCs/100 microm junctional length early on and 0.4 PSCs/100 microm later. Shortly after metamorphosis, PSC sprouts disappeared and NMJs acquired the adult appearance, in which PSCs, NTs, and AChRs were mostly congruent. The results suggest that, although PSCs may not be required for initial nerve-muscle contacts, PSCs sprouts lead synaptic growth and play a role in the extension and maturation of developing NMJs.
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Affiliation(s)
- A A Herrera
- Neurobiology Section, Department of Biological Sciences, University of Southern California, Los Angeles, California 90089-2520, USA.
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40
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Abstract
Pharmacological manipulations were used to examine the role of G proteins in modulating synaptic transmission at the frog neuromuscular junction. Pertussis toxin (PTX, a G protein antagonist) increased end-plate potential (epp) amplitude but had no effect on the amplitude or frequency of miniature end-plate potentials. Mastoparan (a G protein agonist) decreased epp amplitude, while suramin (an antagonist) increased epp amplitude. The results suggest that PTX-sensitive G proteins tonically modulate synaptic transmission by reducing the amount of transmitter released in response to presynaptic action potentials. We also showed that endogenous ATP decreased transmitter release via P2 receptor in a PTX-insensitive manner. Thus, at least two distinct mechanisms regulate neuromuscular transmission; one is coupled to PTX-sensitive G proteins and the other is not.
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Affiliation(s)
- Y Sugiura
- Department of Biological Sciences, University of Southern California, Los Angeles 90089-2520, USA
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41
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Abstract
The perisynaptic Schwann cell (PSC) has gained recent attention with respect to its roles in synaptic function, remodeling, and regeneration at the vertebrate neuromuscular junction (NMJ). Here we test the hypothesis that, following nerve injury, processes extended by PSCs guide regenerating nerve terminals (NTs) in vivo, and that the extension of sprouts by PSCs is triggered by the arrival of regenerating NTs. Frog NMJs were double-stained with a fluorescent dye, FM4-64, for NTs, and fluorescein isothiocyanate (FITC)-tagged peanut agglutinin (PNA) for PSCs. Identified NMJs were imaged in vivo repeatedly for several months after nerve injury. PSCs sprouted profusely beginning 3-4 weeks after nerve transection and, as reinnervation progressed, regenerating NTs closely followed the preceding PSC sprouts, which could extend tens to hundreds of microns beyond the original synaptic site. The pattern of reinnervation was dictated by PSC sprouts, which could form novel routes joining neighboring junctions or develop into new myelinated axonal pathways. In contrast to mammals, profuse PSC sprouting in frog muscles was not seen in response to axotomy alone, and did not occur at chronically denervated NMJs. Instead, sprouting coincided with the arrival of regenerating NTs. Immunofluorescent staining revealed that in muscle undergoing reinnervation 4 weeks after axotomy, 91% of NMJs bore PSC sprouts, compared to only 6% of NMJs in muscle that was chronically denervated for 4 weeks. These results suggest that reciprocal interactions between regenerating NTs and PSCs govern the process of reinnervation at frog NMJs: regenerating NTs induce PSCs to sprout, and PSC sprouts, in turn, lead and guide the elaboration of NTs.
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Affiliation(s)
- S Koirala
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, California 90089-2520, USA
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Koirala S, Ko CP. Neuron-Glial Interactions. The Sixth Annual University of Southern California Neuroscience Symposium, Los Angeles, November 6, 1998. CNS Drug Reviews 1998; 4:380-383. [DOI: 10.1111/j.1527-3458.1998.tb00078.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Abstract
This study aimed to generate a probe for perisynaptic Schwann cells (PSCs) to investigate the emerging role of these synapse-associated glial cells in the formation and maintenance of the neuromuscular junction (NMJ). We have obtained a novel monoclonal antibody, 2A12, which labels the external surface of PSC membranes at the frog NMJ. The antibody reveals PSC fine processes or "fingers" that are interposed between nerve terminal and muscle membrane, interdigitating with bands of acetylcholine receptors. This antibody also labels PSCs at the avian neuromuscular junction and recognizes a 200 kDa protein in Torpedo electric organs. In frog muscles, axotomy induces sprouting of PSC processes beyond clusters of acetylcholine receptors and acetylcholinesterase at denervated junctional branches. PSC branches often extend across several muscle fibers. At some junctions, PSC sprouts join the tips of neighboring branches. The average length of PSC sprouts is approximately 156 microm at 3-week denervated NMJs. PSC sprouting is accompanied by a significant increase in the number of Schwann cell bodies per NMJ. Following nerve regeneration, nerve terminals reinnervate the junction along the PSC processes. In vivo observations of normal frog muscles also show PSC processes longer than nerve terminals at some junctional branches. The results suggest that nerve injury induces profuse PSC sprouting that may play a role in guiding nerve terminal regeneration at frog NMJs. In addition, antibody 2A12 reveals the fine morphology of PSCs in relation to other synaptic elements and is a useful probe in elucidating the function of these synapse-associated glial cells in vivo.
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Affiliation(s)
- S H Astrow
- Department of Biological Sciences, University of Southern California, Los Angeles 90089-2520, USA
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44
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Abstract
Molecules localized to the synapse are potential contributors to processes unique to this specialized region, such as synapse formation and maintenance and synaptic transmission. We used an immunohistochemical strategy to uncover such molecules by generating antibodies that selectively stain synaptic regions and then using the antibodies to analyse their antigens. In this study, we utilized a monoclonal antibody, mAb 6D7, to identify and characterize an antigen concentrated at frog neuromuscular junctions and in peripheral nerves. In adult muscle, immunoelectron microscopy indicates that the antigen is located in the extracellular matrix around perisynaptic Schwann cell at the neuromuscular junction and in association with myelinated and nonmyelinated axons in peripheral nerves. The maintenance of the mAb 6D7 epitope is innervation-dependent but is muscle-independent; it disappears from the synaptic region within 2 weeks after denervation, but persists after muscle damage when the nerve is left intact. mAb 6D7 immunolabelling is also detected at the neuromuscular junction in developing tadpoles. Biochemical analyses of nerve extracts indicate that mAb 6D7 recognizes a glycoprotein of 127 kDa with both N- and O-linked carbohydrate moieties. Taken together, the results suggest that the antigen recognized by mAb 6D7 may be a novel component of the synaptic extracellular matrix overlying the terminal Schwann cell. The innervation-sensitivity of the epitope at the neuromuscular junction suggests a function in the interactions between nerves and Schwann cells.
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Affiliation(s)
- S H Astrow
- Department of Biological Sciences, University of Southern California, Los Angeles 90089-2520, USA
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45
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Sugiura Y, Ko CP. Novel modulatory effect of L-type calcium channels at newly formed neuromuscular junctions. J Neurosci 1997; 17:1101-11. [PMID: 8994064 PMCID: PMC6573170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/1996] [Revised: 11/14/1996] [Accepted: 11/25/1996] [Indexed: 02/03/2023] Open
Abstract
This study aimed to examine changes of presynaptic voltage-sensitive calcium channel (VSCC) subtypes during synapse formation and regeneration in relation to transmitter release at the neuromuscular junction (NMJ). Synaptic potentials were recorded from developing rat NMJs and from regenerating mouse and frog NMJs. As in normal adult NMJs, evoked transmitter release was reduced by an N-type VSCC blocker in the frog and by a P/Q-type VSCC blocker in the mammal at immature NMJs; however, various L-type VSCC blockers, both dihydropyridine and nondihydropyridine antagonists, increased evoked but not spontaneous release in a dose-dependent manner at newly formed NMJs. This presynaptic potentiation disappeared as NMJs matured. A rapid intracellular Ca2+ buffer, bis(O-aminophenoxy)ethane-N,N,N',N'-tetra-acetic acid-AM, prevented the potentiation effect of nifedipine, but a slow Ca2+ buffer, EGTA-AM, did not. Thus, the potentiation effect of L-type blockers requires Ca2+ transients. Pretreatment with Ca2(+)-activated K+ channel blockers, iberiotoxin or charybdotoxin, did not prevent potentiation by nifedipine at regenerating frog NMJs. Thus, Ca(2+)-activated K+ channels were not likely involved in this potentiation. In contrast, no additional potentiation by nifedipine was seen in muscles pretreated with pertussis toxin (PTX), a G-protein blocker, which by itself enhances evoked transmitter release at regenerating frog NMJs. These results suggest the existence of multiple subtypes of VSCCs at newly formed motor nerve terminals. In addition to the normal N- or P/Q-type VSCCs that mediate transmitter release, L-type VSCCs may play a novel modulatory role in evoked transmitter release by activating a mechanism linked to PTX-sensitive G-proteins during synapse maturation.
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Affiliation(s)
- Y Sugiura
- Department of Biological Sciences, University of Southern California, Los Angeles 90089-2520, USA
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46
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Ko CP, Chen L. Synaptic remodeling revealed by repeated in vivo observations and electron microscopy of identified frog neuromuscular junctions. J Neurosci 1996; 16:1780-90. [PMID: 8774446 PMCID: PMC6578680] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
This work aimed to examine the mechanism of synaptic remodeling using repeated in vivo observations, followed by electron microscopy, of identified frog neuromuscular junctions (NMJs). Our previous light microscopic studies suggested that extension of synaptic extracellular matrix (ECM) precedes, and may play a role in, nerve terminal (NT) growth during synaptic remodeling. To test this hypothesis, sartorius muscles were double labeled with a fluorescent dye, 4-(4-diethylamino-styryl)-N-methylpyridinium iodide, for NTs and rhodamine-conjugated peanut agglutinin for synaptic ECM. The double-labeled NMJs were observed in vivo with video-enhanced fluorescence microscopy. Two to three months after nerve sprouting was induced by a nerve graft, the same NMJs were restained and reexamined. After the final in vivo observations, the same NMJs were examined with semiserial thin section electron microscopy. Light microscopic observation of NMJs that showed synaptic ECM longer than the NT was confirmed with electron microscopy. At junctional branches where synaptic ECM extended beyond the NT, a Schwann cell process longer than the NT was observed in one example, whereas a Schwann cell with the same length as the NT was seen in other examples. In both cases, junctional folds were absent at the extended ECM region. In contrast, junctional folds were observed at the region vacated by a retracted NT. These results suggest that extension of synaptic ECM and Schwann cell processes may lead, and play a role in, the NT growth during the remodeling of adult synaptic connections.
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Affiliation(s)
- C P Ko
- Department of Biological Sciences, University of Southern California, Los Angeles 90089-2520, USA
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47
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Bowersox SS, Miljanich GP, Sugiura Y, Li C, Nadasdi L, Hoffman BB, Ramachandran J, Ko CP. Differential blockade of voltage-sensitive calcium channels at the mouse neuromuscular junction by novel omega-conopeptides and omega-agatoxin-IVA. J Pharmacol Exp Ther 1995; 273:248-56. [PMID: 7714772] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
This investigation assessed the ability of a variety of calcium channel blocking peptides to block synaptic transmission in the isolated mouse phrenic nerve-hemidiaphragm. The synthetic version of the naturally occurring N-type voltage-sensitive calcium channel (VSCC) blocker omega-conopeptide MVIIA (SNX-111) had no effect on nerve-evoked muscle contractions. The non-N-, non-L-type VSCC blocker, omega-conopeptide MVIIC (SNX-230), blocked neuromuscular transmission completely, as did the selective P-type VSCC blocker, omega-Aga-IVA. Subsequent evaluation of other synthetic omega-conopeptides and analogs disclosed a significant positive correlation between the test compounds' affinities for high-affinity SNX-230 brain binding sites and their neuromuscular blocking potencies. Quantal analysis of transmitter release showed that SNX-230 abolished evoked endplate potentials completely, but had little effect on the amplitude and frequency of spontaneous miniature endplate potentials. Perineural focal recordings of presynaptic currents showed that SNX-230 did not block the neuronal action potential. These and other findings indicated that SNX-230 prevents transmitter release at the mouse neuromuscular junction by blocking calcium channels at presynaptic nerve endings. These calcium channels correspond pharmacologically to VSCCs associated with high-affinity binding sites in rat brain and are most probably either of the P- or Q-type.
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Sugiura Y, Woppmann A, Miljanich GP, Ko CP. A novel omega-conopeptide for the presynaptic localization of calcium channels at the mammalian neuromuscular junction. J Neurocytol 1995; 24:15-27. [PMID: 7539483 DOI: 10.1007/bf01370157] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Voltage-sensitive Ca2+ channels are essential to transmitter release at the chemical synapse. To demonstrate the localization of voltage-sensitive Ca2+ channels in relation to the site of transmitter release, mouse neuromuscular junctions were double labelled with alpha-bungarotoxin and a novel voltage-sensitive Ca2+ channel probe, SNX-260, a synthetic analog of omega-conopeptide MVIIC. Similar to omega-conopeptide MVIIC, biotinylated SNX-260 blocked nerve-stimulated transmitter release at the mouse neuromuscular junction. Fluorescently-tagged biotinylated SNX-260 labelled the nerve terminal which appeared thinner than and was outlined by acetylcholine receptor clusters as seen in en face view. This SNX-260 labelling was inhibited by preincubation with unconjugated SNX-260. Side-views of the neuromuscular junction indicated that the SNX-260 labelling was on the synaptic side facing the acetylcholine receptor rather than on the nonsynaptic side of the nerve terminal. This presynaptic binding was confirmed by the absence of SNX-260 labelling in denervated muscles following a nerve cut or disjunction after collagenase treatment. Confocal microscopy revealed spots of SNX-260 labelling that may correlate with active zones. The SNX-260 labelling pattern was not affected by preincubation with unconjugated SNX-111 (omega-conopeptide MVIIA), an N-type voltage-sensitive Ca2+ channel blocker. These findings suggest that SNX-260 is a novel probe for localizing non-N type voltage-sensitive Ca2+ channels and that these voltage-sensitive Ca2+ channels are localized near the transmitter release sites at the mammalian motor nerve terminal membrane. The results are consistent with the suggestion that non-N, probably P/Q type voltage-sensitive Ca2+ channels mediate evoked transmitter release at the mammalian neuromuscular junction.
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Affiliation(s)
- Y Sugiura
- Department of Biological Sciences, University of Southern California, Los Angeles 90089-2520, USA
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Chen L, Ko CP. Extension of synaptic extracellular matrix during nerve terminal sprouting in living frog neuromuscular junctions. J Neurosci 1994; 14:796-808. [PMID: 8301362 PMCID: PMC6576822] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Remodeling of the synaptic extracellular matrix (ECM) and its dynamic relationship with nerve terminal plasticity have been demonstrated in normal frog neuromuscular junctions (NMJs) in vivo (Chen et al., 1991). Our previous work has led to a hypothesis that extension of synaptic ECM precedes nerve terminal growth during synaptic remodeling. To test this hypothesis, the present study examined the changes of synaptic ECM in frog NMJs that were primarily undergoing nerve terminal growth and sprouting. Frog sartorius muscles were double stained with a fluorescent nerve terminal dye (4-Di-2-Asp) and rhodamine-tagged peanut agglutinin (PNA), which recognizes synaptic ECM. The double-labeled NMJs were visualized in vivo with video-enhanced fluorescence microscopy. Nerve sprouting was then induced in the muscle by grafting segments of the contralateral sciatic nerve. The identified NMJs were restrained and reexamined 2-3 months later. Extensive sprouting was observed in 46% of 167 identified NMJs. At junctional regions that showed extension or formation of new branches, synaptic ECM was commonly seen to have the same shape and distribution as the nerve terminal. However, extension of synaptic ECM beyond the corresponding nerve terminals, often by tens of microns, was observed in 29% of these newly formed junctional regions. This lack of correlation might be transient, as growth of nerve terminals following extended, PNA-stained ECM was seen. Examination with histological staining not only confirmed a lack of nerve terminal at the extended synaptic ECM region but also indicated an absence of AChE and postsynaptic junctional folds. The absence of these postsynaptic specializations at the extended, PNA-stained ECM region makes it unlikely that this region was previously occupied by nerve terminals that had retracted. Thus, the present study provides further findings consistent with the hypothesis that synaptic ECM precedes nerve terminal outgrowth and that the extension of synaptic ECM may play a role in synaptic remodeling.
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Affiliation(s)
- L Chen
- Department of Biological Sciences, University of Southern California, Los Angeles 90089-2520
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50
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Chen LL, Folsom DB, Ko CP. The remodeling of synaptic extracellular matrix and its dynamic relationship with nerve terminals at living frog neuromuscular junctions. J Neurosci 1991; 11:2920-30. [PMID: 1715392 PMCID: PMC6575249] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The question of whether the synaptic extracellular matrix undergoes remodeling and how this remodeling is related to nerve terminal plasticity was examined in living neuromuscular junctions of adult frogs. Sartorius muscles were double stained with a fluorescent nerve terminal dye 4-(4-diethylamino-styryl)-N-methylpyridinium iodide (4-Di-2-Asp) and rhodamine-tagged peanut agglutinin (PNA) which recognizes synaptic extracellular matrix. Both nerve terminals and synaptic extracellular matrix in 200 identified normal junctions were visualized in vivo two or three times over a period of 2.6-6 months. The majority of neuromuscular junctions (NMJs) showed remodeling of both nerve terminals and synaptic extracellular matrix. Only 2.5% showed no changes in either synaptic element. The most commonly seen remodeling involved correlated changes in both nerve terminals and synaptic extracellular matrix. In this large group, while some junctions (20%) showed overall proportionate changes in all branches, most junctions (68%) showed disproportionate extension and/or retraction of some but not all individual branches. Another group of NMJs (9.5%) showed mismatched changes in the nerve terminal and synaptic extracellular matrix. In this group, some NMJs showed a decrease in the nerve terminal length without a corresponding reduction in synaptic extracellular matrix length. In other junctions that displayed extension of branches, the PNA-stained matrix was longer than the distal tip of the nerve terminal. Morphometric analysis indicated an average increase of 15.6% in total nerve terminal length and 13.6% in total synaptic extracellular matrix length. Although almost all NMJs displayed remodeling in at least one branch, about 50% of the 2201 individual branches examined did not show changes. The average change was 8.9% growth in the length of individual nerve terminal branches and 8.3% growth in the length of individual branches of synaptic extracellular matrix. There was no significant difference in the morphometry between the repeatedly observed junctions and the previously unobserved control junctions. Furthermore, junctions in which the synaptic extracellular matrix was longer than the nerve terminal also were seen in control as well as in experimental muscles. Cases where the nerve terminals were longer than the synaptic extracellular matrix were never observed in newly arising junctional branches. The present study has shown extensive remodeling in not only the nerve terminal but also the synaptic extracellular matrix in adult living frog NMJs. Results suggest that nerve terminals retract before the synaptic extracellular matrix. A hypothesis that extension of synaptic extracellular matrix precedes nerve terminal growth during synaptic remodeling is proposed.
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Affiliation(s)
- L L Chen
- Department of Biological Sciences, University of Southern California, Los Angeles 90089-2520
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