1
|
Bagga P, Singh S, Ram G, Kapil S, Singh A. Diving into progress: a review on current therapeutic advancements in spinal muscular atrophy. Front Neurol 2024; 15:1368658. [PMID: 38854961 PMCID: PMC11157111 DOI: 10.3389/fneur.2024.1368658] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2024] [Accepted: 04/29/2024] [Indexed: 06/11/2024] Open
Abstract
Spinal muscular atrophy (SMA) is an uncommon disorder associated with genes characterized by the gradual weakening and deterioration of muscles, often leading to substantial disability and premature mortality. Over the past decade, remarkable strides have been made in the field of SMA therapeutics, revolutionizing the landscape of patient care. One pivotal advancement is the development of gene-targeted therapies, such as nusinersen, onasemnogene abeparvovec and risdiplam which have demonstrated unprecedented efficacy in slowing disease progression. These therapies aim to address the root cause of SMA by targeting the survival motor neuron (SMN) gene, effectively restoring deficient SMN protein levels. The advent of these innovative approaches has transformed the prognosis for many SMA patients, offering a glimmer of hope where there was once limited therapeutic recourse. Furthermore, the emergence of small molecule compounds and RNA-targeting strategies has expanded the therapeutic arsenal against SMA. These novel interventions exhibit diverse mechanisms of action, including SMN protein stabilization and modulation of RNA splicing, showcasing the multifaceted nature of SMA treatment research. Collective efforts of pharmaceutical industries, research centers, and patient advocacy groups have played an important role in expediting the translation of scientific discoveries into visible clinical benefits. This review not only highlights the remarkable progress achieved in SMA therapeutics but also generates the ray of hope for the ongoing efforts required to enhance accessibility, optimize treatment strategies, rehabilitation (care and therapies) and ultimately pave the way for an improved quality of life for individuals affected by SMA.
Collapse
Affiliation(s)
- Pankaj Bagga
- School of Bioengineering & Biosciences, Lovely Professional University (LPU), Phagwara, India
| | - Sudhakar Singh
- School of Bioengineering & Biosciences, Lovely Professional University (LPU), Phagwara, India
| | - Gobind Ram
- PG Department of Biotechnology, Layalpur Khalsa College, Jalandhar, India
| | - Subham Kapil
- Department of Zoology, DAV College Jalandhar, Jalandhar, India
| | - Avtar Singh
- School of Electrical Engineering and Computing (SoEEC), Adama Science and Technology University (AS-TU), Adama, Ethiopia
| |
Collapse
|
2
|
Iacono D, Murphy EK, Stimpson CD, Perl DP, Day RM. Low-dose brain radiation: lowering hyperphosphorylated-tau without increasing DNA damage or oncogenic activation. Sci Rep 2023; 13:21142. [PMID: 38036591 PMCID: PMC10689500 DOI: 10.1038/s41598-023-48146-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Accepted: 11/22/2023] [Indexed: 12/02/2023] Open
Abstract
Brain radiation has been medically used to alter the metabolism of cancerous cells and induce their elimination. Rarely, though, brain radiation has been used to interfere with the pathomechanisms of non-cancerous brain disorders, especially neurodegenerative disorders. Data from low-dose radiation (LDR) on swine brains demonstrated reduced levels of phosphorylated-tau (CP13) and amyloid precursor protein (APP) in radiated (RAD) versus sham (SH) animals. Phosphorylated-tau and APP are involved in Alzheimer's disease (AD) pathogenesis. We determined if the expression levels of hyperphosphorylated-tau, 3R-tau, 4R-tau, synaptic, intraneuronal damage, and DNA damage/oncogenic activation markers were altered in RAD versus SH swine brains. Quantitative analyses demonstrated reduced levels of AT8 and 3R-tau in hippocampus (H) and striatum (Str), increased levels of synaptophysin and PSD-95 in frontal cortex (FCtx), and reduced levels of NF-L in cerebellum (CRB) of RAD versus SH swine. DNA damage and oncogene activation markers levels did not differ between RAD and SH animals, except for histone-H3 (increased in FCtx and CRB, decreased in Str), and p53 (reduced in FCtx, Str, H and CRB). These findings confirm the region-based effects of sLDR on proteins normally expressed in larger mammalian brains and support the potential applicability of LDR to beneficially interfere against neurodegenerative mechanisms.
Collapse
Affiliation(s)
- Diego Iacono
- DoD/USU Brain Tissue Repository and Neuropathology Program, Uniformed Services University (USU), Bethesda, MD, USA.
- Department of Neurology, F. Edward Hébert School of Medicine, Uniformed Services University (USU), Bethesda, MD, USA.
- Department of Pathology, F. Edward Hébert School of Medicine, Uniformed Services University (USU), Bethesda, MD, USA.
- Neuroscience Program, Department of Anatomy, Physiology and Genetics, F. Edward Hébert School of Medicine, Uniformed Services University (USU), Bethesda, MD, USA.
- The Henry M. Jackson Foundation for the Advancement of Military Medicine (HJF) Inc., Bethesda, MD, USA.
- Neurodegeneration Disorders Clinic, National Institute of Neurological Disorders and Stroke, NINDS, NIH, Bethesda, MD, USA.
| | - Erin K Murphy
- DoD/USU Brain Tissue Repository and Neuropathology Program, Uniformed Services University (USU), Bethesda, MD, USA
- Department of Pathology, F. Edward Hébert School of Medicine, Uniformed Services University (USU), Bethesda, MD, USA
- The Henry M. Jackson Foundation for the Advancement of Military Medicine (HJF) Inc., Bethesda, MD, USA
| | - Cheryl D Stimpson
- DoD/USU Brain Tissue Repository and Neuropathology Program, Uniformed Services University (USU), Bethesda, MD, USA
- Department of Pathology, F. Edward Hébert School of Medicine, Uniformed Services University (USU), Bethesda, MD, USA
- The Henry M. Jackson Foundation for the Advancement of Military Medicine (HJF) Inc., Bethesda, MD, USA
| | - Daniel P Perl
- DoD/USU Brain Tissue Repository and Neuropathology Program, Uniformed Services University (USU), Bethesda, MD, USA
- Department of Pathology, F. Edward Hébert School of Medicine, Uniformed Services University (USU), Bethesda, MD, USA
| | - Regina M Day
- Department of Pharmacology and Molecular Therapeutics, F. Edward Hébert School of Medicine, Uniformed Services University (USU), Bethesda, MD, USA
| |
Collapse
|
3
|
Ponomarev AS, Chulpanova DS, Yanygina LM, Solovyeva VV, Rizvanov AA. Emerging Gene Therapy Approaches in the Management of Spinal Muscular Atrophy (SMA): An Overview of Clinical Trials and Patent Landscape. Int J Mol Sci 2023; 24:13743. [PMID: 37762045 PMCID: PMC10530942 DOI: 10.3390/ijms241813743] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 08/28/2023] [Accepted: 08/29/2023] [Indexed: 09/29/2023] Open
Abstract
Spinal muscular atrophy (SMA) is a rare autosomal recessive neuromuscular disease that is characterized by progressive muscle atrophy (degeneration), including skeletal muscles in charge of the ability to move. SMA is caused by defects in the SMN1 gene (Survival of Motor Neuron 1) which encodes a protein crucial for the survival and functionality of neuron cells called motor neurons. Decreased level of functioning SMN protein leads to progressive degeneration of alpha-motor neurons performing muscular motility. Over the past decade, many strategies directed for SMN-level-restoration emerged, such as gene replacement therapy (GRT), CRISPR/Cas9-based gene editing, usage of antisense oligonucleotides and small-molecule modulators, and all have been showing their perspectives in SMA therapy. In this review, modern SMA therapy strategies are described, making it a valuable resource for researchers, clinicians and everyone interested in the progress of therapy of this serious disorder.
Collapse
Affiliation(s)
| | | | | | | | - Albert A. Rizvanov
- Institute of Fundamental Medicine and Biology, Kazan Federal University, 420008 Kazan, Russia; (A.S.P.); (D.S.C.); (L.M.Y.); (V.V.S.)
| |
Collapse
|
4
|
Reilly A, Chehade L, Kothary R. Curing SMA: Are we there yet? Gene Ther 2023; 30:8-17. [PMID: 35614235 DOI: 10.1038/s41434-022-00349-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Revised: 05/04/2022] [Accepted: 05/12/2022] [Indexed: 11/09/2022]
Abstract
Loss or deletion of survival motor neuron 1 gene (SMN1) is causative for a severe and devastating neuromuscular disease, Spinal Muscular Atrophy (SMA). SMN1 produces SMN, a ubiquitously expressed protein, that is essential for the development and survival of motor neurons. Major advances and developments in SMA therapeutics are shifting the natural history of the disease. With three relatively new available therapies, nusinersen (Spinraza), onasemnogene abeparvovec (Zolgensma), and risdiplam (Evrysdi), patients survive longer and have improved outcomes. However, patients and families continue to face many challenges associated with use of these therapies, including poor treatment response and a variability in the benefits to those that do respond, suggesting that the quest for the SMA cure is not over. In this review, we discuss the current therapies, their limitations, and highlight necessary gaps that need to be addressed to guarantee the best outcomes for SMA patients.
Collapse
Affiliation(s)
- Aoife Reilly
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada.,Centre for Neuromuscular Disease, University of Ottawa, Ottawa, ON, Canada.,Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON, Canada
| | - Lucia Chehade
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada.,Centre for Neuromuscular Disease, University of Ottawa, Ottawa, ON, Canada.,Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON, Canada
| | - Rashmi Kothary
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada. .,Centre for Neuromuscular Disease, University of Ottawa, Ottawa, ON, Canada. .,Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON, Canada. .,Department of Biochemistry, Microbiology, and Immunology, University of Ottawa, Ottawa, ON, Canada. .,Department of Medicine, University of Ottawa, Ottawa, ON, Canada.
| |
Collapse
|
5
|
Woschitz V, Mei I, Hedlund E, Murray LM. Mouse models of SMA show divergent patterns of neuronal vulnerability and resilience. Skelet Muscle 2022; 12:22. [PMID: 36089582 PMCID: PMC9465884 DOI: 10.1186/s13395-022-00305-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Accepted: 08/24/2022] [Indexed: 11/21/2022] Open
Abstract
Background Spinal muscular atrophy (SMA) is a form of motor neuron disease affecting primarily children characterised by the loss of lower motor neurons (MNs). Breakdown of the neuromuscular junctions (NMJs) is an early pathological event in SMA. However, not all motor neurons are equally vulnerable, with some populations being lost early in the disease while others remain intact at the disease end-stage. A thorough understanding of the basis of this selective vulnerability will give critical insight into the factors which prohibit pathology in certain motor neuron populations and consequently help identify novel neuroprotective strategies. Methods To retrieve a comprehensive understanding of motor neuron susceptibility in SMA, we mapped NMJ pathology in 20 muscles from the Smn2B/- SMA mouse model and cross-compared these data with published data from three other commonly used mouse models. To gain insight into the molecular mechanisms regulating selective resilience and vulnerability, we analysed published RNA sequencing data acquired from differentially vulnerable motor neurons from two different SMA mouse models. Results In the Smn2B/- mouse model of SMA, we identified substantial NMJ loss in the muscles from the core, neck, proximal hind limbs and proximal forelimbs, with a marked reduction in denervation in the distal limbs and head. Motor neuron cell body loss was greater at T5 and T11 compared with L5. We subsequently show that although widespread denervation is observed in each SMA mouse model (with the notable exception of the Taiwanese model), all models have a distinct pattern of selective vulnerability. A comparison of previously published data sets reveals novel transcripts upregulated with a disease in selectively resistant motor neurons, including genes involved in axonal transport, RNA processing and mitochondrial bioenergetics. Conclusions Our work demonstrates that the Smn2B/- mouse model shows a pattern of selective vulnerability which bears resemblance to the regional pathology observed in SMA patients. We found drastic differences in patterns of selective vulnerability across the four SMA mouse models, which is critical to consider during experimental design. We also identified transcript groups that potentially contribute to the protection of certain motor neurons in SMA mouse models. Supplementary Information The online version contains supplementary material available at 10.1186/s13395-022-00305-9.
Collapse
|
6
|
Chehade L, Deguise MO, De Repentigny Y, Yaworski R, Beauvais A, Gagnon S, Hensel N, Kothary R. Suppression of the necroptotic cell death pathways improves survival in Smn2B/− mice. Front Cell Neurosci 2022; 16:972029. [PMID: 35990890 PMCID: PMC9381707 DOI: 10.3389/fncel.2022.972029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Accepted: 07/11/2022] [Indexed: 11/13/2022] Open
Abstract
Spinal muscular atrophy (SMA) is a monogenic neuromuscular disease caused by low levels of the Survival Motor Neuron (SMN) protein. Motor neuron degeneration is the central hallmark of the disease. However, the SMN protein is ubiquitously expressed and depletion of the protein in peripheral tissues results in intrinsic disease manifestations, including muscle defects, independent of neurodegeneration. The approved SMN-restoring therapies have led to remarkable clinical improvements in SMA patients. Yet, the presence of a significant number of non-responders stresses the need for complementary therapeutic strategies targeting processes which do not rely solely on restoring SMN. Dysregulated cell death pathways are candidates for SMN-independent pathomechanisms in SMA. Receptor-interacting protein kinase 1 (RIPK1) and RIPK3 have been widely recognized as critical therapeutic targets of necroptosis, an important form of programmed cell death. In addition, Caspase-1 plays a fundamental role in inflammation and cell death. In this study, we evaluate the role of necroptosis, particularly RIPK3 and Caspase-1, in the Smn2B/− mouse model of SMA. We have generated a triple mutant (TKO), the Smn2B/−; Ripk3−/−; Casp1−/− mouse. TKO mice displayed a robust increase in survival and improved motor function compared to Smn2B/− mice. While there was no protection against motor neuron loss or neuromuscular junction pathology, larger muscle fibers were observed in TKO mice compared to Smn2B/− mice. Our study shows that necroptosis modulates survival, motor behavior and muscle fiber size independent of SMN levels and independent of neurodegeneration. Thus, small-molecule inhibitors of necroptosis as a combinatorial approach together with SMN-restoring drugs could be a future strategy for the treatment of SMA.
Collapse
Affiliation(s)
- Lucia Chehade
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada
- Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON, Canada
- Center for Neuromuscular Disease, University of Ottawa, Ottawa, ON, Canada
| | - Marc-Olivier Deguise
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada
- Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON, Canada
- Center for Neuromuscular Disease, University of Ottawa, Ottawa, ON, Canada
- Department of Pediatrics, Children's Hospital of Eastern Ontario, Ottawa, ON, Canada
| | - Yves De Repentigny
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada
| | - Rebecca Yaworski
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada
| | - Ariane Beauvais
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada
| | - Sabrina Gagnon
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada
| | - Niko Hensel
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada
| | - Rashmi Kothary
- Regenerative Medicine Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada
- Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, ON, Canada
- Center for Neuromuscular Disease, University of Ottawa, Ottawa, ON, Canada
- Department of Medicine, University of Ottawa, Ottawa, ON, Canada
- Department of Biochemistry, Microbiology, and Immunology, University of Ottawa, Ottawa, ON, Canada
- *Correspondence: Rashmi Kothary
| |
Collapse
|
7
|
Carlini MJ, Triplett MK, Pellizzoni L. Neuromuscular denervation and deafferentation but not motor neuron death are disease features in the Smn2B/- mouse model of SMA. PLoS One 2022; 17:e0267990. [PMID: 35913953 PMCID: PMC9342749 DOI: 10.1371/journal.pone.0267990] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Accepted: 07/13/2022] [Indexed: 12/02/2022] Open
Abstract
Spinal muscular atrophy (SMA) is a neurodegenerative disease characterized by loss of motor neurons and skeletal muscle atrophy which is caused by ubiquitous deficiency in the survival motor neuron (SMN) protein. Several cellular defects contribute to sensory-motor circuit pathology in SMA mice, but the underlying mechanisms have often been studied in one mouse model without validation in other available models. Here, we used Smn2B/- mice to investigate specific behavioral, morphological, and functional aspects of SMA pathology that we previously characterized in the SMNΔ7 model. Smn2B/- SMA mice on a pure FVB/N background display deficits in body weight gain and muscle strength with onset in the second postnatal week and median survival of 19 days. Morphological analysis revealed severe loss of proprioceptive synapses on the soma of motor neurons and prominent denervation of neuromuscular junctions (NMJs) in axial but not distal muscles. In contrast, no evidence of cell death emerged from analysis of several distinct pools of lumbar motor neurons known to be lost in the disease. Moreover, SMA motor neurons from Smn2B/- mice showed robust nuclear accumulation of p53 but lack of phosphorylation of serine 18 at its amino-terminal, which selectively marks degenerating motor neurons in the SMNΔ7 mouse model. These results indicate that NMJ denervation and deafferentation, but not motor neuron death, are conserved features of SMA pathology in Smn2B/- mice.
Collapse
Affiliation(s)
- Maria J. Carlini
- Center for Motor Neuron Biology and Disease, Columbia University, New York, NY, United States of America
- Department of Neurology, Columbia University, New York, NY, United States of America
| | - Marina K. Triplett
- Center for Motor Neuron Biology and Disease, Columbia University, New York, NY, United States of America
- Department of Neurology, Columbia University, New York, NY, United States of America
| | - Livio Pellizzoni
- Center for Motor Neuron Biology and Disease, Columbia University, New York, NY, United States of America
- Department of Neurology, Columbia University, New York, NY, United States of America
- Department of Pathology and Cell Biology, Columbia University, New York, NY, United States of America
- * E-mail:
| |
Collapse
|
8
|
Sen S, Lagas S, Roy A, Kumar H. Cytoskeleton saga: Its regulation in normal physiology and modulation in neurodegenerative disorders. Eur J Pharmacol 2022; 925:175001. [PMID: 35525310 DOI: 10.1016/j.ejphar.2022.175001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Revised: 03/31/2022] [Accepted: 04/29/2022] [Indexed: 11/25/2022]
Abstract
Cells are fundamental units of life. To ensure the maintenance of homeostasis, integrity of structural and functional counterparts is needed to be essentially balanced. The cytoskeleton plays a vital role in regulating the cellular morphology, signalling and other factors involved in pathological conditions. Microtubules, actin (microfilaments), intermediate filaments (IF) and their interactions are required for these activities. Various proteins associated with these components are primary requirements for directing their functions. Disruption of this organization due to faulty genetics, oxidative stress or impaired transport mechanisms are the major causes of dysregulated signalling cascades leading to various pathological conditions like Alzheimer's (AD), Parkinson's (PD), Huntington's disease (HD) or amyotrophic lateral sclerosis (ALS), hereditary spastic paraplegia (HSP) or any traumatic injury like spinal cord injury (SCI). Novel or conventional therapeutic approaches may be specific or non-specific, targeting either three basic components of the cytoskeleton or various cascades that serve as a cue to numerous pathways like ROCK signalling or the GSK-3β pathway. An enormous number of drugs have been redirected for modulating the cytoskeletal dynamics and thereby may pave the way for inhibiting the progression of these diseases and their complications.
Collapse
Affiliation(s)
- Santimoy Sen
- Department of Pharmacology and Toxicology, National Institute of Pharmaceutical Education and Research (NIPER)-Ahmedabad, Gandhinagar, Gujarat, India
| | - Sheetal Lagas
- Department of Pharmacology and Toxicology, National Institute of Pharmaceutical Education and Research (NIPER)-Ahmedabad, Gandhinagar, Gujarat, India
| | - Abhishek Roy
- Department of Pharmacology and Toxicology, National Institute of Pharmaceutical Education and Research (NIPER)-Ahmedabad, Gandhinagar, Gujarat, India
| | - Hemant Kumar
- Department of Pharmacology and Toxicology, National Institute of Pharmaceutical Education and Research (NIPER)-Ahmedabad, Gandhinagar, Gujarat, India.
| |
Collapse
|
9
|
Comley LH, Kline RA, Thomson AK, Woschitz V, Landeros EV, Osman EY, Lorson CL, Murray LM. OUP accepted manuscript. Hum Mol Genet 2022; 31:3107-3119. [PMID: 35551393 PMCID: PMC9476628 DOI: 10.1093/hmg/ddac097] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Revised: 04/19/2022] [Accepted: 04/23/2022] [Indexed: 11/14/2022] Open
Abstract
Spinal muscular atrophy (SMA) is a childhood motor neuron disease caused by anomalies in the SMN1 gene. Although therapeutics have been approved for the treatment of SMA, there is a therapeutic time window, after which efficacy is reduced. Hallmarks of motor unit pathology in SMA include loss of motor-neurons and neuromuscular junction (NMJs). Following an increase in Smn levels, it is unclear how much damage can be repaired and the degree to which normal connections are re-established. Here, we perform a detailed analysis of motor unit pathology before and after restoration of Smn levels. Using a Smn-inducible mouse model of SMA, we show that genetic restoration of Smn results in a dramatic reduction in NMJ pathology, with restoration of innervation patterns, preservation of axon and endplate number and normalized expression of P53-associated transcripts. Notably, presynaptic swelling and elevated Pmaip levels remained. We analysed the effect of either early or delayed treated of an antisense oligonucleotide (ASO) targeting SMN2 on a range of differentially vulnerable muscles. Following ASO administration, the majority of endplates appeared fully occupied. However, there was an underlying loss of axons and endplates, which was more prevalent following a delay in treatment. There was an increase in average motor unit size following both early and delayed treatment. Together this work demonstrates the remarkably regenerative capacity of the motor neuron following Smn restoration, but highlights that recovery is incomplete. This work suggests that there is an opportunity to enhance neuromuscular junction recovery following administration of Smn-enhancing therapeutics.
Collapse
Affiliation(s)
- Laura H Comley
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH8 9XD, UK
- Euan MacDonald Centre for Motor Neuron Disease Research, University of Edinburgh, Edinburgh, EH16 4SB, UK
| | - Rachel A Kline
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH8 9XD, UK
- Euan MacDonald Centre for Motor Neuron Disease Research, University of Edinburgh, Edinburgh, EH16 4SB, UK
| | - Alison K Thomson
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH8 9XD, UK
- Euan MacDonald Centre for Motor Neuron Disease Research, University of Edinburgh, Edinburgh, EH16 4SB, UK
| | - Victoria Woschitz
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, EH8 9XD, UK
- Euan MacDonald Centre for Motor Neuron Disease Research, University of Edinburgh, Edinburgh, EH16 4SB, UK
| | - Eric Villalón Landeros
- Bond Life Sciences Center, University of Missouri, Columbia, MO 65211, USA
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205-2185, USA
| | - Erkan Y Osman
- Bond Life Sciences Center, University of Missouri, Columbia, MO 65211, USA
- Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, MO 65211, USA
| | - Christian L Lorson
- Bond Life Sciences Center, University of Missouri, Columbia, MO 65211, USA
- Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, MO 65211, USA
| | - Lyndsay M Murray
- To whom correspondence should be addressed at: College of Medicine and Veterinary Medicine, University of Edinburgh, Old Medical School, Teviot Place, Edinburgh EH8 9XD, UK. Tel: +44 131 651 5985;
| |
Collapse
|
10
|
Buettner JM, Sime Longang JK, Gerstner F, Apel KS, Blanco-Redondo B, Sowoidnich L, Janzen E, Langenhan T, Wirth B, Simon CM. Central synaptopathy is the most conserved feature of motor circuit pathology across spinal muscular atrophy mouse models. iScience 2021; 24:103376. [PMID: 34825141 PMCID: PMC8605199 DOI: 10.1016/j.isci.2021.103376] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Revised: 10/12/2021] [Accepted: 10/26/2021] [Indexed: 11/04/2022] Open
Abstract
Spinal muscular atrophy (SMA) is a neurodegenerative disease caused by reduced survival motor neuron (SMN) protein. Recently, SMN dysfunction has been linked to individual aspects of motor circuit pathology in a severe SMA mouse model. To determine whether these disease mechanisms are conserved, we directly compared the motor circuit pathology of three SMA mouse models. The severe SMNΔ7 model exhibits vast motor circuit defects, including degeneration of motor neurons, spinal excitatory synapses, and neuromuscular junctions (NMJs). In contrast, the Taiwanese model shows very mild motor neuron pathology, but early central synaptic loss. In the intermediate Smn2B/- model, strong pathology of central excitatory synapses and NMJs precedes the late onset of p53-dependent motor neuron death. These pathological events correlate with SMN-dependent splicing dysregulation of specific mRNAs. Our study provides a knowledge base for properly tailoring future studies and identifies central excitatory synaptopathy as a key feature of motor circuit pathology in SMA. Comparison of detailed motor circuit pathology across three SMA mouse models Motor circuit pathology correlates with dysregulation of specific mRNAs Motor neuron death in severe and intermediate SMA models is p53-dependent Central excitatory synaptopathy is the most conserved feature of SMA pathology
Collapse
Affiliation(s)
- Jannik M Buettner
- Carl-Ludwig-Institute for Physiology, Leipzig University, Leipzig 04103, Germany
| | | | - Florian Gerstner
- Carl-Ludwig-Institute for Physiology, Leipzig University, Leipzig 04103, Germany
| | - Katharina S Apel
- Carl-Ludwig-Institute for Physiology, Leipzig University, Leipzig 04103, Germany
| | - Beatriz Blanco-Redondo
- Rudolf Schönheimer Institute of Biochemistry, Division of General Biochemistry, Medical Faculty, Leipzig University, Leipzig 04103, Germany
| | - Leonie Sowoidnich
- Carl-Ludwig-Institute for Physiology, Leipzig University, Leipzig 04103, Germany
| | - Eva Janzen
- Institute of Human Genetics, Center for Molecular Medicine Cologne, Institute for Genetics, University of Cologne, Cologne, Germany
| | - Tobias Langenhan
- Rudolf Schönheimer Institute of Biochemistry, Division of General Biochemistry, Medical Faculty, Leipzig University, Leipzig 04103, Germany
| | - Brunhilde Wirth
- Institute of Human Genetics, Center for Molecular Medicine Cologne, Institute for Genetics, University of Cologne, Cologne, Germany.,Center for Rare Diseases Cologne, University Hospital of Cologne, Cologne, Germany
| | - Christian M Simon
- Carl-Ludwig-Institute for Physiology, Leipzig University, Leipzig 04103, Germany
| |
Collapse
|
11
|
Gromova A, La Spada AR. Harmony Lost: Cell-Cell Communication at the Neuromuscular Junction in Motor Neuron Disease. Trends Neurosci 2021; 43:709-724. [PMID: 32846148 DOI: 10.1016/j.tins.2020.07.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Revised: 06/05/2020] [Accepted: 07/07/2020] [Indexed: 12/13/2022]
Abstract
The neuromuscular junction (NMJ) is a specialized synapse that is the point of connection between motor neurons and skeletal muscle. Although developmental studies have established the importance of cell-cell communication at the NMJ for the integrity and full functionality of this synapse, the contribution of this structure as a primary driver in motor neuron disease pathogenesis remains uncertain. Here, we consider the biology of the NMJ and review emerging lines of investigation that are highlighting the importance of cell-cell interaction at the NMJ in spinal muscular atrophy (SMA), X-linked spinal and bulbar muscular atrophy (SBMA), and amyotrophic lateral sclerosis (ALS). Ongoing research may reveal NMJ targets and pathways whose therapeutic modulation will help slow the progression of motor neuron disease, offering a novel treatment paradigm for ALS, SBMA, SMA, and related disorders.
Collapse
Affiliation(s)
- Anastasia Gromova
- Biomedical Sciences Graduate Program, University of California San Diego, La Jolla, CA 92093, USA; Department of Pathology and Laboratory Medicine and Department of Neurology, University of California Irvine, Irvine, CA 92697, USA
| | - Albert R La Spada
- Department of Pathology and Laboratory Medicine and Department of Neurology, University of California Irvine, Irvine, CA 92697, USA; Department of Neurology, Duke University School of Medicine, Durham, NC 27710, USA.
| |
Collapse
|
12
|
Nagano S, Araki T. Axonal Transport and Local Translation of mRNA in Neurodegenerative Diseases. Front Mol Neurosci 2021; 14:697973. [PMID: 34194300 PMCID: PMC8236635 DOI: 10.3389/fnmol.2021.697973] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Accepted: 05/25/2021] [Indexed: 12/13/2022] Open
Abstract
Since neurons have long neurites including axons, it is crucial for the axons to transport many intracellular substances such as proteins and mitochondria in order to maintain their morphology and function. In addition, mRNAs have also been shown to be transported within axons. RNA-binding proteins form complexes with mRNAs, and regulate transport of the mRNAs to axons, as well as locally translate them into proteins. Local translation of mRNAs actively occurs during the development and damage of neurons, and plays an important role in axon elongation, regeneration, and synapse formation. In recent years, it has been reported that impaired axonal transport and local translation of mRNAs may be involved in the pathogenesis of some neurodegenerative diseases. In this review, we discuss the significance of mRNA axonal transport and their local translation in amyotrophic lateral sclerosis/frontotemporal dementia, spinal muscular atrophy, Alzheimer’s disease, and fragile X syndrome.
Collapse
Affiliation(s)
- Seiichi Nagano
- Department of Neurotherapeutics, Osaka University Graduate School of Medicine, Osaka, Japan.,Department of Peripheral Nervous System Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo, Japan
| | - Toshiyuki Araki
- Department of Peripheral Nervous System Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo, Japan
| |
Collapse
|
13
|
In Search of a Cure: The Development of Therapeutics to Alter the Progression of Spinal Muscular Atrophy. Brain Sci 2021; 11:brainsci11020194. [PMID: 33562482 PMCID: PMC7915832 DOI: 10.3390/brainsci11020194] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Revised: 01/29/2021] [Accepted: 02/01/2021] [Indexed: 12/19/2022] Open
Abstract
Until the recent development of disease-modifying therapeutics, spinal muscular atrophy (SMA) was considered a devastating neuromuscular disease with a poor prognosis for most affected individuals. Symptoms generally present during early childhood and manifest as muscle weakness and progressive paralysis, severely compromising the affected individual’s quality of life, independence, and lifespan. SMA is most commonly caused by the inheritance of homozygously deleted SMN1 alleles with retention of one or more copies of a paralog gene, SMN2, which inversely correlates with disease severity. The recent advent and use of genetically targeted therapies have transformed SMA into a prototype for monogenic disease treatment in the era of genetic medicine. Many SMA-affected individuals receiving these therapies achieve traditionally unobtainable motor milestones and survival rates as medicines drastically alter the natural progression of this disease. This review discusses historical SMA progression and underlying disease mechanisms, highlights advances made in therapeutic research, clinical trials, and FDA-approved medicines, and discusses possible second-generation and complementary medicines as well as optimal temporal intervention windows in order to optimize motor function and improve quality of life for all SMA-affected individuals.
Collapse
|
14
|
Lu JX, Wang Y, Zhang YJ, Shen MF, Li HY, Yu ZQ, Chen G. Axonal mRNA localization and local translation in neurodegenerative disease. Neural Regen Res 2021; 16:1950-1957. [PMID: 33642365 PMCID: PMC8343310 DOI: 10.4103/1673-5374.308074] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The regulation of mRNA localization and local translation play vital roles in the maintenance of cellular structure and function. Many human neurodegenerative diseases, such as fragile X syndrome, amyotrophic lateral sclerosis, Alzheimer's disease, and spinal muscular atrophy, have been characterized by pathological changes in neuronal axons, including abnormal mRNA translation, the loss of protein expression, or abnormal axon transport. Moreover, the same protein and mRNA molecules have been associated with variable functions in different diseases due to differences in their interaction networks. In this review, we briefly examine fragile X syndrome, amyotrophic lateral sclerosis, Alzheimer's disease, and spinal muscular atrophy, with a focus on disease pathogenesis with regard to local mRNA translation and axon transport, suggesting possible treatment directions.
Collapse
Affiliation(s)
- Jin-Xin Lu
- Department of Neurosurgery & Brain and Nerve Research Laboratory, The First Affiliated Hospital of Soochow University, Suzhou, Jiangsu Province, China
| | - Yang Wang
- Department of Neurosurgery & Brain and Nerve Research Laboratory, The First Affiliated Hospital of Soochow University, Suzhou, Jiangsu Province; Department of Neurosurgery, The First Affiliated Hospital of University of Science and Technology of China, Hefei, Anhui Province, China
| | - Yi-Jie Zhang
- Department of Neurosurgery & Brain and Nerve Research Laboratory, The First Affiliated Hospital of Soochow University, Suzhou, Jiangsu Province, China
| | - Mei-Fen Shen
- Department of Neurosurgery & Brain and Nerve Research Laboratory, The First Affiliated Hospital of Soochow University, Suzhou, Jiangsu Province, China
| | - Hai-Ying Li
- Department of Neurosurgery & Brain and Nerve Research Laboratory, The First Affiliated Hospital of Soochow University, Suzhou, Jiangsu Province, China
| | - Zheng-Quan Yu
- Department of Neurosurgery & Brain and Nerve Research Laboratory, The First Affiliated Hospital of Soochow University, Suzhou, Jiangsu Province, China
| | - Gang Chen
- Department of Neurosurgery & Brain and Nerve Research Laboratory, The First Affiliated Hospital of Soochow University, Suzhou, Jiangsu Province, China
| |
Collapse
|
15
|
Gollapalli K, Kim JK, Monani UR. Emerging concepts underlying selective neuromuscular dysfunction in infantile-onset spinal muscular atrophy. Neural Regen Res 2021; 16:1978-1984. [PMID: 33642371 PMCID: PMC8343306 DOI: 10.4103/1673-5374.308073] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Infantile-onset spinal muscular atrophy is the quintessential example of a disorder characterized by a predominantly neurodegenerative phenotype that nevertheless stems from perturbations in a housekeeping protein. Resulting from low levels of the Survival of Motor Neuron (SMN) protein, spinal muscular atrophy manifests mainly as a lower motor neuron disease. Why this is so and whether other cell types contribute to the classic spinal muscular atrophy phenotype continue to be the subject of intense investigation and are only now gaining appreciation. Yet, what is emerging is sometimes as puzzling as it is instructive, arguing for a careful re-examination of recent study outcomes, raising questions about established dogma in the field and making the case for a greater focus on milder spinal muscular atrophy models as tools to identify key mechanisms driving selective neuromuscular dysfunction in the disease. This review examines the evidence for novel molecular and cellular mechanisms that have recently been implicated in spinal muscular atrophy, highlights breakthroughs, points out caveats and poses questions that ought to serve as the basis of new investigations to better understand and treat this and other more common neurodegenerative disorders.
Collapse
Affiliation(s)
- Kishore Gollapalli
- Department of Neurology; Center for Motor Neuron Biology and Disease, Columbia University Medical Center, New York, NY, USA
| | - Jeong-Ki Kim
- Department of Neurology; Center for Motor Neuron Biology and Disease, Columbia University Medical Center, New York, NY, USA
| | - Umrao R Monani
- Department of Neurology; Department of Pathology & Cell Biology; Center for Motor Neuron Biology and Disease, Columbia University Medical Center, New York, NY, USA
| |
Collapse
|
16
|
Reedich EJ, Kalski M, Armijo N, Cox GA, DiDonato CJ. Spinal motor neuron loss occurs through a p53-and-p21-independent mechanism in the Smn 2B/- mouse model of spinal muscular atrophy. Exp Neurol 2020; 337:113587. [PMID: 33382987 DOI: 10.1016/j.expneurol.2020.113587] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Revised: 12/12/2020] [Accepted: 12/23/2020] [Indexed: 12/22/2022]
Abstract
Spinal muscular atrophy (SMA) is a pediatric neuromuscular disease caused by genetic deficiency of the survival motor neuron (SMN) protein. Pathological hallmarks of SMA are spinal motor neuron loss and skeletal muscle atrophy. The molecular mechanisms that elicit and drive preferential motor neuron degeneration and death in SMA remain unclear. Transcriptomic studies consistently report p53 pathway activation in motor neurons and spinal cord tissue of SMA mice. Recent work has identified p53 as an inducer of spinal motor neuron loss in severe Δ7 SMA mice. Additionally, the cyclin-dependent kinase inhibitor P21 (Cdkn1a), an inducer of cell cycle arrest and mediator of skeletal muscle atrophy, is consistently increased in motor neurons, spinal cords, and other tissues of various SMA models. p21 is a p53 transcriptional target but can be independently induced by cellular stressors. To ascertain whether p53 and p21 signaling pathways mediate spinal motor neuron death in milder SMA mice, and how they affect the overall SMA phenotype, we introduced Trp53 and P21 null alleles onto the Smn2B/- background. We found that p53 and p21 depletion did not modulate the timing or degree of Smn2B/- motor neuron loss as evaluated using electrophysiological and immunohistochemical methods. Moreover, we determined that Trp53 and P21 knockout differentially affected Smn2B/- mouse lifespan: p53 ablation impaired survival while p21 ablation extended survival through Smn-independent mechanisms. These results demonstrate that p53 and p21 are not primary drivers of spinal motor neuron death in Smn2B/- mice, a milder SMA mouse model, as motor neuron loss is not alleviated by their ablation.
Collapse
Affiliation(s)
- Emily J Reedich
- Human Molecular Genetics and Physiology Program, Stanley Manne Children's Research Institute at Ann & Robert H. Lurie Children's Hospital, Chicago, IL, USA; Department of Pediatrics, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Martin Kalski
- Human Molecular Genetics and Physiology Program, Stanley Manne Children's Research Institute at Ann & Robert H. Lurie Children's Hospital, Chicago, IL, USA
| | - Nicholas Armijo
- Human Molecular Genetics and Physiology Program, Stanley Manne Children's Research Institute at Ann & Robert H. Lurie Children's Hospital, Chicago, IL, USA
| | - Gregory A Cox
- The Jackson Laboratory, Bar Harbor, ME, USA; Graduate School of Biomedical Sciences and Engineering, University of Maine, Orono, ME, USA
| | - Christine J DiDonato
- Human Molecular Genetics and Physiology Program, Stanley Manne Children's Research Institute at Ann & Robert H. Lurie Children's Hospital, Chicago, IL, USA; Department of Pediatrics, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.
| |
Collapse
|
17
|
Deguise MO, De Repentigny Y, Tierney A, Beauvais A, Michaud J, Chehade L, Thabet M, Paul B, Reilly A, Gagnon S, Renaud JM, Kothary R. Motor transmission defects with sex differences in a new mouse model of mild spinal muscular atrophy. EBioMedicine 2020; 55:102750. [PMID: 32339936 PMCID: PMC7184161 DOI: 10.1016/j.ebiom.2020.102750] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2019] [Revised: 02/25/2020] [Accepted: 03/19/2020] [Indexed: 12/31/2022] Open
Abstract
Background Mouse models of mild spinal muscular atrophy (SMA) have been extremely challenging to generate. This paucity of model systems has limited our understanding of pathophysiological events in milder forms of the disease and of the effect of SMN depletion during aging. Methods A mild mouse model of SMA, termed Smn2B/−;SMN2+/−, was generated by crossing Smn−/−;SMN2 and Smn2B/2B mice. This new model was characterized using behavioral testing, histology, western blot, muscle-nerve electrophysiology as well as ultrasonography to study classical SMA features and extra-neuronal involvement. Findings Smn2B/−;SMN2+/− mice have normal survival, mild but sustained motor weakness, denervation and neuronal/neuromuscular junction (NMJ) transmission defects, and neurogenic muscle atrophy that are more prominent in male mice. Increased centrally located nuclei, intrinsic contractile and relaxation muscle defects were also identified in both female and male mice, with some male predominance. There was an absence of extra-neuronal pathology. Interpretation The Smn2B/−;SMN2+/− mouse provides a model of mild SMA, displaying some hallmark features including reduced weight, sustained motor weakness, electrophysiological transmission deficit, NMJ defects, and muscle atrophy. Early and prominent increase central nucleation and intrinsic electrophysiological deficits demonstrate the potential role played by muscle in SMA disease. The use of this model will allow for the understanding of the most susceptible pathogenic molecular changes in motor neurons and muscles, investigation of the effects of SMN depletion in aging, sex differences and most importantly will provide guidance for the currently aging SMA patients treated with the recently approved genetic therapies. Funding : This work was supported by Cure SMA/Families of SMA Canada (grant numbers KOT-1819 and KOT-2021); Muscular Dystrophy Association (USA) (grant number 575466); and Canadian Institutes of Health Research (CIHR) (grant number PJT-156379).
Collapse
Affiliation(s)
- Marc-Olivier Deguise
- Regenerative Medicine Program, Ottawa Hospital Research Institute, 501 Smyth Road, Ottawa, Ontario K1H 8L6, Canada; Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada; Centre for Neuromuscular Disease, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
| | - Yves De Repentigny
- Regenerative Medicine Program, Ottawa Hospital Research Institute, 501 Smyth Road, Ottawa, Ontario K1H 8L6, Canada
| | - Alexandra Tierney
- Regenerative Medicine Program, Ottawa Hospital Research Institute, 501 Smyth Road, Ottawa, Ontario K1H 8L6, Canada
| | - Ariane Beauvais
- Regenerative Medicine Program, Ottawa Hospital Research Institute, 501 Smyth Road, Ottawa, Ontario K1H 8L6, Canada
| | - Jean Michaud
- Department of Pathology and Laboratory Medicine, Faculty of Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
| | - Lucia Chehade
- Regenerative Medicine Program, Ottawa Hospital Research Institute, 501 Smyth Road, Ottawa, Ontario K1H 8L6, Canada; Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada; Centre for Neuromuscular Disease, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
| | - Mohamed Thabet
- Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
| | - Brittany Paul
- Regenerative Medicine Program, Ottawa Hospital Research Institute, 501 Smyth Road, Ottawa, Ontario K1H 8L6, Canada; Centre for Neuromuscular Disease, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
| | - Aoife Reilly
- Regenerative Medicine Program, Ottawa Hospital Research Institute, 501 Smyth Road, Ottawa, Ontario K1H 8L6, Canada; Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada; Centre for Neuromuscular Disease, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
| | - Sabrina Gagnon
- Regenerative Medicine Program, Ottawa Hospital Research Institute, 501 Smyth Road, Ottawa, Ontario K1H 8L6, Canada
| | - Jean-Marc Renaud
- Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada; Centre for Neuromuscular Disease, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
| | - Rashmi Kothary
- Regenerative Medicine Program, Ottawa Hospital Research Institute, 501 Smyth Road, Ottawa, Ontario K1H 8L6, Canada; Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada; Centre for Neuromuscular Disease, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada; Department of Biochemistry, Microbiology, and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada; Department of Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada.
| |
Collapse
|
18
|
Mole AJ, Bell S, Thomson AK, Dissanayake KN, Ribchester RR, Murray LM. Synaptic withdrawal following nerve injury is influenced by postnatal maturity, muscle-specific properties, and the presence of underlying pathology in mice. J Anat 2020; 237:263-274. [PMID: 32311115 PMCID: PMC7369188 DOI: 10.1111/joa.13187] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2019] [Revised: 01/30/2020] [Accepted: 03/02/2020] [Indexed: 01/13/2023] Open
Abstract
Axonal and synaptic degeneration occur following nerve injury and during disease. Traumatic nerve injury results in rapid fragmentation of the distal axon and loss of synaptic terminals, in a process known as Wallerian degeneration (WD). Identifying and understanding factors that influence the rate of WD is of significant biological and clinical importance, as it will facilitate understanding of the mechanisms of neurodegeneration and identification of novel therapeutic targets. Here, we investigate levels of synaptic loss following nerve injury under a range of conditions, including during postnatal development, in a range of anatomically distinct muscles and in a mouse model of motor neuron disease. By utilising an ex vivo model of nerve injury, we show that synaptic withdrawal is slower during early postnatal development. Significantly more neuromuscular junctions remained fully innervated in the cranial nerve/muscle preparations analysed at P15 than at P25. Furthermore, we demonstrate variability in the level of synaptic withdrawal in response to injury in different muscles, with retraction being slower in abdominal preparations than in cranial muscles across all time points analysed. Importantly, differences between the cranial and thoracoabdominal musculature seen here are not consistent with differences in muscle vulnerability that have been previously reported in mouse models of the childhood motor neuron disease, spinal muscular atrophy (SMA), caused by depletion of survival motor neuron protein (Smn). To further investigate the relationship between synaptic degeneration in SMA and WD, we induced WD in preparations from the Smn2B/− mouse model of SMA. In a disease‐resistant muscle (rostral band of levator auris longus), where there is minimal denervation, there was no change in the level of synaptic loss, which suggests that the process of synaptic withdrawal following injury is Smn‐independent. However, in a muscle with ongoing degeneration (transvs. abdominis), the level of synaptic loss significantly increased, with the percentage of denervated endplates increasing by 33% following injury, compared to disease alone. We therefore conclude that the presence of a die‐back can accelerate synaptic loss after injury in Smn2B/− mice.
Collapse
Affiliation(s)
- Alannah J Mole
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK.,The Euan MacDonald Centre for Motor Neurone Disease Research, Edinburgh, UK
| | - Sarah Bell
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK.,The Euan MacDonald Centre for Motor Neurone Disease Research, Edinburgh, UK
| | - Alison K Thomson
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK.,The Euan MacDonald Centre for Motor Neurone Disease Research, Edinburgh, UK
| | - Kosala N Dissanayake
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK.,The Euan MacDonald Centre for Motor Neurone Disease Research, Edinburgh, UK
| | - Richard R Ribchester
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK.,The Euan MacDonald Centre for Motor Neurone Disease Research, Edinburgh, UK
| | - Lyndsay M Murray
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK.,The Euan MacDonald Centre for Motor Neurone Disease Research, Edinburgh, UK
| |
Collapse
|