36 results on '"Spendiff S"'
Search Results
2. P.90 Understanding the role of GFPT1 in congenital myasthenic syndromes
- Author
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Holland, S., primary, O'Neil, D., additional, Spendiff, S., additional, and Lochmüller, H., additional
- Published
- 2022
- Full Text
- View/download PDF
3. Biomarkers for central nervous system involvement in Myotonic dystrophy type 1
- Author
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Varghese, A., Spendiff, S., Ross, A., and Lochmüller, H.
- Subjects
Medizin - Published
- 2022
4. Targeted Therapies for Metabolic Myopathies Related to Glycogen Storage and Lipid Metabolism: a Systematic Review and Steps Towards a ‘Treatabolome’
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Manta, A., primary, Spendiff, S., additional, Lochmüller, H., additional, and Thompson, R., additional
- Published
- 2021
- Full Text
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5. Strengthening the neuromuscular junction as a concept for the treatment of congenital myasthenic syndromes and motor neuropathies with synaptic dysfunction
- Author
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Howarth, R., primary, Spendiff, S., additional, McMacken, G., additional, Cipriani, S., additional, Roos, A., additional, Horvath, R., additional, and Lochmuller, H., additional
- Published
- 2018
- Full Text
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6. Anthracycline-containing chemotherapy causes long-term impairment of mitochondrial respiration and increased reactive oxygen species release in skeletal muscle
- Author
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Gouspillou G, Scheede-Bergdahl C, Spendiff S, Vuda M, Hepple RT, and Jagoe RT
- Abstract
Anticancer treatments for childhood acute lymphoblastic leukaemia (ALL) are highly effective but are now implicated in causing impaired muscle function in long term survivors. However no comprehensive assessment of skeletal muscle mitochondrial functions in long term survivors has been performed and the presence of persistent chemotherapy induced skeletal muscle mitochondrial dysfunction remains a strong possibility. Non tumour bearing mice were treated with two drugs that have been used frequently in ALL treatment (doxorubicin and dexamethasone) for up to 4 cycles at 3 week intervals and euthanized 3 months after the 4th cycle. Treated animals had impaired growth and lower muscle mass as well as reduced mitochondrial respiration and increased reactive oxygen species production per unit oxygen consumption. Mitochondrial DNA content and protein levels of key mitochondrial membrane proteins and markers of mitochondrial biogenesis were unchanged but protein levels of Parkin were reduced. This suggests a novel pattern of chemotherapy induced mitochondrial dysfunction in skeletal muscle that persists because of an acquired defect in mitophagy signaling. The results could explain the observed functional impairments in adult survivors of childhood ALL and may also be relevant to long term survivors of other cancers treated with similar regimes.
- Published
- 2015
7. P61 Resistance training in patients with mitochondrial myopathy
- Author
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Murphy, J.L., primary, Newman, J., additional, Ratnaike, T.E., additional, Spendiff, S., additional, Falkous, G., additional, Blakely, E.L., additional, Alston, C.L., additional, Taylor, R.W., additional, Trenell, M.I., additional, Gorman, G.S., additional, and Turnbull, D.M., additional
- Published
- 2012
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8. P57 Mitochondrial DNA mutations in satellite cells
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Spendiff, S., primary, Horvath, R., additional, Lochmüller, H., additional, Reza, M., additional, Murphy, J.L., additional, Taylor, R.W., additional, and Turnbull, D.M., additional
- Published
- 2011
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9. P74 Finding the missing gap – mitochondrial DNA deletions in muscle stem cells
- Author
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Spendiff, S., primary, Horvath, R., additional, Murphy, J.L., additional, Taylor, R.W., additional, Reza, M., additional, Lochmüller, H., additional, and Turnbull, D.M., additional
- Published
- 2010
- Full Text
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10. Partial loss of desmin expression due to a leaky splice site variant in the human DES gene is associated with neuromuscular transmission defects.
- Author
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Polavarapu K, O'Neil D, Thompson R, Spendiff S, Nandeesh B, Vengalil S, Huddar A, Baskar D, Arunachal G, Kotambail A, Bhatia S, Tumulu SK, Matalonga L, Töpf A, Laurie S, Zeldin J, Nashi S, Unnikrishnan G, Nalini A, and Lochmüller H
- Subjects
- Humans, Male, Female, Young Adult, Adolescent, Muscle, Skeletal pathology, Muscle, Skeletal ultrastructure, Muscle, Skeletal metabolism, RNA Splice Sites genetics, Synaptic Transmission, Phenotype, Mutation, Desmin genetics, Desmin metabolism
- Abstract
Recessive desminopathies are rare and often present as severe early-onset myopathy. Here we report a milder phenotype in three unrelated patients from southern India (2 M, 1F) aged 16, 21, and 22 years, who presented with childhood-onset, gradually progressive, fatigable limb-girdle weakness, ptosis, speech and swallowing difficulties, without cardiac involvement. Serum creatine kinase was elevated, and repetitive nerve stimulation showed decrement in all. Clinical improvement was noted with pyridostigmine and salbutamol in two patients. All three patients had a homozygous substitution in intron 5: DES(NM_001927.4):c.1023+5G>A, predicted to cause a donor splice site defect. Muscle biopsy with ultrastructural analysis suggested myopathy with myofibrillar disarray, and immunohistochemistry showed partial loss of desmin with some residual staining, while western blot analysis showed reduced desmin. RT-PCR of patient muscle RNA revealed two transcripts: a reduced normal desmin transcript and a larger abnormal transcript suggesting leaky splicing at the intron 5 donor site. Sequencing of the PCR products confirmed the inclusion of intron 5 in the longer transcript, predicted to cause a premature stop codon. Thus, we provide evidence for a leaky splice site causing partial loss of desmin associated with a unique phenotypic presentation of a milder form of desmin-related recessive myopathy overlapping with congenital myasthenic syndrome., Competing Interests: Declaration of competing interest The authors declare no competing interests., (Copyright © 2024 Elsevier B.V. All rights reserved.)
- Published
- 2024
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11. Rare disease research workflow using multilayer networks elucidates the molecular determinants of severity in Congenital Myasthenic Syndromes.
- Author
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Núñez-Carpintero I, Rigau M, Bosio M, O'Connor E, Spendiff S, Azuma Y, Topf A, Thompson R, 't Hoen PAC, Chamova T, Tournev I, Guergueltcheva V, Laurie S, Beltran S, Capella-Gutiérrez S, Cirillo D, Lochmüller H, and Valencia A
- Subjects
- Humans, Neuromuscular Junction metabolism, Rare Diseases metabolism, Workflow, Receptors, Cholinergic genetics, Receptors, Cholinergic metabolism, Mutation, Myasthenic Syndromes, Congenital genetics, Myasthenic Syndromes, Congenital diagnosis
- Abstract
Exploring the molecular basis of disease severity in rare disease scenarios is a challenging task provided the limitations on data availability. Causative genes have been described for Congenital Myasthenic Syndromes (CMS), a group of diverse minority neuromuscular junction (NMJ) disorders; yet a molecular explanation for the phenotypic severity differences remains unclear. Here, we present a workflow to explore the functional relationships between CMS causal genes and altered genes from each patient, based on multilayer network community detection analysis of complementary biomedical information provided by relevant data sources, namely protein-protein interactions, pathways and metabolomics. Our results show that CMS severity can be ascribed to the personalized impairment of extracellular matrix components and postsynaptic modulators of acetylcholine receptor (AChR) clustering. This work showcases how coupling multilayer network analysis with personalized -omics information provides molecular explanations to the varying severity of rare diseases; paving the way for sorting out similar cases in other rare diseases., (© 2024. The Author(s).)
- Published
- 2024
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12. 260th ENMC International Workshop: Congenital myasthenic syndromes 11-13 March 2022, Hoofddorp, The Netherlands.
- Author
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Spendiff S, Dong Y, Maggi L, Rodríguez Cruz PM, Beeson D, and Lochmüller H
- Subjects
- Humans, Netherlands, Myasthenic Syndromes, Congenital diagnosis, Myasthenic Syndromes, Congenital genetics, Myasthenic Syndromes, Congenital therapy
- Abstract
Competing Interests: Declaration of Competing Interest DB: Funding from MRC Programme Grant MR/M006824/1 ‘Disease mechanisms and therapies for inherited disorders of the neuromuscular synapse'. SB: Argenx. PMRC receives the support of a Junior Leader fellowship from “la Caixa” Foundation (ID 100010434) and from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 847648. The fellowship code is LCF/BQ/PI21/11830012. HL: Ongoing projects with Argenx, Amplo Biotechnology, and Neurotune. LM: Received honoraria for speaking, advisory boards, and compensation for congress participation from Sanofi Genzyme, Roche, Amicus Therapeutics and Biogen, outside the submitted work. YD: Received funding from Amplo Biotechnology. MM: Received honorarium to serve as associate editor of Neurology Genetics. JP: Support for scientific meetings and honorariums for advisory work from Merck Serono, Novartis, Chugai, Alexion, Roche, Medimmune, Argenx, UCB, Mitsubishi, Amplo, Janssen, Sanofi. Grants from Alexion, Roche, Medimmune, UCB, Amplo biotechnology. Patent ref P37347WO and licence agreement Numares multimarker MS diagnostics. Shares in AstraZenica. Acknowledges Partial funding by Highly specialised services NHS England. SR: Served as investigator in clinical trials for Roche, Sarepta, Genetx, Sathera, Argenx and received honorarium for speaking and serving on advisory boards from Novartis, Roche and Argenx. DS:Funded by NINDS NS109491-01. PS: CEO of Amplo Biotechnology. SS: Ongoing projects with Argenx, Amplo Biotechnology, and Neurotune.
- Published
- 2023
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13. Periostin as a blood biomarker of muscle cell fibrosis, cardiomyopathy and disease severity in myotonic dystrophy type 1.
- Author
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Nguyen CDL, Jimenez-Moreno AC, Merker M, Bowers CJ, Nikolenko N, Hentschel A, Müntefering T, Isham A, Ruck T, Vorgerd M, Dobelmann V, Gourdon G, Schara-Schmidt U, Gangfuss A, Schröder C, Sickmann A, Gross C, Gorman G, Stenzel W, Kollipara L, Hathazi D, Spendiff S, Gagnon C, Preusse C, Duchesne E, Lochmüller H, and Roos A
- Subjects
- Adult, Humans, Mice, Animals, Trinucleotide Repeat Expansion, Proteomics, Muscle, Skeletal, Muscle Cells metabolism, Patient Acuity, Myotonin-Protein Kinase genetics, Myotonic Dystrophy genetics, Cardiomyopathies genetics, Cardiomyopathies metabolism
- Abstract
Background and Purpose: Myotonic dystrophy type 1 (DM1) is the most common form of adult-onset muscular dystrophy and is caused by an repeat expansion [r(CUG)
exp ] located in the 3' untranslated region of the DMPK gene. Symptoms include skeletal and cardiac muscle dysfunction and fibrosis. In DM1, there is a lack of established biomarkers in routine clinical practice. Thus, we aimed to identify a blood biomarker with relevance for DM1-pathophysiology and clinical presentation., Methods: We collected fibroblasts from 11, skeletal muscles from 27, and blood samples from 158 DM1 patients. Moreover, serum, cardiac, and skeletal muscle samples from DMSXL mice were included. We employed proteomics, immunostaining, qPCR and ELISA. Periostin level were correlated with CMRI-data available for some patients., Results: Our studies identified Periostin, a modulator of fibrosis, as a novel biomarker candidate for DM1: proteomic profiling of human fibroblasts and murine skeletal muscles showed significant dysregulation of Periostin. Immunostaining on skeletal and cardiac muscles from DM1 patients and DMSXL mice showed an extracellular increase of Periostin, indicating fibrosis. qPCR studies indicated increased POSTN expression in fibroblasts and muscle. Quantification of Periostin in blood samples from DMSXL mice and two large validation cohorts of DM1 patients showed decreased levels in animals and diseased individuals correlating with repeat expansion and disease severity and presence of cardiac symptoms identified by MRI. Analyses of longitudinal blood samples revealed no correlation with disease progression., Conclusions: Periostin might serve as a novel stratification biomarker for DM1 correlating with disease severity, presence of cardiac malfunction and fibrosis., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany.)- Published
- 2023
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14. Mitochondrial Mutations Can Alter Neuromuscular Transmission in Congenital Myasthenic Syndrome and Mitochondrial Disease.
- Author
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O'Connor K, Spendiff S, Lochmüller H, and Horvath R
- Subjects
- Humans, Neuromuscular Junction genetics, Synapses, Mutation, Mitochondrial Proteins genetics, Myasthenic Syndromes, Congenital genetics, Mitochondrial Diseases, Organic Anion Transporters genetics
- Abstract
Congenital myasthenic syndromes (CMS) are a group of rare, neuromuscular disorders that usually present in childhood or infancy. While the phenotypic presentation of these disorders is diverse, the unifying feature is a pathomechanism that disrupts neuromuscular transmission. Recently, two mitochondrial genes-SLC25A1 and TEFM-have been reported in patients with suspected CMS, prompting a discussion about the role of mitochondria at the neuromuscular junction (NMJ). Mitochondrial disease and CMS can present with similar symptoms, and potentially one in four patients with mitochondrial myopathy exhibit NMJ defects. This review highlights research indicating the prominent roles of mitochondria at both the pre- and postsynapse, demonstrating the potential for mitochondrial involvement in neuromuscular transmission defects. We propose the establishment of a novel subcategorization for CMS-mitochondrial CMS, due to unifying clinical features and the potential for mitochondrial defects to impede transmission at the pre- and postsynapse. Finally, we highlight the potential of targeting the neuromuscular transmission in mitochondrial disease to improve patient outcomes.
- Published
- 2023
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15. Presynaptic Congenital Myasthenic Syndromes: Understanding Clinical Phenotypes through In vivo Models.
- Author
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Pugliese A, Holland SH, Rodolico C, Lochmüller H, and Spendiff S
- Subjects
- Animals, Neuromuscular Junction metabolism, Muscle Weakness, Phenotype, Myasthenic Syndromes, Congenital, Arthrogryposis
- Abstract
Presynaptic congenital myasthenic syndromes (CMS) are a group of genetic disorders affecting the presynaptic side of the neuromuscular junctions (NMJ). They can result from a dysfunction in acetylcholine (ACh) synthesis or recycling, in its packaging into synaptic vesicles, or its subsequent release into the synaptic cleft. Other proteins involved in presynaptic endplate development and maintenance can also be impaired.Presynaptic CMS usually presents during the prenatal or neonatal period, with a severe phenotype including congenital arthrogryposis, developmental delay, and apnoeic crisis. However, milder phenotypes with proximal muscle weakness and good response to treatment have been described. Finally, many presynaptic genes are expressed in the brain, justifying the presence of additional central nervous system symptoms.Several animal models have been developed to study CMS, providing the opportunity to identify disease mechanisms and test treatment options. In this review, we describe presynaptic CMS phenotypes with a focus on in vivo models, to better understand CMS pathophysiology and define new causative genes.
- Published
- 2023
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16. Unbiased proteomics, histochemistry, and mitochondrial DNA copy number reveal better mitochondrial health in muscle of high-functioning octogenarians.
- Author
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Ubaida-Mohien C, Spendiff S, Lyashkov A, Moaddel R, MacMillan NJ, Filion ME, Morais JA, Taivassalo T, Ferrucci L, and Hepple RT
- Subjects
- Aged, 80 and over, Canada, DNA Copy Number Variations, Humans, Mitochondria metabolism, Muscle, Skeletal metabolism, Octogenarians, Quadriceps Muscle, DNA, Mitochondrial genetics, DNA, Mitochondrial metabolism, Proteomics
- Abstract
Background: Master athletes (MAs) prove that preserving a high level of physical function up to very late in life is possible, but the mechanisms responsible for their high function remain unclear., Methods: We performed muscle biopsies in 15 octogenarian world-class track and field MAs and 14 non-athlete age/sex-matched controls (NA) to provide insights into mechanisms for preserving function in advanced age. Muscle samples were assessed for respiratory compromised fibers, mitochondrial DNA (mtDNA) copy number, and proteomics by liquid-chromatography mass spectrometry., Results: MA exhibited markedly better performance on clinical function tests and greater cross-sectional area of the vastus lateralis muscle. Proteomics analysis revealed marked differences, where most of the ~800 differentially represented proteins in MA versus NA pertained to mitochondria structure/function such as electron transport capacity (ETC), cristae formation, mitochondrial biogenesis, and mtDNA-encoded proteins. In contrast, proteins from the spliceosome complex and nuclear pore were downregulated in MA. Consistent with proteomics data, MA had fewer respiratory compromised fibers, higher mtDNA copy number, and an increased protein ratio of the cristae-bound ETC subunits relative to the outer mitochondrial membrane protein voltage-dependent anion channel. There was a substantial overlap of proteins overrepresented in MA versus NA with proteins that decline with aging and that are higher in physically active than sedentary individuals. However, we also found 176 proteins related to mitochondria that are uniquely differentially expressed in MA., Conclusions: We conclude that high function in advanced age is associated with preserving mitochondrial structure/function proteins, with underrepresentation of proteins involved in the spliceosome and nuclear pore complex. Whereas many of these differences in MA appear related to their physical activity habits, others may reflect unique biological (e.g., gene, environment) mechanisms that preserve muscle integrity and function with aging., Funding: Funding for this study was provided by operating grants from the Canadian Institutes of Health Research (MOP 84408 to TT and MOP 125986 to RTH). This work was supported in part by the Intramural Research Program of the National Institute on Aging, NIH, Baltimore, MD, USA., Competing Interests: CU, SS, AL, RM, NM, MF, JM, TT, LF, RH No competing interests declared
- Published
- 2022
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17. Collagen VI Regulates Motor Circuit Plasticity and Motor Performance by Cannabinoid Modulation.
- Author
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Lam DD, Williams RH, Lujan E, Tanabe K, Huber G, Saw NL, Merl-Pham J, Salminen AV, Lohse D, Spendiff S, Plastini MJ, Zech M, Lochmüller H, Geerlof A, Hauck SM, Shamloo M, Wernig M, and Winkelmann J
- Subjects
- Animals, Female, Male, Mice, Mutation, Receptors, Cannabinoid genetics, Receptors, Cannabinoid metabolism, Cannabinoids metabolism, Cannabinoids pharmacology, Collagen Type VI genetics, Collagen Type VI metabolism, Dystonia genetics, Dystonia metabolism, Dystonic Disorders genetics, Dystonic Disorders metabolism, Motor Neurons drug effects, Neuronal Plasticity drug effects
- Abstract
Collagen VI is a key component of muscle basement membranes, and genetic variants can cause monogenic muscular dystrophies. Conversely, human genetic studies recently implicated collagen VI in central nervous system function, with variants causing the movement disorder dystonia. To elucidate the neurophysiological role of collagen VI, we generated mice with a truncation of the dystonia-related collagen α3 VI (COL6A3) C-terminal domain (CTD). These Col6a3
CTT mice showed a recessive dystonia-like phenotype in both sexes. We found that COL6A3 interacts with the cannabinoid receptor 1 (CB1R) complex in a CTD-dependent manner. Col6a3CTT mice of both sexes have impaired homeostasis of excitatory input to the basal pontine nuclei (BPN), a motor control hub with dense COL6A3 expression, consistent with deficient endocannabinoid (eCB) signaling. Aberrant synaptic input in the BPN was normalized by a CB1R agonist, and motor performance in Col6a3CTT mice of both sexes was improved by CB1R agonist treatment. Our findings identify a readily therapeutically addressable synaptic mechanism for motor control. SIGNIFICANCE STATEMENT Dystonia is a movement disorder characterized by involuntary movements. We previously identified genetic variants affecting a specific domain of the COL6A3 protein as a cause of dystonia. Here, we created mice lacking the affected domain and observed an analogous movement disorder. Using a protein interaction screen, we found that the affected COL6A3 domain mediates an interaction with the cannabinoid receptor 1 (CB1R). Concordantly, our COL6A3-deficient mice showed a deficit in synaptic plasticity linked to a deficit in cannabinoid signaling. Pharmacological cannabinoid augmentation rescued the motor impairment of the mice. Thus, cannabinoid augmentation could be a promising avenue for treating dystonia, and we have identified a possible molecular mechanism mediating this., (Copyright © 2022 the authors.)- Published
- 2022
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18. Mitochondrial Content, but Not Function, Is Altered With a Multimodal Resistance Training Protocol and Adequate Protein Intake in Leucine-Supplemented Pre/Frail Women.
- Author
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Jacob KJ, Sonjak V, Spendiff S, Hepple RT, Chevalier S, Perez A, and Morais JA
- Abstract
Background: Frailty is a clinical condition associated with loss of muscle mass and strength (sarcopenia). Mitochondria are centrally implicated in frailty and sarcopenia. Leucine (Leu) can alter mitochondrial content in myocytes, while resistance training (RT) is the strongest stimulus to counteract sarcopenia and may enhance mitochondrial biogenesis. Objective: We determined the effects of Leu supplementation and RT on mitochondrial content and function in pre/frail elderly women in a randomized double-blinded placebo-controlled study. Methods: Nineteen pre/frail elderly women (77.5 ± 1.3 y, BMI: 25.1 ± 0.9 kg/m
2 ), based on the Frailty Phenotype, underwent 3-months of RT 3×/week with protein-optimized diet and were randomized to 7.5 g/d of Leu supplementation or placebo alanine (Ala). Pre/post-intervention mitochondrial respiration, reactive oxygen species (ROS) production, calcium retention capacity (CRC), time to permeability transition pore (mPTP) opening, mitochondrial voltage-dependent anion channel (VDAC) protein content, leg press 1-repetition maximum (1RM), and 6-min walk test (6MWT) were measured. Results: No time, supplementation, or interaction effects were observed for respiration, ROS, time to mPTP opening, and CRC. VDAC levels significantly increased in the Leu group post-intervention ( p = 0.012). Both groups significantly increased leg press 1RM and 6MWT, with no effect of supplementation. Discussion: Leu supplementation with 3 months of RT increased mitochondrial content. Future studies should investigate if there is an increase in mitochondrial turnover or a shift in quality control (mitophagy) in leucine supplemented pre/frail elderly women who undergo 12 weeks of RT. Clinical Trial Registration: ClinicalTrials.gov, identifier: NCT01922167., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Jacob, Sonjak, Spendiff, Hepple, Chevalier, Perez and Morais.)- Published
- 2021
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19. Modulation of the Acetylcholine Receptor Clustering Pathway Improves Neuromuscular Junction Structure and Muscle Strength in a Mouse Model of Congenital Myasthenic Syndrome.
- Author
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Spendiff S, Howarth R, McMacken G, Davey T, Quinlan K, O'Connor E, Slater C, Hettwer S, Mäder A, Roos A, Horvath R, and Lochmüller H
- Abstract
Introduction: Congenital myasthenic syndromes (CMS) are a diverse group of inherited neuromuscular disorders characterized by a failure of synaptic transmission at the neuromuscular junction (NMJ). CMS often present early with fatigable weakness and can be fatal through respiratory complications. The AGRN gene is one of over 30 genes known to harbor mutations causative for CMS. In this study, we aimed to determine if a compound (NT1654), developed to stimulate the acetylcholine receptor (AChR) clustering pathway, would benefit a mouse model of CMS caused by a loss-of-function mutation in Agrn ( Agrn
nmf380 mouse). Methods: Agrnnmf380 mice received an injection of either NT1654 or vehicle compound daily, with wild-type litter mates used for comparison. Animals were weighed daily and underwent grip strength assessments. After 30 days of treatment animals were sacrificed, and muscles collected. Investigations into NMJ and muscle morphology were performed on collected tissue. Results: While minimal improvements in NMJ ultrastructure were observed with electron microscopy, gross NMJ structure analysis using fluorescent labelling and confocal microscopy revealed extensive postsynaptic improvements in Agrnnmf380 mice with NT1654 administration, with variables frequently returning to wild type levels. An improvement in muscle weight and myofiber characteristics helped increase forelimb grip strength and body weight. Conclusions: We conclude that NT1654 restores NMJ postsynaptic structure and improves muscle strength through normalization of muscle fiber composition and the prevention of atrophy. We hypothesize this occurs through the AChR clustering pathway in Agrnnmf380 mice. Future studies should investigate if this may represent a viable treatment option for patients with CMS, especially those with mutations in proteins of the AChR clustering pathway., Competing Interests: SH and AM are employed by Neurotune AG. Remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest, (Copyright © 2020 Spendiff, Howarth, McMacken, Davey, Quinlan, O'Connor, Slater, Hettwer, Mäder, Roos, Horvath and Lochmüller.)- Published
- 2020
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20. Advances in the diagnosis of inherited neuromuscular diseases and implications for therapy development.
- Author
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Thompson R, Spendiff S, Roos A, Bourque PR, Warman Chardon J, Kirschner J, Horvath R, and Lochmüller H
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- Humans, Interdisciplinary Research methods, Neuromuscular Diseases therapy, Precision Medicine trends, Prognosis, Sequence Analysis, DNA, Interdisciplinary Research trends, Neuromuscular Diseases diagnosis, Neuromuscular Diseases genetics
- Abstract
Advances in DNA sequencing technologies have resulted in a near doubling, in under 10 years, of the number of causal genes identified for inherited neuromuscular disorders. However, around half of patients, whether children or adults, do not receive a molecular diagnosis after initial diagnostic workup. Massively parallel technologies targeting RNA, proteins, and metabolites are being increasingly used to diagnose these unsolved cases. The use of these technologies to delineate pathways, biomarkers, and therapeutic targets has led to new approaches entering the drug development pipeline. However, these technologies might give rise to misleading conclusions if used in isolation, and traditional techniques including comprehensive neurological evaluation, histopathology, and biochemistry continue to have a crucial role in diagnostics. For optimal diagnosis, prognosis, and precision medicine, no single ruling technology exists. Instead, an interdisciplinary approach combining novel and traditional neurological techniques with computer-aided analysis and international data sharing is needed to advance the diagnosis and treatment of neuromuscular disorders., (Copyright © 2020 Elsevier Ltd. All rights reserved.)
- Published
- 2020
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21. Reduced Mitochondrial Content, Elevated Reactive Oxygen Species, and Modulation by Denervation in Skeletal Muscle of Prefrail or Frail Elderly Women.
- Author
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Sonjak V, Jacob KJ, Spendiff S, Vuda M, Perez A, Miguez K, Minozzo FC, Spake C, Morais JA, and Hepple RT
- Subjects
- Aged, Biopsy, Case-Control Studies, Female, Humans, Neural Cell Adhesion Molecules metabolism, Oxygen Consumption, Quebec, Surveys and Questionnaires, Young Adult, Denervation, Frail Elderly, Mitochondria, Muscle metabolism, Muscle, Skeletal innervation, Muscle, Skeletal metabolism, Reactive Oxygen Species metabolism
- Abstract
Denervation and mitochondrial impairment are implicated in age-related skeletal muscle atrophy and may play a role in physical frailty. We recently showed that denervation modulates muscle mitochondrial function in octogenarian men, but this has not been examined in elderly women. On this basis, we tested the hypothesis that denervation plays a modulating role in mitochondrial impairment in skeletal muscle from prefrail or frail elderly (FE) women. Mitochondrial respiratory capacity and reactive oxygen species emission were examined in permeabilized myofibers obtained from vastus lateralis muscle biopsies from FE and young inactive women. Muscle respiratory capacity was reduced in proportion to a reduction in a mitochondrial marker protein in FE, and mitochondrial reactive oxygen species emission was elevated in FE versus young inactive group. Consistent with a significant accumulation of neural cell adhesion molecule-positive muscle fibers in FE (indicative of denervation), a 50% reduction in reactive oxygen species production after pharmacologically inhibiting the denervation-mediated reactive oxygen species response in FE women suggests a significant modulation of mitochondrial function by denervation. In conclusion, our data support the hypothesis that denervation plays a modulating role in skeletal muscle mitochondrial function in FE women, suggesting therapeutic strategies in advanced age should focus on the causes and treatment of denervation., (© The Author(s) 2019. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)
- Published
- 2019
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22. Fidelity of muscle fibre reinnervation modulates ageing muscle impact in elderly women.
- Author
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Sonjak V, Jacob K, Morais JA, Rivera-Zengotita M, Spendiff S, Spake C, Taivassalo T, Chevalier S, and Hepple RT
- Subjects
- Aged, Aged, 80 and over, Female, Humans, Muscular Atrophy physiopathology, Aging physiology, Muscle Fibers, Skeletal physiology
- Abstract
Key Points: Susceptibility to age-related muscle atrophy relates to the degree of muscle denervation and the capacity of successful reinnervation. However, the specific role of denervation as a determinant of the severity of muscle aging between populations with low versus high physical function has not been addressed. We show that prefrail/frail elderly women exhibited marked features of muscle denervation, whereas world class octogenarian female master athletes showed attenuated indices of denervation and greater reinnervation capacity. These findings suggest that the difference in age-related muscle impact between low- and high-functioning elderly women is the robustness of the response to denervation of myofibers., Abstract: Ageing muscle degeneration is a key contributor to physical frailty; however, the factors responsible for exacerbated vs. muted ageing muscle impact are largely unknown. Based upon evidence that susceptibility to neurogenic impact is an important determinant of the severity of ageing muscle degeneration, we aimed to determine the presence and extent of denervation in pre-frail/frail elderly (FE, 77.9 ± 6.2 years) women compared to young physically inactive (YI, 24.0 ± 3.5 years) females, and contrast these findings to high-functioning world class octogenarian female masters athletes (MA, 80.9 ± 6.6 years). Muscle biopsies from vastus lateralis muscle were obtained from all three groups to assess denervation-related morphological and transcriptional markers. The FE group displayed marked grouping of slow fibres, accumulation of very small myofibres, a severe reduction in type IIa/I size ratio, highly variable inter-subject accumulation of neural cell adhesion molecule (NCAM)-positive myofibres, and an accumulation of pyknotic nuclei, indicative of recurring cycles of denervation/reinnervation and persistent denervation. The MA group exhibited a smaller decline in type IIa/I size ratio and fewer pyknotic nuclei, accompanied by a higher degree of type I fibre grouping and larger fibre group size, suggesting a greater reinnervation of denervated fibres. Consistent with this interpretation, MA had higher mRNA levels of the reinnervation-promoting cytokine fibroblast growth factor binding protein 1 (FGFBP1) than FE. Our results indicate that the muscle of FE women has significant neurogenic atrophy, whereas MA muscle exhibit superior reinnervation capacity, suggesting that the difference in age-related muscle impact between low- and high-functioning elderly women is the robustness of the response to denervation of myofibres., (© 2019 The Authors. The Journal of Physiology © 2019 The Physiological Society.)
- Published
- 2019
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23. Modulation of Agrin and RhoA Pathways Ameliorates Movement Defects and Synapse Morphology in MYO9A-Depleted Zebrafish.
- Author
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O'Connor E, Cairns G, Spendiff S, Burns D, Hettwer S, Mäder A, Müller J, Horvath R, Slater C, Roos A, and Lochmüller H
- Subjects
- Animals, Mutation, Missense, Myosins genetics, Myosins physiology, Neuromuscular Junction metabolism, Neuromuscular Junction pathology, Zebrafish metabolism, rho-Associated Kinases antagonists & inhibitors
- Abstract
Congenital myasthenic syndromes (CMS) are a group of rare, inherited disorders characterised by impaired function of the neuromuscular junction (NMJ). This is due to defects in one of the many proteins associated with the NMJ. In three patients with CMS, missense mutations in a gene encoding an unconventional myosin protein, MYO9A, were identified as likely causing their disorder. Preliminary studies revealed a potential involvement of the RhoA/ROCK pathway and of a key NMJ protein, agrin, in the pathophysiology of MYO9A-depletion. In this study, a CRISPR/Cas9 approach was used to generate genetic mutants of MYO9A zebrafish orthologues, myo9aa/ab, to expand and refine the morphological analysis of the NMJ. Injection of NT1654, a synthetic agrin fragment compound, improved NMJ structure and zebrafish movement in the absence of Myo9aa/ab. In addition, treatment of zebrafish with fasudil, a ROCK inhibitor, also provided improvements to the morphology of NMJs in early development, as well as rescuing movement defects, but not to the same extent as NT1654 and not at later time points. Therefore, this study highlights a role for MYO9A at the NMJ, the first unconventional myosin motor protein associated with a neuromuscular disease, and provides a potential mechanism of action of MYO9A-pathophysiology.
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- 2019
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24. Salbutamol modifies the neuromuscular junction in a mouse model of ColQ myasthenic syndrome.
- Author
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McMacken GM, Spendiff S, Whittaker RG, O'Connor E, Howarth RM, Boczonadi V, Horvath R, Slater CR, and Lochmüller H
- Subjects
- Acetylcholinesterase metabolism, Agrin metabolism, Animals, Collagen metabolism, Disease Models, Animal, Dystroglycans metabolism, Mice, Mice, Knockout, Muscle Fibers, Skeletal cytology, Muscle Fibers, Skeletal ultrastructure, Muscle Proteins metabolism, Muscle Weakness therapy, Myasthenic Syndromes, Congenital drug therapy, Neuromuscular Junction diagnostic imaging, Neuromuscular Junction metabolism, Receptors, Cholinergic, Signal Transduction, Synaptic Transmission physiology, Acetylcholinesterase genetics, Adrenergic beta-Agonists therapeutic use, Albuterol therapeutic use, Collagen genetics, Muscle Fibers, Skeletal metabolism, Muscle Proteins genetics, Myasthenic Syndromes, Congenital genetics, Neuromuscular Junction drug effects
- Abstract
The β-adrenergic agonists salbutamol and ephedrine have proven to be effective as therapies for human disorders of the neuromuscular junction, in particular many subsets of congenital myasthenic syndromes. However, the mechanisms underlying this clinical benefit are unknown and improved understanding of the effect of adrenergic signalling on the neuromuscular junction is essential to facilitate the development of more targeted therapies. Here, we investigated the effect of salbutamol treatment on the neuromuscular junction in the ColQ deficient mouse, a model of end-plate acetylcholinesterase deficiency. ColQ-/- mice received 7 weeks of daily salbutamol injection, and the effect on muscle strength and neuromuscular junction morphology was analysed. We show that salbutamol leads to a gradual improvement in muscle strength in ColQ-/- mice. In addition, the neuromuscular junctions of salbutamol treated mice showed significant improvements in several postsynaptic morphological defects, including increased synaptic area, acetylcholine receptor area and density, and extent of postjunctional folds. These changes occurred without alterations in skeletal muscle fibre size or type. These findings suggest that β-adrenergic agonists lead to functional benefit in the ColQ-/- mouse and to long-term structural changes at the neuromuscular junction. These effects are primarily at the postsynaptic membrane and may lead to enhanced neuromuscular transmission., (© The Author(s) 2019. Published by Oxford University Press.)
- Published
- 2019
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25. SIL1 deficiency causes degenerative changes of peripheral nerves and neuromuscular junctions in fish, mice and human.
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Phan V, Cox D, Cipriani S, Spendiff S, Buchkremer S, O'Connor E, Horvath R, Goebel HH, Hathazi D, Lochmüller H, Straka T, Rudolf R, Weis J, and Roos A
- Subjects
- Animals, Gene Knockdown Techniques, Guanine Nucleotide Exchange Factors deficiency, Humans, Mice, Transgenic, Muscle, Skeletal innervation, Muscle, Skeletal ultrastructure, Neuromuscular Junction metabolism, Proteomics, Sciatic Nerve metabolism, Spinocerebellar Degenerations metabolism, Zebrafish, Zebrafish Proteins deficiency, Zebrafish Proteins genetics, Guanine Nucleotide Exchange Factors genetics, Neuromuscular Junction pathology, Sciatic Nerve ultrastructure, Spinocerebellar Degenerations genetics, Spinocerebellar Degenerations pathology
- Abstract
Background: Marinesco-Sjögren Syndrome (MSS) is a rare neuromuscular condition caused by recessive mutations in the SIL1 gene resulting in the absence of functional SIL1 protein, a co-chaperone for the major ER chaperone, BiP. As BiP is decisive for proper protein processing, loss of SIL1 results in the accumulation of misshaped proteins. This accumulation likely damages and destroys cells in vulnerable tissues, leading to congenital cataracts, cerebellar ataxia, vacuolar myopathy and other MSS phenotypes. Whether the peripheral nervous system (PNS) is affected in MSS has not been conclusively shown., Methods: To study PNS vulnerability in MSS, intramuscular nerves fibres from MSS patients and from SIL1-deficient mice (woozy) as well as sciatic nerves and neuromuscular junctions (NMJ) from these mice have been investigated via transmission electron microscopic and immunofluorescence studies accompanied by transcript studies and unbiased proteomic profiling. In addition, PNS and NMJ integrity were analyzed via immunofluorescence studies in an MSS-zebrafish model which has been generated for that purpose., Results: Electron microscopy revealed morphological changes indicative of impaired autophagy and mitochondrial maintenance in distal axons and in Schwann cells. Moreover, changes of the morphology of NMJs as well as of transcripts encoding proteins important for NMJ function were detected in woozy mice. These findings were in line with a grossly abnormal structure of NMJs in SIL1-deficient zebrafish embryos. Proteome profiling of sciatic nerve specimens from woozy mice revealed altered levels of proteins implicated in neuronal maintenance suggesting the activation of compensatory mechanisms., Conclusion: Taken together, our combined data expand the spectrum of tissues affected by SIL1-loss and suggest that impaired neuromuscular transmission might be part of MSS pathophysiology., (Copyright © 2018. Published by Elsevier Inc.)
- Published
- 2019
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26. Neuromuscular Junction Changes in a Mouse Model of Charcot-Marie-Tooth Disease Type 4C.
- Author
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Cipriani S, Phan V, Médard JJ, Horvath R, Lochmüller H, Chrast R, Roos A, and Spendiff S
- Subjects
- Animals, Disease Models, Animal, Exons, Gene Knockdown Techniques, Intracellular Signaling Peptides and Proteins, Mice, Mice, Mutant Strains, Carrier Proteins genetics, Carrier Proteins metabolism, Charcot-Marie-Tooth Disease genetics, Charcot-Marie-Tooth Disease metabolism, Charcot-Marie-Tooth Disease pathology, Muscle, Skeletal innervation, Muscle, Skeletal metabolism, Muscle, Skeletal pathology, Mutation, Neuromuscular Junction genetics, Neuromuscular Junction metabolism, Neuromuscular Junction pathology, Sciatic Nerve metabolism, Sciatic Nerve pathology
- Abstract
The neuromuscular junction (NMJ) appears to be a site of pathology in a number of peripheral nerve diseases. Charcot-Marie-Tooth (CMT) 4C is an autosomal recessive, early onset, demyelinating neuropathy. Numerous mutations in the SH3TC2 gene have been shown to underlie the condition often associated with scoliosis, foot deformities, and reduced nerve conduction velocities. Mice with exon 1 of the Sh3tc2 gene knocked out demonstrate many of the features seen in patients. To determine if NMJ pathology is contributory to the pathomechanisms of CMT4C we examined NMJs in the gastrocnemius muscle of SH3TC2-deficient mice. In addition, we performed proteomic assessment of the sciatic nerve to identify protein factors contributing to the NMJ alterations and the survival of demyelinated axons. Morphological and gene expression analysis of NMJs revealed a lack of continuity between the pre- and post-synaptic apparatus, increases in post-synaptic fragmentation and dispersal, and an increase in expression of the gamma subunit of the acetylcholine receptor. There were no changes in axonal width or the number of axonal inputs to the NMJ. Proteome investigations of the sciatic nerve revealed altered expression of extracellular matrix proteins important for NMJ integrity. Together these observations suggest that CMT4C pathology includes a compromised NMJ even in the absence of changes to the innervating axon.
- Published
- 2018
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27. GFPT1 deficiency in muscle leads to myasthenia and myopathy in mice.
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Issop Y, Hathazi D, Khan MM, Rudolf R, Weis J, Spendiff S, Slater CR, Roos A, and Lochmüller H
- Subjects
- Animals, Disease Models, Animal, Gene Expression genetics, Glutamine-Fructose-6-Phosphate Transaminase (Isomerizing), Glycosylation, Humans, Mice, Mice, Knockout, Muscle Weakness physiopathology, Muscle, Skeletal metabolism, Muscle, Skeletal physiopathology, Muscular Diseases physiopathology, Mutation, Myasthenic Syndromes, Congenital physiopathology, Neuromuscular Junction genetics, Neuromuscular Junction physiopathology, Synaptic Transmission genetics, Muscle Weakness genetics, Muscular Diseases genetics, Myasthenic Syndromes, Congenital genetics, Nitrogenous Group Transferases genetics
- Abstract
Glutamine-fructose-6-phosphate transaminase 1 (GFPT1) is the rate-limiting enzyme in the hexosamine biosynthetic pathway which yields precursors required for protein and lipid glycosylation. Mutations in GFPT1 and other genes downstream of this pathway cause congenital myasthenic syndrome (CMS) characterized by fatigable muscle weakness owing to impaired neurotransmission. The precise pathomechanisms at the neuromuscular junction (NMJ) owing to a deficiency in GFPT1 is yet to be discovered. One of the challenges we face is the viability of Gfpt1-/- knockout mice. In this study, we use Cre/LoxP technology to generate a muscle-specific GFPT1 knockout mouse model, Gfpt1tm1d/tm1d, characteristic of the human CMS phenotype. Our data suggest a critical role for muscle derived GFPT1 in the development of the NMJ, neurotransmission, skeletal muscle integrity and highlight that a deficiency in skeletal muscle alone is sufficient to cause morphological postsynaptic NMJ changes that are accompanied by presynaptic alterations despite the conservation of neuronal GFPT1 expression. In addition to the conventional morphological NMJ changes and fatigable muscle weakness, Gfpt1tm1d/tm1d mice display a progressive myopathic phenotype with the presence of tubular aggregates in muscle, characteristic of the GFPT1-CMS phenotype. We further identify an upregulation of skeletal muscle proteins glypican-1, farnesyltransferase/geranylgeranyltransferase type-1 subunit α and muscle-specific kinase, which are known to be involved in the differentiation and maintenance of the NMJ. The Gfpt1tm1d/tm1d model allows for further investigation of pathophysiological consequences on genes and pathways downstream of GFPT1 likely to involve misglycosylation or hypoglycosylation of NMJs and muscle targets.
- Published
- 2018
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28. Influence of nerve cuff channel count and implantation site on the separability of afferent ENG.
- Author
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Silveira C, Brunton E, Spendiff S, and Nazarpour K
- Subjects
- Animals, Electrodes, Implanted, Physical Stimulation methods, Rats, Rats, Sprague-Dawley, Implantable Neurostimulators, Neurons, Afferent physiology, Proprioception physiology, Sciatic Nerve physiology
- Abstract
Objective: Recording of neural signals from intact peripheral nerves in patients with spinal cord injury or stroke survivors offers the possibility for the development of closed-loop sensorimotor prostheses. Nerve cuffs have been found to provide stable recordings from peripheral nerves for prolonged periods of time. However, questions remain over the design and positioning of nerve cuffs such that the separability of neural data recorded from the peripheral nerves is improved., Approach: Afferent electroneurographic (ENG) signals were recorded with nerve cuffs placed on the sciatic nerve of rats in response to various mechanical stimuli to the hindpaw. The mean absolute value of the signal was extracted and input to a classifier. The performance of the classifier was evaluated under two conditions: (1) when information from either a 3- or 16-channel cuff was used; (2) when information was available from a cuff placed either distally or proximally along the nerve., Main Results: We show that both 3- and 16-channel cuffs were able to separate afferent ENG signals with an accuracy greater than chance. The highest classification scores were achieved when the classifier was fed with information obtained from a 16-channel cuff placed distally. While the 16-channel cuff always outperformed the 3-channel cuff, the difference in performance was increased when the 16-channel cuff was placed distally rather than proximally on the nerve., Significance: The results indicate that increasing the complexity of a nerve cuff may only be advantageous if the nerve cuff is to be implanted distally, where the nerve has begun to divide into individual fascicles.
- Published
- 2018
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29. Positioning the Nerve Cuff Distally on the Sciatic Nerve Improves the Classification of Ankle-Movement Proprioceptive ENG Signals.
- Author
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Silveira C, Brunton E, Spendiff S, and Nazarpour K
- Subjects
- Animals, Rats, Rats, Sprague-Dawley, Ankle Joint physiology, Electrodes, Movement, Proprioception, Sciatic Nerve physiology
- Abstract
Recording of neural signals from intact peripheral nerves in patients with spinal cord injury or stroke survivors offers the possibility for the development of closed-loop sensorimotor prostheses. However, questions remain over the positioning of neural interfaces such that the separability of neural data recorded from the peripheral nerves is improved. Afferent electroneurographic signals were recorded with nerve cuffs placed on the sciatic nerve of rats in response to various mechanical stimuli to the hindpaw. The mean absolute value of the signal was extracted and fed into classifiers. The performance of the classifier was evaluated when information was available from a single cuff placed either distally or proximally on the sciatic nerve. Results confirmed earlier findings that proprioceptive ENG signals, elicited by the movement of the ankle, can be identified and separated in neural recordings made with a cuff electrode. In addition, classification scores improved when the nerve cuff was placed distally on the nerve rather than proximally, taking advantage of the nerve's underlying anatomy.
- Published
- 2018
- Full Text
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30. Clinical and research strategies for limb-girdle congenital myasthenic syndromes.
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O'Connor E, Töpf A, Zahedi RP, Spendiff S, Cox D, Roos A, and Lochmüller H
- Subjects
- Animals, Disease Models, Animal, Glycosylation, High-Throughput Nucleotide Sequencing, Humans, Models, Neurological, Mutation, Myasthenic Syndromes, Congenital physiopathology, Myasthenic Syndromes, Congenital therapy, Neuromuscular Junction physiopathology, Phenotype, Research Design, Synapses physiology, Myasthenic Syndromes, Congenital genetics
- Abstract
Congenital myasthenic syndromes (CMS) are a group of rare disorders that cause fatigable muscle weakness due to defective signal transmission at the neuromuscular junction, a specialized synapse between peripheral motor neurons and their target muscle fibers. There are now over 30 causative genes that have been reported for CMS. Of these, there are 10 that are associated with a limb-girdle pattern of muscle weakness and are thus classed as LG-CMS. Next-generation sequencing and advanced methods of data sharing are likely to uncover further genes that are associated with similar clinical phenotypes, contributing to better diagnosis and effective treatment of LG-CMS patients. This review highlights clinical and pathological hallmarks of LG-CMS in relation to the underlying genetic defects and pathways. Tailored animal and cell models are essential to elucidate the exact function and pathomechanisms at the neuromuscular synapse that underlie LG-CMS. The integration of genomics and proteomics data derived from these models and patients reveals new and often unexpected insights that are relevant beyond the rare genetic disorder of LG-CMS and may extend to the functioning of mammalian synapses in health and disease more generally., (© 2018 New York Academy of Sciences.)
- Published
- 2018
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31. The Increasing Genetic and Phenotypical Diversity of Congenital Myasthenic Syndromes.
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McMacken G, Abicht A, Evangelista T, Spendiff S, and Lochmüller H
- Subjects
- Humans, Myasthenic Syndromes, Congenital diagnosis, Myasthenic Syndromes, Congenital drug therapy, Myasthenic Syndromes, Congenital metabolism, Phenotype, Myasthenic Syndromes, Congenital genetics
- Abstract
Competing Interests: Disclosure The authors report no conflicts of interest in this work.
- Published
- 2017
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32. Denervation drives mitochondrial dysfunction in skeletal muscle of octogenarians.
- Author
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Spendiff S, Vuda M, Gouspillou G, Aare S, Perez A, Morais JA, Jagoe RT, Filion ME, Glicksman R, Kapchinsky S, MacMillan NJ, Pion CH, Aubertin-Leheudre M, Hettwer S, Correa JA, Taivassalo T, and Hepple RT
- Subjects
- Adult, Aged, Aged, 80 and over, Animals, Humans, Male, Mice, Transgenic, Middle Aged, Muscle Denervation, Muscle, Skeletal metabolism, Reactive Oxygen Species metabolism, Young Adult, Mitochondria, Muscle metabolism, Muscle, Skeletal innervation
- Abstract
Key Points: Mitochondria are frequently implicated in the ageing of skeletal muscle, although the role of denervation in modulating mitochondrial function in ageing muscle is unknown. We show that increased sensitivity to apoptosis initiation occurs prior to evidence of persistent denervation and is thus a primary mitochondrial defect in ageing muscle worthy of therapeutic targeting. However, at more advanced age, mitochondrial function changes are markedly impacted by persistent sporadic myofibre denervation, suggesting the mitochondrion may be a less viable therapeutic target., Abstract: Experimental denervation modulates mitochondrial function, where changes in both reactive oxygen species (ROS) and sensitivity to permeability transition are implicated in the resultant muscle atrophy. Notably, although denervation occurs sporadically in ageing muscle, its impact on ageing muscle mitochondria is unknown. Because this information has important therapeutic implications concerning targeting the mitochondrion in ageing muscle, we examined mitochondrial function in skeletal muscle from four groups of humans, comprising two active (mean ± SD age: 23.7 ± 2.7 years and 71.2 ± 4.9 years) and two inactive groups (64.8 ± 3.1 years and 82.5 ± 4.8 years), and compared this with a murine model of sporadic denervation. We tested the hypothesis that, although some alterations of mitochondrial function in aged muscle are attributable to a primary organelle defect, mitochondrial dysfunction would be impacted by persistent denervation in advanced age. Both ageing in humans and sporadic denervation in mice increased mitochondrial sensitivity to permeability transition (humans, P = 0.004; mice, P = 0.01). To determine the contribution of sporadic denervation to mitochondrial function, we pharmacologically inhibited the denervation-induced ROS response. This reduced ROS emission by 60% (P = 0.02) in sporadically denervated mouse muscle, which is similar to that seen in humans older than 75 years (-66%, P = 0.02) but not those younger than 75 years. We conclude that an increased sensitivity to permeability transition is a primary mitochondrial defect in ageing muscle. However, at more advanced age, when muscle atrophy becomes more clinically severe, mitochondrial function changes are markedly impacted by persistent sporadic denervation, making the mitochondrion a less viable therapeutic target., (© 2016 The Authors. The Journal of Physiology © 2016 The Physiological Society.)
- Published
- 2016
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33. Failed reinnervation in aging skeletal muscle.
- Author
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Aare S, Spendiff S, Vuda M, Elkrief D, Perez A, Wu Q, Mayaki D, Hussain SN, Hettwer S, and Hepple RT
- Subjects
- Animals, Core Binding Factor Alpha 2 Subunit genetics, Core Binding Factor Alpha 2 Subunit metabolism, Male, Mice, Mice, Inbred C57BL, Muscle, Skeletal growth & development, Muscle, Skeletal metabolism, Muscle, Skeletal physiology, Nerve Growth Factors genetics, Nerve Growth Factors metabolism, Phospholipases A2, Cytosolic genetics, Phospholipases A2, Cytosolic metabolism, Rats, Rats, Inbred F344, Receptor Protein-Tyrosine Kinases genetics, Receptor Protein-Tyrosine Kinases metabolism, Receptors, Cholinergic genetics, Receptors, Cholinergic metabolism, Sarcopenia metabolism, Muscle, Skeletal innervation, Sarcopenia physiopathology
- Abstract
Background: Skeletal muscle displays a marked accumulation of denervated myofibers at advanced age, which coincides with an acceleration of muscle atrophy., Methods: In this study, we evaluated the hypothesis that the accumulation of denervated myofibers in advanced age is due to failed reinnervation by examining muscle from young adult (YA) and very old (VO) rats and from a murine model of sporadic denervation secondary to neurotrypsin over-expression (Sarco mouse)., Results: Both aging rat muscle and Sarco mouse muscle exhibited marked fiber-type grouping, consistent with repeating cycles of denervation and reinnervation, yet in VO muscle, rapsyn at the endplate increased and was associated with only a 10 % decline in acetylcholine receptor (AChR) intensity, whereas in Sarco mice, there was a decline in rapsyn and a 25 % decrease in AChR intensity. Transcripts of muscle-specific kinase (21-fold), acetylcholine receptor subunits α (68-fold), ε (threefold) and γ (47-fold), neural cell adhesion molecule (66-fold), and runt-related transcription factor 1 (33-fold) were upregulated in VO muscle of the rat, consistent with the marked persistent denervation evidenced by a large proportion of very small fibers (>20 %). In the Sarco mice, there were much smaller increases in denervation transcripts (0-3.5-fold) and accumulation of very small fibers (2-6 %) compared to the VO rat, suggesting a reduced capacity for reinnervation in aging muscle. Despite the marked persistent denervation in the VO rat muscle, transcripts of neurotrophins involved in promoting axonal sprouting following denervation exhibited no increase, and several miRNAs predicted to suppress neurotrophins were elevated in VO rat., Conclusions: Our results support the hypothesis that the accumulation of denervated fibers with aging is due to failed reinnervation and that this may be affected by a limited neurotrophin response that mediates axonal sprouting following denervation.
- Published
- 2016
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34. Failed upregulation of TFAM protein and mitochondrial DNA in oxidatively deficient fibers of chronic obstructive pulmonary disease locomotor muscle.
- Author
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Konokhova Y, Spendiff S, Jagoe RT, Aare S, Kapchinsky S, MacMillan NJ, Rozakis P, Picard M, Aubertin-Leheudre M, Pion CH, Bourbeau J, Hepple RT, and Taivassalo T
- Subjects
- Aged, Case-Control Studies, DNA Damage, DNA, Mitochondrial genetics, DNA-Binding Proteins genetics, Electron Transport Complex IV genetics, Electron Transport Complex IV metabolism, Female, Humans, Male, Middle Aged, Mitochondria, Muscle pathology, Mitochondrial Proteins genetics, Muscle Fibers, Skeletal pathology, Organelle Biogenesis, Pulmonary Disease, Chronic Obstructive diagnosis, Pulmonary Disease, Chronic Obstructive genetics, Pulmonary Disease, Chronic Obstructive physiopathology, Quadriceps Muscle pathology, Quadriceps Muscle physiopathology, Succinate Dehydrogenase genetics, Succinate Dehydrogenase metabolism, Transcription Factors genetics, Transcription, Genetic, Up-Regulation, DNA, Mitochondrial metabolism, DNA-Binding Proteins metabolism, Mitochondria, Muscle metabolism, Mitochondrial Proteins metabolism, Muscle Fibers, Skeletal metabolism, Oxidative Stress, Pulmonary Disease, Chronic Obstructive metabolism, Quadriceps Muscle metabolism, Transcription Factors metabolism
- Abstract
Background: Low mitochondrial content and oxidative capacity are well-established features of locomotor muscle dysfunction, a prevalent and debilitating systemic occurrence in patients with chronic obstructive pulmonary disease (COPD). Although the exact cause is not firmly established, physical inactivity and oxidative stress are among the proposed underlying mechanisms. Here, we assess the impact of COPD pathophysiology on mitochondrial DNA (mtDNA) integrity, biogenesis, and cellular oxidative capacity in locomotor muscle of COPD patients and healthy controls. We hypothesized that the high oxidative stress environment of COPD muscle would yield a higher presence of deletion-containing mtDNA and oxidative-deficient fibers and impaired capacity for mitochondrial biogenesis., Methods: Vastus lateralis biopsies were analyzed from 29 COPD patients and 19 healthy age-matched controls for the presence of mtDNA deletions, levels of oxidatively damaged DNA, mtDNA copy number, and regulators of mitochondrial biogenesis as well the proportion of oxidative-deficient fibers (detected histologically as cytochrome c oxidase-deficient, succinate dehydrogenase positive (COX(-)/SDH(+) )). Additionally, mtDNA copy number and mitochondrial transcription factor A (TFAM) content were measured in laser captured COX(-)SDH(+) and normal single fibers of both COPD and controls., Results: Compared to controls, COPD muscle exhibited significantly higher levels of oxidatively damaged DNA (8-hydroxy-2-deoxyguanosine (8-OHdG) levels = 387 ± 41 vs. 258 ± 21 pg/mL) and higher prevalence of mtDNA deletions (74 vs. 15 % of subjects in each group), which was accompanied by a higher abundance of oxidative-deficient fibers (8.0 ± 2.1 vs. 1.5 ± 0.4 %). Interestingly, COPD patients with mtDNA deletions had higher levels of 8-OHdG (457 ± 46 pg/mL) and longer smoking history (66.3 ± 7.5 years) than patients without deletions (197 ± 29 pg/mL; 38.0 ± 7.3 years). Transcript levels of regulators of mitochondrial biogenesis and oxidative metabolism were upregulated in COPD compared to controls. However, single fiber analyses of COX(-)/SDH(+) and normal fibers exposed an impairment in mitochondrial biogenesis in COPD; in healthy controls, we detected a marked upregulation of mtDNA copy number and TFAM protein in COX(-)/SDH(+) compared to normal fibers, reflecting the expected compensatory attempt by the oxidative-deficient cells to increase energy levels; in contrast, they were similar between COX(-)/SDH(+) and normal fibers in COPD patients. Taken together, these findings suggest that although the signaling factors regulating mitochondrial biogenesis are increased in COPD muscle, impairment in the translation of these signals prevents the restoration of normal oxidative capacity., Conclusions: Single fiber analyses provide the first substantive evidence that low muscle oxidative capacity in COPD cannot be explained by physical inactivity alone and is likely driven by the disease pathophysiology.
- Published
- 2016
- Full Text
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35. Reduction in single muscle fiber rate of force development with aging is not attenuated in world class older masters athletes.
- Author
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Power GA, Minozzo FC, Spendiff S, Filion ME, Konokhova Y, Purves-Smith MF, Pion C, Aubertin-Leheudre M, Morais JA, Herzog W, Hepple RT, Taivassalo T, and Rassier DE
- Subjects
- Age Factors, Aged, Aged, 80 and over, Biopsy, Fluorescent Antibody Technique, Humans, Kinetics, Male, Myosin Heavy Chains analysis, Quadriceps Muscle chemistry, Sarcopenia diagnosis, Sarcopenia metabolism, Young Adult, Aging, Athletes, Muscle Contraction, Muscle Fibers, Skeletal chemistry, Muscle Strength, Quadriceps Muscle physiopathology, Sarcopenia physiopathology
- Abstract
Normal adult aging is associated with impaired muscle contractile function; however, to what extent cross-bridge kinetics are altered in aging muscle is not clear. We used a slacken restretch maneuver on single muscle fiber segments biopsied from the vastus lateralis of young adults (∼23 yr), older nonathlete (NA) adults (∼80 yr), and age-matched world class masters athletes (MA; ∼80 yr) to assess the rate of force redevelopment (ktr) and cross-bridge kinetics. A post hoc analysis was performed, and only the mechanical properties of "slow type" fibers based on unloaded shortening velocity (Vo) measurements are reported. The MA and NA were ∼54 and 43% weaker, respectively, for specific force compared with young. Similarly, when force was normalized to cross-sectional area determined via the fiber shape angularity data, both old groups did not differ, and the MA and NA were ∼43 and 48% weaker, respectively, compared with young (P < 0.05). Vo for both MA and NA old groups was 62 and 46% slower, respectively, compared with young. Both MA and NA adults had approximately two times slower values for ktr compared with young. The slower Vo in both old groups relative to young, coupled with a similarly reduced ktr, suggests impaired cross-bridge kinetics are responsible for impaired single fiber contractile properties with aging. These results challenge the widely accepted resilience of slow type fibers to cellular aging., (Copyright © 2016 the American Physiological Society.)
- Published
- 2016
- Full Text
- View/download PDF
36. Mitochondrial DNA deletions in muscle satellite cells: implications for therapies.
- Author
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Spendiff S, Reza M, Murphy JL, Gorman G, Blakely EL, Taylor RW, Horvath R, Campbell G, Newman J, Lochmüller H, and Turnbull DM
- Subjects
- Adult, DNA Copy Number Variations, Female, Gene Deletion, Genetic Variation, Genotype, Humans, Male, Middle Aged, Mitochondria drug effects, Mitochondria pathology, Mitochondrial Myopathies therapy, Muscle Fibers, Skeletal metabolism, Mutation, NADH Dehydrogenase genetics, RNA, Ribosomal, 18S genetics, Real-Time Polymerase Chain Reaction, DNA, Mitochondrial genetics, Mitochondria genetics, Mitochondrial Myopathies genetics, Satellite Cells, Skeletal Muscle metabolism
- Abstract
Progressive myopathy is a major clinical feature of patients with mitochondrial DNA (mtDNA) disease. There is limited treatment available for these patients although exercise and other approaches to activate muscle stem cells (satellite cells) have been proposed. The majority of mtDNA defects are heteroplasmic (a mixture of mutated and wild-type mtDNA present within the muscle) with high levels of mutated mtDNA and low levels of wild-type mtDNA associated with more severe disease. The culture of satellite cell-derived myoblasts often reveals no evidence of the original mtDNA mutation although it is not known if this is lost by selection or simply not present in these cells. We have explored if the mtDNA mutation is present in the satellite cells in one of the commonest genotypes associated with mitochondrial myopathies (patients with single, large-scale mtDNA deletions). Analysis of satellite cells from eight patients showed that the level of mtDNA mutation in the satellite cells is the same as in the mature muscle but is most often subsequently lost during culture. We show that there are two periods of selection against the mutated form, one early on possibly during satellite cell activation and the other during the rapid replication phase of myoblast culture. Our data suggest that the mutations are also lost during rapid replication in vivo, implying that strategies to activate satellite cells remain a viable treatment for mitochondrial myopathies in specific patient groups.
- Published
- 2013
- Full Text
- View/download PDF
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