RESUMEN

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease. Syncytin-1 (Syn), an envelope glycoprotein encoded by the env gene of the human endogenous retrovirus-W family, has been resorted to be highly expressed in biopsies from the muscles from ALS patients; however, the specific regulatory role of Syn during ALS progression remains uncovered. In this study, C57BL/6 mice were injected with adeno-associated virus-overexpressing Syn, with or without Fasudil administration. The Syn expression was assessed by quantitative real-time polymerase chain reaction and immunohistochemistry analysis. The histological change of anterior tibial muscles was determined by hematoxylin-eosin staining. Qualitative ultrastructural analysis of electron micrographs obtained from lumbar spinal cords was carried out. Serum inflammatory cytokines were assessed by enzyme linked immunosorbent assay (ELISA) assay and motor function was recorded using Basso, Beattie, and Bresnahan (BBB) scoring, climbing test and treadmill running test. Immunofluorescence and western blot assays were conducted to examine microglial- and motor neurons-related proteins. Syn overexpression significantly caused systemic inflammatory response, muscle tissue lesions, and motor dysfunction in mice. Meanwhile, Syn overexpression promoted the impairment of motor neuron, evidenced by the damaged structure of the neurons and reduced expression of microtubule-associated protein 2, HB9, neuronal nuclei and neuron-specific enolase in Syn-induced mice. In addition, Syn overexpression greatly promoted the expression of CD16/CD32 and inducible nitric oxide synthase (M1 phenotype markers), and reduced the expression of CD206 and arginase 1 (M2 phenotype markers). Importantly, the above changes caused by Syn overexpression were partly abolished by Fasudil administration. This study provides evidence that Syn-activated microglia plays a pivotal role during the progression of ALS.

Asunto(s)

1-(5-Isoquinolinesulfonil)-2-Metilpiperazina , Ratones Endogámicos C57BL , Microglía , Neuronas Motoras , Animales , Microglía/efectos de los fármacos , Microglía/metabolismo , Neuronas Motoras/efectos de los fármacos , Neuronas Motoras/metabolismo , Ratones , 1-(5-Isoquinolinesulfonil)-2-Metilpiperazina/análogos & derivados , 1-(5-Isoquinolinesulfonil)-2-Metilpiperazina/farmacología , Productos del Gen env , Esclerosis Amiotrófica Lateral/tratamiento farmacológico , Esclerosis Amiotrófica Lateral/metabolismo , Proteínas Gestacionales/metabolismo , Masculino , Citocinas/metabolismo , Modelos Animales de Enfermedad , Actividad Motora/efectos de los fármacos , Médula Espinal/metabolismo , Médula Espinal/efectos de los fármacos

RESUMEN

OBJECTIVE: There is little proof to determine the features of the muscles' motor unit potentials (MUPs) in children with poor posture. Current evaluation could be of value for future studies as a reference. The purpose was to detect the impact of rounded back posture on the characteristics of the MUPs and fascicle length of the shoulder retractors in children. METHODS: Participants in this study were 60 children (boys and girls), their ages were from 7 to 10 years old. Children were allocated into healthy children group (A) and rounded back posture group (B). MUPs and fascicle length of middle trapezius were assessed by electromyography and ultrasonography respectively. RESULTS: When compared to the normal group, the rounded back group's right and left middle trapezius MUPs count and amplitude significantly increased. As regards to the middle trapezius MUPs duration between the two groups, there was no significant difference. Also, the rounded back posture group exhibited significantly lower fascicle length in middle trapezius of both sides than the normal group. CONCLUSION: Forward shoulder posture is accompanied by atypical middle trapezius MUPs characteristics and also lowered fascicle length. Thus, children with forward-leaning posture could increase the likelihood of developing any of the many shoulder disorders.

Asunto(s)

Electromiografía , Postura , Hombro , Humanos , Niño , Femenino , Masculino , Postura/fisiología , Hombro/fisiología , Hombro/diagnóstico por imagen , Electromiografía/métodos , Músculos Superficiales de la Espalda/fisiología , Músculos Superficiales de la Espalda/diagnóstico por imagen , Ultrasonografía/métodos , Neuronas Motoras/fisiología

RESUMEN

Finding optimal bipartite matchings-e.g., matching medical students to hospitals for residency, items to buyers in an auction, or papers to reviewers for peer review-is a fundamental combinatorial optimization problem. We found a distributed algorithm for computing matchings by studying the development of the neuromuscular circuit. The neuromuscular circuit can be viewed as a bipartite graph formed between motor neurons and muscle fibers. In newborn animals, neurons and fibers are densely connected, but after development, each fiber is typically matched (i.e., connected) to exactly one neuron. We cast this synaptic pruning process as a distributed matching (or assignment) algorithm, where motor neurons "compete" with each other to "win" muscle fibers. We show that this algorithm is simple to implement, theoretically sound, and effective in practice when evaluated on real-world bipartite matching problems. Thus, insights from the development of neural circuits can inform the design of algorithms for fundamental computational problems.

Asunto(s)

Algoritmos , Neuronas Motoras , Neuronas Motoras/fisiología , Animales , Humanos , Redes Neurales de la Computación , Modelos Neurológicos

RESUMEN

Amyotrophic Lateral Sclerosis (ALS) is a multisystemic neurodegenerative disorder, with accumulating evidence indicating metabolic disruptions in the skeletal muscle preceding disease symptoms, rather than them manifesting as a secondary consequence of motor neuron (MN) degeneration. Hence, energy homeostasis is deeply implicated in the complex physiopathology of ALS and skeletal muscle has emerged as a key therapeutic target. Here, we describe intrinsic abnormalities in ALS skeletal muscle, both in patient-derived muscle cells and in muscle cell lines with genetic knockdown of genes related to familial ALS, such as TARDBP (TDP-43) and FUS. We found a functional impairment of myogenesis that parallels defects of glucose oxidation in ALS muscle cells. We identified FOXO1 transcription factor as a key mediator of these metabolic and functional features in ALS muscle, via gene expression profiling and biochemical surveys in TDP-43 and FUS-silenced muscle progenitors. Strikingly, inhibition of FOXO1 mitigated the impaired myogenesis in both the genetically modified and the primary ALS myoblasts. In addition, specific in vivo conditional knockdown of TDP-43 or FUS orthologs (TBPH or caz) in Drosophila muscle precursor cells resulted in decreased innervation and profound dysfunction of motor nerve terminals and neuromuscular synapses, accompanied by motor abnormalities and reduced lifespan. Remarkably, these phenotypes were partially corrected by foxo inhibition, bolstering the potential pharmacological management of muscle intrinsic abnormalities associated with ALS. The findings demonstrate an intrinsic muscle dysfunction in ALS, which can be modulated by targeting FOXO factors, paving the way for novel therapeutic approaches that focus on the skeletal muscle as complementary target tissue.

Asunto(s)

Esclerosis Amiotrófica Lateral , Proteína Forkhead Box O1 , Músculo Esquelético , Esclerosis Amiotrófica Lateral/metabolismo , Esclerosis Amiotrófica Lateral/genética , Esclerosis Amiotrófica Lateral/patología , Humanos , Animales , Músculo Esquelético/metabolismo , Músculo Esquelético/patología , Proteína Forkhead Box O1/metabolismo , Proteína Forkhead Box O1/genética , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Masculino , Proteína FUS de Unión a ARN/genética , Proteína FUS de Unión a ARN/metabolismo , Femenino , Drosophila , Desarrollo de Músculos/fisiología , Persona de Mediana Edad , Anciano , Neuronas Motoras/metabolismo , Neuronas Motoras/patología , Mioblastos/metabolismo

RESUMEN

INTRODUCTION: Reliable, noninvasive early diagnostics of neuromuscular function in Bell's palsy, which causes facial paralysis and reduced quality of life, remain to be established. Here, we aimed to evaluate the utility of the motor unit number index (MUNIX) for the quantitative electrophysiological assessment of early-stage Bell's palsy, its correlation with clinical assessments, changes following treatment, and association with clinical prognosis. METHODS: MUNIX measures were recorded from the bilateral zygomaticus, orbicularis oculi, and orbicularis oris muscles of 10 healthy individuals and 64 patients with Bell's palsy. The patients were assessed by two specialist neurologists using the House-Brackmann and Sunnybrook Facial Grading Systems. Repeat assessments were performed on 20 patients with Bell's palsy who received treatment. Additionally, the 64 patients were reassessed using clinical scales after a 1-month interval. RESULTS: The MUNIX values of the main affected muscles on the affected side were lower than those on the healthy side in patients with Bell's palsy (p < .05). The MUNIX measurements significantly correlated with the clinical facial nerve palsy scale scores (p < .05). Significant improvements were observed in the MUNIX values on repeat testing following treatment (p < .05). The baseline motor unit size index (the compound muscle action potential amplitude divided by MUNIX) was positively associated with improved clinical presentation after 1 month (p < .05). CONCLUSION: MUNIX can be used as an electrophysiological biomarker for the quantitative assessment of facial nerve palsy and treatment response, and as a prognostic biomarker, in patients with early Bell's palsy, and is recommended as a complement to conventional neurophysiological examinations.

Asunto(s)

Parálisis de Bell , Electromiografía , Humanos , Parálisis de Bell/fisiopatología , Parálisis de Bell/diagnóstico , Masculino , Femenino , Adulto , Persona de Mediana Edad , Electromiografía/métodos , Músculos Faciales/fisiopatología , Adulto Joven , Anciano , Biomarcadores , Neuronas Motoras/fisiología , Diagnóstico Precoz , Potenciales de Acción/fisiología

RESUMEN

Amyotrophic lateral sclerosis (ALS) is an adult-onset neurodegenerative disease leading to motor neuron loss. Currently mutations in > 40 genes have been linked to ALS, but the contribution of many genes and genetic mutations to the ALS pathogenic process remains poorly understood. Therefore, we first performed comparative interactome analyses of five recently discovered ALS-associated proteins (C21ORF2, KIF5A, NEK1, TBK1, and TUBA4A) which highlighted many novel binding partners, and both unique and shared interactors. The analysis further identified C21ORF2 as a strongly connected protein. The role of C21ORF2 in neurons and in the nervous system, and of ALS-associated C21ORF2 variants is largely unknown. Therefore, we combined human iPSC-derived motor neurons with other models and different molecular cell biological approaches to characterize the potential pathogenic effects of C21ORF2 mutations in ALS. First, our data show C21ORF2 expression in ALS-relevant mouse and human neurons, such as spinal and cortical motor neurons. Further, the prominent ALS-associated variant C21ORF2-V58L caused increased apoptosis in mouse neurons and movement defects in zebrafish embryos. iPSC-derived motor neurons from C21ORF2-V58L-ALS patients, but not isogenic controls, show increased apoptosis, and changes in DNA damage response, mitochondria and neuronal excitability. In addition, C21ORF2-V58L induced post-transcriptional downregulation of NEK1, an ALS-associated protein implicated in apoptosis and DDR. In all, our study defines the pathogenic molecular and cellular effects of ALS-associated C21ORF2 mutations and implicates impaired post-transcriptional regulation of NEK1 downstream of mutant C21ORF72 in ALS.

Asunto(s)

Esclerosis Amiotrófica Lateral , Células Madre Pluripotentes Inducidas , Mitocondrias , Neuronas Motoras , Quinasa 1 Relacionada con NIMA , Pez Cebra , Humanos , Esclerosis Amiotrófica Lateral/genética , Esclerosis Amiotrófica Lateral/metabolismo , Esclerosis Amiotrófica Lateral/patología , Quinasa 1 Relacionada con NIMA/genética , Quinasa 1 Relacionada con NIMA/metabolismo , Animales , Neuronas Motoras/metabolismo , Neuronas Motoras/patología , Células Madre Pluripotentes Inducidas/metabolismo , Ratones , Mitocondrias/metabolismo , Mitocondrias/patología , Reparación del ADN/genética , Daño del ADN , Mutación

RESUMEN

Disrupted copper availability in the central nervous system (CNS) is implicated as a significant feature of the neurodegenerative disease amyotrophic lateral sclerosis (ALS). Solute carrier family 31 member 1 (Slc31a1; Ctr1) governs copper uptake in mammalian cells and mutations affecting Slc31a1 are associated with severe neurological abnormalities. Here, we examined the impact of decreased CNS copper caused by ubiquitous heterozygosity for functional Slc31a1 on spinal cord motor neurons in Slc31a1+/- mice. Congruent with the CNS being relatively susceptible to disrupted copper availability, brain and spinal cord tissue from Slc31a1+/- mice contained significantly less copper than wild-type littermates, even though copper levels in other tissues were unaffected. Slc31a1+/- mice had less spinal cord α-motor neurons compared to wild-type littermates, but they did not develop any overt physical signs of motor impairment. By contrast, ALS model SOD1G37R mice had fewer α-motor neurons than control mice and exhibited clear signs of motor function impairment. With the expression of Slc31a1 notwithstanding, spinal cord expression of genes related to copper handling revealed only minor differences between Slc31a1+/- and wild-type mice. This contrasted with SOD1G37R mice where changes in the expression of copper handling genes were pronounced. Similarly, the expression of genes related to toxic glial activation was unchanged in spinal cords from Slc31a1+/- mice but highly upregulated in SOD1G37R mice. Together, results from the Slc31a1+/- mice and SOD1G37R mice indicate that although depleted CNS copper has a significant impact on spinal cord motor neuron numbers, the manifestation of overt ALS-like motor impairment requires additional factors.

Asunto(s)

Esclerosis Amiotrófica Lateral , Transportador de Cobre 1 , Cobre , Neuronas Motoras , Médula Espinal , Animales , Cobre/metabolismo , Neuronas Motoras/metabolismo , Neuronas Motoras/patología , Médula Espinal/metabolismo , Médula Espinal/patología , Ratones , Transportador de Cobre 1/metabolismo , Esclerosis Amiotrófica Lateral/metabolismo , Esclerosis Amiotrófica Lateral/patología , Esclerosis Amiotrófica Lateral/genética , Sistema Nervioso Central/metabolismo , Ratones Transgénicos , Superóxido Dismutasa-1/genética , Superóxido Dismutasa-1/metabolismo , Modelos Animales de Enfermedad

RESUMEN

Many RNA-binding proteins (RBPs) are linked to the dysregulation of RNA metabolism in motor neuron diseases (MNDs). However, the molecular mechanisms underlying MN vulnerability have yet to be elucidated. Here, we found that such an RBP, Quaking5 (Qki5), contributes to formation of the MN-specific transcriptome profile, termed "MN-ness," through the posttranscriptional network and maintenance of the mature MNs. Immunohistochemical analysis and single-cell RNA sequencing (scRNA-seq) revealed that Qki5 is predominantly expressed in MNs, but not in other neuronal populations of the spinal cord. Furthermore, comprehensive RNA sequencing (RNA-seq) analyses revealed that Qki5-dependent RNA regulation plays a pivotal role in generating the MN-specific transcriptome through pre-messenger ribonucleic acid (mRNA) splicing for the synapse-related molecules and c-Jun N-terminal kinase/stress-activated protein kinase (JNK/SAPK) signaling pathways. Indeed, MN-specific ablation of the Qki5 caused neurodegeneration in postnatal mice and loss of Qki5 function resulted in the aberrant activation of stress-responsive JNK/SAPK pathway both in vitro and in vivo. These data suggested that Qki5 plays a crucial biological role in RNA regulation and safeguarding of MNs and might be associated with pathogenesis of MNDs.

Asunto(s)

Neuronas Motoras , Proteínas de Unión al ARN , Médula Espinal , Transcriptoma , Animales , Proteínas de Unión al ARN/metabolismo , Proteínas de Unión al ARN/genética , Neuronas Motoras/metabolismo , Ratones , Médula Espinal/metabolismo , Precursores del ARN/metabolismo , Precursores del ARN/genética , Empalme del ARN , Ratones Noqueados

RESUMEN

One of the main factors in the pathophysiology of amyotrophic lateral sclerosis is oxidative stress. Mangiferin (MF), a natural plant polyphenol, has anti-inflammatory and antioxidant effects. The aim of our study was to investigate the protective effects and mechanisms of MF in the hSOD1-G93A ALS cell model. Our result revealed that MF treatment reduced the generation of reactive oxygen species (ROS) and malondialdehyde (MDA), decreased oxidative damage, and reduced apoptosis. Additionally, it was observed that MF significantly increased the synthesis of the antioxidant genes hemeoxygenase-1 and NAD(P)H: quinone oxidoreductase 1, which are downstream of the Nrf2 signaling pathway, and increased the expression and activation of nuclear factor erythroid 2-related factor 2 (Nrf2). Nrf2 knockdown greatly promoted apoptosis, which was reversed by MF treatment. To summarize, MF promoted the Nrf2 pathway and scavenged MDA and ROS to protect the ALS cell model.

Asunto(s)

Apoptosis , Neuronas Motoras , Factor 2 Relacionado con NF-E2 , Estrés Oxidativo , Transducción de Señal , Xantonas , Xantonas/farmacología , Factor 2 Relacionado con NF-E2/metabolismo , Factor 2 Relacionado con NF-E2/genética , Estrés Oxidativo/efectos de los fármacos , Apoptosis/efectos de los fármacos , Ratones , Animales , Neuronas Motoras/metabolismo , Neuronas Motoras/efectos de los fármacos , Neuronas Motoras/patología , Transducción de Señal/efectos de los fármacos , Especies Reactivas de Oxígeno/metabolismo , Línea Celular , Esclerosis Amiotrófica Lateral/metabolismo , Esclerosis Amiotrófica Lateral/tratamiento farmacológico , Humanos , NAD(P)H Deshidrogenasa (Quinona)/metabolismo , NAD(P)H Deshidrogenasa (Quinona)/genética

RESUMEN

Patellar tendinopathy (PT) typically affects jumping-sport athletes with functional impairments frequently observed. Alterations to the functional organization of corticomotor neurons within the motor cortex that project to working muscles are evident in some musculoskeletal conditions and linked to functional impairments. We aimed to determine if functional organization of corticomotor neuron projections differs between athletes with PT and asymptomatic controls, and if organization is associated with neuromuscular control. We used a cross-sectional design, and the setting was Monash Biomedical Imaging. Basketball and volleyball athletes with (n = 8) and without PT (n = 8) completed knee extension and ankle dorsiflexion force matching tasks while undergoing fMRI. We determined functional organization via identification of the location of peak corticomotor neuron activation during respective tasks (expressed in X, Y, and Z coordinates) and calculated force matching accuracy for both tasks to quantify neuromuscular control. We observed significant interactions between group and coordinate plane for functional organization of corticomotor projections to knee extensors (p < 0.001) and ankle dorsiflexors (p = 0.016). Compared to controls, PT group peak corticomotor activation during the knee extension task was 9.6 mm medial (p < 0.001) and 5.2 mm posterior (p = 0.036), and during the ankle dorsiflexion task 8.2 mm inferior (p = 0.024). In the PT group, more posterior Y coordinate peak activation location during the knee extension task was associated with greater task accuracy (r = 0.749, p = 0.034). Functional organization of corticomotor neurons differed in jumping athletes with PT compared to controls. Links between functional organization and neuromuscular control in the PT group suggest organizational differences may be relevant to knee extension neuromuscular control preservation.

Asunto(s)

Baloncesto , Imagen por Resonancia Magnética , Corteza Motora , Tendinopatía , Voleibol , Humanos , Voleibol/fisiología , Baloncesto/fisiología , Corteza Motora/fisiología , Corteza Motora/fisiopatología , Estudios Transversales , Tendinopatía/fisiopatología , Masculino , Adulto Joven , Femenino , Adulto , Neuronas Motoras/fisiología , Ligamento Rotuliano/fisiopatología , Ligamento Rotuliano/fisiología , Atletas , Estudios de Casos y Controles

RESUMEN

ER-phagy is a specialized form of autophagy, defined by the lysosomal degradation of ER subdomains. ER-phagy has been implicated in relieving the ER from misfolded proteins during ER stress upon activation of the unfolded protein response (UPR). Here, we identified an essential role for the ER chaperone calnexin in regulating ER-phagy and the UPR in neurons. We showed that chemical induction of ER stress triggers ER-phagy in the somata and axons of primary cultured motoneurons. Under basal conditions, the depletion of calnexin leads to an enhanced ER-phagy in axons. However, upon ER stress induction, ER-phagy did not further increase in calnexin-deficient motoneurons. In addition to increased ER-phagy under basal conditions, we also detected an elevated proteasomal turnover of insoluble proteins, suggesting enhanced protein degradation by default. Surprisingly, we detected a diminished UPR in calnexin-deficient early cortical neurons under ER stress conditions. In summary, our data suggest a central role for calnexin in orchestrating both ER-phagy and the UPR to maintain protein homeostasis within the ER.

Asunto(s)

Calnexina , Estrés del Retículo Endoplásmico , Retículo Endoplásmico , Respuesta de Proteína Desplegada , Calnexina/metabolismo , Animales , Retículo Endoplásmico/metabolismo , Ratones , Autofagia , Neuronas Motoras/metabolismo , Axones/metabolismo , Células Cultivadas , Lisosomas/metabolismo , Neuronas/metabolismo

RESUMEN

EMG filling curve characterizes the EMG filling process and EMG probability density function (PDF) shape change for the entire force range of a muscle. We aim to understand the relation between the physiological and recording variables, and the resulting EMG filling curves. We thereby present an analytical and simulation study to explain how the filling curve patterns relate to specific changes in the motor unit potential (MUP) waveforms and motor unit (MU) firing rates, the two main factors affecting the EMG PDF, but also to recording conditions in terms of noise level. We compare the analytical results with simulated cases verifying a perfect agreement with the analytical model. Finally, we present a set of real EMG filling curves with distinct patterns to explain the information about MUP amplitudes, MU firing rates, and noise level that these patterns provide in the light of the analytical study. Our findings reflect that the filling factor increases when firing rate increases or when newly recruited motor unit have potentials of smaller or equal amplitude than the former ones. On the other hand, the filling factor decreases when newly recruited potentials are larger in amplitude than the previous potentials. Filling curves are shown to be consistent under changes of the MUP waveform, and stretched under MUP amplitude scaling. Our findings also show how additive noise affects the filling curve and can even impede to obtain reliable information from the EMG PDF statistics.

Asunto(s)

Potenciales de Acción , Algoritmos , Simulación por Computador , Electromiografía , Neuronas Motoras , Músculo Esquelético , Relación Señal-Ruido , Electromiografía/métodos , Humanos , Neuronas Motoras/fisiología , Músculo Esquelético/fisiología , Potenciales de Acción/fisiología , Contracción Muscular/fisiología , Reproducibilidad de los Resultados , Reclutamiento Neurofisiológico/fisiología , Modelos Estadísticos

RESUMEN

Motoneurons critically depend on precise spatial and temporal control of translation for axon growth and the establishment and maintenance of neuromuscular connections. While defects in local translation have been implicated in the pathogenesis of motoneuron disorders, little is known about the mechanisms regulating axonal protein synthesis. Here, we report that motoneurons derived from Hnrnpr knockout mice show reduced axon growth accompanied by lowered synthesis of cytoskeletal and synaptic components in axons. Mutant mice display denervated neuromuscular junctions and impaired motor behavior. In axons, hnRNP R is a component of translation initiation complexes and, through interaction with O-linked ß-N-acetylglucosamine (O-GlcNAc) transferase (Ogt), modulates O-GlcNAcylation of eIF4G. Restoring axonal O-GlcNAc levels rescued local protein synthesis and axon growth defects of hnRNP R knockout motoneurons. Together, these findings demonstrate a function of hnRNP R in controlling the local production of key factors required for axon growth and formation of neuromuscular innervations.

Asunto(s)

Axones , Factor 4G Eucariótico de Iniciación , Ribonucleoproteínas Nucleares Heterogéneas , Ratones Noqueados , Neuronas Motoras , Biosíntesis de Proteínas , Animales , Ratones , Acetilglucosamina/metabolismo , Axones/metabolismo , Factor 4G Eucariótico de Iniciación/metabolismo , Factor 4G Eucariótico de Iniciación/genética , Ribonucleoproteínas Nucleares Heterogéneas/metabolismo , Ribonucleoproteínas Nucleares Heterogéneas/genética , Neuronas Motoras/metabolismo , N-Acetilglucosaminiltransferasas/metabolismo , N-Acetilglucosaminiltransferasas/genética , Unión Neuromuscular/metabolismo

RESUMEN

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder distinguished by gradual depletion of motor neurons. RNA binding motif protein 5 (RBM5), an abundantly expressed RNA-binding protein, plays a critical role in the process of cellular death. However, little is known about the role of RBM5 in the pathogenesis of ALS. Here, we found that RBM5 was upregulated in ALS hSOD1G93A-NSC34 cell models and hSOD1G93A mice due to a reduction of miR-141-5p. The upregulation of RBM5 increased the apoptosis of motor neurons by inhibiting Rac1-mediated neuroprotection. In contrast, genetic knockdown of RBM5 rescued motor neurons from hSOD1G93A-induced degeneration by activating Rac1 signaling. The neuroprotective effect of RBM5-knockdown was significantly inhibited by the Rac1 inhibitor, NSC23766. These findings suggest that RBM5 could potentially serve as a therapeutic target in ALS by activating the Rac1 signalling.

Asunto(s)

Esclerosis Amiotrófica Lateral , Apoptosis , Neuronas Motoras , Proteínas Proto-Oncogénicas c-akt , Proteínas de Unión al ARN , Transducción de Señal , Proteína de Unión al GTP rac1 , Esclerosis Amiotrófica Lateral/metabolismo , Esclerosis Amiotrófica Lateral/genética , Esclerosis Amiotrófica Lateral/patología , Animales , Proteína de Unión al GTP rac1/metabolismo , Proteína de Unión al GTP rac1/genética , Neuronas Motoras/metabolismo , Neuronas Motoras/patología , Apoptosis/fisiología , Proteínas de Unión al ARN/metabolismo , Proteínas de Unión al ARN/genética , Ratones , Humanos , Transducción de Señal/fisiología , Proteínas Proto-Oncogénicas c-akt/metabolismo , Ratones Transgénicos , Superóxido Dismutasa/metabolismo , Superóxido Dismutasa/genética , Masculino , Proteínas de Unión al ADN , Proteínas de Ciclo Celular , Proteínas Supresoras de Tumor

RESUMEN

Motoneuronal persistent inward currents (PICs) are facilitated by neuromodulatory inputs but are highly sensitive to local inhibitory circuits. Estimates of PICs are reduced by group Ia reciprocal inhibition, and increased with the diffuse actions of neuromodulators released during remote muscle contraction. However, it remains unknown how motoneurons function in the presence of simultaneous excitatory and inhibitory commands. To probe this topic, we investigated motor unit discharge patterns and estimated PICs during voluntary co-contraction of ankle muscles, which simultaneously demands the contraction of agonist-antagonist pairs. Twenty participants performed triangular ramps of both co-contraction (simultaneous dorsiflexion and plantar flexion) and isometric dorsiflexion to a peak of 30% of their maximum muscle activity from a maximal voluntary contraction. Motor unit spike trains were decomposed from high-density surface EMG activity recorded from tibialis anterior using blind source separation algorithms. Voluntary co-contraction altered motor unit discharge rate characteristics. Discharge rate at recruitment and peak discharge rate were modestly reduced (∼6% change; P < 0.001; d = 0.22) and increased (∼2% change; P = 0.001, d = -0.19), respectively, in the entire dataset but no changes were observed when motor units were tracked across conditions. The largest effects during co-contraction were that estimates of PICs (ΔF) were reduced by ∼20% (4.47 vs. 5.57 pulses per second during isometric dorsiflexion; P < 0.001, d = 0.641). These findings suggest that, during voluntary co-contraction, the inhibitory input from the antagonist muscle overcomes the additional excitatory and neuromodulatory drive that may occur due to the co-contraction of the antagonist muscle, which constrains PIC behaviour. KEY POINTS: Voluntary co-contraction is a unique motor behaviour that concurrently provides excitatory and inhibitory synaptic input to motoneurons. Co-contraction of agonist-antagonist pairs alters agonist motor unit discharge characteristics, consistent with reductions in persistent inward current magnitude.

Asunto(s)

Tobillo , Neuronas Motoras , Contracción Muscular , Músculo Esquelético , Humanos , Músculo Esquelético/fisiología , Músculo Esquelético/inervación , Neuronas Motoras/fisiología , Masculino , Adulto , Femenino , Contracción Muscular/fisiología , Tobillo/fisiología , Adulto Joven , Electromiografía , Potenciales de Acción/fisiología , Contracción Isométrica/fisiología

RESUMEN

Coordinated movement requires the nervous system to continuously compensate for changes in mechanical load across different conditions. For voluntary movements like reaching, the motor cortex is a critical hub that generates commands to move the limbs and counteract loads. How does cortex contribute to load compensation when rhythmic movements are sequenced by a spinal pattern generator? Here, we address this question by manipulating the mass of the forelimb in unrestrained mice during locomotion. While load produces changes in motor output that are robust to inactivation of motor cortex, it also induces a profound shift in cortical dynamics. This shift is minimally affected by cerebellar perturbation and significantly larger than the load response in the spinal motoneuron population. This latent representation may enable motor cortex to generate appropriate commands when a voluntary movement must be integrated with an ongoing, spinally-generated rhythm.

Asunto(s)

Locomoción , Corteza Motora , Neuronas Motoras , Animales , Corteza Motora/fisiología , Ratones , Neuronas Motoras/fisiología , Locomoción/fisiología , Miembro Anterior/fisiología , Masculino , Ratones Endogámicos C57BL , Movimiento/fisiología , Médula Espinal/fisiología , Femenino , Cerebelo/fisiología

RESUMEN

The majority of severe early-onset and juvenile cases of amyotrophic lateral sclerosis (ALS) are caused by mutations in the FUS gene, resulting in rapid disease progression. Mutant FUS accumulates within stress granules (SGs), thereby affecting the dynamics of these ribonucleoprotein complexes. Here, we define the interactome of the severe mutant FUSP525L variant in human induced pluripotent stem cell (iPSC)-derived motor neurons. We find increased interaction of FUSP525L with the PARP1 enzyme, promoting poly-ADP-ribosylation (PARylation) and binding of FUS to histone H1.2. Inhibiting PARylation or reducing H1.2 levels alleviates mutant FUS aggregation, SG alterations, and apoptosis in human motor neurons. Conversely, elevated H1.2 levels exacerbate FUS-ALS phenotypes, driven by the internally disordered terminal domains of H1.2. In C. elegans models, knockdown of H1.2 and PARP1 orthologs also decreases FUSP525L aggregation and neurodegeneration, whereas H1.2 overexpression worsens ALS-related changes. Our findings indicate a link between PARylation, H1.2, and FUS with potential therapeutic implications.

Asunto(s)

Esclerosis Amiotrófica Lateral , Caenorhabditis elegans , Histonas , Mutación , Poli(ADP-Ribosa) Polimerasa-1 , Proteína FUS de Unión a ARN , Esclerosis Amiotrófica Lateral/genética , Esclerosis Amiotrófica Lateral/metabolismo , Esclerosis Amiotrófica Lateral/patología , Humanos , Histonas/metabolismo , Proteína FUS de Unión a ARN/metabolismo , Proteína FUS de Unión a ARN/genética , Caenorhabditis elegans/metabolismo , Caenorhabditis elegans/genética , Animales , Mutación/genética , Poli(ADP-Ribosa) Polimerasa-1/metabolismo , Poli(ADP-Ribosa) Polimerasa-1/genética , Neuronas Motoras/metabolismo , Neuronas Motoras/patología , Poli ADP Ribosilación , Células Madre Pluripotentes Inducidas/metabolismo , Unión Proteica

RESUMEN

Amyotrophic lateral sclerosis (ALS) is a complex disease impacting motor neurons of the brain, brainstem, and spinal cord. Disease etiology is quite heterogeneous with over 40 genes causing the disease and a vast ~90% of patients having no prior family history. Astrocytes are major contributors to ALS, particularly through involvement in accelerating disease progression. Through study of genetic forms of disease including SOD1, TDP43, FUS, C9orf72, VCP, TBK1, and more recently patient-derived cells from sporadic individuals, many biological mechanisms have been identified to cause intrinsic or glial-mediated neurotoxicity to motor neurons. Overall, many of the normally supportive and beneficial roles that astrocytes contribute to neuronal health and survival instead switch to become deleterious and neurotoxic. While the exact pathways may differ based on disease-origin, altered astrocyte-neuron communication is a common feature of ALS. Within this chapter, distinct genetic forms are examined in detail, along with what is known from sporadic patient-derived cells. Overall, this chapter highlights the interplay between astrocytes and neurons in this complex disease and describes the key features underlying: astrocyte-mediated motor neuron toxicity, excitotoxicity, oxidative/nitrosative stress, protein dyshomeostasis, metabolic imbalance, inflammation, trophic factor withdrawal, blood-brain/blood-spinal cord barrier involvement, disease spreading, and the extracellular matrix/cell adhesion/TGF-ß signaling pathways.

Asunto(s)

Esclerosis Amiotrófica Lateral , Astrocitos , Comunicación Celular , Progresión de la Enfermedad , Neuronas Motoras , Esclerosis Amiotrófica Lateral/metabolismo , Esclerosis Amiotrófica Lateral/patología , Humanos , Astrocitos/metabolismo , Neuronas Motoras/metabolismo , Neuronas Motoras/patología , Comunicación Celular/fisiología , Animales

RESUMEN

The primary motor cortex does not uniquely or directly produce alpha motoneurone (α-MN) drive to muscles during voluntary movement. Rather, α-MN drive emerges from the synthesis and competition among excitatory and inhibitory inputs from multiple descending tracts, spinal interneurons, sensory inputs, and proprioceptive afferents. One such fundamental input is velocity-dependent stretch reflexes in lengthening muscles, which should be inhibited to enable voluntary movement. It remains an open question, however, the extent to which unmodulated stretch reflexes disrupt voluntary movement, and whether and how they are inhibited in limbs with numerous multiarticular muscles. We used a computational model of a Rhesus Macaque arm to simulate movements with feedforward α-MN commands only, and with added velocity-dependent stretch reflex feedback. We found that velocity-dependent stretch reflex caused movement-specific, typically large and variable disruptions to arm movements. These disruptions were greatly reduced when modulating velocity-dependent stretch reflex feedback (i) as per the commonly proposed (but yet to be clarified) idealized alpha-gamma (α-γ) coactivation or (ii) an alternative α-MN collateral projection to homonymous γ-MNs. We conclude that such α-MN collaterals are a physiologically tenable propriospinal circuit in the mammalian fusimotor system. These collaterals could still collaborate with α-γ coactivation, and the few skeletofusimotor fibers (ß-MNs) in mammals, to create a flexible fusimotor ecosystem to enable voluntary movement. By locally and automatically regulating the highly nonlinear neuro-musculo-skeletal mechanics of the limb, these collaterals could be a critical low-level enabler of learning, adaptation, and performance via higher-level brainstem, cerebellar, and cortical mechanisms.

Asunto(s)

Macaca mulatta , Neuronas Motoras , Reflejo de Estiramiento , Reflejo de Estiramiento/fisiología , Animales , Neuronas Motoras/fisiología , Movimiento/fisiología , Músculo Esquelético/fisiología , Corteza Motora/fisiología , Simulación por Computador , Modelos Neurológicos , Brazo/fisiología

RESUMEN

Preclinical studies are crucial for developing amyotrophic lateral sclerosis drugs. Current FDA-approved drugs have been created by monitoring limb muscle function and histological analysis of amyotrophic lateral sclerosis model animals. Drug candidates for this disease have yet to be tested for bulbar-onset type due to the limitations of traditional preclinical tools: excessive animal use and discrete detection of disease progress. Here, our study introduces an all-in-one, wireless, integrated wearable system for facilitating continuous drug efficacy assessment of dysphagia-related muscles in animals during natural eating behaviors. By incorporating a kirigami-based strain-isolation mechanism, this device mounted on the skin of animals mitigates electromyography signal contamination caused by unpredictable animal movements. Our findings indicate this system, measuring the progression of motor neuron denervation, offers high precision in monitoring drug effects on dysphagia-responsible bulbar muscles. This study paves the way for more humane and efficient approaches to developing treatment solutions for degenerative neuromuscular diseases.

Asunto(s)

Esclerosis Amiotrófica Lateral , Modelos Animales de Enfermedad , Electromiografía , Dispositivos Electrónicos Vestibles , Esclerosis Amiotrófica Lateral/fisiopatología , Esclerosis Amiotrófica Lateral/tratamiento farmacológico , Animales , Electromiografía/métodos , Evaluación Preclínica de Medicamentos , Trastornos de Deglución/fisiopatología , Trastornos de Deglución/etiología , Músculo Esquelético/efectos de los fármacos , Músculo Esquelético/fisiopatología , Músculo Esquelético/inervación , Humanos , Masculino , Neuronas Motoras/efectos de los fármacos , Neuronas Motoras/fisiología , Ratas