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Leng Y, Li X, Zheng F, Liu H, Wang C, Wang X, Liao Y, Liu J, Meng K, Yu J, Zhang J, Wang B, Tan Y, Liu M, Jia X, Li D, Li Y, Gu Z, Fan Y. Advances in In Vitro Models of Neuromuscular Junction: Focusing on Organ-on-a-Chip, Organoids, and Biohybrid Robotics. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2211059. [PMID: 36934404 DOI: 10.1002/adma.202211059] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2022] [Revised: 02/18/2023] [Indexed: 06/18/2023]
Abstract
The neuromuscular junction (NMJ) is a peripheral synaptic connection between presynaptic motor neurons and postsynaptic skeletal muscle fibers that enables muscle contraction and voluntary motor movement. Many traumatic, neurodegenerative, and neuroimmunological diseases are classically believed to mainly affect either the neuronal or the muscle side of the NMJ, and treatment options are lacking. Recent advances in novel techniques have helped develop in vitro physiological and pathophysiological models of the NMJ as well as enable precise control and evaluation of its functions. This paper reviews the recent developments in in vitro NMJ models with 2D or 3D cultures, from organ-on-a-chip and organoids to biohybrid robotics. Related derivative techniques are introduced for functional analysis of the NMJ, such as the patch-clamp technique, microelectrode arrays, calcium imaging, and stimulus methods, particularly optogenetic-mediated light stimulation, microelectrode-mediated electrical stimulation, and biochemical stimulation. Finally, the applications of the in vitro NMJ models as disease models or for drug screening related to suitable neuromuscular diseases are summarized and their future development trends and challenges are discussed.
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Affiliation(s)
- Yubing Leng
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, and with the School of Engineering Medicine, Beihang University, Beijing, 100083, China
| | - Xiaorui Li
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, and with the School of Engineering Medicine, Beihang University, Beijing, 100083, China
| | - Fuyin Zheng
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, and with the School of Engineering Medicine, Beihang University, Beijing, 100083, China
| | - Hui Liu
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, and with the School of Engineering Medicine, Beihang University, Beijing, 100083, China
| | - Chunyan Wang
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, 100094, China
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing, 210096, China
| | - Xudong Wang
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, and with the School of Engineering Medicine, Beihang University, Beijing, 100083, China
| | - Yulong Liao
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, and with the School of Engineering Medicine, Beihang University, Beijing, 100083, China
| | - Jiangyue Liu
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, and with the School of Engineering Medicine, Beihang University, Beijing, 100083, China
| | - Kaiqi Meng
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, and with the School of Engineering Medicine, Beihang University, Beijing, 100083, China
| | - Jiaheng Yu
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, and with the School of Engineering Medicine, Beihang University, Beijing, 100083, China
| | - Jingyi Zhang
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, and with the School of Engineering Medicine, Beihang University, Beijing, 100083, China
| | - Binyu Wang
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, and with the School of Engineering Medicine, Beihang University, Beijing, 100083, China
| | - Yingjun Tan
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, 100094, China
| | - Meili Liu
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, and with the School of Engineering Medicine, Beihang University, Beijing, 100083, China
| | - Xiaoling Jia
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, and with the School of Engineering Medicine, Beihang University, Beijing, 100083, China
| | - Deyu Li
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, and with the School of Engineering Medicine, Beihang University, Beijing, 100083, China
| | - Yinghui Li
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, 100094, China
| | - Zhongze Gu
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing, 210096, China
| | - Yubo Fan
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, and with the School of Engineering Medicine, Beihang University, Beijing, 100083, China
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Luttrell SM, Smith AST, Mack DL. Creating stem cell-derived neuromuscular junctions in vitro. Muscle Nerve 2021; 64:388-403. [PMID: 34328673 PMCID: PMC9292444 DOI: 10.1002/mus.27360] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2019] [Revised: 05/28/2021] [Accepted: 06/21/2021] [Indexed: 12/14/2022]
Abstract
Recent development of novel therapies has improved mobility and quality of life for people suffering from inheritable neuromuscular disorders. Despite this progress, the majority of neuromuscular disorders are still incurable, in part due to a lack of predictive models of neuromuscular junction (NMJ) breakdown. Improvement of predictive models of a human NMJ would be transformative in terms of expanding our understanding of the mechanisms that underpin development, maintenance, and disease, and as a testbed with which to evaluate novel therapeutics. Induced pluripotent stem cells (iPSCs) are emerging as a clinically relevant and non‐invasive cell source to create human NMJs to study synaptic development and maturation, as well as disease modeling and drug discovery. This review will highlight the recent advances and remaining challenges to generating an NMJ capable of eliciting contraction of stem cell‐derived skeletal muscle in vitro. We explore the advantages and shortcomings of traditional NMJ culturing platforms, as well as the pioneering technologies and novel, biomimetic culturing systems currently in use to guide development and maturation of the neuromuscular synapse and extracellular microenvironment. Then, we will explore how this NMJ‐in‐a‐dish can be used to study normal assembly and function of the efferent portion of the neuromuscular arc, and how neuromuscular disease‐causing mutations disrupt structure, signaling, and function.
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Affiliation(s)
- Shawn M Luttrell
- Department of Rehabilitation Medicine, University of Washington, Seattle, Washington, USA.,Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle, Washington, USA
| | - Alec S T Smith
- Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle, Washington, USA.,Department of Physiology and Biophysics, University of Washington, Seattle, Washington, USA
| | - David L Mack
- Department of Rehabilitation Medicine, University of Washington, Seattle, Washington, USA.,Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle, Washington, USA.,Department of Physiology and Biophysics, University of Washington, Seattle, Washington, USA
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Barbeau S, Tahraoui-Bories J, Legay C, Martinat C. Building neuromuscular junctions in vitro. Development 2020; 147:147/22/dev193920. [PMID: 33199350 DOI: 10.1242/dev.193920] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The neuromuscular junction (NMJ) has been the model of choice to understand the principles of communication at chemical synapses. Following groundbreaking experiments carried out over 60 years ago, many studies have focused on the molecular mechanisms underlying the development and physiology of these synapses. This Review summarizes the progress made to date towards obtaining faithful models of NMJs in vitro We provide a historical approach discussing initial experiments investigating NMJ development and function from Xenopus to mice, the creation of chimeric co-cultures, in vivo approaches and co-culture methods from ex vivo and in vitro derived cells, as well as the most recent developments to generate human NMJs. We discuss the benefits of these techniques and the challenges to be addressed in the future for promoting our understanding of development and human disease.
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Affiliation(s)
- Susie Barbeau
- Université de Paris, CNRS, SPPIN - Saints-Pères Paris Institute for the Neurosciences, F-75006 Paris, France
| | - Julie Tahraoui-Bories
- INSERM/UEPS UMR 861, Paris Saclay Université, I-STEM, 91100 Corbeil-Essonnes, France
| | - Claire Legay
- Université de Paris, CNRS, SPPIN - Saints-Pères Paris Institute for the Neurosciences, F-75006 Paris, France
| | - Cécile Martinat
- INSERM/UEPS UMR 861, Paris Saclay Université, I-STEM, 91100 Corbeil-Essonnes, France
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Busetto G, Cangiano A. Pre- and post-synaptic roles of action potential activity in synapse elimination revealed by using ectopic neuromuscular junction formation by a foreign nerve. Neurosci Lett 2020; 722:134835. [PMID: 32057925 DOI: 10.1016/j.neulet.2020.134835] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Revised: 02/07/2020] [Accepted: 02/09/2020] [Indexed: 10/25/2022]
Abstract
The formation of the neuromuscular junction (nmj) is based on molecular cascades initiated by neural agrin as well as electrical activity in the neuromuscular structures. This review focuses on the latter factor, emphasizing the multiplicity of its mechanisms in the process of synapse elimination following initial polyneuronal innervation. Pre- and post-synaptic components of activity have in fact been identified through experiments on an adult model of nmj formation: ectopic reinnervation of the rat soleus muscle by the fibular nerve. Two activity-dependent elimination processes are thus compared: competition between distributed nmjs, which depends on evoked muscle impulse activity, and competition between axons converging on single nmjs, which instead depends on differences in the timing of impulses in the converging axons.
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Affiliation(s)
- Giuseppe Busetto
- Department of Neurosciences Biomedicine and Movement Sciences, University of Verona, Strada Le Grazie 8, 37134, Verona, Italy; National Institute of Neuroscience, Verona, Italy
| | - Alberto Cangiano
- Department of Neurosciences Biomedicine and Movement Sciences, University of Verona, Strada Le Grazie 8, 37134, Verona, Italy; National Institute of Neuroscience, Verona, Italy.
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Vila OF, Qu Y, Vunjak-Novakovic G. In vitro models of neuromuscular junctions and their potential for novel drug discovery and development. Expert Opin Drug Discov 2019; 15:307-317. [PMID: 31846349 DOI: 10.1080/17460441.2020.1700225] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Introduction: Neuromuscular Junctions (NMJs) are the synapses between motor neurons and skeletal muscle fibers, and they are responsible for voluntary motor function. NMJs are affected at early stages of numerous neurodegenerative and neuroimmunological diseases. Due to the difficulty of systematically studying and manipulating NMJs in live subjects, in vitro systems with human tissue models would provide a powerful complement to simple cell cultures and animal models for mechanistic and drug development studies.Areas covered: The authors review the latest advances in in vitro models of NMJs, from traditional cell co-culture systems to novel tissue culture approaches, with focus on disease modeling and drug testing.Expert opinion: In recent years, more sophisticated in vitro models of human NMJs have been established. The combination of human stem cell technology with advanced tissue culture systems has resulted in systems that better recapitulate the human NMJ structure and function, and thereby allow for high-throughput quantitative functional measurements under both healthy and diseased conditions. Although they still have limitations, these advanced systems are increasingly demonstrating their utility for evaluating new therapies for motoneuron and autoimmune neuromuscular diseases, and we expect them to become an integral part of the drug discovery process in the near future.
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Affiliation(s)
- Olaia F Vila
- Department of Biomedical Engineering, Columbia University, New York, NY, USA
| | - Yihuai Qu
- Department of Biomedical Engineering, Columbia University, New York, NY, USA
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6
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Terminal Schwann cell and vacant site mediated synapse elimination at developing neuromuscular junctions. Sci Rep 2019; 9:18594. [PMID: 31819113 PMCID: PMC6901572 DOI: 10.1038/s41598-019-55017-w] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Accepted: 10/02/2019] [Indexed: 02/08/2023] Open
Abstract
Synapses undergo transition from polyinnervation by multiple axons to single innervation a few weeks after birth. Synaptic activity of axons and interaxonal competition are thought to drive this developmental synapse elimination and tested as key parameters in quantitative models for further understanding. Recent studies of muscle synapses (endplates) show that there are also terminal Schwann cells (tSCs), glial cells associated with motor neurons and their functions, and vacant sites (or vacancies) devoid of tSCs and axons proposing tSCs as key effectors of synapse elimination. However, there is no quantitative model that considers roles of tSCs including vacancies. Here we develop a stochastic model of tSC and vacancy mediated synapse elimination. It employs their areas on individual endplates quantified by electron microscopy-based analyses assuming that vacancies form randomly and are taken over by adjacent axons or tSCs. The model reliably reproduced synapse elimination whereas equal or random probability models, similar to classical interaxonal competition models, did not. Furthermore, the model showed that synapse elimination is accelerated by enhanced synaptic activity of one axon and also by increased areas of vacancies and tSCs suggesting that the areas are important structural correlates of the rate of synapse elimination.
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Epperson HE, Sandage MJ. Neuromuscular Development in Neonates and Postnatal Infants: Implications for Neuromuscular Electrical Stimulation Therapy for Dysphagia. JOURNAL OF SPEECH, LANGUAGE, AND HEARING RESEARCH : JSLHR 2019; 62:2575-2583. [PMID: 31343903 DOI: 10.1044/2019_jslhr-s-18-0502] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Purpose The aim of the current study was to review neuromuscular development, summarize the current body of evidence describing the use of neuromuscular electrical stimulation (NMES) therapy in infants, and identify possible contraindications for the use of NMES in the neonate and young infant. Method After a review of the literature describing neuromuscular development, we created a timeline of the developmental processes. Key milestones were determined, and a literature search was conducted to identify potential effects of electrical stimulation on this process. Results Current evidence supporting the use of NMES in the pediatric population is limited and of poor quality. Contraindications of the use of NMES in the neonate and young infant were identified, including (a) inhibited expression of the neural cell adhesion molecule that is vital for neuromuscular development, (b) alteration of muscle fiber type metabolic profile away from intended muscle fiber type morphology, and (c) interruption of postsynaptic acetylcholine receptor synthesis during neuromuscular junction development. Conclusion The use of NMES for the treatment of dysphagia in the neonate and young infant may influence early neuromuscular development in a manner that is not currently well understood. Future research is needed to further understand the effects of NMES on the developing neuromuscular system.
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Affiliation(s)
| | - Mary J Sandage
- Department of Communication Disorders, Auburn University, AL
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Santhanam N, Kumanchik L, Guo X, Sommerhage F, Cai Y, Jackson M, Martin C, Saad G, McAleer CW, Wang Y, Lavado A, Long CJ, Hickman JJ. Stem cell derived phenotypic human neuromuscular junction model for dose response evaluation of therapeutics. Biomaterials 2018; 166:64-78. [PMID: 29547745 PMCID: PMC5866791 DOI: 10.1016/j.biomaterials.2018.02.047] [Citation(s) in RCA: 80] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Revised: 02/20/2018] [Accepted: 02/24/2018] [Indexed: 01/01/2023]
Abstract
There are currently no functional neuromuscular junction (hNMJ) systems composed of human cells that could be used for drug evaluations or toxicity testing in vitro. These systems are needed to evaluate NMJs for diseases such as amyotrophic lateral sclerosis, spinal muscular atrophy or other neurodegenerative diseases or injury states. There are certainly no model systems, animal or human, that allows for isolated treatment of motoneurons or muscle capable of generating dose response curves to evaluate pharmacological activity of these highly specialized functional units. A system was developed in which human myotubes and motoneurons derived from stem cells were cultured in a serum-free medium in a BioMEMS construct. The system is composed of two chambers linked by microtunnels to enable axonal outgrowth to the muscle chamber that allows separate stimulation of each component and physiological NMJ function and MN stimulated tetanus. The muscle's contractions, induced by motoneuron activation or direct electrical stimulation, were monitored by image subtraction video recording for both frequency and amplitude. Bungarotoxin, BOTOX® and curare dose response curves were generated to demonstrate pharmacological relevance of the phenotypic screening device. This quantifiable functional hNMJ system establishes a platform for generating patient-specific NMJ models by including patient-derived iPSCs.
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Affiliation(s)
- Navaneetha Santhanam
- Hybrid Systems Lab, NanoScience Technology Center, University of Central Florida, 12424 Research Parkway, Suite 400, Orlando, FL 32826, USA
| | - Lee Kumanchik
- Hybrid Systems Lab, NanoScience Technology Center, University of Central Florida, 12424 Research Parkway, Suite 400, Orlando, FL 32826, USA
| | - Xiufang Guo
- Hybrid Systems Lab, NanoScience Technology Center, University of Central Florida, 12424 Research Parkway, Suite 400, Orlando, FL 32826, USA
| | - Frank Sommerhage
- Hybrid Systems Lab, NanoScience Technology Center, University of Central Florida, 12424 Research Parkway, Suite 400, Orlando, FL 32826, USA
| | - Yunqing Cai
- Hybrid Systems Lab, NanoScience Technology Center, University of Central Florida, 12424 Research Parkway, Suite 400, Orlando, FL 32826, USA
| | - Max Jackson
- Hybrid Systems Lab, NanoScience Technology Center, University of Central Florida, 12424 Research Parkway, Suite 400, Orlando, FL 32826, USA
| | - Candace Martin
- Hybrid Systems Lab, NanoScience Technology Center, University of Central Florida, 12424 Research Parkway, Suite 400, Orlando, FL 32826, USA
| | - George Saad
- Hybrid Systems Lab, NanoScience Technology Center, University of Central Florida, 12424 Research Parkway, Suite 400, Orlando, FL 32826, USA
| | - Christopher W. McAleer
- Hybrid Systems Lab, NanoScience Technology Center, University of Central Florida, 12424 Research Parkway, Suite 400, Orlando, FL 32826, USA
| | - Ying Wang
- Hybrid Systems Lab, NanoScience Technology Center, University of Central Florida, 12424 Research Parkway, Suite 400, Orlando, FL 32826, USA,Department of Biomedical Engineering, 305 Weill Hall, Cornell University, Ithaca, NY, 14853, USA
| | - Andrea Lavado
- Hybrid Systems Lab, NanoScience Technology Center, University of Central Florida, 12424 Research Parkway, Suite 400, Orlando, FL 32826, USA
| | - Christopher J. Long
- Hybrid Systems Lab, NanoScience Technology Center, University of Central Florida, 12424 Research Parkway, Suite 400, Orlando, FL 32826, USA
| | - James J. Hickman
- Hybrid Systems Lab, NanoScience Technology Center, University of Central Florida, 12424 Research Parkway, Suite 400, Orlando, FL 32826, USA,correspondence:
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Hadders-Algra M. Early human motor development: From variation to the ability to vary and adapt. Neurosci Biobehav Rev 2018; 90:411-427. [PMID: 29752957 DOI: 10.1016/j.neubiorev.2018.05.009] [Citation(s) in RCA: 131] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2018] [Revised: 05/01/2018] [Accepted: 05/04/2018] [Indexed: 12/17/2022]
Abstract
This review summarizes early human motor development. From early fetal age motor behavior is based on spontaneous neural activity: activity of networks in the brainstem and spinal cord that is modulated by supraspinal activity. The supraspinal activity, first primarily brought about by the cortical subplate, later by the cortical plate, induces movement variation. Initially, movement variation especially serves exploration; its associated afferent information is primarily used to sculpt the developing nervous system, and less to adapt motor behavior. In the next phase, beginning at function-specific ages, movement variation starts to serve adaptation. In sucking and swallowing, this phase emerges shortly before term age. In speech, gross and fine motor development, it emerges from 3 to 4 months post-term onwards, i.e., when developmental focus in the primary sensory and motor cortices has shifted to the permanent cortical circuitries. With increasing age and increasing trial-and-error exploration, the infant improves its ability to use adaptive and efficicient forms of upright gross motor behavior, manual activities and vocalizations belonging to the native language.
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Affiliation(s)
- Mijna Hadders-Algra
- University of Groningen, University Medical Center Groningen, Dept. Pediatrics - Section Developmental Neurology, Groningen, The Netherlands.
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10
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Jean-Xavier C, Sharples SA, Mayr KA, Lognon AP, Whelan PJ. Retracing your footsteps: developmental insights to spinal network plasticity following injury. J Neurophysiol 2017; 119:521-536. [PMID: 29070632 DOI: 10.1152/jn.00575.2017] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
During development of the spinal cord, a precise interaction occurs between descending projections and sensory afferents, with spinal networks that lead to expression of coordinated motor output. In the rodent, during the last embryonic week, motor output first occurs as regular bursts of spontaneous activity, progressing to stochastic patterns of episodes that express bouts of coordinated rhythmic activity perinatally. Locomotor activity becomes functionally mature in the 2nd postnatal wk and is heralded by the onset of weight-bearing locomotion on the 8th and 9th postnatal day. Concomitantly, there is a maturation of intrinsic properties and key conductances mediating plateau potentials. In this review, we discuss spinal neuronal excitability, descending modulation, and afferent modulation in the developing rodent spinal cord. In the adult, plastic mechanisms are much more constrained but become more permissive following neurotrauma, such as spinal cord injury. We discuss parallel mechanisms that contribute to maturation of network function during development to mechanisms of pathological plasticity that contribute to aberrant motor patterns, such as spasticity and clonus, which emerge following central injury.
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Affiliation(s)
- C Jean-Xavier
- Hotchkiss Brain Institute, University of Calgary , Calgary, Alberta , Canada.,Department of Comparative Biology and Experimental Medicine, University of Calgary , Calgary, Alberta , Canada
| | - S A Sharples
- Hotchkiss Brain Institute, University of Calgary , Calgary, Alberta , Canada.,Department of Neuroscience, University of Calgary , Calgary, Alberta , Canada
| | - K A Mayr
- Hotchkiss Brain Institute, University of Calgary , Calgary, Alberta , Canada.,Department of Neuroscience, University of Calgary , Calgary, Alberta , Canada
| | - A P Lognon
- Department of Comparative Biology and Experimental Medicine, University of Calgary , Calgary, Alberta , Canada
| | - P J Whelan
- Hotchkiss Brain Institute, University of Calgary , Calgary, Alberta , Canada.,Department of Comparative Biology and Experimental Medicine, University of Calgary , Calgary, Alberta , Canada
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Uzel SGM, Platt RJ, Subramanian V, Pearl TM, Rowlands CJ, Chan V, Boyer LA, So PTC, Kamm RD. Microfluidic device for the formation of optically excitable, three-dimensional, compartmentalized motor units. SCIENCE ADVANCES 2016; 2:e1501429. [PMID: 27493991 PMCID: PMC4972469 DOI: 10.1126/sciadv.1501429] [Citation(s) in RCA: 146] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Accepted: 07/06/2016] [Indexed: 05/21/2023]
Abstract
Motor units are the fundamental elements responsible for muscle movement. They are formed by lower motor neurons and their muscle targets, synapsed via neuromuscular junctions (NMJs). The loss of NMJs in neurodegenerative disorders (such as amyotrophic lateral sclerosis or spinal muscle atrophy) or as a result of traumatic injuries affects millions of lives each year. Developing in vitro assays that closely recapitulate the physiology of neuromuscular tissues is crucial to understand the formation and maturation of NMJs, as well as to help unravel the mechanisms leading to their degeneration and repair. We present a microfluidic platform designed to coculture myoblast-derived muscle strips and motor neurons differentiated from mouse embryonic stem cells (ESCs) within a three-dimensional (3D) hydrogel. The device geometry mimics the spinal cord-limb physical separation by compartmentalizing the two cell types, which also facilitates the observation of 3D neurite outgrowth and remote muscle innervation. Moreover, the use of compliant pillars as anchors for muscle strips provides a quantitative functional readout of force generation. Finally, photosensitizing the ESC provides a pool of source cells that can be differentiated into optically excitable motor neurons, allowing for spatiodynamic, versatile, and noninvasive in vitro control of the motor units.
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Affiliation(s)
- Sebastien G. M. Uzel
- Department of Mechanical Engineering, Massachusetts Institute of Technology (MIT), Cambridge, MA 02139, USA
| | - Randall J. Platt
- Department of Biological Engineering, MIT, Cambridge, MA 02139, USA
- Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | | | - Taylor M. Pearl
- Department of Biological Engineering, MIT, Cambridge, MA 02139, USA
| | | | - Vincent Chan
- Department of Mechanical Engineering, Massachusetts Institute of Technology (MIT), Cambridge, MA 02139, USA
| | | | - Peter T. C. So
- Department of Mechanical Engineering, Massachusetts Institute of Technology (MIT), Cambridge, MA 02139, USA
- Department of Biological Engineering, MIT, Cambridge, MA 02139, USA
- BioSystems and Micromechanics (BioSyM) IRG, Singapore-MIT Alliance for Research and Technology, Singapore, Singapore
| | - Roger D. Kamm
- Department of Mechanical Engineering, Massachusetts Institute of Technology (MIT), Cambridge, MA 02139, USA
- Department of Biological Engineering, MIT, Cambridge, MA 02139, USA
- BioSystems and Micromechanics (BioSyM) IRG, Singapore-MIT Alliance for Research and Technology, Singapore, Singapore
- Corresponding author.
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12
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Ionescu A, Zahavi EE, Gradus T, Ben-Yaakov K, Perlson E. Compartmental microfluidic system for studying muscle–neuron communication and neuromuscular junction maintenance. Eur J Cell Biol 2016; 95:69-88. [DOI: 10.1016/j.ejcb.2015.11.004] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Revised: 11/01/2015] [Accepted: 11/19/2015] [Indexed: 01/09/2023] Open
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13
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Meng L, Mulcahy B, Cook SJ, Neubauer M, Wan A, Jin Y, Yan D. The Cell Death Pathway Regulates Synapse Elimination through Cleavage of Gelsolin in Caenorhabditis elegans Neurons. Cell Rep 2015; 11:1737-48. [PMID: 26074078 DOI: 10.1016/j.celrep.2015.05.031] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2014] [Revised: 05/01/2015] [Accepted: 05/15/2015] [Indexed: 11/17/2022] Open
Abstract
Synapse elimination occurs in development, plasticity, and disease. Although the importance of synapse elimination has been documented in many studies, the molecular mechanisms underlying this process are unclear. Here, using the development of C. elegans RME neurons as a model, we have uncovered a function for the apoptosis pathway in synapse elimination. We find that the conserved apoptotic cell death (CED) pathway and axonal mitochondria are required for the elimination of transiently formed clusters of presynaptic components in RME neurons. This function of the CED pathway involves the activation of the actin-filament-severing protein, GSNL-1. Furthermore, we show that caspase CED-3 cleaves GSNL-1 at a conserved C-terminal region and that the cleaved active form of GSNL-1 promotes its actin-severing ability. Our data suggest that activation of the CED pathway contributes to selective elimination of synapses through disassembly of the actin filament network.
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Affiliation(s)
- Lingfeng Meng
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Research Drive, Durham, NC 27710, USA
| | - Ben Mulcahy
- Lunenfeld-Tanenbaum Research Institute, Toronto, ON M5G 1X5, Canada
| | - Steven J Cook
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Marianna Neubauer
- Department of Physics and Center for Brain Science, Harvard University, Cambridge, MA 02138, USA
| | - Airong Wan
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Research Drive, Durham, NC 27710, USA
| | - Yishi Jin
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA; Department of Cellular and Molecular Medicine, School of Medicine, University of California, San Diego, La Jolla, CA 92093, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA
| | - Dong Yan
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Research Drive, Durham, NC 27710, USA; Department of Neurobiology and Duke Institute for Brain Sciences, Duke University Medical Center, Research Drive, Durham, NC 27710, USA.
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Zahavi EE, Ionescu A, Gluska S, Gradus T, Ben-Yaakov K, Perlson E. A compartmentalized microfluidic neuromuscular co-culture system reveals spatial aspects of GDNF functions. J Cell Sci 2015; 128:1241-52. [PMID: 25632161 PMCID: PMC4359927 DOI: 10.1242/jcs.167544] [Citation(s) in RCA: 100] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Bidirectional molecular communication between the motoneuron and the muscle is vital for neuromuscular junction (NMJ) formation and maintenance. The molecular mechanisms underlying such communication are of keen interest and could provide new targets for intervention in motoneuron disease. Here, we developed a microfluidic platform with motoneuron cell bodies on one side and muscle cells on the other, connected by motor axons extending through microgrooves to form functional NMJs. Using this system, we were able to differentiate between the proximal and distal effects of oxidative stress and glial-derived neurotrophic factor (GDNF), demonstrating a dying-back degeneration and retrograde transmission of pro-survival signaling, respectively. Furthermore, we show that GDNF acts differently on motoneuron axons versus soma, promoting axonal growth and innervation only when applied locally to axons. Finally, we track for the first time the retrograde transport of secreted GDNF from muscle to neuron. Thus, our data suggests spatially distinct effects of GDNF – facilitating growth and muscle innervation at axon terminals and survival pathways in the soma.
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Affiliation(s)
- Eitan Erez Zahavi
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, and the Sagol School of Neuroscience, Tel Aviv University, Tel Aviv 69978, Israel
| | - Ariel Ionescu
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, and the Sagol School of Neuroscience, Tel Aviv University, Tel Aviv 69978, Israel
| | - Shani Gluska
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, and the Sagol School of Neuroscience, Tel Aviv University, Tel Aviv 69978, Israel
| | - Tal Gradus
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, and the Sagol School of Neuroscience, Tel Aviv University, Tel Aviv 69978, Israel
| | - Keren Ben-Yaakov
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, and the Sagol School of Neuroscience, Tel Aviv University, Tel Aviv 69978, Israel
| | - Eran Perlson
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, and the Sagol School of Neuroscience, Tel Aviv University, Tel Aviv 69978, Israel
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15
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Microfluidic primary culture model of the lower motor neuron–neuromuscular junction circuit. J Neurosci Methods 2013; 218:164-9. [DOI: 10.1016/j.jneumeth.2013.06.002] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2013] [Revised: 06/05/2013] [Accepted: 06/06/2013] [Indexed: 11/20/2022]
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16
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Robinson KG, Mendonca JL, Militar JL, Theroux MC, Dabney KW, Shah SA, Miller F, Akins RE. Disruption of basal lamina components in neuromotor synapses of children with spastic quadriplegic cerebral palsy. PLoS One 2013; 8:e70288. [PMID: 23976945 PMCID: PMC3745387 DOI: 10.1371/journal.pone.0070288] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2012] [Accepted: 06/18/2013] [Indexed: 11/18/2022] Open
Abstract
Cerebral palsy (CP) is a static encephalopathy occurring when a lesion to the developing brain results in disordered movement and posture. Patients present with sometimes overlapping spastic, athetoid/dyskinetic, and ataxic symptoms. Spastic CP, which is characterized by stiff muscles, weakness, and poor motor control, accounts for ∼80% of cases. The detailed mechanisms leading to disordered movement in spastic CP are not completely understood, but clinical experience and recent studies suggest involvement of peripheral motor synapses. For example, it is recognized that CP patients have altered sensitivities to drugs that target neuromuscular junctions (NMJs), and protein localization studies suggest that NMJ microanatomy is disrupted in CP. Since CP originates during maturation, we hypothesized that NMJ disruption in spastic CP is associated with retention of an immature neuromotor phenotype later in life. Scoliosis patients with spastic CP or idiopathic disease were enrolled in a prospective, partially-blinded study to evaluate NMJ organization and neuromotor maturation. The localization of synaptic acetylcholine esterase (AChE) relative to postsynaptic acetylcholine receptor (AChR), synaptic laminin β2, and presynaptic vesicle protein 2 (SV2) appeared mismatched in the CP samples; whereas, no significant disruption was found between AChR and SV2. These data suggest that pre- and postsynaptic NMJ components in CP children were appropriately distributed even though AChE and laminin β2 within the synaptic basal lamina appeared disrupted. Follow up electron microscopy indicated that NMJs from CP patients appeared generally mature and similar to controls with some differences present, including deeper postsynaptic folds and reduced presynaptic mitochondria. Analysis of maturational markers, including myosin, syntrophin, myogenin, and AChR subunit expression, and telomere lengths, all indicated similar levels of motor maturation in the two groups. Thus, NMJ disruption in CP was found to principally involve components of the synaptic basal lamina and subtle ultra-structural modifications but appeared unrelated to neuromotor maturational status.
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Affiliation(s)
- Karyn G. Robinson
- Nemours Biomedical Research, Alfred I. duPont Hospital for Children, Wilmington, Delaware, United States of America
| | - Janet L. Mendonca
- Nemours Biomedical Research, Alfred I. duPont Hospital for Children, Wilmington, Delaware, United States of America
| | - Jaimee L. Militar
- Nemours Biomedical Research, Alfred I. duPont Hospital for Children, Wilmington, Delaware, United States of America
| | - Mary C. Theroux
- Department of Anesthesiology and Critical Care, Alfred I. duPont Hospital for Children, Wilmington, Delaware, United States of America
| | - Kirk W. Dabney
- Department of Orthopedic Surgery, Alfred I. duPont Hospital for Children, Wilmington, Delaware, United States of America
| | - Suken A. Shah
- Department of Orthopedic Surgery, Alfred I. duPont Hospital for Children, Wilmington, Delaware, United States of America
| | - Freeman Miller
- Department of Orthopedic Surgery, Alfred I. duPont Hospital for Children, Wilmington, Delaware, United States of America
| | - Robert E. Akins
- Nemours Biomedical Research, Alfred I. duPont Hospital for Children, Wilmington, Delaware, United States of America
- * E-mail:
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17
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Favero M, Busetto G, Cangiano A. Spike timing plays a key role in synapse elimination at the neuromuscular junction. Proc Natl Acad Sci U S A 2012; 109:E1667-75. [PMID: 22619332 PMCID: PMC3382556 DOI: 10.1073/pnas.1201147109] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Nerve impulse activity produces both developmental and adult plastic changes in neural networks. For development, however, its precise role and the mechanisms involved remain elusive. Using the classic model of synapse competition and elimination at newly formed neuromuscular junctions, we asked whether spike timing is the instructive signal at inputs competing for synaptic space. Using a rat strain whose soleus muscle is innervated by two nerves, we chronically evoked different temporal spike patterns in the two nerves during synapse formation in the adult. We found that asynchronous activity imposed upon the two nerves promotes synapse elimination, provided that their relative spikes are separated by 25 ms or more; remarkably, this elimination occurs even though an equal number of spikes were evoked in the competing axons. On the other hand, when spikes are separated by 20 ms or less, activity is perceived as synchronous, and elimination is prevented. Thus, in development, as in adult plasticity, precise spike timing plays an instructive role in synaptic modification.
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Affiliation(s)
- Morgana Favero
- Department of Neurological, Neuropsychological, Morphological and Motor Sciences, Section of Physiology and Psychology, Universitá di Verona, Strada Le Grazie 8, 37134 Verona, Italy; and
- National Institute of Neuroscience, Universitá di Verona, Strada Le Grazie 8, 37134 Verona, Italy
| | - Giuseppe Busetto
- Department of Neurological, Neuropsychological, Morphological and Motor Sciences, Section of Physiology and Psychology, Universitá di Verona, Strada Le Grazie 8, 37134 Verona, Italy; and
- National Institute of Neuroscience, Universitá di Verona, Strada Le Grazie 8, 37134 Verona, Italy
| | - Alberto Cangiano
- Department of Neurological, Neuropsychological, Morphological and Motor Sciences, Section of Physiology and Psychology, Universitá di Verona, Strada Le Grazie 8, 37134 Verona, Italy; and
- National Institute of Neuroscience, Universitá di Verona, Strada Le Grazie 8, 37134 Verona, Italy
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18
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Abstract
This article reviews developmental processes in the human brain and basic principles underlying typical and atypical motor development. The Neuronal Group Selection Theory is used as theoretical frame of reference. Evidence is accumulating that abundance in cerebral connectivity is the neural basis of human behavioral variability (ie, the ability to select, from a large repertoire of behavioral solutions, the one most appropriate for a specific situation). Indeed, typical human motor development is characterized by variation and the development of adaptive variability. Atypical motor development is characterized by a limited variation (a limited repertoire of motor strategies) and a limited ability to vary motor behavior according to the specifics of the situation (ie, limited variability). Limitations in variation are related to structural anomalies in which disturbances of cortical connectivity may play a prominent role, whereas limitations in variability are present in virtually all children with atypical motor development. The possible applications of variation and variability in diagnostics in children with or at risk for a developmental motor disorder are discussed.
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The timing of impulse activity shapes the process of synaptic competition at the neuromuscular junction. Neuroscience 2010; 167:343-53. [DOI: 10.1016/j.neuroscience.2010.01.055] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2009] [Revised: 11/06/2009] [Accepted: 01/26/2010] [Indexed: 11/18/2022]
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Electrical stimulation of paralyzed vibrissal muscles reduces endplate reinnervation and does not promote motor recovery after facial nerve repair in rats. Ann Anat 2009; 191:356-70. [PMID: 19481914 DOI: 10.1016/j.aanat.2009.03.004] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2009] [Revised: 03/24/2009] [Accepted: 03/24/2009] [Indexed: 01/26/2023]
Abstract
The outcome of peripheral nerve injuries requiring surgical repair is poor. Recent work has suggested that electrical stimulation (ES) of denervated muscles could be beneficial. Here we tested whether ES has a positive influence on functional recovery after injury and surgical repair of the facial nerve. Outcomes at 2 months were compared to animals receiving sham stimulation (SS). Starting on the first day after end-to-end suture (facial-facial anastomosis), electrical stimulation (square 0.1 ms pulses at 5 Hz at an ex tempore established threshold amplitude of between 3.0 and 5.0V) was delivered to the vibrissal muscles for 5 min a day, 3 times a week. Restoration of vibrissal motor performance following ES or SS was evaluated using the video-based motion analysis and correlated with the degree of collateral axonal branching at the lesion site, the number of motor endplates in the target musculature and the quality of their reinnervation, i.e. the degree of mono- versus poly-innervation. Neither protocol reduced collateral branching. ES did not improve functional outcome, but rather reduced the number of innervated motor endplates to approximately one-fifth of normal values and failed to reduce the proportion of poly-innervated motor endplates. We conclude that ES is not beneficial for recovery of whisker function after facial nerve repair in rats.
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Butz M, Wörgötter F, van Ooyen A. Activity-dependent structural plasticity. ACTA ACUST UNITED AC 2009; 60:287-305. [DOI: 10.1016/j.brainresrev.2008.12.023] [Citation(s) in RCA: 161] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2008] [Revised: 12/19/2008] [Accepted: 12/22/2008] [Indexed: 10/21/2022]
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22
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Takeuchi A, Moriguchi H, Kotani K, Miwa K, Lee JK, Noshiro M, Jimbo Y. Development of semi-separated co-culture system of sympathetic neuron and cardiomyocyte. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2009; 2009:1832-1835. [PMID: 19963518 DOI: 10.1109/iembs.2009.5332601] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Rat superior cervical ganglion (SCG) neurons and ventricular myocytes (VMs) were co-cultured in chambers made of polydimethylsyloxane. The chambers were placed on a microelectrode-array (MEA) substrate and connected with a pathway. 24 hours after dissemination of the VMs, neuntes of the SCG neurons outgrew through the pathway and reached the VMs. Spontaneous electrical activities of the SCG neurons and the VMs were observed several days after the dissemination. Constant-voltage stimualtion (1 V, 1 ms, biphasic square pulses) was applied to the SCG neurons at the frequency of 10 Hz using 32 electrodes. Contraction rate of the VMs increased by 153 +/-110 % immediately after the stimulation to the SCG neurons was stopped. Then contraction rate gradually decreased and returned to almost the same rate as before the stimulation 5 minutes after the 1-min stimulation. Propranolol (beta-adrenergic receptor antagonist) prevented contraction rate of the VMs from increasing after electrical stimulation to the SCG neurons. These results suggest that neuromuscular junctions were formed between the SCG neurons and the VMs. Overall the semi-separated co-culture system in this study is available in research on changes in contraction rate of the VMs after applying electrical stimulation to the SCG neurons.
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Affiliation(s)
- Akimasa Takeuchi
- Graduate School of Frontier Sciences, The University of Tokyo, Chiba, Japan.
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23
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Das M, Rumsey JW, Gregory CA, Bhargava N, Kang JF, Molnar P, Riedel L, Guo X, Hickman JJ. Embryonic motoneuron-skeletal muscle co-culture in a defined system. Neuroscience 2007; 146:481-8. [PMID: 17383103 DOI: 10.1016/j.neuroscience.2007.01.068] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2006] [Revised: 01/12/2007] [Accepted: 01/23/2007] [Indexed: 11/29/2022]
Abstract
This paper describes a significant biotechnological advancement by creating a minimalist serum-free defined system to co-culture rat mammalian nerve and muscle cells in order to form functional neuromuscular junctions. To date, all the known in vitro nerve and muscle co-culture models use serum containing media; and while functional neuromuscular junctions (NMJ) are described, they failed to detail or quantify the minimum factors needed to recreate the NMJ in vitro. In this work, we demonstrate the development of a defined motoneuron and muscle co-culture system resulting in the formation of NMJs including: 1) a new culture technique, 2) a novel serum-free medium formulation and 3) a synthetic self-assembled monolayer (SAM) substrate N-1 [3-(trimethoxysilyl) propyl] diethylenetriamine (DETA). We characterized the culture by morphology, immunocytochemistry, electrophysiology and videography. This model system provides a better understanding of the minimal growth factor and substrate interactions necessary for NMJ formation and provides a basic system that can be utilized for nerve-muscle tissue engineering, regenerative medicine and development of limb prosthetics.
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Affiliation(s)
- M Das
- NanoScience Technology Center, 12424 Research Parkway, Suite 400, University of Central Florida, Orlando, FL 32826, USA
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24
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Song Y, Panzer JA, Wyatt RM, Balice-Gordon RJ. Formation and plasticity of neuromuscular synaptic connections. Int Anesthesiol Clin 2006; 44:145-78. [PMID: 16849961 DOI: 10.1097/00004311-200604420-00009] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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25
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Personius KE, Balice-Gordon RJ. Activity-dependent synaptic plasticity: insights from neuromuscular junctions. Neuroscientist 2002; 8:414-22. [PMID: 12374426 DOI: 10.1177/107385802236970] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Experience-dependent editing shapes synaptic connections throughout the developing nervous system, but the underlying cellular mechanisms remain poorly understood. A useful model synapse for addressing these mechanisms is the neuromuscular junction, the connection between spinal motor neurons and skeletal muscle fibers. Here the authors review current ideas about the role of activity in editing neuromuscular synaptic connections. A variety of new tools are being used to address some unanswered questions in vivo and in vitro. Understanding activity-dependent plasticity at developing neuromuscular synapses may reveal how neural circuits in the central nervous system are altered by experience throughout life.
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Affiliation(s)
- Kirkwood E Personius
- Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia 19104-6074, USA
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26
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Hadders-Algra M. Variability in infant motor behavior: A hallmark of the healthy nervous system. Infant Behav Dev 2002. [DOI: 10.1016/s0163-6383(02)00144-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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27
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Lanuza MA, Garcia N, Santafe M, Nelson PG, Fenoll-Brunet MR, Tomas J. Pertussis toxin-sensitive G-protein and protein kinase C activity are involved in normal synapse elimination in the neonatal rat muscle. J Neurosci Res 2001; 63:330-40. [PMID: 11170183 DOI: 10.1002/1097-4547(20010215)63:4<330::aid-jnr1027>3.0.co;2-w] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Individual skeletal muscle fibers in most new-born rodents are innervated at a single endplate by several motor axons. During the first postnatal weeks, the polyneuronal innervation decreases in a process of synaptic elimination. Previous studies showed that the naturally occurring serine-protease thrombin mediates the activity-dependent synapse reduction at the neuromuscular junction (NMJ) in vitro and that thrombin-receptor activation may modulate nerve terminal consolidation through a protein kinase mechanism. To test whether these mechanisms may be operating in vivo, we applied external thrombin and its inhibitor hirudin, and several substances affecting the G protein-protein kinase C system (GP-PKC) directly over the external surface of the neonatal rat Levator auris longus muscle. Muscles were processed for immunocytochemistry to simultaneously detect acetylcholine receptors (AChRs) and axons for counting the percentage of polyinnervated NMJ. We found that exogenous thrombin accelerated synapse loss and hirudin blocked axonal removal. Phorbol-12-myristate-13-acetate, a potent PKC activator, had a similar effect as thrombin, whereas the PKC inhibitors, calphostin C and staurosporine, prevented axonal removal. Pertussis toxin, an effective blocker of GP function, blocked synapse elimination. These findings suggest that the normal synapse elimination in the neonatal rat muscle may be modulated, at least in part, by the pertussis-sensitive G-protein and PKC activity and that thrombin could play a role in the postnatal synaptic maturation in vivo.
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Affiliation(s)
- M A Lanuza
- Unitat d'Histologia i Neurobiologia (UHN), Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, Reus (Tarragona), Spain.
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28
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Abstract
Work over the past four decades has suggested that neural activity edits synaptic connections throughout the developing nervous system. Synaptic editing is shaped in large part by competitive interactions among different inputs innervating the same target cell that profoundly influence synaptic strength and structure. While competition plays out among presynaptic inputs that anterogradely influence their targets, postsynaptic target cells also modulate competition, in part through retrograde interactions that modulate presynaptic neurotransmitter release. One of the most useful synapses for studying how neural activity mediates synaptic editing is the connections between spinal motor neurons and skeletal muscle fibers, called neuromuscular junctions. Here we review current ideas about the role of activity in editing neuromuscular synaptic connections. The mechanisms by which activity mediates synaptic competition at these peripheral synapses are relevant to understanding how neural circuits in the central nervous system are continually altered by experience throughout life.
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Affiliation(s)
- K E Personius
- Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6074, USA
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29
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Abstract
Movement, the fundamental component of behavior and the principal extrinsic action of the brain, is produced when skeletal muscles contract and relax in response to patterns of action potentials generated by motoneurons. The processes that determine the firing behavior of motoneurons are therefore important in understanding the transformation of neural activity to motor behavior. Here, we review recent studies on the control of motoneuronal excitability, focusing on synaptic and cellular properties. We first present a background description of motoneurons: their development, anatomical organization, and membrane properties, both passive and active. We then describe the general anatomical organization of synaptic input to motoneurons, followed by a description of the major transmitter systems that affect motoneuronal excitability, including ligands, receptor distribution, pre- and postsynaptic actions, signal transduction, and functional role. Glutamate is the main excitatory, and GABA and glycine are the main inhibitory transmitters acting through ionotropic receptors. These amino acids signal the principal motor commands from peripheral, spinal, and supraspinal structures. Amines, such as serotonin and norepinephrine, and neuropeptides, as well as the glutamate and GABA acting at metabotropic receptors, modulate motoneuronal excitability through pre- and postsynaptic actions. Acting principally via second messenger systems, their actions converge on common effectors, e.g., leak K(+) current, cationic inward current, hyperpolarization-activated inward current, Ca(2+) channels, or presynaptic release processes. Together, these numerous inputs mediate and modify incoming motor commands, ultimately generating the coordinated firing patterns that underlie muscle contractions during motor behavior.
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Affiliation(s)
- J C Rekling
- Department of Neurobiology, University of California, Los Angeles, California 90095-1763, USA
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30
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Abstract
Synapse competition and elimination are widespread developmental processes, first demonstrated at neonatal neuromuscular junctions. Action potential activity was long shown to exert a powerful influence, but mechanisms and contribution relative to other factors are still not well understood. Here we show that replacement of natural motoneuronal discharge with synchronous activity suppresses elimination of polyneuronal innervation of myofibers. This requires the simultaneous chronic conduction block (tetrodotoxin) and distal electrical stimulation of motor axons during ectopic synaptogenesis in denervated adult soleus muscle. If in fact chronic stimulation is applied without central block of motor axons, the time course of synapse elimination is as fast as in control muscles undergoing natural activity. Our findings follow the prediction of Hebb's postulate and imply that asynchronous activity drives developmental synapse elimination in muscle. They further suggest that motoneurons could become transiently synchronized during development and regeneration, helping to establish the initial polyneuronal innervation.
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31
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Kistler WM, van Hemmen JL. Modeling synaptic plasticity in conjuction with the timing of pre- and postsynaptic action potentials. Neural Comput 2000; 12:385-405. [PMID: 10636948 DOI: 10.1162/089976600300015844] [Citation(s) in RCA: 124] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
We present a spiking neuron model that allows for an analytic calculation of the correlations between pre- and postsynaptic spikes. The neuron model is a generalization of the integrate-and-fire model and equipped with a probabilistic spike-triggering mechanism. We show that under certain biologically plausible conditions, pre- and postsynaptic spike trains can be described simultaneously as an inhomogeneous Poisson process. Inspired by experimental findings, we develop a model for synaptic long-term plasticity that relies on the relative timing of pre- and post-synaptic action potentials. Being given an input statistics, we compute the stationary synaptic weights that result from the temporal correlations between the pre- and postsynaptic spikes. By means of both analytic calculations and computer simulations, we show that such a mechanism of synaptic plasticity is able to strengthen those input synapses that convey precisely timed spikes at the expense of synapses that deliver spikes with a broad temporal distribution. This may be of vital importance for any kind of information processing based on spiking neurons and temporal coding.
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Affiliation(s)
- W M Kistler
- Physik Department der TU München, D-85747 Garching bei München, Germany
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32
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Affiliation(s)
- J Golowasch
- Volen Center for Complex Systems, Brandeis University, Waltham, MA 02454, USA
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33
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Jia M, Li M, Dunlap V, Nelson PG. The thrombin receptor mediates functional activity-dependent neuromuscular synapse reduction via protein kinase C activationin vitro. ACTA ACUST UNITED AC 1999. [DOI: 10.1002/(sici)1097-4695(19990215)38:3<369::aid-neu6>3.0.co;2-q] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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34
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Akaaboune M, Hantaï D, Smirnova I, Lachkar S, Kapsimali M, Verdière-Sahuqué M, Festoff BW. Developmental regulation of the serpin, protease nexin I, localization during activity-dependent polyneuronal synapse elimination in mouse skeletal muscle. J Comp Neurol 1998; 397:572-9. [PMID: 9699917 DOI: 10.1002/(sici)1096-9861(19980810)397:4<572::aid-cne9>3.0.co;2-z] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
During vertebrate neuromuscular development, all muscle fibers are transiently innervated by more than one neuron. Among the numerous factors shown to potentially influence the passage from poly- to mononeuronal innervation, serine proteases and their inhibitors appear to play important roles. In this regard, protease nexin I (PNI), a potent inhibitor of the serine protease, thrombin, is highly localized to the neuromuscular junction (NMJ). In turn, thrombin is responsible for activity-dependent synapse elimination both in an in vitro model, and in vivo. In the present study, we used a monospecific anti-PNI polyclonal antibody to study the developmental kinetics of PNI expression in mouse leg skeletal muscle. By using immunoblotting, we detected PNI at embryonic day 16 (E16), as a 48-kDa band. This 48-kDa PNI band became prominent in leg muscle extracts at postnatal day 5 (P5) and remained so in extracts from adult muscle. In contrast, a higher molecular weight immunoreactive PNI band, which was sodium dodecyl sulfate- and beta-mercaptoethanol-resistant, was first detected at E16, increased at birth (P0), and then decreased at P15, i.e., after the wave of polyneuronal synapse elimination had occurred in these muscles. The results of an enzyme-linked immunosorbent assay, measuring active, complexed, and truncated PNI, correlated with Western blot data. We used immunocytochemistry to probe the localization of PNI at the NMJ and found that PNI was present in the cytoplasm of myotubes at E16, but neither then nor at birth did it colocalize with acetylcholine receptors. PNI became localized at NMJs by P5 and increased by P15, after which it remained stably concentrated there in the adult. Finally, we studied the gene expression of PNI mRNA, by using Northern blotting, and showed that PNI mRNA was present in skeletal muscle and remained stable throughout the time-course studies, suggesting that developmental regulation of muscle PNI occurs principally at the translational and/or post-translational levels. These results suggest that the localization of PNI, through a binding site or "receptor" may play an important role in differentiation and maintenance of synapse.
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MESH Headings
- Aging/metabolism
- Aging/physiology
- Amyloid beta-Protein Precursor
- Animals
- Animals, Newborn/growth & development
- Animals, Newborn/metabolism
- Blotting, Northern
- Blotting, Western
- Carrier Proteins/genetics
- Carrier Proteins/metabolism
- Embryo, Mammalian/metabolism
- Mice/embryology
- Mice/growth & development
- Mice/metabolism
- Muscle Development
- Muscle, Skeletal/embryology
- Muscle, Skeletal/growth & development
- Muscle, Skeletal/physiology
- Neurons/physiology
- Protease Nexins
- RNA, Messenger/metabolism
- Receptors, Cell Surface
- Synapses/physiology
- Tissue Distribution
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Affiliation(s)
- M Akaaboune
- Développement, Pathologie, Régénération du Système Neuromusculaire, INSERM U.153, Institut de Myologie, Hôpital de la Salpêtrière, Paris, France.
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35
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Glazner GW, Yadav K, Fitzgerald S, Coven E, Brenneman DE, Nelson PG. Cholinergic stimulation increases thrombin activity and gene expression in cultured mouse muscle. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 1997; 99:148-54. [PMID: 9125468 DOI: 10.1016/s0165-3806(96)00213-1] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Activity-dependent synapse reduction is a major determinant of neuromuscular innervation. Previous research has shown that nanomolar concentrations of hirudin, a specific thrombin antagonist, significantly attenuates this reduction, and protease nexin 1 (PN1), an endogenous thrombin inhibitor closely localized to the neuromuscular synapse, can inhibit synapse reduction at similar concentrations. Protease inhibitors which do not inhibit thrombin, including cystatin and aprotinin, had no effect on synapse reduction. We present a series of experiments examining whether prothrombin and/or PN1 gene expression, as well as thrombin activity, are regulated in muscle cultures by acetylcholine (ACh) receptor activation. We also studied the effect of exogenous thrombin on synapse elimination in co-cultures of muscle and cholinergic neurons. Cultured muscle cells were electrically blocked with tetrodotoxin (TTX), or co-treated with ACh in order to isolate ACh receptor activation. Electrical blockade resulted in a decrease in thrombin release to about two-thirds of control values. The application of ACh to electrically blocked muscle cultures resulted in a 2.5-fold increase in thrombin activity released into the medium and a 2-fold increase in prothrombin gene expression. In contrast, ACh treatment in the presence of TTX had no effect on PN1 gene expression compared to treatment with TTX alone. In addition, exogenous thrombin significantly increased synapse elimination in unstimulated muscle/cholinergic neuron co-cultures. These results suggest that thrombin or a thrombin-like molecule released from muscle is required for activity-dependent synapse elimination and is regulated by neuromuscular activity.
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Affiliation(s)
- G W Glazner
- Laboratory of Developmental Neurobiology, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-4480, USA
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36
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Chang Q, Balice-Gordon RJ. Nip and tuck at the neuromuscular junction: a role for proteases in developmental synapse elimination. Bioessays 1997; 19:271-5. [PMID: 9136623 DOI: 10.1002/bies.950190402] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
During late embryonic and early postnatal development, synaptic connections are extensively modified so that some functional connections are weakened and eliminated from a neural circuit while others are strengthened and maintained. The mechanisms that underlie synapse elimination are beginning to be understood from studies of the neuromuscular junction. A recent paper provides some intriguing insights into the role proteases may play in the developmental disassembly of neuromuscular synapses.
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Affiliation(s)
- Q Chang
- Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia 19104-6074, USA
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37
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Lohof AM, Bailly Y, Delhaye-Bouchaud N, Mariani J. A Model of Developmental Synapse Elimination in the Central Nervous System: Possible Mechanisms and Functional Consequences. THE SYNAPSE: IN DEVELOPMENT, HEALTH, AND DISEASE 1997. [DOI: 10.1016/s1569-2590(08)60181-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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38
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Abstract
Nerve impulses regulate expression of genes that control receptors, channels, enzymes, and structural proteins. This activity-dependent feedback allows adaptation to changing requirements and environmental conditions. The signal transduction mechanisms carrying information from the cell membrane to the nucleus are becoming well characterized, but a more dynamic view of intracellular signaling is emerging to explain cellular responses to specific patterns of neural impulses. This review analyzes this interface between electrophysiology and molecular cell biology to examine the signals, substrates, and processes that enable the nervous system to regulate its structure and function as a consequence of its own operation.
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Affiliation(s)
- R. Douglas Fields
- Laboratory of Developmental Neurobiology National Institutes of Health, NICHD Bethesda, Maryland
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39
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Abstract
With the aim to study the cellular mechanism underlying the process of muscle spindle regeneration, dorsal root ganglia (DRG) neurons derived from 16-day rat embryos were cocultured with developing myotubes in a compartmentalized culture device. To accomplish the selective survival and neurite formation of the proprioceptive subpopulation, the neurotrophic factor, neurotrophin-3, was added to the culture medium. It appeared that the proprioceptive DRG neurons could develop specialized, Ia afferent terminal-like contacts with myotubes. However, these interactions were scarce and did not result in the induction of differentiation of the contacted myotubes into intrafusal fibers as normally occurs during in vivo development. The present coculture setup apparently lacks appropriate regulatory factors essential for the proper matching of sensory axons and intrafusal fiber precursors and the induction of a functional sensory myoneural connection.
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Affiliation(s)
- S Copray
- Department of Medical Physiology, University of Groningen, The Netherlands
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40
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Jeanprêtre N, Clarke PG, Gabriel JP. Competitive exclusion between axons dependent on a single trophic substance: a mathematical analysis. Math Biosci 1996; 135:23-54. [PMID: 8688564 DOI: 10.1016/0025-5564(95)00134-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
A mathematical model is presented of competition between axons for a trophic substance, such as is believed to occur particularly during development. The model is biologically realistic. The growth-stimulating activity of the trophic molecules is assumed to result from their binding to high-affinity receptors on neurons and their axons, but the model also incorporates uptake by nonneuronal cells possessing only lower affinity receptors. Plausible and fairly general assumptions are made concerning the kinetics of binding and internalization and the effects on axonal growth. The model takes into account the possibility that trophic factor production may be regulated by the afferent axons or autoregulated. The variables specified are the "axonal vigor" of each axon, representing the ability of each axon to take up trophic molecules, and the concentration of trophic molecules in the extracellular space of the axonal target region. Of the several parameters introduced, the most important turns out to be the "zero vigor-growth parameter," which is defined as the concentration of trophic molecules that gives zero growth of the vigor of a given axon. By means of a Lyapunov function, it is shown that the system will approach asymptotically to a stable equilibrium characterized by the survival of only the axon whose zero-growth parameter is lowest. Or, if several axons share the same lowest zero-growth parameter, these will all survive. The model may be particularly relevant to the elimination of polyneuronal innervation from developing muscle fibers and from autonomic ganglion cells.
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Affiliation(s)
- N Jeanprêtre
- Institut d'anatomie, Université de Lausanne, Switzerland
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41
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Lohof AM, Delhaye-Bouchaud N, Mariani J. Synapse elimination in the central nervous system: functional significance and cellular mechanisms. Rev Neurosci 1996; 7:85-101. [PMID: 8819204 DOI: 10.1515/revneuro.1996.7.2.85] [Citation(s) in RCA: 104] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Recent research into the developmental elimination of supernumerary synapses has increased understanding of this process. In this review we discuss synapse elimination both at the neuromuscular junction and in the central nervous system, considering some possible underlying mechanisms suggested by recent studies. In addition a well-described example of central nervous system synapse elimination, the climbing fiber-Purkinje cell synapse of the cerebellum, is used to explore the functional significance of synaptic regression during brain development.
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Affiliation(s)
- A M Lohof
- Laboratoire de Neurobiologie du Développement, Institut des Neurosciences (C.N.R.S. U.R.A. 1488), Université P. et M. Curie, Paris, France
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42
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Nguyen QT, Lichtman JW. Mechanism of synapse disassembly at the developing neuromuscular junction. Curr Opin Neurobiol 1996; 6:104-12. [PMID: 8794054 DOI: 10.1016/s0959-4388(96)80015-8] [Citation(s) in RCA: 94] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Throughout the developing nervous system of higher vertebrates, synaptic connections are concurrently being established and eliminated. The consequence of this synaptic remodeling is that axons strengthen their connections with some targets while completely disconnecting from other postsynaptic cells. The transition from multiple to single axonal innervation of skeletal muscle fibers is the most accessible example of this developmental reorganization. In muscle, the elimination of axonal input appears to be driven by a protracted competition between different axons co-innervating the same junction, with the muscle fiber as intermediary. Asynchronous synaptic activity may be the factor that differentiates the competing inputs. In some circumstances, synapses can also be lost in ways that are independent of activity. Similarities between activity-dependent and activity-independent synapse elimination provide insights into mechanisms underlying developmental synaptic reorganization.
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Affiliation(s)
- Q T Nguyen
- Department of Anatomy and Neurobiology, Washington University School of Medicine, St Louis, Missouri 63110, USA.
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43
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Liu Y, Fields RD, Festoff BW, Nelson PG. Proteolytic action of thrombin is required for electrical activity-dependent synapse reduction. Proc Natl Acad Sci U S A 1994; 91:10300-4. [PMID: 7524091 PMCID: PMC45007 DOI: 10.1073/pnas.91.22.10300] [Citation(s) in RCA: 115] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Molecular mechanisms of activity-dependent synapse reduction were studied in an in vitro mammalian neuromuscular preparation. Synapse reduction in this model is activity-dependent and is substantially reduced by the broad-spectrum protease inhibitor, leupeptin, suggesting the role of activity-dependent proteolytic action in the process. Our present experiments show that a potent and specific thrombin inhibitor, hirudin, at nanomolar concentration completely blocked the activity-dependent synapse reduction. Furthermore, a naturally occurring serine protease inhibitor, protease nexin I (PNI), which closely colocalizes with acetylcholine receptors at the neuromuscular junction, inhibited the synapse reduction at the same low concentration. In contrast, neither cystatin, a cysteine protease inhibitor, nor aprotinin, a serine protease inhibitor that does not inhibit thrombin, blocked the synapse reduction. Similarly, neither of the inhibitors of the calcium-activated proteases calpain I and II prevented the reduction of synapses. These results strongly suggest that serine proteolytic action by thrombin or thrombin-like molecules is required for synapse reduction in our in vitro model of the mammalian neuromuscular junction.
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Affiliation(s)
- Y Liu
- Laboratory of Developmental Neurobiology, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892
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44
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Liu Y, Fields RD, Fitzgerald S, Festoff BW, Nelson PG. Proteolytic activity, synapse elimination, and the Hebb synapse. JOURNAL OF NEUROBIOLOGY 1994; 25:325-35. [PMID: 8195793 DOI: 10.1002/neu.480250312] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The Hebb synapse has been postulated to serve as a mechanism subserving both regulation of synaptic strength in the adult nervous system (long-term potentiation and depression) and developmental activity-dependent plasticity. According to this model, pre- and postsynaptic temporal concordance of activity results in strengthening of connections, while discordant activity results in synapse weakening. Evidence is presented that proteases and protease inhibitors may be involved in modification of synaptic strength. This leads to a modification of the Hebb assumptions, namely that postsynaptic activity results in protease elaboration with a consequent general reduction of synaptic connections to the active postsynaptic element. Further, presynaptic activity, if strong enough, induces local release of a protease inhibitor, such as protease nexin I, which neutralizes proteolytic activity and produces a relative preservation of the active input. This formulation produces many of the effects of the classical Hebbian construction, but the protease/inhibitor model suggests additional specific mechanistic features for activity-dependent plasticity.
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Affiliation(s)
- Y Liu
- Laboratory of Developmental Neurobiology, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892
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45
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Dan Y, Poo MM. Retrograde interactions during formation and elimination of neuromuscular synapses. Curr Opin Neurobiol 1994; 4:95-100. [PMID: 8173331 DOI: 10.1016/0959-4388(94)90037-x] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Maturation of neuromuscular synapses depends on dynamic interactions between presynaptic motor neurons and postsynaptic muscle cells. Recent studies have addressed the cellular mechanisms underlying these interactions in cell cultures and in developing animals. Retrograde signals from the postsynaptic muscle cells appear to play critical roles in all stages of synapse development, from the initial synaptogenesis to the stabilization or elimination of the synapse.
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Affiliation(s)
- Y Dan
- Fairchild Center, Department of Biological Sciences, Columbia University, New York, New York 10027
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46
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Ho GJ, Smirnova IV, Akaaboune M, Hantaï D, Festoff BW. Serine proteases and their serpin inhibitors in Alzheimer's disease. Biomed Pharmacother 1994; 48:296-304. [PMID: 7858160 DOI: 10.1016/0753-3322(94)90175-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Our article documents recent studies in the proteolytic processing of the Alzheimer's beta-amyloid protein precursor (beta-APP), as well as the role of thrombin and its potent inhibitor, protease nexin I in Alzheimer's disease (AD). Since synapse loss correlates best with cognitive decline in AD, we also present in detail, our model of synapse formation and elimination, reviewing recent findings related to the subject as well as our own original data. Recent exciting findings concerning the involvement of thrombin-like activity in synapse elimination, which we feel to be important in neural plasticity are also discussed.
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Affiliation(s)
- G J Ho
- Neurobiology Research laboratory (151), Veterans Affairs Medical Center, Kansas City, MO
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