151
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Nucleocytoplasmic Shuttling of Histone Deacetylase 9 Controls Activity-Dependent Thalamocortical Axon Branching. Sci Rep 2017; 7:6024. [PMID: 28729685 PMCID: PMC5519695 DOI: 10.1038/s41598-017-06243-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Accepted: 06/13/2017] [Indexed: 01/12/2023] Open
Abstract
During development, thalamocortical (TC) axons form branches in an activity-dependent fashion. Here we investigated how neuronal activity is converted to molecular signals, focusing on an epigenetic mechanism involving histone deacetylases (HDACs). Immunohistochemistry demonstrated that HDAC9 was translocated from the nucleus to the cytoplasm of thalamic cells during the first postnatal week in rats. In organotypic co-cultures of the thalamus and cortex, fluorescent protein-tagged HDAC9 also exhibited nuclueocytoplasmic translocation in thalamic cells during culturing, which was reversed by tetrodotoxin treatment. Transfection with a mutant HDAC9 that interferes with the translocation markedly decreased TC axon branching in the culture. Similarly, TC axon branching was significantly decreased by the mutant HDAC9 gene transfer in vivo. However, axonal branching was restored by disrupting the interaction between HDAC9 and myocyte-specific enhancer factor 2 (MEF2). Taken together, the present results demonstrate that the nucleocytoplasmic translocation of HDAC9 plays a critical role in activity-dependent TC axon branching by affecting transcriptional regulation and downstream signaling pathways.
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152
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Decreased Axon Caliber Underlies Loss of Fiber Tract Integrity, Disproportional Reductions in White Matter Volume, and Microcephaly in Angelman Syndrome Model Mice. J Neurosci 2017; 37:7347-7361. [PMID: 28663201 DOI: 10.1523/jneurosci.0037-17.2017] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Revised: 05/24/2017] [Accepted: 06/21/2017] [Indexed: 11/21/2022] Open
Abstract
Angelman syndrome (AS) is a debilitating neurodevelopmental disorder caused by loss of function of the maternally inherited UBE3A allele. It is currently unclear how the consequences of this genetic insult unfold to impair neurodevelopment. We reasoned that by elucidating the basis of microcephaly in AS, a highly penetrant syndromic feature with early postnatal onset, we would gain new insights into the mechanisms by which maternal UBE3A loss derails neurotypical brain growth and function. Detailed anatomical analysis of both male and female maternal Ube3a-null mice reveals that microcephaly in the AS mouse model is primarily driven by deficits in the growth of white matter tracts, which by adulthood are characterized by densely packed axons of disproportionately small caliber. Our results implicate impaired axon growth in the pathogenesis of AS and identify noninvasive structural neuroimaging as a potentially valuable tool for gauging therapeutic efficacy in the disorder.SIGNIFICANCE STATEMENT People who maternally inherit a deletion or nonfunctional copy of the UBE3A gene develop Angelman syndrome (AS), a severe neurodevelopmental disorder. To better understand how loss of maternal UBE3A function derails brain development, we analyzed brain structure in a maternal Ube3a knock-out mouse model of AS. We report that the volume of white matter (WM) is disproportionately reduced in AS mice, indicating that deficits in WM development are a major factor underlying impaired brain growth and microcephaly in the disorder. Notably, we find that axons within the WM pathways of AS model mice are abnormally small in caliber. This defect is associated with slowed nerve conduction, which could contribute to behavioral deficits in AS, including motor dysfunction.
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153
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Li H, Wu W. Microtubule stabilization promoted axonal regeneration and functional recovery after spinal root avulsion. Eur J Neurosci 2017; 46:1650-1662. [PMID: 28444817 DOI: 10.1111/ejn.13585] [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] [Received: 12/14/2016] [Revised: 04/09/2017] [Accepted: 04/09/2017] [Indexed: 12/20/2022]
Abstract
A spinal root avulsion injury disconnects spinal roots with the spinal cord. The rampant motoneuron death, inhibitory CNS/PNS transitional zone (TZ) for axonal regrowth and limited regeneration speed together lead to motor dysfunction. Microtubules rearrange to assemble a new growth cone and disorganized microtubules underline regeneration failure. It has been shown that microtubule-stabilizing drug, Epothilone B, enhanced axonal regeneration and attenuated fibrotic scaring after spinal cord injury. Here, we are reporting that after spinal root avulsion+ re-implantation in adult rats, EpoB treatment improved motor functional recovery and potentiated electrical responses of motor units. It facilitated axons to cross the TZ and promoted more and bigger axons in the peripheral nerve. Neuromuscular junctions were reformed with better preserved postsynaptic structure, and muscle atrophy was prevented by EpoB administration. Our study showed that EpoB was a promising therapy for promoting axonal regeneration after peripheral nerve injury.
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Affiliation(s)
- Heng Li
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, the University of Hong Kong, L1-39, 21 Sassoon Road, Pokfulam, Hong Kong SAR, China
| | - Wutian Wu
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, the University of Hong Kong, L1-39, 21 Sassoon Road, Pokfulam, Hong Kong SAR, China.,State Key Laboratory of Brain and Cognitive Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong SAR, China.,Joint Laboratory of Jinan University and the University of Hong Kong, GHM Institute of CNS Regeneration, Jinan University, Guangzhou, China
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154
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Nitta Y, Sugie A. Identification of glaikit in a genome-wide expression profiling for axonal bifurcation of the mushroom body in Drosophila. Biochem Biophys Res Commun 2017; 487:898-902. [PMID: 28465232 DOI: 10.1016/j.bbrc.2017.04.150] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Revised: 04/27/2017] [Accepted: 04/29/2017] [Indexed: 12/01/2022]
Abstract
Axonal branching is a fundamental requirement for sending electrical signals to multiple targets. However, despite the importance of axonal branching in neural development and function, the molecular mechanisms that control branch formation are poorly understood. Previous studies have hardly addressed the intracellular signaling cascade of axonal bifurcation characterized by growth cone splitting. Recently we reported that DISCO interacting protein 2 (DIP2) regulates bifurcation of mushroom body axons in Drosophila melanogaster. DIP2 mutant displays ectopic bifurcations in α/β neurons. Taking advantage of this phenomenon, we tried to identify genes involved in branching formation by comparing the transcriptome of wild type with that of DIP2 RNAi flies. After the microarray analysis, Glaikit (Gkt), a member of the phospholipase D superfamily, was identified as a downstream target of DIP2 by RNAi against gkt and qRT-PCR experiment. Single cell MARCM analysis of gkt mutant phenocopied the ectopic axonal branches observed in DIP2 mutant. Furthermore, a genetic analysis between gkt and DIP2 revealed that gkt potentially acts in parallel with DIP2. In conclusion, we identified a novel gene underlying the axonal bifurcation process.
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Affiliation(s)
- Yohei Nitta
- Department of Neuroscience of Disease, Center for Transdisciplinary Research, Niigata University, Japan; Brain Research Institute, Niigata University, Japan.
| | - Atsushi Sugie
- Department of Neuroscience of Disease, Center for Transdisciplinary Research, Niigata University, Japan; Brain Research Institute, Niigata University, Japan.
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155
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Armijo-Weingart L, Gallo G. It takes a village to raise a branch: Cellular mechanisms of the initiation of axon collateral branches. Mol Cell Neurosci 2017; 84:36-47. [PMID: 28359843 DOI: 10.1016/j.mcn.2017.03.007] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Revised: 01/03/2017] [Accepted: 03/01/2017] [Indexed: 12/14/2022] Open
Abstract
The formation of axon collateral branches from the pre-existing shafts of axons is an important aspect of neurodevelopment and the response of the nervous system to injury. This article provides an overview of the role of the cytoskeleton and signaling mechanisms in the formation of axon collateral branches. Both the actin filament and microtubule components of the cytoskeleton are required for the formation of axon branches. Recent work has begun to shed light on how these two elements of the cytoskeleton are integrated by proteins that functionally or physically link the cytoskeleton. While a number of signaling pathways have been determined as having a role in the formation of axon branches, the complexity of the downstream mechanisms and links to specific signaling pathways remain to be fully determined. The regulation of intra-axonal protein synthesis and organelle function are also emerging as components of signal-induced axon branching. Although much has been learned in the last couple of decades about the mechanistic basis of axon branching we can look forward to continue elucidating this complex biological phenomenon with the aim of understanding how multiple signaling pathways, cytoskeletal regulators and organelles are coordinated locally along the axon to give rise to a branch.
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Affiliation(s)
- Lorena Armijo-Weingart
- Shriners Pediatric Research Center, Temple University, Department of Anatomy and Cell Biology, 3500 North Broad St, Philadelphia, PA 19140, United States
| | - Gianluca Gallo
- Shriners Pediatric Research Center, Temple University, Department of Anatomy and Cell Biology, 3500 North Broad St, Philadelphia, PA 19140, United States.
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156
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Simitzi C, Ranella A, Stratakis E. Controlling the morphology and outgrowth of nerve and neuroglial cells: The effect of surface topography. Acta Biomater 2017; 51:21-52. [PMID: 28069509 DOI: 10.1016/j.actbio.2017.01.023] [Citation(s) in RCA: 133] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Revised: 12/23/2016] [Accepted: 01/05/2017] [Indexed: 02/07/2023]
Abstract
Unlike other tissue types, like epithelial tissue, which consist of cells with a much more homogeneous structure and function, the nervous tissue spans in a complex multilayer environment whose topographical features display a large spectrum of morphologies and size scales. Traditional cell cultures, which are based on two-dimensional cell-adhesive culture dishes or coverslips, are lacking topographical cues and mainly simulate the biochemical microenvironment of the cells. With the emergence of micro- and nano-fabrication techniques new types of cell culture platforms are developed, where the effect of various topographical cues on cellular morphology, proliferation and differentiation can be studied. Different approaches (regarding the material, fabrication technique, topographical characteristics, etc.) have been implemented. The present review paper aims at reviewing the existing body of literature on the use of artificial micro- and nano-topographical features to control neuronal and neuroglial cells' morphology, outgrowth and neural network topology. The cell responses-from phenomenology to investigation of the underlying mechanisms- on the different topographies, including both deterministic and random ones, are summarized. STATEMENT OF SIGNIFICANCE There is increasing evidence that physical cues, such as topography, can have a significant impact on the neural cell functions. With the aid of micro-and nanofabrication techniques, new types of cell culture platforms are developed and the effect of surface topography on the cells has been studied. The present review article aims at reviewing the existing body of literature reporting on the use of various topographies to study and control the morphology and functions of cells from nervous tissue, i.e. the neuronal and the neuroglial cells. The cell responses-from phenomenology to investigation of the underlying mechanisms- on the different topographies, including both deterministic and random ones, are summarized.
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Affiliation(s)
- C Simitzi
- Institute of Electronic Structure and Laser (IESL), Foundation for Research and Technology-Hellas (FORTH), Heraklion 71003, Greece
| | - A Ranella
- Institute of Electronic Structure and Laser (IESL), Foundation for Research and Technology-Hellas (FORTH), Heraklion 71003, Greece
| | - E Stratakis
- Institute of Electronic Structure and Laser (IESL), Foundation for Research and Technology-Hellas (FORTH), Heraklion 71003, Greece.
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157
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Ikeno T, Konishi Y. Differential retraction of axonal arbor terminals mediated by microtubule and kinesin motor. Commun Integr Biol 2017. [PMCID: PMC5398204 DOI: 10.1080/19420889.2017.1288771] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/29/2022] Open
Affiliation(s)
- Tatsuki Ikeno
- Department of Human and Artificial Intelligence Systems, Graduate School of Engineering, University of Fukui, Fukui, Japan
| | - Yoshiyuki Konishi
- Department of Human and Artificial Intelligence Systems, Graduate School of Engineering, University of Fukui, Fukui, Japan
- Department of Materials Science and Biotechnology, Faculty of Engineering, University of Fukui, Fukui, Japan
- Life Science Innovation Center, University of Fukui, Fukui, Japan
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158
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Moradi M, Sivadasan R, Saal L, Lüningschrör P, Dombert B, Rathod RJ, Dieterich DC, Blum R, Sendtner M. Differential roles of α-, β-, and γ-actin in axon growth and collateral branch formation in motoneurons. J Cell Biol 2017; 216:793-814. [PMID: 28246119 PMCID: PMC5346967 DOI: 10.1083/jcb.201604117] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Revised: 11/11/2016] [Accepted: 01/17/2017] [Indexed: 12/17/2022] Open
Abstract
α-, β-, and γ-actin differentially regulate cytoskeletal dynamics and stability in axons of motoneurons. Locally translated α-actin contributes to stable actin filaments in axonal branches, whereas β- and γ-actin give rise to highly dynamic filaments that modulate growth cone dynamics. Axonal branching and terminal arborization are fundamental events during the establishment of synaptic connectivity. They are triggered by assembly of actin filaments along axon shafts giving rise to filopodia. The specific contribution of the three actin isoforms, Actα, Actβ, and Actγ, to filopodia stability and dynamics during this process is not well understood. Here, we report that Actα, Actβ, and Actγ isoforms are expressed in primary mouse motoneurons and their transcripts are translocated into axons. shRNA-mediated depletion of Actα reduces axonal filopodia dynamics and disturbs collateral branch formation. Knockdown of Actβ reduces dynamic movements of growth cone filopodia and impairs presynaptic differentiation. Ablation of Actβ or Actγ leads to compensatory up-regulation of the two other isoforms, which allows maintenance of total actin levels and preserves F-actin polymerization. Collectively, our data provide evidence for specific roles of different actin isoforms in spatial regulation of actin dynamics and stability in axons of developing motoneurons.
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Affiliation(s)
- Mehri Moradi
- Institute of Clinical Neurobiology, University Hospital Wuerzburg, University of Wuerzburg, 97078 Wuerzburg, Germany
| | - Rajeeve Sivadasan
- Institute of Clinical Neurobiology, University Hospital Wuerzburg, University of Wuerzburg, 97078 Wuerzburg, Germany
| | - Lena Saal
- Institute of Clinical Neurobiology, University Hospital Wuerzburg, University of Wuerzburg, 97078 Wuerzburg, Germany
| | - Patrick Lüningschrör
- Institute of Clinical Neurobiology, University Hospital Wuerzburg, University of Wuerzburg, 97078 Wuerzburg, Germany
| | - Benjamin Dombert
- Institute of Clinical Neurobiology, University Hospital Wuerzburg, University of Wuerzburg, 97078 Wuerzburg, Germany
| | - Reena Jagdish Rathod
- Institute of Clinical Neurobiology, University Hospital Wuerzburg, University of Wuerzburg, 97078 Wuerzburg, Germany
| | - Daniela C Dieterich
- Institute for Pharmacology and Toxicology, Medical Faculty, University of Magdeburg, 39120 Magdeburg, Germany.,Center for Behavioral Brain Sciences, Medical Faculty, University of Magdeburg, 39120 Magdeburg, Germany
| | - Robert Blum
- Institute of Clinical Neurobiology, University Hospital Wuerzburg, University of Wuerzburg, 97078 Wuerzburg, Germany
| | - Michael Sendtner
- Institute of Clinical Neurobiology, University Hospital Wuerzburg, University of Wuerzburg, 97078 Wuerzburg, Germany
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159
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Ran-dependent TPX2 activation promotes acentrosomal microtubule nucleation in neurons. Sci Rep 2017; 7:42297. [PMID: 28205572 PMCID: PMC5304320 DOI: 10.1038/srep42297] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Accepted: 01/05/2017] [Indexed: 01/07/2023] Open
Abstract
The microtubule (MT) cytoskeleton is essential for the formation of morphologically appropriate neurons. The existence of the acentrosomal MT organizing center in neurons has been proposed but its identity remained elusive. Here we provide evidence showing that TPX2 is an important component of this acentrosomal MT organizing center. First, neurite elongation is compromised in TPX2-depleted neurons. In addition, TPX2 localizes to the centrosome and along the neurite shaft bound to MTs. Depleting TPX2 decreases MT formation frequency specifically at the tip and the base of the neurite, and these correlate precisely with the regions where active GTP-bound Ran proteins are enriched. Furthermore, overexpressing the downstream effector of Ran, importin, compromises MT formation and neuronal morphogenesis. Finally, applying a Ran-importin signaling interfering compound phenocopies the effect of TPX2 depletion on MT dynamics. Together, these data suggest a model in which Ran-dependent TPX2 activation promotes acentrosomal MT nucleation in neurons.
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160
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Huang GH, Sun ZL, Li HJ, Feng DF. Rho GTPase-activating proteins: Regulators of Rho GTPase activity in neuronal development and CNS diseases. Mol Cell Neurosci 2017; 80:18-31. [PMID: 28163190 DOI: 10.1016/j.mcn.2017.01.007] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Revised: 01/06/2017] [Accepted: 01/29/2017] [Indexed: 12/22/2022] Open
Abstract
The Rho family of small GTPases was considered as molecular switches in regulating multiple cellular events, including cytoskeleton reorganization. The Rho GTPase-activating proteins (RhoGAPs) are one of the major families of Rho GTPase regulators. RhoGAPs were initially considered negative mediators of Rho signaling pathways via their GAP domain. Recent studies have demonstrated that RhoGAPs also regulate numerous aspects of neuronal development and are related to various neurodegenerative diseases in GAP-dependent and GAP-independent manners. Moreover, RhoGAPs are regulated through various mechanisms, such as phosphorylation. To date, approximately 70 RhoGAPs have been identified; however, only a small portion has been thoroughly investigated. Thus, the characterization of important RhoGAPs in the central nervous system is crucial to understand their spatiotemporal role during different stages of neuronal development. In this review, we summarize the current knowledge of RhoGAPs in the brain with an emphasis on their molecular function, regulation mechanism and disease implications in the central nervous system.
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Affiliation(s)
- Guo-Hui Huang
- Department of Neurosurgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 201900, China
| | - Zhao-Liang Sun
- Department of Neurosurgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 201900, China
| | - Hong-Jiang Li
- Department of Neurosurgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 201900, China
| | - Dong-Fu Feng
- Department of Neurosurgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 201900, China; Institute of Traumatic Medicine, Shanghai Jiao Tong University School of Medicine, Shanghai 201900, China.
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161
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Holland SM, Thomas GM. Roles of palmitoylation in axon growth, degeneration and regeneration. J Neurosci Res 2017; 95:1528-1539. [PMID: 28150429 DOI: 10.1002/jnr.24003] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Revised: 11/09/2016] [Accepted: 11/28/2016] [Indexed: 12/11/2022]
Abstract
The protein-lipid modification palmitoylation plays important roles in neurons, but most attention has focused on roles of this modification in the regulation of mature pre- and post-synapses. However, exciting recent findings suggest that palmitoylation is also critical for both the growth and integrity of neuronal axons and plays previously unappreciated roles in conveying axonal anterograde and retrograde signals. Here we review these emerging roles for palmitoylation in the regulation of axons in health and disease. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Sabrina M Holland
- Shriners Hospitals Pediatric Research Center (Center for Neurorehabilitation and Neural Repair)
| | - Gareth M Thomas
- Shriners Hospitals Pediatric Research Center (Center for Neurorehabilitation and Neural Repair).,Department of Anatomy and Cell Biology, Lewis Katz School of Medicine at Temple University, 3500 N. Broad Street, Philadelphia, PA, 19140
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162
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Lombardi L, Persiconi I, Gallo A, Hoogenraad CC, De Stefano ME. NGF-dependent axon growth and regeneration are altered in sympathetic neurons of dystrophic mdx mice. Mol Cell Neurosci 2017; 80:1-17. [PMID: 28161362 DOI: 10.1016/j.mcn.2017.01.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Revised: 12/09/2016] [Accepted: 01/29/2017] [Indexed: 12/18/2022] Open
Abstract
Duchenne muscular dystrophy (DMD) is a lethal disease, determined by lack of dystrophin (Dp427), a muscular cytoskeletal protein also expressed by selected neuronal populations. Consequently, besides muscular wasting, both human patients and DMD animal models suffer several neural disorders. In previous studies on the superior cervical ganglion (SCG) of wild type and dystrophic mdx mice (Lombardi et al. 2008), we hypothesized that Dp427 could play some role in NGF-dependent axonal growth, both during development and adulthood. To address this issue, we first analyzed axon regeneration potentials of SCG neurons of both genotypes after axotomy in vivo. While noradrenergic innervation of mdx mouse submandibular gland, main source of nerve growth factor (NGF), recovered similarly to wild type, iris innervation (muscular target) never did. We, therefore, evaluated whether dystrophic SCG neurons were poorly responsive to NGF, especially at low concentration. Following in vitro axotomy in the presence of either 10 or 50ng/ml NGF, the number of regenerated axons in mdx mouse neuron cultures was indeed reduced, compared to wild type, at the lower concentration. Neurite growth parameters (i.e. number, length), growth cone dynamics and NGF/TrkA receptor signaling in differentiating neurons (not injured) were also significantly reduced when cultured with 10ng/ml NGF, but also with higher NGF concentrations. In conclusion, we propose a role for Dp427 in NGF-dependent cytoskeletal dynamics associated to growth cone advancement, possibly through indirect stabilization of TrkA receptors. Considering NGF activity in nervous system development/remodeling, this aspect could concur in some of the described DMD-associated neural dysfunctions.
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Affiliation(s)
- Loredana Lombardi
- Dipartimento di Biologia e Biotecnologie "Charles Darwin", Sapienza Università di Roma, Laboratory affiliated to Istituto Pasteur Italia - Fondazione Cenci Bolognetti, 00185 Roma, Italy
| | - Irene Persiconi
- Dipartimento di Biologia e Biotecnologie "Charles Darwin", Sapienza Università di Roma, Laboratory affiliated to Istituto Pasteur Italia - Fondazione Cenci Bolognetti, 00185 Roma, Italy
| | - Alessandra Gallo
- Dipartimento di Biologia e Biotecnologie "Charles Darwin", Sapienza Università di Roma, Laboratory affiliated to Istituto Pasteur Italia - Fondazione Cenci Bolognetti, 00185 Roma, Italy
| | - Casper C Hoogenraad
- Cell Biology, Faculty of Science, Utrecht University, 3584CH Utrecht, The Netherlands
| | - Maria Egle De Stefano
- Dipartimento di Biologia e Biotecnologie "Charles Darwin", Sapienza Università di Roma, Laboratory affiliated to Istituto Pasteur Italia - Fondazione Cenci Bolognetti, 00185 Roma, Italy; Center for Research in Neurobiology "Daniel Bovet", Sapienza Università di Roma, 00185 Roma, Italy.
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163
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MAP7 Regulates Axon Collateral Branch Development in Dorsal Root Ganglion Neurons. J Neurosci 2017; 37:1648-1661. [PMID: 28069923 DOI: 10.1523/jneurosci.3260-16.2017] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Revised: 12/27/2016] [Accepted: 01/04/2017] [Indexed: 01/26/2023] Open
Abstract
Collateral branches from axons are key components of functional neural circuits that allow neurons to connect with multiple synaptic targets. Like axon growth and guidance, formation of collateral branches depends on the regulation of microtubules, but how such regulation is coordinated to ensure proper circuit development is not known. Based on microarray analysis, we have identified a role for microtubule-associated protein 7 (MAP7) during collateral branch development of dorsal root ganglion (DRG) sensory neurons. We show that MAP7 is expressed at the onset of collateral branch formation. Perturbation of its expression by overexpression or shRNA knockdown alters axon branching in cultured DRG neurons. Localization and time-lapse imaging analysis reveals that MAP7 is enriched at branch points and colocalizes with stable microtubules, but enters the new branch with a delay, suggesting a role in branch maturation. We have also investigated a spontaneous mutant mouse that expresses a truncated MAP7 and found a gain-of-function phenotype both in vitro and in vivo Further domain analysis suggests that the amino half of MAP7 is responsible for branch formation, suggesting a mechanism that is independent of its known interaction with kinesin. Moreover, this mouse exhibits increased pain sensitivity, a phenotype that is consistent with increased collateral branch formation. Therefore, our study not only uncovers the first neuronal function of MAP7, but also demonstrates the importance of proper microtubule regulation in neural circuit development. Furthermore, our data provide new insights into microtubule regulation during axonal morphogenesis and may shed light on MAP7 function in neurological disorders.SIGNIFICANCE STATEMENT Neurons communicate with multiple targets by forming axonal branches. In search of intrinsic factors that control collateral branch development, we identified a role for microtubule-associated protein 7 (MAP7) in dorsal root ganglion sensory neurons. We show that MAP7 expression is developmentally regulated and perturbation of this expression alters branch formation. Cell biological analysis indicates that MAP7 promotes branch maturation. Analysis of a spontaneous mouse mutant suggests a molecular mechanism for branch regulation and the potential influence of collateral branches on pain sensitivity. Our studies thus establish the first neuronal function of MAP7 and demonstrate its role in branch morphogenesis and neural circuit function. These findings may help in our understanding of the contribution of MAP7 to neurological disorders and nerve regeneration.
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164
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Sergi PN, Cavalcanti-Adam EA. Biomaterials and computation: a strategic alliance to investigate emergent responses of neural cells. Biomater Sci 2017; 5:648-657. [DOI: 10.1039/c6bm00871b] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Synergistic use of biomaterials and computation allows to identify and unravel neural cell responses.
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Affiliation(s)
- Pier Nicola Sergi
- The Biorobotics Institute
- Sant’ Anna Scuola Universitaria Superiore
- Pontedera
- 56025 Italy
| | - Elisabetta Ada Cavalcanti-Adam
- Max Planck Institute for Medical Research
- Dept Cellular Biophysics and Heidelberg University
- Dept Biophysical Chemistry
- Heidelberg
- Germany
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165
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Sugio S, Nagasawa M, Kojima I, Ishizaki Y, Shibasaki K. Transient receptor potential vanilloid 2 activation by focal mechanical stimulation requires interaction with the actin cytoskeleton and enhances growth cone motility. FASEB J 2016; 31:1368-1381. [PMID: 28007781 DOI: 10.1096/fj.201600686rr] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2016] [Accepted: 12/12/2016] [Indexed: 11/11/2022]
Abstract
We have previously reported that transient receptor potential vanilloid 2 (TRPV2) can be activated by mechanical stimulation, which enhances axonal outgrowth in developing neurons; however, the molecular mechanisms that govern the contribution of TRPV2 activation to axonal outgrowth remain unclear. In the present study, we examined this mechanism by using PC12 cells as a neuronal model. Overexpression of TRPV2 enhanced axonal outgrowth in a mechanical stimulus-dependent manner. Accumulation of TRPV2 at the cell surface was 4-fold greater in the growth cone compared with the soma. In the growth cone, TRPV2 is not static, but dynamically accumulates (within ∼100 ms) to the site of mechanical stimulation. The dynamic and acute clustering of TRPV2 can enhance very weak mechanical stimuli via focal accumulation of TRPV2. Focal application of mechanical stimuli dramatically increased growth cone motility and caused actin reorganization via activation of TRPV2. We also found that TRPV2 physically interacts with actin and that changes in the actin cytoskeleton are required for its activation. Here, we demonstrated for the first time to our knowledge that TRPV2 clustering is induced by mechanical stimulation generated by axonal outgrowth and that TRPV2 activation is triggered by actin rearrangements that result from mechanical stimulation. Moreover, TRPV2 activation enhances growth cone motility and actin accumulation to promote axonal outgrowth. Sugio, S., Nagasawa, M., Kojima, I., Ishizaki, Y., Shibasaki, K. Transient receptor potential vanilloid 2 activation by focal mechanical stimulation requires interaction with the actin cytoskeleton and enhances growth cone motility.
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Affiliation(s)
- Shouta Sugio
- Department of Molecular and Cellular Neurobiology, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Masami Nagasawa
- Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan
| | - Itaru Kojima
- Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan
| | - Yasuki Ishizaki
- Department of Molecular and Cellular Neurobiology, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Koji Shibasaki
- Department of Molecular and Cellular Neurobiology, Gunma University Graduate School of Medicine, Maebashi, Japan;
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166
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Nitta Y, Yamazaki D, Sugie A, Hiroi M, Tabata T. DISCO Interacting Protein 2 regulates axonal bifurcation and guidance of Drosophila mushroom body neurons. Dev Biol 2016; 421:233-244. [PMID: 27908785 DOI: 10.1016/j.ydbio.2016.11.015] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Revised: 11/16/2016] [Accepted: 11/16/2016] [Indexed: 10/20/2022]
Abstract
Axonal branching is one of the key processes within the enormous complexity of the nervous system to enable a single neuron to send information to multiple targets. However, the molecular mechanisms that control branch formation are poorly understood. In particular, previous studies have rarely addressed the mechanisms underlying axonal bifurcation, in which axons form new branches via splitting of the growth cone. We demonstrate that DISCO Interacting Protein 2 (DIP2) is required for precise axonal bifurcation in Drosophila mushroom body (MB) neurons by suppressing ectopic bifurcation and regulating the guidance of sister axons. We also found that DIP2 localize to the plasma membrane. Domain function analysis revealed that the AMP-synthetase domains of DIP2 are essential for its function, which may involve exerting a catalytic activity that modifies fatty acids. Genetic analysis and subsequent biochemical analysis suggested that DIP2 is involved in the fatty acid metabolization of acyl-CoA. Taken together, our results reveal a function of DIP2 in the developing nervous system and provide a potential functional relationship between fatty acid metabolism and axon morphogenesis.
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Affiliation(s)
- Yohei Nitta
- Institute of Molecular and Cellular Biosciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Daisuke Yamazaki
- Institute of Molecular and Cellular Biosciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Atsushi Sugie
- Department of Neuroscience Disease, Center for Transdisciplinary Research, Niigata University, 757, Ichibancho, Asahimachidori, Chuo-ku, Niigata-shi, Niigata 951-8585, Japan
| | - Makoto Hiroi
- Institute of Molecular and Cellular Biosciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Tetsuya Tabata
- Institute of Molecular and Cellular Biosciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan.
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167
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Qu Y, Hahn I, Webb SED, Pearce SP, Prokop A. Periodic actin structures in neuronal axons are required to maintain microtubules. Mol Biol Cell 2016; 28:296-308. [PMID: 27881663 PMCID: PMC5231898 DOI: 10.1091/mbc.e16-10-0727] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Revised: 11/09/2016] [Accepted: 11/15/2016] [Indexed: 12/31/2022] Open
Abstract
Drosophila genetics is combined with high-resolution microscopy and a number of functional readouts to demonstrate key factors required for the presence of regularly spaced rings of cortical actin in axons. The data suggest important roles for the actin rings in microtubule regulation, most likely by sustaining their polymerization. Axons are cable-like neuronal processes wiring the nervous system. They contain parallel bundles of microtubules as structural backbones, surrounded by regularly spaced actin rings termed the periodic membrane skeleton (PMS). Despite being an evolutionarily conserved, ubiquitous, highly ordered feature of axons, the function of PMS is unknown. Here we studied PMS abundance, organization, and function, combining versatile Drosophila genetics with superresolution microscopy and various functional readouts. Analyses with 11 actin regulators and three actin-targeting drugs suggest that PMS contains short actin filaments that are depolymerization resistant and sensitive to spectrin, adducin, and nucleator deficiency, consistent with microscopy-derived models proposing PMS as specialized cortical actin. Upon actin removal, we observed gaps in microtubule bundles, reduced microtubule polymerization, and reduced axon numbers, suggesting a role of PMS in microtubule organization. These effects become strongly enhanced when carried out in neurons lacking the microtubule-stabilizing protein Short stop (Shot). Combining the aforementioned actin manipulations with Shot deficiency revealed a close correlation between PMS abundance and microtubule regulation, consistent with a model in which PMS-dependent microtubule polymerization contributes to their maintenance in axons. We discuss potential implications of this novel PMS function along axon shafts for axon maintenance and regeneration.
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Affiliation(s)
- Yue Qu
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester M13 9PT, United Kingdom
| | - Ines Hahn
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester M13 9PT, United Kingdom
| | - Stephen E D Webb
- Rutherford Appleton Laboratory, Science and Technology Facilities Council, Didcot OX11 0QX, United Kingdom
| | - Simon P Pearce
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester M13 9PT, United Kingdom.,School of Mathematics, University of Manchester, Manchester M13 9PL, United Kingdom
| | - Andreas Prokop
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester M13 9PT, United Kingdom
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168
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Voelzmann A, Hahn I, Pearce SP, Sánchez-Soriano N, Prokop A. A conceptual view at microtubule plus end dynamics in neuronal axons. Brain Res Bull 2016; 126:226-237. [PMID: 27530065 PMCID: PMC5090033 DOI: 10.1016/j.brainresbull.2016.08.006] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Revised: 08/08/2016] [Accepted: 08/11/2016] [Indexed: 12/02/2022]
Abstract
Axons are the cable-like protrusions of neurons which wire up the nervous system. Polar bundles of microtubules (MTs) constitute their structural backbones and are highways for life-sustaining transport between proximal cell bodies and distal synapses. Any morphogenetic changes of axons during development, plastic rearrangement, regeneration or degeneration depend on dynamic changes of these MT bundles. A key mechanism for implementing such changes is the coordinated polymerisation and depolymerisation at the plus ends of MTs within these bundles. To gain an understanding of how such regulation can be achieved at the cellular level, we provide here an integrated overview of the extensive knowledge we have about the molecular mechanisms regulating MT de/polymerisation. We first summarise insights gained from work in vitro, then describe the machinery which supplies the essential tubulin building blocks, the protein complexes associating with MT plus ends, and MT shaft-based mechanisms that influence plus end dynamics. We briefly summarise the contribution of MT plus end dynamics to important cellular functions in axons, and conclude by discussing the challenges and potential strategies of integrating the existing molecular knowledge into conceptual understanding at the level of axons.
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Affiliation(s)
- André Voelzmann
- The University of Manchester, Faculty of Biology, Medicine and Health, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK
| | - Ines Hahn
- The University of Manchester, Faculty of Biology, Medicine and Health, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK
| | - Simon P Pearce
- The University of Manchester, Faculty of Biology, Medicine and Health, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK; The University of Manchester, School of Mathematics, Alan Turing Building, Oxford Road, Manchester M13 9PL, UK
| | - Natalia Sánchez-Soriano
- University of Liverpool, Institute of Translational Medicine, Department of Cellular and Molecular Physiology, Crown Street, Liverpool, L69 3BX, UK
| | - Andreas Prokop
- The University of Manchester, Faculty of Biology, Medicine and Health, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK.
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169
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McLaughlin CN, Nechipurenko IV, Liu N, Broihier HT. A Toll receptor-FoxO pathway represses Pavarotti/MKLP1 to promote microtubule dynamics in motoneurons. J Cell Biol 2016; 214:459-74. [PMID: 27502486 PMCID: PMC4987293 DOI: 10.1083/jcb.201601014] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Accepted: 07/07/2016] [Indexed: 02/06/2023] Open
Abstract
McLaughlin et al. uncover a motoneuronal Toll-6–directed pathway that functions via dSARM and FoxO to attenuate microtubule stability through repression of Pavarotti/MKLP1 transcription. Genetic and pharmacological strategies reveal a novel requirement for dynamic synaptic microtubules in structural plasticity, which are established by Toll-6–FoxO signaling. FoxO proteins are evolutionarily conserved regulators of neuronal structure and function, yet the neuron-specific pathways within which they act are poorly understood. To elucidate neuronal FoxO function in Drosophila melanogaster, we first screened for FoxO’s upstream regulators and downstream effectors. On the upstream side, we present genetic and molecular pathway analyses indicating that the Toll-6 receptor, the Toll/interleukin-1 receptor domain adaptor dSARM, and FoxO function in a linear pathway. On the downstream side, we find that Toll-6–FoxO signaling represses the mitotic kinesin Pavarotti/MKLP1 (Pav-KLP), which itself attenuates microtubule (MT) dynamics. We next probed in vivo functions for this novel pathway and found that it is essential for axon transport and structural plasticity in motoneurons. We demonstrate that elevated expression of Pav-KLP underlies transport and plasticity phenotypes in pathway mutants, indicating that Toll-6–FoxO signaling promotes MT dynamics by limiting Pav-KLP expression. In addition to uncovering a novel molecular pathway, our work reveals an unexpected function for dynamic MTs in enabling rapid activity-dependent structural plasticity.
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Affiliation(s)
- Colleen N McLaughlin
- Department of Neurosciences, Case Western Reserve University, Cleveland, OH 44106
| | - Inna V Nechipurenko
- Department of Neurosciences, Case Western Reserve University, Cleveland, OH 44106
| | - Nan Liu
- Department of Neurosciences, Case Western Reserve University, Cleveland, OH 44106
| | - Heather T Broihier
- Department of Neurosciences, Case Western Reserve University, Cleveland, OH 44106
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170
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Seno T, Ikeno T, Mennya K, Kurishita M, Sakae N, Sato M, Takada H, Konishi Y. Kinesin-1 sorting in axons controls the differential retraction of arbor terminals. J Cell Sci 2016; 129:3499-510. [PMID: 27505885 DOI: 10.1242/jcs.183806] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Accepted: 08/02/2016] [Indexed: 01/13/2023] Open
Abstract
The ability of neurons to generate multiple arbor terminals from a single axon is crucial for establishing proper neuronal wiring. Although growth and retraction of arbor terminals are differentially regulated within the axon, the mechanisms by which neurons locally control their structure remain largely unknown. In the present study, we found that the kinesin-1 (Kif5 proteins) head domain (K5H) preferentially marks a subset of arbor terminals. Time-lapse imaging clarified that these arbor terminals were more stable than others, because of a low retraction rate. Local inhibition of kinesin-1 in the arbor terminal by chromophore-assisted light inactivation (CALI) enhanced the retraction rate. The microtubule turnover was locally regulated depending on the length from the branching point to the terminal end, but did not directly correlate with the presence of K5H. By contrast, F-actin signal values in arbor terminals correlated spatiotemporally with K5H, and inhibition of actin turnover prevented retraction. Results from the present study reveal a new system mediated by kinesin-1 sorting in axons that differentially controls stability of arbor terminals.
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Affiliation(s)
- Takeshi Seno
- Department of Human and Artificial Intelligence Systems, University of Fukui, Fukui 910-8507, Japan
| | - Tatsuki Ikeno
- Department of Human and Artificial Intelligence Systems, University of Fukui, Fukui 910-8507, Japan
| | - Kousuke Mennya
- Department of Human and Artificial Intelligence Systems, University of Fukui, Fukui 910-8507, Japan
| | - Masayuki Kurishita
- Department of Human and Artificial Intelligence Systems, University of Fukui, Fukui 910-8507, Japan
| | - Narumi Sakae
- Department of Human and Artificial Intelligence Systems, University of Fukui, Fukui 910-8507, Japan
| | - Makoto Sato
- Life Science Innovation Center, University of Fukui, Fukui 910-8507, Japan Research Center for Child Mental Development, University of Fukui, Fukui 910-1193, Japan Department of Anatomy and Neuroscience, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan United Graduate School of Child Development, Osaka University, Kanazawa University-Hamamatsu University School of Medicine, Chiba University and University of Fukui, Osaka University, Osaka 565-0871, Japan
| | - Hiroki Takada
- Department of Human and Artificial Intelligence Systems, University of Fukui, Fukui 910-8507, Japan
| | - Yoshiyuki Konishi
- Department of Human and Artificial Intelligence Systems, University of Fukui, Fukui 910-8507, Japan Life Science Innovation Center, University of Fukui, Fukui 910-8507, Japan Department of Materials Science and Biotechnology, Faculty of Engineering, University of Fukui, Fukui 910-8507, Japan
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171
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Sainath R, Ketschek A, Grandi L, Gallo G. CSPGs inhibit axon branching by impairing mitochondria-dependent regulation of actin dynamics and axonal translation. Dev Neurobiol 2016; 77:454-473. [PMID: 27429169 DOI: 10.1002/dneu.22420] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Revised: 06/28/2016] [Accepted: 07/14/2016] [Indexed: 12/27/2022]
Abstract
Chondroitin sulfate proteoglycans (CSPGs) inhibit the formation of axon collateral branches. The regulation of the axonal cytoskeleton and mitochondria are important components of the mechanism of branching. Actin-dependent axonal plasticity, reflected in the dynamics of axonal actin patches and filopodia, is greatest along segments of the axon populated by mitochondria. It is reported that CSPGs partially depolarize the membrane potential of axonal mitochondria, which impairs the dynamics of the axonal actin cytoskeleton and decreases the formation and duration of axonal filopodia, the first steps in the mechanism of branching. The effects of CSPGs on actin cytoskeletal dynamics are specific to axon segments populated by mitochondria. In contrast, CSPGs do not affect the microtubule content of axons, or the localization of microtubules into axonal filopodia, a required step in the mechanism of branch formation. It is also reported that CSPGs decrease the mitochondria-dependent axonal translation of cortactin, an actin associated protein involved in branching. Finally, the inhibitory effects of CSPGs on axon branching, actin cytoskeletal dynamics and the axonal translation of cortactin are reversed by culturing neurons with acetyl-l-carnitine, which promotes mitochondrial respiration. Collectively these data indicate that CSPGs impair mitochondrial function in axons, an effect which contributes to the inhibition of axon branching. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 77: 419-437, 2017.
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Affiliation(s)
- Rajiv Sainath
- Temple University School of Medicine, Department of Anatomy and Cell Biology, Shriners Hospitals Pediatric Research Center, 3500 N Broad St, Philadelphia, Pennsylvania
| | - Andrea Ketschek
- Temple University School of Medicine, Department of Anatomy and Cell Biology, Shriners Hospitals Pediatric Research Center, 3500 N Broad St, Philadelphia, Pennsylvania
| | - Leah Grandi
- Temple University School of Medicine, Department of Anatomy and Cell Biology, Shriners Hospitals Pediatric Research Center, 3500 N Broad St, Philadelphia, Pennsylvania
| | - Gianluca Gallo
- Temple University School of Medicine, Department of Anatomy and Cell Biology, Shriners Hospitals Pediatric Research Center, 3500 N Broad St, Philadelphia, Pennsylvania
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172
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Pacheco A, Gallo G. Actin filament-microtubule interactions in axon initiation and branching. Brain Res Bull 2016; 126:300-310. [PMID: 27491623 DOI: 10.1016/j.brainresbull.2016.07.013] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Revised: 07/28/2016] [Accepted: 07/30/2016] [Indexed: 10/21/2022]
Abstract
Neurons begin life as spherical cells. A major hallmark of neuronal development is the formation of elongating processes from the cell body which subsequently differentiate into dendrites and the axon. The formation and later development of neuronal processes is achieved through the concerted organization of actin filaments and microtubules. Here, we review the literature regarding recent advances in the understanding of cytoskeletal interactions in neurons focusing on the initiation of processes from neuronal cell bodies and the collateral branching of axons. The complex crosstalk between cytoskeletal elements is mediated by a cohort of proteins that either bind both cytoskeletal systems or allow one to regulate the other. Recent studies have highlighted the importance of microtubule plus-tip proteins in the regulation of the dynamics and organization of actin filaments, while also providing a mechanism for the subcellular capture and guidance of microtubule tips by actin filaments. Although the understanding of cytoskeletal crosstalk and interactions in neuronal morphogenesis has advanced significantly in recent years the appreciation of the neuron as an integrated cytoskeletal system remains a frontier.
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Affiliation(s)
- Almudena Pacheco
- Temple University, Lewis Kats School of Medicine, Shriners Hospitals Pediatric Research Center, Department of Anatomy and Cell Biology, 3500 North Broad Street, Philadelphia, PA 19140, United States
| | - Gianluca Gallo
- Temple University, Lewis Kats School of Medicine, Shriners Hospitals Pediatric Research Center, Department of Anatomy and Cell Biology, 3500 North Broad Street, Philadelphia, PA 19140, United States.
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173
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Gonzalez A, Moya-Alvarado G, Gonzalez-Billaut C, Bronfman FC. Cellular and molecular mechanisms regulating neuronal growth by brain-derived neurotrophic factor. Cytoskeleton (Hoboken) 2016; 73:612-628. [PMID: 27223597 DOI: 10.1002/cm.21312] [Citation(s) in RCA: 86] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Revised: 05/20/2016] [Accepted: 05/23/2016] [Indexed: 12/31/2022]
Abstract
Brain-derived neurotrophic factor (BDNF) and its receptors TrkB and p75 regulate dendritic and axonal growth during development and maintenance of the mature nervous system; however, the cellular and molecular mechanisms underlying this process are not fully understood. In recent years, several advances have shed new light on the processes behind the regulation of BDNF-mediated structural plasticity including control of neuronal transcription, local translation of proteins, and regulation of cytoskeleton and membrane dynamics. In this review, we summarize recent advances in the field of BDNF signaling in neurons to induce neuronal growth. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Andres Gonzalez
- MINREB and Center for Ageing and Regeneration (CARE UC), Faculty of Biological Sciences, Department of Physiology, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Guillermo Moya-Alvarado
- MINREB and Center for Ageing and Regeneration (CARE UC), Faculty of Biological Sciences, Department of Physiology, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Christian Gonzalez-Billaut
- Laboratory of Cell and Neuronal Dynamics, Department of Biology, Faculty of Sciences, Universidad de Chile and Geroscience Center for Brain Health and Metabolism, Santiago, Chile
| | - Francisca C Bronfman
- MINREB and Center for Ageing and Regeneration (CARE UC), Faculty of Biological Sciences, Department of Physiology, Pontificia Universidad Católica de Chile, Santiago, Chile.
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174
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Mateo-Lozano S, García M, Rodríguez-Hernández CJ, de Torres C. Regulation of Differentiation by Calcium-Sensing Receptor in Normal and Tumoral Developing Nervous System. Front Physiol 2016; 7:169. [PMID: 27242543 PMCID: PMC4861737 DOI: 10.3389/fphys.2016.00169] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Accepted: 04/25/2016] [Indexed: 12/14/2022] Open
Abstract
During normal development of the nervous system (NS), neural progenitor cells (NPCs) produce specialized populations of neurons and glial cells upon cell fate restriction and terminal differentiation. These sequential processes require the dynamic regulation of thousands of genes. The calcium-sensing receptor (CaSR) is temporally and spatially regulated in both neurons and glial cells during development of the NS. In particular, CaSR expression and function have been shown to play a significant role during differentiation of NPCs toward the oligodendrocyte lineage and also in maturation of cerebellar granule cell precursors (GCPs). Moreover, CaSR regulates axonal and dendritic growth in both central and peripheral nervous systems (PNSs), a process necessary for proper construction of mature neuronal networks. On the other hand, several lines of evidence support a role for CaSR in promotion of cell differentiation and inhibition of proliferation in neuroblastoma, a tumor arising from precursor cells of developing PNS. Thus, among the variety of NS functions in which the CaSR participates, this mini-review focuses on its role in differentiation of normal and tumoral cells. Current knowledge of the mechanisms responsible for CaSR regulation and function in these contexts is also discussed, together with the therapeutic opportunities provided by CaSR allosteric modulators.
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Affiliation(s)
- Silvia Mateo-Lozano
- Developmental Tumor Biology Laboratory, Institut de Recerca Pediàtrica - Hospital Sant Joan de Déu Barcelona, Spain
| | - Marta García
- Developmental Tumor Biology Laboratory, Institut de Recerca Pediàtrica - Hospital Sant Joan de Déu Barcelona, Spain
| | - Carlos J Rodríguez-Hernández
- Developmental Tumor Biology Laboratory, Institut de Recerca Pediàtrica - Hospital Sant Joan de Déu Barcelona, Spain
| | - Carmen de Torres
- Developmental Tumor Biology Laboratory, Institut de Recerca Pediàtrica - Hospital Sant Joan de DéuBarcelona, Spain; Department of Oncology, Institut de Recerca Pediàtrica - Hospital Sant Joan de DéuBarcelona, Spain
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175
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Winkle CC, Taylor KL, Dent EW, Gallo G, Greif KF, Gupton SL. Beyond the cytoskeleton: The emerging role of organelles and membrane remodeling in the regulation of axon collateral branches. Dev Neurobiol 2016; 76:1293-1307. [PMID: 27112549 DOI: 10.1002/dneu.22398] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Revised: 04/11/2016] [Accepted: 04/21/2016] [Indexed: 12/19/2022]
Abstract
The generation of axon collateral branches is a fundamental aspect of the development of the nervous system and the response of axons to injury. Although much has been discovered about the signaling pathways and cytoskeletal dynamics underlying branching, additional aspects of the cell biology of axon branching have received less attention. This review summarizes recent advances in our understanding of key factors involved in axon branching. This article focuses on how cytoskeletal mechanisms, intracellular organelles, such as mitochondria and the endoplasmic reticulum, and membrane remodeling (exocytosis and endocytosis) contribute to branch initiation and formation. Together this growing literature provides valuable insight as well as a platform for continued investigation into how multiple aspects of axonal cell biology are spatially and temporally orchestrated to give rise to axon branches. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 76: 1293-1307, 2016.
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Affiliation(s)
- Cortney C Winkle
- Neurobiology Curriculum, University of North Carolina, Chapel Hill, North Carolina, 27599
| | - Kendra L Taylor
- Neuroscience Training Program, University of Wisconsin-Madison, Madison, Wisconsin, 53705
| | - Erik W Dent
- Department of Neuroscience, University of Wisconsin-Madison, Madison, Wisconsin, 53705
| | - Gianluca Gallo
- Lewis Katz School of Medicine, Department of Anatomy and Cell Biology, Shriners Hospitals Pediatric Research Center, Temple University, Philadelphia, Pennsylvania, 19140
| | - Karen F Greif
- Department of Biology, Bryn Mawr College, Bryn Mawr, Pennsylvania, 19010
| | - Stephanie L Gupton
- Department of Cell Biology and Physiology, Neuroscience Center, University of North Carolina, Chapel Hill, North Carolina, 27599
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176
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Giacosa C, Karpati FJ, Foster NEV, Penhune VB, Hyde KL. Dance and music training have different effects on white matter diffusivity in sensorimotor pathways. Neuroimage 2016; 135:273-86. [PMID: 27114054 DOI: 10.1016/j.neuroimage.2016.04.048] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Revised: 04/18/2016] [Accepted: 04/20/2016] [Indexed: 12/22/2022] Open
Affiliation(s)
- Chiara Giacosa
- International Laboratory for Brain, Music and Sound Research (BRAMS), Pavillon 1420 Mont Royal, FAS, Département de psychologie, CP 6128 Succ. Centre Ville, Montreal, QC H3C 3J7, Canada; Department of Psychology, Concordia University, 7141 Sherbrooke Street West, Montreal, Quebec H4B 1R6, Canada.
| | - Falisha J Karpati
- International Laboratory for Brain, Music and Sound Research (BRAMS), Pavillon 1420 Mont Royal, FAS, Département de psychologie, CP 6128 Succ. Centre Ville, Montreal, QC H3C 3J7, Canada; Faculty of Medicine, McGill University, 3655 Sir William Osler, Montreal, Quebec H3G 1Y6, Canada
| | - Nicholas E V Foster
- International Laboratory for Brain, Music and Sound Research (BRAMS), Pavillon 1420 Mont Royal, FAS, Département de psychologie, CP 6128 Succ. Centre Ville, Montreal, QC H3C 3J7, Canada; Department of Psychology, University of Montreal, Pavillon Marie-Victorin, 90 avenue Vincent d'Indy, Montreal, Quebec H2V 2S9, Canada
| | - Virginia B Penhune
- International Laboratory for Brain, Music and Sound Research (BRAMS), Pavillon 1420 Mont Royal, FAS, Département de psychologie, CP 6128 Succ. Centre Ville, Montreal, QC H3C 3J7, Canada; Department of Psychology, Concordia University, 7141 Sherbrooke Street West, Montreal, Quebec H4B 1R6, Canada
| | - Krista L Hyde
- International Laboratory for Brain, Music and Sound Research (BRAMS), Pavillon 1420 Mont Royal, FAS, Département de psychologie, CP 6128 Succ. Centre Ville, Montreal, QC H3C 3J7, Canada; Faculty of Medicine, McGill University, 3655 Sir William Osler, Montreal, Quebec H3G 1Y6, Canada; Department of Psychology, University of Montreal, Pavillon Marie-Victorin, 90 avenue Vincent d'Indy, Montreal, Quebec H2V 2S9, Canada
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177
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Chalmers K, Kita EM, Scott EK, Goodhill GJ. Quantitative Analysis of Axonal Branch Dynamics in the Developing Nervous System. PLoS Comput Biol 2016; 12:e1004813. [PMID: 26998842 PMCID: PMC4801415 DOI: 10.1371/journal.pcbi.1004813] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Accepted: 02/15/2016] [Indexed: 11/18/2022] Open
Abstract
Branching is an important mechanism by which axons navigate to their targets during neural development. For instance, in the developing zebrafish retinotectal system, selective branching plays a critical role during both initial pathfinding and subsequent arborisation once the target zone has been reached. Here we show how quantitative methods can help extract new information from time-lapse imaging about the nature of the underlying branch dynamics. First, we introduce Dynamic Time Warping to this domain as a method for automatically matching branches between frames, replacing the effort required for manual matching. Second, we model branch dynamics as a birth-death process, i.e. a special case of a continuous-time Markov process. This reveals that the birth rate for branches from zebrafish retinotectal axons, as they navigate across the tectum, increased over time. We observed no significant change in the death rate for branches over this time period. However, blocking neuronal activity with TTX slightly increased the death rate, without a detectable change in the birth rate. Third, we show how the extraction of these rates allows computational simulations of branch dynamics whose statistics closely match the data. Together these results reveal new aspects of the biology of retinotectal pathfinding, and introduce computational techniques which are applicable to the study of axon branching more generally. The complex morphologies of neurons present challenges for analysis. Large data sets can be gathered, but extracting meaningful data from the hundreds of branches from one axon over a few hundred time points can be difficult. One problem in particular is matching a single unique branch through several images, when the branches can extend, retract, or be removed entirely. In addition, if the imaging is done in vivo, the environment itself can grow and shift. Here we introduce Dynamic Time Warping (DTW) analysis to follow the complex structures of neurons through time. DTW identifies individual branches and therefore allows the determination of branch lifetimes. Using this approach we find that for retinal ganglion cell axons, the branch birth rate increases over time as axons navigate to their targets, and that blocking neural activity slightly increases the branch death rate without impacting the birth rate. From the estimated birth and death rate parameters we create simulations based on a continuous-time Markov chain process. These tools expand the techniques available to study the development of neuronal structures and provide more information from large time-lapse imaging datasets.
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Affiliation(s)
- Kelsey Chalmers
- Queensland Brain Institute, The University of Queensland, Brisbane, Queensland, Australia
| | - Elizabeth M. Kita
- Queensland Brain Institute, The University of Queensland, Brisbane, Queensland, Australia
| | - Ethan K. Scott
- School of Biomedical Sciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Geoffrey J. Goodhill
- Queensland Brain Institute, The University of Queensland, Brisbane, Queensland, Australia
- School of Mathematics and Physics, The University of Queensland, Brisbane, Queensland, Australia
- * E-mail:
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178
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Davenport A, Bivona A, Latson W, Lemanski LF, Cheriyath V. Loss of Maspardin Attenuates the Growth and Maturation of Mouse Cortical Neurons. NEURODEGENER DIS 2016; 16:260-72. [PMID: 26978163 DOI: 10.1159/000443666] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2015] [Accepted: 12/23/2015] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Mast syndrome, an autosomal recessive, progressive form of hereditary spastic paraplegia, is associated with mutations in SPG21 loci that encode maspardin protein. Although SPG21-/- mice exhibit lower limb dysfunction, the role of maspardin loss in mast syndrome is unclear. OBJECTIVE To test the hypothesis that loss of maspardin attenuates the growth and maturation of cortical neurons in SPG21-/- mice. METHODS AND RESULTS In a randomized experimental design SPG21-/- mice demonstrated significantly less agility and coordination compared to wild-type mice in beam walk, ledge, and hind limb clasp tests for assessing neuronal dysfunction (p ≤ 0.05). The SPG21-/- mice exhibited symptoms of mast syndrome at 6 months which worsened in 12-month-old cohort, suggesting progressive dysfunction of motor neurons. Ex vivo, wild-type cortical neurons formed synapses, ganglia and aggregates at 96 h, whereas SPG21-/- neurons exhibited attenuated growth with markedly less axonal branches. Additionally, epidermal growth factor markedly promoted the growth and maturation of SPG21+/+ cortical neurons but not SPG21-/- neurons. Consequently, quantitative RT-PCR identified a significant reduction in the expression of a subset of EGF-EGFR signaling targets. CONCLUSIONS Our current study uncovered a direct role for maspardin in normal and EGF-induced growth and maturation of primary cortical neurons. The loss of maspardin resulted in attenuated growth, axonal branching, and attenuation of EGF signaling. Reinstating the functions of maspardin may reverse hind limb impairment associated with neuronal dysfunction in mast syndrome patients.
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Affiliation(s)
- Anne Davenport
- Department of Biological and Environmental Sciences, Texas A&M University-Commerce, Commerce, Tex., USA
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179
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O'Neill E, Kwok B, Day JS, Connor TJ, Harkin A. Amitriptyline protects against TNF-α-induced atrophy and reduction in synaptic markers via a Trk-dependent mechanism. Pharmacol Res Perspect 2016; 4:e00195. [PMID: 27069625 PMCID: PMC4804321 DOI: 10.1002/prp2.195] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Accepted: 10/09/2015] [Indexed: 12/20/2022] Open
Abstract
Neuritic degeneration and synaptic loss are features of both neuroinflammation and neurodegenerative disease. The tricyclic antidepressant amitriptyline has neurotrophic and anti-inflammatory properties and acts as a novel agonist of the neurotrophin Trk receptors. Primary cortical neurons were treated with amitriptyline, nortriptyline and NGF and tested for neuronal complexity by Sholl analysis, protein expression by Western immunoblotting, and synapse number by colocalization of pre and postsynaptic makers. Amitriptyline (500 nmol/L) and its active metabolite nortriptyline (50 nmol/L) are found to induce neurite outgrowth in rat primary cortical neurons. Amitriptyline-induced neurite outgrowth is blocked by inhibition of Trk signaling using Trk antagonist K252a (200 nmol/L) but not by the neurotrophin inhibitor Y1036 (40 μmol/L), indicating that amitriptyline binds directly to the Trk receptor to initiate neurite outgrowth. MEK inhibitor PD98059 (10 μmol/L) also blocks amitriptyline-induced neurite outgrowth, implicating activation of the MAPK signaling pathway downstream of Trk receptor activation. Furthermore, pretreatment of primary cortical neurons with amitriptyline and nortriptyline prevents the effects of the proinflammatory cytokine TNF-α (10 ng/mL) on neurite outgrowth and colocalization of synaptic proteins. These findings suggest that amitriptyline and nortriptyline can exert neurotrophic effects in primary cortical neurons via activation of a Trk/MAPK signaling pathway. These compounds therefore have significant potential to be used in the treatment of neurodegenerative conditions where atrophy and loss of synaptic connections contribute to progression of disease.
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Affiliation(s)
- Eimear O'Neill
- Neuropsychopharmacology Research Group School of Pharmacy & Pharmaceutical Sciences and Trinity College Institute of Neuroscience Dublin Ireland; Neuroimmunology Research Group Department of Physiology School of Medicine and Trinity College Institute of Neuroscience Dublin Ireland
| | - Billy Kwok
- Neuroimmunology Research Group Department of Physiology School of Medicine and Trinity College Institute of Neuroscience Dublin Ireland
| | - Jennifer S Day
- Neuroimmunology Research Group Department of Physiology School of Medicine and Trinity College Institute of Neuroscience Dublin Ireland
| | - Thomas J Connor
- Neuroimmunology Research Group Department of Physiology School of Medicine and Trinity College Institute of Neuroscience Dublin Ireland
| | - Andrew Harkin
- Neuropsychopharmacology Research Group School of Pharmacy & Pharmaceutical Sciences and Trinity College Institute of Neuroscience Dublin Ireland
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180
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Leite SC, Sousa MM. The neuronal and actin commitment: Why do neurons need rings? Cytoskeleton (Hoboken) 2016; 73:424-34. [DOI: 10.1002/cm.21273] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Revised: 01/07/2016] [Accepted: 01/07/2016] [Indexed: 12/17/2022]
Affiliation(s)
- Sérgio Carvalho Leite
- Nerve Regeneration Group, IBMC - Instituto De Biologia Molecular E Celular; Porto Portugal
- Instituto De Investigação E Inovação Em Saúde, Universidade Do Porto; Porto Portugal
- ICBAS, Universidade Do Porto; Porto Portugal
| | - Mónica Mendes Sousa
- Nerve Regeneration Group, IBMC - Instituto De Biologia Molecular E Celular; Porto Portugal
- Instituto De Investigação E Inovação Em Saúde, Universidade Do Porto; Porto Portugal
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181
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Ketschek A, Spillane M, Dun XP, Hardy H, Chilton J, Gallo G. Drebrin coordinates the actin and microtubule cytoskeleton during the initiation of axon collateral branches. Dev Neurobiol 2016; 76:1092-110. [PMID: 26731339 DOI: 10.1002/dneu.22377] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Revised: 12/07/2015] [Accepted: 01/01/2016] [Indexed: 11/10/2022]
Abstract
Drebrin is a cytoskeleton-associated protein which can interact with both actin filaments and the tips of microtubules. Its roles have been studied mostly in dendrites, and the functions of drebrin in axons are less well understood. In this study, we analyzed the role of drebrin, through shRNA-mediated depletion and overexpression, in the collateral branching of chicken embryonic sensory axons. We report that drebrin promotes the formation of axonal filopodia and collateral branches in vivo and in vitro. Live imaging of cytoskeletal dynamics revealed that drebrin promotes the formation of filopodia from precursor structures termed axonal actin patches. Endogenous drebrin localizes to actin patches and depletion studies indicate that drebrin contributes to the development of patches. In filopodia, endogenous drebrin localizes to the proximal portion of the filopodium. Drebrin was found to promote the stability of axonal filopodia and the entry of microtubule plus tips into axonal filopodia. The effects of drebrin on the stabilization of filopodia are independent of its effects on promoting microtubule targeting to filopodia. Inhibition of myosin II induces a redistribution of endogenous drebrin distally into filopodia, and further increases branching in drebrin overexpressing neurons. Finally, a 30 min treatment with the branch-inducing signal nerve growth factor increases the levels of axonal drebrin. This study determines the specific roles of drebrin in the regulation of the axonal cytoskeleton, and provides evidence that drebrin contributes to the coordination of the actin and microtubule cytoskeleton during the initial stages of axon branching. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 76: 1092-1110, 2016.
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Affiliation(s)
- Andrea Ketschek
- Department of Anatomy and Cell Biology, Shriners Hospitals Pediatric Research Center, Temple University School of Medicine, 3500 N. Broad St, Philadelphia, Pennsylvania, 19140
| | - Mirela Spillane
- Department of Anatomy and Cell Biology, Shriners Hospitals Pediatric Research Center, Temple University School of Medicine, 3500 N. Broad St, Philadelphia, Pennsylvania, 19140
| | - Xin-Peng Dun
- Peninsula Schools of Medicine and Dentistry, University of Plymouth, Plymouth Science Park, Research Way, Plymouth, PL6 8BU, United Kingdom
| | - Holly Hardy
- RILD Building, University of Exeter Medical School, Wellcome Wolfson Medical Research Centre, Barrack Road, Exeter, EX2 5DW, United Kingdom
| | - John Chilton
- RILD Building, University of Exeter Medical School, Wellcome Wolfson Medical Research Centre, Barrack Road, Exeter, EX2 5DW, United Kingdom
| | - Gianluca Gallo
- Department of Anatomy and Cell Biology, Shriners Hospitals Pediatric Research Center, Temple University School of Medicine, 3500 N. Broad St, Philadelphia, Pennsylvania, 19140
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182
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Zhou Z, Tanaka KF, Matsunaga S, Iseki M, Watanabe M, Matsuki N, Ikegaya Y, Koyama R. Photoactivated adenylyl cyclase (PAC) reveals novel mechanisms underlying cAMP-dependent axonal morphogenesis. Sci Rep 2016; 5:19679. [PMID: 26795422 PMCID: PMC4726437 DOI: 10.1038/srep19679] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Accepted: 12/16/2015] [Indexed: 01/17/2023] Open
Abstract
Spatiotemporal regulation of axonal branching and elongation is essential in the development of refined neural circuits. cAMP is a key regulator of axonal growth; however, whether and how intracellular cAMP regulates axonal branching and elongation remain unclear, mainly because tools to spatiotemporally manipulate intracellular cAMP levels have been lacking. To overcome this issue, we utilized photoactivated adenylyl cyclase (PAC), which produces cAMP in response to blue-light exposure. In primary cultures of dentate granule cells transfected with PAC, short-term elevation of intracellular cAMP levels induced axonal branching but not elongation, whereas long-term cAMP elevation induced both axonal branching and elongation. The temporal dynamics of intracellular cAMP levels regulated axonal branching and elongation through the activation of protein kinase A (PKA) and exchange protein directly activated by cAMP (Epac), respectively. Thus, using PAC, our study for the first time reveals that temporal cAMP dynamics could regulate axonal branching and elongation via different signaling pathways.
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Affiliation(s)
- Zhiwen Zhou
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan
| | - Kenji F Tanaka
- Department of Neuropsychiatry, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku, Tokyo, Japan
| | - Shigeru Matsunaga
- Central Research Laboratory, Hamamatsu Photonics K.K., 5000 Hirakuchi Hamakita-ku, Hamamatsu, Shizuoka, Japan
| | - Mineo Iseki
- Faculty of Pharmaceutical Sciences, Toho University, 2-2-1 Miyama, Funabashi, Chiba, Japan
| | - Masakatsu Watanabe
- The Graduate School for the Creation of New Photonics Industries, 1955-1 Kurematsu-cho, Nishiku, Hamamatsu, Shizuoka, Japan
| | - Norio Matsuki
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan
| | - Yuji Ikegaya
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan
| | - Ryuta Koyama
- Laboratory of Chemical Pharmacology, Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan
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183
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Gallo G. Localized regulation of the axon shaft during the emergence of collateral branches. Neural Regen Res 2015; 10:1206-8. [PMID: 26487837 PMCID: PMC4590222 DOI: 10.4103/1673-5374.162694] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Affiliation(s)
- Gianluca Gallo
- Shriners Hospitals Pediatric Research Center, Temple University School of Medicine, Department of Anatomy and Cell Biology, Philadelphia, PA, USA
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184
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Mei B, Miao Q, Tang A, Liang G. Enzyme-instructed self-assembly of taxol promotes axonal branching. NANOSCALE 2015; 7:15605-15608. [PMID: 26359218 DOI: 10.1039/c5nr04563k] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Axonal branching is important for vertebrate neuron signaling. Taxol has a biphasic effect on axonal branching (i.e., high concentration inhibits axonal growth but low concentration restores it). To the best of our knowledge, low concentration of taxol to promote axonal branching has not been reported yet. Herein, we rationally designed a taxol derivative Fmoc-Phe-Phe-Lys(taxol)-Tyr(H2PO4)-OH (1) which could be subjected to alkaline phosphatase (ALP)-catalyzed self-assembly to form taxol nanofibers. We found that, at 10 μM, 1 has a microtubule (MT) condensation effect similar to that of taxol on mammalian cells but with more chronic toxicity than taxol on the cells. At a low concentration of 10 nM, 1 not only promoted neurite elongation as taxol did but also promoted axonal branching which was not achieved by using taxol. We propose that self-assembly of 1 along the MTs prohibited their lateral contacts and thus promoted axonal branching. Our strategy of enzyme-instructed self-assembly (EISA) of a taxol derivative provides a new tool for scientists to study the morphology of neurons, as well as their behaviours.
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Affiliation(s)
- Bin Mei
- CAS Key Laboratory of Soft Matter Chemistry, Department of Chemistry, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026, China.
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185
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Hara S, Kaneyama T, Inamata Y, Onodera R, Shirasaki R. Interstitial branch formation within the red nucleus by deep cerebellar nuclei-derived commissural axons during target recognition. J Comp Neurol 2015; 524:999-1014. [DOI: 10.1002/cne.23888] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Revised: 07/29/2015] [Accepted: 08/21/2015] [Indexed: 11/08/2022]
Affiliation(s)
- Satoshi Hara
- Cellular and Molecular Neurobiology Laboratory, Graduate School of Frontier Biosciences; Osaka University; Suita Osaka 565-0871 Japan
| | - Takeshi Kaneyama
- Cellular and Molecular Neurobiology Laboratory, Graduate School of Frontier Biosciences; Osaka University; Suita Osaka 565-0871 Japan
| | - Yasuyuki Inamata
- Cellular and Molecular Neurobiology Laboratory, Graduate School of Frontier Biosciences; Osaka University; Suita Osaka 565-0871 Japan
| | - Ryota Onodera
- Cellular and Molecular Neurobiology Laboratory, Graduate School of Frontier Biosciences; Osaka University; Suita Osaka 565-0871 Japan
| | - Ryuichi Shirasaki
- Cellular and Molecular Neurobiology Laboratory, Graduate School of Frontier Biosciences; Osaka University; Suita Osaka 565-0871 Japan
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186
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Kevenaar JT, Hoogenraad CC. The axonal cytoskeleton: from organization to function. Front Mol Neurosci 2015; 8:44. [PMID: 26321907 PMCID: PMC4536388 DOI: 10.3389/fnmol.2015.00044] [Citation(s) in RCA: 115] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2015] [Accepted: 07/31/2015] [Indexed: 01/20/2023] Open
Abstract
The axon is the single long fiber that extends from the neuron and transmits electrical signals away from the cell body. The neuronal cytoskeleton, composed of microtubules (MTs), actin filaments and neurofilaments, is not only required for axon formation and axonal transport but also provides the structural basis for several specialized axonal structures, such as the axon initial segment (AIS) and presynaptic boutons. Emerging evidence suggest that the unique cytoskeleton organization in the axon is essential for its structure and integrity. In addition, the increasing number of neurodevelopmental and neurodegenerative diseases linked to defect in actin- and microtubule-dependent processes emphasizes the importance of a properly regulated cytoskeleton for normal axonal functioning. Here, we provide an overview of the current understanding of actin and microtubule organization within the axon and discuss models for the functional role of the cytoskeleton at specialized axonal structures.
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Affiliation(s)
- Josta T. Kevenaar
- Cell Biology, Faculty of Science, Utrecht UniversityUtrecht, Netherlands
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187
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Petrovic M, Schmucker D. Axonal wiring in neural development: Target-independent mechanisms help to establish precision and complexity. Bioessays 2015; 37:996-1004. [DOI: 10.1002/bies.201400222] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Milan Petrovic
- Neuronal Wiring Laboratory; VIB; Leuven Belgium
- Department of Oncology, School of Medicine; University of Leuven; Leuven Belgium
| | - Dietmar Schmucker
- Neuronal Wiring Laboratory; VIB; Leuven Belgium
- Department of Oncology, School of Medicine; University of Leuven; Leuven Belgium
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188
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Gillette TA, Ascoli GA. Topological characterization of neuronal arbor morphology via sequence representation: I--motif analysis. BMC Bioinformatics 2015; 16:216. [PMID: 26156313 PMCID: PMC4496917 DOI: 10.1186/s12859-015-0604-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Accepted: 04/30/2015] [Indexed: 01/03/2023] Open
Abstract
BACKGROUND The morphology of neurons offers many insights into developmental processes and signal processing. Numerous reports have focused on metrics at the level of individual branches or whole arbors; however, no studies have attempted to quantify repeated morphological patterns within neuronal trees. We introduce a novel sequential encoding of neurite branching suitable to explore topological patterns. RESULTS Using all possible branching topologies for comparison we show that the relative abundance of short patterns of up to three bifurcations, together with overall tree size, effectively capture the local branching patterns of neurons. Dendrites and axons display broadly similar topological motifs (over-represented patterns) and anti-motifs (under-represented patterns), differing most in their proportions of bifurcations with one terminal branch and in select sub-sequences of three bifurcations. In addition, pyramidal apical dendrites reveal a distinct motif profile. CONCLUSIONS The quantitative characterization of topological motifs in neuronal arbors provides a thorough description of local features and detailed boundaries for growth mechanisms and hypothesized computational functions.
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Affiliation(s)
- Todd A Gillette
- Department of Molecular Neuroscience, Center for Neural Informatics, Structures, and Plasticity, Krasnow Institute for Advanced Study (MS2A1), George Mason University, Fairfax, VA, USA.
| | - Giorgio A Ascoli
- Department of Molecular Neuroscience, Center for Neural Informatics, Structures, and Plasticity, Krasnow Institute for Advanced Study (MS2A1), George Mason University, Fairfax, VA, USA.
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189
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Hand RA, Khalid S, Tam E, Kolodkin AL. Axon Dynamics during Neocortical Laminar Innervation. Cell Rep 2015; 12:172-82. [PMID: 26146079 PMCID: PMC4517581 DOI: 10.1016/j.celrep.2015.06.026] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2015] [Revised: 04/18/2015] [Accepted: 06/05/2015] [Indexed: 11/26/2022] Open
Abstract
The cerebral cortex is a densely interconnected structure with neural circuits that form between cortical laminae and also between distinct cortical areas. However, the precise cell biological and developmental mechanisms that underlie the formation of these neural circuits remain unknown. Here, we visualize laminar innervation of the developing mouse cerebral cortex by layer II/III pyramidal neurons in real time, describing cytoskeletal dynamics during this process. We find that layer II/III pyramidal neurons achieve local laminar-specific innervation through the stabilization of collateral axon branches in target laminae. We also find that loss of neural activity does not abolish local laminar-specific innervation and that cells within the local environment are the likely source of cues that direct layer-specific cortical innervation.
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Affiliation(s)
- Randal A Hand
- The Solomon H. Snyder Department of Neuroscience and Howard Hughes Medical Institute, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Syed Khalid
- The Solomon H. Snyder Department of Neuroscience and Howard Hughes Medical Institute, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Edric Tam
- The Solomon H. Snyder Department of Neuroscience and Howard Hughes Medical Institute, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Alex L Kolodkin
- The Solomon H. Snyder Department of Neuroscience and Howard Hughes Medical Institute, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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190
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Matsumoto N, Hoshiko M, Sugo N, Fukazawa Y, Yamamoto N. Synapse-dependent and independent mechanisms of thalamocortical axon branching are regulated by neuronal activity. Dev Neurobiol 2015; 76:323-36. [PMID: 26061995 DOI: 10.1002/dneu.22317] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2015] [Accepted: 06/06/2015] [Indexed: 12/23/2022]
Abstract
Axon branching and synapse formation are critical processes for establishing precise circuit connectivity. These processes are tightly regulated by neural activity, but the relationship between them remains largely unclear. We use organotypic coculture preparations to examine the role of synapse formation in the activity-dependent axon branching of thalamocortical (TC) projections. To visualize TC axons and their presynaptic sites, two plasmids encoding DsRed and EGFP-tagged synaptophysin (SYP-EGFP) were cotransfected into a small number of thalamic neurons. Time-lapse imaging of individual TC axons showed that most branches emerged from SYP-EGFP puncta, indicating that synapse formation precedes emergences of axonal branches. We also investigated the effects of neuronal activity on axon branching and synapse formation by manipulating spontaneous firing activity of thalamic cells. An inward rectifying potassium channel, Kir2.1, and a bacterial voltage-gated sodium channel, NaChBac, were used to suppress and promote firing activity, respectively. We found suppressing neural activity reduced both axon branching and synapse formation. In contrast, increasing neural activity promoted only axonal branch formation. Time-lapse imaging of NaChBac-expressing cells further revealed that new branches frequently appeared from the locations other than SYP-EGFP puncta, indicating that enhancing activity promotes axonal branch formation due to an increase of branch emergence at nonsynaptic sites. These results suggest that presynaptic locations are hotspots for branch emergence, and that frequent firing activity can shift branch emergence to a synapse-independent process.
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Affiliation(s)
- Naoyuki Matsumoto
- Laboratory of Cellular and Molecular Neurobiology Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, 565-0871, Japan
| | - Maki Hoshiko
- Laboratory of Cellular and Molecular Neurobiology Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, 565-0871, Japan
| | - Noriyuki Sugo
- Laboratory of Cellular and Molecular Neurobiology Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, 565-0871, Japan
| | - Yugo Fukazawa
- Division of Brain Structure and Function, Faculty of Medical Science, University of Fukui, Eiheiji, Yoshida, 910-1193, Japan
| | - Nobuhiko Yamamoto
- Laboratory of Cellular and Molecular Neurobiology Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, 565-0871, Japan
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191
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Bizzoca A, Picocci S, Corsi P, Arbia S, Croci L, Consalez GG, Gennarini G. The gene encoding the mouse contactin-1 axonal glycoprotein is regulated by the collier/Olf1/EBF family early B-Cell factor 2 transcription factor. Dev Neurobiol 2015; 75:1420-40. [DOI: 10.1002/dneu.22293] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Revised: 03/17/2015] [Accepted: 03/22/2015] [Indexed: 01/06/2023]
Affiliation(s)
- Antonella Bizzoca
- Department of Basic Medical Sciences, Neurosciences and Sensory Organs; Medical School, University of Bari; Policlinico Bari I-70124 Italy
| | - Sabrina Picocci
- Department of Basic Medical Sciences, Neurosciences and Sensory Organs; Medical School, University of Bari; Policlinico Bari I-70124 Italy
| | - Patrizia Corsi
- Department of Basic Medical Sciences, Neurosciences and Sensory Organs; Medical School, University of Bari; Policlinico Bari I-70124 Italy
| | - Stefania Arbia
- Department of Basic Medical Sciences, Neurosciences and Sensory Organs; Medical School, University of Bari; Policlinico Bari I-70124 Italy
| | - Laura Croci
- Division of Neuroscience; San Raffaele Scientific Institute; Milano I-20132 Italy
| | - G. Giacomo Consalez
- Division of Neuroscience; San Raffaele Scientific Institute; Milano I-20132 Italy
- Università Vita-Salute San Raffaele; Milano I-20132 Italy
| | - Gianfranco Gennarini
- Department of Basic Medical Sciences, Neurosciences and Sensory Organs; Medical School, University of Bari; Policlinico Bari I-70124 Italy
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192
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Ketschek A, Jones S, Spillane M, Korobova F, Svitkina T, Gallo G. Nerve growth factor promotes reorganization of the axonal microtubule array at sites of axon collateral branching. Dev Neurobiol 2015; 75:1441-61. [PMID: 25846486 DOI: 10.1002/dneu.22294] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Revised: 03/13/2015] [Accepted: 03/30/2015] [Indexed: 12/31/2022]
Abstract
The localized debundling of the axonal microtubule array and the entry of microtubules into axonal filopodia are two defining features of collateral branching. We report that nerve growth factor (NGF), a branch-inducing signal, increases the frequency of microtubule debundling along the axon shaft of chicken embryonic sensory neurons. Sites of debundling correlate strongly with the localized targeting of microtubules into filopodia. Platinum replica electron microscopy suggests physical interactions between debundled microtubules and axonal actin filaments. However, as evidenced by depolymerization of actin filaments and inhibition of myosin II, actomyosin force generation does not promote debundling. In contrast, loss of actin filaments or inhibition of myosin II activity promotes debundling, indicating that axonal actomyosin forces suppress debundling. MAP1B is a microtubule associated protein that represses axon branching. Following treatment with NGF, microtubules penetrating filopodia during the early stages of branching exhibited lower levels of associated MAP1B. NGF increased and decreased the levels of MAP1B phosphorylated at a GSK-3β site (pMAP1B) along the axon shaft and within axonal filopodia, respectively. The levels of MAP1B and pMAP1B were not altered at sites of debundling, relative to the rest of the axon. Unlike the previously determined effects of NGF on the axonal actin cytoskeleton, the effects of NGF on microtubule debundling were not affected by inhibition of protein synthesis. Collectively, these data indicate that NGF promotes localized axonal microtubule debundling, that actomyosin forces antagonize microtubule debundling, and that NGF regulates pMAP1B in axonal filopodia during the early stages of collateral branch formation.
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Affiliation(s)
- Andrea Ketschek
- Department of Anatomy and Cell Biology, Shriners Hospitals Pediatric Research Center, Temple University, Philadelphia, Pennsylvania, 19140
| | - Steven Jones
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, 19104
| | - Mirela Spillane
- Department of Anatomy and Cell Biology, Shriners Hospitals Pediatric Research Center, Temple University, Philadelphia, Pennsylvania, 19140
| | - Farida Korobova
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, 19104
| | - Tatyana Svitkina
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, 19104
| | - Gianluca Gallo
- Department of Anatomy and Cell Biology, Shriners Hospitals Pediatric Research Center, Temple University, Philadelphia, Pennsylvania, 19140
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193
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Huang H, Shao Q, Qu C, Yang T, Dwyer T, Liu G. Coordinated interaction of Down syndrome cell adhesion molecule and deleted in colorectal cancer with dynamic TUBB3 mediates Netrin-1-induced axon branching. Neuroscience 2015; 293:109-22. [PMID: 25754961 DOI: 10.1016/j.neuroscience.2015.02.042] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2014] [Revised: 02/02/2015] [Accepted: 02/23/2015] [Indexed: 10/23/2022]
Abstract
Modulation of actin and microtubule (MT) dynamics in neurons is implicated in guidance cue-dependent axon outgrowth, branching and pathfinding. Although the role of MTs in axon guidance has been well known, how extracellular guidance signals engage MT behavior in axon branching remains unclear. Previously, we have shown that TUBB3, the most dynamic β-tubulin isoform in neurons, directly binds to deleted in colorectal cancer (DCC) to regulate MT dynamics in Netrin-1-mediated axon guidance. Here, we report that TUBB3 directly interacted with another Netrin-1 receptor Down syndrome cell adhesion molecule (DSCAM) and Netrin-1 increased this interaction in primary neurons. MT dynamics were required for Netrin-1-promoted association of DSCAM with TUBB3. Knockdown of either DSCAM or DCC or addition of a function blocking anti-DCC antibody mutually blocked Netrin-1-induced interactions, suggesting that DSCAM interdependently coordinated with DCC in Netrin-1-induced binding to TUBB3. Both DSCAM and DCC were partially colocalized with TUBB3 in the axon branch and the axon branching point of primary neurons and Netrin-1 increased these colocalizations. Netrin-1 induced the interaction of endogenous DSCAM with polymerized TUBB3 in primary neurons and Src family kinases (SFKs) were required for regulating this binding. Knockdown of DSCAM only, DCC only or both was sufficient to block Netrin-1-induced axon branching of E15 mouse cortical neurons. Knocking down TUBB3 inhibited Netrin-1 induced axon branching as well. These results suggest that DSCAM collaborates with DCC to regulate MT dynamics via direct binding to dynamic TUBB3 in Netrin-1-induced axon branching.
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Affiliation(s)
- H Huang
- Department of Biological Sciences, University of Toledo, 2801 West Bancroft Street, Toledo, OH 43606, USA
| | - Q Shao
- Department of Biological Sciences, University of Toledo, 2801 West Bancroft Street, Toledo, OH 43606, USA
| | - C Qu
- Department of Biological Sciences, University of Toledo, 2801 West Bancroft Street, Toledo, OH 43606, USA
| | - T Yang
- Department of Biological Sciences, University of Toledo, 2801 West Bancroft Street, Toledo, OH 43606, USA
| | - T Dwyer
- Department of Biological Sciences, University of Toledo, 2801 West Bancroft Street, Toledo, OH 43606, USA
| | - G Liu
- Department of Biological Sciences, University of Toledo, 2801 West Bancroft Street, Toledo, OH 43606, USA.
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194
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Netrin-4 regulates thalamocortical axon branching in an activity-dependent fashion. Proc Natl Acad Sci U S A 2014; 111:15226-31. [PMID: 25288737 DOI: 10.1073/pnas.1402095111] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Axon branching is remodeled by sensory-evoked and spontaneous neuronal activity. However, the underlying molecular mechanism is largely unknown. Here, we demonstrate that the netrin family member netrin-4 (NTN4) contributes to activity-dependent thalamocortical (TC) axon branching. In the postnatal developmental stages of rodents, ntn4 expression was abundant in and around the TC recipient layers of sensory cortices. Neuronal activity dramatically altered the ntn4 expression level in the cortex in vitro and in vivo. TC axon branching was promoted by exogenous NTN4 and suppressed by depletion of the endogenous protein. Moreover, unc-5 homolog B (Unc5B), which strongly bound to NTN4, was expressed in the sensory thalamus, and knockdown of Unc5B in thalamic cells markedly reduced TC axon branching. These results suggest that NTN4 acts as a positive regulator for TC axon branching through activity-dependent expression.
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195
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Abdanipour A, Schluesener HJ, Tiraihi T, Noori-Zadeh A. Systemic administration of valproic acid stimulates overexpression of microtubule-associated protein 2 in the spinal cord injury model to promote neurite outgrowth. Neurol Res 2014; 37:223-8. [DOI: 10.1179/1743132814y.0000000438] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
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196
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Steinecke A, Gampe C, Nitzsche F, Bolz J. DISC1 knockdown impairs the tangential migration of cortical interneurons by affecting the actin cytoskeleton. Front Cell Neurosci 2014; 8:190. [PMID: 25071449 PMCID: PMC4086047 DOI: 10.3389/fncel.2014.00190] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Accepted: 06/20/2014] [Indexed: 12/29/2022] Open
Abstract
Disrupted-in-Schizophrenia 1 (DISC1) is a risk gene for a spectrum of major mental disorders. It has been shown to regulate radial migration as well as dendritic arborization during neurodevelopment and corticogenesis. In a previous study we demonstrated through in vitro experiments that DISC1 also controls the tangential migration of cortical interneurons originating from the medial ganglionic eminence (MGE). Here we first show that DISC1 is necessary for the proper tangential migration of cortical interneurons in the intact brain. Expression of EGFP under the Lhx6 promotor allowed us to analyze exclusively interneurons transfected in the MGE after in utero electroporation. After 3 days in utero, DISC1 deficient interneurons displayed prolonged leading processes and, compared to control, fewer neurons reached the cortex. Time-lapse video microscopy of cortical feeder-layers revealed a decreased migration velocity due to a reduction of soma translocations. Immunostainings indicated that DISC1 is co-localized with F-actin in the growth cone-like structure of the leading process. DISC1 knockdown reduced F-actin levels whereas the overall actin level was not altered. Moreover, DISC1 knockdown also decreased levels of phosphorylated Girdin, which cross-links F-actin, as well as the Girdin-activator pAkt. In contrast, using time-lapse video microscopy of fluorescence-tagged tubulin and EB3 in fibroblasts, we found no effects on microtubule polymerization when DISC1 was reduced. However, DISC1 affected the acetylation of microtubules in the leading processes of MGE-derived cortical interneurons. Together, our results provide a mechanism how DISC1 might contribute to interneuron migration thereby explaining the reduced number of specific classes of cortical interneurons in some DISC1 mouse models.
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Affiliation(s)
- André Steinecke
- Universität Jena, Institut für Allgemeine Zoologie und Tierphysiologie Jena, Germany
| | - Christin Gampe
- Universität Jena, Institut für Allgemeine Zoologie und Tierphysiologie Jena, Germany
| | - Falk Nitzsche
- Universität Jena, Institut für Allgemeine Zoologie und Tierphysiologie Jena, Germany
| | - Jürgen Bolz
- Universität Jena, Institut für Allgemeine Zoologie und Tierphysiologie Jena, Germany
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197
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Nordman JC, Kabbani N. Microtubule dynamics at the growth cone are mediated by α7 nicotinic receptor activation of a Gαq and IP3 receptor pathway. FASEB J 2014; 28:2995-3006. [PMID: 24687992 DOI: 10.1096/fj.14-251439] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The α7 nicotinic receptor (α7) plays an important role in neuronal growth and structural plasticity in the developing brain. We have recently characterized a G-protein-signaling pathway regulated by α7 that directs the growth of neurites in developing neural cells. Now we show that choline activation of α7 promotes a rise in intracellular calcium from local ER stores via Gαq signaling, leading to IP3 receptor (IP3R) activation at the growth cone of differentiating PC12 cells. A mutant α7 significantly attenuated in calcium conductance (D44A; P<0.001) was found to be unable to promote IP3R signaling and calcium store release. In addition, calcium elevation via α7 correlates with a significant attenuation in the rate of microtubule invasion of the growth cone (P<0.001). This process was also attenuated in the D44A mutant and blocked by an inhibitor of the IP3R, suggesting that calcium flow through the α7 channel and activation of the Gαq pathway are necessary for growth. Taken together, the findings reveal an inhibitory mechanism of α7 on cytoskeletal growth via the intracellular calcium activity of the receptor channel and the Gαq signaling pathway at the growth cone.-Nordman, J. C., Kabbani, N. Microtubule dynamics at the growth cone are mediated by α7 nicotinic receptor activation of a Gαq and IP3 receptor pathway.
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Affiliation(s)
- Jacob C Nordman
- Department of Molecular Neuroscience, Krasnow Institute for Advanced Study, George Mason University, Fairfax, Virginia, USA
| | - Nadine Kabbani
- Department of Molecular Neuroscience, Krasnow Institute for Advanced Study, George Mason University, Fairfax, Virginia, USA
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