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Priest JM, Nichols EL, Smock RG, Hopkins JB, Mendoza JL, Meijers R, Shen K, Özkan E. Structural insights into the formation of repulsive netrin guidance complexes. SCIENCE ADVANCES 2024; 10:eadj8083. [PMID: 38363837 PMCID: PMC10871540 DOI: 10.1126/sciadv.adj8083] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Accepted: 01/17/2024] [Indexed: 02/18/2024]
Abstract
Netrins dictate attractive and repulsive responses during axon growth and cell migration, where the presence of the receptor Uncoordinated-5 (UNC-5) on target cells results in repulsion. Here, we showed that UNC-5 is a heparin-binding protein, determined its structure bound to a heparin fragment, and could modulate UNC-5-heparin affinity using a directed evolution platform or structure-based rational design. We demonstrated that UNC-5 and UNC-6/netrin form a large, stable, and rigid complex in the presence of heparin, and heparin and UNC-5 exclude the attractive UNC-40/DCC receptor from binding to UNC-6/netrin to a large extent. Caenorhabditis elegans with a heparin-binding-deficient UNC-5 fail to establish proper gonad morphology due to abrogated cell migration, which relies on repulsive UNC-5 signaling in response to UNC-6. Combining UNC-5 mutations targeting heparin and UNC-6/netrin contacts results in complete cell migration and axon guidance defects. Our findings establish repulsive netrin responses to be mediated through a glycosaminoglycan-regulated macromolecular complex.
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Affiliation(s)
- Jessica M. Priest
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL 60637, USA
- Institute for Neuroscience, University of Chicago, Chicago, IL 60637, USA
- Institute for Biophysical Dynamics, University of Chicago, Chicago, IL 60637, USA
| | - Ev L. Nichols
- Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305, USA
- Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - Robert G. Smock
- European Molecular Biology Laboratory (EMBL), Hamburg Site, c/o DESY, 22603 Hamburg, Germany
| | - Jesse B. Hopkins
- The Biophysics Collaborative Access Team (BioCAT), Argonne National Laboratory, Illinois Institute of Technology, Chicago, IL 60616, USA
- Department of Physics, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Juan L. Mendoza
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL 60637, USA
- Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL 60637, USA
| | - Rob Meijers
- European Molecular Biology Laboratory (EMBL), Hamburg Site, c/o DESY, 22603 Hamburg, Germany
- Institute for Protein Innovation (IPI), Boston, MA 02115, USA
| | - Kang Shen
- Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305, USA
- Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - Engin Özkan
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL 60637, USA
- Institute for Neuroscience, University of Chicago, Chicago, IL 60637, USA
- Institute for Biophysical Dynamics, University of Chicago, Chicago, IL 60637, USA
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2
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Pillai EK, Franze K. Mechanics in the nervous system: From development to disease. Neuron 2024; 112:342-361. [PMID: 37967561 DOI: 10.1016/j.neuron.2023.10.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 09/29/2023] [Accepted: 10/04/2023] [Indexed: 11/17/2023]
Abstract
Physical forces are ubiquitous in biological processes across scales and diverse contexts. This review highlights the significance of mechanical forces in nervous system development, homeostasis, and disease. We provide an overview of mechanical signals present in the nervous system and delve into mechanotransduction mechanisms translating these mechanical cues into biochemical signals. During development, mechanical cues regulate a plethora of processes, including cell proliferation, differentiation, migration, network formation, and cortex folding. Forces then continue exerting their influence on physiological processes, such as neuronal activity, glial cell function, and the interplay between these different cell types. Notably, changes in tissue mechanics manifest in neurodegenerative diseases and brain tumors, potentially offering new diagnostic and therapeutic target opportunities. Understanding the role of cellular forces and tissue mechanics in nervous system physiology and pathology adds a new facet to neurobiology, shedding new light on many processes that remain incompletely understood.
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Affiliation(s)
- Eva K Pillai
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3DY, UK; Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Meyerhofstraße 1, 69117 Heidelberg, Germany; Developmental Biology Unit, European Molecular Biology Laboratory, Meyerhofstraße 1, 69117 Heidelberg, Germany.
| | - Kristian Franze
- Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3DY, UK; Institute of Medical Physics and Microtissue Engineering, Friedrich-Alexander-Universität Erlangen-Nürnberg, Henkestraße 91, 91052 Erlangen, Germany; Max-Planck-Zentrum für Physik und Medizin, Kussmaulallee 1, 91054 Erlangen, Germany.
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3
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Qiu Z, Minegishi T, Aoki D, Abe K, Baba K, Inagaki N. Adhesion-clutch between DCC and netrin-1 mediates netrin-1-induced axonal haptotaxis. Front Mol Neurosci 2024; 17:1307755. [PMID: 38375502 PMCID: PMC10875621 DOI: 10.3389/fnmol.2024.1307755] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Accepted: 01/08/2024] [Indexed: 02/21/2024] Open
Abstract
The growth cone, a motile structure located at the tip of growing axons, senses extracellular guidance cues and translates them into directional forces that drive axon outgrowth and guidance. Axon guidance directed by chemical cues on the extracellular adhesive substrate is termed haptotaxis. Recent studies reported that netrin-1 on the substrate functions as a haptotactic axon guidance cue. However, the mechanism mediating netrin-1-induced axonal haptotaxis remains unclear. Here, we demonstrate that substrate-bound netrin-1 induces axonal haptotaxis by facilitating physical interactions between the netrin-1 receptor, DCC, and the adhesive substrates. DCC serves as an adhesion receptor for netrin-1. The clutch-linker molecule shootin1a interacted with DCC, linking it to actin filament retrograde flow at the growth cone. Speckle imaging analyses showed that DCC underwent either grip (stop) or retrograde slip on the adhesive substrate. The grip state was more prevalent on netrin-1-coated substrate compared to the control substrate polylysine, thereby transmitting larger traction force on the netrin-1-coated substrate. Furthermore, disruption of the linkage between actin filament retrograde flow and DCC by shootin1 knockout impaired netrin-1-induced axonal haptotaxis. These results suggest that the directional force for netrin-1-induced haptotaxis is exerted on the substrates through the adhesion-clutch between DCC and netrin-1 which occurs asymmetrically within the growth cone.
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Affiliation(s)
| | | | | | | | | | - Naoyuki Inagaki
- Laboratory of Systems Neurobiology and Medicine, Division of Biological Science, Nara Institute of Science and Technology, Nara, Japan
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4
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Anggraini D, Zhang T, Liu X, Okano K, Tanaka Y, Inagaki N, Li M, Hosokawa Y, Yamada S, Yalikun Y. Guided axon outgrowth of neurons by molecular gradients generated from femtosecond laser-fabricated micro-holes. Talanta 2024; 267:125200. [PMID: 37738745 DOI: 10.1016/j.talanta.2023.125200] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Revised: 09/04/2023] [Accepted: 09/11/2023] [Indexed: 09/24/2023]
Abstract
OBJECTIVE Transplantation of scaffold-embedded guided neurons has been reported to increase neuronal regeneration following brain injury. However, precise axonal integration between host and transplant neurons to form functional synapses remains a major problem. Thus, a high-precision tool to actuate neuronal axon outgrowth in real-time conditions is required to attain robust axon regeneration. This study aims to establish a microfluidic platform for precise and real-time axon outgrowth guidance. METHODS A microfluidic device with a 4 μm thick thin-glass sheet as the neuron culture substrate is fabricated. Surface of the glass sheet is chemically modified to facilitate neuron attachment. Femtosecond (fs) laser is used to engrave the glass sheet to achieve micro-holes, where netrin-1 is released for directing the movement of the neuronal axon. RESULTS Numerical simulation and experimental data demonstrate that netrin-1 gradient is formed after it passes through the micro-hole. The neuronal response results show the outgrowth rate of the axon is significantly increased by netrin-1 gradient. Furthermore, a majority of neuronal axons exhibit guided outgrowth characterized by positive turning angles of axon displacement in the direction of netrin-1 gradients. CONCLUSION Integrating fs laser and microfluidic device facilitates controlled and instantaneous axon outgrowth in a non-invasive manner. SIGNIFICANCE The developed real-time microfluidic platform shows potential in the application for on-site neuronal transplantation, which is significant for the treatment of a range of neurological disorders and injuries.
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Affiliation(s)
- Dian Anggraini
- Division of Materials Science, Nara Institute of Science and Technology, Ikoma, 630-0192, Japan
| | - Tianlong Zhang
- College of Mechanical Engineering, Jiangsu University of Science and Technology, Zhenjiang, 212100, China
| | - Xun Liu
- Division of Materials Science, Nara Institute of Science and Technology, Ikoma, 630-0192, Japan
| | - Kazunori Okano
- Division of Materials Science, Nara Institute of Science and Technology, Ikoma, 630-0192, Japan
| | - Yo Tanaka
- Center for Biosystems Dynamics Research (BDR), RIKEN, Osaka, 565-0871, Japan
| | - Naoyuki Inagaki
- Division of Biological Science, Nara Institute of Science and Technology, Ikoma, 630-0192, Japan
| | - Ming Li
- School of Engineering, Macquarie University, Sydney, 2122, Australia
| | - Yoichiroh Hosokawa
- Division of Materials Science, Nara Institute of Science and Technology, Ikoma, 630-0192, Japan
| | - Sohei Yamada
- Division of Materials Science, Nara Institute of Science and Technology, Ikoma, 630-0192, Japan.
| | - Yaxiaer Yalikun
- Division of Materials Science, Nara Institute of Science and Technology, Ikoma, 630-0192, Japan; Center for Biosystems Dynamics Research (BDR), RIKEN, Osaka, 565-0871, Japan.
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Guan K, Curtis ER, Lew DJ, Elston TC. Particle-based simulations reveal two positive feedback loops allow relocation and stabilization of the polarity site during yeast mating. PLoS Comput Biol 2023; 19:e1011523. [PMID: 37782676 PMCID: PMC10569529 DOI: 10.1371/journal.pcbi.1011523] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Revised: 10/12/2023] [Accepted: 09/17/2023] [Indexed: 10/04/2023] Open
Abstract
Many cells adjust the direction of polarized growth or migration in response to external directional cues. The yeast Saccharomyces cerevisiae orient their cell fronts (also called polarity sites) up pheromone gradients in the course of mating. However, the initial polarity site is often not oriented towards the eventual mating partner, and cells relocate the polarity site in an indecisive manner before developing a stable orientation. During this reorientation phase, the polarity site displays erratic assembly-disassembly behavior and moves around the cell cortex. The mechanisms underlying this dynamic behavior remain poorly understood. Particle-based simulations of the core polarity circuit revealed that molecular-level fluctuations are unlikely to overcome the strong positive feedback required for polarization and generate relocating polarity sites. Surprisingly, inclusion of a second pathway that promotes polarity site orientation generated relocating polarity sites with properties similar to those observed experimentally. This pathway forms a second positive feedback loop involving the recruitment of receptors to the cell membrane and couples polarity establishment to gradient sensing. This second positive feedback loop also allows cells to stabilize their polarity site once the site is aligned with the pheromone gradient.
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Affiliation(s)
- Kaiyun Guan
- Curriculum in Bioinformatics and Computational Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Erin R. Curtis
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Daniel J. Lew
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Timothy C. Elston
- Department of Pharmacology and Computational Medicine Program, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
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Ros O, Nicol X. Axon pathfinding and targeting: (R)evolution of insights from in vitro assays. Neuroscience 2023; 508:110-122. [PMID: 36096337 DOI: 10.1016/j.neuroscience.2022.09.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 09/01/2022] [Accepted: 09/05/2022] [Indexed: 01/17/2023]
Abstract
Investigating axonal behaviors while neurons are connecting with each other has been a challenge since the early studies on nervous system development. While molecule-driven axon pathfinding has been theorized by observing neurons at different developmental stages in vivo, direct observation and measurements of axon guidance behaviors required the invention of in vitro systems enabling to test the impact of molecules or cellular extracts on axons growing in vitro. With time, the development of novel in vivo approaches has confirmed the mechanisms highlighted in culture and has led in vitro systems to be adapted for cellular processes that are still inaccessible in intact organisms. We here review the evolution of these in vitro assays, which started with crucial contributions from the Bonhoeffer lab.
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Affiliation(s)
- Oriol Ros
- Universitat de Barcelona, Department of Cell Biology, Physiology and Immunology, Avinguda Diagonal 643, 08028 Barcelona, Catalonia, Spain
| | - Xavier Nicol
- Sorbonne Université, Inserm, CNRS, Institut de la Vision, 17 rue Moreau, F-75012 Paris, France.
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7
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The netrin-1 receptor UNC5C contributes to the homeostasis of undifferentiated spermatogonia in adult mice. Stem Cell Res 2022; 60:102723. [PMID: 35247845 DOI: 10.1016/j.scr.2022.102723] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 02/21/2022] [Accepted: 02/23/2022] [Indexed: 11/24/2022] Open
Abstract
In adult testis, the cell mobility is essential for spermatogonia differentiation and is suspected to regulate spermatogonial stem cell fate. Netrin-1 controls cell migration and/or survival according to the cellular context. Its involvement in some self-renewing lineages raises the possibility that Netrin-1 could have a role in spermatogenesis. We show that in addition to Sertoli cells, a fraction of murine undifferentiated spermatogonia express the Netrin-1 receptor UNC5c and that UNC5c contributes to spermatogonia differentiation. Receptor loss in Unc5crcm males leads to the concomitant accumulation of transit-amplifying progenitors and short syncytia of spermatogonia. Without altering cell death rates, the consequences of Unc5c loss worsen with age: the increase in quiescent undifferentiated progenitors associated with a higher spermatogonial stem cell enriched subset leads to the spermatocyte I decline. We demonstrate in vitro that Netrin-1 promotes a guidance effect as it repulses both undifferentiated and differentiating spermatogonia. Finally, we propose that UNC5c triggers undifferentiated spermatogonia adhesion/ migration and that the repulsive activity of Netrin-1 receptors could regulate spermatogonia differentiation, and maintain germ cell homeostasis.
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8
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Li Y, Wang Y, Xue F, Feng X, Ba Z, Chen J, Zhou Z, Wang Y, Guan G, Yang G, Xi Z, Tian H, Liu Y, Tan J, Li G, Chen X, Yang M, Chen W, Zhu C, Zeng W. Programmable dual responsive system reconstructing nerve interaction with small-diameter tissue-engineered vascular grafts and inhibiting intimal hyperplasia in diabetes. Bioact Mater 2021; 7:466-477. [PMID: 34466746 PMCID: PMC8379357 DOI: 10.1016/j.bioactmat.2021.05.034] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2021] [Revised: 05/20/2021] [Accepted: 05/20/2021] [Indexed: 01/03/2023] Open
Abstract
Small-diameter tissue-engineered vascular grafts (sdTEVGs) with hyperglycemia resistance have not been constructed. The intimal hyperplasia caused by hyperglycemia remains problem to hinder the patency of sdTEVGs. Here, inspired by bionic regulation of nerve on vascular, we found the released neural exosomes could inhibit the abnormal phenotype transformation of vascular smooth muscle cells (VSMCs). The transformation was a prime culprit causing the intimal hyperplasia of sdTEVGs. To address this concern, sdTEVGs were modified with an on-demand programmable dual-responsive system of ultrathin hydrogels. An external primary Reactive Oxygen Species (ROS)-responsive Netrin-1 system was initially triggered by local inflammation to induce nerve remolding of the sdTEVGs overcoming the difficulty of nerve regeneration under hyperglycemia. Then, the internal secondary ATP-responsive DENND1A (guanine nucleotide exchange factor) system was turned on by the neurotransmitter ATP from the immigrated nerve fibers to stimulate effective release of neural exosomes. The results showed nerve fibers grow into the sdTEVGs in diabetic rats 30 days after transplantation. At day 90, the abnormal VSMCs phenotype was not detected in the sdTEVGs, which maintained long-time patency without intima hyperplasia. Our study provides new insights to construct vascular grafts resisting hyperglycemia damage. VSMCs undergo a phenotypic transformation under high glucose, which lead to intimal hyperplasia in sdTEVGs. Neural exosomes could inhibit the abnormal phenotype transformation of VSMCs from contractile to synthetic. SdTEVGs with on-demand programmable dual responsive system inhibited intimal hyperplasia in diabetes.
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Affiliation(s)
- Yanzhao Li
- Department of Anatomy, National and Regional Engineering Laboratory of Tissue Engineering, State and Local Joint Engineering Laboratory for Vascular Implants, Key Lab for Biomechanics and Tissue Engineering of Chongqing, Third Military Medical University, Chongqing, 400038, China
| | - Yeqin Wang
- Department of Cell Biology, Third Military Army Medical University, Chongqing, 400038, China
| | - Fangchao Xue
- Department of Cell Biology, Third Military Army Medical University, Chongqing, 400038, China
| | - Xuli Feng
- Innovative Drug Research Centre of Chongqing University, Chongqing, 401331, China
| | - Zhaojing Ba
- Department of Cell Biology, Third Military Army Medical University, Chongqing, 400038, China
| | - Junjie Chen
- Department of Cell Biology, Third Military Army Medical University, Chongqing, 400038, China
| | - Zhenhua Zhou
- Departments of Neurology, Southwest Hospital, Third Military Medical University, Chongqing, China
| | - Yanhong Wang
- Department of Cell Biology, Third Military Army Medical University, Chongqing, 400038, China
| | - Ge Guan
- Department of Anatomy, National and Regional Engineering Laboratory of Tissue Engineering, State and Local Joint Engineering Laboratory for Vascular Implants, Key Lab for Biomechanics and Tissue Engineering of Chongqing, Third Military Medical University, Chongqing, 400038, China
| | - Guanyuan Yang
- Department of Anatomy, National and Regional Engineering Laboratory of Tissue Engineering, State and Local Joint Engineering Laboratory for Vascular Implants, Key Lab for Biomechanics and Tissue Engineering of Chongqing, Third Military Medical University, Chongqing, 400038, China
| | - Ziwei Xi
- Department of Anatomy, National and Regional Engineering Laboratory of Tissue Engineering, State and Local Joint Engineering Laboratory for Vascular Implants, Key Lab for Biomechanics and Tissue Engineering of Chongqing, Third Military Medical University, Chongqing, 400038, China
| | - Hao Tian
- Department of Anatomy, National and Regional Engineering Laboratory of Tissue Engineering, State and Local Joint Engineering Laboratory for Vascular Implants, Key Lab for Biomechanics and Tissue Engineering of Chongqing, Third Military Medical University, Chongqing, 400038, China
| | - Yong Liu
- Department of Anatomy, National and Regional Engineering Laboratory of Tissue Engineering, State and Local Joint Engineering Laboratory for Vascular Implants, Key Lab for Biomechanics and Tissue Engineering of Chongqing, Third Military Medical University, Chongqing, 400038, China
| | - Ju Tan
- Department of Anatomy, National and Regional Engineering Laboratory of Tissue Engineering, State and Local Joint Engineering Laboratory for Vascular Implants, Key Lab for Biomechanics and Tissue Engineering of Chongqing, Third Military Medical University, Chongqing, 400038, China
| | - Gang Li
- Department of Anatomy, National and Regional Engineering Laboratory of Tissue Engineering, State and Local Joint Engineering Laboratory for Vascular Implants, Key Lab for Biomechanics and Tissue Engineering of Chongqing, Third Military Medical University, Chongqing, 400038, China
| | - Xiewan Chen
- Medical English Department, Third Military Medical University, Chongqing, 400038, China
| | - Mingcan Yang
- Department of Anatomy, National and Regional Engineering Laboratory of Tissue Engineering, State and Local Joint Engineering Laboratory for Vascular Implants, Key Lab for Biomechanics and Tissue Engineering of Chongqing, Third Military Medical University, Chongqing, 400038, China
| | - Wen Chen
- The 8th Medical Center of Chinese PLA General Hospital, Beijing, 100091, China
| | - Chuhong Zhu
- Department of Anatomy, National and Regional Engineering Laboratory of Tissue Engineering, State and Local Joint Engineering Laboratory for Vascular Implants, Key Lab for Biomechanics and Tissue Engineering of Chongqing, Third Military Medical University, Chongqing, 400038, China.,The 8th Medical Center of Chinese PLA General Hospital, Beijing, 100091, China.,Department of Plastic and Aesthetic Surgery, Southwest Hospital, Third Military Medical University, Chongqing, China
| | - Wen Zeng
- Department of Cell Biology, Third Military Army Medical University, Chongqing, 400038, China.,Departments of Neurology, Southwest Hospital, Third Military Medical University, Chongqing, China.,State Key Laboratory of Trauma, Burn and Combined Injury, Chongqing, China
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Raj V, Jagadish C, Gautam V. Understanding, engineering, and modulating the growth of neural networks: An interdisciplinary approach. BIOPHYSICS REVIEWS 2021; 2:021303. [PMID: 38505122 PMCID: PMC10903502 DOI: 10.1063/5.0043014] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Accepted: 05/25/2021] [Indexed: 03/21/2024]
Abstract
A deeper understanding of the brain and its function remains one of the most significant scientific challenges. It not only is required to find cures for a plethora of brain-related diseases and injuries but also opens up possibilities for achieving technological wonders, such as brain-machine interface and highly energy-efficient computing devices. Central to the brain's function is its basic functioning unit (i.e., the neuron). There has been a tremendous effort to understand the underlying mechanisms of neuronal growth on both biochemical and biophysical levels. In the past decade, this increased understanding has led to the possibility of controlling and modulating neuronal growth in vitro through external chemical and physical methods. We provide a detailed overview of the most fundamental aspects of neuronal growth and discuss how researchers are using interdisciplinary ideas to engineer neuronal networks in vitro. We first discuss the biochemical and biophysical mechanisms of neuronal growth as we stress the fact that the biochemical or biophysical processes during neuronal growth are not independent of each other but, rather, are complementary. Next, we discuss how utilizing these fundamental mechanisms can enable control over neuronal growth for advanced neuroengineering and biomedical applications. At the end of this review, we discuss some of the open questions and our perspectives on the challenges and possibilities related to controlling and engineering the growth of neuronal networks, specifically in relation to the materials, substrates, model systems, modulation techniques, data science, and artificial intelligence.
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Affiliation(s)
- Vidur Raj
- Department of Electronic Materials Engineering, Research School of Physics, The Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | | | - Vini Gautam
- Department of Biomedical Engineering, Faculty of Engineering and Information Technology, The University of Melbourne, Melbourne, Victoria 3010, Australia
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10
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Axon Growth of CNS Neurons in Three Dimensions Is Amoeboid and Independent of Adhesions. Cell Rep 2021; 32:107907. [PMID: 32698008 DOI: 10.1016/j.celrep.2020.107907] [Citation(s) in RCA: 54] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Revised: 05/26/2020] [Accepted: 06/23/2020] [Indexed: 01/01/2023] Open
Abstract
During development of the central nervous system (CNS), neurons polarize and rapidly extend their axons to assemble neuronal circuits. The growth cone leads the axon to its target and drives axon growth. Here, we explored the mechanisms underlying axon growth in three dimensions. Live in situ imaging and super-resolution microscopy combined with pharmacological and molecular manipulations as well as biophysical force measurements revealed that growth cones extend CNS axons independent of pulling forces on their substrates and without the need for adhesions in three-dimensional (3D) environments. In 3D, microtubules grow unrestrained from the actomyosin cytoskeleton into the growth cone leading edge to enable rapid axon extension. Axons extend and polarize even in adhesion-inert matrices. Thus, CNS neurons use amoeboid mechanisms to drive axon growth. Together with our understanding that adult CNS axons regenerate by reactivating developmental processes, our findings illuminate how cytoskeletal manipulations enable axon regeneration in the adult CNS.
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11
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Alvarez S, Varadarajan SG, Butler SJ. Dorsal commissural axon guidance in the developing spinal cord. Curr Top Dev Biol 2020; 142:197-231. [PMID: 33706918 DOI: 10.1016/bs.ctdb.2020.10.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Commissural axons have been a key model system for identifying axon guidance signals in vertebrates. This review summarizes the current thinking about the molecular and cellular mechanisms that establish a specific commissural neural circuit: the dI1 neurons in the developing spinal cord. We assess the contribution of long- and short-range signaling while sequentially following the developmental timeline from the birth of dI1 neurons, to the extension of commissural axons first circumferentially and then contralaterally into the ventral funiculus.
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Affiliation(s)
- Sandy Alvarez
- Department of Neurobiology, University of California, Los Angeles, CA, United States; Molecular Biology Interdepartmental Doctoral Program, University of California, Los Angeles, CA, United States
| | | | - Samantha J Butler
- Department of Neurobiology, University of California, Los Angeles, CA, United States; Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California, Los Angeles, CA, United States.
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12
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Torres-Berrío A, Hernandez G, Nestler EJ, Flores C. The Netrin-1/DCC Guidance Cue Pathway as a Molecular Target in Depression: Translational Evidence. Biol Psychiatry 2020; 88:611-624. [PMID: 32593422 PMCID: PMC7529861 DOI: 10.1016/j.biopsych.2020.04.025] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Revised: 04/14/2020] [Accepted: 04/28/2020] [Indexed: 12/15/2022]
Abstract
The Netrin-1/DCC guidance cue pathway plays a critical role in guiding growing axons toward the prefrontal cortex during adolescence and in the maturational organization and adult plasticity of prefrontal cortex connectivity. In this review, we put forward the idea that alterations in prefrontal cortex architecture and function, which are intrinsically linked to the development of major depressive disorder, originate in part from the dysregulation of the Netrin-1/DCC pathway by a mechanism that involves microRNA-218. We discuss evidence derived from mouse models of stress and from human postmortem brain and genome-wide association studies indicating an association between the Netrin-1/DCC pathway and major depressive disorder. We propose a potential role of circulating microRNA-218 as a biomarker of stress vulnerability and major depressive disorder.
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Affiliation(s)
- Angélica Torres-Berrío
- Integrated Program in Neuroscience, Montreal, Quebec, Canada; Nash Family Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, New York
| | | | - Eric J Nestler
- Nash Family Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Cecilia Flores
- Department of Psychiatry, McGill University, Montreal, Quebec, Canada; Douglas Mental Health University Institute, Montreal, Quebec, Canada.
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13
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Ghate K, Mutalik SP, Sthanam LK, Sen S, Ghose A. Fmn2 Regulates Growth Cone Motility by Mediating a Molecular Clutch to Generate Traction Forces. Neuroscience 2020; 448:160-171. [PMID: 33002558 DOI: 10.1016/j.neuroscience.2020.09.046] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Revised: 09/10/2020] [Accepted: 09/22/2020] [Indexed: 01/06/2023]
Abstract
Growth cone-mediated axonal outgrowth and accurate synaptic targeting are central to brain morphogenesis. Translocation of the growth cone necessitates mechanochemical regulation of cell-extracellular matrix interactions and the generation of propulsive traction forces onto the growth environment. However, the molecular mechanisms subserving force generation by growth cones remain poorly characterized. The formin family member, Fmn2, has been identified earlier as a regulator of growth cone motility. Here, we explore the mechanisms underlying Fmn2 function in the growth cone. Evaluation of multiple components of the adhesion complexes suggests that Fmn2 regulates point contact stability. Analysis of F-actin retrograde flow reveals that Fmn2 functions as a clutch molecule and mediates the coupling of the actin cytoskeleton to the growth substrate, via point contact adhesion complexes. Using traction force microscopy, we show that the Fmn2-mediated clutch function is necessary for the generation of traction stresses by neurons. Our findings suggest that Fmn2, a protein associated with neurodevelopmental and neurodegenerative disorders, is a key regulator of a molecular clutch activity and consequently motility of neuronal growth cones.
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Affiliation(s)
- Ketakee Ghate
- Indian Institute of Science Education and Research (IISER) Pune, Dr. Homi Bhabha Road, Pune 411008, India
| | - Sampada P Mutalik
- Indian Institute of Science Education and Research (IISER) Pune, Dr. Homi Bhabha Road, Pune 411008, India
| | - Lakshmi Kavitha Sthanam
- Department of Biosciences and Bioengineering, Indian Institute of Technology (IIT) Bombay, Mumbai 400076, India
| | - Shamik Sen
- Department of Biosciences and Bioengineering, Indian Institute of Technology (IIT) Bombay, Mumbai 400076, India
| | - Aurnab Ghose
- Indian Institute of Science Education and Research (IISER) Pune, Dr. Homi Bhabha Road, Pune 411008, India.
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14
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Mu X, Li W, Ze X, Li L, Wang G, Hong F, Ze Y. Molecular mechanism of nanoparticulate TiO 2 induction of axonal development inhibition in rat primary cultured hippocampal neurons. ENVIRONMENTAL TOXICOLOGY 2020; 35:895-905. [PMID: 32329576 DOI: 10.1002/tox.22926] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Revised: 03/16/2020] [Accepted: 03/20/2020] [Indexed: 06/11/2023]
Abstract
Numerous studies have demonstrated the in vitro and in vivo neurotoxicity of nanoparticulate titanium dioxide (nano-TiO2 ), a mass-produced material for a large number of commercial and industrial applications. The mechanism of nano-TiO2 -induced inhibition of axonal development, however, is still unclear. In our study, primary cultured hippocampal neurons of 24-hour-old fetal Sprague-Dawley rats were exposed to 5, 15, or 30 μg/mL nano-TiO2 for 6, 12, and 24 hours, and the toxic effects of nano-TiO2 exposure on the axons development were detected and its molecular mechanism investigated. Nano-TiO2 accumulated in hippocampal neurons and inhibited the development of axons as nano-TiO2 concentrations increased. Increasing time in culture resulted in decreasing axon length by 32.5%, 36.6%, and 53.8% at 6 hours, by 49.4%, 53.8%, and 69.5% at 12 hours, and by 44.5%, 58.2%, and 63.6% at 24 hours, for 5, 15, and 30 μg/mL nano-TiO2 , respectively. Furthermore, nano-TiO2 downregulated expression of Netrin-1, growth-associated protein-43, and Neuropilin-1, and promoted an increase of semaphorin type 3A and Nogo-A. These studies suggest that nano-TiO2 inhibited axonal development in rat primary cultured hippocampal neurons and this phenomenon is related to changes in the expression of axon growth-related factors.
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Affiliation(s)
- Xu Mu
- Department of Biochemistry and Molecular Biology, School of Basic Medical and Biological Sciences, Soochow University, Suzhou, China
| | - Wuyan Li
- Department of Biochemistry and Molecular Biology, School of Basic Medical and Biological Sciences, Soochow University, Suzhou, China
| | - Xiao Ze
- Department of Orthopedics, The Second Affiliated Hospital of Soochow University, Suzhou, China
| | - Lingjuan Li
- Department of Biochemistry and Molecular Biology, School of Basic Medical and Biological Sciences, Soochow University, Suzhou, China
| | - Guoqing Wang
- Department of Physiology and Neurobiology, School of Basic Medical and Biological Sciences, Soochow University, Suzhou, China
| | - Fashui Hong
- Jiangsu Collaborative Innovation Center of Regional Modern Agriculture and Environmental Protection, Huaiyin Normal University, Huaian, China
- Department of Biotechnology, School of Life Sciences, Huaiyin Normal University, Huaian, China
| | - Yuguan Ze
- Department of Biochemistry and Molecular Biology, School of Basic Medical and Biological Sciences, Soochow University, Suzhou, China
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15
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Abstract
The brain is our most complex organ. During development, neurons extend axons, which may grow over long distances along well-defined pathways to connect to distant targets. Our current understanding of axon pathfinding is largely based on chemical signaling by attractive and repulsive guidance cues. These cues instruct motile growth cones, the leading tips of growing axons, where to turn and where to stop. However, it is not chemical signals that cause motion-motion is driven by forces. Yet our current understanding of the mechanical regulation of axon growth is very limited. In this review, I discuss the origin of the cellular forces controlling axon growth and pathfinding, and how mechanical signals encountered by growing axons may be integrated with chemical signals. This mechanochemical cross talk is an important but often overlooked aspect of cell motility that has major implications for many physiological and pathological processes involving neuronal growth.
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Affiliation(s)
- Kristian Franze
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3DY, United Kingdom;
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16
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Abstract
The spinal cord receives, relays and processes sensory information from the periphery and integrates this information with descending inputs from supraspinal centres to elicit precise and appropriate behavioural responses and orchestrate body movements. Understanding how the spinal cord circuits that achieve this integration are wired during development is the focus of much research interest. Several families of proteins have well-established roles in guiding developing spinal cord axons, and recent findings have identified new axon guidance molecules. Nevertheless, an integrated view of spinal cord network development is lacking, and many current models have neglected the cellular and functional diversity of spinal cord circuits. Recent advances challenge the existing spinal cord axon guidance dogmas and have provided a more complex, but more faithful, picture of the ontogenesis of vertebrate spinal cord circuits.
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17
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Meijers R, Smock RG, Zhang Y, Wang JH. Netrin Synergizes Signaling and Adhesion through DCC. Trends Biochem Sci 2019; 45:6-12. [PMID: 31704057 DOI: 10.1016/j.tibs.2019.10.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Revised: 10/09/2019] [Accepted: 10/14/2019] [Indexed: 01/08/2023]
Abstract
Netrin is a prototypical axon guidance cue. Structural studies have revealed how netrin interacts with the deleted in colorectal cancer (DCC) receptor, other receptors, and co-factors for signaling. Recently, genetic studies suggested that netrin is involved in neuronal haptotaxis, which requires a reversible adhesion process. Structural data indicate that netrin can also mediate trans-adhesion between apposing cells decorated with its receptors on the condition that the auxiliary guidance cue draxin is present. Here, we propose that netrin is involved in conditional adhesion, a reversible and localized process that can contribute to cell adhesion and migration. We suggest that netrin-mediated adhesion and signaling are linked, and that local environmental factors in the ventricular zone, the floor plate, or other tissues coordinate its function.
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Affiliation(s)
- Rob Meijers
- European Molecular Biology Laboratory (EMBL), Hamburg Outstation, Notkestrasse 85, D-22607 Hamburg, Germany.
| | - Robert G Smock
- European Molecular Biology Laboratory (EMBL), Hamburg Outstation, Notkestrasse 85, D-22607 Hamburg, Germany
| | - Yan Zhang
- State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, Beijing 100871 China
| | - Jia-Huai Wang
- State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, Beijing 100871 China; Department of Medical Oncology and Department of Cancer Biology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02215, USA.
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18
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Abstract
For many years, major differences in morphology, motility, and mechanical characteristics have been observed between transformed cancer and normal cells. In this review, we consider these differences as linked to different states of normal and transformed cells that involve distinct mechanosensing and motility pathways. There is a strong correlation between repeated tissue healing and/or inflammation and the probability of cancer, both of which involve growth in adult tissues. Many factors are likely needed to enable growth, including the loss of rigidity sensing, but recent evidence indicates that microRNAs have important roles in causing the depletion of growth-suppressing proteins. One microRNA, miR-21, is overexpressed in many different tissues during both healing and cancer. Normal cells can become transformed by the depletion of cytoskeletal proteins that results in the loss of mechanosensing, particularly rigidity sensing. Conversely, the transformed state can be reversed by the expression of cytoskeletal proteins-without direct alteration of hormone receptor levels. In this review, we consider the different stereotypical forms of motility and mechanosensory systems. A major difference between normal and transformed cells involves a sensitivity of transformed cells to mechanical perturbations. Thus, understanding the different mechanical characteristics of transformed cells may enable new approaches to treating wound healing and cancer.
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Affiliation(s)
- Michael Sheetz
- Mechanobiology Institute and Department of Biological Sciences, National University of Singapore, Singapore 117411
- Molecular MechanoMedicine Program and Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, Texas 77555, USA;
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19
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Chighizola M, Dini T, Lenardi C, Milani P, Podestà A, Schulte C. Mechanotransduction in neuronal cell development and functioning. Biophys Rev 2019; 11:701-720. [PMID: 31617079 PMCID: PMC6815321 DOI: 10.1007/s12551-019-00587-2] [Citation(s) in RCA: 52] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Accepted: 08/29/2019] [Indexed: 12/21/2022] Open
Abstract
Although many details remain still elusive, it became increasingly evident in recent years that mechanosensing of microenvironmental biophysical cues and subsequent mechanotransduction are strongly involved in the regulation of neuronal cell development and functioning. This review gives an overview about the current understanding of brain and neuronal cell mechanobiology and how it impacts on neurogenesis, neuronal migration, differentiation, and maturation. We will focus particularly on the events in the cell/microenvironment interface and the decisive extracellular matrix (ECM) parameters (i.e. rigidity and nanometric spatial organisation of adhesion sites) that modulate integrin adhesion complex-based mechanosensing and mechanotransductive signalling. It will also be outlined how biomaterial approaches mimicking essential ECM features help to understand these processes and how they can be used to control and guide neuronal cell behaviour by providing appropriate biophysical cues. In addition, principal biophysical methods will be highlighted that have been crucial for the study of neuronal mechanobiology.
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Affiliation(s)
- Matteo Chighizola
- Interdisciplinary Centre for Nanostructured Materials and Interfaces (C.I.Ma.I.Na.) and Department of Physics ``Aldo Pontremoli'', Università degli Studi di Milano, via Celoria 16, 20133, Milan, Italy
| | - Tania Dini
- Interdisciplinary Centre for Nanostructured Materials and Interfaces (C.I.Ma.I.Na.) and Department of Physics ``Aldo Pontremoli'', Università degli Studi di Milano, via Celoria 16, 20133, Milan, Italy
| | - Cristina Lenardi
- Interdisciplinary Centre for Nanostructured Materials and Interfaces (C.I.Ma.I.Na.) and Department of Physics ``Aldo Pontremoli'', Università degli Studi di Milano, via Celoria 16, 20133, Milan, Italy
| | - Paolo Milani
- Interdisciplinary Centre for Nanostructured Materials and Interfaces (C.I.Ma.I.Na.) and Department of Physics ``Aldo Pontremoli'', Università degli Studi di Milano, via Celoria 16, 20133, Milan, Italy
| | - Alessandro Podestà
- Interdisciplinary Centre for Nanostructured Materials and Interfaces (C.I.Ma.I.Na.) and Department of Physics ``Aldo Pontremoli'', Università degli Studi di Milano, via Celoria 16, 20133, Milan, Italy
| | - Carsten Schulte
- Interdisciplinary Centre for Nanostructured Materials and Interfaces (C.I.Ma.I.Na.) and Department of Physics ``Aldo Pontremoli'', Università degli Studi di Milano, via Celoria 16, 20133, Milan, Italy.
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20
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Aberle H. Axon Guidance and Collective Cell Migration by Substrate-Derived Attractants. Front Mol Neurosci 2019; 12:148. [PMID: 31244602 PMCID: PMC6563653 DOI: 10.3389/fnmol.2019.00148] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Accepted: 05/20/2019] [Indexed: 01/05/2023] Open
Abstract
Neurons have evolved specialized growth structures to reach and innervate their target cells. These growth cones express specific receptor molecules that sense environmental cues and transform them into steering decisions. Historically, various concepts of axon guidance have been developed to better understand how axons reach and identify their targets. The essence of these efforts seems to be that growth cones require solid substrates and that major guidance decisions are initiated by extracellular cues. These sometimes highly conserved ligands and receptors have been extensively characterized and mediate four major guidance forces: chemoattraction, chemorepulsion, contact attraction and contact repulsion. However, during development, cells, too, do migrate in order to reach molecularly-defined niches at target locations. In fact, axonal growth could be regarded as a special case of cellular migration, where only a highly polarized portion of the cell is elongating. Here, I combine several examples from genetically tractable model organisms, such as Drosophila or zebrafish, in which cells and axons are guided by attractive cues. Regardless, if these cues are secreted into the extracellular space or exposed on cellular surfaces, migrating cells and axons seem to keep close contact with these attractants and seem to detect them right at their source. Migration towards and along such substrate-derived attractants seem to be particularly robust, as genetic deletion induces obvious searching behaviors and permanent guidance errors. In addition, forced expression of these factors in ectopic tissues is highly distractive too, regardless of the pattern of other endogenous cues. Thus, guidance and migration towards and along attractive tissues is a powerful steering mechanism that exploits affinity differences to the surroundings and, in some instances, determines growth trajectories from source to target region.
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Affiliation(s)
- Hermann Aberle
- Functional Cell Morphology Lab, Heinrich Heine University Duesseldorf, Duesseldorf, Germany
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21
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Coppola S, Schmidt T, Ruocco G, Antonacci G. Quantifying cellular forces and biomechanical properties by correlative micropillar traction force and Brillouin microscopy. BIOMEDICAL OPTICS EXPRESS 2019; 10:2202-2212. [PMID: 31149370 PMCID: PMC6524592 DOI: 10.1364/boe.10.002202] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Revised: 02/18/2019] [Accepted: 02/19/2019] [Indexed: 06/09/2023]
Abstract
Cells sense and respond to external physical forces and substrate rigidity by regulating their cell shape, internal cytoskeletal tension, and stiffness. Here we show that the combination of micropillar traction force and noncontact Brillouin microscopy provides access to cell-generated forces and intracellular mechanical properties at optical resolution. Actin-rich cytoplasmic domains of 3T3 fibroblasts showed significantly higher Brillouin shifts, indicating a potential increase in stiffness when adhering on fibronectin-coated glass compared to soft PDMS micropillars. Our findings demonstrate the complementarity of micropillar traction force and Brillouin microscopy to better understand the relation between cell force generation and the intracellular mechanical properties.
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Affiliation(s)
- Stefano Coppola
- Physics of Life Processes - Kamerlingh Onnes-Huygens Laboratory, Leiden Institute of Physics, Leiden University, Leiden,
The Netherlands
| | - Thomas Schmidt
- Physics of Life Processes - Kamerlingh Onnes-Huygens Laboratory, Leiden Institute of Physics, Leiden University, Leiden,
The Netherlands
| | - Giancarlo Ruocco
- Center for Life Nano Science @Sapienza, Istituto Italiano di Tecnologia, Rome,
Italy
| | - Giuseppe Antonacci
- Center for Life Nano Science @Sapienza, Istituto Italiano di Tecnologia, Rome,
Italy
- Photonics Research Group, Ghent University - imec, Ghent,
Belgium
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22
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Bonanomi D, Valenza F, Chivatakarn O, Sternfeld MJ, Driscoll SP, Aslanian A, Lettieri K, Gullo M, Badaloni A, Lewcock JW, Hunter T, Pfaff SL. p190RhoGAP Filters Competing Signals to Resolve Axon Guidance Conflicts. Neuron 2019; 102:602-620.e9. [PMID: 30902550 PMCID: PMC8608148 DOI: 10.1016/j.neuron.2019.02.034] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Revised: 12/05/2018] [Accepted: 02/19/2019] [Indexed: 12/21/2022]
Abstract
The rich functional diversity of the nervous system is founded in the specific connectivity of the underlying neural circuitry. Neurons are often preprogrammed to respond to multiple axon guidance signals because they use sequential guideposts along their pathways, but this necessitates a strict spatiotemporal regulation of intracellular signaling to ensure the cues are detected in the correct order. We performed a mouse mutagenesis screen and identified the Rho GTPase antagonist p190RhoGAP as a critical regulator of motor axon guidance. Rather than acting as a compulsory signal relay, p190RhoGAP uses a non-conventional GAP-independent mode to transiently suppress attraction to Netrin-1 while motor axons exit the spinal cord. Once in the periphery, a subset of axons requires p190RhoGAP-mediated inhibition of Rho signaling to target specific muscles. Thus, the multifunctional activity of p190RhoGAP emerges from its modular design. Our findings reveal a cell-intrinsic gate that filters conflicting signals, establishing temporal windows of signal detection.
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Affiliation(s)
- Dario Bonanomi
- Gene Expression Laboratory and the Howard Hughes Medical Institute, Salk Institute for Biological Studies, 10010 North Torrey Pines, La Jolla, CA 92037, USA; San Raffaele Scientific Institute, Division of Neuroscience, via Olgettina 60, 20132 Milan, Italy.
| | - Fabiola Valenza
- San Raffaele Scientific Institute, Division of Neuroscience, via Olgettina 60, 20132 Milan, Italy
| | - Onanong Chivatakarn
- Gene Expression Laboratory and the Howard Hughes Medical Institute, Salk Institute for Biological Studies, 10010 North Torrey Pines, La Jolla, CA 92037, USA
| | - Matthew J Sternfeld
- Gene Expression Laboratory and the Howard Hughes Medical Institute, Salk Institute for Biological Studies, 10010 North Torrey Pines, La Jolla, CA 92037, USA
| | - Shawn P Driscoll
- Gene Expression Laboratory and the Howard Hughes Medical Institute, Salk Institute for Biological Studies, 10010 North Torrey Pines, La Jolla, CA 92037, USA
| | - Aaron Aslanian
- Molecular and Cell Biology Laboratory, Salk Institute for Biological Studies, 10010 North Torrey Pines, La Jolla, CA 92037, USA
| | - Karen Lettieri
- Gene Expression Laboratory and the Howard Hughes Medical Institute, Salk Institute for Biological Studies, 10010 North Torrey Pines, La Jolla, CA 92037, USA
| | - Miriam Gullo
- Gene Expression Laboratory and the Howard Hughes Medical Institute, Salk Institute for Biological Studies, 10010 North Torrey Pines, La Jolla, CA 92037, USA
| | - Aurora Badaloni
- San Raffaele Scientific Institute, Division of Neuroscience, via Olgettina 60, 20132 Milan, Italy
| | - Joseph W Lewcock
- Gene Expression Laboratory and the Howard Hughes Medical Institute, Salk Institute for Biological Studies, 10010 North Torrey Pines, La Jolla, CA 92037, USA
| | - Tony Hunter
- Molecular and Cell Biology Laboratory, Salk Institute for Biological Studies, 10010 North Torrey Pines, La Jolla, CA 92037, USA
| | - Samuel L Pfaff
- Gene Expression Laboratory and the Howard Hughes Medical Institute, Salk Institute for Biological Studies, 10010 North Torrey Pines, La Jolla, CA 92037, USA.
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23
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Synergistic Activity of Floor-Plate- and Ventricular-Zone-Derived Netrin-1 in Spinal Cord Commissural Axon Guidance. Neuron 2019; 101:625-634.e3. [DOI: 10.1016/j.neuron.2018.12.024] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Revised: 11/14/2018] [Accepted: 12/18/2018] [Indexed: 11/23/2022]
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24
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Zimmermann D, Kovar DR. Feeling the force: formin's role in mechanotransduction. Curr Opin Cell Biol 2019; 56:130-140. [PMID: 30639952 DOI: 10.1016/j.ceb.2018.12.008] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2018] [Revised: 12/13/2018] [Accepted: 12/16/2018] [Indexed: 11/15/2022]
Abstract
Fundamental cellular processes such as division, polarization, and motility require the tightly regulated spatial and temporal assembly and disassembly of the underlying actin cytoskeleton. The actin cytoskeleton has been long viewed as a central player facilitating diverse mechanotransduction pathways due to the notion that it is capable of receiving, processing, transmitting, and generating mechanical stresses. Recent work has begun to uncover the roles of mechanical stresses in modulating the activity of key regulatory actin-binding proteins and their interactions with actin filaments, thereby controlling the assembly (formin and Arp2/3 complex) and disassembly (ADF/Cofilin) of actin filament networks. In this review, we will focus on discussing the current molecular understanding of how members of the formin protein family sense and respond to forces and the potential implications for formin-mediated mechanotransduction in cells.
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Affiliation(s)
- Dennis Zimmermann
- Massachusetts Institute of Technology, David H. Koch Institute for Integrative Cancer Research, 77 Massachusetts Ave, 76-361F, Cambridge, MA 02139-4307, United States.
| | - David R Kovar
- The University of Chicago, Department of Molecular Genetics and Cell Biology, 90 E. 58th Street, CSLC 212, Chicago, IL 60637, United States.
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25
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Boyer NP, Gupton SL. Revisiting Netrin-1: One Who Guides (Axons). Front Cell Neurosci 2018; 12:221. [PMID: 30108487 PMCID: PMC6080411 DOI: 10.3389/fncel.2018.00221] [Citation(s) in RCA: 118] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Accepted: 07/09/2018] [Indexed: 12/28/2022] Open
Abstract
Proper patterning of the nervous system requires that developing axons find appropriate postsynaptic partners; this entails microns to meters of extension through an extracellular milieu exhibiting a wide range of mechanical and chemical properties. Thus, the elaborate networks of fiber tracts and non-fasciculated axons evident in mature organisms are formed via complex pathfinding. The macroscopic structures of axon projections are highly stereotyped across members of the same species, indicating precise mechanisms guide their formation. The developing axon exhibits directionally biased growth toward or away from external guidance cues. One of the most studied guidance cues is netrin-1, however, its presentation in vivo remains debated. Guidance cues can be secreted to form soluble or chemotactic gradients or presented bound to cells or the extracellular matrix to form haptotactic gradients. The growth cone, a highly specialized dynamic structure at the end of the extending axon, detects these guidance cues via transmembrane receptors, such as the netrin-1 receptors deleted in colorectal cancer (DCC) and UNC5. These receptors orchestrate remodeling of the cytoskeleton and cell membrane through both chemical and mechanotransductive pathways, which result in traction forces generated by the cytoskeleton against the extracellular environment and translocation of the growth cone. Through intracellular signaling responses, netrin-1 can trigger either attraction or repulsion of the axon. Here we review the mechanisms by which the classical guidance cue netrin-1 regulates intracellular effectors to respond to the extracellular environment in the context of axon guidance during development of the central nervous system and discuss recent findings that demonstrate the critical importance of mechanical forces in this process.
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Affiliation(s)
- Nicholas P. Boyer
- Neurobiology Curriculum, The University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - Stephanie L. Gupton
- Department of Cell Biology and Physiology, The University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
- Neuroscience Center, The University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
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26
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Gangatharan G, Schneider-Maunoury S, Breau MA. Role of mechanical cues in shaping neuronal morphology and connectivity. Biol Cell 2018; 110:125-136. [PMID: 29698566 DOI: 10.1111/boc.201800003] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2018] [Accepted: 04/09/2018] [Indexed: 02/06/2023]
Abstract
Neuronal circuits, the functional building blocks of the nervous system, assemble during development through a series of dynamic processes including the migration of neurons to their final position, the growth and navigation of axons and their synaptic connection with target cells. While the role of chemical cues in guiding neuronal migration and axonal development has been extensively analysed, the contribution of mechanical inputs, such as forces and stiffness, has received far less attention. In this article, we review the in vitro and more recent in vivo studies supporting the notion that mechanical signals are critical for multiple aspects of neuronal circuit assembly, from the emergence of axons to the formation of functional synapses. By combining live imaging approaches with tools designed to measure and manipulate the mechanical environment of neurons, the emerging field of neuromechanics will add a new paradigm in our understanding of neuronal development and potentially inspire novel regenerative therapies.
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Affiliation(s)
- Girisaran Gangatharan
- Sorbonne Université, CNRS UMR 7622, Laboratoire de Biologie du Développement-Institut de Biologie Paris Seine (LBD-IBPS), INSERM, Paris, 75005, France
| | - Sylvie Schneider-Maunoury
- Sorbonne Université, CNRS UMR 7622, Laboratoire de Biologie du Développement-Institut de Biologie Paris Seine (LBD-IBPS), INSERM, Paris, 75005, France
| | - Marie Anne Breau
- Sorbonne Université, CNRS UMR 7622, Laboratoire de Biologie du Développement-Institut de Biologie Paris Seine (LBD-IBPS), INSERM, Paris, 75005, France.,Sorbonne Université, CNRS UMR 8237, Laboratoire Jean Perrin, Paris, 75005, France
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27
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Moreno-Bravo JA, Roig Puiggros S, Blockus H, Dominici C, Zelina P, Mehlen P, Chédotal A. Commissural neurons transgress the CNS/PNS boundary in absence of ventricular zone-derived netrin 1. Development 2018; 145:dev.159400. [PMID: 29343638 DOI: 10.1242/dev.159400] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Accepted: 12/12/2017] [Indexed: 11/20/2022]
Abstract
During the development of the central nervous system (CNS), only motor axons project into peripheral nerves. Little is known about the cellular and molecular mechanisms that control the development of a boundary at the CNS surface and prevent CNS neuron emigration from the neural tube. It has previously been shown that a subset of spinal cord commissural axons abnormally invades sensory nerves in Ntn1 hypomorphic embryos and Dcc knockouts. However, whether netrin 1 also plays a similar role in the brain is unknown. In the hindbrain, precerebellar neurons migrate tangentially under the pial surface, and their ventral migration is guided by netrin 1. Here, we show that pontine neurons and inferior olivary neurons, two types of precerebellar neurons, are not confined to the CNS in Ntn1 and Dcc mutant mice, but that they invade the trigeminal, auditory and vagus nerves. Using a Ntn1 conditional knockout, we show that netrin 1, which is released at the pial surface by ventricular zone progenitors is responsible for the CNS confinement of precerebellar neurons. We propose, that netrin 1 distribution sculpts the CNS boundary by keeping CNS neurons in netrin 1-rich domains.
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Affiliation(s)
- Juan Antonio Moreno-Bravo
- Sorbonne Universités, UPMC Université Paris 06, INSERM, CNRS, Institut de la Vision, 75012 Paris, France
| | - Sergi Roig Puiggros
- Sorbonne Universités, UPMC Université Paris 06, INSERM, CNRS, Institut de la Vision, 75012 Paris, France
| | - Heike Blockus
- Sorbonne Universités, UPMC Université Paris 06, INSERM, CNRS, Institut de la Vision, 75012 Paris, France
| | - Chloé Dominici
- Sorbonne Universités, UPMC Université Paris 06, INSERM, CNRS, Institut de la Vision, 75012 Paris, France
| | - Pavol Zelina
- Sorbonne Universités, UPMC Université Paris 06, INSERM, CNRS, Institut de la Vision, 75012 Paris, France
| | - Patrick Mehlen
- Apoptosis, Cancer and Development Laboratory, Equipe labellisée 'La Ligue', LabEx DEVweCAN, Centre de Recherche en Cancérologie de Lyon, INSERM U1052-CNRS UMR5286, Université de Lyon, Centre Léon Bérard, 69008 Lyon, France
| | - Alain Chédotal
- Sorbonne Universités, UPMC Université Paris 06, INSERM, CNRS, Institut de la Vision, 75012 Paris, France
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Making Dopamine Connections in Adolescence. Trends Neurosci 2017; 40:709-719. [PMID: 29032842 DOI: 10.1016/j.tins.2017.09.004] [Citation(s) in RCA: 72] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Revised: 09/07/2017] [Accepted: 09/14/2017] [Indexed: 12/13/2022]
Abstract
A dramatic maturational process ongoing in adolescence is prefrontal cortex development, including its dopamine innervation. Dopamine axons grow from the striatum to the prefrontal cortex, the only known case of long-distance axon growth during adolescence. This is coordinated by the Netrin-1 guidance cue receptor DCC (deleted in colorectal cancer), which in turn controls the intrinsic development of the prefrontal cortex itself. Stimulant drugs in adolescence alter DCC in dopamine neurons and, in turn prefrontal cortex maturation, impacting cognitive abilities. Variations in DCC expression are linked to psychiatric conditions of prefrontal cortex dysfunction, and microRNA regulation of DCC may be key to determining adolescent vulnerability or resilience. Since early interventions are proving to effectively ameliorate disease outcome, the Netrin-1 system is a promising therapeutic target.
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Gopal AA, Ricoult SG, Harris SN, Juncker D, Kennedy TE, Wiseman PW. Spatially Selective Dissection of Signal Transduction in Neurons Grown on Netrin-1 Printed Nanoarrays via Segmented Fluorescence Fluctuation Analysis. ACS NANO 2017; 11:8131-8143. [PMID: 28679208 DOI: 10.1021/acsnano.7b03004] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Axonal growth cones extend during neural development in response to precise distributions of extracellular cues. Deleted in colorectal cancer (DCC), a receptor for the chemotropic guidance cue netrin-1, directs F-actin reorganization, and is essential for mammalian neural development. To elucidate how the extracellular distribution of netrin-1 influences the distribution of DCC and F-actin within axonal growth cones, we patterned nanoarrays of substrate bound netrin-1 using lift-off nanocontact printing. The distribution of DCC and F-actin in embryonic rat cortical neuron growth cones was then imaged using total internal reflection fluorescence (TIRF) microscopy. Fluorescence fluctuation analysis via image cross-correlation spectroscopy (ICCS) was applied to extract the molecular density and aggregation state of DCC and F-actin, identifying the fraction of DCC and F-actin colocalizing with the patterned netrin-1 substrate. ICCS measurement of spatially segmented images based on the substrate nanodot patterns revealed distinct molecular distributions of F-actin and DCC in regions directly overlying the nanodots compared to over the reference surface surrounding the nanodots. Quantifiable variations between the populations of DCC and F-actin on and off the nanodots reveal specific responses to the printed protein substrate. We report that nanodots of substrate-bound netrin-1 locally recruit and aggregate DCC and direct F-actin organization. These effects were blocked by tetanus toxin, consistent with netrin-1 locally recruiting DCC to the plasma membrane via a VAMP2-dependent mechanism. Our findings demonstrate the utility of segmented ICCS image analysis, combined with precisely patterned immobilized ligands, to reveal local receptor distribution and signaling within specialized subcellular compartments.
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Affiliation(s)
- Angelica A Gopal
- Department of Chemistry, ‡Department of Neurology and Neurosurgery, Montreal Neurological Institute, §Department of Biomedical Engineering, Genome Quebec Innovation Centre, and ∥Department of Physics, McGill University , Montreal, Quebec H3A 0G4 Canada
| | - Sebastien G Ricoult
- Department of Chemistry, ‡Department of Neurology and Neurosurgery, Montreal Neurological Institute, §Department of Biomedical Engineering, Genome Quebec Innovation Centre, and ∥Department of Physics, McGill University , Montreal, Quebec H3A 0G4 Canada
| | - Stephanie N Harris
- Department of Chemistry, ‡Department of Neurology and Neurosurgery, Montreal Neurological Institute, §Department of Biomedical Engineering, Genome Quebec Innovation Centre, and ∥Department of Physics, McGill University , Montreal, Quebec H3A 0G4 Canada
| | - David Juncker
- Department of Chemistry, ‡Department of Neurology and Neurosurgery, Montreal Neurological Institute, §Department of Biomedical Engineering, Genome Quebec Innovation Centre, and ∥Department of Physics, McGill University , Montreal, Quebec H3A 0G4 Canada
| | - Timothy E Kennedy
- Department of Chemistry, ‡Department of Neurology and Neurosurgery, Montreal Neurological Institute, §Department of Biomedical Engineering, Genome Quebec Innovation Centre, and ∥Department of Physics, McGill University , Montreal, Quebec H3A 0G4 Canada
| | - Paul W Wiseman
- Department of Chemistry, ‡Department of Neurology and Neurosurgery, Montreal Neurological Institute, §Department of Biomedical Engineering, Genome Quebec Innovation Centre, and ∥Department of Physics, McGill University , Montreal, Quebec H3A 0G4 Canada
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Holló G. Demystification of animal symmetry: symmetry is a response to mechanical forces. Biol Direct 2017; 12:11. [PMID: 28514948 PMCID: PMC5436448 DOI: 10.1186/s13062-017-0182-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2016] [Accepted: 05/09/2017] [Indexed: 12/21/2022] Open
Abstract
ᅟ Symmetry is an eye-catching feature of animal body plans, yet its causes are not well enough understood. The evolution of animal form is mainly due to changes in gene regulatory networks (GRNs). Based on theoretical considerations regarding fundamental GRN properties, it has recently been proposed that the animal genome, on large time scales, should be regarded as a system which can construct both the main symmetries – radial and bilateral – simultaneously; and that the expression of any of these depends on functional constraints. Current theories explain biological symmetry as a pattern mostly determined by phylogenetic constraints, and more by chance than by necessity. In contrast to this conception, I suggest that physical effects, which in many cases act as proximate, direct, tissue-shaping factors during ontogenesis, are also the ultimate causes – i.e. the indirect factors which provide a selective advantage – of animal symmetry, from organs to body plan level patterns. In this respect, animal symmetry is a necessary product of evolution. This proposition offers a parsimonious view of symmetry as a basic feature of the animal body plan, suggesting that molecules and physical forces act in a beautiful harmony to create symmetrical structures, but that the concert itself is directed by the latter. Reviewers This article was reviewed by Eugene Koonin, Zoltán Varga and Michaël Manuel.
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Affiliation(s)
- Gábor Holló
- Institute of Psychology, University of Debrecen, H-4002, Debrecen, P.O. Box 400, Hungary.
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Dominici C, Moreno-Bravo JA, Puiggros SR, Rappeneau Q, Rama N, Vieugue P, Bernet A, Mehlen P, Chédotal A. Floor-plate-derived netrin-1 is dispensable for commissural axon guidance. Nature 2017; 545:350-354. [PMID: 28445456 PMCID: PMC5438598 DOI: 10.1038/nature22331] [Citation(s) in RCA: 134] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2016] [Accepted: 04/04/2017] [Indexed: 11/09/2022]
Abstract
Netrin-1 is an evolutionarily conserved, secreted extracellular matrix protein involved in axon guidance at the central nervous system midline. Netrin-1 is expressed by cells localized at the central nervous system midline, such as those of the floor plate in vertebrate embryos. Growth cone turning assays and three-dimensional gel diffusion assays have shown that netrin-1 can attract commissural axons. Loss-of-function experiments further demonstrated that commissural axon extension to the midline is severely impaired in the absence of netrin-1 (refs 3, 7, 8, 9). Together, these data have long supported a model in which commissural axons are attracted by a netrin-1 gradient diffusing from the midline. Here we selectively ablate netrin-1 expression in floor-plate cells using a Ntn1 conditional knockout mouse line. We find that hindbrain and spinal cord commissural axons develop normally in the absence of floor-plate-derived netrin-1. Furthermore, we show that netrin-1 is highly expressed by cells in the ventricular zone, which can release netrin-1 at the pial surface where it binds to commissural axons. Notably, Ntn1 deletion from the ventricular zone phenocopies commissural axon guidance defects previously described in Ntn1-knockout mice. These results show that the classical view that attraction of commissural axons is mediated by a gradient of floor-plate-derived netrin-1 is inaccurate and that netrin-1 primarily acts locally by promoting growth cone adhesion.
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Affiliation(s)
- Chloé Dominici
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, Institut de la Vision, 17 Rue Moreau, 75012 Paris, France
| | - Juan Antonio Moreno-Bravo
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, Institut de la Vision, 17 Rue Moreau, 75012 Paris, France
| | - Sergi Roig Puiggros
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, Institut de la Vision, 17 Rue Moreau, 75012 Paris, France.,Apoptosis, Cancer and Development Laboratory, Equipe labellisée 'La Ligue', LabEx DEVweCAN, Centre de Recherche en Cancérologie de Lyon, INSERM U1052-CNRS UMR5286, Université de Lyon, Centre Léon Bérard, 69008 Lyon, France
| | - Quentin Rappeneau
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, Institut de la Vision, 17 Rue Moreau, 75012 Paris, France
| | - Nicolas Rama
- Apoptosis, Cancer and Development Laboratory, Equipe labellisée 'La Ligue', LabEx DEVweCAN, Centre de Recherche en Cancérologie de Lyon, INSERM U1052-CNRS UMR5286, Université de Lyon, Centre Léon Bérard, 69008 Lyon, France
| | - Pauline Vieugue
- Apoptosis, Cancer and Development Laboratory, Equipe labellisée 'La Ligue', LabEx DEVweCAN, Centre de Recherche en Cancérologie de Lyon, INSERM U1052-CNRS UMR5286, Université de Lyon, Centre Léon Bérard, 69008 Lyon, France
| | - Agnes Bernet
- Apoptosis, Cancer and Development Laboratory, Equipe labellisée 'La Ligue', LabEx DEVweCAN, Centre de Recherche en Cancérologie de Lyon, INSERM U1052-CNRS UMR5286, Université de Lyon, Centre Léon Bérard, 69008 Lyon, France
| | - Patrick Mehlen
- Apoptosis, Cancer and Development Laboratory, Equipe labellisée 'La Ligue', LabEx DEVweCAN, Centre de Recherche en Cancérologie de Lyon, INSERM U1052-CNRS UMR5286, Université de Lyon, Centre Léon Bérard, 69008 Lyon, France
| | - Alain Chédotal
- Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, Institut de la Vision, 17 Rue Moreau, 75012 Paris, France
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Akin O, Zipursky SL. Frazzled promotes growth cone attachment at the source of a Netrin gradient in the Drosophila visual system. eLife 2016; 5:20762. [PMID: 27743477 PMCID: PMC5108592 DOI: 10.7554/elife.20762] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2016] [Accepted: 10/14/2016] [Indexed: 02/06/2023] Open
Abstract
Axon guidance is proposed to act through a combination of long- and short-range attractive and repulsive cues. The ligand-receptor pair, Netrin (Net) and Frazzled (Fra) (DCC, Deleted in Colorectal Cancer, in vertebrates), is recognized as the prototypical effector of chemoattraction, with roles in both long- and short-range guidance. In the Drosophila visual system, R8 photoreceptor growth cones were shown to require Net-Fra to reach their target, the peak of a Net gradient. Using live imaging, we show, however, that R8 growth cones reach and recognize their target without Net, Fra, or Trim9, a conserved binding partner of Fra, but do not remain attached to it. Thus, despite the graded ligand distribution along the guidance path, Net-Fra is not used for chemoattraction. Based on findings in other systems, we propose that adhesion to substrate-bound Net underlies both long- and short-range Net-Fra-dependent guidance in vivo, thereby eroding the distinction between them. DOI:http://dx.doi.org/10.7554/eLife.20762.001 The brain of the fruit fly contains hundreds of thousands of neurons, while the human brain contains more than 80 billion. Each of these consists of a cell body that bears an array of branches called dendrites, plus a single cable-like axon. During development, the neurons organize themselves into complex networks by forming connections with one another via their axons and dendrites. But it is not clear exactly how the correct connections form in the correct places. As they grow out, axons rely on specialized moving structures at their tips – known as growth cones – to probe their environment in search of attractive and repulsive chemical signals released by other cells. When sensors on the surface of growth cones detect a target signal, they initiate processes that cause the growth cone to expand or collapse. This enables the axons to move towards or away from the signal, as appropriate. In all animals studied, proteins called DCC and Netrin form one of the best-known sensor-signal pairs. Growth cones bearing DCC sensors are thought to detect ‘wafting plumes’ or gradients of Netrin and then grow towards the Netrin source. However, nobody had directly watched neurons respond to Netrin in a living intact animal. Using a type of microscope that can look deep into the developing fly brain, Akin and Zipursky have now followed the movement of growth cones on cells called R8 neurons in fruit fly pupae. Unexpectedly, Akin and Zipursky found that the growth cones of mutant flies that lack Netrin or Frazzled (the fruit fly version of DCC) navigate successfully to their intended destinations. Once there, however, the mutant growth cones were unable to attach to their targets. Akin and Zipursky’s work is consistent with other observations in a number of animal and insect systems that suggest that Netrin may not attract growth cones via wafting plumes of signal. Instead, Netrin may form a sticky trail that helps growth cones to gain traction as they crawl towards or stick to their destinations. Further experiments are now needed to test whether other neurons in fruit flies and in different animals use Netrin in this way. DOI:http://dx.doi.org/10.7554/eLife.20762.002
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Affiliation(s)
- Orkun Akin
- Department of Biological Chemistry, Howard Hughes Medical Institute, University of California, Los Angeles, Los Angeles, United States
| | - S Lawrence Zipursky
- Department of Biological Chemistry, Howard Hughes Medical Institute, University of California, Los Angeles, Los Angeles, United States
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Mechanosensing is critical for axon growth in the developing brain. Nat Neurosci 2016; 19:1592-1598. [PMID: 27643431 PMCID: PMC5531257 DOI: 10.1038/nn.4394] [Citation(s) in RCA: 379] [Impact Index Per Article: 47.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Accepted: 08/25/2016] [Indexed: 02/07/2023]
Abstract
During nervous system development, neurons extend axons along well-defined pathways. The current understanding of axon pathfinding is based mainly on chemical signaling. However, growing neurons interact not only chemically but also mechanically with their environment. Here we identify mechanical signals as important regulators of axon pathfinding. In vitro, substrate stiffness determined growth patterns of Xenopus retinal ganglion cell axons. In vivo atomic force microscopy revealed a noticeable pattern of stiffness gradients in the embryonic brain. Retinal ganglion cell axons grew toward softer tissue, which was reproduced in vitro in the absence of chemical gradients. To test the importance of mechanical signals for axon growth in vivo, we altered brain stiffness, blocked mechanotransduction pharmacologically and knocked down the mechanosensitive ion channel piezo1. All treatments resulted in aberrant axonal growth and pathfinding errors, suggesting that local tissue stiffness, read out by mechanosensitive ion channels, is critically involved in instructing neuronal growth in vivo.
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Substrate Deformation Predicts Neuronal Growth Cone Advance. Biophys J 2016; 109:1358-71. [PMID: 26445437 DOI: 10.1016/j.bpj.2015.08.013] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Revised: 08/11/2015] [Accepted: 08/12/2015] [Indexed: 11/23/2022] Open
Abstract
Although pulling forces have been observed in axonal growth for several decades, their underlying mechanisms, absolute magnitudes, and exact roles are not well understood. In this study, using two different experimental approaches, we quantified retrograde traction force in Aplysia californica neuronal growth cones as they develop over time in response to a new adhesion substrate. In the first approach, we developed a novel method, to our knowledge, for measuring traction forces using an atomic force microscope (AFM) with a cantilever that was modified with an Aplysia cell adhesion molecule (apCAM)-coated microbead. In the second approach, we used force-calibrated glass microneedles coated with apCAM ligands to guide growth cone advance. The traction force exerted by the growth cone was measured by monitoring the microneedle deflection using an optical microscope. Both approaches showed that Aplysia growth cones can develop traction forces in the 10(0)-10(2) nN range during adhesion-mediated advance. Moreover, our results suggest that the level of traction force is directly correlated to the stiffness of the microneedle, which is consistent with a reinforcement mechanism previously observed in other cell types. Interestingly, the absolute level of traction force did not correlate with growth cone advance toward the adhesion site, but the amount of microneedle deflection did. In cases of adhesion-mediated growth cone advance, the mean needle deflection was 1.05 ± 0.07 μm. By contrast, the mean deflection was significantly lower (0.48 ± 0.06 μm) when the growth cones did not advance. Our data support a hypothesis that adhesion complexes, which can undergo micron-scale elastic deformation, regulate the coupling between the retrogradely flowing actin cytoskeleton and apCAM substrates, stimulating growth cone advance if sufficiently abundant.
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Rappaz B, Lai Wing Sun K, Correia JP, Wiseman PW, Kennedy TE. FLIM FRET Visualization of Cdc42 Activation by Netrin-1 in Embryonic Spinal Commissural Neuron Growth Cones. PLoS One 2016; 11:e0159405. [PMID: 27482713 PMCID: PMC4970703 DOI: 10.1371/journal.pone.0159405] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Accepted: 07/02/2016] [Indexed: 12/29/2022] Open
Abstract
Netrin-1 is an essential extracellular chemoattractant that signals through its receptor DCC to guide commissural axon extension in the embryonic spinal cord. DCC directs the organization of F-actin in growth cones by activating an intracellular protein complex that includes the Rho GTPase Cdc42, a critical regulator of cell polarity and directional migration. To address the spatial distribution of signaling events downstream of netrin-1, we expressed the FRET biosensor Raichu-Cdc42 in cultured embryonic rat spinal commissural neurons. Using FLIM-FRET imaging we detected rapid activation of Cdc42 in neuronal growth cones following application of netrin-1. Investigating the signaling mechanisms that control Cdc42 activation by netrin-1, we demonstrate that netrin-1 rapidly enriches DCC at the leading edge of commissural neuron growth cones and that netrin-1 induced activation of Cdc42 in the growth cone is blocked by inhibiting src family kinase signaling. These findings reveal the activation of Cdc42 in embryonic spinal commissural axon growth cones and support the conclusion that src family kinase activation downstream of DCC is required for Cdc42 activation by netrin-1.
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Affiliation(s)
- Benjamin Rappaz
- Program in NeuroEngineering, McGill University, Montreal, QC, H3A 2B4, Canada
- Department of Neurology and Neurosurgery, Montréal Neurological Institute, McGill University, Montreal, QC, H3A 2B4, Canada
- Department of Physics, McGill University, Montreal, QC, H3A 2T8, Canada
| | - Karen Lai Wing Sun
- Program in NeuroEngineering, McGill University, Montreal, QC, H3A 2B4, Canada
- Department of Neurology and Neurosurgery, Montréal Neurological Institute, McGill University, Montreal, QC, H3A 2B4, Canada
| | - James P. Correia
- Program in NeuroEngineering, McGill University, Montreal, QC, H3A 2B4, Canada
- Department of Neurology and Neurosurgery, Montréal Neurological Institute, McGill University, Montreal, QC, H3A 2B4, Canada
| | - Paul W. Wiseman
- Program in NeuroEngineering, McGill University, Montreal, QC, H3A 2B4, Canada
- Department of Physics, McGill University, Montreal, QC, H3A 2T8, Canada
- Department of Chemistry, McGill University, Montreal, QC, H3A 0B8, Canada
| | - Timothy E. Kennedy
- Program in NeuroEngineering, McGill University, Montreal, QC, H3A 2B4, Canada
- Department of Neurology and Neurosurgery, Montréal Neurological Institute, McGill University, Montreal, QC, H3A 2B4, Canada
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Abstract
UNLABELLED Growth cones interact with the extracellular matrix (ECM) through integrin receptors at adhesion sites termed point contacts. Point contact adhesions link ECM proteins to the actin cytoskeleton through numerous adaptor and signaling proteins. One presumed function of growth cone point contacts is to restrain or "clutch" myosin-II-based filamentous actin (F-actin) retrograde flow (RF) to promote leading edge membrane protrusion. In motile non-neuronal cells, myosin-II binds and exerts force upon actin filaments at the leading edge, where clutching forces occur. However, in growth cones, it is unclear whether similar F-actin-clutching forces affect axon outgrowth and guidance. Here, we show in Xenopus spinal neurons that RF is reduced in rapidly migrating growth cones on laminin (LN) compared with non-integrin-binding poly-d-lysine (PDL). Moreover, acute stimulation with LN accelerates axon outgrowth over a time course that correlates with point contact formation and reduced RF. These results suggest that RF is restricted by the assembly of point contacts, which we show occurs locally by two-channel imaging of RF and paxillin. Further, using micropatterns of PDL and LN, we demonstrate that individual growth cones have differential RF rates while interacting with two distinct substrata. Opposing effects on RF rates were also observed in growth cones treated with chemoattractive and chemorepulsive axon guidance cues that influence point contact adhesions. Finally, we show that RF is significantly attenuated in vivo, suggesting that it is restrained by molecular clutching forces within the spinal cord. Together, our results suggest that local clutching of RF can control axon guidance on ECM proteins downstream of axon guidance cues. SIGNIFICANCE STATEMENT Here, we correlate point contact adhesions directly with clutching of filamentous actin retrograde flow (RF), which our findings strongly suggest guides developing axons. Acute assembly of new point contact adhesions is temporally and spatially linked to attenuation of RF at sites of forward membrane protrusion. Importantly, clutching of RF is modulated by extracellular matrix (ECM) proteins and soluble axon guidance cues, suggesting that it may regulate axon guidance in vivo. Consistent with this notion, we found that RF rates of spinal neuron growth cones were slower in vivo than what was observed in vitro. Together, our study provides the best evidence that growth cone-ECM adhesions clutch RF locally to guide axons in vivo.
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The E3 Ubiquitin Ligase TRIM9 Is a Filopodia Off Switch Required for Netrin-Dependent Axon Guidance. Dev Cell 2016; 35:698-712. [PMID: 26702829 DOI: 10.1016/j.devcel.2015.11.022] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Revised: 07/09/2015] [Accepted: 10/19/2015] [Indexed: 02/01/2023]
Abstract
Neuronal growth cone filopodia contain guidance receptors and contribute to axon guidance; however, the mechanism by which the guidance cue netrin increases filopodia density is unknown. Here, we demonstrate that TRIM9, an E3 ubiquitin ligase that localizes to filopodia tips and binds the netrin receptor DCC, interacts with and ubiquitinates the barbed-end polymerase VASP to modulate filopodial stability during netrin-dependent axon guidance. Studies with murine Trim9(+/+) and Trim9(-/-) cortical neurons, along with a non-ubiquitinatable VASP mutant, demonstrate that TRIM9-mediated ubiquitination of VASP reduces VASP filopodial tip localization, VASP dynamics at tips, and filopodial stability. Upon netrin treatment, VASP is deubiquitinated, which promotes VASP tip localization and filopodial stability. Trim9 deletion induces axon guidance defects in vitro and in vivo, whereas a gradient of deubiquitinase inhibition promotes axon turning in vitro. We conclude that a gradient of TRIM9-mediated ubiquitination of VASP creates a filopodial stability gradient during axon turning.
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Menon S, Gupton SL. Building Blocks of Functioning Brain: Cytoskeletal Dynamics in Neuronal Development. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2016; 322:183-245. [PMID: 26940519 PMCID: PMC4809367 DOI: 10.1016/bs.ircmb.2015.10.002] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Neural connectivity requires proper polarization of neurons, guidance to appropriate target locations, and establishment of synaptic connections. From when neurons are born to when they finally reach their synaptic partners, neurons undergo constant rearrangment of the cytoskeleton to achieve appropriate shape and polarity. Of particular importance to neuronal guidance to target locations is the growth cone at the tip of the axon. Growth-cone steering is also dictated by the underlying cytoskeleton. All these changes require spatiotemporal control of the cytoskeletal machinery. This review summarizes the proteins that are involved in modulating the actin and microtubule cytoskeleton during the various stages of neuronal development.
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Affiliation(s)
- Shalini Menon
- Department of Cell Biology and Physiology, University of North Carolina, Chapel Hill, NC, United States of America
| | - Stephanie L Gupton
- Department of Cell Biology and Physiology, University of North Carolina, Chapel Hill, NC, United States of America; Neuroscience Center and Curriculum in Neurobiology, University of North Carolina, Chapel Hill, NC, United States of America; Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC, United States of America.
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Sahasrabudhe A, Ghate K, Mutalik S, Jacob A, Ghose A. Formin 2 regulates the stabilization of filopodial tip adhesions in growth cones and affects neuronal outgrowth and pathfinding in vivo. Development 2015; 143:449-60. [PMID: 26718007 DOI: 10.1242/dev.130104] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Accepted: 12/23/2015] [Indexed: 12/28/2022]
Abstract
Growth cone filopodia are actin-based mechanosensory structures that are essential for chemoreception and the generation of contractile forces necessary for directional motility. However, little is known about the influence of filopodial actin structures on substrate adhesion and filopodial contractility. Formin 2 (Fmn2) localizes along filopodial actin bundles and its depletion does not affect filopodia initiation or elongation. However, Fmn2 activity is required for filopodial tip adhesion maturation and the ability of filopodia to generate traction forces. Dysregulation of filopodia in Fmn2-depleted neurons leads to compromised growth cone motility. Additionally, in mouse fibroblasts, Fmn2 regulates ventral stress fiber assembly and affects the stability of focal adhesions. In the developing chick spinal cord, Fmn2 activity is required cell-autonomously for the outgrowth and pathfinding of spinal commissural neurons. Our results reveal an unanticipated function for Fmn2 in neural development. Fmn2 regulates structurally diverse bundled actin structures, parallel filopodial bundles in growth cones and anti-parallel stress fibers in fibroblasts, in turn modulating the stability of substrate adhesions. We propose Fmn2 as a mediator of actin bundle integrity, enabling efficient force transmission to the adhesion sites.
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Affiliation(s)
- Abhishek Sahasrabudhe
- Indian Institute of Science Education and Research (IISER) Pune, Dr Homi Bhaba Road, Pune 411008, India
| | - Ketakee Ghate
- Indian Institute of Science Education and Research (IISER) Pune, Dr Homi Bhaba Road, Pune 411008, India
| | - Sampada Mutalik
- Indian Institute of Science Education and Research (IISER) Pune, Dr Homi Bhaba Road, Pune 411008, India
| | - Ajesh Jacob
- Indian Institute of Science Education and Research (IISER) Pune, Dr Homi Bhaba Road, Pune 411008, India
| | - Aurnab Ghose
- Indian Institute of Science Education and Research (IISER) Pune, Dr Homi Bhaba Road, Pune 411008, India
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Tabdanov E, Gondarenko S, Kumari S, Liapis A, Dustin ML, Sheetz MP, Kam LC, Iskratsch T. Micropatterning of TCR and LFA-1 ligands reveals complementary effects on cytoskeleton mechanics in T cells. Integr Biol (Camb) 2015; 7:1272-84. [PMID: 26156536 PMCID: PMC4593733 DOI: 10.1039/c5ib00032g] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The formation of the immunological synapse between a T cell and the antigen-presenting cell (APC) is critically dependent on actin dynamics, downstream of T cell receptor (TCR) and integrin (LFA-1) signalling. There is also accumulating evidence that mechanical forces, generated by actin polymerization and/or myosin contractility regulate T cell signalling. Because both receptor pathways are intertwined, their contributions towards the cytoskeletal organization remain elusive. Here, we identify the specific roles of TCR and LFA-1 by using a combination of micropatterning to spatially separate signalling systems and nanopillar arrays for high-precision analysis of cellular forces. We identify that Arp2/3 acts downstream of TCRs to nucleate dense actin foci but propagation of the network requires LFA-1 and the formin FHOD1. LFA-1 adhesion enhances actomyosin forces, which in turn modulate actin assembly downstream of the TCR. Together our data shows a mechanically cooperative system through which ligands presented by an APC modulate T cell activation.
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Affiliation(s)
- Erdem Tabdanov
- Department of Biomedical Engineering, Columbia University, New York, NY, USA
| | - Sasha Gondarenko
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | - Sudha Kumari
- Department of Pathology, New York University, New York, NY, USA
| | | | - Michael L. Dustin
- Department of Pathology, New York University, New York, NY, USA
- Kennedy Institute of Rheumatology, University of Oxford, Headington, Oxon, UK
| | - Michael P. Sheetz
- Department of Biological Sciences, Columbia University, New York, NY, USA
- Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore
| | - Lance C. Kam
- Department of Biomedical Engineering, Columbia University, New York, NY, USA
| | - Thomas Iskratsch
- Department of Biological Sciences, Columbia University, New York, NY, USA
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42
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Abstract
The vascular and the nervous system are responsible for oxygen, nutrient, and information transfer and thereby constitute highly important communication systems in higher organisms. These functional similarities are reflected at the anatomical, cellular, and molecular levels, where common developmental principles and mutual crosstalks have evolved to coordinate their action. This resemblance of the two systems at different levels of complexity has been termed the "neurovascular link." Most of the evidence demonstrating neurovascular interactions derives from studies outside the CNS and from the CNS tissue of the retina. However, little is known about the specific properties of the neurovascular link in the brain. Here, we focus on regulatory effects of molecules involved in the neurovascular link on angiogenesis in the periphery and in the brain and distinguish between general and CNS-specific cues for angiogenesis. Moreover, we discuss the emerging molecular interactions of these angiogenic cues with the VEGF-VEGFR-Delta-like ligand 4 (Dll4)-Jagged-Notch pathway.
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43
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Athamneh AIM, Suter DM. Quantifying mechanical force in axonal growth and guidance. Front Cell Neurosci 2015; 9:359. [PMID: 26441530 PMCID: PMC4584967 DOI: 10.3389/fncel.2015.00359] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2015] [Accepted: 08/27/2015] [Indexed: 11/17/2022] Open
Abstract
Mechanical force plays a fundamental role in neuronal development, physiology, and regeneration. In particular, research has shown that force is involved in growth cone-mediated axonal growth and guidance as well as stretch-induced elongation when an organism increases in size after forming initial synaptic connections. However, much of the details about the exact role of force in these fundamental processes remain unknown. In this review, we highlight: (1) standing questions concerning the role of mechanical force in axonal growth and guidance; and (2) different experimental techniques used to quantify forces in axons and growth cones. We believe that satisfying answers to these questions will require quantitative information about the relationship between elongation, forces, cytoskeletal dynamics, axonal transport, signaling, substrate adhesion, and stiffness contributing to directional growth advance. Furthermore, we address why a wide range of force values have been reported in the literature, and what these values mean in the context of neuronal mechanics. We hope that this review will provide a guide for those interested in studying the role of force in development and regeneration of neuronal networks.
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Affiliation(s)
- Ahmad I M Athamneh
- Bindley Bioscience Center, Birck Nanotechnology Center, Department of Biological Sciences, Purdue University West Lafayette, IN, USA
| | - Daniel M Suter
- Bindley Bioscience Center, Birck Nanotechnology Center, Department of Biological Sciences, Purdue University West Lafayette, IN, USA
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44
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Abstract
Neuronal growth cones are exquisite sensory-motor machines capable of transducing features contacted in their local extracellular environment into guided process extension during development. Extensive research has shown that chemical ligands activate cell surface receptors on growth cones leading to intracellular signals that direct cytoskeletal changes. However, the environment also provides mechanical support for growth cone adhesion and traction forces that stabilize leading edge protrusions. Interestingly, recent work suggests that both the mechanical properties of the environment and mechanical forces generated within growth cones influence axon guidance. In this review we discuss novel molecular mechanisms involved in growth cone force production and detection, and speculate how these processes may be necessary for the development of proper neuronal morphogenesis.
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Affiliation(s)
- Patrick C Kerstein
- Neuroscience Training Program, Department of Neuroscience, School of Medicine and Public Health, University of Wisconsin-Madison Madison, WI, USA
| | - Robert H Nichol
- Neuroscience Training Program, Department of Neuroscience, School of Medicine and Public Health, University of Wisconsin-Madison Madison, WI, USA
| | - Timothy M Gomez
- Neuroscience Training Program, Department of Neuroscience, School of Medicine and Public Health, University of Wisconsin-Madison Madison, WI, USA
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45
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Podjaski C, Alvarez JI, Bourbonniere L, Larouche S, Terouz S, Bin JM, Lécuyer MA, Saint-Laurent O, Larochelle C, Darlington PJ, Arbour N, Antel JP, Kennedy TE, Prat A. Netrin 1 regulates blood-brain barrier function and neuroinflammation. Brain 2015; 138:1598-612. [PMID: 25903786 DOI: 10.1093/brain/awv092] [Citation(s) in RCA: 117] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2014] [Accepted: 02/04/2015] [Indexed: 01/06/2023] Open
Abstract
Blood-brain barrier function is driven by the influence of astrocyte-secreted factors. During neuroinflammatory responses the blood-brain barrier is compromised resulting in central nervous system damage and exacerbated pathology. Here, we identified endothelial netrin 1 induction as a vascular response to astrocyte-derived sonic hedgehog that promotes autocrine barrier properties during homeostasis and increases with inflammation. Netrin 1 supports blood-brain barrier integrity by upregulating endothelial junctional protein expression, while netrin 1 knockout mice display disorganized tight junction protein expression and barrier breakdown. Upon inflammatory conditions, blood-brain barrier endothelial cells significantly upregulated netrin 1 levels in vitro and in situ, which prevented junctional breach and endothelial cell activation. Finally, netrin 1 treatment during experimental autoimmune encephalomyelitis significantly reduced blood-brain barrier disruption and decreased clinical and pathological indices of disease severity. Our results demonstrate that netrin 1 is an important regulator of blood-brain barrier maintenance that protects the central nervous system against inflammatory conditions such as multiple sclerosis and experimental autoimmune encephalomyelitis.
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Affiliation(s)
- Cornelia Podjaski
- 1 Neuroimmunology Unit, Department of Neuroscience, Centre de Recherche du CHUM (CRCHUM), Université de Montréal, Montréal, Québec, Canada 2 Department of Neurology and Neurosurgery, Montréal Neurological Institute, McGill University, Montréal, Québec, Canada
| | - Jorge I Alvarez
- 1 Neuroimmunology Unit, Department of Neuroscience, Centre de Recherche du CHUM (CRCHUM), Université de Montréal, Montréal, Québec, Canada
| | - Lyne Bourbonniere
- 1 Neuroimmunology Unit, Department of Neuroscience, Centre de Recherche du CHUM (CRCHUM), Université de Montréal, Montréal, Québec, Canada
| | - Sandra Larouche
- 1 Neuroimmunology Unit, Department of Neuroscience, Centre de Recherche du CHUM (CRCHUM), Université de Montréal, Montréal, Québec, Canada
| | - Simone Terouz
- 1 Neuroimmunology Unit, Department of Neuroscience, Centre de Recherche du CHUM (CRCHUM), Université de Montréal, Montréal, Québec, Canada
| | - Jenea M Bin
- 2 Department of Neurology and Neurosurgery, Montréal Neurological Institute, McGill University, Montréal, Québec, Canada
| | - Marc-André Lécuyer
- 1 Neuroimmunology Unit, Department of Neuroscience, Centre de Recherche du CHUM (CRCHUM), Université de Montréal, Montréal, Québec, Canada
| | - Olivia Saint-Laurent
- 1 Neuroimmunology Unit, Department of Neuroscience, Centre de Recherche du CHUM (CRCHUM), Université de Montréal, Montréal, Québec, Canada
| | - Catherine Larochelle
- 1 Neuroimmunology Unit, Department of Neuroscience, Centre de Recherche du CHUM (CRCHUM), Université de Montréal, Montréal, Québec, Canada
| | - Peter J Darlington
- 2 Department of Neurology and Neurosurgery, Montréal Neurological Institute, McGill University, Montréal, Québec, Canada
| | - Nathalie Arbour
- 1 Neuroimmunology Unit, Department of Neuroscience, Centre de Recherche du CHUM (CRCHUM), Université de Montréal, Montréal, Québec, Canada
| | - Jack P Antel
- 2 Department of Neurology and Neurosurgery, Montréal Neurological Institute, McGill University, Montréal, Québec, Canada
| | - Timothy E Kennedy
- 2 Department of Neurology and Neurosurgery, Montréal Neurological Institute, McGill University, Montréal, Québec, Canada
| | - Alexandre Prat
- 1 Neuroimmunology Unit, Department of Neuroscience, Centre de Recherche du CHUM (CRCHUM), Université de Montréal, Montréal, Québec, Canada
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46
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Progressive disorganization of paranodal junctions and compact myelin due to loss of DCC expression by oligodendrocytes. J Neurosci 2014; 34:9768-78. [PMID: 25031414 DOI: 10.1523/jneurosci.0448-14.2014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Paranodal axoglial junctions are critical for maintaining the segregation of axonal domains along myelinated axons; however, the proteins required to organize and maintain this structure are not fully understood. Netrin-1 and its receptor Deleted in Colorectal Cancer (DCC) are proteins enriched at paranodes that are expressed by neurons and oligodendrocytes. To identify the specific function of DCC expressed by oligodendrocytes in vivo, we selectively eliminated DCC from mature myelinating oligodendrocytes using an inducible cre regulated by the proteolipid protein promoter. We demonstrate that DCC deletion results in progressive disruption of the organization of axonal domains, myelin ultrastructure, and myelin protein composition. Conditional DCC knock-out mice develop balance and coordination deficits and exhibit decreased conduction velocity. We conclude that DCC expression by oligodendrocytes is required for the maintenance and stability of myelin in vivo, which is essential for proper signal conduction in the CNS.
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47
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de Witt B, Joshi R, Meislin H, Mosier JM. Optimizing oxygen delivery in the critically ill: assessment of volume responsiveness in the septic patient. J Emerg Med 2014; 47:608-15. [PMID: 25088530 DOI: 10.1016/j.jemermed.2014.06.015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2014] [Revised: 06/10/2014] [Accepted: 06/29/2014] [Indexed: 01/03/2023]
Abstract
BACKGROUND Assessing volume responsiveness, defined as an increase in cardiac index after infusion of fluids, is important when caring for critically ill patients in septic shock, as both under- and over-resuscitation can worsen outcomes. This review article describes the currently available methods of assessing volume responsiveness for critically ill patients in the emergency department, with a focus on patients in septic shock. OBJECTIVE The single-pump model of the circulation utilizing cardiac-filling pressures is reviewed in detail. Additionally, the dual-pump model evaluating cardiopulmonary interactions both invasively and noninvasively will be described. DISCUSSION Cardiac filling pressures (central venous pressure and pulmonary artery occlusion pressure) have poor performance characteristics when used to predict volume responsiveness. Cardiopulmonary interaction assessments (inferior vena cava distensibility/collapsibility, systolic pressure variation, pulse pressure variation, stroke volume variation, and aortic flow velocities) have superior test characteristics when measured either invasively or noninvasively. CONCLUSION Cardiac filling pressures may be misleading if used to determine volume responsiveness. Assessment of cardiopulmonary interactions has superior performance characteristics, and should be preferentially used for septic shock patients in the emergency department.
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Affiliation(s)
- Benjamin de Witt
- Department of Emergency Medicine, University of Arizona, Tucson, Arizona
| | - Raj Joshi
- Department of Emergency Medicine, University of Arizona, Tucson, Arizona
| | - Harvey Meislin
- Arizona Emergency Medicine Research Center, Tucson, Arizona
| | - Jarrod M Mosier
- Department of Emergency Medicine, University of Arizona, Tucson, Arizona; Department of Internal Medicine, Department of Medicine, Section of Pulmonary, Critical Care, Allergy and Sleep, University of Arizona, Tucson, Arizona
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48
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Dynamic peripheral traction forces balance stable neurite tension in regenerating Aplysia bag cell neurons. Sci Rep 2014; 4:4961. [PMID: 24825441 PMCID: PMC4019958 DOI: 10.1038/srep04961] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2014] [Accepted: 04/24/2014] [Indexed: 11/16/2022] Open
Abstract
Growth cones of elongating neurites exert force against the external environment, but little is known about the role of force in outgrowth or its relationship to the mechanical organization of neurons. We used traction force microscopy to examine patterns of force in growth cones of regenerating Aplysia bag cell neurons. We find that traction is highest in the peripheral actin-rich domain and internal stress reaches a plateau near the transition between peripheral and central microtubule-rich domains. Integrating stress over the area of the growth cone reveals that total scalar force increases with area but net tension on the neurite does not. Tensions fall within a limited range while a substantial fraction of the total force can be balanced locally within the growth cone. Although traction continuously redistributes during extension and retraction of the peripheral domain, tension is stable over time, suggesting that tension is a tightly regulated property of the neurite independent of growth cone dynamics. We observe that redistribution of traction in the peripheral domain can reorient the end of the neurite shaft. This suggests a role for off-axis force in growth cone turning and neuronal guidance.
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49
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Regeneration of Aplysia bag cell neurons is synergistically enhanced by substrate-bound hemolymph proteins and laminin. Sci Rep 2014; 4:4617. [PMID: 24722588 PMCID: PMC3983596 DOI: 10.1038/srep04617] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Accepted: 03/12/2014] [Indexed: 11/08/2022] Open
Abstract
We have investigated Aplysia hemolymph as a source of endogenous factors to promote regeneration of bag cell neurons. We describe a novel synergistic effect between substrate-bound hemolymph proteins and laminin. This combination increased outgrowth and branching relative to either laminin or hemolymph alone. Notably, the addition of hemolymph to laminin substrates accelerated growth cone migration rate over ten-fold. Our results indicate that the active factor is either a high molecular weight protein or protein complex and is not the respiratory protein hemocyanin. Substrate-bound factor(s) from central nervous system-conditioned media also had a synergistic effect with laminin, suggesting a possible cooperation between humoral proteins and nervous system extracellular matrix. Further molecular characterization of active factors and their cellular targets is warranted on account of the magnitude of the effects reported here and their potential relevance for nervous system repair.
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50
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Ricoult SG, Thompson-Steckel G, Correia JP, Kennedy TE, Juncker D. Tuning cell–surface affinity to direct cell specific responses to patterned proteins. Biomaterials 2014; 35:727-36. [DOI: 10.1016/j.biomaterials.2013.10.023] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2013] [Accepted: 10/04/2013] [Indexed: 12/13/2022]
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