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Teixeira-Castro A, Sousa JC, Vieira C, Pereira-Sousa J, Vilasboas-Campos D, Marques F, Pinto-do-Ó P, Maciel P. Learning the Biochemical Basis of Axonal Guidance: Using Caenorhabditis elegans as a Model. Biomedicines 2023; 11:1731. [PMID: 37371826 DOI: 10.3390/biomedicines11061731] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Revised: 06/12/2023] [Accepted: 06/14/2023] [Indexed: 06/29/2023] Open
Abstract
AIM Experimental models are a powerful aid in visualizing molecular phenomena. This work reports how the worm Caenorhabditis elegans (C. elegans) can be effectively explored for students to learn how molecular cues dramatically condition axonal guidance and define nervous system structure and behavior at the organism level. Summary of work: A loosely oriented observational activity preceded detailed discussions on molecules implied in axonal migration. C. elegans mutants were used to introduce second-year medical students to the deleterious effects of gene malfunctioning in neuron response to extracellular biochemical cues and to establish links between molecular function, nervous system structure, and animal behavior. Students observed C. elegans cultures and associated animal behavior alterations with the lack of function of specific axon guidance molecules (the soluble cue netrin/UNC-6 or two receptors, DCC/UNC-40 and UNC-5H). Microscopical observations of these strains, in combination with pan-neuronal GFP expression, allowed optimal visualization of severely affected neurons. Once the list of mutated genes in each strain was displayed, students could also relate abnormal patterns in axon migration/ventral and dorsal nerve cord neuron formation in C. elegans with mutated molecular components homologous to those in humans. SUMMARY OF RESULTS Students rated the importance and effectiveness of the activity very highly. Ninety-three percent found it helpful to grasp human axonal migration, and all students were surprised with the power of the model in helping to visualize the phenomenon.
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Affiliation(s)
- Andreia Teixeira-Castro
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal
- ICVS/3B's-PT Government Associate Laboratory, 4806-909 Guimarães, Portugal
| | - João Carlos Sousa
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal
- ICVS/3B's-PT Government Associate Laboratory, 4806-909 Guimarães, Portugal
| | - Cármen Vieira
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal
- ICVS/3B's-PT Government Associate Laboratory, 4806-909 Guimarães, Portugal
| | - Joana Pereira-Sousa
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal
- ICVS/3B's-PT Government Associate Laboratory, 4806-909 Guimarães, Portugal
| | - Daniela Vilasboas-Campos
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal
- ICVS/3B's-PT Government Associate Laboratory, 4806-909 Guimarães, Portugal
| | - Fernanda Marques
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal
- ICVS/3B's-PT Government Associate Laboratory, 4806-909 Guimarães, Portugal
| | - Perpétua Pinto-do-Ó
- Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, 4200-135 Porto, Portugal
| | - Patrícia Maciel
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal
- ICVS/3B's-PT Government Associate Laboratory, 4806-909 Guimarães, Portugal
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2
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Schneider F, Metz I, Rust MB. Regulation of actin filament assembly and disassembly in growth cone motility and axon guidance. Brain Res Bull 2023; 192:21-35. [PMID: 36336143 DOI: 10.1016/j.brainresbull.2022.10.019] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Revised: 10/26/2022] [Accepted: 10/28/2022] [Indexed: 11/06/2022]
Abstract
Directed outgrowth of axons is fundamental for the establishment of neuronal networks. Axon outgrowth is guided by growth cones, highly motile structures enriched in filamentous actin (F-actin) located at the axons' distal tips. Growth cones exploit F-actin-based protrusions to scan the environment for guidance cues, and they contain the sensory apparatus to translate guidance cue information into intracellular signaling cascades. These cascades act upstream of actin-binding proteins (ABP) and thereby control assembly and disassembly of F-actin. Spatiotemporally controlled F-actin dis-/assembly in growth cones steers the axon towards attractants and away from repellents, and it thereby navigates the axon through the developing nervous system. Hence, ABP that control F-actin dynamics emerged as critical regulators of neuronal network formation. In the present review article, we will summarize and discuss current knowledge of the mechanisms that control remodeling of the actin cytoskeleton in growth cones, focusing on recent progress in the field. Further, we will introduce tools and techniques that allow to study actin regulatory mechanism in growth cones.
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Affiliation(s)
- Felix Schneider
- Molecular Neurobiology Group, Institute of Physiological Chemistry, Philipps-University of Marburg, 35032 Marburg, Germany; DFG Research Training Group 'Membrane Plasticity in Tissue Development and Remodeling', GRK 2213, Philipps-University of Marburg, 35032 Marburg, Germany; Molecular Urooncology, Department of Urology, University Hospital Heidelberg, 69120 Heidelberg, Germany
| | - Isabell Metz
- Molecular Neurobiology Group, Institute of Physiological Chemistry, Philipps-University of Marburg, 35032 Marburg, Germany; DFG Research Training Group 'Membrane Plasticity in Tissue Development and Remodeling', GRK 2213, Philipps-University of Marburg, 35032 Marburg, Germany
| | - Marco B Rust
- Molecular Neurobiology Group, Institute of Physiological Chemistry, Philipps-University of Marburg, 35032 Marburg, Germany; DFG Research Training Group 'Membrane Plasticity in Tissue Development and Remodeling', GRK 2213, Philipps-University of Marburg, 35032 Marburg, Germany; Center for Mind, Brain and Behavior (CMBB), University of Marburg and Justus-Liebig-University Giessen, 35032 Marburg, Germany.
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3
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Godini R, Fallahi H, Pocock R. The regulatory landscape of neurite development in Caenorhabditis elegans. Front Mol Neurosci 2022; 15:974208. [PMID: 36090252 PMCID: PMC9453034 DOI: 10.3389/fnmol.2022.974208] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Accepted: 07/26/2022] [Indexed: 11/18/2022] Open
Abstract
Neuronal communication requires precise connectivity of neurite projections (axons and dendrites). Developing neurites express cell-surface receptors that interpret extracellular cues to enable correct guidance toward, and connection with, target cells. Spatiotemporal regulation of neurite guidance molecule expression by transcription factors (TFs) is critical for nervous system development and function. Here, we review how neurite development is regulated by TFs in the Caenorhabditis elegans nervous system. By collecting publicly available transcriptome and ChIP-sequencing data, we reveal gene expression dynamics during neurite development, providing insight into transcriptional mechanisms governing construction of the nervous system architecture.
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Affiliation(s)
- Rasoul Godini
- Development and Stem Cells Program, Department of Anatomy and Developmental Biology, Monash Biomedicine Discovery Institute, Monash University, Melbourne, VIC, Australia
- *Correspondence: Rasoul Godini,
| | - Hossein Fallahi
- Department of Biology, School of Sciences, Razi University, Kermanshah, Iran
| | - Roger Pocock
- Development and Stem Cells Program, Department of Anatomy and Developmental Biology, Monash Biomedicine Discovery Institute, Monash University, Melbourne, VIC, Australia
- Roger Pocock,
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4
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Grintsevich EE, Ahmed G, Ginosyan AA, Wu H, Rich SK, Reisler E, Terman JR. Profilin and Mical combine to impair F-actin assembly and promote disassembly and remodeling. Nat Commun 2021; 12:5542. [PMID: 34545088 PMCID: PMC8452626 DOI: 10.1038/s41467-021-25781-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Accepted: 08/24/2021] [Indexed: 11/30/2022] Open
Abstract
Cellular events require the spatiotemporal interplay between actin assembly and actin disassembly. Yet, how different factors promote the integration of these two opposing processes is unclear. In particular, cellular monomeric (G)-actin is complexed with profilin, which inhibits spontaneous actin nucleation but fuels actin filament (F-actin) assembly by elongation-promoting factors (formins, Ena/VASP). In contrast, site-specific F-actin oxidation by Mical promotes F-actin disassembly and release of polymerization-impaired Mical-oxidized (Mox)-G-actin. Here we find that these two opposing processes connect with one another to orchestrate actin/cellular remodeling. Specifically, we find that profilin binds Mox-G-actin, yet these complexes do not fuel elongation factors’-mediated F-actin assembly, but instead inhibit polymerization and promote further Mox-F-actin disassembly. Using Drosophila as a model system, we show that similar profilin–Mical connections occur in vivo – where they underlie F-actin/cellular remodeling that accompanies Semaphorin–Plexin cellular/axon repulsion. Thus, profilin and Mical combine to impair F-actin assembly and promote F-actin disassembly, while concomitantly facilitating cellular remodeling and plasticity. Actin-based structures in cells and tissues are built and maintained through a poorly understood balance between assembly and disassembly. Here, our findings provide insights into how factors known to promote these opposing effects dynamically integrate to shape cells and tissue systems.
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Affiliation(s)
- Elena E Grintsevich
- Department of Chemistry and Biochemistry, University of California, Los Angeles (UCLA), Los Angeles, CA, 90095, USA. .,Department of Chemistry and Biochemistry, California State University, Long Beach (CSULB), Long Beach, CA, 90840, USA.
| | - Giasuddin Ahmed
- Departments of Neuroscience and Pharmacology, The University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Anush A Ginosyan
- Department of Chemistry and Biochemistry, University of California, Los Angeles (UCLA), Los Angeles, CA, 90095, USA
| | - Heng Wu
- Departments of Neuroscience and Pharmacology, The University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Shannon K Rich
- Departments of Neuroscience and Pharmacology, The University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Emil Reisler
- Department of Chemistry and Biochemistry, University of California, Los Angeles (UCLA), Los Angeles, CA, 90095, USA. .,Molecular Biology Institute, UCLA, Los Angeles, CA, 90095, USA.
| | - Jonathan R Terman
- Departments of Neuroscience and Pharmacology, The University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA.
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5
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Rapti G. A perspective on C. elegans neurodevelopment: from early visionaries to a booming neuroscience research. J Neurogenet 2021; 34:259-272. [PMID: 33446023 DOI: 10.1080/01677063.2020.1837799] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The formation of the nervous system and its striking complexity is a remarkable feat of development. C. elegans served as a unique model to dissect the molecular events in neurodevelopment, from its early visionaries to the current booming neuroscience community. Soon after being introduced as a model, C. elegans was mapped at the level of genes, cells, and synapses, providing the first metazoan with a complete cell lineage, sequenced genome, and connectome. Here, I summarize mechanisms underlying C. elegans neurodevelopment, from the generation and diversification of neural components to their navigation and connectivity. I point out recent noteworthy findings in the fields of glia biology, sex dimorphism and plasticity in neurodevelopment, highlighting how current research connects back to the pioneering studies by Brenner, Sulston and colleagues. Multifaceted investigations in model organisms, connecting genes to cell function and behavior, expand our mechanistic understanding of neurodevelopment while allowing us to formulate emerging questions for future discoveries.
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Affiliation(s)
- Georgia Rapti
- European Molecular Biology Laboratory, Unit of Developmental Biology, Heidelberg, Germany
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6
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Esse R, Grishok A. Caenorhabditis elegans Deficient in DOT-1.1 Exhibit Increases in H3K9me2 at Enhancer and Certain RNAi-Regulated Regions. Cells 2020; 9:cells9081846. [PMID: 32781660 PMCID: PMC7464606 DOI: 10.3390/cells9081846] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Revised: 07/29/2020] [Accepted: 07/29/2020] [Indexed: 01/06/2023] Open
Abstract
The methylation of histone H3 at lysine 79 is a feature of open chromatin. It is deposited by the conserved histone methyltransferase DOT1. Recently, DOT1 localization and H3K79 methylation (H3K79me) have been correlated with enhancers in C. elegans and mammalian cells. Since earlier research implicated H3K79me in preventing heterochromatin formation both in yeast and leukemic cells, we sought to inquire whether a H3K79me deficiency would lead to higher levels of heterochromatic histone modifications, specifically H3K9me2, at developmental enhancers in C. elegans. Therefore, we used H3K9me2 ChIP-seq to compare its abundance in control and dot-1.1 loss-of-function mutant worms, as well as in rde-4; dot-1.1 and rde-1; dot-1.1 double mutants. The rde-1 and rde-4 genes are components of the RNAi pathway in C. elegans, and RNAi is known to initiate H3K9 methylation in many organisms, including C. elegans. We have previously shown that dot-1.1(-) lethality is rescued by rde-1 and rde-4 loss-of-function. Here we found that H3K9me2 was elevated in enhancer, but not promoter, regions bound by the DOT-1.1/ZFP-1 complex in dot-1.1(-) worms. We also found increased H3K9me2 at genes targeted by the ALG-3/4-dependent small RNAs and repeat regions. Our results suggest that ectopic H3K9me2 in dot-1.1(-) could, in some cases, be induced by small RNAs.
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7
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Sundararajan L, Smith CJ, Watson JD, Millis BA, Tyska MJ, Miller DM. Actin assembly and non-muscle myosin activity drive dendrite retraction in an UNC-6/Netrin dependent self-avoidance response. PLoS Genet 2019; 15:e1008228. [PMID: 31220078 PMCID: PMC6605669 DOI: 10.1371/journal.pgen.1008228] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Revised: 07/02/2019] [Accepted: 06/04/2019] [Indexed: 01/08/2023] Open
Abstract
Dendrite growth is constrained by a self-avoidance response that induces retraction but the downstream pathways that balance these opposing mechanisms are unknown. We have proposed that the diffusible cue UNC-6(Netrin) is captured by UNC-40(DCC) for a short-range interaction with UNC-5 to trigger self-avoidance in the C. elegans PVD neuron. Here we report that the actin-polymerizing proteins UNC-34(Ena/VASP), WSP-1(WASP), UNC-73(Trio), MIG-10(Lamellipodin) and the Arp2/3 complex effect dendrite retraction in the self-avoidance response mediated by UNC-6(Netrin). The paradoxical idea that actin polymerization results in shorter rather than longer dendrites is explained by our finding that NMY-1 (non-muscle myosin II) is necessary for retraction and could therefore mediate this effect in a contractile mechanism. Our results also show that dendrite length is determined by the antagonistic effects on the actin cytoskeleton of separate sets of effectors for retraction mediated by UNC-6(Netrin) versus outgrowth promoted by the DMA-1 receptor. Thus, our findings suggest that the dendrite length depends on an intrinsic mechanism that balances distinct modes of actin assembly for growth versus retraction. Neurons may extend highly branched dendrites to detect input over a broad receptive field. The formation of actin filaments may drive dendrite elongation. The architecture of the dendritic arbor also depends on mechanisms that limit expansion. For example, sister dendrites from a single neuron usually do not overlap due to self-avoidance. Although cell surface proteins are known to mediate self-avoidance, the downstream pathways that drive dendrite retraction in this phenomenon are largely unknown. Studies of the highly branched PVD sensory neuron in C. elegans have suggested a model of self-avoidance in which the UNC-40/DCC receptor captures the diffusible cue UNC-6/Netrin at the tips of PVD dendrites where it interacts with the UNC-5 receptor on an opposing sister dendrite to induce retraction. Here we report genetic evidence that UNC-5-dependent retraction requires downstream actin polymerization. This finding evokes a paradox: How might actin polymerization drive both dendrite growth and retraction? We propose two answers: (1) Distinct sets of effectors are involved in actin assembly for growth vs retraction; (2) Non-muscle myosin interacts with a nascent actin assemblage to trigger retraction. Our results show that dendrite length depends on the balanced effects of specific molecular components that induce growth vs retraction.
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Affiliation(s)
- Lakshmi Sundararajan
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Cody J. Smith
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Joseph D. Watson
- Neuroscience Graduate Program, Vanderbilt University, Nashville, Nashville, Tennessee, United States of America
| | - Bryan A. Millis
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, Tennessee, United States of America
- Cell Imaging Shared Resource, Vanderbilt University, Nashville, Nashville, Tennessee, United States of America
- Vanderbilt Biophotonics Center, Vanderbilt University, Nashville, Nashville, Tennessee, United States of America
| | - Matthew J. Tyska
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, Tennessee, United States of America
| | - David M. Miller
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, Tennessee, United States of America
- Neuroscience Graduate Program, Vanderbilt University, Nashville, Nashville, Tennessee, United States of America
- * E-mail:
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8
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Sundararajan L, Stern J, Miller DM. Mechanisms that regulate morphogenesis of a highly branched neuron in C. elegans. Dev Biol 2019; 451:53-67. [PMID: 31004567 DOI: 10.1016/j.ydbio.2019.04.002] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Revised: 03/09/2019] [Accepted: 04/05/2019] [Indexed: 02/08/2023]
Abstract
The shape of an individual neuron is linked to its function with axons sending signals to other cells and dendrites receiving them. Although much is known of the mechanisms for axonal outgrowth, the striking complexity of dendritic architecture has hindered efforts to uncover pathways that direct dendritic branching. Here we review the results of an experimental strategy that exploits the power of genetic analysis and live cell imaging of the PVD sensory neuron in C. elegans to reveal key molecular drivers of dendrite morphogenesis.
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Affiliation(s)
- Lakshmi Sundararajan
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240, USA
| | - Jamie Stern
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240, USA
| | - David M Miller
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240, USA.
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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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10
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Limerick G, Tang X, Lee WS, Mohamed A, Al-Aamiri A, Wadsworth WG. A Statistically-Oriented Asymmetric Localization (SOAL) Model for Neuronal Outgrowth Patterning by Caenorhabditis elegans UNC-5 (UNC5) and UNC-40 (DCC) Netrin Receptors. Genetics 2018; 208:245-272. [PMID: 29092889 PMCID: PMC5753861 DOI: 10.1534/genetics.117.300460] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Accepted: 10/29/2017] [Indexed: 01/01/2023] Open
Abstract
Neurons extend processes that vary in number, length, and direction of "outgrowth". Extracellular cues help determine outgrowth patterns. In Caenorhabditis elegans, neurons respond to the extracellular UNC-6 (netrin) cue via UNC-40 (DCC) and UNC-5 (UNC5) receptors. Previously, we presented evidence that UNC-40 asymmetric localization at the plasma membrane is self-organizing, and that UNC-40 can localize and mediate outgrowth at randomly selected sites. Here, we provide further evidence for a statistically-oriented asymmetric localization (SOAL) model in which UNC-5 receptor activity affects patterns of axon outgrowth by regulating UNC-40 asymmetric localization. According to the SOAL model, the direction of outgrowth activity fluctuates across the membrane over time. Random walk modeling predicts that increasing the degree to which the direction of outgrowth fluctuates will decrease the outward displacement of the membrane. By differentially affecting the degree to which the direction of outgrowth activity fluctuates over time, extracellular cues can produce different rates of outgrowth along the surface and create patterns of "extension". Consistent with the SOAL model, we show that unc-5 mutations alter UNC-40 asymmetric localization, increase the degree to which the direction of outgrowth fluctuates, and reduce the extent of outgrowth in multiple directions relative to the source of UNC-6 These results are inconsistent with current models, which predict that UNC-5 mediates a "repulsive" response to UNC-6 Genetic interactions suggest that UNC-5 acts through the UNC-53 (NAV2) cytoplasmic protein to regulate UNC-40 asymmetric localization in response to both the UNC-6 and EGL-20 (Wnt) extracellular cues.
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Affiliation(s)
- Gerard Limerick
- Department of Pathology and Laboratory Medicine, Rutgers Robert Wood Johnson Medical School, Piscataway, New Jersey 08854
| | - Xia Tang
- Department of Pathology and Laboratory Medicine, Rutgers Robert Wood Johnson Medical School, Piscataway, New Jersey 08854
| | - Won Suk Lee
- Department of Pathology and Laboratory Medicine, Rutgers Robert Wood Johnson Medical School, Piscataway, New Jersey 08854
| | - Ahmed Mohamed
- Department of Pathology and Laboratory Medicine, Rutgers Robert Wood Johnson Medical School, Piscataway, New Jersey 08854
| | - Aseel Al-Aamiri
- Department of Pathology and Laboratory Medicine, Rutgers Robert Wood Johnson Medical School, Piscataway, New Jersey 08854
| | - William G Wadsworth
- Department of Pathology and Laboratory Medicine, Rutgers Robert Wood Johnson Medical School, Piscataway, New Jersey 08854
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11
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Shen Q, Toulabi LB, Shi H, Nicklow EE, Liu J. The forkhead transcription factor UNC-130/FOXD integrates both BMP and Notch signaling to regulate dorsoventral patterning of the C. elegans postembryonic mesoderm. Dev Biol 2018; 433:75-83. [PMID: 29155044 PMCID: PMC5722696 DOI: 10.1016/j.ydbio.2017.11.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Revised: 11/13/2017] [Accepted: 11/15/2017] [Indexed: 11/17/2022]
Abstract
The proper development of a multicellular organism requires precise spatial and temporal coordination of cell intrinsic and cell extrinsic regulatory mechanisms. Both Notch signaling and bone morphogenetic protein (BMP) signaling function to regulate the proper development of the C. elegans postembryonic mesoderm. We have identified the C. elegans FOXD transcription factor UNC-130 as a major target functioning downstream of both BMP signaling and Notch signaling to regulate dorsoventral patterning of the postembryonic mesoderm. We showed that unc-130 expression in the postembryonic M lineage is asymmetric: its absence of expression in the dorsal side of the M lineage requires the antagonism of BMP signaling by the zinc finger transcription factor SMA-9, while its expression in the ventral side of the M lineage is activated by LIN-12/Notch signaling. We further showed that the regulation of UNC-130 expression by BMP signaling and Notch signaling is specific to the M lineage, as the ventral expression of UNC-130 in the embryonically-derived bodywall muscles was not affected in either BMP pathway or Notch pathway mutants. Finally, we showed that the function of UNC-130 in the M lineage is independent of UNC-129, a gene previously shown to function downstream of and be repressed by UNC-130 for axon guidance. Our studies uncovered a new function of UNC-130/FOXD in the C. elegans postembryonic mesoderm, and identify UNC-130 as a critical factor that integrates two independent spatial cues for the proper patterning and fate specification of the C. elegans postembryonic mesoderm.
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Affiliation(s)
- Qinfang Shen
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, United States
| | - Leila B Toulabi
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, United States
| | - Herong Shi
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, United States
| | - Erin E Nicklow
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, United States
| | - Jun Liu
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, United States.
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12
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The directed migration of gonadal distal tip cells in Caenorhabditis elegans requires NGAT-1, a ß1,4-N-acetylgalactosaminyltransferase enzyme. PLoS One 2017; 12:e0183049. [PMID: 28817611 PMCID: PMC5560668 DOI: 10.1371/journal.pone.0183049] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Accepted: 07/30/2017] [Indexed: 01/01/2023] Open
Abstract
Glycoproteins such as growth factor receptors and extracellular matrix have well-known functions in development and cancer progression, however, the glycans at sites of modification are often heterogeneous molecular populations which makes their functional characterization challenging. Here we provide evidence for a specific, discrete, well-defined glycan modification and regulation of a stage-specific cell migration in Caenorhabditis elegans. We show that a chain-terminating, putative null mutation in the gene encoding a predicted β1,4-N-acetylgalactosaminyltransferase, named ngat-1, causes a maternally rescued temperature sensitive (ts) defect in the second phase of the three phase migration pattern of the posterior, but not the anterior, hermaphrodite Distal Tip Cell (DTC). An amino-terminal partial deletion of ngat-1 causes a similar but lower penetrance ts phenotype. The existence of multiple ts alleles with distinctly different molecular DNA lesions, neither of which is likely to encode a ts protein, indicates that NGAT-1 normally prevents innate temperature sensitivity for phase 2 DTC pathfinding. Temperature shift analyses indicate that the ts period for the ngat-1 mutant defect ends by the beginning of post-embryonic development-nearly 3 full larval stages prior to the defective phase 2 migration affected by ngat-1 mutations. NGAT-1 homologs generate glycan-terminal GalNAc-β1-4GlcNAc, referred to as LacdiNAc modifications, on glycoproteins and glycolipids. We also found that the absence of the GnT1/Mgat1 activity [UDP-N-acetyl-D-glucosamine:α-3-D-mannoside β-1,2-N-acetylglucosaminyltransferase 1 (encoded by C. elegans gly-12, gly-13, and gly-14 and homologous to vertebrate GnT1/Mgat1)], causes a similar spectrum of DTC phenotypes as ngat-1 mutations-primarily affecting posterior DTC phase 2 migration and preventing manifestation of the same innate ts period as ngat-1. GnT1/Mgat1 is a medial Golgi enzyme known to modify mannose residues and initiate N-glycan branching, an essential step in the biosynthesis of hybrid, paucimannose and complex-type N-glycans. Quadruple mutant animals bearing putative null mutations in ngat-1 and the three GnT genes (gly-12, gly-13, gly-14) were not enhanced for DTC migration defects, suggesting NGAT-1 and GnT1 act in the same pathway. These findings suggest that GnTI generates an N-glycan substrate for NGAT-1 modification, which is required at restrictive temperature (25°C) to prevent, stabilize, reverse or compensate a perinatal thermo-labile process (or structure) causing late larval stage DTC phase 2 migration errors.
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Gopal AA, Rappaz B, Rouger V, Martyn IB, Dahlberg PD, Meland RJ, Beamish IV, Kennedy TE, Wiseman PW. Netrin-1-Regulated Distribution of UNC5B and DCC in Live Cells Revealed by TICCS. Biophys J 2017; 110:623-634. [PMID: 26840727 DOI: 10.1016/j.bpj.2015.12.022] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Revised: 12/16/2015] [Accepted: 12/21/2015] [Indexed: 01/01/2023] Open
Abstract
Netrins are secreted proteins that direct cell migration and adhesion during development. Netrin-1 binds its receptors deleted in colorectal cancer (DCC) and the UNC5 homologs (UNC5A-D) to activate downstream signaling that ultimately directs cytoskeletal reorganization. To investigate how netrin-1 regulates the dynamic distribution of DCC and UNC5 homologs, we applied fluorescence confocal and total internal reflection fluorescence microscopy, and sliding window temporal image cross correlation spectroscopy, to measure time profiles of the plasma membrane distribution, aggregation state, and interaction fractions of fluorescently tagged netrin receptors expressed in HEK293T cells. Our measurements reveal changes in receptor aggregation that are consistent with netrin-1-induced recruitment of DCC-enhanced green fluorescent protein (EGFP) from intracellular vesicles to the plasma membrane. Netrin-1 also induced colocalization of coexpressed full-length DCC-EGFP with DCC-T-mCherry, a putative DCC dominant negative that replaces the DCC intracellular domain with mCherry, consistent with netrin-1-induced receptor oligomerization, but with no change in aggregation state with time, providing evidence that signaling via the DCC intracellular domain triggers DCC recruitment to the plasma membrane. UNC5B expressed alone was also recruited by netrin-1 to the plasma membrane. Coexpressed DCC and UNC5 homologs are proposed to form a heteromeric netrin-receptor complex to mediate a chemorepellent response. Application of temporal image cross correlation spectroscopy to image series of cells coexpressing UNC5B-mCherry and DCC-EGFP revealed a netrin-1-induced increase in colocalization, with both receptors recruited to the plasma membrane from preexisting clusters, consistent with vesicular recruitment and receptor heterooligomerization. Plasma membrane recruitment of DCC or UNC5B was blocked by application of the netrin-1 VI-V peptide, which fails to activate chemoattraction, or by pharmacological block of Src family kinase signaling, consistent with receptor recruitment requiring netrin-1-activated signaling. Our findings reveal a mechanism activated by netrin-1 that recruits DCC and UNC5B to the plasma membrane.
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Affiliation(s)
- Angelica A Gopal
- Department of Chemistry, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada; McGill Program in Neuroengineering, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Benjamin Rappaz
- McGill Program in Neuroengineering, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada; Department of Physics, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Vincent Rouger
- Department of Chemistry, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Iain B Martyn
- Department of Physics, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Peter D Dahlberg
- Department of Physics, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Rachel J Meland
- Department of Chemistry, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Ian V Beamish
- McGill Program in Neuroengineering, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada; Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Timothy E Kennedy
- McGill Program in Neuroengineering, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada; Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
| | - Paul W Wiseman
- Department of Chemistry, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada; McGill Program in Neuroengineering, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada; Department of Physics, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada.
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14
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Blanchette CR, Thackeray A, Perrat PN, Hekimi S, Bénard CY. Functional Requirements for Heparan Sulfate Biosynthesis in Morphogenesis and Nervous System Development in C. elegans. PLoS Genet 2017; 13:e1006525. [PMID: 28068429 PMCID: PMC5221758 DOI: 10.1371/journal.pgen.1006525] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Accepted: 12/06/2016] [Indexed: 12/28/2022] Open
Abstract
The regulation of cell migration is essential to animal development and physiology. Heparan sulfate proteoglycans shape the interactions of morphogens and guidance cues with their respective receptors to elicit appropriate cellular responses. Heparan sulfate proteoglycans consist of a protein core with attached heparan sulfate glycosaminoglycan chains, which are synthesized by glycosyltransferases of the exostosin (EXT) family. Abnormal HS chain synthesis results in pleiotropic consequences, including abnormal development and tumor formation. In humans, mutations in either of the exostosin genes EXT1 and EXT2 lead to osteosarcomas or multiple exostoses. Complete loss of any of the exostosin glycosyltransferases in mouse, fish, flies and worms leads to drastic morphogenetic defects and embryonic lethality. Here we identify and study previously unavailable viable hypomorphic mutations in the two C. elegans exostosin glycosyltransferases genes, rib-1 and rib-2. These partial loss-of-function mutations lead to a severe reduction of HS levels and result in profound but specific developmental defects, including abnormal cell and axonal migrations. We find that the expression pattern of the HS copolymerase is dynamic during embryonic and larval morphogenesis, and is sustained throughout life in specific cell types, consistent with HSPGs playing both developmental and post-developmental roles. Cell-type specific expression of the HS copolymerase shows that HS elongation is required in both the migrating neuron and neighboring cells to coordinate migration guidance. Our findings provide insights into general principles underlying HSPG function in development. During animal development, cells and neurons navigate long distances to reach their final target destinations. Migrating cells are guided by extracellular molecular cues, and cellular responses to these cues are regulated by heparan sulfate proteoglycans. Heparan sulfate proteoglycans are proteins with long heparan sulfate polysaccharide chains attached. Here we identify and study previously unavailable viable mutants that disrupt the elongation of the heparan sulfate chains in the nematode C. elegans. Our analysis shows that these HS-chain-elongation mutations affect the development of the nervous system as they result in misguided migrations of neurons and axons. Furthermore, we find that heparan sulfate chain elongation occurs in numerous cell types during development and that the coordinated production of heparan sulfate proteoglycans, in both the migrating cell and neighboring tissues, ensures proper migration. Our findings highlight the critical roles of heparan sulfate proteoglycans in nervous system development and the evolutionary conservation of the molecular mechanisms driving guided migrations.
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Affiliation(s)
- Cassandra R. Blanchette
- Department of Neurobiology, UMass Medical School, Worcester, Massachusetts, United States of America
| | - Andrea Thackeray
- Department of Neurobiology, UMass Medical School, Worcester, Massachusetts, United States of America
| | - Paola N. Perrat
- Department of Neurobiology, UMass Medical School, Worcester, Massachusetts, United States of America
| | | | - Claire Y. Bénard
- Department of Neurobiology, UMass Medical School, Worcester, Massachusetts, United States of America
- Department of Biological Sciences, University of Quebec at Montreal, Montreal, Canada
- * E-mail: ,
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Chisholm AD, Hutter H, Jin Y, Wadsworth WG. The Genetics of Axon Guidance and Axon Regeneration in Caenorhabditis elegans. Genetics 2016; 204:849-882. [PMID: 28114100 PMCID: PMC5105865 DOI: 10.1534/genetics.115.186262] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Accepted: 09/06/2016] [Indexed: 11/18/2022] Open
Abstract
The correct wiring of neuronal circuits depends on outgrowth and guidance of neuronal processes during development. In the past two decades, great progress has been made in understanding the molecular basis of axon outgrowth and guidance. Genetic analysis in Caenorhabditis elegans has played a key role in elucidating conserved pathways regulating axon guidance, including Netrin signaling, the slit Slit/Robo pathway, Wnt signaling, and others. Axon guidance factors were first identified by screens for mutations affecting animal behavior, and by direct visual screens for axon guidance defects. Genetic analysis of these pathways has revealed the complex and combinatorial nature of guidance cues, and has delineated how cues guide growth cones via receptor activity and cytoskeletal rearrangement. Several axon guidance pathways also affect directed migrations of non-neuronal cells in C. elegans, with implications for normal and pathological cell migrations in situations such as tumor metastasis. The small number of neurons and highly stereotyped axonal architecture of the C. elegans nervous system allow analysis of axon guidance at the level of single identified axons, and permit in vivo tests of prevailing models of axon guidance. C. elegans axons also have a robust capacity to undergo regenerative regrowth after precise laser injury (axotomy). Although such axon regrowth shares some similarities with developmental axon outgrowth, screens for regrowth mutants have revealed regeneration-specific pathways and factors that were not identified in developmental screens. Several areas remain poorly understood, including how major axon tracts are formed in the embryo, and the function of axon regeneration in the natural environment.
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Affiliation(s)
| | - Harald Hutter
- Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, V5A 1S6, Canada
| | - Yishi Jin
- Section of Neurobiology, Division of Biological Sciences, and
- Department of Cellular and Molecular Medicine, School of Medicine, University of California, San Diego, La Jolla, California 92093
- Department of Pathology and Laboratory Medicine, Howard Hughes Medical Institute, Chevy Chase, Maryland, and
| | - William G Wadsworth
- Department of Pathology, Rutgers Robert Wood Johnson Medical School, Piscataway, New Jersey 08854
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Klingler E, Martin PM, Garcia M, Moreau-Fauvarque C, Falk J, Chareyre F, Giovannini M, Chédotal A, Girault JA, Goutebroze L. The cytoskeleton-associated protein SCHIP1 is involved in axon guidance, and is required for piriform cortex and anterior commissure development. Development 2015; 142:2026-36. [DOI: 10.1242/dev.119248] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Accepted: 04/10/2015] [Indexed: 01/14/2023]
Abstract
ABSTRACT
SCHIP1 is a cytoplasmic partner of cortical cytoskeleton ankyrins. The IQCJ-SCHIP1 isoform is a component of axon initial segments and nodes of Ranvier of mature axons in peripheral and central nervous systems, where it associates with membrane complexes comprising cell adhesion molecules. SCHIP1 is also expressed in the mouse developing central nervous system during embryonic stages of active axonogenesis. Here, we identify a new and early role for SCHIP1 during axon development and establishment of the anterior commissure (AC). The AC is composed of axons from the piriform cortex, the anterior olfactory nucleus and the amygdala. Schip1 mutant mice displayed early defects in AC development that might result from impaired axon growth and guidance. In addition, mutant mice presented a reduced thickness of the piriform cortex, which affected projection neurons in layers 2/3 and was likely to result from cell death rather than from impairment of neuron generation or migration. Piriform cortex neurons from E14.5 mutant embryos displayed axon initiation/outgrowth delay and guidance defects in vitro. The sensitivity of growth cones to semaphorin 3F and Eph receptor B2, two repulsive guidance cues crucial for AC development, was increased, providing a possible basis for certain fiber tract alterations. Thus, our results reveal new evidence for the involvement of cortical cytoskeleton-associated proteins in the regulation of axon development and their importance for the formation of neuronal circuits.
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Affiliation(s)
- Esther Klingler
- INSERM, UMR-S 839, Paris F-75005, France
- Sorbonne Universités, UPMC Univ Paris 06, Paris F-75005, France
- Institut du Fer à Moulin, Paris F-75005, France
| | - Pierre-Marie Martin
- INSERM, UMR-S 839, Paris F-75005, France
- Sorbonne Universités, UPMC Univ Paris 06, Paris F-75005, France
- Institut du Fer à Moulin, Paris F-75005, France
| | - Marta Garcia
- INSERM, UMR-S 839, Paris F-75005, France
- Sorbonne Universités, UPMC Univ Paris 06, Paris F-75005, France
- Institut du Fer à Moulin, Paris F-75005, France
| | - Caroline Moreau-Fauvarque
- Sorbonne Universités, UPMC Univ Paris 06, Paris F-75005, France
- Institut de la Vision, INSERM, UMR-S 968, Paris F-75012, France
- CNRS, UMR 7210, Paris F-75012, France
| | - Julien Falk
- Université Claude Bernard Lyon 1, CNRS, UMR 5534, CGphiMC, Lyon F-69622, France
| | - Fabrice Chareyre
- House Research Institute, Center for Neural Tumor Research, Los Angeles, CA 90095-1624, USA
| | - Marco Giovannini
- Department of Head and Neck Surgery, David Geffen School of Medicine, UCLA, Los Angeles, CA 90027, USA
| | - Alain Chédotal
- Sorbonne Universités, UPMC Univ Paris 06, Paris F-75005, France
- Institut de la Vision, INSERM, UMR-S 968, Paris F-75012, France
- CNRS, UMR 7210, Paris F-75012, France
| | - Jean-Antoine Girault
- INSERM, UMR-S 839, Paris F-75005, France
- Sorbonne Universités, UPMC Univ Paris 06, Paris F-75005, France
- Institut du Fer à Moulin, Paris F-75005, France
| | - Laurence Goutebroze
- INSERM, UMR-S 839, Paris F-75005, France
- Sorbonne Universités, UPMC Univ Paris 06, Paris F-75005, France
- Institut du Fer à Moulin, Paris F-75005, France
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17
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Norris AD, Sundararajan L, Morgan DE, Roberts ZJ, Lundquist EA. The UNC-6/Netrin receptors UNC-40/DCC and UNC-5 inhibit growth cone filopodial protrusion via UNC-73/Trio, Rac-like GTPases and UNC-33/CRMP. Development 2015; 141:4395-405. [PMID: 25371370 PMCID: PMC4302909 DOI: 10.1242/dev.110437] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
UNC-6/Netrin is a conserved axon guidance cue that can mediate both attraction and repulsion. We previously discovered that attractive UNC-40/DCC receptor signaling stimulates growth cone filopodial protrusion and that repulsive UNC-40–UNC-5 heterodimers inhibit filopodial protrusion in C. elegans. Here, we identify cytoplasmic signaling molecules required for UNC-6-mediated inhibition of filopodial protrusion involved in axon repulsion. We show that the Rac-like GTPases CED-10 and MIG-2, the Rac GTP exchange factor UNC-73/Trio, UNC-44/Ankyrin and UNC-33/CRMP act in inhibitory UNC-6 signaling. These molecules were required for the normal limitation of filopodial protrusion in developing growth cones and for inhibition of growth cone filopodial protrusion caused by activated MYR::UNC-40 and MYR::UNC-5 receptor signaling. Epistasis studies using activated CED-10 and MIG-2 indicated that UNC-44 and UNC-33 act downstream of the Rac-like GTPases in filopodial inhibition. UNC-73, UNC-33 and UNC-44 did not affect the accumulation of full-length UNC-5::GFP and UNC-40::GFP in growth cones, consistent with a model in which UNC-73, UNC-33 and UNC-44 influence cytoskeletal function during growth cone filopodial inhibition.
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Affiliation(s)
- Adam D Norris
- Programs in Genetics and Molecular, Cellular, and Developmental Biology, Department of Molecular Biosciences, The University of Kansas, 1200 Sunnyside Avenue, Lawrence, KS 66045, USA
| | - Lakshmi Sundararajan
- Programs in Genetics and Molecular, Cellular, and Developmental Biology, Department of Molecular Biosciences, The University of Kansas, 1200 Sunnyside Avenue, Lawrence, KS 66045, USA
| | - Dyan E Morgan
- Programs in Genetics and Molecular, Cellular, and Developmental Biology, Department of Molecular Biosciences, The University of Kansas, 1200 Sunnyside Avenue, Lawrence, KS 66045, USA
| | - Zachary J Roberts
- Programs in Genetics and Molecular, Cellular, and Developmental Biology, Department of Molecular Biosciences, The University of Kansas, 1200 Sunnyside Avenue, Lawrence, KS 66045, USA
| | - Erik A Lundquist
- Programs in Genetics and Molecular, Cellular, and Developmental Biology, Department of Molecular Biosciences, The University of Kansas, 1200 Sunnyside Avenue, Lawrence, KS 66045, USA
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Pilon M. Developmental genetics of the Caenorhabditis elegans pharynx. WILEY INTERDISCIPLINARY REVIEWS. DEVELOPMENTAL BIOLOGY 2014; 3:263-80. [PMID: 25262818 PMCID: PMC4314705 DOI: 10.1002/wdev.139] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/03/2014] [Revised: 04/03/2014] [Accepted: 04/15/2014] [Indexed: 11/07/2022]
Abstract
The Caenorhabditis elegans pharynx is a rhythmically pumping organ composed initially of 80 cells that, through fusions, amount to 62 cells in the adult worm. During the first 100 min of development, most future pharyngeal cells are born and gather into a double-plate primordium surrounded by a basal lamina. All pharyngeal cells express the transcription factor PHA-4, of which the concentration increases throughout development, triggering a sequential activation of genes with promoters responding differentially to PHA-4 protein levels. The oblong-shaped pharyngeal primordium becomes polarized, many cells taking on wedge shapes with their narrow ends toward the center, hence forming an epithelial cyst. The primordium then elongates, and reorientations of the cells at the anterior and posterior ends form the mouth and pharyngeal-intestinal openings, respectively. The 20 pharyngeal neurons establish complex but reproducible trajectories using 'fishing line' and growth cone-driven mechanisms, and the gland cells also similarly develop their processes. The genetics behind many fate decisions and morphogenetic processes are being elucidated, and reveal the pharynx to be a fruitful model for developmental biologists.
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Affiliation(s)
- Marc Pilon
- Department of Chemistry and Molecular Biology, University of GothenburgGothenburg, Sweden
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19
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Fritzenwanker JH, Gerhart J, Freeman RM, Lowe CJ. The Fox/Forkhead transcription factor family of the hemichordate Saccoglossus kowalevskii. EvoDevo 2014; 5:17. [PMID: 24987514 PMCID: PMC4077281 DOI: 10.1186/2041-9139-5-17] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Accepted: 04/03/2014] [Indexed: 12/31/2022] Open
Abstract
Background The Fox gene family is a large family of transcription factors that arose early in organismal evolution dating back to at least the common ancestor of metazoans and fungi. They are key components of many gene regulatory networks essential for embryonic development. Although much is known about the role of Fox genes during vertebrate development, comprehensive comparative studies outside vertebrates are sparse. We have characterized the Fox transcription factor gene family from the genome of the enteropneust hemichordate Saccoglossus kowalevskii, including phylogenetic analysis, genomic organization, and expression analysis during early development. Hemichordates are a sister group to echinoderms, closely related to chordates and are a key group for tracing the evolution of gene regulatory mechanisms likely to have been important in the diversification of the deuterostome phyla. Results Of the 22 Fox gene families that were likely present in the last common ancestor of all deuterostomes, S. kowalevskii has a single ortholog of each group except FoxH, which we were unable to detect, and FoxQ2, which has three paralogs. A phylogenetic analysis of the FoxQ2 family identified an ancestral duplication in the FoxQ2 lineage at the base of the bilaterians. The expression analyses of all 23 Fox genes of S. kowalevskii provide insights into the evolution of components of the regulatory networks for the development of pharyngeal gill slits (foxC, foxL1, and foxI), mesoderm patterning (foxD, foxF, foxG), hindgut development (foxD, foxI), cilia formation (foxJ1), and patterning of the embryonic apical territory (foxQ2). Conclusions Comparisons of our results with data from echinoderms, chordates, and other bilaterians help to develop hypotheses about the developmental roles of Fox genes that likely characterized ancestral deuterostomes and bilaterians, and more recent clade-specific innovations.
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Affiliation(s)
- Jens H Fritzenwanker
- Hopkins Marine Station of Stanford University, 120 Oceanview Boulevard, Pacific Grove, CA 93950, USA
| | - John Gerhart
- Department of Molecular and Cell Biology, University of California, 142 Life Sciences Addition #3200, Berkeley, CA 94720, USA
| | - Robert M Freeman
- Department of Systems Biology, Harvard Medical School, 200 Longwood Avenue, Warren Alpert 536, Boston, MA 02115, USA
| | - Christopher J Lowe
- Hopkins Marine Station of Stanford University, 120 Oceanview Boulevard, Pacific Grove, CA 93950, USA
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Tian C, Shi H, Xiong S, Hu F, Xiong WC, Liu J. The neogenin/DCC homolog UNC-40 promotes BMP signaling via the RGM protein DRAG-1 in C. elegans. Development 2013; 140:4070-80. [PMID: 24004951 DOI: 10.1242/dev.099838] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The deleted in colorectal cancer (DCC) homolog neogenin functions in both netrin- and repulsive guidance molecule (RGM)-mediated axon guidance and in bone morphogenetic protein (BMP) signaling. How neogenin functions in mediating BMP signaling is not well understood. We show that the sole C. elegans DCC/neogenin homolog UNC-40 positively modulates a BMP-like pathway by functioning in the signal-receiving cells at the ligand/receptor level. This function of UNC-40 is independent of its role in netrin-mediated axon guidance, but requires its association with the RGM protein DRAG-1. We have identified the key residues in the extracellular domain of UNC-40 that are crucial for UNC-40-DRAG-1 interaction and UNC-40 function. Surprisingly, the extracellular domain of UNC-40 is sufficient to promote BMP signaling, in clear contrast to the requirement of its intracellular domain in mediating axon guidance. Mouse neogenin lacking the intracellular domain is also capable of mediating BMP signaling. These findings reveal an unexpected mode of action for neogenin regulation of BMP signaling.
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Affiliation(s)
- Chenxi Tian
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
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21
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Tian C, Liu J. Repulsive guidance molecules (RGMs) and neogenin in bone morphogenetic protein (BMP) signaling. Mol Reprod Dev 2013; 80:700-17. [PMID: 23740870 DOI: 10.1002/mrd.22199] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2013] [Accepted: 05/28/2013] [Indexed: 02/06/2023]
Abstract
Bone morphogenetic proteins (BMPs) belong to the transforming growth factor-beta (TGFβ) superfamily. BMPs mediate a highly conserved signal transduction cascade through the type-I and type-II serine/threonine kinase receptors and intracellular Smad proteins, which regulate multiple developmental and homeostatic processes. Mutations in this pathway can cause various diseases in humans, such as skeletal disorders, cardiovascular diseases, and various cancers. Multiple levels of regulation, including extracellular regulation, help to ensure proper spatiotemporal control of BMP signaling in the right cellular context. The family of repulsive guidance molecules (RGMs) and the type-I transmembrane protein neogenin, a paralog of DCC (Deleted in Colorectal Cancer), have been implicated in modulating the BMP pathway. In this review, we discuss the properties and functions of RGM proteins and neogenin, focusing on their roles in the modulation of BMP signal transduction.
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Affiliation(s)
- Chenxi Tian
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York
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Abstract
Transforming Growth Factor-β (TGF-β) superfamily ligands regulate many aspects of cell identity, function, and survival in multicellular animals. Genes encoding five TGF-β family members are present in the genome of C. elegans. Two of the ligands, DBL-1 and DAF-7, signal through a canonical receptor-Smad signaling pathway; while a third ligand, UNC-129, interacts with a noncanonical signaling pathway. No function has yet been associated with the remaining two ligands. Here we summarize these signaling pathways and their biological functions.
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Affiliation(s)
- Tina L Gumienny
- Department of Molecular and Cellular Medicine, Texas A&M Health Science Center College of Medicine, College Station, TX 77843, USA
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Bin JM, Rajasekharan S, Kuhlmann T, Hanes I, Marcal N, Han D, Rodrigues SP, Leong SY, Newcombe J, Antel JP, Kennedy TE. Full-length and fragmented netrin-1 in multiple sclerosis plaques are inhibitors of oligodendrocyte precursor cell migration. THE AMERICAN JOURNAL OF PATHOLOGY 2013; 183:673-80. [PMID: 23831296 DOI: 10.1016/j.ajpath.2013.06.004] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2013] [Revised: 05/29/2013] [Accepted: 06/03/2013] [Indexed: 10/26/2022]
Abstract
Oligodendrocytes exhibit a limited capacity to remyelinate in multiple sclerosis. Factors present in multiple sclerosis lesions are thought to inhibit oligodendrocyte precursor cell migration, limiting their recruitment to axons requiring remyelination; however, few inhibitors have been identified. A candidate inhibitor is netrin-1, a secreted protein that repels migrating oligodendrocyte precursor cells during neural development and is expressed by myelinating oligodendrocytes in the mature rodent central nervous system. Herein, we examined the distribution of netrin-1 in adult human white matter and multiple sclerosis lesions. We detected full-length netrin-1 protein and shorter netrin-1 fragments in samples of normal white matter and of multiple sclerosis lesions from adult human brain. We demonstrate that peptides corresponding to amino terminal domains VI and V of netrin-1 repel migrating oligodendrocyte precursor cells, but lack the chemoattractant activity of full-length netrin-1. Furthermore, recombinant domains VI-V of netrin-1 disrupt the chemoattractant activity of full-length netrin-1, consistent with a competitive mechanism of action. These findings indicate that full-length and fragmented forms of netrin-1, found in multiple sclerosis lesions, have the capacity to inhibit oligodendrocyte precursor migration, identifying netrin-1 as a potential target for therapies that promote remyelination.
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Affiliation(s)
- Jenea M Bin
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
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Mizumoto K, Shen K. Interaxonal interaction defines tiled presynaptic innervation in C. elegans. Neuron 2013; 77:655-66. [PMID: 23439119 DOI: 10.1016/j.neuron.2012.12.031] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/07/2012] [Indexed: 10/27/2022]
Abstract
VIDEO ABSTRACT Cellular interactions between neighboring axons are essential for global topographic map formation. Here we show that axonal interactions also precisely instruct the location of synapses. Motoneurons form en passant synapses in Caenorhabditis elegans. Although axons from the same neuron class significantly overlap, each neuron innervates a unique and tiled segment of the muscle field by restricting its synapses to a distinct subaxonal domain-a phenomenon we term synaptic tiling. Using DA8 and DA9 motoneurons, we found that the synaptic tiling requires the PlexinA4 homolog, PLX-1, and two transmembrane semaphorins. In the plexin or semaphorin mutants, synaptic domains from both neurons expand and overlap with each other without guidance defects. In a semaphorin-dependent manner, PLX-1 is concentrated at the synapse-free axonal segment, delineating the tiling border. Furthermore, plexin inhibits presynapse formation by suppressing synaptic F-actin through its cytoplasmic GTPase-activating protein (GAP) domain. Hence, contact-dependent, intra-axonal plexin signaling specifies synaptic circuits by inhibiting synapse formation at the subcellular loci.
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Affiliation(s)
- Kota Mizumoto
- Department of Biology, Howard Hughes Medical Institute, Stanford University, 385 Serra Mall, Stanford, CA 94305, USA
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25
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Abstract
This review is focusing on a critical mediator of embryonic and postnatal development with multiple implications in inflammation, neoplasia, and other pathological situations in brain and peripheral tissues. These morphogenetic guidance and dependence processes are involved in several malignancies targeting the epithelial and immune systems including the progression of human colorectal cancers. We consider the most important findings and their impact on basic, translational, and clinical cancer research. Expected information can bring new cues for innovative, efficient, and safe strategies of personalized medicine based on molecular markers, protagonists, signaling networks, and effectors inherent to the Netrin axis in pathophysiological states.
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Wong MC, Schwarzbauer JE. Gonad morphogenesis and distal tip cell migration in the Caenorhabditis elegans hermaphrodite. WILEY INTERDISCIPLINARY REVIEWS. DEVELOPMENTAL BIOLOGY 2012; 1:519-31. [PMID: 23559979 PMCID: PMC3614366 DOI: 10.1002/wdev.45] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Cell migration and morphogenesis are key events in tissue development and organogenesis. In Caenorhabditis elegans, the migratory path of the distal tip cells determines the morphology of the hermaphroditic gonad. The distal tip cells undergo a series of migratory phases interspersed with turns to form the gonad. A wide variety of genes have been identified as crucial to this process, from genes that encode components and modifiers of the extracellular matrix to signaling proteins and transcriptional regulators. The connections between extracellular and transmembrane protein functions and intracellular pathways are essential for distal tip cell migration, and the integration of this information governs gonad morphogenesis and determines gonad size and shape.
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Affiliation(s)
- Ming-Ching Wong
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
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27
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Mohamed AM, Boudreau JR, Yu FPS, Liu J, Chin-Sang ID. The Caenorhabditis elegans Eph receptor activates NCK and N-WASP, and inhibits Ena/VASP to regulate growth cone dynamics during axon guidance. PLoS Genet 2012; 8:e1002513. [PMID: 22383893 PMCID: PMC3285579 DOI: 10.1371/journal.pgen.1002513] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2011] [Accepted: 12/13/2011] [Indexed: 01/18/2023] Open
Abstract
The Eph receptor tyrosine kinases (RTKs) are regulators of cell migration and axon guidance. However, our understanding of the molecular mechanisms by which Eph RTKs regulate these processes is still incomplete. To understand how Eph receptors regulate axon guidance in Caenorhabditis elegans, we screened for suppressors of axon guidance defects caused by a hyperactive VAB-1/Eph RTK. We identified NCK-1 and WSP-1/N-WASP as downstream effectors of VAB-1. Furthermore, VAB-1, NCK-1, and WSP-1 can form a complex in vitro. We also report that NCK-1 can physically bind UNC-34/Enabled (Ena), and suggest that VAB-1 inhibits the NCK-1/UNC-34 complex and negatively regulates UNC-34. Our results provide a model of the molecular events that allow the VAB-1 RTK to regulate actin dynamics for axon guidance. We suggest that VAB-1/Eph RTK can stop axonal outgrowth by inhibiting filopodia formation at the growth cone by activating Arp2/3 through a VAB-1/NCK-1/WSP-1 complex and by inhibiting UNC-34/Ena activity. The correct wiring of the nervous system depends on the ability of axons to properly interpret extracellular cues that guide them to their targets. The Eph receptor tyrosine kinases (RTKs) have roles in guiding axons, but their signaling pathways are not completely understood. In this study, we used the nematode Caenorhabditis elegans to study how the VAB-1 Eph RTK regulates the growth cone structure for axon guidance. Genetic and molecular data show that VAB-1 regulates the conserved molecules NCK-1, WSP-1/N-WASP, and UNC-34/Ena. Our study provides a model of how the VAB-1 Eph RTK modulates the growth cone structure to inhibit axonal outgrowth. We show that activated VAB-1 can inhibit an NCK-1/UNC-34 interaction by binding to the NCK-1 SH2 domain. We also show that NCK-1 and WSP-1 can physically interact and that VAB-1/NCK-1 and WSP-1 form a complex in vitro. We suggest that the VAB-1 Eph RTK can contribute to the termination of axon outgrowth by two methods: 1) The VAB-1/NCK-1/WSP-1 complex activates ARP-2/3 to change the actin growth cone dynamics to that of a branched structure thus reducing the number of filopodia, and 2) VAB-1 inhibits axon extension by inhibiting UNC-34/Ena's function in actin polymerization.
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Affiliation(s)
| | | | | | - Jun Liu
- Department of Biology, Queen's University, Kingston, Canada
| | - Ian D. Chin-Sang
- Department of Biology, Queen's University, Kingston, Canada
- * E-mail:
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Autocrine netrin function inhibits glioma cell motility and promotes focal adhesion formation. PLoS One 2011; 6:e25408. [PMID: 21980448 PMCID: PMC3182204 DOI: 10.1371/journal.pone.0025408] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2011] [Accepted: 09/02/2011] [Indexed: 01/09/2023] Open
Abstract
Deregulation of mechanisms that control cell motility plays a key role in tumor progression by promoting tumor cell dissemination. Secreted netrins and their receptors, Deleted in Colorectal Cancer (DCC), neogenin, and the UNC5 homologues, regulate cell and axon migration, cell adhesion, and tissue morphogenesis. Netrin and netrin receptor expression have previously been shown to be disrupted in invasive tumors, including glioblastoma. We determined that the human glioblastoma cell lines U87, U343, and U373 all express neogenin, UNC5 homologues, and netrin-1 or netrin-3, but only U87 cells express DCC. Using transfilter migration assays, we demonstrate DCC-dependent chemoattractant migration of U87 cells up a gradient of netrin-1. In contrast, U343 and U373 cells, which do not express DCC, were neither attracted nor repelled. Ectopic expression of DCC by U343 and U373 cells resulted in these cells becoming competent to respond to a gradient of netrin-1 as a chemoattractant, and also slowed their rate of spontaneous migration. Here, in addition to netrins' well-characterized chemotropic activity, we demonstrate an autocrine function for netrin-1 and netrin-3 in U87 and U373 cells that slows migration. We provide evidence that netrins promote the maturation of focal complexes, structures associated with cell movement, into focal adhesions. Consistent with this, netrin, DCC, and UNC5 homologues were associated with focal adhesions, but not focal complexes. Disrupting netrin or DCC function did not alter cell proliferation or survival. Our findings provide evidence that DCC can slow cell migration, and that neogenin and UNC5 homologues are not sufficient to substitute for DCC function in these cells. Furthermore, we identify a role for netrins as autocrine inhibitors of cell motility that promote focal adhesion formation. These findings suggest that disruption of netrin signalling may disable a mechanism that normally restrains inappropriate cell migration.
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29
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Song S, Ge Q, Wang J, Chen H, Tang S, Bi J, Li X, Xie Q, Huang X. TRIM-9 functions in the UNC-6/UNC-40 pathway to regulate ventral guidance. J Genet Genomics 2011; 38:1-11. [PMID: 21338947 DOI: 10.1016/j.jcg.2010.12.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2010] [Revised: 12/06/2010] [Accepted: 12/07/2010] [Indexed: 10/18/2022]
Abstract
TRIpartite Motif (TRIM) family proteins are ring finger domain-containing, multi-domain proteins implicated in many biological processes. Members of the TRIM-9/C-I subfamily of TRIM proteins, including TRIM-9, MID1 and MID2, have neuronal functions and are associated with neurological diseases. To explore whether the functions of C-I TRIM proteins are conserved in invertebrates, we analyzed Caenorhabditis elegans and Drosophila trim-9 mutants. C. elegans trim-9 mutants exhibit defects in the ventral guidance of hermaphrodite specific neuron (HSN) and the touch neuron AVM. Further genetic analyses indicate that TRIM-9 participates in the UNC-6-UNC-40 attraction pathway. Asymmetric distribution of UNC-40 during HSN development is normal in trim-9 mutants. However, the asymmetric localization of MIG-10, a downstream effector of UNC-40, is abolished in trim-9 mutants. These results suggest that TRIM-9 functions upstream of MIG-10 in the UNC-40 pathway. Moreover, we showed that TRIM-9 exhibits E3 ubiquitin ligase activity in vitro and this activity is important for TRIM-9 function in vivo. Additionally, we found that Drosophila trim-9 is required for the midline attraction of a group of sensory neuron axons. Over-expression of the Netrin/UNC-6 receptor Frazzled suppresses the guidance defects in trim-9 mutants. Our study reveals an evolutionarily conserved function of TRIM-9 in the UNC-40/Frazzled-mediated UNC-6/Netrin attraction pathway.
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Affiliation(s)
- Song Song
- Key Laboratory of Molecular and Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
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30
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Lai Wing Sun K, Correia JP, Kennedy TE. Netrins: versatile extracellular cues with diverse functions. Development 2011; 138:2153-69. [PMID: 21558366 DOI: 10.1242/dev.044529] [Citation(s) in RCA: 318] [Impact Index Per Article: 24.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Netrins are secreted proteins that were first identified as guidance cues, directing cell and axon migration during neural development. Subsequent findings have demonstrated that netrins can influence the formation of multiple tissues, including the vasculature, lung, pancreas, muscle and mammary gland, by mediating cell migration, cell-cell interactions and cell-extracellular matrix adhesion. Recent evidence also implicates the ongoing expression of netrins and netrin receptors in the maintenance of cell-cell organisation in mature tissues. Here, we review the mechanisms involved in netrin signalling in vertebrate and invertebrate systems and discuss the functions of netrin signalling during the development of neural and non-neural tissues.
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Affiliation(s)
- Karen Lai Wing Sun
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, QC H3A 2B4, Canada
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31
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mir-35 is involved in intestine cell G1/S transition and germ cell proliferation in C. elegans. Cell Res 2011; 21:1605-18. [PMID: 21691303 DOI: 10.1038/cr.2011.102] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
MicroRNA (miRNA) regulates gene expression in many cellular events, yet functions of only a few miRNAs are known in C. elegans. We analyzed the function of mir-35-41 unique to the worm, and show here that mir-35 regulates the G1/S transition of intestinal cells and germ cell proliferation. Loss of mir-35 leads to a decrease of nuclei numbers in intestine and distal mitotic gonad, while re-introduction of mir-35 rescues the mutant phenotypes. Genetic analysis indicates that mir-35 may act through Rb/E2F and SCF pathways. Further bioinformatic and functional analyses demonstrate that mir-35 targets evolutionally conserved lin-23 and gld-1. Together, our study reveals a novel function of mir-35 family in cell division regulation.
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32
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Park J, Knezevich PL, Wung W, O'Hanlon SN, Goyal A, Benedetti KL, Barsi-Rhyne BJ, Raman M, Mock N, Bremer M, Vanhoven MK. A conserved juxtacrine signal regulates synaptic partner recognition in Caenorhabditis elegans. Neural Dev 2011; 6:28. [PMID: 21663630 PMCID: PMC3130637 DOI: 10.1186/1749-8104-6-28] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2011] [Accepted: 06/10/2011] [Indexed: 02/04/2023] Open
Abstract
Background An essential stage of neural development involves the assembly of neural circuits via formation of inter-neuronal connections. Early steps in neural circuit formation, including cell migration, axon guidance, and the localization of synaptic components, are well described. However, upon reaching their target region, most neurites still contact many potential partners. In order to assemble functional circuits, it is critical that within this group of cells, neurons identify and form connections only with their appropriate partners, a process we call synaptic partner recognition (SPR). To understand how SPR is mediated, we previously developed a genetically encoded fluorescent trans-synaptic marker called NLG-1 GRASP, which labels synaptic contacts between individual neurons of interest in dense cellular environments in the genetic model organism Caenorhabditis elegans. Results Here, we describe the first use of NLG-1 GRASP technology, to identify SPR genes that function in this critical process. The NLG-1 GRASP system allows us to assess synaptogenesis between PHB sensory neurons and AVA interneurons instantly in live animals, making genetic analysis feasible. Additionally, we employ a behavioral assay to specifically test PHB sensory circuit function. Utilizing this approach, we reveal a new role for the secreted UNC-6/Netrin ligand and its transmembrane receptor UNC-40/Deleted in colorectal cancer (DCC) in SPR. Synapses between PHB and AVA are severely reduced in unc-6 and unc-40 animals despite normal axon guidance and subcellular localization of synaptic components. Additionally, behavioral defects indicate a complete disruption of PHB circuit function in unc-40 mutants. Our data indicate that UNC-40 and UNC-6 function in PHB and AVA, respectively, to specify SPR. Strikingly, overexpression of UNC-6 in postsynaptic neurons is sufficient to promote increased PHB-AVA synaptogenesis and to potentiate the behavioral response beyond wild-type levels. Furthermore, an artificially membrane-tethered UNC-6 expressed in the postsynaptic neurons promotes SPR, consistent with a short-range signal between adjacent synaptic partners. Conclusions These results indicate that the conserved UNC-6/Netrin-UNC-40/DCC ligand-receptor pair has a previously unknown function, acting in a juxtacrine manner to specify recognition of individual postsynaptic neurons. Furthermore, they illustrate the potential of this new approach, combining NLG-1 GRASP and behavioral analysis, in gene discovery and characterization.
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Affiliation(s)
- Joori Park
- Department of Biological Sciences, San José State University, San José, CA 95192, USA
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33
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Dent EW, Gupton SL, Gertler FB. The growth cone cytoskeleton in axon outgrowth and guidance. Cold Spring Harb Perspect Biol 2011; 3:cshperspect.a001800. [PMID: 21106647 DOI: 10.1101/cshperspect.a001800] [Citation(s) in RCA: 402] [Impact Index Per Article: 30.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Axon outgrowth and guidance to the proper target requires the coordination of filamentous (F)-actin and microtubules (MTs), the dynamic cytoskeletal polymers that promote shape change and locomotion. Over the past two decades, our knowledge of the many guidance cues, receptors, and downstream signaling cascades involved in neuronal outgrowth and guidance has increased dramatically. Less is known, however, about how those cascades of information converge and direct appropriate remodeling and interaction of cytoskeletal polymers, the ultimate effectors of movement and guidance. During development, much of the communication that occurs between environmental guidance cues and the cytoskeleton takes place at the growing tip of the axon, the neuronal growth cone. Several articles on this topic focus on the "input" to the growth cone, the myriad of receptor types, and their corresponding cognate ligands. Others investigate the signaling cascades initiated by receptors and propagated by second messenger pathways (i.e., kinases, phosphatases, GTPases). Ultimately, this plethora of information converges on proteins that associate directly with the actin and microtubule cytoskeletons. The role of these cytoskeletal-associated proteins, as well as the cytoskeleton itself in axon outgrowth and guidance, is the subject of this article.
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Affiliation(s)
- Erik W Dent
- Department of Anatomy, University of Wisconsin-Madison, 53706, USA
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34
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Yee CS, Sybingco SS, Serdetchania V, Kholkina G, Bueno de Mesquita M, Naqvi Z, Park SH, Lam K, Killeen MT. ENU-3 is a novel motor axon outgrowth and guidance protein in C. elegans. Dev Biol 2011; 352:243-53. [PMID: 21295567 DOI: 10.1016/j.ydbio.2011.01.024] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2010] [Revised: 01/18/2011] [Accepted: 01/19/2011] [Indexed: 11/30/2022]
Abstract
During the development of the nervous system, the migration of many cells and axons is guided by extracellular molecules. These molecules bind to receptors at the tips of the growth cones of migrating axons and trigger intracellular signaling to steer the axons along the correct trajectories. We have identified a novel mutant, enu-3 (enhancer of Unc), that enhances the motor neuron axon outgrowth defects observed in strains of Caenorhabditis elegans that lack either the UNC-5 receptor or its ligand UNC-6/Netrin. Specifically, the double-mutant strains have enhanced axonal outgrowth defects mainly in DB4, DB5 and DB6 motor neurons. enu-3 single mutants have weak motor neuron axon migration defects. Both outgrowth defects of double mutants and axon migration defects of enu-3 mutants were rescued by expression of the H04D03.1 gene product. ENU-3/H04D03.1 encodes a novel predicted putative trans-membrane protein of 204 amino acids. It is a member of a family of highly homologous proteins of previously unknown function in the C. elegans genome. ENU-3 is expressed in the PVT interneuron and is weakly expressed in many cell bodies along the ventral cord, including those of the DA and DB motor neurons. We conclude that ENU-3 is a novel C. elegans protein that affects both motor axon outgrowth and guidance.
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Affiliation(s)
- Callista S Yee
- Graduate Program in Molecular Sciences, Ryerson University, Canada M5B 2K3
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35
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Albrecht S, Altenhein B, Paululat A. The transmembrane receptor Uncoordinated5 (Unc5) is essential for heart lumen formation in Drosophila melanogaster. Dev Biol 2010; 350:89-100. [PMID: 21094637 DOI: 10.1016/j.ydbio.2010.11.016] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2010] [Revised: 11/11/2010] [Accepted: 11/12/2010] [Indexed: 11/17/2022]
Abstract
Transport of liquids or gases in biological tubes is fundamental for many physiological processes. Our knowledge on how tubular organs are formed during organogenesis and tissue remodeling has increased dramatically during the last decade. Studies on different animal systems have helped to unravel some of the molecular mechanisms underlying tubulogenesis. Tube architecture varies dramatically in different organs and different species, ranging from tubes formed by several cells constituting the cross section, tubes formed by single cells wrapping an internal luminal space or tubes that are formed within a cell. Some tubes display branching whereas others remain linear without intersections. The modes of shaping, growing and pre-patterning a tube are also different and it is still not known whether these diverse architectures and modes of differentiation are realized by sharing common signaling pathways or regulatory networks. However, several recent investigations provide evidence for the attractive hypothesis that the Drosophila cardiogenesis and heart tube formation shares many similarities with primary angiogenesis in vertebrates. Additionally, another important step to unravel the complex system of lumen formation has been the outcome of recent studies that junctional proteins, matrix components as well as proteins acting as attractant and repellent cues play a role in the formation of the Drosophila heart lumen. In this study we show the requirement for the repulsively active Unc5 transmembrane receptor to facilitate tubulogenesis in the dorsal vessel of Drosophila. Unc5 is localized in the luminal membrane compartment of cardiomyocytes and animals lacking Unc5 fail to form a heart lumen. Our findings support the idea that Unc5 is crucial for lumen formation and thereby represents a repulsive cue acting during Drosophila heart tube formation.
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Affiliation(s)
- Stefanie Albrecht
- Universität Osnabrück, Fachbereich Biologie/Chemie - Zoologie/Entwicklungsbiologie, Barbarastraße 11, 49069 Osnabrück, Germany
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36
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Ypsilanti AR, Zagar Y, Chédotal A. Moving away from the midline: new developments for Slit and Robo. Development 2010; 137:1939-52. [DOI: 10.1242/dev.044511] [Citation(s) in RCA: 185] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
In most tissues, the precise control of cell migration and cell-cell interaction is of paramount importance to the development of a functional structure. Several families of secreted molecules have been implicated in regulating these aspects of development, including the Slits and their Robo receptors. These proteins have well described roles in axon guidance but by influencing cell polarity and adhesion, they participate in many developmental processes in diverse cell types. We review recent progress in understanding both the molecular mechanisms that modulate Slit/Robo expression and their functions in neural and non-neural tissue.
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Affiliation(s)
- Athena R. Ypsilanti
- INSERM, U968, Paris F-75012, France
- UPMC Univ Paris 06, UMR_S 968, Institut de la Vision, 17 rue Moreau, Paris F-75012, France
- CNRS, UMR_7210, Paris F-75012, France
| | - Yvrick Zagar
- INSERM, U968, Paris F-75012, France
- UPMC Univ Paris 06, UMR_S 968, Institut de la Vision, 17 rue Moreau, Paris F-75012, France
- CNRS, UMR_7210, Paris F-75012, France
| | - Alain Chédotal
- INSERM, U968, Paris F-75012, France
- UPMC Univ Paris 06, UMR_S 968, Institut de la Vision, 17 rue Moreau, Paris F-75012, France
- CNRS, UMR_7210, Paris F-75012, France
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37
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Fleming T, Chien SC, Vanderzalm PJ, Dell M, Gavin MK, Forrester WC, Garriga G. The role of C. elegans Ena/VASP homolog UNC-34 in neuronal polarity and motility. Dev Biol 2010; 344:94-106. [PMID: 20452341 DOI: 10.1016/j.ydbio.2010.04.025] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2010] [Revised: 04/13/2010] [Accepted: 04/22/2010] [Indexed: 12/30/2022]
Abstract
Ena/VASP proteins mediate the effects of guidance cues on the actin cytoskeleton. The single C. elegans homolog of the Ena/VASP family of proteins, UNC-34, is required for the migrations of cells and growth cones. Here we show that unc-34 mutant alleles also interact genetically with Wnt mutants to reveal a role for unc-34 in the establishment of neuronal polarity along the C. elegans anterior-posterior axis. Our mutant analysis shows that eliminating UNC-34 function results in neuronal migration and polarity phenotypes that are enhanced at higher temperatures, revealing a heat-sensitive process that is normally masked by the presence of UNC-34. Finally, we show that the UNC-34 protein is expressed broadly and accumulates in axons and at the apical junctions of epithelial cells. While most mutants lacked detectable UNC-34, three unc-34 mutants that contained missense mutations in the EVH1 domain produced full-length UNC-34 that failed to localize to apical junctions and axons, supporting the role for the EVH1 domain in localizing Ena/VASP family members.
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Affiliation(s)
- Tinya Fleming
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA
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38
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Schmidt KL, Marcus-Gueret N, Adeleye A, Webber J, Baillie D, Stringham EG. The cell migration molecule UNC-53/NAV2 is linked to the ARP2/3 complex by ABI-1. Development 2009; 136:563-74. [PMID: 19168673 DOI: 10.1242/dev.016816] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The shape changes that are required to position a cell to migrate or grow out in a particular direction involve a coordinated reorganization of the actin cytoskeleton. Although it is known that the ARP2/3 complex nucleates actin filament assembly, exactly how the information from guidance cues is integrated to elicit ARP2/3-mediated remodeling during outgrowth remains vague. Previous studies have shown that C. elegans UNC-53 and its vertebrate homolog NAV (Neuronal Navigators) are required for the migration of cells and neuronal processes. We have identified ABI-1 as a novel molecular partner of UNC-53/NAV2 and have found that a restricted calponin homology (CH) domain of UNC-53 is sufficient to bind ABI-1. ABI-1 and UNC-53 have an overlapping expression pattern, and display similar cell migration phenotypes in the excretory cell, and in mechanosensory and motoneurons. Migration defects were also observed after RNAi of proteins known to function with abi-1 in actin dynamics, including nck-1, wve-1 and arx-2. We propose that UNC-53/NAV2, through its CH domain, acts as a scaffold that links ABI-1 to the ARP2/3 complex to regulate actin cytoskeleton remodeling.
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MacNeil LT, Hardy WR, Pawson T, Wrana JL, Culotti JG. UNC-129 regulates the balance between UNC-40 dependent and independent UNC-5 signaling pathways. Nat Neurosci 2009; 12:150-5. [PMID: 19169249 PMCID: PMC2745997 DOI: 10.1038/nn.2256] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2008] [Accepted: 12/08/2008] [Indexed: 11/25/2022]
Abstract
The UNC-5 receptor mediates axon repulsion from UNC-6/netrin through UNC-40 dependent (‘UNC-5+UNC-40’) and independent (‘UNC-5-alone’) signaling pathways. A requirement for UNC-40 dependent signaling has been shown in long-range repulsion from UNC-6/netrin, however, the mechanisms used to regulate distinct UNC-5 signaling pathways are poorly understood. Here we demonstrate that the C. elegans TGF-β family ligand UNC-129, graded opposite to UNC-6/netrin, functions independent of the canonical TGF-β receptors to regulate UNC-5 cellular responses. We provide evidence that UNC-129 facilitates long-range repulsive guidance of UNC-6 by enhancing ‘UNC-5+UNC-40’ signaling at the expense of ‘UNC-5-alone’ signaling through interaction with the UNC-5 receptor. This increases the set point sensitivity of growth cones to UNC-6/netrin as they simultaneously migrate up the UNC-129 gradient and down the UNC-6 gradient. Similar regulatory interactions between oppositely graded extracellular cues may be a common theme in guided cell and axon migrations.
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Affiliation(s)
- Lesley T MacNeil
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, 600 University Avenue, Toronto, Ontario M5G 1X5, Canada
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40
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Abstract
Netrins are a family of proteins that direct cell and axon migration during development. Three secreted netrins (netrin-1, -3 and -4) have been identified in mammals, in addition to two GPI-anchored membrane proteins, netrin-G1 and G2. Orthologues of netrin-1 play a highly conserved role as guidance cues at the midline of the developing CNS of vertebrates and some bilaterally symmetric invertebrates. In vertebrates, floor plate cells at the ventral midline of the embryonic neural tube secrete netrin-1, generating a circumferential gradient of netrin protein in the neuroepithelium. This protein gradient is bifunctional, attracting some axons to the midline and repelling others. Receptors for the secreted netrins include DCC (deleted in colorectal cancer) and the UNC5 homologues: UNC5A, B, C and D in mammals. DCC mediates chemoattraction, while repulsion requires an UNC5 homologue and, in some cases, DCC. The netrin-G proteins bind NGLs (netrin G ligands), single pass transmembrane proteins unrelated to either DCC or the UNC5 homologues. Netrin function is not limited to the developing CNS midline. Various netrins direct cell and axon migration throughout the embryonic CNS, and in some cases continue to be expressed in the mature nervous system. Furthermore, although initially identified for their ability to guide axons, functional roles for netrins have now been identified outside the nervous system where they influence tissue morphogenesis by directing cell migration and regulating cell-cell and cell-matrix adhesion.
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The Hedgehog, TGF-β/BMP and Wnt Families of Morphogens in Axon Guidance. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2008; 621:116-33. [DOI: 10.1007/978-0-387-76715-4_9] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Pilon M. Fishing lines, time-delayed guideposts, and other tricks used by developing pharyngeal neurons in Caenorhabditis elegans. Dev Dyn 2008; 237:2073-80. [PMID: 18651660 DOI: 10.1002/dvdy.21636] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The 20 neurons that innervate the Caenorhabditis elegans pharynx form a simple nervous system that develops and operates in near complete isolation from the rest of the worm body and, therefore, offers a manageable degree of complexity for developmental genetics studies. This review discusses the progress that has been made in determining the mechanisms by which 4 of the 20 pharyngeal neurons develop, and emphasizes surprising processes that add to the classic growth cone guidance model which is usually thought to explain how most axons establish their trajectories.
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Affiliation(s)
- Marc Pilon
- Department of Cell Molecular Biology, University of Göteborg, Göteborg, Sweden.
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Drees F, Gertler FB. Ena/VASP: proteins at the tip of the nervous system. Curr Opin Neurobiol 2008; 18:53-9. [PMID: 18508258 DOI: 10.1016/j.conb.2008.05.007] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2008] [Revised: 05/06/2008] [Accepted: 05/08/2008] [Indexed: 10/22/2022]
Abstract
The emergence of neurites from a symmetrical cell body is an essential feature of nervous system development. Neurites are the precursors of axons and dendrites and are tipped by growth cones, motile structures that guide elongating axons in the developing nervous system. Growth cones steer the axon along a defined path to its appropriate target in response to guidance cues. This navigation involves the dynamic extension and withdrawal of actin-filled finger-like protrusions called filopodia that continuously sample their environment. Ena/VASP proteins, a conserved family of actin-regulatory proteins, are crucial for filopodia formation and function downstream of several guidance cues. Here we review recent findings into Ena/VASP function in neurite initiation, axon outgrowth and guidance.
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Affiliation(s)
- Frauke Drees
- David H Koch Institute for Integrative Cancer Research at MIT, Massachusetts Institute of Technology, Cambridge, MA 02139-4307, USA
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Abstract
We investigated the influence of the bifunctional guidance molecule netrin-1 on axonal growth in the injured adult spinal cord. In the adult, netrin-1 is expressed on mature oligodendrocytes, cells of the central canal, and the meninges. Netrin-1 protein in white matter is selectively enriched adjacent to paranodal loops of myelin in nodes of Ranvier. The repulsion-mediating netrin-1 uncoordinated-5 (UNC5) receptors are expressed by neurons of the corticospinal and rubrospinal projections, and by intrinsic neurons of the spinal cord, both before and after spinal cord injury. Neutralization of netrin-1 in myelin prepared from adult rat spinal cord using UNC5 receptor bodies increases neurite outgrowth from UNC5-expressing spinal motor neurons in vitro. Furthermore, axon regeneration is inhibited in a netrin-1-enriched zone, devoid of other myelin-associated inhibitors, within spinal cord lesion sites in vivo. We conclude that netrin-1 is a novel oligodendrocyte-associated inhibitor that can contribute to axonal growth failure after adult spinal cord injury.
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Ren XR, Hong Y, Feng Z, Yang HM, Mei L, Xiong WC. Tyrosine phosphorylation of netrin receptors in netrin-1 signaling. Neurosignals 2008; 16:235-45. [PMID: 18253061 DOI: 10.1159/000111566] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Deleted in colorectal cancer (DCC) and neogenin are receptors of netrins, a family of guidance cues that promote axon outgrowth and guide growth cones in developing nervous system. The intracellular mechanisms of netrins, however, remain elusive. In this paper, we show that both DCC and neogenin become tyrosine phosphorylated in cortical neurons in response to netrin-1. Using a site-specific antiphosphor DCC antibody, we show that Y1420 phosphorylation is increased in netrin-1-stimulated neurons and that tyrosine-phosphorylated DCC is located in growth cones. In addition, we show that tyrosine-phosphorylated DCC selectively interacts with the Src family kinases Fyn and Lck, but not Src, c-Abl, Grb2, SHIP1, Shc, or tensin, suggesting a role of Fyn or Lck in netrin-1-DCC signaling. Of interest to note is that tyrosine-phosphorylated neogenin and uncoordinated 5 H2 (Unc5H2) not only bind to the Src homology 2 (SH2) domains of Fyn and SHP2, but also interact with the SH2 domain of SHIP1, suggesting a differential signaling between DCC and neogenin/Unc5H2. Furthermore, we demonstrate that inhibition of Src family kinase activity attenuated netrin-1-induced neurite outgrowth. Together, these results suggest a role of Src family kinases and tyrosine phosphorylation of netrin-1 receptors in regulating netrin-1 function.
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Affiliation(s)
- Xiu-Rong Ren
- Department of Pathology, University of Alabama at Birmingham, Birmingham, Alabama, USA
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Zheng H, Coudiere L, Camia C, Colavita A, Culotti JG, Merz DC. C. elegans seu-1 encodes novel nuclear proteins that regulate responses to UNC-6/netrin guidance cues. Dev Biol 2007; 310:44-53. [PMID: 17716643 DOI: 10.1016/j.ydbio.2007.07.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2007] [Revised: 07/13/2007] [Accepted: 07/14/2007] [Indexed: 11/30/2022]
Abstract
In C. elegans, ectopic expression of the UNC-5 netrin receptor is sufficient to cause repulsion of growth cones and cells away from ventral sources of the UNC-6/netrin guidance cue. A genetic suppressor screen identified the seu-1 gene as required for repulsion of touch neuron growth cones ectopically expressing unc-5. We report here that seu-1 mutations also enhance the frequency of distal tip cell migrations of unc-5 or unc-40 mutants. The seu-1 gene encodes two novel proteins (SEU-1A and SEU-1B) containing a charged central domain and several regions of low amino acid complexity. Transgenic rescue experiments indicate that seu-1 can act cell autonomously in the touch neurons and distal tip cells and that SEU-1 function requires both the SEU-1A and SEU-1B isoforms. A GFP fusion construct was expressed in a dynamic pattern throughout development and localized in the nuclei of neuronal and non-neuronal cells, including gonadal leader cells. These results implicate nuclear SEU-1 in the interpretation of UNC-6/netrin directional information by migrating growth cones and cells.
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Affiliation(s)
- Hong Zheng
- Department of Medical and Molecular Genetics, Faculty of Medicine, University of Toronto, and Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Canada
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Byrne AB, Weirauch MT, Wong V, Koeva M, Dixon SJ, Stuart JM, Roy PJ. A global analysis of genetic interactions in Caenorhabditis elegans. J Biol 2007; 6:8. [PMID: 17897480 PMCID: PMC2373897 DOI: 10.1186/jbiol58] [Citation(s) in RCA: 135] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2007] [Revised: 07/31/2007] [Accepted: 08/17/2007] [Indexed: 01/10/2023] Open
Abstract
Background Understanding gene function and genetic relationships is fundamental to our efforts to better understand biological systems. Previous studies systematically describing genetic interactions on a global scale have either focused on core biological processes in protozoans or surveyed catastrophic interactions in metazoans. Here, we describe a reliable high-throughput approach capable of revealing both weak and strong genetic interactions in the nematode Caenorhabditis elegans. Results We investigated interactions between 11 'query' mutants in conserved signal transduction pathways and hundreds of 'target' genes compromised by RNA interference (RNAi). Mutant-RNAi combinations that grew more slowly than controls were identified, and genetic interactions inferred through an unbiased global analysis of the interaction matrix. A network of 1,246 interactions was uncovered, establishing the largest metazoan genetic-interaction network to date. We refer to this approach as systematic genetic interaction analysis (SGI). To investigate how genetic interactions connect genes on a global scale, we superimposed the SGI network on existing networks of physical, genetic, phenotypic and coexpression interactions. We identified 56 putative functional modules within the superimposed network, one of which regulates fat accumulation and is coordinated by interactions with bar-1(ga80), which encodes a homolog of β-catenin. We also discovered that SGI interactions link distinct subnetworks on a global scale. Finally, we showed that the properties of genetic networks are conserved between C. elegans and Saccharomyces cerevisiae, but that the connectivity of interactions within the current networks is not. Conclusions Synthetic genetic interactions may reveal redundancy among functional modules on a global scale, which is a previously unappreciated level of organization within metazoan systems. Although the buffering between functional modules may differ between species, studying these differences may provide insight into the evolution of divergent form and function.
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Affiliation(s)
- Alexandra B Byrne
- Department of Medical Genetics and Microbiology, The Terrence Donnelly Centre for Cellular and Biomolecular Research, 160 College St, University of Toronto, Toronto, ON, M5S 3E1, Canada
- Collaborative Program in Developmental Biology, University of Toronto, Toronto, ON, M5S 3E1, Canada
| | - Matthew T Weirauch
- Department of Biomolecular Engineering, 1156 High Street, Mail Stop SOE2, University of California, Santa Cruz, CA 95064, USA
| | - Victoria Wong
- Department of Medical Genetics and Microbiology, The Terrence Donnelly Centre for Cellular and Biomolecular Research, 160 College St, University of Toronto, Toronto, ON, M5S 3E1, Canada
| | - Martina Koeva
- Department of Biomolecular Engineering, 1156 High Street, Mail Stop SOE2, University of California, Santa Cruz, CA 95064, USA
| | - Scott J Dixon
- Department of Medical Genetics and Microbiology, The Terrence Donnelly Centre for Cellular and Biomolecular Research, 160 College St, University of Toronto, Toronto, ON, M5S 3E1, Canada
- Collaborative Program in Developmental Biology, University of Toronto, Toronto, ON, M5S 3E1, Canada
| | - Joshua M Stuart
- Department of Biomolecular Engineering, 1156 High Street, Mail Stop SOE2, University of California, Santa Cruz, CA 95064, USA
| | - Peter J Roy
- Department of Medical Genetics and Microbiology, The Terrence Donnelly Centre for Cellular and Biomolecular Research, 160 College St, University of Toronto, Toronto, ON, M5S 3E1, Canada
- Collaborative Program in Developmental Biology, University of Toronto, Toronto, ON, M5S 3E1, Canada
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The C. elegans M3 neuron guides the growth cone of its sister cell M2 via the Krüppel-like zinc finger protein MNM-2. Dev Biol 2007; 311:185-99. [PMID: 17916347 DOI: 10.1016/j.ydbio.2007.08.037] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2007] [Revised: 08/14/2007] [Accepted: 08/20/2007] [Indexed: 11/21/2022]
Abstract
The invariant cell-cell interactions occurring during C. elegans development offer unique opportunities to discover how growing axons may receive guidance cues from neighboring cells. The mnm-2 mutant was isolated because of its defects in the axon trajectory of the bilateral M2 pharyngeal neurons in C. elegans. We found that mnm-2 enhances the effects of many growth cone guidance mutations on these axons, suggesting that it performs a novel function during axon guidance. We cloned mnm-2 and found that it encodes a protein with three C2H2 zinc finger domains related to the Krüppel-like Factor protein family. mnm-2 is expressed only transiently in the M2 neuron, but exhibits a sustained expression in its sister cell, the M3 neuron. Strikingly, the expression of mnm-2 is not sustained in the M3 cell of the mnm-2 mutant, indicating that this gene positively regulates itself in that cell. Electropharyngeograms also indicate that the M3 cell is functionally impaired in the mnm-2 mutant. We used an M3-specific promoter to show that the M2 axon defect can be rescued by expression of mnm-2 in its sister cell M3. The same promoter was used to express the pro-apoptotic gene egl-1 to kill the M3 cell, which resulted in an M2 axon guidance defect similar to that found in the mnm-2 mutant. Our results suggest an M2 axon guidance model in which the M3 cell provides an important signal to the growth cone of its sister M2 and that this signal and the proper differentiation of M3 both depend on mnm-2 expression. This mechanism of axon guidance regulation allows fine-tuning of trajectories between sister cells.
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Hearing development and spiral ganglion neurite growth in VASP deficient mice. Brain Res 2007; 1178:73-82. [PMID: 17920567 DOI: 10.1016/j.brainres.2007.06.041] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2006] [Revised: 04/27/2007] [Accepted: 06/07/2007] [Indexed: 10/23/2022]
Abstract
Vasodilator-stimulated phosphoprotein (VASP) has been found to be involved in intracellular signalling pathways and to play an important role in the actin associated organization and formation of the cytoskeleton. Since differential VASP expression was noted in inner ear tissues, the present study was performed to investigate the hearing development in VASP deficient mice. Hearing development in VASP-/- mice and wild type animals was investigated by auditory brain stem (ABR) measurements. In addition, inner ear tissues of wild type animals were tested for VASP expression using PCR, Western blot analysis, in situ hybridisation, and immunohistochemistry. To compare spiral ganglion (SG) neurite growth, SG explants from VASP-/- and wild type mice were analyzed under cell culture conditions. The electroacoustical results of the present study indicate that VASP deficient mice present with a later onset of hearing during postnatal development compared to wild type animals. Transient VASP expression was detected in neonatal SG of wild type mice. Tissue culture experiments with SG explants from VASP-/- animals revealed significant alterations in SG neurite extension compared to wild types. The present findings suggest a role for VASP during neonatal development of the mammalian cochlea and allow speculation on a possible delayed innervation of cochlear hair cells due to changes in SG neurite growth in VASP-deficient mice. Temporary VASP deficits in the neonatal inner ear may be compensated by related proteins like MENA leading to a delayed but complete development of hearing function in VASP-/- animals.
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50
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Abstract
We previously reported a transgenic Caenorhabditis elegans model for tauopathies in which expression of human tau in neurons caused insoluble phosphorylated tau accumulation, neurodegeneration and uncoordinated movement (Unc). To identify genes participating in tau neurotoxicity, we conducted a forward genetic screen for mutations that ameliorate tau-induced uncoordination. The recessive mutation sut-1(bk79) partially suppresses the Unc phenotype, tau aggregation and neurodegenerative changes caused by tau. We identified the sut-1 gene and found it encodes a novel protein. We conducted a yeast two hybrid screen to identify SUT-1 binding partners and found UNC-34, the C. elegans homolog of the cytoskeletal regulatory protein Enabled (ENA). In vitro protein binding assays and genetic studies validated the interaction between SUT-1 and UNC-34. The SUT-1/UNC-34 protein-protein interaction plays a role in both the normal function of UNC-34 and in the tau-induced phenotype. Thus, we have found a conserved molecular pathway participating in tau neurotoxicity in C. elegans.
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Affiliation(s)
- Brian C Kraemer
- Geriatrics Research Education and Clinical Center, Veterans Affairs Puget Sound Health Care System, Seattle, WA 98108, USA.
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