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Liu F, Placzek M, Xu H. Axon guidance effect of classical morphogens Shh and BMP7 in the hypothalamo-pituitary system. Neurosci Lett 2013; 553:104-9. [PMID: 23978511 DOI: 10.1016/j.neulet.2013.08.027] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2013] [Revised: 08/14/2013] [Accepted: 08/14/2013] [Indexed: 12/18/2022]
Abstract
Hypothalamus plays a key role in homeostasis, and functions of the hypothalamus depend on the accurate trajectory of hypothalamic neuroendocrine axons. Thus, understanding the guidance of hypothalamic neuroendocrine axons is crucial for knowing how hypothalamus works. Previous studies suggest FGF10 deriving from the medial ventral midline of the hypothalamus plays an important role in axon guidance of the developing hypothalamus. Here we show that Shh and BMP7, which are from the anterior and posterior hypothalamic ventral midline respectively, together repel hypothalamic axons towards the medial ventral midline.
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Affiliation(s)
- Fang Liu
- School of Basic Medical Sciences, Medical College of Nanchang University, Nanchang, Jiangxi 330006, PR China; MRC Centre for Developmental and Biomedical Genetics and Department of Biomedical Science, University of Sheffield, Sheffield S10 2TN, UK.
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52
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Lee CW, Vitriol EA, Shim S, Wise AL, Velayutham RP, Zheng JQ. Dynamic localization of G-actin during membrane protrusion in neuronal motility. Curr Biol 2013; 23:1046-56. [PMID: 23746641 PMCID: PMC3712510 DOI: 10.1016/j.cub.2013.04.057] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2013] [Revised: 04/19/2013] [Accepted: 04/19/2013] [Indexed: 11/28/2022]
Abstract
BACKGROUND Actin-based cell motility is fundamental for development, function, and malignant events in eukaryotic organisms. During neural development, axonal growth cones depend on rapid assembly and disassembly of actin filaments (F-actin) for their guided extension to specific targets for wiring. Monomeric globular actin (G-actin) is the building block for F-actin but is not considered to play a direct role in spatiotemporal control of actin dynamics in cell motility. RESULTS Here we report that a pool of G-actin dynamically localizes to the leading edge of growth cones and neuroblastoma cells to spatially elevate the G-/F-actin ratio that drives membrane protrusion and cell movement. Loss of G-actin localization leads to the cessation and retraction of membrane protrusions. Moreover, G-actin localization occurs asymmetrically in growth cones during attractive turning. Finally, we identify the actin monomer-binding proteins profilin and thymosin β4 as key molecules that localize actin monomers to the leading edge of lamellipodia for their motility. CONCLUSIONS Our results suggest that dynamic localization of G-actin provides a novel mechanism to regulate the spatiotemporal actin dynamics underlying membrane protrusion in cell locomotion and growth cone chemotaxis.
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Affiliation(s)
- Chi Wai Lee
- Departments of Cell Biology and Neurology, Center for Neurodegenerative Diseases, Emory University School of Medicine, Atlanta, GA 30322
| | - Eric A. Vitriol
- Departments of Cell Biology and Neurology, Center for Neurodegenerative Diseases, Emory University School of Medicine, Atlanta, GA 30322
| | - Sangwoo Shim
- Departments of Cell Biology and Neurology, Center for Neurodegenerative Diseases, Emory University School of Medicine, Atlanta, GA 30322
| | - Ariel L. Wise
- Departments of Cell Biology and Neurology, Center for Neurodegenerative Diseases, Emory University School of Medicine, Atlanta, GA 30322
| | - Radhi P. Velayutham
- Department of Neurosurgery, Winship Cancer Center, Emory University School of Medicine, Atlanta, GA 30322
| | - James Q. Zheng
- Departments of Cell Biology and Neurology, Center for Neurodegenerative Diseases, Emory University School of Medicine, Atlanta, GA 30322
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53
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Charoy C, Castellani V. [The neurotrophic factor GDNF, a novel modulator of the semaphorin signaling pathway during axon guidance]. Med Sci (Paris) 2013; 29:127-30. [PMID: 23452593 DOI: 10.1051/medsci/2013292004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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54
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Gorojankina T, Hoch L, Faure H, Roudaut H, Traiffort E, Schoenfelder A, Girard N, Mann A, Manetti F, Solinas A, Petricci E, Taddei M, Ruat M. Discovery, molecular and pharmacological characterization of GSA-10, a novel small-molecule positive modulator of Smoothened. Mol Pharmacol 2013; 83:1020-9. [PMID: 23448715 DOI: 10.1124/mol.112.084590] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Activation of the Smoothened (Smo) receptor mediates Hedgehog (Hh) signaling. Hh inhibitors are in clinical trials for cancer, and small-molecule Smo agonists may have therapeutic interests in regenerative medicine. Here, we have generated and validated a pharmacophoric model for Smo agonists and used this model for the virtual screening of a library of commercially available compounds. Among the 20 top-scoring ligands, we have identified and characterized a novel quinolinecarboxamide derivative, propyl 4-(1-hexyl-4-hydroxy-2-oxo-1,2-dihydroquinoline-3-carboxamido) benzoate, (GSA-10), as a Smo agonist. GSA-10 fits to the agonist pharmacophoric model with two hydrogen bond acceptor groups and four hydrophobic regions. Using pharmacological, biochemical, and molecular approaches, we provide compelling evidence that GSA-10 acts at Smo to promote the differentiation of multipotent mesenchymal progenitor cells into osteoblasts. However, this molecule does not display the hallmarks of reference Smo agonists. Remarkably, GSA-10 does not recognize the classic bodipy-cyclopamine binding site. Its effect on cell differentiation is inhibited by Smo antagonists, such as MRT-83, SANT-1, LDE225, and M25 in the nanomolar range, by GDC-0449 in the micromolar range, but not by cyclopamine and CUR61414. Thus, GSA-10 allows the pharmacological characterization of a novel Smo active site, which is notably not targeted to the primary cilium and strongly potentiated by forskolin and cholera toxin. GSA-10 belongs to a new class of Smo agonists and will be helpful for dissecting Hh mechanism of action, with important implications in physiology and in therapy.
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Affiliation(s)
- Tatiana Gorojankina
- CNRS, UPR-3294, Laboratoire de Neurobiologie et Développement, Institut de Neurobiologie Alfred Fessard IFR2118, Gif-sur-Yvette, France
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55
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Charoy C, Nawabi H, Reynaud F, Derrington E, Bozon M, Wright K, Falk J, Helmbacher F, Kindbeiter K, Castellani V. gdnf activates midline repulsion by Semaphorin3B via NCAM during commissural axon guidance. Neuron 2012; 75:1051-66. [PMID: 22998873 DOI: 10.1016/j.neuron.2012.08.021] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/15/2012] [Indexed: 02/06/2023]
Abstract
The Neurotrophic factor gdnf plays diverse developmental roles, supporting survival and also acting as a chemoattractant for axon and cell migration. We report that in the developing spinal cord, a focal source of gdnf is present in the floor plate (FP) where commissural axons cross the midline. Gdnf has no direct guidance properties but switches on the responsiveness of crossing commissural growth cones to the midline repellent Semaphorin3B by suppressing calpain-mediated processing of the Sema3B signaling coreceptor Plexin-A1. Analysis of single and double mutant mouse models indicates that although gdnf is the principal trigger of Sema3B midline repulsion, it acts with another FP cue, NrCAM. Finally, genetic and in vitro experiments provide evidence that this gdnf effect is RET independent and mediated by NCAM/GFRα1 signaling. This study identifies a regulator of midline crossing and reveals interplays between Semaphorin and gdnf signaling during axon guidance.
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Affiliation(s)
- Camille Charoy
- University of Lyon, University Claude Bernard Lyon1, CGphiMC UMR CNRS 5534, 69622 Villeurbanne, France
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56
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Philipp M, Niederkofler V, Debrunner M, Alther T, Kunz B, Stoeckli ET. RabGDI controls axonal midline crossing by regulating Robo1 surface expression. Neural Dev 2012; 7:36. [PMID: 23140504 PMCID: PMC3520763 DOI: 10.1186/1749-8104-7-36] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2012] [Accepted: 10/12/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Axons navigate to their future synaptic targets with the help of choice points, intermediate targets that express axon guidance cues. Once they reach a choice point, axons need to switch their response from attraction to repulsion in order to move on with the next stage of their journey. The mechanisms underlying the change in axonal responsiveness are poorly understood. Commissural axons become sensitive to the repulsive activity of Slits when they cross the ventral midline of the CNS. Responsiveness to Slits depends on surface expression of Robo receptors. In Drosophila, Commissureless (Comm) plays a crucial regulatory role in midline crossing by keeping Robo levels low on precommissural axons. Interestingly, to date no vertebrate homolog of comm has been identified. Robo3/Rig1 has been shown to control Slit sensitivity before the midline, but without affecting Robo1 surface expression. RESULTS We had identified RabGDI, a gene linked to human mental retardation and an essential component of the vesicle fusion machinery, in a screen for differentially expressed floor-plate genes. Downregulation of RabGDI by in ovo RNAi caused commissural axons to stall in the floor plate, phenocopying the effect observed after downregulation of Robo1. Conversely, premature expression of RabGDI prevented commissural axons from entering the floor plate. Furthermore, RabGDI triggered Robo1 surface expression in cultured commissural neurons. Taken together, our results identify RabGDI as a component of the switching mechanism that is required for commissural axons to change their response from attraction to repulsion at the intermediate target. CONCLUSION RabGDI takes over the functional role of fly Comm by regulating the surface expression of Robo1 on commissural axons in vertebrates. This in turn allows commissural axons to switch from attraction to repulsion at the midline of the spinal cord.
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Affiliation(s)
- Melanie Philipp
- Institute for Biochemistry and Molecular Biology, University of Ulm, Ulm, Germany
| | | | - Marc Debrunner
- Institute of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, Zurich, CH, 8057, Switzerland
| | - Tobias Alther
- Institute of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, Zurich, CH, 8057, Switzerland
| | - Beat Kunz
- Institute of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, Zurich, CH, 8057, Switzerland
| | - Esther T Stoeckli
- Institute of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, Zurich, CH, 8057, Switzerland
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57
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Abstract
Hedgehog (Hh) proteins regulate the development of a wide range of metazoan embryonic and adult structures, and disruption of Hh signaling pathways results in various human diseases. Here, we provide a comprehensive review of the signaling pathways regulated by Hh, consolidating data from a diverse array of organisms in a variety of scientific disciplines. Similar to the elucidation of many other signaling pathways, our knowledge of Hh signaling developed in a sequential manner centered on its earliest discoveries. Thus, our knowledge of Hh signaling has for the most part focused on elucidating the mechanism by which Hh regulates the Gli family of transcription factors, the so-called "canonical" Hh signaling pathway. However, in the past few years, numerous studies have shown that Hh proteins can also signal through Gli-independent mechanisms collectively referred to as "noncanonical" signaling pathways. Noncanonical Hh signaling is itself subdivided into two distinct signaling modules: (i) those not requiring Smoothened (Smo) and (ii) those downstream of Smo that do not require Gli transcription factors. Thus, Hh signaling is now proposed to occur through a variety of distinct context-dependent signaling modules that have the ability to crosstalk with one another to form an interacting, dynamic Hh signaling network.
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Affiliation(s)
- David J Robbins
- Molecular Oncology Program, Department of Surgery, Miller School of Medicine, University of Miami, Miami, FL 33136, USA.
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58
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Peng J, Charron F. Lateralization of motor control in the human nervous system: genetics of mirror movements. Curr Opin Neurobiol 2012; 23:109-18. [PMID: 22989473 DOI: 10.1016/j.conb.2012.08.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2012] [Revised: 08/21/2012] [Accepted: 08/26/2012] [Indexed: 01/10/2023]
Abstract
Mirror movements (MM) are a peculiar motor defect in humans where the intended unilateral movement of a body part results in involuntary movement of the same body part on the opposite side. This loss in the lateralization of motor control can be caused by genetic mutations that result in an aberrant projection of the corticospinal tract. However, recent evidence suggests that the same genes controlling corticospinal tract development also play roles in the development of other circuits involved in motor control, including local spinal circuits and the corpus callosum. These recent studies in humans and mouse models of MM will be discussed to provide an overview of the basis of MM and the molecular mechanisms underlying the lateralization of motor control.
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Affiliation(s)
- Jimmy Peng
- Molecular Biology of Neural Development, Institut de Recherches Cliniques de Montréal, Montréal, QC, Canada
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59
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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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60
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Affiliation(s)
- Clemens Kiecker
- Medical Research Council (MRC) Center for Developmental Neurobiology, King's College, London SE1 1UL, United Kingdom; ,
| | - Andrew Lumsden
- Medical Research Council (MRC) Center for Developmental Neurobiology, King's College, London SE1 1UL, United Kingdom; ,
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61
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Fantetti KN, Fekete DM. Members of the BMP, Shh, and FGF morphogen families promote chicken statoacoustic ganglion neurite outgrowth and neuron survival in vitro. Dev Neurobiol 2012; 72:1213-28. [PMID: 22006861 DOI: 10.1002/dneu.20988] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2011] [Revised: 06/07/2011] [Accepted: 06/08/2011] [Indexed: 01/20/2023]
Abstract
Mechanosensory hair cells of the chicken inner ear are innervated by the peripheral processes of statoacoustic ganglion (SAG) neurons. Members of several morphogen families are expressed within and surrounding the chick inner ear during stages of SAG axon outgrowth and pathfinding. On the basis of their localized expression patterns, we hypothesized that bone morphogenetic proteins (BMPs), fibroblast growth factors (FGFs), and sonic hedgehog (Shh) may function as guidance cues for growing axons and/or may function as trophic factors once axons have reached their targets. To test this hypothesis, three-dimensional collagen cultures were used to grow Embryonic Day 4 (E4) chick SAG explants for 24 h in the presence of purified proteins or beads soaked in proteins. The density of neurite outgrowth was quantified to determine effects on neurite outgrowth. Explants displayed enhanced neurite outgrowth when cultured in the presence of purified BMP4, BMP7, a low concentration of Shh, FGF8, FGF10, or FGF19. In contrast, SAG neurons appeared unresponsive to FGF2. Collagen gel cultures were labeled with terminal dUTP nick-end labeling and immunostained with anti-phosphohistone H3 to determine effects on neuron survival and proliferation, respectively. Treatments that increased neurite outgrowth also yielded significantly fewer apoptotic cells, with no effect on cell proliferation. When presented as focal sources, BMP4, Shh, and FGFs -8, -10, and -19 promoted asymmetric outgrowth from the ganglion in the direction of the beads. BMP7-soaked beads did not induce this response. These results suggest that a subset of morphogens enhance both survival and axon outgrowth of otic neurons.
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Affiliation(s)
- Kristen N Fantetti
- Department of Biological Sciences and Purdue University Center for Cancer Research, Purdue University, West Lafayette, Indiana 47907-1392, USA
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62
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Benavente F, Pinto C, Parada M, Henríquez JP, Osses N. Bone morphogenetic protein 2 inhibits neurite outgrowth of motor neuron-like NSC-34 cells and up-regulates its type II receptor. J Neurochem 2012; 122:594-604. [PMID: 22612292 DOI: 10.1111/j.1471-4159.2012.07795.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Bone morphogenetic proteins (BMPs) regulate several aspects of neuronal behavior. For instance, BMP-2 has the ability to modulate, either positively or negatively, the outgrowth of neuronal processes in diverse cell types. In Drosophila motor neurons, the BMP type II receptor (BMPRII) homolog wishful thinking plays crucial roles on neuromuscular synaptogenesis signaling through Smad-dependent and Smad-independent pathways. However, a role for BMP signaling at the vertebrate neuromuscular junction has not been addressed. Herein, we have analyzed the expression of BMPRII and the effect of BMP-2 during the morphological differentiation of motor neuron-like NSC-34 cells. Our data indicate that BMPRII is up-regulated and becomes accumulated in somas and growth cones upon motor neuronal differentiation. BMP-2 inhibits the differentiation of NSC-34 cells, an effect that correlates with activation of a Smad-dependent pathway, induction of the inhibitory Id1 transcription factor, and down-regulation of the neurogenic factor Mash1. BMP-2 also activates effectors of Smad-independent pathways. Remarkably, BMP-2 treatment significantly increases the expression of BMPRII. Our findings provide the first evidence to suggest a role for BMP pathways on the differentiation of motor neurons leading to successful assembly and/or regeneration of the vertebrate neuromuscular synapse.
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Affiliation(s)
- Francisca Benavente
- Instituto de Química, Facultad de Ciencias, Pontificia Universidad Católica de Valparaíso, Chile
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63
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Rabe Bernhardt N, Memic F, Gezelius H, Thiebes AL, Vallstedt A, Kullander K. DCC mediated axon guidance of spinal interneurons is essential for normal locomotor central pattern generator function. Dev Biol 2012; 366:279-89. [DOI: 10.1016/j.ydbio.2012.03.017] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2011] [Revised: 03/21/2012] [Accepted: 03/27/2012] [Indexed: 11/16/2022]
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Sakai N, Kaprielian Z. Guidance of longitudinally projecting axons in the developing central nervous system. Front Mol Neurosci 2012; 5:59. [PMID: 22586366 PMCID: PMC3343325 DOI: 10.3389/fnmol.2012.00059] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2012] [Accepted: 04/14/2012] [Indexed: 12/26/2022] Open
Abstract
The directed and stereotypical growth of axons to their synaptic targets is a crucial phase of neural circuit formation. Many axons in the developing vertebrate and invertebrate central nervous systems (CNSs), including those that remain on their own (ipsilateral), and those that cross over to the opposite (commissural), side of the midline project over long distances along the anterior-posterior (A-P) body axis within precisely positioned longitudinally oriented tracts to facilitate the transmission of information between CNS regions. Despite the widespread distribution and functional importance of these longitudinal tracts, the mechanisms that regulate their formation and projection to poorly characterized synaptic targets remain largely unknown. Nevertheless, recent studies carried out in a variety of invertebrate and vertebrate model systems have begun to elucidate the molecular logic that controls longitudinal axon guidance.
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Affiliation(s)
- Nozomi Sakai
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx NY, USA
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65
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Insights into Stem Cell Factor chemotactic guidance of neural crest cells revealed by a real-time directionality-based assay. Eur J Cell Biol 2012; 91:375-90. [DOI: 10.1016/j.ejcb.2011.12.007] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2011] [Revised: 12/19/2011] [Accepted: 12/20/2011] [Indexed: 11/23/2022] Open
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66
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Abstract
In this issue of Neuron, Harwell et al. (2012) identify a new role for the secreted molecule Shh and its receptor Boc in synapse formation. These results add an unexpected new player to the expanding list of extracellular cues regulating the spatial specificity of synapse formation.
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Affiliation(s)
- Julien Courchet
- Department of Cell Biology, Dorris Neuroscience Center, The Scripps Research Institute, La Jolla, CA 92037, USA
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67
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Wong YH, Wang H, Ravasi T, Qian PY. Involvement of Wnt signaling pathways in the metamorphosis of the bryozoan Bugula neritina. PLoS One 2012; 7:e33323. [PMID: 22448242 PMCID: PMC3308966 DOI: 10.1371/journal.pone.0033323] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2011] [Accepted: 02/07/2012] [Indexed: 11/18/2022] Open
Abstract
In this study, we analyzed the metamorphosis of the marine bryozoan Bugula neritina. We observed the morphogenesis of the ancestrula. We defined three distinct pre-ancestrula stages based on the anatomy of the developing polypide and the overall morphology of pre-ancestrula. We then used an annotation based enrichment analysis tool to analyze the B. neritina transcriptome and identified over-representation of genes related to Wnt signaling pathways, suggesting its involvement in metamorphosis. Finally, we studied the temporal-spatial gene expression studies of several Wnt pathway genes. We found that one of the Wnt ligand, BnWnt10, was expressed spatially opposite to the Wnt antagonist BnsFRP within the blastemas, which is the presumptive polypide. Down-stream components of the canonical Wnt signaling pathway were exclusively expressed in the blastemas. Bnβcatenin and BnFz5/8 were exclusively expressed in the blastemas throughout the metamorphosis. Based on the genes expression patterns, we propose that BnWnt10 and BnsFRP may relate to the patterning of the polypide, in which the two genes served as positional signals and contributed to the polarization of the blastemas. Another Wnt ligand, BnWnt6, was expressed in the apical part of the pre-ancestrula epidermis. Overall, our findings suggest that the Wnt signaling pathway may be important to the pattern formation of polypide and the development of epidermis.
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Affiliation(s)
- Yue Him Wong
- KAUST Global Collaborative Research Program, Division of Life Sciences, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR, China
| | - Hao Wang
- KAUST Global Collaborative Research Program, Division of Life Sciences, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR, China
| | - Timothy Ravasi
- Department of Computational Bioscience Research Center, King Abdullah University of Science and Technology, Thuwal, The Kingdom of Saudi Arabia
| | - Pei-Yuan Qian
- KAUST Global Collaborative Research Program, Division of Life Sciences, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR, China
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Ccdc80-l1 Is involved in axon pathfinding of zebrafish motoneurons. PLoS One 2012; 7:e31851. [PMID: 22384085 PMCID: PMC3285184 DOI: 10.1371/journal.pone.0031851] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2011] [Accepted: 01/19/2012] [Indexed: 11/29/2022] Open
Abstract
Axon pathfinding is a subfield of neural development by which neurons send out axons to reach the correct targets. In particular, motoneurons extend their axons toward skeletal muscles, leading to spontaneous motor activity. In this study, we identified the zebrafish Ccdc80 and Ccdc80-like1 (Ccdc80-l1) proteins in silico on the basis of their high aminoacidic sequence identity with the human CCDC80 (Coiled-Coil Domain Containing 80). We focused on ccdc80-l1 gene that is expressed in nervous and non-nervous tissues, in particular in territories correlated with axonal migration, such as adaxial cells and muscle pioneers. Loss of ccdc80-l1 in zebrafish embryos induced motility issues, although somitogenesis and myogenesis were not impaired. Our results strongly suggest that ccdc80-l1 is involved in axon guidance of primary and secondary motoneurons populations, but not in their proper formation. ccdc80-l1 has a differential role as regards the development of ventral and dorsal motoneurons, and this is consistent with the asymmetric distribution of the transcript. The axonal migration defects observed in ccdc80-l1 loss-of-function embryos are similar to the phenotype of several mutants with altered Hedgehog activity. Indeed, we reported that ccdc80-l1 expression is positively regulated by the Hedgehog pathway in adaxial cells and muscle pioneers. These findings strongly indicate ccdc80-l1 as a down-stream effector of the Hedgehog pathway.
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69
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Gil V, del Río JA. Analysis of axonal growth and cell migration in 3D hydrogel cultures of embryonic mouse CNS tissue. Nat Protoc 2012; 7:268-80. [DOI: 10.1038/nprot.2011.445] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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70
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Fantetti KN, Fekete DM. Dissection and culture of chick statoacoustic ganglion and spinal cord explants in collagen gels for neurite outgrowth assays. J Vis Exp 2011:3600. [PMID: 22215150 PMCID: PMC3369645 DOI: 10.3791/3600] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The sensory organs of the chicken inner ear are innervated by the peripheral processes of statoacoustic ganglion (SAG) neurons. Sensory organ innervation depends on a combination of axon guidance cues and survival factors located along the trajectory of growing axons and/or within their sensory organ targets. For example, functional interference with a classic axon guidance signaling pathway, semaphorin-neuropilin, generated misrouting of otic axons. Also, several growth factors expressed in the sensory targets of the inner ear, including Neurotrophin-3 (NT-3) and Brain Derived Neurotrophic Factor (BDNF), have been manipulated in transgenic animals, again leading to misrouting of SAG axons. These same molecules promote both survival and neurite outgrowth of chick SAG neurons in vitro. Here, we describe and demonstrate the in vitro method we are currently using to test the responsiveness of chick SAG neurites to soluble proteins, including known morphogens such as the Wnts, as well as growth factors that are important for promoting SAG neurite outgrowth and neuron survival. Using this model system, we hope to draw conclusions about the effects that secreted ligands can exert on SAG neuron survival and neurite outgrowth. SAG explants are dissected on embryonic day 4 (E4) and cultured in three-dimensional collagen gels under serum-free conditions for 24 hours. First, neurite responsiveness is tested by culturing explants with protein-supplemented medium. Then, to ask whether point sources of secreted ligands can have directional effects on neurite outgrowth, explants are co-cultured with protein-coated beads and assayed for the ability of the bead to locally promote or inhibit outgrowth. We also include a demonstration of the dissection (modified protocol) and culture of E6 spinal cord explants. We routinely use spinal cord explants to confirm bioactivity of the proteins and protein-soaked beads, and to verify species cross-reactivity with chick tissue, under the same culture conditions as SAG explants. These in vitro assays are convenient for quickly screening for molecules that exert trophic (survival) or tropic (directional) effects on SAG neurons, especially before performing studies in vivo. Moreover, this method permits the testing of individual molecules under serum-free conditions, with high neuron survival.
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71
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Ruat M, Angot É, Traiffort É. Sonic Hedgehog, un morphogène en quête de fonction dans le cerveau adulte. Med Sci (Paris) 2011; 27:979-85. [DOI: 10.1051/medsci/20112711014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
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72
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Atkinson-Leadbeater K, McFarlane S. Extrinsic factors as multifunctional regulators of retinal ganglion cell morphogenesis. Dev Neurobiol 2011; 71:1170-85. [DOI: 10.1002/dneu.20924] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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73
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Fernández-Martos CM, González-Fernández C, González P, Maqueda A, Arenas E, Rodríguez FJ. Differential expression of Wnts after spinal cord contusion injury in adult rats. PLoS One 2011; 6:e27000. [PMID: 22073235 PMCID: PMC3206916 DOI: 10.1371/journal.pone.0027000] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2011] [Accepted: 10/07/2011] [Indexed: 01/08/2023] Open
Abstract
BACKGROUND Spinal cord injury is a major cause of disability that has no clinically accepted treatment. Functional decline following spinal cord injury is caused by mechanical damage, secondary cell death, reactive gliosis and a poor regenerative capacity of damaged axons. Wnt proteins are a family of secreted glycoproteins that play key roles in different developmental processes although little is known of the expression patterns and functions of Wnts in the adult central nervous system in normal or diseased states. FINDINGS Using qRT-PCR analysis, we demonstrate that mRNA encoding most Wnt ligands and soluble inhibitors are constitutively expressed in the healthy adult spinal cord. Strikingly, contusion spinal cord injury induced a time-dependent increase in Wnt mRNA expression from 6 hours until 28 days post-injury, and a narrow peak in the expression of soluble Wnt inhibitors between 1 and 3 days post-injury. These results are consistent with the increase in the migration shift, from day 1 to 7, of the intracellular Wnt signalling component, Dishevelled-3. Moreover, after an initial decrease by 1 day, we also found an increase in phosphorylation of the Wnt co-receptor, low-density lipoprotein receptor-related protein 6, and an increase in active β-catenin protein, both of which suffer a dramatic change, from a homogeneous expression pattern in the grey matter to a disorganized injury-induced pattern. CONCLUSIONS Our results suggest a role for Wnts in spinal cord homeostasis and injury. We demonstrate that after injury Wnt signalling is activated via the Wnt/β-catenin and possibly other pathways. These findings provide an important foundation to further address the function of individual Wnt proteins in vivo and the pathophysiology of spinal cord injury.
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Affiliation(s)
| | | | - Pau González
- Laboratorio de Neurología Molecular, Hospital Nacional de Parapléjicos (HNP), Toledo, Spain
| | - Alfredo Maqueda
- Laboratorio de Neurología Molecular, Hospital Nacional de Parapléjicos (HNP), Toledo, Spain
| | - Ernest Arenas
- Molecular Neurobiology Unit, MBB, Karolinska Institute, Stockholm, Sweden
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74
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Abstract
In bilaterally symmetric animals, many axons cross the midline to interconnect the left and right sides of the central nervous system (CNS). This process is critical for the establishment of neural circuits that control the proper integration of information perceived by the organism and the resulting response. While neurons at different levels of the CNS project axons across the midline, the molecules that regulate this process are common to many if not all midline-crossing regions. This article reviews the molecules that function as guidance cues at the midline in the developing vertebrate spinal cord, cortico-spinal tract and corpus callosum. As well, we describe the mutations that have been identified in humans that are linked to axon guidance and midline-crossing defects.
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Affiliation(s)
- L Izzi
- Molecular Biology of Neural Development, Institut de Recherches Cliniques de Montréal (IRCM), Montreal, Quebec, Canada
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75
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Ruiz de Almodovar C, Fabre PJ, Knevels E, Coulon C, Segura I, Haddick PCG, Aerts L, Delattin N, Strasser G, Oh WJ, Lange C, Vinckier S, Haigh J, Fouquet C, Gu C, Alitalo K, Castellani V, Tessier-Lavigne M, Chedotal A, Charron F, Carmeliet P. VEGF mediates commissural axon chemoattraction through its receptor Flk1. Neuron 2011; 70:966-78. [PMID: 21658588 PMCID: PMC3638787 DOI: 10.1016/j.neuron.2011.04.014] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/15/2011] [Indexed: 01/13/2023]
Abstract
Growing axons are guided to their targets by attractive and repulsive cues. In the developing spinal cord, Netrin-1 and Shh guide commissural axons toward the midline. However, the combined inhibition of their activity in commissural axon turning assays does not completely abrogate turning toward floor plate tissue, suggesting that additional guidance cues are present. Here we show that the prototypic angiogenic factor VEGF is secreted by the floor plate and is a chemoattractant for commissural axons in vitro and in vivo. Inactivation of Vegf in the floor plate or of its receptor Flk1 in commissural neurons causes axon guidance defects, whereas Flk1 blockade inhibits turning of axons to VEGF in vitro. Similar to Shh and Netrin-1, VEGF-mediated commissural axon guidance requires the activity of Src family kinases. Our results identify VEGF and Flk1 as a novel ligand/receptor pair controlling commissural axon guidance.
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Affiliation(s)
- Carmen Ruiz de Almodovar
- VIB, Laboratory for Angiogenesis and the Neurovascular link, Vesalius Research Center, KULeuven, Leuven, Belgium
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76
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Izzi L, Lévesque M, Morin S, Laniel D, Wilkes BC, Mille F, Krauss RS, McMahon AP, Allen BL, Charron F. Boc and Gas1 each form distinct Shh receptor complexes with Ptch1 and are required for Shh-mediated cell proliferation. Dev Cell 2011; 20:788-801. [PMID: 21664577 DOI: 10.1016/j.devcel.2011.04.017] [Citation(s) in RCA: 186] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2010] [Revised: 03/17/2011] [Accepted: 04/30/2011] [Indexed: 12/21/2022]
Abstract
Hedgehog (Hh) proteins regulate important developmental processes, including cell proliferation and differentiation. Although Patched acts as the main Hh receptor in Drosophila, Hh signaling absolutely requires the additional Hh-binding proteins Ihog and Boi. Here we show that, unexpectedly, cerebellar granule neuron progenitors (CGNPs) lacking Boc and Cdon, the vertebrate orthologs of Ihog and Boi, still proliferate in response to Hh. This is because in their absence, Gas1, an Hh-binding protein not present in Drosophila, mediates Hh signaling. Consistently, only CGNPs lacking all three molecules-Boc, Cdon, and Gas1-have a complete loss of Hh-dependent proliferation. In a complementary manner, we find that a mutated Hh ligand that binds Patched1 but not Boc, Cdon, or Gas1 cannot activate Hh signaling. Together, this demonstrates an absolute requirement for Boc, Cdon, and Gas1 in Hh signaling and reveals a distinct requirement for ligand-binding components that distinguishes the vertebrate and invertebrate Hh receptor systems.
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Affiliation(s)
- Luisa Izzi
- Molecular Biology of Neural Development, Institut de Recherches Cliniques de Montréal, Canada
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77
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Ueno M, Yamashita T. Strategies for regenerating injured axons after spinal cord injury - insights from brain development. Biologics 2011; 2:253-64. [PMID: 19707358 PMCID: PMC2721354 DOI: 10.2147/btt.s2715] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Axonal regeneration does not occur easily after an adult central nervous system (CNS) injury. Various attempts have partially succeeded in promoting axonal regeneration after the spinal cord injury (SCI). Interestingly, several recent therapeutic concepts have emerged from or been tightly linked to the researches on brain development. In a developing brain, remarkable and dynamic axonal elongation and sprouting occur even after the injury; this finding is essential to the development of a therapy for SCI. In this review, we overview the revealed mechanism of axonal tract formation and plasticity in the developing brain and compare the differences between a developing brain and a lesion site in an adult brain. One of the differences is that mature glial cells participate in the repair process in the case of adult injuries. Interestingly, these cells express inhibitory molecules that impede axonal regeneration such as myelin-associated proteins and the repulsive guidance molecules found originally in the developing brain for navigating axons to specific routes. Some reports have clearly elucidated that any treatment designed to suppress these inhibitory cues is beneficial for promoting regeneration and plasticity after an injury. Thus, understanding the developmental process will provide us with an important clue for designing therapeutic strategies for recovery from SCI.
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Affiliation(s)
- Masaki Ueno
- Department of Molecular Neuroscience, Graduate School of Medicine, Osaka University, 2-2, Yamadaoka, Suita-shi, Osaka 565-0871, Japan
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78
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Massinen S, Hokkanen ME, Matsson H, Tammimies K, Tapia-Páez I, Dahlström-Heuser V, Kuja-Panula J, Burghoorn J, Jeppsson KE, Swoboda P, Peyrard-Janvid M, Toftgård R, Castrén E, Kere J. Increased expression of the dyslexia candidate gene DCDC2 affects length and signaling of primary cilia in neurons. PLoS One 2011; 6:e20580. [PMID: 21698230 PMCID: PMC3116825 DOI: 10.1371/journal.pone.0020580] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2011] [Accepted: 05/04/2011] [Indexed: 12/14/2022] Open
Abstract
DCDC2 is one of the candidate susceptibility genes for dyslexia. It belongs to the superfamily of doublecortin domain containing proteins that bind to microtubules, and it has been shown to be involved in neuronal migration. We show that the Dcdc2 protein localizes to the primary cilium in primary rat hippocampal neurons and that it can be found within close proximity to the ciliary kinesin-2 subunit Kif3a. Overexpression of DCDC2 increases ciliary length and activates Shh signaling, whereas downregulation of Dcdc2 expression enhances Wnt signaling, consistent with a functional role in ciliary signaling. Moreover, DCDC2 overexpression in C. elegans causes an abnormal neuronal phenotype that can only be seen in ciliated neurons. Together our results suggest a potential role for DCDC2 in the structure and function of primary cilia.
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Affiliation(s)
- Satu Massinen
- Research Program's Unit, Molecular Medicine and Department of Medical Genetics, University of Helsinki, Helsinki, Finland
| | | | - Hans Matsson
- Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden
| | - Kristiina Tammimies
- Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden
| | - Isabel Tapia-Páez
- Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden
| | | | | | - Jan Burghoorn
- Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden
- School of Life Sciences, Södertörn University College, Huddinge, Sweden
| | - Kristian E. Jeppsson
- Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden
- School of Life Sciences, Södertörn University College, Huddinge, Sweden
| | - Peter Swoboda
- Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden
- School of Life Sciences, Södertörn University College, Huddinge, Sweden
| | | | - Rune Toftgård
- Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden
| | - Eero Castrén
- Neuroscience Center, University of Helsinki, Helsinki, Finland
- * E-mail:
| | - Juha Kere
- Research Program's Unit, Molecular Medicine and Department of Medical Genetics, University of Helsinki, Helsinki, Finland
- Neuroscience Center, University of Helsinki, Helsinki, Finland
- Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden
- Folkhälsan Institute of Genetics, Helsinki, Finland
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79
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Colvin Wanshura LE, Galvin KE, Ye H, Fernandez-Zapico ME, Wetmore C. Sequential activation of Snail1 and N-Myc modulates sonic hedgehog-induced transformation of neural cells. Cancer Res 2011; 71:5336-45. [PMID: 21646478 DOI: 10.1158/0008-5472.can-10-2633] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Activation of the Sonic hedgehog (Shh) pathway and increased expression of Gli1 play an important role in proliferation and transformation of granule cell progenitors (GCP) in the developing cerebellum. Medulloblastomas arising from cerebellar GCPs are frequently driven by Shh pathway-activating mutations; however, molecular mechanisms of Shh pathway dysregulation and transformation of neural progenitors remain poorly defined. We report that the transcription factor and oncogene Snail1 (Sna1) is directly induced by Shh pathway activity in GCPs, murine medulloblastomas, and human medulloblastoma cells. Enforced expression of Sna1 was sufficient to induce GCPs and medulloblastoma cell proliferation in the absence of Shh/Gli1 exposure. In addition, enforced expression of Sna1 increased transformation of medulloblastoma cells in vitro and in vivo. Analysis of potential Sna1 targets in neural cells revealed a novel Sna1 target, N-Myc, a transcription factor known to play a role in Shh-mediated GCP proliferation and medulloblastoma formation. We found that Sna1 directly induced transcription of N-Myc in human medulloblastoma cells and that depletion of N-Myc ablated the Sna1-induced proliferation and transformation. Taken together, these results provide further insight into the mechanism of Shh-induced transformation of neural progenitor cells and suggest that induction of Sna1 may serve to amplify the oncogenic potential of Shh pathway activation through N-Myc induction.
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Affiliation(s)
- Leah E Colvin Wanshura
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, MN, USA
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80
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Fantetti KN, Zou Y, Fekete DM. Wnts and Wnt inhibitors do not influence axon outgrowth from chicken statoacoustic ganglion neurons. Hear Res 2011; 278:86-95. [PMID: 21530628 DOI: 10.1016/j.heares.2011.04.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2010] [Revised: 03/04/2011] [Accepted: 04/07/2011] [Indexed: 10/18/2022]
Abstract
The peripheral growth cones of statoacoustic ganglion (SAG) neurons are presumed to sense molecular cues to navigate to their sensory targets during development. Based on previously reported expression data for Frizzled receptors, Wnt ligands, and Wnt inhibitors, we hypothesized that some members of the Wnt morphogen family may function as repulsive cues for SAG neurites. The responses of SAG neurons to mammalian Wnts -1, -4, -5a, -6, and -7b, and the Wnt inhibitors sFRP -1, -2, and -3, were tested in vitro by growing SAG explants from embryonic day 4 (E4) chicken embryos for two days in 3D collagen gels. Average neurite length and density were quantified to determine effects on neurite outgrowth. SAG neurites were strongly repelled by human Sema3E, demonstrating SAG neurons are responsive under these assay conditions. In contrast, SAG neurons showed no changes in neurite outgrowth when cultured in the presence of Wnts and Wnt inhibitors. As an alternative approach, Wnt4 and Wnt5a were also tested in vivo by injecting retroviruses encoding these genes into the chicken otocyst on E3. On E6, no differences were evident in the peripheral projections of SAG axons terminating in infected sensory organs as compared to uninfected organs on the contralateral side of the same embryo. For all Wnt sources, bioactivity was confirmed on E6 chick spinal cord explants by observing enhanced axon outgrowth, as reported previously in the mouse. These results suggest that the tested Wnts do not play a role in guiding peripheral axons in the chicken inner ear.
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Affiliation(s)
- Kristen N Fantetti
- Department of Biological Sciences, Purdue University, 915 W State St, West Lafayette, IN 47907-1392, USA.
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81
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Gordon L, Mansh M, Kinsman H, Morris AR. Xenopus sonic hedgehog guides retinal axons along the optic tract. Dev Dyn 2011; 239:2921-32. [PMID: 20931659 DOI: 10.1002/dvdy.22430] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The role of classic morphogens such as Sonic hedgehog (Shh) as axon guidance cues has been reported in a variety of vertebrate organisms (Charron and Tessier-Lavigne [2005] Development 132:2251-2262). In this work, we provide the first evidence that Xenopus sonic hedgehog (Xshh) signaling is involved in guiding retinal ganglion cell (RGC) axons along the optic tract. Xshh is expressed in the brain during retinal axon extension, adjacent to these axons in the ventral diencephalon. Retinal axons themselves express Patched 1 and Smoothened co-receptors during RGC axon growth. Blocking Shh signaling causes abnormal ventral pathfinding, and targeting errors at the optic tectum. Misexpression of exogenous N-Shh peptide in vivo also causes pathfinding errors. Retinal axons grown in culture respond to N-Shh in a dose-dependent manner, either by decreasing extension at lower concentrations, or retracting axons in the presence of higher doses. These data suggest that Shh signaling is required for normal RGC axon pathfinding and tectal targeting in the developing visual system of Xenopus. We propose that Shh serves as a ventral optic tract repellent that helps to define the caudal boundary for retinal axons in the diencephalon, and that this signaling is also required for initial target recognition at the optic tectum.
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Affiliation(s)
- Laura Gordon
- Haverford College Department of Biology, Haverford, Pennsylvania 19041, USA
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82
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Staii C, Viesselman C, Ballweg J, Hart S, Williams JC, Dent EW, Coppersmith SN, Eriksson M. Controlling Neuronal Growth on Au Surfaces by Directed Assembly of Proteins. ACTA ACUST UNITED AC 2011. [DOI: 10.1557/proc-1236-ss01-05] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
AbstractStudying how individual neuronal cells grow and interact with each other is of fundamental importance for understanding the functions of the nervous system. However, the mechanism of axonal navigation to their target region and their specific interactions with guidance factors such as membrane-bound proteins, chemical and temperature gradients, mechanical guidance cues, etc. are not well understood. Here we describe a new approach for controlling the adhesion, growth and interconnectivity of cortical neurons on Au surfaces. Specifically, we use Atomic Force Microscopy (AFM) nanolithography to immobilize growth-factor proteins at well-defined locations on Au surfaces. These surface-immobilized proteins act as a) adhesion proteins for neuronal cells (i.e. well-defined locations where the cells “stick” to the surface), and b) promoters/inhibitors for the growth of neurites. Our results show that protein patterns can be used to confine neuronal cells and to control their growth and interconnectivity on Au surfaces. We also show that AFM nanolithography presents unique advantages for this type of work, such as high degree of control over location and shape of the protein patterns, and application of proteins in aqueous solutions (protein buffers), such that the proteins are very likely to retain their folding conformation/bioactivity.
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83
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Tam SJ, Watts RJ. Connecting vascular and nervous system development: angiogenesis and the blood-brain barrier. Annu Rev Neurosci 2011; 33:379-408. [PMID: 20367445 DOI: 10.1146/annurev-neuro-060909-152829] [Citation(s) in RCA: 134] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The vascular and nervous systems share a common necessity of circuit formation to coordinate nutrient and information transfer, respectively. Shared developmental principles have evolved to orchestrate the formation of both the vascular and the nervous systems. This evolution is highlighted by the identification of specific guidance cues that direct both systems to their target tissues. In addition to sharing cellular and molecular signaling events during development, the vascular and nervous systems also form an intricate interface within the central nervous system called the neurovascular unit. Understanding how the neurovascular unit develops and functions, and more specifically how the blood-brain barrier within this unit is established, is of utmost importance. We explore the history, recent discoveries, and unanswered questions surrounding the relationship between the vascular and nervous systems with a focus on developmental signaling cues that guide network formation and establish the interface between these two systems.
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Affiliation(s)
- Stephen J Tam
- Neurodegeneration Labs, Department of Neuroscience, Genentech, Inc., South San Francisco, California 94080, USA
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84
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Staii C, Viesselmann C, Ballweg J, Williams JC, Dent EW, Coppersmith SN, Eriksson MA. Distance dependence of neuronal growth on nanopatterned gold surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:233-9. [PMID: 21121598 DOI: 10.1021/la102331x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Understanding network development in the brain is of tremendous fundamental importance, but it is immensely challenging because of the complexity of both its architecture and function. The mechanisms of axonal navigation to target regions and the specific interactions with guidance factors such as membrane-bound proteins, chemical gradients, mechanical guidance cues, etc., are largely unknown. A current limitation for the study of neural network formation is the ability to control precisely the connectivity of small groups of neurons. A first step in designing such networks is to understand the "rules" central nervous system (CNS) neurons use to form functional connections with one another. Here we begin to delineate novel rules for growth and connectivity of small numbers of neurons patterned on Au substrates in simplified geometries. These studies yield new insights into the mechanisms determining the organizational features present in intact systems. We use a previously reported atomic force microscopy (AFM) nanolithography method to control precisely the location and growth of neurons on these surfaces. By examining a series of systems with different geometrical parameters, we quantitatively and systematically analyze how neuronal growth depends on these parameters.
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Affiliation(s)
- Cristian Staii
- Department of Physics and Astronomy, Tufts University, Medford, Massachusetts 02155, United States.
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85
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The bone morphogenetic protein roof plate chemorepellent regulates the rate of commissural axonal growth. J Neurosci 2010; 30:15430-40. [PMID: 21084599 DOI: 10.1523/jneurosci.4117-10.2010] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Commissural spinal axons extend away from the roof plate (RP) in response to a chemorepellent mediated by the bone morphogenetic proteins (BMPs). Previous studies have focused on the ability of commissural axons to translate a spatial gradient of BMPs into directional information in vitro. However, a notable feature of this system in vivo is that the gradient of BMPs is thought to act from behind the commissural cell bodies, making it possible for the BMPs to have a continued effect on commissural axons as they grow away from the RP. Here, we demonstrate that BMPs activate the cofilin regulator Lim domain kinase 1 (Limk1) to control the rate of commissural axon extension in the dorsal spinal cord. By modulating Limk1 activity in both rodent and chicken commissural neurons, the rate of axon growth can either be stalled or accelerated. Altering the activation state of Limk1 also influences subsequent guidance decisions: accelerated axons make rostrocaudal projection errors while navigating their intermediate target, the floor plate. These results suggest that guidance cues can specify information about the rate of growth, to ensure that axons reach subsequent signals either at particular times or speeds during development.
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86
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Greenberg ME. Signaling networks that control synapse development and cognitive function. HARVEY LECTURES 2010; 102:73-102. [PMID: 20166564 DOI: 10.1002/9780470593042.ch4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Affiliation(s)
- Michael E Greenberg
- Children's Hospital Boston, Program in Neurobiology, Harvard Medical School, Department of Neurobiology, Boston, Massachusetts, USA
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87
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Camp D, Currie K, Labbé A, van Meyel DJ, Charron F. Ihog and Boi are essential for Hedgehog signaling in Drosophila. Neural Dev 2010; 5:28. [PMID: 21044292 PMCID: PMC2984377 DOI: 10.1186/1749-8104-5-28] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2010] [Accepted: 11/02/2010] [Indexed: 11/17/2022] Open
Abstract
Background The Hedgehog (Hh) signaling pathway is important for the development of a variety of tissues in both vertebrates and invertebrates. For example, in developing nervous systems Hh signaling is required for the normal differentiation of neural progenitors into mature neurons. The molecular signaling mechanism underlying the function of Hh is not fully understood. In Drosophila, Ihog (Interference hedgehog) and Boi (Brother of Ihog) are related transmembrane proteins of the immunoglobulin superfamily (IgSF) with orthologs in vertebrates. Members of this IgSF subfamily have been shown to bind Hh and promote pathway activation but their exact role in the Hh signaling pathway has remained elusive. To better understand this role in vivo, we generated loss-of-function mutations of the ihog and boi genes, and investigated their effects in developing eye and wing imaginal discs. Results While mutation of either ihog or boi alone had no discernible effect on imaginal tissues, cells in the developing eye disc that were mutant for both ihog and boi failed to activate the Hh pathway, causing severe disruption of photoreceptor differentiation in the retina. In the anterior compartment of the developing wing disc, where different concentrations of the Hh morphogen elicit distinct cellular responses, cells mutant for both ihog and boi failed to activate responses at either high or low thresholds of Hh signaling. They also lost their affinity for neighboring cells and aberrantly sorted out from the anterior compartment of the wing disc into posterior territory. We found that ihog and boi are required for the accumulation of the essential Hh signaling mediator Smoothened (Smo) in Hh-responsive cells, providing evidence that Ihog and Boi act upstream of Smo in the Hh signaling pathway. Conclusions The consequences of boi;ihog mutations for eye development, neural differentiation and wing patterning phenocopy those of smo mutations and uncover an essential role for Ihog and Boi in the Hh signaling pathway.
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Affiliation(s)
- Darius Camp
- Molecular Biology of Neural Development, Institut de Recherches Cliniques de Montréal (IRCM), Montreal, QC, Canada
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88
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Fassier C, Hutt JA, Scholpp S, Lumsden A, Giros B, Nothias F, Schneider-Maunoury S, Houart C, Hazan J. Zebrafish atlastin controls motility and spinal motor axon architecture via inhibition of the BMP pathway. Nat Neurosci 2010; 13:1380-7. [PMID: 20935645 DOI: 10.1038/nn.2662] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2010] [Accepted: 08/26/2010] [Indexed: 01/25/2023]
Abstract
To better understand hereditary spastic paraplegia (HSP), we characterized the function of atlastin, a protein that is frequently involved in juvenile forms of HSP, by analyzing loss- and gain-of-function phenotypes in the developing zebrafish. We found that knockdown of the gene for atlastin (atl1) caused a severe decrease in larval mobility that was preceded by abnormal architecture of spinal motor axons and was associated with a substantial upregulation of the bone morphogenetic protein (BMP) signaling pathway. Overexpression analyses confirmed that atlastin inhibits BMP signaling. In primary cultures of zebrafish spinal neurons, Atlastin partially colocalized with type I BMP receptors in late endosomes distributed along neurites, which suggests that atlastin may regulate BMP receptor trafficking. Finally, genetic or pharmacological inhibition of BMP signaling was sufficient to rescue the loss of mobility and spinal motor axon defects of atl1 morphants, emphasizing the importance of fine-tuning the balance of BMP signaling for vertebrate motor axon architecture and stability.
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Affiliation(s)
- Coralie Fassier
- CNRS UMR 7224, Physiopathologie des Maladies du Système Nerveux Central, Paris, France
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89
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Fabre CCG, Casal J, Lawrence PA. Mechanosensilla in the adult abdomen of Drosophila: engrailed and slit help to corral the peripheral sensory axons into segmental bundles. Development 2010; 137:2885-94. [PMID: 20667917 PMCID: PMC2938919 DOI: 10.1242/dev.044552] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/14/2010] [Indexed: 11/20/2022]
Abstract
The abdomen of adult Drosophila bears mechanosensory bristles with axons that connect directly to the CNS, each hemisegment contributing a separate nerve bundle. Here, we alter the amount of Engrailed protein and manipulate the Hedgehog signalling pathway in clones of cells to study their effects on nerve pathfinding within the peripheral nervous system. We find that high levels of Engrailed make the epidermal cells inhospitable to bristle neurons; sensory axons that are too near these cells are either deflected or fail to extend properly or at all. We then searched for the engrailed-dependent agent responsible for these repellent properties. We found slit to be expressed in the P compartment and, using genetic mosaics, present evidence that Slit is the responsible molecule. Blocking the activity of the three Robo genes (putative receptors for Slit) with RNAi supported this hypothesis. We conclude that, during normal development, gradients of Slit protein repel axons away from compartment boundaries - in consequence, the bristles from each segment send their nerves to the CNS in separated sets.
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MESH Headings
- Abdomen/physiology
- Adaptor Proteins, Signal Transducing/genetics
- Adaptor Proteins, Signal Transducing/physiology
- Animals
- Animals, Genetically Modified
- Axons/physiology
- Drosophila/genetics
- Drosophila/growth & development
- Drosophila/physiology
- Drosophila Proteins/genetics
- Drosophila Proteins/physiology
- Gene Expression Regulation, Developmental
- Genes, Insect
- Hedgehog Proteins/genetics
- Hedgehog Proteins/physiology
- Homeodomain Proteins/genetics
- Homeodomain Proteins/physiology
- Mechanoreceptors/physiology
- Models, Neurological
- Nerve Tissue Proteins/antagonists & inhibitors
- Nerve Tissue Proteins/genetics
- Nerve Tissue Proteins/physiology
- Neurogenesis/genetics
- Neurogenesis/physiology
- RNA Interference
- Receptors, Cell Surface/genetics
- Receptors, Cell Surface/physiology
- Receptors, G-Protein-Coupled/genetics
- Receptors, G-Protein-Coupled/physiology
- Receptors, Immunologic/antagonists & inhibitors
- Receptors, Immunologic/genetics
- Receptors, Immunologic/physiology
- Smoothened Receptor
- Transcription Factors/genetics
- Transcription Factors/physiology
- Roundabout Proteins
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90
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Yi JJ, Barnes AP, Hand R, Polleux F, Ehlers MD. TGF-beta signaling specifies axons during brain development. Cell 2010; 142:144-57. [PMID: 20603020 DOI: 10.1016/j.cell.2010.06.010] [Citation(s) in RCA: 212] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2009] [Revised: 01/21/2010] [Accepted: 04/26/2010] [Indexed: 10/19/2022]
Abstract
In the mammalian brain, the specification of a single axon and multiple dendrites occurs early in the differentiation of most neuron types. Numerous intracellular signaling events for axon specification have been described in detail. However, the identity of the extracellular factor(s) that initiate neuronal polarity in vivo is unknown. Here, we report that transforming growth factor beta (TGF-beta) initiates signaling pathways both in vivo and in vitro to fate naive neurites into axons. Neocortical neurons lacking the type II TGF-beta receptor (TbetaR2) fail to initiate axons during development. Exogenous TGF-beta is sufficient to direct the rapid growth and differentiation of an axon, and genetic enhancement of receptor activity promotes the formation of multiple axons. Finally, we show that the bulk of these TGF-beta-dependent events are mediated by site-specific phosphorylation of Par6. These results define an extrinsic cue for neuronal polarity in vivo that patterns neural circuits in the developing brain.
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Affiliation(s)
- Jason J Yi
- Department of Neurobiology, Duke University Medical Center, Durham, NC 27710, USA
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91
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Haklai-Topper L, Mlechkovich G, Savariego D, Gokhman I, Yaron A. Cis interaction between Semaphorin6A and Plexin-A4 modulates the repulsive response to Sema6A. EMBO J 2010; 29:2635-45. [PMID: 20606624 DOI: 10.1038/emboj.2010.147] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2009] [Accepted: 06/10/2010] [Indexed: 11/09/2022] Open
Abstract
The correct navigation of axons to their targets depends on guidance molecules in the extra-cellular environment. Differential responsiveness to a particular guidance cue is largely an outcome of disparity in the expression of its receptors on the reacting axons. Here, we show that the differential responsiveness of sympathetic and sensory neurons to the transmembrane Semaphorin Sema6A is mainly determined by its co-expression in the responding neurons. Both sympathetic and sensory neurons express the Sema6A receptor Plexin-A4, but only sympathetic neurons respond to it. The expression of Sema6A counteracts this responsiveness and is detected only in sensory neurons. Remarkably, sensory neurons that lack Sema6A gain sensitivity to it in a Plexin-A4-dependent manner. Using heterologus systems, we show that the co-expression of Sema6A and Plexin-A4 hinders the binding of exogenous ligand, suggesting that a Sema6A-Plexin-A4 cis interaction serves as an inhibitory mechanism. Finally, we provide evidence for differential modes of interaction in cis versus in trans. Thus, co-expression of a transmembrane cue together with its receptor can serve as a guidance response modulator.
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Affiliation(s)
- Liat Haklai-Topper
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot, Israel
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92
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Synaptic homeostasis is consolidated by the cell fate gene gooseberry, a Drosophila pax3/7 homolog. J Neurosci 2010; 30:8071-82. [PMID: 20554858 DOI: 10.1523/jneurosci.5467-09.2010] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
In a large-scale screening effort, we identified the gene gooseberry (gsb) as being necessary for synaptic homeostasis at the Drosophila neuromuscular junction. The gsb gene encodes a pair-rule transcription factor that participates in embryonic neuronal cell fate specification. Here, we define a new postembryonic role for gooseberry. We show that gsb becomes widely expressed in the postembryonic CNS, including within mature motoneurons. Loss of gsb does not alter neuromuscular growth, morphology, or the distribution of essential synaptic proteins. However, gsb function is required postembryonically for the sustained expression of synaptic homeostasis. In GluRIIA mutant animals, miniature EPSP (mEPSP) amplitudes are significantly decreased, and there is a compensatory homeostatic increase in presynaptic release that restores normal muscle excitation. Loss of gsb significantly impairs the homeostatic increase in presynaptic release in the GluRIIA mutant. Interestingly, gsb is not required for the rapid induction of synaptic homeostasis. Furthermore, gsb seems to be specifically involved in the mechanisms responsible for a homeostatic increase in presynaptic release, since it is not required for the homeostatic decrease in presynaptic release observed following an increase in mEPSP amplitude. Finally, Gsb has been shown to antagonize Wingless signaling during embryonic fate specification, and we present initial evidence that this activity is conserved during synaptic homeostasis. Thus, we have identified a gene (gsb) that distinguishes between rapid induction versus sustained expression of synaptic homeostasis and distinguishes between the mechanisms responsible for homeostatic increase versus decrease in synaptic vesicle release.
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93
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Bonner JF, Blesch A, Neuhuber B, Fischer I. Promoting directional axon growth from neural progenitors grafted into the injured spinal cord. J Neurosci Res 2010; 88:1182-92. [PMID: 19908250 DOI: 10.1002/jnr.22288] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Spinal cord injury (SCI) is a devastating condition characterized by disruption of axonal connections, failure of axonal regeneration, and loss of motor and sensory function. The therapeutic promise of neural stem cells has been focused on cell replacement, but many obstacles remain in obtaining neuronal integration following transplantation into the injured CNS. This study investigated the neurotransmitter identity and axonal growth potential of neural progenitors following grafting into adult rats with a dorsal column lesion. We found that using a combination of neuronal and glial restricted progenitors (NRP and GRP) produced graft-derived glutamatergic and GABAergic neurons within the injury site, with minimal axonal extension. Administration of brain-derived neurotrophic factor (BDNF) with the graft promoted modest axonal growth from grafted cells. In contrast, injecting a lentiviral vector expressing BDNF rostral into the injured area generated a neurotrophin gradient and promoted directional growth of axons for up to 9 mm. Animals injected with BDNF lentivirus (at 2.5 and 5.0 mm) showed significantly more axons and significantly longer axons than control animals injected with GFP lentivirus. However, only the 5.0-mm-BDNF group showed a preference for extension in the rostral direction. We concluded that NRP/GRP grafts can be used to produce excitatory and inhibitory neurons, and neurotrophin gradients can guide axonal growth from graft-derived neurons toward putative targets. Together they can serve as a building block for neuronal cell replacement of local circuits and formation of neuronal relays.
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Affiliation(s)
- Joseph F Bonner
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania
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94
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Lauth M, Rohnalter V, Bergström A, Kooshesh M, Svenningsson P, Toftgård R. Antipsychotic drugs regulate hedgehog signaling by modulation of 7-dehydrocholesterol reductase levels. Mol Pharmacol 2010; 78:486-96. [PMID: 20558592 DOI: 10.1124/mol.110.066431] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Recently we identified GANT61, a small-molecule antagonist of Gli transcription factors, which are the final effectors of the mammalian Hedgehog (HH) signaling pathway. Here we describe a diamine substructure of GANT61 that carries the biological activity and show that this part of the molecule is structurally related to trans-1,4-bis(2-chlorobenzaminomethyl)cyclohexane dihydrochloride (AY9944), an inhibitor of the enzymatic activity and transcriptional inducer of 7-dehydrocholesterol-reductase (Dhcr7, EC 1.3.1.21). Treatment of cells with the GANT61 diamine, AY9944, or overexpression of DHCR7 results in the attenuation of Smoothened-dependent and -independent HH signaling. Whereas GANT61 function is independent of Dhcr7, AY9944 does require up-regulation of endogenous Dhcr7. In line with these findings, Dhcr7-modulating antipsychotic (clozapine, chlorpromazine, haloperidol) and antidepressant (imipramine) drugs regulate HH signaling in vitro and in vivo. Modulation of HH signaling may represent a hitherto undiscovered biological (side) effect of therapeutics used to treat schizophrenia and depression.
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Affiliation(s)
- Matthias Lauth
- Institute of Molecular Biology and Tumor Research, Philipps University, Marburg, Germany.
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95
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Yamazoe H, Keino-Masu K, Masu M. Combining the cell-encapsulation technique and axon guidance for cell transplantation therapy. JOURNAL OF BIOMATERIALS SCIENCE-POLYMER EDITION 2010; 21:1815-26. [PMID: 20557690 DOI: 10.1163/092050609x12567186470615] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
In cell transplantation therapy for the treatment of neurodegenerative disorders, encapsulation of implanted cells in a semipermeable membrane is a promising approach to protect the implanted cells from host immune rejection and inhibit the invasion of tumor into surrounding tissue if the implanted cells form a tumor after transplantation. However, implanted neurons isolated by capsules could not build connections with host neurons, preventing the implanted neurons from responding to stimuli from host neurons. In the present study, we focused on the passage of neurites and axons navigated by axon guidance molecules through membrane pores to enable encapsulated neurons and host neurons to form connections. The type of matrix coated on membranes and the pore size of the membranes greatly affected the successful passage of PC12 neurites through membrane pores. PC12 neurites preferably passed through collagen-coated membranes with pores greater than 0.8 μm in diameter, but the neurites did not pass through albumin- or fibronectin-coated membranes or membranes with pores less than 0.1 μm in diameter. We could navigate the direction of commissural neural axon extensions by utilizing the axon guidance molecules secreted from floor plate and make guided axons pass through the membrane pores. These results suggest the feasibility of building connections between encapsulated neurons and host neurons by encapsulating the implanted neurons and axon guidance molecules, which attract the axons of host neurons into the capsule, in the porous membranes with suitable pore size and matrix coating.
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Affiliation(s)
- Hironori Yamazoe
- Nanotechnology Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan.
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96
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Ferrari A, Cecchini M, Serresi M, Faraci P, Pisignano D, Beltram F. Neuronal polarity selection by topography-induced focal adhesion control. Biomaterials 2010; 31:4682-94. [PMID: 20304485 DOI: 10.1016/j.biomaterials.2010.02.032] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2010] [Accepted: 02/11/2010] [Indexed: 01/09/2023]
Abstract
Interaction between differentiating neurons and the extracellular environment guides the establishment of cell polarity during nervous system development. Developing neurons read the physical properties of the local substrate in a contact-dependent manner and retrieve essential guidance cues. In previous works we demonstrated that PC12 cell interaction with nanogratings (alternating lines of ridges and grooves of submicron size) promotes bipolarity and alignment to the substrate topography. Here, we investigate the role of focal adhesions, cell contractility, and actin dynamics in this process. Exploiting nanoimprint lithography techniques and a cyclic olefin copolymer, we engineered biocompatible nanostructured substrates designed for high-resolution live-cell microscopy. Our results reveal that neuronal polarization and contact guidance are based on a geometrical constraint of focal adhesions resulting in an angular modulation of their maturation and persistence. We report on ROCK1/2-myosin-II pathway activity and demonstrate that ROCK-mediated contractility contributes to polarity selection during neuronal differentiation. Importantly, the selection process confined the generation of actin-supported membrane protrusions and the initiation of new neurites at the poles. Maintenance of the established polarity was independent from NGF stimulation. Altogether our results imply that focal adhesions and cell contractility stably link the topographical configuration of the extracellular environment to a corresponding neuronal polarity state.
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Affiliation(s)
- Aldo Ferrari
- NEST, Istituto Nanoscienze-CNR, I-56126 Pisa, Italy.
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97
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Segregation of ipsilateral retinal ganglion cell axons at the optic chiasm requires the Shh receptor Boc. J Neurosci 2010; 30:266-75. [PMID: 20053908 DOI: 10.1523/jneurosci.3778-09.2010] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The pattern of contralaterally and ipsilaterally projecting retinal ganglion cell (RGC) axons at the optic chiasm is essential for the establishment of binocular vision. Contralateral axons cross the chiasm midline as they progress from the optic nerve to the optic tract. In contrast, ipsilateral axons deviate from the chiasm and continue in the ipsilateral optic tract, avoiding the chiasm midline. The molecular mechanism underlying this phenomenon is not completely understood. Here we show that the Sonic Hedgehog (Shh) receptor Boc is enriched in ipsilateral RGCs of the developing retina. Together with the presence of Shh at the midline, this complementary expression pattern led us to hypothesize that Shh might repel ipsilateral RGC axons at the chiasm. Consistent with this hypothesis, we found that only Boc-positive RGC axons retract in vitro in response to Shh and that this response is lost in Boc mutant RGCs. In vivo, we show that Boc is required for the normal segregation of ipsilateral axons at the optic chiasm and, conversely, that Boc expression in contralateral RGCs prevents their axons from crossing the optic chiasm. Together, these results suggest that Shh repels ipsilateral RGC axons at the optic chiasm via its receptor Boc. This work identifies a novel molecular pathway required for the segregation of axons at the optic chiasm.
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98
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Lee S, Lee CE, Elias CF, Elmquist JK. Expression of the diabetes-associated gene TCF7L2 in adult mouse brain. J Comp Neurol 2010; 517:925-39. [PMID: 19845015 DOI: 10.1002/cne.22199] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Polymorphisms of the gene TCF7L2 (transcription factor 7-like 2) are strongly associated with the development and progression of type 2 diabetes. TCF7L2 is important in the development of peripheral organs such as adipocytes, pancreas, and the intestine. However, very little is known about its expression elsewhere. In this study we used in situ hybridization histochemistry to show that TCF7L2 has a unique expression pattern in the mouse brain. TCF7L2 is expressed in two distinct populations. First, it is highly expressed in thalamic and tectal structures. Additionally, TCF7L2 mRNA is expressed at moderate to low levels in specific cells of the hypothalamus, preoptic nucleus, and circumventricular organs. Collectively, these patterns of expression suggest that TCF7L2 has distinct functions within the brain, with a general role in the development and maintenance of thalamic and midbrain neurons, and then a distinct role in autonomic homeostasis.
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Affiliation(s)
- Syann Lee
- Department of Internal Medicine and Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9077, USA
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99
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Ciceroni C, Mosillo P, Mastrantoni E, Sale P, Ricci-Vitiani L, Biagioni F, Stocchi F, Nicoletti F, Melchiorri D. mGLU3 metabotropic glutamate receptors modulate the differentiation of SVZ-derived neural stem cells towards the astrocytic lineage. Glia 2010; 58:813-22. [DOI: 10.1002/glia.20965] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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100
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Perron JC, Dodd J. ActRIIA and BMPRII Type II BMP receptor subunits selectively required for Smad4-independent BMP7-evoked chemotaxis. PLoS One 2009; 4:e8198. [PMID: 20011660 PMCID: PMC2788225 DOI: 10.1371/journal.pone.0008198] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2009] [Accepted: 11/15/2009] [Indexed: 01/01/2023] Open
Abstract
Bone morphogenetic protein (BMP)-evoked reorientation and chemotaxis of cells occurs with rapid onset and involves events local to the cell membrane. The signaling pathways underlying these rapid processes likely diverge from those mediating classical transcriptional responses to BMPs but it remains unclear how BMP receptors are utilized to generate distinct intracellular mechanisms. We show that BMP7-evoked chemotaxis of monocytic cells depends on the activity of canonical type II BMP receptors. Although the three canonical type II BMP receptors are expressed in monocytic cells, inhibition of receptor subunit expression by RNAi reveals that ActRIIA and BMPRII, but not ActRIIB, are each essential for BMP7-evoked chemotaxis but not required individually for BMP-mediated induction. Furthermore, the chemotactic response to BMP7 does not involve canonical Smad4-dependent signaling but acts through PI3K-dependent signaling, illustrating selective activation of distinct intracellular events through differential engagement of receptors. We suggest a model of a BMP receptor complex in which the coordinated activity of ActRIIA and BMPRII receptor subunits selectively mediates the chemotactic response to BMP7.
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Affiliation(s)
- Jeanette C. Perron
- Departments of Physiology and Cellular Biophysics and Neuroscience, Columbia University, New York, New York, United States of America
| | - Jane Dodd
- Departments of Physiology and Cellular Biophysics and Neuroscience, Columbia University, New York, New York, United States of America
- * E-mail:
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