scholarly journals FLIM FRET Visualization of Cdc42 Activation by Netrin-1 in Embryonic Spinal Commissural Neuron Growth Cones

PLoS ONE ◽  
2016 ◽  
Vol 11 (8) ◽  
pp. e0159405 ◽  
Author(s):  
Benjamin Rappaz ◽  
Karen Lai Wing Sun ◽  
James P. Correia ◽  
Paul W. Wiseman ◽  
Timothy E. Kennedy
Keyword(s):  
Growth Cones ◽  
Commissural Neuron ◽  
Neuron Growth

The zebrafish unplugged gene controls motor axon pathway selection

Development ◽  
2000 ◽  
Vol 127 (10) ◽  
pp. 2099-2111 ◽  
Author(s):  
J. Zhang ◽  
M. Granato
Keyword(s):  
Motor Neuron ◽  
Experimental Studies ◽  
Choice Point ◽  
Growth Cones ◽  
Motor Axon ◽  
Motor Axons ◽  
Independent Mechanism ◽  
Neuron Growth ◽  
Future Path

En route to their targets, motor axons encounter choice points at which they select their future path. Experimental studies predict that at each choice point specialized cells provide local guidance to pathfinding motor axons, however, the identity of these cells and their signals is unknown. Here, we identify the zebrafish unplugged gene as a key component for choice point navigation of pioneering motor axons. We show that in unplugged mutant embryos, motor neuron growth cones reach the choice point but make inappropriate pathway decisions. Analysis of chimeric embryos demonstrates that unplugged activity is produced by a selective group of mesodermal cells located adjacent to the choice point. As the first motor growth cones approach the choice point, these mesodermal cells migrate away, suggesting that unplugged activity influences growth cones by a contact-independent mechanism. These data suggest that unplugged defines a somite-derived signal that elicits differential guidance decisions in motor growth cones.

scholarly journals Phosphorylation by Rho Kinase Regulates CRMP-2 Activity in Growth Cones

2005 ◽  
Vol 25 (22) ◽  
pp. 9973-9984 ◽  
Author(s):  
Nariko Arimura ◽  
Céline Ménager ◽  
Yoji Kawano ◽  
Takeshi Yoshimura ◽  
Saeko Kawabata ◽  
...  
Keyword(s):  
Growth Cone ◽  
Actin Filaments ◽  
Rho Kinase ◽  
Growth Cones ◽  
Binding Activity ◽  
Microtubule Assembly ◽  
Coated Pits ◽  
Growth Cone Collapse ◽  
Mediator Protein ◽  
Neuron Growth

ABSTRACT Collapsin response mediator protein 2 (CRMP-2) enhances the advance of growth cones by regulating microtubule assembly and Numb-mediated endocytosis. We previously showed that Rho kinase phosphorylates CRMP-2 during growth cone collapse; however, the roles of phosphorylated CRMP-2 in growth cone collapse remain to be clarified. Here, we report that CRMP-2 phosphorylation by Rho kinase cancels the binding activity to the tubulin dimer, microtubules, or Numb. CRMP-2 binds to actin, but its binding is not affected by phosphorylation. Electron microscopy revealed that CRMP-2 localizes on microtubules, clathrin-coated pits, and actin filaments in dorsal root ganglion neuron growth cones, while phosphorylated CRMP-2 localizes only on actin filaments. The phosphomimic mutant of CRMP-2 has a weakened ability to enhance neurite elongation. Furthermore, ephrin-A5 induces phosphorylation of CRMP-2 via Rho kinase during growth cone collapse. Taken together, these results suggest that Rho kinase phosphorylates CRMP-2, and inactivates the ability of CRMP-2 to promote microtubule assembly and Numb-mediated endocytosis, during growth cone collapse.

scholarly journals Microtubule behavior during guidance of pioneer neuron growth cones in situ.

1991 ◽  
Vol 115 (2) ◽  
pp. 381-395 ◽  
Author(s):  
J H Sabry ◽  
T P O'Connor ◽  
L Evans ◽  
A Toroian-Raymond ◽  
M Kirschner ◽  
...  
Keyword(s):  
Growth Cone ◽  
Growth Cones ◽  
The Body ◽  
Microtubule Network ◽  
Guidance Cues ◽  
Selective Retention ◽  
Pioneer Neuron ◽  
Neuron Growth

The growth of an axon toward its target results from the reorganization of the cytoskeleton in response to environmental guidance cues. Recently developed imaging technology makes it possible to address the effect of such cues on the neural cytoskeleton directly. Although high resolution studies can be carried out on neurons in vitro, these circumstances do not recreate the complexity of the natural environment. We report here on the arrangement and dynamics of microtubules in live neurons pathfinding in response to natural guidance cues in situ using the embryonic grasshopper limb fillet preparation. A rich microtubule network was present within the body of the growth cone and normally extended into the distal growth cone margin. Complex microtubule loops often formed transiently within the growth cone. Branches both with and without microtubules were regularly observed. Microtubules did not extend into filopodia. During growth cone steering events in response to identified guidance cues, microtubule behaviour could be monitored. In turns towards guidepost cells, microtubules selectively invaded branches derived from filopodia that had contacted the guidepost cell. At limb segment boundaries, microtubules displayed a variety of behaviors, including selective branch invasion, and also invasion of multiple branches followed by selective retention in branches oriented in the correct direction. Microtubule invasion of multiple branches also was seen in growth cones migrating on intrasegmental epithelium. Both selective invasion and selective retention generate asymmetrical microtubule arrangements within the growth cone, and may play a key role in growth cone steering events.

scholarly journals FINE STRUCTURE OF NERVE FIBERS AND GROWTH CONES OF ISOLATED SYMPATHETIC NEURONS IN CULTURE

1973 ◽  
Vol 56 (3) ◽  
pp. 713-735 ◽  
Author(s):  
Mary Bartlett Bunge
Keyword(s):  
Electron Microscopy ◽  
Tissue Culture ◽  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Sensory Neuron ◽  
Sympathetic Neurons ◽  
Growth Cones ◽  
Nerve Fibers ◽  
Cervical Ganglia ◽  
Neuron Growth

The leading tips of elongating nerve fibers are enlarged into "growth cones" which are seen in tissue culture to continually undergo changes in conformation and to foster numerous transitory slender extensions (filopodia) and/or a veillike ruffling sheet. After explantation of 1-day-old rat superior cervical ganglia (as pieces or as individual neurons), nerve fibers and tips were photographed during growth and through the initial stages of aldehyde fixation and then relocated after embedding in plastic. Electron microscopy of serially sectioned tips revealed the following. The moving parts of the cone, the peripheral flange and filopodia, contained a distinctive apparently filamentous feltwork from which all organelles except membranous structures were excluded; microtubules were notably absent from these areas. The cone interior contained varied forms of agranular endoplasmic reticulum, vacuoles, vesicles, coated vesicles, mitochondria, microtubules, and occasional neurofilaments and polysomes. Dense-cored vesicles and lysosomal structures were also present and appeared to be formed locally, at least in part from reticulum. The possible roles of the various forms of agranular membranous components are discussed and it is suggested that structures involved in both the assembly and degradation of membrane are present in the cone. The content of these growing tips resembles that in sensory neuron growth cones studied by others.

MAP1B coordinates microtubule and actin filament remodeling in adult mouse Schwann cell tips and DRG neuron growth cones

2007 ◽  
Vol 36 (2) ◽  
pp. 235-247 ◽  
Author(s):  
Céline Bouquet ◽  
Michèle Ravaille-Veron ◽  
Friedrich Propst ◽  
Fatiha Nothias
Keyword(s):  
Schwann Cell ◽  
Actin Filament ◽  
Adult Mouse ◽  
Growth Cones ◽  
Drg Neuron ◽  
Neuron Growth

scholarly journals Visualising the cytoskeletal machinery in neuronal growth cones using cryo-electron tomography

2021 ◽  
Author(s):  
Joseph Atherton ◽  
Melissa Stouffer ◽  
Fiona Francis ◽  
Carolyn A Moores
Keyword(s):  
Growth Cone ◽  
Electron Tomography ◽  
Three Dimensional ◽  
Growth Cones ◽  
Structural Defects ◽  
Helical Structures ◽  
Actin Bundles ◽  
Mature Brain ◽  
Cryo Electron Tomography ◽  
Neuron Growth

Neurons navigate long distances and extend axons to form the complex circuitry of the mature brain. This depends on the coordinated response and continuous remodelling of the microtubule and F-actin networks in the axonal growth cone. Growth cone architecture remains poorly understood at nanoscales. We therefore investigated mouse hippocampal neuron growth cones using cryo-electron tomography to directly visualise their three-dimensional subcellular architecture with molecular detail. Our data show the hexagonal arrays of actin bundles that form filopodia penetrate the growth cone interior and terminate in the transition zone. We directly observe the modulation of these and other growth cone actin bundles by alteration of individual F-actin helical structures. Blunt-ended microtubules predominate in the growth cone, frequently contain lumenal particles and carry lattice defects. Investigation of the effect of absence of doublecortin, a neurodevelopmental cytoskeleton regulator, on growth cone cytoskeleton shows no major anomalies in overall growth cone organisation or in F-actin subpopulations. However, our data suggest that microtubules sustain more structural defects, highlighting the importance of microtubule integrity during growth cone migration.

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