scholarly journals Microtubule polymer assembly and transport during axonal elongation.

1991 ◽  
Vol 115 (2) ◽  
pp. 365-379 ◽  
Author(s):  
S S Reinsch ◽  
T J Mitchison ◽  
M Kirschner
Keyword(s):  
Cell Body ◽  
Neural Tube ◽  
Growth Cone ◽  
Cell Stage ◽  
Axonal Elongation ◽  
Axon Elongation ◽  
Coherent Phase ◽  
Polymer Translocation ◽  
Characteristic Manner ◽  
Fluorescent Mark

As axons elongate, tubulin, which is synthesized in the cell body, must be transported and assembled into new structures in the axon. The mechanism of transport and the location of assembly are presently unknown. We report here on the use of tubulin tagged with a photoactivatable fluorescent group to investigate these issues. Photoactivatable tubulin, microinjected into frog embryos at the two-cell stage, is incorporated into microtubules in neurons obtained from explants of the neural tube. When activated by light, a fluorescent mark is made on the microtubules in the axon, and transport and turnover can be visualized directly. We find that microtubules are generated in or near the cell body and continually transported distally as a coherent phase of polymer during axon elongation. This vectorial polymer movement was observed at all levels on the axon, even in the absence of axonal elongation. Measurements of the rate of polymer translocation at various places in the axon suggest that new polymer is formed by intercalary assembly along the axon and assembly at the growth cone in addition to transport of polymer from the cell body. Finally, polymer movement near the growth cone appeared to respond in a characteristic manner to growth cone behavior, while polymer proximally in the axon moved more consistently. These results suggest that microtubule translocation is the principal means of tubulin transport and that translocation plays an important role in generating new axon structure at the growth cone.

scholarly journals CRMP4 and CRMP2 Interact to Coordinate Cytoskeleton Dynamics, Regulating Growth Cone Development and Axon Elongation

2015 ◽  
Vol 2015 ◽  
pp. 1-13 ◽  
Author(s):  
Minghui Tan ◽  
Caihui Cha ◽  
Yongheng Ye ◽  
Jifeng Zhang ◽  
Sumei Li ◽  
...  
Keyword(s):  
Growth Cone ◽  
Promoting Effect ◽  
Interaction Domain ◽  
Axonal Elongation ◽  
Axon Elongation ◽  
Cellular Processes ◽  
Cytoskeletal Dynamics ◽  
Cone Development ◽  
Cytoskeleton Dynamics

Cytoskeleton dynamics are critical phenomena that underpin many fundamental cellular processes. Collapsin response mediator proteins (CRMPs) are highly expressed in the developing nervous system, mediating growth cone guidance, neuronal polarity, and axonal elongation. However, whether and how CRMPs associate with microtubules and actin coordinated cytoskeletal dynamics remain unknown. In this study, we demonstrated that CRMP2 and CRMP4 interacted with tubulin and actinin vitroand colocalized with the cytoskeleton in the transition-zone in developing growth cones. CRMP2 and CRMP4 also interacted with one another coordinately to promote growth cone development and axonal elongation. Genetic silencing of CRMP2 enhanced, whereas overexpression of CRMP2 suppressed, the inhibitory effects of CRMP4 knockdown on axonal development. In addition, knockdown of CRMP2 or overexpression of truncated CRMP2 reversed the promoting effect of CRMP4. With the overexpression of truncated CRMP2 or CRMP4 lacking the cytoskeleton interaction domain, the promoting effect of CRMP was suppressed. These data suggest a model in which CRMP2 and CRMP4 form complexes to bridge microtubules and actin and thus work cooperatively to regulate growth cone development and axonal elongation.

scholarly journals Microtubule behavior in the growth cones of living neurons during axon elongation.

1991 ◽  
Vol 115 (2) ◽  
pp. 345-363 ◽  
Author(s):  
E M Tanaka ◽  
M W Kirschner
Keyword(s):  
Neural Tube ◽  
Growth Cone ◽  
Growth Cones ◽  
Early Step ◽  
Axon Elongation ◽  
Major Mechanism ◽  
Microtubule Growth ◽  
Future Direction ◽  
Living Neurons ◽  
Fertilized Egg

To understand how microtubules are generated in the growth cone, we have imaged fluorescently tagged microtubules in living frog embryonic neurons. The neurons were labeled by injecting rhodamine-labeled tubulin into the fertilized egg and explanting the neurons from the neural tube. Microtubules extend deep into the growth cone periphery and adopt three characteristic distributions: (a) dispersed and splayed throughout much of the growth cone; (b) looped and apparently contorted by compression; and (c) bundled into tight arrays. These distributions interconvert on a time scale of several minutes and these interconversions are correlated with the behavior of the growth cone. We observed microtubule growth and shrinkage in growth cones, but are unable to determine their contribution to net assembly. However, translocation of polymer form the axon appears to be a major mechanism of generating new polymer in the growth cone, while bundling of microtubules in the growth cone appears to be the critical step in generating new axon. Neurons that were about to turn spontaneously generated microtubules in the future direction of growth, suggesting that orientation of microtubules might be an important early step in neuronal pathfinding.

scholarly journals Progressive and spatially differentiated stability of microtubules in developing neuronal cells.

1989 ◽  
Vol 109 (1) ◽  
pp. 253-263 ◽  
Author(s):  
S S Lim ◽  
P J Sammak ◽  
G G Borisy
Keyword(s):  
Cell Body ◽  
Growth Cone ◽  
Cellular Differentiation ◽  
Progressive Increase ◽  
Fluorescence Recovery ◽  
Plastic Properties ◽  
Intracellular Location ◽  
Laser Microbeam ◽  
Neuronal Cytoskeleton ◽  
The Stability

The establishment of neural circuits requires both stable and plastic properties in the neuronal cytoskeleton. In this study we show that properties of stability and lability reside in microtubules and these are governed by cellular differentiation and intracellular location. After culture for 3, 7, and 14 d in nerve growth factor-containing medium, PC-12 cells were microinjected with X-rhodamine-labeled tubulin. 8-24 h later, cells were photobleached with a laser microbeam at the cell body, neurite shaft, and growth cone. Replacement of fluorescence in bleached zones was monitored by digital video microscopy. In 3-d cultures, fluorescence recovery in all regions occurred by 26 +/- 17 min. Similarly, in older cultures, complete fluorescence recovery at the cell body and growth cone occurred by 10-30 min. However, in neurite shafts, fluorescence recovery was markedly slower (71 +/- 48 min for 7-d and 201 +/- 94 min for 14-d cultures). This progressive increase in the stability of microtubules in the neurite shafts correlated with an increase of acetylated microtubules. Acetylated microtubules were present specifically in the neurite shaft and not in the regions of fast microtubule turnover, the cell body and growth cone. During the recovery of fluorescence, bleached zones did not move with respect to the cell body. We conclude that the microtubule component of the neuronal cytoskeleton is differentially dynamic but stationary.

Translocation of the neuronal cytoskeleton and axonal locomotion

1982 ◽  
Vol 299 (1095) ◽  
pp. 313-327 ◽  
Keyword(s):  
Plasma Membrane ◽  
Axonal Transport ◽  
Cell Body ◽  
Cytoskeletal Proteins ◽  
The Other ◽  
Current Understanding ◽  
Axonal Elongation ◽  
Neuronal Cytoskeleton ◽  
Other Hand ◽  
Neuron Cell Body

Recent studies of axonal transport indicate that cytoskeletal proteins are assembled into polymers in the neuron cell body and that these polymers move from the cell body toward the end of the axon. On the other hand, membranous elements appear to be inserted into the axonal plasma membrane preferentially at the end of the axon. These new observations are explored in relation to our current understanding of axonal elongation.

scholarly journals THE FINE STRUCTURE OF THE AXON AND GROWTH CONE OF THE DORSAL ROOT NEUROBLAST OF THE RABBIT EMBRYO

1970 ◽  
Vol 44 (1) ◽  
pp. 62-79 ◽  
Author(s):  
Virginia M. Tennyson
Keyword(s):  
Tissue Culture ◽  
Neural Tube ◽  
Growth Cone ◽  
Dorsal Root ◽  
Matrix Material ◽  
Basal Surface ◽  
Dense Bodies ◽  
Dense Membrane ◽  
Large Numbers ◽  
Rabbit Embryo

The centrally directed neurite of the dorsal root neuroblast has been described from the period of its initial entrance into the neural tube until a well-defined dorsal root is formed. Large numbers of microtubules, channels of agranular reticulum, and clusters of ribosomes are found throughout the length of the early axons. The filopodia of the growth cone appear as long thin processes or as broad flanges of cytoplasm having a finely filamentous matrix material and occasionally small ovoid or elongate vesicles. At first the varicosity is a small expansion of cytoplasm, usually containing channels of agranular reticulum and a few other organelles. The widely dilated cisternae of agranular reticulum frequently found within the growth cone probably correspond to the pinocytotic vacuoles seen in neurites in tissue culture. The varicosities enlarge to form bulbous masses of cytoplasm, which may measure up to 5 µ in width and 13 µ in length. They contain channels of agranular reticulum, microtubules, neurofilaments, mitochondria, heterogeneous dense bodies, and a few clusters of ribosomes. Large ovoid mitochondria having ribonucleoprotein particles in their matrix are common. Dense membrane specializations are found at the basal surface of the neuro-epithelial cell close to the area where the early neurites first enter the neural tube.

scholarly journals Disruption of Myosin II Increases Axonal Elongation in Drosophila by Accelerating Bulk Advance of the Growth Cone

2013 ◽  
Vol 104 (2) ◽  
pp. 375a
Author(s):  
Douglas H. Roossien ◽  
Phillip Lamoureux ◽  
Andrew N. George ◽  
David Van Vactor ◽  
Kyle E. Miller
Keyword(s):  
Growth Cone ◽  
Myosin Ii ◽  
Axonal Elongation

scholarly journals A cytochemical study of lectin receptors on isolated chick neural retina neurons in vitro

1982 ◽  
Vol 53 (1) ◽  
pp. 1-20
Author(s):  
J.A. Bee
Keyword(s):  
Sialic Acid ◽  
Cell Body ◽  
Growth Cone ◽  
Ricinus Communis ◽  
Lectin Binding ◽  
Neuronal Cell ◽  
Cytochemical Study ◽  
Lectin Receptors ◽  
Dolichos Biflorus ◽  
Dolichos Biflorus Agglutinin

The cell body, neurite and growth cone of isolated retinal neurons have been compared on the basis of their ability to bind a number of fluorescently labelled lectins, each possessing a unique carbohydrate specificity. The susceptibility of the respective binding patterns following pretreatment of these fixed cells with either neuraminidase or trypsin was also investigated. Neuronal cell bodies displayed the most intense binding of each lectin, with localization of limulin binding (specific for sialic acid) predominantly to the neurite hillock, the point on the cell body from which the neurite projects. Limulin binding was almost totally abolished by pretreatment with either neuraminidase or trypsin. In contrast to the cell body, limulin binding to the neurite or growth cone was not detected. These regions of the cell apparently possessed sialic acid, however, since pretreatment with neuraminidase reduced wheat germ agglutinin binding (to N-acetylglucosamine) and markedly enhanced Dolichos biflorus agglutinin binding (to N-acetylgalactosamine) to both the neurite and growth cone. The initially low binding of Dolichos biflorus agglutinin to the neurite and growth cone was slightly enhanced by pretreatment with trypsin. Uniformly low levels of binding of either Ricinus communis agglutinin 60 (galactose, N-acetylgalactosamine) or R. communis agglutinin 120 (galactose) was observed over the entire neuron. R. communis agglutinin 120 binding was not enhanced by pretreatment with neuraminidase. Receptors for either concanavalin A (mannose, glucose) or Ulex europaeus agglutinin I (fucose) were abundant over the entire nerve cell with the former exhibiting more marked trypsin sensitivity. From these data, it is apparent that the repertoire of lectin binding sites of the neurite and growth cone of these differentiating nerve cells differs markedly from that of the cell body, which itself demonstrates some degree of regionalization.

NrCAM, cerebellar granule cell receptor for the neuronal adhesion molecule F3, displays an actin-dependent mobility in growth cones

1999 ◽  
Vol 112 (18) ◽  
pp. 3015-3027 ◽  
Author(s):  
C. Faivre-Sarrailh ◽  
J. Falk ◽  
E. Pollerberg ◽  
M. Schachner ◽  
G. Rougon
Keyword(s):  
Growth Cone ◽  
Actin Filaments ◽  
Cerebellar Granule Cells ◽  
Leading Edge ◽  
Growth Cones ◽  
Inhibitory Effect ◽  
Immunoglobulin Superfamily ◽  
Cerebellar Granule ◽  
Axonal Elongation ◽  
Neuronal Adhesion

The neuronal adhesion glycoprotein F3 is a multifunctional molecule of the immunoglobulin superfamily that displays heterophilic binding activities. In the present study, NrCAM was identified as the functional receptor mediating the inhibitory effect of F3 on axonal elongation from cerebellar granule cells. F3Fc-conjugated microspheres binding to neuronal growth cones resulted from heterophilic interaction with NrCAM but not with L1. Time-lapse video-microscopy indicated that F3Fc beads bind at the leading edge and move retrogradely to reach the base of the growth cone within a lapse of 30–60 seconds. Such velocity (5.7 microm/minute) is consistent with a coupling between F3 receptors and the retrograde flow of actin filaments. When actin filaments were disrupted by cytochalasin B, the F3Fc beads remained immobile at the leading edge. The retrograde mobility appeared to be dependent on NrCAM clustering since it was induced upon binding with cross-linked but not dimeric F3Fc chimera. These data indicate that F3 may control growth cone motility by modulating the linkage of its receptor, NrCAM, to the cytoskeleton. They provide further insights into the mechanisms by which GPI-anchored adhesion molecules may exert an inhibitory effect on axonal elongation.

Sign in / Sign up

Export Citation Format

Share Document