scholarly journals Myosin 1c and myosin IIB serve opposing roles in lamellipodial dynamics of the neuronal growth cone

2002 ◽  
Vol 158 (7) ◽  
pp. 1207-1217 ◽  
Author(s):  
Thomas J. Diefenbach ◽  
Vaughan M. Latham ◽  
Dean Yimlamai ◽  
Canwen A. Liu ◽  
Ira M. Herman ◽  
...  
Keyword(s):  
Dorsal Root Ganglion ◽  
Neurite Outgrowth ◽  
Growth Cone ◽  
Dorsal Root ◽  
Myosin Ii ◽  
Growth Cones ◽  
Neuronal Growth ◽  
Rapid Reduction ◽  
Neuronal Growth Cone

The myosin family of motor proteins is implicated in mediating actin-based growth cone motility, but the roles of many myosins remain unclear. We previously implicated myosin 1c (M1c; formerly myosin Iβ) in the retention of lamellipodia (Wang et al., 1996). Here we address the role of myosin II (MII) in chick dorsal root ganglion neuronal growth cone motility and the contribution of M1c and MII to retrograde F-actin flow using chromophore-assisted laser inactivation (CALI). CALI of MII reduced neurite outgrowth and growth cone area by 25%, suggesting a role for MII in lamellipodial expansion. Micro-CALI of MII caused a rapid reduction in local lamellipodial protrusion in growth cones with no effects on filopodial dynamics. This is opposite to micro-CALI of M1c, which caused an increase in lamellipodial protrusion. We used fiduciary beads (Forscher et al., 1992) to observe retrograde F-actin flow during the acute loss of M1c or MII. Micro-CALI of M1c reduced retrograde bead flow by 76%, whereas micro-CALI of MII or the MIIB isoform did not. Thus, M1c and MIIB serve opposite and nonredundant roles in regulating lamellipodial dynamics, and M1c activity is specifically required for retrograde F-actin flow.

Hyperpolarization-Activated Currents in the Growth Cone and Soma of Neonatal Rat Dorsal Root Ganglion Neurons in Culture

1997 ◽  
Vol 78 (1) ◽  
pp. 177-186 ◽  
Author(s):  
Z. Wang ◽  
R. J. Van Den Berg ◽  
D. L. Ypey
Keyword(s):  
Dorsal Root Ganglion ◽  
Growth Cone ◽  
Dorsal Root ◽  
Reversal Potential ◽  
Growth Cones ◽  
Dorsal Root Ganglion Neurons ◽  
Neonatal Rat ◽  
Midpoint Potential ◽  
Boltzmann Function ◽  
Ganglion Neurons

Wang, Z., R. J. Van Den Berg, and D. L. Ypey. Hyperpolarization-activated currents in the growth cone and soma of neonatal rat dorsal root ganglion neurons in culture. J. Neurophysiol. 78: 177–186, 1997. Dissociated dorsal root ganglion neuron growth cones and somata from neonatal rats were voltage and current clamped with the use of the perforated-patch whole cell configuration to study the occurrence and properties of slow hyperpolarization-activated currents ( I h) at both regions. Under voltage-clamp conditions I h, blockable by 2 mM extracellular CsCl, was present in 33% of the growth cones tested. Its steady-state activation as a function of voltage could be fitted with a single Boltzmann function with a midpoint potential of −97 mV. The time course of current activation could be best described by a double-exponential function. The magnitude of the fully activated conductance was 3.5 nS and the reversal potential amounted to −29 mV. At the soma, I h was found in 80% of the somata tested, which is much higher than occurrence at the growth cone. The steady-state activation curve of I h at the soma, fitted with a single Boltzmann function, had a midpoint potential of −92 mV, which was more positive than that in the growth cone. The double-exponential activation of the current was faster than in the growth cone. The fully activated conductance of 5.1 nS and the reversal potential of −27 mV were not significantly different from the values obtained at the growth cone. Membrane hyperpolarization by current-clamp pulses elicited depolarizing sags in 30% and 78% of the tested growth cones and somata, respectively, which is in agreement with our voltage-clamp findings. Termination of the hyperpolarizing current pulse evoked a transient membrane depolarization or an action potential at both sites. Application of 2 mM extracellular CsCl hyperpolarized the membrane potential reversibly by ∼5 mV and blocked the depolarizing sags and action potentials following the current injections at these regions. Thus I h contributes to the resting membrane potential and modulates the excitability of both the growth cone and the soma. Intracellular perfusion with the second messenger adenosine 3′,5′-cyclic monophosphate (cAMP) was only possible at the soma by the use of the conventional whole cell configuration. Addition of 100 μM cAMP to the pipette solution shifted the midpoint potential of the I h activation curve from −108 to −78 mV. The current activation time course was also accelerated. The reversal potential and the fully activated conductance underlying I h were not changed by cAMP. These results imply that cAMP primarily affects the gating kinetics of I h. Our results show for the first time quantitative differences in I h properties and occurrence at the growth cone and soma membrane. These differences may reflect differences in intracellular cAMP concentration and in the expression of I h.

Use of calcium imaging technologies to dissect mechanisms underlying neuronal growth cone responses to environmental cues

1995 ◽  
Vol 53 ◽  
pp. 804-805
Author(s):  
C.V. Williams ◽  
S.B. Kater
Keyword(s):  
Nervous System ◽  
Growth Cone ◽  
Local Environment ◽  
Growth Cones ◽  
Neuronal Growth ◽  
Growth Inhibitory ◽  
Direct Growth ◽  
Neuronal Growth Cone ◽  
Mechanical Factors ◽  
Growth Promoting

Since calcium is a key second messenger in both the developmental formation and adult function of the nervous system, the ability to rapidly image changes in this molecule has added greatly to our understanding of how development of the nervous system is regulated. The nervous system is comprised of billions of neurons and glial cells that establish characteristic patterns of connections during development. Neurons extend processes that often must grow long distances to establish appropriate synaptic connections. Neurons perform a pathfinding behavior largely via the highly dynamic behavior of the neuronal growth cone at the distal tip of elongating processes. The motile behavior characteristic of growth cones allows the growth cone to survey the local environment, read local cues and respond to those cues with a change in behavior. A variety of cues are now known to direct growth cones (e.g. electrical activity, depolarization, growth factors, mechanical factors, neurotransmitters, substrate factors). This collection of factors includes both growth promoting and growth inhibitory influences.

scholarly journals Absence of persistent spreading, branching, and adhesion in GAP-43-depleted growth cones.

1995 ◽  
Vol 128 (4) ◽  
pp. 647-660 ◽  
Author(s):  
L Aigner ◽  
P Caroni
Keyword(s):  
Growth Factor ◽  
Neurite Outgrowth ◽  
Growth Cone ◽  
Growth Cones ◽  
Culture Conditions ◽  
Major Protein ◽  
Kinase C ◽  
Competence Factor ◽  
Cone Activity

The growth-associated protein GAP-43 is a major protein kinase C substrate of growth cones and developing nerve terminals. In the growth cone, it accumulates near the plasma membrane, where it associates with the cortical cytoskeleton and membranes. The role of GAP-43 in neurite outgrowth is not yet clear, but recent findings suggest that it may be a crucial competence factor in this process. To define the role of GAP-43 in growth cone activity, we have analyzed neurite outgrowth and growth cone activity in primary sensory neurons depleted of GAP-43 by a specific antisense oligonucleotide procedure. Under optimal culture conditions, but in the absence of GAP-43, growth cones adhered poorly, displayed highly dynamic but unstable lamellar extensions, and were strikingly devoid of local f-actin concentrations. Upon stimulation, they failed to produce NGF-induced spreading or insulin-like growth factor-1-induced branching, whereas growth factor-induced phosphotyrosine immunoreactivity and acceleration of neurite elongation were not impaired. Unlike their GAP-43-expressing counterparts, they readily retracted when exposed to inhibitory central nervous system myelin-derived liposomes. Frequency and extent of induced retraction were attenuated by NGF. Our results indicate that GAP-43 can promote f-actin accumulation, evoked morphogenic activity, and resistance to retraction of the growth cone, suggesting that it may promote regulated neurite outgrowth during development and regeneration.

Discrete roles for secreted and transmembrane semaphorins in neuronal growth cone guidance in vivo

Development ◽  
1999 ◽  
Vol 126 (9) ◽  
pp. 2007-2019 ◽  
Author(s):  
C.M. Isbister ◽  
A. Tsai ◽  
S.T. Wong ◽  
A.L. Kolodkin ◽  
T.P. O'Connor
Keyword(s):  
Growth Cone ◽  
Limb Bud ◽  
Axon Outgrowth ◽  
Neuronal Growth ◽  
Neuronal Growth Cone ◽  
Guidance Molecule ◽  
Neuronal Growth Cones ◽  
Guidance Information

From the initial stages of axon outgrowth to the formation of a functioning synapse, neuronal growth cones continuously integrate and respond to multiple guidance cues. To investigate the role of semaphorins in the establishment of appropriate axon trajectories, we have characterized a novel secreted semaphorin in grasshopper, gSema 2a. Sema 2a is expressed in a gradient in the developing limb bud epithelium during Ti pioneer axon outgrowth. We demonstrate that Sema 2a acts as chemorepulsive guidance molecule critical for axon fasciculation and for determining both the initial direction and subsequent pathfinding events of the Ti axon projection. Interestingly, simultaneous perturbation of both secreted Sema 2a and transmembrane Sema I results in a broader range and increased incidence of abnormal Ti pioneer axon phenotypes, indicating that different semaphorin family members can provide functionally distinct guidance information to the same growth cone in vivo.

scholarly journals Modeling the Role of Myosin 1c in Neuronal Growth Cone Turning

2003 ◽  
Vol 85 (5) ◽  
pp. 3319-3328 ◽  
Author(s):  
Feng-Song Wang ◽  
Can-Wen Liu ◽  
Thomas J. Diefenbach ◽  
Daniel G. Jay
Keyword(s):  
Growth Cone ◽  
Neuronal Growth ◽  
Neuronal Growth Cone

scholarly journals Myosin II Activity Facilitates Microtubule Bundling in the Neuronal Growth Cone Neck

2008 ◽  
Vol 15 (1) ◽  
pp. 163-169 ◽  
Author(s):  
Dylan T. Burnette ◽  
Lin Ji ◽  
Andrew W. Schaefer ◽  
Nelson A. Medeiros ◽  
Gaudenz Danuser ◽  
...  
Keyword(s):  
Growth Cone ◽  
Myosin Ii ◽  
Neuronal Growth ◽  
Neuronal Growth Cone

Direct Neurotoxicity of Tetracaine on Growth Cones and Neurites of Growing Neurons In Vitro 

2001 ◽  
Vol 95 (3) ◽  
pp. 726-733 ◽  
Author(s):  
Shigeru Saito ◽  
Inas Radwan ◽  
Hideaki Obata ◽  
Kenichiro Takahashi ◽  
Fumio Goto
Keyword(s):  
Nerve Growth Factor ◽  
Growth Factor ◽  
Dorsal Root Ganglion ◽  
Growth Cone ◽  
Local Anesthetics ◽  
Dorsal Root ◽  
Sympathetic Ganglion ◽  
Growth Cones ◽  
Growth Cone Collapse ◽  
Neuronal Tissues

Background Local anesthetics have direct neurotoxicity on neurons. However, precise morphologic changes induced by the direct application of local anesthetics to neurons have not yet been fully understood. Also, despite the fact that local anesthetics are sometimes applied to the sites where peripheral nerves may be regenerating after injury, the effects of local anesthetics on growing or regenerating neurons have never been studied. Methods Three different neuronal tissues (dorsal root ganglion, retinal ganglion cell layer, and sympathetic ganglion chain) were isolated from an age-matched chick embryo and cultured for 20 h. Effects of tetracaine were examined microscopically and by a quantitative morphologic assay, growth cone collapse assay. Results Tetracaine induced growth cone collapse and neurite destruction. Three neuronal tissues showed significantly different dose-response, both at 60 min and at 24 h after the application of tetracaine (P < 0.01). The ED50 values (mean +/- SD) at 60 min were 1.53+/-1.05 mM in dorsal root ganglion, 0.15+/-0.05 mM in retinal, and 0.06+/-0.02 mM in sympathetic ganglion chain cultures. The ED50 values at 24 h were 0.43+/-0.15 mM in dorsal root ganglion, 0.07+/-0.03 mM in retinal, and 0.02+/-0.01 mM in sympathetic ganglion chain cultures. Concentration of nerve growth factor in the culture media did not influence the ED50 values. The growth cone collapsing effect was partially reversible in dorsal root ganglion and retinal neurons. However, in the sympathetic ganglion culture, no reversibility was observed after exposure to 1 mM tetracaine for 10 or for 60 min. Bupivacaine had similar neurotoxicity to the three types of growing neurons. (The ED50 values at 60 min were 2.32+/-0.50 mM in dorsal root ganglion, 0.96+/-0.16 mM in retinal, and 0.18+/-0.05 mM in sympathetic ganglion chain cultures. The ED50 values at 24 h were 0.34+/-0.09 mM in dorsal root ganglion, 0.21+/-0.06 mM in retinal, and 0.45+/-0.10 mM in sympathetic ganglion chain cultures.) Conclusions Short-term exposure to tetracaine produced irreversible changes in growing neurons. Growth cones were quickly affected, and neurites degenerated subsequently. Sensitivity varied with neuronal type and was not influenced by the concentration of nerve growth factor. Because a similar phenomenon was observed after exposure to bupivacaine, the toxicity to growing neurons may not be unique to tetracaine.

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