205:
However, no long range signaling molecule has been discovered. Alternatively, it has been suggested that the buildup of axonal growth factors in the neurite destined to become the axon means there is a depletion of axonal growth factors by default, as they must compete for the same proteins. This causes the other neurites to develop into dendrites as they lack sufficient concentrations of axonal growth factors to become axons. This would allow for a mechanism of global inhibition without the need for a long range signaling molecule.
63:) requires a complex interplay of both extracellular and intracellular signals. At every given point along a developing neurite, there are receptors detecting both positive and negative growth cues from every direction in the surrounding space. The developing neurite sums together all of these growth signals in order to determine which direction the neurite will ultimately grow towards. While not all of the growth signals are known, several have been identified and characterized. Among the known extracellular growth signals are
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the cell body simultaneously with one or more other neurites. It has been proposed that a minor neurite could extend outward until it touches an already developed axon of another neuron. At this point, the neurite will begin to differentiate into an axon. This is known as the "touch and go" model. However, this model does not explain how the first axon developed.
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is not precisely understood. It is known that 60% of the time the first neurite that protrudes from the cell body will become the axon. 30% of the time, a neurite not destined to become the axon protrudes from the cell body first. 10% of the time, the neurite that will become the axon protrudes from
98:
of the neuron remains dynamic. Actin filaments retain their dynamic properties in the neurite that will become the axon in order to push the microtubules bundles outward to extend the axon. In all other neurites however, the actin filaments are stabilized by myosin. This prevents the development of
204:
After forming one axon, the neuron must prevent all other neurites from becoming axons as well. This is known as global inhibition. It has been suggested that global inhibition is achieved by a long-range negative feedback signal released from the developed axon and taken up by the other neurite.
169:
An undifferentiated mammalian neuron placed in culture will retract any neurites that it has already grown. 0.5 to 1.5 days after being plated in culture, several minor neurites will begin to protrude out from the cell body. Sometime between day 1.5 and day 3, one of the minor neurites begins to
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is surrounded by thousands of extracellular signals which in turn can be modulated by hundreds of intracellular pathways, and the mechanisms for how these competing chemical signals effect the ultimate differentiation of neurites
120:
Weak endogenous electric fields may be used to both facilitate and direct the growth of projections from cell soma neurites, EFs of moderate strength have been used to direct and enhance neurite outgrowth in both
812:
Jones, Peter D.; Molina-MartĂnez, Beatriz; Niedworok, Anita; Cesare, Paolo (2024). "A microphysiological system for parallelized morphological and electrophysiological read-out of 3D neuronal cell culture".
94:(NGF). Tau proteins can aid in the stabilization of microtubules by binding to the microtubules, protecting them from microtubule severing proteins. Even after the microtubules have stabilized, the
157:
174:. On days 4 to 7, the remaining minor neurites will begin differentiating into dendrites. By day 7, the neuron should be completely polarized, with a functional dendrites and an axon.
197:
Whatever extracellular signals may be involved in inducing axon formation are transduced through at least 4 different pathways: the Rac-1 pathway, the Ras-mediated pathway, the
201:-liver kinase B1 pathway, and the calcium/calmodulin-dependent protein kinase pathway. A deficiency in any of these pathways would lead to the inability to develop a neuron.
117:
There are several software kits available to facilitate neurite tracing in images such as NeuronJ (an ImageJ plugin), Neuromantic, and the
Neurolucida system.
980:
Inagaki, Naoyuki; Toriyama, Michinori; Sakumura, Yuichi (2011-06-01). "Systems biology of symmetry breaking during neuronal polarity formation".
554:"The Atypical Guanine Nucleotide Exchange Factor Dock4 Regulates Neurite Differentiation through Modulation of Rac1 GTPase and Actin Dynamics"
76:
552:
Xiao, Yangui; Peng, Yinghui; Wan, Jun; Tang, Genyun; Chen, Yuewen; Tang, Jing; Ye, Wen-Cai; Ip, Nancy Y.; Shi, Lei (2013-07-05).
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Arimura, Nariko; Kaibuchi, Kozo (2007-03-01). "Neuronal polarity: from extracellular signals to intracellular mechanisms".
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Niclou, Simone P.; Franssen, Elske H. P.; Ehlert, Erich M. E.; Taniguchi, Masahiko; Verhaagen, Joost (2003-12-01).
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103:
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Dorsal root ganglion neurons (left) extend neurites in a microfluidic device (time lapse over 48 hours).
613:"Conversion of a signal into forces for axon outgrowth through Pak1-mediated shootin1 phosphorylation"
43:. The term is frequently used when speaking of immature or developing neurons, especially of cells in
48:
418:"Collapsin: a protein in brain that induces the collapse and paralysis of neuronal growth cones"
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Takano, Tetsuya; Xu, Chundi; Funahashi, Yasuhiro; Namba, Takashi; Kaibuchi, Kozo (2015-06-15).
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624:
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Qiang, Liang; Yu, Wenqian; Andreadis, Athena; Luo, Minhua; Baas, Peter W. (22 March 2006).
478:, Philadelphia : Lippincott Williams & Wilkins; Third Edition (February 1, 2006).
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8:
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Myatt, Darren R.; Hadlington, Tye; Ascoli, Giorgio A.; Nasuto, Slawomir J. (2012-03-16).
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Philosophical
Transactions of the Royal Society of London. Series B, Biological Sciences
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Toriyama, Michinori; Kozawa, Satoshi; Sakumura, Yuichi; Inagaki, Naoyuki (2013-03-18).
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731:"Neuromantic – from Semi-Manual to Semi-Automatic Reconstruction of Neuron Morphology"
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outgrow the other neurites significantly. This neurite will eventually become the
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47:, because it can be difficult to tell axons from dendrites before
360:"Meningeal cell-derived semaphorin 3A inhibits neurite outgrowth"
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Structure and
Function of the Neural Cell Adhesion Molecule NCAM
497:"Tau Protects Microtubules in the Axon from Severing by Katanin"
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32:
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activity of that receptor to induce the growth of neurites.
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tissue also directs neurite outgrowth, as it is rich in
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models. Co-culture of neurons with electrically aligned
1045:
E Meijering's article on the state of neurite detection
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Bear, Mark F; Connors, Barry W.; Paradiso, Michael A.,
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N-CAM simultaneously combines with another N-CAM and a
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416:Luo, Y.; Raible, D.; Raper, J. A. (1993-10-22).
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86:bundles, the growth of which is stimulated by
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303:"Molecular mechanisms of neurite extension"
1055:Synd synapse and neurite detection program
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684:. Springer Science & Business Media.
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241:"The cytoskeleton and neurite initiation"
16:Projection from the cell body of a neuron
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301:Valtorta, F.; Leoni, C. (1999-02-28).
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82:Young neurites are often packed with
367:Molecular and Cellular Neurosciences
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79:, all inhibitors of neurite growth.
35:. This projection can be either an
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27:refers to any projection from the
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1038:
475:Neuroscience, Exploring the Brain
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108:fibroblast growth factor receptor
67:, a midline chemoattractant, and
678:Berezin, Vladimir (2009-12-17).
1050:NeuronJ neurite tracing program
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558:Journal of Biological Chemistry
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513:10.1523/JNEUROSCI.5392-05.2006
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59:The development of a neurite (
1:
735:Frontiers in Neuroinformatics
379:10.1016/s1044-7431(03)00243-4
239:Flynn, Kevin C (2013-01-01).
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104:neural cell adhesion molecule
435:10.1016/0092-8674(93)80064-l
137:that promote nerve growth .
7:
928:Nature Reviews Neuroscience
501:The Journal of Neuroscience
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10:
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982:Developmental Neurobiology
177:
638:10.1016/j.cub.2013.02.017
748:10.3389/fninf.2012.00004
879:"Neuronal polarization"
571:10.1074/jbc.M113.458612
319:10.1098/rstb.1999.0391
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164:
141:Establishing polarity
88:neurotrophic factors
629:2013CBio...23..529T
564:(27): 20034–20045.
92:nerve growth factor
55:Neurite development
994:10.1002/dneu.20837
896:10.1242/dev.114454
827:10.1039/D3LC00963G
257:10.4161/bioa.26259
184:A neurite growing
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889:(12): 2088–2093.
691:978-1-4419-1170-4
507:(12): 3120–3129.
313:(1381): 387–394.
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84:microtubule
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715:2024-06-10
648:10061/8621
226:References
90:, such as
69:semaphorin
1012:1932-846X
948:1471-003X
905:0950-1991
835:1473-0197
757:1662-5196
706:"NeuronJ"
657:1879-0445
580:0021-9258
521:0270-6474
444:0092-8674
387:1044-7431
327:0962-8436
265:1949-0992
77:collapsin
29:cell body
1064:Category
1028:14746741
1020:21557507
964:15556921
956:17311006
913:26081570
843:38348692
775:22438842
665:23453953
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460:46120825
403:12637023
395:14697657
345:10212488
283:24002528
209:See also
147:In vitro
41:dendrite
766:3305991
625:Bibcode
589:3707701
530:6674103
452:8402908
336:1692490
274:4201609
191:in vivo
186:in vivo
179:In vivo
127:xenopus
45:culture
21:neurite
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363:(PDF)
131:glial
39:or a
31:of a
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422:Cell
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