Neurulation
Neurulation | |
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Identifiers | |
MeSH | D054261 |
Anatomical terminology |
Neurulation refers to the folding process in vertebrate embryos, which includes the transformation of the neural plate into the neural tube.[1] The embryo at this stage is termed the neurula.
The process begins when the notochord induces the formation of the central nervous system (CNS) by signaling the ectoderm germ layer above it to form the thick and flat neural plate. The neural plate folds in upon itself to form the neural tube, which will later differentiate into the spinal cord and the brain, eventually forming the central nervous system.[2] Computer simulations found that cell wedging and differential proliferation are sufficient for mammalian neurulation.[3]
Different portions of the neural tube form by two different processes, called primary and secondary neurulation, in different species.[4]
- In primary neurulation, the neural plate creases inward until the edges come in contact and fuse.
- In secondary neurulation, the tube forms by hollowing out of the interior of a solid precursor.
Primary neurulation
Primary neural induction
The concept of induction originated in work by Pandor in 1817.
Subsequent work on inducers by scientists over the 20th century demonstrated that not only could the dorsal lip of the blastopore act as an inducer but so could a huge number of other seemingly unrelated items. This began when boiled ectoderm was found to still be able to induce by
Even before the term induction was popularized, several authors, beginning with Hans Driesch in 1894,[19] suggested that primary neural induction might be mechanical in nature. A mechanochemical-based model for primary neural induction was proposed in 1985 by G.W. Brodland and R. Gordon.[20] An actual physical wave of contraction has been shown to originate from the precise location of the Spemann organizer which then traverses the presumptive neural epithelium[21] and a full working model of how primary neural inductions was proposed in 2006.[22][23] There has long been a general reluctance in the field to consider the possibility that primary neural induction might be initiated by mechanical effects.[24] A full explanation for primary neural induction remains yet to be found.
Shape change
As neurulation proceeds after induction, the cells of the neural plate become
Folding
The process of the flat neural plate folding into the cylindrical neural tube is termed primary neurulation. As a result of the cellular shape changes, the neural plate forms the medial hinge point (MHP). The expanding epidermis puts pressure on the MHP and causes the neural plate to fold resulting in
The notochord plays an integral role in the development of the neural tube. Prior to neurulation, during the migration of epiblastic endoderm cells towards the hypoblastic endoderm, the notochordal process opens into an arch termed the notochordal plate and attaches overlying neuroepithelium of the neural plate. The notochordal plate then serves as an anchor for the neural plate and pushes the two edges of the plate upwards while keeping the middle section anchored. Some of the notochodral cells become incorporated into the center section neural plate to later form the floor plate of the neural tube. The notochord plate separates and forms the solid notochord.[4]
The folding of the neural tube to form an actual tube does not occur all at once. Instead, it begins approximately at the level of the fourth
Patterning
According to the
The dorsal epidermis expresses BMP4 and
Complexities of the model
Neural tube closure is not entirely understood. Closure of the neural tube varies by species. In mammals, closure occurs by meeting at multiple points which then close up and down. In birds, neural tube closure begins at one point of the midbrain and moves anteriorly and posteriorly.[31][32]
Secondary neurulation
Primary neurulation develops into secondary neurulation when the caudal neuropore undergoes final closure. The cavity of the spinal cord extends into the neural cord.[33] In secondary neurulation, the neural ectoderm and some cells from the endoderm form the medullary cord. The medullary cord condenses, separates and then forms cavities.[34] These cavities then merge to form a single tube. Secondary neurulation occurs in the posterior section of most animals but it is better expressed in birds. Tubes from both primary and secondary neurulation eventually connect at around the sixth week of development.[35]
In humans, the mechanisms of secondary neurulation plays an important role given its impact on the proper formation of the human posterior spinal cord. Errors at any point in the process can yield problems. For example, retained medullary cord occurs due to a partial or complete arrest of secondary neurulation that creates a non-functional portion on the vestigial end.[36]
Early brain development
The anterior portion of the
Non-neural ectoderm tissue
Neural crest cells
Masses of tissue called the neural crest that are located at the very edges of the lateral plates of the folding neural tube separate from the neural tube and migrate to become a variety of different but important cells.[citation needed]
Neural crest cells will migrate through the embryo and will give rise to several cell populations, including pigment cells and the cells of the peripheral nervous system.[citation needed]
Neural tube defects
Failure of neurulation, especially failure of closure of the neural tube are among the most common and disabling birth defects in humans, occurring in roughly 1 in every 500 live births.[42] Failure of the rostral end of the neural tube to close results in anencephaly, or lack of brain development, and is most often fatal.[43] Failure of the caudal end of the neural tube to close causes a condition known as spina bifida, in which the spinal cord fails to close.[44]
See also
References
- ISBN 0-443-06583-7
- ^ "Chapter 14. Gastrulation and Neurulation". biology.kenyon.edu. Retrieved 2 February 2016.
- PMID 31986479.
- ^ ISBN 9780198709886.
- ^ Tiedemann, H. Chemical approach to the inducing agents. In: O. Nakamura & S. Toivonen (eds.), Organizer - A Milestone of a Half- Century from Spemann, Amsterdam: Elsevier/North Holland Biomedical Press, p. 91- 117. 1978
- ^ Hamburger, V.. The Heritage of Experimental Embryology: Hans Spemann and the Organizer. New York: Oxford University Press. 1988
- ^ Spemann, H. Über Korrelationen in der Entwicklung des Auges/On correlations in the development of the eye. Verh. anat. Ges. Jena 15, 61-79. 1901
- ^ Lewis, WH Experimental studies on the development of the eye in amphibia. I. On the origin of the lens in Rana palustris. Amer. J. Anat. 3, 505-536. 1904
- ^ a b c Spemann, H. & H. Mangold, Über Induktion von Embryonalanlagen durch Implantation artfremder Organisatoren/On induction of embryo anlagen by implantation of organizers of other species. Archiv mikroskop. Anat. Entwicklungsmech. 100, 599-638 1924
- ^ Spemann, H. & H. Mangold 1924: Induction of embryonic primordia by implantation of organizers from a different species. In: B.H. Willier & J.M. Oppenheimer (eds.), Foundations of Experimental Embryology, (translated 1964 ed.), Englewood Cliffs, New Jersey: Prentice-Hall, p. 144-184
- ^ Gordon, R., N. K. Björklund & P. D. Nieuwkoop. Dialogue on embryonic induction and differentiation waves. Int. Rev. Cytol. 150, 373-420. 1994
- ^ Holtfreter, J. Eigenschaften und Verbreitung induzierender Stoffe/Characteristics and spreading of inducing substances. Naturwissenschaften 21, 766-770. 1933
- ^ Twitty, VC, Of Scientists and Salamanders Freeman, San Francisco, CA.1966
- ^ Spemann, H., F.G. Fischer & E. Wehmeier Fortgesetzte Versuche zur Analyse der Induktionsmittel in der Embryonalentwicklung/Continued attempts at analysis of the cause of induction means in embryonic development. Natuwissenschaften 21, 505-506. 1933
- ^ Weiss, P.A.. The so-called organizer and the problem of organization in amphibian development. Physiol. Rev. 15(4), 639-674. 1935
- ^ De Robertis, E.M., M. Blum, C. Niehrs & H. Steinbeisser, goosecoid and the organizer. Development (Suppl.), 167-171. 1992
- ^ Hahn, M. & H. Jäckle Drosophila goosecoid participates in neural development but not in body axis formation. EMBO J. 15(12), 3077-3084. 1996
- ^ De Robertis, E.M. Dismantling the organizer. Nature 374(6521), 407-408. 1995
- ^ Driesch, HAE. Analytische Theorie der Organischen Entwicklung/Analytic Theory of Organic Development. Leipzig: Verlag Von Wilhelm Engelman. 1984
- ^ Gordon, R. Brodland, GW. The cytoskeletal mechanics of brain morphogenesis: cell state splitters cause primary neural induction. Gell Biophys. 11: 177-238. (1987)
- ^ Brodland, GW” Gordon, R, Scott MJ, Bjorklund NK, Luchka KB, Martin, CC, Matuga, C., Globus, M., Vethamany-Globus S. and Shu, D. Furrowing surface contraction wave coincident with primary neural induction in amphibian embryos. J Morphol. 219: 131-142. 1994
- ^ Gordon, NK, Gordon R The organelle of differentiation in embryos: the cell state splitter Theor Biol Med Model (2016) 13: 11. https://doi.org/10.1186/s12976-016-0037-2
- International Journal of Developmental Biology50 (2-3), 135-141
- ISBN 978-981-02-2268-0.
- ^ Burnside. M. B. Microrubules and microfilaments in amphibian neurulation. Alii. Zool. 13, 989-1006 1973
- ^ Jacobson, A.G. & R. Gordon. Changes in the shape of the developing vertebrate nervous system analyzed experimentally, mathematically and by computer simulation. J. Exp. Zool. 197, 191-246. 1973
- ^ Bordzilovskaya, N.P., T.A. Dettlaff, S.T. Duhon & G.M. Malacinski (1989). Developmental-stage series of axolotl embryos [Erratum: Staging Table 19-1 is for 20°C, not 29°C]. In: J.B. Armstrong & G.M. Malacinski (eds.), Developmental Biology of the Axolotl, New York: Oxford University Press, p. 201-219.
- ^ Youman's Neurological Surgery, H Richard Winn, 6th ed. Volume 1, p 81, 2011 Elsevier Saunders, Philadelphia, PA
- ISBN 978-0-87893-243-6. Retrieved 30 November 2011.
- ^ ISBN 978-0-87893-978-7. Retrieved 22 March 2015.
- ^ Golden J A, Chernoff G F. Intermittent pattern of neural tube closure in two strains of mice. Teratology. 1993;47:73–80.
- ^ Van Allen M I, 15 others Evidence for multi-site closure of the neural tube in humans. Am. J. Med. Genet. 1993;47:723–743.
- .
- ^ Formation of the Neural Tube Developmental Biology NCBI Bookshelf
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- S2CID 25638763. Retrieved 2020-11-19.
- ^ ISBN 978-0878939787.
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- ^ Paraxial Mesoderm: The Somites and Their Derivatives NCBI Bookshelf, Developmental Biology 6th edition. Accessed Nov 29,2017
- ^ Daley, Darrel. Formation of the Nervous System Archived 2008-01-03 at the Wayback Machine. Last accessed on Oct 29, 2007.
- ^ Reference, Genetics Home. "Anencephaly". Genetics Home Reference. Retrieved 2020-03-02.
- ^ CDC (2018-08-31). "Spina Bifida Facts | CDC". Centers for Disease Control and Prevention. Retrieved 2020-03-02.
Further reading
- Almeida, Karla L.; et al. (2010). "Neural Induction". In Henning, Ulrich (ed.). Perspectives of Stem Cells: From Tools for Studying Mechanisms of Neuronal Differentiation Towards Therapy. Springer. ISBN 978-90-481-3374-1.
- Basch, Martín L.; Bonner-Fraser, Marianne (2006). "Neural Crest Inducing Signals". In Saint-Jennet, Jean-Pierre (ed.). Neural crest induction and differentiation. Springer. ISBN 978-0-387-35136-0.
- Harland, Richard M. (1997). "Neural induction in Xenopus". In Cowan, W. Maxwell (ed.). Molecular and cellular approaches to neural development. Oxford University Press. ISBN 978-0-19-511166-8.
- Ladher, Raj; Schoenwolf, Gary C. (2004). "Making a neural tube". In Jacobson, Marcus; Rao, Mahendra S. (eds.). Developmental neurobiology. Springer. ISBN 978-0-306-48330-1.
- Tian, Jing; Sampath, Karuna (2004). "Formation and Functions of the Floor Plate". In Gong, Zhiyuan; Korzh, Vladimir (eds.). Fish development and genetics: the zebrafish and medaka models. World Scientific. pp. 123, 139–140. ISBN 978-981-238-821-6.
- Zhang, Su-Chun (2005). "Neural specification from human embryonic stem cells". In Odorico, John S.; et al. (eds.). Human embryonic stem cells. Garland Science. ISBN 978-1-85996-278-7.
External links
- Overview at uvm.edu
- Neurulation Animation Archived 2016-03-03 at the Wayback Machine