Neural crest
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2008-06-14T15:19:46Z
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robot Modifying: [[eo:Neŭra kresto]]
{{Infobox Embryology |
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Caption = Two stages in the development of the neural crest in the human [[embryo]]. |
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Precursor = [[ectoderm]] |
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The '''neural crest''', a transient component of the [[ectoderm]], is located in between the [[neural tube]] and the epidermis (or the free margins of the [[neural folds]]) of an embryo during neural tube formation. Neural crest cells quickly migrate during or shortly after [[neurulation]], an embryological event marked by [[neural tube]] closure.
It has been referred to as the fourth [[germ layer]], due to its great importance. The neural crest can give rise to neurons and glia of the [[autonomic nervous system]] (ANS); some skeletal elements, tendons and smooth muscle; chondrocytes, osteocytes, melanocytes, [[chromaffin cells]], and supporting cells and hormone producing cells in certain organs.
==Clinical significance==
Diseases due to defects in the neural crest induction, formation or migration are referred to as '''neurocristopathies''', and genes that cause some of these like [[piebaldism]] and [[Hirschprung's disease]] have been cloned in mice models.
==History and Nomenclature==
In 1868 His described Neural Crest as "''zwischenstrang''"- a strip of cells lying between the dorsal ectoderm and the neural tube.<ref>{{cite web |url=http://www.brown.edu/Courses/BI0032/neurcrst/index.htm |title=Neural Crest Introduction |accessdate=2007-09-18 |format= |work=}}</ref>
From this time until the 1950s, most of the work on this structure was done on amphibian embryos, as in a 1950 comprehensive review in a monograph by the Swedish embryologist [[Sven Hörstadius]].<ref>{{cite web |url=http://www.ncbi.nlm.nih.gov/books/bv.fcgi?indexed=google&rid=eurekah.section.67490 |title=Neural Crest and the Origins of Craniofacial Pattern |accessdate=2007-09-18 |format= |work=}}</ref> Newth (who also studied it in fishes)<ref name="pmid15405801">{{cite journal |author=Newth DR |title=Fate of the neural crest in lampreys |journal=Nature |volume=165 |issue=4190 |pages=284 |year=1950 |pmid=15405801 |doi=10.1038/165284a0}}</ref> in 1951 described it as such by "a remarkable embryonic structure" and till another decade its origin still remained an enigma!
In 1960s with the invention of cell labeling with tritiated thymidine by Chibon<ref name="pmid5590717">{{cite journal |author=Chibon P |title=[Nuclear labelling by tritiated thymidine of neural crest derivatives in the amphibian Urodele Pleurodeles waltlii Michah] |language=French |journal=Journal of embryology and experimental morphology |volume=18 |issue=3 |pages=343–58 |year=1967 |pmid=5590717 |doi=}}</ref> and Weston<ref name="pmid14000137">{{cite journal |author=Weston JA |title=A radioautographic analysis of the migration and localization of trunk neural crest cells in the chick |journal=Dev. Biol. |volume=6 |issue= |pages=279–310 |year=1963 |pmid=14000137 |doi=10.1016/0012-1606(63)90016-2}}</ref> gave rise to a major breakthrough in this field through amphibian and avian studies. But this was a transient method of cell labeling and the field had to wait for the chick-quail transfer studies for a definitive confirmation of those results. These extensive works in 1970s was reviewed extensively in "the Neural Crest" by Nicole Le Douarin, first published in [[1982]].<ref name="isbn0-521-62010-4">{{cite book |author=Kalcheim, Chaya; Le Douarin, N. |title=The neural crest |publisher=Cambridge University Press |location=Cambridge, UK |year=1999 |pages= |isbn=0-521-62010-4 |oclc= |doi=}}</ref>
The nomenclature of these cells derives from amphibian and avian studies which demonstrate migration from the ''neural crest'' which forms on the rostral region of the neurulating ectoderm in the trilaminar disc. In humans, the cells actually migrate from the lateral margins of the neural tube however the use of 'crest cells' in this regard is retained.
==Induction==
Cells fated to become neural crest tissue are induced by [[Bone morphogenetic protein|BMP]], [[Wnt signaling pathway|Wnt]] and [[Fibroblast growth factor|FGF]] signaling to express the proteins [[FoxD3]], [[RhoB]] and [[Slug]], and to lose expression of [[E-cadherin]].
* RhoB is likely to signal cytoskeletal changes required for migration. <ref name="pmid9811589">{{cite journal |author=Liu JP, Jessell TM |title=A role for rhoB in the delamination of neural crest cells from the dorsal neural tube |journal=Development |volume=125 |issue=24 |pages=5055–67 |year=1998 |pmid=9811589 |doi=}}</ref>
* Slug is a repressor<ref name="pmid16887825">{{cite journal |author=Vernon AE, LaBonne C |title=Slug stability is dynamically regulated during neural crest development by the F-box protein Ppa |journal=Development |volume=133 |issue=17 |pages=3359–70 |year=2006 |pmid=16887825 |doi=10.1242/dev.02504}}</ref> that leads to an activation of factors that dissociate tight junctions.
==Categories==
There are several main categories of neural crest based upon function:<ref>{{cite web |url=http://www.trinity.edu/rblyston/craftyMol/ncm.htm |title=Neural Crest Migration |accessdate=2007-09-18 |format= |work=}}</ref>
===Cranial neural crest===
* The '''cranial neural crest''' arises in the anterior and populates the face and the pharyngeal arches giving rise to bones, cartilage, nerves and connective tissue.
:''Other Migration Locations:''
:*Into the pharyngeal arches and play an inductive role in [[thymus]] development.
:*Into the pharyngeal arches and form the [[parafollicular cell]] or [[ultimobranchial bodies]] of the [[thyroid gland]].
:*Into the pharyngeal arches and play an inductive role in [[parathyroid gland]] development.
:*Facial [[ectomesenchyme]] of the [[pharyngeal arch]]es forming skeletal muscle, bone, and cartilage in the face.
:*[[Odontoblast]]s ([[dentin]]-producing cells) of the [[teeth]].
:*Into the [[optic vesicle]] and the developing eye and contributes to many anterior eye elements such the cornea, sclera, and ciliary muscle. It also contributes to the attaching skeletal muscles of the eye.
:*Into the otic placode and participates in the [[inner ear]] development.
:*[[Sensory ganglia]] of the fifth, seventh, ninth and tenth [[cranial nerves]].
===Vagal and sacral neural crest===
* The '''vagal and sacral neural crest''' arises in the neck and tail and populates the gut, forming the [[parasympathetic]] neurons that regulates peristalsis and control blood vessel dilation.
:''Other Migration Locations:''
:*Walls of the viscera to become [[enteric ganglia]].
===Trunk neural crest===
* The '''trunk neural crest''' lies between the vagal and sacral neural crest and gives rise to two groups of cells. One group migrates dorsolateral and populates the skin, forming [[pigment cells]] and the other migrates ventrolateral through the anterior [[sclerotome]] to become the epinephrine-producing cells of the [[adrenal gland]] and the neurons of the [[sympathetic nervous system]]. Some cells remain in the sclerotome to form the [[dorsal root ganglia]]
:''Other Migration Locations:''
:*Proximal to the spinal cord and line up symmetrically to form the [[dorsal root ganglia]].
:*Into the skin to form [[melanocytes]] and [[Merkel cells]].
:*[[Chromaffin cell]]s of the [[adrenal medulla]].
:*Near the vertebral column and become [[sympathetic chain ganglia]].
===Cardiac neural crest===
* The '''cardiac neural crest''' overlaps the vagal neural crest and migrates to populate the [[branchial arches|pharyngeal arches]] 3, 4 and 6 (producing structures in the head) and to the [[heart]], forming connective tissue that separates the great vessels of the heart.
:''Other Migration Locations:''
:*Into the [[pharyngeal arches]] and [[Truncus arteriosus (embryology)]], forming the [[aorticopulmonary septum]] and the [[smooth muscle]] of [[great arteries]].
:*Anterior of the aorta to become the four [[pre-aortic ganglia]] ([[celiac ganglion]], [[superior mesenteric ganglion]], [[inferior mesenteric ganglion]] and [[aortical renal ganglia]])
==Migration==
Neural crest cells require extracellular matrix to migrate through interactions between [[integrins]] and [[fibronectin]] and [[laminin]]. Migration is directed by inhibitory and attractive signals from cells. [[Ephrin]] is an inhibitory [[ligand]] in posterior sclerotome that affects ventral pathway trunk neural crest cells and causes them to migrate through the anterior sclerotome instead. [[Thrombospondin]] promotes migration through the anterior sclerotome. Another signal, stem cell factor is involved in specifying the destination of migration. If expressed in the wrong locations, pigment cells migrate to that site and proliferate there.
==Plasticity==
Neural crest cells show varying degrees of plasticity. Some trunk neural crest cells are [[pluripotent]]. Cranial neural crest cells can give rise to trunk neural crest cells if transplanted. However, heart neural crest cells are committed before migration. Individual neural crest cells can take on a new fate, however groups of neural crest cells cannot.
==See also==
* [[Neural plate]]
==References==
{{Reflist|2}}
==External links==
* {{EmbryologyUNSW|Notes/ncrest}}
* {{BrainInfo|ancil|445}}
* [http://www.med.umich.edu/lrc/coursepages/M1/embryology/embryo/images/neural_crest_and_notocord.gif Diagram] at [[University of Michigan]]
* [http://www.palaeos.com/Vertebrates/Bones/Teeth/Images/ChickNeural%20Crest.gif Hox domains in chicks]
{{embryology}}
{{Development of nervous system}}
[[Category:Developmental biology]]
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[[es:Cresta neural]]
[[eo:Neŭra kresto]]
[[fr:Crête neurale]]
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[[pt:Crista neural]]
[[fi:Hermostopiena]]
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