Editing Motor neuron (section)

== Development ==
Motor neurons begin to develop early in [[embryogenesis|embryonic development]], and motor function continues to develop well into childhood.<ref>{{Cite book|title=Principles of Anatomy Physiology|last1=Tortora|first1=Gerard|last2=Derrickson|first2=Bryan|publisher=John Wiley & Sons, Inc.|year=2011|isbn=978-1-118-34500-9|edition=14th|location=New Jersey|pages=[https://archive.org/details/principlesofanat0000tort/page/1090 1090–1099]|url=https://archive.org/details/principlesofanat0000tort/page/1090}}</ref> In the [[Neural tube#Ventral-dorsal patterning|neural tube]] cells are specified to either the rostral-caudal axis or ventral-dorsal axis. The [[axon]]s of motor neurons begin to appear in the fourth week of development from the ventral region of the ventral-dorsal axis (the [[Basal plate (neural tube)|basal plate]]).<ref name="Sadler">{{cite book|last1=Sadler|first1=T.|title=Langman's medical embryology.|date=2010|publisher=Lippincott William & Wilkins|location=Philadelphia|isbn=978-0-7817-9069-7|pages=299–301|edition=11th}}</ref> This homeodomain is known as the motor neural progenitor domain (pMN). [[Transcription factor]]s here include [[PAX6|Pax6]], [[OLIG2]], [[NKX6-1|Nkx-6.1]], and [[NKX6-2|Nkx-6.2]], which are regulated by [[sonic hedgehog]] (Shh). The OLIG2 gene being the most important due to its role in promoting [[Neurogenin#Motor neuron fate|Ngn2 expression]], a gene that causes cell cycle exiting as well as promoting further transcription factors associated with motor neuron development.<ref name=":1">{{cite journal|last1=Davis-Dusenbery|first1=BN|last2=Williams|first2=LA|last3=Klim|first3=JR|last4=Eggan|first4=K|title=How to make spinal motor neurons.|journal=Development|date=February 2014|volume=141|issue=3|pages=491–501|pmid=24449832|doi=10.1242/dev.097410|doi-access=free}}</ref>

Further specification of motor neurons occurs when [[retinoic acid]], [[fibroblast growth factor]], [[Wnt signalling pathway|Wnts]], and [[Transforming growth factor|TGFb]], are integrated into the various [[Hox gene|Hox]] transcription factors. There are 13 Hox transcription factors and along with the signals, determine whether a motor neuron will be more rostral or caudal in character. In the spinal column, Hox 4-11 sort motor neurons to one of the five motor columns.<ref name=":1" /> 
{| class="wikitable"
|+Motor columns of spinal cord <ref name="KerkisEdgar2013">{{cite journal|vauthors = Edgar R, Mazor Y, Rinon A, Blumenthal J, Golan Y, Buzhor E, Livnat I, Ben-Ari S, Lieder I, Shitrit A, Gilboa Y, Ben-Yehudah A, Edri O, Shraga N, Bogoch Y, Leshansky L, Aharoni S, West MD, Warshawsky D, Shtrichman R|title=LifeMap Discovery™: The Embryonic Development, Stem Cells, and Regenerative Medicine Research Portal|journal=PLOS ONE|volume=8|issue=7|year=2013|pages=e66629|issn=1932-6203|doi=10.1371/journal.pone.0066629|pmid=23874394|pmc=3714290|bibcode=2013PLoSO...866629E|doi-access=free}}</ref>
|'''Motor column'''
|'''Location in spinal  cord'''
|'''Target'''
|-
|Median motor column
|Present entire length 
|Axial muscles
|-
|Hypaxial motor  column
|Thoracic region
|Body wall muscles 
|-
|Preganglionic motor  column
|Thoracic region
|Sympathetic  ganglion
|-
|Lateral motor column
|Brachial and lumbar  region (both regions are further divided into medial and lateral domains)
|Muscles of the limbs
|-
|Phrenic motor  column
|Cervical region
|Diaphragm<ref>{{Cite journal|last1=Philippidou|first1=Polyxeni|last2=Walsh|first2=Carolyn|last3=Aubin|first3=Josée|last4=Jeannotte|first4=Lucie|last5=Dasen|first5=Jeremy S.|title=Sustained Hox5 Gene Activity is Required for Respiratory Motor Neuron Development|journal=Nature Neuroscience|volume=15|issue=12|pages=1636–1644|doi=10.1038/nn.3242|issn=1097-6256|pmc=3676175|pmid=23103965|year=2012}}</ref>
|}