Editing Neurulation (section)

=== Patterning ===
[[File:Gray640.png|right|thumb|Transverse section of the neural tube showing the floor plate and roof plate]]

According to the [[French Flag model]] where stages of development are directed by gene product gradients, several genes are considered important for inducing patterns in the open neural plate, especially for the development of [[neurogenic placodes]]. These placodes first become evident histologically in the open neural plate. After [[sonic hedgehog]] (SHH) signalling from the notochord induces its formation, the floor plate of the incipient neural tube also secretes SHH.  After closure, the neural tube forms a basal or [[Floor plate (biology)|floor plate]] and a roof or [[alar plate]] in response to the combined effects of SHH and factors including [[BMP4]] secreted by the roof plate. The basal plate forms most of the ventral portion of the nervous system, including the motor portion of the spinal cord and brain stem; the alar plate forms the dorsal portions, devoted mostly to sensory processing.<ref name="Gilbert 2013">{{cite book|last=Gilbert|first=SF|title=Developmental Biology|year=2013|publisher=Sinauer Associates|location=Sunderland, MA|isbn=978-0-87893-978-7|chapter-url=http://www.sinauer.com/developmental-biology-663.html|edition=10|access-date=22 March 2015|chapter=10: Emergence of the Ectoderm}}</ref>

The dorsal epidermis expresses BMP4 and [[BMP7]]. The roof plate of the neural tube responds to those signals by expressing more BMP4 and other [[transforming growth factor beta]] (TGF-β) signals to form a dorsal/ventral gradient among the neural tube. The notochord expresses SHH. The floor plate responds to SHH by producing its own SHH and forming a gradient. These gradients allow for the differential expression of transcription factors.<ref name="Gilbert 2013"/>