Editing Cerebral cortex (section)

===Asymmetric division===
The first divisions of the progenitor cells are symmetric, which duplicates the total number of progenitor cells at each [[Mitosis|mitotic cycle]]. Then, some progenitor cells begin to divide asymmetrically, producing one postmitotic cell that migrates along the radial glial fibers, leaving the [[ventricular zone]], and one progenitor cell, which continues to divide until the end of development, when it differentiates into a [[astrocyte|glial cell]] or an [[ependyma|ependymal cell]]. As the [[G1 phase]] of [[mitosis]] is elongated, in what is seen as selective cell-cycle lengthening, the newly born neurons migrate to more superficial layers of the cortex.<ref>{{cite journal | vauthors = Calegari F, Haubensak W, Haffner C, Huttner WB | title = Selective lengthening of the cell cycle in the neurogenic subpopulation of neural progenitor cells during mouse brain development | journal = The Journal of Neuroscience | volume = 25 | issue = 28 | pages = 6533–6538 | date = July 2005 | pmid = 16014714 | pmc = 6725437 | doi = 10.1523/jneurosci.0778-05.2005 }}</ref> The migrating daughter cells become the [[pyramidal cell]]s of the cerebral cortex.<ref>{{cite journal | vauthors = Rakic P | title = Specification of cerebral cortical areas | journal = Science | volume = 241 | issue = 4862 | pages = 170–176 | date = July 1988 | pmid = 3291116 | doi = 10.1126/science.3291116 | bibcode = 1988Sci...241..170R }}</ref> The development process is time ordered and regulated by hundreds of genes and [[Epigenetic Regulation of Neurogenesis|epigenetic regulatory mechanisms]].<ref>{{cite journal | vauthors = Hu XL, Wang Y, Shen Q | title = Epigenetic control on cell fate choice in neural stem cells | journal = Protein & Cell | volume = 3 | issue = 4 | pages = 278–290 | date = April 2012 | pmid = 22549586 | pmc = 4729703 | doi = 10.1007/s13238-012-2916-6 }}</ref>