Editing Cellular differentiation (section)

=== Gene regulatory networks ===
[[Image:Cell Differentiation.jpg|upright=1.5|thumb|Mechanisms of cellular differentiation]]

Each specialized cell type in an organism [[Gene expression|expresses]] a [[subset]] of all the [[gene]]s that constitute the genome of that [[species]]. Each cell type is defined by its particular pattern of [[regulation of gene expression|regulated gene expression]]. Cell differentiation is thus a transition of a cell from one cell type to another and it involves a switch from one pattern of gene expression to another. Cellular differentiation during development can be understood as the result of a [[gene regulatory network]]. A regulatory gene and its cis-regulatory modules are nodes in a gene regulatory network; they receive input and create output elsewhere in the network.<ref name=DeLeon>{{cite journal | vauthors = Ben-Tabou de-Leon S, Davidson EH | title = Gene regulation: gene control network in development | journal = Annual Review of Biophysics and Biomolecular Structure | volume = 36 | issue = 191 | pages = 191–212 | year = 2007 | pmid = 17291181 | doi = 10.1146/annurev.biophys.35.040405.102002 | url = https://resolver.caltech.edu/CaltechAUTHORS:LEOarbbs07 }}</ref> The [[systems biology]] approach to developmental biology emphasizes the importance of investigating how developmental mechanisms interact to produce predictable patterns ([[morphogenesis]]). However, recent research suggests there may be an alternative view. Based on [[stochastic]] gene expression, cellular differentiation is the result of a Darwinian selective process occurring among cells. In this frame, protein and gene networks are the result of cellular processes and not their cause.<ref>{{cite journal | vauthors = Capp JP, Laforge B | title = A Darwinian and Physical Look at Stem Cell Biology Helps Understanding the Role of Stochasticity in Development | language = English | journal = Frontiers in Cell and Developmental Biology | volume = 8 | pages = 659 | date = 23 July 2020 | pmid = 32793600 | pmc = 7391792 | doi = 10.3389/fcell.2020.00659 | doi-access = free }}</ref>

[[File:Signal transduction pathways.svg|thumb|left|240px|An overview of major signal transduction pathways.]]