Editing Cellular differentiation (section)

=== Signaling pathways ===
Cellular differentiation is often controlled by [[cell signaling]]. Many of the signal molecules that convey information from cell to cell during the control of cellular differentiation are called [[growth factor]]s. Although the details of specific [[signal transduction]] pathways vary, these pathways often share the following general steps. A ligand produced by one cell binds to a receptor in the extracellular region of another cell, inducing a conformational change in the receptor. The shape of the cytoplasmic domain of the receptor changes, and the receptor acquires enzymatic activity. The receptor then catalyzes reactions that phosphorylate other proteins, activating them. A cascade of phosphorylation reactions eventually activates a dormant transcription factor or cytoskeletal protein, thus contributing to the differentiation process in the target cell.<ref name=Gilbert>{{cite book | vauthors = Knisely K, Gilbert SF |title=Developmental Biology |publisher=Sinauer Associates |location=Sunderland, Mass |year=2009 |page=147 |isbn=978-0-87893-371-6 |edition=8th }}</ref> Cells and tissues can vary in competence, their ability to respond to external signals.<ref name=Rudel>Rudel and Sommer; The evolution of developmental mechanisms. ''Developmental Biology'' 264, 15-37, 2003 {{cite journal | vauthors = Rudel D, Sommer RJ | title = The evolution of developmental mechanisms | journal = Developmental Biology | volume = 264 | issue = 1 | pages = 15–37 | date = December 2003 | pmid = 14623229 | doi = 10.1016/S0012-1606(03)00353-1 | doi-access = free }}</ref>