Editing Fibronectin (section)

== Function ==
Fibronectin has numerous functions that ensure the normal functioning of [[vertebrate]] organisms.<ref name="pmid12244123"/>  It is involved in [[cell adhesion]], [[cell growth|growth]], [[cell migration|migration]], and [[cellular differentiation|differentiation]].  Cellular fibronectin is assembled into the [[extracellular matrix]], an insoluble network that separates and supports the [[organ (anatomy)|organs]] and [[tissue (biology)|tissues]] of an organism.

Fibronectin plays a crucial role in [[wound healing]].<ref>{{cite journal | vauthors = Grinnell F | title = Fibronectin and wound healing | journal = Journal of Cellular Biochemistry | volume = 26 | issue = 2 | pages = 107–116 | year = 1984 | pmid = 6084665 | doi = 10.1002/jcb.240260206 | s2cid = 28645109 }}</ref><ref name="pmid15992798">{{cite journal | vauthors = Valenick LV, Hsia HC, Schwarzbauer JE | title = Fibronectin fragmentation promotes alpha4beta1 integrin-mediated contraction of a fibrin-fibronectin provisional matrix | journal = Experimental Cell Research | volume = 309 | issue = 1 | pages = 48–55 | date = Sep 2005 | pmid = 15992798 | doi = 10.1016/j.yexcr.2005.05.024 }}</ref>  Along with [[fibrin]], [[blood plasma|plasma]] fibronectin is deposited at the site of injury, forming a [[blood clot]] that stops bleeding and protects the underlying [[tissue (biology)|tissue]].  As repair of the injured tissue continues, [[fibroblasts]] and [[macrophages]] begin to remodel the area, degrading the proteins that form the provisional [[blood clot]] matrix and replacing them with a [[extracellular matrix|matrix]] that more resembles the normal, surrounding tissue. Fibroblasts secrete [[proteases]], including [[matrix metalloproteinases]], that digest the plasma fibronectin, and then the fibroblasts secrete [[cell (biology)|cellular]] fibronectin and assemble it into an insoluble [[extracellular matrix|matrix]].  Fragmentation of fibronectin by proteases has been suggested to promote wound contraction, a critical step in [[wound healing]]. Fragmenting fibronectin further exposes its V-region, which contains the site for [[α4β1]] [[integrin]] binding. These fragments of fibronectin are believed to enhance the binding of α4β1 integrin-expressing cells, allowing them to adhere to and forcefully contract the surrounding matrix.

Fibronectin is necessary for [[embryogenesis]], and [[gene knockout|inactivating]] the [[gene]] for fibronectin results in early embryonic lethality.<ref name="pmid8306876">{{cite journal | vauthors = George EL, Georges-Labouesse EN, Patel-King RS, Rayburn H, Hynes RO | title = Defects in mesoderm, neural tube and vascular development in mouse embryos lacking fibronectin | journal = Development | volume = 119 | issue = 4 | pages = 1079–91 | date = Dec 1993 | doi = 10.1242/dev.119.4.1079 | pmid = 8306876 | url = https://dev.biologists.org/cgi/content/abstract/119/4/1079 }}</ref> Fibronectin is important for guiding [[cell adhesion|cell attachment]] and [[cell migration|migration]] during [[embryonic development]].  In [[mammalian]] development, the absence of fibronectin leads to defects in [[mesodermal]], [[neural tube]], and [[Blood vessel|vascular]] development.  Similarly, the absence of a normal fibronectin matrix in developing [[amphibians]] causes defects in [[mesodermal]] patterning and inhibits [[gastrulation]].<ref name="pmid10727862">{{cite journal | vauthors = Darribère T, Schwarzbauer JE | title = Fibronectin matrix composition and organization can regulate cell migration during amphibian development | journal = Mechanisms of Development | volume = 92 | issue = 2 | pages = 239–50 | date = Apr 2000 | pmid = 10727862 | doi = 10.1016/S0925-4773(00)00245-8 | s2cid = 2640979 | doi-access =  }}</ref>

Fibronectin is also found in normal human saliva, which helps prevent [[colonisation (biology)|colonization]] of the [[oral cavity]] and [[pharynx]] by [[pathogenic bacteria]].<ref name="pmid3305363">{{cite journal | vauthors = Hasty DL, Simpson WA | title = Effects of fibronectin and other salivary macromolecules on the adherence of Escherichia coli to buccal epithelial cells | journal = Infection and Immunity | volume = 55 | issue = 9 | pages = 2103–9 | date = Sep 1987 | pmid = 3305363 | pmc = 260663 | doi =  10.1128/IAI.55.9.2103-2109.1987| url = }}</ref>