Editing Extracellular matrix (section)

====Collagen====
[[Collagen]] is the most abundant protein in the ECM, and is the most abundant protein in the human body.<ref>{{cite journal | vauthors = Di Lullo GA, Sweeney SM, Korkko J, Ala-Kokko L, San Antonio JD | title = Mapping the ligand-binding sites and disease-associated mutations on the most abundant protein in the human, type I collagen | journal = The Journal of Biological Chemistry | volume = 277 | issue = 6 | pages = 4223–31 | date = February 2002 | pmid = 11704682 | doi = 10.1074/jbc.M110709200 | doi-access = free }}{{open access}}</ref><ref>{{cite journal | vauthors = Karsenty G, Park RW | title = Regulation of type I collagen genes expression | journal = International Reviews of Immunology | volume = 12 | issue = 2–4 | pages = 177–85 | year = 1995 | pmid = 7650420 | doi = 10.3109/08830189509056711 }}{{closed access}}</ref> It accounts for 90% of bone matrix protein content.<ref>{{cite journal | vauthors = Kern B, Shen J, Starbuck M, Karsenty G | title = Cbfa1 contributes to the osteoblast-specific expression of type I collagen genes | journal = The Journal of Biological Chemistry | volume = 276 | issue = 10 | pages = 7101–7 | date = March 2001 | pmid = 11106645 | doi = 10.1074/jbc.M006215200 | doi-access = free }}{{open access}}</ref> Collagens are present in the ECM as fibrillar proteins and give structural support to resident cells. Collagen is exocytosed in [[Precursor (chemistry)|precursor]] form ([[procollagen]]), which is then cleaved by procollagen [[protease]]s to allow extracellular assembly. Disorders such as [[Ehlers Danlos Syndrome]], [[osteogenesis imperfecta]], and [[epidermolysis bullosa]] are linked with [[genetic defect]]s in collagen-encoding [[gene]]s.<ref name=PG2007/> The collagen can be divided into several families according to the types of structure they form:
# Fibrillar (Type I, II, III, V, XI)
# Facit (Type IX, XII, XIV)
# Short chain (Type VIII, X)
# Basement membrane (Type IV)
# Other (Type VI, VII, XIII)