FN1

FN1, or fibronectin 1, is a gene that encodes fibronectin, a high-molecular-weight glycoprotein of the extracellular matrix and blood plasma. Fibronectin exists in two main forms: soluble plasma fibronectin circulating in blood and insoluble cellular fibronectin assembled into fibrils in the extracellular matrix. The FN1 gene gives rise to multiple isoforms through alternative splicing, including the EDA and EDB variants that are commonly associated with developing tissues and tissue remodeling.

Fibronectin subunits are large polypeptides composed of repeating modules of type I, II, and III domains. Two subunits are disulfide-bonded at the C-termini to form a dimeric protein. The RGD motif present in some type III repeats facilitates binding to integrin receptors on cell surfaces, supporting cell adhesion and signaling. Fibronectin also binds to other extracellular matrix components such as collagens, heparin, and fibrin, allowing it to organize a versatile extracellular network.

Functions of fibronectin include mediating cell adhesion, migration, and differentiation during development, wound healing, and tissue repair. It helps assemble and maintain the extracellular matrix and contributes to processes such as angiogenesis and vessel stabilization. During wound healing, fibronectin supports cellular responses that restore tissue integrity and interacts with components of the clotting cascade.

Clinical significance: Altered FN1 expression and alternative splicing are observed in various cancers and fibrotic diseases, where they can influence cell adhesion, migration, and tumor progression. Plasma fibronectin levels are used in research and, in some contexts, as part of biomarker assessments. Fibronectin remains a key component in studies of development, wound healing, and tissue remodeling.