Fibronectin (UniProt: P02751; also known as FN, Cold-insoluble globulin, CIG) is encoded by the FN1 (also known as FN) gene (Gene ID: 2335) in human. Fibronectin is are involved various biological activities, including cell adhesion, cell motility, opsonization, wound healing, and maintenance of cell shape. It is essential for osteoblast mineralization and participates in the regulation of type I collagen deposition by osteoblasts. Fibronectin is usually present as homodimer of ~250 kDa subunits where subunits are connected by two disulfide bonds at the C-terminal region. Each monomer contains three repeating units, which are designated as type I, II, and III repeats containing about 40, 60, and 90 amino acids, respectively. Plasma fibronectin (soluble dimeric form) is secreted by hepatocytes and the cellular fibronectin (dimeric or cross-linked multimeric forms) is produced by fibroblasts, epithelial and other cell types. Cellular fibronectin is deposited as fibrils in the extracellular matrix. Fibronectin is recognized by integrins alpha5beta1 and alphaVbeta3. The primary sequence motif of fibronectin for integrin binding is a tripeptide, Arg-Gly-Asp (RGD). Mutations in FN gene are known to cause glomerulopathy that is characterized by proteinuria, microscopic hematuria, and hypertension, which can lead to end-stage renal failure.