ASPN siRNA – Asporin Preproprotein (Mouse)

This gene encodes a member of the small leucine-rich proteoglycan family. The encoded protein is an extracellular matrix protein that modulates the transforming growth factor-beta signaling pathway, regulating cartilage matrix gene expression and cartilage formation. The protein plays a role in the pathology of osteoarthritis. Alternative splicing results in multiple transcript variants.[provided by RefSeq, Feb 2010]

ASPN: Negatively regulates periodontal ligament (PDL) differentiation and mineralization to ensure that the PDL is not ossified and to maintain homeostasis of the tooth-supporting system. Inhibits BMP2-induced cytodifferentiation of PDL cells by preventing its binding to BMPR1B/BMP type-1B receptor, resulting in inhibition of BMP-dependent activation of SMAD proteins. Critical regulator of TGF-beta in articular cartilage and plays an essential role in cartilage homeostasis and osteoarthritis (OA) pathogenesis. Negatively regulates chondrogenesis in the articular cartilage by blocking the TGF- beta/receptor interaction on the cell surface and inhibiting the canonical TGF-beta/Smad signal. Binds calcium and plays a role in osteoblast-driven collagen biomineralization activity. Genetic variations in ASPN are associated with susceptibility to osteoarthritis type 3 (OS3); also known as osteoarthritis of knee/hip. Osteoarthritis is a degenerative disease of the joints characterized by degradation of the hyaline articular cartilage and remodeling of the subchondral bone with sclerosis. Clinical symptoms include pain and joint stiffness often leading to significant disability and joint replacement. Susceptibility to osteoarthritis is conferred by a triplet repeat expansion polymorphism. ASPN allele having 14 aspartic acid repeats in the N-terminal region of the protein (D14), is overrepresented relative to the common allele having 13 aspartic acid repeats (D13). The frequency of the D14 allele increases with disease severity. The D14 allele is also overrepresented in individuals with hip osteoarthritis. Defects in ASPN are a cause of susceptibility to intervertebral disk disease (IDD). A common musculo- skeletal disorder caused by degeneration of intervertebral disks of the lumbar spine. It results in low-back pain and unilateral leg pain. Susceptibility to intervertebral disk disease, particularly lumbar disk degeneration, is conferred by a triplet repeat expansion polymorphism. ASPN allele having 14 aspartic acid repeats in the N-terminal region of the protein (D14), is associated with the disorder in some populations (PubMed:18304494). Belongs to the small leucine-rich proteoglycan (SLRP) family. SLRP class I subfamily.

Protein type: Secreted, signal peptide; Extracellular matrix; Secreted

Cellular Component: extracellular matrix; proteinaceous extracellular matrix; cell projection; extracellular region

Molecular Function: collagen binding; protein binding; calcium ion binding

Biological Process: biomineral formation; negative regulation of transforming growth factor beta receptor signaling pathway; bone mineralization