COL9A3 (also known as Collagen α3 Type IX) belongs to the fibril-associated collagens with interrupted helices (FACIT) family. COL9 is expressed in cartilage, cornea and in the vitreous portion of the eye and is a heterotrimer composed of COL9A1 and COL9A2. When expressed in hyaline cartilage, COL9 posseses a large N-terminal globular domain (NC4). Mutations in the COL9A3 gene are associated with multiple epiphyseal dysplasia (MED), a chondrodysplasia, in humans. COL9 is often co-localized with COL2A1, and may play a role in the interaction of fibrils between COL2A1 and COL9.
