COL9a2 is one of the three alpha chains of type IX collagen, the major collagen component of hyaline cartilage. Type IX collagen, a heterotrimeric molecule, is usually found in tissues containing type II collagen, a fibrillar collagen. This chain is unusual in that, unlike the other two type IX alpha chains, it contains a covalently attached glycosaminoglycan side chain. Mutations in this gene are associated with multiple epiphyseal dysplasia.Type IX collagen, a heterotrimer of alpha-1, alpha-2, and alpha-3 chains specific for this type of collagen, is a cartilage-specific fibril-associated collagen. A single-strand conformation polymorphism within the murine gene was used to map Col9a2 to mouse chromosome 4. Since one form of multiple epiphyseal dysplasia maps to the same region of chromosome 1, COL9A2 is a candidate gene for that disorder.