This gene encodes the alpha chain of type XXI collagen, a member of the FACIT collagen family (fibril-associated collagens with interrupted helices). Type XXI collagen is localized to tissues containing type I collagen so, like other members of this collagen family, it may serve to maintain the integrity of the extracellular matrix. An alternatively spliced transcript variant has been described, but its full-length nature has yet to be determined. [provided by RefSeq, Jul 2008].