Background：

This gene encodes the pro-alpha2 chain of type I collagen whose triple helix comprises two alpha1 chains and one alpha2 chain. Type I is a fibril-forming collagen found in most connective tissues and is abundant in bone， cornea， dermis and tendon. Mutations in this gene are associated with osteogenesis imperfecta types I-IV， Ehlers-Danlos syndrome type VIIB， recessive Ehlers-Danlos syndrome Classical type， idiopathic osteoporosis， and atypical Marfan syndrome. Symptoms associated with mutations in this gene， however， tend to be less severe than mutations in the gene for the alpha1 chain of type I collagen (COL1A1) reflecting the different role of alpha2 chains in matrix integrity. Three transcripts， resulting from the use of alternate polyadenylation signals， have been identified for this gene.