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Genetics Home Reference: your guide to understanding genetic conditions     A service of the U.S. National Library of Medicine®


Reviewed November 2007

What is the official name of the COL1A2 gene?

The official name of this gene is “collagen, type I, alpha 2.”

COL1A2 is the gene's official symbol. The COL1A2 gene is also known by other names, listed below.

What is the normal function of the COL1A2 gene?

The COL1A2 gene provides instructions for making part of a large molecule called type I collagen. Collagens are a family of proteins that strengthen and support many tissues in the body, including cartilage, bone, tendon, skin, and the white part of the eye (the sclera). Type I collagen is the most abundant form of collagen in the human body.

The COL1A2 gene produces a component of type I collagen called the pro-α2(I) chain. Collagens begin as procollagen molecules, which must be processed by enzymes outside the cell to remove extra protein segments from their ends. Each rope-like procollagen molecule is made up of three chains: two pro-α1(I) chains, which are produced from the COL1A1 gene, and one pro-α2(I) chain, which is produced from the COL1A2 gene.

After procollagens are processed, the resulting mature collagen molecules arrange themselves into long, thin fibrils. Individual collagen molecules are cross-linked to one another within these fibrils. The formation of cross-links results in very strong type I collagen fibrils, which are found in the spaces around cells.

Does the COL1A2 gene share characteristics with other genes?

The COL1A2 gene belongs to a family of genes called COL (collagens).

A gene family is a group of genes that share important characteristics. Classifying individual genes into families helps researchers describe how genes are related to each other. For more information, see What are gene families? ( in the Handbook.

How are changes in the COL1A2 gene related to health conditions?

Ehlers-Danlos syndrome - caused by mutations in the COL1A2 gene

Several mutations in the COL1A2 gene have been found in people with the arthrochalasia type of Ehlers-Danlos syndrome. These mutations, which affect one copy of the COL1A2 gene in each cell, delete a segment of the pro-α2(I) chain that attaches one collagen molecule to another. The absence of this important segment prevents the normal assembly of type I collagen fibrils and alters the cross-linking between collagen molecules. These changes mainly affect tissues that are rich in type I collagen, such as the skin, bones, and tendons.

Rarely, mutations in both copies of the COL1A2 gene in each cell have been reported in people with the characteristic features of Ehlers-Danlos syndrome. These mutations prevent cells from producing any normal pro-α2(I) chains. As a result, type I collagen fibrils in the skin and other tissues cannot be assembled correctly. The presence of abnormal collagen is associated with a variety of signs and symptoms, including loose joints, cardiac problems, and other complications associated with Ehlers-Danlos syndrome.

osteogenesis imperfecta - caused by mutations in the COL1A2 gene

About 300 disease-causing COL1A2 mutations have been identified. Mutations in this gene occasionally cause osteogenesis imperfecta type I, the mildest form of this disorder. Most COL1A2 mutations, however, cause more severe forms of osteogenesis imperfecta, including types II, III, and IV.

Some COL1A2 mutations delete pieces of the gene, which leads to a pro-α2(I) chain that is missing critical regions. Other genetic changes alter the sequence of protein building blocks (amino acids) in the pro-α2(I) chain, usually replacing the amino acid glycine with a different amino acid. In some cases, amino acid substitutions alter one end of the protein chain (called the C-terminus), which interferes with the assembly of collagen molecules. These COL1A2 mutations prevent the normal production of type I collagen. When abnormal collagen is incorporated into developing bones and other connective tissues, it causes the serious medical problems associated with severe forms of osteogenesis imperfecta.

other disorders - caused by mutations in the COL1A2 gene

Some people with COL1A2 mutations exhibit the signs and symptoms of both osteogenesis imperfecta and Ehlers-Danlos syndrome. These mutations include duplications of a large part of the gene, deletions of an important segment of the pro-α2(I) chain, and genetic changes that result in an abnormally shortened version of the pro-α2(I) chain. Mutations in the COL1A2 gene alter the structure of collagen fibrils or prevent normal cross-linking between collagen molecules. These defects weaken connective tissue, leading to the characteristic features of these two conditions.

Where is the COL1A2 gene located?

Cytogenetic Location: 7q22.1

Molecular Location on chromosome 7: base pairs 94,394,560 to 94,431,231

The COL1A2 gene is located on the long (q) arm of chromosome 7 at position 22.1.

The COL1A2 gene is located on the long (q) arm of chromosome 7 at position 22.1.

More precisely, the COL1A2 gene is located from base pair 94,394,560 to base pair 94,431,231 on chromosome 7.

See How do geneticists indicate the location of a gene? ( in the Handbook.

Where can I find additional information about COL1A2?

You and your healthcare professional may find the following resources about COL1A2 helpful.

You may also be interested in these resources, which are designed for genetics professionals and researchers.

What other names do people use for the COL1A2 gene or gene products?

  • alpha 2 collagen type I
  • Collagen I, alpha-2 polypeptide
  • Collagen of skin, tendon and bone, alpha-2 chain

See How are genetic conditions and genes named? ( in the Handbook.

What glossary definitions help with understanding COL1A2?

acids ; amino acid ; cardiac ; cartilage ; cell ; collagen ; connective tissue ; gene ; glycine ; molecule ; osteogenesis ; Pro ; protein ; sclera ; syndrome ; tendon ; tissue

You may find definitions for these and many other terms in the Genetics Home Reference Glossary (


  • Malfait F, Symoens S, Coucke P, Nunes L, De Almeida S, De Paepe A. Total absence of the alpha2(I) chain of collagen type I causes a rare form of Ehlers-Danlos syndrome with hypermobility and propensity to cardiac valvular problems. J Med Genet. 2006 Jul;43(7):e36. (
  • Marini JC, Forlino A, Cabral WA, Barnes AM, San Antonio JD, Milgrom S, Hyland JC, Körkkö J, Prockop DJ, De Paepe A, Coucke P, Symoens S, Glorieux FH, Roughley PJ, Lund AM, Kuurila-Svahn K, Hartikka H, Cohn DH, Krakow D, Mottes M, Schwarze U, Chen D, Yang K, Kuslich C, Troendle J, Dalgleish R, Byers PH. Consortium for osteogenesis imperfecta mutations in the helical domain of type I collagen: regions rich in lethal mutations align with collagen binding sites for integrins and proteoglycans. Hum Mutat. 2007 Mar;28(3):209-21. Review. (
  • NCBI Gene (
  • Nicholls AC, Valler D, Wallis S, Pope FM. Homozygosity for a splice site mutation of the COL1A2 gene yields a non-functional pro(alpha)2(I) chain and an EDS/OI clinical phenotype. J Med Genet. 2001 Feb;38(2):132-6. (
  • Persikov AV, Pillitteri RJ, Amin P, Schwarze U, Byers PH, Brodsky B. Stability related bias in residues replacing glycines within the collagen triple helix (Gly-Xaa-Yaa) in inherited connective tissue disorders. Hum Mutat. 2004 Oct;24(4):330-7. (
  • Pollitt R, McMahon R, Nunn J, Bamford R, Afifi A, Bishop N, Dalton A. Mutation analysis of COL1A1 and COL1A2 in patients diagnosed with osteogenesis imperfecta type I-IV. Hum Mutat. 2006 Jul;27(7):716. (
  • Raff ML, Craigen WJ, Smith LT, Keene DR, Byers PH. Partial COL1A2 gene duplication produces features of osteogenesis imperfecta and Ehlers-Danlos syndrome type VII. Hum Genet. 2000 Jan;106(1):19-28. (
  • Schwarze U, Hata R, McKusick VA, Shinkai H, Hoyme HE, Pyeritz RE, Byers PH. Rare autosomal recessive cardiac valvular form of Ehlers-Danlos syndrome results from mutations in the COL1A2 gene that activate the nonsense-mediated RNA decay pathway. Am J Hum Genet. 2004 May;74(5):917-30. Epub 2004 Apr 9. (
  • Venturi G, Tedeschi E, Mottes M, Valli M, Camilot M, Viglio S, Antoniazzi F, Tatò L. Osteogenesis imperfecta: clinical, biochemical and molecular findings. Clin Genet. 2006 Aug;70(2):131-9. Erratum in: Clin Genet. 2006 Nov;70(5):455. (


The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? ( in the Handbook.

Reviewed: November 2007
Published: December 22, 2014