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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.
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.
A component of type I collagen called the pro-α2(I) chain is produced from the COL1A2 gene. Collagens begin as rope-like procollagen molecules that are each made up of three chains. Type I collagen is composed of two pro-α1(I) chains (which are produced from the COL1A1 gene) and one pro-α2(I) chain.
The triple-stranded procollagen molecules are processed by enzymes outside the cell to create mature collagen. The collagen molecules then arrange themselves into long, thin fibrils that form stable interactions (cross-links) with one another in the spaces between cells. The cross-links result in the formation of very strong type I collagen fibers.
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? (http://ghr.nlm.nih.gov/handbook/howgeneswork/genefamilies) in the Handbook.
Several mutations in the COL1A2 gene can cause a form of Ehlers-Danlos syndrome known as the arthrochalasia type. Ehlers-Danlos syndrome is a group of disorders that affect the connective tissues that support the skin, bones, blood vessels, and many other organs and tissues. The arthrochalasia type is characterized by an unusually large range of joint movement (hypermobility) and dislocations of both hips at birth. The genetic changes, which affect one copy of the COL1A2 gene in each cell, lead to the production of a pro-α2(I) chain that is missing a critical segment. The absence of this segment interferes with the assembly and processing of pro-α2(I) chains into mature type I 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 a form of Ehlers-Danlos syndrome described as the cardiac valvular type. This rare condition is characterized by abnormalities of the valves in the heart, highly stretchy (elastic) skin, and joint hypermobility. The mutations that cause this form of the disorder 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 abnormal collagen weakens connective tissues, which causes the signs and symptoms of this condition.
Mutations in the COL1A2 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. People with this condition have bones that break easily, often from mild trauma or with no apparent cause.
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.
People with certain COL1A2 mutations exhibit the signs and symptoms of both osteogenesis imperfecta and Ehlers-Danlos syndrome (described above). 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 type I collagen fibrils, which weakens connective tissue and leads to the characteristic features of these two conditions.
Cytogenetic Location: 7q22.1
Molecular Location on chromosome 7: base pairs 94,394,561 to 94,431,232
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 94,394,561 to base pair 94,431,232 on chromosome 7.
See How do geneticists indicate the location of a gene? (http://ghr.nlm.nih.gov/handbook/howgeneswork/genelocation) in the Handbook.
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.
See How are genetic conditions and genes named? (http://ghr.nlm.nih.gov/handbook/mutationsanddisorders/naming) in the Handbook.
acids ; amino acid ; cardiac ; cartilage ; cell ; collagen ; connective tissue ; elastic ; gene ; glycine ; hypermobility ; joint ; molecule ; osteogenesis ; Pro ; protein ; sclera ; syndrome ; tendon ; tissue ; trauma
You may find definitions for these and many other terms in the Genetics Home Reference Glossary.
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? (http://ghr.nlm.nih.gov/handbook/consult/findingprofessional) in the Handbook.