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The official name of this gene is “collagen type XI alpha 2.”
COL11A2 is the gene's official symbol. The COL11A2 gene is also known by other names, listed below.
The COL11A2 gene provides instructions for making one component of type XI collagen, called the pro-alpha2(XI) chain. Type XI collagen adds structure and strength to the connective tissues that support the body's muscles, joints, organs, and skin. Type XI collagen is normally found in cartilage, a tough but flexible tissue that makes up much of the skeleton during early development. Most cartilage is later converted to bone, except for the cartilage that continues to cover and protect the ends of bones and is present in the nose and external ears. Type XI collagen is also part of the clear gel that fills the eyeball (the vitreous), the inner ear, and the center portion of the discs between the vertebrae in the spine (nucleus pulposus).
To construct type XI collagen, the pro-alpha2(XI) chain combines with two other collagen chains (pro-alpha1(XI) and pro-alpha1(II)) to form a procollagen molecule. These triple-stranded, ropelike procollagen molecules are then processed by enzymes in the cell. Once processed, procollagen molecules leave the cell and arrange themselves into long, thin fibrils that link to one another (cross-link) in the spaces around cells. The cross-linkages result in the formation of very strong mature type XI collagen fibers.
Type XI collagen also helps maintain the spacing and diameter of type II collagen fibrils. Type II collagen is an important component of the eye and mature cartilage tissue. The size and arrangement of type II collagen fibrils are essential for the normal structure of these tissues.
The COL11A2 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.
Mutations in the COL11A2 gene have been identified in people with nonsyndromic hearing loss, which is loss of hearing that is not associated with other signs and symptoms. Mutations in this gene can cause two forms of nonsyndromic hearing loss: DFNA13 and DFNB53.
DFNA13 is inherited in an autosomal dominant pattern, which means only one mutated copy of the COL11A2 gene in each cell is sufficient to cause the condition. This type of hearing loss begins in childhood or adolescence. It is classified as postlingual because it starts after a child learns to speak.
At least two COL11A2 gene mutations have been identified in people with DFNA13. Both of these mutations change a single protein building block (amino acid) in the pro-alpha2(XI) chain of type XI collagen. These mutations prevent the normal assembly of type XI collagen, which plays an important role in the structure and function of the inner ear.
DFNB53 is inherited in an autosomal recessive pattern, which means both copies of the COL11A2 gene are mutated in each cell. It is characterized by profound hearing loss that is present before a child learns to speak (prelingual).
At least three mutations in the COL11A2 gene have been found to cause DFNB53. Each of these mutations changes a single amino acid in the pro-alpha2(XI) chain of type XI collagen. Studies suggest that the altered protein causes hearing loss by impairing the assembly of type XI collagen or its ability to interact with other proteins.
Approximately 10 mutations in the COL11A2 gene have been found to cause otospondylomegaepiphyseal dysplasia (OSMED), a bone growth disorder. Most of these mutations result in a complete lack of pro-alpha2(XI) chains, which impairs the function of type XI collagen. Some mutations affect the production of the pro-alpha2(XI) chain and disrupt the assembly of type XI collagen. Type XI collagen is an important component of cartilage and other connective tissues, and its loss or impairment results in the characteristic signs and symptoms of OSMED.
Mutations in the COL11A2 gene can cause Stickler syndrome, a condition characterized by impaired skeletal development and hearing loss. COL11A2 mutations cause abnormal production of the pro-alpha2(XI) chain, part of type XI collagen. As a result, type XI collagen cannot function properly, causing the signs and symptoms of Stickler syndrome.
This type of Stickler syndrome is sometimes called the non-ocular type because it does not affect vision (unlike the other types of Stickler syndrome caused by mutations in other genes). The pro-alpha2(XI) chain is not found in the eyes and COL11A2 mutations do not affect vision. Instead, another type of collagen chain replaces pro-alpha2(XI) to form type XI collagen in the clear gel that fills the eyeball (the vitreous).
At least one mutation in the COL11A2 gene has been found to cause Weissenbacher-Zweymüller syndrome. This mutation replaces the amino acid glycine (a building block of proteins) with the amino acid glutamic acid at position 955 in the collagen pro-alpha2(XI) chain (written as Gly955Glu). This mutation prevents collagen molecules from being assembled properly, which disrupts the structure of type XI collagen. These changes in type XI collagen result in the characteristic signs and symptoms of Weissenbacher-Zweymüller syndrome, including short stature, distinctive facial features, and occasionally, hearing loss.
In some people, variations in the COL11A2 gene may increase the risk of developing osteoarthritis, a degenerative disease of joint cartilage. As a result of these genetic changes, incorrect amino acids are used in making the pro-alpha2(XI) chain of type XI collagen. The altered pro-alpha2(XI) chain may weaken collagen fibers, which could play a role in the erosion of cartilage in the joints, a characteristic feature of osteoarthritis.
Cytogenetic Location: 6p21.3
Molecular Location on chromosome 6: base pairs 33,162,692 to 33,193,152
The COL11A2 gene is located on the short (p) arm of chromosome 6 at position 21.3.
More precisely, the COL11A2 gene is located from base pair 33,162,692 to base pair 33,193,152 on chromosome 6.
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 COL11A2 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 ; autosomal ; autosomal dominant ; autosomal recessive ; cartilage ; cell ; collagen ; cross-link ; degenerative ; diameter ; dysplasia ; gene ; glutamic acid ; glycine ; inherited ; joint ; molecule ; mutation ; nucleus ; postlingual ; prelingual ; Pro ; protein ; recessive ; short stature ; stature ; syndrome ; tissue
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.