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The official name of this gene is “collagen type IV alpha 3.”
COL4A3 is the gene's official symbol. The COL4A3 gene is also known by other names, listed below.
The COL4A3 gene provides instructions for making one component of type IV collagen, which is a flexible protein. Specifically, this gene makes the alpha3(IV) chain of type IV collagen. This chain combines with two other types of alpha (IV) chains (the alpha4 and alpha5 chains) to make a complete type IV collagen molecule. Type IV collagen molecules attach to each other to form complex protein networks. These networks make up a large portion of basement membranes, which are thin sheet-like structures that separate and support cells in many tissues. Type IV collagen alpha3-4-5 networks play an especially important role in the basement membranes of the kidney, inner ear, and eye.
The COL4A3 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.
More than 40 mutations in the COL4A3 gene have been found to cause Alport syndrome. Most of these mutations change single protein building blocks (amino acids) in a region where the alpha3(IV) collagen chain combines with other type IV collagen chains. Other mutations in the COL4A3 gene severely decrease or prevent the production of alpha3(IV) chains. As a result, there is a serious deficiency of the type IV collagen alpha3-4-5 network in the basement membranes of the kidney, inner ear, and eye. In the kidney, other types of collagen accumulate in the basement membranes, eventually leading to scarring of the kidneys and kidney failure. Mutations in this gene can also lead to abnormal function in the inner ear, resulting in hearing loss.
Mutations in the COL4A3 gene have been found to cause thin basement membrane nephropathy. This condition typically causes people to have blood in their urine (hematuria) but no other signs or symptoms of kidney disease. In the past, this condition was often called benign familial hematuria. Thin basement membrane nephropathy rarely progresses to kidney failure.
Goodpasture syndrome is a severe disease of the lungs and the kidneys caused by antibodies to the alpha3(IV) collagen chains. Antibodies are immune system proteins that normally attack foreign substances such as bacteria or viruses, but in Goodpasture syndrome, they target alpha3(IV) collagen chains. It remains unclear why some people make antibodies to their own collagen chains. The antibodies cause inflammation when they attach (bind) to the basement membranes of blood vessels in the air sacs (alveoli) of the lungs and filtering units (glomeruli) of the kidneys. As a result, people with Goodpasture syndrome can develop kidney failure and bleeding in the lungs, which causes them to cough up blood. In some people, antibodies attack only the kidneys. These people are said to have anti-glomerular basement membrane nephritis.
Cytogenetic Location: 2q36-q37
Molecular Location on chromosome 2: base pairs 227,164,565 to 227,314,792
The COL4A3 gene is located on the long (q) arm of chromosome 2 between positions 36 and 37.
More precisely, the COL4A3 gene is located from base pair 227,164,565 to base pair 227,314,792 on chromosome 2.
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 COL4A3 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 ; alveoli ; bacteria ; basement membrane ; basement membranes ; benign ; collagen ; deficiency ; familial ; gene ; hematuria ; immune system ; inflammation ; kidney ; molecule ; nephritis ; nephropathy ; protein ; syndrome
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.