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The official name of this gene is “complement component 3.”
C3 is the gene's official symbol. The C3 gene is also known by other names, listed below.
The C3 gene provides instructions for making a protein called complement component 3 (or C3). This protein plays a key role in a part of the body's immune response known as the complement system. The complement system is a group of proteins that work together to destroy foreign invaders (such as bacteria and viruses), trigger inflammation, and remove debris from cells and tissues.
The C3 protein is essential for turning on (activating) the complement system. The presence of foreign invaders triggers the C3 protein to be cut (cleaved) into two smaller pieces. One of these pieces, called C3b, interacts with several other proteins on the surface of cells to trigger the complement system's response. This process must be carefully regulated so the complement system targets only unwanted materials and does not damage the body's healthy cells.
Researchers have identified two major forms (allotypes) of the C3 protein, which are known as C3S and C3F. In the general population, C3S is more common than C3F. The two allotypes differ by a single protein building block (amino acid), although it is unclear whether they function differently.
The C3 gene belongs to a family of genes called complement (complement system). It also belongs to a family of genes called endogenous ligands (endogenous ligands).
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.
At least one mutation in the C3 gene has been found to cause a rare form of kidney disease called C3 glomerulopathy. This disorder damages the kidneys and can lead to end-stage renal disease (ESRD), a life-threatening condition that prevents the kidneys from filtering fluids and waste products from the body effectively.
The identified C3 gene mutation deletes two amino acids from the C3 protein. This genetic change is described as a "gain-of-function" mutation because it leads to an altered version of the protein that overactivates the complement system. The overactive system damages structures in the kidneys called glomeruli, which are clusters of tiny blood vessels that help filter waste products from the blood. Damage to glomeruli prevents the kidneys from filtering waste products normally and can lead to ESRD.
Several other changes in the C3 gene do not cause C3 glomerulopathy directly but appear to increase the likelihood of developing the disorder. In particular, the C3F allotype is seen more frequently in people with this condition than in the general population. Researchers are working to determine how the C3F allotype may influence disease risk.
At least 17 mutations in the C3 gene have been found to cause C3 deficiency, a rare condition characterized by recurrent bacterial infections beginning in childhood. The genetic changes that cause C3 deficiency lead to an altered version of the C3 protein or prevent cells from producing any of this protein. These mutations are described as "loss-of-function" because the abnormal or missing C3 protein prevents normal activation of the complement system. As a result, the immune system is less able to protect the body against foreign invaders (such as bacteria).
Cytogenetic Location: 19p13.3-p13.2
Molecular Location on chromosome 19: base pairs 6,677,835 to 6,720,682
The C3 gene is located on the short (p) arm of chromosome 19 between positions 13.3 and 13.2.
More precisely, the C3 gene is located from base pair 6,677,835 to base pair 6,720,682 on chromosome 19.
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 C3 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 ; Asp ; atypical ; bacteria ; deficiency ; domain ; end-stage renal disease ; ESRD ; gene ; hydrolysis ; immune response ; immune system ; inflammation ; innate immunity ; kidney ; mutation ; population ; protein ; renal ; renal disease ; stage ; 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.