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


Reviewed December 2015

What is the official name of the C3 gene?

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.

What is the normal function of the C3 gene?

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.

Does the C3 gene share characteristics with other genes?

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? ( in the Handbook.

How are changes in the C3 gene related to health conditions?

C3 glomerulopathy - caused by mutations in the C3 gene

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.

other disorders - caused by mutations in the C3 gene

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).

Where is the C3 gene located?

Cytogenetic Location: 19p13.3-p13.2

Molecular Location on chromosome 19: base pairs 6,677,835 to 6,720,682

(Homo sapiens Annotation Release 107, GRCh38.p2) (NCBI (

The C3 gene is located on the short (p) arm of chromosome 19 between positions 13.3 and 13.2.

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? ( in the Handbook.

Where can I find additional information about C3?

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.

What other names do people use for the C3 gene or gene products?

  • acylation-stimulating protein cleavage product
  • AHUS5
  • ARMD9
  • ASP
  • C3a
  • C3 and PZP-like alpha-2-macroglobulin domain-containing protein 1
  • C3b
  • complement C3
  • CPAMD1

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

What glossary definitions help with understanding C3?

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.


  • Martínez-Barricarte R, Heurich M, Valdes-Cañedo F, Vazquez-Martul E, Torreira E, Montes T, Tortajada A, Pinto S, Lopez-Trascasa M, Morgan BP, Llorca O, Harris CL, Rodríguez de Córdoba S. Human C3 mutation reveals a mechanism of dense deposit disease pathogenesis and provides insights into complement activation and regulation. J Clin Invest. 2010 Oct;120(10):3702-12. doi: 10.1172/JCI43343. Epub 2010 Sep 13. (
  • NCBI Gene (
  • Okura Y, Kobayashi I, Yamada M, Sasaki S, Yamada Y, Kamioka I, Kanai R, Takahashi Y, Ariga T. Clinical characteristics and genotype-phenotype correlations in C3 deficiency. J Allergy Clin Immunol. 2015 Oct 1. pii: S0091-6749(15)01241-5. doi: 10.1016/j.jaci.2015.08.017. [Epub ahead of print]. (
  • Xiao X, Pickering MC, Smith RJ. C3 glomerulopathy: the genetic and clinical findings in dense deposit disease and C3 glomerulonephritis. Semin Thromb Hemost. 2014 Jun;40(4):465-71. doi: 10.1055/s-0034-1376334. Epub 2014 May 5. Review. (
  • Zipfel PF, Skerka C, Chen Q, Wiech T, Goodship T, Johnson S, Fremeaux-Bacchi V, Nester C, de Córdoba SR, Noris M, Pickering M, Smith R. The role of complement in C3 glomerulopathy. Mol Immunol. 2015 Sep;67(1):21-30. doi: 10.1016/j.molimm.2015.03.012. Epub 2015 Apr 28. Review. (


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: December 2015
Published: February 8, 2016