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Genetics Home Reference: your guide to understanding genetic conditions
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FGG

Reviewed February 2012

What is the official name of the FGG gene?

The official name of this gene is “fibrinogen gamma chain.”

FGG is the gene's official symbol. The FGG gene is also known by other names, listed below.

What is the normal function of the FGG gene?

The FGG gene provides instructions for making the fibrinogen gamma (γ) chain, one piece (subunit) of the fibrinogen protein. This protein is important for blood clot formation (coagulation), which is needed to stop excessive bleeding after injury. To form fibrinogen, the γ chain attaches to the fibrinogen A alpha (Aα) and fibrinogen B beta (Bβ) chains, each produced from different genes. Two sets of this three-protein complex combine to form functional fibrinogen.

For coagulation to occur, another protein called thrombin removes a piece from the Aα and the Bβ subunits of the functional fibrinogen protein (the pieces are called the A and B fibrinopeptides). This process converts fibrinogen to fibrin, the main protein in blood clots. Fibrin proteins attach to each other, forming a stable network that makes up the blood clot.

Does the FGG gene share characteristics with other genes?

The FGG gene 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.

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

congenital afibrinogenemia - caused by mutations in the FGG gene

Mutations in the FGG gene can lead to congenital afibrinogenemia, a condition that causes excessive bleeding due to the absence of fibrinogen protein in the blood. Most FGG gene mutations that cause this condition lead to an abnormally short blueprint for protein formation (mRNA). If any fibrinogen γ chain is produced, it is nonfunctional. Because this condition occurs when both copies of the FGG gene are altered, there is a complete absence of functional fibrinogen γ chain. Without the γ subunit, the fibrinogen protein is not assembled, which results in the absence of fibrin. As a result, blood clots do not form in response to injury, leading to the excessive bleeding seen in people with congenital afibrinogenemia.

other disorders - caused by mutations in the FGG gene

Mutations in one or both copies of the FGG gene can cause other bleeding disorders known as hypofibrinogenemia, dysfibrinogenemia, or hypodysfibrinogenemia.

Hypofibrinogenemia is a condition characterized by decreased levels of fibrinogen in the blood. This condition is caused by mutations that reduce but do not eliminate the production of the fibrinogen γ chain. People with hypofibrinogenemia can have bleeding problems that vary from mild to severe. Generally, the less fibrinogen in the blood, the more severe the bleeding problems are.

Dysfibrinogenemia is a condition characterized by abnormally functioning fibrinogen, although the protein is present at normal levels. This condition is usually caused by mutations that change a single protein building block (amino acid) in the fibrinogen γ chain. These mutations alter the function of the fibrinogen protein and, depending on the functional change, can lead to excessive bleeding or abnormal blood clotting (thrombosis).

Hypodysfibrinogenemia is a condition characterized by low levels of abnormally functioning fibrinogen protein in the blood. As in dysfibrinogenemia, this condition can result in excessive bleeding or thrombosis.

Where is the FGG gene located?

Cytogenetic Location: 4q28

Molecular Location on chromosome 4: base pairs 154,604,133 to 154,612,749

The FGG gene is located on the long (q) arm of chromosome 4 at position 28.

The FGG gene is located on the long (q) arm of chromosome 4 at position 28.

More precisely, the FGG gene is located from base pair 154,604,133 to base pair 154,612,749 on chromosome 4.

See How do geneticists indicate the location of a gene? (http://ghr.nlm.nih.gov/handbook/howgeneswork/genelocation) in the Handbook.

Where can I find additional information about FGG?

You and your healthcare professional may find the following resources about FGG 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 FGG gene or gene products?

  • FIBG_HUMAN
  • fibrinogen gamma chain isoform gamma-A precursor
  • fibrinogen gamma chain isoform gamma-B precursor
  • fibrinogen, gamma polypeptide

See How are genetic conditions and genes named? (http://ghr.nlm.nih.gov/handbook/mutationsanddisorders/naming) in the Handbook.

What glossary definitions help with understanding FGG?

amino acid ; blood clotting ; clotting ; coagulation ; congenital ; fibrin ; fibrinogen ; gene ; injury ; mRNA ; precursor ; protein ; subunit ; thrombin ; thrombosis

You may find definitions for these and many other terms in the Genetics Home Reference Glossary (http://www.ghr.nlm.nih.gov/glossary).

References

  • NCBI Gene (http://www.ncbi.nlm.nih.gov/gene/2266)
  • Neerman-Arbez M, de Moerloose P, Honsberger A, Parlier G, Arnuti B, Biron C, Borg JY, Eber S, Meili E, Peter-Salonen K, Ripoll L, Vervel C, d'Oiron R, Staeger P, Antonarakis SE, Morris MA. Molecular analysis of the fibrinogen gene cluster in 16 patients with congenital afibrinogenemia: novel truncating mutations in the FGA and FGG genes. Hum Genet. 2001 Mar;108(3):237-40. (http://www.ncbi.nlm.nih.gov/pubmed/11354637?dopt=Abstract)
  • Neerman-Arbez M. Molecular basis of fibrinogen deficiency. Pathophysiol Haemost Thromb. 2006;35(1-2):187-98. Review. (http://www.ncbi.nlm.nih.gov/pubmed/16855369?dopt=Abstract)
  • OMIM: FIBRINOGEN, G GAMMA POLYPEPTIDE (http://omim.org/entry/134850)
  • Weisel JW. Fibrinogen and fibrin. Adv Protein Chem. 2005;70:247-99. Review. (http://www.ncbi.nlm.nih.gov/pubmed/15837518?dopt=Abstract)

 

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.

 
Reviewed: February 2012
Published: August 18, 2014