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Genetics Home Reference: your guide to understanding genetic conditions
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GNAT2

Reviewed January 2015

What is the official name of the GNAT2 gene?

The official name of this gene is “guanine nucleotide binding protein (G protein), alpha transducing activity polypeptide 2.”

GNAT2 is the gene's official symbol. The GNAT2 gene is also known by other names, listed below.

What is the normal function of the GNAT2 gene?

The GNAT2 gene provides instructions for making one part (called the cone-specific alpha subunit) of a protein called transducin. This protein is found in light-detecting (photoreceptor) cells called cones, which are located in a specialized tissue at the back of the eye known as the retina. Cones provide vision in bright light (daylight vision), including color vision. Other photoreceptor cells, called rods, provide vision in low light (night vision).

Transducin plays an essential role in transmitting visual signals from photoreceptor cells in the retina to the brain through a process called phototransduction. Photoreceptors contain special pigments (called photopigments) that absorb light. The photopigments activate transducin, which triggers a series of chemical reactions within the cell. These reactions alter the cell's electrical charge, ultimately generating a signal that is interpreted by the brain as vision.

How are changes in the GNAT2 gene related to health conditions?

achromatopsia - caused by mutations in the GNAT2 gene

At least 10 mutations in the GNAT2 gene have been found to cause the vision disorder achromatopsia. These mutations are a relatively uncommon cause of complete achromatopsia, a form of the disorder characterized by a total lack of color vision and other vision problems that are present from early infancy. GNAT2 gene mutations have also been identified in a few individuals with incomplete achromatopsia, a milder form of the disorder associated with limited color vision.

The GNAT2 gene mutations that underlie complete achromatopsia lead to an abnormally small, nonfunctional version of the cone-specific alpha subunit of transducin. Without this subunit, cones have no functional transducin, and they are unable to carry out phototransduction. (The subunit produced from the GNAT2 gene is specific to cones, so rods are typically unaffected by this disorder.) A loss of cone function underlies the lack of color vision and other vision problems in people with complete achromatopsia.

At least one known GNAT2 gene mutation causes incomplete achromatopsia. The mutation, which is written as c.461+2G>A, affects the way the gene's instructions are pieced together to form the subunit protein. This mutation allows the production of some functional cone-specific alpha subunit, although the amount of the subunit is greatly reduced. As a result, a small amount of functional transducin is available to play its role in phototransduction, and the partially functioning cones can transmit some visual information to the brain.

Where is the GNAT2 gene located?

Cytogenetic Location: 1p13.1

Molecular Location on chromosome 1: base pairs 109,602,905 to 109,619,661

The GNAT2 gene is located on the short (p) arm of chromosome 1 at position 13.1.

The GNAT2 gene is located on the short (p) arm of chromosome 1 at position 13.1.

More precisely, the GNAT2 gene is located from base pair 109,602,905 to base pair 109,619,661 on chromosome 1.

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 GNAT2?

You and your healthcare professional may find the following resources about GNAT2 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 GNAT2 gene or gene products?

  • ACHM4
  • cone-type transducin alpha subunit
  • GNAT2_HUMAN
  • GNATC
  • guanine nucleotide binding protein, alpha transducing activity polypeptide 2
  • transducin alpha-2 chain
  • transducin, cone-specific, alpha 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 GNAT2?

achromatopsia ; cell ; cones ; gene ; guanine ; mutation ; nucleotide ; photoreceptor ; protein ; retina ; rods ; subunit ; tissue

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

References

  • Aligianis IA, Forshew T, Johnson S, Michaelides M, Johnson CA, Trembath RC, Hunt DM, Moore AT, Maher ER. Mapping of a novel locus for achromatopsia (ACHM4) to 1p and identification of a germline mutation in the alpha subunit of cone transducin (GNAT2). J Med Genet. 2002 Sep;39(9):656-60. (http://www.ncbi.nlm.nih.gov/pubmed/12205108?dopt=Abstract)
  • Gene Review: Achromatopsia (http://www.ncbi.nlm.nih.gov/books/NBK1418)
  • Kohl S, Baumann B, Rosenberg T, Kellner U, Lorenz B, Vadalà M, Jacobson SG, Wissinger B. Mutations in the cone photoreceptor G-protein alpha-subunit gene GNAT2 in patients with achromatopsia. Am J Hum Genet. 2002 Aug;71(2):422-5. Epub 2002 Jun 20. (http://www.ncbi.nlm.nih.gov/pubmed/12077706?dopt=Abstract)
  • Michaelides M, Aligianis IA, Holder GE, Simunovic M, Mollon JD, Maher ER, Hunt DM, Moore AT. Cone dystrophy phenotype associated with a frameshift mutation (M280fsX291) in the alpha-subunit of cone specific transducin (GNAT2). Br J Ophthalmol. 2003 Nov;87(11):1317-20. Erratum in: Br J Ophthalmol. 2004 Feb;88(2):314. (http://www.ncbi.nlm.nih.gov/pubmed/14609822?dopt=Abstract)
  • NCBI Gene (http://www.ncbi.nlm.nih.gov/gene/2780)
  • Ouechtati F, Merdassi A, Bouyacoub Y, Largueche L, Derouiche K, Ouragini H, Nouira S, Tiab L, Baklouti K, Rebai A, Schorderet DF, Munier FL, Zografos L, Abdelhak S, El Matri L. Clinical and genetic investigation of a large Tunisian family with complete achromatopsia: identification of a new nonsense mutation in GNAT2 gene. J Hum Genet. 2011 Jan;56(1):22-8. doi: 10.1038/jhg.2010.128. Epub 2010 Nov 25. (http://www.ncbi.nlm.nih.gov/pubmed/21107338?dopt=Abstract)
  • Piña AL, Baumert U, Loyer M, Koenekoop RK. A three base pair deletion encoding the amino acid (lysine-270) in the alpha-cone transducin gene. Mol Vis. 2004 Apr 8;10:265-71. (http://www.ncbi.nlm.nih.gov/pubmed/15094710?dopt=Abstract)
  • Rosenberg T, Baumann B, Kohl S, Zrenner E, Jorgensen AL, Wissinger B. Variant phenotypes of incomplete achromatopsia in two cousins with GNAT2 gene mutations. Invest Ophthalmol Vis Sci. 2004 Dec;45(12):4256-62. (http://www.ncbi.nlm.nih.gov/pubmed/15557429?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: January 2015
Published: March 23, 2015