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


Reviewed March 2006

What is the official name of the CNGA3 gene?

The official name of this gene is “cyclic nucleotide gated channel alpha 3.”

CNGA3 is the gene's official symbol. The CNGA3 gene is also known by other names, listed below.

What is the normal function of the CNGA3 gene?

The CNGA3 gene provides instructions for making a protein that forms part of an ion channel. Ion channels are openings in the cell membrane that transport electrically charged atoms (ions) into and out of cells. Specifically, the CNGA3 protein is part of a family of proteins that form cyclic nucleotide-gated (CNG) channels. CNG channels are involved in transmitting information about vision and smell from sensory cells to the brain.

The CNGA3 protein forms one part (the alpha subunit) of a CNG channel that is necessary for normal vision. These channels are present in light receptor cells called cones. As part of the light-sensitive tissue at the back of the eye (the retina), cones provide vision in bright light, including color vision. Other light receptor cells in the retina, called rods, are responsible for vision in low light.

In cones, CNG channels remain open under dark conditions. Positively charged ions can flow into the cell through these open channels. In response to light, these channels close to stop the inward flow of ions. This change in ion transport alters the cone cell's electrical charge, which generates a signal that the brain interprets as vision.

Does the CNGA3 gene share characteristics with other genes?

The CNGA3 gene belongs to a family of genes called CNG (cyclic nucleotide-regulated channels).

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 CNGA3 gene related to health conditions?

color vision deficiency - caused by mutations in the CNGA3 gene

More than 50 mutations in the CNGA3 gene have been identified in individuals with color vision deficiency. These mutations typically cause complete achromatopsia, which is a loss of all color vision. Most of the reported mutations change a single protein building block (an amino acid) in the CNGA3 protein, which changes the structure of CNG channels made with this protein. The altered CNG channels cannot regulate the flow of ions into cones. As a result, these light receptor cells are unable to transmit visual signals to the brain. A loss of normal cone function causes a lack of color vision, reduced sharpness, and other vision problems associated with complete achromatopsia.

A few mutations in the CNGA3 gene cause incomplete achromatopsia, a condition that causes impaired color vision. These mutations likely allow partial function of CNG channels in cones. The partially functional cones can transmit some visual information to the brain, causing a form of color vision deficiency that is usually milder than complete achromatopsia.

Where is the CNGA3 gene located?

Cytogenetic Location: 2q11.2

Molecular Location on chromosome 2: base pairs 98,346,154 to 98,398,600

The CNGA3 gene is located on the long (q) arm of chromosome 2 at position 11.2.

The CNGA3 gene is located on the long (q) arm of chromosome 2 at position 11.2.

More precisely, the CNGA3 gene is located from base pair 98,346,154 to base pair 98,398,600 on chromosome 2.

See How do geneticists indicate the location of a gene? ( in the Handbook.

Where can I find additional information about CNGA3?

You and your healthcare professional may find the following resources about CNGA3 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 CNGA3 gene or gene products?

  • ACHM2
  • CCNC1
  • CCNCa
  • CCNCalpha
  • CNCG3
  • CNG3
  • cone photoreceptor cGMP-gated channel alpha subunit

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

What glossary definitions help with understanding CNGA3?

achromatopsia ; amino acid ; cell ; cell membrane ; channel ; cone cell ; cones ; deficiency ; gene ; ions ; ion transport ; nucleotide ; photoreceptor ; protein ; receptor ; retina ; rods ; sensory cells ; subunit ; tissue

You may find definitions for these and many other terms in the Genetics Home Reference Glossary (


  • Gene Review: Achromatopsia (
  • Johnson S, Michaelides M, Aligianis IA, Ainsworth JR, Mollon JD, Maher ER, Moore AT, Hunt DM. Achromatopsia caused by novel mutations in both CNGA3 and CNGB3. J Med Genet. 2004 Feb;41(2):e20. (
  • Koeppen K, Reuter P, Ladewig T, Kohl S, Baumann B, Jacobson SG, Plomp AS, Hamel CP, Janecke AR, Wissinger B. Dissecting the pathogenic mechanisms of mutations in the pore region of the human cone photoreceptor cyclic nucleotide-gated channel. Hum Mutat. 2010 Jul;31(7):830-9. doi: 10.1002/humu.21283. (
  • Kohl S, Marx T, Giddings I, Jägle H, Jacobson SG, Apfelstedt-Sylla E, Zrenner E, Sharpe LT, Wissinger B. Total colourblindness is caused by mutations in the gene encoding the alpha-subunit of the cone photoreceptor cGMP-gated cation channel. Nat Genet. 1998 Jul;19(3):257-9. (
  • NCBI Gene (
  • Patel KA, Bartoli KM, Fandino RA, Ngatchou AN, Woch G, Carey J, Tanaka JC. Transmembrane S1 mutations in CNGA3 from achromatopsia 2 patients cause loss of function and impaired cellular trafficking of the cone CNG channel. Invest Ophthalmol Vis Sci. 2005 Jul;46(7):2282-90. (
  • Reuter P, Koeppen K, Ladewig T, Kohl S, Baumann B, Wissinger B; Achromatopsia Clinical Study Group. Mutations in CNGA3 impair trafficking or function of cone cyclic nucleotide-gated channels, resulting in achromatopsia. Hum Mutat. 2008 Oct;29(10):1228-36. doi: 10.1002/humu.20790. (
  • Tränkner D, Jägle H, Kohl S, Apfelstedt-Sylla E, Sharpe LT, Kaupp UB, Zrenner E, Seifert R, Wissinger B. Molecular basis of an inherited form of incomplete achromatopsia. J Neurosci. 2004 Jan 7;24(1):138-47. (
  • Wissinger B, Gamer D, Jägle H, Giorda R, Marx T, Mayer S, Tippmann S, Broghammer M, Jurklies B, Rosenberg T, Jacobson SG, Sener EC, Tatlipinar S, Hoyng CB, Castellan C, Bitoun P, Andreasson S, Rudolph G, Kellner U, Lorenz B, Wolff G, Verellen-Dumoulin C, Schwartz M, Cremers FP, Apfelstedt-Sylla E, Zrenner E, Salati R, Sharpe LT, Kohl S. CNGA3 mutations in hereditary cone photoreceptor disorders. Am J Hum Genet. 2001 Oct;69(4):722-37. Epub 2001 Aug 30. (


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: March 2006
Published: December 16, 2014