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.
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 98,962,617 to 99,015,063
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 98,962,617 to base pair 99,015,063 on chromosome 2.
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 CNGA3?
You and your healthcare professional may find the following resources about CNGA3 helpful.
Educational resources - Information pages
- Human Vision and Color Perception, Molecular Expressions Optical Microscopy Primer (http://micro.magnet.fsu.edu/primer/lightandcolor/humanvisionintro.html)
- Phototransduction (Neuroscience, Second Edition, 2001) (http://www.ncbi.nlm.nih.gov/books/NBK10806/)
- Gene Reviews - Clinical summary (http://www.ncbi.nlm.nih.gov/books/NBK1418/)
Genetic Testing Registry - Repository of genetic test information
- GTR: Genetic tests for CNGA3 (http://www.ncbi.nlm.nih.gov/gtr/tests/?term=1261%5Bgeneid%5D)
You may also be interested in these resources, which are designed for genetics professionals and researchers.
- PubMed - Recent literature (http://www.ncbi.nlm.nih.gov/pubmed?term=((CNGA3%5BTIAB%5D)%20OR%20(cyclic%20nucleotide%20gated%20channel%20alpha%203%5BTIAB%5D))%20OR%20((ACHM2%5BTIAB%5D)%20OR%20(CCNC1%5BTIAB%5D)%20OR%20(CCNCa%5BTIAB%5D)%20OR%20(CCNCalpha%5BTIAB%5D)%20OR%20(CNCG3%5BTIAB%5D)%20OR%20(CNG3%5BTIAB%5D))%20AND%20((Genes%5BMH%5D)%20OR%20(Genetic%20Phenomena%5BMH%5D))%20AND%20english%5Bla%5D%20AND%20human%5Bmh%5D%20AND%20%22last%202880%20days%22%5Bdp%5D)
- OMIM - Genetic disorder catalog (http://omim.org/entry/600053)
Research Resources - Tools for researchers
- Atlas of Genetics and Cytogenetics in Oncology and Haematology (http://atlasgeneticsoncology.org/Genes/GC_CNGA3.html)
- Entrez Gene (http://www.ncbi.nlm.nih.gov/gene/1261)
- GeneCards (http://www.genecards.org/cgi-bin/carddisp.pl?id_type=entrezgene&id=1261)
- HUGO Gene Nomenclature Committee (http://www.genenames.org/data/hgnc_data.php?hgnc_id=2150)
What other names do people use for the CNGA3 gene or gene products?
- Cone photoreceptor cGMP-gated channel alpha subunit
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 CNGA3?
amino acid ;
cell membrane ;
cone cell ;
ion transport ;
sensory cells ;
You may find definitions for these and many other terms in the Genetics Home Reference
- Deeb SS. Molecular genetics of color-vision deficiencies. Vis Neurosci. 2004 May-Jun;21(3):191-6. Review. (http://www.ncbi.nlm.nih.gov/pubmed/15518188?dopt=Abstract)
- Entrez Gene (http://www.ncbi.nlm.nih.gov/gene/1261)
- Gene Review: Achromatopsia (http://www.ncbi.nlm.nih.gov/books/NBK1418/)
- 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. (http://www.ncbi.nlm.nih.gov/pubmed/14757870?dopt=Abstract)
- 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. (http://www.ncbi.nlm.nih.gov/pubmed/9662398?dopt=Abstract)
- Michaelides M, Hunt DM, Moore AT. The cone dysfunction syndromes. Br J Ophthalmol. 2004 Feb;88(2):291-7. Review. (http://www.ncbi.nlm.nih.gov/pubmed/14736794?dopt=Abstract)
- 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. (http://www.ncbi.nlm.nih.gov/pubmed/15980212?dopt=Abstract)
- 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. (http://www.ncbi.nlm.nih.gov/pubmed/14715947?dopt=Abstract)
- 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. (http://www.ncbi.nlm.nih.gov/pubmed/11536077?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
See How can I find a genetics professional in my area? (http://ghr.nlm.nih.gov/handbook/consult/findingprofessional) in the Handbook.