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CNGA3 gene
URL of this page: https://medlineplus.gov/genetics/gene/cnga3/

CNGA3 gene

cyclic nucleotide gated channel subunit alpha 3

Normal Function

The CNGA3 gene provides instructions for making one part (the alpha subunit) of the cyclic nucleotide-gated (CNG) channel. These channels are found exclusively in light-sensing (photoreceptor) cells called cones, which are located in a specialized tissue at the back of the eye (retina). Cones provide color vision and vision in bright light (daytime vision). Other photoreceptor cells, called rods, provide vision in low light (night vision).

CNG channels are openings in the cell membrane that transport positively charged atoms (ions) into cells. The CNG channels in cones remain open in low light, allowing ions to flow in. When light enters the eye, these channels close, stopping the flow of ions. This change in ion transport alters the cone's electrical charge, which ultimately generates a signal. This signal is sent to the brain, where it combines with other visual information and is interpreted as vision. The process of translating light into an electrical signal is called phototransduction.

Health Conditions Related to Genetic Changes

Achromatopsia

Variants (also called mutations) in the CNGA3 gene can cause achromatopsia. Achromatopsia is a disorder of the retina. Some people with achromatopsia cannot perceive any color; they see only black, white, and shades of gray. Other affected individuals can see some color. Approximately 30 to 40 percent of people with achromatopsia have a variant in the CNGA3 gene. CNGA3 gene variants are more common in affected individuals from the Middle East and China. 

Most of the CNGA3 gene variants that cause achromatopsia result in the substitution of one protein building block (amino acid) for another in the alpha subunit. This altered protein impairs the function of the CNG channels, which impairs the cones' ability to respond to light. This causes the lack of color vision and contributes to the other vision problems found in people with this condition.

More About This Health Condition

Cone-rod dystrophy

MedlinePlus Genetics provides information about Cone-rod dystrophy

More About This Health Condition

Other disorders

Variants in the CNGA3 gene have also been found in some people with progressive cone dystrophy. Like achromatopsia, this condition affects the function of cones. However, individuals with progressive cone dystrophy begin having problems with cone function in childhood or adolescence. Progressive cone dystrophy causes vision problems, such as an increased sensitivity to light and a reduced ability to see color, that worsen over time. It is unclear why some CNGA3 gene variants cause achromatopsia, while others result in progressive cone dystrophy.

Other Names for This Gene

  • ACHM2
  • cyclic nucleotide-gated channel, alpha-3

Additional Information & Resources

Tests Listed in the Genetic Testing Registry

Scientific Articles on PubMed

Catalog of Genes and Diseases from OMIM

Gene and Variant Databases

References

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  • Hirji N, Aboshiha J, Georgiou M, Bainbridge J, Michaelides M. Achromatopsia: clinical features, molecular genetics, animal models and therapeutic options. Ophthalmic Genet. 2018 Apr;39(2):149-157. doi: 10.1080/13816810.2017.1418389. Epub 2018 Jan 5. Citation on PubMed
  • 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. doi: 10.1136/jmg.2003.011437. No abstract available. Citation on PubMed or Free article on PubMed Central
  • 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. Citation on PubMed
  • Kohl S, Jagle H, Wissinger B, Zobor D. Achromatopsia. 2004 Jun 24 [updated 2018 Sep 20]. In: Adam MP, Feldman J, Mirzaa GM, Pagon RA, Wallace SE, Amemiya A, editors. GeneReviews(R) [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2025. Available from http://www.ncbi.nlm.nih.gov/books/NBK1418/ Citation on PubMed
  • Kohl S, Marx T, Giddings I, Jagle 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. doi: 10.1038/935. Citation on PubMed
  • Li S, Huang L, Xiao X, Jia X, Guo X, Zhang Q. Identification of CNGA3 mutations in 46 families: common cause of achromatopsia and cone-rod dystrophies in Chinese patients. JAMA Ophthalmol. 2014 Sep;132(9):1076-83. doi: 10.1001/jamaophthalmol.2014.1032. Citation on PubMed
  • Michalakis S, Gerhardt M, Rudolph G, Priglinger S, Priglinger C. Achromatopsia: Genetics and Gene Therapy. Mol Diagn Ther. 2022 Jan;26(1):51-59. doi: 10.1007/s40291-021-00565-z. Epub 2021 Dec 3. Citation on PubMed
  • 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. doi: 10.1167/iovs.05-0179. Citation on PubMed
  • 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. Citation on PubMed
  • Sun W, Zhang Q. Diseases associated with mutations in CNGA3: Genotype-phenotype correlation and diagnostic guideline. Prog Mol Biol Transl Sci. 2019;161:1-27. doi: 10.1016/bs.pmbts.2018.10.002. Epub 2018 Nov 23. Citation on PubMed
  • Thiadens AA, Roosing S, Collin RW, van Moll-Ramirez N, van Lith-Verhoeven JJ, van Schooneveld MJ, den Hollander AI, van den Born LI, Hoyng CB, Cremers FP, Klaver CC. Comprehensive analysis of the achromatopsia genes CNGA3 and CNGB3 in progressive cone dystrophy. Ophthalmology. 2010 Apr;117(4):825-30.e1. doi: 10.1016/j.ophtha.2009.09.008. Epub 2010 Jan 15. Citation on PubMed
  • Trankner D, Jagle 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. doi: 10.1523/JNEUROSCI.3883-03.2004. Citation on PubMed
  • Wissinger B, Gamer D, Jagle 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. doi: 10.1086/323613. Epub 2001 Aug 30. Citation on PubMed or Free article on PubMed Central

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