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Genetics Home Reference: your guide to understanding genetic conditions
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CNGB3

Reviewed March 2006

What is the official name of the CNGB3 gene?

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

CNGB3 is the gene's official symbol. The CNGB3 gene is also known by other names, listed below.

What is the normal function of the CNGB3 gene?

The CNGB3 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 CNGB3 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 CNGB3 protein forms one part (the beta 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 CNGB3 gene share characteristics with other genes?

The CNGB3 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? (http://ghr.nlm.nih.gov/handbook/howgeneswork/genefamilies) in the Handbook.

How are changes in the CNGB3 gene related to health conditions?

color vision deficiency - caused by mutations in the CNGB3 gene

More than 25 mutations in the CNGB3 gene have been identified in people with color vision deficiency. These mutations cause complete achromatopsia, which is a loss of all color vision. Worldwide, the most common mutation that causes this condition deletes a single DNA building block (a base pair) from the CNGB3 gene. This mutation can be written as 1148delC.

Complete achromatopsia occurs frequently in Pingelapese islanders, who live on one of the Eastern Caroline Islands of Micronesia. Among the Pingelapese, this condition results from a mutation that changes a single protein building block (an amino acid) in the CNGB3 protein. This mutation replaces the amino acid serine with the amino acid phenylalanine at position 435 in the protein (written as Ser435Phe or S435F).

Mutations in the CNGB3 gene probably lead to an abnormally small, nonfunctional version of the CNGB3 protein that cannot form working CNG channels. Without these channels, cones cannot regulate the inward flow of ions. 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.

Where is the CNGB3 gene located?

Cytogenetic Location: 8q21.3

Molecular Location on chromosome 8: base pairs 86,573,934 to 86,743,674

The CNGB3 gene is located on the long (q) arm of chromosome 8 at position 21.3.

The CNGB3 gene is located on the long (q) arm of chromosome 8 at position 21.3.

More precisely, the CNGB3 gene is located from base pair 86,573,934 to base pair 86,743,674 on chromosome 8.

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 CNGB3?

You and your healthcare professional may find the following resources about CNGB3 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 CNGB3 gene or gene products?

  • ACHM3
  • CNGB3_HUMAN
  • cone photoreceptor cGMP-gated cation channel beta-subunit
  • cyclic nucleotide-gated cation channel modulatory 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 CNGB3?

achromatopsia ; amino acid ; base pair ; cation ; cell ; cell membrane ; channel ; cone cell ; cones ; deficiency ; DNA ; gene ; ions ; ion transport ; mutation ; nucleotide ; phenylalanine ; photoreceptor ; protein ; receptor ; retina ; rods ; sensory cells ; serine ; subunit ; tissue

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

References

  • 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)
  • 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, Baumann B, Broghammer M, Jägle H, Sieving P, Kellner U, Spegal R, Anastasi M, Zrenner E, Sharpe LT, Wissinger B. Mutations in the CNGB3 gene encoding the beta-subunit of the cone photoreceptor cGMP-gated channel are responsible for achromatopsia (ACHM3) linked to chromosome 8q21. Hum Mol Genet. 2000 Sep 1;9(14):2107-16. (http://www.ncbi.nlm.nih.gov/pubmed/10958649?dopt=Abstract)
  • Kohl S, Varsanyi B, Antunes GA, Baumann B, Hoyng CB, Jägle H, Rosenberg T, Kellner U, Lorenz B, Salati R, Jurklies B, Farkas A, Andreasson S, Weleber RG, Jacobson SG, Rudolph G, Castellan C, Dollfus H, Legius E, Anastasi M, Bitoun P, Lev D, Sieving PA, Munier FL, Zrenner E, Sharpe LT, Cremers FP, Wissinger B. CNGB3 mutations account for 50% of all cases with autosomal recessive achromatopsia. Eur J Hum Genet. 2005 Mar;13(3):302-8. (http://www.ncbi.nlm.nih.gov/pubmed/15657609?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)
  • NCBI Gene (http://www.ncbi.nlm.nih.gov/gene/54714)
  • Sundin OH, Yang JM, Li Y, Zhu D, Hurd JN, Mitchell TN, Silva ED, Maumenee IH. Genetic basis of total colourblindness among the Pingelapese islanders. Nat Genet. 2000 Jul;25(3):289-93. (http://www.ncbi.nlm.nih.gov/pubmed/10888875?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: March 2006
Published: July 7, 2014