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

CNG gene family

Reviewed August 2013

What are the CNG genes?

Genes in this family provide instructions for making proteins that form cyclic nucleotide-regulated channels. These channels transport positively charged atoms (ions), particularly potassium (K+), sodium (Na+), and calcium (Ca2+), into cells. Two subfamilies of ion channels are produced from genes in this family: cyclic nucleotide-gated (CNG) channels and hyperpolarization-activated cyclic nucleotide-gated (HCN) channels.

Channels in the CNG subfamily are produced from six genes: CNGA1-CNGA4, CNGB1, and CNGB3. CNG channels are found primarily in light-sensing (photoreceptor) cells at the back of the eye and in olfactory neurons, which are nerve cells in the nasal cavity. These channels play important roles in transmitting information about vision and smell from sensory cells to the brain. Studies suggest that abnormalities of CNG channels underlie several eye and vision disorders, including a severe form of color vision deficiency called achromatopsia, which is a loss of all color vision.

Channels in the HCN subfamily are produced from four genes: HCN1, HCN2, HCN3, and HCN4. HCN channels are found in the brain and heart. In the brain, the channels likely have multiple functions, including roles in learning and memory. HCN channels are also found in the heart; in particular, HCN4 channels are abundant in a part of the heart called the sino-atrial (SA) node. This area of specialized cells functions as a natural pacemaker, and the flow of ions through HCN4 channels is often called the "pacemaker current" because it generates electrical impulses that start each heartbeat. Mutations in the HCN4 gene have been found to cause an SA node abnormality called sick sinus syndrome. People with these genetic changes have an increased risk of an abnormally slow heartbeat (bradycardia), which can cause symptoms such as dizziness, light-headedness, and fainting (syncope).

Which genes are included in the CNG gene family?

The HUGO Gene Nomenclature Committee (HGNC) provides an index of gene families ( and their member genes.

Genetics Home Reference summarizes the normal function and health implications of these members of the CNG gene family: CNGA3, CNGB3, and HCN4.

What conditions are related to genes in the CNG gene family?

Genetics Home Reference includes these conditions related to genes in the CNG gene family:

  • achromatopsia
  • Brugada syndrome
  • sick sinus syndrome

Where can I find additional information about the CNG gene family?

You may find the following resources about the CNG gene family helpful.

  • Madame Curie Bioscience Database: Regulation of the Rod Photoreceptor Cyclic Nucleotide-Gated Channel (
  • The Neurobiology of Olfaction (2010): Molecular Mechanisms of Olfactory Transduction (

What glossary definitions help with understanding the CNG gene family?

achromatopsia ; atrial ; bradycardia ; Ca ; calcium ; channel ; deficiency ; fainting ; gene ; ions ; Na ; nucleotide ; pacemaker ; photoreceptor ; potassium ; SA node ; sensory cells ; sinus ; sodium ; syncope ; syndrome

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


These sources were used to develop the Genetics Home Reference summary for the CNG gene family.

  • Biel M, Wahl-Schott C, Michalakis S, Zong X. Hyperpolarization-activated cation channels: from genes to function. Physiol Rev. 2009 Jul;89(3):847-85. doi: 10.1152/physrev.00029.2008. Review. (
  • Hofmann F, Biel M, Kaupp UB. International Union of Pharmacology. LI. Nomenclature and structure-function relationships of cyclic nucleotide-regulated channels. Pharmacol Rev. 2005 Dec;57(4):455-62. Review. (
  • Benarroch EE. HCN channels: function and clinical implications. Neurology. 2013 Jan 15;80(3):304-10. doi: 10.1212/WNL.0b013e31827dec42. Review. (
  • Pifferi S, Boccaccio A, Menini A. Cyclic nucleotide-gated ion channels in sensory transduction. FEBS Lett. 2006 May 22;580(12):2853-9. Epub 2006 Apr 12. Review. (
  • Matulef K, Zagotta WN. Cyclic nucleotide-gated ion channels. Annu Rev Cell Dev Biol. 2003;19:23-44. Review. (


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: August 2013
Published: February 1, 2016