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Genetics Home Reference: your guide to understanding genetic conditions
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KCNQ2

Reviewed April 2013

What is the official name of the KCNQ2 gene?

The official name of this gene is “potassium voltage-gated channel, KQT-like subfamily, member 2.”

KCNQ2 is the gene's official symbol. The KCNQ2 gene is also known by other names, listed below.

What is the normal function of the KCNQ2 gene?

The KCNQ2 gene belongs to a large family of genes that provide instructions for making potassium channels. These channels, which transport positively charged atoms (ions) of potassium into and out of cells, play a key role in a cell's ability to generate and transmit electrical signals.

The specific function of a potassium channel depends on its protein components and its location in the body. Channels made with the KCNQ2 protein are active in nerve cells (neurons) in the brain, where they transport potassium ions out of cells. These channels transmit a particular type of electrical signal called the M-current, which prevents the neuron from continuing to send signals to other neurons. The M-current ensures that the neuron is not constantly active, or excitable.

Potassium channels are made up of several protein components (subunits). Each channel contains four alpha subunits that form the hole (pore) through which potassium ions move. Four alpha subunits from the KCNQ2 gene can form a channel. However, the KCNQ2 alpha subunits can also interact with alpha subunits produced from the KCNQ3 gene to form a functional potassium channel, and these channels transmit a much stronger M-current.

Does the KCNQ2 gene share characteristics with other genes?

The KCNQ2 gene belongs to a family of genes called KCN (potassium 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 KCNQ2 gene related to health conditions?

benign familial neonatal seizures - caused by mutations in the KCNQ2 gene

A mutation in the KCNQ2 gene has been identified in most people with benign familial neonatal seizures (BFNS), a condition characterized by recurrent seizures (epilepsy) in newborn babies. The seizures begin around day 3 of life and usually go away within 1 to 4 months. More than 60 mutations in the KCNQ2 gene have been identified in families with this condition. Sometimes, the mutated protein never gets to the cell surface to form a channel, or the channel may be located in the wrong part of the neuron. Alternatively, the channel formed from the mutated protein may not function properly. As a result of these mutations, the M-current is reduced or altered, which leads to excessive excitability of neurons. Researchers believe that a reduction of the M-current by 25 percent is enough to cause BFNS. Seizures develop when neurons in the brain are abnormally excited. It is unclear why the seizures stop around the age of 4 months. It has been suggested that potassium channels formed from the KCNQ2 and KCNQ3 proteins play a major role in preventing excessive excitability of neurons in newborns, but other mechanisms that prevent constant neuron activity develop during infancy.

other disorders - caused by mutations in the KCNQ2 gene

Mutations in the KCNQ2 gene are also involved in early-onset epileptic encephalopathy, a more severe condition than BFNS (described above) characterized by epilepsy and profound intellectual disability. The seizures begin in the first weeks of life and typically show little response to treatment. They usually go away in a few months to a few years but can return later in childhood. Most affected individuals are unable to talk, and they have low muscle tone (hypotonia) or very stiff muscles, causing difficulty with movement.

It has been suggested that KCNQ2 gene mutations that cause early-onset epileptic encephalopathy lead to production of an abnormal KCNQ2 protein that can still bind to normal subunits to form potassium channels. However, the presence of the abnormal KCNQ2 subunit keeps the channels from functioning, which likely leads to a severe reduction of the M-current. The resulting over-excitability of neurons can lead to seizures and brain dysfunction (encephalopathy).

Early-onset epileptic encephalopathy caused by KCNQ2 gene mutations resembles a condition called Ohtahara syndrome; however, seizures do not usually subside in people with Ohtahara syndrome. It is unclear whether the epileptic encephalopathy caused by KCNQ2 gene mutations is a form of Ohtahara syndrome or a separate disorder.

Where is the KCNQ2 gene located?

Cytogenetic Location: 20q13.3

Molecular Location on chromosome 20: base pairs 63,400,207 to 63,472,639

The KCNQ2 gene is located on the long (q) arm of chromosome 20 at position 13.3.

The KCNQ2 gene is located on the long (q) arm of chromosome 20 at position 13.3.

More precisely, the KCNQ2 gene is located from base pair 63,400,207 to base pair 63,472,639 on chromosome 20.

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 KCNQ2?

You and your healthcare professional may find the following resources about KCNQ2 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 KCNQ2 gene or gene products?

  • BFNC
  • BFNS1
  • EBN
  • EBN1
  • EIEE7
  • ENB1
  • HNSPC
  • KCNA11
  • KCNQ2_HUMAN
  • KQT-like 2
  • KV7.2
  • KVEBN1
  • potassium voltage-gated channel subfamily KQT member 2
  • voltage-gated potassium channel subunit Kv7.2

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 KCNQ2?

benign ; cell ; channel ; disability ; encephalopathy ; epilepsy ; epileptic ; familial ; gene ; hypotonia ; ions ; low muscle tone ; muscle tone ; mutation ; neonatal ; neuron ; potassium ; protein ; subunit ; syndrome ; voltage

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

References

  • Biervert C, Schroeder BC, Kubisch C, Berkovic SF, Propping P, Jentsch TJ, Steinlein OK. A potassium channel mutation in neonatal human epilepsy. Science. 1998 Jan 16;279(5349):403-6. (http://www.ncbi.nlm.nih.gov/pubmed/9430594?dopt=Abstract)
  • Castaldo P, del Giudice EM, Coppola G, Pascotto A, Annunziato L, Taglialatela M. Benign familial neonatal convulsions caused by altered gating of KCNQ2/KCNQ3 potassium channels. J Neurosci. 2002 Jan 15;22(2):RC199. (http://www.ncbi.nlm.nih.gov/pubmed/11784811?dopt=Abstract)
  • Chung HJ, Jan YN, Jan LY. Polarized axonal surface expression of neuronal KCNQ channels is mediated by multiple signals in the KCNQ2 and KCNQ3 C-terminal domains. Proc Natl Acad Sci U S A. 2006 Jun 6;103(23):8870-5. Epub 2006 May 30. (http://www.ncbi.nlm.nih.gov/pubmed/16735477?dopt=Abstract)
  • Lerche H, Biervert C, Alekov AK, Schleithoff L, Lindner M, Klinger W, Bretschneider F, Mitrovic N, Jurkat-Rott K, Bode H, Lehmann-Horn F, Steinlein OK. A reduced K+ current due to a novel mutation in KCNQ2 causes neonatal convulsions. Ann Neurol. 1999 Sep;46(3):305-12. (http://www.ncbi.nlm.nih.gov/pubmed/10482260?dopt=Abstract)
  • Millichap JJ, Cooper EC. KCNQ2 Potassium Channel Epileptic Encephalopathy Syndrome: Divorce of an Electro-Mechanical Couple? Epilepsy Curr. 2012 Jul;12(4):150-2. doi: 10.5698/1535-7511-12.4.150. (http://www.ncbi.nlm.nih.gov/pubmed/22936888?dopt=Abstract)
  • NCBI Gene (http://www.ncbi.nlm.nih.gov/gene/3785)
  • OMIM: POTASSIUM CHANNEL, VOLTAGE-GATED, KQT-LIKE SUBFAMILY, MEMBER 2 (http://omim.org/entry/602235)
  • Rogawski MA. KCNQ2/KCNQ3 K+ channels and the molecular pathogenesis of epilepsy: implications for therapy. Trends Neurosci. 2000 Sep;23(9):393-8. Review. (http://www.ncbi.nlm.nih.gov/pubmed/10941184?dopt=Abstract)
  • Saitsu H, Kato M, Koide A, Goto T, Fujita T, Nishiyama K, Tsurusaki Y, Doi H, Miyake N, Hayasaka K, Matsumoto N. Whole exome sequencing identifies KCNQ2 mutations in Ohtahara syndrome. Ann Neurol. 2012 Aug;72(2):298-300. doi: 10.1002/ana.23620. (http://www.ncbi.nlm.nih.gov/pubmed/22926866?dopt=Abstract)
  • Schroeder BC, Kubisch C, Stein V, Jentsch TJ. Moderate loss of function of cyclic-AMP-modulated KCNQ2/KCNQ3 K+ channels causes epilepsy. Nature. 1998 Dec 17;396(6712):687-90. (http://www.ncbi.nlm.nih.gov/pubmed/9872318?dopt=Abstract)
  • Singh NA, Westenskow P, Charlier C, Pappas C, Leslie J, Dillon J, Anderson VE, Sanguinetti MC, Leppert MF; BFNC Physician Consortium. KCNQ2 and KCNQ3 potassium channel genes in benign familial neonatal convulsions: expansion of the functional and mutation spectrum. Brain. 2003 Dec;126(Pt 12):2726-37. Epub 2003 Oct 8. (http://www.ncbi.nlm.nih.gov/pubmed/14534157?dopt=Abstract)
  • Soldovieri MV, Miceli F, Bellini G, Coppola G, Pascotto A, Taglialatela M. Correlating the clinical and genetic features of benign familial neonatal seizures (BFNS) with the functional consequences of underlying mutations. Channels (Austin). 2007 Jul-Aug;1(4):228-33. Epub 2007 Aug 2. (http://www.ncbi.nlm.nih.gov/pubmed/18698150?dopt=Abstract)
  • Volkers L, Rook MB, Das JH, Verbeek NE, Groenewegen WA, van Kempen MJ, Lindhout D, Koeleman BP. Functional analysis of novel KCNQ2 mutations found in patients with Benign Familial Neonatal Convulsions. Neurosci Lett. 2009 Oct 2;462(1):24-9. doi: 10.1016/j.neulet.2009.06.064. Epub 2009 Jun 25. (http://www.ncbi.nlm.nih.gov/pubmed/19559753?dopt=Abstract)
  • Wang HS, Pan Z, Shi W, Brown BS, Wymore RS, Cohen IS, Dixon JE, McKinnon D. KCNQ2 and KCNQ3 potassium channel subunits: molecular correlates of the M-channel. Science. 1998 Dec 4;282(5395):1890-3. (http://www.ncbi.nlm.nih.gov/pubmed/9836639?dopt=Abstract)
  • Weckhuysen S, Mandelstam S, Suls A, Audenaert D, Deconinck T, Claes LR, Deprez L, Smets K, Hristova D, Yordanova I, Jordanova A, Ceulemans B, Jansen A, Hasaerts D, Roelens F, Lagae L, Yendle S, Stanley T, Heron SE, Mulley JC, Berkovic SF, Scheffer IE, de Jonghe P. KCNQ2 encephalopathy: emerging phenotype of a neonatal epileptic encephalopathy. Ann Neurol. 2012 Jan;71(1):15-25. doi: 10.1002/ana.22644. (http://www.ncbi.nlm.nih.gov/pubmed/22275249?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: April 2013
Published: July 28, 2014