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


Reviewed April 2007

What is the official name of the CLCN1 gene?

The official name of this gene is “chloride channel, voltage-sensitive 1.”

CLCN1 is the gene's official symbol. The CLCN1 gene is also known by other names, listed below.

What is the normal function of the CLCN1 gene?

The CLCN1 gene belongs to the CLC family of genes, which provide instructions for making chloride channels. These channels, which transport negatively charged chlorine atoms (chloride ions), play a key role in a cell's ability to generate and transmit electrical signals. Some CLC channels regulate the flow of chloride ions across cell membranes, while others transport chloride ions within cells.

The CLCN1 gene provides instructions for making a chloride channel called ClC-1. These channels are abundant in muscles used for movement (skeletal muscles). For the body to move normally, skeletal muscles must tense (contract) and relax in a coordinated way. Muscle contraction and relaxation are controlled by the flow of certain ions into and out of muscle cells. ClC-1 channels, which span the cell membrane, control the flow of chloride ions into these cells. This influx stabilizes the cells' electrical charge, which prevents muscles from contracting abnormally.

ClC-1 channels are made of two identical protein subunits, each produced from the CLCN1 gene. Although each subunit forms a separate opening (pore) that allows chloride ions to pass through, the two proteins work together to regulate the flow of chloride ions into skeletal muscle cells.

Does the CLCN1 gene share characteristics with other genes?

The CLCN1 gene belongs to a family of genes called CLCN (chloride channels, voltage-sensitive).

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? ( in the Handbook.

How are changes in the CLCN1 gene related to health conditions?

myotonia congenita - caused by mutations in the CLCN1 gene

More than 80 mutations in the CLCN1 gene have been identified in people with myotonia congenita. Most of these mutations cause the autosomal recessive form of the disorder, which is known as Becker disease. Autosomal recessive inheritance means two copies of the gene in each cell are altered. Becker disease results when CLCN1 mutations change the structure or function of both protein subunits that make up the ClC-1 channel. The altered channels greatly reduce the flow of chloride ions into skeletal muscle cells, which triggers prolonged muscle contractions. Abnormally sustained muscle contractions are the hallmark of myotonia.

CLCN1 mutations also cause the autosomal dominant form of myotonia congenita, which is known as Thomsen disease. Autosomal dominant inheritance means one copy of the altered gene in each cell is sufficient to cause the disorder. Studies suggest that the CLCN1 mutations responsible for Thomsen disease change one of the two protein subunits that make up the ClC-1 channel. The altered protein takes on new, but harmful, properties that disrupt the ability of both subunits to regulate chloride ion flow. Reduced movement of chloride ions into skeletal muscle cells leads to myotonia, which underlies the stiffness and other muscle problems in people with myotonia congenita.

Because several CLCN1 mutations can cause either Becker disease or Thomsen disease, doctors usually rely on characteristic signs and symptoms to distinguish the two forms of myotonia congenita.

Where is the CLCN1 gene located?

Cytogenetic Location: 7q35

Molecular Location on chromosome 7: base pairs 143,316,126 to 143,353,862

(Homo sapiens Annotation Release 107, GRCh38.p2) (NCBI (

The CLCN1 gene is located on the long (q) arm of chromosome 7 at position 35.

The CLCN1 gene is located on the long (q) arm of chromosome 7 at position 35.

More precisely, the CLCN1 gene is located from base pair 143,316,126 to base pair 143,353,862 on chromosome 7.

See How do geneticists indicate the location of a gene? ( in the Handbook.

Where can I find additional information about CLCN1?

You and your healthcare professional may find the following resources about CLCN1 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 CLCN1 gene or gene products?

  • chloride channel 1, skeletal muscle
  • Chloride channel protein 1
  • Chloride channel protein, skeletal muscle
  • CLC1
  • ClC-1
  • MGC138361
  • MGC142055
  • skeletal muscle chloride channel 1

See How are genetic conditions and genes named? ( in the Handbook.

What glossary definitions help with understanding CLCN1?

action potential ; autosomal ; autosomal dominant ; autosomal recessive ; cell ; cell membrane ; channel ; chloride ; chloride channels ; chloride ion ; Cl- ; contraction ; gene ; inheritance ; ions ; muscle cells ; myotonia ; protein ; recessive ; skeletal muscle ; subunit ; voltage

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


  • Colding-Jørgensen E. Phenotypic variability in myotonia congenita. Muscle Nerve. 2005 Jul;32(1):19-34. Review. (
  • Dunø M, Colding-Jørgensen E, Grunnet M, Jespersen T, Vissing J, Schwartz M. Difference in allelic expression of the CLCN1 gene and the possible influence on the myotonia congenita phenotype. Eur J Hum Genet. 2004 Sep;12(9):738-43. (
  • Gene Review: Myotonia Congenita (
  • Grunnet M, Jespersen T, Colding-Jørgensen E, Schwartz M, Klaerke DA, Vissing J, Olesen SP, Dunø M. Characterization of two new dominant ClC-1 channel mutations associated with myotonia. Muscle Nerve. 2003 Dec;28(6):722-32. (
  • Jentsch TJ, Stein V, Weinreich F, Zdebik AA. Molecular structure and physiological function of chloride channels. Physiol Rev. 2002 Apr;82(2):503-68. Review. Erratum in: Physiol Rev. 2003 Apr;83(2):following table of contents. (
  • NCBI Gene (
  • Pusch M. Myotonia caused by mutations in the muscle chloride channel gene CLCN1. Hum Mutat. 2002 Apr;19(4):423-34. Review. (
  • Zhang J, Bendahhou S, Sanguinetti MC, Ptácek LJ. Functional consequences of chloride channel gene (CLCN1) mutations causing myotonia congenita. Neurology. 2000 Feb 22;54(4):937-42. (
  • Zhang J, George AL Jr, Griggs RC, Fouad GT, Roberts J, Kwieciński H, Connolly AM, Ptácek LJ. Mutations in the human skeletal muscle chloride channel gene (CLCN1) associated with dominant and recessive myotonia congenita. Neurology. 1996 Oct;47(4):993-8. (


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: April 2007
Published: February 8, 2016