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


Reviewed March 2009

What is the official name of the CHN1 gene?

The official name of this gene is “chimerin 1.”

CHN1 is the gene's official symbol. The CHN1 gene is also known by other names, listed below.

What is the normal function of the CHN1 gene?

The CHN1 gene provides instructions for making two very similar proteins called α1-chimaerin and α2-chimaerin. These proteins play an important role in the early development of the nervous system. In particular, they help regulate complex chemical signaling pathways during the formation and development of nerve cells (neurons). These proteins help guide the growth of axons and dendrites, which are specialized extensions of neurons that transmit and receive nerve impulses throughout the nervous system.

The CHN1 proteins, particularly α2-chimaerin, appear to be critical for the formation of certain nerves in the head and face. Specifically, they are necessary for the development and function of cranial nerve VI and, to a lesser extent, cranial nerve III. These nerves emerge from the brain and control several of the muscles that surround the eyes (extraocular muscles). The extraocular muscles direct eye movement and determine the position of the eyes.

Does the CHN1 gene share characteristics with other genes?

The CHN1 gene belongs to a family of genes called ARHGAP (Rho GTPase activating proteins). It also belongs to a family of genes called SH2 domain containing (SH2 domain containing).

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 CHN1 gene related to health conditions?

isolated Duane retraction syndrome - caused by mutations in the CHN1 gene

At least seven mutations in the CHN1 gene have been identified in families with isolated Duane retraction syndrome. Researchers believe that the features of this condition result from changes in one of the two versions of the CHN1 protein, α2-chimaerin. Each identified mutation changes a single protein building block (amino acid) in α2-chimaerin. Although several mutations also affect α1-chimaerin, researchers think that changes in α1-chimaerin alone do not cause isolated Duane retraction syndrome.

CHN1 mutations alter the structure and function of α2-chimaerin in the developing nervous system. These genetic changes appear to overactivate the protein, which disrupts the normal growth of neurons in certain parts of the brain. As a result, cranial nerves VI and III and the extraocular muscles they control do not develop normally. Abnormal development and function of these muscles leads to the characteristic features of isolated Duane retraction syndrome, including restricted eye movement and related problems with vision.

Where is the CHN1 gene located?

Cytogenetic Location: 2q31.1

Molecular Location on chromosome 2: base pairs 174,799,314 to 175,005,379

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

The CHN1 gene is located on the long (q) arm of chromosome 2 at position 31.1.

The CHN1 gene is located on the long (q) arm of chromosome 2 at position 31.1.

More precisely, the CHN1 gene is located from base pair 174,799,314 to base pair 175,005,379 on chromosome 2.

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

Where can I find additional information about CHN1?

You and your healthcare professional may find the following resources about CHN1 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 CHN1 gene or gene products?

  • A-chimaerin
  • alpha-chimerin
  • Chimerin 1 (GTPase-activating protein, rho, 2)
  • CHN
  • DURS2
  • N-chimaerin
  • n-chimerin
  • Rho GTPase-activating protein 2

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

What glossary definitions help with understanding CHN1?

amino acid ; axons ; cranial nerves ; extraocular muscles ; gene ; GTP ; mutation ; nervous system ; protein ; syndrome

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


  • Appukuttan B, Gillanders E, Juo SH, Freas-Lutz D, Ott S, Sood R, Van Auken A, Bailey-Wilson J, Wang X, Patel RJ, Robbins CM, Chung M, Annett G, Weinberg K, Borchert MS, Trent JM, Brownstein MJ, Stout JT. Localization of a gene for Duane retraction syndrome to chromosome 2q31. Am J Hum Genet. 1999 Dec;65(6):1639-46. (
  • Beg AA, Sommer JE, Martin JH, Scheiffele P. alpha2-Chimaerin is an essential EphA4 effector in the assembly of neuronal locomotor circuits. Neuron. 2007 Sep 6;55(5):768-78. (
  • Evans JC, Frayling TM, Ellard S, Gutowski NJ. Confirmation of linkage of Duane's syndrome and refinement of the disease locus to an 8.8-cM interval on chromosome 2q31. Hum Genet. 2000 Jun;106(6):636-8. (
  • Hall C, Sin WC, Teo M, Michael GJ, Smith P, Dong JM, Lim HH, Manser E, Spurr NK, Jones TA, et al. Alpha 2-chimerin, an SH2-containing GTPase-activating protein for the ras-related protein p21rac derived by alternate splicing of the human n-chimerin gene, is selectively expressed in brain regions and testes. Mol Cell Biol. 1993 Aug;13(8):4986-98. (
  • Iwasato T, Katoh H, Nishimaru H, Ishikawa Y, Inoue H, Saito YM, Ando R, Iwama M, Takahashi R, Negishi M, Itohara S. Rac-GAP alpha-chimerin regulates motor-circuit formation as a key mediator of EphrinB3/EphA4 forward signaling. Cell. 2007 Aug 24;130(4):742-53. (
  • Miyake N, Chilton J, Psatha M, Cheng L, Andrews C, Chan WM, Law K, Crosier M, Lindsay S, Cheung M, Allen J, Gutowski NJ, Ellard S, Young E, Iannaccone A, Appukuttan B, Stout JT, Christiansen S, Ciccarelli ML, Baldi A, Campioni M, Zenteno JC, Davenport D, Mariani LE, Sahin M, Guthrie S, Engle EC. Human CHN1 mutations hyperactivate alpha2-chimaerin and cause Duane's retraction syndrome. Science. 2008 Aug 8;321(5890):839-43. doi: 10.1126/science.1156121. Epub 2008 Jul 24. (
  • NCBI Gene (
  • Wegmeyer H, Egea J, Rabe N, Gezelius H, Filosa A, Enjin A, Varoqueaux F, Deininger K, Schnütgen F, Brose N, Klein R, Kullander K, Betz A. EphA4-dependent axon guidance is mediated by the RacGAP alpha2-chimaerin. Neuron. 2007 Sep 6;55(5):756-67. (


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: March 2009
Published: February 8, 2016