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CHN1 gene
URL of this page: https://medlineplus.gov/genetics/gene/chn1/

CHN1 gene

chimerin 1

Normal Function

The CHN1 gene provides instructions for making a protein called N-chimaerin. This protein plays an important role in the early development of the nervous system. In particular, it helps regulate complex signaling pathways during the development of nerve cells (neurons). N-chimaerin helps guide the growth of axons and dendrites, which are specialized extensions of neurons that transmit and receive nerve impulses throughout the nervous system.

N-chimaerin appears to be critical for the formation of certain nerves in the head and face, known as cranial nerves. The protein is necessary for the development and function of cranial nerve VI and, to a lesser extent, cranial nerve III. These two 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.

Health Conditions Related to Genetic Changes

Isolated Duane retraction syndrome

Variants (also called mutations) in the CHN1 gene have been identified in families with isolated Duane retraction syndrome. This condition prevents outward movement of the eye (toward the ear), and in some cases it may also limit inward eye movement (toward the nose). This condition is referred to as "isolated" because it causes eye problems with no other signs or symptoms. 

CHN1 gene variants alter the structure and function of N-chimaerin in the developing nervous system. These variants are called "gain of function" variants because they appear to enhance the activity of the protein. This can disrupt the normal growth of neurons in certain parts of the brain. As a result, cranial nerves VI and III do not develop normally and cannot effectively control the extraocular muscles. Impaired function of these muscles leads to the characteristic features of isolated Duane retraction syndrome.

More About This Health Condition

Other Names for This Gene

  • A-chimaerin
  • alpha-chimerin
  • CHIN_HUMAN
  • CHN
  • N-chimaerin
  • n-chimerin
  • RHOGAP2

Additional Information & Resources

Tests Listed in the Genetic Testing Registry

Scientific Articles on PubMed

Catalog of Genes and Diseases from OMIM

Gene and Variant Databases

References

  • Angelini C, Trimouille A, Arveiler B, Espil-Taris C, Ichinose N, Lasseaux E, Tourdias T, Lacombe D. CHN1 and duane retraction syndrome: Expanding the phenotype to cranial nerves development disease. Eur J Med Genet. 2021 Apr;64(4):104188. doi: 10.1016/j.ejmg.2021.104188. Epub 2021 Mar 2. Citation on PubMed
  • Barry BJ, Whitman MC, Hunter DG, Engle EC. Duane Syndrome. 2007 May 25 [updated 2019 Aug 29]. In: Adam MP, Feldman J, Mirzaa GM, Pagon RA, Wallace SE, Amemiya A, editors. GeneReviews(R) [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2024. Available from http://www.ncbi.nlm.nih.gov/books/NBK1190/ Citation on PubMed
  • 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. doi: 10.1016/j.neuron.2007.07.036. Citation on PubMed
  • 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. doi: 10.1016/j.cell.2007.07.022. Citation on PubMed
  • 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. Citation on PubMed or Free article on PubMed Central
  • Wegmeyer H, Egea J, Rabe N, Gezelius H, Filosa A, Enjin A, Varoqueaux F, Deininger K, Schnutgen 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. doi: 10.1016/j.neuron.2007.07.038. Citation on PubMed

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