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.
Health Conditions Related to Genetic Changes
Isolated Duane retraction syndrome
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.More About This Health Condition
Other Names for This Gene
- Chimerin 1 (GTPase-activating protein, rho, 2)
- Rho GTPase-activating protein 2
Additional Information & Resources
Tests Listed in the Genetic Testing Registry
Scientific Articles on PubMed
Catalog of Genes and Diseases from OMIM
- 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. Citation on PubMed or Free article on PubMed Central
- 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. Citation on PubMed
- 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. Citation on PubMed
- 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. Citation on PubMed or Free article on PubMed Central
- 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. 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, 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. Citation on PubMed