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CRX gene

cone-rod homeobox

Normal Function

The CRX gene provides instructions for making a protein called the cone-rod homeobox protein. This protein is found in the eyes, specifically in the light-sensitive tissue at the back of the eye called the retina. The cone-rod homeobox protein attaches (binds) to specific regions of DNA and helps control the activity of particular genes. On the basis of this action, this protein is called a transcription factor.

In the retina, the cone-rod homeobox protein is necessary for the normal development of light-detecting cells called photoreceptors. Through its actions as a transcription factor, the cone-rod homeobox protein helps photoreceptor cells mature into two types: rods and cones. Rods are needed for vision in low light, while cones are needed for vision in bright light, including color vision. The protein also helps maintain these cells and preserve vision.

Health Conditions Related to Genetic Changes

Cone-rod dystrophy

More than 20 mutations in the CRX gene have been found to cause cone-rod dystrophy. The problems associated with this condition include a loss of visual sharpness (acuity), an increased sensitivity to light (photophobia), and impaired color vision. These vision problems worsen over time. Cone-rod dystrophy is caused by mutations that occur in one of the two copies of the CRX gene in each cell. CRX gene mutations are responsible for about one-quarter of the cases of a form of the condition called autosomal dominant cone-rod dystrophy. These mutations lead to a reduction in the amount of functional cone-rod homeobox protein that is available to regulate other genes in the retina. As a result, maintenance of the rod and cone cells is insufficient and these cells deteriorate over time, leading to the vision problems characteristic of cone-rod dystrophy. Researchers believe that there is enough cone-rod homeobox protein function to allow for photoreceptor cell differentiation, but long-term maintenance of the cells cannot be sustained.

Several CRX gene mutations have been found to cause different forms of vision loss in different individuals. It is unclear how mutations in the CRX gene can cause different eye disorders.

More About This Health Condition

Leber congenital amaurosis

MedlinePlus Genetics provides information about Leber congenital amaurosis

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Retinitis pigmentosa

MedlinePlus Genetics provides information about Retinitis pigmentosa

More About This Health Condition

Other Names for This Gene

  • cone-rod homeobox protein
  • CORD2
  • CRD
  • LCA7
  • orthodenticle homeobox 3
  • OTX3

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


  • Huang L, Li S, Xiao X, Jia X, Wang P, Guo X, Zhang Q. Screening for variants in 20 genes in 130 unrelated patients with cone-rod dystrophy. Mol Med Rep. 2013 Jun;7(6):1779-85. doi: 10.3892/mmr.2013.1415. Epub 2013 Apr 5. Citation on PubMed
  • Huang L, Xiao X, Li S, Jia X, Wang P, Guo X, Zhang Q. CRX variants in cone-rod dystrophy and mutation overview. Biochem Biophys Res Commun. 2012 Oct 5;426(4):498-503. doi: 10.1016/j.bbrc.2012.08.110. Epub 2012 Aug 30. Citation on PubMed
  • Huang L, Zhang Q, Li S, Guan L, Xiao X, Zhang J, Jia X, Sun W, Zhu Z, Gao Y, Yin Y, Wang P, Guo X, Wang J, Zhang Q. Exome sequencing of 47 chinese families with cone-rod dystrophy: mutations in 25 known causative genes. PLoS One. 2013 Jun 11;8(6):e65546. doi: 10.1371/journal.pone.0065546. Print 2013. Citation on PubMed or Free article on PubMed Central

The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health.