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CRX gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

CRX gene

The CRX gene provides instructions for making a protein essential for the development and maintenance of light-detecting cells in the retina.

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.

Leber congenital amaurosis

MedlinePlus Genetics provides information about Leber congenital amaurosis.

Retinitis pigmentosa

MedlinePlus Genetics provides information about Retinitis pigmentosa.

Other Names for This Gene

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

Frequently Asked Questions

Currently, there is no cure, but low‑vision aids, vitamin A supplementation (under strict monitoring), and participation in clinical trials for gene therapy or retinal implants may offer benefit. Some patients also use anti‑inflammatory eye drops if inflammation is present. Discuss options with an ophthalmologist who specializes in inherited retinal diseases.
CRX mutations that cause cone‑rod dystrophy are usually autosomal dominant, meaning a single copy of the altered gene can cause disease. If you carry a pathogenic variant, each child has a 50 % chance of inheriting it. Genetic counseling can help you understand the risks and options for prenatal or pre‑implantation testing.
definitive diagnosis usually involves a comprehensive eye exam (visual acuity, color vision, and retinal imaging such as optical coherence tomography) followed by genetic testing. A blood sample is sent for sequencing of the CRX gene, often as part of a retinal dystrophy panel that screens for multiple genes. The results are interpreted by a clinical geneticist who correlates the mutation with the patient’s clinical picture.
The rate of vision loss varies widely, but many patients experience a gradual decline over 5–15 years. Most clinicians recommend a baseline comprehensive eye exam at diagnosis, then annual or biannual follow‑ups, with more frequent visits if symptoms worsen. Early detection of changes can help plan interventions.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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