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


Reviewed November 2013

What is the official name of the RHO gene?

The official name of this gene is “rhodopsin.”

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

What is the normal function of the RHO gene?

The RHO gene provides instructions for making a protein called rhodopsin. This protein is necessary for normal vision, particularly in low-light conditions. Rhodopsin is found in specialized light receptor cells called rods. As part of the light-sensitive tissue at the back of the eye (the retina), rods provide vision in low light. Other light receptor cells in the retina, called cones, are responsible for vision in bright light.

The rhodopsin protein is attached (bound) to a molecule called 11-cis retinal, which is a form of vitamin A. When light hits this molecule, it activates rhodopsin and sets off a series of chemical reactions that create electrical signals. These signals are transmitted to the brain, where they are interpreted as vision.

Does the RHO gene share characteristics with other genes?

The RHO gene belongs to a family of genes called GPCR (G protein-coupled receptors).

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 RHO gene related to health conditions?

autosomal dominant congenital stationary night blindness - caused by mutations in the RHO gene

At least four mutations in the RHO gene have been found to cause autosomal dominant congenital stationary night blindness, which is characterized by a loss of vision in low light that remains stable (stationary) over time. Unlike retinitis pigmentosa (described below), autosomal dominant congenital stationary night blindness does not affect daytime vision.

The RHO gene mutations responsible for autosomal dominant congenital stationary night blindness cause the rhodopsin protein to be constantly turned on (constitutively active). Because the protein no longer needs light to be activated, the signals that rod cells send to the brain are constantly occurring, even in bright light. Visual information from rod cells is then perceived by the brain as not meaningful, resulting in night blindness.

Researchers are uncertain why some constitutively activating mutations in the RHO gene cause congenital stationary night blindness and others result in the more severe vision loss associated with retinitis pigmentosa.

retinitis pigmentosa - caused by mutations in the RHO gene

More than 150 mutations in the RHO gene have been identified in people with retinitis pigmentosa. RHO gene mutations account for 20 to 30 percent of all cases of autosomal dominant retinitis pigmentosa, which is thought to be the most common form of the disorder. Rarely, mutations in the RHO gene cause autosomal recessive retinitis pigmentosa. However, this form of the disorder usually results from mutations in other genes.

Most of the RHO gene mutations responsible for retinitis pigmentosa alter the folding or transport of the rhodopsin protein. A few mutations cause rhodopsin to be constitutively activated instead of being activated in response to light. Studies suggest that altered versions of rhodopsin interfere with essential cell functions, causing rods to self-destruct (undergo apoptosis). Because rods are essential for vision under low-light conditions, the loss of these cells leads to progressive night blindness in people with retinitis pigmentosa.

Retinitis pigmentosa is also associated with a gradual loss of cone cells, which normally provide vision in bright light. The death of cone cells leads to tunnel vision and ultimately blindness in many affected individuals. It is unclear how mutations in the RHO gene affect the function and survival of cone cells.

Where is the RHO gene located?

Cytogenetic Location: 3q22.1

Molecular Location on chromosome 3: base pairs 129,528,639 to 129,535,344

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

The RHO gene is located on the long (q) arm of chromosome 3 at position 22.1.

The RHO gene is located on the long (q) arm of chromosome 3 at position 22.1.

More precisely, the RHO gene is located from base pair 129,528,639 to base pair 129,535,344 on chromosome 3.

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

Where can I find additional information about RHO?

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

  • MGC138309
  • MGC138311
  • OPN2
  • opsin-2
  • opsin 2, rod pigment
  • RP4

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

What glossary definitions help with understanding RHO?

apoptosis ; autosomal ; autosomal dominant ; autosomal recessive ; cell ; cones ; congenital ; gene ; molecule ; photoreceptor ; pigment ; protein ; receptor ; recessive ; retina ; rods ; tissue

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


  • Dryja TP, McGee TL, Reichel E, Hahn LB, Cowley GS, Yandell DW, Sandberg MA, Berson EL. A point mutation of the rhodopsin gene in one form of retinitis pigmentosa. Nature. 1990 Jan 25;343(6256):364-6. (
  • McAlear SD, Kraft TW, Gross AK. 1 rhodopsin mutations in congenital night blindness. Adv Exp Med Biol. 2010;664:263-72. doi: 10.1007/978-1-4419-1399-9_30. Review. (
  • Mendes HF, van der Spuy J, Chapple JP, Cheetham ME. Mechanisms of cell death in rhodopsin retinitis pigmentosa: implications for therapy. Trends Mol Med. 2005 Apr;11(4):177-85. Review. (
  • Morris MB, Dastmalchi S, Church WB. Rhodopsin: structure, signal transduction and oligomerisation. Int J Biochem Cell Biol. 2009 Apr;41(4):721-4. doi: 10.1016/j.biocel.2008.04.025. Epub 2008 Aug 3. Review. (
  • NCBI Gene (
  • Palczewski K, Kumasaka T, Hori T, Behnke CA, Motoshima H, Fox BA, Le Trong I, Teller DC, Okada T, Stenkamp RE, Yamamoto M, Miyano M. Crystal structure of rhodopsin: A G protein-coupled receptor. Science. 2000 Aug 4;289(5480):739-45. (
  • Palczewski K. G protein-coupled receptor rhodopsin. Annu Rev Biochem. 2006;75:743-67. Review. (
  • Saliba RS, Munro PM, Luthert PJ, Cheetham ME. The cellular fate of mutant rhodopsin: quality control, degradation and aggresome formation. J Cell Sci. 2002 Jul 15;115(Pt 14):2907-18. (
  • Smith SO. Structure and activation of the visual pigment rhodopsin. Annu Rev Biophys. 2010;39:309-28. doi: 10.1146/annurev-biophys-101209-104901. Review. (
  • Zeitz C, Gross AK, Leifert D, Kloeckener-Gruissem B, McAlear SD, Lemke J, Neidhardt J, Berger W. Identification and functional characterization of a novel rhodopsin mutation associated with autosomal dominant CSNB. Invest Ophthalmol Vis Sci. 2008 Sep;49(9):4105-14. doi: 10.1167/iovs.08-1717. Epub 2008 May 16. (


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: November 2013
Published: February 1, 2016