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Normal Function
The OPN1SW gene provides instructions for making a protein that is essential for normal color vision. This protein is found in the retina, which is the light-sensitive tissue at the back of the eye. The retina contains two types of light receptor cells, called rods and cones, that transmit visual signals from the eye to the brain. Rods provide vision in low light. Cones provide vision in bright light, including color vision. There are three types of cones. each containing a specific pigment (a photopigment called an opsin) that is most sensitive to particular wavelengths of light.
The OPN1SW gene provides instructions for making an opsin pigment that is more sensitive to light in the blue/violet part of the visible spectrum (short-wavelength light). Cones with this pigment are called short-wavelength-sensitive or S cones. In response to light, the photopigment triggers a series of chemical reactions within an S cone. These reactions ultimately alter the cell's electrical charge, generating a signal that is transmitted to the brain. The brain combines input from all three types of cones to produce normal color vision.
Health Conditions Related to Genetic Changes
Color vision deficiency
At least six mutations in the OPN1SW gene have been found to cause a relatively uncommon form of color vision deficiency called blue-yellow color vision defects or tritan defects. These defects cause problems with differentiating shades of blue and green and cause difficulty distinguishing dark blue from black. Each of the known OPN1SW gene mutations changes a single protein building block (amino acid) in the short-wave-sensitive photopigment, which causes the photopigment to be partially or totally nonfunctional. Researchers suggest that S cone cells without functional photopigment die prematurely or cannot transmit visual signals to the brain normally.
When OPN1SW gene mutations lead to completely nonfunctional S cones, color vision depends entirely on the other two types of cones. The specific type of blue-yellow color vision deficiency that results from a total loss of S cone function is called tritanopia. A less severe blue-yellow color vision defect called tritanomaly occurs when S cones function abnormally.
More About This Health ConditionOther Names for This Gene
- BCP
- blue cone photoreceptor pigment
- blue cone pigment
- blue-sensitive opsin
- BOP
- OPSB_HUMAN
- opsin 1 (cone pigments), short-wave-sensitive
- S-pigment
- short-wave-sensitive pigment
Additional Information & Resources
Tests Listed in the Genetic Testing Registry
Scientific Articles on PubMed
Catalog of Genes and Diseases from OMIM
References
- Baraas RC, Carroll J, Gunther KL, Chung M, Williams DR, Foster DH, Neitz M. Adaptive optics retinal imaging reveals S-cone dystrophy in tritan color-vision deficiency. J Opt Soc Am A Opt Image Sci Vis. 2007 May;24(5):1438-47. doi: 10.1364/josaa.24.001438. Citation on PubMed or Free article on PubMed Central
- Baraas RC, Hagen LA, Dees EW, Neitz M. Substitution of isoleucine for threonine at position 190 of S-opsin causes S-cone-function abnormalities. Vision Res. 2012 Nov 15;73:1-9. doi: 10.1016/j.visres.2012.09.007. Epub 2012 Sep 26. Citation on PubMed or Free article on PubMed Central
- Calkins DJ. Seeing with S cones. Prog Retin Eye Res. 2001 May;20(3):255-87. doi: 10.1016/s1350-9462(00)00026-4. Citation on PubMed
- Deeb SS. Molecular genetics of color-vision deficiencies. Vis Neurosci. 2004 May-Jun;21(3):191-6. doi: 10.1017/s0952523804213244. Citation on PubMed
- Gunther KL, Neitz J, Neitz M. A novel mutation in the short-wavelength-sensitive cone pigment gene associated with a tritan color vision defect. Vis Neurosci. 2006 May-Aug;23(3-4):403-9. doi: 10.1017/S0952523806233169. Citation on PubMed
- Neitz J, Neitz M. The genetics of normal and defective color vision. Vision Res. 2011 Apr 13;51(7):633-51. doi: 10.1016/j.visres.2010.12.002. Epub 2010 Dec 15. Citation on PubMed or Free article on PubMed Central
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