The GUCY2D gene provides instructions for making a protein that plays an essential role in normal vision. This protein is found in the retina, which is the specialized tissue at the back of the eye that detects light and color. Within the retina, the GUCY2D protein is located in light-detecting cells called photoreceptors. The retina contains two types of photoreceptor cells: rods and cones. Rods are needed for vision in low light, while cones are needed for vision in bright light, including color vision.
The GUCY2D protein is involved in a process called phototransduction. When light enters the eye, it stimulates specialized pigments called opsins that "hold" a vitamin A molecule in photoreceptor cells. This stimulation triggers a series of chemical reactions that close the open channel in the cell membranes of rod and cone cells. This closure produces an electrical signal, which is then interpreted by the brain as vision.
Once photoreceptors have been stimulated by light, they must return to their resting (or "dark") state before they can be stimulated again. The GUCY2D protein is involved in a chemical reaction that re-opens the cell membrane channels that helps return photoreceptors to their dark state after light exposure.
Health Conditions Related to Genetic Changes
Some variants (also known as mutations) in the GUCY2D gene have been identified in people with a vision disorder called 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.
The variants that cause cone-rod dystrophy occur in one of the two copies of the GUCY2D gene in each cell. These variants are responsible for about one-quarter of the cases of a form of the condition called autosomal dominant cone-rod dystrophy. Most of these variants affect a particular protein building block (amino acid) in the GUCY2D protein, replacing the amino acid arginine at position 838 with one of several other amino acids. These genetic changes impair normal phototransduction, causing the photoreceptor cells to deteriorate over time. The loss of these cells leads to the progressive vision problems characteristic of cone-rod dystrophy.More About This Health Condition
Leber congenital amaurosis
Many variants in the GUCY2D gene have been found to cause Leber congenital amaurosis. This condition is an eye disorder that primarily affects the retina. People with this disorder typically have severe visual impairment beginning at birth or shortly afterward. Variants in this gene account for 6 to 21 percent of all cases of this condition.
The variants that cause Leber congenital amaurosis occur in both copies of the GUCY2D gene in each cell. Most of these genetic changes lead to an abnormally short, nonfunctional version of the GUCY2D protein. A lack of this protein prevents photoreceptor cells from returning to their dark state after they are exposed to light. As a result, the process of phototransduction is almost totally shut down, leading to severe visual impairment beginning very early in life in Leber congenital amaurosis.More About This Health Condition
Other Names for This Gene
- guanylate cyclase 2D, membrane (retina-specific)
- retinal guanylyl cyclase 1
- rod outer segment membrane guanylate cyclase
Additional Information & Resources
Tests Listed in the Genetic Testing Registry
Scientific Articles on PubMed
Catalog of Genes and Diseases from OMIM
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- Kitiratschky VB, Wilke R, Renner AB, Kellner U, Vadala M, Birch DG, Wissinger B, Zrenner E, Kohl S. Mutation analysis identifies GUCY2D as the major gene responsible for autosomal dominant progressive cone degeneration. Invest Ophthalmol Vis Sci. 2008 Nov;49(11):5015-23. doi: 10.1167/iovs.08-1901. Epub 2008 May 16. Citation on PubMed
- Payne AM, Morris AG, Downes SM, Johnson S, Bird AC, Moore AT, Bhattacharya SS, Hunt DM. Clustering and frequency of mutations in the retinal guanylate cyclase (GUCY2D) gene in patients with dominant cone-rod dystrophies. J Med Genet. 2001 Sep;38(9):611-4. doi: 10.1136/jmg.38.9.611. No abstract available. Citation on PubMed or Free article on PubMed Central
- Rozet JM, Perrault I, Gerber S, Hanein S, Barbet F, Ducroq D, Souied E, Munnich A, Kaplan J. Complete abolition of the retinal-specific guanylyl cyclase (retGC-1) catalytic ability consistently leads to leber congenital amaurosis (LCA). Invest Ophthalmol Vis Sci. 2001 May;42(6):1190-2. Citation on PubMed
- Ugur Iseri SA, Durlu YK, Tolun A. A novel recessive GUCY2D mutation causing cone-rod dystrophy and not Leber's congenital amaurosis. Eur J Hum Genet. 2010 Oct;18(10):1121-6. doi: 10.1038/ejhg.2010.81. Epub 2010 Jun 2. Citation on PubMed or Free article on PubMed Central