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Normal Function
The RGS9BP gene (which is also known as R9AP) provides instructions for making a protein called RGS9 binding protein. 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 protein is associated with light-detecting cells called photoreceptors. As its name suggests, RGS9 binding protein interacts with a protein called RGS9 (which is produced from the RGS9 gene). It anchors the RGS9 protein to photoreceptors and stimulates RGS9's activity.
When light enters the eye, it stimulates specialized pigments in photoreceptor cells. This stimulation triggers a series of chemical reactions that produce an electrical signal, which is interpreted by the brain as vision. (This process is known as phototransduction.) Once photoreceptors have been stimulated by light, they must return to their resting state before they can be stimulated again. RGS9 and RGS9 binding protein are involved in a chemical reaction that helps return photoreceptors to their resting state quickly after light exposure.
Health Conditions Related to Genetic Changes
Bradyopsia
At least six mutations in the RGS9BP gene have been found to cause bradyopsia, a rare condition that affects vision. In people with bradyopsia, the eyes adapt more slowly than usual to changing light conditions (for example, walking out of a darkened movie theater into daylight or driving into a dark tunnel on a sunny day). Some affected individuals also have difficulty seeing small moving objects, such as a tennis ball.
The RGS9BP gene mutations that cause bradyopsia prevent RGS9 binding protein from anchoring the RGS9 protein to photoreceptor cells. The resulting loss of RGS9 protein function prevents photoreceptors from recovering quickly after responding to light. Normally they return to their resting state in a fraction of a second, but in people with RGS9BP gene mutations, it can take ten seconds or longer. During that time, the photoreceptors cannot respond to light. This delay causes temporary blindness in response to changing light conditions and may interfere with seeing small objects when they are in motion.
More About This Health ConditionOther Names for This Gene
- FLJ45744
- R9AP
- regulator of G-protein signaling 9 binding protein
- regulator of G-protein signaling 9-binding protein
- RGS9 anchor protein
- RGS9-anchoring protein
Additional Information & Resources
Tests Listed in the Genetic Testing Registry
Scientific Articles on PubMed
Catalog of Genes and Diseases from OMIM
References
- Cheng JY, Luu CD, Yong VH, Mathur R, Aung T, Vithana EN. Bradyopsia in an Asian man. Arch Ophthalmol. 2007 Aug;125(8):1138-40. doi: 10.1001/archopht.125.8.1138. No abstract available. Citation on PubMed
- Michaelides M, Li Z, Rana NA, Richardson EC, Hykin PG, Moore AT, Holder GE, Webster AR. Novel mutations and electrophysiologic findings in RGS9- and R9AP-associated retinal dysfunction (Bradyopsia). Ophthalmology. 2010 Jan;117(1):120-127.e1. doi: 10.1016/j.ophtha.2009.06.011. Epub 2009 Oct 8. Citation on PubMed
- Nishiguchi KM, Sandberg MA, Kooijman AC, Martemyanov KA, Pott JW, Hagstrom SA, Arshavsky VY, Berson EL, Dryja TP. Defects in RGS9 or its anchor protein R9AP in patients with slow photoreceptor deactivation. Nature. 2004 Jan 1;427(6969):75-8. doi: 10.1038/nature02170. Citation on PubMed
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