Bradiopsia (Bradyopsia) - Genes RGS9 or RGS9BP.
The bradiopsia is a rare disease that affects vision. The term "bradiopsia" comes from the Greek words for slow vision. In affected individuals, the eyes more slowly than usual adapt to changing light conditions. For example, those affected lose sight for several seconds when moving from a dark one bright atmosphere. Some people with bradiopsia also have difficulty seeing some moving objects, particularly small moving objects with a bright background. As a result, they have frequently to see or participate in sports with a ball, like football or tennis problems. Moreover, those affected may have reduced visual acuity, although the sharpness may depend on the conditions under which viewing takes place. The ability to see and distinguish colors is normal. The problems associated with vision bradiopsia become apparent in early childhood and usually are stable.
The bradiopsia may be due to mutations in the gene RGS9, located on the long arm of chromosome 17 (17q24), or RGS9BP gene, located on the long arm of chromosome 19 (19q13.11). These genes encode proteins that are necessary for normal vision. Protein is found in the photoreceptors of the eye. When light enters the eye, it stimulates specialized pigments in these cells. This stimulation triggers a series of chemical reactions that produce an electrical signal, which is interpreted by the brain as vision. Once the photoreceptors have been stimulated by light, they have to return to its resting state before they can be stimulated again. The RGS9 and RGS9BP proteins play an essential role in returning the photoreceptor to its resting state quickly after exposure to light.
They have identified at least two mutations in the gene RGS9 and 6 mutations in the gene associated with bradiopsia RGS9BP. Mutations in these genes in any prevent photoreceptors recover quickly after responding to light. Normally they return to their quiescent state in a split second, but people with mutations in one of these genes, may require ten seconds or more. During that time, the photoreceptors can not respond to light. This delay causes temporary blindness in response to changing light conditions and interferes with the vision of small objects when they are moving. In some people with bradiopsia, we have not found mutations in the gene RGS9 or RGS9BP. The cause of the disease in these individuals is unknown.
This disease is inherited in an autosomal recessive pattern, that is, both copies of the gene in every cell must have mutations for alteration is expressed. The parents of an individual with an autosomal recessive disease have a copy of the mutated gene, but usually show no signs and symptoms of the disease.
Tests in IVAMI: in IVAMI perform detection of mutations associated with bradiopsia, by complete PCR amplification of the exons of RGS9 and RGS9BP, respectively, and subsequent sequencing genes.
Samples recommended: EDTA blood collected for separation of blood leukocytes, or impregnated sample card with dried blood (IVAMI may mail the card to deposit the blood sample).