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Arrestin is a 45 KDa protein and is mainly located in the membrane of photoreceptor rod cells and pineal gland. It is well known that 1147delA nutation in the arrestin gene causes Oguchi disease and autosomal recessive retinitis pigmentosa in Japanese patients. We examined expression of arrestin in mRNA isolated from whole blood cells of patients with Oguchi disease, who had the 1147delA mutation in the arrestin gene. Arrestin was expressed at the level of mRNA in all of three patients with Oguchi disease. mRNA from Oguchi patients did not have the same 1147delA mutation as was seen in the arrestin gene but had the normal sequence. The result indicated the possibility of RNA editing in blood cells in our patients.

Retinitis pigmentosa (RP) is a genetically heterogeneous group of diseases that show progressive degeneration of photoreceptors. Its incidence is about one in 3000 to 10,000 people in many countries, and it is a leading cause of blindness in the adult population. Several kinds of mutations have been reported in patients with autosomal recessive RP (arRP) in genes that are normally expressed in rod photoreceptors and that function in the process of phototransduction. Arrestin, one of the photoreceptorspecific proteins, plays a role in the cycle of rhodopsin regeneration. 1 A homozygous 1-base pair deletion mutation in the arrestin gene, designated the arrestin 1147delA, has been known as a frequent cause of Oguchi disease, a form of congenital stationary night blindness, in Japanese patients. 2 Interestingly, molecular genetic screening in patients with arRP, including a sibling of a patient with Oguchi disease, to search for mutations in the arrestin gene revealed that the same 1147delA mutation is also associated with arRP and is cosegregated with the disease. We report on 3 patients with arRP associated with the homozygous 1147delA mutation in the arrestin gene as evidence of variable expressivity of the mutation in the arrestin gene.

Oguchi disease is known as a type of autosomal recessive congenital stationary night blindness with a golden yellow-reflex of the fundus(1–3). Characteristic clinical features are Mizuo-Nakamura phenomenon(4) and extremely retarded dark adaptation of rod photoreceptors. The cone function usually appears normal.

Oguchi disease is a form of retinal dysfunction in which congenital night blindness is accompanied by a light-dependent discoloration of the fundus, extremely slow dark adaptation and an abnormal rod electroretinogram. This autosomal recessive condition is generally considered to be non-progressive however Oguchi disease and progressive retinal pigmentary degeneration or congenital stationary night blindness has occurred in the same families and even in the same patients. Oguchi disease may therefore represent a disorder involving features of both congenital stationary night blindness and retinitis pigmentosa. Here we summarise molecular genetic analyses which indicate that mutations in the arrestin gene are responsible for at least some cases of Oguchi disease in the Indian and Japanese populations. We speculate that the light-dependent fundus discoloration characteristic of Oguchi disease may reflect hyper-activity of the phototransduction pathway resulting from failure of arrestin to bind to and quench light-activated rhodopsin.