The retinal pigment epithelium (RPE) is very a important part of the eye; It is responsible for absorption of scattered light, the visual cycle and phagocytosis of photoreceptor outer segment membranes. The protein RPE65 is normally abundantly made in the RPE, unless there is a mutation in the RPE65 gene, caused by a deletion of 4 base pairs. This deletion causes a frame shift and also an early stop on the protein, so the protein is shorter and does not function properly. The mutated gene is recessive, so when the mutated RPE65 gene is homozygous in animals, it causes an early onset retinal degeneration. Most sufferers of this mutation experience a lack of rod electroretinography, complete night blindness and weak cone responses. It is thought
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The defective gene causes a block in the visual cycle, which leads to the absence of 22-cis-retinal and rhodopsin, also a build up of all-trans-retinyl esters, eventual retinal degeneration, and very little rod photoreceptor function. 9-cis-retinal can restore the visual pigment and function in the mice which are RPE65 deficient. RPE65 deficient mice were used as a model of Leber congenital amaurosis (LCA), which affects human children, which causes their sight to deteriorate over time. The RPE65 deficient mice suffer from severely impaired rod physiology and have no rod photopigment. Mice were treated with orally delivered 9-cis-retinal, in an attempt to get past the biochemical barricade caused by the mutated gene. Within only 48 hours rod photopigment was forming, and the rod physiology was improving …show more content…
Dogs with the tissue affected by the homozygous mutated genes show prominent RPE inclusions, slightly abnormal rod photo receptor morphology, and slowly progressive photoreceptor degeneration. A culture of RPE cells of affected cells, wild type cells, and affected cells treated with AAV-RPE65 (Figure 1), were labeled positively for RPE65 wild type. The wild type cell show high levels of RPE65, as did the cells with the defective RPE65 gene that were treated with AAV-RPE65, whereas the RPE65 deficient cells did not show the label. AAV-RPE65 was also delivered intraocularly to three dog with the mutant RPE65 gene (Table 1), ten of these dogs light sensitive cells were tested by electroretinography (Figure 3). Dogs with the wild type gene coding for RPE65 responded to increasing stimulus as intensity increased with both bipolar cells, and photoreceptor amplitudes. The dogs with the RPE65 deficient eyes were tested in the same way, the threshold for a stimulus from them was over 4.5 log units more than the dogs with wild type RPE65. The retinal function of the dogs were improved when they were treated with sub-retinal AAV-RPE65. Compared to before the treatment the right eye of BR33 (table 1) had a b-wave threshold that was lowered by approximately 4 log units, which is almost the same as dogs with working RPE65.
The defective gene causes a block in the visual cycle, which leads to the absence of 22-cis-retinal and rhodopsin, also a build up of all-trans-retinyl esters, eventual retinal degeneration, and very little rod photoreceptor function. 9-cis-retinal can restore the visual pigment and function in the mice which are RPE65 deficient. RPE65 deficient mice were used as a model of Leber congenital amaurosis (LCA), which affects human children, which causes their sight to deteriorate over time. The RPE65 deficient mice suffer from severely impaired rod physiology and have no rod photopigment. Mice were treated with orally delivered 9-cis-retinal, in an attempt to get past the biochemical barricade caused by the mutated gene. Within only 48 hours rod photopigment was forming, and the rod physiology was improving …show more content…
Dogs with the tissue affected by the homozygous mutated genes show prominent RPE inclusions, slightly abnormal rod photo receptor morphology, and slowly progressive photoreceptor degeneration. A culture of RPE cells of affected cells, wild type cells, and affected cells treated with AAV-RPE65 (Figure 1), were labeled positively for RPE65 wild type. The wild type cell show high levels of RPE65, as did the cells with the defective RPE65 gene that were treated with AAV-RPE65, whereas the RPE65 deficient cells did not show the label. AAV-RPE65 was also delivered intraocularly to three dog with the mutant RPE65 gene (Table 1), ten of these dogs light sensitive cells were tested by electroretinography (Figure 3). Dogs with the wild type gene coding for RPE65 responded to increasing stimulus as intensity increased with both bipolar cells, and photoreceptor amplitudes. The dogs with the RPE65 deficient eyes were tested in the same way, the threshold for a stimulus from them was over 4.5 log units more than the dogs with wild type RPE65. The retinal function of the dogs were improved when they were treated with sub-retinal AAV-RPE65. Compared to before the treatment the right eye of BR33 (table 1) had a b-wave threshold that was lowered by approximately 4 log units, which is almost the same as dogs with working RPE65.