Leber Congenital Amaurosis Essay

Leber’s congenital amaurosis is an autosomal recessive blindness, more than 30 mutations in the gene RPE65 are thought to be causative of the condition. The disease is onset in childhood and causes sufferers to lose daylight vision and lack night vision. The study found that about 6 -16% of sufferers contained a mutated form of the gene RPE65 (retinal pigment epithelium-specific protein 65 kDa), an important enzyme of the retinoid cycle of vision. RPE65 is a gene that codes for the production of a protein in the retina which works to nourish the retina. It is essential for the visual cycle which is the way light that is entering the eye gets converted into electrical signals that can be recognised by the brain. If an individual suffers from Lebers congenital amaurosis, the light-detection cells die and disrupt communication between the brain and retina, causing blindness.

Photoisomerization of retinaldehyde is essential for vision. When 11-cis retinal chromophore observes a photon of light, it converts to an all-trans state. Mutations in the RPE65 gene lead to loss of function in the RPE65 protein partially or entirely. This in turn disables the mechanism needed to turn all-trans retinal back into 11-cis retinal, causing a build-up in the retinal

The adeno-associated viral vector (AAV2-RPE65) containing RPE65 was injected into the retina of patients and although noticeable improvement was shown in cone photoreceptors, Central visual aculty was not necessarily affected. The study then compared photoreceptor cell loss in retinas of treated individuals versus untreated individuals in 11 patients. Vision was observed to improve and remain stable, however the photoreceptors showed a steady degeneration. Patients were then monitored over 5 to 6 years after