What is the role of ABCA4 in vision and how does it contribute to retinopathies?

During the visual process light is detected by photoreceptor cells (PRC) of the retina using opsin proteins containing the chromophore 11-cisretinal. The retinal pigment epithelium (RPE) provides metabolic support to PRCs and the two cell types co-operate to regenerate 11-cis-retinal from all-trans-retinal. Aberrant retinal recycling underlies numerous visual disorders including Stargardt’s Disease and Retinitis Pigmentosa. These diseases have a genetic basis and are caused by mutations to the gene for ABCA4, a member of the ATP Binding Cassette (ABC) family of transport proteins. ABCA4 is found in the disc membranes of PRCs; however its cellular role in the visual process is not known. Our aim is to ascertain the role of ABCA4 in vision and determine how disease causing mutations affect its function.