Ceramide, ceramide kinase and vision defects: A blind spot for lipids

Abstract

Retinitis Pigmentosa (RP), the most prevalent inherited retinal disorder in humans (1 in 3000), is characterized by progressive, bilateral and symmetrical degeneration of photoreceptors. Prominent clinical features include night blindness and constriction of visual fields, generally leading to complete blindness (Hims et al., 2003). RP is a monogenic disorder with extremely high clinical and genetic heterogeneity. Genetic studies to date have identified around 40 genes and loci (RetNet, Retinal Information Network, http://www.sph.uth.tmc.edu/Retnet/) responsible for the phenotype, yet the causative genes for more than half of the diagnosed cases remain unknown. Allelic heterogeneity, when different mutations of the same gene cause the same phenotype such as ABCA4 (Martínez-Mir et al., 1998) which lead to retinal disease, further complicates the genetic scenario. From photon reception to amplified synaptic transmission and final image integration in the brain, vision is a complex biological process. It is hardly surprising, therefore, that there are so many genes involved in RP. Candidate genes for RP normally participate in a variety of activities, including the phototransduction cascade and the visual cycle, and encode transcription and splicing factors. © Springer-Verlag Tokyo 2006. All rights reserved.