Figure 1.

Progression of a genetic disease through retinal cell death: autosomal dominant retinitis pigmentosa serves as an example. Healthy retina is composed of five neuronal types, with the photoreceptors being the primary neurons. In retinitis pigmentosa, mutations mostly in rod transcripts (shown in blue) lead to degeneration of these cells (stage I) followed by progressive cone (orange) degeneration (stages II and III). In the final stage (stage IV), all photoreceptor cells are lost, leaving the retina blind. Color images available online at www.liebertpub.com/hum