Figure 1.

Targeted cell types and types of genes to be delivered using gene therapy for RP. A, The cell types of the normal retina, with the associated support cells, the retinal pigmented epithelium (RPE) cells. Note that there are many more rods than cones in the photoreceptor layer, approximately 20:1, in both the mouse and the extramacular region of the human retina. In addition, note that the retinal pigmented epithelium processes surround the rod and cone outer segments, providing various types of support functions. The outer segments are membrane-rich and are the location of the phototransduction process. B, The rods typically die first in RP, with a concomitant collapse of the outer segment layer, and a loss of the normal association between the retinal pigmented epithelium processes and the remaining outer segments. Cones exhibit a dramatic change in morphology, modeled here after observations in mice (Lin et al., 2009). The cell types that are being targeted for gene therapy using AAV vectors are shown. For a description of the types of genes being delivered, see Table 1 and the text. HC, horizontal cell; BP, bipolar cells; AC, amacrine cells; MG, Mueller glia; RGC, retinal ganglion cells; ON BP, bipolar cells that hyperpolarize in response to glutamate when light is on. Drawing by Santiago Rompani and C. Cepko.