Figure 2. Quantification of retinal pigment epithelium-(RPE) and photoreceptor-specific gene expression. Quantitative real-time-polymerase chain reaction (QRT–PCR) was performed, comparing retina–RPE samples from intact mice and those grown in organotypic cultures starting from postnatal day 7. Analyzed were expression levels of Rpe65 (the rate-limiting enzyme required to generate 11-cis retinal), one rod-specific gene (rhodopsin), and three cone-specific genes (ultraviolet [UV] and middle-wavelength [MWL] opsin and cone transducin [Gnat2]). Explants contain 2-fold to 3-fold less mRNA for the tested genes at P7+11DIV than age-matched (P18) tissues that developed in vivo. Data are represented as mean±standard deviation of three different sets of experiments.