CRX-bound regions act in a combinatorial fashion to drive photoreceptor gene expression. (A) Distribution of CBRs around the rhodopsin (Rho) gene, which encodes rod opsin, the primary light-sensing molecule of rod photoreceptors. (B) Quantitative analysis of Rho-CBR cis-regulatory activity in electroporated retinas. The indicated Rho-CBRs were cloned into a DsRed reporter and electroporated into P0 mouse retinas along with a Rho-CBR3-eGFP loading control. After 8 d in culture, the retinas were imaged in flat-mount, and promoter activity was quantified by measuring fluorescence (see Methods for details). Shown is the mean ± standard deviation of three replicate electroporations. All values are normalized to that of Rho-CBR3, which is set equal to 100. (C) Quantitative analysis of Rho-CBR cis-regulatory activity when cloned upstream of the Rho proximal promoter region (Rho-CBR3). Shown is the mean ± SD of three replicate electroporations. All values are normalized to that of Rho-CBR3 alone, which is set equal to 100. Note that the y-axis is on a log scale.
