The gene expression changes identified in the rd7 mutant retina in the present study suggest the scheme of gene regulation in mouse rods depicted in Figure 8. As this diagram implies, there appear to be at least two different repressors of cone genes within rods, Nr2e3 and either Nrl itself or an additional unknown transcription factor downstream of Nrl, here termed “transcription factor X.” In fact, it appears that the differences between type I and type II cone genes may simply depend on which repressor—Nr2e3 or transcription factor X—is primarily responsible for the regulation of the gene in question. In the case of type I genes, Nr2e3 is the primary repressor and transcription factor X is of secondary importance. In the case of type II genes, transcription factor X exerts the major repressive effect on transcription, and Nr2e3 plays a lesser, but still important role.