Tsujimura, T., Chinen, A. and Kawamura, S. (2007). Identification of a locus control region for quadruplicated green-sensitive opsin genes in zebrafish. Proceedings of the National Academy of Sciences USA, 104 (31):12813-12818.

We previously showed that zebrafish have four "green" (RH2) subtype opsins with different spectral sensitivities (GENETICS 163: 663-675, 2003) and that the four opsins are expressed in a single-type of photoreceptive cells, the short member of double cones (SDCs), but show a concentric ringed expression pattern in the retina (Journal of Experimental Biology 208: 1337-1345, 2005). In this study, we provide an evidence that the expression of the four opsin genes is controlled by a single regulatory region, which we call RH2-LCR.
@Opsin genes play a central role in the evolution of visual system. It is of vital importance to clarify regulatory mechanisms of the cell type-specific expression of opsin genes in the retina, but the mechanisms have not yet been well understood. In particular, the evolution of regulatory mechanisms associated with opsin gene duplications has only poorly explored albeit its importance. Our data presented in this paper allows the first comparative study of gene regulation of duplicated opsin genes between human (primates) and zebrafish (fish) and provides significant amount of information to promote our understanding visual system evolution through the transgenic studies much feasible in the experimental setup using zebrafish.