Fig. 5

The proposed model of the collective regulation of the RH2 locus in zebrafish. The regulatory activity of the proximal regions in the dorsal and ventral retina is depicted by the top and bottom part of the divided ovals, respectively, at each position. Light green and gray indicate the active and repressive states, respectively. Basically, the RH2-LCR induces gene expression if the upstream region of the target is active as depicted by the arched arrows. However, competition with other members of the locus (whiskered brown bars) and the repressive regulation by the upstream regions of RH2-1 and RH2-2 in the ventral retina (black bars) inhibits the interaction of RH2-3 with the RH2-LCR as indicated by the dashed arrows, restricting its expression into the narrow banded area between the central and ventral retina. Importantly, the dominance in the competitive regulation (indicated by the sizes of the whiskers) greatly depends on the relative position to the RH2-LCR.