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Fig. 8 Gene expression in the embryonic rod lineage of zebrafish. Gene expression summary at right shows the genetic hierarchy of the rod lineage; darkness of font reflects the extent to which the transcription factor is expressed within the identified cells of the lineage. Pax6-positive Müller glia/stem cells are shown in blue with their cell bodies in the inner region of the inl. The summary at right illustrates an alternative scenario in which pax6+ stem cells (in black) generate embryonic Müller glia as well as cells of the rod lineage. As rod progenitors proliferate and migrate toward the onl, some become NeuroD-positive and rx1-positive (green cells), but none remain pax6-positive. All of these progenitors later express crx (yellow). Prior to entering the onl, some rod progenitors express NeuroD, rx1, and Nr2e3, while all continue to express crx (orange). All rod precursors of the onl (red) are NeuroD, rx1, crx, and Nr2e3-positive but do not express nrl, rod opsin, or gnat 1. Postmitotic rod photoreceptors (purple) express NeuroD, rx1, crx, Nr2e3, nrl, rod opsin, and gnat1. onl, outer nuclear layer; p-inl, m-inl, d-inl are proximal, middle, and distal compartments of the inl, respectively, and are delineated by dotted lines.