摘要：SummaryThe transcription factor NRL (neural retina leucine zipper) has been canonized as the master regulator of photoreceptor cell fate in the retina. NRL is necessary and sufficient to specify rod cell fate and to preclude cone cell fate in mice. By engineering zebrafish, we tested if NRL function has conserved roles beyond mammals or beyond nocturnal species, i.e., in a vertebrate possessing a greater and more typical diversity of cone sub-types. Transgenic expression of Nrl from zebrafish or mouse was sufficient to induce rod photoreceptor cells. Zebrafishnrl−/−mutants lacked rods (and had excess UV-sensitive cones) as young larvae; thus, the conservation of Nrl function between mice and zebrafish appears sound. Strikingly, however, rods were abundant in adultnrl−/−null mutant zebrafish. Rods developed in adults despite Nrl protein being undetectable. Therefore, a yet-to-be-revealed non-canonical pathway independent of Nrl is able to specify the fate of some rod photoreceptors.Graphical AbstractDisplay OmittedHighlights•Nrl is conserved and sufficient to specify rod photoreceptors in the zebrafish retina•Nrl is necessary for rod photoreceptors in early ontogeny of zebrafish larvae•Zebrafish Nrl is functionally conserved with mouse and human NRL•Remarkably, Nrl is dispensable for rod specification in adult zebrafishBiological Sciences; Molecular Biology; Developmental Biology
