title: NeuroD regulates proliferation of photoreceptor progenitors in the retina of the zebrafish.
abstract: neuroD is a member of the family of proneural genes, which function to regulate the cell cycle, cell fate determination and cellular differentiation. In the retinas of larval and adult teleosts, neuroD is expressed in two populations of post-mitotic cells, a subset of amacrine cells and nascent cone photoreceptors, and proliferating cells in the lineages that give rise exclusively to rod and cone photoreceptors. Based on previous studies of NeuroD function in vitro and the cellular pattern of neuroD expression in the zebrafish retina, we hypothesized that within the mitotic photoreceptor lineages NeuroD selectively regulates aspects of the cell cycle. To test this hypothesis, gain and loss-of-function approaches were employed, relying on the inducible expression of a NeuroD(EGFP) fusion protein and morpholino oligonucleotides to inhibit protein translation, respectively. Conditional expression of neuroD causes cells to withdraw from the cell cycle, upregulate the expression of the cell cycle inhibitors, p27 and p57, and downregulate the cell cycle progression factors, Cyclin B1, Cyclin D1, and Cyclin E2. In the absence of NeuroD, cells specific for the rod and cone photoreceptor lineage fail to exit the cell cycle, and the number of cells expressing Cyclin D1 is increased. When expression is ectopically induced in multipotent progenitors, neuroD promotes the genesis of rod photoreceptors and inhibits the genesis of Müller glia. These data show that in the teleost retina NeuroD plays a fundamental role in photoreceptor genesis by regulating mechanisms that promote rod and cone progenitors to withdraw from the cell cycle. This is the first in vivo demonstration in the retina of cell cycle regulation by NeuroD.
authors.affiliation: Department of Ophthalmology and Visual Sciences and The Neuroscience Graduate Program, W.K. Kellogg Eye Center, 1000 Wall Street, The University of Michigan, Ann Arbor, MI 48105-0714, USA.
authors.forename: M J
authors.initials: MJ
authors.lastname: Ochocinska
authors.forename: P F
authors.initials: PF
authors.lastname: Hitchcock
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D051792:Basic Helix-Loop-Helix Proteins / Q000378:metabolism*; D002454:Cell Differentiation / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D016213:Cyclins / Q000235:genetics / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D047108:Embryonic Development / Q000187:drug effects; D005306:Fertilization / Q000187:drug effects; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D008938:Mitosis / Q000187:drug effects; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009457:Neuroglia / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D020419:Photoreceptor Cells, Vertebrate / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012160:Retina / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D017948:Retinal Rod Photoreceptor Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D013234:Stem Cells / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects; D015027:Zebrafish / Q000196:embryology / Q000235:genetics / Q000378:metabolism*
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D016213:Cyclins; D009419:Nerve Tissue Proteins; D016376:Oligonucleotides, Antisense; D011993:Recombinant Fusion Proteins; C093564:Neurogenic differentiation factor 1