title: Characterization of primary cilia during the differentiation of retinal ganglion cells in the zebrafish.
abstract: BACKGROUND
  Retinal ganglion cell (RGC) differentiation in vivo is a highly stereotyped process, likely resulting from the interaction of cell type-specific transcription factors and tissue-derived signaling factors. The primary cilium, as a signaling hub in the cell, may have a role during this process but its presence and localization during RGC generation, and its contribution to the process of cell differentiation, have not been previously assessed in vivo.
  
  
  METHODS
  In this work we analyzed the distribution of primary cilia in vivo using laser scanning confocal microscopy, as well as their main ultrastructural features by transmission electron microscopy, in the early stages of retinal histogenesis in the zebrafish, around the time of RGC generation and initial differentiation. In addition, we knocked-down ift88 and elipsa, two genes with an essential role in cilia generation and maintenance, a treatment that caused a general reduction in organelle size. The effect on retinal development and RGC differentiation was assessed by confocal microscopy of transgenic or immunolabeled embryos.
  
  
  RESULTS
  Our results show that retinal neuroepithelial cells have an apically-localized primary cilium usually protruding from the apical membrane. We also found a small proportion of sub-apical cilia, before and during the neurogenic period. This organelle was also present in an apical position in neuroblasts during apical process retraction and dendritogenesis, although between these stages cilia appeared highly dynamic regarding both presence and position. Disruption of cilia caused a decrease in the proliferation of retinal progenitors and a reduction of neural retina volume. In addition, retinal histogenesis was globally delayed albeit RGC layer formation was preferentially reduced with respect to the amacrine and photoreceptor cell layers.
  
  
  CONCLUSIONS
  These results indicate that primary cilia exhibit a highly dynamic behavior during early retinal differentiation, and that they are required for the proliferation and survival of retinal progenitors, as well as for neuronal generation, particularly of RGCs.
authors.affiliation: Human Molecular Genetics Laboratory, Institut Pasteur de Montevideo, Mataojo 2020, Montevideo, 11400, Uruguay.
authors.forename: Paola
authors.initials: P
authors.lastname: Lepanto
authors.affiliation: Cell Biology of Neural Development Laboratory, Institut Pasteur de Montevideo, Mataojo 2020, Montevideo, 11400, Uruguay.|Sección Biología Celular, Departamento de Biología Celular y Molecular, Facultad de Ciencias, Universidad de la República, Iguá 4225, Montevideo, 11400, Uruguay.
authors.forename: Camila
authors.initials: C
authors.lastname: Davison
authors.affiliation: Unidad de Microscopía Electrónica, Facultad de Ciencias, Universidad de la República, Iguá 4225, Montevideo, 11400, Uruguay.
authors.forename: Gabriela
authors.initials: G
authors.lastname: Casanova
authors.affiliation: Human Molecular Genetics Laboratory, Institut Pasteur de Montevideo, Mataojo 2020, Montevideo, 11400, Uruguay. jbadano@pasteur.edu.uy.
authors.forename: Jose L
authors.initials: JL
authors.lastname: Badano
authors.affiliation: Cell Biology of Neural Development Laboratory, Institut Pasteur de Montevideo, Mataojo 2020, Montevideo, 11400, Uruguay. fzolessi@fcien.edu.uy.|Sección Biología Celular, Departamento de Biología Celular y Molecular, Facultad de Ciencias, Universidad de la República, Iguá 4225, Montevideo, 11400, Uruguay. fzolessi@fcien.edu.uy.
authors.forename: Flavio R
authors.initials: FR
authors.lastname: Zolessi
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002454:Cell Differentiation; D002923:Cilia / Q000502:physiology* / Q000648:ultrastructure*; D055785:Gene Knockdown Techniques; D055495:Neurogenesis; D012160:Retina / Q000196:embryology* / Q000648:ultrastructure*; D012165:Retinal Ganglion Cells / Q000502:physiology* / Q000648:ultrastructure*; D015027:Zebrafish; D029961:Zebrafish Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D029961:Zebrafish Proteins; C528684:traf3ip1 protein, zebrafish
keywords: Cilia; Neurogenesis; Retina; Retinal ganglion cell