Pax6a and Pax6b are required at different points in neuronal progenitor cell proliferation during zebrafish photoreceptor regeneration

Thummel, R., Enright, J.M., Kassen, S.C., Montgomery, J.E., Bailey, T.J., and Hyde, D.R.
Experimental Eye Research   90(5): 572-582 (Journal)
Registered Authors
Bailey, Travis, Hyde, David R., Kassen, Sean, Montgomery, Jacob, Thummel, Ryan
Pax6, morpholino, Müller glia, neuronal progenitor, retina, cell migration, stem cell
MeSH Terms
  • Animals
  • Cell Proliferation
  • Dark Adaptation
  • Electroporation
  • Eye Proteins/physiology*
  • Fluorescent Antibody Technique, Indirect
  • Gene Silencing/physiology
  • Homeodomain Proteins/physiology*
  • In Situ Nick-End Labeling
  • Injections
  • Microscopy, Confocal
  • Morpholines/pharmacology
  • Paired Box Transcription Factors/physiology*
  • Radiation Injuries, Experimental/metabolism*
  • Regeneration/physiology*
  • Repressor Proteins/physiology*
  • Retinal Cone Photoreceptor Cells/physiology*
  • Retinal Cone Photoreceptor Cells/radiation effects
  • Retinal Neurons/cytology*
  • Retinal Rod Photoreceptor Cells/physiology*
  • Retinal Rod Photoreceptor Cells/radiation effects
  • Stem Cells/cytology*
  • Vitreous Body
  • Zebrafish
  • Zebrafish Proteins/physiology
20152834 Full text @ Exp. Eye. Res.
The light-damaged zebrafish retina results in the death of photoreceptor cells and the subsequent regeneration of the missing rod and cone cells. Photoreceptor regeneration initiates with asymmetric Müller glial cell division to produce neuronal progenitor cells, which amplify, migrate to the outer nuclear layer (ONL), and differentiate into both classes of photoreceptor cells. In this study, we examined the role of the Pax6 protein in regeneration. In zebrafish, there are two Pax6 proteins, one encoded by the pax6a gene and the other encoded by the pax6b gene. We intravitreally injected and electroporated morpholinos that were complementary to either the pax6a or pax6b mRNA to knockdown the translation of the corresponding protein. Loss of Pax6b expression did not affect Müller glial cell division, but blocked the subsequent first cell division of the neuronal progenitors. In contrast, the paralogous Pax6a protein was required for later neuronal progenitor cell divisions, which maximized the number of neuronal progenitors. Without neuronal progenitor cell amplification, proliferation of resident ONL rod precursor cells, which can only regenerate rods, increased inversely proportional to the number of INL neuronal progenitor cells. This confirmed that Müller glial-derived neuronal progenitor cells are necessary to regenerate cones and that distinct mechanisms selectively regenerate rod and cone photoreceptors. This work also defines distinct roles for Pax6a and Pax6b in regulating neuronal progenitor cell proliferation in the adult zebrafish retina and increases our understanding of the molecular pathways required for photoreceptor cell regeneration.
Genes / Markers
Mutations / Transgenics
Human Disease / Model
Sequence Targeting Reagents
Engineered Foreign Genes