June 2013
Volume 54, Issue 15
Free
ARVO Annual Meeting Abstract  |   June 2013
Synapses of the Outer Plexiform Layer in the Regenerating Zebrafish Retina
Author Affiliations & Notes
  • Tim McGinn
    Biological Sciences, University of Idaho, Moscow, ID
  • Alessandra Minette
    Biological Sciences, University of Idaho, Moscow, ID
  • Tyler Lankford
    Biological Sciences, University of Idaho, Moscow, ID
  • Deborah Stenkamp
    Biological Sciences, University of Idaho, Moscow, ID
  • Footnotes
    Commercial Relationships Tim McGinn, None; Alessandra Minette, National Science Foundation (F); Tyler Lankford, None; Deborah Stenkamp, None
  • Footnotes
    Support None
Investigative Ophthalmology & Visual Science June 2013, Vol.54, 1167. doi:
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      Tim McGinn, Alessandra Minette, Tyler Lankford, Deborah Stenkamp; Synapses of the Outer Plexiform Layer in the Regenerating Zebrafish Retina. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1167.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose: Teleost fish such as the zebrafish have the capacity to regenerate retinal tissue after retinal injury. Following a chemical lesion selectively targeting the inner retina, inner retinal neurons are regenerated, albeit with patterning errors. Recovery of behavioral measures of visual function takes place about 60 days after lesioning. In the current study we address whether newly generated inner retinal neurons establish appropriate synaptic connections and over what time frame.

Methods: The inner layers of the retinas of 9-10 month old adult zebrafish were selectively lesioned by intraocular injection of the neurotoxin ouabain, and were allowed to recover for 3, 21, or 60 days. Retinas were fixed, sectioned at 20 μm, and subjected to confocal imaging. Photoreceptors and bipolar cells were visualized using the transgenic reporter line Tg(UV-GFP) (UV cones), zpr-1 antibody (red and green cones), anti-PKCα (a subpopulation of bipolar cells), and anti-SV2 (synaptic terminals). Measurement of bipolar cell volumes was done using Imaris software, and identification of cone-bipolar synapses was done using Imaris and ImageJ.

Results: By 21 days post-injury (dpi) the numbers of PKCα+ bipolar cells were similar to those of the control retinas. Similarly, the volume of PKCα+ bipolar cells was restored to control levels by 21 dpi. Preliminary observations suggest the morphologies of PKCα+ bipolar cells were not restored. Regenerated PKCα+ bipolar cells had shortened axons or tortuous axonal paths, but dendritic volumes and soma sizes appeared normal. By 21 dpi, UV cones, and red and green cones had reformed synapses with PKCα+ bipolar cells. These same types of connections were also observed in the control retinas. Cone synaptic terminals maintained SV2 expression at all sampling times following injury.

Conclusions: Specific cone bipolar cell synapses reformed relatively rapidly after an injury selective to the inner retina (by 21 days), when compared to the restoration of visual function (60 days). Despite unusual cell morphologies of the bipolar cells, synaptogenesis between photoreceptors and bipolar cells is likely not the limiting step in functional retinal regeneration.

Keywords: 687 regeneration • 650 plasticity • 435 bipolar cells  
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