September 2016
Volume 57, Issue 12
Open Access
ARVO Annual Meeting Abstract  |   September 2016
Müller Glia reactivity follows retinal injury despite the absence of the Glial Fibrillary Acidic Protein gene in Xenopus
Author Affiliations & Notes
  • Reyna Isabel Martinez-De Luna
    Ophthalmology, SUNY Upstate Medical University, Syracuse, New York, United States
  • Ray Yueh Ku
    Neuroscience, SUNY Upstate Medical University, Syracuse, New York, United States
  • Alexandria M. Aruck
    Ophthalmology, SUNY Upstate Medical University, Syracuse, New York, United States
  • Francesca N. Santiago
    Ophthalmology, SUNY Upstate Medical University, Syracuse, New York, United States
  • Diego San Mauro
    Zoology & Physical Anthropology Faculty of Biological Sciences, Complutense University, Madrid, Spain
  • Michael Ezra Zuber
    Ophthalmology, SUNY Upstate Medical University, Syracuse, New York, United States
    Neuroscience, SUNY Upstate Medical University, Syracuse, New York, United States
  • Footnotes
    Commercial Relationships   Reyna Martinez-De Luna, None; Ray Ku, None; Alexandria Aruck, None; Francesca Santiago, None; Diego San Mauro, None; Michael Zuber, None
  • Footnotes
    Support  NIH Grants EY015748 and EY017964
Investigative Ophthalmology & Visual Science September 2016, Vol.57, No Pagination Specified. doi:
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      Reyna Isabel Martinez-De Luna, Ray Yueh Ku, Alexandria M. Aruck, Francesca N. Santiago, Diego San Mauro, Michael Ezra Zuber; Müller Glia reactivity follows retinal injury despite the absence of the Glial Fibrillary Acidic Protein gene in Xenopus. Invest. Ophthalmol. Vis. Sci. 201657(12):.

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

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Abstract

Purpose : Glial fibrillary acidic protein (GFAP) is a class III intermediate filament protein (IFP) that is up-regulated in Müller glia in response to injury or disease, and is thought to play a role in the extensive structural changes observed during Müller cell hypertrophy and glial scar formation. We previously demonstrated that Xenopus laevis Müller glia become reactive and hypertrophy following rod loss in an inducible (XOPNTR) model of retinal degeneration. The purpose of this study was to determine if GFAP is required for Müller cell reactivity in X. laevis.

Methods : Blastn, blastp, and tblastn searches of NCBI and Ensembl databases were used in an attempt to identify a Xenopus GFAP ortholog. MAFFT was used to align IFP sequences, identify conserved regions, and generate phylogenetic trees. Retinal injuries included photoreceptor ablation by metronidazole (Mtz) treatment of XOPNTR transgenic tadpoles and retinal ganglion cell (RGC) axotomy. Antibody specificity and changes in IFP expression were determined by western blot, immunohistochemistry and in situ hybridization of retinal sections. Degenerate PCR was used to detect gfap genes in amphibian and other vertebrate species.

Results : In spite of the morphological changes and GFAP-like immunoreactivity in Müller cells following retinal injury, we discovered that Xenopus lack a gene for gfap. Commonly used GFAP antibodies were not specific and also detect the class III IFPs Vim, Prph, Des, and Ina; suggested that one or more of these proteins was up-regulated in Müller cells following retinal injury in Xenopus. Consistent with this observation, we found that Vim and Prph were significantly induced following both rod photoreceptor ablation and RGC axotomy. Analyses of the X. tropicalis and X. laevis genomes indicated either a small deletion or incomplete inversion event resulted in deletion of the gfap gene during evolution. A PCR-based survey of representative species from all three extant amphibian orders (Anura, Caudata and Gymnophiona) suggests deletion of the gfap locus occurred in the ancestor of all Anura after its divergence from the Caudata ancestor ~290 million years ago.

Conclusions : Our results demonstrate that extensive changes in Müller cell morphology following retinal injury do not require GFAP in X. laevis. Instead, Müller cell changes may require other class III IFPs, potentially including Vim and Prph.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.

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