June 2021
Volume 62, Issue 8
Open Access
ARVO Annual Meeting Abstract  |   June 2021
Inactivation of Mechanistic Target of Rapamycin Complex 1 Results in Loss of Retinal Ganglion cells
Author Affiliations & Notes
  • Dejuan Kong
    Department of Ophthalmology and Visual Science, University of Michigan, Ann Arbor, Michigan, United States
  • Lynda Elghazi
    Department of Ophthalmology and Visual Science, University of Michigan, Ann Arbor, Michigan, United States
  • Heather Hager
    Department of Ophthalmology and Visual Science, University of Michigan, Ann Arbor, Michigan, United States
  • Mandy Losiewicz
    Department of Ophthalmology and Visual Science, University of Michigan, Ann Arbor, Michigan, United States
  • Sumathi Shanmugam
    Department of Ophthalmology and Visual Science, University of Michigan, Ann Arbor, Michigan, United States
  • Patrice E Fort
    Department of Ophthalmology and Visual Science, University of Michigan, Ann Arbor, Michigan, United States
  • Thomas W Gardner
    Department of Ophthalmology and Visual Science, University of Michigan, Ann Arbor, Michigan, United States
  • Steven F Abcouwer
    Department of Ophthalmology and Visual Science, University of Michigan, Ann Arbor, Michigan, United States
  • Footnotes
    Commercial Relationships   Dejuan Kong, None; Lynda Elghazi, None; Heather Hager, None; Mandy Losiewicz, None; Sumathi Shanmugam, None; Patrice Fort, None; Thomas Gardner, None; Steven Abcouwer, None
  • Footnotes
    Support  R01EY031961 (SFA, PEF), R01EY20582 and P30EY007003,
Investigative Ophthalmology & Visual Science June 2021, Vol.62, 1461. doi:
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      Dejuan Kong, Lynda Elghazi, Heather Hager, Mandy Losiewicz, Sumathi Shanmugam, Patrice E Fort, Thomas W Gardner, Steven F Abcouwer; Inactivation of Mechanistic Target of Rapamycin Complex 1 Results in Loss of Retinal Ganglion cells. Invest. Ophthalmol. Vis. Sci. 2021;62(8):1461.

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

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Abstract

Purpose : Mechanistic target of rapamycin (mTOR) signaling is central to trophic factor responses and nutrient sensing pathways. mTOR complex 1 (mTORC1) containing the regulatory-associated protein of mTOR (Raptor) regulates cell metabolism, growth and survival. Recently, we found that expression of mTORC1 components are relatively high in retinal ganglion cells (RGC, PMID:32622801). Here we examined the necessity of mTORC1 on RGC survival by conditional knockout (cKO) of mTOR and Raptor in the adult mouse retina.

Methods : mT/mG Cre-reporter mice were used to test the effectiveness of intravitreal (ivt) injection of AAV2Cre and a novel control virus encoding inactive Cre (AAV2CreΔC) on recombination in retinal cells. Adult mtorf/f and rptorf/f mice were ivt injected with these vectors to cause cKO of mTOR and Raptor, respectively, in cells within the ganglion cell layer (GCL). Activity of the mTORC1 pathway was evaluated by immunofluorescence (IF) analysis of phosphorylation of S6 ribosomal protein (p-S6, Ser240/244) and eukaryotic translation initiation factor 4E-binding protein 1 (p-4EBP1, Thr37/46) in retinal sections. RGC populations were examined using IF of the RGC marker RNA binding protein multiple splicing (RBPMS) and Hoechst staining in retinal sections.

Results : Ivt injection of AAV2Cre caused effective recombination in cells within the GCL, whereas AAV2CreΔC did not. AAV2Cre-mediated cKO of mTOR or Raptor decreased mTORC1 activity in the GCL, as indicated by significant reductions of p-S6 and p-4EBP1 positive cells. At 12 wk after AAV2Cre injection, cKO of mTOR or Raptor did not change RGC or total GCL cell densities. However, at 24 wk after AAV2Cre injection, cKO of mTOR or Raptor caused 47% (p<0.01) and 43% (p<0.01) reductions in RBPMS-positive cells, respectively, relative to the contralateral eye injected with AAV2CreΔC vector. RBPMS IF intensities in RGC were also generally decreased. Densities of nuclei in the GCL decreased by 12% (p=0.2) and 26% (p<0.5), respectively, confirming cell loss

Conclusions : Although some of the total decrease in RBPMS-positive cells may be attributed to down-regulation of RBPMS expression in mTORC1-deficient RGC, the results suggest that cKO of mTOR or Raptor caused an eventual loss of RGC in adult mice. mTORC1 function may thus be necessary for maintaining both RGC differentiation and long-term viability.

This is a 2021 ARVO Annual Meeting abstract.

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