September 2016
Volume 57, Issue 12
Open Access
ARVO Annual Meeting Abstract  |   September 2016
Constitutive Activation of Mechanistic Target of Rapamycin Complex 1 (mTORC1) Caused Degeneration of the Retinal Pigment Epithelium (RPE)
Author Affiliations & Notes
  • Pei Xu
    Department of Ophthalmology and Visual Science, University of Texas Medical Branch, Galveston, Texas, United States
  • Bo Yu
    Department of Ophthalmology and Visual Science, University of Texas Medical Branch, Galveston, Texas, United States
  • Bo Long
    Department of Ophthalmology and Visual Science, University of Texas Medical Branch, Galveston, Texas, United States
  • Zhen-Yang Zhao
    Department of Ophthalmology and Visual Science, University of Texas Medical Branch, Galveston, Texas, United States
  • Alfred S Lewin
    Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, Florida, United States
  • Ralph Nichols
    Departments of Ophthalmology, Baylor College of Medicine, Houston, Texas, United States
  • Theodore G Wensel
    Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, United States
  • Yan Chen
    Department of Ophthalmology and Visual Science, University of Texas Medical Branch, Galveston, Texas, United States
  • Footnotes
    Commercial Relationships   Pei Xu, None; Bo Yu, None; Bo Long, None; Zhen-Yang Zhao, None; Alfred Lewin, None; Ralph Nichols, None; Theodore Wensel, None; Yan Chen, None
  • Footnotes
    Support  NIH grants EY 019706,the BCM Vision Research Core EY002520,the International Retinal Research Foundation
Investigative Ophthalmology & Visual Science September 2016, Vol.57, 6533. doi:
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      Pei Xu, Bo Yu, Bo Long, Zhen-Yang Zhao, Alfred S Lewin, Ralph Nichols, Theodore G Wensel, Yan Chen; Constitutive Activation of Mechanistic Target of Rapamycin Complex 1 (mTORC1) Caused Degeneration of the Retinal Pigment Epithelium (RPE). Invest. Ophthalmol. Vis. Sci. 2016;57(12):6533.

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

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Abstract

Purpose : Signaling pathways mediated by mTORC1 play key roles in regulating cell metabolism, growth, autophagy, and immune responses. Our previous work demonstrated that RPE aging is associated with elevated mTORC1 activity. The causative link between aberrant mTORC1 activation and RPE degeneration has not been established. The goals of this study are to characterize the retinal phenotype of a conditional knockout mice with RPE-specific mTORC1 hyperactivation and to explore the underlying mechanisms.

Methods : Mice with constitutive mTORC1 activation in the RPE were generated by depleting its upstream suppressor protein tuberous sclerosis complex 1 (TSC1), through crossing TSC1flox/flox mice with BEST1-Cre transgenic C57BL/6J mice. The RPE-specific knockout of TSC1 and the resulting mTORC1 hyperactivation were confirmed by western blot or immunostaining of RPE flat mounts. The ocular phenotype was examined by fundus imaging, optical coherence tomography (OCT) and scanning laser ophthalmoscopy (SLO) in live animals, and was further validated by histopathology and transmission electron microscopy (TEM). Visual acuity was assessed by measuring the optokinetic responses. Selected downstream targets of mTORC1 were further analyzed by quantitative RT-PCR and western blot analyses.

Results : TSC1ΔRPE mice displayed mTORC1 hyperactivation specifically in the RPE, without affecting the mTORC2 pathway. RPE pathology was evident in 5-week-old homozygous knockouts and progressed with age. Between 3 to 6 months, TSC1ΔRPE mice showed extensive RPE hypo/hyperpigmentation, lipid droplet accumulation and subretinal cell infiltration. TEM detected membrane whorls between photoreceptor outer segments and apical surface of the RPE, fragmented mitochondria and other signs of defective vesicular trafficking in the RPE. The mRNA level of TFEB and VPS11 was reduced in TSC1ΔRPE mice compared to TSC1flox/flox, BEST1-Cre or wild type mice.

Conclusions : Hyperactivated mTORC1 can lead to RPE and photoreceptor degeneration, by mechanisms that involve disrupted membrane trafficking.

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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