June 2022
Volume 63, Issue 7
Open Access
ARVO Annual Meeting Abstract  |   June 2022
Patient iPSC-RPE implicate mitochondrial defects in Macular Telangiectasia
Author Affiliations & Notes
  • Sarah Giles
    Lowy Medical Research Institute, La Jolla, California, United States
    The Scripps Research Institute, La Jolla, California, United States
  • Brendan Ansell
    Walter and Eliza Hall Institute of Medical Research, Melbourne, Victoria, Australia
  • Sarah Harkins-Perry
    Lowy Medical Research Institute, La Jolla, California, United States
    The Scripps Research Institute, La Jolla, California, United States
  • Martina Wallace
    University College Dublin, Dublin, Ireland
  • Marin Gantner
    Lowy Medical Research Institute, La Jolla, California, United States
    The Scripps Research Institute, La Jolla, California, United States
  • Regis Fallon
    Lowy Medical Research Institute, La Jolla, California, United States
    The Scripps Research Institute, La Jolla, California, United States
  • Alec Johnson
    Lowy Medical Research Institute, La Jolla, California, United States
  • Barbara Hart
    Ophthalmology and Visual Sciences, The University of Utah School of Medicine, Salt Lake City, Utah, United States
  • Melanie Bahlo
    Walter and Eliza Hall Institute of Medical Research, Melbourne, Victoria, Australia
  • Rando Allikmets
    Columbia University, New York, New York, United States
  • Christian Metallo
    Salk Institute for Biological Studies, La Jolla, California, United States
  • Paul S Bernstein
    Ophthalmology and Visual Sciences, The University of Utah School of Medicine, Salt Lake City, Utah, United States
  • Martin Friedlander
    Lowy Medical Research Institute, La Jolla, California, United States
    The Scripps Research Institute, La Jolla, California, United States
  • Kevin Thomas Eade
    Lowy Medical Research Institute, La Jolla, California, United States
    The Scripps Research Institute, La Jolla, California, United States
  • Footnotes
    Commercial Relationships   Sarah Giles None; Brendan Ansell None; Sarah Harkins-Perry None; Martina Wallace None; Marin Gantner None; Regis Fallon None; Alec Johnson None; Barbara Hart None; Melanie Bahlo None; Rando Allikmets None; Christian Metallo None; Paul Bernstein None; Martin Friedlander None; Kevin Eade None
  • Footnotes
    Support  None
Investigative Ophthalmology & Visual Science June 2022, Vol.63, 2449 – F0393. doi:
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      Sarah Giles, Brendan Ansell, Sarah Harkins-Perry, Martina Wallace, Marin Gantner, Regis Fallon, Alec Johnson, Barbara Hart, Melanie Bahlo, Rando Allikmets, Christian Metallo, Paul S Bernstein, Martin Friedlander, Kevin Thomas Eade; Patient iPSC-RPE implicate mitochondrial defects in Macular Telangiectasia. Invest. Ophthalmol. Vis. Sci. 2022;63(7):2449 – F0393.

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

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Abstract

Purpose : Macular Telangiectasia Type 2 (MacTel) is a rare, late-onset, degenerative retinal disease with an extremely heterogenous genetic architecture. MacTel has been linked to metabolic defects including reduced circulating levels of serine and glycine, and increased levels of deoxysphingolipids (dSLs). However, there is likely to be serine/glycine/dSL-independent factors contributing to the onset of MacTel as many patients have normal metabolite levels, and multiple MacTel GWAS loci have been identified that are not clearly linked to serine/glycine/dSL metabolism. Here, we differentiated retinal pigment epithelium from induced pluripotent stem cells (iPSC-RPE) derived from a cohort of MacTel case and control patients with diverse genetic backgrounds to screen for functional defects and identify common cell-intrinsic pathological mechanisms that may drive disease.

Methods : We differentiated iPSC-RPE from 9 MacTel patients and 5 unaffected family members. iPSC-RPE differentiation and functional maturity were validated by cell type specific gene expression and measuring polar secretion of VEGF (apical) and PEDF (basal) over 18 weeks. We measured secreted serine and glycine abundance using mass spectrometry. iPSC-RPE phagocytosis ability was measured by the uptake of fluorescently conjugated porcine outer segments (POS). RNAseq and subsequent GSEA pathway analysis were performed as an untargeted screen to identify common defects. Lastly, we measured oxygen consumption rate (OCR) and mitochondrial function using the mitochondrial stress test with a Seahorse Analyzer.

Results : We observed that MacTel iPSC-RPE had elevated expression of enzymes in the serine synthesis pathway, and reduced levels of serine (21%) and glycine (15%) secretion indicating a defect in serine and glycine metabolism. Phagocytosis of POS and secretion of VEGF and PEDF were comparable between MacTel and control iPSC-RPE. GSEA pathway analysis of RNAseq differential expression identified an enrichment of cellular stress pathways (for example hypoxia, NFKB, Complement) and dysregulation of central carbon metabolism in MacTel iPSC-RPE. Lastly, MacTel iPSC-RPE showed a significant reduction in basal OCR (17%) and maximal OCR output (24%).

Conclusions : We provide a comprehensive analysis of MacTel patient-derived RPE to both validate iPSC-RPE as a model for cellular pathologies linked to MacTel, and discover new disease-associated metabolic phenotypes.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.

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