July 2018
Volume 59, Issue 9
Free
ARVO Annual Meeting Abstract  |   July 2018
A homozygous mutation in the novel gene ARFGAP2 is associated with non-syndromic recessive inherited retinal degeneration (IRD).
Author Affiliations & Notes
  • Pooja Biswas
    Shiley Eye Institute , University of California San Diego, La Jolla, California, United States
  • Anil Kumar Chekuri
    Shiley Eye Institute , University of California San Diego, La Jolla, California, United States
  • Jason Ear
    Departments of Medicine and Cellular and Molecular Medicine, University of California San Diego, La Jolla, California, United States
  • Shyamanga Borooah
    Shiley Eye Institute , University of California San Diego, La Jolla, California, United States
  • Hiroko Matsui
    Institute for Genomic Medicine, University of California San Diego, La Jolla, California, United States
  • Matteo D'Antonio
    Institute for Genomic Medicine, University of California San Diego, La Jolla, California, United States
  • Kelly A. Frazer
    Institute for Genomic Medicine, University of California San Diego, La Jolla, California, United States
    Department of Pediatrics, Division of Genome Information Sciences, Rady Children’s Hospital, La Jolla, California, United States
  • Sindhura Devalaraja
    Shiley Eye Institute , University of California San Diego, La Jolla, California, United States
  • Shahid Yar Khan
    The Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
  • Muhammad Asif Naeem
    National Centre of Excellence in Molecular Biology, University of the Punjab, Lahore, Pakistan, Pakistan
  • Sheikh Riazuddin
    National Centre of Excellence in Molecular Biology, University of the Punjab, Lahore, Pakistan, Pakistan
    National Centre for Genetic Diseases, Shaheed Zulfiqar Ali Bhutto Medical University, Islamabad, Pakistan
  • Javed Akram
    National Centre for Genetic Diseases, Shaheed Zulfiqar Ali Bhutto Medical University, Islamabad, Pakistan
    Allama Iqbal Medical College, University of Health Sciences, Lahore, Punjab, Pakistan
  • J. Fielding Hejtmancik
    Ophthalmic Genetics and Visual Function Branch, National Eye Institute, Bethesda, Maryland, United States
  • Pradipta Ghosh
    Departments of Medicine and Cellular and Molecular Medicine, University of California San Diego, La Jolla, California, United States
  • S Amer Riazuddin
    The Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
  • Radha Ayyagari
    Shiley Eye Institute , University of California San Diego, La Jolla, California, United States
  • Footnotes
    Commercial Relationships   Pooja Biswas, None; Anil Chekuri, None; Jason Ear, None; Shyamanga Borooah, None; Hiroko Matsui, None; Matteo D'Antonio, None; Kelly A. Frazer, None; Sindhura Devalaraja, None; Shahid Khan, None; Muhammad Naeem, None; Sheikh Riazuddin, None; Javed Akram, None; J. Fielding Hejtmancik, None; Pradipta Ghosh, None; S Amer Riazuddin, None; Radha Ayyagari, None
  • Footnotes
    Support  The Foundation Fighting Blindness, Research to Prevent Blindness, Bright Focus Foundation grant, US-UK Fulbright Commission, Fight for sight, NIH-EY21237, P30-EY22589, P30 2P30CA023100-28, NIH-CA160911 and NIH-CA100768.
Investigative Ophthalmology & Visual Science July 2018, Vol.59, 5383. doi:
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    • Get Citation

      Pooja Biswas, Anil Kumar Chekuri, Jason Ear, Shyamanga Borooah, Hiroko Matsui, Matteo D'Antonio, Kelly A. Frazer, Sindhura Devalaraja, Shahid Yar Khan, Muhammad Asif Naeem, Sheikh Riazuddin, Javed Akram, J. Fielding Hejtmancik, Pradipta Ghosh, S Amer Riazuddin, Radha Ayyagari; A homozygous mutation in the novel gene ARFGAP2 is associated with non-syndromic recessive inherited retinal degeneration (IRD).. Invest. Ophthalmol. Vis. Sci. 2018;59(9):5383.

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

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Abstract

Purpose : To delineate the underlying genetic determinants of early-onset IRD in a large pedigree of Pakistani descent by whole exome sequencing (WES) and whole genome sequencing (WGS) analyses.

Methods : A pedigree with three consanguineous marriages, five affected and five unaffected members was enrolled and ophthalmic examination including fundus photography, ERG, and visual acuity measurements was performed. Genome-wide linkage and haplotype analyses were performed using STR markers. Subsequently, WES of one affected member was performed to identify the candidate variants. In addition, WGS of another affected member was performed to detect non-coding sequence alterations. Mapping and variant calling was performed using BWA and GATK. Structural variations were called using GenomeSTRiP and LUMPY. Candidate genes were prioritized by investigating their interactions with known retina-associated genes in the human protein interaction network. Effect of the potential mutation in the ADP Ribosylation Factor GTPase activating protein 2 (ARFGAP2) gene was evaluated by expressing the wild-type and mutant proteins in HeLa cells. Expression profile and localization of ARFGAP2 were studied by qRT-PCR, immunostaining, electron microscopy (EM), immunoblotting and GAP assay.

Results : Linkage (LOD score of 5.2 at θ = 0) and haplotype analysis mapped the disease locus to a 19Mb interval on chromosome 11. WES and WGS identified a rare homozygous mutation (p.R255C) in ARFGAP2. This is the only pathogenic and rare variant residing within the linkage interval that segregated with IRD. Protein interaction network analysis of ARFGAP2 showed a significant association with retinal genes. ARFGAP2 localizes to the photoreceptor inner segments, inner nuclear layer, and ganglion cell layer. HeLa cells expressing the mutant ARFGAP2 show trimerization of the protein, fragmentation of Golgi stacks, and high Arf1 activity, indicative of impaired GAP function. Such impairment could be an allosteric effect of mutant ARFGAP2 forming trimers on Golgi membrane that are stabilized by disulphide bonds, likely enabled by the mutant 255-Cys.

Conclusions : The mutant R255C-ARFGAP2 protein exhibits impaired GAP activity towards Arf1; hyperactivation of Arf1 perturbs Golgi structure. These findings provide mechanistic insights into how the mutant ARFGAP2 may contribute to degeneration of retina in patients with IRD.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.

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