July 2019
Volume 60, Issue 9
Open Access
ARVO Annual Meeting Abstract  |   July 2019
Role of presynaptic LRIT3 expression in the restoration of dim light vision
Author Affiliations & Notes
  • Nazarul Hasan
    Biochemistry and Molecular Genetics, University of Louisville, Louisville, Kentucky, United States
  • gobinda Pangeni
    Ophthalmology and Visual Sciences, University of Louisville, Louisville, Kentucky, United States
  • Catherine Cobb
    Biochemistry and Molecular Genetics, University of Louisville, Louisville, Kentucky, United States
  • Emily R. Nettesheim
    Ophthalmology & Visual Sciences, Medical College of Wisconsin, Milwaukee, Wisconsin, United States
  • Daniel M. Lipinski
    Ophthalmology & Visual Sciences, Medical College of Wisconsin, Milwaukee, Wisconsin, United States
    Nuffield Laboratory of Ophthalmology, University of Oxford, Oxford, United Kingdom
  • Maureen A McCall
    Ophthalmology and Visual Sciences, University of Louisville, Louisville, Kentucky, United States
    Anatomical Sciences & Neurobiology, University of Louisville, Louisville, Kentucky, United States
  • Ronald G Gregg
    Biochemistry and Molecular Genetics, University of Louisville, Louisville, Kentucky, United States
    Anatomical Sciences & Neurobiology, University of Louisville, Louisville, Kentucky, United States
  • Footnotes
    Commercial Relationships   Nazarul Hasan, None; gobinda Pangeni, None; Catherine Cobb, None; Emily Nettesheim, None; Daniel Lipinski, None; Maureen McCall, None; Ronald Gregg, None
  • Footnotes
    Support  R01 EY12354
Investigative Ophthalmology & Visual Science July 2019, Vol.60, 4788. doi:
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      Nazarul Hasan, gobinda Pangeni, Catherine Cobb, Emily R. Nettesheim, Daniel M. Lipinski, Maureen A McCall, Ronald G Gregg; Role of presynaptic LRIT3 expression in the restoration of dim light vision. Invest. Ophthalmol. Vis. Sci. 2019;60(9):4788.

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

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Abstract

Purpose : Complete congenital stationary night blindness (cCSNB) is a genetically heterogeneous disorder of the retina characterized by impairment of low light vision and loss of the b-wave of the electroretinogram (ERG). In mouse models of cCSNB, normal ON retinal ganglion cell responses are absent. Mutations in Grm6, Trpm1, Nyx, Gpr179 and Lrit3, which encode proteins critical to signal transmission in one class of retinal interneurons, the ON bipolar cells, cause cCSNB. LRIT3 is a leucine rich repeat protein that when absent causes loss of TRPM1 and Nyctalopin expression from the dendritic tips of rod bipolar cells, and in addition mGluR6, GPR179 and the RGS complex of proteins from dendritic tips of cone ON bipolar cells. Here we investigate the mechanism by which LRIT3 impacts the rod bipolar cells signalplex, and its cellular location.

Methods : Using a fluorescence based in situ hybridization we examined the expression of Lrit3 mRNA in fixed retinal sections of wild type mice. To express LRIT3 in rod photoreceptors we used a human rhodopsin promoter to control expression in rAAVs. The expression construct was packaged in the rAAV2/2[MAX] capsid. rAAVs were intravitreally injected in mice at postnatal day 5 (P5). We characterized retinal function of rAAV-injected Lrit3-/- mice using ERG and multi-electrode array (MEA). Localization of LRIT3 and TRPM1 were examined by immunohistochemistry.

Results : We show that LRIT3 is a presynaptic protein and its expression in rod photoreceptors via rAAV restores function. LRIT3 restored its expression on the rod axon terminals where it co-localized with mGluR6. This also restored postsynaptic TRPM1 expression to the rod bipolar cells dendrites. Functional analyses showed that AAV mediated LRIT3 expression in rods partially restored the scotopic b-wave of the ERG in Lrit3-/- mice. MEA recordings of retinas from AAV injected Lrit3-/- mice, showed a significant restoration of normal retinal ganglion cell ON responses.

Conclusions : Our data show that LRIT3 acts in a trans-synaptic manner to localize the rod bipolar cell signalplex protein TRPM1. This finding is the first example of such a mechanism in the retina. These data also show the potential for gene therapy in LRIT3 mutant cCSNB patients by AAV mediated gene delivery.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.

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