June 2022
Volume 63, Issue 7
Open Access
ARVO Annual Meeting Abstract  |   June 2022
Analysis of Retinogeniculate Synapses in the DBA/2J Mouse Model of Glaucoma
Author Affiliations & Notes
  • Rebecca King
    Virginia Tech Carilion School of Medicine, Roanoke, Virginia, United States
  • Aboozar Monavarfeshani
    Fralin Biomedical Research Institute at VTC, Roanoke, Virginia, United States
  • Michael Fox
    Fralin Biomedical Research Institute at VTC, Roanoke, Virginia, United States
  • Footnotes
    Commercial Relationships   Rebecca King None; Aboozar Monavarfeshani None; Michael Fox None
  • Footnotes
    Support  None
Investigative Ophthalmology & Visual Science June 2022, Vol.63, 934 – A0403. doi:
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      Rebecca King, Aboozar Monavarfeshani, Michael Fox; Analysis of Retinogeniculate Synapses in the DBA/2J Mouse Model of Glaucoma. Invest. Ophthalmol. Vis. Sci. 2022;63(7):934 – A0403.

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

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Abstract

Purpose : Glaucoma is a degenerative disease of retinal ganglion cells (RGC). More than 30 distinct types of RGCs exist in the mammalian retina, and studies of experimental glaucoma suggest that some types may be more vulnerable to injury from elevated intraocular pressure (IOP). In addition to different morphologies, functional responses, and susceptibility to neurodegeration, RGCs form different types of synapses in retinorecipient nuclei. For example, in the mouse dorsal lateral geniculate nucleus (dLGN), RGC axons generate both simple (single retinal input) and complex (multiple retinal inputs converging on shared regions of relay cell dendrite) retinogeniculate (RG) synapses. At present, it is unclear whether simple and complex RG synapses are generated by distinct RGC types. Here, our goal was to enhance our understanding of RGC vulnerability to injury from elevated IOP by exploring changes to simple and complex RG synapses in the DBA/2J (D2) mouse model of glaucoma.

Methods : To assess RG synapse morphology, we employed serial block-face scanning electron microscopy (SBFSEM), which was performed on dLGN from D2 mice at 6 and 9 months of age. Image analysis and quantification was performed using TrakEM2 in Fiji. Retinal terminals, their axons, and the post-synaptic relay cell dendrites were traced throughout the volume of imaged tissue. At least 50 distinct axons were traced in each data set. Retinal bouton size, complexity, and active zone numbers were quantified and compared to controls.

Results : SBFSEM shows axons with dark axoplasm, a sign of axon degeneration, in the 9-month D2 data set and abnormal membranous organelles in relay cell dendrites in both data sets. In a preliminary analysis of data collected to date, 57% of RG synapses in D2 mice were classified as complex compared to 90% in controls. Additionally, only 11% of complex synapses in D2 mice contained 4 or more retinal terminals while the vast majority (86%) of complex synapses in control mice contained 4 – 14 retinal terminals.

Conclusions : Evidence of axon degeneration suggests the SBFSEM data sets being analyzed are from glaucomatous D2 mice. Currently, our results indicate that glaucomatous D2 mice exhibit changes in relay cell dendrites before axon withdrawal and have significantly fewer complex RG synapses with fewer retinal terminals per complex synapse than controls.

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

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