June 2022
Volume 63, Issue 7
Open Access
ARVO Annual Meeting Abstract  |   June 2022
Ultrastructure of bipolar cell dendritic trees and rod convergence in the simplex retina of L. erinacea
Author Affiliations & Notes
  • Abhiniti Wagh
    Cell and Molecular Biology (CMB), San Francisco State University, San Francisco, California, United States
  • Jessamyn G. Fathi
    Cell and Molecular Biology (CMB), San Francisco State University, San Francisco, California, United States
  • Marta Ramon
    Cell and Molecular Biology (CMB), San Francisco State University, San Francisco, California, United States
  • Yaqoub Yusuf
    Cell and Molecular Biology (CMB), San Francisco State University, San Francisco, California, United States
  • Aya Alazzeh
    Cell and Molecular Biology (CMB), San Francisco State University, San Francisco, California, United States
  • Ivan Anastassov
    Cell and Molecular Biology (CMB), San Francisco State University, San Francisco, California, United States
  • Footnotes
    Commercial Relationships   Abhiniti Wagh None; Jessamyn Fathi None; Marta Ramon None; Yaqoub Yusuf None; Aya Alazzeh None; Ivan Anastassov None
  • Footnotes
    Support  NIH MBRS-RISE R25-GM059298, Genentech Foundation Scholarship, NIH NIGMS grant: 1SC2GM144198
Investigative Ophthalmology & Visual Science June 2022, Vol.63, 4560 – F0422. doi:
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    • Get Citation

      Abhiniti Wagh, Jessamyn G. Fathi, Marta Ramon, Yaqoub Yusuf, Aya Alazzeh, Ivan Anastassov; Ultrastructure of bipolar cell dendritic trees and rod convergence in the simplex retina of L. erinacea. Invest. Ophthalmol. Vis. Sci. 2022;63(7):4560 – F0422.

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

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Abstract

Purpose : Visual information processing under scotopic and photopic conditions is generally divided between the rod and cone systems, which transmit information to dedicated bipolar pathways. However, the simplex retina of L. erinacea utilizes rods across the full range of illumination. We know little about what functional and anatomical features of rod pathways in mixed rod-cone retinas are present in skate. Here, we use SB-3DEM to examine the convergence ratio of rods to postsynaptic partners (identified as putative bipolar cells), as well as the dendritic tree architecture of putative bipolar cell types.

Methods : Retinal pieces were embedded in resin blocks, and serial block-face scanning electron microscopy (SB-3DEM) was performed on individual samples from the tapetal retinal region of adult animals. The dataset analyzed here was from the entire cross section of the retina with a width of 82μm, height of 314 μm, and depth of 29 μm. Section thickness was 65nm, and pixel size was 7nm x 7nm.; the dataset has 452 sections. 3-D representations of dendritic processes and synaptic ribbons were obtained through segmentation in Reconstruct software; quantifications were done in Amira 3D software.

Results : We quantified a total of 97 dendritic processes, or tips, in the initial putative bipolar cell examined. In mouse retina, rod bipolar cell dendritic tips are likely sites of contacts with rods and appose a rod synaptic ribbon ~84% of the time (Anastassov et al., 2019). We have so far determined that ~1/5 of the 97 tips identified are likely apposed to a ribbon. Additional measurements on the rest of the dendritic tips, as well as reconstructions of other putative bipolar cells in the dataset, are ongoing. Preliminary observations show that individual bipolar cell processes may be capable of making both invaginating and basal contacts with the same rod terminal.

Conclusions : We show the rod-only skate retina likely has the same high rod-to-bipolar-cell convergence ratio found in mixed rod-cone retinas, supporting prior electrophysiological evidence of high sensitivity. Invaginating putative bipolar cell dendritic tips are likely sites of contact with individual rods, although exact contact probability is yet to be determined. Finally, putative bipolar cells may posses invaginating (normally ON) and basal (normally OFF) contacts within the same cell, suggesting a hybrid dendritic architecture.

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

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