July 2019
Volume 60, Issue 9
Free
ARVO Annual Meeting Abstract  |   July 2019
Comparative Morphology of Lens Organelle-Free Zone Formation in Three Primate Species Supports the Role of the Nuclear Excisosome
Author Affiliations & Notes
  • M Joseph Costello
    Cell Biology and Physiology, University of North Carolina, Chapel Hill, North Carolina, United States
  • Kurt O Gilliland
    Cell Biology and Physiology, University of North Carolina, Chapel Hill, North Carolina, United States
  • Ashik Mohamed
    Ophthalmic Biophysics, LV Prasad Eye Institute, Hyderabad, Telangana, India
  • Kevin L Schey
    Biochemistry, Vanderbilt University, Nashville, Tennessee, United States
  • Footnotes
    Commercial Relationships   M Costello, None; Kurt Gilliland, None; Ashik Mohamed, None; Kevin Schey, None
  • Footnotes
    Support  NIH Grant EY008148
Investigative Ophthalmology & Visual Science July 2019, Vol.60, 2233. doi:
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      M Joseph Costello, Kurt O Gilliland, Ashik Mohamed, Kevin L Schey; Comparative Morphology of Lens Organelle-Free Zone Formation in Three Primate Species Supports the Role of the Nuclear Excisosome. Invest. Ophthalmol. Vis. Sci. 2019;60(9):2233.

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

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Abstract

Purpose : A chick embryo model was used previously to identify a new organelle, the Nuclear Excisosome (NE), that degraded the nuclear envelope during the formation of the lens organelle-free zone (OFZ). The process was initiated by contact of a filopodial-like extension from an adjacent cell to the outer nuclear envelope. The goal here was to determine if similar unique structures could be found in primate lenses.

Methods : Lenses from human donors (n=6, ages 55-70), macaque monkeys (n=8, ages 8-13) and a Galago bush baby monkey (n=2, age 5) were fixed in formalin followed by paraformaldehyde then Vibratome sectioned. Sections were fixed and processed for thin-section transmission electron microscopy (TEM) or stained with fluorescent dyes for Airyscan confocal microscopy. Nuclei were stained with DAPI, actin with Alexa-phalloidin, lectins with WGA and membranes with DiI.

Results : Each species displayed unique structures involved in nuclear degradation. Human lenses showed large objects near degrading nuclei that stained bright with DiI and contained numerous multiple bilayer aggregates by TEM. The final stages of nuclear breakdown produced reticulated patterns of DAPI staining and corresponding dense interconnecting bands in thin sections that have not been reported previously. Macaque monkey lenses displayed very large oval multi-layered membrane structures, similar to smooth endoplasmic reticulum generated inclusion bodies seen in other tissues, that appear to degrade rapidly within about ten cell layers leaving only small remnants. Galago monkey lenses were characterized by bright DiI stained linear structures that were within the cytoplasm, often quite long (>30 µm) and associated with degrading nuclei. TEM shows multiple membranes in a unique pattern that were observed contacting the outer nuclear membrane to initiate nuclear degradation. In all species the large objects associated with nuclei at the initial stage of degradation disappear at the edge of the OFZ suggesting their involvement in nuclear degradation.

Conclusions : Lenses of higher primates have complex nuclear degradation processes that are compressed into a few fiber cell layers and superimposed on the remodeling zone. Prosimian Galago lens nuclear degradation covers more layers and readily reveals components of the NE. Distinct features in each species support the contribution of the NE.

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

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