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M Joseph Costello, Kurt O Gilliland, Kevin Schey; Extensive autophagy and unique nuclear excisosome formation from mitochondria characterize organelle degradation in lenses from Galago (bush baby) monkeys. Invest. Ophthalmol. Vis. Sci. 2022;63(7):1141.
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Our previous paper described the formation of the nuclear excisosome (NE) in Galago lenses from modified mitochondria that initiated the process in the presence of numerous autophagic vesicles within equatorial epithelium. Further examination revealed how elaborate autophagy processes near the fulcrum produced large degradative bodies in the young fiber cells as extended mitochondria and NE cores elongated into rod-like “beads on a string” structures that degraded nuclei at the organelle-free zone (OFZ).
Lenses from Galago (bush baby) monkeys (n=4, age 2-5) were fixed in formalin followed by paraformaldehyde, then Vibratome sectioned. Sections were fixed and processed for thin-section transmission electron microscopy 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.
Galago monkey lenses formed unique four-membrane organelles in the equatorial epithelium from modified mitochondria with collapsed cristae that condensed and surrounded core proteins with a single membrane. Enlarged beads appeared to assist in fusing smaller rods into longer ones as the complexes migrated into fiber nascent fiber cells and attacked nuclear envelopes near the OFZ. The high cellular activity in transition region was supported by extensive autophagy of the classical type and a new variation of expanded extracellular space (ECS) between epithelial cells where material to be degraded and degradative enzymes entered by exocytosis. These ECS autophagic vesicles became so prominent that they started a new complex interdigitation to isolate them as bounded degradative bodies in young fiber cells. Smaller autophagic vesicles were seen throughout the formation and degradation of organelles in the OFZ.
Autophagy plays a prominent role throughout the degradative process including formation of new large ECS based autophagic vesicles with single plasma membrane borders.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.
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