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Satoshi Yokota, Sahil Shah, Jeffrey L Goldberg; Developmental Regulation of Mitochondrial Axonal Transport in Rat Retinal Ganglion Cells. Invest. Ophthalmol. Vis. Sci. 2019;60(9):664. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Axonal transport of organelles and neurotrophic factors plays a critical role in maintaining function and survival of retinal ganglion cells (RGCs) in vitro and in vivo. Mitochondrial axonal transport in particular is decreased in glaucoma and other neurodegenerative diseases. Kinesin family member 5A (KIF5A) is one of the anterograde motor proteins which transport mitochondria as its cargo, and mutations in KIF5A are causative or associated with several neurodegenerative diseases, such as Charcot-Marie-Tooth and amyotrophic lateral sclerosis (ALS). Additionally, age-dependent differences in the survival of neurons or the length of axonal outgrowth have been previously reported.
To explore the role of kinesin motor transport in the age-related decline of RGCs’ intrinsic axon growth ability, we examined mitochondrial axonal transport at different developmental stages in primary rat RGCs and determined how manipulating KIF5A expression levels changes mitochondrial transport and RGC survival. RGCs were isolated by immunopanning from embryonic day 18 (E18), postnatal day 2 (P2) and P9 rats. After 6 days in culture, mitochondria were labeled and monitored by time-lapse imaging for 3 minutes with 1.5 second intervals. KIF5Aexpression levels were manipulated using adeno associated virus (AAV). Mitochondrial velocity and direction of movement were recorded from kymographs generated from the time-lapse imaging.
Compared to E18 or P2 RGCs, P9 RGCs’ axonal mitochondrial transport was significantly reduced in vitro. Overexpressing KIF5A increased the velocity of mitochondrial axonal transport in P9 RGCs. While we did not observe differences in the fraction of anterograde versus retrograde mitochondrial movement among these different ages, the portion of paused mitochondria were higher in P9 compared to E18 or P2 RGCs.
Overall, mitochondrial axonal transport decreases with advancing developmental ages in primary RGC culture, a finding that may be reversed with overexpression of KIF5A. Future work will explore how endogenous KIF5A is regulated through development, and how KIF5A in turn regulates mitochondrial transport, with the goal of enhancing axon growth and RGC survival in neurodegenerative diseases like glaucoma.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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