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Editors Selection IGR 16-4

Basic Research: Time-lapse imaging of axonal transport

Comment by Chris Leung on:

45465 Dynamic imaging of axonal transport in living retinal ganglion cells in vitro, Takihara Y; Inatani M; Hayashi H et al., Investigative Ophthalmology and Visual Science, 2011; 52: 3039-3045

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Disruption of axoplasmic flow has been demonstrated as a key mechanism leading to axonal degeneration in a number of neurodegenerative diseases including glaucoma. Using a cooled charged coupled device camera, Takihara et al. (587) showed the feasibility of time-lapse imaging of axonal transport in cultured retinal ganglion cells (RGCs). Rat RGCs were purified by immunopanning and transfected with brain-derived neurotrophic factor (BDNF) tagged with green fluorescent protein (GFP). They observed different patterns of BDNF-GFP dynamics (anterograde, retrograde, no movement, fluttering). The movement of BDNF-GFP in the axons and dendrites were tracked and the mean velocity was estimated at 0.86 ± 0.37?m/s and 0.49 ± 0.19?m/s, respectively. They also showed that 1mM colchicines, a natural compound that inhibits microtubule polymerization by binding to tubulin, reduced axonal transport prior to cell death. Measuring the rate of axonal transport could be an important and sensitive biomarker to indicate the health of RGCs. Although live tracking of axonal transport has been extensively investigated in cortical and spinal cord neurons, it is recognized that this is the first report describing BDNF transport in the axons and dendrites of RGCs. A caveat in interpreting the rate of axonal and dendritic transport is that GFP tagging could change normal signaling and trafficking of BDNF. Limited by optical aberrations of the imaging system and the eye, it is not yet feasible to image axonal transport in the retina in vivo. As glaucomatous damage to RGCs cannot be reliably mimicked in a culture system, the current setup may not be relevant to study axonal degeneration in glaucoma. Nevertheless, this study embarks on an important step towards a better understanding of axonal transport in RGCs as well as identifying potential therapies to alleviate neuronal degeneration.

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