Characteristic features of the transport of mitochondria and Golgi-derived vesicles.A. A phase contrast image shows the extensive network formed by neurons after 7 days in cultures (left panel). The morphology of a single transfected neuron is shown by soluble GFP (right panel, color inverted), making it possible to follow the course of the axon (arrow) and dendrites (arrow-heads). We imaged axonal transport in the proximal part of the axon, beginning 30–50 μm beyond the initial segment. Scale bar, 20 μm. B-D. Axonal transport of Golgi-derived vesicles. B. The left panel shows an enlargement of a stretch of axon from a cell transfected with a marker for Golgi-derived vesicles (contrast inverted) and the right panel shows a kymograph quantifying the transport of Golgi-derived vesicles transport in this axon. Golgi-derived vesicles are small and round shaped vesicles. Vesicles undergoing anterograde transport correspond to diagonal lines with positive slope in the kymograph (see Methods for additional details). Horizontal lines represent stationary vesicles. C. Histograms showing the transport velocities of Golgi-derived vesicles (based on 772 events in 15 cells). Anterograde transport (2.1 ± 1 μm/sec) is significantly faster than retrograde transport (1.6 ± 0.81 μm/sec) (Student t-test, P < 0.001). Error bar indicates SD. D. A scatter plot showing the anterograde and retrograde event numbers (number of events/100 μm/minute) for each axon. Golgi-derived vesicles anterograde transport event numbers range from 24 to 78 during the one minute imaging time while the retrograde event numbers only range from 16 to 60 events per minute (anterograde, circle; retrograde, square). The average anterograde to retrograde event ratio was 1.73. E-G. Axonal transport of mitochondria. E. The left panel is an enlargement of a stretch of axon from a cell expressing mitoGFP (contrast inverted) and the right panel is the kymograph illustrating mitochondrial transport in this axon. F. Histograms showing the velocity of mitochondrial transport (based on 321 events from 32 cells). The velocity of mitochondrial transport is similar in both directions (anterograde 0.6 ± 0.41 μm/sec vs. retrograde 0.59 ± 0.35 μm/sec, student t-test, P > 0.9). G. A scatter plot showing the number of anterograde and retrograde movements of mitochondria. Mitochondrial transport had no directional bias, with both anterograde and retrograde event numbers ranging from 0 to 8 events/100 μm/minute. The average anterograde to retrograde event ratio was 1.01 for mitochondria. Error bar indicates SD.
Fang et al. Molecular Neurodegeneration 2012 7:29 doi:10.1186/1750-1326-7-29