Bidirectional movement of dynein complexes containing IC-2C in a PC12 cell neurite. (A) Live cell imaging. Individual frames from a video (Video 1) of GFP–IC-2C dynein puncta moving in a PC12 cell neurite. (left) Arrowheads indicate GFP–IC-2C dynein puncta moving in the anterograde direction. (right) Arrowheads indicate GFP–IC-2C dynein puncta moving in the retrograde direction. The time from the start of the video is indicated to the right and left of the panels. Bar, 10 μm. (B) Displacement tracking of IC-2C dynein excursions in PC12 cell neurites. The positions of representative individual dynein puncta were tracked along the neurite in each frame of the videos, and the linear displacements (in micrometers) of 11 individual dynein puncta are graphed against time (in seconds) of movement. Anterograde movement is recorded as positive displacement and retrograde movement as negative. The initial positions of the puncta were set to 0, whereas the displacements of some of the retrogradely moving puncta were offset on the y axis to distinguish them on the graph. (C) Interval velocity distribution of dynein containing IC-2C in neurites of the stable PC12 cell line. Velocities (μm/s) of individual movements of GFP–IC-2C dynein puncta between two frames were plotted against the frequency of their occurrence; motility in the anterograde direction (blue) or retrograde direction (red) is indicated. (inset) The number of measurements for the anterograde (A) and retrograde (R) directions.