Figure 1.

Dendritic and axonal membrane proteins are transported in distinct vesicles. A, An overlay image of the proximal axon and dendrites of a cell coexpressing TfR-GFP (green) and NgCAM-mCherry (red). B, The enlarged view of the boxed area in A shows the small vesicles labeled by TfR-GFP in dendrites (arrowhead) and the larger NgCAM-mCherry tubules present in both the axon and dendrites (arrows). Boxed area shown as color overlay to right. C, Kymographs generated from dual-color recordings show vesicle transport of TfR-GFP or NgCAM-mCherry labeled vesicles in the axon and dendrite segments shown in A, B. Anterograde or retrograde transport events appear as positively (anterograde) or negatively (retrograde) sloping lines in the kymographs. To facilitate viewing of the transport events, lines were traced manually and are shown to the right of each kymograph as an illustration. TfR-GFP transport events are encoded green and NgCAM-mCherry transport events encoded red. Overlaid kymograph illustrations show that TfR-GFP transport events are virtually absent in the axon, whereas nonoverlapping transport events of both proteins are abundant in the dendrite. Kymographs are shown with time in the x-axis, and distance moving away from the cell body in the y-axis. Contrast in images was nonlinearly adjusted to improve visibility of dim moving vesicles and the grayscale was inverted so that fluorescence in the image appears black (B, C). Scale bars: A, 10 μm; B, 5 μm.