Axon membrane flows from the growth cone to the cell body

During the growth of axons, the surface area of the neuron increases dramatically. Membrane addition as well as exchange could contribute to rapid membrane dynamics or flow. Using diffusing latex beads to monitor membrane flow, we find that axonal membrane flows rapidly (7 μm/min) from growth cone to cell body during axon growth and that flow is inhibited by brefeldin A. To power this flow, there is a membrane tension gradient from growth cone to cell body that could draw the membrane over the axon at that rate. Further, when an artificial flow is induced to the center of the axon by use of laser tweezers, the primary source of the membrane is from the growth cone. We suggest that during neuron growth, there is excess membrane added at the growth cone in chick dorsal root ganglia (DRGs) that undergoes endocytosis at the cell body, thereby creating a flow that can rapidly alter the content of the axon membrane.