Cytoplasmic dynein pushes the cytoskeletal meshwork forward during axonal elongation

Abstract

During development, neurons send out axonal processes that can reach lengths hundreds of times longer than the diameter of their cell bodies. Recent studies indicate en masse microtubule translocation is a significant mechanism underlying axonal elongation, but how cellular forces drive this process is unknown. Cytoplasmic dynein generates forces on microtubules in axons to power their movement via Stop-and-Go transport, but whether these forces influence bulk translocation of long microtubules embedded in the cytoskeletal meshwork has not been tested. Here, we use function-blocking antibodies targeted to the dynein intermediate chain and the pharmacological dynein inhibitor Ciliobrevin D to ask if dynein forces contribute to en bloc cytoskeleton translocation. By tracking docked mitochondria as fiduciary markers for bulk cytoskeleton movements, we find that translocation is reduced after dynein disruption. We then directly measure net force generation after dynein disruption and find a dramatic increase in axonal tension. Together these data indicate dynein generates forces that push the cytoskeletal meshwork forward en masse during axonal elongation.