Local microtubule organization promotes cargo transport in C. elegans dendrites

Abstract

The specific organization of the neuronal microtubule cytoskeleton in axons and dendrites is an evolutionarily conserved determinant of neuronal polarity, allowing for selective cargo sorting. However, how dendritic microtubules are organized and whether local differences influence cargo transport remains largely unknown. Here, we use live-cell imaging to systematically probe the microtubule organization in C. elegans neurons and demonstrate the contribution of distinct mechanisms in the organization of dendritic microtubules. We found that most non-ciliated neurons depend on unc-116 (kinesin-1), unc-33 (CRMP) and unc-44 (ankyrin) for proper microtubule organization and polarized cargo transport, as previously reported. Ciliated neurons and the URX neuron however, use an additional pathway to nucleate microtubules from the tip of the dendrite, at the base of the sensory cilium in ciliated neurons. Since, inhibition of distal microtubule nucleation affects distal dendritic transport, we propose a model in which the presence of a microtubule organizing center at the dendrite tip ensures proper dendritic cargo transport.