The organisation of the microtubule (MT) cytoskeleton in axon and dendrites is crucial for their function. Axonal MTs are organised with their plus-end pointing outwards, whereas MTs in dendrites are either mixed or have a uniform minus-end-out orientation. However, it is not known how this MT organisation in axon and dendrites is established and what the effects of any local differences are. In this work (Harterink et al., 2018), Martin Harterink, Casper Hoogenraad and co-workers use live-cell imaging to systematically probe the MT organisation of diverse neuron types in C. elegans. Their analyses demonstrate that distinct mechanisms are responsible for the organisation of dendritic minus-end-out MTs in different neuronal cell types. Non-ciliated neurons depend on UNC-116 (kinesin-1), UNC-33 (CRMP) and UNC-44 (ankyrin) for proper MT orientation and transport, as has been shown previously. In contrast, ciliated neurons and the URX neuron additionally nucleate MTs from the ciliary base at the dendrite tip, which functions as an MT-organising centre (MTOC) and promotes distal cargo transport. Therefore, the authors propose that an additional pool of MTs that is generated by nucleation at the dendrite tip can fine-tune distal cargo transport. Interestingly, some neurons in more complex animals also appear to organise MTs from ciliary structures at the dendritic tip, suggesting that similar mechanisms to control cargo transport through local MT organisation exist in other organisms.
