Intraflagellar transport delivers tubulin isotypes to sensory cilium middle and distal segments

Abstract

Sensory cilia are assembled and maintained by kinesin-2-dependent intraflagellar transport (IFT). We investigated whether two Caenorhabditis elegans α - and β-tubulin isotypes, identified through mutants that lack their cilium distal segments, are delivered to their assembly sites by IFT. Mutations in conserved residues in both tubulins destabilize distal singlet microtubules. One isotype, TBB-4, assembles into microtubules at the tips of the axoneme core and distal segments, where the microtubule tip tracker EB1 is found, and localizes all along the cilium, whereas the other, TBA-5, concentrates in distal singlets. IFT assays, fluorescence recovery after photobleaching analysis and modelling indicate that the continual transport of sub-stoichiometric numbers of these tubulin subunits by the IFT machinery can maintain sensory cilia at their steady-state length. Sensory cilia assembly has been proposed to occur through the kinesin-2-driven delivery of precursors to the axoneme tip by intraflagellar transport (IFT). Microscopy analysis and mathematical modelling provide evidence that tubulin subunits are transported to their sites of incorporation into microtubules at axonemal tips by IFT.

Cite this article

Hao, L., Thein, M., Brust-Mascher, I. et al. Intraflagellar transport delivers tubulin isotypes to sensory cilium middle and distal segments. Nat Cell Biol 13, 790–798 (2011). https://doi.org/10.1038/ncb2268

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