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. Author manuscript; available in PMC: 2015 Jan 1.
Published in final edited form as: Nat Cell Biol. 2014 Jun 22;16(7):663–672. doi: 10.1038/ncb2988

Figure 8. Model for KIF7-dependent regulation of plus-end dynamics in primary cilia.

Figure 8

(a) Proposed model for the regulation of microtubule dynamics by KIF7. i: KIF7 preferentially binds to the GTP-bound tubulin at microtubule plus-ends, inhibiting addition of tubulin dimers and microtubule growth. ii: By destabilizing the GTP-bound tubulin cap at microtubule plus-ends, KIF7 can promote catastrophe and thereby limit microtubule growth. (b) Model for KIF7 function at the tip of primary cilia. In wild type, KIF7 acts at the distal end of the growing cilium to prevent overgrowth of individual microtubules and to coordinate the growth of 9-doublet microtubules; only organized microtubule arrays are a suitable substrate for post-translational modifications. In the mature cilium, KIF7 creates a single distal tip compartment where IFT81 and Gli-Sufu complexes are enriched. In the absence of KIF7, growth of axonemal microtubules is not limited and synchronized, leading to longer and unstable cilia and ectopic tip-like compartments that contain IFT81 along the axoneme. Gli-Sufu complexes localized to the ectopic tip compartments, where they can be inappropriately activated in the absence of Shh ligand.