Figure 3. Current understanding of functional relationships between kinesin-2 family motors in vertebrate ciliogenesis. (A) In rod photoreceptors, kif3b is necessary for cilia differentiation and cell survival. In cone photoreceptors, on the other hand, kif3b is necessary for cilia formation at 3 dpf. Somewhat later, at 5 dpf, kif3b and kif3c function largely redundantly in cone cilia formation. kif3c does not, however, entirely compensate for the loss of kif3b function, and vice versa kif3b does not seem to entirely substitute for the loss of kif3c. (B) In the ear, two populations of mechanosensory hair cells display very different requirements for kinesin function: while kif3b is required for ciliogenesis in auditory maculae, kif3b and kif3c function redundantly in the cilia of cristae; either is sufficient to drive ciliogenesis in these cells. (C) In olfactory placodes, both kif3b and kif17 are necessary for normal ciliogenesis. The contribution of kif3b is much more significant, compared with kif17. Based on mouse knockout data, Kif3a is necessary for the differentiation of all cilia, except perhaps in photoreceptor cells, where yet another mechanism may be operational (dashed arrow).