The multiple sensory cilia that protrude from olfactory sensory neuron dendrites each require a unique structure, known as a centriole, for their formation. Cells control centriole formation and maturation to ensure that the requisite number of centrioles and cilia are created. We have previously shown that in the mouse olfactory epithelium, centrioles are amplified in progenitor cells located near the basal lamina, often 50–100 μm from the apical surface.
Objective: Here, we define how OSN centrioles traverse this distance from the basal lamina to the apical surface, and how they mature to allow for cilia formation.
Methods: High-resolution expansion microscopy, live imaging, explant culture system.
Results: During dendrite outgrowth, centrioles migrate together, with multiple centrioles per group and multiple groups per OSN. Centrioles migrate slowly, with a maximum rate of 0.18 µm/minute. Centriole migration can be perturbed ex vivo by stabilizing microtubules. Migrating centriole groups are associated with microtubule nucleation factors. In mature OSNs, centrioles also matured, as marked by the acquisition of rootletin and centriolar appendages. One cilium, that nucleated by the parental centriole, has a unique appendage structure and forms a single cilium before other centrioles.
Conclusions: Our results support a model in which the microtubule cytoskeleton is critical for slow centriole migration, perhaps through centrosome-directed microtubule nucleation. Our results also indicate that centriole maturation is spatiotemporally regulated to only occur in mature OSNs, after centrioles arrive in the forming dendritic knob. Finally, our discovery that a single cilium formed before all others and bears unique structural properties suggests that this cilium may be involved in unique signaling important for OSN differentiation.
Funding: National Institutes of Health and the National Science Foundation.