
==== Front
bioRxiv
BIORXIV
bioRxiv
2692-8205
Cold Spring Harbor Laboratory

10.1101/2024.09.09.612100
preprint
1
Article
The Structure of Cilium Inner Junctions Revealed by Electron Cryo-tomography
Li Sam http://orcid.org/0000-0002-0210-8192

Fernandez Jose-Jesus
Ruehle Marisa D.
Howard-Till Rachel A.
Fabritius Amy
Pearson Chad G. http://orcid.org/0000-0003-1915-6593

Agard David A.
Winey Mark E. http://orcid.org/0000-0002-9028-9033

09 9 2024
2024.09.09.612100https://creativecommons.org/licenses/by-nd/4.0/ This work is licensed under a Creative Commons Attribution-NoDerivatives 4.0 International License, which allows reusers to copy and distribute the material in any medium or format in unadapted form only, and only so long as attribution is given to the creator. The license allows for commercial use.
http://biorxiv.org/lookup/doi/10.1101/2024.09.09.612100
nihpp-2024.09.09.612100.pdf
Abstract

The cilium is a microtubule-based organelle critical for many cellular functions. Its assembly initiates at a basal body and continues as an axoneme that projects out of the cell to form a functional cilium. This assembly process is tightly regulated. However, our knowledge of the molecular architecture and the mechanism of assembly is limited. By applying electron cryo-tomography and subtomogram averaging, we obtained subnanometer resolution structures of the inner junction in three distinct regions of the cilium: the proximal region of the basal body, the central core of the basal body, and the flagellar axoneme. The structures allowed us to identify several basal body and axoneme components. While a few proteins are distributed throughout the entire length of the organelle, many are restricted to particular regions of the cilium, forming intricate local interaction networks and bolstering local structural stability. Finally, by knocking out a critical basal body inner junction component Poc1, we found the triplet MT was destabilized, resulting in a defective structure. Surprisingly, several axoneme-specific components were found to “infiltrate” into the mutant basal body. Our findings provide molecular insight into cilium assembly at its inner junctions, underscoring its precise spatial regulation.
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pmc
