
Cryo-electron tomography analysis of purified and membrane-associated ciliary rootlets reveals a complex architecture consisting of flexible longitudinal filaments, two types of cross-striations, and membrane-connecting protrusions, providing insights into the structural basis for rootlet functions.


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Ciliary rootlets are striated bundles of filaments that connect the base of cilia to internal cellular structures. Rootlets are critical for the sensory and motile functions of cilia. However, the mechanisms underlying these functions remain unknown, in part due to a lack of structural information of rootlet organization. In this study, we obtain 3D reconstructions of membrane-associated and purified rootlets using cryo-electron tomography (cryo-ET). We show that flexible protrusions on the rootlet surface, which emanate from the cross-striations, connect to intracellular membranes. In purified rootlets, the striations were classified into amorphous (A)-bands, associated with accumulations on the rootlet surface, and discrete (D)-bands corresponding to punctate lines of density that run through the rootlet. These striations connect a flexible network of longitudinal filaments. Subtomogram averaging suggests the filaments consist of two intertwined coiled coils. The rootlet’s filamentous architecture, with frequent membrane-connecting cross-striations, lends itself well for anchoring large membranes in the cell.

### Competing Interest Statement

The authors have declared no competing interest.

A cryo-ET study of ciliary rootlet organization

cryo-electron-tomography-reveals-the-intricate-ultrastructure-and-membrane-interactions-of-ciliary-rootlets


Cryo-Electron Tomography Reveals the Intricate Ultrastructure and Membrane Interactions of Ciliary Rootlets
