Biology subjects

Louvel, V.

Publications and source records attributed to Louvel, V..

3 recordsLinked to original sources

bioRxiv2026

Investigating the axoneme CCDC40 protein reveals new insights in trypanosome morphogenesis and division

Cilia and flagella contribute to cell morphogenesis in multiple organisms. In the parasite Trypanosoma brucei, the flagellum is attached along the length of the cell body and acts as a guide for cell division, while its motility function is required for the completion of cytokinesis. To tease apart the contributions of flagellum length and motility to trypanosome morphogenesis, we investigated the coiled-coil containing domain 40 (CCDC40 or FAP172) protein. Iterative Ultrastructure Expansion Microscopy (iU-ExM) revealed that CCDC40 is associated to the 96-nm repeats of the trypanosome axoneme. CCDC40 depletion by RNAi leads to loss of components from the dynein regulatory complex, inner dynein arms and radial spokes, resulting in disconnected microtubule doublets and disorganised axoneme structure, abrogating motility and resulting in flagella and cell bodies 2-3 times shorter than normal. We show for the first time that this short flagellum phenotype is associated to slower tubulin incorporation and premature acquisition of the maturation marker FLAM8 but not of the locking protein CEP164C. Surprisingly, these short and immotile trypanosomes grow and divide normally. We discuss the significance of these observations for trypanosome morphogenesis and division.

cell biology↗

bioRxiv2025

The Luminal Ring Protein C2CD3 Acts as a Radial In-to-Out Organizer of the Distal Centriole and Appendages

Centrioles are polarized microtubule-based structures with appendages at their distal end that are essential for cilia formation and function. The protein C2CD3 is critical for distal appendage assembly, with mutations linked to orofaciodigital syndrome and other ciliopathies. However, its precise molecular role in appendage recruitment remains unclear. Using Ultrastructure Expansion Microscopy (U-ExM), iterative U-ExM, and in situ cryo-electron tomography (cryo-ET), we reveal that C2CD3 adopts a radially symmetric 9-fold organization within the centrioles distal lumen. We show that the C-terminal region of C2CD3 localizes close to a [~]100 nm luminal ring structure consisting of [~]27 nodes, while its N-terminal region localizes close to a hook-like structure that attaches to the A-microtubule as it extends from the centriole interior to exterior. This hook structure is adjacent to the DISCO complex (MNR/CEP90/OFD1), which marks future appendage sites. C2CD3 depletion disrupts not only the recruitment of the DISCO complex via direct interaction with MNR but also destabilizes the luminal ring network composed of C2CD3/SFI1/centrin-2/CEP135/NA14, as well as the distal microtubule tip protein CEP162. This reveals an intricate "in-to-out" molecular hub connecting the centriolar lumen, distal microtubule cap, and appendages. Although C2CD3 loss results in shorter centrioles and appendage defects, key structural elements remain intact, permitting continued centriole duplication. We propose that C2CD3 forms the luminal ring structure and extends radially to the space between triplet microtubules, functioning as an architectural hub that scaffolds the distal end of the centriole, orchestrating its assembly and directing appendage formation.

cell biology↗

bioRxiv2022

Nanoscopy of organelles and tissues with iterative ultrastructure expansion microscopy (iU-ExM)

Expansion microscopy is an approach of super-resolution fluorescence microscopy that does not yet achieve the precision of nanoscopy techniques such as single-molecule light microscopy (SMLM). Here, we developed an iterative ultrastructure expansion microscopy approach (iU-ExM), which now matches the SMLM resolution as demonstrated using standard references such as the nuclear pores. Applicable to both cells and tissues, iU-ExM allows a broad research community to access high precision super-resolution microscopy.

cell biology↗