Super-resolution microscopy reveals coupling between mammalian centriole subdistal appendages and distal appendages
Abstract
Subdistal appendages (sDAPs) are centriolar elements observed proximal to the distal appendages (DAPs) in vertebrates. Despite their obvious presence, structural and functional understanding of sDAPs remains elusive. Here, by combining super-resolved localization analysis and CRISPR-Cas9 genetic perturbation, we find that, although DAPs and sDAPs are primarily responsible for distinct functions in ciliogenesis and microtubule anchoring respectively, the presence of one element actually affects the positioning of the other. Specifically, we find dual layers of both ODF2 and CEP89, where their localizations are differentially regulated by DAP and sDAP integrity. DAP depletion relaxes longitudinal occupancy of sDAP protein ninein to cover the DAP region, implying a role of DAPs in sDAP positioning. Removing sDAPs alter the distal border of centrosomal γ-tubulins, illustrating a new role of sDAPs. Together, our results provide an architectural framework of sDAPs to shed light on functional understanding, surprisingly revealing the coupling between DAPs and sDAPs.
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All data generated or analysed during this study are included in the manuscript and supporting files.
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Funding
Ministry of Science and Technology, Taiwan (107-2112-M-001-037)
- Weng Man Chong
- Tzu-Yuan Chiu
- Ting-Jui Chang
- You-Pi Liu
- T Tony Yang
- Jung-Chi Liao
Ministry of Science and Technology, Taiwan (107-2313-B-001-009)
- Weng Man Chong
- Tzu-Yuan Chiu
- Ting-Jui Chang
- You-Pi Liu
- T Tony Yang
- Jung-Chi Liao
Academia Sinica (2317-1040300)
- Weng Man Chong
- Tzu-Yuan Chiu
- Ting-Jui Chang
- You-Pi Liu
- T Tony Yang
- Jung-Chi Liao
Ministry of Science and Technology, Taiwan (108-2313-B-010-001)
- Won-Jing Wang
Ministry of Science and Technology, Taiwan (108-2628-B-010-007)
- Won-Jing Wang
Ministry of Science and Technology, Taiwan (108-2638-B-010-001 -MY2)
- Won-Jing Wang
National Institutes of Health (GM088253)
- Meng-Fu Bryan Tsou
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2020, Chong et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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Further reading
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We investigated the role of the nucleolar protein Treacle in organizing and regulating the nucleolus in human cells. Our results support Treacle’s ability to form liquid-like phase condensates through electrostatic interactions among molecules. The formation of these biomolecular condensates is crucial for segregating nucleolar fibrillar centers from the dense fibrillar component and ensuring high levels of ribosomal RNA (rRNA) gene transcription and accurate rRNA processing. Both the central and C-terminal domains of Treacle are required to form liquid-like condensates. The initiation of phase separation is attributed to the C-terminal domain. The central domain is characterized by repeated stretches of alternatively charged amino acid residues and is vital for condensate stability. Overexpression of mutant forms of Treacle that cannot form liquid-like phase condensates compromises the assembly of fibrillar centers, suppressing rRNA gene transcription and disrupting rRNA processing. These mutant forms also fail to recruit DNA topoisomerase II binding protein 1 (TOPBP1), suppressing the DNA damage response in the nucleolus.
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- Cell Biology
The primary cilium is a microtubule-based organelle that cycles through assembly and disassembly. In many cell types, formation of the cilium is initiated by recruitment of preciliary vesicles to the distal appendage of the mother centriole. However, the distal appendage mechanism that directly captures preciliary vesicles is yet to be identified. In an accompanying paper, we show that the distal appendage protein, CEP89, is important for the preciliary vesicle recruitment, but not for other steps of cilium formation (Kanie et al., 2025). The lack of a membrane-binding motif in CEP89 suggests that it may indirectly recruit preciliary vesicles via another binding partner. Here, we identify Neuronal Calcium Sensor-1 (NCS1) as a stoichiometric interactor of CEP89. NCS1 localizes to the position between CEP89 and the centriole-associated vesicle marker, RAB34, at the distal appendage. This localization was completely abolished in CEP89 knockouts, suggesting that CEP89 recruits NCS1 to the distal appendage. Similar to CEP89 knockouts, preciliary vesicle recruitment as well as subsequent cilium formation was perturbed in NCS1 knockout cells. The ability of NCS1 to recruit the preciliary vesicle is dependent on its myristoylation motif and NCS1 knockout cells expressing a myristoylation defective mutant failed to rescue the vesicle recruitment defect despite localizing properly to the centriole. In sum, our analysis reveals the first known mechanism for how the distal appendage recruits the preciliary vesicles.