MKS and NPHP modules cooperate to establish basal body/transition zone membrane associations and ciliary gate function during ciliogenesis

Meckel-Gruber syndrome (MKS), nephronophthisis (NPHP), and related ciliopathies present with overlapping phenotypes and display considerable allelism between at least twelve different genes of largely unexplained function. We demonstrate that the conserved C. elegans B9 domain (MKS-1, MKSR-1, and MKSR-2), MKS-3/TMEM67, MKS-5/RPGRIP1L, MKS-6/CC2D2A, NPHP-1, and NPHP-4 proteins exhibit essential, collective functions at the transition zone (TZ), an underappreciated region at the base of all cilia characterized by Y-shaped assemblages that link axoneme microtubules to surrounding membrane. These TZ proteins functionally interact as members of two distinct modules, which together contribute to an early ciliogenic event. Specifically, MKS/MKSR/NPHP proteins establish basal body/TZ membrane attachments before or coinciding with intraflagellar transport–dependent axoneme extension and subsequently restrict accumulation of nonciliary components within the ciliary compartment. Together, our findings uncover a unified role for eight TZ-localized proteins in basal body anchoring and establishing a ciliary gate during ciliogenesis, and suggest that disrupting ciliary gate function contributes to phenotypic features of the MKS/NPHP disease spectrum.

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Centrioles initiate cilia assembly but are dispensable for maturation and maintenance in C. elegans

The Journal of Cell Biology ◽

10.1083/jcb.201610070 ◽

2017 ◽

Vol 216 (6) ◽

pp. 1659-1671 ◽

Cited By ~ 26

Author(s):

Daniel Serwas ◽

Tiffany Y. Su ◽

Max Roessler ◽

Shaohe Wang ◽

Alexander Dammermann

Keyword(s):

Fluorescence Microscopy ◽

Transition Zone ◽

Electron Tomography ◽

Intraflagellar Transport ◽

Basal Bodies ◽

C Elegans ◽

Cilia Formation ◽

Syndrome Protein

Cilia are cellular projections that assemble on centriole-derived basal bodies. While cilia assembly is absolutely dependent on centrioles, it is not known to what extent they contribute to downstream events. The nematode C. elegans provides a unique opportunity to address this question, as centrioles do not persist at the base of mature cilia. Using fluorescence microscopy and electron tomography, we find that centrioles degenerate early during ciliogenesis. The transition zone and axoneme are not completely formed at this time, indicating that cilia maturation does not depend on intact centrioles. The hydrolethalus syndrome protein HYLS-1 is the only centriolar protein known to remain at the base of mature cilia and is required for intraflagellar transport trafficking. Surprisingly, targeted degradation of HYLS-1 after initiation of ciliogenesis does not affect ciliary structures. Taken together, our results indicate that while centrioles are essential to initiate cilia formation, they are dispensable for cilia maturation and maintenance.

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The ciliary transition zone functions in cell adhesion but is dispensable for axoneme assembly in C. elegans

The Journal of Cell Biology ◽

10.1083/jcb.201501013 ◽

2015 ◽

Vol 210 (1) ◽

pp. 35-44 ◽

Cited By ~ 37

Author(s):

Clementine Schouteden ◽

Daniel Serwas ◽

Mate Palfy ◽

Alexander Dammermann

Keyword(s):

Cell Adhesion ◽

Caenorhabditis Elegans ◽

Transition Zone ◽

Basal Body ◽

Protein Complexes ◽

Central Cylinder ◽

Zone Structure ◽

C Elegans ◽

Direct Assembly

Cilia are cellular projections that perform sensory and motile functions. A key ciliary subdomain is the transition zone, which lies between basal body and axoneme. Previous work in Caenorhabditis elegans identified two ciliopathy-associated protein complexes or modules that direct assembly of transition zone Y-links. Here, we identify C. elegans CEP290 as a component of a third module required to form an inner scaffolding structure called the central cylinder. Co-inhibition of all three modules completely disrupted transition zone structure. Surprisingly, axoneme assembly was only mildly perturbed. However, dendrite extension by retrograde migration was strongly impaired, revealing an unexpected role for the transition zone in cell adhesion.

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Faculty Opinions recommendation of Loss of C. elegans BBS-7 and BBS-8 protein function results in cilia defects and compromised intraflagellar transport.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1019534.232439 ◽

2004 ◽

Author(s):

George Witman

Keyword(s):

Protein Function ◽

Intraflagellar Transport ◽

C Elegans

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The Caenorhabditis elegans nephrocystins act as global modifiers of cilium structure

The Journal of Cell Biology ◽

10.1083/jcb.200707090 ◽

2008 ◽

Vol 180 (5) ◽

pp. 973-988 ◽

Cited By ~ 80

Author(s):

Andrew R. Jauregui ◽

Ken C.Q. Nguyen ◽

David H. Hall ◽

Maureen M. Barr

Keyword(s):

Caenorhabditis Elegans ◽

Intraflagellar Transport ◽

Basal Bodies ◽

Structural Components ◽

Transition Zones ◽

C Elegans ◽

Cell Type Specific ◽

Children And Young Adults ◽

Stage Renal Disease ◽

End Stage

Nephronophthisis (NPHP) is the most common genetic cause of end-stage renal disease in children and young adults. In Chlamydomonas reinhardtii, Caenorhabditis elegans, and mammals, the NPHP1 and NPHP4 gene products nephrocystin-1 and nephrocystin-4 localize to basal bodies or ciliary transition zones (TZs), but their function in this location remains unknown. We show here that loss of C. elegans NPHP-1 and NPHP-4 from TZs is tolerated in developing cilia but causes changes in localization of specific ciliary components and a broad range of subtle axonemal ultrastructural defects. In amphid channel cilia, nphp-4 mutations cause B tubule defects that further disrupt intraflagellar transport (IFT). We propose that NPHP-1 and NPHP-4 act globally at the TZ to regulate ciliary access of the IFT machinery, axonemal structural components, and signaling molecules, and that perturbing this balance results in cell type–specific phenotypes.

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TRPV channel OCR-2 is distributed along C. elegans chemosensory cilia by diffusion in a local interplay with intraflagellar transport

10.1101/2020.11.19.390005 ◽

2020 ◽

Author(s):

Jaap van Krugten ◽

Noémie Danné ◽

Erwin J.G. Peterman

Keyword(s):

Single Molecule ◽

Transmembrane Proteins ◽

Intraflagellar Transport ◽

Single Molecule Tracking ◽

C Elegans ◽

Normal Diffusion ◽

Cellular Signal ◽

Underlying Mechanisms ◽

And Function

AbstractSensing and reacting to the environment is essential for survival and procreation of most organisms. Caenorhabditis elegans senses soluble chemicals with transmembrane proteins (TPs) in the cilia of its chemosensory neurons. Development, maintenance and function of these cilia relies on intraflagellar transport (IFT), in which motor proteins transport cargo, including sensory TPs, back and forth along the ciliary axoneme. Here we use live fluorescence imaging to show that IFT machinery and the sensory TP OCR-2 reversibly redistribute along the cilium after exposure to repellant chemicals. To elucidate the underlying mechanisms, we performed single-molecule tracking experiments and found that OCR-2 distribution depends on an intricate interplay between IFT-driven transport, normal diffusion and subdiffusion that depends on the specific location in the cilium. These insights in the role of IFT on the dynamics of cellular signal transduction contribute to a deeper understanding of the regulation of sensory TPs and chemosensing.

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Dynamics of the IFT machinery at the ciliary tip

eLife ◽

10.7554/elife.28606 ◽

2017 ◽

Vol 6 ◽

Cited By ~ 53

Author(s):

Alexander Chien ◽

Sheng Min Shih ◽

Raqual Bower ◽

Douglas Tritschler ◽

Mary E Porter ◽

...

Keyword(s):

Basal Body ◽

Full Range ◽

Intraflagellar Transport ◽

Feedback Mechanism ◽

Conventional Imaging ◽

Range Of Movement ◽

Anterograde Transport ◽

Traffic Jam ◽

Negative Feedback Mechanism ◽

Cilia And Flagella

Intraflagellar transport (IFT) is essential for the elongation and maintenance of eukaryotic cilia and flagella. Due to the traffic jam of multiple trains at the ciliary tip, how IFT trains are remodeled in these turnaround zones cannot be determined by conventional imaging. Using PhotoGate, we visualized the full range of movement of single IFT trains and motors in Chlamydomonas flagella. Anterograde trains split apart and IFT complexes mix with each other at the tip to assemble retrograde trains. Dynein-1b is carried to the tip by kinesin-II as inactive cargo on anterograde trains. Unlike dynein-1b, kinesin-II detaches from IFT trains at the tip and diffuses in flagella. As the flagellum grows longer, diffusion delays return of kinesin-II to the basal body, depleting kinesin-II available for anterograde transport. Our results suggest that dissociation of kinesin-II from IFT trains serves as a negative feedback mechanism that facilitates flagellar length control in Chlamydomonas.

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