Abstract
Transition fibres (TFs), together with the transition zone (TZ), are basal ciliary structures thought to be crucial for cilium biogenesis and function by acting as a ciliary gate to regulate selective protein entry and exit. Here we demonstrate that the centriolar and basal body protein HYLS-1, the C. elegans orthologue of hydrolethalus syndrome protein 1, is required for TF formation, TZ organization and ciliary gating. Loss of HYLS-1 compromises the docking and entry of intraflagellar transport (IFT) particles, ciliary gating for both membrane and soluble proteins, and axoneme assembly. Additional depletion of the TF component DYF-19 in hyls-1 mutants further exacerbates TZ anomalies and completely abrogates ciliogenesis. Our data support an important role for HYLS-1 and TFs in establishment of the ciliary gate and underline the importance of selective protein entry for cilia assembly.
Highlights
Transition fibres (TFs), together with the transition zone (TZ), are basal ciliary structures thought to be crucial for cilium biogenesis and function by acting as a ciliary gate to regulate selective protein entry and exit
Loss of DYF-19 compromises the entry of intraflagellar transport (IFT) particles, suggesting that TFs may be a critical site for the docking and sorting of IFT particles[17]
Using mCherrytagged DYF-19 as a TF marker, we examined the localization of HYLS-1 is required for IFT recruitment and entry
Summary
Transition fibres (TFs), together with the transition zone (TZ), are basal ciliary structures thought to be crucial for cilium biogenesis and function by acting as a ciliary gate to regulate selective protein entry and exit. We demonstrate that the centriolar and basal body protein HYLS-1, the C. elegans orthologue of hydrolethalus syndrome protein 1, is required for TF formation, TZ organization and ciliary gating. Loss of HYLS-1 compromises the docking and entry of intraflagellar transport (IFT) particles, ciliary gating for both membrane and soluble proteins, and axoneme assembly. In addition to TF disorganization, hyls-1 mutants display defects in docking and entry of IFT particles, TZ organization, axoneme assembly and ciliary gating. Green fluorescent protein (GFP)-tagged versions of known or predicted ciliary proteins in C. elegans[31,32] This search led us to identify three TF-associated components, GASR-8, the putative homologue of human GAS8, and K10G6.4, related to human ANKRD26, as well as HYLS-1, a conserved centriolar and basal body component[33]. Mutations in HYLS1 have been detected in individuals with hydrolethalus syndrome[38], a putative ciliopathy, and HYLS1 and its worm homologue HYLS-1 have been reported to be required for ciliogenesis in vertebrates and C. elegans, respectively[33]
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