OSM-5 is the C. elegans ortholog of mammalian IFT88/Polaris, a core component of the intraflagellar transport particle B (IFT-B) complex. The protein contains multiple tetratricopeptide repeat (TPR) domains that mediate protein-protein interactions within the IFT machinery. OSM-5 is essential for the assembly and maintenance of sensory cilia in C. elegans neurons. It localizes to the ciliary base and axoneme, where it undergoes bidirectional IFT movement. Loss of osm-5 function results in severely shortened ciliary axonemes with normal transition zones, leading to dye-filling defects and impaired chemosensation. The gene is expressed exclusively in ciliated sensory neurons under control of the RFX-type transcription factor DAF-19. osm-5 mutants display osmotic avoidance defects, chemotaxis impairments, and altered dauer formation, all consequences of defective sensory cilia. The conservation of OSM-5/IFT88 function from worms to humans has made C. elegans an important model for understanding ciliopathies including polycystic kidney disease.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0042073 intraciliary transport | IBA GO_REF:0000033 | ACCEPT | Summary: OSM-5 is a core component of the IFT-B complex and participates directly in intraflagellar transport. PMID:11290289 demonstrated OSM-5::GFP particle migration within cilia. PMID:17314406 assigned OSM-5 to the IFT-B module based on transport and phenotypic profiles. This annotation is well-supported by phylogenetic inference from characterized IFT88 orthologs. Reason: OSM-5/IFT88 is one of the best-characterized IFT-B components. The IBA annotation is accurate and represents a core molecular function. Direct experimental evidence in C. elegans confirms OSM-5 undergoes IFT movement (PMID:11290289). Supporting Evidence: PMID:11290289 time-lapse imaging of OSM-5::GFP fusion protein shows fluorescent particle migration within the cilia PMID:17314406 the C. elegans IFT machinery has a modular design, consisting of modules IFT-subcomplex A, IFT-subcomplex B, and a BBS protein complex file:worm/osm-5/osm-5-deep-research-falcon.md model: Edison Scientific Literature |
| GO:0036064 ciliary basal body | IBA GO_REF:0000033 | ACCEPT | Summary: OSM-5 localizes to the ciliary base, which includes the basal body region. PMID:11290289 showed OSM-5 concentrates at the cilium base using both OSM-5::GFP translational fusions and immunofluorescence. PMID:22922713 also demonstrates IFT-B proteins accumulate at the ciliary base. Reason: The basal body localization is well-documented experimentally and phylogenetically conserved across IFT88 orthologs. This represents a core localization for IFT-B components. Supporting Evidence: PMID:11290289 the OSM-5 protein was found to concentrate at the cilium base and within the cilium axoneme |
| GO:0097730 non-motile cilium | IBA GO_REF:0000033 | ACCEPT | Summary: C. elegans sensory cilia are non-motile primary cilia. OSM-5 localizes to and functions within these non-motile cilia. Multiple studies confirm OSM-5::GFP localization in amphid and phasmid cilia. Reason: All C. elegans cilia are non-motile sensory cilia, and OSM-5 functions specifically in these structures. The IBA annotation correctly captures the cellular component localization. Supporting Evidence: PMID:11290289 osm-5 is expressed in ciliated sensory neurons in C. elegans |
| GO:1905515 non-motile cilium assembly | IBA GO_REF:0000033 | ACCEPT | Summary: OSM-5 is essential for the assembly of sensory cilia in C. elegans. Loss of osm-5 function results in severely shortened axonemes, demonstrating its requirement for cilium assembly (PMID:2428682, PMID:11290289). Reason: This is a core function of OSM-5/IFT88. The gene is required for proper ciliogenesis in sensory neurons, as demonstrated by ultrastructural studies showing truncated cilia in osm-5 mutants. Supporting Evidence: PMID:2428682 The cilia in che-13 (e1805), osm-1 (p808), osm-5 (p813), and osm-6 (p811) mutants have normal transition zones and severely shortened axonemes PMID:11290289 mutations in the Caenorhabditis elegans gene Y41g9a.1 are responsible for the ciliary defects in osm-5 mutant worms |
| GO:0005814 centriole | IBA GO_REF:0000033 | ACCEPT | Summary: IFT88/Polaris orthologs localize to centrioles and basal bodies in various organisms. The C. elegans basal body derives from the centriole. However, direct evidence for OSM-5 centriole localization in C. elegans is limited compared to basal body localization. Reason: The centriole gives rise to the basal body in ciliated cells. Given OSM-5's demonstrated basal body localization and the conservation of this function across IFT88 orthologs, this annotation is reasonable. The IBA inference from mouse and human orthologs is appropriate. Supporting Evidence: PMID:11290289 the OSM-5 protein was found to concentrate at the cilium base |
| GO:0019894 kinesin binding | IBA GO_REF:0000033 | ACCEPT | Summary: IFT-B components associate with kinesin-2 motors for anterograde transport. In C. elegans, kinesin-II and OSM-3 kinesin coordinate anterograde IFT movement of IFT-B particles (PMID:17420466, PMID:22922713). The physical association between IFT-B and kinesin motors is essential for IFT. Reason: IFT-B components must physically associate with kinesin-2 motors to undergo anterograde transport. While direct binding between OSM-5 and kinesin may be indirect (through the IFT-B complex), the functional association is well-established and the IBA annotation is reasonable. Supporting Evidence: PMID:17420466 In the cilia of the nematode Caenorhabditis elegans, anterograde intraflagellar transport (IFT) is mediated by two kinesin-2 complexes |
| GO:0097546 ciliary base | IBA GO_REF:0000033 | ACCEPT | Summary: OSM-5 localizes to the ciliary base, which includes the transition zone and basal body region. This is where IFT particles assemble before transport into the cilium (PMID:11290289, PMID:22922713). Reason: Ciliary base localization is well-documented for OSM-5 and represents the site of IFT particle assembly and turnaround. This is a core localization for IFT-B components. Supporting Evidence: PMID:11290289 the OSM-5 protein was found to concentrate at the cilium base PMID:22922713 A successful IFT cycle depends on the proper assembly of the massive IFT particle at the ciliary base and its turnaround from anterograde to retrograde transport at the ciliary tip |
| GO:0005929 cilium | NAS PMID:28479320 Dynein-Driven Retrograde Intraflagellar Transport Is Triphas... | ACCEPT | Summary: OSM-5 localizes to cilia as demonstrated by multiple fluorescent imaging studies. PMID:28479320 discusses IFT components including IFT-B in the context of ciliary transport in C. elegans sensory cilia. Reason: Cilium localization is well-established for OSM-5 through direct experimental evidence. While NAS is a weaker evidence code, the underlying claim is strongly supported. Supporting Evidence: PMID:11290289 the OSM-5 protein was found to concentrate at the cilium base and within the cilium axoneme |
| GO:0042073 intraciliary transport | NAS PMID:28479320 Dynein-Driven Retrograde Intraflagellar Transport Is Triphas... | ACCEPT | Summary: OSM-5 participates in intraciliary transport as an IFT-B component. PMID:28479320 analyzes IFT dynamics including IFT-B complex movement in C. elegans cilia. This annotation duplicates the IBA annotation but with different evidence. Reason: The annotation is accurate. Having both IBA and NAS evidence for the same term is acceptable as they represent different evidence sources. The core function of OSM-5 in IFT is well-established. Supporting Evidence: PMID:11290289 time-lapse imaging of OSM-5::GFP fusion protein shows fluorescent particle migration within the cilia |
| GO:0060271 cilium assembly | NAS PMID:28479320 Dynein-Driven Retrograde Intraflagellar Transport Is Triphas... | ACCEPT | Summary: OSM-5 is required for cilium assembly. PMID:28479320 discusses the IFT-B complex in the context of cilium formation and maintenance. Loss of IFT-B components leads to truncated or absent cilia. Reason: Cilium assembly is a well-documented function of OSM-5/IFT88. The general term "cilium assembly" is appropriate as it encompasses the more specific "non-motile cilium assembly" annotation. Supporting Evidence: PMID:11290289 mutations in the Caenorhabditis elegans gene Y41g9a.1 are responsible for the ciliary defects in osm-5 mutant worms |
| GO:0006970 response to osmotic stress | IMP PMID:27930654 Whole-Organism Developmental Expression Profiling Identifies... | KEEP AS NON CORE | Summary: osm-5 mutants display osmotic avoidance defects, which reflects impaired chemosensory function due to defective cilia. PMID:27930654 used osm-5 mutants as controls for sensory behavioral assays. The osmotic avoidance defect is a classic phenotype of osm-5 mutants. Reason: The osmotic avoidance defect is a downstream consequence of defective sensory cilia, not a direct molecular function of OSM-5. The gene name "osm" derives from this phenotype. While the annotation is technically correct (osm-5 mutants fail to respond appropriately to osmotic stress), it represents a pleiotropic effect rather than a core function. Supporting Evidence: PMID:27930654 osm-5(p813) worms used as a negative control |
| GO:0035641 locomotory exploration behavior | IMP PMID:27930654 Whole-Organism Developmental Expression Profiling Identifies... | KEEP AS NON CORE | Summary: PMID:27930654 assessed exploration behavior in various ciliary mutants. osm-5 mutants show altered exploration behavior due to sensory defects. This is an indirect consequence of defective chemosensory cilia. Reason: Exploration behavior is influenced by sensory input from ciliated neurons. The behavioral defect in osm-5 mutants is secondary to ciliary dysfunction, not a direct function of the OSM-5 protein. This is a valid but non-core annotation. Supporting Evidence: PMID:27930654 single worm assays that measure roaming (n = 35 for all strains) and osmotic avoidance |
| GO:0050921 positive regulation of chemotaxis | IMP PMID:27930654 Whole-Organism Developmental Expression Profiling Identifies... | KEEP AS NON CORE | Summary: osm-5 mutants have impaired chemotaxis due to defective sensory cilia. PMID:27930654 used osm-5 mutants in chemotaxis assays. The chemotaxis defect is a downstream consequence of ciliary dysfunction. Reason: The chemotaxis defect in osm-5 mutants results from defective sensory cilia that cannot properly detect chemical signals. OSM-5 does not directly regulate chemotaxis pathways; rather, it enables proper cilium structure required for chemosensation. This is a pleiotropic effect. Supporting Evidence: PMID:27930654 Shown is a population-based isoamyl alcohol (IAA) attraction assay (n = 8 for N2 wild type and osm-5; n = 12 for rab-28) |
| GO:0097730 non-motile cilium | IDA PMID:17420466 Mutation of the MAP kinase DYF-5 affects docking and undocki... | ACCEPT | Summary: PMID:17420466 examined IFT protein localization in C. elegans cilia using fluorescence microscopy. OSM-5::GFP was used to visualize IFT-B in sensory (non-motile) cilia. Reason: Direct experimental evidence showing OSM-5 localization in non-motile sensory cilia. This is a core localization well-supported by imaging studies. Supporting Evidence: PMID:17420466 In the cilia of the nematode Caenorhabditis elegans, anterograde intraflagellar transport (IFT) is mediated by two kinesin-2 complexes |
| GO:0043053 dauer entry | IGI PMID:1732156 Genetic analysis of chemosensory control of dauer formation ... | KEEP AS NON CORE | Summary: PMID:1732156 analyzed genetic interactions in dauer formation. osm-5 is one of nine cilium-structure genes whose mutations block dauer formation by disrupting chemosensory cilia. The dauer entry defect is due to inability to sense environmental cues through defective cilia. Reason: Dauer entry requires functional chemosensory cilia to detect pheromone signals. osm-5 mutants fail to form dauers properly because they cannot sense the environmental cues through their defective cilia. This is an indirect effect of ciliary dysfunction, not a direct role in the dauer signaling pathway. Supporting Evidence: PMID:1732156 Dauer-defective mutations in nine genes cause structurally defective chemosensory cilia, thereby blocking chemosensation PMID:1732156 Mutations in all nine of these genes appear to fall at a single step in the epistasis pathway |
| GO:0060271 cilium assembly | IGI PMID:1732156 Genetic analysis of chemosensory control of dauer formation ... | ACCEPT | Summary: PMID:1732156 identified osm-5 among genes required for proper cilium structure. Genetic interaction studies showed osm-5 functions with other ciliary genes in ciliogenesis. The shortened axonemes in osm-5 mutants indicate a role in cilium assembly. Reason: Cilium assembly is a core function of OSM-5. The genetic interaction evidence from PMID:1732156, combined with ultrastructural studies showing truncated cilia, strongly supports this annotation. Supporting Evidence: PMID:1732156 Dauer-defective mutations in nine genes cause structurally defective chemosensory cilia |
| GO:0003674 molecular_function | ND GO_REF:0000015 | REMOVE | Summary: This is a root term annotation indicating no specific molecular function has been curated. However, OSM-5 has well-documented molecular functions as an IFT-B component with protein binding activity. Reason: This ND annotation is outdated. OSM-5 has established molecular functions including its role as an IFT-B structural component and kinesin binding. The ND annotation should be replaced with more informative annotations. |
| GO:0030992 intraciliary transport particle B | IDA PMID:17314406 Sensory ciliogenesis in Caenorhabditis elegans: assignment o... | ACCEPT | Summary: PMID:17314406 systematically analyzed IFT components and assigned them to functional modules. OSM-5 was classified as an IFT-B component based on transport profiles and phenotypic analyses. This is a core component identity for OSM-5. Reason: This is the most fundamental annotation for OSM-5 - its identity as an IFT-B complex component. The experimental assignment in PMID:17314406 is definitive, and this is conserved across IFT88 orthologs. Supporting Evidence: PMID:17314406 the C. elegans IFT machinery has a modular design, consisting of modules IFT-subcomplex A, IFT-subcomplex B, and a BBS protein complex |
| GO:1905515 non-motile cilium assembly | IMP PMID:2428682 Mutant sensory cilia in the nematode Caenorhabditis elegans. | ACCEPT | Summary: PMID:2428682 performed ultrastructural analysis of osm-5(p813) mutants, showing severely shortened axonemes with normal transition zones. This demonstrates OSM-5 is required for proper axoneme extension during cilium assembly. Reason: This is definitive experimental evidence for OSM-5's role in cilium assembly. The mutant phenotype directly shows the protein is required for non-motile cilium formation in sensory neurons. Supporting Evidence: PMID:2428682 The cilia in che-13 (e1805), osm-1 (p808), osm-5 (p813), and osm-6 (p811) mutants have normal transition zones and severely shortened axonemes |
| GO:0043005 neuron projection | IDA PMID:14520415 Basal body dysfunction is a likely cause of pleiotropic Bard... | ACCEPT | Summary: PMID:14520415 examined BBS protein localization and function across organisms. The paper discusses OSM-5 in the context of ciliated sensory neurons. Cilia are specialized projections of sensory neurons. Reason: Cilia extend from the dendritic tips of sensory neurons and are technically neuronal projections. OSM-5 localization to these structures is well-documented. This annotation captures the cellular context of OSM-5 function. Supporting Evidence: PMID:11290289 osm-5 is expressed in ciliated sensory neurons in C. elegans |
| GO:0036064 ciliary basal body | IDA PMID:22922713 The BBSome controls IFT assembly and turnaround in cilia. | ACCEPT | Summary: PMID:22922713 examined IFT particle assembly and localization at the ciliary base. IFT-B components including those homologous to OSM-5 localize to the basal body region where IFT particles assemble. Reason: Basal body localization is experimentally demonstrated and represents a core site of OSM-5 function. This duplicates the IBA annotation but with direct experimental evidence. Supporting Evidence: PMID:22922713 the BBSome (refs 3, 4), a group of conserved proteins affected in human Bardet-Biedl syndrome(5) (BBS), assembles IFT complexes at the ciliary base PMID:11290289 the OSM-5 protein was found to concentrate at the cilium base |
| GO:0097730 non-motile cilium | IDA PMID:11290289 The C. elegans homolog of the murine cystic kidney disease g... | ACCEPT | Summary: PMID:11290289 directly demonstrated OSM-5::GFP localization to sensory cilia using both translational fusions and immunofluorescence. This is the foundational paper establishing OSM-5 ciliary localization. Reason: This is primary experimental evidence for OSM-5 localization in non-motile sensory cilia. The paper established the ciliary identity and function of OSM-5 as an IFT component. Supporting Evidence: PMID:11290289 the OSM-5 protein was found to concentrate at the cilium base and within the cilium axoneme as shown by an OSM-5::GFP translational fusion and immunofluorescence |
| GO:1905515 non-motile cilium assembly | IMP PMID:11290289 The C. elegans homolog of the murine cystic kidney disease g... | ACCEPT | Summary: PMID:11290289 showed that osm-5 mutants have ciliary defects and established OSM-5 as functioning in a conserved ciliogenic pathway. The paper demonstrated transgenic rescue of osm-5 mutants using wild-type OSM-5, confirming the gene's requirement for cilium assembly. Reason: This is the foundational paper establishing OSM-5's role in ciliogenesis. The mutant phenotype and rescue experiments directly demonstrate the requirement for OSM-5 in cilium assembly. Supporting Evidence: PMID:11290289 mutations in the Caenorhabditis elegans gene Y41g9a.1 are responsible for the ciliary defects in osm-5 mutant worms. This was confirmed by transgenic rescue of osm-5(p813) mutants using the wild-type Y41g9a.1 gene PMID:11290289 the data support a crucial role for osm-5 in a conserved ciliogenic pathway, most likely as a component of the IFT process |
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Download this section (compressed HTML)Q: Does OSM-5 have direct protein-protein interactions with specific kinesin subunits, or does it interact through other IFT-B components?
Q: What is the role of OSM-5 TPR domains in IFT-B complex assembly and which partners bind to these domains?
Experiment: Determine the crystal structure of OSM-5 bound to other IFT-B subunits. Structural studies would reveal how OSM-5 integrates into the IFT-B complex and the role of its TPR domains in protein interactions.
Experiment: Identify OSM-5 binding partners by proximity labeling in vivo. BioID or similar proximity labeling approaches in C. elegans ciliated neurons could identify transient or stable OSM-5 interactors.
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