id: G5EDF6
gene_symbol: osm-6
product_type: PROTEIN
status: COMPLETE
taxon:
  id: NCBITaxon:6239
  label: Caenorhabditis elegans
description: >-
  OSM-6 is the Caenorhabditis elegans ortholog of human IFT52 (also called NGD5;
  Chlamydomonas IFT52/BLD1) and is a core structural subunit of the intraflagellar
  transport complex B (IFT-B). Intraflagellar transport is the bidirectional,
  microtubule-motor-driven movement of large multiprotein particles that build and
  maintain cilia: kinesin-2 motors carry IFT particles and their cargo anterogradely
  from the ciliary base to the tip, and cytoplasmic dynein-2 returns them retrogradely.
  OSM-6/IFT52 is itself a component (and moving cargo) of the IFT-B particle rather
  than an enzyme; its GATase-like N-terminal (GIFT) domain, central domain and
  C-terminal domain are used to scaffold the complex. In C. elegans, osm-6 is expressed
  exclusively in ciliated sensory neurons under control of the RFX transcription factor
  DAF-19, and the protein localizes to the ciliary base (basal body, transition zone),
  along the sensory (non-motile) cilium, and in the cytoplasm/cell body of these
  neurons. OSM-6 is required for assembly of the ciliary axoneme: loss-of-function
  mutants retain normal transition zones but have severely truncated axonemes and
  ectopic microtubule assembly, causing dye-filling defects. Because the 60 ciliated
  sensory neurons mediate chemosensation, osmotic avoidance, mechanosensation, and
  dauer-pathway signaling, osm-6 mutants are broadly defective in these sensory
  behaviors as a downstream consequence of lacking functional cilia. OSM-6/IFT52 is
  conserved from algae to humans, and the pathway it serves is central to the biology
  of ciliopathies.
references:
- id: GO_REF:0000015
  title: Use of the ND evidence code for Gene Ontology (GO) terms
  findings: []
- id: GO_REF:0000033
  title: Annotation inferences using phylogenetic trees
  findings: []
- id: PMID:10545497
  title: Role of a class DHC1b dynein in retrograde transport of IFT motors and IFT
    raft particles along cilia, but not dendrites, in chemosensory neurons of living
    Caenorhabditis elegans.
  findings:
  - statement: OSM-6 is a homologue of a Chlamydomonas 16S IFT raft (IFT particle)
      polypeptide and, together with OSM-1 and kinesin-II, undergoes retrograde IFT
      along cilia at ~1.1 um/s; retrograde ciliary transport requires the CHE-3
      (DHC1b/dynein-2) motor.
    supporting_text: OSM-1 and OSM-6, all move at approximately 1.1 microm/s in the
      retrograde direction along cilia and dendrites
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: PubMed-verified (Signor et al., J Cell Biol 1999). Directly assays
      OSM-6::GFP movement and its dependence on dynein; supports IFT-cargo and
      transition-zone localization annotations.
- id: PMID:1732156
  title: Genetic analysis of chemosensory control of dauer formation in Caenorhabditis
    elegans.
  findings:
  - statement: osm-6 is one of nine cilium-structure genes whose mutation causes
      structurally defective chemosensory cilia and blocks chemosensation, placing it
      at a single step in the dauer-formation epistasis pathway.
    supporting_text: Dauer-defective mutations in nine genes cause structurally
      defective chemosensory cilia, thereby blocking chemosensation.
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: Vowels & Thomas 1992; supports the dauer (cilium assembly) IGI as a
      downstream sensory consequence of defective cilia.
- id: PMID:22342749
  title: Endocytosis genes facilitate protein and membrane transport in C. elegans
    sensory cilia.
  findings:
  - statement: OSM-6 is used as an IFT/ciliary marker in C. elegans sensory cilia; the
      study examines transport of ciliary and periciliary membrane and IFT proteins.
    supporting_text: These pathways include cilium-based intraflagellar transport (IFT)
      and poorly understood membrane trafficking events.
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: Kaplan et al. 2012; source of the non-motile cilium IDA localization.
- id: PMID:22922713
  title: The BBSome controls IFT assembly and turnaround in cilia.
  findings:
  - statement: GFP-tagged OSM-6 is the canonical IFT-B reporter (explicitly the ortholog
      of human IFT52) used to screen for IFT assembly/turnaround mutants; OSM-6 marks
      IFT particles at the ciliary base and along cilia.
    supporting_text: the GFP-tagged IFT-B component OSM-6 (the ortholog of human IFT52)
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: Wei et al., Nat Cell Biol 2012. Establishes OSM-6=IFT52=IFT-B component;
      basal body IDA localization.
- id: PMID:24013594
  title: Neuropeptide signaling remodels chemosensory circuit composition in Caenorhabditis
    elegans.
  findings:
  - statement: Hypomorphic osm-6 mutants lack functional sensory cilia and consequently
      show greatly reduced salt (ASEL) and salt/odor (AWC) sensory responses; ciliary
      function is restored cell-autonomously by osm-6 rescue.
    supporting_text: We analyzed hypomorphic osm-6 mutants that lack functional sensory
      cilia (dendritic endings) and found them to have greatly reduced ASEL salt
      responses and AWCON salt and odor responses
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: Leinwand & Chalasani 2013. osm-6 used as a tool to abolish ciliary
      sensory function; the salt-response phenotype is an indirect consequence of
      cilium loss, not a salt-signalling activity of OSM-6.
- id: PMID:2428682
  title: Mutant sensory cilia in the nematode Caenorhabditis elegans.
  findings:
  - statement: osm-6(p811) mutants have normal ciliary transition zones but severely
      shortened axonemes with ectopic doublet microtubules, establishing OSM-6 as
      required for axoneme (cilium) assembly rather than transition-zone formation.
    supporting_text: 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.
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: Perkins et al. 1986; foundational ultrastructural characterization of
      osm-6 ciliary phenotype and dye-filling/chemosensory defects.
- id: PMID:27930654
  title: Whole-Organism Developmental Expression Profiling Identifies RAB-28 as a Novel
    Ciliary GTPase Associated with the BBSome and Intraflagellar Transport.
  findings:
  - statement: OSM-6::GFP (explicitly the IFT52 orthologue) localizes throughout
      normal-length sensory cilia and is used as an established IFT/ciliary marker.
    supporting_text: Localisation of an IFT protein, OSM-6 (IFT52 orthologue), throughout
      normal-length cilia confirms this finding
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: Jensen et al. 2016; source of the cilium IDA localization (OSM-6::GFP
      as a ciliary reference marker).
- id: PMID:28479320
  title: Dynein-Driven Retrograde Intraflagellar Transport Is Triphasic in C. elegans
    Sensory Cilia.
  findings:
  - statement: Ciliary entry of dynein-2 requires an intact IFT-B complex (of which
      OSM-6/IFT52 is a component); this study is the ComplexPortal source (CPX-1290)
      for OSM-6 IFT-B/IFT particle B membership and ciliary localization.
    supporting_text: Disruption of the dynein-2 tail domain, light intermediate chain,
      or intraflagellar transport (IFT)-B complex abolishes dynein-2's ciliary
      localization
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: Yi et al. 2017. Underlies the ComplexPortal NAS annotations for IFT
      particle B membership, intraciliary transport, cilium assembly and cilium.
- id: PMID:730048
  title: Osmotic avoidance defective mutants of the nematode Caenorhabditis elegans.
  findings:
  - statement: Founding screen that isolated osmotic-avoidance-defective (Osm) mutants
      of C. elegans, the phenotypic class for which osm-6 is named; such mutants fail
      to avoid high concentrations of salts/sugars.
    supporting_text: mutants were selected for their inability to avoid high
      concentrations of fructose or NaCl
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: Culotti & Russell 1978; abstract-only. Origin of the osm-6 osmotic
      avoidance phenotype; the WormBase IMP is a curator judgment from the full text.
- id: PMID:8460126
  title: A dual mechanosensory and chemosensory neuron in Caenorhabditis elegans.
  findings:
  - statement: Animals with defective ciliated sensory endings fail to respond to nose
      touch, linking intact sensory cilia (which require osm-6) to mechanosensation.
    supporting_text: Mutant animals that have defective ciliated sensory endings as
      well as laser-operated animals that lack ASH, FLP, and OLQ fail to respond to
      touch to the nose.
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: Kaplan & Horvitz 1993; abstract-only, does not name osm-6. Basis for
      the WormBase mechanosensory-perception IMP as a downstream ciliary phenotype;
      not overruled per curator-defers guidance.
- id: PMID:9475731
  title: Analysis of osm-6, a gene that affects sensory cilium structure and sensory
    neuron function in Caenorhabditis elegans.
  findings:
  - statement: osm-6 was cloned and shown to encode a protein of previously unknown
      function expressed exclusively in ciliated sensory neurons; OSM-6::GFP rescues
      the mutant and localizes to cytoplasm/processes/dendritic endings, and osm-6 acts
      cell-autonomously in cilium structure. DAF-19 is required for OSM-6 accumulation.
    supporting_text: The OSM-6::GFP protein was localized to cytoplasm, including
      processes and dendritic endings where sensory cilia are situated.
  - statement: Genetic mosaic analysis shows osm-6 acts cell-autonomously in the
      ciliated neuron.
    supporting_text: we conclude from an analysis of genetic mosaics that osm-6 acts
      cell autonomously in affecting cilium structure
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: Collet et al. 1998; the defining osm-6 cloning/expression paper.
      Source of cytoplasm and neuronal cell body IDA localizations and the
      DAF-19-dependent, sensory-neuron-restricted expression.
existing_annotations:
- term:
    id: GO:0005929
    label: cilium
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: is_active_in
  review:
    summary: OSM-6/IFT52 localizes to and functions within the cilium; phylogenetic
      (IBA) inference agrees with direct C. elegans localization data.
    action: ACCEPT
    reason: Cilium localization is directly supported by multiple experimental studies
      (OSM-6::GFP is a canonical ciliary/IFT marker) and is a core aspect of osm-6
      function.
    supported_by:
    - reference_id: PMID:22922713
      supporting_text: the GFP-tagged IFT-B component OSM-6 (the ortholog of human IFT52)
- term:
    id: GO:0030992
    label: intraciliary transport particle B
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: part_of
  review:
    summary: OSM-6 is a structural subunit of the IFT-B particle; this is the single
      most important annotation for the gene and is supported by orthology to IFT52 and
      by ComplexPortal (CPX-1290).
    action: ACCEPT
    reason: Core molecular role. OSM-6 is explicitly the IFT-B component / IFT52
      ortholog and a member of Intraflagellar transport complex B (CPX-1290).
    supported_by:
    - reference_id: PMID:22922713
      supporting_text: the GFP-tagged IFT-B component OSM-6 (the ortholog of human IFT52)
- term:
    id: GO:0042073
    label: intraciliary transport
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: involved_in
  review:
    summary: As an IFT-B subunit and moving IFT cargo, OSM-6 is directly involved in
      intraciliary transport.
    action: ACCEPT
    reason: Core biological process. OSM-6::GFP moves bidirectionally by IFT and is part
      of the transported IFT particle.
    supported_by:
    - reference_id: PMID:10545497
      supporting_text: OSM-1 and OSM-6, all move at approximately 1.1 microm/s in the
        retrograde direction along cilia and dendrites
- term:
    id: GO:0060271
    label: cilium assembly
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: involved_in
  review:
    summary: OSM-6 is required for building the ciliary axoneme; phylogenetic inference
      is corroborated by the loss-of-function ultrastructural phenotype.
    action: ACCEPT
    reason: Core process. osm-6 mutants have severely truncated axonemes, establishing a
      role in cilium assembly.
    supported_by:
    - reference_id: PMID:2428682
      supporting_text: 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.
- term:
    id: GO:0005814
    label: centriole
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: is_active_in
  review:
    summary: Phylogenetically propagated centriole localization. In C. elegans the
      directly demonstrated basal-body/transition-zone localization is the relevant
      structure (the ciliary basal body is a docked, modified centriole).
    action: KEEP_AS_NON_CORE
    reason: Plausible but not the core functional site and not directly demonstrated in
      C. elegans; the experimentally supported location is the ciliary basal body
      (GO:0036064). Retained as a non-core, orthology-based location rather than removed.
- term:
    id: GO:0005929
    label: cilium
  evidence_type: NAS
  original_reference_id: PMID:28479320
  qualifier: located_in
  review:
    summary: ComplexPortal (CPX-1290) statement that OSM-6 localizes to the cilium,
      consistent with direct experimental data.
    action: ACCEPT
    reason: Core ciliary localization; corroborated by IDA evidence from multiple studies.
    supported_by:
    - reference_id: PMID:28479320
      supporting_text: Dynein-Driven Retrograde Intraflagellar Transport Is Triphasic in
        C. elegans Sensory Cilia
- term:
    id: GO:0030992
    label: intraciliary transport particle B
  evidence_type: NAS
  original_reference_id: PMID:28479320
  qualifier: part_of
  review:
    summary: ComplexPortal assertion of OSM-6 membership in IFT particle B, the core
      structural annotation, based on the C. elegans IFT-B complex.
    action: ACCEPT
    reason: Core molecular role, redundant with and reinforcing the IBA IFT-B membership
      annotation.
    supported_by:
    - reference_id: PMID:28479320
      supporting_text: Disruption of the dynein-2 tail domain, light intermediate chain,
        or intraflagellar transport (IFT)-B complex abolishes dynein-2's ciliary
        localization
- term:
    id: GO:0042073
    label: intraciliary transport
  evidence_type: NAS
  original_reference_id: PMID:28479320
  qualifier: involved_in
  review:
    summary: ComplexPortal statement of IFT-B involvement in intraciliary transport.
    action: ACCEPT
    reason: Core process consistent with OSM-6 being a transported IFT-B subunit.
    supported_by:
    - reference_id: PMID:28479320
      supporting_text: Disruption of the dynein-2 tail domain, light intermediate chain,
        or intraflagellar transport (IFT)-B complex abolishes dynein-2's ciliary
        localization
- term:
    id: GO:0060271
    label: cilium assembly
  evidence_type: NAS
  original_reference_id: PMID:28479320
  qualifier: involved_in
  review:
    summary: ComplexPortal statement of IFT-B involvement in cilium assembly.
    action: ACCEPT
    reason: Core process; redundant with the IMP/IBA cilium-assembly annotations.
    supported_by:
    - reference_id: PMID:2428682
      supporting_text: 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.
- term:
    id: GO:0060271
    label: cilium assembly
  evidence_type: IMP
  original_reference_id: PMID:24013594
  qualifier: involved_in
  review:
    summary: osm-6 loss abolishes functional sensory cilia (dendritic endings),
      confirming a requirement in cilium assembly.
    action: ACCEPT
    reason: Core process. Although this paper is about a salt circuit, it explicitly
      uses osm-6 as a cilium-assembly loss-of-function allele.
    supported_by:
    - reference_id: PMID:24013594
      supporting_text: We analyzed hypomorphic osm-6 mutants that lack functional sensory
        cilia (dendritic endings)
- term:
    id: GO:1902075
    label: cellular response to salt
  evidence_type: IMP
  original_reference_id: PMID:24013594
  qualifier: involved_in
  review:
    summary: osm-6 mutants have reduced salt-evoked neuronal responses, but only because
      they lack functional cilia; OSM-6 has no salt-sensing or salt-signalling activity
      of its own.
    action: KEEP_AS_NON_CORE
    reason: Indirect, downstream sensory phenotype of ciliary loss rather than a core
      molecular/biological function of OSM-6. Retained (per curator) but marked non-core
      to avoid implying a direct salt-response role.
    supported_by:
    - reference_id: PMID:24013594
      supporting_text: found them to have greatly reduced ASEL salt responses and AWCON
        salt and odor responses
- term:
    id: GO:0005929
    label: cilium
  evidence_type: IDA
  original_reference_id: PMID:27930654
  qualifier: located_in
  review:
    summary: Direct localization of OSM-6::GFP to the cilium, used as a ciliary reference
      marker.
    action: ACCEPT
    reason: Core ciliary localization directly observed; OSM-6::GFP (IFT52 orthologue)
      is imaged throughout normal-length cilia.
    supported_by:
    - reference_id: PMID:27930654
      supporting_text: Localisation of an IFT protein, OSM-6 (IFT52 orthologue),
        throughout normal-length cilia confirms this finding
- term:
    id: GO:1905515
    label: non-motile cilium assembly
  evidence_type: IMP
  original_reference_id: PMID:2428682
  qualifier: involved_in
  review:
    summary: osm-6 mutants fail to build full sensory (non-motile) cilia; this is the
      most precise cilium-assembly term for the worm's sensory cilia.
    action: ACCEPT
    reason: Core process, and appropriately specific (C. elegans sensory cilia are
      non-motile). Directly supported by the ultrastructural phenotype.
    supported_by:
    - reference_id: PMID:2428682
      supporting_text: 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.
- term:
    id: GO:0060271
    label: cilium assembly
  evidence_type: IGI
  original_reference_id: PMID:1732156
  qualifier: involved_in
  review:
    summary: Genetic-interaction evidence placing osm-6 among cilium-structure genes
      required for chemosensory cilium function in the dauer pathway.
    action: ACCEPT
    reason: Core process; osm-6 is one of nine genes whose mutation gives structurally
      defective chemosensory cilia.
    supported_by:
    - reference_id: PMID:1732156
      supporting_text: Dauer-defective mutations in nine genes cause structurally
        defective chemosensory cilia, thereby blocking chemosensation.
- term:
    id: GO:0097730
    label: non-motile cilium
  evidence_type: IDA
  original_reference_id: PMID:22342749
  qualifier: located_in
  review:
    summary: Direct localization of OSM-6 to the sensory (non-motile) cilium.
    action: ACCEPT
    reason: Core ciliary localization; the sensory-cilium term is appropriately specific.
    supported_by:
    - reference_id: PMID:22342749
      supporting_text: cilium-based intraflagellar transport (IFT)
- term:
    id: GO:0003674
    label: molecular_function
  evidence_type: ND
  original_reference_id: GO_REF:0000015
  qualifier: enables
  review:
    summary: Root-level placeholder recording that no specific molecular function had
      been assigned at the time of annotation.
    action: ACCEPT
    reason: Retained as the standard ND placeholder. A subunit-specific molecular
      function (structural molecule activity within IFT-B) is now proposed as a NEW
      annotation and in core_functions; no catalytic activity is known or expected for
      this GATase-fold scaffold.
- term:
    id: GO:0005198
    label: structural molecule activity
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: enables
  review:
    summary: OSM-6/IFT52 has no catalytic activity; as an IFT-B subunit its molecular
      function is best captured as a subunit-specific structural molecule activity.
    action: NEW
    reason: Proposed new molecular-function annotation reflecting OSM-6's role as a
      structural subunit of the IFT-B particle (the current GOA carries only the ND root
      MF for this gene). This IBA/GO_REF:0000033 evidence pairing does NOT currently
      exist in the GOA export; it is the expected phylogenetic evidence basis if the
      annotation were made (IFT52 orthologues across species are IFT-B structural
      subunits). Ideally a more specific 'structural constituent of intraflagellar
      transport particle' term (see proposed_new_terms) would be used.
    supported_by:
    - reference_id: PMID:22922713
      supporting_text: the GFP-tagged IFT-B component OSM-6 (the ortholog of human IFT52)
- term:
    id: GO:0036064
    label: ciliary basal body
  evidence_type: IDA
  original_reference_id: PMID:22922713
  qualifier: located_in
  review:
    summary: OSM-6::GFP directly localizes to the ciliary basal body, where IFT
      particles assemble before entering the cilium.
    action: ACCEPT
    reason: Core localization at the site of IFT assembly.
    supported_by:
    - reference_id: PMID:22922713
      supporting_text: the GFP-tagged IFT-B component OSM-6 (the ortholog of human IFT52)
- term:
    id: GO:0035869
    label: ciliary transition zone
  evidence_type: IDA
  original_reference_id: PMID:10545497
  qualifier: located_in
  review:
    summary: OSM-6::GFP is observed at/through the ciliary transition zone as it moves
      between the base and the axoneme.
    action: ACCEPT
    reason: Core localization consistent with IFT trafficking through the transition zone.
    supported_by:
    - reference_id: PMID:10545497
      supporting_text: OSM-1 and OSM-6, all move at approximately 1.1 microm/s in the
        retrograde direction along cilia and dendrites
- term:
    id: GO:0097730
    label: non-motile cilium
  evidence_type: IDA
  original_reference_id: PMID:10545497
  qualifier: located_in
  review:
    summary: OSM-6::GFP localizes along the sensory (non-motile) cilium.
    action: ACCEPT
    reason: Core ciliary localization, appropriately specific.
    supported_by:
    - reference_id: PMID:10545497
      supporting_text: OSM-1 and OSM-6, all move at approximately 1.1 microm/s in the
        retrograde direction along cilia and dendrites
- term:
    id: GO:0005737
    label: cytoplasm
  evidence_type: IDA
  original_reference_id: PMID:9475731
  qualifier: located_in
  review:
    summary: OSM-6::GFP is present in the cytoplasm (including neuronal processes) prior
      to and outside of ciliary transport.
    action: KEEP_AS_NON_CORE
    reason: Directly observed but a broad, non-informative location; the functionally
      relevant sites are the cilium and its base. Retained as non-core.
    supported_by:
    - reference_id: PMID:9475731
      supporting_text: The OSM-6::GFP protein was localized to cytoplasm, including
        processes and dendritic endings where sensory cilia are situated.
- term:
    id: GO:0006935
    label: chemotaxis
  evidence_type: IMP
  original_reference_id: PMID:2428682
  qualifier: involved_in
  review:
    summary: osm-6 mutants are chemosensory-defective (dye-filling defective) because
      their chemosensory cilia are truncated.
    action: KEEP_AS_NON_CORE
    reason: Downstream sensory consequence of defective cilia rather than a direct role
      of OSM-6 in chemotaxis signalling. Retained but non-core.
    supported_by:
    - reference_id: PMID:2428682
      supporting_text: Mutations in 14 genes prevent dye uptake and disrupt chemosensory
        behaviors.
- term:
    id: GO:0006970
    label: response to osmotic stress
  evidence_type: IMP
  original_reference_id: PMID:730048
  qualifier: involved_in
  review:
    summary: osm-6 is named for its osmotic-avoidance-defective phenotype; mutants fail
      to avoid high osmolarity because their sensory cilia are non-functional.
    action: KEEP_AS_NON_CORE
    reason: Indirect, downstream behavioral phenotype of ciliary loss, not a direct
      osmotic-stress-response activity of OSM-6. Retained (curator IMP) but non-core.
    supported_by:
    - reference_id: PMID:730048
      supporting_text: mutants were selected for their inability to avoid high
        concentrations of fructose or NaCl
- term:
    id: GO:0043025
    label: neuronal cell body
  evidence_type: IDA
  original_reference_id: PMID:9475731
  qualifier: located_in
  review:
    summary: OSM-6::GFP accumulates in the cell bodies of ciliated sensory neurons,
      where the protein is synthesized before delivery to cilia.
    action: KEEP_AS_NON_CORE
    reason: Real localization but reflects the site of synthesis rather than the core
      functional site (the cilium/basal body). Retained as non-core.
    supported_by:
    - reference_id: PMID:9475731
      supporting_text: showed accumulation of GFP in ciliated sensory neurons exclusively
- term:
    id: GO:0050954
    label: sensory perception of mechanical stimulus
  evidence_type: IMP
  original_reference_id: PMID:8460126
  qualifier: involved_in
  review:
    summary: Nose-touch mechanosensation requires intact ciliated sensory endings, which
      osm-6 is needed to build; osm-6 mutants are mechanosensory-defective.
    action: KEEP_AS_NON_CORE
    reason: Downstream sensory consequence of defective cilia rather than a direct
      mechanotransduction role of OSM-6. The cached abstract does not name osm-6, but
      the WormBase IMP reflects curator full-text evidence and is not overruled.
    supported_by:
    - reference_id: PMID:8460126
      supporting_text: Mutant animals that have defective ciliated sensory endings as
        well as laser-operated animals that lack ASH, FLP, and OLQ fail to respond to
        touch to the nose.
core_functions:
- description: OSM-6/IFT52 is a structural subunit of the intraflagellar transport
    complex B (IFT-B), the anterograde IFT particle that is itself carried as cargo by
    kinesin-2 and returned by dynein-2. It scaffolds the IFT-B complex (it does not have
    independent catalytic activity) and is required to build and maintain the sensory
    ciliary axoneme in C. elegans ciliated neurons.
  supported_by:
  - reference_id: PMID:22922713
    supporting_text: the GFP-tagged IFT-B component OSM-6 (the ortholog of human IFT52)
  - reference_id: PMID:2428682
    supporting_text: 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.
  molecular_function:
    id: GO:0005198
    label: structural molecule activity
  directly_involved_in:
  - id: GO:0042073
    label: intraciliary transport
  - id: GO:1905515
    label: non-motile cilium assembly
  locations:
  - id: GO:0097730
    label: non-motile cilium
  - id: GO:0036064
    label: ciliary basal body
  - id: GO:0035869
    label: ciliary transition zone
  in_complex:
    id: GO:0030992
    label: intraciliary transport particle B
knowledge_gaps:
- gap_statement: The specific intra-complex protein contacts of OSM-6/IFT52 within the
    C. elegans IFT-B particle have not been experimentally mapped. In other organisms
    IFT52 bridges the IFT-B1 core (contacting IFT88, IFT70 and IFT46) and links the core
    to peripheral subunits, but which partners its GIFT, central and C-terminal domains
    engage in the worm, and how these contacts are used during IFT-particle assembly and
    tip turnaround, is undetermined.
  boundary: It is firmly established that OSM-6 is an IFT-B/IFT52 structural subunit that
    moves bidirectionally by IFT, localizes to basal body, transition zone and axoneme,
    and is required for axoneme assembly.
  gap_kind:
  - BIOLOGY
  - ONTOLOGY
  dark_aspect: MF_DARK
  status: OPEN
  significance: Defining OSM-6's specific IFT-B contacts would explain how the IFT-B
    particle is built and how ciliopathy-relevant IFT52 mutations destabilize the complex.
  resolution: In vivo proximity labeling (BioID/TurboID) or cross-linking mass
    spectrometry of tagged OSM-6 in ciliated neurons, plus structure determination of the
    C. elegans IFT-B subcomplex, paired with an ontology term for structural constituent
    of the IFT particle.
  provenance:
  - reference_id: PMID:22922713
    supporting_text: the GFP-tagged IFT-B component OSM-6 (the ortholog of human IFT52)
  proposed_terms:
  - proposed_name: structural constituent of intraflagellar transport particle
    proposed_definition: A structural molecule activity in which a protein acts as a
      structural subunit of an intraflagellar transport (IFT) particle (IFT-A or IFT-B),
      contributing to assembly and integrity of the particle trafficked along the
      ciliary axoneme.
    justification: GO currently expresses this role only as the generic 'structural
      molecule activity' (GO:0005198).
- gap_statement: No independent biochemical or enzymatic activity has been demonstrated
    for OSM-6/IFT52, and although its N-terminal domain adopts a class-I
    glutamine-amidotransferase-like (GIFT) fold, whether this fold has any residual
    ligand-binding or catalytic role beyond scaffolding is unknown.
  boundary: The GATase-like fold is annotated structurally (Pfam IFT52_GIFT / SSF52317);
    catalytic residues appear absent, consistent with a purely structural function.
  gap_kind:
  - BIOLOGY
  dark_aspect: MF_DARK
  status: OPEN
  significance: Ruling in or out any ligand-binding role of the GIFT domain would clarify
    whether IFT52 does more than scaffold IFT-B.
  resolution: Structure-guided mutagenesis of the GIFT domain and in vitro binding/activity
    assays to test for retained ligand interaction.
  provenance:
  - reference_id: PMID:9475731
    supporting_text: a protein that is 40% identical in amino acid sequence to a predicted
      mammalian protein of unknown function
proposed_new_terms:
- proposed_name: structural constituent of intraflagellar transport particle
  proposed_definition: A structural molecule activity in which a protein acts as a
    structural subunit of an intraflagellar transport (IFT) particle (IFT-A or IFT-B),
    contributing to the assembly and integrity of the particle that is trafficked along
    the ciliary axoneme by kinesin-2 and dynein-2 motors.
  justification: OSM-6/IFT52 and its IFT-B/IFT-A paralogs act as structural subunits of
    the IFT particle, a role currently expressible only as the generic GO:0005198
    structural molecule activity. A dedicated MF term would capture the shared function
    of IFT structural subunits.
  supported_by:
  - reference_id: PMID:22922713
    supporting_text: the GFP-tagged IFT-B component OSM-6 (the ortholog of human IFT52)
suggested_questions:
- question: Which IFT-B subunits does OSM-6 directly contact in C. elegans, and are the
    GIFT, central and C-terminal domains functionally separable?
  experts:
  - Oliver E. Blacque
- question: Does the IFT52 GIFT domain retain any ligand-binding capacity, or is it a
    purely structural remnant of the glutamine-amidotransferase fold?
  experts: []
suggested_experiments:
- hypothesis: OSM-6/IFT52 bridges the IFT-B core to peripheral subunits via distinct
    domains, and disrupting individual domains selectively destabilizes parts of IFT-B.
  description: Perform in vivo proximity labeling (TurboID) with domain-truncated OSM-6
    variants expressed in ciliated neurons, followed by mass spectrometry, to map
    domain-specific IFT-B interaction partners.
  experiment_type: proximity labeling / interaction mapping
- hypothesis: The severely truncated axoneme of osm-6 mutants reflects failure to deliver
    axonemal tubulin/cargo by IFT-B rather than a transition-zone defect.
  description: Use live imaging of tagged tubulin and IFT trains in osm-6 partial
    loss-of-function backgrounds to quantify anterograde cargo delivery versus
    transition-zone integrity.
  experiment_type: live-cell imaging
tags:
- caeel-ciliopathy