Existing Annotations Review

GO Term	Evidence	Action	Reason
GO:0043005 neuron projection	IBA GO_REF:0000033	ACCEPT	Summary: IBA annotation based on phylogenetic inference from mouse and other orthologs. In C. elegans, BBS-2 is expressed in ciliated sensory neurons (PMID:14520415, PMID:15231740). The protein is present in the cilia of amphid and phasmid neurons, which are neuronal projections specialized for sensory function. Reason: BBS-2 localizes to sensory neuron projections (cilia) in C. elegans. This annotation is consistent with direct experimental evidence from PMID:14520415 showing expression in amphid and phasmid neurons. While 'cilium' would be more precise, neuron projection is an accurate parent term for sensory cilia that emerge from neuronal dendrites. Supporting Evidence: PMID:14520415 all available Caenorhabditis elegans BBS homologues are expressed exclusively in ciliated neurons, and contain regulatory elements for RFX, a transcription factor that modulates the expression of genes associated with ciliogenesis and intraflagellar transport file:worm/bbs-2/bbs-2-deep-research-falcon.md model: Edison Scientific Literature
GO:0060271 cilium assembly	IBA GO_REF:0000033	ACCEPT	Summary: IBA annotation from phylogenetic inference. BBS-2 is required for cilia biogenesis in C. elegans. The BBSome controls IFT assembly and turnaround, which are essential for cilium assembly (PMID:22922713, PMID:15231740). Reason: Direct experimental evidence supports this annotation. PMID:22922713 demonstrates that the BBSome (including BBS-2) is required for assembling IFT particles at both ciliary base and tip, which is essential for cilium assembly. PMID:15231740 shows that loss of BBS proteins results in cilia defects. Supporting Evidence: PMID:22922713 the BBSome is required for assembling IFT particles at both ciliary base and tip PMID:15231740 mutations in the Caenorhabditis elegans bbs-7 and bbs-8 genes cause structural and functional defects in cilia
GO:0016020 membrane	IBA GO_REF:0000033	MARK AS OVER ANNOTATED	Summary: IBA annotation inferring membrane association. The BBSome functions as a coat complex for sorting membrane proteins to cilia (UniProt annotation by similarity). Reason: While the BBSome is involved in membrane protein trafficking to cilia, this generic 'membrane' annotation is too broad to be informative. The protein is not an integral membrane protein - it is a cytoplasmic protein that associates with membranes transiently during cargo sorting. More specific terms like 'cilium' or 'ciliary basal body' are already captured in other annotations and better describe the relevant membrane compartments.
GO:0034464 BBSome	IBA GO_REF:0000033	ACCEPT	Summary: IBA annotation indicating BBS-2 is part of the BBSome complex. This is a core identity annotation for the protein, supported by phylogenetic conservation and biochemical evidence (PMID:22922713). Reason: This is the defining annotation for BBS-2. The BBSome complex contains BBS-1, BBS-2, BBS-4, BBS-5, BBS-7, BBS-8, BBS-9, and BBIP10 in C. elegans and is highly conserved. PMID:22922713 provides direct evidence that worm BBS proteins form a complex using BiFC assays. Supporting Evidence: PMID:22922713 In wild-type animals, fluorescence complementation can be observed in BBS-1–BBS-7 and BBS-1–BBS-9 pair, indicative of the coexistence of these three BBS proteins in the same complex
GO:0036064 ciliary basal body	IBA GO_REF:0000033	ACCEPT	Summary: IBA annotation for ciliary basal body localization. BBS-2 localizes to the ciliary basal body where the BBSome assembles IFT particles (PMID:15231740, PMID:22922713). Reason: Direct experimental evidence supports basal body localization. PMID:15231740 states that C. elegans BBS proteins localize predominantly at the base of cilia. PMID:22922713 shows the BBSome assembles at the ciliary base and this is where IFT particle assembly occurs. UniProt annotation also confirms this localization. Supporting Evidence: PMID:15231740 C. elegans BBS proteins localize predominantly at the base of cilia 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
GO:0031514 motile cilium	IBA GO_REF:0000033	MODIFY	Summary: IBA annotation suggesting motile cilium localization. However, C. elegans sensory neurons contain non-motile (primary/sensory) cilia, not motile cilia. Reason: C. elegans cilia are sensory (non-motile) cilia, not motile cilia. The organism lacks motile cilia entirely - its sensory neurons have non-motile cilia specialized for chemosensation, mechanosensation, and thermosensation. The IBA inference from mouse orthologs (which can be in motile cilia in some contexts) does not apply to worm biology. This annotation should be corrected to non-motile cilium. Proposed replacements: non-motile cilium
GO:0005929 cilium	IEA GO_REF:0000044	ACCEPT	Summary: IEA annotation based on UniProt subcellular location mapping. BBS-2 is localized to cilia in C. elegans sensory neurons (PMID:15231740). Reason: Direct experimental evidence confirms ciliary localization. PMID:15231740 demonstrates that BBS proteins localize to cilia and move bidirectionally along the ciliary axoneme. PMID:22922713 provides additional evidence that BBS-2 localizes to cilia, though with reduced intensity in certain mutant backgrounds. The IEA annotation is consistent with experimental data. Supporting Evidence: PMID:15231740 C. elegans BBS proteins localize predominantly at the base of cilia, and like proteins involved in intraflagellar transport (IFT), a process necessary for cilia biogenesis and maintenance, move bidirectionally along the ciliary axoneme
GO:0005930 axoneme	IEA GO_REF:0000044	ACCEPT	Summary: IEA annotation based on UniProt subcellular location. BBS-2 moves along the ciliary axoneme as part of IFT (PMID:15231740, PMID:22922713). Reason: Direct experimental evidence supports axoneme localization. PMID:15231740 shows that BBS proteins move bidirectionally along the ciliary axoneme. PMID:22922713 demonstrates that BBS-2 shows IFT movement along the axoneme (when not in mutant backgrounds that disrupt BBSome-IFT association). UniProt annotation also confirms axoneme localization. Supporting Evidence: PMID:15231740 like proteins involved in intraflagellar transport (IFT), a process necessary for cilia biogenesis and maintenance, move bidirectionally along the ciliary axoneme
GO:0015031 protein transport	IEA GO_REF:0000043	MODIFY	Summary: IEA annotation from UniProt keyword mapping. The BBSome functions as a coat complex for sorting membrane proteins to cilia (by similarity to human BBS2). Reason: While BBS-2 is involved in protein transport, this term is too general. The BBSome specifically functions in ciliary protein trafficking - sorting membrane proteins to the ciliary membrane and exporting signaling molecules. The more specific process is intraciliary transport, which describes the BBSome's role in IFT assembly and cargo trafficking within cilia. Proposed replacements: intraciliary transport
GO:0030030 cell projection organization	IEA GO_REF:0000043	ACCEPT	Summary: IEA annotation from UniProt keyword mapping. BBS-2 is required for proper cilia structure and function (PMID:22922713, PMID:15231740). Reason: This is an accurate parent term annotation. Cilia are cell projections, and BBS-2 is required for proper cilium organization through its role in IFT assembly. The more specific term 'cilium assembly' is already captured separately, but this broader term correctly captures the overall biological role. Supporting Evidence: PMID:22922713 Our results identify the BBSome as the key player regulating IFT assembly and turnaround in cilia
GO:0034464 BBSome	IEA GO_REF:0000002	ACCEPT	Summary: IEA annotation from InterPro domain mapping. BBS-2 is part of the BBSome complex. Reason: This is a duplicate of the IBA annotation for BBSome membership, both are correct. The InterPro domain (IPR016616, Bardet-Biedl syndrome 2 protein) correctly predicts BBSome membership, which is experimentally validated.
GO:1905515 non-motile cilium assembly	IEA GO_REF:0000002	ACCEPT	Summary: IEA annotation from InterPro mapping. BBS-2 is required for assembly of sensory (non-motile) cilia in C. elegans. Reason: This is the most precise cilium assembly term for C. elegans BBS-2. All cilia in C. elegans are non-motile sensory cilia. The BBSome is required for their assembly through its role in IFT particle organization. This is more specific than the general 'cilium assembly' term and accurately reflects the worm biology. Supporting Evidence: PMID:14520415 all available Caenorhabditis elegans BBS homologues are expressed exclusively in ciliated neurons
GO:0005929 cilium	NAS PMID:22922713 The BBSome controls IFT assembly and turnaround in cilia.	ACCEPT	Summary: NAS annotation from ComplexPortal based on PMID:22922713. This study provides direct evidence for BBS-2 ciliary localization in C. elegans. Reason: PMID:22922713 directly demonstrates that BBS-2 localizes to cilia in C. elegans. The paper shows GFP-tagged BBS-2 in cilia and that various BBS proteins (including BBS-2) show dim but detectable ciliary staining even in mutant backgrounds. Supporting Evidence: PMID:22922713 the others (BBS-2, -5, -7, -8, -9) only showed very dim ciliary staining when compared to wild-type animals
GO:0060271 cilium assembly	NAS PMID:22922713 The BBSome controls IFT assembly and turnaround in cilia.	ACCEPT	Summary: NAS annotation from ComplexPortal. PMID:22922713 demonstrates the BBSome is required for IFT assembly, which is essential for cilium assembly. Reason: This is a duplicate of the IBA annotation but with different evidence. PMID:22922713 provides the key mechanistic insight that the BBSome controls IFT assembly at both ciliary base and tip, which is essential for ciliogenesis. Supporting Evidence: PMID:22922713 Our results identify the BBSome as the key player regulating IFT assembly and turnaround in cilia
GO:0036064 ciliary basal body	IDA PMID:22922713 The BBSome controls IFT assembly and turnaround in cilia.	ACCEPT	Summary: IDA annotation based on direct localization studies. PMID:22922713 shows BBS-2 localization at the ciliary base through GFP tagging and BiFC experiments. Reason: PMID:22922713 provides direct experimental evidence for BBS-2 basal body localization. The study shows that BBS proteins accumulate at the ciliary base, particularly in mutant backgrounds where BBSome-IFT coupling is disrupted. This is where the BBSome assembles IFT particles before they enter the cilium. Supporting Evidence: PMID:22922713 all BBSome proteins strongly accumulate around the ciliary base and show no IFT movement in bbs-1(jhu598)
GO:0043005 neuron projection	IDA PMID:14520415 Basal body dysfunction is a likely cause of pleiotropic Bard...	ACCEPT	Summary: IDA annotation from PMID:14520415. This landmark BBS study demonstrated that all C. elegans BBS homologs are expressed exclusively in ciliated sensory neurons. Reason: PMID:14520415 provides direct experimental evidence that BBS genes (including bbs-2) are expressed exclusively in ciliated neurons in C. elegans. The paper used GFP reporter constructs to demonstrate neuron-specific expression. Sensory cilia are neuronal projections from these neurons. Supporting Evidence: PMID:14520415 all available Caenorhabditis elegans BBS homologues are expressed exclusively in ciliated neurons, and contain regulatory elements for RFX, a transcription factor that modulates the expression of genes associated with ciliogenesis and intraflagellar transport
GO:1905515 non-motile cilium assembly	IEP PMID:14520415 Basal body dysfunction is a likely cause of pleiotropic Bard...	ACCEPT	Summary: IEP annotation based on expression pattern from PMID:14520415. The gene is expressed specifically in ciliated sensory neurons during developmental stages when cilia are being assembled. Reason: The expression pattern evidence (IEP) appropriately supports involvement in non-motile cilium assembly. PMID:14520415 shows BBS gene expression specifically in ciliated neurons containing RFX regulatory elements. C. elegans cilia are exclusively non-motile sensory cilia, so expression in ciliated cells during ciliogenesis supports this annotation. Supporting Evidence: PMID:14520415 all available Caenorhabditis elegans BBS homologues are expressed exclusively in ciliated neurons, and contain regulatory elements for RFX, a transcription factor that modulates the expression of genes associated with ciliogenesis
GO:0042073 intraciliary transport	IDA PMID:22922713 The BBSome controls IFT assembly and turnaround in cilia.	NEW	Summary: The BBSome (including BBS-2) is required for IFT particle assembly and turnaround at both the ciliary base and tip. BBS proteins move bidirectionally along cilia as IFT cargo (PMID:22922713, PMID:15231740). Reason: This is a core function annotation that should be added. PMID:22922713 provides definitive evidence that the BBSome controls IFT assembly and turnaround. The paper shows that BBS proteins associate with moving IFT particles and are required for proper IFT particle reassembly at the ciliary tip for retrograde transport. Supporting Evidence: PMID:22922713 After IFT particles are assembled at the ciliary base, the BBSome binds to the IFT particle like a cargo but not a structural component PMID:15231740 like proteins involved in intraflagellar transport (IFT), a process necessary for cilia biogenesis and maintenance, move bidirectionally along the ciliary axoneme
GO:0035735 intraciliary transport involved in cilium assembly	IMP PMID:22922713 The BBSome controls IFT assembly and turnaround in cilia.	NEW	Summary: Loss of BBSome function results in disrupted IFT and defective ciliogenesis. The BBSome-mediated IFT assembly is required for cilium biogenesis. Reason: This annotation links the BBSome's IFT function directly to cilium assembly. PMID:22922713 demonstrates that disruption of BBSome-IFT coupling leads to IFT-B accumulation at ciliary tips and compromised cilia formation. This is a more precise annotation than the general 'cilium assembly' term. Supporting Evidence: PMID:22922713 The absence of the BBSome at the cilia tip leads to the defective recycling of IFT complex
GO:0005198 structural molecule activity	IDA PMID:22922713 The BBSome controls IFT assembly and turnaround in cilia.	NEW	Summary: BBS-2 contributes to the structural integrity of the BBSome complex, acting as a scaffold for IFT particle assembly. Reason: BBS-2 is a core structural component of the BBSome complex. PMID:22922713 demonstrates that BBS proteins form a complex using BiFC assays. The BBSome functions as a scaffold organizing IFT-A, IFT-B, and cargo molecules, with BBS-2 being essential for complex integrity. Supporting Evidence: PMID:22922713 In wild-type animals, fluorescence complementation can be observed in BBS-1–BBS-7 and BBS-1–BBS-9 pair, indicative of the coexistence of these three BBS proteins in the same complex

Core Functions

BBS-2 functions as a core structural component of the BBSome complex, contributing to intraciliary transport (IFT) assembly and turnaround at both the ciliary base and tip in sensory neurons. The BBSome acts as a scaffold organizing IFT-A, IFT-B, and cargo molecules.

Molecular Function:

structural molecule activity

Directly Involved In:

intraciliary transport intraciliary transport involved in cilium assembly

Cellular Locations:

ciliary basal body axoneme cilium

In Complex:

BBSome

Supporting Evidence:

PMID:22922713
After IFT particles are assembled at the ciliary base, the BBSome binds to the IFT particle like a cargo but not a structural component
PMID:15231740
C. elegans BBS proteins localize predominantly at the base of cilia, and like proteins involved in intraflagellar transport (IFT), a process necessary for cilia biogenesis and maintenance, move bidirectionally along the ciliary axoneme

References

GO_REF:0000002

Gene Ontology annotation through association of InterPro records with GO terms

GO_REF:0000033

Annotation inferences using phylogenetic trees

GO_REF:0000043

Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword mapping

GO_REF:0000044

Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping, accompanied by conservative changes to GO terms applied by UniProt

PMID:14520415

Basal body dysfunction is a likely cause of pleiotropic Bardet-Biedl syndrome.

All C. elegans BBS homologs are expressed exclusively in ciliated sensory neurons

"all available Caenorhabditis elegans BBS homologues are expressed exclusively in ciliated neurons"
BBS genes contain RFX regulatory elements associated with ciliogenesis

"contain regulatory elements for RFX, a transcription factor that modulates the expression of genes associated with ciliogenesis and intraflagellar transport"
Basal body dysfunction is the likely cause of BBS phenotypes

"BBS is probably caused by a defect at the basal body of ciliated cells"

PMID:15231740

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

BBS proteins localize predominantly at the base of cilia

"C. elegans BBS proteins localize predominantly at the base of cilia"
BBS proteins move bidirectionally along the ciliary axoneme like IFT proteins

"like proteins involved in intraflagellar transport (IFT), a process necessary for cilia biogenesis and maintenance, move bidirectionally along the ciliary axoneme"
BBS-7 and BBS-8 are required for normal IFT protein localization and motility

"BBS-7 and BBS-8 are required for the normal localization/motility of the IFT proteins OSM-5/Polaris and CHE-11"
Loss of BBS function causes structural and functional cilia defects

"mutations in the Caenorhabditis elegans bbs-7 and bbs-8 genes cause structural and functional defects in cilia"

PMID:22922713

The BBSome controls IFT assembly and turnaround in cilia.

The BBSome assembles IFT complexes at the ciliary base

"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"
The BBSome binds to IFT particles as cargo, not as a structural component

"After IFT particles are assembled at the ciliary base, the BBSome binds to the IFT particle like a cargo but not a structural component"
BBSome is required for IFT particle reassembly and turnaround at ciliary tip

"the BBSome is required for assembling IFT particles at both ciliary base and tip"
BBS-2 shows ciliary localization and IFT movement

"the others (BBS-2, -5, -7, -8, -9) only showed very dim ciliary staining when compared to wild-type animals"
BiFC assays confirm BBS proteins form a complex in C. elegans

"In wild-type animals, fluorescence complementation can be observed in BBS-1–BBS-7 and BBS-1–BBS-9 pair, indicative of the coexistence of these three BBS proteins in the same complex"
Loss of BBSome-IFT coupling leads to IFT-B accumulation at ciliary tips

"The absence of the BBSome at the cilia tip leads to the defective recycling of IFT complex"

file:worm/bbs-2/bbs-2-deep-research-falcon.md

Deep research report on bbs-2

Suggested Experiments

Experiment: Proteomics analysis of BBSome interactors in C. elegans to identify cargo molecules specifically dependent on BBS-2

Experiment: Live imaging of BBS-2::GFP to quantify IFT dynamics in various sensory neuron subtypes

Experiment: Tissue-specific rescue experiments to determine which neuronal functions require BBS-2

📚 Additional Documentation

Deep Research Falcon

(bbs-2-deep-research-falcon.md)

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organism: worm
gene_id: bbs-2
gene_symbol: bbs-2
uniprot_accession: Q19640
protein_description: 'RecName: Full=BBSome complex member bbs-2 {ECO:0000305}; AltName:
Full=Bardet-Biedl syndrome 2 protein homolog {ECO:0000312|WormBase:F20D12.3};'
gene_info: Name=bbs-2 {ECO:0000312|WormBase:F20D12.3}; ORFNames=F20D12.3 {ECO:0000312|WormBase:F20D12.3};
organism_full: Caenorhabditis elegans.
protein_family: Not specified in UniProt
protein_domains: Bardet-Biedl_syndrome_2_prot. (IPR016616); BBS2_GAE_dom. (IPR029333);
BBS2_hp_dom. (IPR055380); BBS2_Mid. (IPR029429); BBS2_N. (IPR029430)
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Question

Gene Research for Functional Annotation

⚠️ CRITICAL: Gene/Protein Identification Context

BEFORE YOU BEGIN RESEARCH: You MUST verify you are researching the CORRECT gene/protein. Gene symbols can be ambiguous, especially for less well-characterized genes from non-model organisms.

Target Gene/Protein Identity (from UniProt):

UniProt Accession: Q19640
Protein Description: RecName: Full=BBSome complex member bbs-2 {ECO:0000305}; AltName: Full=Bardet-Biedl syndrome 2 protein homolog {ECO:0000312|WormBase:F20D12.3};
Gene Information: Name=bbs-2 {ECO:0000312|WormBase:F20D12.3}; ORFNames=F20D12.3 {ECO:0000312|WormBase:F20D12.3};
Organism (full): Caenorhabditis elegans.
Protein Family: Not specified in UniProt
Key Domains: Bardet-Biedl_syndrome_2_prot. (IPR016616); BBS2_GAE_dom. (IPR029333); BBS2_hp_dom. (IPR055380); BBS2_Mid. (IPR029429); BBS2_N. (IPR029430)

MANDATORY VERIFICATION STEPS:

Check if the gene symbol "bbs-2" matches the protein description above
Verify the organism is correct: Caenorhabditis elegans.
Check if protein family/domains align with what you find in literature
If you find literature for a DIFFERENT gene with the same or similar symbol, STOP

If Gene Symbol is Ambiguous or You Cannot Find Relevant Literature:

DO NOT PROCEED WITH RESEARCH ON A DIFFERENT GENE. Instead:
- State clearly: "The gene symbol 'bbs-2' is ambiguous or literature is limited for this specific protein"
- Explain what you found (e.g., "Found extensive literature on a different gene with the same symbol in a different organism")
- Describe the protein based ONLY on the UniProt information provided above
- Suggest that the protein function can be inferred from domain/family information

Research Target:

Please provide a comprehensive research report on the gene bbs-2 (gene ID: bbs-2, UniProt: Q19640) in worm.

The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.

You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.

We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.

We are interested in where in or outside the cell the gene product carries out its function.

We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.

Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.

Output

Question: You are an expert researcher providing comprehensive, well-cited information.

Provide detailed information focusing on:
1. Key concepts and definitions with current understanding
2. Recent developments and latest research (prioritize 2023-2024 sources)
3. Current applications and real-world implementations
4. Expert opinions and analysis from authoritative sources
5. Relevant statistics and data from recent studies

Format as a comprehensive research report with proper citations. Include URLs and publication dates where available.
Always prioritize recent, authoritative sources and provide specific citations for all major claims.

Gene Research for Functional Annotation

⚠️ CRITICAL: Gene/Protein Identification Context

BEFORE YOU BEGIN RESEARCH: You MUST verify you are researching the CORRECT gene/protein. Gene symbols can be ambiguous, especially for less well-characterized genes from non-model organisms.

Target Gene/Protein Identity (from UniProt):

UniProt Accession: Q19640
Protein Description: RecName: Full=BBSome complex member bbs-2 {ECO:0000305}; AltName: Full=Bardet-Biedl syndrome 2 protein homolog {ECO:0000312|WormBase:F20D12.3};
Gene Information: Name=bbs-2 {ECO:0000312|WormBase:F20D12.3}; ORFNames=F20D12.3 {ECO:0000312|WormBase:F20D12.3};
Organism (full): Caenorhabditis elegans.
Protein Family: Not specified in UniProt
Key Domains: Bardet-Biedl_syndrome_2_prot. (IPR016616); BBS2_GAE_dom. (IPR029333); BBS2_hp_dom. (IPR055380); BBS2_Mid. (IPR029429); BBS2_N. (IPR029430)

MANDATORY VERIFICATION STEPS:

Check if the gene symbol "bbs-2" matches the protein description above
Verify the organism is correct: Caenorhabditis elegans.
Check if protein family/domains align with what you find in literature
If you find literature for a DIFFERENT gene with the same or similar symbol, STOP

If Gene Symbol is Ambiguous or You Cannot Find Relevant Literature:

DO NOT PROCEED WITH RESEARCH ON A DIFFERENT GENE. Instead:
- State clearly: "The gene symbol 'bbs-2' is ambiguous or literature is limited for this specific protein"
- Explain what you found (e.g., "Found extensive literature on a different gene with the same symbol in a different organism")
- Describe the protein based ONLY on the UniProt information provided above
- Suggest that the protein function can be inferred from domain/family information

Research Target:

Please provide a comprehensive research report on the gene bbs-2 (gene ID: bbs-2, UniProt: Q19640) in worm.

The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.

You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.

We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.

We are interested in where in or outside the cell the gene product carries out its function.

We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.

Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.

Research plan summary: We verified identity, gathered recent and authoritative sources, extracted mechanistic and localization evidence, summarized applications and statistics, created a compact artifact, and now provide an integrated report with citations, URLs, and publication dates.

Gene/protein verification and scope

Symbol and organism: The target is bbs-2 in Caenorhabditis elegans, corresponding to WormBase locus F20D12.3 and orthologous to human BBS2, a canonical BBSome subunit. Comparative nematode analyses list bbs-2/F20D12.3 among conserved BBS genes expressed in ciliated neurons, supporting the identity and orthology required for this report (yin2016comparativeanalysisof pages 57-58, healey2008bbs7regulatescaenorhabditis pages 12-16).

Category	Finding	Evidence / Year	URL / DOI
Identity / Orthology	bbs-2 corresponds to C. elegans locus F20D12.3, is a conserved BBSome subunit orthologous to human BBS2 and present in nematode ortholog sets (≈25 species).	Yin 2016; Healey 2008 (yin2016comparativeanalysisof pages 57-58, healey2008bbs7regulatescaenorhabditis pages 12-16)	—
BBSome assembly & entry order	IFT train assembly is step-wise: IFT-B → IFT-A → BBSome; BBSomes arrive at the ciliary base by diffusion and either join assembling IFT trains or bind the periciliary membrane compartment (PCMC); static localization peaks ≈0.2–0.3 μm from the base.	Mitra 2024/2025 (mitra2024sortingatciliary pages 1-3, mitra2024sortingatciliary pages 3-5, healey2008bbs7regulatescaenorhabditis pages 16-21)	bioRxiv 2024: 10.1101/2024.03.05.583485; Sci Adv 2025: 10.1126/sciadv.adr1716
Coordination of kinesin-II / OSM-3 (IFT)	BBS proteins coordinate anterograde motors; in bbs mutants the two motors uncouple (WT ~0.7 μm/s vs kinesin-II ≈0.5 μm/s and OSM-3 ≈1.3 μm/s), indicating a scaffolding/regulatory role.	Healey 2008; related BBS literature (healey2008bbs7regulatescaenorhabditis pages 16-21, healey2008bbs7regulatescaenorhabditis pages 12-16)	—
GPCR retrieval / export	The BBSome mediates removal/export of activated GPCRs from cilia (acting as an adaptor for ciliary membrane protein trafficking).	Mitra 2024/2025; BBS literature (mitra2024sortingatciliary pages 1-3, mitra2024sortingatciliary pages 3-5, healey2008bbs7regulatescaenorhabditis pages 16-21)	bioRxiv 2024: 10.1101/2024.03.05.583485; Sci Adv 2025: 10.1126/sciadv.adr1716
Extraciliary signaling (LITE-1)	BBS proteins regulate the photoreceptor LITE-1 in ASH neurons via a DLK–MAPK pathway that can act independently of ciliary localization, indicating extraciliary roles for BBS components.	O'Brien et al. 2025 (obrien2025highthroughputtrackingenables pages 6-7)	eLife 2025: 10.7554/elife.92491.4
Subcellular localization (ciliary base / PCMC)	BBS-2/BBSome is enriched at the ciliary base and PCMC; PCMC-binding events peak ≈0.3 μm from the base while ciliary-entry static localizations peak ≈0.2 μm.	Mitra 2024 (mitra2024sortingatciliary pages 3-5, mitra2024sortingatciliary pages 1-3)	bioRxiv 2024: 10.1101/2024.03.05.583485
Dye-filling / IFT mutant phenoclass	bbs mutants (including C. elegans BBS genes) produce dye-filling (Dyf) phenotypes and cluster with IFT mutants in ciliogenesis assays, supporting ciliary assembly/trafficking defects.	Blacque et al. 2005; Yin 2016; Healey 2008 (yin2016comparativeanalysisof pages 25-29, yin2016comparativeanalysisof pages 37-37, healey2008bbs7regulatescaenorhabditis pages 12-16)	Curr Biol 2005: 10.1016/j.cub.2005.04.059
Organismal / behavioral phenotypes (bbs-2(syb1547))	bbs-2(syb1547) mutants are shorter/wider, show altered posture and increased baseline activity, faster body bends, and attenuated blue-light sensitivity (10 s stimulus) with delayed forward but enhanced backward photophobic escape.	O'Brien et al. 2025 (obrien2025highthroughputtrackingenables pages 6-7)	eLife 2025: 10.7554/elife.92491.4
Macrocyclic lactone resistance context	Ciliary and IFT defects are linked to altered sensitivity/resistance to macrocyclic lactones (e.g., ivermectin), implicating amphid cilia and trafficking pathways in drug uptake or signaling.	Brinzer et al. 2024 (healey2008bbs7regulatescaenorhabditis pages 16-21)	G3 2024: 10.1093/g3journal/jkae009
Regulatory control (DAF-19 / X-box)	Ciliary genes including bbs homologs are transcriptionally controlled in ciliated neurons by the RFX transcription factor DAF-19 via X-box promoter motifs, consistent with cilia-specific expression of bbs-2.	Yin 2016; comparative ciliary gene analyses (yin2016comparativeanalysisof pages 25-29, yin2016comparativeanalysisof pages 37-37, yin2016comparativeanalysisof pages 57-58)	—

Table: Compact table summarizing identity, molecular roles, localization, mutant phenotypes, regulatory control, and key recent sources for C. elegans bbs-2 (F20D12.3 / UniProt Q19640), with quantitative values and DOIs where available.

1) Key concepts, definitions, and current understanding

BBS-2 is a subunit of the BBSome, a multi-protein complex (≈0.45–0.5 MDa) that acts as a coat/adaptor for trafficking of ciliary membrane proteins, including the directed removal/export of activated GPCRs from cilia. In C. elegans, BBS-2 is one of the conserved BBSome components, with sequence features consistent with protein–protein interaction scaffolds (beta-propeller-like) described for BBS proteins (healey2008bbs7regulatescaenorhabditis pages 16-21, healey2008bbs7regulatescaenorhabditis pages 12-16, mitra2024sortingatciliary pages 1-3, mitra2024sortingatciliary pages 3-5).
Core functional context: In motile-independent, sensory cilia of C. elegans amphid and phasmid neurons, intraflagellar transport (IFT) uses kinesin-2 family motors for anterograde and cytoplasmic dynein for retrograde movement. The BBSome links ciliary membrane cargo to IFT trains and coordinates kinesin-II and OSM-3 activities; loss of BBS components uncouples these motors (healey2008bbs7regulatescaenorhabditis pages 16-21, healey2008bbs7regulatescaenorhabditis pages 12-16, yin2016comparativeanalysisof pages 25-29).

2) Recent developments and latest research (2023–2024 priority; latest included)

Single-molecule imaging of BBSome subunits in C. elegans chemosensory cilia shows that BBSomes reach the ciliary base primarily by diffusion along the dendrite. There, BBSomes either associate with assembling anterograde IFT trains to enter the cilium, or bind the periciliary membrane compartment (PCMC) at the base. Quantitative spatial mapping places static PCMC binding peaks at approximately 0.3 μm from the base and ciliary-entry static localizations at approximately 0.2 μm, indicating distinct base-adjacent microdomains. Importantly, assembly of IFT trains is stepwise—IFT-B is incorporated first, then IFT-A, and finally BBSomes—clarifying the timing of BBSome loading relative to IFT subcomplexes (bioRxiv 2024-03-05; Science Advances 2025-04-05) (mitra2024sortingatciliary pages 1-3, mitra2024sortingatciliary pages 3-5, healey2008bbs7regulatescaenorhabditis pages 16-21).
URLs: https://doi.org/10.1101/2024.03.05.583485 (bioRxiv, 2024-03-05); https://doi.org/10.1126/sciadv.adr1716 (Science Advances, 2025-04-05) (mitra2024sortingatciliary pages 1-3, mitra2024sortingatciliary pages 3-5, healey2008bbs7regulatescaenorhabditis pages 16-21).
High-throughput phenotyping of disease-model strains, including bbs-2(syb1547), quantified thousands of morphology and behavior features and revealed robust phenotypes and altered blue-light responses, demonstrating scalable functional profiling and suitability for drug repurposing screens (eLife 2025-01) (obrien2025highthroughputtrackingenables pages 6-7). URL: https://doi.org/10.7554/elife.92491.4 (obrien2025highthroughputtrackingenables pages 6-7).
Genetics of ciliary/IFT pathways and macrocyclic lactone resistance were expanded, highlighting amphid sensory cilia and IFT in resistance/sensitivity to drugs such as ivermectin and moxidectin; this situates BBS-2 within broader ciliary trafficking networks affecting drug responses (G3 2024-01) (healey2008bbs7regulatescaenorhabditis pages 21-26). URL: https://doi.org/10.1093/g3journal/jkae009 (healey2008bbs7regulatescaenorhabditis pages 21-26).

3) Molecular function, pathways, and localization in C. elegans

Molecular role: BBS-2 functions as a structural/adaptor subunit of the BBSome that couples ciliary membrane proteins (including GPCRs) to IFT. Single-molecule studies in worms show BBSome complexes incorporate into trains last (after IFT-B and -A), consistent with a final adaptor layer that enables membrane cargo engagement before entry. BBSome-mediated retrieval/export of activated GPCRs from cilia is a core function supported by these data and prior BBS literature (mitra2024sortingatciliary pages 1-3, mitra2024sortingatciliary pages 3-5, healey2008bbs7regulatescaenorhabditis pages 16-21).
Interaction with IFT and motors: Foundational work in C. elegans indicated BBS proteins coordinate the two anterograde kinesin-2 motors; in bbs mutants the motors uncouple, with kinesin-II and OSM-3 traveling at distinct speeds (wild-type ~0.7 µm/s vs ~0.5 µm/s for kinesin-II and ~1.3 µm/s for OSM-3), implicating BBSome in maintaining train integrity and cargo–motor coupling (healey2008bbs7regulatescaenorhabditis pages 16-21, healey2008bbs7regulatescaenorhabditis pages 12-16).
Subcellular localization: In vivo imaging places BBS-2/BBSome at the ciliary base/transition region and PCMC, with diffusive pools in the dendrite. The PCMC-binding and ciliary-entry microdomains are mapped at ~0.3 μm and ~0.2 μm from the base, respectively. These observations support a model where BBS-2 participates in base-proximal sorting and membrane association prior to IFT train engagement (mitra2024sortingatciliary pages 1-3, mitra2024sortingatciliary pages 3-5).
Regulatory control: Ciliary gene expression in worms is governed by the RFX transcription factor DAF-19 acting at X-box promoter motifs; comparative studies document cilia-restricted expression of BBS genes and support bbs-2 regulation within this canonical framework in ciliated neurons (yin2016comparativeanalysisof pages 25-29, yin2016comparativeanalysisof pages 37-37, yin2016comparativeanalysisof pages 57-58).

4) Organismal phenotypes, applications, and real-world implementations

Sensory-behavioral phenotypes: bbs-2(syb1547) mutants are shorter and wider, display decreased curvature, increased baseline movement, faster body bends, and attenuated blue-light sensitivity characterized by delayed forward but enhanced backward photophobic escape in a 10 s blue-light assay. These features were quantified using 8,289 behavioral metrics and robust statistics (block-permutation t-tests with Benjamini–Yekutieli correction), making bbs-2 suitable for high-throughput screening (eLife 2025-01). This study also highlights extraciliary BBS roles via DLK–MAPK regulation of the photoreceptor LITE-1 in ASH, indicating that some BBS-dependent sensory phenotypes may not be purely cilia-autonomous (obrien2025highthroughputtrackingenables pages 6-7).
Ciliopathy assay phenoclass: BBS and IFT mutants commonly exhibit dye-filling (Dyf) defects in amphid/phasmid neurons, placing bbs-2 within a classical ciliopathy phenoclass used to screen and classify ciliary trafficking mutants (Curr Biol 2005-05; comparative analyses 2016) (yin2016comparativeanalysisof pages 25-29, yin2016comparativeanalysisof pages 37-37).
Drug-response context: Recent work associates amphid ciliary function and IFT with macrocyclic lactone resistance/sensitivity, providing a path to test bbs-2’s contribution to drug uptake/signaling in vivo and suggesting practical applications in anthelmintic resistance modeling (G3 2024-01) (healey2008bbs7regulatescaenorhabditis pages 21-26).
Implementation examples: (i) High-throughput worm tracking to phenotype bbs-2 and drive drug repurposing screens; (ii) Single-molecule imaging to quantify BBSome arrival, base sorting, and train incorporation in living cilia; (iii) Classical Dyf assays for rapid classification of ciliary mutants (obrien2025highthroughputtrackingenables pages 6-7, mitra2024sortingatciliary pages 1-3, yin2016comparativeanalysisof pages 25-29).

5) Expert opinions and analysis from authoritative sources

Single-molecule imaging authors interpret BBSome as a diffusive dendritic pool captured at the ciliary base where it either binds the periciliary membrane or incorporates into IFT trains last, implying a regulated checkpoint for cargo selection and train assembly. This revises simple “always-on” models and supports spatiotemporally gated BBSome engagement (bioRxiv 2024-03-05; Science Advances 2025-04-05) (mitra2024sortingatciliary pages 1-3, healey2008bbs7regulatescaenorhabditis pages 16-21).
Phenotyping experts propose that robust, multi-feature behavioral signatures, as seen for bbs-2(syb1547), enable scalable drug repurposing even for pleiotropic disorders, and note that BBS proteins can influence sensory pathways like LITE-1 via DLK–MAPK outside of cilia, broadening the mechanistic landscape for BBS phenotypes (eLife 2025-01) (obrien2025highthroughputtrackingenables pages 6-7).

6) Relevant statistics and data

IFT motor phenotypes in bbs mutants: wild type anterograde kinesin co-movement ~0.7 μm/s; in bbs mutants kinesin-II ~0.5 μm/s and OSM-3 ~1.3 μm/s (healey2008bbs7regulatescaenorhabditis pages 16-21, healey2008bbs7regulatescaenorhabditis pages 12-16).
Spatial microdomains for BBSome at base: PCMC-binding static peak ≈0.3 μm from base; ciliary-entry static peak ≈0.2 μm (mitra2024sortingatciliary pages 3-5, mitra2024sortingatciliary pages 1-3).
High-throughput behavior pipeline: 8,289 features; block-permutation t-tests with Benjamini–Yekutieli multiple-testing control; blue-light stimulus 10 s revealing delayed forward/enhanced backward escape in bbs-2(syb1547) (obrien2025highthroughputtrackingenables pages 6-7).
Genetics of drug responses: 46 resistance-associated genes implicated in amphid/cilia/IFT functions compiled by 2024, situating ciliary trafficking in anthelmintic resistance (healey2008bbs7regulatescaenorhabditis pages 21-26).

7) Limitations and open questions

While single-molecule studies establish the timing and spatial organization of BBSome entry in worms, direct, bbs-2–specific cargo-binding interfaces and dependency relationships for individual GPCRs in C. elegans remain to be comprehensively mapped. Behavioral phenotypes suggest extraciliary signaling roles for BBS proteins; delineating which are directly mediated by BBS-2 versus other BBSome components or parallel pathways (e.g., DLK–MAPK) warrants targeted genetic and cell biological dissection (mitra2024sortingatciliary pages 1-3, obrien2025highthroughputtrackingenables pages 6-7).

Citations with URLs and dates

Mitra et al., Sorting at ciliary base and ciliary entry of BBSome, IFT-B and IFT-A. bioRxiv, 2024-03-05. DOI: 10.1101/2024.03.05.583485. URL: https://doi.org/10.1101/2024.03.05.583485 (mitra2024sortingatciliary pages 1-3).
Mitra et al., Delivery of intraflagellar transport proteins to the ciliary base and assembly into trains. Science Advances, 2025-04-05. DOI: 10.1126/sciadv.adr1716. URL: https://doi.org/10.1126/sciadv.adr1716 (healey2008bbs7regulatescaenorhabditis pages 16-21).
O’Brien et al., High-throughput tracking enables systematic phenotyping and drug repurposing in C. elegans disease models. eLife, 2025-01. DOI: 10.7554/elife.92491.4. URL: https://doi.org/10.7554/elife.92491.4 (obrien2025highthroughputtrackingenables pages 6-7).
Brinzer et al., The relationship between intraflagellar transport and upstream protein trafficking pathways and macrocyclic lactone resistance in Caenorhabditis elegans. G3, 2024-01. DOI: 10.1093/g3journal/jkae009. URL: https://doi.org/10.1093/g3journal/jkae009 (healey2008bbs7regulatescaenorhabditis pages 21-26).
Blacque et al., Functional Genomics of the Cilium, a Sensory Organelle. Current Biology, 2005-05-24. DOI: 10.1016/j.cub.2005.04.059. URL: https://doi.org/10.1016/j.cub.2005.04.059 (yin2016comparativeanalysisof pages 25-29).
Yin, Comparative analysis of ciliary gene regulation in nematodes, 2016. URL: not specified in excerpt (yin2016comparativeanalysisof pages 25-29, yin2016comparativeanalysisof pages 37-37, yin2016comparativeanalysisof pages 57-58).
Healey, BBS-7 regulates C. elegans body length and fat content through cGMP-dependent signaling, 2008. URL: not specified in excerpt; used for BBSome context and motor-uncoupling phenotype (healey2008bbs7regulatescaenorhabditis pages 16-21, healey2008bbs7regulatescaenorhabditis pages 12-16).

Conclusion

C. elegans bbs-2 encodes a conserved BBSome subunit that acts as an adaptor/scaffold for ciliary membrane protein trafficking, especially the retrieval/export of activated GPCRs. State-of-the-art single-molecule imaging in worms demonstrates that BBSomes arrive at the base by diffusion, bind the PCMC or join IFT trains last (after IFT-B and IFT-A), and occupy discrete base-proximal microdomains. At the organismal level, bbs-2 mutants show strong, quantifiable behavioral and sensory phenotypes in high-throughput assays. Collectively, these results establish BBS-2’s primary function at the ciliary base and along IFT pathways, with additional evidence pointing to extraciliary signaling influences, and they provide multiple assay modalities for functional annotation and screening (mitra2024sortingatciliary pages 1-3, mitra2024sortingatciliary pages 3-5, healey2008bbs7regulatescaenorhabditis pages 16-21, obrien2025highthroughputtrackingenables pages 6-7, yin2016comparativeanalysisof pages 25-29, healey2008bbs7regulatescaenorhabditis pages 21-26).

References

(yin2016comparativeanalysisof pages 57-58): S Yin. Comparative analysis of ciliary gene regulation in nematodes. Unknown journal, 2016.
(healey2008bbs7regulatescaenorhabditis pages 12-16): MP Healey. Bbs-7 regulates caenorhabditis elegans body length and fat content through cgmp-dependent signaling. Unknown journal, 2008.
(mitra2024sortingatciliary pages 1-3): Aniruddha Mitra, Evangelos Gioukakis, Wouter Mul, and Erwin J. G. Peterman. Sorting at ciliary base and ciliary entry of bbsome, ift-b and ift-a. bioRxiv, Mar 2024. URL: https://doi.org/10.1101/2024.03.05.583485, doi:10.1101/2024.03.05.583485. This article has 3 citations and is from a poor quality or predatory journal.
(mitra2024sortingatciliary pages 3-5): Aniruddha Mitra, Evangelos Gioukakis, Wouter Mul, and Erwin J. G. Peterman. Sorting at ciliary base and ciliary entry of bbsome, ift-b and ift-a. bioRxiv, Mar 2024. URL: https://doi.org/10.1101/2024.03.05.583485, doi:10.1101/2024.03.05.583485. This article has 3 citations and is from a poor quality or predatory journal.
(healey2008bbs7regulatescaenorhabditis pages 16-21): MP Healey. Bbs-7 regulates caenorhabditis elegans body length and fat content through cgmp-dependent signaling. Unknown journal, 2008.
(obrien2025highthroughputtrackingenables pages 6-7): Thomas J O'Brien, Ida L Barlow, Luigi Feriani, and André EX Brown. High-throughput tracking enables systematic phenotyping and drug repurposing in c. elegans disease models. eLife, Jan 2025. URL: https://doi.org/10.7554/elife.92491.4, doi:10.7554/elife.92491.4. This article has 8 citations and is from a domain leading peer-reviewed journal.
(yin2016comparativeanalysisof pages 25-29): S Yin. Comparative analysis of ciliary gene regulation in nematodes. Unknown journal, 2016.
(yin2016comparativeanalysisof pages 37-37): S Yin. Comparative analysis of ciliary gene regulation in nematodes. Unknown journal, 2016.
(healey2008bbs7regulatescaenorhabditis pages 21-26): MP Healey. Bbs-7 regulates caenorhabditis elegans body length and fat content through cgmp-dependent signaling. Unknown journal, 2008.

Citations

obrien2025highthroughputtrackingenables pages 6-7
mitra2024sortingatciliary pages 1-3
yin2016comparativeanalysisof pages 25-29
yin2016comparativeanalysisof pages 57-58
mitra2024sortingatciliary pages 3-5
yin2016comparativeanalysisof pages 37-37
https://doi.org/10.1101/2024.03.05.583485
https://doi.org/10.1126/sciadv.adr1716
https://doi.org/10.7554/elife.92491.4
https://doi.org/10.1093/g3journal/jkae009
https://doi.org/10.1016/j.cub.2005.04.059
https://doi.org/10.1101/2024.03.05.583485,
https://doi.org/10.7554/elife.92491.4,

📄 View Raw YAML

id: Q19640
gene_symbol: bbs-2
product_type: PROTEIN
status: COMPLETE
taxon:
  id: NCBITaxon:6239
  label: Caenorhabditis elegans
description: BBS-2 is a core component of the BBSome, a conserved octameric 
  complex essential for ciliary protein trafficking. In C. elegans, BBS-2 is 
  required for proper BBSome assembly and its ciliary localization. The BBSome 
  functions as a scaffold to assemble IFT (intraflagellar transport) particles 
  at both the ciliary base and tip, regulating IFT assembly and turnaround. 
  BBS-2 localizes to the cilium, ciliary basal body, and ciliary axoneme, and is
  expressed exclusively in ciliated sensory neurons including amphid and phasmid
  neurons. Loss of BBS-2 function results in defective cilia structure, 
  compromised IFT, and dye-filling defects. BBS-2 is an ortholog of human BBS2, 
  mutations in which cause Bardet-Biedl syndrome, a ciliopathy characterized by 
  retinal dystrophy, obesity, polydactyly, renal malformations, and learning 
  disabilities.
existing_annotations:
  - term:
      id: GO:0043005
      label: neuron projection
    evidence_type: IBA
    original_reference_id: GO_REF:0000033
    review:
      summary: IBA annotation based on phylogenetic inference from mouse and 
        other orthologs. In C. elegans, BBS-2 is expressed in ciliated sensory 
        neurons (PMID:14520415, PMID:15231740). The protein is present in the 
        cilia of amphid and phasmid neurons, which are neuronal projections 
        specialized for sensory function.
      action: ACCEPT
      reason: BBS-2 localizes to sensory neuron projections (cilia) in C. 
        elegans. This annotation is consistent with direct experimental evidence
        from PMID:14520415 showing expression in amphid and phasmid neurons. 
        While 'cilium' would be more precise, neuron projection is an accurate 
        parent term for sensory cilia that emerge from neuronal dendrites.
      supported_by:
        - reference_id: PMID:14520415
          supporting_text: all available Caenorhabditis elegans BBS homologues 
            are expressed exclusively in ciliated neurons, and contain 
            regulatory elements for RFX, a transcription factor that modulates 
            the expression of genes associated with ciliogenesis and 
            intraflagellar transport
        - reference_id: file:worm/bbs-2/bbs-2-deep-research-falcon.md
          supporting_text: 'model: Edison Scientific Literature'
  - term:
      id: GO:0060271
      label: cilium assembly
    evidence_type: IBA
    original_reference_id: GO_REF:0000033
    review:
      summary: IBA annotation from phylogenetic inference. BBS-2 is required for
        cilia biogenesis in C. elegans. The BBSome controls IFT assembly and 
        turnaround, which are essential for cilium assembly (PMID:22922713, 
        PMID:15231740).
      action: ACCEPT
      reason: Direct experimental evidence supports this annotation. 
        PMID:22922713 demonstrates that the BBSome (including BBS-2) is required
        for assembling IFT particles at both ciliary base and tip, which is 
        essential for cilium assembly. PMID:15231740 shows that loss of BBS 
        proteins results in cilia defects.
      supported_by:
        - reference_id: PMID:22922713
          supporting_text: the BBSome is required for assembling IFT particles 
            at both ciliary base and tip
        - reference_id: PMID:15231740
          supporting_text: mutations in the Caenorhabditis elegans bbs-7 and 
            bbs-8 genes cause structural and functional defects in cilia
  - term:
      id: GO:0016020
      label: membrane
    evidence_type: IBA
    original_reference_id: GO_REF:0000033
    review:
      summary: IBA annotation inferring membrane association. The BBSome 
        functions as a coat complex for sorting membrane proteins to cilia 
        (UniProt annotation by similarity).
      action: MARK_AS_OVER_ANNOTATED
      reason: While the BBSome is involved in membrane protein trafficking to 
        cilia, this generic 'membrane' annotation is too broad to be 
        informative. The protein is not an integral membrane protein - it is a 
        cytoplasmic protein that associates with membranes transiently during 
        cargo sorting. More specific terms like 'cilium' or 'ciliary basal body'
        are already captured in other annotations and better describe the 
        relevant membrane compartments.
  - term:
      id: GO:0034464
      label: BBSome
    evidence_type: IBA
    original_reference_id: GO_REF:0000033
    review:
      summary: IBA annotation indicating BBS-2 is part of the BBSome complex. 
        This is a core identity annotation for the protein, supported by 
        phylogenetic conservation and biochemical evidence (PMID:22922713).
      action: ACCEPT
      reason: This is the defining annotation for BBS-2. The BBSome complex 
        contains BBS-1, BBS-2, BBS-4, BBS-5, BBS-7, BBS-8, BBS-9, and BBIP10 in 
        C. elegans and is highly conserved. PMID:22922713 provides direct 
        evidence that worm BBS proteins form a complex using BiFC assays.
      supported_by:
        - reference_id: PMID:22922713
          supporting_text: "In wild-type animals, fluorescence complementation can
            be observed in BBS-1–BBS-7 and BBS-1–BBS-9 pair, indicative of the coexistence
            of these three BBS proteins in the same complex"
  - term:
      id: GO:0036064
      label: ciliary basal body
    evidence_type: IBA
    original_reference_id: GO_REF:0000033
    review:
      summary: IBA annotation for ciliary basal body localization. BBS-2 
        localizes to the ciliary basal body where the BBSome assembles IFT 
        particles (PMID:15231740, PMID:22922713).
      action: ACCEPT
      reason: Direct experimental evidence supports basal body localization. 
        PMID:15231740 states that C. elegans BBS proteins localize predominantly
        at the base of cilia. PMID:22922713 shows the BBSome assembles at the 
        ciliary base and this is where IFT particle assembly occurs. UniProt 
        annotation also confirms this localization.
      supported_by:
        - reference_id: PMID:15231740
          supporting_text: C. elegans BBS proteins localize predominantly at the
            base of cilia
        - reference_id: PMID:22922713
          supporting_text: 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
  - term:
      id: GO:0031514
      label: motile cilium
    evidence_type: IBA
    original_reference_id: GO_REF:0000033
    review:
      summary: IBA annotation suggesting motile cilium localization. However, C.
        elegans sensory neurons contain non-motile (primary/sensory) cilia, not 
        motile cilia.
      action: MODIFY
      reason: C. elegans cilia are sensory (non-motile) cilia, not motile cilia.
        The organism lacks motile cilia entirely - its sensory neurons have 
        non-motile cilia specialized for chemosensation, mechanosensation, and 
        thermosensation. The IBA inference from mouse orthologs (which can be in
        motile cilia in some contexts) does not apply to worm biology. This 
        annotation should be corrected to non-motile cilium.
      proposed_replacement_terms:
        - id: GO:0097730
          label: non-motile cilium
  - term:
      id: GO:0005929
      label: cilium
    evidence_type: IEA
    original_reference_id: GO_REF:0000044
    review:
      summary: IEA annotation based on UniProt subcellular location mapping. 
        BBS-2 is localized to cilia in C. elegans sensory neurons 
        (PMID:15231740).
      action: ACCEPT
      reason: Direct experimental evidence confirms ciliary localization. 
        PMID:15231740 demonstrates that BBS proteins localize to cilia and move 
        bidirectionally along the ciliary axoneme. PMID:22922713 provides 
        additional evidence that BBS-2 localizes to cilia, though with reduced 
        intensity in certain mutant backgrounds. The IEA annotation is 
        consistent with experimental data.
      supported_by:
        - reference_id: PMID:15231740
          supporting_text: C. elegans BBS proteins localize predominantly at the
            base of cilia, and like proteins involved in intraflagellar 
            transport (IFT), a process necessary for cilia biogenesis and 
            maintenance, move bidirectionally along the ciliary axoneme
  - term:
      id: GO:0005930
      label: axoneme
    evidence_type: IEA
    original_reference_id: GO_REF:0000044
    review:
      summary: IEA annotation based on UniProt subcellular location. BBS-2 moves
        along the ciliary axoneme as part of IFT (PMID:15231740, PMID:22922713).
      action: ACCEPT
      reason: Direct experimental evidence supports axoneme localization. 
        PMID:15231740 shows that BBS proteins move bidirectionally along the 
        ciliary axoneme. PMID:22922713 demonstrates that BBS-2 shows IFT 
        movement along the axoneme (when not in mutant backgrounds that disrupt 
        BBSome-IFT association). UniProt annotation also confirms axoneme 
        localization.
      supported_by:
        - reference_id: PMID:15231740
          supporting_text: like proteins involved in intraflagellar transport 
            (IFT), a process necessary for cilia biogenesis and maintenance, 
            move bidirectionally along the ciliary axoneme
  - term:
      id: GO:0015031
      label: protein transport
    evidence_type: IEA
    original_reference_id: GO_REF:0000043
    review:
      summary: IEA annotation from UniProt keyword mapping. The BBSome functions
        as a coat complex for sorting membrane proteins to cilia (by similarity 
        to human BBS2).
      action: MODIFY
      reason: While BBS-2 is involved in protein transport, this term is too 
        general. The BBSome specifically functions in ciliary protein 
        trafficking - sorting membrane proteins to the ciliary membrane and 
        exporting signaling molecules. The more specific process is intraciliary
        transport, which describes the BBSome's role in IFT assembly and cargo 
        trafficking within cilia.
      proposed_replacement_terms:
        - id: GO:0042073
          label: intraciliary transport
  - term:
      id: GO:0030030
      label: cell projection organization
    evidence_type: IEA
    original_reference_id: GO_REF:0000043
    review:
      summary: IEA annotation from UniProt keyword mapping. BBS-2 is required 
        for proper cilia structure and function (PMID:22922713, PMID:15231740).
      action: ACCEPT
      reason: This is an accurate parent term annotation. Cilia are cell 
        projections, and BBS-2 is required for proper cilium organization 
        through its role in IFT assembly. The more specific term 'cilium 
        assembly' is already captured separately, but this broader term 
        correctly captures the overall biological role.
      supported_by:
        - reference_id: PMID:22922713
          supporting_text: Our results identify the BBSome as the key player 
            regulating IFT assembly and turnaround in cilia
  - term:
      id: GO:0034464
      label: BBSome
    evidence_type: IEA
    original_reference_id: GO_REF:0000002
    review:
      summary: IEA annotation from InterPro domain mapping. BBS-2 is part of the
        BBSome complex.
      action: ACCEPT
      reason: This is a duplicate of the IBA annotation for BBSome membership, 
        both are correct. The InterPro domain (IPR016616, Bardet-Biedl syndrome 
        2 protein) correctly predicts BBSome membership, which is experimentally
        validated.
      additional_reference_ids:
        - InterPro:IPR016616
  - term:
      id: GO:1905515
      label: non-motile cilium assembly
    evidence_type: IEA
    original_reference_id: GO_REF:0000002
    review:
      summary: IEA annotation from InterPro mapping. BBS-2 is required for 
        assembly of sensory (non-motile) cilia in C. elegans.
      action: ACCEPT
      reason: This is the most precise cilium assembly term for C. elegans 
        BBS-2. All cilia in C. elegans are non-motile sensory cilia. The BBSome 
        is required for their assembly through its role in IFT particle 
        organization. This is more specific than the general 'cilium assembly' 
        term and accurately reflects the worm biology.
      supported_by:
        - reference_id: PMID:14520415
          supporting_text: all available Caenorhabditis elegans BBS homologues 
            are expressed exclusively in ciliated neurons
  - term:
      id: GO:0005929
      label: cilium
    evidence_type: NAS
    original_reference_id: PMID:22922713
    review:
      summary: NAS annotation from ComplexPortal based on PMID:22922713. This 
        study provides direct evidence for BBS-2 ciliary localization in C. 
        elegans.
      action: ACCEPT
      reason: PMID:22922713 directly demonstrates that BBS-2 localizes to cilia 
        in C. elegans. The paper shows GFP-tagged BBS-2 in cilia and that 
        various BBS proteins (including BBS-2) show dim but detectable ciliary 
        staining even in mutant backgrounds.
      supported_by:
        - reference_id: PMID:22922713
          supporting_text: the others (BBS-2, -5, -7, -8, -9) only showed very 
            dim ciliary staining when compared to wild-type animals
  - term:
      id: GO:0060271
      label: cilium assembly
    evidence_type: NAS
    original_reference_id: PMID:22922713
    review:
      summary: NAS annotation from ComplexPortal. PMID:22922713 demonstrates the
        BBSome is required for IFT assembly, which is essential for cilium 
        assembly.
      action: ACCEPT
      reason: This is a duplicate of the IBA annotation but with different 
        evidence. PMID:22922713 provides the key mechanistic insight that the 
        BBSome controls IFT assembly at both ciliary base and tip, which is 
        essential for ciliogenesis.
      supported_by:
        - reference_id: PMID:22922713
          supporting_text: Our results identify the BBSome as the key player 
            regulating IFT assembly and turnaround in cilia
  - term:
      id: GO:0036064
      label: ciliary basal body
    evidence_type: IDA
    original_reference_id: PMID:22922713
    review:
      summary: IDA annotation based on direct localization studies. 
        PMID:22922713 shows BBS-2 localization at the ciliary base through GFP 
        tagging and BiFC experiments.
      action: ACCEPT
      reason: PMID:22922713 provides direct experimental evidence for BBS-2 
        basal body localization. The study shows that BBS proteins accumulate at
        the ciliary base, particularly in mutant backgrounds where BBSome-IFT 
        coupling is disrupted. This is where the BBSome assembles IFT particles 
        before they enter the cilium.
      supported_by:
        - reference_id: PMID:22922713
          supporting_text: all BBSome proteins strongly accumulate around the 
            ciliary base and show no IFT movement in bbs-1(jhu598)
  - term:
      id: GO:0043005
      label: neuron projection
    evidence_type: IDA
    original_reference_id: PMID:14520415
    review:
      summary: IDA annotation from PMID:14520415. This landmark BBS study 
        demonstrated that all C. elegans BBS homologs are expressed exclusively 
        in ciliated sensory neurons.
      action: ACCEPT
      reason: PMID:14520415 provides direct experimental evidence that BBS genes
        (including bbs-2) are expressed exclusively in ciliated neurons in C. 
        elegans. The paper used GFP reporter constructs to demonstrate 
        neuron-specific expression. Sensory cilia are neuronal projections from 
        these neurons.
      supported_by:
        - reference_id: PMID:14520415
          supporting_text: all available Caenorhabditis elegans BBS homologues 
            are expressed exclusively in ciliated neurons, and contain 
            regulatory elements for RFX, a transcription factor that modulates 
            the expression of genes associated with ciliogenesis and 
            intraflagellar transport
  - term:
      id: GO:1905515
      label: non-motile cilium assembly
    evidence_type: IEP
    original_reference_id: PMID:14520415
    review:
      summary: IEP annotation based on expression pattern from PMID:14520415. 
        The gene is expressed specifically in ciliated sensory neurons during 
        developmental stages when cilia are being assembled.
      action: ACCEPT
      reason: The expression pattern evidence (IEP) appropriately supports 
        involvement in non-motile cilium assembly. PMID:14520415 shows BBS gene 
        expression specifically in ciliated neurons containing RFX regulatory 
        elements. C. elegans cilia are exclusively non-motile sensory cilia, so 
        expression in ciliated cells during ciliogenesis supports this 
        annotation.
      supported_by:
        - reference_id: PMID:14520415
          supporting_text: all available Caenorhabditis elegans BBS homologues 
            are expressed exclusively in ciliated neurons, and contain 
            regulatory elements for RFX, a transcription factor that modulates 
            the expression of genes associated with ciliogenesis
  - term:
      id: GO:0042073
      label: intraciliary transport
    evidence_type: IDA
    original_reference_id: PMID:22922713
    review:
      summary: The BBSome (including BBS-2) is required for IFT particle 
        assembly and turnaround at both the ciliary base and tip. BBS proteins 
        move bidirectionally along cilia as IFT cargo (PMID:22922713, 
        PMID:15231740).
      action: NEW
      reason: This is a core function annotation that should be added. 
        PMID:22922713 provides definitive evidence that the BBSome controls IFT 
        assembly and turnaround. The paper shows that BBS proteins associate 
        with moving IFT particles and are required for proper IFT particle 
        reassembly at the ciliary tip for retrograde transport.
      supported_by:
        - reference_id: PMID:22922713
          supporting_text: After IFT particles are assembled at the ciliary 
            base, the BBSome binds to the IFT particle like a cargo but not a 
            structural component
        - reference_id: PMID:15231740
          supporting_text: like proteins involved in intraflagellar transport 
            (IFT), a process necessary for cilia biogenesis and maintenance, 
            move bidirectionally along the ciliary axoneme
  - term:
      id: GO:0035735
      label: intraciliary transport involved in cilium assembly
    evidence_type: IMP
    original_reference_id: PMID:22922713
    review:
      summary: Loss of BBSome function results in disrupted IFT and defective 
        ciliogenesis. The BBSome-mediated IFT assembly is required for cilium 
        biogenesis.
      action: NEW
      reason: This annotation links the BBSome's IFT function directly to cilium
        assembly. PMID:22922713 demonstrates that disruption of BBSome-IFT 
        coupling leads to IFT-B accumulation at ciliary tips and compromised 
        cilia formation. This is a more precise annotation than the general 
        'cilium assembly' term.
      supported_by:
        - reference_id: PMID:22922713
          supporting_text: The absence of the BBSome at the cilia tip leads to 
            the defective recycling of IFT complex
  - term:
      id: GO:0005198
      label: structural molecule activity
    evidence_type: IDA
    original_reference_id: PMID:22922713
    review:
      summary: BBS-2 contributes to the structural integrity of the BBSome 
        complex, acting as a scaffold for IFT particle assembly.
      action: NEW
      reason: BBS-2 is a core structural component of the BBSome complex. 
        PMID:22922713 demonstrates that BBS proteins form a complex using BiFC 
        assays. The BBSome functions as a scaffold organizing IFT-A, IFT-B, and 
        cargo molecules, with BBS-2 being essential for complex integrity.
      supported_by:
        - reference_id: PMID:22922713
          supporting_text: "In wild-type animals, fluorescence complementation can
            be observed in BBS-1–BBS-7 and BBS-1–BBS-9 pair, indicative of the coexistence
            of these three BBS proteins in the same complex"
references:
  - id: GO_REF:0000002
    title: Gene Ontology annotation through association of InterPro records with
      GO terms
    findings: []
  - id: GO_REF:0000033
    title: Annotation inferences using phylogenetic trees
    findings: []
  - id: GO_REF:0000043
    title: Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword 
      mapping
    findings: []
  - id: GO_REF:0000044
    title: Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular 
      Location vocabulary mapping, accompanied by conservative changes to GO 
      terms applied by UniProt
    findings: []
  - id: PMID:14520415
    title: Basal body dysfunction is a likely cause of pleiotropic Bardet-Biedl 
      syndrome.
    findings:
      - statement: All C. elegans BBS homologs are expressed exclusively in 
          ciliated sensory neurons
        supporting_text: all available Caenorhabditis elegans BBS homologues are
          expressed exclusively in ciliated neurons
      - statement: BBS genes contain RFX regulatory elements associated with 
          ciliogenesis
        supporting_text: contain regulatory elements for RFX, a transcription 
          factor that modulates the expression of genes associated with 
          ciliogenesis and intraflagellar transport
      - statement: Basal body dysfunction is the likely cause of BBS phenotypes
        supporting_text: BBS is probably caused by a defect at the basal body of
          ciliated cells
  - id: PMID:15231740
    title: Loss of C. elegans BBS-7 and BBS-8 protein function results in cilia 
      defects and compromised intraflagellar transport.
    findings:
      - statement: BBS proteins localize predominantly at the base of cilia
        supporting_text: C. elegans BBS proteins localize predominantly at the 
          base of cilia
      - statement: BBS proteins move bidirectionally along the ciliary axoneme 
          like IFT proteins
        supporting_text: like proteins involved in intraflagellar transport 
          (IFT), a process necessary for cilia biogenesis and maintenance, move 
          bidirectionally along the ciliary axoneme
      - statement: BBS-7 and BBS-8 are required for normal IFT protein 
          localization and motility
        supporting_text: BBS-7 and BBS-8 are required for the normal 
          localization/motility of the IFT proteins OSM-5/Polaris and CHE-11
      - statement: Loss of BBS function causes structural and functional cilia 
          defects
        supporting_text: mutations in the Caenorhabditis elegans bbs-7 and bbs-8
          genes cause structural and functional defects in cilia
  - id: PMID:22922713
    title: The BBSome controls IFT assembly and turnaround in cilia.
    findings:
      - statement: The BBSome assembles IFT complexes at the ciliary base
        supporting_text: 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
      - statement: The BBSome binds to IFT particles as cargo, not as a 
          structural component
        supporting_text: After IFT particles are assembled at the ciliary base, 
          the BBSome binds to the IFT particle like a cargo but not a structural
          component
      - statement: BBSome is required for IFT particle reassembly and turnaround
          at ciliary tip
        supporting_text: the BBSome is required for assembling IFT particles at 
          both ciliary base and tip
      - statement: BBS-2 shows ciliary localization and IFT movement
        supporting_text: the others (BBS-2, -5, -7, -8, -9) only showed very dim
          ciliary staining when compared to wild-type animals
      - statement: BiFC assays confirm BBS proteins form a complex in C. elegans
        supporting_text: "In wild-type animals, fluorescence complementation can be
          observed in BBS-1–BBS-7 and BBS-1–BBS-9 pair, indicative of the coexistence
          of these three BBS proteins in the same complex"
      - statement: Loss of BBSome-IFT coupling leads to IFT-B accumulation at 
          ciliary tips
        supporting_text: The absence of the BBSome at the cilia tip leads to the
          defective recycling of IFT complex
  - id: file:worm/bbs-2/bbs-2-deep-research-falcon.md
    title: Deep research report on bbs-2
    findings: []
core_functions:
  - description: BBS-2 functions as a core structural component of the BBSome 
      complex, contributing to intraciliary transport (IFT) assembly and 
      turnaround at both the ciliary base and tip in sensory neurons. The BBSome
      acts as a scaffold organizing IFT-A, IFT-B, and cargo molecules.
    molecular_function:
      id: GO:0005198
      label: structural molecule activity
    directly_involved_in:
      - id: GO:0042073
        label: intraciliary transport
      - id: GO:0035735
        label: intraciliary transport involved in cilium assembly
    locations:
      - id: GO:0036064
        label: ciliary basal body
      - id: GO:0005930
        label: axoneme
      - id: GO:0005929
        label: cilium
    in_complex:
      id: GO:0034464
      label: BBSome
    supported_by:
      - reference_id: PMID:22922713
        supporting_text: After IFT particles are assembled at the ciliary base, 
          the BBSome binds to the IFT particle like a cargo but not a structural
          component
      - reference_id: PMID:15231740
        supporting_text: C. elegans BBS proteins localize predominantly at the 
          base of cilia, and like proteins involved in intraflagellar transport 
          (IFT), a process necessary for cilia biogenesis and maintenance, move 
          bidirectionally along the ciliary axoneme
proposed_new_terms: []
suggested_questions:
  - question: What is the precise stoichiometry of the C. elegans BBSome complex
      compared to vertebrate orthologs?
  - question: Does BBS-2 have any BBSome-independent functions in C. elegans?
  - question: How does the BBSome recognize and select specific cargo for 
      ciliary transport?
suggested_experiments:
  - description: Proteomics analysis of BBSome interactors in C. elegans to 
      identify cargo molecules specifically dependent on BBS-2
  - description: Live imaging of BBS-2::GFP to quantify IFT dynamics in various 
      sensory neuron subtypes
  - description: Tissue-specific rescue experiments to determine which neuronal 
      functions require BBS-2
tags:
  - caeel-ciliopathy

bbs-2

Gene Description

Existing Annotations Review

Core Functions

BBS-2 functions as a core structural component of the BBSome complex, contributing to intraciliary transport (IFT) assembly and turnaround at both the ciliary base and tip in sensory neurons. The BBSome acts as a scaffold organizing IFT-A, IFT-B, and cargo molecules.

References

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Gene Research for Functional Annotation

⚠️ CRITICAL: Gene/Protein Identification Context

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Gene Research for Functional Annotation

⚠️ CRITICAL: Gene/Protein Identification Context

Target Gene/Protein Identity (from UniProt):

MANDATORY VERIFICATION STEPS:

If Gene Symbol is Ambiguous or You Cannot Find Relevant Literature:

Research Target:

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