{"gene":"BBS7","run_date":"2026-04-28T17:12:38","timeline":{"discoveries":[{"year":2004,"finding":"C. elegans BBS-7 localizes predominantly at the base of cilia and moves bidirectionally along the ciliary axoneme like IFT proteins; loss of BBS-7 causes structural and functional cilia defects and disrupts normal localization/motility of IFT proteins OSM-5/Polaris and CHE-11 (and to a lesser extent CHE-2), demonstrating that BBS-7 plays a selective role in the assembly and/or function of IFT particle components.","method":"Live imaging of fluorescently tagged proteins in C. elegans, loss-of-function mutant analysis, behavioral assays for cilia function","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (localization, motility, structural analysis), highly cited foundational study replicated in subsequent work","pmids":["15231740"],"is_preprint":false},{"year":2003,"finding":"BBS7 was identified as a novel BBS protein that shares structural features (overlapping motifs) with BBS1 and BBS2, defining a potential functional domain present in three known BBS proteins; BBS2L1 (BBS7) mutations cause Bardet-Biedl syndrome, establishing BBS7 as a disease gene.","method":"Phylogenetic and genomic sequence analysis, positional cloning, mutation screening in BBS patients","journal":"American journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 3 — sequence/structural similarity and mutation identification; no direct biochemical functional assay in this paper","pmids":["12567324"],"is_preprint":false},{"year":2013,"finding":"BBS7 is required for BBSome formation: Bbs7 knockout mice lack a properly assembled BBSome complex, and BBS7 and BBS2 depend on each other for protein stability. BBS7 also physically interacts with the BBS chaperonin complex. Loss of BBS7 causes selective accumulation of dopamine D1 receptor at the ciliary membrane but does not affect localization of polycystin-1, polycystin-2, or bitter taste receptors, revealing a selective role in ciliary membrane protein trafficking.","method":"Bbs7 knockout mouse generation, co-immunoprecipitation, immunofluorescence/localization of BBSome subunits and ciliary membrane proteins, western blot for protein stability","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 — knockout mouse with multiple orthogonal methods (Co-IP, protein stability assay, receptor localization), moderately cited","pmids":["23572516"],"is_preprint":false},{"year":2014,"finding":"In zebrafish, bbs7 knockdown disrupts formation of the Kupffer's vesicle (a ciliated organ) and causes a retrograde intraflagellar transport delay in melanosomes. Planar cell polarity (PCP) and BBS function independently in cilia: bbs7 activity is not required for Prickle2 (Pk2) asymmetric localization, and BBSome complex formation is preserved in Pk2-deficient mice. Knockdown of pk2 or ift22 suppresses the bbs7-related retrograde transport delay, placing BBS7 in the anterograde/retrograde IFT balance pathway.","method":"Zebrafish gene knockdown (morpholino), Kupffer's vesicle analysis, melanosome transport assay, neural tube cell polarity measurement, BBSome Co-IP in Pk2-/- mouse tissue","journal":"Developmental biology","confidence":"Medium","confidence_rationale":"Tier 2 — genetic epistasis with multiple readouts, single lab study","pmids":["24938409"],"is_preprint":false},{"year":2014,"finding":"A missense mutation (my13) in C. elegans bbs-7 disrupts PKD-2 receptor localization to cilia, impairs cilia-mediated sensory behaviors, compromises cilia structural integrity, and also affects the glial cells that support cilia, confirming bbs-7 as the causative locus via forward genetic screening.","method":"Forward genetic screen, Sanger sequencing to identify lesion, behavioral assays, fluorescence imaging of receptor localization, structural analysis of cilia","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 — direct identification of causative allele with multiple functional readouts, single lab","pmids":["25486278"],"is_preprint":false},{"year":2021,"finding":"BBS7 knockdown in periodontal ligament cells suppresses Sonic hedgehog (SHH) signaling activity, impairs cell migration, and reduces angiogenesis in vitro, indicating BBS7 regulates primary cilia-dependent SHH signaling for tissue homeostasis.","method":"siRNA knockdown, RT-qPCR, Western blot, wound healing assay, tubule formation assay","journal":"Frontiers in cell and developmental biology","confidence":"Low","confidence_rationale":"Tier 3 — single lab, single knockdown approach with phenotypic readouts but no direct pathway epistasis confirmation","pmids":["34957122"],"is_preprint":false}],"current_model":"BBS7 is a core subunit of the BBSome (together with BBS1, 2, 4, 5, 8, and 9) that is required for BBSome assembly and stability (particularly mutual stabilization with BBS2), localizes to the base of cilia, moves bidirectionally along the ciliary axoneme in an IFT-dependent manner, and selectively regulates the trafficking of specific membrane proteins (e.g., dopamine D1 receptor) to and from the ciliary membrane, with loss of BBS7 disrupting IFT particle composition/motility and causing the multisystem Bardet-Biedl syndrome phenotype."},"narrative":{"teleology":[{"year":2003,"claim":"Identification of BBS7 as a disease gene established that a third member of a structurally related protein family (with BBS1 and BBS2) underlies Bardet-Biedl syndrome, raising the question of whether these proteins share a common molecular function.","evidence":"Positional cloning and mutation screening in BBS patient cohorts","pmids":["12567324"],"confidence":"Medium","gaps":["No biochemical function or subcellular localization was determined","Structural similarity to BBS1/BBS2 was inferred computationally but not tested functionally"]},{"year":2004,"claim":"Demonstration that BBS-7 localizes to the ciliary base, undergoes IFT-like bidirectional transport, and selectively regulates IFT particle composition established BBS-7 as an IFT-associated protein rather than a structural ciliary component.","evidence":"Live fluorescence imaging and loss-of-function mutant analysis in C. elegans","pmids":["15231740"],"confidence":"High","gaps":["Mechanism by which BBS-7 selectively affects certain IFT components (OSM-5, CHE-11) but not others (CHE-2) was not resolved","Whether BBS-7 functions within a multi-protein complex was unknown"]},{"year":2013,"claim":"Knockout studies revealed that BBS7 is required for BBSome assembly and mutual BBS2-BBS7 protein stabilization, and that BBS7 selectively controls trafficking of specific ciliary membrane receptors (D1R accumulates, but polycystins and taste receptors are unaffected), resolving the question of whether BBSome function is globally or selectively required for ciliary protein transport.","evidence":"Bbs7 knockout mouse, co-immunoprecipitation, immunofluorescence of ciliary membrane proteins, western blot for protein stability","pmids":["23572516"],"confidence":"High","gaps":["Molecular basis for cargo selectivity (why D1R but not polycystins) is unknown","Whether BBS7 directly contacts specific cargo or acts indirectly through BBSome conformation is unresolved","Interaction with the BBS chaperonin complex was shown but the mechanistic role of this interaction in BBSome assembly was not dissected"]},{"year":2014,"claim":"Genetic epistasis in zebrafish and a forward genetic screen in C. elegans independently confirmed BBS7's role in IFT-dependent retrograde transport balance and ciliary receptor (PKD-2) localization, and established that BBS7 functions independently of the planar cell polarity pathway.","evidence":"Zebrafish morpholino knockdown with melanosome transport and Kupffer's vesicle assays; C. elegans forward genetic screen with PKD-2 localization imaging","pmids":["24938409","25486278"],"confidence":"Medium","gaps":["Morpholino-based knockdown in zebrafish lacks genetic confirmation with stable mutants","How pk2 or ift22 knockdown suppresses the bbs7 retrograde transport phenotype mechanistically is unclear","Whether the glial cell defects observed in C. elegans bbs-7 mutants are cell-autonomous is untested"]},{"year":null,"claim":"The molecular determinants of BBSome cargo selectivity mediated by BBS7, the structural basis for BBS7–BBS2 co-stabilization, and the precise role of BBS7 within the BBS chaperonin assembly pathway remain unresolved.","evidence":"","pmids":[],"confidence":"High","gaps":["No structural model of BBS7 within the BBSome at atomic resolution reported in the timeline","Direct binding interface between BBS7 and specific cargo receptors has not been mapped","Whether BBS7 has enzymatic or regulatory activity beyond its scaffolding role is unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[0,3]}],"localization":[{"term_id":"GO:0005929","term_label":"cilium","supporting_discovery_ids":[0,2,4]}],"pathway":[{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[0,2,3]},{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[2,4]}],"complexes":["BBSome"],"partners":["BBS1","BBS2","BBS4","BBS5","BBS8","BBS9"],"other_free_text":[]},"mechanistic_narrative":"BBS7 is a core subunit of the BBSome complex that is essential for its assembly and stability, functioning in intraflagellar transport (IFT)-dependent trafficking of specific membrane proteins at cilia [PMID:23572516, PMID:15231740]. BBS7 localizes to the base of cilia and moves bidirectionally along the ciliary axoneme; loss of BBS7 disrupts IFT particle composition and motility, causing structural and functional cilia defects [PMID:15231740]. BBS7 and BBS2 are mutually required for protein stability, and BBS7 loss selectively alters ciliary membrane protein trafficking—for example, causing accumulation of dopamine D1 receptor at the ciliary membrane without affecting polycystin or bitter taste receptor localization [PMID:23572516]. Mutations in BBS7 cause Bardet-Biedl syndrome, a multisystem ciliopathy [PMID:12567324]."},"prefetch_data":{"uniprot":{"accession":"Q8IWZ6","full_name":"BBSome complex member BBS7","aliases":["BBS2-like protein 1","Bardet-Biedl syndrome 7 protein"],"length_aa":715,"mass_kda":80.4,"function":"The BBSome complex is thought to function as a coat complex required for sorting of specific membrane proteins to the primary cilia. The BBSome complex is required for ciliogenesis but is dispensable for centriolar satellite function. This ciliogenic function is mediated in part by the Rab8 GDP/GTP exchange factor, which localizes to the basal body and contacts the BBSome. Rab8(GTP) enters the primary cilium and promotes extension of the ciliary membrane. Firstly the BBSome associates with the ciliary membrane and binds to RAB3IP/Rabin8, the guanosyl exchange factor (GEF) for Rab8 and then the Rab8-GTP localizes to the cilium and promotes docking and fusion of carrier vesicles to the base of the ciliary membrane. The BBSome complex, together with the LTZL1, controls SMO ciliary trafficking and contributes to the sonic hedgehog (SHH) pathway regulation. Required for proper BBSome complex assembly and its ciliary localization","subcellular_location":"Cell projection, cilium membrane; Cytoplasm; Cytoplasm, cytoskeleton, microtubule organizing center, centrosome, centriolar satellite; Cytoplasm, cytoskeleton, cilium basal body","url":"https://www.uniprot.org/uniprotkb/Q8IWZ6/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/BBS7","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/BBS7","total_profiled":1310},"omim":[{"mim_id":"620951","title":"WD REPEAT-CONTAINING PROTEIN 31; WDR31","url":"https://www.omim.org/entry/620951"},{"mim_id":"618616","title":"MITOGEN-ACTIVATED PROTEIN KINASE 15; MAPK15","url":"https://www.omim.org/entry/618616"},{"mim_id":"617119","title":"BARDET-BIEDL SYNDROME 22; BBS22","url":"https://www.omim.org/entry/617119"},{"mim_id":"615984","title":"BARDET-BIEDL SYNDROME 7; BBS7","url":"https://www.omim.org/entry/615984"},{"mim_id":"615427","title":"ELMO/CED12 DOMAIN-CONTAINING PROTEIN 3; ELMOD3","url":"https://www.omim.org/entry/615427"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"retina","ntpm":52.4}],"url":"https://www.proteinatlas.org/search/BBS7"},"hgnc":{"alias_symbol":["FLJ10715","BBS2L1"],"prev_symbol":[]},"alphafold":{"accession":"Q8IWZ6","domains":[{"cath_id":"2.130.10.10","chopping":"5-317","consensus_level":"medium","plddt":94.728,"start":5,"end":317},{"cath_id":"2.60.40","chopping":"380-487","consensus_level":"high","plddt":92.6802,"start":380,"end":487},{"cath_id":"3.30.160","chopping":"493-597","consensus_level":"medium","plddt":95.6321,"start":493,"end":597},{"cath_id":"-","chopping":"599-713","consensus_level":"medium","plddt":92.0434,"start":599,"end":713}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8IWZ6","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8IWZ6-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8IWZ6-F1-predicted_aligned_error_v6.png","plddt_mean":92.94},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=BBS7","jax_strain_url":"https://www.jax.org/strain/search?query=BBS7"},"sequence":{"accession":"Q8IWZ6","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8IWZ6.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8IWZ6/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8IWZ6"}},"corpus_meta":[{"pmid":"15231740","id":"PMC_15231740","title":"Loss of C. elegans BBS-7 and BBS-8 protein function results in cilia defects and compromised intraflagellar transport.","date":"2004","source":"Genes & development","url":"https://pubmed.ncbi.nlm.nih.gov/15231740","citation_count":284,"is_preprint":false},{"pmid":"12567324","id":"PMC_12567324","title":"Identification of a novel Bardet-Biedl syndrome protein, BBS7, that shares structural features with BBS1 and BBS2.","date":"2003","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/12567324","citation_count":172,"is_preprint":false},{"pmid":"23572516","id":"PMC_23572516","title":"BBS7 is required for BBSome formation and its absence in mice results in Bardet-Biedl syndrome phenotypes and selective abnormalities in membrane protein trafficking.","date":"2013","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/23572516","citation_count":105,"is_preprint":false},{"pmid":"26518167","id":"PMC_26518167","title":"Targeted multi-gene panel testing for the diagnosis of Bardet Biedl syndrome: Identification of nine novel mutations across BBS1, BBS2, BBS4, BBS7, BBS9, BBS10 genes.","date":"2015","source":"European journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/26518167","citation_count":39,"is_preprint":false},{"pmid":"19402160","id":"PMC_19402160","title":"BBS7 and TTC8 (BBS8) mutations play a minor role in the mutational load of Bardet-Biedl syndrome in a multiethnic population.","date":"2009","source":"Human mutation","url":"https://pubmed.ncbi.nlm.nih.gov/19402160","citation_count":34,"is_preprint":false},{"pmid":"19093007","id":"PMC_19093007","title":"A novel mutation in BBS7 gene causes Bardet-Biedl syndrome in a Chinese family.","date":"2008","source":"Molecular vision","url":"https://pubmed.ncbi.nlm.nih.gov/19093007","citation_count":16,"is_preprint":false},{"pmid":"33729075","id":"PMC_33729075","title":"Bardet-Biedl syndrome-7 (BBS7) shows treatment potential and a cone-rod dystrophy phenotype that recapitulates the non-human primate model.","date":"2021","source":"Ophthalmic genetics","url":"https://pubmed.ncbi.nlm.nih.gov/33729075","citation_count":16,"is_preprint":false},{"pmid":"26557828","id":"PMC_26557828","title":"Exome Sequencing of a Family with Bardet-Biedl Syndrome Identifies the Common Russian Mutation c.1967_1968delTAinsC in BBS7.","date":"2015","source":"Molecular syndromology","url":"https://pubmed.ncbi.nlm.nih.gov/26557828","citation_count":9,"is_preprint":false},{"pmid":"30839500","id":"PMC_30839500","title":"Identification of a homozygous BBS7 frameshift mutation in two (related) Chinese Miao families with Bardet-Biedl Syndrome.","date":"2019","source":"Journal of the Chinese Medical Association : JCMA","url":"https://pubmed.ncbi.nlm.nih.gov/30839500","citation_count":8,"is_preprint":false},{"pmid":"34957122","id":"PMC_34957122","title":"BBS7-SHH Signaling Activity Regulates Primary Cilia for Periodontal Homeostasis.","date":"2021","source":"Frontiers in cell and developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/34957122","citation_count":8,"is_preprint":false},{"pmid":"24938409","id":"PMC_24938409","title":"Functional characterization of Prickle2 and BBS7 identify overlapping phenotypes yet distinct mechanisms.","date":"2014","source":"Developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/24938409","citation_count":7,"is_preprint":false},{"pmid":"35912300","id":"PMC_35912300","title":"Novel Mutations in the MKKS, BBS7, and ALMS1 Genes in Iranian Children with Clinically Suspected Bardet-Biedl Syndrome.","date":"2022","source":"Case reports in ophthalmological medicine","url":"https://pubmed.ncbi.nlm.nih.gov/35912300","citation_count":6,"is_preprint":false},{"pmid":"36672825","id":"PMC_36672825","title":"Dental Anomalies in Ciliopathies: Lessons from Patients with BBS2, BBS7, and EVC2 Mutations.","date":"2022","source":"Genes","url":"https://pubmed.ncbi.nlm.nih.gov/36672825","citation_count":5,"is_preprint":false},{"pmid":"31469663","id":"PMC_31469663","title":"A novel missense variant in the BBS7 gene underlying Bardet-Biedl syndrome in a consanguineous Pakistani family.","date":"2020","source":"Clinical dysmorphology","url":"https://pubmed.ncbi.nlm.nih.gov/31469663","citation_count":5,"is_preprint":false},{"pmid":"36361806","id":"PMC_36361806","title":"A 5' UTR Mutation Contributes to Down-Regulation of Bbs7 in the Berlin Fat Mouse.","date":"2022","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/36361806","citation_count":4,"is_preprint":false},{"pmid":"34910225","id":"PMC_34910225","title":"A deletion containing a CTCF-element in intron 8 of the Bbs7 gene is partially responsible for juvenile obesity in the Berlin Fat Mouse.","date":"2021","source":"Mammalian genome : official journal of the International Mammalian Genome Society","url":"https://pubmed.ncbi.nlm.nih.gov/34910225","citation_count":4,"is_preprint":false},{"pmid":"31521835","id":"PMC_31521835","title":"RIN2 and BBS7 variants as cause of a coincidental syndrome.","date":"2019","source":"European journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/31521835","citation_count":3,"is_preprint":false},{"pmid":"25486278","id":"PMC_25486278","title":"Identification and characterization of a novel allele of Caenorhabditis elegans bbs-7.","date":"2014","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/25486278","citation_count":3,"is_preprint":false},{"pmid":"39092430","id":"PMC_39092430","title":"Spectrum of pathogenic variants and high prevalence of pathogenic BBS7 variants in Russian patients with Bardet-Biedl syndrome.","date":"2024","source":"Frontiers in genetics","url":"https://pubmed.ncbi.nlm.nih.gov/39092430","citation_count":0,"is_preprint":false},{"pmid":"41064051","id":"PMC_41064051","title":"A Rare Case of Bardet-Biedl Syndrome Caused by a Heterozygous Point Variant in BBS7 and a CNV Involved BBS7.","date":"2025","source":"Molecular syndromology","url":"https://pubmed.ncbi.nlm.nih.gov/41064051","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":10517,"output_tokens":1615,"usd":0.027888},"stage2":{"model":"claude-opus-4-6","input_tokens":4849,"output_tokens":1563,"usd":0.09498},"total_usd":0.122868,"stage1_batch_id":"msgbatch_01TqNM6p6FsoMBT2jzQTwKBr","stage2_batch_id":"msgbatch_01Ya473eco8sTHbvRymQaU8o","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2004,\n      \"finding\": \"C. elegans BBS-7 localizes predominantly at the base of cilia and moves bidirectionally along the ciliary axoneme like IFT proteins; loss of BBS-7 causes structural and functional cilia defects and disrupts normal localization/motility of IFT proteins OSM-5/Polaris and CHE-11 (and to a lesser extent CHE-2), demonstrating that BBS-7 plays a selective role in the assembly and/or function of IFT particle components.\",\n      \"method\": \"Live imaging of fluorescently tagged proteins in C. elegans, loss-of-function mutant analysis, behavioral assays for cilia function\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (localization, motility, structural analysis), highly cited foundational study replicated in subsequent work\",\n      \"pmids\": [\"15231740\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"BBS7 was identified as a novel BBS protein that shares structural features (overlapping motifs) with BBS1 and BBS2, defining a potential functional domain present in three known BBS proteins; BBS2L1 (BBS7) mutations cause Bardet-Biedl syndrome, establishing BBS7 as a disease gene.\",\n      \"method\": \"Phylogenetic and genomic sequence analysis, positional cloning, mutation screening in BBS patients\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — sequence/structural similarity and mutation identification; no direct biochemical functional assay in this paper\",\n      \"pmids\": [\"12567324\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"BBS7 is required for BBSome formation: Bbs7 knockout mice lack a properly assembled BBSome complex, and BBS7 and BBS2 depend on each other for protein stability. BBS7 also physically interacts with the BBS chaperonin complex. Loss of BBS7 causes selective accumulation of dopamine D1 receptor at the ciliary membrane but does not affect localization of polycystin-1, polycystin-2, or bitter taste receptors, revealing a selective role in ciliary membrane protein trafficking.\",\n      \"method\": \"Bbs7 knockout mouse generation, co-immunoprecipitation, immunofluorescence/localization of BBSome subunits and ciliary membrane proteins, western blot for protein stability\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — knockout mouse with multiple orthogonal methods (Co-IP, protein stability assay, receptor localization), moderately cited\",\n      \"pmids\": [\"23572516\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"In zebrafish, bbs7 knockdown disrupts formation of the Kupffer's vesicle (a ciliated organ) and causes a retrograde intraflagellar transport delay in melanosomes. Planar cell polarity (PCP) and BBS function independently in cilia: bbs7 activity is not required for Prickle2 (Pk2) asymmetric localization, and BBSome complex formation is preserved in Pk2-deficient mice. Knockdown of pk2 or ift22 suppresses the bbs7-related retrograde transport delay, placing BBS7 in the anterograde/retrograde IFT balance pathway.\",\n      \"method\": \"Zebrafish gene knockdown (morpholino), Kupffer's vesicle analysis, melanosome transport assay, neural tube cell polarity measurement, BBSome Co-IP in Pk2-/- mouse tissue\",\n      \"journal\": \"Developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis with multiple readouts, single lab study\",\n      \"pmids\": [\"24938409\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"A missense mutation (my13) in C. elegans bbs-7 disrupts PKD-2 receptor localization to cilia, impairs cilia-mediated sensory behaviors, compromises cilia structural integrity, and also affects the glial cells that support cilia, confirming bbs-7 as the causative locus via forward genetic screening.\",\n      \"method\": \"Forward genetic screen, Sanger sequencing to identify lesion, behavioral assays, fluorescence imaging of receptor localization, structural analysis of cilia\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct identification of causative allele with multiple functional readouts, single lab\",\n      \"pmids\": [\"25486278\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"BBS7 knockdown in periodontal ligament cells suppresses Sonic hedgehog (SHH) signaling activity, impairs cell migration, and reduces angiogenesis in vitro, indicating BBS7 regulates primary cilia-dependent SHH signaling for tissue homeostasis.\",\n      \"method\": \"siRNA knockdown, RT-qPCR, Western blot, wound healing assay, tubule formation assay\",\n      \"journal\": \"Frontiers in cell and developmental biology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single lab, single knockdown approach with phenotypic readouts but no direct pathway epistasis confirmation\",\n      \"pmids\": [\"34957122\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"BBS7 is a core subunit of the BBSome (together with BBS1, 2, 4, 5, 8, and 9) that is required for BBSome assembly and stability (particularly mutual stabilization with BBS2), localizes to the base of cilia, moves bidirectionally along the ciliary axoneme in an IFT-dependent manner, and selectively regulates the trafficking of specific membrane proteins (e.g., dopamine D1 receptor) to and from the ciliary membrane, with loss of BBS7 disrupting IFT particle composition/motility and causing the multisystem Bardet-Biedl syndrome phenotype.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"BBS7 is a core subunit of the BBSome complex that is essential for its assembly and stability, functioning in intraflagellar transport (IFT)-dependent trafficking of specific membrane proteins at cilia [PMID:23572516, PMID:15231740]. BBS7 localizes to the base of cilia and moves bidirectionally along the ciliary axoneme; loss of BBS7 disrupts IFT particle composition and motility, causing structural and functional cilia defects [PMID:15231740]. BBS7 and BBS2 are mutually required for protein stability, and BBS7 loss selectively alters ciliary membrane protein trafficking—for example, causing accumulation of dopamine D1 receptor at the ciliary membrane without affecting polycystin or bitter taste receptor localization [PMID:23572516]. Mutations in BBS7 cause Bardet-Biedl syndrome, a multisystem ciliopathy [PMID:12567324].\",\n  \"teleology\": [\n    {\n      \"year\": 2003,\n      \"claim\": \"Identification of BBS7 as a disease gene established that a third member of a structurally related protein family (with BBS1 and BBS2) underlies Bardet-Biedl syndrome, raising the question of whether these proteins share a common molecular function.\",\n      \"evidence\": \"Positional cloning and mutation screening in BBS patient cohorts\",\n      \"pmids\": [\"12567324\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No biochemical function or subcellular localization was determined\",\n        \"Structural similarity to BBS1/BBS2 was inferred computationally but not tested functionally\"\n      ]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Demonstration that BBS-7 localizes to the ciliary base, undergoes IFT-like bidirectional transport, and selectively regulates IFT particle composition established BBS-7 as an IFT-associated protein rather than a structural ciliary component.\",\n      \"evidence\": \"Live fluorescence imaging and loss-of-function mutant analysis in C. elegans\",\n      \"pmids\": [\"15231740\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Mechanism by which BBS-7 selectively affects certain IFT components (OSM-5, CHE-11) but not others (CHE-2) was not resolved\",\n        \"Whether BBS-7 functions within a multi-protein complex was unknown\"\n      ]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Knockout studies revealed that BBS7 is required for BBSome assembly and mutual BBS2-BBS7 protein stabilization, and that BBS7 selectively controls trafficking of specific ciliary membrane receptors (D1R accumulates, but polycystins and taste receptors are unaffected), resolving the question of whether BBSome function is globally or selectively required for ciliary protein transport.\",\n      \"evidence\": \"Bbs7 knockout mouse, co-immunoprecipitation, immunofluorescence of ciliary membrane proteins, western blot for protein stability\",\n      \"pmids\": [\"23572516\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Molecular basis for cargo selectivity (why D1R but not polycystins) is unknown\",\n        \"Whether BBS7 directly contacts specific cargo or acts indirectly through BBSome conformation is unresolved\",\n        \"Interaction with the BBS chaperonin complex was shown but the mechanistic role of this interaction in BBSome assembly was not dissected\"\n      ]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Genetic epistasis in zebrafish and a forward genetic screen in C. elegans independently confirmed BBS7's role in IFT-dependent retrograde transport balance and ciliary receptor (PKD-2) localization, and established that BBS7 functions independently of the planar cell polarity pathway.\",\n      \"evidence\": \"Zebrafish morpholino knockdown with melanosome transport and Kupffer's vesicle assays; C. elegans forward genetic screen with PKD-2 localization imaging\",\n      \"pmids\": [\"24938409\", \"25486278\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Morpholino-based knockdown in zebrafish lacks genetic confirmation with stable mutants\",\n        \"How pk2 or ift22 knockdown suppresses the bbs7 retrograde transport phenotype mechanistically is unclear\",\n        \"Whether the glial cell defects observed in C. elegans bbs-7 mutants are cell-autonomous is untested\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The molecular determinants of BBSome cargo selectivity mediated by BBS7, the structural basis for BBS7–BBS2 co-stabilization, and the precise role of BBS7 within the BBS chaperonin assembly pathway remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"No structural model of BBS7 within the BBSome at atomic resolution reported in the timeline\",\n        \"Direct binding interface between BBS7 and specific cargo receptors has not been mapped\",\n        \"Whether BBS7 has enzymatic or regulatory activity beyond its scaffolding role is unknown\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [0, 3]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005929\", \"supporting_discovery_ids\": [0, 2, 4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [0, 2, 3]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [2, 4]}\n    ],\n    \"complexes\": [\n      \"BBSome\"\n    ],\n    \"partners\": [\n      \"BBS1\",\n      \"BBS2\",\n      \"BBS4\",\n      \"BBS5\",\n      \"BBS8\",\n      \"BBS9\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}