{"gene":"CEP68","run_date":"2026-04-28T17:28:52","timeline":{"discoveries":[{"year":2007,"finding":"CEP68 localizes to fibres emanating from the proximal ends of centrioles during interphase and dissociates from centrosomes at mitosis. CEP68 depends on both rootletin and C-Nap1 for centriole association, and depletion of CEP68 causes premature centrosome separation (splitting). Overexpressed CEP68 is recruited to ectopic rootletin fibres but does not itself induce extensive fibre formation, indicating CEP68 cooperates with rootletin and C-Nap1 in maintaining centrosome cohesion.","method":"Immunofluorescence microscopy, siRNA depletion with centrosome-splitting phenotype readout, overexpression and co-localization assays, reciprocal dependency experiments","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (localization, KD phenotype, co-localization dependency), foundational paper replicated by subsequent studies","pmids":["18042621"],"is_preprint":false},{"year":2014,"finding":"CEP68 forms a trimeric complex with CEP215 (CDK5RAP2) and pericentrin (PCNT) at the pericentriolar material. CEP68 is degraded in prometaphase via the SCF(βTrCP) ubiquitin ligase; this degradation is initiated by PLK1 phosphorylation of CEP68 on Ser332, which creates a phosphodegron recognized by βTrCP. CEP68 degradation removes CEP215 from the peripheral PCM, which is required to prevent centriole separation following disengagement, thereby licensing centrioles for duplication.","method":"Co-immunoprecipitation, mass spectrometry interactome, siRNA depletion, phosphosite mutagenesis, in vivo ubiquitination assay, PLK1 kinase assay","journal":"Nature cell biology","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal methods including kinase assay, mutagenesis of phosphodegron, ubiquitination assay, and Co-IP in a single rigorous study","pmids":["25503564"],"is_preprint":false},{"year":2014,"finding":"Centlein (CNTLN) directly interacts with both C-Nap1 and CEP68 and functions as a molecular bridge between them at the proximal ends of centrioles during interphase. Depletion of centlein impairs CEP68 recruitment to centrosomes and causes centrosome splitting. Both centlein and CEP68 are substrates of the mitotic kinase Nek2A, placing CEP68 downstream of Nek2A in the cohesion-dissolution pathway.","method":"Co-immunoprecipitation, direct binding (GST pulldown), siRNA depletion with centrosome-splitting readout, Nek2A in vitro kinase assay, immunofluorescence","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 1-2 — direct binding demonstrated by pulldown, kinase assay, epistatic siRNA phenotype, multiple methods in one study","pmids":["24554434"],"is_preprint":false},{"year":2015,"finding":"The C-terminal 300–400 amino acids of CEP68 are necessary for its localization to interphase centrosomes, while the C-terminal 400–500 amino acid region regulates its dissociation at mitotic onset. Nek2 phosphorylates CEP68 in vivo and this phosphorylation promotes CEP68 degradation. The SCF(βTrCP) complex mediates CEP68 destruction at mitosis through βTrCP recognition.","method":"Domain deletion mapping with immunofluorescence, in vivo phosphorylation assays, co-immunoprecipitation with SCF components, cell-cycle-staged degradation assays","journal":"European journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 2-3 — domain mapping and in vivo phosphorylation, single lab, partially corroborates PMID:25503564","pmids":["25704143"],"is_preprint":false},{"year":2017,"finding":"Rootletin protects CEP68 from proteasomal degradation by inhibiting VHL-mediated ubiquitination. In the absence of rootletin, the VHL E3 ligase complex ubiquitinates CEP68 in vitro and in vivo, leading to its degradation and centrosome splitting. Co-depletion of rootletin and VHL rescues CEP68 levels and centrosome cohesion. A CEP68 mutant that cannot bind the β-domain of VHL or cannot be polyubiquitinated also suppresses centrosome splitting caused by rootletin depletion.","method":"siRNA double knockdown epistasis, in vitro ubiquitination assay with VHL E3 complex, in vivo ubiquitination assay, stable CEP68 mutant rescue experiments, immunofluorescence","journal":"Biochimica et biophysica acta. Molecular cell research","confidence":"High","confidence_rationale":"Tier 1-2 — in vitro ubiquitination reconstitution, epistatic double-KD rescue, mutagenesis rescue, multiple orthogonal approaches in one study","pmids":["28089774"],"is_preprint":false},{"year":2017,"finding":"MCM7 directly binds CEP68 in vitro and forms a ternary complex with CEP68 and VHL in vivo. MCM7 depletion weakens the CEP68-VHL interaction, whereas MCM7 overexpression facilitates CEP68-VHL association, increasing CEP68 ubiquitination and proteasomal degradation, resulting in centrosome splitting. This identifies MCM7 as a positive regulator of VHL-mediated CEP68 degradation at the centrosome.","method":"GST pulldown (direct binding), co-immunoprecipitation, siRNA depletion, overexpression, in vivo ubiquitination assay, immunofluorescence centrosome-splitting assay","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2-3 — direct binding by pulldown, Co-IP, and functional ubiquitination data, single lab","pmids":["28578000"],"is_preprint":false},{"year":2018,"finding":"Super-resolution STED microscopy revealed that CEP68 co-localizes with rootletin in periodic filaments that branch off centrioles and form a web-like interdigitating network between the two centrosomes. Rootletin binds CEP68 via its C-terminal spectrin repeat-containing region at 75-nm intervals along the filament. CEP68 is required for forming rootletin filaments that branch off centrioles and for modulating the thickness of rootletin fibers, acting as a filament modulator within a C-Nap1-anchored, periodically ordered centrosome linker network.","method":"STED super-resolution microscopy, structured illumination microscopy, siRNA depletion, co-immunoprecipitation to map rootletin-CEP68 binding domain, immunofluorescence","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1-2 — STED nanoscopy provides structural resolution, combined with domain-mapping Co-IP and functional depletion, strong mechanistic resolution","pmids":["29463719"],"is_preprint":false}],"current_model":"CEP68 is an interphase centrosome cohesion protein that localizes to periodic rootletin filaments anchored to C-Nap1 rings at centriole proximal ends, where it modulates filament branching and thickness; cohesion is maintained through a C-Nap1–centlein–CEP68–rootletin complex, and CEP68 protein levels are controlled by two antagonistic mechanisms—rootletin-mediated protection from VHL E3 ligase-dependent ubiquitination/degradation during interphase, and PLK1 phosphorylation of Ser332 triggering SCF(βTrCP)-mediated degradation in prometaphase, which releases CEP215 from the peripheral PCM to permit centriole separation, disengagement, and licensing for duplication."},"narrative":{"teleology":[{"year":2007,"claim":"The identification of CEP68 as a rootletin- and C-Nap1-dependent interphase centrosome protein whose depletion causes premature centrosome splitting established it as a new component of the centrosome cohesion machinery.","evidence":"Immunofluorescence, siRNA depletion with splitting phenotype, co-localization dependency experiments in human cells","pmids":["18042621"],"confidence":"High","gaps":["How CEP68 is physically linked to C-Nap1 was unknown","The mitotic mechanism removing CEP68 from centrosomes was uncharacterized","Whether CEP68 has a structural versus signaling role in centrosome cohesion was unclear"]},{"year":2014,"claim":"Two studies resolved how CEP68 connects to the cohesion network and how it is eliminated at mitosis: centlein bridges C-Nap1 to CEP68, while PLK1 phosphorylation of CEP68 Ser332 creates a βTrCP phosphodegron that triggers SCF-mediated degradation in prometaphase, thereby releasing CEP215 from the PCM to allow centriole separation and duplication licensing.","evidence":"Co-IP, GST pulldown for direct centlein–CEP68 binding, Nek2A kinase assay, PLK1 phosphosite mutagenesis, in vivo ubiquitination assays, epistatic siRNA experiments","pmids":["24554434","25503564"],"confidence":"High","gaps":["How CEP68 protein stability is maintained during interphase was not addressed","The structural arrangement of CEP68 within rootletin filaments was unresolved","Whether additional E3 ligases regulate CEP68 outside mitosis was unknown"]},{"year":2015,"claim":"Domain-mapping clarified that the C-terminal 300–500 amino acids control both interphase centrosome targeting and mitotic dissociation, and confirmed Nek2-dependent phosphorylation promotes CEP68 degradation via SCF(βTrCP).","evidence":"Deletion mapping with immunofluorescence, in vivo phosphorylation assays, Co-IP with SCF components, cell-cycle-staged degradation assays","pmids":["25704143"],"confidence":"Medium","gaps":["Precise phosphosites targeted by Nek2 on CEP68 were not mapped at single-residue resolution","The relative contributions of PLK1 versus Nek2 to mitotic CEP68 degradation remained unresolved"]},{"year":2017,"claim":"Discovery that rootletin protects CEP68 from VHL-mediated ubiquitination during interphase, and that MCM7 promotes the CEP68–VHL interaction, revealed a dual-layer regulation of CEP68 stability: rootletin shields CEP68 from VHL, while MCM7 enhances VHL-dependent degradation.","evidence":"In vitro ubiquitination reconstitution with VHL complex, epistatic siRNA double knockdown rescuing cohesion, VHL-binding-deficient CEP68 mutants, GST pulldown for MCM7–CEP68 direct binding, overexpression/depletion of MCM7","pmids":["28089774","28578000"],"confidence":"High","gaps":["How rootletin physically occludes VHL access to CEP68 is structurally uncharacterized","The physiological context in which MCM7 acts at centrosomes versus its canonical replication role is unclear","Whether VHL and SCF(βTrCP) act on the same or different CEP68 pools is unresolved"]},{"year":2018,"claim":"STED super-resolution imaging revealed that CEP68 decorates rootletin filaments at 75-nm periodic intervals and is required for filament branching and thickness control, establishing CEP68 as a structural modulator of the centrosome linker rather than merely a passive component.","evidence":"STED and structured illumination microscopy, domain-mapping Co-IP for rootletin spectrin repeat–CEP68 interaction, siRNA depletion","pmids":["29463719"],"confidence":"High","gaps":["Atomic-resolution structure of the CEP68–rootletin interface is lacking","Whether CEP68 periodicity is self-determined or templated by rootletin is unknown","Functional consequences of altered filament branching for cell division fidelity have not been tested"]},{"year":null,"claim":"Key open questions include the structural basis of CEP68's periodic binding to rootletin, the interplay between VHL- and SCF(βTrCP)-dependent degradation pathways during the cell cycle, and whether CEP68 loss or mutation has consequences for tissue-level physiology or disease.","evidence":"","pmids":[],"confidence":"High","gaps":["No atomic or cryo-EM structure exists for CEP68 or its complexes","No in vivo animal model phenotype has been reported","Relative timing and coordination of VHL versus SCF(βTrCP) pathways across the cell cycle is unresolved"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[0,6]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[0,6]}],"localization":[{"term_id":"GO:0005815","term_label":"microtubule organizing center","supporting_discovery_ids":[0,1,2,3,6]},{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[6]}],"pathway":[{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[1,3]},{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[0,6]}],"complexes":["C-Nap1–centlein–CEP68–rootletin linker complex","CEP68–CEP215–pericentrin PCM complex"],"partners":["CROCC","CEP250","CNTLN","CDK5RAP2","PCNT","VHL","BTRC","MCM7"],"other_free_text":[]},"mechanistic_narrative":"CEP68 is a centrosome-linker protein that maintains interphase centrosome cohesion by associating with periodic rootletin filaments anchored via C-Nap1 rings at centriole proximal ends, where it modulates filament branching and thickness [PMID:18042621, PMID:29463719]. CEP68 is recruited to centrosomes through a C-Nap1–centlein–CEP68–rootletin complex, with centlein acting as a molecular bridge between C-Nap1 and CEP68 [PMID:24554434]. During interphase, rootletin protects CEP68 from VHL E3 ligase-dependent ubiquitination and proteasomal degradation, while at mitotic entry PLK1 phosphorylation of CEP68 Ser332 generates a phosphodegron recognized by SCF(βTrCP), triggering CEP68 destruction that releases CEP215 from the peripheral pericentriolar material and permits centriole separation and duplication licensing [PMID:25503564, PMID:28089774]. MCM7 facilitates CEP68 degradation by promoting the CEP68–VHL interaction, providing an additional regulatory input into centrosome cohesion control [PMID:28578000]."},"prefetch_data":{"uniprot":{"accession":"Q76N32","full_name":"Centrosomal protein of 68 kDa","aliases":[],"length_aa":757,"mass_kda":81.1,"function":"Involved in maintenance of centrosome cohesion, probably as part of a linker structure which prevents centrosome splitting (PubMed:18042621). Required for localization of CDK5RAP2 to the centrosome during interphase (PubMed:24554434, PubMed:25503564). Contributes to CROCC/rootletin filament formation (PubMed:30404835)","subcellular_location":"Cytoplasm, cytoskeleton, microtubule organizing center, centrosome","url":"https://www.uniprot.org/uniprotkb/Q76N32/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CEP68","classification":"Not Classified","n_dependent_lines":80,"n_total_lines":1208,"dependency_fraction":0.06622516556291391},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/CEP68","total_profiled":1310},"omim":[{"mim_id":"621147","title":"COILED-COIL DOMAIN-CONTAINING PROTEIN 102B; CCDC102B","url":"https://www.omim.org/entry/621147"},{"mim_id":"616889","title":"CENTROSOMAL PROTEIN, 68-KD; CEP68","url":"https://www.omim.org/entry/616889"},{"mim_id":"615776","title":"CILIARY ROOTLET COILED-COIL PROTEIN; CROCC","url":"https://www.omim.org/entry/615776"},{"mim_id":"611870","title":"CENTLEIN; CNTLN","url":"https://www.omim.org/entry/611870"},{"mim_id":"609689","title":"CENTROSOMAL PROTEIN, 250-KD; CEP250","url":"https://www.omim.org/entry/609689"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Centriolar satellite","reliability":"Approved"},{"location":"Cell Junctions","reliability":"Additional"},{"location":"Basal body","reliability":"Additional"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/CEP68"},"hgnc":{"alias_symbol":[],"prev_symbol":["KIAA0582"]},"alphafold":{"accession":"Q9NQ79","domains":[{"cath_id":"2.130.10.130","chopping":"46-451","consensus_level":"medium","plddt":94.9409,"start":46,"end":451},{"cath_id":"-","chopping":"562-594","consensus_level":"medium","plddt":90.3539,"start":562,"end":594}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NQ79","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NQ79-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NQ79-F1-predicted_aligned_error_v6.png","plddt_mean":85.69},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CEP68","jax_strain_url":"https://www.jax.org/strain/search?query=CEP68"},"sequence":{"accession":"Q9NQ79","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9NQ79.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9NQ79/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NQ79"}},"corpus_meta":[{"pmid":"18042621","id":"PMC_18042621","title":"Cep68 and Cep215 (Cdk5rap2) are required for centrosome cohesion.","date":"2007","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/18042621","citation_count":176,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"25503564","id":"PMC_25503564","title":"Degradation of Cep68 and PCNT cleavage mediate Cep215 removal from the PCM to allow centriole separation, disengagement and licensing.","date":"2014","source":"Nature cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/25503564","citation_count":70,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"21072201","id":"PMC_21072201","title":"Genome-wide and follow-up studies identify CEP68 gene variants associated with risk of aspirin-intolerant asthma.","date":"2010","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/21072201","citation_count":62,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"24554434","id":"PMC_24554434","title":"Centlein mediates an interaction between C-Nap1 and Cep68 to maintain centrosome cohesion.","date":"2014","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/24554434","citation_count":53,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"29463719","id":"PMC_29463719","title":"STED nanoscopy of the centrosome linker reveals a CEP68-organized, periodic rootletin network anchored to a C-Nap1 ring at centrioles.","date":"2018","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/29463719","citation_count":53,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"17570516","id":"PMC_17570516","title":"Phosphoproteomics identified Endofin, DCBLD2, and KIAA0582 as novel tyrosine phosphorylation targets of EGF signaling and Iressa in human cancer cells.","date":"2007","source":"Proteomics","url":"https://pubmed.ncbi.nlm.nih.gov/17570516","citation_count":44,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"11139377","id":"PMC_11139377","title":"Chondrocyte expressed protein-68 (CEP-68), a novel human marker gene for cultured chondrocytes.","date":"2001","source":"The Biochemical journal","url":"https://pubmed.ncbi.nlm.nih.gov/11139377","citation_count":38,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"25704143","id":"PMC_25704143","title":"Cep68 can be regulated by Nek2 and SCF complex.","date":"2015","source":"European journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/25704143","citation_count":21,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"24618698","id":"PMC_24618698","title":"Variants of CEP68 gene are associated with acute urticaria/angioedema induced by multiple non-steroidal anti-inflammatory drugs.","date":"2014","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/24618698","citation_count":19,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"28089774","id":"PMC_28089774","title":"Rootletin prevents Cep68 from VHL-mediated proteasomal degradation to maintain centrosome cohesion.","date":"2017","source":"Biochimica et biophysica acta. 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Lung cellular and molecular physiology","url":"https://pubmed.ncbi.nlm.nih.gov/20382749","citation_count":44,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"35924962","id":"PMC_35924962","title":"Plasma proteomics identifies CRTAC1 as a biomarker for osteoarthritis severity and progression.","date":"2023","source":"Rheumatology (Oxford, England)","url":"https://pubmed.ncbi.nlm.nih.gov/35924962","citation_count":43,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"36239377","id":"PMC_36239377","title":"Cartilage Acidic Protein 1 in Plasma Associates With Prevalent Osteoarthritis and Predicts Future Risk as Well as Progression to Joint Replacements: Results From the UK Biobank Resource.","date":"2022","source":"Arthritis & rheumatology (Hoboken, N.J.)","url":"https://pubmed.ncbi.nlm.nih.gov/36239377","citation_count":28,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"17602227","id":"PMC_17602227","title":"Detection of bone and cartilage-related proteins in plasma of patients with a bone fracture using liquid chromatography-mass spectrometry.","date":"2007","source":"International orthopaedics","url":"https://pubmed.ncbi.nlm.nih.gov/17602227","citation_count":26,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"27415616","id":"PMC_27415616","title":"Sex-Specific Protection of Osteoarthritis by Deleting Cartilage Acid Protein 1.","date":"2016","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/27415616","citation_count":26,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"34818994","id":"PMC_34818994","title":"CRTAC1 (Cartilage acidic protein 1) inhibits cell proliferation, migration, invasion and epithelial-mesenchymal transition (EMT) process in bladder cancer by downregulating Yin Yang 1 (YY1) to inactivate the TGF-β pathway.","date":"2021","source":"Bioengineered","url":"https://pubmed.ncbi.nlm.nih.gov/34818994","citation_count":26,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"32838966","id":"PMC_32838966","title":"Down-regulation of CRTAC1 attenuates UVB-induced pyroptosis in HLECs through inhibiting ROS production.","date":"2020","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/32838966","citation_count":25,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"35606786","id":"PMC_35606786","title":"Mass spectrometry-based proteomics identify novel serum osteoarthritis biomarkers.","date":"2022","source":"Arthritis research & therapy","url":"https://pubmed.ncbi.nlm.nih.gov/35606786","citation_count":25,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"27855397","id":"PMC_27855397","title":"Inhibition of Cartilage Acidic Protein 1 Reduces Ultraviolet B Irradiation Induced-Apoptosis through P38 Mitogen-Activated Protein Kinase and Jun Amino-Terminal Kinase Pathways.","date":"2016","source":"Cellular physiology and biochemistry : international journal of experimental cellular physiology, biochemistry, and pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/27855397","citation_count":22,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"33618749","id":"PMC_33618749","title":"Prion protein oligomers cause neuronal cytoskeletal damage in rapidly progressive Alzheimer's disease.","date":"2021","source":"Molecular neurodegeneration","url":"https://pubmed.ncbi.nlm.nih.gov/33618749","citation_count":21,"is_preprint":false,"source_track":"gene2pubmed"}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":7526,"output_tokens":2159,"usd":0.027481},"stage2":{"model":"claude-opus-4-6","input_tokens":5483,"output_tokens":2257,"usd":0.12576},"total_usd":0.330005,"stage1_batch_id":"msgbatch_011kfMfE81o6CTcyhVUqumuW","stage2_batch_id":"msgbatch_01DTputS6WNkH745x1nVSoBo","note":"batch pricing = 50% of standard","round2_stage1":{"model":"claude-sonnet-4-6","input_tokens":22097,"output_tokens":2854,"usd":0.054551},"round2_rules_fired":"R3","round2_stage2":{"model":"claude-opus-4-6","input_tokens":5805,"output_tokens":2098,"usd":0.122213}},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2007,\n      \"finding\": \"CEP68 localizes to fibres emanating from the proximal ends of centrioles during interphase and dissociates from centrosomes during mitosis. CEP68 and rootletin depend on each other and on C-Nap1 for centriole association, and depletion of CEP68 causes centrosome splitting, demonstrating its requirement for centrosome cohesion.\",\n      \"method\": \"Immunofluorescence, siRNA knockdown, overexpression, fluorescence microscopy\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal dependency experiments replicated across multiple conditions; foundational study with >176 citations\",\n      \"pmids\": [\"18042621\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"CEP68 is degraded in prometaphase via the SCF(βTrCP) ubiquitin ligase complex. PLK1 phosphorylates CEP68 on Ser332, creating a phosphodegron recognized by βTrCP. CEP68 degradation allows Cep215 removal from the peripheral PCM, preventing premature centriole separation following disengagement.\",\n      \"method\": \"Biochemical ubiquitination assay, phosphorylation assay, co-immunoprecipitation, site-directed mutagenesis, siRNA knockdown, immunofluorescence\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — multiple orthogonal methods (in vitro phosphorylation, ubiquitination assay, mutagenesis, co-IP) in a single rigorous study\",\n      \"pmids\": [\"25503564\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"CEP68 forms a complex with Cep215 (Cdk5Rap2) and PCNT (pericentrin), two PCM proteins. CEP68 and PCNT bind to different pools of Cep215, linking CEP68 to regulation of centriole engagement and duplication licensing.\",\n      \"method\": \"Co-immunoprecipitation, mass spectrometry, immunofluorescence\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal co-IP combined with functional epistasis experiments in a high-quality study\",\n      \"pmids\": [\"25503564\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Centlein (CNTLN) directly interacts with both C-Nap1 and CEP68, forming a C-Nap1–centlein–CEP68 complex at proximal centriole ends during interphase. Centlein functions as a molecular bridge between C-Nap1 and CEP68; depletion of centlein impairs CEP68 recruitment to centrosomes and causes centrosome splitting. Both centlein and CEP68 are substrates of Nek2A.\",\n      \"method\": \"Co-immunoprecipitation, in vitro binding assay, siRNA knockdown, immunofluorescence, in vitro kinase assay\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — direct binding demonstrated in vitro plus functional epistasis via depletion, replicated with multiple methods\",\n      \"pmids\": [\"24554434\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"STED super-resolution microscopy revealed that C-Nap1 rings at the proximal ends of centrioles organize rootletin rings and multiple rootletin/CEP68 fibers. Rootletin/CEP68 fibers from two centrosomes form an interdigitating network; rootletin binds CEP68 via its C-terminal spectrin repeat-containing region at 75-nm intervals. CEP68 is required for the branching of rootletin filaments from centrioles and modulates the thickness of rootletin fibers.\",\n      \"method\": \"STED nanoscopy, immunofluorescence, siRNA knockdown, co-immunoprecipitation\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — structural resolution by STED combined with interaction mapping and functional knockdown, replicated across multiple experiments\",\n      \"pmids\": [\"29463719\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"The C-terminal 300–400 amino acids of Cep68 are necessary for localization to interphase centrosomes, while the C-terminal 400–500 amino acid region regulates Cep68 dissociation at mitotic onset. Nek2 phosphorylates Cep68 in vivo to promote its degradation in mitosis, and the SCF complex, through the βTrCP F-box subunit, targets Cep68 for destruction at mitosis.\",\n      \"method\": \"Truncation mutagenesis, immunofluorescence, in vivo phosphorylation assay, co-immunoprecipitation\",\n      \"journal\": \"European journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — in vivo phosphorylation and domain mapping experiments; single lab study\",\n      \"pmids\": [\"25704143\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Rootletin prevents CEP68 from VHL-mediated proteasomal degradation to maintain centrosome cohesion. The VHL E3 ligase complex ubiquitinates CEP68 in vitro and in vivo; loss of rootletin triggers VHL-dependent CEP68 degradation and centrosome splitting. Co-silencing of rootletin and VHL reverses CEP68 loss, and a stable Cep68 mutant that cannot be polyubiquitinated or cannot bind the β-domain of VHL suppresses centrosome splitting caused by rootletin depletion.\",\n      \"method\": \"In vitro ubiquitination assay, siRNA knockdown, immunofluorescence, site-directed mutagenesis, co-immunoprecipitation\",\n      \"journal\": \"Biochimica et biophysica acta. Molecular cell research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — in vitro ubiquitination reconstitution, genetic epistasis via double knockdown, and mutagenesis validation in a single study\",\n      \"pmids\": [\"28089774\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"MCM7 directly binds CEP68 in vitro and forms a complex with CEP68 and VHL in vivo. MCM7 overexpression facilitates the CEP68–VHL interaction, promoting CEP68 ubiquitination and proteasomal degradation, leading to centrosome splitting. Absence of MCM7 weakens CEP68–VHL interaction.\",\n      \"method\": \"In vitro binding assay, co-immunoprecipitation, overexpression, siRNA knockdown, immunofluorescence, ubiquitination assay\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — direct binding confirmed in vitro and in vivo with functional consequence; single lab study\",\n      \"pmids\": [\"28578000\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CEP68 is a centrosomal linker protein that localizes to proximal centriole-associated rootletin fibers during interphase as part of a C-Nap1–centlein–CEP68 complex; it modulates rootletin fiber architecture to maintain centrosome cohesion, and is regulated by Nek2-mediated phosphorylation and PLK1-initiated SCF(βTrCP)-dependent ubiquitin-proteasomal degradation at mitotic entry, while rootletin protects CEP68 from VHL-mediated degradation in interphase, with CEP68 levels controlling downstream Cep215 and PCNT interactions required for centriole engagement and duplication licensing.\"\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\nI'll classify each paper first, then extract discoveries from KEPT papers.\n\n**Classification:**\n\n**KEEP (CEP68 = centrosomal protein of 68 kDa):**\n- [1] PMID:18042621 — Graser et al., foundational CEP68 centrosome cohesion paper ✓\n- [2] PMID:25503564 — Pagan et al., CEP68 degradation/SCF/PLK1 ✓\n- [3] PMID:21072201 — GWAS on CEP68 variants (expression-based, exclude for mechanism)\n- [4] PMID:24554434 — Centlein/C-Nap1/Cep68 complex ✓\n- [5] PMID:29463719 — STED nanoscopy of centrosome linker with CEP68 ✓\n- [8] PMID:25704143 — Nek2/SCF regulation of Cep68 ✓\n- [10] PMID:28089774 — Rootletin/VHL/Cep68 ✓\n- [12] PMID:28578000 — MCM7/Cep68/VHL ✓\n- [13] PMID:41683918 — AF/CEP68 (GWAS/expression, no mechanism) → EXCLUDE\n\n**EXCLUDE (alias collision — CEP-68 = CRTAC1, chondrocyte expressed protein-68):**\n- [7] PMID:11139377 — CEP-68 = chondrocyte marker (CRTAC1) ✗\n- [6] PMID:17570516 — KIAA0582 phosphoproteomics (not CEP68) ✗\n- [9] PMID:24618698 — NSAID/CEP68 GWAS (no mechanism) ✗\n- [11] PMID:30093714 — NSAID/CEP68 GWAS (no mechanism) ✗\n\n**ADDITIONAL papers — mostly CRTAC1 alias collision or unrelated GWAS:**\n- All additional gene2pubmed papers are either about CRTAC1 (chondrocyte/OA biomarker), large-scale cDNA/interactome databases, or completely unrelated topics → EXCLUDE for mechanistic extraction\n\n```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2007,\n      \"finding\": \"CEP68 localizes to fibres emanating from the proximal ends of centrioles during interphase and dissociates from centrosomes at mitosis. CEP68 depends on both rootletin and C-Nap1 for centriole association, and depletion of CEP68 causes premature centrosome separation (splitting). Overexpressed CEP68 is recruited to ectopic rootletin fibres but does not itself induce extensive fibre formation, indicating CEP68 cooperates with rootletin and C-Nap1 in maintaining centrosome cohesion.\",\n      \"method\": \"Immunofluorescence microscopy, siRNA depletion with centrosome-splitting phenotype readout, overexpression and co-localization assays, reciprocal dependency experiments\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (localization, KD phenotype, co-localization dependency), foundational paper replicated by subsequent studies\",\n      \"pmids\": [\"18042621\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"CEP68 forms a trimeric complex with CEP215 (CDK5RAP2) and pericentrin (PCNT) at the pericentriolar material. CEP68 is degraded in prometaphase via the SCF(βTrCP) ubiquitin ligase; this degradation is initiated by PLK1 phosphorylation of CEP68 on Ser332, which creates a phosphodegron recognized by βTrCP. CEP68 degradation removes CEP215 from the peripheral PCM, which is required to prevent centriole separation following disengagement, thereby licensing centrioles for duplication.\",\n      \"method\": \"Co-immunoprecipitation, mass spectrometry interactome, siRNA depletion, phosphosite mutagenesis, in vivo ubiquitination assay, PLK1 kinase assay\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods including kinase assay, mutagenesis of phosphodegron, ubiquitination assay, and Co-IP in a single rigorous study\",\n      \"pmids\": [\"25503564\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Centlein (CNTLN) directly interacts with both C-Nap1 and CEP68 and functions as a molecular bridge between them at the proximal ends of centrioles during interphase. Depletion of centlein impairs CEP68 recruitment to centrosomes and causes centrosome splitting. Both centlein and CEP68 are substrates of the mitotic kinase Nek2A, placing CEP68 downstream of Nek2A in the cohesion-dissolution pathway.\",\n      \"method\": \"Co-immunoprecipitation, direct binding (GST pulldown), siRNA depletion with centrosome-splitting readout, Nek2A in vitro kinase assay, immunofluorescence\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — direct binding demonstrated by pulldown, kinase assay, epistatic siRNA phenotype, multiple methods in one study\",\n      \"pmids\": [\"24554434\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"The C-terminal 300–400 amino acids of CEP68 are necessary for its localization to interphase centrosomes, while the C-terminal 400–500 amino acid region regulates its dissociation at mitotic onset. Nek2 phosphorylates CEP68 in vivo and this phosphorylation promotes CEP68 degradation. The SCF(βTrCP) complex mediates CEP68 destruction at mitosis through βTrCP recognition.\",\n      \"method\": \"Domain deletion mapping with immunofluorescence, in vivo phosphorylation assays, co-immunoprecipitation with SCF components, cell-cycle-staged degradation assays\",\n      \"journal\": \"European journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — domain mapping and in vivo phosphorylation, single lab, partially corroborates PMID:25503564\",\n      \"pmids\": [\"25704143\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Rootletin protects CEP68 from proteasomal degradation by inhibiting VHL-mediated ubiquitination. In the absence of rootletin, the VHL E3 ligase complex ubiquitinates CEP68 in vitro and in vivo, leading to its degradation and centrosome splitting. Co-depletion of rootletin and VHL rescues CEP68 levels and centrosome cohesion. A CEP68 mutant that cannot bind the β-domain of VHL or cannot be polyubiquitinated also suppresses centrosome splitting caused by rootletin depletion.\",\n      \"method\": \"siRNA double knockdown epistasis, in vitro ubiquitination assay with VHL E3 complex, in vivo ubiquitination assay, stable CEP68 mutant rescue experiments, immunofluorescence\",\n      \"journal\": \"Biochimica et biophysica acta. Molecular cell research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro ubiquitination reconstitution, epistatic double-KD rescue, mutagenesis rescue, multiple orthogonal approaches in one study\",\n      \"pmids\": [\"28089774\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"MCM7 directly binds CEP68 in vitro and forms a ternary complex with CEP68 and VHL in vivo. MCM7 depletion weakens the CEP68-VHL interaction, whereas MCM7 overexpression facilitates CEP68-VHL association, increasing CEP68 ubiquitination and proteasomal degradation, resulting in centrosome splitting. This identifies MCM7 as a positive regulator of VHL-mediated CEP68 degradation at the centrosome.\",\n      \"method\": \"GST pulldown (direct binding), co-immunoprecipitation, siRNA depletion, overexpression, in vivo ubiquitination assay, immunofluorescence centrosome-splitting assay\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — direct binding by pulldown, Co-IP, and functional ubiquitination data, single lab\",\n      \"pmids\": [\"28578000\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Super-resolution STED microscopy revealed that CEP68 co-localizes with rootletin in periodic filaments that branch off centrioles and form a web-like interdigitating network between the two centrosomes. Rootletin binds CEP68 via its C-terminal spectrin repeat-containing region at 75-nm intervals along the filament. CEP68 is required for forming rootletin filaments that branch off centrioles and for modulating the thickness of rootletin fibers, acting as a filament modulator within a C-Nap1-anchored, periodically ordered centrosome linker network.\",\n      \"method\": \"STED super-resolution microscopy, structured illumination microscopy, siRNA depletion, co-immunoprecipitation to map rootletin-CEP68 binding domain, immunofluorescence\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — STED nanoscopy provides structural resolution, combined with domain-mapping Co-IP and functional depletion, strong mechanistic resolution\",\n      \"pmids\": [\"29463719\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CEP68 is an interphase centrosome cohesion protein that localizes to periodic rootletin filaments anchored to C-Nap1 rings at centriole proximal ends, where it modulates filament branching and thickness; cohesion is maintained through a C-Nap1–centlein–CEP68–rootletin complex, and CEP68 protein levels are controlled by two antagonistic mechanisms—rootletin-mediated protection from VHL E3 ligase-dependent ubiquitination/degradation during interphase, and PLK1 phosphorylation of Ser332 triggering SCF(βTrCP)-mediated degradation in prometaphase, which releases CEP215 from the peripheral PCM to permit centriole separation, disengagement, and licensing for duplication.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"CEP68 is a centrosomal linker protein essential for maintaining centrosome cohesion during interphase and whose regulated destruction at mitotic entry licenses centriole separation. It localizes to rootletin fibers emanating from proximal centriole ends as part of a C-Nap1–centlein–CEP68 complex, where it promotes rootletin fiber branching and modulates fiber thickness to form an interdigitating network between the two centrosomes [PMID:18042621, PMID:24554434, PMID:29463719]. CEP68 stability is governed by two opposing ubiquitin ligase pathways: rootletin shields CEP68 from VHL-mediated degradation in interphase, while PLK1 phosphorylation of Ser332 at mitotic entry creates a phosphodegron recognized by SCF(βTrCP), triggering CEP68 destruction and consequent removal of Cep215 from the peripheral pericentriolar material to prevent premature centriole separation [PMID:25503564, PMID:28089774]. CEP68 additionally forms complexes with Cep215 and pericentrin, linking centrosome cohesion to centriole engagement and duplication licensing [PMID:25503564].\",\n  \"teleology\": [\n    {\n      \"year\": 2007,\n      \"claim\": \"Establishing that CEP68 is a centrosomal linker protein answered the question of what structural components beyond rootletin and C-Nap1 maintain centrosome cohesion in interphase.\",\n      \"evidence\": \"Immunofluorescence and siRNA knockdown in human cells showed mutual dependency of CEP68, rootletin, and C-Nap1 for centriole localization, with CEP68 depletion causing centrosome splitting\",\n      \"pmids\": [\"18042621\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Mechanism by which CEP68 physically connects to rootletin fibers was unknown\",\n        \"How CEP68 dissociates from centrosomes at mitosis was not addressed\",\n        \"Whether CEP68 has functions beyond structural cohesion was unexplored\"\n      ]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Identification of centlein as a molecular bridge between C-Nap1 and CEP68 resolved how CEP68 is recruited to proximal centriole ends and placed Nek2A as a kinase acting on both linker components.\",\n      \"evidence\": \"In vitro binding assays and co-IP showed direct centlein–C-Nap1 and centlein–CEP68 interactions; centlein depletion impaired CEP68 recruitment and caused splitting; in vitro kinase assay confirmed Nek2A phosphorylation of centlein and CEP68\",\n      \"pmids\": [\"24554434\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Specific Nek2A phosphorylation sites on CEP68 and their functional consequences were not mapped\",\n        \"Whether additional adaptors contribute to CEP68 recruitment was not tested\"\n      ]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Demonstrating that PLK1-dependent phosphorylation of CEP68 Ser332 creates a βTrCP phosphodegron answered how CEP68 is eliminated at mitotic entry and revealed that CEP68 degradation controls Cep215 retention and centriole engagement.\",\n      \"evidence\": \"In vitro phosphorylation, ubiquitination assays, site-directed mutagenesis, co-IP, and functional knockdown in human cells\",\n      \"pmids\": [\"25503564\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether PLK1 and Nek2 pathways act sequentially or in parallel on CEP68 was not resolved\",\n        \"Structural basis of CEP68–Cep215 interaction was not determined\"\n      ]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Domain mapping of CEP68 resolved which regions govern interphase centrosomal localization versus mitotic dissociation, and confirmed Nek2 as an in vivo kinase promoting CEP68 degradation.\",\n      \"evidence\": \"Truncation mutagenesis, in vivo phosphorylation assay, and co-IP in human cells\",\n      \"pmids\": [\"25704143\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Precise Nek2 phosphorylation sites were not identified\",\n        \"Functional relationship between the C-terminal localization domain and rootletin binding was not established\",\n        \"Single-lab study without independent replication\"\n      ]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Discovery that rootletin protects CEP68 from VHL-mediated ubiquitination established an interphase stabilization mechanism opposing mitotic degradation, explaining how centrosome cohesion is actively maintained.\",\n      \"evidence\": \"In vitro ubiquitination reconstitution, double-knockdown epistasis (rootletin + VHL), and non-degradable CEP68 mutant rescue of centrosome splitting\",\n      \"pmids\": [\"28089774\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Mechanism by which rootletin physically shields CEP68 from VHL access was not defined\",\n        \"VHL ubiquitination sites on CEP68 were not fully mapped\"\n      ]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Identification of MCM7 as a facilitator of the CEP68–VHL interaction linked the replication licensing machinery to centrosome cohesion regulation.\",\n      \"evidence\": \"In vitro binding, co-IP, and overexpression/knockdown of MCM7 modulating CEP68 ubiquitination and centrosome splitting in human cells\",\n      \"pmids\": [\"28578000\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Single-lab finding without independent confirmation\",\n        \"Physiological context in which MCM7 promotes VHL-dependent CEP68 degradation (e.g., cell cycle stage) was not defined\",\n        \"Whether MCM7 acts as part of the MCM2-7 complex or independently in this context is unknown\"\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Super-resolution imaging resolved the nanoscale architecture of rootletin/CEP68 fibers, showing that CEP68 decorates rootletin at 75-nm intervals and is required for fiber branching, answering how the interdigitating linker network is organized.\",\n      \"evidence\": \"STED nanoscopy combined with siRNA knockdown and co-IP in human cells\",\n      \"pmids\": [\"29463719\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Molecular determinants of the 75-nm periodicity are unknown\",\n        \"How CEP68 promotes branching at the molecular level is not resolved\",\n        \"Whether the interdigitating network architecture is conserved across cell types was not tested\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unknown how the dual ubiquitin ligase regulation (VHL in interphase, SCF-βTrCP at mitosis) is temporally coordinated, what structural features of CEP68 mediate rootletin-dependent protection from VHL, and whether CEP68 has functions beyond centrosome cohesion.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"No high-resolution structural model of CEP68 or its complexes exists\",\n        \"Relationship between Nek2 and PLK1 phosphorylation events on CEP68 is unresolved\",\n        \"Potential roles of CEP68 in ciliogenesis or signaling have not been investigated\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 4]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005815\", \"supporting_discovery_ids\": [0, 3, 4]},\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [1, 5]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [1, 6]}\n    ],\n    \"complexes\": [\n      \"C-Nap1–centlein–CEP68 linker complex\"\n    ],\n    \"partners\": [\n      \"CROCC\",\n      \"CEP250\",\n      \"CNTLN\",\n      \"CDK5RAP2\",\n      \"PCNT\",\n      \"VHL\",\n      \"MCM7\",\n      \"BTRC\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\n```json\n{\n  \"mechanistic_narrative\": \"CEP68 is a centrosome-linker protein that maintains interphase centrosome cohesion by associating with periodic rootletin filaments anchored via C-Nap1 rings at centriole proximal ends, where it modulates filament branching and thickness [PMID:18042621, PMID:29463719]. CEP68 is recruited to centrosomes through a C-Nap1–centlein–CEP68–rootletin complex, with centlein acting as a molecular bridge between C-Nap1 and CEP68 [PMID:24554434]. During interphase, rootletin protects CEP68 from VHL E3 ligase-dependent ubiquitination and proteasomal degradation, while at mitotic entry PLK1 phosphorylation of CEP68 Ser332 generates a phosphodegron recognized by SCF(βTrCP), triggering CEP68 destruction that releases CEP215 from the peripheral pericentriolar material and permits centriole separation and duplication licensing [PMID:25503564, PMID:28089774]. MCM7 facilitates CEP68 degradation by promoting the CEP68–VHL interaction, providing an additional regulatory input into centrosome cohesion control [PMID:28578000].\",\n  \"teleology\": [\n    {\n      \"year\": 2007,\n      \"claim\": \"The identification of CEP68 as a rootletin- and C-Nap1-dependent interphase centrosome protein whose depletion causes premature centrosome splitting established it as a new component of the centrosome cohesion machinery.\",\n      \"evidence\": \"Immunofluorescence, siRNA depletion with splitting phenotype, co-localization dependency experiments in human cells\",\n      \"pmids\": [\"18042621\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"How CEP68 is physically linked to C-Nap1 was unknown\",\n        \"The mitotic mechanism removing CEP68 from centrosomes was uncharacterized\",\n        \"Whether CEP68 has a structural versus signaling role in centrosome cohesion was unclear\"\n      ]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Two studies resolved how CEP68 connects to the cohesion network and how it is eliminated at mitosis: centlein bridges C-Nap1 to CEP68, while PLK1 phosphorylation of CEP68 Ser332 creates a βTrCP phosphodegron that triggers SCF-mediated degradation in prometaphase, thereby releasing CEP215 from the PCM to allow centriole separation and duplication licensing.\",\n      \"evidence\": \"Co-IP, GST pulldown for direct centlein–CEP68 binding, Nek2A kinase assay, PLK1 phosphosite mutagenesis, in vivo ubiquitination assays, epistatic siRNA experiments\",\n      \"pmids\": [\"24554434\", \"25503564\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"How CEP68 protein stability is maintained during interphase was not addressed\",\n        \"The structural arrangement of CEP68 within rootletin filaments was unresolved\",\n        \"Whether additional E3 ligases regulate CEP68 outside mitosis was unknown\"\n      ]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Domain-mapping clarified that the C-terminal 300–500 amino acids control both interphase centrosome targeting and mitotic dissociation, and confirmed Nek2-dependent phosphorylation promotes CEP68 degradation via SCF(βTrCP).\",\n      \"evidence\": \"Deletion mapping with immunofluorescence, in vivo phosphorylation assays, Co-IP with SCF components, cell-cycle-staged degradation assays\",\n      \"pmids\": [\"25704143\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Precise phosphosites targeted by Nek2 on CEP68 were not mapped at single-residue resolution\",\n        \"The relative contributions of PLK1 versus Nek2 to mitotic CEP68 degradation remained unresolved\"\n      ]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Discovery that rootletin protects CEP68 from VHL-mediated ubiquitination during interphase, and that MCM7 promotes the CEP68–VHL interaction, revealed a dual-layer regulation of CEP68 stability: rootletin shields CEP68 from VHL, while MCM7 enhances VHL-dependent degradation.\",\n      \"evidence\": \"In vitro ubiquitination reconstitution with VHL complex, epistatic siRNA double knockdown rescuing cohesion, VHL-binding-deficient CEP68 mutants, GST pulldown for MCM7–CEP68 direct binding, overexpression/depletion of MCM7\",\n      \"pmids\": [\"28089774\", \"28578000\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"How rootletin physically occludes VHL access to CEP68 is structurally uncharacterized\",\n        \"The physiological context in which MCM7 acts at centrosomes versus its canonical replication role is unclear\",\n        \"Whether VHL and SCF(βTrCP) act on the same or different CEP68 pools is unresolved\"\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"STED super-resolution imaging revealed that CEP68 decorates rootletin filaments at 75-nm periodic intervals and is required for filament branching and thickness control, establishing CEP68 as a structural modulator of the centrosome linker rather than merely a passive component.\",\n      \"evidence\": \"STED and structured illumination microscopy, domain-mapping Co-IP for rootletin spectrin repeat–CEP68 interaction, siRNA depletion\",\n      \"pmids\": [\"29463719\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Atomic-resolution structure of the CEP68–rootletin interface is lacking\",\n        \"Whether CEP68 periodicity is self-determined or templated by rootletin is unknown\",\n        \"Functional consequences of altered filament branching for cell division fidelity have not been tested\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key open questions include the structural basis of CEP68's periodic binding to rootletin, the interplay between VHL- and SCF(βTrCP)-dependent degradation pathways during the cell cycle, and whether CEP68 loss or mutation has consequences for tissue-level physiology or disease.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"No atomic or cryo-EM structure exists for CEP68 or its complexes\",\n        \"No in vivo animal model phenotype has been reported\",\n        \"Relative timing and coordination of VHL versus SCF(βTrCP) pathways across the cell cycle is unresolved\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 6]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [0, 6]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005815\", \"supporting_discovery_ids\": [0, 1, 2, 3, 6]},\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [6]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [1, 3]},\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [0, 6]}\n    ],\n    \"complexes\": [\n      \"C-Nap1–centlein–CEP68–rootletin linker complex\",\n      \"CEP68–CEP215–pericentrin PCM complex\"\n    ],\n    \"partners\": [\n      \"CROCC\",\n      \"CEP250\",\n      \"CNTLN\",\n      \"CDK5RAP2\",\n      \"PCNT\",\n      \"VHL\",\n      \"BTRC\",\n      \"MCM7\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}