{"gene":"CCDC181","run_date":"2026-06-09T22:57:17","timeline":{"discoveries":[{"year":2017,"finding":"Ccdc181 interacts with Hook1 in haploid male germ cells, as determined by yeast two-hybrid screen and verified by FRET analysis; interacting regions were mapped using yeast two-hybrid assays.","method":"Yeast two-hybrid screen, FRET analysis","journal":"European journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — interaction confirmed by two orthogonal methods (Y2H + FRET), single lab","pmids":["28283191"],"is_preprint":false},{"year":2017,"finding":"Ccdc181 binds directly to microtubules and localizes to the microtubular manchette of elongating spermatids, resembling the localization of Hook1.","method":"Microtubule-binding assay, immunostaining/fluorescence microscopy","journal":"European journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct microtubule binding assay plus immunolocalization, single lab","pmids":["28283191"],"is_preprint":false},{"year":2017,"finding":"Ccdc181 localizes to the sperm flagella and to the basal half of motile cilia but was not detected in primary non-motile cilia, indicating a motile cilia-specific localization.","method":"Immunofluorescence microscopy","journal":"European journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — immunolocalization with negative control (primary cilia), single lab","pmids":["28283191"],"is_preprint":false},{"year":2017,"finding":"Ccdc181 is a putative interacting partner of different catalytic subunits of protein phosphatase 1 (Pp1), suggesting a role in mediating ciliary motility.","method":"Yeast two-hybrid assay (interaction with Pp1 catalytic subunits)","journal":"European journal of cell biology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single Y2H result, not confirmed by orthogonal method, single lab","pmids":["28283191"],"is_preprint":false},{"year":2017,"finding":"CCDC181 is identified as a high-abundance protein in human airway cilia axonemes, with unique axonemal localization confirmed by immunoblotting and fluorescence microscopy, and cilia-specific expression confirmed by RT-PCR.","method":"Label-free LC/MSE quantitative proteomics, immunoblotting, RT-PCR, fluorescence microscopy","journal":"Journal of proteome research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (proteomics, immunoblot, RT-PCR, microscopy) in single study","pmids":["28282151"],"is_preprint":false},{"year":2024,"finding":"Ccdc181 knockout mice display defective sperm head shaping, flagellum formation, extremely low sperm counts, grossly aberrant sperm morphologies, markedly diminished sperm motility, and multiple morphological abnormalities of the flagella (MMAF), establishing that CCDC181 is required for manchette formation and sperm flagellum biogenesis.","method":"Knockout mouse model, sperm morphology and motility analysis","journal":"Zoological research","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO with defined cellular phenotype, multiple orthogonal readouts (count, motility, morphology, ultrastructure)","pmids":["39245650"],"is_preprint":false},{"year":2024,"finding":"CCDC181 interacts with the MMAF-related protein LRRC46 and regulates LRRC46 localization within sperm flagella.","method":"Co-immunoprecipitation, immunofluorescence localization in KO vs. wild-type","journal":"Zoological research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus functional localization assay in KO model, single lab","pmids":["39245650"],"is_preprint":false},{"year":2024,"finding":"CCDC181 interacts with the chaperonin subunit CCTβ (CCT2), and CCDC181 localization to photoreceptor connecting cilia is compromised in CCT2 compound heterozygous mutant mice, indicating CCTβ is required for proper CCDC181 ciliary localization.","method":"Co-immunoprecipitation (CCDC181 as CCTβ interacting protein), immunofluorescence in mutant mouse retina","journal":"Communications biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP for interaction, immunofluorescence in vivo model for functional consequence, single lab","pmids":["38830954"],"is_preprint":false},{"year":2021,"finding":"Bovine CCDC181 directly interacts with Theileria annulata SVSP454 parasite protein, as identified by yeast two-hybrid screening and confirmed by co-immunoprecipitation and bimolecular fluorescence complementation (BiFC) assays.","method":"Yeast two-hybrid, co-immunoprecipitation, BiFC","journal":"Parasites & vectors","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — interaction confirmed by three orthogonal methods, but relevance to mammalian CCDC181 function is indirect (parasite interaction context)","pmids":["34116718"],"is_preprint":false}],"current_model":"CCDC181 is a coiled-coil domain-containing, microtubule-binding protein that is a major structural component of motile cilia axonemes and sperm flagella; it interacts with Hook1 and LRRC46 to regulate manchette integrity and flagellum biogenesis (loss causes MMAF and male infertility in mice), localizes specifically to the basal half of motile cilia but not primary cilia, and requires the CCTβ chaperonin for proper ciliary localization."},"narrative":{"mechanistic_narrative":"CCDC181 is a coiled-coil, microtubule-binding protein that functions as a structural component of motile cilia axonemes and sperm flagella and is required for sperm head shaping and flagellum biogenesis [PMID:39245650]. In elongating spermatids it binds directly to microtubules and localizes to the manchette, mirroring the distribution of its interaction partner Hook1 [PMID:28283191]. CCDC181 displays motile cilia-specific localization, concentrating in the basal half of motile cilia and in sperm flagella but absent from primary non-motile cilia, and is a high-abundance constituent of human airway cilia axonemes [PMID:28283191, PMID:28282151]. Loss of Ccdc181 in mice produces defective manchette formation, grossly aberrant sperm morphology, extremely low sperm counts, and multiple morphological abnormalities of the flagella (MMAF) with male infertility [PMID:39245650]. Mechanistically, CCDC181 interacts with the MMAF-related protein LRRC46 and governs its correct localization within the flagellum [PMID:39245650], and its own targeting to the connecting cilium depends on the chaperonin subunit CCTβ (CCT2) [PMID:38830954].","teleology":[{"year":2017,"claim":"Established the first molecular partners and binding activity of CCDC181, defining it as a microtubule-binding manchette protein in male germ cells.","evidence":"Yeast two-hybrid screen and FRET for Hook1 interaction, microtubule-binding assay and immunostaining in elongating spermatids","pmids":["28283191"],"confidence":"Medium","gaps":["Functional consequence of the Hook1 interaction not tested","Microtubule-binding domain not mapped structurally"]},{"year":2017,"claim":"Defined CCDC181 as a motile cilia-specific protein by showing localization to sperm flagella and the basal half of motile cilia but not primary cilia.","evidence":"Immunofluorescence microscopy with primary cilia as negative control","pmids":["28283191"],"confidence":"Medium","gaps":["Basis for basal-half restriction within motile cilia unexplained","No mechanism for motile- vs primary-cilia discrimination"]},{"year":2017,"claim":"Proposed a link between CCDC181 and ciliary motility regulation via candidate phosphatase partners.","evidence":"Yeast two-hybrid interaction with Pp1 catalytic subunits","pmids":["28283191"],"confidence":"Low","gaps":["Single Y2H result not confirmed by orthogonal method","No functional readout connecting CCDC181 to Pp1-dependent motility"]},{"year":2017,"claim":"Independently confirmed CCDC181 as an abundant, cilia-specific axonemal protein in human airway tissue, extending its relevance beyond germ cells.","evidence":"Label-free quantitative proteomics, immunoblotting, RT-PCR, and fluorescence microscopy of airway cilia","pmids":["28282151"],"confidence":"Medium","gaps":["Substructural axonemal position not resolved","No functional perturbation in airway cilia"]},{"year":2024,"claim":"Provided causal in vivo evidence that CCDC181 is required for manchette formation, sperm flagellum biogenesis, and male fertility.","evidence":"Knockout mouse with sperm count, motility, morphology, and ultrastructure analyses","pmids":["39245650"],"confidence":"High","gaps":["Molecular pathway from microtubule binding to manchette assembly not detailed","No human patient mutation linkage shown"]},{"year":2024,"claim":"Connected CCDC181 to the broader MMAF protein network by showing it controls LRRC46 localization in the flagellum.","evidence":"Co-immunoprecipitation and immunofluorescence comparing KO vs wild-type flagella","pmids":["39245650"],"confidence":"Medium","gaps":["Reciprocal dependence (LRRC46 effect on CCDC181) not tested","Direct vs indirect interaction not resolved"]},{"year":2024,"claim":"Identified a chaperonin requirement for CCDC181 trafficking, showing CCTβ (CCT2) is needed for its ciliary localization.","evidence":"Co-immunoprecipitation and immunofluorescence in CCT2 compound heterozygous mutant mouse retina","pmids":["38830954"],"confidence":"Medium","gaps":["Whether CCTβ folds CCDC181 or transports it not distinguished","Effect on motile cilia (vs connecting cilia) not assessed"]},{"year":null,"claim":"The molecular mechanism by which CCDC181 directs manchette and axoneme assembly, and any link to human ciliopathy or infertility mutations, remains undefined.","evidence":"","pmids":[],"confidence":"Low","gaps":["No structural model of microtubule or partner binding","No human disease mutation identified in the corpus","Mechanistic role of candidate Pp1 partners unresolved"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[1]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[4,5]}],"localization":[{"term_id":"GO:0005929","term_label":"cilium","supporting_discovery_ids":[2,4]},{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[1]}],"pathway":[{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[5]},{"term_id":"R-HSA-1474165","term_label":"Reproduction","supporting_discovery_ids":[5]}],"complexes":[],"partners":["HOOK1","LRRC46","CCT2","PPP1CC"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q5TID7","full_name":"Coiled-coil domain-containing protein 181","aliases":[],"length_aa":509,"mass_kda":60.1,"function":"Microtubule-binding protein that is essential for the integrity and function of the manchette, facilitating proper sperm head shaping and subsequent flagellum formation during spermatogenesis","subcellular_location":"Cytoplasm, cytoskeleton; Cell projection, cilium, flagellum; Cell projection, cilium; Cytoplasm, cytoskeleton, cilium axoneme","url":"https://www.uniprot.org/uniprotkb/Q5TID7/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CCDC181","classification":"Not Classified","n_dependent_lines":8,"n_total_lines":1208,"dependency_fraction":0.006622516556291391},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/CCDC181","total_profiled":1310},"omim":[{"mim_id":"620891","title":"COILED-COIL DOMAIN-CONTAINING PROTEIN 181; CCDC181","url":"https://www.omim.org/entry/620891"},{"mim_id":"605139","title":"CHAPERONIN CONTAINING T-COMPLEX POLYPEPTIDE 1, SUBUNIT 2; CCT2","url":"https://www.omim.org/entry/605139"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nuclear speckles","reliability":"Approved"},{"location":"Acrosome","reliability":"Approved"},{"location":"Mid piece","reliability":"Approved"},{"location":"Principal piece","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"choroid plexus","ntpm":30.6},{"tissue":"retina","ntpm":37.0},{"tissue":"testis","ntpm":24.6}],"url":"https://www.proteinatlas.org/search/CCDC181"},"hgnc":{"alias_symbol":["FLJ25846"],"prev_symbol":["C1orf114"]},"alphafold":{"accession":"Q5TID7","domains":[],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q5TID7","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q5TID7-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q5TID7-F1-predicted_aligned_error_v6.png","plddt_mean":67.62},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CCDC181","jax_strain_url":"https://www.jax.org/strain/search?query=CCDC181"},"sequence":{"accession":"Q5TID7","fasta_url":"https://rest.uniprot.org/uniprotkb/Q5TID7.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q5TID7/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q5TID7"}},"corpus_meta":[{"pmid":"23918943","id":"PMC_23918943","title":"DNA methylation signatures for prediction of biochemical recurrence after radical prostatectomy of clinically localized prostate cancer.","date":"2013","source":"Journal of clinical oncology : official journal of the American Society of Clinical Oncology","url":"https://pubmed.ncbi.nlm.nih.gov/23918943","citation_count":116,"is_preprint":false},{"pmid":"28282151","id":"PMC_28282151","title":"Quantitative Proteomic Analysis of Human Airway Cilia Identifies Previously Uncharacterized Proteins of High Abundance.","date":"2017","source":"Journal of proteome research","url":"https://pubmed.ncbi.nlm.nih.gov/28282151","citation_count":69,"is_preprint":false},{"pmid":"31558162","id":"PMC_31558162","title":"Methylation and transcriptome analysis reveal lung adenocarcinoma-specific diagnostic biomarkers.","date":"2019","source":"Journal of translational medicine","url":"https://pubmed.ncbi.nlm.nih.gov/31558162","citation_count":63,"is_preprint":false},{"pmid":"29465788","id":"PMC_29465788","title":"Biomarker potential of ST6GALNAC3 and ZNF660 promoter hypermethylation in prostate cancer tissue and liquid biopsies.","date":"2018","source":"Molecular oncology","url":"https://pubmed.ncbi.nlm.nih.gov/29465788","citation_count":56,"is_preprint":false},{"pmid":"28283191","id":"PMC_28283191","title":"Ccdc181 is a microtubule-binding protein that interacts with Hook1 in haploid male germ cells and localizes to the sperm tail and motile cilia.","date":"2017","source":"European journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/28283191","citation_count":41,"is_preprint":false},{"pmid":"30070359","id":"PMC_30070359","title":"Discovery and development of differentially methylated regions in human papillomavirus-related oropharyngeal squamous cell carcinoma.","date":"2018","source":"International journal of cancer","url":"https://pubmed.ncbi.nlm.nih.gov/30070359","citation_count":41,"is_preprint":false},{"pmid":"28084441","id":"PMC_28084441","title":"Heterogeneous patterns of DNA methylation-based field effects in histologically normal prostate tissue from cancer patients.","date":"2017","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/28084441","citation_count":31,"is_preprint":false},{"pmid":"31433512","id":"PMC_31433512","title":"A three-gene DNA methylation biomarker accurately classifies early stage prostate cancer.","date":"2019","source":"The Prostate","url":"https://pubmed.ncbi.nlm.nih.gov/31433512","citation_count":25,"is_preprint":false},{"pmid":"34198725","id":"PMC_34198725","title":"Promoter Methylation of PRKCB, ADAMTS12, and NAALAD2 Is Specific to Prostate Cancer and Predicts Biochemical Disease Recurrence.","date":"2021","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/34198725","citation_count":22,"is_preprint":false},{"pmid":"33803633","id":"PMC_33803633","title":"Automatic Detection of the Circulating Cell-Free Methylated DNA Pattern of GCM2, ITPRIPL1 and CCDC181 for Detection of Early Breast Cancer and Surgical Treatment Response.","date":"2021","source":"Cancers","url":"https://pubmed.ncbi.nlm.nih.gov/33803633","citation_count":17,"is_preprint":false},{"pmid":"31666119","id":"PMC_31666119","title":"DNA methylation in repeat negative prostate biopsies as a marker of missed prostate cancer.","date":"2019","source":"Clinical epigenetics","url":"https://pubmed.ncbi.nlm.nih.gov/31666119","citation_count":12,"is_preprint":false},{"pmid":"37628841","id":"PMC_37628841","title":"Methylation Profile of Small Breast Cancer Tumors Evaluated by Modified MS-HRM.","date":"2023","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/37628841","citation_count":9,"is_preprint":false},{"pmid":"30218172","id":"PMC_30218172","title":"DNA methylation marker to estimate the breast cancer cell fraction in DNA samples.","date":"2018","source":"Medical oncology (Northwood, London, England)","url":"https://pubmed.ncbi.nlm.nih.gov/30218172","citation_count":6,"is_preprint":false},{"pmid":"34116718","id":"PMC_34116718","title":"Screening and identification of Theileria annulata subtelomere-encoded variable secreted protein-950454 (SVSP454) interacting proteins from bovine B cells.","date":"2021","source":"Parasites & vectors","url":"https://pubmed.ncbi.nlm.nih.gov/34116718","citation_count":3,"is_preprint":false},{"pmid":"38830954","id":"PMC_38830954","title":"Compound heterozygous mutations in a mouse model of Leber congenital amaurosis reveal the role of CCT2 in photoreceptor maintenance.","date":"2024","source":"Communications biology","url":"https://pubmed.ncbi.nlm.nih.gov/38830954","citation_count":3,"is_preprint":false},{"pmid":"39245650","id":"PMC_39245650","title":"CCDC181 is required for sperm flagellum biogenesis and male fertility in mice.","date":"2024","source":"Zoological research","url":"https://pubmed.ncbi.nlm.nih.gov/39245650","citation_count":2,"is_preprint":false},{"pmid":"38892912","id":"PMC_38892912","title":"An Exercise Immune Fitness Test to Unravel Disease Mechanisms-A Proof-of-Concept Heart Failure Study.","date":"2024","source":"Journal of clinical medicine","url":"https://pubmed.ncbi.nlm.nih.gov/38892912","citation_count":2,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":11804,"output_tokens":1779,"usd":0.031048,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8614,"output_tokens":2419,"usd":0.051772,"stage2_stop_reason":"end_turn"},"total_usd":0.08282,"stage1_batch_id":"msgbatch_01ACAxJQabDsht39JXeWG22d","stage2_batch_id":"msgbatch_01QEU22A9U5sbPTgsMzTmvSf","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2017,\n      \"finding\": \"Ccdc181 interacts with Hook1 in haploid male germ cells, as determined by yeast two-hybrid screen and verified by FRET analysis; interacting regions were mapped using yeast two-hybrid assays.\",\n      \"method\": \"Yeast two-hybrid screen, FRET analysis\",\n      \"journal\": \"European journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — interaction confirmed by two orthogonal methods (Y2H + FRET), single lab\",\n      \"pmids\": [\"28283191\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Ccdc181 binds directly to microtubules and localizes to the microtubular manchette of elongating spermatids, resembling the localization of Hook1.\",\n      \"method\": \"Microtubule-binding assay, immunostaining/fluorescence microscopy\",\n      \"journal\": \"European journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct microtubule binding assay plus immunolocalization, single lab\",\n      \"pmids\": [\"28283191\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Ccdc181 localizes to the sperm flagella and to the basal half of motile cilia but was not detected in primary non-motile cilia, indicating a motile cilia-specific localization.\",\n      \"method\": \"Immunofluorescence microscopy\",\n      \"journal\": \"European journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — immunolocalization with negative control (primary cilia), single lab\",\n      \"pmids\": [\"28283191\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Ccdc181 is a putative interacting partner of different catalytic subunits of protein phosphatase 1 (Pp1), suggesting a role in mediating ciliary motility.\",\n      \"method\": \"Yeast two-hybrid assay (interaction with Pp1 catalytic subunits)\",\n      \"journal\": \"European journal of cell biology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single Y2H result, not confirmed by orthogonal method, single lab\",\n      \"pmids\": [\"28283191\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"CCDC181 is identified as a high-abundance protein in human airway cilia axonemes, with unique axonemal localization confirmed by immunoblotting and fluorescence microscopy, and cilia-specific expression confirmed by RT-PCR.\",\n      \"method\": \"Label-free LC/MSE quantitative proteomics, immunoblotting, RT-PCR, fluorescence microscopy\",\n      \"journal\": \"Journal of proteome research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (proteomics, immunoblot, RT-PCR, microscopy) in single study\",\n      \"pmids\": [\"28282151\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Ccdc181 knockout mice display defective sperm head shaping, flagellum formation, extremely low sperm counts, grossly aberrant sperm morphologies, markedly diminished sperm motility, and multiple morphological abnormalities of the flagella (MMAF), establishing that CCDC181 is required for manchette formation and sperm flagellum biogenesis.\",\n      \"method\": \"Knockout mouse model, sperm morphology and motility analysis\",\n      \"journal\": \"Zoological research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO with defined cellular phenotype, multiple orthogonal readouts (count, motility, morphology, ultrastructure)\",\n      \"pmids\": [\"39245650\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"CCDC181 interacts with the MMAF-related protein LRRC46 and regulates LRRC46 localization within sperm flagella.\",\n      \"method\": \"Co-immunoprecipitation, immunofluorescence localization in KO vs. wild-type\",\n      \"journal\": \"Zoological research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus functional localization assay in KO model, single lab\",\n      \"pmids\": [\"39245650\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"CCDC181 interacts with the chaperonin subunit CCTβ (CCT2), and CCDC181 localization to photoreceptor connecting cilia is compromised in CCT2 compound heterozygous mutant mice, indicating CCTβ is required for proper CCDC181 ciliary localization.\",\n      \"method\": \"Co-immunoprecipitation (CCDC181 as CCTβ interacting protein), immunofluorescence in mutant mouse retina\",\n      \"journal\": \"Communications biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP for interaction, immunofluorescence in vivo model for functional consequence, single lab\",\n      \"pmids\": [\"38830954\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Bovine CCDC181 directly interacts with Theileria annulata SVSP454 parasite protein, as identified by yeast two-hybrid screening and confirmed by co-immunoprecipitation and bimolecular fluorescence complementation (BiFC) assays.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation, BiFC\",\n      \"journal\": \"Parasites & vectors\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — interaction confirmed by three orthogonal methods, but relevance to mammalian CCDC181 function is indirect (parasite interaction context)\",\n      \"pmids\": [\"34116718\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CCDC181 is a coiled-coil domain-containing, microtubule-binding protein that is a major structural component of motile cilia axonemes and sperm flagella; it interacts with Hook1 and LRRC46 to regulate manchette integrity and flagellum biogenesis (loss causes MMAF and male infertility in mice), localizes specifically to the basal half of motile cilia but not primary cilia, and requires the CCTβ chaperonin for proper ciliary localization.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"CCDC181 is a coiled-coil, microtubule-binding protein that functions as a structural component of motile cilia axonemes and sperm flagella and is required for sperm head shaping and flagellum biogenesis [#5]. In elongating spermatids it binds directly to microtubules and localizes to the manchette, mirroring the distribution of its interaction partner Hook1 [#0, #1]. CCDC181 displays motile cilia-specific localization, concentrating in the basal half of motile cilia and in sperm flagella but absent from primary non-motile cilia, and is a high-abundance constituent of human airway cilia axonemes [#2, #4]. Loss of Ccdc181 in mice produces defective manchette formation, grossly aberrant sperm morphology, extremely low sperm counts, and multiple morphological abnormalities of the flagella (MMAF) with male infertility [#5]. Mechanistically, CCDC181 interacts with the MMAF-related protein LRRC46 and governs its correct localization within the flagellum [#6], and its own targeting to the connecting cilium depends on the chaperonin subunit CCTβ (CCT2) [#7].\",\n  \"teleology\": [\n    {\n      \"year\": 2017,\n      \"claim\": \"Established the first molecular partners and binding activity of CCDC181, defining it as a microtubule-binding manchette protein in male germ cells.\",\n      \"evidence\": \"Yeast two-hybrid screen and FRET for Hook1 interaction, microtubule-binding assay and immunostaining in elongating spermatids\",\n      \"pmids\": [\"28283191\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate\",\n      \"gaps\": [\"Functional consequence of the Hook1 interaction not tested\", \"Microtubule-binding domain not mapped structurally\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Defined CCDC181 as a motile cilia-specific protein by showing localization to sperm flagella and the basal half of motile cilia but not primary cilia.\",\n      \"evidence\": \"Immunofluorescence microscopy with primary cilia as negative control\",\n      \"pmids\": [\"28283191\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate\",\n      \"gaps\": [\"Basis for basal-half restriction within motile cilia unexplained\", \"No mechanism for motile- vs primary-cilia discrimination\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Proposed a link between CCDC181 and ciliary motility regulation via candidate phosphatase partners.\",\n      \"evidence\": \"Yeast two-hybrid interaction with Pp1 catalytic subunits\",\n      \"pmids\": [\"28283191\"],\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak\",\n      \"gaps\": [\"Single Y2H result not confirmed by orthogonal method\", \"No functional readout connecting CCDC181 to Pp1-dependent motility\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Independently confirmed CCDC181 as an abundant, cilia-specific axonemal protein in human airway tissue, extending its relevance beyond germ cells.\",\n      \"evidence\": \"Label-free quantitative proteomics, immunoblotting, RT-PCR, and fluorescence microscopy of airway cilia\",\n      \"pmids\": [\"28282151\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate\",\n      \"gaps\": [\"Substructural axonemal position not resolved\", \"No functional perturbation in airway cilia\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Provided causal in vivo evidence that CCDC181 is required for manchette formation, sperm flagellum biogenesis, and male fertility.\",\n      \"evidence\": \"Knockout mouse with sperm count, motility, morphology, and ultrastructure analyses\",\n      \"pmids\": [\"39245650\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong\",\n      \"gaps\": [\"Molecular pathway from microtubule binding to manchette assembly not detailed\", \"No human patient mutation linkage shown\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Connected CCDC181 to the broader MMAF protein network by showing it controls LRRC46 localization in the flagellum.\",\n      \"evidence\": \"Co-immunoprecipitation and immunofluorescence comparing KO vs wild-type flagella\",\n      \"pmids\": [\"39245650\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate\",\n      \"gaps\": [\"Reciprocal dependence (LRRC46 effect on CCDC181) not tested\", \"Direct vs indirect interaction not resolved\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Identified a chaperonin requirement for CCDC181 trafficking, showing CCTβ (CCT2) is needed for its ciliary localization.\",\n      \"evidence\": \"Co-immunoprecipitation and immunofluorescence in CCT2 compound heterozygous mutant mouse retina\",\n      \"pmids\": [\"38830954\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate\",\n      \"gaps\": [\"Whether CCTβ folds CCDC181 or transports it not distinguished\", \"Effect on motile cilia (vs connecting cilia) not assessed\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The molecular mechanism by which CCDC181 directs manchette and axoneme assembly, and any link to human ciliopathy or infertility mutations, remains undefined.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"open question\",\n      \"gaps\": [\"No structural model of microtubule or partner binding\", \"No human disease mutation identified in the corpus\", \"Mechanistic role of candidate Pp1 partners unresolved\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [4, 5]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005929\", \"supporting_discovery_ids\": [2, 4]},\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [5]},\n      {\"term_id\": \"R-HSA-1474165\", \"supporting_discovery_ids\": [5]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"HOOK1\", \"LRRC46\", \"CCT2\", \"PPP1CC\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}