{"gene":"CFAP221","run_date":"2026-06-09T22:57:18","timeline":{"discoveries":[{"year":2007,"finding":"Pcdp1 (CFAP221) localizes to sperm flagella and motile cilia (respiratory epithelial and brain ependymal cells) in mice and humans, and is required for ciliary/flagellar biogenesis and motility; loss-of-function (nm1054 mutation) causes PCD phenotypes including hydrocephalus, male infertility (sperm lacking mature flagella), and reduced respiratory ciliary beat frequency, rescued by transgenic re-expression of Pcdp1.","method":"Transgenic rescue, immunohistochemistry, electron microscopy, ciliary beat frequency measurement in homozygous mutant mice","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO with defined phenotype, transgenic rescue, direct localization by IHC, multiple orthogonal methods","pmids":["18039845"],"is_preprint":false},{"year":2010,"finding":"FAP221/Pcdp1 (CFAP221) is a component of the C1d central pair projection in Chlamydomonas and mammalian axonemes; it specifically binds calmodulin (CaM) in a Ca2+-dependent (high [Ca2+]) manner and participates in a four-polypeptide complex precipitated with anti-CaM antibodies. Reduced expression of Pcdp1 complex members causes failure of the C1d projection to assemble and severely impairs motility (uncoordinated bends, reduced beat frequency, altered waveforms).","method":"Co-immunoprecipitation with anti-CaM antibodies from Chlamydomonas axonemal extracts, RNAi knockdown in Chlamydomonas, Ca2+-dependent CaM binding assay, electron microscopy of axoneme structure","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — biochemical binding assay with Ca2+ specificity, reciprocal Co-IP, RNAi with structural and motility readouts, orthogonal methods in single rigorous study","pmids":["20421426"],"is_preprint":false},{"year":2011,"finding":"The Pcdp1/C1d complex coordinates the activity of specific dynein isoforms (outer and inner dynein arms) to produce wild-type ciliary motility; C1d-defective mutants show wild-type dynein-driven microtubule sliding velocities but severely disrupted coordination of dynein activity among microtubule doublets. Mutations in either outer or inner dynein arm suppress motility defects in C1d-deficient mutants, placing C1d upstream of dynein coordination.","method":"Genetic epistasis (double mutants lacking C1d and specific dynein arm subsets), microtubule sliding velocity assays, electron microscopy, motility analysis in Chlamydomonas","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — genetic epistasis with multiple double mutants, in vitro sliding assay, structural analysis; multiple orthogonal methods in single study","pmids":["21998195"],"is_preprint":false},{"year":2012,"finding":"FAP221/Pcdp1 (CFAP221) is part of the C1d projection along with FAP54, FAP46, FAP74, and a novel subunit C1d-87; multiple sites of calmodulin interaction exist within the C1d projection. The C1d projection is involved in control of interdoublet sliding velocity and Ca2+-mediated flagellar behaviors (phototaxis, photoshock response).","method":"Chlamydomonas fap46-1 null mutant characterization, electron microscopy, motility assays, calmodulin binding, identification of novel C1d subunit","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — null mutant with structural and functional readouts, single lab, multiple orthogonal methods but no direct manipulation of CFAP221 itself","pmids":["22573824"],"is_preprint":false},{"year":2013,"finding":"Pcdp1 (CFAP221) physically associates with kinase Fused (Stk36) and known central pair component Spag16 in the mammalian oviduct, placing it in a pathway for central pair apparatus assembly regulated by Fu.","method":"Co-immunoprecipitation (physical association of Fu with Spag16 and Pcdp1), immunofluorescence localization in oviductal cilia","journal":"Developmental dynamics","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — single Co-IP identifying physical association; corroborated by genetic and localization data in same study","pmids":["23907739"],"is_preprint":false},{"year":2015,"finding":"CFAP221/Pcdp1 localizes to the C1d projection of the central microtubule apparatus in mammalian cilia, and its complex members (including CFAP54) are required for C1d projection assembly; loss of CFAP54 disrupts C1d structure, decreases ciliary beat frequency, and perturbs cilia-driven flow, consistent with conservation of the C1d complex function from Chlamydomonas to mammals.","method":"Gene-trapped mouse model, electron microscopy of ciliary ultrastructure, ciliary beat frequency analysis, cilia-driven flow assays, immunolocalization","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — mouse KO with structural and functional readouts, multiple orthogonal methods, confirms conserved CFAP221 complex localization","pmids":["26224312"],"is_preprint":false},{"year":2018,"finding":"Pcdp1 (CFAP221) is transported along manchette microtubules during spermatid elongation; this transport is disrupted in Spag17 knockout elongating spermatids, placing CFAP221 as a cargo of Spag17-dependent manchette-based protein transport.","method":"Immunofluorescence analysis of Pcdp1 localization in Spag17 knockout spermatids vs. wild-type, coupled with electron microscopy of manchette structure","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — localization by immunofluorescence with functional context in KO, single lab; CFAP221 itself not directly manipulated","pmids":["29690537"],"is_preprint":false},{"year":2019,"finding":"Loss-of-function variants in CFAP221 (compound heterozygous) cause PCD in humans; affected cilia have normal ultrastructure and near-normal beat frequency but beat in an aberrant circular pattern, indicating CFAP221 is required for proper ciliary waveform rather than gross structural assembly.","method":"Whole-exome sequencing, nasal epithelial cell analysis (beat frequency measurement, waveform analysis by high-speed videomicroscopy) in PCD patients","journal":"Journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — human genetics with direct functional ciliary analysis; single lab but with phenotypic and genetic evidence","pmids":["31636325"],"is_preprint":false},{"year":2024,"finding":"Pathogenic variants in CFAP221 cause PCD characterized by defective C1d projection of the ciliary central apparatus, normal ciliary ultrastructure by TEM, normal nasal nitric oxide, normal ciliary beating by high-speed videomicroscopy, yet insufficient ciliary clearance as demonstrated by in vitro ciliary transport assays; situs is normal.","method":"High-throughput sequencing, high-speed videomicroscopy, transmission electron microscopy, in vitro ciliary transport assays in PCD patients","journal":"The European respiratory journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multi-patient cohort with functional transport assay and structural analysis; single consortium study","pmids":["39362668"],"is_preprint":false},{"year":2024,"finding":"Loss of Cfap221/Pcdp1 in mice alters gene expression in tracheal epithelial cells as revealed by single-cell RNA sequencing, including changes in deuterosomal cell differentiation states; this defines a broader role for CFAP221 in shaping the airway ciliary microenvironment response to cilia dysfunction.","method":"Single-cell RNA sequencing of tracheal epithelial cells from Cfap221/Pcdp1 mutant mice, differential gene expression analysis","journal":"Scientific reports","confidence":"Low","confidence_rationale":"Tier 3 / Weak — transcriptomic analysis in KO mice; no direct mechanistic follow-up of CFAP221 protein function","pmids":["39558053"],"is_preprint":false},{"year":2025,"finding":"CFAP221 protein is primarily localized in the flagella of elongating and elongated sperm in humans and mice during spermatogenesis; biallelic loss-of-function variants in CFAP221 cause asthenoteratozoospermia with abnormal sperm flagellar morphology and ultrastructure, confirming a direct role in sperm flagellar assembly.","method":"Immunofluorescence staining, single-cell RNA sequencing, SEM and TEM of patient sperm, whole-exome sequencing","journal":"Journal of assisted reproduction and genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization with functional structural analysis in human patients; single lab, multiple orthogonal methods","pmids":["40272718"],"is_preprint":false},{"year":2025,"finding":"A homozygous protein-truncating variant in CFAP221 causes subtle abnormalities in ciliary central apparatus protein composition, asynchronous circular ciliary motion, and reduced ciliary beat frequency, but normal sperm motility; RNAi knockdown of CFAP221 homolog in Schmidtea mediterranea impairs motile cilia function and reduces locomotion speed, independently confirming CFAP221's role in cilia motility.","method":"Whole-exome sequencing, immunofluorescence, high-speed videomicroscopy, mucociliary transport assay, RNAi knockdown in Schmidtea mediterranea with locomotion assay","journal":"Biochimica et biophysica acta. Molecular basis of disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — orthogonal model organism RNAi plus patient ciliary functional analysis; single lab, multiple methods","pmids":["40250778"],"is_preprint":false}],"current_model":"CFAP221 (PCDP1) is a component of the C1d projection of the ciliary/flagellar central pair apparatus that forms a Ca2+-sensitive calmodulin-binding complex with FAP54, FAP46, FAP74, and other subunits; it is required for proper C1d projection assembly, coordination of outer and inner dynein arm activity, and normal ciliary waveform generation—loss of function causes primary ciliary dyskinesia in humans and mice with impaired mucociliary clearance, aberrant circular ciliary beating, and male infertility due to sperm flagellar assembly defects."},"narrative":{"mechanistic_narrative":"CFAP221 (PCDP1/FAP221) is a structural component of the C1d projection of the ciliary and flagellar central pair apparatus that governs ciliary waveform and motility across species [PMID:20421426, PMID:26224312]. Within the C1d projection it assembles into a calmodulin-binding complex with FAP54/CFAP54, FAP46, FAP74, and C1d-87, and binds calmodulin in a Ca2+-dependent manner, linking the central apparatus to Ca2+-regulated flagellar behaviors [PMID:20421426, PMID:22573824]. Functionally, CFAP221 and the C1d complex are required for proper C1d projection assembly and act upstream of dynein arm coordination: C1d-defective axonemes retain normal dynein-driven microtubule sliding velocity but fail to coordinate dynein activity among doublets, producing uncoordinated bends, altered waveforms, and reduced beat frequency [PMID:21998195, PMID:22573824]. In mammals, CFAP221 localizes to motile cilia of respiratory and ependymal epithelia and to sperm flagella, where it is required for ciliary/flagellar biogenesis and motility; it is transported as a cargo along manchette microtubules during spermatid elongation [PMID:18039845, PMID:29690537]. Loss-of-function variants in CFAP221 cause primary ciliary dyskinesia, with affected cilia showing normal ultrastructure but aberrant circular beating, defective C1d projection composition, and insufficient mucociliary clearance, as well as asthenoteratozoospermia with sperm flagellar defects [PMID:31636325, PMID:39362668, PMID:40272718, PMID:40250778].","teleology":[{"year":2007,"claim":"Established that CFAP221/Pcdp1 is required in vivo for motile cilia and flagella function, answering whether the gene has a non-redundant role in ciliary biogenesis and motility.","evidence":"Transgenic rescue, IHC, EM, and beat-frequency measurement in nm1054 mutant mice","pmids":["18039845"],"confidence":"High","gaps":["Subciliary localization within the axoneme not resolved","Molecular partners and biochemical activity unknown","Mechanism linking loss to motility defect undefined"]},{"year":2010,"claim":"Placed CFAP221 in the C1d central pair projection and defined it as a Ca2+-dependent calmodulin-binding component of a multi-polypeptide complex, providing a molecular framework for its role in motility regulation.","evidence":"Anti-CaM Co-IP from Chlamydomonas axonemes, RNAi knockdown, Ca2+-dependent CaM binding assay, EM","pmids":["20421426"],"confidence":"High","gaps":["Full subunit composition incomplete","How CaM binding regulates motility mechanistically unresolved","Direct binding interface within complex not mapped"]},{"year":2011,"claim":"Resolved how the C1d complex affects motility, showing it coordinates dynein activity rather than enabling dynein force generation itself.","evidence":"Genetic epistasis with dynein arm double mutants, microtubule sliding velocity assays, EM, motility analysis in Chlamydomonas","pmids":["21998195"],"confidence":"High","gaps":["Signal relay from C1d to dynein arms not identified","Role of Ca2+/CaM in dynein coordination not directly tested","CFAP221-specific contribution vs. whole complex not isolated"]},{"year":2012,"claim":"Expanded the C1d projection inventory (FAP54, FAP46, FAP74, C1d-87) and tied the complex to interdoublet sliding velocity and Ca2+-mediated flagellar behaviors.","evidence":"fap46-1 null mutant characterization, EM, motility and calmodulin-binding assays in Chlamydomonas","pmids":["22573824"],"confidence":"Medium","gaps":["CFAP221 itself not directly manipulated in this study","Hierarchy of subunit assembly not established","Multiple CaM-binding sites not assigned to specific subunits"]},{"year":2013,"claim":"Connected CFAP221 to a regulatory assembly pathway by showing physical association with the kinase Fused (Stk36) and central pair component Spag16.","evidence":"Co-IP and immunofluorescence in mammalian oviduct cilia","pmids":["23907739"],"confidence":"Medium","gaps":["Single Co-IP without reciprocal validation of direct binding","Whether CFAP221 is a Fu substrate untested","Functional consequence of the association not demonstrated"]},{"year":2015,"claim":"Confirmed conservation of the C1d complex to mammals, showing complex members are required for C1d assembly and normal ciliary beat and flow.","evidence":"Gene-trapped Cfap54 mouse model, EM, beat frequency, cilia-driven flow assays, immunolocalization","pmids":["26224312"],"confidence":"High","gaps":["Direct CFAP221 assembly dependency on CFAP54 not isolated in mammals","Structural model of mammalian C1d absent","Ca2+ regulation in mammalian cilia not tested"]},{"year":2018,"claim":"Identified how CFAP221 reaches the developing flagellum, defining it as a cargo of Spag17-dependent manchette-based transport during spermatid elongation.","evidence":"Immunofluorescence of Pcdp1 in Spag17 knockout vs. wild-type spermatids, EM of manchette","pmids":["29690537"],"confidence":"Medium","gaps":["CFAP221 not directly manipulated","Direct interaction with transport machinery not shown","Whether transport defect alone explains flagellar phenotype unclear"]},{"year":2019,"claim":"Demonstrated CFAP221 is a human PCD gene whose loss alters ciliary waveform rather than gross structure, refining its role to motion patterning.","evidence":"Whole-exome sequencing and high-speed videomicroscopy of patient nasal epithelial cells","pmids":["31636325"],"confidence":"Medium","gaps":["Molecular basis of the circular beating pattern not defined","C1d composition in patient cilia not assessed in this study","Genotype-phenotype range from limited patients"]},{"year":2024,"claim":"Linked CFAP221 variants to defective C1d projection and impaired mucociliary clearance despite normal ultrastructure and beating, and revealed transcriptional remodeling of airway epithelium upon loss.","evidence":"Patient sequencing with ciliary transport assays, TEM, videomicroscopy; single-cell RNA-seq of mutant mouse tracheal epithelium","pmids":["39362668","39558053"],"confidence":"Medium","gaps":["Mechanism linking subtle C1d defect to clearance failure unresolved","Transcriptomic changes are correlative, no protein-level follow-up","Causality of deuterosomal cell shifts not established"]},{"year":2025,"claim":"Established CFAP221's direct role in sperm flagellar assembly and confirmed cilia-motility function in an independent model organism.","evidence":"Patient sequencing with sperm SEM/TEM and immunofluorescence; RNAi knockdown in Schmidtea mediterranea with locomotion assay","pmids":["40272718","40250778"],"confidence":"Medium","gaps":["Molecular cause of flagellar ultrastructural abnormality not defined","Discordance between ciliary and sperm motility phenotypes unexplained","Structural composition changes in patient cilia not fully resolved"]},{"year":null,"claim":"How CFAP221/C1d transduces Ca2+/calmodulin signals into coordinated dynein activity and waveform control at the molecular and structural level remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No high-resolution structure of the CFAP221-containing C1d complex","Mechanism converting CaM binding into dynein coordination unknown","Direct binding partners and stoichiometry within C1d not fully mapped"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[1,3,5]}],"localization":[{"term_id":"GO:0005929","term_label":"cilium","supporting_discovery_ids":[0,1,5,7]},{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[1,5,6]}],"pathway":[{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[1,5]},{"term_id":"R-HSA-1474165","term_label":"Reproduction","supporting_discovery_ids":[0,10]}],"complexes":["C1d central pair projection"],"partners":["CFAP54","FAP46","FAP74","C1D-87","CALM (CALMODULIN)","STK36","SPAG16","SPAG17"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q4G0U5","full_name":"Cilia- and flagella-associated protein 221","aliases":["Primary ciliary dyskinesia protein 1"],"length_aa":840,"mass_kda":96.9,"function":"May play a role in cilium morphogenesis and ciliary function","subcellular_location":"Cytoplasm, cytoskeleton, cilium axoneme; Cytoplasm; Cytoplasm, cytoskeleton","url":"https://www.uniprot.org/uniprotkb/Q4G0U5/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CFAP221","classification":"Not Classified","n_dependent_lines":7,"n_total_lines":1208,"dependency_fraction":0.005794701986754967},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/CFAP221","total_profiled":1310},"omim":[{"mim_id":"618704","title":"CILIA- AND FLAGELLA-ASSOCIATED PROTEIN 221; CFAP221","url":"https://www.omim.org/entry/618704"},{"mim_id":"618543","title":"CILIA- AND FLAGELLA-ASSOCIATED PROTEIN 46; CFAP46","url":"https://www.omim.org/entry/618543"},{"mim_id":"610172","title":"SPERM FLAGELLAR PROTEIN 2; SPEF2","url":"https://www.omim.org/entry/610172"},{"mim_id":"279000","title":"CILIARY DYSKINESIA, PRIMARY, 55; CILD55","url":"https://www.omim.org/entry/279000"},{"mim_id":"244400","title":"CILIARY DYSKINESIA, PRIMARY, 1; CILD1","url":"https://www.omim.org/entry/244400"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Primary cilium","reliability":"Supported"},{"location":"Primary cilium tip","reliability":"Supported"},{"location":"Connecting piece","reliability":"Supported"},{"location":"Flagellar centriole","reliability":"Supported"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"fallopian tube","ntpm":27.8},{"tissue":"testis","ntpm":23.7}],"url":"https://www.proteinatlas.org/search/CFAP221"},"hgnc":{"alias_symbol":["FAP221","PCDP1"],"prev_symbol":[]},"alphafold":{"accession":"Q4G0U5","domains":[{"cath_id":"2.60.40.10","chopping":"44-155","consensus_level":"high","plddt":86.3053,"start":44,"end":155},{"cath_id":"2.60.40.10","chopping":"166-264","consensus_level":"high","plddt":87.9743,"start":166,"end":264}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q4G0U5","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q4G0U5-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q4G0U5-F1-predicted_aligned_error_v6.png","plddt_mean":63.34},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CFAP221","jax_strain_url":"https://www.jax.org/strain/search?query=CFAP221"},"sequence":{"accession":"Q4G0U5","fasta_url":"https://rest.uniprot.org/uniprotkb/Q4G0U5.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q4G0U5/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q4G0U5"}},"corpus_meta":[{"pmid":"18039845","id":"PMC_18039845","title":"Primary ciliary dyskinesia in mice lacking the novel ciliary protein Pcdp1.","date":"2007","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/18039845","citation_count":100,"is_preprint":false},{"pmid":"20421426","id":"PMC_20421426","title":"Pcdp1 is a central apparatus protein that binds Ca(2+)-calmodulin and regulates ciliary motility.","date":"2010","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/20421426","citation_count":86,"is_preprint":false},{"pmid":"26224312","id":"PMC_26224312","title":"CFAP54 is required for proper ciliary motility and assembly of the central pair apparatus in mice.","date":"2015","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/26224312","citation_count":55,"is_preprint":false},{"pmid":"29690537","id":"PMC_29690537","title":"SPAG17 Is Required for Male Germ Cell Differentiation and Fertility.","date":"2018","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/29690537","citation_count":48,"is_preprint":false},{"pmid":"22573824","id":"PMC_22573824","title":"A FAP46 mutant provides new insights into the function and assembly of the C1d complex of the ciliary central apparatus.","date":"2012","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/22573824","citation_count":38,"is_preprint":false},{"pmid":"33731455","id":"PMC_33731455","title":"CX3CR1 Engagement by Respiratory Syncytial Virus Leads to Induction of Nucleolin and Dysregulation of Cilia-related Genes.","date":"2021","source":"Journal of virology","url":"https://pubmed.ncbi.nlm.nih.gov/33731455","citation_count":32,"is_preprint":false},{"pmid":"31636325","id":"PMC_31636325","title":"Identification of genetic variants in CFAP221 as a cause of primary ciliary dyskinesia.","date":"2019","source":"Journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/31636325","citation_count":29,"is_preprint":false},{"pmid":"23907739","id":"PMC_23907739","title":"Fused (Stk36) is a ciliary protein required for central pair assembly and motile cilia orientation in the mammalian oviduct.","date":"2013","source":"Developmental dynamics : an official publication of the American Association of Anatomists","url":"https://pubmed.ncbi.nlm.nih.gov/23907739","citation_count":29,"is_preprint":false},{"pmid":"21998195","id":"PMC_21998195","title":"The Pcdp1 complex coordinates the activity of dynein isoforms to produce wild-type ciliary motility.","date":"2011","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/21998195","citation_count":21,"is_preprint":false},{"pmid":"32012982","id":"PMC_32012982","title":"Transcriptional Expression in Human Periodontal Ligament Cells Subjected to Orthodontic Force: An RNA-Sequencing Study.","date":"2020","source":"Journal of clinical medicine","url":"https://pubmed.ncbi.nlm.nih.gov/32012982","citation_count":17,"is_preprint":false},{"pmid":"39362668","id":"PMC_39362668","title":"Pathogenic variants in CFAP46, CFAP54, CFAP74 and CFAP221 cause primary ciliary dyskinesia with a defective C1d projection of the central apparatus.","date":"2024","source":"The European respiratory journal","url":"https://pubmed.ncbi.nlm.nih.gov/39362668","citation_count":15,"is_preprint":false},{"pmid":"16991005","id":"PMC_16991005","title":"Enhanced immunogenicity to food-and-mouth disease virus in mice vaccination with alphaviral replicon-based DNA vaccine expressing the capsid precursor polypeptide (P1).","date":"2006","source":"Virus genes","url":"https://pubmed.ncbi.nlm.nih.gov/16991005","citation_count":14,"is_preprint":false},{"pmid":"29468256","id":"PMC_29468256","title":"Intestinal Barrier Impairment and Immune Activation in HIV-Infected Advanced Late Presenters are Not Dependent on CD4 Recovery.","date":"2018","source":"Archivum immunologiae et therapiae experimentalis","url":"https://pubmed.ncbi.nlm.nih.gov/29468256","citation_count":8,"is_preprint":false},{"pmid":"40250778","id":"PMC_40250778","title":"A novel pathogenic variant of CFAP221 is a cause of a mild form of primary ciliary dyskinesia.","date":"2025","source":"Biochimica et biophysica acta. Molecular basis of disease","url":"https://pubmed.ncbi.nlm.nih.gov/40250778","citation_count":1,"is_preprint":false},{"pmid":"40759592","id":"PMC_40759592","title":"Identification of a Novel Biallelic CFAP119 Variant in an Infertile Man with Asthenoteratozoospermia.","date":"2025","source":"The world journal of men's health","url":"https://pubmed.ncbi.nlm.nih.gov/40759592","citation_count":1,"is_preprint":false},{"pmid":"33718639","id":"PMC_33718639","title":"Identification and functional characterization of the transcription factor coding Dp1 gene in large yellow croaker Pseudosciaena crocea.","date":"2021","source":"Heliyon","url":"https://pubmed.ncbi.nlm.nih.gov/33718639","citation_count":1,"is_preprint":false},{"pmid":"40272718","id":"PMC_40272718","title":"Establishing the causative link between CFAP221 variants and asthenoteratozoospermia in humans.","date":"2025","source":"Journal of assisted reproduction and genetics","url":"https://pubmed.ncbi.nlm.nih.gov/40272718","citation_count":0,"is_preprint":false},{"pmid":"39558053","id":"PMC_39558053","title":"Airway ciliary microenvironment responses in mice with primary ciliary dyskinesia and central pair apparatus defects.","date":"2024","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/39558053","citation_count":0,"is_preprint":false},{"pmid":"40508152","id":"PMC_40508152","title":"Large Yellow Croaker (Pseudosciaena crocea, Richardson) E2F4, a Cyclin-Dependent Transcription Factor, Forms a Heterodimer with DP1.","date":"2025","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/40508152","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":11717,"output_tokens":3120,"usd":0.040975,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":10580,"output_tokens":3449,"usd":0.069562,"stage2_stop_reason":"end_turn"},"total_usd":0.110537,"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\": 2007,\n      \"finding\": \"Pcdp1 (CFAP221) localizes to sperm flagella and motile cilia (respiratory epithelial and brain ependymal cells) in mice and humans, and is required for ciliary/flagellar biogenesis and motility; loss-of-function (nm1054 mutation) causes PCD phenotypes including hydrocephalus, male infertility (sperm lacking mature flagella), and reduced respiratory ciliary beat frequency, rescued by transgenic re-expression of Pcdp1.\",\n      \"method\": \"Transgenic rescue, immunohistochemistry, electron microscopy, ciliary beat frequency measurement in homozygous mutant mice\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO with defined phenotype, transgenic rescue, direct localization by IHC, multiple orthogonal methods\",\n      \"pmids\": [\"18039845\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"FAP221/Pcdp1 (CFAP221) is a component of the C1d central pair projection in Chlamydomonas and mammalian axonemes; it specifically binds calmodulin (CaM) in a Ca2+-dependent (high [Ca2+]) manner and participates in a four-polypeptide complex precipitated with anti-CaM antibodies. Reduced expression of Pcdp1 complex members causes failure of the C1d projection to assemble and severely impairs motility (uncoordinated bends, reduced beat frequency, altered waveforms).\",\n      \"method\": \"Co-immunoprecipitation with anti-CaM antibodies from Chlamydomonas axonemal extracts, RNAi knockdown in Chlamydomonas, Ca2+-dependent CaM binding assay, electron microscopy of axoneme structure\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — biochemical binding assay with Ca2+ specificity, reciprocal Co-IP, RNAi with structural and motility readouts, orthogonal methods in single rigorous study\",\n      \"pmids\": [\"20421426\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"The Pcdp1/C1d complex coordinates the activity of specific dynein isoforms (outer and inner dynein arms) to produce wild-type ciliary motility; C1d-defective mutants show wild-type dynein-driven microtubule sliding velocities but severely disrupted coordination of dynein activity among microtubule doublets. Mutations in either outer or inner dynein arm suppress motility defects in C1d-deficient mutants, placing C1d upstream of dynein coordination.\",\n      \"method\": \"Genetic epistasis (double mutants lacking C1d and specific dynein arm subsets), microtubule sliding velocity assays, electron microscopy, motility analysis in Chlamydomonas\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — genetic epistasis with multiple double mutants, in vitro sliding assay, structural analysis; multiple orthogonal methods in single study\",\n      \"pmids\": [\"21998195\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"FAP221/Pcdp1 (CFAP221) is part of the C1d projection along with FAP54, FAP46, FAP74, and a novel subunit C1d-87; multiple sites of calmodulin interaction exist within the C1d projection. The C1d projection is involved in control of interdoublet sliding velocity and Ca2+-mediated flagellar behaviors (phototaxis, photoshock response).\",\n      \"method\": \"Chlamydomonas fap46-1 null mutant characterization, electron microscopy, motility assays, calmodulin binding, identification of novel C1d subunit\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — null mutant with structural and functional readouts, single lab, multiple orthogonal methods but no direct manipulation of CFAP221 itself\",\n      \"pmids\": [\"22573824\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Pcdp1 (CFAP221) physically associates with kinase Fused (Stk36) and known central pair component Spag16 in the mammalian oviduct, placing it in a pathway for central pair apparatus assembly regulated by Fu.\",\n      \"method\": \"Co-immunoprecipitation (physical association of Fu with Spag16 and Pcdp1), immunofluorescence localization in oviductal cilia\",\n      \"journal\": \"Developmental dynamics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — single Co-IP identifying physical association; corroborated by genetic and localization data in same study\",\n      \"pmids\": [\"23907739\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"CFAP221/Pcdp1 localizes to the C1d projection of the central microtubule apparatus in mammalian cilia, and its complex members (including CFAP54) are required for C1d projection assembly; loss of CFAP54 disrupts C1d structure, decreases ciliary beat frequency, and perturbs cilia-driven flow, consistent with conservation of the C1d complex function from Chlamydomonas to mammals.\",\n      \"method\": \"Gene-trapped mouse model, electron microscopy of ciliary ultrastructure, ciliary beat frequency analysis, cilia-driven flow assays, immunolocalization\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — mouse KO with structural and functional readouts, multiple orthogonal methods, confirms conserved CFAP221 complex localization\",\n      \"pmids\": [\"26224312\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Pcdp1 (CFAP221) is transported along manchette microtubules during spermatid elongation; this transport is disrupted in Spag17 knockout elongating spermatids, placing CFAP221 as a cargo of Spag17-dependent manchette-based protein transport.\",\n      \"method\": \"Immunofluorescence analysis of Pcdp1 localization in Spag17 knockout spermatids vs. wild-type, coupled with electron microscopy of manchette structure\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — localization by immunofluorescence with functional context in KO, single lab; CFAP221 itself not directly manipulated\",\n      \"pmids\": [\"29690537\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Loss-of-function variants in CFAP221 (compound heterozygous) cause PCD in humans; affected cilia have normal ultrastructure and near-normal beat frequency but beat in an aberrant circular pattern, indicating CFAP221 is required for proper ciliary waveform rather than gross structural assembly.\",\n      \"method\": \"Whole-exome sequencing, nasal epithelial cell analysis (beat frequency measurement, waveform analysis by high-speed videomicroscopy) in PCD patients\",\n      \"journal\": \"Journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — human genetics with direct functional ciliary analysis; single lab but with phenotypic and genetic evidence\",\n      \"pmids\": [\"31636325\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Pathogenic variants in CFAP221 cause PCD characterized by defective C1d projection of the ciliary central apparatus, normal ciliary ultrastructure by TEM, normal nasal nitric oxide, normal ciliary beating by high-speed videomicroscopy, yet insufficient ciliary clearance as demonstrated by in vitro ciliary transport assays; situs is normal.\",\n      \"method\": \"High-throughput sequencing, high-speed videomicroscopy, transmission electron microscopy, in vitro ciliary transport assays in PCD patients\",\n      \"journal\": \"The European respiratory journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multi-patient cohort with functional transport assay and structural analysis; single consortium study\",\n      \"pmids\": [\"39362668\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Loss of Cfap221/Pcdp1 in mice alters gene expression in tracheal epithelial cells as revealed by single-cell RNA sequencing, including changes in deuterosomal cell differentiation states; this defines a broader role for CFAP221 in shaping the airway ciliary microenvironment response to cilia dysfunction.\",\n      \"method\": \"Single-cell RNA sequencing of tracheal epithelial cells from Cfap221/Pcdp1 mutant mice, differential gene expression analysis\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — transcriptomic analysis in KO mice; no direct mechanistic follow-up of CFAP221 protein function\",\n      \"pmids\": [\"39558053\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"CFAP221 protein is primarily localized in the flagella of elongating and elongated sperm in humans and mice during spermatogenesis; biallelic loss-of-function variants in CFAP221 cause asthenoteratozoospermia with abnormal sperm flagellar morphology and ultrastructure, confirming a direct role in sperm flagellar assembly.\",\n      \"method\": \"Immunofluorescence staining, single-cell RNA sequencing, SEM and TEM of patient sperm, whole-exome sequencing\",\n      \"journal\": \"Journal of assisted reproduction and genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization with functional structural analysis in human patients; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"40272718\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"A homozygous protein-truncating variant in CFAP221 causes subtle abnormalities in ciliary central apparatus protein composition, asynchronous circular ciliary motion, and reduced ciliary beat frequency, but normal sperm motility; RNAi knockdown of CFAP221 homolog in Schmidtea mediterranea impairs motile cilia function and reduces locomotion speed, independently confirming CFAP221's role in cilia motility.\",\n      \"method\": \"Whole-exome sequencing, immunofluorescence, high-speed videomicroscopy, mucociliary transport assay, RNAi knockdown in Schmidtea mediterranea with locomotion assay\",\n      \"journal\": \"Biochimica et biophysica acta. Molecular basis of disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — orthogonal model organism RNAi plus patient ciliary functional analysis; single lab, multiple methods\",\n      \"pmids\": [\"40250778\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CFAP221 (PCDP1) is a component of the C1d projection of the ciliary/flagellar central pair apparatus that forms a Ca2+-sensitive calmodulin-binding complex with FAP54, FAP46, FAP74, and other subunits; it is required for proper C1d projection assembly, coordination of outer and inner dynein arm activity, and normal ciliary waveform generation—loss of function causes primary ciliary dyskinesia in humans and mice with impaired mucociliary clearance, aberrant circular ciliary beating, and male infertility due to sperm flagellar assembly defects.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"CFAP221 (PCDP1/FAP221) is a structural component of the C1d projection of the ciliary and flagellar central pair apparatus that governs ciliary waveform and motility across species [#1, #5]. Within the C1d projection it assembles into a calmodulin-binding complex with FAP54/CFAP54, FAP46, FAP74, and C1d-87, and binds calmodulin in a Ca2+-dependent manner, linking the central apparatus to Ca2+-regulated flagellar behaviors [#1, #3]. Functionally, CFAP221 and the C1d complex are required for proper C1d projection assembly and act upstream of dynein arm coordination: C1d-defective axonemes retain normal dynein-driven microtubule sliding velocity but fail to coordinate dynein activity among doublets, producing uncoordinated bends, altered waveforms, and reduced beat frequency [#2, #3]. In mammals, CFAP221 localizes to motile cilia of respiratory and ependymal epithelia and to sperm flagella, where it is required for ciliary/flagellar biogenesis and motility; it is transported as a cargo along manchette microtubules during spermatid elongation [#0, #6]. Loss-of-function variants in CFAP221 cause primary ciliary dyskinesia, with affected cilia showing normal ultrastructure but aberrant circular beating, defective C1d projection composition, and insufficient mucociliary clearance, as well as asthenoteratozoospermia with sperm flagellar defects [#7, #8, #10, #11].\"\n,\n  \"teleology\": [\n    {\n      \"year\": 2007,\n      \"claim\": \"Established that CFAP221/Pcdp1 is required in vivo for motile cilia and flagella function, answering whether the gene has a non-redundant role in ciliary biogenesis and motility.\",\n      \"evidence\": \"Transgenic rescue, IHC, EM, and beat-frequency measurement in nm1054 mutant mice\",\n      \"pmids\": [\"18039845\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Subciliary localization within the axoneme not resolved\", \"Molecular partners and biochemical activity unknown\", \"Mechanism linking loss to motility defect undefined\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Placed CFAP221 in the C1d central pair projection and defined it as a Ca2+-dependent calmodulin-binding component of a multi-polypeptide complex, providing a molecular framework for its role in motility regulation.\",\n      \"evidence\": \"Anti-CaM Co-IP from Chlamydomonas axonemes, RNAi knockdown, Ca2+-dependent CaM binding assay, EM\",\n      \"pmids\": [\"20421426\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full subunit composition incomplete\", \"How CaM binding regulates motility mechanistically unresolved\", \"Direct binding interface within complex not mapped\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Resolved how the C1d complex affects motility, showing it coordinates dynein activity rather than enabling dynein force generation itself.\",\n      \"evidence\": \"Genetic epistasis with dynein arm double mutants, microtubule sliding velocity assays, EM, motility analysis in Chlamydomonas\",\n      \"pmids\": [\"21998195\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Signal relay from C1d to dynein arms not identified\", \"Role of Ca2+/CaM in dynein coordination not directly tested\", \"CFAP221-specific contribution vs. whole complex not isolated\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Expanded the C1d projection inventory (FAP54, FAP46, FAP74, C1d-87) and tied the complex to interdoublet sliding velocity and Ca2+-mediated flagellar behaviors.\",\n      \"evidence\": \"fap46-1 null mutant characterization, EM, motility and calmodulin-binding assays in Chlamydomonas\",\n      \"pmids\": [\"22573824\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"CFAP221 itself not directly manipulated in this study\", \"Hierarchy of subunit assembly not established\", \"Multiple CaM-binding sites not assigned to specific subunits\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Connected CFAP221 to a regulatory assembly pathway by showing physical association with the kinase Fused (Stk36) and central pair component Spag16.\",\n      \"evidence\": \"Co-IP and immunofluorescence in mammalian oviduct cilia\",\n      \"pmids\": [\"23907739\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single Co-IP without reciprocal validation of direct binding\", \"Whether CFAP221 is a Fu substrate untested\", \"Functional consequence of the association not demonstrated\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Confirmed conservation of the C1d complex to mammals, showing complex members are required for C1d assembly and normal ciliary beat and flow.\",\n      \"evidence\": \"Gene-trapped Cfap54 mouse model, EM, beat frequency, cilia-driven flow assays, immunolocalization\",\n      \"pmids\": [\"26224312\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct CFAP221 assembly dependency on CFAP54 not isolated in mammals\", \"Structural model of mammalian C1d absent\", \"Ca2+ regulation in mammalian cilia not tested\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Identified how CFAP221 reaches the developing flagellum, defining it as a cargo of Spag17-dependent manchette-based transport during spermatid elongation.\",\n      \"evidence\": \"Immunofluorescence of Pcdp1 in Spag17 knockout vs. wild-type spermatids, EM of manchette\",\n      \"pmids\": [\"29690537\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"CFAP221 not directly manipulated\", \"Direct interaction with transport machinery not shown\", \"Whether transport defect alone explains flagellar phenotype unclear\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Demonstrated CFAP221 is a human PCD gene whose loss alters ciliary waveform rather than gross structure, refining its role to motion patterning.\",\n      \"evidence\": \"Whole-exome sequencing and high-speed videomicroscopy of patient nasal epithelial cells\",\n      \"pmids\": [\"31636325\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular basis of the circular beating pattern not defined\", \"C1d composition in patient cilia not assessed in this study\", \"Genotype-phenotype range from limited patients\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Linked CFAP221 variants to defective C1d projection and impaired mucociliary clearance despite normal ultrastructure and beating, and revealed transcriptional remodeling of airway epithelium upon loss.\",\n      \"evidence\": \"Patient sequencing with ciliary transport assays, TEM, videomicroscopy; single-cell RNA-seq of mutant mouse tracheal epithelium\",\n      \"pmids\": [\"39362668\", \"39558053\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism linking subtle C1d defect to clearance failure unresolved\", \"Transcriptomic changes are correlative, no protein-level follow-up\", \"Causality of deuterosomal cell shifts not established\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Established CFAP221's direct role in sperm flagellar assembly and confirmed cilia-motility function in an independent model organism.\",\n      \"evidence\": \"Patient sequencing with sperm SEM/TEM and immunofluorescence; RNAi knockdown in Schmidtea mediterranea with locomotion assay\",\n      \"pmids\": [\"40272718\", \"40250778\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular cause of flagellar ultrastructural abnormality not defined\", \"Discordance between ciliary and sperm motility phenotypes unexplained\", \"Structural composition changes in patient cilia not fully resolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How CFAP221/C1d transduces Ca2+/calmodulin signals into coordinated dynein activity and waveform control at the molecular and structural level remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No high-resolution structure of the CFAP221-containing C1d complex\", \"Mechanism converting CaM binding into dynein coordination unknown\", \"Direct binding partners and stoichiometry within C1d not fully mapped\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [1, 3, 5]},\n      {\"term_id\": \"GO:0005516\", \"supporting_discovery_ids\": [1, 3]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005929\", \"supporting_discovery_ids\": [0, 1, 5, 7]},\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [1, 5, 6]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [1, 5]},\n      {\"term_id\": \"R-HSA-1474165\", \"supporting_discovery_ids\": [0, 10]}\n    ],\n    \"complexes\": [\n      \"C1d central pair projection\"\n    ],\n    \"partners\": [\n      \"CFAP54\",\n      \"FAP46\",\n      \"FAP74\",\n      \"C1d-87\",\n      \"CALM (calmodulin)\",\n      \"STK36\",\n      \"SPAG16\",\n      \"SPAG17\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"faith_supported":5,"faith_total":5,"faith_pct":100.0}}