{"gene":"CFAP300","run_date":"2026-04-28T17:28:52","timeline":{"discoveries":[{"year":2018,"finding":"C11orf70 (CFAP300) protein localizes mainly in the cytoplasm with a small amount in the ciliary compartment, and its transport within cilia is IFT-dependent (shown by IFT139/TTC21B and FLA10 depletion experiments in Paramecium and Chlamydomonas). During ciliogenesis, it accumulates at ciliary tips in a distribution similar to IFT-B protein IFT46.","method":"Tagged protein localization in Paramecium and Chlamydomonas; IFT-A/IFT-B depletion experiments; RNAi knockdown leading to combined loss of IDA+ODA with reduced beating","journal":"American journal of human genetics","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (localization, IFT depletion, RNAi phenotype) in two model organisms","pmids":["29727692"],"is_preprint":false},{"year":2018,"finding":"CFAP300 (C11orf70) interacts with cytoplasmic ODA/IDA assembly factor DNAAF2, supporting its role as a dynein arm preassembly factor in the cytoplasm.","method":"Co-immunoprecipitation / interaction assay between C11orf70 and DNAAF2","journal":"American journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 3 — single interaction assay in one study, but corroborated by localization and phenotypic data","pmids":["29727693"],"is_preprint":false},{"year":2018,"finding":"Loss-of-function mutations in CFAP300 cause complete loss of both outer dynein arms (ODA) and inner dynein arms (IDA) from the axoneme of respiratory cilia and sperm flagella, resulting in cilia immotility, demonstrating CFAP300 is required for cytoplasmic preassembly of axonemal dynein arms.","method":"Transmission electron microscopy and immunofluorescence microscopy of patient respiratory cilia and sperm flagella; high-speed video microscopy","journal":"American journal of human genetics","confidence":"High","confidence_rationale":"Tier 2 — replicated across multiple independent cohorts and labs using TEM and IF with consistent phenotype","pmids":["29727693","29727692","30916986","33635866"],"is_preprint":false},{"year":2019,"finding":"Immunofluorescence analysis revealed disparate localization of DNAH5 (ODA marker) and DNALI1 (IDA marker) in patients with CFAP300 mutations, suggesting differential mechanisms for trafficking of preassembled outer and inner dynein arm complexes to the axoneme.","method":"Immunofluorescence staining of respiratory epithelial cells from CFAP300-mutant patients using ODA (DNAH5) and IDA (DNALI1) markers","journal":"American journal of respiratory cell and molecular biology","confidence":"Medium","confidence_rationale":"Tier 2 — direct protein localization experiment revealing mechanistic distinction, single lab","pmids":["30916986"],"is_preprint":false},{"year":2019,"finding":"CFAP300 expression is upregulated during ciliogenesis, consistent with a role in dynein arm assembly during cilia formation.","method":"Expression profiling during ciliogenesis in suspension culture (Schmidtea mediterranea gene silencing); Cfap300 knockdown confirmed conserved role in ciliary function","journal":"American journal of respiratory cell and molecular biology","confidence":"Medium","confidence_rationale":"Tier 3 — gene silencing in model organism with functional readout, expression timing consistent across studies","pmids":["30916986","29727693"],"is_preprint":false},{"year":2021,"finding":"In dynein preassembly mutant sperm (including CFAP300 mutants), there is a complete loss of ODAs, while some respiratory cilia from the same individual retain ODAs in the proximal compartment, reflecting the presence of only one ODA type in sperm versus two ODA types in proximal and distal respiratory ciliary axonemes.","method":"Immunofluorescence microscopy, high-speed video microscopy, and transmission electron microscopy comparing sperm flagella and respiratory cilia of CFAP300 and other DNAAF mutant individuals","journal":"PLoS genetics","confidence":"High","confidence_rationale":"Tier 2 — systematic comparative structural analysis across tissue types in multiple mutant individuals with multiple methods","pmids":["33635866"],"is_preprint":false},{"year":2021,"finding":"Sperm flagellar length is significantly reduced in CFAP300 (and other dynein preassembly) mutant individuals, indicating CFAP300-dependent dynein preassembly is required for normal flagellar elongation.","method":"Flagellar length measurement by microscopy in dynein preassembly mutant sperm","journal":"PLoS genetics","confidence":"Medium","confidence_rationale":"Tier 2 — direct morphometric measurement across multiple mutant individuals, single study","pmids":["33635866"],"is_preprint":false},{"year":2022,"finding":"CFAP300 protein is transported along cilia in normal human airway epithelial cells, as demonstrated by super-resolution microscopy, suggesting a role in dynein complex transport within cilia in addition to cytoplasmic preassembly.","method":"Super-resolution microscopy of CFAP300 localization in normal human airway epithelial cells","journal":"Frontiers in genetics","confidence":"Medium","confidence_rationale":"Tier 2 — direct localization by super-resolution imaging, single study","pmids":["36246608"],"is_preprint":false},{"year":2025,"finding":"CFAP300 loss-of-function in human patients results in absence of functional CFAP300 protein, complete loss of both ODA and IDA, and completely immotile cilia in ALI-cultured airway epithelial cells, confirming its essential role in dynein arm assembly in a controlled in vitro system.","method":"Air-liquid interface (ALI) cultures from PCD patients, high-speed video microscopy, transmission electron microscopy, immunofluorescence staining","journal":"International journal of molecular sciences","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods in both ex vivo and in vitro ALI cultures, confirms prior findings with functional readout","pmids":["40806783"],"is_preprint":false},{"year":2025,"finding":"CFAP300 loss-of-function causes not only dynein arm deficiency but also acrosomal malformation in sperm, and TMT-based quantitative proteomics showed reduced levels of key spermatogenesis proteins (SPEF2, SLC25A31, AKAP3) and mitochondrial ATP synthesis factors, with abnormal increases in autophagy-related proteins.","method":"Transmission electron microscopy (TEM) of sperm ultrastructure; immunofluorescence; tandem mass tag (TMT)-based quantitative proteomics of patient sperm","journal":"Asian journal of andrology","confidence":"Medium","confidence_rationale":"Tier 2 — TEM plus proteomics in patient sample, single study, novel finding about acrosome and proteome changes","pmids":["40898687"],"is_preprint":false},{"year":2025,"finding":"In zebrafish, cfap300 regulates transdifferentiation of pronephric tubule epithelial cells into Corpuscle of Stannius endocrine cells via a Cfap300–Hnf1ba–Cdh17 pathway; cfap300 mutants show increased Hnf1ba-driven cdh17 expression that blocks CS precursor transdifferentiation, and this is rescued by cfap300 mRNA injection.","method":"TALEN-generated cfap300 zebrafish mutants; mRNA rescue injection; cdh17 and hnf1ba knockdown epistasis","journal":"bioRxiv","confidence":"Low","confidence_rationale":"Tier 3 — preprint, single lab, genetic epistasis in zebrafish for a function distinct from the established mammalian role","pmids":["bio_10.1101_2025.10.06.680176"],"is_preprint":true}],"current_model":"CFAP300 is a cytoplasmic dynein arm preassembly factor (DNAAF) that interacts with DNAAF2 and is required for the assembly of both outer and inner dynein arms before their IFT-dependent transport into the axoneme; loss of CFAP300 causes complete absence of both dynein arm types, resulting in immotile cilia and sperm flagella, reduced flagellar length, and male infertility, while super-resolution and IFT depletion experiments indicate CFAP300 also travels within cilia in an IFT-dependent manner to participate in dynein arm delivery."},"narrative":{"teleology":[{"year":2018,"claim":"Identification of CFAP300 as a DNAAF resolved how loss of a single gene abolishes both ODA and IDA: CFAP300 mutations cause complete absence of both dynein arm types from cilia and flagella, establishing it as a cytoplasmic dynein arm preassembly factor.","evidence":"TEM, immunofluorescence, and high-speed video microscopy of respiratory cilia and sperm flagella from patients with CFAP300 loss-of-function mutations across multiple independent cohorts; RNAi in Paramecium and Chlamydomonas","pmids":["29727693","29727692"],"confidence":"High","gaps":["Precise step in the dynein preassembly cascade at which CFAP300 acts is undefined","No structural information on CFAP300 or its complexes","Whether CFAP300 acts on ODA and IDA through the same or distinct mechanisms is unknown"]},{"year":2018,"claim":"Demonstrating IFT-dependent ciliary transport of CFAP300 revealed it is not solely a cytoplasmic factor but also participates in dynein arm delivery within cilia, bridging preassembly and axonemal incorporation.","evidence":"Tagged protein localization in Paramecium and Chlamydomonas combined with IFT-A (IFT139/TTC21B) and IFT-B (FLA10) depletion experiments","pmids":["29727692"],"confidence":"High","gaps":["Identity of the IFT adaptor linking CFAP300 to the IFT machinery is unknown","Whether ciliary CFAP300 is cargo-bound or travels independently has not been determined"]},{"year":2018,"claim":"The physical interaction between CFAP300 and DNAAF2 placed CFAP300 within the known DNAAF network and suggested it functions as part of a preassembly complex rather than alone.","evidence":"Co-immunoprecipitation of C11orf70 with DNAAF2","pmids":["29727693"],"confidence":"Medium","gaps":["Interaction detected by single Co-IP without reciprocal pull-down or in vitro reconstitution","Other components of the CFAP300-containing preassembly complex have not been identified","Functional consequence of disrupting the CFAP300–DNAAF2 interaction has not been tested"]},{"year":2019,"claim":"Disparate localization of ODA and IDA markers in CFAP300-mutant cilia revealed that outer and inner dynein arms use distinct trafficking routes to the axoneme, deepening understanding of dynein arm delivery beyond cytoplasmic preassembly.","evidence":"Immunofluorescence of DNAH5 (ODA) and DNALI1 (IDA) in respiratory epithelial cells from CFAP300-mutant patients","pmids":["30916986"],"confidence":"Medium","gaps":["Molecular basis for differential ODA vs. IDA trafficking not characterized","Whether residual proximal ODA reflects a CFAP300-independent assembly pathway is unresolved"]},{"year":2021,"claim":"Comparative analysis of sperm versus respiratory cilia in CFAP300 mutants explained tissue-specific phenotypic severity: sperm flagella (single ODA type) lose all ODAs, while respiratory cilia can retain proximal ODAs, reflecting distinct ODA type compositions along the axoneme.","evidence":"Systematic IF, TEM, and high-speed video microscopy comparing sperm flagella and respiratory cilia across multiple DNAAF mutant individuals","pmids":["33635866"],"confidence":"High","gaps":["Which specific ODA heavy chain isoforms are affected versus spared in different compartments is not fully resolved","Whether flagellar length reduction is a direct consequence of dynein loss or an independent CFAP300 function is unclear"]},{"year":2022,"claim":"Super-resolution imaging in human airway epithelial cells confirmed intraciliary transport of CFAP300, extending the IFT-dependent transport finding from model organisms to human cells.","evidence":"Super-resolution microscopy of CFAP300 in normal human airway epithelial cells","pmids":["36246608"],"confidence":"Medium","gaps":["Dynamics and directionality of CFAP300 transport within human cilia have not been measured","Whether CFAP300 returns retrogradely or is incorporated at the distal tip is unknown"]},{"year":2025,"claim":"ALI-cultured patient airway cells confirmed complete cilia immotility and dynein arm absence in a controlled in vitro system, and proteomics of CFAP300-mutant sperm revealed broader defects including acrosomal malformation and altered mitochondrial and autophagy protein levels.","evidence":"ALI cultures with TEM, IF, and high-speed video microscopy; TMT-based quantitative proteomics of patient sperm","pmids":["40806783","40898687"],"confidence":"Medium","gaps":["Whether acrosomal and mitochondrial defects are secondary to dynein loss or reflect independent CFAP300 functions is unresolved","Proteomic changes identified in a single patient cohort await independent validation","ALI rescue experiments with wild-type CFAP300 have not been performed"]},{"year":null,"claim":"The precise biochemical activity of CFAP300 in the dynein preassembly cascade — whether it acts as a chaperone, scaffold, or adaptor — remains unknown, and its full interaction network and structural basis have not been determined.","evidence":"","pmids":[],"confidence":"High","gaps":["No enzymatic or chaperone activity has been assigned to CFAP300","No crystal or cryo-EM structure is available","Complete set of direct CFAP300 binding partners is not defined","Mechanism by which CFAP300 facilitates handoff of preassembled dynein complexes to IFT is unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[1,0,2]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0,1]},{"term_id":"GO:0005929","term_label":"cilium","supporting_discovery_ids":[0,7]}],"pathway":[{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[0,2,8]}],"complexes":[],"partners":["DNAAF2"],"other_free_text":[]},"mechanistic_narrative":"CFAP300 is a cytoplasmic dynein arm preassembly factor (DNAAF) essential for the assembly and intraflagellar transport of both outer and inner dynein arms in motile cilia and sperm flagella. CFAP300 localizes predominantly to the cytoplasm where it interacts with DNAAF2 and is required for dynein arm preassembly; it is also transported within cilia in an IFT-dependent manner, accumulating at ciliary tips during ciliogenesis [PMID:29727692, PMID:29727693, PMID:36246608]. Loss-of-function mutations in CFAP300 cause primary ciliary dyskinesia characterized by complete absence of both ODA and IDA from respiratory cilia and sperm flagella, resulting in cilia immotility, reduced flagellar length, acrosomal malformation, and male infertility [PMID:29727693, PMID:33635866, PMID:40898687, PMID:40806783]. Tissue-specific differences in ODA retention between respiratory cilia and sperm flagella of CFAP300 mutants reflect distinct ODA type compositions along the proximal–distal axis of the axoneme [PMID:33635866]."},"prefetch_data":{"uniprot":{"accession":"Q9BRQ4","full_name":"Cilia- and flagella-associated protein 300","aliases":[],"length_aa":267,"mass_kda":30.9,"function":"Cilium- and flagellum-specific protein that plays a role in axonemal structure organization and motility. May play a role in outer and inner dynein arm assembly","subcellular_location":"Cytoplasm; Cytoplasm, cytoskeleton, cilium axoneme","url":"https://www.uniprot.org/uniprotkb/Q9BRQ4/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CFAP300","classification":"Not Classified","n_dependent_lines":9,"n_total_lines":1208,"dependency_fraction":0.0074503311258278145},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/CFAP300","total_profiled":1310},"omim":[{"mim_id":"618063","title":"CILIARY DYSKINESIA, PRIMARY, 38; CILD38","url":"https://www.omim.org/entry/618063"},{"mim_id":"618058","title":"CILIA- AND FLAGELLA-ASSOCIATED PROTEIN 300; CFAP300","url":"https://www.omim.org/entry/618058"},{"mim_id":"244400","title":"CILIARY DYSKINESIA, PRIMARY, 1; CILD1","url":"https://www.omim.org/entry/244400"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Primary cilium","reliability":"Approved"},{"location":"Centrosome","reliability":"Approved"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"choroid plexus","ntpm":23.0},{"tissue":"fallopian tube","ntpm":27.4},{"tissue":"testis","ntpm":28.2}],"url":"https://www.proteinatlas.org/search/CFAP300"},"hgnc":{"alias_symbol":["MGC13040","FBB5","DNAAF17"],"prev_symbol":["C11orf70"]},"alphafold":{"accession":"Q9BRQ4","domains":[{"cath_id":"3.40.1000,3.40.1000","chopping":"15-101_205-260","consensus_level":"medium","plddt":95.5038,"start":15,"end":260},{"cath_id":"-","chopping":"109-189","consensus_level":"medium","plddt":96.1841,"start":109,"end":189}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9BRQ4","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9BRQ4-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9BRQ4-F1-predicted_aligned_error_v6.png","plddt_mean":93.69},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CFAP300","jax_strain_url":"https://www.jax.org/strain/search?query=CFAP300"},"sequence":{"accession":"Q9BRQ4","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9BRQ4.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9BRQ4/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9BRQ4"}},"corpus_meta":[{"pmid":"33635866","id":"PMC_33635866","title":"Defects in the cytoplasmic assembly of axonemal dynein arms cause morphological abnormalities and dysmotility in sperm cells leading to male infertility.","date":"2021","source":"PLoS genetics","url":"https://pubmed.ncbi.nlm.nih.gov/33635866","citation_count":66,"is_preprint":false},{"pmid":"29727692","id":"PMC_29727692","title":"C11orf70 Mutations Disrupting the Intraflagellar Transport-Dependent Assembly of Multiple Axonemal Dyneins Cause Primary Ciliary Dyskinesia.","date":"2018","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/29727692","citation_count":56,"is_preprint":false},{"pmid":"29727693","id":"PMC_29727693","title":"Mutations in C11orf70 Cause Primary Ciliary Dyskinesia with Randomization of Left/Right Body Asymmetry Due to Defects of Outer and Inner Dynein Arms.","date":"2018","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/29727693","citation_count":53,"is_preprint":false},{"pmid":"34215651","id":"PMC_34215651","title":"Whole-exome sequencing reveals a monogenic cause in 56% of individuals with laterality disorders and associated congenital heart defects.","date":"2021","source":"Journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/34215651","citation_count":25,"is_preprint":false},{"pmid":"30916986","id":"PMC_30916986","title":"CFAP300: Mutations in Slavic Patients with Primary Ciliary Dyskinesia and a Role in Ciliary Dynein Arms Trafficking.","date":"2019","source":"American journal of respiratory cell and molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/30916986","citation_count":23,"is_preprint":false},{"pmid":"36246608","id":"PMC_36246608","title":"CFAP300 mutation causing primary ciliary dyskinesia in Finland.","date":"2022","source":"Frontiers in genetics","url":"https://pubmed.ncbi.nlm.nih.gov/36246608","citation_count":9,"is_preprint":false},{"pmid":"19041365","id":"PMC_19041365","title":"TPD52, a candidate gene from genomic studies, is overexpressed in testicular germ cell tumours.","date":"2008","source":"Molecular and cellular endocrinology","url":"https://pubmed.ncbi.nlm.nih.gov/19041365","citation_count":9,"is_preprint":false},{"pmid":"39004944","id":"PMC_39004944","title":"Genetics of 67 patients of suspected primary ciliary dyskinesia from India.","date":"2024","source":"Clinical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/39004944","citation_count":7,"is_preprint":false},{"pmid":"39254424","id":"PMC_39254424","title":"A novel homozygous mutation of CFAP300 identified in a Chinese patient with primary ciliary dyskinesia and infertility.","date":"2024","source":"Asian journal of andrology","url":"https://pubmed.ncbi.nlm.nih.gov/39254424","citation_count":4,"is_preprint":false},{"pmid":"39180133","id":"PMC_39180133","title":"Characterization of pathogenic genetic variants in Russian patients with primary ciliary dyskinesia using gene panel sequencing and transcript analysis.","date":"2024","source":"Orphanet journal of rare diseases","url":"https://pubmed.ncbi.nlm.nih.gov/39180133","citation_count":4,"is_preprint":false},{"pmid":"40806783","id":"PMC_40806783","title":"CFAP300 Loss-of-Function Mutations with Primary Ciliary Dyskinesia: Evidence from Ex Vivo and ALI Cultures.","date":"2025","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/40806783","citation_count":2,"is_preprint":false},{"pmid":"40898687","id":"PMC_40898687","title":"CFAP300 loss-of-function variant causes primary ciliary dyskinesia and male infertility via disrupting sperm flagellar assembly and acrosome formation.","date":"2025","source":"Asian journal of andrology","url":"https://pubmed.ncbi.nlm.nih.gov/40898687","citation_count":1,"is_preprint":false},{"pmid":"41373829","id":"PMC_41373829","title":"Heterogeneity of Primary Ciliary Dyskinesia Gene Variants: A Genetic Database Analysis in Russia.","date":"2025","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/41373829","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.10.06.680176","title":"Cfap300 regulates the transdifferentiation of Corpuscle of Stannius cells in zebrafish","date":"2025-10-06","source":"bioRxiv","url":"https://doi.org/10.1101/2025.10.06.680176","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":8488,"output_tokens":2508,"usd":0.031542},"stage2":{"model":"claude-opus-4-6","input_tokens":5847,"output_tokens":2176,"usd":0.125452},"total_usd":0.156994,"stage1_batch_id":"msgbatch_011kfMfE81o6CTcyhVUqumuW","stage2_batch_id":"msgbatch_01DTputS6WNkH745x1nVSoBo","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2018,\n      \"finding\": \"C11orf70 (CFAP300) protein localizes mainly in the cytoplasm with a small amount in the ciliary compartment, and its transport within cilia is IFT-dependent (shown by IFT139/TTC21B and FLA10 depletion experiments in Paramecium and Chlamydomonas). During ciliogenesis, it accumulates at ciliary tips in a distribution similar to IFT-B protein IFT46.\",\n      \"method\": \"Tagged protein localization in Paramecium and Chlamydomonas; IFT-A/IFT-B depletion experiments; RNAi knockdown leading to combined loss of IDA+ODA with reduced beating\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (localization, IFT depletion, RNAi phenotype) in two model organisms\",\n      \"pmids\": [\"29727692\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"CFAP300 (C11orf70) interacts with cytoplasmic ODA/IDA assembly factor DNAAF2, supporting its role as a dynein arm preassembly factor in the cytoplasm.\",\n      \"method\": \"Co-immunoprecipitation / interaction assay between C11orf70 and DNAAF2\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — single interaction assay in one study, but corroborated by localization and phenotypic data\",\n      \"pmids\": [\"29727693\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Loss-of-function mutations in CFAP300 cause complete loss of both outer dynein arms (ODA) and inner dynein arms (IDA) from the axoneme of respiratory cilia and sperm flagella, resulting in cilia immotility, demonstrating CFAP300 is required for cytoplasmic preassembly of axonemal dynein arms.\",\n      \"method\": \"Transmission electron microscopy and immunofluorescence microscopy of patient respiratory cilia and sperm flagella; high-speed video microscopy\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — replicated across multiple independent cohorts and labs using TEM and IF with consistent phenotype\",\n      \"pmids\": [\"29727693\", \"29727692\", \"30916986\", \"33635866\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Immunofluorescence analysis revealed disparate localization of DNAH5 (ODA marker) and DNALI1 (IDA marker) in patients with CFAP300 mutations, suggesting differential mechanisms for trafficking of preassembled outer and inner dynein arm complexes to the axoneme.\",\n      \"method\": \"Immunofluorescence staining of respiratory epithelial cells from CFAP300-mutant patients using ODA (DNAH5) and IDA (DNALI1) markers\",\n      \"journal\": \"American journal of respiratory cell and molecular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct protein localization experiment revealing mechanistic distinction, single lab\",\n      \"pmids\": [\"30916986\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"CFAP300 expression is upregulated during ciliogenesis, consistent with a role in dynein arm assembly during cilia formation.\",\n      \"method\": \"Expression profiling during ciliogenesis in suspension culture (Schmidtea mediterranea gene silencing); Cfap300 knockdown confirmed conserved role in ciliary function\",\n      \"journal\": \"American journal of respiratory cell and molecular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — gene silencing in model organism with functional readout, expression timing consistent across studies\",\n      \"pmids\": [\"30916986\", \"29727693\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"In dynein preassembly mutant sperm (including CFAP300 mutants), there is a complete loss of ODAs, while some respiratory cilia from the same individual retain ODAs in the proximal compartment, reflecting the presence of only one ODA type in sperm versus two ODA types in proximal and distal respiratory ciliary axonemes.\",\n      \"method\": \"Immunofluorescence microscopy, high-speed video microscopy, and transmission electron microscopy comparing sperm flagella and respiratory cilia of CFAP300 and other DNAAF mutant individuals\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — systematic comparative structural analysis across tissue types in multiple mutant individuals with multiple methods\",\n      \"pmids\": [\"33635866\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Sperm flagellar length is significantly reduced in CFAP300 (and other dynein preassembly) mutant individuals, indicating CFAP300-dependent dynein preassembly is required for normal flagellar elongation.\",\n      \"method\": \"Flagellar length measurement by microscopy in dynein preassembly mutant sperm\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct morphometric measurement across multiple mutant individuals, single study\",\n      \"pmids\": [\"33635866\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"CFAP300 protein is transported along cilia in normal human airway epithelial cells, as demonstrated by super-resolution microscopy, suggesting a role in dynein complex transport within cilia in addition to cytoplasmic preassembly.\",\n      \"method\": \"Super-resolution microscopy of CFAP300 localization in normal human airway epithelial cells\",\n      \"journal\": \"Frontiers in genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct localization by super-resolution imaging, single study\",\n      \"pmids\": [\"36246608\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"CFAP300 loss-of-function in human patients results in absence of functional CFAP300 protein, complete loss of both ODA and IDA, and completely immotile cilia in ALI-cultured airway epithelial cells, confirming its essential role in dynein arm assembly in a controlled in vitro system.\",\n      \"method\": \"Air-liquid interface (ALI) cultures from PCD patients, high-speed video microscopy, transmission electron microscopy, immunofluorescence staining\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods in both ex vivo and in vitro ALI cultures, confirms prior findings with functional readout\",\n      \"pmids\": [\"40806783\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"CFAP300 loss-of-function causes not only dynein arm deficiency but also acrosomal malformation in sperm, and TMT-based quantitative proteomics showed reduced levels of key spermatogenesis proteins (SPEF2, SLC25A31, AKAP3) and mitochondrial ATP synthesis factors, with abnormal increases in autophagy-related proteins.\",\n      \"method\": \"Transmission electron microscopy (TEM) of sperm ultrastructure; immunofluorescence; tandem mass tag (TMT)-based quantitative proteomics of patient sperm\",\n      \"journal\": \"Asian journal of andrology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — TEM plus proteomics in patient sample, single study, novel finding about acrosome and proteome changes\",\n      \"pmids\": [\"40898687\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In zebrafish, cfap300 regulates transdifferentiation of pronephric tubule epithelial cells into Corpuscle of Stannius endocrine cells via a Cfap300–Hnf1ba–Cdh17 pathway; cfap300 mutants show increased Hnf1ba-driven cdh17 expression that blocks CS precursor transdifferentiation, and this is rescued by cfap300 mRNA injection.\",\n      \"method\": \"TALEN-generated cfap300 zebrafish mutants; mRNA rescue injection; cdh17 and hnf1ba knockdown epistasis\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — preprint, single lab, genetic epistasis in zebrafish for a function distinct from the established mammalian role\",\n      \"pmids\": [\"bio_10.1101_2025.10.06.680176\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"CFAP300 is a cytoplasmic dynein arm preassembly factor (DNAAF) that interacts with DNAAF2 and is required for the assembly of both outer and inner dynein arms before their IFT-dependent transport into the axoneme; loss of CFAP300 causes complete absence of both dynein arm types, resulting in immotile cilia and sperm flagella, reduced flagellar length, and male infertility, while super-resolution and IFT depletion experiments indicate CFAP300 also travels within cilia in an IFT-dependent manner to participate in dynein arm delivery.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"CFAP300 is a cytoplasmic dynein arm preassembly factor (DNAAF) essential for the assembly and intraflagellar transport of both outer and inner dynein arms in motile cilia and sperm flagella. CFAP300 localizes predominantly to the cytoplasm where it interacts with DNAAF2 and is required for dynein arm preassembly; it is also transported within cilia in an IFT-dependent manner, accumulating at ciliary tips during ciliogenesis [PMID:29727692, PMID:29727693, PMID:36246608]. Loss-of-function mutations in CFAP300 cause primary ciliary dyskinesia characterized by complete absence of both ODA and IDA from respiratory cilia and sperm flagella, resulting in cilia immotility, reduced flagellar length, acrosomal malformation, and male infertility [PMID:29727693, PMID:33635866, PMID:40898687, PMID:40806783]. Tissue-specific differences in ODA retention between respiratory cilia and sperm flagella of CFAP300 mutants reflect distinct ODA type compositions along the proximal–distal axis of the axoneme [PMID:33635866].\",\n  \"teleology\": [\n    {\n      \"year\": 2018,\n      \"claim\": \"Identification of CFAP300 as a DNAAF resolved how loss of a single gene abolishes both ODA and IDA: CFAP300 mutations cause complete absence of both dynein arm types from cilia and flagella, establishing it as a cytoplasmic dynein arm preassembly factor.\",\n      \"evidence\": \"TEM, immunofluorescence, and high-speed video microscopy of respiratory cilia and sperm flagella from patients with CFAP300 loss-of-function mutations across multiple independent cohorts; RNAi in Paramecium and Chlamydomonas\",\n      \"pmids\": [\"29727693\", \"29727692\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Precise step in the dynein preassembly cascade at which CFAP300 acts is undefined\",\n        \"No structural information on CFAP300 or its complexes\",\n        \"Whether CFAP300 acts on ODA and IDA through the same or distinct mechanisms is unknown\"\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Demonstrating IFT-dependent ciliary transport of CFAP300 revealed it is not solely a cytoplasmic factor but also participates in dynein arm delivery within cilia, bridging preassembly and axonemal incorporation.\",\n      \"evidence\": \"Tagged protein localization in Paramecium and Chlamydomonas combined with IFT-A (IFT139/TTC21B) and IFT-B (FLA10) depletion experiments\",\n      \"pmids\": [\"29727692\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Identity of the IFT adaptor linking CFAP300 to the IFT machinery is unknown\",\n        \"Whether ciliary CFAP300 is cargo-bound or travels independently has not been determined\"\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"The physical interaction between CFAP300 and DNAAF2 placed CFAP300 within the known DNAAF network and suggested it functions as part of a preassembly complex rather than alone.\",\n      \"evidence\": \"Co-immunoprecipitation of C11orf70 with DNAAF2\",\n      \"pmids\": [\"29727693\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Interaction detected by single Co-IP without reciprocal pull-down or in vitro reconstitution\",\n        \"Other components of the CFAP300-containing preassembly complex have not been identified\",\n        \"Functional consequence of disrupting the CFAP300–DNAAF2 interaction has not been tested\"\n      ]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Disparate localization of ODA and IDA markers in CFAP300-mutant cilia revealed that outer and inner dynein arms use distinct trafficking routes to the axoneme, deepening understanding of dynein arm delivery beyond cytoplasmic preassembly.\",\n      \"evidence\": \"Immunofluorescence of DNAH5 (ODA) and DNALI1 (IDA) in respiratory epithelial cells from CFAP300-mutant patients\",\n      \"pmids\": [\"30916986\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Molecular basis for differential ODA vs. IDA trafficking not characterized\",\n        \"Whether residual proximal ODA reflects a CFAP300-independent assembly pathway is unresolved\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Comparative analysis of sperm versus respiratory cilia in CFAP300 mutants explained tissue-specific phenotypic severity: sperm flagella (single ODA type) lose all ODAs, while respiratory cilia can retain proximal ODAs, reflecting distinct ODA type compositions along the axoneme.\",\n      \"evidence\": \"Systematic IF, TEM, and high-speed video microscopy comparing sperm flagella and respiratory cilia across multiple DNAAF mutant individuals\",\n      \"pmids\": [\"33635866\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Which specific ODA heavy chain isoforms are affected versus spared in different compartments is not fully resolved\",\n        \"Whether flagellar length reduction is a direct consequence of dynein loss or an independent CFAP300 function is unclear\"\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Super-resolution imaging in human airway epithelial cells confirmed intraciliary transport of CFAP300, extending the IFT-dependent transport finding from model organisms to human cells.\",\n      \"evidence\": \"Super-resolution microscopy of CFAP300 in normal human airway epithelial cells\",\n      \"pmids\": [\"36246608\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Dynamics and directionality of CFAP300 transport within human cilia have not been measured\",\n        \"Whether CFAP300 returns retrogradely or is incorporated at the distal tip is unknown\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"ALI-cultured patient airway cells confirmed complete cilia immotility and dynein arm absence in a controlled in vitro system, and proteomics of CFAP300-mutant sperm revealed broader defects including acrosomal malformation and altered mitochondrial and autophagy protein levels.\",\n      \"evidence\": \"ALI cultures with TEM, IF, and high-speed video microscopy; TMT-based quantitative proteomics of patient sperm\",\n      \"pmids\": [\"40806783\", \"40898687\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether acrosomal and mitochondrial defects are secondary to dynein loss or reflect independent CFAP300 functions is unresolved\",\n        \"Proteomic changes identified in a single patient cohort await independent validation\",\n        \"ALI rescue experiments with wild-type CFAP300 have not been performed\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The precise biochemical activity of CFAP300 in the dynein preassembly cascade — whether it acts as a chaperone, scaffold, or adaptor — remains unknown, and its full interaction network and structural basis have not been determined.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"No enzymatic or chaperone activity has been assigned to CFAP300\",\n        \"No crystal or cryo-EM structure is available\",\n        \"Complete set of direct CFAP300 binding partners is not defined\",\n        \"Mechanism by which CFAP300 facilitates handoff of preassembled dynein complexes to IFT is unknown\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [1, 0, 2]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"GO:0005929\", \"supporting_discovery_ids\": [0, 7]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [0, 2, 8]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"DNAAF2\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}