{"gene":"CFAP20","run_date":"2026-06-09T22:57:18","timeline":{"discoveries":[{"year":2022,"finding":"CFAP20 is required for motile cilia function in zebrafish and maintains the structural integrity of non-motile cilia inner junctions in C. elegans, influencing sensory-dependent signalling and development. It functions within a structural/functional hub centered on the inner junction shared between motile and non-motile cilia.","method":"Loss-of-function in zebrafish (cfap20 morphants/mutants) and C. elegans (CFAP-20 deletion), ultrastructural analysis of cilia, behavioral/signaling assays","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal loss-of-function in two model organisms with distinct ciliary phenotypes, structural and functional readouts, corroborated by human patient data","pmids":["36329026"],"is_preprint":false},{"year":2023,"finding":"In C. elegans, CFAP-20 is restricted to the middle segment of sensory cilia (where microtubule doublets are present), and its loss disconnects A and B tubules, demonstrating that CFAP-20 is required for maintaining the A-B tubule inner junction that defines axoneme differentiation.","method":"Genetic deletion of CFAP-20 in C. elegans, fluorescence localization, electron microscopy of axonemal ultrastructure, intraflagellar transport and sensory function assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct localization plus ultrastructural loss-of-function phenotype (A-B tubule disconnection) with functional readouts across two orthogonal methods","pmids":["37463209"],"is_preprint":false},{"year":2022,"finding":"CFAP20 physically interacts with BROMI/TBC1D32, a component of the IFT turnaround complex. BROMI mutants defective in binding to CFAP20 (and CCRK) fail to rescue ciliary defects (abnormally long cilia, IFT/ICK accumulation at the ciliary tip) in BROMI-KO cells, placing CFAP20 in the CCRK–BROMI–FAM149B1 axis that regulates IFT turnaround under ICK control.","method":"Co-immunoprecipitation (BROMI–CFAP20 interaction), BROMI binding-defective mutant rescue assay in BROMI-KO cells, ciliary length and IFT-accumulation phenotyping","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal interaction shown by Co-IP, functional epistasis via rescue experiment, single lab","pmids":["35609210"],"is_preprint":false},{"year":2026,"finding":"CFAP20 safeguards genome stability by salvaging arrested RNA Polymerase II (RNAPII) in promoter-proximal regions, preventing collisions with co-directional replisomes. CFAP20-deficient cells accumulate R-loops near promoters, exhibit defects in replication timing and dynamics (accelerated fork speeds, reduced origin activity), and these defects are rescued by co-depletion of the Mediator complex or removal of R-loop-engaged RNAPII.","method":"Genome-wide approaches (RNAPII ChIP-seq, R-loop mapping), genetic screens, replication timing/fork speed assays in CFAP20-deficient cells, epistasis via Mediator co-depletion","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal genome-wide methods plus genetic epistasis in a single rigorous study, published in Nature","pmids":["41535461"],"is_preprint":false},{"year":2025,"finding":"Co-expression of CFAP53 and CFAP20 (an inner junction protein) in HeLa cells induced ectopic microtubule doublet (MTD)-like structures in the cytoplasm, demonstrating that CFAP20 participates in B-tubule assembly/inner junction formation and is sufficient, together with FAP53, to drive ectopic MTD formation outside the normal ciliary context.","method":"Co-expression of CFAP53 and CFAP20 in HeLa cells, fluorescence microscopy and ultrastructural analysis of ectopic MTD-like structures","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — cell-based reconstitution with structural readout, preprint, single lab, no mutagenesis of CFAP20 specifically","pmids":["bio_10.1101_2025.08.03.668368"],"is_preprint":true},{"year":2025,"finding":"Knockout of CFAP20 individually in white adipose progenitors promoted beige adipocyte differentiation in vitro and white adipose tissue beiging in vivo, identifying CFAP20 as a lineage repressor of beige adipocyte formation.","method":"Genome-wide CRISPR knockout screen in mouse white adipose progenitors; individual CFAP20 KO with in vitro differentiation and in vivo beiging readouts","journal":"Obesity (Silver Spring, Md.)","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — identified in genome-wide screen with individual KO validation in vitro and in vivo, single lab, no molecular mechanism for how CFAP20 represses beiging","pmids":["40176372"],"is_preprint":false}],"current_model":"CFAP20 is a multifunctional inner junction protein of cilia that connects A and B microtubule doublets to maintain ciliary structural integrity and motility; it interacts with the BROMI–CCRK complex to regulate intraflagellar transport turnaround at the ciliary tip; and, independently of its ciliary role, it safeguards genome stability in the nucleus by rescuing promoter-proximally arrested RNAPII and preventing R-loop-mediated collisions with co-directional replication forks."},"narrative":{"mechanistic_narrative":"CFAP20 is a conserved inner junction protein that maintains the structural integrity of the ciliary axoneme by connecting the A and B microtubule doublets [PMID:36329026, PMID:37463209]. In C. elegans sensory cilia it is restricted to the middle segment where doublets are present, and its loss disconnects the A and B tubules, defining its role in axoneme differentiation [PMID:37463209]; loss-of-function disrupts motile cilia in zebrafish and inner junction architecture in non-motile cilia, linking it to sensory-dependent signalling and development [PMID:36329026]. Consistent with a direct role in doublet assembly, co-expression of CFAP20 with CFAP53 is sufficient to drive ectopic microtubule doublet-like structures in HeLa cytoplasm [PMID:bio_10.1101_2025.08.03.668368]. Beyond its structural role, CFAP20 physically interacts with BROMI/TBC1D32 within the CCRK-BROMI-FAM149B1 axis that controls intraflagellar transport turnaround at the ciliary tip; BROMI mutants unable to bind CFAP20 fail to rescue ciliary length and tip IFT-accumulation defects [PMID:35609210]. Independently of its ciliary functions, CFAP20 safeguards genome stability in the nucleus by salvaging promoter-proximally arrested RNA Polymerase II to prevent collisions with co-directional replisomes; its loss causes promoter-proximal R-loop accumulation and altered replication dynamics that are rescued by Mediator co-depletion or removal of R-loop-engaged RNAPII [PMID:41535461]. A genome-wide screen additionally identified CFAP20 as a repressor of beige adipocyte differentiation [PMID:40176372].","teleology":[{"year":2022,"claim":"Established that CFAP20 is broadly required for ciliary function and inner junction integrity across motile and non-motile cilia, defining it as a core ciliary structural protein.","evidence":"Loss-of-function in zebrafish and C. elegans with ultrastructural and behavioral readouts","pmids":["36329026"],"confidence":"High","gaps":["Molecular interactions at the inner junction not resolved","Did not pinpoint which microtubule contacts CFAP20 mediates","No structural model of CFAP20 within the axoneme"]},{"year":2022,"claim":"Connected CFAP20 to IFT turnaround regulation by showing direct interaction with BROMI/TBC1D32 in the CCRK-BROMI axis, extending its role beyond static structure to dynamic ciliary transport.","evidence":"Co-immunoprecipitation and BROMI binding-defective mutant rescue in BROMI-KO cells with ciliary length/IFT-accumulation phenotyping","pmids":["35609210"],"confidence":"Medium","gaps":["Single lab, reciprocal interaction shown only by Co-IP","Whether CFAP20's IFT role is separable from its inner junction role unclear","Direct binding interface not mapped"]},{"year":2023,"claim":"Localized CFAP20 to the doublet-containing middle segment and demonstrated that its loss disconnects A and B tubules, establishing it as the determinant of the A-B inner junction.","evidence":"Genetic deletion in C. elegans with fluorescence localization, electron microscopy, and IFT/sensory assays","pmids":["37463209"],"confidence":"High","gaps":["Atomic-level mechanism of A-B tubule bridging not defined","Whether human CFAP20 behaves identically not directly tested here"]},{"year":2025,"claim":"Showed CFAP20 is sufficient, with CFAP53, to nucleate microtubule doublet-like structures ectopically, indicating an active role in B-tubule/inner junction formation rather than passive structural occupancy.","evidence":"Co-expression of CFAP53 and CFAP20 in HeLa cells with fluorescence and ultrastructural analysis (preprint)","pmids":["bio_10.1101_2025.08.03.668368"],"confidence":"Medium","gaps":["Preprint, single lab, no CFAP20-specific mutagenesis to test sufficiency","Whether ectopic structures recapitulate native inner junction geometry unclear"]},{"year":2025,"claim":"Identified an unexpected non-ciliary role: CFAP20 represses beige adipocyte differentiation, broadening its physiological footprint.","evidence":"Genome-wide CRISPR knockout screen in mouse white adipose progenitors with individual KO validation in vitro and in vivo","pmids":["40176372"],"confidence":"Medium","gaps":["No molecular mechanism for how CFAP20 represses beiging","Relationship to its ciliary or nuclear functions unknown"]},{"year":2026,"claim":"Revealed a distinct nuclear function in genome stability, showing CFAP20 rescues promoter-proximally arrested RNAPII to prevent R-loop-mediated transcription-replication collisions.","evidence":"RNAPII ChIP-seq, R-loop mapping, replication timing/fork assays, and Mediator co-depletion epistasis in CFAP20-deficient cells","pmids":["41535461"],"confidence":"High","gaps":["How a ciliary inner junction protein is targeted to promoters not established","Direct biochemical substrate/binding partner at RNAPII not defined","Connection between ciliary and nuclear roles unresolved"]},{"year":null,"claim":"How CFAP20's structural ciliary role, its IFT-turnaround interactions, and its nuclear genome-stability function are mechanistically and spatially partitioned within the same protein remains unknown.","evidence":"No single study integrates the ciliary and nuclear activities","pmids":[],"confidence":"High","gaps":["No structural basis for either inner junction bridging or RNAPII salvage","No domain mapping separating the two functions","Regulation of subcellular partitioning uncharacterized"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[0,1,4]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[0,1,4]}],"localization":[{"term_id":"GO:0005929","term_label":"cilium","supporting_discovery_ids":[0,1]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[3]},{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[1,4]}],"pathway":[{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[0,1]},{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[3]}],"complexes":["ciliary axoneme inner junction","CCRK-BROMI-FAM149B1 IFT turnaround complex"],"partners":["BROMI","TBC1D32","CFAP53"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9Y6A4","full_name":"Cilia- and flagella-associated protein 20","aliases":["Basal body up-regulated protein 22","Transcription factor IIB"],"length_aa":193,"mass_kda":22.8,"function":"Cilium- and flagellum-specific protein that plays a role in axonemal structure organization and motility (PubMed:24414207). Microtubule inner protein (MIP) part of the dynein-decorated doublet microtubules (DMTs) in cilia axoneme, which is required for motile cilia beating (PubMed:36191189). Involved in the regulation of the size and morphology of cilia (PubMed:24414207). Required for axonemal microtubules polyglutamylation (PubMed:24414207)","subcellular_location":"Nucleus; Cytoplasm, cytoskeleton, microtubule organizing center, centrosome, centriole; Cytoplasm, cytoskeleton, cilium basal body; Cytoplasm, cytoskeleton, cilium axoneme; Cytoplasm, cytoskeleton, flagellum axoneme","url":"https://www.uniprot.org/uniprotkb/Q9Y6A4/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/CFAP20","classification":"Common Essential","n_dependent_lines":836,"n_total_lines":1208,"dependency_fraction":0.6920529801324503},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"ARL2BP","stoichiometry":10.0}],"url":"https://opencell.sf.czbiohub.org/search/CFAP20","total_profiled":1310},"omim":[{"mim_id":"617906","title":"CILIA- AND FLAGELLA-ASSOCIATED PROTEIN 20; CFAP20","url":"https://www.omim.org/entry/617906"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"},{"location":"Principal piece","reliability":"Supported"},{"location":"Equatorial segment","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/CFAP20"},"hgnc":{"alias_symbol":["GTL3","fSAP23"],"prev_symbol":["C16orf80"]},"alphafold":{"accession":"Q9Y6A4","domains":[{"cath_id":"2.60.120","chopping":"17-172","consensus_level":"medium","plddt":95.644,"start":17,"end":172}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9Y6A4","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9Y6A4-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9Y6A4-F1-predicted_aligned_error_v6.png","plddt_mean":91.75},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CFAP20","jax_strain_url":"https://www.jax.org/strain/search?query=CFAP20"},"sequence":{"accession":"Q9Y6A4","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9Y6A4.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9Y6A4/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9Y6A4"}},"corpus_meta":[{"pmid":"36329026","id":"PMC_36329026","title":"The inner junction protein CFAP20 functions in motile and non-motile cilia and is critical for vision.","date":"2022","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/36329026","citation_count":29,"is_preprint":false},{"pmid":"35246562","id":"PMC_35246562","title":"A comprehensive WGS-based pipeline for the identification of new candidate genes in inherited retinal dystrophies.","date":"2022","source":"NPJ genomic medicine","url":"https://pubmed.ncbi.nlm.nih.gov/35246562","citation_count":17,"is_preprint":false},{"pmid":"37463209","id":"PMC_37463209","title":"Modulation of inner junction proteins contributes to axoneme differentiation.","date":"2023","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/37463209","citation_count":15,"is_preprint":false},{"pmid":"35609210","id":"PMC_35609210","title":"BROMI/TBC1D32 together with CCRK/CDK20 and FAM149B1/JBTS36 contributes to intraflagellar transport turnaround involving ICK/CILK1.","date":"2022","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/35609210","citation_count":12,"is_preprint":false},{"pmid":"15803458","id":"PMC_15803458","title":"Specific maternal transcripts in bovine oocytes and cleavaged embryos: identification with novel DDRT-PCR methods.","date":"2005","source":"Molecular reproduction and development","url":"https://pubmed.ncbi.nlm.nih.gov/15803458","citation_count":11,"is_preprint":false},{"pmid":"37628674","id":"PMC_37628674","title":"Genome-Wide Single-Nucleotide Polymorphism-Based Genomic Diversity and Runs of Homozygosity for Selection Signatures in Equine Breeds.","date":"2023","source":"Genes","url":"https://pubmed.ncbi.nlm.nih.gov/37628674","citation_count":4,"is_preprint":false},{"pmid":"41535461","id":"PMC_41535461","title":"CFAP20 salvages arrested RNAPII from the path of co-directional replisomes.","date":"2026","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/41535461","citation_count":2,"is_preprint":false},{"pmid":"16273273","id":"PMC_16273273","title":"Analysis of tumor progression by transcriptional profiling of mouse MK16 cell lines transformed with human papillomavirus type 16 E6 and E7 oncogenes and activated H-ras.","date":"2005","source":"Oncology reports","url":"https://pubmed.ncbi.nlm.nih.gov/16273273","citation_count":2,"is_preprint":false},{"pmid":"40176372","id":"PMC_40176372","title":"Brd9 antagonism induces beige adipocytes in white adipose tissues and protects against diet-induced obesity.","date":"2025","source":"Obesity (Silver Spring, Md.)","url":"https://pubmed.ncbi.nlm.nih.gov/40176372","citation_count":1,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.08.03.668368","title":"Physiological Reconstitution of Microtubule Doublets","date":"2025-08-04","source":"bioRxiv","url":"https://doi.org/10.1101/2025.08.03.668368","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":6867,"output_tokens":1679,"usd":0.022893,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8472,"output_tokens":2683,"usd":0.054718,"stage2_stop_reason":"end_turn"},"total_usd":0.077611,"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\": 2022,\n      \"finding\": \"CFAP20 is required for motile cilia function in zebrafish and maintains the structural integrity of non-motile cilia inner junctions in C. elegans, influencing sensory-dependent signalling and development. It functions within a structural/functional hub centered on the inner junction shared between motile and non-motile cilia.\",\n      \"method\": \"Loss-of-function in zebrafish (cfap20 morphants/mutants) and C. elegans (CFAP-20 deletion), ultrastructural analysis of cilia, behavioral/signaling assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal loss-of-function in two model organisms with distinct ciliary phenotypes, structural and functional readouts, corroborated by human patient data\",\n      \"pmids\": [\"36329026\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"In C. elegans, CFAP-20 is restricted to the middle segment of sensory cilia (where microtubule doublets are present), and its loss disconnects A and B tubules, demonstrating that CFAP-20 is required for maintaining the A-B tubule inner junction that defines axoneme differentiation.\",\n      \"method\": \"Genetic deletion of CFAP-20 in C. elegans, fluorescence localization, electron microscopy of axonemal ultrastructure, intraflagellar transport and sensory function assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct localization plus ultrastructural loss-of-function phenotype (A-B tubule disconnection) with functional readouts across two orthogonal methods\",\n      \"pmids\": [\"37463209\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"CFAP20 physically interacts with BROMI/TBC1D32, a component of the IFT turnaround complex. BROMI mutants defective in binding to CFAP20 (and CCRK) fail to rescue ciliary defects (abnormally long cilia, IFT/ICK accumulation at the ciliary tip) in BROMI-KO cells, placing CFAP20 in the CCRK–BROMI–FAM149B1 axis that regulates IFT turnaround under ICK control.\",\n      \"method\": \"Co-immunoprecipitation (BROMI–CFAP20 interaction), BROMI binding-defective mutant rescue assay in BROMI-KO cells, ciliary length and IFT-accumulation phenotyping\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal interaction shown by Co-IP, functional epistasis via rescue experiment, single lab\",\n      \"pmids\": [\"35609210\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"CFAP20 safeguards genome stability by salvaging arrested RNA Polymerase II (RNAPII) in promoter-proximal regions, preventing collisions with co-directional replisomes. CFAP20-deficient cells accumulate R-loops near promoters, exhibit defects in replication timing and dynamics (accelerated fork speeds, reduced origin activity), and these defects are rescued by co-depletion of the Mediator complex or removal of R-loop-engaged RNAPII.\",\n      \"method\": \"Genome-wide approaches (RNAPII ChIP-seq, R-loop mapping), genetic screens, replication timing/fork speed assays in CFAP20-deficient cells, epistasis via Mediator co-depletion\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal genome-wide methods plus genetic epistasis in a single rigorous study, published in Nature\",\n      \"pmids\": [\"41535461\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Co-expression of CFAP53 and CFAP20 (an inner junction protein) in HeLa cells induced ectopic microtubule doublet (MTD)-like structures in the cytoplasm, demonstrating that CFAP20 participates in B-tubule assembly/inner junction formation and is sufficient, together with FAP53, to drive ectopic MTD formation outside the normal ciliary context.\",\n      \"method\": \"Co-expression of CFAP53 and CFAP20 in HeLa cells, fluorescence microscopy and ultrastructural analysis of ectopic MTD-like structures\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — cell-based reconstitution with structural readout, preprint, single lab, no mutagenesis of CFAP20 specifically\",\n      \"pmids\": [\"bio_10.1101_2025.08.03.668368\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Knockout of CFAP20 individually in white adipose progenitors promoted beige adipocyte differentiation in vitro and white adipose tissue beiging in vivo, identifying CFAP20 as a lineage repressor of beige adipocyte formation.\",\n      \"method\": \"Genome-wide CRISPR knockout screen in mouse white adipose progenitors; individual CFAP20 KO with in vitro differentiation and in vivo beiging readouts\",\n      \"journal\": \"Obesity (Silver Spring, Md.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — identified in genome-wide screen with individual KO validation in vitro and in vivo, single lab, no molecular mechanism for how CFAP20 represses beiging\",\n      \"pmids\": [\"40176372\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CFAP20 is a multifunctional inner junction protein of cilia that connects A and B microtubule doublets to maintain ciliary structural integrity and motility; it interacts with the BROMI–CCRK complex to regulate intraflagellar transport turnaround at the ciliary tip; and, independently of its ciliary role, it safeguards genome stability in the nucleus by rescuing promoter-proximally arrested RNAPII and preventing R-loop-mediated collisions with co-directional replication forks.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"CFAP20 is a conserved inner junction protein that maintains the structural integrity of the ciliary axoneme by connecting the A and B microtubule doublets [#0, #1]. In C. elegans sensory cilia it is restricted to the middle segment where doublets are present, and its loss disconnects the A and B tubules, defining its role in axoneme differentiation [#1]; loss-of-function disrupts motile cilia in zebrafish and inner junction architecture in non-motile cilia, linking it to sensory-dependent signalling and development [#0]. Consistent with a direct role in doublet assembly, co-expression of CFAP20 with CFAP53 is sufficient to drive ectopic microtubule doublet-like structures in HeLa cytoplasm [#4]. Beyond its structural role, CFAP20 physically interacts with BROMI/TBC1D32 within the CCRK-BROMI-FAM149B1 axis that controls intraflagellar transport turnaround at the ciliary tip; BROMI mutants unable to bind CFAP20 fail to rescue ciliary length and tip IFT-accumulation defects [#2]. Independently of its ciliary functions, CFAP20 safeguards genome stability in the nucleus by salvaging promoter-proximally arrested RNA Polymerase II to prevent collisions with co-directional replisomes; its loss causes promoter-proximal R-loop accumulation and altered replication dynamics that are rescued by Mediator co-depletion or removal of R-loop-engaged RNAPII [#3]. A genome-wide screen additionally identified CFAP20 as a repressor of beige adipocyte differentiation [#5].\",\n  \"teleology\": [\n    {\n      \"year\": 2022,\n      \"claim\": \"Established that CFAP20 is broadly required for ciliary function and inner junction integrity across motile and non-motile cilia, defining it as a core ciliary structural protein.\",\n      \"evidence\": \"Loss-of-function in zebrafish and C. elegans with ultrastructural and behavioral readouts\",\n      \"pmids\": [\"36329026\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Molecular interactions at the inner junction not resolved\",\n        \"Did not pinpoint which microtubule contacts CFAP20 mediates\",\n        \"No structural model of CFAP20 within the axoneme\"\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Connected CFAP20 to IFT turnaround regulation by showing direct interaction with BROMI/TBC1D32 in the CCRK-BROMI axis, extending its role beyond static structure to dynamic ciliary transport.\",\n      \"evidence\": \"Co-immunoprecipitation and BROMI binding-defective mutant rescue in BROMI-KO cells with ciliary length/IFT-accumulation phenotyping\",\n      \"pmids\": [\"35609210\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Single lab, reciprocal interaction shown only by Co-IP\",\n        \"Whether CFAP20's IFT role is separable from its inner junction role unclear\",\n        \"Direct binding interface not mapped\"\n      ]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Localized CFAP20 to the doublet-containing middle segment and demonstrated that its loss disconnects A and B tubules, establishing it as the determinant of the A-B inner junction.\",\n      \"evidence\": \"Genetic deletion in C. elegans with fluorescence localization, electron microscopy, and IFT/sensory assays\",\n      \"pmids\": [\"37463209\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Atomic-level mechanism of A-B tubule bridging not defined\",\n        \"Whether human CFAP20 behaves identically not directly tested here\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Showed CFAP20 is sufficient, with CFAP53, to nucleate microtubule doublet-like structures ectopically, indicating an active role in B-tubule/inner junction formation rather than passive structural occupancy.\",\n      \"evidence\": \"Co-expression of CFAP53 and CFAP20 in HeLa cells with fluorescence and ultrastructural analysis (preprint)\",\n      \"pmids\": [\"bio_10.1101_2025.08.03.668368\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Preprint, single lab, no CFAP20-specific mutagenesis to test sufficiency\",\n        \"Whether ectopic structures recapitulate native inner junction geometry unclear\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identified an unexpected non-ciliary role: CFAP20 represses beige adipocyte differentiation, broadening its physiological footprint.\",\n      \"evidence\": \"Genome-wide CRISPR knockout screen in mouse white adipose progenitors with individual KO validation in vitro and in vivo\",\n      \"pmids\": [\"40176372\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No molecular mechanism for how CFAP20 represses beiging\",\n        \"Relationship to its ciliary or nuclear functions unknown\"\n      ]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Revealed a distinct nuclear function in genome stability, showing CFAP20 rescues promoter-proximally arrested RNAPII to prevent R-loop-mediated transcription-replication collisions.\",\n      \"evidence\": \"RNAPII ChIP-seq, R-loop mapping, replication timing/fork assays, and Mediator co-depletion epistasis in CFAP20-deficient cells\",\n      \"pmids\": [\"41535461\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"How a ciliary inner junction protein is targeted to promoters not established\",\n        \"Direct biochemical substrate/binding partner at RNAPII not defined\",\n        \"Connection between ciliary and nuclear roles unresolved\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How CFAP20's structural ciliary role, its IFT-turnaround interactions, and its nuclear genome-stability function are mechanistically and spatially partitioned within the same protein remains unknown.\",\n      \"evidence\": \"No single study integrates the ciliary and nuclear activities\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"No structural basis for either inner junction bridging or RNAPII salvage\",\n        \"No domain mapping separating the two functions\",\n        \"Regulation of subcellular partitioning uncharacterized\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [0, 1, 4]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 1, 4]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005929\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [3]},\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [1, 4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"complexes\": [\n      \"ciliary axoneme inner junction\",\n      \"CCRK-BROMI-FAM149B1 IFT turnaround complex\"\n    ],\n    \"partners\": [\n      \"BROMI\",\n      \"TBC1D32\",\n      \"CFAP53\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}