{"gene":"DNAH2","run_date":"2026-04-28T17:46:02","timeline":{"discoveries":[{"year":2019,"finding":"DNAH2 is an inner dynein arm component of the sperm axoneme; loss-of-function mutations in DNAH17 abolish outer dynein arms from sperm but leave DNAH2 and DNALI (inner dynein arm components) present, establishing DNAH2's localization to the inner dynein arm of the sperm flagellum.","method":"Immunoblot and immunofluorescence on human sperm cells from patients with DNAH17 mutations","journal":"American journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 2 — direct localization by immunofluorescence/immunoblot on patient sperm, single study","pmids":["31178125"],"is_preprint":false},{"year":2019,"finding":"Mutations in DNAH2 cause loss of inner dynein arms and severely disarranged axonemal structures in human sperm, demonstrating that DNAH2 is required for inner dynein arm assembly in the sperm flagellum.","method":"Whole-exome sequencing, Sanger sequencing validation, immunofluorescence, transmission electron microscopy of sperm from MMAF patients","journal":"Clinical genetics","confidence":"Medium","confidence_rationale":"Tier 2 — direct loss-of-function with structural readout by TEM and immunofluorescence, single lab","pmids":["30811583"],"is_preprint":false},{"year":2019,"finding":"Vertebrate DNAH2 (a Dynein-f heavy chain) associates with the intermediate chain WDR78 (vertebrate IC138 orthologue) and WDR63 (IC140 orthologue) as part of the Dynein-f complex in motile cilia; RNAi depletion of DNAH2 paralyzes mouse ependymal cilia, demonstrating DNAH2 is essential for ciliary beat.","method":"Co-immunoprecipitation/association assays for complex subunits, RNAi knockdown in mouse ependymal cells with ciliary beat analysis, zebrafish morpholino experiments","journal":"Journal of molecular cell biology","confidence":"High","confidence_rationale":"Tier 2 — reciprocal association, clean KD with defined ciliary beat phenotype, replicated in two model systems (mouse and zebrafish)","pmids":["30060180"],"is_preprint":false},{"year":2021,"finding":"DNAH2 is essential for multiple steps in sperm flagella formation during spermiogenesis; Dnah2-null mice (CRISPR/Cas9 knockout) are male-infertile with MMAF phenotype, show misexpression of centriolar proteins, delocalization of annulus proteins, severe ultrastructural disorganization of flagella, and compromised expression of other axonemal components DNAH1 and RSPH3.","method":"CRISPR/Cas9 knockout mouse model, scanning and transmission electron microscopy, immunofluorescence for centriolar and annulus proteins, Western blot","journal":"Frontiers in cell and developmental biology","confidence":"High","confidence_rationale":"Tier 1-2 — CRISPR/Cas9 KO mouse with multiple orthogonal structural and molecular readouts, moderate evidence","pmids":["33968937"],"is_preprint":false},{"year":2021,"finding":"Bi-allelic DNAH2 variants cause absence of inner dynein arms and loss of the central pair of microtubules in sperm, as demonstrated by transmission electron microscopy and reduced DNAH2 protein expression by immunofluorescence.","method":"Transmission electron microscopy, immunofluorescence on human patient sperm, whole-exome sequencing","journal":"Reproductive biomedicine online","confidence":"Medium","confidence_rationale":"Tier 2 — direct structural and protein localization evidence in patient sperm, single lab","pmids":["33771466"],"is_preprint":false},{"year":2021,"finding":"DNAH2 modulates homologous recombination repair of the Fanconi anemia pathway by facilitating FANCD2 ubiquitination and enrichment at DNA damage sites; DNAH2 knockdown in U2OS cells increases sensitivity to mitomycin C-induced DNA interstrand crosslinks and reduces FANCD2 recruitment to damage foci.","method":"DNAH2 knockdown in U2OS/DR-U2OS cells, MMC sensitivity assay, immunofluorescence for FANCD2 at damage sites, ubiquitination assay","journal":"Blood science (Baltimore, Md.)","confidence":"Medium","confidence_rationale":"Tier 2 — clean KD with multiple functional assays (MMC sensitivity, FANCD2 localization, ubiquitination), single lab","pmids":["35402838"],"is_preprint":false},{"year":2014,"finding":"The VE1 antibody cross-reacts with DNAH2 epitopes in axonemal cilia and sperm flagella, establishing that DNAH2 protein is a major component of axonemes where it drives microtubule sliding; ELISA assays confirmed VE1 antibody recognition of DNAH2 epitopes.","method":"ELISA, immunohistochemistry, sequence homology analysis","journal":"Modern pathology","confidence":"Low","confidence_rationale":"Tier 3 — ELISA cross-reactivity confirms protein presence in axonemes but provides only indirect mechanistic information","pmids":["25412847"],"is_preprint":false},{"year":2022,"finding":"Loss of CCDC40 function causes loss of DNAH2 protein from both respiratory cilia and sperm flagella, placing DNAH2 downstream of CCDC40 in the inner dynein arm assembly pathway.","method":"Immunofluorescence on patient cilia and sperm with CCDC40 variants, high-speed video microscopy","journal":"Pharmacogenomics and personalized medicine","confidence":"Medium","confidence_rationale":"Tier 2 — epistasis by loss-of-function with direct protein localization readout, single study","pmids":["35449766"],"is_preprint":false},{"year":2024,"finding":"CEP76 is required for DNAH2 entry into the sperm tail through the transition zone; in Cep76-mutant mice, DNAH2 (along with AKAP4) accumulates at the sperm neck rather than distributing along the flagellum, demonstrating that DNAH2 localization to the sperm tail depends on CEP76-mediated selective protein entry at the ciliary gate.","method":"Cep76 mutant mouse model, immunofluorescence localization of DNAH2 in sperm, electron microscopy","journal":"Life science alliance","confidence":"Medium","confidence_rationale":"Tier 2 — genetic mutant with direct protein mislocalization phenotype, single lab","pmids":["38570187"],"is_preprint":false}],"current_model":"DNAH2 is an axonemal dynein heavy chain that functions as a subunit of the inner dynein arm (Dynein-f complex) in motile cilia and sperm flagella, where it associates with intermediate chains WDR78 and WDR63 to drive microtubule sliding and ciliary/flagellar beat; its localization to the sperm tail requires CEP76-mediated transit through the transition zone, its assembly into axonemes depends on CCDC40, and it additionally participates in nuclear DNA damage responses by facilitating FANCD2 ubiquitination and recruitment to Fanconi anemia pathway repair sites."},"narrative":{"teleology":[{"year":2014,"claim":"DNAH2 protein was confirmed as a structural component of axonemes in cilia and sperm flagella, establishing its identity as an axonemal dynein heavy chain prior to functional studies.","evidence":"ELISA and immunohistochemistry using VE1 antibody cross-reactivity against DNAH2 epitopes in human tissues","pmids":["25412847"],"confidence":"Low","gaps":["Only indirect evidence via antibody cross-reactivity, not a dedicated anti-DNAH2 reagent","No functional or loss-of-function data provided","Mechanistic role in the axoneme not addressed"]},{"year":2019,"claim":"DNAH2 was established as a bona fide inner dynein arm component essential for ciliary and flagellar motility: it was shown to reside specifically in the inner dynein arm of human sperm, its loss caused inner dynein arm absence and axonemal disorganization, and it was identified as a Dynein-f heavy chain that associates with WDR78 and WDR63 to drive ciliary beat.","evidence":"Immunofluorescence/immunoblot on patient sperm with DNAH17 mutations (distinguishing inner vs. outer arms), TEM and whole-exome sequencing of DNAH2-mutant MMAF patients, co-immunoprecipitation of Dynein-f subunits plus RNAi knockdown in mouse ependymal cells and zebrafish morpholino experiments","pmids":["31178125","30811583","30060180"],"confidence":"High","gaps":["Structural basis of DNAH2 interaction with WDR78/WDR63 not resolved","Contribution of DNAH2 versus other inner arm dyneins to specific beat patterns unknown","No cryo-EM or high-resolution structural data for the Dynein-f complex"]},{"year":2021,"claim":"Knockout mouse and additional human genetic studies demonstrated that DNAH2 is essential for multiple steps of sperm flagellum assembly — not only inner dynein arm integrity but also centriolar protein organization, annulus positioning, and expression of other axonemal components such as DNAH1 and RSPH3.","evidence":"CRISPR/Cas9 Dnah2-knockout mice with SEM/TEM, immunofluorescence for centriolar and annulus markers, Western blot; TEM on sperm from patients with bi-allelic DNAH2 variants","pmids":["33968937","33771466"],"confidence":"High","gaps":["Whether DNAH2 directly stabilizes DNAH1/RSPH3 or affects them indirectly through axonemal scaffold collapse is unresolved","How DNAH2 loss causes central pair defects is unknown","No rescue experiments in the mouse model"]},{"year":2021,"claim":"An unexpected nuclear role was uncovered: DNAH2 facilitates FANCD2 ubiquitination and recruitment to DNA interstrand crosslink repair sites in the Fanconi anemia pathway, broadening its function beyond motile cilia.","evidence":"DNAH2 knockdown in U2OS cells with mitomycin C sensitivity assays, FANCD2 foci immunofluorescence, and ubiquitination assays","pmids":["35402838"],"confidence":"Medium","gaps":["Mechanism by which a dynein heavy chain modulates FANCD2 ubiquitination is unexplained","Not independently replicated in a second lab or cell type","Whether DNAH2 localizes to the nucleus or acts indirectly is not established"]},{"year":2022,"claim":"CCDC40 was placed upstream of DNAH2 in the inner dynein arm assembly pathway, as loss of CCDC40 function abolishes DNAH2 from both respiratory cilia and sperm flagella.","evidence":"Immunofluorescence on cilia and sperm from patients with CCDC40 variants, high-speed video microscopy","pmids":["35449766"],"confidence":"Medium","gaps":["Whether CCDC40 directly interacts with DNAH2 or acts through an intermediate scaffold is not determined","Single study with limited patient numbers"]},{"year":2024,"claim":"CEP76 was identified as a gatekeeper required for DNAH2 entry through the sperm flagellar transition zone, revealing the trafficking step that delivers DNAH2 to its site of action.","evidence":"Cep76 mutant mouse model with immunofluorescence showing DNAH2 accumulation at the sperm neck instead of the flagellum","pmids":["38570187"],"confidence":"Medium","gaps":["Whether CEP76 acts directly on DNAH2 or on a shared transport carrier is unknown","Mechanism of transition zone gating for inner arm dyneins not defined","Single lab, no biochemical interaction data between CEP76 and DNAH2"]},{"year":null,"claim":"Key unresolved questions include the high-resolution structure of the DNAH2-containing Dynein-f complex, the molecular mechanism by which DNAH2 participates in FANCD2-mediated DNA repair, and whether the assembly and trafficking dependencies (CCDC40, CEP76) involve direct physical interactions with DNAH2.","evidence":"","pmids":[],"confidence":"Low","gaps":["No cryo-EM or crystal structure of DNAH2 or its Dynein-f complex","Nuclear localization and direct binding to FA pathway components not demonstrated","Relative contribution of DNAH2 versus other inner arm dyneins to specific motility parameters in vivo is uncharacterized"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003774","term_label":"cytoskeletal motor activity","supporting_discovery_ids":[2,3]},{"term_id":"GO:0140657","term_label":"ATP-dependent activity","supporting_discovery_ids":[2,3]}],"localization":[{"term_id":"GO:0005929","term_label":"cilium","supporting_discovery_ids":[0,1,2,3,4,7,8]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[2,3]}],"pathway":[{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[2,3,7,8]}],"complexes":["Dynein-f (inner dynein arm)"],"partners":["WDR78","WDR63","CCDC40","CEP76","FANCD2"],"other_free_text":[]},"mechanistic_narrative":"DNAH2 is an axonemal inner dynein arm heavy chain that drives microtubule sliding in motile cilia and sperm flagella. It functions as a subunit of the vertebrate Dynein-f complex together with intermediate chains WDR78 and WDR63, and its depletion paralyzes ependymal cilia in mouse and causes multiple morphological abnormalities of the sperm flagella (MMAF) with loss of inner dynein arms and central pair disorganization in human patients and knockout mice [PMID:30060180, PMID:33968937, PMID:30811583]. Assembly of DNAH2 into axonemes requires CCDC40, and its transport through the sperm flagellar transition zone depends on CEP76 [PMID:35449766, PMID:38570187]. DNAH2 also participates in nuclear DNA damage responses by facilitating FANCD2 ubiquitination and recruitment to interstrand crosslink repair sites in the Fanconi anemia pathway [PMID:35402838]."},"prefetch_data":{"uniprot":{"accession":"Q9P225","full_name":"Dynein axonemal heavy chain 2","aliases":["Axonemal beta dynein heavy chain 2","Ciliary dynein heavy chain 2","Dynein heavy chain domain-containing protein 3"],"length_aa":4427,"mass_kda":507.7,"function":"As part of the axonemal inner dynein arm complex plays a central role in ciliary beat (PubMed:30811583). Expressed in sperm flagellum, it is required for sperm motility (PubMed:30811583). Dyneins are microtubule-based molecular motors possessing ATPase activities that can convert the chemical energy of ATP into relative sliding between adjacent microtubule doublets to generate ciliary bending (PubMed:30811583)","subcellular_location":"Cytoplasm, cytoskeleton, cilium axoneme; Cytoplasm, cytoskeleton, flagellum axoneme","url":"https://www.uniprot.org/uniprotkb/Q9P225/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/DNAH2","classification":"Not Classified","n_dependent_lines":10,"n_total_lines":1208,"dependency_fraction":0.008278145695364239},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/DNAH2","total_profiled":1310},"omim":[{"mim_id":"619156","title":"DYNEIN, AXONEMAL, INTERMEDIATE CHAIN 4; DNAI4","url":"https://www.omim.org/entry/619156"},{"mim_id":"619094","title":"SPERMATOGENIC FAILURE 45; SPGF45","url":"https://www.omim.org/entry/619094"},{"mim_id":"603333","title":"DYNEIN, AXONEMAL, HEAVY CHAIN 2; DNAH2","url":"https://www.omim.org/entry/603333"},{"mim_id":"258150","title":"SPERMATOGENIC FAILURE 1; SPGF1","url":"https://www.omim.org/entry/258150"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Microtubules","reliability":"Approved"},{"location":"Primary cilium","reliability":"Approved"},{"location":"Flagellar centriole","reliability":"Approved"},{"location":"End piece","reliability":"Approved"},{"location":"Cytokinetic bridge","reliability":"Additional"},{"location":"Mitotic spindle","reliability":"Additional"},{"location":"Basal body","reliability":"Additional"}],"tissue_specificity":"Group enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"fallopian tube","ntpm":12.3},{"tissue":"parathyroid gland","ntpm":9.9},{"tissue":"retina","ntpm":19.2},{"tissue":"testis","ntpm":6.2}],"url":"https://www.proteinatlas.org/search/DNAH2"},"hgnc":{"alias_symbol":["KIAA1503","FLJ46675"],"prev_symbol":["DNHD3"]},"alphafold":{"accession":"Q9P225","domains":[],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9P225","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9P225-3-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9P225-3-F1-predicted_aligned_error_v6.png","plddt_mean":73.0},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=DNAH2","jax_strain_url":"https://www.jax.org/strain/search?query=DNAH2"},"sequence":{"accession":"Q9P225","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9P225.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9P225/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9P225"}},"corpus_meta":[{"pmid":"31178125","id":"PMC_31178125","title":"Mutations in DNAH17, Encoding a Sperm-Specific Axonemal Outer Dynein Arm Heavy Chain, Cause Isolated Male Infertility Due to Asthenozoospermia.","date":"2019","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/31178125","citation_count":143,"is_preprint":false},{"pmid":"26648538","id":"PMC_26648538","title":"Age-related mutations and chronic myelomonocytic leukemia.","date":"2015","source":"Leukemia","url":"https://pubmed.ncbi.nlm.nih.gov/26648538","citation_count":111,"is_preprint":false},{"pmid":"30811583","id":"PMC_30811583","title":"DNAH2 is a novel candidate gene associated with multiple morphological abnormalities of the sperm flagella.","date":"2019","source":"Clinical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/30811583","citation_count":81,"is_preprint":false},{"pmid":"33968937","id":"PMC_33968937","title":"Genetic Defects in DNAH2 Underlie Male Infertility With Multiple Morphological Abnormalities of the Sperm Flagella in Humans and Mice.","date":"2021","source":"Frontiers in cell and developmental 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DNAH17 abolish outer dynein arms from sperm but leave DNAH2 and DNALI (inner dynein arm components) present, establishing DNAH2's localization to the inner dynein arm of the sperm flagellum.\",\n      \"method\": \"Immunoblot and immunofluorescence on human sperm cells from patients with DNAH17 mutations\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct localization by immunofluorescence/immunoblot on patient sperm, single study\",\n      \"pmids\": [\"31178125\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Mutations in DNAH2 cause loss of inner dynein arms and severely disarranged axonemal structures in human sperm, demonstrating that DNAH2 is required for inner dynein arm assembly in the sperm flagellum.\",\n      \"method\": \"Whole-exome sequencing, Sanger sequencing validation, immunofluorescence, transmission electron microscopy of sperm from MMAF patients\",\n      \"journal\": \"Clinical genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct loss-of-function with structural readout by TEM and immunofluorescence, single lab\",\n      \"pmids\": [\"30811583\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Vertebrate DNAH2 (a Dynein-f heavy chain) associates with the intermediate chain WDR78 (vertebrate IC138 orthologue) and WDR63 (IC140 orthologue) as part of the Dynein-f complex in motile cilia; RNAi depletion of DNAH2 paralyzes mouse ependymal cilia, demonstrating DNAH2 is essential for ciliary beat.\",\n      \"method\": \"Co-immunoprecipitation/association assays for complex subunits, RNAi knockdown in mouse ependymal cells with ciliary beat analysis, zebrafish morpholino experiments\",\n      \"journal\": \"Journal of molecular cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal association, clean KD with defined ciliary beat phenotype, replicated in two model systems (mouse and zebrafish)\",\n      \"pmids\": [\"30060180\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"DNAH2 is essential for multiple steps in sperm flagella formation during spermiogenesis; Dnah2-null mice (CRISPR/Cas9 knockout) are male-infertile with MMAF phenotype, show misexpression of centriolar proteins, delocalization of annulus proteins, severe ultrastructural disorganization of flagella, and compromised expression of other axonemal components DNAH1 and RSPH3.\",\n      \"method\": \"CRISPR/Cas9 knockout mouse model, scanning and transmission electron microscopy, immunofluorescence for centriolar and annulus proteins, Western blot\",\n      \"journal\": \"Frontiers in cell and developmental biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — CRISPR/Cas9 KO mouse with multiple orthogonal structural and molecular readouts, moderate evidence\",\n      \"pmids\": [\"33968937\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Bi-allelic DNAH2 variants cause absence of inner dynein arms and loss of the central pair of microtubules in sperm, as demonstrated by transmission electron microscopy and reduced DNAH2 protein expression by immunofluorescence.\",\n      \"method\": \"Transmission electron microscopy, immunofluorescence on human patient sperm, whole-exome sequencing\",\n      \"journal\": \"Reproductive biomedicine online\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct structural and protein localization evidence in patient sperm, single lab\",\n      \"pmids\": [\"33771466\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"DNAH2 modulates homologous recombination repair of the Fanconi anemia pathway by facilitating FANCD2 ubiquitination and enrichment at DNA damage sites; DNAH2 knockdown in U2OS cells increases sensitivity to mitomycin C-induced DNA interstrand crosslinks and reduces FANCD2 recruitment to damage foci.\",\n      \"method\": \"DNAH2 knockdown in U2OS/DR-U2OS cells, MMC sensitivity assay, immunofluorescence for FANCD2 at damage sites, ubiquitination assay\",\n      \"journal\": \"Blood science (Baltimore, Md.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean KD with multiple functional assays (MMC sensitivity, FANCD2 localization, ubiquitination), single lab\",\n      \"pmids\": [\"35402838\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"The VE1 antibody cross-reacts with DNAH2 epitopes in axonemal cilia and sperm flagella, establishing that DNAH2 protein is a major component of axonemes where it drives microtubule sliding; ELISA assays confirmed VE1 antibody recognition of DNAH2 epitopes.\",\n      \"method\": \"ELISA, immunohistochemistry, sequence homology analysis\",\n      \"journal\": \"Modern pathology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — ELISA cross-reactivity confirms protein presence in axonemes but provides only indirect mechanistic information\",\n      \"pmids\": [\"25412847\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Loss of CCDC40 function causes loss of DNAH2 protein from both respiratory cilia and sperm flagella, placing DNAH2 downstream of CCDC40 in the inner dynein arm assembly pathway.\",\n      \"method\": \"Immunofluorescence on patient cilia and sperm with CCDC40 variants, high-speed video microscopy\",\n      \"journal\": \"Pharmacogenomics and personalized medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — epistasis by loss-of-function with direct protein localization readout, single study\",\n      \"pmids\": [\"35449766\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"CEP76 is required for DNAH2 entry into the sperm tail through the transition zone; in Cep76-mutant mice, DNAH2 (along with AKAP4) accumulates at the sperm neck rather than distributing along the flagellum, demonstrating that DNAH2 localization to the sperm tail depends on CEP76-mediated selective protein entry at the ciliary gate.\",\n      \"method\": \"Cep76 mutant mouse model, immunofluorescence localization of DNAH2 in sperm, electron microscopy\",\n      \"journal\": \"Life science alliance\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic mutant with direct protein mislocalization phenotype, single lab\",\n      \"pmids\": [\"38570187\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"DNAH2 is an axonemal dynein heavy chain that functions as a subunit of the inner dynein arm (Dynein-f complex) in motile cilia and sperm flagella, where it associates with intermediate chains WDR78 and WDR63 to drive microtubule sliding and ciliary/flagellar beat; its localization to the sperm tail requires CEP76-mediated transit through the transition zone, its assembly into axonemes depends on CCDC40, and it additionally participates in nuclear DNA damage responses by facilitating FANCD2 ubiquitination and recruitment to Fanconi anemia pathway repair sites.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"DNAH2 is an axonemal inner dynein arm heavy chain that drives microtubule sliding in motile cilia and sperm flagella. It functions as a subunit of the vertebrate Dynein-f complex together with intermediate chains WDR78 and WDR63, and its depletion paralyzes ependymal cilia in mouse and causes multiple morphological abnormalities of the sperm flagella (MMAF) with loss of inner dynein arms and central pair disorganization in human patients and knockout mice [PMID:30060180, PMID:33968937, PMID:30811583]. Assembly of DNAH2 into axonemes requires CCDC40, and its transport through the sperm flagellar transition zone depends on CEP76 [PMID:35449766, PMID:38570187]. DNAH2 also participates in nuclear DNA damage responses by facilitating FANCD2 ubiquitination and recruitment to interstrand crosslink repair sites in the Fanconi anemia pathway [PMID:35402838].\",\n  \"teleology\": [\n    {\n      \"year\": 2014,\n      \"claim\": \"DNAH2 protein was confirmed as a structural component of axonemes in cilia and sperm flagella, establishing its identity as an axonemal dynein heavy chain prior to functional studies.\",\n      \"evidence\": \"ELISA and immunohistochemistry using VE1 antibody cross-reactivity against DNAH2 epitopes in human tissues\",\n      \"pmids\": [\"25412847\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Only indirect evidence via antibody cross-reactivity, not a dedicated anti-DNAH2 reagent\", \"No functional or loss-of-function data provided\", \"Mechanistic role in the axoneme not addressed\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"DNAH2 was established as a bona fide inner dynein arm component essential for ciliary and flagellar motility: it was shown to reside specifically in the inner dynein arm of human sperm, its loss caused inner dynein arm absence and axonemal disorganization, and it was identified as a Dynein-f heavy chain that associates with WDR78 and WDR63 to drive ciliary beat.\",\n      \"evidence\": \"Immunofluorescence/immunoblot on patient sperm with DNAH17 mutations (distinguishing inner vs. outer arms), TEM and whole-exome sequencing of DNAH2-mutant MMAF patients, co-immunoprecipitation of Dynein-f subunits plus RNAi knockdown in mouse ependymal cells and zebrafish morpholino experiments\",\n      \"pmids\": [\"31178125\", \"30811583\", \"30060180\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of DNAH2 interaction with WDR78/WDR63 not resolved\", \"Contribution of DNAH2 versus other inner arm dyneins to specific beat patterns unknown\", \"No cryo-EM or high-resolution structural data for the Dynein-f complex\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Knockout mouse and additional human genetic studies demonstrated that DNAH2 is essential for multiple steps of sperm flagellum assembly — not only inner dynein arm integrity but also centriolar protein organization, annulus positioning, and expression of other axonemal components such as DNAH1 and RSPH3.\",\n      \"evidence\": \"CRISPR/Cas9 Dnah2-knockout mice with SEM/TEM, immunofluorescence for centriolar and annulus markers, Western blot; TEM on sperm from patients with bi-allelic DNAH2 variants\",\n      \"pmids\": [\"33968937\", \"33771466\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether DNAH2 directly stabilizes DNAH1/RSPH3 or affects them indirectly through axonemal scaffold collapse is unresolved\", \"How DNAH2 loss causes central pair defects is unknown\", \"No rescue experiments in the mouse model\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"An unexpected nuclear role was uncovered: DNAH2 facilitates FANCD2 ubiquitination and recruitment to DNA interstrand crosslink repair sites in the Fanconi anemia pathway, broadening its function beyond motile cilia.\",\n      \"evidence\": \"DNAH2 knockdown in U2OS cells with mitomycin C sensitivity assays, FANCD2 foci immunofluorescence, and ubiquitination assays\",\n      \"pmids\": [\"35402838\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which a dynein heavy chain modulates FANCD2 ubiquitination is unexplained\", \"Not independently replicated in a second lab or cell type\", \"Whether DNAH2 localizes to the nucleus or acts indirectly is not established\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"CCDC40 was placed upstream of DNAH2 in the inner dynein arm assembly pathway, as loss of CCDC40 function abolishes DNAH2 from both respiratory cilia and sperm flagella.\",\n      \"evidence\": \"Immunofluorescence on cilia and sperm from patients with CCDC40 variants, high-speed video microscopy\",\n      \"pmids\": [\"35449766\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether CCDC40 directly interacts with DNAH2 or acts through an intermediate scaffold is not determined\", \"Single study with limited patient numbers\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"CEP76 was identified as a gatekeeper required for DNAH2 entry through the sperm flagellar transition zone, revealing the trafficking step that delivers DNAH2 to its site of action.\",\n      \"evidence\": \"Cep76 mutant mouse model with immunofluorescence showing DNAH2 accumulation at the sperm neck instead of the flagellum\",\n      \"pmids\": [\"38570187\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether CEP76 acts directly on DNAH2 or on a shared transport carrier is unknown\", \"Mechanism of transition zone gating for inner arm dyneins not defined\", \"Single lab, no biochemical interaction data between CEP76 and DNAH2\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the high-resolution structure of the DNAH2-containing Dynein-f complex, the molecular mechanism by which DNAH2 participates in FANCD2-mediated DNA repair, and whether the assembly and trafficking dependencies (CCDC40, CEP76) involve direct physical interactions with DNAH2.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No cryo-EM or crystal structure of DNAH2 or its Dynein-f complex\", \"Nuclear localization and direct binding to FA pathway components not demonstrated\", \"Relative contribution of DNAH2 versus other inner arm dyneins to specific motility parameters in vivo is uncharacterized\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003774\", \"supporting_discovery_ids\": [2, 3]},\n      {\"term_id\": \"GO:0140657\", \"supporting_discovery_ids\": [2, 3]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005929\", \"supporting_discovery_ids\": [0, 1, 2, 3, 4, 7, 8]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [2, 3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [2, 3, 7, 8]}\n    ],\n    \"complexes\": [\"Dynein-f (inner dynein arm)\"],\n    \"partners\": [\"WDR78\", \"WDR63\", \"CCDC40\", \"CEP76\", \"FANCD2\"],\n    \"other_free_text\": []\n  }\n}\n```"}