{"gene":"ARMC2","run_date":"2026-04-28T17:12:37","timeline":{"discoveries":[{"year":2019,"finding":"Bi-allelic loss-of-function mutations in ARMC2 cause absence of axonemal central pair complex (CPC) proteins SPAG6 and SPEF2 in sperm flagella, while other axonemal and peri-axonemal components remain present, indicating ARMC2 is specifically required for CPC assembly and/or stability. CRISPR-Cas9 Armc2 knockout mice recapitulate the MMAF phenotype.","method":"CRISPR-Cas9 knockout mouse generation, immunostaining of sperm from mutant mice and human patients, transmission electron microscopy","journal":"American journal of human genetics","confidence":"High","confidence_rationale":"Tier 2 — reciprocal orthogonal methods (KO mouse + human patient immunostaining + TEM), replicated across species","pmids":["30686508"],"is_preprint":false},{"year":2022,"finding":"Chlamydomonas ARMC2/PF27 functions as an obligate cargo adapter for intraflagellar transport (IFT) of radial spokes: tagged ARMC2 and radial spoke protein RSP3 co-migrate on anterograde IFT trains, ARMC2 unloads at the flagellar tip and diffuses back to the cell body while RSP3 attaches to the axoneme, and in armc2/pf27 mutants IFT of radial spokes is abolished with spokes restricted to the proximal flagellar region.","method":"Live fluorescence imaging of tagged proteins in Chlamydomonas, IFT velocity analysis, armc2/pf27 mutant analysis, co-migration assays","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1-2 — direct live imaging of IFT co-migration plus genetic loss-of-function with specific cargo transport phenotype, multiple orthogonal methods in single study","pmids":["34982025"],"is_preprint":false},{"year":2022,"finding":"ARMC2 interacts with proteins CEP78, PGAM5, RHOA, FXR1, and SKIV2L2, identified by co-immunoprecipitation and mass spectrometry from patient sperm, suggesting involvement of ARMC2 in multiple processes of spermatogenesis.","method":"Co-immunoprecipitation (co-IP) and mass spectrometry from human sperm","journal":"Journal of assisted reproduction and genetics","confidence":"Low","confidence_rationale":"Tier 3 — single pulldown/MS experiment, no functional validation of individual interactions","pmids":["35543806"],"is_preprint":false},{"year":2021,"finding":"A homozygous stop-gain mutation in ARMC2 leads to complete absence of the central pair complex (CPC) and disorganized axonemal ultrastructure in patient sperm, confirming ARMC2 is required for CPC assembly and/or stability of the axonemal complex.","method":"Whole-exome sequencing, Sanger sequencing, transmission electron microscopy of patient spermatozoa","journal":"Reproductive biomedicine online","confidence":"Medium","confidence_rationale":"Tier 2 — TEM ultrastructural analysis in human patient corroborating mechanistic role, consistent with prior KO mouse data","pmids":["34493464"],"is_preprint":false},{"year":2025,"finding":"ARMC2 mutations cause absence of axonemal CPC and disorganized peri-axonemal structures in human sperm, and ARMC2 variants are linked to pulmonary Primary Ciliary Dyskinesia phenotypes, indicating ARMC2 function is not restricted to sperm flagella but extends to respiratory cilia.","method":"Transmission electron microscopy, immunoblotting, immunofluorescence of patient spermatozoa, whole-exome sequencing","journal":"Reproductive biology and endocrinology : RB&E","confidence":"Medium","confidence_rationale":"Tier 2 — TEM and IF with functional ciliary phenotype in patient, single study","pmids":["40158138"],"is_preprint":false},{"year":2026,"finding":"In vivo testicular delivery of Armc2 mRNA by injection and electroporation restores morphologically normal and motile sperm in Armc2-deficient mice, with rescued sperm capable of producing embryos via IVF and ICSI, demonstrating that ARMC2 function in spermatogenesis can be rescued by mRNA supplementation.","method":"In vivo mRNA electroporation in Armc2 KO mice, sperm morphology analysis, IVF, ICSI, embryo development assessment","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1-2 — functional rescue by mRNA in KO model with multiple readouts (morphology, motility, fertilization), provides strong causal evidence","pmids":["41773826"],"is_preprint":false},{"year":2025,"finding":"In Armc2-/- knockout mice, sperm show nuclear defects (morphology, DNA compaction, chromosomal architecture, ploidy abnormalities) and markedly decreased capacity to support embryo development to blastocyst after ICSI, compared to wild-type sperm.","method":"Knockout mouse model (Armc2-/-), nuclear morphology analysis, DNA compaction assay, chromosomal architecture analysis, ploidy determination, ICSI with embryo development monitoring","journal":"Molecular human reproduction","confidence":"Medium","confidence_rationale":"Tier 2 — clean KO with defined cellular and developmental phenotypes, comparative study with other MMAF genes","pmids":["40070084"],"is_preprint":false}],"current_model":"ARMC2 is an armadillo repeat-containing protein that functions as an obligate cargo adapter for intraflagellar transport (IFT) of radial spokes in cilia and flagella, co-migrating with radial spoke proteins on anterograde IFT trains and recycling to the cell body after unloading; loss of ARMC2 abolishes radial spoke IFT and specifically disrupts axonemal central pair complex (CPC) assembly and stability in sperm flagella (and respiratory cilia), causing multiple morphological abnormalities of the flagella (MMAF) and male infertility, a defect reversible by mRNA-based restoration of ARMC2 in spermatogenic cells."},"narrative":{"teleology":[{"year":2019,"claim":"Establishing ARMC2 as a disease gene: bi-allelic ARMC2 mutations were shown to cause MMAF by specifically disrupting CPC assembly/stability in sperm flagella, resolving the question of whether ARMC2 has a ciliary structural role.","evidence":"CRISPR-Cas9 knockout mice and human patient sperm immunostaining plus TEM","pmids":["30686508"],"confidence":"High","gaps":["Mechanism by which ARMC2 supports CPC assembly was unknown","Whether ARMC2 acts in transport or structural scaffolding was unresolved","Role in non-sperm cilia not addressed"]},{"year":2021,"claim":"Independent patient studies confirmed the CPC-specific defect, reinforcing that ARMC2 loss-of-function selectively destroys the central pair rather than globally disrupting the axoneme.","evidence":"Whole-exome sequencing and TEM of patient spermatozoa carrying a homozygous stop-gain ARMC2 mutation","pmids":["34493464"],"confidence":"Medium","gaps":["No biochemical reconstitution of ARMC2–CPC interaction","Genotype–phenotype relationship across mutation types not systematically characterized"]},{"year":2022,"claim":"The mechanistic basis was resolved: ARMC2 functions as an obligate IFT cargo adapter for radial spokes, co-migrating with RSP3 on anterograde IFT trains and recycling after unloading, explaining how CPC assembly depends on ARMC2-mediated transport.","evidence":"Live fluorescence imaging of tagged ARMC2 and RSP3 in Chlamydomonas, with armc2/pf27 mutant analysis","pmids":["34982025"],"confidence":"High","gaps":["Structural basis of ARMC2–radial spoke or ARMC2–IFT train interaction unknown","Whether ARMC2 transports additional cargo beyond radial spokes not determined","Mammalian live-imaging confirmation of IFT adapter function lacking"]},{"year":2025,"claim":"ARMC2 function was extended beyond sperm flagella: patient variants linked to pulmonary primary ciliary dyskinesia phenotypes, establishing ARMC2 as a general motile cilia gene.","evidence":"TEM, immunofluorescence, and immunoblotting of patient spermatozoa combined with respiratory ciliary phenotyping","pmids":["40158138"],"confidence":"Medium","gaps":["Respiratory cilia ultrastructural analysis not shown in detail","Whether the same CPC-specific defect underlies the respiratory phenotype not directly demonstrated"]},{"year":2025,"claim":"ARMC2 deficiency was shown to impair not only flagellar structure but also sperm nuclear integrity and embryo developmental competence, broadening understanding of its spermatogenic role.","evidence":"Armc2-/- knockout mice with nuclear morphology, DNA compaction, ploidy, and ICSI embryo development assays","pmids":["40070084"],"confidence":"Medium","gaps":["Whether nuclear defects are a direct consequence of ARMC2 loss or secondary to flagellar disorganization is unknown","Molecular mechanism linking ARMC2 to nuclear compaction not identified"]},{"year":2026,"claim":"Functional rescue by in vivo mRNA delivery proved that ARMC2 is both necessary and sufficient for restoring spermatogenesis in the knockout, providing proof-of-concept for therapeutic correction.","evidence":"Testicular Armc2 mRNA electroporation in KO mice with sperm morphology, motility, IVF, and ICSI readouts","pmids":["41773826"],"confidence":"High","gaps":["Duration and efficiency of mRNA-based rescue in long-term spermatogenesis not characterized","Applicability of electroporation-based delivery to clinical settings unknown"]},{"year":null,"claim":"The structural basis of ARMC2's interaction with IFT trains and radial spoke cargo, and whether ARMC2 transports additional axonemal subcomplexes in mammalian cilia, remain unresolved.","evidence":"","pmids":[],"confidence":"High","gaps":["No cryo-EM or crystal structure of ARMC2 or its complexes","Mammalian live-imaging of ARMC2 IFT behavior not performed","Whether ARMC2 nuclear effects are direct or indirect is unresolved"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[1]}],"localization":[{"term_id":"GO:0005929","term_label":"cilium","supporting_discovery_ids":[0,1,3,4]}],"pathway":[{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[0,1]},{"term_id":"R-HSA-1474165","term_label":"Reproduction","supporting_discovery_ids":[0,5,6]}],"complexes":[],"partners":["RSP3"],"other_free_text":[]},"mechanistic_narrative":"ARMC2 is an armadillo repeat-containing protein that functions as an obligate cargo adapter for intraflagellar transport (IFT), specifically mediating anterograde delivery of radial spoke complexes along the axoneme; after cargo unloading at the flagellar tip, ARMC2 recycles to the cell body by diffusion [PMID:34982025]. Loss of ARMC2 abolishes radial spoke IFT and causes selective absence of the axonemal central pair complex (CPC) in sperm flagella and respiratory cilia, resulting in multiple morphological abnormalities of the flagella (MMAF), male infertility, and primary ciliary dyskinesia phenotypes [PMID:30686508, PMID:40158138]. Armc2 deficiency additionally impairs sperm nuclear integrity, including DNA compaction and chromosomal architecture, compromising embryo developmental competence [PMID:40070084]. In vivo delivery of Armc2 mRNA to spermatogenic cells in knockout mice restores normal sperm morphology, motility, and fertilization capacity, confirming that ARMC2 is the causative gene for the observed infertility [PMID:41773826]."},"prefetch_data":{"uniprot":{"accession":"Q8NEN0","full_name":"Armadillo repeat-containing protein 2","aliases":[],"length_aa":867,"mass_kda":96.9,"function":"Required for sperm flagellum axoneme organization and function (By similarity). Involved in axonemal central pair complex assembly and/or stability (By similarity)","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/Q8NEN0/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/ARMC2","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/ARMC2","total_profiled":1310},"omim":[{"mim_id":"618745","title":"SPERMATOGENIC FAILURE 42; SPGF42","url":"https://www.omim.org/entry/618745"},{"mim_id":"618670","title":"SPERMATOGENIC FAILURE 41; SPGF41","url":"https://www.omim.org/entry/618670"},{"mim_id":"618664","title":"SPERMATOGENIC FAILURE 40; SPGF40","url":"https://www.omim.org/entry/618664"},{"mim_id":"618433","title":"SPERMATOGENIC FAILURE 38; SPGF38","url":"https://www.omim.org/entry/618433"},{"mim_id":"618424","title":"ARMADILLO REPEAT-CONTAINING PROTEIN 2; ARMC2","url":"https://www.omim.org/entry/618424"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Uncertain","locations":[{"location":"Nucleoplasm","reliability":"Uncertain"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"testis","ntpm":31.2}],"url":"https://www.proteinatlas.org/search/ARMC2"},"hgnc":{"alias_symbol":["DKFZp434P0714","bA787I22.1"],"prev_symbol":[]},"alphafold":{"accession":"Q8NEN0","domains":[{"cath_id":"1.25.10,1.25.40","chopping":"363-505","consensus_level":"medium","plddt":94.9922,"start":363,"end":505},{"cath_id":"1.25.10.10","chopping":"515-580_598-717","consensus_level":"medium","plddt":95.8478,"start":515,"end":717},{"cath_id":"1.20.930","chopping":"266-345","consensus_level":"medium","plddt":89.6356,"start":266,"end":345}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8NEN0","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8NEN0-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8NEN0-F1-predicted_aligned_error_v6.png","plddt_mean":75.31},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=ARMC2","jax_strain_url":"https://www.jax.org/strain/search?query=ARMC2"},"sequence":{"accession":"Q8NEN0","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8NEN0.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8NEN0/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8NEN0"}},"corpus_meta":[{"pmid":"30686508","id":"PMC_30686508","title":"Bi-allelic Mutations in ARMC2 Lead to Severe Astheno-Teratozoospermia Due to Sperm Flagellum Malformations in Humans and Mice.","date":"2019","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/30686508","citation_count":113,"is_preprint":false},{"pmid":"31621862","id":"PMC_31621862","title":"CFAP70 mutations lead to male infertility due to severe astheno-teratozoospermia. A case report.","date":"2019","source":"Human reproduction (Oxford, England)","url":"https://pubmed.ncbi.nlm.nih.gov/31621862","citation_count":49,"is_preprint":false},{"pmid":"36533425","id":"PMC_36533425","title":"Cargo adapters expand the transport range of intraflagellar transport.","date":"2022","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/36533425","citation_count":37,"is_preprint":false},{"pmid":"34982025","id":"PMC_34982025","title":"Chlamydomonas ARMC2/PF27 is an obligate cargo adapter for intraflagellar transport of radial spokes.","date":"2022","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/34982025","citation_count":25,"is_preprint":false},{"pmid":"39417902","id":"PMC_39417902","title":"Genetic etiological spectrum of sperm morphological abnormalities.","date":"2024","source":"Journal of assisted reproduction and genetics","url":"https://pubmed.ncbi.nlm.nih.gov/39417902","citation_count":12,"is_preprint":false},{"pmid":"35543806","id":"PMC_35543806","title":"Patient with multiple morphological abnormalities of sperm flagella caused by a novel ARMC2 mutation has a favorable pregnancy outcome from intracytoplasmic sperm injection.","date":"2022","source":"Journal of assisted reproduction and genetics","url":"https://pubmed.ncbi.nlm.nih.gov/35543806","citation_count":11,"is_preprint":false},{"pmid":"34493464","id":"PMC_34493464","title":"A novel stop-gain mutation in ARMC2 is associated with multiple morphological abnormalities of the sperm flagella.","date":"2021","source":"Reproductive biomedicine online","url":"https://pubmed.ncbi.nlm.nih.gov/34493464","citation_count":11,"is_preprint":false},{"pmid":"30666567","id":"PMC_30666567","title":"Exome sequencing in genomic regions related to racing performance of Quarter Horses.","date":"2019","source":"Journal of applied genetics","url":"https://pubmed.ncbi.nlm.nih.gov/30666567","citation_count":9,"is_preprint":false},{"pmid":"38492154","id":"PMC_38492154","title":"Identification of novel homozygous asthenoteratospermia-causing ARMC2 mutations associated with multiple morphological abnormalities of the sperm flagella.","date":"2024","source":"Journal of assisted reproduction and genetics","url":"https://pubmed.ncbi.nlm.nih.gov/38492154","citation_count":4,"is_preprint":false},{"pmid":"40158138","id":"PMC_40158138","title":"Broadening the ARMC2 mutational phenotype: linking multiple morphological abnormalities of the Flagella to Pulmonary Manifestations in Primary Ciliary Dyskinesia.","date":"2025","source":"Reproductive biology and endocrinology : RB&E","url":"https://pubmed.ncbi.nlm.nih.gov/40158138","citation_count":1,"is_preprint":false},{"pmid":"40070084","id":"PMC_40070084","title":"A comprehensive study of the sperm head defects in MMAF condition and their impact on embryo development in mice.","date":"2025","source":"Molecular human reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/40070084","citation_count":0,"is_preprint":false},{"pmid":"41773826","id":"PMC_41773826","title":"Sperm motility in mice with oligo-astheno-teratozoospermia restored by in vivo injection and electroporation of naked mRNA.","date":"2026","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/41773826","citation_count":0,"is_preprint":false},{"pmid":"40376536","id":"PMC_40376536","title":"Establishment and clinical significance of genetic factor screening method for patients with nonobstructive azoospermia based on whole exon sequencing technology.","date":"2025","source":"Translational andrology and urology","url":"https://pubmed.ncbi.nlm.nih.gov/40376536","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.07.18.25331799","title":"Profiling Neoadjuvant Therapy Response in Rectal Cancer Using Publicly Available Transcriptomic RNA-seq Datasets","date":"2025-07-23","source":"bioRxiv","url":"https://doi.org/10.1101/2025.07.18.25331799","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":8916,"output_tokens":1775,"usd":0.026686},"stage2":{"model":"claude-opus-4-6","input_tokens":5028,"output_tokens":1789,"usd":0.104798},"total_usd":0.131484,"stage1_batch_id":"msgbatch_01TqNM6p6FsoMBT2jzQTwKBr","stage2_batch_id":"msgbatch_01Ya473eco8sTHbvRymQaU8o","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2019,\n      \"finding\": \"Bi-allelic loss-of-function mutations in ARMC2 cause absence of axonemal central pair complex (CPC) proteins SPAG6 and SPEF2 in sperm flagella, while other axonemal and peri-axonemal components remain present, indicating ARMC2 is specifically required for CPC assembly and/or stability. CRISPR-Cas9 Armc2 knockout mice recapitulate the MMAF phenotype.\",\n      \"method\": \"CRISPR-Cas9 knockout mouse generation, immunostaining of sperm from mutant mice and human patients, transmission electron microscopy\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal orthogonal methods (KO mouse + human patient immunostaining + TEM), replicated across species\",\n      \"pmids\": [\"30686508\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Chlamydomonas ARMC2/PF27 functions as an obligate cargo adapter for intraflagellar transport (IFT) of radial spokes: tagged ARMC2 and radial spoke protein RSP3 co-migrate on anterograde IFT trains, ARMC2 unloads at the flagellar tip and diffuses back to the cell body while RSP3 attaches to the axoneme, and in armc2/pf27 mutants IFT of radial spokes is abolished with spokes restricted to the proximal flagellar region.\",\n      \"method\": \"Live fluorescence imaging of tagged proteins in Chlamydomonas, IFT velocity analysis, armc2/pf27 mutant analysis, co-migration assays\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — direct live imaging of IFT co-migration plus genetic loss-of-function with specific cargo transport phenotype, multiple orthogonal methods in single study\",\n      \"pmids\": [\"34982025\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"ARMC2 interacts with proteins CEP78, PGAM5, RHOA, FXR1, and SKIV2L2, identified by co-immunoprecipitation and mass spectrometry from patient sperm, suggesting involvement of ARMC2 in multiple processes of spermatogenesis.\",\n      \"method\": \"Co-immunoprecipitation (co-IP) and mass spectrometry from human sperm\",\n      \"journal\": \"Journal of assisted reproduction and genetics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single pulldown/MS experiment, no functional validation of individual interactions\",\n      \"pmids\": [\"35543806\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"A homozygous stop-gain mutation in ARMC2 leads to complete absence of the central pair complex (CPC) and disorganized axonemal ultrastructure in patient sperm, confirming ARMC2 is required for CPC assembly and/or stability of the axonemal complex.\",\n      \"method\": \"Whole-exome sequencing, Sanger sequencing, transmission electron microscopy of patient spermatozoa\",\n      \"journal\": \"Reproductive biomedicine online\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — TEM ultrastructural analysis in human patient corroborating mechanistic role, consistent with prior KO mouse data\",\n      \"pmids\": [\"34493464\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"ARMC2 mutations cause absence of axonemal CPC and disorganized peri-axonemal structures in human sperm, and ARMC2 variants are linked to pulmonary Primary Ciliary Dyskinesia phenotypes, indicating ARMC2 function is not restricted to sperm flagella but extends to respiratory cilia.\",\n      \"method\": \"Transmission electron microscopy, immunoblotting, immunofluorescence of patient spermatozoa, whole-exome sequencing\",\n      \"journal\": \"Reproductive biology and endocrinology : RB&E\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — TEM and IF with functional ciliary phenotype in patient, single study\",\n      \"pmids\": [\"40158138\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"In vivo testicular delivery of Armc2 mRNA by injection and electroporation restores morphologically normal and motile sperm in Armc2-deficient mice, with rescued sperm capable of producing embryos via IVF and ICSI, demonstrating that ARMC2 function in spermatogenesis can be rescued by mRNA supplementation.\",\n      \"method\": \"In vivo mRNA electroporation in Armc2 KO mice, sperm morphology analysis, IVF, ICSI, embryo development assessment\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — functional rescue by mRNA in KO model with multiple readouts (morphology, motility, fertilization), provides strong causal evidence\",\n      \"pmids\": [\"41773826\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In Armc2-/- knockout mice, sperm show nuclear defects (morphology, DNA compaction, chromosomal architecture, ploidy abnormalities) and markedly decreased capacity to support embryo development to blastocyst after ICSI, compared to wild-type sperm.\",\n      \"method\": \"Knockout mouse model (Armc2-/-), nuclear morphology analysis, DNA compaction assay, chromosomal architecture analysis, ploidy determination, ICSI with embryo development monitoring\",\n      \"journal\": \"Molecular human reproduction\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with defined cellular and developmental phenotypes, comparative study with other MMAF genes\",\n      \"pmids\": [\"40070084\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"ARMC2 is an armadillo repeat-containing protein that functions as an obligate cargo adapter for intraflagellar transport (IFT) of radial spokes in cilia and flagella, co-migrating with radial spoke proteins on anterograde IFT trains and recycling to the cell body after unloading; loss of ARMC2 abolishes radial spoke IFT and specifically disrupts axonemal central pair complex (CPC) assembly and stability in sperm flagella (and respiratory cilia), causing multiple morphological abnormalities of the flagella (MMAF) and male infertility, a defect reversible by mRNA-based restoration of ARMC2 in spermatogenic cells.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"ARMC2 is an armadillo repeat-containing protein that functions as an obligate cargo adapter for intraflagellar transport (IFT), specifically mediating anterograde delivery of radial spoke complexes along the axoneme; after cargo unloading at the flagellar tip, ARMC2 recycles to the cell body by diffusion [PMID:34982025]. Loss of ARMC2 abolishes radial spoke IFT and causes selective absence of the axonemal central pair complex (CPC) in sperm flagella and respiratory cilia, resulting in multiple morphological abnormalities of the flagella (MMAF), male infertility, and primary ciliary dyskinesia phenotypes [PMID:30686508, PMID:40158138]. Armc2 deficiency additionally impairs sperm nuclear integrity, including DNA compaction and chromosomal architecture, compromising embryo developmental competence [PMID:40070084]. In vivo delivery of Armc2 mRNA to spermatogenic cells in knockout mice restores normal sperm morphology, motility, and fertilization capacity, confirming that ARMC2 is the causative gene for the observed infertility [PMID:41773826].\",\n  \"teleology\": [\n    {\n      \"year\": 2019,\n      \"claim\": \"Establishing ARMC2 as a disease gene: bi-allelic ARMC2 mutations were shown to cause MMAF by specifically disrupting CPC assembly/stability in sperm flagella, resolving the question of whether ARMC2 has a ciliary structural role.\",\n      \"evidence\": \"CRISPR-Cas9 knockout mice and human patient sperm immunostaining plus TEM\",\n      \"pmids\": [\"30686508\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Mechanism by which ARMC2 supports CPC assembly was unknown\",\n        \"Whether ARMC2 acts in transport or structural scaffolding was unresolved\",\n        \"Role in non-sperm cilia not addressed\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Independent patient studies confirmed the CPC-specific defect, reinforcing that ARMC2 loss-of-function selectively destroys the central pair rather than globally disrupting the axoneme.\",\n      \"evidence\": \"Whole-exome sequencing and TEM of patient spermatozoa carrying a homozygous stop-gain ARMC2 mutation\",\n      \"pmids\": [\"34493464\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No biochemical reconstitution of ARMC2–CPC interaction\",\n        \"Genotype–phenotype relationship across mutation types not systematically characterized\"\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"The mechanistic basis was resolved: ARMC2 functions as an obligate IFT cargo adapter for radial spokes, co-migrating with RSP3 on anterograde IFT trains and recycling after unloading, explaining how CPC assembly depends on ARMC2-mediated transport.\",\n      \"evidence\": \"Live fluorescence imaging of tagged ARMC2 and RSP3 in Chlamydomonas, with armc2/pf27 mutant analysis\",\n      \"pmids\": [\"34982025\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural basis of ARMC2–radial spoke or ARMC2–IFT train interaction unknown\",\n        \"Whether ARMC2 transports additional cargo beyond radial spokes not determined\",\n        \"Mammalian live-imaging confirmation of IFT adapter function lacking\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"ARMC2 function was extended beyond sperm flagella: patient variants linked to pulmonary primary ciliary dyskinesia phenotypes, establishing ARMC2 as a general motile cilia gene.\",\n      \"evidence\": \"TEM, immunofluorescence, and immunoblotting of patient spermatozoa combined with respiratory ciliary phenotyping\",\n      \"pmids\": [\"40158138\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Respiratory cilia ultrastructural analysis not shown in detail\",\n        \"Whether the same CPC-specific defect underlies the respiratory phenotype not directly demonstrated\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"ARMC2 deficiency was shown to impair not only flagellar structure but also sperm nuclear integrity and embryo developmental competence, broadening understanding of its spermatogenic role.\",\n      \"evidence\": \"Armc2-/- knockout mice with nuclear morphology, DNA compaction, ploidy, and ICSI embryo development assays\",\n      \"pmids\": [\"40070084\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether nuclear defects are a direct consequence of ARMC2 loss or secondary to flagellar disorganization is unknown\",\n        \"Molecular mechanism linking ARMC2 to nuclear compaction not identified\"\n      ]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Functional rescue by in vivo mRNA delivery proved that ARMC2 is both necessary and sufficient for restoring spermatogenesis in the knockout, providing proof-of-concept for therapeutic correction.\",\n      \"evidence\": \"Testicular Armc2 mRNA electroporation in KO mice with sperm morphology, motility, IVF, and ICSI readouts\",\n      \"pmids\": [\"41773826\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Duration and efficiency of mRNA-based rescue in long-term spermatogenesis not characterized\",\n        \"Applicability of electroporation-based delivery to clinical settings unknown\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The structural basis of ARMC2's interaction with IFT trains and radial spoke cargo, and whether ARMC2 transports additional axonemal subcomplexes in mammalian cilia, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"No cryo-EM or crystal structure of ARMC2 or its complexes\",\n        \"Mammalian live-imaging of ARMC2 IFT behavior not performed\",\n        \"Whether ARMC2 nuclear effects are direct or indirect is unresolved\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005929\", \"supporting_discovery_ids\": [0, 1, 3, 4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"R-HSA-1474165\", \"supporting_discovery_ids\": [0, 5, 6]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"RSP3\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}