{"gene":"ARMC2","run_date":"2026-06-09T22:02:44","timeline":{"discoveries":[{"year":2019,"finding":"Bi-allelic loss-of-function mutations in ARMC2 cause MMAF (multiple morphological abnormalities of the flagella) in humans and mice. Immunostaining in ARMC2-mutated individuals and Armc2 knockout mice showed absence of axonemal central pair complex (CPC) proteins SPAG6 and SPEF2, while other axonemal and peri-axonemal components were present, indicating ARMC2 is specifically required for CPC assembly and/or stability.","method":"CRISPR-Cas9 knockout mouse generation, whole-exome sequencing, immunostaining/immunofluorescence","journal":"American journal of human genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal validation in human patients and CRISPR KO mouse model with specific immunostaining readout, replicated across multiple unrelated affected individuals","pmids":["30686508"],"is_preprint":false},{"year":2022,"finding":"ARMC2 (ortholog PF27 in Chlamydomonas) functions as an obligate cargo adapter for intraflagellar transport (IFT) of radial spokes. Tagged ARMC2 and radial spoke protein RSP3 co-migrated on anterograde IFT trains; after unloading at the flagellar tip, RSP3 attached to the axoneme while ARMC2 diffused back to the cell body. In armc2/pf27 mutants, IFT of radial spokes was abolished and radial spokes were limited to the proximal flagellar region.","method":"Live fluorescence imaging of tagged proteins in Chlamydomonas, IFT motility assays, genetic mutant analysis","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — direct live imaging of co-migration, genetic loss-of-function with specific cargo transport phenotype, multiple orthogonal approaches in a single rigorous study","pmids":["34982025"],"is_preprint":false},{"year":2021,"finding":"A homozygous stop-gain mutation in ARMC2 (c.182C>G, p.S61X) causes MMAF with complete absence of the central pair complex (CPC) and axonemal disorganization in patient spermatozoa, as shown by transmission electron microscopy.","method":"Whole-exome sequencing, Sanger sequencing, transmission electron microscopy of patient sperm ultrastructure","journal":"Reproductive biomedicine online","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — single family, single lab, TEM with specific ultrastructural phenotype but limited mechanistic follow-up","pmids":["34493464"],"is_preprint":false},{"year":2022,"finding":"Co-immunoprecipitation and mass spectrometry from patient sperm identified CEP78, PGAM5, RHOA, FXR1, and SKIV2L2 as proteins interacting with ARMC2, suggesting ARMC2 participates in multiple processes of spermatogenesis.","method":"Co-immunoprecipitation (co-IP) and mass spectrometry","journal":"Journal of assisted reproduction and genetics","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single co-IP/MS experiment, single lab, no reciprocal validation or functional follow-up of interactions","pmids":["35543806"],"is_preprint":false},{"year":2024,"finding":"Two novel homozygous missense ARMC2 variants (p.P105L and p.N743D) cause MMAF with absence of the CPC and disrupted axonemal ultrastructure. In vitro experiments in HEK293T cells showed both variants caused slightly increased ARMC2 protein expression, indicating these are partial loss-of-function variants rather than null alleles.","method":"Whole-exome sequencing, transmission electron microscopy, immunostaining, in vitro expression in HEK293T cells","journal":"Journal of assisted reproduction and genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — in vitro functional validation combined with patient ultrastructural analysis, single lab","pmids":["38492154"],"is_preprint":false},{"year":2025,"finding":"ARMC2 mutations are associated with primary ciliary dyskinesia (PCD) pulmonary phenotypes in addition to MMAF. Immunoblotting and immunofluorescence of patient spermatozoa showed reduced ARMC2 expression and absence/disorganization of multiple axonemal structural proteins including the CPC, extending the ciliary role of ARMC2 beyond sperm flagella.","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 / Weak — multiple orthogonal methods (TEM, WB, IF) in patient material, single lab, novel phenotypic extension","pmids":["40158138"],"is_preprint":false},{"year":2026,"finding":"In vivo testicular injection and electroporation of Armc2 mRNA in Armc2-deficient mice restored morphologically normal and motile sperm capable of producing embryos via IVF and ICSI, providing proof-of-concept that loss of ARMC2 protein is the direct cause of the OAT phenotype.","method":"In vivo mRNA delivery by testicular electroporation in Armc2 knockout mice, sperm morphology and motility analysis, IVF/ICSI embryo production","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — functional rescue of genetic deficiency by mRNA replacement with multiple phenotypic readouts (morphology, motility, fertilization), single lab but rigorous design","pmids":["41773826"],"is_preprint":false},{"year":2025,"finding":"Armc2 knockout mice exhibit sperm nuclear defects (morphology, DNA compaction, chromosomal architecture, ploidy) and a marked decrease in embryo developmental potential after ICSI into wild-type oocytes, with developmental failure rates intermediate among four MMAF-associated KO lines (Ccdc146 > Cfap43 > Armc2 ≈ Cfap44).","method":"Knockout mouse comparative study, sperm nuclear morphology analysis, DNA compaction assay, chromosomal architecture analysis, ploidy measurement, ICSI with embryo development tracking to blastocyst stage","journal":"Molecular human reproduction","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — controlled comparative KO study with multiple orthogonal readouts, but single lab","pmids":["40070084"],"is_preprint":false}],"current_model":"ARMC2 is an armadillo repeat protein that functions as an obligate cargo adapter for intraflagellar transport (IFT) of radial spokes in cilia and flagella; it co-migrates with radial spoke proteins on anterograde IFT trains, unloads at the flagellar tip, and returns to the cell body, and its loss abolishes radial spoke transport and causes absence of the axonemal central pair complex, leading to severe sperm flagellar structural defects (MMAF), male infertility, and in some cases primary ciliary dyskinesia with pulmonary manifestations."},"narrative":{"mechanistic_narrative":"ARMC2 is an armadillo repeat protein that functions as an obligate cargo adapter for intraflagellar transport (IFT) of radial spokes during ciliary and flagellar assembly [PMID:34982025]. Live imaging of its Chlamydomonas ortholog (PF27) showed that tagged ARMC2 co-migrates with the radial spoke protein RSP3 on anterograde IFT trains, then diffuses back to the cell body after RSP3 is unloaded and incorporated at the flagellar tip; in armc2/pf27 mutants radial spoke transport is abolished and spokes are confined to the proximal flagellum [PMID:34982025]. Loss of ARMC2 in humans and mice causes multiple morphological abnormalities of the flagella (MMAF) and male infertility, with specific absence of the axonemal central pair complex proteins (e.g. SPAG6, SPEF2) while other axonemal components persist, establishing a selective requirement in central pair complex assembly and/or stability [PMID:30686508, PMID:34493464]. ARMC2 deficiency also produces sperm nuclear and chromatin defects and reduced embryo developmental potential after ICSI [PMID:40070084], and bi-allelic ARMC2 mutations extend to primary ciliary dyskinesia with pulmonary manifestations [PMID:40158138]. Testicular mRNA replacement in Armc2-deficient mice restores normal, motile sperm competent for fertilization, demonstrating that loss of ARMC2 protein is the direct cause of the phenotype [PMID:41773826].","teleology":[{"year":2019,"claim":"Established that ARMC2 is genetically required for sperm flagellar formation and, specifically, for assembly or stability of the axonemal central pair complex, defining its first biological role.","evidence":"Whole-exome sequencing of MMAF patients, CRISPR-Cas9 Armc2 knockout mice, and immunostaining for central pair proteins SPAG6/SPEF2","pmids":["30686508"],"confidence":"High","gaps":["Did not reveal the molecular activity through which ARMC2 supports central pair assembly","No direct interaction partners or transport mechanism identified","Restricted to sperm flagella; broader ciliary role untested"]},{"year":2021,"claim":"Confirmed in an additional family that a null ARMC2 allele produces MMAF with complete absence of the central pair complex, reinforcing the genotype-phenotype link.","evidence":"Whole-exome and Sanger sequencing plus transmission electron microscopy of patient sperm ultrastructure","pmids":["34493464"],"confidence":"Medium","gaps":["Single family, no mechanistic follow-up","Does not address how ARMC2 acts at the molecular level"]},{"year":2022,"claim":"Resolved the molecular mechanism by showing ARMC2 is an obligate IFT cargo adapter that ferries radial spokes into the flagellum, explaining why its loss disrupts axonemal architecture.","evidence":"Live fluorescence imaging of tagged ARMC2 and RSP3, IFT motility assays, and genetic mutant analysis in Chlamydomonas","pmids":["34982025"],"confidence":"High","gaps":["Direct biochemical interaction between ARMC2 and radial spoke proteins not reconstituted","How ARMC2 links cargo to IFT trains and triggers unloading at the tip unknown","Relationship between radial spoke adapter role and central pair complex loss not mechanistically connected"]},{"year":2022,"claim":"Attempted to define the ARMC2 interactome in sperm, nominating candidate partners involved in spermatogenesis.","evidence":"Co-immunoprecipitation and mass spectrometry from patient sperm identifying CEP78, PGAM5, RHOA, FXR1, SKIV2L2","pmids":["35543806"],"confidence":"Low","gaps":["Single co-IP/MS without reciprocal validation or functional follow-up","Interactions may be indirect or non-specific","No link established between these candidates and the IFT/central pair role"]},{"year":2024,"claim":"Demonstrated that missense ARMC2 variants act as partial loss-of-function alleles yet still abolish the central pair complex, refining the allelic spectrum of disease.","evidence":"Whole-exome sequencing, TEM and immunostaining of patient sperm, and in vitro expression of variants in HEK293T cells","pmids":["38492154"],"confidence":"Medium","gaps":["Expression-level effects measured but functional consequence on transport not assayed","Single lab, limited families"]},{"year":2025,"claim":"Extended the ciliary role of ARMC2 beyond sperm by linking its mutations to primary ciliary dyskinesia pulmonary phenotypes.","evidence":"TEM, immunoblotting and immunofluorescence of patient spermatozoa plus whole-exome sequencing","pmids":["40158138"],"confidence":"Medium","gaps":["Direct evidence of ARMC2 function in respiratory cilia not shown","Mechanism of pulmonary manifestation inferred from sperm data"]},{"year":2025,"claim":"Showed that ARMC2 loss compromises sperm nuclear integrity and post-fertilization embryo development, broadening its phenotypic impact beyond flagellar structure.","evidence":"Comparative knockout mouse study with sperm nuclear morphology, DNA compaction, chromosomal architecture, ploidy assays and ICSI embryo tracking","pmids":["40070084"],"confidence":"Medium","gaps":["Mechanistic link between an IFT cargo adapter and nuclear/chromatin defects unclear","Single lab comparative study"]},{"year":2026,"claim":"Provided causal proof that absence of ARMC2 protein directly produces the infertility phenotype by rescuing it with mRNA replacement.","evidence":"In vivo testicular electroporation of Armc2 mRNA in knockout mice with sperm morphology/motility analysis and IVF/ICSI embryo production","pmids":["41773826"],"confidence":"High","gaps":["Durability and developmental window of rescue not fully defined","Does not resolve the molecular steps between ARMC2 restoration and central pair assembly"]},{"year":null,"claim":"How ARMC2 biochemically couples radial spoke cargo to IFT trains, and how this adapter role mechanistically governs central pair complex assembly and sperm nuclear integrity, remains unresolved.","evidence":"","pmids":[],"confidence":"High","gaps":["No structural model of ARMC2-cargo or ARMC2-IFT engagement","No reconstituted biochemistry of the adapter function","Connection between radial spoke transport and central pair loss not directly demonstrated"]}],"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":[1,5]},{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[0,1]}],"pathway":[{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[1]},{"term_id":"R-HSA-1474165","term_label":"Reproduction","supporting_discovery_ids":[0,6]}],"complexes":[],"partners":["RSP3"],"other_free_text":[]}},"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":114,"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":50,"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":17,"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":"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":"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":"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":1,"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":"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":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":9687,"output_tokens":2063,"usd":0.030003,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9051,"output_tokens":2891,"usd":0.058765,"stage2_stop_reason":"end_turn"},"total_usd":0.088768,"stage1_batch_id":"msgbatch_0179Z2pxRYBsXi2xADneafRw","stage2_batch_id":"msgbatch_01LaY9ZaVdgjWArcZo9eqQE5","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 MMAF (multiple morphological abnormalities of the flagella) in humans and mice. Immunostaining in ARMC2-mutated individuals and Armc2 knockout mice showed absence of axonemal central pair complex (CPC) proteins SPAG6 and SPEF2, while other axonemal and peri-axonemal components were present, indicating ARMC2 is specifically required for CPC assembly and/or stability.\",\n      \"method\": \"CRISPR-Cas9 knockout mouse generation, whole-exome sequencing, immunostaining/immunofluorescence\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal validation in human patients and CRISPR KO mouse model with specific immunostaining readout, replicated across multiple unrelated affected individuals\",\n      \"pmids\": [\"30686508\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"ARMC2 (ortholog PF27 in Chlamydomonas) functions as an obligate cargo adapter for intraflagellar transport (IFT) of radial spokes. Tagged ARMC2 and radial spoke protein RSP3 co-migrated on anterograde IFT trains; after unloading at the flagellar tip, RSP3 attached to the axoneme while ARMC2 diffused back to the cell body. In armc2/pf27 mutants, IFT of radial spokes was abolished and radial spokes were limited to the proximal flagellar region.\",\n      \"method\": \"Live fluorescence imaging of tagged proteins in Chlamydomonas, IFT motility assays, genetic mutant analysis\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — direct live imaging of co-migration, genetic loss-of-function with specific cargo transport phenotype, multiple orthogonal approaches in a single rigorous study\",\n      \"pmids\": [\"34982025\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"A homozygous stop-gain mutation in ARMC2 (c.182C>G, p.S61X) causes MMAF with complete absence of the central pair complex (CPC) and axonemal disorganization in patient spermatozoa, as shown by transmission electron microscopy.\",\n      \"method\": \"Whole-exome sequencing, Sanger sequencing, transmission electron microscopy of patient sperm ultrastructure\",\n      \"journal\": \"Reproductive biomedicine online\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — single family, single lab, TEM with specific ultrastructural phenotype but limited mechanistic follow-up\",\n      \"pmids\": [\"34493464\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Co-immunoprecipitation and mass spectrometry from patient sperm identified CEP78, PGAM5, RHOA, FXR1, and SKIV2L2 as proteins interacting with ARMC2, suggesting ARMC2 participates in multiple processes of spermatogenesis.\",\n      \"method\": \"Co-immunoprecipitation (co-IP) and mass spectrometry\",\n      \"journal\": \"Journal of assisted reproduction and genetics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single co-IP/MS experiment, single lab, no reciprocal validation or functional follow-up of interactions\",\n      \"pmids\": [\"35543806\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Two novel homozygous missense ARMC2 variants (p.P105L and p.N743D) cause MMAF with absence of the CPC and disrupted axonemal ultrastructure. In vitro experiments in HEK293T cells showed both variants caused slightly increased ARMC2 protein expression, indicating these are partial loss-of-function variants rather than null alleles.\",\n      \"method\": \"Whole-exome sequencing, transmission electron microscopy, immunostaining, in vitro expression in HEK293T cells\",\n      \"journal\": \"Journal of assisted reproduction and genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — in vitro functional validation combined with patient ultrastructural analysis, single lab\",\n      \"pmids\": [\"38492154\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"ARMC2 mutations are associated with primary ciliary dyskinesia (PCD) pulmonary phenotypes in addition to MMAF. Immunoblotting and immunofluorescence of patient spermatozoa showed reduced ARMC2 expression and absence/disorganization of multiple axonemal structural proteins including the CPC, extending the ciliary role of ARMC2 beyond sperm flagella.\",\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 / Weak — multiple orthogonal methods (TEM, WB, IF) in patient material, single lab, novel phenotypic extension\",\n      \"pmids\": [\"40158138\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"In vivo testicular injection and electroporation of Armc2 mRNA in Armc2-deficient mice restored morphologically normal and motile sperm capable of producing embryos via IVF and ICSI, providing proof-of-concept that loss of ARMC2 protein is the direct cause of the OAT phenotype.\",\n      \"method\": \"In vivo mRNA delivery by testicular electroporation in Armc2 knockout mice, sperm morphology and motility analysis, IVF/ICSI embryo production\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — functional rescue of genetic deficiency by mRNA replacement with multiple phenotypic readouts (morphology, motility, fertilization), single lab but rigorous design\",\n      \"pmids\": [\"41773826\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Armc2 knockout mice exhibit sperm nuclear defects (morphology, DNA compaction, chromosomal architecture, ploidy) and a marked decrease in embryo developmental potential after ICSI into wild-type oocytes, with developmental failure rates intermediate among four MMAF-associated KO lines (Ccdc146 > Cfap43 > Armc2 ≈ Cfap44).\",\n      \"method\": \"Knockout mouse comparative study, sperm nuclear morphology analysis, DNA compaction assay, chromosomal architecture analysis, ploidy measurement, ICSI with embryo development tracking to blastocyst stage\",\n      \"journal\": \"Molecular human reproduction\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — controlled comparative KO study with multiple orthogonal readouts, but single lab\",\n      \"pmids\": [\"40070084\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"ARMC2 is an armadillo repeat protein that functions as an obligate cargo adapter for intraflagellar transport (IFT) of radial spokes in cilia and flagella; it co-migrates with radial spoke proteins on anterograde IFT trains, unloads at the flagellar tip, and returns to the cell body, and its loss abolishes radial spoke transport and causes absence of the axonemal central pair complex, leading to severe sperm flagellar structural defects (MMAF), male infertility, and in some cases primary ciliary dyskinesia with pulmonary manifestations.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"ARMC2 is an armadillo repeat protein that functions as an obligate cargo adapter for intraflagellar transport (IFT) of radial spokes during ciliary and flagellar assembly [#1]. Live imaging of its Chlamydomonas ortholog (PF27) showed that tagged ARMC2 co-migrates with the radial spoke protein RSP3 on anterograde IFT trains, then diffuses back to the cell body after RSP3 is unloaded and incorporated at the flagellar tip; in armc2/pf27 mutants radial spoke transport is abolished and spokes are confined to the proximal flagellum [#1]. Loss of ARMC2 in humans and mice causes multiple morphological abnormalities of the flagella (MMAF) and male infertility, with specific absence of the axonemal central pair complex proteins (e.g. SPAG6, SPEF2) while other axonemal components persist, establishing a selective requirement in central pair complex assembly and/or stability [#0, #2]. ARMC2 deficiency also produces sperm nuclear and chromatin defects and reduced embryo developmental potential after ICSI [#7], and bi-allelic ARMC2 mutations extend to primary ciliary dyskinesia with pulmonary manifestations [#5]. Testicular mRNA replacement in Armc2-deficient mice restores normal, motile sperm competent for fertilization, demonstrating that loss of ARMC2 protein is the direct cause of the phenotype [#6].\",\n  \"teleology\": [\n    {\n      \"year\": 2019,\n      \"claim\": \"Established that ARMC2 is genetically required for sperm flagellar formation and, specifically, for assembly or stability of the axonemal central pair complex, defining its first biological role.\",\n      \"evidence\": \"Whole-exome sequencing of MMAF patients, CRISPR-Cas9 Armc2 knockout mice, and immunostaining for central pair proteins SPAG6/SPEF2\",\n      \"pmids\": [\"30686508\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Did not reveal the molecular activity through which ARMC2 supports central pair assembly\",\n        \"No direct interaction partners or transport mechanism identified\",\n        \"Restricted to sperm flagella; broader ciliary role untested\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Confirmed in an additional family that a null ARMC2 allele produces MMAF with complete absence of the central pair complex, reinforcing the genotype-phenotype link.\",\n      \"evidence\": \"Whole-exome and Sanger sequencing plus transmission electron microscopy of patient sperm ultrastructure\",\n      \"pmids\": [\"34493464\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Single family, no mechanistic follow-up\",\n        \"Does not address how ARMC2 acts at the molecular level\"\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Resolved the molecular mechanism by showing ARMC2 is an obligate IFT cargo adapter that ferries radial spokes into the flagellum, explaining why its loss disrupts axonemal architecture.\",\n      \"evidence\": \"Live fluorescence imaging of tagged ARMC2 and RSP3, IFT motility assays, and genetic mutant analysis in Chlamydomonas\",\n      \"pmids\": [\"34982025\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Direct biochemical interaction between ARMC2 and radial spoke proteins not reconstituted\",\n        \"How ARMC2 links cargo to IFT trains and triggers unloading at the tip unknown\",\n        \"Relationship between radial spoke adapter role and central pair complex loss not mechanistically connected\"\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Attempted to define the ARMC2 interactome in sperm, nominating candidate partners involved in spermatogenesis.\",\n      \"evidence\": \"Co-immunoprecipitation and mass spectrometry from patient sperm identifying CEP78, PGAM5, RHOA, FXR1, SKIV2L2\",\n      \"pmids\": [\"35543806\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"Single co-IP/MS without reciprocal validation or functional follow-up\",\n        \"Interactions may be indirect or non-specific\",\n        \"No link established between these candidates and the IFT/central pair role\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Demonstrated that missense ARMC2 variants act as partial loss-of-function alleles yet still abolish the central pair complex, refining the allelic spectrum of disease.\",\n      \"evidence\": \"Whole-exome sequencing, TEM and immunostaining of patient sperm, and in vitro expression of variants in HEK293T cells\",\n      \"pmids\": [\"38492154\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Expression-level effects measured but functional consequence on transport not assayed\",\n        \"Single lab, limited families\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Extended the ciliary role of ARMC2 beyond sperm by linking its mutations to primary ciliary dyskinesia pulmonary phenotypes.\",\n      \"evidence\": \"TEM, immunoblotting and immunofluorescence of patient spermatozoa plus whole-exome sequencing\",\n      \"pmids\": [\"40158138\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Direct evidence of ARMC2 function in respiratory cilia not shown\",\n        \"Mechanism of pulmonary manifestation inferred from sperm data\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Showed that ARMC2 loss compromises sperm nuclear integrity and post-fertilization embryo development, broadening its phenotypic impact beyond flagellar structure.\",\n      \"evidence\": \"Comparative knockout mouse study with sperm nuclear morphology, DNA compaction, chromosomal architecture, ploidy assays and ICSI embryo tracking\",\n      \"pmids\": [\"40070084\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Mechanistic link between an IFT cargo adapter and nuclear/chromatin defects unclear\",\n        \"Single lab comparative study\"\n      ]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Provided causal proof that absence of ARMC2 protein directly produces the infertility phenotype by rescuing it with mRNA replacement.\",\n      \"evidence\": \"In vivo testicular electroporation of Armc2 mRNA in knockout mice with sperm morphology/motility analysis and IVF/ICSI embryo production\",\n      \"pmids\": [\"41773826\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Durability and developmental window of rescue not fully defined\",\n        \"Does not resolve the molecular steps between ARMC2 restoration and central pair assembly\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How ARMC2 biochemically couples radial spoke cargo to IFT trains, and how this adapter role mechanistically governs central pair complex assembly and sperm nuclear integrity, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"No structural model of ARMC2-cargo or ARMC2-IFT engagement\",\n        \"No reconstituted biochemistry of the adapter function\",\n        \"Connection between radial spoke transport and central pair loss not directly demonstrated\"\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\": [1, 5]},\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"R-HSA-1474165\", \"supporting_discovery_ids\": [0, 6]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"RSP3\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}