{"gene":"TERB1","run_date":"2026-06-10T10:51:54","timeline":{"discoveries":[{"year":2014,"finding":"TERB1 (CCDC79) is a meiosis-specific Myb-domain protein that localizes to telomeres in mouse germ cells, forms a heterocomplex with the canonical telomeric protein TRF1, and binds telomere repeat DNA. TERB1 promotes telomere association with the nuclear envelope and deposition of the SUN-KASH complex (which recruits cytoplasmic motor complexes), and also recruits cohesin to telomeres to develop structural rigidity. Disruption of Terb1 abolishes meiotic chromosomal movement and impairs homologous pairing and synapsis, causing infertility in both sexes.","method":"Mouse knockout, Co-immunoprecipitation, telomere DNA binding assay, immunofluorescence localization, genetic epistasis","journal":"Nature cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, mouse KO with defined phenotypes, multiple orthogonal methods, replicated by independent study (PMID:24885367)","pmids":["24413433"],"is_preprint":false},{"year":2014,"finding":"CCDC79 (TERB1) is a meiosis-specific protein that localizes to telomeres from leptotene to diplotene stages. CCDC79 associates with telomeres independently of SUN1-mediated nuclear envelope attachment (localization persists in SUN1-deficient spermatocytes), but is largely absent from telomeres that fail to connect to SUN1 in SMC1B-deficient spermatocytes.","method":"Immunofluorescence localization in wild-type and mutant (SUN1-deficient, SMC1B-deficient) spermatocytes","journal":"BMC cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct localization experiments in multiple genetic backgrounds, independently corroborating PMID:24413433","pmids":["24885367"],"is_preprint":false},{"year":2017,"finding":"Crystal structure of the TRF1-binding motif (TBM) of human TERB1 in complex with the TRFH domain of TRF1 was solved. A specific point mutation disrupting the TERB1-TRF1 interaction in mice causes infertility only in males, with arrest at the zygotene-early pachytene stage, mild telomere abnormalities on autosomes, and failure of X-Y chromosome pairing at the pseudoautosomal region (PAR) in pachytene.","method":"Crystal structure determination, point-mutant knock-in mouse, immunofluorescence, FISH","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure with functional validation via knock-in point mutant mouse, single lab but two orthogonal methods","pmids":["29083416"],"is_preprint":false},{"year":2017,"finding":"TERB1 contains distinct functional domains: a TRF1-binding motif required for TRF1 interaction; a TERB2-binding (T2B) domain required for TERB1-TERB2 interaction and telomere attachment to the nuclear envelope (but dispensable for TRF1-TERB1 interaction); and an MYB-like domain required for cohesin recruitment at telomeres (but not for TERB2-MAJIN assembly). TRF1 directs the sequential assembly of TERB1-TERB2-MAJIN.","method":"Germ-cell-specific TRF1 knockout mouse, domain-specific TERB1 mutant analysis, Co-immunoprecipitation, immunofluorescence","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional KO plus domain-specific mutants with orthogonal Co-IP and localization readouts, mechanistic dissection of multiple domains","pmids":["29141207"],"is_preprint":false},{"year":2018,"finding":"Crystal structure of the MAJIN-TERB2 complex (2:2 hetero-tetramer) was determined; MAJIN-TERB2 strongly binds DNA and is tethered via long flexible linkers to the inner nuclear membrane and to two TRF1-binding 1:1 TERB2-TERB1 complexes. Structured illumination microscopy and biochemical data revealed a telomere attachment mechanism in which MAJIN-TERB2-TERB1 first recruits telomere-bound TRF1, which is then displaced during pachytene, allowing MAJIN-TERB2-TERB1 to bind telomeric DNA and form a mature attachment plate.","method":"Crystal structure determination, X-ray scattering, biochemical DNA binding assays, structured illumination microscopy","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure plus multiple orthogonal biochemical and imaging methods in a single study","pmids":["30559341"],"is_preprint":false},{"year":2019,"finding":"Crystal structures of human TERB1-TERB2 and TERB2-MAJIN subcomplexes were determined. Specific disruption of either the TERB1-TERB2 interaction or the TERB2-MAJIN interaction by point mutations in the mouse Terb2 gene abolishes telomere attachment to the nuclear envelope and causes aberrant homologous pairing and disordered synapsis. SUN1 depletion partially disrupts the telomere-NE connection, suggesting that the telomere-TRF1-TERB1-TERB2-MAJIN-NE pathway and the LINC complex pathway are two separate but cooperative routes for stable telomere-NE recruitment.","method":"Crystal structure determination, knock-in point mutant mice (Terb2 gene), SUN1 depletion, immunofluorescence, chromosome spreading","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structures plus in vivo knock-in mouse validation with multiple interaction-specific mutations and epistasis analysis","pmids":["30718482"],"is_preprint":false},{"year":2022,"finding":"The TERB1 MYB domain has lost its canonical DNA-binding activity. In Terb1 point-mutant mice lacking the functional MYB domain, telomere localization of TERB1 and the downstream TERB2-MAJIN complex, homologous pairing, and fertility are unaffected. Instead, the MYB domain is required for cohesin enrichment at telomeres and remodeling of axial elements at the early-to-late pachytene transition, thereby suppressing telomere erosion during meiotic prophase I.","method":"In vitro DNA-binding assay, Terb1 MYB-domain point-mutant knock-in mouse, immunofluorescence, telomere FISH, chromosome spreading","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — in vitro activity assay for DNA binding plus knock-in mouse with defined molecular and cellular readouts, single lab with multiple orthogonal methods","pmids":["35081355"],"is_preprint":false},{"year":2024,"finding":"In medaka (fish ortholog), loss of terb1 causes failure to complete synaptonemal complex formation despite initiation of lateral elements and fragmented transverse filaments, and results in aberrant homologous chromosome arrangement. The oogenesis-spermatogenesis checkpoint response to terb1 loss is sexually dimorphic: oogenesis arrests at zygotene-like stage while spermatogenesis continues to produce sperm-like cells with abnormal DNA content.","method":"Medaka terb1 mutant (loss-of-function), immunofluorescence, FISH, cytological analysis of SC","journal":"Zoological science","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — single lab, clean KO with defined cellular phenotypes in a non-mammalian model (medaka), no molecular interaction data","pmids":["38809870"],"is_preprint":false}],"current_model":"TERB1 is a meiosis-specific telomere-associated protein that acts as a central scaffold at meiotic telomeres: it binds TRF1 via its TRF1-binding motif (structurally defined by crystal structure), recruits TERB2-MAJIN through its T2B domain to tether telomeres to the nuclear envelope, promotes SUN-KASH (LINC) complex deposition to transmit cytoskeletal forces for chromosome movement, recruits cohesin via its MYB domain (which has lost canonical DNA-binding activity) to confer telomere structural rigidity and suppress telomere erosion in late pachytene, and coordinates sequential assembly of the entire meiotic telomere complex (TRF1→TERB1→TERB2→MAJIN) culminating in TRF1 displacement and direct MAJIN-TERB2-TERB1 binding to telomeric DNA at the mature attachment plate; loss of TERB1 function abolishes meiotic chromosomal movement, impairs homologous pairing and synapsis, and causes infertility in both sexes."},"narrative":{"mechanistic_narrative":"TERB1 (CCDC79) is a meiosis-specific telomere protein that serves as the central scaffold tethering telomeres to the nuclear envelope to drive chromosome movement, homologous pairing, and synapsis during meiotic prophase I [PMID:24413433]. It localizes to telomeres from leptotene to diplotene and engages the canonical telomeric protein TRF1 through a dedicated TRF1-binding motif, whose interaction with the TRFH domain of TRF1 is defined at atomic resolution [PMID:24413433, PMID:29083416]. TERB1 is organized into separable functional modules: the TRF1-binding motif, a TERB2-binding (T2B) domain that recruits the TERB2-MAJIN subcomplex for nuclear-envelope attachment, and an MYB-like domain dedicated to cohesin recruitment [PMID:29141207]. Within the assembled complex, TRF1 directs sequential recruitment of TERB1→TERB2→MAJIN, and the MAJIN-TERB2-TERB1 module first captures telomere-bound TRF1 and then displaces it during pachytene, taking over direct telomeric DNA binding to form a mature attachment plate [PMID:29141207, PMID:30559341]. The MYB domain has lost canonical DNA-binding activity and instead enriches cohesin at telomeres and remodels axial elements at the early-to-late pachytene transition, conferring structural rigidity that suppresses telomere erosion without affecting pairing or fertility [PMID:35081355]. This nuclear-envelope tethering pathway operates cooperatively with, but separably from, the SUN-KASH LINC complex route to stably anchor telomeres [PMID:30718482]. Disruption of TERB1 abolishes meiotic chromosomal movement and impairs pairing and synapsis, causing infertility, with the requirement conserved in fish meiosis [PMID:24413433, PMID:38809870].","teleology":[{"year":2014,"claim":"Established TERB1 as a meiosis-specific telomere factor that physically links telomeres to the nuclear envelope and is essential for the chromosome movements underlying pairing and synapsis.","evidence":"Mouse knockout with reciprocal Co-IP, telomere DNA-binding and localization assays, genetic epistasis","pmids":["24413433"],"confidence":"High","gaps":["Domain-level basis for TRF1 binding, NE attachment, and cohesin recruitment not yet resolved","Order of complex assembly undefined"]},{"year":2014,"claim":"Defined TERB1's place in the telomere-NE attachment hierarchy, showing it loads onto telomeres independently of SUN1 but depends on cohesin (SMC1B) for stable association.","evidence":"Immunofluorescence in SUN1-deficient and SMC1B-deficient spermatocytes","pmids":["24885367"],"confidence":"High","gaps":["Did not resolve direct versus indirect dependence on cohesin","Molecular interactions not tested"]},{"year":2017,"claim":"Provided the structural basis of the TERB1-TRF1 interaction and demonstrated its specific in vivo requirement for meiotic telomere function.","evidence":"Crystal structure of TERB1 TBM with the TRF1 TRFH domain plus interaction-disrupting knock-in mouse, IF and FISH","pmids":["29083416"],"confidence":"High","gaps":["Why disruption causes male-only infertility unexplained","Mechanism of PAR/X-Y pairing failure not resolved"]},{"year":2017,"claim":"Dissected TERB1 into separable functional domains and placed TRF1 at the top of a sequential TERB1-TERB2-MAJIN assembly pathway.","evidence":"Germ-cell TRF1 conditional knockout, domain-specific TERB1 mutants, Co-IP and IF","pmids":["29141207"],"confidence":"High","gaps":["Structural mechanism of TERB2/MAJIN engagement not yet shown","Function of MYB-domain cohesin recruitment not phenotypically isolated"]},{"year":2018,"claim":"Solved the MAJIN-TERB2 architecture and proposed a handover model in which the complex first recruits TRF1 then displaces it to bind telomeric DNA directly at a mature attachment plate.","evidence":"Crystal structure, X-ray scattering, biochemical DNA-binding assays, structured illumination microscopy","pmids":["30559341"],"confidence":"High","gaps":["Trigger and timing of TRF1 displacement in vivo not defined","Stoichiometry at native telomeres not directly measured"]},{"year":2019,"claim":"Resolved the TERB1-TERB2 and TERB2-MAJIN interfaces and showed the TRF1-TERB1-TERB2-MAJIN pathway acts as a separate but cooperative route to the LINC complex for telomere-NE anchoring.","evidence":"Crystal structures, interaction-specific Terb2 knock-in mice, SUN1 depletion, chromosome spreading","pmids":["30718482"],"confidence":"High","gaps":["Quantitative contribution of each pathway to force transmission unresolved","Crosstalk mechanism between the two routes unknown"]},{"year":2022,"claim":"Separated the MYB domain's role from telomere tethering, showing it has lost DNA binding and instead recruits cohesin to remodel axial elements and prevent telomere erosion.","evidence":"In vitro DNA-binding assay, MYB-domain point-mutant knock-in mouse, IF, telomere FISH, chromosome spreading","pmids":["35081355"],"confidence":"High","gaps":["Direct cohesin-binding partner of the MYB domain not identified","Molecular basis of axial-element remodeling unresolved"]},{"year":2024,"claim":"Extended TERB1's requirement for synaptonemal complex completion and homolog arrangement to a non-mammalian vertebrate, revealing sexually dimorphic checkpoint responses to its loss.","evidence":"Medaka terb1 loss-of-function mutant, IF, FISH, cytological SC analysis","pmids":["38809870"],"confidence":"Medium","gaps":["No molecular interaction data in fish","Basis of sexually dimorphic checkpoint not defined"]},{"year":null,"claim":"How the assembled attachment plate transduces cytoskeletal force and how TRF1 displacement is temporally controlled in vivo remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No direct measurement of force transmission through the TERB1 scaffold","In vivo trigger for the TRF1-to-MAJIN handover unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,3,4]},{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[0,4]}],"localization":[{"term_id":"GO:0005635","term_label":"nuclear envelope","supporting_discovery_ids":[0,4,5]},{"term_id":"GO:0005694","term_label":"chromosome","supporting_discovery_ids":[0,1,2]}],"pathway":[{"term_id":"R-HSA-1474165","term_label":"Reproduction","supporting_discovery_ids":[0,2,7]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[0]}],"complexes":["TERB1-TERB2-MAJIN complex","LINC (SUN-KASH) complex"],"partners":["TRF1","TERB2","MAJIN","SUN1","SMC1B"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q8NA31","full_name":"Telomere repeats-binding bouquet formation protein 1","aliases":["Coiled-coil domain-containing protein 79"],"length_aa":727,"mass_kda":83.1,"function":"Meiosis-specific telomere-associated protein involved in meiotic telomere attachment to the nucleus inner membrane, a crucial step for homologous pairing and synapsis. Component of the MAJIN-TERB1-TERB2 complex, which promotes telomere cap exchange by mediating attachment of telomeric DNA to the inner nuclear membrane and replacement of the protective cap of telomeric chromosomes: in early meiosis, the MAJIN-TERB1-TERB2 complex associates with telomeric DNA and the shelterin/telosome complex. During prophase, the complex matures and promotes release of the shelterin/telosome complex from telomeric DNA. In the MAJIN-TERB1-TERB2 complex, TERB1 probably mediates association with the shelterin/telosome complex via interaction with TERF1, promoting priming telomeric DNA attachment'. Promotes telomere association with the nuclear envelope and deposition of the SUN-KASH/LINC complex. Also recruits cohesin to telomeres to develop structural rigidity","subcellular_location":"Chromosome, telomere; Nucleus inner membrane","url":"https://www.uniprot.org/uniprotkb/Q8NA31/entry"},"depmap":{"release":"DepMap","has_data":false,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/TERB1"},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/TERB1","total_profiled":1310},"omim":[{"mim_id":"619646","title":"SPERMATOGENIC FAILURE 60; SPGF60","url":"https://www.omim.org/entry/619646"},{"mim_id":"619645","title":"SPERMATOGENIC FAILURE 59; SPGF59","url":"https://www.omim.org/entry/619645"},{"mim_id":"617332","title":"TELOMERE REPEAT-BINDING BOUQUET FORMATION PROTEIN 1; TERB1","url":"https://www.omim.org/entry/617332"},{"mim_id":"617131","title":"TELOMERE REPEAT-BINDING BOUQUET FORMATION PROTEIN 2; TERB2","url":"https://www.omim.org/entry/617131"},{"mim_id":"617130","title":"MEMBRANE-ANCHORED JUNCTION PROTEIN; MAJIN","url":"https://www.omim.org/entry/617130"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Cell Junctions","reliability":"Additional"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"testis","ntpm":11.7}],"url":"https://www.proteinatlas.org/search/TERB1"},"hgnc":{"alias_symbol":["FLJ35894"],"prev_symbol":["CCDC79"]},"alphafold":{"accession":"Q8NA31","domains":[{"cath_id":"1.25.10.10","chopping":"230-378","consensus_level":"medium","plddt":90.9548,"start":230,"end":378},{"cath_id":"1.10.10.60","chopping":"677-721","consensus_level":"medium","plddt":88.5247,"start":677,"end":721}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8NA31","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8NA31-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8NA31-F1-predicted_aligned_error_v6.png","plddt_mean":71.56},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=TERB1","jax_strain_url":"https://www.jax.org/strain/search?query=TERB1"},"sequence":{"accession":"Q8NA31","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8NA31.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8NA31/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8NA31"}},"corpus_meta":[{"pmid":"24413433","id":"PMC_24413433","title":"The TRF1-binding protein TERB1 promotes chromosome movement and telomere rigidity in meiosis.","date":"2014","source":"Nature cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/24413433","citation_count":151,"is_preprint":false},{"pmid":"30718482","id":"PMC_30718482","title":"The meiotic TERB1-TERB2-MAJIN complex tethers telomeres to the nuclear envelope.","date":"2019","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/30718482","citation_count":41,"is_preprint":false},{"pmid":"29083416","id":"PMC_29083416","title":"Telomeric TERB1-TRF1 interaction is crucial for male meiosis.","date":"2017","source":"Nature structural & molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/29083416","citation_count":41,"is_preprint":false},{"pmid":"33211200","id":"PMC_33211200","title":"Disruption of human meiotic telomere complex genes TERB1, TERB2 and MAJIN in men with non-obstructive azoospermia.","date":"2020","source":"Human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/33211200","citation_count":37,"is_preprint":false},{"pmid":"24885367","id":"PMC_24885367","title":"Mouse CCDC79 (TERB1) is a meiosis-specific telomere associated protein.","date":"2014","source":"BMC cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/24885367","citation_count":33,"is_preprint":false},{"pmid":"30559341","id":"PMC_30559341","title":"Structural basis of meiotic telomere attachment to the nuclear envelope by MAJIN-TERB2-TERB1.","date":"2018","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/30559341","citation_count":33,"is_preprint":false},{"pmid":"29141207","id":"PMC_29141207","title":"Distinct TERB1 Domains Regulate Different Protein Interactions in Meiotic Telomere Movement.","date":"2017","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/29141207","citation_count":30,"is_preprint":false},{"pmid":"32408858","id":"PMC_32408858","title":"The TERB1-TERB2-MAJIN complex of mouse meiotic telomeres dates back to the common ancestor of metazoans.","date":"2020","source":"BMC evolutionary biology","url":"https://pubmed.ncbi.nlm.nih.gov/32408858","citation_count":17,"is_preprint":false},{"pmid":"35081355","id":"PMC_35081355","title":"The TERB1 MYB domain suppresses telomere erosion in meiotic prophase I.","date":"2022","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/35081355","citation_count":10,"is_preprint":false},{"pmid":"38277113","id":"PMC_38277113","title":"A report of two homozygous TERB1 protein-truncating variants in two unrelated women with primary infertility.","date":"2024","source":"Journal of assisted reproduction and genetics","url":"https://pubmed.ncbi.nlm.nih.gov/38277113","citation_count":3,"is_preprint":false},{"pmid":"38809870","id":"PMC_38809870","title":"Medaka Terb1 Mutant Displays Defects of Synaptonemal Complex Formation and Sexual Difference in Gametogenesis.","date":"2024","source":"Zoological science","url":"https://pubmed.ncbi.nlm.nih.gov/38809870","citation_count":1,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":7154,"output_tokens":2527,"usd":0.029684,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9638,"output_tokens":2900,"usd":0.060345,"stage2_stop_reason":"end_turn"},"total_usd":0.090029,"stage1_batch_id":"msgbatch_017qqVz33Ga63SCDwzb35XPb","stage2_batch_id":"msgbatch_01Scr2Ei9x4HJMiRGxwrmvLK","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2014,\n      \"finding\": \"TERB1 (CCDC79) is a meiosis-specific Myb-domain protein that localizes to telomeres in mouse germ cells, forms a heterocomplex with the canonical telomeric protein TRF1, and binds telomere repeat DNA. TERB1 promotes telomere association with the nuclear envelope and deposition of the SUN-KASH complex (which recruits cytoplasmic motor complexes), and also recruits cohesin to telomeres to develop structural rigidity. Disruption of Terb1 abolishes meiotic chromosomal movement and impairs homologous pairing and synapsis, causing infertility in both sexes.\",\n      \"method\": \"Mouse knockout, Co-immunoprecipitation, telomere DNA binding assay, immunofluorescence localization, genetic epistasis\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, mouse KO with defined phenotypes, multiple orthogonal methods, replicated by independent study (PMID:24885367)\",\n      \"pmids\": [\"24413433\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"CCDC79 (TERB1) is a meiosis-specific protein that localizes to telomeres from leptotene to diplotene stages. CCDC79 associates with telomeres independently of SUN1-mediated nuclear envelope attachment (localization persists in SUN1-deficient spermatocytes), but is largely absent from telomeres that fail to connect to SUN1 in SMC1B-deficient spermatocytes.\",\n      \"method\": \"Immunofluorescence localization in wild-type and mutant (SUN1-deficient, SMC1B-deficient) spermatocytes\",\n      \"journal\": \"BMC cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct localization experiments in multiple genetic backgrounds, independently corroborating PMID:24413433\",\n      \"pmids\": [\"24885367\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Crystal structure of the TRF1-binding motif (TBM) of human TERB1 in complex with the TRFH domain of TRF1 was solved. A specific point mutation disrupting the TERB1-TRF1 interaction in mice causes infertility only in males, with arrest at the zygotene-early pachytene stage, mild telomere abnormalities on autosomes, and failure of X-Y chromosome pairing at the pseudoautosomal region (PAR) in pachytene.\",\n      \"method\": \"Crystal structure determination, point-mutant knock-in mouse, immunofluorescence, FISH\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure with functional validation via knock-in point mutant mouse, single lab but two orthogonal methods\",\n      \"pmids\": [\"29083416\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"TERB1 contains distinct functional domains: a TRF1-binding motif required for TRF1 interaction; a TERB2-binding (T2B) domain required for TERB1-TERB2 interaction and telomere attachment to the nuclear envelope (but dispensable for TRF1-TERB1 interaction); and an MYB-like domain required for cohesin recruitment at telomeres (but not for TERB2-MAJIN assembly). TRF1 directs the sequential assembly of TERB1-TERB2-MAJIN.\",\n      \"method\": \"Germ-cell-specific TRF1 knockout mouse, domain-specific TERB1 mutant analysis, Co-immunoprecipitation, immunofluorescence\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional KO plus domain-specific mutants with orthogonal Co-IP and localization readouts, mechanistic dissection of multiple domains\",\n      \"pmids\": [\"29141207\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Crystal structure of the MAJIN-TERB2 complex (2:2 hetero-tetramer) was determined; MAJIN-TERB2 strongly binds DNA and is tethered via long flexible linkers to the inner nuclear membrane and to two TRF1-binding 1:1 TERB2-TERB1 complexes. Structured illumination microscopy and biochemical data revealed a telomere attachment mechanism in which MAJIN-TERB2-TERB1 first recruits telomere-bound TRF1, which is then displaced during pachytene, allowing MAJIN-TERB2-TERB1 to bind telomeric DNA and form a mature attachment plate.\",\n      \"method\": \"Crystal structure determination, X-ray scattering, biochemical DNA binding assays, structured illumination microscopy\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure plus multiple orthogonal biochemical and imaging methods in a single study\",\n      \"pmids\": [\"30559341\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Crystal structures of human TERB1-TERB2 and TERB2-MAJIN subcomplexes were determined. Specific disruption of either the TERB1-TERB2 interaction or the TERB2-MAJIN interaction by point mutations in the mouse Terb2 gene abolishes telomere attachment to the nuclear envelope and causes aberrant homologous pairing and disordered synapsis. SUN1 depletion partially disrupts the telomere-NE connection, suggesting that the telomere-TRF1-TERB1-TERB2-MAJIN-NE pathway and the LINC complex pathway are two separate but cooperative routes for stable telomere-NE recruitment.\",\n      \"method\": \"Crystal structure determination, knock-in point mutant mice (Terb2 gene), SUN1 depletion, immunofluorescence, chromosome spreading\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structures plus in vivo knock-in mouse validation with multiple interaction-specific mutations and epistasis analysis\",\n      \"pmids\": [\"30718482\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"The TERB1 MYB domain has lost its canonical DNA-binding activity. In Terb1 point-mutant mice lacking the functional MYB domain, telomere localization of TERB1 and the downstream TERB2-MAJIN complex, homologous pairing, and fertility are unaffected. Instead, the MYB domain is required for cohesin enrichment at telomeres and remodeling of axial elements at the early-to-late pachytene transition, thereby suppressing telomere erosion during meiotic prophase I.\",\n      \"method\": \"In vitro DNA-binding assay, Terb1 MYB-domain point-mutant knock-in mouse, immunofluorescence, telomere FISH, chromosome spreading\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro activity assay for DNA binding plus knock-in mouse with defined molecular and cellular readouts, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"35081355\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"In medaka (fish ortholog), loss of terb1 causes failure to complete synaptonemal complex formation despite initiation of lateral elements and fragmented transverse filaments, and results in aberrant homologous chromosome arrangement. The oogenesis-spermatogenesis checkpoint response to terb1 loss is sexually dimorphic: oogenesis arrests at zygotene-like stage while spermatogenesis continues to produce sperm-like cells with abnormal DNA content.\",\n      \"method\": \"Medaka terb1 mutant (loss-of-function), immunofluorescence, FISH, cytological analysis of SC\",\n      \"journal\": \"Zoological science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — single lab, clean KO with defined cellular phenotypes in a non-mammalian model (medaka), no molecular interaction data\",\n      \"pmids\": [\"38809870\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"TERB1 is a meiosis-specific telomere-associated protein that acts as a central scaffold at meiotic telomeres: it binds TRF1 via its TRF1-binding motif (structurally defined by crystal structure), recruits TERB2-MAJIN through its T2B domain to tether telomeres to the nuclear envelope, promotes SUN-KASH (LINC) complex deposition to transmit cytoskeletal forces for chromosome movement, recruits cohesin via its MYB domain (which has lost canonical DNA-binding activity) to confer telomere structural rigidity and suppress telomere erosion in late pachytene, and coordinates sequential assembly of the entire meiotic telomere complex (TRF1→TERB1→TERB2→MAJIN) culminating in TRF1 displacement and direct MAJIN-TERB2-TERB1 binding to telomeric DNA at the mature attachment plate; loss of TERB1 function abolishes meiotic chromosomal movement, impairs homologous pairing and synapsis, and causes infertility in both sexes.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"TERB1 (CCDC79) is a meiosis-specific telomere protein that serves as the central scaffold tethering telomeres to the nuclear envelope to drive chromosome movement, homologous pairing, and synapsis during meiotic prophase I [#0]. It localizes to telomeres from leptotene to diplotene and engages the canonical telomeric protein TRF1 through a dedicated TRF1-binding motif, whose interaction with the TRFH domain of TRF1 is defined at atomic resolution [#0, #2]. TERB1 is organized into separable functional modules: the TRF1-binding motif, a TERB2-binding (T2B) domain that recruits the TERB2-MAJIN subcomplex for nuclear-envelope attachment, and an MYB-like domain dedicated to cohesin recruitment [#3]. Within the assembled complex, TRF1 directs sequential recruitment of TERB1\\u2192TERB2\\u2192MAJIN, and the MAJIN-TERB2-TERB1 module first captures telomere-bound TRF1 and then displaces it during pachytene, taking over direct telomeric DNA binding to form a mature attachment plate [#3, #4]. The MYB domain has lost canonical DNA-binding activity and instead enriches cohesin at telomeres and remodels axial elements at the early-to-late pachytene transition, conferring structural rigidity that suppresses telomere erosion without affecting pairing or fertility [#6]. This nuclear-envelope tethering pathway operates cooperatively with, but separably from, the SUN-KASH LINC complex route to stably anchor telomeres [#5]. Disruption of TERB1 abolishes meiotic chromosomal movement and impairs pairing and synapsis, causing infertility, with the requirement conserved in fish meiosis [#0, #7].\",\n  \"teleology\": [\n    {\n      \"year\": 2014,\n      \"claim\": \"Established TERB1 as a meiosis-specific telomere factor that physically links telomeres to the nuclear envelope and is essential for the chromosome movements underlying pairing and synapsis.\",\n      \"evidence\": \"Mouse knockout with reciprocal Co-IP, telomere DNA-binding and localization assays, genetic epistasis\",\n      \"pmids\": [\"24413433\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Domain-level basis for TRF1 binding, NE attachment, and cohesin recruitment not yet resolved\", \"Order of complex assembly undefined\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Defined TERB1's place in the telomere-NE attachment hierarchy, showing it loads onto telomeres independently of SUN1 but depends on cohesin (SMC1B) for stable association.\",\n      \"evidence\": \"Immunofluorescence in SUN1-deficient and SMC1B-deficient spermatocytes\",\n      \"pmids\": [\"24885367\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve direct versus indirect dependence on cohesin\", \"Molecular interactions not tested\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Provided the structural basis of the TERB1-TRF1 interaction and demonstrated its specific in vivo requirement for meiotic telomere function.\",\n      \"evidence\": \"Crystal structure of TERB1 TBM with the TRF1 TRFH domain plus interaction-disrupting knock-in mouse, IF and FISH\",\n      \"pmids\": [\"29083416\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Why disruption causes male-only infertility unexplained\", \"Mechanism of PAR/X-Y pairing failure not resolved\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Dissected TERB1 into separable functional domains and placed TRF1 at the top of a sequential TERB1-TERB2-MAJIN assembly pathway.\",\n      \"evidence\": \"Germ-cell TRF1 conditional knockout, domain-specific TERB1 mutants, Co-IP and IF\",\n      \"pmids\": [\"29141207\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural mechanism of TERB2/MAJIN engagement not yet shown\", \"Function of MYB-domain cohesin recruitment not phenotypically isolated\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Solved the MAJIN-TERB2 architecture and proposed a handover model in which the complex first recruits TRF1 then displaces it to bind telomeric DNA directly at a mature attachment plate.\",\n      \"evidence\": \"Crystal structure, X-ray scattering, biochemical DNA-binding assays, structured illumination microscopy\",\n      \"pmids\": [\"30559341\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Trigger and timing of TRF1 displacement in vivo not defined\", \"Stoichiometry at native telomeres not directly measured\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Resolved the TERB1-TERB2 and TERB2-MAJIN interfaces and showed the TRF1-TERB1-TERB2-MAJIN pathway acts as a separate but cooperative route to the LINC complex for telomere-NE anchoring.\",\n      \"evidence\": \"Crystal structures, interaction-specific Terb2 knock-in mice, SUN1 depletion, chromosome spreading\",\n      \"pmids\": [\"30718482\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Quantitative contribution of each pathway to force transmission unresolved\", \"Crosstalk mechanism between the two routes unknown\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Separated the MYB domain's role from telomere tethering, showing it has lost DNA binding and instead recruits cohesin to remodel axial elements and prevent telomere erosion.\",\n      \"evidence\": \"In vitro DNA-binding assay, MYB-domain point-mutant knock-in mouse, IF, telomere FISH, chromosome spreading\",\n      \"pmids\": [\"35081355\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct cohesin-binding partner of the MYB domain not identified\", \"Molecular basis of axial-element remodeling unresolved\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Extended TERB1's requirement for synaptonemal complex completion and homolog arrangement to a non-mammalian vertebrate, revealing sexually dimorphic checkpoint responses to its loss.\",\n      \"evidence\": \"Medaka terb1 loss-of-function mutant, IF, FISH, cytological SC analysis\",\n      \"pmids\": [\"38809870\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No molecular interaction data in fish\", \"Basis of sexually dimorphic checkpoint not defined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the assembled attachment plate transduces cytoskeletal force and how TRF1 displacement is temporally controlled in vivo remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No direct measurement of force transmission through the TERB1 scaffold\", \"In vivo trigger for the TRF1-to-MAJIN handover unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 3, 4]},\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [0, 4]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005635\", \"supporting_discovery_ids\": [0, 4, 5]},\n      {\"term_id\": \"GO:0005694\", \"supporting_discovery_ids\": [0, 1, 2]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1474165\", \"supporting_discovery_ids\": [0, 2, 7]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"complexes\": [\"TERB1-TERB2-MAJIN complex\", \"LINC (SUN-KASH) complex\"],\n    \"partners\": [\"TRF1\", \"TERB2\", \"MAJIN\", \"SUN1\", \"SMC1B\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":7,"faith_pct":85.71428571428571}}