{"gene":"CNTD1","run_date":"2026-06-09T22:57:18","timeline":{"discoveries":[{"year":2014,"finding":"CNTD1 is required for maturation of meiotic crossovers (COs): disruption of Cntd1 causes failure to localize CO-specific factors MutLγ (MLH1/MLH3) and HEI10 at designated CO sites, and leads to prolonged high levels of pre-CO intermediates marked by MutSγ and RNF212. CNTD1 coordinates CO maturation by regulating the association between the RING finger proteins HEI10 and RNF212 and components of the CO machinery.","method":"Mouse knockout (Cntd1 disruption), immunofluorescence localization of CO-specific factors (MutLγ, HEI10, MutSγ, RNF212) on meiotic chromosome spreads","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean loss-of-function mouse model with defined molecular phenotype, multiple orthogonal protein localization readouts, foundational study replicated in later work","pmids":["24891606"],"is_preprint":false},{"year":2016,"finding":"In C. elegans, the CNTD1 ortholog COSA-1 acts downstream of the MAP kinase pathway (MPK-1) as a crossover-promoting factor; inactivation of MAP kinase at late pachytene is required for timely disassembly of SC proteins from chromosome long arms, and this process depends on ZHP-3/RNF212/Zip3 and COSA-1/CNTD1.","method":"C. elegans genetic epistasis: RAS/ERK pathway mutants combined with cosa-1 and zhp-3 mutants, immunofluorescence of SC components and crossover markers","journal":"eLife","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis in C. elegans with multiple mutant combinations; ortholog evidence, single lab","pmids":["26920220"],"is_preprint":false},{"year":2020,"finding":"CNTD1 physically interacts with the proline-rich protein PRR19; PRR19 and CNTD1 co-localise at crossover sites, are interdependent for accumulation, and both are required for timely DSB repair and formation of crossover-specific recombination complexes. Additionally, CNTD1 interacts with CDK2, which also accumulates in crossover-specific recombination complexes.","method":"Co-immunoprecipitation (physical interaction), co-immunofluorescence on meiotic chromosome spreads, mouse knockouts of Prr19 and Cntd1 with analysis of DSB repair and CO-specific complexes","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal co-IP establishing physical interaction, co-localization, interdependence by KO, and CDK2 interaction, multiple orthogonal methods in one study","pmids":["32555348"],"is_preprint":false},{"year":2020,"finding":"A short isoform of CNTD1 lacking the predicted N-terminal cyclin domain does not bind cyclin-dependent kinases; instead it associates with components of the replication factor C (RFC) machinery to facilitate crossover formation, and with the E2 ubiquitin-conjugating enzyme CDC34 to regulate ubiquitylation and subsequent degradation of the WEE1 kinase, thereby modulating cell-cycle progression during meiotic prophase I.","method":"Epitope-tagged Cntd1 knock-in mouse, co-immunoprecipitation with RFC components and CDC34, isoform characterization, in vivo ubiquitylation/degradation assay for WEE1","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — epitope-tagged allele in vivo, co-IP with multiple interactors, isoform biochemistry, WEE1 degradation readout, multiple orthogonal methods","pmids":["32640224"],"is_preprint":false},{"year":2024,"finding":"RNF212B co-localizes and interacts with CNTD1 at late CO foci by late pachynema; genetic analysis shows that the unloading of RNF212B from chromosomes at the end of pachynema is dependent on HEI10 and CNTD1, placing CNTD1 as a regulator of RNF212B dynamics.","method":"Mouse knockouts (Cntd1, Hei10, Rnf212b), immunofluorescence co-localization on meiotic chromosome spreads, genetic epistasis with Rnf212b/Rnf212 double mutants","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis and co-localization in mouse KO models, single lab, co-localization only (no co-IP shown for CNTD1-RNF212B directly)","pmids":["38865271"],"is_preprint":false},{"year":2024,"finding":"Knockout of cntd1 in zebrafish (CRISPR/Cas9) impairs meiotic crossover formation, leading to cell-cycle arrest during meiotic metaphase and apoptosis of spermatocytes; in females, cntd1 loss causes production of unreduced (haploid, aneuploid, or diploid) eggs, demonstrating a sex-specific role for CNTD1 in maintaining ploidy integrity during meiosis.","method":"CRISPR/Cas9 knockout of cntd1 in zebrafish, cytological analysis of meiotic progression, ploidy analysis of gametes and offspring","journal":"Molecular biology and evolution","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean KO with defined cellular and ploidy phenotypes in vertebrate model, single lab","pmids":["38421617"],"is_preprint":false},{"year":2025,"finding":"CNTD1-deficient oocytes fail to form crossovers. Additionally, loss of CNTD1 causes severe depletion of the follicle pool shortly after birth; this follicle loss is CHK2-dependent and results from inappropriate retention of HORMAD1 and absence of SKP1, establishing a novel role for CNTD1 in establishing the ovarian follicular reserve beyond its role in CO designation.","method":"Mouse conditional/full knockout of Cntd1, immunofluorescence for HORMAD1/SKP1, genetic interaction with Chk2 knockout, histological analysis of ovarian follicle pools","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean loss-of-function mouse model with multiple molecular readouts (HORMAD1, SKP1, CHK2 epistasis) and defined cellular phenotype","pmids":["40488668"],"is_preprint":false}],"current_model":"CNTD1 is a cyclin-related protein that acts as a critical coordinator of meiotic crossover (CO) maturation: it regulates the redistribution and activity of RING-finger E3 ligases HEI10 and RNF212 at designated CO sites, physically partners with PRR19 and CDK2 to promote CO-specific recombination complexes, and through a short isoform lacking the cyclin domain, associates with RFC machinery and the E2 enzyme CDC34 to drive ubiquitin-mediated WEE1 degradation, thereby coupling CO completion to meiotic cell-cycle progression; in females it additionally controls establishment of the ovarian follicular reserve via a CHK2-dependent mechanism involving HORMAD1 retention and SKP1 absence."},"narrative":{"mechanistic_narrative":"CNTD1 is a cyclin-related protein that functions as a central coordinator of meiotic crossover (CO) maturation, ensuring that designated recombination intermediates are converted into mature, correctly positioned crossovers during prophase I [PMID:24891606]. It acts by regulating the chromosomal dynamics and redistribution of RING-finger E3 ligases at CO sites: loss of CNTD1 prevents localization of the CO-specific factors MutLγ (MLH1/MLH3) and HEI10 while leaving cells in a prolonged pre-CO state marked by MutSγ and RNF212, and CNTD1 governs the late-pachynema unloading of RNF212B together with HEI10 [PMID:24891606, PMID:38865271]. CNTD1 builds CO-specific recombination complexes through physical interaction with the proline-rich protein PRR19 and with CDK2, with PRR19 and CNTD1 being interdependent for accumulation at CO sites and jointly required for timely double-strand break repair [PMID:32555348]. A short CNTD1 isoform lacking the N-terminal cyclin domain forgoes CDK binding and instead associates with the replication factor C (RFC) machinery and with the E2 ubiquitin-conjugating enzyme CDC34 to drive ubiquitylation and degradation of WEE1 kinase, thereby coupling CO formation to meiotic cell-cycle progression [PMID:32640224]. Beyond CO designation, CNTD1 establishes the ovarian follicular reserve: its loss triggers CHK2-dependent follicle depletion associated with inappropriate HORMAD1 retention and absence of SKP1 [PMID:40488668]. Across vertebrate and invertebrate models, CNTD1/COSA-1 loss impairs crossover formation and compromises ploidy integrity, causing meiotic arrest, spermatocyte apoptosis, and production of aneuploid gametes [PMID:26920220, PMID:38421617].","teleology":[{"year":2014,"claim":"Established CNTD1 as a required factor for crossover maturation by showing it controls whether pre-CO intermediates are resolved into mature crossovers, defining its place at the designation step of meiotic recombination.","evidence":"Mouse Cntd1 knockout with immunofluorescence of CO markers (MutLγ, HEI10, MutSγ, RNF212) on meiotic chromosome spreads","pmids":["24891606"],"confidence":"High","gaps":["Did not resolve whether CNTD1 acts directly on the RING-finger ligases or through partner proteins","No biochemical demonstration of CNTD1 enzymatic or scaffolding activity"]},{"year":2016,"claim":"Placed the CNTD1 ortholog COSA-1 downstream of MAP kinase signaling in crossover promotion, linking a conserved kinase pathway to crossover-associated SC disassembly.","evidence":"C. elegans genetic epistasis of RAS/ERK (MPK-1) mutants with cosa-1 and zhp-3 mutants, immunofluorescence of SC and CO markers","pmids":["26920220"],"confidence":"Medium","gaps":["Ortholog-based; mammalian CNTD1 not directly tested for MAP kinase dependence","Did not establish direct molecular contact between COSA-1 and MAP kinase components"]},{"year":2020,"claim":"Identified the physical CO-complex partners of CNTD1, showing it works with PRR19 and CDK2 to assemble crossover-specific recombination complexes and promote DSB repair.","evidence":"Reciprocal co-immunoprecipitation, co-immunofluorescence on chromosome spreads, and Prr19/Cntd1 mouse knockouts","pmids":["32555348"],"confidence":"High","gaps":["Did not define the structural basis or stoichiometry of the CNTD1–PRR19–CDK2 complex","Whether CDK2 kinase activity within the complex is required was not resolved"]},{"year":2020,"claim":"Revealed an isoform-specific dual function: a cyclin-domain-lacking CNTD1 isoform couples crossover formation to cell-cycle control via RFC association and CDC34-dependent WEE1 degradation, distinguishing CNTD1's recombination and cell-cycle roles.","evidence":"Epitope-tagged Cntd1 knock-in mouse, co-IP with RFC components and CDC34, isoform characterization, and in vivo WEE1 ubiquitylation/degradation assay","pmids":["32640224"],"confidence":"High","gaps":["Mechanism by which CNTD1 directs CDC34 substrate selection toward WEE1 was not defined","How the two isoforms are produced and balanced in vivo remains uncharacterized"]},{"year":2024,"claim":"Extended CNTD1's role in RING-finger ligase regulation by showing it, together with HEI10, governs the chromosomal unloading of RNF212B at late pachynema.","evidence":"Cntd1, Hei10, and Rnf212b mouse knockouts with co-localization on chromosome spreads and Rnf212b/Rnf212 genetic epistasis","pmids":["38865271"],"confidence":"Medium","gaps":["No direct co-IP demonstrating CNTD1–RNF212B physical interaction","Single lab; mechanism of unloading not biochemically defined"]},{"year":2024,"claim":"Demonstrated the functional consequence of CNTD1 loss for genome integrity across sexes in a vertebrate model, tying crossover failure to meiotic arrest, apoptosis, and aneuploid gamete production.","evidence":"CRISPR/Cas9 cntd1 knockout in zebrafish with cytological meiotic analysis and gamete ploidy assessment","pmids":["38421617"],"confidence":"Medium","gaps":["Did not address whether zebrafish CNTD1 uses the same isoform/WEE1 mechanism as mouse","Molecular basis of sex-specific ploidy outcomes not resolved"]},{"year":2025,"claim":"Uncovered a CO-independent role for CNTD1 in establishing the ovarian follicular reserve, acting through a CHK2-dependent surveillance pathway linked to HORMAD1 retention and SKP1 absence.","evidence":"Mouse Cntd1 knockout with HORMAD1/SKP1 immunofluorescence, Chk2 genetic epistasis, and histological follicle quantification","pmids":["40488668"],"confidence":"High","gaps":["How CNTD1 normally promotes HORMAD1 removal and SKP1 presence is not mechanistically defined","Whether follicle loss is a direct CNTD1 function or a downstream consequence of CO failure was not fully separated"]},{"year":null,"claim":"The biochemical activity of CNTD1 itself — whether it acts as a bona fide cyclin partner, a scaffold, or an adaptor that licenses E3 ligase and E2 activity — and the structural basis of its assembled complexes remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of CNTD1 or its complexes","Direct enzymatic or scaffolding mechanism not biochemically reconstituted","Human disease relevance not established in the available corpus"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,4]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[2,3]}],"localization":[{"term_id":"GO:0000228","term_label":"nuclear chromosome","supporting_discovery_ids":[0,2,4]}],"pathway":[{"term_id":"R-HSA-1474165","term_label":"Reproduction","supporting_discovery_ids":[0,5,6]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[3,5]},{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[0,2]}],"complexes":["CO-specific recombination complex (CNTD1-PRR19-CDK2)","RFC machinery (short isoform)"],"partners":["PRR19","CDK2","CDC34","HEI10","RNF212B","WEE1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q8N815","full_name":"Cyclin N-terminal domain-containing protein 1","aliases":[],"length_aa":330,"mass_kda":36.9,"function":"Plays a role in the different steps of crossover formation during meiotic recombination. Participates in the crossover differentiation step of crossover-specific recombination intermediates through its interaction with PRR19. In addition, stimulates crossover formation through the interactions with RFC3 and RFC4 and simultaneously regulates cell-cycle progression through interactions with CDC34 and subsequent ubiquitination of WEE1. May also participates in an active deselection process that destabilizes or removes excess pre-CO intermediates","subcellular_location":"Nucleus; Cytoplasm; Chromosome","url":"https://www.uniprot.org/uniprotkb/Q8N815/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CNTD1","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/CNTD1","total_profiled":1310},"omim":[{"mim_id":"621177","title":"PROLINE-RICH PROTEIN 19; PRR19","url":"https://www.omim.org/entry/621177"},{"mim_id":"621020","title":"RING FINGER PROTEIN 212B; RNF212B","url":"https://www.omim.org/entry/621020"},{"mim_id":"618166","title":"CYCLIN N-TERMINAL DOMAIN-CONTAINING PROTEIN 1; CNTD1","url":"https://www.omim.org/entry/618166"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Vesicles","reliability":"Additional"}],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"testis","ntpm":39.5}],"url":"https://www.proteinatlas.org/search/CNTD1"},"hgnc":{"alias_symbol":["FLJ40137"],"prev_symbol":["CNTD"]},"alphafold":{"accession":"Q8N815","domains":[{"cath_id":"1.10.472.10","chopping":"50-174","consensus_level":"high","plddt":90.9152,"start":50,"end":174},{"cath_id":"-","chopping":"183-303","consensus_level":"high","plddt":92.7409,"start":183,"end":303}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8N815","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8N815-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8N815-F1-predicted_aligned_error_v6.png","plddt_mean":84.56},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CNTD1","jax_strain_url":"https://www.jax.org/strain/search?query=CNTD1"},"sequence":{"accession":"Q8N815","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8N815.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8N815/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8N815"}},"corpus_meta":[{"pmid":"24891606","id":"PMC_24891606","title":"Mammalian CNTD1 is critical for meiotic crossover maturation and deselection of excess precrossover sites.","date":"2014","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/24891606","citation_count":64,"is_preprint":false},{"pmid":"24080485","id":"PMC_24080485","title":"MRNA and miRNA expression patterns associated to pathways linked to metal mixture health effects.","date":"2013","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/24080485","citation_count":55,"is_preprint":false},{"pmid":"26920220","id":"PMC_26920220","title":"The MAP kinase pathway coordinates crossover designation with disassembly of synaptonemal complex proteins during meiosis.","date":"2016","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/26920220","citation_count":38,"is_preprint":false},{"pmid":"32555348","id":"PMC_32555348","title":"Proline-rich protein PRR19 functions with cyclin-like CNTD1 to promote meiotic crossing over in mouse.","date":"2020","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/32555348","citation_count":28,"is_preprint":false},{"pmid":"32640224","id":"PMC_32640224","title":"Cyclin N-Terminal Domain-Containing-1 Coordinates Meiotic Crossover Formation with Cell-Cycle Progression in a Cyclin-Independent Manner.","date":"2020","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/32640224","citation_count":21,"is_preprint":false},{"pmid":"38865271","id":"PMC_38865271","title":"RNF212B E3 ligase is essential for crossover designation and maturation during male and female meiosis in the mouse.","date":"2024","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/38865271","citation_count":18,"is_preprint":false},{"pmid":"38421617","id":"PMC_38421617","title":"Formation of Different Polyploids Through Disrupting Meiotic Crossover Frequencies Based on cntd1 Knockout in Zebrafish.","date":"2024","source":"Molecular biology and evolution","url":"https://pubmed.ncbi.nlm.nih.gov/38421617","citation_count":6,"is_preprint":false},{"pmid":"40488668","id":"PMC_40488668","title":"CNTD1 is crucial for crossover formation in female meiosis and for establishing the ovarian reserve.","date":"2025","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/40488668","citation_count":2,"is_preprint":false},{"pmid":"42221552","id":"PMC_42221552","title":"Meiotic gene variants contribute to recurrent blastulation failure.","date":"2026","source":"Human reproduction open","url":"https://pubmed.ncbi.nlm.nih.gov/42221552","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":6731,"output_tokens":2119,"usd":0.025989,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9069,"output_tokens":3121,"usd":0.061685,"stage2_stop_reason":"end_turn"},"total_usd":0.087674,"stage1_batch_id":"msgbatch_01ACAxJQabDsht39JXeWG22d","stage2_batch_id":"msgbatch_01QEU22A9U5sbPTgsMzTmvSf","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2014,\n      \"finding\": \"CNTD1 is required for maturation of meiotic crossovers (COs): disruption of Cntd1 causes failure to localize CO-specific factors MutLγ (MLH1/MLH3) and HEI10 at designated CO sites, and leads to prolonged high levels of pre-CO intermediates marked by MutSγ and RNF212. CNTD1 coordinates CO maturation by regulating the association between the RING finger proteins HEI10 and RNF212 and components of the CO machinery.\",\n      \"method\": \"Mouse knockout (Cntd1 disruption), immunofluorescence localization of CO-specific factors (MutLγ, HEI10, MutSγ, RNF212) on meiotic chromosome spreads\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean loss-of-function mouse model with defined molecular phenotype, multiple orthogonal protein localization readouts, foundational study replicated in later work\",\n      \"pmids\": [\"24891606\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"In C. elegans, the CNTD1 ortholog COSA-1 acts downstream of the MAP kinase pathway (MPK-1) as a crossover-promoting factor; inactivation of MAP kinase at late pachytene is required for timely disassembly of SC proteins from chromosome long arms, and this process depends on ZHP-3/RNF212/Zip3 and COSA-1/CNTD1.\",\n      \"method\": \"C. elegans genetic epistasis: RAS/ERK pathway mutants combined with cosa-1 and zhp-3 mutants, immunofluorescence of SC components and crossover markers\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis in C. elegans with multiple mutant combinations; ortholog evidence, single lab\",\n      \"pmids\": [\"26920220\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"CNTD1 physically interacts with the proline-rich protein PRR19; PRR19 and CNTD1 co-localise at crossover sites, are interdependent for accumulation, and both are required for timely DSB repair and formation of crossover-specific recombination complexes. Additionally, CNTD1 interacts with CDK2, which also accumulates in crossover-specific recombination complexes.\",\n      \"method\": \"Co-immunoprecipitation (physical interaction), co-immunofluorescence on meiotic chromosome spreads, mouse knockouts of Prr19 and Cntd1 with analysis of DSB repair and CO-specific complexes\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal co-IP establishing physical interaction, co-localization, interdependence by KO, and CDK2 interaction, multiple orthogonal methods in one study\",\n      \"pmids\": [\"32555348\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"A short isoform of CNTD1 lacking the predicted N-terminal cyclin domain does not bind cyclin-dependent kinases; instead it associates with components of the replication factor C (RFC) machinery to facilitate crossover formation, and with the E2 ubiquitin-conjugating enzyme CDC34 to regulate ubiquitylation and subsequent degradation of the WEE1 kinase, thereby modulating cell-cycle progression during meiotic prophase I.\",\n      \"method\": \"Epitope-tagged Cntd1 knock-in mouse, co-immunoprecipitation with RFC components and CDC34, isoform characterization, in vivo ubiquitylation/degradation assay for WEE1\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — epitope-tagged allele in vivo, co-IP with multiple interactors, isoform biochemistry, WEE1 degradation readout, multiple orthogonal methods\",\n      \"pmids\": [\"32640224\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"RNF212B co-localizes and interacts with CNTD1 at late CO foci by late pachynema; genetic analysis shows that the unloading of RNF212B from chromosomes at the end of pachynema is dependent on HEI10 and CNTD1, placing CNTD1 as a regulator of RNF212B dynamics.\",\n      \"method\": \"Mouse knockouts (Cntd1, Hei10, Rnf212b), immunofluorescence co-localization on meiotic chromosome spreads, genetic epistasis with Rnf212b/Rnf212 double mutants\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis and co-localization in mouse KO models, single lab, co-localization only (no co-IP shown for CNTD1-RNF212B directly)\",\n      \"pmids\": [\"38865271\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Knockout of cntd1 in zebrafish (CRISPR/Cas9) impairs meiotic crossover formation, leading to cell-cycle arrest during meiotic metaphase and apoptosis of spermatocytes; in females, cntd1 loss causes production of unreduced (haploid, aneuploid, or diploid) eggs, demonstrating a sex-specific role for CNTD1 in maintaining ploidy integrity during meiosis.\",\n      \"method\": \"CRISPR/Cas9 knockout of cntd1 in zebrafish, cytological analysis of meiotic progression, ploidy analysis of gametes and offspring\",\n      \"journal\": \"Molecular biology and evolution\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean KO with defined cellular and ploidy phenotypes in vertebrate model, single lab\",\n      \"pmids\": [\"38421617\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"CNTD1-deficient oocytes fail to form crossovers. Additionally, loss of CNTD1 causes severe depletion of the follicle pool shortly after birth; this follicle loss is CHK2-dependent and results from inappropriate retention of HORMAD1 and absence of SKP1, establishing a novel role for CNTD1 in establishing the ovarian follicular reserve beyond its role in CO designation.\",\n      \"method\": \"Mouse conditional/full knockout of Cntd1, immunofluorescence for HORMAD1/SKP1, genetic interaction with Chk2 knockout, histological analysis of ovarian follicle pools\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean loss-of-function mouse model with multiple molecular readouts (HORMAD1, SKP1, CHK2 epistasis) and defined cellular phenotype\",\n      \"pmids\": [\"40488668\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CNTD1 is a cyclin-related protein that acts as a critical coordinator of meiotic crossover (CO) maturation: it regulates the redistribution and activity of RING-finger E3 ligases HEI10 and RNF212 at designated CO sites, physically partners with PRR19 and CDK2 to promote CO-specific recombination complexes, and through a short isoform lacking the cyclin domain, associates with RFC machinery and the E2 enzyme CDC34 to drive ubiquitin-mediated WEE1 degradation, thereby coupling CO completion to meiotic cell-cycle progression; in females it additionally controls establishment of the ovarian follicular reserve via a CHK2-dependent mechanism involving HORMAD1 retention and SKP1 absence.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"CNTD1 is a cyclin-related protein that functions as a central coordinator of meiotic crossover (CO) maturation, ensuring that designated recombination intermediates are converted into mature, correctly positioned crossovers during prophase I [#0]. It acts by regulating the chromosomal dynamics and redistribution of RING-finger E3 ligases at CO sites: loss of CNTD1 prevents localization of the CO-specific factors MutL\\u03b3 (MLH1/MLH3) and HEI10 while leaving cells in a prolonged pre-CO state marked by MutS\\u03b3 and RNF212, and CNTD1 governs the late-pachynema unloading of RNF212B together with HEI10 [#0, #4]. CNTD1 builds CO-specific recombination complexes through physical interaction with the proline-rich protein PRR19 and with CDK2, with PRR19 and CNTD1 being interdependent for accumulation at CO sites and jointly required for timely double-strand break repair [#2]. A short CNTD1 isoform lacking the N-terminal cyclin domain forgoes CDK binding and instead associates with the replication factor C (RFC) machinery and with the E2 ubiquitin-conjugating enzyme CDC34 to drive ubiquitylation and degradation of WEE1 kinase, thereby coupling CO formation to meiotic cell-cycle progression [#3]. Beyond CO designation, CNTD1 establishes the ovarian follicular reserve: its loss triggers CHK2-dependent follicle depletion associated with inappropriate HORMAD1 retention and absence of SKP1 [#6]. Across vertebrate and invertebrate models, CNTD1/COSA-1 loss impairs crossover formation and compromises ploidy integrity, causing meiotic arrest, spermatocyte apoptosis, and production of aneuploid gametes [#1, #5].\",\n  \"teleology\": [\n    {\n      \"year\": 2014,\n      \"claim\": \"Established CNTD1 as a required factor for crossover maturation by showing it controls whether pre-CO intermediates are resolved into mature crossovers, defining its place at the designation step of meiotic recombination.\",\n      \"evidence\": \"Mouse Cntd1 knockout with immunofluorescence of CO markers (MutL\\u03b3, HEI10, MutS\\u03b3, RNF212) on meiotic chromosome spreads\",\n      \"pmids\": [\"24891606\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve whether CNTD1 acts directly on the RING-finger ligases or through partner proteins\", \"No biochemical demonstration of CNTD1 enzymatic or scaffolding activity\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Placed the CNTD1 ortholog COSA-1 downstream of MAP kinase signaling in crossover promotion, linking a conserved kinase pathway to crossover-associated SC disassembly.\",\n      \"evidence\": \"C. elegans genetic epistasis of RAS/ERK (MPK-1) mutants with cosa-1 and zhp-3 mutants, immunofluorescence of SC and CO markers\",\n      \"pmids\": [\"26920220\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Ortholog-based; mammalian CNTD1 not directly tested for MAP kinase dependence\", \"Did not establish direct molecular contact between COSA-1 and MAP kinase components\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identified the physical CO-complex partners of CNTD1, showing it works with PRR19 and CDK2 to assemble crossover-specific recombination complexes and promote DSB repair.\",\n      \"evidence\": \"Reciprocal co-immunoprecipitation, co-immunofluorescence on chromosome spreads, and Prr19/Cntd1 mouse knockouts\",\n      \"pmids\": [\"32555348\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the structural basis or stoichiometry of the CNTD1\\u2013PRR19\\u2013CDK2 complex\", \"Whether CDK2 kinase activity within the complex is required was not resolved\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Revealed an isoform-specific dual function: a cyclin-domain-lacking CNTD1 isoform couples crossover formation to cell-cycle control via RFC association and CDC34-dependent WEE1 degradation, distinguishing CNTD1's recombination and cell-cycle roles.\",\n      \"evidence\": \"Epitope-tagged Cntd1 knock-in mouse, co-IP with RFC components and CDC34, isoform characterization, and in vivo WEE1 ubiquitylation/degradation assay\",\n      \"pmids\": [\"32640224\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which CNTD1 directs CDC34 substrate selection toward WEE1 was not defined\", \"How the two isoforms are produced and balanced in vivo remains uncharacterized\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Extended CNTD1's role in RING-finger ligase regulation by showing it, together with HEI10, governs the chromosomal unloading of RNF212B at late pachynema.\",\n      \"evidence\": \"Cntd1, Hei10, and Rnf212b mouse knockouts with co-localization on chromosome spreads and Rnf212b/Rnf212 genetic epistasis\",\n      \"pmids\": [\"38865271\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No direct co-IP demonstrating CNTD1\\u2013RNF212B physical interaction\", \"Single lab; mechanism of unloading not biochemically defined\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Demonstrated the functional consequence of CNTD1 loss for genome integrity across sexes in a vertebrate model, tying crossover failure to meiotic arrest, apoptosis, and aneuploid gamete production.\",\n      \"evidence\": \"CRISPR/Cas9 cntd1 knockout in zebrafish with cytological meiotic analysis and gamete ploidy assessment\",\n      \"pmids\": [\"38421617\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Did not address whether zebrafish CNTD1 uses the same isoform/WEE1 mechanism as mouse\", \"Molecular basis of sex-specific ploidy outcomes not resolved\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Uncovered a CO-independent role for CNTD1 in establishing the ovarian follicular reserve, acting through a CHK2-dependent surveillance pathway linked to HORMAD1 retention and SKP1 absence.\",\n      \"evidence\": \"Mouse Cntd1 knockout with HORMAD1/SKP1 immunofluorescence, Chk2 genetic epistasis, and histological follicle quantification\",\n      \"pmids\": [\"40488668\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How CNTD1 normally promotes HORMAD1 removal and SKP1 presence is not mechanistically defined\", \"Whether follicle loss is a direct CNTD1 function or a downstream consequence of CO failure was not fully separated\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The biochemical activity of CNTD1 itself \\u2014 whether it acts as a bona fide cyclin partner, a scaffold, or an adaptor that licenses E3 ligase and E2 activity \\u2014 and the structural basis of its assembled complexes remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of CNTD1 or its complexes\", \"Direct enzymatic or scaffolding mechanism not biochemically reconstituted\", \"Human disease relevance not established in the available corpus\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 4]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [2, 3]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0000228\", \"supporting_discovery_ids\": [0, 2, 4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1474165\", \"supporting_discovery_ids\": [0, 5, 6]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [3, 5]},\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [0, 2]}\n    ],\n    \"complexes\": [\"CO-specific recombination complex (CNTD1-PRR19-CDK2)\", \"RFC machinery (short isoform)\"],\n    \"partners\": [\"PRR19\", \"CDK2\", \"CDC34\", \"HEI10\", \"RNF212B\", \"WEE1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}