{"gene":"SYCE1","run_date":"2026-06-10T10:51:54","timeline":{"discoveries":[{"year":2009,"finding":"SYCE1 null mutation in mouse disrupts meiotic synapsis and reveals a biochemical interaction between the synaptonemal complex structural protein SYCE2 and the DNA repair protein RAD51, suggesting this interaction promotes homologous synapsis from sites of recombination.","method":"Mouse knockout (null mutation), co-immunoprecipitation/biochemical interaction assay","journal":"PLoS genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal biochemical interaction established in vivo using null mutant mouse model with defined cellular phenotype (synapsis failure); replicated context of SC structural-repair protein link","pmids":["19247432"],"is_preprint":false},{"year":2019,"finding":"The structural core of human SYCE1 (amino acids 25–179) mediates SYCE1 homodimerization via an anti-parallel curved coiled-coil structure of ~20 nm length; full-length SYCE1 adopts an elongated molecule of >50 nm with extended C-termini, consistent with it functioning as a physical strut tethering other SC central element components.","method":"Solution biophysics: multi-angle light scattering (MALS) and small-angle X-ray scattering (SAXS)","journal":"Chromosoma","confidence":"High","confidence_rationale":"Tier 1 / Moderate — direct structural characterization using two orthogonal biophysical methods (MALS and SAXS) in a single focused study","pmids":["30607510"],"is_preprint":false},{"year":2020,"finding":"SYCE1 undergoes multivalent interactions with SC component SIX6OS1: the N-terminus of SIX6OS1 binds and disrupts SYCE1's core dimeric structure to form a 1:1 complex, while downstream sequences provide a distinct second binding interface. Both interfaces are required for SC assembly and meiotic chromosome synapsis, as demonstrated by infertile mice carrying SYCE1's POF mutation and a targeted SIX6OS1 N-terminal deletion.","method":"Mouse genetics (targeted mutations), biochemical binding assays, cellular co-localization studies","journal":"Science advances","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — combined mouse genetics, cellular imaging, and biochemical interaction studies across multiple orthogonal approaches in a single study, with functional validation by infertility phenotype","pmids":["32917591"],"is_preprint":false},{"year":2020,"finding":"A CRISPR/Cas9-generated humanized mouse carrying the SYCE1 c.721C>T (p.R241*) equivalent mutation shows complete absence of SYCE1 protein, highly diminished Syce1 transcript (suggesting nonsense-mediated mRNA decay), and failure of homologous chromosome synapsis, establishing this mutation as causative for POI via synapsis defects.","method":"CRISPR/Cas9 humanized mouse model, immunofluorescence, qRT-PCR, cytological analysis of meiotic spreads","journal":"Molecular human reproduction","confidence":"High","confidence_rationale":"Tier 2 / Moderate — direct functional validation in humanized mouse model with multiple orthogonal readouts (protein detection, transcript quantification, synapsis cytology)","pmids":["32402064"],"is_preprint":false},{"year":2022,"finding":"A frameshift mutation in SYCE1 (c.689_690del; p.F230fs) causes decreased protein expression and aberrant cytoplasmic rather than nuclear localization of SYCE1 in vitro, indicating the C-terminal region is required for proper nuclear targeting.","method":"In vitro transfection of wild-type and mutant SYCE1 constructs into human cell lines, immunofluorescence, Western blot","journal":"Journal of cellular and molecular medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — defined localization defect with functional implication in a single lab using cell-based overexpression system","pmids":["35023261"],"is_preprint":false},{"year":2022,"finding":"SYCE1 variants identified in POI and NOA patients disrupt SYCE1's interaction with SYCP1 or C14ORF39 (SIX6OS1), thereby affecting SC assembly and meiosis, as shown by functional interaction studies.","method":"Functional protein interaction assays (co-immunoprecipitation/pulldown) of wild-type vs. patient-variant SYCE1","journal":"The Journal of clinical endocrinology and metabolism","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — interaction disruption shown by binding assay in single study; no orthogonal structural or in vivo confirmation reported in the abstract","pmids":["34718620"],"is_preprint":false},{"year":2022,"finding":"Overexpression of Syce1 in mouse Sertoli and Leydig cells activates steroidogenic genes Star and Hsd3b, upregulating testosterone synthesis, and specifically increases Srd5a1 expression to promote DHT secretion. Syce1 and Syce3 overexpression synergistically promotes each other's abundance.","method":"Transfection (overexpression and siRNA knockdown) of Syce1/Syce3 in primary mouse Sertoli and Leydig cells, RT-PCR/qPCR for steroidogenic gene expression, hormone assay","journal":"The Journal of steroid biochemistry and molecular biology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, cell-based overexpression/knockdown without in vivo validation or direct enzymatic mechanistic evidence; unexpected function distinct from canonical meiotic role","pmids":["35697131"],"is_preprint":false},{"year":2025,"finding":"Humanized mice carrying the SYCE1 c.197-2A>G splice site mutation are infertile; SYCE1 protein is absent and Syce1 transcript is at minimal levels (consistent with transcript degradation), with impaired homologous chromosome synapsis, meiotic arrest before the pachytene stage, and increased apoptosis of meiotic cells in both sexes.","method":"CRISPR/Cas9 humanized mouse model, immunofluorescence, RT-PCR, cytological analysis, TUNEL apoptosis assay","journal":"Molecular human reproduction","confidence":"High","confidence_rationale":"Tier 2 / Moderate — direct functional validation in humanized mouse model with multiple orthogonal readouts (protein, transcript, synapsis, apoptosis) in a single focused study","pmids":["39909494"],"is_preprint":false}],"current_model":"SYCE1 is a synaptonemal complex (SC) central element protein that homodimerizes via an anti-parallel coiled-coil core (aa 25–179) to form an elongated structural strut; it undergoes multivalent interactions with SIX6OS1 (C14ORF39) and also contacts SYCP1, and both binding interfaces are essential for SC assembly and full homologous chromosome synapsis during meiosis, with loss of SYCE1 causing meiotic arrest, increased apoptosis, and infertility in both sexes, and certain mutations additionally disrupting nuclear localization or promoting transcript degradation."},"narrative":{"mechanistic_narrative":"SYCE1 is a central-element structural protein of the meiotic synaptonemal complex (SC) required for homologous chromosome synapsis, and its loss disrupts meiotic synapsis in mouse [PMID:19247432]. The structural core of human SYCE1 (aa 25–179) homodimerizes through an anti-parallel curved coiled-coil of ~20 nm, and the full-length molecule extends beyond 50 nm with elongated C-termini, consistent with a physical strut that tethers central-element components [PMID:30607510]. SYCE1 engages SIX6OS1 (C14ORF39) through multivalent contacts—an N-terminal interface that opens the SYCE1 core dimer to form a 1:1 complex plus a distinct downstream interface—and both interfaces are required for SC assembly and synapsis, while a separate interaction with SYCP1 contributes to complex integrity [PMID:32917591, PMID:34718620]. Disruption of either the SIX6OS1 or SYCP1 interaction by patient-derived variants impairs SC assembly and meiosis [PMID:34718620]. Human pathogenic alleles modeled in humanized mice—including p.R241* and the c.197-2A>G splice mutation—abolish SYCE1 protein and reduce transcript to minimal levels through transcript degradation, producing failure of homologous synapsis, meiotic arrest before pachytene, increased apoptosis, and infertility in both sexes, establishing SYCE1 as causative for premature ovarian insufficiency and meiotic arrest [PMID:32402064, PMID:39909494]. A frameshift allele (p.F230fs) lowers expression and mislocalizes SYCE1 to the cytoplasm, indicating the C-terminal region is needed for nuclear targeting [PMID:35023261].","teleology":[{"year":2009,"claim":"Establishing whether SYCE1 is required for meiotic synapsis was the first step in defining its in vivo role, and the null mouse showed it is essential while linking SC structural proteins to recombination machinery.","evidence":"Mouse knockout with co-immunoprecipitation linking SC proteins and RAD51","pmids":["19247432"],"confidence":"High","gaps":["Did not resolve SYCE1's own structure or direct binding partners","Mechanism of how synapsis initiates from recombination sites not defined for SYCE1 itself"]},{"year":2019,"claim":"How SYCE1 contributes architecturally to the SC was unknown; biophysical analysis showed it homodimerizes into an elongated anti-parallel coiled-coil strut, providing a structural basis for tethering central-element components.","evidence":"Solution biophysics (MALS, SAXS) on human SYCE1 core and full-length protein","pmids":["30607510"],"confidence":"High","gaps":["No high-resolution atomic structure","Binding partners contacted by the extended C-termini not mapped in this study"]},{"year":2020,"claim":"The molecular basis of SYCE1 integration into the SC was clarified by demonstrating multivalent SIX6OS1 binding that remodels the SYCE1 core dimer, with both interfaces functionally required for synapsis.","evidence":"Mouse genetics with targeted mutations plus biochemical binding and co-localization assays","pmids":["32917591"],"confidence":"High","gaps":["Stoichiometry within the assembled SC lattice not fully defined","Relationship of the SIX6OS1 interface to the SYCP1 contact not resolved"]},{"year":2020,"claim":"Whether a specific human SYCE1 nonsense allele causes ovarian insufficiency was tested by humanizing the mutation in mouse, showing loss of protein via transcript degradation and synapsis failure.","evidence":"CRISPR/Cas9 humanized mouse, immunofluorescence, qRT-PCR, meiotic spread cytology","pmids":["32402064"],"confidence":"High","gaps":["Did not address partial-function or missense alleles","Did not separate transcript decay from protein instability mechanistically"]},{"year":2022,"claim":"How disease variants act at the molecular level was addressed by showing POI and NOA variants disrupt SYCE1 binding to SYCP1 or SIX6OS1, tying clinical phenotypes to specific interaction interfaces.","evidence":"Co-immunoprecipitation/pulldown of wild-type versus patient-variant SYCE1","pmids":["34718620"],"confidence":"Medium","gaps":["No orthogonal structural or in vivo confirmation of disrupted interactions","Quantitative effect on SC assembly not measured"]},{"year":2022,"claim":"A frameshift variant revealed that the SYCE1 C-terminus is required for correct nuclear targeting, since the mutant mislocalized to the cytoplasm with reduced expression.","evidence":"In vitro transfection of WT and mutant constructs in human cell lines, immunofluorescence, Western blot","pmids":["35023261"],"confidence":"Medium","gaps":["Cell-based overexpression only, not validated in meiotic cells in vivo","Nuclear import signal not mapped"]},{"year":2022,"claim":"A potential non-meiotic role was explored by overexpression in somatic gonadal cells, where SYCE1 activated steroidogenic genes and increased androgen synthesis.","evidence":"Overexpression/knockdown of Syce1/Syce3 in primary mouse Sertoli and Leydig cells with steroidogenic gene and hormone assays","pmids":["35697131"],"confidence":"Low","gaps":["Single-lab cell-based overexpression without in vivo validation","No direct mechanistic link between SYCE1 and steroidogenic gene regulation","Function distinct from canonical meiotic role not independently confirmed"]},{"year":2025,"claim":"Whether a splice-site human allele recapitulates infertility was confirmed in humanized mice, extending the loss-of-function/transcript-degradation mechanism to meiotic arrest and apoptosis in both sexes.","evidence":"CRISPR/Cas9 humanized mouse, immunofluorescence, RT-PCR, cytology, TUNEL apoptosis assay","pmids":["39909494"],"confidence":"High","gaps":["Does not distinguish which downstream events trigger apoptosis","Timing of arrest relative to recombination checkpoints not dissected"]},{"year":null,"claim":"The atomic-resolution architecture of the assembled SYCE1–SIX6OS1–SYCP1 central-element lattice and the molecular basis of any non-meiotic SYCE1 functions remain open.","evidence":"","pmids":[],"confidence":"Low","gaps":["No high-resolution structure of the assembled central element","Non-meiotic steroidogenic role unvalidated in vivo","Nuclear import determinants not mapped"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[1,2]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[1,2]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[4]},{"term_id":"GO:0005694","term_label":"chromosome","supporting_discovery_ids":[0,2,3]}],"pathway":[{"term_id":"R-HSA-1474165","term_label":"Reproduction","supporting_discovery_ids":[0,3,7]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[0,2]}],"complexes":["synaptonemal complex central element"],"partners":["SIX6OS1","SYCP1","SYCE2","SYCE3"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q8N0S2","full_name":"Synaptonemal complex central element protein 1","aliases":["Cancer/testis antigen 76","CT76"],"length_aa":351,"mass_kda":39.7,"function":"Major component of the transverse central element of synaptonemal complexes (SCS), formed between homologous chromosomes during meiotic prophase. Requires SYCP1 in order to be incorporated into the central element. May have a role in the synaptonemal complex assembly, stabilization and recombination","subcellular_location":"Nucleus; Chromosome","url":"https://www.uniprot.org/uniprotkb/Q8N0S2/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/SYCE1","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/SYCE1","total_profiled":1310},"omim":[{"mim_id":"619954","title":"SYNAPTONEMAL COMPLEX CENTRAL ELEMENT PROTEIN 1-LIKE; SYCE1L","url":"https://www.omim.org/entry/619954"},{"mim_id":"619203","title":"PREMATURE OVARIAN FAILURE 18; POF18","url":"https://www.omim.org/entry/619203"},{"mim_id":"619202","title":"SPERMATOGENIC FAILURE 52; SPGF52","url":"https://www.omim.org/entry/619202"},{"mim_id":"618842","title":"HORMA DOMAIN-CONTAINING PROTEIN 2; HORMAD2","url":"https://www.omim.org/entry/618842"},{"mim_id":"617307","title":"CHROMOSOME 14 OPEN READING FRAME 39; C14ORF39","url":"https://www.omim.org/entry/617307"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Vesicles","reliability":"Additional"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Group enriched","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"brain","ntpm":17.7},{"tissue":"testis","ntpm":69.5}],"url":"https://www.proteinatlas.org/search/SYCE1"},"hgnc":{"alias_symbol":["bA108K14.6","CT76"],"prev_symbol":["C10orf94"]},"alphafold":{"accession":"Q8N0S2","domains":[],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8N0S2","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8N0S2-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8N0S2-F1-predicted_aligned_error_v6.png","plddt_mean":77.5},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=SYCE1","jax_strain_url":"https://www.jax.org/strain/search?query=SYCE1"},"sequence":{"accession":"Q8N0S2","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8N0S2.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8N0S2/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8N0S2"}},"corpus_meta":[{"pmid":"19247432","id":"PMC_19247432","title":"Mutation of the mouse Syce1 gene disrupts synapsis and suggests a link between synaptonemal complex structural components and DNA repair.","date":"2009","source":"PLoS genetics","url":"https://pubmed.ncbi.nlm.nih.gov/19247432","citation_count":166,"is_preprint":false},{"pmid":"25062452","id":"PMC_25062452","title":"Exome sequencing reveals SYCE1 mutation associated with autosomal recessive primary ovarian insufficiency.","date":"2014","source":"The Journal of clinical endocrinology and metabolism","url":"https://pubmed.ncbi.nlm.nih.gov/25062452","citation_count":123,"is_preprint":false},{"pmid":"25899990","id":"PMC_25899990","title":"Deleterious mutation in SYCE1 is associated with non-obstructive azoospermia.","date":"2015","source":"Journal of assisted reproduction and genetics","url":"https://pubmed.ncbi.nlm.nih.gov/25899990","citation_count":88,"is_preprint":false},{"pmid":"32917591","id":"PMC_32917591","title":"Meiotic chromosome synapsis depends on multivalent SYCE1-SIX6OS1 interactions that are disrupted in cases of human infertility.","date":"2020","source":"Science advances","url":"https://pubmed.ncbi.nlm.nih.gov/32917591","citation_count":41,"is_preprint":false},{"pmid":"30607510","id":"PMC_30607510","title":"Molecular structure of human synaptonemal complex protein SYCE1.","date":"2019","source":"Chromosoma","url":"https://pubmed.ncbi.nlm.nih.gov/30607510","citation_count":37,"is_preprint":false},{"pmid":"31916078","id":"PMC_31916078","title":"The second mutation of SYCE1 gene associated with autosomal recessive nonobstructive azoospermia.","date":"2020","source":"Journal of assisted reproduction and genetics","url":"https://pubmed.ncbi.nlm.nih.gov/31916078","citation_count":35,"is_preprint":false},{"pmid":"34718620","id":"PMC_34718620","title":"Variations of C14ORF39 and SYCE1 Identified in Idiopathic Premature Ovarian Insufficiency and Nonobstructive Azoospermia.","date":"2022","source":"The Journal of clinical endocrinology and metabolism","url":"https://pubmed.ncbi.nlm.nih.gov/34718620","citation_count":32,"is_preprint":false},{"pmid":"31925770","id":"PMC_31925770","title":"Consanguineous Chinese Familial Study Reveals that a Gross Deletion that Includes the SYCE1 Gene Region Is Associated with Premature Ovarian Insufficiency.","date":"2020","source":"Reproductive sciences (Thousand Oaks, Calif.)","url":"https://pubmed.ncbi.nlm.nih.gov/31925770","citation_count":21,"is_preprint":false},{"pmid":"32402064","id":"PMC_32402064","title":"Familial primary ovarian insufficiency associated with an SYCE1 point mutation: defective meiosis elucidated in humanized mice.","date":"2020","source":"Molecular human reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/32402064","citation_count":17,"is_preprint":false},{"pmid":"35023261","id":"PMC_35023261","title":"Novel exon mutation in SYCE1 gene is associated with non-obstructive azoospermia.","date":"2022","source":"Journal of cellular and molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/35023261","citation_count":14,"is_preprint":false},{"pmid":"35718780","id":"PMC_35718780","title":"Novel copy number variations within SYCE1 caused meiotic arrest and non-obstructive azoospermia.","date":"2022","source":"BMC medical genomics","url":"https://pubmed.ncbi.nlm.nih.gov/35718780","citation_count":8,"is_preprint":false},{"pmid":"35697131","id":"PMC_35697131","title":"Syce1 and Syce3 regulate testosterone and dihydrotestosterone synthesis via steroidogenic pathways in mouse Sertoli and Leydig cells.","date":"2022","source":"The Journal of steroid biochemistry and molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/35697131","citation_count":7,"is_preprint":false},{"pmid":"39208330","id":"PMC_39208330","title":"Differential expression and regulation of ADAD1, DMRTC2, PRSS54, SYCE1, SYCP1, TEX101, TEX48, and TMPRSS12 gene profiles in colon cancer tissues and their in vitro response to epigenetic drugs.","date":"2024","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/39208330","citation_count":5,"is_preprint":false},{"pmid":"37957469","id":"PMC_37957469","title":"Novel Mutations Reduce Expression of Meiotic Regulators SYCE1 and BOLL in Testis of Azoospermic Men from West Bengal, India.","date":"2023","source":"Reproductive sciences (Thousand Oaks, Calif.)","url":"https://pubmed.ncbi.nlm.nih.gov/37957469","citation_count":2,"is_preprint":false},{"pmid":"39909494","id":"PMC_39909494","title":"Mouse modeling of familial human SYCE1 c.197-2A>G splice site mutation leads to meiotic recombination failure and non-obstructive azoospermia.","date":"2025","source":"Molecular human reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/39909494","citation_count":2,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":9744,"output_tokens":2036,"usd":0.029886,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9038,"output_tokens":2913,"usd":0.059007,"stage2_stop_reason":"end_turn"},"total_usd":0.088893,"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\": 2009,\n      \"finding\": \"SYCE1 null mutation in mouse disrupts meiotic synapsis and reveals a biochemical interaction between the synaptonemal complex structural protein SYCE2 and the DNA repair protein RAD51, suggesting this interaction promotes homologous synapsis from sites of recombination.\",\n      \"method\": \"Mouse knockout (null mutation), co-immunoprecipitation/biochemical interaction assay\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal biochemical interaction established in vivo using null mutant mouse model with defined cellular phenotype (synapsis failure); replicated context of SC structural-repair protein link\",\n      \"pmids\": [\"19247432\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"The structural core of human SYCE1 (amino acids 25–179) mediates SYCE1 homodimerization via an anti-parallel curved coiled-coil structure of ~20 nm length; full-length SYCE1 adopts an elongated molecule of >50 nm with extended C-termini, consistent with it functioning as a physical strut tethering other SC central element components.\",\n      \"method\": \"Solution biophysics: multi-angle light scattering (MALS) and small-angle X-ray scattering (SAXS)\",\n      \"journal\": \"Chromosoma\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct structural characterization using two orthogonal biophysical methods (MALS and SAXS) in a single focused study\",\n      \"pmids\": [\"30607510\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"SYCE1 undergoes multivalent interactions with SC component SIX6OS1: the N-terminus of SIX6OS1 binds and disrupts SYCE1's core dimeric structure to form a 1:1 complex, while downstream sequences provide a distinct second binding interface. Both interfaces are required for SC assembly and meiotic chromosome synapsis, as demonstrated by infertile mice carrying SYCE1's POF mutation and a targeted SIX6OS1 N-terminal deletion.\",\n      \"method\": \"Mouse genetics (targeted mutations), biochemical binding assays, cellular co-localization studies\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — combined mouse genetics, cellular imaging, and biochemical interaction studies across multiple orthogonal approaches in a single study, with functional validation by infertility phenotype\",\n      \"pmids\": [\"32917591\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"A CRISPR/Cas9-generated humanized mouse carrying the SYCE1 c.721C>T (p.R241*) equivalent mutation shows complete absence of SYCE1 protein, highly diminished Syce1 transcript (suggesting nonsense-mediated mRNA decay), and failure of homologous chromosome synapsis, establishing this mutation as causative for POI via synapsis defects.\",\n      \"method\": \"CRISPR/Cas9 humanized mouse model, immunofluorescence, qRT-PCR, cytological analysis of meiotic spreads\",\n      \"journal\": \"Molecular human reproduction\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct functional validation in humanized mouse model with multiple orthogonal readouts (protein detection, transcript quantification, synapsis cytology)\",\n      \"pmids\": [\"32402064\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"A frameshift mutation in SYCE1 (c.689_690del; p.F230fs) causes decreased protein expression and aberrant cytoplasmic rather than nuclear localization of SYCE1 in vitro, indicating the C-terminal region is required for proper nuclear targeting.\",\n      \"method\": \"In vitro transfection of wild-type and mutant SYCE1 constructs into human cell lines, immunofluorescence, Western blot\",\n      \"journal\": \"Journal of cellular and molecular medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — defined localization defect with functional implication in a single lab using cell-based overexpression system\",\n      \"pmids\": [\"35023261\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"SYCE1 variants identified in POI and NOA patients disrupt SYCE1's interaction with SYCP1 or C14ORF39 (SIX6OS1), thereby affecting SC assembly and meiosis, as shown by functional interaction studies.\",\n      \"method\": \"Functional protein interaction assays (co-immunoprecipitation/pulldown) of wild-type vs. patient-variant SYCE1\",\n      \"journal\": \"The Journal of clinical endocrinology and metabolism\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — interaction disruption shown by binding assay in single study; no orthogonal structural or in vivo confirmation reported in the abstract\",\n      \"pmids\": [\"34718620\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Overexpression of Syce1 in mouse Sertoli and Leydig cells activates steroidogenic genes Star and Hsd3b, upregulating testosterone synthesis, and specifically increases Srd5a1 expression to promote DHT secretion. Syce1 and Syce3 overexpression synergistically promotes each other's abundance.\",\n      \"method\": \"Transfection (overexpression and siRNA knockdown) of Syce1/Syce3 in primary mouse Sertoli and Leydig cells, RT-PCR/qPCR for steroidogenic gene expression, hormone assay\",\n      \"journal\": \"The Journal of steroid biochemistry and molecular biology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, cell-based overexpression/knockdown without in vivo validation or direct enzymatic mechanistic evidence; unexpected function distinct from canonical meiotic role\",\n      \"pmids\": [\"35697131\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Humanized mice carrying the SYCE1 c.197-2A>G splice site mutation are infertile; SYCE1 protein is absent and Syce1 transcript is at minimal levels (consistent with transcript degradation), with impaired homologous chromosome synapsis, meiotic arrest before the pachytene stage, and increased apoptosis of meiotic cells in both sexes.\",\n      \"method\": \"CRISPR/Cas9 humanized mouse model, immunofluorescence, RT-PCR, cytological analysis, TUNEL apoptosis assay\",\n      \"journal\": \"Molecular human reproduction\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct functional validation in humanized mouse model with multiple orthogonal readouts (protein, transcript, synapsis, apoptosis) in a single focused study\",\n      \"pmids\": [\"39909494\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"SYCE1 is a synaptonemal complex (SC) central element protein that homodimerizes via an anti-parallel coiled-coil core (aa 25–179) to form an elongated structural strut; it undergoes multivalent interactions with SIX6OS1 (C14ORF39) and also contacts SYCP1, and both binding interfaces are essential for SC assembly and full homologous chromosome synapsis during meiosis, with loss of SYCE1 causing meiotic arrest, increased apoptosis, and infertility in both sexes, and certain mutations additionally disrupting nuclear localization or promoting transcript degradation.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"SYCE1 is a central-element structural protein of the meiotic synaptonemal complex (SC) required for homologous chromosome synapsis, and its loss disrupts meiotic synapsis in mouse [#0]. The structural core of human SYCE1 (aa 25–179) homodimerizes through an anti-parallel curved coiled-coil of ~20 nm, and the full-length molecule extends beyond 50 nm with elongated C-termini, consistent with a physical strut that tethers central-element components [#1]. SYCE1 engages SIX6OS1 (C14ORF39) through multivalent contacts—an N-terminal interface that opens the SYCE1 core dimer to form a 1:1 complex plus a distinct downstream interface—and both interfaces are required for SC assembly and synapsis, while a separate interaction with SYCP1 contributes to complex integrity [#2, #5]. Disruption of either the SIX6OS1 or SYCP1 interaction by patient-derived variants impairs SC assembly and meiosis [#5]. Human pathogenic alleles modeled in humanized mice—including p.R241* and the c.197-2A>G splice mutation—abolish SYCE1 protein and reduce transcript to minimal levels through transcript degradation, producing failure of homologous synapsis, meiotic arrest before pachytene, increased apoptosis, and infertility in both sexes, establishing SYCE1 as causative for premature ovarian insufficiency and meiotic arrest [#3, #7]. A frameshift allele (p.F230fs) lowers expression and mislocalizes SYCE1 to the cytoplasm, indicating the C-terminal region is needed for nuclear targeting [#4].\",\n  \"teleology\": [\n    {\n      \"year\": 2009,\n      \"claim\": \"Establishing whether SYCE1 is required for meiotic synapsis was the first step in defining its in vivo role, and the null mouse showed it is essential while linking SC structural proteins to recombination machinery.\",\n      \"evidence\": \"Mouse knockout with co-immunoprecipitation linking SC proteins and RAD51\",\n      \"pmids\": [\"19247432\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve SYCE1's own structure or direct binding partners\", \"Mechanism of how synapsis initiates from recombination sites not defined for SYCE1 itself\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"How SYCE1 contributes architecturally to the SC was unknown; biophysical analysis showed it homodimerizes into an elongated anti-parallel coiled-coil strut, providing a structural basis for tethering central-element components.\",\n      \"evidence\": \"Solution biophysics (MALS, SAXS) on human SYCE1 core and full-length protein\",\n      \"pmids\": [\"30607510\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No high-resolution atomic structure\", \"Binding partners contacted by the extended C-termini not mapped in this study\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"The molecular basis of SYCE1 integration into the SC was clarified by demonstrating multivalent SIX6OS1 binding that remodels the SYCE1 core dimer, with both interfaces functionally required for synapsis.\",\n      \"evidence\": \"Mouse genetics with targeted mutations plus biochemical binding and co-localization assays\",\n      \"pmids\": [\"32917591\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry within the assembled SC lattice not fully defined\", \"Relationship of the SIX6OS1 interface to the SYCP1 contact not resolved\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Whether a specific human SYCE1 nonsense allele causes ovarian insufficiency was tested by humanizing the mutation in mouse, showing loss of protein via transcript degradation and synapsis failure.\",\n      \"evidence\": \"CRISPR/Cas9 humanized mouse, immunofluorescence, qRT-PCR, meiotic spread cytology\",\n      \"pmids\": [\"32402064\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not address partial-function or missense alleles\", \"Did not separate transcript decay from protein instability mechanistically\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"How disease variants act at the molecular level was addressed by showing POI and NOA variants disrupt SYCE1 binding to SYCP1 or SIX6OS1, tying clinical phenotypes to specific interaction interfaces.\",\n      \"evidence\": \"Co-immunoprecipitation/pulldown of wild-type versus patient-variant SYCE1\",\n      \"pmids\": [\"34718620\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No orthogonal structural or in vivo confirmation of disrupted interactions\", \"Quantitative effect on SC assembly not measured\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"A frameshift variant revealed that the SYCE1 C-terminus is required for correct nuclear targeting, since the mutant mislocalized to the cytoplasm with reduced expression.\",\n      \"evidence\": \"In vitro transfection of WT and mutant constructs in human cell lines, immunofluorescence, Western blot\",\n      \"pmids\": [\"35023261\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Cell-based overexpression only, not validated in meiotic cells in vivo\", \"Nuclear import signal not mapped\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"A potential non-meiotic role was explored by overexpression in somatic gonadal cells, where SYCE1 activated steroidogenic genes and increased androgen synthesis.\",\n      \"evidence\": \"Overexpression/knockdown of Syce1/Syce3 in primary mouse Sertoli and Leydig cells with steroidogenic gene and hormone assays\",\n      \"pmids\": [\"35697131\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Single-lab cell-based overexpression without in vivo validation\", \"No direct mechanistic link between SYCE1 and steroidogenic gene regulation\", \"Function distinct from canonical meiotic role not independently confirmed\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Whether a splice-site human allele recapitulates infertility was confirmed in humanized mice, extending the loss-of-function/transcript-degradation mechanism to meiotic arrest and apoptosis in both sexes.\",\n      \"evidence\": \"CRISPR/Cas9 humanized mouse, immunofluorescence, RT-PCR, cytology, TUNEL apoptosis assay\",\n      \"pmids\": [\"39909494\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not distinguish which downstream events trigger apoptosis\", \"Timing of arrest relative to recombination checkpoints not dissected\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The atomic-resolution architecture of the assembled SYCE1–SIX6OS1–SYCP1 central-element lattice and the molecular basis of any non-meiotic SYCE1 functions remain open.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No high-resolution structure of the assembled central element\", \"Non-meiotic steroidogenic role unvalidated in vivo\", \"Nuclear import determinants not mapped\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [1, 2]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [1, 2]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [4]},\n      {\"term_id\": \"GO:0005694\", \"supporting_discovery_ids\": [0, 2, 3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1474165\", \"supporting_discovery_ids\": [0, 3, 7]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [0, 2]}\n    ],\n    \"complexes\": [\"synaptonemal complex central element\"],\n    \"partners\": [\"SIX6OS1\", \"SYCP1\", \"SYCE2\", \"SYCE3\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}