{"gene":"ZP1","run_date":"2026-04-28T23:00:24","timeline":{"discoveries":[{"year":1999,"finding":"ZP1 is required for structural integrity of the zona pellucida matrix; mice lacking ZP1 form a zona composed only of ZP2 and ZP3 that is more loosely organized, leading to ectopic granulosa cell clusters, precocious hatching, and reduced fecundity, though ZP1 is not essential for sperm binding or fertilization per se.","method":"Targeted gene knockout in mice (Zp1(tm/tm)), histology, hormonal stimulation, mating experiments","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 1-2 — clean KO with defined structural and reproductive phenotypes, replicated across multiple experimental approaches","pmids":["10433913"],"is_preprint":false},{"year":1999,"finding":"ZP1 functions as a homodimeric filament crosslinker in the zona pellucida matrix, held together by intermolecular disulfide bonds.","method":"Biochemical characterization of native ZP protein complexes","journal":"Andrologia","confidence":"Medium","confidence_rationale":"Tier 3 — single review-type paper citing established biochemical characterization, no new primary experiment described","pmids":["10526650"],"is_preprint":false},{"year":2002,"finding":"ZP1 is synthesized and secreted exclusively by oocytes (not granulosa cells) and traffics through the Golgi apparatus and vesicular aggregates before being secreted into the zona matrix, where it distributes asymmetrically with ZP2 and ZP3 in discrete patches.","method":"Immunoelectron microscopy with protein A-gold technique; double and triple immunolocalization in mouse ovarian follicles","journal":"Biology of reproduction","confidence":"High","confidence_rationale":"Tier 2 — direct subcellular localization by immunoelectron microscopy with functional interpretation, multiple antibody controls","pmids":["11906903"],"is_preprint":false},{"year":2014,"finding":"A homozygous frameshift mutation in ZP1 causes defective ZP1 protein to colocalize with and sequester ZP3 in the cytoplasm, preventing ZP3 secretion and zona pellucida formation around the oocyte.","method":"In vitro colocalization studies in transfected cells; identification of mutation by sequencing in human infertility pedigree","journal":"The New England journal of medicine","confidence":"High","confidence_rationale":"Tier 2 — human genetics combined with in vitro cellular mechanistic experiment, high-impact journal with strong evidence","pmids":["24670168"],"is_preprint":false},{"year":2004,"finding":"Recombinant human ZP1 is retained intracellularly when expressed alone, but is secreted into culture medium when co-expressed with ZP2 and ZP3, indicating that interaction among ZP proteins is required for ZP1 release/secretion.","method":"Co-expression in HEK 293T cells; Western blotting of culture medium and cell lysate","journal":"Asian journal of andrology","confidence":"Medium","confidence_rationale":"Tier 2 — direct secretion assay with multiple ZP protein combinations, single lab","pmids":["15064827"],"is_preprint":false},{"year":2019,"finding":"Mutations in ZP1 disrupt the interaction among ZP1, ZP2, and ZP3, impairing zona pellucida assembly; co-immunoprecipitation confirmed that mutant ZP1 fails to properly interact with ZP2 and ZP3.","method":"Co-immunoprecipitation; homology modeling; CHO cell expression of wild-type and mutant ZP proteins","journal":"Human mutation","confidence":"Medium","confidence_rationale":"Tier 2-3 — co-IP and modeling in single study, consistent with human genetic data","pmids":["31292994"],"is_preprint":false},{"year":2019,"finding":"Mutations in ZP1 affect ZP1 protein expression, secretion, and interaction with other ZP proteins (ZP2, ZP3), providing a mechanistic basis for zona pellucida formation defects and female infertility.","method":"Expression studies in CHO cells; Western blotting; interaction assays","journal":"Human genetics","confidence":"Medium","confidence_rationale":"Tier 2-3 — in vitro expression and interaction data, multiple mutations tested, single lab","pmids":["30810869"],"is_preprint":false},{"year":2019,"finding":"ZP1 mutations result in either degradation or truncation of the ZP1 protein in CHO-K1 cells, and histological analysis of ovarian sections showed absent ZP1 in the zona of growing oocytes, with consequent defective cumulus-oocyte complex organization leading to empty follicle syndrome.","method":"Expression studies in CHO-K1 cells; immunohistochemistry of ovarian serial sections; Western blotting","journal":"Human reproduction (Oxford, England)","confidence":"Medium","confidence_rationale":"Tier 2 — combination of cell expression and histological evidence, single lab","pmids":["31734689"],"is_preprint":false},{"year":2020,"finding":"A nonsense mutation in ZP1 (p.Q257*) produces a mutant protein that fails to interact with either ZP2 or ZP3, as demonstrated by co-immunoprecipitation assay.","method":"In vitro co-immunoprecipitation assay with mutant ZP1 and wild-type ZP2/ZP3","journal":"Molecular genetics & genomic medicine","confidence":"Medium","confidence_rationale":"Tier 2-3 — direct binding assay, single study, single method","pmids":["32329253"],"is_preprint":false},{"year":2021,"finding":"A mutant Zp1 (point mutation) in rats produces a truncated ZP1 protein that is intracellularly sequestered and interacts with wild-type ZP3 and ZP4, preventing their incorporation into the zona pellucida and causing zona absence and female infertility.","method":"Rat knock-in model; expression studies in 293T cells; co-immunoprecipitation; immunofluorescence; superovulation and fertilization assays","journal":"Biology of reproduction","confidence":"High","confidence_rationale":"Tier 1-2 — in vivo rat model combined with in vitro mechanistic experiments (co-IP, cell expression), multiple orthogonal methods","pmids":["33624742"],"is_preprint":false},{"year":2020,"finding":"A missense mutation c.2T>A (p.M1K) in ZP1 results in near-complete loss of protein production; a splice site mutation c.1112+1G>T causes truncation of ZP1 protein as shown by minigene assay.","method":"Western blotting; immunofluorescence staining; minigene assay in transfected cells","journal":"Journal of assisted reproduction and genetics","confidence":"Medium","confidence_rationale":"Tier 2 — multiple orthogonal methods (Western blot, IF, minigene), single lab","pmids":["32556881"],"is_preprint":false},{"year":2020,"finding":"A homozygous splice site mutation in ZP1 (c.1775-3C>A) causes intron 11 retention between exon 11 and exon 12, resulting in a frameshift and likely truncated protein, as demonstrated by minigene experiments.","method":"Minigene splicing assay; whole exome sequencing; Sanger sequencing","journal":"Genes","confidence":"Medium","confidence_rationale":"Tier 2 — direct functional splicing assay confirms molecular mechanism, single lab","pmids":["32244758"],"is_preprint":false},{"year":2021,"finding":"A mutant truncated ZP1 protein (Y420X) localizes to cytoplasm similarly to wild-type, indicating that the truncating mutation does not alter subcellular localization of ZP1.","method":"Western blot; subcellular localization by immunofluorescence in transfected cells","journal":"Reproductive sciences (Thousand Oaks, Calif.)","confidence":"Low","confidence_rationale":"Tier 3 — single method per parameter, single lab","pmids":["35773450"],"is_preprint":false},{"year":2024,"finding":"A homozygous missense ZP1 mutation (p.Arg366Trp) impairs ZP1 protein secretion and weakens interactions between ZP1 and other ZP proteins, affecting zona pellucida assembly.","method":"Immunostaining; immunoblotting; co-immunoprecipitation; molecular dynamics simulation in transfected cells","journal":"Clinical genetics","confidence":"Medium","confidence_rationale":"Tier 2-3 — multiple methods including co-IP and structural modeling, single lab","pmids":["39380244"],"is_preprint":false},{"year":2025,"finding":"ZP1 compound heterozygous mutations (p.[Met1?];[Gly477*]) reduce ZP1 protein expression and inhibit ZP1 secretion, and alter the interaction between ZP1 and ZP2, without affecting subcellular localization.","method":"Western blotting; immunofluorescence; ELISA; co-immunoprecipitation in transfected cells","journal":"Journal of ovarian research","confidence":"Medium","confidence_rationale":"Tier 2-3 — multiple functional assays, single lab","pmids":["40287760"],"is_preprint":false},{"year":2025,"finding":"CRISPR/Cas9 knockout of ZP1 in cynomolgus macaques causes zona pellucida-deficient oocytes, reduced oocyte maturation rates, disrupted folliculogenesis, and phenotypes consistent with human empty follicle syndrome, establishing ZP1's role in primate ZP assembly and folliculogenesis.","method":"CRISPR/Cas9 genome editing in non-human primates; immunofluorescence staining; transmission electron microscopy; transcriptomic profiling; histopathology","journal":"Zoological research","confidence":"High","confidence_rationale":"Tier 1-2 — non-human primate KO model with multiple orthogonal analyses, directly relevant to human ZP1 function","pmids":["40923306"],"is_preprint":false},{"year":2013,"finding":"Two peptides from the ZP1-N domain of human ZP1 self-assemble into amyloid-like fibrils, suggesting the ZP-N domain drives ZP protein polymerization through an amyloid-like mechanism contributing to zona pellucida matrix formation.","method":"Transmission electron microscopy; X-ray diffraction; Congo red staining; ATR FT-IR spectroscopy of synthetic peptides","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 1 — multiple biophysical methods on synthetic peptides, single lab; functional implication inferred","pmids":["24069181"],"is_preprint":false},{"year":2018,"finding":"ZP1 ubiquitination in porcine oocytes is regulated by PSMD4; inhibition of PSMD4 significantly decreases ZP1 ubiquitination and reduces sperm-oocyte binding capacity.","method":"Antibody-mediated inhibition of PSMD4 in porcine oocytes; Western blotting for ubiquitination; sperm binding assay","journal":"Reproduction in domestic animals","confidence":"Medium","confidence_rationale":"Tier 2-3 — direct functional link between ZP1 ubiquitination state and sperm binding, single lab","pmids":["29575084"],"is_preprint":false},{"year":1996,"finding":"Recombinant pig ZP1 binds to acrosome-reacted spermatozoa (but not acrosome-intact), acting as a secondary sperm-binding receptor; binding site localizes to equatorial/midpiece/tail regions and ZP1 binds proacrosin (55 kDa) and a 40 kDa sperm protein.","method":"Immunofluorescence binding assay; immunoblotting with recombinant pZP1 and boar sperm extracts","journal":"Journal of reproduction and fertility. Supplement","confidence":"Medium","confidence_rationale":"Tier 2-3 — direct binding assay with specific sperm protein identification, single lab","pmids":["8984189"],"is_preprint":false}],"current_model":"ZP1 is a zona pellucida glycoprotein that functions as a homodimeric crosslinker of the extracellular zona matrix; it is synthesized and secreted by oocytes via Golgi and vesicular trafficking, where it is required for structural integrity of the zona by crosslinking ZP2/ZP3 filaments, and interacts directly with ZP2, ZP3 (and ZP4 in four-ZP species) such that loss-of-function mutations cause intracellular sequestration of ZP3, failure of zona assembly, oocyte degeneration, and female infertility (empty follicle syndrome)."},"narrative":{"teleology":[{"year":1996,"claim":"Before ZP1's structural role was established, recombinant porcine ZP1 was shown to function as a secondary sperm receptor that binds acrosome-reacted spermatozoa and proacrosin, indicating ZP1 participates directly in gamete recognition beyond matrix formation.","evidence":"Immunofluorescence binding assay and immunoblotting with recombinant pZP1 and boar sperm extracts","pmids":["8984189"],"confidence":"Medium","gaps":["Binding was demonstrated only in pig; relevance to human or mouse ZP1 not tested","Identity of the 40 kDa sperm binding partner unresolved","No in vivo validation of secondary receptor function"]},{"year":1999,"claim":"Mouse Zp1 knockout established that ZP1 is required for structural integrity of the zona pellucida — without it, a zona still forms from ZP2/ZP3 but is loosely organized — resolving the question of whether ZP1 is a structural crosslinker versus an essential assembly factor.","evidence":"Targeted Zp1 gene knockout in mice with histological, hormonal, and mating analyses","pmids":["10433913","10526650"],"confidence":"High","gaps":["Molecular mechanism of crosslinking (disulfide topology) not resolved at atomic level","Whether ZP1 loss affects sperm binding independently of zona loosening was uncertain"]},{"year":2002,"claim":"Immunoelectron microscopy resolved that ZP1 is synthesized exclusively by oocytes and traffics through the Golgi and vesicular aggregates before secretion, establishing the biosynthetic pathway and ruling out granulosa cell contribution.","evidence":"Protein A-gold immunoelectron microscopy with double/triple immunolocalization in mouse ovarian follicles","pmids":["11906903"],"confidence":"High","gaps":["Signals controlling ZP1 sorting from Golgi to secretory vesicles not identified","Asymmetric distribution of ZP proteins in the matrix mechanistically unexplained"]},{"year":2004,"claim":"Co-expression studies demonstrated that ZP1 secretion requires co-expression with ZP2 and ZP3, establishing that ZP protein hetero-interactions are prerequisite for secretion rather than just extracellular assembly.","evidence":"Co-expression of recombinant human ZP proteins in HEK 293T cells with Western blotting of medium and lysate","pmids":["15064827"],"confidence":"Medium","gaps":["Which domain of ZP1 mediates the co-secretion interaction was not mapped","Whether ZP1 secretion also requires ZP4 in human oocytes was not tested"]},{"year":2013,"claim":"Biophysical characterization of ZP1-N domain peptides revealed amyloid-like fibril self-assembly, suggesting a polymerization mechanism for zona matrix formation beyond simple disulfide crosslinking.","evidence":"TEM, X-ray diffraction, Congo red staining, and ATR FT-IR spectroscopy of synthetic ZP1-N peptides","pmids":["24069181"],"confidence":"Medium","gaps":["Whether amyloid-like assembly occurs in vivo within the zona is unresolved","Contribution of amyloid-like polymerization relative to disulfide crosslinking not quantified","Only two short peptides tested — full ZP-N domain behavior unknown"]},{"year":2014,"claim":"A human homozygous frameshift ZP1 mutation was shown to cause intracellular sequestration of ZP3 by defective ZP1, directly linking ZP1 loss-of-function to human infertility through a dominant-negative intracellular trapping mechanism.","evidence":"Whole-exome sequencing of infertile pedigree combined with co-localization studies in transfected cells","pmids":["24670168"],"confidence":"High","gaps":["Whether heterozygous carriers have subclinical zona thinning was not assessed","Rescue experiment restoring ZP1 was not performed"]},{"year":2018,"claim":"ZP1 ubiquitination by the proteasome pathway was linked to sperm-binding competence, revealing a post-translational regulatory layer on zona function beyond assembly.","evidence":"PSMD4 antibody-mediated inhibition in porcine oocytes with ubiquitination Western blotting and sperm binding assay","pmids":["29575084"],"confidence":"Medium","gaps":["Direct E3 ligase responsible for ZP1 ubiquitination not identified","Whether ubiquitination modifies ZP1 surface exposure versus degradation unclear","Only shown in porcine system"]},{"year":2019,"claim":"Multiple human ZP1 mutation studies converged to show that pathogenic variants disrupt ZP1–ZP2 and ZP1–ZP3 interactions as assessed by co-immunoprecipitation, establishing interaction loss as the common molecular defect underlying zona absence and empty follicle syndrome.","evidence":"Co-immunoprecipitation, Western blotting, and homology modeling of wild-type and mutant ZP proteins in CHO/CHO-K1 cells across multiple patient cohorts","pmids":["31292994","30810869","31734689"],"confidence":"Medium","gaps":["Binding interfaces between ZP1 and ZP2/ZP3 not structurally resolved","Genotype-phenotype correlation across different mutation types not systematically established"]},{"year":2021,"claim":"A rat knock-in model demonstrated that a truncated ZP1 acts as a dominant-negative by binding and sequestering ZP3 and ZP4 intracellularly, extending the intracellular trapping mechanism from in vitro systems to an in vivo mammalian model.","evidence":"Rat Zp1 knock-in mutant with co-IP, immunofluorescence, and superovulation/fertilization assays","pmids":["33624742"],"confidence":"High","gaps":["Whether ZP4 sequestration contributes to human pathology (humans express ZP4) not confirmed","Threshold level of ZP1 needed for functional zona not determined"]},{"year":2025,"claim":"CRISPR knockout of ZP1 in cynomolgus macaques confirmed that ZP1 is essential for zona pellucida assembly and normal folliculogenesis in primates, validating the translational relevance of rodent findings to the human four-ZP-protein system.","evidence":"CRISPR/Cas9 knockout in non-human primates with immunofluorescence, TEM, transcriptomics, and histopathology","pmids":["40923306"],"confidence":"High","gaps":["Downstream transcriptomic changes not mechanistically dissected","Whether ZP1-null primate oocytes can be rescued by exogenous ZP1 is untested"]},{"year":null,"claim":"The atomic-resolution structure of ZP1 homodimer and its interfaces with ZP2/ZP3 filaments remain unresolved, leaving the precise mechanism of crosslink formation and the determinants of species-specific zona architecture unknown.","evidence":"","pmids":[],"confidence":"High","gaps":["No crystal or cryo-EM structure of ZP1 homodimer or ZP1-ZP2/ZP3 complex","Disulfide bond topology of the crosslink not mapped","Molecular basis of species differences in ZP composition (3 vs 4 ZP proteins) not mechanistically explained"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[0,1,15]}],"localization":[{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[0,2]},{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[2]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[2]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[3,9]}],"pathway":[{"term_id":"R-HSA-1474165","term_label":"Reproduction","supporting_discovery_ids":[0,15]},{"term_id":"R-HSA-1474244","term_label":"Extracellular matrix organization","supporting_discovery_ids":[0,1,15]}],"complexes":["Zona pellucida matrix (ZP1/ZP2/ZP3 polymer)"],"partners":["ZP2","ZP3","ZP4"],"other_free_text":[]},"mechanistic_narrative":"ZP1 is a zona pellucida glycoprotein that serves as the structural crosslinker of the extracellular zona matrix surrounding mammalian oocytes, essential for female fertility. ZP1 forms disulfide-bonded homodimers that crosslink ZP2/ZP3 filaments; loss of ZP1 results in a loosely organized zona, defective cumulus-oocyte complex formation, and empty follicle syndrome in both rodent and primate models [PMID:10433913, PMID:40923306]. ZP1 is synthesized exclusively by oocytes and traffics through the Golgi apparatus and vesicular intermediates before secretion, a process that depends on co-expression with ZP2 and ZP3, since mutant ZP1 proteins sequester ZP3 (and ZP4 in non-murine species) intracellularly and block zona assembly [PMID:11906903, PMID:24670168, PMID:33624742]. Homozygous or compound heterozygous loss-of-function mutations in human ZP1 cause zona pellucida deficiency and female infertility presenting as empty follicle syndrome [PMID:24670168, PMID:31734689]."},"prefetch_data":{"uniprot":{"accession":"P60852","full_name":"Zona pellucida sperm-binding protein 1","aliases":["Zona pellucida glycoprotein 1","Zp-1"],"length_aa":638,"mass_kda":70.0,"function":"Component of the zona pellucida, an extracellular matrix surrounding oocytes which mediates sperm binding, induction of the acrosome reaction and prevents post-fertilization polyspermy. The zona pellucida is composed of 3 to 4 glycoproteins, ZP1, ZP2, ZP3, and ZP4. ZP1 ensures the structural integrity of the zona pellucida","subcellular_location":"Cell membrane","url":"https://www.uniprot.org/uniprotkb/P60852/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/ZP1","classification":"Not Classified","n_dependent_lines":2,"n_total_lines":1208,"dependency_fraction":0.0016556291390728477},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/ZP1","total_profiled":1310},"omim":[{"mim_id":"618353","title":"OOCYTE/ZYGOTE/EMBRYO MATURATION ARREST 6; OZEMA6","url":"https://www.omim.org/entry/618353"},{"mim_id":"617712","title":"OOCYTE/ZYGOTE/EMBRYO MATURATION ARREST 3; OZEMA3","url":"https://www.omim.org/entry/617712"},{"mim_id":"615915","title":"ZONA PELLUCIDA-LIKE DOMAIN-CONTAINING PROTEIN 1; ZPLD1","url":"https://www.omim.org/entry/615915"},{"mim_id":"615774","title":"OOCYTE/ZYGOTE/EMBRYO MATURATION ARREST 1; OZEMA1","url":"https://www.omim.org/entry/615774"},{"mim_id":"195000","title":"ZONA PELLUCIDA GLYCOPROTEIN 1; ZP1","url":"https://www.omim.org/entry/195000"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Not detected","tissue_distribution":"Not detected","driving_tissues":[],"url":"https://www.proteinatlas.org/search/ZP1"},"hgnc":{"alias_symbol":["ZPB1"],"prev_symbol":[]},"alphafold":{"accession":"P60852","domains":[{"cath_id":"2.60.40","chopping":"38-134","consensus_level":"high","plddt":87.4974,"start":38,"end":134},{"cath_id":"2.60.40.3210","chopping":"232-355_368-380","consensus_level":"high","plddt":87.4399,"start":232,"end":380},{"cath_id":"2.60.40.4100","chopping":"406-537_567-578","consensus_level":"high","plddt":90.0059,"start":406,"end":578}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P60852","model_url":"https://alphafold.ebi.ac.uk/files/AF-P60852-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P60852-F1-predicted_aligned_error_v6.png","plddt_mean":72.94},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=ZP1","jax_strain_url":"https://www.jax.org/strain/search?query=ZP1"},"sequence":{"accession":"P60852","fasta_url":"https://rest.uniprot.org/uniprotkb/P60852.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P60852/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P60852"}},"corpus_meta":[{"pmid":"10433913","id":"PMC_10433913","title":"Abnormal zonae pellucidae in mice lacking ZP1 result in early embryonic loss.","date":"1999","source":"Development (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/10433913","citation_count":227,"is_preprint":false},{"pmid":"24670168","id":"PMC_24670168","title":"Mutant ZP1 in familial infertility.","date":"2014","source":"The New England journal of medicine","url":"https://pubmed.ncbi.nlm.nih.gov/24670168","citation_count":115,"is_preprint":false},{"pmid":"10979984","id":"PMC_10979984","title":"The major chicken egg envelope protein ZP1 is different from ZPB and is synthesized in the liver.","date":"2000","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/10979984","citation_count":102,"is_preprint":false},{"pmid":"30810869","id":"PMC_30810869","title":"Novel mutations in ZP1, ZP2, and ZP3 cause female infertility due to abnormal zona pellucida formation.","date":"2019","source":"Human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/30810869","citation_count":97,"is_preprint":false},{"pmid":"10542331","id":"PMC_10542331","title":"Identification of the true human orthologue of the mouse Zp1 gene: evidence for greater complexity in the mammalian zona pellucida?","date":"1999","source":"Biochimica et biophysica acta","url":"https://pubmed.ncbi.nlm.nih.gov/10542331","citation_count":91,"is_preprint":false},{"pmid":"7592984","id":"PMC_7592984","title":"Mouse Zp1 encodes a zona pellucida protein homologous to egg envelope proteins in mammals and fish.","date":"1995","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/7592984","citation_count":77,"is_preprint":false},{"pmid":"15264999","id":"PMC_15264999","title":"A newly identified zona pellucida glycoprotein, ZPD, and dimeric ZP1 of chicken egg envelope are involved in sperm activation on sperm-egg interaction.","date":"2004","source":"The Biochemical journal","url":"https://pubmed.ncbi.nlm.nih.gov/15264999","citation_count":66,"is_preprint":false},{"pmid":"32573113","id":"PMC_32573113","title":"Heterozygous mutations in ZP1 and ZP3 cause formation disorder of ZP and female infertility in human.","date":"2020","source":"Journal of cellular and molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/32573113","citation_count":49,"is_preprint":false},{"pmid":"31292994","id":"PMC_31292994","title":"Compound heterozygous ZP1 mutations cause empty follicle syndrome in infertile sisters.","date":"2019","source":"Human mutation","url":"https://pubmed.ncbi.nlm.nih.gov/31292994","citation_count":45,"is_preprint":false},{"pmid":"12968942","id":"PMC_12968942","title":"Analysis of fish ZP1/ZPB homologous genes--evidence for both genome duplication and species-specific amplification models of evolution.","date":"2003","source":"Reproduction (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/12968942","citation_count":45,"is_preprint":false},{"pmid":"31734689","id":"PMC_31734689","title":"ZP1 mutations are associated with empty follicle syndrome: evidence for the existence of an intact oocyte and a zona pellucida in follicles up to the early antral stage. A case report.","date":"2019","source":"Human reproduction (Oxford, England)","url":"https://pubmed.ncbi.nlm.nih.gov/31734689","citation_count":44,"is_preprint":false},{"pmid":"17850962","id":"PMC_17850962","title":"Isolation and characterization of phenanthrene-degrading strains Sphingomonas sp. ZP1 and Tistrella sp. ZP5.","date":"2007","source":"Journal of hazardous materials","url":"https://pubmed.ncbi.nlm.nih.gov/17850962","citation_count":43,"is_preprint":false},{"pmid":"15064827","id":"PMC_15064827","title":"Recombinant human zona pellucida proteins ZP1, ZP2 and ZP3 co-expressed in a human cell line.","date":"2004","source":"Asian journal of andrology","url":"https://pubmed.ncbi.nlm.nih.gov/15064827","citation_count":42,"is_preprint":false},{"pmid":"12648530","id":"PMC_12648530","title":"Expression of perivitelline membrane glycoprotein ZP1 in the liver of Japanese quail (Coturnix japonica) after in vivo treatment with diethylstilbestrol.","date":"2003","source":"The Journal of steroid biochemistry and molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/12648530","citation_count":36,"is_preprint":false},{"pmid":"11906903","id":"PMC_11906903","title":"Subcellular distribution of ZP1, ZP2, and ZP3 glycoproteins during folliculogenesis and demonstration of their topographical disposition within the zona matrix of mouse ovarian oocytes.","date":"2002","source":"Biology of reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/11906903","citation_count":35,"is_preprint":false},{"pmid":"30778819","id":"PMC_30778819","title":"Novel mutation in the ZP1 gene and clinical implications.","date":"2019","source":"Journal of assisted reproduction and genetics","url":"https://pubmed.ncbi.nlm.nih.gov/30778819","citation_count":35,"is_preprint":false},{"pmid":"7864874","id":"PMC_7864874","title":"Cloning of a cDNA coding for porcine zona pellucida glycoprotein ZP1 and its genomic organization.","date":"1995","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/7864874","citation_count":34,"is_preprint":false},{"pmid":"32829425","id":"PMC_32829425","title":"Novel mutations in ZP1 and ZP2 cause primary infertility due to empty follicle syndrome and abnormal zona pellucida.","date":"2020","source":"Journal of assisted reproduction and genetics","url":"https://pubmed.ncbi.nlm.nih.gov/32829425","citation_count":32,"is_preprint":false},{"pmid":"32329253","id":"PMC_32329253","title":"A novel homozygous nonsense ZP1 variant causes human female infertility associated with empty follicle syndrome (EFS).","date":"2020","source":"Molecular genetics & genomic medicine","url":"https://pubmed.ncbi.nlm.nih.gov/32329253","citation_count":31,"is_preprint":false},{"pmid":"24069181","id":"PMC_24069181","title":"Structural analysis of peptide-analogues of human Zona Pellucida ZP1 protein with amyloidogenic properties: insights into mammalian Zona Pellucida formation.","date":"2013","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/24069181","citation_count":30,"is_preprint":false},{"pmid":"9282987","id":"PMC_9282987","title":"Sequence of complementary deoxyribonucleic acid encoding bonnet monkey (Macaca radiata) zona pellucida glycoprotein-ZP1 and its high-level expression in Escherichia 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with empty follicle syndrome in infertile women.","date":"2021","source":"Clinical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/33423275","citation_count":11,"is_preprint":false},{"pmid":"10526650","id":"PMC_10526650","title":"The zona pellucida 'receptors' ZP1, ZP2 and ZP3.","date":"1999","source":"Andrologia","url":"https://pubmed.ncbi.nlm.nih.gov/10526650","citation_count":11,"is_preprint":false},{"pmid":"36529558","id":"PMC_36529558","title":"A ZP1 gene mutation in a patient with empty follicle syndrome: A case report and literature review.","date":"2022","source":"European journal of obstetrics, gynecology, and reproductive biology","url":"https://pubmed.ncbi.nlm.nih.gov/36529558","citation_count":11,"is_preprint":false},{"pmid":"30611916","id":"PMC_30611916","title":"Mutation analysis of ZP1, ZP2, ZP3 and ZP4 genes in 152 Han Chinese samples with ovarian endometriosis.","date":"2018","source":"Mutation 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Toxicology & pharmacology : CBP","url":"https://pubmed.ncbi.nlm.nih.gov/17188579","citation_count":9,"is_preprint":false},{"pmid":"22439578","id":"PMC_22439578","title":"Isolation and characterization of catechol 2,3-dioxygenase genes from phenanthrene degraders Sphingomonas, sp. ZP1 and Pseudomonas sp. ZP2.","date":"2011","source":"Environmental technology","url":"https://pubmed.ncbi.nlm.nih.gov/22439578","citation_count":9,"is_preprint":false},{"pmid":"10569978","id":"PMC_10569978","title":"Mapping of dominant B-cell epitopes of a human zona pellucida protein (ZP1).","date":"1999","source":"Biology of reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/10569978","citation_count":8,"is_preprint":false},{"pmid":"28679462","id":"PMC_28679462","title":"Analysis of ZP1 gene reveals differences in zona pellucida composition in carnivores.","date":"2018","source":"Reproduction, fertility, and development","url":"https://pubmed.ncbi.nlm.nih.gov/28679462","citation_count":7,"is_preprint":false},{"pmid":"29575084","id":"PMC_29575084","title":"Inhibition of PSMD4 alters ZP1 ubiquitination state and sperm-oocyte-binding ability in pigs.","date":"2018","source":"Reproduction in domestic animals = Zuchthygiene","url":"https://pubmed.ncbi.nlm.nih.gov/29575084","citation_count":7,"is_preprint":false},{"pmid":"32908412","id":"PMC_32908412","title":"Egg Envelope Glycoproteins ZP1 and ZP3 Mediate Sperm-Egg Interaction in the Japanese Quail.","date":"2017","source":"The journal of poultry science","url":"https://pubmed.ncbi.nlm.nih.gov/32908412","citation_count":7,"is_preprint":false},{"pmid":"8984189","id":"PMC_8984189","title":"Binding of recombinant pig zona pellucida protein 1 (ZP1) to acrosome-reacted spermatozoa.","date":"1996","source":"Journal of reproduction and fertility. Supplement","url":"https://pubmed.ncbi.nlm.nih.gov/8984189","citation_count":7,"is_preprint":false},{"pmid":"35773450","id":"PMC_35773450","title":"A Novel Homozygous Nonsense Mutation in ZP1 Causes Female Infertility due to Empty Follicle Syndrome.","date":"2022","source":"Reproductive sciences (Thousand Oaks, Calif.)","url":"https://pubmed.ncbi.nlm.nih.gov/35773450","citation_count":6,"is_preprint":false},{"pmid":"40148979","id":"PMC_40148979","title":"Elevated accumulation of lutein and zeaxanthin in a novel high-biomass yielding strain Dunaliella sp. ZP-1 obtained through EMS mutagenesis.","date":"2025","source":"Biotechnology for biofuels and bioproducts","url":"https://pubmed.ncbi.nlm.nih.gov/40148979","citation_count":5,"is_preprint":false},{"pmid":"10497063","id":"PMC_10497063","title":"Expression of a recombinant porcine zona pellucida glycoprotein ZP1 in mammalian cells.","date":"1999","source":"Protein expression and purification","url":"https://pubmed.ncbi.nlm.nih.gov/10497063","citation_count":5,"is_preprint":false},{"pmid":"32619266","id":"PMC_32619266","title":"[Loss of zona pellucida in oocytes due to compound heterozygous variants of ZP1 gene].","date":"2020","source":"Zhonghua yi xue yi chuan xue za zhi = Zhonghua yixue yichuanxue zazhi = Chinese journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/32619266","citation_count":5,"is_preprint":false},{"pmid":"38966008","id":"PMC_38966008","title":"ZP1-Y262C mutation causes abnormal zona pellucida formation and female infertility in humans.","date":"2024","source":"Frontiers in genetics","url":"https://pubmed.ncbi.nlm.nih.gov/38966008","citation_count":4,"is_preprint":false},{"pmid":"39380244","id":"PMC_39380244","title":"A Novel Homozygous Missense ZP1 Variant Result in Human Female Empty Follicle Syndrome.","date":"2024","source":"Clinical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/39380244","citation_count":4,"is_preprint":false},{"pmid":"21689136","id":"PMC_21689136","title":"Quantification of ZP1, ZP2 and ZP3 mRNA of marmoset monkey (Callithrix jacchus) oocytes from periantral and antral follicles.","date":"2011","source":"Andrologia","url":"https://pubmed.ncbi.nlm.nih.gov/21689136","citation_count":3,"is_preprint":false},{"pmid":"40287760","id":"PMC_40287760","title":"A compound heterozygous mutation in ZP1 and two novel heterozygous cis mutations in ZP3 causes infertility in women presenting with empty follicle syndrome.","date":"2025","source":"Journal of ovarian research","url":"https://pubmed.ncbi.nlm.nih.gov/40287760","citation_count":2,"is_preprint":false},{"pmid":"8984183","id":"PMC_8984183","title":"Genomic organization of the gene for pig zona pellucida glycoprotein ZP1 and its expression in mammalian cells.","date":"1996","source":"Journal of reproduction and fertility. 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mice lacking ZP1 form a zona composed only of ZP2 and ZP3 that is more loosely organized, leading to ectopic granulosa cell clusters, precocious hatching, and reduced fecundity, though ZP1 is not essential for sperm binding or fertilization per se.\",\n      \"method\": \"Targeted gene knockout in mice (Zp1(tm/tm)), histology, hormonal stimulation, mating experiments\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — clean KO with defined structural and reproductive phenotypes, replicated across multiple experimental approaches\",\n      \"pmids\": [\"10433913\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"ZP1 functions as a homodimeric filament crosslinker in the zona pellucida matrix, held together by intermolecular disulfide bonds.\",\n      \"method\": \"Biochemical characterization of native ZP protein complexes\",\n      \"journal\": \"Andrologia\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — single review-type paper citing established biochemical characterization, no new primary experiment described\",\n      \"pmids\": [\"10526650\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"ZP1 is synthesized and secreted exclusively by oocytes (not granulosa cells) and traffics through the Golgi apparatus and vesicular aggregates before being secreted into the zona matrix, where it distributes asymmetrically with ZP2 and ZP3 in discrete patches.\",\n      \"method\": \"Immunoelectron microscopy with protein A-gold technique; double and triple immunolocalization in mouse ovarian follicles\",\n      \"journal\": \"Biology of reproduction\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct subcellular localization by immunoelectron microscopy with functional interpretation, multiple antibody controls\",\n      \"pmids\": [\"11906903\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"A homozygous frameshift mutation in ZP1 causes defective ZP1 protein to colocalize with and sequester ZP3 in the cytoplasm, preventing ZP3 secretion and zona pellucida formation around the oocyte.\",\n      \"method\": \"In vitro colocalization studies in transfected cells; identification of mutation by sequencing in human infertility pedigree\",\n      \"journal\": \"The New England journal of medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — human genetics combined with in vitro cellular mechanistic experiment, high-impact journal with strong evidence\",\n      \"pmids\": [\"24670168\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Recombinant human ZP1 is retained intracellularly when expressed alone, but is secreted into culture medium when co-expressed with ZP2 and ZP3, indicating that interaction among ZP proteins is required for ZP1 release/secretion.\",\n      \"method\": \"Co-expression in HEK 293T cells; Western blotting of culture medium and cell lysate\",\n      \"journal\": \"Asian journal of andrology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct secretion assay with multiple ZP protein combinations, single lab\",\n      \"pmids\": [\"15064827\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Mutations in ZP1 disrupt the interaction among ZP1, ZP2, and ZP3, impairing zona pellucida assembly; co-immunoprecipitation confirmed that mutant ZP1 fails to properly interact with ZP2 and ZP3.\",\n      \"method\": \"Co-immunoprecipitation; homology modeling; CHO cell expression of wild-type and mutant ZP proteins\",\n      \"journal\": \"Human mutation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — co-IP and modeling in single study, consistent with human genetic data\",\n      \"pmids\": [\"31292994\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Mutations in ZP1 affect ZP1 protein expression, secretion, and interaction with other ZP proteins (ZP2, ZP3), providing a mechanistic basis for zona pellucida formation defects and female infertility.\",\n      \"method\": \"Expression studies in CHO cells; Western blotting; interaction assays\",\n      \"journal\": \"Human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — in vitro expression and interaction data, multiple mutations tested, single lab\",\n      \"pmids\": [\"30810869\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"ZP1 mutations result in either degradation or truncation of the ZP1 protein in CHO-K1 cells, and histological analysis of ovarian sections showed absent ZP1 in the zona of growing oocytes, with consequent defective cumulus-oocyte complex organization leading to empty follicle syndrome.\",\n      \"method\": \"Expression studies in CHO-K1 cells; immunohistochemistry of ovarian serial sections; Western blotting\",\n      \"journal\": \"Human reproduction (Oxford, England)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — combination of cell expression and histological evidence, single lab\",\n      \"pmids\": [\"31734689\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"A nonsense mutation in ZP1 (p.Q257*) produces a mutant protein that fails to interact with either ZP2 or ZP3, as demonstrated by co-immunoprecipitation assay.\",\n      \"method\": \"In vitro co-immunoprecipitation assay with mutant ZP1 and wild-type ZP2/ZP3\",\n      \"journal\": \"Molecular genetics & genomic medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — direct binding assay, single study, single method\",\n      \"pmids\": [\"32329253\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"A mutant Zp1 (point mutation) in rats produces a truncated ZP1 protein that is intracellularly sequestered and interacts with wild-type ZP3 and ZP4, preventing their incorporation into the zona pellucida and causing zona absence and female infertility.\",\n      \"method\": \"Rat knock-in model; expression studies in 293T cells; co-immunoprecipitation; immunofluorescence; superovulation and fertilization assays\",\n      \"journal\": \"Biology of reproduction\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vivo rat model combined with in vitro mechanistic experiments (co-IP, cell expression), multiple orthogonal methods\",\n      \"pmids\": [\"33624742\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"A missense mutation c.2T>A (p.M1K) in ZP1 results in near-complete loss of protein production; a splice site mutation c.1112+1G>T causes truncation of ZP1 protein as shown by minigene assay.\",\n      \"method\": \"Western blotting; immunofluorescence staining; minigene assay in transfected cells\",\n      \"journal\": \"Journal of assisted reproduction and genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (Western blot, IF, minigene), single lab\",\n      \"pmids\": [\"32556881\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"A homozygous splice site mutation in ZP1 (c.1775-3C>A) causes intron 11 retention between exon 11 and exon 12, resulting in a frameshift and likely truncated protein, as demonstrated by minigene experiments.\",\n      \"method\": \"Minigene splicing assay; whole exome sequencing; Sanger sequencing\",\n      \"journal\": \"Genes\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct functional splicing assay confirms molecular mechanism, single lab\",\n      \"pmids\": [\"32244758\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"A mutant truncated ZP1 protein (Y420X) localizes to cytoplasm similarly to wild-type, indicating that the truncating mutation does not alter subcellular localization of ZP1.\",\n      \"method\": \"Western blot; subcellular localization by immunofluorescence in transfected cells\",\n      \"journal\": \"Reproductive sciences (Thousand Oaks, Calif.)\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single method per parameter, single lab\",\n      \"pmids\": [\"35773450\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"A homozygous missense ZP1 mutation (p.Arg366Trp) impairs ZP1 protein secretion and weakens interactions between ZP1 and other ZP proteins, affecting zona pellucida assembly.\",\n      \"method\": \"Immunostaining; immunoblotting; co-immunoprecipitation; molecular dynamics simulation in transfected cells\",\n      \"journal\": \"Clinical genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — multiple methods including co-IP and structural modeling, single lab\",\n      \"pmids\": [\"39380244\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"ZP1 compound heterozygous mutations (p.[Met1?];[Gly477*]) reduce ZP1 protein expression and inhibit ZP1 secretion, and alter the interaction between ZP1 and ZP2, without affecting subcellular localization.\",\n      \"method\": \"Western blotting; immunofluorescence; ELISA; co-immunoprecipitation in transfected cells\",\n      \"journal\": \"Journal of ovarian research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — multiple functional assays, single lab\",\n      \"pmids\": [\"40287760\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"CRISPR/Cas9 knockout of ZP1 in cynomolgus macaques causes zona pellucida-deficient oocytes, reduced oocyte maturation rates, disrupted folliculogenesis, and phenotypes consistent with human empty follicle syndrome, establishing ZP1's role in primate ZP assembly and folliculogenesis.\",\n      \"method\": \"CRISPR/Cas9 genome editing in non-human primates; immunofluorescence staining; transmission electron microscopy; transcriptomic profiling; histopathology\",\n      \"journal\": \"Zoological research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — non-human primate KO model with multiple orthogonal analyses, directly relevant to human ZP1 function\",\n      \"pmids\": [\"40923306\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Two peptides from the ZP1-N domain of human ZP1 self-assemble into amyloid-like fibrils, suggesting the ZP-N domain drives ZP protein polymerization through an amyloid-like mechanism contributing to zona pellucida matrix formation.\",\n      \"method\": \"Transmission electron microscopy; X-ray diffraction; Congo red staining; ATR FT-IR spectroscopy of synthetic peptides\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 — multiple biophysical methods on synthetic peptides, single lab; functional implication inferred\",\n      \"pmids\": [\"24069181\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"ZP1 ubiquitination in porcine oocytes is regulated by PSMD4; inhibition of PSMD4 significantly decreases ZP1 ubiquitination and reduces sperm-oocyte binding capacity.\",\n      \"method\": \"Antibody-mediated inhibition of PSMD4 in porcine oocytes; Western blotting for ubiquitination; sperm binding assay\",\n      \"journal\": \"Reproduction in domestic animals\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — direct functional link between ZP1 ubiquitination state and sperm binding, single lab\",\n      \"pmids\": [\"29575084\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"Recombinant pig ZP1 binds to acrosome-reacted spermatozoa (but not acrosome-intact), acting as a secondary sperm-binding receptor; binding site localizes to equatorial/midpiece/tail regions and ZP1 binds proacrosin (55 kDa) and a 40 kDa sperm protein.\",\n      \"method\": \"Immunofluorescence binding assay; immunoblotting with recombinant pZP1 and boar sperm extracts\",\n      \"journal\": \"Journal of reproduction and fertility. Supplement\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — direct binding assay with specific sperm protein identification, single lab\",\n      \"pmids\": [\"8984189\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"ZP1 is a zona pellucida glycoprotein that functions as a homodimeric crosslinker of the extracellular zona matrix; it is synthesized and secreted by oocytes via Golgi and vesicular trafficking, where it is required for structural integrity of the zona by crosslinking ZP2/ZP3 filaments, and interacts directly with ZP2, ZP3 (and ZP4 in four-ZP species) such that loss-of-function mutations cause intracellular sequestration of ZP3, failure of zona assembly, oocyte degeneration, and female infertility (empty follicle syndrome).\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"ZP1 is a zona pellucida glycoprotein that serves as the structural crosslinker of the extracellular zona matrix surrounding mammalian oocytes, essential for female fertility. ZP1 forms disulfide-bonded homodimers that crosslink ZP2/ZP3 filaments; loss of ZP1 results in a loosely organized zona, defective cumulus-oocyte complex formation, and empty follicle syndrome in both rodent and primate models [PMID:10433913, PMID:40923306]. ZP1 is synthesized exclusively by oocytes and traffics through the Golgi apparatus and vesicular intermediates before secretion, a process that depends on co-expression with ZP2 and ZP3, since mutant ZP1 proteins sequester ZP3 (and ZP4 in non-murine species) intracellularly and block zona assembly [PMID:11906903, PMID:24670168, PMID:33624742]. Homozygous or compound heterozygous loss-of-function mutations in human ZP1 cause zona pellucida deficiency and female infertility presenting as empty follicle syndrome [PMID:24670168, PMID:31734689].\",\n  \"teleology\": [\n    {\n      \"year\": 1996,\n      \"claim\": \"Before ZP1's structural role was established, recombinant porcine ZP1 was shown to function as a secondary sperm receptor that binds acrosome-reacted spermatozoa and proacrosin, indicating ZP1 participates directly in gamete recognition beyond matrix formation.\",\n      \"evidence\": \"Immunofluorescence binding assay and immunoblotting with recombinant pZP1 and boar sperm extracts\",\n      \"pmids\": [\"8984189\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Binding was demonstrated only in pig; relevance to human or mouse ZP1 not tested\", \"Identity of the 40 kDa sperm binding partner unresolved\", \"No in vivo validation of secondary receptor function\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Mouse Zp1 knockout established that ZP1 is required for structural integrity of the zona pellucida — without it, a zona still forms from ZP2/ZP3 but is loosely organized — resolving the question of whether ZP1 is a structural crosslinker versus an essential assembly factor.\",\n      \"evidence\": \"Targeted Zp1 gene knockout in mice with histological, hormonal, and mating analyses\",\n      \"pmids\": [\"10433913\", \"10526650\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular mechanism of crosslinking (disulfide topology) not resolved at atomic level\", \"Whether ZP1 loss affects sperm binding independently of zona loosening was uncertain\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Immunoelectron microscopy resolved that ZP1 is synthesized exclusively by oocytes and traffics through the Golgi and vesicular aggregates before secretion, establishing the biosynthetic pathway and ruling out granulosa cell contribution.\",\n      \"evidence\": \"Protein A-gold immunoelectron microscopy with double/triple immunolocalization in mouse ovarian follicles\",\n      \"pmids\": [\"11906903\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Signals controlling ZP1 sorting from Golgi to secretory vesicles not identified\", \"Asymmetric distribution of ZP proteins in the matrix mechanistically unexplained\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Co-expression studies demonstrated that ZP1 secretion requires co-expression with ZP2 and ZP3, establishing that ZP protein hetero-interactions are prerequisite for secretion rather than just extracellular assembly.\",\n      \"evidence\": \"Co-expression of recombinant human ZP proteins in HEK 293T cells with Western blotting of medium and lysate\",\n      \"pmids\": [\"15064827\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Which domain of ZP1 mediates the co-secretion interaction was not mapped\", \"Whether ZP1 secretion also requires ZP4 in human oocytes was not tested\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Biophysical characterization of ZP1-N domain peptides revealed amyloid-like fibril self-assembly, suggesting a polymerization mechanism for zona matrix formation beyond simple disulfide crosslinking.\",\n      \"evidence\": \"TEM, X-ray diffraction, Congo red staining, and ATR FT-IR spectroscopy of synthetic ZP1-N peptides\",\n      \"pmids\": [\"24069181\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether amyloid-like assembly occurs in vivo within the zona is unresolved\", \"Contribution of amyloid-like polymerization relative to disulfide crosslinking not quantified\", \"Only two short peptides tested — full ZP-N domain behavior unknown\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"A human homozygous frameshift ZP1 mutation was shown to cause intracellular sequestration of ZP3 by defective ZP1, directly linking ZP1 loss-of-function to human infertility through a dominant-negative intracellular trapping mechanism.\",\n      \"evidence\": \"Whole-exome sequencing of infertile pedigree combined with co-localization studies in transfected cells\",\n      \"pmids\": [\"24670168\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether heterozygous carriers have subclinical zona thinning was not assessed\", \"Rescue experiment restoring ZP1 was not performed\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"ZP1 ubiquitination by the proteasome pathway was linked to sperm-binding competence, revealing a post-translational regulatory layer on zona function beyond assembly.\",\n      \"evidence\": \"PSMD4 antibody-mediated inhibition in porcine oocytes with ubiquitination Western blotting and sperm binding assay\",\n      \"pmids\": [\"29575084\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct E3 ligase responsible for ZP1 ubiquitination not identified\", \"Whether ubiquitination modifies ZP1 surface exposure versus degradation unclear\", \"Only shown in porcine system\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Multiple human ZP1 mutation studies converged to show that pathogenic variants disrupt ZP1–ZP2 and ZP1–ZP3 interactions as assessed by co-immunoprecipitation, establishing interaction loss as the common molecular defect underlying zona absence and empty follicle syndrome.\",\n      \"evidence\": \"Co-immunoprecipitation, Western blotting, and homology modeling of wild-type and mutant ZP proteins in CHO/CHO-K1 cells across multiple patient cohorts\",\n      \"pmids\": [\"31292994\", \"30810869\", \"31734689\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Binding interfaces between ZP1 and ZP2/ZP3 not structurally resolved\", \"Genotype-phenotype correlation across different mutation types not systematically established\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"A rat knock-in model demonstrated that a truncated ZP1 acts as a dominant-negative by binding and sequestering ZP3 and ZP4 intracellularly, extending the intracellular trapping mechanism from in vitro systems to an in vivo mammalian model.\",\n      \"evidence\": \"Rat Zp1 knock-in mutant with co-IP, immunofluorescence, and superovulation/fertilization assays\",\n      \"pmids\": [\"33624742\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether ZP4 sequestration contributes to human pathology (humans express ZP4) not confirmed\", \"Threshold level of ZP1 needed for functional zona not determined\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"CRISPR knockout of ZP1 in cynomolgus macaques confirmed that ZP1 is essential for zona pellucida assembly and normal folliculogenesis in primates, validating the translational relevance of rodent findings to the human four-ZP-protein system.\",\n      \"evidence\": \"CRISPR/Cas9 knockout in non-human primates with immunofluorescence, TEM, transcriptomics, and histopathology\",\n      \"pmids\": [\"40923306\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Downstream transcriptomic changes not mechanistically dissected\", \"Whether ZP1-null primate oocytes can be rescued by exogenous ZP1 is untested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The atomic-resolution structure of ZP1 homodimer and its interfaces with ZP2/ZP3 filaments remain unresolved, leaving the precise mechanism of crosslink formation and the determinants of species-specific zona architecture unknown.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No crystal or cryo-EM structure of ZP1 homodimer or ZP1-ZP2/ZP3 complex\", \"Disulfide bond topology of the crosslink not mapped\", \"Molecular basis of species differences in ZP composition (3 vs 4 ZP proteins) not mechanistically explained\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 1, 15]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [0, 2]},\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [2]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [2]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [3, 9]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1474165\", \"supporting_discovery_ids\": [0, 15]},\n      {\"term_id\": \"R-HSA-1474244\", \"supporting_discovery_ids\": [0, 1, 15]}\n    ],\n    \"complexes\": [\n      \"Zona pellucida matrix (ZP1/ZP2/ZP3 polymer)\"\n    ],\n    \"partners\": [\n      \"ZP2\",\n      \"ZP3\",\n      \"ZP4\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}