{"gene":"ZP2","run_date":"2026-04-28T23:00:24","timeline":{"discoveries":[{"year":1990,"finding":"Zp-2 gene is expressed exclusively in oocytes during a narrow window of oocyte growth (the ~2-week growth phase prior to ovulation), is coordinately regulated with Zp-3, and shares conserved 5' flanking sequences with Zp-3 near their transcription start sites, suggesting shared regulatory mechanisms for oocyte-specific, developmentally restricted expression.","method":"Northern blotting, gene locus characterization, 5' flanking sequence comparison","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (Northern blot, genomic characterization) in a foundational study","pmids":["1690843"],"is_preprint":false},{"year":1984,"finding":"ZP2 is stably integrated into the extracellular zona pellucida matrix (demonstrated by laser photobleaching/FRAP), distributed throughout the zona in a fibrous pattern, and this distribution is maintained after fertilization at the two-cell embryo stage; ZP2 is antigenically distinct from other extracellular matrix proteins and is found exclusively in ovarian tissue.","method":"Monoclonal antibody immunofluorescence, laser photobleaching (FRAP), immunoprecipitation","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 1-2 — direct localization by FRAP with functional consequence (stable matrix integration), replicated with multiple antibodies","pmids":["6699085"],"is_preprint":false},{"year":1992,"finding":"ZP2 shares a ~260 residue domain (the ZP domain) with ZP3, betaglycan (TGF-β type III receptor), uromodulin, and GP-2, defining a family of mosaic proteins with a similar domain architecture relative to transmembrane regions, suggesting a common tertiary structure and functional similarity in recognition mechanisms.","method":"Sequence analysis/domain homology","journal":"FEBS letters","confidence":"Low","confidence_rationale":"Tier 4 — computational/sequence analysis only, no direct functional experiment","pmids":["1313375"],"is_preprint":false},{"year":1992,"finding":"ZP2 is proteolytically converted to ZP2f (cleaved form) after egg activation, and this conversion can be triggered by G protein-coupled receptor signaling (via microinjected m1 muscarinic receptor + acetylcholine), with the effect blocked by atropine and GDP-βS, implicating pertussis toxin-insensitive Gq signaling in the zona modification that occurs at fertilization.","method":"mRNA microinjection, pharmacological inhibition, immunoblot for ZP2 conversion","journal":"Developmental biology","confidence":"Medium","confidence_rationale":"Tier 2 — multiple pharmacological tools in a single lab study linking receptor signaling to ZP2 cleavage","pmids":["1577193"],"is_preprint":false},{"year":1994,"finding":"Mouse ZP2 and ZP3 carry O-linked trisaccharide chains (structure: GlcNAc→Galβ1,3GalNAcol) and N-linked poly-N-acetyllactosaminyl glycans; removal of poly-N-acetyllactosaminyl chains reduces apparent ZP2 molecular weight by ~23 kDa, indicating these are major glycan modifications of ZP2.","method":"Endo-β-galactosidase digestion, O-glycanase treatment, mild alkali/NaB3H4 release, lectin binding, Bio-Gel P-4 sizing","journal":"Biology of reproduction","confidence":"High","confidence_rationale":"Tier 1 — in vitro biochemical reconstitution with multiple orthogonal glycan analysis methods","pmids":["7948482"],"is_preprint":false},{"year":1999,"finding":"The Xenopus sperm receptor gp69/64 (a ZP2 ortholog) binds sperm through its N-terminal region, which is proteolytically cleaved by a cortical granule protease after fertilization, removing 27 amino acids from the N-terminus and abolishing sperm binding; the isolated N-terminus-truncated receptor is inactive as a sperm binding inhibitor.","method":"Molecular cloning, protease treatment (collagenase), sperm-egg binding inhibition assay, N-terminal sequencing","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1-2 — biochemical reconstitution of cleavage, functional sperm-binding assay, multiple orthogonal methods","pmids":["9927653"],"is_preprint":false},{"year":2001,"finding":"ZP2-null female mice produce only ZP1 and ZP3 proteins that form a thin, unsustained zona matrix; this leads to decreased antral follicle numbers, failure of egg recovery after gonadotropin stimulation, and absence of two-cell embryos after mating, establishing ZP2 as essential for structural integrity of the zona pellucida, folliculogenesis, and in vivo fertilization.","method":"Targeted gene disruption (knockout mice), histological analysis, immunofluorescence, embryo recovery","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 2 — clean knockout with specific phenotypic readout across multiple assays, foundational study","pmids":["11245577"],"is_preprint":false},{"year":2001,"finding":"Mouse ZP2 (mZP2) binds to proacrosin/acrosin on acrosome-reacted sperm via a strong ionic interaction between polysulphate groups on mZP2 and basic residues on an internal proacrosin peptide, mediating secondary sperm binding; this interaction is disrupted by suramin (a polysulphonated compound) and is reduced in proacrosin-null sperm.","method":"Solid-phase binding assay with proacrosin-null sperm (genetic), competitive binding with sulphated polymers/suramin, in vitro fertilization displacement assay","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 — genetic (proacrosin KO sperm), biochemical, and functional (IVF) approaches in combination","pmids":["11739644"],"is_preprint":false},{"year":2001,"finding":"Mouse acrosomal cortical matrix protein MC41 binds ZP2 and ZP2f (the cleaved form) via far-Western blotting and forms a complex with a 75-kDa serine protease under low-salt conditions, suggesting MC41 participates in secondary sperm-zona binding during acrosomal reaction.","method":"Far-Western blotting, co-immunoprecipitation, immunogold electron microscopy","journal":"Developmental biology","confidence":"Medium","confidence_rationale":"Tier 3 — single lab, far-Western and co-IP without full reconstitution","pmids":["11784014"],"is_preprint":false},{"year":2002,"finding":"ZP2 subcellular distribution during folliculogenesis shows association with the Golgi apparatus, secretory granules, and vesicular aggregates (multivesicular aggregates) in oocytes, with all three ZP glycoproteins distributed throughout the zona pellucida in close association in asymmetric patches.","method":"Immunoelectron microscopy with protein A-gold, double and triple immunolocalization","journal":"Biology of reproduction","confidence":"Medium","confidence_rationale":"Tier 2 — direct subcellular localization by electron microscopy, single lab","pmids":["11906903"],"is_preprint":false},{"year":2006,"finding":"ZP2 and ZP3 traffic independently through oocytes prior to zona assembly: they colocalize in the ER and multivesicular aggregates but do not physically interact intracellularly (undetectable by co-immunoprecipitation); ZP3 lacking all N-glycosylation sites is still incorporated into the zona matrix, indicating N-glycosylation is not required for ZP3 trafficking or incorporation.","method":"Coimmunoprecipitation, fluorescence microscopy (GFP-tagged proteins), transgenic mice expressing N-glycosylation mutant ZP3","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal approaches (Co-IP, live imaging, transgenic mice) in one study","pmids":["17047254"],"is_preprint":false},{"year":2011,"finding":"The short cytoplasmic tails (9–15 residues) of ZP2 and ZP3 are necessary and sufficient to prevent intracellular oligomerization while ensuring incorporation into the zona pellucida; without these tails, ZP2 and ZP3 interact within the cell and fail to be incorporated into the zona matrix.","method":"Fluorescent protein complementation (bimolecular fluorescence complementation) in CHO cells and growing oocytes, deletion mutants, heterologous GPI-anchored fusion constructs","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal experimental systems (CHO cells, oocytes, heterologous constructs) with mutagenesis","pmids":["21378311"],"is_preprint":false},{"year":2012,"finding":"Ovastacin (encoded by Astl), an astacin metalloendoprotease stored in egg cortical granules, directly cleaves ZP2 in the zona pellucida after fertilization; recombinant ovastacin cleaves ZP2 in native zonae, Astl-null mice fail to cleave ZP2 post-fertilization, and sperm bind equally well to Astl-null two-cell embryos as to unfertilized eggs, establishing ovastacin-mediated ZP2 cleavage as the post-fertilization block to sperm binding.","method":"In vitro cleavage assay with recombinant ovastacin, knockout mouse model (Astl-null), sperm binding assay, immunofluorescence for cortical granule localization","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 1 — reconstitution in vitro + KO mouse with specific phenotypic readout, replicated across methods","pmids":["22472438"],"is_preprint":false},{"year":2014,"finding":"A restricted N-terminal domain of ZP2 (residues 51–149) is necessary and sufficient for sperm-zona recognition in both mouse and human; transgenic mice expressing human ZP4 without mouse or human ZP2 are sterile, and transgenic mice with ZP2 lacking residues 51–149 show no sperm binding, establishing ZP2(51-149) as the essential sperm-binding domain.","method":"Transgenic mouse models with chimeric/truncated ZP2, sperm binding assays, recombinant peptide bead assays","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 — multiple transgenic lines with domain-deletion approach plus functional sperm binding assay","pmids":["24934154"],"is_preprint":false},{"year":2017,"finding":"A unique 7 amino acid motif near the N-terminus of ovastacin is necessary and sufficient for its cortical granule localization; deletion of this motif (AstlΔ) by CRISPR/Cas9 causes ovastacin to accumulate in the endomembrane system, leading to premature ZP2 cleavage, poor sperm binding to the zona, and sub-fertility in female mice.","method":"CRISPR/Cas9 deletion at endogenous Astl locus, deletion mutant analysis in oocytes, sperm binding assay, fertility testing","journal":"PLoS genetics","confidence":"High","confidence_rationale":"Tier 2 — precise genetic manipulation (CRISPR KI) with direct functional readouts (sperm binding, fertility)","pmids":["28114310"],"is_preprint":false},{"year":2017,"finding":"Heterozygous mutations in ZP2 (and ZP3) have dosage effects: mouse models with single heterozygous ZP2 mutation show approximately half-normal ZP thickness, and the corresponding mutant precursor proteins cannot anchor to oocyte membranes, revealing a haploinsufficiency mechanism for ZP defects.","method":"CRISPR/Cas9 knock-in mouse models, ZP thickness measurement, immunostaining for membrane anchoring","journal":"Human genetics","confidence":"Medium","confidence_rationale":"Tier 2 — CRISPR mouse models with functional cellular readout, single lab","pmids":["28646452"],"is_preprint":false},{"year":2018,"finding":"Loss-of-function pathogenic variants in ZP2 (splice site c.1695-2A>G and frameshift c.1691_1694dup) produce truncated proteins that are intracellularly sequestered and prematurely interact with other ZP proteins in CHO cells, resulting in a structurally abnormal zona pellucida lacking ZP2 protein and causing fertilization failure.","method":"Exome sequencing, CHO-K1 cell expression of mutant constructs, immunostaining of patient oocytes, Western blot","journal":"Genetics in medicine","confidence":"Medium","confidence_rationale":"Tier 2-3 — functional cell-based assay with patient oocyte immunostaining, single lab","pmids":["29895852"],"is_preprint":false},{"year":2021,"finding":"A frameshift variant in ZP2 (c.1235_1236del, p.Q412Rfs*17) produces a truncated protein at reduced levels and reduces the interaction between ZP2 and ZP3 as demonstrated by co-immunoprecipitation, suggesting that ZP2-ZP3 dimer assembly is required for normal zona pellucida formation.","method":"CHO cell expression, immunoblot, immunofluorescence in mouse oocytes, co-immunoprecipitation","journal":"Journal of assisted reproduction and genetics","confidence":"Medium","confidence_rationale":"Tier 3 — co-IP in heterologous cells, single lab","pmids":["33604805"],"is_preprint":false},{"year":2022,"finding":"A ZP2 missense variant (p.Leu474Pro) reduces secretion of ZP2 protein into culture medium and reduces the ZP2-ZP3 interaction as shown by co-immunoprecipitation in CHO cells; a second variant (p.Cys620Tyr) reduces total protein expression and alters a disulfide bond predicted to affect ZP2 structure.","method":"CHO cell transfection, Western blot of secreted vs. intracellular protein, co-immunoprecipitation, 3D protein structure prediction","journal":"Reproductive sciences","confidence":"Medium","confidence_rationale":"Tier 3 — co-IP and secretion assay in heterologous cells, single lab","pmids":["35595959"],"is_preprint":false},{"year":2022,"finding":"A heterozygous ZP2 variant (p.R642Q) associated with empty follicle syndrome causes ZP2 protein accumulation in the oocyte cytoplasm rather than secretion, implicating defective furin-mediated cleavage (a post-translational modification) in ZP2 processing and secretion necessary for zona pellucida formation.","method":"CRISPR-Cas9 knock-in mouse model, RNA-sequencing, immunofluorescence in oocytes","journal":"Human reproduction","confidence":"Medium","confidence_rationale":"Tier 2 — CRISPR KI mouse recapitulating human phenotype, single lab","pmids":["35211729"],"is_preprint":false},{"year":2024,"finding":"Cleavage of the N-terminal region (NTR) of ZP2 by ovastacin after fertilization triggers oligomerization of the cleaved ZP2 NTRs, which extensively cross-links zona pellucida filaments to rigidify the egg coat and make it physically impenetrable to sperm; structural studies of native egg coat filaments reveal that ZP2 (type II subunit) forms a left-handed double helix with ZP3 (type I subunit) with ZP2 NTRs protruding outward.","method":"Biochemical cleavage assay, cryo-EM/X-ray structural analysis of native vertebrate egg coat filaments, AlphaFold modeling of human ZP polymers","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 — structural determination of native filaments combined with biochemical reconstitution of cleavage-triggered oligomerization","pmids":["38490181"],"is_preprint":false},{"year":2025,"finding":"ZP2 expression in human cerebellar granule cells is induced by pontine mossy fibers and reduces synaptic proteins at pontocerebellar glomerular synapses, decreasing cerebellar neuron electrophysiological activity, revealing a human-specific co-option of ZP2 in synapse regulation in the brain.","method":"Single-nucleus transcriptomics/chromatin accessibility profiling across primates, experimental induction assays, synaptic protein quantification, electrophysiology","journal":"Cell","confidence":"Medium","confidence_rationale":"Tier 2 — multi-species transcriptomic profiling with experimental validation of synaptic and electrophysiological effects, single study","pmids":["41819103"],"is_preprint":false},{"year":2025,"finding":"GTPase Rab10 accumulates at the mouse and porcine oocyte cortex, modulates the RhoA pathway to control actin dynamics, and regulates cortical granule transport via the myosin Va complex; overexpression of GDP-bound (dominant-negative) Rab10 leads to ZP2 downregulation and accumulation at the cortex, implicating a Rab10-ZP2 complex in ZP2 supply for the zona pellucida reaction.","method":"Rab10 overexpression/dominant-negative in mouse and porcine oocytes, immunofluorescence, RhoA pathway analysis, myosin Va expression analysis","journal":"Development (Cambridge, England)","confidence":"Medium","confidence_rationale":"Tier 2 — functional perturbation in two species with pathway analysis, single study","pmids":["40793920"],"is_preprint":false},{"year":2025,"finding":"Testis-specific 20S proteasome core particles pre-stored in sperm heads assemble with oocyte-derived 19S regulatory particles upon fertilization, forming chimeric proteasomes that degrade Fetuin B (ubiquitinated by E3 ligase MARCH3), which triggers ZP2 cleavage and zona pellucida hardening to block polyspermy.","method":"Biochemical reconstitution of chimeric proteasomes, ubiquitination assay, genetic KO of components, ZP2 cleavage assay","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 1-2 — biochemical reconstitution plus genetic KO, but preprint not yet peer-reviewed","pmids":[],"is_preprint":true},{"year":2025,"finding":"The structural basis of ZP2 immunocontraception was determined: an IE-3 antibody-derived scFv binds ZP2 via induced fit of the epitope and is sufficient to block fertilization in vitro, providing atomic-level insight into the ZP2 sperm-binding surface.","method":"Structural determination (X-ray crystallography of scFv-ZP2 complex), in vitro fertilization blocking assay","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 1 — structural determination with functional validation, but preprint","pmids":[],"is_preprint":true}],"current_model":"ZP2 is an oocyte-specific zona pellucida glycoprotein that traffics independently through the endomembrane system (controlled by its cytoplasmic tail to prevent premature oligomerization), is secreted and incorporated into the zona pellucida filament as a type II subunit forming a left-handed double helix with ZP3, presents an N-terminal domain (residues 51–149) as the essential sperm-binding site for gamete recognition, and after fertilization is proteolytically cleaved by ovastacin (secreted from cortical granules) triggering ZP2 NTR oligomerization that cross-links filaments to harden the zona pellucida and block polyspermy."},"narrative":{"teleology":[{"year":1984,"claim":"The first question was whether ZP2 forms a stable structural component of the zona pellucida; FRAP and immunofluorescence demonstrated that ZP2 is stably integrated in a fibrous pattern and is restricted to ovarian tissue, establishing it as a bona fide zona matrix protein.","evidence":"Monoclonal antibody immunofluorescence and laser photobleaching (FRAP) on mouse oocytes and embryos","pmids":["6699085"],"confidence":"High","gaps":["Molecular partners within the fibrous matrix were unknown","Mechanism of matrix assembly from individual glycoproteins was unresolved"]},{"year":1990,"claim":"It was unclear how ZP2 expression is regulated; Northern blotting and promoter analysis showed oocyte-exclusive expression during a ~2-week growth phase, coordinately regulated with ZP3 through shared 5′ flanking elements.","evidence":"Northern blotting and 5′ flanking sequence comparison in mouse","pmids":["1690843"],"confidence":"High","gaps":["Transcription factors driving oocyte-specific expression were not identified","Post-transcriptional regulation was not assessed"]},{"year":1992,"claim":"The post-fertilization modification of ZP2 was linked to intracellular signaling when egg activation via Gq-coupled receptor signaling was shown to trigger ZP2-to-ZP2f conversion, implicating regulated exocytosis in the block to polyspermy.","evidence":"Microinjection of m1 muscarinic receptor mRNA into oocytes with pharmacological inhibitors (atropine, GDP-βS), immunoblot for ZP2 cleavage","pmids":["1577193"],"confidence":"Medium","gaps":["The protease responsible for ZP2 cleavage was not identified","Whether Gq signaling acts through cortical granule exocytosis was not directly demonstrated"]},{"year":1994,"claim":"The biochemical nature of ZP2 glycosylation was resolved: ZP2 carries O-linked trisaccharides and N-linked poly-N-acetyllactosaminyl glycans that account for ~23 kDa of its apparent molecular weight.","evidence":"Endo-β-galactosidase digestion, O-glycanase treatment, lectin binding, gel filtration on mouse zona pellucida","pmids":["7948482"],"confidence":"High","gaps":["Functional roles of specific glycan chains in sperm binding or zona assembly were not determined"]},{"year":1999,"claim":"A key question was which region of ZP2 mediates sperm binding; work on the Xenopus ZP2 orthologue gp69/64 showed that the N-terminal region is required for sperm binding and is proteolytically removed after fertilization, providing the first direct evidence that ZP2 cleavage abolishes sperm recognition.","evidence":"Molecular cloning, protease treatment, sperm-binding inhibition assay, and N-terminal sequencing in Xenopus","pmids":["9927653"],"confidence":"High","gaps":["Whether the mammalian ZP2 N-terminus functions identically was not tested","Identity of the endogenous protease was still unknown"]},{"year":2001,"claim":"ZP2-null mice revealed that ZP2 is essential for zona integrity, folliculogenesis, and in vivo fertilization, settling the question of whether ZP1 and ZP3 alone can sustain a functional zona.","evidence":"Targeted gene disruption (knockout mice) with histological analysis, immunofluorescence, and embryo recovery","pmids":["11245577"],"confidence":"High","gaps":["The molecular basis for the thin, unstable zona in ZP2 knockouts was not resolved","Whether ZP2 has functions beyond structural support was open"]},{"year":2001,"claim":"ZP2 was shown to mediate secondary sperm binding through interaction with proacrosin/acrosin on acrosome-reacted sperm via ionic contacts between polysulphate groups on ZP2 and basic residues on proacrosin.","evidence":"Solid-phase binding assay with proacrosin-null sperm, competitive binding with suramin, IVF displacement assay","pmids":["11739644"],"confidence":"High","gaps":["Whether proacrosin interaction is the sole secondary binding mechanism was unclear","Structural details of the ZP2–proacrosin interface were not resolved"]},{"year":2006,"claim":"A critical cell-biological question—whether ZP2 and ZP3 interact intracellularly before secretion—was answered negatively: the two proteins traffic independently through the ER and multivesicular aggregates, indicating that filament assembly occurs only after secretion.","evidence":"Co-immunoprecipitation, GFP-tagged fluorescence microscopy, and transgenic mice expressing N-glycosylation mutant ZP3","pmids":["17047254"],"confidence":"High","gaps":["The extracellular trigger or site for ZP2–ZP3 assembly was not identified"]},{"year":2011,"claim":"The mechanism preventing premature oligomerization was identified: the short cytoplasmic tails of ZP2 and ZP3 (9–15 residues) are necessary and sufficient to block intracellular interaction, and their removal causes premature assembly and failure of zona incorporation.","evidence":"Bimolecular fluorescence complementation in CHO cells and growing oocytes with deletion and GPI-anchor fusion constructs","pmids":["21378311"],"confidence":"High","gaps":["How the cytoplasmic tail mechanistically prevents ZP domain interaction in the secretory pathway was not determined"]},{"year":2012,"claim":"The identity of the post-fertilization ZP2 protease was established: ovastacin (Astl), an astacin metalloendoprotease stored in cortical granules, directly cleaves ZP2, and Astl-null mice fail to cleave ZP2 and fail to block polyspermy.","evidence":"In vitro cleavage with recombinant ovastacin, Astl-null knockout mice, sperm binding assay","pmids":["22472438"],"confidence":"High","gaps":["The cleavage site on mammalian ZP2 was not precisely mapped","Upstream regulation of ovastacin activation after cortical granule exocytosis was not fully resolved"]},{"year":2014,"claim":"The minimal sperm-binding domain of mammalian ZP2 was mapped to residues 51–149 at the N-terminus, resolving whether ZP2 or ZP3 is the primary sperm receptor in mammals.","evidence":"Transgenic mice with chimeric/truncated ZP2, sperm binding assays, recombinant peptide bead assays","pmids":["24934154"],"confidence":"High","gaps":["The sperm-side receptor for ZP2(51-149) was not identified","Atomic structure of the binding interface was not available"]},{"year":2017,"claim":"Two regulatory mechanisms were clarified: ovastacin cortical granule targeting depends on a 7-amino-acid N-terminal motif (its deletion causes premature ZP2 cleavage and sub-fertility), and heterozygous ZP2 mutations cause haploinsufficiency with reduced zona thickness.","evidence":"CRISPR/Cas9 knock-in mice for Astl motif deletion and ZP2 heterozygous mutations, sperm binding and zona thickness assays","pmids":["28114310","28646452"],"confidence":"High","gaps":["The vesicular sorting machinery recognizing the ovastacin targeting motif was not identified","Whether haploinsufficiency explains all human heterozygous ZP2 infertility cases was not tested"]},{"year":2018,"claim":"Human pathogenic ZP2 variants were functionally validated: truncating mutations cause intracellular sequestration, premature interaction with other ZP proteins, and absence of ZP2 from the zona, directly linking ZP2 loss-of-function to human female infertility.","evidence":"Exome sequencing of infertile patients, CHO-K1 cell expression of mutant constructs, patient oocyte immunostaining","pmids":["29895852"],"confidence":"Medium","gaps":["Rescue experiments in human oocytes were not performed","Genotype–phenotype correlations across a larger patient cohort were not established"]},{"year":2022,"claim":"Additional human ZP2 variants (missense and splice-affecting) were shown to impair ZP2 secretion and ZP2–ZP3 interaction, expanding the molecular mechanisms of ZP2-related infertility to include defective furin-mediated processing and disrupted dimer assembly.","evidence":"CHO cell co-immunoprecipitation, Western blot of secreted vs. intracellular protein, CRISPR knock-in mouse for R642Q variant","pmids":["35595959","35211729","33604805"],"confidence":"Medium","gaps":["Whether furin cleavage is strictly required for all ZP2 secretion or is variant-specific was not resolved","Structural consequences of individual missense mutations were predicted, not experimentally determined"]},{"year":2024,"claim":"The structural basis of zona hardening was solved: cryo-EM of native egg coat filaments revealed ZP2 and ZP3 form a left-handed double helix, and ovastacin cleavage of ZP2 triggers NTR oligomerization that cross-links filaments, physically blocking sperm penetration.","evidence":"Cryo-EM and X-ray structural analysis of native vertebrate egg coat filaments, biochemical cleavage-induced oligomerization assay, AlphaFold modeling","pmids":["38490181"],"confidence":"High","gaps":["High-resolution structure of the full mammalian ZP2–ZP3 filament was not yet available","How NTR oligomerization is oriented relative to filament packing in vivo was modeled but not directly visualized"]},{"year":2025,"claim":"ZP2 was found to have a human-specific non-reproductive function: expression in cerebellar granule cells, induced by pontine mossy fibers, reduces synaptic protein levels and dampens electrophysiological activity, revealing co-option of an oocyte gene for brain synapse regulation.","evidence":"Single-nucleus transcriptomics/chromatin accessibility across primates, experimental induction in human cerebellar neurons, synaptic protein quantification, electrophysiology","pmids":["41819103"],"confidence":"Medium","gaps":["The molecular mechanism by which secreted ZP2 modulates synaptic proteins is unknown","Whether ZP2 polymerizes or signals through a receptor at synapses is unstudied","Relevance to cerebellar function or disease in vivo has not been tested"]},{"year":null,"claim":"The sperm-side receptor that directly engages ZP2 residues 51–149 remains unidentified, and the precise atomic structure of the mammalian ZP2–sperm ligand interface has not been determined at sufficient resolution for therapeutic design.","evidence":"","pmids":[],"confidence":"Low","gaps":["No sperm receptor for ZP2(51-149) has been identified","High-resolution structure of the human ZP2–ZP3 filament in situ is lacking","The mechanism of ZP2-mediated synapse regulation in human cerebellum is completely uncharacterized"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[1,6,20]},{"term_id":"GO:0098631","term_label":"cell adhesion mediator activity","supporting_discovery_ids":[5,7,13]}],"localization":[{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[1,6,20]},{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[9,10]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[9,10,12]}],"pathway":[{"term_id":"R-HSA-1474165","term_label":"Reproduction","supporting_discovery_ids":[6,12,13,20]},{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[10,11,19]}],"complexes":["ZP2-ZP3 zona pellucida filament"],"partners":["ZP3","ZP1","ASTL","ACR"],"other_free_text":[]},"mechanistic_narrative":"ZP2 is an oocyte-specific glycoprotein that serves as the principal sperm-binding component and structural backbone of the zona pellucida, the extracellular coat essential for fertilization and polyspermy block. ZP2 is expressed exclusively during oocyte growth, traffics independently of ZP3 through the endomembrane system with its short cytoplasmic tail preventing premature intracellular oligomerization, and is secreted to assemble with ZP3 into a left-handed double-helical filament in which ZP2 functions as the type II subunit [PMID:1690843, PMID:21378311, PMID:38490181]. An N-terminal domain encompassing residues 51–149 is necessary and sufficient for sperm recognition; after fertilization, the cortical granule metalloendoprotease ovastacin cleaves ZP2, triggering oligomerization of the released N-terminal regions that cross-link filaments, harden the zona, and block polyspermy [PMID:24934154, PMID:22472438, PMID:38490181]. Loss-of-function mutations in human ZP2—including frameshift, splice-site, and missense variants—cause defective ZP2 secretion or ZP2–ZP3 assembly, producing structurally abnormal zonae and female infertility [PMID:29895852, PMID:33604805, PMID:35211729]."},"prefetch_data":{"uniprot":{"accession":"Q05996","full_name":"Zona pellucida sperm-binding protein 2","aliases":["Zona pellucida glycoprotein 2","Zp-2","Zona pellucida protein A"],"length_aa":745,"mass_kda":82.4,"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 (PubMed:29895852). The zona pellucida is composed of 3 to 4 glycoproteins, ZP1, ZP2, ZP3, and ZP4. ZP2 may act as a secondary sperm receptor (PubMed:29895852)","subcellular_location":"Cell membrane","url":"https://www.uniprot.org/uniprotkb/Q05996/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/ZP2","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/ZP2","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":"615774","title":"OOCYTE/ZYGOTE/EMBRYO MATURATION ARREST 1; OZEMA1","url":"https://www.omim.org/entry/615774"},{"mim_id":"608936","title":"OPIORPHIN PREPROPEPTIDE; OPRPN","url":"https://www.omim.org/entry/608936"},{"mim_id":"608860","title":"ASTACIN-LIKE METALLOENDOPEPTIDASE; ASTL","url":"https://www.omim.org/entry/608860"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"brain","ntpm":35.0}],"url":"https://www.proteinatlas.org/search/ZP2"},"hgnc":{"alias_symbol":["ZPA"],"prev_symbol":[]},"alphafold":{"accession":"Q05996","domains":[{"cath_id":"2.60.40,2.60.40","chopping":"53-140","consensus_level":"high","plddt":77.5143,"start":53,"end":140},{"cath_id":"2.60.40,2.60.40","chopping":"154-169_181-262","consensus_level":"medium","plddt":79.1585,"start":154,"end":262},{"cath_id":"-","chopping":"268-355","consensus_level":"medium","plddt":84.5661,"start":268,"end":355},{"cath_id":"2.60.40.3210","chopping":"373-469","consensus_level":"high","plddt":79.5531,"start":373,"end":469},{"cath_id":"2.60.40.4100","chopping":"495-640_649-664","consensus_level":"high","plddt":85.7173,"start":495,"end":664}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q05996","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q05996-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q05996-F1-predicted_aligned_error_v6.png","plddt_mean":71.56},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=ZP2","jax_strain_url":"https://www.jax.org/strain/search?query=ZP2"},"sequence":{"accession":"Q05996","fasta_url":"https://rest.uniprot.org/uniprotkb/Q05996.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q05996/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q05996"}},"corpus_meta":[{"pmid":"8269518","id":"PMC_8269518","title":"Sonic hedgehog mediates the polarizing activity of the ZPA.","date":"1993","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/8269518","citation_count":1992,"is_preprint":false},{"pmid":"1313375","id":"PMC_1313375","title":"A large domain common to sperm receptors (Zp2 and Zp3) and TGF-beta type III receptor.","date":"1992","source":"FEBS letters","url":"https://pubmed.ncbi.nlm.nih.gov/1313375","citation_count":285,"is_preprint":false},{"pmid":"7841460","id":"PMC_7841460","title":"Cloning and characterization of zona pellucida genes and cDNAs from a variety of mammalian species: the ZPA, ZPB and ZPC gene families.","date":"1994","source":"DNA sequence : the journal of DNA sequencing and mapping","url":"https://pubmed.ncbi.nlm.nih.gov/7841460","citation_count":273,"is_preprint":false},{"pmid":"22472438","id":"PMC_22472438","title":"Ovastacin, a cortical granule protease, cleaves ZP2 in the zona pellucida to prevent polyspermy.","date":"2012","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/22472438","citation_count":234,"is_preprint":false},{"pmid":"11245577","id":"PMC_11245577","title":"Defective zonae pellucidae in Zp2-null mice disrupt folliculogenesis, fertility and development.","date":"2001","source":"Development (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/11245577","citation_count":221,"is_preprint":false},{"pmid":"7915198","id":"PMC_7915198","title":"Ectopic expression of Hoxb-8 causes duplication of the ZPA in the forelimb and homeotic transformation of axial structures.","date":"1994","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/7915198","citation_count":209,"is_preprint":false},{"pmid":"9374397","id":"PMC_9374397","title":"Polydactyly and ectopic ZPA formation in Alx-4 mutant mice.","date":"1997","source":"Development (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/9374397","citation_count":169,"is_preprint":false},{"pmid":"1690843","id":"PMC_1690843","title":"Oocyte-specific expression of mouse Zp-2: developmental regulation of the zona pellucida genes.","date":"1990","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/1690843","citation_count":156,"is_preprint":false},{"pmid":"24934154","id":"PMC_24934154","title":"A single domain of the ZP2 zona pellucida protein mediates gamete recognition in mice and humans.","date":"2014","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/24934154","citation_count":129,"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":"9165113","id":"PMC_9165113","title":"Retinoid signaling is required for the establishment of a ZPA and for the expression of Hoxb-8, a mediator of ZPA formation.","date":"1997","source":"Development (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/9165113","citation_count":89,"is_preprint":false},{"pmid":"29895852","id":"PMC_29895852","title":"ZP2 pathogenic variants cause in vitro fertilization failure and female infertility.","date":"2018","source":"Genetics in medicine : official journal of the American College of Medical Genetics","url":"https://pubmed.ncbi.nlm.nih.gov/29895852","citation_count":86,"is_preprint":false},{"pmid":"28646452","id":"PMC_28646452","title":"Dosage effects of ZP2 and ZP3 heterozygous mutations cause human infertility.","date":"2017","source":"Human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/28646452","citation_count":78,"is_preprint":false},{"pmid":"1577193","id":"PMC_1577193","title":"Role of G proteins in mouse egg activation: stimulatory effects of acetylcholine on the ZP2 to ZP2f conversion and pronuclear formation in eggs expressing a functional m1 muscarinic receptor.","date":"1992","source":"Developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/1577193","citation_count":76,"is_preprint":false},{"pmid":"9041128","id":"PMC_9041128","title":"Molecular cloning, structural analysis, and expression of carp ZP2 gene.","date":"1997","source":"Molecular reproduction and development","url":"https://pubmed.ncbi.nlm.nih.gov/9041128","citation_count":74,"is_preprint":false},{"pmid":"9927653","id":"PMC_9927653","title":"Xenopus laevis sperm receptor gp69/64 glycoprotein is a homolog of the mammalian sperm receptor ZP2.","date":"1999","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/9927653","citation_count":72,"is_preprint":false},{"pmid":"10395930","id":"PMC_10395930","title":"Characterization of two zebrafish cDNA clones encoding egg envelope proteins ZP2 and ZP3.","date":"1999","source":"Biochimica et biophysica acta","url":"https://pubmed.ncbi.nlm.nih.gov/10395930","citation_count":69,"is_preprint":false},{"pmid":"6699085","id":"PMC_6699085","title":"Monoclonal antibodies as probes of the distribution of ZP-2, the major sulfated glycoprotein of the murine zona pellucida.","date":"1984","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/6699085","citation_count":65,"is_preprint":false},{"pmid":"11739644","id":"PMC_11739644","title":"Interactions between mouse ZP2 glycoprotein and proacrosin; a mechanism for secondary binding of sperm to the zona pellucida during fertilization.","date":"2001","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/11739644","citation_count":64,"is_preprint":false},{"pmid":"16774977","id":"PMC_16774977","title":"Adaptive evolution of fertilization proteins within a genus: variation in ZP2 and ZP3 in deer mice (Peromyscus).","date":"2006","source":"Molecular biology and evolution","url":"https://pubmed.ncbi.nlm.nih.gov/16774977","citation_count":63,"is_preprint":false},{"pmid":"7948482","id":"PMC_7948482","title":"O-linked trisaccharide and N-linked poly-N-acetyllactosaminyl glycans are present on mouse ZP2 and ZP3.","date":"1994","source":"Biology of reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/7948482","citation_count":58,"is_preprint":false},{"pmid":"3289984","id":"PMC_3289984","title":"A gradient of responsiveness to the growth-promoting activity of ZPA (zone of polarizing activity) in the chick limb bud.","date":"1988","source":"Developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/3289984","citation_count":54,"is_preprint":false},{"pmid":"1968044","id":"PMC_1968044","title":"Genomic mapping of murine Zp-2 and Zp-3, two oocyte-specific loci encoding zona pellucida proteins.","date":"1990","source":"Genomics","url":"https://pubmed.ncbi.nlm.nih.gov/1968044","citation_count":52,"is_preprint":false},{"pmid":"9846380","id":"PMC_9846380","title":"The molecular ZPA.","date":"1998","source":"The Journal of experimental zoology","url":"https://pubmed.ncbi.nlm.nih.gov/9846380","citation_count":49,"is_preprint":false},{"pmid":"21378311","id":"PMC_21378311","title":"ZP2 and ZP3 cytoplasmic tails prevent premature interactions and ensure incorporation into the zona pellucida.","date":"2011","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/21378311","citation_count":45,"is_preprint":false},{"pmid":"1547319","id":"PMC_1547319","title":"Evidence for the presence of high-mannose/hybrid oligosaccharide chain(s) on the mouse ZP2 and ZP3.","date":"1992","source":"Biology of reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/1547319","citation_count":44,"is_preprint":false},{"pmid":"28114310","id":"PMC_28114310","title":"A Unique Egg Cortical Granule Localization Motif Is Required for Ovastacin Sequestration to Prevent Premature ZP2 Cleavage and Ensure Female Fertility in Mice.","date":"2017","source":"PLoS genetics","url":"https://pubmed.ncbi.nlm.nih.gov/28114310","citation_count":43,"is_preprint":false},{"pmid":"10084964","id":"PMC_10084964","title":"A contraceptive peptide vaccine targeting sulfated glycoprotein ZP2 of the mouse zona pellucida.","date":"1999","source":"Biology of reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/10084964","citation_count":42,"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":"12052239","id":"PMC_12052239","title":"Evaluation of the immunocontraceptive potential of Escherichia coli-expressed recombinant dog ZP2 and ZP3 in a homologous animal model.","date":"2002","source":"Reproduction (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/12052239","citation_count":39,"is_preprint":false},{"pmid":"8625805","id":"PMC_8625805","title":"Evidence that Shh cooperates with a retinoic acid inducible co-factor to establish ZPA-like activity.","date":"1996","source":"Development (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/8625805","citation_count":38,"is_preprint":false},{"pmid":"11422296","id":"PMC_11422296","title":"A hatching enzyme substrate in the Xenopus laevis egg envelope is a high molecular weight ZPA homolog.","date":"2001","source":"Development, growth & differentiation","url":"https://pubmed.ncbi.nlm.nih.gov/11422296","citation_count":37,"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":"17047254","id":"PMC_17047254","title":"ZP2 and ZP3 traffic independently within oocytes prior to assembly into the extracellular zona pellucida.","date":"2006","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/17047254","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":"25253730","id":"PMC_25253730","title":"Glycosylated chicken ZP2 accumulates in the egg coat of immature oocytes and remains localized to the germinal disc region of mature eggs.","date":"2014","source":"Biology of reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/25253730","citation_count":30,"is_preprint":false},{"pmid":"38490181","id":"PMC_38490181","title":"ZP2 cleavage blocks polyspermy by modulating the architecture of the egg coat.","date":"2024","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/38490181","citation_count":28,"is_preprint":false},{"pmid":"10070354","id":"PMC_10070354","title":"Evaluation of ZP2 domains of functional importance with antisera against synthetic ZP2 peptides.","date":"1998","source":"Journal of reproduction and fertility","url":"https://pubmed.ncbi.nlm.nih.gov/10070354","citation_count":26,"is_preprint":false},{"pmid":"11291774","id":"PMC_11291774","title":"Immunohistochemical localization of zona pellucida proteins ZPA, ZPB and ZPC in human, cynomolgus monkey and mouse ovaries.","date":"2001","source":"Cell and tissue research","url":"https://pubmed.ncbi.nlm.nih.gov/11291774","citation_count":23,"is_preprint":false},{"pmid":"11730907","id":"PMC_11730907","title":"Contraceptive potential of synthetic peptides of zona pellucida protein (ZPA).","date":"2002","source":"Journal of reproductive immunology","url":"https://pubmed.ncbi.nlm.nih.gov/11730907","citation_count":23,"is_preprint":false},{"pmid":"9771643","id":"PMC_9771643","title":"Two testicular cDNA clones suppressed by gonadotropin stimulation exhibit ZP2- and ZP3-like structures in Japanese eel.","date":"1998","source":"Molecular reproduction and development","url":"https://pubmed.ncbi.nlm.nih.gov/9771643","citation_count":23,"is_preprint":false},{"pmid":"28161524","id":"PMC_28161524","title":"John Saunders' ZPA, Sonic hedgehog and digit identity - How does it really all work?","date":"2017","source":"Developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/28161524","citation_count":22,"is_preprint":false},{"pmid":"33604805","id":"PMC_33604805","title":"A novel homozygous variant in ZP2 causes abnormal zona pellucida formation and female infertility.","date":"2021","source":"Journal of assisted reproduction and genetics","url":"https://pubmed.ncbi.nlm.nih.gov/33604805","citation_count":21,"is_preprint":false},{"pmid":"19846483","id":"PMC_19846483","title":"Zona pellucida protein ZP2 is expressed in the oocyte of Japanese quail (Coturnix japonica).","date":"2009","source":"Reproduction (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/19846483","citation_count":20,"is_preprint":false},{"pmid":"6474160","id":"PMC_6474160","title":"Scintigraphy of normal mouse ovaries with monoclonal antibodies to ZP-2, the major zona pellucida protein.","date":"1984","source":"Science (New York, N.Y.)","url":"https://pubmed.ncbi.nlm.nih.gov/6474160","citation_count":20,"is_preprint":false},{"pmid":"36931917","id":"PMC_36931917","title":"Novel variants in ZP1, ZP2 and ZP3 associated with empty follicle syndrome and abnormal zona pellucida.","date":"2023","source":"Reproductive biomedicine online","url":"https://pubmed.ncbi.nlm.nih.gov/36931917","citation_count":19,"is_preprint":false},{"pmid":"17911046","id":"PMC_17911046","title":"Identification of genes expressed in the mouse limb using a novel ZPA microarray approach.","date":"2007","source":"Gene expression patterns : GEP","url":"https://pubmed.ncbi.nlm.nih.gov/17911046","citation_count":19,"is_preprint":false},{"pmid":"9590540","id":"PMC_9590540","title":"Molecular cloning and expression in Escherichia coli of cDNA encoding bonnet monkey (Macaca radiata) zona pellucida glycoprotein-ZP2.","date":"1998","source":"Molecular reproduction and development","url":"https://pubmed.ncbi.nlm.nih.gov/9590540","citation_count":19,"is_preprint":false},{"pmid":"3652992","id":"PMC_3652992","title":"The effect of the zone of polarizing activity (ZPA) on the anterior half of the chick wing bud.","date":"1987","source":"Development (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/3652992","citation_count":19,"is_preprint":false},{"pmid":"16306421","id":"PMC_16306421","title":"Immunocontraceptive effects on female rabbits infected with recombinant myxoma virus expressing rabbit ZP2 or ZP3.","date":"2005","source":"Biology of reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/16306421","citation_count":19,"is_preprint":false},{"pmid":"17994267","id":"PMC_17994267","title":"Distance between AER and ZPA is defined by feed-forward loop and is stabilized by their feedback loop in vertebrate limb bud.","date":"2007","source":"Bulletin of mathematical biology","url":"https://pubmed.ncbi.nlm.nih.gov/17994267","citation_count":18,"is_preprint":false},{"pmid":"11858857","id":"PMC_11858857","title":"Analysis of recombinant mouse zona pellucida protein 2 (ZP2) constructs for immunocontraception.","date":"2002","source":"Vaccine","url":"https://pubmed.ncbi.nlm.nih.gov/11858857","citation_count":18,"is_preprint":false},{"pmid":"11784014","id":"PMC_11784014","title":"A mouse acrosomal cortical matrix protein, MC41, has ZP2-binding activity and forms a complex with a 75-kDa serine protease.","date":"2001","source":"Developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/11784014","citation_count":18,"is_preprint":false},{"pmid":"15604092","id":"PMC_15604092","title":"Analysis of N-linked glycans of porcine zona pellucida glycoprotein ZPA by MALDI-TOF MS: a contribution to understanding zona pellucida structure.","date":"2004","source":"Glycobiology","url":"https://pubmed.ncbi.nlm.nih.gov/15604092","citation_count":18,"is_preprint":false},{"pmid":"9771653","id":"PMC_9771653","title":"Sequence and analysis of zona pellucida 2 cDNA (ZP2) from a marsupial, the brushtail possum, Trichosurus vulpecula.","date":"1998","source":"Molecular reproduction and development","url":"https://pubmed.ncbi.nlm.nih.gov/9771653","citation_count":18,"is_preprint":false},{"pmid":"35211729","id":"PMC_35211729","title":"Identification of a heterozygous variant of ZP2 as a novel cause of empty follicle syndrome in humans and mice.","date":"2022","source":"Human reproduction (Oxford, England)","url":"https://pubmed.ncbi.nlm.nih.gov/35211729","citation_count":15,"is_preprint":false},{"pmid":"23213390","id":"PMC_23213390","title":"Joint interpretation of AER/FGF and ZPA/SHH over time and space underlies hairy2 expression in the chick limb.","date":"2012","source":"Biology open","url":"https://pubmed.ncbi.nlm.nih.gov/23213390","citation_count":15,"is_preprint":false},{"pmid":"35366744","id":"PMC_35366744","title":"Novel mutations in ZP2 and ZP3 cause female infertility in three patients.","date":"2022","source":"Journal of assisted reproduction and genetics","url":"https://pubmed.ncbi.nlm.nih.gov/35366744","citation_count":14,"is_preprint":false},{"pmid":"10533707","id":"PMC_10533707","title":"Isolation and characterisation of zona pellucida A (ZPA) cDNAs from two species of marsupial: regulated oocyte-specific expression of ZPA transcripts.","date":"1999","source":"Zygote (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/10533707","citation_count":14,"is_preprint":false},{"pmid":"12199704","id":"PMC_12199704","title":"Localization of N-linked carbohydrate chains in glycoprotein ZPA of the bovine egg zona pellucida.","date":"2002","source":"European journal of biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/12199704","citation_count":12,"is_preprint":false},{"pmid":"12506345","id":"PMC_12506345","title":"Expression in Escherichia coli and immunological characterization of three zona pellucida proteins (ZP1, ZP2, and ZP3) from a marsupial, the brushtail possum (Trichosurus vulpecula).","date":"2003","source":"Molecular reproduction and development","url":"https://pubmed.ncbi.nlm.nih.gov/12506345","citation_count":12,"is_preprint":false},{"pmid":"35595959","id":"PMC_35595959","title":"Novel Heterozygous Mutations in ZP2 Cause Abnormal Zona Pellucida and Female Infertility.","date":"2022","source":"Reproductive sciences (Thousand Oaks, Calif.)","url":"https://pubmed.ncbi.nlm.nih.gov/35595959","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":"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 research","url":"https://pubmed.ncbi.nlm.nih.gov/30611916","citation_count":10,"is_preprint":false},{"pmid":"9739427","id":"PMC_9739427","title":"Immunological identification of zona pellucida 2 (ZP2) protein in human oocytes.","date":"1998","source":"Andrologia","url":"https://pubmed.ncbi.nlm.nih.gov/9739427","citation_count":10,"is_preprint":false},{"pmid":"11389548","id":"PMC_11389548","title":"Primary structure and developmental expression of Dp ZP2, a vitelline envelope glycoprotein homolog of mouse ZP2, in Discoglossus pictus, one of the oldest living Anuran species.","date":"2001","source":"Molecular reproduction and development","url":"https://pubmed.ncbi.nlm.nih.gov/11389548","citation_count":10,"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":"37281366","id":"PMC_37281366","title":"Cooperative Activation of HoxD Homeobox Genes by Factors from the Polarizing Region and the Apical Ridge in Chick Limb Morphogenesis: (chick limb bud/HoxD homeobox genes/ZPA factor/AER factor/in situ hybridization).","date":"1993","source":"Development, growth & differentiation","url":"https://pubmed.ncbi.nlm.nih.gov/37281366","citation_count":8,"is_preprint":false},{"pmid":"33917056","id":"PMC_33917056","title":"Zona Pellucida Protein 2 (ZP2) Is Expressed in Colon Cancer and Promotes Cell Proliferation.","date":"2021","source":"Cancers","url":"https://pubmed.ncbi.nlm.nih.gov/33917056","citation_count":8,"is_preprint":false},{"pmid":"37293489","id":"PMC_37293489","title":"Identification of zona pellucida defects revealed a novel loss-of-function mutation in ZP2 in humans and rats.","date":"2023","source":"Frontiers in endocrinology","url":"https://pubmed.ncbi.nlm.nih.gov/37293489","citation_count":7,"is_preprint":false},{"pmid":"32520719","id":"PMC_32520719","title":"Mutation of rat Zp2 causes ROS-mediated oocyte apoptosis.","date":"2020","source":"Reproduction (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/32520719","citation_count":7,"is_preprint":false},{"pmid":"10976814","id":"PMC_10976814","title":"Blocking effect of antisera to recombinant zona pellucida proteins (r-ZPA) on in vitro fertilization.","date":"2000","source":"American journal of reproductive immunology (New York, N.Y. : 1989)","url":"https://pubmed.ncbi.nlm.nih.gov/10976814","citation_count":7,"is_preprint":false},{"pmid":"21266067","id":"PMC_21266067","title":"Evolutionary patterns of two major reproduction candidate genes (Zp2 and Zp3) reveal no contribution to reproductive isolation between bovine species.","date":"2011","source":"BMC evolutionary biology","url":"https://pubmed.ncbi.nlm.nih.gov/21266067","citation_count":7,"is_preprint":false},{"pmid":"14511786","id":"PMC_14511786","title":"Localization and functional importance of a conserved zona pellucida 2 protein domain in the human and bovine ovary using monoclonal anti-ZP2 peptide antibodies.","date":"2003","source":"Theriogenology","url":"https://pubmed.ncbi.nlm.nih.gov/14511786","citation_count":7,"is_preprint":false},{"pmid":"17597472","id":"PMC_17597472","title":"Identification of novel and known ovary-specific genes including ZP2, in a marsupial, the stripe-faced dunnart.","date":"2008","source":"Molecular reproduction and development","url":"https://pubmed.ncbi.nlm.nih.gov/17597472","citation_count":6,"is_preprint":false},{"pmid":"3989453","id":"PMC_3989453","title":"Experimental analysis of the role of the ZPA in the development of the wing buds of wingless (ws) mutant embryos.","date":"1985","source":"Journal of embryology and experimental morphology","url":"https://pubmed.ncbi.nlm.nih.gov/3989453","citation_count":6,"is_preprint":false},{"pmid":"37281147","id":"PMC_37281147","title":"Control of the Expression of AV-1 Protein, a Position-Specific Antigen, by ZPA (Zone of Polarizing Activity) Factor in the Chick Limb Bud: (Zone of polarizing activity/Position specific antigen/Limb pattern formation).","date":"1991","source":"Development, growth & differentiation","url":"https://pubmed.ncbi.nlm.nih.gov/37281147","citation_count":5,"is_preprint":false},{"pmid":"37736051","id":"PMC_37736051","title":"A heterozygous ZP2 mutation causes zona pellucida defects and female infertility in mouse and human.","date":"2023","source":"iScience","url":"https://pubmed.ncbi.nlm.nih.gov/37736051","citation_count":5,"is_preprint":false},{"pmid":"33065540","id":"PMC_33065540","title":"Sperm binding to ZP2-coated beads improve the efficiency of porcine in vitro fertilisation.","date":"2020","source":"Reproduction (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/33065540","citation_count":4,"is_preprint":false},{"pmid":"34869353","id":"PMC_34869353","title":"Identification and in silico Characterization of Deleterious Single Nucleotide Variations in Human ZP2 Gene.","date":"2021","source":"Frontiers in cell and developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/34869353","citation_count":3,"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":"8462741","id":"PMC_8462741","title":"Expression of AV-1, a position-specific molecule, in response to retinoic acid beads and ZPA grafts in chick limb development.","date":"1993","source":"Developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/8462741","citation_count":3,"is_preprint":false},{"pmid":"36288183","id":"PMC_36288183","title":"Prediction of the Effect of Methylation in the Promoter Region of ZP2 Gene on Egg Production in Jinghai Yellow Chickens.","date":"2022","source":"Veterinary sciences","url":"https://pubmed.ncbi.nlm.nih.gov/36288183","citation_count":2,"is_preprint":false},{"pmid":"17973629","id":"PMC_17973629","title":"Cellular origin of the Bufo arenarum sperm receptor gp75, a ZP2 family member: its proteolysis after fertilization.","date":"2008","source":"Biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/17973629","citation_count":2,"is_preprint":false},{"pmid":"35916458","id":"PMC_35916458","title":"Dietary Soybean (Glycine max (L.) Merr.) Improved the ZP2 Expression in Female Swiss Mice.","date":"2023","source":"JBRA assisted reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/35916458","citation_count":1,"is_preprint":false},{"pmid":"39443359","id":"PMC_39443359","title":"A Compound Heterozygous Pathogenic Variant in ZP2 Gene Causes Female Infertility.","date":"2024","source":"Reproductive sciences (Thousand Oaks, Calif.)","url":"https://pubmed.ncbi.nlm.nih.gov/39443359","citation_count":1,"is_preprint":false},{"pmid":"38138105","id":"PMC_38138105","title":"Complete Genome Sequence and Pan-Genome Analysis of Shewanella oncorhynchi Z-P2, a Siderophore Putrebactin-Producing Bacterium.","date":"2023","source":"Microorganisms","url":"https://pubmed.ncbi.nlm.nih.gov/38138105","citation_count":1,"is_preprint":false},{"pmid":"40964325","id":"PMC_40964325","title":"Human-specific features of the cerebellum and ZP2-regulated synapse development.","date":"2025","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/40964325","citation_count":0,"is_preprint":false},{"pmid":"41819103","id":"PMC_41819103","title":"Human-specific features of the cerebellum and ZP2-regulated synapse development.","date":"2026","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/41819103","citation_count":0,"is_preprint":false},{"pmid":"40793920","id":"PMC_40793920","title":"Rab10 regulates cortical granule translocation and ZP2 dynamics for zona pellucida function during oocyte maturation.","date":"2025","source":"Development (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/40793920","citation_count":0,"is_preprint":false},{"pmid":"40986357","id":"PMC_40986357","title":"Dual Bmp-negative feedback loops modulate function of both AER and ZPA to buffer and constrain postaxial digit number.","date":"2025","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/40986357","citation_count":0,"is_preprint":false},{"pmid":"27193969","id":"PMC_27193969","title":"The bioactivities of the central segment of Zp2 polypeptide.","date":"2016","source":"Zygote (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/27193969","citation_count":0,"is_preprint":false},{"pmid":"40673271","id":"PMC_40673271","title":"The 3' region of the ZPA regulatory sequence (ZRS) is required for activity and contains a critical E-box.","date":"2025","source":"Frontiers in cell and developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/40673271","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2024.10.11.617896","title":"Balanced polymorphisms in gamete-binding genes are not associated with human infertility","date":"2024-10-15","source":"bioRxiv","url":"https://doi.org/10.1101/2024.10.11.617896","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.07.17.665402","title":"Dual Bmp-negative feedback loops modulate both AER and ZPA function to buffer and constrain postaxial digit number","date":"2025-07-22","source":"bioRxiv","url":"https://doi.org/10.1101/2025.07.17.665402","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.03.03.641048","title":"Structural basis of ZP2-targeted immunocontraception","date":"2025-03-06","source":"bioRxiv","url":"https://doi.org/10.1101/2025.03.03.641048","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.02.01.636055","title":"The 3’ Region of the ZPA Regulatory Sequence (ZRS) is required for activity and contains a critical E-box","date":"2025-02-03","source":"bioRxiv","url":"https://doi.org/10.1101/2025.02.01.636055","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.09.01.673592","title":"Separately prestored proteasome components to prevent polyspermy","date":"2025-09-04","source":"bioRxiv","url":"https://doi.org/10.1101/2025.09.01.673592","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.04.16.648507","title":"Dorsoventral limb patterning in paired appendages emerged via regulatory repurposing of an ancestral posterior fin module","date":"2025-04-21","source":"bioRxiv","url":"https://doi.org/10.1101/2025.04.16.648507","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":46655,"output_tokens":5782,"usd":0.113348},"stage2":{"model":"claude-opus-4-6","input_tokens":9377,"output_tokens":3838,"usd":0.214253},"total_usd":0.327601,"stage1_batch_id":"msgbatch_01BparvgRZ9S2LMidvaoo86K","stage2_batch_id":"msgbatch_01NkBfv9SVZWthhS7j6mU6G3","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1990,\n      \"finding\": \"Zp-2 gene is expressed exclusively in oocytes during a narrow window of oocyte growth (the ~2-week growth phase prior to ovulation), is coordinately regulated with Zp-3, and shares conserved 5' flanking sequences with Zp-3 near their transcription start sites, suggesting shared regulatory mechanisms for oocyte-specific, developmentally restricted expression.\",\n      \"method\": \"Northern blotting, gene locus characterization, 5' flanking sequence comparison\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (Northern blot, genomic characterization) in a foundational study\",\n      \"pmids\": [\"1690843\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1984,\n      \"finding\": \"ZP2 is stably integrated into the extracellular zona pellucida matrix (demonstrated by laser photobleaching/FRAP), distributed throughout the zona in a fibrous pattern, and this distribution is maintained after fertilization at the two-cell embryo stage; ZP2 is antigenically distinct from other extracellular matrix proteins and is found exclusively in ovarian tissue.\",\n      \"method\": \"Monoclonal antibody immunofluorescence, laser photobleaching (FRAP), immunoprecipitation\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — direct localization by FRAP with functional consequence (stable matrix integration), replicated with multiple antibodies\",\n      \"pmids\": [\"6699085\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"ZP2 shares a ~260 residue domain (the ZP domain) with ZP3, betaglycan (TGF-β type III receptor), uromodulin, and GP-2, defining a family of mosaic proteins with a similar domain architecture relative to transmembrane regions, suggesting a common tertiary structure and functional similarity in recognition mechanisms.\",\n      \"method\": \"Sequence analysis/domain homology\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 4 — computational/sequence analysis only, no direct functional experiment\",\n      \"pmids\": [\"1313375\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"ZP2 is proteolytically converted to ZP2f (cleaved form) after egg activation, and this conversion can be triggered by G protein-coupled receptor signaling (via microinjected m1 muscarinic receptor + acetylcholine), with the effect blocked by atropine and GDP-βS, implicating pertussis toxin-insensitive Gq signaling in the zona modification that occurs at fertilization.\",\n      \"method\": \"mRNA microinjection, pharmacological inhibition, immunoblot for ZP2 conversion\",\n      \"journal\": \"Developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple pharmacological tools in a single lab study linking receptor signaling to ZP2 cleavage\",\n      \"pmids\": [\"1577193\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"Mouse ZP2 and ZP3 carry O-linked trisaccharide chains (structure: GlcNAc→Galβ1,3GalNAcol) and N-linked poly-N-acetyllactosaminyl glycans; removal of poly-N-acetyllactosaminyl chains reduces apparent ZP2 molecular weight by ~23 kDa, indicating these are major glycan modifications of ZP2.\",\n      \"method\": \"Endo-β-galactosidase digestion, O-glycanase treatment, mild alkali/NaB3H4 release, lectin binding, Bio-Gel P-4 sizing\",\n      \"journal\": \"Biology of reproduction\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro biochemical reconstitution with multiple orthogonal glycan analysis methods\",\n      \"pmids\": [\"7948482\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"The Xenopus sperm receptor gp69/64 (a ZP2 ortholog) binds sperm through its N-terminal region, which is proteolytically cleaved by a cortical granule protease after fertilization, removing 27 amino acids from the N-terminus and abolishing sperm binding; the isolated N-terminus-truncated receptor is inactive as a sperm binding inhibitor.\",\n      \"method\": \"Molecular cloning, protease treatment (collagenase), sperm-egg binding inhibition assay, N-terminal sequencing\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — biochemical reconstitution of cleavage, functional sperm-binding assay, multiple orthogonal methods\",\n      \"pmids\": [\"9927653\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"ZP2-null female mice produce only ZP1 and ZP3 proteins that form a thin, unsustained zona matrix; this leads to decreased antral follicle numbers, failure of egg recovery after gonadotropin stimulation, and absence of two-cell embryos after mating, establishing ZP2 as essential for structural integrity of the zona pellucida, folliculogenesis, and in vivo fertilization.\",\n      \"method\": \"Targeted gene disruption (knockout mice), histological analysis, immunofluorescence, embryo recovery\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean knockout with specific phenotypic readout across multiple assays, foundational study\",\n      \"pmids\": [\"11245577\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Mouse ZP2 (mZP2) binds to proacrosin/acrosin on acrosome-reacted sperm via a strong ionic interaction between polysulphate groups on mZP2 and basic residues on an internal proacrosin peptide, mediating secondary sperm binding; this interaction is disrupted by suramin (a polysulphonated compound) and is reduced in proacrosin-null sperm.\",\n      \"method\": \"Solid-phase binding assay with proacrosin-null sperm (genetic), competitive binding with sulphated polymers/suramin, in vitro fertilization displacement assay\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic (proacrosin KO sperm), biochemical, and functional (IVF) approaches in combination\",\n      \"pmids\": [\"11739644\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Mouse acrosomal cortical matrix protein MC41 binds ZP2 and ZP2f (the cleaved form) via far-Western blotting and forms a complex with a 75-kDa serine protease under low-salt conditions, suggesting MC41 participates in secondary sperm-zona binding during acrosomal reaction.\",\n      \"method\": \"Far-Western blotting, co-immunoprecipitation, immunogold electron microscopy\",\n      \"journal\": \"Developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — single lab, far-Western and co-IP without full reconstitution\",\n      \"pmids\": [\"11784014\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"ZP2 subcellular distribution during folliculogenesis shows association with the Golgi apparatus, secretory granules, and vesicular aggregates (multivesicular aggregates) in oocytes, with all three ZP glycoproteins distributed throughout the zona pellucida in close association in asymmetric patches.\",\n      \"method\": \"Immunoelectron microscopy with protein A-gold, double and triple immunolocalization\",\n      \"journal\": \"Biology of reproduction\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct subcellular localization by electron microscopy, single lab\",\n      \"pmids\": [\"11906903\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"ZP2 and ZP3 traffic independently through oocytes prior to zona assembly: they colocalize in the ER and multivesicular aggregates but do not physically interact intracellularly (undetectable by co-immunoprecipitation); ZP3 lacking all N-glycosylation sites is still incorporated into the zona matrix, indicating N-glycosylation is not required for ZP3 trafficking or incorporation.\",\n      \"method\": \"Coimmunoprecipitation, fluorescence microscopy (GFP-tagged proteins), transgenic mice expressing N-glycosylation mutant ZP3\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal approaches (Co-IP, live imaging, transgenic mice) in one study\",\n      \"pmids\": [\"17047254\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"The short cytoplasmic tails (9–15 residues) of ZP2 and ZP3 are necessary and sufficient to prevent intracellular oligomerization while ensuring incorporation into the zona pellucida; without these tails, ZP2 and ZP3 interact within the cell and fail to be incorporated into the zona matrix.\",\n      \"method\": \"Fluorescent protein complementation (bimolecular fluorescence complementation) in CHO cells and growing oocytes, deletion mutants, heterologous GPI-anchored fusion constructs\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal experimental systems (CHO cells, oocytes, heterologous constructs) with mutagenesis\",\n      \"pmids\": [\"21378311\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Ovastacin (encoded by Astl), an astacin metalloendoprotease stored in egg cortical granules, directly cleaves ZP2 in the zona pellucida after fertilization; recombinant ovastacin cleaves ZP2 in native zonae, Astl-null mice fail to cleave ZP2 post-fertilization, and sperm bind equally well to Astl-null two-cell embryos as to unfertilized eggs, establishing ovastacin-mediated ZP2 cleavage as the post-fertilization block to sperm binding.\",\n      \"method\": \"In vitro cleavage assay with recombinant ovastacin, knockout mouse model (Astl-null), sperm binding assay, immunofluorescence for cortical granule localization\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstitution in vitro + KO mouse with specific phenotypic readout, replicated across methods\",\n      \"pmids\": [\"22472438\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"A restricted N-terminal domain of ZP2 (residues 51–149) is necessary and sufficient for sperm-zona recognition in both mouse and human; transgenic mice expressing human ZP4 without mouse or human ZP2 are sterile, and transgenic mice with ZP2 lacking residues 51–149 show no sperm binding, establishing ZP2(51-149) as the essential sperm-binding domain.\",\n      \"method\": \"Transgenic mouse models with chimeric/truncated ZP2, sperm binding assays, recombinant peptide bead assays\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple transgenic lines with domain-deletion approach plus functional sperm binding assay\",\n      \"pmids\": [\"24934154\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"A unique 7 amino acid motif near the N-terminus of ovastacin is necessary and sufficient for its cortical granule localization; deletion of this motif (AstlΔ) by CRISPR/Cas9 causes ovastacin to accumulate in the endomembrane system, leading to premature ZP2 cleavage, poor sperm binding to the zona, and sub-fertility in female mice.\",\n      \"method\": \"CRISPR/Cas9 deletion at endogenous Astl locus, deletion mutant analysis in oocytes, sperm binding assay, fertility testing\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — precise genetic manipulation (CRISPR KI) with direct functional readouts (sperm binding, fertility)\",\n      \"pmids\": [\"28114310\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Heterozygous mutations in ZP2 (and ZP3) have dosage effects: mouse models with single heterozygous ZP2 mutation show approximately half-normal ZP thickness, and the corresponding mutant precursor proteins cannot anchor to oocyte membranes, revealing a haploinsufficiency mechanism for ZP defects.\",\n      \"method\": \"CRISPR/Cas9 knock-in mouse models, ZP thickness measurement, immunostaining for membrane anchoring\",\n      \"journal\": \"Human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — CRISPR mouse models with functional cellular readout, single lab\",\n      \"pmids\": [\"28646452\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Loss-of-function pathogenic variants in ZP2 (splice site c.1695-2A>G and frameshift c.1691_1694dup) produce truncated proteins that are intracellularly sequestered and prematurely interact with other ZP proteins in CHO cells, resulting in a structurally abnormal zona pellucida lacking ZP2 protein and causing fertilization failure.\",\n      \"method\": \"Exome sequencing, CHO-K1 cell expression of mutant constructs, immunostaining of patient oocytes, Western blot\",\n      \"journal\": \"Genetics in medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — functional cell-based assay with patient oocyte immunostaining, single lab\",\n      \"pmids\": [\"29895852\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"A frameshift variant in ZP2 (c.1235_1236del, p.Q412Rfs*17) produces a truncated protein at reduced levels and reduces the interaction between ZP2 and ZP3 as demonstrated by co-immunoprecipitation, suggesting that ZP2-ZP3 dimer assembly is required for normal zona pellucida formation.\",\n      \"method\": \"CHO cell expression, immunoblot, immunofluorescence in mouse oocytes, co-immunoprecipitation\",\n      \"journal\": \"Journal of assisted reproduction and genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — co-IP in heterologous cells, single lab\",\n      \"pmids\": [\"33604805\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"A ZP2 missense variant (p.Leu474Pro) reduces secretion of ZP2 protein into culture medium and reduces the ZP2-ZP3 interaction as shown by co-immunoprecipitation in CHO cells; a second variant (p.Cys620Tyr) reduces total protein expression and alters a disulfide bond predicted to affect ZP2 structure.\",\n      \"method\": \"CHO cell transfection, Western blot of secreted vs. intracellular protein, co-immunoprecipitation, 3D protein structure prediction\",\n      \"journal\": \"Reproductive sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — co-IP and secretion assay in heterologous cells, single lab\",\n      \"pmids\": [\"35595959\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"A heterozygous ZP2 variant (p.R642Q) associated with empty follicle syndrome causes ZP2 protein accumulation in the oocyte cytoplasm rather than secretion, implicating defective furin-mediated cleavage (a post-translational modification) in ZP2 processing and secretion necessary for zona pellucida formation.\",\n      \"method\": \"CRISPR-Cas9 knock-in mouse model, RNA-sequencing, immunofluorescence in oocytes\",\n      \"journal\": \"Human reproduction\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — CRISPR KI mouse recapitulating human phenotype, single lab\",\n      \"pmids\": [\"35211729\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Cleavage of the N-terminal region (NTR) of ZP2 by ovastacin after fertilization triggers oligomerization of the cleaved ZP2 NTRs, which extensively cross-links zona pellucida filaments to rigidify the egg coat and make it physically impenetrable to sperm; structural studies of native egg coat filaments reveal that ZP2 (type II subunit) forms a left-handed double helix with ZP3 (type I subunit) with ZP2 NTRs protruding outward.\",\n      \"method\": \"Biochemical cleavage assay, cryo-EM/X-ray structural analysis of native vertebrate egg coat filaments, AlphaFold modeling of human ZP polymers\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — structural determination of native filaments combined with biochemical reconstitution of cleavage-triggered oligomerization\",\n      \"pmids\": [\"38490181\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"ZP2 expression in human cerebellar granule cells is induced by pontine mossy fibers and reduces synaptic proteins at pontocerebellar glomerular synapses, decreasing cerebellar neuron electrophysiological activity, revealing a human-specific co-option of ZP2 in synapse regulation in the brain.\",\n      \"method\": \"Single-nucleus transcriptomics/chromatin accessibility profiling across primates, experimental induction assays, synaptic protein quantification, electrophysiology\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multi-species transcriptomic profiling with experimental validation of synaptic and electrophysiological effects, single study\",\n      \"pmids\": [\"41819103\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"GTPase Rab10 accumulates at the mouse and porcine oocyte cortex, modulates the RhoA pathway to control actin dynamics, and regulates cortical granule transport via the myosin Va complex; overexpression of GDP-bound (dominant-negative) Rab10 leads to ZP2 downregulation and accumulation at the cortex, implicating a Rab10-ZP2 complex in ZP2 supply for the zona pellucida reaction.\",\n      \"method\": \"Rab10 overexpression/dominant-negative in mouse and porcine oocytes, immunofluorescence, RhoA pathway analysis, myosin Va expression analysis\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — functional perturbation in two species with pathway analysis, single study\",\n      \"pmids\": [\"40793920\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Testis-specific 20S proteasome core particles pre-stored in sperm heads assemble with oocyte-derived 19S regulatory particles upon fertilization, forming chimeric proteasomes that degrade Fetuin B (ubiquitinated by E3 ligase MARCH3), which triggers ZP2 cleavage and zona pellucida hardening to block polyspermy.\",\n      \"method\": \"Biochemical reconstitution of chimeric proteasomes, ubiquitination assay, genetic KO of components, ZP2 cleavage assay\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 — biochemical reconstitution plus genetic KO, but preprint not yet peer-reviewed\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"The structural basis of ZP2 immunocontraception was determined: an IE-3 antibody-derived scFv binds ZP2 via induced fit of the epitope and is sufficient to block fertilization in vitro, providing atomic-level insight into the ZP2 sperm-binding surface.\",\n      \"method\": \"Structural determination (X-ray crystallography of scFv-ZP2 complex), in vitro fertilization blocking assay\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 — structural determination with functional validation, but preprint\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"ZP2 is an oocyte-specific zona pellucida glycoprotein that traffics independently through the endomembrane system (controlled by its cytoplasmic tail to prevent premature oligomerization), is secreted and incorporated into the zona pellucida filament as a type II subunit forming a left-handed double helix with ZP3, presents an N-terminal domain (residues 51–149) as the essential sperm-binding site for gamete recognition, and after fertilization is proteolytically cleaved by ovastacin (secreted from cortical granules) triggering ZP2 NTR oligomerization that cross-links filaments to harden the zona pellucida and block polyspermy.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"ZP2 is an oocyte-specific glycoprotein that serves as the principal sperm-binding component and structural backbone of the zona pellucida, the extracellular coat essential for fertilization and polyspermy block. ZP2 is expressed exclusively during oocyte growth, traffics independently of ZP3 through the endomembrane system with its short cytoplasmic tail preventing premature intracellular oligomerization, and is secreted to assemble with ZP3 into a left-handed double-helical filament in which ZP2 functions as the type II subunit [PMID:1690843, PMID:21378311, PMID:38490181]. An N-terminal domain encompassing residues 51–149 is necessary and sufficient for sperm recognition; after fertilization, the cortical granule metalloendoprotease ovastacin cleaves ZP2, triggering oligomerization of the released N-terminal regions that cross-link filaments, harden the zona, and block polyspermy [PMID:24934154, PMID:22472438, PMID:38490181]. Loss-of-function mutations in human ZP2—including frameshift, splice-site, and missense variants—cause defective ZP2 secretion or ZP2–ZP3 assembly, producing structurally abnormal zonae and female infertility [PMID:29895852, PMID:33604805, PMID:35211729].\",\n  \"teleology\": [\n    {\n      \"year\": 1984,\n      \"claim\": \"The first question was whether ZP2 forms a stable structural component of the zona pellucida; FRAP and immunofluorescence demonstrated that ZP2 is stably integrated in a fibrous pattern and is restricted to ovarian tissue, establishing it as a bona fide zona matrix protein.\",\n      \"evidence\": \"Monoclonal antibody immunofluorescence and laser photobleaching (FRAP) on mouse oocytes and embryos\",\n      \"pmids\": [\"6699085\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular partners within the fibrous matrix were unknown\", \"Mechanism of matrix assembly from individual glycoproteins was unresolved\"]\n    },\n    {\n      \"year\": 1990,\n      \"claim\": \"It was unclear how ZP2 expression is regulated; Northern blotting and promoter analysis showed oocyte-exclusive expression during a ~2-week growth phase, coordinately regulated with ZP3 through shared 5′ flanking elements.\",\n      \"evidence\": \"Northern blotting and 5′ flanking sequence comparison in mouse\",\n      \"pmids\": [\"1690843\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Transcription factors driving oocyte-specific expression were not identified\", \"Post-transcriptional regulation was not assessed\"]\n    },\n    {\n      \"year\": 1992,\n      \"claim\": \"The post-fertilization modification of ZP2 was linked to intracellular signaling when egg activation via Gq-coupled receptor signaling was shown to trigger ZP2-to-ZP2f conversion, implicating regulated exocytosis in the block to polyspermy.\",\n      \"evidence\": \"Microinjection of m1 muscarinic receptor mRNA into oocytes with pharmacological inhibitors (atropine, GDP-βS), immunoblot for ZP2 cleavage\",\n      \"pmids\": [\"1577193\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"The protease responsible for ZP2 cleavage was not identified\", \"Whether Gq signaling acts through cortical granule exocytosis was not directly demonstrated\"]\n    },\n    {\n      \"year\": 1994,\n      \"claim\": \"The biochemical nature of ZP2 glycosylation was resolved: ZP2 carries O-linked trisaccharides and N-linked poly-N-acetyllactosaminyl glycans that account for ~23 kDa of its apparent molecular weight.\",\n      \"evidence\": \"Endo-β-galactosidase digestion, O-glycanase treatment, lectin binding, gel filtration on mouse zona pellucida\",\n      \"pmids\": [\"7948482\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional roles of specific glycan chains in sperm binding or zona assembly were not determined\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"A key question was which region of ZP2 mediates sperm binding; work on the Xenopus ZP2 orthologue gp69/64 showed that the N-terminal region is required for sperm binding and is proteolytically removed after fertilization, providing the first direct evidence that ZP2 cleavage abolishes sperm recognition.\",\n      \"evidence\": \"Molecular cloning, protease treatment, sperm-binding inhibition assay, and N-terminal sequencing in Xenopus\",\n      \"pmids\": [\"9927653\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether the mammalian ZP2 N-terminus functions identically was not tested\", \"Identity of the endogenous protease was still unknown\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"ZP2-null mice revealed that ZP2 is essential for zona integrity, folliculogenesis, and in vivo fertilization, settling the question of whether ZP1 and ZP3 alone can sustain a functional zona.\",\n      \"evidence\": \"Targeted gene disruption (knockout mice) with histological analysis, immunofluorescence, and embryo recovery\",\n      \"pmids\": [\"11245577\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The molecular basis for the thin, unstable zona in ZP2 knockouts was not resolved\", \"Whether ZP2 has functions beyond structural support was open\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"ZP2 was shown to mediate secondary sperm binding through interaction with proacrosin/acrosin on acrosome-reacted sperm via ionic contacts between polysulphate groups on ZP2 and basic residues on proacrosin.\",\n      \"evidence\": \"Solid-phase binding assay with proacrosin-null sperm, competitive binding with suramin, IVF displacement assay\",\n      \"pmids\": [\"11739644\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether proacrosin interaction is the sole secondary binding mechanism was unclear\", \"Structural details of the ZP2–proacrosin interface were not resolved\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"A critical cell-biological question—whether ZP2 and ZP3 interact intracellularly before secretion—was answered negatively: the two proteins traffic independently through the ER and multivesicular aggregates, indicating that filament assembly occurs only after secretion.\",\n      \"evidence\": \"Co-immunoprecipitation, GFP-tagged fluorescence microscopy, and transgenic mice expressing N-glycosylation mutant ZP3\",\n      \"pmids\": [\"17047254\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The extracellular trigger or site for ZP2–ZP3 assembly was not identified\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"The mechanism preventing premature oligomerization was identified: the short cytoplasmic tails of ZP2 and ZP3 (9–15 residues) are necessary and sufficient to block intracellular interaction, and their removal causes premature assembly and failure of zona incorporation.\",\n      \"evidence\": \"Bimolecular fluorescence complementation in CHO cells and growing oocytes with deletion and GPI-anchor fusion constructs\",\n      \"pmids\": [\"21378311\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How the cytoplasmic tail mechanistically prevents ZP domain interaction in the secretory pathway was not determined\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"The identity of the post-fertilization ZP2 protease was established: ovastacin (Astl), an astacin metalloendoprotease stored in cortical granules, directly cleaves ZP2, and Astl-null mice fail to cleave ZP2 and fail to block polyspermy.\",\n      \"evidence\": \"In vitro cleavage with recombinant ovastacin, Astl-null knockout mice, sperm binding assay\",\n      \"pmids\": [\"22472438\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The cleavage site on mammalian ZP2 was not precisely mapped\", \"Upstream regulation of ovastacin activation after cortical granule exocytosis was not fully resolved\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"The minimal sperm-binding domain of mammalian ZP2 was mapped to residues 51–149 at the N-terminus, resolving whether ZP2 or ZP3 is the primary sperm receptor in mammals.\",\n      \"evidence\": \"Transgenic mice with chimeric/truncated ZP2, sperm binding assays, recombinant peptide bead assays\",\n      \"pmids\": [\"24934154\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The sperm-side receptor for ZP2(51-149) was not identified\", \"Atomic structure of the binding interface was not available\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Two regulatory mechanisms were clarified: ovastacin cortical granule targeting depends on a 7-amino-acid N-terminal motif (its deletion causes premature ZP2 cleavage and sub-fertility), and heterozygous ZP2 mutations cause haploinsufficiency with reduced zona thickness.\",\n      \"evidence\": \"CRISPR/Cas9 knock-in mice for Astl motif deletion and ZP2 heterozygous mutations, sperm binding and zona thickness assays\",\n      \"pmids\": [\"28114310\", \"28646452\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The vesicular sorting machinery recognizing the ovastacin targeting motif was not identified\", \"Whether haploinsufficiency explains all human heterozygous ZP2 infertility cases was not tested\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Human pathogenic ZP2 variants were functionally validated: truncating mutations cause intracellular sequestration, premature interaction with other ZP proteins, and absence of ZP2 from the zona, directly linking ZP2 loss-of-function to human female infertility.\",\n      \"evidence\": \"Exome sequencing of infertile patients, CHO-K1 cell expression of mutant constructs, patient oocyte immunostaining\",\n      \"pmids\": [\"29895852\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Rescue experiments in human oocytes were not performed\", \"Genotype–phenotype correlations across a larger patient cohort were not established\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Additional human ZP2 variants (missense and splice-affecting) were shown to impair ZP2 secretion and ZP2–ZP3 interaction, expanding the molecular mechanisms of ZP2-related infertility to include defective furin-mediated processing and disrupted dimer assembly.\",\n      \"evidence\": \"CHO cell co-immunoprecipitation, Western blot of secreted vs. intracellular protein, CRISPR knock-in mouse for R642Q variant\",\n      \"pmids\": [\"35595959\", \"35211729\", \"33604805\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether furin cleavage is strictly required for all ZP2 secretion or is variant-specific was not resolved\", \"Structural consequences of individual missense mutations were predicted, not experimentally determined\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"The structural basis of zona hardening was solved: cryo-EM of native egg coat filaments revealed ZP2 and ZP3 form a left-handed double helix, and ovastacin cleavage of ZP2 triggers NTR oligomerization that cross-links filaments, physically blocking sperm penetration.\",\n      \"evidence\": \"Cryo-EM and X-ray structural analysis of native vertebrate egg coat filaments, biochemical cleavage-induced oligomerization assay, AlphaFold modeling\",\n      \"pmids\": [\"38490181\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"High-resolution structure of the full mammalian ZP2–ZP3 filament was not yet available\", \"How NTR oligomerization is oriented relative to filament packing in vivo was modeled but not directly visualized\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"ZP2 was found to have a human-specific non-reproductive function: expression in cerebellar granule cells, induced by pontine mossy fibers, reduces synaptic protein levels and dampens electrophysiological activity, revealing co-option of an oocyte gene for brain synapse regulation.\",\n      \"evidence\": \"Single-nucleus transcriptomics/chromatin accessibility across primates, experimental induction in human cerebellar neurons, synaptic protein quantification, electrophysiology\",\n      \"pmids\": [\"41819103\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"The molecular mechanism by which secreted ZP2 modulates synaptic proteins is unknown\", \"Whether ZP2 polymerizes or signals through a receptor at synapses is unstudied\", \"Relevance to cerebellar function or disease in vivo has not been tested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The sperm-side receptor that directly engages ZP2 residues 51–149 remains unidentified, and the precise atomic structure of the mammalian ZP2–sperm ligand interface has not been determined at sufficient resolution for therapeutic design.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No sperm receptor for ZP2(51-149) has been identified\", \"High-resolution structure of the human ZP2–ZP3 filament in situ is lacking\", \"The mechanism of ZP2-mediated synapse regulation in human cerebellum is completely uncharacterized\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [1, 6, 20]},\n      {\"term_id\": \"GO:0098631\", \"supporting_discovery_ids\": [5, 7, 13]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [1, 6, 20]},\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [9, 10]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [9, 10, 12]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1474165\", \"supporting_discovery_ids\": [6, 12, 13, 20]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [10, 11, 19]}\n    ],\n    \"complexes\": [\n      \"ZP2-ZP3 zona pellucida filament\"\n    ],\n    \"partners\": [\n      \"ZP3\",\n      \"ZP1\",\n      \"ASTL\",\n      \"ACR\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}