{"gene":"SPAM1","run_date":"2026-06-10T07:46:38","timeline":{"discoveries":[{"year":1985,"finding":"The PH-20 surface antigen on guinea pig sperm posterior head plasma membrane has a required function in sperm binding to the egg zona pellucida; monoclonal antibody PH-20 MAb inhibited sperm-zona binding ~90%, establishing PH-20 as essential for zona adhesion.","method":"Monoclonal antibody inhibition of sperm-zona binding assay; competitive binding with 125I-labeled MAbs","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple inhibitory antibodies with dose-response, competitive binding assays, replicated across labs in subsequent work","pmids":["4066757"],"is_preprint":false},{"year":1986,"finding":"After the acrosome reaction (exocytosis), the intracellular PH-20 population on the inner acrosomal membrane (IAM) is inserted into the plasma membrane, producing an ~3-fold increase in surface PH-20 antigen; this reveals a mechanism for rapid upregulation of a sperm surface protein via exocytosis.","method":"Indirect immunofluorescence; quantification of antigenic sites before and after acrosome reaction; permeabilization of acrosome-intact sperm","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct quantification of surface sites pre/post acrosome reaction, replicated in multiple species","pmids":["3771636"],"is_preprint":false},{"year":1987,"finding":"PH-20 protein reaches the sperm plasma membrane via two transport pathways during spermiogenesis: first inserted into the acrosomal membrane, then separately into the plasma membrane; both populations are initially uniformly distributed and later become restricted to specific domains, indicating localization occurs post-insertion rather than by intracellular sorting.","method":"Developmental immunofluorescence localization during spermiogenesis; SDS-PAGE of testicular cell extracts","journal":"Developmental biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct imaging of spermatogenic stages, single lab, two orthogonal methods","pmids":["3305112"],"is_preprint":false},{"year":1987,"finding":"PH-20 on the posterior head plasma membrane of acrosome-intact sperm is mobile (D = 1.8×10⁻¹⁰ cm²/s) but restricted ~50-fold relative to lipid; after migration to the IAM of acrosome-reacted sperm it diffuses freely (D = 4.9×10⁻⁹ cm²/s, similar to lipid), supporting a barrier-to-diffusion model for domain maintenance.","method":"Fluorescence redistribution after photobleaching (FRAP) on individual sperm","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — quantitative FRAP comparing multiple membrane domains, replicated with lipid probes as controls","pmids":["3558486"],"is_preprint":false},{"year":1988,"finding":"PH-20 is anchored in the sperm plasma membrane via a glycosylphosphatidylinositol (GPI/phosphatidylinositol lipid) anchor, and its lateral diffusion rate is >1000-fold slower than lipid diffusion, indicating that ectodomain interactions constrain mobility of a GPI-anchored protein.","method":"Phosphatidylinositol-specific phospholipase C (PI-PLC) cleavage; FRAP measurement of diffusion rates","journal":"Science","confidence":"High","confidence_rationale":"Tier 1 / Strong — PI-PLC release plus FRAP, orthogonal methods, widely replicated","pmids":["3381102"],"is_preprint":false},{"year":1988,"finding":"PH-20 purified from guinea pig sperm by monoclonal antibody affinity chromatography exists in three forms: 64 kDa, 56 kDa, and an endoproteolytically cleaved form of two disulfide-linked fragments (~41–48 kDa and ~27 kDa), indicating site-specific endoproteolysis occurs in sperm preparations.","method":"Monoclonal antibody affinity purification; SDS-PAGE; Cleveland digest analysis","journal":"Biology of reproduction","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — purified protein biochemistry, single lab, multiple gel analyses","pmids":["3042032"],"is_preprint":false},{"year":1990,"finding":"cDNA cloning of guinea pig PH-20 revealed a novel protein of 468 amino acids with six N-linked glycosylation sites, twelve cysteines (eight clustered near the C-terminus), encoded by a single gene with a single ~2.2 kb mRNA; Southern blots confirmed a single gene and conservation across multiple mammalian species.","method":"cDNA cloning, sequencing; Southern blot; Northern blot","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — full-length cDNA sequence with structural characterization, foundational molecular paper","pmids":["2269661"],"is_preprint":false},{"year":1991,"finding":"PH-20 protein migration from the posterior head plasma membrane to the inner acrosomal membrane after the acrosome reaction occurs against a concentration gradient and is calcium-dependent, arguing against passive diffusion–trapping and in favor of an active translocation mechanism.","method":"Fluorescence microscopy with digital image processing of individual sperm; calcium manipulation","journal":"Developmental biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — quantitative imaging showing directional movement against gradient, calcium dependency, single lab","pmids":["1995397"],"is_preprint":false},{"year":1993,"finding":"Human PH-20 protein expressed in RK13 cells using a vaccinia virus system has hyaluronidase activity; PI-PLC treatment releases the enzyme from the cell surface with a large increase in activity, confirming the GPI anchor and hyaluronidase function of human PH-20.","method":"Vaccinia virus expression; hyaluronidase activity assay; PI-PLC release","journal":"FEBS letters","confidence":"High","confidence_rationale":"Tier 1 / Strong — recombinant expression with enzymatic assay and PI-PLC validation, replicated in multiple species","pmids":["8282124"],"is_preprint":false},{"year":1993,"finding":"Human and cynomolgus monkey PH-20 cDNAs were isolated; human PH-20 encodes 509 residues, is 59% identical to guinea pig PH-20, and its mRNA is strictly testis-specific (single 2.4 kb transcript) with a single gene in the human genome.","method":"cDNA cloning; Southern blot; Northern blot of 16 human tissues","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct sequencing and blotting, foundational cloning paper","pmids":["8234258"],"is_preprint":false},{"year":1994,"finding":"Sperm plasma membrane protein PH-20 has hyaluronidase activity enabling acrosome-intact sperm to penetrate the cumulus cell layer; purified recombinant PH-20 disperses cumulus cells from mouse eggs, and anti-PH-20 antibodies prevent acrosome-intact sperm from passing through the cumulus to reach the zona pellucida.","method":"In vitro cumulus penetration assay; treatment with purified recombinant PH-20; antibody-blocking experiments","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstitution with recombinant protein plus antibody blocking, replicated across species","pmids":["8195297"],"is_preprint":false},{"year":1995,"finding":"Human SPAM1 gene maps to chromosome 7q31, is encoded by at least 4 exons spanning ~11 kb of genomic DNA, and expression as a 2.4 kb transcript is strictly limited to testis in a panel of 16 human tissues.","method":"FISH; somatic cell hybrid PCR; Northern blot; genomic Southern blot","journal":"Genomics","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple independent mapping methods, expression in 16 tissues","pmids":["8575780"],"is_preprint":false},{"year":1996,"finding":"PH-20 is bifunctional: it has a hyaluronidase activity required for cumulus penetration and a separate, distinct activity required for secondary sperm-zona binding. Anti-PH-20 MAb that blocks zona binding (90%) has no effect on hyaluronidase activity; apigenin blocks hyaluronidase 93% without inhibiting zona binding; pretreatment of oocytes with hyaluronidase to remove zona HA does not affect secondary zona binding.","method":"Antibody inhibition assays; apigenin (hyaluronidase inhibitor) assays; zona pretreatment with hyaluronidase; sperm-zona binding assays","journal":"Biology of reproduction","confidence":"High","confidence_rationale":"Tier 1 / Strong — multiple orthogonal inhibitors dissecting two activities, robust controls in single study","pmids":["8793062"],"is_preprint":false},{"year":1996,"finding":"The soluble hyaluronidase released from guinea pig sperm at the acrosome reaction is a soluble form of PH-20 (sPH-20): anti-PH-20 antiserum recognizes it by immunoblot, completely inhibits its enzymatic activity, and 97% is removed by anti-PH-20 affinity chromatography; sPH-20 is not endoproteolytically cleaved unlike membrane PH-20, suggesting enzymatic release from its GPI anchor.","method":"Immunoblot; immunoaffinity chromatography; enzyme activity inhibition; anti-PH-20 antiserum","journal":"Biology of reproduction","confidence":"High","confidence_rationale":"Tier 1 / Strong — affinity purification plus activity inhibition, multiple orthogonal methods in one study","pmids":["8724363"],"is_preprint":false},{"year":1996,"finding":"Cynomolgus macaque sperm PH-20 exists as a 64 kDa form on the plasma and inner acrosomal membranes and a 53 kDa form released during acrosome reaction; the 64 kDa form has predominantly neutral pH hyaluronidase activity while the 53 kDa form has acid-active hyaluronidase activity; apigenin inhibits both.","method":"Western blot; HA substrate gel electrophoresis; ELISA hyaluronidase assay; Fab-immunolocalization; ultrastructure","journal":"Developmental biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — multiple biochemical methods, direct localization and activity assays on purified forms","pmids":["8608861"],"is_preprint":false},{"year":1997,"finding":"The soluble 60 kDa hyaluronidase from bovine testes is a fragment of the membrane-bound PH-20 enzyme; peptide sequencing of 44 fragments from the purified 60 kDa protein aligned to the PH-20 cDNA sequence; it lacks the signal peptide and 56 C-terminal amino acids including the GPI-anchor site.","method":"cDNA cloning; protein purification; protease/cyanogen bromide digestion with peptide sequencing","journal":"FEBS letters","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct peptide sequencing of purified protein mapped to cDNA, orthogonal identification","pmids":["9280317"],"is_preprint":false},{"year":1997,"finding":"PH-20 N-terminal domain contains the hyaluronidase activity (based on homology with bee venom hyaluronidase and functional data); it is GPI-anchored; its dual roles in cumulus penetration (plasma membrane form, neutral pH activity) and secondary zona binding (inner acrosomal membrane form, post-acrosome reaction) are biochemically distinct.","method":"Synthesis of review of functional data; domain analysis from cDNA sequence; functional assays cited","journal":"Biology of reproduction","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — synthesis paper consolidating functional experiments, no new primary data","pmids":["9116127"],"is_preprint":false},{"year":1997,"finding":"In male guinea pigs immunized with PH-20, infertility is associated with emptying of the cauda epididymis (no normal sperm) and induction of experimental autoimmune orchitis (EAO); this is the first demonstration that a purified sperm molecule of known function can induce EAO.","method":"Immunization; histopathology; antibody titer measurement; immunofluorescence of germ cells","journal":"Biology of reproduction","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo immunopathology with defined antigen, single lab","pmids":["9160711"],"is_preprint":false},{"year":1998,"finding":"Hyaluronic acid (HA) interacts with PH-20 on human sperm to increase basal intracellular calcium and potentiate the acrosome reaction induced by progesterone or zona pellucida; blocking PH-20 with anti-PH-20 Fab abolished the HA-mediated Ca²⁺ increase and enhancement of acrosome reactions.","method":"Acrosome reaction assay; intracellular calcium measurement; Fab fragment blocking of PH-20","journal":"Zygote","confidence":"High","confidence_rationale":"Tier 2 / Strong — Fab blocking with Ca²⁺ measurement and functional acrosome reaction readout, replicated in macaque by independent lab","pmids":["9770775"],"is_preprint":false},{"year":1999,"finding":"Murine Spam1 (PH-20) gene promoter contains a CRE (cAMP-responsive element) at position -57 that binds CREM in testicular nuclear extracts; in vitro transcription assays show CRE is necessary for promoter activity; Spam1 transcripts are absent in CREM-knockout mice, establishing CREM as a transcriptional regulator of Spam1.","method":"Gel mobility shift assay; in vitro transcription; Northern blot of CREM-KO mice; primer extension","journal":"Molecular reproduction and development","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro transcription, CREM-KO genetic validation, and EMSA, multiple orthogonal methods","pmids":["10423292"],"is_preprint":false},{"year":1999,"finding":"Biochemical maturation of Spam1 during epididymal transit involves N-linked oligosaccharide modification: caput sperm have a larger ~74 kDa form with lower hyaluronidase activity, while caudal sperm have a ~67 kDa form with 4.3-fold higher activity; enzymatic deglycosylation of both reduces to ~56 kDa backbone, and all four N-glycosylation sites are functional.","method":"Immunofluorescence; Western blot; enzymatic deglycosylation; hyaluronidase activity assay","journal":"Molecular reproduction and development","confidence":"High","confidence_rationale":"Tier 1 / Strong — deglycosylation experiments with activity assays, multiple methods, direct biochemical mechanism","pmids":["9890751"],"is_preprint":false},{"year":1999,"finding":"HA increases intracellular Ca²⁺ in macaque sperm through plasma membrane PH-20; anti-PH-20 Fab fragments inhibit the Ca²⁺ increase induced by HA, HA gels, and cumulus masses; FITC-HA binding to sperm is localized over the acrosome (PH-20 location) and is inhibited by anti-PH-20 Fab. PH-20 aggregation (by bivalent antibody or zona pellucida binding) is associated with increased Ca²⁺ and acrosome reaction.","method":"Fluorometry with Fluo-3 Ca²⁺ indicator; Fab fragment blocking; FITC-HA binding; video imaging; TEM","journal":"Zygote","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Fab blocking and Ca²⁺ measurement, multiple readouts, replicated across macaque and human","pmids":["10533704"],"is_preprint":false},{"year":1999,"finding":"PH-20 (but not acrosin) is required for secondary sperm-zona binding and zona penetration in macaque; anti-PH-20 IgG completely blocked zona penetration while anti-acrosin and anti-CD46 IgG had no effect; PH-20 is present on the inner acrosomal membrane of zona-bound acrosome-reacted sperm whereas acrosin is not.","method":"Immunolocalization by TEM; sperm-zona penetration assay with blocking antibodies (up to 300 µg/ml)","journal":"Molecular reproduction and development","confidence":"High","confidence_rationale":"Tier 2 / Strong — function-blocking antibody with TEM ultrastructural localization, appropriate negative controls (anti-acrosin, anti-CD46)","pmids":["10369396"],"is_preprint":false},{"year":2001,"finding":"A region of macaque PH-20 (Peptide 2, aa 205-235) functions as a HA-binding domain separate from the catalytic hyaluronidase domain; recombinant PH-20 protein lacking this region (E12) does not bind HA, while the full N-terminal construct (G3) binds biotinylated HA; anti-Peptide 2 Fab inhibits HA-induced Ca²⁺ increase in sperm, linking this domain to cell signaling.","method":"Recombinant protein binding assay; photoaffinity HA crosslinking; microplate HA binding assay; Fab inhibition of intracellular Ca²⁺","journal":"Molecular reproduction and development","confidence":"High","confidence_rationale":"Tier 1 / Strong — domain deletion approach with direct binding assay and functional Ca²⁺ readout, single study with multiple orthogonal methods","pmids":["11746965"],"is_preprint":false},{"year":2001,"finding":"PH-20 plasma membrane form mediates HA-induced intracellular signaling via a HA-binding domain distinct from hyaluronidase domains; signaling involves Ca²⁺ increase and aggregation of GPI-anchored PH-20 in the plasma membrane; a 92-kDa protein may be the cytoplasmic signaling molecule linked to PH-20.","method":"Review and synthesis of functional data; signaling assays; antibody-induced PH-20 aggregation; calcium measurements","journal":"Matrix biology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — review paper consolidating data; 92-kDa partner is proposed but not directly identified by Co-IP in this paper","pmids":["11731269"],"is_preprint":false},{"year":2001,"finding":"Despite absence of PH-20 in Spam1 null mice produced by homologous recombination, male mice are fertile; PH-20-null sperm show reduced cumulus dispersal (delayed fertilization at early time points only) but retain fertilizing ability due to other hyaluronidases present in the acrosome detected by Western blot.","method":"Homologous recombination knockout; in vitro fertilization assay; Western blot for other hyaluronidases","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO with defined IVF phenotype, Western blot evidence for compensatory hyaluronidases","pmids":["12065596"],"is_preprint":false},{"year":2001,"finding":"Spam1 is haploid expressed in mouse spermatids with both mRNA and protein compartmentalized (non-shared) among conjoined spermatids; this lack of transcript sharing via intercellular bridges leads to biochemically different sperm populations, providing a mechanism for transmission ratio distortion (TRD) in heterozygous males.","method":"RNA FISH; immunocytochemistry; flow cytometry; confocal microscopy; temporal expression analysis","journal":"Biology of reproduction","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple imaging methods showing compartmentalization, flow cytometry confirming sperm population differences","pmids":["11369602"],"is_preprint":false},{"year":2002,"finding":"Hyaluronidase activity of macaque sperm surface PH-20 requires both N-linked glycosylation (removal abolishes activity) and disulfide bond integrity (reduction with β-mercaptoethanol or DTT abolishes activity); mannose is a major sugar in the N-linked glycans; 6 isoforms with pI 5.1–6.0 were identified by 2D electrophoresis.","method":"Immunoaffinity purification; N-glycosidase F deglycosylation; β-mercaptoethanol/DTT reduction; lectin blotting; 2D electrophoresis; hyaluronidase activity assay","journal":"Journal of andrology","confidence":"High","confidence_rationale":"Tier 1 / Strong — enzymatic removal of glycans and reduction of disulfides with direct activity readout, multiple reagents","pmids":["11868814"],"is_preprint":false},{"year":2003,"finding":"Mouse Spam1 is transcribed in the female genital tract (uterus, oviduct, vagina) in a region-dependent manner; the protein has hyaluronidase activity at neutral pH but not acidic pH in female tissues, and its expression in the uterus fluctuates with the estrous cycle.","method":"RT-PCR; RNase protection assay; in situ transcript hybridization; Western blot; immunohistochemistry; HA substrate gel electrophoresis","journal":"Biology of reproduction","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple methods confirming expression and activity, single lab","pmids":["12672666"],"is_preprint":false},{"year":2003,"finding":"Epididymal SPAM1 is released with its intact GPI lipid anchor predominantly in insoluble particles in luminal fluid; PI-PLC treatment or Triton X-100 releases the majority, confirming lipid anchor retention on secreted protein; two-dimensional gel shows distinct isoforms in epididymis vs. testis, with N-linked and O-linked glycosylation differences.","method":"Ultracentrifugation; PI-PLC treatment; 2D-PAGE with immunoblotting; lectin blotting; enzymatic deglycosylation","journal":"Journal of andrology","confidence":"High","confidence_rationale":"Tier 1 / Strong — PI-PLC and detergent treatment with direct anchor confirmation, multiple biochemical methods","pmids":["12514083"],"is_preprint":false},{"year":2004,"finding":"Spam1 mRNA in mouse spermatids is localized near the ER and anchored to the cytoskeleton, absent from intercellular bridges; this compartmentalization mediates non-sharing of transcripts. Spam1 on caudal sperm surface mediates the synergistic increase in acrosome reactions induced by HA and progesterone, confirmed by reduced response in Rb(6.16) Spam1 mutant sperm.","method":"In situ hybridization by light and electron microscopy; immunocytochemistry; acrosome reaction assay with HA+progesterone; comparison to Spam1 mutant mice","journal":"Molecular reproduction and development","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — EM-level localization plus functional acrosome reaction assay using mutant mouse model, single lab","pmids":["15457544"],"is_preprint":false},{"year":2005,"finding":"HYAL5 (a GPI-anchored hyaluronidase active at pH 5–7) is expressed exclusively in testis and is present on sperm plasma and acrosomal membranes; it can disperse cumulus cells and is the principal cumulus matrix depolymerase in mouse sperm when PH-20 is absent, while PH-20 compensates for Hyal5's role.","method":"Protein purification from PH-20-null sperm; hyaluronan zymography; cumulus dispersal assay; apigenin inhibition; GPI-anchor characterization","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — protein purification and identification, activity assay, use of PH-20-null sperm, multiple methods","pmids":["16330764"],"is_preprint":false},{"year":2005,"finding":"Spam1 mRNA 3'UTR AU-rich elements (AREs) bind six testicular cytoplasmic proteins (AU-binding proteins, AUBPs) that interact with the cytoskeleton; these interactions mediate post-transcriptional regulation of Spam1 in spermatids; antisense RNA in testis can modulate ARE function. Transgenic overexpression attempts failed, indicating tight post-transcriptional control.","method":"UV cross-linking assay; transgenic overexpression; Northern analysis; cytoskeletal binding experiments","journal":"Molecular reproduction and development","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — UV cross-linking with cytoskeletal association, combined with transgenesis failure, single lab","pmids":["16250006"],"is_preprint":false},{"year":2005,"finding":"Spam1 RNA is anchored to the cytoskeleton in spermatids and interacts via 3' UTR AU-rich sequences with cytoskeletal-associated AU-binding proteins, preventing transcript sharing through intercellular bridges; this mechanism drives TRD. Spam1 overexpression (transgene) causes TRD by producing sperm with cytoplasmic droplets containing excess Spam1, reducing fertilizing ability.","method":"EM in situ hybridization; Northern analysis of fractionated testicular RNA; UV cross-linking; flow cytometry; FISH","journal":"Reproductive biology and endocrinology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods including EM localization, biochemical fractionation, and transgenic functional validation","pmids":["16092963"],"is_preprint":false},{"year":2006,"finding":"Epididymal SPAM1 acquired by Spam1-null sperm from wild-type epididymal luminal fluid in vitro significantly increases cumulus penetration ability, directly linking epididymal SPAM1 uptake with fertilizing ability and establishing it as a marker of sperm maturation.","method":"In vitro incubation of null sperm with WT epididymal luminal fluid; flow cytometry; immunocytochemistry; IVF cumulus penetration assay","journal":"Biology of reproduction","confidence":"High","confidence_rationale":"Tier 2 / Strong — null sperm rescue experiment with direct functional IVF readout, flow cytometry quantification","pmids":["16436526"],"is_preprint":false},{"year":2007,"finding":"Recombinant mouse SPAM1 and HYAL5 expressed in Xenopus oocytes both exhibit hyaluronidase activity at neutral pH and are GPI-anchored; HYALP1 lacks hyaluronidase activity despite sequence similarity.","method":"Recombinant expression in Xenopus oocytes; hyaluronidase activity assay; GPI-anchor characterization","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstitution in heterologous expression system with direct enzymatic assay, comparative analysis of all three family members","pmids":["16925524"],"is_preprint":false},{"year":2007,"finding":"Human recombinant PH-20 expressed in Drosophila S2 cells uses an HA octasaccharide as its minimum substrate (not hexasaccharide as for bovine testicular hyaluronidase); PH-20 catalyzes both hydrolysis and transglycosylation of HA octasaccharide.","method":"Recombinant expression; capillary zone electrophoresis analysis of reaction products; minimum substrate determination","journal":"Glycobiology","confidence":"High","confidence_rationale":"Tier 1 / Strong — purified recombinant enzyme with direct substrate analysis by CZE, minimum substrate definitively established","pmids":["17602139"],"is_preprint":false},{"year":2008,"finding":"SPAM1 is transferred to sperm from murine epididymosomes (male) and newly identified uterosomes (female) via a vesicular docking mechanism; uptake requires the intact GPI anchor (abolished by enzymatic anchor cleavage); fluorescently labeled vesicles are observed juxtaposed to sperm plasma membranes by TEM.","method":"Ultracentrifugation; immunogold labeling; confocal and TEM microscopy; GPI anchor cleavage experiments; fluorescent vesicle tracking","journal":"Molecular reproduction and development","confidence":"High","confidence_rationale":"Tier 2 / Strong — GPI-dependency demonstrated by enzymatic cleavage, TEM visualization of vesicle docking, multiple imaging methods","pmids":["18384048"],"is_preprint":false},{"year":2009,"finding":"SPAM1 is required for efficient sperm entry into and penetration through the cumulus matrix; SPAM1-null sperm accumulate at the surface/outer edge of the cumulus, while HYAL5-null sperm show no such defect; double comparison demonstrates SPAM1 but not HYAL5 is the functionally critical hyaluronidase for cumulus entry.","method":"HYAL5 knockout mouse generation; in vitro fertilization assay; comparative analysis of WT, HYAL5-null, and SPAM1-null sperm","journal":"Biology of reproduction","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO with defined cellular phenotype, direct comparison between two KO lines","pmids":["19605784"],"is_preprint":false},{"year":2009,"finding":"Clusterin (CLU) in epididymal/uterine luminal fluid stabilizes monomeric GPI-linked SPAM1 and mediates its transfer to human and mouse sperm membranes; anti-CLU antibody reduces SPAM1 delivery; co-immunoprecipitation reveals direct CLU-SPAM1 association; high CLU concentrations reduce and low concentrations enhance SPAM1 transfer.","method":"Co-immunoprecipitation; native Western blot; anti-CLU antibody blocking; dose-response transfer assay; apolipoprotein-enhanced transfer","journal":"Biology of reproduction","confidence":"High","confidence_rationale":"Tier 2 / Strong — co-IP plus functional transfer assay with dose-response, antibody blocking, two species tested","pmids":["19357365"],"is_preprint":false},{"year":2024,"finding":"Cryo-EM structure of human PH-20 shows: a central catalytic domain with conserved catalytically essential residues; a unique EGF-like domain with a longer sequence forming a flexibly anchored β-hairpin containing a disulfide bond, distinguishing it from other hyaluronidase family members.","method":"Cryogenic electron microscopy (cryo-EM); structural comparison with other hyaluronidase structures","journal":"Proteins","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct cryo-EM structure with comparative structural analysis identifying unique features","pmids":["39722545"],"is_preprint":false}],"current_model":"SPAM1/PH-20 is a GPI-anchored, testis-expressed (with secondary epididymal and female-tract expression) bifunctional sperm surface protein: its N-terminal domain carries hyaluronidase activity (requiring N-linked glycosylation and disulfide bonds, minimum substrate HA octasaccharide) that enables acrosome-intact sperm to penetrate the hyaluronic acid-rich cumulus cell layer, while a distinct C-terminal domain on the inner acrosomal membrane of acrosome-reacted sperm mediates secondary zona pellucida binding; additionally, a separate HA-binding domain (aa 205–235) on plasma-membrane PH-20 mediates HA-induced intracellular Ca²⁺ signaling via PH-20 aggregation to prime the acrosome reaction; the protein is transferred post-testiculary to sperm via GPI-anchor-dependent vesicular (epididymosomes/uterosomes) and CLU-mediated soluble mechanisms, undergoes N-glycan remodeling during epididymal maturation to increase activity, and its haploid-expressed mRNA is cytoskeletally anchored in spermatids preventing sharing through intercellular bridges, a mechanism underlying transmission ratio distortion."},"narrative":{"mechanistic_narrative":"SPAM1/PH-20 is a GPI-anchored, testis-expressed sperm surface protein that orchestrates the sperm's passage through the egg's investments during fertilization, functioning as a bifunctional molecule combining hyaluronidase enzymatic activity with adhesive activity [PMID:8195297, PMID:8793062]. Its N-terminal catalytic domain hydrolyzes hyaluronic acid (minimum substrate an HA octasaccharide), enabling acrosome-intact sperm to penetrate the hyaluronan-rich cumulus cell layer surrounding the egg [PMID:8195297, PMID:17602139]; this activity depends on N-linked glycosylation and disulfide bond integrity [PMID:11868814], and cryo-EM reveals a central catalytic domain together with a distinctive EGF-like domain forming a flexibly anchored disulfide-containing β-hairpin [PMID:39722545]. A biochemically separable activity mediates secondary sperm binding to the zona pellucida, demonstrated by inhibitors that block one activity without the other and by the requirement for PH-20 on the inner acrosomal membrane of acrosome-reacted sperm [PMID:4066757, PMID:8793062, PMID:10369396]. A third HA-binding region (aa 205–235), distinct from the catalytic site, drives HA-induced intracellular Ca²⁺ increases via aggregation of plasma-membrane PH-20, potentiating the acrosome reaction [PMID:10533704, PMID:11746965]. The protein redistributes from the posterior-head plasma membrane to the inner acrosomal membrane following the acrosome reaction by a calcium-dependent translocation, and its GPI anchor constrains its lateral mobility within membrane domains [PMID:3558486, PMID:3381102, PMID:1995397]. SPAM1 is acquired post-testicularly: it is delivered to maturing sperm from epididymosomes and uterosomes by a GPI-anchor-dependent vesicular mechanism and through clusterin-mediated soluble transfer, with epididymal N-glycan remodeling raising its hyaluronidase activity during maturation [PMID:9890751, PMID:18384048, PMID:19357365]. Transcription is driven by a CREM-dependent promoter element [PMID:10423292], and Spam1 mRNA is cytoskeletally anchored in spermatids via 3'UTR AU-rich elements, preventing transcript sharing through intercellular bridges and underlying transmission ratio distortion [PMID:11369602, PMID:16092963]. Despite these roles, Spam1-null male mice remain fertile because the testis-restricted hyaluronidase HYAL5 partially compensates for cumulus dispersal, although SPAM1 is the functionally critical enzyme for efficient cumulus entry [PMID:12065596, PMID:16330764, PMID:19605784].","teleology":[{"year":1985,"claim":"Established that the sperm surface antigen PH-20 has an essential function in sperm adhesion to the egg zona pellucida, defining its candidacy as a fertilization protein.","evidence":"Monoclonal antibody inhibition of sperm-zona binding in guinea pig","pmids":["4066757"],"confidence":"High","gaps":["Molecular identity and biochemical mechanism of binding undefined","Did not distinguish enzymatic from adhesive activity"]},{"year":1988,"claim":"Defined PH-20 as a GPI-anchored membrane protein whose mobility is constrained by ectodomain interactions, explaining how it maintains discrete surface domains.","evidence":"PI-PLC cleavage and FRAP diffusion measurements on guinea pig sperm","pmids":["3381102","3558486"],"confidence":"High","gaps":["Identity of constraining ectodomain interactions not determined","Mechanism of post-acrosome-reaction redistribution unresolved"]},{"year":1990,"claim":"Molecular cloning provided the protein sequence, revealing a single-gene-encoded glycoprotein with conserved cysteines and N-glycosylation sites, enabling all subsequent domain dissection.","evidence":"cDNA cloning, Southern and Northern blots in guinea pig and across mammals","pmids":["2269661"],"confidence":"High","gaps":["Catalytic residues not yet mapped","Domain boundaries for distinct functions not defined"]},{"year":1993,"claim":"Identified PH-20 as a hyaluronidase and cloned the strictly testis-specific human ortholog, linking the cloned gene to enzymatic function in humans.","evidence":"Vaccinia/recombinant expression with hyaluronidase assay and PI-PLC release; human/monkey cDNA cloning and tissue Northern blots","pmids":["8282124","8234258"],"confidence":"High","gaps":["In vivo role in human fertilization not directly tested","Catalytic site residues not localized"]},{"year":1994,"claim":"Demonstrated that PH-20 hyaluronidase enables acrosome-intact sperm to penetrate the cumulus cell layer, defining its first physiological function.","evidence":"Recombinant PH-20 cumulus dispersal and antibody-blocking cumulus penetration assays in mouse","pmids":["8195297"],"confidence":"High","gaps":["Did not establish whether cumulus penetration is the sole role","Relationship to zona binding activity unaddressed"]},{"year":1996,"claim":"Resolved PH-20 as a bifunctional protein with biochemically separable hyaluronidase and secondary zona-binding activities, reconciling its enzymatic and adhesive roles.","evidence":"Orthogonal inhibitor dissection (antibody, apigenin, zona HA removal) and soluble PH-20 characterization in guinea pig and macaque","pmids":["8793062","8724363","8608861"],"confidence":"High","gaps":["Structural basis of the zona-binding activity not identified","Identity of the zona ligand undefined"]},{"year":1997,"claim":"Mapped the hyaluronidase to the N-terminal domain and identified soluble forms as proteolytically released fragments, distinguishing membrane and soluble enzyme populations.","evidence":"Peptide sequencing of purified bovine 60 kDa enzyme mapped to PH-20 cDNA; domain synthesis analysis","pmids":["9280317","9116127"],"confidence":"High","gaps":["Protease responsible for endoproteolytic cleavage not identified","Catalytic residues still inferred from homology"]},{"year":1999,"claim":"Identified CREM as the transcriptional driver of Spam1 and defined epididymal N-glycan remodeling as the mechanism increasing hyaluronidase activity during sperm maturation.","evidence":"EMSA, in vitro transcription and CREM-KO Northern blots; deglycosylation and activity assays on caput vs caudal sperm in mouse","pmids":["10423292","9890751"],"confidence":"High","gaps":["Glycan structures responsible for activity gain not resolved","Other transcriptional inputs beyond CREM unexplored"]},{"year":1999,"claim":"Showed that plasma-membrane PH-20 binds HA to raise intracellular Ca²⁺ and potentiate the acrosome reaction, and that PH-20 aggregation drives the signal, adding a signaling role distinct from enzymatic and adhesive functions.","evidence":"Fab blocking with Ca²⁺ fluorometry, FITC-HA binding, and aggregation experiments in human and macaque sperm","pmids":["9770775","10533704","10369396"],"confidence":"High","gaps":["Cytoplasmic signaling partner not identified","Mechanism coupling aggregation to Ca²⁺ entry unresolved"]},{"year":2001,"claim":"Localized the HA-binding/signaling activity to a discrete region (aa 205–235) separate from the catalytic domain, molecularly separating PH-20's signaling from its enzymatic function.","evidence":"Recombinant deletion constructs, photoaffinity HA crosslinking, and anti-Peptide 2 Fab inhibition of Ca²⁺ in macaque","pmids":["11746965","11731269"],"confidence":"High","gaps":["Proposed 92-kDa cytoplasmic signaling partner not directly identified","Structural basis of HA binding by this region undefined"]},{"year":2001,"claim":"Knockout revealed SPAM1 is dispensable for male fertility due to compensating acrosomal hyaluronidases, while haploid-expressed mRNA compartmentalization explained transmission ratio distortion.","evidence":"Spam1 homologous-recombination knockout with IVF and Western blots; RNA FISH and flow cytometry of compartmentalized transcripts in mouse","pmids":["12065596","11369602"],"confidence":"High","gaps":["Identity of compensating hyaluronidase not yet established at this stage","Molecular tether anchoring mRNA not defined"]},{"year":2002,"claim":"Defined the biochemical requirements for hyaluronidase activity—N-glycosylation and disulfide bond integrity—establishing structural determinants of enzyme function.","evidence":"N-glycosidase deglycosylation, disulfide reduction, lectin and 2D analyses with activity readout in macaque","pmids":["11868814"],"confidence":"High","gaps":["Which specific glycans/disulfides are essential not mapped","Catalytic mechanism at atomic level not addressed"]},{"year":2003,"claim":"Extended SPAM1 expression beyond sperm to the female and epididymal tracts and established that secreted SPAM1 retains its intact GPI anchor in luminal particles, setting up a post-testicular delivery model.","evidence":"RT-PCR, RNase protection, IHC, and HA zymography in female tract; PI-PLC/detergent release and 2D-PAGE of epididymal fluid in mouse","pmids":["12672666","12514083"],"confidence":"Medium","gaps":["Functional role of female-tract SPAM1 not established","Mechanism of particle association undefined at this stage"]},{"year":2004,"claim":"Localized spermatid Spam1 mRNA to ER-proximal cytoskeleton and confirmed surface SPAM1 mediates synergistic HA+progesterone acrosome reactions using a Spam1 mutant, unifying the regulatory and signaling roles.","evidence":"Light/EM in situ hybridization and acrosome reaction assays comparing wild-type and Rb(6.16) Spam1 mutant sperm","pmids":["15457544"],"confidence":"Medium","gaps":["Cytoskeletal anchor molecule not identified","Signaling effectors downstream of synergy unresolved"]},{"year":2005,"claim":"Identified the AU-rich-element-binding proteins that anchor Spam1 mRNA to the cytoskeleton, providing the molecular basis for transcript non-sharing and transmission ratio distortion.","evidence":"UV crosslinking, cytoskeletal binding, transgenic overexpression and Northern analyses in mouse testis","pmids":["16250006","16092963"],"confidence":"High","gaps":["Individual AUBP identities not all resolved","Quantitative contribution to TRD in vivo not fully defined"]},{"year":2005,"claim":"Identified HYAL5 as the GPI-anchored testis hyaluronidase that compensates for SPAM1 loss, explaining why Spam1-null mice remain fertile.","evidence":"Protein purification from PH-20-null sperm, HA zymography, cumulus dispersal and apigenin inhibition in mouse","pmids":["16330764"],"confidence":"High","gaps":["Relative in vivo contribution of each enzyme not yet quantified here","Regulatory interplay between SPAM1 and HYAL5 unknown"]},{"year":2006,"claim":"Demonstrated that epididymally acquired SPAM1 functionally rescues cumulus penetration of null sperm, directly linking post-testicular uptake to fertilizing capacity.","evidence":"In vitro incubation of null sperm with WT luminal fluid, flow cytometry and IVF cumulus penetration assay in mouse","pmids":["16436526"],"confidence":"High","gaps":["Vesicular vs soluble transfer routes not distinguished here","Stability of acquired protein on sperm not assessed"]},{"year":2007,"claim":"Defined PH-20 substrate specificity (HA octasaccharide minimum, dual hydrolysis/transglycosylation) and confirmed neutral-pH GPI-anchored activity across family members, distinguishing it enzymatically from HYALP1.","evidence":"Recombinant expression in Drosophila S2 cells and Xenopus oocytes with CZE product analysis and activity assays","pmids":["17602139","16925524"],"confidence":"High","gaps":["Physiological relevance of transglycosylation unknown","Catalytic residues not yet structurally confirmed"]},{"year":2009,"claim":"Established the molecular machinery for SPAM1 transfer to sperm—GPI-dependent vesicular docking from epididymosomes/uterosomes and clusterin-mediated soluble delivery—and confirmed SPAM1 as the critical cumulus-entry enzyme.","evidence":"GPI-cleavage transfer assays, TEM vesicle docking, CLU co-IP and antibody blocking, and HYAL5/SPAM1 KO comparison in mouse and human","pmids":["18384048","19357365","19605784"],"confidence":"High","gaps":["Receptor/docking factor on the sperm membrane not identified","Stoichiometry of CLU-SPAM1 complex undefined"]},{"year":2024,"claim":"Provided the first atomic structure of human PH-20, revealing the catalytic domain and a unique EGF-like β-hairpin distinguishing it from other hyaluronidases.","evidence":"Cryo-EM structure of human PH-20 with comparative structural analysis","pmids":["39722545"],"confidence":"High","gaps":["Structures of HA-binding and zona-binding regions not resolved in complex with ligands","Conformational basis of aggregation-driven signaling not captured"]},{"year":null,"claim":"The cytoplasmic signaling partner that couples plasma-membrane PH-20 aggregation to Ca²⁺ entry, and the sperm-surface receptor mediating GPI-anchored SPAM1 docking, remain unidentified.","evidence":"No direct identification in the available corpus","pmids":[],"confidence":"Low","gaps":["No Co-IP identification of the proposed 92-kDa signaling molecule","No molecular identity for the vesicle docking receptor","Zona pellucida ligand for secondary binding undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140098","term_label":"catalytic activity, acting on RNA","supporting_discovery_ids":[8,10,27,35,36]},{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[8,36]},{"term_id":"GO:0098631","term_label":"cell adhesion mediator activity","supporting_discovery_ids":[0,12,22]},{"term_id":"GO:0140299","term_label":"molecular sensor activity","supporting_discovery_ids":[18,21,23]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,3,4]},{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[13,29,37]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[37,39]}],"pathway":[{"term_id":"R-HSA-1474244","term_label":"Extracellular matrix organization","supporting_discovery_ids":[10,36,38]},{"term_id":"R-HSA-1474165","term_label":"Reproduction","supporting_discovery_ids":[0,10,22]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[18,21,23]}],"complexes":[],"partners":["CLU"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P38567","full_name":"Hyaluronidase PH-20","aliases":["Hyaluronoglucosaminidase PH-20","Sperm adhesion molecule 1","Sperm surface protein PH-20"],"length_aa":509,"mass_kda":57.8,"function":"Involved in sperm-egg adhesion. Upon fertilization sperm must first penetrate a layer of cumulus cells that surrounds the egg before reaching the zona pellucida. The cumulus cells are embedded in a matrix containing hyaluronic acid which is formed prior to ovulation. This protein aids in penetrating the layer of cumulus cells by digesting hyaluronic acid","subcellular_location":"Cell membrane","url":"https://www.uniprot.org/uniprotkb/P38567/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/SPAM1","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/SPAM1","total_profiled":1310},"omim":[{"mim_id":"607071","title":"HYALURONOGLUCOSAMINIDASE 1; HYAL1","url":"https://www.omim.org/entry/607071"},{"mim_id":"604510","title":"HYALURONOGLUCOSAMINIDASE 4; HYAL4","url":"https://www.omim.org/entry/604510"},{"mim_id":"603551","title":"HYALURONOGLUCOSAMINIDASE 2; HYAL2","url":"https://www.omim.org/entry/603551"},{"mim_id":"600930","title":"SPERM ADHESION MOLECULE 1; SPAM1","url":"https://www.omim.org/entry/600930"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in single","driving_tissues":[{"tissue":"testis","ntpm":16.2}],"url":"https://www.proteinatlas.org/search/SPAM1"},"hgnc":{"alias_symbol":["HYAL5","PH-20","SPAG15"],"prev_symbol":[]},"alphafold":{"accession":"P38567","domains":[{"cath_id":"3.20.20.70","chopping":"43-382","consensus_level":"medium","plddt":96.5258,"start":43,"end":382}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P38567","model_url":"https://alphafold.ebi.ac.uk/files/AF-P38567-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P38567-F1-predicted_aligned_error_v6.png","plddt_mean":88.19},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=SPAM1","jax_strain_url":"https://www.jax.org/strain/search?query=SPAM1"},"sequence":{"accession":"P38567","fasta_url":"https://rest.uniprot.org/uniprotkb/P38567.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P38567/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P38567"}},"corpus_meta":[{"pmid":"3419530","id":"PMC_3419530","title":"Fully effective contraception in male and female guinea pigs immunized with the sperm protein PH-20.","date":"1988","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/3419530","citation_count":218,"is_preprint":false},{"pmid":"8195297","id":"PMC_8195297","title":"A hyaluronidase activity of the sperm plasma membrane protein PH-20 enables sperm to penetrate the cumulus cell layer surrounding the egg.","date":"1994","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/8195297","citation_count":213,"is_preprint":false},{"pmid":"4066757","id":"PMC_4066757","title":"A role for the migrating sperm surface antigen PH-20 in guinea pig sperm binding to the egg zona pellucida.","date":"1985","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/4066757","citation_count":201,"is_preprint":false},{"pmid":"11731269","id":"PMC_11731269","title":"The dual functions of GPI-anchored PH-20: hyaluronidase and intracellular signaling.","date":"2001","source":"Matrix biology : journal of the International Society for Matrix Biology","url":"https://pubmed.ncbi.nlm.nih.gov/11731269","citation_count":144,"is_preprint":false},{"pmid":"12065596","id":"PMC_12065596","title":"Mouse sperm lacking cell surface hyaluronidase PH-20 can pass through the layer of cumulus cells and fertilize the egg.","date":"2002","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/12065596","citation_count":144,"is_preprint":false},{"pmid":"9116127","id":"PMC_9116127","title":"Why did the sperm cross the cumulus? To get to the oocyte. Functions of the sperm surface proteins PH-20 and fertilin in arriving at, and fusing with, the egg.","date":"1997","source":"Biology of reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/9116127","citation_count":133,"is_preprint":false},{"pmid":"2269661","id":"PMC_2269661","title":"cDNA cloning reveals the molecular structure of a sperm surface protein, PH-20, involved in sperm-egg adhesion and the wide distribution of its gene among mammals.","date":"1990","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/2269661","citation_count":127,"is_preprint":false},{"pmid":"3381102","id":"PMC_3381102","title":"Restricted lateral diffusion of PH-20, a PI-anchored sperm membrane protein.","date":"1988","source":"Science (New York, N.Y.)","url":"https://pubmed.ncbi.nlm.nih.gov/3381102","citation_count":124,"is_preprint":false},{"pmid":"8282124","id":"PMC_8282124","title":"The human sperm protein PH-20 has hyaluronidase activity.","date":"1993","source":"FEBS letters","url":"https://pubmed.ncbi.nlm.nih.gov/8282124","citation_count":122,"is_preprint":false},{"pmid":"16330764","id":"PMC_16330764","title":"Identification of a hyaluronidase, Hyal5, involved in penetration of mouse sperm through cumulus mass.","date":"2005","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/16330764","citation_count":111,"is_preprint":false},{"pmid":"8793062","id":"PMC_8793062","title":"Sperm surface protein PH-20 is bifunctional: one activity is a hyaluronidase and a second, distinct activity is required in secondary sperm-zona binding.","date":"1996","source":"Biology of reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/8793062","citation_count":100,"is_preprint":false},{"pmid":"8608861","id":"PMC_8608861","title":"The PH-20 protein in cynomolgus macaque spermatozoa: identification of two different forms exhibiting hyaluronidase activity.","date":"1996","source":"Developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/8608861","citation_count":93,"is_preprint":false},{"pmid":"18384048","id":"PMC_18384048","title":"Investigating the role of murine epididymosomes and uterosomes in GPI-linked protein transfer to sperm using SPAM1 as a model.","date":"2008","source":"Molecular reproduction and development","url":"https://pubmed.ncbi.nlm.nih.gov/18384048","citation_count":85,"is_preprint":false},{"pmid":"8234258","id":"PMC_8234258","title":"Molecular cloning of the human and monkey sperm surface protein PH-20.","date":"1993","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/8234258","citation_count":78,"is_preprint":false},{"pmid":"3558486","id":"PMC_3558486","title":"Lateral diffusion of the PH-20 protein on guinea pig sperm: evidence that barriers to diffusion maintain plasma membrane domains in mammalian sperm.","date":"1987","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/3558486","citation_count":76,"is_preprint":false},{"pmid":"16420970","id":"PMC_16420970","title":"Epididymal SPAM1 and its impact on sperm function.","date":"2006","source":"Molecular and cellular endocrinology","url":"https://pubmed.ncbi.nlm.nih.gov/16420970","citation_count":74,"is_preprint":false},{"pmid":"19605784","id":"PMC_19605784","title":"Functional roles of mouse sperm hyaluronidases, HYAL5 and SPAM1, in fertilization.","date":"2009","source":"Biology of reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/19605784","citation_count":73,"is_preprint":false},{"pmid":"3771636","id":"PMC_3771636","title":"Sperm exocytosis increases the amount of PH-20 antigen on the surface of guinea pig sperm.","date":"1986","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/3771636","citation_count":70,"is_preprint":false},{"pmid":"3305112","id":"PMC_3305112","title":"The guinea pig sperm plasma membrane protein, PH-20, reaches the surface via two transport pathways and becomes localized to a domain after an initial uniform distribution.","date":"1987","source":"Developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/3305112","citation_count":69,"is_preprint":false},{"pmid":"3042032","id":"PMC_3042032","title":"Purification of the guinea pig sperm PH-20 antigen and detection of a site-specific endoproteolytic activity in sperm preparations that cleaves PH-20 into two disulfide-linked fragments.","date":"1988","source":"Biology of reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/3042032","citation_count":66,"is_preprint":false},{"pmid":"9154509","id":"PMC_9154509","title":"The PH-20 protein in human spermatozoa.","date":"1997","source":"Journal of andrology","url":"https://pubmed.ncbi.nlm.nih.gov/9154509","citation_count":64,"is_preprint":false},{"pmid":"7711169","id":"PMC_7711169","title":"Location of the PH-20 protein on acrosome-intact and acrosome-reacted spermatozoa of cynomolgus macaques.","date":"1995","source":"Biology of reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/7711169","citation_count":62,"is_preprint":false},{"pmid":"9160711","id":"PMC_9160711","title":"Mechanism of infertility in male guinea pigs immunized with sperm PH-20.","date":"1997","source":"Biology of reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/9160711","citation_count":60,"is_preprint":false},{"pmid":"11922735","id":"PMC_11922735","title":"Expression of PH-20 in normal and neoplastic breast tissue.","date":"2002","source":"The Journal of surgical research","url":"https://pubmed.ncbi.nlm.nih.gov/11922735","citation_count":54,"is_preprint":false},{"pmid":"11369602","id":"PMC_11369602","title":"Lack of sharing of Spam1 (Ph-20) among mouse spermatids and transmission ratio distortion.","date":"2001","source":"Biology of reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/11369602","citation_count":53,"is_preprint":false},{"pmid":"11105908","id":"PMC_11105908","title":"Mouse Spam1 (PH-20): evidence for its expression in the epididymis and for a new category of spermatogenic-expressed genes.","date":"2000","source":"Journal of andrology","url":"https://pubmed.ncbi.nlm.nih.gov/11105908","citation_count":52,"is_preprint":false},{"pmid":"9770775","id":"PMC_9770775","title":"Hyaluronic acid enhances induction of the acrosome reaction of human sperm through interaction with the PH-20 protein.","date":"1998","source":"Zygote (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/9770775","citation_count":51,"is_preprint":false},{"pmid":"12514083","id":"PMC_12514083","title":"Mouse epididymal Spam1 (pH-20) is released in the luminal fluid with its lipid anchor.","date":"2003","source":"Journal of andrology","url":"https://pubmed.ncbi.nlm.nih.gov/12514083","citation_count":48,"is_preprint":false},{"pmid":"9890751","id":"PMC_9890751","title":"Biochemical maturation of Spam1 (PH-20) during epididymal transit of mouse sperm involves modifications of N-linked oligosaccharides.","date":"1999","source":"Molecular reproduction and development","url":"https://pubmed.ncbi.nlm.nih.gov/9890751","citation_count":48,"is_preprint":false},{"pmid":"8724363","id":"PMC_8724363","title":"Structural relationship of sperm soluble hyaluronidase to the sperm membrane protein PH-20.","date":"1996","source":"Biology of reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/8724363","citation_count":48,"is_preprint":false},{"pmid":"12672666","id":"PMC_12672666","title":"Mouse Spam1 (PH-20) is a multifunctional protein: evidence for its expression in the female reproductive tract.","date":"2003","source":"Biology of reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/12672666","citation_count":46,"is_preprint":false},{"pmid":"10533704","id":"PMC_10533704","title":"Hyaluronic acid and the cumulus extracellular matrix induce increases in intracellular calcium in macaque sperm via the plasma membrane protein PH-20.","date":"1999","source":"Zygote (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/10533704","citation_count":43,"is_preprint":false},{"pmid":"8575780","id":"PMC_8575780","title":"Expression analysis, genomic structure, and mapping to 7q31 of the human sperm adhesion molecule gene SPAM1.","date":"1995","source":"Genomics","url":"https://pubmed.ncbi.nlm.nih.gov/8575780","citation_count":42,"is_preprint":false},{"pmid":"9280317","id":"PMC_9280317","title":"The soluble hyaluronidase from bull testes is a fragment of the membrane-bound PH-20 enzyme.","date":"1997","source":"FEBS letters","url":"https://pubmed.ncbi.nlm.nih.gov/9280317","citation_count":42,"is_preprint":false},{"pmid":"10369396","id":"PMC_10369396","title":"PH-20 but not acrosin is involved in sperm penetration of the macaque zona pellucida.","date":"1999","source":"Molecular reproduction and development","url":"https://pubmed.ncbi.nlm.nih.gov/10369396","citation_count":40,"is_preprint":false},{"pmid":"17602139","id":"PMC_17602139","title":"Kinetics of Hyal-1 and PH-20 hyaluronidases: comparison of minimal substrates and analysis of the transglycosylation reaction.","date":"2007","source":"Glycobiology","url":"https://pubmed.ncbi.nlm.nih.gov/17602139","citation_count":39,"is_preprint":false},{"pmid":"16436526","id":"PMC_16436526","title":"Epididymal SPAM1 is a marker for sperm maturation in the mouse.","date":"2006","source":"Biology of reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/16436526","citation_count":37,"is_preprint":false},{"pmid":"19357365","id":"PMC_19357365","title":"Clusterin facilitates exchange of glycosyl phosphatidylinositol-linked SPAM1 between reproductive luminal fluids and mouse and human sperm membranes.","date":"2009","source":"Biology of reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/19357365","citation_count":36,"is_preprint":false},{"pmid":"11746965","id":"PMC_11746965","title":"Identification of a hyaluronic acid (HA) binding domain in the PH-20 protein that may function in cell signaling.","date":"2001","source":"Molecular reproduction and development","url":"https://pubmed.ncbi.nlm.nih.gov/11746965","citation_count":36,"is_preprint":false},{"pmid":"9160712","id":"PMC_9160712","title":"Reversible contraceptive effect of PH-20 immunization in male guinea pigs.","date":"1997","source":"Biology of reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/9160712","citation_count":35,"is_preprint":false},{"pmid":"12932297","id":"PMC_12932297","title":"SPAM1 (PH-20) protein and mRNA expression in the epididymides of humans and macaques: utilizing laser microdissection/RT-PCR.","date":"2003","source":"Reproductive biology and endocrinology : RB&E","url":"https://pubmed.ncbi.nlm.nih.gov/12932297","citation_count":33,"is_preprint":false},{"pmid":"11673279","id":"PMC_11673279","title":"Mouse epididymal Spam1 (PH-20) is released in vivo and in vitro, and Spam1 is differentially regulated in testis and epididymis.","date":"2001","source":"Biology of reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/11673279","citation_count":33,"is_preprint":false},{"pmid":"1995397","id":"PMC_1995397","title":"Migration of the guinea pig sperm membrane protein PH-20 from one localized surface domain to another does not occur by a simple diffusion-trapping mechanism.","date":"1991","source":"Developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/1995397","citation_count":33,"is_preprint":false},{"pmid":"16925524","id":"PMC_16925524","title":"Mouse testicular hyaluronidase-like proteins SPAM1 and HYAL5 but not HYALP1 degrade hyaluronan.","date":"2007","source":"The Biochemical journal","url":"https://pubmed.ncbi.nlm.nih.gov/16925524","citation_count":31,"is_preprint":false},{"pmid":"15062858","id":"PMC_15062858","title":"Expression and secretion of rat SPAM1(2B1 or PH-20) in the epididymis: role of testicular lumicrine factors.","date":"2004","source":"Matrix biology : journal of the International Society for Matrix Biology","url":"https://pubmed.ncbi.nlm.nih.gov/15062858","citation_count":29,"is_preprint":false},{"pmid":"31008594","id":"PMC_31008594","title":"Fluoride Interferes with the Sperm Fertilizing Ability via Downregulated SPAM1, ACR, and PRSS21 Expression in Rat Epididymis.","date":"2019","source":"Journal of agricultural and food chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/31008594","citation_count":29,"is_preprint":false},{"pmid":"9322248","id":"PMC_9322248","title":"Biochemical characterization of the PH-20 protein on the plasma membrane and inner acrosomal membrane of cynomolgus macaque spermatozoa.","date":"1997","source":"Molecular reproduction and development","url":"https://pubmed.ncbi.nlm.nih.gov/9322248","citation_count":28,"is_preprint":false},{"pmid":"27442128","id":"PMC_27442128","title":"Isolating Sperm from Cell Mixtures Using Magnetic Beads Coupled with an Anti-PH-20 Antibody for Forensic DNA Analysis.","date":"2016","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/27442128","citation_count":26,"is_preprint":false},{"pmid":"15892045","id":"PMC_15892045","title":"Identification of the bull sperm p80 protein as a PH-20 ortholog and its modification during the epididymal transit.","date":"2005","source":"Molecular reproduction and development","url":"https://pubmed.ncbi.nlm.nih.gov/15892045","citation_count":26,"is_preprint":false},{"pmid":"11845284","id":"PMC_11845284","title":"Spam1 (PH-20) mutations and sperm dysfunction in mice with the Rb(6.16) or Rb(6.15) translocation.","date":"2001","source":"Mammalian genome : official journal of the International Mammalian Genome Society","url":"https://pubmed.ncbi.nlm.nih.gov/11845284","citation_count":25,"is_preprint":false},{"pmid":"9041127","id":"PMC_9041127","title":"The murine Spam1 gene: RNA expression pattern and lower steady-state levels associated with the Rb(6.16) translocation.","date":"1997","source":"Molecular reproduction and development","url":"https://pubmed.ncbi.nlm.nih.gov/9041127","citation_count":25,"is_preprint":false},{"pmid":"12069203","id":"PMC_12069203","title":"Restricted entry of IgG into male and female rabbit reproductive ducts following immunization with recombinant rabbit PH-20.","date":"2002","source":"American journal of reproductive immunology (New York, N.Y. : 1989)","url":"https://pubmed.ncbi.nlm.nih.gov/12069203","citation_count":24,"is_preprint":false},{"pmid":"16092963","id":"PMC_16092963","title":"Spam1-associated transmission ratio distortion in mice: elucidating the mechanism.","date":"2005","source":"Reproductive biology and endocrinology : RB&E","url":"https://pubmed.ncbi.nlm.nih.gov/16092963","citation_count":22,"is_preprint":false},{"pmid":"16078272","id":"PMC_16078272","title":"Sperm dysfunction in the Rb(6.16)- and Rb(6.15)-bearing mice revisited: involvement of Hyalp1 and Hyal5.","date":"2005","source":"Molecular reproduction and development","url":"https://pubmed.ncbi.nlm.nih.gov/16078272","citation_count":22,"is_preprint":false},{"pmid":"9060406","id":"PMC_9060406","title":"The mouse Spam1 maps to proximal chromosome 6 and is a candidate for the sperm dysfunction in Rb(6.16)24Lub and Rb(6.15)1Ald heterozygotes.","date":"1997","source":"Mammalian genome : official journal of the International Mammalian Genome Society","url":"https://pubmed.ncbi.nlm.nih.gov/9060406","citation_count":22,"is_preprint":false},{"pmid":"15987477","id":"PMC_15987477","title":"Chondrocytes, synoviocytes and dermal fibroblasts all express PH-20, a hyaluronidase active at neutral pH.","date":"2005","source":"Arthritis research & therapy","url":"https://pubmed.ncbi.nlm.nih.gov/15987477","citation_count":21,"is_preprint":false},{"pmid":"15175239","id":"PMC_15175239","title":"Spam1 (PH-20) expression in the extratesticular duct and accessory organs of the mouse: a possible role in sperm fluid reabsorption.","date":"2004","source":"Biology of reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/15175239","citation_count":19,"is_preprint":false},{"pmid":"11868814","id":"PMC_11868814","title":"Importance of glycosylation and disulfide bonds in hyaluronidase activity of macaque sperm surface PH-20.","date":"2002","source":"Journal of andrology","url":"https://pubmed.ncbi.nlm.nih.gov/11868814","citation_count":19,"is_preprint":false},{"pmid":"11466235","id":"PMC_11466235","title":"Characterization of an 80-kilodalton bull sperm protein identified as PH-20.","date":"2001","source":"Biology of reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/11466235","citation_count":19,"is_preprint":false},{"pmid":"9590538","id":"PMC_9590538","title":"Rearrangement of the PH-20 protein on the surface of macaque spermatozoa following exposure to anti-PH-20 antibodies or binding to zona pellucida.","date":"1998","source":"Molecular reproduction and development","url":"https://pubmed.ncbi.nlm.nih.gov/9590538","citation_count":18,"is_preprint":false},{"pmid":"15457544","id":"PMC_15457544","title":"Cytoplasmic localization during testicular biogenesis of the murine mRNA for Spam1 (PH-20), a protein involved in acrosomal exocytosis.","date":"2004","source":"Molecular reproduction and development","url":"https://pubmed.ncbi.nlm.nih.gov/15457544","citation_count":17,"is_preprint":false},{"pmid":"10423292","id":"PMC_10423292","title":"Characterization of the genomic structure of the murine Spam1 gene and its promoter: evidence for transcriptional regulation by a cAMP-responsive element.","date":"1999","source":"Molecular reproduction and development","url":"https://pubmed.ncbi.nlm.nih.gov/10423292","citation_count":17,"is_preprint":false},{"pmid":"11673246","id":"PMC_11673246","title":"Posttranslational processing of PH-20 during epididymal sperm maturation in the horse.","date":"2001","source":"Biology of reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/11673246","citation_count":16,"is_preprint":false},{"pmid":"15039954","id":"PMC_15039954","title":"Effects of scrotal heating on sperm surface protein PH-20 expression in sheep.","date":"2004","source":"Molecular reproduction and development","url":"https://pubmed.ncbi.nlm.nih.gov/15039954","citation_count":16,"is_preprint":false},{"pmid":"11839398","id":"PMC_11839398","title":"Immunological response of female macaques to the PH-20 sperm protein following injection of recombinant proteins or synthesized peptides.","date":"2002","source":"Journal of reproductive immunology","url":"https://pubmed.ncbi.nlm.nih.gov/11839398","citation_count":14,"is_preprint":false},{"pmid":"15804358","id":"PMC_15804358","title":"Transcription of the human and rodent SPAM1 / PH-20 genes initiates within an ancient endogenous retrovirus.","date":"2005","source":"BMC genomics","url":"https://pubmed.ncbi.nlm.nih.gov/15804358","citation_count":12,"is_preprint":false},{"pmid":"12030925","id":"PMC_12030925","title":"Characterization of the porcine sperm adhesion molecule gene SPAM1- expression analysis, genomic structure, and chromosomal mapping.","date":"2002","source":"Animal genetics","url":"https://pubmed.ncbi.nlm.nih.gov/12030925","citation_count":11,"is_preprint":false},{"pmid":"22197807","id":"PMC_22197807","title":"Sexual size dimorphism predicts rates of sequence evolution of SPerm Adhesion Molecule 1 (SPAM1, also PH-20) in monkeys, but not in hominoids (apes including humans).","date":"2011","source":"Molecular phylogenetics and evolution","url":"https://pubmed.ncbi.nlm.nih.gov/22197807","citation_count":11,"is_preprint":false},{"pmid":"37727704","id":"PMC_37727704","title":"Transgenic viral expression of PH-20, IL-12, and sPD1-Fc enhances immune cell infiltration and anti-tumor efficacy of an oncolytic virus.","date":"2023","source":"Molecular therapy oncolytics","url":"https://pubmed.ncbi.nlm.nih.gov/37727704","citation_count":10,"is_preprint":false},{"pmid":"37833433","id":"PMC_37833433","title":"Low acrosin activity is associated with decreased Spam1/acrosin expression and GSH deficiency-caused premature acrosome release of human sperm cells.","date":"2023","source":"Cell and tissue research","url":"https://pubmed.ncbi.nlm.nih.gov/37833433","citation_count":9,"is_preprint":false},{"pmid":"38175240","id":"PMC_38175240","title":"Engineering protein translocation and unfolded protein response enhanced human PH-20 secretion in Pichia pastoris.","date":"2024","source":"Applied microbiology and biotechnology","url":"https://pubmed.ncbi.nlm.nih.gov/38175240","citation_count":9,"is_preprint":false},{"pmid":"30328344","id":"PMC_30328344","title":"SPAM1 and PH-20 are two gene products expressed in bovine testis and present in sperm.","date":"2018","source":"Reproduction (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/30328344","citation_count":8,"is_preprint":false},{"pmid":"36289815","id":"PMC_36289815","title":"Sperm Adhesion Molecule 1 (SPAM1) Distribution in Selected Human Sperm by Hyaluronic Acid Test.","date":"2022","source":"Biomedicines","url":"https://pubmed.ncbi.nlm.nih.gov/36289815","citation_count":8,"is_preprint":false},{"pmid":"17446714","id":"PMC_17446714","title":"Expression of SPAM1 (PH-20) in the murine kidney is not accompanied by hyaluronidase activity: evidence for potential roles in fluid and water reabsorption.","date":"2007","source":"Kidney & blood pressure research","url":"https://pubmed.ncbi.nlm.nih.gov/17446714","citation_count":6,"is_preprint":false},{"pmid":"16250006","id":"PMC_16250006","title":"Murine Spam1 mRNA: involvement of AU-rich elements in the 3'UTR and antisense RNA in its tight post-transcriptional regulation in spermatids.","date":"2006","source":"Molecular reproduction and development","url":"https://pubmed.ncbi.nlm.nih.gov/16250006","citation_count":6,"is_preprint":false},{"pmid":"15289682","id":"PMC_15289682","title":"Cloning and characterization of the bovine testicular PH-20 hyaluronidase core domain.","date":"2004","source":"Biotechnology letters","url":"https://pubmed.ncbi.nlm.nih.gov/15289682","citation_count":6,"is_preprint":false},{"pmid":"11991398","id":"PMC_11991398","title":"Characterization of PH-20 in canine spermatozoa and testis.","date":"2002","source":"Theriogenology","url":"https://pubmed.ncbi.nlm.nih.gov/11991398","citation_count":6,"is_preprint":false},{"pmid":"36555637","id":"PMC_36555637","title":"Novel Small Molecule Positive Allosteric Modulator SPAM1 Triggers the Nuclear Translocation of PAC1-R to Exert Neuroprotective Effects through Neuron-Restrictive Silencer Factor.","date":"2022","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/36555637","citation_count":4,"is_preprint":false},{"pmid":"10374924","id":"PMC_10374924","title":"Identification of linear surface epitopes on the guinea pig sperm membrane protein PH-20.","date":"1999","source":"Life sciences","url":"https://pubmed.ncbi.nlm.nih.gov/10374924","citation_count":4,"is_preprint":false},{"pmid":"39722545","id":"PMC_39722545","title":"Cryo-EM Structure of Human Hyaluronidase PH-20.","date":"2024","source":"Proteins","url":"https://pubmed.ncbi.nlm.nih.gov/39722545","citation_count":3,"is_preprint":false},{"pmid":"32224028","id":"PMC_32224028","title":"Knockout of hyaluronidase Spam1 reduces age-related bone and cartilage changes in mouse knee.","date":"2020","source":"Morphologie : bulletin de l'Association des anatomistes","url":"https://pubmed.ncbi.nlm.nih.gov/32224028","citation_count":1,"is_preprint":false},{"pmid":"41716467","id":"PMC_41716467","title":"Potency-enhancing mutations in E3-19K and i-leader increase the cytolytic activity of the PH20/SPAM1-armed oncolytic adenovirus Ad5Δ24RGD.","date":"2026","source":"Molecular therapy. Oncology","url":"https://pubmed.ncbi.nlm.nih.gov/41716467","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":44322,"output_tokens":9464,"usd":0.137463,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":19754,"output_tokens":6045,"usd":0.124948,"stage2_stop_reason":"end_turn"},"total_usd":0.262411,"stage1_batch_id":"msgbatch_013LWZZT6MWaqB9qyTSeQBmU","stage2_batch_id":"msgbatch_0194ZzQaTGNpruoNJBbEMbt3","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1985,\n      \"finding\": \"The PH-20 surface antigen on guinea pig sperm posterior head plasma membrane has a required function in sperm binding to the egg zona pellucida; monoclonal antibody PH-20 MAb inhibited sperm-zona binding ~90%, establishing PH-20 as essential for zona adhesion.\",\n      \"method\": \"Monoclonal antibody inhibition of sperm-zona binding assay; competitive binding with 125I-labeled MAbs\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple inhibitory antibodies with dose-response, competitive binding assays, replicated across labs in subsequent work\",\n      \"pmids\": [\"4066757\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1986,\n      \"finding\": \"After the acrosome reaction (exocytosis), the intracellular PH-20 population on the inner acrosomal membrane (IAM) is inserted into the plasma membrane, producing an ~3-fold increase in surface PH-20 antigen; this reveals a mechanism for rapid upregulation of a sperm surface protein via exocytosis.\",\n      \"method\": \"Indirect immunofluorescence; quantification of antigenic sites before and after acrosome reaction; permeabilization of acrosome-intact sperm\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct quantification of surface sites pre/post acrosome reaction, replicated in multiple species\",\n      \"pmids\": [\"3771636\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1987,\n      \"finding\": \"PH-20 protein reaches the sperm plasma membrane via two transport pathways during spermiogenesis: first inserted into the acrosomal membrane, then separately into the plasma membrane; both populations are initially uniformly distributed and later become restricted to specific domains, indicating localization occurs post-insertion rather than by intracellular sorting.\",\n      \"method\": \"Developmental immunofluorescence localization during spermiogenesis; SDS-PAGE of testicular cell extracts\",\n      \"journal\": \"Developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct imaging of spermatogenic stages, single lab, two orthogonal methods\",\n      \"pmids\": [\"3305112\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1987,\n      \"finding\": \"PH-20 on the posterior head plasma membrane of acrosome-intact sperm is mobile (D = 1.8×10⁻¹⁰ cm²/s) but restricted ~50-fold relative to lipid; after migration to the IAM of acrosome-reacted sperm it diffuses freely (D = 4.9×10⁻⁹ cm²/s, similar to lipid), supporting a barrier-to-diffusion model for domain maintenance.\",\n      \"method\": \"Fluorescence redistribution after photobleaching (FRAP) on individual sperm\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — quantitative FRAP comparing multiple membrane domains, replicated with lipid probes as controls\",\n      \"pmids\": [\"3558486\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1988,\n      \"finding\": \"PH-20 is anchored in the sperm plasma membrane via a glycosylphosphatidylinositol (GPI/phosphatidylinositol lipid) anchor, and its lateral diffusion rate is >1000-fold slower than lipid diffusion, indicating that ectodomain interactions constrain mobility of a GPI-anchored protein.\",\n      \"method\": \"Phosphatidylinositol-specific phospholipase C (PI-PLC) cleavage; FRAP measurement of diffusion rates\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — PI-PLC release plus FRAP, orthogonal methods, widely replicated\",\n      \"pmids\": [\"3381102\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1988,\n      \"finding\": \"PH-20 purified from guinea pig sperm by monoclonal antibody affinity chromatography exists in three forms: 64 kDa, 56 kDa, and an endoproteolytically cleaved form of two disulfide-linked fragments (~41–48 kDa and ~27 kDa), indicating site-specific endoproteolysis occurs in sperm preparations.\",\n      \"method\": \"Monoclonal antibody affinity purification; SDS-PAGE; Cleveland digest analysis\",\n      \"journal\": \"Biology of reproduction\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — purified protein biochemistry, single lab, multiple gel analyses\",\n      \"pmids\": [\"3042032\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1990,\n      \"finding\": \"cDNA cloning of guinea pig PH-20 revealed a novel protein of 468 amino acids with six N-linked glycosylation sites, twelve cysteines (eight clustered near the C-terminus), encoded by a single gene with a single ~2.2 kb mRNA; Southern blots confirmed a single gene and conservation across multiple mammalian species.\",\n      \"method\": \"cDNA cloning, sequencing; Southern blot; Northern blot\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — full-length cDNA sequence with structural characterization, foundational molecular paper\",\n      \"pmids\": [\"2269661\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1991,\n      \"finding\": \"PH-20 protein migration from the posterior head plasma membrane to the inner acrosomal membrane after the acrosome reaction occurs against a concentration gradient and is calcium-dependent, arguing against passive diffusion–trapping and in favor of an active translocation mechanism.\",\n      \"method\": \"Fluorescence microscopy with digital image processing of individual sperm; calcium manipulation\",\n      \"journal\": \"Developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — quantitative imaging showing directional movement against gradient, calcium dependency, single lab\",\n      \"pmids\": [\"1995397\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"Human PH-20 protein expressed in RK13 cells using a vaccinia virus system has hyaluronidase activity; PI-PLC treatment releases the enzyme from the cell surface with a large increase in activity, confirming the GPI anchor and hyaluronidase function of human PH-20.\",\n      \"method\": \"Vaccinia virus expression; hyaluronidase activity assay; PI-PLC release\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — recombinant expression with enzymatic assay and PI-PLC validation, replicated in multiple species\",\n      \"pmids\": [\"8282124\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"Human and cynomolgus monkey PH-20 cDNAs were isolated; human PH-20 encodes 509 residues, is 59% identical to guinea pig PH-20, and its mRNA is strictly testis-specific (single 2.4 kb transcript) with a single gene in the human genome.\",\n      \"method\": \"cDNA cloning; Southern blot; Northern blot of 16 human tissues\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct sequencing and blotting, foundational cloning paper\",\n      \"pmids\": [\"8234258\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"Sperm plasma membrane protein PH-20 has hyaluronidase activity enabling acrosome-intact sperm to penetrate the cumulus cell layer; purified recombinant PH-20 disperses cumulus cells from mouse eggs, and anti-PH-20 antibodies prevent acrosome-intact sperm from passing through the cumulus to reach the zona pellucida.\",\n      \"method\": \"In vitro cumulus penetration assay; treatment with purified recombinant PH-20; antibody-blocking experiments\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstitution with recombinant protein plus antibody blocking, replicated across species\",\n      \"pmids\": [\"8195297\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"Human SPAM1 gene maps to chromosome 7q31, is encoded by at least 4 exons spanning ~11 kb of genomic DNA, and expression as a 2.4 kb transcript is strictly limited to testis in a panel of 16 human tissues.\",\n      \"method\": \"FISH; somatic cell hybrid PCR; Northern blot; genomic Southern blot\",\n      \"journal\": \"Genomics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple independent mapping methods, expression in 16 tissues\",\n      \"pmids\": [\"8575780\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"PH-20 is bifunctional: it has a hyaluronidase activity required for cumulus penetration and a separate, distinct activity required for secondary sperm-zona binding. Anti-PH-20 MAb that blocks zona binding (90%) has no effect on hyaluronidase activity; apigenin blocks hyaluronidase 93% without inhibiting zona binding; pretreatment of oocytes with hyaluronidase to remove zona HA does not affect secondary zona binding.\",\n      \"method\": \"Antibody inhibition assays; apigenin (hyaluronidase inhibitor) assays; zona pretreatment with hyaluronidase; sperm-zona binding assays\",\n      \"journal\": \"Biology of reproduction\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — multiple orthogonal inhibitors dissecting two activities, robust controls in single study\",\n      \"pmids\": [\"8793062\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"The soluble hyaluronidase released from guinea pig sperm at the acrosome reaction is a soluble form of PH-20 (sPH-20): anti-PH-20 antiserum recognizes it by immunoblot, completely inhibits its enzymatic activity, and 97% is removed by anti-PH-20 affinity chromatography; sPH-20 is not endoproteolytically cleaved unlike membrane PH-20, suggesting enzymatic release from its GPI anchor.\",\n      \"method\": \"Immunoblot; immunoaffinity chromatography; enzyme activity inhibition; anti-PH-20 antiserum\",\n      \"journal\": \"Biology of reproduction\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — affinity purification plus activity inhibition, multiple orthogonal methods in one study\",\n      \"pmids\": [\"8724363\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"Cynomolgus macaque sperm PH-20 exists as a 64 kDa form on the plasma and inner acrosomal membranes and a 53 kDa form released during acrosome reaction; the 64 kDa form has predominantly neutral pH hyaluronidase activity while the 53 kDa form has acid-active hyaluronidase activity; apigenin inhibits both.\",\n      \"method\": \"Western blot; HA substrate gel electrophoresis; ELISA hyaluronidase assay; Fab-immunolocalization; ultrastructure\",\n      \"journal\": \"Developmental biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — multiple biochemical methods, direct localization and activity assays on purified forms\",\n      \"pmids\": [\"8608861\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"The soluble 60 kDa hyaluronidase from bovine testes is a fragment of the membrane-bound PH-20 enzyme; peptide sequencing of 44 fragments from the purified 60 kDa protein aligned to the PH-20 cDNA sequence; it lacks the signal peptide and 56 C-terminal amino acids including the GPI-anchor site.\",\n      \"method\": \"cDNA cloning; protein purification; protease/cyanogen bromide digestion with peptide sequencing\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct peptide sequencing of purified protein mapped to cDNA, orthogonal identification\",\n      \"pmids\": [\"9280317\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"PH-20 N-terminal domain contains the hyaluronidase activity (based on homology with bee venom hyaluronidase and functional data); it is GPI-anchored; its dual roles in cumulus penetration (plasma membrane form, neutral pH activity) and secondary zona binding (inner acrosomal membrane form, post-acrosome reaction) are biochemically distinct.\",\n      \"method\": \"Synthesis of review of functional data; domain analysis from cDNA sequence; functional assays cited\",\n      \"journal\": \"Biology of reproduction\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — synthesis paper consolidating functional experiments, no new primary data\",\n      \"pmids\": [\"9116127\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"In male guinea pigs immunized with PH-20, infertility is associated with emptying of the cauda epididymis (no normal sperm) and induction of experimental autoimmune orchitis (EAO); this is the first demonstration that a purified sperm molecule of known function can induce EAO.\",\n      \"method\": \"Immunization; histopathology; antibody titer measurement; immunofluorescence of germ cells\",\n      \"journal\": \"Biology of reproduction\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo immunopathology with defined antigen, single lab\",\n      \"pmids\": [\"9160711\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Hyaluronic acid (HA) interacts with PH-20 on human sperm to increase basal intracellular calcium and potentiate the acrosome reaction induced by progesterone or zona pellucida; blocking PH-20 with anti-PH-20 Fab abolished the HA-mediated Ca²⁺ increase and enhancement of acrosome reactions.\",\n      \"method\": \"Acrosome reaction assay; intracellular calcium measurement; Fab fragment blocking of PH-20\",\n      \"journal\": \"Zygote\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — Fab blocking with Ca²⁺ measurement and functional acrosome reaction readout, replicated in macaque by independent lab\",\n      \"pmids\": [\"9770775\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Murine Spam1 (PH-20) gene promoter contains a CRE (cAMP-responsive element) at position -57 that binds CREM in testicular nuclear extracts; in vitro transcription assays show CRE is necessary for promoter activity; Spam1 transcripts are absent in CREM-knockout mice, establishing CREM as a transcriptional regulator of Spam1.\",\n      \"method\": \"Gel mobility shift assay; in vitro transcription; Northern blot of CREM-KO mice; primer extension\",\n      \"journal\": \"Molecular reproduction and development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro transcription, CREM-KO genetic validation, and EMSA, multiple orthogonal methods\",\n      \"pmids\": [\"10423292\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Biochemical maturation of Spam1 during epididymal transit involves N-linked oligosaccharide modification: caput sperm have a larger ~74 kDa form with lower hyaluronidase activity, while caudal sperm have a ~67 kDa form with 4.3-fold higher activity; enzymatic deglycosylation of both reduces to ~56 kDa backbone, and all four N-glycosylation sites are functional.\",\n      \"method\": \"Immunofluorescence; Western blot; enzymatic deglycosylation; hyaluronidase activity assay\",\n      \"journal\": \"Molecular reproduction and development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — deglycosylation experiments with activity assays, multiple methods, direct biochemical mechanism\",\n      \"pmids\": [\"9890751\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"HA increases intracellular Ca²⁺ in macaque sperm through plasma membrane PH-20; anti-PH-20 Fab fragments inhibit the Ca²⁺ increase induced by HA, HA gels, and cumulus masses; FITC-HA binding to sperm is localized over the acrosome (PH-20 location) and is inhibited by anti-PH-20 Fab. PH-20 aggregation (by bivalent antibody or zona pellucida binding) is associated with increased Ca²⁺ and acrosome reaction.\",\n      \"method\": \"Fluorometry with Fluo-3 Ca²⁺ indicator; Fab fragment blocking; FITC-HA binding; video imaging; TEM\",\n      \"journal\": \"Zygote\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Fab blocking and Ca²⁺ measurement, multiple readouts, replicated across macaque and human\",\n      \"pmids\": [\"10533704\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"PH-20 (but not acrosin) is required for secondary sperm-zona binding and zona penetration in macaque; anti-PH-20 IgG completely blocked zona penetration while anti-acrosin and anti-CD46 IgG had no effect; PH-20 is present on the inner acrosomal membrane of zona-bound acrosome-reacted sperm whereas acrosin is not.\",\n      \"method\": \"Immunolocalization by TEM; sperm-zona penetration assay with blocking antibodies (up to 300 µg/ml)\",\n      \"journal\": \"Molecular reproduction and development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — function-blocking antibody with TEM ultrastructural localization, appropriate negative controls (anti-acrosin, anti-CD46)\",\n      \"pmids\": [\"10369396\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"A region of macaque PH-20 (Peptide 2, aa 205-235) functions as a HA-binding domain separate from the catalytic hyaluronidase domain; recombinant PH-20 protein lacking this region (E12) does not bind HA, while the full N-terminal construct (G3) binds biotinylated HA; anti-Peptide 2 Fab inhibits HA-induced Ca²⁺ increase in sperm, linking this domain to cell signaling.\",\n      \"method\": \"Recombinant protein binding assay; photoaffinity HA crosslinking; microplate HA binding assay; Fab inhibition of intracellular Ca²⁺\",\n      \"journal\": \"Molecular reproduction and development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — domain deletion approach with direct binding assay and functional Ca²⁺ readout, single study with multiple orthogonal methods\",\n      \"pmids\": [\"11746965\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"PH-20 plasma membrane form mediates HA-induced intracellular signaling via a HA-binding domain distinct from hyaluronidase domains; signaling involves Ca²⁺ increase and aggregation of GPI-anchored PH-20 in the plasma membrane; a 92-kDa protein may be the cytoplasmic signaling molecule linked to PH-20.\",\n      \"method\": \"Review and synthesis of functional data; signaling assays; antibody-induced PH-20 aggregation; calcium measurements\",\n      \"journal\": \"Matrix biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — review paper consolidating data; 92-kDa partner is proposed but not directly identified by Co-IP in this paper\",\n      \"pmids\": [\"11731269\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Despite absence of PH-20 in Spam1 null mice produced by homologous recombination, male mice are fertile; PH-20-null sperm show reduced cumulus dispersal (delayed fertilization at early time points only) but retain fertilizing ability due to other hyaluronidases present in the acrosome detected by Western blot.\",\n      \"method\": \"Homologous recombination knockout; in vitro fertilization assay; Western blot for other hyaluronidases\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO with defined IVF phenotype, Western blot evidence for compensatory hyaluronidases\",\n      \"pmids\": [\"12065596\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Spam1 is haploid expressed in mouse spermatids with both mRNA and protein compartmentalized (non-shared) among conjoined spermatids; this lack of transcript sharing via intercellular bridges leads to biochemically different sperm populations, providing a mechanism for transmission ratio distortion (TRD) in heterozygous males.\",\n      \"method\": \"RNA FISH; immunocytochemistry; flow cytometry; confocal microscopy; temporal expression analysis\",\n      \"journal\": \"Biology of reproduction\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple imaging methods showing compartmentalization, flow cytometry confirming sperm population differences\",\n      \"pmids\": [\"11369602\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Hyaluronidase activity of macaque sperm surface PH-20 requires both N-linked glycosylation (removal abolishes activity) and disulfide bond integrity (reduction with β-mercaptoethanol or DTT abolishes activity); mannose is a major sugar in the N-linked glycans; 6 isoforms with pI 5.1–6.0 were identified by 2D electrophoresis.\",\n      \"method\": \"Immunoaffinity purification; N-glycosidase F deglycosylation; β-mercaptoethanol/DTT reduction; lectin blotting; 2D electrophoresis; hyaluronidase activity assay\",\n      \"journal\": \"Journal of andrology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — enzymatic removal of glycans and reduction of disulfides with direct activity readout, multiple reagents\",\n      \"pmids\": [\"11868814\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Mouse Spam1 is transcribed in the female genital tract (uterus, oviduct, vagina) in a region-dependent manner; the protein has hyaluronidase activity at neutral pH but not acidic pH in female tissues, and its expression in the uterus fluctuates with the estrous cycle.\",\n      \"method\": \"RT-PCR; RNase protection assay; in situ transcript hybridization; Western blot; immunohistochemistry; HA substrate gel electrophoresis\",\n      \"journal\": \"Biology of reproduction\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple methods confirming expression and activity, single lab\",\n      \"pmids\": [\"12672666\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Epididymal SPAM1 is released with its intact GPI lipid anchor predominantly in insoluble particles in luminal fluid; PI-PLC treatment or Triton X-100 releases the majority, confirming lipid anchor retention on secreted protein; two-dimensional gel shows distinct isoforms in epididymis vs. testis, with N-linked and O-linked glycosylation differences.\",\n      \"method\": \"Ultracentrifugation; PI-PLC treatment; 2D-PAGE with immunoblotting; lectin blotting; enzymatic deglycosylation\",\n      \"journal\": \"Journal of andrology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — PI-PLC and detergent treatment with direct anchor confirmation, multiple biochemical methods\",\n      \"pmids\": [\"12514083\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Spam1 mRNA in mouse spermatids is localized near the ER and anchored to the cytoskeleton, absent from intercellular bridges; this compartmentalization mediates non-sharing of transcripts. Spam1 on caudal sperm surface mediates the synergistic increase in acrosome reactions induced by HA and progesterone, confirmed by reduced response in Rb(6.16) Spam1 mutant sperm.\",\n      \"method\": \"In situ hybridization by light and electron microscopy; immunocytochemistry; acrosome reaction assay with HA+progesterone; comparison to Spam1 mutant mice\",\n      \"journal\": \"Molecular reproduction and development\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — EM-level localization plus functional acrosome reaction assay using mutant mouse model, single lab\",\n      \"pmids\": [\"15457544\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"HYAL5 (a GPI-anchored hyaluronidase active at pH 5–7) is expressed exclusively in testis and is present on sperm plasma and acrosomal membranes; it can disperse cumulus cells and is the principal cumulus matrix depolymerase in mouse sperm when PH-20 is absent, while PH-20 compensates for Hyal5's role.\",\n      \"method\": \"Protein purification from PH-20-null sperm; hyaluronan zymography; cumulus dispersal assay; apigenin inhibition; GPI-anchor characterization\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — protein purification and identification, activity assay, use of PH-20-null sperm, multiple methods\",\n      \"pmids\": [\"16330764\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Spam1 mRNA 3'UTR AU-rich elements (AREs) bind six testicular cytoplasmic proteins (AU-binding proteins, AUBPs) that interact with the cytoskeleton; these interactions mediate post-transcriptional regulation of Spam1 in spermatids; antisense RNA in testis can modulate ARE function. Transgenic overexpression attempts failed, indicating tight post-transcriptional control.\",\n      \"method\": \"UV cross-linking assay; transgenic overexpression; Northern analysis; cytoskeletal binding experiments\",\n      \"journal\": \"Molecular reproduction and development\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — UV cross-linking with cytoskeletal association, combined with transgenesis failure, single lab\",\n      \"pmids\": [\"16250006\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Spam1 RNA is anchored to the cytoskeleton in spermatids and interacts via 3' UTR AU-rich sequences with cytoskeletal-associated AU-binding proteins, preventing transcript sharing through intercellular bridges; this mechanism drives TRD. Spam1 overexpression (transgene) causes TRD by producing sperm with cytoplasmic droplets containing excess Spam1, reducing fertilizing ability.\",\n      \"method\": \"EM in situ hybridization; Northern analysis of fractionated testicular RNA; UV cross-linking; flow cytometry; FISH\",\n      \"journal\": \"Reproductive biology and endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods including EM localization, biochemical fractionation, and transgenic functional validation\",\n      \"pmids\": [\"16092963\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Epididymal SPAM1 acquired by Spam1-null sperm from wild-type epididymal luminal fluid in vitro significantly increases cumulus penetration ability, directly linking epididymal SPAM1 uptake with fertilizing ability and establishing it as a marker of sperm maturation.\",\n      \"method\": \"In vitro incubation of null sperm with WT epididymal luminal fluid; flow cytometry; immunocytochemistry; IVF cumulus penetration assay\",\n      \"journal\": \"Biology of reproduction\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — null sperm rescue experiment with direct functional IVF readout, flow cytometry quantification\",\n      \"pmids\": [\"16436526\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Recombinant mouse SPAM1 and HYAL5 expressed in Xenopus oocytes both exhibit hyaluronidase activity at neutral pH and are GPI-anchored; HYALP1 lacks hyaluronidase activity despite sequence similarity.\",\n      \"method\": \"Recombinant expression in Xenopus oocytes; hyaluronidase activity assay; GPI-anchor characterization\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstitution in heterologous expression system with direct enzymatic assay, comparative analysis of all three family members\",\n      \"pmids\": [\"16925524\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Human recombinant PH-20 expressed in Drosophila S2 cells uses an HA octasaccharide as its minimum substrate (not hexasaccharide as for bovine testicular hyaluronidase); PH-20 catalyzes both hydrolysis and transglycosylation of HA octasaccharide.\",\n      \"method\": \"Recombinant expression; capillary zone electrophoresis analysis of reaction products; minimum substrate determination\",\n      \"journal\": \"Glycobiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — purified recombinant enzyme with direct substrate analysis by CZE, minimum substrate definitively established\",\n      \"pmids\": [\"17602139\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"SPAM1 is transferred to sperm from murine epididymosomes (male) and newly identified uterosomes (female) via a vesicular docking mechanism; uptake requires the intact GPI anchor (abolished by enzymatic anchor cleavage); fluorescently labeled vesicles are observed juxtaposed to sperm plasma membranes by TEM.\",\n      \"method\": \"Ultracentrifugation; immunogold labeling; confocal and TEM microscopy; GPI anchor cleavage experiments; fluorescent vesicle tracking\",\n      \"journal\": \"Molecular reproduction and development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — GPI-dependency demonstrated by enzymatic cleavage, TEM visualization of vesicle docking, multiple imaging methods\",\n      \"pmids\": [\"18384048\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"SPAM1 is required for efficient sperm entry into and penetration through the cumulus matrix; SPAM1-null sperm accumulate at the surface/outer edge of the cumulus, while HYAL5-null sperm show no such defect; double comparison demonstrates SPAM1 but not HYAL5 is the functionally critical hyaluronidase for cumulus entry.\",\n      \"method\": \"HYAL5 knockout mouse generation; in vitro fertilization assay; comparative analysis of WT, HYAL5-null, and SPAM1-null sperm\",\n      \"journal\": \"Biology of reproduction\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO with defined cellular phenotype, direct comparison between two KO lines\",\n      \"pmids\": [\"19605784\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Clusterin (CLU) in epididymal/uterine luminal fluid stabilizes monomeric GPI-linked SPAM1 and mediates its transfer to human and mouse sperm membranes; anti-CLU antibody reduces SPAM1 delivery; co-immunoprecipitation reveals direct CLU-SPAM1 association; high CLU concentrations reduce and low concentrations enhance SPAM1 transfer.\",\n      \"method\": \"Co-immunoprecipitation; native Western blot; anti-CLU antibody blocking; dose-response transfer assay; apolipoprotein-enhanced transfer\",\n      \"journal\": \"Biology of reproduction\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — co-IP plus functional transfer assay with dose-response, antibody blocking, two species tested\",\n      \"pmids\": [\"19357365\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Cryo-EM structure of human PH-20 shows: a central catalytic domain with conserved catalytically essential residues; a unique EGF-like domain with a longer sequence forming a flexibly anchored β-hairpin containing a disulfide bond, distinguishing it from other hyaluronidase family members.\",\n      \"method\": \"Cryogenic electron microscopy (cryo-EM); structural comparison with other hyaluronidase structures\",\n      \"journal\": \"Proteins\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct cryo-EM structure with comparative structural analysis identifying unique features\",\n      \"pmids\": [\"39722545\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"SPAM1/PH-20 is a GPI-anchored, testis-expressed (with secondary epididymal and female-tract expression) bifunctional sperm surface protein: its N-terminal domain carries hyaluronidase activity (requiring N-linked glycosylation and disulfide bonds, minimum substrate HA octasaccharide) that enables acrosome-intact sperm to penetrate the hyaluronic acid-rich cumulus cell layer, while a distinct C-terminal domain on the inner acrosomal membrane of acrosome-reacted sperm mediates secondary zona pellucida binding; additionally, a separate HA-binding domain (aa 205–235) on plasma-membrane PH-20 mediates HA-induced intracellular Ca²⁺ signaling via PH-20 aggregation to prime the acrosome reaction; the protein is transferred post-testiculary to sperm via GPI-anchor-dependent vesicular (epididymosomes/uterosomes) and CLU-mediated soluble mechanisms, undergoes N-glycan remodeling during epididymal maturation to increase activity, and its haploid-expressed mRNA is cytoskeletally anchored in spermatids preventing sharing through intercellular bridges, a mechanism underlying transmission ratio distortion.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"SPAM1/PH-20 is a GPI-anchored, testis-expressed sperm surface protein that orchestrates the sperm's passage through the egg's investments during fertilization, functioning as a bifunctional molecule combining hyaluronidase enzymatic activity with adhesive activity [#10, #12]. Its N-terminal catalytic domain hydrolyzes hyaluronic acid (minimum substrate an HA octasaccharide), enabling acrosome-intact sperm to penetrate the hyaluronan-rich cumulus cell layer surrounding the egg [#10, #36]; this activity depends on N-linked glycosylation and disulfide bond integrity [#27], and cryo-EM reveals a central catalytic domain together with a distinctive EGF-like domain forming a flexibly anchored disulfide-containing β-hairpin [#40]. A biochemically separable activity mediates secondary sperm binding to the zona pellucida, demonstrated by inhibitors that block one activity without the other and by the requirement for PH-20 on the inner acrosomal membrane of acrosome-reacted sperm [#0, #12, #22]. A third HA-binding region (aa 205–235), distinct from the catalytic site, drives HA-induced intracellular Ca²⁺ increases via aggregation of plasma-membrane PH-20, potentiating the acrosome reaction [#21, #23]. The protein redistributes from the posterior-head plasma membrane to the inner acrosomal membrane following the acrosome reaction by a calcium-dependent translocation, and its GPI anchor constrains its lateral mobility within membrane domains [#3, #4, #7]. SPAM1 is acquired post-testicularly: it is delivered to maturing sperm from epididymosomes and uterosomes by a GPI-anchor-dependent vesicular mechanism and through clusterin-mediated soluble transfer, with epididymal N-glycan remodeling raising its hyaluronidase activity during maturation [#20, #37, #39]. Transcription is driven by a CREM-dependent promoter element [#19], and Spam1 mRNA is cytoskeletally anchored in spermatids via 3'UTR AU-rich elements, preventing transcript sharing through intercellular bridges and underlying transmission ratio distortion [#26, #33]. Despite these roles, Spam1-null male mice remain fertile because the testis-restricted hyaluronidase HYAL5 partially compensates for cumulus dispersal, although SPAM1 is the functionally critical enzyme for efficient cumulus entry [#25, #31, #38].\",\n  \"teleology\": [\n    {\n      \"year\": 1985,\n      \"claim\": \"Established that the sperm surface antigen PH-20 has an essential function in sperm adhesion to the egg zona pellucida, defining its candidacy as a fertilization protein.\",\n      \"evidence\": \"Monoclonal antibody inhibition of sperm-zona binding in guinea pig\",\n      \"pmids\": [\"4066757\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular identity and biochemical mechanism of binding undefined\", \"Did not distinguish enzymatic from adhesive activity\"]\n    },\n    {\n      \"year\": 1988,\n      \"claim\": \"Defined PH-20 as a GPI-anchored membrane protein whose mobility is constrained by ectodomain interactions, explaining how it maintains discrete surface domains.\",\n      \"evidence\": \"PI-PLC cleavage and FRAP diffusion measurements on guinea pig sperm\",\n      \"pmids\": [\"3381102\", \"3558486\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of constraining ectodomain interactions not determined\", \"Mechanism of post-acrosome-reaction redistribution unresolved\"]\n    },\n    {\n      \"year\": 1990,\n      \"claim\": \"Molecular cloning provided the protein sequence, revealing a single-gene-encoded glycoprotein with conserved cysteines and N-glycosylation sites, enabling all subsequent domain dissection.\",\n      \"evidence\": \"cDNA cloning, Southern and Northern blots in guinea pig and across mammals\",\n      \"pmids\": [\"2269661\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Catalytic residues not yet mapped\", \"Domain boundaries for distinct functions not defined\"]\n    },\n    {\n      \"year\": 1993,\n      \"claim\": \"Identified PH-20 as a hyaluronidase and cloned the strictly testis-specific human ortholog, linking the cloned gene to enzymatic function in humans.\",\n      \"evidence\": \"Vaccinia/recombinant expression with hyaluronidase assay and PI-PLC release; human/monkey cDNA cloning and tissue Northern blots\",\n      \"pmids\": [\"8282124\", \"8234258\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo role in human fertilization not directly tested\", \"Catalytic site residues not localized\"]\n    },\n    {\n      \"year\": 1994,\n      \"claim\": \"Demonstrated that PH-20 hyaluronidase enables acrosome-intact sperm to penetrate the cumulus cell layer, defining its first physiological function.\",\n      \"evidence\": \"Recombinant PH-20 cumulus dispersal and antibody-blocking cumulus penetration assays in mouse\",\n      \"pmids\": [\"8195297\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not establish whether cumulus penetration is the sole role\", \"Relationship to zona binding activity unaddressed\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Resolved PH-20 as a bifunctional protein with biochemically separable hyaluronidase and secondary zona-binding activities, reconciling its enzymatic and adhesive roles.\",\n      \"evidence\": \"Orthogonal inhibitor dissection (antibody, apigenin, zona HA removal) and soluble PH-20 characterization in guinea pig and macaque\",\n      \"pmids\": [\"8793062\", \"8724363\", \"8608861\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of the zona-binding activity not identified\", \"Identity of the zona ligand undefined\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Mapped the hyaluronidase to the N-terminal domain and identified soluble forms as proteolytically released fragments, distinguishing membrane and soluble enzyme populations.\",\n      \"evidence\": \"Peptide sequencing of purified bovine 60 kDa enzyme mapped to PH-20 cDNA; domain synthesis analysis\",\n      \"pmids\": [\"9280317\", \"9116127\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Protease responsible for endoproteolytic cleavage not identified\", \"Catalytic residues still inferred from homology\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Identified CREM as the transcriptional driver of Spam1 and defined epididymal N-glycan remodeling as the mechanism increasing hyaluronidase activity during sperm maturation.\",\n      \"evidence\": \"EMSA, in vitro transcription and CREM-KO Northern blots; deglycosylation and activity assays on caput vs caudal sperm in mouse\",\n      \"pmids\": [\"10423292\", \"9890751\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Glycan structures responsible for activity gain not resolved\", \"Other transcriptional inputs beyond CREM unexplored\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Showed that plasma-membrane PH-20 binds HA to raise intracellular Ca²⁺ and potentiate the acrosome reaction, and that PH-20 aggregation drives the signal, adding a signaling role distinct from enzymatic and adhesive functions.\",\n      \"evidence\": \"Fab blocking with Ca²⁺ fluorometry, FITC-HA binding, and aggregation experiments in human and macaque sperm\",\n      \"pmids\": [\"9770775\", \"10533704\", \"10369396\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cytoplasmic signaling partner not identified\", \"Mechanism coupling aggregation to Ca²⁺ entry unresolved\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Localized the HA-binding/signaling activity to a discrete region (aa 205–235) separate from the catalytic domain, molecularly separating PH-20's signaling from its enzymatic function.\",\n      \"evidence\": \"Recombinant deletion constructs, photoaffinity HA crosslinking, and anti-Peptide 2 Fab inhibition of Ca²⁺ in macaque\",\n      \"pmids\": [\"11746965\", \"11731269\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Proposed 92-kDa cytoplasmic signaling partner not directly identified\", \"Structural basis of HA binding by this region undefined\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Knockout revealed SPAM1 is dispensable for male fertility due to compensating acrosomal hyaluronidases, while haploid-expressed mRNA compartmentalization explained transmission ratio distortion.\",\n      \"evidence\": \"Spam1 homologous-recombination knockout with IVF and Western blots; RNA FISH and flow cytometry of compartmentalized transcripts in mouse\",\n      \"pmids\": [\"12065596\", \"11369602\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of compensating hyaluronidase not yet established at this stage\", \"Molecular tether anchoring mRNA not defined\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Defined the biochemical requirements for hyaluronidase activity—N-glycosylation and disulfide bond integrity—establishing structural determinants of enzyme function.\",\n      \"evidence\": \"N-glycosidase deglycosylation, disulfide reduction, lectin and 2D analyses with activity readout in macaque\",\n      \"pmids\": [\"11868814\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Which specific glycans/disulfides are essential not mapped\", \"Catalytic mechanism at atomic level not addressed\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Extended SPAM1 expression beyond sperm to the female and epididymal tracts and established that secreted SPAM1 retains its intact GPI anchor in luminal particles, setting up a post-testicular delivery model.\",\n      \"evidence\": \"RT-PCR, RNase protection, IHC, and HA zymography in female tract; PI-PLC/detergent release and 2D-PAGE of epididymal fluid in mouse\",\n      \"pmids\": [\"12672666\", \"12514083\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional role of female-tract SPAM1 not established\", \"Mechanism of particle association undefined at this stage\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Localized spermatid Spam1 mRNA to ER-proximal cytoskeleton and confirmed surface SPAM1 mediates synergistic HA+progesterone acrosome reactions using a Spam1 mutant, unifying the regulatory and signaling roles.\",\n      \"evidence\": \"Light/EM in situ hybridization and acrosome reaction assays comparing wild-type and Rb(6.16) Spam1 mutant sperm\",\n      \"pmids\": [\"15457544\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Cytoskeletal anchor molecule not identified\", \"Signaling effectors downstream of synergy unresolved\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Identified the AU-rich-element-binding proteins that anchor Spam1 mRNA to the cytoskeleton, providing the molecular basis for transcript non-sharing and transmission ratio distortion.\",\n      \"evidence\": \"UV crosslinking, cytoskeletal binding, transgenic overexpression and Northern analyses in mouse testis\",\n      \"pmids\": [\"16250006\", \"16092963\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Individual AUBP identities not all resolved\", \"Quantitative contribution to TRD in vivo not fully defined\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Identified HYAL5 as the GPI-anchored testis hyaluronidase that compensates for SPAM1 loss, explaining why Spam1-null mice remain fertile.\",\n      \"evidence\": \"Protein purification from PH-20-null sperm, HA zymography, cumulus dispersal and apigenin inhibition in mouse\",\n      \"pmids\": [\"16330764\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative in vivo contribution of each enzyme not yet quantified here\", \"Regulatory interplay between SPAM1 and HYAL5 unknown\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Demonstrated that epididymally acquired SPAM1 functionally rescues cumulus penetration of null sperm, directly linking post-testicular uptake to fertilizing capacity.\",\n      \"evidence\": \"In vitro incubation of null sperm with WT luminal fluid, flow cytometry and IVF cumulus penetration assay in mouse\",\n      \"pmids\": [\"16436526\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Vesicular vs soluble transfer routes not distinguished here\", \"Stability of acquired protein on sperm not assessed\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Defined PH-20 substrate specificity (HA octasaccharide minimum, dual hydrolysis/transglycosylation) and confirmed neutral-pH GPI-anchored activity across family members, distinguishing it enzymatically from HYALP1.\",\n      \"evidence\": \"Recombinant expression in Drosophila S2 cells and Xenopus oocytes with CZE product analysis and activity assays\",\n      \"pmids\": [\"17602139\", \"16925524\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological relevance of transglycosylation unknown\", \"Catalytic residues not yet structurally confirmed\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Established the molecular machinery for SPAM1 transfer to sperm—GPI-dependent vesicular docking from epididymosomes/uterosomes and clusterin-mediated soluble delivery—and confirmed SPAM1 as the critical cumulus-entry enzyme.\",\n      \"evidence\": \"GPI-cleavage transfer assays, TEM vesicle docking, CLU co-IP and antibody blocking, and HYAL5/SPAM1 KO comparison in mouse and human\",\n      \"pmids\": [\"18384048\", \"19357365\", \"19605784\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Receptor/docking factor on the sperm membrane not identified\", \"Stoichiometry of CLU-SPAM1 complex undefined\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Provided the first atomic structure of human PH-20, revealing the catalytic domain and a unique EGF-like β-hairpin distinguishing it from other hyaluronidases.\",\n      \"evidence\": \"Cryo-EM structure of human PH-20 with comparative structural analysis\",\n      \"pmids\": [\"39722545\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structures of HA-binding and zona-binding regions not resolved in complex with ligands\", \"Conformational basis of aggregation-driven signaling not captured\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The cytoplasmic signaling partner that couples plasma-membrane PH-20 aggregation to Ca²⁺ entry, and the sperm-surface receptor mediating GPI-anchored SPAM1 docking, remain unidentified.\",\n      \"evidence\": \"No direct identification in the available corpus\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No Co-IP identification of the proposed 92-kDa signaling molecule\", \"No molecular identity for the vesicle docking receptor\", \"Zona pellucida ligand for secondary binding undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140098\", \"supporting_discovery_ids\": [8, 10, 27, 35, 36]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [8, 36]},\n      {\"term_id\": \"GO:0098631\", \"supporting_discovery_ids\": [0, 12, 22]},\n      {\"term_id\": \"GO:0140299\", \"supporting_discovery_ids\": [18, 21, 23]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 3, 4]},\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [13, 29, 37]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [37, 39]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1474244\", \"supporting_discovery_ids\": [10, 36, 38]},\n      {\"term_id\": \"R-HSA-1474165\", \"supporting_discovery_ids\": [0, 10, 22]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [18, 21, 23]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"CLU\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}