{"gene":"GP9","run_date":"2026-06-10T01:55:21","timeline":{"discoveries":[{"year":1999,"finding":"GPIbβ interaction with GPIX is essential for surface expression of GPIbα: a frameshift mutation in GPIbβ (Ala80 codon deletion) caused absence of GPIX on the platelet surface, and transfection of wild-type GPIbβ into CHO cells stably expressing GPIbα rescued GPIX surface expression, while the mutant GPIbβ did not.","method":"Transient co-expression in 293T cells and stable CHO cell transfection; flow cytometry; DNA sequencing","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal functional rescue experiments in two cell systems with clear positive and negative controls, replicated across multiple patient-derived mutations","pmids":["10216092"],"is_preprint":false},{"year":2002,"finding":"The N-terminal cysteine knot (residues 1–14) of GPIbβ is critical for the conformational interaction with GPIX; N-terminal truncations of GPIbβ missing residues 1–14, 1–26, or 1–31 failed to support GPIX surface expression, and residues 15–32 of GPIbβ are implicated in the key contact with GPIX.","method":"N-terminal truncation mutants and GPIbβ/GPIX chimeras expressed in mammalian cells; surface expression by flow cytometry; anti-GPIbβ monoclonal antibody MBC 257.4 developed to map epitope","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 / Strong — systematic domain deletion and chimera experiments with clear functional readout; consistent with independent structural data","pmids":["12036872"],"is_preprint":false},{"year":2011,"finding":"Crystal structures of GPIbβ ectodomain and a GPIbβ/GPIX chimera revealed a quaternary interface between GPIbβ and GPIX, with GPIbβ Tyr106 inserting into a pocket formed by GPIX loops b and c; mutagenesis confirmed this interface, and two BSS mutations A108P and P74R disrupted GPIX surface expression by perturbing this interface.","method":"X-ray crystallography of GPIbβ ectodomain and GPIbβ(Eabc) chimera; site-directed mutagenesis; surface expression assays","journal":"Blood","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure combined with mutagenesis validation and functional surface expression assay in one study","pmids":["21908432"],"is_preprint":false},{"year":1994,"finding":"Truncated GPIbα lacking the transmembrane domain and cytoplasmic tail (due to Ser444→stop mutation) is produced, normally glycosylated, and secreted into plasma; residual GPIbβ and GPIX are expressed on the platelet surface without GPIbα, indicating that GPIbβ and GPIX can partially assemble independently of the GPIbα transmembrane/cytoplasmic region.","method":"DNA sequencing; neuraminidase digestion; SDS-PAGE; Western blot; flow cytometry of patient platelets","journal":"Blood","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — patient-derived biochemical characterization with multiple methods but single case, no cell transfection reconstitution","pmids":["7949089"],"is_preprint":false},{"year":1998,"finding":"A Leu40Pro mutation in GPIX causes Bernard-Soulier syndrome with near-normal GPIbα surface levels but severely reduced GPIX and GPV, and GPIbα in this context fails to bind conformation-dependent monoclonal antibodies and cannot support ristocetin-induced agglutination, indicating GPIX is required for proper GPIbα conformation and function.","method":"Flow cytometry; GPIX gene sequencing; allele-specific restriction enzyme analysis; ristocetin-induced platelet agglutination; monoclonal antibody binding assays","journal":"British journal of haematology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — patient platelet characterization with multiple functional assays and genetic confirmation but no cell reconstitution","pmids":["9886312"],"is_preprint":false},{"year":2003,"finding":"The quinine-dependent antibody binding site on GPIX is localized to the C-terminal extracellular region (amino acids 64–135), with Arg110 and Gln115 being critical residues; mutation of Arg110 to Gln caused the most pronounced reduction in quinine-dependent antibody binding from patient sera.","method":"Chimeric mouse/human GPIX constructs expressed in stable CHO cell lines; patient serum binding assays; site-directed mutagenesis","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 / Strong — systematic chimera and mutagenesis approach validated against 6 independent patient sera with consistent results","pmids":["12738668"],"is_preprint":false},{"year":2002,"finding":"A Leu7Pro mutation in the signal peptide hydrophobic core of GPIX abolishes surface expression of the entire GPIb-V-IX complex; co-transfection of GPIXPro7 with normal GPIbα and GPIbβ in CHO cells reproduced the platelet phenotype (no detectable GPIX, low intracellular GPIbα/β, no surface expression), establishing a critical role for the GPIX signal peptide in correct ER insertion and complex biogenesis.","method":"DNA sequencing; flow cytometry; Western blot; co-transfection in CHO cells","journal":"British journal of haematology","confidence":"High","confidence_rationale":"Tier 2 / Strong — patient data replicated by cell transfection reconstitution with multiple orthogonal readouts","pmids":["12100158"],"is_preprint":false},{"year":2001,"finding":"A Cys8→Arg mutation in mature GPIX disrupts a putative disulfide bond between Cys8 and Cys12, altering secondary structure and causing absence of the GPIb/IX/V complex from the platelet surface in a BSS patient.","method":"DNA sequencing; restriction enzyme analysis (BsaAI); flow cytometry; structural inference from disulfide bond disruption","journal":"British journal of haematology","confidence":"Medium","confidence_rationale":"Tier 3 / Weak — genetic and flow cytometric data from a single patient case; disulfide bond disruption is inferred but not biochemically reconstituted","pmids":["11167791"],"is_preprint":false},{"year":2001,"finding":"Asn45Ser mutation in GPIX causes BSS with decreased disulfide bridge formation between GPIbα and GPIbβ, suggesting GPIX is required not only for correct assembly of the GPIb-IX complex but also for proper disulfide bonding between GPIbα and GPIbβ.","method":"Flow cytometry; Western blotting; DNA sequencing; restriction analysis with Fnu4H1","journal":"Platelets","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — patient platelet biochemistry with multiple methods; replicated across multiple unrelated patients in multiple studies (PMIDs 11297032, 14510954, 17804902)","pmids":["11297032","14510954","17804902"],"is_preprint":false},{"year":2012,"finding":"GPIX W127X (nonsense) mutation leads to absence of GPIX but residual GPIbα/β heterodimer is still expressed on platelets and CHO-K1 cells; this residual GPIbα/β complex supports adhesion to immobilized von Willebrand factor, type III collagen, and ristocetin-induced agglutination, demonstrating that GPIbα/β can form a functional complex independently of GPIX.","method":"Flow cytometry; stable CHO-K1 cell expression; platelet adhesion assay to immobilized VWF and collagen; ristocetin-induced platelet agglutination","journal":"International journal of hematology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cell model recapitulates patient phenotype with functional adhesion assays, single lab","pmids":["23143686"],"is_preprint":false},{"year":2023,"finding":"Lentiviral gene therapy restoring GPIX expression in GP9-knockout megakaryoblastic cell lines and iPSC-derived platelets reverts absence of GPIX on the membrane surface and normalizes platelet size, confirming that GP9/GPIX is necessary and sufficient for correct GPIb-IX-V complex surface localization and normal platelet morphology.","method":"CRISPR/gene-editing KO models; lentiviral transduction; flow cytometry; iPSC differentiation to megakaryocytes/platelets; hematopoietic stem cell transduction from BSS patients","journal":"Molecular therapy. Nucleic acids","confidence":"High","confidence_rationale":"Tier 2 / Strong — loss-of-function KO and gain-of-function gene therapy rescue in multiple human cellular models including patient HSCs, with consistent phenotypic readouts","pmids":["37416759"],"is_preprint":false},{"year":2021,"finding":"Cancer cells (A549, MCF-7, MV3) take up intact platelets by dynamin-dependent phagocytosis and subsequently recycle the platelet-specific protein CD42a (GPIX) into their own plasma membrane; this was not observed in non-cancerous 16HBE14o- cells.","method":"Confocal laser scanning microscopy; flow cytometry; dynamin inhibitor Dyngo4a; incubation of cancer cells with fluorescently labeled platelets","journal":"Journal of thrombosis and haemostasis","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — direct imaging and pharmacological inhibition in multiple cancer cell lines with appropriate non-cancerous control; single lab","pmids":["34592045"],"is_preprint":false},{"year":2019,"finding":"A 2460 bp deletion in the canine GP9 gene causing a frameshift and premature stop codon truncating ~two-thirds of the protein abolishes functional GPIb-IX-V complex expression (confirmed by immunocytochemistry) and causes macrothrombocytopenia with platelet adhesion defect resembling human BSS type C, establishing GP9 as the causal gene in Cocker Spaniel BSS.","method":"Whole genome sequencing; PCR-based genotyping; immunocytochemistry; pedigree/recessive inheritance analysis","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — genetic and immunocytochemical evidence in a canine model; no in vitro reconstitution but functional complex absence confirmed directly","pmids":["31484196"],"is_preprint":false},{"year":2025,"finding":"Homozygous deletion of GP9 in immortalized megakaryocyte cell lines (imMKCL) reduced proplatelet formation by 96%, and transcriptomic analysis of GP9-/- MKs showed dysregulation of RNA metabolism and actin/tubulin folding pathways, identifying specific molecular pathways dependent on GPIX during megakaryopoiesis.","method":"Homozygous GP9 deletion in imMKCL; proplatelet formation assay; RNA-seq at four MK differentiation stages; patient platelet RNA-seq","journal":"HemaSphere","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct KO with quantitative cellular phenotype and transcriptomic pathway analysis; single lab, single study","pmids":["41017962"],"is_preprint":false}],"current_model":"GP9 encodes GPIX, a single leucine-rich repeat transmembrane subunit that assembles with GPIbα, GPIbβ (2:1:2:1 stoichiometry) and GPV to form the platelet GPIb-IX-V complex; GPIX is required for correct ER insertion, disulfide bond formation, and surface trafficking of the entire complex, interacts directly with GPIbβ through a quaternary interface involving GPIbβ Tyr106 and GPIX loops b/c (resolved by crystal structure), and its N-terminal Cys8–Cys12 disulfide and signal peptide integrity are essential for proper folding; loss-of-function mutations in GP9 cause Bernard-Soulier syndrome type C through absence of the VWF receptor complex on the platelet surface, impaired proplatelet formation, and dysregulation of actin/tubulin folding pathways in megakaryocytes, and lentiviral GP9 gene therapy rescues GPIX surface expression and normalizes platelet size."},"narrative":{"mechanistic_narrative":"GP9 encodes GPIX, a transmembrane subunit of the platelet GPIb-IX-V von Willebrand factor receptor complex, where it is essential for assembly and surface expression of the entire complex [PMID:12100158, PMID:37416759]. GPIX engages GPIbβ through a defined quaternary interface in which GPIbβ Tyr106 inserts into a pocket formed by GPIX loops b and c, an interface resolved by crystallography and validated by Bernard-Soulier mutations (A108P, P74R) that abolish GPIX surface expression [PMID:21908432]. Proper biogenesis of GPIX depends on the integrity of its signal peptide for correct ER insertion [PMID:12100158] and on intramolecular and inter-subunit disulfide bonding, including the mature Cys8–Cys12 bond, whose disruption eliminates the complex from the platelet surface and impairs GPIbα–GPIbβ disulfide formation [PMID:11167791, PMID:11297032, PMID:14510954, PMID:17804902]. GPIX is required for the native conformation and adhesive function of GPIbα: loss of GPIX prevents conformation-dependent antibody binding and ristocetin-induced agglutination [PMID:9886312], although a residual GPIbα/β heterodimer can assemble and support VWF and collagen adhesion independently of GPIX [PMID:7949089, PMID:23143686]. Loss-of-function mutations in GP9 cause Bernard-Soulier syndrome type C through absence of the surface VWF receptor complex, with downstream consequences for megakaryopoiesis including a severe (96%) reduction in proplatelet formation and dysregulation of actin/tubulin folding pathways [PMID:37416759, PMID:41017962]; lentiviral restoration of GPIX rescues surface complex expression and normalizes platelet size [PMID:37416759].","teleology":[{"year":1994,"claim":"Established that GPIbβ and GPIX can assemble and reach the platelet surface partially independently of the GPIbα transmembrane and cytoplasmic regions, defining the modular nature of complex assembly.","evidence":"Biochemical and flow cytometric characterization of patient platelets carrying a truncating GPIbα Ser444stop mutation","pmids":["7949089"],"confidence":"Medium","gaps":["Single patient case without cell reconstitution","Does not define the GPIX-GPIbβ contact directly"]},{"year":1998,"claim":"Showed that GPIX is required for proper GPIbα conformation and adhesive function, not merely surface presence, since GPIX loss left GPIbα present but non-functional.","evidence":"Patient platelet flow cytometry, conformation-dependent antibody binding, and ristocetin agglutination with a GPIX Leu40Pro mutation","pmids":["9886312"],"confidence":"Medium","gaps":["No cell reconstitution","Mechanism linking GPIX to GPIbα conformation not resolved"]},{"year":1999,"claim":"Demonstrated reciprocal dependence between GPIbβ and GPIX for surface expression, framing the complex as an obligate co-assembly.","evidence":"Reciprocal functional rescue by wild-type vs mutant GPIbβ transfection in CHO/293T cells expressing GPIbα","pmids":["10216092"],"confidence":"High","gaps":["Atomic interface not defined","Focused on GPIbβ rather than GPIX residues"]},{"year":2001,"claim":"Linked GPIX disulfide bonding (Cys8–Cys12) and a conserved Asn residue to both intramolecular folding and inter-subunit GPIbα–GPIbβ disulfide formation, implicating GPIX in oxidative assembly of the complex.","evidence":"Patient platelet biochemistry and sequencing of Cys8Arg and Asn45Ser BSS mutations, replicated across unrelated patients","pmids":["11167791","11297032","14510954","17804902"],"confidence":"Medium","gaps":["Disulfide disruption inferred, not biochemically reconstituted","Single-case data for Cys8Arg"]},{"year":2002,"claim":"Identified the GPIX signal peptide hydrophobic core as essential for correct ER insertion and biogenesis of the entire GPIb-V-IX complex.","evidence":"Co-transfection of GPIX Leu7Pro with normal GPIbα/β in CHO cells recapitulating the patient phenotype","pmids":["12100158"],"confidence":"High","gaps":["Step at which mistargeted GPIX is degraded not defined"]},{"year":2002,"claim":"Mapped the conformational GPIbβ region (cysteine knot, residues 1-14 and 15-32) required for interaction with GPIX, localizing the assembly contact on the GPIbβ side.","evidence":"N-terminal truncation and chimera mutants of GPIbβ with surface expression readout and epitope-mapping antibody","pmids":["12036872"],"confidence":"High","gaps":["GPIX-side contact residues not yet defined","No structural model at this stage"]},{"year":2003,"claim":"Localized the drug-dependent (quinine) antibody epitope to the GPIX C-terminal extracellular region, identifying surface-exposed residues Arg110 and Gln115.","evidence":"Mouse/human GPIX chimeras and site-directed mutagenesis in CHO cells tested against patient sera","pmids":["12738668"],"confidence":"High","gaps":["Relevance to assembly versus immunogenicity not separated"]},{"year":2011,"claim":"Resolved the atomic GPIbβ-GPIX quaternary interface, defining how GPIbβ Tyr106 docks into GPIX loops b/c and explaining BSS mutations that perturb this contact.","evidence":"X-ray crystallography of GPIbβ ectodomain and GPIbβ/GPIX chimera with mutagenesis and surface expression validation","pmids":["21908432"],"confidence":"High","gaps":["Structure of full-length GPIX in the intact complex not solved","Stoichiometric arrangement with GPV not directly resolved"]},{"year":2012,"claim":"Established that GPIbα/β can form a functional adhesive complex independent of GPIX, refining which functions strictly require GPIX.","evidence":"Stable CHO-K1 expression and platelet adhesion/agglutination assays with a GPIX W127X nonsense mutation","pmids":["23143686"],"confidence":"Medium","gaps":["Single lab","Reconciliation with GPIX requirement for GPIbα conformation not fully resolved"]},{"year":2019,"claim":"Confirmed GP9 as a causal gene for Bernard-Soulier-type macrothrombocytopenia in a non-human (canine) model, supporting cross-species conservation of GPIX function.","evidence":"Whole genome sequencing, genotyping and immunocytochemistry of a frameshift GP9 deletion in Cocker Spaniels","pmids":["31484196"],"confidence":"Medium","gaps":["No in vitro reconstitution","Megakaryocyte-level mechanism not examined"]},{"year":2021,"claim":"Showed that cancer cells acquire GPIX (CD42a) by phagocytosing platelets and recycling the protein into their own membrane, indicating GPIX can mark tumor cells via platelet uptake.","evidence":"Confocal imaging, flow cytometry and dynamin inhibition in cancer cell lines with a non-cancerous control","pmids":["34592045"],"confidence":"Medium","gaps":["Functional consequence of acquired GPIX on tumor cells unknown","Single lab"]},{"year":2023,"claim":"Demonstrated that GP9 is both necessary and sufficient for GPIb-IX-V surface localization and normal platelet size, enabling gene-therapy rescue of BSS phenotypes.","evidence":"CRISPR knockout and lentiviral GP9 rescue in megakaryoblastic lines, iPSC-derived platelets and patient HSCs with flow cytometry readouts","pmids":["37416759"],"confidence":"High","gaps":["Durability and in vivo efficacy of gene therapy not addressed in this corpus"]},{"year":2025,"claim":"Defined megakaryocyte-intrinsic consequences of GPIX loss, quantifying a severe proplatelet defect and linking GPIX to RNA metabolism and actin/tubulin folding pathways during megakaryopoiesis.","evidence":"Homozygous GP9 deletion in imMKCL with proplatelet assays and staged RNA-seq plus patient platelet transcriptomics","pmids":["41017962"],"confidence":"Medium","gaps":["Single lab/single study","Causal mechanism connecting GPIX loss to cytoskeletal-folding dysregulation not established"]},{"year":null,"claim":"How GPIX coordinates oxidative folding, ER insertion, and cytoskeletal/RNA pathways into a single biogenesis program remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No full-length structure of GPIX within the intact GPIb-IX-V complex","Causal chain from GPIX loss to actin/tubulin folding dysregulation undefined","Mechanism of GPIX-dependent GPIbα conformation not biochemically reconstituted"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[2,6,10]},{"term_id":"GO:0001618","term_label":"virus receptor activity","supporting_discovery_ids":[4,9]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,6,10]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[6]}],"pathway":[{"term_id":"R-HSA-109582","term_label":"Hemostasis","supporting_discovery_ids":[4,9,10]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[6,7,8]}],"complexes":["GPIb-IX-V complex"],"partners":["GP1BB","GP1BA","GP5"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P14770","full_name":"Platelet glycoprotein IX","aliases":["Glycoprotein 9"],"length_aa":177,"mass_kda":19.0,"function":"The GPIb-V-IX complex functions as the vWF receptor and mediates vWF-dependent platelet adhesion to blood vessels. The adhesion of platelets to injured vascular surfaces in the arterial circulation is a critical initiating event in hemostasis. GP-IX may provide for membrane insertion and orientation of GP-Ib","subcellular_location":"Membrane","url":"https://www.uniprot.org/uniprotkb/P14770/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/GP9","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/GP9","total_profiled":1310},"omim":[{"mim_id":"621264","title":"FETOMATERNAL ALLOIMMUNE THROMBOCYTOPENIA 1; FMAIT1","url":"https://www.omim.org/entry/621264"},{"mim_id":"617443","title":"BLEEDING DISORDER, PLATELET-TYPE, 21; BDPLT21","url":"https://www.omim.org/entry/617443"},{"mim_id":"613160","title":"VON WILLEBRAND FACTOR; VWF","url":"https://www.omim.org/entry/613160"},{"mim_id":"606672","title":"GLYCOPROTEIN Ib, PLATELET, ALPHA POLYPEPTIDE; GP1BA","url":"https://www.omim.org/entry/606672"},{"mim_id":"231200","title":"BERNARD-SOULIER SYNDROME; BSS","url":"https://www.omim.org/entry/231200"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Plasma membrane","reliability":"Approved"},{"location":"Cytosol","reliability":"Approved"},{"location":"Nucleoplasm","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"bone marrow","ntpm":4.8},{"tissue":"lung","ntpm":3.2},{"tissue":"lymphoid tissue","ntpm":8.8}],"url":"https://www.proteinatlas.org/search/GP9"},"hgnc":{"alias_symbol":["CD42a","GPIX"],"prev_symbol":[]},"alphafold":{"accession":"P14770","domains":[{"cath_id":"3.80.10.10","chopping":"4-133","consensus_level":"high","plddt":87.5642,"start":4,"end":133},{"cath_id":"1.20.5","chopping":"143-177","consensus_level":"medium","plddt":84.5614,"start":143,"end":177}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P14770","model_url":"https://alphafold.ebi.ac.uk/files/AF-P14770-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P14770-F1-predicted_aligned_error_v6.png","plddt_mean":84.69},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=GP9","jax_strain_url":"https://www.jax.org/strain/search?query=GP9"},"sequence":{"accession":"P14770","fasta_url":"https://rest.uniprot.org/uniprotkb/P14770.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P14770/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P14770"}},"corpus_meta":[{"pmid":"7949089","id":"PMC_7949089","title":"Bernard-Soulier syndrome Kagoshima: Ser 444-->stop mutation of glycoprotein (GP) Ib alpha resulting in circulating truncated GPIb alpha and surface expression of GPIb beta and GPIX.","date":"1994","source":"Blood","url":"https://pubmed.ncbi.nlm.nih.gov/7949089","citation_count":62,"is_preprint":false},{"pmid":"10216092","id":"PMC_10216092","title":"The critical interaction of glycoprotein (GP) IBbeta with GPIX-a genetic cause of Bernard-Soulier syndrome.","date":"1999","source":"Blood","url":"https://pubmed.ncbi.nlm.nih.gov/10216092","citation_count":57,"is_preprint":false},{"pmid":"21908432","id":"PMC_21908432","title":"Quaternary organization of GPIb-IX complex and insights into Bernard-Soulier syndrome revealed by the structures of GPIbβ and a GPIbβ/GPIX chimera.","date":"2011","source":"Blood","url":"https://pubmed.ncbi.nlm.nih.gov/21908432","citation_count":43,"is_preprint":false},{"pmid":"15987877","id":"PMC_15987877","title":"Molecular evolutionary analyses of the odorant-binding protein gene Gp-9 in fire ants and other Solenopsis species.","date":"2005","source":"Molecular biology and evolution","url":"https://pubmed.ncbi.nlm.nih.gov/15987877","citation_count":41,"is_preprint":false},{"pmid":"11410606","id":"PMC_11410606","title":"High-resolution CryoFESEM of individual cell adhesion molecules (CAMs) in the glycocalyx of human platelets: detection of P-selectin (CD62P), GPI-IX complex (CD42A/CD42B alpha,B beta), and integrin GPIIbIIIa (CD41/CD61) by immunogold labeling and stereo imaging.","date":"2001","source":"The journal of histochemistry and cytochemistry : official journal of the Histochemistry Society","url":"https://pubmed.ncbi.nlm.nih.gov/11410606","citation_count":34,"is_preprint":false},{"pmid":"9886312","id":"PMC_9886312","title":"A new variant of Bernard-Soulier syndrome characterized by dysfunctional glycoprotein (GP) Ib and severely reduced amounts of GPIX and GPV.","date":"1998","source":"British journal of haematology","url":"https://pubmed.ncbi.nlm.nih.gov/9886312","citation_count":33,"is_preprint":false},{"pmid":"12738668","id":"PMC_12738668","title":"Drug-induced thrombocytopenia: localization of the binding site of GPIX-specific quinine-dependent antibodies.","date":"2003","source":"Blood","url":"https://pubmed.ncbi.nlm.nih.gov/12738668","citation_count":33,"is_preprint":false},{"pmid":"22535783","id":"PMC_22535783","title":"Male reproductive fitness and queen polyandry are linked to variation in the supergene Gp-9 in the fire ant Solenopsis invicta.","date":"2012","source":"Proceedings. Biological sciences","url":"https://pubmed.ncbi.nlm.nih.gov/22535783","citation_count":33,"is_preprint":false},{"pmid":"14510954","id":"PMC_14510954","title":"Bernard-Soulier syndrome due to the homozygous Asn-45Ser mutation in GPIX: an unexpected, frequent finding in Germany.","date":"2003","source":"British journal of haematology","url":"https://pubmed.ncbi.nlm.nih.gov/14510954","citation_count":29,"is_preprint":false},{"pmid":"11167791","id":"PMC_11167791","title":"Identification of a new mutation in platelet glycoprotein IX (GPIX) in a patient with Bernard-Soulier syndrome.","date":"2001","source":"British journal of haematology","url":"https://pubmed.ncbi.nlm.nih.gov/11167791","citation_count":27,"is_preprint":false},{"pmid":"14960363","id":"PMC_14960363","title":"CYP4AB1, CYP4AB2, and Gp-9 gene overexpression associated with workers of the red imported fire ant, Solenopsis invicta Buren.","date":"2004","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/14960363","citation_count":27,"is_preprint":false},{"pmid":"12100158","id":"PMC_12100158","title":"A Leu7Pro mutation in the signal peptide of platelet glycoprotein (GP)IX in a case of Bernard-Soulier syndrome abolishes surface expression of the GPIb-V-IX complex.","date":"2002","source":"British journal of haematology","url":"https://pubmed.ncbi.nlm.nih.gov/12100158","citation_count":26,"is_preprint":false},{"pmid":"34592045","id":"PMC_34592045","title":"Uptake of platelets by cancer cells and recycling of the platelet protein CD42a.","date":"2021","source":"Journal of thrombosis and haemostasis : JTH","url":"https://pubmed.ncbi.nlm.nih.gov/34592045","citation_count":25,"is_preprint":false},{"pmid":"19893635","id":"PMC_19893635","title":"Current status of a model system: the gene Gp-9 and its association with social organization in fire ants.","date":"2009","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/19893635","citation_count":24,"is_preprint":false},{"pmid":"12036872","id":"PMC_12036872","title":"The cysteine knot of platelet glycoprotein Ib beta (GPIb beta) is critical for the interaction of GPIb beta with GPIX.","date":"2002","source":"Blood","url":"https://pubmed.ncbi.nlm.nih.gov/12036872","citation_count":16,"is_preprint":false},{"pmid":"25315753","id":"PMC_25315753","title":"Expression of foraging and Gp-9 are associated with social organization in the fire ant Solenopsis invicta.","date":"2014","source":"Insect molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/25315753","citation_count":15,"is_preprint":false},{"pmid":"21943062","id":"PMC_21943062","title":"Membrane insertion and assembly of epitope-tagged gp9 at the tip of the M13 phage.","date":"2011","source":"BMC microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/21943062","citation_count":13,"is_preprint":false},{"pmid":"11297032","id":"PMC_11297032","title":"Occurrence of the Asn45Ser mutation in the GPIX gene in a Belgian patient with Bernard Soulier syndrome.","date":"2001","source":"Platelets","url":"https://pubmed.ncbi.nlm.nih.gov/11297032","citation_count":13,"is_preprint":false},{"pmid":"27346198","id":"PMC_27346198","title":"Generation of induced pluripotent stem cells (iPSCs) from a Bernard-Soulier syndrome patient carrying a W71R mutation in the GPIX gene.","date":"2016","source":"Stem cell research","url":"https://pubmed.ncbi.nlm.nih.gov/27346198","citation_count":8,"is_preprint":false},{"pmid":"17804902","id":"PMC_17804902","title":"First Turkish case of Bernard-Soulier syndrome associated with GPIX N45S.","date":"2007","source":"Acta haematologica","url":"https://pubmed.ncbi.nlm.nih.gov/17804902","citation_count":8,"is_preprint":false},{"pmid":"37416759","id":"PMC_37416759","title":"Lentiviral gene therapy reverts GPIX expression and phenotype in Bernard-Soulier syndrome type C.","date":"2023","source":"Molecular therapy. Nucleic acids","url":"https://pubmed.ncbi.nlm.nih.gov/37416759","citation_count":7,"is_preprint":false},{"pmid":"9054700","id":"PMC_9054700","title":"Flow cytometric platelet enumeration utilizing monoclonal antibody CD42a.","date":"1996","source":"Clinical and laboratory haematology","url":"https://pubmed.ncbi.nlm.nih.gov/9054700","citation_count":7,"is_preprint":false},{"pmid":"31484196","id":"PMC_31484196","title":"A large deletion in the GP9 gene in Cocker Spaniel dogs with Bernard-Soulier syndrome.","date":"2019","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/31484196","citation_count":4,"is_preprint":false},{"pmid":"23143686","id":"PMC_23143686","title":"Platelets with a W127X mutation in GPIX express sufficient residual amounts of GPIbα to support adhesion to von Willebrand factor and collagen.","date":"2012","source":"International journal of hematology","url":"https://pubmed.ncbi.nlm.nih.gov/23143686","citation_count":4,"is_preprint":false},{"pmid":"27934591","id":"PMC_27934591","title":"Generation of a human induced pluripotent stem cell (iPSC) line from a Bernard-Soulier syndrome patient with the mutation p.Asn45Ser in the GPIX gene.","date":"2016","source":"Stem cell research","url":"https://pubmed.ncbi.nlm.nih.gov/27934591","citation_count":2,"is_preprint":false},{"pmid":"38750089","id":"PMC_38750089","title":"Dysregulation of platelet serotonin, 14-3-3, and GPIX in sudden infant death syndrome.","date":"2024","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/38750089","citation_count":1,"is_preprint":false},{"pmid":"28395735","id":"PMC_28395735","title":"Induced pluripotent stem cells derived from Bernard-Soulier Syndrome patient's peripheral blood cells with a p.Phe55Ser mutation in the GPIX gene.","date":"2017","source":"Stem cell research","url":"https://pubmed.ncbi.nlm.nih.gov/28395735","citation_count":1,"is_preprint":false},{"pmid":"29119855","id":"PMC_29119855","title":"Two novel variants of uncertain significance in GP9 associated with Bernard-Soulier syndrome: Are they true mutations?","date":"2017","source":"Platelets","url":"https://pubmed.ncbi.nlm.nih.gov/29119855","citation_count":1,"is_preprint":false},{"pmid":"41017962","id":"PMC_41017962","title":"Transcriptome profiling of megakaryocytes and platelets: Application to GP9- and IKZF5-related thrombocytopenia.","date":"2025","source":"HemaSphere","url":"https://pubmed.ncbi.nlm.nih.gov/41017962","citation_count":0,"is_preprint":false},{"pmid":"39867007","id":"PMC_39867007","title":"A Novel Variant of GP9 Gene Resulting in Bernard-Soulier Syndrome: A Case Report.","date":"2024","source":"Cureus","url":"https://pubmed.ncbi.nlm.nih.gov/39867007","citation_count":0,"is_preprint":false},{"pmid":"42126138","id":"PMC_42126138","title":"Screening and structure-activity relationship analysis of benzoate repellents against Solenopsis invicta targeting odorant-binding protein GP-9.","date":"2026","source":"Pest management science","url":"https://pubmed.ncbi.nlm.nih.gov/42126138","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.01.09.632094","title":"Single-cell transcriptomics-guided development of flow cytometric tests predicting chronic myeloid leukemia blast crisis transformation at chronic phase diagnosis","date":"2025-01-15","source":"bioRxiv","url":"https://doi.org/10.1101/2025.01.09.632094","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":16658,"output_tokens":3579,"usd":0.05183,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":11413,"output_tokens":3886,"usd":0.077107,"stage2_stop_reason":"end_turn"},"total_usd":0.128937,"stage1_batch_id":"msgbatch_01DUPACZi7AAWwuZiUjseQF4","stage2_batch_id":"msgbatch_018yt7chE3f48PEFtDwtj6AE","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1999,\n      \"finding\": \"GPIbβ interaction with GPIX is essential for surface expression of GPIbα: a frameshift mutation in GPIbβ (Ala80 codon deletion) caused absence of GPIX on the platelet surface, and transfection of wild-type GPIbβ into CHO cells stably expressing GPIbα rescued GPIX surface expression, while the mutant GPIbβ did not.\",\n      \"method\": \"Transient co-expression in 293T cells and stable CHO cell transfection; flow cytometry; DNA sequencing\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal functional rescue experiments in two cell systems with clear positive and negative controls, replicated across multiple patient-derived mutations\",\n      \"pmids\": [\"10216092\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"The N-terminal cysteine knot (residues 1–14) of GPIbβ is critical for the conformational interaction with GPIX; N-terminal truncations of GPIbβ missing residues 1–14, 1–26, or 1–31 failed to support GPIX surface expression, and residues 15–32 of GPIbβ are implicated in the key contact with GPIX.\",\n      \"method\": \"N-terminal truncation mutants and GPIbβ/GPIX chimeras expressed in mammalian cells; surface expression by flow cytometry; anti-GPIbβ monoclonal antibody MBC 257.4 developed to map epitope\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — systematic domain deletion and chimera experiments with clear functional readout; consistent with independent structural data\",\n      \"pmids\": [\"12036872\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Crystal structures of GPIbβ ectodomain and a GPIbβ/GPIX chimera revealed a quaternary interface between GPIbβ and GPIX, with GPIbβ Tyr106 inserting into a pocket formed by GPIX loops b and c; mutagenesis confirmed this interface, and two BSS mutations A108P and P74R disrupted GPIX surface expression by perturbing this interface.\",\n      \"method\": \"X-ray crystallography of GPIbβ ectodomain and GPIbβ(Eabc) chimera; site-directed mutagenesis; surface expression assays\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure combined with mutagenesis validation and functional surface expression assay in one study\",\n      \"pmids\": [\"21908432\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"Truncated GPIbα lacking the transmembrane domain and cytoplasmic tail (due to Ser444→stop mutation) is produced, normally glycosylated, and secreted into plasma; residual GPIbβ and GPIX are expressed on the platelet surface without GPIbα, indicating that GPIbβ and GPIX can partially assemble independently of the GPIbα transmembrane/cytoplasmic region.\",\n      \"method\": \"DNA sequencing; neuraminidase digestion; SDS-PAGE; Western blot; flow cytometry of patient platelets\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — patient-derived biochemical characterization with multiple methods but single case, no cell transfection reconstitution\",\n      \"pmids\": [\"7949089\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"A Leu40Pro mutation in GPIX causes Bernard-Soulier syndrome with near-normal GPIbα surface levels but severely reduced GPIX and GPV, and GPIbα in this context fails to bind conformation-dependent monoclonal antibodies and cannot support ristocetin-induced agglutination, indicating GPIX is required for proper GPIbα conformation and function.\",\n      \"method\": \"Flow cytometry; GPIX gene sequencing; allele-specific restriction enzyme analysis; ristocetin-induced platelet agglutination; monoclonal antibody binding assays\",\n      \"journal\": \"British journal of haematology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — patient platelet characterization with multiple functional assays and genetic confirmation but no cell reconstitution\",\n      \"pmids\": [\"9886312\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"The quinine-dependent antibody binding site on GPIX is localized to the C-terminal extracellular region (amino acids 64–135), with Arg110 and Gln115 being critical residues; mutation of Arg110 to Gln caused the most pronounced reduction in quinine-dependent antibody binding from patient sera.\",\n      \"method\": \"Chimeric mouse/human GPIX constructs expressed in stable CHO cell lines; patient serum binding assays; site-directed mutagenesis\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — systematic chimera and mutagenesis approach validated against 6 independent patient sera with consistent results\",\n      \"pmids\": [\"12738668\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"A Leu7Pro mutation in the signal peptide hydrophobic core of GPIX abolishes surface expression of the entire GPIb-V-IX complex; co-transfection of GPIXPro7 with normal GPIbα and GPIbβ in CHO cells reproduced the platelet phenotype (no detectable GPIX, low intracellular GPIbα/β, no surface expression), establishing a critical role for the GPIX signal peptide in correct ER insertion and complex biogenesis.\",\n      \"method\": \"DNA sequencing; flow cytometry; Western blot; co-transfection in CHO cells\",\n      \"journal\": \"British journal of haematology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — patient data replicated by cell transfection reconstitution with multiple orthogonal readouts\",\n      \"pmids\": [\"12100158\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"A Cys8→Arg mutation in mature GPIX disrupts a putative disulfide bond between Cys8 and Cys12, altering secondary structure and causing absence of the GPIb/IX/V complex from the platelet surface in a BSS patient.\",\n      \"method\": \"DNA sequencing; restriction enzyme analysis (BsaAI); flow cytometry; structural inference from disulfide bond disruption\",\n      \"journal\": \"British journal of haematology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Weak — genetic and flow cytometric data from a single patient case; disulfide bond disruption is inferred but not biochemically reconstituted\",\n      \"pmids\": [\"11167791\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Asn45Ser mutation in GPIX causes BSS with decreased disulfide bridge formation between GPIbα and GPIbβ, suggesting GPIX is required not only for correct assembly of the GPIb-IX complex but also for proper disulfide bonding between GPIbα and GPIbβ.\",\n      \"method\": \"Flow cytometry; Western blotting; DNA sequencing; restriction analysis with Fnu4H1\",\n      \"journal\": \"Platelets\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — patient platelet biochemistry with multiple methods; replicated across multiple unrelated patients in multiple studies (PMIDs 11297032, 14510954, 17804902)\",\n      \"pmids\": [\"11297032\", \"14510954\", \"17804902\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"GPIX W127X (nonsense) mutation leads to absence of GPIX but residual GPIbα/β heterodimer is still expressed on platelets and CHO-K1 cells; this residual GPIbα/β complex supports adhesion to immobilized von Willebrand factor, type III collagen, and ristocetin-induced agglutination, demonstrating that GPIbα/β can form a functional complex independently of GPIX.\",\n      \"method\": \"Flow cytometry; stable CHO-K1 cell expression; platelet adhesion assay to immobilized VWF and collagen; ristocetin-induced platelet agglutination\",\n      \"journal\": \"International journal of hematology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell model recapitulates patient phenotype with functional adhesion assays, single lab\",\n      \"pmids\": [\"23143686\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Lentiviral gene therapy restoring GPIX expression in GP9-knockout megakaryoblastic cell lines and iPSC-derived platelets reverts absence of GPIX on the membrane surface and normalizes platelet size, confirming that GP9/GPIX is necessary and sufficient for correct GPIb-IX-V complex surface localization and normal platelet morphology.\",\n      \"method\": \"CRISPR/gene-editing KO models; lentiviral transduction; flow cytometry; iPSC differentiation to megakaryocytes/platelets; hematopoietic stem cell transduction from BSS patients\",\n      \"journal\": \"Molecular therapy. Nucleic acids\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — loss-of-function KO and gain-of-function gene therapy rescue in multiple human cellular models including patient HSCs, with consistent phenotypic readouts\",\n      \"pmids\": [\"37416759\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Cancer cells (A549, MCF-7, MV3) take up intact platelets by dynamin-dependent phagocytosis and subsequently recycle the platelet-specific protein CD42a (GPIX) into their own plasma membrane; this was not observed in non-cancerous 16HBE14o- cells.\",\n      \"method\": \"Confocal laser scanning microscopy; flow cytometry; dynamin inhibitor Dyngo4a; incubation of cancer cells with fluorescently labeled platelets\",\n      \"journal\": \"Journal of thrombosis and haemostasis\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct imaging and pharmacological inhibition in multiple cancer cell lines with appropriate non-cancerous control; single lab\",\n      \"pmids\": [\"34592045\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"A 2460 bp deletion in the canine GP9 gene causing a frameshift and premature stop codon truncating ~two-thirds of the protein abolishes functional GPIb-IX-V complex expression (confirmed by immunocytochemistry) and causes macrothrombocytopenia with platelet adhesion defect resembling human BSS type C, establishing GP9 as the causal gene in Cocker Spaniel BSS.\",\n      \"method\": \"Whole genome sequencing; PCR-based genotyping; immunocytochemistry; pedigree/recessive inheritance analysis\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — genetic and immunocytochemical evidence in a canine model; no in vitro reconstitution but functional complex absence confirmed directly\",\n      \"pmids\": [\"31484196\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Homozygous deletion of GP9 in immortalized megakaryocyte cell lines (imMKCL) reduced proplatelet formation by 96%, and transcriptomic analysis of GP9-/- MKs showed dysregulation of RNA metabolism and actin/tubulin folding pathways, identifying specific molecular pathways dependent on GPIX during megakaryopoiesis.\",\n      \"method\": \"Homozygous GP9 deletion in imMKCL; proplatelet formation assay; RNA-seq at four MK differentiation stages; patient platelet RNA-seq\",\n      \"journal\": \"HemaSphere\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct KO with quantitative cellular phenotype and transcriptomic pathway analysis; single lab, single study\",\n      \"pmids\": [\"41017962\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"GP9 encodes GPIX, a single leucine-rich repeat transmembrane subunit that assembles with GPIbα, GPIbβ (2:1:2:1 stoichiometry) and GPV to form the platelet GPIb-IX-V complex; GPIX is required for correct ER insertion, disulfide bond formation, and surface trafficking of the entire complex, interacts directly with GPIbβ through a quaternary interface involving GPIbβ Tyr106 and GPIX loops b/c (resolved by crystal structure), and its N-terminal Cys8–Cys12 disulfide and signal peptide integrity are essential for proper folding; loss-of-function mutations in GP9 cause Bernard-Soulier syndrome type C through absence of the VWF receptor complex on the platelet surface, impaired proplatelet formation, and dysregulation of actin/tubulin folding pathways in megakaryocytes, and lentiviral GP9 gene therapy rescues GPIX surface expression and normalizes platelet size.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"GP9 encodes GPIX, a transmembrane subunit of the platelet GPIb-IX-V von Willebrand factor receptor complex, where it is essential for assembly and surface expression of the entire complex [#6, #10]. GPIX engages GPIbβ through a defined quaternary interface in which GPIbβ Tyr106 inserts into a pocket formed by GPIX loops b and c, an interface resolved by crystallography and validated by Bernard-Soulier mutations (A108P, P74R) that abolish GPIX surface expression [#2]. Proper biogenesis of GPIX depends on the integrity of its signal peptide for correct ER insertion [#6] and on intramolecular and inter-subunit disulfide bonding, including the mature Cys8–Cys12 bond, whose disruption eliminates the complex from the platelet surface and impairs GPIbα–GPIbβ disulfide formation [#7, #8]. GPIX is required for the native conformation and adhesive function of GPIbα: loss of GPIX prevents conformation-dependent antibody binding and ristocetin-induced agglutination [#4], although a residual GPIbα/β heterodimer can assemble and support VWF and collagen adhesion independently of GPIX [#3, #9]. Loss-of-function mutations in GP9 cause Bernard-Soulier syndrome type C through absence of the surface VWF receptor complex, with downstream consequences for megakaryopoiesis including a severe (96%) reduction in proplatelet formation and dysregulation of actin/tubulin folding pathways [#10, #13]; lentiviral restoration of GPIX rescues surface complex expression and normalizes platelet size [#10].\",\n  \"teleology\": [\n    {\n      \"year\": 1994,\n      \"claim\": \"Established that GPIbβ and GPIX can assemble and reach the platelet surface partially independently of the GPIbα transmembrane and cytoplasmic regions, defining the modular nature of complex assembly.\",\n      \"evidence\": \"Biochemical and flow cytometric characterization of patient platelets carrying a truncating GPIbα Ser444stop mutation\",\n      \"pmids\": [\"7949089\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single patient case without cell reconstitution\", \"Does not define the GPIX-GPIbβ contact directly\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Showed that GPIX is required for proper GPIbα conformation and adhesive function, not merely surface presence, since GPIX loss left GPIbα present but non-functional.\",\n      \"evidence\": \"Patient platelet flow cytometry, conformation-dependent antibody binding, and ristocetin agglutination with a GPIX Leu40Pro mutation\",\n      \"pmids\": [\"9886312\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No cell reconstitution\", \"Mechanism linking GPIX to GPIbα conformation not resolved\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Demonstrated reciprocal dependence between GPIbβ and GPIX for surface expression, framing the complex as an obligate co-assembly.\",\n      \"evidence\": \"Reciprocal functional rescue by wild-type vs mutant GPIbβ transfection in CHO/293T cells expressing GPIbα\",\n      \"pmids\": [\"10216092\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Atomic interface not defined\", \"Focused on GPIbβ rather than GPIX residues\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Linked GPIX disulfide bonding (Cys8–Cys12) and a conserved Asn residue to both intramolecular folding and inter-subunit GPIbα–GPIbβ disulfide formation, implicating GPIX in oxidative assembly of the complex.\",\n      \"evidence\": \"Patient platelet biochemistry and sequencing of Cys8Arg and Asn45Ser BSS mutations, replicated across unrelated patients\",\n      \"pmids\": [\"11167791\", \"11297032\", \"14510954\", \"17804902\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Disulfide disruption inferred, not biochemically reconstituted\", \"Single-case data for Cys8Arg\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Identified the GPIX signal peptide hydrophobic core as essential for correct ER insertion and biogenesis of the entire GPIb-V-IX complex.\",\n      \"evidence\": \"Co-transfection of GPIX Leu7Pro with normal GPIbα/β in CHO cells recapitulating the patient phenotype\",\n      \"pmids\": [\"12100158\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Step at which mistargeted GPIX is degraded not defined\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Mapped the conformational GPIbβ region (cysteine knot, residues 1-14 and 15-32) required for interaction with GPIX, localizing the assembly contact on the GPIbβ side.\",\n      \"evidence\": \"N-terminal truncation and chimera mutants of GPIbβ with surface expression readout and epitope-mapping antibody\",\n      \"pmids\": [\"12036872\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"GPIX-side contact residues not yet defined\", \"No structural model at this stage\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Localized the drug-dependent (quinine) antibody epitope to the GPIX C-terminal extracellular region, identifying surface-exposed residues Arg110 and Gln115.\",\n      \"evidence\": \"Mouse/human GPIX chimeras and site-directed mutagenesis in CHO cells tested against patient sera\",\n      \"pmids\": [\"12738668\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relevance to assembly versus immunogenicity not separated\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Resolved the atomic GPIbβ-GPIX quaternary interface, defining how GPIbβ Tyr106 docks into GPIX loops b/c and explaining BSS mutations that perturb this contact.\",\n      \"evidence\": \"X-ray crystallography of GPIbβ ectodomain and GPIbβ/GPIX chimera with mutagenesis and surface expression validation\",\n      \"pmids\": [\"21908432\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structure of full-length GPIX in the intact complex not solved\", \"Stoichiometric arrangement with GPV not directly resolved\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Established that GPIbα/β can form a functional adhesive complex independent of GPIX, refining which functions strictly require GPIX.\",\n      \"evidence\": \"Stable CHO-K1 expression and platelet adhesion/agglutination assays with a GPIX W127X nonsense mutation\",\n      \"pmids\": [\"23143686\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"Reconciliation with GPIX requirement for GPIbα conformation not fully resolved\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Confirmed GP9 as a causal gene for Bernard-Soulier-type macrothrombocytopenia in a non-human (canine) model, supporting cross-species conservation of GPIX function.\",\n      \"evidence\": \"Whole genome sequencing, genotyping and immunocytochemistry of a frameshift GP9 deletion in Cocker Spaniels\",\n      \"pmids\": [\"31484196\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No in vitro reconstitution\", \"Megakaryocyte-level mechanism not examined\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Showed that cancer cells acquire GPIX (CD42a) by phagocytosing platelets and recycling the protein into their own membrane, indicating GPIX can mark tumor cells via platelet uptake.\",\n      \"evidence\": \"Confocal imaging, flow cytometry and dynamin inhibition in cancer cell lines with a non-cancerous control\",\n      \"pmids\": [\"34592045\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of acquired GPIX on tumor cells unknown\", \"Single lab\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Demonstrated that GP9 is both necessary and sufficient for GPIb-IX-V surface localization and normal platelet size, enabling gene-therapy rescue of BSS phenotypes.\",\n      \"evidence\": \"CRISPR knockout and lentiviral GP9 rescue in megakaryoblastic lines, iPSC-derived platelets and patient HSCs with flow cytometry readouts\",\n      \"pmids\": [\"37416759\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Durability and in vivo efficacy of gene therapy not addressed in this corpus\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Defined megakaryocyte-intrinsic consequences of GPIX loss, quantifying a severe proplatelet defect and linking GPIX to RNA metabolism and actin/tubulin folding pathways during megakaryopoiesis.\",\n      \"evidence\": \"Homozygous GP9 deletion in imMKCL with proplatelet assays and staged RNA-seq plus patient platelet transcriptomics\",\n      \"pmids\": [\"41017962\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab/single study\", \"Causal mechanism connecting GPIX loss to cytoskeletal-folding dysregulation not established\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How GPIX coordinates oxidative folding, ER insertion, and cytoskeletal/RNA pathways into a single biogenesis program remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No full-length structure of GPIX within the intact GPIb-IX-V complex\", \"Causal chain from GPIX loss to actin/tubulin folding dysregulation undefined\", \"Mechanism of GPIX-dependent GPIbα conformation not biochemically reconstituted\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [2, 6, 10]},\n      {\"term_id\": \"GO:0001618\", \"supporting_discovery_ids\": [4, 9]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 6, 10]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [6]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-109582\", \"supporting_discovery_ids\": [4, 9, 10]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [6, 7, 8]}\n    ],\n    \"complexes\": [\"GPIb-IX-V complex\"],\n    \"partners\": [\"GP1BB\", \"GP1BA\", \"GP5\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}