{"gene":"STX1B","run_date":"2026-06-10T10:51:54","timeline":{"discoveries":[{"year":2014,"finding":"STX1B encodes syntaxin-1B, a presynaptic protein required for neurotransmitter release; antisense knockdown of stx1b in zebrafish larvae caused seizure-like behavior and epileptiform discharges that were highly temperature-sensitive, and these effects were rescued by wild-type human syntaxin-1B but not by a mutated (loss-of-function) protein, establishing STX1B's causal role in the presynaptic release machinery.","method":"Antisense morpholino knockdown in zebrafish combined with rescue with wild-type vs. mutant human STX1B; video and local field potential analysis","journal":"Nature genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo loss-of-function with specific seizure phenotype, rescued by wild-type but not mutant protein; multiple orthogonal readouts (behavior + LFP)","pmids":["25362483"],"is_preprint":false},{"year":2020,"finding":"STX1B is a core SNARE complex component at the presynapse; the STX1BG226R epileptic encephalopathy mutation strongly reduces interaction with Munc18-1, decreases expression of both STX1B and Munc18-1, shrinks the readily releasable pool of vesicles, and reduces Ca2+-triggered neurotransmitter release in STX1-null neurons. In contrast, STX1BV216E only mildly diminishes Munc18-1 and Munc13 interactions but instead enhances fusogenicity and increases vesicular release probability. The STX1BInDel (K45/RMCIE, L46M) Habc-domain mutation produces an unfolded protein unable to sustain neurotransmission.","method":"Biochemical interaction assays (co-immunoprecipitation), patch-clamp electrophysiology in STX1-null mouse hippocampal neurons expressing STX1B mutants, Western blotting for protein expression levels","journal":"Brain : a journal of neurology","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — multiple orthogonal methods (Co-IP, electrophysiology, protein expression), in defined null-neuron background, distinct molecular mechanisms assigned to specific mutations","pmids":["32572454"],"is_preprint":false},{"year":2020,"finding":"STX1B function in SNARE-mediated vesicle fusion is assisted by Munc18-1 (which recruits STX1B in the auto-inhibited conformation) and Munc13 (which catalyses SNARE helix pairing); disruption of the STX1B–Munc18-1 interface by disease mutations translates into distinct neurophysiological phenotypes ranging from reduced release to enhanced fusogenicity.","method":"Biochemical co-immunoprecipitation of STX1B mutants with Munc18-1 and Munc13; electrophysiological measurement of readily releasable pool size and release probability in STX1-null neurons","journal":"Brain : a journal of neurology","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — reciprocal Co-IP plus functional electrophysiology in defined genetic background; multiple mutations tested with consistent mechanistic framework","pmids":["32572454"],"is_preprint":false},{"year":2019,"finding":"Missense variants located within the SNARE motif of syntaxin-1B are associated with more severe epileptic encephalopathy phenotypes, whereas loss-of-function (truncating) mutations are associated with milder/benign epilepsy syndromes, indicating that the SNARE domain is functionally critical and that gain-of-dysfunction at this domain is more pathogenic than haploinsufficiency.","method":"Genotype-phenotype correlation across 49 patients in 23 families, with in silico variant pathogenicity prediction; retrospective clinical review with next-generation sequencing","journal":"Neurology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — large patient cohort supports the genotype-phenotype pattern but relies on clinical correlation and in silico prediction rather than direct functional assays","pmids":["30737342"],"is_preprint":false},{"year":2018,"finding":"PRRT2 (proline-rich transmembrane protein 2) directly interacts with syntaxin-1B (STX1B); a truncating PRRT2 variant (p.Ser208Ilefs*17) that lacks the helix-loop-helix domain fails to bind STX1B, indicating that loss of PRRT2–STX1B interaction may contribute to paroxysmal kinesigenic dyskinesia/benign familial infantile seizures pathogenesis.","method":"Co-immunoprecipitation of PRRT2 and STX1B from transfected cells; immunofluorescence for subcellular localization; Western blotting for expression of PRRT2 truncation mutant","journal":"Epilepsia","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — single Co-IP experiment in a transfected cell system; interaction confirmed with wild-type and loss confirmed with truncation mutant, single lab","pmids":["30009426"],"is_preprint":false}],"current_model":"STX1B encodes syntaxin-1B, a core presynaptic SNARE complex protein that is recruited by Munc18-1 in its auto-inhibited conformation and activated by Munc13 for SNARE helix pairing, thereby driving Ca2+-triggered synaptic vesicle fusion and neurotransmitter release; disease-causing mutations in its Habc domain abolish folding/function, mutations disrupting the STX1B–Munc18-1 interface reduce the readily releasable pool and evoked release, while SNARE-domain mutations enhance fusogenicity and release probability, collectively explaining why different STX1B mutations cause epilepsy phenotypes of varying severity."},"narrative":{"mechanistic_narrative":"STX1B encodes syntaxin-1B, a core presynaptic SNARE protein required for Ca2+-triggered neurotransmitter release at the synapse [PMID:25362483, PMID:32572454]. Its function in SNARE-mediated synaptic vesicle fusion is organized by two regulators: Munc18-1 recruits STX1B in an auto-inhibited conformation, and Munc13 catalyzes SNARE helix pairing, so that disruption of the STX1B–Munc18-1 interface produces distinct neurophysiological consequences [PMID:32572454]. Disease-causing mutations partition mechanistically by domain: the G226R encephalopathy mutation reduces Munc18-1 binding, lowers STX1B and Munc18-1 expression, shrinks the readily releasable vesicle pool, and reduces evoked release, whereas the SNARE-region V216E mutation only mildly perturbs Munc18-1/Munc13 binding but enhances fusogenicity and increases release probability, and a Habc-domain InDel yields an unfolded protein that cannot sustain neurotransmission [PMID:32572454]. Genotype-phenotype analysis links SNARE-motif missense variants to more severe epileptic encephalopathy and truncating loss-of-function alleles to milder epilepsy, establishing STX1B as a cause of inherited epilepsy syndromes [PMID:25362483, PMID:30737342]. STX1B also directly binds PRRT2, an interaction lost with a PRRT2 truncation lacking its helix-loop-helix domain [PMID:30009426].","teleology":[{"year":2014,"claim":"Whether STX1B causally controls neurotransmitter release in vivo and underlies an epilepsy phenotype was unknown; this established its essential role in the presynaptic release machinery.","evidence":"Antisense morpholino knockdown in zebrafish with wild-type vs. mutant human STX1B rescue, scored by behavior and local field potentials","pmids":["25362483"],"confidence":"High","gaps":["Does not resolve the molecular interactions or specific fusion step STX1B controls","Zebrafish knockdown does not map domain-specific functions"]},{"year":2018,"claim":"It was unknown whether STX1B physically links to other paroxysmal-disorder proteins; this showed STX1B directly binds PRRT2 and that a disease truncation abolishes the interaction.","evidence":"Co-immunoprecipitation of PRRT2 and STX1B from transfected cells, immunofluorescence localization, Western blot of the truncation mutant","pmids":["30009426"],"confidence":"Medium","gaps":["Single Co-IP in a transfected, non-neuronal system without reciprocal validation","Functional consequence of lost PRRT2–STX1B binding on release not measured"]},{"year":2019,"claim":"The relationship between mutation type/location and disease severity was unclear; this established that SNARE-motif missense variants drive severe encephalopathy while truncating alleles cause milder epilepsy.","evidence":"Genotype-phenotype correlation across 49 patients in 23 families with next-generation sequencing and in silico pathogenicity prediction","pmids":["30737342"],"confidence":"Medium","gaps":["Relies on clinical correlation and in silico prediction rather than direct functional assays","Does not define the molecular mechanism distinguishing SNARE-domain gain-of-dysfunction from haploinsufficiency"]},{"year":2020,"claim":"How specific STX1B mutations alter the molecular machinery was unresolved; this assigned distinct mechanisms—loss of Munc18-1 binding and reduced release, enhanced fusogenicity, or protein unfolding—to individual mutations.","evidence":"Co-IP of STX1B mutants with Munc18-1 and Munc13, patch-clamp electrophysiology in STX1-null mouse hippocampal neurons, and Western blot of expression","pmids":["32572454"],"confidence":"High","gaps":["No structural model of the mutant SNARE/Munc18-1 interfaces","Mechanism by which V216E enhances fusogenicity at the molecular level not fully defined"]},{"year":null,"claim":"How the PRRT2–STX1B interaction and the Munc18-1/Munc13-regulated SNARE cycle are integrated to set release probability across neuron types remains open.","evidence":"","pmids":[],"confidence":"Medium","gaps":["Functional role of PRRT2 binding in STX1B-dependent release untested in neurons","No reconstituted or structural account unifying the domain-specific mutation effects"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[0,1,2]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,1]}],"pathway":[{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[0,1,2]},{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[1,2]}],"complexes":["SNARE complex"],"partners":["STXBP1","UNC13A","PRRT2"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P61266","full_name":"Syntaxin-1B","aliases":["Syntaxin-1B1","Syntaxin-1B2"],"length_aa":288,"mass_kda":33.2,"function":"Potentially involved in docking of synaptic vesicles at presynaptic active zones. May mediate Ca(2+)-regulation of exocytosis acrosomal reaction in sperm (By similarity)","subcellular_location":"Nucleus; Cytoplasm, cytoskeleton, microtubule organizing center, centrosome; Cytoplasm, cytoskeleton, spindle","url":"https://www.uniprot.org/uniprotkb/P61266/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/STX1B","classification":"Not Classified","n_dependent_lines":4,"n_total_lines":1208,"dependency_fraction":0.0033112582781456954},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/STX1B","total_profiled":1310},"omim":[{"mim_id":"616172","title":"GENERALIZED EPILEPSY WITH FEBRILE SEIZURES PLUS, TYPE 9; GEFSP9","url":"https://www.omim.org/entry/616172"},{"mim_id":"604233","title":"GENERALIZED EPILEPSY WITH FEBRILE SEIZURES PLUS, TYPE 1; GEFSP1","url":"https://www.omim.org/entry/604233"},{"mim_id":"603177","title":"VESICLE-ASSOCIATED MEMBRANE PROTEIN 8; VAMP8","url":"https://www.omim.org/entry/603177"},{"mim_id":"602534","title":"SYNAPTOSOMAL-ASSOCIATED PROTEIN, 23-KD; SNAP23","url":"https://www.omim.org/entry/602534"},{"mim_id":"601485","title":"SYNTAXIN 1B; STX1B","url":"https://www.omim.org/entry/601485"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Uncertain","locations":[{"location":"Nuclear membrane","reliability":"Uncertain"},{"location":"Vesicles","reliability":"Uncertain"}],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"brain","ntpm":141.4}],"url":"https://www.proteinatlas.org/search/STX1B"},"hgnc":{"alias_symbol":[],"prev_symbol":["STX1B1","STX1B2"]},"alphafold":{"accession":"P61266","domains":[{"cath_id":"1.20.58.70","chopping":"28-223","consensus_level":"high","plddt":90.5417,"start":28,"end":223}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P61266","model_url":"https://alphafold.ebi.ac.uk/files/AF-P61266-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P61266-F1-predicted_aligned_error_v6.png","plddt_mean":84.12},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=STX1B","jax_strain_url":"https://www.jax.org/strain/search?query=STX1B"},"sequence":{"accession":"P61266","fasta_url":"https://rest.uniprot.org/uniprotkb/P61266.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P61266/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P61266"}},"corpus_meta":[{"pmid":"25362483","id":"PMC_25362483","title":"Mutations in STX1B, encoding a presynaptic protein, cause fever-associated epilepsy syndromes.","date":"2014","source":"Nature genetics","url":"https://pubmed.ncbi.nlm.nih.gov/25362483","citation_count":153,"is_preprint":false},{"pmid":"30737342","id":"PMC_30737342","title":"Clinical spectrum of STX1B-related epileptic disorders.","date":"2019","source":"Neurology","url":"https://pubmed.ncbi.nlm.nih.gov/30737342","citation_count":42,"is_preprint":false},{"pmid":"21816831","id":"PMC_21816831","title":"Shiga toxin (Stx)1B and Stx2B induce von Willebrand factor secretion from human umbilical vein endothelial cells through different signaling pathways.","date":"2011","source":"Blood","url":"https://pubmed.ncbi.nlm.nih.gov/21816831","citation_count":34,"is_preprint":false},{"pmid":"21338683","id":"PMC_21338683","title":"Subcutaneous and intranasal immunization with Stx2B-Tir-Stx1B-Zot reduces colonization and shedding of Escherichia coli O157:H7 in mice.","date":"2011","source":"Vaccine","url":"https://pubmed.ncbi.nlm.nih.gov/21338683","citation_count":32,"is_preprint":false},{"pmid":"26818399","id":"PMC_26818399","title":"Haploinsufficiency of the STX1B gene is associated with myoclonic astatic epilepsy.","date":"2016","source":"European journal of paediatric neurology : EJPN : official journal of the European Paediatric Neurology Society","url":"https://pubmed.ncbi.nlm.nih.gov/26818399","citation_count":32,"is_preprint":false},{"pmid":"21134452","id":"PMC_21134452","title":"Enhanced immunogenicity of a novel Stx2Am-Stx1B fusion protein in a mice model of enterohemorrhagic Escherichia coli O157:H7 infection.","date":"2010","source":"Vaccine","url":"https://pubmed.ncbi.nlm.nih.gov/21134452","citation_count":28,"is_preprint":false},{"pmid":"19428832","id":"PMC_19428832","title":"Immunogenicity of a novel Stx2B-Stx1B fusion protein in a mice model of Enterohemorrhagic Escherichia coli O157:H7 infection.","date":"2009","source":"Vaccine","url":"https://pubmed.ncbi.nlm.nih.gov/19428832","citation_count":28,"is_preprint":false},{"pmid":"32572454","id":"PMC_32572454","title":"Epilepsy-causing STX1B mutations translate altered protein functions into distinct phenotypes in mouse neurons.","date":"2020","source":"Brain : a journal of neurology","url":"https://pubmed.ncbi.nlm.nih.gov/32572454","citation_count":22,"is_preprint":false},{"pmid":"34058286","id":"PMC_34058286","title":"BDNF promotes neuronal survival after neonatal hypoxic-ischemic encephalopathy by up-regulating Stx1b and suppressing VDAC1.","date":"2021","source":"Brain research bulletin","url":"https://pubmed.ncbi.nlm.nih.gov/34058286","citation_count":17,"is_preprint":false},{"pmid":"30009426","id":"PMC_30009426","title":"A PRRT2 variant in a Chinese family with paroxysmal kinesigenic dyskinesia and benign familial infantile seizures results in loss of interaction with STX1B.","date":"2018","source":"Epilepsia","url":"https://pubmed.ncbi.nlm.nih.gov/30009426","citation_count":12,"is_preprint":false},{"pmid":"30719275","id":"PMC_30719275","title":"Polymorphisms of ACMSD-TMEM163, MCCC1, and BCKDK-STX1B Are Not Associated with Parkinson's Disease in Taiwan.","date":"2019","source":"Parkinson's disease","url":"https://pubmed.ncbi.nlm.nih.gov/30719275","citation_count":8,"is_preprint":false},{"pmid":"29101845","id":"PMC_29101845","title":"Motor cortex excitability in seizure-free STX1B mutation carriers with a history of epilepsy and febrile seizures.","date":"2017","source":"Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology","url":"https://pubmed.ncbi.nlm.nih.gov/29101845","citation_count":7,"is_preprint":false},{"pmid":"20715986","id":"PMC_20715986","title":"Prokaryotic expression of Stx1B subunit of Escherichia coli O157:H7 used to generate monoclonal antibody.","date":"2010","source":"Hybridoma (2005)","url":"https://pubmed.ncbi.nlm.nih.gov/20715986","citation_count":7,"is_preprint":false},{"pmid":"22186381","id":"PMC_22186381","title":"Intranasal immunisation with Stx2B-Tir-Stx1B-Zot protein leads to decreased shedding in goats after challenge with Escherichia coli O157:H7.","date":"2011","source":"The Veterinary record","url":"https://pubmed.ncbi.nlm.nih.gov/22186381","citation_count":7,"is_preprint":false},{"pmid":"10483717","id":"PMC_10483717","title":"Reconstitution of active recombinant Shiga toxin (Stx)1 from recombinant Stx1-A and Stx1-B subunits independently produced by E. coli clones.","date":"1999","source":"FEMS microbiology letters","url":"https://pubmed.ncbi.nlm.nih.gov/10483717","citation_count":7,"is_preprint":false},{"pmid":"20854398","id":"PMC_20854398","title":"Monoclonal antibodies against Stx1B subunit of Escherichia coli O157:H7 distinguish the bacterium from other bacteria.","date":"2010","source":"Letters in applied microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/20854398","citation_count":6,"is_preprint":false},{"pmid":"26224037","id":"PMC_26224037","title":"No association of FAM47E rs6812193, SCARB2 rs6825004 and STX1B rs4889603 polymorphisms with Parkinson's disease in a Chinese Han population.","date":"2015","source":"Journal of neural transmission (Vienna, Austria : 1996)","url":"https://pubmed.ncbi.nlm.nih.gov/26224037","citation_count":6,"is_preprint":false},{"pmid":"29102116","id":"PMC_29102116","title":"Secretion of the Shiga toxin B subunit (Stx1B) via an autotransporter protein optimizes the protective immune response to the antigen expressed in an attenuated E. coli (rEPEC E22Δler) vaccine strain.","date":"2017","source":"Veterinary microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/29102116","citation_count":5,"is_preprint":false},{"pmid":"34305610","id":"PMC_34305610","title":"The Association Between STX1B Polymorphisms and Treatment Response in Patients With Epilepsy.","date":"2021","source":"Frontiers in pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/34305610","citation_count":4,"is_preprint":false},{"pmid":"30818898","id":"PMC_30818898","title":"[A novel inherited STX1B mutation associated with generalized epilepsy with febrile seizures plus: a family analysis and literature review].","date":"2019","source":"Zhonghua er ke za zhi = Chinese journal of pediatrics","url":"https://pubmed.ncbi.nlm.nih.gov/30818898","citation_count":4,"is_preprint":false},{"pmid":"16165112","id":"PMC_16165112","title":"A comparison of Verotoxin B-subunit (Stx1B) and CD77 antibody to define germinal centre populations.","date":"2005","source":"Cellular immunology","url":"https://pubmed.ncbi.nlm.nih.gov/16165112","citation_count":3,"is_preprint":false},{"pmid":"33426515","id":"PMC_33426515","title":"STX1B-related epilepsy in a 24-month-old female infant.","date":"2020","source":"Epilepsy & behavior reports","url":"https://pubmed.ncbi.nlm.nih.gov/33426515","citation_count":2,"is_preprint":false},{"pmid":"36652844","id":"PMC_36652844","title":"Generation of an induced pluripotent stem cell (iPSC) line from a patient with GEFS+ carrying a STX1B (p.Lys45delinsArgMetCysIleGlu and p.Leu46Met) mutation.","date":"2023","source":"Stem cell research","url":"https://pubmed.ncbi.nlm.nih.gov/36652844","citation_count":1,"is_preprint":false},{"pmid":"41478480","id":"PMC_41478480","title":"Modular pentameric protein scaffold based on glutaraldehyde-crosslinked Stx1B for superior multivalent therapeutics.","date":"2025","source":"International journal of biological macromolecules","url":"https://pubmed.ncbi.nlm.nih.gov/41478480","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2024.12.21.626268","title":"Cryo-EM structures of engineered Shiga toxin-based immunogens capable of eliciting neutralizing antibodies with therapeutic potential against Hemolytic Uremic Syndrome","date":"2024-12-21","source":"bioRxiv","url":"https://doi.org/10.1101/2024.12.21.626268","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.10.26.620404","title":"<i>B4GALT5</i>  -deficient CHO-Lec2 cells expressing human α1,4-galactosyltransferase: a glycoengineered cell model for studying Shiga toxin receptors","date":"2024-10-26","source":"bioRxiv","url":"https://doi.org/10.1101/2024.10.26.620404","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":15135,"output_tokens":1969,"usd":0.03747,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8369,"output_tokens":1973,"usd":0.045585,"stage2_stop_reason":"end_turn"},"total_usd":0.083055,"stage1_batch_id":"msgbatch_017qqVz33Ga63SCDwzb35XPb","stage2_batch_id":"msgbatch_01Scr2Ei9x4HJMiRGxwrmvLK","note":"batch pricing = 50% of standard"},"stage1_raw":"Looking at the papers, I need to distinguish between:\n1. STX1B = human syntaxin-1B (presynaptic SNARE protein) - the target gene\n2. Stx1B = Shiga toxin 1 B subunit (bacterial toxin) - a different entity entirely\n\nPapers 3, 4, 6, 7, 13, 14, 15, 16, 18, 21, 24, 25, 26 are about the bacterial Shiga toxin B subunit - NOT the human syntaxin-1B gene. I will exclude these.\n\nPapers 11, 17 are GWAS/association studies with no mechanistic findings.\nPapers 12, 19, 20, 22, 23 are clinical/case reports or expression studies with limited mechanism.\nPaper 9 is an expression correlation study.\nPaper 5 mentions STX1B-STXBP1 interaction but only as background knowledge, not as an experimental finding from that paper.\n\nPapers with mechanistic findings about syntaxin-1B:\n- Paper 1 (PMID:25362483): zebrafish knockdown, rescue experiments\n- Paper 2 (PMID:30737342): genotype-phenotype (missense in SNARE motif = severe)\n- Paper 8 (PMID:32572454): biochemical/electrophysiological analysis of mutations\n- Paper 10 (PMID:30009426): Co-IP showing PRRT2 interacts with STX1B\n\n```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2014,\n      \"finding\": \"STX1B encodes syntaxin-1B, a presynaptic protein required for neurotransmitter release; antisense knockdown of stx1b in zebrafish larvae caused seizure-like behavior and epileptiform discharges that were highly temperature-sensitive, and these effects were rescued by wild-type human syntaxin-1B but not by a mutated (loss-of-function) protein, establishing STX1B's causal role in the presynaptic release machinery.\",\n      \"method\": \"Antisense morpholino knockdown in zebrafish combined with rescue with wild-type vs. mutant human STX1B; video and local field potential analysis\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo loss-of-function with specific seizure phenotype, rescued by wild-type but not mutant protein; multiple orthogonal readouts (behavior + LFP)\",\n      \"pmids\": [\"25362483\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"STX1B is a core SNARE complex component at the presynapse; the STX1BG226R epileptic encephalopathy mutation strongly reduces interaction with Munc18-1, decreases expression of both STX1B and Munc18-1, shrinks the readily releasable pool of vesicles, and reduces Ca2+-triggered neurotransmitter release in STX1-null neurons. In contrast, STX1BV216E only mildly diminishes Munc18-1 and Munc13 interactions but instead enhances fusogenicity and increases vesicular release probability. The STX1BInDel (K45/RMCIE, L46M) Habc-domain mutation produces an unfolded protein unable to sustain neurotransmission.\",\n      \"method\": \"Biochemical interaction assays (co-immunoprecipitation), patch-clamp electrophysiology in STX1-null mouse hippocampal neurons expressing STX1B mutants, Western blotting for protein expression levels\",\n      \"journal\": \"Brain : a journal of neurology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — multiple orthogonal methods (Co-IP, electrophysiology, protein expression), in defined null-neuron background, distinct molecular mechanisms assigned to specific mutations\",\n      \"pmids\": [\"32572454\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"STX1B function in SNARE-mediated vesicle fusion is assisted by Munc18-1 (which recruits STX1B in the auto-inhibited conformation) and Munc13 (which catalyses SNARE helix pairing); disruption of the STX1B–Munc18-1 interface by disease mutations translates into distinct neurophysiological phenotypes ranging from reduced release to enhanced fusogenicity.\",\n      \"method\": \"Biochemical co-immunoprecipitation of STX1B mutants with Munc18-1 and Munc13; electrophysiological measurement of readily releasable pool size and release probability in STX1-null neurons\",\n      \"journal\": \"Brain : a journal of neurology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — reciprocal Co-IP plus functional electrophysiology in defined genetic background; multiple mutations tested with consistent mechanistic framework\",\n      \"pmids\": [\"32572454\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Missense variants located within the SNARE motif of syntaxin-1B are associated with more severe epileptic encephalopathy phenotypes, whereas loss-of-function (truncating) mutations are associated with milder/benign epilepsy syndromes, indicating that the SNARE domain is functionally critical and that gain-of-dysfunction at this domain is more pathogenic than haploinsufficiency.\",\n      \"method\": \"Genotype-phenotype correlation across 49 patients in 23 families, with in silico variant pathogenicity prediction; retrospective clinical review with next-generation sequencing\",\n      \"journal\": \"Neurology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — large patient cohort supports the genotype-phenotype pattern but relies on clinical correlation and in silico prediction rather than direct functional assays\",\n      \"pmids\": [\"30737342\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"PRRT2 (proline-rich transmembrane protein 2) directly interacts with syntaxin-1B (STX1B); a truncating PRRT2 variant (p.Ser208Ilefs*17) that lacks the helix-loop-helix domain fails to bind STX1B, indicating that loss of PRRT2–STX1B interaction may contribute to paroxysmal kinesigenic dyskinesia/benign familial infantile seizures pathogenesis.\",\n      \"method\": \"Co-immunoprecipitation of PRRT2 and STX1B from transfected cells; immunofluorescence for subcellular localization; Western blotting for expression of PRRT2 truncation mutant\",\n      \"journal\": \"Epilepsia\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — single Co-IP experiment in a transfected cell system; interaction confirmed with wild-type and loss confirmed with truncation mutant, single lab\",\n      \"pmids\": [\"30009426\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"STX1B encodes syntaxin-1B, a core presynaptic SNARE complex protein that is recruited by Munc18-1 in its auto-inhibited conformation and activated by Munc13 for SNARE helix pairing, thereby driving Ca2+-triggered synaptic vesicle fusion and neurotransmitter release; disease-causing mutations in its Habc domain abolish folding/function, mutations disrupting the STX1B–Munc18-1 interface reduce the readily releasable pool and evoked release, while SNARE-domain mutations enhance fusogenicity and release probability, collectively explaining why different STX1B mutations cause epilepsy phenotypes of varying severity.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"STX1B encodes syntaxin-1B, a core presynaptic SNARE protein required for Ca2+-triggered neurotransmitter release at the synapse [#0, #1]. Its function in SNARE-mediated synaptic vesicle fusion is organized by two regulators: Munc18-1 recruits STX1B in an auto-inhibited conformation, and Munc13 catalyzes SNARE helix pairing, so that disruption of the STX1B\\u2013Munc18-1 interface produces distinct neurophysiological consequences [#2]. Disease-causing mutations partition mechanistically by domain: the G226R encephalopathy mutation reduces Munc18-1 binding, lowers STX1B and Munc18-1 expression, shrinks the readily releasable vesicle pool, and reduces evoked release, whereas the SNARE-region V216E mutation only mildly perturbs Munc18-1/Munc13 binding but enhances fusogenicity and increases release probability, and a Habc-domain InDel yields an unfolded protein that cannot sustain neurotransmission [#1]. Genotype-phenotype analysis links SNARE-motif missense variants to more severe epileptic encephalopathy and truncating loss-of-function alleles to milder epilepsy, establishing STX1B as a cause of inherited epilepsy syndromes [#0, #3]. STX1B also directly binds PRRT2, an interaction lost with a PRRT2 truncation lacking its helix-loop-helix domain [#4].\"\n,\n  \"teleology\": [\n    {\n      \"year\": 2014,\n      \"claim\": \"Whether STX1B causally controls neurotransmitter release in vivo and underlies an epilepsy phenotype was unknown; this established its essential role in the presynaptic release machinery.\",\n      \"evidence\": \"Antisense morpholino knockdown in zebrafish with wild-type vs. mutant human STX1B rescue, scored by behavior and local field potentials\",\n      \"pmids\": [\"25362483\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not resolve the molecular interactions or specific fusion step STX1B controls\", \"Zebrafish knockdown does not map domain-specific functions\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"It was unknown whether STX1B physically links to other paroxysmal-disorder proteins; this showed STX1B directly binds PRRT2 and that a disease truncation abolishes the interaction.\",\n      \"evidence\": \"Co-immunoprecipitation of PRRT2 and STX1B from transfected cells, immunofluorescence localization, Western blot of the truncation mutant\",\n      \"pmids\": [\"30009426\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single Co-IP in a transfected, non-neuronal system without reciprocal validation\", \"Functional consequence of lost PRRT2\\u2013STX1B binding on release not measured\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"The relationship between mutation type/location and disease severity was unclear; this established that SNARE-motif missense variants drive severe encephalopathy while truncating alleles cause milder epilepsy.\",\n      \"evidence\": \"Genotype-phenotype correlation across 49 patients in 23 families with next-generation sequencing and in silico pathogenicity prediction\",\n      \"pmids\": [\"30737342\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Relies on clinical correlation and in silico prediction rather than direct functional assays\", \"Does not define the molecular mechanism distinguishing SNARE-domain gain-of-dysfunction from haploinsufficiency\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"How specific STX1B mutations alter the molecular machinery was unresolved; this assigned distinct mechanisms\\u2014loss of Munc18-1 binding and reduced release, enhanced fusogenicity, or protein unfolding\\u2014to individual mutations.\",\n      \"evidence\": \"Co-IP of STX1B mutants with Munc18-1 and Munc13, patch-clamp electrophysiology in STX1-null mouse hippocampal neurons, and Western blot of expression\",\n      \"pmids\": [\"32572454\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No structural model of the mutant SNARE/Munc18-1 interfaces\", \"Mechanism by which V216E enhances fusogenicity at the molecular level not fully defined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the PRRT2\\u2013STX1B interaction and the Munc18-1/Munc13-regulated SNARE cycle are integrated to set release probability across neuron types remains open.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional role of PRRT2 binding in STX1B-dependent release untested in neurons\", \"No reconstituted or structural account unifying the domain-specific mutation effects\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 1, 2]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [0, 1, 2]},\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [1, 2]}\n    ],\n    \"complexes\": [\"SNARE complex\"],\n    \"partners\": [\"STXBP1\", \"UNC13A\", \"PRRT2\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}