{"gene":"GOSR2","run_date":"2026-06-10T01:55:21","timeline":{"discoveries":[{"year":1990,"finding":"BOS1 (yeast ortholog of GOSR2/GS27) genetically interacts with BET1 and SEC22 in ER-to-Golgi transport: overproduction of BOS1 suppresses growth and secretory defects of sec22-3 and bet1-1 mutants in a gene dosage-dependent manner; a bet1 sec22 double mutant is inviable, placing these genes in the same transport step.","method":"Yeast genetic suppressor screen, multicopy suppression, double-mutant lethality analysis","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis with multiple allele combinations, replicated interactions across several mutant backgrounds","pmids":["2192256"],"is_preprint":false},{"year":1991,"finding":"BOS1 (yeast ortholog of GOSR2) encodes an essential 27-kDa membrane protein required for vesicular transport from the ER to the Golgi complex; cells depleted of Bos1 accumulate an extensive ER network and small vesicles and fail to transport pro-alpha-factor and CPY to the Golgi. Differential centrifugation confirmed Bos1 membrane association.","method":"Yeast depletion (essential gene), secretory cargo trafficking assay, differential centrifugation fractionation, DNA sequence analysis","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — loss-of-function with defined cargo trafficking phenotype, membrane fractionation, and sequence prediction validated by biochemistry","pmids":["2007627"],"is_preprint":false},{"year":1999,"finding":"Human GS27 (GOSR2) encodes a 212-amino-acid Golgi SNARE trafficking protein involved in transport between the ER and Golgi and between Golgi subcompartments; chromosomal mapping places GS27 on chromosome 17q21.","method":"cDNA cloning, sequence analysis, chromosomal mapping (FISH/radiation hybrid)","journal":"Genomics","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — cDNA characterization with chromosomal mapping; functional role inferred from sequence homology and prior yeast work, not directly tested in this paper","pmids":["10198168"],"is_preprint":false},{"year":2011,"finding":"The p.Gly144Trp mutation in GOSR2 is equivalent to a loss of function and results in failure of the GOSR2 protein to localize to the cis-Golgi, establishing that correct cis-Golgi localization is required for GOSR2 function.","method":"Patient mutation identification, cellular localization assay (immunofluorescence of GOSR2 in patient-derived cells)","journal":"American journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization experiment with functional consequence (loss of cis-Golgi targeting = loss of function), single lab","pmids":["21549339"],"is_preprint":false},{"year":2013,"finding":"GOSR2/GS27 (Membrin, Qb-SNARE) and GS28 are enriched in Golgi COPI vesicles and are depleted from Golgi cisternae when intra-Golgi transport is blocked; fusion of these vesicles with cisternae during active transport delivers GS27 and GS28 to cisternae. In vitro, re-addition of isolated Golgi vesicles containing GS27/GS28 (but not the sugar transporter) restores intra-Golgi transport, indicating GS27 and GS28 in vesicles are sufficient for this activity.","method":"Subcellular fractionation, in vitro intra-Golgi transport assay, selective vesicle re-addition, inhibitor-based transport block","journal":"Traffic (Copenhagen, Denmark)","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution assay with fractionation and re-addition of isolated vesicles; multiple orthogonal methods in single study","pmids":["23387339"],"is_preprint":false},{"year":2017,"finding":"GOSR2 (Membrin) forms a SNARE complex with syntaxin-5, Bet1, and Sec22b to mediate ER-to-Golgi membrane fusion. The pathogenic p.Gly144Trp mutation causes partial reduction in SNARE-mediated membrane fusion; the equivalent Bos1 p.Gly176Trp and p.Arg196del mutations can still form SNARE complexes but with partly reduced activity. Molecular dynamics simulations showed p.Gly144Trp compromises the hydrophobic core triggering SNARE complex assembly, while p.Lys164del disrupts hydrogen bonds between GOSR2 and syntaxin-5.","method":"Yeast complementation growth assay, fluorescence anisotropy, gel filtration, molecular dynamics simulation","journal":"Disease models & mechanisms","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro SNARE complex formation assay with mutagenesis, biophysical methods, and MD simulation; multiple orthogonal methods in single study","pmids":["28982678"],"is_preprint":false},{"year":2017,"finding":"Pathogenic GOSR2 mutations cause partial reductions in SNARE-mediated membrane fusion sufficient to profoundly impair dendritic growth in Drosophila models of GOSR2-PME; GOSR2/Membrin mutations also cause fragmentation of the presynaptic cytoskeleton, transsynaptic instability, and hyperactive neurotransmission, revealing a role for Membrin in synaptic integrity.","method":"Drosophila loss-of-function models (dendritic morphology assay, electrophysiology, cytoskeletal imaging), SNARE fusion assay","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal functional assays (dendritic growth, synaptic cytoskeleton, neurotransmission) in a defined genetic model with mechanistic context","pmids":["28978487"],"is_preprint":false},{"year":2018,"finding":"Compound heterozygous GOSR2 mutations (c.430G>T and c.2T>G) are associated with hypoglycosylation of α-dystroglycan; however, cellular biological analyses on patient fibroblasts using two different model cargo proteins did not reveal detectable defects in protein transport, indicating the glycosylation defect is not simply due to bulk trafficking impairment.","method":"Patient fibroblast analysis, immunofluorescence and western blotting for α-dystroglycan glycosylation, live cell transport assays with model cargo proteins","journal":"Skeletal muscle","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — direct biochemical assay (α-dystroglycan glycosylation) with negative result for bulk transport; single lab, single patient","pmids":["29855340"],"is_preprint":false}],"current_model":"GOSR2 (GS27/Membrin/Bos1) is a Qb-SNARE membrane protein that localizes to the cis-Golgi and forms a SNARE complex with syntaxin-5, Bet1, and Sec22b to drive COPII vesicle fusion at the ER-to-Golgi step; it is also enriched in COPI Golgi vesicles where, together with GS28, it facilitates intra-Golgi transport by enabling inter-cisternal connections, and pathogenic missense mutations (especially p.Gly144Trp) cause partial loss of SNARE-mediated membrane fusion, failure of cis-Golgi localization, impaired dendritic growth, presynaptic cytoskeletal instability, and α-dystroglycan hypoglycosylation, collectively underlying progressive myoclonus epilepsy and congenital muscular dystrophy."},"narrative":{"mechanistic_narrative":"GOSR2 (GS27/Membrin/Bos1) is a Golgi Qb-SNARE membrane protein that drives vesicular membrane fusion in the early secretory pathway [PMID:2007627, PMID:28982678]. Genetic and biochemical work first placed its yeast ortholog BOS1 in the ER-to-Golgi transport step, where it is an essential membrane protein whose loss causes accumulation of ER and transport vesicles and failure to deliver secretory cargo to the Golgi [PMID:2192256, PMID:2007627]. The human protein executes this function by assembling into a SNARE complex with syntaxin-5, Bet1, and Sec22b to catalyze ER-to-Golgi membrane fusion [PMID:28982678]. Beyond this step, GOSR2 together with GS28 is enriched in COPI Golgi vesicles, and re-addition of isolated GS27/GS28-bearing vesicles is sufficient to restore intra-Golgi transport, indicating a role in inter-cisternal transport [PMID:23387339]. Correct cis-Golgi localization is required for activity [PMID:21549339]. The pathogenic p.Gly144Trp mutation causes loss of cis-Golgi targeting and partially reduces SNARE-mediated fusion by compromising the hydrophobic core that triggers SNARE assembly, while other mutations disrupt GOSR2–syntaxin-5 hydrogen bonding [PMID:21549339, PMID:28982678]; these partial fusion deficits impair dendritic growth and destabilize the presynaptic cytoskeleton, underlying GOSR2 progressive myoclonus epilepsy [PMID:28978487]. GOSR2 mutations are also associated with α-dystroglycan hypoglycosylation in patient fibroblasts that lack detectable bulk transport defects, linking GOSR2 to congenital muscular dystrophy [PMID:29855340].","teleology":[{"year":1990,"claim":"Established that the GOSR2 ortholog BOS1 acts in the same ER-to-Golgi transport step as BET1 and SEC22, defining its functional pathway before any molecular activity was known.","evidence":"Yeast multicopy suppression and double-mutant lethality analysis across multiple secretory mutant alleles","pmids":["2192256"],"confidence":"High","gaps":["Genetic epistasis does not establish direct physical interaction or molecular mechanism","Does not define the biochemical activity of the gene product"]},{"year":1991,"claim":"Showed BOS1 encodes an essential ~27-kDa membrane protein required for ER-to-Golgi cargo transport, converting a genetic interactor into a defined membrane trafficking component.","evidence":"Yeast depletion of essential gene, secretory cargo (pro-alpha-factor, CPY) trafficking assay, differential centrifugation","pmids":["2007627"],"confidence":"High","gaps":["Molecular fusion mechanism not yet defined","SNARE partners not biochemically identified"]},{"year":1999,"claim":"Cloned the human ortholog GS27/GOSR2 and mapped it to 17q21, transferring the yeast trafficking role into a human SNARE candidate.","evidence":"cDNA cloning, sequence analysis, chromosomal mapping","pmids":["10198168"],"confidence":"Medium","gaps":["Function inferred from homology, not directly tested in human cells","SNARE complex membership not experimentally shown here"]},{"year":2011,"claim":"Demonstrated that the disease mutation p.Gly144Trp abolishes cis-Golgi localization, establishing correct localization as a functional requirement and the molecular basis of loss of function.","evidence":"Patient mutation identification and immunofluorescence localization in patient-derived cells","pmids":["21549339"],"confidence":"Medium","gaps":["Mechanism of mislocalization at the protein level not resolved","Single-lab observation","Downstream trafficking consequences not quantified here"]},{"year":2013,"claim":"Reconstituted a vesicle-level role for GS27/GS28, showing the two SNAREs are enriched in COPI vesicles and sufficient to restore intra-Golgi transport, extending GOSR2 function beyond the ER-to-Golgi step.","evidence":"Subcellular fractionation, in vitro intra-Golgi transport assay with selective vesicle re-addition under transport block","pmids":["23387339"],"confidence":"High","gaps":["Does not resolve the specific SNARE pairing for intra-Golgi fusion","Relationship between COPI vesicle role and ER-Golgi role unclear"]},{"year":2017,"claim":"Identified the human SNARE complex (GOSR2-syntaxin-5-Bet1-Sec22b) and showed disease mutations cause partial fusion deficits, providing the molecular mechanism linking genotype to impaired membrane fusion.","evidence":"Yeast complementation, fluorescence anisotropy, gel filtration, molecular dynamics simulation with mutagenesis","pmids":["28982678"],"confidence":"High","gaps":["Quantitative link between residual fusion activity and tissue-specific disease severity not established","In vivo fusion kinetics not measured"]},{"year":2017,"claim":"Connected partial SNARE fusion deficits to neuronal phenotypes, revealing roles for Membrin in dendritic growth and presynaptic cytoskeletal/transsynaptic integrity relevant to progressive myoclonus epilepsy.","evidence":"Drosophila loss-of-function models (dendritic morphology, electrophysiology, cytoskeletal imaging) plus SNARE fusion assay","pmids":["28978487"],"confidence":"High","gaps":["Mechanistic link between trafficking deficit and cytoskeletal fragmentation not fully defined","Findings in Drosophila not validated in mammalian neurons here"]},{"year":2018,"claim":"Linked GOSR2 mutations to α-dystroglycan hypoglycosylation and congenital muscular dystrophy while showing no detectable bulk transport defect, indicating a selective rather than global trafficking consequence.","evidence":"Patient fibroblast analysis, western blotting/immunofluorescence for α-dystroglycan glycosylation, live-cell transport assays with model cargoes","pmids":["29855340"],"confidence":"Medium","gaps":["Mechanism connecting GOSR2 dysfunction to selective glycosylation defect unresolved","Single patient, single lab","Negative transport result may reflect assay sensitivity"]},{"year":null,"claim":"How partial GOSR2 fusion deficits produce tissue-selective outcomes (neuronal epilepsy versus muscle glycosylation defects) without overt bulk secretory failure remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No mechanism explaining selective vulnerability of specific cargoes or tissues","Direct structural model of the assembled human SNARE complex absent","Link between intra-Golgi role and glycosylation phenotype not established"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[4,5]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[5]}],"localization":[{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[3,4]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[4]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[1]}],"pathway":[{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[0,1,4]},{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[1,5]}],"complexes":["SNARE complex (syntaxin-5/Bet1/Sec22b/GOSR2)"],"partners":["STX5","BET1","SEC22B","GOSR1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O14653","full_name":"Golgi SNAP receptor complex 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FAM210A","url":"https://www.omim.org/entry/617975"},{"mim_id":"614018","title":"EPILEPSY, PROGRESSIVE MYOCLONIC, 6; EPM6","url":"https://www.omim.org/entry/614018"},{"mim_id":"606975","title":"COMPONENT OF OLIGOMERIC GOLGI COMPLEX 3; COG3","url":"https://www.omim.org/entry/606975"},{"mim_id":"605456","title":"BET1 GOLGI VESICULAR MEMBRANE-TRAFFICKING PROTEIN; BET1","url":"https://www.omim.org/entry/605456"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"},{"location":"Golgi apparatus","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/GOSR2"},"hgnc":{"alias_symbol":["GS27","Bos1"],"prev_symbol":[]},"alphafold":{"accession":"O14653","domains":[{"cath_id":"1.20.58.400","chopping":"2-107_147-212","consensus_level":"medium","plddt":86.4176,"start":2,"end":212}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O14653","model_url":"https://alphafold.ebi.ac.uk/files/AF-O14653-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O14653-F1-predicted_aligned_error_v6.png","plddt_mean":83.12},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=GOSR2","jax_strain_url":"https://www.jax.org/strain/search?query=GOSR2"},"sequence":{"accession":"O14653","fasta_url":"https://rest.uniprot.org/uniprotkb/O14653.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O14653/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O14653"}},"corpus_meta":[{"pmid":"2192256","id":"PMC_2192256","title":"BET1, BOS1, and SEC22 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Botrytis cinerea is negatively regulated by the upstream histidine kinase Bos1 and is not involved in dicarboximide- and phenylpyrrole-resistance.","date":"2008","source":"Fungal genetics and biology : FG & B","url":"https://pubmed.ncbi.nlm.nih.gov/18495505","citation_count":76,"is_preprint":false},{"pmid":"23449775","id":"PMC_23449775","title":"'North Sea' progressive myoclonus epilepsy: phenotype of subjects with GOSR2 mutation.","date":"2013","source":"Brain : a journal of neurology","url":"https://pubmed.ncbi.nlm.nih.gov/23449775","citation_count":53,"is_preprint":false},{"pmid":"22912706","id":"PMC_22912706","title":"Functional and structural comparison of pyrrolnitrin- and iprodione-induced modifications in the class III histidine-kinase Bos1 of Botrytis cinerea.","date":"2012","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/22912706","citation_count":51,"is_preprint":false},{"pmid":"29855340","id":"PMC_29855340","title":"TRAPPC11 and GOSR2 mutations associate with 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Genetics","url":"https://pubmed.ncbi.nlm.nih.gov/39035823","citation_count":1,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":15073,"output_tokens":2234,"usd":0.039364,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9260,"output_tokens":3032,"usd":0.06105,"stage2_stop_reason":"end_turn"},"total_usd":0.100414,"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\": 1990,\n      \"finding\": \"BOS1 (yeast ortholog of GOSR2/GS27) genetically interacts with BET1 and SEC22 in ER-to-Golgi transport: overproduction of BOS1 suppresses growth and secretory defects of sec22-3 and bet1-1 mutants in a gene dosage-dependent manner; a bet1 sec22 double mutant is inviable, placing these genes in the same transport step.\",\n      \"method\": \"Yeast genetic suppressor screen, multicopy suppression, double-mutant lethality analysis\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis with multiple allele combinations, replicated interactions across several mutant backgrounds\",\n      \"pmids\": [\"2192256\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1991,\n      \"finding\": \"BOS1 (yeast ortholog of GOSR2) encodes an essential 27-kDa membrane protein required for vesicular transport from the ER to the Golgi complex; cells depleted of Bos1 accumulate an extensive ER network and small vesicles and fail to transport pro-alpha-factor and CPY to the Golgi. Differential centrifugation confirmed Bos1 membrane association.\",\n      \"method\": \"Yeast depletion (essential gene), secretory cargo trafficking assay, differential centrifugation fractionation, DNA sequence analysis\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — loss-of-function with defined cargo trafficking phenotype, membrane fractionation, and sequence prediction validated by biochemistry\",\n      \"pmids\": [\"2007627\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Human GS27 (GOSR2) encodes a 212-amino-acid Golgi SNARE trafficking protein involved in transport between the ER and Golgi and between Golgi subcompartments; chromosomal mapping places GS27 on chromosome 17q21.\",\n      \"method\": \"cDNA cloning, sequence analysis, chromosomal mapping (FISH/radiation hybrid)\",\n      \"journal\": \"Genomics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — cDNA characterization with chromosomal mapping; functional role inferred from sequence homology and prior yeast work, not directly tested in this paper\",\n      \"pmids\": [\"10198168\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"The p.Gly144Trp mutation in GOSR2 is equivalent to a loss of function and results in failure of the GOSR2 protein to localize to the cis-Golgi, establishing that correct cis-Golgi localization is required for GOSR2 function.\",\n      \"method\": \"Patient mutation identification, cellular localization assay (immunofluorescence of GOSR2 in patient-derived cells)\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization experiment with functional consequence (loss of cis-Golgi targeting = loss of function), single lab\",\n      \"pmids\": [\"21549339\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"GOSR2/GS27 (Membrin, Qb-SNARE) and GS28 are enriched in Golgi COPI vesicles and are depleted from Golgi cisternae when intra-Golgi transport is blocked; fusion of these vesicles with cisternae during active transport delivers GS27 and GS28 to cisternae. In vitro, re-addition of isolated Golgi vesicles containing GS27/GS28 (but not the sugar transporter) restores intra-Golgi transport, indicating GS27 and GS28 in vesicles are sufficient for this activity.\",\n      \"method\": \"Subcellular fractionation, in vitro intra-Golgi transport assay, selective vesicle re-addition, inhibitor-based transport block\",\n      \"journal\": \"Traffic (Copenhagen, Denmark)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution assay with fractionation and re-addition of isolated vesicles; multiple orthogonal methods in single study\",\n      \"pmids\": [\"23387339\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"GOSR2 (Membrin) forms a SNARE complex with syntaxin-5, Bet1, and Sec22b to mediate ER-to-Golgi membrane fusion. The pathogenic p.Gly144Trp mutation causes partial reduction in SNARE-mediated membrane fusion; the equivalent Bos1 p.Gly176Trp and p.Arg196del mutations can still form SNARE complexes but with partly reduced activity. Molecular dynamics simulations showed p.Gly144Trp compromises the hydrophobic core triggering SNARE complex assembly, while p.Lys164del disrupts hydrogen bonds between GOSR2 and syntaxin-5.\",\n      \"method\": \"Yeast complementation growth assay, fluorescence anisotropy, gel filtration, molecular dynamics simulation\",\n      \"journal\": \"Disease models & mechanisms\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro SNARE complex formation assay with mutagenesis, biophysical methods, and MD simulation; multiple orthogonal methods in single study\",\n      \"pmids\": [\"28982678\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Pathogenic GOSR2 mutations cause partial reductions in SNARE-mediated membrane fusion sufficient to profoundly impair dendritic growth in Drosophila models of GOSR2-PME; GOSR2/Membrin mutations also cause fragmentation of the presynaptic cytoskeleton, transsynaptic instability, and hyperactive neurotransmission, revealing a role for Membrin in synaptic integrity.\",\n      \"method\": \"Drosophila loss-of-function models (dendritic morphology assay, electrophysiology, cytoskeletal imaging), SNARE fusion assay\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal functional assays (dendritic growth, synaptic cytoskeleton, neurotransmission) in a defined genetic model with mechanistic context\",\n      \"pmids\": [\"28978487\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Compound heterozygous GOSR2 mutations (c.430G>T and c.2T>G) are associated with hypoglycosylation of α-dystroglycan; however, cellular biological analyses on patient fibroblasts using two different model cargo proteins did not reveal detectable defects in protein transport, indicating the glycosylation defect is not simply due to bulk trafficking impairment.\",\n      \"method\": \"Patient fibroblast analysis, immunofluorescence and western blotting for α-dystroglycan glycosylation, live cell transport assays with model cargo proteins\",\n      \"journal\": \"Skeletal muscle\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — direct biochemical assay (α-dystroglycan glycosylation) with negative result for bulk transport; single lab, single patient\",\n      \"pmids\": [\"29855340\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"GOSR2 (GS27/Membrin/Bos1) is a Qb-SNARE membrane protein that localizes to the cis-Golgi and forms a SNARE complex with syntaxin-5, Bet1, and Sec22b to drive COPII vesicle fusion at the ER-to-Golgi step; it is also enriched in COPI Golgi vesicles where, together with GS28, it facilitates intra-Golgi transport by enabling inter-cisternal connections, and pathogenic missense mutations (especially p.Gly144Trp) cause partial loss of SNARE-mediated membrane fusion, failure of cis-Golgi localization, impaired dendritic growth, presynaptic cytoskeletal instability, and α-dystroglycan hypoglycosylation, collectively underlying progressive myoclonus epilepsy and congenital muscular dystrophy.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"GOSR2 (GS27/Membrin/Bos1) is a Golgi Qb-SNARE membrane protein that drives vesicular membrane fusion in the early secretory pathway [#1, #5]. Genetic and biochemical work first placed its yeast ortholog BOS1 in the ER-to-Golgi transport step, where it is an essential membrane protein whose loss causes accumulation of ER and transport vesicles and failure to deliver secretory cargo to the Golgi [#0, #1]. The human protein executes this function by assembling into a SNARE complex with syntaxin-5, Bet1, and Sec22b to catalyze ER-to-Golgi membrane fusion [#5]. Beyond this step, GOSR2 together with GS28 is enriched in COPI Golgi vesicles, and re-addition of isolated GS27/GS28-bearing vesicles is sufficient to restore intra-Golgi transport, indicating a role in inter-cisternal transport [#4]. Correct cis-Golgi localization is required for activity [#3]. The pathogenic p.Gly144Trp mutation causes loss of cis-Golgi targeting and partially reduces SNARE-mediated fusion by compromising the hydrophobic core that triggers SNARE assembly, while other mutations disrupt GOSR2–syntaxin-5 hydrogen bonding [#3, #5]; these partial fusion deficits impair dendritic growth and destabilize the presynaptic cytoskeleton, underlying GOSR2 progressive myoclonus epilepsy [#6]. GOSR2 mutations are also associated with α-dystroglycan hypoglycosylation in patient fibroblasts that lack detectable bulk transport defects, linking GOSR2 to congenital muscular dystrophy [#7].\",\n  \"teleology\": [\n    {\n      \"year\": 1990,\n      \"claim\": \"Established that the GOSR2 ortholog BOS1 acts in the same ER-to-Golgi transport step as BET1 and SEC22, defining its functional pathway before any molecular activity was known.\",\n      \"evidence\": \"Yeast multicopy suppression and double-mutant lethality analysis across multiple secretory mutant alleles\",\n      \"pmids\": [\"2192256\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Genetic epistasis does not establish direct physical interaction or molecular mechanism\", \"Does not define the biochemical activity of the gene product\"]\n    },\n    {\n      \"year\": 1991,\n      \"claim\": \"Showed BOS1 encodes an essential ~27-kDa membrane protein required for ER-to-Golgi cargo transport, converting a genetic interactor into a defined membrane trafficking component.\",\n      \"evidence\": \"Yeast depletion of essential gene, secretory cargo (pro-alpha-factor, CPY) trafficking assay, differential centrifugation\",\n      \"pmids\": [\"2007627\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular fusion mechanism not yet defined\", \"SNARE partners not biochemically identified\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Cloned the human ortholog GS27/GOSR2 and mapped it to 17q21, transferring the yeast trafficking role into a human SNARE candidate.\",\n      \"evidence\": \"cDNA cloning, sequence analysis, chromosomal mapping\",\n      \"pmids\": [\"10198168\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Function inferred from homology, not directly tested in human cells\", \"SNARE complex membership not experimentally shown here\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Demonstrated that the disease mutation p.Gly144Trp abolishes cis-Golgi localization, establishing correct localization as a functional requirement and the molecular basis of loss of function.\",\n      \"evidence\": \"Patient mutation identification and immunofluorescence localization in patient-derived cells\",\n      \"pmids\": [\"21549339\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of mislocalization at the protein level not resolved\", \"Single-lab observation\", \"Downstream trafficking consequences not quantified here\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Reconstituted a vesicle-level role for GS27/GS28, showing the two SNAREs are enriched in COPI vesicles and sufficient to restore intra-Golgi transport, extending GOSR2 function beyond the ER-to-Golgi step.\",\n      \"evidence\": \"Subcellular fractionation, in vitro intra-Golgi transport assay with selective vesicle re-addition under transport block\",\n      \"pmids\": [\"23387339\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not resolve the specific SNARE pairing for intra-Golgi fusion\", \"Relationship between COPI vesicle role and ER-Golgi role unclear\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Identified the human SNARE complex (GOSR2-syntaxin-5-Bet1-Sec22b) and showed disease mutations cause partial fusion deficits, providing the molecular mechanism linking genotype to impaired membrane fusion.\",\n      \"evidence\": \"Yeast complementation, fluorescence anisotropy, gel filtration, molecular dynamics simulation with mutagenesis\",\n      \"pmids\": [\"28982678\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Quantitative link between residual fusion activity and tissue-specific disease severity not established\", \"In vivo fusion kinetics not measured\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Connected partial SNARE fusion deficits to neuronal phenotypes, revealing roles for Membrin in dendritic growth and presynaptic cytoskeletal/transsynaptic integrity relevant to progressive myoclonus epilepsy.\",\n      \"evidence\": \"Drosophila loss-of-function models (dendritic morphology, electrophysiology, cytoskeletal imaging) plus SNARE fusion assay\",\n      \"pmids\": [\"28978487\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanistic link between trafficking deficit and cytoskeletal fragmentation not fully defined\", \"Findings in Drosophila not validated in mammalian neurons here\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Linked GOSR2 mutations to α-dystroglycan hypoglycosylation and congenital muscular dystrophy while showing no detectable bulk transport defect, indicating a selective rather than global trafficking consequence.\",\n      \"evidence\": \"Patient fibroblast analysis, western blotting/immunofluorescence for α-dystroglycan glycosylation, live-cell transport assays with model cargoes\",\n      \"pmids\": [\"29855340\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism connecting GOSR2 dysfunction to selective glycosylation defect unresolved\", \"Single patient, single lab\", \"Negative transport result may reflect assay sensitivity\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How partial GOSR2 fusion deficits produce tissue-selective outcomes (neuronal epilepsy versus muscle glycosylation defects) without overt bulk secretory failure remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No mechanism explaining selective vulnerability of specific cargoes or tissues\", \"Direct structural model of the assembled human SNARE complex absent\", \"Link between intra-Golgi role and glycosylation phenotype not established\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [4, 5]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [5]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [3, 4]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [4]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [0, 1, 4]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [1, 5]}\n    ],\n    \"complexes\": [\"SNARE complex (syntaxin-5/Bet1/Sec22b/GOSR2)\"],\n    \"partners\": [\"STX5\", \"BET1\", \"SEC22B\", \"GOSR1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}