{"gene":"GLRB","run_date":"2026-06-10T01:55:21","timeline":{"discoveries":[{"year":2002,"finding":"A missense mutation G229D in GLRB reduces agonist sensitivity of α1β(G229D) GlyRs, demonstrating that the β-subunit plays a functional role in ligand binding/receptor activation, not merely structural integrity or modulation.","method":"Electrophysiological studies of recombinant α1β(G229D) GlyRs expressed in cells, measuring agonist-mediated activation","journal":"Human molecular genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct electrophysiology on recombinant mutant receptor, single lab, single method but clear functional readout","pmids":["11929858"],"is_preprint":false},{"year":2012,"finding":"GLRB null mutations (nonsense, frameshift, large deletion, splice) cause loss of GlyR β-subunit surface expression, establishing GLRB as the third major gene for hyperekplexia; cell-surface biotinylation confirmed that loss-of-function mutations reduce β-subunit at the plasma membrane.","method":"Cell-surface biotinylation, splicing assays, deletion mapping, expression studies, molecular modelling","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (splicing assay, biotinylation, deletion mapping, expression) in a large cohort study, single lab but comprehensive","pmids":["23184146"],"is_preprint":false},{"year":2012,"finding":"GLRB missense mutation M177R inserts a positive charge into a hydrophobic pocket in the extracellular domain, increasing EC50 and decreasing maximal glycine responses of α1β GlyRs. Mutation L285R at the pore-lining 9' position destabilizes the channel closed state, producing spontaneously active (leak) channels and reducing peak currents. Mutation W310C, predicted to disrupt hydrophobic stacking between M1, M2, and M3 transmembrane helices, reduces maximal currents without affecting glycine sensitivity, in both homozygous and heterozygous stoichiometries.","method":"Whole-cell patch-clamp electrophysiology of recombinant α1β mutant GlyRs; structural/molecular modelling to interpret domain effects","journal":"Neurobiology of disease","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — direct electrophysiology with multiple distinct mutations each providing mechanistic insight into specific domains, single lab but multiple orthogonal constructs and readouts","pmids":["23238346"],"is_preprint":false},{"year":1998,"finding":"The GLRB coding region is distributed over nine exons with structural homology to GLRA1; the GLRB gene maps to chromosome 4q31.3. A β-B transcript variant differing in its 5'-UTR was identified, indicating alternative promoter usage or transcription start site usage.","method":"Genomic organization analysis, in situ hybridization for chromosomal localization, cDNA library screening","journal":"Genomics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct experimental genomic mapping and library screening, single lab, multiple methods","pmids":["9676428"],"is_preprint":false},{"year":2012,"finding":"In the murine spastic (Glrb-spa) allele, exon 6 skipping requires two co-operative hits: (1) inactivation of an exonic splicing enhancer (ESE) within exon 6, and (2) a full-length LINE1 retrotransposon insertion in intron 6. Reconstitution of the ESE by a single nucleotide substitution prevented exon skipping. Regions within the 5' and 3' UTR of the LINE1 also act as determinants of exon skipping.","method":"Minigene splicing assay, sequence comparison, motif prediction, mutational analysis of ESE and LINE1 sequences","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — minigene reconstitution with mutagenesis identifying both ESE and LINE1 elements as required, multiple mutants tested, clear mechanistic dissection","pmids":["22782896"],"is_preprint":false},{"year":2017,"finding":"Non-coding SNPs in GLRB (rs78726293, rs191260602, rs17035816, rs7688285) are associated with increased acoustic startle response and fear network activation. The SNP rs7688285 modulates GLRB gene expression in brain tissue and in cell culture, indicating a regulatory role for these variants. Partial Glrb knockout mice display an agoraphobic phenotype, directly linking reduced GLRB expression to anxiety-related behavior.","method":"GWAS, gene expression analysis (brain tissue and cell culture), partial Glrb knockout mouse behavioral assays","journal":"Molecular psychiatry","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — gene expression modulation confirmed in vitro and in tissue; KO mouse behavioral phenotype established; GWAS genetic association data supporting but not mechanistically definitive alone","pmids":["28167838"],"is_preprint":false},{"year":2020,"finding":"Heterozygous spastic mice (reduced full-length GlyR β-subunit due to aberrant Glrb splicing) show no startle phenotype in neutral or conditioning contexts, while homozygous spasmodic mice (Glra1 point mutation) show enhanced startle and fear-related behavioral changes. This distinguishes the behavioral consequences of Glrb vs. Glra1 loss-of-function in vivo.","method":"Behavioral phenotyping (startle paradigm, fear conditioning) in Glrb spastic and Glra1 spasmodic mouse mutants","journal":"Frontiers in molecular neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct behavioral comparison of two mouse mutant lines, clean genetic models, single lab","pmids":["32848605"],"is_preprint":false}],"current_model":"GLRB encodes the β-subunit of the heteropentameric inhibitory glycine receptor (GlyR), which assembles in a 2α1:3β stoichiometry; the β-subunit contributes directly to agonist binding and channel gating (not merely structural support), as shown by mutations that reduce glycine sensitivity (M177R, G229D), produce spontaneously active channels by destabilizing the closed state (L285R at the 9' pore-lining position), or reduce maximal currents by disrupting transmembrane helix packing (W310C); loss-of-function mutations abolish surface expression of the receptor and cause hyperekplexia, while in the mouse spastic allele exon skipping of Glrb requires cooperative inactivation of an exonic splicing enhancer plus a LINE1 retrotransposon insertion in the adjacent intron."},"narrative":{"mechanistic_narrative":"GLRB encodes the β-subunit of the heteropentameric inhibitory glycine receptor, where it contributes directly to agonist binding and channel gating rather than serving a purely structural role [PMID:11929858, PMID:23238346]. Mutational electrophysiology established that distinct β-subunit residues control specific steps of receptor function: G229D and the extracellular-domain M177R reduce glycine sensitivity and maximal currents, the pore-lining 9' position L285R destabilizes the closed state to produce spontaneously active leak channels, and W310C disrupts hydrophobic packing between the M1, M2, and M3 transmembrane helices to reduce maximal currents without altering glycine sensitivity [PMID:11929858, PMID:23238346]. Loss-of-function GLRB mutations — nonsense, frameshift, deletion, and splice variants — abolish β-subunit surface expression and cause hyperekplexia, defining GLRB as a major hyperekplexia gene [PMID:23184146]. Beyond its synaptic role, non-coding GLRB variants modulate gene expression in brain tissue and are associated with elevated acoustic startle and fear-network activation, and partial Glrb knockout produces anxiety-related behavior in mice [PMID:28167838]. The murine spastic allele illustrates a splicing-level disease mechanism in which exon 6 skipping requires cooperative inactivation of an exonic splicing enhancer together with a LINE1 retrotransposon insertion in the adjacent intron [PMID:22782896].","teleology":[{"year":1998,"claim":"Established the genomic architecture of GLRB, defining it as a nine-exon gene homologous to GLRA1 and revealing alternative 5'-UTR transcript usage, which framed how its expression and splicing could be regulated.","evidence":"Genomic organization analysis, in situ hybridization, and cDNA library screening","pmids":["9676428"],"confidence":"Medium","gaps":["Does not address protein function or assembly","Functional significance of the β-B 5'-UTR variant not resolved"]},{"year":2002,"claim":"Resolved whether the β-subunit is merely structural by showing the G229D mutation reduces agonist sensitivity, establishing a direct functional contribution of β to receptor activation.","evidence":"Electrophysiology of recombinant α1β(G229D) GlyRs measuring agonist-mediated activation","pmids":["11929858"],"confidence":"Medium","gaps":["Single mutation, single lab","Does not map which domain mediates the ligand-binding contribution"]},{"year":2012,"claim":"Defined the molecular pathology of multiple β-subunit point mutations, assigning specific residues to extracellular agonist binding (M177R), closed-state stability at the pore 9' position (L285R), and transmembrane helix packing (W310C).","evidence":"Whole-cell patch-clamp of recombinant α1β mutant GlyRs with structural modelling","pmids":["23238346"],"confidence":"High","gaps":["Mechanistic interpretations rest partly on modelling, not experimental structure","Effects characterized in recombinant rather than native synaptic receptors"]},{"year":2012,"claim":"Established GLRB as the third major hyperekplexia gene by linking null mutations to loss of β-subunit surface expression, connecting genotype to a defect in receptor trafficking/assembly.","evidence":"Cell-surface biotinylation, splicing assays, deletion mapping, and expression studies in a patient cohort","pmids":["23184146"],"confidence":"High","gaps":["Mechanism of surface-expression loss (assembly vs trafficking) not fully dissected","Single lab cohort"]},{"year":2012,"claim":"Dissected the splicing mechanism of the murine spastic allele, showing exon 6 skipping requires cooperative loss of an exonic splicing enhancer plus a LINE1 intronic insertion, illustrating how retrotransposon-driven mis-splicing reduces functional β-subunit.","evidence":"Minigene splicing assays with mutational reconstitution of the ESE and LINE1 elements","pmids":["22782896"],"confidence":"High","gaps":["A mouse-allele mechanism; relevance to human splice variants not established here","Identity of the trans-acting splicing factors not defined"]},{"year":2017,"claim":"Extended GLRB function beyond hyperekplexia by showing non-coding variants modulate brain GLRB expression and associate with startle and fear-network activation, with partial knockout mice displaying anxiety-related behavior.","evidence":"GWAS, expression analysis in brain tissue and cell culture, and behavioral assays in partial Glrb knockout mice","pmids":["28167838"],"confidence":"Medium","gaps":["GWAS association not mechanistically definitive alone","Circuit linking reduced GLRB to anxiety not resolved"]},{"year":2020,"claim":"Distinguished the in vivo behavioral consequences of β-subunit versus α1-subunit loss, showing heterozygous spastic (Glrb) mice lack a startle phenotype whereas spasmodic (Glra1) mice show enhanced startle and fear changes.","evidence":"Startle and fear-conditioning behavioral phenotyping of Glrb spastic and Glra1 spasmodic mouse mutants","pmids":["32848605"],"confidence":"Medium","gaps":["Only heterozygous Glrb tested in this comparison","Does not resolve the molecular basis of the differing behavioral outcomes"]},{"year":null,"claim":"How GLRB β-subunit dosage and synaptic GlyR composition translate into specific affective and startle circuit outputs remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No experimental structure of the human β-containing receptor in the corpus","Trans-acting regulators of GLRB splicing/expression unidentified","Circuit-level link between GLRB expression and anxiety behavior not mechanistically mapped"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[0,2]},{"term_id":"GO:0005215","term_label":"transporter activity","supporting_discovery_ids":[2]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[1,2]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[1]}],"pathway":[{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[0,2,5]}],"complexes":["inhibitory glycine receptor"],"partners":["GLRA1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P48167","full_name":"Glycine receptor subunit beta","aliases":["Glycine receptor 58 kDa subunit"],"length_aa":497,"mass_kda":56.1,"function":"Subunit of heteromeric glycine-gated chloride channels (PubMed:11929858, PubMed:15302677, PubMed:16144831, PubMed:22715885, PubMed:23238346, PubMed:25445488, PubMed:34473954, PubMed:8717357). Plays an important role in the down-regulation of neuronal excitability (PubMed:11929858, PubMed:23238346). Contributes to the generation of inhibitory postsynaptic currents (PubMed:25445488)","subcellular_location":"Postsynaptic cell membrane; Synapse; Cell projection, dendrite; Cell membrane; Cytoplasm","url":"https://www.uniprot.org/uniprotkb/P48167/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/GLRB","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/GLRB","total_profiled":1310},"omim":[{"mim_id":"614619","title":"HYPEREKPLEXIA 2; HKPX2","url":"https://www.omim.org/entry/614619"},{"mim_id":"603930","title":"GEPHYRIN; GPHN","url":"https://www.omim.org/entry/603930"},{"mim_id":"184850","title":"STIFF-PERSON SYNDROME; SPS","url":"https://www.omim.org/entry/184850"},{"mim_id":"149400","title":"HYPEREKPLEXIA 1; HKPX1","url":"https://www.omim.org/entry/149400"},{"mim_id":"138492","title":"GLYCINE RECEPTOR, BETA SUBUNIT; GLRB","url":"https://www.omim.org/entry/138492"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"brain","ntpm":41.3},{"tissue":"parathyroid gland","ntpm":31.1}],"url":"https://www.proteinatlas.org/search/GLRB"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"P48167","domains":[{"cath_id":"2.70.170.10","chopping":"71-265","consensus_level":"high","plddt":91.2441,"start":71,"end":265},{"cath_id":"1.20.58.390","chopping":"269-358_478-497","consensus_level":"high","plddt":91.0489,"start":269,"end":497}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P48167","model_url":"https://alphafold.ebi.ac.uk/files/AF-P48167-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P48167-F1-predicted_aligned_error_v6.png","plddt_mean":78.06},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=GLRB","jax_strain_url":"https://www.jax.org/strain/search?query=GLRB"},"sequence":{"accession":"P48167","fasta_url":"https://rest.uniprot.org/uniprotkb/P48167.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P48167/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P48167"}},"corpus_meta":[{"pmid":"11929858","id":"PMC_11929858","title":"Hyperekplexia associated with compound heterozygote mutations in the beta-subunit of the human inhibitory glycine receptor (GLRB).","date":"2002","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/11929858","citation_count":137,"is_preprint":false},{"pmid":"15090072","id":"PMC_15090072","title":"A case of autism with an interstitial deletion on 4q leading to hemizygosity for genes encoding for glutamine and glycine neurotransmitter receptor sub-units (AMPA 2, GLRA3, GLRB) and neuropeptide receptors NPY1R, NPY5R.","date":"2004","source":"BMC medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/15090072","citation_count":64,"is_preprint":false},{"pmid":"23184146","id":"PMC_23184146","title":"GLRB is the third major gene of effect in hyperekplexia.","date":"2012","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/23184146","citation_count":50,"is_preprint":false},{"pmid":"23238346","id":"PMC_23238346","title":"Novel missense mutations in the glycine receptor β subunit gene (GLRB) in startle disease.","date":"2012","source":"Neurobiology of disease","url":"https://pubmed.ncbi.nlm.nih.gov/23238346","citation_count":48,"is_preprint":false},{"pmid":"28167838","id":"PMC_28167838","title":"GLRB allelic variation associated with agoraphobic cognitions, increased startle response and fear network activation: a potential neurogenetic pathway to panic disorder.","date":"2017","source":"Molecular psychiatry","url":"https://pubmed.ncbi.nlm.nih.gov/28167838","citation_count":41,"is_preprint":false},{"pmid":"21391991","id":"PMC_21391991","title":"Novel mutation in GLRB in a large family with hereditary hyperekplexia.","date":"2011","source":"Clinical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/21391991","citation_count":30,"is_preprint":false},{"pmid":"22669415","id":"PMC_22669415","title":"Partial deletion of GLRB and GRIA2 in a patient with intellectual disability.","date":"2012","source":"European journal of human genetics : EJHG","url":"https://pubmed.ncbi.nlm.nih.gov/22669415","citation_count":22,"is_preprint":false},{"pmid":"9676428","id":"PMC_9676428","title":"The human glycine receptor beta subunit gene (GLRB): structure, refined chromosomal localization, and population polymorphism.","date":"1998","source":"Genomics","url":"https://pubmed.ncbi.nlm.nih.gov/9676428","citation_count":20,"is_preprint":false},{"pmid":"32848605","id":"PMC_32848605","title":"Anxiety and Startle Phenotypes in Glrb Spastic and Glra1 Spasmodic Mouse Mutants.","date":"2020","source":"Frontiers in molecular neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/32848605","citation_count":12,"is_preprint":false},{"pmid":"28872638","id":"PMC_28872638","title":"Modulation of defensive reactivity by GLRB allelic variation: converging evidence from an intermediate phenotype approach.","date":"2017","source":"Translational psychiatry","url":"https://pubmed.ncbi.nlm.nih.gov/28872638","citation_count":12,"is_preprint":false},{"pmid":"22782896","id":"PMC_22782896","title":"A retroelement modifies pre-mRNA splicing: the murine Glrb(spa) allele is a splicing signal polymorphism amplified by long interspersed nuclear element insertion.","date":"2012","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/22782896","citation_count":12,"is_preprint":false},{"pmid":"11496371","id":"PMC_11496371","title":"Genetic variation of the human glycine receptor subunit genes GLRA3 and GLRB and susceptibility to idiopathic generalized epilepsies.","date":"2001","source":"American journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/11496371","citation_count":8,"is_preprint":false},{"pmid":"23182654","id":"PMC_23182654","title":"A 14-year-old girl with hyperekplexia having GLRB mutations.","date":"2012","source":"Brain & development","url":"https://pubmed.ncbi.nlm.nih.gov/23182654","citation_count":7,"is_preprint":false},{"pmid":"31444036","id":"PMC_31444036","title":"Association of rs7688285 allelic variation coding for GLRB with fear reactivity and exposure-based therapy in patients with panic disorder and agoraphobia.","date":"2019","source":"European neuropsychopharmacology : the journal of the European College of Neuropsychopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/31444036","citation_count":5,"is_preprint":false},{"pmid":"33323420","id":"PMC_33323420","title":"Abnormal neurodevelopment outcome in case of neonatal hyperekplexia secondary to missense mutation in GLRB gene.","date":"2020","source":"BMJ case reports","url":"https://pubmed.ncbi.nlm.nih.gov/33323420","citation_count":4,"is_preprint":false},{"pmid":"40337415","id":"PMC_40337415","title":"A novel GLRB mutation in neonatal hyperekplexia with divergent EEG findings: a case series.","date":"2025","source":"Annals of medicine and surgery (2012)","url":"https://pubmed.ncbi.nlm.nih.gov/40337415","citation_count":1,"is_preprint":false},{"pmid":"36927330","id":"PMC_36927330","title":"Association analysis of polymorphisms at GLRB, GRIA2, and GASK1B genes with reproductive traits in Dazu Black Goats.","date":"2023","source":"Animal biotechnology","url":"https://pubmed.ncbi.nlm.nih.gov/36927330","citation_count":1,"is_preprint":false},{"pmid":"39414323","id":"PMC_39414323","title":"Neonatal hyperekplexia: a non-epileptic paroxysmal movement disorder with a novel homozygous mutation in the GLRB gene, a seizure mimic.","date":"2024","source":"BMJ case reports","url":"https://pubmed.ncbi.nlm.nih.gov/39414323","citation_count":1,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":10941,"output_tokens":1912,"usd":0.030752,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8905,"output_tokens":2529,"usd":0.053875,"stage2_stop_reason":"end_turn"},"total_usd":0.084627,"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\": 2002,\n      \"finding\": \"A missense mutation G229D in GLRB reduces agonist sensitivity of α1β(G229D) GlyRs, demonstrating that the β-subunit plays a functional role in ligand binding/receptor activation, not merely structural integrity or modulation.\",\n      \"method\": \"Electrophysiological studies of recombinant α1β(G229D) GlyRs expressed in cells, measuring agonist-mediated activation\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct electrophysiology on recombinant mutant receptor, single lab, single method but clear functional readout\",\n      \"pmids\": [\"11929858\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"GLRB null mutations (nonsense, frameshift, large deletion, splice) cause loss of GlyR β-subunit surface expression, establishing GLRB as the third major gene for hyperekplexia; cell-surface biotinylation confirmed that loss-of-function mutations reduce β-subunit at the plasma membrane.\",\n      \"method\": \"Cell-surface biotinylation, splicing assays, deletion mapping, expression studies, molecular modelling\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (splicing assay, biotinylation, deletion mapping, expression) in a large cohort study, single lab but comprehensive\",\n      \"pmids\": [\"23184146\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"GLRB missense mutation M177R inserts a positive charge into a hydrophobic pocket in the extracellular domain, increasing EC50 and decreasing maximal glycine responses of α1β GlyRs. Mutation L285R at the pore-lining 9' position destabilizes the channel closed state, producing spontaneously active (leak) channels and reducing peak currents. Mutation W310C, predicted to disrupt hydrophobic stacking between M1, M2, and M3 transmembrane helices, reduces maximal currents without affecting glycine sensitivity, in both homozygous and heterozygous stoichiometries.\",\n      \"method\": \"Whole-cell patch-clamp electrophysiology of recombinant α1β mutant GlyRs; structural/molecular modelling to interpret domain effects\",\n      \"journal\": \"Neurobiology of disease\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — direct electrophysiology with multiple distinct mutations each providing mechanistic insight into specific domains, single lab but multiple orthogonal constructs and readouts\",\n      \"pmids\": [\"23238346\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"The GLRB coding region is distributed over nine exons with structural homology to GLRA1; the GLRB gene maps to chromosome 4q31.3. A β-B transcript variant differing in its 5'-UTR was identified, indicating alternative promoter usage or transcription start site usage.\",\n      \"method\": \"Genomic organization analysis, in situ hybridization for chromosomal localization, cDNA library screening\",\n      \"journal\": \"Genomics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct experimental genomic mapping and library screening, single lab, multiple methods\",\n      \"pmids\": [\"9676428\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"In the murine spastic (Glrb-spa) allele, exon 6 skipping requires two co-operative hits: (1) inactivation of an exonic splicing enhancer (ESE) within exon 6, and (2) a full-length LINE1 retrotransposon insertion in intron 6. Reconstitution of the ESE by a single nucleotide substitution prevented exon skipping. Regions within the 5' and 3' UTR of the LINE1 also act as determinants of exon skipping.\",\n      \"method\": \"Minigene splicing assay, sequence comparison, motif prediction, mutational analysis of ESE and LINE1 sequences\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — minigene reconstitution with mutagenesis identifying both ESE and LINE1 elements as required, multiple mutants tested, clear mechanistic dissection\",\n      \"pmids\": [\"22782896\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Non-coding SNPs in GLRB (rs78726293, rs191260602, rs17035816, rs7688285) are associated with increased acoustic startle response and fear network activation. The SNP rs7688285 modulates GLRB gene expression in brain tissue and in cell culture, indicating a regulatory role for these variants. Partial Glrb knockout mice display an agoraphobic phenotype, directly linking reduced GLRB expression to anxiety-related behavior.\",\n      \"method\": \"GWAS, gene expression analysis (brain tissue and cell culture), partial Glrb knockout mouse behavioral assays\",\n      \"journal\": \"Molecular psychiatry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — gene expression modulation confirmed in vitro and in tissue; KO mouse behavioral phenotype established; GWAS genetic association data supporting but not mechanistically definitive alone\",\n      \"pmids\": [\"28167838\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Heterozygous spastic mice (reduced full-length GlyR β-subunit due to aberrant Glrb splicing) show no startle phenotype in neutral or conditioning contexts, while homozygous spasmodic mice (Glra1 point mutation) show enhanced startle and fear-related behavioral changes. This distinguishes the behavioral consequences of Glrb vs. Glra1 loss-of-function in vivo.\",\n      \"method\": \"Behavioral phenotyping (startle paradigm, fear conditioning) in Glrb spastic and Glra1 spasmodic mouse mutants\",\n      \"journal\": \"Frontiers in molecular neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct behavioral comparison of two mouse mutant lines, clean genetic models, single lab\",\n      \"pmids\": [\"32848605\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"GLRB encodes the β-subunit of the heteropentameric inhibitory glycine receptor (GlyR), which assembles in a 2α1:3β stoichiometry; the β-subunit contributes directly to agonist binding and channel gating (not merely structural support), as shown by mutations that reduce glycine sensitivity (M177R, G229D), produce spontaneously active channels by destabilizing the closed state (L285R at the 9' pore-lining position), or reduce maximal currents by disrupting transmembrane helix packing (W310C); loss-of-function mutations abolish surface expression of the receptor and cause hyperekplexia, while in the mouse spastic allele exon skipping of Glrb requires cooperative inactivation of an exonic splicing enhancer plus a LINE1 retrotransposon insertion in the adjacent intron.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"GLRB encodes the β-subunit of the heteropentameric inhibitory glycine receptor, where it contributes directly to agonist binding and channel gating rather than serving a purely structural role [#0, #2]. Mutational electrophysiology established that distinct β-subunit residues control specific steps of receptor function: G229D and the extracellular-domain M177R reduce glycine sensitivity and maximal currents, the pore-lining 9' position L285R destabilizes the closed state to produce spontaneously active leak channels, and W310C disrupts hydrophobic packing between the M1, M2, and M3 transmembrane helices to reduce maximal currents without altering glycine sensitivity [#0, #2]. Loss-of-function GLRB mutations — nonsense, frameshift, deletion, and splice variants — abolish β-subunit surface expression and cause hyperekplexia, defining GLRB as a major hyperekplexia gene [#1]. Beyond its synaptic role, non-coding GLRB variants modulate gene expression in brain tissue and are associated with elevated acoustic startle and fear-network activation, and partial Glrb knockout produces anxiety-related behavior in mice [#5]. The murine spastic allele illustrates a splicing-level disease mechanism in which exon 6 skipping requires cooperative inactivation of an exonic splicing enhancer together with a LINE1 retrotransposon insertion in the adjacent intron [#4].\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"Established the genomic architecture of GLRB, defining it as a nine-exon gene homologous to GLRA1 and revealing alternative 5'-UTR transcript usage, which framed how its expression and splicing could be regulated.\",\n      \"evidence\": \"Genomic organization analysis, in situ hybridization, and cDNA library screening\",\n      \"pmids\": [\"9676428\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Does not address protein function or assembly\", \"Functional significance of the β-B 5'-UTR variant not resolved\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Resolved whether the β-subunit is merely structural by showing the G229D mutation reduces agonist sensitivity, establishing a direct functional contribution of β to receptor activation.\",\n      \"evidence\": \"Electrophysiology of recombinant α1β(G229D) GlyRs measuring agonist-mediated activation\",\n      \"pmids\": [\"11929858\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single mutation, single lab\", \"Does not map which domain mediates the ligand-binding contribution\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Defined the molecular pathology of multiple β-subunit point mutations, assigning specific residues to extracellular agonist binding (M177R), closed-state stability at the pore 9' position (L285R), and transmembrane helix packing (W310C).\",\n      \"evidence\": \"Whole-cell patch-clamp of recombinant α1β mutant GlyRs with structural modelling\",\n      \"pmids\": [\"23238346\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanistic interpretations rest partly on modelling, not experimental structure\", \"Effects characterized in recombinant rather than native synaptic receptors\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Established GLRB as the third major hyperekplexia gene by linking null mutations to loss of β-subunit surface expression, connecting genotype to a defect in receptor trafficking/assembly.\",\n      \"evidence\": \"Cell-surface biotinylation, splicing assays, deletion mapping, and expression studies in a patient cohort\",\n      \"pmids\": [\"23184146\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of surface-expression loss (assembly vs trafficking) not fully dissected\", \"Single lab cohort\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Dissected the splicing mechanism of the murine spastic allele, showing exon 6 skipping requires cooperative loss of an exonic splicing enhancer plus a LINE1 intronic insertion, illustrating how retrotransposon-driven mis-splicing reduces functional β-subunit.\",\n      \"evidence\": \"Minigene splicing assays with mutational reconstitution of the ESE and LINE1 elements\",\n      \"pmids\": [\"22782896\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"A mouse-allele mechanism; relevance to human splice variants not established here\", \"Identity of the trans-acting splicing factors not defined\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Extended GLRB function beyond hyperekplexia by showing non-coding variants modulate brain GLRB expression and associate with startle and fear-network activation, with partial knockout mice displaying anxiety-related behavior.\",\n      \"evidence\": \"GWAS, expression analysis in brain tissue and cell culture, and behavioral assays in partial Glrb knockout mice\",\n      \"pmids\": [\"28167838\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"GWAS association not mechanistically definitive alone\", \"Circuit linking reduced GLRB to anxiety not resolved\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Distinguished the in vivo behavioral consequences of β-subunit versus α1-subunit loss, showing heterozygous spastic (Glrb) mice lack a startle phenotype whereas spasmodic (Glra1) mice show enhanced startle and fear changes.\",\n      \"evidence\": \"Startle and fear-conditioning behavioral phenotyping of Glrb spastic and Glra1 spasmodic mouse mutants\",\n      \"pmids\": [\"32848605\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Only heterozygous Glrb tested in this comparison\", \"Does not resolve the molecular basis of the differing behavioral outcomes\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How GLRB β-subunit dosage and synaptic GlyR composition translate into specific affective and startle circuit outputs remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No experimental structure of the human β-containing receptor in the corpus\", \"Trans-acting regulators of GLRB splicing/expression unidentified\", \"Circuit-level link between GLRB expression and anxiety behavior not mechanistically mapped\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0, 2]},\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": [2]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [1, 2]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [0, 2, 5]}\n    ],\n    \"complexes\": [\"inhibitory glycine receptor\"],\n    \"partners\": [\"GLRA1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}