{"gene":"GNB1","run_date":"2026-06-10T01:55:21","timeline":{"discoveries":[{"year":2016,"finding":"De novo missense mutations in GNB1 cluster in a sub-region affecting known Gα-Gβγ interaction interfaces and Gβγ-effector interaction sites, suggesting either constitutive Gβγ activation (when Gα binding is disrupted) or reduced effector interaction as disease mechanisms.","method":"Whole-exome sequencing with mapping of mutations to known structural binding sites; functional inference from known somatic gain-of-function mutations at overlapping residues","journal":"American journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — structural mapping of mutations to known interaction interfaces with support from prior somatic mutation functional studies; no direct in vitro reconstitution in this paper","pmids":["27108799"],"is_preprint":false},{"year":2017,"finding":"GNB1 missense mutations R52G, G64V, A92T, P94S, P96L, A106T, and D118G alter Gβ1 complex formation with Gγ and impair mutant Gβγ coupling to dopamine D1R receptors, as measured by BRET assays. Mutations L30F, H91R, and K337Q did not show altered functionality in these assays.","method":"BRET (bioluminescence resonance energy transfer) assays for Gβγ-Gα complex formation and GPCR coupling; functional testing of 10 missense variants","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — direct functional assay (BRET) testing multiple mutations with clear positive and negative results in a single rigorous study","pmids":["28087732"],"is_preprint":false},{"year":2017,"finding":"The GNB1 K89M mutation in ETV6-ABL1-positive leukemic cells activates PI3K/Akt/mTOR and MAPK signaling pathways independently of the ETV6-ABL1 oncogene, conferring resistance to tyrosine kinase inhibitors.","method":"shRNA-mediated silencing of ETV6-ABL1 in resistant cells; genomic and proteomic profiling; pathway activity measurement (PI3K/Akt/mTOR and MAPK)","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic knockdown with pathway analysis and proteomic profiling in a single lab study; mechanistic link to GNB1 K89M established by genomic and functional data","pmids":["28650474"],"is_preprint":false},{"year":2020,"finding":"Loss-of-function GNB1 variants (a splice variant causing cryptic splice site usage and a truncating variant) fail to form dimers with Gγ subunit and are deficient in inducing GPCR-mediated G protein activation, establishing haploinsufficiency as a disease mechanism.","method":"RNA sequencing to confirm splice variant effect; BRET and BiFC (bimolecular fluorescence complementation) assays for Gβγ dimer formation and GPCR-induced G protein activation","journal":"Molecular genetics & genomic medicine","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — two orthogonal functional assays (BRET and BiFC) plus molecular characterization of splice variant; mechanistically conclusive within single study","pmids":["32918542"],"is_preprint":false},{"year":2021,"finding":"GNB1 encephalopathy mutations K78R, I80N, and I80T do not alter Gi/o coupling or Gβγ regulation of CaV2.2, but profoundly affect Gβγ regulation of GIRK channels: K78R causes gain-of-function and I80T/N cause loss-of-function in a GIRK subunit-specific manner, with altered Gβ1 protein expression levels and Gβγ binding to cytosolic GIRK segments.","method":"Heterologous expression, electrophysiology, protein expression analysis, Gβγ binding assays to cytosolic GIRK segments; computational modeling","journal":"iScience","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — multiple orthogonal methods (electrophysiology, binding assays, expression analysis, computation) in a single rigorous study with specific gain- and loss-of-function distinctions","pmids":["34522861"],"is_preprint":false},{"year":2023,"finding":"The K78R GNB1 mutation causes gain-of-function (GoF) by increasing GIRK channel activation in cortical neurons and Xenopus oocytes; ethosuximide (ETX) suppresses this GoF effect and alleviates seizures in K78R knock-in mice, identifying GIRK channel hyperactivation as an epileptic mechanism in GNB1 encephalopathy.","method":"K78R knock-in mouse model; multi-electrode array recordings of cultured neurons; in vivo EEG; Xenopus oocyte electrophysiology; pharmacological inhibition with ETX","journal":"Frontiers in cellular neuroscience","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — in vivo mouse model with EEG, in vitro MEA recordings, and Xenopus oocyte electrophysiology across multiple orthogonal readouts; replicated GoF finding from prior study (PMID:34522861)","pmids":["37275776"],"is_preprint":false},{"year":2023,"finding":"GNB1 physically interacts with BAG2 (co-immunoprecipitation followed by LC-MS), and this interaction activates the P38/MAPK signaling pathway to promote hepatocellular carcinoma cell proliferation, migration, invasion, and epithelial-to-mesenchymal transition.","method":"Co-immunoprecipitation followed by liquid chromatography-mass spectrometry; P38 inhibitor intervention; xenograft tumor model","journal":"Cancer science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP/MS identifies BAG2 as binding partner; pathway inhibition confirms P38 as downstream effector; single lab study","pmids":["36718954"],"is_preprint":false},{"year":2025,"finding":"Gβ1γ2 complex associates with voltage-gated sodium channels (Navs) in mouse brain, and co-expression of Gβ1γ2 functionally inhibits Nav1.1 and Nav1.6 in heterologous cells in a subtype-selective manner. The K78R GNB1 mutation reduces spontaneous GABAergic transmission and decreases sodium current density in parvalbumin-expressing interneurons in cortical slices.","method":"Co-immunoprecipitation from mouse brain; heterologous expression electrophysiology; cortical slice electrophysiology in Gnb1K78R/+ mice; dissociated interneuron recordings","journal":"Neurobiology of disease","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — direct Co-IP from brain tissue plus functional electrophysiology in heterologous and native neuronal systems; multiple orthogonal methods in single study","pmids":["40482731"],"is_preprint":false},{"year":2025,"finding":"The L95P GNB1 encephalopathy mutation reduces Gβ1 protein expression and, even when expression is restored, fails to effectively activate GIRK2 and GIRK1/2 channels in Xenopus oocytes; structural modeling indicates L95P primarily destabilizes the Gβ1 protein and the Gβ1-effector complex rather than disrupting the Gβγ-effector interface directly.","method":"Xenopus laevis oocyte heterologous expression with RNA co-injection; electrophysiology; rigid-body docking; thermodynamic calculations","journal":"Frontiers in pharmacology","confidence":"Medium","confidence_rationale":"Tier 1-2 / Moderate — direct functional assay in heterologous system with structural modeling support; single lab, single mutation studied","pmids":["40417225"],"is_preprint":false},{"year":2025,"finding":"GNB1 knockdown in human subcutaneous adipocytes reduces lipid droplet accumulation and alters the lipidome (decreasing cholesterol esters, increasing phosphatidylcholines, phosphatidylinositols, and ceramides) and proteome (upregulating PLPP1 and CDH13, downregulating HSPA8), indicating a role for GNB1 in adipocyte lipid storage and metabolism.","method":"RNA interference knockdown; lipidomic analysis by mass spectrometry; proteomic analysis by mass spectrometry; digital PCR for knockdown confirmation","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — two orthogonal omics methods (lipidomics + proteomics) with confirmed knockdown; single lab, no rescue experiments","pmids":["40127054"],"is_preprint":false},{"year":2022,"finding":"In Gnb1 mutant mice, thalamocortical (TC) neurons are activated prior to spike-wave discharge (SWD) onset and inhibited during SWD, while reticular thalamic (RT) neurons show the opposite pattern; chemogenetic activation of TC cells enhances SWD, demonstrating that sensory input regulates absence seizures through the thalamocortical pathway in GNB1 encephalopathy.","method":"In vivo recording in Gnb1 mutant mice; chemogenetic (DREADD) activation of thalamocortical neurons; EEG","journal":"iScience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo recordings with chemogenetic intervention defining circuit mechanism; single lab study in mouse model","pmids":["36405774"],"is_preprint":false},{"year":2005,"finding":"In Neurospora crassa, GNB-1 (Gβ) and GNG-1 (Gγ) physically associate in vivo (co-immunoprecipitation), GNB-1 is required for normal steady-state levels of GNG-1, and both subunits are required for maintaining Gα protein levels at the plasma membrane and for normal cAMP levels.","method":"Co-immunoprecipitation; genetic deletion analysis; plasma membrane fractionation; cAMP measurement","journal":"Eukaryotic cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP and genetic analysis with biochemical readouts; ortholog study in filamentous fungus with conserved Gβγ function","pmids":["15701799"],"is_preprint":false}],"current_model":"GNB1 encodes the Gβ1 subunit of heterotrimeric G proteins that obligatorily dimerizes with Gγ to form Gβγ, which couples to Gα and GPCRs; pathogenic GNB1 mutations disrupt Gβγ-Gα complex formation and/or alter Gβγ regulation of downstream effectors—particularly GIRK channels (with mutation-specific gain- or loss-of-function effects), voltage-gated sodium channels Nav1.1/1.6, and signaling cascades including PI3K/Akt/mTOR, MAPK/P38, and Ras—while haploinsufficiency (truncating/splice variants) causes loss of Gγ dimerization and GPCR-mediated G protein activation, collectively producing neuronal hyperexcitability and GNB1 encephalopathy."},"narrative":{"mechanistic_narrative":"GNB1 encodes the Gβ1 subunit of heterotrimeric G proteins, which obligatorily dimerizes with a Gγ subunit to form a Gβγ complex that couples to GPCRs and regulates downstream effectors; the integrity of this assembly is central to GNB1-associated neurodevelopmental disease [PMID:28087732, PMID:32918542]. The Gβ1-Gγ interaction is conserved across eukaryotes, where Gβ stabilizes Gγ and both subunits maintain Gα at the plasma membrane [PMID:15701799]. Disease-causing de novo missense mutations cluster at Gα-Gβγ and Gβγ-effector interfaces, and direct BRET/BiFC assays show that variants such as R52G, G64V, A92T, P94S, P96L, A106T, and D118G impair Gβ1-Gγ complex formation and GPCR coupling, while truncating and splice variants abolish Gγ dimerization and GPCR-mediated G protein activation, establishing both interface disruption and haploinsufficiency as mechanisms [PMID:27108799, PMID:28087732, PMID:32918542]. A principal effector axis is the GIRK potassium channel: encephalopathy mutations exert subunit-specific, mutation-specific effects, with K78R producing gain-of-function and I80T/N and L95P producing loss-of-function GIRK regulation [PMID:34522861, PMID:40417225]. The K78R gain-of-function increases GIRK activation in cortical neurons and is suppressed by ethosuximide in knock-in mice, linking GIRK hyperactivation to seizures [PMID:37275776], with absence seizures further driven through the thalamocortical circuit [PMID:36405774]. Gβ1γ2 also associates with voltage-gated sodium channels and subtype-selectively inhibits Nav1.1 and Nav1.6, and K78R reduces sodium current and GABAergic transmission in parvalbumin interneurons [PMID:40482731]. Beyond the nervous system, GNB1 signals through PI3K/Akt/mTOR and MAPK in leukemic cells [PMID:28650474], interacts with BAG2 to activate P38/MAPK in hepatocellular carcinoma [PMID:36718954], and supports adipocyte lipid droplet accumulation and lipid metabolism [PMID:40127054].","teleology":[{"year":2016,"claim":"Established a structural hypothesis for how GNB1 mutations cause disease by mapping de novo variants onto Gα-Gβγ and Gβγ-effector interfaces.","evidence":"Whole-exome sequencing with structural mapping of mutation positions to known binding sites","pmids":["27108799"],"confidence":"Medium","gaps":["No direct in vitro reconstitution of mutant effects in this study","Functional consequence inferred from structure rather than measured","Did not distinguish gain- from loss-of-function per variant"]},{"year":2017,"claim":"Provided direct functional evidence that specific missense variants impair Gβ1-Gγ assembly and GPCR coupling, converting the structural hypothesis into measured defects.","evidence":"BRET assays of Gβγ-Gα complex formation and D1R coupling across 10 missense variants","pmids":["28087732"],"confidence":"High","gaps":["Did not assess effector-channel regulation","Negative variants (L30F, H91R, K337Q) lack mechanistic explanation","Limited to single GPCR readout"]},{"year":2017,"claim":"Linked GNB1 to oncogenic signaling by showing a somatic mutation activates PI3K/Akt/mTOR and MAPK independently of a driver fusion, conferring drug resistance.","evidence":"shRNA silencing of ETV6-ABL1 plus genomic/proteomic pathway profiling in leukemic cells","pmids":["28650474"],"confidence":"Medium","gaps":["Single lab study","Direct effector of K78M-driven pathway activation not defined","No structural basis for gain-of-function established"]},{"year":2020,"claim":"Confirmed haploinsufficiency as a disease mechanism by demonstrating that truncating and splice variants fail to dimerize with Gγ and cannot activate G proteins.","evidence":"RNA-seq plus orthogonal BRET and BiFC assays of dimer formation and GPCR-induced activation","pmids":["32918542"],"confidence":"High","gaps":["Downstream neuronal consequences not assessed","No in vivo model","Effector-level phenotype not measured"]},{"year":2021,"claim":"Identified GIRK channels as the key effector axis and showed encephalopathy mutations produce subunit-specific gain- or loss-of-function while sparing Gi/o coupling and CaV2.2.","evidence":"Heterologous electrophysiology, Gβγ-GIRK binding assays, expression analysis, and computational modeling of K78R/I80N/I80T","pmids":["34522861"],"confidence":"High","gaps":["In vivo relevance not yet established","Mechanism of subunit selectivity incompletely defined","Limited to three variants"]},{"year":2022,"claim":"Defined the circuit-level basis of absence seizures, showing thalamocortical input regulates spike-wave discharges in Gnb1 mutant mice.","evidence":"In vivo recording with chemogenetic DREADD activation of thalamocortical neurons and EEG","pmids":["36405774"],"confidence":"Medium","gaps":["Single lab study","Molecular link between GNB1 variant and circuit activity not fully resolved","Specific mutation context not detailed"]},{"year":2023,"claim":"Validated GIRK hyperactivation as an in vivo seizure mechanism and demonstrated pharmacological rescue, providing therapeutic rationale.","evidence":"K78R knock-in mice, MEA recordings, in vivo EEG, Xenopus oocyte electrophysiology, and ethosuximide intervention","pmids":["37275776"],"confidence":"High","gaps":["Ethosuximide mechanism on GIRK GoF not fully defined","Generalizability to loss-of-function variants unknown","Long-term efficacy not addressed"]},{"year":2023,"claim":"Extended GNB1 oncogenic signaling by identifying BAG2 as a physical partner driving P38/MAPK-dependent hepatocellular carcinoma progression.","evidence":"Co-IP/LC-MS, P38 inhibitor intervention, and xenograft tumor model","pmids":["36718954"],"confidence":"Medium","gaps":["Single lab study","Whether interaction is direct or complex-mediated unresolved","No reciprocal structural validation"]},{"year":2025,"claim":"Broadened the effector repertoire to voltage-gated sodium channels, showing Gβ1γ2 inhibits Nav1.1/Nav1.6 and K78R alters interneuron excitability and GABAergic transmission.","evidence":"Co-IP from mouse brain, heterologous electrophysiology, and cortical slice/dissociated interneuron recordings in Gnb1K78R/+ mice","pmids":["40482731"],"confidence":"High","gaps":["Structural basis of Nav subtype selectivity unknown","Relative contribution of Nav vs GIRK effects to seizures unresolved","Direct binding interface not mapped"]},{"year":2025,"claim":"Demonstrated a distinct loss-of-function mechanism for L95P via protein destabilization rather than direct effector-interface disruption.","evidence":"Xenopus oocyte expression with RNA co-injection, electrophysiology, rigid-body docking, and thermodynamic calculations","pmids":["40417225"],"confidence":"Medium","gaps":["Single mutation, single lab","Destabilization not confirmed by direct protein stability assays in vivo","No structural data beyond modeling"]},{"year":2025,"claim":"Revealed a non-neuronal metabolic role for GNB1 in adipocyte lipid storage and lipidome/proteome regulation.","evidence":"RNAi knockdown in human subcutaneous adipocytes with lipidomic and proteomic mass spectrometry","pmids":["40127054"],"confidence":"Medium","gaps":["No rescue experiments","Single lab study","Signaling pathway linking GNB1 to lipid metabolism not defined"]},{"year":null,"claim":"How the spectrum of mutation-specific GIRK and Nav effects integrates into a unified predictive model of GNB1 encephalopathy phenotypes, and how GPCR/Gα coupling defects translate to specific circuit outcomes, remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No genotype-to-phenotype framework spanning gain- and loss-of-function variants","Structural mechanism of effector subtype selectivity unmapped","Relative weighting of GIRK, Nav, and GPCR-coupling contributions to seizures undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[1,3,11]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[4,7,8]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[1,3]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[11]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[4]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[1,2,3,6]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[4,5,7,10]},{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[9]}],"complexes":["Gβγ heterodimer","heterotrimeric G protein"],"partners":["GNG1","GNG2","BAG2","GIRK","NAV1.1","NAV1.6"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P62873","full_name":"Guanine nucleotide-binding protein G(I)/G(S)/G(T) subunit beta-1","aliases":["Transducin beta chain 1"],"length_aa":340,"mass_kda":37.4,"function":"Guanine nucleotide-binding proteins (G proteins) are involved as a modulator or transducer in various transmembrane signaling systems (PubMed:29925951, PubMed:33762731, PubMed:34239069, PubMed:35610220, PubMed:35714614, PubMed:35835867, PubMed:36087581, PubMed:36989299, PubMed:37327704, PubMed:37935376, PubMed:37935377, PubMed:37963465, PubMed:37991948, PubMed:38168118, PubMed:38552625). The beta and gamma chains are required for the GTPase activity, for replacement of GDP by GTP, and for G protein-effector interaction (PubMed:29925951, PubMed:33762731, PubMed:34239069, PubMed:35610220, PubMed:35714614, PubMed:35835867, PubMed:36087581, PubMed:36989299, PubMed:37327704, PubMed:37935376, PubMed:37935377, PubMed:37963465, PubMed:38168118, PubMed:38552625)","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/P62873/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/GNB1","classification":"Not Classified","n_dependent_lines":85,"n_total_lines":1208,"dependency_fraction":0.07036423841059603},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000078369","cell_line_id":"CID001766","localizations":[{"compartment":"membrane","grade":3},{"compartment":"vesicles","grade":3},{"compartment":"er","grade":1}],"interactors":[{"gene":"GNG12","stoichiometry":10.0},{"gene":"GNA11","stoichiometry":10.0},{"gene":"GNAI2;GNAI1;GNAO1","stoichiometry":10.0},{"gene":"GNAS","stoichiometry":4.0},{"gene":"CCT2","stoichiometry":0.2},{"gene":"CCT6A","stoichiometry":0.2},{"gene":"FKBP8","stoichiometry":0.2},{"gene":"GNG5","stoichiometry":0.2},{"gene":"GNA12","stoichiometry":0.2},{"gene":"GNG2","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/target/CID001766","total_profiled":1310},"omim":[{"mim_id":"620055","title":"PWP1 HOMOLOG, ENDONUCLEIN; PWP1","url":"https://www.omim.org/entry/620055"},{"mim_id":"619503","title":"NEURODEVELOPMENTAL DISORDER WITH HYPOTONIA AND DYSMORPHIC FACIES; NEDHYDF","url":"https://www.omim.org/entry/619503"},{"mim_id":"618558","title":"G PROTEIN SIGNALING MODULATOR 3; GPSM3","url":"https://www.omim.org/entry/618558"},{"mim_id":"616973","title":"INTELLECTUAL DEVELOPMENTAL DISORDER, AUTOSOMAL DOMINANT 42; MRD42","url":"https://www.omim.org/entry/616973"},{"mim_id":"614286","title":"MYELODYSPLASTIC SYNDROME; MDS","url":"https://www.omim.org/entry/614286"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Plasma membrane","reliability":"Approved"},{"location":"Golgi apparatus","reliability":"Additional"}],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"retina","ntpm":2147.2}],"url":"https://www.proteinatlas.org/search/GNB1"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"P62873","domains":[{"cath_id":"2.130.10.10","chopping":"36-338","consensus_level":"high","plddt":97.2715,"start":36,"end":338}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P62873","model_url":"https://alphafold.ebi.ac.uk/files/AF-P62873-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P62873-F1-predicted_aligned_error_v6.png","plddt_mean":97.06},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=GNB1","jax_strain_url":"https://www.jax.org/strain/search?query=GNB1"},"sequence":{"accession":"P62873","fasta_url":"https://rest.uniprot.org/uniprotkb/P62873.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P62873/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P62873"}},"corpus_meta":[{"pmid":"27108799","id":"PMC_27108799","title":"Germline De Novo Mutations in GNB1 Cause Severe Neurodevelopmental Disability, Hypotonia, and Seizures.","date":"2016","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/27108799","citation_count":94,"is_preprint":false},{"pmid":"15701799","id":"PMC_15701799","title":"The heterotrimeric G-protein subunits GNG-1 and GNB-1 form a Gbetagamma dimer required for normal female fertility, asexual development, and galpha protein levels in Neurospora crassa.","date":"2005","source":"Eukaryotic cell","url":"https://pubmed.ncbi.nlm.nih.gov/15701799","citation_count":64,"is_preprint":false},{"pmid":"28087732","id":"PMC_28087732","title":"Novel GNB1 mutations disrupt assembly and function of G protein heterotrimers and cause global developmental delay in humans.","date":"2017","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/28087732","citation_count":62,"is_preprint":false},{"pmid":"30194818","id":"PMC_30194818","title":"Refining the phenotype associated with GNB1 mutations: Clinical data on 18 newly identified patients and review of the literature.","date":"2018","source":"American journal of medical genetics. 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Analysis of ASFV pI73R Reveals GNB1 Binding and Host Gene Modulation.","date":"2025","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/41465200","citation_count":1,"is_preprint":false},{"pmid":"38737931","id":"PMC_38737931","title":"Investigation of GNB1 derivative circular RNAs hsa_circ_0009361 and hsa_circ_0009362 expressions in colorectal cancer patients: potential new diagnostic factors.","date":"2024","source":"Gastroenterology and hepatology from bed to bench","url":"https://pubmed.ncbi.nlm.nih.gov/38737931","citation_count":1,"is_preprint":false},{"pmid":"36324816","id":"PMC_36324816","title":"BCORL1 S878G, GNB1 G116S, SH2B3 A536T, and KMT2D S3708R tetramutation co-contribute to a pediatric acute myeloid leukemia: Case report and literature review.","date":"2022","source":"Frontiers in 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mapping of mutations to known structural binding sites; functional inference from known somatic gain-of-function mutations at overlapping residues\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — structural mapping of mutations to known interaction interfaces with support from prior somatic mutation functional studies; no direct in vitro reconstitution in this paper\",\n      \"pmids\": [\"27108799\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"GNB1 missense mutations R52G, G64V, A92T, P94S, P96L, A106T, and D118G alter Gβ1 complex formation with Gγ and impair mutant Gβγ coupling to dopamine D1R receptors, as measured by BRET assays. Mutations L30F, H91R, and K337Q did not show altered functionality in these assays.\",\n      \"method\": \"BRET (bioluminescence resonance energy transfer) assays for Gβγ-Gα complex formation and GPCR coupling; functional testing of 10 missense variants\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — direct functional assay (BRET) testing multiple mutations with clear positive and negative results in a single rigorous study\",\n      \"pmids\": [\"28087732\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"The GNB1 K89M mutation in ETV6-ABL1-positive leukemic cells activates PI3K/Akt/mTOR and MAPK signaling pathways independently of the ETV6-ABL1 oncogene, conferring resistance to tyrosine kinase inhibitors.\",\n      \"method\": \"shRNA-mediated silencing of ETV6-ABL1 in resistant cells; genomic and proteomic profiling; pathway activity measurement (PI3K/Akt/mTOR and MAPK)\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic knockdown with pathway analysis and proteomic profiling in a single lab study; mechanistic link to GNB1 K89M established by genomic and functional data\",\n      \"pmids\": [\"28650474\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Loss-of-function GNB1 variants (a splice variant causing cryptic splice site usage and a truncating variant) fail to form dimers with Gγ subunit and are deficient in inducing GPCR-mediated G protein activation, establishing haploinsufficiency as a disease mechanism.\",\n      \"method\": \"RNA sequencing to confirm splice variant effect; BRET and BiFC (bimolecular fluorescence complementation) assays for Gβγ dimer formation and GPCR-induced G protein activation\",\n      \"journal\": \"Molecular genetics & genomic medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — two orthogonal functional assays (BRET and BiFC) plus molecular characterization of splice variant; mechanistically conclusive within single study\",\n      \"pmids\": [\"32918542\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"GNB1 encephalopathy mutations K78R, I80N, and I80T do not alter Gi/o coupling or Gβγ regulation of CaV2.2, but profoundly affect Gβγ regulation of GIRK channels: K78R causes gain-of-function and I80T/N cause loss-of-function in a GIRK subunit-specific manner, with altered Gβ1 protein expression levels and Gβγ binding to cytosolic GIRK segments.\",\n      \"method\": \"Heterologous expression, electrophysiology, protein expression analysis, Gβγ binding assays to cytosolic GIRK segments; computational modeling\",\n      \"journal\": \"iScience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — multiple orthogonal methods (electrophysiology, binding assays, expression analysis, computation) in a single rigorous study with specific gain- and loss-of-function distinctions\",\n      \"pmids\": [\"34522861\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"The K78R GNB1 mutation causes gain-of-function (GoF) by increasing GIRK channel activation in cortical neurons and Xenopus oocytes; ethosuximide (ETX) suppresses this GoF effect and alleviates seizures in K78R knock-in mice, identifying GIRK channel hyperactivation as an epileptic mechanism in GNB1 encephalopathy.\",\n      \"method\": \"K78R knock-in mouse model; multi-electrode array recordings of cultured neurons; in vivo EEG; Xenopus oocyte electrophysiology; pharmacological inhibition with ETX\",\n      \"journal\": \"Frontiers in cellular neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — in vivo mouse model with EEG, in vitro MEA recordings, and Xenopus oocyte electrophysiology across multiple orthogonal readouts; replicated GoF finding from prior study (PMID:34522861)\",\n      \"pmids\": [\"37275776\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"GNB1 physically interacts with BAG2 (co-immunoprecipitation followed by LC-MS), and this interaction activates the P38/MAPK signaling pathway to promote hepatocellular carcinoma cell proliferation, migration, invasion, and epithelial-to-mesenchymal transition.\",\n      \"method\": \"Co-immunoprecipitation followed by liquid chromatography-mass spectrometry; P38 inhibitor intervention; xenograft tumor model\",\n      \"journal\": \"Cancer science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP/MS identifies BAG2 as binding partner; pathway inhibition confirms P38 as downstream effector; single lab study\",\n      \"pmids\": [\"36718954\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Gβ1γ2 complex associates with voltage-gated sodium channels (Navs) in mouse brain, and co-expression of Gβ1γ2 functionally inhibits Nav1.1 and Nav1.6 in heterologous cells in a subtype-selective manner. The K78R GNB1 mutation reduces spontaneous GABAergic transmission and decreases sodium current density in parvalbumin-expressing interneurons in cortical slices.\",\n      \"method\": \"Co-immunoprecipitation from mouse brain; heterologous expression electrophysiology; cortical slice electrophysiology in Gnb1K78R/+ mice; dissociated interneuron recordings\",\n      \"journal\": \"Neurobiology of disease\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — direct Co-IP from brain tissue plus functional electrophysiology in heterologous and native neuronal systems; multiple orthogonal methods in single study\",\n      \"pmids\": [\"40482731\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"The L95P GNB1 encephalopathy mutation reduces Gβ1 protein expression and, even when expression is restored, fails to effectively activate GIRK2 and GIRK1/2 channels in Xenopus oocytes; structural modeling indicates L95P primarily destabilizes the Gβ1 protein and the Gβ1-effector complex rather than disrupting the Gβγ-effector interface directly.\",\n      \"method\": \"Xenopus laevis oocyte heterologous expression with RNA co-injection; electrophysiology; rigid-body docking; thermodynamic calculations\",\n      \"journal\": \"Frontiers in pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — direct functional assay in heterologous system with structural modeling support; single lab, single mutation studied\",\n      \"pmids\": [\"40417225\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"GNB1 knockdown in human subcutaneous adipocytes reduces lipid droplet accumulation and alters the lipidome (decreasing cholesterol esters, increasing phosphatidylcholines, phosphatidylinositols, and ceramides) and proteome (upregulating PLPP1 and CDH13, downregulating HSPA8), indicating a role for GNB1 in adipocyte lipid storage and metabolism.\",\n      \"method\": \"RNA interference knockdown; lipidomic analysis by mass spectrometry; proteomic analysis by mass spectrometry; digital PCR for knockdown confirmation\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — two orthogonal omics methods (lipidomics + proteomics) with confirmed knockdown; single lab, no rescue experiments\",\n      \"pmids\": [\"40127054\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"In Gnb1 mutant mice, thalamocortical (TC) neurons are activated prior to spike-wave discharge (SWD) onset and inhibited during SWD, while reticular thalamic (RT) neurons show the opposite pattern; chemogenetic activation of TC cells enhances SWD, demonstrating that sensory input regulates absence seizures through the thalamocortical pathway in GNB1 encephalopathy.\",\n      \"method\": \"In vivo recording in Gnb1 mutant mice; chemogenetic (DREADD) activation of thalamocortical neurons; EEG\",\n      \"journal\": \"iScience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo recordings with chemogenetic intervention defining circuit mechanism; single lab study in mouse model\",\n      \"pmids\": [\"36405774\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"In Neurospora crassa, GNB-1 (Gβ) and GNG-1 (Gγ) physically associate in vivo (co-immunoprecipitation), GNB-1 is required for normal steady-state levels of GNG-1, and both subunits are required for maintaining Gα protein levels at the plasma membrane and for normal cAMP levels.\",\n      \"method\": \"Co-immunoprecipitation; genetic deletion analysis; plasma membrane fractionation; cAMP measurement\",\n      \"journal\": \"Eukaryotic cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP and genetic analysis with biochemical readouts; ortholog study in filamentous fungus with conserved Gβγ function\",\n      \"pmids\": [\"15701799\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"GNB1 encodes the Gβ1 subunit of heterotrimeric G proteins that obligatorily dimerizes with Gγ to form Gβγ, which couples to Gα and GPCRs; pathogenic GNB1 mutations disrupt Gβγ-Gα complex formation and/or alter Gβγ regulation of downstream effectors—particularly GIRK channels (with mutation-specific gain- or loss-of-function effects), voltage-gated sodium channels Nav1.1/1.6, and signaling cascades including PI3K/Akt/mTOR, MAPK/P38, and Ras—while haploinsufficiency (truncating/splice variants) causes loss of Gγ dimerization and GPCR-mediated G protein activation, collectively producing neuronal hyperexcitability and GNB1 encephalopathy.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"GNB1 encodes the Gβ1 subunit of heterotrimeric G proteins, which obligatorily dimerizes with a Gγ subunit to form a Gβγ complex that couples to GPCRs and regulates downstream effectors; the integrity of this assembly is central to GNB1-associated neurodevelopmental disease [#1, #3]. The Gβ1-Gγ interaction is conserved across eukaryotes, where Gβ stabilizes Gγ and both subunits maintain Gα at the plasma membrane [#11]. Disease-causing de novo missense mutations cluster at Gα-Gβγ and Gβγ-effector interfaces, and direct BRET/BiFC assays show that variants such as R52G, G64V, A92T, P94S, P96L, A106T, and D118G impair Gβ1-Gγ complex formation and GPCR coupling, while truncating and splice variants abolish Gγ dimerization and GPCR-mediated G protein activation, establishing both interface disruption and haploinsufficiency as mechanisms [#0, #1, #3]. A principal effector axis is the GIRK potassium channel: encephalopathy mutations exert subunit-specific, mutation-specific effects, with K78R producing gain-of-function and I80T/N and L95P producing loss-of-function GIRK regulation [#4, #8]. The K78R gain-of-function increases GIRK activation in cortical neurons and is suppressed by ethosuximide in knock-in mice, linking GIRK hyperactivation to seizures [#5], with absence seizures further driven through the thalamocortical circuit [#10]. Gβ1γ2 also associates with voltage-gated sodium channels and subtype-selectively inhibits Nav1.1 and Nav1.6, and K78R reduces sodium current and GABAergic transmission in parvalbumin interneurons [#7]. Beyond the nervous system, GNB1 signals through PI3K/Akt/mTOR and MAPK in leukemic cells [#2], interacts with BAG2 to activate P38/MAPK in hepatocellular carcinoma [#6], and supports adipocyte lipid droplet accumulation and lipid metabolism [#9].\",\n  \"teleology\": [\n    {\n      \"year\": 2016,\n      \"claim\": \"Established a structural hypothesis for how GNB1 mutations cause disease by mapping de novo variants onto Gα-Gβγ and Gβγ-effector interfaces.\",\n      \"evidence\": \"Whole-exome sequencing with structural mapping of mutation positions to known binding sites\",\n      \"pmids\": [\"27108799\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No direct in vitro reconstitution of mutant effects in this study\", \"Functional consequence inferred from structure rather than measured\", \"Did not distinguish gain- from loss-of-function per variant\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Provided direct functional evidence that specific missense variants impair Gβ1-Gγ assembly and GPCR coupling, converting the structural hypothesis into measured defects.\",\n      \"evidence\": \"BRET assays of Gβγ-Gα complex formation and D1R coupling across 10 missense variants\",\n      \"pmids\": [\"28087732\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not assess effector-channel regulation\", \"Negative variants (L30F, H91R, K337Q) lack mechanistic explanation\", \"Limited to single GPCR readout\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Linked GNB1 to oncogenic signaling by showing a somatic mutation activates PI3K/Akt/mTOR and MAPK independently of a driver fusion, conferring drug resistance.\",\n      \"evidence\": \"shRNA silencing of ETV6-ABL1 plus genomic/proteomic pathway profiling in leukemic cells\",\n      \"pmids\": [\"28650474\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab study\", \"Direct effector of K78M-driven pathway activation not defined\", \"No structural basis for gain-of-function established\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Confirmed haploinsufficiency as a disease mechanism by demonstrating that truncating and splice variants fail to dimerize with Gγ and cannot activate G proteins.\",\n      \"evidence\": \"RNA-seq plus orthogonal BRET and BiFC assays of dimer formation and GPCR-induced activation\",\n      \"pmids\": [\"32918542\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Downstream neuronal consequences not assessed\", \"No in vivo model\", \"Effector-level phenotype not measured\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Identified GIRK channels as the key effector axis and showed encephalopathy mutations produce subunit-specific gain- or loss-of-function while sparing Gi/o coupling and CaV2.2.\",\n      \"evidence\": \"Heterologous electrophysiology, Gβγ-GIRK binding assays, expression analysis, and computational modeling of K78R/I80N/I80T\",\n      \"pmids\": [\"34522861\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo relevance not yet established\", \"Mechanism of subunit selectivity incompletely defined\", \"Limited to three variants\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Defined the circuit-level basis of absence seizures, showing thalamocortical input regulates spike-wave discharges in Gnb1 mutant mice.\",\n      \"evidence\": \"In vivo recording with chemogenetic DREADD activation of thalamocortical neurons and EEG\",\n      \"pmids\": [\"36405774\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab study\", \"Molecular link between GNB1 variant and circuit activity not fully resolved\", \"Specific mutation context not detailed\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Validated GIRK hyperactivation as an in vivo seizure mechanism and demonstrated pharmacological rescue, providing therapeutic rationale.\",\n      \"evidence\": \"K78R knock-in mice, MEA recordings, in vivo EEG, Xenopus oocyte electrophysiology, and ethosuximide intervention\",\n      \"pmids\": [\"37275776\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Ethosuximide mechanism on GIRK GoF not fully defined\", \"Generalizability to loss-of-function variants unknown\", \"Long-term efficacy not addressed\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Extended GNB1 oncogenic signaling by identifying BAG2 as a physical partner driving P38/MAPK-dependent hepatocellular carcinoma progression.\",\n      \"evidence\": \"Co-IP/LC-MS, P38 inhibitor intervention, and xenograft tumor model\",\n      \"pmids\": [\"36718954\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab study\", \"Whether interaction is direct or complex-mediated unresolved\", \"No reciprocal structural validation\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Broadened the effector repertoire to voltage-gated sodium channels, showing Gβ1γ2 inhibits Nav1.1/Nav1.6 and K78R alters interneuron excitability and GABAergic transmission.\",\n      \"evidence\": \"Co-IP from mouse brain, heterologous electrophysiology, and cortical slice/dissociated interneuron recordings in Gnb1K78R/+ mice\",\n      \"pmids\": [\"40482731\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of Nav subtype selectivity unknown\", \"Relative contribution of Nav vs GIRK effects to seizures unresolved\", \"Direct binding interface not mapped\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Demonstrated a distinct loss-of-function mechanism for L95P via protein destabilization rather than direct effector-interface disruption.\",\n      \"evidence\": \"Xenopus oocyte expression with RNA co-injection, electrophysiology, rigid-body docking, and thermodynamic calculations\",\n      \"pmids\": [\"40417225\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single mutation, single lab\", \"Destabilization not confirmed by direct protein stability assays in vivo\", \"No structural data beyond modeling\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Revealed a non-neuronal metabolic role for GNB1 in adipocyte lipid storage and lipidome/proteome regulation.\",\n      \"evidence\": \"RNAi knockdown in human subcutaneous adipocytes with lipidomic and proteomic mass spectrometry\",\n      \"pmids\": [\"40127054\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No rescue experiments\", \"Single lab study\", \"Signaling pathway linking GNB1 to lipid metabolism not defined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the spectrum of mutation-specific GIRK and Nav effects integrates into a unified predictive model of GNB1 encephalopathy phenotypes, and how GPCR/Gα coupling defects translate to specific circuit outcomes, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No genotype-to-phenotype framework spanning gain- and loss-of-function variants\", \"Structural mechanism of effector subtype selectivity unmapped\", \"Relative weighting of GIRK, Nav, and GPCR-coupling contributions to seizures undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [1, 3, 11]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [4, 7, 8]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [1, 3]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [11]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [1, 2, 3, 6]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [4, 5, 7, 10]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [9]}\n    ],\n    \"complexes\": [\"Gβγ heterodimer\", \"heterotrimeric G protein\"],\n    \"partners\": [\"GNG1\", \"GNG2\", \"BAG2\", \"GIRK\", \"Nav1.1\", \"Nav1.6\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":7,"faith_pct":85.71428571428571}}