{"gene":"CACNB4","run_date":"2026-06-09T22:57:17","timeline":{"discoveries":[{"year":2000,"finding":"The truncated CACNB4 mutant R482X (lacking 38 C-terminal amino acids containing part of the alpha1 subunit interaction domain) showed a small decrease in the fast time constant for inactivation of the co-transfected alpha1 subunit when tested in Xenopus laevis oocytes, demonstrating that the C-terminus of β4 modulates channel inactivation kinetics.","method":"Electrophysiological recording in Xenopus oocyte heterologous expression system","journal":"American journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro functional assay in oocytes, single lab, single method, modest effect size","pmids":["10762541"],"is_preprint":false},{"year":1999,"finding":"Loss of the β4 subunit's binding site for α1 subunits in lethargic (Cacnb4-null) mice results in a selective reduction of glutamatergic (NMDA and non-NMDA) synaptic transmission in somatosensory thalamic neurons, with no significant change in GABAergic transmission, indicating that CACNB4-dependent P/Q-type channel function specifically supports glutamatergic neurotransmitter release.","method":"Whole-cell patch-clamp recordings in thalamic slice preparations from lethargic mice vs. controls","journal":"Journal of neurophysiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean loss-of-function mouse model with defined cellular phenotype, two receptor subtypes examined, replicated in parallel tottering model","pmids":["10322048"],"is_preprint":false},{"year":2008,"finding":"The CACNB4 missense mutation R468Q increased Ba2+ current density (Ca2+ current amplitude) through CaV2.1 channels compared to wild-type CACNB4, indicating that this variant gain-of-function enhances P/Q-type calcium channel activity.","method":"Electrophysiological recording in heterologous expression system (whole-cell patch clamp) with wild-type vs. R468Q-CACNB4","journal":"Neurobiology of disease","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro electrophysiology with mutant vs. WT comparison, single lab, single method","pmids":["18755274"],"is_preprint":false},{"year":2008,"finding":"In zebrafish, β4 protein (encoded by CACNB4) is required in the yolk syncytial layer for initiation of epiboly (the first morphogenetic movement), and this function is Ca2+-channel-independent: rescue was achieved with mutant β4 cRNA incapable of binding Ca2+ channel α1 subunits, revealing a novel cytoskeletal/MAGUK function of β4.","method":"Morpholino knockdown in zebrafish, rescue with human β4 cRNA and α1-binding-deficient β4 cRNA, nocodazole comparison","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — loss-of-function in vivo with specific morphogenetic phenotype, multiple rescue constructs including domain-specific mutant, replicated with pharmacological comparator","pmids":["18172207"],"is_preprint":false},{"year":2013,"finding":"Neuronal electrical stimulation triggers nuclear translocation of β4 (CACNB4) through its interaction with PPP2R5D (B56δ), a regulatory subunit of PP2A, forming a β4/PPP2R5D/PP2A complex; this nuclear translocation and complex formation are abolished by the epilepsy-associated R482X truncation mutation. Nuclear β4 regulates transcription of multiple genes including tyrosine hydroxylase.","method":"Co-immunoprecipitation, subcellular fractionation/imaging of nuclear translocation, gene expression analysis in HEK293 and NG108-15 cells, comparison of WT vs. R482X mutant","journal":"Channels (Austin, Tex.)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP and localization with functional (transcriptional) readout, single lab, multiple cell lines and methods","pmids":["23511121"],"is_preprint":false},{"year":2017,"finding":"Nuclear β4 (CACNB4) inhibits Wnt/β-catenin-responsive gene transcription by co-immunoprecipitating with TCF4 transcription factor; overexpression of TCF4 reverses this inhibition. Nuclear localization of β4 is required, as nuclear-targeting-deficient β4 mutants have no effect. β4 thus acts as a TCF4 repressor downstream of GSK3.","method":"Co-immunoprecipitation of β4 with TCF4, Wnt-reporter transcription assays, LiCl treatment (GSK3 inhibition), nuclear-targeting-deficient mutants in hepatoma cell line","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus functional reporter assay plus domain-deletion mutants, single lab","pmids":["29021340"],"is_preprint":false},{"year":2017,"finding":"Full-length β4 (CACNB4) localizes to the cell nucleus and nucleolus in CHO-K1 cells and reduces cell proliferation by arresting cells at the G1/S transition, whereas the C-terminally truncated epileptic mutant β1-481 is excluded from nucleoli and fails to reduce proliferation. This nuclear cell-cycle function partially involves binding to PPP2R5D (B56δ), which β1-481 cannot bind.","method":"Stable transfection of CHO-K1 cells with full-length vs. truncated β4, fluorescence imaging of subcellular localization, flow cytometry cell-cycle analysis, Co-IP with B56δ","journal":"The international journal of biochemistry & cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss/gain-of-function in stable cell line with defined cell-cycle phenotype and Co-IP, single lab, multiple orthogonal methods","pmids":["28587927"],"is_preprint":false},{"year":2020,"finding":"The β4b-L125P mutation (corresponding to human p.Leu126Pro) disrupts stable association of β4b with native CaV2.1 calcium channel complexes in hippocampal neurons (fails to cluster presynaptically) and abolishes nuclear targeting of β4b in myotubes and neurons, while complex formation with TNIK (neuronal TRAF2- and NCK-interacting kinase) is also disturbed; however, interaction with PPP2R5D (B56δ) is unaffected by this mutation. Current density augmentation by heterologously expressed β4b-L125P in tsA201 cells is preserved despite failed stable α1 complex formation.","method":"Heterologous expression in tsA201 cells and hippocampal neurons, Co-immunoprecipitation, fluorescence imaging of presynaptic clustering and nuclear localization, whole-cell patch clamp, Co-IP with PPP2R5D and TNIK","journal":"PLoS genetics","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — multiple orthogonal methods (electrophysiology, Co-IP, live/fixed imaging in multiple cell types) with mutagenesis, single rigorous study","pmids":["32176688"],"is_preprint":false},{"year":2024,"finding":"Overexpression of CACNB4 selectively reduces small-spine density in female mouse cortex in vivo. The β4 interactome showed sex differences: β1b VGCC subunit was significantly enriched in the β4 interactome of male mice relative to female mice, suggesting that β1b interaction may mitigate β4-driven small-spine loss in males.","method":"In vivo CACNB4 overexpression in early mouse development, spine morphology analysis in adult cortex, co-immunoprecipitation/interactome profiling comparing male and female β4 complexes","journal":"Translational psychiatry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo overexpression with morphological phenotype and interactome Co-IP, single lab, sex-stratified analysis","pmids":["39632796"],"is_preprint":false},{"year":2025,"finding":"CACNB4 interacts with RyR2 (ryanodine receptor 2) in cardiomyocytes; overexpression of CACNB4 in hypoxic/heart-failure conditions enhances intracellular Ca2+ and ATP levels and improves cardiac function, implicating CACNB4-RyR2 interaction in regulation of cardiac calcium handling.","method":"Co-immunoprecipitation of CACNB4 with RyR2, Western blot, CACNB4 overexpression in hypoxic myocardial cells and heart failure mice with Ca2+/ATP measurements and cardiac function readouts","journal":"European journal of medical research","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single Co-IP plus overexpression phenotype, single lab, limited mechanistic detail in abstract","pmids":["41194296"],"is_preprint":false}],"current_model":"CACNB4 encodes the β4 auxiliary subunit of voltage-gated calcium channels (principally CaV2.1/P/Q-type), where it modulates channel inactivation kinetics, promotes α1 subunit membrane trafficking, and supports glutamatergic neurotransmitter release; beyond its channel role, β4 undergoes activity-dependent nuclear translocation via a complex with PPP2R5D/PP2A, where it regulates gene transcription by acting as a TCF4 repressor to inhibit Wnt/β-catenin signaling, suppresses cell proliferation by arresting the G1/S transition, and controls dendritic small-spine density, while a Ca2+-channel-independent cytoskeletal function (as a MAGUK protein) drives epiboly in zebrafish—with epilepsy-associated truncation and missense mutations disrupting these nuclear/non-channel functions."},"narrative":{"mechanistic_narrative":"CACNB4 encodes the β4 auxiliary subunit of voltage-gated calcium channels, which modulates the inactivation kinetics of co-assembled α1 subunits and supports calcium-dependent neurotransmission [PMID:10762541, PMID:10322048]. Loss of the β4–α1 interaction in Cacnb4-null (lethargic) mice selectively reduces glutamatergic synaptic transmission in thalamic neurons without affecting GABAergic transmission, establishing that β4-dependent P/Q-type (CaV2.1) channel function specifically supports excitatory neurotransmitter release [PMID:10322048]. Disease-associated variants alter channel behavior in divergent ways: the C-terminal truncation R482X subtly reduces fast inactivation [PMID:10762541], whereas the missense variant R468Q acts as a gain-of-function that increases current density through CaV2.1 [PMID:18755274]. Beyond its channel role, β4 has a calcium-channel-independent function: in zebrafish it is required in the yolk syncytial layer for epiboly, a role rescued by an α1-binding-deficient β4, revealing a cytoskeletal/MAGUK activity [PMID:18172207]. β4 also undergoes activity-dependent nuclear translocation via a complex with the PP2A regulatory subunit PPP2R5D (B56δ), entering the nucleus and nucleolus where it regulates transcription, including tyrosine hydroxylase [PMID:23511121, PMID:28587927]. In the nucleus β4 represses Wnt/β-catenin-responsive transcription by binding TCF4 downstream of GSK3 [PMID:29021340] and arrests proliferation at the G1/S transition [PMID:28587927]; the epilepsy-associated truncation, which is excluded from nucleoli and cannot bind B56δ, abolishes these nuclear functions [PMID:23511121, PMID:28587927]. The disease variant L125P/L126P disrupts stable assembly into native CaV2.1 complexes and nuclear targeting and perturbs association with the kinase TNIK while sparing PPP2R5D binding and current augmentation, dissociating β4's trafficking/nuclear roles from its current-enhancing activity [PMID:32176688]. β4 overexpression reduces cortical small-spine density in a sex-dependent manner correlated with differential β1b interaction [PMID:39632796].","teleology":[{"year":1999,"claim":"Establishing what β4-dependent channel activity does at synapses, the lethargic null showed β4 selectively supports excitatory but not inhibitory transmission, linking the subunit to glutamatergic release.","evidence":"Whole-cell patch clamp in thalamic slices from Cacnb4-null (lethargic) mice vs. controls","pmids":["10322048"],"confidence":"Medium","gaps":["Does not resolve whether the synaptic deficit is presynaptic release vs. postsynaptic receptor function","Mechanism of glutamatergic selectivity not defined"]},{"year":2000,"claim":"Addressing how the β4 C-terminus contributes to channel gating, a truncation removing part of the α1-interaction domain modestly altered inactivation, mapping a regulatory role to the C-terminus.","evidence":"Electrophysiology of R482X mutant co-transfected with α1 in Xenopus oocytes","pmids":["10762541"],"confidence":"Medium","gaps":["Small effect size in a heterologous system","Does not address non-channel consequences of the truncation"]},{"year":2008,"claim":"To understand how an epilepsy-associated missense variant affects channel function, R468Q was shown to increase current density, defining a gain-of-function mode distinct from truncation.","evidence":"Whole-cell patch clamp of CaV2.1 with WT vs. R468Q-CACNB4 in heterologous cells","pmids":["18755274"],"confidence":"Medium","gaps":["Single lab/single method","In vivo consequences of the gain-of-function not established"]},{"year":2008,"claim":"Testing whether β4 has functions independent of calcium channels, zebrafish epiboly required β4 in a manner rescued by an α1-binding-deficient mutant, revealing a cytoskeletal/MAGUK role.","evidence":"Morpholino knockdown with WT and α1-binding-deficient β4 cRNA rescue and nocodazole comparison in zebrafish","pmids":["18172207"],"confidence":"High","gaps":["Molecular partners of the cytoskeletal function not identified","Whether this role operates in mammalian tissues unknown"]},{"year":2013,"claim":"To explain how β4 reaches the nucleus, activity-dependent translocation was shown to require a β4/PPP2R5D/PP2A complex abolished by the R482X truncation, connecting a channel subunit to transcriptional control.","evidence":"Co-IP, subcellular fractionation/imaging, and gene expression in HEK293 and NG108-15 cells comparing WT vs. R482X","pmids":["23511121"],"confidence":"Medium","gaps":["Direct transcriptional targets beyond tyrosine hydroxylase not mapped","Signaling cascade linking electrical activity to translocation not resolved"]},{"year":2017,"claim":"Defining the nuclear transcriptional mechanism, β4 was shown to bind TCF4 and repress Wnt/β-catenin-responsive transcription downstream of GSK3, requiring nuclear localization.","evidence":"Co-IP with TCF4, Wnt-reporter assays, LiCl treatment, and nuclear-targeting-deficient mutants in hepatoma cells","pmids":["29021340"],"confidence":"Medium","gaps":["Whether β4 directly contacts promoter DNA or acts only via TCF4 unclear","Physiological neuronal relevance of Wnt repression not tested"]},{"year":2017,"claim":"Linking nuclear β4 to cell-cycle control, full-length β4 localized to nucleus/nucleolus and arrested cells at G1/S, while the truncated epilepsy mutant was nucleolus-excluded and failed to bind B56δ, tying the phenotype to nuclear targeting.","evidence":"Stable CHO-K1 transfection with full-length vs. truncated β4, imaging, flow cytometry, and Co-IP with B56δ","pmids":["28587927"],"confidence":"Medium","gaps":["Nucleolar molecular targets unknown","Mechanism of G1/S arrest not defined"]},{"year":2020,"claim":"Dissecting how a missense mutation separates β4's functions, L125P disrupted stable CaV2.1 assembly, presynaptic clustering, nuclear targeting, and TNIK association while sparing PPP2R5D binding and current augmentation.","evidence":"Heterologous expression, Co-IP (PPP2R5D, TNIK), imaging in tsA201 cells/hippocampal neurons/myotubes, and patch clamp with mutagenesis","pmids":["32176688"],"confidence":"High","gaps":["Functional consequence of disrupted TNIK interaction not established","How current augmentation persists without stable complex formation unexplained"]},{"year":2024,"claim":"Probing β4's role in neuronal morphology, overexpression reduced cortical small-spine density in a sex-dependent manner correlated with differential β1b enrichment in the β4 interactome.","evidence":"In vivo CACNB4 overexpression with cortical spine analysis and sex-stratified interactome Co-IP in mice","pmids":["39632796"],"confidence":"Medium","gaps":["Causal role of β1b in mitigating spine loss not directly tested","Mechanism linking β4 to spine morphology unknown"]},{"year":2025,"claim":"Extending β4 beyond neurons, an interaction with RyR2 in cardiomyocytes was reported, with overexpression improving Ca2+/ATP and cardiac function under stress.","evidence":"Co-IP of CACNB4 with RyR2 and overexpression in hypoxic cells and heart-failure mice with functional readouts","pmids":["41194296"],"confidence":"Low","gaps":["Single Co-IP without reciprocal validation or structural mapping","Whether the effect is direct or secondary to altered calcium handling unresolved"]},{"year":null,"claim":"How β4's calcium-channel, cytoskeletal/MAGUK, and nuclear transcriptional activities are coordinated within a single neuron, and how each contributes to epilepsy pathogenesis, remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model integrating channel vs. nuclear functions","Direct genomic targets of nuclear β4 in neurons unmapped","Structural basis for partner selectivity (α1, PPP2R5D, TCF4, TNIK) undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,1,2]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[4,5]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[4,7]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[4,6]},{"term_id":"GO:0005730","term_label":"nucleolus","supporting_discovery_ids":[6]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[1,7]}],"pathway":[{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[1,7]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[4,5]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[5]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[6]}],"complexes":["CaV2.1 (P/Q-type) voltage-gated calcium channel","β4/PPP2R5D/PP2A complex"],"partners":["PPP2R5D","TCF4","TNIK","RYR2","CACNB1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O00305","full_name":"Voltage-dependent L-type calcium channel subunit beta-4","aliases":["Calcium channel voltage-dependent subunit beta 4"],"length_aa":520,"mass_kda":58.2,"function":"The beta subunit of voltage-dependent calcium channels contributes to the function of the calcium channel by increasing peak calcium current, shifting the voltage dependencies of activation and inactivation, modulating G protein inhibition and controlling the alpha-1 subunit membrane targeting","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/O00305/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CACNB4","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/CACNB4","total_profiled":1310},"omim":[{"mim_id":"619817","title":"EPIDERMOLYSIS BULLOSA, JUNCTIONAL 6, WITH PYLORIC ATRESIA; JEB6","url":"https://www.omim.org/entry/619817"},{"mim_id":"618501","title":"CEREBELLAR ATROPHY WITH SEIZURES AND VARIABLE DEVELOPMENTAL DELAY; CASVDD","url":"https://www.omim.org/entry/618501"},{"mim_id":"613855","title":"EPISODIC ATAXIA, TYPE 5; EA5","url":"https://www.omim.org/entry/613855"},{"mim_id":"607682","title":"EPILEPSY, IDIOPATHIC GENERALIZED, SUSCEPTIBILITY TO, 9; EIG9","url":"https://www.omim.org/entry/607682"},{"mim_id":"607082","title":"CALCIUM CHANNEL, VOLTAGE-DEPENDENT, ALPHA-2/DELTA SUBUNIT 2; CACNA2D2","url":"https://www.omim.org/entry/607082"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Group enriched","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"brain","ntpm":24.9},{"tissue":"skin 1","ntpm":6.9}],"url":"https://www.proteinatlas.org/search/CACNB4"},"hgnc":{"alias_symbol":["EJM4"],"prev_symbol":[]},"alphafold":{"accession":"O00305","domains":[{"cath_id":"2.30.30.40","chopping":"67-167","consensus_level":"high","plddt":94.0458,"start":67,"end":167},{"cath_id":"3.40.50.300","chopping":"219-401","consensus_level":"high","plddt":92.8855,"start":219,"end":401}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O00305","model_url":"https://alphafold.ebi.ac.uk/files/AF-O00305-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O00305-F1-predicted_aligned_error_v6.png","plddt_mean":71.81},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CACNB4","jax_strain_url":"https://www.jax.org/strain/search?query=CACNB4"},"sequence":{"accession":"O00305","fasta_url":"https://rest.uniprot.org/uniprotkb/O00305.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O00305/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O00305"}},"corpus_meta":[{"pmid":"10762541","id":"PMC_10762541","title":"Coding and noncoding variation of the human calcium-channel beta4-subunit gene CACNB4 in patients with idiopathic generalized epilepsy and episodic ataxia.","date":"2000","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/10762541","citation_count":299,"is_preprint":false},{"pmid":"10322048","id":"PMC_10322048","title":"Excitatory but not inhibitory synaptic transmission is reduced in lethargic (Cacnb4(lh)) and tottering (Cacna1atg) mouse thalami.","date":"1999","source":"Journal of neurophysiology","url":"https://pubmed.ncbi.nlm.nih.gov/10322048","citation_count":96,"is_preprint":false},{"pmid":"16866717","id":"PMC_16866717","title":"Migrainous vertigo: mutation analysis of the candidate genes CACNA1A, ATP1A2, SCN1A, and CACNB4.","date":"2006","source":"Headache","url":"https://pubmed.ncbi.nlm.nih.gov/16866717","citation_count":58,"is_preprint":false},{"pmid":"18755274","id":"PMC_18755274","title":"A CACNB4 mutation shows that altered Ca(v)2.1 function may be a genetic modifier of severe myoclonic epilepsy in infancy.","date":"2008","source":"Neurobiology of disease","url":"https://pubmed.ncbi.nlm.nih.gov/18755274","citation_count":46,"is_preprint":false},{"pmid":"32176688","id":"PMC_32176688","title":"A homozygous missense variant in CACNB4 encoding the auxiliary calcium channel beta4 subunit causes a severe neurodevelopmental disorder and impairs channel and non-channel functions.","date":"2020","source":"PLoS genetics","url":"https://pubmed.ncbi.nlm.nih.gov/32176688","citation_count":28,"is_preprint":false},{"pmid":"23511121","id":"PMC_23511121","title":"Nuclear life of the voltage-gated Cacnb4 subunit and its role in gene transcription regulation.","date":"2013","source":"Channels (Austin, Tex.)","url":"https://pubmed.ncbi.nlm.nih.gov/23511121","citation_count":28,"is_preprint":false},{"pmid":"18172207","id":"PMC_18172207","title":"Ca2+ channel-independent requirement for MAGUK family CACNB4 genes in initiation of zebrafish epiboly.","date":"2008","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/18172207","citation_count":27,"is_preprint":false},{"pmid":"9628818","id":"PMC_9628818","title":"Calcium channel beta 4 (CACNB4): human ortholog of the mouse epilepsy gene lethargic.","date":"1998","source":"Genomics","url":"https://pubmed.ncbi.nlm.nih.gov/9628818","citation_count":26,"is_preprint":false},{"pmid":"29021340","id":"PMC_29021340","title":"Down-regulation of the Wnt/β-catenin signaling pathway by Cacnb4.","date":"2017","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/29021340","citation_count":19,"is_preprint":false},{"pmid":"28587927","id":"PMC_28587927","title":"The β4 subunit of the voltage-gated calcium channel (Cacnb4) regulates the rate of cell proliferation in Chinese Hamster Ovary cells.","date":"2017","source":"The international journal of biochemistry & cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/28587927","citation_count":14,"is_preprint":false},{"pmid":"35813387","id":"PMC_35813387","title":"Whole-Exome Sequencing Identifies Novel SCN1A and CACNB4 Genes Mutations in the Cohort of Saudi Patients With Epilepsy.","date":"2022","source":"Frontiers in pediatrics","url":"https://pubmed.ncbi.nlm.nih.gov/35813387","citation_count":6,"is_preprint":false},{"pmid":"17868079","id":"PMC_17868079","title":"Analysis and mapping of CACNB4, CHRNA1, KCNJ3, SCN2A and SPG4, physiological candidate genes for porcine congenital progressive ataxia and spastic paresis.","date":"2007","source":"Journal of animal breeding and genetics = Zeitschrift fur Tierzuchtung und Zuchtungsbiologie","url":"https://pubmed.ncbi.nlm.nih.gov/17868079","citation_count":5,"is_preprint":false},{"pmid":"39632796","id":"PMC_39632796","title":"Impacts of CACNB4 overexpression on dendritic spine density in both sexes and relevance to schizophrenia.","date":"2024","source":"Translational psychiatry","url":"https://pubmed.ncbi.nlm.nih.gov/39632796","citation_count":4,"is_preprint":false},{"pmid":"41498379","id":"PMC_41498379","title":"Integrative Human Genomic and Pharmacological Analyses Identify CACNB4 as a Druggable Target for Periodontitis.","date":"2026","source":"Journal of periodontal research","url":"https://pubmed.ncbi.nlm.nih.gov/41498379","citation_count":0,"is_preprint":false},{"pmid":"41194296","id":"PMC_41194296","title":"CACNB4 attenuates cardiac dysfunction by regulating calcium and ATP levels via interaction with RyR2.","date":"2025","source":"European journal of medical research","url":"https://pubmed.ncbi.nlm.nih.gov/41194296","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.05.17.654645","title":"Integrated transcriptomic analyses identifies host-targeting repurposing drugs for hepatitis C virus infection and related hepatocellular carcinoma","date":"2025-05-23","source":"bioRxiv","url":"https://doi.org/10.1101/2025.05.17.654645","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":10524,"output_tokens":2847,"usd":0.037138,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":10268,"output_tokens":3850,"usd":0.073795,"stage2_stop_reason":"end_turn"},"total_usd":0.110933,"stage1_batch_id":"msgbatch_01ACAxJQabDsht39JXeWG22d","stage2_batch_id":"msgbatch_01QEU22A9U5sbPTgsMzTmvSf","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2000,\n      \"finding\": \"The truncated CACNB4 mutant R482X (lacking 38 C-terminal amino acids containing part of the alpha1 subunit interaction domain) showed a small decrease in the fast time constant for inactivation of the co-transfected alpha1 subunit when tested in Xenopus laevis oocytes, demonstrating that the C-terminus of β4 modulates channel inactivation kinetics.\",\n      \"method\": \"Electrophysiological recording in Xenopus oocyte heterologous expression system\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro functional assay in oocytes, single lab, single method, modest effect size\",\n      \"pmids\": [\"10762541\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Loss of the β4 subunit's binding site for α1 subunits in lethargic (Cacnb4-null) mice results in a selective reduction of glutamatergic (NMDA and non-NMDA) synaptic transmission in somatosensory thalamic neurons, with no significant change in GABAergic transmission, indicating that CACNB4-dependent P/Q-type channel function specifically supports glutamatergic neurotransmitter release.\",\n      \"method\": \"Whole-cell patch-clamp recordings in thalamic slice preparations from lethargic mice vs. controls\",\n      \"journal\": \"Journal of neurophysiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean loss-of-function mouse model with defined cellular phenotype, two receptor subtypes examined, replicated in parallel tottering model\",\n      \"pmids\": [\"10322048\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"The CACNB4 missense mutation R468Q increased Ba2+ current density (Ca2+ current amplitude) through CaV2.1 channels compared to wild-type CACNB4, indicating that this variant gain-of-function enhances P/Q-type calcium channel activity.\",\n      \"method\": \"Electrophysiological recording in heterologous expression system (whole-cell patch clamp) with wild-type vs. R468Q-CACNB4\",\n      \"journal\": \"Neurobiology of disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro electrophysiology with mutant vs. WT comparison, single lab, single method\",\n      \"pmids\": [\"18755274\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"In zebrafish, β4 protein (encoded by CACNB4) is required in the yolk syncytial layer for initiation of epiboly (the first morphogenetic movement), and this function is Ca2+-channel-independent: rescue was achieved with mutant β4 cRNA incapable of binding Ca2+ channel α1 subunits, revealing a novel cytoskeletal/MAGUK function of β4.\",\n      \"method\": \"Morpholino knockdown in zebrafish, rescue with human β4 cRNA and α1-binding-deficient β4 cRNA, nocodazole comparison\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — loss-of-function in vivo with specific morphogenetic phenotype, multiple rescue constructs including domain-specific mutant, replicated with pharmacological comparator\",\n      \"pmids\": [\"18172207\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Neuronal electrical stimulation triggers nuclear translocation of β4 (CACNB4) through its interaction with PPP2R5D (B56δ), a regulatory subunit of PP2A, forming a β4/PPP2R5D/PP2A complex; this nuclear translocation and complex formation are abolished by the epilepsy-associated R482X truncation mutation. Nuclear β4 regulates transcription of multiple genes including tyrosine hydroxylase.\",\n      \"method\": \"Co-immunoprecipitation, subcellular fractionation/imaging of nuclear translocation, gene expression analysis in HEK293 and NG108-15 cells, comparison of WT vs. R482X mutant\",\n      \"journal\": \"Channels (Austin, Tex.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP and localization with functional (transcriptional) readout, single lab, multiple cell lines and methods\",\n      \"pmids\": [\"23511121\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Nuclear β4 (CACNB4) inhibits Wnt/β-catenin-responsive gene transcription by co-immunoprecipitating with TCF4 transcription factor; overexpression of TCF4 reverses this inhibition. Nuclear localization of β4 is required, as nuclear-targeting-deficient β4 mutants have no effect. β4 thus acts as a TCF4 repressor downstream of GSK3.\",\n      \"method\": \"Co-immunoprecipitation of β4 with TCF4, Wnt-reporter transcription assays, LiCl treatment (GSK3 inhibition), nuclear-targeting-deficient mutants in hepatoma cell line\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus functional reporter assay plus domain-deletion mutants, single lab\",\n      \"pmids\": [\"29021340\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Full-length β4 (CACNB4) localizes to the cell nucleus and nucleolus in CHO-K1 cells and reduces cell proliferation by arresting cells at the G1/S transition, whereas the C-terminally truncated epileptic mutant β1-481 is excluded from nucleoli and fails to reduce proliferation. This nuclear cell-cycle function partially involves binding to PPP2R5D (B56δ), which β1-481 cannot bind.\",\n      \"method\": \"Stable transfection of CHO-K1 cells with full-length vs. truncated β4, fluorescence imaging of subcellular localization, flow cytometry cell-cycle analysis, Co-IP with B56δ\",\n      \"journal\": \"The international journal of biochemistry & cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss/gain-of-function in stable cell line with defined cell-cycle phenotype and Co-IP, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"28587927\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"The β4b-L125P mutation (corresponding to human p.Leu126Pro) disrupts stable association of β4b with native CaV2.1 calcium channel complexes in hippocampal neurons (fails to cluster presynaptically) and abolishes nuclear targeting of β4b in myotubes and neurons, while complex formation with TNIK (neuronal TRAF2- and NCK-interacting kinase) is also disturbed; however, interaction with PPP2R5D (B56δ) is unaffected by this mutation. Current density augmentation by heterologously expressed β4b-L125P in tsA201 cells is preserved despite failed stable α1 complex formation.\",\n      \"method\": \"Heterologous expression in tsA201 cells and hippocampal neurons, Co-immunoprecipitation, fluorescence imaging of presynaptic clustering and nuclear localization, whole-cell patch clamp, Co-IP with PPP2R5D and TNIK\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — multiple orthogonal methods (electrophysiology, Co-IP, live/fixed imaging in multiple cell types) with mutagenesis, single rigorous study\",\n      \"pmids\": [\"32176688\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Overexpression of CACNB4 selectively reduces small-spine density in female mouse cortex in vivo. The β4 interactome showed sex differences: β1b VGCC subunit was significantly enriched in the β4 interactome of male mice relative to female mice, suggesting that β1b interaction may mitigate β4-driven small-spine loss in males.\",\n      \"method\": \"In vivo CACNB4 overexpression in early mouse development, spine morphology analysis in adult cortex, co-immunoprecipitation/interactome profiling comparing male and female β4 complexes\",\n      \"journal\": \"Translational psychiatry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo overexpression with morphological phenotype and interactome Co-IP, single lab, sex-stratified analysis\",\n      \"pmids\": [\"39632796\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"CACNB4 interacts with RyR2 (ryanodine receptor 2) in cardiomyocytes; overexpression of CACNB4 in hypoxic/heart-failure conditions enhances intracellular Ca2+ and ATP levels and improves cardiac function, implicating CACNB4-RyR2 interaction in regulation of cardiac calcium handling.\",\n      \"method\": \"Co-immunoprecipitation of CACNB4 with RyR2, Western blot, CACNB4 overexpression in hypoxic myocardial cells and heart failure mice with Ca2+/ATP measurements and cardiac function readouts\",\n      \"journal\": \"European journal of medical research\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single Co-IP plus overexpression phenotype, single lab, limited mechanistic detail in abstract\",\n      \"pmids\": [\"41194296\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CACNB4 encodes the β4 auxiliary subunit of voltage-gated calcium channels (principally CaV2.1/P/Q-type), where it modulates channel inactivation kinetics, promotes α1 subunit membrane trafficking, and supports glutamatergic neurotransmitter release; beyond its channel role, β4 undergoes activity-dependent nuclear translocation via a complex with PPP2R5D/PP2A, where it regulates gene transcription by acting as a TCF4 repressor to inhibit Wnt/β-catenin signaling, suppresses cell proliferation by arresting the G1/S transition, and controls dendritic small-spine density, while a Ca2+-channel-independent cytoskeletal function (as a MAGUK protein) drives epiboly in zebrafish—with epilepsy-associated truncation and missense mutations disrupting these nuclear/non-channel functions.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"CACNB4 encodes the β4 auxiliary subunit of voltage-gated calcium channels, which modulates the inactivation kinetics of co-assembled α1 subunits and supports calcium-dependent neurotransmission [#0, #1]. Loss of the β4–α1 interaction in Cacnb4-null (lethargic) mice selectively reduces glutamatergic synaptic transmission in thalamic neurons without affecting GABAergic transmission, establishing that β4-dependent P/Q-type (CaV2.1) channel function specifically supports excitatory neurotransmitter release [#1]. Disease-associated variants alter channel behavior in divergent ways: the C-terminal truncation R482X subtly reduces fast inactivation [#0], whereas the missense variant R468Q acts as a gain-of-function that increases current density through CaV2.1 [#2]. Beyond its channel role, β4 has a calcium-channel-independent function: in zebrafish it is required in the yolk syncytial layer for epiboly, a role rescued by an α1-binding-deficient β4, revealing a cytoskeletal/MAGUK activity [#3]. β4 also undergoes activity-dependent nuclear translocation via a complex with the PP2A regulatory subunit PPP2R5D (B56δ), entering the nucleus and nucleolus where it regulates transcription, including tyrosine hydroxylase [#4, #6]. In the nucleus β4 represses Wnt/β-catenin-responsive transcription by binding TCF4 downstream of GSK3 [#5] and arrests proliferation at the G1/S transition [#6]; the epilepsy-associated truncation, which is excluded from nucleoli and cannot bind B56δ, abolishes these nuclear functions [#4, #6]. The disease variant L125P/L126P disrupts stable assembly into native CaV2.1 complexes and nuclear targeting and perturbs association with the kinase TNIK while sparing PPP2R5D binding and current augmentation, dissociating β4's trafficking/nuclear roles from its current-enhancing activity [#7]. β4 overexpression reduces cortical small-spine density in a sex-dependent manner correlated with differential β1b interaction [#8].\",\n  \"teleology\": [\n    {\n      \"year\": 1999,\n      \"claim\": \"Establishing what β4-dependent channel activity does at synapses, the lethargic null showed β4 selectively supports excitatory but not inhibitory transmission, linking the subunit to glutamatergic release.\",\n      \"evidence\": \"Whole-cell patch clamp in thalamic slices from Cacnb4-null (lethargic) mice vs. controls\",\n      \"pmids\": [\"10322048\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Does not resolve whether the synaptic deficit is presynaptic release vs. postsynaptic receptor function\", \"Mechanism of glutamatergic selectivity not defined\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Addressing how the β4 C-terminus contributes to channel gating, a truncation removing part of the α1-interaction domain modestly altered inactivation, mapping a regulatory role to the C-terminus.\",\n      \"evidence\": \"Electrophysiology of R482X mutant co-transfected with α1 in Xenopus oocytes\",\n      \"pmids\": [\"10762541\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Small effect size in a heterologous system\", \"Does not address non-channel consequences of the truncation\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"To understand how an epilepsy-associated missense variant affects channel function, R468Q was shown to increase current density, defining a gain-of-function mode distinct from truncation.\",\n      \"evidence\": \"Whole-cell patch clamp of CaV2.1 with WT vs. R468Q-CACNB4 in heterologous cells\",\n      \"pmids\": [\"18755274\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab/single method\", \"In vivo consequences of the gain-of-function not established\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Testing whether β4 has functions independent of calcium channels, zebrafish epiboly required β4 in a manner rescued by an α1-binding-deficient mutant, revealing a cytoskeletal/MAGUK role.\",\n      \"evidence\": \"Morpholino knockdown with WT and α1-binding-deficient β4 cRNA rescue and nocodazole comparison in zebrafish\",\n      \"pmids\": [\"18172207\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular partners of the cytoskeletal function not identified\", \"Whether this role operates in mammalian tissues unknown\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"To explain how β4 reaches the nucleus, activity-dependent translocation was shown to require a β4/PPP2R5D/PP2A complex abolished by the R482X truncation, connecting a channel subunit to transcriptional control.\",\n      \"evidence\": \"Co-IP, subcellular fractionation/imaging, and gene expression in HEK293 and NG108-15 cells comparing WT vs. R482X\",\n      \"pmids\": [\"23511121\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct transcriptional targets beyond tyrosine hydroxylase not mapped\", \"Signaling cascade linking electrical activity to translocation not resolved\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Defining the nuclear transcriptional mechanism, β4 was shown to bind TCF4 and repress Wnt/β-catenin-responsive transcription downstream of GSK3, requiring nuclear localization.\",\n      \"evidence\": \"Co-IP with TCF4, Wnt-reporter assays, LiCl treatment, and nuclear-targeting-deficient mutants in hepatoma cells\",\n      \"pmids\": [\"29021340\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether β4 directly contacts promoter DNA or acts only via TCF4 unclear\", \"Physiological neuronal relevance of Wnt repression not tested\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Linking nuclear β4 to cell-cycle control, full-length β4 localized to nucleus/nucleolus and arrested cells at G1/S, while the truncated epilepsy mutant was nucleolus-excluded and failed to bind B56δ, tying the phenotype to nuclear targeting.\",\n      \"evidence\": \"Stable CHO-K1 transfection with full-length vs. truncated β4, imaging, flow cytometry, and Co-IP with B56δ\",\n      \"pmids\": [\"28587927\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Nucleolar molecular targets unknown\", \"Mechanism of G1/S arrest not defined\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Dissecting how a missense mutation separates β4's functions, L125P disrupted stable CaV2.1 assembly, presynaptic clustering, nuclear targeting, and TNIK association while sparing PPP2R5D binding and current augmentation.\",\n      \"evidence\": \"Heterologous expression, Co-IP (PPP2R5D, TNIK), imaging in tsA201 cells/hippocampal neurons/myotubes, and patch clamp with mutagenesis\",\n      \"pmids\": [\"32176688\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of disrupted TNIK interaction not established\", \"How current augmentation persists without stable complex formation unexplained\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Probing β4's role in neuronal morphology, overexpression reduced cortical small-spine density in a sex-dependent manner correlated with differential β1b enrichment in the β4 interactome.\",\n      \"evidence\": \"In vivo CACNB4 overexpression with cortical spine analysis and sex-stratified interactome Co-IP in mice\",\n      \"pmids\": [\"39632796\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Causal role of β1b in mitigating spine loss not directly tested\", \"Mechanism linking β4 to spine morphology unknown\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Extending β4 beyond neurons, an interaction with RyR2 in cardiomyocytes was reported, with overexpression improving Ca2+/ATP and cardiac function under stress.\",\n      \"evidence\": \"Co-IP of CACNB4 with RyR2 and overexpression in hypoxic cells and heart-failure mice with functional readouts\",\n      \"pmids\": [\"41194296\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Single Co-IP without reciprocal validation or structural mapping\", \"Whether the effect is direct or secondary to altered calcium handling unresolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How β4's calcium-channel, cytoskeletal/MAGUK, and nuclear transcriptional activities are coordinated within a single neuron, and how each contributes to epilepsy pathogenesis, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified model integrating channel vs. nuclear functions\", \"Direct genomic targets of nuclear β4 in neurons unmapped\", \"Structural basis for partner selectivity (α1, PPP2R5D, TCF4, TNIK) undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 1, 2]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [4, 5]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [4, 7]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [4, 6]},\n      {\"term_id\": \"GO:0005730\", \"supporting_discovery_ids\": [6]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [1, 7]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0112316\", \"supporting_discovery_ids\": []},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [1, 7]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [4, 5]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [5]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [6]}\n    ],\n    \"complexes\": [\"CaV2.1 (P/Q-type) voltage-gated calcium channel\", \"β4/PPP2R5D/PP2A complex\"],\n    \"partners\": [\"PPP2R5D\", \"TCF4\", \"TNIK\", \"RYR2\", \"CACNB1\"],\n    \"other_free_text\": []\n  }\n}\n```","audit_flag":null,"evaluation":{"pairwise":"tie","faith_supported":6,"faith_total":6,"faith_pct":100.0}}