Affinage

SPTBN4

Spectrin beta chain, non-erythrocytic 4 · UniProt Q9H254

Round 2 corrected
Length
2564 aa
Mass
289.0 kDa
Annotated
2026-04-28
56 papers in source corpus 12 papers cited in narrative 12 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

SPTBN4 encodes βIV spectrin, a cytoskeletal scaffolding protein that anchors voltage-gated ion channels at axon initial segments, nodes of Ranvier, and auditory brainstem heminodes through a mutually stabilizing interaction with ankyrinG (PMID:11086001, PMID:11807096, PMID:35393465). Loss of βIV spectrin disrupts clustering of Nav channels and KCNQ2/3 K+ channels at nodes, elevates action potential threshold, and impairs high-frequency conduction; partial compensation by ankyrinR/βI spectrin rescues some Nav clustering but not KCNQ channel organization (PMID:29861105, PMID:35393465). Bi-allelic pathogenic SPTBN4 variants cause congenital hypotonia, intellectual disability, motor axonal neuropathy, and auditory neuropathy in humans, and the associated myopathy is neurogenic rather than muscle-autonomous (PMID:29861105, PMID:28540413, PMID:38441922). In cardiomyocytes, SPTBN4 is transcriptionally repressed by Tbx5 and modulates the late Na+ current; a truncated nuclear isoform (βIVΣ5) localizes to PML bodies, and βIV spectrin is a substrate of GSK3 phosphorylation with altered levels in schizophrenia neurons (PMID:33576403, PMID:11294830, PMID:39920295).

Mechanistic history

Synthesis pass · year-by-year structured walk · 10 steps
  1. 2000 High

    Identification of βIV spectrin as a novel spectrin enriched at AIS and nodes of Ranvier established it as a candidate scaffold for ion channel clustering at excitable membrane domains.

    Evidence cDNA cloning, Northern blot, immunofluorescence/confocal co-localization with ankyrinG in rat neurons

    PMID:11086001

    Open questions at the time
    • Direct binding to ankyrinG not biochemically demonstrated in this study
    • Functional consequences of loss not tested
  2. 2001 High

    Discovery of the truncated βIVΣ5 isoform at PML nuclear bodies and nuclear matrix revealed an unexpected subnuclear role for a spectrin, raising the question of whether βIV spectrin functions in gene regulatory scaffolding.

    Evidence GFP-fusion expression and deletion mutagenesis showing partial repeats 10 and 16 required for nuclear dot formation

    PMID:11294830

    Open questions at the time
    • No transcriptional target or nuclear function identified
    • Mechanism of nuclear import not defined
  3. 2002 High

    Reciprocal knockout experiments proved that βIV spectrin and ankyrinG mutually stabilize each other and are both required for proper Nav channel clustering at AIS and nodes, establishing the mechanistic basis for channel scaffolding.

    Evidence Gene-trap βIV spectrin-null mouse compared with ankyrinG-null cerebellum; immunofluorescence for Nav, ankyrinG, and βIV spectrin

    PMID:11807096

    Open questions at the time
    • Electrophysiological consequences not measured
    • Which Nav isoforms are affected not resolved
  4. 2007 Medium

    Identification of Arc/Arg3.1 as a physical interactor of βIVΣ5 at PML bodies suggested a link between activity-dependent gene regulation and nuclear spectrin scaffolding.

    Evidence Co-immunoprecipitation and co-localization in hippocampal neurons and HEK293T cells with domain-deletion mapping

    PMID:17466953

    Open questions at the time
    • Functional consequence of Arc–βIVΣ5 interaction on transcription not tested
    • Not independently confirmed by a second group
    • Reciprocal Co-IP not demonstrated
  5. 2017 High

    The first human case of SPTBN4 loss-of-function (p.Q533*) connected βIV spectrin deficiency to congenital myopathy and deafness, and mouse modeling revealed complete loss of type 1 muscle fibers, linking the protein to neuromuscular and auditory disease.

    Evidence Autozygosity mapping, exome sequencing, Western blot confirming protein absence in patient tissues; quivering mouse histology

    PMID:28540413

    Open questions at the time
    • Neurogenic versus myopathic origin of muscle disease not resolved at this stage
    • Only single patient studied
  6. 2018 High

    Analysis of multiple bi-allelic SPTBN4 variants defined the full clinical syndrome and, critically, showed that ankyrinR/βI spectrin can partially compensate for Nav clustering at nodes but cannot rescue KCNQ2/3 clustering, explaining persistent K+ channelopathy in patients.

    Evidence Neuronal expression of 7 disease variants, phosphoinositide-binding assay, nerve biopsy immunostaining, mouse model

    PMID:29861105

    Open questions at the time
    • Structural basis for selective KCNQ2/3 dependence on βIV spectrin–ankyrinG versus ankyrinR–βI spectrin unknown
    • Genotype–phenotype severity correlation not fully resolved
  7. 2022 High

    Direct presynaptic recordings demonstrated that βIV spectrin is required for Nav clustering specifically at auditory brainstem heminodes, providing the cellular mechanism for central auditory neuropathy in SPTBN4 deficiency.

    Evidence Sptbn4geo null mouse with presynaptic terminal electrophysiology, ABR, immunofluorescence at calyx of Held

    PMID:35393465

    Open questions at the time
    • Whether heminode defect extends to other fast-spiking circuits not examined
    • Molecular distinction between heminode and nodal spectrin requirements unclear
  8. 2022 High

    Identification of SPTBN4 as a Tbx5-repressed gene in cardiomyocytes revealed that excess βIV spectrin amplifies late Na+ current (INaL), linking spectrin scaffolding to cardiac electrophysiology and long QT pathogenesis.

    Evidence hiPSC-derived cardiomyocytes, mouse trans-expression, patch-clamp electrophysiology, ranolazine rescue of QT prolongation

    PMID:33576403

    Open questions at the time
    • Direct mechanism by which βIV spectrin augments INaL not resolved
    • Whether βIV spectrin scaffolds cardiac Nav1.5 analogously to neuronal Nav not tested
  9. 2024 High

    Muscle-specific conditional knockout proved that βIV spectrin is dispensable in skeletal muscle itself, definitively establishing that SPTBN4-related myopathy is neurogenic in origin.

    Evidence Muscle-specific Cre-mediated βIV spectrin deletion in mice, muscle histology and functional assays

    PMID:38441922

    Open questions at the time
    • The specific neuronal population whose βIV spectrin loss causes myopathy is not identified
    • Whether motor neuron AIS or nodal defects are primarily responsible is unresolved
  10. 2025 Medium

    Validation of GSK3 phosphorylation sites on βIV spectrin and altered spectrin levels in schizophrenia iPSC-neurons implicated AKT/GSK3 signaling as a post-translational regulator of βIV spectrin stability in disease.

    Evidence In vitro GSK3 kinase assay, postmortem prefrontal cortex immunofluorescence, iPSC-derived neuron pharmacological perturbation

    PMID:39920295

    Open questions at the time
    • In vivo phosphorylation at these sites not confirmed
    • Causal relationship between βIV spectrin reduction and schizophrenia pathophysiology not established
    • Single-lab observation requiring independent replication

Open questions

Synthesis pass · forward-looking unresolved questions
  • The structural basis for βIV spectrin's selective requirement for KCNQ2/3 versus Nav clustering, the functional role of nuclear βIVΣ5 in transcriptional regulation, and the direct mechanism by which βIV spectrin modulates late Na+ current in cardiomyocytes remain unresolved.
  • No structural model of the βIV spectrin–ankyrinG–KCNQ complex exists
  • Nuclear βIVΣ5 has no identified transcriptional target or regulatory mechanism
  • Cardiac mechanism linking βIV spectrin to INaL augmentation not defined

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0005198 structural molecule activity 5 GO:0008092 cytoskeletal protein binding 4
Localization
GO:0005856 cytoskeleton 4 GO:0005886 plasma membrane 4 GO:0005634 nucleus 2
Pathway
R-HSA-112316 Neuronal System 3 R-HSA-162582 Signal Transduction 2
Partners
ANK3ARCKCNQ2KCNQ3SCN1ATBX5
Complex memberships
AnkyrinG–βIV spectrin complex

Evidence

Reading pass · 12 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2000 βIV spectrin (SPTBN4) was identified as a novel spectrin localized at axon initial segments (AIS) and nodes of Ranvier in the central and peripheral nervous system. Alternative splicing generates at least four isoforms (βIVΣ1–βIVΣ4). The longest isoform (βIVΣ1) contains an actin-binding domain, 17 spectrin repeats, ERQES repeat domain, SH3-binding sites, and a pleckstrin homology domain. βIVΣ1 spectrin co-localizes with ankyrin G 480/270-kDa at AIS and nodes of Ranvier, suggesting it participates in clustering voltage-gated Na+ channels and cell-adhesion molecules at these sites. βIVΣ1 was isolated as an interactor of the receptor tyrosine phosphatase-like protein ICA512. cDNA cloning, Northern blot, immunoblotting, subcellular fractionation, immunofluorescence/confocal microscopy, co-localization with ankyrinG The Journal of cell biology High 11086001
2001 A truncated major isoform of βIV spectrin (βIVΣ5, ~72–77 kDa) lacks the N-terminal actin-binding domain and localizes to promyelocytic leukemia (PML) nuclear bodies and the nuclear matrix. Deletion analysis showed that partial repeats 10 and 16 of βIVΣ5 are necessary for nuclear dot formation. βIV spectrin is the first β-spectrin associated with a subnuclear structure, suggesting a role in gene regulatory scaffolding. cDNA cloning, GFP-fusion expression, immunostaining, whole-mount nuclear matrix preparation, deletion mutagenesis The Journal of biological chemistry High 11294830
2002 Gene-trap null mutation of βIV spectrin in mice causes tremors and hindlimb contraction. βIV spectrin colocalizes with and binds ankyrinG at AIS and nodes of Ranvier. In βIV spectrin-null neurons, ankyrinG and voltage-gated sodium channels (VGSC) are not correctly clustered at AIS and nodes of Ranvier. Conversely, in ankyrinG-null neurons, βIV spectrin fails to localize to these sites, demonstrating mutual stabilization of the membrane protein cluster and cytoskeleton at AIS and nodes. Gene-trap knockout mouse, immunofluorescence, immunohistochemistry, co-localization, ankyrinG-null comparison The Journal of cell biology High 11807096
2007 Arc/Arg3.1 co-localizes and physically interacts with the nuclear βIV spectrin splice variant βSpIVΣ5 in hippocampal neurons and HEK293T cells. Arc contains a coiled-coil domain sufficient for restriction to βSpIVΣ5-positive nuclear puncta. Arc and βSpIVΣ5 synergistically increase the number of PML bodies, suggesting a functional complex at sites of nuclear transcriptional regulation. Fluorescence microscopy, co-immunoprecipitation, domain-deletion mapping, co-expression in HEK293T and hippocampal neurons Brain research Medium 17466953
2017 A homozygous nonsense mutation in SPTBN4 [p.Q533*] causes congenital myopathy, deafness, and neuropathy in a human patient. Western blot confirmed absence of the full-length 288 kDa isoform in muscle and the 72 kDa isoform in fibroblasts. Immunohistology confirmed βIV spectrin expression at the sarcolemma in normal human and mouse muscle and its complete absence in the patient and in quivering (qv4J) mice. Loss of βIV spectrin in quivering mice results in complete absence of type 1 muscle fibers (fiber-type 2 uniformity). Autozygosity mapping, whole exome sequencing, Western blot, immunohistology, quivering mouse model characterization Human genetics High 28540413
2017 Random transgene insertion into the SPTBN4 locus greatly reduced βIV spectrin protein expression in L25 mice. Homozygous affected mice developed postnatal spastic paresis/paralysis of hindlimbs with tremor, confirmed by Western blot showing reduced βIV spectrin levels. Motor endplates remained fully innervated, indicating a central rather than peripheral motor pathway defect. Whole-genome sequencing to map transgene insertion, Western blot, behavioral scoring Journal of neuromuscular diseases Medium 28582869
2018 Bi-allelic pathogenic SPTBN4 variants (three homozygous and two compound heterozygous) cause congenital hypotonia, intellectual disability, motor axonal neuropathy, and auditory neuropathy. When introduced into neurons, 5/7 variants were loss-of-function: they disrupted AIS localization or abolished phosphoinositide binding of βIV spectrin. Nerve biopsies showed reduced nodal Na+ channels and no nodal KCNQ2 K+ channels. Mouse modeling revealed that ankyrinR (AnkR) and βI spectrin can partially compensate for loss of ankyrinG and βIV spectrin at nodes of Ranvier for Na+ channel clustering, but cannot cluster KCNQ2/KCNQ3 K+ channels. Exome sequencing, neuronal expression of disease variants, AIS localization assay, phosphoinositide-binding assay, nerve biopsy immunostaining, mouse model American journal of human genetics High 29861105
2019 A recessive 16-bp frameshift deletion in SPTBN4 causes severe myopathy, hindlimb paralysis, and tremors in pigs, leading to postnatal mortality. Histopathology showed degeneration and loss of cross-striations in dorsal and hindlimb muscle fibers. The deletion produces a truncated, impaired SPTBN4 protein, confirming SPTBN4 is essential for skeletal muscle function in mammals. Whole-genome sequencing, SNP genotyping, histopathological examination of affected piglets Frontiers in genetics Medium 31850074
2022 Loss of β4-spectrin (Sptbn4geo null mice) impairs voltage-gated sodium channel (Nav) clustering specifically at the heminode along nerve terminals in the developing auditory brainstem, but does not affect nodal or AIS Nav cluster formation. Presynaptic terminal recordings showed elevated action potential threshold and increased failures during high-frequency trains. Sptbn4geo mice had slower central conduction and no startle responses but normal cochlear function, indicating central auditory processing deficits. β4-spectrin null mouse (Sptbn4geo), immunofluorescence, direct presynaptic terminal electrophysiology, auditory brainstem response (ABR), acoustic startle Scientific reports High 35393465
2022 Tbx5 transcriptionally represses SPTBN4 (encoding βIV spectrin) and CAMK2D in cardiomyocytes. The TBX5 variant p.D111Y failed to repress SPTBN4 and CAMK2D, leading to increased βIV spectrin and CaMKIIδ levels, which augmented the late Na+ current (INaL) and prolonged action potential duration in hiPSC-CMs and mouse cardiomyocytes. Ranolazine (selective INaL inhibitor) eliminated the QT prolongation in p.D111Y trans-expressing mice. hiPSC-derived cardiomyocytes, mouse trans-expression models, electrophysiology (patch-clamp), in vivo ECG, pharmacological rescue Cardiovascular research High 33576403
2024 Using a muscle-specific conditional knockout mouse, β4 spectrin was shown to be absent from skeletal muscle, demonstrating that the myopathy associated with pathogenic SPTBN4 variants is neurogenic in origin rather than a direct muscle cell-autonomous defect. β4 spectrin conditional knockout in muscle had no effect on muscle health or function. Muscle-specific conditional knockout mouse, immunofluorescence, muscle function assays The Journal of physiology High 38441922
2025 βIV spectrin protein levels are reduced in neurons of the dorsolateral prefrontal cortex in schizophrenia postmortem samples. Two GSK3 phosphorylation sites on βIV spectrin were identified computationally and validated by in vitro kinase assays. In iPSC-derived neurons from schizophrenia patients, βIV spectrin levels and sensitivity to AKT/GSK3 inhibitors were altered, indicating that the AKT/GSK3 pathway regulates βIV spectrin in the context of schizophrenia. Postmortem immunofluorescence, in vitro GSK3 phosphorylation assay, iPSC-derived neurons, AKT/GSK3 inhibitor treatment, random forest classifier on imaging data Molecular psychiatry Medium 39920295

Source papers

Stage 0 corpus · 56 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2006 Global, in vivo, and site-specific phosphorylation dynamics in signaling networks. Cell 2861 17081983
2015 The BioPlex Network: A Systematic Exploration of the Human Interactome. Cell 1118 26186194
2017 Architecture of the human interactome defines protein communities and disease networks. Nature 1085 28514442
1993 Human Sos1: a guanine nucleotide exchange factor for Ras that binds to GRB2. Science (New York, N.Y.) 772 8493579
2003 Complete sequencing and characterization of 21,243 full-length human cDNAs. Nature genetics 754 14702039
2021 Dual proteome-scale networks reveal cell-specific remodeling of the human interactome. Cell 705 33961781
2011 Phylogenetic-based propagation of functional annotations within the Gene Ontology consortium. Briefings in bioinformatics 656 21873635
2005 Diversification of transcriptional modulation: large-scale identification and characterization of putative alternative promoters of human genes. Genome research 409 16344560
2003 DISC1 (Disrupted-In-Schizophrenia 1) is a centrosome-associated protein that interacts with MAP1A, MIPT3, ATF4/5 and NUDEL: regulation and loss of interaction with mutation. Human molecular genetics 314 12812986
2017 Genome-wide CRISPR screen identifies HNRNPL as a prostate cancer dependency regulating RNA splicing. Proceedings of the National Academy of Sciences of the United States of America 282 28611215
2011 A directed protein interaction network for investigating intracellular signal transduction. Science signaling 258 21900206
2002 [Beta]IV-spectrin regulates sodium channel clustering through ankyrin-G at axon initial segments and nodes of Ranvier. The Journal of cell biology 249 11807096
2000 betaIV spectrin, a new spectrin localized at axon initial segments and nodes of ranvier in the central and peripheral nervous system. The Journal of cell biology 233 11086001
2011 Protein interactome reveals converging molecular pathways among autism disorders. Science translational medicine 180 21653829
2013 In-depth proteomic analyses of exosomes isolated from expressed prostatic secretions in urine. Proteomics 138 23533145
2017 Expanding the genetic heterogeneity of intellectual disability. Human genetics 133 28940097
2013 DNA methylation map of mouse and human brain identifies target genes in Alzheimer's disease. Brain : a journal of neurology 117 24030951
2010 Personalized smoking cessation: interactions between nicotine dose, dependence and quit-success genotype score. Molecular medicine (Cambridge, Mass.) 108 20379614
2018 Histone Interaction Landscapes Visualized by Crosslinking Mass Spectrometry in Intact Cell Nuclei. Molecular & cellular proteomics : MCP 101 30021884
2000 Prediction of the coding sequences of unidentified human genes. XVIII. The complete sequences of 100 new cDNA clones from brain which code for large proteins in vitro. DNA research : an international journal for rapid publication of reports on genes and genomes 88 10997877
2021 SARS-CoV-2-host proteome interactions for antiviral drug discovery. Molecular systems biology 86 34709727
2002 Protein-protein interactions between large proteins: two-hybrid screening using a functionally classified library composed of long cDNAs. Genome research 82 12421765
2019 The Genomics of Arthrogryposis, a Complex Trait: Candidate Genes and Further Evidence for Oligogenic Inheritance. American journal of human genetics 80 31230720
2019 The midbody interactome reveals unexpected roles for PP1 phosphatases in cytokinesis. Nature communications 74 31586073
2023 Cross-linking mass spectrometry discovers, evaluates, and corroborates structures and protein-protein interactions in the human cell. Proceedings of the National Academy of Sciences of the United States of America 60 37071682
2020 Extensive rewiring of the EGFR network in colorectal cancer cells expressing transforming levels of KRASG13D. Nature communications 60 31980649
2018 βIV Spectrinopathies Cause Profound Intellectual Disability, Congenital Hypotonia, and Motor Axonal Neuropathy. American journal of human genetics 54 29861105
2007 Activity-regulated cytoskeleton-associated protein Arc/Arg3.1 binds to spectrin and associates with nuclear promyelocytic leukemia (PML) bodies. Brain research 51 17466953
2016 High-throughput analyses of hnRNP H1 dissects its multi-functional aspect. RNA biology 50 26760575
2001 A new spectrin, beta IV, has a major truncated isoform that associates with promyelocytic leukemia protein nuclear bodies and the nuclear matrix. The Journal of biological chemistry 49 11294830
2023 Spectrins: molecular organizers and targets of neurological disorders. Nature reviews. Neuroscience 48 36697767
2017 A recessive mutation in beta-IV-spectrin (SPTBN4) associates with congenital myopathy, neuropathy, and central deafness. Human genetics 48 28540413
2019 A Genome-Wide Knockout Screen in Human Macrophages Identified Host Factors Modulating Salmonella Infection. mBio 45 31594818
2006 alphaII-Spectrin interacts with five groups of functionally important proteins in the nucleus. Cell biology international 45 16889989
2013 Perturbation of the mutated EGFR interactome identifies vulnerabilities and resistance mechanisms. Molecular systems biology 43 24189400
2022 Tbx5 variants disrupt Nav1.5 function differently in patients diagnosed with Brugada or Long QT Syndrome. Cardiovascular research 25 33576403
2018 Whole-exome sequencing for variant discovery in blepharospasm. Molecular genetics & genomic medicine 22 29770609
2021 Heterozygous variants in SPTBN1 cause intellectual disability and autism. American journal of medical genetics. Part A 20 33847457
2020 Genome-Wide Profiling of Human Papillomavirus DNA Integration into Human Genome and Its Influence on PD-L1 Expression in Chinese Uygur Cervical Cancer Women. Journal of immunology research 20 32411801
2022 Newborn differential DNA methylation and subcortical brain volumes as early signs of severe neurodevelopmental delay in a South African Birth Cohort Study. The world journal of biological psychiatry : the official journal of the World Federation of Societies of Biological Psychiatry 17 34895032
2021 Applications of Machine Learning to Predict Cisplatin Resistance in Lung Cancer. International journal of general medicine 15 34588799
2022 SPTBN5, Encoding the βV-Spectrin Protein, Leads to a Syndrome of Intellectual Disability, Developmental Delay, and Seizures. Frontiers in molecular neuroscience 14 35782384
2018 Transcriptome analysis reveals enrichment of genes associated with auditory system in swimbladder of channel catfish. Comparative biochemistry and physiology. Part D, Genomics & proteomics 11 29738887
2024 Postsynaptic β1 spectrin maintains Na+ channels at the neuromuscular junction. The Journal of physiology 9 38441922
2019 Detection of a Frameshift Deletion in the SPTBN4 Gene Leads to Prevention of Severe Myopathy and Postnatal Mortality in Pigs. Frontiers in genetics 8 31850074
2019 A novel homozygous splice-site mutation in the SPTBN4 gene causes axonal neuropathy without intellectual disability. European journal of medical genetics 8 31857255
2022 Loss of β4-spectrin impairs Nav channel clustering at the heminode and temporal fidelity of presynaptic spikes in developing auditory brain. Scientific reports 6 35393465
2021 Severe Form of ßIV-Spectrin Deficiency With Mitochondrial Dysfunction and Cardiomyopathy-A Case Report. Frontiers in neurology 5 33986717
2025 Advancing Personalized Medicine in Alzheimer's Disease: Liquid Biopsy Epigenomics Unveil APOE ε4-Linked Methylation Signatures. International journal of molecular sciences 3 40244264
2025 βIV spectrin abundancy, cellular distribution and sensitivity to AKT/GSK3 regulation in schizophrenia. Molecular psychiatry 2 39920295
2024 Heterozygous loss-of-function variants in SPTAN1 cause a novel early childhood onset distal myopathy with chronic neurogenic features. medRxiv : the preprint server for health sciences 2 39371122
2025 Natural history of SPTBN4-related neurodevelopmental disorder with hypotonia, neuropathy, and deafness. Orphanet journal of rare diseases 1 40781329
2017 Postnatal Development of Spasticity Following Transgene Insertion in the Mouse βIV Spectrin Gene (SPTBN4). Journal of neuromuscular diseases 1 28582869
2026 Study on the regulation mechanism of TBX5 gene and Gegen Qinlian decoction on colorectal cancer. Frontiers in oncology 0 41613545
2026 Early pacing in a child with Lodder-Merla syndrome and progressive sinus node dysfunction: a case report. European heart journal. Case reports 0 41757252
2026 Clinical characterization of SPTBN1, SPTBN2, and SPTBN5 variants: A case series and systematic review. Seizure 0 41819009