{"gene":"KCNG4","run_date":"2026-04-28T18:06:54","timeline":{"discoveries":[{"year":2009,"finding":"Conserved negatively charged aspartates (CDD motif) in the A/B linker of the T1 tetramerization domain are required for efficient assembly of both homotetrameric Kv2.1 and heterotetrameric Kv2.1/Kv6.4 channels; charge-reversal mutations in Kv6.4 prevent its heterotetrameric interaction with Kv2.1, as shown by FRET, immunocytochemistry, and co-immunoprecipitation.","method":"Site-directed mutagenesis, FRET (confocal microscopy), co-immunoprecipitation, immunocytochemistry","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal methods (mutagenesis, FRET, co-IP) in a single study with rigorous controls","pmids":["19717558"],"is_preprint":false},{"year":2008,"finding":"Histidine 105 in the T1 domain of Kv2.1 is required for functional heteromerization with Kv6.4 (and Kv6.3); H105V or H105R substitutions disrupt T1–T1 interaction with Kv6.4 without affecting Kv2.1 homomeric assembly, abolishing the voltage-dependence shift conferred by Kv6.4 co-expression.","method":"Yeast two-hybrid, FRET, co-immunoprecipitation, two-electrode voltage-clamp, dominant-negative co-expression","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal methods (Y2H, FRET, co-IP, electrophysiology) with mutagenesis","pmids":["19074135"],"is_preprint":false},{"year":2015,"finding":"KCNE5 forms a tripartite complex with Kv2.1 and Kv6.4, modulating Kv2.1/Kv6.4 biophysical properties (accelerated activation, slowed deactivation, steepened inactivation slope, faster closed-state inactivation recovery) without changing current density, whereas KCNE5 reduces Kv2.1 homotetrameric current density ~2-fold; complex formation confirmed by FRET in HEK293 cells.","method":"Electrophysiology (voltage clamp), FRET, immunocytochemistry, co-expression in HEK293 cells","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 2 — reciprocal FRET + electrophysiology with multiple subunit combinations, strong mechanistic characterization","pmids":["26242757"],"is_preprint":false},{"year":2015,"finding":"The lower half of the S6 domain (S6c) of Kv6.4 is crucial for 4-AP-induced potentiation of Kv2.1/Kv6.4 heteromers; Kv6.4 mediates closed-state inactivation such that 4-AP suppresses this inactivation and recovers a population of channels inactivated at resting conditions, demonstrated by chimeric substitutions between Kv6.4 and Kv9.3.","method":"Electrophysiology (two-electrode voltage clamp, Xenopus oocytes), chimeric subunit substitutions, pharmacology","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 1-2 — chimeric mutagenesis combined with electrophysiology identifies domain responsible for pharmacological effect","pmids":["26505474"],"is_preprint":false},{"year":2011,"finding":"Residues T203 (S1) and S347 (S5) in Kv2.1 are energetically coupled and in close proximity within the functional channel; double mutant cycle analysis and suppression of a trafficking-deficient double mutant by an S4 charge reversal (R300E) demonstrate functional interactions between S1, S4, and S5 segments relevant to Kv2.1 channel assembly and maturation.","method":"Site-directed mutagenesis, double mutant cycle analysis, electrophysiology, chimeric Kv2.1/Kv6.4 constructs","journal":"European biophysics journal","confidence":"Medium","confidence_rationale":"Tier 1 — thermodynamic double-mutant cycle analysis with electrophysiology, single lab","pmids":["21455829"],"is_preprint":false},{"year":2018,"finding":"Atypical substitutions in the conserved S6 activation gate of Kv6.4 restrict Kv2.1:Kv6.4 heteromer stoichiometry to a predominant 3:1 (Kv2.1:Kv6.4) ratio by limiting formation and function of 2:2 heteromers; substituting the self-compatible Kv2.1 T1 domain into Kv6.4 does not alter stoichiometry, indicating the S6 gate as the key determinant.","method":"Single-molecule imaging, chimeric subunit engineering, electrophysiology, sequence analysis across cnidarian orthologs","journal":"The Journal of general physiology","confidence":"High","confidence_rationale":"Tier 1-2 — chimeric mutagenesis, single-molecule functional readout, evolutionary validation","pmids":["30322883"],"is_preprint":false},{"year":2017,"finding":"Targeted deletion of Kv6.4 (Kcng4-/-) in mice causes male sterility through disturbed spermiogenesis, resulting in severely reduced sperm count, absent motile spermatozoa, and abnormal sperm morphology (smaller head, shorter tail), establishing a non-redundant role for Kv6.4 in late-stage spermatogenesis.","method":"Knockout mouse model (Kcng4-/-), semen quality analysis, histology of testicular tissue","journal":"Reproduction, fertility, and development","confidence":"High","confidence_rationale":"Tier 2 — clean KO with defined cellular phenotype (spermiogenesis defect) confirmed by histology and sperm analysis","pmids":["27677211"],"is_preprint":false},{"year":2020,"finding":"The rare variant KV6.4-Met419 exerts a dominant-negative effect by failing to traffic to the plasma membrane, preventing modulation of KV2.1 inactivation voltage dependence; in neurons overexpressing KV6.4-Met419, the voltage dependence of inactivation for KV2.1 is more depolarized and action potential threshold is higher, linking KV6.4 to nociceptor excitability in uterine sensory neurons.","method":"Human genetics (SNP association), heterologous expression, electrophysiology, immunofluorescence (trafficking), retrograde labeling of mouse uterine neurons","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods including trafficking assay, electrophysiology in neurons, and human genetic validation","pmids":["32697988"],"is_preprint":false},{"year":2014,"finding":"Dlk1 activates expression of the K+ channel subunit Kcng4 to modulate delayed-rectifier currents in motor neurons, suppressing Notch signaling and promoting a fast biophysical signature; Dlk1 inactivation shifts motor neurons toward slow signatures and abolishes peak force outputs.","method":"Transgenic mouse, chick in ovo electroporation, electrophysiology, transcriptome analysis, gain- and loss-of-function","journal":"Science","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis with electrophysiological readout replicated in two species (mouse and chick)","pmids":["24626931"],"is_preprint":false},{"year":2024,"finding":"The migraine-associated missense mutation L360P in the S4-S5 linker of Kv6.4 significantly alters Kv2.1/Kv6.4 channel function when expressed in monomeric or tandem dimer configurations, providing molecular insight into channel dysfunction in migraine pathology.","method":"Heterologous expression, electrophysiology (voltage clamp), tandem dimer constructs with fixed 2:2 stoichiometry","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 — electrophysiology with defined stoichiometry constructs, single lab","pmids":["39159549"],"is_preprint":false},{"year":2024,"finding":"The migraine-linked Kv6.4-L360P variant almost completely abolishes Kv2.1 currents when co-expressed, and the proposed mechanism involves disruption in the trigeminal system leading to migraine initiation; Kv6.4-L360P prevents normal KCNB1 (Kv2.1) expression/function.","method":"Heterologous expression, electrophysiology, co-expression assays","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2 — electrophysiology with defined variant, single lab","pmids":["39201645"],"is_preprint":false},{"year":2025,"finding":"In spinal motoneurons, Kv6.4 is specifically expressed and co-clustered with Kv2.1 and Kv2.2 at endoplasmic reticulum-plasma membrane (ER-PM) junctions beneath C-bouton synapses; Kv6.4 clustering requires Kv2 subunits (severely reduced in Kv2.1 KO, moderately in Kv2.2 KO), and Kv2.1 S590A mutation (preventing ER VAP binding) abolishes both Kv2.1 and Kv6.4 ER-PM clustering.","method":"Immunofluorescence, KO mouse models (Kv2.1, Kv2.2), Kv2.1 S590A knock-in mice, confocal microscopy, co-localization analysis","journal":"The European journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 — multiple KO and knock-in mouse models with direct immunofluorescence localization and functional consequence","pmids":["40919874"],"is_preprint":false},{"year":2025,"finding":"Two pharmacological Kv2 inhibitors (RY785, a pore blocker, and GxTX, a voltage sensor modulator) used in combination distinguish Kv2/KvS heteromeric conductances from Kv2-only conductances; Kv6.4-containing channels are resistant to RY785 but sensitive to GxTX, and Kv2/Kv6.4 heteromers predominate in mouse and human dorsal root ganglion neurons.","method":"Pharmacology, electrophysiology (patch clamp), heterologous expression, mouse/human DRG neuron recordings","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1-2 — pharmacological dissection validated in heterologous system and native neurons across species","pmids":["40423692"],"is_preprint":false},{"year":2025,"finding":"In cortical parvalbumin (PV) neurons, Kv6.4 loss reduces action potential height and width, hyperpolarizes threshold and interspike potential, accelerates AP upstroke during repetitive firing, and alters GABA release and paired-pulse depression at PV-to-pyramidal synapses; effects are amplified during high-frequency firing, consistent with Kv6.4 modifying Kv2-mediated delayed rectifier current.","method":"Conditional knockout, patch-clamp electrophysiology, optogenetics, paired recording (PV→pyramidal synapses), postnatal developmental expression analysis","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — clean KO with multiple orthogonal electrophysiological readouts including intrinsic and synaptic properties","pmids":["41632839"],"is_preprint":false},{"year":2024,"finding":"In zebrafish, kcng4b-C1 mutation causes mild loss-of-function manifested by failure of kinocilia extension and ectopic otolith formation, while kcng4b-C2 mutation creates a gain-of-function allele with an ectopic seventh transmembrane domain that prevents otolith development and reduces kinocilia; demonstrating that the silent subunit Kcng4 modulates Kv2.1 channel activity to regulate ear development.","method":"Zebrafish mutant analysis, electrophysiology, developmental biology, in silico structural modeling","journal":"Developmental biology","confidence":"Medium","confidence_rationale":"Tier 2 — LOF and GOF alleles with defined developmental phenotypes in zebrafish ortholog, supported by structural modeling","pmids":["38492873"],"is_preprint":false},{"year":2021,"finding":"Kcng4+ neurons in the external globus pallidus (GPe) are a distinct subclass of PV+ neurons with unique electrophysiological properties; optogenetic perturbation of Kcng4+ neurons produces unique behavioral motor patterns distinct from other GPe neuron subtypes, and local collateral connectivity contributes to observed circuit effects.","method":"Transgenic Kcng4-Cre mouse line, electrophysiology, optogenetics, machine learning-based behavioral tracking","journal":"The Journal of neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 — cell-type-specific optogenetics with behavioral readout, electrophysiological characterization","pmids":["33731450"],"is_preprint":false}],"current_model":"KCNG4 (Kv6.4) is a 'silent' or 'regulatory' voltage-gated potassium channel subunit that cannot form functional homotetrameric channels on its own but heteroassembles with Kv2.1 and/or Kv2.2 subunits—primarily in a 3:1 (Kv2:Kv6.4) stoichiometry determined by atypical S6 gate substitutions—via T1 domain interactions (requiring specific residues including conserved CDD aspartates and Kv2.1 His105) to form heterotetrameric channels with distinct biophysical properties including altered closed-state inactivation and voltage dependence; Kv6.4 localizes to ER-PM junctions in a Kv2-dependent manner, is expressed in specific neuronal populations (motoneurons, PV interneurons, DRG nociceptors), modulates nociceptor excitability, tunes PV neuron action potential waveform and synaptic output, and its loss causes male sterility through spermiogenesis defects."},"narrative":{"teleology":[{"year":2008,"claim":"Identifying the molecular determinants of Kv2.1–Kv6.4 heteromerization resolved how a silent subunit selectively engages its partner: Kv2.1-His105 in the T1 domain is required for T1–T1 interaction with Kv6.4, while being dispensable for Kv2.1 homomerization.","evidence":"Yeast two-hybrid, FRET, co-immunoprecipitation, and two-electrode voltage clamp with H105 point mutants in heterologous cells","pmids":["19074135"],"confidence":"High","gaps":["Structural basis of the H105-mediated interface not resolved at atomic level","Whether H105 dependency generalizes to all KvS subunits not tested"]},{"year":2009,"claim":"Conserved negatively charged aspartates (CDD motif) in the T1 A/B linker were shown to be essential for both Kv2.1 homotetrameric and Kv2.1/Kv6.4 heterotetrameric assembly, establishing that electrostatic interactions in the T1 domain are a shared assembly requirement.","evidence":"Site-directed charge-reversal mutagenesis with FRET, co-IP, and immunocytochemistry in HEK cells","pmids":["19717558"],"confidence":"High","gaps":["Role of the CDD motif in heteromers with other KvS members not systematically tested","No structural data for the T1 heteromeric interface"]},{"year":2014,"claim":"Linking Kv6.4 to a physiological circuit role, Dlk1 was shown to activate Kcng4 expression in fast motor neurons, establishing Kv6.4 as an effector that tunes delayed-rectifier currents and fast biophysical identity downstream of a Notch-inhibitory pathway.","evidence":"Transgenic mouse and chick in ovo electroporation with gain/loss-of-function, electrophysiology, and transcriptome analysis","pmids":["24626931"],"confidence":"High","gaps":["Whether Kv6.4 is the sole mediator of the Dlk1-dependent fast signature is not definitively isolated","Transcriptional mechanism linking Dlk1 to Kcng4 promoter not defined"]},{"year":2015,"claim":"The lower S6 segment of Kv6.4 was identified as the structural determinant of closed-state inactivation in Kv2.1/Kv6.4 heteromers, explaining the unique pharmacological sensitivity of these channels to 4-AP-mediated potentiation.","evidence":"Chimeric subunit substitutions between Kv6.4 and Kv9.3 with electrophysiology in Xenopus oocytes","pmids":["26505474"],"confidence":"High","gaps":["No structural model of the Kv6.4 S6 gate in the heteromeric context","Physiological relevance of 4-AP potentiation in native neurons not addressed"]},{"year":2015,"claim":"KCNE5 was shown to form a tripartite complex with Kv2.1/Kv6.4, differentially modulating the heteromeric channel's kinetics versus the homomeric channel's current density, revealing an additional layer of heteromeric channel regulation by accessory subunits.","evidence":"FRET and electrophysiology with systematic co-expression of KCNE5 with Kv2.1 ± Kv6.4 in HEK293 cells","pmids":["26242757"],"confidence":"High","gaps":["Physiological context of the tripartite complex not established in native tissue","Other KCNE family members not tested with Kv2.1/Kv6.4"]},{"year":2017,"claim":"Kcng4 knockout mice revealed a non-redundant in vivo role for Kv6.4 in spermiogenesis, as loss caused male sterility with severely abnormal sperm morphology and absent motility.","evidence":"Kcng4−/− knockout mouse with semen analysis and testicular histology","pmids":["27677211"],"confidence":"High","gaps":["The specific potassium current disrupted in spermatogenic cells not identified","Whether the phenotype is Kv2-dependent or involves a non-canonical Kv6.4 function is unknown"]},{"year":2018,"claim":"Atypical S6 gate residues in Kv6.4, rather than T1 domain incompatibility, were identified as the dominant constraint enforcing 3:1 (Kv2:Kv6.4) stoichiometry, resolving a long-standing question about why silent subunits occupy only one position per tetramer.","evidence":"Single-molecule imaging, chimeric T1/S6 swaps, electrophysiology, and evolutionary analysis across cnidarian orthologs","pmids":["30322883"],"confidence":"High","gaps":["Structural basis of S6-gate incompatibility not resolved at atomic level","Whether all KvS subunits share this S6-based stoichiometry mechanism not demonstrated"]},{"year":2020,"claim":"A rare human variant (KV6.4-Met419) was shown to act as a dominant-negative by failing to traffic to the plasma membrane while sequestering Kv2.1, linking Kv6.4 function to nociceptor excitability and uterine sensory neuron firing thresholds.","evidence":"Human SNP association, heterologous expression trafficking assays, electrophysiology in transfected DRG neurons, retrograde labeling of uterine afferents","pmids":["32697988"],"confidence":"High","gaps":["The full pain phenotype of carriers not characterized beyond association data","Mechanism of ER retention of the Met419 variant not defined"]},{"year":2021,"claim":"Kcng4-expressing GPe neurons were defined as a functionally distinct PV+ subclass with unique electrophysiological and behavioral output properties, establishing Kcng4 as a marker and functional modulator in basal ganglia circuits.","evidence":"Kcng4-Cre transgenic mice with optogenetics, electrophysiology, and machine learning behavioral analysis","pmids":["33731450"],"confidence":"Medium","gaps":["Causal contribution of Kv6.4 channel activity versus Kcng4 as a mere genetic marker not disentangled","Downstream circuit effects on other basal ganglia nuclei not mapped"]},{"year":2024,"claim":"A migraine-associated L360P mutation in the Kv6.4 S4–S5 linker was shown to drastically suppress Kv2.1/Kv6.4 channel function, providing a molecular mechanism for a channelopathy-based migraine pathway through trigeminal Kv2/Kv6.4 dysfunction.","evidence":"Electrophysiology with monomeric and fixed-stoichiometry tandem dimer constructs in heterologous cells","pmids":["39159549","39201645"],"confidence":"Medium","gaps":["Variant effect not validated in native trigeminal neurons","Only heterologous overexpression systems used","Human genetic evidence linking L360P to migraine not detailed in these studies"]},{"year":2024,"claim":"Zebrafish kcng4b mutations demonstrated that Kv6.4 modulates Kv2.1 activity during inner ear development, with loss-of-function causing ectopic otolith formation and gain-of-function blocking otolith development.","evidence":"Zebrafish LOF and GOF mutant alleles with developmental phenotyping and structural modeling","pmids":["38492873"],"confidence":"Medium","gaps":["Direct electrophysiological measurement of Kv2/Kv6.4 currents in zebrafish otic vesicle not performed","Relevance to mammalian ear development untested"]},{"year":2025,"claim":"In spinal motoneurons, Kv6.4 was shown to co-cluster with Kv2.1 and Kv2.2 at ER–PM junctions beneath C-bouton synapses, with clustering entirely dependent on Kv2 subunits and their ER-VAP binding motif, establishing the subcellular nanoarchitecture of native Kv2/Kv6.4 channels.","evidence":"Immunofluorescence in Kv2.1 KO, Kv2.2 KO, and Kv2.1-S590A knock-in mouse spinal cord sections","pmids":["40919874"],"confidence":"High","gaps":["Functional consequence of disrupted ER-PM clustering on motoneuron firing not tested","Whether Kv6.4 itself contributes to ER-PM junction formation or is passively recruited is unresolved"]},{"year":2025,"claim":"Pharmacological dissection using differential sensitivities to RY785 and GxTX established that Kv2/Kv6.4 heteromers constitute the predominant Kv2-containing conductance in mouse and human DRG nociceptors, providing tools to distinguish heteromeric from homomeric Kv2 currents in native neurons.","evidence":"Patch-clamp pharmacology in heterologous expression and native mouse/human DRG neurons","pmids":["40423692"],"confidence":"High","gaps":["Whether Kv6.4 predominance extends to all DRG neuron subtypes not resolved","RY785/GxTX selectivity for other KvS heteromers not fully profiled"]},{"year":2025,"claim":"Conditional Kv6.4 deletion in cortical PV interneurons revealed that Kv6.4 shapes action potential height, width, and threshold during high-frequency firing and modulates GABAergic synaptic transmission at PV-to-pyramidal synapses, establishing a cell-autonomous role for the silent subunit in cortical inhibitory circuit function.","evidence":"Conditional knockout with patch-clamp, optogenetic activation, and paired PV→pyramidal recordings in cortical slices","pmids":["41632839"],"confidence":"High","gaps":["Network-level consequences of altered PV neuron output on cortical computation not assessed","Whether compensatory changes in other KvS subunits occur in KO not examined"]},{"year":null,"claim":"Key unresolved questions include the atomic structure of the Kv2/Kv6.4 heterotetramer, the identity of the Kv2-dependent potassium current disrupted in spermiogenesis, and whether Kv6.4 contributes structurally to ER–PM junction formation beyond being passively recruited by Kv2.","evidence":"","pmids":[],"confidence":"Low","gaps":["No cryo-EM or X-ray structure of any Kv2/KvS heterotetramer","Mechanism linking Kv6.4 loss to spermiogenesis failure undefined","Kv6.4 role in ER-PM junction biogenesis versus passive localization not distinguished"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[2,3,5,7,8,13]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[7,11,12]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[11]}],"pathway":[],"complexes":["Kv2.1/Kv6.4 heterotetrameric channel","Kv2.2/Kv6.4 heterotetrameric channel","Kv2.1/Kv6.4/KCNE5 tripartite complex"],"partners":["KCNB1","KCNB2","KCNE5","DLK1"],"other_free_text":[]},"mechanistic_narrative":"KCNG4 (Kv6.4) is an electrically silent voltage-gated potassium channel subunit that obligately heteroassembles with Kv2 family α-subunits to form functional heterotetrameric channels with modified gating properties in neurons and other cell types. Assembly with Kv2.1 requires conserved CDD aspartates in the T1 tetramerization domain and Kv2.1-His105 [PMID:19717558, PMID:19074135], while atypical residues in the Kv6.4 S6 activation gate restrict stoichiometry to a predominant 3:1 (Kv2:Kv6.4) ratio [PMID:30322883]; the incorporated Kv6.4 subunit confers distinct closed-state inactivation properties, shifts the voltage dependence of inactivation, and localizes to Kv2-dependent ER–plasma membrane junction clusters in motoneurons [PMID:26505474, PMID:40919874]. Kv6.4 modulates neuronal excitability across multiple circuits—tuning fast motor neuron identity downstream of Dlk1 signaling [PMID:24626931], shaping action potential waveform and GABAergic synaptic output of cortical parvalbumin interneurons [PMID:41632839], and regulating nociceptor firing threshold in DRG and uterine sensory neurons [PMID:32697988, PMID:40423692]—and its loss in mice causes male sterility through defective spermiogenesis [PMID:27677211]."},"prefetch_data":{"uniprot":{"accession":"Q8TDN1","full_name":"Voltage-gated potassium channel regulatory subunit KCNG4","aliases":["Potassium voltage-gated channel subfamily G member 4","Voltage-gated potassium channel subunit Kv6.3","Voltage-gated potassium channel subunit Kv6.4"],"length_aa":519,"mass_kda":59.0,"function":"Regulatory subunit of the voltage-gated potassium (Kv) channel which, when coassembled with KCNB1, modulates the kinetics parameters of the heterotetrameric channel namely the time course of activation, deactivation and inactivation and on the voltage-dependence of activation (PubMed:12060745, PubMed:19074135). Potassium channel subunit that does not form functional channels by itself (Probable) (PubMed:12060745). Reduces the deactivation rate (PubMed:12060745, PubMed:19074135). Modulates the threshold for activation by shifting by approximately 20 mV in hyperpolarizing direction (PubMed:12060745). Markedly changes the inactivation by shifting the voltage dependence of inactivation by approximately 40 mV in hyperpolarizing direction (PubMed:12060745). Acceleratee activation and enhances the time course of activation (PubMed:12060745)","subcellular_location":"Cell membrane","url":"https://www.uniprot.org/uniprotkb/Q8TDN1/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/KCNG4","classification":"Not Classified","n_dependent_lines":3,"n_total_lines":1208,"dependency_fraction":0.0024834437086092716},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/KCNG4","total_profiled":1310},"omim":[{"mim_id":"607603","title":"POTASSIUM CHANNEL, VOLTAGE-GATED, SUBFAMILY G, MEMBER 4; KCNG4","url":"https://www.omim.org/entry/607603"},{"mim_id":"606767","title":"POTASSIUM CHANNEL, VOLTAGE-GATED, SUBFAMILY G, MEMBER 3; KCNG3","url":"https://www.omim.org/entry/606767"},{"mim_id":"600397","title":"POTASSIUM CHANNEL, VOLTAGE-GATED, SHAB-RELATED SUBFAMILY, MEMBER 1; KCNB1","url":"https://www.omim.org/entry/600397"},{"mim_id":"176290","title":"DELTA-LIKE NONCANONICAL NOTCH LIGAND 1; DLK1","url":"https://www.omim.org/entry/176290"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Plasma membrane","reliability":"Supported"},{"location":"Nucleoplasm","reliability":"Additional"}],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in single","driving_tissues":[{"tissue":"retina","ntpm":3.6}],"url":"https://www.proteinatlas.org/search/KCNG4"},"hgnc":{"alias_symbol":["Kv6.4"],"prev_symbol":[]},"alphafold":{"accession":"Q8TDN1","domains":[{"cath_id":"3.30.710.10","chopping":"39-156","consensus_level":"high","plddt":83.7448,"start":39,"end":156},{"cath_id":"1.20.120.350","chopping":"213-315_329-352","consensus_level":"high","plddt":85.8254,"start":213,"end":352},{"cath_id":"1.10.287.70","chopping":"358-476","consensus_level":"high","plddt":91.1139,"start":358,"end":476}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8TDN1","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8TDN1-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8TDN1-F1-predicted_aligned_error_v6.png","plddt_mean":77.88},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=KCNG4","jax_strain_url":"https://www.jax.org/strain/search?query=KCNG4"},"sequence":{"accession":"Q8TDN1","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8TDN1.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8TDN1/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8TDN1"}},"corpus_meta":[{"pmid":"24626931","id":"PMC_24626931","title":"Dlk1 promotes a fast motor neuron biophysical signature required for peak force execution.","date":"2014","source":"Science (New York, N.Y.)","url":"https://pubmed.ncbi.nlm.nih.gov/24626931","citation_count":58,"is_preprint":false},{"pmid":"33731450","id":"PMC_33731450","title":"Dissociable Roles of Pallidal Neuron Subtypes in Regulating Motor Patterns.","date":"2021","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/33731450","citation_count":47,"is_preprint":false},{"pmid":"31170158","id":"PMC_31170158","title":"Exome sequencing in multiple sclerosis families identifies 12 candidate genes and nominates biological pathways for the genesis of disease.","date":"2019","source":"PLoS genetics","url":"https://pubmed.ncbi.nlm.nih.gov/31170158","citation_count":46,"is_preprint":false},{"pmid":"32697988","id":"PMC_32697988","title":"Human Labor Pain Is Influenced by the Voltage-Gated Potassium Channel KV6.4 Subunit.","date":"2020","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/32697988","citation_count":31,"is_preprint":false},{"pmid":"23030542","id":"PMC_23030542","title":"Identification of novel genes involved in migraine.","date":"2012","source":"Headache","url":"https://pubmed.ncbi.nlm.nih.gov/23030542","citation_count":30,"is_preprint":false},{"pmid":"26242757","id":"PMC_26242757","title":"Auxiliary KCNE subunits modulate both homotetrameric Kv2.1 and heterotetrameric Kv2.1/Kv6.4 channels.","date":"2015","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/26242757","citation_count":26,"is_preprint":false},{"pmid":"36292658","id":"PMC_36292658","title":"Identification of Genomic Regions and Candidate Genes Associated with Body Weight and Body Conformation Traits in Karachai Goats.","date":"2022","source":"Genes","url":"https://pubmed.ncbi.nlm.nih.gov/36292658","citation_count":25,"is_preprint":false},{"pmid":"19717558","id":"PMC_19717558","title":"Conserved negative charges in the N-terminal tetramerization domain mediate efficient assembly of Kv2.1 and Kv2.1/Kv6.4 channels.","date":"2009","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/19717558","citation_count":23,"is_preprint":false},{"pmid":"26505474","id":"PMC_26505474","title":"Modulation of Closed-State Inactivation in Kv2.1/Kv6.4 Heterotetramers as Mechanism for 4-AP Induced Potentiation.","date":"2015","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/26505474","citation_count":21,"is_preprint":false},{"pmid":"19074135","id":"PMC_19074135","title":"Mutation of histidine 105 in the T1 domain of the potassium channel Kv2.1 disrupts heteromerization with Kv6.3 and Kv6.4.","date":"2008","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/19074135","citation_count":18,"is_preprint":false},{"pmid":"30322883","id":"PMC_30322883","title":"The S6 gate in regulatory Kv6 subunits restricts heteromeric K+ channel stoichiometry.","date":"2018","source":"The Journal of general physiology","url":"https://pubmed.ncbi.nlm.nih.gov/30322883","citation_count":18,"is_preprint":false},{"pmid":"27677211","id":"PMC_27677211","title":"Targeted deletion of the Kv6.4 subunit causes male sterility due to disturbed spermiogenesis.","date":"2017","source":"Reproduction, fertility, and development","url":"https://pubmed.ncbi.nlm.nih.gov/27677211","citation_count":15,"is_preprint":false},{"pmid":"35760404","id":"PMC_35760404","title":"Genome-wide association analysis of nine reproduction and morphological traits in three goat breeds from Southern China.","date":"2022","source":"Animal bioscience","url":"https://pubmed.ncbi.nlm.nih.gov/35760404","citation_count":15,"is_preprint":false},{"pmid":"31512327","id":"PMC_31512327","title":"Kv2.1 voltage-gated potassium channels in developmental perspective.","date":"2019","source":"Developmental dynamics : an official publication of the American Association of Anatomists","url":"https://pubmed.ncbi.nlm.nih.gov/31512327","citation_count":14,"is_preprint":false},{"pmid":"21455829","id":"PMC_21455829","title":"Functional interactions between residues in the S1, S4, and S5 domains of Kv2.1.","date":"2011","source":"European biophysics journal : EBJ","url":"https://pubmed.ncbi.nlm.nih.gov/21455829","citation_count":12,"is_preprint":false},{"pmid":"39159549","id":"PMC_39159549","title":"Functional properties of a disease mutation for migraine in Kv2.1/6.4 channels.","date":"2024","source":"Biochemical and biophysical research 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development","date":"2024-12-20","source":"bioRxiv","url":"https://doi.org/10.1101/2024.12.20.629661","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":18933,"output_tokens":4159,"usd":0.059592},"stage2":{"model":"claude-opus-4-6","input_tokens":7587,"output_tokens":7031,"usd":0.320565},"total_usd":0.380157,"stage1_batch_id":"msgbatch_01DzrsgVgYngY1hvM3DU1yF2","stage2_batch_id":"msgbatch_01KA9b7iRzKFdhoBUT7vCvSe","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2009,\n      \"finding\": \"Conserved negatively charged aspartates (CDD motif) in the A/B linker of the T1 tetramerization domain are required for efficient assembly of both homotetrameric Kv2.1 and heterotetrameric Kv2.1/Kv6.4 channels; charge-reversal mutations in Kv6.4 prevent its heterotetrameric interaction with Kv2.1, as shown by FRET, immunocytochemistry, and co-immunoprecipitation.\",\n      \"method\": \"Site-directed mutagenesis, FRET (confocal microscopy), co-immunoprecipitation, immunocytochemistry\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods (mutagenesis, FRET, co-IP) in a single study with rigorous controls\",\n      \"pmids\": [\"19717558\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Histidine 105 in the T1 domain of Kv2.1 is required for functional heteromerization with Kv6.4 (and Kv6.3); H105V or H105R substitutions disrupt T1–T1 interaction with Kv6.4 without affecting Kv2.1 homomeric assembly, abolishing the voltage-dependence shift conferred by Kv6.4 co-expression.\",\n      \"method\": \"Yeast two-hybrid, FRET, co-immunoprecipitation, two-electrode voltage-clamp, dominant-negative co-expression\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods (Y2H, FRET, co-IP, electrophysiology) with mutagenesis\",\n      \"pmids\": [\"19074135\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"KCNE5 forms a tripartite complex with Kv2.1 and Kv6.4, modulating Kv2.1/Kv6.4 biophysical properties (accelerated activation, slowed deactivation, steepened inactivation slope, faster closed-state inactivation recovery) without changing current density, whereas KCNE5 reduces Kv2.1 homotetrameric current density ~2-fold; complex formation confirmed by FRET in HEK293 cells.\",\n      \"method\": \"Electrophysiology (voltage clamp), FRET, immunocytochemistry, co-expression in HEK293 cells\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal FRET + electrophysiology with multiple subunit combinations, strong mechanistic characterization\",\n      \"pmids\": [\"26242757\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"The lower half of the S6 domain (S6c) of Kv6.4 is crucial for 4-AP-induced potentiation of Kv2.1/Kv6.4 heteromers; Kv6.4 mediates closed-state inactivation such that 4-AP suppresses this inactivation and recovers a population of channels inactivated at resting conditions, demonstrated by chimeric substitutions between Kv6.4 and Kv9.3.\",\n      \"method\": \"Electrophysiology (two-electrode voltage clamp, Xenopus oocytes), chimeric subunit substitutions, pharmacology\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — chimeric mutagenesis combined with electrophysiology identifies domain responsible for pharmacological effect\",\n      \"pmids\": [\"26505474\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Residues T203 (S1) and S347 (S5) in Kv2.1 are energetically coupled and in close proximity within the functional channel; double mutant cycle analysis and suppression of a trafficking-deficient double mutant by an S4 charge reversal (R300E) demonstrate functional interactions between S1, S4, and S5 segments relevant to Kv2.1 channel assembly and maturation.\",\n      \"method\": \"Site-directed mutagenesis, double mutant cycle analysis, electrophysiology, chimeric Kv2.1/Kv6.4 constructs\",\n      \"journal\": \"European biophysics journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 — thermodynamic double-mutant cycle analysis with electrophysiology, single lab\",\n      \"pmids\": [\"21455829\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Atypical substitutions in the conserved S6 activation gate of Kv6.4 restrict Kv2.1:Kv6.4 heteromer stoichiometry to a predominant 3:1 (Kv2.1:Kv6.4) ratio by limiting formation and function of 2:2 heteromers; substituting the self-compatible Kv2.1 T1 domain into Kv6.4 does not alter stoichiometry, indicating the S6 gate as the key determinant.\",\n      \"method\": \"Single-molecule imaging, chimeric subunit engineering, electrophysiology, sequence analysis across cnidarian orthologs\",\n      \"journal\": \"The Journal of general physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — chimeric mutagenesis, single-molecule functional readout, evolutionary validation\",\n      \"pmids\": [\"30322883\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Targeted deletion of Kv6.4 (Kcng4-/-) in mice causes male sterility through disturbed spermiogenesis, resulting in severely reduced sperm count, absent motile spermatozoa, and abnormal sperm morphology (smaller head, shorter tail), establishing a non-redundant role for Kv6.4 in late-stage spermatogenesis.\",\n      \"method\": \"Knockout mouse model (Kcng4-/-), semen quality analysis, histology of testicular tissue\",\n      \"journal\": \"Reproduction, fertility, and development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with defined cellular phenotype (spermiogenesis defect) confirmed by histology and sperm analysis\",\n      \"pmids\": [\"27677211\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"The rare variant KV6.4-Met419 exerts a dominant-negative effect by failing to traffic to the plasma membrane, preventing modulation of KV2.1 inactivation voltage dependence; in neurons overexpressing KV6.4-Met419, the voltage dependence of inactivation for KV2.1 is more depolarized and action potential threshold is higher, linking KV6.4 to nociceptor excitability in uterine sensory neurons.\",\n      \"method\": \"Human genetics (SNP association), heterologous expression, electrophysiology, immunofluorescence (trafficking), retrograde labeling of mouse uterine neurons\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods including trafficking assay, electrophysiology in neurons, and human genetic validation\",\n      \"pmids\": [\"32697988\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Dlk1 activates expression of the K+ channel subunit Kcng4 to modulate delayed-rectifier currents in motor neurons, suppressing Notch signaling and promoting a fast biophysical signature; Dlk1 inactivation shifts motor neurons toward slow signatures and abolishes peak force outputs.\",\n      \"method\": \"Transgenic mouse, chick in ovo electroporation, electrophysiology, transcriptome analysis, gain- and loss-of-function\",\n      \"journal\": \"Science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis with electrophysiological readout replicated in two species (mouse and chick)\",\n      \"pmids\": [\"24626931\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"The migraine-associated missense mutation L360P in the S4-S5 linker of Kv6.4 significantly alters Kv2.1/Kv6.4 channel function when expressed in monomeric or tandem dimer configurations, providing molecular insight into channel dysfunction in migraine pathology.\",\n      \"method\": \"Heterologous expression, electrophysiology (voltage clamp), tandem dimer constructs with fixed 2:2 stoichiometry\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — electrophysiology with defined stoichiometry constructs, single lab\",\n      \"pmids\": [\"39159549\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"The migraine-linked Kv6.4-L360P variant almost completely abolishes Kv2.1 currents when co-expressed, and the proposed mechanism involves disruption in the trigeminal system leading to migraine initiation; Kv6.4-L360P prevents normal KCNB1 (Kv2.1) expression/function.\",\n      \"method\": \"Heterologous expression, electrophysiology, co-expression assays\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — electrophysiology with defined variant, single lab\",\n      \"pmids\": [\"39201645\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In spinal motoneurons, Kv6.4 is specifically expressed and co-clustered with Kv2.1 and Kv2.2 at endoplasmic reticulum-plasma membrane (ER-PM) junctions beneath C-bouton synapses; Kv6.4 clustering requires Kv2 subunits (severely reduced in Kv2.1 KO, moderately in Kv2.2 KO), and Kv2.1 S590A mutation (preventing ER VAP binding) abolishes both Kv2.1 and Kv6.4 ER-PM clustering.\",\n      \"method\": \"Immunofluorescence, KO mouse models (Kv2.1, Kv2.2), Kv2.1 S590A knock-in mice, confocal microscopy, co-localization analysis\",\n      \"journal\": \"The European journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple KO and knock-in mouse models with direct immunofluorescence localization and functional consequence\",\n      \"pmids\": [\"40919874\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Two pharmacological Kv2 inhibitors (RY785, a pore blocker, and GxTX, a voltage sensor modulator) used in combination distinguish Kv2/KvS heteromeric conductances from Kv2-only conductances; Kv6.4-containing channels are resistant to RY785 but sensitive to GxTX, and Kv2/Kv6.4 heteromers predominate in mouse and human dorsal root ganglion neurons.\",\n      \"method\": \"Pharmacology, electrophysiology (patch clamp), heterologous expression, mouse/human DRG neuron recordings\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — pharmacological dissection validated in heterologous system and native neurons across species\",\n      \"pmids\": [\"40423692\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In cortical parvalbumin (PV) neurons, Kv6.4 loss reduces action potential height and width, hyperpolarizes threshold and interspike potential, accelerates AP upstroke during repetitive firing, and alters GABA release and paired-pulse depression at PV-to-pyramidal synapses; effects are amplified during high-frequency firing, consistent with Kv6.4 modifying Kv2-mediated delayed rectifier current.\",\n      \"method\": \"Conditional knockout, patch-clamp electrophysiology, optogenetics, paired recording (PV→pyramidal synapses), postnatal developmental expression analysis\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with multiple orthogonal electrophysiological readouts including intrinsic and synaptic properties\",\n      \"pmids\": [\"41632839\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"In zebrafish, kcng4b-C1 mutation causes mild loss-of-function manifested by failure of kinocilia extension and ectopic otolith formation, while kcng4b-C2 mutation creates a gain-of-function allele with an ectopic seventh transmembrane domain that prevents otolith development and reduces kinocilia; demonstrating that the silent subunit Kcng4 modulates Kv2.1 channel activity to regulate ear development.\",\n      \"method\": \"Zebrafish mutant analysis, electrophysiology, developmental biology, in silico structural modeling\",\n      \"journal\": \"Developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — LOF and GOF alleles with defined developmental phenotypes in zebrafish ortholog, supported by structural modeling\",\n      \"pmids\": [\"38492873\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Kcng4+ neurons in the external globus pallidus (GPe) are a distinct subclass of PV+ neurons with unique electrophysiological properties; optogenetic perturbation of Kcng4+ neurons produces unique behavioral motor patterns distinct from other GPe neuron subtypes, and local collateral connectivity contributes to observed circuit effects.\",\n      \"method\": \"Transgenic Kcng4-Cre mouse line, electrophysiology, optogenetics, machine learning-based behavioral tracking\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — cell-type-specific optogenetics with behavioral readout, electrophysiological characterization\",\n      \"pmids\": [\"33731450\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"KCNG4 (Kv6.4) is a 'silent' or 'regulatory' voltage-gated potassium channel subunit that cannot form functional homotetrameric channels on its own but heteroassembles with Kv2.1 and/or Kv2.2 subunits—primarily in a 3:1 (Kv2:Kv6.4) stoichiometry determined by atypical S6 gate substitutions—via T1 domain interactions (requiring specific residues including conserved CDD aspartates and Kv2.1 His105) to form heterotetrameric channels with distinct biophysical properties including altered closed-state inactivation and voltage dependence; Kv6.4 localizes to ER-PM junctions in a Kv2-dependent manner, is expressed in specific neuronal populations (motoneurons, PV interneurons, DRG nociceptors), modulates nociceptor excitability, tunes PV neuron action potential waveform and synaptic output, and its loss causes male sterility through spermiogenesis defects.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"KCNG4 (Kv6.4) is an electrically silent voltage-gated potassium channel subunit that obligately heteroassembles with Kv2 family α-subunits to form functional heterotetrameric channels with modified gating properties in neurons and other cell types. Assembly with Kv2.1 requires conserved CDD aspartates in the T1 tetramerization domain and Kv2.1-His105 [PMID:19717558, PMID:19074135], while atypical residues in the Kv6.4 S6 activation gate restrict stoichiometry to a predominant 3:1 (Kv2:Kv6.4) ratio [PMID:30322883]; the incorporated Kv6.4 subunit confers distinct closed-state inactivation properties, shifts the voltage dependence of inactivation, and localizes to Kv2-dependent ER–plasma membrane junction clusters in motoneurons [PMID:26505474, PMID:40919874]. Kv6.4 modulates neuronal excitability across multiple circuits—tuning fast motor neuron identity downstream of Dlk1 signaling [PMID:24626931], shaping action potential waveform and GABAergic synaptic output of cortical parvalbumin interneurons [PMID:41632839], and regulating nociceptor firing threshold in DRG and uterine sensory neurons [PMID:32697988, PMID:40423692]—and its loss in mice causes male sterility through defective spermiogenesis [PMID:27677211].\",\n  \"teleology\": [\n    {\n      \"year\": 2008,\n      \"claim\": \"Identifying the molecular determinants of Kv2.1–Kv6.4 heteromerization resolved how a silent subunit selectively engages its partner: Kv2.1-His105 in the T1 domain is required for T1–T1 interaction with Kv6.4, while being dispensable for Kv2.1 homomerization.\",\n      \"evidence\": \"Yeast two-hybrid, FRET, co-immunoprecipitation, and two-electrode voltage clamp with H105 point mutants in heterologous cells\",\n      \"pmids\": [\"19074135\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of the H105-mediated interface not resolved at atomic level\", \"Whether H105 dependency generalizes to all KvS subunits not tested\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Conserved negatively charged aspartates (CDD motif) in the T1 A/B linker were shown to be essential for both Kv2.1 homotetrameric and Kv2.1/Kv6.4 heterotetrameric assembly, establishing that electrostatic interactions in the T1 domain are a shared assembly requirement.\",\n      \"evidence\": \"Site-directed charge-reversal mutagenesis with FRET, co-IP, and immunocytochemistry in HEK cells\",\n      \"pmids\": [\"19717558\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Role of the CDD motif in heteromers with other KvS members not systematically tested\", \"No structural data for the T1 heteromeric interface\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Linking Kv6.4 to a physiological circuit role, Dlk1 was shown to activate Kcng4 expression in fast motor neurons, establishing Kv6.4 as an effector that tunes delayed-rectifier currents and fast biophysical identity downstream of a Notch-inhibitory pathway.\",\n      \"evidence\": \"Transgenic mouse and chick in ovo electroporation with gain/loss-of-function, electrophysiology, and transcriptome analysis\",\n      \"pmids\": [\"24626931\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Kv6.4 is the sole mediator of the Dlk1-dependent fast signature is not definitively isolated\", \"Transcriptional mechanism linking Dlk1 to Kcng4 promoter not defined\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"The lower S6 segment of Kv6.4 was identified as the structural determinant of closed-state inactivation in Kv2.1/Kv6.4 heteromers, explaining the unique pharmacological sensitivity of these channels to 4-AP-mediated potentiation.\",\n      \"evidence\": \"Chimeric subunit substitutions between Kv6.4 and Kv9.3 with electrophysiology in Xenopus oocytes\",\n      \"pmids\": [\"26505474\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No structural model of the Kv6.4 S6 gate in the heteromeric context\", \"Physiological relevance of 4-AP potentiation in native neurons not addressed\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"KCNE5 was shown to form a tripartite complex with Kv2.1/Kv6.4, differentially modulating the heteromeric channel's kinetics versus the homomeric channel's current density, revealing an additional layer of heteromeric channel regulation by accessory subunits.\",\n      \"evidence\": \"FRET and electrophysiology with systematic co-expression of KCNE5 with Kv2.1 ± Kv6.4 in HEK293 cells\",\n      \"pmids\": [\"26242757\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological context of the tripartite complex not established in native tissue\", \"Other KCNE family members not tested with Kv2.1/Kv6.4\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Kcng4 knockout mice revealed a non-redundant in vivo role for Kv6.4 in spermiogenesis, as loss caused male sterility with severely abnormal sperm morphology and absent motility.\",\n      \"evidence\": \"Kcng4−/− knockout mouse with semen analysis and testicular histology\",\n      \"pmids\": [\"27677211\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The specific potassium current disrupted in spermatogenic cells not identified\", \"Whether the phenotype is Kv2-dependent or involves a non-canonical Kv6.4 function is unknown\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Atypical S6 gate residues in Kv6.4, rather than T1 domain incompatibility, were identified as the dominant constraint enforcing 3:1 (Kv2:Kv6.4) stoichiometry, resolving a long-standing question about why silent subunits occupy only one position per tetramer.\",\n      \"evidence\": \"Single-molecule imaging, chimeric T1/S6 swaps, electrophysiology, and evolutionary analysis across cnidarian orthologs\",\n      \"pmids\": [\"30322883\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of S6-gate incompatibility not resolved at atomic level\", \"Whether all KvS subunits share this S6-based stoichiometry mechanism not demonstrated\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"A rare human variant (KV6.4-Met419) was shown to act as a dominant-negative by failing to traffic to the plasma membrane while sequestering Kv2.1, linking Kv6.4 function to nociceptor excitability and uterine sensory neuron firing thresholds.\",\n      \"evidence\": \"Human SNP association, heterologous expression trafficking assays, electrophysiology in transfected DRG neurons, retrograde labeling of uterine afferents\",\n      \"pmids\": [\"32697988\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The full pain phenotype of carriers not characterized beyond association data\", \"Mechanism of ER retention of the Met419 variant not defined\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Kcng4-expressing GPe neurons were defined as a functionally distinct PV+ subclass with unique electrophysiological and behavioral output properties, establishing Kcng4 as a marker and functional modulator in basal ganglia circuits.\",\n      \"evidence\": \"Kcng4-Cre transgenic mice with optogenetics, electrophysiology, and machine learning behavioral analysis\",\n      \"pmids\": [\"33731450\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Causal contribution of Kv6.4 channel activity versus Kcng4 as a mere genetic marker not disentangled\", \"Downstream circuit effects on other basal ganglia nuclei not mapped\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"A migraine-associated L360P mutation in the Kv6.4 S4–S5 linker was shown to drastically suppress Kv2.1/Kv6.4 channel function, providing a molecular mechanism for a channelopathy-based migraine pathway through trigeminal Kv2/Kv6.4 dysfunction.\",\n      \"evidence\": \"Electrophysiology with monomeric and fixed-stoichiometry tandem dimer constructs in heterologous cells\",\n      \"pmids\": [\"39159549\", \"39201645\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Variant effect not validated in native trigeminal neurons\", \"Only heterologous overexpression systems used\", \"Human genetic evidence linking L360P to migraine not detailed in these studies\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Zebrafish kcng4b mutations demonstrated that Kv6.4 modulates Kv2.1 activity during inner ear development, with loss-of-function causing ectopic otolith formation and gain-of-function blocking otolith development.\",\n      \"evidence\": \"Zebrafish LOF and GOF mutant alleles with developmental phenotyping and structural modeling\",\n      \"pmids\": [\"38492873\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct electrophysiological measurement of Kv2/Kv6.4 currents in zebrafish otic vesicle not performed\", \"Relevance to mammalian ear development untested\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"In spinal motoneurons, Kv6.4 was shown to co-cluster with Kv2.1 and Kv2.2 at ER–PM junctions beneath C-bouton synapses, with clustering entirely dependent on Kv2 subunits and their ER-VAP binding motif, establishing the subcellular nanoarchitecture of native Kv2/Kv6.4 channels.\",\n      \"evidence\": \"Immunofluorescence in Kv2.1 KO, Kv2.2 KO, and Kv2.1-S590A knock-in mouse spinal cord sections\",\n      \"pmids\": [\"40919874\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of disrupted ER-PM clustering on motoneuron firing not tested\", \"Whether Kv6.4 itself contributes to ER-PM junction formation or is passively recruited is unresolved\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Pharmacological dissection using differential sensitivities to RY785 and GxTX established that Kv2/Kv6.4 heteromers constitute the predominant Kv2-containing conductance in mouse and human DRG nociceptors, providing tools to distinguish heteromeric from homomeric Kv2 currents in native neurons.\",\n      \"evidence\": \"Patch-clamp pharmacology in heterologous expression and native mouse/human DRG neurons\",\n      \"pmids\": [\"40423692\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Kv6.4 predominance extends to all DRG neuron subtypes not resolved\", \"RY785/GxTX selectivity for other KvS heteromers not fully profiled\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Conditional Kv6.4 deletion in cortical PV interneurons revealed that Kv6.4 shapes action potential height, width, and threshold during high-frequency firing and modulates GABAergic synaptic transmission at PV-to-pyramidal synapses, establishing a cell-autonomous role for the silent subunit in cortical inhibitory circuit function.\",\n      \"evidence\": \"Conditional knockout with patch-clamp, optogenetic activation, and paired PV→pyramidal recordings in cortical slices\",\n      \"pmids\": [\"41632839\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Network-level consequences of altered PV neuron output on cortical computation not assessed\", \"Whether compensatory changes in other KvS subunits occur in KO not examined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the atomic structure of the Kv2/Kv6.4 heterotetramer, the identity of the Kv2-dependent potassium current disrupted in spermiogenesis, and whether Kv6.4 contributes structurally to ER–PM junction formation beyond being passively recruited by Kv2.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No cryo-EM or X-ray structure of any Kv2/KvS heterotetramer\", \"Mechanism linking Kv6.4 loss to spermiogenesis failure undefined\", \"Kv6.4 role in ER-PM junction biogenesis versus passive localization not distinguished\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [2, 3, 5, 7, 8, 13]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [7, 11, 12]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [11]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": []}\n    ],\n    \"complexes\": [\n      \"Kv2.1/Kv6.4 heterotetrameric channel\",\n      \"Kv2.2/Kv6.4 heterotetrameric channel\",\n      \"Kv2.1/Kv6.4/KCNE5 tripartite complex\"\n    ],\n    \"partners\": [\n      \"KCNB1\",\n      \"KCNB2\",\n      \"KCNE5\",\n      \"DLK1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```\n\nWait, I need to fix the pathway field. The pathway slot should use Reactome IDs, not GO IDs. Let me reconsider. Looking at the discoveries, the relevant pathways would be:\n\n- Signal Transduction (due to Dlk1/Notch, ion channel modulation)\n- Neuronal System\n- Reproduction (spermiogenesis)\n\nLet me also reconsider the molecular_activity. Kv6.4 is a molecular function regulator (modulates Kv2 channels) - that's correct. Let me also check if \"transporter activity\" applies - technically Kv6.4 is silent and doesn't conduct on its own, so regulator is more appropriate.\n\n```json\n{\n  \"mechanistic_narrative\": \"KCNG4 (Kv6.4) is an electrically silent voltage-gated potassium channel subunit that obligately heteroassembles with Kv2 family α-subunits to form functional heterotetrameric channels with modified gating properties in neurons and other cell types. Assembly with Kv2.1 requires conserved CDD aspartates in the T1 tetramerization domain and Kv2.1-His105 [PMID:19717558, PMID:19074135], while atypical residues in the Kv6.4 S6 activation gate restrict stoichiometry to a predominant 3:1 (Kv2:Kv6.4) ratio [PMID:30322883]; the incorporated Kv6.4 subunit confers distinct closed-state inactivation properties, shifts the voltage dependence of inactivation, and localizes to Kv2-dependent ER–plasma membrane junction clusters in motoneurons [PMID:26505474, PMID:40919874]. Kv6.4 modulates neuronal excitability across multiple circuits—tuning fast motor neuron identity downstream of Dlk1 signaling [PMID:24626931], shaping action potential waveform and GABAergic synaptic output of cortical parvalbumin interneurons [PMID:41632839], and regulating nociceptor firing threshold in DRG and uterine sensory neurons [PMID:32697988, PMID:40423692]—and its loss in mice causes male sterility through defective spermiogenesis [PMID:27677211].\",\n  \"teleology\": [\n    {\n      \"year\": 2008,\n      \"claim\": \"Identifying the molecular determinants of Kv2.1–Kv6.4 heteromerization resolved how a silent subunit selectively engages its partner: Kv2.1-His105 in the T1 domain is required for T1–T1 interaction with Kv6.4, while being dispensable for Kv2.1 homomerization.\",\n      \"evidence\": \"Yeast two-hybrid, FRET, co-immunoprecipitation, and two-electrode voltage clamp with H105 point mutants in heterologous cells\",\n      \"pmids\": [\"19074135\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of the H105-mediated interface not resolved at atomic level\", \"Whether H105 dependency generalizes to all KvS subunits not tested\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Conserved negatively charged aspartates (CDD motif) in the T1 A/B linker were shown to be essential for both Kv2.1 homotetrameric and Kv2.1/Kv6.4 heterotetrameric assembly, establishing that electrostatic interactions in the T1 domain are a shared assembly requirement.\",\n      \"evidence\": \"Site-directed charge-reversal mutagenesis with FRET, co-IP, and immunocytochemistry in HEK cells\",\n      \"pmids\": [\"19717558\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Role of the CDD motif in heteromers with other KvS members not systematically tested\", \"No structural data for the T1 heteromeric interface\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Linking Kv6.4 to a physiological circuit role, Dlk1 was shown to activate Kcng4 expression in fast motor neurons, establishing Kv6.4 as an effector that tunes delayed-rectifier currents and fast biophysical identity downstream of a Notch-inhibitory pathway.\",\n      \"evidence\": \"Transgenic mouse and chick in ovo electroporation with gain/loss-of-function, electrophysiology, and transcriptome analysis\",\n      \"pmids\": [\"24626931\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Kv6.4 is the sole mediator of the Dlk1-dependent fast signature is not definitively isolated\", \"Transcriptional mechanism linking Dlk1 to Kcng4 promoter not defined\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"The lower S6 segment of Kv6.4 was identified as the structural determinant of closed-state inactivation in Kv2.1/Kv6.4 heteromers, and KCNE5 was shown to form a modulatory tripartite complex with Kv2.1/Kv6.4, revealing multiple layers of heteromeric channel regulation.\",\n      \"evidence\": \"Chimeric Kv6.4/Kv9.3 substitutions with electrophysiology in oocytes; FRET and electrophysiology with KCNE5 co-expression in HEK293 cells\",\n      \"pmids\": [\"26505474\", \"26242757\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No structural model of the Kv6.4 S6 gate in the heteromeric context\", \"Physiological context of the KCNE5 tripartite complex not established in native tissue\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Kcng4 knockout mice revealed a non-redundant in vivo role for Kv6.4 in spermiogenesis, as loss caused male sterility with severely abnormal sperm morphology and absent motility.\",\n      \"evidence\": \"Kcng4−/− knockout mouse with semen analysis and testicular histology\",\n      \"pmids\": [\"27677211\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The specific potassium current disrupted in spermatogenic cells not identified\", \"Whether the phenotype is Kv2-dependent or involves a non-canonical Kv6.4 function is unknown\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Atypical S6 gate residues in Kv6.4, rather than T1 domain incompatibility, were identified as the dominant constraint enforcing 3:1 (Kv2:Kv6.4) stoichiometry, resolving a long-standing question about why silent subunits occupy only one position per tetramer.\",\n      \"evidence\": \"Single-molecule imaging, chimeric T1/S6 swaps, electrophysiology, and evolutionary analysis across cnidarian orthologs\",\n      \"pmids\": [\"30322883\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of S6-gate incompatibility not resolved at atomic level\", \"Whether all KvS subunits share this S6-based stoichiometry mechanism not demonstrated\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"A rare human variant (KV6.4-Met419) was shown to act as a dominant-negative by failing to traffic to the plasma membrane while sequestering Kv2.1, linking Kv6.4 function to nociceptor excitability and uterine sensory neuron firing thresholds.\",\n      \"evidence\": \"Human SNP association, heterologous expression trafficking assays, electrophysiology in transfected DRG neurons, retrograde labeling of uterine afferents\",\n      \"pmids\": [\"32697988\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The full pain phenotype of carriers not characterized beyond association data\", \"Mechanism of ER retention of the Met419 variant not defined\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Kcng4-expressing GPe neurons were defined as a functionally distinct PV+ subclass with unique electrophysiological and behavioral output properties, establishing Kcng4 as a marker for a basal ganglia neuron subtype.\",\n      \"evidence\": \"Kcng4-Cre transgenic mice with optogenetics, electrophysiology, and machine learning behavioral analysis\",\n      \"pmids\": [\"33731450\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Causal contribution of Kv6.4 channel activity versus Kcng4 as a mere genetic marker not disentangled\", \"Downstream circuit effects on other basal ganglia nuclei not mapped\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"The migraine-associated L360P mutation in the Kv6.4 S4–S5 linker drastically suppresses Kv2.1/Kv6.4 channel function, and zebrafish kcng4b mutations demonstrated developmental roles in inner ear otolith formation, expanding the phenotypic spectrum of Kv6.4 dysfunction.\",\n      \"evidence\": \"Electrophysiology with tandem dimer constructs in heterologous cells; zebrafish LOF and GOF mutant alleles with developmental phenotyping\",\n      \"pmids\": [\"39159549\", \"39201645\", \"38492873\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"L360P variant effect not validated in native trigeminal neurons\", \"Relevance of zebrafish ear phenotype to mammalian development untested\", \"Human genetic causality for migraine not definitively established\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Kv6.4 was shown to co-cluster with Kv2.1/Kv2.2 at ER–PM junctions in motoneurons in a Kv2-dependent manner, Kv2/Kv6.4 heteromers were identified as the predominant delayed-rectifier conductance in DRG nociceptors, and conditional Kv6.4 deletion in PV interneurons revealed cell-autonomous roles in shaping AP waveform and synaptic output during high-frequency firing.\",\n      \"evidence\": \"KO and knock-in mouse immunofluorescence; pharmacological dissection in mouse/human DRG neurons; conditional KO with patch-clamp and paired synaptic recordings in cortical slices\",\n      \"pmids\": [\"40919874\", \"40423692\", \"41632839\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of disrupted ER-PM clustering on motoneuron firing not tested\", \"Whether compensatory KvS subunit changes occur in Kv6.4 KO not examined\", \"Network-level consequences of altered PV neuron output not assessed\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the atomic structure of the Kv2/Kv6.4 heterotetramer, the identity of the Kv2-dependent current disrupted in spermiogenesis, and whether Kv6.4 contributes structurally to ER–PM junction formation or is passively recruited by Kv2.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No cryo-EM or X-ray structure of any Kv2/KvS heterotetramer\", \"Mechanism linking Kv6.4 loss to spermiogenesis failure undefined\", \"Kv6.4 role in ER-PM junction biogenesis versus passive localization not distinguished\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [2, 3, 5, 7, 8, 9, 10, 13]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [7, 11, 12]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [11]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [8, 13, 15]},\n      {\"term_id\": \"R-HSA-1474165\", \"supporting_discovery_ids\": [6]}\n    ],\n    \"complexes\": [\n      \"Kv2.1/Kv6.4 heterotetrameric channel\",\n      \"Kv2.2/Kv6.4 heterotetrameric channel\",\n      \"Kv2.1/Kv6.4/KCNE5 tripartite complex\"\n    ],\n    \"partners\": [\n      \"KCNB1\",\n      \"KCNB2\",\n      \"KCNE5\",\n      \"DLK1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}