{"gene":"KCTD7","run_date":"2026-06-10T02:59:49","timeline":{"discoveries":[{"year":2011,"finding":"KCTD7 expression hyperpolarizes the cell membrane and reduces the excitability of transfected neurons, as demonstrated by patch clamp experiments. The effect on resting membrane potential is mediated through K+ conductance changes.","method":"Patch clamp electrophysiology in transfected neurons","journal":"Molecular neurobiology","confidence":"Medium","confidence_rationale":"Tier 1-2 / Weak — direct electrophysiology experiment in transfected neurons, single lab, single method","pmids":["21710140"],"is_preprint":false},{"year":2011,"finding":"KCTD7 directly interacts with Cullin-3 (a ubiquitin-ligase component), as demonstrated by co-immunoprecipitation assays.","method":"Co-immunoprecipitation","journal":"Molecular neurobiology","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP replicated independently across multiple papers (PMIDs 21710140, 22748208, 30295347, 35921411, 36964131)","pmids":["21710140","22748208","30295347","35921411","36964131"],"is_preprint":false},{"year":2012,"finding":"The disease-causing missense mutation p.Arg184Cys in KCTD7 alters its subcellular localization and abrogates interaction with Cullin-3, linking loss of this interaction to NCL pathogenesis.","method":"Co-immunoprecipitation and subcellular localization imaging of mutant vs wild-type KCTD7","journal":"American journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP and localization assay in cell-based system, single lab, two orthogonal methods","pmids":["22748208"],"is_preprint":false},{"year":2012,"finding":"Three patient missense mutations in KCTD7 did not affect its cytosolic subcellular distribution, indicating that these mutations do not alter localization.","method":"Subcellular localization imaging of mutant KCTD7 in cellular cultures","journal":"Journal of medical genetics","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — direct imaging experiment, single lab, result is negative for localization change","pmids":["22693283"],"is_preprint":false},{"year":2016,"finding":"Wild-type KCTD7 hyperpolarizes cells in a K+-dependent manner and regulates activity of the neuronal glutamine transporter SAT2 (Slc38a2) when expressed in Xenopus laevis oocytes. The disease-causing frameshift variant F232fs impairs K+ fluxes and obliterates SAT2-dependent glutamine transport. Four additional disease variants (R94W, R184C, N273I, Y276C) also showed impaired K+ flux regulation.","method":"Heterologous expression and electrophysiology/transport assays in Xenopus laevis oocytes","journal":"Brain : a journal of neurology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — reconstituted function in Xenopus oocytes with multiple patient variant alleles tested, two orthogonal functional readouts (K+ flux and glutamine transport), single lab","pmids":["27742667"],"is_preprint":false},{"year":2018,"finding":"Patient-derived KCTD7-deficient fibroblasts and yeast lacking Whi2 (a protein with sequence similarity to KCTD7) both exhibit impaired autophagy, consistent with brain pathology, suggesting KCTD7 has a conserved role in the autophagy-lysosome pathway.","method":"Cell-based functional assays in patient fibroblasts and knockout yeast, electron microscopy","journal":"Annals of neurology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — orthogonal models (patient fibroblasts + yeast), two methods (functional assay + EM), single lab","pmids":["30295347"],"is_preprint":false},{"year":2019,"finding":"Neuronal Kctd7 (absent from vessels) is required for proper retinal vascular patterning; deletion of Kctd7 in mice causes defective superficial and deep vascular layer development, increased bipolar cell number, and retinal function deficits, demonstrating that neuronal Kctd7 drives vascular growth and patterning.","method":"Kctd7 knockout mouse, immunohistochemistry, electroretinography, vascular imaging","journal":"Neurochemistry international","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic KO mouse with multiple phenotypic readouts, single lab","pmids":["31175897"],"is_preprint":false},{"year":2022,"finding":"The CRL3-KCTD7 E3 ubiquitin ligase complex ubiquitinates CLN5 and targets it for proteasomal degradation. Patient-derived KCTD7 mutations disrupt either KCTD7-CUL3 or KCTD7-CLN5 interactions, leading to CLN5 accumulation in the ER, which in turn disrupts the CLN6/8-lysosomal enzyme interaction and impairs ER-to-Golgi trafficking of lysosomal enzymes.","method":"Co-immunoprecipitation, ubiquitination assays, subcellular fractionation/trafficking assays in KCTD7-deficient cells with patient-derived mutations","journal":"Science advances","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — multiple orthogonal biochemical methods (Co-IP, ubiquitination assay, trafficking assay), mechanistic pathway established with patient variants, single lab","pmids":["35921411","36368077"],"is_preprint":false},{"year":2022,"finding":"Kctd7 is required for Purkinje cell survival in the cerebellum; Kctd7-deficient mice develop seizures, locomotor defects, selective Purkinje cell degeneration, and cerebellar microvascular disorganization.","method":"Kctd7 knockout mouse, histology, EEG, behavioral assays","journal":"Disease models & mechanisms","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic KO mouse with multiple phenotypic readouts, single lab","pmids":["35972048"],"is_preprint":false},{"year":2023,"finding":"KCTD7 works in complex with Cullin-3 and Rbx1 to execute atypical, non-degradative ubiquitination of calpain 1 (at K398) and calpain 2 (at K280 and K674). KCTD7 mediates K6-, K27-, K29-, and K63-linked ubiquitin chains on calpain 1, and K6-linked chains on calpain 2. Loss of this ubiquitination leads to calpain hyperactivation, aberrant substrate cleavage, and caspase-3 activation. Kctd7 CRISPR/Cas9 knockout mice recapitulate human disease, and pharmacological calpain inhibition largely prevents behavioral and neurodegenerative phenotypes in these mice. CUL3-KCTD7 mediates ubiquitination of all ubiquitous calpains.","method":"In vitro ubiquitination assays, single-lysine ubiquitin mutants, Co-IP, CRISPR/Cas9 KO mice, pharmacological rescue, caspase-3 activity assay, proteomics (mass spectrometry)","journal":"Cell discovery","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstitution of ubiquitination with mutagenesis, in vivo genetic KO with pharmacological rescue, multiple orthogonal methods in a single rigorous study","pmids":["36964131"],"is_preprint":false},{"year":2021,"finding":"Whole-cell patch-clamp analysis of neuroblastoma cells overexpressing patient KCTD7 variant alleles demonstrated aberrant potassium regulation, confirming that disease variants impair K+ conductance. Kctd7 knockout zebrafish showed global dysregulation of gene expression and increased c-fos transcription (correlated with seizure activity).","method":"Whole-cell patch-clamp in neuroblastoma cells, kctd7 knockout zebrafish with transcriptomic analysis","journal":"Journal of neurogenetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct electrophysiology with patient variants, orthogonal animal model, single lab","pmids":["33970744"],"is_preprint":false}],"current_model":"KCTD7 is a cytosolic adaptor subunit of the CUL3-RBX1 E3 ubiquitin ligase complex that (1) negatively regulates calpain activity via non-degradative, atypical ubiquitination of calpains 1 and 2 at specific lysine residues; (2) targets CLN5 for ubiquitin-proteasomal degradation, thereby maintaining lysosomal enzyme trafficking from the ER to Golgi; (3) modulates neuronal K+ conductance and hyperpolarizes the resting membrane potential, also regulating the glutamine transporter SAT2; and (4) supports Purkinje cell survival and neurovascular patterning—with loss-of-function mutations in KCTD7 causing progressive myoclonic epilepsy (EPM3) and neuronal ceroid lipofuscinosis (CLN14) through calpain hyperactivation, lysosomal dysfunction, and impaired autophagy."},"narrative":{"mechanistic_narrative":"KCTD7 is a cytosolic substrate-adaptor subunit of a CUL3-RBX1 (CRL3) E3 ubiquitin ligase that governs neuronal proteostasis and excitability, and its loss-of-function causes progressive myoclonic epilepsy and neuronal ceroid lipofuscinosis [PMID:21710140, PMID:22748208, PMID:30295347, PMID:35921411, PMID:36964131]. KCTD7 binds Cullin-3 directly, an interaction abrogated by the disease-causing p.Arg184Cys mutation [PMID:21710140, PMID:22748208, PMID:30295347, PMID:35921411, PMID:36964131]. As the adaptor of this complex, KCTD7 directs two distinct ubiquitination programs: it executes atypical, non-degradative ubiquitination of the ubiquitous calpains—modifying calpain 1 at K398 with K6/K27/K29/K63 chains and calpain 2 with K6 chains—so that loss of KCTD7 drives calpain hyperactivation, aberrant substrate cleavage, and caspase-3 activation [PMID:36964131]; and it targets CLN5 for proteasomal degradation, with patient mutations that disrupt KCTD7-CUL3 or KCTD7-CLN5 binding causing CLN5 to accumulate in the ER, disrupting CLN6/8-dependent lysosomal enzyme trafficking from ER to Golgi [PMID:35921411, PMID:36368077]. Consistent with these proteostatic roles, KCTD7-deficient cells exhibit impaired autophagy [PMID:30295347]. Independently, KCTD7 hyperpolarizes the resting membrane potential and lowers neuronal excitability through K+ conductance, and regulates the glutamine transporter SAT2, with multiple patient variants impairing K+ flux and glutamine transport [PMID:21710140, PMID:27742667]. In vivo, Kctd7 is required for Purkinje cell survival, cerebellar and retinal microvascular patterning, and normal neuronal function, and pharmacological calpain inhibition largely prevents the neurodegenerative phenotype of Kctd7 knockout mice [PMID:35972048, PMID:31175897, PMID:36964131].","teleology":[{"year":2011,"claim":"Established that KCTD7 is functionally an ion-conductance modulator and physically an E3-ligase adaptor, answering what molecular activities the protein carries.","evidence":"Patch clamp in transfected neurons plus Co-IP with Cullin-3","pmids":["21710140"],"confidence":"High","gaps":["Whether K+ effect is direct channel modulation or indirect was not resolved","No structural basis for the CUL3 interaction"]},{"year":2012,"claim":"Linked disease pathogenesis to loss of the KCTD7-CUL3 interaction, connecting a clinical mutation to a defined molecular lesion.","evidence":"Co-IP and localization imaging of p.Arg184Cys vs wild-type KCTD7","pmids":["22748208"],"confidence":"Medium","gaps":["Did not identify the ubiquitination substrate downstream of CUL3 binding","Single lab, cell-based system"]},{"year":2012,"claim":"Showed that several patient mutations do not perturb cytosolic localization, indicating mislocalization is not the universal disease mechanism.","evidence":"Subcellular localization imaging of mutant KCTD7 in culture","pmids":["22693283"],"confidence":"Medium","gaps":["Negative result; functional consequence of these mutations not tested","No biochemical readout"]},{"year":2016,"claim":"Reconstituted KCTD7's K+-dependent hyperpolarization and SAT2/glutamine-transport regulation and demonstrated multiple patient variants impair these functions, tying excitability defects to disease.","evidence":"Heterologous expression and electrophysiology/transport assays in Xenopus oocytes with multiple variant alleles","pmids":["27742667"],"confidence":"High","gaps":["Molecular mechanism by which KCTD7 affects K+ flux and SAT2 not defined","Relationship to its E3-adaptor role unclear"]},{"year":2018,"claim":"Implicated KCTD7 in the autophagy-lysosome pathway across species, broadening its role from excitability to proteostasis.","evidence":"Functional assays and EM in patient fibroblasts and Whi2-deficient yeast","pmids":["30295347"],"confidence":"Medium","gaps":["Molecular target linking KCTD7 to autophagy not identified","Yeast Whi2 similarity is suggestive, not mechanistic"]},{"year":2019,"claim":"Demonstrated a non-cell-autonomous developmental role, showing neuronal Kctd7 drives retinal vascular patterning.","evidence":"Kctd7 knockout mouse with IHC, electroretinography, and vascular imaging","pmids":["31175897"],"confidence":"Medium","gaps":["Signal mediating neuron-to-vessel communication unknown","Connection to ubiquitination/K+ activities not established"]},{"year":2021,"claim":"Confirmed in a neuronal cell type that disease variants impair K+ regulation and that Kctd7 loss produces seizure-correlated transcriptional changes in vivo.","evidence":"Whole-cell patch-clamp in neuroblastoma cells and kctd7 knockout zebrafish transcriptomics","pmids":["33970744"],"confidence":"Medium","gaps":["Transcriptomic changes are downstream and non-specific","Direct channel target not identified"]},{"year":2022,"claim":"Defined a substrate of the CRL3-KCTD7 ligase, showing it degrades CLN5 to maintain lysosomal enzyme trafficking, mechanistically connecting KCTD7 loss to lysosomal dysfunction.","evidence":"Co-IP, ubiquitination and trafficking assays in KCTD7-deficient cells with patient mutations","pmids":["35921411","36368077"],"confidence":"High","gaps":["Whether CLN5 turnover defects fully account for disease versus calpain effects unresolved","Single lab"]},{"year":2022,"claim":"Established a required role for Kctd7 in Purkinje cell survival and recapitulated the human neurodegenerative and seizure phenotype in mice.","evidence":"Kctd7 knockout mouse with histology, EEG, and behavioral assays","pmids":["35972048"],"confidence":"Medium","gaps":["Cause of selective Purkinje vulnerability not defined","Molecular driver of degeneration not pinned down in this study"]},{"year":2023,"claim":"Identified calpains as direct substrates and showed KCTD7 mediates atypical non-degradative ubiquitination restraining calpain activity, with calpain inhibition rescuing the knockout phenotype—establishing a treatable mechanistic axis.","evidence":"In vitro ubiquitination with single-lysine mutants, proteomics, CRISPR/Cas9 KO mice, and pharmacological calpain-inhibitor rescue","pmids":["36964131"],"confidence":"High","gaps":["How the non-degradative ubiquitin chains restrain calpain activity mechanistically is unresolved","Relative contribution of calpain versus CLN5 axes to disease not quantified"]},{"year":null,"claim":"How KCTD7's E3-adaptor activity, its K+/SAT2 regulatory function, and its autophagy and vascular-patterning roles are mechanistically integrated remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of the KCTD7-CUL3 complex or substrate engagement","Mechanism coupling KCTD7 to K+ conductance and SAT2 unknown","Whether ion-conductance and ubiquitination roles are independent or linked"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[7,9]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[1,7,9]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,4,9]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[2,3]}],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[7,9]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[5]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[0,4]}],"complexes":["CRL3 (CUL3-RBX1-KCTD7) E3 ubiquitin ligase"],"partners":["CUL3","RBX1","CLN5","CAPN1","CAPN2","SLC38A2"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q96MP8","full_name":"BTB/POZ domain-containing protein KCTD7","aliases":[],"length_aa":289,"mass_kda":33.1,"function":"May be involved in the control of excitability of cortical neurons","subcellular_location":"Cell membrane; Cytoplasm, cytosol","url":"https://www.uniprot.org/uniprotkb/Q96MP8/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/KCTD7","classification":"Not Classified","n_dependent_lines":5,"n_total_lines":1208,"dependency_fraction":0.0041390728476821195},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/KCTD7","total_profiled":1310},"omim":[{"mim_id":"611726","title":"EPILEPSY, PROGRESSIVE MYOCLONIC, 3, WITH OR WITHOUT INTRACELLULAR INCLUSIONS; EPM3","url":"https://www.omim.org/entry/611726"},{"mim_id":"611725","title":"POTASSIUM CHANNEL TETRAMERIZATION DOMAIN-CONTAINING PROTEIN 7; KCTD7","url":"https://www.omim.org/entry/611725"},{"mim_id":"256730","title":"CEROID LIPOFUSCINOSIS, NEURONAL, 1; CLN1","url":"https://www.omim.org/entry/256730"},{"mim_id":"254800","title":"MYOCLONIC EPILEPSY OF UNVERRICHT AND LUNDBORG","url":"https://www.omim.org/entry/254800"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"retina","ntpm":60.9}],"url":"https://www.proteinatlas.org/search/KCTD7"},"hgnc":{"alias_symbol":["FLJ32069","EPM3","CLN14"],"prev_symbol":[]},"alphafold":{"accession":"Q96MP8","domains":[{"cath_id":"3.30.710.10","chopping":"51-144","consensus_level":"high","plddt":96.0824,"start":51,"end":144},{"cath_id":"-","chopping":"156-199_225-286","consensus_level":"high","plddt":89.688,"start":156,"end":286}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q96MP8","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q96MP8-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q96MP8-F1-predicted_aligned_error_v6.png","plddt_mean":81.12},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=KCTD7","jax_strain_url":"https://www.jax.org/strain/search?query=KCTD7"},"sequence":{"accession":"Q96MP8","fasta_url":"https://rest.uniprot.org/uniprotkb/Q96MP8.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q96MP8/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q96MP8"}},"corpus_meta":[{"pmid":"22748208","id":"PMC_22748208","title":"A homozygous mutation in KCTD7 links neuronal ceroid lipofuscinosis to the ubiquitin-proteasome system.","date":"2012","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/22748208","citation_count":89,"is_preprint":false},{"pmid":"22693283","id":"PMC_22693283","title":"Novel mutations consolidate KCTD7 as a progressive myoclonus epilepsy gene.","date":"2012","source":"Journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/22693283","citation_count":61,"is_preprint":false},{"pmid":"21710140","id":"PMC_21710140","title":"Progressive myoclonic epilepsy-associated gene KCTD7 is a regulator of potassium conductance in neurons.","date":"2011","source":"Molecular neurobiology","url":"https://pubmed.ncbi.nlm.nih.gov/21710140","citation_count":59,"is_preprint":false},{"pmid":"30295347","id":"PMC_30295347","title":"KCTD7 deficiency defines a distinct neurodegenerative disorder with a conserved autophagy-lysosome defect.","date":"2018","source":"Annals of neurology","url":"https://pubmed.ncbi.nlm.nih.gov/30295347","citation_count":51,"is_preprint":false},{"pmid":"22638565","id":"PMC_22638565","title":"A compound heterozygous missense mutation and a large deletion in the KCTD7 gene presenting as an opsoclonus-myoclonus ataxia-like syndrome.","date":"2012","source":"Journal of neurology","url":"https://pubmed.ncbi.nlm.nih.gov/22638565","citation_count":45,"is_preprint":false},{"pmid":"22606975","id":"PMC_22606975","title":"Novel mutation in potassium channel related gene KCTD7 and progressive myoclonic epilepsy.","date":"2012","source":"Annals of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/22606975","citation_count":32,"is_preprint":false},{"pmid":"27742667","id":"PMC_27742667","title":"Pathogenic variants in KCTD7 perturb neuronal K+ fluxes and glutamine transport.","date":"2016","source":"Brain : a journal of neurology","url":"https://pubmed.ncbi.nlm.nih.gov/27742667","citation_count":30,"is_preprint":false},{"pmid":"25060828","id":"PMC_25060828","title":"Linkage analysis and exome sequencing identify a novel mutation in KCTD7 in patients with progressive myoclonus epilepsy with ataxia.","date":"2014","source":"Epilepsia","url":"https://pubmed.ncbi.nlm.nih.gov/25060828","citation_count":28,"is_preprint":false},{"pmid":"27629772","id":"PMC_27629772","title":"KCTD7-related progressive myoclonus epilepsy.","date":"2016","source":"Epileptic disorders : international epilepsy journal with videotape","url":"https://pubmed.ncbi.nlm.nih.gov/27629772","citation_count":24,"is_preprint":false},{"pmid":"35921411","id":"PMC_35921411","title":"KCTD7 mutations impair the trafficking of lysosomal enzymes through CLN5 accumulation to cause neuronal ceroid lipofuscinoses.","date":"2022","source":"Science advances","url":"https://pubmed.ncbi.nlm.nih.gov/35921411","citation_count":22,"is_preprint":false},{"pmid":"30500434","id":"PMC_30500434","title":"Progressive myoclonus epilepsy and ceroidolipofuscinosis 14: The multifaceted phenotypic spectrum of KCTD7-related disorders.","date":"2018","source":"European journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/30500434","citation_count":18,"is_preprint":false},{"pmid":"36964131","id":"PMC_36964131","title":"Calpain activity is negatively regulated by a KCTD7-Cullin-3 complex via non-degradative ubiquitination.","date":"2023","source":"Cell discovery","url":"https://pubmed.ncbi.nlm.nih.gov/36964131","citation_count":11,"is_preprint":false},{"pmid":"38231304","id":"PMC_38231304","title":"KCTD7-related progressive myoclonic epilepsy: Report of 42 cases and review of literature.","date":"2024","source":"Epilepsia","url":"https://pubmed.ncbi.nlm.nih.gov/38231304","citation_count":9,"is_preprint":false},{"pmid":"35972048","id":"PMC_35972048","title":"Kctd7 deficiency induces myoclonic seizures associated with Purkinje cell death and microvascular defects.","date":"2022","source":"Disease models & mechanisms","url":"https://pubmed.ncbi.nlm.nih.gov/35972048","citation_count":9,"is_preprint":false},{"pmid":"31175897","id":"PMC_31175897","title":"Progressive myoclonic epilepsy-associated gene Kctd7 regulates retinal neurovascular patterning and function.","date":"2019","source":"Neurochemistry international","url":"https://pubmed.ncbi.nlm.nih.gov/31175897","citation_count":9,"is_preprint":false},{"pmid":"36368077","id":"PMC_36368077","title":"Lysosomal dysfunction, autophagic defects, and CLN5 accumulation underlie the pathogenesis of KCTD7-mutated neuronal ceroid lipofuscinoses.","date":"2022","source":"Autophagy","url":"https://pubmed.ncbi.nlm.nih.gov/36368077","citation_count":9,"is_preprint":false},{"pmid":"34866617","id":"PMC_34866617","title":"KCTD7-related progressive myoclonic epilepsy: report of three Indian families and review of literature.","date":"2022","source":"Clinical dysmorphology","url":"https://pubmed.ncbi.nlm.nih.gov/34866617","citation_count":8,"is_preprint":false},{"pmid":"30825425","id":"PMC_30825425","title":"Exome sequencing identifies compound heterozygous KCTD7 mutations in a girl with progressivemyoclonus epilepsy.","date":"2019","source":"Clinica chimica acta; international journal of clinical chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/30825425","citation_count":8,"is_preprint":false},{"pmid":"33970744","id":"PMC_33970744","title":"Compound heterozygous KCTD7 variants in progressive myoclonus epilepsy.","date":"2021","source":"Journal of 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reports","url":"https://pubmed.ncbi.nlm.nih.gov/40123863","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":13888,"output_tokens":2736,"usd":0.041352,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9949,"output_tokens":3348,"usd":0.066723,"stage2_stop_reason":"end_turn"},"total_usd":0.108075,"stage1_batch_id":"msgbatch_01BbTCMyrRPyhtEq6b1MdwCN","stage2_batch_id":"msgbatch_011dEed5bbxYvTAaQWKJevxu","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2011,\n      \"finding\": \"KCTD7 expression hyperpolarizes the cell membrane and reduces the excitability of transfected neurons, as demonstrated by patch clamp experiments. The effect on resting membrane potential is mediated through K+ conductance changes.\",\n      \"method\": \"Patch clamp electrophysiology in transfected neurons\",\n      \"journal\": \"Molecular neurobiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 / Weak — direct electrophysiology experiment in transfected neurons, single lab, single method\",\n      \"pmids\": [\"21710140\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"KCTD7 directly interacts with Cullin-3 (a ubiquitin-ligase component), as demonstrated by co-immunoprecipitation assays.\",\n      \"method\": \"Co-immunoprecipitation\",\n      \"journal\": \"Molecular neurobiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP replicated independently across multiple papers (PMIDs 21710140, 22748208, 30295347, 35921411, 36964131)\",\n      \"pmids\": [\"21710140\", \"22748208\", \"30295347\", \"35921411\", \"36964131\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"The disease-causing missense mutation p.Arg184Cys in KCTD7 alters its subcellular localization and abrogates interaction with Cullin-3, linking loss of this interaction to NCL pathogenesis.\",\n      \"method\": \"Co-immunoprecipitation and subcellular localization imaging of mutant vs wild-type KCTD7\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP and localization assay in cell-based system, single lab, two orthogonal methods\",\n      \"pmids\": [\"22748208\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Three patient missense mutations in KCTD7 did not affect its cytosolic subcellular distribution, indicating that these mutations do not alter localization.\",\n      \"method\": \"Subcellular localization imaging of mutant KCTD7 in cellular cultures\",\n      \"journal\": \"Journal of medical genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct imaging experiment, single lab, result is negative for localization change\",\n      \"pmids\": [\"22693283\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Wild-type KCTD7 hyperpolarizes cells in a K+-dependent manner and regulates activity of the neuronal glutamine transporter SAT2 (Slc38a2) when expressed in Xenopus laevis oocytes. The disease-causing frameshift variant F232fs impairs K+ fluxes and obliterates SAT2-dependent glutamine transport. Four additional disease variants (R94W, R184C, N273I, Y276C) also showed impaired K+ flux regulation.\",\n      \"method\": \"Heterologous expression and electrophysiology/transport assays in Xenopus laevis oocytes\",\n      \"journal\": \"Brain : a journal of neurology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — reconstituted function in Xenopus oocytes with multiple patient variant alleles tested, two orthogonal functional readouts (K+ flux and glutamine transport), single lab\",\n      \"pmids\": [\"27742667\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Patient-derived KCTD7-deficient fibroblasts and yeast lacking Whi2 (a protein with sequence similarity to KCTD7) both exhibit impaired autophagy, consistent with brain pathology, suggesting KCTD7 has a conserved role in the autophagy-lysosome pathway.\",\n      \"method\": \"Cell-based functional assays in patient fibroblasts and knockout yeast, electron microscopy\",\n      \"journal\": \"Annals of neurology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — orthogonal models (patient fibroblasts + yeast), two methods (functional assay + EM), single lab\",\n      \"pmids\": [\"30295347\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Neuronal Kctd7 (absent from vessels) is required for proper retinal vascular patterning; deletion of Kctd7 in mice causes defective superficial and deep vascular layer development, increased bipolar cell number, and retinal function deficits, demonstrating that neuronal Kctd7 drives vascular growth and patterning.\",\n      \"method\": \"Kctd7 knockout mouse, immunohistochemistry, electroretinography, vascular imaging\",\n      \"journal\": \"Neurochemistry international\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO mouse with multiple phenotypic readouts, single lab\",\n      \"pmids\": [\"31175897\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"The CRL3-KCTD7 E3 ubiquitin ligase complex ubiquitinates CLN5 and targets it for proteasomal degradation. Patient-derived KCTD7 mutations disrupt either KCTD7-CUL3 or KCTD7-CLN5 interactions, leading to CLN5 accumulation in the ER, which in turn disrupts the CLN6/8-lysosomal enzyme interaction and impairs ER-to-Golgi trafficking of lysosomal enzymes.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assays, subcellular fractionation/trafficking assays in KCTD7-deficient cells with patient-derived mutations\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — multiple orthogonal biochemical methods (Co-IP, ubiquitination assay, trafficking assay), mechanistic pathway established with patient variants, single lab\",\n      \"pmids\": [\"35921411\", \"36368077\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Kctd7 is required for Purkinje cell survival in the cerebellum; Kctd7-deficient mice develop seizures, locomotor defects, selective Purkinje cell degeneration, and cerebellar microvascular disorganization.\",\n      \"method\": \"Kctd7 knockout mouse, histology, EEG, behavioral assays\",\n      \"journal\": \"Disease models & mechanisms\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO mouse with multiple phenotypic readouts, single lab\",\n      \"pmids\": [\"35972048\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"KCTD7 works in complex with Cullin-3 and Rbx1 to execute atypical, non-degradative ubiquitination of calpain 1 (at K398) and calpain 2 (at K280 and K674). KCTD7 mediates K6-, K27-, K29-, and K63-linked ubiquitin chains on calpain 1, and K6-linked chains on calpain 2. Loss of this ubiquitination leads to calpain hyperactivation, aberrant substrate cleavage, and caspase-3 activation. Kctd7 CRISPR/Cas9 knockout mice recapitulate human disease, and pharmacological calpain inhibition largely prevents behavioral and neurodegenerative phenotypes in these mice. CUL3-KCTD7 mediates ubiquitination of all ubiquitous calpains.\",\n      \"method\": \"In vitro ubiquitination assays, single-lysine ubiquitin mutants, Co-IP, CRISPR/Cas9 KO mice, pharmacological rescue, caspase-3 activity assay, proteomics (mass spectrometry)\",\n      \"journal\": \"Cell discovery\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstitution of ubiquitination with mutagenesis, in vivo genetic KO with pharmacological rescue, multiple orthogonal methods in a single rigorous study\",\n      \"pmids\": [\"36964131\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Whole-cell patch-clamp analysis of neuroblastoma cells overexpressing patient KCTD7 variant alleles demonstrated aberrant potassium regulation, confirming that disease variants impair K+ conductance. Kctd7 knockout zebrafish showed global dysregulation of gene expression and increased c-fos transcription (correlated with seizure activity).\",\n      \"method\": \"Whole-cell patch-clamp in neuroblastoma cells, kctd7 knockout zebrafish with transcriptomic analysis\",\n      \"journal\": \"Journal of neurogenetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct electrophysiology with patient variants, orthogonal animal model, single lab\",\n      \"pmids\": [\"33970744\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"KCTD7 is a cytosolic adaptor subunit of the CUL3-RBX1 E3 ubiquitin ligase complex that (1) negatively regulates calpain activity via non-degradative, atypical ubiquitination of calpains 1 and 2 at specific lysine residues; (2) targets CLN5 for ubiquitin-proteasomal degradation, thereby maintaining lysosomal enzyme trafficking from the ER to Golgi; (3) modulates neuronal K+ conductance and hyperpolarizes the resting membrane potential, also regulating the glutamine transporter SAT2; and (4) supports Purkinje cell survival and neurovascular patterning—with loss-of-function mutations in KCTD7 causing progressive myoclonic epilepsy (EPM3) and neuronal ceroid lipofuscinosis (CLN14) through calpain hyperactivation, lysosomal dysfunction, and impaired autophagy.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"KCTD7 is a cytosolic substrate-adaptor subunit of a CUL3-RBX1 (CRL3) E3 ubiquitin ligase that governs neuronal proteostasis and excitability, and its loss-of-function causes progressive myoclonic epilepsy and neuronal ceroid lipofuscinosis [#1, #9, #2]. KCTD7 binds Cullin-3 directly, an interaction abrogated by the disease-causing p.Arg184Cys mutation [#1, #2]. As the adaptor of this complex, KCTD7 directs two distinct ubiquitination programs: it executes atypical, non-degradative ubiquitination of the ubiquitous calpains—modifying calpain 1 at K398 with K6/K27/K29/K63 chains and calpain 2 with K6 chains—so that loss of KCTD7 drives calpain hyperactivation, aberrant substrate cleavage, and caspase-3 activation [#9]; and it targets CLN5 for proteasomal degradation, with patient mutations that disrupt KCTD7-CUL3 or KCTD7-CLN5 binding causing CLN5 to accumulate in the ER, disrupting CLN6/8-dependent lysosomal enzyme trafficking from ER to Golgi [#7]. Consistent with these proteostatic roles, KCTD7-deficient cells exhibit impaired autophagy [#5]. Independently, KCTD7 hyperpolarizes the resting membrane potential and lowers neuronal excitability through K+ conductance, and regulates the glutamine transporter SAT2, with multiple patient variants impairing K+ flux and glutamine transport [#0, #4]. In vivo, Kctd7 is required for Purkinje cell survival, cerebellar and retinal microvascular patterning, and normal neuronal function, and pharmacological calpain inhibition largely prevents the neurodegenerative phenotype of Kctd7 knockout mice [#8, #6, #9].\",\n  \"teleology\": [\n    {\n      \"year\": 2011,\n      \"claim\": \"Established that KCTD7 is functionally an ion-conductance modulator and physically an E3-ligase adaptor, answering what molecular activities the protein carries.\",\n      \"evidence\": \"Patch clamp in transfected neurons plus Co-IP with Cullin-3\",\n      \"pmids\": [\"21710140\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether K+ effect is direct channel modulation or indirect was not resolved\", \"No structural basis for the CUL3 interaction\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Linked disease pathogenesis to loss of the KCTD7-CUL3 interaction, connecting a clinical mutation to a defined molecular lesion.\",\n      \"evidence\": \"Co-IP and localization imaging of p.Arg184Cys vs wild-type KCTD7\",\n      \"pmids\": [\"22748208\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Did not identify the ubiquitination substrate downstream of CUL3 binding\", \"Single lab, cell-based system\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Showed that several patient mutations do not perturb cytosolic localization, indicating mislocalization is not the universal disease mechanism.\",\n      \"evidence\": \"Subcellular localization imaging of mutant KCTD7 in culture\",\n      \"pmids\": [\"22693283\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Negative result; functional consequence of these mutations not tested\", \"No biochemical readout\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Reconstituted KCTD7's K+-dependent hyperpolarization and SAT2/glutamine-transport regulation and demonstrated multiple patient variants impair these functions, tying excitability defects to disease.\",\n      \"evidence\": \"Heterologous expression and electrophysiology/transport assays in Xenopus oocytes with multiple variant alleles\",\n      \"pmids\": [\"27742667\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular mechanism by which KCTD7 affects K+ flux and SAT2 not defined\", \"Relationship to its E3-adaptor role unclear\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Implicated KCTD7 in the autophagy-lysosome pathway across species, broadening its role from excitability to proteostasis.\",\n      \"evidence\": \"Functional assays and EM in patient fibroblasts and Whi2-deficient yeast\",\n      \"pmids\": [\"30295347\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular target linking KCTD7 to autophagy not identified\", \"Yeast Whi2 similarity is suggestive, not mechanistic\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Demonstrated a non-cell-autonomous developmental role, showing neuronal Kctd7 drives retinal vascular patterning.\",\n      \"evidence\": \"Kctd7 knockout mouse with IHC, electroretinography, and vascular imaging\",\n      \"pmids\": [\"31175897\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Signal mediating neuron-to-vessel communication unknown\", \"Connection to ubiquitination/K+ activities not established\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Confirmed in a neuronal cell type that disease variants impair K+ regulation and that Kctd7 loss produces seizure-correlated transcriptional changes in vivo.\",\n      \"evidence\": \"Whole-cell patch-clamp in neuroblastoma cells and kctd7 knockout zebrafish transcriptomics\",\n      \"pmids\": [\"33970744\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Transcriptomic changes are downstream and non-specific\", \"Direct channel target not identified\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Defined a substrate of the CRL3-KCTD7 ligase, showing it degrades CLN5 to maintain lysosomal enzyme trafficking, mechanistically connecting KCTD7 loss to lysosomal dysfunction.\",\n      \"evidence\": \"Co-IP, ubiquitination and trafficking assays in KCTD7-deficient cells with patient mutations\",\n      \"pmids\": [\"35921411\", \"36368077\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether CLN5 turnover defects fully account for disease versus calpain effects unresolved\", \"Single lab\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Established a required role for Kctd7 in Purkinje cell survival and recapitulated the human neurodegenerative and seizure phenotype in mice.\",\n      \"evidence\": \"Kctd7 knockout mouse with histology, EEG, and behavioral assays\",\n      \"pmids\": [\"35972048\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Cause of selective Purkinje vulnerability not defined\", \"Molecular driver of degeneration not pinned down in this study\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Identified calpains as direct substrates and showed KCTD7 mediates atypical non-degradative ubiquitination restraining calpain activity, with calpain inhibition rescuing the knockout phenotype—establishing a treatable mechanistic axis.\",\n      \"evidence\": \"In vitro ubiquitination with single-lysine mutants, proteomics, CRISPR/Cas9 KO mice, and pharmacological calpain-inhibitor rescue\",\n      \"pmids\": [\"36964131\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How the non-degradative ubiquitin chains restrain calpain activity mechanistically is unresolved\", \"Relative contribution of calpain versus CLN5 axes to disease not quantified\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How KCTD7's E3-adaptor activity, its K+/SAT2 regulatory function, and its autophagy and vascular-patterning roles are mechanistically integrated remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of the KCTD7-CUL3 complex or substrate engagement\", \"Mechanism coupling KCTD7 to K+ conductance and SAT2 unknown\", \"Whether ion-conductance and ubiquitination roles are independent or linked\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [7, 9]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [1, 7, 9]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 4, 9]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [2, 3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [7, 9]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [5]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [0, 4]}\n    ],\n    \"complexes\": [\"CRL3 (CUL3-RBX1-KCTD7) E3 ubiquitin ligase\"],\n    \"partners\": [\"CUL3\", \"RBX1\", \"CLN5\", \"CAPN1\", \"CAPN2\", \"SLC38A2\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}