{"gene":"KCTD12","run_date":"2026-04-28T18:30:27","timeline":{"discoveries":[{"year":2013,"finding":"KCTD12 assembles with GABAB receptors in the endoplasmic reticulum and remains associated through receptor activity and internalization; KCTD12 reduces constitutive receptor internalization, thereby increasing the magnitude of GABAB receptor signaling at the neuronal plasma membrane. Knockout or knockdown of KCTD12 in hippocampal neurons reduces GABAB receptor-mediated K+ current response.","method":"Bimolecular fluorescence complementation, metabolic labeling, glycosylation assays, immunoprecipitation, bioluminescence resonance energy transfer (BRET), electrophysiology in hippocampal neurons","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal methods in heterologous cells and neurons, with KO/KD functional validation","pmids":["23843457"],"is_preprint":false},{"year":2014,"finding":"KCTD12-induced fast desensitization of GABAB receptor-mediated K+ currents is regulated by PKA-dependent phosphorylation of serine-892 on GABAB2: serine-892 phosphorylation rearranges KCTD12 at the receptor complex and slows KCTD12-induced desensitization. Conversely, KCTD12 assembly promotes tonic serine-892 phosphorylation, creating a cross-regulatory loop. This was abolished in KCTD12 KO and S892A knock-in mice.","method":"Heterologous cell expression, hippocampal neuron electrophysiology, PKA pharmacology, KCTD12 KO mice, S892A knock-in mice","journal":"Biochemical pharmacology","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal methods including genetic knock-in/KO and pharmacological validation in vivo","pmids":["25065880"],"is_preprint":false},{"year":2013,"finding":"The N-terminal BTB/POZ domain (KCTD12BTB) and C-terminal domain (KCTD12H1) of KCTD12 each independently form tetramers and bind each other with good affinity. KCTD12BTB binds the C-terminal region of GABAB2 with low micromolar affinity, and a GABAB2-derived peptide binds KCTD12BTB with very high affinity.","method":"CD spectroscopy, analytical ultracentrifugation/SEC, binding assays (ITC/fluorescence), recombinant domain expression","journal":"Journal of molecular recognition : JMR","confidence":"High","confidence_rationale":"Tier 1 — biophysical reconstitution with multiple structural/biochemical methods in a single rigorous study","pmids":["23996491"],"is_preprint":false},{"year":2017,"finding":"KCTD12 interacts with CDK1 (identified by immunoprecipitation and mass spectrometry) and activates CDK1 and Aurora kinase A to facilitate G2/M transition. CDC25B silencing abrogates KCTD12 effects on CDK1 phosphorylation and cell proliferation. Aurora A phosphorylates KCTD12 at serine 243, creating a positive feedback loop.","method":"Immunoprecipitation, mass spectrometry, Co-IP, siRNA knockdown, phosphorylation assays, cell cycle analysis, xenograft tumor model","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2-3 — Co-IP/MS identification of CDK1 interaction with functional epistasis by CDC25B silencing; single lab","pmids":["28869606"],"is_preprint":false},{"year":2017,"finding":"KCTD12 auxiliary proteins are highly expressed in CCK-expressing interneurons and mediate desensitization of GABAB receptor-mediated inhibitory postsynaptic currents; desensitization was absent in KCTD12-deficient mice, demonstrating KCTD12 controls both kinetics and desensitization of GABABR-mediated currents in CCK interneurons.","method":"Immunoelectron microscopy, whole-cell electrophysiology in hippocampal slices, KCTD12 knockout mice","journal":"Cerebral cortex","confidence":"High","confidence_rationale":"Tier 2 — direct electrophysiological phenotype confirmed in KO mice with morphological correlation","pmids":["27073217"],"is_preprint":false},{"year":2015,"finding":"Loss of KCTD12 (KO mice) increases intrinsic excitability of hippocampal pyramidal neurons, demonstrating that KCTD12 as a GABAB receptor auxiliary subunit regulates neuronal excitability in vivo. KCTD12-deficient mice also show increased fear learning.","method":"Electrophysiological recordings from hippocampal slices of KCTD12 KO mice, behavioral assays","journal":"Translational psychiatry","confidence":"High","confidence_rationale":"Tier 2 — clean KO with direct electrophysiological phenotype, replicated across behavioral paradigms","pmids":["25689571"],"is_preprint":false},{"year":2022,"finding":"KCTD8 and KCTD12 facilitate axonal expression of GABAB receptors in habenula cholinergic neurons and contribute to presynaptic GABAB-mediated excitation (potentiation of glutamate release and Ca2+ entry); knockout of KCTD8/12 reduced axonal GABAB expression and presynaptic excitation, and overexpression of either KCTD8 or KCTD12 rescued these deficits.","method":"KCTD triple/double KO mouse lines, Ca2+ imaging, glutamate release assays, immunofluorescence, behavioral assays, AAV-mediated overexpression rescue","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 — genetic KO with rescue, multiple orthogonal readouts including physiology and neuroanatomy","pmids":["35017224"],"is_preprint":false},{"year":2014,"finding":"In zebrafish habenular neurons, Kctd12 negatively regulates the kinase Ulk2 via a proline-serine rich domain interaction, restraining Ulk2-driven dendritic branching and elaboration. Loss of Kctd12 results in increased dendritic branching and decreased anxiety behavior.","method":"Zebrafish genetic loss-of-function, protein interaction domain mapping, morphological imaging, behavioral assays","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2-3 — genetic epistasis in zebrafish (ortholog) with domain-level interaction mapping; single lab","pmids":["25329151"],"is_preprint":false},{"year":2017,"finding":"Human KCTD12 co-expression accelerates both activation and desensitization kinetics of GABAB receptor-mediated GIRK channel currents and enhances the potentiating effects of the positive allosteric modulator CGP7930 on GABABR. KCTD12 KO mice show reduced seizure susceptibility and altered ethanol consumption.","method":"Automated electrophysiology (QPatch), heterologous co-expression, KCTD12 KO mice, behavioral pharmacology","journal":"Pharmacology research & perspectives","confidence":"Medium","confidence_rationale":"Tier 2 — automated electrophysiology with KO mouse validation; single lab","pmids":["28713569"],"is_preprint":false},{"year":2019,"finding":"The KCTD12-CDK1 protein-protein interaction is required for CDK1 activation; disruption of this interaction by adefovir dipivoxil (identified by screening an FDA-approved drug library) induces G2 phase arrest and inhibits cancer cell proliferation.","method":"Drug library screen, Co-IP disruption assay, cell cycle analysis, proliferation assays, xenograft tumor model","journal":"Cancer letters","confidence":"Medium","confidence_rationale":"Tier 2-3 — mechanistic follow-up of KCTD12-CDK1 interaction with pharmacological disruption and in vivo validation; single lab","pmids":["30872078"],"is_preprint":false},{"year":2018,"finding":"KIT signaling negatively regulates KCTD12 expression in GIST cells; KIT knockdown upregulates KCTD12 at both mRNA and protein level, and KCTD12 knockdown accelerates GIST cell growth, establishing KCTD12 as a downstream tumor suppressor in KIT signaling.","method":"KIT siRNA knockdown in GIST T1 cells, Western blot, qPCR, cell growth assays","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2-3 — genetic epistasis by knockdown in relevant cell line; single lab","pmids":["29930747"],"is_preprint":false},{"year":2019,"finding":"Lithium induces KCTD12 expression via inhibition of GSK-3, which leads to CREB-mediated KCTD12 promoter activation. GADL1 overexpression enhances GSK-3 activity and suppresses KCTD12 expression, demonstrating that GSK-3/CREB signaling is an upstream regulator of KCTD12 transcription.","method":"Pharmacological GSK-3 inhibition, GADL1 overexpression, KCTD12 promoter reporter assay, Western blot in SH-SY5Y cells","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2-3 — promoter reporter assay with pharmacological and genetic manipulation; single lab","pmids":["31311980"],"is_preprint":false},{"year":2020,"finding":"Kctd12 overexpression in the dentate gyrus increases vulnerability to social stress and regulates excitability of granule cells; Kctd12 knockdown in dentate gyrus prevents social avoidance and stimulates neuronal activity, contributing to antidepressant-like effects of fluoxetine. GABAB receptor antagonist CGP35348 reduced stress-induced behavior and suppressed excess Kctd12 expression.","method":"AAV-mediated Kctd12 overexpression/knockdown in mouse dentate gyrus, electrophysiology (granule cell excitability), behavioral assays (CSDS model), pharmacological manipulation","journal":"Pharmacological research","confidence":"Medium","confidence_rationale":"Tier 2 — direct in vivo region-specific manipulation with electrophysiology and behavioral readouts; single lab","pmids":["33285230"],"is_preprint":false},{"year":2025,"finding":"MSL1 negatively regulates KCTD12 expression; in colon cancer cells, Erastin (ferroptosis inducer) suppresses MSL1, leading to KCTD12 upregulation, which in turn suppresses SLC7A11 and promotes ferroptosis. The MSL1-KCTD12-SLC7A11 axis regulates ROS, GSH, and MDA levels in ferroptosis.","method":"Biochemical assays, siRNA knockdown, overexpression studies, ROS/GSH/MDA measurement, ferroptosis assays","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2-3 — biochemical and genetic epistasis establishing pathway position; single lab","pmids":["40221412"],"is_preprint":false},{"year":2019,"finding":"KCTD12 knockdown in melanoma cells enhances stemness markers including CD271, and KCTD12 interacts with CD271; this interaction regulates melanoma cell stemness transformation and metastatic capacity in vitro and in vivo.","method":"KCTD12 KO A375 cells (CRISPR), spheroid formation, mouse metastatic model, Western blot for CD271","journal":"Cancer biology & medicine","confidence":"Low","confidence_rationale":"Tier 3 — interaction with CD271 established without rigorous biochemical validation of direct binding; single lab","pmids":["31565480"],"is_preprint":false}],"current_model":"KCTD12 is an auxiliary subunit of GABAB receptors that assembles with the receptor complex in the ER and remains associated through trafficking to and internalization from the plasma membrane; it reduces constitutive receptor internalization to increase surface GABAB signaling, accelerates GIRK channel activation and desensitization kinetics by interfering with Gβγ binding, is regulated by PKA-mediated phosphorylation of GABAB2-S892, facilitates axonal GABAB expression and presynaptic excitatory signaling in habenula neurons, negatively regulates Ulk2-driven dendritogenesis, and in non-neuronal contexts promotes G2/M cell cycle progression by interacting with CDK1 and CDC25B while itself being phosphorylated by Aurora A at S243 in a positive feedback loop."},"narrative":{"teleology":[{"year":2013,"claim":"Establishing how KCTD12 assembles with GABAB receptors and controls receptor surface availability resolved a key question about how auxiliary subunits regulate GABAB signaling magnitude.","evidence":"Bimolecular fluorescence complementation, metabolic labeling, glycosylation assays, BRET, and electrophysiology in hippocampal neurons with KCTD12 KO/KD","pmids":["23843457"],"confidence":"High","gaps":["Structural basis of KCTD12-mediated reduction of constitutive internalization unknown","Whether KCTD12 directly contacts endocytic machinery or acts indirectly not resolved"]},{"year":2013,"claim":"Biophysical characterization of KCTD12 domain architecture showed that both BTB and H1 domains independently tetramerize and that the BTB domain directly binds GABAB2 C-terminus with low micromolar affinity, establishing the structural basis of the interaction.","evidence":"CD spectroscopy, analytical ultracentrifugation/SEC, ITC and fluorescence binding assays with recombinant domains","pmids":["23996491"],"confidence":"High","gaps":["No high-resolution structure of the KCTD12–GABAB2 complex","Stoichiometry of KCTD12 tetramers within the full receptor complex not fully defined"]},{"year":2014,"claim":"Demonstrating that PKA-dependent phosphorylation of GABAB2-S892 rearranges KCTD12 at the receptor complex and slows desensitization revealed a cross-regulatory mechanism tuning GABAB kinetics, validated by S892A knock-in mice.","evidence":"Heterologous cell expression, hippocampal neuron electrophysiology, pharmacology, KCTD12 KO mice, S892A knock-in mice","pmids":["25065880"],"confidence":"High","gaps":["Nature of the S892 phosphorylation-induced structural rearrangement at KCTD12 is unknown","Whether other kinases besides PKA regulate this rearrangement not tested"]},{"year":2014,"claim":"Identification of Ulk2 as a KCTD12 interactor in zebrafish habenula established a non-GABAB function for KCTD12 in restricting dendritic branching, raising the question of whether this mechanism is conserved in mammals.","evidence":"Zebrafish genetic loss-of-function, domain interaction mapping, morphological imaging","pmids":["25329151"],"confidence":"Medium","gaps":["Mammalian replication of KCTD12–Ulk2 interaction not established","Whether this interaction occurs independently of GABAB receptors unclear","Direct binding stoichiometry and affinity not measured"]},{"year":2015,"claim":"Showing that KCTD12 KO mice have increased hippocampal pyramidal neuron excitability and enhanced fear learning connected the auxiliary subunit to circuit-level excitability control and behavior.","evidence":"Electrophysiological recordings from hippocampal slices of KCTD12 KO mice, behavioral assays","pmids":["25689571"],"confidence":"High","gaps":["Which specific GABAB-mediated conductances account for the excitability change not dissected","Contribution of developmental compensation in KO not excluded"]},{"year":2017,"claim":"Cell-type resolution analysis in CCK interneurons demonstrated that KCTD12 is necessary and sufficient for GABAB-mediated IPSC desensitization in these neurons, confirming its role as a desensitization switch in defined interneuron subtypes.","evidence":"Immunoelectron microscopy, whole-cell electrophysiology in hippocampal slices, KCTD12 KO mice","pmids":["27073217"],"confidence":"High","gaps":["Whether other KCTD family members compensate in non-CCK interneurons not fully explored","Mechanism by which KCTD12 interferes with Gβγ–GIRK coupling at the molecular level not resolved"]},{"year":2017,"claim":"Discovery that KCTD12 interacts with CDK1 and promotes G2/M progression through CDC25B and Aurora A phosphorylation of KCTD12-S243 revealed a cell cycle regulatory function entirely distinct from its GABAB role.","evidence":"Co-IP/mass spectrometry, siRNA epistasis, phosphorylation assays, cell cycle analysis, xenograft model","pmids":["28869606"],"confidence":"Medium","gaps":["Whether KCTD12 acts as a scaffold or allosteric activator of CDK1 is unclear","Structural basis of CDK1–KCTD12 interaction unknown","Physiological relevance outside cancer cell lines not established"]},{"year":2019,"claim":"Pharmacological disruption of the KCTD12–CDK1 interaction by adefovir dipivoxil causing G2 arrest validated this interaction as functionally required for CDK1 activation and suggested therapeutic targetability.","evidence":"FDA-approved drug library screen, Co-IP disruption, cell cycle analysis, xenograft model","pmids":["30872078"],"confidence":"Medium","gaps":["Selectivity of adefovir dipivoxil for KCTD12–CDK1 versus other targets not fully established","In vivo pharmacokinetic relevance of drug doses used unclear"]},{"year":2022,"claim":"Demonstrating that KCTD8/12 facilitate axonal GABAB expression and presynaptic excitatory signaling in habenula cholinergic neurons, with single-gene rescue, established a trafficking role for KCTD12 in polarized neuronal compartments beyond the somatodendritic domain.","evidence":"KCTD triple/double KO mouse lines, Ca²⁺ imaging, glutamate release assays, AAV-mediated rescue","pmids":["35017224"],"confidence":"High","gaps":["Mechanism by which KCTD12 promotes axonal versus dendritic GABAB targeting unknown","Whether KCTD12 directly participates in axonal transport or simply stabilizes receptors at axonal membranes not resolved"]},{"year":null,"claim":"A high-resolution structure of the KCTD12–GABAB receptor complex, the molecular mechanism by which KCTD12 promotes axonal receptor targeting, and the physiological significance of KCTD12's cell cycle role in non-transformed tissues remain unresolved.","evidence":"","pmids":[],"confidence":"High","gaps":["No atomic-resolution structure of KCTD12 bound to GABAB receptor","Mechanism of axonal GABAB targeting by KCTD12 not determined","Whether KCTD12–CDK1 interaction operates in normal dividing cells unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,1,4,8]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[3,9]}],"localization":[{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[0]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,6]}],"pathway":[{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[0,1,4,5,6,8]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,1,6]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[3,9]}],"complexes":["GABAB receptor complex"],"partners":["GABBR2","CDK1","CDC25B","AURKA","ULK2","KCTD8"],"other_free_text":[]},"mechanistic_narrative":"KCTD12 is an auxiliary subunit of GABAB receptors that shapes receptor trafficking, signaling kinetics, and neuronal excitability, while also functioning in cell cycle regulation independently of its neuronal role. Through its N-terminal BTB/POZ domain, KCTD12 assembles with GABAB2 in the endoplasmic reticulum and remains associated through surface trafficking and internalization; it reduces constitutive receptor internalization to increase surface GABAB signaling, accelerates GIRK channel activation and desensitization kinetics, and is cross-regulated by PKA-dependent phosphorylation of GABAB2-S892 [PMID:23843457, PMID:25065880, PMID:23996491, PMID:28713569]. Loss of KCTD12 abolishes GABAB-mediated desensitization in CCK interneurons, increases pyramidal neuron excitability and fear learning, and reduces axonal GABAB expression and presynaptic excitation in habenula neurons [PMID:27073217, PMID:25689571, PMID:35017224]. In non-neuronal contexts, KCTD12 interacts with CDK1 and promotes G2/M cell cycle progression through CDC25B-dependent CDK1 activation and a positive feedback loop involving Aurora A phosphorylation of KCTD12-S243 [PMID:28869606, PMID:30872078]."},"prefetch_data":{"uniprot":{"accession":"Q96CX2","full_name":"BTB/POZ domain-containing protein KCTD12","aliases":["Pfetin","Predominantly fetal expressed T1 domain"],"length_aa":325,"mass_kda":35.7,"function":"Auxiliary subunit of GABA-B receptors that determine the pharmacology and kinetics of the receptor response. Increases agonist potency and markedly alter the G-protein signaling of the receptors by accelerating onset and promoting desensitization (By similarity)","subcellular_location":"Presynaptic cell membrane; Postsynaptic cell membrane","url":"https://www.uniprot.org/uniprotkb/Q96CX2/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/KCTD12","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/KCTD12","total_profiled":1310},"omim":[{"mim_id":"610521","title":"POTASSIUM CHANNEL TETRAMERIZATION DOMAIN-CONTAINING PROTEIN 12; KCTD12","url":"https://www.omim.org/entry/610521"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Uncertain","locations":[{"location":"Mitochondria","reliability":"Uncertain"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/KCTD12"},"hgnc":{"alias_symbol":["KIAA1778","PFET1"],"prev_symbol":["C13orf2"]},"alphafold":{"accession":"Q96CX2","domains":[{"cath_id":"3.30.710.10","chopping":"34-129","consensus_level":"high","plddt":94.5213,"start":34,"end":129},{"cath_id":"-","chopping":"207-323","consensus_level":"high","plddt":87.059,"start":207,"end":323}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q96CX2","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q96CX2-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q96CX2-F1-predicted_aligned_error_v6.png","plddt_mean":75.81},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=KCTD12","jax_strain_url":"https://www.jax.org/strain/search?query=KCTD12"},"sequence":{"accession":"Q96CX2","fasta_url":"https://rest.uniprot.org/uniprotkb/Q96CX2.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q96CX2/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q96CX2"}},"corpus_meta":[{"pmid":"28869606","id":"PMC_28869606","title":"KCTD12 promotes tumorigenesis by facilitating CDC25B/CDK1/Aurora A-dependent G2/M transition.","date":"2017","source":"Oncogene","url":"https://pubmed.ncbi.nlm.nih.gov/28869606","citation_count":56,"is_preprint":false},{"pmid":"25689571","id":"PMC_25689571","title":"Altered emotionality and neuronal excitability in mice lacking KCTD12, an auxiliary subunit of GABAB receptors associated with mood disorders.","date":"2015","source":"Translational psychiatry","url":"https://pubmed.ncbi.nlm.nih.gov/25689571","citation_count":43,"is_preprint":false},{"pmid":"23843457","id":"PMC_23843457","title":"Up-regulation of GABA(B) receptor signaling by constitutive assembly with the K+ channel tetramerization domain-containing protein 12 (KCTD12).","date":"2013","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/23843457","citation_count":36,"is_preprint":false},{"pmid":"26847701","id":"PMC_26847701","title":"KCTD12 Regulates Colorectal Cancer Cell Stemness through the ERK Pathway.","date":"2016","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/26847701","citation_count":34,"is_preprint":false},{"pmid":"30872078","id":"PMC_30872078","title":"Adefovir dipivoxil sensitizes colon cancer cells to vemurafenib by disrupting the KCTD12-CDK1 interaction.","date":"2019","source":"Cancer letters","url":"https://pubmed.ncbi.nlm.nih.gov/30872078","citation_count":32,"is_preprint":false},{"pmid":"27073217","id":"PMC_27073217","title":"KCTD12 Auxiliary Proteins Modulate Kinetics of GABAB Receptor-Mediated Inhibition in Cholecystokinin-Containing Interneurons.","date":"2017","source":"Cerebral cortex (New York, N.Y. : 1991)","url":"https://pubmed.ncbi.nlm.nih.gov/27073217","citation_count":31,"is_preprint":false},{"pmid":"25065880","id":"PMC_25065880","title":"GABAB receptor phosphorylation regulates KCTD12-induced K⁺ current desensitization.","date":"2014","source":"Biochemical 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partner to regulate dendritogenesis and behavior in the habenular nuclei.","date":"2014","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/25329151","citation_count":4,"is_preprint":false},{"pmid":"41944200","id":"PMC_41944200","title":"RETRACTION: KCTD12 Promotes G1/S Transition of Breast Cancer Cell through Activating the AKT/FOXO1 Signaling.","date":"2026","source":"Journal of clinical laboratory analysis","url":"https://pubmed.ncbi.nlm.nih.gov/41944200","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":13855,"output_tokens":3670,"usd":0.048308},"stage2":{"model":"claude-opus-4-6","input_tokens":7075,"output_tokens":5203,"usd":0.248175},"total_usd":0.296483,"stage1_batch_id":"msgbatch_01Mgbec4vM6c9vXht7JVJzss","stage2_batch_id":"msgbatch_01JkuuH5RB2BdJNsgnhjbC6s","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2013,\n      \"finding\": \"KCTD12 assembles with GABAB receptors in the endoplasmic reticulum and remains associated through receptor activity and internalization; KCTD12 reduces constitutive receptor internalization, thereby increasing the magnitude of GABAB receptor signaling at the neuronal plasma membrane. Knockout or knockdown of KCTD12 in hippocampal neurons reduces GABAB receptor-mediated K+ current response.\",\n      \"method\": \"Bimolecular fluorescence complementation, metabolic labeling, glycosylation assays, immunoprecipitation, bioluminescence resonance energy transfer (BRET), electrophysiology in hippocampal neurons\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods in heterologous cells and neurons, with KO/KD functional validation\",\n      \"pmids\": [\"23843457\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"KCTD12-induced fast desensitization of GABAB receptor-mediated K+ currents is regulated by PKA-dependent phosphorylation of serine-892 on GABAB2: serine-892 phosphorylation rearranges KCTD12 at the receptor complex and slows KCTD12-induced desensitization. Conversely, KCTD12 assembly promotes tonic serine-892 phosphorylation, creating a cross-regulatory loop. This was abolished in KCTD12 KO and S892A knock-in mice.\",\n      \"method\": \"Heterologous cell expression, hippocampal neuron electrophysiology, PKA pharmacology, KCTD12 KO mice, S892A knock-in mice\",\n      \"journal\": \"Biochemical pharmacology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods including genetic knock-in/KO and pharmacological validation in vivo\",\n      \"pmids\": [\"25065880\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"The N-terminal BTB/POZ domain (KCTD12BTB) and C-terminal domain (KCTD12H1) of KCTD12 each independently form tetramers and bind each other with good affinity. KCTD12BTB binds the C-terminal region of GABAB2 with low micromolar affinity, and a GABAB2-derived peptide binds KCTD12BTB with very high affinity.\",\n      \"method\": \"CD spectroscopy, analytical ultracentrifugation/SEC, binding assays (ITC/fluorescence), recombinant domain expression\",\n      \"journal\": \"Journal of molecular recognition : JMR\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — biophysical reconstitution with multiple structural/biochemical methods in a single rigorous study\",\n      \"pmids\": [\"23996491\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"KCTD12 interacts with CDK1 (identified by immunoprecipitation and mass spectrometry) and activates CDK1 and Aurora kinase A to facilitate G2/M transition. CDC25B silencing abrogates KCTD12 effects on CDK1 phosphorylation and cell proliferation. Aurora A phosphorylates KCTD12 at serine 243, creating a positive feedback loop.\",\n      \"method\": \"Immunoprecipitation, mass spectrometry, Co-IP, siRNA knockdown, phosphorylation assays, cell cycle analysis, xenograft tumor model\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — Co-IP/MS identification of CDK1 interaction with functional epistasis by CDC25B silencing; single lab\",\n      \"pmids\": [\"28869606\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"KCTD12 auxiliary proteins are highly expressed in CCK-expressing interneurons and mediate desensitization of GABAB receptor-mediated inhibitory postsynaptic currents; desensitization was absent in KCTD12-deficient mice, demonstrating KCTD12 controls both kinetics and desensitization of GABABR-mediated currents in CCK interneurons.\",\n      \"method\": \"Immunoelectron microscopy, whole-cell electrophysiology in hippocampal slices, KCTD12 knockout mice\",\n      \"journal\": \"Cerebral cortex\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct electrophysiological phenotype confirmed in KO mice with morphological correlation\",\n      \"pmids\": [\"27073217\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Loss of KCTD12 (KO mice) increases intrinsic excitability of hippocampal pyramidal neurons, demonstrating that KCTD12 as a GABAB receptor auxiliary subunit regulates neuronal excitability in vivo. KCTD12-deficient mice also show increased fear learning.\",\n      \"method\": \"Electrophysiological recordings from hippocampal slices of KCTD12 KO mice, behavioral assays\",\n      \"journal\": \"Translational psychiatry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with direct electrophysiological phenotype, replicated across behavioral paradigms\",\n      \"pmids\": [\"25689571\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"KCTD8 and KCTD12 facilitate axonal expression of GABAB receptors in habenula cholinergic neurons and contribute to presynaptic GABAB-mediated excitation (potentiation of glutamate release and Ca2+ entry); knockout of KCTD8/12 reduced axonal GABAB expression and presynaptic excitation, and overexpression of either KCTD8 or KCTD12 rescued these deficits.\",\n      \"method\": \"KCTD triple/double KO mouse lines, Ca2+ imaging, glutamate release assays, immunofluorescence, behavioral assays, AAV-mediated overexpression rescue\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO with rescue, multiple orthogonal readouts including physiology and neuroanatomy\",\n      \"pmids\": [\"35017224\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"In zebrafish habenular neurons, Kctd12 negatively regulates the kinase Ulk2 via a proline-serine rich domain interaction, restraining Ulk2-driven dendritic branching and elaboration. Loss of Kctd12 results in increased dendritic branching and decreased anxiety behavior.\",\n      \"method\": \"Zebrafish genetic loss-of-function, protein interaction domain mapping, morphological imaging, behavioral assays\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — genetic epistasis in zebrafish (ortholog) with domain-level interaction mapping; single lab\",\n      \"pmids\": [\"25329151\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Human KCTD12 co-expression accelerates both activation and desensitization kinetics of GABAB receptor-mediated GIRK channel currents and enhances the potentiating effects of the positive allosteric modulator CGP7930 on GABABR. KCTD12 KO mice show reduced seizure susceptibility and altered ethanol consumption.\",\n      \"method\": \"Automated electrophysiology (QPatch), heterologous co-expression, KCTD12 KO mice, behavioral pharmacology\",\n      \"journal\": \"Pharmacology research & perspectives\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — automated electrophysiology with KO mouse validation; single lab\",\n      \"pmids\": [\"28713569\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"The KCTD12-CDK1 protein-protein interaction is required for CDK1 activation; disruption of this interaction by adefovir dipivoxil (identified by screening an FDA-approved drug library) induces G2 phase arrest and inhibits cancer cell proliferation.\",\n      \"method\": \"Drug library screen, Co-IP disruption assay, cell cycle analysis, proliferation assays, xenograft tumor model\",\n      \"journal\": \"Cancer letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — mechanistic follow-up of KCTD12-CDK1 interaction with pharmacological disruption and in vivo validation; single lab\",\n      \"pmids\": [\"30872078\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"KIT signaling negatively regulates KCTD12 expression in GIST cells; KIT knockdown upregulates KCTD12 at both mRNA and protein level, and KCTD12 knockdown accelerates GIST cell growth, establishing KCTD12 as a downstream tumor suppressor in KIT signaling.\",\n      \"method\": \"KIT siRNA knockdown in GIST T1 cells, Western blot, qPCR, cell growth assays\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — genetic epistasis by knockdown in relevant cell line; single lab\",\n      \"pmids\": [\"29930747\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Lithium induces KCTD12 expression via inhibition of GSK-3, which leads to CREB-mediated KCTD12 promoter activation. GADL1 overexpression enhances GSK-3 activity and suppresses KCTD12 expression, demonstrating that GSK-3/CREB signaling is an upstream regulator of KCTD12 transcription.\",\n      \"method\": \"Pharmacological GSK-3 inhibition, GADL1 overexpression, KCTD12 promoter reporter assay, Western blot in SH-SY5Y cells\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — promoter reporter assay with pharmacological and genetic manipulation; single lab\",\n      \"pmids\": [\"31311980\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Kctd12 overexpression in the dentate gyrus increases vulnerability to social stress and regulates excitability of granule cells; Kctd12 knockdown in dentate gyrus prevents social avoidance and stimulates neuronal activity, contributing to antidepressant-like effects of fluoxetine. GABAB receptor antagonist CGP35348 reduced stress-induced behavior and suppressed excess Kctd12 expression.\",\n      \"method\": \"AAV-mediated Kctd12 overexpression/knockdown in mouse dentate gyrus, electrophysiology (granule cell excitability), behavioral assays (CSDS model), pharmacological manipulation\",\n      \"journal\": \"Pharmacological research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct in vivo region-specific manipulation with electrophysiology and behavioral readouts; single lab\",\n      \"pmids\": [\"33285230\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"MSL1 negatively regulates KCTD12 expression; in colon cancer cells, Erastin (ferroptosis inducer) suppresses MSL1, leading to KCTD12 upregulation, which in turn suppresses SLC7A11 and promotes ferroptosis. The MSL1-KCTD12-SLC7A11 axis regulates ROS, GSH, and MDA levels in ferroptosis.\",\n      \"method\": \"Biochemical assays, siRNA knockdown, overexpression studies, ROS/GSH/MDA measurement, ferroptosis assays\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — biochemical and genetic epistasis establishing pathway position; single lab\",\n      \"pmids\": [\"40221412\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"KCTD12 knockdown in melanoma cells enhances stemness markers including CD271, and KCTD12 interacts with CD271; this interaction regulates melanoma cell stemness transformation and metastatic capacity in vitro and in vivo.\",\n      \"method\": \"KCTD12 KO A375 cells (CRISPR), spheroid formation, mouse metastatic model, Western blot for CD271\",\n      \"journal\": \"Cancer biology & medicine\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — interaction with CD271 established without rigorous biochemical validation of direct binding; single lab\",\n      \"pmids\": [\"31565480\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"KCTD12 is an auxiliary subunit of GABAB receptors that assembles with the receptor complex in the ER and remains associated through trafficking to and internalization from the plasma membrane; it reduces constitutive receptor internalization to increase surface GABAB signaling, accelerates GIRK channel activation and desensitization kinetics by interfering with Gβγ binding, is regulated by PKA-mediated phosphorylation of GABAB2-S892, facilitates axonal GABAB expression and presynaptic excitatory signaling in habenula neurons, negatively regulates Ulk2-driven dendritogenesis, and in non-neuronal contexts promotes G2/M cell cycle progression by interacting with CDK1 and CDC25B while itself being phosphorylated by Aurora A at S243 in a positive feedback loop.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"KCTD12 is an auxiliary subunit of GABAB receptors that shapes receptor trafficking, signaling kinetics, and neuronal excitability, while also functioning in cell cycle regulation independently of its neuronal role. Through its N-terminal BTB/POZ domain, KCTD12 assembles with GABAB2 in the endoplasmic reticulum and remains associated through surface trafficking and internalization; it reduces constitutive receptor internalization to increase surface GABAB signaling, accelerates GIRK channel activation and desensitization kinetics, and is cross-regulated by PKA-dependent phosphorylation of GABAB2-S892 [PMID:23843457, PMID:25065880, PMID:23996491, PMID:28713569]. Loss of KCTD12 abolishes GABAB-mediated desensitization in CCK interneurons, increases pyramidal neuron excitability and fear learning, and reduces axonal GABAB expression and presynaptic excitation in habenula neurons [PMID:27073217, PMID:25689571, PMID:35017224]. In non-neuronal contexts, KCTD12 interacts with CDK1 and promotes G2/M cell cycle progression through CDC25B-dependent CDK1 activation and a positive feedback loop involving Aurora A phosphorylation of KCTD12-S243 [PMID:28869606, PMID:30872078].\",\n  \"teleology\": [\n    {\n      \"year\": 2013,\n      \"claim\": \"Establishing how KCTD12 assembles with GABAB receptors and controls receptor surface availability resolved a key question about how auxiliary subunits regulate GABAB signaling magnitude.\",\n      \"evidence\": \"Bimolecular fluorescence complementation, metabolic labeling, glycosylation assays, BRET, and electrophysiology in hippocampal neurons with KCTD12 KO/KD\",\n      \"pmids\": [\"23843457\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of KCTD12-mediated reduction of constitutive internalization unknown\", \"Whether KCTD12 directly contacts endocytic machinery or acts indirectly not resolved\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Biophysical characterization of KCTD12 domain architecture showed that both BTB and H1 domains independently tetramerize and that the BTB domain directly binds GABAB2 C-terminus with low micromolar affinity, establishing the structural basis of the interaction.\",\n      \"evidence\": \"CD spectroscopy, analytical ultracentrifugation/SEC, ITC and fluorescence binding assays with recombinant domains\",\n      \"pmids\": [\"23996491\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No high-resolution structure of the KCTD12–GABAB2 complex\", \"Stoichiometry of KCTD12 tetramers within the full receptor complex not fully defined\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Demonstrating that PKA-dependent phosphorylation of GABAB2-S892 rearranges KCTD12 at the receptor complex and slows desensitization revealed a cross-regulatory mechanism tuning GABAB kinetics, validated by S892A knock-in mice.\",\n      \"evidence\": \"Heterologous cell expression, hippocampal neuron electrophysiology, pharmacology, KCTD12 KO mice, S892A knock-in mice\",\n      \"pmids\": [\"25065880\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Nature of the S892 phosphorylation-induced structural rearrangement at KCTD12 is unknown\", \"Whether other kinases besides PKA regulate this rearrangement not tested\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Identification of Ulk2 as a KCTD12 interactor in zebrafish habenula established a non-GABAB function for KCTD12 in restricting dendritic branching, raising the question of whether this mechanism is conserved in mammals.\",\n      \"evidence\": \"Zebrafish genetic loss-of-function, domain interaction mapping, morphological imaging\",\n      \"pmids\": [\"25329151\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mammalian replication of KCTD12–Ulk2 interaction not established\", \"Whether this interaction occurs independently of GABAB receptors unclear\", \"Direct binding stoichiometry and affinity not measured\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Showing that KCTD12 KO mice have increased hippocampal pyramidal neuron excitability and enhanced fear learning connected the auxiliary subunit to circuit-level excitability control and behavior.\",\n      \"evidence\": \"Electrophysiological recordings from hippocampal slices of KCTD12 KO mice, behavioral assays\",\n      \"pmids\": [\"25689571\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Which specific GABAB-mediated conductances account for the excitability change not dissected\", \"Contribution of developmental compensation in KO not excluded\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Cell-type resolution analysis in CCK interneurons demonstrated that KCTD12 is necessary and sufficient for GABAB-mediated IPSC desensitization in these neurons, confirming its role as a desensitization switch in defined interneuron subtypes.\",\n      \"evidence\": \"Immunoelectron microscopy, whole-cell electrophysiology in hippocampal slices, KCTD12 KO mice\",\n      \"pmids\": [\"27073217\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether other KCTD family members compensate in non-CCK interneurons not fully explored\", \"Mechanism by which KCTD12 interferes with Gβγ–GIRK coupling at the molecular level not resolved\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Discovery that KCTD12 interacts with CDK1 and promotes G2/M progression through CDC25B and Aurora A phosphorylation of KCTD12-S243 revealed a cell cycle regulatory function entirely distinct from its GABAB role.\",\n      \"evidence\": \"Co-IP/mass spectrometry, siRNA epistasis, phosphorylation assays, cell cycle analysis, xenograft model\",\n      \"pmids\": [\"28869606\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether KCTD12 acts as a scaffold or allosteric activator of CDK1 is unclear\", \"Structural basis of CDK1–KCTD12 interaction unknown\", \"Physiological relevance outside cancer cell lines not established\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Pharmacological disruption of the KCTD12–CDK1 interaction by adefovir dipivoxil causing G2 arrest validated this interaction as functionally required for CDK1 activation and suggested therapeutic targetability.\",\n      \"evidence\": \"FDA-approved drug library screen, Co-IP disruption, cell cycle analysis, xenograft model\",\n      \"pmids\": [\"30872078\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Selectivity of adefovir dipivoxil for KCTD12–CDK1 versus other targets not fully established\", \"In vivo pharmacokinetic relevance of drug doses used unclear\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Demonstrating that KCTD8/12 facilitate axonal GABAB expression and presynaptic excitatory signaling in habenula cholinergic neurons, with single-gene rescue, established a trafficking role for KCTD12 in polarized neuronal compartments beyond the somatodendritic domain.\",\n      \"evidence\": \"KCTD triple/double KO mouse lines, Ca²⁺ imaging, glutamate release assays, AAV-mediated rescue\",\n      \"pmids\": [\"35017224\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which KCTD12 promotes axonal versus dendritic GABAB targeting unknown\", \"Whether KCTD12 directly participates in axonal transport or simply stabilizes receptors at axonal membranes not resolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"A high-resolution structure of the KCTD12–GABAB receptor complex, the molecular mechanism by which KCTD12 promotes axonal receptor targeting, and the physiological significance of KCTD12's cell cycle role in non-transformed tissues remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No atomic-resolution structure of KCTD12 bound to GABAB receptor\", \"Mechanism of axonal GABAB targeting by KCTD12 not determined\", \"Whether KCTD12–CDK1 interaction operates in normal dividing cells unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 1, 4, 8]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [3, 9]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 6]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": []},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [0, 1, 4, 5, 6, 8]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 1, 6]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [3, 9]}\n    ],\n    \"complexes\": [\n      \"GABAB receptor complex\"\n    ],\n    \"partners\": [\n      \"GABBR2\",\n      \"CDK1\",\n      \"CDC25B\",\n      \"AURKA\",\n      \"ULK2\",\n      \"KCTD8\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```\n\nWait, I need to fix the pathway section - I accidentally included a GO cellular component term. Let me correct:\n\n```json\n{\n  \"mechanistic_narrative\": \"KCTD12 is an auxiliary subunit of GABAB receptors that shapes receptor trafficking, signaling kinetics, and neuronal excitability, while also functioning in cell cycle regulation independently of its neuronal role. Through its N-terminal BTB/POZ domain, KCTD12 assembles with GABAB2 in the endoplasmic reticulum and remains associated through surface trafficking and internalization; it reduces constitutive receptor internalization to increase surface GABAB signaling, accelerates GIRK channel activation and desensitization kinetics, and is cross-regulated by PKA-dependent phosphorylation of GABAB2-S892 [PMID:23843457, PMID:25065880, PMID:23996491, PMID:28713569]. Loss of KCTD12 abolishes GABAB-mediated desensitization in CCK interneurons, increases pyramidal neuron excitability and fear learning, and reduces axonal GABAB expression and presynaptic excitation in habenula neurons [PMID:27073217, PMID:25689571, PMID:35017224]. In non-neuronal contexts, KCTD12 interacts with CDK1 and promotes G2/M cell cycle progression through CDC25B-dependent CDK1 activation and a positive feedback loop involving Aurora A phosphorylation of KCTD12-S243 [PMID:28869606, PMID:30872078].\",\n  \"teleology\": [\n    {\n      \"year\": 2013,\n      \"claim\": \"Establishing how KCTD12 assembles with GABAB receptors and controls receptor surface availability resolved a key question about how auxiliary subunits regulate GABAB signaling magnitude.\",\n      \"evidence\": \"Bimolecular fluorescence complementation, metabolic labeling, glycosylation assays, BRET, and electrophysiology in hippocampal neurons with KCTD12 KO/KD\",\n      \"pmids\": [\"23843457\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of KCTD12-mediated reduction of constitutive internalization unknown\", \"Whether KCTD12 directly contacts endocytic machinery or acts indirectly not resolved\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Biophysical characterization of KCTD12 domain architecture showed that both BTB and H1 domains independently tetramerize and that the BTB domain directly binds GABAB2 C-terminus with low micromolar affinity, establishing the structural basis of the interaction.\",\n      \"evidence\": \"CD spectroscopy, analytical ultracentrifugation/SEC, ITC and fluorescence binding assays with recombinant domains\",\n      \"pmids\": [\"23996491\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No high-resolution structure of the KCTD12–GABAB2 complex\", \"Stoichiometry of KCTD12 tetramers within the full receptor complex not fully defined\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Demonstrating that PKA-dependent phosphorylation of GABAB2-S892 rearranges KCTD12 at the receptor complex and slows desensitization revealed a cross-regulatory mechanism tuning GABAB kinetics, validated by S892A knock-in mice.\",\n      \"evidence\": \"Heterologous cell expression, hippocampal neuron electrophysiology, pharmacology, KCTD12 KO mice, S892A knock-in mice\",\n      \"pmids\": [\"25065880\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Nature of the S892 phosphorylation-induced structural rearrangement at KCTD12 is unknown\", \"Whether other kinases besides PKA regulate this rearrangement not tested\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Identification of Ulk2 as a KCTD12 interactor in zebrafish habenula established a non-GABAB function for KCTD12 in restricting dendritic branching, raising the question of whether this mechanism is conserved in mammals.\",\n      \"evidence\": \"Zebrafish genetic loss-of-function, domain interaction mapping, morphological imaging\",\n      \"pmids\": [\"25329151\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mammalian replication of KCTD12–Ulk2 interaction not established\", \"Whether this interaction occurs independently of GABAB receptors unclear\", \"Direct binding stoichiometry and affinity not measured\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Showing that KCTD12 KO mice have increased hippocampal pyramidal neuron excitability and enhanced fear learning connected the auxiliary subunit to circuit-level excitability control and behavior.\",\n      \"evidence\": \"Electrophysiological recordings from hippocampal slices of KCTD12 KO mice, behavioral assays\",\n      \"pmids\": [\"25689571\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Which specific GABAB-mediated conductances account for the excitability change not dissected\", \"Contribution of developmental compensation in KO not excluded\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Cell-type resolution analysis in CCK interneurons demonstrated that KCTD12 is necessary and sufficient for GABAB-mediated IPSC desensitization in these neurons, confirming its role as a desensitization switch in defined interneuron subtypes.\",\n      \"evidence\": \"Immunoelectron microscopy, whole-cell electrophysiology in hippocampal slices, KCTD12 KO mice\",\n      \"pmids\": [\"27073217\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether other KCTD family members compensate in non-CCK interneurons not fully explored\", \"Mechanism by which KCTD12 interferes with Gβγ–GIRK coupling at the molecular level not resolved\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Discovery that KCTD12 interacts with CDK1 and promotes G2/M progression through CDC25B and Aurora A phosphorylation of KCTD12-S243 revealed a cell cycle regulatory function entirely distinct from its GABAB role.\",\n      \"evidence\": \"Co-IP/mass spectrometry, siRNA epistasis, phosphorylation assays, cell cycle analysis, xenograft model\",\n      \"pmids\": [\"28869606\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether KCTD12 acts as a scaffold or allosteric activator of CDK1 is unclear\", \"Structural basis of CDK1–KCTD12 interaction unknown\", \"Physiological relevance outside cancer cell lines not established\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Pharmacological disruption of the KCTD12–CDK1 interaction by adefovir dipivoxil causing G2 arrest validated this interaction as functionally required for CDK1 activation and suggested therapeutic targetability.\",\n      \"evidence\": \"FDA-approved drug library screen, Co-IP disruption, cell cycle analysis, xenograft model\",\n      \"pmids\": [\"30872078\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Selectivity of adefovir dipivoxil for KCTD12–CDK1 versus other targets not fully established\", \"In vivo pharmacokinetic relevance of drug doses used unclear\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Demonstrating that KCTD8/12 facilitate axonal GABAB expression and presynaptic excitatory signaling in habenula cholinergic neurons, with single-gene rescue, established a trafficking role for KCTD12 in polarized neuronal compartments beyond the somatodendritic domain.\",\n      \"evidence\": \"KCTD triple/double KO mouse lines, Ca²⁺ imaging, glutamate release assays, AAV-mediated rescue\",\n      \"pmids\": [\"35017224\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which KCTD12 promotes axonal versus dendritic GABAB targeting unknown\", \"Whether KCTD12 directly participates in axonal transport or simply stabilizes receptors at axonal membranes not resolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"A high-resolution structure of the KCTD12–GABAB receptor complex, the molecular mechanism by which KCTD12 promotes axonal receptor targeting, and the physiological significance of KCTD12's cell cycle role in non-transformed tissues remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No atomic-resolution structure of KCTD12 bound to GABAB receptor\", \"Mechanism of axonal GABAB targeting by KCTD12 not determined\", \"Whether KCTD12–CDK1 interaction operates in normal dividing cells unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 1, 4, 8]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [3, 9]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 6]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [0, 1, 4, 5, 6, 8]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 1, 6]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [3, 9]}\n    ],\n    \"complexes\": [\n      \"GABAB receptor complex\"\n    ],\n    \"partners\": [\n      \"GABBR2\",\n      \"CDK1\",\n      \"CDC25B\",\n      \"AURKA\",\n      \"ULK2\",\n      \"KCTD8\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}