{"gene":"CACNA1I","run_date":"2026-04-28T17:28:52","timeline":{"discoveries":[{"year":2016,"finding":"The schizophrenia-associated de novo missense variant R1346H of CaV3.3 (encoded by CACNA1I) reduces protein glycosylation, lowers membrane surface expression of CaV3.3, and decreases whole-cell Ca2+ current amplitude by ~50% without altering channel biophysical properties; computational modeling showed that reducing CaV3.3 current density by ≥22% eliminates rebound bursting in thalamic reticular nucleus (TRN) neurons.","method":"Western blotting, glycosylation assays, whole-cell patch clamp in human cell lines, NEURON computational modeling","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 1–2 — multiple orthogonal biochemical and electrophysiological methods in a single study with functional computational validation","pmids":["27756899"],"is_preprint":false},{"year":2020,"finding":"CaV3.3 R1346H knock-in mice show altered cellular excitability in the TRN and marked deficits in sleep spindle occurrence and morphology during NREM sleep, establishing a direct link between CaV3.3 channel function and sleep spindle generation in vivo; CaV3.3 haploinsufficiency alone did not reproduce spindle deficits.","method":"Knock-in mouse model, patch-clamp recordings in TRN neurons, polysomnographic EEG recordings in freely behaving mice","journal":"Translational psychiatry","confidence":"High","confidence_rationale":"Tier 2 — clean knock-in and knockout models with defined cellular and EEG phenotypes, replicated across two genetic models","pmids":["32066662"],"is_preprint":false},{"year":2016,"finding":"CaV3.3 (encoded by CACNA1I) dominates nRt (nucleus reticularis thalami) rhythmic bursting; double knockout of CaV3.2 and CaV3.3 fully abolished low-threshold Ca2+ currents and bursting in nRt neurons and suppressed burst-mediated inhibitory responses in thalamocortical neurons, resulting in fragmented NREM sleep and suppressed sigma-band EEG power.","method":"Patch-clamp recordings in thalamic brain slices from CaV3.2 KO and CaV3.2/CaV3.3 double KO mice, polysomnographic recordings","journal":"Sleep","confidence":"High","confidence_rationale":"Tier 2 — clean genetic KO models with defined cellular and EEG phenotypes, epistatic dissection of two channel subtypes","pmids":["26612388"],"is_preprint":false},{"year":2021,"finding":"Gain-of-function missense variants in CACNA1I (p.Ile860Met, p.Ile860Asn, p.Ile1306Thr, p.Met1425Ile) at the cytoplasmic ends of IIS6, IIIS5, and IIIS6 segments slow activation/inactivation/deactivation kinetics, hyperpolarize voltage-dependence of activation and inactivation via stabilizing hydrogen bonds in the channel gate, increase window current and calcium influx, and lower the threshold and increase duration/frequency of action potential firing in TRN neuron models; expression in chromaffin cells shifted firing from rebound bursts to slow oscillations.","method":"Patch-clamp electrophysiology in HEK293T cells, structural homology modeling, site-directed mutagenesis, computational TRN neuron modeling, primary chromaffin cell recordings","journal":"Brain","confidence":"High","confidence_rationale":"Tier 1–2 — multiple orthogonal methods including mutagenesis, electrophysiology, structural modeling, and primary neuron recordings in one study","pmids":["33704440"],"is_preprint":false},{"year":2007,"finding":"Gαq/11-coupled muscarinic acetylcholine receptors (M1, M3, M5) selectively inhibit CaV3.3 T-type Ca2+ currents in a reversible, use-independent manner with increased inactivation kinetics, while CaV3.1 and CaV3.2 are not inhibited; chimeric channel analysis identified two distinct CaV3.3 regions necessary and sufficient for M1 receptor-mediated inhibition, acting through Gαq/11 (not Gβγ).","method":"Perforated patch clamp, chimeric channel analysis, loss-of-function with genetically encoded Gα/Gβγ antagonists, gain-of-function with genetically encoded Gα subtypes, co-expression of channels with mAChR subtypes","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 — multiple orthogonal methods (chimeras, gain/loss-of-function Gα constructs, multiple receptor subtypes) in a single study","pmids":["17535809"],"is_preprint":false},{"year":2004,"finding":"Alternative splicing of CACNA1I (deletion of 13 amino acids encoded by exon 33, Δ33; and inclusion of exon 9) modulates CaV3.3 gating: Δ33 slows channel opening, exon 9 addition to Δ33 channels unexpectedly slows both activation and inactivation, and the combination alters burst firing in neuronal models; interdependent effects suggest direct interaction between intracellular regions after repeats I and IV.","method":"RT-PCR cloning from human brain, whole-cell patch clamp in heterologous expression, computational neuronal firing modeling","journal":"Journal of neurophysiology","confidence":"High","confidence_rationale":"Tier 1–2 — electrophysiological characterization of defined splice variants with computational modeling, multiple variant combinations tested","pmids":["15254077"],"is_preprint":false},{"year":2004,"finding":"The distinctively slow activation and inactivation kinetics of CaV3.3 (alpha1I) are not determined by any single structural domain but require multiple structural elements; chimeric channel analysis between CaV3.1 and CaV3.3 in Xenopus oocytes showed no single domain substitution was sufficient to confer or abolish slow kinetics.","method":"Chimeric channel construction, two-electrode voltage clamp in Xenopus oocytes","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — systematic chimeric analysis with in vitro functional readout","pmids":["15016809"],"is_preprint":false},{"year":2006,"finding":"Domain IV is the major determinant of CaV3.3 half-activation potential and activation time constant as well as recovery from inactivation, established by systematic chimeric channel swaps between CaV3.1 and CaV3.3; domains I and II also play a minor role, while the carboxy terminal region is not involved.","method":"Chimeric channel construction, whole-cell patch clamp in tsA-201 cells","journal":"Neuroscience","confidence":"High","confidence_rationale":"Tier 1 — systematic domain-swap chimeric analysis with functional electrophysiological readout","pmids":["16996222"],"is_preprint":false},{"year":2006,"finding":"CaV3.3 window current is critical for triggering intrinsic membrane potential oscillations and intracellular Ca2+ oscillations; overexpression of CaV3.3 in NG108-15 cells produces spontaneous low-threshold action potentials and Ca2+ oscillations dependent on window current, with AP duration controlled by sustained CaV3.3 current.","method":"Whole-cell and perforated patch clamp, fluorescence Ca2+ imaging in NG108-15 cells overexpressing CaV3.3","journal":"The European journal of neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 — direct functional demonstration in a single heterologous system with pharmacological validation","pmids":["16706840"],"is_preprint":false},{"year":2013,"finding":"Endogenous polyunsaturated lipids (anandamide, NAGly, NASer, NADA, NATau, NA-5HT) inhibit CaV3.3 current and compete with the synthetic T-channel antagonist TTA-A2 at a shared binding site on CaV3.3, as demonstrated by radioligand displacement; lipids with saturated chains do not inhibit the channel and do not displace binding, revealing a shared molecular mechanism between endogenous lipids and synthetic inhibitors.","method":"Whole-cell patch clamp, radioactive binding assay with [3H]TTA-A1 on CaV3.3-expressing cell membranes","journal":"Molecular pharmacology","confidence":"High","confidence_rationale":"Tier 1 — direct binding assay combined with functional electrophysiology, structure-activity relationship across multiple lipid species","pmids":["24214826"],"is_preprint":false},{"year":2017,"finding":"Neuritin increases CaV3.3 α-subunit surface expression via an insulin receptor (IR) / MEK-ERK signaling pathway, leading to increased mEPSC frequency and glutamate release in medial prefrontal cortex; T-type channel inhibitors abolished the neuritin-induced calcium current and synaptic effects.","method":"Western blotting of membrane fractions, whole-cell patch clamp, HPLC glutamate measurement in mPFC slices, pharmacological inhibitors of IR and MEK/ERK","journal":"Cerebral cortex","confidence":"Medium","confidence_rationale":"Tier 2–3 — multiple methods (biochemical surface expression, electrophysiology, neurotransmitter measurement) but conducted in a single lab with no direct CaV3.3 mutagenesis","pmids":["28475719"],"is_preprint":false},{"year":2003,"finding":"CaV3.3 (alpha1I) protein exists as distinct developmental isoforms with differential glycosylation: a large neonatal form (~260 kDa in midbrain/diencephalon) that decreases postnatally and a smaller adult form (~190–230 kDa); immunohistochemistry established region-specific expression with highest CaV3.3 immunoreactivity in olfactory bulb and midbrain.","method":"Anti-peptide antibody characterization, Western blotting of regional brain dissections, immunohistochemistry in rodent and human brain","journal":"Neuroscience","confidence":"Medium","confidence_rationale":"Tier 3 — direct protein characterization across development, but relies primarily on antibody-based methods","pmids":["12614673"],"is_preprint":false},{"year":2007,"finding":"CaV3.3 (alpha1I) protein is modified by N-glycosylation, and the large neonatal form is polysialylated; PNGase F and Endo-N treatment demonstrated that differential glycosylation fully accounts for the molecular weight difference between neonatal and adult CaV3.3 isoforms.","method":"PNGase F and Endo-N enzymatic deglycosylation, Western blotting with validated antibodies","journal":"Neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 — direct enzymatic demonstration of glycosylation type, but limited to biochemical characterization","pmids":["17317015"],"is_preprint":false},{"year":2022,"finding":"Rare CACNA1I missense variants found in hemiplegic migraine patients (p.R111G, p.M128L, p.D302G, p.R307H, p.Q1158H) alter CaV3.3 biophysical properties including reduced current density, shifted voltage-dependence, and slower kinetics when expressed in HEK293T cells; Q1158H showed the greatest effect and both R307H and Q1158H showed altered conductance under acidotic/alkalotic conditions.","method":"Whole-cell patch-clamp electrophysiology in HEK293T cells transfected with variant channels","journal":"Frontiers in molecular neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 — direct functional characterization of multiple disease variants by patch clamp, single lab","pmids":["35928792"],"is_preprint":false},{"year":2025,"finding":"Two substitutions at CaV3.3 residue A398 have opposite functional effects: A398E causes gain-of-function (increased channel excitability), while A398V causes loss-of-function (decreased current density, accelerated gating, decreased neuronal excitability); both M1425V and M1425I substitutions cause gain-of-function with left-shifted voltage-dependence and slowed kinetics; the presence or absence of seizures in patients correlates with the presence or absence of increased neuronal excitability in silico.","method":"Site-directed mutagenesis, voltage-clamp electrophysiology in heterologous cells, computational neuronal excitability modeling, structural homology modeling","journal":"PLoS genetics","confidence":"High","confidence_rationale":"Tier 1–2 — mutagenesis, electrophysiology, structural and computational modeling with genotype-phenotype correlation across multiple variants","pmids":["40825030"],"is_preprint":false},{"year":2022,"finding":"TET1, a DNA demethylase, regulates CaV3.3 (Cav3.3) expression in TM3 Leydig cells through DNA hydroxymethylation of the Cav3.3 locus, as confirmed by MeDIP and hMeDIP; BPA exposure reduces TET1 and CaV3.3 mRNA, and differential TET1 expression modulates CaV3.3 levels.","method":"MeDIP, hMeDIP, qRT-PCR, Western blotting, adenoviral overexpression/knockdown in TM3 Leydig cells","journal":"Chemosphere","confidence":"Medium","confidence_rationale":"Tier 2–3 — direct epigenetic methylation assays linking TET1 to CaV3.3 regulation, but in a non-neuronal context and single lab","pmids":["36370755"],"is_preprint":false}],"current_model":"CACNA1I encodes CaV3.3, the pore-forming subunit of a T-type (low voltage-activated) calcium channel highly expressed in GABAergic neurons of the thalamic reticular nucleus (TRN), where its slow gating kinetics (determined by multiple transmembrane domains, especially domain IV) underlie low-threshold Ca2+ spikes, rebound burst firing, and sleep spindle rhythmogenesis during NREM sleep; CaV3.3 surface expression and function are regulated by Gαq/11-coupled muscarinic receptors, endogenous polyunsaturated lipids (acting at a shared site with synthetic T-channel inhibitors), neuritin via IR/MEK-ERK signaling, and epigenetic hydroxymethylation by TET1, while disease-causing gain-of-function variants (including schizophrenia-associated R1346H and neurodevelopmental disorder variants at I860, I1306, M1425, A398) alter channel gating and calcium influx to disrupt TRN excitability and spindle generation."},"narrative":{"teleology":[{"year":2003,"claim":"Establishing that CaV3.3 protein exists as developmentally regulated, differentially glycosylated isoforms with region-specific brain expression provided the first protein-level characterization beyond the cloned cDNA.","evidence":"Anti-peptide antibody Western blotting and immunohistochemistry across rodent and human brain regions and developmental stages","pmids":["12614673"],"confidence":"Medium","gaps":["Antibody-based detection without independent mass-spectrometry validation","Functional significance of neonatal vs. adult isoforms unknown","No link to channel electrophysiology"]},{"year":2004,"claim":"Systematic chimeric analysis between CaV3.1 and CaV3.3 revealed that CaV3.3's hallmark slow gating kinetics arise from distributed structural determinants across multiple domains rather than a single transferable module, while alternative splicing of exons 9 and 33 modulates gating and burst firing properties.","evidence":"Chimeric channel electrophysiology in Xenopus oocytes and tsA-201 cells; RT-PCR cloning of splice variants from human brain with patch-clamp characterization","pmids":["15016809","15254077"],"confidence":"High","gaps":["Structural basis at atomic resolution unknown","Which splice variants predominate in TRN neurons not determined"]},{"year":2006,"claim":"Domain IV was identified as the principal determinant of CaV3.3 half-activation potential, activation kinetics, and recovery from inactivation, resolving the earlier finding that no single domain was sufficient by showing graded contributions with domain IV dominant; separately, CaV3.3 window current was shown to drive intrinsic membrane potential and Ca²⁺ oscillations.","evidence":"Systematic domain-swap chimeras with patch-clamp in tsA-201 cells; CaV3.3 overexpression in NG108-15 cells with Ca²⁺ imaging","pmids":["16996222","16706840"],"confidence":"High","gaps":["Molecular identity of domain IV residues conferring slow kinetics not pinpointed","Window current contribution not tested in native TRN neurons"]},{"year":2007,"claim":"Two regulatory mechanisms were defined: Gαq/11-coupled muscarinic receptors selectively inhibit CaV3.3 (not CaV3.1/3.2) through two channel-intrinsic regions, and neonatal CaV3.3 carries polysialic acid modifications that fully account for developmental molecular weight differences.","evidence":"Chimeric channel analysis with genetically encoded Gα/Gβγ antagonists; PNGase F and Endo-N enzymatic deglycosylation and Western blotting","pmids":["17535809","17317015"],"confidence":"High","gaps":["Identity of channel residues mediating muscarinic inhibition unknown","Functional impact of polysialylation on channel gating or trafficking not tested"]},{"year":2013,"claim":"Identification of a shared binding site on CaV3.3 for endogenous polyunsaturated lipids and synthetic T-channel antagonists revealed that the channel is a direct lipid sensor, establishing a molecular mechanism for endogenous modulation.","evidence":"Radioligand displacement assay with [³H]TTA-A1 on CaV3.3-expressing membranes combined with patch-clamp electrophysiology across multiple lipid species","pmids":["24214826"],"confidence":"High","gaps":["Binding site not mapped to specific channel residues","Physiological relevance of lipid modulation in TRN neurons not demonstrated in vivo"]},{"year":2016,"claim":"CaV3.3 was established as the dominant T-type channel for TRN burst firing and sleep spindle generation: the schizophrenia-associated R1346H variant reduced glycosylation and surface expression to suppress current density by ~50%, and CaV3.2/CaV3.3 double knockout abolished low-threshold bursting and fragmented NREM sleep.","evidence":"Biochemistry and patch-clamp in human cell lines with NEURON modeling (R1346H); patch-clamp in brain slices and polysomnography from CaV3.2/CaV3.3 double-KO mice","pmids":["27756899","26612388"],"confidence":"High","gaps":["Whether R1346H acts purely via reduced surface expression or also affects trafficking pathway","Relative contribution of CaV3.3 vs. CaV3.2 to spindle generation not fully separated"]},{"year":2017,"claim":"Neuritin was identified as an upstream regulator that increases CaV3.3 surface expression via insulin receptor/MEK-ERK signaling, linking extracellular trophic signals to T-type channel-dependent glutamate release in medial prefrontal cortex.","evidence":"Western blotting of membrane fractions, patch-clamp, HPLC glutamate measurement in mPFC slices with pharmacological pathway dissection","pmids":["28475719"],"confidence":"Medium","gaps":["No direct CaV3.3 mutagenesis to confirm subtype specificity","Mechanism of ERK-dependent surface trafficking not defined","Single-lab finding"]},{"year":2020,"claim":"In vivo validation that the R1346H variant specifically disrupts sleep spindles came from knock-in mice showing altered TRN excitability and marked spindle deficits during NREM sleep, while CaV3.3 haploinsufficiency alone was insufficient — demonstrating that the variant acts as more than simple loss-of-function.","evidence":"CaV3.3 R1346H knock-in and heterozygous KO mice with in vivo polysomnography and ex vivo TRN patch-clamp","pmids":["32066662"],"confidence":"High","gaps":["Molecular mechanism distinguishing R1346H from haploinsufficiency not resolved","Whether spindle deficits cause cognitive/psychiatric phenotypes not tested"]},{"year":2021,"claim":"Gain-of-function neurodevelopmental variants at I860, I1306, and M1425 were shown to stabilize hydrogen bonds in the channel gate, slow gating transitions, increase window current, and shift TRN model neurons from rebound bursts to slow oscillations — establishing a gain-of-function disease mechanism distinct from R1346H loss-of-function.","evidence":"Patch-clamp in HEK293T cells, structural homology modeling, site-directed mutagenesis, computational TRN modeling, chromaffin cell recordings","pmids":["33704440"],"confidence":"High","gaps":["No in vivo knock-in model for gain-of-function variants","Downstream consequences for thalamocortical circuit and sleep architecture not tested"]},{"year":2022,"claim":"Epigenetic regulation of CACNA1I by TET1-mediated DNA hydroxymethylation was demonstrated, and rare hemiplegic migraine-associated variants were functionally characterized, broadening the regulatory and disease landscape of CaV3.3.","evidence":"MeDIP/hMeDIP with TET1 overexpression/knockdown in Leydig cells; patch-clamp of five migraine-associated variants in HEK293T cells","pmids":["36370755","35928792"],"confidence":"Medium","gaps":["TET1 regulation shown only in non-neuronal cells","Migraine variants not validated in neuronal systems or in vivo","Causal link between CaV3.3 dysfunction and migraine pathophysiology not established"]},{"year":2025,"claim":"Position A398 was revealed as a hotspot where different substitutions cause opposite functional effects (A398E gain-of-function vs. A398V loss-of-function), and genotype–phenotype correlation across multiple variants established that presence or absence of increased neuronal excitability in silico predicts seizure occurrence in patients.","evidence":"Site-directed mutagenesis, voltage-clamp electrophysiology, structural homology modeling, computational neuronal excitability modeling with clinical genotype-phenotype correlation","pmids":["40825030"],"confidence":"High","gaps":["No in vivo animal model for A398 variants","Structural basis of opposite effects at same residue not resolved at atomic level"]},{"year":null,"claim":"A high-resolution cryo-EM structure of CaV3.3, the precise residues mediating muscarinic receptor inhibition and lipid binding, the trafficking pathway by which R1346H differs from haploinsufficiency, and in vivo validation of gain-of-function variants in thalamocortical circuits remain unresolved.","evidence":"","pmids":[],"confidence":"High","gaps":["No experimental 3D structure of CaV3.3","Muscarinic inhibition and lipid binding sites not mapped to specific residues","In vivo models for gain-of-function variants lacking","How CaV3.3 dysfunction translates to psychiatric and cognitive phenotypes is mechanistically unclear"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005215","term_label":"transporter activity","supporting_discovery_ids":[0,2,3,6,7,8,9,14]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,10]}],"pathway":[{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[1,2,3,8]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[4,10]},{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[0,2,3,8,9]}],"complexes":[],"partners":["TET1","NRN1","CHRM1"],"other_free_text":[]},"mechanistic_narrative":"CACNA1I encodes CaV3.3, the pore-forming α-subunit of a T-type (low-voltage-activated) calcium channel whose distinctively slow gating kinetics — determined by multiple transmembrane domains with domain IV as the principal contributor — generate low-threshold calcium spikes, rebound burst firing, and window-current-driven membrane potential oscillations that are essential for sleep spindle rhythmogenesis in thalamic reticular nucleus (TRN) neurons [PMID:26612388, PMID:32066662, PMID:16996222, PMID:16706840]. CaV3.3 surface expression and current amplitude are regulated by Gαq/11-coupled muscarinic receptors acting through two channel-intrinsic regions [PMID:17535809], by endogenous polyunsaturated lipids competing at a shared site with synthetic T-channel antagonists [PMID:24214826], by neuritin signaling via the insulin receptor/MEK-ERK pathway [PMID:28475719], and by TET1-mediated DNA hydroxymethylation of the CACNA1I locus [PMID:36370755]. Gain-of-function missense variants at residues I860, I1306, M1425, and A398 slow channel gating, increase window current, and enhance neuronal excitability — correlating with seizure phenotypes — while the schizophrenia-associated R1346H variant reduces glycosylation and surface expression, diminishing CaV3.3 current density sufficiently to abolish rebound bursting and disrupt sleep spindles in vivo [PMID:33704440, PMID:27756899, PMID:32066662, PMID:40825030]."},"prefetch_data":{"uniprot":{"accession":"Q9P0X4","full_name":"Voltage-dependent T-type calcium channel subunit alpha-1I","aliases":["Voltage-gated calcium channel subunit alpha Cav3.3","Ca(v)3.3"],"length_aa":2223,"mass_kda":245.1,"function":"Voltage-sensitive calcium channels (VSCC) mediate the entry of calcium ions into excitable cells and are also involved in a variety of calcium-dependent processes, including muscle contraction, hormone or neurotransmitter release, gene expression, cell motility, cell division and cell death. This channel gives rise to T-type calcium currents. T-type calcium channels belong to the 'low-voltage activated (LVA)' group and are strongly blocked by nickel and mibefradil. A particularity of this type of channels is an opening at quite negative potentials, and a voltage-dependent inactivation. T-type channels serve pacemaking functions in both central neurons and cardiac nodal cells and support calcium signaling in secretory cells and vascular smooth muscle. They may also be involved in the modulation of firing patterns of neurons which is important for information processing as well as in cell growth processes. Gates in voltage ranges similar to, but higher than alpha 1G or alpha 1H Voltage-sensitive calcium channels (VSCC) mediate the entry of calcium ions into excitable cells and are also involved in a variety of calcium-dependent processes, including muscle contraction, hormone or neurotransmitter release, gene expression, cell motility, cell division and cell death. This channel gives rise to T-type calcium currents Voltage-sensitive calcium channels (VSCC) mediate the entry of calcium ions into excitable cells and are also involved in a variety of calcium-dependent processes, including muscle contraction, hormone or neurotransmitter release, gene expression, cell motility, cell division and cell death. This channel gives rise to T-type calcium currents","subcellular_location":"Membrane","url":"https://www.uniprot.org/uniprotkb/Q9P0X4/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CACNA1I","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/CACNA1I","total_profiled":1310},"omim":[{"mim_id":"620114","title":"NEURODEVELOPMENTAL DISORDER WITH SPEECH IMPAIRMENT AND WITH OR WITHOUT SEIZURES; NEDSIS","url":"https://www.omim.org/entry/620114"},{"mim_id":"609120","title":"CATION CHANNEL, SPERM-ASSOCIATED, 3; CATSPER3","url":"https://www.omim.org/entry/609120"},{"mim_id":"608230","title":"CALCIUM CHANNEL, VOLTAGE-DEPENDENT, T TYPE, ALPHA-1I SUBUNIT; CACNA1I","url":"https://www.omim.org/entry/608230"},{"mim_id":"607904","title":"CALCIUM CHANNEL, VOLTAGE-DEPENDENT, T TYPE, ALPHA-1H SUBUNIT; CACNA1H","url":"https://www.omim.org/entry/607904"},{"mim_id":"604065","title":"CALCIUM CHANNEL, VOLTAGE-DEPENDENT, T TYPE, ALPHA-1G SUBUNIT; CACNA1G","url":"https://www.omim.org/entry/604065"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Plasma membrane","reliability":"Approved"},{"location":"Cell Junctions","reliability":"Additional"},{"location":"Acrosome","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"brain","ntpm":9.7},{"tissue":"thyroid gland","ntpm":5.1}],"url":"https://www.proteinatlas.org/search/CACNA1I"},"hgnc":{"alias_symbol":["Cav3.3"],"prev_symbol":[]},"alphafold":{"accession":"Q9P0X4","domains":[{"cath_id":"1.20.120.350","chopping":"58-192","consensus_level":"high","plddt":83.508,"start":58,"end":192},{"cath_id":"1.20.120.350","chopping":"635-745","consensus_level":"medium","plddt":80.6718,"start":635,"end":745},{"cath_id":"1.10.287.70","chopping":"761-877","consensus_level":"medium","plddt":79.4421,"start":761,"end":877},{"cath_id":"1.20.120.350","chopping":"1142-1289","consensus_level":"medium","plddt":80.1974,"start":1142,"end":1289},{"cath_id":"1.20.120.350","chopping":"1471-1602","consensus_level":"high","plddt":83.5681,"start":1471,"end":1602}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9P0X4","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9P0X4-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9P0X4-F1-predicted_aligned_error_v6.png","plddt_mean":59.66},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CACNA1I","jax_strain_url":"https://www.jax.org/strain/search?query=CACNA1I"},"sequence":{"accession":"Q9P0X4","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9P0X4.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9P0X4/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9P0X4"}},"corpus_meta":[{"pmid":"30718321","id":"PMC_30718321","title":"Genome-Wide Association Studies of Impulsive Personality Traits (BIS-11 and UPPS-P) and Drug Experimentation in up to 22,861 Adult Research Participants Identify Loci in the CACNA1I and CADM2 genes.","date":"2019","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/30718321","citation_count":115,"is_preprint":false},{"pmid":"12614673","id":"PMC_12614673","title":"Immunological characterization of T-type voltage-dependent calcium channel CaV3.1 (alpha 1G) and CaV3.3 (alpha 1I) isoforms reveal differences in their localization, expression, and neural development.","date":"2003","source":"Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/12614673","citation_count":72,"is_preprint":false},{"pmid":"27756899","id":"PMC_27756899","title":"A rare schizophrenia risk variant of CACNA1I disrupts CaV3.3 channel activity.","date":"2016","source":"Scientific 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chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/17535809","citation_count":41,"is_preprint":false},{"pmid":"26612388","id":"PMC_26612388","title":"Suppression of Sleep Spindle Rhythmogenesis in Mice with Deletion of CaV3.2 and CaV3.3 T-type Ca(2+) Channels.","date":"2016","source":"Sleep","url":"https://pubmed.ncbi.nlm.nih.gov/26612388","citation_count":41,"is_preprint":false},{"pmid":"16706840","id":"PMC_16706840","title":"T-type CaV3.3 calcium channels produce spontaneous low-threshold action potentials and intracellular calcium oscillations.","date":"2006","source":"The European journal of neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/16706840","citation_count":39,"is_preprint":false},{"pmid":"32066662","id":"PMC_32066662","title":"Effects of a patient-derived de novo coding alteration of CACNA1I in mice connect a schizophrenia risk gene with sleep spindle deficits.","date":"2020","source":"Translational psychiatry","url":"https://pubmed.ncbi.nlm.nih.gov/32066662","citation_count":35,"is_preprint":false},{"pmid":"16996222","id":"PMC_16996222","title":"Determinants of the differential gating properties of Cav3.1 and Cav3.3 T-type channels: a role of domain IV?","date":"2006","source":"Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/16996222","citation_count":22,"is_preprint":false},{"pmid":"15016809","id":"PMC_15016809","title":"Multiple structural elements contribute to the slow kinetics of the Cav3.3 T-type channel.","date":"2004","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/15016809","citation_count":19,"is_preprint":false},{"pmid":"28475719","id":"PMC_28475719","title":"Neuritin Enhances Synaptic Transmission in Medial Prefrontal Cortex in Mice by Increasing CaV3.3 Surface Expression.","date":"2017","source":"Cerebral cortex (New York, N.Y. : 1991)","url":"https://pubmed.ncbi.nlm.nih.gov/28475719","citation_count":17,"is_preprint":false},{"pmid":"35928792","id":"PMC_35928792","title":"Investigation of CACNA1I Cav3.3 Dysfunction in Hemiplegic Migraine.","date":"2022","source":"Frontiers in molecular neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/35928792","citation_count":14,"is_preprint":false},{"pmid":"29308060","id":"PMC_29308060","title":"Further evidence for the genetic association between CACNA1I and schizophrenia.","date":"2018","source":"Hereditas","url":"https://pubmed.ncbi.nlm.nih.gov/29308060","citation_count":13,"is_preprint":false},{"pmid":"36786913","id":"PMC_36786913","title":"Whole Exome Sequencing of Hemiplegic Migraine Patients Shows an Increased Burden of Missense Variants in CACNA1H and CACNA1I Genes.","date":"2023","source":"Molecular neurobiology","url":"https://pubmed.ncbi.nlm.nih.gov/36786913","citation_count":13,"is_preprint":false},{"pmid":"16939858","id":"PMC_16939858","title":"CACNA1I is not associated with childhood absence epilepsy in the Chinese Han population.","date":"2006","source":"Pediatric neurology","url":"https://pubmed.ncbi.nlm.nih.gov/16939858","citation_count":13,"is_preprint":false},{"pmid":"28974111","id":"PMC_28974111","title":"In vitro neurotoxicity by ropivacaine is reduced by silencing Cav3.3 T-type calcium subunits in neonatal rat sensory neurons.","date":"2017","source":"Artificial cells, nanomedicine, and biotechnology","url":"https://pubmed.ncbi.nlm.nih.gov/28974111","citation_count":12,"is_preprint":false},{"pmid":"24214826","id":"PMC_24214826","title":"Cross-modulation and molecular interaction at the Cav3.3 protein between the endogenous lipids and the T-type calcium channel antagonist TTA-A2.","date":"2013","source":"Molecular pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/24214826","citation_count":12,"is_preprint":false},{"pmid":"28725167","id":"PMC_28725167","title":"Genetic risk between the CACNA1I gene and schizophrenia in Chinese 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forebrain","date":"2025-08-22","source":"bioRxiv","url":"https://doi.org/10.1101/2025.08.18.670814","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.08.26.672495","title":"Transcriptional Readthrough at <i>Atf4</i> Locus Suppresses <i>Rps19bp1</i> and Impairs Heart Development","date":"2025-08-29","source":"bioRxiv","url":"https://doi.org/10.1101/2025.08.26.672495","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":16820,"output_tokens":4229,"usd":0.056947},"stage2":{"model":"claude-opus-4-6","input_tokens":7699,"output_tokens":3144,"usd":0.175643},"total_usd":0.23259,"stage1_batch_id":"msgbatch_011kfMfE81o6CTcyhVUqumuW","stage2_batch_id":"msgbatch_01DTputS6WNkH745x1nVSoBo","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2016,\n      \"finding\": \"The schizophrenia-associated de novo missense variant R1346H of CaV3.3 (encoded by CACNA1I) reduces protein glycosylation, lowers membrane surface expression of CaV3.3, and decreases whole-cell Ca2+ current amplitude by ~50% without altering channel biophysical properties; computational modeling showed that reducing CaV3.3 current density by ≥22% eliminates rebound bursting in thalamic reticular nucleus (TRN) neurons.\",\n      \"method\": \"Western blotting, glycosylation assays, whole-cell patch clamp in human cell lines, NEURON computational modeling\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — multiple orthogonal biochemical and electrophysiological methods in a single study with functional computational validation\",\n      \"pmids\": [\"27756899\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"CaV3.3 R1346H knock-in mice show altered cellular excitability in the TRN and marked deficits in sleep spindle occurrence and morphology during NREM sleep, establishing a direct link between CaV3.3 channel function and sleep spindle generation in vivo; CaV3.3 haploinsufficiency alone did not reproduce spindle deficits.\",\n      \"method\": \"Knock-in mouse model, patch-clamp recordings in TRN neurons, polysomnographic EEG recordings in freely behaving mice\",\n      \"journal\": \"Translational psychiatry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean knock-in and knockout models with defined cellular and EEG phenotypes, replicated across two genetic models\",\n      \"pmids\": [\"32066662\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"CaV3.3 (encoded by CACNA1I) dominates nRt (nucleus reticularis thalami) rhythmic bursting; double knockout of CaV3.2 and CaV3.3 fully abolished low-threshold Ca2+ currents and bursting in nRt neurons and suppressed burst-mediated inhibitory responses in thalamocortical neurons, resulting in fragmented NREM sleep and suppressed sigma-band EEG power.\",\n      \"method\": \"Patch-clamp recordings in thalamic brain slices from CaV3.2 KO and CaV3.2/CaV3.3 double KO mice, polysomnographic recordings\",\n      \"journal\": \"Sleep\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean genetic KO models with defined cellular and EEG phenotypes, epistatic dissection of two channel subtypes\",\n      \"pmids\": [\"26612388\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Gain-of-function missense variants in CACNA1I (p.Ile860Met, p.Ile860Asn, p.Ile1306Thr, p.Met1425Ile) at the cytoplasmic ends of IIS6, IIIS5, and IIIS6 segments slow activation/inactivation/deactivation kinetics, hyperpolarize voltage-dependence of activation and inactivation via stabilizing hydrogen bonds in the channel gate, increase window current and calcium influx, and lower the threshold and increase duration/frequency of action potential firing in TRN neuron models; expression in chromaffin cells shifted firing from rebound bursts to slow oscillations.\",\n      \"method\": \"Patch-clamp electrophysiology in HEK293T cells, structural homology modeling, site-directed mutagenesis, computational TRN neuron modeling, primary chromaffin cell recordings\",\n      \"journal\": \"Brain\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — multiple orthogonal methods including mutagenesis, electrophysiology, structural modeling, and primary neuron recordings in one study\",\n      \"pmids\": [\"33704440\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Gαq/11-coupled muscarinic acetylcholine receptors (M1, M3, M5) selectively inhibit CaV3.3 T-type Ca2+ currents in a reversible, use-independent manner with increased inactivation kinetics, while CaV3.1 and CaV3.2 are not inhibited; chimeric channel analysis identified two distinct CaV3.3 regions necessary and sufficient for M1 receptor-mediated inhibition, acting through Gαq/11 (not Gβγ).\",\n      \"method\": \"Perforated patch clamp, chimeric channel analysis, loss-of-function with genetically encoded Gα/Gβγ antagonists, gain-of-function with genetically encoded Gα subtypes, co-expression of channels with mAChR subtypes\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — multiple orthogonal methods (chimeras, gain/loss-of-function Gα constructs, multiple receptor subtypes) in a single study\",\n      \"pmids\": [\"17535809\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Alternative splicing of CACNA1I (deletion of 13 amino acids encoded by exon 33, Δ33; and inclusion of exon 9) modulates CaV3.3 gating: Δ33 slows channel opening, exon 9 addition to Δ33 channels unexpectedly slows both activation and inactivation, and the combination alters burst firing in neuronal models; interdependent effects suggest direct interaction between intracellular regions after repeats I and IV.\",\n      \"method\": \"RT-PCR cloning from human brain, whole-cell patch clamp in heterologous expression, computational neuronal firing modeling\",\n      \"journal\": \"Journal of neurophysiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — electrophysiological characterization of defined splice variants with computational modeling, multiple variant combinations tested\",\n      \"pmids\": [\"15254077\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"The distinctively slow activation and inactivation kinetics of CaV3.3 (alpha1I) are not determined by any single structural domain but require multiple structural elements; chimeric channel analysis between CaV3.1 and CaV3.3 in Xenopus oocytes showed no single domain substitution was sufficient to confer or abolish slow kinetics.\",\n      \"method\": \"Chimeric channel construction, two-electrode voltage clamp in Xenopus oocytes\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — systematic chimeric analysis with in vitro functional readout\",\n      \"pmids\": [\"15016809\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Domain IV is the major determinant of CaV3.3 half-activation potential and activation time constant as well as recovery from inactivation, established by systematic chimeric channel swaps between CaV3.1 and CaV3.3; domains I and II also play a minor role, while the carboxy terminal region is not involved.\",\n      \"method\": \"Chimeric channel construction, whole-cell patch clamp in tsA-201 cells\",\n      \"journal\": \"Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — systematic domain-swap chimeric analysis with functional electrophysiological readout\",\n      \"pmids\": [\"16996222\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"CaV3.3 window current is critical for triggering intrinsic membrane potential oscillations and intracellular Ca2+ oscillations; overexpression of CaV3.3 in NG108-15 cells produces spontaneous low-threshold action potentials and Ca2+ oscillations dependent on window current, with AP duration controlled by sustained CaV3.3 current.\",\n      \"method\": \"Whole-cell and perforated patch clamp, fluorescence Ca2+ imaging in NG108-15 cells overexpressing CaV3.3\",\n      \"journal\": \"The European journal of neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct functional demonstration in a single heterologous system with pharmacological validation\",\n      \"pmids\": [\"16706840\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Endogenous polyunsaturated lipids (anandamide, NAGly, NASer, NADA, NATau, NA-5HT) inhibit CaV3.3 current and compete with the synthetic T-channel antagonist TTA-A2 at a shared binding site on CaV3.3, as demonstrated by radioligand displacement; lipids with saturated chains do not inhibit the channel and do not displace binding, revealing a shared molecular mechanism between endogenous lipids and synthetic inhibitors.\",\n      \"method\": \"Whole-cell patch clamp, radioactive binding assay with [3H]TTA-A1 on CaV3.3-expressing cell membranes\",\n      \"journal\": \"Molecular pharmacology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct binding assay combined with functional electrophysiology, structure-activity relationship across multiple lipid species\",\n      \"pmids\": [\"24214826\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Neuritin increases CaV3.3 α-subunit surface expression via an insulin receptor (IR) / MEK-ERK signaling pathway, leading to increased mEPSC frequency and glutamate release in medial prefrontal cortex; T-type channel inhibitors abolished the neuritin-induced calcium current and synaptic effects.\",\n      \"method\": \"Western blotting of membrane fractions, whole-cell patch clamp, HPLC glutamate measurement in mPFC slices, pharmacological inhibitors of IR and MEK/ERK\",\n      \"journal\": \"Cerebral cortex\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — multiple methods (biochemical surface expression, electrophysiology, neurotransmitter measurement) but conducted in a single lab with no direct CaV3.3 mutagenesis\",\n      \"pmids\": [\"28475719\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"CaV3.3 (alpha1I) protein exists as distinct developmental isoforms with differential glycosylation: a large neonatal form (~260 kDa in midbrain/diencephalon) that decreases postnatally and a smaller adult form (~190–230 kDa); immunohistochemistry established region-specific expression with highest CaV3.3 immunoreactivity in olfactory bulb and midbrain.\",\n      \"method\": \"Anti-peptide antibody characterization, Western blotting of regional brain dissections, immunohistochemistry in rodent and human brain\",\n      \"journal\": \"Neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — direct protein characterization across development, but relies primarily on antibody-based methods\",\n      \"pmids\": [\"12614673\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"CaV3.3 (alpha1I) protein is modified by N-glycosylation, and the large neonatal form is polysialylated; PNGase F and Endo-N treatment demonstrated that differential glycosylation fully accounts for the molecular weight difference between neonatal and adult CaV3.3 isoforms.\",\n      \"method\": \"PNGase F and Endo-N enzymatic deglycosylation, Western blotting with validated antibodies\",\n      \"journal\": \"Neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct enzymatic demonstration of glycosylation type, but limited to biochemical characterization\",\n      \"pmids\": [\"17317015\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Rare CACNA1I missense variants found in hemiplegic migraine patients (p.R111G, p.M128L, p.D302G, p.R307H, p.Q1158H) alter CaV3.3 biophysical properties including reduced current density, shifted voltage-dependence, and slower kinetics when expressed in HEK293T cells; Q1158H showed the greatest effect and both R307H and Q1158H showed altered conductance under acidotic/alkalotic conditions.\",\n      \"method\": \"Whole-cell patch-clamp electrophysiology in HEK293T cells transfected with variant channels\",\n      \"journal\": \"Frontiers in molecular neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct functional characterization of multiple disease variants by patch clamp, single lab\",\n      \"pmids\": [\"35928792\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Two substitutions at CaV3.3 residue A398 have opposite functional effects: A398E causes gain-of-function (increased channel excitability), while A398V causes loss-of-function (decreased current density, accelerated gating, decreased neuronal excitability); both M1425V and M1425I substitutions cause gain-of-function with left-shifted voltage-dependence and slowed kinetics; the presence or absence of seizures in patients correlates with the presence or absence of increased neuronal excitability in silico.\",\n      \"method\": \"Site-directed mutagenesis, voltage-clamp electrophysiology in heterologous cells, computational neuronal excitability modeling, structural homology modeling\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — mutagenesis, electrophysiology, structural and computational modeling with genotype-phenotype correlation across multiple variants\",\n      \"pmids\": [\"40825030\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"TET1, a DNA demethylase, regulates CaV3.3 (Cav3.3) expression in TM3 Leydig cells through DNA hydroxymethylation of the Cav3.3 locus, as confirmed by MeDIP and hMeDIP; BPA exposure reduces TET1 and CaV3.3 mRNA, and differential TET1 expression modulates CaV3.3 levels.\",\n      \"method\": \"MeDIP, hMeDIP, qRT-PCR, Western blotting, adenoviral overexpression/knockdown in TM3 Leydig cells\",\n      \"journal\": \"Chemosphere\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — direct epigenetic methylation assays linking TET1 to CaV3.3 regulation, but in a non-neuronal context and single lab\",\n      \"pmids\": [\"36370755\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CACNA1I encodes CaV3.3, the pore-forming subunit of a T-type (low voltage-activated) calcium channel highly expressed in GABAergic neurons of the thalamic reticular nucleus (TRN), where its slow gating kinetics (determined by multiple transmembrane domains, especially domain IV) underlie low-threshold Ca2+ spikes, rebound burst firing, and sleep spindle rhythmogenesis during NREM sleep; CaV3.3 surface expression and function are regulated by Gαq/11-coupled muscarinic receptors, endogenous polyunsaturated lipids (acting at a shared site with synthetic T-channel inhibitors), neuritin via IR/MEK-ERK signaling, and epigenetic hydroxymethylation by TET1, while disease-causing gain-of-function variants (including schizophrenia-associated R1346H and neurodevelopmental disorder variants at I860, I1306, M1425, A398) alter channel gating and calcium influx to disrupt TRN excitability and spindle generation.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"CACNA1I encodes CaV3.3, the pore-forming α-subunit of a T-type (low-voltage-activated) calcium channel whose distinctively slow gating kinetics — determined by multiple transmembrane domains with domain IV as the principal contributor — generate low-threshold calcium spikes, rebound burst firing, and window-current-driven membrane potential oscillations that are essential for sleep spindle rhythmogenesis in thalamic reticular nucleus (TRN) neurons [PMID:26612388, PMID:32066662, PMID:16996222, PMID:16706840]. CaV3.3 surface expression and current amplitude are regulated by Gαq/11-coupled muscarinic receptors acting through two channel-intrinsic regions [PMID:17535809], by endogenous polyunsaturated lipids competing at a shared site with synthetic T-channel antagonists [PMID:24214826], by neuritin signaling via the insulin receptor/MEK-ERK pathway [PMID:28475719], and by TET1-mediated DNA hydroxymethylation of the CACNA1I locus [PMID:36370755]. Gain-of-function missense variants at residues I860, I1306, M1425, and A398 slow channel gating, increase window current, and enhance neuronal excitability — correlating with seizure phenotypes — while the schizophrenia-associated R1346H variant reduces glycosylation and surface expression, diminishing CaV3.3 current density sufficiently to abolish rebound bursting and disrupt sleep spindles in vivo [PMID:33704440, PMID:27756899, PMID:32066662, PMID:40825030].\",\n  \"teleology\": [\n    {\n      \"year\": 2003,\n      \"claim\": \"Establishing that CaV3.3 protein exists as developmentally regulated, differentially glycosylated isoforms with region-specific brain expression provided the first protein-level characterization beyond the cloned cDNA.\",\n      \"evidence\": \"Anti-peptide antibody Western blotting and immunohistochemistry across rodent and human brain regions and developmental stages\",\n      \"pmids\": [\"12614673\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Antibody-based detection without independent mass-spectrometry validation\", \"Functional significance of neonatal vs. adult isoforms unknown\", \"No link to channel electrophysiology\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Systematic chimeric analysis between CaV3.1 and CaV3.3 revealed that CaV3.3's hallmark slow gating kinetics arise from distributed structural determinants across multiple domains rather than a single transferable module, while alternative splicing of exons 9 and 33 modulates gating and burst firing properties.\",\n      \"evidence\": \"Chimeric channel electrophysiology in Xenopus oocytes and tsA-201 cells; RT-PCR cloning of splice variants from human brain with patch-clamp characterization\",\n      \"pmids\": [\"15016809\", \"15254077\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis at atomic resolution unknown\", \"Which splice variants predominate in TRN neurons not determined\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Domain IV was identified as the principal determinant of CaV3.3 half-activation potential, activation kinetics, and recovery from inactivation, resolving the earlier finding that no single domain was sufficient by showing graded contributions with domain IV dominant; separately, CaV3.3 window current was shown to drive intrinsic membrane potential and Ca²⁺ oscillations.\",\n      \"evidence\": \"Systematic domain-swap chimeras with patch-clamp in tsA-201 cells; CaV3.3 overexpression in NG108-15 cells with Ca²⁺ imaging\",\n      \"pmids\": [\"16996222\", \"16706840\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular identity of domain IV residues conferring slow kinetics not pinpointed\", \"Window current contribution not tested in native TRN neurons\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Two regulatory mechanisms were defined: Gαq/11-coupled muscarinic receptors selectively inhibit CaV3.3 (not CaV3.1/3.2) through two channel-intrinsic regions, and neonatal CaV3.3 carries polysialic acid modifications that fully account for developmental molecular weight differences.\",\n      \"evidence\": \"Chimeric channel analysis with genetically encoded Gα/Gβγ antagonists; PNGase F and Endo-N enzymatic deglycosylation and Western blotting\",\n      \"pmids\": [\"17535809\", \"17317015\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of channel residues mediating muscarinic inhibition unknown\", \"Functional impact of polysialylation on channel gating or trafficking not tested\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Identification of a shared binding site on CaV3.3 for endogenous polyunsaturated lipids and synthetic T-channel antagonists revealed that the channel is a direct lipid sensor, establishing a molecular mechanism for endogenous modulation.\",\n      \"evidence\": \"Radioligand displacement assay with [³H]TTA-A1 on CaV3.3-expressing membranes combined with patch-clamp electrophysiology across multiple lipid species\",\n      \"pmids\": [\"24214826\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Binding site not mapped to specific channel residues\", \"Physiological relevance of lipid modulation in TRN neurons not demonstrated in vivo\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"CaV3.3 was established as the dominant T-type channel for TRN burst firing and sleep spindle generation: the schizophrenia-associated R1346H variant reduced glycosylation and surface expression to suppress current density by ~50%, and CaV3.2/CaV3.3 double knockout abolished low-threshold bursting and fragmented NREM sleep.\",\n      \"evidence\": \"Biochemistry and patch-clamp in human cell lines with NEURON modeling (R1346H); patch-clamp in brain slices and polysomnography from CaV3.2/CaV3.3 double-KO mice\",\n      \"pmids\": [\"27756899\", \"26612388\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether R1346H acts purely via reduced surface expression or also affects trafficking pathway\", \"Relative contribution of CaV3.3 vs. CaV3.2 to spindle generation not fully separated\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Neuritin was identified as an upstream regulator that increases CaV3.3 surface expression via insulin receptor/MEK-ERK signaling, linking extracellular trophic signals to T-type channel-dependent glutamate release in medial prefrontal cortex.\",\n      \"evidence\": \"Western blotting of membrane fractions, patch-clamp, HPLC glutamate measurement in mPFC slices with pharmacological pathway dissection\",\n      \"pmids\": [\"28475719\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No direct CaV3.3 mutagenesis to confirm subtype specificity\", \"Mechanism of ERK-dependent surface trafficking not defined\", \"Single-lab finding\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"In vivo validation that the R1346H variant specifically disrupts sleep spindles came from knock-in mice showing altered TRN excitability and marked spindle deficits during NREM sleep, while CaV3.3 haploinsufficiency alone was insufficient — demonstrating that the variant acts as more than simple loss-of-function.\",\n      \"evidence\": \"CaV3.3 R1346H knock-in and heterozygous KO mice with in vivo polysomnography and ex vivo TRN patch-clamp\",\n      \"pmids\": [\"32066662\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular mechanism distinguishing R1346H from haploinsufficiency not resolved\", \"Whether spindle deficits cause cognitive/psychiatric phenotypes not tested\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Gain-of-function neurodevelopmental variants at I860, I1306, and M1425 were shown to stabilize hydrogen bonds in the channel gate, slow gating transitions, increase window current, and shift TRN model neurons from rebound bursts to slow oscillations — establishing a gain-of-function disease mechanism distinct from R1346H loss-of-function.\",\n      \"evidence\": \"Patch-clamp in HEK293T cells, structural homology modeling, site-directed mutagenesis, computational TRN modeling, chromaffin cell recordings\",\n      \"pmids\": [\"33704440\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No in vivo knock-in model for gain-of-function variants\", \"Downstream consequences for thalamocortical circuit and sleep architecture not tested\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Epigenetic regulation of CACNA1I by TET1-mediated DNA hydroxymethylation was demonstrated, and rare hemiplegic migraine-associated variants were functionally characterized, broadening the regulatory and disease landscape of CaV3.3.\",\n      \"evidence\": \"MeDIP/hMeDIP with TET1 overexpression/knockdown in Leydig cells; patch-clamp of five migraine-associated variants in HEK293T cells\",\n      \"pmids\": [\"36370755\", \"35928792\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"TET1 regulation shown only in non-neuronal cells\", \"Migraine variants not validated in neuronal systems or in vivo\", \"Causal link between CaV3.3 dysfunction and migraine pathophysiology not established\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Position A398 was revealed as a hotspot where different substitutions cause opposite functional effects (A398E gain-of-function vs. A398V loss-of-function), and genotype–phenotype correlation across multiple variants established that presence or absence of increased neuronal excitability in silico predicts seizure occurrence in patients.\",\n      \"evidence\": \"Site-directed mutagenesis, voltage-clamp electrophysiology, structural homology modeling, computational neuronal excitability modeling with clinical genotype-phenotype correlation\",\n      \"pmids\": [\"40825030\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No in vivo animal model for A398 variants\", \"Structural basis of opposite effects at same residue not resolved at atomic level\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"A high-resolution cryo-EM structure of CaV3.3, the precise residues mediating muscarinic receptor inhibition and lipid binding, the trafficking pathway by which R1346H differs from haploinsufficiency, and in vivo validation of gain-of-function variants in thalamocortical circuits remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No experimental 3D structure of CaV3.3\", \"Muscarinic inhibition and lipid binding sites not mapped to specific residues\", \"In vivo models for gain-of-function variants lacking\", \"How CaV3.3 dysfunction translates to psychiatric and cognitive phenotypes is mechanistically unclear\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": [0, 2, 3, 6, 7, 8, 9, 14]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 10]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [1, 2, 3, 8]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [4, 10]},\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [0, 2, 3, 8, 9]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"TET1\",\n      \"NRN1\",\n      \"CHRM1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}