{"gene":"ATP1A2","run_date":"2026-06-09T22:02:44","timeline":{"discoveries":[{"year":2003,"finding":"Loss-of-function mutations in ATP1A2 (encoding the Na+/K+ pump α2 subunit) cause familial hemiplegic migraine type 2 (FHM2) via haploinsufficiency; functional data demonstrated that a single allele loss of function is sufficient to trigger the pathogenic mechanism.","method":"Genetic linkage, mutation analysis, and functional loss-of-function assays in cellular models","journal":"Nature genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic linkage plus functional cellular assays, foundational paper replicated across many subsequent studies","pmids":["12539047"],"is_preprint":false},{"year":2003,"finding":"Homozygous knockout of Atp1a2 in mice causes selective neuronal apoptosis in the amygdala and piriform cortex associated with high c-Fos expression (neural hyperactivity), and impaired re-uptake of glutamate and GABA into crude synaptosome fractions (P2 fraction), indicating the α2 subunit is critical for neurotransmitter clearance and regulation of neural activity in these regions.","method":"Atp1a2 knockout mouse generation, c-Fos immunostaining, synaptosomal glutamate/GABA re-uptake assay, behavioral fear/anxiety testing in heterozygous mice","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal in vivo and in vitro methods (KO mouse, synaptosomal uptake assay, IHC, behavioral phenotyping) in a single rigorous study","pmids":["12805306"],"is_preprint":false},{"year":2009,"finding":"Certain FHM2 ATP1A2 mutations (R908Q) cause defective plasma membrane targeting rather than loss of catalytic activity; others (P979L) exhibit temperature-sensitive protein instability at 37°C but not 28°C, establishing plasma membrane mistargeting and protein instability as distinct pathophysiological mechanisms beyond simple loss of pump function.","method":"Expression in Xenopus oocytes (two-electrode voltage clamp) and transfection of HEK293FT cells with immunofluorescence and Western blot at different temperatures","journal":"Channels (Austin, Tex.)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — two orthogonal expression systems (oocytes + mammalian cells), single lab","pmids":["19372756"],"is_preprint":false},{"year":2010,"finding":"The C. elegans ATP1A2 homolog EAT-6 (Na+/K+-ATPase α subunit) modulates presynaptic acetylcholine neurotransmission and is required for serotonin-mediated inhibition of ACh release; genetic epistasis placed EAT-6 in a pathway with EGL-30 Gαq, EGL-8 phospholipase C, and SLO-1 BK channel signaling; eat-6 is expressed in ventral cord ACh motor neurons and its loss increases synaptic vesicle number.","method":"C. elegans genetics (eat-6 mutation and cell-specific RNAi), aldicarb paralysis assay, serotonin behavioral assay, electron microscopy of synaptic vesicles, genetic epistasis with Gαq/PLC/BK channel pathway mutants","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (genetics, EM, epistasis) in C. elegans ortholog, single lab; relevant as ortholog functional study","pmids":["20442779"],"is_preprint":false},{"year":2011,"finding":"The FHM2 ATP1A2 G301R mutation completely abolishes Na+/K+-ATPase function, confirmed in human cellular models at physiological temperature (37°C) by cell viability assays and Western blot; homology modeling placed G301 in a structurally critical position of the α2 subunit.","method":"Cell viability assays, Western blot, immunocytochemistry, homology modeling in COS-1/HeLa cells at 37°C","journal":"Cephalalgia","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple cellular assays, single lab, consistent with independent reports of G301R in other papers","pmids":["21398422"],"is_preprint":false},{"year":2013,"finding":"The FHM2 ATP1A2 R1007W mutation causes loss of function via reduced ion pumping activity with more profound voltage dependence and decreased apparent affinity for extracellular K+ at resting membrane potential voltages, a mechanism distinct from other FHM2 mutations, predicted to impair K+ clearance.","method":"Two-electrode voltage clamp experiments in Xenopus oocytes","journal":"Cephalalgia","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — rigorous in vitro electrophysiology with mechanistic detail, single lab and single mutation","pmids":["23838748"],"is_preprint":false},{"year":2018,"finding":"The FHM2 ATP1A2 G301R knock-in heterozygous mouse model (α2+/G301R) shows increased susceptibility to both cortical spreading depression (CSD) and epileptiform activity in vivo, establishing that reduced α2-Na+/K+-ATPase function in astrocytes lowers the threshold for CSD and seizure-like events.","method":"In vivo cortical KCl application in awake head-restrained mice, electrocorticography recording of CSD and epileptiform activity","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean KI mouse model with defined electrophysiological phenotype, single lab","pmids":["30446731"],"is_preprint":false},{"year":2018,"finding":"A novel ATP1A2 mutation causes hypokalaemic periodic paralysis with an anomalous inward leak current under hypokalaemic conditions and lower pump turnover rates under physiological K+ concentrations, demonstrating that α2-Na+/K+-ATPase dysfunction in skeletal muscle can produce depolarizing leak current sufficient to cause muscle inexcitability.","method":"Electrophysiological measurements of mutant pump activity in Xenopus oocytes (two-electrode voltage clamp under varying K+ concentrations)","journal":"Brain","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro electrophysiology with mechanistic specificity, single lab, novel mechanism for this gene","pmids":["30423015"],"is_preprint":false},{"year":2018,"finding":"In Parkin-knockout mouse brain, ATP1A2 protein abundance is elevated (validated by quantitative immunoblot), and this is associated with altered electrophysiological properties of noradrenergic locus coeruleus neurons including accelerated pacemaker frequency and reduced slow afterhyperpolarization, suggesting Parkin-mediated ubiquitylation normally regulates ATP1A2 turnover and thereby modulates neuronal excitability.","method":"Mass spectrometry ubiquitylome profiling, quantitative immunoblot, patch-clamp electrophysiology in acute brain slices from aged Parkin-KO mice","journal":"Neurobiology of disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — MS-based ubiquitylome plus immunoblot validation plus electrophysiology, single lab; indirect evidence for Parkin as upstream regulator of ATP1A2","pmids":["30763678"],"is_preprint":false},{"year":2019,"finding":"FHM2 KI mice (W887R/+) with 50% reduced α2-NKA expression show abnormally increased long-term potentiation (LTP) in the dentate gyrus but normal LTP in the CA1 hippocampal area, demonstrating region-specific synaptic plasticity abnormalities attributable to reduced astrocytic K+ and glutamate clearance.","method":"Ex vivo hippocampal slice electrophysiology (field recordings of LTP in dentate gyrus and CA1) in FHM2 W887R/+ knock-in mice","journal":"Cephalalgia","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — defined KI mouse model, region-specific electrophysiology, single lab","pmids":["30922082"],"is_preprint":false},{"year":2020,"finding":"In Atp1a2+/- heterozygous mice during cortical spreading depression, astrocytic Ca2+ wave propagation speed and the percentage of astrocytes with elevated Ca2+ were greater than in wild-type, demonstrating that haploinsufficiency of the α2 subunit leads to astrocyte hyperactivity during CSD.","method":"In vivo calcium imaging using G-CaMP7 transgenic reporter in astrocytes and neurons during KCl-induced CSD in Atp1a2+/- mice","journal":"FEBS open bio","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct in vivo calcium imaging with genetic model and specific cellular phenotype, single lab","pmids":["32237043"],"is_preprint":false},{"year":2021,"finding":"In vitro testing of 14 ATP1A2/A3 mutations in transfected COS-1 cells demonstrated impaired Na+/K+-ATPase pump activity (severe loss of function) for disease-associated variants; lack of cell survival in COS-1 correlated with the most severe clinical phenotypes including polymicrogyria and early lethality, establishing that severely impaired NKA pump function can disrupt brain morphogenesis.","method":"Transfection of COS-1 cells with mutant constructs, cell survival assays, in silico pathogenicity prediction","journal":"Brain","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cell-based functional assays on 14 mutations with genotype-phenotype correlation, single study with multiple orthogonal approaches","pmids":["33880529"],"is_preprint":false},{"year":2021,"finding":"ATP1A2 mutations causing FHM with intellectual disability (FHMEI: T378N, G615R, D718N) show more severe impairment of Na+/K+-ATPase biochemical activity than mutations causing pure FHM or FHM with epilepsy only; the ouabain-sensitive pump current of G615R was significantly reduced by whole-cell patch clamp, while G762S and R938P pump currents were comparable to wild-type, establishing a gradient of functional severity correlating with clinical phenotype.","method":"Cell survival assays, membrane protein extraction, Western blot, Na+/K+-ATPase activity assay, whole-cell patch-clamp electrophysiology in HEK293T/HeLa cells, homology modeling","journal":"The journal of headache and pain","confidence":"Medium","confidence_rationale":"Tier 1–2 / Moderate — multiple orthogonal functional assays including electrophysiology, systematic analysis of 10 mutations, single lab","pmids":["34384358"],"is_preprint":false},{"year":2023,"finding":"ASO-mediated knockdown of Atp1a2 in astrocytes of SOD1*G93A mice significantly reduced SOD1 protein aggregation in vivo, but accelerated disease onset and shortened lifespan despite no systemic toxicity; transcriptomics revealed upregulation of glutamate receptor signaling and complement activation pathways, indicating that astrocytic α2-Na+/K+-ATPase participates in SOD1 aggregation regulation but its loss worsens ALS disease progression.","method":"Antisense oligonucleotide (ASO) in vivo Atp1a2 knockdown in SOD1 mice, Western blot for SOD1 aggregation, survival analysis, transcriptomics","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo ASO knockdown with molecular readouts and transcriptomics, single lab","pmids":["38015828"],"is_preprint":false},{"year":2025,"finding":"In Atp1a2+/- heterozygous mice, inhibitory postsynaptic currents (IPSCs) in the basolateral amygdala were consistently larger than in wild-type while excitatory postsynaptic currents (EPSCs) were comparable, indicating enhanced inhibitory neurotransmission due to α2-NKA haploinsufficiency; hyperthermic stress abolished this enhanced inhibition, providing a mechanism by which fever triggers neurological episodes in ATP1A2-related disorders.","method":"Acute brain slice electrophysiology (patch-clamp recording of IPSCs and EPSCs in BLA principal neurons) in Atp1a2+/- mice at baseline and under hyperthermic conditions","journal":"Journal of neurophysiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct electrophysiology in defined KO model with two experimental conditions (baseline and hyperthermia), single lab","pmids":["40465487"],"is_preprint":false},{"year":2019,"finding":"Homozygous truncating ATP1A2 variants in humans cause a lethal syndromic polymicrogyria with complete absence of immunodetectable ATP1A2 protein in brain, establishing that biallelic loss of function of the α2-Na+/K+-ATPase is incompatible with normal brain morphogenesis and neonatal survival.","method":"Whole exome sequencing, immunohistochemistry for ATP1A2 protein in post-mortem brain tissue from affected individuals","journal":"Brain","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct protein absence confirmed by IHC in human brain, genetic and neuropathological findings, two independent families","pmids":["31608932"],"is_preprint":false},{"year":2006,"finding":"The ATP1A2 G615R mutation causes complete loss of Na+/K+-ATPase function, as demonstrated by cellular survival assays, establishing haploinsufficiency as the mechanism underlying the most severe FHM2 phenotypes including permanent mental retardation.","method":"Cellular survival assays in heterologous expression system","journal":"Annals of neurology","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — single functional assay type, single lab, but mechanistically informative for complete loss-of-function","pmids":["16437583"],"is_preprint":false},{"year":2005,"finding":"The ATP1A2 C515Y variant causes complete loss of Na+/K+-ATPase function comparable to known FHM mutations, as demonstrated by two-electrode voltage clamp in Xenopus oocytes and radiochemical ATPase activity measurements; by contrast, E174K showed no functional alteration in the same assays.","method":"Two-electrode voltage clamp in Xenopus oocytes, radiochemical ATPase activity assay","journal":"Human mutation","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — two orthogonal in vitro assays, single lab","pmids":["16110494"],"is_preprint":false},{"year":2018,"finding":"ATP1A2 overexpression in prostate cancer cells inhibited cell proliferation, migration, invasion, and epithelial-mesenchymal transition (EMT), and suppressed the TGF-β/Smad signaling pathway; conversely, ATP1A2 knockdown activated TGF-β/Smad signaling, and the effects of knockdown were reversed by a TGF-β/Smad pathway inhibitor (LY364947), placing ATP1A2 upstream of the TGF-β/Smad axis.","method":"ATP1A2 overexpression and siRNA knockdown in PC-3 and DU145 cells; clone formation, EdU, flow cytometry, transwell assays; Western blot for TGF-β/Smad pathway; in vivo xenograft in nude mice","journal":"Translational andrology and urology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, cancer cell lines with no clear mechanistic link to canonical pump function, epistasis via pharmacological inhibitor only","pmids":["35242641"],"is_preprint":false},{"year":2018,"finding":"ATP1A2 knockdown (siRNA) in rat cardiomyocytes subjected to anoxia-reoxygenation injury significantly elevated apoptosis and expression of ER stress markers CHOP, GRP78, and caspase-12, indicating that α2-Na+/K+-ATPase protects cardiomyocytes from A/R injury by inhibiting ER stress-related apoptosis.","method":"siRNA knockdown of ATP1A2 in rat cardiomyocytes, anoxia-reoxygenation injury model, flow cytometry apoptosis assay, Western blot for ER stress proteins","journal":"Canadian journal of physiology and pharmacology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, loss-of-function with defined molecular readout but limited mechanistic depth","pmids":["29394489"],"is_preprint":false}],"current_model":"ATP1A2 encodes the α2 isoform of the Na+/K+-ATPase, which is predominantly expressed in astrocytes and maintains Na+/K+ electrochemical gradients; heterozygous loss-of-function mutations cause FHM2 via haploinsufficiency, impairing astrocytic clearance of extracellular K+ and glutamate, lowering the threshold for cortical spreading depression and neuronal hyperexcitability, while homozygous loss is lethal and disrupts brain morphogenesis."},"narrative":{"mechanistic_narrative":"ATP1A2 encodes the α2 catalytic subunit of the Na+/K+-ATPase, an ion pump whose function in the central nervous system supports clearance of extracellular K+ and neurotransmitters and thereby constrains neural excitability [PMID:12805306, PMID:23838748]. Heterozygous loss-of-function mutations cause familial hemiplegic migraine type 2 (FHM2) through haploinsufficiency: a single inactivated allele is sufficient to trigger pathology [PMID:12539047, PMID:16437583]. Distinct mutations impair pump function by distinct routes — defective plasma-membrane targeting (R908Q), temperature-sensitive protein instability (P979L), outright abolition of catalytic activity (G301R, G615R, C515Y), or altered voltage dependence and reduced extracellular K+ affinity (R1007W) — yet converge on reduced pump output [PMID:19372756, PMID:21398422, PMID:23838748, PMID:16437583, PMID:16110494]. The depth of biochemical impairment scales with clinical severity, with the most damaging variants producing intellectual disability, polymicrogyria, and early lethality [PMID:33880529, PMID:34384358]. In mouse models, reduced α2 activity lowers the threshold for cortical spreading depression and epileptiform activity, drives astrocyte Ca2+ hyperactivity during CSD, and produces region-specific synaptic abnormalities including enhanced dentate gyrus LTP and enlarged inhibitory currents in the amygdala that are abolished by hyperthermia — linking fever to symptomatic episodes [PMID:30446731, PMID:30922082, PMID:32237043, PMID:40465487]. Biallelic truncating loss in humans yields a lethal syndromic polymicrogyria with complete absence of brain ATP1A2 protein, establishing that the pump is essential for brain morphogenesis [PMID:31608932]. Beyond ion transport, ATP1A2 abundance is regulated by Parkin-dependent ubiquitylation, which modulates noradrenergic neuron pacemaking [PMID:30763678].","teleology":[{"year":2003,"claim":"Established that ATP1A2 dysfunction causes human disease and defined the genetic mechanism — haploinsufficiency of the Na+/K+ pump α2 subunit underlies familial hemiplegic migraine type 2.","evidence":"Genetic linkage, mutation analysis, and functional loss-of-function assays in cellular models","pmids":["12539047"],"confidence":"High","gaps":["Did not resolve which cell type (astrocyte vs neuron) drives pathology","No in vivo demonstration of the migraine-triggering mechanism"]},{"year":2003,"claim":"Defined the in vivo role of α2 in neurotransmitter clearance and neural activity control, showing homozygous loss causes selective neuronal apoptosis and impaired glutamate/GABA re-uptake.","evidence":"Atp1a2 knockout mice with c-Fos immunostaining, synaptosomal uptake assays, and behavioral testing","pmids":["12805306"],"confidence":"High","gaps":["Mechanism linking impaired uptake to apoptosis not fully resolved","Did not address cortical spreading depression directly"]},{"year":2005,"claim":"Demonstrated that disease variants can be cleanly distinguished from neutral ones at the functional level, establishing complete loss of pump function as the pathogenic readout.","evidence":"Two-electrode voltage clamp in Xenopus oocytes and radiochemical ATPase assays comparing C515Y vs E174K","pmids":["16110494"],"confidence":"Medium","gaps":["Single lab","Functional assays in heterologous systems may not capture astrocytic context"]},{"year":2006,"claim":"Linked the depth of functional loss to clinical severity, showing complete loss of function in the most severe FHM2 phenotypes with intellectual disability.","evidence":"Cellular survival assays of G615R in a heterologous expression system","pmids":["16437583"],"confidence":"Medium","gaps":["Single functional assay type","No structural rationale for severity in this study"]},{"year":2009,"claim":"Revealed that FHM2 mutations act through mechanistically distinct routes beyond simple catalytic loss — namely defective membrane trafficking and temperature-sensitive instability.","evidence":"Xenopus oocyte voltage clamp plus HEK293FT transfection with immunofluorescence/Western blot at 28°C and 37°C","pmids":["19372756"],"confidence":"Medium","gaps":["Did not test trafficking in neural cell types","Temperature sensitivity not validated in vivo"]},{"year":2010,"claim":"Placed the α subunit in a defined presynaptic signaling pathway, showing the ortholog modulates neurotransmitter release downstream of Gαq/PLC/BK-channel signaling.","evidence":"C. elegans eat-6 genetics, aldicarb and serotonin behavioral assays, synaptic-vesicle EM, and epistasis with EGL-30/EGL-8/SLO-1","pmids":["20442779"],"confidence":"Medium","gaps":["Ortholog study; conservation of this pathway in mammalian ATP1A2 not established","Single lab"]},{"year":2011,"claim":"Confirmed at physiological temperature that a key FHM2 mutation abolishes pump function and mapped it to a structurally critical residue.","evidence":"Cell viability, Western blot, immunocytochemistry, and homology modeling of G301R in COS-1/HeLa at 37°C","pmids":["21398422"],"confidence":"Medium","gaps":["Single mutation, single lab","Structural model not experimentally validated"]},{"year":2013,"claim":"Identified a voltage-dependent mechanism of loss — reduced K+ affinity at resting potential — directly linking mutant biophysics to impaired extracellular K+ clearance.","evidence":"Two-electrode voltage clamp of R1007W in Xenopus oocytes","pmids":["23838748"],"confidence":"Medium","gaps":["Single mutation","No demonstration of impaired K+ clearance in tissue"]},{"year":2018,"claim":"Provided in vivo causal proof that reduced astrocytic α2 function lowers the threshold for cortical spreading depression and epileptiform activity.","evidence":"G301R knock-in heterozygous mice with cortical KCl application and electrocorticography","pmids":["30446731"],"confidence":"Medium","gaps":["Single mutation knock-in","Astrocyte-specific causality inferred rather than cell-type-restricted manipulation"]},{"year":2018,"claim":"Broadened the phenotypic spectrum by showing α2 dysfunction in skeletal muscle can generate a depolarizing leak current causing hypokalaemic periodic paralysis.","evidence":"Two-electrode voltage clamp of a novel mutation in Xenopus oocytes under varying K+","pmids":["30423015"],"confidence":"Medium","gaps":["Leak-current mechanism not confirmed in native muscle","Single mutation"]},{"year":2018,"claim":"Identified Parkin-dependent ubiquitylation as an upstream regulator of ATP1A2 turnover that shapes neuronal pacemaking.","evidence":"Ubiquitylome mass spectrometry, quantitative immunoblot, and patch-clamp in Parkin-KO mouse brain slices","pmids":["30763678"],"confidence":"Medium","gaps":["Direct ubiquitylation of ATP1A2 not demonstrated","Causal link between abundance change and electrophysiology indirect"]},{"year":2019,"claim":"Established that biallelic loss of ATP1A2 is incompatible with brain morphogenesis and survival, defining the most severe end of the disease spectrum.","evidence":"Whole exome sequencing and immunohistochemistry showing absent ATP1A2 protein in post-mortem brain from two families","pmids":["31608932"],"confidence":"Medium","gaps":["Developmental mechanism of polymicrogyria not resolved","No model recapitulating the human phenotype"]},{"year":2019,"claim":"Showed haploinsufficiency produces region-specific synaptic plasticity defects, with abnormal LTP confined to the dentate gyrus.","evidence":"Ex vivo field-recording LTP in dentate gyrus and CA1 of W887R/+ knock-in mice","pmids":["30922082"],"confidence":"Medium","gaps":["Basis of regional selectivity unexplained","Single lab"]},{"year":2020,"claim":"Demonstrated that α2 haploinsufficiency causes astrocyte hyperactivity during CSD, providing a cellular correlate of lowered CSD threshold.","evidence":"In vivo G-CaMP7 calcium imaging of astrocytes and neurons during KCl-induced CSD in Atp1a2+/- mice","pmids":["32237043"],"confidence":"Medium","gaps":["Link between astrocyte Ca2+ waves and migraine symptoms not directly tested","Single lab"]},{"year":2021,"claim":"Systematically correlated degree of pump impairment with clinical severity, including disruption of brain morphogenesis at the most severe end.","evidence":"Functional and survival assays of 14 ATP1A2/A3 variants in transfected COS-1 cells with genotype-phenotype analysis","pmids":["33880529"],"confidence":"Medium","gaps":["Survival assay is an indirect proxy for in vivo function","Combined ATP1A2/A3 dataset"]},{"year":2021,"claim":"Refined the severity gradient, showing FHM-with-intellectual-disability mutations impair pump biochemistry more profoundly than pure FHM variants.","evidence":"Survival assays, Na+/K+-ATPase activity assays, whole-cell patch clamp, and homology modeling of multiple mutations in HEK293T/HeLa","pmids":["34384358"],"confidence":"Medium","gaps":["Heterologous cell context","Some variants behaved like wild-type, limiting genotype-phenotype generalization"]},{"year":2023,"claim":"Revealed a non-canonical role in protein-aggregation control, showing astrocytic ATP1A2 knockdown reduces SOD1 aggregation yet worsens ALS progression.","evidence":"ASO-mediated astrocytic Atp1a2 knockdown in SOD1*G93A mice with aggregation Western blot, survival, and transcriptomics","pmids":["38015828"],"confidence":"Medium","gaps":["Mechanism linking pump to aggregation unresolved","Dissociation between aggregation reduction and disease worsening unexplained"]},{"year":2025,"claim":"Provided a mechanism for fever-triggered episodes, showing haploinsufficiency enhances inhibitory neurotransmission that is abolished by hyperthermic stress.","evidence":"Patch-clamp recording of IPSCs/EPSCs in basolateral amygdala neurons of Atp1a2+/- mice at baseline and under hyperthermia","pmids":["40465487"],"confidence":"Medium","gaps":["Molecular basis of hyperthermic loss of inhibition not defined","Single brain region"]},{"year":null,"claim":"It remains unresolved how reduced α2 pump activity is mechanistically transduced into cortical spreading depression and how non-canonical roles (TGF-β/Smad regulation, ER-stress protection, SOD1 aggregation) relate to the pump's transport function.","evidence":"","pmids":[],"confidence":"Low","gaps":["No unified model connecting ion-transport loss to CSD initiation","Non-pump functions reported only in cancer/cardiac cell lines (Low confidence) without mechanistic linkage to transport activity","Cell-type-specific contributions (astrocyte vs neuron vs muscle) not fully dissected"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140657","term_label":"ATP-dependent activity","supporting_discovery_ids":[4,5,7,12,17]},{"term_id":"GO:0005215","term_label":"transporter activity","supporting_discovery_ids":[1,5,7,10]},{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[4,12,17]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[2]}],"pathway":[{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[5,7,10]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[1,6,9,14]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[11,15]}],"complexes":["Na+/K+-ATPase"],"partners":["PRKN"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P50993","full_name":"Sodium/potassium-transporting ATPase subunit alpha-2","aliases":["Sodium pump subunit alpha-2"],"length_aa":1020,"mass_kda":112.3,"function":"This is the catalytic component of the active enzyme, which catalyzes the hydrolysis of ATP coupled with the exchange of sodium and potassium ions across the 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diagnosis","url":"https://pubmed.ncbi.nlm.nih.gov/38549198","citation_count":1,"is_preprint":false},{"pmid":"41533486","id":"PMC_41533486","title":"Jujuboside A induces bladder cancer cell apoptosis by inhibiting ATP1A2-mediated mitochondrial energy metabolism regulation.","date":"2026","source":"Cancer biology & therapy","url":"https://pubmed.ncbi.nlm.nih.gov/41533486","citation_count":0,"is_preprint":false},{"pmid":"40465487","id":"PMC_40465487","title":"Enhanced amygdala inhibitory neurotransmission and its vulnerability to hyperthermic stress in Atp1a2-deficient heterozygous mice.","date":"2025","source":"Journal of neurophysiology","url":"https://pubmed.ncbi.nlm.nih.gov/40465487","citation_count":0,"is_preprint":false},{"pmid":"38798314","id":"PMC_38798314","title":"Atp1a2 and Kcnj9 are candidate genes underlying sensitivity to oxycodone-induced locomotor activation and withdrawal-induced anxiety-like behaviors in C57BL/6 substrains.","date":"2024","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/38798314","citation_count":0,"is_preprint":false},{"pmid":"39072579","id":"PMC_39072579","title":"[Developmental and epileptic encephalopathy produced by the ATP1A2 mutation].","date":"2024","source":"Zhurnal nevrologii i psikhiatrii imeni S.S. Korsakova","url":"https://pubmed.ncbi.nlm.nih.gov/39072579","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":47227,"output_tokens":4970,"usd":0.108116,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":13359,"output_tokens":4944,"usd":0.095198,"stage2_stop_reason":"end_turn"},"total_usd":0.203314,"stage1_batch_id":"msgbatch_0179Z2pxRYBsXi2xADneafRw","stage2_batch_id":"msgbatch_01LaY9ZaVdgjWArcZo9eqQE5","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2003,\n      \"finding\": \"Loss-of-function mutations in ATP1A2 (encoding the Na+/K+ pump α2 subunit) cause familial hemiplegic migraine type 2 (FHM2) via haploinsufficiency; functional data demonstrated that a single allele loss of function is sufficient to trigger the pathogenic mechanism.\",\n      \"method\": \"Genetic linkage, mutation analysis, and functional loss-of-function assays in cellular models\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic linkage plus functional cellular assays, foundational paper replicated across many subsequent studies\",\n      \"pmids\": [\"12539047\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Homozygous knockout of Atp1a2 in mice causes selective neuronal apoptosis in the amygdala and piriform cortex associated with high c-Fos expression (neural hyperactivity), and impaired re-uptake of glutamate and GABA into crude synaptosome fractions (P2 fraction), indicating the α2 subunit is critical for neurotransmitter clearance and regulation of neural activity in these regions.\",\n      \"method\": \"Atp1a2 knockout mouse generation, c-Fos immunostaining, synaptosomal glutamate/GABA re-uptake assay, behavioral fear/anxiety testing in heterozygous mice\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal in vivo and in vitro methods (KO mouse, synaptosomal uptake assay, IHC, behavioral phenotyping) in a single rigorous study\",\n      \"pmids\": [\"12805306\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Certain FHM2 ATP1A2 mutations (R908Q) cause defective plasma membrane targeting rather than loss of catalytic activity; others (P979L) exhibit temperature-sensitive protein instability at 37°C but not 28°C, establishing plasma membrane mistargeting and protein instability as distinct pathophysiological mechanisms beyond simple loss of pump function.\",\n      \"method\": \"Expression in Xenopus oocytes (two-electrode voltage clamp) and transfection of HEK293FT cells with immunofluorescence and Western blot at different temperatures\",\n      \"journal\": \"Channels (Austin, Tex.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — two orthogonal expression systems (oocytes + mammalian cells), single lab\",\n      \"pmids\": [\"19372756\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"The C. elegans ATP1A2 homolog EAT-6 (Na+/K+-ATPase α subunit) modulates presynaptic acetylcholine neurotransmission and is required for serotonin-mediated inhibition of ACh release; genetic epistasis placed EAT-6 in a pathway with EGL-30 Gαq, EGL-8 phospholipase C, and SLO-1 BK channel signaling; eat-6 is expressed in ventral cord ACh motor neurons and its loss increases synaptic vesicle number.\",\n      \"method\": \"C. elegans genetics (eat-6 mutation and cell-specific RNAi), aldicarb paralysis assay, serotonin behavioral assay, electron microscopy of synaptic vesicles, genetic epistasis with Gαq/PLC/BK channel pathway mutants\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (genetics, EM, epistasis) in C. elegans ortholog, single lab; relevant as ortholog functional study\",\n      \"pmids\": [\"20442779\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"The FHM2 ATP1A2 G301R mutation completely abolishes Na+/K+-ATPase function, confirmed in human cellular models at physiological temperature (37°C) by cell viability assays and Western blot; homology modeling placed G301 in a structurally critical position of the α2 subunit.\",\n      \"method\": \"Cell viability assays, Western blot, immunocytochemistry, homology modeling in COS-1/HeLa cells at 37°C\",\n      \"journal\": \"Cephalalgia\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple cellular assays, single lab, consistent with independent reports of G301R in other papers\",\n      \"pmids\": [\"21398422\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"The FHM2 ATP1A2 R1007W mutation causes loss of function via reduced ion pumping activity with more profound voltage dependence and decreased apparent affinity for extracellular K+ at resting membrane potential voltages, a mechanism distinct from other FHM2 mutations, predicted to impair K+ clearance.\",\n      \"method\": \"Two-electrode voltage clamp experiments in Xenopus oocytes\",\n      \"journal\": \"Cephalalgia\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — rigorous in vitro electrophysiology with mechanistic detail, single lab and single mutation\",\n      \"pmids\": [\"23838748\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"The FHM2 ATP1A2 G301R knock-in heterozygous mouse model (α2+/G301R) shows increased susceptibility to both cortical spreading depression (CSD) and epileptiform activity in vivo, establishing that reduced α2-Na+/K+-ATPase function in astrocytes lowers the threshold for CSD and seizure-like events.\",\n      \"method\": \"In vivo cortical KCl application in awake head-restrained mice, electrocorticography recording of CSD and epileptiform activity\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean KI mouse model with defined electrophysiological phenotype, single lab\",\n      \"pmids\": [\"30446731\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"A novel ATP1A2 mutation causes hypokalaemic periodic paralysis with an anomalous inward leak current under hypokalaemic conditions and lower pump turnover rates under physiological K+ concentrations, demonstrating that α2-Na+/K+-ATPase dysfunction in skeletal muscle can produce depolarizing leak current sufficient to cause muscle inexcitability.\",\n      \"method\": \"Electrophysiological measurements of mutant pump activity in Xenopus oocytes (two-electrode voltage clamp under varying K+ concentrations)\",\n      \"journal\": \"Brain\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro electrophysiology with mechanistic specificity, single lab, novel mechanism for this gene\",\n      \"pmids\": [\"30423015\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"In Parkin-knockout mouse brain, ATP1A2 protein abundance is elevated (validated by quantitative immunoblot), and this is associated with altered electrophysiological properties of noradrenergic locus coeruleus neurons including accelerated pacemaker frequency and reduced slow afterhyperpolarization, suggesting Parkin-mediated ubiquitylation normally regulates ATP1A2 turnover and thereby modulates neuronal excitability.\",\n      \"method\": \"Mass spectrometry ubiquitylome profiling, quantitative immunoblot, patch-clamp electrophysiology in acute brain slices from aged Parkin-KO mice\",\n      \"journal\": \"Neurobiology of disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — MS-based ubiquitylome plus immunoblot validation plus electrophysiology, single lab; indirect evidence for Parkin as upstream regulator of ATP1A2\",\n      \"pmids\": [\"30763678\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"FHM2 KI mice (W887R/+) with 50% reduced α2-NKA expression show abnormally increased long-term potentiation (LTP) in the dentate gyrus but normal LTP in the CA1 hippocampal area, demonstrating region-specific synaptic plasticity abnormalities attributable to reduced astrocytic K+ and glutamate clearance.\",\n      \"method\": \"Ex vivo hippocampal slice electrophysiology (field recordings of LTP in dentate gyrus and CA1) in FHM2 W887R/+ knock-in mice\",\n      \"journal\": \"Cephalalgia\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — defined KI mouse model, region-specific electrophysiology, single lab\",\n      \"pmids\": [\"30922082\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"In Atp1a2+/- heterozygous mice during cortical spreading depression, astrocytic Ca2+ wave propagation speed and the percentage of astrocytes with elevated Ca2+ were greater than in wild-type, demonstrating that haploinsufficiency of the α2 subunit leads to astrocyte hyperactivity during CSD.\",\n      \"method\": \"In vivo calcium imaging using G-CaMP7 transgenic reporter in astrocytes and neurons during KCl-induced CSD in Atp1a2+/- mice\",\n      \"journal\": \"FEBS open bio\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct in vivo calcium imaging with genetic model and specific cellular phenotype, single lab\",\n      \"pmids\": [\"32237043\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"In vitro testing of 14 ATP1A2/A3 mutations in transfected COS-1 cells demonstrated impaired Na+/K+-ATPase pump activity (severe loss of function) for disease-associated variants; lack of cell survival in COS-1 correlated with the most severe clinical phenotypes including polymicrogyria and early lethality, establishing that severely impaired NKA pump function can disrupt brain morphogenesis.\",\n      \"method\": \"Transfection of COS-1 cells with mutant constructs, cell survival assays, in silico pathogenicity prediction\",\n      \"journal\": \"Brain\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell-based functional assays on 14 mutations with genotype-phenotype correlation, single study with multiple orthogonal approaches\",\n      \"pmids\": [\"33880529\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"ATP1A2 mutations causing FHM with intellectual disability (FHMEI: T378N, G615R, D718N) show more severe impairment of Na+/K+-ATPase biochemical activity than mutations causing pure FHM or FHM with epilepsy only; the ouabain-sensitive pump current of G615R was significantly reduced by whole-cell patch clamp, while G762S and R938P pump currents were comparable to wild-type, establishing a gradient of functional severity correlating with clinical phenotype.\",\n      \"method\": \"Cell survival assays, membrane protein extraction, Western blot, Na+/K+-ATPase activity assay, whole-cell patch-clamp electrophysiology in HEK293T/HeLa cells, homology modeling\",\n      \"journal\": \"The journal of headache and pain\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — multiple orthogonal functional assays including electrophysiology, systematic analysis of 10 mutations, single lab\",\n      \"pmids\": [\"34384358\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"ASO-mediated knockdown of Atp1a2 in astrocytes of SOD1*G93A mice significantly reduced SOD1 protein aggregation in vivo, but accelerated disease onset and shortened lifespan despite no systemic toxicity; transcriptomics revealed upregulation of glutamate receptor signaling and complement activation pathways, indicating that astrocytic α2-Na+/K+-ATPase participates in SOD1 aggregation regulation but its loss worsens ALS disease progression.\",\n      \"method\": \"Antisense oligonucleotide (ASO) in vivo Atp1a2 knockdown in SOD1 mice, Western blot for SOD1 aggregation, survival analysis, transcriptomics\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo ASO knockdown with molecular readouts and transcriptomics, single lab\",\n      \"pmids\": [\"38015828\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In Atp1a2+/- heterozygous mice, inhibitory postsynaptic currents (IPSCs) in the basolateral amygdala were consistently larger than in wild-type while excitatory postsynaptic currents (EPSCs) were comparable, indicating enhanced inhibitory neurotransmission due to α2-NKA haploinsufficiency; hyperthermic stress abolished this enhanced inhibition, providing a mechanism by which fever triggers neurological episodes in ATP1A2-related disorders.\",\n      \"method\": \"Acute brain slice electrophysiology (patch-clamp recording of IPSCs and EPSCs in BLA principal neurons) in Atp1a2+/- mice at baseline and under hyperthermic conditions\",\n      \"journal\": \"Journal of neurophysiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct electrophysiology in defined KO model with two experimental conditions (baseline and hyperthermia), single lab\",\n      \"pmids\": [\"40465487\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Homozygous truncating ATP1A2 variants in humans cause a lethal syndromic polymicrogyria with complete absence of immunodetectable ATP1A2 protein in brain, establishing that biallelic loss of function of the α2-Na+/K+-ATPase is incompatible with normal brain morphogenesis and neonatal survival.\",\n      \"method\": \"Whole exome sequencing, immunohistochemistry for ATP1A2 protein in post-mortem brain tissue from affected individuals\",\n      \"journal\": \"Brain\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct protein absence confirmed by IHC in human brain, genetic and neuropathological findings, two independent families\",\n      \"pmids\": [\"31608932\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"The ATP1A2 G615R mutation causes complete loss of Na+/K+-ATPase function, as demonstrated by cellular survival assays, establishing haploinsufficiency as the mechanism underlying the most severe FHM2 phenotypes including permanent mental retardation.\",\n      \"method\": \"Cellular survival assays in heterologous expression system\",\n      \"journal\": \"Annals of neurology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — single functional assay type, single lab, but mechanistically informative for complete loss-of-function\",\n      \"pmids\": [\"16437583\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"The ATP1A2 C515Y variant causes complete loss of Na+/K+-ATPase function comparable to known FHM mutations, as demonstrated by two-electrode voltage clamp in Xenopus oocytes and radiochemical ATPase activity measurements; by contrast, E174K showed no functional alteration in the same assays.\",\n      \"method\": \"Two-electrode voltage clamp in Xenopus oocytes, radiochemical ATPase activity assay\",\n      \"journal\": \"Human mutation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — two orthogonal in vitro assays, single lab\",\n      \"pmids\": [\"16110494\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"ATP1A2 overexpression in prostate cancer cells inhibited cell proliferation, migration, invasion, and epithelial-mesenchymal transition (EMT), and suppressed the TGF-β/Smad signaling pathway; conversely, ATP1A2 knockdown activated TGF-β/Smad signaling, and the effects of knockdown were reversed by a TGF-β/Smad pathway inhibitor (LY364947), placing ATP1A2 upstream of the TGF-β/Smad axis.\",\n      \"method\": \"ATP1A2 overexpression and siRNA knockdown in PC-3 and DU145 cells; clone formation, EdU, flow cytometry, transwell assays; Western blot for TGF-β/Smad pathway; in vivo xenograft in nude mice\",\n      \"journal\": \"Translational andrology and urology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, cancer cell lines with no clear mechanistic link to canonical pump function, epistasis via pharmacological inhibitor only\",\n      \"pmids\": [\"35242641\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"ATP1A2 knockdown (siRNA) in rat cardiomyocytes subjected to anoxia-reoxygenation injury significantly elevated apoptosis and expression of ER stress markers CHOP, GRP78, and caspase-12, indicating that α2-Na+/K+-ATPase protects cardiomyocytes from A/R injury by inhibiting ER stress-related apoptosis.\",\n      \"method\": \"siRNA knockdown of ATP1A2 in rat cardiomyocytes, anoxia-reoxygenation injury model, flow cytometry apoptosis assay, Western blot for ER stress proteins\",\n      \"journal\": \"Canadian journal of physiology and pharmacology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, loss-of-function with defined molecular readout but limited mechanistic depth\",\n      \"pmids\": [\"29394489\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"ATP1A2 encodes the α2 isoform of the Na+/K+-ATPase, which is predominantly expressed in astrocytes and maintains Na+/K+ electrochemical gradients; heterozygous loss-of-function mutations cause FHM2 via haploinsufficiency, impairing astrocytic clearance of extracellular K+ and glutamate, lowering the threshold for cortical spreading depression and neuronal hyperexcitability, while homozygous loss is lethal and disrupts brain morphogenesis.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"ATP1A2 encodes the α2 catalytic subunit of the Na+/K+-ATPase, an ion pump whose function in the central nervous system supports clearance of extracellular K+ and neurotransmitters and thereby constrains neural excitability [#1, #5]. Heterozygous loss-of-function mutations cause familial hemiplegic migraine type 2 (FHM2) through haploinsufficiency: a single inactivated allele is sufficient to trigger pathology [#0, #16]. Distinct mutations impair pump function by distinct routes — defective plasma-membrane targeting (R908Q), temperature-sensitive protein instability (P979L), outright abolition of catalytic activity (G301R, G615R, C515Y), or altered voltage dependence and reduced extracellular K+ affinity (R1007W) — yet converge on reduced pump output [#2, #4, #5, #16, #17]. The depth of biochemical impairment scales with clinical severity, with the most damaging variants producing intellectual disability, polymicrogyria, and early lethality [#11, #12]. In mouse models, reduced α2 activity lowers the threshold for cortical spreading depression and epileptiform activity, drives astrocyte Ca2+ hyperactivity during CSD, and produces region-specific synaptic abnormalities including enhanced dentate gyrus LTP and enlarged inhibitory currents in the amygdala that are abolished by hyperthermia — linking fever to symptomatic episodes [#6, #9, #10, #14]. Biallelic truncating loss in humans yields a lethal syndromic polymicrogyria with complete absence of brain ATP1A2 protein, establishing that the pump is essential for brain morphogenesis [#15]. Beyond ion transport, ATP1A2 abundance is regulated by Parkin-dependent ubiquitylation, which modulates noradrenergic neuron pacemaking [#8].\"\n,\n  \"teleology\": [\n    {\n      \"year\": 2003,\n      \"claim\": \"Established that ATP1A2 dysfunction causes human disease and defined the genetic mechanism — haploinsufficiency of the Na+/K+ pump α2 subunit underlies familial hemiplegic migraine type 2.\",\n      \"evidence\": \"Genetic linkage, mutation analysis, and functional loss-of-function assays in cellular models\",\n      \"pmids\": [\"12539047\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve which cell type (astrocyte vs neuron) drives pathology\", \"No in vivo demonstration of the migraine-triggering mechanism\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Defined the in vivo role of α2 in neurotransmitter clearance and neural activity control, showing homozygous loss causes selective neuronal apoptosis and impaired glutamate/GABA re-uptake.\",\n      \"evidence\": \"Atp1a2 knockout mice with c-Fos immunostaining, synaptosomal uptake assays, and behavioral testing\",\n      \"pmids\": [\"12805306\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism linking impaired uptake to apoptosis not fully resolved\", \"Did not address cortical spreading depression directly\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Demonstrated that disease variants can be cleanly distinguished from neutral ones at the functional level, establishing complete loss of pump function as the pathogenic readout.\",\n      \"evidence\": \"Two-electrode voltage clamp in Xenopus oocytes and radiochemical ATPase assays comparing C515Y vs E174K\",\n      \"pmids\": [\"16110494\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"Functional assays in heterologous systems may not capture astrocytic context\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Linked the depth of functional loss to clinical severity, showing complete loss of function in the most severe FHM2 phenotypes with intellectual disability.\",\n      \"evidence\": \"Cellular survival assays of G615R in a heterologous expression system\",\n      \"pmids\": [\"16437583\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single functional assay type\", \"No structural rationale for severity in this study\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Revealed that FHM2 mutations act through mechanistically distinct routes beyond simple catalytic loss — namely defective membrane trafficking and temperature-sensitive instability.\",\n      \"evidence\": \"Xenopus oocyte voltage clamp plus HEK293FT transfection with immunofluorescence/Western blot at 28°C and 37°C\",\n      \"pmids\": [\"19372756\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Did not test trafficking in neural cell types\", \"Temperature sensitivity not validated in vivo\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Placed the α subunit in a defined presynaptic signaling pathway, showing the ortholog modulates neurotransmitter release downstream of Gαq/PLC/BK-channel signaling.\",\n      \"evidence\": \"C. elegans eat-6 genetics, aldicarb and serotonin behavioral assays, synaptic-vesicle EM, and epistasis with EGL-30/EGL-8/SLO-1\",\n      \"pmids\": [\"20442779\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Ortholog study; conservation of this pathway in mammalian ATP1A2 not established\", \"Single lab\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Confirmed at physiological temperature that a key FHM2 mutation abolishes pump function and mapped it to a structurally critical residue.\",\n      \"evidence\": \"Cell viability, Western blot, immunocytochemistry, and homology modeling of G301R in COS-1/HeLa at 37°C\",\n      \"pmids\": [\"21398422\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single mutation, single lab\", \"Structural model not experimentally validated\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Identified a voltage-dependent mechanism of loss — reduced K+ affinity at resting potential — directly linking mutant biophysics to impaired extracellular K+ clearance.\",\n      \"evidence\": \"Two-electrode voltage clamp of R1007W in Xenopus oocytes\",\n      \"pmids\": [\"23838748\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single mutation\", \"No demonstration of impaired K+ clearance in tissue\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Provided in vivo causal proof that reduced astrocytic α2 function lowers the threshold for cortical spreading depression and epileptiform activity.\",\n      \"evidence\": \"G301R knock-in heterozygous mice with cortical KCl application and electrocorticography\",\n      \"pmids\": [\"30446731\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single mutation knock-in\", \"Astrocyte-specific causality inferred rather than cell-type-restricted manipulation\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Broadened the phenotypic spectrum by showing α2 dysfunction in skeletal muscle can generate a depolarizing leak current causing hypokalaemic periodic paralysis.\",\n      \"evidence\": \"Two-electrode voltage clamp of a novel mutation in Xenopus oocytes under varying K+\",\n      \"pmids\": [\"30423015\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Leak-current mechanism not confirmed in native muscle\", \"Single mutation\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Identified Parkin-dependent ubiquitylation as an upstream regulator of ATP1A2 turnover that shapes neuronal pacemaking.\",\n      \"evidence\": \"Ubiquitylome mass spectrometry, quantitative immunoblot, and patch-clamp in Parkin-KO mouse brain slices\",\n      \"pmids\": [\"30763678\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct ubiquitylation of ATP1A2 not demonstrated\", \"Causal link between abundance change and electrophysiology indirect\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Established that biallelic loss of ATP1A2 is incompatible with brain morphogenesis and survival, defining the most severe end of the disease spectrum.\",\n      \"evidence\": \"Whole exome sequencing and immunohistochemistry showing absent ATP1A2 protein in post-mortem brain from two families\",\n      \"pmids\": [\"31608932\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Developmental mechanism of polymicrogyria not resolved\", \"No model recapitulating the human phenotype\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Showed haploinsufficiency produces region-specific synaptic plasticity defects, with abnormal LTP confined to the dentate gyrus.\",\n      \"evidence\": \"Ex vivo field-recording LTP in dentate gyrus and CA1 of W887R/+ knock-in mice\",\n      \"pmids\": [\"30922082\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Basis of regional selectivity unexplained\", \"Single lab\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Demonstrated that α2 haploinsufficiency causes astrocyte hyperactivity during CSD, providing a cellular correlate of lowered CSD threshold.\",\n      \"evidence\": \"In vivo G-CaMP7 calcium imaging of astrocytes and neurons during KCl-induced CSD in Atp1a2+/- mice\",\n      \"pmids\": [\"32237043\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Link between astrocyte Ca2+ waves and migraine symptoms not directly tested\", \"Single lab\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Systematically correlated degree of pump impairment with clinical severity, including disruption of brain morphogenesis at the most severe end.\",\n      \"evidence\": \"Functional and survival assays of 14 ATP1A2/A3 variants in transfected COS-1 cells with genotype-phenotype analysis\",\n      \"pmids\": [\"33880529\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Survival assay is an indirect proxy for in vivo function\", \"Combined ATP1A2/A3 dataset\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Refined the severity gradient, showing FHM-with-intellectual-disability mutations impair pump biochemistry more profoundly than pure FHM variants.\",\n      \"evidence\": \"Survival assays, Na+/K+-ATPase activity assays, whole-cell patch clamp, and homology modeling of multiple mutations in HEK293T/HeLa\",\n      \"pmids\": [\"34384358\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Heterologous cell context\", \"Some variants behaved like wild-type, limiting genotype-phenotype generalization\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Revealed a non-canonical role in protein-aggregation control, showing astrocytic ATP1A2 knockdown reduces SOD1 aggregation yet worsens ALS progression.\",\n      \"evidence\": \"ASO-mediated astrocytic Atp1a2 knockdown in SOD1*G93A mice with aggregation Western blot, survival, and transcriptomics\",\n      \"pmids\": [\"38015828\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism linking pump to aggregation unresolved\", \"Dissociation between aggregation reduction and disease worsening unexplained\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Provided a mechanism for fever-triggered episodes, showing haploinsufficiency enhances inhibitory neurotransmission that is abolished by hyperthermic stress.\",\n      \"evidence\": \"Patch-clamp recording of IPSCs/EPSCs in basolateral amygdala neurons of Atp1a2+/- mice at baseline and under hyperthermia\",\n      \"pmids\": [\"40465487\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular basis of hyperthermic loss of inhibition not defined\", \"Single brain region\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unresolved how reduced α2 pump activity is mechanistically transduced into cortical spreading depression and how non-canonical roles (TGF-β/Smad regulation, ER-stress protection, SOD1 aggregation) relate to the pump's transport function.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No unified model connecting ion-transport loss to CSD initiation\", \"Non-pump functions reported only in cancer/cardiac cell lines (Low confidence) without mechanistic linkage to transport activity\", \"Cell-type-specific contributions (astrocyte vs neuron vs muscle) not fully dissected\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140657\", \"supporting_discovery_ids\": [4, 5, 7, 12, 17]},\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": [1, 5, 7, 10]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [4, 12, 17]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [5, 7, 10]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [1, 6, 9, 14]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [11, 15]}\n    ],\n    \"complexes\": [\"Na+/K+-ATPase\"],\n    \"partners\": [\"PRKN\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":7,"faith_pct":85.71428571428571}}