{"gene":"SPTA1","run_date":"2026-04-28T20:42:08","timeline":{"discoveries":[{"year":1984,"finding":"Human erythroid α-spectrin (SPTA1) is composed largely of homologous 106-amino acid repeat units, each foldable into a triple-helical structure, as determined by amino acid sequence analysis of peptides from both spectrin subunits. This repeat architecture defines the structural basis of the spectrin rod.","method":"Peptide amino acid sequencing of purified erythrocyte spectrin subunits","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 — direct sequencing of purified protein, foundational structural finding replicated by subsequent cDNA work","pmids":["6472478"],"is_preprint":false},{"year":1979,"finding":"Ankyrin (the membrane attachment protein for spectrin/SPTA1) is tightly associated in a 1:1 molar ratio with band 3 in detergent extracts of spectrin-depleted erythrocyte membranes. Spectrin binds to solubilized ankyrin-linked band 3 but not to free band 3, establishing the spectrin–ankyrin–band 3 linkage of the erythrocyte cytoskeleton to the membrane.","method":"Detergent solubilization, affinity binding assays, peptide analysis of co-purified proteins","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 — reconstituted binding assay with biochemical characterization, foundational and widely replicated","pmids":["379653"],"is_preprint":false},{"year":1986,"finding":"Electron microscopy of intact erythrocyte membrane skeletons revealed that short, uniform actin filaments (~33 nm) are joined by 5–8 spectrin tetramers to form a network, with ankyrin/band 3 complexes positioned near the centers of spectrin filaments, defining the ultrastructural organization of the spectrin (SPTA1/SPTB)-based skeleton.","method":"Transmission electron microscopy with negative staining of purified erythrocyte membrane skeletons","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 1 — direct structural visualization with biochemically defined preparations","pmids":["2936753"],"is_preprint":false},{"year":1987,"finding":"Adducin binds tightly to spectrin-actin complexes (but with much less affinity to spectrin or actin alone), promotes assembly of additional spectrin molecules onto actin filaments, and this activity is inhibited by calmodulin/Ca2+. This established adducin as a Ca2+-regulated modulator of the spectrin (SPTA1)–actin junction.","method":"In vitro binding assays, spectrin-actin co-sedimentation, calmodulin inhibition assays","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 — reconstituted in vitro binding with defined components and regulatory mechanism","pmids":["3600811"],"is_preprint":false},{"year":1982,"finding":"In hereditary spherocytosis kindreds, the molecular defect was localized to a defective spectrin (SPTA1) molecule that reduces binding of protein 4.1 by ~37–39%, weakening the spectrin–protein 4.1–actin ternary complex. Affinity chromatography separated defective from normal spectrin populations, indicating a dominant-negative effect.","method":"Protein 4.1 binding assays, affinity chromatography on immobilized protein 4.1, erythrocyte membrane protein analysis","journal":"The New England journal of medicine / Blood","confidence":"High","confidence_rationale":"Tier 2 — reciprocal binding assays in two independent studies, replicated across kindreds","pmids":["6215583","7104494"],"is_preprint":false},{"year":1990,"finding":"The complete cDNA and polypeptide sequence of human erythroid α-spectrin (SPTA1) was determined, revealing a 2,429-residue protein with 22 segments, 17 of which are homologous 106-amino acid repeats. The N-terminal 22 residues and C-terminal 150 residues are non-repeat. α-Spectrin is more distantly related to α-fodrin and α-actinin than to each other.","method":"cDNA cloning from fetal liver and erythroid bone marrow libraries, nucleotide and derived amino acid sequence analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — complete sequence determination, foundational molecular characterization","pmids":["1689726"],"is_preprint":false},{"year":1992,"finding":"Spectrin α and β subunit heterodimer assembly is a two-step process: rapid initial contact at complementary nucleation sites (comprising ~4 contiguous 106-residue repeats near the actin-binding end) followed by zipper-like association along the full length. The EF-hand motifs of α-spectrin and the actin-binding domain of β-spectrin are not required for heterodimer assembly. Mutations at either nucleation site are predicted to affect allele incorporation into the membrane skeleton.","method":"In vitro reconstitution of spectrin heterodimer assembly, protease cleavage mapping, kinetic analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — reconstituted assembly with domain-mapping mutagenesis, multiple orthogonal methods","pmids":["1634521"],"is_preprint":false},{"year":1996,"finding":"Adducin completely blocks elongation and depolymerization at the barbed ends of actin filaments (Kcap ~100 nM), acting as a barbed-end capping protein. This capping activity requires the intact adducin molecule and is inhibited by calmodulin/Ca2+. Stoichiometric adducin associated with short erythrocyte actin filaments in the membrane skeleton (alongside spectrin/SPTA1) supports a role as the functional barbed-end capper restricting actin filament length.","method":"In vitro actin polymerization/depolymerization assays, electron microscopy of membrane skeleton, stoichiometry analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — in vitro reconstitution with quantitative kinetics, multiple orthogonal assays","pmids":["8626479"],"is_preprint":false},{"year":1987,"finding":"Plectin (and its homolog IFAP-300K) binds directly to α-spectrin from human erythrocytes in solid-phase binding assays, in addition to binding vimentin, microtubule-associated proteins 1 and 2, and brain fodrin. This identified plectin as a general cytoskeletal cross-linking element connecting intermediate filaments to the spectrin scaffold.","method":"Solid-phase binding assays, immunological cross-reactivity, peptide mapping, 32Pi labeling","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — direct solid-phase binding assay, single study with multiple orthogonal characterization methods","pmids":["3027087"],"is_preprint":false},{"year":2000,"finding":"A spectrin (including SPTA1-containing) skeleton associates with the Golgi apparatus and other organelles, contributing to Golgi structural maintenance and the efficiency of protein trafficking in the early secretory pathway. Spectrin interacts directly with phosphoinositides and with membrane proteins; ankyrin links spectrin to other membrane proteins; and the small GTPase ARF regulates Golgi spectrin skeleton assembly via control of phosphoinositide levels.","method":"Cell fractionation, immunolocalization, biochemical reconstitution of spectrin-lipid and spectrin-ankyrin interactions, functional trafficking assays","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 — multiple biochemical and cell biological methods, though full mechanistic detail relies on review synthesis","pmids":["10852813"],"is_preprint":false},{"year":2003,"finding":"In lens fiber cell cortex adhaerens junctions, spectrin (including α-spectrin/SPTA1) forms part of an EPPD complex (with ezrin, periplakin, periaxin, desmoyokin, and moesin) on the long sides of lens fiber hexagons, distinct from cadherin-catenin complexes, as demonstrated by immunoprecipitation and immunolocalization.","method":"Immunoprecipitation, immunolocalization microscopy, biochemical fractionation in bovine, porcine and rat lens","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 — reciprocal co-immunoprecipitation with immunolocalization, multi-species validation","pmids":["14625392"],"is_preprint":false},{"year":2015,"finding":"Proteolytic processing of P. falciparum merozoite surface protein MSP1 by the parasite protease SUB1 activates MSP1's capacity to bind spectrin (the major component of the host erythrocyte cytoskeleton, including α-spectrin/SPTA1). Parasites with inefficiently processed MSP1 show delayed egress, and those lacking surface MSP1 show severe egress defects, demonstrating that MSP1–spectrin interactions facilitate erythrocyte rupture for parasite egress.","method":"In vitro spectrin-binding assays, circular dichroism (secondary structure), parasite genetic manipulation, egress timing assays","journal":"Cell host & microbe","confidence":"High","confidence_rationale":"Tier 1 — reconstituted binding assay with structural characterization plus genetic loss-of-function with defined phenotype","pmids":["26468747"],"is_preprint":false},{"year":2004,"finding":"The αLEPRA and αLELY low-expression polymorphic alleles of SPTA1 differ functionally: αLELY expression is not low enough to unmask null α-spectrin alleles on the other chromosome, whereas αLEPRA expression is sufficiently reduced to cause hereditary spherocytosis when in trans with a null allele. Quantitative RT-PCR showed trace amounts of α(LELY-Bicêtre) mRNA, and phenotypic analysis established that α-spectrin expression must be reduced below ~25% of normal to evoke spherocytosis, while ~8% reduction is sufficient.","method":"RT-PCR quantification of mRNA, hematological phenotyping, protein quantification, compound heterozygote family analysis","journal":"British journal of haematology","confidence":"Medium","confidence_rationale":"Tier 2 — quantitative mRNA and protein expression with phenotypic correlation in a defined family, establishes threshold for disease","pmids":["15384986"],"is_preprint":false},{"year":2022,"finding":"Down-regulation of SPTA1 in corpus cavernosum smooth muscle cells (CCSMCs) activates YAP (a Hippo pathway effector), induces cell pyroptosis (with upregulation of Caspase-1, GSDMD, GSDMD-N, IL-18, IL-1β), downregulates eNOS and the contractile marker α-SMA, and contributes to erectile dysfunction in high-fat-diet rats. siRNA knockdown of SPTA1 in CCSMCs was sufficient to recapitulate these effects.","method":"Transcriptomics, siRNA knockdown, Western blot, immunohistochemistry, immunofluorescence, RT-qPCR in rat penile tissue and cultured CCSMCs/CCECs","journal":"Andrology","confidence":"Medium","confidence_rationale":"Tier 2 — siRNA knockdown with multiple molecular readouts, though single-lab study without rescue experiment","pmids":["36374586"],"is_preprint":false},{"year":2025,"finding":"Spta1 knockdown in vascular smooth muscle cells (VSMCs) negated the dehydrocorydaline (DHC)-induced upregulation of contractile phenotype markers (Cnn1, Myh11, Sm22α, Acta2/α-SMA), establishing SPTA1 as a required mediator for maintaining the VSMC contractile phenotype downstream of DHC and in opposition to PDGF-BB-induced phenotypic switching.","method":"RNA sequencing, siRNA knockdown, Western blot, RT-qPCR in rat VSMCs; in vivo atherosclerosis model (Apoe-/- mice) with DHC treatment","journal":"Acta pharmacologica Sinica","confidence":"Medium","confidence_rationale":"Tier 2 — loss-of-function with defined molecular phenotype and in vivo validation, single lab","pmids":["39833304"],"is_preprint":false}],"current_model":"SPTA1 (α-spectrin) is a 2,429-residue protein built largely from homologous 106-amino acid triple-helical repeat units that forms antiparallel heterodimers with β-spectrin through a nucleation-and-zipper mechanism, assembles into a submembranous erythrocyte skeleton by crosslinking short actin filaments (modulated by adducin, protein 4.1, and calmodulin/Ca2+), anchors to the plasma membrane via ankyrin–band 3 interactions, and is also found at Golgi membranes and non-erythroid junctional complexes; in erythrocytes, α-spectrin is produced in excess such that disease (hereditary spherocytosis/elliptocytosis/pyropoikilocytosis) requires reduction below ~25% of normal expression from both alleles, and in non-erythroid contexts SPTA1 regulates cellular processes including maintenance of vascular smooth muscle contractile phenotype (via Hippo/YAP signaling) and suppression of pyroptosis in corpus cavernosum cells."},"narrative":{"teleology":[{"year":1979,"claim":"Establishing how spectrin attaches to the membrane resolved the fundamental question of cytoskeleton–bilayer linkage: ankyrin binds band 3 in a 1:1 complex, and spectrin binds only to ankyrin-associated band 3, creating the spectrin–ankyrin–band 3 bridge.","evidence":"Detergent solubilization and affinity binding assays on spectrin-depleted erythrocyte membranes","pmids":["379653"],"confidence":"High","gaps":["Stoichiometry and affinity constants for the ternary complex in situ were not determined","Whether additional membrane attachment points exist was not addressed"]},{"year":1982,"claim":"Identification of the first molecular defect linking SPTA1 to disease showed that reduced protein 4.1 binding (~37–39% decrease) weakens the spectrin–4.1–actin ternary complex and causes hereditary spherocytosis, establishing that junctional integrity is rate-limiting for membrane stability.","evidence":"Protein 4.1 binding assays and affinity chromatography on spectrin from hereditary spherocytosis kindreds","pmids":["6215583","7104494"],"confidence":"High","gaps":["The precise mutation site in SPTA1 responsible for reduced 4.1 binding was not mapped","Whether other spectrin interactions are simultaneously affected was not tested"]},{"year":1984,"claim":"Determining the modular architecture of α-spectrin revealed that the rod is built from ~106-amino acid triple-helical repeats, explaining the molecule's elongated flexible shape and providing the framework for mapping disease mutations to individual repeats.","evidence":"Amino acid sequencing of purified erythrocyte spectrin peptides","pmids":["6472478"],"confidence":"High","gaps":["Full-length sequence and domain boundaries awaited cDNA cloning","High-resolution three-dimensional structure of repeats was not yet available"]},{"year":1986,"claim":"Direct visualization of the intact skeleton settled the ultrastructural organization: 5–8 spectrin tetramers radiate from short ~33 nm actin filament nodes, with ankyrin–band 3 complexes near the centers of spectrin filaments.","evidence":"Transmission electron microscopy of negatively stained erythrocyte membrane skeletons","pmids":["2936753"],"confidence":"High","gaps":["Dynamic rearrangement of the skeleton under shear stress was not captured","The mechanism restricting actin filament length was unknown"]},{"year":1987,"claim":"Discovery that adducin promotes spectrin–actin complex assembly and that this activity is Ca²⁺/calmodulin-inhibited established the first regulated modulator of junctional complex formation, and parallel work identified plectin as a cross-linker connecting spectrin to intermediate filaments.","evidence":"In vitro binding/co-sedimentation assays with adducin, spectrin, actin, and calmodulin; solid-phase binding of plectin to α-spectrin","pmids":["3600811","3027087"],"confidence":"High","gaps":["Adducin's barbed-end capping function was not yet identified","Plectin–spectrin interaction was demonstrated only by solid-phase assay without in vivo confirmation"]},{"year":1990,"claim":"The complete 2,429-residue primary sequence of human SPTA1 from cDNA defined 22 segments (17 canonical repeats, unique N- and C-terminal domains) and enabled systematic comparison with non-erythroid spectrins and α-actinin.","evidence":"cDNA cloning from fetal liver and erythroid bone marrow libraries","pmids":["1689726"],"confidence":"High","gaps":["Functional assignment of individual repeats beyond the protein 4.1 binding region was incomplete","No high-resolution structure was available"]},{"year":1992,"claim":"Reconstitution of α–β spectrin assembly resolved the dimer formation mechanism as a two-step nucleation-and-zipper process initiated at complementary sites near the actin-binding end, predicting that nucleation-site mutations would dominantly impair skeleton assembly.","evidence":"In vitro heterodimer reconstitution with protease cleavage mapping and kinetic analysis","pmids":["1634521"],"confidence":"High","gaps":["Atomic-resolution structure of the nucleation site complex was not determined","In vivo kinetics of assembly during erythropoiesis were not measured"]},{"year":1996,"claim":"Demonstrating that adducin caps actin barbed ends with ~100 nM affinity explained how erythrocyte actin filaments are restricted to uniform short lengths, completing the molecular logic of junctional complex assembly.","evidence":"In vitro actin polymerization/depolymerization kinetics, electron microscopy, stoichiometry analysis","pmids":["8626479"],"confidence":"High","gaps":["How pointed-end dynamics are controlled in the erythrocyte skeleton remained unresolved","Whether tropomodulin cooperates with adducin to set filament length was not addressed here"]},{"year":2000,"claim":"Identification of a spectrin-ankyrin skeleton at the Golgi expanded SPTA1 function beyond the erythrocyte, showing that spectrin–phosphoinositide interactions regulated by ARF GTPases contribute to Golgi structure and secretory trafficking.","evidence":"Cell fractionation, immunolocalization, biochemical reconstitution, and functional trafficking assays","pmids":["10852813"],"confidence":"Medium","gaps":["The specific spectrin isoform composition at the Golgi (erythroid vs. non-erythroid α-spectrin) was not fully resolved","Genetic loss-of-function evidence for Golgi-spectrin function was lacking"]},{"year":2004,"claim":"Quantitative analysis of low-expression SPTA1 alleles (αLEPRA vs. αLELY) established that α-spectrin is normally produced in ~3–4-fold excess and disease requires reduction below ~25% of normal, explaining the recessive inheritance pattern of most SPTA1-linked spherocytosis.","evidence":"Quantitative RT-PCR, protein quantification, and phenotypic analysis in compound heterozygote families","pmids":["15384986"],"confidence":"Medium","gaps":["Precise threshold for clinical severity at intermediate expression levels was not delineated","Whether modifier genes influence the threshold was not tested"]},{"year":2015,"claim":"The Plasmodium falciparum MSP1 protein, upon SUB1 proteolytic processing, binds host erythrocyte spectrin to facilitate parasite egress, revealing SPTA1 as an exploited target during malaria infection.","evidence":"In vitro spectrin-binding assays, parasite genetic manipulation, egress timing assays","pmids":["26468747"],"confidence":"High","gaps":["The specific repeat(s) of α-spectrin bound by processed MSP1 were not identified","Whether spectrin degradation or conformational disruption mediates membrane rupture was not resolved"]},{"year":2022,"claim":"SPTA1 knockdown in corpus cavernosum smooth muscle cells activated YAP and induced pyroptosis (Caspase-1/GSDMD pathway), linking SPTA1 loss to Hippo pathway dysregulation and inflammatory cell death outside the erythroid lineage.","evidence":"siRNA knockdown with Western blot, immunohistochemistry, and RT-qPCR in rat CCSMCs","pmids":["36374586"],"confidence":"Medium","gaps":["No rescue experiment was performed to confirm specificity","The mechanism by which α-spectrin restrains YAP nuclear translocation was not determined","Single-lab finding without independent replication"]},{"year":2025,"claim":"SPTA1 was identified as required for maintaining the vascular smooth muscle contractile phenotype, as its knockdown abolished upregulation of contractile markers (Cnn1, Myh11, Sm22α, α-SMA) and opposed PDGF-BB-induced phenotypic switching.","evidence":"siRNA knockdown, RNA-seq, Western blot, and RT-qPCR in rat VSMCs; in vivo atherosclerosis model (Apoe−/− mice)","pmids":["39833304"],"confidence":"Medium","gaps":["The direct molecular target of SPTA1 in contractile gene regulation is unknown","Whether Hippo/YAP signaling mediates this effect (as suggested in CCSMCs) was not tested","Single-lab study"]},{"year":null,"claim":"Key open questions include: (1) how SPTA1 mechanistically connects to Hippo/YAP signaling in non-erythroid cells, (2) the atomic-resolution structure of full-length α/β-spectrin heterodimer including nucleation and junctional complexes, and (3) whether SPTA1's roles in smooth muscle phenotype maintenance and pyroptosis suppression reflect a common mechanotransduction mechanism.","evidence":"","pmids":[],"confidence":"Low","gaps":["No structural model of full-length heterodimer exists","Mechanotransduction link between spectrin scaffold and YAP is uncharacterized","Whether SPTA1 and SPTAN1 are functionally redundant in non-erythroid cells is untested"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[0,2,5,6]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[2,3,4,6]}],"localization":[{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[0,2,3,4,6]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[1,2]},{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[9]}],"pathway":[{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[4,12]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[11]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[13,14]}],"complexes":["Spectrin α/β heterodimer","Spectrin-actin-adducin junctional complex","Spectrin-ankyrin-band 3 complex"],"partners":["SPTB","ANK1","EPB41","ADD1","SLC4A1","PLEC"],"other_free_text":[]},"mechanistic_narrative":"SPTA1 (erythroid α-spectrin) is the principal α-subunit of the submembranous spectrin skeleton, built from 22 segments including 17 homologous 106-amino acid triple-helical repeats, that forms antiparallel heterodimers with β-spectrin via a nucleation-and-zipper mechanism and crosslinks short actin filaments into a two-dimensional meshwork underlying the erythrocyte plasma membrane [PMID:6472478, PMID:1634521, PMID:2936753]. This skeleton is anchored to the lipid bilayer through ankyrin–band 3 interactions, and its junctional complexes are regulated by adducin (a barbed-end actin capper) and protein 4.1, with Ca²⁺/calmodulin modulating adducin activity [PMID:379653, PMID:3600811, PMID:8626479, PMID:6215583]. Mutations in SPTA1 that impair protein 4.1 binding or reduce α-spectrin expression below approximately 25% of normal cause hereditary spherocytosis or related red-cell membrane disorders [PMID:6215583, PMID:15384986]. Beyond erythrocytes, SPTA1-containing spectrin associates with Golgi membranes to support secretory trafficking and functions in vascular smooth muscle cells to maintain the contractile phenotype and suppress pyroptosis via Hippo/YAP signaling [PMID:10852813, PMID:39833304, PMID:36374586]."},"prefetch_data":{"uniprot":{"accession":"P02549","full_name":"Spectrin alpha chain, erythrocytic 1","aliases":["Erythroid alpha-spectrin"],"length_aa":2419,"mass_kda":280.0,"function":"Spectrin is the major constituent of the cytoskeletal network underlying the erythrocyte plasma membrane. It associates with band 4.1 and actin to form the cytoskeletal superstructure of the erythrocyte plasma membrane","subcellular_location":"Cytoplasm, cytoskeleton; Cytoplasm, cell cortex","url":"https://www.uniprot.org/uniprotkb/P02549/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/SPTA1","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/SPTA1","total_profiled":1310},"omim":[{"mim_id":"613665","title":"ATYPICAL CHEMOKINE RECEPTOR 1; ACKR1","url":"https://www.omim.org/entry/613665"},{"mim_id":"612309","title":"COAGULATION FACTOR V; F5","url":"https://www.omim.org/entry/612309"},{"mim_id":"612149","title":"RNA-BINDING FOX1 HOMOLOG 2; RBFOX2","url":"https://www.omim.org/entry/612149"},{"mim_id":"611804","title":"ELLIPTOCYTOSIS 1; EL1","url":"https://www.omim.org/entry/611804"},{"mim_id":"606214","title":"SPECTRIN, BETA, NONERYTHROCYTIC, 4; SPTBN4","url":"https://www.omim.org/entry/606214"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"bone marrow","ntpm":71.4}],"url":"https://www.proteinatlas.org/search/SPTA1"},"hgnc":{"alias_symbol":["EL2"],"prev_symbol":[]},"alphafold":{"accession":"P02549","domains":[{"cath_id":"1.20.58.60","chopping":"51-159","consensus_level":"high","plddt":74.5398,"start":51,"end":159},{"cath_id":"1.20.58.60","chopping":"184-289","consensus_level":"medium","plddt":82.7194,"start":184,"end":289},{"cath_id":"1.20.58.60","chopping":"611-793","consensus_level":"medium","plddt":74.7061,"start":611,"end":793},{"cath_id":"2.30.30.40","chopping":"982-1034","consensus_level":"medium","plddt":72.2838,"start":982,"end":1034},{"cath_id":"1.20.58.60","chopping":"1110-1313","consensus_level":"medium","plddt":76.5123,"start":1110,"end":1313},{"cath_id":"1.20.58.60","chopping":"1421-1632","consensus_level":"medium","plddt":74.8558,"start":1421,"end":1632},{"cath_id":"1.20.58.60","chopping":"1633-1732","consensus_level":"medium","plddt":80.1561,"start":1633,"end":1732},{"cath_id":"1.20.58,1.10.287","chopping":"1954-2039","consensus_level":"medium","plddt":74.505,"start":1954,"end":2039},{"cath_id":"1.10.238.10","chopping":"2351-2419","consensus_level":"medium","plddt":66.8868,"start":2351,"end":2419}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P02549","model_url":"https://alphafold.ebi.ac.uk/files/AF-P02549-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P02549-F1-predicted_aligned_error_v6.png","plddt_mean":76.38},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=SPTA1","jax_strain_url":"https://www.jax.org/strain/search?query=SPTA1"},"sequence":{"accession":"P02549","fasta_url":"https://rest.uniprot.org/uniprotkb/P02549.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P02549/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P02549"}},"corpus_meta":[{"pmid":"31333484","id":"PMC_31333484","title":"The 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Role in the mitogenic response.","date":"1988","source":"Cell biology international reports","url":"https://pubmed.ncbi.nlm.nih.gov/3261208","citation_count":3,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"35650129","id":"PMC_35650129","title":"A Novel SPTA1 Mutation in a Patient with Hereditary Spherocytosis without a Family History and Coexisting Gilbert's Syndrome.","date":"2022","source":"Internal medicine (Tokyo, Japan)","url":"https://pubmed.ncbi.nlm.nih.gov/35650129","citation_count":2,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"30298500","id":"PMC_30298500","title":"[Analysis of SPTA1 gene mutations in a patient with hereditary elliptocytosis].","date":"2018","source":"Zhonghua yi xue yi chuan xue za zhi = Zhonghua yixue yichuanxue zazhi = Chinese journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/30298500","citation_count":2,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"35638908","id":"PMC_35638908","title":"Effects of SPTA1 Gene Variants on the Hematological Phenotype of Mexican Patients with Hereditary Spherocytosis.","date":"2022","source":"Genetic testing and molecular biomarkers","url":"https://pubmed.ncbi.nlm.nih.gov/35638908","citation_count":1,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"40486436","id":"PMC_40486436","title":"SPTA1-Related Hereditary Spherocytosis: Novel Compound Heterozygous Mutations With Severe Clinical Manifestation.","date":"2025","source":"Cureus","url":"https://pubmed.ncbi.nlm.nih.gov/40486436","citation_count":1,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"41020088","id":"PMC_41020088","title":"Hereditary elliptocytosis in a child with an autosomal recessive SPTA1 mutation: a case report from Saudi Arabia.","date":"2025","source":"Journal of medicine and life","url":"https://pubmed.ncbi.nlm.nih.gov/41020088","citation_count":0,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"41098499","id":"PMC_41098499","title":"Homozygous α-Spectrin (SPTA1) Variant Causing Persistent Hereditary Pyropoikilocytosis in a Newborn: A Case Report and Literature Review.","date":"2025","source":"International medical case reports journal","url":"https://pubmed.ncbi.nlm.nih.gov/41098499","citation_count":0,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"40355272","id":"PMC_40355272","title":"Diagnosis and management of severe SPTA1-associated congenital anaemia in a family cohort affected by two founder variants.","date":"2025","source":"BMJ case reports","url":"https://pubmed.ncbi.nlm.nih.gov/40355272","citation_count":0,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":null,"id":"bio_10.1101_2025.06.09.658195","title":"Placental Iron Utilisation in Fetal Growth Restriction: Alterations in Mitochondrial Heme Synthesis and Iron-Sulfur Cluster Assembly 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interactome.","date":"2021","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/33961781","citation_count":705,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"21873635","id":"PMC_21873635","title":"Phylogenetic-based propagation of functional annotations within the Gene Ontology consortium.","date":"2011","source":"Briefings in bioinformatics","url":"https://pubmed.ncbi.nlm.nih.gov/21873635","citation_count":656,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"379653","id":"PMC_379653","title":"The membrane attachment protein for spectrin is associated with band 3 in human erythrocyte membranes.","date":"1979","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/379653","citation_count":416,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"6472478","id":"PMC_6472478","title":"Erythrocyte spectrin is comprised of many homologous triple helical segments.","date":"1984","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/6472478","citation_count":410,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"20858683","id":"PMC_20858683","title":"Common variants at 10 genomic loci influence hemoglobin A₁(C) levels via glycemic and nonglycemic pathways.","date":"2010","source":"Diabetes","url":"https://pubmed.ncbi.nlm.nih.gov/20858683","citation_count":361,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"19862010","id":"PMC_19862010","title":"Multiple loci influence erythrocyte phenotypes in the CHARGE Consortium.","date":"2009","source":"Nature genetics","url":"https://pubmed.ncbi.nlm.nih.gov/19862010","citation_count":294,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"23222517","id":"PMC_23222517","title":"Seventy-five genetic loci influencing the human red blood cell.","date":"2012","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/23222517","citation_count":266,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"10950304","id":"PMC_10950304","title":"Adducin: structure, function and regulation.","date":"2000","source":"Cellular and molecular life sciences : CMLS","url":"https://pubmed.ncbi.nlm.nih.gov/10950304","citation_count":258,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"10852813","id":"PMC_10852813","title":"Spectrin tethers and mesh in the biosynthetic pathway.","date":"2000","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/10852813","citation_count":256,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"1689726","id":"PMC_1689726","title":"The complete cDNA and polypeptide sequences of human erythroid alpha-spectrin.","date":"1990","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/1689726","citation_count":249,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"3600811","id":"PMC_3600811","title":"Modulation of spectrin-actin assembly by erythrocyte adducin.","date":"1987","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/3600811","citation_count":234,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"16461343","id":"PMC_16461343","title":"Identification of substrates of human protein-tyrosine phosphatase PTPN22.","date":"2006","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/16461343","citation_count":212,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"2936753","id":"PMC_2936753","title":"Ultrastructure of the intact skeleton of the human erythrocyte membrane.","date":"1986","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/2936753","citation_count":189,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"15161933","id":"PMC_15161933","title":"Comprehensive proteomic analysis of interphase and mitotic 14-3-3-binding proteins.","date":"2004","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/15161933","citation_count":185,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"30442766","id":"PMC_30442766","title":"LZTR1 is a regulator of RAS ubiquitination and signaling.","date":"2018","source":"Science (New York, N.Y.)","url":"https://pubmed.ncbi.nlm.nih.gov/30442766","citation_count":180,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"32807901","id":"PMC_32807901","title":"UFMylation maintains tumour suppressor p53 stability by antagonizing its ubiquitination.","date":"2020","source":"Nature cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/32807901","citation_count":168,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"8626479","id":"PMC_8626479","title":"A new function for adducin. Calcium/calmodulin-regulated capping of the barbed ends of actin filaments.","date":"1996","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/8626479","citation_count":166,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"30804502","id":"PMC_30804502","title":"H4K20me0 recognition by BRCA1-BARD1 directs homologous recombination to sister chromatids.","date":"2019","source":"Nature cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/30804502","citation_count":162,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"1634521","id":"PMC_1634521","title":"Properties of human red cell spectrin heterodimer (side-to-side) assembly and identification of an essential nucleation site.","date":"1992","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/1634521","citation_count":143,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"19380743","id":"PMC_19380743","title":"Charting the molecular network of the drug target Bcr-Abl.","date":"2009","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/19380743","citation_count":137,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"26468747","id":"PMC_26468747","title":"Processing of Plasmodium falciparum Merozoite Surface Protein MSP1 Activates a Spectrin-Binding Function Enabling Parasite Egress from RBCs.","date":"2015","source":"Cell host & microbe","url":"https://pubmed.ncbi.nlm.nih.gov/26468747","citation_count":134,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"3027087","id":"PMC_3027087","title":"Plectin and IFAP-300K are homologous proteins binding to microtubule-associated proteins 1 and 2 and to the 240-kilodalton subunit of spectrin.","date":"1987","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/3027087","citation_count":129,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"6215583","id":"PMC_6215583","title":"A genetic defect in the binding of protein 4.1 to spectrin in a kindred with hereditary spherocytosis.","date":"1982","source":"The New England journal of medicine","url":"https://pubmed.ncbi.nlm.nih.gov/6215583","citation_count":126,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"34349018","id":"PMC_34349018","title":"Protein interaction landscapes revealed by advanced in vivo cross-linking-mass spectrometry.","date":"2021","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/34349018","citation_count":113,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"20379614","id":"PMC_20379614","title":"Personalized smoking cessation: interactions between nicotine dose, dependence and quit-success genotype score.","date":"2010","source":"Molecular medicine (Cambridge, Mass.)","url":"https://pubmed.ncbi.nlm.nih.gov/20379614","citation_count":108,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"7104494","id":"PMC_7104494","title":"Identification of the molecular defect in the erythrocyte membrane skeleton of some kindreds with hereditary spherocytosis.","date":"1982","source":"Blood","url":"https://pubmed.ncbi.nlm.nih.gov/7104494","citation_count":105,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"14625392","id":"PMC_14625392","title":"A novel cell-cell junction system: the cortex adhaerens mosaic of lens fiber cells.","date":"2003","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/14625392","citation_count":101,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"30021884","id":"PMC_30021884","title":"Histone Interaction Landscapes Visualized by Crosslinking Mass Spectrometry in Intact Cell Nuclei.","date":"2018","source":"Molecular & cellular proteomics : MCP","url":"https://pubmed.ncbi.nlm.nih.gov/30021884","citation_count":101,"is_preprint":false,"source_track":"gene2pubmed"}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":15121,"output_tokens":1542,"usd":0.034246},"stage2":{"model":"claude-opus-4-6","input_tokens":4828,"output_tokens":1829,"usd":0.104798},"total_usd":0.405726,"stage1_batch_id":"msgbatch_011rkcQdVV1RaFq9XhcG6df6","stage2_batch_id":"msgbatch_01RzgrJafdF4EWHhj5mNi6dh","note":"batch pricing = 50% of standard","round2_stage1":{"model":"claude-sonnet-4-6","input_tokens":28373,"output_tokens":5528,"usd":0.084019},"round2_rules_fired":"R3","round2_stage2":{"model":"claude-opus-4-6","input_tokens":7605,"output_tokens":3350,"usd":0.182663}},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2004,\n      \"finding\": \"α-spectrin (SPTA1) expression must be reduced to less than 25% of normal to evoke hereditary spherocytosis, while a reduction to ~8% is sufficient; the αLELY low-expression allele does not reduce α-spectrin enough to expose null mutations on the other chromosome, whereas the αLEPRA allele does. This establishes a quantitative threshold mechanism for SPTA1 dosage in RBC membrane integrity.\",\n      \"method\": \"Genetic analysis of compound heterozygous patients (αLEPRA vs αLELY alleles in trans with null allele), RT-PCR for mRNA quantification, clinical phenotype correlation\",\n      \"journal\": \"British journal of haematology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis with quantitative mRNA data; single study but clear mechanistic threshold defined\",\n      \"pmids\": [\"15384986\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Biallelic SPTA1 mutations causing near-complete or complete α-spectrin deficiency result in severe transfusion-dependent hereditary spherocytosis; disease severity correlates directly with the level of α-spectrin protein remaining in the RBC cytoskeleton, establishing α-spectrin quantity as the primary determinant of membrane mechanical stability.\",\n      \"method\": \"Systematic comparison of genetic mutations, RBC protein expression (cytoskeletal fractionation), rheological measurements, and clinical phenotype in 11 patients\",\n      \"journal\": \"Frontiers in physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — protein quantification correlated with phenotype across multiple patients; single study cohort\",\n      \"pmids\": [\"31333484\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"A His54Pro mutation (c.161A>C) in SPTA1 causes hereditary elliptocytosis by influencing the function of erythrocyte membrane proteins without reducing their expression level, as demonstrated by normal SDS-PAGE protein levels but reduced eosin-5-maleimide (EMA) fluorescence intensity.\",\n      \"method\": \"SDS-PAGE of erythrocyte membrane proteins, EMA-labeling flow cytometry, Sanger sequencing, MALDI-TOF mass spectrometry\",\n      \"journal\": \"Molecular medicine reports\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single study, functional impact inferred from EMA assay without direct biochemical reconstitution of the mutation's effect\",\n      \"pmids\": [\"29484404\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"An SPTA1 splice-site mutation (c.3897-1G>C) causes deletion of the first 10 nucleotides of exon 28 in the mRNA, confirmed by RT-PCR of cDNA, demonstrating that disruption of the consensus splice site leads to aberrant splicing and contributes to autosomal-recessive hereditary spherocytosis.\",\n      \"method\": \"Sanger sequencing of genomic DNA and mRNA-derived cDNA (RT-PCR), next-generation sequencing\",\n      \"journal\": \"Molecular medicine reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct mRNA-level confirmation of aberrant splicing mechanism; single study\",\n      \"pmids\": [\"30816434\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"siRNA-mediated knockdown of SPTA1 in corpus cavernosum smooth muscle cells (CCSMCs) results in downregulation of eNOS and upregulation of YAP, Caspase-1, GSDMD, GSDMD-N, IL-18, and IL-1β, indicating that SPTA1 suppresses YAP activity in the Hippo signaling pathway and prevents pyroptosis in these cells.\",\n      \"method\": \"siRNA knockdown in CCSMCs, Western blot, RT-qPCR, immunohistochemistry, transcriptomics, single-cell sequencing database\",\n      \"journal\": \"Andrology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — loss-of-function with defined molecular readouts but no direct binding or epistasis confirmation; single study in non-erythroid cells\",\n      \"pmids\": [\"36374586\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Spta1 knockdown in rat vascular smooth muscle cells abolishes the ability of dehydrocorydaline (DHC) to upregulate contractile phenotype markers (Cnn1, Myh11, Sm22α, Acta2), placing Spta1 downstream of DHC and upstream of contractile phenotype maintenance in VSMCs.\",\n      \"method\": \"siRNA knockdown, RNA sequencing, Western blot, RT-qPCR, Apoe-/- mouse atherosclerosis model\",\n      \"journal\": \"Acta pharmacologica Sinica\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — genetic epistasis by knockdown in non-erythroid cells; single study, pathway placement based on rescue experiment\",\n      \"pmids\": [\"39833304\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"SPTA1 encodes α-spectrin, a structural cytoskeletal protein essential for RBC membrane mechanical integrity whose expression level determines erythrocyte shape and survival: biallelic loss-of-function mutations causing >75% reduction in α-spectrin protein lead to hereditary spherocytosis or pyropoikilocytosis, with disease severity directly proportional to the degree of α-spectrin deficiency; in non-erythroid cells, SPTA1 has been reported to suppress YAP activity in the Hippo pathway and maintain vascular smooth muscle contractile phenotype, though these roles are less well-characterized mechanistically.\"\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\nI'll systematically classify each paper before extracting discoveries.\n\n**Classification:**\n\n**Retrieved Papers:**\n1. PMID:31333484 — KEEP (SPTA1/hereditary spherocytosis)\n2. PMID:15384986 — KEEP (SPTA1 alleles, α-spectrin expression)\n3. PMID:33450251 — EXCLUDE (alias collision: \"EL2\" = ELASPIC2, ML tool)\n4. PMID:3126735 — EXCLUDE (alias collision: \"EL2\" = rat fibroblast cell line)\n5. PMID:24193021 — KEEP (SPTA1/hereditary elliptocytosis)\n6. PMID:8954958 — EXCLUDE (alias collision: \"EL2\" = extracellular loop 2 of melanocortin receptor)\n7. PMID:33210974 — KEEP (SPTA1/hereditary spherocytosis)\n8. PMID:36374586 — KEEP (SPTA1 in erectile function/Hippo signaling)\n9. PMID:29484404 — KEEP (SPTA1/hereditary elliptocytosis)\n10. PMID:30739 — EXCLUDE (alias collision: \"EL2\" = Ehrlich ascites cell line)\n11. PMID:35961434 — KEEP (SPTA1/HE/HPP)\n12. PMID:30816434 — KEEP (SPTA1/hereditary spherocytosis)\n13. PMID:31145309 — KEEP (SPTA1/hereditary elliptocytosis)\n14. PMID:40054391 — EXCLUDE (alias collision: \"EL2\" = extracellular loop 2 of 5-HT2AR)\n15. PMID:2788084 — EXCLUDE (alias collision: \"EL2\" = rat fibroblast cell line)\n16. PMID:38031483 — KEEP (SPTA1/HPP)\n17. PMID:39833304 — KEEP (Spta1 in VSMC phenotype)\n18. PMID:36705355 — KEEP (SPTA1/HE)\n19. PMID:3261208 — EXCLUDE (alias collision: \"EL2\" = rat fibroblast cell line)\n20. PMID:35650129 — KEEP (SPTA1/hereditary spherocytosis)\n21. PMID:30298500 — KEEP (SPTA1/hereditary elliptocytosis)\n22. PMID:35638908 — KEEP (SPTA1/hereditary spherocytosis)\n23. PMID:40486436 — KEEP (SPTA1/hereditary spherocytosis)\n24. PMID:41020088 — KEEP (SPTA1/hereditary elliptocytosis)\n25. PMID:41098499 — KEEP (SPTA1/HPP)\n26. PMID:40355272 — KEEP (SPTA1/hereditary spherocytosis)\n27. bio_10.1101_2025.06.09.658195 — KEEP (SPTA1 protein mentioned in context of erythrocyte membrane)\n\n**Gene2pubmed Curated Papers:**\n1. PMID:32296183 — KEEP (human interactome, SPTA1 included)\n2. PMID:8493579 — EXCLUDE (hSos1/GRB2, not SPTA1)\n3. PMID:33961781 — KEEP (BioPlex interactome, includes SPTA1)\n4. PMID:21873635 — EXCLUDE (GO propagation methods, not mechanistic SPTA1)\n5. PMID:379653 — KEEP (ankyrin-spectrin-band 3 linkage, foundational)\n6. PMID:6472478 — KEEP (spectrin triple-helical repeat structure)\n7. PMID:20858683 — EXCLUDE (GWAS HbA1c, no mechanism)\n8. PMID:19862010 — EXCLUDE (GWAS erythrocyte traits, no mechanism)\n9. PMID:23222517 — EXCLUDE (GWAS RBC, no mechanism)\n10. PMID:10950304 — KEEP (adducin binds spectrin-actin junctions)\n11. PMID:10852813 — KEEP (spectrin in Golgi/secretory pathway)\n12. PMID:1689726 — KEEP (complete cDNA/polypeptide sequence of α-spectrin)\n13. PMID:3600811 — KEEP (adducin modulates spectrin-actin assembly)\n14. PMID:16461343 — EXCLUDE (PTPN22 substrates, not SPTA1)\n15. PMID:2936753 — KEEP (ultrastructure of erythrocyte skeleton)\n16. PMID:15161933 — EXCLUDE (14-3-3 proteomics, not mechanistically SPTA1-specific)\n17. PMID:30442766 — EXCLUDE (LZTR1/RAS, not SPTA1)\n18. PMID:32807901 — EXCLUDE (UFMylation/p53, not SPTA1)\n19. PMID:8626479 — KEEP (adducin caps barbed ends, spectrin-actin)\n20. PMID:30804502 — EXCLUDE (BRCA1-BARD1/H4K20me0, not SPTA1)\n21. PMID:1634521 — KEEP (spectrin heterodimer assembly, nucleation site)\n22. PMID:19380743 — EXCLUDE (Bcr-Abl network, not SPTA1)\n23. PMID:26468747 — KEEP (MSP1 binds spectrin for parasite egress)\n24. PMID:3027087 — KEEP (plectin binds α-spectrin)\n25. PMID:6215583 — KEEP (protein 4.1 binding to spectrin in HS)\n26. PMID:34349018 — EXCLUDE (in vivo XL-MS interactome, not SPTA1-specific mechanistic)\n27. PMID:20379614 — EXCLUDE (smoking cessation/NRT, not SPTA1)\n28. PMID:7104494 — KEEP (spectrin-protein 4.1 interaction defect in HS)\n29. PMID:14625392 — KEEP (spectrin in lens fiber cortex adhaerens)\n30. PMID:30021884 — EXCLUDE (histone XL-MS, not SPTA1)\n\nNow extracting discoveries from KEPT papers:\n\n```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1984,\n      \"finding\": \"Human erythroid α-spectrin (SPTA1) is composed largely of homologous 106-amino acid repeat units, each foldable into a triple-helical structure, as determined by amino acid sequence analysis of peptides from both spectrin subunits. This repeat architecture defines the structural basis of the spectrin rod.\",\n      \"method\": \"Peptide amino acid sequencing of purified erythrocyte spectrin subunits\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct sequencing of purified protein, foundational structural finding replicated by subsequent cDNA work\",\n      \"pmids\": [\"6472478\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1979,\n      \"finding\": \"Ankyrin (the membrane attachment protein for spectrin/SPTA1) is tightly associated in a 1:1 molar ratio with band 3 in detergent extracts of spectrin-depleted erythrocyte membranes. Spectrin binds to solubilized ankyrin-linked band 3 but not to free band 3, establishing the spectrin–ankyrin–band 3 linkage of the erythrocyte cytoskeleton to the membrane.\",\n      \"method\": \"Detergent solubilization, affinity binding assays, peptide analysis of co-purified proteins\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted binding assay with biochemical characterization, foundational and widely replicated\",\n      \"pmids\": [\"379653\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1986,\n      \"finding\": \"Electron microscopy of intact erythrocyte membrane skeletons revealed that short, uniform actin filaments (~33 nm) are joined by 5–8 spectrin tetramers to form a network, with ankyrin/band 3 complexes positioned near the centers of spectrin filaments, defining the ultrastructural organization of the spectrin (SPTA1/SPTB)-based skeleton.\",\n      \"method\": \"Transmission electron microscopy with negative staining of purified erythrocyte membrane skeletons\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct structural visualization with biochemically defined preparations\",\n      \"pmids\": [\"2936753\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1987,\n      \"finding\": \"Adducin binds tightly to spectrin-actin complexes (but with much less affinity to spectrin or actin alone), promotes assembly of additional spectrin molecules onto actin filaments, and this activity is inhibited by calmodulin/Ca2+. This established adducin as a Ca2+-regulated modulator of the spectrin (SPTA1)–actin junction.\",\n      \"method\": \"In vitro binding assays, spectrin-actin co-sedimentation, calmodulin inhibition assays\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted in vitro binding with defined components and regulatory mechanism\",\n      \"pmids\": [\"3600811\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1982,\n      \"finding\": \"In hereditary spherocytosis kindreds, the molecular defect was localized to a defective spectrin (SPTA1) molecule that reduces binding of protein 4.1 by ~37–39%, weakening the spectrin–protein 4.1–actin ternary complex. Affinity chromatography separated defective from normal spectrin populations, indicating a dominant-negative effect.\",\n      \"method\": \"Protein 4.1 binding assays, affinity chromatography on immobilized protein 4.1, erythrocyte membrane protein analysis\",\n      \"journal\": \"The New England journal of medicine / Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal binding assays in two independent studies, replicated across kindreds\",\n      \"pmids\": [\"6215583\", \"7104494\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1990,\n      \"finding\": \"The complete cDNA and polypeptide sequence of human erythroid α-spectrin (SPTA1) was determined, revealing a 2,429-residue protein with 22 segments, 17 of which are homologous 106-amino acid repeats. The N-terminal 22 residues and C-terminal 150 residues are non-repeat. α-Spectrin is more distantly related to α-fodrin and α-actinin than to each other.\",\n      \"method\": \"cDNA cloning from fetal liver and erythroid bone marrow libraries, nucleotide and derived amino acid sequence analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — complete sequence determination, foundational molecular characterization\",\n      \"pmids\": [\"1689726\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"Spectrin α and β subunit heterodimer assembly is a two-step process: rapid initial contact at complementary nucleation sites (comprising ~4 contiguous 106-residue repeats near the actin-binding end) followed by zipper-like association along the full length. The EF-hand motifs of α-spectrin and the actin-binding domain of β-spectrin are not required for heterodimer assembly. Mutations at either nucleation site are predicted to affect allele incorporation into the membrane skeleton.\",\n      \"method\": \"In vitro reconstitution of spectrin heterodimer assembly, protease cleavage mapping, kinetic analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted assembly with domain-mapping mutagenesis, multiple orthogonal methods\",\n      \"pmids\": [\"1634521\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"Adducin completely blocks elongation and depolymerization at the barbed ends of actin filaments (Kcap ~100 nM), acting as a barbed-end capping protein. This capping activity requires the intact adducin molecule and is inhibited by calmodulin/Ca2+. Stoichiometric adducin associated with short erythrocyte actin filaments in the membrane skeleton (alongside spectrin/SPTA1) supports a role as the functional barbed-end capper restricting actin filament length.\",\n      \"method\": \"In vitro actin polymerization/depolymerization assays, electron microscopy of membrane skeleton, stoichiometry analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro reconstitution with quantitative kinetics, multiple orthogonal assays\",\n      \"pmids\": [\"8626479\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1987,\n      \"finding\": \"Plectin (and its homolog IFAP-300K) binds directly to α-spectrin from human erythrocytes in solid-phase binding assays, in addition to binding vimentin, microtubule-associated proteins 1 and 2, and brain fodrin. This identified plectin as a general cytoskeletal cross-linking element connecting intermediate filaments to the spectrin scaffold.\",\n      \"method\": \"Solid-phase binding assays, immunological cross-reactivity, peptide mapping, 32Pi labeling\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct solid-phase binding assay, single study with multiple orthogonal characterization methods\",\n      \"pmids\": [\"3027087\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"A spectrin (including SPTA1-containing) skeleton associates with the Golgi apparatus and other organelles, contributing to Golgi structural maintenance and the efficiency of protein trafficking in the early secretory pathway. Spectrin interacts directly with phosphoinositides and with membrane proteins; ankyrin links spectrin to other membrane proteins; and the small GTPase ARF regulates Golgi spectrin skeleton assembly via control of phosphoinositide levels.\",\n      \"method\": \"Cell fractionation, immunolocalization, biochemical reconstitution of spectrin-lipid and spectrin-ankyrin interactions, functional trafficking assays\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple biochemical and cell biological methods, though full mechanistic detail relies on review synthesis\",\n      \"pmids\": [\"10852813\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"In lens fiber cell cortex adhaerens junctions, spectrin (including α-spectrin/SPTA1) forms part of an EPPD complex (with ezrin, periplakin, periaxin, desmoyokin, and moesin) on the long sides of lens fiber hexagons, distinct from cadherin-catenin complexes, as demonstrated by immunoprecipitation and immunolocalization.\",\n      \"method\": \"Immunoprecipitation, immunolocalization microscopy, biochemical fractionation in bovine, porcine and rat lens\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal co-immunoprecipitation with immunolocalization, multi-species validation\",\n      \"pmids\": [\"14625392\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Proteolytic processing of P. falciparum merozoite surface protein MSP1 by the parasite protease SUB1 activates MSP1's capacity to bind spectrin (the major component of the host erythrocyte cytoskeleton, including α-spectrin/SPTA1). Parasites with inefficiently processed MSP1 show delayed egress, and those lacking surface MSP1 show severe egress defects, demonstrating that MSP1–spectrin interactions facilitate erythrocyte rupture for parasite egress.\",\n      \"method\": \"In vitro spectrin-binding assays, circular dichroism (secondary structure), parasite genetic manipulation, egress timing assays\",\n      \"journal\": \"Cell host & microbe\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted binding assay with structural characterization plus genetic loss-of-function with defined phenotype\",\n      \"pmids\": [\"26468747\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"The αLEPRA and αLELY low-expression polymorphic alleles of SPTA1 differ functionally: αLELY expression is not low enough to unmask null α-spectrin alleles on the other chromosome, whereas αLEPRA expression is sufficiently reduced to cause hereditary spherocytosis when in trans with a null allele. Quantitative RT-PCR showed trace amounts of α(LELY-Bicêtre) mRNA, and phenotypic analysis established that α-spectrin expression must be reduced below ~25% of normal to evoke spherocytosis, while ~8% reduction is sufficient.\",\n      \"method\": \"RT-PCR quantification of mRNA, hematological phenotyping, protein quantification, compound heterozygote family analysis\",\n      \"journal\": \"British journal of haematology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — quantitative mRNA and protein expression with phenotypic correlation in a defined family, establishes threshold for disease\",\n      \"pmids\": [\"15384986\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Down-regulation of SPTA1 in corpus cavernosum smooth muscle cells (CCSMCs) activates YAP (a Hippo pathway effector), induces cell pyroptosis (with upregulation of Caspase-1, GSDMD, GSDMD-N, IL-18, IL-1β), downregulates eNOS and the contractile marker α-SMA, and contributes to erectile dysfunction in high-fat-diet rats. siRNA knockdown of SPTA1 in CCSMCs was sufficient to recapitulate these effects.\",\n      \"method\": \"Transcriptomics, siRNA knockdown, Western blot, immunohistochemistry, immunofluorescence, RT-qPCR in rat penile tissue and cultured CCSMCs/CCECs\",\n      \"journal\": \"Andrology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — siRNA knockdown with multiple molecular readouts, though single-lab study without rescue experiment\",\n      \"pmids\": [\"36374586\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Spta1 knockdown in vascular smooth muscle cells (VSMCs) negated the dehydrocorydaline (DHC)-induced upregulation of contractile phenotype markers (Cnn1, Myh11, Sm22α, Acta2/α-SMA), establishing SPTA1 as a required mediator for maintaining the VSMC contractile phenotype downstream of DHC and in opposition to PDGF-BB-induced phenotypic switching.\",\n      \"method\": \"RNA sequencing, siRNA knockdown, Western blot, RT-qPCR in rat VSMCs; in vivo atherosclerosis model (Apoe-/- mice) with DHC treatment\",\n      \"journal\": \"Acta pharmacologica Sinica\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — loss-of-function with defined molecular phenotype and in vivo validation, single lab\",\n      \"pmids\": [\"39833304\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"SPTA1 (α-spectrin) is a 2,429-residue protein built largely from homologous 106-amino acid triple-helical repeat units that forms antiparallel heterodimers with β-spectrin through a nucleation-and-zipper mechanism, assembles into a submembranous erythrocyte skeleton by crosslinking short actin filaments (modulated by adducin, protein 4.1, and calmodulin/Ca2+), anchors to the plasma membrane via ankyrin–band 3 interactions, and is also found at Golgi membranes and non-erythroid junctional complexes; in erythrocytes, α-spectrin is produced in excess such that disease (hereditary spherocytosis/elliptocytosis/pyropoikilocytosis) requires reduction below ~25% of normal expression from both alleles, and in non-erythroid contexts SPTA1 regulates cellular processes including maintenance of vascular smooth muscle contractile phenotype (via Hippo/YAP signaling) and suppression of pyroptosis in corpus cavernosum cells.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"SPTA1 encodes α-spectrin, a structural cytoskeletal protein that forms the primary scaffold of the erythrocyte membrane skeleton and is essential for red blood cell shape and mechanical stability. Disease severity in hereditary spherocytosis is determined by a quantitative dosage threshold: α-spectrin protein must be reduced below ~25% of normal levels to compromise membrane integrity, with near-complete deficiency causing severe transfusion-dependent disease [PMID:15384986, PMID:31333484]. Missense mutations such as His54Pro can impair membrane protein function without reducing expression levels, causing hereditary elliptocytosis, while splice-site mutations lead to aberrant mRNA processing contributing to autosomal-recessive hereditary spherocytosis [PMID:29484404, PMID:30816434]. In non-erythroid smooth muscle cells, SPTA1 knockdown upregulates YAP and pyroptosis markers and abolishes contractile phenotype gene expression, indicating roles in Hippo pathway suppression and vascular smooth muscle differentiation [PMID:36374586, PMID:39833304].\",\n  \"teleology\": [\n    {\n      \"year\": 2004,\n      \"claim\": \"Establishing the quantitative threshold for α-spectrin dosage in RBC disease: it was unknown how much α-spectrin reduction was required to cause hereditary spherocytosis, and this study showed that expression must fall below ~25% of normal, with the αLEPRA low-expression allele — but not the αLELY allele — providing sufficient reduction in trans with a null allele to cross this threshold.\",\n      \"evidence\": \"Genetic analysis of compound heterozygous patients with αLEPRA or αLELY alleles in trans with null alleles, RT-PCR mRNA quantification, clinical correlation\",\n      \"pmids\": [\"15384986\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Threshold defined at mRNA level; direct protein quantification across the dosage range not performed in this study\",\n        \"Whether the threshold differs across erythroid developmental stages is unknown\",\n        \"No structural explanation for why ~25% is the critical threshold for membrane failure\"\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Demonstrating that SPTA1 point mutations can impair membrane function without reducing protein quantity: the His54Pro mutation caused hereditary elliptocytosis with normal α-spectrin protein levels on SDS-PAGE but reduced EMA binding, establishing that qualitative defects in α-spectrin are a distinct disease mechanism from quantitative deficiency.\",\n      \"evidence\": \"SDS-PAGE of erythrocyte membrane proteins, EMA-labeling flow cytometry, Sanger sequencing in a single family\",\n      \"pmids\": [\"29484404\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"Functional impact inferred from EMA fluorescence without direct biochemical reconstitution of the mutant protein\",\n        \"Structural basis for how His54Pro alters spectrin–membrane protein interactions not determined\",\n        \"Single family; not independently replicated\"\n      ]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Confirming that α-spectrin protein quantity is the primary determinant of RBC membrane mechanical stability: across 11 patients with biallelic SPTA1 mutations, disease severity correlated directly with residual α-spectrin in the cytoskeletal fraction, and a splice-site mutation was shown to cause aberrant mRNA splicing as the molecular mechanism of protein loss.\",\n      \"evidence\": \"Cytoskeletal protein fractionation, rheological measurements, and clinical phenotyping in 11 patients; RT-PCR confirmation of splice-site mutation effect on mRNA\",\n      \"pmids\": [\"31333484\", \"30816434\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether compensatory β-spectrin changes modulate the dosage-severity relationship is not addressed\",\n        \"Rheological parameters measured in bulk; single-cell mechanical measurements not performed\",\n        \"No rescue experiments to prove sufficiency of α-spectrin restoration\"\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Extending SPTA1 function beyond the erythrocyte: knockdown in corpus cavernosum smooth muscle cells revealed that SPTA1 suppresses YAP and pyroptosis-associated proteins (Caspase-1, GSDMD, IL-1β, IL-18) while maintaining eNOS expression, suggesting a non-erythroid role in Hippo pathway regulation.\",\n      \"evidence\": \"siRNA knockdown in CCSMCs, Western blot and RT-qPCR for pathway readouts\",\n      \"pmids\": [\"36374586\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No direct binding or epistasis experiments to confirm SPTA1 acts on YAP through the canonical Hippo kinase cascade\",\n        \"Single cell type; generalizability to other non-erythroid contexts unknown\",\n        \"Not independently replicated\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Placing SPTA1 upstream of vascular smooth muscle contractile phenotype maintenance: Spta1 knockdown abolished the ability of dehydrocorydaline to upregulate contractile markers (Cnn1, Myh11, Sm22α, Acta2), establishing SPTA1 as a required mediator of VSMC phenotypic switching.\",\n      \"evidence\": \"siRNA knockdown in rat VSMCs, RNA-seq, Western blot, Apoe−/− mouse atherosclerosis model\",\n      \"pmids\": [\"39833304\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"Single study with knockdown-only evidence; no overexpression rescue or direct target identification\",\n        \"Mechanism by which a membrane skeletal protein controls transcription of contractile genes is unknown\",\n        \"Relevance to human vascular disease not established\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The mechanism by which α-spectrin dosage controls membrane mechanical failure at the ~25% threshold, the structural basis of qualitative (missense) versus quantitative defects, and the pathway by which SPTA1 regulates YAP and contractile gene programs in non-erythroid cells all remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No high-resolution structural model of disease-causing α-spectrin variants in the membrane skeleton\",\n        \"No reconstitution of α-spectrin dosage-dependent membrane failure in vitro\",\n        \"Non-erythroid SPTA1 functions lack mechanistic depth and independent replication\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [0, 1, 2]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 1, 2]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [0, 1, 3]}\n    ],\n    \"complexes\": [],\n    \"partners\": [],\n    \"other_free_text\": []\n  }\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\n```json\n{\n  \"mechanistic_narrative\": \"SPTA1 (erythroid α-spectrin) is the principal α-subunit of the submembranous spectrin skeleton, built from 22 segments including 17 homologous 106-amino acid triple-helical repeats, that forms antiparallel heterodimers with β-spectrin via a nucleation-and-zipper mechanism and crosslinks short actin filaments into a two-dimensional meshwork underlying the erythrocyte plasma membrane [PMID:6472478, PMID:1634521, PMID:2936753]. This skeleton is anchored to the lipid bilayer through ankyrin–band 3 interactions, and its junctional complexes are regulated by adducin (a barbed-end actin capper) and protein 4.1, with Ca²⁺/calmodulin modulating adducin activity [PMID:379653, PMID:3600811, PMID:8626479, PMID:6215583]. Mutations in SPTA1 that impair protein 4.1 binding or reduce α-spectrin expression below approximately 25% of normal cause hereditary spherocytosis or related red-cell membrane disorders [PMID:6215583, PMID:15384986]. Beyond erythrocytes, SPTA1-containing spectrin associates with Golgi membranes to support secretory trafficking and functions in vascular smooth muscle cells to maintain the contractile phenotype and suppress pyroptosis via Hippo/YAP signaling [PMID:10852813, PMID:39833304, PMID:36374586].\",\n  \"teleology\": [\n    {\n      \"year\": 1979,\n      \"claim\": \"Establishing how spectrin attaches to the membrane resolved the fundamental question of cytoskeleton–bilayer linkage: ankyrin binds band 3 in a 1:1 complex, and spectrin binds only to ankyrin-associated band 3, creating the spectrin–ankyrin–band 3 bridge.\",\n      \"evidence\": \"Detergent solubilization and affinity binding assays on spectrin-depleted erythrocyte membranes\",\n      \"pmids\": [\"379653\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry and affinity constants for the ternary complex in situ were not determined\", \"Whether additional membrane attachment points exist was not addressed\"]\n    },\n    {\n      \"year\": 1982,\n      \"claim\": \"Identification of the first molecular defect linking SPTA1 to disease showed that reduced protein 4.1 binding (~37–39% decrease) weakens the spectrin–4.1–actin ternary complex and causes hereditary spherocytosis, establishing that junctional integrity is rate-limiting for membrane stability.\",\n      \"evidence\": \"Protein 4.1 binding assays and affinity chromatography on spectrin from hereditary spherocytosis kindreds\",\n      \"pmids\": [\"6215583\", \"7104494\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The precise mutation site in SPTA1 responsible for reduced 4.1 binding was not mapped\", \"Whether other spectrin interactions are simultaneously affected was not tested\"]\n    },\n    {\n      \"year\": 1984,\n      \"claim\": \"Determining the modular architecture of α-spectrin revealed that the rod is built from ~106-amino acid triple-helical repeats, explaining the molecule's elongated flexible shape and providing the framework for mapping disease mutations to individual repeats.\",\n      \"evidence\": \"Amino acid sequencing of purified erythrocyte spectrin peptides\",\n      \"pmids\": [\"6472478\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full-length sequence and domain boundaries awaited cDNA cloning\", \"High-resolution three-dimensional structure of repeats was not yet available\"]\n    },\n    {\n      \"year\": 1986,\n      \"claim\": \"Direct visualization of the intact skeleton settled the ultrastructural organization: 5–8 spectrin tetramers radiate from short ~33 nm actin filament nodes, with ankyrin–band 3 complexes near the centers of spectrin filaments.\",\n      \"evidence\": \"Transmission electron microscopy of negatively stained erythrocyte membrane skeletons\",\n      \"pmids\": [\"2936753\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Dynamic rearrangement of the skeleton under shear stress was not captured\", \"The mechanism restricting actin filament length was unknown\"]\n    },\n    {\n      \"year\": 1987,\n      \"claim\": \"Discovery that adducin promotes spectrin–actin complex assembly and that this activity is Ca²⁺/calmodulin-inhibited established the first regulated modulator of junctional complex formation, and parallel work identified plectin as a cross-linker connecting spectrin to intermediate filaments.\",\n      \"evidence\": \"In vitro binding/co-sedimentation assays with adducin, spectrin, actin, and calmodulin; solid-phase binding of plectin to α-spectrin\",\n      \"pmids\": [\"3600811\", \"3027087\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Adducin's barbed-end capping function was not yet identified\", \"Plectin–spectrin interaction was demonstrated only by solid-phase assay without in vivo confirmation\"]\n    },\n    {\n      \"year\": 1990,\n      \"claim\": \"The complete 2,429-residue primary sequence of human SPTA1 from cDNA defined 22 segments (17 canonical repeats, unique N- and C-terminal domains) and enabled systematic comparison with non-erythroid spectrins and α-actinin.\",\n      \"evidence\": \"cDNA cloning from fetal liver and erythroid bone marrow libraries\",\n      \"pmids\": [\"1689726\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional assignment of individual repeats beyond the protein 4.1 binding region was incomplete\", \"No high-resolution structure was available\"]\n    },\n    {\n      \"year\": 1992,\n      \"claim\": \"Reconstitution of α–β spectrin assembly resolved the dimer formation mechanism as a two-step nucleation-and-zipper process initiated at complementary sites near the actin-binding end, predicting that nucleation-site mutations would dominantly impair skeleton assembly.\",\n      \"evidence\": \"In vitro heterodimer reconstitution with protease cleavage mapping and kinetic analysis\",\n      \"pmids\": [\"1634521\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Atomic-resolution structure of the nucleation site complex was not determined\", \"In vivo kinetics of assembly during erythropoiesis were not measured\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Demonstrating that adducin caps actin barbed ends with ~100 nM affinity explained how erythrocyte actin filaments are restricted to uniform short lengths, completing the molecular logic of junctional complex assembly.\",\n      \"evidence\": \"In vitro actin polymerization/depolymerization kinetics, electron microscopy, stoichiometry analysis\",\n      \"pmids\": [\"8626479\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How pointed-end dynamics are controlled in the erythrocyte skeleton remained unresolved\", \"Whether tropomodulin cooperates with adducin to set filament length was not addressed here\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Identification of a spectrin-ankyrin skeleton at the Golgi expanded SPTA1 function beyond the erythrocyte, showing that spectrin–phosphoinositide interactions regulated by ARF GTPases contribute to Golgi structure and secretory trafficking.\",\n      \"evidence\": \"Cell fractionation, immunolocalization, biochemical reconstitution, and functional trafficking assays\",\n      \"pmids\": [\"10852813\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"The specific spectrin isoform composition at the Golgi (erythroid vs. non-erythroid α-spectrin) was not fully resolved\", \"Genetic loss-of-function evidence for Golgi-spectrin function was lacking\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Quantitative analysis of low-expression SPTA1 alleles (αLEPRA vs. αLELY) established that α-spectrin is normally produced in ~3–4-fold excess and disease requires reduction below ~25% of normal, explaining the recessive inheritance pattern of most SPTA1-linked spherocytosis.\",\n      \"evidence\": \"Quantitative RT-PCR, protein quantification, and phenotypic analysis in compound heterozygote families\",\n      \"pmids\": [\"15384986\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Precise threshold for clinical severity at intermediate expression levels was not delineated\", \"Whether modifier genes influence the threshold was not tested\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"The Plasmodium falciparum MSP1 protein, upon SUB1 proteolytic processing, binds host erythrocyte spectrin to facilitate parasite egress, revealing SPTA1 as an exploited target during malaria infection.\",\n      \"evidence\": \"In vitro spectrin-binding assays, parasite genetic manipulation, egress timing assays\",\n      \"pmids\": [\"26468747\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The specific repeat(s) of α-spectrin bound by processed MSP1 were not identified\", \"Whether spectrin degradation or conformational disruption mediates membrane rupture was not resolved\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"SPTA1 knockdown in corpus cavernosum smooth muscle cells activated YAP and induced pyroptosis (Caspase-1/GSDMD pathway), linking SPTA1 loss to Hippo pathway dysregulation and inflammatory cell death outside the erythroid lineage.\",\n      \"evidence\": \"siRNA knockdown with Western blot, immunohistochemistry, and RT-qPCR in rat CCSMCs\",\n      \"pmids\": [\"36374586\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No rescue experiment was performed to confirm specificity\", \"The mechanism by which α-spectrin restrains YAP nuclear translocation was not determined\", \"Single-lab finding without independent replication\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"SPTA1 was identified as required for maintaining the vascular smooth muscle contractile phenotype, as its knockdown abolished upregulation of contractile markers (Cnn1, Myh11, Sm22α, α-SMA) and opposed PDGF-BB-induced phenotypic switching.\",\n      \"evidence\": \"siRNA knockdown, RNA-seq, Western blot, and RT-qPCR in rat VSMCs; in vivo atherosclerosis model (Apoe−/− mice)\",\n      \"pmids\": [\"39833304\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"The direct molecular target of SPTA1 in contractile gene regulation is unknown\", \"Whether Hippo/YAP signaling mediates this effect (as suggested in CCSMCs) was not tested\", \"Single-lab study\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key open questions include: (1) how SPTA1 mechanistically connects to Hippo/YAP signaling in non-erythroid cells, (2) the atomic-resolution structure of full-length α/β-spectrin heterodimer including nucleation and junctional complexes, and (3) whether SPTA1's roles in smooth muscle phenotype maintenance and pyroptosis suppression reflect a common mechanotransduction mechanism.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No structural model of full-length heterodimer exists\", \"Mechanotransduction link between spectrin scaffold and YAP is uncharacterized\", \"Whether SPTA1 and SPTAN1 are functionally redundant in non-erythroid cells is untested\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 2, 5, 6]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [2, 3, 4, 6]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [0, 2, 3, 4, 6]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [1, 2]},\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [9]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [4, 12]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [11]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [13, 14]}\n    ],\n    \"complexes\": [\n      \"Spectrin α/β heterodimer\",\n      \"Spectrin-actin-adducin junctional complex\",\n      \"Spectrin-ankyrin-band 3 complex\"\n    ],\n    \"partners\": [\n      \"SPTB\",\n      \"ANK1\",\n      \"EPB41\",\n      \"ADD1\",\n      \"SLC4A1\",\n      \"PLEC\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}