{"gene":"OC90","run_date":"2026-06-10T05:19:52","timeline":{"discoveries":[{"year":1998,"finding":"OC90 (otoconin-90) is the major protein component of murine otoconia and contains two domains homologous to secretory phospholipase A2 (sPLA2). The gene is specifically expressed in the developing mouse otocyst, and the mature mouse OC90 is composed of 453 residues.","method":"cDNA cloning, sequence analysis, and in situ hybridization showing otocyst-specific expression","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct molecular cloning with sequence characterization and validated tissue-specific expression, replicated across subsequent studies","pmids":["9860971"],"is_preprint":false},{"year":2007,"finding":"OC90 is essential for formation of the organic matrix of otoconia by specifically recruiting other matrix components including otolin. In Oc90 null mice, the organic matrix fails to form properly, leading to absent/reduced otoconia; the organic matrix forms prior to CaCO3 deposition and controls otoconia growth and morphology by embedding crystallites during seeding and growth.","method":"Gene targeting (Oc90 knockout mice), protein analysis, histological and ultrastructural examination","journal":"Developmental biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO with defined cellular phenotype plus protein analysis, replicated by subsequent studies","pmids":["17300776"],"is_preprint":false},{"year":2008,"finding":"Oc90 deletion leads to formation of giant otoconia (not absent otoconia), causing vestibular imbalance but normal hearing as measured by auditory brainstem responses and otoacoustic emissions. The remnant otoconia mass in Oc90 null mice is still capable of stimulating gravity receptor organs.","method":"Behavioral balance tests (righting reflex, rotorod, beam-crossing, gait), vestibular evoked potentials (VsEPs), auditory brainstem responses (ABRs), distortion products of otoacoustic emissions (DPOAEs)","journal":"Neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal electrophysiological and behavioral readouts in KO model","pmids":["18355969"],"is_preprint":false},{"year":2008,"finding":"Otoc1, the zebrafish ortholog of OC90, is expressed in the ear between 15–72 hpf and is required for otolith mineralization; morpholino knockdown of otoc1 mRNA translation produces aberrant otolith phenotypes, suggesting Otoc1 nucleates calcium carbonate mineralization of aragonitic otoliths.","method":"In situ hybridization, antisense morpholino knockdown in zebrafish","journal":"Developmental neurobiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — morpholino knockdown with defined phenotype in zebrafish ortholog, single lab","pmids":["18000829"],"is_preprint":false},{"year":2010,"finding":"Recombinant OC90 facilitates nucleation of calcite crystals and inhibits crystal growth in a concentration-dependent manner in vitro, and induces morphologic changes characteristic of native otoconia. Homology modeling of the sPLA2-like domains of OC90 indicates that a surface of anionic clusters formed upon tertiary folding compensates for the lower density of acidic residues in the primary sequence.","method":"In vitro calcite crystal growth assay with recombinant OC90, HR-SEM, homology modeling","journal":"Hearing research","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro biochemical reconstitution with recombinant protein, single lab","pmids":["20595020"],"is_preprint":false},{"year":2010,"finding":"In Oc90 null otoconia, Sparc-like 1 (Sc1/hevin) is drastically upregulated as a compensatory matrix protein. Stable transfection of full-length Oc90 or Sc1 expression constructs in NIH/3T3 cells promotes matrix calcification, demonstrating a direct role for OC90 in driving calcification.","method":"Protein analysis of Oc90 null vs. wildtype otoconia, stable transfection of NIH/3T3 cells with calcification assay","journal":"Developmental dynamics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cell-based functional assay with defined readout plus KO protein analysis, single lab","pmids":["20803598"],"is_preprint":false},{"year":2011,"finding":"OC90 binds otolin through both the TH and C1q domains of otolin, with full-length otolin showing the strongest interaction. OC90 recruits otolin to the crystal matrix and sequesters Ca2+ in the luminal matrices of the utricle and saccule; absence of OC90 in null mice leads to drastically reduced matrix Ca2+. In vitro, co-expression of OC90 and otolin has a synergistic effect on calcification.","method":"Co-immunoprecipitation/binding assay, in vivo Ca2+ measurements (utricle/saccule enrichment), cell culture calcification assay, molecular modeling","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal binding assay, in vivo Ca2+ measurement in KO vs. WT, and functional calcification assay, multiple orthogonal methods","pmids":["21655225"],"is_preprint":false},{"year":2011,"finding":"Recombinant otoconin-22 (rOC22, a related sPLA2-like otoconin) selects calcite over aragonite in vitro; alternate folding produces vaterite. Molecular models of OC90 show a surface of uniform negative electrostatic potential proposed to enable localized supersaturation. OC90 is proposed to interact with Otolin in formation of iso-oriented columns of nano-crystallites.","method":"In vitro crystal growth, circular dichroism, HR-SEM, micro-Raman, molecular modeling","journal":"Acta oto-laryngologica","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — multiple biophysical methods on recombinant protein, single lab; some conclusions are modeling-based","pmids":["21401448"],"is_preprint":false},{"year":2014,"finding":"OC90 modulates in vitro calcite crystal morphology; coadministration of OC90 and Otolin-1 produces synergistic effects on crystal morphology contributing to otoconia-like shape. OC90 films on mica significantly reduce the interfacial energy for heterogeneous calcite nucleation compared to bulk solution, and OC90 possesses negative surface charge that correlates inversely with interfacial energy.","method":"In vitro calcium carbonate crystal growth, rotary shadowing, atomic force microscopy (AFM), scanning electron microscopy, zeta potential measurements","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 1 / Strong — multiple orthogonal in vitro biophysical methods (AFM, SEM, nucleation kinetics), independently consistent with PMID:20595020","pmids":["24748133","25709560"],"is_preprint":false},{"year":2019,"finding":"In zebrafish pks1 mutants that lack otoliths, OC90 expression within the otocyst is diffuse rather than localized, demonstrating that proper OC90 localization is not sufficient for otolith biomineralization in the absence of pks1, and that additional factors beyond OC90 are required for otolith nucleation.","method":"Genetic mutant analysis (pks1 loss-of-function), immunofluorescence/in situ hybridization for OC90 localization in zebrafish","journal":"Mechanisms of development","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — epistatic genetic analysis in zebrafish with localization readout, single lab","pmids":["30974150"],"is_preprint":false},{"year":2021,"finding":"OC90 and NADPH oxidase Nox3 are functionally cooperative: double heterozygous Oc90/Nox3 mice display severe imbalance and otoconia defects (while single heterozygotes are normal), and cells stably co-expressing both proteins show much greater calcification than cells expressing either alone, indicating that OC90 and Nox3 augment each other's function in otoconia formation and hair bundle maintenance.","method":"Double heterozygous/null mouse genetics, behavioral and electrophysiological analysis, stable transfection calcification assay","journal":"Journal of vestibular research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis with double-mutant rescue plus cell-based functional assay, single lab","pmids":["33554930"],"is_preprint":false},{"year":2021,"finding":"Estrogen receptor (ER) and estrogen-related receptor α (ERRα) interact with each other and cooperatively regulate OC90 expression in rat utricles; bilateral ovariectomy reduces ERRα levels and loosens otoliths, an effect reversed by E2 supplementation.","method":"Co-immunoprecipitation (ER–ERRα interaction), Western blotting and qPCR for OC90 expression, ovariectomy rat model, scanning electron microscopy of otolith morphology","journal":"Current medical science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-immunoprecipitation plus in vivo OVX model with multiple readouts, single lab","pmids":["34403090"],"is_preprint":false}],"current_model":"OC90 (otoconin-90) is the predominant matrix protein of mammalian otoconia, containing two sPLA2-like domains whose tertiary folding creates anionic surface clusters that facilitate calcite nucleation, inhibit crystal growth in a concentration-dependent manner, and reduce the interfacial energy barrier to heterogeneous nucleation; OC90 recruits otolin (via otolin's TH and C1q domains) and other matrix components to assemble the organic matrix that sequesters Ca²⁺ and templates spatially specific CaCO3 crystallization, with OC90 and NADPH oxidase Nox3 cooperating synergistically in this process, and with OC90 expression itself regulated by estrogen receptors ER and ERRα in the utricle."},"narrative":{"mechanistic_narrative":"OC90 (otoconin-90) is the predominant secreted matrix protein of mammalian otoconia, a structural protein that organizes the organic scaffold templating spatially specific CaCO3 biomineralization in the inner ear vestibular organs [PMID:9860971, PMID:17300776]. It contains two domains homologous to secretory phospholipase A2 (sPLA2) whose tertiary folding generates a surface of anionic clusters with uniform negative electrostatic potential, compensating for a low density of acidic residues in the primary sequence [PMID:9860971, PMID:20595020, PMID:21401448]. Functionally, OC90 nucleates calcite crystals while inhibiting their growth in a concentration-dependent manner, drives matrix calcification in cultured cells, and lowers the interfacial energy barrier to heterogeneous nucleation in proportion to its negative surface charge [PMID:20595020, PMID:20803598, PMID:24748133, PMID:25709560]. OC90 assembles the organic matrix by recruiting otolin—binding through otolin's TH and C1q domains—and sequesters Ca2+ within the luminal matrices of the utricle and saccule, with co-expression of the two proteins producing synergistic effects on calcification and otoconia-like crystal morphology [PMID:21655225, PMID:24748133, PMID:25709560]. Loss of Oc90 in mice causes failure of proper matrix formation, giant or reduced otoconia, drastically lowered matrix Ca2+, and vestibular imbalance with preserved hearing, alongside compensatory upregulation of Sparc-like 1 (Sc1/hevin) [PMID:17300776, PMID:18355969, PMID:20803598, PMID:21655225]. OC90 acts cooperatively with NADPH oxidase Nox3 in otoconia formation, and its expression is regulated by estrogen receptor and ERRα in the utricle [PMID:33554930, PMID:34403090]. The zebrafish ortholog Otoc1 is similarly required for otolith mineralization, though additional factors such as pks1 are required for nucleation beyond OC90 localization alone [PMID:18000829, PMID:30974150].","teleology":[{"year":1998,"claim":"Establishing the molecular identity of the dominant otoconial protein was the first step; cloning OC90 revealed an inner-ear-specific protein built from two sPLA2-homologous domains, framing the biomineralization question around a phospholipase-fold scaffold rather than an enzyme.","evidence":"cDNA cloning, sequence analysis, and in situ hybridization in mouse otocyst","pmids":["9860971"],"confidence":"High","gaps":["Sequence homology to sPLA2 did not establish whether OC90 retains catalytic activity","Did not address how the protein contributes to crystal nucleation"]},{"year":2007,"claim":"Genetic ablation tested whether OC90 is causally required for otoconia, showing it is essential for assembling the organic matrix and recruiting other matrix components, establishing OC90 as a scaffold acting upstream of CaCO3 deposition.","evidence":"Oc90 knockout mouse with histological and ultrastructural analysis","pmids":["17300776"],"confidence":"High","gaps":["Did not define the biophysical mechanism of nucleation","Identity of all recruited matrix partners incomplete"]},{"year":2008,"claim":"Phenotypic characterization clarified that OC90 loss produces aberrant giant otoconia rather than total absence, linking the molecular defect to selective vestibular dysfunction with intact hearing.","evidence":"Behavioral balance tests, VsEPs, ABRs and DPOAEs in Oc90 null mice","pmids":["18355969"],"confidence":"High","gaps":["Did not explain why residual mineralization still occurs without OC90","Compensatory mechanisms not identified at this stage"]},{"year":2008,"claim":"Cross-species testing in zebrafish addressed conservation, showing the ortholog Otoc1 is required for otolith mineralization and implicating it in calcium carbonate nucleation across vertebrates.","evidence":"In situ hybridization and antisense morpholino knockdown in zebrafish","pmids":["18000829"],"confidence":"Medium","gaps":["Morpholino knockdown lacks genetic mutant confirmation","Aragonite vs. calcite polymorph control by Otoc1 not directly demonstrated"]},{"year":2010,"claim":"In vitro reconstitution and cell assays demonstrated direct biochemical function, showing recombinant OC90 nucleates calcite while inhibiting growth and drives matrix calcification, and that anionic clusters arise from tertiary folding.","evidence":"Recombinant OC90 calcite growth assay, HR-SEM, homology modeling, and NIH/3T3 calcification with Oc90 transfection","pmids":["20595020","20803598"],"confidence":"Medium","gaps":["Single-lab in vitro reconstitution","Compensatory Sc1/hevin upregulation mechanism in null mice not resolved"]},{"year":2011,"claim":"Partner mapping and Ca2+ measurements defined how OC90 builds the matrix, showing it binds otolin via TH and C1q domains, sequesters luminal Ca2+, and synergizes with otolin in calcification.","evidence":"Co-immunoprecipitation/binding assays, in vivo Ca2+ measurement in KO vs WT, cell calcification assay, and biophysical modeling of negative electrostatic surface","pmids":["21655225","21401448"],"confidence":"High","gaps":["Stoichiometry and structural basis of the OC90–otolin complex not resolved at atomic level","Polymorph selection conclusions remain modeling-based"]},{"year":2014,"claim":"Quantitative biophysics established the nucleation mechanism, showing OC90 films reduce the interfacial energy barrier to heterogeneous calcite nucleation in proportion to negative surface charge and that OC90 plus otolin synergistically shape crystal morphology.","evidence":"In vitro CaCO3 growth, AFM, SEM, rotary shadowing, and zeta potential measurements","pmids":["24748133","25709560"],"confidence":"High","gaps":["In vitro mica/film system may not fully recapitulate the in vivo luminal matrix","Does not address temporal control of nucleation during development"]},{"year":2019,"claim":"Epistatic analysis tested sufficiency, showing that proper OC90 localization is not enough for otolith formation in zebrafish lacking pks1, establishing that additional factors are required for nucleation.","evidence":"pks1 loss-of-function zebrafish mutant analysis with OC90 localization readout","pmids":["30974150"],"confidence":"Medium","gaps":["Molecular role of pks1 relative to OC90 not defined","Whether the mouse pathway has an analogous requirement unknown"]},{"year":2021,"claim":"Genetic interaction and hormonal regulation studies expanded the functional network, showing OC90 cooperates with Nox3 in otoconia formation and that its expression is regulated by ER/ERRα in the utricle.","evidence":"Double heterozygous Oc90/Nox3 mouse genetics with cell calcification assays; ER–ERRα co-IP and ovariectomy rat model with qPCR/Western readouts","pmids":["33554930","34403090"],"confidence":"Medium","gaps":["Mechanism by which Nox3 augments OC90-driven calcification unresolved","Direct transcriptional binding of ER/ERRα to the Oc90 locus not demonstrated","Single-lab findings"]},{"year":null,"claim":"How the OC90-anchored matrix achieves spatially and temporally restricted nucleation in vivo, and the atomic-level structure of the OC90–otolin scaffold, remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No experimental structure of OC90 or the OC90–otolin complex","Mechanistic link between Nox3 redox activity and OC90 matrix assembly undefined","Full set of matrix components recruited by OC90 incompletely mapped"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[1,6,8]},{"term_id":"GO:0140313","term_label":"molecular sequestering activity","supporting_discovery_ids":[6]}],"localization":[{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[1,6]},{"term_id":"GO:0031012","term_label":"extracellular matrix","supporting_discovery_ids":[1,6]}],"pathway":[{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[1,2]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[0,3]}],"complexes":["otoconial organic matrix"],"partners":["OTOL1","NOX3","ESR1","ESRRA","SPARCL1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q02509","full_name":"Otoconin-90","aliases":["Phospholipase A2 homolog"],"length_aa":477,"mass_kda":51.7,"function":"Major protein of the otoconia, a calcium carbonate structure in the saccule and utricle of the ear. Together with OTOL1, acts as a scaffold for otoconia biomineralization: sequesters calcium and forms interconnecting fibrils between otoconia that are incorporated into the calcium crystal structure. Together with OTOL1, modulates calcite crystal morphology and growth kinetics. It is unlikely that this protein has phospholipase A2 activity","subcellular_location":"Secreted","url":"https://www.uniprot.org/uniprotkb/Q02509/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/OC90","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/OC90","total_profiled":1310},"omim":[{"mim_id":"621480","title":"OTOLIN 1; OTOL1","url":"https://www.omim.org/entry/621480"},{"mim_id":"607806","title":"OTOPETRIN 1; OTOP1","url":"https://www.omim.org/entry/607806"},{"mim_id":"604109","title":"HUMAN ENDOGENOUS RETROVIRUS-H LONG TERMINAL REPEAT-ASSOCIATING 1; HHLA1","url":"https://www.omim.org/entry/604109"},{"mim_id":"601658","title":"OTOCONIN 90; OC90","url":"https://www.omim.org/entry/601658"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Not detected","tissue_distribution":"Not detected","driving_tissues":[],"url":"https://www.proteinatlas.org/search/OC90"},"hgnc":{"alias_symbol":[],"prev_symbol":["PLA2L"]},"alphafold":{"accession":"Q02509","domains":[{"cath_id":"1.20.90.10","chopping":"50-189","consensus_level":"high","plddt":89.7586,"start":50,"end":189},{"cath_id":"1.20.90.10","chopping":"294-418","consensus_level":"high","plddt":85.7291,"start":294,"end":418}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q02509","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q02509-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q02509-F1-predicted_aligned_error_v6.png","plddt_mean":65.81},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=OC90","jax_strain_url":"https://www.jax.org/strain/search?query=OC90"},"sequence":{"accession":"Q02509","fasta_url":"https://rest.uniprot.org/uniprotkb/Q02509.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q02509/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q02509"}},"corpus_meta":[{"pmid":"9860971","id":"PMC_9860971","title":"Otoconin-90, the mammalian otoconial matrix protein, contains two domains of homology to secretory phospholipase A2.","date":"1998","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/9860971","citation_count":105,"is_preprint":false},{"pmid":"17300776","id":"PMC_17300776","title":"Gene targeting reveals the role of Oc90 as the essential organizer of the otoconial organic matrix.","date":"2007","source":"Developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/17300776","citation_count":70,"is_preprint":false},{"pmid":"10329003","id":"PMC_10329003","title":"Intergenic splicing between a HERV-H endogenous retrovirus and two adjacent human genes.","date":"1999","source":"Genomics","url":"https://pubmed.ncbi.nlm.nih.gov/10329003","citation_count":61,"is_preprint":false},{"pmid":"18355969","id":"PMC_18355969","title":"Otoconin-90 deletion leads to imbalance but normal hearing: a comparison with other otoconia mutants.","date":"2008","source":"Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/18355969","citation_count":49,"is_preprint":false},{"pmid":"21655225","id":"PMC_21655225","title":"Matrix recruitment and calcium sequestration for spatial specific otoconia development.","date":"2011","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/21655225","citation_count":46,"is_preprint":false},{"pmid":"25852475","id":"PMC_25852475","title":"Identification and characterization of mouse otic sensory lineage genes.","date":"2015","source":"Frontiers in cellular neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/25852475","citation_count":40,"is_preprint":false},{"pmid":"33103083","id":"PMC_33103083","title":"Genomic Analyses Reveal Genetic Adaptations to Tropical Climates in Chickens.","date":"2020","source":"iScience","url":"https://pubmed.ncbi.nlm.nih.gov/33103083","citation_count":38,"is_preprint":false},{"pmid":"18000829","id":"PMC_18000829","title":"Otoc1: a novel otoconin-90 ortholog required for otolith mineralization in zebrafish.","date":"2008","source":"Developmental neurobiology","url":"https://pubmed.ncbi.nlm.nih.gov/18000829","citation_count":35,"is_preprint":false},{"pmid":"20803598","id":"PMC_20803598","title":"Expression, functional, and structural analysis of proteins critical for otoconia development.","date":"2010","source":"Developmental dynamics : an official publication of the American Association of Anatomists","url":"https://pubmed.ncbi.nlm.nih.gov/20803598","citation_count":26,"is_preprint":false},{"pmid":"30248354","id":"PMC_30248354","title":"Expression and function of lncRNA MALAT-1 in the embryonic development of zebrafish.","date":"2018","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/30248354","citation_count":25,"is_preprint":false},{"pmid":"24748133","id":"PMC_24748133","title":"In vitro calcite crystal morphology is modulated by otoconial proteins otolin-1 and otoconin-90.","date":"2014","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/24748133","citation_count":25,"is_preprint":false},{"pmid":"20595020","id":"PMC_20595020","title":"In vitro effects of recombinant otoconin 90 upon calcite crystal growth. Significance of tertiary structure.","date":"2010","source":"Hearing research","url":"https://pubmed.ncbi.nlm.nih.gov/20595020","citation_count":17,"is_preprint":false},{"pmid":"30974150","id":"PMC_30974150","title":"Zebrafish otolith biomineralization requires polyketide synthase.","date":"2019","source":"Mechanisms of development","url":"https://pubmed.ncbi.nlm.nih.gov/30974150","citation_count":14,"is_preprint":false},{"pmid":"18459000","id":"PMC_18459000","title":"Osteopontin is not critical for otoconia formation or balance function.","date":"2008","source":"Journal of the Association for Research in Otolaryngology : JARO","url":"https://pubmed.ncbi.nlm.nih.gov/18459000","citation_count":13,"is_preprint":false},{"pmid":"30763339","id":"PMC_30763339","title":"Ectopic Otoconin 90 expression in triple negative breast cancer cell lines is associated with metastasis functions.","date":"2019","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/30763339","citation_count":9,"is_preprint":false},{"pmid":"25709560","id":"PMC_25709560","title":"Effect of Otoconial Proteins Fetuin A, Osteopontin, and Otoconin 90 on the Nucleation and Growth of Calcite.","date":"2014","source":"Crystal growth & design","url":"https://pubmed.ncbi.nlm.nih.gov/25709560","citation_count":8,"is_preprint":false},{"pmid":"39456211","id":"PMC_39456211","title":"Serum Otoconin-90 and Otolin-1 Concentrations in Benign Paroxysmal Positional Vertigo.","date":"2024","source":"Biomolecules","url":"https://pubmed.ncbi.nlm.nih.gov/39456211","citation_count":6,"is_preprint":false},{"pmid":"21401448","id":"PMC_21401448","title":"Significance of tertiary conformation of otoconial matrix proteins - clinical implications.","date":"2011","source":"Acta oto-laryngologica","url":"https://pubmed.ncbi.nlm.nih.gov/21401448","citation_count":5,"is_preprint":false},{"pmid":"33554930","id":"PMC_33554930","title":"Functional cooperation between two otoconial proteins Oc90 and Nox3.","date":"2021","source":"Journal of vestibular research : equilibrium & orientation","url":"https://pubmed.ncbi.nlm.nih.gov/33554930","citation_count":4,"is_preprint":false},{"pmid":"34403090","id":"PMC_34403090","title":"Molecular Mediators of Estrogen Reduction-induced Otolith Shedding.","date":"2021","source":"Current medical science","url":"https://pubmed.ncbi.nlm.nih.gov/34403090","citation_count":2,"is_preprint":false},{"pmid":"41835937","id":"PMC_41835937","title":"Serum Otolin-1 and Otoconin-90 are not elevated in vestibular migraine: a preliminary case-control study.","date":"2026","source":"Frontiers in neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/41835937","citation_count":0,"is_preprint":false},{"pmid":"41836934","id":"PMC_41836934","title":"Association of sleep quality and inner-ear-specific biomarkers Otolin-1 and otoconin-90 with disease severity in benign paroxysmal positional vertigo.","date":"2026","source":"Frontiers in medicine","url":"https://pubmed.ncbi.nlm.nih.gov/41836934","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":12354,"output_tokens":2966,"usd":0.040776,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":10344,"output_tokens":3343,"usd":0.067647,"stage2_stop_reason":"end_turn"},"total_usd":0.108423,"stage1_batch_id":"msgbatch_013a8chtv3AWyTqv4z4sEF4C","stage2_batch_id":"msgbatch_01AHsuW63vinsvuTgzmQ3n62","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1998,\n      \"finding\": \"OC90 (otoconin-90) is the major protein component of murine otoconia and contains two domains homologous to secretory phospholipase A2 (sPLA2). The gene is specifically expressed in the developing mouse otocyst, and the mature mouse OC90 is composed of 453 residues.\",\n      \"method\": \"cDNA cloning, sequence analysis, and in situ hybridization showing otocyst-specific expression\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct molecular cloning with sequence characterization and validated tissue-specific expression, replicated across subsequent studies\",\n      \"pmids\": [\"9860971\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"OC90 is essential for formation of the organic matrix of otoconia by specifically recruiting other matrix components including otolin. In Oc90 null mice, the organic matrix fails to form properly, leading to absent/reduced otoconia; the organic matrix forms prior to CaCO3 deposition and controls otoconia growth and morphology by embedding crystallites during seeding and growth.\",\n      \"method\": \"Gene targeting (Oc90 knockout mice), protein analysis, histological and ultrastructural examination\",\n      \"journal\": \"Developmental biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO with defined cellular phenotype plus protein analysis, replicated by subsequent studies\",\n      \"pmids\": [\"17300776\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Oc90 deletion leads to formation of giant otoconia (not absent otoconia), causing vestibular imbalance but normal hearing as measured by auditory brainstem responses and otoacoustic emissions. The remnant otoconia mass in Oc90 null mice is still capable of stimulating gravity receptor organs.\",\n      \"method\": \"Behavioral balance tests (righting reflex, rotorod, beam-crossing, gait), vestibular evoked potentials (VsEPs), auditory brainstem responses (ABRs), distortion products of otoacoustic emissions (DPOAEs)\",\n      \"journal\": \"Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal electrophysiological and behavioral readouts in KO model\",\n      \"pmids\": [\"18355969\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Otoc1, the zebrafish ortholog of OC90, is expressed in the ear between 15–72 hpf and is required for otolith mineralization; morpholino knockdown of otoc1 mRNA translation produces aberrant otolith phenotypes, suggesting Otoc1 nucleates calcium carbonate mineralization of aragonitic otoliths.\",\n      \"method\": \"In situ hybridization, antisense morpholino knockdown in zebrafish\",\n      \"journal\": \"Developmental neurobiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — morpholino knockdown with defined phenotype in zebrafish ortholog, single lab\",\n      \"pmids\": [\"18000829\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Recombinant OC90 facilitates nucleation of calcite crystals and inhibits crystal growth in a concentration-dependent manner in vitro, and induces morphologic changes characteristic of native otoconia. Homology modeling of the sPLA2-like domains of OC90 indicates that a surface of anionic clusters formed upon tertiary folding compensates for the lower density of acidic residues in the primary sequence.\",\n      \"method\": \"In vitro calcite crystal growth assay with recombinant OC90, HR-SEM, homology modeling\",\n      \"journal\": \"Hearing research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro biochemical reconstitution with recombinant protein, single lab\",\n      \"pmids\": [\"20595020\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"In Oc90 null otoconia, Sparc-like 1 (Sc1/hevin) is drastically upregulated as a compensatory matrix protein. Stable transfection of full-length Oc90 or Sc1 expression constructs in NIH/3T3 cells promotes matrix calcification, demonstrating a direct role for OC90 in driving calcification.\",\n      \"method\": \"Protein analysis of Oc90 null vs. wildtype otoconia, stable transfection of NIH/3T3 cells with calcification assay\",\n      \"journal\": \"Developmental dynamics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell-based functional assay with defined readout plus KO protein analysis, single lab\",\n      \"pmids\": [\"20803598\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"OC90 binds otolin through both the TH and C1q domains of otolin, with full-length otolin showing the strongest interaction. OC90 recruits otolin to the crystal matrix and sequesters Ca2+ in the luminal matrices of the utricle and saccule; absence of OC90 in null mice leads to drastically reduced matrix Ca2+. In vitro, co-expression of OC90 and otolin has a synergistic effect on calcification.\",\n      \"method\": \"Co-immunoprecipitation/binding assay, in vivo Ca2+ measurements (utricle/saccule enrichment), cell culture calcification assay, molecular modeling\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal binding assay, in vivo Ca2+ measurement in KO vs. WT, and functional calcification assay, multiple orthogonal methods\",\n      \"pmids\": [\"21655225\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Recombinant otoconin-22 (rOC22, a related sPLA2-like otoconin) selects calcite over aragonite in vitro; alternate folding produces vaterite. Molecular models of OC90 show a surface of uniform negative electrostatic potential proposed to enable localized supersaturation. OC90 is proposed to interact with Otolin in formation of iso-oriented columns of nano-crystallites.\",\n      \"method\": \"In vitro crystal growth, circular dichroism, HR-SEM, micro-Raman, molecular modeling\",\n      \"journal\": \"Acta oto-laryngologica\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — multiple biophysical methods on recombinant protein, single lab; some conclusions are modeling-based\",\n      \"pmids\": [\"21401448\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"OC90 modulates in vitro calcite crystal morphology; coadministration of OC90 and Otolin-1 produces synergistic effects on crystal morphology contributing to otoconia-like shape. OC90 films on mica significantly reduce the interfacial energy for heterogeneous calcite nucleation compared to bulk solution, and OC90 possesses negative surface charge that correlates inversely with interfacial energy.\",\n      \"method\": \"In vitro calcium carbonate crystal growth, rotary shadowing, atomic force microscopy (AFM), scanning electron microscopy, zeta potential measurements\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — multiple orthogonal in vitro biophysical methods (AFM, SEM, nucleation kinetics), independently consistent with PMID:20595020\",\n      \"pmids\": [\"24748133\", \"25709560\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"In zebrafish pks1 mutants that lack otoliths, OC90 expression within the otocyst is diffuse rather than localized, demonstrating that proper OC90 localization is not sufficient for otolith biomineralization in the absence of pks1, and that additional factors beyond OC90 are required for otolith nucleation.\",\n      \"method\": \"Genetic mutant analysis (pks1 loss-of-function), immunofluorescence/in situ hybridization for OC90 localization in zebrafish\",\n      \"journal\": \"Mechanisms of development\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — epistatic genetic analysis in zebrafish with localization readout, single lab\",\n      \"pmids\": [\"30974150\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"OC90 and NADPH oxidase Nox3 are functionally cooperative: double heterozygous Oc90/Nox3 mice display severe imbalance and otoconia defects (while single heterozygotes are normal), and cells stably co-expressing both proteins show much greater calcification than cells expressing either alone, indicating that OC90 and Nox3 augment each other's function in otoconia formation and hair bundle maintenance.\",\n      \"method\": \"Double heterozygous/null mouse genetics, behavioral and electrophysiological analysis, stable transfection calcification assay\",\n      \"journal\": \"Journal of vestibular research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis with double-mutant rescue plus cell-based functional assay, single lab\",\n      \"pmids\": [\"33554930\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Estrogen receptor (ER) and estrogen-related receptor α (ERRα) interact with each other and cooperatively regulate OC90 expression in rat utricles; bilateral ovariectomy reduces ERRα levels and loosens otoliths, an effect reversed by E2 supplementation.\",\n      \"method\": \"Co-immunoprecipitation (ER–ERRα interaction), Western blotting and qPCR for OC90 expression, ovariectomy rat model, scanning electron microscopy of otolith morphology\",\n      \"journal\": \"Current medical science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-immunoprecipitation plus in vivo OVX model with multiple readouts, single lab\",\n      \"pmids\": [\"34403090\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"OC90 (otoconin-90) is the predominant matrix protein of mammalian otoconia, containing two sPLA2-like domains whose tertiary folding creates anionic surface clusters that facilitate calcite nucleation, inhibit crystal growth in a concentration-dependent manner, and reduce the interfacial energy barrier to heterogeneous nucleation; OC90 recruits otolin (via otolin's TH and C1q domains) and other matrix components to assemble the organic matrix that sequesters Ca²⁺ and templates spatially specific CaCO3 crystallization, with OC90 and NADPH oxidase Nox3 cooperating synergistically in this process, and with OC90 expression itself regulated by estrogen receptors ER and ERRα in the utricle.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"OC90 (otoconin-90) is the predominant secreted matrix protein of mammalian otoconia, a structural protein that organizes the organic scaffold templating spatially specific CaCO3 biomineralization in the inner ear vestibular organs [#0, #1]. It contains two domains homologous to secretory phospholipase A2 (sPLA2) whose tertiary folding generates a surface of anionic clusters with uniform negative electrostatic potential, compensating for a low density of acidic residues in the primary sequence [#0, #4, #7]. Functionally, OC90 nucleates calcite crystals while inhibiting their growth in a concentration-dependent manner, drives matrix calcification in cultured cells, and lowers the interfacial energy barrier to heterogeneous nucleation in proportion to its negative surface charge [#4, #5, #8]. OC90 assembles the organic matrix by recruiting otolin—binding through otolin's TH and C1q domains—and sequesters Ca2+ within the luminal matrices of the utricle and saccule, with co-expression of the two proteins producing synergistic effects on calcification and otoconia-like crystal morphology [#6, #8]. Loss of Oc90 in mice causes failure of proper matrix formation, giant or reduced otoconia, drastically lowered matrix Ca2+, and vestibular imbalance with preserved hearing, alongside compensatory upregulation of Sparc-like 1 (Sc1/hevin) [#1, #2, #5, #6]. OC90 acts cooperatively with NADPH oxidase Nox3 in otoconia formation, and its expression is regulated by estrogen receptor and ERRα in the utricle [#10, #11]. The zebrafish ortholog Otoc1 is similarly required for otolith mineralization, though additional factors such as pks1 are required for nucleation beyond OC90 localization alone [#3, #9].\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"Establishing the molecular identity of the dominant otoconial protein was the first step; cloning OC90 revealed an inner-ear-specific protein built from two sPLA2-homologous domains, framing the biomineralization question around a phospholipase-fold scaffold rather than an enzyme.\",\n      \"evidence\": \"cDNA cloning, sequence analysis, and in situ hybridization in mouse otocyst\",\n      \"pmids\": [\"9860971\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Sequence homology to sPLA2 did not establish whether OC90 retains catalytic activity\", \"Did not address how the protein contributes to crystal nucleation\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Genetic ablation tested whether OC90 is causally required for otoconia, showing it is essential for assembling the organic matrix and recruiting other matrix components, establishing OC90 as a scaffold acting upstream of CaCO3 deposition.\",\n      \"evidence\": \"Oc90 knockout mouse with histological and ultrastructural analysis\",\n      \"pmids\": [\"17300776\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the biophysical mechanism of nucleation\", \"Identity of all recruited matrix partners incomplete\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Phenotypic characterization clarified that OC90 loss produces aberrant giant otoconia rather than total absence, linking the molecular defect to selective vestibular dysfunction with intact hearing.\",\n      \"evidence\": \"Behavioral balance tests, VsEPs, ABRs and DPOAEs in Oc90 null mice\",\n      \"pmids\": [\"18355969\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not explain why residual mineralization still occurs without OC90\", \"Compensatory mechanisms not identified at this stage\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Cross-species testing in zebrafish addressed conservation, showing the ortholog Otoc1 is required for otolith mineralization and implicating it in calcium carbonate nucleation across vertebrates.\",\n      \"evidence\": \"In situ hybridization and antisense morpholino knockdown in zebrafish\",\n      \"pmids\": [\"18000829\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Morpholino knockdown lacks genetic mutant confirmation\", \"Aragonite vs. calcite polymorph control by Otoc1 not directly demonstrated\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"In vitro reconstitution and cell assays demonstrated direct biochemical function, showing recombinant OC90 nucleates calcite while inhibiting growth and drives matrix calcification, and that anionic clusters arise from tertiary folding.\",\n      \"evidence\": \"Recombinant OC90 calcite growth assay, HR-SEM, homology modeling, and NIH/3T3 calcification with Oc90 transfection\",\n      \"pmids\": [\"20595020\", \"20803598\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab in vitro reconstitution\", \"Compensatory Sc1/hevin upregulation mechanism in null mice not resolved\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Partner mapping and Ca2+ measurements defined how OC90 builds the matrix, showing it binds otolin via TH and C1q domains, sequesters luminal Ca2+, and synergizes with otolin in calcification.\",\n      \"evidence\": \"Co-immunoprecipitation/binding assays, in vivo Ca2+ measurement in KO vs WT, cell calcification assay, and biophysical modeling of negative electrostatic surface\",\n      \"pmids\": [\"21655225\", \"21401448\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry and structural basis of the OC90–otolin complex not resolved at atomic level\", \"Polymorph selection conclusions remain modeling-based\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Quantitative biophysics established the nucleation mechanism, showing OC90 films reduce the interfacial energy barrier to heterogeneous calcite nucleation in proportion to negative surface charge and that OC90 plus otolin synergistically shape crystal morphology.\",\n      \"evidence\": \"In vitro CaCO3 growth, AFM, SEM, rotary shadowing, and zeta potential measurements\",\n      \"pmids\": [\"24748133\", \"25709560\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vitro mica/film system may not fully recapitulate the in vivo luminal matrix\", \"Does not address temporal control of nucleation during development\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Epistatic analysis tested sufficiency, showing that proper OC90 localization is not enough for otolith formation in zebrafish lacking pks1, establishing that additional factors are required for nucleation.\",\n      \"evidence\": \"pks1 loss-of-function zebrafish mutant analysis with OC90 localization readout\",\n      \"pmids\": [\"30974150\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular role of pks1 relative to OC90 not defined\", \"Whether the mouse pathway has an analogous requirement unknown\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Genetic interaction and hormonal regulation studies expanded the functional network, showing OC90 cooperates with Nox3 in otoconia formation and that its expression is regulated by ER/ERRα in the utricle.\",\n      \"evidence\": \"Double heterozygous Oc90/Nox3 mouse genetics with cell calcification assays; ER–ERRα co-IP and ovariectomy rat model with qPCR/Western readouts\",\n      \"pmids\": [\"33554930\", \"34403090\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which Nox3 augments OC90-driven calcification unresolved\", \"Direct transcriptional binding of ER/ERRα to the Oc90 locus not demonstrated\", \"Single-lab findings\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the OC90-anchored matrix achieves spatially and temporally restricted nucleation in vivo, and the atomic-level structure of the OC90–otolin scaffold, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No experimental structure of OC90 or the OC90–otolin complex\", \"Mechanistic link between Nox3 redox activity and OC90 matrix assembly undefined\", \"Full set of matrix components recruited by OC90 incompletely mapped\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [1, 6, 8]},\n      {\"term_id\": \"GO:0140313\", \"supporting_discovery_ids\": [6]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [1, 6]},\n      {\"term_id\": \"GO:0031012\", \"supporting_discovery_ids\": [1, 6]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [1, 2]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [0, 3]}\n    ],\n    \"complexes\": [\"otoconial organic matrix\"],\n    \"partners\": [\"OTOL1\", \"NOX3\", \"ESR1\", \"ESRRA\", \"SPARCL1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}