{"gene":"TPRN","run_date":"2026-06-10T10:51:55","timeline":{"discoveries":[{"year":2010,"finding":"TPRN (taperin) protein localizes to the taper region of hair cell stereocilia in the mouse cochlea, as shown by immunolocalization.","method":"Immunolocalization in mouse cochlea","journal":"American journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct immunolocalization experiment with clear subcellular localization, single lab but consistent with subsequent studies","pmids":["20170899"],"is_preprint":false},{"year":2011,"finding":"Taperin (TPRN) preferentially docks the alpha isoform of PP1 (PP1α) through a canonical 'RVxF' motif, and suppresses the general phosphatase activity of PP1α.","method":"Biochemical assays, proteomic approaches, in vitro phosphatase activity assay, mutagenesis of RVxF motif","journal":"Biology open","confidence":"Medium","confidence_rationale":"Tier 1–2 / Moderate — biochemical reconstitution with enzymatic activity assay and motif-based mutagenesis in a single lab","pmids":["23213405"],"is_preprint":false},{"year":2011,"finding":"Taperin localizes predominantly to the nucleus but shuttles between the nucleus and cytoplasm, and is found complexed with PP1 in both compartments.","method":"Western blot, subcellular fractionation, biochemical co-purification","journal":"Biology open","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — fractionation and co-purification experiments in single lab with two orthogonal methods","pmids":["23213405"],"is_preprint":false},{"year":2011,"finding":"Taperin is actively recruited to sites of DNA damage, and interacts with DNA damage response proteins Ku70, Ku80, PARP, and topoisomerases I and IIα, as revealed by SILAC-based mass spectrometry.","method":"SILAC-based quantitative mass spectrometry, live cell imaging of DNA damage recruitment","journal":"Biology open","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — quantitative MS interactome plus live imaging of recruitment, single lab","pmids":["23213405"],"is_preprint":false},{"year":2013,"finding":"TPRN (taperin) forms a molecular complex with CLIC5, radixin (RDX), and myosin VI (MYO6) at the base of hair cell stereocilia; loss of CLIC5 causes mislocalization of TPRN from the stereocilia base.","method":"Biochemical interaction assays (co-IP/pulldown), confocal microscopy, analysis of CLIC5-deficient (jitterbug) mice","journal":"Cytoskeleton (Hoboken, N.J.)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal biochemical interaction assays combined with in vivo mislocalization phenotype, single lab","pmids":["24285636"],"is_preprint":false},{"year":2016,"finding":"TPRN knockout mice generated by TALEN show progressive degeneration of inner and outer hair cell stereocilia and progressive sensorineural hearing loss, establishing that taperin is required for maintenance of hair cell stereocilia.","method":"TALEN-mediated knockout, auditory brainstem response, scanning electron microscopy, phalloidin labeling","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — defined loss-of-function with specific cellular and functional phenotype, single lab","pmids":["27693694"],"is_preprint":false},{"year":2018,"finding":"Tprn-null mice show disruption of stereociliary rootlet integrity, with curved rootlet shafts and hollow central cores; radixin is abnormally dispersed along stereocilia shafts, and both radixin and β-actin expression levels decrease, establishing that Tprn is critical for stereociliary rootlet structural integrity.","method":"CRISPR/Cas9 knockout, transmission electron microscopy, immunofluorescence, Western blot","journal":"Frontiers of medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean KO with defined ultrastructural phenotype and molecular marker mislocalization, single lab with multiple methods","pmids":["30159668"],"is_preprint":false},{"year":2023,"finding":"TPRN, together with its binding partners CLIC5 and PTPRQ, forms concentric rings in the taper region of stereocilia; disruption of these rings (via competitive inhibition of TPRN–CLIC5 interaction or TPRN overexpression) causes stereocilia degeneration and severe hearing loss; AAV-mediated restoration of TPRN expression rescues auditory function in Tprn knockout mice.","method":"Biochemistry (co-IP), dual stimulated emission depletion (STED) microscopy, competitive inhibition experiments, AAV gene delivery in Tprn KO mice, auditory brainstem response","journal":"Molecular therapy","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — super-resolution imaging of protein complex architecture combined with functional disruption and rescue experiments, multiple orthogonal methods in one study","pmids":["37952086"],"is_preprint":false},{"year":2025,"finding":"Purified full-length TPRN cross-links F-actin into bendable bundles in vitro, with the F-actin-bundling activity attributed to the N-terminal region; TPRN also interacts with the membrane receptor PTPRQ, connecting the F-actin core to the plasma membrane to stabilize stereocilia.","method":"In vitro F-actin bundling assay with purified recombinant TPRN, domain mapping, co-IP with PTPRQ, TPRN-deficient and overexpression mouse models","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution of F-actin bundling with purified protein plus domain mapping, complemented by in vivo KO and OE phenotypes and PTPRQ interaction, multiple orthogonal methods","pmids":["40471101"],"is_preprint":false},{"year":2025,"finding":"TPRN-deficient mice show progressive loss of TRIOBP-5 and ANKRD24 from mechanosensory stereocilia rows starting postnatally, indicating that TPRN is required for the retention of these rootlet-associated proteins at the pivot point.","method":"Immunofluorescence in TPRN-deficient mice, confocal microscopy","journal":"The Journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean KO with specific molecular marker mislocalization phenotype, single study","pmids":["40471101"],"is_preprint":false},{"year":2026,"finding":"AAV-mediated delivery of TPRN driven by a hair cell-specific promoter (coProB2) restores auditory function to near wild-type levels in DFNB79 (Tprn mutant) mice, establishing functional rescue by gene replacement.","method":"AAV gene therapy in DFNB79 mouse model, auditory brainstem response","journal":"Cell reports. Medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — defined rescue of auditory function by gene replacement in KO model, single lab","pmids":["41923624"],"is_preprint":false}],"current_model":"TPRN (taperin) is a vertebrate-specific F-actin bundling protein that localizes to the taper/pivot region of inner ear hair cell stereocilia, where it forms concentric rings with CLIC5 and PTPRQ, cross-links actin filaments through its N-terminal domain, connects the F-actin core to the plasma membrane via PTPRQ, stabilizes stereociliary rootlets, and retains TRIOBP-5 and ANKRD24 at the pivot point; in the nucleus, taperin docks PP1α via an RVxF motif to suppress phosphatase activity and is recruited to DNA damage sites in complex with Ku70/Ku80/PARP/topoisomerases."},"narrative":{"mechanistic_narrative":"TPRN (taperin) is a vertebrate F-actin bundling protein that maintains the structural integrity of inner ear hair cell stereocilia, where it localizes specifically to the taper/pivot region at the base of the stereocilium [PMID:20170899, PMID:27693694]. Purified TPRN cross-links F-actin into bendable bundles through its N-terminal region and connects the actin core to the plasma membrane via the membrane receptor PTPRQ, anchoring the stereocilium [PMID:40471101]. Within the taper region, TPRN assembles with CLIC5 and PTPRQ into concentric rings; this architecture also depends on a complex with CLIC5, radixin, and myosin VI, and loss of CLIC5 mislocalizes TPRN from the stereocilia base [PMID:24285636, PMID:37952086]. Functionally, TPRN is required to preserve stereociliary rootlet integrity and to retain the rootlet-associated proteins TRIOBP-5 and ANKRD24 at the pivot point [PMID:30159668, PMID:40471101]. Loss of TPRN causes progressive degeneration of hair cell stereocilia and progressive sensorineural hearing loss, and AAV-mediated TPRN gene replacement restores auditory function in Tprn-mutant (DFNB79) mice [PMID:27693694, PMID:37952086, PMID:41923624]. Beyond its stereociliary role, taperin docks the PP1α phosphatase isoform through a canonical RVxF motif and suppresses its activity, shuttles between nucleus and cytoplasm, and is recruited to sites of DNA damage in association with Ku70, Ku80, PARP, and topoisomerases I and IIα [PMID:23213405].","teleology":[{"year":2010,"claim":"Establishing where TPRN acts began with showing the protein concentrates at the taper region of hair cell stereocilia, pointing to a structural role at the stereocilium base rather than diffuse function.","evidence":"Immunolocalization in mouse cochlea","pmids":["20170899"],"confidence":"Medium","gaps":["Localization alone did not define molecular activity","No binding partners identified at this stage"]},{"year":2011,"claim":"A parallel line of work asked whether taperin has biochemical activity beyond the ear, showing it docks PP1α via an RVxF motif and suppresses its phosphatase activity, that it shuttles between nucleus and cytoplasm complexed with PP1, and that it is recruited to DNA damage sites with Ku70/Ku80/PARP and topoisomerases.","evidence":"In vitro phosphatase assay, RVxF mutagenesis, subcellular fractionation, SILAC mass spectrometry, live-cell DNA damage imaging","pmids":["23213405"],"confidence":"Medium","gaps":["Functional consequence of PP1 suppression in hair cells not established","Role of DNA damage recruitment not linked to a phenotype","Single-lab interactome without reciprocal validation in vivo"]},{"year":2013,"claim":"To place TPRN in a molecular assembly, it was shown to form a complex with CLIC5, radixin, and myosin VI at the stereocilia base, with CLIC5 required to position TPRN there, defining an interdependent base-of-stereocilium machine.","evidence":"Co-IP/pulldown, confocal microscopy, CLIC5-deficient jitterbug mice","pmids":["24285636"],"confidence":"Medium","gaps":["Direct versus indirect nature of each interaction not resolved","Stoichiometry and order of assembly unknown"]},{"year":2016,"claim":"Whether TPRN is actually required for hearing was tested by knockout, demonstrating progressive stereocilia degeneration and sensorineural hearing loss and establishing taperin as a maintenance factor for stereocilia.","evidence":"TALEN knockout mice, ABR, scanning electron microscopy, phalloidin labeling","pmids":["27693694"],"confidence":"Medium","gaps":["Molecular mechanism of degeneration not defined","Did not distinguish development from maintenance defect"]},{"year":2018,"claim":"The structural target of TPRN was localized to the rootlet, with knockout causing curved rootlet shafts, hollow cores, and dispersed radixin plus reduced β-actin, implicating taperin in rootlet integrity.","evidence":"CRISPR/Cas9 knockout, transmission electron microscopy, immunofluorescence, Western blot","pmids":["30159668"],"confidence":"Medium","gaps":["Whether rootlet defect is direct or secondary not resolved","Mechanism linking TPRN loss to reduced actin levels unknown"]},{"year":2023,"claim":"Super-resolution imaging resolved the supramolecular architecture, showing TPRN, CLIC5, and PTPRQ form concentric rings whose disruption causes degeneration and hearing loss, while AAV restoration of TPRN rescued auditory function.","evidence":"Co-IP, dual-STED microscopy, competitive inhibition, AAV delivery in Tprn KO mice, ABR","pmids":["37952086"],"confidence":"High","gaps":["Molecular basis of ring self-organization not defined","Why overexpression is also disruptive not mechanistically explained"]},{"year":2025,"claim":"The biochemical activity underlying the structural role was defined by reconstitution: purified TPRN cross-links F-actin into bendable bundles via its N-terminal region and binds PTPRQ to link the actin core to the membrane, and TPRN loss depletes TRIOBP-5 and ANKRD24 from the pivot point.","evidence":"In vitro F-actin bundling with recombinant protein, domain mapping, PTPRQ co-IP, TPRN-deficient and overexpression mice, immunofluorescence","pmids":["40471101"],"confidence":"High","gaps":["Structural basis of actin cross-linking not determined","Whether TRIOBP-5/ANKRD24 retention is via direct binding unknown"]},{"year":2026,"claim":"Translational potential was demonstrated by hair cell-specific AAV delivery of TPRN restoring near wild-type hearing in DFNB79 mice, confirming gene replacement reverses the loss-of-function phenotype.","evidence":"AAV gene therapy with coProB2 promoter in DFNB79 mouse model, ABR","pmids":["41923624"],"confidence":"Medium","gaps":["Durability and developmental-window dependence not addressed","Single-lab rescue not yet in additional models"]},{"year":null,"claim":"How taperin's nuclear PP1/DNA-damage functions relate to its stereociliary actin-bundling role, and whether they operate in the same or distinct cell contexts, remains unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No integration of nuclear and stereociliary functions","No structural model of the actin-bundling N-terminal domain","Mechanism of recruitment to DNA damage sites not defined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[8]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[1]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[8]}],"localization":[{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[0,5,8]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[2,3]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[2]}],"pathway":[{"term_id":"R-HSA-9709957","term_label":"Sensory Perception","supporting_discovery_ids":[5,7]}],"complexes":[],"partners":["CLIC5","PTPRQ","RDX","MYO6","PPP1CA","TRIOBP","ANKRD24"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q4KMQ1","full_name":"Taperin","aliases":[],"length_aa":711,"mass_kda":75.6,"function":"Essential for hearing (By similarity). Required for maintenance of stereocilia on both inner and outer hair cells (By similarity). Necessary for the integrity of the stereociliary rootlet (By similarity). May act as an actin cytoskeleton regulator involved in the regulation of actin dynamics at the pointed end in hair cells (By similarity). Forms rings at the base of stereocilia and binds actin filaments in the stereocilia which may stabilize the stereocilia (By similarity). Acts as a strong inhibitor of PPP1CA phosphatase activity (PubMed:23213405). Recruited to sites of DNA damage and may play a role in DNA damage repair (PubMed:23213405)","subcellular_location":"Cell projection, stereocilium; Cell projection, microvillus; Nucleus, nucleoplasm; Cytoplasm","url":"https://www.uniprot.org/uniprotkb/Q4KMQ1/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/TPRN","classification":"Not Classified","n_dependent_lines":2,"n_total_lines":1208,"dependency_fraction":0.0016556291390728477},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/TPRN","total_profiled":1310},"omim":[{"mim_id":"613354","title":"TAPERIN; TPRN","url":"https://www.omim.org/entry/613354"},{"mim_id":"613307","title":"DEAFNESS, AUTOSOMAL RECESSIVE 79; DFNB79","url":"https://www.omim.org/entry/613307"},{"mim_id":"611410","title":"RHO FAMILY-INTERACTING CELL POLARIZATION REGULATOR 2; RIPOR2","url":"https://www.omim.org/entry/611410"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Plasma membrane","reliability":"Approved"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"brain","ntpm":55.9},{"tissue":"pancreas","ntpm":89.1}],"url":"https://www.proteinatlas.org/search/TPRN"},"hgnc":{"alias_symbol":["FLJ90254"],"prev_symbol":["C9orf75","DFNB79"]},"alphafold":{"accession":"Q4KMQ1","domains":[{"cath_id":"-","chopping":"61-103","consensus_level":"medium","plddt":73.9733,"start":61,"end":103}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q4KMQ1","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q4KMQ1-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q4KMQ1-F1-predicted_aligned_error_v6.png","plddt_mean":54.44},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=TPRN","jax_strain_url":"https://www.jax.org/strain/search?query=TPRN"},"sequence":{"accession":"Q4KMQ1","fasta_url":"https://rest.uniprot.org/uniprotkb/Q4KMQ1.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q4KMQ1/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q4KMQ1"}},"corpus_meta":[{"pmid":"20170899","id":"PMC_20170899","title":"Targeted capture and next-generation sequencing identifies C9orf75, encoding taperin, as the mutated gene in nonsyndromic deafness DFNB79.","date":"2010","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/20170899","citation_count":148,"is_preprint":false},{"pmid":"24285636","id":"PMC_24285636","title":"CLIC5 stabilizes membrane-actin filament linkages at the base of hair cell stereocilia in a molecular complex with radixin, taperin, and myosin VI.","date":"2013","source":"Cytoskeleton (Hoboken, N.J.)","url":"https://pubmed.ncbi.nlm.nih.gov/24285636","citation_count":64,"is_preprint":false},{"pmid":"20170898","id":"PMC_20170898","title":"Mutations in TPRN cause a progressive form of autosomal-recessive nonsyndromic hearing loss.","date":"2010","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/20170898","citation_count":47,"is_preprint":false},{"pmid":"23213405","id":"PMC_23213405","title":"Taperin (c9orf75), a mutated gene in nonsyndromic deafness, encodes a vertebrate specific, nuclear localized protein phosphatase one alpha (PP1α) docking protein.","date":"2011","source":"Biology open","url":"https://pubmed.ncbi.nlm.nih.gov/23213405","citation_count":16,"is_preprint":false},{"pmid":"28968992","id":"PMC_28968992","title":"Target sequencing of 307 deafness genes identifies candidate genes implicated in microtia.","date":"2017","source":"Oncotarget","url":"https://pubmed.ncbi.nlm.nih.gov/28968992","citation_count":14,"is_preprint":false},{"pmid":"37952086","id":"PMC_37952086","title":"Critical role of TPRN rings in the stereocilia for hearing.","date":"2023","source":"Molecular therapy : the journal of the American Society of Gene Therapy","url":"https://pubmed.ncbi.nlm.nih.gov/37952086","citation_count":12,"is_preprint":false},{"pmid":"30159668","id":"PMC_30159668","title":"Tprn is essential for the integrity of stereociliary rootlet in cochlear hair cells in mice.","date":"2018","source":"Frontiers of medicine","url":"https://pubmed.ncbi.nlm.nih.gov/30159668","citation_count":12,"is_preprint":false},{"pmid":"19603065","id":"PMC_19603065","title":"DFNB79: reincarnation of a nonsyndromic deafness locus on chromosome 9q34.3.","date":"2010","source":"European journal of human genetics : EJHG","url":"https://pubmed.ncbi.nlm.nih.gov/19603065","citation_count":10,"is_preprint":false},{"pmid":"34360009","id":"PMC_34360009","title":"Transcriptomic Profile Reveals Deregulation of Hearing-Loss Related Genes in Vestibular Schwannoma Cells Following Electromagnetic Field Exposure.","date":"2021","source":"Cells","url":"https://pubmed.ncbi.nlm.nih.gov/34360009","citation_count":9,"is_preprint":false},{"pmid":"36986449","id":"PMC_36986449","title":"Functionalized Lipid Nanocarriers for Simultaneous Delivery of Docetaxel and Tariquidar to Chemoresistant Cancer Cells.","date":"2023","source":"Pharmaceuticals (Basel, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/36986449","citation_count":9,"is_preprint":false},{"pmid":"27693694","id":"PMC_27693694","title":"Progressive hearing loss and degeneration of hair cell stereocilia in taperin gene knockout mice.","date":"2016","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/27693694","citation_count":7,"is_preprint":false},{"pmid":"39432560","id":"PMC_39432560","title":"Proteogenomic analysis of air-pollution-associated lung cancer reveals prevention and therapeutic opportunities.","date":"2024","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/39432560","citation_count":7,"is_preprint":false},{"pmid":"23340767","id":"PMC_23340767","title":"The c.42_52del11 mutation in TPRN and progressive hearing loss in a family from Pakistan.","date":"2013","source":"Biochemical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/23340767","citation_count":4,"is_preprint":false},{"pmid":"37729465","id":"PMC_37729465","title":"Whole-genome resequencing reveals new mutations in candidate genes for Beichuan-white goat prolificacya.","date":"2023","source":"Animal biotechnology","url":"https://pubmed.ncbi.nlm.nih.gov/37729465","citation_count":4,"is_preprint":false},{"pmid":"40471101","id":"PMC_40471101","title":"Taperin bundles F-actin at stereocilia pivot points enabling optimal lifelong mechanosensitivity.","date":"2025","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/40471101","citation_count":1,"is_preprint":false},{"pmid":"41923624","id":"PMC_41923624","title":"Human promoter-driven AAV tools enable precision gene therapy targeting cochlear hair cells.","date":"2026","source":"Cell reports. Medicine","url":"https://pubmed.ncbi.nlm.nih.gov/41923624","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":9135,"output_tokens":2377,"usd":0.03153,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9516,"output_tokens":3020,"usd":0.06154,"stage2_stop_reason":"end_turn"},"total_usd":0.09307,"stage1_batch_id":"msgbatch_017qqVz33Ga63SCDwzb35XPb","stage2_batch_id":"msgbatch_01Scr2Ei9x4HJMiRGxwrmvLK","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2010,\n      \"finding\": \"TPRN (taperin) protein localizes to the taper region of hair cell stereocilia in the mouse cochlea, as shown by immunolocalization.\",\n      \"method\": \"Immunolocalization in mouse cochlea\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct immunolocalization experiment with clear subcellular localization, single lab but consistent with subsequent studies\",\n      \"pmids\": [\"20170899\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Taperin (TPRN) preferentially docks the alpha isoform of PP1 (PP1α) through a canonical 'RVxF' motif, and suppresses the general phosphatase activity of PP1α.\",\n      \"method\": \"Biochemical assays, proteomic approaches, in vitro phosphatase activity assay, mutagenesis of RVxF motif\",\n      \"journal\": \"Biology open\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — biochemical reconstitution with enzymatic activity assay and motif-based mutagenesis in a single lab\",\n      \"pmids\": [\"23213405\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Taperin localizes predominantly to the nucleus but shuttles between the nucleus and cytoplasm, and is found complexed with PP1 in both compartments.\",\n      \"method\": \"Western blot, subcellular fractionation, biochemical co-purification\",\n      \"journal\": \"Biology open\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — fractionation and co-purification experiments in single lab with two orthogonal methods\",\n      \"pmids\": [\"23213405\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Taperin is actively recruited to sites of DNA damage, and interacts with DNA damage response proteins Ku70, Ku80, PARP, and topoisomerases I and IIα, as revealed by SILAC-based mass spectrometry.\",\n      \"method\": \"SILAC-based quantitative mass spectrometry, live cell imaging of DNA damage recruitment\",\n      \"journal\": \"Biology open\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — quantitative MS interactome plus live imaging of recruitment, single lab\",\n      \"pmids\": [\"23213405\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"TPRN (taperin) forms a molecular complex with CLIC5, radixin (RDX), and myosin VI (MYO6) at the base of hair cell stereocilia; loss of CLIC5 causes mislocalization of TPRN from the stereocilia base.\",\n      \"method\": \"Biochemical interaction assays (co-IP/pulldown), confocal microscopy, analysis of CLIC5-deficient (jitterbug) mice\",\n      \"journal\": \"Cytoskeleton (Hoboken, N.J.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal biochemical interaction assays combined with in vivo mislocalization phenotype, single lab\",\n      \"pmids\": [\"24285636\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"TPRN knockout mice generated by TALEN show progressive degeneration of inner and outer hair cell stereocilia and progressive sensorineural hearing loss, establishing that taperin is required for maintenance of hair cell stereocilia.\",\n      \"method\": \"TALEN-mediated knockout, auditory brainstem response, scanning electron microscopy, phalloidin labeling\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — defined loss-of-function with specific cellular and functional phenotype, single lab\",\n      \"pmids\": [\"27693694\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Tprn-null mice show disruption of stereociliary rootlet integrity, with curved rootlet shafts and hollow central cores; radixin is abnormally dispersed along stereocilia shafts, and both radixin and β-actin expression levels decrease, establishing that Tprn is critical for stereociliary rootlet structural integrity.\",\n      \"method\": \"CRISPR/Cas9 knockout, transmission electron microscopy, immunofluorescence, Western blot\",\n      \"journal\": \"Frontiers of medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean KO with defined ultrastructural phenotype and molecular marker mislocalization, single lab with multiple methods\",\n      \"pmids\": [\"30159668\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"TPRN, together with its binding partners CLIC5 and PTPRQ, forms concentric rings in the taper region of stereocilia; disruption of these rings (via competitive inhibition of TPRN–CLIC5 interaction or TPRN overexpression) causes stereocilia degeneration and severe hearing loss; AAV-mediated restoration of TPRN expression rescues auditory function in Tprn knockout mice.\",\n      \"method\": \"Biochemistry (co-IP), dual stimulated emission depletion (STED) microscopy, competitive inhibition experiments, AAV gene delivery in Tprn KO mice, auditory brainstem response\",\n      \"journal\": \"Molecular therapy\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — super-resolution imaging of protein complex architecture combined with functional disruption and rescue experiments, multiple orthogonal methods in one study\",\n      \"pmids\": [\"37952086\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Purified full-length TPRN cross-links F-actin into bendable bundles in vitro, with the F-actin-bundling activity attributed to the N-terminal region; TPRN also interacts with the membrane receptor PTPRQ, connecting the F-actin core to the plasma membrane to stabilize stereocilia.\",\n      \"method\": \"In vitro F-actin bundling assay with purified recombinant TPRN, domain mapping, co-IP with PTPRQ, TPRN-deficient and overexpression mouse models\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution of F-actin bundling with purified protein plus domain mapping, complemented by in vivo KO and OE phenotypes and PTPRQ interaction, multiple orthogonal methods\",\n      \"pmids\": [\"40471101\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"TPRN-deficient mice show progressive loss of TRIOBP-5 and ANKRD24 from mechanosensory stereocilia rows starting postnatally, indicating that TPRN is required for the retention of these rootlet-associated proteins at the pivot point.\",\n      \"method\": \"Immunofluorescence in TPRN-deficient mice, confocal microscopy\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean KO with specific molecular marker mislocalization phenotype, single study\",\n      \"pmids\": [\"40471101\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"AAV-mediated delivery of TPRN driven by a hair cell-specific promoter (coProB2) restores auditory function to near wild-type levels in DFNB79 (Tprn mutant) mice, establishing functional rescue by gene replacement.\",\n      \"method\": \"AAV gene therapy in DFNB79 mouse model, auditory brainstem response\",\n      \"journal\": \"Cell reports. Medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — defined rescue of auditory function by gene replacement in KO model, single lab\",\n      \"pmids\": [\"41923624\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"TPRN (taperin) is a vertebrate-specific F-actin bundling protein that localizes to the taper/pivot region of inner ear hair cell stereocilia, where it forms concentric rings with CLIC5 and PTPRQ, cross-links actin filaments through its N-terminal domain, connects the F-actin core to the plasma membrane via PTPRQ, stabilizes stereociliary rootlets, and retains TRIOBP-5 and ANKRD24 at the pivot point; in the nucleus, taperin docks PP1α via an RVxF motif to suppress phosphatase activity and is recruited to DNA damage sites in complex with Ku70/Ku80/PARP/topoisomerases.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"TPRN (taperin) is a vertebrate F-actin bundling protein that maintains the structural integrity of inner ear hair cell stereocilia, where it localizes specifically to the taper/pivot region at the base of the stereocilium [#0, #5]. Purified TPRN cross-links F-actin into bendable bundles through its N-terminal region and connects the actin core to the plasma membrane via the membrane receptor PTPRQ, anchoring the stereocilium [#8]. Within the taper region, TPRN assembles with CLIC5 and PTPRQ into concentric rings; this architecture also depends on a complex with CLIC5, radixin, and myosin VI, and loss of CLIC5 mislocalizes TPRN from the stereocilia base [#4, #7]. Functionally, TPRN is required to preserve stereociliary rootlet integrity and to retain the rootlet-associated proteins TRIOBP-5 and ANKRD24 at the pivot point [#6, #9]. Loss of TPRN causes progressive degeneration of hair cell stereocilia and progressive sensorineural hearing loss, and AAV-mediated TPRN gene replacement restores auditory function in Tprn-mutant (DFNB79) mice [#5, #7, #10]. Beyond its stereociliary role, taperin docks the PP1\\u03b1 phosphatase isoform through a canonical RVxF motif and suppresses its activity, shuttles between nucleus and cytoplasm, and is recruited to sites of DNA damage in association with Ku70, Ku80, PARP, and topoisomerases I and II\\u03b1 [#1, #2, #3].\",\n  \"teleology\": [\n    {\n      \"year\": 2010,\n      \"claim\": \"Establishing where TPRN acts began with showing the protein concentrates at the taper region of hair cell stereocilia, pointing to a structural role at the stereocilium base rather than diffuse function.\",\n      \"evidence\": \"Immunolocalization in mouse cochlea\",\n      \"pmids\": [\"20170899\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Localization alone did not define molecular activity\", \"No binding partners identified at this stage\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"A parallel line of work asked whether taperin has biochemical activity beyond the ear, showing it docks PP1\\u03b1 via an RVxF motif and suppresses its phosphatase activity, that it shuttles between nucleus and cytoplasm complexed with PP1, and that it is recruited to DNA damage sites with Ku70/Ku80/PARP and topoisomerases.\",\n      \"evidence\": \"In vitro phosphatase assay, RVxF mutagenesis, subcellular fractionation, SILAC mass spectrometry, live-cell DNA damage imaging\",\n      \"pmids\": [\"23213405\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of PP1 suppression in hair cells not established\", \"Role of DNA damage recruitment not linked to a phenotype\", \"Single-lab interactome without reciprocal validation in vivo\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"To place TPRN in a molecular assembly, it was shown to form a complex with CLIC5, radixin, and myosin VI at the stereocilia base, with CLIC5 required to position TPRN there, defining an interdependent base-of-stereocilium machine.\",\n      \"evidence\": \"Co-IP/pulldown, confocal microscopy, CLIC5-deficient jitterbug mice\",\n      \"pmids\": [\"24285636\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct versus indirect nature of each interaction not resolved\", \"Stoichiometry and order of assembly unknown\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Whether TPRN is actually required for hearing was tested by knockout, demonstrating progressive stereocilia degeneration and sensorineural hearing loss and establishing taperin as a maintenance factor for stereocilia.\",\n      \"evidence\": \"TALEN knockout mice, ABR, scanning electron microscopy, phalloidin labeling\",\n      \"pmids\": [\"27693694\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular mechanism of degeneration not defined\", \"Did not distinguish development from maintenance defect\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"The structural target of TPRN was localized to the rootlet, with knockout causing curved rootlet shafts, hollow cores, and dispersed radixin plus reduced \\u03b2-actin, implicating taperin in rootlet integrity.\",\n      \"evidence\": \"CRISPR/Cas9 knockout, transmission electron microscopy, immunofluorescence, Western blot\",\n      \"pmids\": [\"30159668\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether rootlet defect is direct or secondary not resolved\", \"Mechanism linking TPRN loss to reduced actin levels unknown\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Super-resolution imaging resolved the supramolecular architecture, showing TPRN, CLIC5, and PTPRQ form concentric rings whose disruption causes degeneration and hearing loss, while AAV restoration of TPRN rescued auditory function.\",\n      \"evidence\": \"Co-IP, dual-STED microscopy, competitive inhibition, AAV delivery in Tprn KO mice, ABR\",\n      \"pmids\": [\"37952086\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis of ring self-organization not defined\", \"Why overexpression is also disruptive not mechanistically explained\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"The biochemical activity underlying the structural role was defined by reconstitution: purified TPRN cross-links F-actin into bendable bundles via its N-terminal region and binds PTPRQ to link the actin core to the membrane, and TPRN loss depletes TRIOBP-5 and ANKRD24 from the pivot point.\",\n      \"evidence\": \"In vitro F-actin bundling with recombinant protein, domain mapping, PTPRQ co-IP, TPRN-deficient and overexpression mice, immunofluorescence\",\n      \"pmids\": [\"40471101\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of actin cross-linking not determined\", \"Whether TRIOBP-5/ANKRD24 retention is via direct binding unknown\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Translational potential was demonstrated by hair cell-specific AAV delivery of TPRN restoring near wild-type hearing in DFNB79 mice, confirming gene replacement reverses the loss-of-function phenotype.\",\n      \"evidence\": \"AAV gene therapy with coProB2 promoter in DFNB79 mouse model, ABR\",\n      \"pmids\": [\"41923624\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Durability and developmental-window dependence not addressed\", \"Single-lab rescue not yet in additional models\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How taperin's nuclear PP1/DNA-damage functions relate to its stereociliary actin-bundling role, and whether they operate in the same or distinct cell contexts, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No integration of nuclear and stereociliary functions\", \"No structural model of the actin-bundling N-terminal domain\", \"Mechanism of recruitment to DNA damage sites not defined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [8]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [8]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [0, 5, 8]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [2, 3]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-9709957\", \"supporting_discovery_ids\": [5, 7]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"CLIC5\", \"PTPRQ\", \"RDX\", \"MYO6\", \"PPP1CA\", \"TRIOBP\", \"ANKRD24\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}