{"gene":"TSPAN12","run_date":"2026-04-28T21:43:00","timeline":{"discoveries":[{"year":2009,"finding":"TSPAN12 is expressed in retinal vasculature and loss of Tspan12 phenocopies defects seen in Fzd4, Lrp5, and Norrin mutant mice. Overexpressed TSPAN12 associates with the Norrin-receptor complex and significantly increases Norrin/β-catenin but not Wnt/β-catenin signaling. TSPAN12 siRNA abolishes transcriptional responses to Norrin but not Wnt3A in retinal endothelial cells. TSPAN12 cooperatively promotes multimerization of FZD4 and associated proteins to elicit physiological levels of Norrin signaling.","method":"Mouse knockout genetics, Co-IP, siRNA knockdown, luciferase reporter assay, genetic epistasis with Norrin/Lrp5","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (KO phenotype, epistasis, Co-IP, siRNA, reporter assay), foundational paper with 323 citations replicated by subsequent labs","pmids":["19837033"],"is_preprint":false},{"year":2017,"finding":"TSPAN12 functions as a co-receptor in the Norrin (NDP) receptor complex, interacting with FZD4 and NDP via its extracellular loops to enhance FZD4 ligand selectivity for NDP over Wnt. FEVR-linked mutations in TSPAN12 prevent incorporation into the NDP receptor complex. TSPAN12 alleviates defects of FZD4 M105V mutation that destabilizes NDP/FZD4 interaction, demonstrated both in vitro and in Xenopus embryos.","method":"Co-IP, pulldown, cell-based signaling assays, Xenopus embryo functional rescue, FEVR mutation analysis","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP, in vivo Xenopus rescue, and mechanistic mutagenesis in a single study with moderate citation count","pmids":["28658627"],"is_preprint":false},{"year":2013,"finding":"TSPAN12 ablation from human MDA-MB-231 cells causes diminished association between FZD4 and its co-receptor LRP5, leading to enhanced proteasomal degradation of β-catenin. TSPAN12 stabilizes FZD4-LRP5 association to support canonical Wnt-pathway signaling.","method":"Lentiviral shRNA knockdown, Co-IP, western blot, tumor xenograft assay","journal":"Cellular and molecular life sciences : CMLS","confidence":"Medium","confidence_rationale":"Tier 3 — Co-IP and KD with cellular phenotype, single lab","pmids":["23955570"],"is_preprint":false},{"year":2014,"finding":"In p53-depleted fibroblasts (cancer-associated fibroblasts), TSPAN12 is derepressed by p53 knockdown. TSPAN12 in fibroblasts transduces β-catenin signaling in response to cancer cell contact, leading to CXCL6 secretion that promotes cancer cell invasion. TSPAN12 knockdown in p53-depleted fibroblasts inhibits CXCL6 secretion and cancer invasion.","method":"siRNA knockdown, coculture assay, DNA chip, in vivo tumor model, β-catenin pathway reporter","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 — KD with defined cellular phenotype and CXCL6 pathway placement, single lab","pmids":["25512506"],"is_preprint":false},{"year":2017,"finding":"An anti-Tspan12 antibody inhibits the interaction between Tspan12 and FZD4, effectively modulating β-catenin levels and target gene expression in vascular endothelial cells. Tspan12/β-catenin signaling is activated in rodent models of oxygen-induced retinopathy and VLDLR knockout proliferative retinopathy. Intravitreal application of the antibody showed significant therapeutic effects in both models.","method":"Phage display antibody development, Co-IP inhibition assay, in vitro endothelial cell migration/tube formation, in vivo oxygen-induced retinopathy model, western blot","journal":"Circulation","confidence":"Medium","confidence_rationale":"Tier 2 — antibody blocks TSPAN12-FZD4 interaction with in vitro and in vivo functional consequences, single lab","pmids":["28356444"],"is_preprint":false},{"year":2018,"finding":"TSPAN12 functions specifically in endothelial cells to promote vascular morphogenesis and blood-retina barrier (BRB) formation during development and BRB maintenance in adult mice. Early endothelial-specific loss of TSPAN12 causes lack of intraretinal capillaries and increased VE-cadherin expression (premature vascular quiescence). Late loss of TSPAN12 strongly impairs BRB maintenance without affecting vascular morphogenesis, associated with immunoglobulin extravasation, complement deposition, cystoid edema, and impaired ERG b-wave.","method":"Conditional knockout (Cdh5-CreERT2 tamoxifen-inducible), confocal microscopy, RNA-Seq, histopathology, electroretinogram","journal":"Arteriosclerosis, thrombosis, and vascular biology","confidence":"High","confidence_rationale":"Tier 2 — cell-type-specific conditional KO with multiple orthogonal phenotypic readouts establishing endothelial-specific function","pmids":["30354230"],"is_preprint":false},{"year":2021,"finding":"RNF152 (an E3 ubiquitin ligase) interacts with TSPAN12 and targets it for ubiquitination and proteasomal degradation, thereby inhibiting TSPAN12-dependent CXCL6 expression and HCC progression. FoxO1 transcriptionally regulates RNF152 expression.","method":"Co-IP, in vivo ubiquitination assay, RNAi, luciferase/ChIP assay for FoxO1-RNF152 axis, xenograft model","journal":"Cancer cell international","confidence":"Medium","confidence_rationale":"Tier 2 — Co-IP plus in vivo ubiquitination assay establishing TSPAN12 as RNF152 substrate, single lab","pmids":["33602225"],"is_preprint":false},{"year":2021,"finding":"IL-13 reduces TSPAN12 expression in esophageal endothelial cells. TSPAN12 gene silencing in endothelial cells increases endothelial cell permeability and dysregulates extracellular matrix pathway genes, promoting endothelial cell-fibroblast crosstalk relevant to esophageal remodeling in eosinophilic esophagitis.","method":"siRNA knockdown, in vitro permeability assay, RNA sequencing, cytokine stimulation, anti-IL-13 therapy reversal","journal":"Gastroenterology","confidence":"Medium","confidence_rationale":"Tier 2 — siRNA KD with defined permeability phenotype and transcriptomic pathway analysis, large cohort correlation","pmids":["34687736"],"is_preprint":false},{"year":2022,"finding":"TSPAN12 is a negative regulator of aldosterone production: TSPAN12 gene silencing in human adrenocortical (HAC15) cells increased aldosterone secretion under basal and angiotensin II-stimulated conditions. Angiotensin II increases TSPAN12 expression in adrenocortical cells via calcium-dependent signaling (blocked by nifedipine and W-7).","method":"siRNA knockdown, hormone secretion assay, pharmacological inhibitors (nifedipine, W-7), in vivo pig adrenal dietary sodium model, immunostaining","journal":"Hypertension (Dallas, Tex. : 1979)","confidence":"Medium","confidence_rationale":"Tier 2 — siRNA KD with defined aldosterone secretion phenotype plus in vivo model, single lab","pmids":["36458545"],"is_preprint":false},{"year":2022,"finding":"Missense variants in TSPAN12 associated with FEVR compromise interactions between TSPAN12 and its binding partners (FZD4, NDP) in the Norrin/β-catenin pathway, as shown by co-immunoprecipitation. Some variants also cause abnormal subcellular trafficking of TSPAN12. Overexpression of wild-type TSPAN12 enhances Norrin/β-catenin signaling by strengthening the binding affinity of mutant Norrin with FZD4 or LRP5.","method":"Co-IP, dual-luciferase reporter assay, western blot, immunofluorescence, subcellular fractionation","journal":"Clinical genetics","confidence":"Medium","confidence_rationale":"Tier 2 — multiple orthogonal methods in single lab establishing interaction and trafficking defects for disease variants","pmids":["36453149"],"is_preprint":false},{"year":2025,"finding":"Cryo-EM structure of TSPAN12 in complex with FZD4 at 3.4 Å resolution reveals: (1) FZD4 and TSPAN12 form a direct complex in the absence of Norrin, with contact between the lower hinge of FZD4 and the extracellular loops of TSPAN12; (2) the transmembrane domain of TSPAN12 forms a tightly packed four-helix bundle and interacts with TM2 of FZD4 to promote TSPAN12 trafficking to the cell surface; (3) the C-D helices of TSPAN12 that mediate Norrin binding remain exposed in the FZD4 complex, enabling higher-affinity Norrin binding; (4) TSPAN12 and FZD4 remain associated after Norrin recognition, indicating TSPAN12 is a core component of the FZD4-Norrin-LRP5/6 signaling complex. The complex enables FZD4 to respond with a more gradual response to a wider range of Norrin concentrations.","method":"Cryo-EM structure determination, cell-based signaling assays","journal":"bioRxiv","confidence":"High","confidence_rationale":"Tier 1 — cryo-EM structure with functional validation by cell-based assays, directly resolving molecular mechanism of TSPAN12-FZD4 interaction","pmids":["bio_10.1101_2025.09.25.678640"],"is_preprint":true},{"year":2024,"finding":"lnc-TSPAN12 (a long noncoding RNA overlapping TSPAN12 locus) acts as a scaffold that directly interacts with both EIF3I and SENP1, enhancing the SENP1-EIF3I interaction. This inhibits SUMOylation of EIF3I, preventing its ubiquitin-mediated degradation, and ultimately activates the Wnt/β-catenin signaling pathway to stimulate EMT and metastasis in hepatocellular carcinoma. METTL3-mediated m6A modification stabilizes lnc-TSPAN12.","method":"RNA pulldown, Co-IP, RIP (RNA immunoprecipitation), m6A modification assay, in vitro/in vivo migration assays","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 — mechanistic scaffold function established by RNA pulldown and Co-IP; note this is lnc-TSPAN12, not the TSPAN12 protein itself","pmids":["38374407"],"is_preprint":false}],"current_model":"TSPAN12 is a tetraspanin co-receptor that directly binds FZD4 (via its extracellular loops contacting the FZD4 lower hinge, as resolved by cryo-EM) and the ligand Norrin (NDP) to form a core signaling complex that selectively amplifies Norrin/β-catenin—but not Wnt/β-catenin—signaling; it promotes FZD4-LRP5 association and receptor multimerization, is required in endothelial cells for blood-retina barrier formation and maintenance, and is subject to proteasomal degradation mediated by the E3 ubiquitin ligase RNF152."},"narrative":{"teleology":[{"year":2009,"claim":"The foundational question—whether a tetraspanin participates in Norrin/β-catenin signaling—was resolved by showing that Tspan12-null mice phenocopy Fzd4/Lrp5/Norrin mutants and that TSPAN12 selectively amplifies Norrin but not Wnt3A signaling via FZD4 multimerization.","evidence":"Mouse knockout, Co-IP, siRNA, luciferase reporter in retinal endothelial cells","pmids":["19837033"],"confidence":"High","gaps":["Direct physical contact interface between TSPAN12 and FZD4 was unresolved","Whether TSPAN12 contacts Norrin directly was unknown","Endothelial cell–autonomous requirement versus broader tissue role was not separated"]},{"year":2013,"claim":"TSPAN12 was shown to stabilize the FZD4–LRP5 co-receptor association, explaining how it supports downstream β-catenin signaling beyond simple FZD4 multimerization.","evidence":"shRNA knockdown and Co-IP in MDA-MB-231 breast cancer cells, western blot for β-catenin stability","pmids":["23955570"],"confidence":"Medium","gaps":["Demonstrated in a cancer cell line; relevance to endothelial physiology not directly tested","Mechanism by which TSPAN12 stabilizes FZD4–LRP5 was unclear"]},{"year":2014,"claim":"A non-vascular role for TSPAN12 was identified: in p53-depleted fibroblasts, TSPAN12 transduces β-catenin signaling upon cancer cell contact, driving CXCL6 secretion and tumor invasion.","evidence":"siRNA, coculture assay, in vivo tumor model, β-catenin reporter in cancer-associated fibroblasts","pmids":["25512506"],"confidence":"Medium","gaps":["Whether TSPAN12 in fibroblasts also acts through FZD4/Norrin axis or an alternative β-catenin entry point was not determined","Single-lab observation in engineered fibroblast system"]},{"year":2017,"claim":"Two studies established that TSPAN12 extracellular loops interact with both FZD4 and Norrin (NDP) to confer ligand selectivity, and that FEVR-linked TSPAN12 mutations disrupt this complex; separately, an anti-TSPAN12 antibody blocking the TSPAN12–FZD4 interaction reduced pathological retinal angiogenesis in vivo.","evidence":"Co-IP, pulldown, Xenopus rescue of FZD4 M105V mutant; phage-display antibody in oxygen-induced retinopathy models","pmids":["28658627","28356444"],"confidence":"High","gaps":["Atomic-level details of the TSPAN12–FZD4 and TSPAN12–Norrin interfaces remained unknown","Therapeutic antibody efficacy not tested in genetic FEVR models"]},{"year":2018,"claim":"Conditional endothelial-specific Tspan12 knockout definitively established that TSPAN12 functions cell-autonomously in endothelial cells for both developmental retinal vascular morphogenesis and adult blood–retina barrier maintenance.","evidence":"Cdh5-CreERT2 tamoxifen-inducible conditional knockout, confocal imaging, RNA-Seq, electroretinogram, histopathology","pmids":["30354230"],"confidence":"High","gaps":["Downstream transcriptional targets mediating barrier maintenance versus morphogenesis were not fully resolved","Whether TSPAN12 functions in other vascular beds in vivo was not tested"]},{"year":2021,"claim":"TSPAN12 protein turnover was shown to be regulated by the E3 ubiquitin ligase RNF152 through ubiquitination and proteasomal degradation, connecting FoxO1 transcriptional control of RNF152 to TSPAN12 abundance and downstream CXCL6 expression in hepatocellular carcinoma.","evidence":"Co-IP, in vivo ubiquitination assay, RNAi, ChIP, xenograft model in HCC cells","pmids":["33602225"],"confidence":"Medium","gaps":["Ubiquitination sites on TSPAN12 were not mapped","Whether RNF152-mediated degradation regulates TSPAN12 in endothelial cells or other physiological contexts is unknown"]},{"year":2021,"claim":"IL-13 was identified as an upstream suppressor of TSPAN12 in esophageal endothelial cells, and TSPAN12 silencing increased endothelial permeability and dysregulated extracellular matrix genes, extending TSPAN12's barrier function beyond the retina.","evidence":"siRNA knockdown, in vitro permeability assay, RNA-Seq, cytokine stimulation, anti-IL-13 therapy reversal in eosinophilic esophagitis cohort","pmids":["34687736"],"confidence":"Medium","gaps":["Whether endothelial permeability increase depends on the FZD4/Norrin pathway or a distinct mechanism was not tested","Single-lab in vitro observation"]},{"year":2022,"claim":"Systematic analysis of FEVR-associated TSPAN12 missense variants demonstrated that disease mutations compromise interactions with FZD4 and NDP and, in some cases, impair TSPAN12 subcellular trafficking, while wild-type TSPAN12 overexpression can rescue signaling defects of certain Norrin mutants.","evidence":"Co-IP, dual-luciferase reporter, immunofluorescence, subcellular fractionation for multiple TSPAN12 variants","pmids":["36453149"],"confidence":"Medium","gaps":["Structural basis for trafficking defects of specific variants was not resolved","In vivo functional rescue of FEVR phenotype not attempted"]},{"year":2022,"claim":"TSPAN12 was identified as a negative regulator of aldosterone production in adrenocortical cells, revealing a non-canonical, non-vascular physiological role.","evidence":"siRNA knockdown in HAC15 adrenocortical cells, hormone secretion assay, pharmacological inhibitors, pig adrenal dietary sodium model","pmids":["36458545"],"confidence":"Medium","gaps":["Whether aldosterone regulation involves FZD4/β-catenin signaling or a distinct mechanism was not determined","Single-lab observation; not replicated independently"]},{"year":2025,"claim":"The cryo-EM structure of TSPAN12–FZD4 at 3.4 Å resolution resolved the molecular interface: TSPAN12 extracellular loops contact the FZD4 lower hinge, TM helices engage FZD4 TM2, and the C–D helices that bind Norrin remain exposed, explaining how TSPAN12 pre-organizes FZD4 for graded Norrin sensing.","evidence":"Cryo-EM structure determination, cell-based signaling assays (preprint)","pmids":["bio_10.1101_2025.09.25.678640"],"confidence":"High","gaps":["Preprint; awaits peer review","Structure of the full quaternary complex with Norrin and LRP5/6 not yet resolved","Structural basis for TSPAN12-promoted FZD4 multimerization not captured in the binary complex"]},{"year":null,"claim":"Key unresolved questions include the full quaternary structure of the TSPAN12–FZD4–Norrin–LRP5/6 signaling complex, the structural basis for TSPAN12-promoted receptor multimerization, and whether TSPAN12's non-vascular roles (aldosterone regulation, esophageal barrier) operate through FZD4/β-catenin or independent pathways.","evidence":"","pmids":[],"confidence":"Low","gaps":["No structure of the full signaling holocomplex","Mechanism linking TSPAN12 to aldosterone regulation is undefined","In vivo therapeutic validation of TSPAN12-targeting strategies in FEVR patients is lacking"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,1,2,10]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,1,8]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,1,10]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,1,2,3,9]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[0,5]}],"complexes":["Norrin–FZD4–LRP5–TSPAN12 receptor complex"],"partners":["FZD4","NDP","LRP5","RNF152"],"other_free_text":[]},"mechanistic_narrative":"TSPAN12 is a tetraspanin family co-receptor that selectively amplifies Norrin/β-catenin signaling by assembling a multiprotein receptor complex with FZD4, LRP5, and the ligand Norrin (NDP). TSPAN12 directly contacts FZD4 through its extracellular loops engaging the FZD4 lower hinge and through transmembrane interactions with FZD4 TM2, forming a stable binary complex that pre-organizes the receptor for higher-affinity Norrin binding and promotes FZD4-LRP5 association and receptor multimerization [PMID:19837033, PMID:28658627, PMID:23955570]. In endothelial cells, TSPAN12 is required for retinal vascular morphogenesis and blood–retina barrier formation and maintenance; conditional endothelial-specific knockout causes failure of intraretinal capillary development and, in adults, barrier breakdown with cystoid edema and complement deposition [PMID:30354230]. Loss-of-function mutations in TSPAN12 cause familial exudative vitreoretinopathy (FEVR) by disrupting incorporation into the Norrin receptor complex and, in some cases, impairing subcellular trafficking [PMID:28658627, PMID:36453149]."},"prefetch_data":{"uniprot":{"accession":"O95859","full_name":"Tetraspanin-12","aliases":["Tetraspan NET-2","Transmembrane 4 superfamily member 12"],"length_aa":305,"mass_kda":35.4,"function":"Regulator of cell surface receptor signal transduction. Plays a central role in retinal vascularization by regulating norrin (NDP) signal transduction. Acts in concert with norrin (NDP) to promote FZD4 multimerization and subsequent activation of FZD4, leading to promote accumulation of beta-catenin (CTNNB1) and stimulate LEF/TCF-mediated transcriptional programs. Suprisingly, it only activates the norrin (NDP)-dependent activation of FZD4, while it does not activate the Wnt-dependent activation of FZD4, suggesting the existence of a Wnt-independent signaling that also promote accumulation the beta-catenin (CTNNB1) (By similarity). Acts as a regulator of membrane proteinases such as ADAM10 and MMP14/MT1-MMP. Activates ADAM10-dependent cleavage activity of amyloid precursor protein (APP). Activates MMP14/MT1-MMP-dependent cleavage activity","subcellular_location":"Cell membrane","url":"https://www.uniprot.org/uniprotkb/O95859/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/TSPAN12","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/TSPAN12","total_profiled":1310},"omim":[{"mim_id":"613310","title":"EXUDATIVE VITREORETINOPATHY 5; EVR5","url":"https://www.omim.org/entry/613310"},{"mim_id":"613138","title":"TETRASPANIN 12; TSPAN12","url":"https://www.omim.org/entry/613138"},{"mim_id":"605750","title":"EXUDATIVE VITREORETINOPATHY 3; EVR3","url":"https://www.omim.org/entry/605750"},{"mim_id":"601813","title":"EXUDATIVE VITREORETINOPATHY 4; EVR4","url":"https://www.omim.org/entry/601813"},{"mim_id":"305390","title":"EXUDATIVE VITREORETINOPATHY 2, X-LINKED; EVR2","url":"https://www.omim.org/entry/305390"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Microtubules","reliability":"Approved"},{"location":"Vesicles","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"kidney","ntpm":85.5}],"url":"https://www.proteinatlas.org/search/TSPAN12"},"hgnc":{"alias_symbol":["NET-2"],"prev_symbol":["TM4SF12"]},"alphafold":{"accession":"O95859","domains":[{"cath_id":"-","chopping":"1-46_57-120_225-252","consensus_level":"medium","plddt":87.6849,"start":1,"end":252},{"cath_id":"1.10.1450.10","chopping":"125-210","consensus_level":"high","plddt":90.2494,"start":125,"end":210}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O95859","model_url":"https://alphafold.ebi.ac.uk/files/AF-O95859-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O95859-F1-predicted_aligned_error_v6.png","plddt_mean":80.31},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=TSPAN12","jax_strain_url":"https://www.jax.org/strain/search?query=TSPAN12"},"sequence":{"accession":"O95859","fasta_url":"https://rest.uniprot.org/uniprotkb/O95859.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O95859/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O95859"}},"corpus_meta":[{"pmid":"19837033","id":"PMC_19837033","title":"TSPAN12 regulates retinal vascular development by promoting Norrin- but not Wnt-induced FZD4/beta-catenin signaling.","date":"2009","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/19837033","citation_count":323,"is_preprint":false},{"pmid":"20159111","id":"PMC_20159111","title":"Next-generation sequencing of a 40 Mb linkage interval reveals TSPAN12 mutations in patients with familial exudative vitreoretinopathy.","date":"2010","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/20159111","citation_count":176,"is_preprint":false},{"pmid":"20159112","id":"PMC_20159112","title":"Mutations in TSPAN12 cause autosomal-dominant familial exudative vitreoretinopathy.","date":"2010","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/20159112","citation_count":155,"is_preprint":false},{"pmid":"32041891","id":"PMC_32041891","title":"miR-196b-5p-mediated downregulation of TSPAN12 and GATA6 promotes tumor progression in non-small cell lung cancer.","date":"2020","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/32041891","citation_count":147,"is_preprint":false},{"pmid":"28658627","id":"PMC_28658627","title":"TSPAN12 Is a Norrin Co-receptor that Amplifies Frizzled4 Ligand Selectivity and Signaling.","date":"2017","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/28658627","citation_count":77,"is_preprint":false},{"pmid":"25512506","id":"PMC_25512506","title":"TSPAN12 is a critical factor for cancer-fibroblast cell contact-mediated cancer invasion.","date":"2014","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/25512506","citation_count":65,"is_preprint":false},{"pmid":"22427576","id":"PMC_22427576","title":"Recessive mutations in TSPAN12 cause retinal dysplasia and severe familial exudative vitreoretinopathy (FEVR).","date":"2012","source":"Investigative ophthalmology & visual science","url":"https://pubmed.ncbi.nlm.nih.gov/22427576","citation_count":62,"is_preprint":false},{"pmid":"28494495","id":"PMC_28494495","title":"Mutations in LRP5,FZD4, TSPAN12, NDP, ZNF408, or KIF11 Genes Account for 38.7% of Chinese Patients With Familial Exudative Vitreoretinopathy.","date":"2017","source":"Investigative ophthalmology & visual science","url":"https://pubmed.ncbi.nlm.nih.gov/28494495","citation_count":58,"is_preprint":false},{"pmid":"23955570","id":"PMC_23955570","title":"Tetraspanin TSPAN12 regulates tumor growth and metastasis and inhibits β-catenin degradation.","date":"2013","source":"Cellular and molecular life sciences : CMLS","url":"https://pubmed.ncbi.nlm.nih.gov/23955570","citation_count":49,"is_preprint":false},{"pmid":"26244290","id":"PMC_26244290","title":"Molecular Characterization of FZD4, LRP5, and TSPAN12 in Familial Exudative Vitreoretinopathy.","date":"2015","source":"Investigative ophthalmology & visual science","url":"https://pubmed.ncbi.nlm.nih.gov/26244290","citation_count":49,"is_preprint":false},{"pmid":"34687736","id":"PMC_34687736","title":"Loss of Endothelial TSPAN12 Promotes Fibrostenotic Eosinophilic Esophagitis via Endothelial Cell-Fibroblast Crosstalk.","date":"2021","source":"Gastroenterology","url":"https://pubmed.ncbi.nlm.nih.gov/34687736","citation_count":44,"is_preprint":false},{"pmid":"30354230","id":"PMC_30354230","title":"Endothelial Cell-Specific Inactivation of TSPAN12 (Tetraspanin 12) Reveals Pathological Consequences of Barrier Defects in an Otherwise Intact Vasculature.","date":"2018","source":"Arteriosclerosis, thrombosis, and vascular biology","url":"https://pubmed.ncbi.nlm.nih.gov/30354230","citation_count":40,"is_preprint":false},{"pmid":"29181528","id":"PMC_29181528","title":"Mutation Spectrum of the LRP5, NDP, and TSPAN12 Genes in Chinese Patients With Familial Exudative Vitreoretinopathy.","date":"2017","source":"Investigative ophthalmology & visual science","url":"https://pubmed.ncbi.nlm.nih.gov/29181528","citation_count":34,"is_preprint":false},{"pmid":"21552475","id":"PMC_21552475","title":"Novel TSPAN12 mutations in patients with familial exudative vitreoretinopathy and their associated phenotypes.","date":"2011","source":"Molecular vision","url":"https://pubmed.ncbi.nlm.nih.gov/21552475","citation_count":34,"is_preprint":false},{"pmid":"27316669","id":"PMC_27316669","title":"Mutation spectrum of the FZD-4, TSPAN12 AND ZNF408 genes in Indian FEVR patients.","date":"2016","source":"BMC ophthalmology","url":"https://pubmed.ncbi.nlm.nih.gov/27316669","citation_count":30,"is_preprint":false},{"pmid":"21334594","id":"PMC_21334594","title":"Mutations in the TSPAN12 gene in Japanese patients with familial exudative vitreoretinopathy.","date":"2011","source":"American journal of ophthalmology","url":"https://pubmed.ncbi.nlm.nih.gov/21334594","citation_count":29,"is_preprint":false},{"pmid":"28302484","id":"PMC_28302484","title":"TSPAN12 promotes chemoresistance and proliferation of SCLC under the regulation of miR-495.","date":"2017","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/28302484","citation_count":26,"is_preprint":false},{"pmid":"21626674","id":"PMC_21626674","title":"Submicroscopic deletion in 7q31 encompassing CADPS2 and TSPAN12 in a child with autism spectrum disorder and PHPV.","date":"2011","source":"American journal of medical genetics. 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seen in Fzd4, Lrp5, and Norrin mutant mice. Overexpressed TSPAN12 associates with the Norrin-receptor complex and significantly increases Norrin/β-catenin but not Wnt/β-catenin signaling. TSPAN12 siRNA abolishes transcriptional responses to Norrin but not Wnt3A in retinal endothelial cells. TSPAN12 cooperatively promotes multimerization of FZD4 and associated proteins to elicit physiological levels of Norrin signaling.\",\n      \"method\": \"Mouse knockout genetics, Co-IP, siRNA knockdown, luciferase reporter assay, genetic epistasis with Norrin/Lrp5\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (KO phenotype, epistasis, Co-IP, siRNA, reporter assay), foundational paper with 323 citations replicated by subsequent labs\",\n      \"pmids\": [\"19837033\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"TSPAN12 functions as a co-receptor in the Norrin (NDP) receptor complex, interacting with FZD4 and NDP via its extracellular loops to enhance FZD4 ligand selectivity for NDP over Wnt. FEVR-linked mutations in TSPAN12 prevent incorporation into the NDP receptor complex. TSPAN12 alleviates defects of FZD4 M105V mutation that destabilizes NDP/FZD4 interaction, demonstrated both in vitro and in Xenopus embryos.\",\n      \"method\": \"Co-IP, pulldown, cell-based signaling assays, Xenopus embryo functional rescue, FEVR mutation analysis\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP, in vivo Xenopus rescue, and mechanistic mutagenesis in a single study with moderate citation count\",\n      \"pmids\": [\"28658627\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"TSPAN12 ablation from human MDA-MB-231 cells causes diminished association between FZD4 and its co-receptor LRP5, leading to enhanced proteasomal degradation of β-catenin. TSPAN12 stabilizes FZD4-LRP5 association to support canonical Wnt-pathway signaling.\",\n      \"method\": \"Lentiviral shRNA knockdown, Co-IP, western blot, tumor xenograft assay\",\n      \"journal\": \"Cellular and molecular life sciences : CMLS\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — Co-IP and KD with cellular phenotype, single lab\",\n      \"pmids\": [\"23955570\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"In p53-depleted fibroblasts (cancer-associated fibroblasts), TSPAN12 is derepressed by p53 knockdown. TSPAN12 in fibroblasts transduces β-catenin signaling in response to cancer cell contact, leading to CXCL6 secretion that promotes cancer cell invasion. TSPAN12 knockdown in p53-depleted fibroblasts inhibits CXCL6 secretion and cancer invasion.\",\n      \"method\": \"siRNA knockdown, coculture assay, DNA chip, in vivo tumor model, β-catenin pathway reporter\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — KD with defined cellular phenotype and CXCL6 pathway placement, single lab\",\n      \"pmids\": [\"25512506\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"An anti-Tspan12 antibody inhibits the interaction between Tspan12 and FZD4, effectively modulating β-catenin levels and target gene expression in vascular endothelial cells. Tspan12/β-catenin signaling is activated in rodent models of oxygen-induced retinopathy and VLDLR knockout proliferative retinopathy. Intravitreal application of the antibody showed significant therapeutic effects in both models.\",\n      \"method\": \"Phage display antibody development, Co-IP inhibition assay, in vitro endothelial cell migration/tube formation, in vivo oxygen-induced retinopathy model, western blot\",\n      \"journal\": \"Circulation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — antibody blocks TSPAN12-FZD4 interaction with in vitro and in vivo functional consequences, single lab\",\n      \"pmids\": [\"28356444\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"TSPAN12 functions specifically in endothelial cells to promote vascular morphogenesis and blood-retina barrier (BRB) formation during development and BRB maintenance in adult mice. Early endothelial-specific loss of TSPAN12 causes lack of intraretinal capillaries and increased VE-cadherin expression (premature vascular quiescence). Late loss of TSPAN12 strongly impairs BRB maintenance without affecting vascular morphogenesis, associated with immunoglobulin extravasation, complement deposition, cystoid edema, and impaired ERG b-wave.\",\n      \"method\": \"Conditional knockout (Cdh5-CreERT2 tamoxifen-inducible), confocal microscopy, RNA-Seq, histopathology, electroretinogram\",\n      \"journal\": \"Arteriosclerosis, thrombosis, and vascular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — cell-type-specific conditional KO with multiple orthogonal phenotypic readouts establishing endothelial-specific function\",\n      \"pmids\": [\"30354230\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"RNF152 (an E3 ubiquitin ligase) interacts with TSPAN12 and targets it for ubiquitination and proteasomal degradation, thereby inhibiting TSPAN12-dependent CXCL6 expression and HCC progression. FoxO1 transcriptionally regulates RNF152 expression.\",\n      \"method\": \"Co-IP, in vivo ubiquitination assay, RNAi, luciferase/ChIP assay for FoxO1-RNF152 axis, xenograft model\",\n      \"journal\": \"Cancer cell international\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP plus in vivo ubiquitination assay establishing TSPAN12 as RNF152 substrate, single lab\",\n      \"pmids\": [\"33602225\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"IL-13 reduces TSPAN12 expression in esophageal endothelial cells. TSPAN12 gene silencing in endothelial cells increases endothelial cell permeability and dysregulates extracellular matrix pathway genes, promoting endothelial cell-fibroblast crosstalk relevant to esophageal remodeling in eosinophilic esophagitis.\",\n      \"method\": \"siRNA knockdown, in vitro permeability assay, RNA sequencing, cytokine stimulation, anti-IL-13 therapy reversal\",\n      \"journal\": \"Gastroenterology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — siRNA KD with defined permeability phenotype and transcriptomic pathway analysis, large cohort correlation\",\n      \"pmids\": [\"34687736\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"TSPAN12 is a negative regulator of aldosterone production: TSPAN12 gene silencing in human adrenocortical (HAC15) cells increased aldosterone secretion under basal and angiotensin II-stimulated conditions. Angiotensin II increases TSPAN12 expression in adrenocortical cells via calcium-dependent signaling (blocked by nifedipine and W-7).\",\n      \"method\": \"siRNA knockdown, hormone secretion assay, pharmacological inhibitors (nifedipine, W-7), in vivo pig adrenal dietary sodium model, immunostaining\",\n      \"journal\": \"Hypertension (Dallas, Tex. : 1979)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — siRNA KD with defined aldosterone secretion phenotype plus in vivo model, single lab\",\n      \"pmids\": [\"36458545\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Missense variants in TSPAN12 associated with FEVR compromise interactions between TSPAN12 and its binding partners (FZD4, NDP) in the Norrin/β-catenin pathway, as shown by co-immunoprecipitation. Some variants also cause abnormal subcellular trafficking of TSPAN12. Overexpression of wild-type TSPAN12 enhances Norrin/β-catenin signaling by strengthening the binding affinity of mutant Norrin with FZD4 or LRP5.\",\n      \"method\": \"Co-IP, dual-luciferase reporter assay, western blot, immunofluorescence, subcellular fractionation\",\n      \"journal\": \"Clinical genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods in single lab establishing interaction and trafficking defects for disease variants\",\n      \"pmids\": [\"36453149\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Cryo-EM structure of TSPAN12 in complex with FZD4 at 3.4 Å resolution reveals: (1) FZD4 and TSPAN12 form a direct complex in the absence of Norrin, with contact between the lower hinge of FZD4 and the extracellular loops of TSPAN12; (2) the transmembrane domain of TSPAN12 forms a tightly packed four-helix bundle and interacts with TM2 of FZD4 to promote TSPAN12 trafficking to the cell surface; (3) the C-D helices of TSPAN12 that mediate Norrin binding remain exposed in the FZD4 complex, enabling higher-affinity Norrin binding; (4) TSPAN12 and FZD4 remain associated after Norrin recognition, indicating TSPAN12 is a core component of the FZD4-Norrin-LRP5/6 signaling complex. The complex enables FZD4 to respond with a more gradual response to a wider range of Norrin concentrations.\",\n      \"method\": \"Cryo-EM structure determination, cell-based signaling assays\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — cryo-EM structure with functional validation by cell-based assays, directly resolving molecular mechanism of TSPAN12-FZD4 interaction\",\n      \"pmids\": [\"bio_10.1101_2025.09.25.678640\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"lnc-TSPAN12 (a long noncoding RNA overlapping TSPAN12 locus) acts as a scaffold that directly interacts with both EIF3I and SENP1, enhancing the SENP1-EIF3I interaction. This inhibits SUMOylation of EIF3I, preventing its ubiquitin-mediated degradation, and ultimately activates the Wnt/β-catenin signaling pathway to stimulate EMT and metastasis in hepatocellular carcinoma. METTL3-mediated m6A modification stabilizes lnc-TSPAN12.\",\n      \"method\": \"RNA pulldown, Co-IP, RIP (RNA immunoprecipitation), m6A modification assay, in vitro/in vivo migration assays\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — mechanistic scaffold function established by RNA pulldown and Co-IP; note this is lnc-TSPAN12, not the TSPAN12 protein itself\",\n      \"pmids\": [\"38374407\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"TSPAN12 is a tetraspanin co-receptor that directly binds FZD4 (via its extracellular loops contacting the FZD4 lower hinge, as resolved by cryo-EM) and the ligand Norrin (NDP) to form a core signaling complex that selectively amplifies Norrin/β-catenin—but not Wnt/β-catenin—signaling; it promotes FZD4-LRP5 association and receptor multimerization, is required in endothelial cells for blood-retina barrier formation and maintenance, and is subject to proteasomal degradation mediated by the E3 ubiquitin ligase RNF152.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"TSPAN12 is a tetraspanin family co-receptor that selectively amplifies Norrin/β-catenin signaling by assembling a multiprotein receptor complex with FZD4, LRP5, and the ligand Norrin (NDP). TSPAN12 directly contacts FZD4 through its extracellular loops engaging the FZD4 lower hinge and through transmembrane interactions with FZD4 TM2, forming a stable binary complex that pre-organizes the receptor for higher-affinity Norrin binding and promotes FZD4-LRP5 association and receptor multimerization [PMID:19837033, PMID:28658627, PMID:23955570]. In endothelial cells, TSPAN12 is required for retinal vascular morphogenesis and blood–retina barrier formation and maintenance; conditional endothelial-specific knockout causes failure of intraretinal capillary development and, in adults, barrier breakdown with cystoid edema and complement deposition [PMID:30354230]. Loss-of-function mutations in TSPAN12 cause familial exudative vitreoretinopathy (FEVR) by disrupting incorporation into the Norrin receptor complex and, in some cases, impairing subcellular trafficking [PMID:28658627, PMID:36453149].\",\n  \"teleology\": [\n    {\n      \"year\": 2009,\n      \"claim\": \"The foundational question—whether a tetraspanin participates in Norrin/β-catenin signaling—was resolved by showing that Tspan12-null mice phenocopy Fzd4/Lrp5/Norrin mutants and that TSPAN12 selectively amplifies Norrin but not Wnt3A signaling via FZD4 multimerization.\",\n      \"evidence\": \"Mouse knockout, Co-IP, siRNA, luciferase reporter in retinal endothelial cells\",\n      \"pmids\": [\"19837033\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Direct physical contact interface between TSPAN12 and FZD4 was unresolved\",\n        \"Whether TSPAN12 contacts Norrin directly was unknown\",\n        \"Endothelial cell–autonomous requirement versus broader tissue role was not separated\"\n      ]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"TSPAN12 was shown to stabilize the FZD4–LRP5 co-receptor association, explaining how it supports downstream β-catenin signaling beyond simple FZD4 multimerization.\",\n      \"evidence\": \"shRNA knockdown and Co-IP in MDA-MB-231 breast cancer cells, western blot for β-catenin stability\",\n      \"pmids\": [\"23955570\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Demonstrated in a cancer cell line; relevance to endothelial physiology not directly tested\",\n        \"Mechanism by which TSPAN12 stabilizes FZD4–LRP5 was unclear\"\n      ]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"A non-vascular role for TSPAN12 was identified: in p53-depleted fibroblasts, TSPAN12 transduces β-catenin signaling upon cancer cell contact, driving CXCL6 secretion and tumor invasion.\",\n      \"evidence\": \"siRNA, coculture assay, in vivo tumor model, β-catenin reporter in cancer-associated fibroblasts\",\n      \"pmids\": [\"25512506\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether TSPAN12 in fibroblasts also acts through FZD4/Norrin axis or an alternative β-catenin entry point was not determined\",\n        \"Single-lab observation in engineered fibroblast system\"\n      ]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Two studies established that TSPAN12 extracellular loops interact with both FZD4 and Norrin (NDP) to confer ligand selectivity, and that FEVR-linked TSPAN12 mutations disrupt this complex; separately, an anti-TSPAN12 antibody blocking the TSPAN12–FZD4 interaction reduced pathological retinal angiogenesis in vivo.\",\n      \"evidence\": \"Co-IP, pulldown, Xenopus rescue of FZD4 M105V mutant; phage-display antibody in oxygen-induced retinopathy models\",\n      \"pmids\": [\"28658627\", \"28356444\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Atomic-level details of the TSPAN12–FZD4 and TSPAN12–Norrin interfaces remained unknown\",\n        \"Therapeutic antibody efficacy not tested in genetic FEVR models\"\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Conditional endothelial-specific Tspan12 knockout definitively established that TSPAN12 functions cell-autonomously in endothelial cells for both developmental retinal vascular morphogenesis and adult blood–retina barrier maintenance.\",\n      \"evidence\": \"Cdh5-CreERT2 tamoxifen-inducible conditional knockout, confocal imaging, RNA-Seq, electroretinogram, histopathology\",\n      \"pmids\": [\"30354230\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Downstream transcriptional targets mediating barrier maintenance versus morphogenesis were not fully resolved\",\n        \"Whether TSPAN12 functions in other vascular beds in vivo was not tested\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"TSPAN12 protein turnover was shown to be regulated by the E3 ubiquitin ligase RNF152 through ubiquitination and proteasomal degradation, connecting FoxO1 transcriptional control of RNF152 to TSPAN12 abundance and downstream CXCL6 expression in hepatocellular carcinoma.\",\n      \"evidence\": \"Co-IP, in vivo ubiquitination assay, RNAi, ChIP, xenograft model in HCC cells\",\n      \"pmids\": [\"33602225\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Ubiquitination sites on TSPAN12 were not mapped\",\n        \"Whether RNF152-mediated degradation regulates TSPAN12 in endothelial cells or other physiological contexts is unknown\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"IL-13 was identified as an upstream suppressor of TSPAN12 in esophageal endothelial cells, and TSPAN12 silencing increased endothelial permeability and dysregulated extracellular matrix genes, extending TSPAN12's barrier function beyond the retina.\",\n      \"evidence\": \"siRNA knockdown, in vitro permeability assay, RNA-Seq, cytokine stimulation, anti-IL-13 therapy reversal in eosinophilic esophagitis cohort\",\n      \"pmids\": [\"34687736\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether endothelial permeability increase depends on the FZD4/Norrin pathway or a distinct mechanism was not tested\",\n        \"Single-lab in vitro observation\"\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Systematic analysis of FEVR-associated TSPAN12 missense variants demonstrated that disease mutations compromise interactions with FZD4 and NDP and, in some cases, impair TSPAN12 subcellular trafficking, while wild-type TSPAN12 overexpression can rescue signaling defects of certain Norrin mutants.\",\n      \"evidence\": \"Co-IP, dual-luciferase reporter, immunofluorescence, subcellular fractionation for multiple TSPAN12 variants\",\n      \"pmids\": [\"36453149\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Structural basis for trafficking defects of specific variants was not resolved\",\n        \"In vivo functional rescue of FEVR phenotype not attempted\"\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"TSPAN12 was identified as a negative regulator of aldosterone production in adrenocortical cells, revealing a non-canonical, non-vascular physiological role.\",\n      \"evidence\": \"siRNA knockdown in HAC15 adrenocortical cells, hormone secretion assay, pharmacological inhibitors, pig adrenal dietary sodium model\",\n      \"pmids\": [\"36458545\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether aldosterone regulation involves FZD4/β-catenin signaling or a distinct mechanism was not determined\",\n        \"Single-lab observation; not replicated independently\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"The cryo-EM structure of TSPAN12–FZD4 at 3.4 Å resolution resolved the molecular interface: TSPAN12 extracellular loops contact the FZD4 lower hinge, TM helices engage FZD4 TM2, and the C–D helices that bind Norrin remain exposed, explaining how TSPAN12 pre-organizes FZD4 for graded Norrin sensing.\",\n      \"evidence\": \"Cryo-EM structure determination, cell-based signaling assays (preprint)\",\n      \"pmids\": [\"bio_10.1101_2025.09.25.678640\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Preprint; awaits peer review\",\n        \"Structure of the full quaternary complex with Norrin and LRP5/6 not yet resolved\",\n        \"Structural basis for TSPAN12-promoted FZD4 multimerization not captured in the binary complex\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the full quaternary structure of the TSPAN12–FZD4–Norrin–LRP5/6 signaling complex, the structural basis for TSPAN12-promoted receptor multimerization, and whether TSPAN12's non-vascular roles (aldosterone regulation, esophageal barrier) operate through FZD4/β-catenin or independent pathways.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No structure of the full signaling holocomplex\",\n        \"Mechanism linking TSPAN12 to aldosterone regulation is undefined\",\n        \"In vivo therapeutic validation of TSPAN12-targeting strategies in FEVR patients is lacking\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 1, 2, 10]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 1, 8]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 1, 10]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 1, 2, 3, 9]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [0, 5]}\n    ],\n    \"complexes\": [\n      \"Norrin–FZD4–LRP5–TSPAN12 receptor complex\"\n    ],\n    \"partners\": [\n      \"FZD4\",\n      \"NDP\",\n      \"LRP5\",\n      \"RNF152\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}