{"gene":"LIN7C","run_date":"2026-06-10T02:59:49","timeline":{"discoveries":[{"year":2006,"finding":"MPP4 (Mpp4) is essential for correct localization of Veli3 (LIN7C) at the presynaptic photoreceptor membrane in the retinal outer plexiform layer; in Mpp4 knockout mice, Veli3 is mislocalized though total protein levels remain unchanged, indicating Mpp4 recruits LIN7C to the synaptic membrane.","method":"Mpp4 knockout mouse analysis, immunofluorescence, western blot","journal":"Human molecular genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic knockout with defined localization phenotype and protein level quantification, single lab","pmids":["16520334"],"is_preprint":false},{"year":2005,"finding":"MPP4 directly interacts with Veli3 (LIN7C) via L27 domain heterodimerization in vitro, and MPP4 and MPP5 associate with Veli3 at distinct intercellular junctions in the mouse retina (OPL synaptic terminals and OLM, respectively).","method":"In vitro L27 heterodimerization assay, immunofluorescence colocalization, antibody generation","journal":"The Journal of comparative neurology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct in vitro interaction assay plus colocalization, single lab with two orthogonal methods","pmids":["15558731"],"is_preprint":false},{"year":2007,"finding":"MALS-3 (LIN7C) is the only known core component shared between the Crumbs tight junction complex and the Discs Large basolateral polarity complex in mammalian kidney; it mediates stable assembly of both complexes, and its knockout causes disruption of both complexes leading to hypomorphic, cystic, and fibrotic kidneys.","method":"MALS-3 knockout mice, proteomic analysis (mass spectrometry), immunofluorescence, histology","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal proteomics, KO phenotype with defined molecular pathway disruption, multiple orthogonal methods in a single rigorous study","pmids":["17923534"],"is_preprint":false},{"year":2007,"finding":"Overexpression of Lin-7C in an OSCC cell clone results in a non-invasive phenotype with elevated β-catenin expression, and suppresses experimental metastasis in immunodeficient mice, placing Lin-7C in the β-catenin pathway as a suppressor of invasion.","method":"Inducible overexpression in cancer cell lines, in vivo metastasis assay in immunodeficient mice, western blot","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — gain-of-function with in vivo metastasis readout and molecular marker (β-catenin), single lab","pmids":["17942893"],"is_preprint":false},{"year":2008,"finding":"MALS-3 (LIN7C) localizes to the apical domain of neural progenitor cells (NPCs) in the developing cerebral cortex and is required for apical localization of PATJ and PALS1; mice lacking all three MALS genes show failure of apical PATJ/PALS1 localization, slower NPC cell cycle progression, and premature neuronal differentiation.","method":"MALS triple knockout mice, immunofluorescence, cell cycle analysis, BrdU labeling","journal":"Development (Cambridge, England)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic KO with defined polarity protein mislocalization and cell cycle phenotype, single lab with multiple readouts","pmids":["18403412"],"is_preprint":false},{"year":2009,"finding":"CASK is required for basolateral localization of LIN7C in intestinal epithelial cells; intestine-specific CASK knockout mice show mislocalization of LIN7C from basolateral membranes, while LIN7C localization is CASK-independent in the stomach. CASK and LIN7C localization are mutually independent (LIN7C localizes normally in dlg1-/- intestine).","method":"Intestine-specific CASK knockout mice, heterozygous mosaic females, immunofluorescence","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — tissue-specific genetic KO with defined localization phenotype, single lab, two mouse models tested","pmids":["19726564"],"is_preprint":false},{"year":2013,"finding":"In zebrafish retinal epithelium, apical localization of Lin7c depends on Crumbs complex members Oko meduzy (Crb2b) and Nagie oko (MPP5/Pals1); fluorescently tagged Lin7c transitions from cytosolic to apical as polarity matures, establishing Lin7c as a dynamic Crb complex member.","method":"Live fluorescence imaging of RFP-Lin7c in zebrafish, genetic epistasis with crb/mpp5 mutants","journal":"Biology open","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — live imaging with genetic epistasis in zebrafish, single lab","pmids":["24143272"],"is_preprint":false},{"year":2014,"finding":"Mirtazapine, an antagonist of HTR2C (an upstream molecule of Lin-7C), upregulates the Lin-7C/β-catenin pathway in metastatic squamous cell carcinoma and melanoma cells, suppressing their metastatic potential in vivo, placing HTR2C as an upstream negative regulator of LIN7C.","method":"Drug treatment in vitro and in vivo mouse metastasis assay, western blot, Ingenuity Pathway Analysis","journal":"Scientific reports","confidence":"Low","confidence_rationale":"Tier 3 / Weak — pharmacological intervention with pathway inference, indirect evidence for upstream regulation, single lab","pmids":["24961284"],"is_preprint":false},{"year":2021,"finding":"LIN7C is required for transport of BLT2 (a GPCR) from the Golgi apparatus to the lateral plasma membrane; knockdown of LIN7C causes accumulation of BLT2 in the Golgi and diminishes epithelial barrier function.","method":"siRNA knockdown of LIN7C, chimeric receptor/deletion mutant analysis, proximity biotinylation proteomics (APEX2), immunofluorescence","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KD with defined Golgi accumulation phenotype, proximity proteomics identifying LIN7C as proximal interactor, single lab with multiple orthogonal methods","pmids":["33481310"],"is_preprint":false},{"year":2022,"finding":"LIN7C is a direct target of miR-124 in retinal pigment epithelial cells (confirmed by luciferase reporter assay); overexpression of LIN7C suppresses EMT and cell migration (reduces fibronectin and α-SMA, increases E-cadherin and ZO-1), and miR-124 abrogates this inhibitory effect.","method":"Luciferase reporter assay, LIN7C overexpression, transwell migration assay, western blot","journal":"Experimental and therapeutic medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct luciferase validation of miR-124 targeting, gain-of-function with defined EMT markers, single lab","pmids":["35761801"],"is_preprint":false}],"current_model":"LIN7C (MALS-3/VELI3) is a PDZ domain scaffold protein that serves as the only shared core component of both the Crumbs apical tight junction complex and the Discs Large basolateral polarity complex; it is recruited to synaptic and junctional membranes via L27-domain heterodimerization with MAGUK proteins (MPP4, MPP5, CASK), mediates stable assembly and apical/basolateral localization of polarity complexes (PATJ, PALS1, DLG1) in epithelia and neural progenitors, facilitates Golgi-to-lateral-membrane trafficking of GPCRs such as BLT2, and suppresses epithelial-mesenchymal transition and metastasis partly through the β-catenin pathway."},"narrative":{"mechanistic_narrative":"LIN7C (MALS-3/Veli3) is a PDZ/L27-domain scaffold protein that organizes membrane polarity complexes at epithelial junctions and neuronal synapses [PMID:17923534]. It is the only shared core component of both the Crumbs apical tight junction complex and the Discs Large basolateral polarity complex in mammalian kidney, where it mediates stable assembly of both; loss of LIN7C disrupts both complexes and produces hypomorphic, cystic, fibrotic kidneys [PMID:17923534]. LIN7C does not localize autonomously but is recruited to specific membrane domains by L27-domain heterodimerization with MAGUK partners: MPP4 positions it at presynaptic photoreceptor terminals [PMID:16520334, PMID:15558731], the Crumbs members Crb2b and MPP5/Pals1 drive its apical localization in retinal epithelium [PMID:24143272], and CASK targets it to basolateral membranes in intestinal epithelium [PMID:19726564]. Through this scaffolding role it controls apical localization of PATJ and PALS1 in cortical neural progenitors, where its loss slows cell cycle progression and causes premature neuronal differentiation [PMID:18403412]. LIN7C also facilitates Golgi-to-lateral-membrane trafficking of the GPCR BLT2, with its depletion trapping BLT2 in the Golgi and impairing epithelial barrier function [PMID:33481310]. In cancer and retinal pigment epithelial cells LIN7C acts through the β-catenin pathway to suppress epithelial-mesenchymal transition, invasion, and metastasis [PMID:17942893, PMID:35761801].","teleology":[{"year":2005,"claim":"Established that LIN7C physically engages MAGUK scaffolds via L27-domain heterodimerization, defining its mode of membrane recruitment.","evidence":"In vitro L27 heterodimerization assay with MPP4 plus immunofluorescence colocalization in mouse retina","pmids":["15558731"],"confidence":"Medium","gaps":["Did not establish whether the interaction recruits LIN7C in vivo","Distinct MPP4 vs MPP5 junctional contexts not mechanistically resolved"]},{"year":2006,"claim":"Demonstrated that MPP4 recruits LIN7C to the synaptic membrane in vivo, showing LIN7C localization is partner-dependent rather than autonomous.","evidence":"Mpp4 knockout mouse with immunofluorescence and western blot showing mislocalization without protein loss","pmids":["16520334"],"confidence":"Medium","gaps":["Functional consequence of LIN7C mislocalization for synaptic transmission not addressed","Single tissue (photoreceptor OPL)"]},{"year":2007,"claim":"Identified LIN7C as the shared scaffold linking the Crumbs and Discs Large polarity complexes and required for their assembly, defining its core organizing role in epithelial polarity.","evidence":"MALS-3 knockout mice with reciprocal mass spectrometry proteomics, immunofluorescence, and renal histology","pmids":["17923534"],"confidence":"High","gaps":["Structural basis for simultaneous engagement of both complexes not resolved","Whether assembly defect is direct or secondary to mislocalization unclear"]},{"year":2007,"claim":"Connected LIN7C to suppression of invasion and metastasis through the β-catenin pathway, extending its role beyond polarity scaffolding.","evidence":"Inducible LIN7C overexpression in OSCC cells with in vivo metastasis assay and β-catenin western blot","pmids":["17942893"],"confidence":"Medium","gaps":["Mechanistic link between scaffold function and β-catenin regulation undefined","Gain-of-function only; loss-of-function not tested"]},{"year":2008,"claim":"Showed LIN7C is required for apical localization of PATJ/PALS1 in neural progenitors and links polarity to cell cycle and differentiation timing.","evidence":"MALS triple knockout mice with immunofluorescence, BrdU labeling, and cell cycle analysis in developing cortex","pmids":["18403412"],"confidence":"Medium","gaps":["Redundancy among MALS paralogs requires triple knockout, obscuring LIN7C-specific contribution","Direct vs indirect coupling of polarity to cell cycle not resolved"]},{"year":2009,"claim":"Defined tissue-specific and partner-specific recruitment: CASK targets LIN7C basolaterally in intestine but not stomach, and LIN7C/CASK localization is mutually independent of DLG1.","evidence":"Intestine-specific CASK knockout and mosaic mouse models with immunofluorescence","pmids":["19726564"],"confidence":"Medium","gaps":["Identity of CASK-independent recruiting factor in stomach unknown","Functional consequence of basolateral mislocalization not characterized"]},{"year":2013,"claim":"Demonstrated LIN7C is a dynamic Crumbs complex member whose apical recruitment depends on Crb2b and MPP5 as polarity matures.","evidence":"Live RFP-Lin7c imaging with crb/mpp5 genetic epistasis in zebrafish retinal epithelium","pmids":["24143272"],"confidence":"Medium","gaps":["Trigger for cytosolic-to-apical transition not identified","Whether dynamics are conserved in mammalian epithelia not shown"]},{"year":2021,"claim":"Revealed a trafficking function: LIN7C mediates Golgi-to-lateral-membrane transport of the GPCR BLT2 and supports epithelial barrier integrity.","evidence":"LIN7C siRNA knockdown with chimeric/deletion receptor analysis, APEX2 proximity proteomics, and immunofluorescence","pmids":["33481310"],"confidence":"Medium","gaps":["Whether LIN7C traffics other cargoes beyond BLT2 unknown","Direct vs scaffold-mediated role in transport not distinguished"]},{"year":2022,"claim":"Placed LIN7C under miR-124 control and confirmed its suppression of EMT/migration through epithelial marker regulation.","evidence":"Luciferase reporter validation of miR-124 targeting, LIN7C overexpression, transwell migration, EMT marker western blot in retinal pigment epithelial cells","pmids":["35761801"],"confidence":"Medium","gaps":["Mechanistic link between LIN7C scaffolding and EMT marker changes not defined","Single cell context"]},{"year":2014,"claim":"Proposed HTR2C as an upstream negative regulator of the LIN7C/β-catenin axis, pharmacologically targetable to suppress metastasis.","evidence":"Mirtazapine treatment in vitro and in vivo metastasis assay with western blot and pathway analysis","pmids":["24961284"],"confidence":"Low","gaps":["Pathway inference is indirect; direct HTR2C–LIN7C regulatory link not demonstrated","Drug effects may act through targets other than LIN7C","Not independently confirmed"]},{"year":null,"claim":"How LIN7C structurally coordinates simultaneous engagement of distinct MAGUK partners and polarity complexes, and how its scaffold function mechanistically connects to β-catenin/EMT control, remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of multi-partner assembly","Direct molecular link between scaffolding and β-catenin pathway undefined","Cargo repertoire for trafficking function unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[1,2]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,5,6]},{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[8]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[6]}],"pathway":[{"term_id":"R-HSA-1500931","term_label":"Cell-Cell communication","supporting_discovery_ids":[2]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[4]},{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[8]}],"complexes":["Crumbs apical polarity complex","Discs Large basolateral polarity complex"],"partners":["MPP4","MPP5","CASK","PATJ","PALS1","CRB2"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9NUP9","full_name":"Protein lin-7 homolog C","aliases":["Mammalian lin-seven protein 3","MALS-3","Vertebrate lin-7 homolog 3","Veli-3"],"length_aa":197,"mass_kda":21.8,"function":"Plays a role in establishing and maintaining the asymmetric distribution of channels and receptors at the plasma membrane of polarized cells. Forms membrane-associated multiprotein complexes that may regulate delivery and recycling of proteins to the correct membrane domains. The tripartite complex composed of LIN7 (LIN7A, LIN7B or LIN7C), CASK and APBA1 associates with the motor protein KIF17 to transport vesicles containing N-methyl-D-aspartate (NMDA) receptor subunit NR2B along microtubules (By similarity). This complex may have the potential to couple synaptic vesicle exocytosis to cell adhesion in brain. Ensures the proper localization of GRIN2B (subunit 2B of the NMDA receptor) to neuronal postsynaptic density and may function in localizing synaptic vesicles at synapses where it is recruited by beta-catenin and cadherin. Required to localize Kir2 channels, GABA transporter (SLC6A12) and EGFR/ERBB1, ERBB2, ERBB3 and ERBB4 to the basolateral membrane of epithelial cells","subcellular_location":"Cell membrane; Basolateral cell membrane; Cell junction; Postsynaptic density membrane; Cell junction, tight junction","url":"https://www.uniprot.org/uniprotkb/Q9NUP9/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/LIN7C","classification":"Not Classified","n_dependent_lines":125,"n_total_lines":1208,"dependency_fraction":0.10347682119205298},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"SRP9","stoichiometry":4.0},{"gene":"CALM3","stoichiometry":0.2},{"gene":"CAPZB","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/LIN7C","total_profiled":1310},"omim":[{"mim_id":"613338","title":"MEMBRANE-ASSOCIATED RING-CH FINGER PROTEIN 11; MARCHF11","url":"https://www.omim.org/entry/613338"},{"mim_id":"612332","title":"LIN7 HOMOLOG C, CRUMBS CELL POLARITY COMPLEX COMPONENT; LIN7C","url":"https://www.omim.org/entry/612332"},{"mim_id":"612331","title":"LIN7 HOMOLOG B, CRUMBS CELL POLARITY COMPLEX COMPONENT; LIN7B","url":"https://www.omim.org/entry/612331"},{"mim_id":"610973","title":"MEMBRANE PROTEIN, PALMITOYLATED 7; MPP7","url":"https://www.omim.org/entry/610973"},{"mim_id":"606575","title":"MEMBRANE PROTEIN, PALMITOYLATED 4; MPP4","url":"https://www.omim.org/entry/606575"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/LIN7C"},"hgnc":{"alias_symbol":["MALS-3","LIN-7C","LIN-7-C","VELI3","FLJ11215"],"prev_symbol":[]},"alphafold":{"accession":"Q9NUP9","domains":[{"cath_id":"1.20.1270.460","chopping":"9-75","consensus_level":"high","plddt":85.7445,"start":9,"end":75},{"cath_id":"2.30.42.10","chopping":"91-191","consensus_level":"high","plddt":94.2058,"start":91,"end":191}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NUP9","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NUP9-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NUP9-F1-predicted_aligned_error_v6.png","plddt_mean":87.38},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=LIN7C","jax_strain_url":"https://www.jax.org/strain/search?query=LIN7C"},"sequence":{"accession":"Q9NUP9","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9NUP9.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9NUP9/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NUP9"}},"corpus_meta":[{"pmid":"16520334","id":"PMC_16520334","title":"Mpp4 recruits Psd95 and Veli3 towards the photoreceptor synapse.","date":"2006","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/16520334","citation_count":48,"is_preprint":false},{"pmid":"17923534","id":"PMC_17923534","title":"Renal defects associated with improper polarization of the CRB and DLG polarity complexes in MALS-3 knockout mice.","date":"2007","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/17923534","citation_count":40,"is_preprint":false},{"pmid":"15558731","id":"PMC_15558731","title":"Membrane-associated guanylate kinase proteins MPP4 and MPP5 associate with Veli3 at distinct intercellular junctions of the neurosensory retina.","date":"2005","source":"The Journal of comparative neurology","url":"https://pubmed.ncbi.nlm.nih.gov/15558731","citation_count":38,"is_preprint":false},{"pmid":"17942893","id":"PMC_17942893","title":"Lin-7C/VELI3/MALS-3: an essential component in metastasis of human squamous cell carcinoma.","date":"2007","source":"Cancer research","url":"https://pubmed.ncbi.nlm.nih.gov/17942893","citation_count":24,"is_preprint":false},{"pmid":"18403412","id":"PMC_18403412","title":"MALS-3 regulates polarity and early neurogenesis in the developing cerebral cortex.","date":"2008","source":"Development (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/18403412","citation_count":22,"is_preprint":false},{"pmid":"19726564","id":"PMC_19726564","title":"CASK deletion in intestinal epithelia causes mislocalization of LIN7C and the DLG1/Scrib polarity complex without affecting cell polarity.","date":"2009","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/19726564","citation_count":20,"is_preprint":false},{"pmid":"24961284","id":"PMC_24961284","title":"Suppression of metastasis by mirtazapine via restoration of the Lin-7C/β-catenin pathway in human cancer cells.","date":"2014","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/24961284","citation_count":15,"is_preprint":false},{"pmid":"33481310","id":"PMC_33481310","title":"The c-terminal region of BLT2 restricts its localization to the lateral membrane in a LIN7C-dependent manner.","date":"2021","source":"FASEB journal : official publication of the Federation of American Societies for Experimental Biology","url":"https://pubmed.ncbi.nlm.nih.gov/33481310","citation_count":7,"is_preprint":false},{"pmid":"35761801","id":"PMC_35761801","title":"miRNA-124 regulates palmitic acid-induced epithelial-mesenchymal transition and cell migration in human retinal pigment epithelial cells by targeting LIN7C.","date":"2022","source":"Experimental and therapeutic medicine","url":"https://pubmed.ncbi.nlm.nih.gov/35761801","citation_count":3,"is_preprint":false},{"pmid":"24143272","id":"PMC_24143272","title":"Fluorescently tagged Lin7c is a dynamic marker for polarity maturation in the zebrafish retinal epithelium.","date":"2013","source":"Biology open","url":"https://pubmed.ncbi.nlm.nih.gov/24143272","citation_count":2,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2024.09.30.615192","title":"The solute carrier superfamily interactome","date":"2024-10-01","source":"bioRxiv","url":"https://doi.org/10.1101/2024.09.30.615192","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":7381,"output_tokens":2404,"usd":0.029101,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9509,"output_tokens":3330,"usd":0.065397,"stage2_stop_reason":"end_turn"},"total_usd":0.094498,"stage1_batch_id":"msgbatch_01BbTCMyrRPyhtEq6b1MdwCN","stage2_batch_id":"msgbatch_011dEed5bbxYvTAaQWKJevxu","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2006,\n      \"finding\": \"MPP4 (Mpp4) is essential for correct localization of Veli3 (LIN7C) at the presynaptic photoreceptor membrane in the retinal outer plexiform layer; in Mpp4 knockout mice, Veli3 is mislocalized though total protein levels remain unchanged, indicating Mpp4 recruits LIN7C to the synaptic membrane.\",\n      \"method\": \"Mpp4 knockout mouse analysis, immunofluorescence, western blot\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic knockout with defined localization phenotype and protein level quantification, single lab\",\n      \"pmids\": [\"16520334\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"MPP4 directly interacts with Veli3 (LIN7C) via L27 domain heterodimerization in vitro, and MPP4 and MPP5 associate with Veli3 at distinct intercellular junctions in the mouse retina (OPL synaptic terminals and OLM, respectively).\",\n      \"method\": \"In vitro L27 heterodimerization assay, immunofluorescence colocalization, antibody generation\",\n      \"journal\": \"The Journal of comparative neurology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct in vitro interaction assay plus colocalization, single lab with two orthogonal methods\",\n      \"pmids\": [\"15558731\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"MALS-3 (LIN7C) is the only known core component shared between the Crumbs tight junction complex and the Discs Large basolateral polarity complex in mammalian kidney; it mediates stable assembly of both complexes, and its knockout causes disruption of both complexes leading to hypomorphic, cystic, and fibrotic kidneys.\",\n      \"method\": \"MALS-3 knockout mice, proteomic analysis (mass spectrometry), immunofluorescence, histology\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal proteomics, KO phenotype with defined molecular pathway disruption, multiple orthogonal methods in a single rigorous study\",\n      \"pmids\": [\"17923534\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Overexpression of Lin-7C in an OSCC cell clone results in a non-invasive phenotype with elevated β-catenin expression, and suppresses experimental metastasis in immunodeficient mice, placing Lin-7C in the β-catenin pathway as a suppressor of invasion.\",\n      \"method\": \"Inducible overexpression in cancer cell lines, in vivo metastasis assay in immunodeficient mice, western blot\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — gain-of-function with in vivo metastasis readout and molecular marker (β-catenin), single lab\",\n      \"pmids\": [\"17942893\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"MALS-3 (LIN7C) localizes to the apical domain of neural progenitor cells (NPCs) in the developing cerebral cortex and is required for apical localization of PATJ and PALS1; mice lacking all three MALS genes show failure of apical PATJ/PALS1 localization, slower NPC cell cycle progression, and premature neuronal differentiation.\",\n      \"method\": \"MALS triple knockout mice, immunofluorescence, cell cycle analysis, BrdU labeling\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO with defined polarity protein mislocalization and cell cycle phenotype, single lab with multiple readouts\",\n      \"pmids\": [\"18403412\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"CASK is required for basolateral localization of LIN7C in intestinal epithelial cells; intestine-specific CASK knockout mice show mislocalization of LIN7C from basolateral membranes, while LIN7C localization is CASK-independent in the stomach. CASK and LIN7C localization are mutually independent (LIN7C localizes normally in dlg1-/- intestine).\",\n      \"method\": \"Intestine-specific CASK knockout mice, heterozygous mosaic females, immunofluorescence\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — tissue-specific genetic KO with defined localization phenotype, single lab, two mouse models tested\",\n      \"pmids\": [\"19726564\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"In zebrafish retinal epithelium, apical localization of Lin7c depends on Crumbs complex members Oko meduzy (Crb2b) and Nagie oko (MPP5/Pals1); fluorescently tagged Lin7c transitions from cytosolic to apical as polarity matures, establishing Lin7c as a dynamic Crb complex member.\",\n      \"method\": \"Live fluorescence imaging of RFP-Lin7c in zebrafish, genetic epistasis with crb/mpp5 mutants\",\n      \"journal\": \"Biology open\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — live imaging with genetic epistasis in zebrafish, single lab\",\n      \"pmids\": [\"24143272\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Mirtazapine, an antagonist of HTR2C (an upstream molecule of Lin-7C), upregulates the Lin-7C/β-catenin pathway in metastatic squamous cell carcinoma and melanoma cells, suppressing their metastatic potential in vivo, placing HTR2C as an upstream negative regulator of LIN7C.\",\n      \"method\": \"Drug treatment in vitro and in vivo mouse metastasis assay, western blot, Ingenuity Pathway Analysis\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — pharmacological intervention with pathway inference, indirect evidence for upstream regulation, single lab\",\n      \"pmids\": [\"24961284\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"LIN7C is required for transport of BLT2 (a GPCR) from the Golgi apparatus to the lateral plasma membrane; knockdown of LIN7C causes accumulation of BLT2 in the Golgi and diminishes epithelial barrier function.\",\n      \"method\": \"siRNA knockdown of LIN7C, chimeric receptor/deletion mutant analysis, proximity biotinylation proteomics (APEX2), immunofluorescence\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KD with defined Golgi accumulation phenotype, proximity proteomics identifying LIN7C as proximal interactor, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"33481310\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"LIN7C is a direct target of miR-124 in retinal pigment epithelial cells (confirmed by luciferase reporter assay); overexpression of LIN7C suppresses EMT and cell migration (reduces fibronectin and α-SMA, increases E-cadherin and ZO-1), and miR-124 abrogates this inhibitory effect.\",\n      \"method\": \"Luciferase reporter assay, LIN7C overexpression, transwell migration assay, western blot\",\n      \"journal\": \"Experimental and therapeutic medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct luciferase validation of miR-124 targeting, gain-of-function with defined EMT markers, single lab\",\n      \"pmids\": [\"35761801\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"LIN7C (MALS-3/VELI3) is a PDZ domain scaffold protein that serves as the only shared core component of both the Crumbs apical tight junction complex and the Discs Large basolateral polarity complex; it is recruited to synaptic and junctional membranes via L27-domain heterodimerization with MAGUK proteins (MPP4, MPP5, CASK), mediates stable assembly and apical/basolateral localization of polarity complexes (PATJ, PALS1, DLG1) in epithelia and neural progenitors, facilitates Golgi-to-lateral-membrane trafficking of GPCRs such as BLT2, and suppresses epithelial-mesenchymal transition and metastasis partly through the β-catenin pathway.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"LIN7C (MALS-3/Veli3) is a PDZ/L27-domain scaffold protein that organizes membrane polarity complexes at epithelial junctions and neuronal synapses [#2]. It is the only shared core component of both the Crumbs apical tight junction complex and the Discs Large basolateral polarity complex in mammalian kidney, where it mediates stable assembly of both; loss of LIN7C disrupts both complexes and produces hypomorphic, cystic, fibrotic kidneys [#2]. LIN7C does not localize autonomously but is recruited to specific membrane domains by L27-domain heterodimerization with MAGUK partners: MPP4 positions it at presynaptic photoreceptor terminals [#0, #1], the Crumbs members Crb2b and MPP5/Pals1 drive its apical localization in retinal epithelium [#6], and CASK targets it to basolateral membranes in intestinal epithelium [#5]. Through this scaffolding role it controls apical localization of PATJ and PALS1 in cortical neural progenitors, where its loss slows cell cycle progression and causes premature neuronal differentiation [#4]. LIN7C also facilitates Golgi-to-lateral-membrane trafficking of the GPCR BLT2, with its depletion trapping BLT2 in the Golgi and impairing epithelial barrier function [#8]. In cancer and retinal pigment epithelial cells LIN7C acts through the \\u03b2-catenin pathway to suppress epithelial-mesenchymal transition, invasion, and metastasis [#3, #9].\",\n  \"teleology\": [\n    {\n      \"year\": 2005,\n      \"claim\": \"Established that LIN7C physically engages MAGUK scaffolds via L27-domain heterodimerization, defining its mode of membrane recruitment.\",\n      \"evidence\": \"In vitro L27 heterodimerization assay with MPP4 plus immunofluorescence colocalization in mouse retina\",\n      \"pmids\": [\"15558731\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Did not establish whether the interaction recruits LIN7C in vivo\", \"Distinct MPP4 vs MPP5 junctional contexts not mechanistically resolved\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Demonstrated that MPP4 recruits LIN7C to the synaptic membrane in vivo, showing LIN7C localization is partner-dependent rather than autonomous.\",\n      \"evidence\": \"Mpp4 knockout mouse with immunofluorescence and western blot showing mislocalization without protein loss\",\n      \"pmids\": [\"16520334\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of LIN7C mislocalization for synaptic transmission not addressed\", \"Single tissue (photoreceptor OPL)\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Identified LIN7C as the shared scaffold linking the Crumbs and Discs Large polarity complexes and required for their assembly, defining its core organizing role in epithelial polarity.\",\n      \"evidence\": \"MALS-3 knockout mice with reciprocal mass spectrometry proteomics, immunofluorescence, and renal histology\",\n      \"pmids\": [\"17923534\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis for simultaneous engagement of both complexes not resolved\", \"Whether assembly defect is direct or secondary to mislocalization unclear\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Connected LIN7C to suppression of invasion and metastasis through the \\u03b2-catenin pathway, extending its role beyond polarity scaffolding.\",\n      \"evidence\": \"Inducible LIN7C overexpression in OSCC cells with in vivo metastasis assay and \\u03b2-catenin western blot\",\n      \"pmids\": [\"17942893\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanistic link between scaffold function and \\u03b2-catenin regulation undefined\", \"Gain-of-function only; loss-of-function not tested\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Showed LIN7C is required for apical localization of PATJ/PALS1 in neural progenitors and links polarity to cell cycle and differentiation timing.\",\n      \"evidence\": \"MALS triple knockout mice with immunofluorescence, BrdU labeling, and cell cycle analysis in developing cortex\",\n      \"pmids\": [\"18403412\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Redundancy among MALS paralogs requires triple knockout, obscuring LIN7C-specific contribution\", \"Direct vs indirect coupling of polarity to cell cycle not resolved\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Defined tissue-specific and partner-specific recruitment: CASK targets LIN7C basolaterally in intestine but not stomach, and LIN7C/CASK localization is mutually independent of DLG1.\",\n      \"evidence\": \"Intestine-specific CASK knockout and mosaic mouse models with immunofluorescence\",\n      \"pmids\": [\"19726564\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Identity of CASK-independent recruiting factor in stomach unknown\", \"Functional consequence of basolateral mislocalization not characterized\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Demonstrated LIN7C is a dynamic Crumbs complex member whose apical recruitment depends on Crb2b and MPP5 as polarity matures.\",\n      \"evidence\": \"Live RFP-Lin7c imaging with crb/mpp5 genetic epistasis in zebrafish retinal epithelium\",\n      \"pmids\": [\"24143272\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Trigger for cytosolic-to-apical transition not identified\", \"Whether dynamics are conserved in mammalian epithelia not shown\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Revealed a trafficking function: LIN7C mediates Golgi-to-lateral-membrane transport of the GPCR BLT2 and supports epithelial barrier integrity.\",\n      \"evidence\": \"LIN7C siRNA knockdown with chimeric/deletion receptor analysis, APEX2 proximity proteomics, and immunofluorescence\",\n      \"pmids\": [\"33481310\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether LIN7C traffics other cargoes beyond BLT2 unknown\", \"Direct vs scaffold-mediated role in transport not distinguished\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Placed LIN7C under miR-124 control and confirmed its suppression of EMT/migration through epithelial marker regulation.\",\n      \"evidence\": \"Luciferase reporter validation of miR-124 targeting, LIN7C overexpression, transwell migration, EMT marker western blot in retinal pigment epithelial cells\",\n      \"pmids\": [\"35761801\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanistic link between LIN7C scaffolding and EMT marker changes not defined\", \"Single cell context\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Proposed HTR2C as an upstream negative regulator of the LIN7C/\\u03b2-catenin axis, pharmacologically targetable to suppress metastasis.\",\n      \"evidence\": \"Mirtazapine treatment in vitro and in vivo metastasis assay with western blot and pathway analysis\",\n      \"pmids\": [\"24961284\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Pathway inference is indirect; direct HTR2C\\u2013LIN7C regulatory link not demonstrated\", \"Drug effects may act through targets other than LIN7C\", \"Not independently confirmed\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How LIN7C structurally coordinates simultaneous engagement of distinct MAGUK partners and polarity complexes, and how its scaffold function mechanistically connects to \\u03b2-catenin/EMT control, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of multi-partner assembly\", \"Direct molecular link between scaffolding and \\u03b2-catenin pathway undefined\", \"Cargo repertoire for trafficking function unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [1, 2]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 5, 6]},\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [8]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [6]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1500931\", \"supporting_discovery_ids\": [2]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [4]},\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [8]}\n    ],\n    \"complexes\": [\"Crumbs apical polarity complex\", \"Discs Large basolateral polarity complex\"],\n    \"partners\": [\"MPP4\", \"MPP5\", \"CASK\", \"PATJ\", \"PALS1\", \"CRB2\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}