{"gene":"CLDND1","run_date":"2026-06-09T22:57:18","timeline":{"discoveries":[{"year":2015,"finding":"CLDND1 knockdown in basal-like breast cancer cell lines (MDA-MB-231, MDA-MB-468, BT-549) induces caspase-dependent apoptosis via the intrinsic pathway, evidenced by nuclear fragmentation, caspase-3 and PARP cleavage, and cytochrome C release from mitochondria. CLDND1 depletion also augments ERK1/2 phosphorylation, which partially protects against apoptosis; co-inhibition of MEK1/2 suppresses this ERK1/2 activation and markedly potentiates cell death.","method":"siRNA knockdown, caspase activity assays, western blot for caspase-3/PARP cleavage and cytochrome C release, MEK1/2 and JNK inhibitor epistasis","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (siRNA, apoptosis markers, pathway inhibitor epistasis) in a single lab","pmids":["26083392"],"is_preprint":false},{"year":2018,"finding":"miR-124 post-transcriptionally regulates CLDND1 by binding a conserved site in the 3'-UTR of Cldnd1 mRNA, as demonstrated by luciferase reporter assays with sequence-specific mutations. In human brain endothelial cells transfected with miR-124 mimic, CLDND1 mRNA levels decreased. In stroke-prone spontaneously hypertensive rat (SHRSP) brains, lower miR-124 levels correlated with higher Cldnd1 mRNA and protein levels.","method":"Luciferase reporter assay with 3'-UTR constructs, miR-124 mimic transfection, RT-qPCR, western blot, in vivo SHRSP model","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — sequence-specific luciferase reporter plus cell-based and in vivo corroboration, single lab","pmids":["29530526"],"is_preprint":false},{"year":2020,"finding":"The transcription factor myeloid zinc finger 1 (MZF1) directly activates CLDND1 transcription by binding to a silencer element within the first intron of CLDND1. MZF1 overexpression increased CLDND1 mRNA and protein levels, while siRNA-mediated MZF1 knockdown suppressed them and increased FITC-dextran permeability in human brain endothelial cells.","method":"Luciferase reporter assay, chromatin immunoprecipitation (ChIP), MZF1 expression vector overexpression, siRNA knockdown, RT-qPCR, western blot, FITC-dextran permeability assay","journal":"Clinical and experimental pharmacology & physiology","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — ChIP plus luciferase reporter with functional permeability readout, multiple orthogonal methods in single lab","pmids":["33037622"],"is_preprint":false},{"year":2022,"finding":"EGF-dependent activation of ELK1 (via EGFR-MAPK signaling) induces CLDND1 expression. ELK1 acts as a transcriptional activator of an enhancer region near the CLDND1 promoter; ELK1 overexpression increased CLDND1 mRNA and protein, EGF treatment enhanced ELK1 phosphorylation and CLDND1 expression, and the EGFR inhibitor gefitinib suppressed this induction.","method":"Luciferase reporter assay, chromatin immunoprecipitation (ChIP), ELK1 overexpression, EGF stimulation, gefitinib treatment, RT-qPCR, western blot","journal":"Biomedicines","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — ChIP plus luciferase reporter with pharmacological inhibition, multiple orthogonal methods in single lab","pmids":["35892692"],"is_preprint":false},{"year":2025,"finding":"MZF1 transcriptionally activates CLDND1 in NSCLC cells (A549). Upstream, miR-199a-3p targets FTO (an m6A demethylase), leading to enhanced m6A modification and decreased expression of MZF1 mRNA, thereby reducing CLDND1 expression and suppressing malignant cell behavior.","method":"Dual-luciferase reporter assay, methylated RNA immunoprecipitation (MeRIP), CLIP (PAR-CLIP), western blot, RT-qPCR, siRNA knockdown, overexpression","journal":"Molecular medicine reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (luciferase, MeRIP, CLIP) confirming the axis, single lab","pmids":["41201047"],"is_preprint":false},{"year":2026,"finding":"miR-124-3p directly targets CLDND1 3'-UTR (confirmed by dual-luciferase assay). In cerebral ischemia-reperfusion models, CLDND1 downregulation promotes endothelial-mesenchymal transition (EndMT); restoring CLDND1 (via miR-124-3p inhibition or circ_0017866 sponging of miR-124-3p) upregulates occludin, downregulates α-SMA and Snail, and improves endothelial function both in vitro and in vivo.","method":"Dual-luciferase reporter assay, OGD/R cell model, MCAO/R mouse model, siRNA/overexpression, RT-qPCR, western blot, immunofluorescence, CCK-8, Transwell, tube formation assays","journal":"Neurochemical research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — luciferase reporter plus multiple functional assays in vitro and in vivo, single lab","pmids":["42176037"],"is_preprint":false}],"current_model":"CLDND1 (claudin domain-containing 1) is a claudin-like tight junction protein whose expression is transcriptionally activated by MZF1 and ELK1 (downstream of EGFR-MAPK signaling), post-transcriptionally repressed by miR-124 via 3'-UTR binding, and functionally required for tight junction integrity and endothelial barrier function; in cancer cells, CLDND1 acts as a survival factor by suppressing the intrinsic apoptotic pathway, partly through augmenting ERK1/2 phosphorylation, such that its loss triggers caspase-3-dependent apoptosis."},"narrative":{"mechanistic_narrative":"CLDND1 (claudin domain-containing 1) is a claudin-like protein that maintains endothelial tight junction integrity and barrier function, with its expression controlled by a converging set of transcriptional and post-transcriptional inputs [PMID:33037622, PMID:42176037]. Transcriptionally, CLDND1 is directly activated by MZF1, which binds a silencer element in the first intron; MZF1 loss reduces CLDND1 and increases endothelial permeability [PMID:33037622]. EGFR-MAPK signaling provides a second activating input through EGF-dependent ELK1 phosphorylation, which drives CLDND1 expression via an enhancer near the promoter and is blocked by the EGFR inhibitor gefitinib [PMID:35892692]. Post-transcriptionally, miR-124/miR-124-3p represses CLDND1 by binding a conserved 3'-UTR site, and loss of CLDND1 in cerebral ischemia-reperfusion models drives endothelial-mesenchymal transition with downregulated occludin and upregulated α-SMA and Snail, while restoring CLDND1 rescues endothelial function [PMID:29530526, PMID:42176037]. In cancer cells, CLDND1 functions as a survival factor: its knockdown induces caspase-3-dependent intrinsic apoptosis with cytochrome C release, partly buffered by compensatory ERK1/2 activation whose pharmacological blockade potentiates cell death [PMID:26083392]. An upstream miR-199a-3p–FTO–m6A axis modulates MZF1 and thereby CLDND1 levels in NSCLC cells [PMID:41201047].","teleology":[{"year":2015,"claim":"Established that CLDND1 is not merely a structural junction protein but a survival factor in cancer cells, defining the apoptotic consequence of its loss and a compensatory ERK1/2 escape mechanism.","evidence":"siRNA knockdown with apoptosis markers (caspase-3/PARP cleavage, cytochrome C release) and MEK1/2 inhibitor epistasis in basal-like breast cancer lines","pmids":["26083392"],"confidence":"Medium","gaps":["Molecular mechanism linking CLDND1 loss to mitochondrial apoptosis not defined","How CLDND1 depletion augments ERK1/2 phosphorylation unknown","Single-lab observation in breast cancer lines only"]},{"year":2018,"claim":"Identified the first post-transcriptional regulator of CLDND1, showing miR-124 directly represses it via a 3'-UTR site, linking CLDND1 dosage to endothelial/vascular contexts.","evidence":"Luciferase reporter with sequence-specific 3'-UTR mutations, miR-124 mimic in brain endothelial cells, and in vivo SHRSP correlation","pmids":["29530526"],"confidence":"Medium","gaps":["Functional barrier consequence of the miR-124–CLDND1 axis not tested here","Correlative in vivo data do not prove causation in SHRSP"]},{"year":2020,"claim":"Defined the first direct transcriptional activator of CLDND1 and tied its regulation to a measurable barrier function readout.","evidence":"ChIP and luciferase reporter mapping MZF1 to an intronic silencer element, with MZF1 knockdown increasing FITC-dextran permeability in brain endothelial cells","pmids":["33037622"],"confidence":"High","gaps":["Whether MZF1 cooperates with other factors at the locus unknown","Mechanism by which CLDND1 maintains barrier tightness not addressed"]},{"year":2022,"claim":"Connected CLDND1 transcription to upstream growth-factor signaling, showing EGFR-MAPK acts through ELK1 to induce expression.","evidence":"ChIP and luciferase reporter for ELK1 at an enhancer, EGF stimulation, and gefitinib inhibition with RT-qPCR/western readouts","pmids":["35892692"],"confidence":"High","gaps":["Cell-type breadth of EGF-ELK1-CLDND1 induction not established","Functional outcome of EGF-driven CLDND1 induction not tested"]},{"year":2025,"claim":"Extended MZF1 control of CLDND1 to NSCLC and placed an epitranscriptomic miR-199a-3p–FTO–m6A axis upstream of MZF1.","evidence":"Dual-luciferase, MeRIP, PAR-CLIP, siRNA/overexpression in A549 cells","pmids":["41201047"],"confidence":"Medium","gaps":["Direct effect of CLDND1 on malignant behavior not isolated from upstream axis","Single cell line and single lab"]},{"year":2026,"claim":"Demonstrated a functional consequence of CLDND1 loss in vascular disease, showing it suppresses endothelial-mesenchymal transition and that restoring it rescues barrier markers.","evidence":"Dual-luciferase, OGD/R and MCAO/R models, circ_0017866 sponging of miR-124-3p, with occludin/α-SMA/Snail readouts in vitro and in vivo","pmids":["42176037"],"confidence":"Medium","gaps":["Direct molecular role of CLDND1 in suppressing EndMT not mechanistically resolved","Single-lab ischemia-reperfusion models"]},{"year":null,"claim":"The biochemical mechanism by which CLDND1 itself maintains tight junctions and suppresses apoptosis—its junctional partners, structure, and direct molecular activity—remains uncharacterized.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No direct physical interaction partners identified","No structural or domain-level mechanism for barrier function","Mechanistic link between CLDND1 and intrinsic apoptosis machinery unresolved"]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[0]},{"term_id":"R-HSA-1500931","term_label":"Cell-Cell communication","supporting_discovery_ids":[2,5]}],"complexes":[],"partners":[],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9NY35","full_name":"Claudin domain-containing protein 1","aliases":["Claudin-25","Membrane protein GENX-3745"],"length_aa":253,"mass_kda":28.6,"function":"Plays a role in negatively regulating the permeability of cells to small molecules","subcellular_location":"Cell junction, tight junction; Cell membrane","url":"https://www.uniprot.org/uniprotkb/Q9NY35/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CLDND1","classification":"Not Classified","n_dependent_lines":7,"n_total_lines":1208,"dependency_fraction":0.005794701986754967},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"GOLGA7","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/CLDND1","total_profiled":1310},"omim":[{"mim_id":"619677","title":"CLAUDIN DOMAIN-CONTAINING PROTEIN 1; CLDND1","url":"https://www.omim.org/entry/619677"},{"mim_id":"600825","title":"RAR-RELATED ORPHAN RECEPTOR A; RORA","url":"https://www.omim.org/entry/600825"},{"mim_id":"194550","title":"MYELOID ZINC FINGER 1; MZF1","url":"https://www.omim.org/entry/194550"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Nucleoli","reliability":"Additional"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"brain","ntpm":1440.2}],"url":"https://www.proteinatlas.org/search/CLDND1"},"hgnc":{"alias_symbol":["Z38"],"prev_symbol":["C3orf4"]},"alphafold":{"accession":"Q9NY35","domains":[{"cath_id":"1.20.140.150","chopping":"2-247","consensus_level":"medium","plddt":87.5911,"start":2,"end":247}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NY35","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NY35-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NY35-F1-predicted_aligned_error_v6.png","plddt_mean":87.12},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CLDND1","jax_strain_url":"https://www.jax.org/strain/search?query=CLDND1"},"sequence":{"accession":"Q9NY35","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9NY35.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9NY35/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NY35"}},"corpus_meta":[{"pmid":"27053956","id":"PMC_27053956","title":"High Expression of the Newly Found Long Noncoding RNA Z38 Promotes Cell Proliferation and Oncogenic Activity in Breast Cancer.","date":"2016","source":"Journal of Cancer","url":"https://pubmed.ncbi.nlm.nih.gov/27053956","citation_count":35,"is_preprint":false},{"pmid":"29530526","id":"PMC_29530526","title":"Levels of tight junction protein CLDND1 are regulated by microRNA-124 in the cerebellum of stroke-prone spontaneously hypertensive rats.","date":"2018","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/29530526","citation_count":21,"is_preprint":false},{"pmid":"26083392","id":"PMC_26083392","title":"Down Regulation of CLDND1 Induces Apoptosis in Breast Cancer Cells.","date":"2015","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/26083392","citation_count":17,"is_preprint":false},{"pmid":"33037622","id":"PMC_33037622","title":"Transcription of CLDND1 in human brain endothelial cells is regulated by the myeloid zinc finger 1.","date":"2020","source":"Clinical and experimental pharmacology & physiology","url":"https://pubmed.ncbi.nlm.nih.gov/33037622","citation_count":16,"is_preprint":false},{"pmid":"35892692","id":"PMC_35892692","title":"EGF-Dependent Activation of ELK1 Contributes to the Induction of CLDND1 Expression Involved in Tight Junction Formation.","date":"2022","source":"Biomedicines","url":"https://pubmed.ncbi.nlm.nih.gov/35892692","citation_count":4,"is_preprint":false},{"pmid":"30333877","id":"PMC_30333877","title":"Long noncoding RNA Z38 promotes cell proliferation and metastasis and inhibits cell apoptosis in human gastric cancer.","date":"2018","source":"Oncology letters","url":"https://pubmed.ncbi.nlm.nih.gov/30333877","citation_count":4,"is_preprint":false},{"pmid":"39739707","id":"PMC_39739707","title":"MiR-595 and Cldnd1: Potential related factors for bone loss in postmenopausal women with hip osteoporotic fracture.","date":"2024","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/39739707","citation_count":2,"is_preprint":false},{"pmid":"28849012","id":"PMC_28849012","title":"Long non-coding RNA Z38 promotes cell proliferation and metastasis in human renal cell carcinoma.","date":"2017","source":"Molecular medicine reports","url":"https://pubmed.ncbi.nlm.nih.gov/28849012","citation_count":2,"is_preprint":false},{"pmid":"41201047","id":"PMC_41201047","title":"MicroRNA‑199a‑3p suppresses non‑small cell lung cancer progression by targeting FTO to enhance m6A‑mediated downregulation of MZF1 and its transcriptional activation of CLDND1.","date":"2025","source":"Molecular medicine reports","url":"https://pubmed.ncbi.nlm.nih.gov/41201047","citation_count":0,"is_preprint":false},{"pmid":"42176037","id":"PMC_42176037","title":"Lipid Nanoparticle-Delivered Circ_0017866 Alleviates Cerebral Ischemia-Reperfusion Injury by Suppressing Endothelial-Mesenchymal Transition via the miR-124-3p/CLDND1 Axis.","date":"2026","source":"Neurochemical research","url":"https://pubmed.ncbi.nlm.nih.gov/42176037","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":7620,"output_tokens":1910,"usd":0.025755,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8677,"output_tokens":2348,"usd":0.051042,"stage2_stop_reason":"end_turn"},"total_usd":0.076797,"stage1_batch_id":"msgbatch_01ACAxJQabDsht39JXeWG22d","stage2_batch_id":"msgbatch_01QEU22A9U5sbPTgsMzTmvSf","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2015,\n      \"finding\": \"CLDND1 knockdown in basal-like breast cancer cell lines (MDA-MB-231, MDA-MB-468, BT-549) induces caspase-dependent apoptosis via the intrinsic pathway, evidenced by nuclear fragmentation, caspase-3 and PARP cleavage, and cytochrome C release from mitochondria. CLDND1 depletion also augments ERK1/2 phosphorylation, which partially protects against apoptosis; co-inhibition of MEK1/2 suppresses this ERK1/2 activation and markedly potentiates cell death.\",\n      \"method\": \"siRNA knockdown, caspase activity assays, western blot for caspase-3/PARP cleavage and cytochrome C release, MEK1/2 and JNK inhibitor epistasis\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (siRNA, apoptosis markers, pathway inhibitor epistasis) in a single lab\",\n      \"pmids\": [\"26083392\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"miR-124 post-transcriptionally regulates CLDND1 by binding a conserved site in the 3'-UTR of Cldnd1 mRNA, as demonstrated by luciferase reporter assays with sequence-specific mutations. In human brain endothelial cells transfected with miR-124 mimic, CLDND1 mRNA levels decreased. In stroke-prone spontaneously hypertensive rat (SHRSP) brains, lower miR-124 levels correlated with higher Cldnd1 mRNA and protein levels.\",\n      \"method\": \"Luciferase reporter assay with 3'-UTR constructs, miR-124 mimic transfection, RT-qPCR, western blot, in vivo SHRSP model\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — sequence-specific luciferase reporter plus cell-based and in vivo corroboration, single lab\",\n      \"pmids\": [\"29530526\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"The transcription factor myeloid zinc finger 1 (MZF1) directly activates CLDND1 transcription by binding to a silencer element within the first intron of CLDND1. MZF1 overexpression increased CLDND1 mRNA and protein levels, while siRNA-mediated MZF1 knockdown suppressed them and increased FITC-dextran permeability in human brain endothelial cells.\",\n      \"method\": \"Luciferase reporter assay, chromatin immunoprecipitation (ChIP), MZF1 expression vector overexpression, siRNA knockdown, RT-qPCR, western blot, FITC-dextran permeability assay\",\n      \"journal\": \"Clinical and experimental pharmacology & physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — ChIP plus luciferase reporter with functional permeability readout, multiple orthogonal methods in single lab\",\n      \"pmids\": [\"33037622\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"EGF-dependent activation of ELK1 (via EGFR-MAPK signaling) induces CLDND1 expression. ELK1 acts as a transcriptional activator of an enhancer region near the CLDND1 promoter; ELK1 overexpression increased CLDND1 mRNA and protein, EGF treatment enhanced ELK1 phosphorylation and CLDND1 expression, and the EGFR inhibitor gefitinib suppressed this induction.\",\n      \"method\": \"Luciferase reporter assay, chromatin immunoprecipitation (ChIP), ELK1 overexpression, EGF stimulation, gefitinib treatment, RT-qPCR, western blot\",\n      \"journal\": \"Biomedicines\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — ChIP plus luciferase reporter with pharmacological inhibition, multiple orthogonal methods in single lab\",\n      \"pmids\": [\"35892692\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"MZF1 transcriptionally activates CLDND1 in NSCLC cells (A549). Upstream, miR-199a-3p targets FTO (an m6A demethylase), leading to enhanced m6A modification and decreased expression of MZF1 mRNA, thereby reducing CLDND1 expression and suppressing malignant cell behavior.\",\n      \"method\": \"Dual-luciferase reporter assay, methylated RNA immunoprecipitation (MeRIP), CLIP (PAR-CLIP), western blot, RT-qPCR, siRNA knockdown, overexpression\",\n      \"journal\": \"Molecular medicine reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (luciferase, MeRIP, CLIP) confirming the axis, single lab\",\n      \"pmids\": [\"41201047\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"miR-124-3p directly targets CLDND1 3'-UTR (confirmed by dual-luciferase assay). In cerebral ischemia-reperfusion models, CLDND1 downregulation promotes endothelial-mesenchymal transition (EndMT); restoring CLDND1 (via miR-124-3p inhibition or circ_0017866 sponging of miR-124-3p) upregulates occludin, downregulates α-SMA and Snail, and improves endothelial function both in vitro and in vivo.\",\n      \"method\": \"Dual-luciferase reporter assay, OGD/R cell model, MCAO/R mouse model, siRNA/overexpression, RT-qPCR, western blot, immunofluorescence, CCK-8, Transwell, tube formation assays\",\n      \"journal\": \"Neurochemical research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — luciferase reporter plus multiple functional assays in vitro and in vivo, single lab\",\n      \"pmids\": [\"42176037\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CLDND1 (claudin domain-containing 1) is a claudin-like tight junction protein whose expression is transcriptionally activated by MZF1 and ELK1 (downstream of EGFR-MAPK signaling), post-transcriptionally repressed by miR-124 via 3'-UTR binding, and functionally required for tight junction integrity and endothelial barrier function; in cancer cells, CLDND1 acts as a survival factor by suppressing the intrinsic apoptotic pathway, partly through augmenting ERK1/2 phosphorylation, such that its loss triggers caspase-3-dependent apoptosis.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"CLDND1 (claudin domain-containing 1) is a claudin-like protein that maintains endothelial tight junction integrity and barrier function, with its expression controlled by a converging set of transcriptional and post-transcriptional inputs [#2, #5]. Transcriptionally, CLDND1 is directly activated by MZF1, which binds a silencer element in the first intron; MZF1 loss reduces CLDND1 and increases endothelial permeability [#2]. EGFR-MAPK signaling provides a second activating input through EGF-dependent ELK1 phosphorylation, which drives CLDND1 expression via an enhancer near the promoter and is blocked by the EGFR inhibitor gefitinib [#3]. Post-transcriptionally, miR-124/miR-124-3p represses CLDND1 by binding a conserved 3'-UTR site, and loss of CLDND1 in cerebral ischemia-reperfusion models drives endothelial-mesenchymal transition with downregulated occludin and upregulated \\u03b1-SMA and Snail, while restoring CLDND1 rescues endothelial function [#1, #5]. In cancer cells, CLDND1 functions as a survival factor: its knockdown induces caspase-3-dependent intrinsic apoptosis with cytochrome C release, partly buffered by compensatory ERK1/2 activation whose pharmacological blockade potentiates cell death [#0]. An upstream miR-199a-3p–FTO–m6A axis modulates MZF1 and thereby CLDND1 levels in NSCLC cells [#4].\",\n  \"teleology\": [\n    {\n      \"year\": 2015,\n      \"claim\": \"Established that CLDND1 is not merely a structural junction protein but a survival factor in cancer cells, defining the apoptotic consequence of its loss and a compensatory ERK1/2 escape mechanism.\",\n      \"evidence\": \"siRNA knockdown with apoptosis markers (caspase-3/PARP cleavage, cytochrome C release) and MEK1/2 inhibitor epistasis in basal-like breast cancer lines\",\n      \"pmids\": [\"26083392\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular mechanism linking CLDND1 loss to mitochondrial apoptosis not defined\", \"How CLDND1 depletion augments ERK1/2 phosphorylation unknown\", \"Single-lab observation in breast cancer lines only\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Identified the first post-transcriptional regulator of CLDND1, showing miR-124 directly represses it via a 3'-UTR site, linking CLDND1 dosage to endothelial/vascular contexts.\",\n      \"evidence\": \"Luciferase reporter with sequence-specific 3'-UTR mutations, miR-124 mimic in brain endothelial cells, and in vivo SHRSP correlation\",\n      \"pmids\": [\"29530526\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional barrier consequence of the miR-124–CLDND1 axis not tested here\", \"Correlative in vivo data do not prove causation in SHRSP\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Defined the first direct transcriptional activator of CLDND1 and tied its regulation to a measurable barrier function readout.\",\n      \"evidence\": \"ChIP and luciferase reporter mapping MZF1 to an intronic silencer element, with MZF1 knockdown increasing FITC-dextran permeability in brain endothelial cells\",\n      \"pmids\": [\"33037622\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether MZF1 cooperates with other factors at the locus unknown\", \"Mechanism by which CLDND1 maintains barrier tightness not addressed\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Connected CLDND1 transcription to upstream growth-factor signaling, showing EGFR-MAPK acts through ELK1 to induce expression.\",\n      \"evidence\": \"ChIP and luciferase reporter for ELK1 at an enhancer, EGF stimulation, and gefitinib inhibition with RT-qPCR/western readouts\",\n      \"pmids\": [\"35892692\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cell-type breadth of EGF-ELK1-CLDND1 induction not established\", \"Functional outcome of EGF-driven CLDND1 induction not tested\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Extended MZF1 control of CLDND1 to NSCLC and placed an epitranscriptomic miR-199a-3p–FTO–m6A axis upstream of MZF1.\",\n      \"evidence\": \"Dual-luciferase, MeRIP, PAR-CLIP, siRNA/overexpression in A549 cells\",\n      \"pmids\": [\"41201047\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct effect of CLDND1 on malignant behavior not isolated from upstream axis\", \"Single cell line and single lab\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Demonstrated a functional consequence of CLDND1 loss in vascular disease, showing it suppresses endothelial-mesenchymal transition and that restoring it rescues barrier markers.\",\n      \"evidence\": \"Dual-luciferase, OGD/R and MCAO/R models, circ_0017866 sponging of miR-124-3p, with occludin/\\u03b1-SMA/Snail readouts in vitro and in vivo\",\n      \"pmids\": [\"42176037\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct molecular role of CLDND1 in suppressing EndMT not mechanistically resolved\", \"Single-lab ischemia-reperfusion models\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The biochemical mechanism by which CLDND1 itself maintains tight junctions and suppresses apoptosis—its junctional partners, structure, and direct molecular activity—remains uncharacterized.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No direct physical interaction partners identified\", \"No structural or domain-level mechanism for barrier function\", \"Mechanistic link between CLDND1 and intrinsic apoptosis machinery unresolved\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [],\n    \"localization\": [],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"R-HSA-1500931\", \"supporting_discovery_ids\": [2, 5]}\n    ],\n    \"complexes\": [],\n    \"partners\": [],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}