{"gene":"FBLN2","run_date":"2026-06-09T23:54:43","timeline":{"discoveries":[{"year":1994,"finding":"Fibulin-2 protein domain architecture was determined: the mature protein contains an N-terminal cysteine-rich subdomain (Na) and acidic subdomain (Nb), followed by three anaphylatoxin-related segments (domain I), ten EGF-like repeats (domain II, nine with calcium-binding consensus), and a C-terminal domain III similar to fibulin-1 variant C. The gene was localized to human chromosome 3p24-p25 and mouse chromosome 6D-E.","method":"cDNA sequencing, Northern blot, in situ hybridization","journal":"Genomics","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct sequencing and structural characterization of the full-length protein; foundational characterization replicated in subsequent domain studies","pmids":["7806230"],"is_preprint":false},{"year":2021,"finding":"FBLN2 knockdown reduces the anoikis-promoting and anti-metastatic functions downstream of AKT in gastric cancer cells; ITGBL1 promotes anoikis resistance and metastasis through the AKT/FBLN2 axis, placing FBLN2 as a downstream effector of AKT signaling that suppresses anoikis resistance.","method":"siRNA knockdown, overexpression, in vitro anoikis assay, in vivo xenograft, western blot","journal":"Journal of cellular and molecular medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss- and gain-of-function with defined phenotypic readout in vitro and in vivo, single lab","pmids":["38332530"],"is_preprint":false},{"year":2021,"finding":"Enteric neurons secrete Fbln2 (and Nid1), and this ENS-derived Fbln2 enhances migration of colorectal cancer cells; loss of NDRG4 in enteric neurons leads to increased Fbln2 secretion that promotes intestinal tumor growth.","method":"Ndrg4 knockout mouse models, indirect co-culture with intestinal organoids, quantitative proteomics, immunostaining, cell migration assay","journal":"EMBO reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic knockout combined with proteomics and functional migration assays, single lab","pmids":["33890711"],"is_preprint":false},{"year":2022,"finding":"FBLN2 physically interacts with vitronectin (VTN) and negatively regulates its expression; FBLN2 knockdown suppresses TGF-β1-induced fibroblast migration, proliferation, and fibrosis (reduced α-SMA, collagen, fibronectin, MMP2, MMP9) via downregulation of VTN and attenuation of FAK signaling.","method":"Co-immunoprecipitation, siRNA knockdown, overexpression rescue, wound healing assay, western blot, immunofluorescence, CCK-8 assay","journal":"Tissue & cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal co-IP for interaction plus functional rescue experiment, single lab","pmids":["36608640"],"is_preprint":false},{"year":2022,"finding":"In alcoholic hepatitis, a distinct Lrat+Fbln2+ hepatic stellate cell (HSC) subpopulation emerges, which is highly profibrotic, myofibroblastic, and immunoregulatory; Fbln2 expression marks a subset of HSCs (distinct from portal fibroblasts) that expands dramatically in AH relative to other fibrosis models.","method":"scRNA-seq with FACS sorting, Lrat-Cre lineage tracing, immunohistochemistry, in situ hybridization","journal":"Hepatology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic lineage tracing combined with scRNA-seq and histology, single lab","pmids":["36181700"],"is_preprint":false},{"year":2024,"finding":"fbln2 knockout in zebrafish (CRISPR/Cas9) causes craniofacial malformations with abnormal chondrocyte morphology, impaired chondrogenic differentiation, increased apoptosis and altered proliferation of cranial neural crest cells (CNCCs), and downregulation of BMP signaling pathway.","method":"CRISPR/Cas9 knockout in zebrafish, immunostaining, apoptosis and proliferation assays, BMP pathway analysis","journal":"Annals of the New York Academy of Sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic knockout with defined cellular phenotype and pathway placement, single lab","pmids":["38970771"],"is_preprint":false},{"year":2024,"finding":"FBLN2 knockdown in mouse mammary epithelial cells reduces KRT14 (basal marker) and increases KRT18 (luminal marker), indicating FBLN2 supports basal/myoepithelial cell identity; TGFβ3 treatment upregulates FBLN2 in vitro.","method":"siRNA knockdown, immunoblotting, immunocytochemistry, TGFβ3 treatment in EpH4 cells","journal":"Breast cancer research and treatment","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, limited mechanistic follow-up, primarily marker expression readout","pmids":["39110274"],"is_preprint":false},{"year":2025,"finding":"Exclusion of exon 9 of FBLN2 (a recurrent cancer-associated splicing event) eliminates a single N-glycosylation site, causing protein misfolding and reduced stability and secretion efficiency of fibulin-2; the resulting FBLN2 deficiency in the tumor ECM, combined with increased fibronectin 1, promotes adhesion and migration of colorectal cancer cells.","method":"Alternative splicing analysis, glycosylation assay, protein stability/secretion assay, colorectal cancer tissue ECM analysis, cell adhesion and migration assay","journal":"Genes to cells","confidence":"Medium","confidence_rationale":"Tier 1-2 / Moderate — direct biochemical characterization of glycosylation and protein folding consequences of splicing, functional validation in cancer cells, single lab","pmids":["40400104"],"is_preprint":false},{"year":2025,"finding":"FBLN2 overexpression suppresses gastric cancer cell proliferation, migration and invasion; FBLN2 acts through the TGFβ/TGIF2 axis, as identified by RNA-seq of FBLN2 knockout vs. wild-type GC cells and KEGG enrichment analysis, with FBLN2 downregulating TGIF2.","method":"FBLN2 overexpression and knockout in GC cells, in vivo and in vitro experiments, RNA-seq with KEGG pathway analysis","journal":"Pathology, research and practice","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic loss- and gain-of-function with transcriptomic pathway identification, single lab","pmids":["40168772"],"is_preprint":false},{"year":2026,"finding":"In zebrafish cardiac regeneration, Fbln2 regulates epicardial cell activation; mechanistically, Fbln2 controls epicardial myofibroblast abundance via nuclear protein 1b (Nupr1b) as a downstream effector — epicardial-specific overexpression of nupr1b rescued fbln2 mutant phenotypes, establishing Fbln2→Nupr1b as a signaling axis that balances fibrosis and regeneration after cardiac injury.","method":"Fbln2 genetic dosage manipulation, gain- and loss-of-function for Nupr1b, epicardial-specific overexpression rescue experiments in zebrafish cardiac injury model","journal":"Nature cardiovascular research","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis via rescue experiment (nupr1b OE rescues fbln2 mutant), multiple orthogonal gain/loss-of-function approaches in defined in vivo model","pmids":["41776059"],"is_preprint":false},{"year":2018,"finding":"miR-192-5p directly targets FBLN2 mRNA (validated by dual-luciferase reporter assay); FBLN2 positively regulates the TGF-β1 signaling pathway in mouse hippocampus under depression conditions, and suppression of Fbln2 by miR-192-5p attenuates this pathway to improve cognitive function.","method":"Dual-luciferase reporter assay, miRNA mimic/inhibitor transfection, siRNA knockdown, hippocampal electrophysiology, behavioral assays in CUMS mouse model","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct target validation by luciferase assay plus in vivo functional rescue, single lab","pmids":["30118321"],"is_preprint":false}],"current_model":"Fibulin-2 (FBLN2) is a secreted extracellular matrix glycoprotein with a defined multi-domain architecture (anaphylatoxin domains, calcium-binding EGF-like repeats, and fibulin-type C-terminal domain) whose N-glycosylation (dependent on exon 9 inclusion) is required for proper folding, stability, and secretion; it physically interacts with vitronectin to modulate FAK signaling and fibrosis, acts downstream of AKT to suppress anoikis resistance, regulates BMP signaling in cranial neural crest cells, controls epicardial myofibroblast abundance via a Fbln2→Nupr1b axis during cardiac regeneration, and can be regulated post-transcriptionally by miR-192-5p targeting to modulate TGF-β1 pathway activity."},"narrative":{"mechanistic_narrative":"Fibulin-2 (FBLN2) is a secreted, multi-domain extracellular matrix glycoprotein built from an N-terminal cysteine-rich and acidic region, three anaphylatoxin-related segments, ten EGF-like repeats (nine calcium-binding), and a fibulin-type C-terminal domain [PMID:7806230]. Its proper folding, stability, and secretion depend on N-glycosylation: cancer-associated exclusion of exon 9 removes a single N-glycosylation site and causes misfolding and reduced secretion, depleting FBLN2 from the tumor ECM [PMID:40400104]. As a matrix component, FBLN2 regulates fibrogenic and developmental signaling: it physically interacts with vitronectin and negatively regulates it, attenuating TGF-β1-driven fibroblast migration, proliferation, and fibrosis through reduced FAK signaling [PMID:36608640], while in the mouse hippocampus FBLN2 positively drives TGF-β1 signaling and is held in check post-transcriptionally by miR-192-5p [PMID:30118321]. In development and regeneration, FBLN2 supports cranial neural crest chondrogenesis via BMP signaling [PMID:38970771] and balances fibrosis versus regeneration in the injured zebrafish heart by controlling epicardial myofibroblast abundance through a Fbln2→Nupr1b axis [PMID:41776059]. In cancer, FBLN2 has context-dependent roles, acting as a downstream effector of AKT that suppresses anoikis resistance and as a suppressor of gastric cancer proliferation and invasion via the TGFβ/TGIF2 axis [PMID:38332530, PMID:40168772].","teleology":[{"year":1994,"claim":"Established the primary structure and domain organization of fibulin-2, defining it as a calcium-binding, EGF-repeat-containing matrix glycoprotein and providing the framework for all later functional studies.","evidence":"cDNA sequencing, Northern blot, and in situ hybridization with chromosomal mapping","pmids":["7806230"],"confidence":"High","gaps":["No functional role assigned to individual domains","No binding partners identified at this stage"]},{"year":2018,"claim":"Identified post-transcriptional control of FBLN2 by miR-192-5p and placed FBLN2 as a positive regulator of TGF-β1 signaling in the brain, linking the matrix protein to neuronal/cognitive phenotypes.","evidence":"Dual-luciferase reporter assay, miRNA mimic/inhibitor, hippocampal electrophysiology and behavioral assays in a CUMS mouse model","pmids":["30118321"],"confidence":"Medium","gaps":["Direction of TGF-β1 regulation (positive here) differs from fibrosis context","Mechanism by which a secreted ECM protein modulates hippocampal signaling unresolved"]},{"year":2021,"claim":"Positioned FBLN2 in cancer cell behavior as a downstream effector of AKT signaling that suppresses anoikis resistance, and as an ENS-secreted factor that can promote colorectal cancer migration.","evidence":"siRNA/overexpression with anoikis and xenograft assays; Ndrg4 knockout mice with organoid co-culture and proteomics","pmids":["38332530","33890711"],"confidence":"Medium","gaps":["Opposing pro- and anti-tumor roles across tissues not reconciled","No direct receptor or signaling intermediary identified"]},{"year":2022,"claim":"Defined a vitronectin-FAK fibrosis axis and identified an Fbln2-marked profibrotic hepatic stellate cell subpopulation, connecting FBLN2 to TGF-β1-driven fibrogenesis.","evidence":"Reciprocal co-IP and rescue in fibroblasts; scRNA-seq with Lrat-Cre lineage tracing in alcoholic hepatitis","pmids":["36608640","36181700"],"confidence":"Medium","gaps":["Whether the Fbln2+ HSC marker reflects a functional role for FBLN2 protein not established","VTN-FAK mechanism not confirmed in vivo"]},{"year":2024,"claim":"Demonstrated a developmental requirement for FBLN2 in craniofacial chondrogenesis via BMP signaling and a role in maintaining basal/myoepithelial mammary cell identity.","evidence":"CRISPR/Cas9 fbln2 knockout in zebrafish with BMP pathway analysis; siRNA in EpH4 mammary cells with marker readouts","pmids":["38970771","39110274"],"confidence":"Medium","gaps":["How FBLN2 mechanistically activates BMP signaling unknown","Mammary findings rest on marker expression only (Low confidence)"]},{"year":2025,"claim":"Provided biochemical mechanism linking a cancer-associated splicing event to FBLN2 dysfunction, showing exon 9 exclusion removes an N-glycosylation site needed for folding and secretion, and identified the TGFβ/TGIF2 axis for its tumor-suppressive activity.","evidence":"Splicing/glycosylation/secretion assays with ECM analysis in colorectal cancer; FBLN2 knockout/overexpression with RNA-seq and KEGG in gastric cancer cells","pmids":["40400104","40168772"],"confidence":"Medium","gaps":["Structural basis of misfolding not resolved","Direct molecular target downstream of TGIF2 not defined"]},{"year":2026,"claim":"Established Fbln2 as a regulator of epicardial activation in cardiac regeneration acting through Nupr1b, demonstrating genetic epistasis that balances fibrosis and regeneration after injury.","evidence":"Genetic dosage manipulation with epicardial-specific nupr1b overexpression rescue in zebrafish cardiac injury","pmids":["41776059"],"confidence":"High","gaps":["How secreted Fbln2 controls nuclear Nupr1b expression mechanistically unknown","Conservation of the axis in mammalian heart untested"]},{"year":null,"claim":"How a single secreted ECM glycoprotein produces opposing context-dependent outputs on TGF-β signaling and tumor behavior across tissues remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unifying receptor or signaling mechanism identified across contexts","Domain-level structure-function mapping to specific signaling partners absent"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[0]}],"localization":[{"term_id":"GO:0031012","term_label":"extracellular matrix","supporting_discovery_ids":[7]},{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[2,7]}],"pathway":[{"term_id":"R-HSA-1474244","term_label":"Extracellular matrix organization","supporting_discovery_ids":[7]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[3,8,9]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[5,9]}],"complexes":[],"partners":["VTN"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P98095","full_name":"Fibulin-2","aliases":[],"length_aa":1184,"mass_kda":126.6,"function":"Its binding to fibronectin and some other ligands is calcium dependent. May act as an adapter that mediates the interaction between FBN1 and ELN (PubMed:17255108)","subcellular_location":"Secreted, extracellular space, extracellular matrix","url":"https://www.uniprot.org/uniprotkb/P98095/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/FBLN2","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/FBLN2","total_profiled":1310},"omim":[{"mim_id":"610168","title":"LOEYS-DIETZ SYNDROME 2; LDS2","url":"https://www.omim.org/entry/610168"},{"mim_id":"606217","title":"ATRIOVENTRICULAR SEPTAL DEFECT, SUSCEPTIBILITY TO, 2; AVSD2","url":"https://www.omim.org/entry/606217"},{"mim_id":"606215","title":"ATRIOVENTRICULAR SEPTAL DEFECT; AVSD","url":"https://www.omim.org/entry/606215"},{"mim_id":"605399","title":"NIDOGEN 2; NID2","url":"https://www.omim.org/entry/605399"},{"mim_id":"605083","title":"FRIZZLED-RELATED PROTEIN; FRZB","url":"https://www.omim.org/entry/605083"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Uncertain","locations":[{"location":"Plasma membrane","reliability":"Uncertain"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"heart muscle","ntpm":287.6}],"url":"https://www.proteinatlas.org/search/FBLN2"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"P98095","domains":[{"cath_id":"-","chopping":"41-114","consensus_level":"medium","plddt":81.0532,"start":41,"end":114},{"cath_id":"-","chopping":"440-501_514-555","consensus_level":"medium","plddt":83.9356,"start":440,"end":555},{"cath_id":"2.10.25.10","chopping":"683-728","consensus_level":"medium","plddt":79.8572,"start":683,"end":728},{"cath_id":"-","chopping":"762-792","consensus_level":"medium","plddt":79.6577,"start":762,"end":792},{"cath_id":"2.60.40.60","chopping":"1066-1181","consensus_level":"high","plddt":89.7899,"start":1066,"end":1181}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P98095","model_url":"https://alphafold.ebi.ac.uk/files/AF-P98095-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P98095-F1-predicted_aligned_error_v6.png","plddt_mean":67.38},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=FBLN2","jax_strain_url":"https://www.jax.org/strain/search?query=FBLN2"},"sequence":{"accession":"P98095","fasta_url":"https://rest.uniprot.org/uniprotkb/P98095.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P98095/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P98095"}},"corpus_meta":[{"pmid":"33971972","id":"PMC_33971972","title":"Rare variant analysis of 4241 pulmonary arterial hypertension cases from an international consortium implicates FBLN2, PDGFD, and rare de novo variants in PAH.","date":"2021","source":"Genome medicine","url":"https://pubmed.ncbi.nlm.nih.gov/33971972","citation_count":69,"is_preprint":false},{"pmid":"7806230","id":"PMC_7806230","title":"Fibulin-2 (FBLN2): human cDNA sequence, mRNA expression, and mapping of the gene on human and mouse chromosomes.","date":"1994","source":"Genomics","url":"https://pubmed.ncbi.nlm.nih.gov/7806230","citation_count":47,"is_preprint":false},{"pmid":"30118321","id":"PMC_30118321","title":"Up-regulated miR-192-5p expression rescues cognitive impairment and restores neural function in mice with depression via the Fbln2-mediated TGF-β1 signaling pathway.","date":"2018","source":"FASEB journal : official publication of the Federation of American Societies for Experimental Biology","url":"https://pubmed.ncbi.nlm.nih.gov/30118321","citation_count":41,"is_preprint":false},{"pmid":"33890711","id":"PMC_33890711","title":"Loss of enteric neuronal Ndrg4 promotes colorectal cancer via increased release of Nid1 and Fbln2.","date":"2021","source":"EMBO reports","url":"https://pubmed.ncbi.nlm.nih.gov/33890711","citation_count":33,"is_preprint":false},{"pmid":"36608640","id":"PMC_36608640","title":"Knockdown of FBLN2 suppresses TGF-β1-induced MRC-5 cell migration and fibrosis by downregulating VTN.","date":"2022","source":"Tissue & cell","url":"https://pubmed.ncbi.nlm.nih.gov/36608640","citation_count":17,"is_preprint":false},{"pmid":"39110274","id":"PMC_39110274","title":"FBLN2 is associated with basal cell markers Krt14 and ITGB1 in mouse mammary epithelial cells and has a preferential expression in molecular subtypes of human breast cancer.","date":"2024","source":"Breast cancer research and treatment","url":"https://pubmed.ncbi.nlm.nih.gov/39110274","citation_count":13,"is_preprint":false},{"pmid":"38332530","id":"PMC_38332530","title":"ITGBL1 promotes anoikis resistance and metastasis in human gastric cancer via the AKT/FBLN2 axis.","date":"2024","source":"Journal of cellular and molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/38332530","citation_count":11,"is_preprint":false},{"pmid":"36181700","id":"PMC_36181700","title":"Emergence of highly profibrotic and proinflammatory Lrat+Fbln2+ HSC subpopulation in alcoholic hepatitis.","date":"2022","source":"Hepatology (Baltimore, Md.)","url":"https://pubmed.ncbi.nlm.nih.gov/36181700","citation_count":9,"is_preprint":false},{"pmid":"38970771","id":"PMC_38970771","title":"FBLN2 is associated with Goldenhar syndrome and is essential for cranial neural crest cell development.","date":"2024","source":"Annals of the New York Academy of Sciences","url":"https://pubmed.ncbi.nlm.nih.gov/38970771","citation_count":8,"is_preprint":false},{"pmid":"33074219","id":"PMC_33074219","title":"Long non-coding RNA GAS5 knockdown facilitates proliferation and impedes apoptosis by regulating miR-128-3p/FBLN2 axis in ox-LDL-induced THP-1 cells.","date":"2021","source":"Clinical hemorheology and microcirculation","url":"https://pubmed.ncbi.nlm.nih.gov/33074219","citation_count":7,"is_preprint":false},{"pmid":"37543430","id":"PMC_37543430","title":"TMT-based quantitative proteomic analysis revealed that FBLN2 and NPR3 are involved in the early osteogenic differentiation of mesenchymal stem cells (MSCs).","date":"2023","source":"Aging","url":"https://pubmed.ncbi.nlm.nih.gov/37543430","citation_count":5,"is_preprint":false},{"pmid":"39624827","id":"PMC_39624827","title":"Circ_0001944 Targets the miR-1292-5p/FBLN2 Axis to Facilitate Sorafenib Resistance in Hepatocellular Carcinoma by Impeding Ferroptosis.","date":"2024","source":"ImmunoTargets and therapy","url":"https://pubmed.ncbi.nlm.nih.gov/39624827","citation_count":4,"is_preprint":false},{"pmid":"40168772","id":"PMC_40168772","title":"FBLN2 inhibits gastric cancer proliferation and metastasis via the TGFβ/TGIF2 pathway.","date":"2025","source":"Pathology, research and practice","url":"https://pubmed.ncbi.nlm.nih.gov/40168772","citation_count":1,"is_preprint":false},{"pmid":"40400104","id":"PMC_40400104","title":"Alternative Splicing of FBLN2 Generates a Prometastatic Extracellular Matrix in Gastrointestinal Cancers by Determining N-Glycosylation of Fibulin 2.","date":"2025","source":"Genes to cells : devoted to molecular & cellular mechanisms","url":"https://pubmed.ncbi.nlm.nih.gov/40400104","citation_count":1,"is_preprint":false},{"pmid":"41776059","id":"PMC_41776059","title":"Attenuation of epicardial activation and myofibroblast abundance via the Fbln2-Nupr1b axis stimulates cardiac regeneration in zebrafish.","date":"2026","source":"Nature cardiovascular research","url":"https://pubmed.ncbi.nlm.nih.gov/41776059","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":11029,"output_tokens":2782,"usd":0.037408,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":10100,"output_tokens":2814,"usd":0.060425,"stage2_stop_reason":"end_turn"},"total_usd":0.097833,"stage1_batch_id":"msgbatch_01AsR7g8dGTEiEw9U83bJeWn","stage2_batch_id":"msgbatch_01YV5ZyxtFNUZEjxRcpd9jzb","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1994,\n      \"finding\": \"Fibulin-2 protein domain architecture was determined: the mature protein contains an N-terminal cysteine-rich subdomain (Na) and acidic subdomain (Nb), followed by three anaphylatoxin-related segments (domain I), ten EGF-like repeats (domain II, nine with calcium-binding consensus), and a C-terminal domain III similar to fibulin-1 variant C. The gene was localized to human chromosome 3p24-p25 and mouse chromosome 6D-E.\",\n      \"method\": \"cDNA sequencing, Northern blot, in situ hybridization\",\n      \"journal\": \"Genomics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct sequencing and structural characterization of the full-length protein; foundational characterization replicated in subsequent domain studies\",\n      \"pmids\": [\"7806230\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"FBLN2 knockdown reduces the anoikis-promoting and anti-metastatic functions downstream of AKT in gastric cancer cells; ITGBL1 promotes anoikis resistance and metastasis through the AKT/FBLN2 axis, placing FBLN2 as a downstream effector of AKT signaling that suppresses anoikis resistance.\",\n      \"method\": \"siRNA knockdown, overexpression, in vitro anoikis assay, in vivo xenograft, western blot\",\n      \"journal\": \"Journal of cellular and molecular medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss- and gain-of-function with defined phenotypic readout in vitro and in vivo, single lab\",\n      \"pmids\": [\"38332530\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Enteric neurons secrete Fbln2 (and Nid1), and this ENS-derived Fbln2 enhances migration of colorectal cancer cells; loss of NDRG4 in enteric neurons leads to increased Fbln2 secretion that promotes intestinal tumor growth.\",\n      \"method\": \"Ndrg4 knockout mouse models, indirect co-culture with intestinal organoids, quantitative proteomics, immunostaining, cell migration assay\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic knockout combined with proteomics and functional migration assays, single lab\",\n      \"pmids\": [\"33890711\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"FBLN2 physically interacts with vitronectin (VTN) and negatively regulates its expression; FBLN2 knockdown suppresses TGF-β1-induced fibroblast migration, proliferation, and fibrosis (reduced α-SMA, collagen, fibronectin, MMP2, MMP9) via downregulation of VTN and attenuation of FAK signaling.\",\n      \"method\": \"Co-immunoprecipitation, siRNA knockdown, overexpression rescue, wound healing assay, western blot, immunofluorescence, CCK-8 assay\",\n      \"journal\": \"Tissue & cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal co-IP for interaction plus functional rescue experiment, single lab\",\n      \"pmids\": [\"36608640\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"In alcoholic hepatitis, a distinct Lrat+Fbln2+ hepatic stellate cell (HSC) subpopulation emerges, which is highly profibrotic, myofibroblastic, and immunoregulatory; Fbln2 expression marks a subset of HSCs (distinct from portal fibroblasts) that expands dramatically in AH relative to other fibrosis models.\",\n      \"method\": \"scRNA-seq with FACS sorting, Lrat-Cre lineage tracing, immunohistochemistry, in situ hybridization\",\n      \"journal\": \"Hepatology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic lineage tracing combined with scRNA-seq and histology, single lab\",\n      \"pmids\": [\"36181700\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"fbln2 knockout in zebrafish (CRISPR/Cas9) causes craniofacial malformations with abnormal chondrocyte morphology, impaired chondrogenic differentiation, increased apoptosis and altered proliferation of cranial neural crest cells (CNCCs), and downregulation of BMP signaling pathway.\",\n      \"method\": \"CRISPR/Cas9 knockout in zebrafish, immunostaining, apoptosis and proliferation assays, BMP pathway analysis\",\n      \"journal\": \"Annals of the New York Academy of Sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic knockout with defined cellular phenotype and pathway placement, single lab\",\n      \"pmids\": [\"38970771\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"FBLN2 knockdown in mouse mammary epithelial cells reduces KRT14 (basal marker) and increases KRT18 (luminal marker), indicating FBLN2 supports basal/myoepithelial cell identity; TGFβ3 treatment upregulates FBLN2 in vitro.\",\n      \"method\": \"siRNA knockdown, immunoblotting, immunocytochemistry, TGFβ3 treatment in EpH4 cells\",\n      \"journal\": \"Breast cancer research and treatment\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, limited mechanistic follow-up, primarily marker expression readout\",\n      \"pmids\": [\"39110274\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Exclusion of exon 9 of FBLN2 (a recurrent cancer-associated splicing event) eliminates a single N-glycosylation site, causing protein misfolding and reduced stability and secretion efficiency of fibulin-2; the resulting FBLN2 deficiency in the tumor ECM, combined with increased fibronectin 1, promotes adhesion and migration of colorectal cancer cells.\",\n      \"method\": \"Alternative splicing analysis, glycosylation assay, protein stability/secretion assay, colorectal cancer tissue ECM analysis, cell adhesion and migration assay\",\n      \"journal\": \"Genes to cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — direct biochemical characterization of glycosylation and protein folding consequences of splicing, functional validation in cancer cells, single lab\",\n      \"pmids\": [\"40400104\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"FBLN2 overexpression suppresses gastric cancer cell proliferation, migration and invasion; FBLN2 acts through the TGFβ/TGIF2 axis, as identified by RNA-seq of FBLN2 knockout vs. wild-type GC cells and KEGG enrichment analysis, with FBLN2 downregulating TGIF2.\",\n      \"method\": \"FBLN2 overexpression and knockout in GC cells, in vivo and in vitro experiments, RNA-seq with KEGG pathway analysis\",\n      \"journal\": \"Pathology, research and practice\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic loss- and gain-of-function with transcriptomic pathway identification, single lab\",\n      \"pmids\": [\"40168772\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"In zebrafish cardiac regeneration, Fbln2 regulates epicardial cell activation; mechanistically, Fbln2 controls epicardial myofibroblast abundance via nuclear protein 1b (Nupr1b) as a downstream effector — epicardial-specific overexpression of nupr1b rescued fbln2 mutant phenotypes, establishing Fbln2→Nupr1b as a signaling axis that balances fibrosis and regeneration after cardiac injury.\",\n      \"method\": \"Fbln2 genetic dosage manipulation, gain- and loss-of-function for Nupr1b, epicardial-specific overexpression rescue experiments in zebrafish cardiac injury model\",\n      \"journal\": \"Nature cardiovascular research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis via rescue experiment (nupr1b OE rescues fbln2 mutant), multiple orthogonal gain/loss-of-function approaches in defined in vivo model\",\n      \"pmids\": [\"41776059\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"miR-192-5p directly targets FBLN2 mRNA (validated by dual-luciferase reporter assay); FBLN2 positively regulates the TGF-β1 signaling pathway in mouse hippocampus under depression conditions, and suppression of Fbln2 by miR-192-5p attenuates this pathway to improve cognitive function.\",\n      \"method\": \"Dual-luciferase reporter assay, miRNA mimic/inhibitor transfection, siRNA knockdown, hippocampal electrophysiology, behavioral assays in CUMS mouse model\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct target validation by luciferase assay plus in vivo functional rescue, single lab\",\n      \"pmids\": [\"30118321\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"Fibulin-2 (FBLN2) is a secreted extracellular matrix glycoprotein with a defined multi-domain architecture (anaphylatoxin domains, calcium-binding EGF-like repeats, and fibulin-type C-terminal domain) whose N-glycosylation (dependent on exon 9 inclusion) is required for proper folding, stability, and secretion; it physically interacts with vitronectin to modulate FAK signaling and fibrosis, acts downstream of AKT to suppress anoikis resistance, regulates BMP signaling in cranial neural crest cells, controls epicardial myofibroblast abundance via a Fbln2→Nupr1b axis during cardiac regeneration, and can be regulated post-transcriptionally by miR-192-5p targeting to modulate TGF-β1 pathway activity.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"Fibulin-2 (FBLN2) is a secreted, multi-domain extracellular matrix glycoprotein built from an N-terminal cysteine-rich and acidic region, three anaphylatoxin-related segments, ten EGF-like repeats (nine calcium-binding), and a fibulin-type C-terminal domain [#0]. Its proper folding, stability, and secretion depend on N-glycosylation: cancer-associated exclusion of exon 9 removes a single N-glycosylation site and causes misfolding and reduced secretion, depleting FBLN2 from the tumor ECM [#7]. As a matrix component, FBLN2 regulates fibrogenic and developmental signaling: it physically interacts with vitronectin and negatively regulates it, attenuating TGF-\\u03b21-driven fibroblast migration, proliferation, and fibrosis through reduced FAK signaling [#3], while in the mouse hippocampus FBLN2 positively drives TGF-\\u03b21 signaling and is held in check post-transcriptionally by miR-192-5p [#10]. In development and regeneration, FBLN2 supports cranial neural crest chondrogenesis via BMP signaling [#5] and balances fibrosis versus regeneration in the injured zebrafish heart by controlling epicardial myofibroblast abundance through a Fbln2\\u2192Nupr1b axis [#9]. In cancer, FBLN2 has context-dependent roles, acting as a downstream effector of AKT that suppresses anoikis resistance and as a suppressor of gastric cancer proliferation and invasion via the TGF\\u03b2/TGIF2 axis [#1, #8].\",\n  \"teleology\": [\n    {\n      \"year\": 1994,\n      \"claim\": \"Established the primary structure and domain organization of fibulin-2, defining it as a calcium-binding, EGF-repeat-containing matrix glycoprotein and providing the framework for all later functional studies.\",\n      \"evidence\": \"cDNA sequencing, Northern blot, and in situ hybridization with chromosomal mapping\",\n      \"pmids\": [\"7806230\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No functional role assigned to individual domains\", \"No binding partners identified at this stage\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Identified post-transcriptional control of FBLN2 by miR-192-5p and placed FBLN2 as a positive regulator of TGF-\\u03b21 signaling in the brain, linking the matrix protein to neuronal/cognitive phenotypes.\",\n      \"evidence\": \"Dual-luciferase reporter assay, miRNA mimic/inhibitor, hippocampal electrophysiology and behavioral assays in a CUMS mouse model\",\n      \"pmids\": [\"30118321\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direction of TGF-\\u03b21 regulation (positive here) differs from fibrosis context\", \"Mechanism by which a secreted ECM protein modulates hippocampal signaling unresolved\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Positioned FBLN2 in cancer cell behavior as a downstream effector of AKT signaling that suppresses anoikis resistance, and as an ENS-secreted factor that can promote colorectal cancer migration.\",\n      \"evidence\": \"siRNA/overexpression with anoikis and xenograft assays; Ndrg4 knockout mice with organoid co-culture and proteomics\",\n      \"pmids\": [\"38332530\", \"33890711\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Opposing pro- and anti-tumor roles across tissues not reconciled\", \"No direct receptor or signaling intermediary identified\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Defined a vitronectin-FAK fibrosis axis and identified an Fbln2-marked profibrotic hepatic stellate cell subpopulation, connecting FBLN2 to TGF-\\u03b21-driven fibrogenesis.\",\n      \"evidence\": \"Reciprocal co-IP and rescue in fibroblasts; scRNA-seq with Lrat-Cre lineage tracing in alcoholic hepatitis\",\n      \"pmids\": [\"36608640\", \"36181700\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether the Fbln2+ HSC marker reflects a functional role for FBLN2 protein not established\", \"VTN-FAK mechanism not confirmed in vivo\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Demonstrated a developmental requirement for FBLN2 in craniofacial chondrogenesis via BMP signaling and a role in maintaining basal/myoepithelial mammary cell identity.\",\n      \"evidence\": \"CRISPR/Cas9 fbln2 knockout in zebrafish with BMP pathway analysis; siRNA in EpH4 mammary cells with marker readouts\",\n      \"pmids\": [\"38970771\", \"39110274\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How FBLN2 mechanistically activates BMP signaling unknown\", \"Mammary findings rest on marker expression only (Low confidence)\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Provided biochemical mechanism linking a cancer-associated splicing event to FBLN2 dysfunction, showing exon 9 exclusion removes an N-glycosylation site needed for folding and secretion, and identified the TGF\\u03b2/TGIF2 axis for its tumor-suppressive activity.\",\n      \"evidence\": \"Splicing/glycosylation/secretion assays with ECM analysis in colorectal cancer; FBLN2 knockout/overexpression with RNA-seq and KEGG in gastric cancer cells\",\n      \"pmids\": [\"40400104\", \"40168772\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural basis of misfolding not resolved\", \"Direct molecular target downstream of TGIF2 not defined\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Established Fbln2 as a regulator of epicardial activation in cardiac regeneration acting through Nupr1b, demonstrating genetic epistasis that balances fibrosis and regeneration after injury.\",\n      \"evidence\": \"Genetic dosage manipulation with epicardial-specific nupr1b overexpression rescue in zebrafish cardiac injury\",\n      \"pmids\": [\"41776059\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How secreted Fbln2 controls nuclear Nupr1b expression mechanistically unknown\", \"Conservation of the axis in mammalian heart untested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How a single secreted ECM glycoprotein produces opposing context-dependent outputs on TGF-\\u03b2 signaling and tumor behavior across tissues remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unifying receptor or signaling mechanism identified across contexts\", \"Domain-level structure-function mapping to specific signaling partners absent\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0005509\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0031012\", \"supporting_discovery_ids\": [7]},\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [2, 7]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1474244\", \"supporting_discovery_ids\": [7]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [3, 8, 9]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [5, 9]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"VTN\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}