{"gene":"HEG1","run_date":"2026-06-10T01:55:22","timeline":{"discoveries":[{"year":2013,"finding":"The KRIT1 FERM domain binds both Rap1 GTPase and the HEG1 cytoplasmic tail simultaneously; crystal structure of the KRIT1-Rap1-HEG1 ternary complex revealed that HEG1 binds in a hydrophobic pocket at the KRIT1 F1-F3 interface with no overlap with the Rap1-binding site (Kd ~1.2 µM), and Rap1 binds on the F1-F2 surface. A KRIT1(K570I) mutant with 8-fold reduced Rap1 affinity confirmed the specific ionic interaction between the F2 lobe and Rap1.","method":"Crystal structure of ternary complex, surface plasmon resonance / binding affinity measurements, mutagenesis (KRIT1 K570I)","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure plus mutagenesis plus quantitative binding assays in a single rigorous study","pmids":["23814056"],"is_preprint":false},{"year":2021,"finding":"A small-molecule inhibitor (HKi2) competes orthosterically with the HEG1 cytoplasmic tail for the KRIT1 FERM domain binding pocket; crystal structure of HKi2-KRIT1 FERM confirmed it occupies the same pocket as HEG1. Acute inhibition of the HEG1-KRIT1 interaction in human endothelial cells increased KLF4 and KLF2 mRNA and protein levels and triggered PI3K-dependent Akt phosphorylation.","method":"Crystal structure of inhibitor-KRIT1 complex, in vitro colocalization displacement assay, siRNA knockdown, pharmacological inhibition in endothelial cells, genome-wide RNA-seq, zebrafish in vivo reporter","journal":"FASEB bioAdvances","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure of inhibitor bound to KRIT1 FERM domain plus multiple orthogonal functional assays in one study","pmids":["33977234"],"is_preprint":false},{"year":2018,"finding":"Zebrafish Heg1 stabilizes Krit1 protein levels; Heg1 expression is positively regulated by blood flow; both Heg1 and Krit1 dampen expression of the mechanosensitive gene klf2a, and loss of Krit1 causes increased klf2a and notch1b expression throughout the endocardium, preventing cardiac valve leaflet formation.","method":"Zebrafish genetic loss-of-function (mutants/morpholinos), in vivo reporter assays for klf2a and notch1b, Western blot for Krit1 protein levels, blood-flow manipulation experiments","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis in zebrafish with multiple orthogonal readouts, replicated across multiple gene combinations","pmids":["29364115"],"is_preprint":false},{"year":2013,"finding":"Ccm2l (a novel CCM2 paralog) binds CCM1/KRIT1 directly, and CCM2 overexpression can partially rescue ccm2l morphant cardiovascular defects. Deletion and mutational analyses mapped the regions of CCM1 that mediate its binding to Ccm2l, CCM2, and HEG1, placing ccm2l as a component of the Heg-CCM pathway in cardiovascular development.","method":"Morpholino knockdown in zebrafish, genetic epistasis (morpholino co-injection), biochemical binding/deletion analysis (pulldown/Co-IP)","journal":"Developmental biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — epistasis in zebrafish plus biochemical interaction mapping, single lab","pmids":["23328253"],"is_preprint":false},{"year":2017,"finding":"HEG1 is a sialylated mucin-like membrane protein (~400 kDa); gene silencing of HEG1 significantly suppressed the survival and proliferation of mesothelioma cells, indicating HEG1 supports mesothelioma cell viability.","method":"siRNA gene silencing in mesothelioma cell lines, cell viability/proliferation assays, monoclonal antibody characterization (SKM9-2)","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function with defined cellular phenotype, single lab, two methods","pmids":["28361969"],"is_preprint":false},{"year":2018,"finding":"The SKM9-2 epitope on HEG1 was identified as the O-glycosylated region 893-SKSPSLVSLPT-903; the SKxPSxVS sequence is essential for antibody recognition. Mass spectrometry and lectin analysis showed the epitope contains two disialylated core 1 O-linked glycan-modified serine residues (Ser893 and Ser900), while Ser897 is not glycosylated.","method":"Truncated HEG1 binding assays, alanine scanning mutagenesis, mass spectrometry, lectin binding analysis, neuraminidase treatment","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 1 / Moderate — epitope mapped by mutagenesis plus mass spectrometry in a single rigorous study with multiple orthogonal methods","pmids":["30250045"],"is_preprint":false},{"year":2023,"finding":"Stable flow induces HEG1 mRNA and protein expression in endothelial cells, promotes HEG1 translocation to the downstream side of cells and release into the media. HEG1 knockdown prevents stable flow-induced KLF2/4 expression by regulating KRIT1 and the MEKK3-MEK5-ERK5-MEF2 pathway. Endothelial-specific HEG1 knockout mice develop exacerbated atherosclerotic plaques.","method":"siRNA knockdown in human aortic endothelial cells under defined flow conditions, endothelial-specific inducible knockout mice (HEG1iECKO), partial carotid ligation model, Western blot, qPCR, immunostaining","journal":"Circulation","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vitro mechanistic pathway dissection plus in vivo conditional knockout with multiple orthogonal readouts","pmids":["38099436"],"is_preprint":false},{"year":2025,"finding":"HEG1 regulates NO bioavailability via a flow-dependent direct interaction with eNOS (NOS3) in endothelial cells. Endothelial-specific Heg1 knockout mice develop spontaneous hypertension and severe atherosclerosis, both of which are prevented by ACE inhibition.","method":"Endothelial-specific Heg1 knockout mice, co-immunoprecipitation (HEG1-eNOS interaction), blood pressure monitoring, ACE inhibitor treatment","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — in vivo knockout plus co-IP for novel interaction, single preprint not yet peer-reviewed","pmids":["40667131"],"is_preprint":true},{"year":2026,"finding":"Endothelial HEG1 facilitates CUL3-mediated proteasomal degradation of PHACTR1. HEG1 deletion leads to increased PHACTR1 levels, its nuclear translocation, and suppression of SP1-mediated eNOS transcription and NO production, resulting in impaired vasodilation and hypertension.","method":"Endothelial-specific Heg1 deletion mice, proteomics, transcriptomics, ubiquitination assays, pharmacological PHACTR1 inhibition (CCG-1423), vascular function analysis","journal":"European heart journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ubiquitination assay plus transcriptomics plus rescue pharmacology in a single study, single lab","pmids":["40986512"],"is_preprint":false},{"year":2022,"finding":"Liver endothelial Heg deficiency reduces expression of Wnt ligands/agonists (Wnt2, Wnt9b, Rspo3) in endothelial cells, limiting Axin2-mediated canonical Wnt signaling and cytochrome P450 expression in hepatocytes, thereby altering liver metabolic zonation.","method":"Global (Heg-/-) and liver endothelial-specific (Lyve1-Cre;Hegfl/fl) conditional knockout mice, RNA-seq, histology, biochemical assays, 3D vascular network visualization","journal":"Cellular and molecular gastroenterology and hepatology","confidence":"High","confidence_rationale":"Tier 2 / Strong — two independent knockout models with pathway-level mechanistic dissection via RNA-seq and histological readouts","pmids":["35202885"],"is_preprint":false},{"year":2026,"finding":"Endothelial Heg1 deletion exacerbates hepatic steatosis under metabolic stress by downregulating BMP signaling, reducing Wnt2, Wnt9b, and Rspo3 expression in endothelial cells, which attenuates hepatocyte Wnt signaling, decreases PPARα and fatty acid oxidation enzyme expression. Restoration of RSPO3 in endothelial cells reversed the steatotic phenotype.","method":"Two endothelial-specific Heg1 knockout models, three liver disease models (HFD, MCD diet, alcohol), transcriptomics, lipidomics, RSPO3 conditional knock-in rescue, BMP activator treatment","journal":"Cellular and molecular gastroenterology and hepatology","confidence":"High","confidence_rationale":"Tier 2 / Strong — two independent KO models, rescue experiment (RSPO3 knock-in), pharmacological rescue, multiple disease models, single lab with multiple orthogonal methods","pmids":["42119921"],"is_preprint":false},{"year":2024,"finding":"Zebrafish Heg1 is dynamically localized at endothelial cell-cell junctions during anastomosis and is required for oscillatory actomyosin contractility along junctions. In heg1 and krit1 mutants, cell-cell interfaces become entangled due to lack of junctional actomyosin contractility, preventing continuous lumen formation; optogenetic RhoA activation restores junction straightening in mutants.","method":"Live imaging with Heg1 and Myosin reporters in zebrafish, CRISPR/Cas9 mutants, optogenetic RhoA activation, confocal microscopy","journal":"Angiogenesis","confidence":"High","confidence_rationale":"Tier 2 / Moderate — live imaging with multiple reporters in genetic mutants plus optogenetic rescue, multiple orthogonal approaches","pmids":["39249713"],"is_preprint":false},{"year":2025,"finding":"HEG1 stabilizes AKT1 by reducing its ubiquitination in gastric cancer cells, leading to sustained AKT signaling. The deubiquitinase USP48 directly interacts with HEG1 and stabilizes it by removing K48-linked polyubiquitin chains, preventing its proteasomal degradation.","method":"Immunoprecipitation, ubiquitination assays (K48-linked polyubiquitin chain analysis), siRNA/overexpression in gastric cancer cells, in vivo tumor xenograft, RNA-seq","journal":"European journal of medical research","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — Co-IP and ubiquitination assays from single lab with in vivo validation, but no structural or reconstitution data","pmids":["41013721"],"is_preprint":false},{"year":2025,"finding":"HEG1 protein is decorated with low-sulfated keratan sulfate (KS) O-glycans in malignant pleural mesothelioma; the KS modification is carried on the HEG1 core protein as demonstrated by western blot of HEG1·IgG recombinant fusion proteins secreted from KS-expressing cells, and sensitivity to endo-β-galactosidase and keratanase II but not PNGase F confirmed O-linked glycan attachment.","method":"Immunohistochemistry with endoglycosidase treatments, reversed-phase ion-pair HPLC disaccharide analysis, western blot of recombinant HEG1·IgG glycoforms","journal":"Pathology international","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — biochemical glycan characterization with recombinant protein and enzymatic validation, single lab","pmids":["40525709"],"is_preprint":false},{"year":2020,"finding":"HEG1 suppression in malignant mesothelioma cell lines reduces cell proliferation and induces apoptosis; microRNA-23b (miR-23b) acts downstream of HEG1 to support cell proliferation by suppressing apoptosis and autophagy (LC3-II induction). Combined inhibition of miR-23b and HEG1 showed additive antiproliferative effects.","method":"siRNA knockdown, miRNA inhibitor transfection in mesothelioma cell lines, MTS assay, Annexin V apoptosis assay, western blot (LC3-II)","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — loss-of-function with defined phenotypic readouts, single lab, functional pathway placement via miR-23b","pmids":["32284171"],"is_preprint":false}],"current_model":"HEG1 is a flow-sensitive, sialylated mucin-like transmembrane protein that acts as a membrane anchor recruiting KRIT1 (via its cytoplasmic tail binding the KRIT1 FERM domain simultaneously with Rap1) to endothelial junctions, where the HEG1-KRIT1 complex maintains junctional integrity, supports actomyosin contractility, dampens mechanosensitive KLF2/KLF4 expression via the MEKK3-MEK5-ERK5-MEF2 pathway, and regulates NO bioavailability through direct eNOS interaction and CUL3-mediated PHACTR1 degradation; in the liver, endothelial HEG1 sustains Wnt ligand (Wnt2/Wnt9b/Rspo3) production to regulate hepatocyte zonation and lipid metabolism, and in cancer cells HEG1 stabilizes AKT1 by reducing its ubiquitination in a process itself controlled by the deubiquitinase USP48."},"narrative":{"mechanistic_narrative":"HEG1 is a large sialylated, mucin-like transmembrane protein whose cytoplasmic tail functions as a membrane anchor for the CCM signaling machinery at endothelial cell-cell junctions, where it governs flow-responsive vascular homeostasis [PMID:23814056, PMID:38099436]. Its tail binds a hydrophobic pocket at the F1-F3 interface of the KRIT1 FERM domain, a site distinct from and non-overlapping with the adjacent Rap1 GTPase binding surface, allowing assembly of a KRIT1-Rap1-HEG1 ternary complex [PMID:23814056]; this interaction can be displaced orthosterically by a small molecule that occupies the same pocket [PMID:33977234], and KRIT1 further engages the CCM2 paralog Ccm2l within the Heg-CCM pathway during cardiovascular development [PMID:23328253]. Through this complex HEG1 stabilizes KRIT1 protein and dampens the mechanosensitive transcription factors KLF2/KLF4, acting via the MEKK3-MEK5-ERK5-MEF2 pathway, with HEG1 itself being transcriptionally and post-translationally induced by stable laminar flow [PMID:29364115, PMID:38099436]; loss of endothelial HEG1 derepresses KLF2/4 and exacerbates atherosclerosis [PMID:38099436]. At forming vessel junctions HEG1 drives oscillatory actomyosin contractility required for junction straightening and continuous lumen formation, a defect rescuable by optogenetic RhoA activation [PMID:39249713]. HEG1 additionally controls nitric oxide bioavailability through a flow-dependent interaction with eNOS and by promoting CUL3-mediated proteasomal degradation of PHACTR1, sustaining SP1-driven eNOS transcription; its endothelial loss causes hypertension and atherosclerosis [PMID:40667131, PMID:40986512]. In the liver, endothelial HEG1 sustains Wnt2/Wnt9b/Rspo3 ligand production to maintain hepatocyte canonical Wnt signaling, metabolic zonation, and protection from steatosis [PMID:35202885, PMID:42119921]. Distinct from its vascular roles, HEG1 is exploited in mesothelioma and gastric cancer, where it supports tumor cell viability and proliferation [PMID:28361969, PMID:32284171] and stabilizes AKT1 by reducing its ubiquitination, a function itself regulated by the deubiquitinase USP48 [PMID:41013721].","teleology":[{"year":2013,"claim":"Established the structural basis for how HEG1 couples to CCM signaling, showing its tail and Rap1 bind KRIT1 simultaneously rather than competitively.","evidence":"Crystal structure of the KRIT1-Rap1-HEG1 ternary complex with SPR affinity measurement and KRIT1(K570I) mutagenesis","pmids":["23814056"],"confidence":"High","gaps":["Does not address how the complex is regulated in cells","No demonstration of the functional consequence of complex assembly in vivo"]},{"year":2013,"claim":"Placed the CCM2 paralog Ccm2l within the Heg-CCM interaction network and mapped the KRIT1 regions binding each partner, expanding the molecular roster of the pathway.","evidence":"Zebrafish morpholino epistasis and biochemical deletion/pulldown mapping","pmids":["23328253"],"confidence":"Medium","gaps":["Morpholino-based, single lab","Direct HEG1-Ccm2l functional relationship not resolved"]},{"year":2017,"claim":"Identified HEG1 as a sialylated mucin-like protein supporting tumor cell viability, opening a cancer-relevant role distinct from its vascular function.","evidence":"siRNA silencing and viability assays in mesothelioma cell lines with monoclonal antibody characterization","pmids":["28361969"],"confidence":"Medium","gaps":["Molecular mechanism of viability support not defined in this study","Single tumor type"]},{"year":2018,"claim":"Demonstrated that HEG1 stabilizes KRIT1 protein and that the pair dampens flow-responsive klf2a, linking HEG1 to mechanosensitive gene control and cardiac valve formation.","evidence":"Zebrafish loss-of-function with klf2a/notch1b reporters, Western blot, and flow manipulation","pmids":["29364115"],"confidence":"High","gaps":["Downstream signaling pathway from KRIT1 to klf2a not dissected here","Mammalian validation absent in this study"]},{"year":2018,"claim":"Defined the O-glycosylated SKM9-2 epitope and its disialylated core-1 glycan structure, characterizing the post-translational decoration of HEG1.","evidence":"Truncation/alanine-scanning mutagenesis, mass spectrometry, lectin binding, and neuraminidase treatment","pmids":["30250045"],"confidence":"High","gaps":["Functional role of the glycosylation not established","Limited to the antibody epitope region"]},{"year":2020,"claim":"Connected HEG1 to a miR-23b-dependent anti-apoptotic, anti-autophagic axis sustaining mesothelioma proliferation.","evidence":"siRNA and miRNA-inhibitor transfection with proliferation, apoptosis, and LC3-II assays","pmids":["32284171"],"confidence":"Medium","gaps":["Mechanistic link between HEG1 and miR-23b unresolved","Single lab, cell-line only"]},{"year":2022,"claim":"Revealed a non-junctional paracrine role: liver endothelial HEG1 drives Wnt ligand production controlling hepatocyte Wnt signaling and metabolic zonation.","evidence":"Global and liver endothelial-specific knockout mice with RNA-seq, histology, and 3D vascular imaging","pmids":["35202885"],"confidence":"High","gaps":["How HEG1 controls Wnt ligand expression mechanistically is unclear","Junctional/CCM contribution to this role not separated"]},{"year":2023,"claim":"Established HEG1 as a flow-induced atheroprotective regulator acting through KRIT1 and the MEKK3-MEK5-ERK5-MEF2 pathway to restrain KLF2/4.","evidence":"Flow-chamber siRNA experiments in human aortic endothelial cells plus endothelial-specific knockout mice and carotid ligation","pmids":["38099436"],"confidence":"High","gaps":["Mechanism of HEG1 release into media not defined","Connection between HEG1 polarization and pathway activation incomplete"]},{"year":2024,"claim":"Showed HEG1 drives junctional actomyosin contractility needed for lumen formation, linking the complex to mechanical junction remodeling.","evidence":"Live imaging of Heg1/Myosin reporters in zebrafish CRISPR mutants with optogenetic RhoA rescue","pmids":["39249713"],"confidence":"High","gaps":["Molecular link from HEG1-KRIT1 to RhoA/actomyosin not defined","Mammalian confirmation absent"]},{"year":2025,"claim":"Implicated HEG1 in NO bioavailability via a direct flow-dependent eNOS interaction, connecting it to blood pressure control.","evidence":"Endothelial-specific knockout mice, HEG1-eNOS co-IP, blood pressure monitoring, ACE inhibition (preprint)","pmids":["40667131"],"confidence":"Medium","gaps":["Single co-IP without reciprocal/structural validation","Preprint not yet peer-reviewed","Mechanism by which HEG1 modulates eNOS activity unresolved"]},{"year":2025,"claim":"Identified a cancer mechanism whereby HEG1 stabilizes AKT1 by reducing its ubiquitination, with USP48 acting as the deubiquitinase stabilizing HEG1.","evidence":"Co-IP, K48-ubiquitination assays, knockdown/overexpression in gastric cancer cells, and xenografts","pmids":["41013721"],"confidence":"Medium","gaps":["No structural or reconstitution data","Whether HEG1 acts directly on AKT1 ubiquitination is unclear","Single lab"]},{"year":2025,"claim":"Characterized a malignancy-specific keratan sulfate O-glycan modification of the HEG1 core protein in mesothelioma.","evidence":"Immunohistochemistry with endoglycosidase treatments, HPLC disaccharide analysis, and recombinant HEG1·IgG glycoform Western blots","pmids":["40525709"],"confidence":"Medium","gaps":["Functional consequence of KS modification not established","Single lab biochemical study"]},{"year":2026,"claim":"Showed HEG1 promotes CUL3-mediated PHACTR1 degradation to sustain SP1-driven eNOS transcription, providing a transcriptional route to NO control and hypertension protection.","evidence":"Endothelial-specific knockout mice, proteomics/transcriptomics, ubiquitination assays, and PHACTR1 pharmacological inhibition","pmids":["40986512"],"confidence":"Medium","gaps":["Direct HEG1 role in the CUL3-PHACTR1 ubiquitination machinery not structurally defined","Relationship to the direct eNOS interaction pathway not integrated"]},{"year":2026,"claim":"Extended the liver paracrine axis, showing endothelial HEG1 protects against steatosis via BMP signaling and Wnt2/Wnt9b/Rspo3-dependent hepatocyte fatty-acid oxidation, with RSPO3 restoration sufficient for rescue.","evidence":"Two endothelial knockout models across three liver disease models with transcriptomics, lipidomics, RSPO3 knock-in rescue, and BMP activator treatment","pmids":["42119921"],"confidence":"High","gaps":["Upstream control of BMP signaling by HEG1 unresolved","Connection to CCM/junctional functions not delineated"]},{"year":null,"claim":"How HEG1's molecular activities are partitioned between its junctional CCM-anchoring role, its paracrine Wnt-ligand-supporting role, and its tumor-intrinsic AKT-stabilizing role within a single protein remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unifying mechanism linking the vascular, hepatic, and oncogenic functions","Role and regulation of the extensive O-glycosylation in signaling is undefined","No mammalian structural data on HEG1 tail function beyond the KRIT1 interface"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,6]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[4,13]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,6,11]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,6,9]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[2,11]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[8,12]}],"complexes":["KRIT1-Rap1-HEG1 ternary complex"],"partners":["KRIT1","RAP1","CCM2L","NOS3","USP48","PHACTR1","AKT1","CUL3"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9ULI3","full_name":"Protein HEG homolog 1","aliases":[],"length_aa":1381,"mass_kda":147.5,"function":"Receptor component of the CCM signaling pathway which is a crucial regulator of heart and vessel formation and integrity. May act through the stabilization of endothelial cell junctions","subcellular_location":"Secreted","url":"https://www.uniprot.org/uniprotkb/Q9ULI3/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/HEG1","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/HEG1","total_profiled":1310},"omim":[{"mim_id":"614182","title":"HEART DEVELOPMENT PROTEIN WITH EGF-LIKE DOMAINS 1; HEG1","url":"https://www.omim.org/entry/614182"},{"mim_id":"607929","title":"CCM2 SCAFFOLD PROTEIN; CCM2","url":"https://www.omim.org/entry/607929"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Vesicles","reliability":"Approved"},{"location":"Plasma membrane","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/HEG1"},"hgnc":{"alias_symbol":["KIAA1237","HEG"],"prev_symbol":[]},"alphafold":{"accession":"Q9ULI3","domains":[{"cath_id":"2.10.25.10","chopping":"989-1027","consensus_level":"medium","plddt":84.5272,"start":989,"end":1027},{"cath_id":"-","chopping":"1035-1065","consensus_level":"medium","plddt":88.0529,"start":1035,"end":1065},{"cath_id":"3.30.300","chopping":"1068-1175","consensus_level":"medium","plddt":78.5433,"start":1068,"end":1175},{"cath_id":"-","chopping":"1180-1248","consensus_level":"medium","plddt":74.7106,"start":1180,"end":1248}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9ULI3","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9ULI3-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9ULI3-F1-predicted_aligned_error_v6.png","plddt_mean":42.25},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=HEG1","jax_strain_url":"https://www.jax.org/strain/search?query=HEG1"},"sequence":{"accession":"Q9ULI3","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9ULI3.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9ULI3/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9ULI3"}},"corpus_meta":[{"pmid":"17933767","id":"PMC_17933767","title":"HEG-DB: a database of predicted highly expressed genes in prokaryotic complete genomes under translational selection.","date":"2007","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/17933767","citation_count":66,"is_preprint":false},{"pmid":"28361969","id":"PMC_28361969","title":"HEG1 is a novel mucin-like membrane protein that serves as a diagnostic and therapeutic target for malignant mesothelioma.","date":"2017","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/28361969","citation_count":54,"is_preprint":false},{"pmid":"29364115","id":"PMC_29364115","title":"Heg1 and Ccm1/2 proteins control endocardial mechanosensitivity during zebrafish valvulogenesis.","date":"2018","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/29364115","citation_count":50,"is_preprint":false},{"pmid":"25703932","id":"PMC_25703932","title":"Hericium erinaceus polysaccharide-protein HEG-5 inhibits SGC-7901 cell growth via cell cycle arrest and 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hepatology","url":"https://pubmed.ncbi.nlm.nih.gov/42119921","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":20771,"output_tokens":4143,"usd":0.062229,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":11943,"output_tokens":4455,"usd":0.085545,"stage2_stop_reason":"end_turn"},"total_usd":0.147774,"stage1_batch_id":"msgbatch_01DUPACZi7AAWwuZiUjseQF4","stage2_batch_id":"msgbatch_018yt7chE3f48PEFtDwtj6AE","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2013,\n      \"finding\": \"The KRIT1 FERM domain binds both Rap1 GTPase and the HEG1 cytoplasmic tail simultaneously; crystal structure of the KRIT1-Rap1-HEG1 ternary complex revealed that HEG1 binds in a hydrophobic pocket at the KRIT1 F1-F3 interface with no overlap with the Rap1-binding site (Kd ~1.2 µM), and Rap1 binds on the F1-F2 surface. A KRIT1(K570I) mutant with 8-fold reduced Rap1 affinity confirmed the specific ionic interaction between the F2 lobe and Rap1.\",\n      \"method\": \"Crystal structure of ternary complex, surface plasmon resonance / binding affinity measurements, mutagenesis (KRIT1 K570I)\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure plus mutagenesis plus quantitative binding assays in a single rigorous study\",\n      \"pmids\": [\"23814056\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"A small-molecule inhibitor (HKi2) competes orthosterically with the HEG1 cytoplasmic tail for the KRIT1 FERM domain binding pocket; crystal structure of HKi2-KRIT1 FERM confirmed it occupies the same pocket as HEG1. Acute inhibition of the HEG1-KRIT1 interaction in human endothelial cells increased KLF4 and KLF2 mRNA and protein levels and triggered PI3K-dependent Akt phosphorylation.\",\n      \"method\": \"Crystal structure of inhibitor-KRIT1 complex, in vitro colocalization displacement assay, siRNA knockdown, pharmacological inhibition in endothelial cells, genome-wide RNA-seq, zebrafish in vivo reporter\",\n      \"journal\": \"FASEB bioAdvances\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure of inhibitor bound to KRIT1 FERM domain plus multiple orthogonal functional assays in one study\",\n      \"pmids\": [\"33977234\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Zebrafish Heg1 stabilizes Krit1 protein levels; Heg1 expression is positively regulated by blood flow; both Heg1 and Krit1 dampen expression of the mechanosensitive gene klf2a, and loss of Krit1 causes increased klf2a and notch1b expression throughout the endocardium, preventing cardiac valve leaflet formation.\",\n      \"method\": \"Zebrafish genetic loss-of-function (mutants/morpholinos), in vivo reporter assays for klf2a and notch1b, Western blot for Krit1 protein levels, blood-flow manipulation experiments\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis in zebrafish with multiple orthogonal readouts, replicated across multiple gene combinations\",\n      \"pmids\": [\"29364115\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Ccm2l (a novel CCM2 paralog) binds CCM1/KRIT1 directly, and CCM2 overexpression can partially rescue ccm2l morphant cardiovascular defects. Deletion and mutational analyses mapped the regions of CCM1 that mediate its binding to Ccm2l, CCM2, and HEG1, placing ccm2l as a component of the Heg-CCM pathway in cardiovascular development.\",\n      \"method\": \"Morpholino knockdown in zebrafish, genetic epistasis (morpholino co-injection), biochemical binding/deletion analysis (pulldown/Co-IP)\",\n      \"journal\": \"Developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — epistasis in zebrafish plus biochemical interaction mapping, single lab\",\n      \"pmids\": [\"23328253\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"HEG1 is a sialylated mucin-like membrane protein (~400 kDa); gene silencing of HEG1 significantly suppressed the survival and proliferation of mesothelioma cells, indicating HEG1 supports mesothelioma cell viability.\",\n      \"method\": \"siRNA gene silencing in mesothelioma cell lines, cell viability/proliferation assays, monoclonal antibody characterization (SKM9-2)\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function with defined cellular phenotype, single lab, two methods\",\n      \"pmids\": [\"28361969\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"The SKM9-2 epitope on HEG1 was identified as the O-glycosylated region 893-SKSPSLVSLPT-903; the SKxPSxVS sequence is essential for antibody recognition. Mass spectrometry and lectin analysis showed the epitope contains two disialylated core 1 O-linked glycan-modified serine residues (Ser893 and Ser900), while Ser897 is not glycosylated.\",\n      \"method\": \"Truncated HEG1 binding assays, alanine scanning mutagenesis, mass spectrometry, lectin binding analysis, neuraminidase treatment\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — epitope mapped by mutagenesis plus mass spectrometry in a single rigorous study with multiple orthogonal methods\",\n      \"pmids\": [\"30250045\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Stable flow induces HEG1 mRNA and protein expression in endothelial cells, promotes HEG1 translocation to the downstream side of cells and release into the media. HEG1 knockdown prevents stable flow-induced KLF2/4 expression by regulating KRIT1 and the MEKK3-MEK5-ERK5-MEF2 pathway. Endothelial-specific HEG1 knockout mice develop exacerbated atherosclerotic plaques.\",\n      \"method\": \"siRNA knockdown in human aortic endothelial cells under defined flow conditions, endothelial-specific inducible knockout mice (HEG1iECKO), partial carotid ligation model, Western blot, qPCR, immunostaining\",\n      \"journal\": \"Circulation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vitro mechanistic pathway dissection plus in vivo conditional knockout with multiple orthogonal readouts\",\n      \"pmids\": [\"38099436\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"HEG1 regulates NO bioavailability via a flow-dependent direct interaction with eNOS (NOS3) in endothelial cells. Endothelial-specific Heg1 knockout mice develop spontaneous hypertension and severe atherosclerosis, both of which are prevented by ACE inhibition.\",\n      \"method\": \"Endothelial-specific Heg1 knockout mice, co-immunoprecipitation (HEG1-eNOS interaction), blood pressure monitoring, ACE inhibitor treatment\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — in vivo knockout plus co-IP for novel interaction, single preprint not yet peer-reviewed\",\n      \"pmids\": [\"40667131\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"Endothelial HEG1 facilitates CUL3-mediated proteasomal degradation of PHACTR1. HEG1 deletion leads to increased PHACTR1 levels, its nuclear translocation, and suppression of SP1-mediated eNOS transcription and NO production, resulting in impaired vasodilation and hypertension.\",\n      \"method\": \"Endothelial-specific Heg1 deletion mice, proteomics, transcriptomics, ubiquitination assays, pharmacological PHACTR1 inhibition (CCG-1423), vascular function analysis\",\n      \"journal\": \"European heart journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ubiquitination assay plus transcriptomics plus rescue pharmacology in a single study, single lab\",\n      \"pmids\": [\"40986512\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Liver endothelial Heg deficiency reduces expression of Wnt ligands/agonists (Wnt2, Wnt9b, Rspo3) in endothelial cells, limiting Axin2-mediated canonical Wnt signaling and cytochrome P450 expression in hepatocytes, thereby altering liver metabolic zonation.\",\n      \"method\": \"Global (Heg-/-) and liver endothelial-specific (Lyve1-Cre;Hegfl/fl) conditional knockout mice, RNA-seq, histology, biochemical assays, 3D vascular network visualization\",\n      \"journal\": \"Cellular and molecular gastroenterology and hepatology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — two independent knockout models with pathway-level mechanistic dissection via RNA-seq and histological readouts\",\n      \"pmids\": [\"35202885\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"Endothelial Heg1 deletion exacerbates hepatic steatosis under metabolic stress by downregulating BMP signaling, reducing Wnt2, Wnt9b, and Rspo3 expression in endothelial cells, which attenuates hepatocyte Wnt signaling, decreases PPARα and fatty acid oxidation enzyme expression. Restoration of RSPO3 in endothelial cells reversed the steatotic phenotype.\",\n      \"method\": \"Two endothelial-specific Heg1 knockout models, three liver disease models (HFD, MCD diet, alcohol), transcriptomics, lipidomics, RSPO3 conditional knock-in rescue, BMP activator treatment\",\n      \"journal\": \"Cellular and molecular gastroenterology and hepatology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — two independent KO models, rescue experiment (RSPO3 knock-in), pharmacological rescue, multiple disease models, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"42119921\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Zebrafish Heg1 is dynamically localized at endothelial cell-cell junctions during anastomosis and is required for oscillatory actomyosin contractility along junctions. In heg1 and krit1 mutants, cell-cell interfaces become entangled due to lack of junctional actomyosin contractility, preventing continuous lumen formation; optogenetic RhoA activation restores junction straightening in mutants.\",\n      \"method\": \"Live imaging with Heg1 and Myosin reporters in zebrafish, CRISPR/Cas9 mutants, optogenetic RhoA activation, confocal microscopy\",\n      \"journal\": \"Angiogenesis\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — live imaging with multiple reporters in genetic mutants plus optogenetic rescue, multiple orthogonal approaches\",\n      \"pmids\": [\"39249713\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"HEG1 stabilizes AKT1 by reducing its ubiquitination in gastric cancer cells, leading to sustained AKT signaling. The deubiquitinase USP48 directly interacts with HEG1 and stabilizes it by removing K48-linked polyubiquitin chains, preventing its proteasomal degradation.\",\n      \"method\": \"Immunoprecipitation, ubiquitination assays (K48-linked polyubiquitin chain analysis), siRNA/overexpression in gastric cancer cells, in vivo tumor xenograft, RNA-seq\",\n      \"journal\": \"European journal of medical research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — Co-IP and ubiquitination assays from single lab with in vivo validation, but no structural or reconstitution data\",\n      \"pmids\": [\"41013721\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"HEG1 protein is decorated with low-sulfated keratan sulfate (KS) O-glycans in malignant pleural mesothelioma; the KS modification is carried on the HEG1 core protein as demonstrated by western blot of HEG1·IgG recombinant fusion proteins secreted from KS-expressing cells, and sensitivity to endo-β-galactosidase and keratanase II but not PNGase F confirmed O-linked glycan attachment.\",\n      \"method\": \"Immunohistochemistry with endoglycosidase treatments, reversed-phase ion-pair HPLC disaccharide analysis, western blot of recombinant HEG1·IgG glycoforms\",\n      \"journal\": \"Pathology international\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — biochemical glycan characterization with recombinant protein and enzymatic validation, single lab\",\n      \"pmids\": [\"40525709\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"HEG1 suppression in malignant mesothelioma cell lines reduces cell proliferation and induces apoptosis; microRNA-23b (miR-23b) acts downstream of HEG1 to support cell proliferation by suppressing apoptosis and autophagy (LC3-II induction). Combined inhibition of miR-23b and HEG1 showed additive antiproliferative effects.\",\n      \"method\": \"siRNA knockdown, miRNA inhibitor transfection in mesothelioma cell lines, MTS assay, Annexin V apoptosis assay, western blot (LC3-II)\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — loss-of-function with defined phenotypic readouts, single lab, functional pathway placement via miR-23b\",\n      \"pmids\": [\"32284171\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"HEG1 is a flow-sensitive, sialylated mucin-like transmembrane protein that acts as a membrane anchor recruiting KRIT1 (via its cytoplasmic tail binding the KRIT1 FERM domain simultaneously with Rap1) to endothelial junctions, where the HEG1-KRIT1 complex maintains junctional integrity, supports actomyosin contractility, dampens mechanosensitive KLF2/KLF4 expression via the MEKK3-MEK5-ERK5-MEF2 pathway, and regulates NO bioavailability through direct eNOS interaction and CUL3-mediated PHACTR1 degradation; in the liver, endothelial HEG1 sustains Wnt ligand (Wnt2/Wnt9b/Rspo3) production to regulate hepatocyte zonation and lipid metabolism, and in cancer cells HEG1 stabilizes AKT1 by reducing its ubiquitination in a process itself controlled by the deubiquitinase USP48.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"HEG1 is a large sialylated, mucin-like transmembrane protein whose cytoplasmic tail functions as a membrane anchor for the CCM signaling machinery at endothelial cell-cell junctions, where it governs flow-responsive vascular homeostasis [#0, #6]. Its tail binds a hydrophobic pocket at the F1-F3 interface of the KRIT1 FERM domain, a site distinct from and non-overlapping with the adjacent Rap1 GTPase binding surface, allowing assembly of a KRIT1-Rap1-HEG1 ternary complex [#0]; this interaction can be displaced orthosterically by a small molecule that occupies the same pocket [#1], and KRIT1 further engages the CCM2 paralog Ccm2l within the Heg-CCM pathway during cardiovascular development [#3]. Through this complex HEG1 stabilizes KRIT1 protein and dampens the mechanosensitive transcription factors KLF2/KLF4, acting via the MEKK3-MEK5-ERK5-MEF2 pathway, with HEG1 itself being transcriptionally and post-translationally induced by stable laminar flow [#2, #6]; loss of endothelial HEG1 derepresses KLF2/4 and exacerbates atherosclerosis [#6]. At forming vessel junctions HEG1 drives oscillatory actomyosin contractility required for junction straightening and continuous lumen formation, a defect rescuable by optogenetic RhoA activation [#11]. HEG1 additionally controls nitric oxide bioavailability through a flow-dependent interaction with eNOS and by promoting CUL3-mediated proteasomal degradation of PHACTR1, sustaining SP1-driven eNOS transcription; its endothelial loss causes hypertension and atherosclerosis [#7, #8]. In the liver, endothelial HEG1 sustains Wnt2/Wnt9b/Rspo3 ligand production to maintain hepatocyte canonical Wnt signaling, metabolic zonation, and protection from steatosis [#9, #10]. Distinct from its vascular roles, HEG1 is exploited in mesothelioma and gastric cancer, where it supports tumor cell viability and proliferation [#4, #14] and stabilizes AKT1 by reducing its ubiquitination, a function itself regulated by the deubiquitinase USP48 [#12].\",\n  \"teleology\": [\n    {\n      \"year\": 2013,\n      \"claim\": \"Established the structural basis for how HEG1 couples to CCM signaling, showing its tail and Rap1 bind KRIT1 simultaneously rather than competitively.\",\n      \"evidence\": \"Crystal structure of the KRIT1-Rap1-HEG1 ternary complex with SPR affinity measurement and KRIT1(K570I) mutagenesis\",\n      \"pmids\": [\"23814056\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not address how the complex is regulated in cells\", \"No demonstration of the functional consequence of complex assembly in vivo\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Placed the CCM2 paralog Ccm2l within the Heg-CCM interaction network and mapped the KRIT1 regions binding each partner, expanding the molecular roster of the pathway.\",\n      \"evidence\": \"Zebrafish morpholino epistasis and biochemical deletion/pulldown mapping\",\n      \"pmids\": [\"23328253\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Morpholino-based, single lab\", \"Direct HEG1-Ccm2l functional relationship not resolved\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Identified HEG1 as a sialylated mucin-like protein supporting tumor cell viability, opening a cancer-relevant role distinct from its vascular function.\",\n      \"evidence\": \"siRNA silencing and viability assays in mesothelioma cell lines with monoclonal antibody characterization\",\n      \"pmids\": [\"28361969\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular mechanism of viability support not defined in this study\", \"Single tumor type\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Demonstrated that HEG1 stabilizes KRIT1 protein and that the pair dampens flow-responsive klf2a, linking HEG1 to mechanosensitive gene control and cardiac valve formation.\",\n      \"evidence\": \"Zebrafish loss-of-function with klf2a/notch1b reporters, Western blot, and flow manipulation\",\n      \"pmids\": [\"29364115\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Downstream signaling pathway from KRIT1 to klf2a not dissected here\", \"Mammalian validation absent in this study\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Defined the O-glycosylated SKM9-2 epitope and its disialylated core-1 glycan structure, characterizing the post-translational decoration of HEG1.\",\n      \"evidence\": \"Truncation/alanine-scanning mutagenesis, mass spectrometry, lectin binding, and neuraminidase treatment\",\n      \"pmids\": [\"30250045\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional role of the glycosylation not established\", \"Limited to the antibody epitope region\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Connected HEG1 to a miR-23b-dependent anti-apoptotic, anti-autophagic axis sustaining mesothelioma proliferation.\",\n      \"evidence\": \"siRNA and miRNA-inhibitor transfection with proliferation, apoptosis, and LC3-II assays\",\n      \"pmids\": [\"32284171\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanistic link between HEG1 and miR-23b unresolved\", \"Single lab, cell-line only\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Revealed a non-junctional paracrine role: liver endothelial HEG1 drives Wnt ligand production controlling hepatocyte Wnt signaling and metabolic zonation.\",\n      \"evidence\": \"Global and liver endothelial-specific knockout mice with RNA-seq, histology, and 3D vascular imaging\",\n      \"pmids\": [\"35202885\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How HEG1 controls Wnt ligand expression mechanistically is unclear\", \"Junctional/CCM contribution to this role not separated\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Established HEG1 as a flow-induced atheroprotective regulator acting through KRIT1 and the MEKK3-MEK5-ERK5-MEF2 pathway to restrain KLF2/4.\",\n      \"evidence\": \"Flow-chamber siRNA experiments in human aortic endothelial cells plus endothelial-specific knockout mice and carotid ligation\",\n      \"pmids\": [\"38099436\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of HEG1 release into media not defined\", \"Connection between HEG1 polarization and pathway activation incomplete\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Showed HEG1 drives junctional actomyosin contractility needed for lumen formation, linking the complex to mechanical junction remodeling.\",\n      \"evidence\": \"Live imaging of Heg1/Myosin reporters in zebrafish CRISPR mutants with optogenetic RhoA rescue\",\n      \"pmids\": [\"39249713\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular link from HEG1-KRIT1 to RhoA/actomyosin not defined\", \"Mammalian confirmation absent\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Implicated HEG1 in NO bioavailability via a direct flow-dependent eNOS interaction, connecting it to blood pressure control.\",\n      \"evidence\": \"Endothelial-specific knockout mice, HEG1-eNOS co-IP, blood pressure monitoring, ACE inhibition (preprint)\",\n      \"pmids\": [\"40667131\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single co-IP without reciprocal/structural validation\", \"Preprint not yet peer-reviewed\", \"Mechanism by which HEG1 modulates eNOS activity unresolved\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identified a cancer mechanism whereby HEG1 stabilizes AKT1 by reducing its ubiquitination, with USP48 acting as the deubiquitinase stabilizing HEG1.\",\n      \"evidence\": \"Co-IP, K48-ubiquitination assays, knockdown/overexpression in gastric cancer cells, and xenografts\",\n      \"pmids\": [\"41013721\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural or reconstitution data\", \"Whether HEG1 acts directly on AKT1 ubiquitination is unclear\", \"Single lab\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Characterized a malignancy-specific keratan sulfate O-glycan modification of the HEG1 core protein in mesothelioma.\",\n      \"evidence\": \"Immunohistochemistry with endoglycosidase treatments, HPLC disaccharide analysis, and recombinant HEG1·IgG glycoform Western blots\",\n      \"pmids\": [\"40525709\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of KS modification not established\", \"Single lab biochemical study\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Showed HEG1 promotes CUL3-mediated PHACTR1 degradation to sustain SP1-driven eNOS transcription, providing a transcriptional route to NO control and hypertension protection.\",\n      \"evidence\": \"Endothelial-specific knockout mice, proteomics/transcriptomics, ubiquitination assays, and PHACTR1 pharmacological inhibition\",\n      \"pmids\": [\"40986512\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct HEG1 role in the CUL3-PHACTR1 ubiquitination machinery not structurally defined\", \"Relationship to the direct eNOS interaction pathway not integrated\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Extended the liver paracrine axis, showing endothelial HEG1 protects against steatosis via BMP signaling and Wnt2/Wnt9b/Rspo3-dependent hepatocyte fatty-acid oxidation, with RSPO3 restoration sufficient for rescue.\",\n      \"evidence\": \"Two endothelial knockout models across three liver disease models with transcriptomics, lipidomics, RSPO3 knock-in rescue, and BMP activator treatment\",\n      \"pmids\": [\"42119921\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Upstream control of BMP signaling by HEG1 unresolved\", \"Connection to CCM/junctional functions not delineated\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How HEG1's molecular activities are partitioned between its junctional CCM-anchoring role, its paracrine Wnt-ligand-supporting role, and its tumor-intrinsic AKT-stabilizing role within a single protein remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unifying mechanism linking the vascular, hepatic, and oncogenic functions\", \"Role and regulation of the extensive O-glycosylation in signaling is undefined\", \"No mammalian structural data on HEG1 tail function beyond the KRIT1 interface\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 6]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [4, 13]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 6, 11]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 6, 9]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [2, 11]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [8, 12]}\n    ],\n    \"complexes\": [\"KRIT1-Rap1-HEG1 ternary complex\"],\n    \"partners\": [\"KRIT1\", \"RAP1\", \"CCM2L\", \"NOS3\", \"USP48\", \"PHACTR1\", \"AKT1\", \"CUL3\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}