{"gene":"KRIT1","run_date":"2026-06-10T02:59:49","timeline":{"discoveries":[{"year":1999,"finding":"KRIT1 protein physically interacts with RAP1A (Krev-1/rap1a), a member of the RAS family of GTPases; truncating mutations in CCM1/KRIT1 cause hereditary cavernous angiomas, implicating the RAP1A signal transduction pathway in vasculogenesis/angiogenesis.","method":"Yeast two-hybrid interaction (previously established); positional cloning and mutation identification in CCM1 families","journal":"Nature genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — interaction with RAP1A confirmed across multiple independent labs (PMID:10508515, PMID:10545614), replicated by subsequent structural and biochemical studies","pmids":["10508515","10545614"],"is_preprint":false},{"year":2002,"finding":"KRIT1 colocalizes with microtubules in interphase cells and localizes to spindle pole bodies, mitotic spindle, and microtubule plus ends during mitosis; coimmunoprecipitation confirmed KRIT1 association with microtubules, establishing KRIT1 as a microtubule-associated protein.","method":"Immunofluorescence microscopy with anti-KRIT1 antibodies; coimmunoprecipitation from endothelial cells","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal coimmunoprecipitation plus microscopy in a single lab; not independently replicated","pmids":["12140362"],"is_preprint":false},{"year":2002,"finding":"KRIT1 physically interacts with ICAP-1 (integrin cytoplasmic domain-associated protein-1); interaction is mediated by the N-terminal NPXY motif of KRIT1, and mutagenesis of this motif abrogates binding; ICAP-1 is a known β1 integrin cytoplasmic tail binder, suggesting KRIT1 participates in integrin–cytoskeleton signaling.","method":"Yeast two-hybrid screen of human fetal brain and HeLa cDNA libraries; GST-KRIT1 pulldown of endogenous ICAP-1 from 293T cells; site-directed mutagenesis of NPXY motif","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — GST pulldown with mutagenesis confirmation; replicated by multiple subsequent studies","pmids":["11854171"],"is_preprint":false},{"year":2005,"finding":"KRIT1 (CCM1) interacts with CCM2 (malcavernin/OSM) protein; this interaction is dependent on the phosphotyrosine binding (PTB) domain of CCM2 and the NPXY motif of CCM1; a familial CCM2 missense mutation abrogates this interaction; CCM1 associates with CCM2 and MEKK3 in a ternary complex; CCM2 and ICAP-1 differentially influence CCM1 subcellular localization.","method":"Coimmunoprecipitation; fluorescence resonance energy transfer (FRET); subcellular localization assays; analysis of disease-associated CCM2 missense mutation","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP plus FRET, replicated in subsequent studies; multiple orthogonal methods in single lab","pmids":["16037064"],"is_preprint":false},{"year":2007,"finding":"KRIT1 is expressed in endothelial cells and localizes to cell-cell junctions via its FERM domain; Rap1 GTPase activity regulates the junctional localization of KRIT1 and its physical association with junctional proteins; siRNA depletion of KRIT1 blocked Rap1-mediated stabilization of endothelial junctions and was associated with increased actin stress fibers, establishing KRIT1 as a Rap1 effector at endothelial junctions.","method":"Immunofluorescence localization; coimmunoprecipitation; siRNA knockdown with functional readout (junction stability, actin stress fibers); domain mapping with isolated FERM domain","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, localization, domain analysis, and siRNA phenotype; multiple orthogonal methods in single study","pmids":["17954608"],"is_preprint":false},{"year":2007,"finding":"KRIT1 (krit1) interacts with CCM2 (malcavernin) through two of the three NPXY motifs in KRIT1; CCM2 protein shuttles between nucleus and cytoplasm; KRIT1 co-localizes with ICAP-1 in both nucleus and cytoplasm, and KRIT1 depletion causes loss of ICAP-1 from cytoplasm and nucleus, suggesting KRIT1 stabilizes and shuttles ICAP-1.","method":"Yeast two-hybrid; coimmunoprecipitation; epitope mapping; immunocytochemistry; siRNA knockdown","journal":"Neurosurgery","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple methods (Y2H, Co-IP, imaging), single lab","pmids":["17290187"],"is_preprint":false},{"year":2008,"finding":"Loss of ccm1 in zebrafish leads to progressive dilation of major vessels due to cell-autonomous spreading of endothelial cells and thinning of vessel walls, with ultrastructurally normal cell-cell contacts; rescue experiments confirmed cell-autonomous function of ccm1 in endothelial morphogenesis.","method":"Zebrafish genetic loss-of-function; chimeric transplantation experiments establishing cell autonomy; electron microscopy","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic loss-of-function with cell autonomy rescue, multiple readouts","pmids":["18469344"],"is_preprint":false},{"year":2009,"finding":"KRIT1/CCM1, acting downstream of Rap1 GTPase, negatively regulates canonical β-catenin signaling in endothelial cells; KRIT1 depletion causes β-catenin to dissociate from VE-cadherin and accumulate in the nucleus with increased β-catenin-dependent transcription; Rap1 activation inhibits β-catenin transcription in a manner dependent on intact cell-cell junctions and KRIT1; hemizygous Krit1 deficiency in Apc(Min/+) mice increased intestinal polyp burden.","method":"siRNA knockdown; nuclear fractionation; transcriptional reporter assays; in vivo Krit1(+/-) × Apc(Min/+) mouse epistasis","journal":"Disease models & mechanisms","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vitro knockdown with pathway readout plus in vivo genetic epistasis, multiple orthogonal methods","pmids":["20007487"],"is_preprint":false},{"year":2010,"finding":"CCM1 (KRIT1) induces DLL4-NOTCH signaling in endothelial cells, inhibiting sprouting angiogenesis; CCM1 promotes AKT phosphorylation but reduces ERK phosphorylation; blocking NOTCH activity alleviates CCM1 effects; CCM1 silencing in human endothelial cells transplanted into SCID mice recapitulates CCM pathology.","method":"siRNA knockdown; western blotting; NOTCH pharmacological inhibition; SCID mouse xenograft model; ERK/AKT phosphorylation assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vitro and in vivo loss-of-function with pathway rescue, multiple orthogonal methods","pmids":["20616044"],"is_preprint":false},{"year":2010,"finding":"CCM1 (KRIT1) interacts with VE-cadherin and is required for proper adherens junction (AJ) organization and AJ association with the Par polarity complex (Par3 and PKCζ); CCM1 and VE-cadherin control Rap1 concentration at cell-cell junctions; loss of CCM1 leads to loss of endothelial apicobasal polarity and severe alterations in vascular lumen structure.","method":"Coimmunoprecipitation; siRNA knockdown; immunofluorescence; PKCζ activation assays; analysis of human CCM1 lesions","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 / Strong — Co-IP, siRNA, functional polarity assay, human tissue validation; multiple orthogonal methods","pmids":["20332120"],"is_preprint":false},{"year":2010,"finding":"KRIT1 loss/down-regulation increases intracellular ROS levels and decreases expression of antioxidant protein SOD2 and transcription factor FoxO1; restoration of KRIT1 expression dose-dependently reduces ROS levels; KRIT1-dependent low ROS levels facilitate downregulation of cyclin D1 for cell quiescence; KRIT1 loss increases susceptibility to oxidative DNA damage and induces Gadd45α and declines mitochondrial metabolism.","method":"ROS measurement assays; western blotting; KRIT1 reconstitution in knockout cells; cyclin D1 expression analysis; Gadd45α induction; mitochondrial metabolism assays","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple assays, KO rescue approach, single lab","pmids":["20668652"],"is_preprint":false},{"year":2012,"finding":"Crystal structure of KRIT1 FERM domain in complex with Rap1 determined at 1.95 Å; Rap1-KRIT1 interaction spans an extended surface including Rap1 Switch I and II and KRIT1 FERM F1 and F2 lobes; Rap1 binds KRIT1-F1 via a GTPase-ubiquitin-like fold interaction and KRIT1-F2 via a novel interaction; point mutagenesis confirms the interaction surface; KRIT1 FERM domain is structurally similar to talin.","method":"Co-crystal structure determination (1.95 Å resolution); point mutagenesis; structural comparison","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — high-resolution co-crystal structure with mutagenesis validation","pmids":["22577140"],"is_preprint":false},{"year":2013,"finding":"KRIT1 functions as a switch for β1 integrin activation by antagonizing ICAP1-mediated inside-out activation; co-crystal structures of KRIT1 with ICAP1 (2.54 Å) and ICAP1 with integrin β1 cytoplasmic tail (3.0 Å) show that KRIT1 binds ICAP1 by a bidentate surface that directly competes with integrin β1; KRIT1 contains an N-terminal Nudix domain in a region previously thought to be unstructured.","method":"Co-crystal structure determination (2.54 Å and 3.0 Å); in vitro competition binding assays; integrin activation assay; structural mutagenesis","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — two co-crystal structures with functional competition assay validation","pmids":["23317506"],"is_preprint":false},{"year":2013,"finding":"CCM1 (KRIT1)/CCM2 complex interacts with ICAP-1 to regulate β1 integrin activation; CCM1/2 loss results in ICAP-1 destabilization, increased β1 integrin activation, increased RhoA-dependent contractility, and aberrant ECM remodeling; a positive feedback loop between aberrant ECM and internal cellular tension leads to decreased endothelial barrier function.","method":"RNAi knockdown; force/traction microscopy; β1 integrin activation assays; immunofluorescence; CCM1/2 knockout mouse ECM analysis","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods including in vivo mouse data and quantitative force measurements","pmids":["23918940"],"is_preprint":false},{"year":2013,"finding":"KRIT1 loss of function leads to enhanced expression and phosphorylation of c-Jun and induction of its target COX-2 in a ROS-dependent manner; c-Jun upregulation can be reversed by KRIT1 re-expression or ROS scavenging; KRIT1 overexpression prevents forced c-Jun upregulation induced by oxidative stimuli.","method":"Western blotting; qPCR; KRIT1 re-expression and ROS scavenging rescue experiments; analysis of human CCM tissues","journal":"Free radical biology & medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss and gain of function with ROS rescue, single lab, multiple readouts","pmids":["24291398"],"is_preprint":false},{"year":2014,"finding":"KRIT1 depletion increases nuclear β-catenin signaling and upregulates VEGF-A protein expression; increased VEGF-A activates VEGFR2 leading to altered cytoskeletal organization, migration, barrier function, and in vivo endothelial permeability in KRIT1-deficient animals; loss of KRIT1 but not CCM2 specifically triggers this VEGF signaling axis.","method":"siRNA knockdown; western blotting; VEGFR2 inhibition; intravital permeability assay in Krit1(+/-) mice; migration and barrier function assays","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro and in vivo loss-of-function, single lab, pathway inhibitor confirmation","pmids":["25320085"],"is_preprint":false},{"year":2017,"finding":"KRIT1 depletion increases endothelial ROS production via NADPH oxidase (Nox4 upregulation) and NF-κB-dependent signaling; targeted antioxidant delivery reversed increased permeability in KRIT1-heterozygous mice; rescue of redox state restored TNF-α responsiveness in KRIT1-deficient arterioles but not venules.","method":"KRIT1 siRNA; intravital microscopy with targeted antioxidant enzymes; NF-κB reporter assay; Nox4 western blotting; Krit1(+/-) mouse model","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo rescue with targeted antioxidants plus in vitro mechanistic studies, single lab","pmids":["28811547"],"is_preprint":false},{"year":2018,"finding":"CCM1 (KRIT1) acts as a scaffold promoting ROCK2 interaction with VE-cadherin and limiting ROCK1 kinase activity; loss of CCM1 produces excessive ROCK1-dependent actin stress fibers and destabilizes intercellular junctions; ROCK1 silencing (but not ROCK2) restores adhesive and mechanical homeostasis of CCM1-depleted endothelial monolayers and rescues cardiovascular defects in ccm1 mutant zebrafish; ROCK2 knockdown in wild-type zebrafish generates CCM1-like defects.","method":"Co-immunoprecipitation; siRNA knockdown; traction force microscopy; zebrafish genetic rescue experiments; ROCK1/2 isoform-specific knockdown","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, in vitro mechanics, and in vivo zebrafish epistasis with isoform specificity","pmids":["30030370"],"is_preprint":false},{"year":2018,"finding":"Zebrafish Krit1 regulates cardiac valve formation by damping mechanosensitive KLF2a expression; HEG1 binding partner stabilizes Krit1 protein levels; Heg1 and Krit1 suppress klf2a and notch1b expression throughout the endocardium; loss of Krit1 results in increased klf2a and notch1b and prevents cardiac valve leaflet formation.","method":"Zebrafish genetic loss-of-function; quantitative gene expression analysis; protein level assessment; heg1/krit1 double-mutant analysis","journal":"eLife","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic loss-of-function in zebrafish with mechanosensitive pathway analysis, single lab","pmids":["29364115"],"is_preprint":false},{"year":2021,"finding":"HEG1 directly binds to KRIT1 FERM domain and recruits it to endothelial junctions; a small-molecule inhibitor (HKi2) occupies the HEG1-binding pocket on KRIT1 FERM, and acute inhibition of HEG1-KRIT1 interaction increases KLF4 and KLF2 expression in endothelial cells and activates PI3K-dependent Akt phosphorylation.","method":"Crystal structure of HKi2-KRIT1 FERM complex; high-throughput screening; colocalization assay in CHO cells; RNA transcriptome analysis; pharmacological inhibition with inactive analog control; zebrafish klf2a expression assay","journal":"FASEB bioAdvances","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure of inhibitor-protein complex with functional rescue experiments and in vivo zebrafish validation","pmids":["33977234"],"is_preprint":false},{"year":2008,"finding":"KRIT1 depletion reduces endothelial cell proliferation and decreases phosphorylation along the FAK→ERK/MAPK pathway downstream of β1 integrin; ICAP-1α depletion produces similar effects, suggesting synergistic function; KRIT1 stabilizes ICAP-1 and shuttles it between cytoplasm and nucleus.","method":"siRNA knockdown in HeLa, HUVEC, and microvascular endothelial cells; cell counting; phospho-FAK/ERK western blotting; immunocytochemistry","journal":"Neurosurgery","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — siRNA with defined signaling pathway readout, single lab, multiple cell types","pmids":["18812969"],"is_preprint":false},{"year":2008,"finding":"An in-frame deletion of CCM2 exon 2 (CCM2:p.P11_K68del) can form a complex with CCM3 but loses the ability to interact with CCM1 and to form a CCM1/CCM2/CCM3 ternary complex, identifying an N-terminal CCM2 domain required for CCM1 binding and establishing full-length CCM2 as the essential core protein in the CCM1/CCM2/CCM3 complex.","method":"Cell-based expression; coimmunoprecipitation; functional mutation analysis","journal":"Human mutation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with defined deletion mutant, single lab","pmids":["18300272"],"is_preprint":false},{"year":2020,"finding":"KRIT1 loss-of-function in stromal cells (fibroblasts) upregulates NADPH oxidase isoform NOX1 and activates inflammatory pathways, leading to increased production of VEGF and PGE2; conditioned media from KRIT1-null fibroblasts promotes proliferation, migration, MMP2 activation, and VE-cadherin redistribution in wild-type endothelial cells, demonstrating a paracrine pro-angiogenic mechanism.","method":"KRIT1 siRNA in fibroblasts; ELISA for VEGF/PGE2; conditioned media transfer to endothelial cells; MMP2 zymography; immunofluorescence","journal":"Cellular signalling","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function with mechanistic paracrine readout, multiple assays, single lab","pmids":["31917192"],"is_preprint":false},{"year":2022,"finding":"NOGOB receptor (NGBR) is required for maintaining CCM1 and CCM2 expression in endothelial cells via HBO1-mediated histone H4 acetylation; ChIP-qPCR demonstrated that NGBR loss impairs binding of HBO1 and acetylated histone H4K5/H4K12 to the CCM1 and CCM2 gene promoters, establishing epigenetic regulation of KRIT1/CCM1 expression.","method":"Endothelial-specific Ngbr knockout mice; RNA-sequencing; ChIP-qPCR; western blotting for histone acetylation marks; HBO1 manipulation","journal":"The Journal of clinical investigation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo knockout with ChIP-qPCR mechanistic evidence, single lab","pmids":["35316220"],"is_preprint":false}],"current_model":"KRIT1 is an intracellular scaffold protein that functions as a Rap1 GTPase effector at endothelial cell-cell junctions, where its FERM domain mediates binding to HEG1, VE-cadherin, and junctional proteins; it competes with β1 integrin for ICAP-1 binding (via its NPXY motifs) to regulate inside-out integrin activation and RhoA/ROCK1-dependent cytoskeletal tension; it forms a ternary complex with CCM2 and CCM3, and through CCM2 associates with MEKK3; loss of KRIT1 causes increased ROS via NADPH oxidase/Nox4, NF-κB activation, upregulation of c-Jun/COX-2, nuclear β-catenin accumulation with increased VEGF-A signaling, and derepression of KLF2/KLF4 and Notch/DLL4 pathways, collectively resulting in destabilized endothelial junctions, loss of apicobasal polarity, excessive angiogenic sprouting, and the vascular malformations characteristic of cerebral cavernous malformation disease."},"narrative":{"mechanistic_narrative":"KRIT1 (CCM1) is an intracellular scaffold protein that acts as a Rap1 GTPase effector at endothelial cell-cell junctions to maintain vascular barrier integrity, apicobasal polarity, and quiescence [PMID:17954608, PMID:22577140]. Its FERM domain binds active Rap1 across an extended surface spanning Rap1 Switch I/II and the F1 and F2 lobes, and is structurally similar to talin [PMID:22577140]; the same FERM domain is recruited to junctions by direct binding to the transmembrane receptor HEG1, which also stabilizes KRIT1 protein levels [PMID:33977234, PMID:29364115]. At junctions KRIT1 associates with VE-cadherin and is required for adherens-junction organization and coupling to the Par3/PKCζ polarity complex [PMID:20332120]. Through its N-terminal NPXY motifs KRIT1 nucleates a CCM signaling unit, binding ICAP-1 and the CCM2 PTB domain to form a CCM1/CCM2/CCM3 ternary complex with CCM2 as the essential core, which in turn links to MEKK3 [PMID:11854171, PMID:16037064, PMID:18300272]. Co-crystallography shows KRIT1 binds ICAP1 by a bidentate surface that directly competes with the β1 integrin cytoplasmic tail, making KRIT1 a switch that antagonizes ICAP1-mediated inside-out β1 integrin activation [PMID:23317506, PMID:23918940]. Loss of KRIT1 destabilizes junctions and drives pathology through several convergent axes: excessive ROCK1-dependent actin stress fibers and contractility, since KRIT1 normally scaffolds ROCK2 to VE-cadherin while limiting ROCK1 activity [PMID:30030370, PMID:23918940]; dissociation of β-catenin from VE-cadherin with nuclear accumulation, increased β-catenin transcription and VEGF-A/VEGFR2 signaling [PMID:20007487, PMID:25320085]; elevated ROS via NADPH oxidase (Nox4) and NF-κB, with downstream c-Jun/COX-2 induction [PMID:28811547, PMID:24291398]; and derepression of mechanosensitive KLF2/KLF4 and Notch/DLL4 programs that control sprouting and cardiac valve formation [PMID:29364115, PMID:33977234, PMID:20616044]. Truncating mutations in KRIT1 cause hereditary cerebral cavernous malformations, and KRIT1 loss is cell-autonomously required for normal endothelial morphogenesis in vivo [PMID:10508515, PMID:10545614, PMID:18469344].","teleology":[{"year":1999,"claim":"Established the molecular entry point: KRIT1 binds the Ras-family GTPase RAP1A and KRIT1 truncating mutations cause hereditary cavernous angiomas, placing KRIT1 in a Rap1-dependent vascular signaling pathway.","evidence":"Yeast two-hybrid interaction with RAP1A; positional cloning and mutation identification in CCM1 families","pmids":["10508515","10545614"],"confidence":"High","gaps":["Did not define how Rap1 binding controls KRIT1 function","No cellular localization or downstream effector identified"]},{"year":2002,"claim":"Identified KRIT1's first molecular interfaces, linking it to integrin signaling via the NPXY motif and to microtubules, beginning to define its scaffolding role.","evidence":"Yeast two-hybrid, GST pulldown with NPXY mutagenesis for ICAP-1; immunofluorescence and Co-IP for microtubule association in endothelial cells","pmids":["11854171","12140362"],"confidence":"High","gaps":["Functional consequence of ICAP-1 binding for integrin activation not yet shown","Microtubule association not independently replicated","Did not connect interactions to vascular phenotype"]},{"year":2005,"claim":"Assembled the CCM signaling complex, showing KRIT1 bridges CCM2 (via its NPXY/CCM2-PTB interface) and MEKK3 in a ternary complex, with disease mutations disrupting the interaction.","evidence":"Co-IP, FRET, subcellular localization, and disease-associated CCM2 missense mutation analysis","pmids":["16037064"],"confidence":"High","gaps":["Downstream signaling output of the KRIT1/CCM2/MEKK3 complex not resolved","Stoichiometry and regulation of complex assembly unclear"]},{"year":2007,"claim":"Defined KRIT1 as a Rap1 effector at endothelial junctions, demonstrating Rap1-dependent junctional recruitment via the FERM domain and a requirement for junction stability.","evidence":"Immunofluorescence, Co-IP, FERM domain mapping, and siRNA knockdown with junction/stress-fiber readouts in endothelial cells","pmids":["17954608","17290187"],"confidence":"High","gaps":["Junctional binding partners not fully enumerated","Mechanism linking junctional KRIT1 to actin remodeling not defined"]},{"year":2008,"claim":"Established cell-autonomous in vivo requirement for KRIT1 in vascular morphogenesis and refined the CCM complex architecture, while linking KRIT1/ICAP-1 to FAK→ERK proliferation signaling.","evidence":"Zebrafish loss-of-function with chimeric transplantation and EM; CCM2 deletion-mutant Co-IP; siRNA with phospho-FAK/ERK readout across cell types","pmids":["18469344","18300272","18812969"],"confidence":"High","gaps":["Molecular cause of endothelial spreading not pinpointed","Relationship between proliferation signaling and junction phenotype unclear"]},{"year":2009,"claim":"Connected KRIT1 to transcriptional control, showing it acts downstream of Rap1 to restrain nuclear β-catenin signaling and that Krit1 deficiency cooperates with Apc loss in vivo.","evidence":"siRNA, nuclear fractionation, reporter assays, and Krit1(+/-) × Apc(Min/+) mouse epistasis","pmids":["20007487"],"confidence":"High","gaps":["Direct vs indirect effect on β-catenin pool not separated","Downstream β-catenin target genes driving pathology not identified"]},{"year":2010,"claim":"Broadened the pathway map, showing KRIT1 controls DLL4-Notch sprouting, VE-cadherin/Par-complex polarity, and redox/quiescence programs, and that silencing recapitulates CCM pathology in vivo.","evidence":"siRNA, Notch inhibition, SCID xenograft, VE-cadherin Co-IP/polarity assays, and ROS/SOD2/FoxO1 measurements with KRIT1 reconstitution","pmids":["20616044","20332120","20668652"],"confidence":"High","gaps":["Causal hierarchy among Notch, polarity, and ROS axes not established","ROS findings from a single lab not independently replicated"]},{"year":2012,"claim":"Provided atomic-resolution mechanism for Rap1 recognition, showing the KRIT1 FERM domain engages Rap1 across F1 and F2 lobes and resembles the talin FERM fold.","evidence":"1.95 Å co-crystal structure of KRIT1 FERM–Rap1 with point mutagenesis","pmids":["22577140"],"confidence":"High","gaps":["Structure does not explain how Rap1 binding drives junctional recruitment","Conformational regulation of full-length KRIT1 not captured"]},{"year":2013,"claim":"Resolved the integrin switch and the mechanotransduction consequences, showing KRIT1 competes with β1 integrin for ICAP1 and that CCM1/2 loss raises β1 integrin activation, RhoA contractility, and aberrant ECM remodeling.","evidence":"Co-crystal structures of KRIT1–ICAP1 and ICAP1–β1 tail with competition/integrin-activation assays; RNAi, traction microscopy, and CCM knockout mouse ECM analysis","pmids":["23317506","23918940"],"confidence":"High","gaps":["How junctional Rap1/HEG1 cues are coordinated with the integrin switch not defined","Feedback between ECM stiffness and intracellular tension only partially mapped"]},{"year":2013,"claim":"Linked KRIT1 loss to inflammatory signaling, showing ROS-dependent induction and phosphorylation of c-Jun and its target COX-2, reversible by KRIT1 re-expression or ROS scavenging.","evidence":"Western blot, qPCR, KRIT1 re-expression and ROS scavenging rescue, and human CCM tissue analysis","pmids":["24291398"],"confidence":"Medium","gaps":["Single-lab finding","Mechanism connecting ROS to c-Jun activation not detailed"]},{"year":2014,"claim":"Identified a KRIT1-specific VEGF axis, showing KRIT1 (but not CCM2) loss elevates nuclear β-catenin and VEGF-A to activate VEGFR2 and increase endothelial permeability in vivo.","evidence":"siRNA, VEGFR2 inhibition, intravital permeability in Krit1(+/-) mice, and migration/barrier assays","pmids":["25320085"],"confidence":"Medium","gaps":["Why the VEGF axis is KRIT1-specific and CCM2-independent not mechanistically explained","Single-lab finding"]},{"year":2017,"claim":"Defined the redox source and a therapeutic handle, showing KRIT1 loss drives Nox4/NF-κB-dependent ROS and that targeted antioxidants reverse permeability in vivo.","evidence":"siRNA, intravital microscopy with targeted antioxidant enzymes, NF-κB reporter, Nox4 western, and Krit1(+/-) mice","pmids":["28811547"],"confidence":"Medium","gaps":["Arteriole-vs-venule difference in TNF-α responsiveness unexplained","Single-lab finding"]},{"year":2018,"claim":"Refined the cytoskeletal mechanism and mechanosensitive transcription control, showing KRIT1 scaffolds ROCK2 to VE-cadherin while limiting ROCK1, and that Krit1/Heg1 damp KLF2a/Notch1b to permit cardiac valve formation.","evidence":"Co-IP, isoform-specific ROCK1/2 knockdown, traction microscopy, and zebrafish genetic rescue/double-mutant analysis","pmids":["30030370","29364115"],"confidence":"High","gaps":["How KRIT1 selectively partitions ROCK1 vs ROCK2 activity not resolved","KLF2a link from mechanosensing in mammalian endothelium not directly tested here"]},{"year":2020,"claim":"Extended KRIT1 function beyond endothelium, showing stromal-cell KRIT1 loss activates NOX1/inflammatory signaling and drives a paracrine pro-angiogenic program acting on neighboring endothelial cells.","evidence":"Fibroblast KRIT1 siRNA, VEGF/PGE2 ELISA, conditioned-media transfer, MMP2 zymography, and immunofluorescence","pmids":["31917192"],"confidence":"Medium","gaps":["In vivo relevance of stromal paracrine mechanism not established","Single-lab finding"]},{"year":2021,"claim":"Validated the HEG1–KRIT1 junctional recruitment interface as druggable, showing direct FERM-domain binding and that pharmacological disruption de-represses KLF4/KLF2 and activates PI3K/Akt.","evidence":"Crystal structure of HKi2–KRIT1 FERM, high-throughput screening, colocalization, transcriptome analysis, and zebrafish klf2a assay","pmids":["33977234"],"confidence":"High","gaps":["Therapeutic consequence of acute HEG1-KRIT1 disruption in CCM disease models not shown","Specificity of KLF/Akt response over other junctional pathways unclear"]},{"year":2022,"claim":"Identified upstream transcriptional/epigenetic regulation of KRIT1, showing NGBR sustains CCM1/CCM2 expression via HBO1-mediated histone H4 acetylation at their promoters.","evidence":"Endothelial-specific Ngbr knockout mice, RNA-seq, ChIP-qPCR, and histone-acetylation westerns","pmids":["35316220"],"confidence":"Medium","gaps":["Whether NGBR/HBO1 regulation is dynamically used to tune KRIT1 in normal vasculature unclear","Single-lab finding"]},{"year":null,"claim":"How the multiple downstream axes — integrin/RhoA-ROCK tension, β-catenin/VEGF, ROS/NF-κB, and KLF/Notch derepression — are causally ordered into a single hierarchy from junctional KRIT1 loss remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified epistasis study ranking the axes","Tissue-specific contributions (endothelial vs stromal) not integrated","Structure of full-length KRIT1 and its autoregulation not determined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[4,12,17]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[12,13]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[1,4,17]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[4,9,19]},{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[1,4]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[5,7]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[5,13]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,4,11]},{"term_id":"R-HSA-1474244","term_label":"Extracellular matrix organization","supporting_discovery_ids":[13]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[6,8,18]},{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[10,16]}],"complexes":["CCM1/CCM2/CCM3 complex"],"partners":["RAP1A","ICAP-1","CCM2","VE-CADHERIN","HEG1","ROCK2","MEKK3","ITGB1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O00522","full_name":"Krev interaction trapped protein 1","aliases":["Cerebral cavernous malformations 1 protein"],"length_aa":736,"mass_kda":84.3,"function":"Component of the CCM signaling pathway which is a crucial regulator of heart and vessel formation and integrity (By similarity). Negative regulator of angiogenesis. Inhibits endothelial proliferation, apoptosis, migration, lumen formation and sprouting angiogenesis in primary endothelial cells. Promotes AKT phosphorylation in a NOTCH-dependent and independent manner, and inhibits ERK1/2 phosphorylation indirectly through activation of the DELTA-NOTCH cascade. Acts in concert with CDH5 to establish and maintain correct endothelial cell polarity and vascular lumen and these effects are mediated by recruitment and activation of the Par polarity complex and RAP1B. Required for the localization of phosphorylated PRKCZ, PARD3, TIAM1 and RAP1B to the cell junction, and cell junction stabilization. Plays a role in integrin signaling via its interaction with ITGB1BP1; this prevents the interaction between ITGB1 and ITGB1BP1. Microtubule-associated protein that binds to phosphatidylinositol 4,5-bisphosphate (PIP2)-containing membranes in a GTP-bound RAP1-dependent manner. Plays an important role in the maintenance of the intracellular reactive oxygen species (ROS) homeostasis to prevent oxidative cellular damage. Regulates the homeostasis of intracellular ROS through an antioxidant pathway involving FOXO1 and SOD2. Facilitates the down-regulation of cyclin-D1 (CCND1) levels required for cell transition from proliferative growth to quiescence by preventing the accumulation of intracellular ROS through the modulation of FOXO1 and SOD2 levels. 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neighborhood.","date":"2011","source":"Cell adhesion & migration","url":"https://pubmed.ncbi.nlm.nih.gov/20948304","citation_count":24,"is_preprint":false},{"pmid":"29483251","id":"PMC_29483251","title":"Grip and slip of L1-CAM on adhesive substrates direct growth cone haptotaxis.","date":"2018","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/29483251","citation_count":24,"is_preprint":false},{"pmid":"35316220","id":"PMC_35316220","title":"NOGOB receptor deficiency increases cerebrovascular permeability and hemorrhage via impairing histone acetylation-mediated CCM1/2 expression.","date":"2022","source":"The Journal of clinical investigation","url":"https://pubmed.ncbi.nlm.nih.gov/35316220","citation_count":22,"is_preprint":false},{"pmid":"23872064","id":"PMC_23872064","title":"miR-21 coordinates tumor growth and modulates KRIT1 levels.","date":"2013","source":"Biochemical and biophysical research 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survival.","date":"2012","source":"Journal of cellular biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/22173970","citation_count":18,"is_preprint":false},{"pmid":"27088716","id":"PMC_27088716","title":"Australia lacks stem succulents but is it depauperate in plants with crassulacean acid metabolism (CAM)?","date":"2016","source":"Current opinion in plant biology","url":"https://pubmed.ncbi.nlm.nih.gov/27088716","citation_count":17,"is_preprint":false},{"pmid":"33977234","id":"PMC_33977234","title":"Inhibition of the HEG1-KRIT1 interaction increases KLF4 and KLF2 expression in endothelial cells.","date":"2021","source":"FASEB bioAdvances","url":"https://pubmed.ncbi.nlm.nih.gov/33977234","citation_count":16,"is_preprint":false},{"pmid":"28441650","id":"PMC_28441650","title":"MicroRNA-1185 Induces Endothelial Cell Apoptosis by Targeting UVRAG and KRIT1.","date":"2017","source":"Cellular physiology and biochemistry : international journal of experimental cellular physiology, biochemistry, and pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/28441650","citation_count":16,"is_preprint":false},{"pmid":"31619570","id":"PMC_31619570","title":"CaM kinase II regulates cardiac hemoglobin expression through histone phosphorylation upon sympathetic activation.","date":"2019","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/31619570","citation_count":16,"is_preprint":false},{"pmid":"28698152","id":"PMC_28698152","title":"Novel functions of CCM1 delimit the relationship of PTB/PH domains.","date":"2017","source":"Biochimica et biophysica acta. Proteins and proteomics","url":"https://pubmed.ncbi.nlm.nih.gov/28698152","citation_count":16,"is_preprint":false},{"pmid":"33524363","id":"PMC_33524363","title":"The CAM assay in the study of the metastatic process.","date":"2021","source":"Experimental cell research","url":"https://pubmed.ncbi.nlm.nih.gov/33524363","citation_count":16,"is_preprint":false},{"pmid":"26991244","id":"PMC_26991244","title":"CRISPR-Cas-Assisted Multiplexing (CAM): Simple Same-Day Multi-Locus Engineering in Yeast.","date":"2016","source":"Journal of cellular physiology","url":"https://pubmed.ncbi.nlm.nih.gov/26991244","citation_count":16,"is_preprint":false},{"pmid":"35774275","id":"PMC_35774275","title":"Proteomic Analysis of Chicken Chorioallantoic Membrane (CAM) during Embryonic Development Provides Functional Insight.","date":"2022","source":"BioMed research international","url":"https://pubmed.ncbi.nlm.nih.gov/35774275","citation_count":16,"is_preprint":false},{"pmid":"12837237","id":"PMC_12837237","title":"Extracellular crosstalk: when GDNF meets N-CAM.","date":"2003","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/12837237","citation_count":15,"is_preprint":false},{"pmid":"31917192","id":"PMC_31917192","title":"KRIT1 loss-mediated upregulation of NOX1 in stromal cells promotes paracrine pro-angiogenic responses.","date":"2020","source":"Cellular signalling","url":"https://pubmed.ncbi.nlm.nih.gov/31917192","citation_count":15,"is_preprint":false},{"pmid":"12618200","id":"PMC_12618200","title":"Mel-CAM (CD146) expression in parotid mucoepidermoid carcinoma.","date":"2003","source":"Oral oncology","url":"https://pubmed.ncbi.nlm.nih.gov/12618200","citation_count":15,"is_preprint":false},{"pmid":"33651268","id":"PMC_33651268","title":"KRIT1 Gene in Patients with Cerebral Cavernous Malformations: Clinical Features and Molecular Characterization of Novel Variants.","date":"2021","source":"Journal of molecular neuroscience : MN","url":"https://pubmed.ncbi.nlm.nih.gov/33651268","citation_count":15,"is_preprint":false},{"pmid":"37587696","id":"PMC_37587696","title":"Gene duplications facilitate C4-CAM compatibility in common purslane.","date":"2023","source":"Plant physiology","url":"https://pubmed.ncbi.nlm.nih.gov/37587696","citation_count":14,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":46564,"output_tokens":6391,"usd":0.117778,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":15237,"output_tokens":5626,"usd":0.108417,"stage2_stop_reason":"end_turn"},"total_usd":0.226195,"stage1_batch_id":"msgbatch_01BbTCMyrRPyhtEq6b1MdwCN","stage2_batch_id":"msgbatch_011dEed5bbxYvTAaQWKJevxu","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1999,\n      \"finding\": \"KRIT1 protein physically interacts with RAP1A (Krev-1/rap1a), a member of the RAS family of GTPases; truncating mutations in CCM1/KRIT1 cause hereditary cavernous angiomas, implicating the RAP1A signal transduction pathway in vasculogenesis/angiogenesis.\",\n      \"method\": \"Yeast two-hybrid interaction (previously established); positional cloning and mutation identification in CCM1 families\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — interaction with RAP1A confirmed across multiple independent labs (PMID:10508515, PMID:10545614), replicated by subsequent structural and biochemical studies\",\n      \"pmids\": [\"10508515\", \"10545614\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"KRIT1 colocalizes with microtubules in interphase cells and localizes to spindle pole bodies, mitotic spindle, and microtubule plus ends during mitosis; coimmunoprecipitation confirmed KRIT1 association with microtubules, establishing KRIT1 as a microtubule-associated protein.\",\n      \"method\": \"Immunofluorescence microscopy with anti-KRIT1 antibodies; coimmunoprecipitation from endothelial cells\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal coimmunoprecipitation plus microscopy in a single lab; not independently replicated\",\n      \"pmids\": [\"12140362\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"KRIT1 physically interacts with ICAP-1 (integrin cytoplasmic domain-associated protein-1); interaction is mediated by the N-terminal NPXY motif of KRIT1, and mutagenesis of this motif abrogates binding; ICAP-1 is a known β1 integrin cytoplasmic tail binder, suggesting KRIT1 participates in integrin–cytoskeleton signaling.\",\n      \"method\": \"Yeast two-hybrid screen of human fetal brain and HeLa cDNA libraries; GST-KRIT1 pulldown of endogenous ICAP-1 from 293T cells; site-directed mutagenesis of NPXY motif\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — GST pulldown with mutagenesis confirmation; replicated by multiple subsequent studies\",\n      \"pmids\": [\"11854171\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"KRIT1 (CCM1) interacts with CCM2 (malcavernin/OSM) protein; this interaction is dependent on the phosphotyrosine binding (PTB) domain of CCM2 and the NPXY motif of CCM1; a familial CCM2 missense mutation abrogates this interaction; CCM1 associates with CCM2 and MEKK3 in a ternary complex; CCM2 and ICAP-1 differentially influence CCM1 subcellular localization.\",\n      \"method\": \"Coimmunoprecipitation; fluorescence resonance energy transfer (FRET); subcellular localization assays; analysis of disease-associated CCM2 missense mutation\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP plus FRET, replicated in subsequent studies; multiple orthogonal methods in single lab\",\n      \"pmids\": [\"16037064\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"KRIT1 is expressed in endothelial cells and localizes to cell-cell junctions via its FERM domain; Rap1 GTPase activity regulates the junctional localization of KRIT1 and its physical association with junctional proteins; siRNA depletion of KRIT1 blocked Rap1-mediated stabilization of endothelial junctions and was associated with increased actin stress fibers, establishing KRIT1 as a Rap1 effector at endothelial junctions.\",\n      \"method\": \"Immunofluorescence localization; coimmunoprecipitation; siRNA knockdown with functional readout (junction stability, actin stress fibers); domain mapping with isolated FERM domain\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, localization, domain analysis, and siRNA phenotype; multiple orthogonal methods in single study\",\n      \"pmids\": [\"17954608\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"KRIT1 (krit1) interacts with CCM2 (malcavernin) through two of the three NPXY motifs in KRIT1; CCM2 protein shuttles between nucleus and cytoplasm; KRIT1 co-localizes with ICAP-1 in both nucleus and cytoplasm, and KRIT1 depletion causes loss of ICAP-1 from cytoplasm and nucleus, suggesting KRIT1 stabilizes and shuttles ICAP-1.\",\n      \"method\": \"Yeast two-hybrid; coimmunoprecipitation; epitope mapping; immunocytochemistry; siRNA knockdown\",\n      \"journal\": \"Neurosurgery\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple methods (Y2H, Co-IP, imaging), single lab\",\n      \"pmids\": [\"17290187\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Loss of ccm1 in zebrafish leads to progressive dilation of major vessels due to cell-autonomous spreading of endothelial cells and thinning of vessel walls, with ultrastructurally normal cell-cell contacts; rescue experiments confirmed cell-autonomous function of ccm1 in endothelial morphogenesis.\",\n      \"method\": \"Zebrafish genetic loss-of-function; chimeric transplantation experiments establishing cell autonomy; electron microscopy\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic loss-of-function with cell autonomy rescue, multiple readouts\",\n      \"pmids\": [\"18469344\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"KRIT1/CCM1, acting downstream of Rap1 GTPase, negatively regulates canonical β-catenin signaling in endothelial cells; KRIT1 depletion causes β-catenin to dissociate from VE-cadherin and accumulate in the nucleus with increased β-catenin-dependent transcription; Rap1 activation inhibits β-catenin transcription in a manner dependent on intact cell-cell junctions and KRIT1; hemizygous Krit1 deficiency in Apc(Min/+) mice increased intestinal polyp burden.\",\n      \"method\": \"siRNA knockdown; nuclear fractionation; transcriptional reporter assays; in vivo Krit1(+/-) × Apc(Min/+) mouse epistasis\",\n      \"journal\": \"Disease models & mechanisms\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vitro knockdown with pathway readout plus in vivo genetic epistasis, multiple orthogonal methods\",\n      \"pmids\": [\"20007487\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"CCM1 (KRIT1) induces DLL4-NOTCH signaling in endothelial cells, inhibiting sprouting angiogenesis; CCM1 promotes AKT phosphorylation but reduces ERK phosphorylation; blocking NOTCH activity alleviates CCM1 effects; CCM1 silencing in human endothelial cells transplanted into SCID mice recapitulates CCM pathology.\",\n      \"method\": \"siRNA knockdown; western blotting; NOTCH pharmacological inhibition; SCID mouse xenograft model; ERK/AKT phosphorylation assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vitro and in vivo loss-of-function with pathway rescue, multiple orthogonal methods\",\n      \"pmids\": [\"20616044\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"CCM1 (KRIT1) interacts with VE-cadherin and is required for proper adherens junction (AJ) organization and AJ association with the Par polarity complex (Par3 and PKCζ); CCM1 and VE-cadherin control Rap1 concentration at cell-cell junctions; loss of CCM1 leads to loss of endothelial apicobasal polarity and severe alterations in vascular lumen structure.\",\n      \"method\": \"Coimmunoprecipitation; siRNA knockdown; immunofluorescence; PKCζ activation assays; analysis of human CCM1 lesions\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — Co-IP, siRNA, functional polarity assay, human tissue validation; multiple orthogonal methods\",\n      \"pmids\": [\"20332120\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"KRIT1 loss/down-regulation increases intracellular ROS levels and decreases expression of antioxidant protein SOD2 and transcription factor FoxO1; restoration of KRIT1 expression dose-dependently reduces ROS levels; KRIT1-dependent low ROS levels facilitate downregulation of cyclin D1 for cell quiescence; KRIT1 loss increases susceptibility to oxidative DNA damage and induces Gadd45α and declines mitochondrial metabolism.\",\n      \"method\": \"ROS measurement assays; western blotting; KRIT1 reconstitution in knockout cells; cyclin D1 expression analysis; Gadd45α induction; mitochondrial metabolism assays\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple assays, KO rescue approach, single lab\",\n      \"pmids\": [\"20668652\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Crystal structure of KRIT1 FERM domain in complex with Rap1 determined at 1.95 Å; Rap1-KRIT1 interaction spans an extended surface including Rap1 Switch I and II and KRIT1 FERM F1 and F2 lobes; Rap1 binds KRIT1-F1 via a GTPase-ubiquitin-like fold interaction and KRIT1-F2 via a novel interaction; point mutagenesis confirms the interaction surface; KRIT1 FERM domain is structurally similar to talin.\",\n      \"method\": \"Co-crystal structure determination (1.95 Å resolution); point mutagenesis; structural comparison\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — high-resolution co-crystal structure with mutagenesis validation\",\n      \"pmids\": [\"22577140\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"KRIT1 functions as a switch for β1 integrin activation by antagonizing ICAP1-mediated inside-out activation; co-crystal structures of KRIT1 with ICAP1 (2.54 Å) and ICAP1 with integrin β1 cytoplasmic tail (3.0 Å) show that KRIT1 binds ICAP1 by a bidentate surface that directly competes with integrin β1; KRIT1 contains an N-terminal Nudix domain in a region previously thought to be unstructured.\",\n      \"method\": \"Co-crystal structure determination (2.54 Å and 3.0 Å); in vitro competition binding assays; integrin activation assay; structural mutagenesis\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — two co-crystal structures with functional competition assay validation\",\n      \"pmids\": [\"23317506\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"CCM1 (KRIT1)/CCM2 complex interacts with ICAP-1 to regulate β1 integrin activation; CCM1/2 loss results in ICAP-1 destabilization, increased β1 integrin activation, increased RhoA-dependent contractility, and aberrant ECM remodeling; a positive feedback loop between aberrant ECM and internal cellular tension leads to decreased endothelial barrier function.\",\n      \"method\": \"RNAi knockdown; force/traction microscopy; β1 integrin activation assays; immunofluorescence; CCM1/2 knockout mouse ECM analysis\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods including in vivo mouse data and quantitative force measurements\",\n      \"pmids\": [\"23918940\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"KRIT1 loss of function leads to enhanced expression and phosphorylation of c-Jun and induction of its target COX-2 in a ROS-dependent manner; c-Jun upregulation can be reversed by KRIT1 re-expression or ROS scavenging; KRIT1 overexpression prevents forced c-Jun upregulation induced by oxidative stimuli.\",\n      \"method\": \"Western blotting; qPCR; KRIT1 re-expression and ROS scavenging rescue experiments; analysis of human CCM tissues\",\n      \"journal\": \"Free radical biology & medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss and gain of function with ROS rescue, single lab, multiple readouts\",\n      \"pmids\": [\"24291398\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"KRIT1 depletion increases nuclear β-catenin signaling and upregulates VEGF-A protein expression; increased VEGF-A activates VEGFR2 leading to altered cytoskeletal organization, migration, barrier function, and in vivo endothelial permeability in KRIT1-deficient animals; loss of KRIT1 but not CCM2 specifically triggers this VEGF signaling axis.\",\n      \"method\": \"siRNA knockdown; western blotting; VEGFR2 inhibition; intravital permeability assay in Krit1(+/-) mice; migration and barrier function assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro and in vivo loss-of-function, single lab, pathway inhibitor confirmation\",\n      \"pmids\": [\"25320085\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"KRIT1 depletion increases endothelial ROS production via NADPH oxidase (Nox4 upregulation) and NF-κB-dependent signaling; targeted antioxidant delivery reversed increased permeability in KRIT1-heterozygous mice; rescue of redox state restored TNF-α responsiveness in KRIT1-deficient arterioles but not venules.\",\n      \"method\": \"KRIT1 siRNA; intravital microscopy with targeted antioxidant enzymes; NF-κB reporter assay; Nox4 western blotting; Krit1(+/-) mouse model\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo rescue with targeted antioxidants plus in vitro mechanistic studies, single lab\",\n      \"pmids\": [\"28811547\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"CCM1 (KRIT1) acts as a scaffold promoting ROCK2 interaction with VE-cadherin and limiting ROCK1 kinase activity; loss of CCM1 produces excessive ROCK1-dependent actin stress fibers and destabilizes intercellular junctions; ROCK1 silencing (but not ROCK2) restores adhesive and mechanical homeostasis of CCM1-depleted endothelial monolayers and rescues cardiovascular defects in ccm1 mutant zebrafish; ROCK2 knockdown in wild-type zebrafish generates CCM1-like defects.\",\n      \"method\": \"Co-immunoprecipitation; siRNA knockdown; traction force microscopy; zebrafish genetic rescue experiments; ROCK1/2 isoform-specific knockdown\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, in vitro mechanics, and in vivo zebrafish epistasis with isoform specificity\",\n      \"pmids\": [\"30030370\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Zebrafish Krit1 regulates cardiac valve formation by damping mechanosensitive KLF2a expression; HEG1 binding partner stabilizes Krit1 protein levels; Heg1 and Krit1 suppress klf2a and notch1b expression throughout the endocardium; loss of Krit1 results in increased klf2a and notch1b and prevents cardiac valve leaflet formation.\",\n      \"method\": \"Zebrafish genetic loss-of-function; quantitative gene expression analysis; protein level assessment; heg1/krit1 double-mutant analysis\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic loss-of-function in zebrafish with mechanosensitive pathway analysis, single lab\",\n      \"pmids\": [\"29364115\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"HEG1 directly binds to KRIT1 FERM domain and recruits it to endothelial junctions; a small-molecule inhibitor (HKi2) occupies the HEG1-binding pocket on KRIT1 FERM, and acute inhibition of HEG1-KRIT1 interaction increases KLF4 and KLF2 expression in endothelial cells and activates PI3K-dependent Akt phosphorylation.\",\n      \"method\": \"Crystal structure of HKi2-KRIT1 FERM complex; high-throughput screening; colocalization assay in CHO cells; RNA transcriptome analysis; pharmacological inhibition with inactive analog control; zebrafish klf2a expression assay\",\n      \"journal\": \"FASEB bioAdvances\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure of inhibitor-protein complex with functional rescue experiments and in vivo zebrafish validation\",\n      \"pmids\": [\"33977234\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"KRIT1 depletion reduces endothelial cell proliferation and decreases phosphorylation along the FAK→ERK/MAPK pathway downstream of β1 integrin; ICAP-1α depletion produces similar effects, suggesting synergistic function; KRIT1 stabilizes ICAP-1 and shuttles it between cytoplasm and nucleus.\",\n      \"method\": \"siRNA knockdown in HeLa, HUVEC, and microvascular endothelial cells; cell counting; phospho-FAK/ERK western blotting; immunocytochemistry\",\n      \"journal\": \"Neurosurgery\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — siRNA with defined signaling pathway readout, single lab, multiple cell types\",\n      \"pmids\": [\"18812969\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"An in-frame deletion of CCM2 exon 2 (CCM2:p.P11_K68del) can form a complex with CCM3 but loses the ability to interact with CCM1 and to form a CCM1/CCM2/CCM3 ternary complex, identifying an N-terminal CCM2 domain required for CCM1 binding and establishing full-length CCM2 as the essential core protein in the CCM1/CCM2/CCM3 complex.\",\n      \"method\": \"Cell-based expression; coimmunoprecipitation; functional mutation analysis\",\n      \"journal\": \"Human mutation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with defined deletion mutant, single lab\",\n      \"pmids\": [\"18300272\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"KRIT1 loss-of-function in stromal cells (fibroblasts) upregulates NADPH oxidase isoform NOX1 and activates inflammatory pathways, leading to increased production of VEGF and PGE2; conditioned media from KRIT1-null fibroblasts promotes proliferation, migration, MMP2 activation, and VE-cadherin redistribution in wild-type endothelial cells, demonstrating a paracrine pro-angiogenic mechanism.\",\n      \"method\": \"KRIT1 siRNA in fibroblasts; ELISA for VEGF/PGE2; conditioned media transfer to endothelial cells; MMP2 zymography; immunofluorescence\",\n      \"journal\": \"Cellular signalling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function with mechanistic paracrine readout, multiple assays, single lab\",\n      \"pmids\": [\"31917192\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"NOGOB receptor (NGBR) is required for maintaining CCM1 and CCM2 expression in endothelial cells via HBO1-mediated histone H4 acetylation; ChIP-qPCR demonstrated that NGBR loss impairs binding of HBO1 and acetylated histone H4K5/H4K12 to the CCM1 and CCM2 gene promoters, establishing epigenetic regulation of KRIT1/CCM1 expression.\",\n      \"method\": \"Endothelial-specific Ngbr knockout mice; RNA-sequencing; ChIP-qPCR; western blotting for histone acetylation marks; HBO1 manipulation\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo knockout with ChIP-qPCR mechanistic evidence, single lab\",\n      \"pmids\": [\"35316220\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"KRIT1 is an intracellular scaffold protein that functions as a Rap1 GTPase effector at endothelial cell-cell junctions, where its FERM domain mediates binding to HEG1, VE-cadherin, and junctional proteins; it competes with β1 integrin for ICAP-1 binding (via its NPXY motifs) to regulate inside-out integrin activation and RhoA/ROCK1-dependent cytoskeletal tension; it forms a ternary complex with CCM2 and CCM3, and through CCM2 associates with MEKK3; loss of KRIT1 causes increased ROS via NADPH oxidase/Nox4, NF-κB activation, upregulation of c-Jun/COX-2, nuclear β-catenin accumulation with increased VEGF-A signaling, and derepression of KLF2/KLF4 and Notch/DLL4 pathways, collectively resulting in destabilized endothelial junctions, loss of apicobasal polarity, excessive angiogenic sprouting, and the vascular malformations characteristic of cerebral cavernous malformation disease.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"KRIT1 (CCM1) is an intracellular scaffold protein that acts as a Rap1 GTPase effector at endothelial cell-cell junctions to maintain vascular barrier integrity, apicobasal polarity, and quiescence [#4, #11]. Its FERM domain binds active Rap1 across an extended surface spanning Rap1 Switch I/II and the F1 and F2 lobes, and is structurally similar to talin [#11]; the same FERM domain is recruited to junctions by direct binding to the transmembrane receptor HEG1, which also stabilizes KRIT1 protein levels [#19, #18]. At junctions KRIT1 associates with VE-cadherin and is required for adherens-junction organization and coupling to the Par3/PKCζ polarity complex [#9]. Through its N-terminal NPXY motifs KRIT1 nucleates a CCM signaling unit, binding ICAP-1 and the CCM2 PTB domain to form a CCM1/CCM2/CCM3 ternary complex with CCM2 as the essential core, which in turn links to MEKK3 [#2, #3, #21]. Co-crystallography shows KRIT1 binds ICAP1 by a bidentate surface that directly competes with the β1 integrin cytoplasmic tail, making KRIT1 a switch that antagonizes ICAP1-mediated inside-out β1 integrin activation [#12, #13]. Loss of KRIT1 destabilizes junctions and drives pathology through several convergent axes: excessive ROCK1-dependent actin stress fibers and contractility, since KRIT1 normally scaffolds ROCK2 to VE-cadherin while limiting ROCK1 activity [#17, #13]; dissociation of β-catenin from VE-cadherin with nuclear accumulation, increased β-catenin transcription and VEGF-A/VEGFR2 signaling [#7, #15]; elevated ROS via NADPH oxidase (Nox4) and NF-κB, with downstream c-Jun/COX-2 induction [#16, #14]; and derepression of mechanosensitive KLF2/KLF4 and Notch/DLL4 programs that control sprouting and cardiac valve formation [#18, #19, #8]. Truncating mutations in KRIT1 cause hereditary cerebral cavernous malformations, and KRIT1 loss is cell-autonomously required for normal endothelial morphogenesis in vivo [#0, #6].\",\n  \"teleology\": [\n    {\n      \"year\": 1999,\n      \"claim\": \"Established the molecular entry point: KRIT1 binds the Ras-family GTPase RAP1A and KRIT1 truncating mutations cause hereditary cavernous angiomas, placing KRIT1 in a Rap1-dependent vascular signaling pathway.\",\n      \"evidence\": \"Yeast two-hybrid interaction with RAP1A; positional cloning and mutation identification in CCM1 families\",\n      \"pmids\": [\"10508515\", \"10545614\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define how Rap1 binding controls KRIT1 function\", \"No cellular localization or downstream effector identified\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Identified KRIT1's first molecular interfaces, linking it to integrin signaling via the NPXY motif and to microtubules, beginning to define its scaffolding role.\",\n      \"evidence\": \"Yeast two-hybrid, GST pulldown with NPXY mutagenesis for ICAP-1; immunofluorescence and Co-IP for microtubule association in endothelial cells\",\n      \"pmids\": [\"11854171\", \"12140362\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of ICAP-1 binding for integrin activation not yet shown\", \"Microtubule association not independently replicated\", \"Did not connect interactions to vascular phenotype\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Assembled the CCM signaling complex, showing KRIT1 bridges CCM2 (via its NPXY/CCM2-PTB interface) and MEKK3 in a ternary complex, with disease mutations disrupting the interaction.\",\n      \"evidence\": \"Co-IP, FRET, subcellular localization, and disease-associated CCM2 missense mutation analysis\",\n      \"pmids\": [\"16037064\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Downstream signaling output of the KRIT1/CCM2/MEKK3 complex not resolved\", \"Stoichiometry and regulation of complex assembly unclear\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Defined KRIT1 as a Rap1 effector at endothelial junctions, demonstrating Rap1-dependent junctional recruitment via the FERM domain and a requirement for junction stability.\",\n      \"evidence\": \"Immunofluorescence, Co-IP, FERM domain mapping, and siRNA knockdown with junction/stress-fiber readouts in endothelial cells\",\n      \"pmids\": [\"17954608\", \"17290187\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Junctional binding partners not fully enumerated\", \"Mechanism linking junctional KRIT1 to actin remodeling not defined\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Established cell-autonomous in vivo requirement for KRIT1 in vascular morphogenesis and refined the CCM complex architecture, while linking KRIT1/ICAP-1 to FAK→ERK proliferation signaling.\",\n      \"evidence\": \"Zebrafish loss-of-function with chimeric transplantation and EM; CCM2 deletion-mutant Co-IP; siRNA with phospho-FAK/ERK readout across cell types\",\n      \"pmids\": [\"18469344\", \"18300272\", \"18812969\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular cause of endothelial spreading not pinpointed\", \"Relationship between proliferation signaling and junction phenotype unclear\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Connected KRIT1 to transcriptional control, showing it acts downstream of Rap1 to restrain nuclear β-catenin signaling and that Krit1 deficiency cooperates with Apc loss in vivo.\",\n      \"evidence\": \"siRNA, nuclear fractionation, reporter assays, and Krit1(+/-) × Apc(Min/+) mouse epistasis\",\n      \"pmids\": [\"20007487\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct vs indirect effect on β-catenin pool not separated\", \"Downstream β-catenin target genes driving pathology not identified\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Broadened the pathway map, showing KRIT1 controls DLL4-Notch sprouting, VE-cadherin/Par-complex polarity, and redox/quiescence programs, and that silencing recapitulates CCM pathology in vivo.\",\n      \"evidence\": \"siRNA, Notch inhibition, SCID xenograft, VE-cadherin Co-IP/polarity assays, and ROS/SOD2/FoxO1 measurements with KRIT1 reconstitution\",\n      \"pmids\": [\"20616044\", \"20332120\", \"20668652\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Causal hierarchy among Notch, polarity, and ROS axes not established\", \"ROS findings from a single lab not independently replicated\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Provided atomic-resolution mechanism for Rap1 recognition, showing the KRIT1 FERM domain engages Rap1 across F1 and F2 lobes and resembles the talin FERM fold.\",\n      \"evidence\": \"1.95 Å co-crystal structure of KRIT1 FERM–Rap1 with point mutagenesis\",\n      \"pmids\": [\"22577140\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structure does not explain how Rap1 binding drives junctional recruitment\", \"Conformational regulation of full-length KRIT1 not captured\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Resolved the integrin switch and the mechanotransduction consequences, showing KRIT1 competes with β1 integrin for ICAP1 and that CCM1/2 loss raises β1 integrin activation, RhoA contractility, and aberrant ECM remodeling.\",\n      \"evidence\": \"Co-crystal structures of KRIT1–ICAP1 and ICAP1–β1 tail with competition/integrin-activation assays; RNAi, traction microscopy, and CCM knockout mouse ECM analysis\",\n      \"pmids\": [\"23317506\", \"23918940\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How junctional Rap1/HEG1 cues are coordinated with the integrin switch not defined\", \"Feedback between ECM stiffness and intracellular tension only partially mapped\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Linked KRIT1 loss to inflammatory signaling, showing ROS-dependent induction and phosphorylation of c-Jun and its target COX-2, reversible by KRIT1 re-expression or ROS scavenging.\",\n      \"evidence\": \"Western blot, qPCR, KRIT1 re-expression and ROS scavenging rescue, and human CCM tissue analysis\",\n      \"pmids\": [\"24291398\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab finding\", \"Mechanism connecting ROS to c-Jun activation not detailed\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Identified a KRIT1-specific VEGF axis, showing KRIT1 (but not CCM2) loss elevates nuclear β-catenin and VEGF-A to activate VEGFR2 and increase endothelial permeability in vivo.\",\n      \"evidence\": \"siRNA, VEGFR2 inhibition, intravital permeability in Krit1(+/-) mice, and migration/barrier assays\",\n      \"pmids\": [\"25320085\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Why the VEGF axis is KRIT1-specific and CCM2-independent not mechanistically explained\", \"Single-lab finding\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Defined the redox source and a therapeutic handle, showing KRIT1 loss drives Nox4/NF-κB-dependent ROS and that targeted antioxidants reverse permeability in vivo.\",\n      \"evidence\": \"siRNA, intravital microscopy with targeted antioxidant enzymes, NF-κB reporter, Nox4 western, and Krit1(+/-) mice\",\n      \"pmids\": [\"28811547\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Arteriole-vs-venule difference in TNF-α responsiveness unexplained\", \"Single-lab finding\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Refined the cytoskeletal mechanism and mechanosensitive transcription control, showing KRIT1 scaffolds ROCK2 to VE-cadherin while limiting ROCK1, and that Krit1/Heg1 damp KLF2a/Notch1b to permit cardiac valve formation.\",\n      \"evidence\": \"Co-IP, isoform-specific ROCK1/2 knockdown, traction microscopy, and zebrafish genetic rescue/double-mutant analysis\",\n      \"pmids\": [\"30030370\", \"29364115\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How KRIT1 selectively partitions ROCK1 vs ROCK2 activity not resolved\", \"KLF2a link from mechanosensing in mammalian endothelium not directly tested here\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Extended KRIT1 function beyond endothelium, showing stromal-cell KRIT1 loss activates NOX1/inflammatory signaling and drives a paracrine pro-angiogenic program acting on neighboring endothelial cells.\",\n      \"evidence\": \"Fibroblast KRIT1 siRNA, VEGF/PGE2 ELISA, conditioned-media transfer, MMP2 zymography, and immunofluorescence\",\n      \"pmids\": [\"31917192\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"In vivo relevance of stromal paracrine mechanism not established\", \"Single-lab finding\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Validated the HEG1–KRIT1 junctional recruitment interface as druggable, showing direct FERM-domain binding and that pharmacological disruption de-represses KLF4/KLF2 and activates PI3K/Akt.\",\n      \"evidence\": \"Crystal structure of HKi2–KRIT1 FERM, high-throughput screening, colocalization, transcriptome analysis, and zebrafish klf2a assay\",\n      \"pmids\": [\"33977234\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Therapeutic consequence of acute HEG1-KRIT1 disruption in CCM disease models not shown\", \"Specificity of KLF/Akt response over other junctional pathways unclear\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Identified upstream transcriptional/epigenetic regulation of KRIT1, showing NGBR sustains CCM1/CCM2 expression via HBO1-mediated histone H4 acetylation at their promoters.\",\n      \"evidence\": \"Endothelial-specific Ngbr knockout mice, RNA-seq, ChIP-qPCR, and histone-acetylation westerns\",\n      \"pmids\": [\"35316220\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether NGBR/HBO1 regulation is dynamically used to tune KRIT1 in normal vasculature unclear\", \"Single-lab finding\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the multiple downstream axes — integrin/RhoA-ROCK tension, β-catenin/VEGF, ROS/NF-κB, and KLF/Notch derepression — are causally ordered into a single hierarchy from junctional KRIT1 loss remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified epistasis study ranking the axes\", \"Tissue-specific contributions (endothelial vs stromal) not integrated\", \"Structure of full-length KRIT1 and its autoregulation not determined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [4, 12, 17]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [12, 13]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [1, 4, 17]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [4, 9, 19]},\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [1, 4]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [5, 7]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [5, 13]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 4, 11]},\n      {\"term_id\": \"R-HSA-1474244\", \"supporting_discovery_ids\": [13]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [6, 8, 18]},\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [10, 16]}\n    ],\n    \"complexes\": [\n      \"CCM1/CCM2/CCM3 complex\"\n    ],\n    \"partners\": [\n      \"RAP1A\",\n      \"ICAP-1\",\n      \"CCM2\",\n      \"VE-cadherin\",\n      \"HEG1\",\n      \"ROCK2\",\n      \"MEKK3\",\n      \"ITGB1\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}