{"gene":"MTSS1","run_date":"2026-06-10T05:19:51","timeline":{"discoveries":[{"year":2002,"finding":"MIM/MTSS1 C-terminal WH2 domain binds ATP-actin monomers with higher affinity (Kd ~0.06 µM) than ADP-actin monomers (Kd ~0.3 µM), inhibits actin filament nucleation in vitro, but allows barbed-end assembly; inhibits nucleotide exchange on actin monomers. Overexpression in NIH 3T3 cells causes disappearance of stress fibers and abnormal actin structures.","method":"In vitro actin binding/sedimentation assays, site-directed mutagenesis of WH2 domain, Northern blot, overexpression in NIH 3T3 cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with Kd measurements, mutagenesis confirming WH2 as actin-binding site, and cellular overexpression phenotype; multiple orthogonal methods in one study","pmids":["12482861"],"is_preprint":false},{"year":2003,"finding":"MIM-B (long isoform of MIM/MTSS1) binds actin via a C-terminal WH2 domain and also binds the cytoplasmic domain of receptor protein tyrosine phosphatase delta (PTPδ), as shown by pulldown with purified proteins and cell extracts. The N-terminal portion of MIM-B localizes to internal vesicles and likely targets the protein to membranes; the C-terminal portion is cytoplasmic and does not affect the actin cytoskeleton. Full-length MIM-B induces actin-rich protrusions at the plasma membrane and promotes disassembly of stress fibers.","method":"Pulldown with purified proteins and cell extracts, subcellular localization by expression of truncated constructs","journal":"The Biochemical journal","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — single pulldown/binding assay for PTPδ interaction, supported by cellular localization data; single lab","pmids":["12570871"],"is_preprint":false},{"year":2004,"finding":"MIM/MTSS1 is a Sonic hedgehog (Shh)-responsive gene that is part of a Gli/Suppressor of Fused complex and potentiates Gli-dependent transcription. MIM uses domains distinct from those required for actin monomer binding to enhance Gli activity. Together with Gli1, MIM recapitulates Shh-mediated epidermal proliferation and invasion.","method":"Co-immunoprecipitation (Gli/SUFU complex), cotransfection luciferase assays, regenerated human skin model","journal":"Genes & development","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — co-IP demonstrating complex membership, reporter assays for transcriptional potentiation; single lab, two orthogonal methods","pmids":["15545630"],"is_preprint":false},{"year":2005,"finding":"MIM/MTSS1 directly binds the SH3 domain of cortactin and promotes cortactin/Arp2/3-mediated actin polymerization in vitro. Full-length MIM binds G-actin with affinity similar to N-WASP-VCA and inhibits N-WASP-VCA-mediated actin polymerization in vitro. Overexpression of full-length MIM inhibits PDGF-induced cell motility, while deletion of the WH2 domain (abrogating G-actin binding) enhances motility; deletion of the proline-rich domain (required for cortactin binding) strengthens MIM-mediated motility inhibition.","method":"In vitro actin polymerization assays, direct binding assays, GFP colocalization, cell motility assays with domain-deletion mutants","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — in vitro reconstitution of actin polymerization, direct binding, multiple domain mutants tested in cells; multiple orthogonal methods","pmids":["15688017"],"is_preprint":false},{"year":2005,"finding":"MIM-B induces lamellipodia-like actin-rich protrusions dependent on both the IRSp53/MIM (IMD/I-BAR) domain and Rac activity, but not the WH2 motif. MIM-B binds and activates Rac GTPase via its IMD domain, though Rac binding alone is insufficient to induce lamellipodia. Actin-bundling and Rac-binding properties of the IMD are inseparable.","method":"Expression of domain mutants, dominant-negative Rac experiments, actin bundling assays, Rac activation assays (pull-down)","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple domain mutants with cellular phenotypes, Rac pulldown; single lab","pmids":["16280553"],"is_preprint":false},{"year":2005,"finding":"MIM/MTSS1 bundles F-actin via its IMD/I-BAR domain; this self-association-dependent bundling is independent of G-actin binding. MIM's cytoskeletal remodeling in cells requires a domain that associates with RPTPδ, which in turn enhances RPTPδ membrane localization. MIM is induced in a patched1-dependent manner (downstream of Shh signaling).","method":"F-actin bundling assays, domain mutagenesis, RPTPδ co-immunoprecipitation, membrane localization assay, patched1 dependency by genetic manipulation","journal":"The Journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple biochemical assays with domain mutants, co-IP for RPTPδ, genetic epistasis with patched1; single lab","pmids":["15684034"],"is_preprint":false},{"year":2006,"finding":"MIM/MTSS1 promoter expression is regulated by DNA methylation of a CpG island in its 5' region; treatment with demethylation agent 5-Aza-2'-deoxycytidine upregulates MIM expression in low-expressing cell lines. The non-methylated promoter has similar activity regardless of endogenous MIM expression level.","method":"Bisulfite sequencing, luciferase reporter assay, 5-Aza-2'-deoxycytidine treatment","journal":"International journal of cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — bisulfite sequencing and reporter assay with pharmacological demethylation; single lab, two orthogonal methods","pmids":["16921485"],"is_preprint":false},{"year":2010,"finding":"MIM/MTSS1 is required at the basal body of mesenchymal cells for cilia maintenance and Shh responsiveness. MIM knockdown results in increased Src kinase activity and hyperphosphorylation of cortactin. Inhibition of Src or depletion of cortactin compensates for the ciliogenesis defect in MIM knockdown cells; overexpression of Src or phospho-mimetic cortactin is sufficient to inhibit ciliogenesis. Thus, MIM promotes ciliogenesis by antagonizing Src-dependent phosphorylation of cortactin.","method":"siRNA knockdown, Src kinase activity assays, phospho-cortactin immunoblotting, Src inhibitor treatment, cortactin depletion, cilia immunofluorescence, hair follicle regeneration assay","journal":"Developmental cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis (Src and cortactin rescue), biochemical confirmation of Src/cortactin hyperphosphorylation, multiple orthogonal approaches; single lab but rigorous","pmids":["20708589"],"is_preprint":false},{"year":2011,"finding":"MIM/MTSS1 promotes Arp2/3-mediated actin assembly at adherens junctions in kidney epithelial (MDCK) cells; this requires both membrane binding (I-BAR domain) and actin monomer interaction (WH2 domain). MIM-deficient mice develop severe urinary concentration defects due to compromised kidney epithelial junction integrity, leading to end-stage renal failure. MIM is dispensable for embryonic development and, in this in vivo context, is not required for Shh signaling.","method":"Knockout mouse phenotyping, MDCK cell culture with domain mutants, actin assembly assays, junction integrity assays","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 / Strong — knockout mouse with specific renal phenotype, mechanistic dissection using domain mutants in cell culture, two orthogonal systems","pmids":["21406566"],"is_preprint":false},{"year":2011,"finding":"MIM-deficient mice develop B-cell lymphomas (~78% incidence by 1–2 years). MIM-deficient B-cells fail to undergo chemotaxis or morphological changes in response to CXCL13 and fail to internalize CXCR5. MIM is the only I-BAR family member highly expressed in human B cells.","method":"MIM knockout mouse autopsy/histology, CXCL13 chemotaxis assays, CXCR5 internalization assays, microarray gene expression","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 2 / Strong — knockout mouse model with tumor phenotype and mechanistic B-cell signaling assays; multiple assays in single rigorous study","pmids":["22081072"],"is_preprint":false},{"year":2011,"finding":"MIM/MTSS1 specifically binds Daam1 (through a conserved domain in Daam1) and couples non-canonical Wnt signaling to neural tube closure in Xenopus. This interaction is positively regulated by Wnt stimulation. MIM depletion inhibits anterior neural fold closure but not convergent extension; the function requires both the membrane-remodeling (I-BAR) and actin-binding (WH2) domains.","method":"Co-immunoprecipitation of MIM and Daam1, Xenopus morpholino knockdown, domain rescue experiments, in situ hybridization","journal":"Development (Cambridge, England)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP confirmed interaction, morpholino phenotype with domain rescue; single lab","pmids":["21471152"],"is_preprint":false},{"year":2011,"finding":"MIM/MTSS1 expression in hepatocellular carcinoma is silenced by DNMT3B binding directly to the MTSS1 5'-flanking region (-865/-645), independently of DNA methylation. MTSS1 overexpression arrests HCC cells in G2/M phase. Methylation inhibitors fail to restore DNMT3B-mediated MTSS1 silencing.","method":"Chromatin immunoprecipitation (ChIP), luciferase reporter assay, methylation-specific PCR, bisulfite sequencing, cell cycle analysis","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP confirms direct DNMT3B binding to MTSS1 promoter, reporter and methylation assays; single lab","pmids":["21909138"],"is_preprint":false},{"year":2012,"finding":"Mtss1 promotes cell-cell junction assembly and stability by elevating Rac1-GTP levels and driving actin recruitment to junctions. Mtss1 depletion reduces F-actin at cell-cell junctions, and Mtss1 makes cells resistant to HGF-induced junction disassembly and scatter.","method":"siRNA knockdown, wound healing and HGF scatter assays, Rac-GTP pulldown, F-actin immunofluorescence at junctions","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Rac pulldown and junction assays with knockdown; single lab, two methods","pmids":["22479308"],"is_preprint":false},{"year":2013,"finding":"MIM/MTSS1 suppresses RhoA activity and stress fiber formation in breast cancer cells. miR-182 targets MIM directly (3'UTR luciferase assay), and restoring MIM expression blocks the pro-metastasis function of miR-182; RhoA inhibition reverses the phenotypes of both miR-182 overexpression and MIM knockdown.","method":"3'UTR luciferase reporter assay, RhoA activity assay, rescue experiments, in vivo xenograft","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — luciferase validation of miR-182/MIM axis, RhoA activity assay, rescue experiment; single lab","pmids":["23474751"],"is_preprint":false},{"year":2013,"finding":"SCFβ-TRCP E3 ubiquitin ligase targets MTSS1 for ubiquitination and proteasomal degradation. Casein Kinase Iδ (CKIδ) phosphorylates Ser322 within a DSGXXS degron in MTSS1, triggering interaction with β-TRCP. Depletion of Cullin1 or β-TRCP1 increases MTSS1 levels. A non-degradable S322A mutant more strongly inhibits cancer cell proliferation and migration than wild-type MTSS1.","method":"Co-immunoprecipitation, ubiquitination assay, site-directed mutagenesis (S322A), shRNA knockdown of Cullin1/β-TRCP, cell proliferation and migration assays","journal":"Oncotarget","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — co-IP, ubiquitination assay, site-directed mutagenesis identifying degron and kinase; multiple orthogonal methods in single study","pmids":["24318128"],"is_preprint":false},{"year":2014,"finding":"High MTSS1 expression in a subset of primary melanomas promotes metastatic ability via engagement of actin dynamics through Rho-GTPases and cofilin, demonstrated by loss- and gain-of-function approaches in vitro and in vivo.","method":"Loss/gain-of-function assays, in vitro invasion assays, in vivo xenograft, Rho-GTPase activation assay, cofilin pathway analysis","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo and in vitro loss/gain-of-function with Rho-GTPase/cofilin pathway readouts; single lab","pmids":["24632752"],"is_preprint":false},{"year":2015,"finding":"MIM/MTSS1 I-BAR domain accumulates at future dendritic spine initiation sites in a PIP2-dependent manner and deforms the plasma membrane outward into a proto-protrusion, initiating spine formation independent of actin polymerization. Subsequent elongation requires PIP2-dependent Arp2/3-mediated actin assembly. MIM-deficient mice show decreased spine density, larger spine heads, altered glutamatergic transmission, and compatible behavioral defects.","method":"Live imaging of MIM accumulation, PIP2 manipulation, Arp2/3 inhibition, MIM knockout mice, electrophysiology, behavioral tests","journal":"Developmental cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — live imaging, pharmacological dissection of actin vs. membrane steps, knockout mouse phenotype with electrophysiology; multiple orthogonal methods","pmids":["26051541"],"is_preprint":false},{"year":2015,"finding":"ΔNp63 transcription factor drives MTSS1 expression by binding to a p63-responsive element in the MTSS1 locus, and this axis promotes migration of breast tumor cells.","method":"ChIP, luciferase reporter assay, siRNA knockdown, migration assays","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP and reporter assay confirm p63 binding and transcriptional activation of MTSS1; single lab","pmids":["26119942"],"is_preprint":false},{"year":2016,"finding":"MIM/MTSS1 regulates CXCR4 surface expression and internalization in bone marrow cells. MIM-deficient cells show increased surface CXCR4, impaired CXCR4 internalization, constitutive activation of Rac, Cdc42, and p38, and enhanced homing to bone marrow. This enhanced homing is abolished by p38 antagonist treatment.","method":"MIM knockout mouse bone marrow transplantation, CXCR4 surface expression by flow cytometry, CXCR4 internalization assay, Rac/Cdc42/p38 activity assays, pharmacological p38 inhibition","journal":"Leukemia","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo transplant with pharmacological rescue, multiple GTPase activity assays, receptor internalization assay; multiple orthogonal methods","pmids":["26965284"],"is_preprint":false},{"year":2018,"finding":"MTSS1 inhibits the actin-nucleating formin DAAM1 in Purkinje cell dendritic filopodia by directly binding DAAM1 through its C-terminus, pausing DAAM1-mediated F-actin polymerization as shown by single-molecule speckle microscopy. MTSS1 plays a dual role: inhibiting formin DAAM1 and activating ARP2/3, thus balancing filopodia morphology and determining final neuronal morphology.","method":"Co-immunoprecipitation, single-molecule speckle microscopy, conditional knockout mice, overactivation of DAAM1 phenocopy, domain-binding assays","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — single-molecule imaging plus co-IP and knockout mouse with formin phenocopy; multiple orthogonal methods, mechanistically rigorous","pmids":["29972794"],"is_preprint":false},{"year":2018,"finding":"MTSS1 is a suppressor of Src family kinase (SFK) activity in Purkinje neurons. MTSS1 loss results in increased SFK activity, reduced Purkinje neuron arborization, low basal firing, and subsequent cell death. Mouse models of SCA1 and SCA2 show elevated SFK activity and dramatically reduced MTSS1 protein levels (SCA1 via reduced gene expression; SCA2 via reduced protein translation). Treatment with a clinically approved Src inhibitor corrects Purkinje neuron basal firing and delays ataxia progression.","method":"MTSS1 knockout mice, Src kinase activity assays, electrophysiology, SCA1/SCA2/SCA5 mouse models, Src inhibitor pharmacological rescue, protein expression analysis","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple SCA mouse models with SFK activity measurements, electrophysiology, pharmacological rescue; independently validated across multiple disease models","pmids":["30530649"],"is_preprint":false},{"year":2020,"finding":"MTSS1 interacts with the E3 ubiquitin ligase RBCK1 to facilitate RBCK1-mediated ubiquitination and degradation of NF-κB p65, thereby suppressing NF-κB signaling and tumor-initiating cell (TIC) expansion. ACTBL2 competes with RBCK1 for MTSS1 binding, leading to p65 stabilization when ACTBL2 is present.","method":"Co-immunoprecipitation (MTSS1-RBCK1 and MTSS1-ACTBL2), ubiquitination assay for p65, knockout mouse mammary tumor models, patient-derived organoid and xenograft experiments","journal":"Nature cancer","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — co-IP, ubiquitination assay, competitive binding with ACTBL2, in vivo knockout models; multiple orthogonal methods in single rigorous study","pmids":["35122005"],"is_preprint":false},{"year":2021,"finding":"MIM/MTSS1 I-BAR protein generates large extracellular vesicles (filopodia-derived vesicles, FDVs) by scission of filopodia. MIM-containing FDV production is promoted by external forces and by suppression of ALIX. These FDVs contain lysophospholipids, IRS4, and Rac1, and stimulate migration of recipient cells through lamellipodia formation.","method":"Live imaging, electron microscopy, FDV isolation and proteomics/lipidomics, Rac1 activity assay in recipient cells, ALIX suppression, force application experiments","journal":"Developmental cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — live imaging of filopodia scission, vesicle proteomics/lipidomics, functional assay in recipient cells; multiple orthogonal methods in single study","pmids":["33756122"],"is_preprint":false},{"year":2011,"finding":"Mtss1 enhances EGF receptor localization to the plasma membrane in head and neck squamous cell carcinoma cells, prolongs EGF signaling, and results in enhanced Erk1/2 and Akt phosphorylation. Depletion of Mtss1 decreases EGF receptor levels and reduces Erk1/2 and Akt phosphorylation.","method":"siRNA knockdown, EGF receptor localization by immunofluorescence, phospho-Erk1/2 and phospho-Akt immunoblotting, proliferation assays, organotypic assay, xenograft","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — knockdown with receptor localization and signaling readouts; single lab","pmids":["21927027"],"is_preprint":false},{"year":2011,"finding":"MIM/MTSS1 regulates cell polarity, Rho GTPase activity, and endocytosis in mouse embryonic fibroblasts. MIM-deficient MEFs show impaired stress fiber and focal adhesion assembly with reduced Rho GTPase activity; this is rescued by constitutively active RhoA. MIM-null cells show attenuated internalization of transferrin, PDGF receptor, and foreign DNAs, and elevated PDGF receptor tyrosine phosphorylation upon PDGF treatment.","method":"MIM gene-trap knockout MEFs, Rho GTPase activity assays, constitutively active RhoA rescue, internalization assays, PDGF receptor phosphorylation immunoblotting, cell migration assays","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — knockout cells with GTPase activation assay and endocytosis readouts; single lab, multiple assays","pmids":["21695258"],"is_preprint":false}],"current_model":"MTSS1/MIM is an I-BAR (inverse-BAR) domain scaffold protein that deforms membranes into outward protrusions via its I-BAR domain in a PIP2-dependent manner, binds and sequesters ATP-actin monomers through its WH2 domain, bundles F-actin, activates Rac1 and Arp2/3-mediated actin assembly at junctions, inhibits the formin DAAM1, and suppresses Src family kinase activity in neurons; it is degraded by the SCFβ-TRCP/CKIδ ubiquitin-proteasome pathway, potentiates Gli-dependent Hedgehog transcription, facilitates RBCK1-mediated NF-κB p65 ubiquitination, regulates CXCR4 surface expression and internalization, and generates filopodia-derived extracellular vesicles, collectively coordinating actin and membrane dynamics, cell polarity, receptor trafficking, and intercellular signaling across diverse cell types."},"narrative":{"mechanistic_narrative":"MTSS1 (MIM) is a membrane-deforming, actin-regulatory scaffold that couples the plasma membrane to the actin cytoskeleton to build and stabilize cellular protrusions, junctions, and receptor-trafficking machinery across epithelial, neuronal, and hematopoietic cells [PMID:26051541, PMID:21406566]. Its I-BAR (IMD) domain binds PIP2-rich membrane and deforms it outward into nascent protrusions while also bundling F-actin and binding/activating Rac1, whereas its C-terminal WH2 domain sequesters ATP-actin monomers and modulates nucleation [PMID:12482861, PMID:15684034, PMID:26051541]. Through these activities MTSS1 promotes Arp2/3-dependent actin assembly at adherens junctions and dendritic spines while restraining opposing actin machinery—directly binding and pausing the formin DAAM1 and suppressing Src family kinase activity (and downstream cortactin phosphorylation) in Purkinje and ciliated cells [PMID:29972794, PMID:30530649, PMID:20708589, PMID:21406566]. By regulating endocytic internalization, MTSS1 controls the surface levels and signaling output of multiple receptors including CXCR4/CXCR5 and EGFR [PMID:26965284, PMID:22081072, PMID:21927027]. MTSS1 abundance is tightly controlled: it is degraded via CKIδ-primed phosphorylation of a DSGXXS degron that recruits the SCFβ-TRCP ubiquitin ligase [PMID:24318128], and it acts as a tumor and lymphoma suppressor, with loss producing renal junction failure, B-cell lymphoma, and dysregulated NF-κB signaling through its scaffolding of the RBCK1 E3 ligase that ubiquitinates p65 [PMID:21406566, PMID:22081072, PMID:35122005]. In neurons, reduced MTSS1 with elevated Src activity links it mechanistically to spinocerebellar ataxia models [PMID:30530649].","teleology":[{"year":2002,"claim":"Established the biochemical basis of MTSS1's actin engagement, defining the C-terminal WH2 domain as an ATP-actin-monomer-binding module that regulates filament nucleation.","evidence":"In vitro actin binding/sedimentation with Kd measurements, WH2 mutagenesis, and NIH 3T3 overexpression","pmids":["12482861"],"confidence":"High","gaps":["Did not address membrane-deforming activity","Cellular consequence shown only by overexpression phenotype"]},{"year":2003,"claim":"Linked MTSS1's actin function to membrane targeting and a receptor partner, showing the N-terminus localizes to membranes and the protein binds the phosphatase PTPδ while inducing actin-rich protrusions.","evidence":"Pulldown with purified proteins and cell extracts, truncation-construct localization","pmids":["12570871"],"confidence":"Medium","gaps":["PTPδ interaction shown by single pulldown without reciprocal validation","Functional consequence of PTPδ binding unresolved"]},{"year":2004,"claim":"Identified a transcriptional/signaling role distinct from actin, placing MTSS1 in a Gli/SUFU complex that potentiates Hedgehog-dependent transcription.","evidence":"Co-IP of Gli/SUFU complex, luciferase reporter assays, regenerated skin model","pmids":["15545630"],"confidence":"Medium","gaps":["Mechanism of Gli potentiation unclear","Later in vivo work found MTSS1 dispensable for Shh signaling in some contexts"]},{"year":2005,"claim":"Defined MTSS1 as a bifunctional actin/membrane regulator: the IMD/I-BAR domain bundles F-actin and binds/activates Rac, while the protein modulates cortactin- and N-WASP-driven Arp2/3 polymerization and cell motility.","evidence":"In vitro actin polymerization and bundling assays, direct binding assays, domain-deletion motility experiments, RPTPδ co-IP and Rac pulldown","pmids":["15688017","16280553","15684034"],"confidence":"High","gaps":["How Rac binding and actin bundling are mechanistically coupled within the IMD remains unresolved","Directionality of motility effects context-dependent"]},{"year":2006,"claim":"Showed MTSS1 expression is epigenetically controlled, with CpG-island methylation silencing the promoter in low-expressing cells.","evidence":"Bisulfite sequencing, luciferase reporter, 5-Aza-2'-deoxycytidine treatment","pmids":["16921485"],"confidence":"Medium","gaps":["Upstream signals controlling methylation not identified"]},{"year":2010,"claim":"Revealed MTSS1 as a ciliogenesis factor that acts by antagonizing Src-dependent cortactin phosphorylation at the basal body.","evidence":"siRNA knockdown, Src activity assays, phospho-cortactin immunoblotting, epistatic rescue by Src inhibition or cortactin depletion, cilia immunofluorescence","pmids":["20708589"],"confidence":"High","gaps":["How MTSS1 restrains Src is not established","Direct Src interaction not demonstrated"]},{"year":2011,"claim":"Established physiological in vivo functions through knockout phenotypes—renal epithelial junction integrity and B-cell lymphoma suppression with defective CXCR5 chemotaxis/internalization—and defined MTSS1's role in receptor endocytosis and Rho-GTPase-dependent polarity.","evidence":"MIM knockout mice (renal, lymphoma), MDCK domain-mutant junction assays, CXCL13 chemotaxis and CXCR5 internalization assays, knockout MEF endocytosis and Rho-GTPase assays, EGFR localization in HNSCC","pmids":["21406566","22081072","21695258","21927027"],"confidence":"High","gaps":["Molecular machinery coupling MTSS1 to receptor internalization not fully defined","Tissue-specific contributions of I-BAR vs WH2 incompletely separated"]},{"year":2011,"claim":"Connected MTSS1 to developmental Wnt signaling and additional transcriptional silencing, showing it binds DAAM1 to drive neural fold closure and is repressed by DNMT3B in hepatocellular carcinoma.","evidence":"Co-IP of MIM-Daam1, Xenopus morpholino knockdown with domain rescue; ChIP, reporter, methylation assays, cell-cycle analysis in HCC","pmids":["21471152","21909138"],"confidence":"Medium","gaps":["DAAM1 functional consequence not yet mechanistically resolved at this stage","DNMT3B silencing mechanism methylation-independent but undefined"]},{"year":2012,"claim":"Demonstrated MTSS1 stabilizes cell-cell junctions by elevating Rac1-GTP and recruiting F-actin, conferring resistance to scatter-inducing signals.","evidence":"siRNA knockdown, HGF scatter and wound-healing assays, Rac-GTP pulldown, junctional F-actin imaging","pmids":["22479308"],"confidence":"Medium","gaps":["Mechanism of Rac1 activation at junctions not detailed"]},{"year":2013,"claim":"Positioned MTSS1 within a RhoA-suppressing, anti-metastatic axis regulated by miR-182.","evidence":"3'UTR luciferase reporter, RhoA activity assay, rescue experiments, xenograft","pmids":["23474751"],"confidence":"Medium","gaps":["How MTSS1 suppresses RhoA mechanistically unresolved","Context-dependence vs pro-metastatic roles unexplained"]},{"year":2013,"claim":"Defined the degradation pathway controlling MTSS1 levels: CKIδ phosphorylation of Ser322 in a DSGXXS degron recruits SCFβ-TRCP for ubiquitin-proteasome turnover.","evidence":"Co-IP, ubiquitination assay, S322A mutagenesis, Cullin1/β-TRCP knockdown, proliferation/migration assays","pmids":["24318128"],"confidence":"High","gaps":["Signals triggering CKIδ phosphorylation not identified","Structural basis of degron recognition not determined"]},{"year":2014,"claim":"Showed MTSS1 can also promote metastasis in a subset of melanomas through Rho-GTPase and cofilin-mediated actin dynamics, highlighting context-dependent function.","evidence":"Loss/gain-of-function, invasion assays, xenograft, Rho-GTPase and cofilin pathway analysis","pmids":["24632752"],"confidence":"Medium","gaps":["Determinants of pro- vs anti-metastatic switch not defined"]},{"year":2015,"claim":"Resolved the temporal mechanics of protrusion initiation, showing the I-BAR domain deforms PIP2 membrane outward independent of actin to nucleate dendritic spines, with Arp2/3 actin assembly driving subsequent elongation; identified ΔNp63 as a transcriptional activator.","evidence":"Live imaging, PIP2 manipulation, Arp2/3 inhibition, MIM knockout mice with electrophysiology and behavior; ChIP and reporter for ΔNp63","pmids":["26051541","26119942"],"confidence":"High","gaps":["Trigger localizing MTSS1 to spine initiation sites unknown","Coordination between membrane deformation and actin handoff incompletely mapped"]},{"year":2016,"claim":"Established MTSS1 as a controller of CXCR4 surface expression and internalization in hematopoietic cells, with loss causing constitutive Rac/Cdc42/p38 activation and enhanced bone marrow homing.","evidence":"Knockout bone marrow transplantation, CXCR4 flow cytometry and internalization assays, GTPase activity assays, p38 pharmacological inhibition","pmids":["26965284"],"confidence":"High","gaps":["Direct link between MTSS1 and CXCR4 endocytic machinery undefined"]},{"year":2018,"claim":"Revealed MTSS1's dual balancing role in neuronal protrusion morphology—directly binding and pausing the formin DAAM1 while activating Arp2/3—and as a suppressor of Src family kinases relevant to spinocerebellar ataxia.","evidence":"Single-molecule speckle microscopy, co-IP, conditional knockout mice, SCA1/SCA2 models, Src activity assays, electrophysiology, Src-inhibitor rescue","pmids":["29972794","30530649"],"confidence":"High","gaps":["Mechanism by which MTSS1 inhibits SFK activity not molecularly defined","Whether MTSS1 directly binds Src unresolved"]},{"year":2020,"claim":"Identified a scaffolding role in NF-κB control, with MTSS1 promoting RBCK1-mediated ubiquitination of p65 to restrain tumor-initiating-cell expansion, antagonized by ACTBL2 competition.","evidence":"Co-IP (MTSS1-RBCK1, MTSS1-ACTBL2), p65 ubiquitination assay, knockout mammary tumor models, patient-derived organoid/xenograft","pmids":["35122005"],"confidence":"High","gaps":["How MTSS1's actin/membrane domains relate to its E3-scaffolding function unclear"]},{"year":2021,"claim":"Demonstrated MTSS1 generates filopodia-derived extracellular vesicles by membrane scission, enabling intercellular signaling that promotes recipient-cell migration.","evidence":"Live imaging, electron microscopy, FDV proteomics/lipidomics, recipient-cell Rac1 assays, ALIX suppression, force application","pmids":["33756122"],"confidence":"High","gaps":["Physiological contexts and in vivo relevance of FDVs not established","Mechanism of force-promoted scission not detailed"]},{"year":null,"claim":"The molecular basis for how MTSS1 simultaneously coordinates its membrane-deforming, actin-regulating, receptor-trafficking, and ubiquitin-ligase-scaffolding activities—and what dictates its context-dependent tumor-suppressive versus pro-metastatic behavior—remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified structural model integrating I-BAR, WH2, and protein-scaffolding regions","Determinants of opposing cancer roles undefined","Direct mechanism of Src kinase suppression unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[0,3,5,16]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[16]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[21,5]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[5,19,20]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[16,22]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[1,8,16]},{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[0,5]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[1]},{"term_id":"GO:0005815","term_label":"microtubule organizing center","supporting_discovery_ids":[7]}],"pathway":[{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[18,9,23,24]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[12,18,21]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[16,10,8]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[14,21]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[9,21,20]}],"complexes":["Gli/SUFU complex","SCFβ-TRCP ubiquitin ligase complex"],"partners":["ACTB (ACTIN)","CTTN (CORTACTIN)","DAAM1","RBCK1","PTPRD (PTPΔ)","RAC1","BTRC 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genetics","url":"https://pubmed.ncbi.nlm.nih.gov/8322815","citation_count":30,"is_preprint":false},{"pmid":"29456723","id":"PMC_29456723","title":"miR-96 promotes breast cancer metastasis by suppressing MTSS1.","date":"2018","source":"Oncology letters","url":"https://pubmed.ncbi.nlm.nih.gov/29456723","citation_count":29,"is_preprint":false},{"pmid":"22081072","id":"PMC_22081072","title":"Mice deficient in MIM expression are predisposed to lymphomagenesis.","date":"2011","source":"Oncogene","url":"https://pubmed.ncbi.nlm.nih.gov/22081072","citation_count":29,"is_preprint":false},{"pmid":"21965727","id":"PMC_21965727","title":"Metastasis suppressor-1, MTSS1, acts as a putative tumour suppressor in human bladder cancer.","date":"2011","source":"Anticancer research","url":"https://pubmed.ncbi.nlm.nih.gov/21965727","citation_count":28,"is_preprint":false},{"pmid":"30241080","id":"PMC_30241080","title":"Negative impact of the imidazolium-based ionic liquid [C8mim]Br on silver carp (Hypophthalmichthys molitrix): Long-term and low-level exposure.","date":"2018","source":"Chemosphere","url":"https://pubmed.ncbi.nlm.nih.gov/30241080","citation_count":28,"is_preprint":false},{"pmid":"27164937","id":"PMC_27164937","title":"miR-96 promotes the growth of prostate carcinoma cells by suppressing MTSS1.","date":"2016","source":"Tumour biology : the journal of the International Society for Oncodevelopmental Biology and Medicine","url":"https://pubmed.ncbi.nlm.nih.gov/27164937","citation_count":27,"is_preprint":false},{"pmid":"12573255","id":"PMC_12573255","title":"Genomic basis of mucopolysaccharidosis type IIID (MIM 252940) revealed by sequencing of GNS encoding N-acetylglucosamine-6-sulfatase.","date":"2003","source":"Genomics","url":"https://pubmed.ncbi.nlm.nih.gov/12573255","citation_count":27,"is_preprint":false},{"pmid":"25385572","id":"PMC_25385572","title":"MTSS1 suppresses cell migration and invasion by targeting CTTN in glioblastoma.","date":"2014","source":"Journal of neuro-oncology","url":"https://pubmed.ncbi.nlm.nih.gov/25385572","citation_count":26,"is_preprint":false},{"pmid":"29453719","id":"PMC_29453719","title":"MicroRNA-411 promoted the osteosarcoma progression by suppressing MTSS1 expression.","date":"2018","source":"Environmental science and pollution research international","url":"https://pubmed.ncbi.nlm.nih.gov/29453719","citation_count":26,"is_preprint":false},{"pmid":"29842889","id":"PMC_29842889","title":"Toxicity of imidazoles ionic liquid [C16mim]Cl to HepG2 cells.","date":"2018","source":"Toxicology in vitro : an international journal published in association with BIBRA","url":"https://pubmed.ncbi.nlm.nih.gov/29842889","citation_count":25,"is_preprint":false},{"pmid":"28618302","id":"PMC_28618302","title":"Growth and physiological responses of a marine diatom (Phaeodactylum tricornutum) against two imidazolium-based ionic liquids ([C4mim]BF4 and [C8mim]BF4).","date":"2017","source":"Aquatic toxicology (Amsterdam, Netherlands)","url":"https://pubmed.ncbi.nlm.nih.gov/28618302","citation_count":25,"is_preprint":false},{"pmid":"32929338","id":"PMC_32929338","title":"A reciprocal feedback of Myc and lncRNA MTSS1-AS contributes to extracellular acidity-promoted metastasis of pancreatic cancer.","date":"2020","source":"Theranostics","url":"https://pubmed.ncbi.nlm.nih.gov/32929338","citation_count":24,"is_preprint":false},{"pmid":"30530649","id":"PMC_30530649","title":"MTSS1/Src family kinase dysregulation underlies multiple inherited ataxias.","date":"2018","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/30530649","citation_count":24,"is_preprint":false},{"pmid":"35122005","id":"PMC_35122005","title":"MTSS1 suppresses mammary tumor-initiating cells by enhancing RBCK1-mediated p65 ubiquitination.","date":"2020","source":"Nature cancer","url":"https://pubmed.ncbi.nlm.nih.gov/35122005","citation_count":24,"is_preprint":false},{"pmid":"25996952","id":"PMC_25996952","title":"Identification of the Adapter Molecule MTSS1 as a Potential Oncogene-Specific Tumor Suppressor in Acute Myeloid Leukemia.","date":"2015","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/25996952","citation_count":24,"is_preprint":false},{"pmid":"23350348","id":"PMC_23350348","title":"The tumour suppressive role of metastasis suppressor-1, MTSS1, in human kidney cancer, a possible connection with the SHH pathway.","date":"2012","source":"Journal of experimental therapeutics & oncology","url":"https://pubmed.ncbi.nlm.nih.gov/23350348","citation_count":23,"is_preprint":false},{"pmid":"14661080","id":"PMC_14661080","title":"CKN1 (MIM 216400): mutations in Cockayne syndrome type A and a new common polymorphism.","date":"2003","source":"Journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/14661080","citation_count":23,"is_preprint":false},{"pmid":"20961464","id":"PMC_20961464","title":"The association of the Clock 3111 T/C SNP with lipids and lipoproteins including small dense low-density lipoprotein: results from the Mima study.","date":"2010","source":"BMC medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/20961464","citation_count":23,"is_preprint":false},{"pmid":"27446348","id":"PMC_27446348","title":"Differential effects of MTSS1 on invasion and proliferation in subtypes of non-small cell lung cancer cells.","date":"2016","source":"Experimental and therapeutic medicine","url":"https://pubmed.ncbi.nlm.nih.gov/27446348","citation_count":22,"is_preprint":false},{"pmid":"12409274","id":"PMC_12409274","title":"Four novel mutations associated with autosomal recessive inclusion body myopathy (MIM: 600737).","date":"2002","source":"Molecular genetics and metabolism","url":"https://pubmed.ncbi.nlm.nih.gov/12409274","citation_count":22,"is_preprint":false},{"pmid":"26629033","id":"PMC_26629033","title":"MTSS1 gene regulated by miR-96 inhibits cell proliferation and metastasis in tongue squamous cellular carcinoma Tca8113 cell line.","date":"2015","source":"International journal of clinical and experimental medicine","url":"https://pubmed.ncbi.nlm.nih.gov/26629033","citation_count":21,"is_preprint":false},{"pmid":"21471152","id":"PMC_21471152","title":"MIM regulates vertebrate neural tube closure.","date":"2011","source":"Development (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/21471152","citation_count":21,"is_preprint":false},{"pmid":"11896450","id":"PMC_11896450","title":"X-linked Coffin-Lowry syndrome (CLS, MIM 303600, RPS6KA3 gene, protein product known under various names: pp90(rsk2), RSK2, ISPK, MAPKAP1).","date":"2002","source":"European journal of human genetics : EJHG","url":"https://pubmed.ncbi.nlm.nih.gov/11896450","citation_count":21,"is_preprint":false},{"pmid":"21695258","id":"PMC_21695258","title":"Murine missing in metastasis (MIM) mediates cell polarity and regulates the motility response to growth factors.","date":"2011","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/21695258","citation_count":20,"is_preprint":false},{"pmid":"21820140","id":"PMC_21820140","title":"The relationship between adiponectin, an adiponectin gene polymorphism, and high-density lipoprotein particle size: from the Mima study.","date":"2011","source":"Metabolism: clinical and experimental","url":"https://pubmed.ncbi.nlm.nih.gov/21820140","citation_count":20,"is_preprint":false},{"pmid":"30135068","id":"PMC_30135068","title":"MIM through MOM: the awakening of Bax and Bak pores.","date":"2018","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/30135068","citation_count":20,"is_preprint":false},{"pmid":"35942339","id":"PMC_35942339","title":"Experimental and computational workflow for the analysis of tRNA pools from eukaryotic cells by mim-tRNAseq.","date":"2022","source":"STAR protocols","url":"https://pubmed.ncbi.nlm.nih.gov/35942339","citation_count":20,"is_preprint":false},{"pmid":"33396149","id":"PMC_33396149","title":"New insight into the negative impact of imidazolium-based ionic liquid [C10mim]Cl on Hela cells: From membrane damage to biochemical alterations.","date":"2020","source":"Ecotoxicology and environmental safety","url":"https://pubmed.ncbi.nlm.nih.gov/33396149","citation_count":20,"is_preprint":false},{"pmid":"26965284","id":"PMC_26965284","title":"MIM regulates the trafficking of bone marrow cells via modulating surface expression of CXCR4.","date":"2016","source":"Leukemia","url":"https://pubmed.ncbi.nlm.nih.gov/26965284","citation_count":20,"is_preprint":false},{"pmid":"26775612","id":"PMC_26775612","title":"Promiscuous metallo-β-lactamases: MIM-1 and MIM-2 may play an essential role in quorum sensing networks.","date":"2015","source":"Journal of inorganic biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/26775612","citation_count":19,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":48983,"output_tokens":6780,"usd":0.124325,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":15710,"output_tokens":5596,"usd":0.109225,"stage2_stop_reason":"end_turn"},"total_usd":0.23355,"stage1_batch_id":"msgbatch_013a8chtv3AWyTqv4z4sEF4C","stage2_batch_id":"msgbatch_01AHsuW63vinsvuTgzmQ3n62","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2002,\n      \"finding\": \"MIM/MTSS1 C-terminal WH2 domain binds ATP-actin monomers with higher affinity (Kd ~0.06 µM) than ADP-actin monomers (Kd ~0.3 µM), inhibits actin filament nucleation in vitro, but allows barbed-end assembly; inhibits nucleotide exchange on actin monomers. Overexpression in NIH 3T3 cells causes disappearance of stress fibers and abnormal actin structures.\",\n      \"method\": \"In vitro actin binding/sedimentation assays, site-directed mutagenesis of WH2 domain, Northern blot, overexpression in NIH 3T3 cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with Kd measurements, mutagenesis confirming WH2 as actin-binding site, and cellular overexpression phenotype; multiple orthogonal methods in one study\",\n      \"pmids\": [\"12482861\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"MIM-B (long isoform of MIM/MTSS1) binds actin via a C-terminal WH2 domain and also binds the cytoplasmic domain of receptor protein tyrosine phosphatase delta (PTPδ), as shown by pulldown with purified proteins and cell extracts. The N-terminal portion of MIM-B localizes to internal vesicles and likely targets the protein to membranes; the C-terminal portion is cytoplasmic and does not affect the actin cytoskeleton. Full-length MIM-B induces actin-rich protrusions at the plasma membrane and promotes disassembly of stress fibers.\",\n      \"method\": \"Pulldown with purified proteins and cell extracts, subcellular localization by expression of truncated constructs\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — single pulldown/binding assay for PTPδ interaction, supported by cellular localization data; single lab\",\n      \"pmids\": [\"12570871\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"MIM/MTSS1 is a Sonic hedgehog (Shh)-responsive gene that is part of a Gli/Suppressor of Fused complex and potentiates Gli-dependent transcription. MIM uses domains distinct from those required for actin monomer binding to enhance Gli activity. Together with Gli1, MIM recapitulates Shh-mediated epidermal proliferation and invasion.\",\n      \"method\": \"Co-immunoprecipitation (Gli/SUFU complex), cotransfection luciferase assays, regenerated human skin model\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — co-IP demonstrating complex membership, reporter assays for transcriptional potentiation; single lab, two orthogonal methods\",\n      \"pmids\": [\"15545630\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"MIM/MTSS1 directly binds the SH3 domain of cortactin and promotes cortactin/Arp2/3-mediated actin polymerization in vitro. Full-length MIM binds G-actin with affinity similar to N-WASP-VCA and inhibits N-WASP-VCA-mediated actin polymerization in vitro. Overexpression of full-length MIM inhibits PDGF-induced cell motility, while deletion of the WH2 domain (abrogating G-actin binding) enhances motility; deletion of the proline-rich domain (required for cortactin binding) strengthens MIM-mediated motility inhibition.\",\n      \"method\": \"In vitro actin polymerization assays, direct binding assays, GFP colocalization, cell motility assays with domain-deletion mutants\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — in vitro reconstitution of actin polymerization, direct binding, multiple domain mutants tested in cells; multiple orthogonal methods\",\n      \"pmids\": [\"15688017\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"MIM-B induces lamellipodia-like actin-rich protrusions dependent on both the IRSp53/MIM (IMD/I-BAR) domain and Rac activity, but not the WH2 motif. MIM-B binds and activates Rac GTPase via its IMD domain, though Rac binding alone is insufficient to induce lamellipodia. Actin-bundling and Rac-binding properties of the IMD are inseparable.\",\n      \"method\": \"Expression of domain mutants, dominant-negative Rac experiments, actin bundling assays, Rac activation assays (pull-down)\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple domain mutants with cellular phenotypes, Rac pulldown; single lab\",\n      \"pmids\": [\"16280553\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"MIM/MTSS1 bundles F-actin via its IMD/I-BAR domain; this self-association-dependent bundling is independent of G-actin binding. MIM's cytoskeletal remodeling in cells requires a domain that associates with RPTPδ, which in turn enhances RPTPδ membrane localization. MIM is induced in a patched1-dependent manner (downstream of Shh signaling).\",\n      \"method\": \"F-actin bundling assays, domain mutagenesis, RPTPδ co-immunoprecipitation, membrane localization assay, patched1 dependency by genetic manipulation\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple biochemical assays with domain mutants, co-IP for RPTPδ, genetic epistasis with patched1; single lab\",\n      \"pmids\": [\"15684034\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"MIM/MTSS1 promoter expression is regulated by DNA methylation of a CpG island in its 5' region; treatment with demethylation agent 5-Aza-2'-deoxycytidine upregulates MIM expression in low-expressing cell lines. The non-methylated promoter has similar activity regardless of endogenous MIM expression level.\",\n      \"method\": \"Bisulfite sequencing, luciferase reporter assay, 5-Aza-2'-deoxycytidine treatment\",\n      \"journal\": \"International journal of cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — bisulfite sequencing and reporter assay with pharmacological demethylation; single lab, two orthogonal methods\",\n      \"pmids\": [\"16921485\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"MIM/MTSS1 is required at the basal body of mesenchymal cells for cilia maintenance and Shh responsiveness. MIM knockdown results in increased Src kinase activity and hyperphosphorylation of cortactin. Inhibition of Src or depletion of cortactin compensates for the ciliogenesis defect in MIM knockdown cells; overexpression of Src or phospho-mimetic cortactin is sufficient to inhibit ciliogenesis. Thus, MIM promotes ciliogenesis by antagonizing Src-dependent phosphorylation of cortactin.\",\n      \"method\": \"siRNA knockdown, Src kinase activity assays, phospho-cortactin immunoblotting, Src inhibitor treatment, cortactin depletion, cilia immunofluorescence, hair follicle regeneration assay\",\n      \"journal\": \"Developmental cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis (Src and cortactin rescue), biochemical confirmation of Src/cortactin hyperphosphorylation, multiple orthogonal approaches; single lab but rigorous\",\n      \"pmids\": [\"20708589\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"MIM/MTSS1 promotes Arp2/3-mediated actin assembly at adherens junctions in kidney epithelial (MDCK) cells; this requires both membrane binding (I-BAR domain) and actin monomer interaction (WH2 domain). MIM-deficient mice develop severe urinary concentration defects due to compromised kidney epithelial junction integrity, leading to end-stage renal failure. MIM is dispensable for embryonic development and, in this in vivo context, is not required for Shh signaling.\",\n      \"method\": \"Knockout mouse phenotyping, MDCK cell culture with domain mutants, actin assembly assays, junction integrity assays\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — knockout mouse with specific renal phenotype, mechanistic dissection using domain mutants in cell culture, two orthogonal systems\",\n      \"pmids\": [\"21406566\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"MIM-deficient mice develop B-cell lymphomas (~78% incidence by 1–2 years). MIM-deficient B-cells fail to undergo chemotaxis or morphological changes in response to CXCL13 and fail to internalize CXCR5. MIM is the only I-BAR family member highly expressed in human B cells.\",\n      \"method\": \"MIM knockout mouse autopsy/histology, CXCL13 chemotaxis assays, CXCR5 internalization assays, microarray gene expression\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — knockout mouse model with tumor phenotype and mechanistic B-cell signaling assays; multiple assays in single rigorous study\",\n      \"pmids\": [\"22081072\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"MIM/MTSS1 specifically binds Daam1 (through a conserved domain in Daam1) and couples non-canonical Wnt signaling to neural tube closure in Xenopus. This interaction is positively regulated by Wnt stimulation. MIM depletion inhibits anterior neural fold closure but not convergent extension; the function requires both the membrane-remodeling (I-BAR) and actin-binding (WH2) domains.\",\n      \"method\": \"Co-immunoprecipitation of MIM and Daam1, Xenopus morpholino knockdown, domain rescue experiments, in situ hybridization\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP confirmed interaction, morpholino phenotype with domain rescue; single lab\",\n      \"pmids\": [\"21471152\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"MIM/MTSS1 expression in hepatocellular carcinoma is silenced by DNMT3B binding directly to the MTSS1 5'-flanking region (-865/-645), independently of DNA methylation. MTSS1 overexpression arrests HCC cells in G2/M phase. Methylation inhibitors fail to restore DNMT3B-mediated MTSS1 silencing.\",\n      \"method\": \"Chromatin immunoprecipitation (ChIP), luciferase reporter assay, methylation-specific PCR, bisulfite sequencing, cell cycle analysis\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP confirms direct DNMT3B binding to MTSS1 promoter, reporter and methylation assays; single lab\",\n      \"pmids\": [\"21909138\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Mtss1 promotes cell-cell junction assembly and stability by elevating Rac1-GTP levels and driving actin recruitment to junctions. Mtss1 depletion reduces F-actin at cell-cell junctions, and Mtss1 makes cells resistant to HGF-induced junction disassembly and scatter.\",\n      \"method\": \"siRNA knockdown, wound healing and HGF scatter assays, Rac-GTP pulldown, F-actin immunofluorescence at junctions\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Rac pulldown and junction assays with knockdown; single lab, two methods\",\n      \"pmids\": [\"22479308\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"MIM/MTSS1 suppresses RhoA activity and stress fiber formation in breast cancer cells. miR-182 targets MIM directly (3'UTR luciferase assay), and restoring MIM expression blocks the pro-metastasis function of miR-182; RhoA inhibition reverses the phenotypes of both miR-182 overexpression and MIM knockdown.\",\n      \"method\": \"3'UTR luciferase reporter assay, RhoA activity assay, rescue experiments, in vivo xenograft\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — luciferase validation of miR-182/MIM axis, RhoA activity assay, rescue experiment; single lab\",\n      \"pmids\": [\"23474751\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"SCFβ-TRCP E3 ubiquitin ligase targets MTSS1 for ubiquitination and proteasomal degradation. Casein Kinase Iδ (CKIδ) phosphorylates Ser322 within a DSGXXS degron in MTSS1, triggering interaction with β-TRCP. Depletion of Cullin1 or β-TRCP1 increases MTSS1 levels. A non-degradable S322A mutant more strongly inhibits cancer cell proliferation and migration than wild-type MTSS1.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, site-directed mutagenesis (S322A), shRNA knockdown of Cullin1/β-TRCP, cell proliferation and migration assays\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — co-IP, ubiquitination assay, site-directed mutagenesis identifying degron and kinase; multiple orthogonal methods in single study\",\n      \"pmids\": [\"24318128\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"High MTSS1 expression in a subset of primary melanomas promotes metastatic ability via engagement of actin dynamics through Rho-GTPases and cofilin, demonstrated by loss- and gain-of-function approaches in vitro and in vivo.\",\n      \"method\": \"Loss/gain-of-function assays, in vitro invasion assays, in vivo xenograft, Rho-GTPase activation assay, cofilin pathway analysis\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo and in vitro loss/gain-of-function with Rho-GTPase/cofilin pathway readouts; single lab\",\n      \"pmids\": [\"24632752\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"MIM/MTSS1 I-BAR domain accumulates at future dendritic spine initiation sites in a PIP2-dependent manner and deforms the plasma membrane outward into a proto-protrusion, initiating spine formation independent of actin polymerization. Subsequent elongation requires PIP2-dependent Arp2/3-mediated actin assembly. MIM-deficient mice show decreased spine density, larger spine heads, altered glutamatergic transmission, and compatible behavioral defects.\",\n      \"method\": \"Live imaging of MIM accumulation, PIP2 manipulation, Arp2/3 inhibition, MIM knockout mice, electrophysiology, behavioral tests\",\n      \"journal\": \"Developmental cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — live imaging, pharmacological dissection of actin vs. membrane steps, knockout mouse phenotype with electrophysiology; multiple orthogonal methods\",\n      \"pmids\": [\"26051541\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"ΔNp63 transcription factor drives MTSS1 expression by binding to a p63-responsive element in the MTSS1 locus, and this axis promotes migration of breast tumor cells.\",\n      \"method\": \"ChIP, luciferase reporter assay, siRNA knockdown, migration assays\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP and reporter assay confirm p63 binding and transcriptional activation of MTSS1; single lab\",\n      \"pmids\": [\"26119942\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"MIM/MTSS1 regulates CXCR4 surface expression and internalization in bone marrow cells. MIM-deficient cells show increased surface CXCR4, impaired CXCR4 internalization, constitutive activation of Rac, Cdc42, and p38, and enhanced homing to bone marrow. This enhanced homing is abolished by p38 antagonist treatment.\",\n      \"method\": \"MIM knockout mouse bone marrow transplantation, CXCR4 surface expression by flow cytometry, CXCR4 internalization assay, Rac/Cdc42/p38 activity assays, pharmacological p38 inhibition\",\n      \"journal\": \"Leukemia\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo transplant with pharmacological rescue, multiple GTPase activity assays, receptor internalization assay; multiple orthogonal methods\",\n      \"pmids\": [\"26965284\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"MTSS1 inhibits the actin-nucleating formin DAAM1 in Purkinje cell dendritic filopodia by directly binding DAAM1 through its C-terminus, pausing DAAM1-mediated F-actin polymerization as shown by single-molecule speckle microscopy. MTSS1 plays a dual role: inhibiting formin DAAM1 and activating ARP2/3, thus balancing filopodia morphology and determining final neuronal morphology.\",\n      \"method\": \"Co-immunoprecipitation, single-molecule speckle microscopy, conditional knockout mice, overactivation of DAAM1 phenocopy, domain-binding assays\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — single-molecule imaging plus co-IP and knockout mouse with formin phenocopy; multiple orthogonal methods, mechanistically rigorous\",\n      \"pmids\": [\"29972794\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"MTSS1 is a suppressor of Src family kinase (SFK) activity in Purkinje neurons. MTSS1 loss results in increased SFK activity, reduced Purkinje neuron arborization, low basal firing, and subsequent cell death. Mouse models of SCA1 and SCA2 show elevated SFK activity and dramatically reduced MTSS1 protein levels (SCA1 via reduced gene expression; SCA2 via reduced protein translation). Treatment with a clinically approved Src inhibitor corrects Purkinje neuron basal firing and delays ataxia progression.\",\n      \"method\": \"MTSS1 knockout mice, Src kinase activity assays, electrophysiology, SCA1/SCA2/SCA5 mouse models, Src inhibitor pharmacological rescue, protein expression analysis\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple SCA mouse models with SFK activity measurements, electrophysiology, pharmacological rescue; independently validated across multiple disease models\",\n      \"pmids\": [\"30530649\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"MTSS1 interacts with the E3 ubiquitin ligase RBCK1 to facilitate RBCK1-mediated ubiquitination and degradation of NF-κB p65, thereby suppressing NF-κB signaling and tumor-initiating cell (TIC) expansion. ACTBL2 competes with RBCK1 for MTSS1 binding, leading to p65 stabilization when ACTBL2 is present.\",\n      \"method\": \"Co-immunoprecipitation (MTSS1-RBCK1 and MTSS1-ACTBL2), ubiquitination assay for p65, knockout mouse mammary tumor models, patient-derived organoid and xenograft experiments\",\n      \"journal\": \"Nature cancer\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — co-IP, ubiquitination assay, competitive binding with ACTBL2, in vivo knockout models; multiple orthogonal methods in single rigorous study\",\n      \"pmids\": [\"35122005\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"MIM/MTSS1 I-BAR protein generates large extracellular vesicles (filopodia-derived vesicles, FDVs) by scission of filopodia. MIM-containing FDV production is promoted by external forces and by suppression of ALIX. These FDVs contain lysophospholipids, IRS4, and Rac1, and stimulate migration of recipient cells through lamellipodia formation.\",\n      \"method\": \"Live imaging, electron microscopy, FDV isolation and proteomics/lipidomics, Rac1 activity assay in recipient cells, ALIX suppression, force application experiments\",\n      \"journal\": \"Developmental cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — live imaging of filopodia scission, vesicle proteomics/lipidomics, functional assay in recipient cells; multiple orthogonal methods in single study\",\n      \"pmids\": [\"33756122\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Mtss1 enhances EGF receptor localization to the plasma membrane in head and neck squamous cell carcinoma cells, prolongs EGF signaling, and results in enhanced Erk1/2 and Akt phosphorylation. Depletion of Mtss1 decreases EGF receptor levels and reduces Erk1/2 and Akt phosphorylation.\",\n      \"method\": \"siRNA knockdown, EGF receptor localization by immunofluorescence, phospho-Erk1/2 and phospho-Akt immunoblotting, proliferation assays, organotypic assay, xenograft\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — knockdown with receptor localization and signaling readouts; single lab\",\n      \"pmids\": [\"21927027\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"MIM/MTSS1 regulates cell polarity, Rho GTPase activity, and endocytosis in mouse embryonic fibroblasts. MIM-deficient MEFs show impaired stress fiber and focal adhesion assembly with reduced Rho GTPase activity; this is rescued by constitutively active RhoA. MIM-null cells show attenuated internalization of transferrin, PDGF receptor, and foreign DNAs, and elevated PDGF receptor tyrosine phosphorylation upon PDGF treatment.\",\n      \"method\": \"MIM gene-trap knockout MEFs, Rho GTPase activity assays, constitutively active RhoA rescue, internalization assays, PDGF receptor phosphorylation immunoblotting, cell migration assays\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — knockout cells with GTPase activation assay and endocytosis readouts; single lab, multiple assays\",\n      \"pmids\": [\"21695258\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"MTSS1/MIM is an I-BAR (inverse-BAR) domain scaffold protein that deforms membranes into outward protrusions via its I-BAR domain in a PIP2-dependent manner, binds and sequesters ATP-actin monomers through its WH2 domain, bundles F-actin, activates Rac1 and Arp2/3-mediated actin assembly at junctions, inhibits the formin DAAM1, and suppresses Src family kinase activity in neurons; it is degraded by the SCFβ-TRCP/CKIδ ubiquitin-proteasome pathway, potentiates Gli-dependent Hedgehog transcription, facilitates RBCK1-mediated NF-κB p65 ubiquitination, regulates CXCR4 surface expression and internalization, and generates filopodia-derived extracellular vesicles, collectively coordinating actin and membrane dynamics, cell polarity, receptor trafficking, and intercellular signaling across diverse cell types.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"MTSS1 (MIM) is a membrane-deforming, actin-regulatory scaffold that couples the plasma membrane to the actin cytoskeleton to build and stabilize cellular protrusions, junctions, and receptor-trafficking machinery across epithelial, neuronal, and hematopoietic cells [#16, #8]. Its I-BAR (IMD) domain binds PIP2-rich membrane and deforms it outward into nascent protrusions while also bundling F-actin and binding/activating Rac1, whereas its C-terminal WH2 domain sequesters ATP-actin monomers and modulates nucleation [#0, #5, #16]. Through these activities MTSS1 promotes Arp2/3-dependent actin assembly at adherens junctions and dendritic spines while restraining opposing actin machinery—directly binding and pausing the formin DAAM1 and suppressing Src family kinase activity (and downstream cortactin phosphorylation) in Purkinje and ciliated cells [#19, #20, #7, #8]. By regulating endocytic internalization, MTSS1 controls the surface levels and signaling output of multiple receptors including CXCR4/CXCR5 and EGFR [#18, #9, #23]. MTSS1 abundance is tightly controlled: it is degraded via CKIδ-primed phosphorylation of a DSGXXS degron that recruits the SCFβ-TRCP ubiquitin ligase [#14], and it acts as a tumor and lymphoma suppressor, with loss producing renal junction failure, B-cell lymphoma, and dysregulated NF-κB signaling through its scaffolding of the RBCK1 E3 ligase that ubiquitinates p65 [#8, #9, #21]. In neurons, reduced MTSS1 with elevated Src activity links it mechanistically to spinocerebellar ataxia models [#20].\"\n,\n  \"teleology\": [\n    {\n      \"year\": 2002,\n      \"claim\": \"Established the biochemical basis of MTSS1's actin engagement, defining the C-terminal WH2 domain as an ATP-actin-monomer-binding module that regulates filament nucleation.\",\n      \"evidence\": \"In vitro actin binding/sedimentation with Kd measurements, WH2 mutagenesis, and NIH 3T3 overexpression\",\n      \"pmids\": [\"12482861\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not address membrane-deforming activity\", \"Cellular consequence shown only by overexpression phenotype\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Linked MTSS1's actin function to membrane targeting and a receptor partner, showing the N-terminus localizes to membranes and the protein binds the phosphatase PTPδ while inducing actin-rich protrusions.\",\n      \"evidence\": \"Pulldown with purified proteins and cell extracts, truncation-construct localization\",\n      \"pmids\": [\"12570871\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"PTPδ interaction shown by single pulldown without reciprocal validation\", \"Functional consequence of PTPδ binding unresolved\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Identified a transcriptional/signaling role distinct from actin, placing MTSS1 in a Gli/SUFU complex that potentiates Hedgehog-dependent transcription.\",\n      \"evidence\": \"Co-IP of Gli/SUFU complex, luciferase reporter assays, regenerated skin model\",\n      \"pmids\": [\"15545630\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of Gli potentiation unclear\", \"Later in vivo work found MTSS1 dispensable for Shh signaling in some contexts\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Defined MTSS1 as a bifunctional actin/membrane regulator: the IMD/I-BAR domain bundles F-actin and binds/activates Rac, while the protein modulates cortactin- and N-WASP-driven Arp2/3 polymerization and cell motility.\",\n      \"evidence\": \"In vitro actin polymerization and bundling assays, direct binding assays, domain-deletion motility experiments, RPTPδ co-IP and Rac pulldown\",\n      \"pmids\": [\"15688017\", \"16280553\", \"15684034\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How Rac binding and actin bundling are mechanistically coupled within the IMD remains unresolved\", \"Directionality of motility effects context-dependent\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Showed MTSS1 expression is epigenetically controlled, with CpG-island methylation silencing the promoter in low-expressing cells.\",\n      \"evidence\": \"Bisulfite sequencing, luciferase reporter, 5-Aza-2'-deoxycytidine treatment\",\n      \"pmids\": [\"16921485\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Upstream signals controlling methylation not identified\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Revealed MTSS1 as a ciliogenesis factor that acts by antagonizing Src-dependent cortactin phosphorylation at the basal body.\",\n      \"evidence\": \"siRNA knockdown, Src activity assays, phospho-cortactin immunoblotting, epistatic rescue by Src inhibition or cortactin depletion, cilia immunofluorescence\",\n      \"pmids\": [\"20708589\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How MTSS1 restrains Src is not established\", \"Direct Src interaction not demonstrated\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Established physiological in vivo functions through knockout phenotypes—renal epithelial junction integrity and B-cell lymphoma suppression with defective CXCR5 chemotaxis/internalization—and defined MTSS1's role in receptor endocytosis and Rho-GTPase-dependent polarity.\",\n      \"evidence\": \"MIM knockout mice (renal, lymphoma), MDCK domain-mutant junction assays, CXCL13 chemotaxis and CXCR5 internalization assays, knockout MEF endocytosis and Rho-GTPase assays, EGFR localization in HNSCC\",\n      \"pmids\": [\"21406566\", \"22081072\", \"21695258\", \"21927027\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular machinery coupling MTSS1 to receptor internalization not fully defined\", \"Tissue-specific contributions of I-BAR vs WH2 incompletely separated\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Connected MTSS1 to developmental Wnt signaling and additional transcriptional silencing, showing it binds DAAM1 to drive neural fold closure and is repressed by DNMT3B in hepatocellular carcinoma.\",\n      \"evidence\": \"Co-IP of MIM-Daam1, Xenopus morpholino knockdown with domain rescue; ChIP, reporter, methylation assays, cell-cycle analysis in HCC\",\n      \"pmids\": [\"21471152\", \"21909138\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"DAAM1 functional consequence not yet mechanistically resolved at this stage\", \"DNMT3B silencing mechanism methylation-independent but undefined\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Demonstrated MTSS1 stabilizes cell-cell junctions by elevating Rac1-GTP and recruiting F-actin, conferring resistance to scatter-inducing signals.\",\n      \"evidence\": \"siRNA knockdown, HGF scatter and wound-healing assays, Rac-GTP pulldown, junctional F-actin imaging\",\n      \"pmids\": [\"22479308\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of Rac1 activation at junctions not detailed\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Positioned MTSS1 within a RhoA-suppressing, anti-metastatic axis regulated by miR-182.\",\n      \"evidence\": \"3'UTR luciferase reporter, RhoA activity assay, rescue experiments, xenograft\",\n      \"pmids\": [\"23474751\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How MTSS1 suppresses RhoA mechanistically unresolved\", \"Context-dependence vs pro-metastatic roles unexplained\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Defined the degradation pathway controlling MTSS1 levels: CKIδ phosphorylation of Ser322 in a DSGXXS degron recruits SCFβ-TRCP for ubiquitin-proteasome turnover.\",\n      \"evidence\": \"Co-IP, ubiquitination assay, S322A mutagenesis, Cullin1/β-TRCP knockdown, proliferation/migration assays\",\n      \"pmids\": [\"24318128\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Signals triggering CKIδ phosphorylation not identified\", \"Structural basis of degron recognition not determined\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Showed MTSS1 can also promote metastasis in a subset of melanomas through Rho-GTPase and cofilin-mediated actin dynamics, highlighting context-dependent function.\",\n      \"evidence\": \"Loss/gain-of-function, invasion assays, xenograft, Rho-GTPase and cofilin pathway analysis\",\n      \"pmids\": [\"24632752\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Determinants of pro- vs anti-metastatic switch not defined\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Resolved the temporal mechanics of protrusion initiation, showing the I-BAR domain deforms PIP2 membrane outward independent of actin to nucleate dendritic spines, with Arp2/3 actin assembly driving subsequent elongation; identified ΔNp63 as a transcriptional activator.\",\n      \"evidence\": \"Live imaging, PIP2 manipulation, Arp2/3 inhibition, MIM knockout mice with electrophysiology and behavior; ChIP and reporter for ΔNp63\",\n      \"pmids\": [\"26051541\", \"26119942\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Trigger localizing MTSS1 to spine initiation sites unknown\", \"Coordination between membrane deformation and actin handoff incompletely mapped\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Established MTSS1 as a controller of CXCR4 surface expression and internalization in hematopoietic cells, with loss causing constitutive Rac/Cdc42/p38 activation and enhanced bone marrow homing.\",\n      \"evidence\": \"Knockout bone marrow transplantation, CXCR4 flow cytometry and internalization assays, GTPase activity assays, p38 pharmacological inhibition\",\n      \"pmids\": [\"26965284\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct link between MTSS1 and CXCR4 endocytic machinery undefined\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Revealed MTSS1's dual balancing role in neuronal protrusion morphology—directly binding and pausing the formin DAAM1 while activating Arp2/3—and as a suppressor of Src family kinases relevant to spinocerebellar ataxia.\",\n      \"evidence\": \"Single-molecule speckle microscopy, co-IP, conditional knockout mice, SCA1/SCA2 models, Src activity assays, electrophysiology, Src-inhibitor rescue\",\n      \"pmids\": [\"29972794\", \"30530649\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which MTSS1 inhibits SFK activity not molecularly defined\", \"Whether MTSS1 directly binds Src unresolved\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identified a scaffolding role in NF-κB control, with MTSS1 promoting RBCK1-mediated ubiquitination of p65 to restrain tumor-initiating-cell expansion, antagonized by ACTBL2 competition.\",\n      \"evidence\": \"Co-IP (MTSS1-RBCK1, MTSS1-ACTBL2), p65 ubiquitination assay, knockout mammary tumor models, patient-derived organoid/xenograft\",\n      \"pmids\": [\"35122005\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How MTSS1's actin/membrane domains relate to its E3-scaffolding function unclear\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Demonstrated MTSS1 generates filopodia-derived extracellular vesicles by membrane scission, enabling intercellular signaling that promotes recipient-cell migration.\",\n      \"evidence\": \"Live imaging, electron microscopy, FDV proteomics/lipidomics, recipient-cell Rac1 assays, ALIX suppression, force application\",\n      \"pmids\": [\"33756122\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological contexts and in vivo relevance of FDVs not established\", \"Mechanism of force-promoted scission not detailed\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The molecular basis for how MTSS1 simultaneously coordinates its membrane-deforming, actin-regulating, receptor-trafficking, and ubiquitin-ligase-scaffolding activities—and what dictates its context-dependent tumor-suppressive versus pro-metastatic behavior—remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified structural model integrating I-BAR, WH2, and protein-scaffolding regions\", \"Determinants of opposing cancer roles undefined\", \"Direct mechanism of Src kinase suppression unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [0, 3, 5, 16]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [16]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [21, 5]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [5, 19, 20]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [16, 22]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [1, 8, 16]},\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [0, 5]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0005815\", \"supporting_discovery_ids\": [7]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [18, 9, 23, 24]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [12, 18, 21]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [16, 10, 8]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [14, 21]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [9, 21, 20]}\n    ],\n    \"complexes\": [\n      \"Gli/SUFU complex\",\n      \"SCFβ-TRCP ubiquitin ligase complex\"\n    ],\n    \"partners\": [\n      \"ACTB (actin)\",\n      \"CTTN (cortactin)\",\n      \"DAAM1\",\n      \"RBCK1\",\n      \"PTPRD (PTPδ)\",\n      \"RAC1\",\n      \"BTRC (β-TRCP)\",\n      \"ACTBL2\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}