{"gene":"FMN2","run_date":"2026-06-09T23:54:44","timeline":{"discoveries":[{"year":2013,"finding":"FMN2 is induced upon p14ARF activation via a NF-κB-dependent mechanism (involving relief of repression by RelA and E2F1 at the FMN2 promoter), independently of p53; increased FMN2 protein prevents degradation of the cyclin-dependent kinase inhibitor p21, thereby promoting cell-cycle arrest. The N-terminus of FMN2 is the domain required for p21 stability.","method":"SILAC mass spectrometry, NF-κB pathway inhibition, ChIP (RelA/E2F1 binding to FMN2 promoter), western blotting, exogenous FMN2 overexpression, deletion/domain mutagenesis","journal":"Molecular Cell / Cell Cycle","confidence":"High","confidence_rationale":"Tier 2 / Strong — two complementary papers from the same lab using multiple orthogonal methods (proteomics discovery, promoter binding, protein stability assays, domain mutants) with consistent results","pmids":["23375502","23839046"],"is_preprint":false},{"year":2014,"finding":"FMN2 localizes to punctae along dendrites; germline inactivation of mouse Fmn2 results in decreased dendritic spine density, and patient iPSC-derived neural cells show decreased synaptic density, linking FMN2-mediated actin cytoskeleton nucleation to synaptic spine formation.","method":"Immunofluorescence localization in neurons, mouse germline knockout phenotyping (spine density quantification), iPSC-derived neural cell analysis","journal":"American Journal of Human Genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization experiment with functional consequence (spine density readout in KO mice and patient cells), single lab, two orthogonal models","pmids":["25480035"],"is_preprint":false},{"year":2016,"finding":"FMN2 associates with and generates a perinuclear actin/focal adhesion system distinct from other actin/FA structures; this system controls nuclear shape and positioning during 2D migration and limits nuclear envelope damage and DNA double-strand breaks during confined 3D migration, thereby promoting cell survival and metastasis.","method":"Live-cell imaging, fluorescence microscopy (perinuclear actin structure), FMN2 knockdown/knockout with nuclear damage assays (γH2AX, nuclear envelope rupture reporters), mouse melanoma extravasation/metastasis assay","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (imaging of novel actin structure, KD functional rescue, in vivo metastasis), published in high-profile peer-reviewed journal, mechanistically defined","pmids":["27839864"],"is_preprint":false},{"year":2010,"finding":"Mouse Fmn2 overexpression induces anchorage-independent growth and causes a drastic modification in cell shape with disruption of the actin cytoskeleton, consistent with an oncogenic function linked to actin regulation.","method":"Soft agar colony formation (anchorage-independent growth assay), cell morphology and actin cytoskeleton staining upon Fmn2 overexpression","journal":"Blood","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — functional overexpression assay with two phenotypic readouts (growth and actin), single lab","pmids":["21135260"],"is_preprint":false},{"year":2020,"finding":"Fmn2 regulates point contact stability in neuronal growth cones and functions as a molecular clutch by coupling the actin cytoskeleton to the growth substrate via point contact adhesion complexes; Fmn2-mediated clutch activity is necessary for generation of traction forces by growth cones and consequently for growth cone motility.","method":"F-actin retrograde flow analysis, traction force microscopy, point contact adhesion complex component analysis, loss-of-function (knockdown) with traction stress quantification","journal":"Neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — traction force microscopy and retrograde flow measurements are direct mechanistic assays; single lab with multiple orthogonal approaches","pmids":["33002558"],"is_preprint":false},{"year":2017,"finding":"FMN2 is a direct downstream target of miR-144 in acute lymphoblastic leukemia cells; miR-144 binds the FMN2 3′UTR (validated by dual-luciferase assay), suppresses FMN2 expression, and overexpression of FMN2 rescues the anti-proliferative and cell-cycle arrest effects of miR-144 upregulation.","method":"Dual-luciferase reporter assay, qRT-PCR, western blotting, FMN2 overexpression rescue experiment, in vivo xenograft","journal":"The Journal of Gene Medicine","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — direct 3′UTR binding validated by luciferase assay plus functional rescue, single lab","pmids":["27556228"],"is_preprint":false},{"year":2022,"finding":"FMN2 missense variants (p.Arg656His) are associated with reduced FMN2 and p21 protein levels and increased γH2AX (DNA damage marker) in POI patient cells, and chromosomal breakage frequency is significantly elevated in patient cells compared to controls, suggesting FMN2 participates in DNA damage/p21 signaling in oocytes.","method":"Western blot (FMN2, p21, H2AX levels in patient vs. control cells), chromosomal breakage analysis","journal":"Journal of Ovarian Research","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single patient case, limited controls, single lab, no functional rescue experiment","pmids":["35227295"],"is_preprint":false}],"current_model":"FMN2 is a formin-family actin nucleator that (1) stabilizes the cell-cycle inhibitor p21 protein (preventing its degradation) downstream of p14ARF/NF-κB signaling to enforce cell-cycle arrest; (2) generates a perinuclear actin/focal adhesion system that controls nuclear shape and protects the nucleus from damage during confined migration; (3) mediates a molecular clutch between the actin cytoskeleton and the substratum to generate traction forces in neuronal growth cones; and (4) localizes to dendritic punctae where it promotes actin-dependent synaptic spine formation in neurons."},"narrative":{"mechanistic_narrative":"FMN2 is a formin-family actin nucleator that couples cytoskeletal remodeling to cell-cycle control, nuclear protection, and neuronal architecture [PMID:23375502, PMID:23839046, PMID:27839864]. In the cell-cycle arm, FMN2 is transcriptionally induced upon p14ARF activation through an NF-κB-dependent relief of RelA/E2F1 repression at its promoter, independently of p53; its N-terminus then stabilizes the CDK inhibitor p21 against degradation to enforce cell-cycle arrest [PMID:23375502, PMID:23839046]. In the cytoskeletal arm, FMN2 builds a dedicated perinuclear actin/focal-adhesion system that governs nuclear shape and positioning and limits nuclear-envelope rupture and DNA double-strand breaks during confined migration, thereby supporting cell survival and metastasis [PMID:27839864]. The same actin-nucleating activity underlies neuronal roles: FMN2 localizes to dendritic punctae and is required for dendritic spine formation [PMID:25480035], and in growth cones it functions as a molecular clutch coupling actin to the substrate to generate the traction forces needed for motility [PMID:33002558]. FMN2 expression is constrained post-transcriptionally by miR-144 binding to its 3′UTR, with consequences for proliferation and cell-cycle arrest [PMID:27556228].","teleology":[{"year":2010,"claim":"Established a link between FMN2 and transformation by showing its overexpression drives anchorage-independent growth alongside actin cytoskeleton disruption, framing FMN2 as an actin-regulating factor with oncogenic potential.","evidence":"Soft agar colony formation and actin/morphology staining upon mouse Fmn2 overexpression","pmids":["21135260"],"confidence":"Medium","gaps":["Mechanism connecting actin disruption to transformation not defined","No endogenous loss-of-function counterpart","Single overexpression system"]},{"year":2013,"claim":"Resolved how FMN2 enters cell-cycle control by placing it downstream of p14ARF/NF-κB signaling and identifying its N-terminus as the determinant that stabilizes p21 to enforce arrest, independently of p53.","evidence":"SILAC proteomics, ChIP of RelA/E2F1 at the FMN2 promoter, NF-κB inhibition, p21 stability and domain-mutagenesis assays","pmids":["23375502","23839046"],"confidence":"High","gaps":["Biochemical mechanism by which the N-terminus protects p21 from degradation unresolved","Whether actin-nucleation activity is required for p21 stabilization untested"]},{"year":2014,"claim":"Connected FMN2-mediated actin nucleation to neuronal connectivity by localizing it to dendritic punctae and showing spine density falls in Fmn2-knockout mice and patient-derived neural cells.","evidence":"Immunofluorescence localization, mouse germline knockout spine-density phenotyping, iPSC-derived neural cell synaptic density","pmids":["25480035"],"confidence":"Medium","gaps":["Molecular partners at dendritic punctae not identified","Causal nucleation mechanism for spine formation not directly demonstrated"]},{"year":2016,"claim":"Defined a distinct cytoskeletal function: FMN2 generates a perinuclear actin/focal-adhesion system that controls nuclear shape and shields the nucleus from envelope rupture and DNA damage during confined migration, promoting survival and metastasis.","evidence":"Live-cell imaging of the perinuclear structure, knockdown/knockout with γH2AX and envelope-rupture reporters, mouse melanoma extravasation/metastasis assay","pmids":["27839864"],"confidence":"High","gaps":["How FMN2 is targeted to the perinuclear region unknown","Relationship between this structure and the p21/cell-cycle role unexplored"]},{"year":2017,"claim":"Showed FMN2 is post-transcriptionally regulated by miR-144 via direct 3′UTR binding, with FMN2 overexpression rescuing miR-144's anti-proliferative and cell-cycle-arrest effects in leukemia cells.","evidence":"Dual-luciferase 3′UTR reporter, qRT-PCR, western blot, FMN2 rescue, in vivo xenograft","pmids":["27556228"],"confidence":"Medium","gaps":["Whether miR-144 regulation operates outside leukemia untested","Downstream effectors of the rescue not dissected"]},{"year":2020,"claim":"Provided a mechanistic basis for FMN2 in axon guidance by demonstrating it stabilizes growth-cone point contacts and acts as a molecular clutch coupling actin flow to the substrate to generate traction.","evidence":"F-actin retrograde flow analysis, traction force microscopy, point-contact component analysis, knockdown with traction-stress quantification","pmids":["33002558"],"confidence":"Medium","gaps":["Direct binding partners linking FMN2 to adhesion complexes not identified","Single lab and model system"]},{"year":2022,"claim":"Extended FMN2's DNA-damage/p21 axis to oocytes by associating a missense variant with reduced FMN2 and p21, elevated γH2AX, and increased chromosomal breakage in premature ovarian insufficiency patient cells.","evidence":"Western blot of FMN2/p21/H2AX and chromosomal breakage analysis in patient versus control cells","pmids":["35227295"],"confidence":"Low","gaps":["Single patient case with limited controls and no functional rescue","Causality of the variant not established","Tissue-specific mechanism in oocytes undefined"]},{"year":null,"claim":"It remains unresolved whether FMN2's actin-nucleation activity, p21 stabilization, and perinuclear/genome-protective functions are mechanistically linked or represent separable activities of the same protein.","evidence":"No single study in the corpus integrates the cytoskeletal and cell-cycle arms","pmids":[],"confidence":"Low","gaps":["No structure-function study tying nucleation activity to p21 stabilization","Direct molecular partners of FMN2 largely uncharacterized"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[2,4]},{"term_id":"GO:0140313","term_label":"molecular sequestering activity","supporting_discovery_ids":[0]}],"localization":[{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[2,3]},{"term_id":"GO:0005635","term_label":"nuclear envelope","supporting_discovery_ids":[2]}],"pathway":[{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[0]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[1,4]}],"complexes":[],"partners":["P21","RELA","E2F1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9NZ56","full_name":"Formin-2","aliases":[],"length_aa":1722,"mass_kda":180.1,"function":"Actin-binding protein that is involved in actin cytoskeleton assembly and reorganization (PubMed:21730168, PubMed:22330775). Acts as an actin nucleation factor and promotes assembly of actin filaments together with SPIRE1 and SPIRE2 (PubMed:21730168, PubMed:22330775). Involved in intracellular vesicle transport along actin fibers, providing a novel link between actin cytoskeleton dynamics and intracellular transport (By similarity). Required for asymmetric spindle positioning, asymmetric oocyte division and polar body extrusion during female germ cell meiosis (By similarity). Plays a role in responses to DNA damage, cellular stress and hypoxia by protecting CDKN1A against degradation, and thereby plays a role in stress-induced cell cycle arrest (PubMed:23375502). Also acts in the nucleus: together with SPIRE1 and SPIRE2, promotes assembly of nuclear actin filaments in response to DNA damage in order to facilitate movement of chromatin and repair factors after DNA damage (PubMed:26287480). Protects cells against apoptosis by protecting CDKN1A against degradation (PubMed:23375502)","subcellular_location":"Cytoplasm, cytoskeleton; Cytoplasm, cytosol; Cytoplasm, perinuclear region; Nucleus; Nucleus, nucleolus; Cell membrane; Cytoplasmic vesicle membrane; Cytoplasm, cell cortex","url":"https://www.uniprot.org/uniprotkb/Q9NZ56/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/FMN2","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"ACTG1","stoichiometry":0.2},{"gene":"PFN1","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/FMN2","total_profiled":1310},"omim":[{"mim_id":"616193","title":"INTELLECTUAL DEVELOPMENTAL DISORDER, AUTOSOMAL RECESSIVE 47; MRT47","url":"https://www.omim.org/entry/616193"},{"mim_id":"606373","title":"FORMIN 2; FMN2","url":"https://www.omim.org/entry/606373"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Actin filaments","reliability":"Supported"},{"location":"Plasma membrane","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"brain","ntpm":36.0},{"tissue":"parathyroid gland","ntpm":18.5},{"tissue":"retina","ntpm":15.4}],"url":"https://www.proteinatlas.org/search/FMN2"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"Q9NZ56","domains":[{"cath_id":"-","chopping":"534-577","consensus_level":"medium","plddt":53.9561,"start":534,"end":577},{"cath_id":"1.20.58","chopping":"1359-1445","consensus_level":"medium","plddt":84.8928,"start":1359,"end":1445},{"cath_id":"1.20.58.2220","chopping":"1448-1702","consensus_level":"high","plddt":92.9431,"start":1448,"end":1702}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NZ56","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NZ56-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NZ56-F1-predicted_aligned_error_v6.png","plddt_mean":49.97},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=FMN2","jax_strain_url":"https://www.jax.org/strain/search?query=FMN2"},"sequence":{"accession":"Q9NZ56","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9NZ56.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9NZ56/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NZ56"}},"corpus_meta":[{"pmid":"25480035","id":"PMC_25480035","title":"Biallelic truncating mutations in FMN2, encoding the actin-regulatory protein Formin 2, cause nonsyndromic autosomal-recessive intellectual disability.","date":"2014","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/25480035","citation_count":54,"is_preprint":false},{"pmid":"23375502","id":"PMC_23375502","title":"Identification and functional characterization of FMN2, a regulator of the cyclin-dependent kinase inhibitor p21.","date":"2013","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/23375502","citation_count":45,"is_preprint":false},{"pmid":"27839864","id":"PMC_27839864","title":"FMN2 Makes Perinuclear Actin to Protect Nuclei during Confined Migration and Promote Metastasis.","date":"2016","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/27839864","citation_count":38,"is_preprint":false},{"pmid":"21135260","id":"PMC_21135260","title":"Gene profiling of Graffi murine leukemia virus-induced lymphoid leukemias: identification of leukemia markers and Fmn2 as a potential oncogene.","date":"2010","source":"Blood","url":"https://pubmed.ncbi.nlm.nih.gov/21135260","citation_count":25,"is_preprint":false},{"pmid":"27556228","id":"PMC_27556228","title":"MicroRNA-144 regulates cancer cell proliferation and cell-cycle transition in acute lymphoblastic leukemia through the interaction of FMN2.","date":"2017","source":"The journal of gene medicine","url":"https://pubmed.ncbi.nlm.nih.gov/27556228","citation_count":21,"is_preprint":false},{"pmid":"36995659","id":"PMC_36995659","title":"Exosomal Circ_FMN2 Derived from the Serum of Colorectal Cancer Patients Promotes Cancer Progression by miR-338-3p/MSI1 Axis.","date":"2023","source":"Applied biochemistry and biotechnology","url":"https://pubmed.ncbi.nlm.nih.gov/36995659","citation_count":20,"is_preprint":false},{"pmid":"24161494","id":"PMC_24161494","title":"De novo deletion of FMN2 in a girl with mild non-syndromic intellectual disability.","date":"2013","source":"European journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/24161494","citation_count":17,"is_preprint":false},{"pmid":"15866570","id":"PMC_15866570","title":"Characterization and mutation analysis of the human formin-2 (FMN2) gene in women with unexplained infertility.","date":"2005","source":"Fertility and sterility","url":"https://pubmed.ncbi.nlm.nih.gov/15866570","citation_count":16,"is_preprint":false},{"pmid":"15289902","id":"PMC_15289902","title":"Characterization of FMN2 gene at human chromosome 1q43.","date":"2004","source":"International journal of molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/15289902","citation_count":12,"is_preprint":false},{"pmid":"23839046","id":"PMC_23839046","title":"FMN2 is a novel regulator of the cyclin-dependent kinase inhibitor p21.","date":"2013","source":"Cell cycle (Georgetown, Tex.)","url":"https://pubmed.ncbi.nlm.nih.gov/23839046","citation_count":12,"is_preprint":false},{"pmid":"33002558","id":"PMC_33002558","title":"Fmn2 Regulates Growth Cone Motility by Mediating a Molecular Clutch to Generate Traction Forces.","date":"2020","source":"Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/33002558","citation_count":10,"is_preprint":false},{"pmid":"35227295","id":"PMC_35227295","title":"Heterozygous FMN2 missense variant found in a family case of premature ovarian insufficiency.","date":"2022","source":"Journal of ovarian research","url":"https://pubmed.ncbi.nlm.nih.gov/35227295","citation_count":4,"is_preprint":false},{"pmid":"32162566","id":"PMC_32162566","title":"A Novel Nonsense FMN2 Mutation in Nonsyndromic Autosomal Recessive Intellectual Disability Syndrome.","date":"2020","source":"Fetal and pediatric pathology","url":"https://pubmed.ncbi.nlm.nih.gov/32162566","citation_count":4,"is_preprint":false},{"pmid":"41214804","id":"PMC_41214804","title":"Spontaneous ovarian hyperstimulation in a nonpregnant woman with PCOS: a rare case highlighting FMN2 missense mutation and androgen receptor gene deletion.","date":"2025","source":"Journal of ovarian research","url":"https://pubmed.ncbi.nlm.nih.gov/41214804","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":8583,"output_tokens":1824,"usd":0.026555,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8727,"output_tokens":2680,"usd":0.055317,"stage2_stop_reason":"end_turn"},"total_usd":0.081872,"stage1_batch_id":"msgbatch_01AsR7g8dGTEiEw9U83bJeWn","stage2_batch_id":"msgbatch_01YV5ZyxtFNUZEjxRcpd9jzb","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2013,\n      \"finding\": \"FMN2 is induced upon p14ARF activation via a NF-κB-dependent mechanism (involving relief of repression by RelA and E2F1 at the FMN2 promoter), independently of p53; increased FMN2 protein prevents degradation of the cyclin-dependent kinase inhibitor p21, thereby promoting cell-cycle arrest. The N-terminus of FMN2 is the domain required for p21 stability.\",\n      \"method\": \"SILAC mass spectrometry, NF-κB pathway inhibition, ChIP (RelA/E2F1 binding to FMN2 promoter), western blotting, exogenous FMN2 overexpression, deletion/domain mutagenesis\",\n      \"journal\": \"Molecular Cell / Cell Cycle\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — two complementary papers from the same lab using multiple orthogonal methods (proteomics discovery, promoter binding, protein stability assays, domain mutants) with consistent results\",\n      \"pmids\": [\"23375502\", \"23839046\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"FMN2 localizes to punctae along dendrites; germline inactivation of mouse Fmn2 results in decreased dendritic spine density, and patient iPSC-derived neural cells show decreased synaptic density, linking FMN2-mediated actin cytoskeleton nucleation to synaptic spine formation.\",\n      \"method\": \"Immunofluorescence localization in neurons, mouse germline knockout phenotyping (spine density quantification), iPSC-derived neural cell analysis\",\n      \"journal\": \"American Journal of Human Genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization experiment with functional consequence (spine density readout in KO mice and patient cells), single lab, two orthogonal models\",\n      \"pmids\": [\"25480035\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"FMN2 associates with and generates a perinuclear actin/focal adhesion system distinct from other actin/FA structures; this system controls nuclear shape and positioning during 2D migration and limits nuclear envelope damage and DNA double-strand breaks during confined 3D migration, thereby promoting cell survival and metastasis.\",\n      \"method\": \"Live-cell imaging, fluorescence microscopy (perinuclear actin structure), FMN2 knockdown/knockout with nuclear damage assays (γH2AX, nuclear envelope rupture reporters), mouse melanoma extravasation/metastasis assay\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (imaging of novel actin structure, KD functional rescue, in vivo metastasis), published in high-profile peer-reviewed journal, mechanistically defined\",\n      \"pmids\": [\"27839864\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Mouse Fmn2 overexpression induces anchorage-independent growth and causes a drastic modification in cell shape with disruption of the actin cytoskeleton, consistent with an oncogenic function linked to actin regulation.\",\n      \"method\": \"Soft agar colony formation (anchorage-independent growth assay), cell morphology and actin cytoskeleton staining upon Fmn2 overexpression\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — functional overexpression assay with two phenotypic readouts (growth and actin), single lab\",\n      \"pmids\": [\"21135260\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Fmn2 regulates point contact stability in neuronal growth cones and functions as a molecular clutch by coupling the actin cytoskeleton to the growth substrate via point contact adhesion complexes; Fmn2-mediated clutch activity is necessary for generation of traction forces by growth cones and consequently for growth cone motility.\",\n      \"method\": \"F-actin retrograde flow analysis, traction force microscopy, point contact adhesion complex component analysis, loss-of-function (knockdown) with traction stress quantification\",\n      \"journal\": \"Neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — traction force microscopy and retrograde flow measurements are direct mechanistic assays; single lab with multiple orthogonal approaches\",\n      \"pmids\": [\"33002558\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"FMN2 is a direct downstream target of miR-144 in acute lymphoblastic leukemia cells; miR-144 binds the FMN2 3′UTR (validated by dual-luciferase assay), suppresses FMN2 expression, and overexpression of FMN2 rescues the anti-proliferative and cell-cycle arrest effects of miR-144 upregulation.\",\n      \"method\": \"Dual-luciferase reporter assay, qRT-PCR, western blotting, FMN2 overexpression rescue experiment, in vivo xenograft\",\n      \"journal\": \"The Journal of Gene Medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct 3′UTR binding validated by luciferase assay plus functional rescue, single lab\",\n      \"pmids\": [\"27556228\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"FMN2 missense variants (p.Arg656His) are associated with reduced FMN2 and p21 protein levels and increased γH2AX (DNA damage marker) in POI patient cells, and chromosomal breakage frequency is significantly elevated in patient cells compared to controls, suggesting FMN2 participates in DNA damage/p21 signaling in oocytes.\",\n      \"method\": \"Western blot (FMN2, p21, H2AX levels in patient vs. control cells), chromosomal breakage analysis\",\n      \"journal\": \"Journal of Ovarian Research\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single patient case, limited controls, single lab, no functional rescue experiment\",\n      \"pmids\": [\"35227295\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"FMN2 is a formin-family actin nucleator that (1) stabilizes the cell-cycle inhibitor p21 protein (preventing its degradation) downstream of p14ARF/NF-κB signaling to enforce cell-cycle arrest; (2) generates a perinuclear actin/focal adhesion system that controls nuclear shape and protects the nucleus from damage during confined migration; (3) mediates a molecular clutch between the actin cytoskeleton and the substratum to generate traction forces in neuronal growth cones; and (4) localizes to dendritic punctae where it promotes actin-dependent synaptic spine formation in neurons.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"FMN2 is a formin-family actin nucleator that couples cytoskeletal remodeling to cell-cycle control, nuclear protection, and neuronal architecture [#0, #2]. In the cell-cycle arm, FMN2 is transcriptionally induced upon p14ARF activation through an NF-\\u03baB-dependent relief of RelA/E2F1 repression at its promoter, independently of p53; its N-terminus then stabilizes the CDK inhibitor p21 against degradation to enforce cell-cycle arrest [#0]. In the cytoskeletal arm, FMN2 builds a dedicated perinuclear actin/focal-adhesion system that governs nuclear shape and positioning and limits nuclear-envelope rupture and DNA double-strand breaks during confined migration, thereby supporting cell survival and metastasis [#2]. The same actin-nucleating activity underlies neuronal roles: FMN2 localizes to dendritic punctae and is required for dendritic spine formation [#1], and in growth cones it functions as a molecular clutch coupling actin to the substrate to generate the traction forces needed for motility [#4]. FMN2 expression is constrained post-transcriptionally by miR-144 binding to its 3\\u2032UTR, with consequences for proliferation and cell-cycle arrest [#5].\",\n  \"teleology\": [\n    {\n      \"year\": 2010,\n      \"claim\": \"Established a link between FMN2 and transformation by showing its overexpression drives anchorage-independent growth alongside actin cytoskeleton disruption, framing FMN2 as an actin-regulating factor with oncogenic potential.\",\n      \"evidence\": \"Soft agar colony formation and actin/morphology staining upon mouse Fmn2 overexpression\",\n      \"pmids\": [\"21135260\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism connecting actin disruption to transformation not defined\", \"No endogenous loss-of-function counterpart\", \"Single overexpression system\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Resolved how FMN2 enters cell-cycle control by placing it downstream of p14ARF/NF-\\u03baB signaling and identifying its N-terminus as the determinant that stabilizes p21 to enforce arrest, independently of p53.\",\n      \"evidence\": \"SILAC proteomics, ChIP of RelA/E2F1 at the FMN2 promoter, NF-\\u03baB inhibition, p21 stability and domain-mutagenesis assays\",\n      \"pmids\": [\"23375502\", \"23839046\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Biochemical mechanism by which the N-terminus protects p21 from degradation unresolved\", \"Whether actin-nucleation activity is required for p21 stabilization untested\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Connected FMN2-mediated actin nucleation to neuronal connectivity by localizing it to dendritic punctae and showing spine density falls in Fmn2-knockout mice and patient-derived neural cells.\",\n      \"evidence\": \"Immunofluorescence localization, mouse germline knockout spine-density phenotyping, iPSC-derived neural cell synaptic density\",\n      \"pmids\": [\"25480035\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular partners at dendritic punctae not identified\", \"Causal nucleation mechanism for spine formation not directly demonstrated\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Defined a distinct cytoskeletal function: FMN2 generates a perinuclear actin/focal-adhesion system that controls nuclear shape and shields the nucleus from envelope rupture and DNA damage during confined migration, promoting survival and metastasis.\",\n      \"evidence\": \"Live-cell imaging of the perinuclear structure, knockdown/knockout with \\u03b3H2AX and envelope-rupture reporters, mouse melanoma extravasation/metastasis assay\",\n      \"pmids\": [\"27839864\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How FMN2 is targeted to the perinuclear region unknown\", \"Relationship between this structure and the p21/cell-cycle role unexplored\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Showed FMN2 is post-transcriptionally regulated by miR-144 via direct 3\\u2032UTR binding, with FMN2 overexpression rescuing miR-144's anti-proliferative and cell-cycle-arrest effects in leukemia cells.\",\n      \"evidence\": \"Dual-luciferase 3\\u2032UTR reporter, qRT-PCR, western blot, FMN2 rescue, in vivo xenograft\",\n      \"pmids\": [\"27556228\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether miR-144 regulation operates outside leukemia untested\", \"Downstream effectors of the rescue not dissected\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Provided a mechanistic basis for FMN2 in axon guidance by demonstrating it stabilizes growth-cone point contacts and acts as a molecular clutch coupling actin flow to the substrate to generate traction.\",\n      \"evidence\": \"F-actin retrograde flow analysis, traction force microscopy, point-contact component analysis, knockdown with traction-stress quantification\",\n      \"pmids\": [\"33002558\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct binding partners linking FMN2 to adhesion complexes not identified\", \"Single lab and model system\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Extended FMN2's DNA-damage/p21 axis to oocytes by associating a missense variant with reduced FMN2 and p21, elevated \\u03b3H2AX, and increased chromosomal breakage in premature ovarian insufficiency patient cells.\",\n      \"evidence\": \"Western blot of FMN2/p21/H2AX and chromosomal breakage analysis in patient versus control cells\",\n      \"pmids\": [\"35227295\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Single patient case with limited controls and no functional rescue\", \"Causality of the variant not established\", \"Tissue-specific mechanism in oocytes undefined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unresolved whether FMN2's actin-nucleation activity, p21 stabilization, and perinuclear/genome-protective functions are mechanistically linked or represent separable activities of the same protein.\",\n      \"evidence\": \"No single study in the corpus integrates the cytoskeletal and cell-cycle arms\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No structure-function study tying nucleation activity to p21 stabilization\", \"Direct molecular partners of FMN2 largely uncharacterized\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [2, 4]},\n      {\"term_id\": \"GO:0140313\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [2, 3]},\n      {\"term_id\": \"GO:0005635\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [1, 4]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"p21\", \"RelA\", \"E2F1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}