{"gene":"FRAT2","run_date":"2026-04-28T17:46:04","timeline":{"discoveries":[{"year":2001,"finding":"FRAT2 encodes a 233 amino acid protein with a GSK-3β binding domain (100% identical to FRAT1), and wild-type FRAT2 mRNA (but not a mutant lacking the acidic domain and proline-rich domain) induces secondary axis duplication in Xenopus, demonstrating it positively regulates the WNT signaling pathway through its acidic and proline-rich domains.","method":"Xenopus axis duplication assay with wild-type vs. deletion mutant FRAT2 mRNA injection","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 1 — functional in vivo assay with domain-deletion mutagenesis establishing mechanism","pmids":["11237732"],"is_preprint":false},{"year":2002,"finding":"Human FRAT2 protein binds to GSK-3 (glycogen synthase kinase-3) and Dishevelled, two core components of Wnt signal transduction, and when transiently overexpressed in COS-1 cells localizes to the cytosol and is concentrated in the nucleus.","method":"Protein interaction studies; transient overexpression with subcellular fractionation/localization in COS-1 cells","journal":"Gene","confidence":"Medium","confidence_rationale":"Tier 2–3 — direct binding shown, subcellular localization by overexpression","pmids":["12095675"],"is_preprint":false},{"year":2004,"finding":"Murine Frat2 binds GSK3β, is phosphorylated (first evidence of post-translational modification of Frat proteins), but is a less potent activator of the canonical Wnt/β-catenin–TCF pathway compared to Frat1, suggesting Frat2 may participate in a divergent intracellular GSK3β pathway.","method":"Co-immunoprecipitation (GSK3β binding), β-catenin/TCF reporter assay, phosphorylation detection in transfected cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP, functional reporter assay, and phosphorylation all performed in same study","pmids":["15073180"],"is_preprint":false},{"year":2004,"finding":"FRAT-2 associates with GSK3β and selectively enhances GSK3β-mediated phosphorylation of primed substrates (but not unprimed substrates), resulting in enhanced tau phosphorylation at primed epitopes; additionally, FRAT-2 is itself phosphorylated by GSK3β.","method":"Co-immunoprecipitation, in situ phosphorylation assays, in vitro kinase assay with recombinant proteins","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — reconstituted in vitro with recombinant proteins plus co-IP and in situ assays, multiple orthogonal methods","pmids":["15522877"],"is_preprint":false},{"year":2012,"finding":"FRAT2 mediates oncogenic Rac GTPase activation downstream of MLL fusion oncogenes; FRAT2 activates Rac through a signaling mechanism requiring GSK3 and DVL (Dishevelled); loss of Frat in hematopoietic progenitor cells transformed by MLL fusions results in reduced Rac activation and increased chemosensitivity.","method":"Genetic knockout of Frat genes in hematopoietic progenitors, modulation of FRAT2 expression with concomitant Rac activity measurement, pathway disruption assays","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 — loss-of-function genetics, defined cellular phenotype, pathway placement via epistasis with GSK3 and DVL","pmids":["23074275"],"is_preprint":false},{"year":2015,"finding":"FRAT2 is a direct target of the miR-29 family in chondrocytes; miR-29 negatively regulates canonical WNT signaling partly by suppressing FRAT2 expression.","method":"Direct target validation of miR-29 family on FRAT2 (luciferase reporter assay implied by 'validated as direct targets'); expression analysis in chondrocytes","journal":"Journal of molecular medicine (Berlin, Germany)","confidence":"Medium","confidence_rationale":"Tier 3 — direct target validation reported but mechanistic follow-up limited to pathway-level readout","pmids":["26687115"],"is_preprint":false},{"year":2015,"finding":"FRAT2 is a direct target of miR-29c in pancreatic cancer cells; miR-29c suppresses FRAT2 along with LRP6, FZD4, and FZD5, thereby inhibiting Wnt cascade hyperactivation; TGF-β inhibits miR-29c, leading to FRAT2 upregulation and Wnt activation.","method":"miR-29c overexpression/knockdown with luciferase reporter assay for direct targeting; pathway activity measurement","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 3 — direct target validated by reporter assay, pathway consequence shown, single lab","pmids":["25605017"],"is_preprint":false},{"year":2020,"finding":"TMEM98, a putative transmembrane protein recycled between the plasma membrane and Golgi, physically interacts with FRAT2, reduces FRAT2 protein levels, and inhibits FRAT2-mediated induction of β-catenin/TCF signaling, acting as a negative regulator of FRAT-mediated Wnt signaling.","method":"Co-immunoprecipitation (TMEM98–FRAT2 interaction), protein level quantification upon TMEM98 expression, β-catenin/TCF reporter assay, intracellular trafficking characterization","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2–3 — Co-IP interaction, functional reporter assay, and protein stability data from single lab","pmids":["31961879"],"is_preprint":false},{"year":2022,"finding":"miR-3648 directly targets FRAT2 (and FRAT1) to inhibit their expression, suppressing FRAT1/FRAT2-mediated invasion and motility in gastric cancer cells; FRAT1 and FRAT2 physically interact with each other; siRNA-mediated repression of FRAT2 in FRAT1-overexpressing cells reverses FRAT1-driven invasive potential; the miR-3648/FRAT1-FRAT2/c-Myc axis forms a negative feedback loop via Wnt/β-catenin signaling.","method":"Direct targeting by miR-3648 validated; Co-immunoprecipitation (FRAT1–FRAT2 physical interaction); siRNA knockdown of FRAT2 in FRAT1-overexpressing cells; in vitro invasion/motility assays; in vivo metastasis assay","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP for FRAT1–FRAT2 interaction, direct target validation, loss-of-function with defined invasion phenotype, in vivo confirmation","pmids":["36153370"],"is_preprint":false}],"current_model":"FRAT2 is a GSK-3β-binding protein that positively regulates the canonical Wnt/β-catenin–TCF signaling pathway by binding GSK3β (via its GSK-3β binding domain) and Dishevelled; it selectively enhances GSK3β-mediated phosphorylation of primed substrates (including tau), is itself phosphorylated by GSK3β, physically interacts with FRAT1, activates Rac GTPase through a GSK3/DVL-dependent mechanism downstream of MLL fusions, and is negatively regulated at the protein level by TMEM98 and at the mRNA level by miR-29 family members and miR-3648."},"narrative":{"teleology":[{"year":2001,"claim":"Establishing that FRAT2 is a functional Wnt pathway activator whose activity depends on its acidic and proline-rich domains resolved the question of whether FRAT2 — newly cloned alongside FRAT1 — shared its paralog's axis-inducing capacity.","evidence":"Xenopus axis duplication assay comparing wild-type and domain-deletion mutant FRAT2 mRNA injections","pmids":["11237732"],"confidence":"High","gaps":["Endogenous expression pattern and physiological requirement for FRAT2 in vertebrate Wnt signaling not addressed","Mechanism by which the acidic/proline-rich domains contribute to signaling undefined"]},{"year":2002,"claim":"Demonstrating that FRAT2 directly binds both GSK-3 and Dishevelled placed it at the core signal transduction node where Wnt signals converge, answering whether FRAT2 engages the same molecular partners as FRAT1.","evidence":"Protein interaction studies and subcellular fractionation in transiently transfected COS-1 cells","pmids":["12095675"],"confidence":"Medium","gaps":["Binding shown only with overexpressed proteins; endogenous interaction not confirmed","Relative affinities for GSK-3 versus Dishevelled not determined"]},{"year":2004,"claim":"Two independent studies resolved FRAT2's enzymatic relationship with GSK-3β: FRAT2 is a weaker Wnt–TCF activator than FRAT1 yet selectively enhances GSK-3β phosphorylation of primed substrates (e.g., tau) and is itself a GSK-3β substrate, suggesting a non-redundant modulatory role.","evidence":"Co-immunoprecipitation, β-catenin/TCF reporter assays, in vitro kinase assays with recombinant proteins, and phosphorylation detection","pmids":["15073180","15522877"],"confidence":"High","gaps":["The basis for differential potency between FRAT1 and FRAT2 in Wnt activation is unknown","Functional consequence of FRAT2 phosphorylation by GSK-3β on its activity or stability not determined","Whether FRAT2 enhances primed phosphorylation of endogenous substrates in vivo is untested"]},{"year":2012,"claim":"Genetic loss-of-function experiments revealed a Wnt-independent output of FRAT2: activation of Rac GTPase downstream of MLL fusion oncogenes via GSK-3 and Dishevelled, explaining how FRAT2 contributes to leukemic transformation and chemoresistance.","evidence":"Frat-knockout hematopoietic progenitors transformed by MLL fusions, Rac activity assays, epistasis analysis with GSK3/DVL perturbation","pmids":["23074275"],"confidence":"High","gaps":["Direct mechanism linking FRAT2–GSK3–DVL to Rac GEF activation unresolved","Relative contributions of FRAT1 versus FRAT2 in MLL-driven Rac activation not separated"]},{"year":2015,"claim":"Identification of miR-29 family members as direct negative regulators of FRAT2 in chondrocytes and pancreatic cancer cells established a post-transcriptional control layer that tunes Wnt pathway output, with TGF-β acting upstream to relieve miR-29-mediated FRAT2 repression.","evidence":"Luciferase reporter assays validating direct miR-29 targeting of FRAT2 3′-UTR; miR-29c overexpression/knockdown in pancreatic cancer cells","pmids":["26687115","25605017"],"confidence":"Medium","gaps":["Quantitative contribution of FRAT2 repression versus co-targeted Wnt components (LRP6, FZD4/5) not dissected","In vivo relevance of miR-29–FRAT2 axis in cartilage or pancreatic homeostasis not tested"]},{"year":2020,"claim":"Discovery that TMEM98 physically interacts with FRAT2 and reduces its protein levels provided the first evidence of a protein-level negative regulator that constrains FRAT2-mediated β-catenin/TCF signaling.","evidence":"Co-immunoprecipitation, TMEM98 overexpression with FRAT2 protein quantification, β-catenin/TCF reporter assays","pmids":["31961879"],"confidence":"Medium","gaps":["Mechanism of FRAT2 protein reduction (degradation versus translational inhibition) by TMEM98 unknown","Endogenous co-expression and interaction of TMEM98 and FRAT2 not demonstrated","Single-lab finding without independent replication"]},{"year":2022,"claim":"Demonstration that FRAT1 and FRAT2 physically interact and cooperatively promote invasion — with FRAT2 knockdown reversing FRAT1-driven invasiveness — established a functional heteromeric relationship and identified a miR-3648/FRAT1-FRAT2/c-Myc negative feedback loop in gastric cancer.","evidence":"Reciprocal co-immunoprecipitation, siRNA knockdown of FRAT2 in FRAT1-overexpressing gastric cancer cells, in vitro invasion and in vivo metastasis assays, miR-3648 direct target validation","pmids":["36153370"],"confidence":"High","gaps":["Stoichiometry and structural basis of the FRAT1–FRAT2 complex unknown","Whether FRAT1–FRAT2 interaction modulates GSK-3β substrate selection or Rac activation not tested"]},{"year":null,"claim":"The structural basis of the FRAT1–FRAT2 heteromeric complex, the mechanism by which FRAT2 differentially channels GSK-3β activity toward primed substrates versus β-catenin, and the physiological requirement for FRAT2 in normal development remain unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No structural data for FRAT2 or FRAT1–FRAT2 complex","No FRAT2-specific knockout phenotype in whole-organism models","Direct GEF or effector linking FRAT2–GSK3–DVL axis to Rac activation not identified"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,2,3,4]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[1]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[1]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,1,2,3,5,6,7,8]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[4,6,8]}],"complexes":[],"partners":["GSK3B","DVL1","FRAT1","TMEM98"],"other_free_text":[]},"mechanistic_narrative":"FRAT2 is a positive regulator of the canonical Wnt/β-catenin–TCF signaling pathway that functions by binding GSK-3β and Dishevelled to modulate GSK-3β substrate specificity and downstream signal transduction. FRAT2 contains a GSK-3β binding domain identical to that of FRAT1, and its acidic and proline-rich domains are required for axis-inducing activity; it selectively enhances GSK-3β-mediated phosphorylation of primed substrates such as tau while being itself phosphorylated by GSK-3β [PMID:11237732, PMID:15522877]. Beyond canonical Wnt signaling, FRAT2 activates Rac GTPase through a GSK-3/Dishevelled-dependent mechanism downstream of MLL fusion oncogenes in hematopoietic progenitors, linking it to leukemogenesis and chemosensitivity [PMID:23074275]. FRAT2 physically interacts with FRAT1 to cooperatively drive invasion and is negatively regulated at the protein level by TMEM98 and at the mRNA level by miR-29 family members and miR-3648, establishing multiple feedback controls on Wnt pathway output [PMID:36153370, PMID:31961879, PMID:25605017]."},"prefetch_data":{"uniprot":{"accession":"O75474","full_name":"GSK-3-binding protein FRAT2","aliases":["Frequently rearranged in advanced T-cell lymphomas 2","FRAT-2"],"length_aa":233,"mass_kda":24.1,"function":"Positively regulates the Wnt signaling pathway by stabilizing beta-catenin through the association with GSK-3","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/O75474/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/FRAT2","classification":"Not Classified","n_dependent_lines":46,"n_total_lines":1208,"dependency_fraction":0.0380794701986755},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/FRAT2","total_profiled":1310},"omim":[{"mim_id":"606784","title":"GLYCOGEN SYNTHASE KINASE 3-ALPHA; GSK3A","url":"https://www.omim.org/entry/606784"},{"mim_id":"605006","title":"FREQUENTLY REARRANGED IN ADVANCED T-CELL LYMPHOMAS 2; FRAT2","url":"https://www.omim.org/entry/605006"},{"mim_id":"602503","title":"FREQUENTLY REARRANGED IN ADVANCED T-CELL LYMPHOMAS; FRAT1","url":"https://www.omim.org/entry/602503"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Mitochondria","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/FRAT2"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"O75474","domains":[{"cath_id":"-","chopping":"177-203","consensus_level":"medium","plddt":95.663,"start":177,"end":203}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O75474","model_url":"https://alphafold.ebi.ac.uk/files/AF-O75474-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O75474-F1-predicted_aligned_error_v6.png","plddt_mean":62.12},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=FRAT2","jax_strain_url":"https://www.jax.org/strain/search?query=FRAT2"},"sequence":{"accession":"O75474","fasta_url":"https://rest.uniprot.org/uniprotkb/O75474.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O75474/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O75474"}},"corpus_meta":[{"pmid":"17873379","id":"PMC_17873379","title":"Networking of WNT, FGF, Notch, BMP, and Hedgehog 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wild-type FRAT2 mRNA (but not a mutant lacking the acidic domain and proline-rich domain) induces secondary axis duplication in Xenopus, demonstrating it positively regulates the WNT signaling pathway through its acidic and proline-rich domains.\",\n      \"method\": \"Xenopus axis duplication assay with wild-type vs. deletion mutant FRAT2 mRNA injection\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — functional in vivo assay with domain-deletion mutagenesis establishing mechanism\",\n      \"pmids\": [\"11237732\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Human FRAT2 protein binds to GSK-3 (glycogen synthase kinase-3) and Dishevelled, two core components of Wnt signal transduction, and when transiently overexpressed in COS-1 cells localizes to the cytosol and is concentrated in the nucleus.\",\n      \"method\": \"Protein interaction studies; transient overexpression with subcellular fractionation/localization in COS-1 cells\",\n      \"journal\": \"Gene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — direct binding shown, subcellular localization by overexpression\",\n      \"pmids\": [\"12095675\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Murine Frat2 binds GSK3β, is phosphorylated (first evidence of post-translational modification of Frat proteins), but is a less potent activator of the canonical Wnt/β-catenin–TCF pathway compared to Frat1, suggesting Frat2 may participate in a divergent intracellular GSK3β pathway.\",\n      \"method\": \"Co-immunoprecipitation (GSK3β binding), β-catenin/TCF reporter assay, phosphorylation detection in transfected cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP, functional reporter assay, and phosphorylation all performed in same study\",\n      \"pmids\": [\"15073180\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"FRAT-2 associates with GSK3β and selectively enhances GSK3β-mediated phosphorylation of primed substrates (but not unprimed substrates), resulting in enhanced tau phosphorylation at primed epitopes; additionally, FRAT-2 is itself phosphorylated by GSK3β.\",\n      \"method\": \"Co-immunoprecipitation, in situ phosphorylation assays, in vitro kinase assay with recombinant proteins\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted in vitro with recombinant proteins plus co-IP and in situ assays, multiple orthogonal methods\",\n      \"pmids\": [\"15522877\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"FRAT2 mediates oncogenic Rac GTPase activation downstream of MLL fusion oncogenes; FRAT2 activates Rac through a signaling mechanism requiring GSK3 and DVL (Dishevelled); loss of Frat in hematopoietic progenitor cells transformed by MLL fusions results in reduced Rac activation and increased chemosensitivity.\",\n      \"method\": \"Genetic knockout of Frat genes in hematopoietic progenitors, modulation of FRAT2 expression with concomitant Rac activity measurement, pathway disruption assays\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — loss-of-function genetics, defined cellular phenotype, pathway placement via epistasis with GSK3 and DVL\",\n      \"pmids\": [\"23074275\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"FRAT2 is a direct target of the miR-29 family in chondrocytes; miR-29 negatively regulates canonical WNT signaling partly by suppressing FRAT2 expression.\",\n      \"method\": \"Direct target validation of miR-29 family on FRAT2 (luciferase reporter assay implied by 'validated as direct targets'); expression analysis in chondrocytes\",\n      \"journal\": \"Journal of molecular medicine (Berlin, Germany)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — direct target validation reported but mechanistic follow-up limited to pathway-level readout\",\n      \"pmids\": [\"26687115\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"FRAT2 is a direct target of miR-29c in pancreatic cancer cells; miR-29c suppresses FRAT2 along with LRP6, FZD4, and FZD5, thereby inhibiting Wnt cascade hyperactivation; TGF-β inhibits miR-29c, leading to FRAT2 upregulation and Wnt activation.\",\n      \"method\": \"miR-29c overexpression/knockdown with luciferase reporter assay for direct targeting; pathway activity measurement\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — direct target validated by reporter assay, pathway consequence shown, single lab\",\n      \"pmids\": [\"25605017\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"TMEM98, a putative transmembrane protein recycled between the plasma membrane and Golgi, physically interacts with FRAT2, reduces FRAT2 protein levels, and inhibits FRAT2-mediated induction of β-catenin/TCF signaling, acting as a negative regulator of FRAT-mediated Wnt signaling.\",\n      \"method\": \"Co-immunoprecipitation (TMEM98–FRAT2 interaction), protein level quantification upon TMEM98 expression, β-catenin/TCF reporter assay, intracellular trafficking characterization\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — Co-IP interaction, functional reporter assay, and protein stability data from single lab\",\n      \"pmids\": [\"31961879\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"miR-3648 directly targets FRAT2 (and FRAT1) to inhibit their expression, suppressing FRAT1/FRAT2-mediated invasion and motility in gastric cancer cells; FRAT1 and FRAT2 physically interact with each other; siRNA-mediated repression of FRAT2 in FRAT1-overexpressing cells reverses FRAT1-driven invasive potential; the miR-3648/FRAT1-FRAT2/c-Myc axis forms a negative feedback loop via Wnt/β-catenin signaling.\",\n      \"method\": \"Direct targeting by miR-3648 validated; Co-immunoprecipitation (FRAT1–FRAT2 physical interaction); siRNA knockdown of FRAT2 in FRAT1-overexpressing cells; in vitro invasion/motility assays; in vivo metastasis assay\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP for FRAT1–FRAT2 interaction, direct target validation, loss-of-function with defined invasion phenotype, in vivo confirmation\",\n      \"pmids\": [\"36153370\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"FRAT2 is a GSK-3β-binding protein that positively regulates the canonical Wnt/β-catenin–TCF signaling pathway by binding GSK3β (via its GSK-3β binding domain) and Dishevelled; it selectively enhances GSK3β-mediated phosphorylation of primed substrates (including tau), is itself phosphorylated by GSK3β, physically interacts with FRAT1, activates Rac GTPase through a GSK3/DVL-dependent mechanism downstream of MLL fusions, and is negatively regulated at the protein level by TMEM98 and at the mRNA level by miR-29 family members and miR-3648.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"FRAT2 is a positive regulator of the canonical Wnt/β-catenin–TCF signaling pathway that functions by binding GSK-3β and Dishevelled to modulate GSK-3β substrate specificity and downstream signal transduction. FRAT2 contains a GSK-3β binding domain identical to that of FRAT1, and its acidic and proline-rich domains are required for axis-inducing activity; it selectively enhances GSK-3β-mediated phosphorylation of primed substrates such as tau while being itself phosphorylated by GSK-3β [PMID:11237732, PMID:15522877]. Beyond canonical Wnt signaling, FRAT2 activates Rac GTPase through a GSK-3/Dishevelled-dependent mechanism downstream of MLL fusion oncogenes in hematopoietic progenitors, linking it to leukemogenesis and chemosensitivity [PMID:23074275]. FRAT2 physically interacts with FRAT1 to cooperatively drive invasion and is negatively regulated at the protein level by TMEM98 and at the mRNA level by miR-29 family members and miR-3648, establishing multiple feedback controls on Wnt pathway output [PMID:36153370, PMID:31961879, PMID:25605017].\",\n  \"teleology\": [\n    {\n      \"year\": 2001,\n      \"claim\": \"Establishing that FRAT2 is a functional Wnt pathway activator whose activity depends on its acidic and proline-rich domains resolved the question of whether FRAT2 — newly cloned alongside FRAT1 — shared its paralog's axis-inducing capacity.\",\n      \"evidence\": \"Xenopus axis duplication assay comparing wild-type and domain-deletion mutant FRAT2 mRNA injections\",\n      \"pmids\": [\"11237732\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Endogenous expression pattern and physiological requirement for FRAT2 in vertebrate Wnt signaling not addressed\", \"Mechanism by which the acidic/proline-rich domains contribute to signaling undefined\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Demonstrating that FRAT2 directly binds both GSK-3 and Dishevelled placed it at the core signal transduction node where Wnt signals converge, answering whether FRAT2 engages the same molecular partners as FRAT1.\",\n      \"evidence\": \"Protein interaction studies and subcellular fractionation in transiently transfected COS-1 cells\",\n      \"pmids\": [\"12095675\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Binding shown only with overexpressed proteins; endogenous interaction not confirmed\", \"Relative affinities for GSK-3 versus Dishevelled not determined\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Two independent studies resolved FRAT2's enzymatic relationship with GSK-3β: FRAT2 is a weaker Wnt–TCF activator than FRAT1 yet selectively enhances GSK-3β phosphorylation of primed substrates (e.g., tau) and is itself a GSK-3β substrate, suggesting a non-redundant modulatory role.\",\n      \"evidence\": \"Co-immunoprecipitation, β-catenin/TCF reporter assays, in vitro kinase assays with recombinant proteins, and phosphorylation detection\",\n      \"pmids\": [\"15073180\", \"15522877\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The basis for differential potency between FRAT1 and FRAT2 in Wnt activation is unknown\", \"Functional consequence of FRAT2 phosphorylation by GSK-3β on its activity or stability not determined\", \"Whether FRAT2 enhances primed phosphorylation of endogenous substrates in vivo is untested\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Genetic loss-of-function experiments revealed a Wnt-independent output of FRAT2: activation of Rac GTPase downstream of MLL fusion oncogenes via GSK-3 and Dishevelled, explaining how FRAT2 contributes to leukemic transformation and chemoresistance.\",\n      \"evidence\": \"Frat-knockout hematopoietic progenitors transformed by MLL fusions, Rac activity assays, epistasis analysis with GSK3/DVL perturbation\",\n      \"pmids\": [\"23074275\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct mechanism linking FRAT2–GSK3–DVL to Rac GEF activation unresolved\", \"Relative contributions of FRAT1 versus FRAT2 in MLL-driven Rac activation not separated\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Identification of miR-29 family members as direct negative regulators of FRAT2 in chondrocytes and pancreatic cancer cells established a post-transcriptional control layer that tunes Wnt pathway output, with TGF-β acting upstream to relieve miR-29-mediated FRAT2 repression.\",\n      \"evidence\": \"Luciferase reporter assays validating direct miR-29 targeting of FRAT2 3′-UTR; miR-29c overexpression/knockdown in pancreatic cancer cells\",\n      \"pmids\": [\"26687115\", \"25605017\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Quantitative contribution of FRAT2 repression versus co-targeted Wnt components (LRP6, FZD4/5) not dissected\", \"In vivo relevance of miR-29–FRAT2 axis in cartilage or pancreatic homeostasis not tested\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Discovery that TMEM98 physically interacts with FRAT2 and reduces its protein levels provided the first evidence of a protein-level negative regulator that constrains FRAT2-mediated β-catenin/TCF signaling.\",\n      \"evidence\": \"Co-immunoprecipitation, TMEM98 overexpression with FRAT2 protein quantification, β-catenin/TCF reporter assays\",\n      \"pmids\": [\"31961879\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of FRAT2 protein reduction (degradation versus translational inhibition) by TMEM98 unknown\", \"Endogenous co-expression and interaction of TMEM98 and FRAT2 not demonstrated\", \"Single-lab finding without independent replication\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Demonstration that FRAT1 and FRAT2 physically interact and cooperatively promote invasion — with FRAT2 knockdown reversing FRAT1-driven invasiveness — established a functional heteromeric relationship and identified a miR-3648/FRAT1-FRAT2/c-Myc negative feedback loop in gastric cancer.\",\n      \"evidence\": \"Reciprocal co-immunoprecipitation, siRNA knockdown of FRAT2 in FRAT1-overexpressing gastric cancer cells, in vitro invasion and in vivo metastasis assays, miR-3648 direct target validation\",\n      \"pmids\": [\"36153370\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry and structural basis of the FRAT1–FRAT2 complex unknown\", \"Whether FRAT1–FRAT2 interaction modulates GSK-3β substrate selection or Rac activation not tested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The structural basis of the FRAT1–FRAT2 heteromeric complex, the mechanism by which FRAT2 differentially channels GSK-3β activity toward primed substrates versus β-catenin, and the physiological requirement for FRAT2 in normal development remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No structural data for FRAT2 or FRAT1–FRAT2 complex\", \"No FRAT2-specific knockout phenotype in whole-organism models\", \"Direct GEF or effector linking FRAT2–GSK3–DVL axis to Rac activation not identified\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 2, 3, 4]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 1, 2, 3, 5, 6, 7, 8]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [4, 6, 8]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"GSK3B\", \"DVL1\", \"FRAT1\", \"TMEM98\"],\n    \"other_free_text\": []\n  }\n}\n```"}