{"gene":"TGIF1","run_date":"2026-06-10T10:51:55","timeline":{"discoveries":[{"year":2010,"finding":"Tgif1 and Tgif2 act as transcriptional co-repressors that limit the response to Nodal signaling during gastrulation; genetic reduction of Nodal dose partially rescues gastrulation defects in Tgif1/Tgif2 double-null embryos, placing Tgifs upstream of Nodal-responsive transcription in early embryogenesis.","method":"Conditional knockout mouse genetics, genetic epistasis with Nodal dosage reduction","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal conditional knockout with genetic epistasis, replicated across multiple allele combinations and strain backgrounds in a single rigorous developmental study","pmids":["20040491"],"is_preprint":false},{"year":2010,"finding":"The E3 ubiquitin ligase substrate-recognition factor Fbxw7 targets TGIF1 for proteasomal degradation in a phosphorylation-dependent manner; inactivation of Fbxw7 leads to accumulation of phosphorylated TGIF1 and repression of TGFβ-dependent transcription, thereby attenuating TGFβ-regulated cell growth and migration.","method":"Co-immunoprecipitation, ubiquitination assays, cancer cell lines with Fbxw7 loss-of-function mutations, cell growth and migration assays","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP and functional assays in multiple cell lines, single lab","pmids":["20622901"],"is_preprint":false},{"year":2018,"finding":"The TGIF1 homeodomain (HD) binds the TGACA DNA motif through both the HD core/major groove and the N-terminal arm/minor groove; additionally, the TGIF1-HD directly interacts with the MH1 domain of Smad proteins, and this HD-MH1 interaction partially occludes the DNA-binding site of the complex, providing a mechanism by which TGIF1 is released from promoters to actively repress Smad-induced TGFβ signaling.","method":"Crystal structure of TGIF1-HD bound to DNA, NMR, in vitro binding assays, functional reporter assays","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure combined with NMR and functional validation in a single rigorous study","pmids":["30060237"],"is_preprint":false},{"year":2019,"finding":"Tgif1 is a PTH target gene in osteoblasts; deletion of Tgif1 in osteoblasts/osteocytes impairs osteoblast differentiation and reduces bone formation, and also decreases bone resorption by increasing secretion of the osteoclast-inhibiting factor Semaphorin 3E (Sema3E). PTH failed to increase bone formation in Tgif1-deficient mice, identifying Tgif1 as an essential component of PTH anabolic action.","method":"Conditional knockout mice, bone histomorphometry, PTH treatment experiments, Sema3E secretion assays","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional KO with multiple orthogonal in vivo and in vitro readouts, PTH rescue experiments","pmids":["30902975"],"is_preprint":false},{"year":2013,"finding":"Tgif1 regulates hematopoietic stem cell (HSC) quiescence and self-renewal; Tgif1-null bone marrow cells show greater self-renewal, reduced proliferation, and increased quiescence, whereas Tgif1 overexpression increases proliferation but reduces long-term survival in transplant assays, indicating Tgif1 suppresses stem cell self-renewal.","method":"CFU assays, competitive repopulation/serial transplantation in mice, BrdU labeling for quiescence","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple in vivo transplantation and in vitro assays with both loss- and gain-of-function, single lab","pmids":["24100014"],"is_preprint":false},{"year":2015,"finding":"Tgif1 directly represses core pluripotency factors (Oct4, Sox2, Nanog) in mouse embryonic stem cells independently of TGFβ/activin/nodal signaling; Tgif1 physically associates with Oct4, Nanog, and HDAC1/2, counterbalancing the autoregulatory amplification of core pluripotency factors.","method":"Co-immunoprecipitation, overexpression and knockdown in ESCs, reporter assays, treatment with activin/nodal pathway inhibitors","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP and functional gain/loss-of-function, single lab","pmids":["26411691"],"is_preprint":false},{"year":2012,"finding":"Primary MEFs lacking Tgif1 senesce prematurely, accumulate increased DNA damage, and are more sensitive to TGFβ-mediated growth inhibition; treatment with a TGFβ receptor kinase inhibitor rescues proliferation of Tgif1-null MEFs, demonstrating that elevated TGFβ signaling in the absence of Tgif1 contributes to premature senescence.","method":"Primary MEF culture, proliferation assays, senescence markers (SA-β-gal), DNA damage markers (γH2AX), TGFβ receptor kinase inhibitor treatment","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO primary cells with pharmacological rescue and multiple orthogonal readouts, single lab","pmids":["22514746"],"is_preprint":false},{"year":2011,"finding":"TGIF1 functions as a GnRH pulse-frequency-sensitive corepressor of FSHβ gene transcription; overexpression of binding- or phosphorylation-defective TGIF1 mutants fails to repress Fshb promoter activity, and TGIF1 occupies the FSHβ promoter in a cyclical manner after GnRH stimulation as shown by ChIP.","method":"Chromatin immunoprecipitation (ChIP), Fshb promoter reporter assays, siRNA knockdown, overexpression of TGIF1 mutants, GnRH pulse experiments","journal":"Molecular endocrinology (Baltimore, Md.)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP plus loss- and gain-of-function with mutants, single lab","pmids":["21659477"],"is_preprint":false},{"year":2017,"finding":"TGIF1 binds to a conserved consensus TGIF site 5' of the Evi5l gene and represses its expression; loss of both Tgif1 and Tgif2 increases Evi5l expression, reduces primary cilia numbers in MEFs, and impairs the Shh transcriptional response; reducing Evi5l in double-null MEFs partially restores cilia numbers and Shh signaling.","method":"Transcriptome profiling, ChIP, Evi5l knockdown rescue experiments, cilia quantification by microscopy, Shh pathway reporter assays","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct ChIP demonstrating TGIF1 binding at Evi5l promoter, genetic rescue epistasis, and multiple orthogonal functional readouts","pmids":["27956704"],"is_preprint":false},{"year":2018,"finding":"NMR structure of TGIF1-HD (TALE-type homeodomain) determined; holoprosencephaly-associated mutations P192A and R219C disrupt packing of helices α1 and α2 against α3, destabilize the HD structure, and reduce DNA-binding affinity by 23-fold and 10-fold respectively, as measured by isothermal titration calorimetry.","method":"NMR structure determination, circular dichroism, isothermal titration calorimetry, 1H-15N HSQC of P192A mutant","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 1 / Strong — NMR structure plus ITC quantification of binding defects for two disease mutations in a single rigorous study","pmids":["29355528"],"is_preprint":false},{"year":2018,"finding":"ZIC2 (an HPE-causative transcription factor) directly binds to Zic2-binding sites (ZBS) on the 5' flanking region of the Tgif1 gene and activates Tgif1 transcription, as demonstrated by ChIP and in vitro DNA binding assays; ZBS are required for Zic2-dependent transcriptional activation in reporter assays, linking two HPE-causative genes in a direct regulatory relationship.","method":"Chromatin immunoprecipitation (ChIP), in vitro DNA binding assays, reporter gene assays","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP plus in vitro DNA binding and reporter assays, single lab","pmids":["29391420"],"is_preprint":false},{"year":2019,"finding":"TGIF1 associates with Twist1 and inhibits Twist1 expression and activity; KrasG12D/MAPK-mediated TGIF1 phosphorylation suppresses this function in human PDACs; ablating Twist1 in KrasG12D;Tgif1KO mice completely blunts PDAC formation, establishing that TGIF1 restrains KrasG12D-driven PDAC through antagonism of Twist1.","method":"Co-immunoprecipitation, conditional knockout mouse PDAC models, genetic epistasis (Twist1 ablation rescue), mechanistic phosphorylation experiments","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, genetic epistasis rescue in vivo, and phosphorylation mechanistic experiments in one study","pmids":["31268604"],"is_preprint":false},{"year":2014,"finding":"TGIF1 interferes with MEIS1-dependent transcriptional programs in MLL-rearranged AML by associating with MEIS1-bound chromatin regions in a competitive manner; forced TGIF1 expression promotes differentiation and cell cycle exit in MLL-AF9-transformed cells and delays leukemic onset in vivo.","method":"ChIP, in vitro differentiation and cell cycle assays, in vivo leukemia transplantation model, gene expression analysis","journal":"Leukemia","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP demonstrating competitive occupancy at MEIS1-bound loci plus in vivo functional experiments, single lab","pmids":["25349154"],"is_preprint":false},{"year":2012,"finding":"TGIF1 plays a role in TNF-α- and radiation-induced proinflammatory phenotype of endothelial cells; TGIF1 knockdown inhibits both TNF-α- and radiation-induced p38 MAPK pathway activation (but not NF-κB activation), and TGIF1 deficiency reduces radiation-induced proinflammatory cytokine expression in vivo, identifying p38 MAPK as the signaling pathway through which TGIF1 promotes inflammation.","method":"TGIF1 overexpression and siRNA knockdown in HUVECs, p38 MAPK and NF-κB pathway activation assays, in vivo radiation enteropathy model with Tgif1-/- mice","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KD/KO with specific pathway dissection (p38 vs NF-κB), in vitro and in vivo concordance, single lab","pmids":["22995913"],"is_preprint":false},{"year":2021,"finding":"TGIF1 utilizes a C-terminal SIN3A-interacting domain (SID) that adopts an amphipathic helix to bind the hydrophobic cleft of SIN3A PAH2; residues F379, L382, and V383 are critical for binding; the same SID also mediates TGIF1 homodimerization, suggesting a competitive relationship between dimerization and SIN3A-PAH2 binding.","method":"NMR structure determination of TGIF1-SID bound to SIN3A PAH2, mutagenesis of critical residues, ITC binding assays","journal":"International journal of molecular sciences","confidence":"High","confidence_rationale":"Tier 1 / Strong — NMR structure with mutagenesis of critical residues and ITC quantification in a single rigorous structural study","pmids":["34884456"],"is_preprint":false},{"year":2018,"finding":"The helix α3 of TGIF1-HD constitutes the primary DNA-binding interface as determined by hydrogen-deuterium exchange mass spectrometry (HDX-MS) and confirmed by CEST NMR spectroscopy; residues R220 and R221 in α3 are crucial for DNA binding, and DNA binding induces conformational changes in α1 and α2 as well.","method":"HDX-MS, CEST NMR spectroscopy, NMR titration","journal":"Biochimica et biophysica acta. Proteins and proteomics","confidence":"High","confidence_rationale":"Tier 1 / Strong — two independent structural/biophysical methods (HDX-MS and CEST NMR) converging on the same binding interface identification","pmids":["30048701"],"is_preprint":false},{"year":2025,"finding":"A vertebrate-conserved short motif (I302-L310) of TGIF1 binds to a groove on the SMAD2 MH2 domain surface that overlaps with coactivator binding sites; BiFC assays confirmed that the α2-β8 loop of SMAD2-MH2 is key for TGIF1 binding, suggesting TGIF1 represses TGFβ signaling by competing with coactivators for SMAD2-MH2 binding.","method":"NMR titration, HDX-MS, AlphaFold3 modeling, bimolecular fluorescence complementation (BiFC) assays","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 1-2 / Moderate — NMR titration and HDX-MS with BiFC validation, single lab, AlphaFold3 used for modeling (not fully experimental structure)","pmids":["40395157"],"is_preprint":false},{"year":2024,"finding":"Tgif1 acts as a transcriptional repressor of p21-activated kinase 3 (Pak3) in osteoblasts; absence of Tgif1 leads to increased Pak3 expression, which impairs focal adhesion formation, osteoblast spreading, and migration on collagen type I matrices; Tgif1 is also required for osteoblast recruitment to bone surfaces during regeneration and PTH 1-34 treatment in vivo.","method":"Conditional KO osteoblasts, cell morphology and adhesion assays, migration assays on collagen I, ChIP/transcriptional repression assays for Pak3, in vivo bone regeneration and PTH treatment models","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 / Strong — transcriptional repression mechanism established by ChIP, functional rescue with multiple orthogonal in vitro and in vivo assays","pmids":["38661167"],"is_preprint":false},{"year":2025,"finding":"Tgif1 is expressed in osteoclast precursors with increasing expression during RANKL/M-CSF-induced differentiation; cell-autonomous deletion of Tgif1 in the osteoclast lineage impairs differentiation and resorption capacity; mechanistically, Tgif1 restricts ERK1/2 dephosphorylation by suppressing protein phosphatase 2A (PP2A), and PP2A inhibition restores differentiation of Tgif1-deficient osteoclasts.","method":"Conditional KO in osteoclast lineage, in vitro differentiation assays, PP2A inhibition rescue, ERK1/2 phosphorylation analysis, in vivo aging bone loss model","journal":"Journal of bone and mineral research","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional KO with pharmacological rescue epistasis establishing PP2A-ERK1/2 mechanism, in vitro and in vivo concordance","pmids":["40810487"],"is_preprint":false},{"year":2022,"finding":"TFEB transcriptionally activates TGIF1 expression by binding the Tgif1 promoter; in epicardial cells, TFEB overexpression prevents TGFβ-induced EMT, and this effect is abolished by Tgif1 silencing, establishing a TFEB→TGIF1 axis that represses TGFβ-driven EMT.","method":"Reporter assays, qRT-PCR, TGIF1 silencing rescue experiments, in vitro EMT assays, in vivo epicardial TFEB overexpression mouse model","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — promoter reporter assays plus genetic rescue, in vivo and in vitro concordance, single lab","pmids":["36057632"],"is_preprint":false},{"year":2016,"finding":"TGIF1 interacts with the PAH2 domain of SIN3A; SID decoy peptides that disrupt this interaction dissociate TGIF1 from the SIN3A complex, inhibit Wnt target gene expression, reduce nuclear β-catenin, and suppress cancer cell invasion; TGIF1 knockdown phenocopies SID decoy effects on Wnt targets and invasion.","method":"SID decoy peptide treatment, TGIF1 knockdown, Wnt reporter assays, β-catenin localization by immunofluorescence, Transwell invasion assays","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — SID decoy disruption of SIN3A-TGIF1 complex with multiple functional readouts, mechanistic link to Wnt pathway supported by KD phenocopy","pmids":["29179446"],"is_preprint":false},{"year":2015,"finding":"TGIF1 represses Sox9 expression by interacting with TGFβ-activated Smad2, suppressing Smad2 phosphorylation, and thereby inhibiting chondrogenic differentiation of tendon-derived stem cells; TGIF1 silencing upregulates chondrogenic markers and increases fibrocartilage formation at the tendon-bone interface in a rat model.","method":"siRNA knockdown, TGIF1 overexpression in TDSCs, Co-IP for Smad2 interaction, Western blot for Smad2 phosphorylation, in vivo rat tendon repair model","journal":"Cellular physiology and biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP demonstrating Smad2 interaction and phosphorylation changes, in vitro and in vivo functional assays, single lab","pmids":["26599628"],"is_preprint":false},{"year":2016,"finding":"Tgif1 deficiency in extra-embryonic tissue (but not epiblast) is the critical cause of gastrulation failure in Tgif1/Tgif2 double-null embryos; a single wild-type allele of Tgif1 in extra-embryonic tissue rescues gastrulation, demonstrating that extra-embryonic Tgif function is required for patterning the epiblast.","method":"Epiblast-specific conditional deletion of Tgif1 using Cre-lox genetics","journal":"PloS one (Tgif1 and Tgif2 Regulate Axial Patterning in Mouse)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — tissue-specific conditional deletion establishing cell-non-autonomous requirement, single lab (follows up on PMID 20040491)","pmids":["20040491","27187787"],"is_preprint":false},{"year":2025,"finding":"TGIF1 is enriched on the miR-106b-5p promoter and promotes miR-106b-5p expression; miR-106b-5p in turn suppresses EGR2; in a T2D mouse model, TGIF1 overexpression reduces hyperglycemia and lipid accumulation through the miR-106b-5p/EGR2 axis, and miR-106b-5p inhibition or EGR2 overexpression partially reverses the TGIF1 effect.","method":"ChIP for TGIF1 at miR-106b-5p promoter, dual-luciferase reporter assays, TGIF1 overexpression in T2D mice, rescue experiments","journal":"BMJ open diabetes research & care","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP plus in vivo and in vitro functional rescue experiments, single lab","pmids":["39842865"],"is_preprint":false}],"current_model":"TGIF1 is a TALE-class homeodomain transcriptional co-repressor that limits TGFβ/Smad and Nodal signaling by binding Smad2 MH1 and MH2 domains (competing with coactivators) and recruiting the SIN3A–HDAC1/2 corepressor complex via its C-terminal amphipathic helix; it is targeted for phosphorylation-dependent proteasomal degradation by Fbxw7; it additionally represses direct target genes (including Evi5l, Pak3, Twist1, and pluripotency factors) through promoter binding, thereby controlling gastrulation, axial patterning, HSC quiescence, osteoblast/osteoclast differentiation, ciliogenesis, and EMT."},"narrative":{"mechanistic_narrative":"TGIF1 is a TALE-class homeodomain transcriptional co-repressor that restrains TGFβ/Nodal signaling and represses defined target genes to control embryonic patterning and adult cell-fate decisions [PMID:20040491, PMID:30060237]. It engages DNA through its homeodomain, which recognizes the TGACA motif via the helix-α3 interface (R220/R221) and minor-groove contacts, with disease-associated mutations (P192A, R219C) destabilizing the fold and weakening DNA affinity [PMID:30060237, PMID:30048701, PMID:29355528]. Its repressive output operates on two convergent axes against Smad signaling: the homeodomain directly contacts the Smad MH1 domain in a manner that occludes DNA binding [PMID:30060237], while a conserved C-terminal motif binds the SMAD2 MH2 domain at a surface overlapping coactivator-binding sites, displacing coactivators [PMID:40395157]. Repression is enforced by a C-terminal SIN3A-interacting domain that folds into an amphipathic helix engaging the SIN3A PAH2 cleft (F379/L382/V383), the same element that mediates TGIF1 homodimerization [PMID:34884456, PMID:29179446]. During development, TGIF1 (with TGIF2) limits Nodal-responsive transcription, and its requirement in extra-embryonic tissue is critical for proper epiblast patterning during gastrulation [PMID:20040491, PMID:27187787]; it also represses Evi5l to support ciliogenesis and Shh signaling [PMID:27956704]. In adult tissues, TGIF1 directly represses target genes to govern HSC quiescence and self-renewal [PMID:24100014], osteoblast differentiation and migration (repressing Pak3, mediating PTH anabolic action) [PMID:30902975, PMID:38661167], osteoclast differentiation via restriction of PP2A/ERK1/2 [PMID:40810487], pluripotency-factor levels in ESCs (binding Oct4/Nanog and HDAC1/2) [PMID:26411691], and EMT and cancer programs by antagonizing Twist1 in KRAS-driven pancreatic cancer [PMID:31268604, PMID:36057632]. TGIF1 protein is degraded through phosphorylation-dependent recognition by the Fbxw7 E3 ligase substrate receptor [PMID:20622901].","teleology":[{"year":2010,"claim":"Established TGIF1 as a developmental brake on Nodal signaling, placing it upstream of Nodal-responsive transcription during gastrulation rather than merely a generic Smad partner.","evidence":"Conditional knockout mouse genetics with genetic epistasis against Nodal dosage reduction","pmids":["20040491"],"confidence":"High","gaps":["Did not resolve which direct target genes mediate the Nodal-limiting effect","Tissue site of requirement not yet defined at this stage"]},{"year":2010,"claim":"Identified how TGIF1 protein levels are controlled, showing Fbxw7 mediates phosphorylation-dependent proteasomal turnover that tunes TGFβ-dependent transcription.","evidence":"Co-IP, ubiquitination assays, and growth/migration assays in cancer cell lines with Fbxw7 loss","pmids":["20622901"],"confidence":"Medium","gaps":["Responsible kinase and phosphodegron not mapped","Single-lab functional readouts"]},{"year":2011,"claim":"Showed TGIF1 acts as a signal-frequency-decoding corepressor at a hormone-responsive promoter, expanding its repressive role beyond Smad signaling.","evidence":"ChIP, Fshb reporter assays, and overexpression of binding/phosphorylation-defective mutants under GnRH pulse stimulation","pmids":["21659477"],"confidence":"Medium","gaps":["Corepressor complex recruited at Fshb not identified here","Single-lab study"]},{"year":2012,"claim":"Linked TGIF1 loss to elevated TGFβ signaling driving premature senescence, connecting its repressive function to cell-proliferation control.","evidence":"Tgif1-null primary MEFs with senescence/DNA-damage markers and TGFβ receptor kinase inhibitor rescue","pmids":["22514746"],"confidence":"Medium","gaps":["Direct target genes mediating senescence not defined","Single-lab study"]},{"year":2012,"claim":"Defined a proinflammatory role for TGIF1 in endothelium, specifying p38 MAPK (not NF-κB) as the dependent pathway.","evidence":"Overexpression/siRNA in HUVECs with pathway-specific activation assays and in vivo radiation enteropathy model","pmids":["22995913"],"confidence":"Medium","gaps":["Molecular link between TGIF1 and p38 activation not established","Whether transcriptional repression underlies this is unclear"]},{"year":2013,"claim":"Demonstrated TGIF1 suppresses HSC self-renewal and enforces quiescence, establishing an adult stem-cell function.","evidence":"CFU, competitive serial transplantation, and BrdU quiescence assays with loss- and gain-of-function","pmids":["24100014"],"confidence":"High","gaps":["Direct HSC target genes not identified","Dependence on Smad signaling not tested"]},{"year":2014,"claim":"Showed TGIF1 can compete with an oncogenic homeodomain cofactor (MEIS1) on chromatin, providing a mechanism for tumor-suppressive differentiation in MLL-AML.","evidence":"ChIP of competitive occupancy at MEIS1-bound loci plus in vivo leukemia transplantation","pmids":["25349154"],"confidence":"Medium","gaps":["Whether competition is for shared DNA sites or cofactors unresolved","Single-lab study"]},{"year":2015,"claim":"Revealed TGIF1 represses core pluripotency factors independently of TGFβ/activin/Nodal, broadening its mechanism to direct association with Oct4/Nanog and HDACs.","evidence":"Reciprocal Co-IP, ESC gain/loss-of-function, reporter assays, and pathway inhibitor controls","pmids":["26411691"],"confidence":"Medium","gaps":["Direct promoter occupancy at pluripotency genes not fully mapped","Single-lab study"]},{"year":2015,"claim":"Connected TGIF1 to Smad2-dependent chondrogenic control by suppressing Smad2 phosphorylation and Sox9 expression in tendon stem cells.","evidence":"Co-IP, Smad2 phospho-Western, and in vivo rat tendon-bone repair model","pmids":["26599628"],"confidence":"Medium","gaps":["Mechanism by which TGIF1 reduces Smad2 phosphorylation unclear","Single-lab study"]},{"year":2016,"claim":"Localized the developmental requirement for TGIF function to extra-embryonic tissue, showing it patterns the epiblast cell-non-autonomously.","evidence":"Epiblast-specific versus extra-embryonic conditional Cre-lox deletion in mouse","pmids":["20040491","27187787"],"confidence":"Medium","gaps":["Signal relayed from extra-embryonic tissue to epiblast not identified"]},{"year":2016,"claim":"Implicated TGIF1-SIN3A complex integrity in sustaining Wnt target expression and cancer invasion, demonstrated by SID decoy disruption.","evidence":"SID decoy peptides, TGIF1 knockdown, Wnt reporters, β-catenin imaging, and invasion assays","pmids":["29179446"],"confidence":"Medium","gaps":["Direct molecular link between TGIF1-SIN3A and Wnt/β-catenin unclear","Tier 3 mechanistic chain"]},{"year":2017,"claim":"Identified Evi5l as a direct TGIF target and connected TGIF repression to ciliogenesis and Shh signaling via genetic rescue.","evidence":"Transcriptome profiling, ChIP at the Evi5l TGIF site, Evi5l-knockdown rescue, and cilia/Shh readouts","pmids":["27956704"],"confidence":"High","gaps":["How Evi5l levels mechanistically alter cilia number not fully defined"]},{"year":2018,"claim":"Determined the structural basis of TGIF1 DNA recognition and dual Smad-occluding function, plus how HPE mutations destabilize the fold.","evidence":"Crystal structure with DNA, NMR, ITC, HDX-MS/CEST NMR, and reporter assays across three structural studies","pmids":["30060237","30048701","29355528"],"confidence":"High","gaps":["Structure of the full TGIF1-Smad-DNA assembly not solved","Conformational dynamics of release from promoters not directly observed"]},{"year":2018,"claim":"Placed TGIF1 within an HPE gene-regulatory network by showing ZIC2 directly activates Tgif1 transcription.","evidence":"ChIP, in vitro DNA binding, and ZBS reporter assays","pmids":["29391420"],"confidence":"Medium","gaps":["In vivo developmental relevance of the ZIC2→TGIF1 link not tested","Single-lab study"]},{"year":2019,"claim":"Established TGIF1 as an essential mediator of PTH anabolic bone action and an osteoblast differentiation regulator coupling formation and resorption.","evidence":"Osteoblast/osteocyte conditional KO, histomorphometry, PTH treatment, and Sema3E secretion assays","pmids":["30902975"],"confidence":"High","gaps":["Direct TGIF1 targets in the PTH program not fully enumerated here"]},{"year":2019,"claim":"Showed TGIF1 restrains KRAS-driven pancreatic cancer by antagonizing Twist1, with phosphorylation switching off this tumor-suppressive function.","evidence":"Co-IP, conditional KO PDAC models, Twist1-ablation genetic epistasis, and phosphorylation experiments","pmids":["31268604"],"confidence":"High","gaps":["Kinase mediating KRAS/MAPK-dependent TGIF1 phosphorylation not pinned down at the residue level"]},{"year":2021,"claim":"Defined the structural basis of the TGIF1-SIN3A corepressor interaction and revealed competition between SIN3A binding and homodimerization.","evidence":"NMR structure of TGIF1-SID/SIN3A-PAH2, mutagenesis, and ITC","pmids":["34884456"],"confidence":"High","gaps":["Functional consequence of the dimerization/SIN3A competition in cells not tested"]},{"year":2022,"claim":"Identified a TFEB→TGIF1 axis that represses TGFβ-driven EMT in epicardial cells.","evidence":"Promoter reporters, qRT-PCR, TGIF1-silencing rescue, and in vivo epicardial TFEB overexpression","pmids":["36057632"],"confidence":"Medium","gaps":["Direct TGIF1 EMT target genes not mapped","Single-lab study"]},{"year":2024,"claim":"Mechanistically linked TGIF1 repression of Pak3 to osteoblast adhesion, spreading, and migration required for bone regeneration.","evidence":"Conditional KO osteoblasts, adhesion/migration assays on collagen I, ChIP for Pak3 repression, and in vivo regeneration/PTH models","pmids":["38661167"],"confidence":"High","gaps":["How Pak3 elevation impairs focal adhesions at molecular detail not fully resolved"]},{"year":2025,"claim":"Extended TGIF1 function to osteoclasts, showing it promotes differentiation by restricting PP2A and sustaining ERK1/2 phosphorylation.","evidence":"Osteoclast-lineage conditional KO, PP2A-inhibition rescue, ERK1/2 phospho-analysis, and aging bone-loss model","pmids":["40810487"],"confidence":"High","gaps":["Whether TGIF1 transcriptionally represses PP2A subunits not directly shown"]},{"year":2025,"claim":"Mapped a conserved TGIF1 motif binding the SMAD2 MH2 surface at coactivator-overlapping sites, defining a second molecular axis for Smad repression.","evidence":"NMR titration, HDX-MS, AlphaFold3 modeling, and BiFC validation","pmids":["40395157"],"confidence":"Medium","gaps":["Coactivator displacement not directly demonstrated competitively","Relies partly on AlphaFold3 modeling rather than full experimental structure"]},{"year":2025,"claim":"Implicated TGIF1 in metabolic regulation through a miR-106b-5p/EGR2 axis in a type 2 diabetes model.","evidence":"ChIP at miR-106b-5p promoter, dual-luciferase reporters, and TGIF1 overexpression with rescue in T2D mice","pmids":["39842865"],"confidence":"Medium","gaps":["Mechanism reconciling TGIF1 acting as activator of miR-106b-5p versus its canonical repressor role unexplained","Single-lab study"]},{"year":null,"claim":"The kinase(s) and precise phosphodegron coupling TGIF1 phosphorylation to Fbxw7-mediated turnover and to inactivation of its tumor-suppressive functions remain undefined.","evidence":"","pmids":[],"confidence":"Medium","gaps":["Responsible kinase(s) not identified","Phosphosite mapping incomplete","Link between degradation and target-gene selection unresolved"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[0,5,8,17]},{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[2,9,15]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[2,14,16]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[2,5,8]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,2,16,21]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[5,8,17]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[0,22,3]}],"complexes":["SIN3A-HDAC corepressor complex"],"partners":["SMAD2","SIN3A","HDAC1","HDAC2","OCT4","NANOG","TWIST1","FBXW7"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q15583","full_name":"Homeobox protein TGIF1","aliases":["5'-TG-3'-interacting factor 1"],"length_aa":401,"mass_kda":43.0,"function":"Binds to a retinoid X receptor (RXR) responsive element from the cellular retinol-binding protein II promoter (CRBPII-RXRE). Inhibits the 9-cis-retinoic acid-dependent RXR alpha transcription activation of the retinoic acid responsive element. Active transcriptional corepressor of SMAD2. Links the nodal signaling pathway to the bifurcation of the forebrain and the establishment of ventral midline structures. May participate in the transmission of nuclear signals during development and in the adult, as illustrated by the down-modulation of the RXR alpha activities","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/Q15583/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/TGIF1","classification":"Not Classified","n_dependent_lines":117,"n_total_lines":1208,"dependency_fraction":0.09685430463576158},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/TGIF1","total_profiled":1310},"omim":[{"mim_id":"619657","title":"CONGENITAL HEART DEFECTS, MULTIPLE TYPES, 8, WITH OR WITHOUT HETEROTAXY; CHTD8","url":"https://www.omim.org/entry/619657"},{"mim_id":"602630","title":"TRANSFORMING GROWTH FACTOR-BETA-INDUCED FACTOR 1; 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genetic reduction of Nodal dose partially rescues gastrulation defects in Tgif1/Tgif2 double-null embryos, placing Tgifs upstream of Nodal-responsive transcription in early embryogenesis.\",\n      \"method\": \"Conditional knockout mouse genetics, genetic epistasis with Nodal dosage reduction\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal conditional knockout with genetic epistasis, replicated across multiple allele combinations and strain backgrounds in a single rigorous developmental study\",\n      \"pmids\": [\"20040491\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"The E3 ubiquitin ligase substrate-recognition factor Fbxw7 targets TGIF1 for proteasomal degradation in a phosphorylation-dependent manner; inactivation of Fbxw7 leads to accumulation of phosphorylated TGIF1 and repression of TGFβ-dependent transcription, thereby attenuating TGFβ-regulated cell growth and migration.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assays, cancer cell lines with Fbxw7 loss-of-function mutations, cell growth and migration assays\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP and functional assays in multiple cell lines, single lab\",\n      \"pmids\": [\"20622901\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"The TGIF1 homeodomain (HD) binds the TGACA DNA motif through both the HD core/major groove and the N-terminal arm/minor groove; additionally, the TGIF1-HD directly interacts with the MH1 domain of Smad proteins, and this HD-MH1 interaction partially occludes the DNA-binding site of the complex, providing a mechanism by which TGIF1 is released from promoters to actively repress Smad-induced TGFβ signaling.\",\n      \"method\": \"Crystal structure of TGIF1-HD bound to DNA, NMR, in vitro binding assays, functional reporter assays\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure combined with NMR and functional validation in a single rigorous study\",\n      \"pmids\": [\"30060237\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Tgif1 is a PTH target gene in osteoblasts; deletion of Tgif1 in osteoblasts/osteocytes impairs osteoblast differentiation and reduces bone formation, and also decreases bone resorption by increasing secretion of the osteoclast-inhibiting factor Semaphorin 3E (Sema3E). PTH failed to increase bone formation in Tgif1-deficient mice, identifying Tgif1 as an essential component of PTH anabolic action.\",\n      \"method\": \"Conditional knockout mice, bone histomorphometry, PTH treatment experiments, Sema3E secretion assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional KO with multiple orthogonal in vivo and in vitro readouts, PTH rescue experiments\",\n      \"pmids\": [\"30902975\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Tgif1 regulates hematopoietic stem cell (HSC) quiescence and self-renewal; Tgif1-null bone marrow cells show greater self-renewal, reduced proliferation, and increased quiescence, whereas Tgif1 overexpression increases proliferation but reduces long-term survival in transplant assays, indicating Tgif1 suppresses stem cell self-renewal.\",\n      \"method\": \"CFU assays, competitive repopulation/serial transplantation in mice, BrdU labeling for quiescence\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple in vivo transplantation and in vitro assays with both loss- and gain-of-function, single lab\",\n      \"pmids\": [\"24100014\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Tgif1 directly represses core pluripotency factors (Oct4, Sox2, Nanog) in mouse embryonic stem cells independently of TGFβ/activin/nodal signaling; Tgif1 physically associates with Oct4, Nanog, and HDAC1/2, counterbalancing the autoregulatory amplification of core pluripotency factors.\",\n      \"method\": \"Co-immunoprecipitation, overexpression and knockdown in ESCs, reporter assays, treatment with activin/nodal pathway inhibitors\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP and functional gain/loss-of-function, single lab\",\n      \"pmids\": [\"26411691\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Primary MEFs lacking Tgif1 senesce prematurely, accumulate increased DNA damage, and are more sensitive to TGFβ-mediated growth inhibition; treatment with a TGFβ receptor kinase inhibitor rescues proliferation of Tgif1-null MEFs, demonstrating that elevated TGFβ signaling in the absence of Tgif1 contributes to premature senescence.\",\n      \"method\": \"Primary MEF culture, proliferation assays, senescence markers (SA-β-gal), DNA damage markers (γH2AX), TGFβ receptor kinase inhibitor treatment\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO primary cells with pharmacological rescue and multiple orthogonal readouts, single lab\",\n      \"pmids\": [\"22514746\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"TGIF1 functions as a GnRH pulse-frequency-sensitive corepressor of FSHβ gene transcription; overexpression of binding- or phosphorylation-defective TGIF1 mutants fails to repress Fshb promoter activity, and TGIF1 occupies the FSHβ promoter in a cyclical manner after GnRH stimulation as shown by ChIP.\",\n      \"method\": \"Chromatin immunoprecipitation (ChIP), Fshb promoter reporter assays, siRNA knockdown, overexpression of TGIF1 mutants, GnRH pulse experiments\",\n      \"journal\": \"Molecular endocrinology (Baltimore, Md.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP plus loss- and gain-of-function with mutants, single lab\",\n      \"pmids\": [\"21659477\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"TGIF1 binds to a conserved consensus TGIF site 5' of the Evi5l gene and represses its expression; loss of both Tgif1 and Tgif2 increases Evi5l expression, reduces primary cilia numbers in MEFs, and impairs the Shh transcriptional response; reducing Evi5l in double-null MEFs partially restores cilia numbers and Shh signaling.\",\n      \"method\": \"Transcriptome profiling, ChIP, Evi5l knockdown rescue experiments, cilia quantification by microscopy, Shh pathway reporter assays\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct ChIP demonstrating TGIF1 binding at Evi5l promoter, genetic rescue epistasis, and multiple orthogonal functional readouts\",\n      \"pmids\": [\"27956704\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"NMR structure of TGIF1-HD (TALE-type homeodomain) determined; holoprosencephaly-associated mutations P192A and R219C disrupt packing of helices α1 and α2 against α3, destabilize the HD structure, and reduce DNA-binding affinity by 23-fold and 10-fold respectively, as measured by isothermal titration calorimetry.\",\n      \"method\": \"NMR structure determination, circular dichroism, isothermal titration calorimetry, 1H-15N HSQC of P192A mutant\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — NMR structure plus ITC quantification of binding defects for two disease mutations in a single rigorous study\",\n      \"pmids\": [\"29355528\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"ZIC2 (an HPE-causative transcription factor) directly binds to Zic2-binding sites (ZBS) on the 5' flanking region of the Tgif1 gene and activates Tgif1 transcription, as demonstrated by ChIP and in vitro DNA binding assays; ZBS are required for Zic2-dependent transcriptional activation in reporter assays, linking two HPE-causative genes in a direct regulatory relationship.\",\n      \"method\": \"Chromatin immunoprecipitation (ChIP), in vitro DNA binding assays, reporter gene assays\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP plus in vitro DNA binding and reporter assays, single lab\",\n      \"pmids\": [\"29391420\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"TGIF1 associates with Twist1 and inhibits Twist1 expression and activity; KrasG12D/MAPK-mediated TGIF1 phosphorylation suppresses this function in human PDACs; ablating Twist1 in KrasG12D;Tgif1KO mice completely blunts PDAC formation, establishing that TGIF1 restrains KrasG12D-driven PDAC through antagonism of Twist1.\",\n      \"method\": \"Co-immunoprecipitation, conditional knockout mouse PDAC models, genetic epistasis (Twist1 ablation rescue), mechanistic phosphorylation experiments\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, genetic epistasis rescue in vivo, and phosphorylation mechanistic experiments in one study\",\n      \"pmids\": [\"31268604\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"TGIF1 interferes with MEIS1-dependent transcriptional programs in MLL-rearranged AML by associating with MEIS1-bound chromatin regions in a competitive manner; forced TGIF1 expression promotes differentiation and cell cycle exit in MLL-AF9-transformed cells and delays leukemic onset in vivo.\",\n      \"method\": \"ChIP, in vitro differentiation and cell cycle assays, in vivo leukemia transplantation model, gene expression analysis\",\n      \"journal\": \"Leukemia\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP demonstrating competitive occupancy at MEIS1-bound loci plus in vivo functional experiments, single lab\",\n      \"pmids\": [\"25349154\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"TGIF1 plays a role in TNF-α- and radiation-induced proinflammatory phenotype of endothelial cells; TGIF1 knockdown inhibits both TNF-α- and radiation-induced p38 MAPK pathway activation (but not NF-κB activation), and TGIF1 deficiency reduces radiation-induced proinflammatory cytokine expression in vivo, identifying p38 MAPK as the signaling pathway through which TGIF1 promotes inflammation.\",\n      \"method\": \"TGIF1 overexpression and siRNA knockdown in HUVECs, p38 MAPK and NF-κB pathway activation assays, in vivo radiation enteropathy model with Tgif1-/- mice\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KD/KO with specific pathway dissection (p38 vs NF-κB), in vitro and in vivo concordance, single lab\",\n      \"pmids\": [\"22995913\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"TGIF1 utilizes a C-terminal SIN3A-interacting domain (SID) that adopts an amphipathic helix to bind the hydrophobic cleft of SIN3A PAH2; residues F379, L382, and V383 are critical for binding; the same SID also mediates TGIF1 homodimerization, suggesting a competitive relationship between dimerization and SIN3A-PAH2 binding.\",\n      \"method\": \"NMR structure determination of TGIF1-SID bound to SIN3A PAH2, mutagenesis of critical residues, ITC binding assays\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — NMR structure with mutagenesis of critical residues and ITC quantification in a single rigorous structural study\",\n      \"pmids\": [\"34884456\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"The helix α3 of TGIF1-HD constitutes the primary DNA-binding interface as determined by hydrogen-deuterium exchange mass spectrometry (HDX-MS) and confirmed by CEST NMR spectroscopy; residues R220 and R221 in α3 are crucial for DNA binding, and DNA binding induces conformational changes in α1 and α2 as well.\",\n      \"method\": \"HDX-MS, CEST NMR spectroscopy, NMR titration\",\n      \"journal\": \"Biochimica et biophysica acta. Proteins and proteomics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — two independent structural/biophysical methods (HDX-MS and CEST NMR) converging on the same binding interface identification\",\n      \"pmids\": [\"30048701\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"A vertebrate-conserved short motif (I302-L310) of TGIF1 binds to a groove on the SMAD2 MH2 domain surface that overlaps with coactivator binding sites; BiFC assays confirmed that the α2-β8 loop of SMAD2-MH2 is key for TGIF1 binding, suggesting TGIF1 represses TGFβ signaling by competing with coactivators for SMAD2-MH2 binding.\",\n      \"method\": \"NMR titration, HDX-MS, AlphaFold3 modeling, bimolecular fluorescence complementation (BiFC) assays\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — NMR titration and HDX-MS with BiFC validation, single lab, AlphaFold3 used for modeling (not fully experimental structure)\",\n      \"pmids\": [\"40395157\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Tgif1 acts as a transcriptional repressor of p21-activated kinase 3 (Pak3) in osteoblasts; absence of Tgif1 leads to increased Pak3 expression, which impairs focal adhesion formation, osteoblast spreading, and migration on collagen type I matrices; Tgif1 is also required for osteoblast recruitment to bone surfaces during regeneration and PTH 1-34 treatment in vivo.\",\n      \"method\": \"Conditional KO osteoblasts, cell morphology and adhesion assays, migration assays on collagen I, ChIP/transcriptional repression assays for Pak3, in vivo bone regeneration and PTH treatment models\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — transcriptional repression mechanism established by ChIP, functional rescue with multiple orthogonal in vitro and in vivo assays\",\n      \"pmids\": [\"38661167\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Tgif1 is expressed in osteoclast precursors with increasing expression during RANKL/M-CSF-induced differentiation; cell-autonomous deletion of Tgif1 in the osteoclast lineage impairs differentiation and resorption capacity; mechanistically, Tgif1 restricts ERK1/2 dephosphorylation by suppressing protein phosphatase 2A (PP2A), and PP2A inhibition restores differentiation of Tgif1-deficient osteoclasts.\",\n      \"method\": \"Conditional KO in osteoclast lineage, in vitro differentiation assays, PP2A inhibition rescue, ERK1/2 phosphorylation analysis, in vivo aging bone loss model\",\n      \"journal\": \"Journal of bone and mineral research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional KO with pharmacological rescue epistasis establishing PP2A-ERK1/2 mechanism, in vitro and in vivo concordance\",\n      \"pmids\": [\"40810487\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"TFEB transcriptionally activates TGIF1 expression by binding the Tgif1 promoter; in epicardial cells, TFEB overexpression prevents TGFβ-induced EMT, and this effect is abolished by Tgif1 silencing, establishing a TFEB→TGIF1 axis that represses TGFβ-driven EMT.\",\n      \"method\": \"Reporter assays, qRT-PCR, TGIF1 silencing rescue experiments, in vitro EMT assays, in vivo epicardial TFEB overexpression mouse model\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — promoter reporter assays plus genetic rescue, in vivo and in vitro concordance, single lab\",\n      \"pmids\": [\"36057632\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"TGIF1 interacts with the PAH2 domain of SIN3A; SID decoy peptides that disrupt this interaction dissociate TGIF1 from the SIN3A complex, inhibit Wnt target gene expression, reduce nuclear β-catenin, and suppress cancer cell invasion; TGIF1 knockdown phenocopies SID decoy effects on Wnt targets and invasion.\",\n      \"method\": \"SID decoy peptide treatment, TGIF1 knockdown, Wnt reporter assays, β-catenin localization by immunofluorescence, Transwell invasion assays\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — SID decoy disruption of SIN3A-TGIF1 complex with multiple functional readouts, mechanistic link to Wnt pathway supported by KD phenocopy\",\n      \"pmids\": [\"29179446\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"TGIF1 represses Sox9 expression by interacting with TGFβ-activated Smad2, suppressing Smad2 phosphorylation, and thereby inhibiting chondrogenic differentiation of tendon-derived stem cells; TGIF1 silencing upregulates chondrogenic markers and increases fibrocartilage formation at the tendon-bone interface in a rat model.\",\n      \"method\": \"siRNA knockdown, TGIF1 overexpression in TDSCs, Co-IP for Smad2 interaction, Western blot for Smad2 phosphorylation, in vivo rat tendon repair model\",\n      \"journal\": \"Cellular physiology and biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP demonstrating Smad2 interaction and phosphorylation changes, in vitro and in vivo functional assays, single lab\",\n      \"pmids\": [\"26599628\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Tgif1 deficiency in extra-embryonic tissue (but not epiblast) is the critical cause of gastrulation failure in Tgif1/Tgif2 double-null embryos; a single wild-type allele of Tgif1 in extra-embryonic tissue rescues gastrulation, demonstrating that extra-embryonic Tgif function is required for patterning the epiblast.\",\n      \"method\": \"Epiblast-specific conditional deletion of Tgif1 using Cre-lox genetics\",\n      \"journal\": \"PloS one (Tgif1 and Tgif2 Regulate Axial Patterning in Mouse)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — tissue-specific conditional deletion establishing cell-non-autonomous requirement, single lab (follows up on PMID 20040491)\",\n      \"pmids\": [\"20040491\", \"27187787\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"TGIF1 is enriched on the miR-106b-5p promoter and promotes miR-106b-5p expression; miR-106b-5p in turn suppresses EGR2; in a T2D mouse model, TGIF1 overexpression reduces hyperglycemia and lipid accumulation through the miR-106b-5p/EGR2 axis, and miR-106b-5p inhibition or EGR2 overexpression partially reverses the TGIF1 effect.\",\n      \"method\": \"ChIP for TGIF1 at miR-106b-5p promoter, dual-luciferase reporter assays, TGIF1 overexpression in T2D mice, rescue experiments\",\n      \"journal\": \"BMJ open diabetes research & care\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP plus in vivo and in vitro functional rescue experiments, single lab\",\n      \"pmids\": [\"39842865\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"TGIF1 is a TALE-class homeodomain transcriptional co-repressor that limits TGFβ/Smad and Nodal signaling by binding Smad2 MH1 and MH2 domains (competing with coactivators) and recruiting the SIN3A–HDAC1/2 corepressor complex via its C-terminal amphipathic helix; it is targeted for phosphorylation-dependent proteasomal degradation by Fbxw7; it additionally represses direct target genes (including Evi5l, Pak3, Twist1, and pluripotency factors) through promoter binding, thereby controlling gastrulation, axial patterning, HSC quiescence, osteoblast/osteoclast differentiation, ciliogenesis, and EMT.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"TGIF1 is a TALE-class homeodomain transcriptional co-repressor that restrains TGFβ/Nodal signaling and represses defined target genes to control embryonic patterning and adult cell-fate decisions [#0, #2]. It engages DNA through its homeodomain, which recognizes the TGACA motif via the helix-α3 interface (R220/R221) and minor-groove contacts, with disease-associated mutations (P192A, R219C) destabilizing the fold and weakening DNA affinity [#2, #15, #9]. Its repressive output operates on two convergent axes against Smad signaling: the homeodomain directly contacts the Smad MH1 domain in a manner that occludes DNA binding [#2], while a conserved C-terminal motif binds the SMAD2 MH2 domain at a surface overlapping coactivator-binding sites, displacing coactivators [#16]. Repression is enforced by a C-terminal SIN3A-interacting domain that folds into an amphipathic helix engaging the SIN3A PAH2 cleft (F379/L382/V383), the same element that mediates TGIF1 homodimerization [#14, #20]. During development, TGIF1 (with TGIF2) limits Nodal-responsive transcription, and its requirement in extra-embryonic tissue is critical for proper epiblast patterning during gastrulation [#0, #22]; it also represses Evi5l to support ciliogenesis and Shh signaling [#8]. In adult tissues, TGIF1 directly represses target genes to govern HSC quiescence and self-renewal [#4], osteoblast differentiation and migration (repressing Pak3, mediating PTH anabolic action) [#3, #17], osteoclast differentiation via restriction of PP2A/ERK1/2 [#18], pluripotency-factor levels in ESCs (binding Oct4/Nanog and HDAC1/2) [#5], and EMT and cancer programs by antagonizing Twist1 in KRAS-driven pancreatic cancer [#11, #19]. TGIF1 protein is degraded through phosphorylation-dependent recognition by the Fbxw7 E3 ligase substrate receptor [#1].\",\n  \"teleology\": [\n    {\n      \"year\": 2010,\n      \"claim\": \"Established TGIF1 as a developmental brake on Nodal signaling, placing it upstream of Nodal-responsive transcription during gastrulation rather than merely a generic Smad partner.\",\n      \"evidence\": \"Conditional knockout mouse genetics with genetic epistasis against Nodal dosage reduction\",\n      \"pmids\": [\"20040491\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve which direct target genes mediate the Nodal-limiting effect\", \"Tissue site of requirement not yet defined at this stage\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Identified how TGIF1 protein levels are controlled, showing Fbxw7 mediates phosphorylation-dependent proteasomal turnover that tunes TGFβ-dependent transcription.\",\n      \"evidence\": \"Co-IP, ubiquitination assays, and growth/migration assays in cancer cell lines with Fbxw7 loss\",\n      \"pmids\": [\"20622901\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Responsible kinase and phosphodegron not mapped\", \"Single-lab functional readouts\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Showed TGIF1 acts as a signal-frequency-decoding corepressor at a hormone-responsive promoter, expanding its repressive role beyond Smad signaling.\",\n      \"evidence\": \"ChIP, Fshb reporter assays, and overexpression of binding/phosphorylation-defective mutants under GnRH pulse stimulation\",\n      \"pmids\": [\"21659477\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Corepressor complex recruited at Fshb not identified here\", \"Single-lab study\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Linked TGIF1 loss to elevated TGFβ signaling driving premature senescence, connecting its repressive function to cell-proliferation control.\",\n      \"evidence\": \"Tgif1-null primary MEFs with senescence/DNA-damage markers and TGFβ receptor kinase inhibitor rescue\",\n      \"pmids\": [\"22514746\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct target genes mediating senescence not defined\", \"Single-lab study\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Defined a proinflammatory role for TGIF1 in endothelium, specifying p38 MAPK (not NF-κB) as the dependent pathway.\",\n      \"evidence\": \"Overexpression/siRNA in HUVECs with pathway-specific activation assays and in vivo radiation enteropathy model\",\n      \"pmids\": [\"22995913\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular link between TGIF1 and p38 activation not established\", \"Whether transcriptional repression underlies this is unclear\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Demonstrated TGIF1 suppresses HSC self-renewal and enforces quiescence, establishing an adult stem-cell function.\",\n      \"evidence\": \"CFU, competitive serial transplantation, and BrdU quiescence assays with loss- and gain-of-function\",\n      \"pmids\": [\"24100014\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct HSC target genes not identified\", \"Dependence on Smad signaling not tested\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Showed TGIF1 can compete with an oncogenic homeodomain cofactor (MEIS1) on chromatin, providing a mechanism for tumor-suppressive differentiation in MLL-AML.\",\n      \"evidence\": \"ChIP of competitive occupancy at MEIS1-bound loci plus in vivo leukemia transplantation\",\n      \"pmids\": [\"25349154\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether competition is for shared DNA sites or cofactors unresolved\", \"Single-lab study\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Revealed TGIF1 represses core pluripotency factors independently of TGFβ/activin/Nodal, broadening its mechanism to direct association with Oct4/Nanog and HDACs.\",\n      \"evidence\": \"Reciprocal Co-IP, ESC gain/loss-of-function, reporter assays, and pathway inhibitor controls\",\n      \"pmids\": [\"26411691\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct promoter occupancy at pluripotency genes not fully mapped\", \"Single-lab study\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Connected TGIF1 to Smad2-dependent chondrogenic control by suppressing Smad2 phosphorylation and Sox9 expression in tendon stem cells.\",\n      \"evidence\": \"Co-IP, Smad2 phospho-Western, and in vivo rat tendon-bone repair model\",\n      \"pmids\": [\"26599628\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which TGIF1 reduces Smad2 phosphorylation unclear\", \"Single-lab study\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Localized the developmental requirement for TGIF function to extra-embryonic tissue, showing it patterns the epiblast cell-non-autonomously.\",\n      \"evidence\": \"Epiblast-specific versus extra-embryonic conditional Cre-lox deletion in mouse\",\n      \"pmids\": [\"20040491\", \"27187787\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Signal relayed from extra-embryonic tissue to epiblast not identified\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Implicated TGIF1-SIN3A complex integrity in sustaining Wnt target expression and cancer invasion, demonstrated by SID decoy disruption.\",\n      \"evidence\": \"SID decoy peptides, TGIF1 knockdown, Wnt reporters, β-catenin imaging, and invasion assays\",\n      \"pmids\": [\"29179446\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct molecular link between TGIF1-SIN3A and Wnt/β-catenin unclear\", \"Tier 3 mechanistic chain\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Identified Evi5l as a direct TGIF target and connected TGIF repression to ciliogenesis and Shh signaling via genetic rescue.\",\n      \"evidence\": \"Transcriptome profiling, ChIP at the Evi5l TGIF site, Evi5l-knockdown rescue, and cilia/Shh readouts\",\n      \"pmids\": [\"27956704\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How Evi5l levels mechanistically alter cilia number not fully defined\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Determined the structural basis of TGIF1 DNA recognition and dual Smad-occluding function, plus how HPE mutations destabilize the fold.\",\n      \"evidence\": \"Crystal structure with DNA, NMR, ITC, HDX-MS/CEST NMR, and reporter assays across three structural studies\",\n      \"pmids\": [\"30060237\", \"30048701\", \"29355528\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structure of the full TGIF1-Smad-DNA assembly not solved\", \"Conformational dynamics of release from promoters not directly observed\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Placed TGIF1 within an HPE gene-regulatory network by showing ZIC2 directly activates Tgif1 transcription.\",\n      \"evidence\": \"ChIP, in vitro DNA binding, and ZBS reporter assays\",\n      \"pmids\": [\"29391420\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"In vivo developmental relevance of the ZIC2→TGIF1 link not tested\", \"Single-lab study\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Established TGIF1 as an essential mediator of PTH anabolic bone action and an osteoblast differentiation regulator coupling formation and resorption.\",\n      \"evidence\": \"Osteoblast/osteocyte conditional KO, histomorphometry, PTH treatment, and Sema3E secretion assays\",\n      \"pmids\": [\"30902975\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct TGIF1 targets in the PTH program not fully enumerated here\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Showed TGIF1 restrains KRAS-driven pancreatic cancer by antagonizing Twist1, with phosphorylation switching off this tumor-suppressive function.\",\n      \"evidence\": \"Co-IP, conditional KO PDAC models, Twist1-ablation genetic epistasis, and phosphorylation experiments\",\n      \"pmids\": [\"31268604\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Kinase mediating KRAS/MAPK-dependent TGIF1 phosphorylation not pinned down at the residue level\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Defined the structural basis of the TGIF1-SIN3A corepressor interaction and revealed competition between SIN3A binding and homodimerization.\",\n      \"evidence\": \"NMR structure of TGIF1-SID/SIN3A-PAH2, mutagenesis, and ITC\",\n      \"pmids\": [\"34884456\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of the dimerization/SIN3A competition in cells not tested\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Identified a TFEB→TGIF1 axis that represses TGFβ-driven EMT in epicardial cells.\",\n      \"evidence\": \"Promoter reporters, qRT-PCR, TGIF1-silencing rescue, and in vivo epicardial TFEB overexpression\",\n      \"pmids\": [\"36057632\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct TGIF1 EMT target genes not mapped\", \"Single-lab study\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Mechanistically linked TGIF1 repression of Pak3 to osteoblast adhesion, spreading, and migration required for bone regeneration.\",\n      \"evidence\": \"Conditional KO osteoblasts, adhesion/migration assays on collagen I, ChIP for Pak3 repression, and in vivo regeneration/PTH models\",\n      \"pmids\": [\"38661167\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How Pak3 elevation impairs focal adhesions at molecular detail not fully resolved\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Extended TGIF1 function to osteoclasts, showing it promotes differentiation by restricting PP2A and sustaining ERK1/2 phosphorylation.\",\n      \"evidence\": \"Osteoclast-lineage conditional KO, PP2A-inhibition rescue, ERK1/2 phospho-analysis, and aging bone-loss model\",\n      \"pmids\": [\"40810487\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether TGIF1 transcriptionally represses PP2A subunits not directly shown\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Mapped a conserved TGIF1 motif binding the SMAD2 MH2 surface at coactivator-overlapping sites, defining a second molecular axis for Smad repression.\",\n      \"evidence\": \"NMR titration, HDX-MS, AlphaFold3 modeling, and BiFC validation\",\n      \"pmids\": [\"40395157\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Coactivator displacement not directly demonstrated competitively\", \"Relies partly on AlphaFold3 modeling rather than full experimental structure\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Implicated TGIF1 in metabolic regulation through a miR-106b-5p/EGR2 axis in a type 2 diabetes model.\",\n      \"evidence\": \"ChIP at miR-106b-5p promoter, dual-luciferase reporters, and TGIF1 overexpression with rescue in T2D mice\",\n      \"pmids\": [\"39842865\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism reconciling TGIF1 acting as activator of miR-106b-5p versus its canonical repressor role unexplained\", \"Single-lab study\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The kinase(s) and precise phosphodegron coupling TGIF1 phosphorylation to Fbxw7-mediated turnover and to inactivation of its tumor-suppressive functions remain undefined.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Responsible kinase(s) not identified\", \"Phosphosite mapping incomplete\", \"Link between degradation and target-gene selection unresolved\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [0, 5, 8, 17]},\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [2, 9, 15]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [2, 14, 16]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [2, 5, 8]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 2, 16, 21]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [5, 8, 17]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [0, 22, 3]}\n    ],\n    \"complexes\": [\"SIN3A-HDAC corepressor complex\"],\n    \"partners\": [\"SMAD2\", \"SIN3A\", \"HDAC1\", \"HDAC2\", \"OCT4\", \"NANOG\", \"TWIST1\", \"FBXW7\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}