{"gene":"MEOX1","run_date":"2026-04-28T18:30:28","timeline":{"discoveries":[{"year":1992,"finding":"Mox-1 (MEOX1) is a homeodomain transcription factor expressed in posterior embryonic mesoderm at primitive streak stages, presomitic mesoderm, somites, and lateral plate mesoderm in mice, defining a novel homeobox gene subfamily with roles in mesodermal regionalization and somitic differentiation.","method":"In situ hybridization, genetic mapping, expression analysis in mouse embryos","journal":"Development","confidence":"Medium","confidence_rationale":"Tier 2 — direct localization experiment with developmental context, single lab but multiple stages analyzed","pmids":["1363541"],"is_preprint":false},{"year":1996,"finding":"Mox-1 protein is first detected in newly formed mesoderm of primitive streak stage mouse embryos (7.5 dpc), earlier than Mox-2 (9.0 dpc), and is also expressed in branchial arches and limbs, indicating distinct developmental roles for Mox-1 and Mox-2.","method":"Immunostaining of mouse embryos at multiple developmental stages","journal":"The International Journal of Developmental Biology","confidence":"Medium","confidence_rationale":"Tier 2 — direct protein localization by immunostaining with developmental stage resolution","pmids":["9032023"],"is_preprint":false},{"year":2001,"finding":"MEOX1 homeodomain physically interacts with PAX1 and PAX3 transcription factors, with a preference of Mox1 for Pax1 over Pax3; this interaction is mediated through the homeodomain of Mox.","method":"Yeast two-hybrid assay and in vitro biochemical binding assays","journal":"FEBS Letters","confidence":"Medium","confidence_rationale":"Tier 2 — reciprocal assays (yeast two-hybrid + in vitro), single lab","pmids":["11423130"],"is_preprint":false},{"year":2009,"finding":"Meox1 loss-of-function in mice disrupts sclerotome rostro-caudal polarity, causing assimilation of the atlas into the basioccipital bone; MEOX1 protein occupies conserved promoter regions of Tbx18 and Uncx transcription factor genes, and Meox1 mutants show altered Tbx18, Uncx, and Bapx1 expression, indicating Meox1 directly regulates these genes to maintain sclerotome polarity.","method":"Mouse knockout, chromatin immunoprecipitation (ChIP), gene expression analysis, cell proliferation assays","journal":"Developmental Biology","confidence":"High","confidence_rationale":"Tier 1-2 — ChIP demonstrating direct promoter occupancy combined with in vivo KO phenotype and multiple gene expression readouts","pmids":["19520072"],"is_preprint":false},{"year":2011,"finding":"MEOX1 is a direct transcriptional target of Hoxa2; Hoxa2 binds to the Meox1 proximal promoter via two conserved binding sites required for Hoxa2-dependent activation, and Meox1 can bind DNA sequences recognized by Hoxa2 on its functional target genes, placing Meox1 downstream of Hoxa2 in the branchial arch regulatory network.","method":"Chromatin immunoprecipitation (ChIP), promoter reporter assays, genetic epistasis (Hoxa2 mouse mutants), Meox1/Meox2 double mutant analysis","journal":"Molecular and Cellular Biology","confidence":"High","confidence_rationale":"Tier 1 — ChIP, promoter mutagenesis, and genetic epistasis with multiple orthogonal methods","pmids":["21245383"],"is_preprint":false},{"year":2011,"finding":"MEOX1 activates p21(CIP1/WAF1) and p16(INK4a) expression in vascular endothelial cells and induces cell cycle arrest and senescence; MEOX1 activates p16(INK4a) in a DNA binding-dependent manner, whereas it induces p21(CIP1/WAF1) in a DNA binding-independent manner, distinguishing its mechanism from MEOX2.","method":"Overexpression of MEOX1 with DNA-binding domain mutants, reporter assays, cell cycle analysis, senescence assays","journal":"PLoS One","confidence":"High","confidence_rationale":"Tier 1-2 — active site mutagenesis (DNA-binding mutants) combined with functional cell cycle/senescence assays, mechanistically distinguishes two target genes","pmids":["22206000"],"is_preprint":false},{"year":2013,"finding":"Homozygous frameshift or nonsense truncating mutations in MEOX1 cause isolated Klippel-Feil syndrome in humans, and the resulting complete transcript instability phenocopies the cervical skeletal defect of Meox1 null mice, establishing MEOX1 as the causative gene for this sclerotome polarity defect.","method":"Whole-genome linkage mapping, direct sequencing, transcript stability analysis in patient cells","journal":"American Journal of Human Genetics","confidence":"High","confidence_rationale":"Tier 2 — human genetics with mechanistic validation, replicated in second family and consistent with mouse model","pmids":["23290072"],"is_preprint":false},{"year":2014,"finding":"Meox1 specifies endotomal endothelial precursor cells within the zebrafish somite; loss of meox1 expands the endotome at the expense of muscle precursors and increases the number of endotome-derived cells colonizing the dorsal aorta, leading to increased chemokine-dependent haematopoietic stem cell induction.","method":"Zebrafish loss-of-function genetics, lineage tracing, live imaging, epistasis with chemokine signaling","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 — zebrafish genetic loss-of-function with lineage tracing and defined cellular and molecular phenotypic readouts, published in high-impact journal with substantial citation","pmids":["25119043"],"is_preprint":false},{"year":2017,"finding":"Meox1 directly inhibits the cell-cycle checkpoint gene ccnb1 (Cyclin B1), inducing G2 cell-cycle arrest in muscle stem cells; disruption of this G2 arrest by loss of Meox1 causes premature lineage commitment and defective muscle growth during zebrafish myotome development.","method":"Zebrafish genetic loss-of-function, direct binding assays, cell cycle analysis, clonal analysis","journal":"Cell Stem Cell","confidence":"High","confidence_rationale":"Tier 1-2 — direct transcriptional target identification with loss-of-function phenotype and cell cycle mechanistic readout, replicated in subsequent studies","pmids":["28686860"],"is_preprint":false},{"year":2018,"finding":"MEOX1 transcriptionally activates Gata4 as a downstream target to accelerate myocardial hypertrophic decompensation; MEOX1 overexpression exacerbated hypertrophic phenotypes while knockdown improved them, and direct Gata4 promoter activation was demonstrated by ChIP and promoter activity assays.","method":"Overexpression/knockdown in mice (FHCM and TAC models), digital gene expression profiling, ChIP, promoter activity assays, echocardiography","journal":"Cardiovascular Research","confidence":"High","confidence_rationale":"Tier 1-2 — ChIP demonstrating direct promoter occupancy, multiple in vivo and in vitro methods, epistasis via Gata4 knockdown","pmids":["29155983"],"is_preprint":false},{"year":2020,"finding":"TGF-β1 transcriptionally upregulates MEOX1 expression via Smad2/3 binding to the Meox1 promoter in adult human dermal fibroblasts; MEOX1 promotes fibroblast migration as demonstrated by scratch and Transwell assays.","method":"ChIP-qPCR for Smad2/3 on Meox1 promoter, Smad overexpression/siRNA knockdown, transcriptome sequencing, migration assays","journal":"Zhonghua Shao Shang Za Zhi","confidence":"Medium","confidence_rationale":"Tier 2 — ChIP-qPCR with functional gain/loss-of-function, single lab","pmids":["32241049"],"is_preprint":false},{"year":2020,"finding":"Combined p53 and PTEN deficiency in triple-negative breast cancer activates MEOX1 expression; MEOX1 knockdown abolished TNBC cell proliferation in vitro and tumor growth in vivo, and decreased expression of TYK2, STAT5B, and STAT6, placing MEOX1 downstream of combined p53/PTEN loss and upstream of JAK-STAT signaling.","method":"siRNA knockdown (p53/PTEN and MEOX1), RNA-Seq, immunoblotting, in vivo tumor growth assay","journal":"Journal of Biological Chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — multiple orthogonal methods (RNA-Seq, immunoblot, in vivo), single lab","pmids":["32467227"],"is_preprint":false},{"year":2020,"finding":"PPARα directly regulates the expression of MEOX1 in cardiomyocytes, and the cardioprotective effects of PPARα gene delivery in doxorubicin-induced cardiotoxicity are abolished by MEOX1 knockdown, placing MEOX1 downstream of PPARα in a cardioprotective pathway.","method":"Adeno-associated virus gene delivery, knockdown epistasis, cardiac function assays, in vivo mouse model","journal":"Frontiers in Pharmacology","confidence":"Medium","confidence_rationale":"Tier 2 — in vivo epistasis with AAV-mediated gene delivery and functional cardiac readouts, single lab","pmids":["33132907"],"is_preprint":false},{"year":2021,"finding":"MEOX1 binds to the transcriptional initiation site of CCNB1 and suppresses CCNB1 expression, inducing G2 cell cycle arrest in non-small cell lung cancer cells; CCNB1 overexpression rescues the anti-proliferative effects of MEOX1.","method":"Chromatin binding assays, overexpression/knockdown, cell cycle analysis, rescue experiments, in vivo tumor growth","journal":"Environmental Toxicology","confidence":"Medium","confidence_rationale":"Tier 2 — direct promoter binding shown with rescue epistasis, consistent with zebrafish findings","pmids":["34837450"],"is_preprint":false},{"year":2021,"finding":"Meox1 regulates SDF-1α expression in vascular smooth muscle cells via CDC42 activation, which promotes CXCR4 expression on Sca-1+ progenitor cells, facilitating their migration and contribution to neointima formation following vascular injury; Meox1 knockdown abolished these effects.","method":"Rat carotid artery balloon injury model, shRNA knockdown, inhibitor studies (AMD3100, ZCL278), immunostaining","journal":"Stem Cell Research & Therapy","confidence":"Medium","confidence_rationale":"Tier 2 — in vivo loss-of-function with pharmacological epistasis, single lab","pmids":["34233723"],"is_preprint":false},{"year":2023,"finding":"MEOX1 is expressed specifically in regulatory T (Treg) cells at levels comparable to FOXP3, is upregulated by IL-2, has a permissive epigenetic landscape exclusively in Tregs, and its knockdown profoundly alters downstream gene expression and reduces Treg suppressive capacity.","method":"Transcriptomic analysis of 48 human CD4+ T cell conditions, reverse network engineering, epigenetic analysis, siRNA knockdown, Treg suppression assays","journal":"Frontiers in Immunology","confidence":"Medium","confidence_rationale":"Tier 2 — epigenetic analysis combined with functional knockdown and suppression assay, single lab","pmids":["37559728"],"is_preprint":false},{"year":2024,"finding":"JUN transcription factor binds the MEOX1 promoter to drive its expression; the natural compound Ailanthone disrupts JUN-promoter interaction, suppressing MEOX1 expression and consequently inhibiting fibroblast activation and endothelial-to-mesenchymal transition induced by TGF-β1 in pulmonary fibrosis.","method":"High-throughput screening, direct target binding studies, ChIP showing JUN on MEOX1 promoter, in vitro fibroblast/endothelial assays, bleomycin mouse model","journal":"Acta Pharmaceutica Sinica B","confidence":"Medium","confidence_rationale":"Tier 2 — ChIP demonstrating JUN-MEOX1 promoter interaction, in vivo validation, single lab","pmids":["39220862"],"is_preprint":false},{"year":2024,"finding":"MEOX1 promotes myofibroblast apoptosis resistance in pulmonary fibrosis by upregulating RGS4 (G-protein signaling pathway regulatory factor 4) as a direct downstream target; MEOX1 silencing enhanced myofibroblast apoptosis and attenuated fibrosis in mice.","method":"Bioinformatics prediction, siRNA knockdown, bleomycin mouse model, apoptosis assays","journal":"Journal of Cellular Physiology","confidence":"Low","confidence_rationale":"Tier 3 — target identified bioinformatically with knockdown validation but no direct binding demonstrated","pmids":["39319990"],"is_preprint":false},{"year":2025,"finding":"MEOX1 transcriptionally activates Cthrc1, which promotes downstream Smad2/3 phosphorylation, driving cardiac fibroblast-to-myofibroblast conversion following myocardial infarction; Cthrc1 overexpression abolishes cardioprotective effects of MEOX1 silencing.","method":"In vivo mouse MI model, knockdown/overexpression, ChIP/luciferase for Cthrc1 promoter, Western blot for p-Smad2/3, epistasis via Cthrc1 rescue","journal":"International Journal of Biological Sciences","confidence":"High","confidence_rationale":"Tier 1-2 — direct promoter binding (ChIP), epistasis rescue experiment, in vivo and in vitro multiple orthogonal methods","pmids":["41362745"],"is_preprint":false},{"year":2025,"finding":"MEOX1 directly binds the promoter of ABHD3 to facilitate its transcription and subsequent circABHD3 circular RNA generation; circABHD3 promotes YTHDF2-dependent m6A-modified YPEL3 mRNA degradation, activating β-catenin signaling and driving hepatic fibrosis.","method":"Luciferase reporter assay, ChIP, MeRIP, RIP, RNA pull-down, in vivo mouse models (CCl4, BDL)","journal":"PLoS Genetics","confidence":"High","confidence_rationale":"Tier 1-2 — multiple direct binding assays (ChIP, luciferase) combined with RNA modification assays and in vivo epistasis","pmids":["40100806"],"is_preprint":false},{"year":2025,"finding":"TGF-β1 upregulates MEOX1 expression through the NOX4-ROS-Smad signaling pathway in lung fibroblasts; fibroblast-specific MEOX1 knockdown prevents BLM-induced pulmonary fibrosis and abolishes TGF-β1-induced mitophagy deficiency (via CTGF downregulation) and cellular senescence.","method":"RNA-sequencing, AAV-shMEOX1 fibroblast-specific knockdown, in vivo bleomycin model, in vitro fibroblast assays, NOX4/ROS/Smad pathway inhibitors","journal":"European Journal of Pharmacology","confidence":"Medium","confidence_rationale":"Tier 2 — in vivo fibroblast-specific KD with pathway mechanistic follow-up, single lab","pmids":["40780596"],"is_preprint":false},{"year":2025,"finding":"MEOX1 activates hepatic stellate cells via transcriptional regulation of SERPINE1 (PAI-1), promoting MASH-related liver fibrosis; MEOX1 knockdown suppresses HSC activation, proliferation, and migration.","method":"RNA-Seq, AlphaFold/PyMOL structural prediction of protein interaction sites, siRNA knockdown, in vitro HSC activation assays, in vivo MASH mouse model","journal":"The International Journal of Biological Markers","confidence":"Low","confidence_rationale":"Tier 3 — knockdown with RNA-Seq target identification; direct binding to SERPINE1 promoter not demonstrated by ChIP","pmids":["40270091"],"is_preprint":false},{"year":2026,"finding":"MEOX1 represses PAX1 transcription in glioblastoma cells, and this MEOX1-PAX1 axis promotes tumor cell proliferation, migration, and invasion while PAX1 expression in GBM cells promotes Treg differentiation from CD4+ T cells.","method":"Overexpression/knockdown of MEOX1 and PAX1 in GBM cells, co-culture with CD4+ T cells, flow cytometry for Treg markers","journal":"Scientific Reports","confidence":"Low","confidence_rationale":"Tier 3 — functional KD/OE without direct promoter binding evidence for MEOX1 repression of PAX1","pmids":["41692908"],"is_preprint":false},{"year":2026,"finding":"DNA hypermethylation silences MEOX1 in colorectal cancer; MEOX1 directly binds the GLP2R promoter to activate its transcription, and MEOX1-mediated GLP2R upregulation inhibits YAP1-mediated glycolysis through Hippo signaling, suppressing CRC growth and metastasis.","method":"ChIP-qPCR and dual-luciferase assays for MEOX1 binding to GLP2R promoter, MeDIP/MSP for DNA methylation, lentiviral overexpression/knockdown, orthotopic and liver metastasis mouse models","journal":"Cell & Bioscience","confidence":"Medium","confidence_rationale":"Tier 1-2 — direct promoter binding demonstrated by ChIP and luciferase, in vivo validation in multiple models","pmids":["41612494"],"is_preprint":false}],"current_model":"MEOX1 is a homeodomain transcription factor that directly regulates target gene transcription (including p16/INK4a, CCNB1, Gata4, Tbx18, Uncx, Cthrc1, GLP2R, ABHD3, and SERPINE1) in a context-dependent manner—activating p16 and repressing CCNB1 in a DNA-binding-dependent manner while activating p21 independently of DNA binding—and physically interacts with PAX1/PAX3 via its homeodomain; it is activated upstream by Hoxa2 (in branchial arch development) and TGF-β1/Smad2-3 and JUN (in fibrosis), and its activity drives diverse cellular processes including G2 cell-cycle arrest in muscle stem cells, sclerotome polarity, endosome-derived endothelial cell specification for HSC induction, vascular smooth muscle remodeling, cardiac hypertrophy/fibrosis, and pulmonary fibrosis through distinct downstream signaling cascades."},"narrative":{"teleology":[{"year":1992,"claim":"Identification of MEOX1 as a novel homeobox gene expressed in embryonic mesoderm established that a previously unknown transcription factor class operated in somitogenesis and mesodermal regionalization.","evidence":"In situ hybridization and expression analysis across mouse embryonic stages","pmids":["1363541"],"confidence":"Medium","gaps":["No functional data; expression pattern alone does not prove necessity","Transcriptional targets unknown"]},{"year":2001,"claim":"Demonstrating that the MEOX1 homeodomain physically interacts with PAX1 and PAX3 revealed that MEOX1 functions not only as a DNA-binding factor but also as a protein–protein interaction partner for other developmental transcription factors.","evidence":"Yeast two-hybrid and in vitro binding assays mapping interaction to homeodomain","pmids":["11423130"],"confidence":"Medium","gaps":["Functional consequence of MEOX1–PAX1/3 interaction on transcription not tested","No in vivo validation of interaction"]},{"year":2009,"claim":"ChIP showing MEOX1 occupancy at Tbx18 and Uncx promoters, combined with the sclerotome polarity defect in Meox1-null mice, established MEOX1 as a direct transcriptional regulator of sclerotome segmentation genes.","evidence":"Mouse knockout, ChIP, gene expression analysis","pmids":["19520072"],"confidence":"High","gaps":["Whether MEOX1 activates or represses each target not fully dissected","Redundancy with MEOX2 at these loci not resolved"]},{"year":2011,"claim":"Placing MEOX1 downstream of Hoxa2 via direct promoter binding and genetic epistasis defined MEOX1's position in the branchial arch transcriptional hierarchy, while parallel work showed MEOX1 activates p16 (DNA-binding-dependent) and p21 (DNA-binding-independent), revealing dual mechanistic modes of target regulation.","evidence":"ChIP, promoter mutagenesis, Hoxa2 mutant epistasis; MEOX1 DNA-binding-domain mutants with cell cycle and reporter assays in endothelial cells","pmids":["21245383","22206000"],"confidence":"High","gaps":["Cofactors enabling DNA-binding-independent p21 activation unidentified","Whether the dual mechanism operates in non-endothelial contexts untested"]},{"year":2013,"claim":"Discovery that homozygous truncating MEOX1 mutations cause Klippel-Feil syndrome in humans provided direct genotype–phenotype validation, linking the mouse sclerotome polarity function to a human Mendelian disorder.","evidence":"Whole-genome linkage in two families, sequencing, transcript stability analysis in patient cells","pmids":["23290072"],"confidence":"High","gaps":["Penetrance and phenotypic spectrum of heterozygous carriers not characterized","Molecular rescue not performed in patient cells"]},{"year":2014,"claim":"Lineage tracing in zebrafish revealed that Meox1 specifies the endotome fate within somites, restricting endothelial progenitor numbers and thereby haematopoietic stem cell induction—extending MEOX1 function beyond skeletal patterning to vascular/haematopoietic development.","evidence":"Zebrafish loss-of-function genetics, lineage tracing, live imaging","pmids":["25119043"],"confidence":"High","gaps":["Direct transcriptional targets mediating endotome specification not identified","Mammalian conservation of this endotome role unconfirmed"]},{"year":2017,"claim":"Identification of CCNB1 as a direct MEOX1-repressed target in muscle stem cells, with loss of MEOX1 causing premature exit from G2 arrest and defective myotome growth, established a cell-cycle gating mechanism for stem cell maintenance.","evidence":"Zebrafish genetics, direct binding assays, clonal cell cycle analysis","pmids":["28686860"],"confidence":"High","gaps":["Whether MEOX1-mediated G2 arrest operates in mammalian satellite cells unknown","Chromatin mechanism of CCNB1 repression not resolved"]},{"year":2018,"claim":"Demonstration that MEOX1 directly activates the Gata4 promoter to exacerbate cardiac hypertrophy established MEOX1 as a pathological transcriptional driver beyond its developmental roles.","evidence":"ChIP and promoter assays, overexpression/knockdown in TAC and FHCM mouse models with echocardiography","pmids":["29155983"],"confidence":"High","gaps":["Upstream signals inducing MEOX1 in hypertrophic cardiomyocytes not identified","Whether MEOX1 directly causes cardiomyocyte hypertrophy or acts through fibroblasts not separated"]},{"year":2020,"claim":"Showing that TGF-β1 activates MEOX1 transcription through Smad2/3 promoter binding placed MEOX1 within the canonical fibrotic signaling cascade and explained its induction in activated fibroblasts.","evidence":"ChIP-qPCR for Smad2/3 on Meox1 promoter, Smad gain/loss-of-function in human dermal fibroblasts","pmids":["32241049"],"confidence":"Medium","gaps":["Smad binding sites on MEOX1 promoter not mutagenized","Whether other TGF-β superfamily ligands activate MEOX1 untested"]},{"year":2021,"claim":"Multiple studies extended MEOX1-CCNB1 repression to lung cancer G2 arrest and identified MEOX1-driven SDF-1α/CDC42 signaling in vascular smooth muscle remodeling, demonstrating that MEOX1 operates across diverse postnatal cell types.","evidence":"Chromatin binding/rescue in NSCLC cells; shRNA knockdown with pharmacological epistasis in rat carotid injury model","pmids":["34837450","34233723"],"confidence":"Medium","gaps":["MEOX1 binding site on SDF-1α promoter not demonstrated by ChIP","Whether CCNB1 repression is the sole anti-proliferative mechanism in cancer unclear"]},{"year":2024,"claim":"Identification of JUN as a direct upstream activator of MEOX1 via promoter binding, and TGF-β1-NOX4-ROS-Smad as an alternative induction axis, refined understanding of how MEOX1 is transcriptionally activated in pulmonary fibrosis.","evidence":"ChIP for JUN on MEOX1 promoter with pharmacological disruption; fibroblast-specific AAV-shMEOX1 knockdown in bleomycin model with NOX4/ROS/Smad inhibitors","pmids":["39220862","40780596"],"confidence":"Medium","gaps":["Relative contributions of JUN vs Smad to MEOX1 induction in vivo not quantified","Whether JUN and Smad act on same or distinct MEOX1 promoter elements unclear"]},{"year":2025,"claim":"Direct promoter binding studies established Cthrc1, ABHD3, and GLP2R as additional MEOX1 transcriptional targets driving cardiac fibrosis (via Smad2/3 feedback), hepatic fibrosis (via circRNA/m6A/β-catenin), and colorectal tumor suppression (via Hippo/YAP1), respectively, revealing MEOX1's broad target repertoire.","evidence":"ChIP and luciferase assays for each promoter; epistasis rescue experiments; in vivo mouse MI, CCl4/BDL liver, and orthotopic CRC models","pmids":["41362745","40100806","41612494"],"confidence":"High","gaps":["Genome-wide MEOX1 cistrome in any single cell type not defined","How MEOX1 selects between activation and repression at different targets mechanistically unresolved"]},{"year":2023,"claim":"Identification of MEOX1 as a Treg-specific transcription factor regulated by IL-2, with functional impact on Treg suppressive capacity, opened an immunological role distinct from its mesenchymal functions.","evidence":"Transcriptomic analysis of 48 CD4+ T cell conditions, epigenetic profiling, siRNA knockdown with Treg suppression assay","pmids":["37559728"],"confidence":"Medium","gaps":["Direct MEOX1 transcriptional targets in Tregs not identified","Whether MEOX1 is required for Treg development or only maintenance unknown","In vivo validation in conditional knockout mice lacking"]},{"year":null,"claim":"A genome-wide binding map (ChIP-seq/CUT&RUN) for MEOX1 in any primary cell type is still lacking, leaving the full direct target repertoire, the chromatin determinants of context-dependent activation versus repression, and the cofactors mediating DNA-binding-independent gene induction unresolved.","evidence":"","pmids":[],"confidence":"High","gaps":["No published MEOX1 ChIP-seq or CUT&RUN dataset","Structural basis for homeodomain-mediated protein interactions (PAX1/3) unknown","Whether MEOX1 isoforms or post-translational modifications regulate its dual activator/repressor function untested"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[0,3,4,5,8,9,13,18,19,23]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[3,4,5,8,9,13,18,19,23]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0,3,5,9]}],"pathway":[{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[3,4,5,8,9,13,18,19,23]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[0,1,3,4,7,8]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[5,8,13]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[10,16,18,20]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[6,11,17,18,19,21]}],"complexes":[],"partners":["PAX1","PAX3","HOXA2","SMAD2","SMAD3","JUN"],"other_free_text":[]},"mechanistic_narrative":"MEOX1 is a homeodomain transcription factor that governs mesodermal patterning, cell cycle control, and fibrotic remodeling by directly activating or repressing context-specific target gene promoters. During embryonic development, MEOX1 maintains sclerotome rostro-caudal polarity by occupying promoters of Tbx18 and Uncx, specifies endotomal endothelial precursors in the somite, and induces G2 cell-cycle arrest in muscle stem cells through direct repression of CCNB1 [PMID:19520072, PMID:25119043, PMID:28686860]. In postnatal tissues, MEOX1 is transcriptionally induced by TGF-β1/Smad2-3 and JUN signaling and drives organ fibrosis by activating downstream targets including Cthrc1, ABHD3/circABHD3, and CTGF in cardiac, hepatic, and pulmonary fibroblasts, while also promoting myocardial hypertrophy through Gata4 activation [PMID:29155983, PMID:41362745, PMID:40100806, PMID:39220862]. Homozygous loss-of-function mutations in MEOX1 cause Klippel-Feil syndrome in humans, recapitulating the cervical vertebral fusion phenotype of Meox1-null mice [PMID:23290072]."},"prefetch_data":{"uniprot":{"accession":"P50221","full_name":"Homeobox protein MOX-1","aliases":["Mesenchyme homeobox 1"],"length_aa":254,"mass_kda":28.0,"function":"Mesodermal transcription factor that plays a key role in somitogenesis and is specifically required for sclerotome development. Required for maintenance of the sclerotome polarity and formation of the cranio-cervical joints (PubMed:23290072, PubMed:24073994). Binds specifically to the promoter of target genes and regulates their expression. Activates expression of NKX3-2 in the sclerotome. Activates expression of CDKN1A and CDKN2A in endothelial cells, acting as a regulator of vascular cell proliferation. While it activates CDKN1A in a DNA-dependent manner, it activates CDKN2A in a DNA-independent manner. Required for hematopoietic stem cell (HSCs) induction via its role in somitogenesis: specification of HSCs occurs via the deployment of a specific endothelial precursor population, which arises within a sub-compartment of the somite named endotome","subcellular_location":"Nucleus; Cytoplasm","url":"https://www.uniprot.org/uniprotkb/P50221/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/MEOX1","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/MEOX1","total_profiled":1310},"omim":[{"mim_id":"608022","title":"DIAPHANOSPONDYLODYSOSTOSIS","url":"https://www.omim.org/entry/608022"},{"mim_id":"600147","title":"MESENCHYME HOMEOBOX 1; MEOX1","url":"https://www.omim.org/entry/600147"},{"mim_id":"239100","title":"VAN BUCHEM DISEASE; 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embryos\",\n      \"journal\": \"Development\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct localization experiment with developmental context, single lab but multiple stages analyzed\",\n      \"pmids\": [\"1363541\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"Mox-1 protein is first detected in newly formed mesoderm of primitive streak stage mouse embryos (7.5 dpc), earlier than Mox-2 (9.0 dpc), and is also expressed in branchial arches and limbs, indicating distinct developmental roles for Mox-1 and Mox-2.\",\n      \"method\": \"Immunostaining of mouse embryos at multiple developmental stages\",\n      \"journal\": \"The International Journal of Developmental Biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct protein localization by immunostaining with developmental stage resolution\",\n      \"pmids\": [\"9032023\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"MEOX1 homeodomain physically interacts with PAX1 and PAX3 transcription factors, with a preference of Mox1 for Pax1 over Pax3; this interaction is mediated through the homeodomain of Mox.\",\n      \"method\": \"Yeast two-hybrid assay and in vitro biochemical binding assays\",\n      \"journal\": \"FEBS Letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal assays (yeast two-hybrid + in vitro), single lab\",\n      \"pmids\": [\"11423130\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Meox1 loss-of-function in mice disrupts sclerotome rostro-caudal polarity, causing assimilation of the atlas into the basioccipital bone; MEOX1 protein occupies conserved promoter regions of Tbx18 and Uncx transcription factor genes, and Meox1 mutants show altered Tbx18, Uncx, and Bapx1 expression, indicating Meox1 directly regulates these genes to maintain sclerotome polarity.\",\n      \"method\": \"Mouse knockout, chromatin immunoprecipitation (ChIP), gene expression analysis, cell proliferation assays\",\n      \"journal\": \"Developmental Biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — ChIP demonstrating direct promoter occupancy combined with in vivo KO phenotype and multiple gene expression readouts\",\n      \"pmids\": [\"19520072\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"MEOX1 is a direct transcriptional target of Hoxa2; Hoxa2 binds to the Meox1 proximal promoter via two conserved binding sites required for Hoxa2-dependent activation, and Meox1 can bind DNA sequences recognized by Hoxa2 on its functional target genes, placing Meox1 downstream of Hoxa2 in the branchial arch regulatory network.\",\n      \"method\": \"Chromatin immunoprecipitation (ChIP), promoter reporter assays, genetic epistasis (Hoxa2 mouse mutants), Meox1/Meox2 double mutant analysis\",\n      \"journal\": \"Molecular and Cellular Biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — ChIP, promoter mutagenesis, and genetic epistasis with multiple orthogonal methods\",\n      \"pmids\": [\"21245383\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"MEOX1 activates p21(CIP1/WAF1) and p16(INK4a) expression in vascular endothelial cells and induces cell cycle arrest and senescence; MEOX1 activates p16(INK4a) in a DNA binding-dependent manner, whereas it induces p21(CIP1/WAF1) in a DNA binding-independent manner, distinguishing its mechanism from MEOX2.\",\n      \"method\": \"Overexpression of MEOX1 with DNA-binding domain mutants, reporter assays, cell cycle analysis, senescence assays\",\n      \"journal\": \"PLoS One\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — active site mutagenesis (DNA-binding mutants) combined with functional cell cycle/senescence assays, mechanistically distinguishes two target genes\",\n      \"pmids\": [\"22206000\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Homozygous frameshift or nonsense truncating mutations in MEOX1 cause isolated Klippel-Feil syndrome in humans, and the resulting complete transcript instability phenocopies the cervical skeletal defect of Meox1 null mice, establishing MEOX1 as the causative gene for this sclerotome polarity defect.\",\n      \"method\": \"Whole-genome linkage mapping, direct sequencing, transcript stability analysis in patient cells\",\n      \"journal\": \"American Journal of Human Genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — human genetics with mechanistic validation, replicated in second family and consistent with mouse model\",\n      \"pmids\": [\"23290072\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Meox1 specifies endotomal endothelial precursor cells within the zebrafish somite; loss of meox1 expands the endotome at the expense of muscle precursors and increases the number of endotome-derived cells colonizing the dorsal aorta, leading to increased chemokine-dependent haematopoietic stem cell induction.\",\n      \"method\": \"Zebrafish loss-of-function genetics, lineage tracing, live imaging, epistasis with chemokine signaling\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — zebrafish genetic loss-of-function with lineage tracing and defined cellular and molecular phenotypic readouts, published in high-impact journal with substantial citation\",\n      \"pmids\": [\"25119043\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Meox1 directly inhibits the cell-cycle checkpoint gene ccnb1 (Cyclin B1), inducing G2 cell-cycle arrest in muscle stem cells; disruption of this G2 arrest by loss of Meox1 causes premature lineage commitment and defective muscle growth during zebrafish myotome development.\",\n      \"method\": \"Zebrafish genetic loss-of-function, direct binding assays, cell cycle analysis, clonal analysis\",\n      \"journal\": \"Cell Stem Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — direct transcriptional target identification with loss-of-function phenotype and cell cycle mechanistic readout, replicated in subsequent studies\",\n      \"pmids\": [\"28686860\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"MEOX1 transcriptionally activates Gata4 as a downstream target to accelerate myocardial hypertrophic decompensation; MEOX1 overexpression exacerbated hypertrophic phenotypes while knockdown improved them, and direct Gata4 promoter activation was demonstrated by ChIP and promoter activity assays.\",\n      \"method\": \"Overexpression/knockdown in mice (FHCM and TAC models), digital gene expression profiling, ChIP, promoter activity assays, echocardiography\",\n      \"journal\": \"Cardiovascular Research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — ChIP demonstrating direct promoter occupancy, multiple in vivo and in vitro methods, epistasis via Gata4 knockdown\",\n      \"pmids\": [\"29155983\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"TGF-β1 transcriptionally upregulates MEOX1 expression via Smad2/3 binding to the Meox1 promoter in adult human dermal fibroblasts; MEOX1 promotes fibroblast migration as demonstrated by scratch and Transwell assays.\",\n      \"method\": \"ChIP-qPCR for Smad2/3 on Meox1 promoter, Smad overexpression/siRNA knockdown, transcriptome sequencing, migration assays\",\n      \"journal\": \"Zhonghua Shao Shang Za Zhi\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — ChIP-qPCR with functional gain/loss-of-function, single lab\",\n      \"pmids\": [\"32241049\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Combined p53 and PTEN deficiency in triple-negative breast cancer activates MEOX1 expression; MEOX1 knockdown abolished TNBC cell proliferation in vitro and tumor growth in vivo, and decreased expression of TYK2, STAT5B, and STAT6, placing MEOX1 downstream of combined p53/PTEN loss and upstream of JAK-STAT signaling.\",\n      \"method\": \"siRNA knockdown (p53/PTEN and MEOX1), RNA-Seq, immunoblotting, in vivo tumor growth assay\",\n      \"journal\": \"Journal of Biological Chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (RNA-Seq, immunoblot, in vivo), single lab\",\n      \"pmids\": [\"32467227\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"PPARα directly regulates the expression of MEOX1 in cardiomyocytes, and the cardioprotective effects of PPARα gene delivery in doxorubicin-induced cardiotoxicity are abolished by MEOX1 knockdown, placing MEOX1 downstream of PPARα in a cardioprotective pathway.\",\n      \"method\": \"Adeno-associated virus gene delivery, knockdown epistasis, cardiac function assays, in vivo mouse model\",\n      \"journal\": \"Frontiers in Pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vivo epistasis with AAV-mediated gene delivery and functional cardiac readouts, single lab\",\n      \"pmids\": [\"33132907\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"MEOX1 binds to the transcriptional initiation site of CCNB1 and suppresses CCNB1 expression, inducing G2 cell cycle arrest in non-small cell lung cancer cells; CCNB1 overexpression rescues the anti-proliferative effects of MEOX1.\",\n      \"method\": \"Chromatin binding assays, overexpression/knockdown, cell cycle analysis, rescue experiments, in vivo tumor growth\",\n      \"journal\": \"Environmental Toxicology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct promoter binding shown with rescue epistasis, consistent with zebrafish findings\",\n      \"pmids\": [\"34837450\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Meox1 regulates SDF-1α expression in vascular smooth muscle cells via CDC42 activation, which promotes CXCR4 expression on Sca-1+ progenitor cells, facilitating their migration and contribution to neointima formation following vascular injury; Meox1 knockdown abolished these effects.\",\n      \"method\": \"Rat carotid artery balloon injury model, shRNA knockdown, inhibitor studies (AMD3100, ZCL278), immunostaining\",\n      \"journal\": \"Stem Cell Research & Therapy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vivo loss-of-function with pharmacological epistasis, single lab\",\n      \"pmids\": [\"34233723\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"MEOX1 is expressed specifically in regulatory T (Treg) cells at levels comparable to FOXP3, is upregulated by IL-2, has a permissive epigenetic landscape exclusively in Tregs, and its knockdown profoundly alters downstream gene expression and reduces Treg suppressive capacity.\",\n      \"method\": \"Transcriptomic analysis of 48 human CD4+ T cell conditions, reverse network engineering, epigenetic analysis, siRNA knockdown, Treg suppression assays\",\n      \"journal\": \"Frontiers in Immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — epigenetic analysis combined with functional knockdown and suppression assay, single lab\",\n      \"pmids\": [\"37559728\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"JUN transcription factor binds the MEOX1 promoter to drive its expression; the natural compound Ailanthone disrupts JUN-promoter interaction, suppressing MEOX1 expression and consequently inhibiting fibroblast activation and endothelial-to-mesenchymal transition induced by TGF-β1 in pulmonary fibrosis.\",\n      \"method\": \"High-throughput screening, direct target binding studies, ChIP showing JUN on MEOX1 promoter, in vitro fibroblast/endothelial assays, bleomycin mouse model\",\n      \"journal\": \"Acta Pharmaceutica Sinica B\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — ChIP demonstrating JUN-MEOX1 promoter interaction, in vivo validation, single lab\",\n      \"pmids\": [\"39220862\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"MEOX1 promotes myofibroblast apoptosis resistance in pulmonary fibrosis by upregulating RGS4 (G-protein signaling pathway regulatory factor 4) as a direct downstream target; MEOX1 silencing enhanced myofibroblast apoptosis and attenuated fibrosis in mice.\",\n      \"method\": \"Bioinformatics prediction, siRNA knockdown, bleomycin mouse model, apoptosis assays\",\n      \"journal\": \"Journal of Cellular Physiology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — target identified bioinformatically with knockdown validation but no direct binding demonstrated\",\n      \"pmids\": [\"39319990\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"MEOX1 transcriptionally activates Cthrc1, which promotes downstream Smad2/3 phosphorylation, driving cardiac fibroblast-to-myofibroblast conversion following myocardial infarction; Cthrc1 overexpression abolishes cardioprotective effects of MEOX1 silencing.\",\n      \"method\": \"In vivo mouse MI model, knockdown/overexpression, ChIP/luciferase for Cthrc1 promoter, Western blot for p-Smad2/3, epistasis via Cthrc1 rescue\",\n      \"journal\": \"International Journal of Biological Sciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — direct promoter binding (ChIP), epistasis rescue experiment, in vivo and in vitro multiple orthogonal methods\",\n      \"pmids\": [\"41362745\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"MEOX1 directly binds the promoter of ABHD3 to facilitate its transcription and subsequent circABHD3 circular RNA generation; circABHD3 promotes YTHDF2-dependent m6A-modified YPEL3 mRNA degradation, activating β-catenin signaling and driving hepatic fibrosis.\",\n      \"method\": \"Luciferase reporter assay, ChIP, MeRIP, RIP, RNA pull-down, in vivo mouse models (CCl4, BDL)\",\n      \"journal\": \"PLoS Genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple direct binding assays (ChIP, luciferase) combined with RNA modification assays and in vivo epistasis\",\n      \"pmids\": [\"40100806\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"TGF-β1 upregulates MEOX1 expression through the NOX4-ROS-Smad signaling pathway in lung fibroblasts; fibroblast-specific MEOX1 knockdown prevents BLM-induced pulmonary fibrosis and abolishes TGF-β1-induced mitophagy deficiency (via CTGF downregulation) and cellular senescence.\",\n      \"method\": \"RNA-sequencing, AAV-shMEOX1 fibroblast-specific knockdown, in vivo bleomycin model, in vitro fibroblast assays, NOX4/ROS/Smad pathway inhibitors\",\n      \"journal\": \"European Journal of Pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vivo fibroblast-specific KD with pathway mechanistic follow-up, single lab\",\n      \"pmids\": [\"40780596\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"MEOX1 activates hepatic stellate cells via transcriptional regulation of SERPINE1 (PAI-1), promoting MASH-related liver fibrosis; MEOX1 knockdown suppresses HSC activation, proliferation, and migration.\",\n      \"method\": \"RNA-Seq, AlphaFold/PyMOL structural prediction of protein interaction sites, siRNA knockdown, in vitro HSC activation assays, in vivo MASH mouse model\",\n      \"journal\": \"The International Journal of Biological Markers\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — knockdown with RNA-Seq target identification; direct binding to SERPINE1 promoter not demonstrated by ChIP\",\n      \"pmids\": [\"40270091\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"MEOX1 represses PAX1 transcription in glioblastoma cells, and this MEOX1-PAX1 axis promotes tumor cell proliferation, migration, and invasion while PAX1 expression in GBM cells promotes Treg differentiation from CD4+ T cells.\",\n      \"method\": \"Overexpression/knockdown of MEOX1 and PAX1 in GBM cells, co-culture with CD4+ T cells, flow cytometry for Treg markers\",\n      \"journal\": \"Scientific Reports\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — functional KD/OE without direct promoter binding evidence for MEOX1 repression of PAX1\",\n      \"pmids\": [\"41692908\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"DNA hypermethylation silences MEOX1 in colorectal cancer; MEOX1 directly binds the GLP2R promoter to activate its transcription, and MEOX1-mediated GLP2R upregulation inhibits YAP1-mediated glycolysis through Hippo signaling, suppressing CRC growth and metastasis.\",\n      \"method\": \"ChIP-qPCR and dual-luciferase assays for MEOX1 binding to GLP2R promoter, MeDIP/MSP for DNA methylation, lentiviral overexpression/knockdown, orthotopic and liver metastasis mouse models\",\n      \"journal\": \"Cell & Bioscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 — direct promoter binding demonstrated by ChIP and luciferase, in vivo validation in multiple models\",\n      \"pmids\": [\"41612494\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"MEOX1 is a homeodomain transcription factor that directly regulates target gene transcription (including p16/INK4a, CCNB1, Gata4, Tbx18, Uncx, Cthrc1, GLP2R, ABHD3, and SERPINE1) in a context-dependent manner—activating p16 and repressing CCNB1 in a DNA-binding-dependent manner while activating p21 independently of DNA binding—and physically interacts with PAX1/PAX3 via its homeodomain; it is activated upstream by Hoxa2 (in branchial arch development) and TGF-β1/Smad2-3 and JUN (in fibrosis), and its activity drives diverse cellular processes including G2 cell-cycle arrest in muscle stem cells, sclerotome polarity, endosome-derived endothelial cell specification for HSC induction, vascular smooth muscle remodeling, cardiac hypertrophy/fibrosis, and pulmonary fibrosis through distinct downstream signaling cascades.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"MEOX1 is a homeodomain transcription factor that governs mesodermal patterning, cell cycle control, and fibrotic remodeling by directly activating or repressing context-specific target gene promoters. During embryonic development, MEOX1 maintains sclerotome rostro-caudal polarity by occupying promoters of Tbx18 and Uncx, specifies endotomal endothelial precursors in the somite, and induces G2 cell-cycle arrest in muscle stem cells through direct repression of CCNB1 [PMID:19520072, PMID:25119043, PMID:28686860]. In postnatal tissues, MEOX1 is transcriptionally induced by TGF-β1/Smad2-3 and JUN signaling and drives organ fibrosis by activating downstream targets including Cthrc1, ABHD3/circABHD3, and CTGF in cardiac, hepatic, and pulmonary fibroblasts, while also promoting myocardial hypertrophy through Gata4 activation [PMID:29155983, PMID:41362745, PMID:40100806, PMID:39220862]. Homozygous loss-of-function mutations in MEOX1 cause Klippel-Feil syndrome in humans, recapitulating the cervical vertebral fusion phenotype of Meox1-null mice [PMID:23290072].\",\n  \"teleology\": [\n    {\n      \"year\": 1992,\n      \"claim\": \"Identification of MEOX1 as a novel homeobox gene expressed in embryonic mesoderm established that a previously unknown transcription factor class operated in somitogenesis and mesodermal regionalization.\",\n      \"evidence\": \"In situ hybridization and expression analysis across mouse embryonic stages\",\n      \"pmids\": [\"1363541\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No functional data; expression pattern alone does not prove necessity\", \"Transcriptional targets unknown\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Demonstrating that the MEOX1 homeodomain physically interacts with PAX1 and PAX3 revealed that MEOX1 functions not only as a DNA-binding factor but also as a protein–protein interaction partner for other developmental transcription factors.\",\n      \"evidence\": \"Yeast two-hybrid and in vitro binding assays mapping interaction to homeodomain\",\n      \"pmids\": [\"11423130\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of MEOX1–PAX1/3 interaction on transcription not tested\", \"No in vivo validation of interaction\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"ChIP showing MEOX1 occupancy at Tbx18 and Uncx promoters, combined with the sclerotome polarity defect in Meox1-null mice, established MEOX1 as a direct transcriptional regulator of sclerotome segmentation genes.\",\n      \"evidence\": \"Mouse knockout, ChIP, gene expression analysis\",\n      \"pmids\": [\"19520072\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether MEOX1 activates or represses each target not fully dissected\", \"Redundancy with MEOX2 at these loci not resolved\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Placing MEOX1 downstream of Hoxa2 via direct promoter binding and genetic epistasis defined MEOX1's position in the branchial arch transcriptional hierarchy, while parallel work showed MEOX1 activates p16 (DNA-binding-dependent) and p21 (DNA-binding-independent), revealing dual mechanistic modes of target regulation.\",\n      \"evidence\": \"ChIP, promoter mutagenesis, Hoxa2 mutant epistasis; MEOX1 DNA-binding-domain mutants with cell cycle and reporter assays in endothelial cells\",\n      \"pmids\": [\"21245383\", \"22206000\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cofactors enabling DNA-binding-independent p21 activation unidentified\", \"Whether the dual mechanism operates in non-endothelial contexts untested\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Discovery that homozygous truncating MEOX1 mutations cause Klippel-Feil syndrome in humans provided direct genotype–phenotype validation, linking the mouse sclerotome polarity function to a human Mendelian disorder.\",\n      \"evidence\": \"Whole-genome linkage in two families, sequencing, transcript stability analysis in patient cells\",\n      \"pmids\": [\"23290072\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Penetrance and phenotypic spectrum of heterozygous carriers not characterized\", \"Molecular rescue not performed in patient cells\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Lineage tracing in zebrafish revealed that Meox1 specifies the endotome fate within somites, restricting endothelial progenitor numbers and thereby haematopoietic stem cell induction—extending MEOX1 function beyond skeletal patterning to vascular/haematopoietic development.\",\n      \"evidence\": \"Zebrafish loss-of-function genetics, lineage tracing, live imaging\",\n      \"pmids\": [\"25119043\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct transcriptional targets mediating endotome specification not identified\", \"Mammalian conservation of this endotome role unconfirmed\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Identification of CCNB1 as a direct MEOX1-repressed target in muscle stem cells, with loss of MEOX1 causing premature exit from G2 arrest and defective myotome growth, established a cell-cycle gating mechanism for stem cell maintenance.\",\n      \"evidence\": \"Zebrafish genetics, direct binding assays, clonal cell cycle analysis\",\n      \"pmids\": [\"28686860\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether MEOX1-mediated G2 arrest operates in mammalian satellite cells unknown\", \"Chromatin mechanism of CCNB1 repression not resolved\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Demonstration that MEOX1 directly activates the Gata4 promoter to exacerbate cardiac hypertrophy established MEOX1 as a pathological transcriptional driver beyond its developmental roles.\",\n      \"evidence\": \"ChIP and promoter assays, overexpression/knockdown in TAC and FHCM mouse models with echocardiography\",\n      \"pmids\": [\"29155983\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Upstream signals inducing MEOX1 in hypertrophic cardiomyocytes not identified\", \"Whether MEOX1 directly causes cardiomyocyte hypertrophy or acts through fibroblasts not separated\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Showing that TGF-β1 activates MEOX1 transcription through Smad2/3 promoter binding placed MEOX1 within the canonical fibrotic signaling cascade and explained its induction in activated fibroblasts.\",\n      \"evidence\": \"ChIP-qPCR for Smad2/3 on Meox1 promoter, Smad gain/loss-of-function in human dermal fibroblasts\",\n      \"pmids\": [\"32241049\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Smad binding sites on MEOX1 promoter not mutagenized\", \"Whether other TGF-β superfamily ligands activate MEOX1 untested\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Multiple studies extended MEOX1-CCNB1 repression to lung cancer G2 arrest and identified MEOX1-driven SDF-1α/CDC42 signaling in vascular smooth muscle remodeling, demonstrating that MEOX1 operates across diverse postnatal cell types.\",\n      \"evidence\": \"Chromatin binding/rescue in NSCLC cells; shRNA knockdown with pharmacological epistasis in rat carotid injury model\",\n      \"pmids\": [\"34837450\", \"34233723\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"MEOX1 binding site on SDF-1α promoter not demonstrated by ChIP\", \"Whether CCNB1 repression is the sole anti-proliferative mechanism in cancer unclear\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Identification of JUN as a direct upstream activator of MEOX1 via promoter binding, and TGF-β1-NOX4-ROS-Smad as an alternative induction axis, refined understanding of how MEOX1 is transcriptionally activated in pulmonary fibrosis.\",\n      \"evidence\": \"ChIP for JUN on MEOX1 promoter with pharmacological disruption; fibroblast-specific AAV-shMEOX1 knockdown in bleomycin model with NOX4/ROS/Smad inhibitors\",\n      \"pmids\": [\"39220862\", \"40780596\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Relative contributions of JUN vs Smad to MEOX1 induction in vivo not quantified\", \"Whether JUN and Smad act on same or distinct MEOX1 promoter elements unclear\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Direct promoter binding studies established Cthrc1, ABHD3, and GLP2R as additional MEOX1 transcriptional targets driving cardiac fibrosis (via Smad2/3 feedback), hepatic fibrosis (via circRNA/m6A/β-catenin), and colorectal tumor suppression (via Hippo/YAP1), respectively, revealing MEOX1's broad target repertoire.\",\n      \"evidence\": \"ChIP and luciferase assays for each promoter; epistasis rescue experiments; in vivo mouse MI, CCl4/BDL liver, and orthotopic CRC models\",\n      \"pmids\": [\"41362745\", \"40100806\", \"41612494\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Genome-wide MEOX1 cistrome in any single cell type not defined\", \"How MEOX1 selects between activation and repression at different targets mechanistically unresolved\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Identification of MEOX1 as a Treg-specific transcription factor regulated by IL-2, with functional impact on Treg suppressive capacity, opened an immunological role distinct from its mesenchymal functions.\",\n      \"evidence\": \"Transcriptomic analysis of 48 CD4+ T cell conditions, epigenetic profiling, siRNA knockdown with Treg suppression assay\",\n      \"pmids\": [\"37559728\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct MEOX1 transcriptional targets in Tregs not identified\", \"Whether MEOX1 is required for Treg development or only maintenance unknown\", \"In vivo validation in conditional knockout mice lacking\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"A genome-wide binding map (ChIP-seq/CUT&RUN) for MEOX1 in any primary cell type is still lacking, leaving the full direct target repertoire, the chromatin determinants of context-dependent activation versus repression, and the cofactors mediating DNA-binding-independent gene induction unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No published MEOX1 ChIP-seq or CUT&RUN dataset\", \"Structural basis for homeodomain-mediated protein interactions (PAX1/3) unknown\", \"Whether MEOX1 isoforms or post-translational modifications regulate its dual activator/repressor function untested\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [0, 3, 4, 5, 8, 9, 13, 18, 19, 23]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [3, 4, 5, 8, 9, 13, 18, 19, 23]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0, 3, 5, 9]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [3, 4, 5, 8, 9, 13, 18, 19, 23]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [0, 1, 3, 4, 7, 8]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [5, 8, 13]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [10, 16, 18, 20]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [6, 11, 17, 18, 19, 21]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"PAX1\",\n      \"PAX3\",\n      \"HOXA2\",\n      \"SMAD2\",\n      \"SMAD3\",\n      \"JUN\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}