{"gene":"PROX1","run_date":"2026-04-28T19:45:45","timeline":{"discoveries":[{"year":2002,"finding":"Prox1 is required for lymphatic endothelial cell (LEC) fate specification: in Prox1-null embryos, venous endothelial cells that bud from cardinal veins fail to acquire lymphatic markers (VEGFR-3, LYVE-1, SLC) and instead retain a blood vascular phenotype (laminin, CD34 expression), establishing Prox1 as essential for the budding and lymphatic differentiation of venous endothelial cells.","method":"Genetic knockout (Prox1-/- mice), immunostaining, marker analysis","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 — clean KO with defined cellular phenotype, replicated across multiple labs","pmids":["11927535"],"is_preprint":false},{"year":2002,"finding":"Ectopic expression of Prox1 in primary human blood vascular endothelial cells is sufficient to reprogram them toward a lymphatic endothelial phenotype, upregulating lymphatic markers (podoplanin, VEGFR-3) and downregulating blood vascular markers (laminin, neuropilin-1, ICAM-1), establishing Prox1 as a master switch for LEC fate.","method":"Adenoviral gene transfer of Prox1 cDNA into blood vascular endothelial cells, transcriptional profiling, RT-PCR, Western blotting, immunostaining","journal":"Developmental dynamics","confidence":"High","confidence_rationale":"Tier 1-2 — gain-of-function reprogramming with multiple orthogonal readouts, replicated","pmids":["12412020"],"is_preprint":false},{"year":2008,"finding":"Prox1 activity is continuously required to maintain LEC identity; conditional down-regulation of Prox1 during embryonic, postnatal, or adult stages causes LECs to revert to a blood vascular endothelial phenotype, demonstrating that Prox1 acts as a binary switch suppressing BEC identity and maintaining LEC identity in a cell-autonomous manner.","method":"Conditional (inducible) Prox1 knockout in mice, siRNA knockdown in cultured LECs, marker analysis","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 2 — multiple conditional KO timepoints plus in vitro siRNA validation","pmids":["19056883"],"is_preprint":false},{"year":2008,"finding":"Prox1 physically interacts with COUP-TFII to form a stable complex in lymphatic endothelial cells; this complex co-regulates LEC-specific genes including VEGFR-3, FGFR-3, and neuropilin-1, and COUP-TFII is required along with Prox1 to maintain the LEC phenotype.","method":"Co-immunoprecipitation, ChIP, gene expression analysis, loss-of-function studies","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP plus functional co-regulation data, confirmed by multiple methods","pmids":["18815287"],"is_preprint":false},{"year":2005,"finding":"Prox1 directly binds to Prox1-response elements in the FGFR-3 promoter to transcriptionally activate FGFR-3 expression specifically in lymphatic endothelial cells, identifying FGFR-3 as a direct Prox1 target gene during LEC fate specification.","method":"Prox1 overexpression in blood vascular ECs, promoter binding assays, siRNA knockdown of Prox1 in LECs, embryonic mouse immunostaining","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 1-2 — direct promoter binding demonstrated with functional consequence","pmids":["16291864"],"is_preprint":false},{"year":2007,"finding":"Prox1 induces expression of integrin alpha9 in endothelial cells, which in turn inhibits sheet formation and stimulates cell motility; knockdown of Prox1 in LECs decreases integrin alpha9 and VEGFR3 expression and reduces chemotaxis toward VEGF-C.","method":"Prox1 overexpression, siRNA knockdown in LECs, migration assays, immunostaining in mouse embryos","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 — gain- and loss-of-function with defined cellular phenotype and molecular readouts","pmids":["17287396"],"is_preprint":false},{"year":2009,"finding":"SUMO-1 modifies Prox1 at lysine 556 (K556); mutation K556R reduces DNA binding and transcriptional activity of Prox1, and abolishes its ability to induce VEGFR3, FGFR3, and p57 expression and lymphatic phenotypes in endothelial cells; SENP2 overexpression reduces Prox1 sumoylation and Prox1-induced VEGFR3 expression.","method":"In vitro and in vivo sumoylation assays, mutagenesis (K556R), luciferase reporter assays, SENP2 overexpression","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 1 — biochemical PTM mapping with mutagenesis and functional validation","pmids":["19706680"],"is_preprint":false},{"year":2010,"finding":"Prox1 interacts with ERRalpha and PGC-1alpha, occupies promoters of metabolic genes genome-wide, and inhibits the transcriptional activity of the ERRalpha/PGC-1alpha complex; ablation of Prox1 and ERRalpha have opposite effects on respiratory capacity of liver cells, revealing Prox1 as a negative modulator of ERRalpha/PGC-1alpha bioenergetic functions.","method":"Co-immunoprecipitation, genome-wide ChIP, luciferase reporter assays, Prox1 ablation with respirometry","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 1-2 — genome-wide binding plus in vitro interaction and functional KO with metabolic phenotype","pmids":["20194433"],"is_preprint":false},{"year":2009,"finding":"NF-kappaB activates Prox1 expression in response to inflammatory stimuli, and Prox1 synergizes with the p50 subunit of NF-kappaB to drive VEGFR-3 promoter activity, thereby enhancing LEC responsiveness and lymphangiogenesis.","method":"In vivo time-course of inflammation-induced lymphangiogenesis, promoter reporter assays, NF-kappaB inhibition, siRNA knockdown in LECs","journal":"Blood","confidence":"Medium","confidence_rationale":"Tier 2 — in vivo and in vitro evidence with promoter assays, single lab","pmids":["19901262"],"is_preprint":false},{"year":2011,"finding":"Prox1 dosage controls the number of LEC progenitors; heterozygous Prox1 mice lack lymphovenous valves due to reduced COUP-TFII/Prox1 complex formation, impairing maintenance of Prox1 expression in venous endothelial cells.","method":"Prox1 heterozygous and conditional mouse models, Co-IP for COUP-TFII/Prox1 complex, immunostaining","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 2 — genetic dosage model with molecular mechanism (complex formation) identified","pmids":["22012621"],"is_preprint":false},{"year":2012,"finding":"PROX1 and FOXC2, cooperating with shear stress/mechanotransduction, coordinately control connexin37 expression and calcineurin/NFAT signaling to mediate lymphatic valve formation; connexin37 and calcineurin are required for assembly and maintenance of lymphatic valve territory.","method":"Genetic mouse models (PROX1, FOXC2 conditional deletion), in vitro shear stress experiments, signaling analysis","journal":"Developmental cell","confidence":"High","confidence_rationale":"Tier 2 — multiple in vivo and in vitro models with defined molecular pathway","pmids":["22306086"],"is_preprint":false},{"year":2014,"finding":"Prox1 directly regulates Vegfr3 expression in a dosage-dependent manner in vivo; a Prox1-Vegfr3 feedback loop operates such that Vegfc-mediated activation of Vegfr3 signaling maintains Prox1 expression in LEC progenitors, controlling progenitor number and lymphatic vasculature formation.","method":"Multiple mouse genetic models (heterozygous, conditional KO), ChIP for Prox1 binding to Vegfr3 locus, Vegfc neutralization","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 1-2 — in vivo ChIP plus multiple genetic models establishing feedback loop","pmids":["25274728"],"is_preprint":false},{"year":2013,"finding":"COUP-TFII (NR2F2) homodimers maintain venous EC identity by binding HEY1/HEY2 promoters to inhibit arterial differentiation, whereas NR2F2/PROX1 heterodimers shift toward LEC fate by inducing LEC-specific genes and allowing non-canonical HEY1/2 expression; PROX1 DNA binding is additionally required for some LEC-specific gene expression.","method":"Co-IP, promoter-binding assays, overexpression/knockdown of COUP-TFII and PROX1 in ECs, gene expression profiling","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 — reciprocal protein interactions with direct promoter binding and functional differentiation readouts","pmids":["23345397"],"is_preprint":false},{"year":2011,"finding":"Ets-2 physically interacts with endogenous Prox1 in LECs and acts as a transcriptional cofactor; both Prox1 and Ets-2 bind the VEGFR3 promoter in intact chromatin, and Ets-2 enhances Prox1-induced VEGFR3 expression and VEGF-C-directed LEC migration.","method":"Co-immunoprecipitation of endogenous proteins, ChIP on VEGFR3 promoter, in vivo peritonitis model, dominant-negative Ets-1","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 — endogenous Co-IP plus ChIP and functional lymphangiogenesis assay","pmids":["21807940"],"is_preprint":false},{"year":2013,"finding":"Prox1 directly interacts with LSD1 (identified by IP-MS), recruits the LSD1/NuRD complex to the CYP7A1 promoter in HepG2 cells, causing H3K4 demethylation and H3/H4 deacetylation to co-repress CYP7A1 transcription (bile acid synthesis); this mechanism mediates bile acid-induced negative feedback on CYP7A1.","method":"Immunoprecipitation/mass spectrometry, GST pulldown, sequential ChIP, siRNA knockdown, reporter assays","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 1-2 — direct interaction by IP-MS/pulldown confirmed by sequential ChIP with histone modification readouts","pmids":["23626788"],"is_preprint":false},{"year":2014,"finding":"SUMOylation of LRH-1 at K289 promotes its interaction with PROX1 as a corepressor; abolishing LRH-1 SUMOylation (K289R mutation) compromises LRH-1/PROX1 interaction, increases reverse cholesterol transport gene expression and protects against atherosclerosis.","method":"SUMOylation-deficient knock-in mice, Co-IP for LRH-1/PROX1 interaction, gene expression analysis, atherosclerosis model","journal":"Cell metabolism","confidence":"High","confidence_rationale":"Tier 2 — genetic mouse model with molecular mechanism (PTM-dependent protein interaction) and defined metabolic phenotype","pmids":["25176150"],"is_preprint":false},{"year":2017,"finding":"PROX1 forms a co-repressor module with HDAC3 on the liver genome; HDAC3 and PROX1 are co-recruited by HNF4α, co-localize extensively genome-wide in mouse liver, and together regulate a lipid homeostasis gene program; hepatic-specific ablation of either HDAC3 or PROX1 increases liver triglyceride content.","method":"Cross-linking mass spectrometry (HDAC3 interactome), ChIP-seq for HDAC3 and PROX1, liver-specific knockout mice, metabolic phenotyping","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1-2 — in vivo interactome by XL-MS plus ChIP-seq and two conditional KO models","pmids":["28916805"],"is_preprint":false},{"year":2011,"finding":"ERRalpha directly regulates PROX1 target genes in circadian metabolic control; genome-wide location analysis shows extensive overlap of ERRalpha, PROX1, and BMAL1 binding sites in liver, establishing PROX1 as part of a transcriptional regulatory loop between circadian and metabolic networks.","method":"Genome-wide ChIP (ERRalpha, PROX1, BMAL1), ERRalpha-null mice, circadian/metabolic phenotyping","journal":"PLoS genetics","confidence":"High","confidence_rationale":"Tier 1-2 — genome-wide binding data from three factors plus genetic mouse model","pmids":["21731503"],"is_preprint":false},{"year":2008,"finding":"Cardiac-specific inactivation of Prox1 disrupts expression and localization of sarcomeric proteins (alpha-actinin, N-RAP, zyxin), causing myofibril disarray and growth-retarded hearts; Prox1 directly transcriptionally regulates genes encoding these structural proteins.","method":"Cardiac-specific conditional Prox1 knockout mice, microarray, qRT-PCR, immunostaining, ChIP/promoter assays","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 2 — tissue-specific KO with defined molecular targets and structural phenotype","pmids":["19091769"],"is_preprint":false},{"year":2010,"finding":"Prox1 is required for granule cell maturation and intermediate progenitor maintenance in the dentate gyrus; ectopic Prox1 expression induces premature differentiation of neural stem cells, and Prox1-expressing intermediate progenitors non-cell-autonomously regulate adult neural stem cell self-maintenance.","method":"Conditional Prox1 knockout mice, ectopic Prox1 overexpression, BrdU labeling, immunostaining","journal":"PLoS biology","confidence":"High","confidence_rationale":"Tier 2 — conditional KO plus gain-of-function with defined neural phenotype","pmids":["20808958"],"is_preprint":false},{"year":2011,"finding":"Prox1 is a direct transcriptional target of canonical Wnt/beta-catenin-TCF/LEF signaling in neural stem cells; Prox1 overexpression enhances neuronal differentiation while shRNA knockdown impairs neuron generation in vitro and in the hippocampal niche, with a stage-specific role in initial granule cell differentiation but not maintenance of mature granule cells.","method":"TCF/LEF reporter assays, ChIP for beta-catenin at Prox1 locus, shRNA knockdown, retroviral Prox1 overexpression in adult hippocampus","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — direct promoter binding by ChIP plus in vivo gain/loss-of-function","pmids":["21436036"],"is_preprint":false},{"year":2012,"finding":"Prox1 postmitotically functions as a cell fate determinant in the hippocampus: conditional elimination of Prox1 in immature dentate gyrus neurons causes them to adopt CA3 pyramidal neuron identity, while Prox1 overexpression in presumptive pyramidal cells suppresses that fate, demonstrating Prox1 specifies DG granule cell identity over CA3 pyramidal cell fate.","method":"Conditional Prox1 knockout in postmitotic neurons, Prox1 overexpression, immunostaining for cell type markers","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 2 — reciprocal gain/loss-of-function in postmitotic neurons with defined fate phenotype","pmids":["22791897"],"is_preprint":false},{"year":2008,"finding":"Prox1 acts as a transcriptional repressor of Atoh1 and Gfi1 in inner ear hair cells; adenoviral Prox1 transduction represses these transcription factors critical for hair cell differentiation, and luciferase assays show Prox1 can repress Gfi1 transcriptional activity independently of Atoh1.","method":"Adenoviral Prox1 transduction in cochlear explants, luciferase reporter assays, immunostaining","journal":"Developmental biology","confidence":"High","confidence_rationale":"Tier 2 — gain-of-function with mechanistic reporter assay and defined cellular phenotype","pmids":["18652815"],"is_preprint":false},{"year":2014,"finding":"Prox1 ablation in hepatoblasts reduces expression of multiple hepatocyte genes and leads to defective hepatocyte morphogenesis, excessive commitment to cholangiocytes, and premature bile duct morphogenesis; Prox1 is a regulator of bipotent hepatoblast fate allocation between hepatocytes and cholangiocytes.","method":"Conditional (hepatoblast-specific) Prox1 knockout mice, immunostaining, gene expression analysis, histology","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 2 — conditional KO with defined cell fate phenotype","pmids":["24449835"],"is_preprint":false},{"year":2011,"finding":"Pancreas-specific deletion of Prox1 causes premature acinar cell differentiation, increased ductal cell proliferation, imbalanced claudin protein expression, altered duct morphogenesis, and progressive exocrine degeneration, identifying Prox1 as a regulator of tip progenitor expansion and duct morphogenesis in the exocrine pancreas.","method":"Pancreas-specific Prox1 conditional knockout mice, immunohistochemistry, electron microscopy, qRT-PCR, Western blot","journal":"Gastroenterology","confidence":"High","confidence_rationale":"Tier 2 — tissue-specific KO with defined morphological and molecular phenotype","pmids":["22178591"],"is_preprint":false},{"year":2016,"finding":"Prox1 activates NFAT signaling and is necessary and sufficient for maintenance of the slow muscle fibre gene program; Prox1-positive satellite cells differentiate into muscle fibres, and Prox1 is required for myoblast differentiation via bi-directional crosstalk with Notch1.","method":"Lineage tracing, conditional KO and overexpression in rodent/human skeletal muscle, NFAT reporter assays, Notch pathway analysis","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 — multiple genetic tools with defined pathway (NFAT, Notch) and cellular phenotype","pmids":["27731315"],"is_preprint":false},{"year":2014,"finding":"PROX1 transcriptional repression of podoplanin (PDPN) is direct: Prox1 binds to the 5' regulatory region of the Pdpn gene in LECs as demonstrated by ChIP and DNA pulldown, and luciferase assays confirm Prox1 binding regulates Pdpn gene expression.","method":"ChIP in LECs, DNA pulldown assay, luciferase reporter assay","journal":"Microvascular research","confidence":"High","confidence_rationale":"Tier 1-2 — direct promoter binding validated by three complementary methods","pmids":["24944097"],"is_preprint":false},{"year":2016,"finding":"Crystal structure of SOX18 HMG box bound to a DNA element regulating Prox1 transcription was solved at 1.75Å resolution; SOX18 directly binds the Prox1 promoter, and decoy oligonucleotides based on the Prox1-DNA element potently inhibit SOX18 binding and repress SOX18-dependent reporter gene expression, establishing SOX18 as an upstream regulator of Prox1.","method":"X-ray crystallography, in vitro DNA binding assays, decoy oligonucleotide competition, luciferase reporter assay","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 1 — crystal structure with functional validation","pmids":["26939885"],"is_preprint":false},{"year":2018,"finding":"PROX1 forms a complex with beta-catenin and TCF7L1 to enhance Wnt/beta-catenin signaling in LECs, thereby promoting FOXC2 and GATA2 expression; oscillatory shear stress activates autocrine Wnt signaling in LECs that is channeled through this PROX1-containing complex.","method":"Co-immunoprecipitation of PROX1/beta-catenin/TCF7L1 complex, Wntless tissue-specific KO mice, in vitro shear stress, reporter assays","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 — protein complex identified by Co-IP plus genetic mouse model with defined signaling phenotype","pmids":["30332639"],"is_preprint":false},{"year":2019,"finding":"YAP/TAZ hyperactivation suppresses PROX1 transcription by recruiting the NuRD (nucleosome remodeling and deacetylase) complex via TEAD binding to the PROX1 promoter; conversely, YAP/TAZ depletion upregulates Prox1 and disturbs lymphatic plexus patterning.","method":"LEC-specific Yap/Taz conditional KO and hyperactivation mice, ChIP for TEAD/NuRD at PROX1 promoter, reporter assays, cornea lymphangiogenesis model","journal":"Circulation research","confidence":"High","confidence_rationale":"Tier 2 — reciprocal genetic models plus direct promoter mechanistic ChIP data","pmids":["30582452"],"is_preprint":false},{"year":2018,"finding":"HHEX is an upstream transcriptional regulator of VEGFC, FLT4, and PROX1 in vascular and lymphatic development; genetic deletion in mouse and knockdown in human endothelial cells impairs sprouting angiogenesis from the cardinal vein and lymphangiogenesis.","method":"Zebrafish hhex mutants, tissue-specific genetic deletions in mouse, human EC knockdown, molecular pathway analysis","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 — multiple vertebrate models with conserved function established upstream of PROX1","pmids":["30006544"],"is_preprint":false},{"year":2014,"finding":"PROX1 is a dosage-dependent direct target of beta-catenin/TCF signaling in intestinal tumors; PROX1 promotes colorectal cancer stem cell expansion through induction of annexin A1, reduction of filamin A, and promotion of autophagy/cell survival under hypoxia.","method":"In vivo mouse adenoma models, 3D organoid cultures, Prox1 deletion, AnnexinA1/Filamin A expression analysis","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 — multiple in vivo/ex vivo models but mechanistic targets partially defined","pmids":["25242330"],"is_preprint":false},{"year":2018,"finding":"PROX1 interacts with the NuRD complex to suppress the Notch pathway in colorectal cancer stem cells; PROX1 deletion increases Notch target gene expression and NOTCH1 promoter activity, revealing reciprocal suppression between PROX1 and Notch.","method":"Co-immunoprecipitation of PROX1/NuRD complex, NOTCH1 promoter reporter assays, PROX1 deletion in organoids and transgenic mouse models","journal":"Cancer research","confidence":"High","confidence_rationale":"Tier 2 — direct protein complex identification plus promoter assays and multiple model validation","pmids":["30154153"],"is_preprint":false},{"year":2022,"finding":"AMPK phosphorylates PROX1 at Ser79, promoting recruitment of CUL4-DDB1 ubiquitin ligase and subsequent PROX1 degradation; loss of PROX1 activates branched-chain amino acid (BCAA) degradation via epigenetic modifications and inhibits mTOR signaling.","method":"AMPK kinase assay, phospho-site mutagenesis, Co-IP of PROX1/CUL4-DDB1, PROX1 KO with BCAA metabolomics and mTOR signaling analysis","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1-2 — biochemical phosphorylation assay with mutagenesis and E3 ligase complex identification","pmids":["36433955"],"is_preprint":false},{"year":2009,"finding":"PROX1 represses hepatitis B virus replication by acting as a corepressor of LRH-1 at the HBV enhancer II/core promoter and by interacting with HNF-1 to partially repress the preS1 promoter, reducing HBV antigen expression and genome replication in hepatocytes.","method":"Reporter gene analysis of HBV promoters, Co-IP/interaction studies with LRH-1 and HNF-1, HBV antigen expression assays in hepatocytes","journal":"The Journal of general virology","confidence":"Medium","confidence_rationale":"Tier 2 — direct protein interactions with functional promoter repression, single lab","pmids":["19264593"],"is_preprint":false},{"year":2014,"finding":"Prox1 directly regulates Olig2 gene regulatory elements: ChIP in the mouse neural tube shows Prox1 binds the proximal Olig2 promoter and the K23 enhancer, suppressing Olig2 expression and thus controlling V2 interneuron versus motor neuron fate in ventral spinal cord.","method":"Gain/loss-of-function in mouse NPCs and chick neural tube, ChIP for Prox1 at Olig2 locus, luciferase reporter assays","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 1-2 — direct in vivo ChIP plus functional reporter assays and reciprocal gain/loss-of-function","pmids":["25411508"],"is_preprint":false},{"year":2013,"finding":"Prox1 expression is transcriptionally activated by hypoxia through direct binding of HIF-1alpha and HIF-2alpha to a hypoxia-response element (HRE) in the Prox1 promoter/regulatory region, as confirmed by EMSA, ChIP, and promoter reporter assays.","method":"EMSA, ChIP, luciferase reporter assay, HIF overexpression and knockdown","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 1-2 — direct binding demonstrated by two methods with functional readout, single lab","pmids":["23395615"],"is_preprint":false},{"year":2022,"finding":"Autophagy (lipophagy) in LECs supports fatty acid oxidation (FAO) and mitochondrial ATP production; when lipophagy is impaired, acetyl-CoA levels and expression of PROX1 target genes (including VEGFR3) decrease; restoring FAO via acetate supplementation rescues VEGFR3 levels and lymphangiogenesis, establishing a mitochondrial-PROX1 gene expression circuit.","method":"LEC-specific Atg5 knockout mice, DRP1 silencing, fatty acid oxidation assays, acetate rescue, corneal lymphangiogenesis model","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 — multiple genetic and metabolic interventions with defined molecular circuit","pmids":["35589749"],"is_preprint":false},{"year":2021,"finding":"Mitochondrial complex III activity regulates the Prox1-Vegfr3 feedback loop; conditional deletion of QPC subunit in LECs results in loss of lymphatic vasculature through down-regulation of LEC fate regulators (Vegfr3, Prox1) associated with reduced H3K4me3 and H3K27ac at their genomic loci.","method":"Conditional QPC knockout in mouse LECs, ChIP for H3K4me3 and H3K27ac at Vegfr3/Prox1 loci, immunostaining","journal":"Science advances","confidence":"High","confidence_rationale":"Tier 2 — genetic mouse model with defined epigenetic mechanism at specific genomic loci","pmids":["33931446"],"is_preprint":false},{"year":2023,"finding":"A Prox1 transcriptional enhancer element containing a GATA2-binding site is bound by GATA2, FOXC2, NFATC1, and PROX1 in LECs; genome editing of the enhancer (5-nt deletion of GATA2 site) causes profound lymphatic defects and perinatal death, and enhancer-mutant LECs acquire haemogenic capacity normally suppressed by Prox1 activity.","method":"Genome editing of enhancer in mice, ChIP for transcription factors, RNA-seq of mutant LECs, haematopoietic colony assays","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1-2 — precise genome editing with mechanistic enhancer dissection and functional haematopoietic readout","pmids":["36697821"],"is_preprint":false},{"year":2022,"finding":"PROX1 interacts with hnRNPK in breast cancer cells; this interaction inhibits ubiquitination of hnRNPK, stabilizing it and activating WNT/beta-catenin signaling to promote invasion and metastasis.","method":"Co-immunoprecipitation, immunofluorescence, ubiquitination assay, luciferase promoter assay, in vitro transwell invasion, in vivo lung metastasis model","journal":"International journal of biological sciences","confidence":"Medium","confidence_rationale":"Tier 2 — Co-IP with functional ubiquitination assay and in vivo validation, single lab","pmids":["35342346"],"is_preprint":false},{"year":2023,"finding":"Exosomal circ_0026611 interacts with NAA10 (N-alpha-acetyltransferase 10) to inhibit NAA10-mediated PROX1 acetylation; reduced PROX1 acetylation blocks its subsequent ubiquitination and degradation, thereby stabilizing PROX1 and promoting lymphangiogenesis in esophageal cancer.","method":"RNA immunoprecipitation, Co-IP, acetylation/ubiquitination assays in LECs, tube formation assay","journal":"Cellular & molecular biology letters","confidence":"Medium","confidence_rationale":"Tier 2 — biochemical PTM assays with functional lymphangiogenesis readout, single lab","pmids":["36803975"],"is_preprint":false},{"year":2014,"finding":"PROX1 acquires lymphatic identity and controls Schlemm's canal (SC) integrity; SC originates from blood vessels postnatally but upregulates PROX1 to acquire lymphatic identity; PROX1 expression levels linearly correlate with SC functionality, and reduced AHO alters SC fate and PROX1 expression.","method":"Lymphatic/blood vascular reporter mice, ocular puncture model, immunostaining, PROX1 quantification in functional vs. pathological SCs","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 — multiple mouse models with defined functional and molecular phenotype","pmids":["25061877"],"is_preprint":false},{"year":2020,"finding":"PROX1 interacts with ORF50 (the viral initiator of lytic replication of KSHV) and binds to the KSHV genome at the ORF50 promoter region, increasing its transactivation activity and KSHV spontaneous lytic gene expression and infectious virus release from LECs.","method":"Co-immunoprecipitation of PROX1/ORF50, ChIP on KSHV genome, PROX1 genetic depletion, KSHV genome copy quantification, viral protein assays","journal":"Cancer research","confidence":"High","confidence_rationale":"Tier 2 — direct protein-DNA and protein-protein interactions with functional viral replication phenotype","pmids":["32518203"],"is_preprint":false},{"year":2001,"finding":"Prox1 and Six3 act antagonistically on the gamma-crystallin promoter: Prox1 activates CRYG promoter activity while Six3 represses it to ~10% of basal activity; specific response elements for each factor were mapped (Prox1-responsive: -151 to -174; Six3-responsive: -101 to -123).","method":"Promoter-reporter (luciferase) assays in lens epithelial cell lines, mutational analysis of promoter fragments, transfection in cells with/without endogenous Prox1","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 — direct promoter element mapping with functional antagonism, single lab","pmids":["11139622"],"is_preprint":false},{"year":2012,"finding":"Sox1 maintains neural progenitor identity by suppressing Prox1-mediated neurogenic cell divisions; loss of Sox1 increases Prox1-dependent cell cycle exit and neuronal differentiation, placing Sox1 upstream of Prox1 in the regulation of cortical neural progenitor pool size.","method":"Sox1-null mouse embryo-derived NPCs, Prox1 overexpression/knockdown, cell cycle analysis, in vivo and in vitro differentiation assays","journal":"Stem cells (Dayton, Ohio)","confidence":"Medium","confidence_rationale":"Tier 2 — genetic epistasis with Sox1 KO plus Prox1 rescue, defined cell cycle phenotype","pmids":["21280160"],"is_preprint":false},{"year":2012,"finding":"Prox1 suppresses neuroblastoma cell proliferation by inducing p27-Kip1 and decreasing Cdc25A expression; rescue of Prox1's effects on Cdc25A and p27-Kip1 restores cell cycle progression, establishing the mechanistic basis for Prox1 antiproliferative activity in neuroblastoma.","method":"Inducible Prox1-overexpressing Neuro2A cells, shRNA knockdown, cell cycle analysis, SCID mouse xenograft, Western blotting for cyclins/Cdc25A/p27","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 — inducible OE with rescue experiment defining downstream effectors, single lab","pmids":["22508481"],"is_preprint":false},{"year":2010,"finding":"Prox1 knockdown in hematopoietic stem cells (HSCs) leads to in vivo accumulation of primitive and differentiated cells and enhanced in vitro HSC activity; overexpression has the reverse phenotype, identifying Prox1 as a negative regulator/antagonist of HSC self-renewal.","method":"In vivo RNAi screen in mouse HSCs, bone marrow transplantation, Prox1 overexpression vector, gene expression profiling","journal":"Cell stem cell","confidence":"Medium","confidence_rationale":"Tier 2 — in vivo KD with transplantation assay and reciprocal OE, defined HSC phenotype","pmids":["20621054"],"is_preprint":false}],"current_model":"PROX1 is a homeodomain transcription factor that acts as the master binary switch for lymphatic endothelial cell (LEC) fate, continuously required to suppress blood vascular identity and maintain LEC identity by directly regulating target genes (VEGFR3, FGFR3, podoplanin, integrin alpha9) through binding their promoters; it physically interacts with co-regulators including COUP-TFII, Ets-2, the LSD1/NuRD complex, HDAC3, ERRalpha/PGC-1alpha, and beta-catenin/TCF complexes to control lymphangiogenesis, hepatic lipid and bile acid metabolism, cardiac sarcomere integrity, neural and pancreatic cell fate, and circadian metabolic gene networks; its activity is post-translationally regulated by SUMO-1 (at K556), AMPK-driven phosphorylation (at Ser79) triggering CUL4-DDB1-mediated ubiquitin degradation, NAA10-mediated acetylation, and by upstream transcriptional regulators including HIF-1alpha/HIF-2alpha, Wnt/beta-catenin, and YAP/TAZ-TEAD/NuRD acting on its promoter and enhancer elements."},"narrative":{"teleology":[{"year":2001,"claim":"Early work established that PROX1 functions as a sequence-specific transcriptional activator, demonstrating direct binding to the γ-crystallin promoter and antagonism with Six3, providing the first evidence of PROX1 as a DNA-binding transcription factor with defined cis-elements.","evidence":"Promoter-reporter assays with mutational mapping in lens epithelial cells","pmids":["11139622"],"confidence":"Medium","gaps":["Single lab; no in vivo validation of crystallin regulation","Whether these binding elements are conserved in non-lens contexts was unknown"]},{"year":2002,"claim":"The central question of whether PROX1 has a specific developmental role was answered: PROX1 is essential for lymphatic endothelial cell fate specification, as knockout embryos fail to generate LECs from venous endothelium, and ectopic PROX1 expression suffices to reprogram blood vascular ECs toward lymphatic identity.","evidence":"Prox1-null mouse embryos with marker analysis; adenoviral Prox1 gain-of-function in human BECs with transcriptional profiling","pmids":["11927535","12412020"],"confidence":"High","gaps":["Whether PROX1 acts alone or requires cofactors was unknown","Direct transcriptional targets had not been identified"]},{"year":2005,"claim":"The question of which genes PROX1 directly regulates in LECs was addressed: PROX1 binds response elements in the FGFR3 promoter to directly activate transcription, identifying the first direct target gene of PROX1 in lymphatic fate specification.","evidence":"Promoter binding assays and siRNA knockdown in LECs with FGFR3 expression readout","pmids":["16291864"],"confidence":"High","gaps":["Full repertoire of direct targets remained unknown","Whether FGFR3 is functionally required for PROX1-driven lymphangiogenesis was not tested"]},{"year":2007,"claim":"PROX1's functional output in LEC biology was extended beyond gene expression to cell behavior: PROX1 induces integrin α9 and VEGFR3, which together drive chemotactic migration toward VEGF-C while inhibiting sheet formation, connecting transcriptional targets to lymphatic morphogenetic behavior.","evidence":"Gain- and loss-of-function in LECs with migration and sheet formation assays","pmids":["17287396"],"confidence":"High","gaps":["Whether integrin α9 is a direct transcriptional target was not shown by ChIP","In vivo validation of migration phenotype was lacking"]},{"year":2008,"claim":"Multiple studies resolved the temporal and tissue-specific requirements of PROX1: conditional deletion showed PROX1 is continuously required to maintain LEC identity at all life stages, while cardiac-specific KO revealed a separate role in sarcomere gene regulation, and PROX1/COUP-TFII complex formation was identified as essential for co-regulation of LEC genes.","evidence":"Inducible conditional KO mice at embryonic/postnatal/adult stages; cardiac-specific KO with microarray; reciprocal Co-IP of PROX1/COUP-TFII with ChIP on VEGFR3/FGFR3 promoters","pmids":["19056883","19091769","18815287"],"confidence":"High","gaps":["Structural basis of PROX1/COUP-TFII interaction was undefined","Whether PROX1 recruits distinct cofactors in cardiac vs. lymphatic contexts was unknown"]},{"year":2008,"claim":"PROX1 was shown to function as a transcriptional repressor in non-vascular contexts: in inner ear hair cells, PROX1 represses Atoh1 and Gfi1, transcription factors critical for hair cell differentiation, demonstrating context-dependent activating versus repressing functions.","evidence":"Adenoviral PROX1 transduction in cochlear explants with luciferase reporter assays","pmids":["18652815"],"confidence":"High","gaps":["No ChIP data for direct binding at Atoh1/Gfi1 loci","In vivo hair cell phenotype of Prox1 loss not examined in this study"]},{"year":2009,"claim":"Post-translational regulation of PROX1 was first characterized: SUMO-1 modification at K556 is required for DNA binding and transcriptional activation of lymphatic target genes, providing a mechanistic basis for fine-tuning PROX1 activity.","evidence":"In vitro/in vivo SUMOylation assays with K556R mutagenesis and SENP2 overexpression","pmids":["19706680"],"confidence":"High","gaps":["Whether SUMOylation of PROX1 is dynamically regulated during lymphangiogenesis in vivo was untested","Structural mechanism of SUMO-enhanced DNA binding was unknown"]},{"year":2010,"claim":"PROX1's roles expanded beyond vascular and sensory systems: it was identified as a negative modulator of ERRα/PGC-1α-driven bioenergetic programs in liver through direct interaction and promoter co-occupancy, and as a required factor for granule cell maturation and intermediate progenitor maintenance in the hippocampal dentate gyrus.","evidence":"Genome-wide ChIP, Co-IP, respirometry in PROX1-ablated liver; conditional Prox1 KO and gain-of-function in mouse dentate gyrus","pmids":["20194433","20808958"],"confidence":"High","gaps":["Specific metabolic gene targets of the PROX1/ERRα complex were not fully enumerated","Mechanism by which PROX1 intermediate progenitors non-cell-autonomously maintain stem cells was undefined"]},{"year":2011,"claim":"Multiple cofactors and regulatory inputs for PROX1 were resolved: Ets-2 was identified as a direct physical cofactor on the VEGFR3 promoter; PROX1 dosage was shown to control LEC progenitor number through COUP-TFII complex stoichiometry; Wnt/β-catenin was established as a direct upstream activator of PROX1 transcription in neural stem cells; and PROX1/ERRα/BMAL1 co-occupancy linked PROX1 to circadian metabolic regulation.","evidence":"Endogenous Co-IP/ChIP in LECs; Prox1 heterozygous mice; ChIP for β-catenin at Prox1 locus in neural stem cells; genome-wide co-binding analysis in liver","pmids":["21807940","22012621","21436036","21731503"],"confidence":"High","gaps":["Whether Ets-2 and COUP-TFII cooperate or compete on the same promoters was unknown","Circadian regulation of PROX1 protein stability was not addressed"]},{"year":2012,"claim":"PROX1's cell-fate specification role was generalized to the hippocampus—postmitotic PROX1 loss converts dentate granule neurons to CA3 pyramidal identity—and its role in lymphatic valve morphogenesis was mechanistically linked to connexin37/calcineurin/NFAT signaling cooperating with FOXC2.","evidence":"Conditional Prox1 KO in postmitotic hippocampal neurons with reciprocal gain-of-function; PROX1/FOXC2 conditional deletions with shear stress experiments","pmids":["22791897","22306086"],"confidence":"High","gaps":["Which PROX1 target genes mediate the granule-to-pyramidal fate switch was not identified","Whether PROX1 directly binds the connexin37 promoter was not shown"]},{"year":2013,"claim":"The mechanism of PROX1-mediated transcriptional repression was elucidated: PROX1 recruits the LSD1/NuRD complex to induce H3K4 demethylation and histone deacetylation at the CYP7A1 promoter in hepatocytes, establishing an epigenetic corepressor mechanism; separately, COUP-TFII/PROX1 heterodimer formation was shown to redirect COUP-TFII from venous to lymphatic gene programs.","evidence":"IP-MS identification of LSD1, sequential ChIP showing H3K4me/H3-H4ac changes; COUP-TFII/PROX1 Co-IP with promoter-binding and expression profiling in ECs","pmids":["23626788","23345397"],"confidence":"High","gaps":["Whether LSD1/NuRD recruitment is a general mechanism at all PROX1-repressed genes was unknown","Structural basis of COUP-TFII homodimer versus heterodimer gene target switching was unresolved"]},{"year":2014,"claim":"A self-sustaining PROX1-VEGFR3 feedback loop was defined: PROX1 directly binds the Vegfr3 locus in a dosage-dependent manner, and VEGFC/VEGFR3 signaling maintains PROX1 expression, controlling LEC progenitor number; simultaneously, PROX1's roles in hepatoblast fate allocation, spinal cord V2/motor neuron specification (via Olig2 repression), and Schlemm's canal identity were established.","evidence":"Multiple mouse genetic models with ChIP at Vegfr3; hepatoblast-specific KO; ChIP at Olig2 locus in neural tube; ocular reporter mice","pmids":["25274728","24449835","25411508","25061877"],"confidence":"High","gaps":["Signaling intermediates between VEGFR3 and PROX1 transcription were not identified","Genome-wide direct target repertoire in hepatoblasts was not mapped"]},{"year":2014,"claim":"PROX1 was linked to colorectal cancer stem cell biology as a dosage-dependent Wnt/β-catenin target that promotes stemness via annexin A1 induction, and SUMOylation of LRH-1 was shown to promote its corepressor interaction with PROX1 to regulate reverse cholesterol transport.","evidence":"Mouse adenoma models and 3D organoids with PROX1 deletion; LRH-1 K289R knock-in mice with PROX1 Co-IP and atherosclerosis phenotyping","pmids":["25242330","25176150"],"confidence":"High","gaps":["Whether PROX1 directly binds annexin A1 or filamin A promoters was not shown","How SUMOylation-dependent PROX1/LRH-1 interaction is structurally mediated was unresolved"]},{"year":2016,"claim":"SOX18 was structurally validated as a direct upstream activator of PROX1: the crystal structure of SOX18 HMG domain bound to the Prox1 regulatory element was solved, and PROX1 was shown to maintain slow muscle fiber identity via NFAT signaling and Notch crosstalk.","evidence":"X-ray crystallography at 1.75Å with decoy oligo competition assays; lineage tracing and conditional KO/OE in skeletal muscle with NFAT reporter","pmids":["26939885","27731315"],"confidence":"High","gaps":["Whether SOX18 acts combinatorially with other factors at the Prox1 promoter in vivo was not tested","Direct PROX1 targets in slow fiber gene program were not identified by ChIP"]},{"year":2017,"claim":"The PROX1/HDAC3 co-repressor module was mapped genome-wide in liver: cross-linking mass spectrometry and ChIP-seq revealed extensive co-recruitment by HNF4α, and dual conditional knockouts showed both factors control hepatic lipid homeostasis.","evidence":"XL-MS for HDAC3 interactome, ChIP-seq co-localization, liver-specific KO of HDAC3 and PROX1 with triglyceride measurements","pmids":["28916805"],"confidence":"High","gaps":["Whether PROX1/HDAC3 interaction is direct or bridged entirely by HNF4α was not resolved","Dynamic regulation of this module during fasting/feeding cycles was not examined"]},{"year":2018,"claim":"Mechanotransduction was integrated into PROX1 signaling: oscillatory shear stress activates Wnt signaling that is channeled through a PROX1/β-catenin/TCF7L1 complex to drive lymphatic valve genes FOXC2 and GATA2; separately, PROX1 was shown to suppress Notch in colorectal cancer stem cells via NuRD complex recruitment, and YAP/TAZ-TEAD was identified as a negative regulator of PROX1 transcription through NuRD recruitment to the PROX1 promoter.","evidence":"Co-IP of PROX1/β-catenin/TCF7L1 with Wntless KO mice; Co-IP of PROX1/NuRD with NOTCH1 reporter in organoids; ChIP for TEAD/NuRD at PROX1 promoter in LECs with reciprocal genetic models","pmids":["30332639","30154153","30582452"],"confidence":"High","gaps":["How PROX1 distinguishes Wnt-amplifying versus Notch-suppressing roles in different cell types was mechanistically unclear","Whether YAP/TAZ regulation of PROX1 operates in non-LEC contexts was untested"]},{"year":2021,"claim":"Metabolic regulation of the PROX1–VEGFR3 axis was uncovered: mitochondrial complex III activity maintains active histone marks (H3K4me3, H3K27ac) at PROX1 and VEGFR3 genomic loci, linking mitochondrial function to epigenetic maintenance of LEC identity.","evidence":"Conditional QPC knockout in mouse LECs with ChIP for histone modifications at Vegfr3/Prox1 loci","pmids":["33931446"],"confidence":"High","gaps":["The metabolite(s) connecting complex III to histone methyltransferase/acetyltransferase activity were not identified","Whether this mechanism operates in adult lymphatic maintenance was not shown"]},{"year":2022,"claim":"Two modes of PROX1 post-translational degradation were defined: AMPK phosphorylates PROX1 at Ser79, recruiting CUL4-DDB1 E3 ligase for ubiquitin-dependent degradation that links energy sensing to BCAA catabolism and mTOR signaling; and lipophagy-derived acetyl-CoA sustains PROX1-dependent VEGFR3 expression, establishing a metabolic-transcriptional circuit in LECs.","evidence":"AMPK kinase assay with S79 mutagenesis and CUL4-DDB1 Co-IP; LEC-specific Atg5 KO with FAO and acetate rescue experiments","pmids":["36433955","35589749"],"confidence":"High","gaps":["Whether AMPK-driven PROX1 degradation occurs in LECs or is liver-specific was not clarified","How acetyl-CoA mechanistically sustains PROX1 transcriptional activity (histone acetylation vs. protein modification) was not fully resolved"]},{"year":2023,"claim":"A critical Prox1 enhancer element was dissected at nucleotide resolution: a GATA2-binding site within the enhancer is co-occupied by GATA2, FOXC2, NFATC1, and PROX1 itself, and its disruption causes lethal lymphatic defects and acquisition of haemogenic capacity by LECs, revealing that PROX1 autoregulation suppresses alternative blood-forming fates.","evidence":"5-nt enhancer deletion by genome editing in mice, ChIP for TF occupancy, RNA-seq, haematopoietic colony assays from mutant LECs","pmids":["36697821"],"confidence":"High","gaps":["Whether PROX1 binding to its own enhancer is direct or mediated via GATA2 was not resolved","The haemogenic potential of adult (rather than embryonic) enhancer-mutant LECs was not tested"]},{"year":null,"claim":"Key unresolved questions include the structural basis of PROX1's context-dependent switch between transcriptional activation and repression, the full genome-wide direct target repertoire across different tissues, and how PROX1 integrates metabolic, mechanical, and signaling inputs to maintain cell identity throughout life.","evidence":"","pmids":[],"confidence":"High","gaps":["No full-length PROX1 structure or structure of PROX1 bound to any cofactor","Genome-wide direct target identification by CUT&RUN or similar in primary LECs at multiple developmental stages is lacking","Mechanism by which PROX1 suppresses haemogenic fate in LECs is unknown beyond enhancer requirement"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[4,6,14,26,35,44]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[0,1,2,4,7,14,16,22,35]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[6,7,14,16,35]}],"pathway":[{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[0,1,2,9,10,11,19,21,23,24,39]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[4,7,14,16,17,22,35]},{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[7,15,16,17,33]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[10,20,28,29,31]},{"term_id":"R-HSA-4839726","term_label":"Chromatin organization","supporting_discovery_ids":[14,38]}],"complexes":["PROX1/COUP-TFII","PROX1/HDAC3/HNF4α","PROX1/LSD1/NuRD","PROX1/β-catenin/TCF7L1"],"partners":["NR2F2","HDAC3","KDM1A","ETS2","ESRRA","CTNNB1","TCF7L1","FOXC2"],"other_free_text":[]},"mechanistic_narrative":"PROX1 is a homeodomain transcription factor that functions as a master cell-fate determinant across multiple tissues, most prominently serving as the obligate binary switch for lymphatic endothelial cell (LEC) identity. In LECs, PROX1 is both necessary and continuously required to suppress blood vascular gene programs and maintain lymphatic identity by directly binding and regulating promoters of VEGFR3, FGFR3, podoplanin, and integrin α9, operating through cofactor complexes with COUP-TFII, Ets-2, and β-catenin/TCF7L1, and participating in a self-sustaining PROX1–VEGFR3 feedback loop [PMID:11927535, PMID:19056883, PMID:25274728, PMID:18815287, PMID:30332639]. Beyond the lymphatic vasculature, PROX1 specifies dentate gyrus granule cell versus CA3 pyramidal neuron fate, regulates hepatoblast allocation between hepatocyte and cholangiocyte lineages, maintains cardiac sarcomere integrity, controls slow muscle fiber identity via NFAT signaling, and modulates hematopoietic stem cell self-renewal [PMID:22791897, PMID:24449835, PMID:19091769, PMID:27731315, PMID:20621054]. In liver, PROX1 partners with HDAC3 (recruited by HNF4α) and the LSD1/NuRD complex to co-repress lipid and bile acid metabolism genes, intersects with ERRα/PGC-1α to negatively regulate bioenergetic programs, and integrates circadian transcriptional networks through co-occupancy with BMAL1 [PMID:28916805, PMID:23626788, PMID:20194433, PMID:21731503]. PROX1 activity is post-translationally tuned by SUMO-1 conjugation at K556 (required for DNA binding), AMPK-mediated phosphorylation at Ser79 triggering CUL4-DDB1 ubiquitin-dependent degradation, and NAA10-mediated acetylation that primes ubiquitination [PMID:19706680, PMID:36433955, PMID:36803975]."},"prefetch_data":{"uniprot":{"accession":"Q92786","full_name":"Prospero homeobox protein 1","aliases":["Homeobox prospero-like protein PROX1","PROX-1"],"length_aa":737,"mass_kda":83.2,"function":"Transcription factor involved in developmental processes such as cell fate determination, gene transcriptional regulation and progenitor cell regulation in a number of organs. Plays a critical role in embryonic development and functions as a key regulatory protein in neurogenesis and the development of the heart, eye lens, liver, pancreas and the lymphatic system. Involved in the regulation of the circadian rhythm. Represses: transcription of the retinoid-related orphan receptor RORG, transcriptional activator activity of RORA and RORG and the expression of RORA/G-target genes including core clock components: BMAL1, NPAS2 and CRY1 and metabolic genes: AVPR1A and ELOVL3","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/Q92786/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PROX1","classification":"Not Classified","n_dependent_lines":7,"n_total_lines":1208,"dependency_fraction":0.005794701986754967},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/PROX1","total_profiled":1310},"omim":[{"mim_id":"612743","title":"MICRO RNA 181A2; MIR181A2","url":"https://www.omim.org/entry/612743"},{"mim_id":"612742","title":"MICRO RNA 181A1; MIR181A1","url":"https://www.omim.org/entry/612742"},{"mim_id":"609429","title":"FORKHEAD BOX N4; FOXN4","url":"https://www.omim.org/entry/609429"},{"mim_id":"608863","title":"PODOPLANIN; PDPN","url":"https://www.omim.org/entry/608863"},{"mim_id":"601618","title":"SRY-BOX 18; SOX18","url":"https://www.omim.org/entry/601618"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Enhanced","locations":[{"location":"Nucleoplasm","reliability":"Enhanced"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"liver","ntpm":81.1}],"url":"https://www.proteinatlas.org/search/PROX1"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"Q92786","domains":[{"cath_id":"1.10.10.500","chopping":"581-733","consensus_level":"high","plddt":95.5048,"start":581,"end":733}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q92786","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q92786-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q92786-F1-predicted_aligned_error_v6.png","plddt_mean":60.44},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PROX1","jax_strain_url":"https://www.jax.org/strain/search?query=PROX1"},"sequence":{"accession":"Q92786","fasta_url":"https://rest.uniprot.org/uniprotkb/Q92786.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q92786/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q92786"}},"corpus_meta":[{"pmid":"11927535","id":"PMC_11927535","title":"An 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\"confidence_rationale\": \"Tier 1-2 — gain-of-function reprogramming with multiple orthogonal readouts, replicated\",\n      \"pmids\": [\"12412020\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Prox1 activity is continuously required to maintain LEC identity; conditional down-regulation of Prox1 during embryonic, postnatal, or adult stages causes LECs to revert to a blood vascular endothelial phenotype, demonstrating that Prox1 acts as a binary switch suppressing BEC identity and maintaining LEC identity in a cell-autonomous manner.\",\n      \"method\": \"Conditional (inducible) Prox1 knockout in mice, siRNA knockdown in cultured LECs, marker analysis\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple conditional KO timepoints plus in vitro siRNA validation\",\n      \"pmids\": [\"19056883\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Prox1 physically interacts with COUP-TFII to form a stable complex in lymphatic endothelial cells; this complex co-regulates LEC-specific genes including VEGFR-3, FGFR-3, and neuropilin-1, and COUP-TFII is required along with Prox1 to maintain the LEC phenotype.\",\n      \"method\": \"Co-immunoprecipitation, ChIP, gene expression analysis, loss-of-function studies\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP plus functional co-regulation data, confirmed by multiple methods\",\n      \"pmids\": [\"18815287\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Prox1 directly binds to Prox1-response elements in the FGFR-3 promoter to transcriptionally activate FGFR-3 expression specifically in lymphatic endothelial cells, identifying FGFR-3 as a direct Prox1 target gene during LEC fate specification.\",\n      \"method\": \"Prox1 overexpression in blood vascular ECs, promoter binding assays, siRNA knockdown of Prox1 in LECs, embryonic mouse immunostaining\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — direct promoter binding demonstrated with functional consequence\",\n      \"pmids\": [\"16291864\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Prox1 induces expression of integrin alpha9 in endothelial cells, which in turn inhibits sheet formation and stimulates cell motility; knockdown of Prox1 in LECs decreases integrin alpha9 and VEGFR3 expression and reduces chemotaxis toward VEGF-C.\",\n      \"method\": \"Prox1 overexpression, siRNA knockdown in LECs, migration assays, immunostaining in mouse embryos\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — gain- and loss-of-function with defined cellular phenotype and molecular readouts\",\n      \"pmids\": [\"17287396\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"SUMO-1 modifies Prox1 at lysine 556 (K556); mutation K556R reduces DNA binding and transcriptional activity of Prox1, and abolishes its ability to induce VEGFR3, FGFR3, and p57 expression and lymphatic phenotypes in endothelial cells; SENP2 overexpression reduces Prox1 sumoylation and Prox1-induced VEGFR3 expression.\",\n      \"method\": \"In vitro and in vivo sumoylation assays, mutagenesis (K556R), luciferase reporter assays, SENP2 overexpression\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — biochemical PTM mapping with mutagenesis and functional validation\",\n      \"pmids\": [\"19706680\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Prox1 interacts with ERRalpha and PGC-1alpha, occupies promoters of metabolic genes genome-wide, and inhibits the transcriptional activity of the ERRalpha/PGC-1alpha complex; ablation of Prox1 and ERRalpha have opposite effects on respiratory capacity of liver cells, revealing Prox1 as a negative modulator of ERRalpha/PGC-1alpha bioenergetic functions.\",\n      \"method\": \"Co-immunoprecipitation, genome-wide ChIP, luciferase reporter assays, Prox1 ablation with respirometry\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — genome-wide binding plus in vitro interaction and functional KO with metabolic phenotype\",\n      \"pmids\": [\"20194433\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"NF-kappaB activates Prox1 expression in response to inflammatory stimuli, and Prox1 synergizes with the p50 subunit of NF-kappaB to drive VEGFR-3 promoter activity, thereby enhancing LEC responsiveness and lymphangiogenesis.\",\n      \"method\": \"In vivo time-course of inflammation-induced lymphangiogenesis, promoter reporter assays, NF-kappaB inhibition, siRNA knockdown in LECs\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vivo and in vitro evidence with promoter assays, single lab\",\n      \"pmids\": [\"19901262\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Prox1 dosage controls the number of LEC progenitors; heterozygous Prox1 mice lack lymphovenous valves due to reduced COUP-TFII/Prox1 complex formation, impairing maintenance of Prox1 expression in venous endothelial cells.\",\n      \"method\": \"Prox1 heterozygous and conditional mouse models, Co-IP for COUP-TFII/Prox1 complex, immunostaining\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic dosage model with molecular mechanism (complex formation) identified\",\n      \"pmids\": [\"22012621\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"PROX1 and FOXC2, cooperating with shear stress/mechanotransduction, coordinately control connexin37 expression and calcineurin/NFAT signaling to mediate lymphatic valve formation; connexin37 and calcineurin are required for assembly and maintenance of lymphatic valve territory.\",\n      \"method\": \"Genetic mouse models (PROX1, FOXC2 conditional deletion), in vitro shear stress experiments, signaling analysis\",\n      \"journal\": \"Developmental cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple in vivo and in vitro models with defined molecular pathway\",\n      \"pmids\": [\"22306086\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Prox1 directly regulates Vegfr3 expression in a dosage-dependent manner in vivo; a Prox1-Vegfr3 feedback loop operates such that Vegfc-mediated activation of Vegfr3 signaling maintains Prox1 expression in LEC progenitors, controlling progenitor number and lymphatic vasculature formation.\",\n      \"method\": \"Multiple mouse genetic models (heterozygous, conditional KO), ChIP for Prox1 binding to Vegfr3 locus, Vegfc neutralization\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vivo ChIP plus multiple genetic models establishing feedback loop\",\n      \"pmids\": [\"25274728\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"COUP-TFII (NR2F2) homodimers maintain venous EC identity by binding HEY1/HEY2 promoters to inhibit arterial differentiation, whereas NR2F2/PROX1 heterodimers shift toward LEC fate by inducing LEC-specific genes and allowing non-canonical HEY1/2 expression; PROX1 DNA binding is additionally required for some LEC-specific gene expression.\",\n      \"method\": \"Co-IP, promoter-binding assays, overexpression/knockdown of COUP-TFII and PROX1 in ECs, gene expression profiling\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal protein interactions with direct promoter binding and functional differentiation readouts\",\n      \"pmids\": [\"23345397\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Ets-2 physically interacts with endogenous Prox1 in LECs and acts as a transcriptional cofactor; both Prox1 and Ets-2 bind the VEGFR3 promoter in intact chromatin, and Ets-2 enhances Prox1-induced VEGFR3 expression and VEGF-C-directed LEC migration.\",\n      \"method\": \"Co-immunoprecipitation of endogenous proteins, ChIP on VEGFR3 promoter, in vivo peritonitis model, dominant-negative Ets-1\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — endogenous Co-IP plus ChIP and functional lymphangiogenesis assay\",\n      \"pmids\": [\"21807940\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Prox1 directly interacts with LSD1 (identified by IP-MS), recruits the LSD1/NuRD complex to the CYP7A1 promoter in HepG2 cells, causing H3K4 demethylation and H3/H4 deacetylation to co-repress CYP7A1 transcription (bile acid synthesis); this mechanism mediates bile acid-induced negative feedback on CYP7A1.\",\n      \"method\": \"Immunoprecipitation/mass spectrometry, GST pulldown, sequential ChIP, siRNA knockdown, reporter assays\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — direct interaction by IP-MS/pulldown confirmed by sequential ChIP with histone modification readouts\",\n      \"pmids\": [\"23626788\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"SUMOylation of LRH-1 at K289 promotes its interaction with PROX1 as a corepressor; abolishing LRH-1 SUMOylation (K289R mutation) compromises LRH-1/PROX1 interaction, increases reverse cholesterol transport gene expression and protects against atherosclerosis.\",\n      \"method\": \"SUMOylation-deficient knock-in mice, Co-IP for LRH-1/PROX1 interaction, gene expression analysis, atherosclerosis model\",\n      \"journal\": \"Cell metabolism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic mouse model with molecular mechanism (PTM-dependent protein interaction) and defined metabolic phenotype\",\n      \"pmids\": [\"25176150\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"PROX1 forms a co-repressor module with HDAC3 on the liver genome; HDAC3 and PROX1 are co-recruited by HNF4α, co-localize extensively genome-wide in mouse liver, and together regulate a lipid homeostasis gene program; hepatic-specific ablation of either HDAC3 or PROX1 increases liver triglyceride content.\",\n      \"method\": \"Cross-linking mass spectrometry (HDAC3 interactome), ChIP-seq for HDAC3 and PROX1, liver-specific knockout mice, metabolic phenotyping\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vivo interactome by XL-MS plus ChIP-seq and two conditional KO models\",\n      \"pmids\": [\"28916805\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"ERRalpha directly regulates PROX1 target genes in circadian metabolic control; genome-wide location analysis shows extensive overlap of ERRalpha, PROX1, and BMAL1 binding sites in liver, establishing PROX1 as part of a transcriptional regulatory loop between circadian and metabolic networks.\",\n      \"method\": \"Genome-wide ChIP (ERRalpha, PROX1, BMAL1), ERRalpha-null mice, circadian/metabolic phenotyping\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — genome-wide binding data from three factors plus genetic mouse model\",\n      \"pmids\": [\"21731503\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Cardiac-specific inactivation of Prox1 disrupts expression and localization of sarcomeric proteins (alpha-actinin, N-RAP, zyxin), causing myofibril disarray and growth-retarded hearts; Prox1 directly transcriptionally regulates genes encoding these structural proteins.\",\n      \"method\": \"Cardiac-specific conditional Prox1 knockout mice, microarray, qRT-PCR, immunostaining, ChIP/promoter assays\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — tissue-specific KO with defined molecular targets and structural phenotype\",\n      \"pmids\": [\"19091769\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Prox1 is required for granule cell maturation and intermediate progenitor maintenance in the dentate gyrus; ectopic Prox1 expression induces premature differentiation of neural stem cells, and Prox1-expressing intermediate progenitors non-cell-autonomously regulate adult neural stem cell self-maintenance.\",\n      \"method\": \"Conditional Prox1 knockout mice, ectopic Prox1 overexpression, BrdU labeling, immunostaining\",\n      \"journal\": \"PLoS biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — conditional KO plus gain-of-function with defined neural phenotype\",\n      \"pmids\": [\"20808958\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Prox1 is a direct transcriptional target of canonical Wnt/beta-catenin-TCF/LEF signaling in neural stem cells; Prox1 overexpression enhances neuronal differentiation while shRNA knockdown impairs neuron generation in vitro and in the hippocampal niche, with a stage-specific role in initial granule cell differentiation but not maintenance of mature granule cells.\",\n      \"method\": \"TCF/LEF reporter assays, ChIP for beta-catenin at Prox1 locus, shRNA knockdown, retroviral Prox1 overexpression in adult hippocampus\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct promoter binding by ChIP plus in vivo gain/loss-of-function\",\n      \"pmids\": [\"21436036\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Prox1 postmitotically functions as a cell fate determinant in the hippocampus: conditional elimination of Prox1 in immature dentate gyrus neurons causes them to adopt CA3 pyramidal neuron identity, while Prox1 overexpression in presumptive pyramidal cells suppresses that fate, demonstrating Prox1 specifies DG granule cell identity over CA3 pyramidal cell fate.\",\n      \"method\": \"Conditional Prox1 knockout in postmitotic neurons, Prox1 overexpression, immunostaining for cell type markers\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal gain/loss-of-function in postmitotic neurons with defined fate phenotype\",\n      \"pmids\": [\"22791897\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Prox1 acts as a transcriptional repressor of Atoh1 and Gfi1 in inner ear hair cells; adenoviral Prox1 transduction represses these transcription factors critical for hair cell differentiation, and luciferase assays show Prox1 can repress Gfi1 transcriptional activity independently of Atoh1.\",\n      \"method\": \"Adenoviral Prox1 transduction in cochlear explants, luciferase reporter assays, immunostaining\",\n      \"journal\": \"Developmental biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — gain-of-function with mechanistic reporter assay and defined cellular phenotype\",\n      \"pmids\": [\"18652815\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Prox1 ablation in hepatoblasts reduces expression of multiple hepatocyte genes and leads to defective hepatocyte morphogenesis, excessive commitment to cholangiocytes, and premature bile duct morphogenesis; Prox1 is a regulator of bipotent hepatoblast fate allocation between hepatocytes and cholangiocytes.\",\n      \"method\": \"Conditional (hepatoblast-specific) Prox1 knockout mice, immunostaining, gene expression analysis, histology\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — conditional KO with defined cell fate phenotype\",\n      \"pmids\": [\"24449835\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Pancreas-specific deletion of Prox1 causes premature acinar cell differentiation, increased ductal cell proliferation, imbalanced claudin protein expression, altered duct morphogenesis, and progressive exocrine degeneration, identifying Prox1 as a regulator of tip progenitor expansion and duct morphogenesis in the exocrine pancreas.\",\n      \"method\": \"Pancreas-specific Prox1 conditional knockout mice, immunohistochemistry, electron microscopy, qRT-PCR, Western blot\",\n      \"journal\": \"Gastroenterology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — tissue-specific KO with defined morphological and molecular phenotype\",\n      \"pmids\": [\"22178591\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Prox1 activates NFAT signaling and is necessary and sufficient for maintenance of the slow muscle fibre gene program; Prox1-positive satellite cells differentiate into muscle fibres, and Prox1 is required for myoblast differentiation via bi-directional crosstalk with Notch1.\",\n      \"method\": \"Lineage tracing, conditional KO and overexpression in rodent/human skeletal muscle, NFAT reporter assays, Notch pathway analysis\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple genetic tools with defined pathway (NFAT, Notch) and cellular phenotype\",\n      \"pmids\": [\"27731315\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"PROX1 transcriptional repression of podoplanin (PDPN) is direct: Prox1 binds to the 5' regulatory region of the Pdpn gene in LECs as demonstrated by ChIP and DNA pulldown, and luciferase assays confirm Prox1 binding regulates Pdpn gene expression.\",\n      \"method\": \"ChIP in LECs, DNA pulldown assay, luciferase reporter assay\",\n      \"journal\": \"Microvascular research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — direct promoter binding validated by three complementary methods\",\n      \"pmids\": [\"24944097\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Crystal structure of SOX18 HMG box bound to a DNA element regulating Prox1 transcription was solved at 1.75Å resolution; SOX18 directly binds the Prox1 promoter, and decoy oligonucleotides based on the Prox1-DNA element potently inhibit SOX18 binding and repress SOX18-dependent reporter gene expression, establishing SOX18 as an upstream regulator of Prox1.\",\n      \"method\": \"X-ray crystallography, in vitro DNA binding assays, decoy oligonucleotide competition, luciferase reporter assay\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure with functional validation\",\n      \"pmids\": [\"26939885\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"PROX1 forms a complex with beta-catenin and TCF7L1 to enhance Wnt/beta-catenin signaling in LECs, thereby promoting FOXC2 and GATA2 expression; oscillatory shear stress activates autocrine Wnt signaling in LECs that is channeled through this PROX1-containing complex.\",\n      \"method\": \"Co-immunoprecipitation of PROX1/beta-catenin/TCF7L1 complex, Wntless tissue-specific KO mice, in vitro shear stress, reporter assays\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — protein complex identified by Co-IP plus genetic mouse model with defined signaling phenotype\",\n      \"pmids\": [\"30332639\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"YAP/TAZ hyperactivation suppresses PROX1 transcription by recruiting the NuRD (nucleosome remodeling and deacetylase) complex via TEAD binding to the PROX1 promoter; conversely, YAP/TAZ depletion upregulates Prox1 and disturbs lymphatic plexus patterning.\",\n      \"method\": \"LEC-specific Yap/Taz conditional KO and hyperactivation mice, ChIP for TEAD/NuRD at PROX1 promoter, reporter assays, cornea lymphangiogenesis model\",\n      \"journal\": \"Circulation research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal genetic models plus direct promoter mechanistic ChIP data\",\n      \"pmids\": [\"30582452\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"HHEX is an upstream transcriptional regulator of VEGFC, FLT4, and PROX1 in vascular and lymphatic development; genetic deletion in mouse and knockdown in human endothelial cells impairs sprouting angiogenesis from the cardinal vein and lymphangiogenesis.\",\n      \"method\": \"Zebrafish hhex mutants, tissue-specific genetic deletions in mouse, human EC knockdown, molecular pathway analysis\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple vertebrate models with conserved function established upstream of PROX1\",\n      \"pmids\": [\"30006544\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"PROX1 is a dosage-dependent direct target of beta-catenin/TCF signaling in intestinal tumors; PROX1 promotes colorectal cancer stem cell expansion through induction of annexin A1, reduction of filamin A, and promotion of autophagy/cell survival under hypoxia.\",\n      \"method\": \"In vivo mouse adenoma models, 3D organoid cultures, Prox1 deletion, AnnexinA1/Filamin A expression analysis\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple in vivo/ex vivo models but mechanistic targets partially defined\",\n      \"pmids\": [\"25242330\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"PROX1 interacts with the NuRD complex to suppress the Notch pathway in colorectal cancer stem cells; PROX1 deletion increases Notch target gene expression and NOTCH1 promoter activity, revealing reciprocal suppression between PROX1 and Notch.\",\n      \"method\": \"Co-immunoprecipitation of PROX1/NuRD complex, NOTCH1 promoter reporter assays, PROX1 deletion in organoids and transgenic mouse models\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct protein complex identification plus promoter assays and multiple model validation\",\n      \"pmids\": [\"30154153\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"AMPK phosphorylates PROX1 at Ser79, promoting recruitment of CUL4-DDB1 ubiquitin ligase and subsequent PROX1 degradation; loss of PROX1 activates branched-chain amino acid (BCAA) degradation via epigenetic modifications and inhibits mTOR signaling.\",\n      \"method\": \"AMPK kinase assay, phospho-site mutagenesis, Co-IP of PROX1/CUL4-DDB1, PROX1 KO with BCAA metabolomics and mTOR signaling analysis\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — biochemical phosphorylation assay with mutagenesis and E3 ligase complex identification\",\n      \"pmids\": [\"36433955\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"PROX1 represses hepatitis B virus replication by acting as a corepressor of LRH-1 at the HBV enhancer II/core promoter and by interacting with HNF-1 to partially repress the preS1 promoter, reducing HBV antigen expression and genome replication in hepatocytes.\",\n      \"method\": \"Reporter gene analysis of HBV promoters, Co-IP/interaction studies with LRH-1 and HNF-1, HBV antigen expression assays in hepatocytes\",\n      \"journal\": \"The Journal of general virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct protein interactions with functional promoter repression, single lab\",\n      \"pmids\": [\"19264593\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Prox1 directly regulates Olig2 gene regulatory elements: ChIP in the mouse neural tube shows Prox1 binds the proximal Olig2 promoter and the K23 enhancer, suppressing Olig2 expression and thus controlling V2 interneuron versus motor neuron fate in ventral spinal cord.\",\n      \"method\": \"Gain/loss-of-function in mouse NPCs and chick neural tube, ChIP for Prox1 at Olig2 locus, luciferase reporter assays\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — direct in vivo ChIP plus functional reporter assays and reciprocal gain/loss-of-function\",\n      \"pmids\": [\"25411508\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Prox1 expression is transcriptionally activated by hypoxia through direct binding of HIF-1alpha and HIF-2alpha to a hypoxia-response element (HRE) in the Prox1 promoter/regulatory region, as confirmed by EMSA, ChIP, and promoter reporter assays.\",\n      \"method\": \"EMSA, ChIP, luciferase reporter assay, HIF overexpression and knockdown\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 — direct binding demonstrated by two methods with functional readout, single lab\",\n      \"pmids\": [\"23395615\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Autophagy (lipophagy) in LECs supports fatty acid oxidation (FAO) and mitochondrial ATP production; when lipophagy is impaired, acetyl-CoA levels and expression of PROX1 target genes (including VEGFR3) decrease; restoring FAO via acetate supplementation rescues VEGFR3 levels and lymphangiogenesis, establishing a mitochondrial-PROX1 gene expression circuit.\",\n      \"method\": \"LEC-specific Atg5 knockout mice, DRP1 silencing, fatty acid oxidation assays, acetate rescue, corneal lymphangiogenesis model\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple genetic and metabolic interventions with defined molecular circuit\",\n      \"pmids\": [\"35589749\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Mitochondrial complex III activity regulates the Prox1-Vegfr3 feedback loop; conditional deletion of QPC subunit in LECs results in loss of lymphatic vasculature through down-regulation of LEC fate regulators (Vegfr3, Prox1) associated with reduced H3K4me3 and H3K27ac at their genomic loci.\",\n      \"method\": \"Conditional QPC knockout in mouse LECs, ChIP for H3K4me3 and H3K27ac at Vegfr3/Prox1 loci, immunostaining\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic mouse model with defined epigenetic mechanism at specific genomic loci\",\n      \"pmids\": [\"33931446\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"A Prox1 transcriptional enhancer element containing a GATA2-binding site is bound by GATA2, FOXC2, NFATC1, and PROX1 in LECs; genome editing of the enhancer (5-nt deletion of GATA2 site) causes profound lymphatic defects and perinatal death, and enhancer-mutant LECs acquire haemogenic capacity normally suppressed by Prox1 activity.\",\n      \"method\": \"Genome editing of enhancer in mice, ChIP for transcription factors, RNA-seq of mutant LECs, haematopoietic colony assays\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — precise genome editing with mechanistic enhancer dissection and functional haematopoietic readout\",\n      \"pmids\": [\"36697821\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PROX1 interacts with hnRNPK in breast cancer cells; this interaction inhibits ubiquitination of hnRNPK, stabilizing it and activating WNT/beta-catenin signaling to promote invasion and metastasis.\",\n      \"method\": \"Co-immunoprecipitation, immunofluorescence, ubiquitination assay, luciferase promoter assay, in vitro transwell invasion, in vivo lung metastasis model\",\n      \"journal\": \"International journal of biological sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP with functional ubiquitination assay and in vivo validation, single lab\",\n      \"pmids\": [\"35342346\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Exosomal circ_0026611 interacts with NAA10 (N-alpha-acetyltransferase 10) to inhibit NAA10-mediated PROX1 acetylation; reduced PROX1 acetylation blocks its subsequent ubiquitination and degradation, thereby stabilizing PROX1 and promoting lymphangiogenesis in esophageal cancer.\",\n      \"method\": \"RNA immunoprecipitation, Co-IP, acetylation/ubiquitination assays in LECs, tube formation assay\",\n      \"journal\": \"Cellular & molecular biology letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — biochemical PTM assays with functional lymphangiogenesis readout, single lab\",\n      \"pmids\": [\"36803975\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"PROX1 acquires lymphatic identity and controls Schlemm's canal (SC) integrity; SC originates from blood vessels postnatally but upregulates PROX1 to acquire lymphatic identity; PROX1 expression levels linearly correlate with SC functionality, and reduced AHO alters SC fate and PROX1 expression.\",\n      \"method\": \"Lymphatic/blood vascular reporter mice, ocular puncture model, immunostaining, PROX1 quantification in functional vs. pathological SCs\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple mouse models with defined functional and molecular phenotype\",\n      \"pmids\": [\"25061877\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"PROX1 interacts with ORF50 (the viral initiator of lytic replication of KSHV) and binds to the KSHV genome at the ORF50 promoter region, increasing its transactivation activity and KSHV spontaneous lytic gene expression and infectious virus release from LECs.\",\n      \"method\": \"Co-immunoprecipitation of PROX1/ORF50, ChIP on KSHV genome, PROX1 genetic depletion, KSHV genome copy quantification, viral protein assays\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct protein-DNA and protein-protein interactions with functional viral replication phenotype\",\n      \"pmids\": [\"32518203\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Prox1 and Six3 act antagonistically on the gamma-crystallin promoter: Prox1 activates CRYG promoter activity while Six3 represses it to ~10% of basal activity; specific response elements for each factor were mapped (Prox1-responsive: -151 to -174; Six3-responsive: -101 to -123).\",\n      \"method\": \"Promoter-reporter (luciferase) assays in lens epithelial cell lines, mutational analysis of promoter fragments, transfection in cells with/without endogenous Prox1\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct promoter element mapping with functional antagonism, single lab\",\n      \"pmids\": [\"11139622\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Sox1 maintains neural progenitor identity by suppressing Prox1-mediated neurogenic cell divisions; loss of Sox1 increases Prox1-dependent cell cycle exit and neuronal differentiation, placing Sox1 upstream of Prox1 in the regulation of cortical neural progenitor pool size.\",\n      \"method\": \"Sox1-null mouse embryo-derived NPCs, Prox1 overexpression/knockdown, cell cycle analysis, in vivo and in vitro differentiation assays\",\n      \"journal\": \"Stem cells (Dayton, Ohio)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis with Sox1 KO plus Prox1 rescue, defined cell cycle phenotype\",\n      \"pmids\": [\"21280160\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Prox1 suppresses neuroblastoma cell proliferation by inducing p27-Kip1 and decreasing Cdc25A expression; rescue of Prox1's effects on Cdc25A and p27-Kip1 restores cell cycle progression, establishing the mechanistic basis for Prox1 antiproliferative activity in neuroblastoma.\",\n      \"method\": \"Inducible Prox1-overexpressing Neuro2A cells, shRNA knockdown, cell cycle analysis, SCID mouse xenograft, Western blotting for cyclins/Cdc25A/p27\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — inducible OE with rescue experiment defining downstream effectors, single lab\",\n      \"pmids\": [\"22508481\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Prox1 knockdown in hematopoietic stem cells (HSCs) leads to in vivo accumulation of primitive and differentiated cells and enhanced in vitro HSC activity; overexpression has the reverse phenotype, identifying Prox1 as a negative regulator/antagonist of HSC self-renewal.\",\n      \"method\": \"In vivo RNAi screen in mouse HSCs, bone marrow transplantation, Prox1 overexpression vector, gene expression profiling\",\n      \"journal\": \"Cell stem cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vivo KD with transplantation assay and reciprocal OE, defined HSC phenotype\",\n      \"pmids\": [\"20621054\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PROX1 is a homeodomain transcription factor that acts as the master binary switch for lymphatic endothelial cell (LEC) fate, continuously required to suppress blood vascular identity and maintain LEC identity by directly regulating target genes (VEGFR3, FGFR3, podoplanin, integrin alpha9) through binding their promoters; it physically interacts with co-regulators including COUP-TFII, Ets-2, the LSD1/NuRD complex, HDAC3, ERRalpha/PGC-1alpha, and beta-catenin/TCF complexes to control lymphangiogenesis, hepatic lipid and bile acid metabolism, cardiac sarcomere integrity, neural and pancreatic cell fate, and circadian metabolic gene networks; its activity is post-translationally regulated by SUMO-1 (at K556), AMPK-driven phosphorylation (at Ser79) triggering CUL4-DDB1-mediated ubiquitin degradation, NAA10-mediated acetylation, and by upstream transcriptional regulators including HIF-1alpha/HIF-2alpha, Wnt/beta-catenin, and YAP/TAZ-TEAD/NuRD acting on its promoter and enhancer elements.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"PROX1 is a homeodomain transcription factor that functions as a master cell-fate determinant across multiple tissues, most prominently serving as the obligate binary switch for lymphatic endothelial cell (LEC) identity. In LECs, PROX1 is both necessary and continuously required to suppress blood vascular gene programs and maintain lymphatic identity by directly binding and regulating promoters of VEGFR3, FGFR3, podoplanin, and integrin α9, operating through cofactor complexes with COUP-TFII, Ets-2, and β-catenin/TCF7L1, and participating in a self-sustaining PROX1–VEGFR3 feedback loop [PMID:11927535, PMID:19056883, PMID:25274728, PMID:18815287, PMID:30332639]. Beyond the lymphatic vasculature, PROX1 specifies dentate gyrus granule cell versus CA3 pyramidal neuron fate, regulates hepatoblast allocation between hepatocyte and cholangiocyte lineages, maintains cardiac sarcomere integrity, controls slow muscle fiber identity via NFAT signaling, and modulates hematopoietic stem cell self-renewal [PMID:22791897, PMID:24449835, PMID:19091769, PMID:27731315, PMID:20621054]. In liver, PROX1 partners with HDAC3 (recruited by HNF4α) and the LSD1/NuRD complex to co-repress lipid and bile acid metabolism genes, intersects with ERRα/PGC-1α to negatively regulate bioenergetic programs, and integrates circadian transcriptional networks through co-occupancy with BMAL1 [PMID:28916805, PMID:23626788, PMID:20194433, PMID:21731503]. PROX1 activity is post-translationally tuned by SUMO-1 conjugation at K556 (required for DNA binding), AMPK-mediated phosphorylation at Ser79 triggering CUL4-DDB1 ubiquitin-dependent degradation, and NAA10-mediated acetylation that primes ubiquitination [PMID:19706680, PMID:36433955, PMID:36803975].\",\n  \"teleology\": [\n    {\n      \"year\": 2001,\n      \"claim\": \"Early work established that PROX1 functions as a sequence-specific transcriptional activator, demonstrating direct binding to the γ-crystallin promoter and antagonism with Six3, providing the first evidence of PROX1 as a DNA-binding transcription factor with defined cis-elements.\",\n      \"evidence\": \"Promoter-reporter assays with mutational mapping in lens epithelial cells\",\n      \"pmids\": [\"11139622\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab; no in vivo validation of crystallin regulation\", \"Whether these binding elements are conserved in non-lens contexts was unknown\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"The central question of whether PROX1 has a specific developmental role was answered: PROX1 is essential for lymphatic endothelial cell fate specification, as knockout embryos fail to generate LECs from venous endothelium, and ectopic PROX1 expression suffices to reprogram blood vascular ECs toward lymphatic identity.\",\n      \"evidence\": \"Prox1-null mouse embryos with marker analysis; adenoviral Prox1 gain-of-function in human BECs with transcriptional profiling\",\n      \"pmids\": [\"11927535\", \"12412020\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether PROX1 acts alone or requires cofactors was unknown\", \"Direct transcriptional targets had not been identified\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"The question of which genes PROX1 directly regulates in LECs was addressed: PROX1 binds response elements in the FGFR3 promoter to directly activate transcription, identifying the first direct target gene of PROX1 in lymphatic fate specification.\",\n      \"evidence\": \"Promoter binding assays and siRNA knockdown in LECs with FGFR3 expression readout\",\n      \"pmids\": [\"16291864\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full repertoire of direct targets remained unknown\", \"Whether FGFR3 is functionally required for PROX1-driven lymphangiogenesis was not tested\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"PROX1's functional output in LEC biology was extended beyond gene expression to cell behavior: PROX1 induces integrin α9 and VEGFR3, which together drive chemotactic migration toward VEGF-C while inhibiting sheet formation, connecting transcriptional targets to lymphatic morphogenetic behavior.\",\n      \"evidence\": \"Gain- and loss-of-function in LECs with migration and sheet formation assays\",\n      \"pmids\": [\"17287396\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether integrin α9 is a direct transcriptional target was not shown by ChIP\", \"In vivo validation of migration phenotype was lacking\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Multiple studies resolved the temporal and tissue-specific requirements of PROX1: conditional deletion showed PROX1 is continuously required to maintain LEC identity at all life stages, while cardiac-specific KO revealed a separate role in sarcomere gene regulation, and PROX1/COUP-TFII complex formation was identified as essential for co-regulation of LEC genes.\",\n      \"evidence\": \"Inducible conditional KO mice at embryonic/postnatal/adult stages; cardiac-specific KO with microarray; reciprocal Co-IP of PROX1/COUP-TFII with ChIP on VEGFR3/FGFR3 promoters\",\n      \"pmids\": [\"19056883\", \"19091769\", \"18815287\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of PROX1/COUP-TFII interaction was undefined\", \"Whether PROX1 recruits distinct cofactors in cardiac vs. lymphatic contexts was unknown\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"PROX1 was shown to function as a transcriptional repressor in non-vascular contexts: in inner ear hair cells, PROX1 represses Atoh1 and Gfi1, transcription factors critical for hair cell differentiation, demonstrating context-dependent activating versus repressing functions.\",\n      \"evidence\": \"Adenoviral PROX1 transduction in cochlear explants with luciferase reporter assays\",\n      \"pmids\": [\"18652815\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No ChIP data for direct binding at Atoh1/Gfi1 loci\", \"In vivo hair cell phenotype of Prox1 loss not examined in this study\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Post-translational regulation of PROX1 was first characterized: SUMO-1 modification at K556 is required for DNA binding and transcriptional activation of lymphatic target genes, providing a mechanistic basis for fine-tuning PROX1 activity.\",\n      \"evidence\": \"In vitro/in vivo SUMOylation assays with K556R mutagenesis and SENP2 overexpression\",\n      \"pmids\": [\"19706680\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether SUMOylation of PROX1 is dynamically regulated during lymphangiogenesis in vivo was untested\", \"Structural mechanism of SUMO-enhanced DNA binding was unknown\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"PROX1's roles expanded beyond vascular and sensory systems: it was identified as a negative modulator of ERRα/PGC-1α-driven bioenergetic programs in liver through direct interaction and promoter co-occupancy, and as a required factor for granule cell maturation and intermediate progenitor maintenance in the hippocampal dentate gyrus.\",\n      \"evidence\": \"Genome-wide ChIP, Co-IP, respirometry in PROX1-ablated liver; conditional Prox1 KO and gain-of-function in mouse dentate gyrus\",\n      \"pmids\": [\"20194433\", \"20808958\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific metabolic gene targets of the PROX1/ERRα complex were not fully enumerated\", \"Mechanism by which PROX1 intermediate progenitors non-cell-autonomously maintain stem cells was undefined\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Multiple cofactors and regulatory inputs for PROX1 were resolved: Ets-2 was identified as a direct physical cofactor on the VEGFR3 promoter; PROX1 dosage was shown to control LEC progenitor number through COUP-TFII complex stoichiometry; Wnt/β-catenin was established as a direct upstream activator of PROX1 transcription in neural stem cells; and PROX1/ERRα/BMAL1 co-occupancy linked PROX1 to circadian metabolic regulation.\",\n      \"evidence\": \"Endogenous Co-IP/ChIP in LECs; Prox1 heterozygous mice; ChIP for β-catenin at Prox1 locus in neural stem cells; genome-wide co-binding analysis in liver\",\n      \"pmids\": [\"21807940\", \"22012621\", \"21436036\", \"21731503\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Ets-2 and COUP-TFII cooperate or compete on the same promoters was unknown\", \"Circadian regulation of PROX1 protein stability was not addressed\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"PROX1's cell-fate specification role was generalized to the hippocampus—postmitotic PROX1 loss converts dentate granule neurons to CA3 pyramidal identity—and its role in lymphatic valve morphogenesis was mechanistically linked to connexin37/calcineurin/NFAT signaling cooperating with FOXC2.\",\n      \"evidence\": \"Conditional Prox1 KO in postmitotic hippocampal neurons with reciprocal gain-of-function; PROX1/FOXC2 conditional deletions with shear stress experiments\",\n      \"pmids\": [\"22791897\", \"22306086\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Which PROX1 target genes mediate the granule-to-pyramidal fate switch was not identified\", \"Whether PROX1 directly binds the connexin37 promoter was not shown\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"The mechanism of PROX1-mediated transcriptional repression was elucidated: PROX1 recruits the LSD1/NuRD complex to induce H3K4 demethylation and histone deacetylation at the CYP7A1 promoter in hepatocytes, establishing an epigenetic corepressor mechanism; separately, COUP-TFII/PROX1 heterodimer formation was shown to redirect COUP-TFII from venous to lymphatic gene programs.\",\n      \"evidence\": \"IP-MS identification of LSD1, sequential ChIP showing H3K4me/H3-H4ac changes; COUP-TFII/PROX1 Co-IP with promoter-binding and expression profiling in ECs\",\n      \"pmids\": [\"23626788\", \"23345397\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether LSD1/NuRD recruitment is a general mechanism at all PROX1-repressed genes was unknown\", \"Structural basis of COUP-TFII homodimer versus heterodimer gene target switching was unresolved\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"A self-sustaining PROX1-VEGFR3 feedback loop was defined: PROX1 directly binds the Vegfr3 locus in a dosage-dependent manner, and VEGFC/VEGFR3 signaling maintains PROX1 expression, controlling LEC progenitor number; simultaneously, PROX1's roles in hepatoblast fate allocation, spinal cord V2/motor neuron specification (via Olig2 repression), and Schlemm's canal identity were established.\",\n      \"evidence\": \"Multiple mouse genetic models with ChIP at Vegfr3; hepatoblast-specific KO; ChIP at Olig2 locus in neural tube; ocular reporter mice\",\n      \"pmids\": [\"25274728\", \"24449835\", \"25411508\", \"25061877\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Signaling intermediates between VEGFR3 and PROX1 transcription were not identified\", \"Genome-wide direct target repertoire in hepatoblasts was not mapped\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"PROX1 was linked to colorectal cancer stem cell biology as a dosage-dependent Wnt/β-catenin target that promotes stemness via annexin A1 induction, and SUMOylation of LRH-1 was shown to promote its corepressor interaction with PROX1 to regulate reverse cholesterol transport.\",\n      \"evidence\": \"Mouse adenoma models and 3D organoids with PROX1 deletion; LRH-1 K289R knock-in mice with PROX1 Co-IP and atherosclerosis phenotyping\",\n      \"pmids\": [\"25242330\", \"25176150\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether PROX1 directly binds annexin A1 or filamin A promoters was not shown\", \"How SUMOylation-dependent PROX1/LRH-1 interaction is structurally mediated was unresolved\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"SOX18 was structurally validated as a direct upstream activator of PROX1: the crystal structure of SOX18 HMG domain bound to the Prox1 regulatory element was solved, and PROX1 was shown to maintain slow muscle fiber identity via NFAT signaling and Notch crosstalk.\",\n      \"evidence\": \"X-ray crystallography at 1.75Å with decoy oligo competition assays; lineage tracing and conditional KO/OE in skeletal muscle with NFAT reporter\",\n      \"pmids\": [\"26939885\", \"27731315\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether SOX18 acts combinatorially with other factors at the Prox1 promoter in vivo was not tested\", \"Direct PROX1 targets in slow fiber gene program were not identified by ChIP\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"The PROX1/HDAC3 co-repressor module was mapped genome-wide in liver: cross-linking mass spectrometry and ChIP-seq revealed extensive co-recruitment by HNF4α, and dual conditional knockouts showed both factors control hepatic lipid homeostasis.\",\n      \"evidence\": \"XL-MS for HDAC3 interactome, ChIP-seq co-localization, liver-specific KO of HDAC3 and PROX1 with triglyceride measurements\",\n      \"pmids\": [\"28916805\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether PROX1/HDAC3 interaction is direct or bridged entirely by HNF4α was not resolved\", \"Dynamic regulation of this module during fasting/feeding cycles was not examined\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Mechanotransduction was integrated into PROX1 signaling: oscillatory shear stress activates Wnt signaling that is channeled through a PROX1/β-catenin/TCF7L1 complex to drive lymphatic valve genes FOXC2 and GATA2; separately, PROX1 was shown to suppress Notch in colorectal cancer stem cells via NuRD complex recruitment, and YAP/TAZ-TEAD was identified as a negative regulator of PROX1 transcription through NuRD recruitment to the PROX1 promoter.\",\n      \"evidence\": \"Co-IP of PROX1/β-catenin/TCF7L1 with Wntless KO mice; Co-IP of PROX1/NuRD with NOTCH1 reporter in organoids; ChIP for TEAD/NuRD at PROX1 promoter in LECs with reciprocal genetic models\",\n      \"pmids\": [\"30332639\", \"30154153\", \"30582452\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How PROX1 distinguishes Wnt-amplifying versus Notch-suppressing roles in different cell types was mechanistically unclear\", \"Whether YAP/TAZ regulation of PROX1 operates in non-LEC contexts was untested\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Metabolic regulation of the PROX1–VEGFR3 axis was uncovered: mitochondrial complex III activity maintains active histone marks (H3K4me3, H3K27ac) at PROX1 and VEGFR3 genomic loci, linking mitochondrial function to epigenetic maintenance of LEC identity.\",\n      \"evidence\": \"Conditional QPC knockout in mouse LECs with ChIP for histone modifications at Vegfr3/Prox1 loci\",\n      \"pmids\": [\"33931446\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The metabolite(s) connecting complex III to histone methyltransferase/acetyltransferase activity were not identified\", \"Whether this mechanism operates in adult lymphatic maintenance was not shown\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Two modes of PROX1 post-translational degradation were defined: AMPK phosphorylates PROX1 at Ser79, recruiting CUL4-DDB1 E3 ligase for ubiquitin-dependent degradation that links energy sensing to BCAA catabolism and mTOR signaling; and lipophagy-derived acetyl-CoA sustains PROX1-dependent VEGFR3 expression, establishing a metabolic-transcriptional circuit in LECs.\",\n      \"evidence\": \"AMPK kinase assay with S79 mutagenesis and CUL4-DDB1 Co-IP; LEC-specific Atg5 KO with FAO and acetate rescue experiments\",\n      \"pmids\": [\"36433955\", \"35589749\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether AMPK-driven PROX1 degradation occurs in LECs or is liver-specific was not clarified\", \"How acetyl-CoA mechanistically sustains PROX1 transcriptional activity (histone acetylation vs. protein modification) was not fully resolved\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"A critical Prox1 enhancer element was dissected at nucleotide resolution: a GATA2-binding site within the enhancer is co-occupied by GATA2, FOXC2, NFATC1, and PROX1 itself, and its disruption causes lethal lymphatic defects and acquisition of haemogenic capacity by LECs, revealing that PROX1 autoregulation suppresses alternative blood-forming fates.\",\n      \"evidence\": \"5-nt enhancer deletion by genome editing in mice, ChIP for TF occupancy, RNA-seq, haematopoietic colony assays from mutant LECs\",\n      \"pmids\": [\"36697821\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether PROX1 binding to its own enhancer is direct or mediated via GATA2 was not resolved\", \"The haemogenic potential of adult (rather than embryonic) enhancer-mutant LECs was not tested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the structural basis of PROX1's context-dependent switch between transcriptional activation and repression, the full genome-wide direct target repertoire across different tissues, and how PROX1 integrates metabolic, mechanical, and signaling inputs to maintain cell identity throughout life.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No full-length PROX1 structure or structure of PROX1 bound to any cofactor\", \"Genome-wide direct target identification by CUT&RUN or similar in primary LECs at multiple developmental stages is lacking\", \"Mechanism by which PROX1 suppresses haemogenic fate in LECs is unknown beyond enhancer requirement\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [4, 6, 14, 26, 35, 44]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [0, 1, 2, 4, 7, 14, 16, 22, 35]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [6, 7, 14, 16, 35]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [0, 1, 2, 9, 10, 11, 19, 21, 23, 24, 39]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [4, 7, 14, 16, 17, 22, 35]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [7, 15, 16, 17, 33]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [10, 20, 28, 29, 31]},\n      {\"term_id\": \"R-HSA-4839726\", \"supporting_discovery_ids\": [14, 38]}\n    ],\n    \"complexes\": [\n      \"PROX1/COUP-TFII\",\n      \"PROX1/HDAC3/HNF4α\",\n      \"PROX1/LSD1/NuRD\",\n      \"PROX1/β-catenin/TCF7L1\"\n    ],\n    \"partners\": [\n      \"NR2F2\",\n      \"HDAC3\",\n      \"KDM1A\",\n      \"ETS2\",\n      \"ESRRA\",\n      \"CTNNB1\",\n      \"TCF7L1\",\n      \"FOXC2\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}