{"gene":"MEIS1","run_date":"2026-06-10T02:59:50","timeline":{"discoveries":[{"year":1995,"finding":"MEIS1 was identified as a novel homeobox gene (TALE family) activated by retroviral integration in 15% of BXH-2 myeloid leukemia tumors; its homeodomain is most closely related to PBX/exd family proteins, suggesting cooperative binding with HOX proteins.","method":"Retroviral insertion site cloning, Northern blot, cDNA cloning and sequence analysis","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct cloning of integration site and cDNA sequence with in vivo leukemia association, single lab but multiple methods","pmids":["7565694"],"is_preprint":false},{"year":1997,"finding":"MEIS1 (AbdB-like HOX group 9-13) proteins physically interact with HOXA9 and other AbdB-like HOX proteins (HOXA10, HOXA11, HOXD12, HOXB13) by forming heterodimeric DNA binding complexes on a composite MEIS1 site (TGACAG) + AbdB-like HOX site (TTTTACGAC); HOX proteins dramatically stabilize MEIS1-DNA complexes (much slower dissociation), whereas HOX proteins from other paralog groups do not interact with MEIS1.","method":"Electrophoretic mobility shift assay (EMSA), in vitro DNA binding, heterodimer complex formation","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstituted DNA binding with mutagenesis-level specificity across multiple paralog groups, replicated across multiple HOX proteins in one rigorous study","pmids":["9343407"],"is_preprint":false},{"year":1997,"finding":"MEIS1 and pKNOX1 dimerize with PBX1 on a TGATTGAC motif; the MEIS1/pKNOX1 interaction domain in PBX1 resides predominantly in a conserved N-terminal PBX domain that is deleted in the leukemic oncoprotein E2a-PBX1, and the Meis1-PBX interaction does not require the tryptophan residue N-terminal to the homeodomain (unlike HOX-PBX interactions), indicating a unique interaction mechanism.","method":"EMSA, DNA binding competition assay, domain mapping with deletion mutants, site-directed mutagenesis","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with mutagenesis defining the interaction surface, multiple orthogonal methods in one study","pmids":["9405651"],"is_preprint":false},{"year":1998,"finding":"MEIS1 and PBX1 cooperatively bind the cAMP-responsive sequence CRS1 from bovine CYP17, with purification of endogenous MEIS1-PBX1 complexes from adrenal cell nuclear extracts; the Meis1 N-terminal tryptophan is NOT required for this cooperative binding (unlike HOX-PBX), and the interaction is evolutionarily conserved with Drosophila exd and C. elegans ceh-20.","method":"CRS1 affinity chromatography purification, EMSA, site-directed mutagenesis, Western blot","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — biochemical purification of endogenous complex plus mutagenesis defining binding requirements, multiple orthogonal methods","pmids":["9525891"],"is_preprint":false},{"year":1999,"finding":"HOXA9, PBX2, and MEIS1 form trimeric complexes in myeloid leukemia cell nuclei: MEIS1 enhances in vitro HOXA9-PBX protein complex formation in the absence of DNA and forms a trimeric EMSA complex on a PBX-HOXA9 consensus site; co-immunoprecipitation of HOXA9 from myeloid cell extracts co-precipitates PBX2 and MEIS1; all three proteins are co-localized within nuclear speckles.","method":"EMSA, co-immunoprecipitation, in vitro DNA site selection, immunofluorescence co-localization","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — in vitro reconstitution of trimeric complex combined with endogenous co-IP and nuclear co-localization, multiple orthogonal methods in one study","pmids":["10082572"],"is_preprint":false},{"year":1999,"finding":"MEIS1 regulates proximal limb identity by promoting nuclear import of PBX1: Meis1 expression is restricted to proximal limb domains coinciding with nuclear PBX1 localization; ectopic Meis1 expression in chick and homothorax in Drosophila disrupts distal limb development and induces proximal-to-distal transformations.","method":"In situ hybridization, ectopic expression in chick embryos and Drosophila, immunolocalization of PBX1 nuclear translocation","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct manipulation experiments in two independent model organisms with defined molecular mechanism (PBX nuclear import), replicated across vertebrate and insect models","pmids":["10586884"],"is_preprint":false},{"year":1999,"finding":"PBX-MEIS1/PREP1 complexes bind DNA cooperatively with myogenic bHLH heterodimers (E2a-MyoD, myogenin, Mrf-4, Myf-5) through a conserved tryptophan motif N-terminal to the bHLH DNA-binding domain; in vivo, MyoD requires this tryptophan motif to remodel chromatin at and activate the Myogenin promoter.","method":"EMSA cooperative binding assay, mutagenesis, in vivo chromatin remodeling assay, transfection reporter assay","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with mutagenesis plus in vivo chromatin remodeling validation, multiple orthogonal methods","pmids":["10471746"],"is_preprint":false},{"year":2001,"finding":"MEIS1 genetically collaborates with both HOXA9 and HOXB3 (structurally divergent HOX genes) to generate acute myeloid leukemia; MEIS1 functions to accelerate leukemic onset while the HOX gene defines leukemia identity; PREP1 (despite sharing PBX nuclear retention activity with MEIS1) cannot substitute for MEIS1 in accelerating HOXA9-induced AML, indicating MEIS1 has transformation-specific functions beyond PBX nuclear localization.","method":"Retroviral bone marrow transduction/transplantation, genetic epistasis with PREP1 overexpression, in vivo leukemia latency assays","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis with multiple HOX partners, negative control with PREP1, replicated across two HOX gene contexts in vivo","pmids":["11113197"],"is_preprint":false},{"year":2004,"finding":"Meis1 is required in vivo for megakaryocyte production, definitive hematopoietic progenitor proliferation/self-renewal, vascular patterning (capillary formation), and normal eye development (lens and retina); Meis1-deficient embryos die by E14.5 with complete absence of megakaryocytes, hemorrhaging, and reduced colony-forming cells, and fail to radioprotect irradiated recipients.","method":"Meis1 knockout mouse generation, colony-forming assay, competitive repopulation, histology, radioprotection assay","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic loss-of-function with multiple specific phenotypic readouts across hematopoietic and vascular systems, confirmed by functional transplantation assays","pmids":["14713950"],"is_preprint":false},{"year":2004,"finding":"Enforced co-expression of HOXA9 and MEIS1 is sufficient to substitute for MLL-ENL fusion activity and immortalize hematopoietic cells; HOXA9+MEIS1 co-expression is required for continued proliferation and differentiation arrest in MLL-ENL-dependent cells.","method":"Inducible MLL-ENL-ERtm system, retroviral overexpression, 4-OHT withdrawal/differentiation assay, microarray","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — inducible genetic system with defined molecular replacement experiment, multiple orthogonal readouts","pmids":["14701735"],"is_preprint":false},{"year":2004,"finding":"MEIS1 overexpression strongly induces caspase-dependent apoptosis in multiple cell types; this requires a functional homeodomain and PBX-interaction motif; co-expression of HOXA9 suppresses MEIS1-induced apoptosis and confers protection from apoptotic stimuli, whereas PBX1-induced apoptosis is not rescued by HOXA9.","method":"Retroviral overexpression, caspase inhibitor assays, apoptosis assays, domain deletion mutants","journal":"Blood","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional mutagenesis with apoptosis readouts, single lab, two orthogonal methods","pmids":["15479723"],"is_preprint":false},{"year":2005,"finding":"Meis1 programs leukemic stem cell (cancer-initiating) potential in Hoxa9-immortalized myeloid progenitors; this requires PBX binding, DNA binding, and a conserved C-terminal domain function; Meis1 induces expression of FLT3 and CD34 (HSC-associated genes), and is the first example of a transcription factor oncoprotein (Meis1) establishing expression of a tyrosine kinase oncoprotein (FLT3).","method":"Retroviral overexpression, domain deletion mutagenesis, transplantation leukemia assay, gene expression analysis","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 / Strong — functional domain dissection with in vivo leukemia readout, multiple orthogonal methods, mechanistic target (FLT3) identified","pmids":["15755900"],"is_preprint":false},{"year":2005,"finding":"Meis1 is required for establishment of definitive hematopoiesis in the mouse embryo, including HSC specification in the AGM, formation of hematopoietic clusters in dorsal aorta/vitelline/umbilical arteries, and Runx1-expressing AGM mesenchymal cells; Meis1 mutants also show complete megakaryocyte lineage agenesis and vascular patterning defects.","method":"Meis1 gene inactivation in mice, fetal liver colony assay, immunohistochemistry, radioprotection assay","journal":"Developmental biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — targeted gene disruption with multiple specific hematopoietic and vascular readouts, functional transplantation data","pmids":["15882575"],"is_preprint":false},{"year":2006,"finding":"Meis1 leukemogenic activity requires co-occupancy of Meis1-Pbx and Hox-Pbx complexes on target gene promoters (including Flt3); a VP16-Meis1 fusion acts as an autonomous oncoprotein replacing both Meis1 C-terminal domain and Hoxa9 N-terminal domain functions, establishing that these domains cooperate in transcriptional activation of leukemia-associated target genes; ChIP confirmed co-occupancy of Hoxa9 and Meis1 on the Flt3 promoter.","method":"VP16/engrailed fusion proteins, retroviral overexpression, chromatin immunoprecipitation (ChIP), leukemia transplantation assay","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — ChIP demonstrating in vivo co-occupancy plus functional domain-swapping experiments with in vivo leukemia readout, multiple orthogonal methods","pmids":["16648484"],"is_preprint":false},{"year":2006,"finding":"Meis1 transforming activity requires three conserved domains: the Pbx interaction motif (PIM), the homeodomain, and the C-terminal region; PIM and homeodomain deletion mutants are individually non-functional but domain-swap complementation restores full oncogenic activity; VP16 transactivation domain can replace the C-terminal domain and induce spontaneous leukemia accompanied by endogenous Hoxa9/Hoxa7 activation, establishing that Hoxa gene activation is a key downstream event for Meis1 oncogenesis.","method":"Domain deletion/swap mutagenesis, retroviral bone marrow transplantation, gene expression analysis","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 / Strong — systematic domain mutagenesis with in vivo leukemia readout, complementation experiments, multiple constructs tested","pmids":["16469876"],"is_preprint":false},{"year":2007,"finding":"Meis1 is an essential and rate-limiting regulator of MLL leukemia stem cell (LSC) potential: Meis1 knockout/knockdown/dominant-negative abrogates MLL oncoprotein-induced AML; Meis1 quantitatively controls extent of self-renewal, differentiation arrest, cycling, and rate of in vivo LSC generation from myeloid progenitors; codependent on redundant contributions of Pbx2 and Pbx3.","method":"Conditional knockout, shRNA knockdown, dominant-negative genetic techniques, serial transplantation, LSC frequency analysis","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple genetic approaches (KO, KD, dominant-negative) with quantitative LSC frequency readouts, single lab but highly rigorous with orthogonal methods","pmids":["17942707"],"is_preprint":false},{"year":2008,"finding":"Meis1 leukemogenic activity with NUP98-HOXD13 requires the PBX-interaction domain, homeodomain, and C-terminal domain but not the N-terminal domain; the N-terminal domain is specifically required for Flt3 upregulation; ChIP revealed in vivo occupancy of MEIS1 on regulatory sequences of Trib2, Flt3, Dlk1, Ccl3, Ccl4, Pf4, and Rgs1; Trib2 overexpression complements ND13 to induce AML.","method":"Structure-function mutagenesis, retroviral bone marrow transplantation, ChIP, gene expression profiling","journal":"Experimental hematology","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — ChIP demonstrating direct in vivo target binding combined with systematic domain mutagenesis and in vivo leukemia assays","pmids":["18375036"],"is_preprint":false},{"year":2008,"finding":"meis1 acts as a positive cell cycle regulator in early zebrafish retinal progenitor cells by directly regulating cyclin D1 and c-myc transcription; meis1 morpholino knockdown causes G1-to-S phase transition delay and severely reduced eyes; forced maintenance of meis1 expression is incompatible with normal retinal differentiation.","method":"Morpholino knockdown in zebrafish, cell cycle analysis, gene expression analysis, mosaic expression assay","journal":"Development (Cambridge, England)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function with specific cell cycle and gene expression readouts, single organism but two orthogonal approaches","pmids":["18216175"],"is_preprint":false},{"year":2008,"finding":"In chick and mouse retina, Meis1 and Meis2 maintain retinal progenitor cells in a rapidly proliferating state; Meis-inactivating constructs impair RPC proliferation and cause microphthalmia; Meis protein knockdown reduces cyclin D1 (Ccnd1) expression in the eye primordium, and co-transfection of cyclin D1 partially rescues RPC proliferation.","method":"Transfection of dominant-negative Meis constructs, RNA interference, cyclin D1 rescue experiment, in chick and mouse","journal":"Development (Cambridge, England)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function with functional rescue experiment, replicated in two species (chick and mouse)","pmids":["18216174"],"is_preprint":false},{"year":2008,"finding":"MEIS1 directly regulates meis1 target gene Trib2, and Meis1 directly binds regulatory sequences of Trib1; Trib1 and Evi1 are key collaborators in Hoxa9/Meis1-induced AML (identified by retroviral insertional mutagenesis), with Trib1 acting as a novel myeloid oncogene that enhances ERK phosphorylation to inhibit apoptosis.","method":"Retroviral insertional mutagenesis screen, retroviral co-expression, AML transplantation assay","journal":"Blood","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo insertional mutagenesis screen with functional validation, single lab","pmids":["17227832"],"is_preprint":false},{"year":2008,"finding":"miR-155 directly targets the 3'-UTR of MEIS1 mRNA, downregulating MEIS1 expression; enforced miR-155 expression impairs megakaryocytic differentiation and proliferation of hematopoietic progenitor cells, with MEIS1 identified as a functional target.","method":"3'-UTR luciferase reporter assay, Western blot, overexpression of miR-155, MK differentiation assay","journal":"British journal of haematology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct 3'-UTR targeting confirmed by reporter assay plus functional phenotype, single lab","pmids":["18950466"],"is_preprint":false},{"year":2009,"finding":"HOXA9 indirectly regulates Meis1 expression through direct transcriptional activation of CREB1 and PKNOX1, whose protein products induce Meis1; HOXA9 does not directly bind Meis1 promoter/enhancer regions by ChIP analysis; forced CREB1 expression in Hoxa9-/- bone marrow increases Meis1 mRNA, establishing CREB1 as an intermediary in HOXA9-mediated Meis1 regulation.","method":"ChIP, quantitative RT-PCR, Hoxa9-/- mouse genetics, retroviral CREB1 overexpression, compound Meis1+/-/Hoxa9-/- mice","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — ChIP negative for direct binding combined with genetic and functional epistasis establishing indirect mechanism via CREB1, multiple orthogonal methods","pmids":["19620287"],"is_preprint":false},{"year":2009,"finding":"Ectopic Meis1 expression in the distal mouse limb bud causes proximal-to-distal patterning defects (proximal shift of limb identities and Hox gene expression domains); this P-D patterning function of Meis1 is independent of Pbx1, as Pbx1 deficiency does not modify the Msx2:Meis1 transgenic limb phenotype.","method":"Msx2:Meis1 transgenic mouse generation, in situ hybridization for Hox gene expression, genetic epistasis with Pbx1-/- mice","journal":"The International journal of developmental biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — transgenic gain-of-function with genetic epistasis, single lab","pmids":["19247936"],"is_preprint":false},{"year":2010,"finding":"Meis1 and Pbx act upstream of gata1 in the zebrafish erythropoietic transcription factor hierarchy: Meis1/Pbx-depleted embryos show severe loss of gata1 expression, reduced embryonic hemoglobin, and increased pu.1-positive myeloid cells; gata1 overexpression rescues hemoglobin expression in Pbx/Meis1-depleted embryos, placing Meis1/Pbx upstream of gata1.","method":"Morpholino knockdown in zebrafish, genetic epistasis by gata1 mRNA rescue, in situ hybridization","journal":"Developmental biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis by mRNA rescue in zebrafish, single lab, well-defined pathway placement","pmids":["20123093"],"is_preprint":false},{"year":2010,"finding":"Meis1 directly activates cyclin D3 transcription; M33-MEIS1 (transcriptional repressor form) impedes G1-to-S phase progression correlating with reduced cyclin D3 levels and inhibition of retinoblastoma (pRb) hyperphosphorylation; cyclin D3 overexpression partially rescues the G1 accumulation and growth suppression caused by M33-Meis1.","method":"Retroviral M33-MEIS1 expression, cell cycle analysis, Western blot for cyclin D3 and pRb, ChIP, cyclin D3 rescue experiments","journal":"Blood","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — direct target identification by ChIP combined with functional rescue experiment and mechanistic pathway (cyclin D3-pRb axis), multiple orthogonal methods","pmids":["20237320"],"is_preprint":false},{"year":2010,"finding":"Meis1 directly binds an enhancer element 35 kb upstream of the Gfi1 gene in early hematopoietic cells (fetal liver and dorsal aorta), acting as an upstream regulator of Gfi1 transcription in hematopoietic stem cell emergence.","method":"Locus-wide ChIP, transgenic enhancer assay in mice","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct ChIP binding on identified enhancer plus transgenic functional validation, single lab","pmids":["20516218"],"is_preprint":false},{"year":2011,"finding":"MEIS1 RNAi in C. elegans (MEIS1 orthologue) increases ferritin expression; the RLS-associated MEIS1 risk haplotype leads to increased expression of ferritin and DMT1 in RLS brain tissues; human cells under iron-deficient conditions show reduced MEIS1 expression, establishing a link between MEIS1 and iron homeostasis regulation.","method":"RNAi in C. elegans, gene expression analysis in human RLS brain tissue, iron deprivation experiment in human cells","journal":"Annals of neurology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional RNAi in model organism plus human tissue gene expression, single lab, two orthogonal approaches","pmids":["21710629"],"is_preprint":false},{"year":2011,"finding":"MN1-induced leukemogenesis requires the MEIS1/AbdB-like HOX protein complex: common myeloid progenitors (CMP) but not granulocyte-macrophage progenitors (GMP) are susceptible to MN1 transformation; MEIS1/AbdB-like HOX complementation of GMPs restores susceptibility; ChIP-seq identified common target genes of MN1 and MEIS1 with identical binding sites for a large proportion of chromatin targets.","method":"Progenitor-specific transformation assay, CMP vs GMP complementation, ChIP-seq, shRNA knockdown","journal":"Cancer cell","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — ChIP-seq genome-wide target mapping combined with functional complementation in defined cell populations and genetic knockdown with antileukemic readout","pmids":["21741595"],"is_preprint":false},{"year":2012,"finding":"Meis1 deletion leads to accumulation of reactive oxygen species (ROS) in HSCs, loss of quiescence, and decreased expression of hypoxia-response genes; ROS scavenging with N-acetyl cysteine or VHL knockdown (hypoxia pathway stabilization) reverses effects of Meis1 deletion on HSC maintenance, placing Meis1 in a pathway regulating oxidative metabolism in HSCs.","method":"Inducible Meis1 knockout mice, ROS measurement, colony formation assay, NAC rescue, VHL shRNA rescue, gene expression analysis","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO with two independent rescue strategies (pharmacological and genetic), defining pathway position, multiple orthogonal methods","pmids":["23091297"],"is_preprint":false},{"year":2013,"finding":"Meis1 is a critical transcriptional regulator of cardiomyocyte cell cycle arrest: Meis1 deletion in mouse cardiomyocytes extends the postnatal proliferative window and re-activates cardiomyocyte mitosis in the adult heart; Meis1 overexpression decreases neonatal myocyte proliferation and inhibits neonatal heart regeneration; Meis1 is required for transcriptional activation of CDK inhibitors p15, p16, and p21.","method":"Cardiomyocyte-specific Meis1 conditional KO, Meis1 overexpression, BrdU/pH3 proliferation assays, cardiac injury/regeneration assay, qRT-PCR/Western blot for CDK inhibitors","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal gain- and loss-of-function in vivo with defined molecular mechanism (p15/p16/p21 CDK inhibitors), multiple orthogonal methods, high-impact journal","pmids":["23594737"],"is_preprint":false},{"year":2013,"finding":"Gfi1b, together with co-factors LSD1 and CoREST, directly represses meis1 transcription in erythroid cells (but not megakaryocytes) by occupying distinct regions of the Meis1 promoter; Meis1 is substantially upregulated in gfi1b-/- fetal liver cells; SNAG-domain mutant or DNA-binding-deficient Gfi1b fails to repress the meis1 promoter reporter.","method":"ChIP, gene expression profiling of gfi1b-/- cells, LSD1 inhibitor treatment, promoter reporter transfection with mutagenesis","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — ChIP demonstrating direct promoter occupancy, genetic KO, functional mutagenesis of Gfi1b, rescue with LSD1 inhibition; multiple orthogonal methods","pmids":["23308270"],"is_preprint":false},{"year":2014,"finding":"MEIS1 functions as a novel androgen receptor (AR) co-repressor: MEIS1 inhibits AR transcriptional activity and reduces AR target gene (PSA) expression; MEIS1-AR protein-protein interaction was demonstrated by co-immunoprecipitation and GST pull-down; MEIS1 modulates AR nuclear translocation and recruitment to the PSA promoter androgen response element; MEIS1 promotes recruitment of NCoR and SMRT co-repressors in the presence of androgen.","method":"Co-immunoprecipitation, GST pull-down, luciferase reporter assay, ChIP at PSA promoter, nuclear translocation assay","journal":"Experimental cell research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal co-IP and GST pulldown confirming direct interaction, ChIP confirming promoter regulation, single lab","pmids":["25158280"],"is_preprint":false},{"year":2014,"finding":"Pbx3 stabilizes Meis1 protein by preventing its ubiquitination and proteasomal degradation: in the absence of Pbx3, Meis1 is highly unstable; deletion of the Pbx-binding domain on Meis1 or binding to Pbx3 prolongs Meis1 half-life; ubiquitin-proteasome inhibition blocks Meis1 degradation; Pbx3 overexpression also induces endogenous Meis1 transcription; Meis1/Pbx3 dimerization is required for high-affinity DNA/Hoxa9/Meis1/Pbx3 complex formation in vitro.","method":"Protein stability/half-life assays, ubiquitination assay, proteasome inhibitor treatment, domain deletion analysis, EMSA, retroviral overexpression, leukemia transplantation","journal":"Haematologica","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — biochemical ubiquitination assay plus half-life measurement plus in vitro DNA binding reconstitution plus in vivo leukemia assay, multiple orthogonal methods in one study","pmids":["25911551"],"is_preprint":false},{"year":2014,"finding":"PREP1 competitively heterodimerizes with PBX1 against MEIS1: MEIS1 alone transforms PREP1-deficient fibroblasts; PREP1 overexpression inhibits MEIS1 tumorigenicity; PREP1 post-translationally decreases MEIS1 stability by sequestering PBX1; MEIS1 interaction with DDX3X and DDX5 is essential for MEIS1 tumorigenesis and is disrupted when PREP1 reduces MEIS1 levels.","method":"Transformation assay in MEFs, Western blot protein stability, co-immunoprecipitation for DDX3X/DDX5 interaction, overexpression competition assay","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP for DDX3X/DDX5 binding, protein stability assay, functional transformation readout; single lab","pmids":["24578510"],"is_preprint":false},{"year":2014,"finding":"C/EBPα is a critical collaborator required for HOXA9/MEIS1-mediated leukemogenesis: loss of C/EBPα greatly improves survival in murine Hoxa9/Meis1 leukemia models; over 50% of Hoxa9 genome-wide binding sites are co-bound by C/EBPα; Hoxa9 represses the Cdkn2a/b locus in concert with C/EBPα to overcome G1 cell cycle arrest.","method":"ChIP-seq, conditional C/EBPα knockout, leukemia transplantation, cell proliferation assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — ChIP-seq genome-wide target co-occupancy combined with genetic KO and in vivo leukemia readout, multiple orthogonal methods","pmids":["24958854"],"is_preprint":false},{"year":2015,"finding":"MEIS1 regulates Pax6 transcription in cerebellar granule cell precursors (GCPs) by binding an upstream Pax6 sequence; the Meis1-Pax6 cascade upregulates Smad protein expression to increase BMP signaling, which promotes Atoh1 degradation in the inner external granule layer, driving GCP differentiation; Meis1 conditional KO in GC lineage results in smaller cerebella with disorganized lobules and ectopic Atoh1-positive GCPs.","method":"Conditional Meis1 knockout in GC lineage, in vitro promoter binding assays, BMP signaling analysis (Smad phosphorylation), cerebellar slice culture with BMP inhibitors, knockdown experiments","journal":"The Journal of neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — conditional KO with multiple mechanistic readouts (Pax6, Smad, Atoh1), single lab but orthogonal approaches","pmids":["29317485"],"is_preprint":false},{"year":2015,"finding":"During cardiac differentiation, MEIS1 and NKX2-5 bind overlapping sites in a mutually exclusive manner to regulate common target genes (exemplified by Popdc2); as cardiac progenitors differentiate, they sequentially experience high MEIS1 and then increasing NKX2-5, providing a spatial-temporal regulatory switch.","method":"ChIP, EMSA competitive binding assay, reporter assays, in situ hybridization during cardiac differentiation","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP and EMSA demonstrating mutually exclusive binding at overlapping sites, single lab but orthogonal methods","pmids":["26411676"],"is_preprint":false},{"year":2015,"finding":"Meis1 loss leads to increased oxidative stress, oxygen flux, and apoptosis in MLL-AF9 leukemia cells; MEIS1 directly occupies the hepatic leukemia factor (HLF) promoter by ChIP; HLF expression (or hypoxia) reverses oxidative stress and rescues leukemia development in Meis1-deficient cells, establishing a Meis1-HLF-oxidative stress axis.","method":"Inducible Meis1-KO in MLL-AF9 knockin model, ChIP for HLF promoter, oxidative stress measurement, HLF overexpression rescue, hypoxia rescue","journal":"Blood","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — direct ChIP target identification plus two independent rescue experiments (genetic and pharmacological) in both murine and human cells","pmids":["25740828"],"is_preprint":false},{"year":2015,"finding":"In the eye primordium, Meis1 binds Hox/Pbx-independent chromatin sites (distinct from its trunk binding preference for Hox-Pbx sites); Meis1 haploinsufficiency causes microphthalmic traits by dose-dependently regulating retinal proliferation/differentiation genes and components of the Notch signaling pathway and eye territory-specific transcription factors.","method":"ChIP-seq, RNA-seq, conditional Meis1 loss-of-function and functional rescue, Meis1-/- embryo analysis","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — ChIP-seq defining genome-wide binding landscape combined with RNA-seq and genetic rescue, multiple orthogonal methods in one study","pmids":["26253404"],"is_preprint":false},{"year":2016,"finding":"PBX3 and MEIS1 co-expression (without ectopic HOX gene) is sufficient to transform normal hematopoietic stem/progenitor cells and cause AML in vivo; disruption of the MEIS1-PBX3 binding interaction abolishes cell transformation and HOX gene upregulation; PBX3/MEIS1 (but not HOXA9/MEIS1) recapitulates the MLL-fusion core transcriptome.","method":"Retroviral co-expression, murine AML transplantation, PBX3-MEIS1 interaction-disrupting mutations, gene expression profiling","journal":"Cancer research","confidence":"High","confidence_rationale":"Tier 2 / Strong — sufficiency demonstrated in vivo with interaction-disrupting mutation showing requirement for direct binding, multiple readouts","pmids":["26747896"],"is_preprint":false},{"year":2016,"finding":"MEIS1 directly activates synaptotagmin-like 1 (SYTL1/Slp1) transcription (global MEIS1 ChIP-seq and gene expression in MEIS1-deficient cells); SYTL1 restores cell migration and engraftment in MEIS1-deficient leukemia cells; SYTL1 promotes CXCR4-dependent cell migration by controlling intracellular trafficking of CXCR4, revealing a MEIS1→SYTL1→CXCL12/CXCR4 pathway for leukemic homing.","method":"ChIP-seq, gene expression profiling of Meis1-deficient cells, SYTL1 rescue experiment, CXCR4 trafficking assay, in vivo homing/engraftment assay","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — ChIP-seq direct target identification, genetic rescue, and mechanistic trafficking assay defining pathway, multiple orthogonal methods","pmids":["27018596"],"is_preprint":false},{"year":2017,"finding":"In Hoxa9/Meis1-driven AML, Meis1 increases Syk protein expression and activity through a feedback loop: Meis1 indirectly regulates miR-146a expression through transcription factor PU.1, and miR-146a directly targets Syk; in the context of Hoxa9, Syk signaling induces Meis1, creating a regulatory loop; Syk inhibition disrupts this loop and prolongs survival of mice with Hoxa9/Meis1 leukemia.","method":"Phosphoproteomics, Western blot, miR-146a target validation, PU.1 ChIP, Syk inhibitor treatment in vivo","journal":"Cancer cell","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — phosphoproteomic discovery combined with ChIP, miRNA target validation, and in vivo therapeutic experiment, multiple orthogonal methods","pmids":["28399410"],"is_preprint":false},{"year":2018,"finding":"PPM1K (a mitochondrial Ser/Thr phosphatase that promotes BCAA catabolism) maintains MEIS1 and p21 protein levels by decreasing their ubiquitination-mediated degradation controlled by the E3 ubiquitin ligase CDC20; PPM1K deficiency leads to decreased MEIS1/p21 signaling, reduced HSC glycolysis and quiescence.","method":"BCAA fluorescent sensor, PPM1K KO mouse, MEIS1/p21 ubiquitination assay, CDC20 interaction studies, leukemia model","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ubiquitination assay identifying specific E3 ligase (CDC20), genetic KO with defined signaling readouts, single lab","pmids":["29719258"],"is_preprint":false},{"year":2018,"finding":"MEIS1 controls human pluripotent stem cell hematopoietic differentiation by targeting TAL1 (which mediates HEP specification) and FLI1 (which is required for megakaryopoiesis); MEIS1 is vital for specification of APLNR+ mesoderm progenitors to hemogenic endothelial progenitors.","method":"hPSC differentiation, MEIS1 overexpression/knockdown, downstream target identification (TAL1, FLI1), flow cytometry","journal":"Stem cell reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — gain/loss-of-function in hPSC system with downstream target identification, single lab","pmids":["29358086"],"is_preprint":false},{"year":2018,"finding":"MEIS1 directly binds and positively regulates the SKOR1 promoter at two specific sites, and this regulation is modified by an RLS-associated SNP in the SKOR1 promoter region, establishing a direct molecular link between two RLS-associated genes.","method":"Luciferase reporter assay, ChIP, SNP-dependent promoter activity assay","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP plus reporter assay with allele-specific SNP effect, single lab","pmids":["30111810"],"is_preprint":false},{"year":2018,"finding":"PAF1c (through subunit CDC73) interacts with SETDB1 (H3K9 methyltransferase); stabilization of PAF1c-SETDB1 interaction reduces transcription of Meis1 and Hoxa9 by increasing H3K9me3 at their promoters in AML cells.","method":"Proteomics (CDC73 interactome), ChIP for H3K9me3 at Meis1/Hoxa9 promoters, AML cell growth assay","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — proteomics-identified interaction validated by ChIP demonstrating H3K9me3 at specific loci, single lab","pmids":["29774127"],"is_preprint":false},{"year":2019,"finding":"MEIS1 suppression by siRNA in fetal cardiomyocytes increases maximal oxygen consumption and mitochondrial activity while decreasing glycolytic gene expression, establishing MEIS1 as a regulator of the cardiomyocyte metabolic program (glycolysis vs. oxidative phosphorylation).","method":"siRNA knockdown, Seahorse metabolic flux analysis, MitoTracker staining, gene expression analysis","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct siRNA knockdown with quantitative metabolic readout (oxygen consumption rate), single lab","pmids":["30884246"],"is_preprint":false},{"year":2022,"finding":"MEIS1 transcription is epigenetically suppressed by EZH2-DNMT3a recruited to the MEIS1 promoter with the aid of lncRNA ELFN1-AS1; MEIS1 suppression following this axis increases FEN1 expression, which mediates oxaliplatin resistance in colorectal cancer.","method":"ChIP for EZH2/DNMT3a at MEIS1 promoter, ELFN1-AS1 ASO knockdown, EZH2 inhibitor GSK126, FEN1 expression analysis, in vivo tumor growth","journal":"Signal transduction and targeted therapy","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP confirming promoter occupancy plus functional rescue experiments with ASO and inhibitor, single lab","pmids":["35351858"],"is_preprint":false}],"current_model":"MEIS1 is a TALE-class homeodomain transcription factor that forms heterodimeric and trimeric complexes with PBX and HOX proteins (especially AbdB-like HOX group 9–13) on composite DNA binding sites to activate target gene transcription; it promotes hematopoietic stem cell quiescence and self-renewal by restricting reactive oxygen species via an HLF-dependent hypoxia pathway, drives leukemogenesis by directly activating cyclin D3, FLT3, SYTL1, and HLF while requiring its PBX-interaction, homeodomain, and C-terminal transactivation domains, and controls cardiomyocyte cell cycle arrest through transcriptional activation of CDK inhibitors p15, p16, and p21; its protein stability is regulated by CDC20-mediated ubiquitination (countered by PPM1K) and by competitive PBX1 binding with PREP1/PKNOX1."},"narrative":{"mechanistic_narrative":"MEIS1 is a TALE-class homeodomain transcription factor that operates as a combinatorial DNA-binding partner, dimerizing with PBX proteins and forming heterodimeric and trimeric complexes with AbdB-like HOX group 9–13 proteins (HOXA9, HOXA10, HOXA11, HOXD12, HOXB13) on composite recognition sites to activate target gene transcription [PMID:9343407, PMID:9405651, PMID:10082572]. Cooperative assembly on DNA stabilizes the HOX-MEIS1 complex and, distinct from HOX-PBX interactions, the MEIS1-PBX interface does not require the conserved N-terminal tryptophan motif [PMID:9343407, PMID:9405651, PMID:9525891]; MEIS1 also promotes nuclear import of PBX1 to control proximal limb identity, a patterning function that can be PBX1-independent in some contexts [PMID:10586884, PMID:19247936]. In hematopoiesis MEIS1 is essential for definitive HSC specification in the AGM, megakaryocyte production, and vascular patterning, acting upstream of regulators including Gfi1 and gata1 [PMID:14713950, PMID:15882575, PMID:20123093, PMID:20516218], and it sustains HSC quiescence by restricting reactive oxygen species through a directly activated HLF/hypoxia-response axis [PMID:23091297, PMID:25740828]. MEIS1 is a rate-limiting driver of HOX- and MLL-rearranged acute myeloid leukemia, where it programs leukemic stem cell self-renewal and differentiation arrest through cooperatively assembled MEIS1-PBX/HOX-PBX complexes that co-occupy and activate target promoters; its transforming activity requires the PBX-interaction motif, the homeodomain, and a C-terminal transactivation domain, and direct targets include FLT3, cyclin D3, SYTL1, Trib2, and HLF [PMID:11113197, PMID:14701735, PMID:15755900, PMID:16648484, PMID:16469876, PMID:17942707, PMID:20237320, PMID:27018596]. PBX3/MEIS1 co-expression alone is sufficient to transform hematopoietic progenitors and induce AML [PMID:26747896]. Beyond hematopoiesis, MEIS1 enforces cardiomyocyte cell-cycle arrest by transcriptionally activating the CDK inhibitors p15, p16, and p21 and shapes the cardiomyocyte glycolytic-versus-oxidative metabolic program [PMID:23594737, PMID:30884246], and it controls retinal and cerebellar progenitor proliferation and differentiation through cyclin D1/D3, c-myc, and a Pax6-BMP-Atoh1 cascade [PMID:18216175, PMID:18216174, PMID:29317485, PMID:26253404]. MEIS1 protein levels are tuned post-translationally: PBX3 binding stabilizes MEIS1 against ubiquitin-proteasome degradation, CDC20-mediated ubiquitination (countered by PPM1K) destabilizes it, and PREP1/PKNOX1 lowers MEIS1 stability by competitively sequestering PBX1 [PMID:25911551, PMID:24578510, PMID:29719258].","teleology":[{"year":1995,"claim":"Established MEIS1 as a homeobox oncogene by identifying it as a recurrent retroviral integration target in myeloid leukemia and placing it in the TALE family related to PBX/exd.","evidence":"Retroviral insertion site cloning and cDNA sequencing in BXH-2 myeloid leukemias","pmids":["7565694"],"confidence":"Medium","gaps":["No demonstration of DNA-binding partners or target genes at this stage","Leukemogenic mechanism inferred only from integration frequency"]},{"year":1997,"claim":"Defined MEIS1's biochemical mode of action as a partner-selective DNA-binding factor that heterodimerizes specifically with AbdB-like HOX proteins and with PBX1 through a unique interaction surface.","evidence":"EMSA with composite sites, paralog-specificity tests, and domain-mapping mutagenesis in vitro","pmids":["9343407","9405651"],"confidence":"High","gaps":["In vitro binding did not establish in vivo target genes","Functional consequence of complex formation on transcription not yet shown"]},{"year":1998,"claim":"Confirmed that endogenous MEIS1-PBX1 complexes form on a physiological target sequence and that the cooperative binding mechanism is evolutionarily conserved.","evidence":"Affinity purification of endogenous complexes from adrenal nuclear extracts plus EMSA and mutagenesis on the CYP17 CRS1 element","pmids":["9525891"],"confidence":"High","gaps":["Direct transcriptional output at the endogenous CYP17 locus not measured","Single tissue context"]},{"year":1999,"claim":"Showed MEIS1 nucleates trimeric HOX-PBX-MEIS1 complexes in leukemia nuclei and controls PBX1 nuclear import to direct limb patterning, linking complex assembly to in vivo developmental and oncogenic function.","evidence":"Co-IP and nuclear co-localization in myeloid cells; ectopic expression in chick and Drosophila with PBX1 immunolocalization","pmids":["10082572","10586884"],"confidence":"High","gaps":["Target genes downstream of the trimeric complex not yet identified","Mechanism coupling nuclear import to transcription incomplete"]},{"year":1999,"claim":"Broadened MEIS1's partner repertoire by showing PBX-MEIS1/PREP1 complexes cooperate with myogenic bHLH factors to remodel chromatin and activate differentiation genes.","evidence":"Cooperative EMSA, tryptophan-motif mutagenesis, and in vivo chromatin remodeling at the Myogenin promoter","pmids":["10471746"],"confidence":"High","gaps":["Direct MEIS1 occupancy at myogenic promoters in vivo not shown","Relative contribution of MEIS1 versus PREP1 not separated"]},{"year":2001,"claim":"Demonstrated MEIS1 has transformation-specific oncogenic function beyond PBX nuclear localization by showing it accelerates HOX-induced AML where the redundant PBX-retention factor PREP1 cannot.","evidence":"Retroviral bone marrow transduction/transplantation with HOXA9/HOXB3 and PREP1 substitution controls","pmids":["11113197"],"confidence":"High","gaps":["Molecular basis of the transformation-specific activity unresolved","Direct leukemic target genes not yet defined"]},{"year":2004,"claim":"Established MEIS1 as required in vivo for definitive hematopoiesis, megakaryopoiesis, and vascular patterning, and showed HOXA9+MEIS1 co-expression is sufficient to replace an MLL fusion for immortalization.","evidence":"Meis1 knockout mice with transplantation/colony assays; inducible MLL-ENL replacement system","pmids":["14713950","14701735"],"confidence":"High","gaps":["Embryonic lethality limits adult HSC analysis in constitutive KO","Direct transcriptional targets driving immortalization not yet mapped"]},{"year":2004,"claim":"Revealed MEIS1 overexpression triggers caspase-dependent apoptosis that HOXA9 co-expression suppresses, linking complex partnership to cell-survival output and requiring homeodomain and PBX-interaction motifs.","evidence":"Retroviral overexpression with caspase inhibitors and domain-deletion mutants","pmids":["15479723"],"confidence":"Medium","gaps":["Pro-apoptotic target genes not identified","Single-lab functional study"]},{"year":2005,"claim":"Defined MEIS1 as a programmer of leukemic stem cell potential and identified its first direct kinase target, showing a transcription-factor oncoprotein establishing tyrosine-kinase oncoprotein FLT3 expression.","evidence":"Domain-deletion mutagenesis with in vivo leukemia transplantation and gene expression analysis; AGM/embryo gene inactivation studies","pmids":["15755900","15882575"],"confidence":"High","gaps":["Direct promoter occupancy of FLT3 not yet shown at this stage","C-terminal domain mechanism undefined"]},{"year":2006,"claim":"Established that MEIS1 leukemogenesis requires co-occupancy of MEIS1-PBX and HOX-PBX complexes on target promoters and dissected the three essential domains needed for transformation.","evidence":"ChIP at the Flt3 promoter, VP16/engrailed domain-swap fusions, and systematic domain mutagenesis with leukemia transplantation","pmids":["16648484","16469876"],"confidence":"High","gaps":["Full set of co-occupied target genes not yet genome-wide","Hoxa autoactivation mechanism not detailed"]},{"year":2007,"claim":"Established MEIS1 as an essential, rate-limiting and dose-dependent regulator of MLL leukemia stem cell self-renewal, codependent on PBX2/PBX3.","evidence":"Conditional KO, shRNA, and dominant-negative approaches with serial transplantation and LSC frequency analysis","pmids":["17942707"],"confidence":"High","gaps":["Quantitative target genes mediating dose effect not enumerated","Relative PBX2 versus PBX3 contributions not separated"]},{"year":2008,"claim":"Expanded the direct MEIS1 leukemic target set by ChIP and identified domain-specific requirements, while linking MEIS1 to additional roles in cell-cycle control of progenitors and to its own regulation by miR-155.","evidence":"ChIP across multiple loci with NUP98-HOXD13 model; zebrafish/chick/mouse retinal loss-of-function with cyclin D1/D3 and c-myc readouts; miR-155 3'-UTR reporter assays","pmids":["18375036","18216175","18216174","18950466","17227832"],"confidence":"High","gaps":["N-terminal domain mechanism for Flt3 upregulation undefined","Whether retinal and leukemic target programs share regulatory logic unknown"]},{"year":2009,"claim":"Clarified the regulatory hierarchy by showing HOXA9 induces Meis1 only indirectly through direct activation of CREB1 and PKNOX1 rather than direct promoter binding.","evidence":"ChIP (negative for direct binding), Hoxa9-/- genetics, and CREB1 rescue in bone marrow","pmids":["19620287"],"confidence":"High","gaps":["Additional upstream inputs into Meis1 transcription not exhaustively mapped"]},{"year":2010,"claim":"Connected MEIS1 transcriptional control directly to cell-cycle progression and to early hematopoietic and erythroid programs through specific target loci.","evidence":"ChIP and rescue at cyclin D3 (pRb axis); Gfi1 enhancer ChIP/transgenic assay; zebrafish epistasis placing Meis1/Pbx upstream of gata1","pmids":["20237320","20516218","20123093"],"confidence":"High","gaps":["Combined contribution of these targets to a unified program not integrated","Cardiac and metabolic cell-cycle roles not yet examined"]},{"year":2011,"claim":"Linked MEIS1 to iron homeostasis and restless legs syndrome biology and demonstrated genome-wide MEIS1/HOX target overlap underlying MN1-driven leukemia susceptibility.","evidence":"C. elegans RNAi and human RLS brain expression for ferritin/DMT1; ChIP-seq and progenitor complementation in MN1 leukemia","pmids":["21710629","21741595"],"confidence":"High","gaps":["Mechanism connecting MEIS1 to ferritin regulation undefined","Whether iron regulation reflects direct transcriptional targets unknown"]},{"year":2013,"claim":"Established MEIS1 as a transcriptional enforcer of cardiomyocyte cell-cycle arrest and revealed a repressive regulatory circuit controlling its own expression in erythroid cells.","evidence":"Reciprocal cardiomyocyte gain/loss-of-function in vivo with p15/p16/p21 readouts; Gfi1b/LSD1/CoREST ChIP and reporter mutagenesis on the Meis1 promoter","pmids":["23594737","23308270"],"confidence":"High","gaps":["Direct MEIS1 occupancy at CDK-inhibitor loci not fully resolved","How the same factor activates CDK inhibitors in heart yet drives proliferation elsewhere unexplained"]},{"year":2014,"claim":"Defined post-translational and competitive control of MEIS1 protein levels and uncovered new physical partners and a co-repressor function for nuclear receptor signaling.","evidence":"Pbx3 stabilization via ubiquitination/half-life assays and EMSA; PREP1 competition for PBX1 with DDX3X/DDX5 co-IP; MEIS1-AR co-IP/GST pull-down with PSA ChIP; C/EBPalpha co-occupancy ChIP-seq with KO","pmids":["25911551","24578510","25158280","24958854"],"confidence":"High","gaps":["The E3 ligase ubiquitinating MEIS1 not identified in these studies","Functional role of DDX3X/DDX5 binding in transcription not detailed"]},{"year":2015,"claim":"Mapped genome-wide MEIS1 binding in developmental contexts, revealing HOX/PBX-independent target sites, mutually exclusive switching with NKX2-5 in heart, a Pax6-BMP-Atoh1 cerebellar cascade, and a direct HLF-oxidative stress axis in leukemia.","evidence":"ChIP-seq/RNA-seq in eye primordium; ChIP/EMSA competition with NKX2-5; conditional KO with BMP/Atoh1 readouts in cerebellum; HLF promoter ChIP with HLF and hypoxia rescue in MLL-AF9 cells","pmids":["26253404","26411676","29317485","25740828"],"confidence":"High","gaps":["Determinants of context-specific HOX-independent binding undefined","How redox control integrates with self-renewal program incomplete"]},{"year":2016,"claim":"Identified a direct MEIS1 target driving leukemic homing and showed PBX3/MEIS1 alone is sufficient to transform hematopoietic cells without ectopic HOX.","evidence":"ChIP-seq and rescue defining MEIS1->SYTL1->CXCR4 trafficking pathway; retroviral PBX3/MEIS1 co-expression with interaction-disrupting mutants and AML transplantation","pmids":["27018596","26747896"],"confidence":"High","gaps":["Source of HOX gene upregulation under PBX3/MEIS1 not fully resolved","Whether SYTL1 contributes outside leukemia unknown"]},{"year":2017,"claim":"Revealed a Syk-Meis1 feedback loop in HOXA9/Meis1 AML operating through PU.1 and miR-146a, providing a therapeutic vulnerability.","evidence":"Phosphoproteomics, PU.1 ChIP, miR-146a target validation, and in vivo Syk inhibition","pmids":["28399410"],"confidence":"High","gaps":["Direct versus indirect steps of the loop not fully separated","Generalizability beyond HOXA9/Meis1 context untested"]},{"year":2018,"claim":"Extended post-translational regulation by linking BCAA metabolism via PPM1K to CDC20-dependent MEIS1/p21 ubiquitination, and detailed MEIS1's role in human pluripotent stem cell hematopoietic specification and RLS gene regulation.","evidence":"PPM1K KO mouse with MEIS1/p21 ubiquitination and CDC20 studies; hPSC differentiation targeting TAL1/FLI1; SKOR1 promoter ChIP/reporter with RLS SNP; PAF1c-SETDB1 H3K9me3 ChIP at Meis1/Hoxa9","pmids":["29719258","29358086","30111810","29774127"],"confidence":"Medium","gaps":["Direct CDC20-MEIS1 enzymatic relationship requires further biochemical dissection","Single-lab studies for several mechanisms"]},{"year":2019,"claim":"Established MEIS1 as a regulator of cardiomyocyte metabolic identity, controlling the balance between glycolysis and oxidative phosphorylation.","evidence":"siRNA knockdown with Seahorse metabolic flux and MitoTracker in fetal cardiomyocytes","pmids":["30884246"],"confidence":"Medium","gaps":["Direct metabolic-gene targets not identified","Single-lab study"]},{"year":2022,"claim":"Showed MEIS1 expression is epigenetically silenced by an EZH2-DNMT3a axis guided by lncRNA ELFN1-AS1, with downstream FEN1-mediated chemoresistance in colorectal cancer.","evidence":"ChIP at MEIS1 promoter, ELFN1-AS1 ASO knockdown, EZH2 inhibition, and in vivo tumor growth","pmids":["35351858"],"confidence":"Medium","gaps":["Direct MEIS1 regulation of FEN1 versus indirect not fully separated","Single-lab study in one cancer type"]},{"year":null,"claim":"It remains unresolved how MEIS1 selects context-specific (HOX-dependent versus HOX-independent) genomic binding sites and how the same factor switches between promoting proliferation/self-renewal in stem and leukemic cells and enforcing cell-cycle arrest in cardiomyocytes.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model linking partner choice to opposing cell-cycle outputs","Structural basis of context-dependent site selection unknown","Direct enzymatic mechanism of MEIS1 ubiquitination not reconstituted"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[1,13,16,24,29,37,40,31]},{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[1,2,3,4,25,38]},{"term_id":"GO:0140097","term_label":"catalytic activity, acting on DNA","supporting_discovery_ids":[1,2,3]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[4,5]},{"term_id":"GO:0005654","term_label":"nucleoplasm","supporting_discovery_ids":[4]}],"pathway":[{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[13,16,24,29,37,40]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[7,9,11,15,39,47]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[5,8,12,17,18,35,38,43]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[24,29,17,18]}],"complexes":["MEIS1-PBX heterodimer","HOX-PBX-MEIS1 trimeric complex"],"partners":["PBX1","PBX3","HOXA9","PKNOX1","AR","DDX3X","DDX5","NKX2-5"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O00470","full_name":"Homeobox protein Meis1","aliases":[],"length_aa":390,"mass_kda":43.0,"function":"Acts as a transcriptional regulator of PAX6. Acts as a transcriptional activator of PF4 in complex with PBX1 or PBX2. Required for hematopoiesis, megakaryocyte lineage development and vascular patterning. May function as a cofactor for HOXA7 and HOXA9 in the induction of myeloid leukemias","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/O00470/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/MEIS1","classification":"Not Classified","n_dependent_lines":20,"n_total_lines":1208,"dependency_fraction":0.016556291390728478},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/MEIS1","total_profiled":1310},"omim":[{"mim_id":"619443","title":"MEIS HOMEOBOX 3; MEIS3","url":"https://www.omim.org/entry/619443"},{"mim_id":"618774","title":"CEBALID SYNDROME; CEBALID","url":"https://www.omim.org/entry/618774"},{"mim_id":"612853","title":"RESTLESS LEGS SYNDROME, SUSCEPTIBILITY TO, 7; RLS7","url":"https://www.omim.org/entry/612853"},{"mim_id":"611185","title":"RESTLESS LEGS SYNDROME, SUSCEPTIBILITY TO, 6; RLS6","url":"https://www.omim.org/entry/611185"},{"mim_id":"607108","title":"PAIRED BOX GENE 6; PAX6","url":"https://www.omim.org/entry/607108"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/MEIS1"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"O00470","domains":[{"cath_id":"1.10.10.60","chopping":"280-339","consensus_level":"high","plddt":93.0375,"start":280,"end":339},{"cath_id":"1.20.58","chopping":"68-178","consensus_level":"high","plddt":83.5297,"start":68,"end":178}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O00470","model_url":"https://alphafold.ebi.ac.uk/files/AF-O00470-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O00470-F1-predicted_aligned_error_v6.png","plddt_mean":65.31},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=MEIS1","jax_strain_url":"https://www.jax.org/strain/search?query=MEIS1"},"sequence":{"accession":"O00470","fasta_url":"https://rest.uniprot.org/uniprotkb/O00470.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O00470/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O00470"}},"corpus_meta":[{"pmid":"23594737","id":"PMC_23594737","title":"Meis1 regulates postnatal cardiomyocyte cell cycle arrest.","date":"2013","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/23594737","citation_count":465,"is_preprint":false},{"pmid":"14701735","id":"PMC_14701735","title":"Hoxa9 and Meis1 are key targets for MLL-ENL-mediated cellular immortalization.","date":"2004","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/14701735","citation_count":273,"is_preprint":false},{"pmid":"7565694","id":"PMC_7565694","title":"Meis1, a PBX1-related homeobox gene involved in myeloid leukemia in BXH-2 mice.","date":"1995","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/7565694","citation_count":272,"is_preprint":false},{"pmid":"11113197","id":"PMC_11113197","title":"Defining roles for HOX and MEIS1 genes in induction of acute myeloid leukemia.","date":"2001","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/11113197","citation_count":248,"is_preprint":false},{"pmid":"14713950","id":"PMC_14713950","title":"Hematopoietic, angiogenic and eye defects in Meis1 mutant animals.","date":"2004","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/14713950","citation_count":242,"is_preprint":false},{"pmid":"10586884","id":"PMC_10586884","title":"Conserved regulation of proximodistal limb axis development by Meis1/Hth.","date":"1999","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/10586884","citation_count":236,"is_preprint":false},{"pmid":"17942707","id":"PMC_17942707","title":"Meis1 is an essential and rate-limiting regulator of MLL leukemia stem cell potential.","date":"2007","source":"Genes & development","url":"https://pubmed.ncbi.nlm.nih.gov/17942707","citation_count":228,"is_preprint":false},{"pmid":"9343407","id":"PMC_9343407","title":"AbdB-like Hox proteins stabilize DNA binding by the Meis1 homeodomain proteins.","date":"1997","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/9343407","citation_count":226,"is_preprint":false},{"pmid":"11823037","id":"PMC_11823037","title":"Differential expression of Hox, Meis1, and Pbx1 genes in primitive cells throughout murine hematopoietic ontogeny.","date":"2002","source":"Experimental hematology","url":"https://pubmed.ncbi.nlm.nih.gov/11823037","citation_count":225,"is_preprint":false},{"pmid":"10082572","id":"PMC_10082572","title":"HOXA9 forms triple complexes with PBX2 and MEIS1 in myeloid cells.","date":"1999","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/10082572","citation_count":206,"is_preprint":false},{"pmid":"10602420","id":"PMC_10602420","title":"Frequent co-expression of the HOXA9 and MEIS1 homeobox genes in human myeloid 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Nucleic acids","url":"https://pubmed.ncbi.nlm.nih.gov/33473327","citation_count":21,"is_preprint":false},{"pmid":"31623926","id":"PMC_31623926","title":"Homeobox gene Meis1 modulates cardiovascular regeneration.","date":"2019","source":"Seminars in cell & developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/31623926","citation_count":19,"is_preprint":false},{"pmid":"34318904","id":"PMC_34318904","title":"MEIS1 and its potential as a cancer therapeutic target (Review).","date":"2021","source":"International journal of molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/34318904","citation_count":19,"is_preprint":false},{"pmid":"23554940","id":"PMC_23554940","title":"Zebrafish hoxd4a acts upstream of meis1.1 to direct vasculogenesis, angiogenesis and hematopoiesis.","date":"2013","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/23554940","citation_count":19,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":51120,"output_tokens":12413,"usd":0.169777,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":23714,"output_tokens":7468,"usd":0.152635,"stage2_stop_reason":"end_turn"},"total_usd":0.322412,"stage1_batch_id":"msgbatch_01BbTCMyrRPyhtEq6b1MdwCN","stage2_batch_id":"msgbatch_011dEed5bbxYvTAaQWKJevxu","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1995,\n      \"finding\": \"MEIS1 was identified as a novel homeobox gene (TALE family) activated by retroviral integration in 15% of BXH-2 myeloid leukemia tumors; its homeodomain is most closely related to PBX/exd family proteins, suggesting cooperative binding with HOX proteins.\",\n      \"method\": \"Retroviral insertion site cloning, Northern blot, cDNA cloning and sequence analysis\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct cloning of integration site and cDNA sequence with in vivo leukemia association, single lab but multiple methods\",\n      \"pmids\": [\"7565694\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"MEIS1 (AbdB-like HOX group 9-13) proteins physically interact with HOXA9 and other AbdB-like HOX proteins (HOXA10, HOXA11, HOXD12, HOXB13) by forming heterodimeric DNA binding complexes on a composite MEIS1 site (TGACAG) + AbdB-like HOX site (TTTTACGAC); HOX proteins dramatically stabilize MEIS1-DNA complexes (much slower dissociation), whereas HOX proteins from other paralog groups do not interact with MEIS1.\",\n      \"method\": \"Electrophoretic mobility shift assay (EMSA), in vitro DNA binding, heterodimer complex formation\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstituted DNA binding with mutagenesis-level specificity across multiple paralog groups, replicated across multiple HOX proteins in one rigorous study\",\n      \"pmids\": [\"9343407\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"MEIS1 and pKNOX1 dimerize with PBX1 on a TGATTGAC motif; the MEIS1/pKNOX1 interaction domain in PBX1 resides predominantly in a conserved N-terminal PBX domain that is deleted in the leukemic oncoprotein E2a-PBX1, and the Meis1-PBX interaction does not require the tryptophan residue N-terminal to the homeodomain (unlike HOX-PBX interactions), indicating a unique interaction mechanism.\",\n      \"method\": \"EMSA, DNA binding competition assay, domain mapping with deletion mutants, site-directed mutagenesis\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with mutagenesis defining the interaction surface, multiple orthogonal methods in one study\",\n      \"pmids\": [\"9405651\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"MEIS1 and PBX1 cooperatively bind the cAMP-responsive sequence CRS1 from bovine CYP17, with purification of endogenous MEIS1-PBX1 complexes from adrenal cell nuclear extracts; the Meis1 N-terminal tryptophan is NOT required for this cooperative binding (unlike HOX-PBX), and the interaction is evolutionarily conserved with Drosophila exd and C. elegans ceh-20.\",\n      \"method\": \"CRS1 affinity chromatography purification, EMSA, site-directed mutagenesis, Western blot\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — biochemical purification of endogenous complex plus mutagenesis defining binding requirements, multiple orthogonal methods\",\n      \"pmids\": [\"9525891\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"HOXA9, PBX2, and MEIS1 form trimeric complexes in myeloid leukemia cell nuclei: MEIS1 enhances in vitro HOXA9-PBX protein complex formation in the absence of DNA and forms a trimeric EMSA complex on a PBX-HOXA9 consensus site; co-immunoprecipitation of HOXA9 from myeloid cell extracts co-precipitates PBX2 and MEIS1; all three proteins are co-localized within nuclear speckles.\",\n      \"method\": \"EMSA, co-immunoprecipitation, in vitro DNA site selection, immunofluorescence co-localization\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — in vitro reconstitution of trimeric complex combined with endogenous co-IP and nuclear co-localization, multiple orthogonal methods in one study\",\n      \"pmids\": [\"10082572\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"MEIS1 regulates proximal limb identity by promoting nuclear import of PBX1: Meis1 expression is restricted to proximal limb domains coinciding with nuclear PBX1 localization; ectopic Meis1 expression in chick and homothorax in Drosophila disrupts distal limb development and induces proximal-to-distal transformations.\",\n      \"method\": \"In situ hybridization, ectopic expression in chick embryos and Drosophila, immunolocalization of PBX1 nuclear translocation\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct manipulation experiments in two independent model organisms with defined molecular mechanism (PBX nuclear import), replicated across vertebrate and insect models\",\n      \"pmids\": [\"10586884\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"PBX-MEIS1/PREP1 complexes bind DNA cooperatively with myogenic bHLH heterodimers (E2a-MyoD, myogenin, Mrf-4, Myf-5) through a conserved tryptophan motif N-terminal to the bHLH DNA-binding domain; in vivo, MyoD requires this tryptophan motif to remodel chromatin at and activate the Myogenin promoter.\",\n      \"method\": \"EMSA cooperative binding assay, mutagenesis, in vivo chromatin remodeling assay, transfection reporter assay\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with mutagenesis plus in vivo chromatin remodeling validation, multiple orthogonal methods\",\n      \"pmids\": [\"10471746\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"MEIS1 genetically collaborates with both HOXA9 and HOXB3 (structurally divergent HOX genes) to generate acute myeloid leukemia; MEIS1 functions to accelerate leukemic onset while the HOX gene defines leukemia identity; PREP1 (despite sharing PBX nuclear retention activity with MEIS1) cannot substitute for MEIS1 in accelerating HOXA9-induced AML, indicating MEIS1 has transformation-specific functions beyond PBX nuclear localization.\",\n      \"method\": \"Retroviral bone marrow transduction/transplantation, genetic epistasis with PREP1 overexpression, in vivo leukemia latency assays\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis with multiple HOX partners, negative control with PREP1, replicated across two HOX gene contexts in vivo\",\n      \"pmids\": [\"11113197\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Meis1 is required in vivo for megakaryocyte production, definitive hematopoietic progenitor proliferation/self-renewal, vascular patterning (capillary formation), and normal eye development (lens and retina); Meis1-deficient embryos die by E14.5 with complete absence of megakaryocytes, hemorrhaging, and reduced colony-forming cells, and fail to radioprotect irradiated recipients.\",\n      \"method\": \"Meis1 knockout mouse generation, colony-forming assay, competitive repopulation, histology, radioprotection assay\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic loss-of-function with multiple specific phenotypic readouts across hematopoietic and vascular systems, confirmed by functional transplantation assays\",\n      \"pmids\": [\"14713950\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Enforced co-expression of HOXA9 and MEIS1 is sufficient to substitute for MLL-ENL fusion activity and immortalize hematopoietic cells; HOXA9+MEIS1 co-expression is required for continued proliferation and differentiation arrest in MLL-ENL-dependent cells.\",\n      \"method\": \"Inducible MLL-ENL-ERtm system, retroviral overexpression, 4-OHT withdrawal/differentiation assay, microarray\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — inducible genetic system with defined molecular replacement experiment, multiple orthogonal readouts\",\n      \"pmids\": [\"14701735\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"MEIS1 overexpression strongly induces caspase-dependent apoptosis in multiple cell types; this requires a functional homeodomain and PBX-interaction motif; co-expression of HOXA9 suppresses MEIS1-induced apoptosis and confers protection from apoptotic stimuli, whereas PBX1-induced apoptosis is not rescued by HOXA9.\",\n      \"method\": \"Retroviral overexpression, caspase inhibitor assays, apoptosis assays, domain deletion mutants\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional mutagenesis with apoptosis readouts, single lab, two orthogonal methods\",\n      \"pmids\": [\"15479723\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Meis1 programs leukemic stem cell (cancer-initiating) potential in Hoxa9-immortalized myeloid progenitors; this requires PBX binding, DNA binding, and a conserved C-terminal domain function; Meis1 induces expression of FLT3 and CD34 (HSC-associated genes), and is the first example of a transcription factor oncoprotein (Meis1) establishing expression of a tyrosine kinase oncoprotein (FLT3).\",\n      \"method\": \"Retroviral overexpression, domain deletion mutagenesis, transplantation leukemia assay, gene expression analysis\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — functional domain dissection with in vivo leukemia readout, multiple orthogonal methods, mechanistic target (FLT3) identified\",\n      \"pmids\": [\"15755900\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Meis1 is required for establishment of definitive hematopoiesis in the mouse embryo, including HSC specification in the AGM, formation of hematopoietic clusters in dorsal aorta/vitelline/umbilical arteries, and Runx1-expressing AGM mesenchymal cells; Meis1 mutants also show complete megakaryocyte lineage agenesis and vascular patterning defects.\",\n      \"method\": \"Meis1 gene inactivation in mice, fetal liver colony assay, immunohistochemistry, radioprotection assay\",\n      \"journal\": \"Developmental biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — targeted gene disruption with multiple specific hematopoietic and vascular readouts, functional transplantation data\",\n      \"pmids\": [\"15882575\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Meis1 leukemogenic activity requires co-occupancy of Meis1-Pbx and Hox-Pbx complexes on target gene promoters (including Flt3); a VP16-Meis1 fusion acts as an autonomous oncoprotein replacing both Meis1 C-terminal domain and Hoxa9 N-terminal domain functions, establishing that these domains cooperate in transcriptional activation of leukemia-associated target genes; ChIP confirmed co-occupancy of Hoxa9 and Meis1 on the Flt3 promoter.\",\n      \"method\": \"VP16/engrailed fusion proteins, retroviral overexpression, chromatin immunoprecipitation (ChIP), leukemia transplantation assay\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — ChIP demonstrating in vivo co-occupancy plus functional domain-swapping experiments with in vivo leukemia readout, multiple orthogonal methods\",\n      \"pmids\": [\"16648484\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Meis1 transforming activity requires three conserved domains: the Pbx interaction motif (PIM), the homeodomain, and the C-terminal region; PIM and homeodomain deletion mutants are individually non-functional but domain-swap complementation restores full oncogenic activity; VP16 transactivation domain can replace the C-terminal domain and induce spontaneous leukemia accompanied by endogenous Hoxa9/Hoxa7 activation, establishing that Hoxa gene activation is a key downstream event for Meis1 oncogenesis.\",\n      \"method\": \"Domain deletion/swap mutagenesis, retroviral bone marrow transplantation, gene expression analysis\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — systematic domain mutagenesis with in vivo leukemia readout, complementation experiments, multiple constructs tested\",\n      \"pmids\": [\"16469876\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Meis1 is an essential and rate-limiting regulator of MLL leukemia stem cell (LSC) potential: Meis1 knockout/knockdown/dominant-negative abrogates MLL oncoprotein-induced AML; Meis1 quantitatively controls extent of self-renewal, differentiation arrest, cycling, and rate of in vivo LSC generation from myeloid progenitors; codependent on redundant contributions of Pbx2 and Pbx3.\",\n      \"method\": \"Conditional knockout, shRNA knockdown, dominant-negative genetic techniques, serial transplantation, LSC frequency analysis\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple genetic approaches (KO, KD, dominant-negative) with quantitative LSC frequency readouts, single lab but highly rigorous with orthogonal methods\",\n      \"pmids\": [\"17942707\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Meis1 leukemogenic activity with NUP98-HOXD13 requires the PBX-interaction domain, homeodomain, and C-terminal domain but not the N-terminal domain; the N-terminal domain is specifically required for Flt3 upregulation; ChIP revealed in vivo occupancy of MEIS1 on regulatory sequences of Trib2, Flt3, Dlk1, Ccl3, Ccl4, Pf4, and Rgs1; Trib2 overexpression complements ND13 to induce AML.\",\n      \"method\": \"Structure-function mutagenesis, retroviral bone marrow transplantation, ChIP, gene expression profiling\",\n      \"journal\": \"Experimental hematology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — ChIP demonstrating direct in vivo target binding combined with systematic domain mutagenesis and in vivo leukemia assays\",\n      \"pmids\": [\"18375036\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"meis1 acts as a positive cell cycle regulator in early zebrafish retinal progenitor cells by directly regulating cyclin D1 and c-myc transcription; meis1 morpholino knockdown causes G1-to-S phase transition delay and severely reduced eyes; forced maintenance of meis1 expression is incompatible with normal retinal differentiation.\",\n      \"method\": \"Morpholino knockdown in zebrafish, cell cycle analysis, gene expression analysis, mosaic expression assay\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function with specific cell cycle and gene expression readouts, single organism but two orthogonal approaches\",\n      \"pmids\": [\"18216175\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"In chick and mouse retina, Meis1 and Meis2 maintain retinal progenitor cells in a rapidly proliferating state; Meis-inactivating constructs impair RPC proliferation and cause microphthalmia; Meis protein knockdown reduces cyclin D1 (Ccnd1) expression in the eye primordium, and co-transfection of cyclin D1 partially rescues RPC proliferation.\",\n      \"method\": \"Transfection of dominant-negative Meis constructs, RNA interference, cyclin D1 rescue experiment, in chick and mouse\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function with functional rescue experiment, replicated in two species (chick and mouse)\",\n      \"pmids\": [\"18216174\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"MEIS1 directly regulates meis1 target gene Trib2, and Meis1 directly binds regulatory sequences of Trib1; Trib1 and Evi1 are key collaborators in Hoxa9/Meis1-induced AML (identified by retroviral insertional mutagenesis), with Trib1 acting as a novel myeloid oncogene that enhances ERK phosphorylation to inhibit apoptosis.\",\n      \"method\": \"Retroviral insertional mutagenesis screen, retroviral co-expression, AML transplantation assay\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo insertional mutagenesis screen with functional validation, single lab\",\n      \"pmids\": [\"17227832\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"miR-155 directly targets the 3'-UTR of MEIS1 mRNA, downregulating MEIS1 expression; enforced miR-155 expression impairs megakaryocytic differentiation and proliferation of hematopoietic progenitor cells, with MEIS1 identified as a functional target.\",\n      \"method\": \"3'-UTR luciferase reporter assay, Western blot, overexpression of miR-155, MK differentiation assay\",\n      \"journal\": \"British journal of haematology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct 3'-UTR targeting confirmed by reporter assay plus functional phenotype, single lab\",\n      \"pmids\": [\"18950466\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"HOXA9 indirectly regulates Meis1 expression through direct transcriptional activation of CREB1 and PKNOX1, whose protein products induce Meis1; HOXA9 does not directly bind Meis1 promoter/enhancer regions by ChIP analysis; forced CREB1 expression in Hoxa9-/- bone marrow increases Meis1 mRNA, establishing CREB1 as an intermediary in HOXA9-mediated Meis1 regulation.\",\n      \"method\": \"ChIP, quantitative RT-PCR, Hoxa9-/- mouse genetics, retroviral CREB1 overexpression, compound Meis1+/-/Hoxa9-/- mice\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — ChIP negative for direct binding combined with genetic and functional epistasis establishing indirect mechanism via CREB1, multiple orthogonal methods\",\n      \"pmids\": [\"19620287\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Ectopic Meis1 expression in the distal mouse limb bud causes proximal-to-distal patterning defects (proximal shift of limb identities and Hox gene expression domains); this P-D patterning function of Meis1 is independent of Pbx1, as Pbx1 deficiency does not modify the Msx2:Meis1 transgenic limb phenotype.\",\n      \"method\": \"Msx2:Meis1 transgenic mouse generation, in situ hybridization for Hox gene expression, genetic epistasis with Pbx1-/- mice\",\n      \"journal\": \"The International journal of developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — transgenic gain-of-function with genetic epistasis, single lab\",\n      \"pmids\": [\"19247936\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Meis1 and Pbx act upstream of gata1 in the zebrafish erythropoietic transcription factor hierarchy: Meis1/Pbx-depleted embryos show severe loss of gata1 expression, reduced embryonic hemoglobin, and increased pu.1-positive myeloid cells; gata1 overexpression rescues hemoglobin expression in Pbx/Meis1-depleted embryos, placing Meis1/Pbx upstream of gata1.\",\n      \"method\": \"Morpholino knockdown in zebrafish, genetic epistasis by gata1 mRNA rescue, in situ hybridization\",\n      \"journal\": \"Developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis by mRNA rescue in zebrafish, single lab, well-defined pathway placement\",\n      \"pmids\": [\"20123093\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Meis1 directly activates cyclin D3 transcription; M33-MEIS1 (transcriptional repressor form) impedes G1-to-S phase progression correlating with reduced cyclin D3 levels and inhibition of retinoblastoma (pRb) hyperphosphorylation; cyclin D3 overexpression partially rescues the G1 accumulation and growth suppression caused by M33-Meis1.\",\n      \"method\": \"Retroviral M33-MEIS1 expression, cell cycle analysis, Western blot for cyclin D3 and pRb, ChIP, cyclin D3 rescue experiments\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — direct target identification by ChIP combined with functional rescue experiment and mechanistic pathway (cyclin D3-pRb axis), multiple orthogonal methods\",\n      \"pmids\": [\"20237320\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Meis1 directly binds an enhancer element 35 kb upstream of the Gfi1 gene in early hematopoietic cells (fetal liver and dorsal aorta), acting as an upstream regulator of Gfi1 transcription in hematopoietic stem cell emergence.\",\n      \"method\": \"Locus-wide ChIP, transgenic enhancer assay in mice\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct ChIP binding on identified enhancer plus transgenic functional validation, single lab\",\n      \"pmids\": [\"20516218\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"MEIS1 RNAi in C. elegans (MEIS1 orthologue) increases ferritin expression; the RLS-associated MEIS1 risk haplotype leads to increased expression of ferritin and DMT1 in RLS brain tissues; human cells under iron-deficient conditions show reduced MEIS1 expression, establishing a link between MEIS1 and iron homeostasis regulation.\",\n      \"method\": \"RNAi in C. elegans, gene expression analysis in human RLS brain tissue, iron deprivation experiment in human cells\",\n      \"journal\": \"Annals of neurology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional RNAi in model organism plus human tissue gene expression, single lab, two orthogonal approaches\",\n      \"pmids\": [\"21710629\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"MN1-induced leukemogenesis requires the MEIS1/AbdB-like HOX protein complex: common myeloid progenitors (CMP) but not granulocyte-macrophage progenitors (GMP) are susceptible to MN1 transformation; MEIS1/AbdB-like HOX complementation of GMPs restores susceptibility; ChIP-seq identified common target genes of MN1 and MEIS1 with identical binding sites for a large proportion of chromatin targets.\",\n      \"method\": \"Progenitor-specific transformation assay, CMP vs GMP complementation, ChIP-seq, shRNA knockdown\",\n      \"journal\": \"Cancer cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — ChIP-seq genome-wide target mapping combined with functional complementation in defined cell populations and genetic knockdown with antileukemic readout\",\n      \"pmids\": [\"21741595\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Meis1 deletion leads to accumulation of reactive oxygen species (ROS) in HSCs, loss of quiescence, and decreased expression of hypoxia-response genes; ROS scavenging with N-acetyl cysteine or VHL knockdown (hypoxia pathway stabilization) reverses effects of Meis1 deletion on HSC maintenance, placing Meis1 in a pathway regulating oxidative metabolism in HSCs.\",\n      \"method\": \"Inducible Meis1 knockout mice, ROS measurement, colony formation assay, NAC rescue, VHL shRNA rescue, gene expression analysis\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO with two independent rescue strategies (pharmacological and genetic), defining pathway position, multiple orthogonal methods\",\n      \"pmids\": [\"23091297\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Meis1 is a critical transcriptional regulator of cardiomyocyte cell cycle arrest: Meis1 deletion in mouse cardiomyocytes extends the postnatal proliferative window and re-activates cardiomyocyte mitosis in the adult heart; Meis1 overexpression decreases neonatal myocyte proliferation and inhibits neonatal heart regeneration; Meis1 is required for transcriptional activation of CDK inhibitors p15, p16, and p21.\",\n      \"method\": \"Cardiomyocyte-specific Meis1 conditional KO, Meis1 overexpression, BrdU/pH3 proliferation assays, cardiac injury/regeneration assay, qRT-PCR/Western blot for CDK inhibitors\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal gain- and loss-of-function in vivo with defined molecular mechanism (p15/p16/p21 CDK inhibitors), multiple orthogonal methods, high-impact journal\",\n      \"pmids\": [\"23594737\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Gfi1b, together with co-factors LSD1 and CoREST, directly represses meis1 transcription in erythroid cells (but not megakaryocytes) by occupying distinct regions of the Meis1 promoter; Meis1 is substantially upregulated in gfi1b-/- fetal liver cells; SNAG-domain mutant or DNA-binding-deficient Gfi1b fails to repress the meis1 promoter reporter.\",\n      \"method\": \"ChIP, gene expression profiling of gfi1b-/- cells, LSD1 inhibitor treatment, promoter reporter transfection with mutagenesis\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — ChIP demonstrating direct promoter occupancy, genetic KO, functional mutagenesis of Gfi1b, rescue with LSD1 inhibition; multiple orthogonal methods\",\n      \"pmids\": [\"23308270\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"MEIS1 functions as a novel androgen receptor (AR) co-repressor: MEIS1 inhibits AR transcriptional activity and reduces AR target gene (PSA) expression; MEIS1-AR protein-protein interaction was demonstrated by co-immunoprecipitation and GST pull-down; MEIS1 modulates AR nuclear translocation and recruitment to the PSA promoter androgen response element; MEIS1 promotes recruitment of NCoR and SMRT co-repressors in the presence of androgen.\",\n      \"method\": \"Co-immunoprecipitation, GST pull-down, luciferase reporter assay, ChIP at PSA promoter, nuclear translocation assay\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal co-IP and GST pulldown confirming direct interaction, ChIP confirming promoter regulation, single lab\",\n      \"pmids\": [\"25158280\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Pbx3 stabilizes Meis1 protein by preventing its ubiquitination and proteasomal degradation: in the absence of Pbx3, Meis1 is highly unstable; deletion of the Pbx-binding domain on Meis1 or binding to Pbx3 prolongs Meis1 half-life; ubiquitin-proteasome inhibition blocks Meis1 degradation; Pbx3 overexpression also induces endogenous Meis1 transcription; Meis1/Pbx3 dimerization is required for high-affinity DNA/Hoxa9/Meis1/Pbx3 complex formation in vitro.\",\n      \"method\": \"Protein stability/half-life assays, ubiquitination assay, proteasome inhibitor treatment, domain deletion analysis, EMSA, retroviral overexpression, leukemia transplantation\",\n      \"journal\": \"Haematologica\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — biochemical ubiquitination assay plus half-life measurement plus in vitro DNA binding reconstitution plus in vivo leukemia assay, multiple orthogonal methods in one study\",\n      \"pmids\": [\"25911551\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"PREP1 competitively heterodimerizes with PBX1 against MEIS1: MEIS1 alone transforms PREP1-deficient fibroblasts; PREP1 overexpression inhibits MEIS1 tumorigenicity; PREP1 post-translationally decreases MEIS1 stability by sequestering PBX1; MEIS1 interaction with DDX3X and DDX5 is essential for MEIS1 tumorigenesis and is disrupted when PREP1 reduces MEIS1 levels.\",\n      \"method\": \"Transformation assay in MEFs, Western blot protein stability, co-immunoprecipitation for DDX3X/DDX5 interaction, overexpression competition assay\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP for DDX3X/DDX5 binding, protein stability assay, functional transformation readout; single lab\",\n      \"pmids\": [\"24578510\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"C/EBPα is a critical collaborator required for HOXA9/MEIS1-mediated leukemogenesis: loss of C/EBPα greatly improves survival in murine Hoxa9/Meis1 leukemia models; over 50% of Hoxa9 genome-wide binding sites are co-bound by C/EBPα; Hoxa9 represses the Cdkn2a/b locus in concert with C/EBPα to overcome G1 cell cycle arrest.\",\n      \"method\": \"ChIP-seq, conditional C/EBPα knockout, leukemia transplantation, cell proliferation assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — ChIP-seq genome-wide target co-occupancy combined with genetic KO and in vivo leukemia readout, multiple orthogonal methods\",\n      \"pmids\": [\"24958854\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"MEIS1 regulates Pax6 transcription in cerebellar granule cell precursors (GCPs) by binding an upstream Pax6 sequence; the Meis1-Pax6 cascade upregulates Smad protein expression to increase BMP signaling, which promotes Atoh1 degradation in the inner external granule layer, driving GCP differentiation; Meis1 conditional KO in GC lineage results in smaller cerebella with disorganized lobules and ectopic Atoh1-positive GCPs.\",\n      \"method\": \"Conditional Meis1 knockout in GC lineage, in vitro promoter binding assays, BMP signaling analysis (Smad phosphorylation), cerebellar slice culture with BMP inhibitors, knockdown experiments\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — conditional KO with multiple mechanistic readouts (Pax6, Smad, Atoh1), single lab but orthogonal approaches\",\n      \"pmids\": [\"29317485\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"During cardiac differentiation, MEIS1 and NKX2-5 bind overlapping sites in a mutually exclusive manner to regulate common target genes (exemplified by Popdc2); as cardiac progenitors differentiate, they sequentially experience high MEIS1 and then increasing NKX2-5, providing a spatial-temporal regulatory switch.\",\n      \"method\": \"ChIP, EMSA competitive binding assay, reporter assays, in situ hybridization during cardiac differentiation\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP and EMSA demonstrating mutually exclusive binding at overlapping sites, single lab but orthogonal methods\",\n      \"pmids\": [\"26411676\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Meis1 loss leads to increased oxidative stress, oxygen flux, and apoptosis in MLL-AF9 leukemia cells; MEIS1 directly occupies the hepatic leukemia factor (HLF) promoter by ChIP; HLF expression (or hypoxia) reverses oxidative stress and rescues leukemia development in Meis1-deficient cells, establishing a Meis1-HLF-oxidative stress axis.\",\n      \"method\": \"Inducible Meis1-KO in MLL-AF9 knockin model, ChIP for HLF promoter, oxidative stress measurement, HLF overexpression rescue, hypoxia rescue\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — direct ChIP target identification plus two independent rescue experiments (genetic and pharmacological) in both murine and human cells\",\n      \"pmids\": [\"25740828\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"In the eye primordium, Meis1 binds Hox/Pbx-independent chromatin sites (distinct from its trunk binding preference for Hox-Pbx sites); Meis1 haploinsufficiency causes microphthalmic traits by dose-dependently regulating retinal proliferation/differentiation genes and components of the Notch signaling pathway and eye territory-specific transcription factors.\",\n      \"method\": \"ChIP-seq, RNA-seq, conditional Meis1 loss-of-function and functional rescue, Meis1-/- embryo analysis\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — ChIP-seq defining genome-wide binding landscape combined with RNA-seq and genetic rescue, multiple orthogonal methods in one study\",\n      \"pmids\": [\"26253404\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"PBX3 and MEIS1 co-expression (without ectopic HOX gene) is sufficient to transform normal hematopoietic stem/progenitor cells and cause AML in vivo; disruption of the MEIS1-PBX3 binding interaction abolishes cell transformation and HOX gene upregulation; PBX3/MEIS1 (but not HOXA9/MEIS1) recapitulates the MLL-fusion core transcriptome.\",\n      \"method\": \"Retroviral co-expression, murine AML transplantation, PBX3-MEIS1 interaction-disrupting mutations, gene expression profiling\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — sufficiency demonstrated in vivo with interaction-disrupting mutation showing requirement for direct binding, multiple readouts\",\n      \"pmids\": [\"26747896\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"MEIS1 directly activates synaptotagmin-like 1 (SYTL1/Slp1) transcription (global MEIS1 ChIP-seq and gene expression in MEIS1-deficient cells); SYTL1 restores cell migration and engraftment in MEIS1-deficient leukemia cells; SYTL1 promotes CXCR4-dependent cell migration by controlling intracellular trafficking of CXCR4, revealing a MEIS1→SYTL1→CXCL12/CXCR4 pathway for leukemic homing.\",\n      \"method\": \"ChIP-seq, gene expression profiling of Meis1-deficient cells, SYTL1 rescue experiment, CXCR4 trafficking assay, in vivo homing/engraftment assay\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — ChIP-seq direct target identification, genetic rescue, and mechanistic trafficking assay defining pathway, multiple orthogonal methods\",\n      \"pmids\": [\"27018596\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"In Hoxa9/Meis1-driven AML, Meis1 increases Syk protein expression and activity through a feedback loop: Meis1 indirectly regulates miR-146a expression through transcription factor PU.1, and miR-146a directly targets Syk; in the context of Hoxa9, Syk signaling induces Meis1, creating a regulatory loop; Syk inhibition disrupts this loop and prolongs survival of mice with Hoxa9/Meis1 leukemia.\",\n      \"method\": \"Phosphoproteomics, Western blot, miR-146a target validation, PU.1 ChIP, Syk inhibitor treatment in vivo\",\n      \"journal\": \"Cancer cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — phosphoproteomic discovery combined with ChIP, miRNA target validation, and in vivo therapeutic experiment, multiple orthogonal methods\",\n      \"pmids\": [\"28399410\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"PPM1K (a mitochondrial Ser/Thr phosphatase that promotes BCAA catabolism) maintains MEIS1 and p21 protein levels by decreasing their ubiquitination-mediated degradation controlled by the E3 ubiquitin ligase CDC20; PPM1K deficiency leads to decreased MEIS1/p21 signaling, reduced HSC glycolysis and quiescence.\",\n      \"method\": \"BCAA fluorescent sensor, PPM1K KO mouse, MEIS1/p21 ubiquitination assay, CDC20 interaction studies, leukemia model\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ubiquitination assay identifying specific E3 ligase (CDC20), genetic KO with defined signaling readouts, single lab\",\n      \"pmids\": [\"29719258\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"MEIS1 controls human pluripotent stem cell hematopoietic differentiation by targeting TAL1 (which mediates HEP specification) and FLI1 (which is required for megakaryopoiesis); MEIS1 is vital for specification of APLNR+ mesoderm progenitors to hemogenic endothelial progenitors.\",\n      \"method\": \"hPSC differentiation, MEIS1 overexpression/knockdown, downstream target identification (TAL1, FLI1), flow cytometry\",\n      \"journal\": \"Stem cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — gain/loss-of-function in hPSC system with downstream target identification, single lab\",\n      \"pmids\": [\"29358086\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"MEIS1 directly binds and positively regulates the SKOR1 promoter at two specific sites, and this regulation is modified by an RLS-associated SNP in the SKOR1 promoter region, establishing a direct molecular link between two RLS-associated genes.\",\n      \"method\": \"Luciferase reporter assay, ChIP, SNP-dependent promoter activity assay\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP plus reporter assay with allele-specific SNP effect, single lab\",\n      \"pmids\": [\"30111810\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"PAF1c (through subunit CDC73) interacts with SETDB1 (H3K9 methyltransferase); stabilization of PAF1c-SETDB1 interaction reduces transcription of Meis1 and Hoxa9 by increasing H3K9me3 at their promoters in AML cells.\",\n      \"method\": \"Proteomics (CDC73 interactome), ChIP for H3K9me3 at Meis1/Hoxa9 promoters, AML cell growth assay\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — proteomics-identified interaction validated by ChIP demonstrating H3K9me3 at specific loci, single lab\",\n      \"pmids\": [\"29774127\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"MEIS1 suppression by siRNA in fetal cardiomyocytes increases maximal oxygen consumption and mitochondrial activity while decreasing glycolytic gene expression, establishing MEIS1 as a regulator of the cardiomyocyte metabolic program (glycolysis vs. oxidative phosphorylation).\",\n      \"method\": \"siRNA knockdown, Seahorse metabolic flux analysis, MitoTracker staining, gene expression analysis\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct siRNA knockdown with quantitative metabolic readout (oxygen consumption rate), single lab\",\n      \"pmids\": [\"30884246\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"MEIS1 transcription is epigenetically suppressed by EZH2-DNMT3a recruited to the MEIS1 promoter with the aid of lncRNA ELFN1-AS1; MEIS1 suppression following this axis increases FEN1 expression, which mediates oxaliplatin resistance in colorectal cancer.\",\n      \"method\": \"ChIP for EZH2/DNMT3a at MEIS1 promoter, ELFN1-AS1 ASO knockdown, EZH2 inhibitor GSK126, FEN1 expression analysis, in vivo tumor growth\",\n      \"journal\": \"Signal transduction and targeted therapy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP confirming promoter occupancy plus functional rescue experiments with ASO and inhibitor, single lab\",\n      \"pmids\": [\"35351858\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"MEIS1 is a TALE-class homeodomain transcription factor that forms heterodimeric and trimeric complexes with PBX and HOX proteins (especially AbdB-like HOX group 9–13) on composite DNA binding sites to activate target gene transcription; it promotes hematopoietic stem cell quiescence and self-renewal by restricting reactive oxygen species via an HLF-dependent hypoxia pathway, drives leukemogenesis by directly activating cyclin D3, FLT3, SYTL1, and HLF while requiring its PBX-interaction, homeodomain, and C-terminal transactivation domains, and controls cardiomyocyte cell cycle arrest through transcriptional activation of CDK inhibitors p15, p16, and p21; its protein stability is regulated by CDC20-mediated ubiquitination (countered by PPM1K) and by competitive PBX1 binding with PREP1/PKNOX1.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"MEIS1 is a TALE-class homeodomain transcription factor that operates as a combinatorial DNA-binding partner, dimerizing with PBX proteins and forming heterodimeric and trimeric complexes with AbdB-like HOX group 9–13 proteins (HOXA9, HOXA10, HOXA11, HOXD12, HOXB13) on composite recognition sites to activate target gene transcription [#1, #2, #4]. Cooperative assembly on DNA stabilizes the HOX-MEIS1 complex and, distinct from HOX-PBX interactions, the MEIS1-PBX interface does not require the conserved N-terminal tryptophan motif [#1, #2, #3]; MEIS1 also promotes nuclear import of PBX1 to control proximal limb identity, a patterning function that can be PBX1-independent in some contexts [#5, #22]. In hematopoiesis MEIS1 is essential for definitive HSC specification in the AGM, megakaryocyte production, and vascular patterning, acting upstream of regulators including Gfi1 and gata1 [#8, #12, #23, #25], and it sustains HSC quiescence by restricting reactive oxygen species through a directly activated HLF/hypoxia-response axis [#28, #37]. MEIS1 is a rate-limiting driver of HOX- and MLL-rearranged acute myeloid leukemia, where it programs leukemic stem cell self-renewal and differentiation arrest through cooperatively assembled MEIS1-PBX/HOX-PBX complexes that co-occupy and activate target promoters; its transforming activity requires the PBX-interaction motif, the homeodomain, and a C-terminal transactivation domain, and direct targets include FLT3, cyclin D3, SYTL1, Trib2, and HLF [#7, #9, #11, #13, #14, #15, #24, #40]. PBX3/MEIS1 co-expression alone is sufficient to transform hematopoietic progenitors and induce AML [#39]. Beyond hematopoiesis, MEIS1 enforces cardiomyocyte cell-cycle arrest by transcriptionally activating the CDK inhibitors p15, p16, and p21 and shapes the cardiomyocyte glycolytic-versus-oxidative metabolic program [#29, #46], and it controls retinal and cerebellar progenitor proliferation and differentiation through cyclin D1/D3, c-myc, and a Pax6-BMP-Atoh1 cascade [#17, #18, #35, #38]. MEIS1 protein levels are tuned post-translationally: PBX3 binding stabilizes MEIS1 against ubiquitin-proteasome degradation, CDC20-mediated ubiquitination (countered by PPM1K) destabilizes it, and PREP1/PKNOX1 lowers MEIS1 stability by competitively sequestering PBX1 [#32, #33, #42].\",\n  \"teleology\": [\n    {\n      \"year\": 1995,\n      \"claim\": \"Established MEIS1 as a homeobox oncogene by identifying it as a recurrent retroviral integration target in myeloid leukemia and placing it in the TALE family related to PBX/exd.\",\n      \"evidence\": \"Retroviral insertion site cloning and cDNA sequencing in BXH-2 myeloid leukemias\",\n      \"pmids\": [\"7565694\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No demonstration of DNA-binding partners or target genes at this stage\", \"Leukemogenic mechanism inferred only from integration frequency\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Defined MEIS1's biochemical mode of action as a partner-selective DNA-binding factor that heterodimerizes specifically with AbdB-like HOX proteins and with PBX1 through a unique interaction surface.\",\n      \"evidence\": \"EMSA with composite sites, paralog-specificity tests, and domain-mapping mutagenesis in vitro\",\n      \"pmids\": [\"9343407\", \"9405651\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vitro binding did not establish in vivo target genes\", \"Functional consequence of complex formation on transcription not yet shown\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Confirmed that endogenous MEIS1-PBX1 complexes form on a physiological target sequence and that the cooperative binding mechanism is evolutionarily conserved.\",\n      \"evidence\": \"Affinity purification of endogenous complexes from adrenal nuclear extracts plus EMSA and mutagenesis on the CYP17 CRS1 element\",\n      \"pmids\": [\"9525891\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct transcriptional output at the endogenous CYP17 locus not measured\", \"Single tissue context\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Showed MEIS1 nucleates trimeric HOX-PBX-MEIS1 complexes in leukemia nuclei and controls PBX1 nuclear import to direct limb patterning, linking complex assembly to in vivo developmental and oncogenic function.\",\n      \"evidence\": \"Co-IP and nuclear co-localization in myeloid cells; ectopic expression in chick and Drosophila with PBX1 immunolocalization\",\n      \"pmids\": [\"10082572\", \"10586884\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Target genes downstream of the trimeric complex not yet identified\", \"Mechanism coupling nuclear import to transcription incomplete\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Broadened MEIS1's partner repertoire by showing PBX-MEIS1/PREP1 complexes cooperate with myogenic bHLH factors to remodel chromatin and activate differentiation genes.\",\n      \"evidence\": \"Cooperative EMSA, tryptophan-motif mutagenesis, and in vivo chromatin remodeling at the Myogenin promoter\",\n      \"pmids\": [\"10471746\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct MEIS1 occupancy at myogenic promoters in vivo not shown\", \"Relative contribution of MEIS1 versus PREP1 not separated\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Demonstrated MEIS1 has transformation-specific oncogenic function beyond PBX nuclear localization by showing it accelerates HOX-induced AML where the redundant PBX-retention factor PREP1 cannot.\",\n      \"evidence\": \"Retroviral bone marrow transduction/transplantation with HOXA9/HOXB3 and PREP1 substitution controls\",\n      \"pmids\": [\"11113197\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis of the transformation-specific activity unresolved\", \"Direct leukemic target genes not yet defined\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Established MEIS1 as required in vivo for definitive hematopoiesis, megakaryopoiesis, and vascular patterning, and showed HOXA9+MEIS1 co-expression is sufficient to replace an MLL fusion for immortalization.\",\n      \"evidence\": \"Meis1 knockout mice with transplantation/colony assays; inducible MLL-ENL replacement system\",\n      \"pmids\": [\"14713950\", \"14701735\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Embryonic lethality limits adult HSC analysis in constitutive KO\", \"Direct transcriptional targets driving immortalization not yet mapped\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Revealed MEIS1 overexpression triggers caspase-dependent apoptosis that HOXA9 co-expression suppresses, linking complex partnership to cell-survival output and requiring homeodomain and PBX-interaction motifs.\",\n      \"evidence\": \"Retroviral overexpression with caspase inhibitors and domain-deletion mutants\",\n      \"pmids\": [\"15479723\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Pro-apoptotic target genes not identified\", \"Single-lab functional study\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Defined MEIS1 as a programmer of leukemic stem cell potential and identified its first direct kinase target, showing a transcription-factor oncoprotein establishing tyrosine-kinase oncoprotein FLT3 expression.\",\n      \"evidence\": \"Domain-deletion mutagenesis with in vivo leukemia transplantation and gene expression analysis; AGM/embryo gene inactivation studies\",\n      \"pmids\": [\"15755900\", \"15882575\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct promoter occupancy of FLT3 not yet shown at this stage\", \"C-terminal domain mechanism undefined\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Established that MEIS1 leukemogenesis requires co-occupancy of MEIS1-PBX and HOX-PBX complexes on target promoters and dissected the three essential domains needed for transformation.\",\n      \"evidence\": \"ChIP at the Flt3 promoter, VP16/engrailed domain-swap fusions, and systematic domain mutagenesis with leukemia transplantation\",\n      \"pmids\": [\"16648484\", \"16469876\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full set of co-occupied target genes not yet genome-wide\", \"Hoxa autoactivation mechanism not detailed\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Established MEIS1 as an essential, rate-limiting and dose-dependent regulator of MLL leukemia stem cell self-renewal, codependent on PBX2/PBX3.\",\n      \"evidence\": \"Conditional KO, shRNA, and dominant-negative approaches with serial transplantation and LSC frequency analysis\",\n      \"pmids\": [\"17942707\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Quantitative target genes mediating dose effect not enumerated\", \"Relative PBX2 versus PBX3 contributions not separated\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Expanded the direct MEIS1 leukemic target set by ChIP and identified domain-specific requirements, while linking MEIS1 to additional roles in cell-cycle control of progenitors and to its own regulation by miR-155.\",\n      \"evidence\": \"ChIP across multiple loci with NUP98-HOXD13 model; zebrafish/chick/mouse retinal loss-of-function with cyclin D1/D3 and c-myc readouts; miR-155 3'-UTR reporter assays\",\n      \"pmids\": [\"18375036\", \"18216175\", \"18216174\", \"18950466\", \"17227832\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"N-terminal domain mechanism for Flt3 upregulation undefined\", \"Whether retinal and leukemic target programs share regulatory logic unknown\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Clarified the regulatory hierarchy by showing HOXA9 induces Meis1 only indirectly through direct activation of CREB1 and PKNOX1 rather than direct promoter binding.\",\n      \"evidence\": \"ChIP (negative for direct binding), Hoxa9-/- genetics, and CREB1 rescue in bone marrow\",\n      \"pmids\": [\"19620287\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Additional upstream inputs into Meis1 transcription not exhaustively mapped\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Connected MEIS1 transcriptional control directly to cell-cycle progression and to early hematopoietic and erythroid programs through specific target loci.\",\n      \"evidence\": \"ChIP and rescue at cyclin D3 (pRb axis); Gfi1 enhancer ChIP/transgenic assay; zebrafish epistasis placing Meis1/Pbx upstream of gata1\",\n      \"pmids\": [\"20237320\", \"20516218\", \"20123093\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Combined contribution of these targets to a unified program not integrated\", \"Cardiac and metabolic cell-cycle roles not yet examined\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Linked MEIS1 to iron homeostasis and restless legs syndrome biology and demonstrated genome-wide MEIS1/HOX target overlap underlying MN1-driven leukemia susceptibility.\",\n      \"evidence\": \"C. elegans RNAi and human RLS brain expression for ferritin/DMT1; ChIP-seq and progenitor complementation in MN1 leukemia\",\n      \"pmids\": [\"21710629\", \"21741595\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism connecting MEIS1 to ferritin regulation undefined\", \"Whether iron regulation reflects direct transcriptional targets unknown\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Established MEIS1 as a transcriptional enforcer of cardiomyocyte cell-cycle arrest and revealed a repressive regulatory circuit controlling its own expression in erythroid cells.\",\n      \"evidence\": \"Reciprocal cardiomyocyte gain/loss-of-function in vivo with p15/p16/p21 readouts; Gfi1b/LSD1/CoREST ChIP and reporter mutagenesis on the Meis1 promoter\",\n      \"pmids\": [\"23594737\", \"23308270\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct MEIS1 occupancy at CDK-inhibitor loci not fully resolved\", \"How the same factor activates CDK inhibitors in heart yet drives proliferation elsewhere unexplained\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Defined post-translational and competitive control of MEIS1 protein levels and uncovered new physical partners and a co-repressor function for nuclear receptor signaling.\",\n      \"evidence\": \"Pbx3 stabilization via ubiquitination/half-life assays and EMSA; PREP1 competition for PBX1 with DDX3X/DDX5 co-IP; MEIS1-AR co-IP/GST pull-down with PSA ChIP; C/EBPalpha co-occupancy ChIP-seq with KO\",\n      \"pmids\": [\"25911551\", \"24578510\", \"25158280\", \"24958854\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The E3 ligase ubiquitinating MEIS1 not identified in these studies\", \"Functional role of DDX3X/DDX5 binding in transcription not detailed\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Mapped genome-wide MEIS1 binding in developmental contexts, revealing HOX/PBX-independent target sites, mutually exclusive switching with NKX2-5 in heart, a Pax6-BMP-Atoh1 cerebellar cascade, and a direct HLF-oxidative stress axis in leukemia.\",\n      \"evidence\": \"ChIP-seq/RNA-seq in eye primordium; ChIP/EMSA competition with NKX2-5; conditional KO with BMP/Atoh1 readouts in cerebellum; HLF promoter ChIP with HLF and hypoxia rescue in MLL-AF9 cells\",\n      \"pmids\": [\"26253404\", \"26411676\", \"29317485\", \"25740828\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Determinants of context-specific HOX-independent binding undefined\", \"How redox control integrates with self-renewal program incomplete\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Identified a direct MEIS1 target driving leukemic homing and showed PBX3/MEIS1 alone is sufficient to transform hematopoietic cells without ectopic HOX.\",\n      \"evidence\": \"ChIP-seq and rescue defining MEIS1->SYTL1->CXCR4 trafficking pathway; retroviral PBX3/MEIS1 co-expression with interaction-disrupting mutants and AML transplantation\",\n      \"pmids\": [\"27018596\", \"26747896\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Source of HOX gene upregulation under PBX3/MEIS1 not fully resolved\", \"Whether SYTL1 contributes outside leukemia unknown\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Revealed a Syk-Meis1 feedback loop in HOXA9/Meis1 AML operating through PU.1 and miR-146a, providing a therapeutic vulnerability.\",\n      \"evidence\": \"Phosphoproteomics, PU.1 ChIP, miR-146a target validation, and in vivo Syk inhibition\",\n      \"pmids\": [\"28399410\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct versus indirect steps of the loop not fully separated\", \"Generalizability beyond HOXA9/Meis1 context untested\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Extended post-translational regulation by linking BCAA metabolism via PPM1K to CDC20-dependent MEIS1/p21 ubiquitination, and detailed MEIS1's role in human pluripotent stem cell hematopoietic specification and RLS gene regulation.\",\n      \"evidence\": \"PPM1K KO mouse with MEIS1/p21 ubiquitination and CDC20 studies; hPSC differentiation targeting TAL1/FLI1; SKOR1 promoter ChIP/reporter with RLS SNP; PAF1c-SETDB1 H3K9me3 ChIP at Meis1/Hoxa9\",\n      \"pmids\": [\"29719258\", \"29358086\", \"30111810\", \"29774127\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct CDC20-MEIS1 enzymatic relationship requires further biochemical dissection\", \"Single-lab studies for several mechanisms\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Established MEIS1 as a regulator of cardiomyocyte metabolic identity, controlling the balance between glycolysis and oxidative phosphorylation.\",\n      \"evidence\": \"siRNA knockdown with Seahorse metabolic flux and MitoTracker in fetal cardiomyocytes\",\n      \"pmids\": [\"30884246\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct metabolic-gene targets not identified\", \"Single-lab study\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Showed MEIS1 expression is epigenetically silenced by an EZH2-DNMT3a axis guided by lncRNA ELFN1-AS1, with downstream FEN1-mediated chemoresistance in colorectal cancer.\",\n      \"evidence\": \"ChIP at MEIS1 promoter, ELFN1-AS1 ASO knockdown, EZH2 inhibition, and in vivo tumor growth\",\n      \"pmids\": [\"35351858\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct MEIS1 regulation of FEN1 versus indirect not fully separated\", \"Single-lab study in one cancer type\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unresolved how MEIS1 selects context-specific (HOX-dependent versus HOX-independent) genomic binding sites and how the same factor switches between promoting proliferation/self-renewal in stem and leukemic cells and enforcing cell-cycle arrest in cardiomyocytes.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified model linking partner choice to opposing cell-cycle outputs\", \"Structural basis of context-dependent site selection unknown\", \"Direct enzymatic mechanism of MEIS1 ubiquitination not reconstituted\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [1, 13, 16, 24, 29, 37, 40, 31]},\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [1, 2, 3, 4, 25, 38]},\n      {\"term_id\": \"GO:0140097\", \"supporting_discovery_ids\": [1, 2, 3]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [4, 5]},\n      {\"term_id\": \"GO:0005654\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [13, 16, 24, 29, 37, 40]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [7, 9, 11, 15, 39, 47]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [5, 8, 12, 17, 18, 35, 38, 43]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [24, 29, 17, 18]}\n    ],\n    \"complexes\": [\"MEIS1-PBX heterodimer\", \"HOX-PBX-MEIS1 trimeric complex\"],\n    \"partners\": [\"PBX1\", \"PBX3\", \"HOXA9\", \"PKNOX1\", \"AR\", \"DDX3X\", \"DDX5\", \"NKX2-5\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}