{"gene":"IRX5","run_date":"2026-06-10T01:55:23","timeline":{"discoveries":[{"year":2005,"finding":"Irx5 represses Kv4.2 (Kcnd2) potassium-channel gene expression in endocardial myocardium by recruiting mBop (a cardiac transcriptional repressor), establishing an inverse Ito,f gradient that ensures coordinated cardiac ventricular repolarization and prevents arrhythmias.","method":"Irx5 knockout mice, chromatin co-IP (recruitment of mBop), electrophysiology (Ito,f measurement), immunofluorescence gradient analysis","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal interaction assay (Irx5-mBop recruitment), KO mice with specific electrophysiological phenotype (Ito,f), replicated across multiple methods in a single rigorous study","pmids":["16239150"],"is_preprint":false},{"year":2005,"finding":"Irx5 is expressed in a subset of cone bipolar cells in the mature mouse retina (Type 2 and Type 3 OFF cone bipolar cells) starting at postnatal day 5, and is required for their differentiation independently of the Vsx1 pathway, as Irx5-deficient mice lack certain bipolar cell markers while Vsx1 expression is unaffected.","method":"Irx5 knockout mice, immunohistochemistry with cell-type specific markers, genetic epistasis (Irx5/Vsx1 double mutant analysis)","journal":"Developmental biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — KO mice with defined cellular phenotype plus genetic epistasis establishing independence from Vsx1 pathway, multiple orthogonal methods","pmids":["16182275"],"is_preprint":false},{"year":2008,"finding":"Vsx1 and Irx5 together control response threshold, gain, range, and contrast adaptation specifically in OFF (not ON) retinal ganglion cell circuits, demonstrated by loss-of-function in Vsx1−/−Irx5−/− double-mutant mice; bipolar cell morphology was normal but OFF circuit function was selectively impaired.","method":"Vsx1/Irx5 double knockout mice, multi-electrode array retinal ganglion cell recording, linear-nonlinear model of contrast adaptation","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean double KO with specific electrophysiological phenotype readout, circuit-level functional analysis with cell-type specificity","pmids":["18322081"],"is_preprint":false},{"year":2012,"finding":"Irx5 modulates migration of progenitor cell populations in branchial arches and gonads by repressing Sdf1 expression; transcriptional control by Irx5 is modulated by direct protein-protein interaction with GATA3 and TRPS1 zinc-finger proteins.","method":"In vivo modeling in Xenopus laevis embryos (loss-of-function), protein-protein interaction assays, homozygosity mapping in human patients with IRX5 mutations","journal":"Nature genetics","confidence":"High","confidence_rationale":"Tier 2 / Moderate — in vivo Xenopus epistasis establishing Sdf1 repression plus direct protein-protein interaction with GATA3/TRPS1, two orthogonal methods","pmids":["22581230"],"is_preprint":false},{"year":2012,"finding":"Irx3 and Irx5 have redundant function in the endocardium to regulate atrioventricular canal morphogenesis and outflow tract formation via direct transcriptional repression of Bmp10; combined postnatal loss of Irx3 and Irx5 in the myocardium activates Nav1.5 expression and prolongs atrioventricular conduction; postnatal Irx5 can repress Irx3 activity, as combined loss restores the repolarization gradient lost in Irx5-single mutants.","method":"Irx3/Irx5 double knockout and conditional knockout mice, RT-PCR, electrophysiology, genetic epistasis","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple conditional KO models with defined cardiac phenotypes, epistasis between Irx3 and Irx5, multiple orthogonal methods","pmids":["22992950"],"is_preprint":false},{"year":2021,"finding":"IRX5 forms a transcription factor complex with GATA4 in cardiac cells, in which IRX5 potentiates GATA4-induction of SCN5A (Nav1.5) expression; loss-of-function mutations in IRX5 in human hiPSC-derived cardiomyocytes reduce Nav1.5 and Cx40 expression and slow ventricular action potential depolarization due to reduced sodium current.","method":"hiPSC-derived cardiomyocytes from Hamamy syndrome patients with IRX5 loss-of-function mutations, electrophysiology (patch clamp), Co-IP (IRX5-GATA4 complex identification), transcriptomic analysis","journal":"Cardiovascular research","confidence":"High","confidence_rationale":"Tier 2 / Moderate — patient-derived hiPSC cardiomyocytes with electrophysiology plus Co-IP identifying novel IRX5-GATA4 complex, two orthogonal methods in single rigorous study","pmids":["32898233"],"is_preprint":false},{"year":2003,"finding":"Irx5 is a direct, positively regulated downstream transcriptional target of Hoxb4.","method":"Chick embryo gain-of-function experiments, reporter assays demonstrating direct transcriptional regulation","journal":"Developmental dynamics","confidence":"Medium","confidence_rationale":"Tier 3 / Weak — single lab, reporter assay showing direct regulation, limited mechanistic detail in abstract","pmids":["12701098"],"is_preprint":false},{"year":2018,"finding":"IRX5 promotes proliferation, migration, and invasion of tongue squamous cell carcinoma cells by directly targeting the osteopontin (OPN) promoter and activating the NF-κB pathway.","method":"Gain- and loss-of-function in CAL27 cells, promoter binding assays, xenograft tumor model, Western blot","journal":"Journal of cellular and molecular medicine","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — gain/loss-of-function with promoter binding assay and in vivo xenograft, single lab but multiple methods","pmids":["29761910"],"is_preprint":false},{"year":2018,"finding":"IRX5 regulates adipocyte amyloid precursor protein (APP) expression by increasing APP promoter activity; both IRX5 and APP inhibit transactivation of PGC-1α and UCP1; knockdown of Irx5 or App increases mitochondrial respiration in adipocytes; Irx5 knockout mice are protected from diet-induced fat accumulation with upregulated Pgc-1α and Ucp1.","method":"Irx5 knockout mice (HF diet model), stable Irx5 knockdown in adipocytes, transcriptome analysis, transcriptional activation assays (APP promoter-luciferase), Seahorse metabolic assay","journal":"International journal of obesity","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo KO plus in vitro promoter assay and respiration measurement, single lab with multiple orthogonal methods","pmids":["30538277"],"is_preprint":false},{"year":2019,"finding":"IRX5 promotes colorectal cancer cell migration and invasion by inhibiting the core components of the RHOA/ROCK1/LIMK1 signaling pathway; overexpression of LIMK1 reverses the enhanced cellular motility caused by IRX5 overexpression.","method":"IRX5 overexpression/knockdown in CRC cells, migration/invasion assays, rescue with LIMK1 overexpression, in vivo nude mouse metastasis model","journal":"Molecular carcinogenesis","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — gain/loss-of-function with pathway rescue experiment and in vivo model, single lab","pmids":["31432570"],"is_preprint":false},{"year":2016,"finding":"IRX5 promotes G1/S-phase transition in vascular smooth muscle cells (VSMCs) via CDK2-dependent activation; Irx5 gain- and loss-of-function modulates DNA synthesis and regulates expression of p27(kip1), E2F1, and PCNA; IRX5 overexpression also induces apoptosis via caspase-3 activation; Irx5 expression is elevated in vivo in balloon-injured rat carotid arteries.","method":"Thymidine/BrdU incorporation assays in primary rat aortic VSMCs, RT-PCR, immunohistochemistry of injured arteries, caspase-3 activation assay","journal":"American journal of physiology. Cell physiology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — gain/loss-of-function with multiple functional readouts (DNA synthesis, target gene expression, apoptosis), single lab","pmids":["27170637"],"is_preprint":false},{"year":2018,"finding":"During follicle development, Irx3 and Irx5 are colocalized in pre-granulosa cells; Irx5 transitions to granulosa cell-specific expression during primordial follicle formation. Loss of both Irx3 and Irx5 causes defects in granulosa cell basement membrane deposition, mis-localization of gap junction proteins, and fewer cell projections, compromising granulosa cell-oocyte communication.","method":"Multiple Irx3/Irx5 mutant mouse models, reporter mice for lineage tracing, immunofluorescence, histology","journal":"PLoS genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple genetic mouse models with defined cellular phenotypes and localization experiments, single lab","pmids":["30071018"],"is_preprint":false},{"year":2020,"finding":"Canonical Wnt/β-catenin signaling directly stimulates Irx3 and Irx5 transcription in the developing ovary through TCF/LEF-binding sequences in two distal enhancers of the IrxB locus; in the developing testis, these same sites carry H3K27me3 marks that suppress Irx3 and Irx5 transcription.","method":"ATAC-seq and ChIP-seq database analysis, mouse gonad explant transfection/reporter assays, β-catenin gain/loss-of-function in gonads","journal":"Development (Cambridge, England)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reporter assays in gonad explants plus epigenetic ChIP-seq data identifying TCF/LEF binding sites, single lab with orthogonal methods","pmids":["32108023"],"is_preprint":false},{"year":2020,"finding":"IRX3 and IRX5 inhibit adipogenic differentiation of hypertrophic chondrocytes and promote their transition to osteoblasts; this function is downstream of WNT/β-catenin signaling, as β-catenin gain- and loss-of-function in hypertrophic chondrocytes affects Irx3 and Irx5 expression.","method":"Irx3/Irx5 single and compound null mutant mice, lineage tracing, bone histomorphometry, micro-CT, β-catenin conditional KO and gain-of-function in hypertrophic chondrocytes","journal":"Journal of bone and mineral research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple genetic models with lineage tracing plus upstream epistasis to β-catenin, single lab","pmids":["32662900"],"is_preprint":false},{"year":2021,"finding":"Irx3 and Irx5 regulate postnatal hypothalamic neurogenesis from a radial glia-like neural stem cell (RGL-NSC) population; reduced Irx3/Irx5 dosage promotes neurogenesis leading to elevated numbers of leptin-sensing arcuate neurons, resulting in enhanced leptin response and lower food intake.","method":"Irx3/Irx5 double heterozygous mice, Ins2-Cre lineage tracing, single-cell RNA sequencing, leptin response assays, food intake measurement","journal":"Nature metabolism","confidence":"High","confidence_rationale":"Tier 2 / Strong — lineage tracing plus scRNA-seq plus functional leptin/food intake assays, multiple orthogonal methods in single study","pmids":["33859429"],"is_preprint":false},{"year":2021,"finding":"Irx3 and Irx5 are ectopically expressed in Sim1+ PVH neurons of Sim1+/− mice; reducing Irx3/Irx5 dosage or PVH-specific deletion of Irx3 rescues PVH neuron defects and hyperphagia in Sim1+/− mice, demonstrating that misexpression of Irx3 and Irx5 is a central mechanism disrupting PVH development and feeding regulation in Sim1 haploinsufficiency.","method":"Single-cell RNA sequencing, Irx3/Irx5 dosage reduction in Sim1+/− mice, PVH-specific conditional Irx3 deletion, food intake measurement","journal":"Science advances","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis via conditional deletion plus scRNA-seq, single lab","pmids":["34705510"],"is_preprint":false},{"year":2022,"finding":"Irx5 is a vital transcription factor that establishes transmural heterogeneity of ventricular myocyte contractility by regulating Ito,f gradients (via Kcnd2 and Kcnip2 expression specifically in endocardium); Irx5-KO mice show decreased global LV contractility and reduced cell shortening/Ca2+ transients in endocardial but not epicardial cardiomyocytes; double KO of Irx5 and Kcnd2 restores contractility to KV4.2-KO levels, demonstrating dominant role of Irx5-dependent Ito,f.","method":"Irx5-KO, KV4.2-KO, and Irx5/KV4.2 double-KO mice, isolated cardiomyocyte contractility/Ca2+ measurements, transcriptional profiling, echocardiography","journal":"American journal of physiology. Heart and circulatory physiology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple KO models with epistasis, cardiomyocyte-level functional measurements plus transcriptional profiling, multiple orthogonal methods","pmids":["35245131"],"is_preprint":false},{"year":2022,"finding":"IRX5 promotes adipogenesis of human bone marrow-derived mesenchymal stem cells (hMSCs) by transcriptionally activating PGC-1α and inhibiting glycolysis; metformin and PGC-1α inhibitor reverse IRX5-induced adipogenesis.","method":"Lentiviral IRX5 gain/loss-of-function in hMSCs, RNA-seq, metabolomics, dual-luciferase reporter assay (PGC-1α promoter), adipogenesis assays","journal":"Cell death discovery","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — gain/loss-of-function with promoter reporter assay and metabolomics, single lab, multiple methods","pmids":["35428362"],"is_preprint":false},{"year":2022,"finding":"Irx5 deficiency in mice protects against diet-induced obesity primarily through increased adipose thermogenesis (upregulation of PGC-1α and UCP1) and improved hypothalamic leptin response; scRNA-seq of the arcuate-median eminence region shows elevated neuron numbers in Irx5KO mice.","method":"Irx5 knockout mice on high-fat diet, body composition measurement, energy expenditure assays, scRNA-seq of hypothalamic ARC-ME region","journal":"International journal of obesity","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo KO with metabolic phenotyping plus scRNA-seq, single lab","pmids":["36115924"],"is_preprint":false},{"year":2023,"finding":"IRX5 promotes DNA damage repair and hair follicle stem cell (HFSC) activation; Irx5-/- mice show delayed anagen onset, increased DNA damage, diminished HFSC proliferation, and open chromatin near cell cycle and DNA damage repair genes; BRCA1 is an IRX5 downstream transcriptional target; Irx5-/- quiescence is partly due to failure to suppress Fgf18, as FGF kinase signaling inhibition partially rescues the anagen delay.","method":"Irx5-/- mice, ATAC-seq of HFSCs, ChIP/reporter assays for BRCA1 as downstream target, pharmacological rescue with FGF kinase inhibitor, proliferation/DNA damage assays","journal":"Stem cell reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO mice with ATAC-seq, target gene validation, and pharmacological rescue, single lab with orthogonal methods","pmids":["37084727"],"is_preprint":false},{"year":2018,"finding":"IRX3 and IRX5 are essential for mammalian nephrogenesis; in Wilms tumour, IRX5 expression is activated in early proliferative blastema and IRX5-/- Wilms tumour cells activate Hippo and non-canonical WNT signaling, generating small tumours with abundant tubulogenesis.","method":"Irx3-/Irx5- double knockout mice (embryonic nephron formation), orthotopic xenograft mouse model with IRX3-/- and IRX5-/- Wilms tumour cells, pathway analysis","journal":"The Journal of pathology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO mice with defined developmental phenotype plus xenograft model revealing pathway activation, single lab","pmids":["30246301"],"is_preprint":false},{"year":2018,"finding":"Id2 represses Irx5 in the midgut endoderm to establish intestinal identity; transgenic mice expressing Irx5 in midgut endoderm develop gastric metaplasia-like intestinal tumors, recapitulating the Id2-/- phenotype.","method":"Id2-/- mice, Irx5 transgenic mice with midgut-specific expression, gene expression analysis, histology","journal":"Molecular and cellular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis via transgenic rescue experiment establishing Id2 upstream of Irx5, single lab","pmids":["29463648"],"is_preprint":false},{"year":2024,"finding":"IRX5 interacts directly with HMGN4; HMGN4 drives IRX5 nuclear translocation and co-localizes with IRX5 in the nucleus; IRX5 promotes de novo fatty acid synthesis in hepatocellular carcinoma, accelerating cancer cell proliferation and progression.","method":"GST pull-down combined with GC/MS, co-immunoprecipitation, immunofluorescence co-localization, HMGN4 overexpression effects on IRX5 nuclear transport","journal":"Journal of cellular and molecular medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — GST pull-down plus CoIP plus immunofluorescence establishing protein-protein interaction and nuclear translocation mechanism, single lab","pmids":["40208102"],"is_preprint":false},{"year":2024,"finding":"IRX5 suppresses osteogenic differentiation of human BMSCs by inhibiting mTOR-mediated ribosomal translation and impairing mitochondrial oxidative phosphorylation; mTOR activator MHY1485 reverses the inhibitory impact of IRX5 on osteogenesis.","method":"IRX5 gain/loss-of-function in hBMSCs, RNA-seq, transmission electron microscopy, Seahorse mito-stress assay, Surface Sensing of Translation (SUnSET) assay, pharmacological rescue with mTOR activator","journal":"Journal of cellular physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — gain/loss-of-function with multiple orthogonal mechanistic assays (translational, metabolic, pharmacological rescue), single lab","pmids":["38666481"],"is_preprint":false},{"year":2024,"finding":"IRX5 transcriptionally regulates YWHAB (14-3-3β) expression by acting on its promoter sequence upstream of the transcription start site, as demonstrated by dual luciferase assay.","method":"Dual luciferase reporter assay, gain/loss-of-function in breast cancer cells","journal":"Oncology letters","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single luciferase assay, single lab, limited mechanistic detail","pmids":["39119237"],"is_preprint":false},{"year":2026,"finding":"PLAGL1 transcriptionally activates Irx5 synergistically with KLF4 in periosteal stem/progenitor cells (PSPCs), and IRX5 in turn induces downstream osteogenic genes; this PLAGL1-KLF4-IRX5 axis controls osteoblast differentiation of PSPCs during mandibular bone regeneration.","method":"PLAGL1 KO mice, CRISPR-dCas9-Tet1 epigenetic activation system, transcriptional reporter assays, mandible regeneration model","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO mice with defined regeneration phenotype, identification of PLAGL1-KLF4-IRX5 axis via transcriptional assays, single lab","pmids":["42168182"],"is_preprint":false}],"current_model":"IRX5 is a homeodomain transcription factor that acts primarily as a transcriptional repressor or activator depending on context: in the heart it represses Kv4.2 (Kcnd2) by recruiting mBop to establish the ventricular repolarization gradient and forms a complex with GATA4 to regulate Nav1.5/SCN5A expression; in adipose tissue it represses thermogenesis by inhibiting PGC-1α/UCP1 and activating APP; in the retina and brain it controls bipolar cell differentiation and hypothalamic neurogenesis; it modulates cell fate decisions in chondrocyte-to-osteoblast transitions downstream of Wnt/β-catenin signaling; it promotes DNA damage repair and hair follicle stem cell activation via BRCA1; it is subject to upstream regulation by Hoxb4 and Id2, interacts directly with GATA3, TRPS1, and GATA4 proteins, and requires HMGN4 for its nuclear translocation."},"narrative":{"mechanistic_narrative":"IRX5 is a homeodomain transcription factor that controls cell-type identity, differentiation, and excitable-cell function across the heart, retina, brain, gonad, skeleton, and adipose tissue, acting context-dependently as a transcriptional repressor or activator [PMID:16239150, PMID:35245131, PMID:33859429]. In the ventricular myocardium it establishes transmural electrical and contractile heterogeneity by repressing the Kv4.2 (Kcnd2) potassium-channel gene—through recruitment of the cardiac repressor mBop—to generate the inverse Ito,f gradient required for coordinated repolarization, with loss of Irx5 reducing endocardial cardiomyocyte contractility in a Kcnd2-dependent manner [PMID:16239150, PMID:35245131]. It also forms a complex with GATA4 that potentiates SCN5A/Nav1.5 induction, and its loss in patient-derived cardiomyocytes slows depolarization through reduced sodium current [PMID:32898233]; in conduction tissue Irx5 acts redundantly with Irx3, the pair repressing Bmp10 and Nav1.5 [PMID:22992950]. In retinal development Irx5 specifies OFF cone bipolar cell differentiation independently of Vsx1 and, together with Vsx1, tunes OFF-circuit response properties [PMID:16182275, PMID:18322081]. In the hypothalamus Irx3/Irx5 restrain neurogenesis from radial-glia-like neural stem cells, controlling the number of leptin-sensing arcuate neurons and thereby feeding and energy balance [PMID:33859429, PMID:34705510]. In metabolic and skeletal tissues IRX5 acts downstream of WNT/β-catenin to direct chondrocyte-to-osteoblast and mesenchymal cell-fate decisions and to modulate thermogenesis via PGC-1α/UCP1 [PMID:32662900, PMID:32108023, PMID:36115924]. IRX5 transcriptional output is shaped by direct protein partners GATA3, TRPS1, and GATA4, and its nuclear translocation requires HMGN4 [PMID:22581230, PMID:32898233, PMID:40208102]. Human loss-of-function mutations in IRX5 cause Hamamy syndrome [PMID:32898233].","teleology":[{"year":2005,"claim":"Established the first molecular mechanism for IRX5 in cardiac physiology by showing it sets the ventricular repolarization gradient through repression of a specific ion-channel gene.","evidence":"Irx5 knockout mice with chromatin co-IP, electrophysiology, and gradient immunofluorescence","pmids":["16239150"],"confidence":"High","gaps":["Did not define how Irx5 binds the Kcnd2 locus","mBop recruitment shown in heart only; generality to other Irx5 targets unknown"]},{"year":2005,"claim":"Defined a developmental role for Irx5 in retinal cell-type specification, distinct from the known Vsx1 bipolar-cell pathway.","evidence":"Irx5 knockout mice, cell-type marker IHC, Irx5/Vsx1 epistasis","pmids":["16182275"],"confidence":"High","gaps":["Direct transcriptional targets in bipolar cells not identified","Cofactors mediating differentiation unknown"]},{"year":2008,"claim":"Extended the retinal role to circuit-level function, showing Irx5 with Vsx1 selectively tunes OFF visual pathway physiology rather than morphology.","evidence":"Vsx1/Irx5 double-KO mice, multi-electrode array recording, contrast adaptation modeling","pmids":["18322081"],"confidence":"High","gaps":["Molecular targets underlying altered gain/threshold unknown","Functional separation of Irx5 vs Vsx1 contributions not resolved"]},{"year":2012,"claim":"Identified direct protein partners (GATA3, TRPS1) for IRX5 and linked it to progenitor migration via Sdf1 repression, while connecting IRX5 mutations to human disease.","evidence":"Xenopus loss-of-function, protein-protein interaction assays, human homozygosity mapping","pmids":["22581230"],"confidence":"High","gaps":["Structural basis of GATA3/TRPS1 interaction not defined","Whether Sdf1 repression generalizes beyond branchial arches/gonads unknown"]},{"year":2012,"claim":"Resolved functional redundancy and antagonism between Irx3 and Irx5 in the endocardium and myocardium, refining the model of cardiac patterning and conduction.","evidence":"Irx3/Irx5 double and conditional KO mice, RT-PCR, electrophysiology, epistasis","pmids":["22992950"],"confidence":"High","gaps":["Mechanism by which Irx5 represses Irx3 activity unknown","Direct vs indirect repression of Bmp10/Nav1.5 not fully separated"]},{"year":2021,"claim":"Defined a positive, GATA4-dependent arm of IRX5 cardiac function on SCN5A, complementing its repressive role and explaining the depolarization defect in patient cells.","evidence":"Hamamy-syndrome hiPSC-cardiomyocytes, patch clamp, Co-IP, transcriptomics","pmids":["32898233"],"confidence":"High","gaps":["Structure/stoichiometry of the IRX5-GATA4 complex unknown","Whether the same complex acts at other cardiac genes untested"]},{"year":2021,"claim":"Established Irx3/Irx5 as dosage-sensitive regulators of postnatal hypothalamic neurogenesis controlling feeding and leptin response.","evidence":"Irx3/Irx5 double-heterozygous mice, lineage tracing, scRNA-seq, leptin/food-intake assays","pmids":["33859429"],"confidence":"High","gaps":["Direct transcriptional targets in radial-glia-like NSCs not identified","Relative contribution of Irx3 vs Irx5 not separated"]},{"year":2021,"claim":"Showed that ectopic Irx3/Irx5 expression is the mechanism disrupting PVH development in Sim1 haploinsufficiency, linking IRX dosage to a genetic obesity syndrome.","evidence":"scRNA-seq, Irx dosage reduction in Sim1+/- mice, PVH-specific Irx3 deletion, food intake","pmids":["34705510"],"confidence":"Medium","gaps":["How Sim1 normally restrains Irx3/Irx5 not defined","Irx5-specific contribution within the rescue not isolated"]},{"year":2022,"claim":"Linked the Irx5-Ito,f axis to mechanical function, showing Irx5 controls transmural contractility, not just electrical repolarization.","evidence":"Irx5-KO, KV4.2-KO, double-KO mice, cardiomyocyte contractility/Ca2+ measurement, echocardiography","pmids":["35245131"],"confidence":"High","gaps":["Mechanistic coupling of Ito,f gradient to contractility incompletely defined","Role of Kcnip2 regulation by Irx5 not fully separated from Kcnd2"]},{"year":2020,"claim":"Placed Irx3/Irx5 downstream of WNT/β-catenin in gonad and skeletal cell-fate decisions, identifying TCF/LEF enhancers and sex-specific epigenetic control of the IrxB locus.","evidence":"ATAC/ChIP-seq analysis, gonad explant reporter assays, β-catenin gain/loss, lineage tracing, micro-CT (two studies)","pmids":["32108023","32662900"],"confidence":"Medium","gaps":["Downstream osteoblast/chondrocyte targets of Irx5 not enumerated","Irx5-specific versus Irx3 roles not separated"]},{"year":2018,"claim":"Documented context-dependent roles of IRX5 in adipose metabolism and multiple cancers, mapping target promoters and signaling outputs.","evidence":"Irx5-KO mice, adipocyte knockdown, promoter-luciferase, Seahorse; gain/loss in TSCC, CRC cells with promoter assays and xenografts","pmids":["30538277","29761910","29463648"],"confidence":"Medium","gaps":["Apparent opposing effects on PGC-1α/UCP1 across tissues unresolved","Direct vs indirect regulation of cancer-associated targets not always established"]},{"year":2024,"claim":"Identified HMGN4 as the factor driving IRX5 nuclear translocation, providing a mechanism for regulated IRX5 activity, and extended IRX5 function to hepatic lipid synthesis.","evidence":"GST pull-down, Co-IP, immunofluorescence co-localization in HCC cells","pmids":["40208102"],"confidence":"Medium","gaps":["Whether HMGN4-dependent import operates in non-cancer tissues unknown","Interaction not reciprocally validated across systems"]},{"year":2024,"claim":"Defined IRX5 as a suppressor of osteogenesis through inhibition of mTOR-dependent translation and oxidative phosphorylation in human BMSCs.","evidence":"Gain/loss-of-function in hBMSCs, RNA-seq, SUnSET translation assay, Seahorse, mTOR-activator rescue","pmids":["38666481"],"confidence":"Medium","gaps":["Direct transcriptional targets linking IRX5 to mTOR not identified","Reconciliation with PLAGL1-KLF4-IRX5 pro-osteogenic axis unresolved"]},{"year":2023,"claim":"Revealed a chromatin/repair role for IRX5 in hair follicle stem cell activation, with BRCA1 as a downstream target and Fgf18 suppression contributing to anagen onset.","evidence":"Irx5-/- mice, ATAC-seq of HFSCs, ChIP/reporter for BRCA1, FGF-kinase-inhibitor rescue","pmids":["37084727"],"confidence":"Medium","gaps":["Direct binding of IRX5 to BRCA1/Fgf18 loci versus indirect effects not fully resolved","Generality of DNA-repair role beyond HFSCs unknown"]},{"year":2026,"claim":"Positioned IRX5 within a PLAGL1-KLF4-IRX5 transcriptional axis driving osteoblast differentiation during bone regeneration.","evidence":"PLAGL1-KO mice, CRISPR-dCas9-Tet1 epigenetic activation, reporter assays, mandible regeneration model","pmids":["42168182"],"confidence":"Medium","gaps":["Direct osteogenic targets induced by IRX5 not enumerated","Apparent contradiction with IRX5 suppression of osteogenesis in hBMSCs unresolved"]},{"year":null,"claim":"The molecular logic dictating whether IRX5 represses or activates a given target—and how its cofactor repertoire (mBop, GATA4, GATA3, TRPS1, HMGN4) selects context-specific programs—remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of IRX5 DNA binding or cofactor complexes","Tissue-specific direct target catalogs largely undefined","Opposing metabolic/osteogenic phenotypes across tissues not mechanistically reconciled"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[0,3,4,5,8,16,19]},{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[5,7,8,17,24]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[22]}],"pathway":[{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[0,5,16]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[1,2,11,13,14,20]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[12,13,9]}],"complexes":[],"partners":["GATA4","GATA3","TRPS1","HMGN4","BHLHB9"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P78411","full_name":"Iroquois-class homeodomain protein IRX-5","aliases":["Homeodomain protein IRX-2A","Homeodomain protein IRXB2","Iroquois homeobox protein 5"],"length_aa":483,"mass_kda":50.4,"function":"Establishes the cardiac repolarization gradient by its repressive actions on the KCND2 potassium-channel gene. Required for retinal cone bipolar cell differentiation. May regulate contrast adaptation in the retina and control specific aspects of visual function in circuits of the mammalian retina (By similarity). Could be involved in the regulation of both the cell cycle and apoptosis in prostate cancer cells. Involved in craniofacial and gonadal development. Modulates the migration of progenitor cell populations in branchial arches and gonads by repressing CXCL12","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/P78411/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/IRX5","classification":"Not Classified","n_dependent_lines":8,"n_total_lines":1208,"dependency_fraction":0.006622516556291391},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/IRX5","total_profiled":1310},"omim":[{"mim_id":"619649","title":"CHROMOSOME 16q12 DUPLICATION SYNDROME","url":"https://www.omim.org/entry/619649"},{"mim_id":"615624","title":"COLORECTAL NEOPLASIA DIFFERENTIALLY EXPRESSED GENE, NONCODING; CRNDE","url":"https://www.omim.org/entry/615624"},{"mim_id":"612985","title":"IROQUOIS HOMEOBOX PROTEIN 3; IRX3","url":"https://www.omim.org/entry/612985"},{"mim_id":"612460","title":"BODY MASS INDEX QUANTITATIVE TRAIT LOCUS 14; BMIQ14","url":"https://www.omim.org/entry/612460"},{"mim_id":"611174","title":"HAMAMY SYNDROME; HMMS","url":"https://www.omim.org/entry/611174"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nuclear speckles","reliability":"Approved"},{"location":"Microtubules","reliability":"Additional"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"breast","ntpm":13.2},{"tissue":"skin 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Heart and circulatory physiology","url":"https://pubmed.ncbi.nlm.nih.gov/35245131","citation_count":2,"is_preprint":false},{"pmid":"39401533","id":"PMC_39401533","title":"A novel genetic mouse model of osteoporosis with double heterozygosity of Irx3 and Irx5 characterizes sex-dependent phenotypes in bone homeostasis.","date":"2024","source":"Bone","url":"https://pubmed.ncbi.nlm.nih.gov/39401533","citation_count":1,"is_preprint":false},{"pmid":"42168182","id":"PMC_42168182","title":"The PLAGL1-KLF4-IRX5 axis promotes the osteogenesis of periosteal progenitors during mandible regeneration.","date":"2026","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/42168182","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.10.06.680592","title":"Single-nucleus transcriptional and chromatin accessibility profiling of mouse hypothalamic LepRb neurons reveals cell type-specific cis-regulatory elements linked to human obesity","date":"2025-10-07","source":"bioRxiv","url":"https://doi.org/10.1101/2025.10.06.680592","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.10.24.620152","title":"Irx3/5 define the cochlear sensory domain and regulate vestibular and cochlear sensory patterning in the mammalian inner ear","date":"2024-10-26","source":"bioRxiv","url":"https://doi.org/10.1101/2024.10.24.620152","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.06.26.600851","title":"Conserved Noncoding Cis-Elements Associated with Hibernation Modulate Metabolic and Behavioral Adaptations in Mice","date":"2024-06-27","source":"bioRxiv","url":"https://doi.org/10.1101/2024.06.26.600851","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":21208,"output_tokens":6561,"usd":0.081019,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":15510,"output_tokens":4716,"usd":0.097725,"stage2_stop_reason":"end_turn"},"total_usd":0.178744,"stage1_batch_id":"msgbatch_01DUPACZi7AAWwuZiUjseQF4","stage2_batch_id":"msgbatch_018yt7chE3f48PEFtDwtj6AE","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n \"discoveries\": [\n {\n \"year\": 2005,\n \"finding\": \"Irx5 represses Kv4.2 (Kcnd2) potassium-channel gene expression in endocardial myocardium by recruiting mBop (a cardiac transcriptional repressor), establishing an inverse Ito,f gradient that ensures coordinated cardiac ventricular repolarization and prevents arrhythmias.\",\n \"method\": \"Irx5 knockout mice, chromatin co-IP (recruitment of mBop), electrophysiology (Ito,f measurement), immunofluorescence gradient analysis\",\n \"journal\": \"Cell\",\n \"confidence\": \"High\",\n \"confidence_rationale\": \"Tier 2 / Strong — reciprocal interaction assay (Irx5-mBop recruitment), KO mice with specific electrophysiological phenotype (Ito,f), replicated across multiple methods in a single rigorous study\",\n \"pmids\": [\"16239150\"],\n \"is_preprint\": false\n },\n {\n \"year\": 2005,\n \"finding\": \"Irx5 is expressed in a subset of cone bipolar cells in the mature mouse retina (Type 2 and Type 3 OFF cone bipolar cells) starting at postnatal day 5, and is required for their differentiation independently of the Vsx1 pathway, as Irx5-deficient mice lack certain bipolar cell markers while Vsx1 expression is unaffected.\",\n \"method\": \"Irx5 knockout mice, immunohistochemistry with cell-type specific markers, genetic epistasis (Irx5/Vsx1 double mutant analysis)\",\n \"journal\": \"Developmental biology\",\n \"confidence\": \"High\",\n \"confidence_rationale\": \"Tier 2 / Strong — KO mice with defined cellular phenotype plus genetic epistasis establishing independence from Vsx1 pathway, multiple orthogonal methods\",\n \"pmids\": [\"16182275\"],\n \"is_preprint\": false\n },\n {\n \"year\": 2008,\n \"finding\": \"Vsx1 and Irx5 together control response threshold, gain, range, and contrast adaptation specifically in OFF (not ON) retinal ganglion cell circuits, demonstrated by loss-of-function in Vsx1−/−Irx5−/− double-mutant mice; bipolar cell morphology was normal but OFF circuit function was selectively impaired.\",\n \"method\": \"Vsx1/Irx5 double knockout mice, multi-electrode array retinal ganglion cell recording, linear-nonlinear model of contrast adaptation\",\n \"journal\": \"The Journal of neuroscience\",\n \"confidence\": \"High\",\n \"confidence_rationale\": \"Tier 2 / Strong — clean double KO with specific electrophysiological phenotype readout, circuit-level functional analysis with cell-type specificity\",\n \"pmids\": [\"18322081\"],\n \"is_preprint\": false\n },\n {\n \"year\": 2012,\n \"finding\": \"Irx5 modulates migration of progenitor cell populations in branchial arches and gonads by repressing Sdf1 expression; transcriptional control by Irx5 is modulated by direct protein-protein interaction with GATA3 and TRPS1 zinc-finger proteins.\",\n \"method\": \"In vivo modeling in Xenopus laevis embryos (loss-of-function), protein-protein interaction assays, homozygosity mapping in human patients with IRX5 mutations\",\n \"journal\": \"Nature genetics\",\n \"confidence\": \"High\",\n \"confidence_rationale\": \"Tier 2 / Moderate — in vivo Xenopus epistasis establishing Sdf1 repression plus direct protein-protein interaction with GATA3/TRPS1, two orthogonal methods\",\n \"pmids\": [\"22581230\"],\n \"is_preprint\": false\n },\n {\n \"year\": 2012,\n \"finding\": \"Irx3 and Irx5 have redundant function in the endocardium to regulate atrioventricular canal morphogenesis and outflow tract formation via direct transcriptional repression of Bmp10; combined postnatal loss of Irx3 and Irx5 in the myocardium activates Nav1.5 expression and prolongs atrioventricular conduction; postnatal Irx5 can repress Irx3 activity, as combined loss restores the repolarization gradient lost in Irx5-single mutants.\",\n \"method\": \"Irx3/Irx5 double knockout and conditional knockout mice, RT-PCR, electrophysiology, genetic epistasis\",\n \"journal\": \"Development (Cambridge, England)\",\n \"confidence\": \"High\",\n \"confidence_rationale\": \"Tier 2 / Strong — multiple conditional KO models with defined cardiac phenotypes, epistasis between Irx3 and Irx5, multiple orthogonal methods\",\n \"pmids\": [\"22992950\"],\n \"is_preprint\": false\n },\n {\n \"year\": 2021,\n \"finding\": \"IRX5 forms a transcription factor complex with GATA4 in cardiac cells, in which IRX5 potentiates GATA4-induction of SCN5A (Nav1.5) expression; loss-of-function mutations in IRX5 in human hiPSC-derived cardiomyocytes reduce Nav1.5 and Cx40 expression and slow ventricular action potential depolarization due to reduced sodium current.\",\n \"method\": \"hiPSC-derived cardiomyocytes from Hamamy syndrome patients with IRX5 loss-of-function mutations, electrophysiology (patch clamp), Co-IP (IRX5-GATA4 complex identification), transcriptomic analysis\",\n \"journal\": \"Cardiovascular research\",\n \"confidence\": \"High\",\n \"confidence_rationale\": \"Tier 2 / Moderate — patient-derived hiPSC cardiomyocytes with electrophysiology plus Co-IP identifying novel IRX5-GATA4 complex, two orthogonal methods in single rigorous study\",\n \"pmids\": [\"32898233\"],\n \"is_preprint\": false\n },\n {\n \"year\": 2003,\n \"finding\": \"Irx5 is a direct, positively regulated downstream transcriptional target of Hoxb4.\",\n \"method\": \"Chick embryo gain-of-function experiments, reporter assays demonstrating direct transcriptional regulation\",\n \"journal\": \"Developmental dynamics\",\n \"confidence\": \"Medium\",\n \"confidence_rationale\": \"Tier 3 / Weak — single lab, reporter assay showing direct regulation, limited mechanistic detail in abstract\",\n \"pmids\": [\"12701098\"],\n \"is_preprint\": false\n },\n {\n \"year\": 2018,\n \"finding\": \"IRX5 promotes proliferation, migration, and invasion of tongue squamous cell carcinoma cells by directly targeting the osteopontin (OPN) promoter and activating the NF-κB pathway.\",\n \"method\": \"Gain- and loss-of-function in CAL27 cells, promoter binding assays, xenograft tumor model, Western blot\",\n \"journal\": \"Journal of cellular and molecular medicine\",\n \"confidence\": \"Medium\",\n \"confidence_rationale\": \"Tier 3 / Moderate — gain/loss-of-function with promoter binding assay and in vivo xenograft, single lab but multiple methods\",\n \"pmids\": [\"29761910\"],\n \"is_preprint\": false\n },\n {\n \"year\": 2018,\n \"finding\": \"IRX5 regulates adipocyte amyloid precursor protein (APP) expression by increasing APP promoter activity; both IRX5 and APP inhibit transactivation of PGC-1α and UCP1; knockdown of Irx5 or App increases mitochondrial respiration in adipocytes; Irx5 knockout mice are protected from diet-induced fat accumulation with upregulated Pgc-1α and Ucp1.\",\n \"method\": \"Irx5 knockout mice (HF diet model), stable Irx5 knockdown in adipocytes, transcriptome analysis, transcriptional activation assays (APP promoter-luciferase), Seahorse metabolic assay\",\n \"journal\": \"International journal of obesity\",\n \"confidence\": \"Medium\",\n \"confidence_rationale\": \"Tier 2 / Moderate — in vivo KO plus in vitro promoter assay and respiration measurement, single lab with multiple orthogonal methods\",\n \"pmids\": [\"30538277\"],\n \"is_preprint\": false\n },\n {\n \"year\": 2019,\n \"finding\": \"IRX5 promotes colorectal cancer cell migration and invasion by inhibiting the core components of the RHOA/ROCK1/LIMK1 signaling pathway; overexpression of LIMK1 reverses the enhanced cellular motility caused by IRX5 overexpression.\",\n \"method\": \"IRX5 overexpression/knockdown in CRC cells, migration/invasion assays, rescue with LIMK1 overexpression, in vivo nude mouse metastasis model\",\n \"journal\": \"Molecular carcinogenesis\",\n \"confidence\": \"Medium\",\n \"confidence_rationale\": \"Tier 3 / Moderate — gain/loss-of-function with pathway rescue experiment and in vivo model, single lab\",\n \"pmids\": [\"31432570\"],\n \"is_preprint\": false\n },\n {\n \"year\": 2016,\n \"finding\": \"IRX5 promotes G1/S-phase transition in vascular smooth muscle cells (VSMCs) via CDK2-dependent activation; Irx5 gain- and loss-of-function modulates DNA synthesis and regulates expression of p27(kip1), E2F1, and PCNA; IRX5 overexpression also induces apoptosis via caspase-3 activation; Irx5 expression is elevated in vivo in balloon-injured rat carotid arteries.\",\n \"method\": \"Thymidine/BrdU incorporation assays in primary rat aortic VSMCs, RT-PCR, immunohistochemistry of injured arteries, caspase-3 activation assay\",\n \"journal\": \"American journal of physiology. Cell physiology\",\n \"confidence\": \"Medium\",\n \"confidence_rationale\": \"Tier 3 / Moderate — gain/loss-of-function with multiple functional readouts (DNA synthesis, target gene expression, apoptosis), single lab\",\n \"pmids\": [\"27170637\"],\n \"is_preprint\": false\n },\n {\n \"year\": 2018,\n \"finding\": \"During follicle development, Irx3 and Irx5 are colocalized in pre-granulosa cells; Irx5 transitions to granulosa cell-specific expression during primordial follicle formation. Loss of both Irx3 and Irx5 causes defects in granulosa cell basement membrane deposition, mis-localization of gap junction proteins, and fewer cell projections, compromising granulosa cell-oocyte communication.\",\n \"method\": \"Multiple Irx3/Irx5 mutant mouse models, reporter mice for lineage tracing, immunofluorescence, histology\",\n \"journal\": \"PLoS genetics\",\n \"confidence\": \"Medium\",\n \"confidence_rationale\": \"Tier 2 / Moderate — multiple genetic mouse models with defined cellular phenotypes and localization experiments, single lab\",\n \"pmids\": [\"30071018\"],\n \"is_preprint\": false\n },\n {\n \"year\": 2020,\n \"finding\": \"Canonical Wnt/β-catenin signaling directly stimulates Irx3 and Irx5 transcription in the developing ovary through TCF/LEF-binding sequences in two distal enhancers of the IrxB locus; in the developing testis, these same sites carry H3K27me3 marks that suppress Irx3 and Irx5 transcription.\",\n \"method\": \"ATAC-seq and ChIP-seq database analysis, mouse gonad explant transfection/reporter assays, β-catenin gain/loss-of-function in gonads\",\n \"journal\": \"Development (Cambridge, England)\",\n \"confidence\": \"Medium\",\n \"confidence_rationale\": \"Tier 2 / Moderate — reporter assays in gonad explants plus epigenetic ChIP-seq data identifying TCF/LEF binding sites, single lab with orthogonal methods\",\n \"pmids\": [\"32108023\"],\n \"is_preprint\": false\n },\n {\n \"year\": 2020,\n \"finding\": \"IRX3 and IRX5 inhibit adipogenic differentiation of hypertrophic chondrocytes and promote their transition to osteoblasts; this function is downstream of WNT/β-catenin signaling, as β-catenin gain- and loss-of-function in hypertrophic chondrocytes affects Irx3 and Irx5 expression.\",\n \"method\": \"Irx3/Irx5 single and compound null mutant mice, lineage tracing, bone histomorphometry, micro-CT, β-catenin conditional KO and gain-of-function in hypertrophic chondrocytes\",\n \"journal\": \"Journal of bone and mineral research\",\n \"confidence\": \"Medium\",\n \"confidence_rationale\": \"Tier 2 / Moderate — multiple genetic models with lineage tracing plus upstream epistasis to β-catenin, single lab\",\n \"pmids\": [\"32662900\"],\n \"is_preprint\": false\n },\n {\n \"year\": 2021,\n \"finding\": \"Irx3 and Irx5 regulate postnatal hypothalamic neurogenesis from a radial glia-like neural stem cell (RGL-NSC) population; reduced Irx3/Irx5 dosage promotes neurogenesis leading to elevated numbers of leptin-sensing arcuate neurons, resulting in enhanced leptin response and lower food intake.\",\n \"method\": \"Irx3/Irx5 double heterozygous mice, Ins2-Cre lineage tracing, single-cell RNA sequencing, leptin response assays, food intake measurement\",\n \"journal\": \"Nature metabolism\",\n \"confidence\": \"High\",\n \"confidence_rationale\": \"Tier 2 / Strong — lineage tracing plus scRNA-seq plus functional leptin/food intake assays, multiple orthogonal methods in single study\",\n \"pmids\": [\"33859429\"],\n \"is_preprint\": false\n },\n {\n \"year\": 2021,\n \"finding\": \"Irx3 and Irx5 are ectopically expressed in Sim1+ PVH neurons of Sim1+/− mice; reducing Irx3/Irx5 dosage or PVH-specific deletion of Irx3 rescues PVH neuron defects and hyperphagia in Sim1+/− mice, demonstrating that misexpression of Irx3 and Irx5 is a central mechanism disrupting PVH development and feeding regulation in Sim1 haploinsufficiency.\",\n \"method\": \"Single-cell RNA sequencing, Irx3/Irx5 dosage reduction in Sim1+/− mice, PVH-specific conditional Irx3 deletion, food intake measurement\",\n \"journal\": \"Science advances\",\n \"confidence\": \"Medium\",\n \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis via conditional deletion plus scRNA-seq, single lab\",\n \"pmids\": [\"34705510\"],\n \"is_preprint\": false\n },\n {\n \"year\": 2022,\n \"finding\": \"Irx5 is a vital transcription factor that establishes transmural heterogeneity of ventricular myocyte contractility by regulating Ito,f gradients (via Kcnd2 and Kcnip2 expression specifically in endocardium); Irx5-KO mice show decreased global LV contractility and reduced cell shortening/Ca2+ transients in endocardial but not epicardial cardiomyocytes; double KO of Irx5 and Kcnd2 restores contractility to KV4.2-KO levels, demonstrating dominant role of Irx5-dependent Ito,f.\",\n \"method\": \"Irx5-KO, KV4.2-KO, and Irx5/KV4.2 double-KO mice, isolated cardiomyocyte contractility/Ca2+ measurements, transcriptional profiling, echocardiography\",\n \"journal\": \"American journal of physiology. Heart and circulatory physiology\",\n \"confidence\": \"High\",\n \"confidence_rationale\": \"Tier 2 / Strong — multiple KO models with epistasis, cardiomyocyte-level functional measurements plus transcriptional profiling, multiple orthogonal methods\",\n \"pmids\": [\"35245131\"],\n \"is_preprint\": false\n },\n {\n \"year\": 2022,\n \"finding\": \"IRX5 promotes adipogenesis of human bone marrow-derived mesenchymal stem cells (hMSCs) by transcriptionally activating PGC-1α and inhibiting glycolysis; metformin and PGC-1α inhibitor reverse IRX5-induced adipogenesis.\",\n \"method\": \"Lentiviral IRX5 gain/loss-of-function in hMSCs, RNA-seq, metabolomics, dual-luciferase reporter assay (PGC-1α promoter), adipogenesis assays\",\n \"journal\": \"Cell death discovery\",\n \"confidence\": \"Medium\",\n \"confidence_rationale\": \"Tier 3 / Moderate — gain/loss-of-function with promoter reporter assay and metabolomics, single lab, multiple methods\",\n \"pmids\": [\"35428362\"],\n \"is_preprint\": false\n },\n {\n \"year\": 2022,\n \"finding\": \"Irx5 deficiency in mice protects against diet-induced obesity primarily through increased adipose thermogenesis (upregulation of PGC-1α and UCP1) and improved hypothalamic leptin response; scRNA-seq of the arcuate-median eminence region shows elevated neuron numbers in Irx5KO mice.\",\n \"method\": \"Irx5 knockout mice on high-fat diet, body composition measurement, energy expenditure assays, scRNA-seq of hypothalamic ARC-ME region\",\n \"journal\": \"International journal of obesity\",\n \"confidence\": \"Medium\",\n \"confidence_rationale\": \"Tier 2 / Moderate — in vivo KO with metabolic phenotyping plus scRNA-seq, single lab\",\n \"pmids\": [\"36115924\"],\n \"is_preprint\": false\n },\n {\n \"year\": 2023,\n \"finding\": \"IRX5 promotes DNA damage repair and hair follicle stem cell (HFSC) activation; Irx5-/- mice show delayed anagen onset, increased DNA damage, diminished HFSC proliferation, and open chromatin near cell cycle and DNA damage repair genes; BRCA1 is an IRX5 downstream transcriptional target; Irx5-/- quiescence is partly due to failure to suppress Fgf18, as FGF kinase signaling inhibition partially rescues the anagen delay.\",\n \"method\": \"Irx5-/- mice, ATAC-seq of HFSCs, ChIP/reporter assays for BRCA1 as downstream target, pharmacological rescue with FGF kinase inhibitor, proliferation/DNA damage assays\",\n \"journal\": \"Stem cell reports\",\n \"confidence\": \"Medium\",\n \"confidence_rationale\": \"Tier 2 / Moderate — KO mice with ATAC-seq, target gene validation, and pharmacological rescue, single lab with orthogonal methods\",\n \"pmids\": [\"37084727\"],\n \"is_preprint\": false\n },\n {\n \"year\": 2018,\n \"finding\": \"IRX3 and IRX5 are essential for mammalian nephrogenesis; in Wilms tumour, IRX5 expression is activated in early proliferative blastema and IRX5-/- Wilms tumour cells activate Hippo and non-canonical WNT signaling, generating small tumours with abundant tubulogenesis.\",\n \"method\": \"Irx3-/Irx5- double knockout mice (embryonic nephron formation), orthotopic xenograft mouse model with IRX3-/- and IRX5-/- Wilms tumour cells, pathway analysis\",\n \"journal\": \"The Journal of pathology\",\n \"confidence\": \"Medium\",\n \"confidence_rationale\": \"Tier 2 / Moderate — KO mice with defined developmental phenotype plus xenograft model revealing pathway activation, single lab\",\n \"pmids\": [\"30246301\"],\n \"is_preprint\": false\n },\n {\n \"year\": 2018,\n \"finding\": \"Id2 represses Irx5 in the midgut endoderm to establish intestinal identity; transgenic mice expressing Irx5 in midgut endoderm develop gastric metaplasia-like intestinal tumors, recapitulating the Id2-/- phenotype.\",\n \"method\": \"Id2-/- mice, Irx5 transgenic mice with midgut-specific expression, gene expression analysis, histology\",\n \"journal\": \"Molecular and cellular biology\",\n \"confidence\": \"Medium\",\n \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis via transgenic rescue experiment establishing Id2 upstream of Irx5, single lab\",\n \"pmids\": [\"29463648\"],\n \"is_preprint\": false\n },\n {\n \"year\": 2024,\n \"finding\": \"IRX5 interacts directly with HMGN4; HMGN4 drives IRX5 nuclear translocation and co-localizes with IRX5 in the nucleus; IRX5 promotes de novo fatty acid synthesis in hepatocellular carcinoma, accelerating cancer cell proliferation and progression.\",\n \"method\": \"GST pull-down combined with GC/MS, co-immunoprecipitation, immunofluorescence co-localization, HMGN4 overexpression effects on IRX5 nuclear transport\",\n \"journal\": \"Journal of cellular and molecular medicine\",\n \"confidence\": \"Medium\",\n \"confidence_rationale\": \"Tier 2 / Moderate — GST pull-down plus CoIP plus immunofluorescence establishing protein-protein interaction and nuclear translocation mechanism, single lab\",\n \"pmids\": [\"40208102\"],\n \"is_preprint\": false\n },\n {\n \"year\": 2024,\n \"finding\": \"IRX5 suppresses osteogenic differentiation of human BMSCs by inhibiting mTOR-mediated ribosomal translation and impairing mitochondrial oxidative phosphorylation; mTOR activator MHY1485 reverses the inhibitory impact of IRX5 on osteogenesis.\",\n \"method\": \"IRX5 gain/loss-of-function in hBMSCs, RNA-seq, transmission electron microscopy, Seahorse mito-stress assay, Surface Sensing of Translation (SUnSET) assay, pharmacological rescue with mTOR activator\",\n \"journal\": \"Journal of cellular physiology\",\n \"confidence\": \"Medium\",\n \"confidence_rationale\": \"Tier 2 / Moderate — gain/loss-of-function with multiple orthogonal mechanistic assays (translational, metabolic, pharmacological rescue), single lab\",\n \"pmids\": [\"38666481\"],\n \"is_preprint\": false\n },\n {\n \"year\": 2024,\n \"finding\": \"IRX5 transcriptionally regulates YWHAB (14-3-3β) expression by acting on its promoter sequence upstream of the transcription start site, as demonstrated by dual luciferase assay.\",\n \"method\": \"Dual luciferase reporter assay, gain/loss-of-function in breast cancer cells\",\n \"journal\": \"Oncology letters\",\n \"confidence\": \"Low\",\n \"confidence_rationale\": \"Tier 3 / Weak — single luciferase assay, single lab, limited mechanistic detail\",\n \"pmids\": [\"39119237\"],\n \"is_preprint\": false\n },\n {\n \"year\": 2026,\n \"finding\": \"PLAGL1 transcriptionally activates Irx5 synergistically with KLF4 in periosteal stem/progenitor cells (PSPCs), and IRX5 in turn induces downstream osteogenic genes; this PLAGL1-KLF4-IRX5 axis controls osteoblast differentiation of PSPCs during mandibular bone regeneration.\",\n \"method\": \"PLAGL1 KO mice, CRISPR-dCas9-Tet1 epigenetic activation system, transcriptional reporter assays, mandible regeneration model\",\n \"journal\": \"Nature communications\",\n \"confidence\": \"Medium\",\n \"confidence_rationale\": \"Tier 2 / Moderate — KO mice with defined regeneration phenotype, identification of PLAGL1-KLF4-IRX5 axis via transcriptional assays, single lab\",\n \"pmids\": [\"42168182\"],\n \"is_preprint\": false\n }\n ],\n \"current_model\": \"IRX5 is a homeodomain transcription factor that acts primarily as a transcriptional repressor or activator depending on context: in the heart it represses Kv4.2 (Kcnd2) by recruiting mBop to establish the ventricular repolarization gradient and forms a complex with GATA4 to regulate Nav1.5/SCN5A expression; in adipose tissue it represses thermogenesis by inhibiting PGC-1α/UCP1 and activating APP; in the retina and brain it controls bipolar cell differentiation and hypothalamic neurogenesis; it modulates cell fate decisions in chondrocyte-to-osteoblast transitions downstream of Wnt/β-catenin signaling; it promotes DNA damage repair and hair follicle stem cell activation via BRCA1; it is subject to upstream regulation by Hoxb4 and Id2, interacts directly with GATA3, TRPS1, and GATA4 proteins, and requires HMGN4 for its nuclear translocation.\"\n}\n```","stage2_raw":"{\n \"mechanistic_narrative\": \"IRX5 is a homeodomain transcription factor that controls cell-type identity, differentiation, and excitable-cell function across the heart, retina, brain, gonad, skeleton, and adipose tissue, acting context-dependently as a transcriptional repressor or activator [#0, #16, #14]. In the ventricular myocardium it establishes transmural electrical and contractile heterogeneity by repressing the Kv4.2 (Kcnd2) potassium-channel gene—through recruitment of the cardiac repressor mBop—to generate the inverse Ito,f gradient required for coordinated repolarization, with loss of Irx5 reducing endocardial cardiomyocyte contractility in a Kcnd2-dependent manner [#0, #16]. It also forms a complex with GATA4 that potentiates SCN5A/Nav1.5 induction, and its loss in patient-derived cardiomyocytes slows depolarization through reduced sodium current [#5]; in conduction tissue Irx5 acts redundantly with Irx3, the pair repressing Bmp10 and Nav1.5 [#4]. In retinal development Irx5 specifies OFF cone bipolar cell differentiation independently of Vsx1 and, together with Vsx1, tunes OFF-circuit response properties [#1, #2]. In the hypothalamus Irx3/Irx5 restrain neurogenesis from radial-glia-like neural stem cells, controlling the number of leptin-sensing arcuate neurons and thereby feeding and energy balance [#14, #15]. In metabolic and skeletal tissues IRX5 acts downstream of WNT/β-catenin to direct chondrocyte-to-osteoblast and mesenchymal cell-fate decisions and to modulate thermogenesis via PGC-1α/UCP1 [#13, #12, #18]. IRX5 transcriptional output is shaped by direct protein partners GATA3, TRPS1, and GATA4, and its nuclear translocation requires HMGN4 [#3, #5, #22]. Human loss-of-function mutations in IRX5 cause Hamamy syndrome [#5].\",\n \"teleology\": [\n {\n \"year\": 2005,\n \"claim\": \"Established the first molecular mechanism for IRX5 in cardiac physiology by showing it sets the ventricular repolarization gradient through repression of a specific ion-channel gene.\",\n \"evidence\": \"Irx5 knockout mice with chromatin co-IP, electrophysiology, and gradient immunofluorescence\",\n \"pmids\": [\"16239150\"],\n \"confidence\": \"High\",\n \"gaps\": [\"Did not define how Irx5 binds the Kcnd2 locus\", \"mBop recruitment shown in heart only; generality to other Irx5 targets unknown\"]\n },\n {\n \"year\": 2005,\n \"claim\": \"Defined a developmental role for Irx5 in retinal cell-type specification, distinct from the known Vsx1 bipolar-cell pathway.\",\n \"evidence\": \"Irx5 knockout mice, cell-type marker IHC, Irx5/Vsx1 epistasis\",\n \"pmids\": [\"16182275\"],\n \"confidence\": \"High\",\n \"gaps\": [\"Direct transcriptional targets in bipolar cells not identified\", \"Cofactors mediating differentiation unknown\"]\n },\n {\n \"year\": 2008,\n \"claim\": \"Extended the retinal role to circuit-level function, showing Irx5 with Vsx1 selectively tunes OFF visual pathway physiology rather than morphology.\",\n \"evidence\": \"Vsx1/Irx5 double-KO mice, multi-electrode array recording, contrast adaptation modeling\",\n \"pmids\": [\"18322081\"],\n \"confidence\": \"High\",\n \"gaps\": [\"Molecular targets underlying altered gain/threshold unknown\", \"Functional separation of Irx5 vs Vsx1 contributions not resolved\"]\n },\n {\n \"year\": 2012,\n \"claim\": \"Identified direct protein partners (GATA3, TRPS1) for IRX5 and linked it to progenitor migration via Sdf1 repression, while connecting IRX5 mutations to human disease.\",\n \"evidence\": \"Xenopus loss-of-function, protein-protein interaction assays, human homozygosity mapping\",\n \"pmids\": [\"22581230\"],\n \"confidence\": \"High\",\n \"gaps\": [\"Structural basis of GATA3/TRPS1 interaction not defined\", \"Whether Sdf1 repression generalizes beyond branchial arches/gonads unknown\"]\n },\n {\n \"year\": 2012,\n \"claim\": \"Resolved functional redundancy and antagonism between Irx3 and Irx5 in the endocardium and myocardium, refining the model of cardiac patterning and conduction.\",\n \"evidence\": \"Irx3/Irx5 double and conditional KO mice, RT-PCR, electrophysiology, epistasis\",\n \"pmids\": [\"22992950\"],\n \"confidence\": \"High\",\n \"gaps\": [\"Mechanism by which Irx5 represses Irx3 activity unknown\", \"Direct vs indirect repression of Bmp10/Nav1.5 not fully separated\"]\n },\n {\n \"year\": 2021,\n \"claim\": \"Defined a positive, GATA4-dependent arm of IRX5 cardiac function on SCN5A, complementing its repressive role and explaining the depolarization defect in patient cells.\",\n \"evidence\": \"Hamamy-syndrome hiPSC-cardiomyocytes, patch clamp, Co-IP, transcriptomics\",\n \"pmids\": [\"32898233\"],\n \"confidence\": \"High\",\n \"gaps\": [\"Structure/stoichiometry of the IRX5-GATA4 complex unknown\", \"Whether the same complex acts at other cardiac genes untested\"]\n },\n {\n \"year\": 2021,\n \"claim\": \"Established Irx3/Irx5 as dosage-sensitive regulators of postnatal hypothalamic neurogenesis controlling feeding and leptin response.\",\n \"evidence\": \"Irx3/Irx5 double-heterozygous mice, lineage tracing, scRNA-seq, leptin/food-intake assays\",\n \"pmids\": [\"33859429\"],\n \"confidence\": \"High\",\n \"gaps\": [\"Direct transcriptional targets in radial-glia-like NSCs not identified\", \"Relative contribution of Irx3 vs Irx5 not separated\"]\n },\n {\n \"year\": 2021,\n \"claim\": \"Showed that ectopic Irx3/Irx5 expression is the mechanism disrupting PVH development in Sim1 haploinsufficiency, linking IRX dosage to a genetic obesity syndrome.\",\n \"evidence\": \"scRNA-seq, Irx dosage reduction in Sim1+/- mice, PVH-specific Irx3 deletion, food intake\",\n \"pmids\": [\"34705510\"],\n \"confidence\": \"Medium\",\n \"gaps\": [\"How Sim1 normally restrains Irx3/Irx5 not defined\", \"Irx5-specific contribution within the rescue not isolated\"]\n },\n {\n \"year\": 2022,\n \"claim\": \"Linked the Irx5-Ito,f axis to mechanical function, showing Irx5 controls transmural contractility, not just electrical repolarization.\",\n \"evidence\": \"Irx5-KO, KV4.2-KO, double-KO mice, cardiomyocyte contractility/Ca2+ measurement, echocardiography\",\n \"pmids\": [\"35245131\"],\n \"confidence\": \"High\",\n \"gaps\": [\"Mechanistic coupling of Ito,f gradient to contractility incompletely defined\", \"Role of Kcnip2 regulation by Irx5 not fully separated from Kcnd2\"]\n },\n {\n \"year\": 2020,\n \"claim\": \"Placed Irx3/Irx5 downstream of WNT/β-catenin in gonad and skeletal cell-fate decisions, identifying TCF/LEF enhancers and sex-specific epigenetic control of the IrxB locus.\",\n \"evidence\": \"ATAC/ChIP-seq analysis, gonad explant reporter assays, β-catenin gain/loss, lineage tracing, micro-CT (two studies)\",\n \"pmids\": [\"32108023\", \"32662900\"],\n \"confidence\": \"Medium\",\n \"gaps\": [\"Downstream osteoblast/chondrocyte targets of Irx5 not enumerated\", \"Irx5-specific versus Irx3 roles not separated\"]\n },\n {\n \"year\": 2018,\n \"claim\": \"Documented context-dependent roles of IRX5 in adipose metabolism and multiple cancers, mapping target promoters and signaling outputs.\",\n \"evidence\": \"Irx5-KO mice, adipocyte knockdown, promoter-luciferase, Seahorse; gain/loss in TSCC, CRC cells with promoter assays and xenografts\",\n \"pmids\": [\"30538277\", \"29761910\", \"29463648\"],\n \"confidence\": \"Medium\",\n \"gaps\": [\"Apparent opposing effects on PGC-1α/UCP1 across tissues unresolved\", \"Direct vs indirect regulation of cancer-associated targets not always established\"]\n },\n {\n \"year\": 2024,\n \"claim\": \"Identified HMGN4 as the factor driving IRX5 nuclear translocation, providing a mechanism for regulated IRX5 activity, and extended IRX5 function to hepatic lipid synthesis.\",\n \"evidence\": \"GST pull-down, Co-IP, immunofluorescence co-localization in HCC cells\",\n \"pmids\": [\"40208102\"],\n \"confidence\": \"Medium\",\n \"gaps\": [\"Whether HMGN4-dependent import operates in non-cancer tissues unknown\", \"Interaction not reciprocally validated across systems\"]\n },\n {\n \"year\": 2024,\n \"claim\": \"Defined IRX5 as a suppressor of osteogenesis through inhibition of mTOR-dependent translation and oxidative phosphorylation in human BMSCs.\",\n \"evidence\": \"Gain/loss-of-function in hBMSCs, RNA-seq, SUnSET translation assay, Seahorse, mTOR-activator rescue\",\n \"pmids\": [\"38666481\"],\n \"confidence\": \"Medium\",\n \"gaps\": [\"Direct transcriptional targets linking IRX5 to mTOR not identified\", \"Reconciliation with PLAGL1-KLF4-IRX5 pro-osteogenic axis unresolved\"]\n },\n {\n \"year\": 2023,\n \"claim\": \"Revealed a chromatin/repair role for IRX5 in hair follicle stem cell activation, with BRCA1 as a downstream target and Fgf18 suppression contributing to anagen onset.\",\n \"evidence\": \"Irx5-/- mice, ATAC-seq of HFSCs, ChIP/reporter for BRCA1, FGF-kinase-inhibitor rescue\",\n \"pmids\": [\"37084727\"],\n \"confidence\": \"Medium\",\n \"gaps\": [\"Direct binding of IRX5 to BRCA1/Fgf18 loci versus indirect effects not fully resolved\", \"Generality of DNA-repair role beyond HFSCs unknown\"]\n },\n {\n \"year\": 2026,\n \"claim\": \"Positioned IRX5 within a PLAGL1-KLF4-IRX5 transcriptional axis driving osteoblast differentiation during bone regeneration.\",\n \"evidence\": \"PLAGL1-KO mice, CRISPR-dCas9-Tet1 epigenetic activation, reporter assays, mandible regeneration model\",\n \"pmids\": [\"42168182\"],\n \"confidence\": \"Medium\",\n \"gaps\": [\"Direct osteogenic targets induced by IRX5 not enumerated\", \"Apparent contradiction with IRX5 suppression of osteogenesis in hBMSCs unresolved\"]\n },\n {\n \"year\": null,\n \"claim\": \"The molecular logic dictating whether IRX5 represses or activates a given target—and how its cofactor repertoire (mBop, GATA4, GATA3, TRPS1, HMGN4) selects context-specific programs—remains unresolved.\",\n \"evidence\": \"\",\n \"pmids\": [],\n \"confidence\": \"Medium\",\n \"gaps\": [\"No structural model of IRX5 DNA binding or cofactor complexes\", \"Tissue-specific direct target catalogs largely undefined\", \"Opposing metabolic/osteogenic phenotypes across tissues not mechanistically reconciled\"]\n }\n ],\n \"mechanism_profile\": {\n \"molecular_activity\": [\n {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [0, 3, 4, 5, 8, 16, 19]},\n {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [5, 7, 8, 17, 24]}\n ],\n \"localization\": [\n {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [22]}\n ],\n \"pathway\": [\n {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [0, 5, 16]},\n {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [1, 2, 11, 13, 14, 20]},\n {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [12, 13, 9]}\n ],\n \"complexes\": [],\n \"partners\": [\"GATA4\", \"GATA3\", \"TRPS1\", \"HMGN4\", \"BHLHB9\"],\n \"other_free_text\": []\n }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":8,"faith_pct":87.5}}