{"gene":"HMGN3","run_date":"2026-04-28T18:06:53","timeline":{"discoveries":[{"year":2009,"finding":"HMGN3 binds to nucleosomes and modulates chromatin function in pancreatic beta cells; loss of HMGN3 impairs glucose-stimulated insulin secretion and reduces GLUT2 protein levels. ChIP reveals that HMGN3 and transcription factor PDX1 mutually reinforce their binding to chromatin at the Glut2 gene promoter, thereby regulating GLUT2 expression.","method":"Knockout mouse model (Hmgn3-/- mice), chromatin immunoprecipitation (ChIP), transcription profiling","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 — KO mouse with defined phenotype, ChIP demonstrating co-occupancy with PDX1 at Glut2 promoter, multiple orthogonal methods in one study","pmids":["19651901"],"is_preprint":false},{"year":2012,"finding":"HMGN3a stimulates PCAF-mediated acetylation of nucleosomal H3 at K14 in vitro, promoting transcription elongation across the Glyt1 gene, while the HMGN3b splice variant (lacking the C-terminal regulatory domain) does not stimulate this acetylation. Both splice variants bind across the Glyt1 locus without preferential promoter enrichment.","method":"In vitro acetylation assay with PCAF and nucleosomal substrates, ChIP across Glyt1 locus, overexpression of HMGN3a and HMGN3b splice variants","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 1 — in vitro reconstitution assay with mutagenesis-equivalent splice variant comparison, supported by ChIP and expression data","pmids":["22150271"],"is_preprint":false},{"year":2002,"finding":"HMGN3 is expressed in a tissue-specific manner with highest expression in mouse brain, particularly in astrocyte-rich regions (lateral olfactory tract, corpus callosum, etc.), with an expression pattern closely resembling GFAP, suggesting a role in astrocyte function distinct from the related HMGN2.","method":"Western blotting, Northern blotting, immunohistochemistry in mouse brain sections","journal":"The journal of histochemistry and cytochemistry","confidence":"Medium","confidence_rationale":"Tier 3 — localization established by IHC and blotting without direct functional consequence demonstrated","pmids":["12185205"],"is_preprint":false},{"year":2010,"finding":"HMGN3 is expressed in all pancreatic endocrine islet cells including alpha-cells; Hmgn3-/- mice show reduced plasma glucagon levels, but deletion of HMGN3 in alphaTC1-9 cells does not affect glucagon gene expression or secretion directly, indicating the effect on glucagon is not cell-autonomous.","method":"Knockout mouse model (Hmgn3-/- mice), siRNA knockdown in alphaTC1-9 cells, glucagon secretion assays","journal":"Journal of cellular biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 — KO mouse plus cell-based loss-of-function with secretion readout, single lab","pmids":["19885867"],"is_preprint":false},{"year":2015,"finding":"HMGN3 (both HMGN3a and HMGN3b variants) promotes uterine decidualization by enhancing expression of decidualization markers (Prl8a2, Prl3c1) and mediates effects of Hoxa10 and cAMP on these markers; HMGN3 directs decidualization through regulation of Hand2 expression, and its expression is induced by progesterone in a Hoxa10-dependent manner.","method":"Overexpression and siRNA knockdown of Hmgn3 variants in uterine stromal cells, progesterone treatment of ovariectomized mice, siRNA knockdown of Hoxa10","journal":"Molecular and cellular endocrinology","confidence":"Medium","confidence_rationale":"Tier 2 — loss- and gain-of-function with defined marker readouts, epistasis with Hoxa10, single lab","pmids":["26112184"],"is_preprint":false},{"year":2022,"finding":"HMGN3 represses epithelial regulator genes CDH1/E-cadherin and TJAP1 in cholangiocarcinoma cells in a SNAI2-dependent manner; ChIP-seq shows HMGN3 requires SNAI2 to bind these gene loci, and repression involves histone deacetylases (HDACs), as pharmacological HDAC inhibition reactivates these epithelial regulators and impairs cell migration.","method":"Knockdown of HMGN3, ChIP-seq, HDAC inhibitor treatment, migration/invasion assays, colony formation assay","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 2 — ChIP-seq demonstrating SNAI2-dependent chromatin binding, multiple functional readouts, single lab","pmids":["35635715"],"is_preprint":false},{"year":2022,"finding":"WTAP stabilizes HMGN3 mRNA through m6A modification at +485A and +522A sites in the 3'-UTR of HMGN3, recognized by IGF2BP1; WTAP knockdown reduces IGF2BP1 binding to HMGN3 mRNA, destabilizing it and thereby inhibiting trophoblast invasion in preeclampsia.","method":"MeRIP-microarray, RNA immunoprecipitation (RIP), luciferase reporter assay, RNA-seq, WTAP knockdown","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 2 — MeRIP identifies specific m6A sites, RIP confirms IGF2BP1 binding, luciferase validates functional 3'-UTR sites; single lab","pmids":["36412513"],"is_preprint":false},{"year":2022,"finding":"Overexpression of Hmgn3 in mouse embryonic stem cells facilitates their conversion to trophoblast stem cells, acting downstream of Rif1; Rif1 deletion upregulates Hmgn3 as one of the key events activating trophectoderm properties.","method":"Rif1 knockout ESCs, global transcriptome analysis, Hmgn3 overexpression, chimeric embryo assays","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 — genetic epistasis (Rif1 KO upregulates Hmgn3) plus Hmgn3 overexpression rescue, multiple functional readouts; single lab","pmids":["35354046"],"is_preprint":false},{"year":2025,"finding":"WTAP promotes m6A methylation of HMGN3 mRNA to enhance HMGN3 protein expression; elevated HMGN3 mediates WTAP's anti-inflammatory effects in microglia and its pro-neurogenic effects on neural stem/progenitor cell differentiation, as HMGN3 knockdown abolishes these WTAP-induced effects.","method":"WTAP overexpression in BV-2 cells and NSPCs, HMGN3 knockdown, m6A methylation assays, inflammatory marker and neuronal differentiation readouts","journal":"Bulletin of experimental biology and medicine","confidence":"Low","confidence_rationale":"Tier 3 — single lab, no direct m6A site mapping on HMGN3 mRNA, functional link inferred from rescue experiment","pmids":["41191238"],"is_preprint":false}],"current_model":"HMGN3 is a nucleosome-binding chromatin architectural protein that reduces chromatin compaction, stimulates PCAF-mediated H3K14 acetylation to enhance transcription elongation, cooperates with transcription factors (PDX1, SNAI2, Hoxa10) at specific gene loci, has its own mRNA stability regulated by WTAP-mediated m6A modification via IGF2BP1, and thereby controls tissue-specific transcription programs including glucose-stimulated insulin secretion, trophoblast invasion, decidualization, and epithelial-to-mesenchymal transition."},"narrative":{"teleology":[{"year":2002,"claim":"Establishing that HMGN3 has a tissue-restricted expression pattern—highest in brain astrocytes—distinguished it from the ubiquitous HMGN2 and raised the question of what tissue-specific chromatin functions it performs.","evidence":"Western/Northern blotting and immunohistochemistry in mouse brain sections","pmids":["12185205"],"confidence":"Medium","gaps":["No functional consequence of astrocyte expression demonstrated","Brain-specific target genes unknown","Expression pattern not confirmed by single-cell approaches"]},{"year":2009,"claim":"Demonstrating that HMGN3 loss in knockout mice impaired glucose-stimulated insulin secretion and GLUT2 levels, while ChIP showed mutual reinforcement of HMGN3 and PDX1 binding at the Glut2 promoter, established HMGN3 as a functionally required chromatin factor in beta-cell gene regulation.","evidence":"Hmgn3−/− knockout mouse model, ChIP, and transcription profiling in pancreatic islets","pmids":["19651901"],"confidence":"High","gaps":["Mechanism by which HMGN3 and PDX1 reinforce each other's binding is unclear","Genome-wide targets in beta cells not mapped","Whether the insulin secretion defect is solely GLUT2-dependent was not resolved"]},{"year":2010,"claim":"Showing that HMGN3 deletion reduced plasma glucagon without a cell-autonomous effect in alpha cells clarified that HMGN3's endocrine role extends beyond beta cells but acts through indirect, non-cell-autonomous mechanisms on glucagon.","evidence":"Hmgn3−/− mice combined with siRNA knockdown in alphaTC1-9 cells and glucagon secretion assays","pmids":["19885867"],"confidence":"Medium","gaps":["Identity of the indirect signal from beta cells or other tissues not determined","Only one alpha-cell line tested","No rescue experiment performed"]},{"year":2012,"claim":"Reconstituting HMGN3a-dependent stimulation of PCAF acetylation on nucleosomal H3K14 in vitro, and showing this promotes transcription elongation while the HMGN3b isoform cannot, defined the molecular activity of the C-terminal regulatory domain as a cofactor for histone acetyltransferase activity.","evidence":"In vitro acetylation assay with PCAF and nucleosomal substrates, ChIP across the Glyt1 locus, splice variant comparison","pmids":["22150271"],"confidence":"High","gaps":["Structural basis for C-terminal domain interaction with PCAF unknown","Whether other HATs are similarly stimulated not tested","In vivo isoform-specific contributions not separated genetically"]},{"year":2015,"claim":"Demonstrating that HMGN3 mediates progesterone- and Hoxa10-driven decidualization by regulating Hand2 extended its role to a reproductive chromatin effector that integrates hormonal and homeobox transcription factor signals.","evidence":"Overexpression and siRNA knockdown in uterine stromal cells, progesterone treatment in ovariectomized mice, Hoxa10 epistasis","pmids":["26112184"],"confidence":"Medium","gaps":["Direct versus indirect regulation of Hand2 by HMGN3 not resolved","Genome-wide chromatin occupancy in decidualizing cells not mapped","In vivo fertility or implantation phenotype of Hmgn3−/− females not reported"]},{"year":2022,"claim":"ChIP-seq revealing that HMGN3 requires SNAI2 for binding to epithelial gene loci (CDH1, TJAP1) and that repression depends on HDACs established a mechanism by which HMGN3 can repress rather than activate transcription, contingent on its transcription factor partner.","evidence":"HMGN3 knockdown, ChIP-seq, HDAC inhibitor rescue, migration/invasion assays in cholangiocarcinoma cells","pmids":["35635715"],"confidence":"Medium","gaps":["Whether HMGN3 directly recruits HDACs or acts through SNAI2-dependent corepressors is unresolved","Observations limited to cholangiocarcinoma lines; generality across EMT contexts unknown","No structural or biochemical detail on HMGN3–SNAI2 interaction"]},{"year":2022,"claim":"Identifying WTAP-dependent m6A modification at specific 3′-UTR sites of HMGN3 mRNA, read by IGF2BP1 to stabilize the transcript, revealed an epitranscriptomic layer controlling HMGN3 protein abundance relevant to trophoblast invasion.","evidence":"MeRIP-microarray, RIP for IGF2BP1, luciferase reporter with mutated m6A sites, WTAP knockdown in trophoblast cells","pmids":["36412513"],"confidence":"Medium","gaps":["In vivo relevance in preeclampsia not established with animal models","Whether m6A regulation of HMGN3 operates in other HMGN3-expressing tissues is unknown","Contribution of other m6A readers besides IGF2BP1 not excluded"]},{"year":2022,"claim":"Showing that Hmgn3 overexpression facilitates ESC-to-trophoblast stem cell conversion downstream of Rif1 deletion implicated HMGN3 in the earliest lineage decisions of mammalian development.","evidence":"Rif1 knockout ESCs, transcriptomics, Hmgn3 overexpression, chimeric embryo assays","pmids":["35354046"],"confidence":"Medium","gaps":["Whether HMGN3 is sufficient or only contributory to trophoblast conversion unclear","Mechanism linking HMGN3 chromatin remodeling to trophectoderm gene activation not defined","Single-lab finding without independent replication"]},{"year":null,"claim":"How HMGN3 switches between transcriptional activation (via PCAF/H3K14ac) and repression (via SNAI2/HDACs) at different loci, and whether its isoforms partition these opposing functions in vivo, remains unresolved.","evidence":"","pmids":[],"confidence":"High","gaps":["No genome-wide occupancy map exists in primary tissues","Isoform-specific knockout models have not been generated","Structural basis for partner-dependent functional switching is unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0042393","term_label":"histone binding","supporting_discovery_ids":[1]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[0,1,4,5]}],"localization":[{"term_id":"GO:0000228","term_label":"nuclear chromosome","supporting_discovery_ids":[0,1,5]}],"pathway":[{"term_id":"R-HSA-4839726","term_label":"Chromatin organization","supporting_discovery_ids":[0,1,5]}],"complexes":[],"partners":["PDX1","PCAF","SNAI2","HOXA10","WTAP","IGF2BP1","RIF1"],"other_free_text":[]},"mechanistic_narrative":"HMGN3 is a nucleosome-binding chromatin architectural protein that modulates transcription in a tissue-specific manner by reducing chromatin compaction and facilitating histone modification. The full-length HMGN3a isoform stimulates PCAF-mediated acetylation of histone H3K14 on nucleosomal substrates, promoting transcription elongation, while the truncated HMGN3b splice variant lacks this activity [PMID:22150271]. HMGN3 cooperates with transcription factors—reinforcing PDX1 occupancy at the Glut2 promoter to sustain glucose-stimulated insulin secretion in pancreatic beta cells [PMID:19651901], partnering with SNAI2 to repress epithelial genes via HDAC-dependent mechanisms in cholangiocarcinoma [PMID:35635715], and acting downstream of Hoxa10 to direct uterine decidualization through Hand2 regulation [PMID:26112184]. HMGN3 mRNA is itself stabilized by WTAP-mediated m6A modification at specific 3′-UTR sites recognized by the reader IGF2BP1, linking epitranscriptomic regulation to HMGN3 protein abundance in trophoblasts and microglia [PMID:36412513]."},"prefetch_data":{"uniprot":{"accession":"Q15651","full_name":"High mobility group nucleosome-binding domain-containing protein 3","aliases":["Thyroid receptor-interacting protein 7","TR-interacting protein 7","TRIP-7"],"length_aa":99,"mass_kda":10.7,"function":"Binds to nucleosomes, regulating chromatin structure and consequently, chromatin-dependent processes such as transcription, DNA replication and DNA repair. Affects both insulin and glucagon levels and modulates the expression of pancreatic genes involved in insulin secretion. Regulates the expression of the glucose transporter SLC2A2 by binding specifically to its promoter region and recruiting PDX1 and additional transcription factors. Regulates the expression of SLC6A9, a glycine transporter which regulates the glycine concentration in synaptic junctions in the central nervous system, by binding to its transcription start site. May play a role in ocular development and astrocyte function (By similarity)","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/Q15651/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/HMGN3","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/HMGN3","total_profiled":1310},"omim":[{"mim_id":"609333","title":"TRACE AMINE-ASSOCIATED RECEPTOR 1; TAAR1","url":"https://www.omim.org/entry/609333"},{"mim_id":"604502","title":"HIGH MOBILITY GROUP NUCLEOSOMAL BINDING PROTEIN 3; HMGN3","url":"https://www.omim.org/entry/604502"},{"mim_id":"601019","title":"SOLUTE CARRIER FAMILY 6 (NEUROTRANSMITTER TRANSPORTER, GLYCINE), MEMBER 9; SLC6A9","url":"https://www.omim.org/entry/601019"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/HMGN3"},"hgnc":{"alias_symbol":[],"prev_symbol":["TRIP7"]},"alphafold":{"accession":"Q15651","domains":[],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q15651","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q15651-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q15651-F1-predicted_aligned_error_v6.png","plddt_mean":65.25},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=HMGN3","jax_strain_url":"https://www.jax.org/strain/search?query=HMGN3"},"sequence":{"accession":"Q15651","fasta_url":"https://rest.uniprot.org/uniprotkb/Q15651.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q15651/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q15651"}},"corpus_meta":[{"pmid":"19651901","id":"PMC_19651901","title":"The nucleosome binding protein HMGN3 modulates the transcription profile of pancreatic beta cells and affects insulin secretion.","date":"2009","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/19651901","citation_count":44,"is_preprint":false},{"pmid":"36412513","id":"PMC_36412513","title":"WTAP dysregulation-mediated HMGN3-m6A modification inhibited trophoblast invasion in early-onset preeclampsia.","date":"2022","source":"FASEB journal : official publication of the Federation of American Societies for Experimental Biology","url":"https://pubmed.ncbi.nlm.nih.gov/36412513","citation_count":21,"is_preprint":false},{"pmid":"22150271","id":"PMC_22150271","title":"The chromatin-binding protein HMGN3 stimulates histone acetylation and transcription across the Glyt1 gene.","date":"2012","source":"The Biochemical journal","url":"https://pubmed.ncbi.nlm.nih.gov/22150271","citation_count":20,"is_preprint":false},{"pmid":"35354046","id":"PMC_35354046","title":"Rif1 and Hmgn3 regulate the conversion of murine trophoblast stem cells.","date":"2022","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/35354046","citation_count":19,"is_preprint":false},{"pmid":"12185205","id":"PMC_12185205","title":"Immunohistochemical localization of the nucleosome-binding protein HMGN3 in mouse brain.","date":"2002","source":"The journal of histochemistry and cytochemistry : official journal of the Histochemistry Society","url":"https://pubmed.ncbi.nlm.nih.gov/12185205","citation_count":18,"is_preprint":false},{"pmid":"19885867","id":"PMC_19885867","title":"The nucleosome binding protein HMGN3 is expressed in pancreatic alpha-cells and affects plasma glucagon levels in mice.","date":"2010","source":"Journal of cellular biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/19885867","citation_count":11,"is_preprint":false},{"pmid":"26112184","id":"PMC_26112184","title":"Expression, regulation and function of Hmgn3 during decidualization in mice.","date":"2015","source":"Molecular and cellular endocrinology","url":"https://pubmed.ncbi.nlm.nih.gov/26112184","citation_count":6,"is_preprint":false},{"pmid":"21947420","id":"PMC_21947420","title":"Genome-wide association study identifies HMGN3 locus for spine bone size variation in Chinese.","date":"2011","source":"Human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/21947420","citation_count":4,"is_preprint":false},{"pmid":"35635715","id":"PMC_35635715","title":"HMGN3 represses transcription of epithelial regulators to promote migration of cholangiocarcinoma in a SNAI2-dependent manner.","date":"2022","source":"FASEB journal : official publication of the Federation of American Societies for Experimental Biology","url":"https://pubmed.ncbi.nlm.nih.gov/35635715","citation_count":4,"is_preprint":false},{"pmid":"41191238","id":"PMC_41191238","title":"Wilms Tumor 1 Associated Protein (WTAP) Inhibits Inflammation Provoked by Mycobacterium tuberculosis in Microglial BV-2 Cells and Promotes Differentiation of Neural Stem/Progenitor Cells into Neurons by Elevating Expression of HMGN3 Protein Resulted from Modulation of m6A Metilation of Its RNA.","date":"2025","source":"Bulletin of experimental biology and medicine","url":"https://pubmed.ncbi.nlm.nih.gov/41191238","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":5793,"output_tokens":2317,"usd":0.026067},"stage2":{"model":"claude-opus-4-6","input_tokens":5607,"output_tokens":2445,"usd":0.13374},"total_usd":0.159807,"stage1_batch_id":"msgbatch_01DzrsgVgYngY1hvM3DU1yF2","stage2_batch_id":"msgbatch_01KA9b7iRzKFdhoBUT7vCvSe","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2009,\n      \"finding\": \"HMGN3 binds to nucleosomes and modulates chromatin function in pancreatic beta cells; loss of HMGN3 impairs glucose-stimulated insulin secretion and reduces GLUT2 protein levels. ChIP reveals that HMGN3 and transcription factor PDX1 mutually reinforce their binding to chromatin at the Glut2 gene promoter, thereby regulating GLUT2 expression.\",\n      \"method\": \"Knockout mouse model (Hmgn3-/- mice), chromatin immunoprecipitation (ChIP), transcription profiling\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — KO mouse with defined phenotype, ChIP demonstrating co-occupancy with PDX1 at Glut2 promoter, multiple orthogonal methods in one study\",\n      \"pmids\": [\"19651901\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"HMGN3a stimulates PCAF-mediated acetylation of nucleosomal H3 at K14 in vitro, promoting transcription elongation across the Glyt1 gene, while the HMGN3b splice variant (lacking the C-terminal regulatory domain) does not stimulate this acetylation. Both splice variants bind across the Glyt1 locus without preferential promoter enrichment.\",\n      \"method\": \"In vitro acetylation assay with PCAF and nucleosomal substrates, ChIP across Glyt1 locus, overexpression of HMGN3a and HMGN3b splice variants\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro reconstitution assay with mutagenesis-equivalent splice variant comparison, supported by ChIP and expression data\",\n      \"pmids\": [\"22150271\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"HMGN3 is expressed in a tissue-specific manner with highest expression in mouse brain, particularly in astrocyte-rich regions (lateral olfactory tract, corpus callosum, etc.), with an expression pattern closely resembling GFAP, suggesting a role in astrocyte function distinct from the related HMGN2.\",\n      \"method\": \"Western blotting, Northern blotting, immunohistochemistry in mouse brain sections\",\n      \"journal\": \"The journal of histochemistry and cytochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — localization established by IHC and blotting without direct functional consequence demonstrated\",\n      \"pmids\": [\"12185205\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"HMGN3 is expressed in all pancreatic endocrine islet cells including alpha-cells; Hmgn3-/- mice show reduced plasma glucagon levels, but deletion of HMGN3 in alphaTC1-9 cells does not affect glucagon gene expression or secretion directly, indicating the effect on glucagon is not cell-autonomous.\",\n      \"method\": \"Knockout mouse model (Hmgn3-/- mice), siRNA knockdown in alphaTC1-9 cells, glucagon secretion assays\",\n      \"journal\": \"Journal of cellular biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — KO mouse plus cell-based loss-of-function with secretion readout, single lab\",\n      \"pmids\": [\"19885867\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"HMGN3 (both HMGN3a and HMGN3b variants) promotes uterine decidualization by enhancing expression of decidualization markers (Prl8a2, Prl3c1) and mediates effects of Hoxa10 and cAMP on these markers; HMGN3 directs decidualization through regulation of Hand2 expression, and its expression is induced by progesterone in a Hoxa10-dependent manner.\",\n      \"method\": \"Overexpression and siRNA knockdown of Hmgn3 variants in uterine stromal cells, progesterone treatment of ovariectomized mice, siRNA knockdown of Hoxa10\",\n      \"journal\": \"Molecular and cellular endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — loss- and gain-of-function with defined marker readouts, epistasis with Hoxa10, single lab\",\n      \"pmids\": [\"26112184\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"HMGN3 represses epithelial regulator genes CDH1/E-cadherin and TJAP1 in cholangiocarcinoma cells in a SNAI2-dependent manner; ChIP-seq shows HMGN3 requires SNAI2 to bind these gene loci, and repression involves histone deacetylases (HDACs), as pharmacological HDAC inhibition reactivates these epithelial regulators and impairs cell migration.\",\n      \"method\": \"Knockdown of HMGN3, ChIP-seq, HDAC inhibitor treatment, migration/invasion assays, colony formation assay\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — ChIP-seq demonstrating SNAI2-dependent chromatin binding, multiple functional readouts, single lab\",\n      \"pmids\": [\"35635715\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"WTAP stabilizes HMGN3 mRNA through m6A modification at +485A and +522A sites in the 3'-UTR of HMGN3, recognized by IGF2BP1; WTAP knockdown reduces IGF2BP1 binding to HMGN3 mRNA, destabilizing it and thereby inhibiting trophoblast invasion in preeclampsia.\",\n      \"method\": \"MeRIP-microarray, RNA immunoprecipitation (RIP), luciferase reporter assay, RNA-seq, WTAP knockdown\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — MeRIP identifies specific m6A sites, RIP confirms IGF2BP1 binding, luciferase validates functional 3'-UTR sites; single lab\",\n      \"pmids\": [\"36412513\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Overexpression of Hmgn3 in mouse embryonic stem cells facilitates their conversion to trophoblast stem cells, acting downstream of Rif1; Rif1 deletion upregulates Hmgn3 as one of the key events activating trophectoderm properties.\",\n      \"method\": \"Rif1 knockout ESCs, global transcriptome analysis, Hmgn3 overexpression, chimeric embryo assays\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis (Rif1 KO upregulates Hmgn3) plus Hmgn3 overexpression rescue, multiple functional readouts; single lab\",\n      \"pmids\": [\"35354046\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"WTAP promotes m6A methylation of HMGN3 mRNA to enhance HMGN3 protein expression; elevated HMGN3 mediates WTAP's anti-inflammatory effects in microglia and its pro-neurogenic effects on neural stem/progenitor cell differentiation, as HMGN3 knockdown abolishes these WTAP-induced effects.\",\n      \"method\": \"WTAP overexpression in BV-2 cells and NSPCs, HMGN3 knockdown, m6A methylation assays, inflammatory marker and neuronal differentiation readouts\",\n      \"journal\": \"Bulletin of experimental biology and medicine\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single lab, no direct m6A site mapping on HMGN3 mRNA, functional link inferred from rescue experiment\",\n      \"pmids\": [\"41191238\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"HMGN3 is a nucleosome-binding chromatin architectural protein that reduces chromatin compaction, stimulates PCAF-mediated H3K14 acetylation to enhance transcription elongation, cooperates with transcription factors (PDX1, SNAI2, Hoxa10) at specific gene loci, has its own mRNA stability regulated by WTAP-mediated m6A modification via IGF2BP1, and thereby controls tissue-specific transcription programs including glucose-stimulated insulin secretion, trophoblast invasion, decidualization, and epithelial-to-mesenchymal transition.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"HMGN3 is a nucleosome-binding chromatin architectural protein that modulates transcription in a tissue-specific manner by reducing chromatin compaction and facilitating histone modification. The full-length HMGN3a isoform stimulates PCAF-mediated acetylation of histone H3K14 on nucleosomal substrates, promoting transcription elongation, while the truncated HMGN3b splice variant lacks this activity [PMID:22150271]. HMGN3 cooperates with transcription factors—reinforcing PDX1 occupancy at the Glut2 promoter to sustain glucose-stimulated insulin secretion in pancreatic beta cells [PMID:19651901], partnering with SNAI2 to repress epithelial genes via HDAC-dependent mechanisms in cholangiocarcinoma [PMID:35635715], and acting downstream of Hoxa10 to direct uterine decidualization through Hand2 regulation [PMID:26112184]. HMGN3 mRNA is itself stabilized by WTAP-mediated m6A modification at specific 3′-UTR sites recognized by the reader IGF2BP1, linking epitranscriptomic regulation to HMGN3 protein abundance in trophoblasts and microglia [PMID:36412513].\",\n  \"teleology\": [\n    {\n      \"year\": 2002,\n      \"claim\": \"Establishing that HMGN3 has a tissue-restricted expression pattern—highest in brain astrocytes—distinguished it from the ubiquitous HMGN2 and raised the question of what tissue-specific chromatin functions it performs.\",\n      \"evidence\": \"Western/Northern blotting and immunohistochemistry in mouse brain sections\",\n      \"pmids\": [\"12185205\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No functional consequence of astrocyte expression demonstrated\",\n        \"Brain-specific target genes unknown\",\n        \"Expression pattern not confirmed by single-cell approaches\"\n      ]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Demonstrating that HMGN3 loss in knockout mice impaired glucose-stimulated insulin secretion and GLUT2 levels, while ChIP showed mutual reinforcement of HMGN3 and PDX1 binding at the Glut2 promoter, established HMGN3 as a functionally required chromatin factor in beta-cell gene regulation.\",\n      \"evidence\": \"Hmgn3−/− knockout mouse model, ChIP, and transcription profiling in pancreatic islets\",\n      \"pmids\": [\"19651901\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Mechanism by which HMGN3 and PDX1 reinforce each other's binding is unclear\",\n        \"Genome-wide targets in beta cells not mapped\",\n        \"Whether the insulin secretion defect is solely GLUT2-dependent was not resolved\"\n      ]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Showing that HMGN3 deletion reduced plasma glucagon without a cell-autonomous effect in alpha cells clarified that HMGN3's endocrine role extends beyond beta cells but acts through indirect, non-cell-autonomous mechanisms on glucagon.\",\n      \"evidence\": \"Hmgn3−/− mice combined with siRNA knockdown in alphaTC1-9 cells and glucagon secretion assays\",\n      \"pmids\": [\"19885867\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Identity of the indirect signal from beta cells or other tissues not determined\",\n        \"Only one alpha-cell line tested\",\n        \"No rescue experiment performed\"\n      ]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Reconstituting HMGN3a-dependent stimulation of PCAF acetylation on nucleosomal H3K14 in vitro, and showing this promotes transcription elongation while the HMGN3b isoform cannot, defined the molecular activity of the C-terminal regulatory domain as a cofactor for histone acetyltransferase activity.\",\n      \"evidence\": \"In vitro acetylation assay with PCAF and nucleosomal substrates, ChIP across the Glyt1 locus, splice variant comparison\",\n      \"pmids\": [\"22150271\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural basis for C-terminal domain interaction with PCAF unknown\",\n        \"Whether other HATs are similarly stimulated not tested\",\n        \"In vivo isoform-specific contributions not separated genetically\"\n      ]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Demonstrating that HMGN3 mediates progesterone- and Hoxa10-driven decidualization by regulating Hand2 extended its role to a reproductive chromatin effector that integrates hormonal and homeobox transcription factor signals.\",\n      \"evidence\": \"Overexpression and siRNA knockdown in uterine stromal cells, progesterone treatment in ovariectomized mice, Hoxa10 epistasis\",\n      \"pmids\": [\"26112184\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Direct versus indirect regulation of Hand2 by HMGN3 not resolved\",\n        \"Genome-wide chromatin occupancy in decidualizing cells not mapped\",\n        \"In vivo fertility or implantation phenotype of Hmgn3−/− females not reported\"\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"ChIP-seq revealing that HMGN3 requires SNAI2 for binding to epithelial gene loci (CDH1, TJAP1) and that repression depends on HDACs established a mechanism by which HMGN3 can repress rather than activate transcription, contingent on its transcription factor partner.\",\n      \"evidence\": \"HMGN3 knockdown, ChIP-seq, HDAC inhibitor rescue, migration/invasion assays in cholangiocarcinoma cells\",\n      \"pmids\": [\"35635715\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether HMGN3 directly recruits HDACs or acts through SNAI2-dependent corepressors is unresolved\",\n        \"Observations limited to cholangiocarcinoma lines; generality across EMT contexts unknown\",\n        \"No structural or biochemical detail on HMGN3–SNAI2 interaction\"\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Identifying WTAP-dependent m6A modification at specific 3′-UTR sites of HMGN3 mRNA, read by IGF2BP1 to stabilize the transcript, revealed an epitranscriptomic layer controlling HMGN3 protein abundance relevant to trophoblast invasion.\",\n      \"evidence\": \"MeRIP-microarray, RIP for IGF2BP1, luciferase reporter with mutated m6A sites, WTAP knockdown in trophoblast cells\",\n      \"pmids\": [\"36412513\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"In vivo relevance in preeclampsia not established with animal models\",\n        \"Whether m6A regulation of HMGN3 operates in other HMGN3-expressing tissues is unknown\",\n        \"Contribution of other m6A readers besides IGF2BP1 not excluded\"\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Showing that Hmgn3 overexpression facilitates ESC-to-trophoblast stem cell conversion downstream of Rif1 deletion implicated HMGN3 in the earliest lineage decisions of mammalian development.\",\n      \"evidence\": \"Rif1 knockout ESCs, transcriptomics, Hmgn3 overexpression, chimeric embryo assays\",\n      \"pmids\": [\"35354046\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether HMGN3 is sufficient or only contributory to trophoblast conversion unclear\",\n        \"Mechanism linking HMGN3 chromatin remodeling to trophectoderm gene activation not defined\",\n        \"Single-lab finding without independent replication\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How HMGN3 switches between transcriptional activation (via PCAF/H3K14ac) and repression (via SNAI2/HDACs) at different loci, and whether its isoforms partition these opposing functions in vivo, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"No genome-wide occupancy map exists in primary tissues\",\n        \"Isoform-specific knockout models have not been generated\",\n        \"Structural basis for partner-dependent functional switching is unknown\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0042393\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [0, 1, 4, 5]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0000228\", \"supporting_discovery_ids\": [0, 1, 5]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0074160\", \"supporting_discovery_ids\": [0, 1, 4, 5]},\n      {\"term_id\": \"R-HSA-4839726\", \"supporting_discovery_ids\": [0, 1, 5]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"PDX1\", \"PCAF\", \"SNAI2\", \"HOXA10\", \"WTAP\", \"IGF2BP1\", \"RIF1\"],\n    \"other_free_text\": []\n  }\n}\n```"}