{"gene":"METTL23","run_date":"2026-04-28T18:30:28","timeline":{"discoveries":[{"year":2014,"finding":"METTL23 protein physically interacts with GABPA (GA-binding protein transcription factor, alpha subunit), and overexpression of METTL23 increased transcriptional activity at the THPO promoter, while knockdown of METTL23 reduced expression of ATP5B, establishing METTL23 as a transcriptional co-regulator of GABPA function.","method":"Co-immunoprecipitation (physical interaction), overexpression and siRNA knockdown with reporter/expression assays","journal":"Human molecular genetics","confidence":"Medium","confidence_rationale":"Tier 2-3 — co-IP plus functional transcriptional assays in a single study; moderate evidence","pmids":["24501276"],"is_preprint":false},{"year":2014,"finding":"Truncating mutations in METTL23 that disrupt the predicted catalytic SAM-binding domain alter the cellular localization of the protein, and 3D modelling predicts METTL23 functions as an SAM-dependent methyltransferase; expression analysis indicated association with heat shock proteins as putative substrates.","method":"Frameshift/nonsense mutation analysis, cellular localization studies, 3D structural modelling, expression analysis","journal":"Human molecular genetics","confidence":"Low","confidence_rationale":"Tier 3-4 — localization effect of truncation shown experimentally, but substrate identification is computational; single study","pmids":["24626631"],"is_preprint":false},{"year":2017,"finding":"METTL23 knockout in K562 cells did not result in any loss of eEF1A methylation, indicating METTL23 does not methylate elongation factor eEF1A in human cells.","method":"CRISPR/Cas9 knockout followed by targeted mass spectrometry","journal":"Molecular & cellular proteomics : MCP","confidence":"Medium","confidence_rationale":"Tier 1-2 — clean genetic knockout with mass spectrometry readout, single study","pmids":["28663172"],"is_preprint":false},{"year":2017,"finding":"Mouse maternal Mettl23 functions as a protein arginine methyltransferase (PRMT) that catalyzes asymmetric dimethylation of histone H3 at arginine 17 (H3R17me2a), as demonstrated by in vitro methyltransferase assays and inhibitor treatment; this activity is required for incorporation of histone H3.3 into the male pronucleus during paternal genome reprogramming.","method":"In vitro methyltransferase assay, PRMT inhibitor (TBBD) treatment, depletion from oocytes with functional readout (H3.3 incorporation, pronuclear assembly)","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1-2 — in vitro enzymatic assay plus inhibitor treatment plus loss-of-function with defined cellular phenotype; multiple orthogonal methods","pmids":["28930672"],"is_preprint":false},{"year":2017,"finding":"Mettl23 interacts with Tet3 (a 5mC-oxidizing enzyme) via the maternal factor GSE (gonad-specific expression), and depletion of Mettl23 from oocytes impairs accumulation of GSE, Tet3, and 5-hydroxymethylcytosine (5hmC) in the male pronucleus, suggesting Mettl23 recruits the GSE-Tet3 complex to chromatin for active DNA demethylation.","method":"Co-immunoprecipitation (Mettl23-GSE-Tet3 interaction), oocyte depletion with immunofluorescence readout of GSE, Tet3, 5hmC localization","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2-3 — co-IP and functional depletion with localization readout; single study","pmids":["28930672"],"is_preprint":false},{"year":2022,"finding":"METTL23 catalyzes dimethylation of histone H3R17 in the retina; loss of METTL23 in retinal ganglion cells reduces H3R17 dimethylation, impairs transcription of pS2 (an estrogen receptor α target gene), and derepresses NF-κB-mediated TNF-α and IL-1β signaling, leading to retinal ganglion cell death and a glaucoma phenotype.","method":"Mettl23 knock-in and knockout mouse models, histone methylation assays, gene expression analysis, NF-κB pathway activity measurement","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 1-2 — enzymatic activity demonstrated in tissue, combined with genetic mouse models and defined downstream pathway; multiple orthogonal methods in single rigorous study","pmids":["36099048"],"is_preprint":false}],"current_model":"METTL23 is an SAM-dependent protein arginine methyltransferase (PRMT) that catalyzes asymmetric dimethylation of histone H3 at arginine 17 (H3R17me2a); in oocytes this activity recruits the GSE-Tet3 complex to the paternal chromatin for active DNA demethylation during zygotic reprogramming, while in retinal ganglion cells it sustains pS2 transcription and suppresses NF-κB-mediated neuroinflammation, and in the nucleus it also acts as a transcriptional co-regulator by physically interacting with the GABPA transcription factor."},"narrative":{"teleology":[{"year":2014,"claim":"Establishing that METTL23 functions as a nuclear transcriptional co-regulator resolved its initial cellular role: interaction with GABPA and modulation of GABPA-dependent promoters showed METTL23 participates directly in gene regulation rather than acting solely as a structural or metabolic enzyme.","evidence":"Co-immunoprecipitation with GABPA, overexpression/siRNA knockdown with THPO reporter and ATP5B expression assays in human cells","pmids":["24501276"],"confidence":"Medium","gaps":["Whether the GABPA interaction depends on METTL23 catalytic activity was not tested","No genome-wide identification of METTL23-GABPA co-regulated targets","Reciprocal validation of the GABPA interaction with endogenous proteins not shown"]},{"year":2014,"claim":"Demonstrating that disease-associated truncating mutations disrupt METTL23 localization and its predicted SAM-binding domain supported, but did not prove, an enzymatic methyltransferase function.","evidence":"Frameshift/nonsense mutation analysis with cellular localization imaging and 3D structural modelling","pmids":["24626631"],"confidence":"Low","gaps":["No direct enzymatic assay was performed; catalytic activity remained computationally predicted","Putative heat-shock-protein substrates were identified only by expression correlation, not by biochemical demonstration","Single study without independent replication"]},{"year":2017,"claim":"Ruling out eEF1A as a substrate narrowed the search for METTL23's bona fide targets and distinguished it from related methyltransferases that act on translation factors.","evidence":"CRISPR/Cas9 knockout of METTL23 in K562 cells followed by targeted mass spectrometry of eEF1A methylation","pmids":["28663172"],"confidence":"Medium","gaps":["Only one candidate substrate was excluded; systematic substrate identification was not performed","Single cell line tested"]},{"year":2017,"claim":"Identifying METTL23 as a histone H3R17 asymmetric dimethyltransferase and showing this mark is essential for paternal pronuclear H3.3 incorporation and GSE–Tet3-mediated DNA demethylation established the enzyme's catalytic specificity and its biological role in zygotic epigenetic reprogramming.","evidence":"In vitro methyltransferase assay, PRMT inhibitor (TBBD) treatment, oocyte depletion with H3.3/5hmC immunofluorescence, co-IP of METTL23–GSE–Tet3 complex in mouse oocytes","pmids":["28930672"],"confidence":"High","gaps":["Whether METTL23 has additional non-histone substrates in oocytes was not addressed","Structural basis of METTL23 specificity for H3R17 over other arginine residues is unknown","Mechanism by which H3R17me2a promotes H3.3 incorporation is not defined"]},{"year":2022,"claim":"Demonstrating that METTL23 loss in retinal ganglion cells reduces H3R17me2a, silences pS2, and derepresses NF-κB-driven neuroinflammation leading to glaucoma extended the enzyme's physiological significance beyond early development to adult neuronal survival.","evidence":"Mettl23 knock-in and knockout mouse models with histone methylation assays, gene expression profiling, and NF-κB pathway activity measurement in retina","pmids":["36099048"],"confidence":"High","gaps":["Direct chromatin occupancy of METTL23 at the pS2 or NF-κB target loci has not been shown","Whether the glaucoma phenotype is cell-autonomous to retinal ganglion cells versus involving glia was not fully resolved","Therapeutic rescue of the phenotype by restoring METTL23 activity was not demonstrated"]},{"year":null,"claim":"A comprehensive substrate map for METTL23 beyond histone H3R17 is lacking, and the structural basis for its arginine specificity, its relationship to other PRMTs, and whether its interaction with GABPA requires catalytic activity remain unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No crystal structure or cryo-EM structure of METTL23 is available","Genome-wide chromatin profiling of H3R17me2a deposited by METTL23 has not been performed","Whether METTL23 catalytic activity and GABPA co-regulatory function are mechanistically linked is untested"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[3,5]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[0,5]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0,1]}],"pathway":[{"term_id":"R-HSA-4839726","term_label":"Chromatin organization","supporting_discovery_ids":[3,5]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[0,5]}],"complexes":[],"partners":["GABPA","TET3","GSE1"],"other_free_text":[]},"mechanistic_narrative":"METTL23 is an SAM-dependent protein arginine methyltransferase that catalyzes asymmetric dimethylation of histone H3 at arginine 17 (H3R17me2a), functioning in chromatin regulation during zygotic reprogramming and in retinal neuronal homeostasis [PMID:28930672, PMID:36099048]. In oocytes, METTL23-mediated H3R17me2a is required for histone H3.3 incorporation into the male pronucleus and recruits the GSE–Tet3 complex to paternal chromatin, enabling active DNA demethylation via 5-hydroxymethylcytosine accumulation [PMID:28930672]. In retinal ganglion cells, loss of METTL23 reduces H3R17 dimethylation, impairs pS2 transcription, and derepresses NF-κB-driven neuroinflammatory signaling (TNF-α, IL-1β), leading to ganglion cell death and a glaucoma phenotype [PMID:36099048]. METTL23 also physically interacts with the transcription factor GABPA and co-regulates its transcriptional targets, linking its methyltransferase activity to broader transcriptional control [PMID:24501276]."},"prefetch_data":{"uniprot":{"accession":"Q86XA0","full_name":"Histone-arginine methyltransferase METTL23","aliases":["Methyltransferase-like protein 23"],"length_aa":190,"mass_kda":21.5,"function":"Histone methyltransferase that dimethylates histone H3 at 'Arg-17', forming asymmetric dimethylarginine (H3R17me2a), leading to activate transcription via chromatin remodeling (By similarity). Maternal factor involved in epigenetic chromatin reprogramming of the paternal genome in the zygote: mediates H3R17me2a, promoting histone H3.3 incorporation in the male pronucleus, leading to TET3 recruitment and subsequent DNA demethylation (By similarity)","subcellular_location":"Nucleus; Cytoplasm","url":"https://www.uniprot.org/uniprotkb/Q86XA0/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/METTL23","classification":"Not Classified","n_dependent_lines":158,"n_total_lines":1208,"dependency_fraction":0.13079470198675497},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/METTL23","total_profiled":1310},"omim":[{"mim_id":"615942","title":"INTELLECTUAL DEVELOPMENTAL DISORDER, AUTOSOMAL RECESSIVE 44; MRT44","url":"https://www.omim.org/entry/615942"},{"mim_id":"615262","title":"METHYLTRANSFERASE-LIKE 23; METTL23","url":"https://www.omim.org/entry/615262"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Vesicles","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/METTL23"},"hgnc":{"alias_symbol":["LOC124512"],"prev_symbol":["C17orf95"]},"alphafold":{"accession":"Q86XA0","domains":[{"cath_id":"3.40.50.150","chopping":"25-94","consensus_level":"medium","plddt":97.3199,"start":25,"end":94},{"cath_id":"-","chopping":"128-190","consensus_level":"medium","plddt":90.6467,"start":128,"end":190}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q86XA0","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q86XA0-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q86XA0-F1-predicted_aligned_error_v6.png","plddt_mean":93.88},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=METTL23","jax_strain_url":"https://www.jax.org/strain/search?query=METTL23"},"sequence":{"accession":"Q86XA0","fasta_url":"https://rest.uniprot.org/uniprotkb/Q86XA0.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q86XA0/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q86XA0"}},"corpus_meta":[{"pmid":"28663172","id":"PMC_28663172","title":"METTL21B Is a Novel Human Lysine Methyltransferase of Translation Elongation Factor 1A: Discovery by CRISPR/Cas9 Knockout.","date":"2017","source":"Molecular & cellular proteomics : MCP","url":"https://pubmed.ncbi.nlm.nih.gov/28663172","citation_count":42,"is_preprint":false},{"pmid":"28930672","id":"PMC_28930672","title":"Histone H3 Methylated at Arginine 17 Is Essential for Reprogramming the Paternal Genome in Zygotes.","date":"2017","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/28930672","citation_count":40,"is_preprint":false},{"pmid":"24501276","id":"PMC_24501276","title":"METTL23, a transcriptional partner of GABPA, is essential for human cognition.","date":"2014","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/24501276","citation_count":36,"is_preprint":false},{"pmid":"24626631","id":"PMC_24626631","title":"Disruption of the methyltransferase-like 23 gene METTL23 causes mild autosomal recessive intellectual disability.","date":"2014","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/24626631","citation_count":28,"is_preprint":false},{"pmid":"36099048","id":"PMC_36099048","title":"METTL23 mutation alters histone H3R17 methylation in normal-tension glaucoma.","date":"2022","source":"The Journal of clinical investigation","url":"https://pubmed.ncbi.nlm.nih.gov/36099048","citation_count":24,"is_preprint":false},{"pmid":"33448881","id":"PMC_33448881","title":"Exome Sequencing and Congenital Heart Disease in Sub-Saharan Africa.","date":"2021","source":"Circulation. Genomic and precision medicine","url":"https://pubmed.ncbi.nlm.nih.gov/33448881","citation_count":22,"is_preprint":false},{"pmid":"38203567","id":"PMC_38203567","title":"Metabolic Pathway Engineering Improves Dendrobine Production in Dendrobium catenatum.","date":"2023","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/38203567","citation_count":12,"is_preprint":false},{"pmid":"32439618","id":"PMC_32439618","title":"Exome sequencing revealed a novel homozygous METTL23 gene mutation leading to familial mild intellectual disability with dysmorphic features.","date":"2020","source":"European journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/32439618","citation_count":10,"is_preprint":false},{"pmid":"32067349","id":"PMC_32067349","title":"Further delineation of METTL23-associated intellectual disability.","date":"2020","source":"American journal of medical genetics. Part A","url":"https://pubmed.ncbi.nlm.nih.gov/32067349","citation_count":7,"is_preprint":false},{"pmid":"35581286","id":"PMC_35581286","title":"Identification of candidate genes associated with bacterial and viral infections in wild boars hunted in Tuscany (Italy).","date":"2022","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/35581286","citation_count":7,"is_preprint":false},{"pmid":"38389252","id":"PMC_38389252","title":"Molecular genetics of inherited normal tension glaucoma.","date":"2024","source":"Indian journal of ophthalmology","url":"https://pubmed.ncbi.nlm.nih.gov/38389252","citation_count":6,"is_preprint":false},{"pmid":"36317630","id":"PMC_36317630","title":"Epigenetics in glaucoma: a link between histone methylation and neurodegeneration.","date":"2022","source":"The Journal of clinical investigation","url":"https://pubmed.ncbi.nlm.nih.gov/36317630","citation_count":5,"is_preprint":false},{"pmid":"39202421","id":"PMC_39202421","title":"Association Analysis of METTL23 Gene Polymorphisms with Reproductive Traits in Kele Pigs.","date":"2024","source":"Genes","url":"https://pubmed.ncbi.nlm.nih.gov/39202421","citation_count":3,"is_preprint":false},{"pmid":"39026940","id":"PMC_39026940","title":"Identification of a novel METTL23 gene variant in a patient with an intellectual development disorder: a literature review and case report.","date":"2024","source":"Frontiers in pediatrics","url":"https://pubmed.ncbi.nlm.nih.gov/39026940","citation_count":1,"is_preprint":false},{"pmid":"39325437","id":"PMC_39325437","title":"METTL23 Variants and Patients With Normal-Tension Glaucoma.","date":"2024","source":"JAMA ophthalmology","url":"https://pubmed.ncbi.nlm.nih.gov/39325437","citation_count":1,"is_preprint":false},{"pmid":"41809128","id":"PMC_41809128","title":"Emerging role of epigenetic mechanisms in glaucoma and their translational potential.","date":"2026","source":"Frontiers in genetics","url":"https://pubmed.ncbi.nlm.nih.gov/41809128","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":9158,"output_tokens":1562,"usd":0.025452},"stage2":{"model":"claude-opus-4-6","input_tokens":4822,"output_tokens":1877,"usd":0.106552},"total_usd":0.132004,"stage1_batch_id":"msgbatch_01Mgbec4vM6c9vXht7JVJzss","stage2_batch_id":"msgbatch_01JkuuH5RB2BdJNsgnhjbC6s","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2014,\n      \"finding\": \"METTL23 protein physically interacts with GABPA (GA-binding protein transcription factor, alpha subunit), and overexpression of METTL23 increased transcriptional activity at the THPO promoter, while knockdown of METTL23 reduced expression of ATP5B, establishing METTL23 as a transcriptional co-regulator of GABPA function.\",\n      \"method\": \"Co-immunoprecipitation (physical interaction), overexpression and siRNA knockdown with reporter/expression assays\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — co-IP plus functional transcriptional assays in a single study; moderate evidence\",\n      \"pmids\": [\"24501276\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Truncating mutations in METTL23 that disrupt the predicted catalytic SAM-binding domain alter the cellular localization of the protein, and 3D modelling predicts METTL23 functions as an SAM-dependent methyltransferase; expression analysis indicated association with heat shock proteins as putative substrates.\",\n      \"method\": \"Frameshift/nonsense mutation analysis, cellular localization studies, 3D structural modelling, expression analysis\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3-4 — localization effect of truncation shown experimentally, but substrate identification is computational; single study\",\n      \"pmids\": [\"24626631\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"METTL23 knockout in K562 cells did not result in any loss of eEF1A methylation, indicating METTL23 does not methylate elongation factor eEF1A in human cells.\",\n      \"method\": \"CRISPR/Cas9 knockout followed by targeted mass spectrometry\",\n      \"journal\": \"Molecular & cellular proteomics : MCP\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 — clean genetic knockout with mass spectrometry readout, single study\",\n      \"pmids\": [\"28663172\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Mouse maternal Mettl23 functions as a protein arginine methyltransferase (PRMT) that catalyzes asymmetric dimethylation of histone H3 at arginine 17 (H3R17me2a), as demonstrated by in vitro methyltransferase assays and inhibitor treatment; this activity is required for incorporation of histone H3.3 into the male pronucleus during paternal genome reprogramming.\",\n      \"method\": \"In vitro methyltransferase assay, PRMT inhibitor (TBBD) treatment, depletion from oocytes with functional readout (H3.3 incorporation, pronuclear assembly)\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro enzymatic assay plus inhibitor treatment plus loss-of-function with defined cellular phenotype; multiple orthogonal methods\",\n      \"pmids\": [\"28930672\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Mettl23 interacts with Tet3 (a 5mC-oxidizing enzyme) via the maternal factor GSE (gonad-specific expression), and depletion of Mettl23 from oocytes impairs accumulation of GSE, Tet3, and 5-hydroxymethylcytosine (5hmC) in the male pronucleus, suggesting Mettl23 recruits the GSE-Tet3 complex to chromatin for active DNA demethylation.\",\n      \"method\": \"Co-immunoprecipitation (Mettl23-GSE-Tet3 interaction), oocyte depletion with immunofluorescence readout of GSE, Tet3, 5hmC localization\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — co-IP and functional depletion with localization readout; single study\",\n      \"pmids\": [\"28930672\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"METTL23 catalyzes dimethylation of histone H3R17 in the retina; loss of METTL23 in retinal ganglion cells reduces H3R17 dimethylation, impairs transcription of pS2 (an estrogen receptor α target gene), and derepresses NF-κB-mediated TNF-α and IL-1β signaling, leading to retinal ganglion cell death and a glaucoma phenotype.\",\n      \"method\": \"Mettl23 knock-in and knockout mouse models, histone methylation assays, gene expression analysis, NF-κB pathway activity measurement\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — enzymatic activity demonstrated in tissue, combined with genetic mouse models and defined downstream pathway; multiple orthogonal methods in single rigorous study\",\n      \"pmids\": [\"36099048\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"METTL23 is an SAM-dependent protein arginine methyltransferase (PRMT) that catalyzes asymmetric dimethylation of histone H3 at arginine 17 (H3R17me2a); in oocytes this activity recruits the GSE-Tet3 complex to the paternal chromatin for active DNA demethylation during zygotic reprogramming, while in retinal ganglion cells it sustains pS2 transcription and suppresses NF-κB-mediated neuroinflammation, and in the nucleus it also acts as a transcriptional co-regulator by physically interacting with the GABPA transcription factor.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"METTL23 is an SAM-dependent protein arginine methyltransferase that catalyzes asymmetric dimethylation of histone H3 at arginine 17 (H3R17me2a), functioning in chromatin regulation during zygotic reprogramming and in retinal neuronal homeostasis [PMID:28930672, PMID:36099048]. In oocytes, METTL23-mediated H3R17me2a is required for histone H3.3 incorporation into the male pronucleus and recruits the GSE–Tet3 complex to paternal chromatin, enabling active DNA demethylation via 5-hydroxymethylcytosine accumulation [PMID:28930672]. In retinal ganglion cells, loss of METTL23 reduces H3R17 dimethylation, impairs pS2 transcription, and derepresses NF-κB-driven neuroinflammatory signaling (TNF-α, IL-1β), leading to ganglion cell death and a glaucoma phenotype [PMID:36099048]. METTL23 also physically interacts with the transcription factor GABPA and co-regulates its transcriptional targets, linking its methyltransferase activity to broader transcriptional control [PMID:24501276].\",\n  \"teleology\": [\n    {\n      \"year\": 2014,\n      \"claim\": \"Establishing that METTL23 functions as a nuclear transcriptional co-regulator resolved its initial cellular role: interaction with GABPA and modulation of GABPA-dependent promoters showed METTL23 participates directly in gene regulation rather than acting solely as a structural or metabolic enzyme.\",\n      \"evidence\": \"Co-immunoprecipitation with GABPA, overexpression/siRNA knockdown with THPO reporter and ATP5B expression assays in human cells\",\n      \"pmids\": [\"24501276\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether the GABPA interaction depends on METTL23 catalytic activity was not tested\",\n        \"No genome-wide identification of METTL23-GABPA co-regulated targets\",\n        \"Reciprocal validation of the GABPA interaction with endogenous proteins not shown\"\n      ]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Demonstrating that disease-associated truncating mutations disrupt METTL23 localization and its predicted SAM-binding domain supported, but did not prove, an enzymatic methyltransferase function.\",\n      \"evidence\": \"Frameshift/nonsense mutation analysis with cellular localization imaging and 3D structural modelling\",\n      \"pmids\": [\"24626631\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No direct enzymatic assay was performed; catalytic activity remained computationally predicted\",\n        \"Putative heat-shock-protein substrates were identified only by expression correlation, not by biochemical demonstration\",\n        \"Single study without independent replication\"\n      ]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Ruling out eEF1A as a substrate narrowed the search for METTL23's bona fide targets and distinguished it from related methyltransferases that act on translation factors.\",\n      \"evidence\": \"CRISPR/Cas9 knockout of METTL23 in K562 cells followed by targeted mass spectrometry of eEF1A methylation\",\n      \"pmids\": [\"28663172\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Only one candidate substrate was excluded; systematic substrate identification was not performed\",\n        \"Single cell line tested\"\n      ]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Identifying METTL23 as a histone H3R17 asymmetric dimethyltransferase and showing this mark is essential for paternal pronuclear H3.3 incorporation and GSE–Tet3-mediated DNA demethylation established the enzyme's catalytic specificity and its biological role in zygotic epigenetic reprogramming.\",\n      \"evidence\": \"In vitro methyltransferase assay, PRMT inhibitor (TBBD) treatment, oocyte depletion with H3.3/5hmC immunofluorescence, co-IP of METTL23–GSE–Tet3 complex in mouse oocytes\",\n      \"pmids\": [\"28930672\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether METTL23 has additional non-histone substrates in oocytes was not addressed\",\n        \"Structural basis of METTL23 specificity for H3R17 over other arginine residues is unknown\",\n        \"Mechanism by which H3R17me2a promotes H3.3 incorporation is not defined\"\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Demonstrating that METTL23 loss in retinal ganglion cells reduces H3R17me2a, silences pS2, and derepresses NF-κB-driven neuroinflammation leading to glaucoma extended the enzyme's physiological significance beyond early development to adult neuronal survival.\",\n      \"evidence\": \"Mettl23 knock-in and knockout mouse models with histone methylation assays, gene expression profiling, and NF-κB pathway activity measurement in retina\",\n      \"pmids\": [\"36099048\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Direct chromatin occupancy of METTL23 at the pS2 or NF-κB target loci has not been shown\",\n        \"Whether the glaucoma phenotype is cell-autonomous to retinal ganglion cells versus involving glia was not fully resolved\",\n        \"Therapeutic rescue of the phenotype by restoring METTL23 activity was not demonstrated\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"A comprehensive substrate map for METTL23 beyond histone H3R17 is lacking, and the structural basis for its arginine specificity, its relationship to other PRMTs, and whether its interaction with GABPA requires catalytic activity remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No crystal structure or cryo-EM structure of METTL23 is available\",\n        \"Genome-wide chromatin profiling of H3R17me2a deposited by METTL23 has not been performed\",\n        \"Whether METTL23 catalytic activity and GABPA co-regulatory function are mechanistically linked is untested\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [3, 5]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [0, 5]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-4839726\", \"supporting_discovery_ids\": [3, 5]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [0, 5]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"GABPA\",\n      \"TET3\",\n      \"GSE1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}