{"gene":"HECTD4","run_date":"2026-06-10T01:55:22","timeline":{"discoveries":[{"year":2025,"finding":"Purified HECTD4 mediates ubiquitin conjugation in vitro, functioning as a HECT-domain E3 ubiquitin ligase. Proteomic studies combined with ubiquitin remnant profiling identify COX-2 (PTGS2) as a major degradation target, and HECTD4 also targets COX-2's regulatory kinase MKK7. HECTD4 expression is induced upon loss of matrix adhesion, and its depletion increases COX-2 expression, enhancing anchorage-independent proliferation and tumorigenesis; genetic or pharmacologic COX-2 suppression reverses the pro-tumorigenic and pro-metastatic phenotype of HECTD4-depleted cells.","method":"In vitro ubiquitin conjugation assay with purified protein; in vivo genome-wide CRISPR-inactivation screen; ubiquitin remnant profiling (proteomics); loss-of-function (depletion) with genetic/pharmacologic rescue","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution of E3 ligase activity with purified protein, combined with ubiquitin remnant profiling and genetic/pharmacologic epistasis rescue experiments in a peer-reviewed publication (confirmed by matched preprint)","pmids":["40768362"],"is_preprint":false},{"year":2022,"finding":"HECTD4 interacts with GluN2B (identified by reverse-phase nano-liquid chromatography-tandem mass spectrometry) and ubiquitinates both GluN2B and MALT1. In ischemic stroke, HECTD4 is downregulated, weakening its interaction with GluN2B; HECTD4 knockdown decreases GluN2B and MALT1 ubiquitination, increases GluN2B phosphorylation (with decreased STEP61), elevates intracellular calcium, and exacerbates hypoxia/NMDA-induced neuronal injury. MALT1 siRNA or inhibitor counteracts these effects, placing MALT1 downstream of HECTD4 in regulating STEP61 stability and GluN2B phosphorylation.","method":"Reverse-phase nano-LC-MS/MS (interaction identification); HECTD4 knockdown in nerve cells; ubiquitination assays; calcium measurement; MALT1 siRNA/inhibitor epistasis; ischemia-reperfusion rat model","journal":"Molecular neurobiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (MS-based interaction, ubiquitination assays, genetic epistasis with MALT1 siRNA, calcium readout) in a single lab study","pmids":["36527595"],"is_preprint":false},{"year":2026,"finding":"HECTD4 (delivered via UC-MSC-derived exosomes) promotes ubiquitination and degradation of METTL3, thereby reducing RANK m6A modification and suppressing osteoclast differentiation. Overexpression of METTL3 in the presence of UC-MSC exosomes enhanced osteoclast differentiation, and RANK silencing reversed this, establishing the HECTD4 → METTL3 ubiquitination → RANK m6A → osteoclast differentiation axis.","method":"Ubiquitination assays; MeRIP-qPCR; Western blot; TRAP staining; METTL3 and RANK overexpression/knockdown epistasis; HECTD4 silencing","journal":"Journal of molecular histology","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — ubiquitination assay plus MeRIP-qPCR with epistasis, but single lab and single publication","pmids":["42141331"],"is_preprint":false},{"year":2026,"finding":"HECTD4 knockdown in prostate cancer cell lines (LNCaP, PC-3, DU145) altered ubiquitination profiles of proteins including NUSAP1, CDK6, and MED13L, implicating HECTD4 as an E3 ligase regulating cell cycle and tumor suppressor pathways (PI3K-AKT, Ras-MAPK, mTOR) via targeted ubiquitination.","method":"HECTD4 knockdown; LC-MS/MS proteomics; ubiquitination profiling; gene ontology and pathway analysis; proliferation assay","journal":"Cancer genomics & proteomics","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, primarily proteomics-based association without direct in vitro ubiquitination assays for individual substrates","pmids":["42055625"],"is_preprint":false},{"year":2022,"finding":"Biallelic loss-of-function variants in HECTD4 (homozygous and compound heterozygous missense variants) cause a neurodevelopmental syndrome with seizures, movement disorders, and neurobehavioral phenotypes overlapping with Angelman syndrome, establishing HECTD4 as a disease gene. RNA studies in patient cells confirmed the loss-of-function effect of the variants.","method":"Exome sequencing; RNA studies in patient-derived cells confirming LoF effect","journal":"Genetics in medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — exome sequencing plus RNA-level functional validation of LoF in patient cells, replicated across multiple unrelated families","pmids":["36401616"],"is_preprint":false},{"year":2022,"finding":"Ethanol increases HECTD4 expression in liver cells, and this increase is suppressed by NAC treatment. Loss of HECTD4 in ethanol-treated cells reduces CYP2E1 and lipogenic gene expression while increasing ALDH2 expression, indicating HECTD4 participates in ethanol metabolism and ethanol-induced hepatotoxicity signaling.","method":"HECTD4 knockdown in ethanol-treated cells; gene expression analysis; mouse liver samples treated with alcohol","journal":"Archives of toxicology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, cell-based gene expression readouts without direct mechanistic (ubiquitination substrate) evidence","pmids":["35713687"],"is_preprint":false}],"current_model":"HECTD4 is a HECT-domain E3 ubiquitin ligase (confirmed by in vitro ubiquitin conjugation) whose established substrates include COX-2 and its regulatory kinase MKK7 (in cancer/metastasis suppression), GluN2B and MALT1 (in neuroprotection against ischemic injury), and METTL3 (in regulation of osteoclast differentiation); biallelic loss-of-function variants cause an Angelman-like neurodevelopmental syndrome, and ethanol modulates its expression to influence hepatic lipid and oxidative stress signaling."},"narrative":{"mechanistic_narrative":"HECTD4 is a HECT-domain E3 ubiquitin ligase that shapes diverse cellular programs by directing substrate ubiquitination, with in vitro reconstitution of ubiquitin conjugation using purified protein establishing its catalytic activity [PMID:40768362]. In epithelial cancer, HECTD4 is induced upon loss of matrix adhesion and ubiquitinates COX-2 (PTGS2) and its regulatory kinase MKK7, so that its depletion stabilizes COX-2 and drives anchorage-independent proliferation, tumorigenesis, and metastasis—phenotypes reversed by COX-2 suppression [PMID:40768362]. In neurons, HECTD4 ubiquitinates GluN2B and MALT1, and its downregulation in ischemic stroke weakens GluN2B engagement, elevating GluN2B phosphorylation through MALT1-dependent loss of STEP61, raising intracellular calcium and worsening excitotoxic injury [PMID:36527595]. HECTD4 also targets METTL3 for degradation, reducing RANK m6A modification to suppress osteoclast differentiation [PMID:42141331]. Biallelic loss-of-function variants in HECTD4 cause an Angelman-like neurodevelopmental syndrome with seizures and movement disorders [PMID:36401616]. Beyond these substrate-defined axes, the structural basis of substrate recognition and the determinants of HECTD4 regulation across tissues have not been characterized in the available corpus.","teleology":[{"year":2022,"claim":"Establishing HECTD4 as a human disease gene answered whether its loss has organismal consequence, linking it to an Angelman-like neurodevelopmental phenotype.","evidence":"Exome sequencing across unrelated families with RNA-level confirmation of loss-of-function in patient cells","pmids":["36401616"],"confidence":"Medium","gaps":["Does not identify the molecular substrate(s) whose dysregulation drives the neurodevelopmental phenotype","No mechanistic link from variant to ubiquitination defect"]},{"year":2022,"claim":"Defining GluN2B and MALT1 as ubiquitination targets answered how HECTD4 protects neurons, placing it upstream of STEP61-controlled GluN2B phosphorylation and calcium homeostasis.","evidence":"MS-based interaction mapping, ubiquitination assays, MALT1 siRNA/inhibitor epistasis, and calcium readouts in an ischemia-reperfusion rat model","pmids":["36527595"],"confidence":"Medium","gaps":["No in vitro reconstitution of GluN2B or MALT1 ubiquitination with purified components","Single lab study without reciprocal interaction validation"]},{"year":2022,"claim":"Linking HECTD4 to ethanol-responsive hepatic signaling raised the question of whether it participates in ethanol metabolism, showing its expression is ROS-dependently induced and tied to CYP2E1, lipogenic, and ALDH2 expression.","evidence":"HECTD4 knockdown in ethanol-treated cells with gene expression readouts and alcohol-treated mouse liver","pmids":["35713687"],"confidence":"Low","gaps":["No ubiquitination substrate identified in this context","Gene-expression association only, no direct mechanistic evidence"]},{"year":2025,"claim":"In vitro reconstitution settled whether HECTD4 is itself a catalytically active E3 ligase and identified COX-2 and MKK7 as substrates governing anchorage-independent growth.","evidence":"In vitro ubiquitin conjugation with purified protein, genome-wide CRISPR screen, ubiquitin remnant profiling, and genetic/pharmacologic COX-2 rescue","pmids":["40768362"],"confidence":"High","gaps":["Structural basis of substrate recognition unresolved","Mechanism of adhesion-loss-induced HECTD4 induction not defined"]},{"year":2026,"claim":"Identifying METTL3 as a degradation target extended HECTD4's reach into m6A-dependent gene regulation, defining a HECTD4 → METTL3 → RANK m6A → osteoclast differentiation axis.","evidence":"Ubiquitination assays, MeRIP-qPCR, TRAP staining, and METTL3/RANK epistasis with exosome-delivered HECTD4","pmids":["42141331"],"confidence":"Medium","gaps":["Single lab and single publication","No direct demonstration HECTD4 ubiquitinates METTL3 with purified components"]},{"year":2026,"claim":"Proteomic profiling in prostate cancer broadened the candidate substrate landscape, associating HECTD4 with ubiquitination of cell-cycle and signaling proteins.","evidence":"HECTD4 knockdown with LC-MS/MS ubiquitination profiling and pathway analysis in prostate cancer cell lines","pmids":["42055625"],"confidence":"Low","gaps":["No direct in vitro ubiquitination assays for individual candidate substrates (NUSAP1, CDK6, MED13L)","Association-level evidence only"]},{"year":null,"claim":"The structural and regulatory logic by which a single HECT ligase selects such distinct substrates across cancer, neurons, and bone remains unresolved.","evidence":"","pmids":[],"confidence":"High","gaps":["No structural model of substrate engagement","Determinants of tissue-specific substrate selection unknown","Mechanism linking disease variants to substrate dysregulation undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016874","term_label":"ligase activity","supporting_discovery_ids":[0]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,1,2]}],"localization":[],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0,1,2]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[4]}],"complexes":[],"partners":["PTGS2","MKK7","GRIN2B","MALT1","METTL3"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9Y4D8","full_name":"Probable E3 ubiquitin-protein ligase HECTD4","aliases":["HECT domain-containing protein 4","HECT-type E3 ubiquitin transferase HECTD4"],"length_aa":3996,"mass_kda":439.3,"function":"E3 ubiquitin-protein ligase which accepts ubiquitin from an E2 ubiquitin-conjugating enzyme in the form of a thioester and then directly transfers the ubiquitin to targeted substrates","subcellular_location":"Membrane","url":"https://www.uniprot.org/uniprotkb/Q9Y4D8/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/HECTD4","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":74,"dependency_fraction":0.013513513513513514},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/HECTD4","total_profiled":1310},"omim":[{"mim_id":"620270","title":"NEURODEVELOPMENTAL DISORDER WITH ABSENT SPEECH AND MOVEMENT AND BEHAVIORAL ABNORMALITIES; NEDSMB","url":"https://www.omim.org/entry/620270"},{"mim_id":"620250","title":"NEURODEVELOPMENTAL DISORDER WITH SEIZURES, SPASTICITY, AND COMPLETE OR PARTIAL AGENESIS OF THE CORPUS CALLOSUM; NEDSSCC","url":"https://www.omim.org/entry/620250"},{"mim_id":"620209","title":"HECT DOMAIN E3 UBIQUITIN PROTEIN LIGASE 4; HECTD4","url":"https://www.omim.org/entry/620209"},{"mim_id":"618615","title":"HEPATOCELLULAR CARCINOMA-UPREGULATED EZH2-ASSOCIATED LONG NONCODING RNA; HEIH","url":"https://www.omim.org/entry/618615"},{"mim_id":"614454","title":"UBIQUITIN PROTEIN LIGASE E3C; UBE3C","url":"https://www.omim.org/entry/614454"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nuclear speckles","reliability":"Approved"},{"location":"Vesicles","reliability":"Approved"},{"location":"Nucleoplasm","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/HECTD4"},"hgnc":{"alias_symbol":["FLJ34154","KIAA0614"],"prev_symbol":["C12orf51"]},"alphafold":{"accession":"Q9Y4D8","domains":[],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9Y4D8","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9Y4D8-5-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9Y4D8-5-F1-predicted_aligned_error_v6.png","plddt_mean":71.25},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=HECTD4","jax_strain_url":"https://www.jax.org/strain/search?query=HECTD4"},"sequence":{"accession":"Q9Y4D8","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9Y4D8.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9Y4D8/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9Y4D8"}},"corpus_meta":[{"pmid":"32062383","id":"PMC_32062383","title":"LncRNA HEIH promotes cell proliferation, migration and invasion in cholangiocarcinoma by modulating miR-98-5p/HECTD4.","date":"2020","source":"Biomedicine & pharmacotherapy = Biomedecine & pharmacotherapie","url":"https://pubmed.ncbi.nlm.nih.gov/32062383","citation_count":31,"is_preprint":false},{"pmid":"36527595","id":"PMC_36527595","title":"The Weakened Interaction Between HECTD4 and GluN2B in Ischemic Stroke Promotes Calcium Overload and Brain Injury Through a Mechanism Involving the Decrease of GluN2B and MALT1 Ubiquitination.","date":"2022","source":"Molecular neurobiology","url":"https://pubmed.ncbi.nlm.nih.gov/36527595","citation_count":18,"is_preprint":false},{"pmid":"36401616","id":"PMC_36401616","title":"Biallelic variants in HECT E3 paralogs, HECTD4 and UBE3C, encoding ubiquitin ligases cause neurodevelopmental disorders that overlap with Angelman syndrome.","date":"2022","source":"Genetics in medicine : official journal of the American College of Medical Genetics","url":"https://pubmed.ncbi.nlm.nih.gov/36401616","citation_count":10,"is_preprint":false},{"pmid":"35713687","id":"PMC_35713687","title":"The potential effects of HECTD4 variants on fasting glucose and triglyceride levels in relation to prevalence of type 2 diabetes based on alcohol intake.","date":"2022","source":"Archives of toxicology","url":"https://pubmed.ncbi.nlm.nih.gov/35713687","citation_count":8,"is_preprint":false},{"pmid":"40768362","id":"PMC_40768362","title":"The E3 ligase HECTD4 regulates COX-2-dependent tumor progression and metastasis.","date":"2025","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/40768362","citation_count":5,"is_preprint":false},{"pmid":"28212632","id":"PMC_28212632","title":"Exome-wide association study identifies genetic polymorphisms of C12orf51, MYL2, and ALDH2 associated with blood lead levels in the general Korean population.","date":"2017","source":"Environmental health : a global access science source","url":"https://pubmed.ncbi.nlm.nih.gov/28212632","citation_count":3,"is_preprint":false},{"pmid":"39521882","id":"PMC_39521882","title":"Relationship between HECTD4 gene variants, obesity, and coffee consumption.","date":"2024","source":"European journal of clinical nutrition","url":"https://pubmed.ncbi.nlm.nih.gov/39521882","citation_count":2,"is_preprint":false},{"pmid":"38523829","id":"PMC_38523829","title":"The Association of Low-Carbohydrate Diet and HECTD4 rs11066280 Polymorphism with Risk of Colorectal Cancer: A Case-Control Study in Korea.","date":"2024","source":"Current developments in nutrition","url":"https://pubmed.ncbi.nlm.nih.gov/38523829","citation_count":1,"is_preprint":false},{"pmid":"42055625","id":"PMC_42055625","title":"Proteomic Profiling Reveals HECTD4-dependent Regulation of Protein Ubiquitination and Signaling Pathways in Prostate Cancer.","date":"2026","source":"Cancer genomics & proteomics","url":"https://pubmed.ncbi.nlm.nih.gov/42055625","citation_count":0,"is_preprint":false},{"pmid":"42141331","id":"PMC_42141331","title":"HECTD4 in human umbilical cord mesenchymal stem cells-derived exosomes alleviates osteoclast differentiation in osteoporosis progression by suppressing RANK m6A modification via promoting METTL3 ubiquitination.","date":"2026","source":"Journal of molecular histology","url":"https://pubmed.ncbi.nlm.nih.gov/42141331","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.04.09.647907","title":"The E3 ligase HECTD4 regulates COX-2 dependent tumor progression and metastasis","date":"2025-04-15","source":"bioRxiv","url":"https://doi.org/10.1101/2025.04.09.647907","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":8468,"output_tokens":1907,"usd":0.027005,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8823,"output_tokens":2357,"usd":0.05152,"stage2_stop_reason":"end_turn"},"total_usd":0.078525,"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\": 2025,\n      \"finding\": \"Purified HECTD4 mediates ubiquitin conjugation in vitro, functioning as a HECT-domain E3 ubiquitin ligase. Proteomic studies combined with ubiquitin remnant profiling identify COX-2 (PTGS2) as a major degradation target, and HECTD4 also targets COX-2's regulatory kinase MKK7. HECTD4 expression is induced upon loss of matrix adhesion, and its depletion increases COX-2 expression, enhancing anchorage-independent proliferation and tumorigenesis; genetic or pharmacologic COX-2 suppression reverses the pro-tumorigenic and pro-metastatic phenotype of HECTD4-depleted cells.\",\n      \"method\": \"In vitro ubiquitin conjugation assay with purified protein; in vivo genome-wide CRISPR-inactivation screen; ubiquitin remnant profiling (proteomics); loss-of-function (depletion) with genetic/pharmacologic rescue\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution of E3 ligase activity with purified protein, combined with ubiquitin remnant profiling and genetic/pharmacologic epistasis rescue experiments in a peer-reviewed publication (confirmed by matched preprint)\",\n      \"pmids\": [\"40768362\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"HECTD4 interacts with GluN2B (identified by reverse-phase nano-liquid chromatography-tandem mass spectrometry) and ubiquitinates both GluN2B and MALT1. In ischemic stroke, HECTD4 is downregulated, weakening its interaction with GluN2B; HECTD4 knockdown decreases GluN2B and MALT1 ubiquitination, increases GluN2B phosphorylation (with decreased STEP61), elevates intracellular calcium, and exacerbates hypoxia/NMDA-induced neuronal injury. MALT1 siRNA or inhibitor counteracts these effects, placing MALT1 downstream of HECTD4 in regulating STEP61 stability and GluN2B phosphorylation.\",\n      \"method\": \"Reverse-phase nano-LC-MS/MS (interaction identification); HECTD4 knockdown in nerve cells; ubiquitination assays; calcium measurement; MALT1 siRNA/inhibitor epistasis; ischemia-reperfusion rat model\",\n      \"journal\": \"Molecular neurobiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (MS-based interaction, ubiquitination assays, genetic epistasis with MALT1 siRNA, calcium readout) in a single lab study\",\n      \"pmids\": [\"36527595\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"HECTD4 (delivered via UC-MSC-derived exosomes) promotes ubiquitination and degradation of METTL3, thereby reducing RANK m6A modification and suppressing osteoclast differentiation. Overexpression of METTL3 in the presence of UC-MSC exosomes enhanced osteoclast differentiation, and RANK silencing reversed this, establishing the HECTD4 → METTL3 ubiquitination → RANK m6A → osteoclast differentiation axis.\",\n      \"method\": \"Ubiquitination assays; MeRIP-qPCR; Western blot; TRAP staining; METTL3 and RANK overexpression/knockdown epistasis; HECTD4 silencing\",\n      \"journal\": \"Journal of molecular histology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — ubiquitination assay plus MeRIP-qPCR with epistasis, but single lab and single publication\",\n      \"pmids\": [\"42141331\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"HECTD4 knockdown in prostate cancer cell lines (LNCaP, PC-3, DU145) altered ubiquitination profiles of proteins including NUSAP1, CDK6, and MED13L, implicating HECTD4 as an E3 ligase regulating cell cycle and tumor suppressor pathways (PI3K-AKT, Ras-MAPK, mTOR) via targeted ubiquitination.\",\n      \"method\": \"HECTD4 knockdown; LC-MS/MS proteomics; ubiquitination profiling; gene ontology and pathway analysis; proliferation assay\",\n      \"journal\": \"Cancer genomics & proteomics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, primarily proteomics-based association without direct in vitro ubiquitination assays for individual substrates\",\n      \"pmids\": [\"42055625\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Biallelic loss-of-function variants in HECTD4 (homozygous and compound heterozygous missense variants) cause a neurodevelopmental syndrome with seizures, movement disorders, and neurobehavioral phenotypes overlapping with Angelman syndrome, establishing HECTD4 as a disease gene. RNA studies in patient cells confirmed the loss-of-function effect of the variants.\",\n      \"method\": \"Exome sequencing; RNA studies in patient-derived cells confirming LoF effect\",\n      \"journal\": \"Genetics in medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — exome sequencing plus RNA-level functional validation of LoF in patient cells, replicated across multiple unrelated families\",\n      \"pmids\": [\"36401616\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Ethanol increases HECTD4 expression in liver cells, and this increase is suppressed by NAC treatment. Loss of HECTD4 in ethanol-treated cells reduces CYP2E1 and lipogenic gene expression while increasing ALDH2 expression, indicating HECTD4 participates in ethanol metabolism and ethanol-induced hepatotoxicity signaling.\",\n      \"method\": \"HECTD4 knockdown in ethanol-treated cells; gene expression analysis; mouse liver samples treated with alcohol\",\n      \"journal\": \"Archives of toxicology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, cell-based gene expression readouts without direct mechanistic (ubiquitination substrate) evidence\",\n      \"pmids\": [\"35713687\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"HECTD4 is a HECT-domain E3 ubiquitin ligase (confirmed by in vitro ubiquitin conjugation) whose established substrates include COX-2 and its regulatory kinase MKK7 (in cancer/metastasis suppression), GluN2B and MALT1 (in neuroprotection against ischemic injury), and METTL3 (in regulation of osteoclast differentiation); biallelic loss-of-function variants cause an Angelman-like neurodevelopmental syndrome, and ethanol modulates its expression to influence hepatic lipid and oxidative stress signaling.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"HECTD4 is a HECT-domain E3 ubiquitin ligase that shapes diverse cellular programs by directing substrate ubiquitination, with in vitro reconstitution of ubiquitin conjugation using purified protein establishing its catalytic activity [#0]. In epithelial cancer, HECTD4 is induced upon loss of matrix adhesion and ubiquitinates COX-2 (PTGS2) and its regulatory kinase MKK7, so that its depletion stabilizes COX-2 and drives anchorage-independent proliferation, tumorigenesis, and metastasis—phenotypes reversed by COX-2 suppression [#0]. In neurons, HECTD4 ubiquitinates GluN2B and MALT1, and its downregulation in ischemic stroke weakens GluN2B engagement, elevating GluN2B phosphorylation through MALT1-dependent loss of STEP61, raising intracellular calcium and worsening excitotoxic injury [#1]. HECTD4 also targets METTL3 for degradation, reducing RANK m6A modification to suppress osteoclast differentiation [#2]. Biallelic loss-of-function variants in HECTD4 cause an Angelman-like neurodevelopmental syndrome with seizures and movement disorders [#4]. Beyond these substrate-defined axes, the structural basis of substrate recognition and the determinants of HECTD4 regulation across tissues have not been characterized in the available corpus.\",\n  \"teleology\": [\n    {\n      \"year\": 2022,\n      \"claim\": \"Establishing HECTD4 as a human disease gene answered whether its loss has organismal consequence, linking it to an Angelman-like neurodevelopmental phenotype.\",\n      \"evidence\": \"Exome sequencing across unrelated families with RNA-level confirmation of loss-of-function in patient cells\",\n      \"pmids\": [\"36401616\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Does not identify the molecular substrate(s) whose dysregulation drives the neurodevelopmental phenotype\", \"No mechanistic link from variant to ubiquitination defect\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Defining GluN2B and MALT1 as ubiquitination targets answered how HECTD4 protects neurons, placing it upstream of STEP61-controlled GluN2B phosphorylation and calcium homeostasis.\",\n      \"evidence\": \"MS-based interaction mapping, ubiquitination assays, MALT1 siRNA/inhibitor epistasis, and calcium readouts in an ischemia-reperfusion rat model\",\n      \"pmids\": [\"36527595\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No in vitro reconstitution of GluN2B or MALT1 ubiquitination with purified components\", \"Single lab study without reciprocal interaction validation\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Linking HECTD4 to ethanol-responsive hepatic signaling raised the question of whether it participates in ethanol metabolism, showing its expression is ROS-dependently induced and tied to CYP2E1, lipogenic, and ALDH2 expression.\",\n      \"evidence\": \"HECTD4 knockdown in ethanol-treated cells with gene expression readouts and alcohol-treated mouse liver\",\n      \"pmids\": [\"35713687\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No ubiquitination substrate identified in this context\", \"Gene-expression association only, no direct mechanistic evidence\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"In vitro reconstitution settled whether HECTD4 is itself a catalytically active E3 ligase and identified COX-2 and MKK7 as substrates governing anchorage-independent growth.\",\n      \"evidence\": \"In vitro ubiquitin conjugation with purified protein, genome-wide CRISPR screen, ubiquitin remnant profiling, and genetic/pharmacologic COX-2 rescue\",\n      \"pmids\": [\"40768362\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of substrate recognition unresolved\", \"Mechanism of adhesion-loss-induced HECTD4 induction not defined\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Identifying METTL3 as a degradation target extended HECTD4's reach into m6A-dependent gene regulation, defining a HECTD4 → METTL3 → RANK m6A → osteoclast differentiation axis.\",\n      \"evidence\": \"Ubiquitination assays, MeRIP-qPCR, TRAP staining, and METTL3/RANK epistasis with exosome-delivered HECTD4\",\n      \"pmids\": [\"42141331\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab and single publication\", \"No direct demonstration HECTD4 ubiquitinates METTL3 with purified components\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Proteomic profiling in prostate cancer broadened the candidate substrate landscape, associating HECTD4 with ubiquitination of cell-cycle and signaling proteins.\",\n      \"evidence\": \"HECTD4 knockdown with LC-MS/MS ubiquitination profiling and pathway analysis in prostate cancer cell lines\",\n      \"pmids\": [\"42055625\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No direct in vitro ubiquitination assays for individual candidate substrates (NUSAP1, CDK6, MED13L)\", \"Association-level evidence only\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The structural and regulatory logic by which a single HECT ligase selects such distinct substrates across cancer, neurons, and bone remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No structural model of substrate engagement\", \"Determinants of tissue-specific substrate selection unknown\", \"Mechanism linking disease variants to substrate dysregulation undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016874\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 1, 2]}\n    ],\n    \"localization\": [],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0, 1, 2]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"PTGS2\", \"MKK7\", \"GRIN2B\", \"MALT1\", \"METTL3\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":4,"faith_total":5,"faith_pct":80.0}}