{"gene":"GLT8D1","run_date":"2026-06-10T01:55:21","timeline":{"discoveries":[{"year":2019,"finding":"ALS-associated mutations R92C and G78W in GLT8D1 map to the substrate binding site of the glycosyltransferase domain and impair GLT8D1 enzyme activity in vitro. Mutated GLT8D1 exhibits in vitro cytotoxicity and induces motor deficits in zebrafish consistent with ALS, with relative toxicity mirroring clinical severity.","method":"Exome sequencing, in vitro enzyme activity assay, zebrafish motor deficit model, cytotoxicity assay","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — in vitro enzymatic activity assay with specific mutations, functional validation in zebrafish, multiple orthogonal methods in one study","pmids":["30811981"],"is_preprint":false},{"year":2023,"finding":"GLT8D1 is a UDP-dependent galactosyltransferase that transfers galactose from UDP-galactose onto N-acetylgalactosamine. It is stabilized by Mn2+ and UDP nucleotides, is itself N-glycosylated, and adopts a GT-A fold consistent with CAZy family GT8, with a retaining catalytic mechanism.","method":"Recombinant protein production and purification, differential scanning fluorimetry, in vitro glycosyltransferase activity assay, structural modeling","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 1 / Moderate — direct in vitro enzymatic assay with purified recombinant protein, multiple orthogonal biochemical methods, single lab","pmids":["38066107"],"is_preprint":false},{"year":2022,"finding":"The enzymatic (glycosyltransferase) activity of GLT8D1 promotes glioblastoma cell migration; point mutations introduced into the predicted active site reduced glycosyltransferase activity in vitro and impaired GBM tumor cell migration. LC-MS/MS of GLT8D1 interaction partners identified cytoskeleton- and intracellular transport-associated proteins as potential substrates.","method":"In vitro overexpression, active-site mutagenesis, in vitro glycosyltransferase activity assay, cell migration assay, LC-MS/MS interactome analysis, in silico 3D structure prediction","journal":"iScience","confidence":"Medium","confidence_rationale":"Tier 1–2 / Moderate — active-site mutagenesis linked to enzymatic activity and functional phenotype, single lab, substrate identity remains tentative (LC-MS/MS only)","pmids":["35198895"],"is_preprint":false},{"year":2022,"finding":"Under hypoxia, HIF-1α induces GLT8D1 expression, and GLT8D1 stabilizes the stem cell marker CD133 by N-linked glycosylation and direct protein-protein interaction, preventing its degradation via the endosomal-lysosomal pathway. This GLT8D1/CD133 complex sustains Wnt/β-catenin signaling to promote glioma stem cell self-renewal and tumor growth. GLT8D1 knockdown promotes G2/M cell cycle arrest and apoptosis.","method":"GLT8D1 knockdown/depletion, co-immunoprecipitation (GLT8D1/CD133 complex), N-glycosylation analysis, endosomal-lysosomal pathway assay, Wnt/β-catenin reporter assay, in vitro self-renewal assays, glioma mouse models and patient-derived xenografts, dominant-negative CD133 peptide (FECD133) and lercanidipine inhibition","journal":"Cell death and differentiation","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, multiple orthogonal functional assays, in vivo validation in mouse models and PDX, loss-of-function with defined molecular mechanism","pmids":["35301431"],"is_preprint":false},{"year":2018,"finding":"GLT8D1 knockdown in neural stem cells promotes their proliferation and inhibits their differentiation, and alters neuronal morphology and synaptic transmission.","method":"shRNA knockdown in neural stem cells, proliferation and differentiation assays, neuronal morphology and electrophysiology measurements","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function with defined cellular phenotypes (proliferation, differentiation, synaptic transmission), single lab, multiple readouts","pmids":["29483533"],"is_preprint":false}],"current_model":"GLT8D1 is a UDP-dependent galactosyltransferase (GT-A fold, CAZy GT8 family) that transfers galactose from UDP-galactose onto acceptor substrates including N-acetylgalactosamine via a retaining mechanism; ALS-linked mutations in its substrate-binding site (R92C, G78W) reduce enzyme activity and cause motor neuron toxicity, while in glioma contexts HIF-1α-induced GLT8D1 N-glycosylates and stabilizes CD133 to sustain Wnt/β-catenin signaling and stem cell self-renewal, and its enzymatic activity also promotes glioblastoma cell migration through cytoskeletal substrates; in neural stem cells, GLT8D1 loss promotes proliferation and impairs differentiation."},"narrative":{"mechanistic_narrative":"GLT8D1 is a UDP-dependent galactosyltransferase that transfers galactose from UDP-galactose onto N-acetylgalactosamine through a retaining catalytic mechanism, adopting a GT-A fold and depending on Mn2+ and UDP nucleotides for stability [PMID:38066107]. Its enzymatic activity is central to its cellular functions: in glioblastoma, GLT8D1 activity promotes tumor cell migration, with cytoskeleton- and intracellular transport-associated proteins recovered as candidate substrates [PMID:35198895]. Under hypoxia, HIF-1α induces GLT8D1, which N-glycosylates and directly binds the stem cell marker CD133 to prevent its endosomal-lysosomal degradation, sustaining Wnt/β-catenin signaling and glioma stem cell self-renewal; GLT8D1 depletion triggers G2/M arrest and apoptosis [PMID:35301431]. In neural stem cells, loss of GLT8D1 drives proliferation, impairs differentiation, and alters neuronal morphology and synaptic transmission [PMID:29483533]. ALS-associated mutations R92C and G78W map to the substrate-binding site, impair enzyme activity, and confer cytotoxicity and motor deficits, linking GLT8D1 to amyotrophic lateral sclerosis [PMID:30811981].","teleology":[{"year":2018,"claim":"Established a first cellular role for GLT8D1 by asking whether it influences neural stem cell fate, showing it constrains proliferation and is required for proper differentiation.","evidence":"shRNA knockdown in neural stem cells with proliferation, differentiation, morphology and electrophysiology readouts","pmids":["29483533"],"confidence":"Medium","gaps":["Molecular mechanism linking GLT8D1 enzyme activity to the phenotypes not defined","No substrate identified in neural stem cells","Single lab, single system"]},{"year":2019,"claim":"Connected GLT8D1 to disease by asking whether its variants cause ALS, showing substrate-site mutations impair enzyme activity and produce motor neuron toxicity that tracks with clinical severity.","evidence":"Exome sequencing, in vitro enzyme activity assays of R92C/G78W mutants, zebrafish motor model and cytotoxicity assays","pmids":["30811981"],"confidence":"High","gaps":["Physiological substrate whose loss drives motor neuron toxicity unknown","Mechanism linking reduced glycosyltransferase activity to neurodegeneration not resolved"]},{"year":2022,"claim":"Addressed whether GLT8D1 enzymatic activity drives cancer cell behavior, showing active-site mutations reducing glycosyltransferase activity impair glioblastoma migration and implicating cytoskeletal/transport proteins as substrates.","evidence":"Overexpression, active-site mutagenesis, in vitro glycosyltransferase assays, migration assays, LC-MS/MS interactome, structure prediction","pmids":["35198895"],"confidence":"Medium","gaps":["Substrate identity is tentative (LC-MS/MS interactors only, no validated glycosylation site)","Direct glycosylation of cytoskeletal proteins not demonstrated"]},{"year":2022,"claim":"Defined a complete signaling axis by asking how hypoxia-induced GLT8D1 supports glioma stemness, showing it N-glycosylates and binds CD133 to block its lysosomal degradation and sustain Wnt/β-catenin signaling.","evidence":"Knockdown, reciprocal Co-IP, N-glycosylation and endosomal-lysosomal degradation assays, Wnt/β-catenin reporter, self-renewal assays, mouse models and PDX, inhibitor and dominant-negative peptide","pmids":["35301431"],"confidence":"High","gaps":["Specific CD133 glycosylation site and stoichiometry not mapped","Whether other clients are stabilized similarly unknown"]},{"year":2023,"claim":"Resolved the core biochemistry by asking what reaction GLT8D1 catalyzes, defining it as a Mn2+/UDP-dependent retaining galactosyltransferase transferring galactose onto N-acetylgalactosamine with a GT-A fold.","evidence":"Recombinant protein purification, differential scanning fluorimetry, in vitro glycosyltransferase assay, structural modeling","pmids":["38066107"],"confidence":"High","gaps":["Physiological acceptor substrates in vivo not established","No experimental crystal/cryo-EM structure","Link between defined in vitro activity and cellular phenotypes not directly tested"]},{"year":null,"claim":"The endogenous physiological substrates of GLT8D1 and how its galactosyltransferase activity mechanistically produces motor neuron, neural stem cell, and glioma phenotypes remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No validated in vivo glycosylation substrate beyond candidate interactors","Subcellular localization not characterized in the corpus","Structural basis of substrate recognition not experimentally determined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[0,1,2]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[1,3]}],"localization":[],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[1,3]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[3]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[0,3]}],"complexes":[],"partners":["CD133"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q68CQ7","full_name":"Glycosyltransferase 8 domain-containing protein 1","aliases":[],"length_aa":371,"mass_kda":41.9,"function":"In vitro, catalyzes the transfer of a galactose residue from UDP-galactose onto GalNAc and GlcNAc structures","subcellular_location":"Golgi apparatus membrane","url":"https://www.uniprot.org/uniprotkb/Q68CQ7/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/GLT8D1","classification":"Not Classified","n_dependent_lines":5,"n_total_lines":1208,"dependency_fraction":0.0041390728476821195},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"CANX","stoichiometry":0.2},{"gene":"MVD","stoichiometry":0.2},{"gene":"RAD17","stoichiometry":0.2},{"gene":"TMED10","stoichiometry":0.2},{"gene":"TMED2","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/GLT8D1","total_profiled":1310},"omim":[{"mim_id":"618399","title":"GLYCOSYLTRANSFERASE 8 DOMAIN-CONTAINING PROTEIN 1; GLT8D1","url":"https://www.omim.org/entry/618399"},{"mim_id":"606279","title":"ABI FAMILY MEMBER 3 BINDING PROTEIN; ABI3BP","url":"https://www.omim.org/entry/606279"},{"mim_id":"115441","title":"CASEIN KINASE II, BETA; CSNK2B","url":"https://www.omim.org/entry/115441"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Golgi apparatus","reliability":"Approved"},{"location":"Centrosome","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/GLT8D1"},"hgnc":{"alias_symbol":["AD-017","FLJ14611"],"prev_symbol":[]},"alphafold":{"accession":"Q68CQ7","domains":[{"cath_id":"3.90.550.10","chopping":"65-347","consensus_level":"high","plddt":91.1614,"start":65,"end":347}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q68CQ7","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q68CQ7-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q68CQ7-F1-predicted_aligned_error_v6.png","plddt_mean":84.75},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=GLT8D1","jax_strain_url":"https://www.jax.org/strain/search?query=GLT8D1"},"sequence":{"accession":"Q68CQ7","fasta_url":"https://rest.uniprot.org/uniprotkb/Q68CQ7.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q68CQ7/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q68CQ7"}},"corpus_meta":[{"pmid":"29483533","id":"PMC_29483533","title":"Comprehensive integrative analyses identify GLT8D1 and CSNK2B as schizophrenia risk genes.","date":"2018","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/29483533","citation_count":88,"is_preprint":false},{"pmid":"30811981","id":"PMC_30811981","title":"Mutations in the Glycosyltransferase Domain of GLT8D1 Are Associated with Familial Amyotrophic Lateral Sclerosis.","date":"2019","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/30811981","citation_count":65,"is_preprint":false},{"pmid":"35301431","id":"PMC_35301431","title":"Hypoxia-induced GLT8D1 promotes glioma stem cell maintenance by inhibiting CD133 degradation through N-linked glycosylation.","date":"2022","source":"Cell death and differentiation","url":"https://pubmed.ncbi.nlm.nih.gov/35301431","citation_count":59,"is_preprint":false},{"pmid":"31653410","id":"PMC_31653410","title":"Mutation analysis of GLT8D1 and ARPP21 genes in amyotrophic lateral sclerosis patients from mainland China.","date":"2019","source":"Neurobiology of aging","url":"https://pubmed.ncbi.nlm.nih.gov/31653410","citation_count":19,"is_preprint":false},{"pmid":"36836762","id":"PMC_36836762","title":"Intergenic Interactions of SBNO1, NFAT5 and GLT8D1 Determine the Susceptibility to Knee Osteoarthritis among Europeans of Russia.","date":"2023","source":"Life (Basel, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/36836762","citation_count":13,"is_preprint":false},{"pmid":"33581934","id":"PMC_33581934","title":"Genetic analysis of GLT8D1 and ARPP21 in Australian familial and sporadic amyotrophic lateral sclerosis.","date":"2021","source":"Neurobiology of aging","url":"https://pubmed.ncbi.nlm.nih.gov/33581934","citation_count":10,"is_preprint":false},{"pmid":"35198895","id":"PMC_35198895","title":"Enzymatic activity of glycosyltransferase GLT8D1 promotes human glioblastoma cell migration.","date":"2022","source":"iScience","url":"https://pubmed.ncbi.nlm.nih.gov/35198895","citation_count":8,"is_preprint":false},{"pmid":"38066107","id":"PMC_38066107","title":"Glycosyltransferase 8 domain-containing protein 1 (GLT8D1) is a UDP-dependent galactosyltransferase.","date":"2023","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/38066107","citation_count":7,"is_preprint":false},{"pmid":"33581933","id":"PMC_33581933","title":"Mutation screening and burden analysis of GLT8D1 in Chinese patients with amyotrophic lateral sclerosis.","date":"2020","source":"Neurobiology of aging","url":"https://pubmed.ncbi.nlm.nih.gov/33581933","citation_count":5,"is_preprint":false},{"pmid":"33714647","id":"PMC_33714647","title":"GLT8D1 may not be significant in Chinese sporadic amyotrophic lateral sclerosis patients.","date":"2021","source":"Neurobiology of aging","url":"https://pubmed.ncbi.nlm.nih.gov/33714647","citation_count":5,"is_preprint":false},{"pmid":"33963205","id":"PMC_33963205","title":"Germinal GLT8D1, GATAD2A and SLC25A39 mutations in a patient with a glomangiopericytal tumor and five different sarcomas over a 10-year period.","date":"2021","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/33963205","citation_count":5,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":6874,"output_tokens":1483,"usd":0.021434,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8244,"output_tokens":2311,"usd":0.049497,"stage2_stop_reason":"end_turn"},"total_usd":0.070931,"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\": 2019,\n      \"finding\": \"ALS-associated mutations R92C and G78W in GLT8D1 map to the substrate binding site of the glycosyltransferase domain and impair GLT8D1 enzyme activity in vitro. Mutated GLT8D1 exhibits in vitro cytotoxicity and induces motor deficits in zebrafish consistent with ALS, with relative toxicity mirroring clinical severity.\",\n      \"method\": \"Exome sequencing, in vitro enzyme activity assay, zebrafish motor deficit model, cytotoxicity assay\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro enzymatic activity assay with specific mutations, functional validation in zebrafish, multiple orthogonal methods in one study\",\n      \"pmids\": [\"30811981\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"GLT8D1 is a UDP-dependent galactosyltransferase that transfers galactose from UDP-galactose onto N-acetylgalactosamine. It is stabilized by Mn2+ and UDP nucleotides, is itself N-glycosylated, and adopts a GT-A fold consistent with CAZy family GT8, with a retaining catalytic mechanism.\",\n      \"method\": \"Recombinant protein production and purification, differential scanning fluorimetry, in vitro glycosyltransferase activity assay, structural modeling\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct in vitro enzymatic assay with purified recombinant protein, multiple orthogonal biochemical methods, single lab\",\n      \"pmids\": [\"38066107\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"The enzymatic (glycosyltransferase) activity of GLT8D1 promotes glioblastoma cell migration; point mutations introduced into the predicted active site reduced glycosyltransferase activity in vitro and impaired GBM tumor cell migration. LC-MS/MS of GLT8D1 interaction partners identified cytoskeleton- and intracellular transport-associated proteins as potential substrates.\",\n      \"method\": \"In vitro overexpression, active-site mutagenesis, in vitro glycosyltransferase activity assay, cell migration assay, LC-MS/MS interactome analysis, in silico 3D structure prediction\",\n      \"journal\": \"iScience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — active-site mutagenesis linked to enzymatic activity and functional phenotype, single lab, substrate identity remains tentative (LC-MS/MS only)\",\n      \"pmids\": [\"35198895\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Under hypoxia, HIF-1α induces GLT8D1 expression, and GLT8D1 stabilizes the stem cell marker CD133 by N-linked glycosylation and direct protein-protein interaction, preventing its degradation via the endosomal-lysosomal pathway. This GLT8D1/CD133 complex sustains Wnt/β-catenin signaling to promote glioma stem cell self-renewal and tumor growth. GLT8D1 knockdown promotes G2/M cell cycle arrest and apoptosis.\",\n      \"method\": \"GLT8D1 knockdown/depletion, co-immunoprecipitation (GLT8D1/CD133 complex), N-glycosylation analysis, endosomal-lysosomal pathway assay, Wnt/β-catenin reporter assay, in vitro self-renewal assays, glioma mouse models and patient-derived xenografts, dominant-negative CD133 peptide (FECD133) and lercanidipine inhibition\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, multiple orthogonal functional assays, in vivo validation in mouse models and PDX, loss-of-function with defined molecular mechanism\",\n      \"pmids\": [\"35301431\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"GLT8D1 knockdown in neural stem cells promotes their proliferation and inhibits their differentiation, and alters neuronal morphology and synaptic transmission.\",\n      \"method\": \"shRNA knockdown in neural stem cells, proliferation and differentiation assays, neuronal morphology and electrophysiology measurements\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function with defined cellular phenotypes (proliferation, differentiation, synaptic transmission), single lab, multiple readouts\",\n      \"pmids\": [\"29483533\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"GLT8D1 is a UDP-dependent galactosyltransferase (GT-A fold, CAZy GT8 family) that transfers galactose from UDP-galactose onto acceptor substrates including N-acetylgalactosamine via a retaining mechanism; ALS-linked mutations in its substrate-binding site (R92C, G78W) reduce enzyme activity and cause motor neuron toxicity, while in glioma contexts HIF-1α-induced GLT8D1 N-glycosylates and stabilizes CD133 to sustain Wnt/β-catenin signaling and stem cell self-renewal, and its enzymatic activity also promotes glioblastoma cell migration through cytoskeletal substrates; in neural stem cells, GLT8D1 loss promotes proliferation and impairs differentiation.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"GLT8D1 is a UDP-dependent galactosyltransferase that transfers galactose from UDP-galactose onto N-acetylgalactosamine through a retaining catalytic mechanism, adopting a GT-A fold and depending on Mn2+ and UDP nucleotides for stability [#1]. Its enzymatic activity is central to its cellular functions: in glioblastoma, GLT8D1 activity promotes tumor cell migration, with cytoskeleton- and intracellular transport-associated proteins recovered as candidate substrates [#2]. Under hypoxia, HIF-1\\u03b1 induces GLT8D1, which N-glycosylates and directly binds the stem cell marker CD133 to prevent its endosomal-lysosomal degradation, sustaining Wnt/\\u03b2-catenin signaling and glioma stem cell self-renewal; GLT8D1 depletion triggers G2/M arrest and apoptosis [#3]. In neural stem cells, loss of GLT8D1 drives proliferation, impairs differentiation, and alters neuronal morphology and synaptic transmission [#4]. ALS-associated mutations R92C and G78W map to the substrate-binding site, impair enzyme activity, and confer cytotoxicity and motor deficits, linking GLT8D1 to amyotrophic lateral sclerosis [#0].\"\n  ,\n  \"teleology\": [\n    {\n      \"year\": 2018,\n      \"claim\": \"Established a first cellular role for GLT8D1 by asking whether it influences neural stem cell fate, showing it constrains proliferation and is required for proper differentiation.\",\n      \"evidence\": \"shRNA knockdown in neural stem cells with proliferation, differentiation, morphology and electrophysiology readouts\",\n      \"pmids\": [\"29483533\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Molecular mechanism linking GLT8D1 enzyme activity to the phenotypes not defined\", \"No substrate identified in neural stem cells\", \"Single lab, single system\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Connected GLT8D1 to disease by asking whether its variants cause ALS, showing substrate-site mutations impair enzyme activity and produce motor neuron toxicity that tracks with clinical severity.\",\n      \"evidence\": \"Exome sequencing, in vitro enzyme activity assays of R92C/G78W mutants, zebrafish motor model and cytotoxicity assays\",\n      \"pmids\": [\"30811981\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Physiological substrate whose loss drives motor neuron toxicity unknown\", \"Mechanism linking reduced glycosyltransferase activity to neurodegeneration not resolved\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Addressed whether GLT8D1 enzymatic activity drives cancer cell behavior, showing active-site mutations reducing glycosyltransferase activity impair glioblastoma migration and implicating cytoskeletal/transport proteins as substrates.\",\n      \"evidence\": \"Overexpression, active-site mutagenesis, in vitro glycosyltransferase assays, migration assays, LC-MS/MS interactome, structure prediction\",\n      \"pmids\": [\"35198895\"],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Substrate identity is tentative (LC-MS/MS interactors only, no validated glycosylation site)\", \"Direct glycosylation of cytoskeletal proteins not demonstrated\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Defined a complete signaling axis by asking how hypoxia-induced GLT8D1 supports glioma stemness, showing it N-glycosylates and binds CD133 to block its lysosomal degradation and sustain Wnt/\\u03b2-catenin signaling.\",\n      \"evidence\": \"Knockdown, reciprocal Co-IP, N-glycosylation and endosomal-lysosomal degradation assays, Wnt/\\u03b2-catenin reporter, self-renewal assays, mouse models and PDX, inhibitor and dominant-negative peptide\",\n      \"pmids\": [\"35301431\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Specific CD133 glycosylation site and stoichiometry not mapped\", \"Whether other clients are stabilized similarly unknown\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Resolved the core biochemistry by asking what reaction GLT8D1 catalyzes, defining it as a Mn2+/UDP-dependent retaining galactosyltransferase transferring galactose onto N-acetylgalactosamine with a GT-A fold.\",\n      \"evidence\": \"Recombinant protein purification, differential scanning fluorimetry, in vitro glycosyltransferase assay, structural modeling\",\n      \"pmids\": [\"38066107\"],\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"Physiological acceptor substrates in vivo not established\", \"No experimental crystal/cryo-EM structure\", \"Link between defined in vitro activity and cellular phenotypes not directly tested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The endogenous physiological substrates of GLT8D1 and how its galactosyltransferase activity mechanistically produces motor neuron, neural stem cell, and glioma phenotypes remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"\",\n      \"gaps\": [\"No validated in vivo glycosylation substrate beyond candidate interactors\", \"Subcellular localization not characterized in the corpus\", \"Structural basis of substrate recognition not experimentally determined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [0, 1, 2]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [1, 3]}\n    ],\n    \"localization\": [],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [1, 3]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [3]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [0, 3]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"CD133\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}