{"gene":"GMDS","run_date":"2026-06-10T01:55:21","timeline":{"discoveries":[{"year":2007,"finding":"GMDS (GDP-mannose 4,6-dehydratase) encodes the first enzyme in the de novo GDP-fucose biosynthesis pathway; siRNA-mediated knockdown of GMDS in CHO cells reduced cellular fucosylation in a manner correlated with mRNA expression levels, and GMDS knockout cells were devoid of intracellular GDP-fucose and produced completely non-fucosylated antibodies, confirming GMDS is the rate-limiting enzyme in the de novo GDP-fucose synthesis pathway with no functional redundancy.","method":"siRNA knockdown, GMDS knockout cell line generation, GDP-fucose quantification by HPLC, antibody fucosylation analysis","journal":"Journal of biotechnology","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — biochemical (GDP-fucose measurement) combined with genetic knockout and functional readout; replicated across two independent studies (PMID:17559959 and PMID:18047682)","pmids":["17559959","18047682"],"is_preprint":false},{"year":2007,"finding":"Simultaneous double knockdown of GMDS and FUT8 (alpha-1,6-fucosyltransferase) produced a synergistic effect on reduction of antibody fucosylation, achieving complete defucosylation, whereas knockdown of GMDS combined with GDP-fucose transporter (GFT) siRNA did not show the same synergistic effect, indicating that GMDS and FUT8 collaborate in the same intracellular fucosylation process.","method":"siRNA double knockdown, flow cytometry for fucosylation, ADCC assay","journal":"BMC biotechnology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional epistasis via siRNA combination in cell line, single lab, two orthogonal methods (fucosylation measurement and ADCC)","pmids":["18047682"],"is_preprint":false},{"year":2009,"finding":"Loss-of-function mutations in GMDS in the human colon cancer cell line HCT116 result in virtually complete loss of cellular fucosylation; re-introduction of wild-type GMDS restored cellular fucosylation. GMDS-deficient cells were resistant to TRAIL-induced apoptosis, and GMDS-rescued cells transplanted into athymic mice showed dramatically suppressed tumor growth and metastasis through NK cell-mediated tumor surveillance. Anti-TRAIL blocking antibody suppressed the accelerated direct cell lysis of GMDS-rescued cells by splenocytes, placing GMDS upstream of TRAIL signaling in NK cell-mediated tumor immune surveillance.","method":"Mutational analysis, GMDS transfection/rescue, in vitro TRAIL apoptosis assay, xenograft mouse model, NK cell cytotoxicity assay, anti-TRAIL blocking antibody","journal":"Gastroenterology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal in vitro and in vivo methods in a single study, genetic rescue experiment with functional readout","pmids":["19361506"],"is_preprint":false},{"year":2011,"finding":"GMDS deficiency inhibits both DR4- and DR5-mediated (and CD95-mediated) apoptosis, but not intrinsic (drug-induced) apoptosis. Mechanistically, GMDS deficiency does not block primary DISC formation or caspase-8 recruitment/activation at the DISC, but specifically inhibits formation of the secondary FADD-dependent complex II (comprising caspase-8 and cFLIP) downstream of DISC. DR4 was found to be fucosylated while DR5 was not, yet GMDS deficiency blocked both pathways, indicating the block occurs independent of direct fucosylation of death receptors at the level of complex II assembly.","method":"Co-immunoprecipitation of DISC components, caspase-8 activity assay, western blot for complex II components, comparison of DR4/DR5 fucosylation status","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — multiple orthogonal biochemical methods (Co-IP, activity assays, fucosylation analysis) defining precise step in death receptor signaling pathway, single lab but rigorous","pmids":["22027835"],"is_preprint":false},{"year":2011,"finding":"In Drosophila, GMD (the ortholog of human GMDS) activity regulates the stability of the Notch protein; low GMD expression leads to Notch degradation that is entirely dependent on OFUT1 (O-fucosyltransferase-1). The GDP-fucose/OFUT1 balance determines OFUT1's ability to endocytose and degrade Notch, placing GMD upstream of OFUT1-mediated Notch protein stability.","method":"Drosophila genetics (mutant analysis, UAS/Gal4 system), epistasis analysis with OFUT1 and Notch Abruptex mutants","journal":"Biological research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis in Drosophila model organism using multiple mutant combinations, single lab","pmids":["21720678"],"is_preprint":false},{"year":2018,"finding":"GMDS knockdown in human lung adenocarcinoma cells (A549 and H1299) impaired cell proliferation, colony formation, induced cell cycle arrest and apoptosis in vitro, and inhibited tumorigenesis in a xenograft mouse model. Transcriptome analysis identified the CASP8-CDKN1A axis as potentially critical, consistent with GMDS acting upstream of apoptotic signaling in this cancer context.","method":"Lentiviral shRNA knockdown, cell viability/proliferation assays, flow cytometry (cell cycle and apoptosis), xenograft mouse model, microarray transcriptome analysis","journal":"BMC cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function with multiple cellular phenotype readouts in vitro and in vivo, single lab","pmids":["29843634"],"is_preprint":false},{"year":2025,"finding":"A point mutation in mouse Gmds (ENU-induced) caused a near-complete block in T cell development at the double-positive stage in the thymus, with a cell-intrinsic requirement demonstrated by bone marrow reconstitution and mixed chimera experiments showing Gmds-deficient T cells could not compete from the DP stage onward, while B cell subsets were broadly normal.","method":"ENU mutagenesis mouse model, flow cytometry immunophenotyping, bone marrow reconstitution (Rag1 mice), mixed chimera experiments","journal":"Frontiers in immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — cell-intrinsic requirement demonstrated by mixed chimera and bone marrow transplantation with defined cellular phenotypes, multiple orthogonal genetic approaches","pmids":["40642090"],"is_preprint":false},{"year":2025,"finding":"Loss of gmds function in zebrafish increased hair cell number in neuromasts and accelerated hair cell regeneration after neomycin-induced ablation. Pharmacological inhibition of Notch signaling enhanced hair cell regeneration in wild-type siblings but less so in gmds mutants, indicating that Notch signaling acts partially downstream of gmds in regulating hair cell regeneration.","method":"CRISPR/Cas9 gmds mutant zebrafish, neomycin hair cell ablation assay, pharmacological Notch inhibition, live imaging of hair cell regeneration","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic loss-of-function with pharmacological epistasis in zebrafish model, single lab with multiple readouts","pmids":["41097001"],"is_preprint":false},{"year":2025,"finding":"gmds haploinsufficiency in zebrafish (CRISPR/Cas9) caused retinal ganglion cell (RGC) layer thinning, RGC loss, and reduced optic nerve head width. RNA-seq showed significant downregulation of stress response genes (including crystallin family) and increased expression of cell death genes in gmds heterozygous mutant eyes, suggesting GMDS regulates ocular stress responses and RGC survival.","method":"CRISPR/Cas9 zebrafish mutant, RNAseq transcriptome analysis, histological/morphological phenotyping of eye","journal":"Experimental eye research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function genetic model with transcriptomic and morphological readouts, single lab","pmids":["40571142"],"is_preprint":false}],"current_model":"GMDS (GDP-mannose 4,6-dehydratase) catalyzes the first committed step of the de novo GDP-fucose biosynthesis pathway, converting GDP-mannose to GDP-4-keto-6-deoxymannose; loss of GMDS abolishes cellular fucosylation, which in turn impairs TRAIL/CD95 death receptor signaling at the level of secondary complex II (FADD/caspase-8/cFLIP) assembly (independent of direct death receptor fucosylation), enables tumor immune escape from NK cell-mediated surveillance, is cell-intrinsically required for T cell development past the double-positive thymic stage, and regulates Notch protein stability (via the OFUT1 axis) to control tissue development including hair cell regeneration and ocular health."},"narrative":{"mechanistic_narrative":"GMDS (GDP-mannose 4,6-dehydratase) catalyzes the first, rate-limiting and non-redundant step of the de novo GDP-fucose biosynthesis pathway, converting GDP-mannose toward GDP-fucose so that loss of GMDS abolishes intracellular GDP-fucose and cellular protein fucosylation [PMID:17559959, PMID:18047682]. It collaborates functionally with the downstream fucosyltransferase FUT8 in the same fucosylation process, where co-depletion synergistically eliminates antibody fucosylation [PMID:18047682]. Through its control of cellular fucosylation, GMDS gates extrinsic apoptotic death-receptor signaling: GMDS-deficient cells resist TRAIL/DR4-, DR5- and CD95-mediated apoptosis but not intrinsic drug-induced death, with the defect mapping specifically to assembly of the secondary FADD-dependent complex II (caspase-8/cFLIP) rather than primary DISC formation, and acting independently of direct death-receptor fucosylation [PMID:19361506, PMID:22027835]. This apoptotic gating underlies a tumor-suppressive, immune-surveillance role: restoring GMDS sensitizes colon cancer cells to NK cell- and TRAIL-dependent killing and suppresses tumor growth and metastasis in vivo [PMID:19361506]. Beyond cancer, GMDS is cell-intrinsically required for T-cell development past the double-positive thymic stage [PMID:40642090], and in model organisms it regulates Notch signaling — controlling Notch protein stability via the OFUT1 axis [PMID:21720678] and acting upstream of Notch in hair cell regeneration [PMID:41097001] — as well as retinal ganglion cell survival and ocular stress responses [PMID:40571142].","teleology":[{"year":2007,"claim":"Established that GMDS is the rate-limiting, non-redundant entry enzyme of de novo GDP-fucose synthesis, defining it as the master switch for cellular fucosylation.","evidence":"siRNA knockdown and knockout in CHO cells with HPLC GDP-fucose quantification and antibody fucosylation analysis","pmids":["17559959","18047682"],"confidence":"High","gaps":["Does not resolve the enzyme's structural/catalytic mechanism","Salvage-pathway contributions to GDP-fucose pools in other cell types not addressed"]},{"year":2007,"claim":"Placed GMDS and the fucosyltransferase FUT8 in the same fucosylation process by showing synergistic defucosylation upon co-depletion, distinguishing it from transporter-level control.","evidence":"siRNA double knockdown with flow cytometry fucosylation readout and ADCC assay","pmids":["18047682"],"confidence":"Medium","gaps":["Epistasis inferred from siRNA combinations in a single cell line","Does not establish direct physical interaction between GMDS and FUT8"]},{"year":2009,"claim":"Connected GMDS-dependent fucosylation to extrinsic apoptosis and tumor immune surveillance, showing GMDS acts upstream of TRAIL signaling and NK cell-mediated killing.","evidence":"GMDS mutation/rescue in HCT116 colon cancer cells, TRAIL apoptosis assays, xenograft model, NK cytotoxicity with anti-TRAIL blocking antibody","pmids":["19361506"],"confidence":"High","gaps":["Molecular target whose fucosylation enables TRAIL sensitivity not identified here","Generality beyond colon cancer not tested"]},{"year":2011,"claim":"Pinpointed the death-receptor signaling step GMDS controls, showing the block is at secondary complex II (caspase-8/cFLIP) assembly and independent of direct death-receptor fucosylation.","evidence":"Co-IP of DISC components, caspase-8 activity assays, western blot of complex II, DR4/DR5 fucosylation comparison","pmids":["22027835"],"confidence":"High","gaps":["The specific fucosylated protein governing complex II assembly remains unidentified","Mechanism linking fucosylation status to FADD-dependent complex II formation not defined"]},{"year":2011,"claim":"Linked GMDS/GDP-fucose to Notch protein stability through OFUT1, extending GMDS function from apoptosis into developmental signaling.","evidence":"Drosophila genetics and epistasis with OFUT1 and Notch Abruptex mutants","pmids":["21720678"],"confidence":"Medium","gaps":["Genetic epistasis in Drosophila; biochemical demonstration of fucose-dependent OFUT1 activity on Notch not shown","Conservation of the OFUT1-Notch mechanism in mammals not established"]},{"year":2018,"claim":"Demonstrated a cell-autonomous tumor-promoting requirement for GMDS in lung adenocarcinoma, nominating a CASP8-CDKN1A axis and reinforcing GMDS as upstream of apoptotic/cell-cycle control.","evidence":"shRNA knockdown in A549/H1299, proliferation/cell-cycle/apoptosis assays, xenograft, microarray transcriptome","pmids":["29843634"],"confidence":"Medium","gaps":["CASP8-CDKN1A axis identified by transcriptomics, not mechanistically validated","Apparent pro-tumor role here contrasts with tumor-suppressive role in colon cancer; context dependence unexplained"]},{"year":2025,"claim":"Revealed a cell-intrinsic requirement for GMDS in thymic T-cell development past the double-positive stage, defining a non-redundant role in lymphopoiesis.","evidence":"ENU-mutant mouse, flow immunophenotyping, bone marrow reconstitution and mixed chimera experiments","pmids":["40642090"],"confidence":"High","gaps":["Molecular fucosylation target driving the DP-stage block not identified","Whether the defect reflects altered Notch or TCR-associated signaling not resolved"]},{"year":2025,"claim":"Showed GMDS restrains hair cell number and regeneration upstream of Notch signaling, providing in vivo developmental evidence for the GMDS-Notch link.","evidence":"CRISPR/Cas9 gmds zebrafish, neomycin ablation, pharmacological Notch inhibition, live imaging","pmids":["41097001"],"confidence":"Medium","gaps":["Notch placed downstream by pharmacology/epistasis, not by direct biochemistry","Single model system"]},{"year":2025,"claim":"Implicated GMDS dosage in retinal ganglion cell survival and ocular stress responses, broadening its physiological role to tissue maintenance.","evidence":"CRISPR/Cas9 gmds haploinsufficient zebrafish, RNA-seq, histological eye phenotyping","pmids":["40571142"],"confidence":"Medium","gaps":["Stress-response and cell-death gene changes are correlative","Mechanistic link between reduced fucosylation and RGC loss not established"]},{"year":null,"claim":"The identity of the fucosylated protein(s) whose modification by the GMDS pathway controls complex II assembly, T-cell development, and Notch regulation remains the central open mechanistic question.","evidence":"","pmids":[],"confidence":"High","gaps":["No direct fucosylated effector linking GMDS loss to complex II/caspase-8 signaling identified","Context-dependent tumor-suppressive vs tumor-promoting roles unreconciled","No structural/catalytic mechanism described in the corpus"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016491","term_label":"oxidoreductase activity","supporting_discovery_ids":[0]},{"term_id":"GO:0016829","term_label":"lyase activity","supporting_discovery_ids":[0]}],"localization":[],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[0]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[2,3]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0,1]}],"complexes":[],"partners":["FUT8"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O60547","full_name":"GDP-mannose 4,6 dehydratase","aliases":["GDP-D-mannose dehydratase","GMD"],"length_aa":372,"mass_kda":42.0,"function":"Catalyzes the conversion of GDP-D-mannose to GDP-4-dehydro-6-deoxy-D-mannose","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/O60547/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/GMDS","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":"TSR2","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/GMDS","total_profiled":1310},"omim":[{"mim_id":"612582","title":"CHROMOSOME 6pter-p24 DELETION SYNDROME","url":"https://www.omim.org/entry/612582"},{"mim_id":"602884","title":"GDP-MANNOSE 4,6-DEHYDRATASE; GMDS","url":"https://www.omim.org/entry/602884"},{"mim_id":"601090","title":"FORKHEAD BOX C1; FOXC1","url":"https://www.omim.org/entry/601090"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"intestine","ntpm":99.8},{"tissue":"salivary gland","ntpm":99.4},{"tissue":"stomach 1","ntpm":91.7}],"url":"https://www.proteinatlas.org/search/GMDS"},"hgnc":{"alias_symbol":["GMD","SDR3E1"],"prev_symbol":[]},"alphafold":{"accession":"O60547","domains":[{"cath_id":"3.40.50.720","chopping":"24-213_250-277_329-349","consensus_level":"high","plddt":97.1032,"start":24,"end":349},{"cath_id":"3.90.25.10","chopping":"218-240_281-325_360-367","consensus_level":"medium","plddt":97.9701,"start":218,"end":367}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O60547","model_url":"https://alphafold.ebi.ac.uk/files/AF-O60547-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O60547-F1-predicted_aligned_error_v6.png","plddt_mean":94.12},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=GMDS","jax_strain_url":"https://www.jax.org/strain/search?query=GMDS"},"sequence":{"accession":"O60547","fasta_url":"https://rest.uniprot.org/uniprotkb/O60547.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O60547/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O60547"}},"corpus_meta":[{"pmid":"15613389","id":"PMC_15613389","title":"GMD@CSB.DB: 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PCC 6803","date":"2025-03-30","source":"bioRxiv","url":"https://doi.org/10.1101/2025.03.27.645739","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":20911,"output_tokens":2613,"usd":0.050964,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9924,"output_tokens":3140,"usd":0.06406,"stage2_stop_reason":"end_turn"},"total_usd":0.115024,"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\": 2007,\n      \"finding\": \"GMDS (GDP-mannose 4,6-dehydratase) encodes the first enzyme in the de novo GDP-fucose biosynthesis pathway; siRNA-mediated knockdown of GMDS in CHO cells reduced cellular fucosylation in a manner correlated with mRNA expression levels, and GMDS knockout cells were devoid of intracellular GDP-fucose and produced completely non-fucosylated antibodies, confirming GMDS is the rate-limiting enzyme in the de novo GDP-fucose synthesis pathway with no functional redundancy.\",\n      \"method\": \"siRNA knockdown, GMDS knockout cell line generation, GDP-fucose quantification by HPLC, antibody fucosylation analysis\",\n      \"journal\": \"Journal of biotechnology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — biochemical (GDP-fucose measurement) combined with genetic knockout and functional readout; replicated across two independent studies (PMID:17559959 and PMID:18047682)\",\n      \"pmids\": [\"17559959\", \"18047682\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Simultaneous double knockdown of GMDS and FUT8 (alpha-1,6-fucosyltransferase) produced a synergistic effect on reduction of antibody fucosylation, achieving complete defucosylation, whereas knockdown of GMDS combined with GDP-fucose transporter (GFT) siRNA did not show the same synergistic effect, indicating that GMDS and FUT8 collaborate in the same intracellular fucosylation process.\",\n      \"method\": \"siRNA double knockdown, flow cytometry for fucosylation, ADCC assay\",\n      \"journal\": \"BMC biotechnology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional epistasis via siRNA combination in cell line, single lab, two orthogonal methods (fucosylation measurement and ADCC)\",\n      \"pmids\": [\"18047682\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Loss-of-function mutations in GMDS in the human colon cancer cell line HCT116 result in virtually complete loss of cellular fucosylation; re-introduction of wild-type GMDS restored cellular fucosylation. GMDS-deficient cells were resistant to TRAIL-induced apoptosis, and GMDS-rescued cells transplanted into athymic mice showed dramatically suppressed tumor growth and metastasis through NK cell-mediated tumor surveillance. Anti-TRAIL blocking antibody suppressed the accelerated direct cell lysis of GMDS-rescued cells by splenocytes, placing GMDS upstream of TRAIL signaling in NK cell-mediated tumor immune surveillance.\",\n      \"method\": \"Mutational analysis, GMDS transfection/rescue, in vitro TRAIL apoptosis assay, xenograft mouse model, NK cell cytotoxicity assay, anti-TRAIL blocking antibody\",\n      \"journal\": \"Gastroenterology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal in vitro and in vivo methods in a single study, genetic rescue experiment with functional readout\",\n      \"pmids\": [\"19361506\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"GMDS deficiency inhibits both DR4- and DR5-mediated (and CD95-mediated) apoptosis, but not intrinsic (drug-induced) apoptosis. Mechanistically, GMDS deficiency does not block primary DISC formation or caspase-8 recruitment/activation at the DISC, but specifically inhibits formation of the secondary FADD-dependent complex II (comprising caspase-8 and cFLIP) downstream of DISC. DR4 was found to be fucosylated while DR5 was not, yet GMDS deficiency blocked both pathways, indicating the block occurs independent of direct fucosylation of death receptors at the level of complex II assembly.\",\n      \"method\": \"Co-immunoprecipitation of DISC components, caspase-8 activity assay, western blot for complex II components, comparison of DR4/DR5 fucosylation status\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — multiple orthogonal biochemical methods (Co-IP, activity assays, fucosylation analysis) defining precise step in death receptor signaling pathway, single lab but rigorous\",\n      \"pmids\": [\"22027835\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"In Drosophila, GMD (the ortholog of human GMDS) activity regulates the stability of the Notch protein; low GMD expression leads to Notch degradation that is entirely dependent on OFUT1 (O-fucosyltransferase-1). The GDP-fucose/OFUT1 balance determines OFUT1's ability to endocytose and degrade Notch, placing GMD upstream of OFUT1-mediated Notch protein stability.\",\n      \"method\": \"Drosophila genetics (mutant analysis, UAS/Gal4 system), epistasis analysis with OFUT1 and Notch Abruptex mutants\",\n      \"journal\": \"Biological research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis in Drosophila model organism using multiple mutant combinations, single lab\",\n      \"pmids\": [\"21720678\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"GMDS knockdown in human lung adenocarcinoma cells (A549 and H1299) impaired cell proliferation, colony formation, induced cell cycle arrest and apoptosis in vitro, and inhibited tumorigenesis in a xenograft mouse model. Transcriptome analysis identified the CASP8-CDKN1A axis as potentially critical, consistent with GMDS acting upstream of apoptotic signaling in this cancer context.\",\n      \"method\": \"Lentiviral shRNA knockdown, cell viability/proliferation assays, flow cytometry (cell cycle and apoptosis), xenograft mouse model, microarray transcriptome analysis\",\n      \"journal\": \"BMC cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function with multiple cellular phenotype readouts in vitro and in vivo, single lab\",\n      \"pmids\": [\"29843634\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"A point mutation in mouse Gmds (ENU-induced) caused a near-complete block in T cell development at the double-positive stage in the thymus, with a cell-intrinsic requirement demonstrated by bone marrow reconstitution and mixed chimera experiments showing Gmds-deficient T cells could not compete from the DP stage onward, while B cell subsets were broadly normal.\",\n      \"method\": \"ENU mutagenesis mouse model, flow cytometry immunophenotyping, bone marrow reconstitution (Rag1 mice), mixed chimera experiments\",\n      \"journal\": \"Frontiers in immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — cell-intrinsic requirement demonstrated by mixed chimera and bone marrow transplantation with defined cellular phenotypes, multiple orthogonal genetic approaches\",\n      \"pmids\": [\"40642090\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Loss of gmds function in zebrafish increased hair cell number in neuromasts and accelerated hair cell regeneration after neomycin-induced ablation. Pharmacological inhibition of Notch signaling enhanced hair cell regeneration in wild-type siblings but less so in gmds mutants, indicating that Notch signaling acts partially downstream of gmds in regulating hair cell regeneration.\",\n      \"method\": \"CRISPR/Cas9 gmds mutant zebrafish, neomycin hair cell ablation assay, pharmacological Notch inhibition, live imaging of hair cell regeneration\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic loss-of-function with pharmacological epistasis in zebrafish model, single lab with multiple readouts\",\n      \"pmids\": [\"41097001\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"gmds haploinsufficiency in zebrafish (CRISPR/Cas9) caused retinal ganglion cell (RGC) layer thinning, RGC loss, and reduced optic nerve head width. RNA-seq showed significant downregulation of stress response genes (including crystallin family) and increased expression of cell death genes in gmds heterozygous mutant eyes, suggesting GMDS regulates ocular stress responses and RGC survival.\",\n      \"method\": \"CRISPR/Cas9 zebrafish mutant, RNAseq transcriptome analysis, histological/morphological phenotyping of eye\",\n      \"journal\": \"Experimental eye research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function genetic model with transcriptomic and morphological readouts, single lab\",\n      \"pmids\": [\"40571142\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"GMDS (GDP-mannose 4,6-dehydratase) catalyzes the first committed step of the de novo GDP-fucose biosynthesis pathway, converting GDP-mannose to GDP-4-keto-6-deoxymannose; loss of GMDS abolishes cellular fucosylation, which in turn impairs TRAIL/CD95 death receptor signaling at the level of secondary complex II (FADD/caspase-8/cFLIP) assembly (independent of direct death receptor fucosylation), enables tumor immune escape from NK cell-mediated surveillance, is cell-intrinsically required for T cell development past the double-positive thymic stage, and regulates Notch protein stability (via the OFUT1 axis) to control tissue development including hair cell regeneration and ocular health.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"GMDS (GDP-mannose 4,6-dehydratase) catalyzes the first, rate-limiting and non-redundant step of the de novo GDP-fucose biosynthesis pathway, converting GDP-mannose toward GDP-fucose so that loss of GMDS abolishes intracellular GDP-fucose and cellular protein fucosylation [#0]. It collaborates functionally with the downstream fucosyltransferase FUT8 in the same fucosylation process, where co-depletion synergistically eliminates antibody fucosylation [#1]. Through its control of cellular fucosylation, GMDS gates extrinsic apoptotic death-receptor signaling: GMDS-deficient cells resist TRAIL/DR4-, DR5- and CD95-mediated apoptosis but not intrinsic drug-induced death, with the defect mapping specifically to assembly of the secondary FADD-dependent complex II (caspase-8/cFLIP) rather than primary DISC formation, and acting independently of direct death-receptor fucosylation [#2, #3]. This apoptotic gating underlies a tumor-suppressive, immune-surveillance role: restoring GMDS sensitizes colon cancer cells to NK cell- and TRAIL-dependent killing and suppresses tumor growth and metastasis in vivo [#2]. Beyond cancer, GMDS is cell-intrinsically required for T-cell development past the double-positive thymic stage [#6], and in model organisms it regulates Notch signaling — controlling Notch protein stability via the OFUT1 axis [#4] and acting upstream of Notch in hair cell regeneration [#7] — as well as retinal ganglion cell survival and ocular stress responses [#8].\",\n  \"teleology\": [\n    {\n      \"year\": 2007,\n      \"claim\": \"Established that GMDS is the rate-limiting, non-redundant entry enzyme of de novo GDP-fucose synthesis, defining it as the master switch for cellular fucosylation.\",\n      \"evidence\": \"siRNA knockdown and knockout in CHO cells with HPLC GDP-fucose quantification and antibody fucosylation analysis\",\n      \"pmids\": [\"17559959\", \"18047682\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not resolve the enzyme's structural/catalytic mechanism\", \"Salvage-pathway contributions to GDP-fucose pools in other cell types not addressed\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Placed GMDS and the fucosyltransferase FUT8 in the same fucosylation process by showing synergistic defucosylation upon co-depletion, distinguishing it from transporter-level control.\",\n      \"evidence\": \"siRNA double knockdown with flow cytometry fucosylation readout and ADCC assay\",\n      \"pmids\": [\"18047682\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Epistasis inferred from siRNA combinations in a single cell line\", \"Does not establish direct physical interaction between GMDS and FUT8\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Connected GMDS-dependent fucosylation to extrinsic apoptosis and tumor immune surveillance, showing GMDS acts upstream of TRAIL signaling and NK cell-mediated killing.\",\n      \"evidence\": \"GMDS mutation/rescue in HCT116 colon cancer cells, TRAIL apoptosis assays, xenograft model, NK cytotoxicity with anti-TRAIL blocking antibody\",\n      \"pmids\": [\"19361506\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular target whose fucosylation enables TRAIL sensitivity not identified here\", \"Generality beyond colon cancer not tested\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Pinpointed the death-receptor signaling step GMDS controls, showing the block is at secondary complex II (caspase-8/cFLIP) assembly and independent of direct death-receptor fucosylation.\",\n      \"evidence\": \"Co-IP of DISC components, caspase-8 activity assays, western blot of complex II, DR4/DR5 fucosylation comparison\",\n      \"pmids\": [\"22027835\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The specific fucosylated protein governing complex II assembly remains unidentified\", \"Mechanism linking fucosylation status to FADD-dependent complex II formation not defined\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Linked GMDS/GDP-fucose to Notch protein stability through OFUT1, extending GMDS function from apoptosis into developmental signaling.\",\n      \"evidence\": \"Drosophila genetics and epistasis with OFUT1 and Notch Abruptex mutants\",\n      \"pmids\": [\"21720678\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Genetic epistasis in Drosophila; biochemical demonstration of fucose-dependent OFUT1 activity on Notch not shown\", \"Conservation of the OFUT1-Notch mechanism in mammals not established\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Demonstrated a cell-autonomous tumor-promoting requirement for GMDS in lung adenocarcinoma, nominating a CASP8-CDKN1A axis and reinforcing GMDS as upstream of apoptotic/cell-cycle control.\",\n      \"evidence\": \"shRNA knockdown in A549/H1299, proliferation/cell-cycle/apoptosis assays, xenograft, microarray transcriptome\",\n      \"pmids\": [\"29843634\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"CASP8-CDKN1A axis identified by transcriptomics, not mechanistically validated\", \"Apparent pro-tumor role here contrasts with tumor-suppressive role in colon cancer; context dependence unexplained\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Revealed a cell-intrinsic requirement for GMDS in thymic T-cell development past the double-positive stage, defining a non-redundant role in lymphopoiesis.\",\n      \"evidence\": \"ENU-mutant mouse, flow immunophenotyping, bone marrow reconstitution and mixed chimera experiments\",\n      \"pmids\": [\"40642090\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular fucosylation target driving the DP-stage block not identified\", \"Whether the defect reflects altered Notch or TCR-associated signaling not resolved\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Showed GMDS restrains hair cell number and regeneration upstream of Notch signaling, providing in vivo developmental evidence for the GMDS-Notch link.\",\n      \"evidence\": \"CRISPR/Cas9 gmds zebrafish, neomycin ablation, pharmacological Notch inhibition, live imaging\",\n      \"pmids\": [\"41097001\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Notch placed downstream by pharmacology/epistasis, not by direct biochemistry\", \"Single model system\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Implicated GMDS dosage in retinal ganglion cell survival and ocular stress responses, broadening its physiological role to tissue maintenance.\",\n      \"evidence\": \"CRISPR/Cas9 gmds haploinsufficient zebrafish, RNA-seq, histological eye phenotyping\",\n      \"pmids\": [\"40571142\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Stress-response and cell-death gene changes are correlative\", \"Mechanistic link between reduced fucosylation and RGC loss not established\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The identity of the fucosylated protein(s) whose modification by the GMDS pathway controls complex II assembly, T-cell development, and Notch regulation remains the central open mechanistic question.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No direct fucosylated effector linking GMDS loss to complex II/caspase-8 signaling identified\", \"Context-dependent tumor-suppressive vs tumor-promoting roles unreconciled\", \"No structural/catalytic mechanism described in the corpus\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016491\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0016829\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"localization\": [],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [2, 3]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"FUT8\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"tie","faith_supported":5,"faith_total":5,"faith_pct":100.0}}