{"gene":"MAN2A1","run_date":"2026-06-10T02:59:50","timeline":{"discoveries":[{"year":1990,"finding":"Alpha-mannosidase II (MAN2A1) deficiency in a HEMPAS patient caused incomplete processing of asparagine-linked oligosaccharides in erythrocyte membranes, as demonstrated by cell-surface labeling, FAB mass spectrometry of glycopeptides, and enzyme activity assays showing decreased alpha-ManII activity; reduced MAN2A1 mRNA expression (<10% of normal) was detected by Northern blot, establishing that MAN2A1 is required for the maturation of N-linked oligosaccharides and that its defect underlies at least one form of congenital dyserythropoietic anemia type II (HEMPAS).","method":"Cell-surface labeling, FAB mass spectrometry, enzyme activity assay, Northern blot","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — multiple orthogonal biochemical methods (enzyme assay, mass spectrometry, Northern blot) in a single focused study establishing a direct causal link between MAN2A1 deficiency and impaired N-glycan processing","pmids":["2217175"],"is_preprint":false},{"year":2009,"finding":"Mutations in both alleles of MAN2A1 in the HEK293T-derived Lec36 cell line result in accumulation of hybrid-type N-glycans instead of complex-type N-glycans; one allele carried an active-site point mutation and the other an in-frame 12-nucleotide deletion. Expression of wild-type but not mutant MAN2A1 in Lec36 cells restored processing of a reporter glycoprotein to complex-type glycosylation, demonstrating that MAN2A1 catalytic activity is required for conversion of hybrid- to complex-type N-glycans.","method":"Nucleotide sequencing, mass spectrometry (negative ion nano-ESI-MS, CID), complementation assay with wild-type vs. mutant MAN2A1 expression","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — active-site mutagenesis combined with complementation assay and mass spectrometric glycan analysis; multiple orthogonal methods in one study","pmids":["19465480"],"is_preprint":false},{"year":2017,"finding":"The MAN2A1-FER fusion protein retains the MAN2A1 signal peptide for Golgi localization and translocates from the cytoplasm to the Golgi in cancer cell lines. The fusion protein has tyrosine kinase activity approximately 4-fold higher than wild-type FER and phosphorylates EGFR at tyrosine 88 in its N-terminus, activating downstream BRAF, MEK, and AKT signaling, thereby driving proliferation, invasion, and tumor formation.","method":"Tagged protein expression and Golgi fractionation, kinase activity assay, phosphorylation analysis, KO/OE in multiple cell lines, xenograft mouse model","journal":"Gastroenterology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple cell lines tested, KO and OE, Golgi fractionation, kinase assay, in vivo xenograft with multiple orthogonal readouts","pmids":["28245430"],"is_preprint":false},{"year":2011,"finding":"MAN2A1 is severely mislocalized upon siRNA-mediated depletion of COG complex subunits, and COG-depleted cells are deficient in Brefeldin A- and Sar1 DN-induced redistribution of MAN2A1 to the ER, establishing that the conserved oligomeric Golgi (COG) complex is required for retrograde trafficking and maintenance of MAN2A1 at its correct Golgi location.","method":"siRNA knockdown, immunofluorescence localization, BFA redistribution assay, lectin staining, MALDI-TOF glycan analysis","journal":"Glycobiology","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal functional rescue, multiple COG subunit depletions, orthogonal glycan and localization readouts in one study","pmids":["21421995"],"is_preprint":false},{"year":2010,"finding":"RNAi-mediated knockdown of the lipid phosphatase SAC1 caused mislocalization of MAN2A1 (mannosidase-II) from its normal medial-Golgi position to aberrant intracellular structures and to the cell surface, accompanied by specific defects in N- and O-linked glycosylation, establishing that SAC1-controlled PI(4)P distribution is required for correct MAN2A1 Golgi localization.","method":"RNAi knockdown, immunofluorescence, ultrastructural analysis, glycosylation assay","journal":"Traffic (Copenhagen, Denmark)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean KD with defined localization phenotype and functional glycosylation readout, single lab","pmids":["20573065"],"is_preprint":false},{"year":2009,"finding":"Raising Golgi luminal pH with chloroquine did not induce mislocalization of MAN2A1 (MANII) at moderate pH increases (0.2 units) that were sufficient to mislocalize the alpha(2,3)-sialyltransferase ST3, indicating that MAN2A1 Golgi localization is relatively insensitive to moderate pH elevations compared to late-acting glycosyltransferases.","method":"Chloroquine pH manipulation, immunofluorescence localization of Golgi enzymes, glycosylation reporter assay","journal":"Journal of cellular physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization experiment with functional consequence; single lab; result is a negative finding for MAN2A1 mislocalization under moderate pH elevation","pmids":["19277980"],"is_preprint":false},{"year":2016,"finding":"Ethanol treatment induces medial-to-cis relocation of MAN2A1 (Man-II) within the Golgi, an effect mimicked by silencing beta-COP or expressing GDP-bound mutant Arf1(T31N), demonstrating that MAN2A1 correct medial-Golgi positioning depends on functional Arf1 GTPase activity and intact COPI vesicle formation.","method":"3D structured illumination microscopy, beta-COP siRNA, dominant-negative Arf1 expression, electron microscopy","journal":"Alcoholism, clinical and experimental research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal perturbations (ethanol, siRNA, DN mutant) with direct localization readout; single lab","pmids":["27748959"],"is_preprint":false},{"year":2018,"finding":"IEC-specific deletion of MAN2A1 (alpha-MII) in mice impaired N-glycan maturation specifically in intestinal epithelial cells (where the isozyme alpha-MIIx does not compensate), reduced neutrophil infiltration in colonic mucosa, and downregulated neutrophil-attracting chemokine gene expression, establishing that IEC-intrinsic MAN2A1 promotes intestinal inflammation by facilitating chemokine expression.","method":"Conditional (IEC-specific) knockout mouse, DSS-induced colitis model, histology, flow cytometry, gene expression analysis","journal":"Cell structure and function","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional KO with tissue-specific glycan phenotype confirmed, in vivo disease model, molecular mechanism identified; single lab but multiple orthogonal readouts","pmids":["29343654"],"is_preprint":false},{"year":2019,"finding":"RNAi-mediated knockdown of MAN2A1 impaired correct plasma membrane trafficking of the sodium iodide symporter (NIS) in MCF-7 breast cancer cells, establishing that MAN2A1-dependent N-glycan processing is required for correct subcellular localization of NIS.","method":"RNAi knockdown, immunofluorescence, glycosylation RT-Profiler array","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — RNAi with defined localization phenotype of a specific substrate; single lab; limited mechanistic follow-up beyond knockdown","pmids":["31455607"],"is_preprint":false},{"year":2020,"finding":"Loss of Man2a1 in cancer cells increased their sensitivity to T-cell-mediated killing and enhanced response to anti-PD-L1 treatment with higher cytotoxic T-cell infiltration; pharmacologic inhibition of MAN2A1 with swainsonine synergized with anti-PD-L1 in syngeneic melanoma and lung cancer models, establishing that MAN2A1-dependent N-glycan maturation in cancer cells promotes immune evasion.","method":"CRISPR knockout, in vitro T-cell co-culture killing assay, in vivo syngeneic tumor growth assay, pharmacologic inhibition (swainsonine)","journal":"Clinical cancer research","confidence":"High","confidence_rationale":"Tier 2 / Strong — CRISPR KO, pharmacologic inhibition, in vitro and in vivo assays, multiple tumor models; single lab but multiple orthogonal methods","pmids":["32723834"],"is_preprint":false},{"year":2024,"finding":"The MAN2A1-FER fusion protein ectopically phosphorylates the extracellular domains of PDGFRA, MET, AXL, and N-cadherin, activating their kinase activities and downstream signaling cascades. A monoclonal antibody targeting the ectopic phosphotyrosine epitope in the extracellular domain of PDGFRA deactivated growth signaling and induced cell death selectively in MAN2A1-FER-positive cancer cells, with no effect on MAN2A1-FER-knockout cells.","method":"Phosphorylation analysis, monoclonal antibody development and specificity assay, cell growth assay, xenograft mouse model with antibody-drug conjugate","journal":"Hepatology communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct phosphorylation analysis with functional antibody validation and isogenic KO controls; single lab","pmids":["39082961"],"is_preprint":false},{"year":2017,"finding":"Cas9-mediated insertion of a suicide gene (HSV1-tk) at the genomic breakpoint of the MAN2A1-FER fusion caused breakpoint-dependent EGFP-tk expression and ganciclovir-mediated apoptosis selectively in cancer cells carrying the fusion, demonstrating that the MAN2A1-FER genomic rearrangement breakpoint is transcriptionally active and targetable.","method":"CRISPR-Cas9 nickase, homology-directed repair, adenoviral delivery, ganciclovir treatment, xenograft mouse model","journal":"Nature biotechnology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct genome editing with functional readout; confirms MAN2A1-FER fusion breakpoint activity; single lab","pmids":["28459452"],"is_preprint":false},{"year":2021,"finding":"Knockout of MAN2A1 and MAN2A2 together in HEK293 cells (M2D-KO) abolished production of complex-type N-glycans, resulting in proteins carrying predominantly hybrid-type N-glycans, establishing that MAN2A1 and MAN2A2 together are responsible for complex N-glycan maturation in this cell line.","method":"Gene knockout (MAN2A1 and MAN2A2 double KO), glycan structural analysis, recombinant protein expression","journal":"Journal of biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — double KO with direct glycan structural readout; single lab; MAN2A1-specific contribution partially confounded by double KO design","pmids":["33878161"],"is_preprint":false},{"year":2015,"finding":"Swainsonine treatment of BRL-3A cells significantly reduced alpha-mannosidase activity and decreased MAN2A1 mRNA and protein expression in a time- and dose-dependent manner, establishing that swainsonine acts as both an inhibitor of MAN2A1 enzymatic activity and a suppressor of MAN2A1 expression.","method":"Enzyme substrate activity assay, qPCR, Western blot","journal":"Toxicon","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — enzyme activity assay plus mRNA/protein quantification; single lab; two orthogonal methods","pmids":["25797317"],"is_preprint":false},{"year":2014,"finding":"Reduced expression of MAN2A1 (man2a1 gene) during TGFβ-induced epithelial-mesenchymal transition in HCV29 bladder epithelial cells contributed to decreased proportions of bi-, tri-, and tetra-antennary complex N-glycans and increased hybrid-type N-glycans, as confirmed by mass spectrometry, lectin microarray, and RT-PCR.","method":"GlycoV4 microarray, mass spectrometry, lectin microarray, RT-PCR","journal":"Molecules (Basel, Switzerland)","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — correlation of MAN2A1 expression with specific N-glycan changes confirmed by multiple analytical methods; association rather than direct functional manipulation","pmids":["25470275"],"is_preprint":false}],"current_model":"MAN2A1 encodes Golgi alpha-mannosidase II, a medial-Golgi-resident enzyme that cleaves terminal mannose residues from Man5GlcNAc2 hybrid-type N-glycan intermediates to produce the substrate for complex N-glycan elaboration; its correct Golgi localization depends on COPI retrograde trafficking (requiring Arf1 GTPase activity and the COG tethering complex) and on SAC1-controlled Golgi PI(4)P distribution; in intestinal epithelial cells, MAN2A1 promotes inflammation by supporting chemokine expression; in tumors, a MAN2A1-FER chromosomal fusion places a constitutively active, Golgi-localized tyrosine kinase that phosphorylates EGFR, PDGFRA, MET, AXL, and N-cadherin extracellular domains to activate BRAF/MEK/AKT oncogenic signaling, while MAN2A1-dependent N-glycan maturation on cancer cells suppresses anti-tumor T-cell killing."},"narrative":{"mechanistic_narrative":"MAN2A1 encodes Golgi alpha-mannosidase II, a medial-Golgi-resident enzyme whose catalytic activity is required to convert hybrid-type N-glycans into the precursors of complex-type N-glycans; loss of its activity causes accumulation of hybrid-type structures and failure of complex N-glycan maturation [PMID:19465480, PMID:33878161]. Deficiency in N-glycan processing from reduced MAN2A1 underlies a form of congenital dyserythropoietic anemia type II (HEMPAS) [PMID:2217175]. Correct medial-Golgi positioning of MAN2A1 is maintained by retrograde trafficking machinery, depending on the COG tethering complex [PMID:21421995] and on Arf1-GTPase-driven COPI vesicle formation [PMID:27748959], as well as on SAC1-controlled Golgi PI(4)P distribution [PMID:20573065]. Through its control of N-glycan maturation, MAN2A1 governs the cell-surface trafficking and glycosylation of client glycoproteins [PMID:31455607] and shapes physiological and pathological outcomes: intestinal-epithelial MAN2A1 promotes inflammation by supporting neutrophil-attracting chemokine expression [PMID:29343654], and MAN2A1-dependent N-glycan maturation on tumor cells suppresses cytotoxic T-cell killing and anti-PD-L1 responses, an effect reversed by the inhibitor swainsonine [PMID:32723834, PMID:25797317]. Independently, a MAN2A1-FER chromosomal fusion exploits the MAN2A1 Golgi-targeting signal to deliver a constitutively active tyrosine kinase to the Golgi, where it phosphorylates the extracellular domains of EGFR, PDGFRA, MET, AXL, and N-cadherin to drive BRAF/MEK/AKT oncogenic signaling [PMID:28245430, PMID:39082961].","teleology":[{"year":1990,"claim":"Established that MAN2A1 is required for N-linked oligosaccharide maturation in vivo and that its deficiency causes human disease, framing the gene as a glycan-processing enzyme with physiological consequence.","evidence":"Cell-surface labeling, FAB mass spectrometry, enzyme activity assay, and Northern blot in a HEMPAS patient","pmids":["2217175"],"confidence":"High","gaps":["Did not define the precise catalytic step or substrate specificity","Causal mutation in MAN2A1 not molecularly resolved"]},{"year":2009,"claim":"Pinpointed the specific catalytic role of MAN2A1 as the enzyme converting hybrid- to complex-type N-glycans, using active-site mutation plus complementation rescue.","evidence":"Sequencing of Lec36 alleles, nano-ESI-MS glycan analysis, and wild-type vs. mutant complementation","pmids":["19465480"],"confidence":"High","gaps":["Did not address redundancy with the MAN2A2 isozyme","No structural basis for substrate selectivity"]},{"year":2010,"claim":"Addressed how MAN2A1 is retained in the medial-Golgi by linking its localization to phosphoinositide control.","evidence":"SAC1 RNAi knockdown with immunofluorescence, ultrastructure, and glycosylation readouts","pmids":["20573065"],"confidence":"Medium","gaps":["Single lab","Mechanism connecting PI(4)P levels to enzyme retention not resolved"]},{"year":2011,"claim":"Showed that MAN2A1 Golgi residence requires active retrograde transport via the COG tethering complex, distinguishing localization maintenance from biosynthetic delivery.","evidence":"COG subunit siRNA depletion with BFA/Sar1-DN redistribution assays and glycan analysis","pmids":["21421995"],"confidence":"High","gaps":["Direct physical interaction between MAN2A1 and COG not demonstrated","Cargo recognition mechanism unknown"]},{"year":2016,"claim":"Extended the trafficking model by demonstrating that medial-Golgi positioning depends on Arf1 GTPase activity and COPI vesicle formation.","evidence":"3D-SIM, beta-COP siRNA, dominant-negative Arf1(T31N), and electron microscopy under ethanol perturbation","pmids":["27748959"],"confidence":"Medium","gaps":["Single lab","Did not establish whether COPI directly packages MAN2A1"]},{"year":2017,"claim":"Revealed an oncogenic gain-of-function in which the MAN2A1 Golgi-targeting signal mislocalizes a hyperactive FER kinase that phosphorylates EGFR to drive proliferation and tumorigenesis.","evidence":"Golgi fractionation, kinase assays, phospho-analysis, KO/OE in cell lines, and xenografts","pmids":["28245430"],"confidence":"High","gaps":["Mechanism of extracellular-domain phosphorylation by a Golgi-luminal kinase not fully explained","Prevalence of the fusion across tumor types not defined here"]},{"year":2017,"claim":"Demonstrated that the MAN2A1-FER genomic breakpoint is transcriptionally active and can be exploited as a tumor-selective therapeutic target.","evidence":"CRISPR-Cas9 nickase HDR insertion of HSV1-tk at the breakpoint with ganciclovir killing and xenografts","pmids":["28459452"],"confidence":"Medium","gaps":["Single lab","Delivery efficiency to clinical tumors untested"]},{"year":2018,"claim":"Connected MAN2A1 N-glycan processing to inflammation, showing tissue-intrinsic enzyme activity drives chemokine-mediated neutrophil recruitment.","evidence":"IEC-specific conditional knockout mice in DSS colitis with histology, flow cytometry, and expression analysis","pmids":["29343654"],"confidence":"High","gaps":["Specific glycoproteins mediating chemokine induction not identified","Role of alpha-MIIx compensation in other tissues unresolved"]},{"year":2019,"claim":"Provided a specific client example by showing MAN2A1-dependent glycosylation is needed for plasma-membrane trafficking of the sodium iodide symporter.","evidence":"MAN2A1 RNAi with immunofluorescence and glycosylation profiling in MCF-7 cells","pmids":["31455607"],"confidence":"Medium","gaps":["Single substrate, single lab","Glycan site responsible for NIS mistrafficking not mapped"]},{"year":2020,"claim":"Established MAN2A1-driven N-glycan maturation as a mechanism of tumor immune evasion and a druggable target with checkpoint inhibitors.","evidence":"CRISPR KO, T-cell co-culture killing, syngeneic tumor models, and swainsonine inhibition with anti-PD-L1","pmids":["32723834"],"confidence":"High","gaps":["Specific glycoproteins shielding tumor cells from T cells not identified","Swainsonine specificity beyond MAN2A1 not delimited"]},{"year":2024,"claim":"Broadened the MAN2A1-FER oncogenic mechanism to multiple receptor substrates and validated a phospho-epitope-directed therapeutic antibody.","evidence":"Phospho-analysis of PDGFRA/MET/AXL/N-cadherin, monoclonal antibody specificity, and ADC xenografts with isogenic KO controls","pmids":["39082961"],"confidence":"Medium","gaps":["Single lab","Structural basis of ectopic extracellular-domain phosphorylation unresolved"]},{"year":null,"claim":"How MAN2A1-FER, a Golgi-localized kinase, gains access to and phosphorylates the extracellular domains of cell-surface receptors remains mechanistically unexplained.","evidence":"","pmids":[],"confidence":"Medium","gaps":["Topological mechanism of extracellular-domain phosphorylation unknown","Structural model of the fusion protein lacking"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[0,1,12]},{"term_id":"GO:0140098","term_label":"catalytic activity, acting on RNA","supporting_discovery_ids":[1,12]}],"localization":[{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[2,3,4,6]}],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0,1,12]},{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[3,6]}],"complexes":[],"partners":[],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q16706","full_name":"Alpha-mannosidase 2","aliases":["Golgi alpha-mannosidase II","AMan II","Man II","Mannosidase alpha class 2A member 1","Mannosyl-oligosaccharide 1,3-1,6-alpha-mannosidase"],"length_aa":1144,"mass_kda":131.1,"function":"Catalyzes the first committed step in the biosynthesis of complex N-glycans. It controls conversion of high mannose to complex N-glycans; the final hydrolytic step in the N-glycan maturation pathway","subcellular_location":"Golgi apparatus membrane","url":"https://www.uniprot.org/uniprotkb/Q16706/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/MAN2A1","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"CANX","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/MAN2A1","total_profiled":1310},"omim":[{"mim_id":"615291","title":"BETA-1,3-GALACTOSYLTRANSFERASE 6; B3GALT6","url":"https://www.omim.org/entry/615291"},{"mim_id":"610302","title":"ENDOPLASMIC RETICULUM DEGRADATION-ENHANCING ALPHA-MANNOSIDASE-LIKE PROTEIN 2; EDEM2","url":"https://www.omim.org/entry/610302"},{"mim_id":"604345","title":"MANNOSIDASE, ALPHA, CLASS 1A, MEMBER 2; MAN1A2","url":"https://www.omim.org/entry/604345"},{"mim_id":"604344","title":"MANNOSIDASE, ALPHA, CLASS 1A, MEMBER 1; MAN1A1","url":"https://www.omim.org/entry/604344"},{"mim_id":"600988","title":"MANNOSIDASE, ALPHA, CLASS 2A, MEMBER 2; MAN2A2","url":"https://www.omim.org/entry/600988"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Golgi apparatus","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/MAN2A1"},"hgnc":{"alias_symbol":["GOLIM7","MANII"],"prev_symbol":["MANA2"]},"alphafold":{"accession":"Q16706","domains":[{"cath_id":"3.20.110.10","chopping":"121-494","consensus_level":"medium","plddt":95.1765,"start":121,"end":494},{"cath_id":"1.20.1270.50","chopping":"503-639","consensus_level":"medium","plddt":95.5017,"start":503,"end":639},{"cath_id":"2.60.40.1180","chopping":"641-731_1017-1037","consensus_level":"medium","plddt":92.0988,"start":641,"end":1037},{"cath_id":"2.60.40.1360","chopping":"1040-1144","consensus_level":"high","plddt":90.9349,"start":1040,"end":1144}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q16706","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q16706-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q16706-F1-predicted_aligned_error_v6.png","plddt_mean":90.0},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=MAN2A1","jax_strain_url":"https://www.jax.org/strain/search?query=MAN2A1"},"sequence":{"accession":"Q16706","fasta_url":"https://rest.uniprot.org/uniprotkb/Q16706.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q16706/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q16706"}},"corpus_meta":[{"pmid":"16435400","id":"PMC_16435400","title":"Modulation 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showing decreased alpha-ManII activity; reduced MAN2A1 mRNA expression (<10% of normal) was detected by Northern blot, establishing that MAN2A1 is required for the maturation of N-linked oligosaccharides and that its defect underlies at least one form of congenital dyserythropoietic anemia type II (HEMPAS).\",\n      \"method\": \"Cell-surface labeling, FAB mass spectrometry, enzyme activity assay, Northern blot\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — multiple orthogonal biochemical methods (enzyme assay, mass spectrometry, Northern blot) in a single focused study establishing a direct causal link between MAN2A1 deficiency and impaired N-glycan processing\",\n      \"pmids\": [\"2217175\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Mutations in both alleles of MAN2A1 in the HEK293T-derived Lec36 cell line result in accumulation of hybrid-type N-glycans instead of complex-type N-glycans; one allele carried an active-site point mutation and the other an in-frame 12-nucleotide deletion. Expression of wild-type but not mutant MAN2A1 in Lec36 cells restored processing of a reporter glycoprotein to complex-type glycosylation, demonstrating that MAN2A1 catalytic activity is required for conversion of hybrid- to complex-type N-glycans.\",\n      \"method\": \"Nucleotide sequencing, mass spectrometry (negative ion nano-ESI-MS, CID), complementation assay with wild-type vs. mutant MAN2A1 expression\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — active-site mutagenesis combined with complementation assay and mass spectrometric glycan analysis; multiple orthogonal methods in one study\",\n      \"pmids\": [\"19465480\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"The MAN2A1-FER fusion protein retains the MAN2A1 signal peptide for Golgi localization and translocates from the cytoplasm to the Golgi in cancer cell lines. The fusion protein has tyrosine kinase activity approximately 4-fold higher than wild-type FER and phosphorylates EGFR at tyrosine 88 in its N-terminus, activating downstream BRAF, MEK, and AKT signaling, thereby driving proliferation, invasion, and tumor formation.\",\n      \"method\": \"Tagged protein expression and Golgi fractionation, kinase activity assay, phosphorylation analysis, KO/OE in multiple cell lines, xenograft mouse model\",\n      \"journal\": \"Gastroenterology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple cell lines tested, KO and OE, Golgi fractionation, kinase assay, in vivo xenograft with multiple orthogonal readouts\",\n      \"pmids\": [\"28245430\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"MAN2A1 is severely mislocalized upon siRNA-mediated depletion of COG complex subunits, and COG-depleted cells are deficient in Brefeldin A- and Sar1 DN-induced redistribution of MAN2A1 to the ER, establishing that the conserved oligomeric Golgi (COG) complex is required for retrograde trafficking and maintenance of MAN2A1 at its correct Golgi location.\",\n      \"method\": \"siRNA knockdown, immunofluorescence localization, BFA redistribution assay, lectin staining, MALDI-TOF glycan analysis\",\n      \"journal\": \"Glycobiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal functional rescue, multiple COG subunit depletions, orthogonal glycan and localization readouts in one study\",\n      \"pmids\": [\"21421995\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"RNAi-mediated knockdown of the lipid phosphatase SAC1 caused mislocalization of MAN2A1 (mannosidase-II) from its normal medial-Golgi position to aberrant intracellular structures and to the cell surface, accompanied by specific defects in N- and O-linked glycosylation, establishing that SAC1-controlled PI(4)P distribution is required for correct MAN2A1 Golgi localization.\",\n      \"method\": \"RNAi knockdown, immunofluorescence, ultrastructural analysis, glycosylation assay\",\n      \"journal\": \"Traffic (Copenhagen, Denmark)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean KD with defined localization phenotype and functional glycosylation readout, single lab\",\n      \"pmids\": [\"20573065\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Raising Golgi luminal pH with chloroquine did not induce mislocalization of MAN2A1 (MANII) at moderate pH increases (0.2 units) that were sufficient to mislocalize the alpha(2,3)-sialyltransferase ST3, indicating that MAN2A1 Golgi localization is relatively insensitive to moderate pH elevations compared to late-acting glycosyltransferases.\",\n      \"method\": \"Chloroquine pH manipulation, immunofluorescence localization of Golgi enzymes, glycosylation reporter assay\",\n      \"journal\": \"Journal of cellular physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization experiment with functional consequence; single lab; result is a negative finding for MAN2A1 mislocalization under moderate pH elevation\",\n      \"pmids\": [\"19277980\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Ethanol treatment induces medial-to-cis relocation of MAN2A1 (Man-II) within the Golgi, an effect mimicked by silencing beta-COP or expressing GDP-bound mutant Arf1(T31N), demonstrating that MAN2A1 correct medial-Golgi positioning depends on functional Arf1 GTPase activity and intact COPI vesicle formation.\",\n      \"method\": \"3D structured illumination microscopy, beta-COP siRNA, dominant-negative Arf1 expression, electron microscopy\",\n      \"journal\": \"Alcoholism, clinical and experimental research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal perturbations (ethanol, siRNA, DN mutant) with direct localization readout; single lab\",\n      \"pmids\": [\"27748959\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"IEC-specific deletion of MAN2A1 (alpha-MII) in mice impaired N-glycan maturation specifically in intestinal epithelial cells (where the isozyme alpha-MIIx does not compensate), reduced neutrophil infiltration in colonic mucosa, and downregulated neutrophil-attracting chemokine gene expression, establishing that IEC-intrinsic MAN2A1 promotes intestinal inflammation by facilitating chemokine expression.\",\n      \"method\": \"Conditional (IEC-specific) knockout mouse, DSS-induced colitis model, histology, flow cytometry, gene expression analysis\",\n      \"journal\": \"Cell structure and function\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional KO with tissue-specific glycan phenotype confirmed, in vivo disease model, molecular mechanism identified; single lab but multiple orthogonal readouts\",\n      \"pmids\": [\"29343654\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"RNAi-mediated knockdown of MAN2A1 impaired correct plasma membrane trafficking of the sodium iodide symporter (NIS) in MCF-7 breast cancer cells, establishing that MAN2A1-dependent N-glycan processing is required for correct subcellular localization of NIS.\",\n      \"method\": \"RNAi knockdown, immunofluorescence, glycosylation RT-Profiler array\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — RNAi with defined localization phenotype of a specific substrate; single lab; limited mechanistic follow-up beyond knockdown\",\n      \"pmids\": [\"31455607\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Loss of Man2a1 in cancer cells increased their sensitivity to T-cell-mediated killing and enhanced response to anti-PD-L1 treatment with higher cytotoxic T-cell infiltration; pharmacologic inhibition of MAN2A1 with swainsonine synergized with anti-PD-L1 in syngeneic melanoma and lung cancer models, establishing that MAN2A1-dependent N-glycan maturation in cancer cells promotes immune evasion.\",\n      \"method\": \"CRISPR knockout, in vitro T-cell co-culture killing assay, in vivo syngeneic tumor growth assay, pharmacologic inhibition (swainsonine)\",\n      \"journal\": \"Clinical cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — CRISPR KO, pharmacologic inhibition, in vitro and in vivo assays, multiple tumor models; single lab but multiple orthogonal methods\",\n      \"pmids\": [\"32723834\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"The MAN2A1-FER fusion protein ectopically phosphorylates the extracellular domains of PDGFRA, MET, AXL, and N-cadherin, activating their kinase activities and downstream signaling cascades. A monoclonal antibody targeting the ectopic phosphotyrosine epitope in the extracellular domain of PDGFRA deactivated growth signaling and induced cell death selectively in MAN2A1-FER-positive cancer cells, with no effect on MAN2A1-FER-knockout cells.\",\n      \"method\": \"Phosphorylation analysis, monoclonal antibody development and specificity assay, cell growth assay, xenograft mouse model with antibody-drug conjugate\",\n      \"journal\": \"Hepatology communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct phosphorylation analysis with functional antibody validation and isogenic KO controls; single lab\",\n      \"pmids\": [\"39082961\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Cas9-mediated insertion of a suicide gene (HSV1-tk) at the genomic breakpoint of the MAN2A1-FER fusion caused breakpoint-dependent EGFP-tk expression and ganciclovir-mediated apoptosis selectively in cancer cells carrying the fusion, demonstrating that the MAN2A1-FER genomic rearrangement breakpoint is transcriptionally active and targetable.\",\n      \"method\": \"CRISPR-Cas9 nickase, homology-directed repair, adenoviral delivery, ganciclovir treatment, xenograft mouse model\",\n      \"journal\": \"Nature biotechnology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct genome editing with functional readout; confirms MAN2A1-FER fusion breakpoint activity; single lab\",\n      \"pmids\": [\"28459452\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Knockout of MAN2A1 and MAN2A2 together in HEK293 cells (M2D-KO) abolished production of complex-type N-glycans, resulting in proteins carrying predominantly hybrid-type N-glycans, establishing that MAN2A1 and MAN2A2 together are responsible for complex N-glycan maturation in this cell line.\",\n      \"method\": \"Gene knockout (MAN2A1 and MAN2A2 double KO), glycan structural analysis, recombinant protein expression\",\n      \"journal\": \"Journal of biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — double KO with direct glycan structural readout; single lab; MAN2A1-specific contribution partially confounded by double KO design\",\n      \"pmids\": [\"33878161\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Swainsonine treatment of BRL-3A cells significantly reduced alpha-mannosidase activity and decreased MAN2A1 mRNA and protein expression in a time- and dose-dependent manner, establishing that swainsonine acts as both an inhibitor of MAN2A1 enzymatic activity and a suppressor of MAN2A1 expression.\",\n      \"method\": \"Enzyme substrate activity assay, qPCR, Western blot\",\n      \"journal\": \"Toxicon\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — enzyme activity assay plus mRNA/protein quantification; single lab; two orthogonal methods\",\n      \"pmids\": [\"25797317\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Reduced expression of MAN2A1 (man2a1 gene) during TGFβ-induced epithelial-mesenchymal transition in HCV29 bladder epithelial cells contributed to decreased proportions of bi-, tri-, and tetra-antennary complex N-glycans and increased hybrid-type N-glycans, as confirmed by mass spectrometry, lectin microarray, and RT-PCR.\",\n      \"method\": \"GlycoV4 microarray, mass spectrometry, lectin microarray, RT-PCR\",\n      \"journal\": \"Molecules (Basel, Switzerland)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — correlation of MAN2A1 expression with specific N-glycan changes confirmed by multiple analytical methods; association rather than direct functional manipulation\",\n      \"pmids\": [\"25470275\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"MAN2A1 encodes Golgi alpha-mannosidase II, a medial-Golgi-resident enzyme that cleaves terminal mannose residues from Man5GlcNAc2 hybrid-type N-glycan intermediates to produce the substrate for complex N-glycan elaboration; its correct Golgi localization depends on COPI retrograde trafficking (requiring Arf1 GTPase activity and the COG tethering complex) and on SAC1-controlled Golgi PI(4)P distribution; in intestinal epithelial cells, MAN2A1 promotes inflammation by supporting chemokine expression; in tumors, a MAN2A1-FER chromosomal fusion places a constitutively active, Golgi-localized tyrosine kinase that phosphorylates EGFR, PDGFRA, MET, AXL, and N-cadherin extracellular domains to activate BRAF/MEK/AKT oncogenic signaling, while MAN2A1-dependent N-glycan maturation on cancer cells suppresses anti-tumor T-cell killing.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"MAN2A1 encodes Golgi alpha-mannosidase II, a medial-Golgi-resident enzyme whose catalytic activity is required to convert hybrid-type N-glycans into the precursors of complex-type N-glycans; loss of its activity causes accumulation of hybrid-type structures and failure of complex N-glycan maturation [#1, #12]. Deficiency in N-glycan processing from reduced MAN2A1 underlies a form of congenital dyserythropoietic anemia type II (HEMPAS) [#0]. Correct medial-Golgi positioning of MAN2A1 is maintained by retrograde trafficking machinery, depending on the COG tethering complex [#3] and on Arf1-GTPase-driven COPI vesicle formation [#6], as well as on SAC1-controlled Golgi PI(4)P distribution [#4]. Through its control of N-glycan maturation, MAN2A1 governs the cell-surface trafficking and glycosylation of client glycoproteins [#8] and shapes physiological and pathological outcomes: intestinal-epithelial MAN2A1 promotes inflammation by supporting neutrophil-attracting chemokine expression [#7], and MAN2A1-dependent N-glycan maturation on tumor cells suppresses cytotoxic T-cell killing and anti-PD-L1 responses, an effect reversed by the inhibitor swainsonine [#9, #13]. Independently, a MAN2A1-FER chromosomal fusion exploits the MAN2A1 Golgi-targeting signal to deliver a constitutively active tyrosine kinase to the Golgi, where it phosphorylates the extracellular domains of EGFR, PDGFRA, MET, AXL, and N-cadherin to drive BRAF/MEK/AKT oncogenic signaling [#2, #10].\",\n  \"teleology\": [\n    {\n      \"year\": 1990,\n      \"claim\": \"Established that MAN2A1 is required for N-linked oligosaccharide maturation in vivo and that its deficiency causes human disease, framing the gene as a glycan-processing enzyme with physiological consequence.\",\n      \"evidence\": \"Cell-surface labeling, FAB mass spectrometry, enzyme activity assay, and Northern blot in a HEMPAS patient\",\n      \"pmids\": [\"2217175\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the precise catalytic step or substrate specificity\", \"Causal mutation in MAN2A1 not molecularly resolved\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Pinpointed the specific catalytic role of MAN2A1 as the enzyme converting hybrid- to complex-type N-glycans, using active-site mutation plus complementation rescue.\",\n      \"evidence\": \"Sequencing of Lec36 alleles, nano-ESI-MS glycan analysis, and wild-type vs. mutant complementation\",\n      \"pmids\": [\"19465480\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not address redundancy with the MAN2A2 isozyme\", \"No structural basis for substrate selectivity\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Addressed how MAN2A1 is retained in the medial-Golgi by linking its localization to phosphoinositide control.\",\n      \"evidence\": \"SAC1 RNAi knockdown with immunofluorescence, ultrastructure, and glycosylation readouts\",\n      \"pmids\": [\"20573065\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"Mechanism connecting PI(4)P levels to enzyme retention not resolved\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Showed that MAN2A1 Golgi residence requires active retrograde transport via the COG tethering complex, distinguishing localization maintenance from biosynthetic delivery.\",\n      \"evidence\": \"COG subunit siRNA depletion with BFA/Sar1-DN redistribution assays and glycan analysis\",\n      \"pmids\": [\"21421995\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct physical interaction between MAN2A1 and COG not demonstrated\", \"Cargo recognition mechanism unknown\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Extended the trafficking model by demonstrating that medial-Golgi positioning depends on Arf1 GTPase activity and COPI vesicle formation.\",\n      \"evidence\": \"3D-SIM, beta-COP siRNA, dominant-negative Arf1(T31N), and electron microscopy under ethanol perturbation\",\n      \"pmids\": [\"27748959\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"Did not establish whether COPI directly packages MAN2A1\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Revealed an oncogenic gain-of-function in which the MAN2A1 Golgi-targeting signal mislocalizes a hyperactive FER kinase that phosphorylates EGFR to drive proliferation and tumorigenesis.\",\n      \"evidence\": \"Golgi fractionation, kinase assays, phospho-analysis, KO/OE in cell lines, and xenografts\",\n      \"pmids\": [\"28245430\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of extracellular-domain phosphorylation by a Golgi-luminal kinase not fully explained\", \"Prevalence of the fusion across tumor types not defined here\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Demonstrated that the MAN2A1-FER genomic breakpoint is transcriptionally active and can be exploited as a tumor-selective therapeutic target.\",\n      \"evidence\": \"CRISPR-Cas9 nickase HDR insertion of HSV1-tk at the breakpoint with ganciclovir killing and xenografts\",\n      \"pmids\": [\"28459452\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"Delivery efficiency to clinical tumors untested\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Connected MAN2A1 N-glycan processing to inflammation, showing tissue-intrinsic enzyme activity drives chemokine-mediated neutrophil recruitment.\",\n      \"evidence\": \"IEC-specific conditional knockout mice in DSS colitis with histology, flow cytometry, and expression analysis\",\n      \"pmids\": [\"29343654\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific glycoproteins mediating chemokine induction not identified\", \"Role of alpha-MIIx compensation in other tissues unresolved\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Provided a specific client example by showing MAN2A1-dependent glycosylation is needed for plasma-membrane trafficking of the sodium iodide symporter.\",\n      \"evidence\": \"MAN2A1 RNAi with immunofluorescence and glycosylation profiling in MCF-7 cells\",\n      \"pmids\": [\"31455607\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single substrate, single lab\", \"Glycan site responsible for NIS mistrafficking not mapped\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Established MAN2A1-driven N-glycan maturation as a mechanism of tumor immune evasion and a druggable target with checkpoint inhibitors.\",\n      \"evidence\": \"CRISPR KO, T-cell co-culture killing, syngeneic tumor models, and swainsonine inhibition with anti-PD-L1\",\n      \"pmids\": [\"32723834\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific glycoproteins shielding tumor cells from T cells not identified\", \"Swainsonine specificity beyond MAN2A1 not delimited\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Broadened the MAN2A1-FER oncogenic mechanism to multiple receptor substrates and validated a phospho-epitope-directed therapeutic antibody.\",\n      \"evidence\": \"Phospho-analysis of PDGFRA/MET/AXL/N-cadherin, monoclonal antibody specificity, and ADC xenografts with isogenic KO controls\",\n      \"pmids\": [\"39082961\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"Structural basis of ectopic extracellular-domain phosphorylation unresolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How MAN2A1-FER, a Golgi-localized kinase, gains access to and phosphorylates the extracellular domains of cell-surface receptors remains mechanistically unexplained.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Topological mechanism of extracellular-domain phosphorylation unknown\", \"Structural model of the fusion protein lacking\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [0, 1, 12]},\n      {\"term_id\": \"GO:0140098\", \"supporting_discovery_ids\": [1, 12]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [2, 3, 4, 6]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0, 1, 12]},\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [3, 6]}\n    ],\n    \"complexes\": [],\n    \"partners\": [],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}