{"gene":"GANAB","run_date":"2026-06-10T01:55:20","timeline":{"discoveries":[{"year":2016,"finding":"GANAB (GIIα, the α-subunit of glucosidase II) is absolutely required for maturation and surface/ciliary localization of the ADPKD proteins polycystin-1 (PC1) and polycystin-2 (PC2); GANAB-null cells show complete failure of PC1 and PC2 to reach the cell surface and cilia, and reduced mature PC1 is seen in GANAB(+/-) cells. Wild-type but not disease-mutant GIIα rescues PC1 surface localization in GANAB(-/-) cells, placing GANAB in the PC1/PC2 maturation pathway and establishing that cystogenesis is driven by defects in PC1 maturation.","method":"GANAB-null cell lines, rescue with wild-type vs. mutant GIIα constructs, surface and ciliary localization assays, western blot for mature PC1","journal":"American journal of human genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal rescue experiment with null cells and wild-type vs. mutant constructs, multiple orthogonal readouts (surface localization, ciliary localization, protein maturation), single lab but rigorous controls","pmids":["27259053"],"is_preprint":false},{"year":2018,"finding":"A noncoding intronic 9 bp deletion near the GANAB exon 24 splice donor causes skipping of exon 24, establishing that non-coding variants in GANAB can disrupt pre-mRNA splicing and cause polycystic liver disease.","method":"Minigene splicing assay in cell lines and primary human cholangiocytes","journal":"Human mutation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — minigene assay in two independent cell systems (cell lines and primary cholangiocytes), single lab","pmids":["29243290"],"is_preprint":false},{"year":2020,"finding":"Homozygous loss of Ganab in mice results in early embryonic lethality, demonstrating an essential developmental role for GIIα. Heterozygous (Ganab+/-) mice show at least 50% reduction in Ganab protein but no reduction in PC1, PC2, or acetylated tubulin expression, and develop no kidney or liver cysts, indicating that Ganab haploinsufficiency alone is not sufficient to cause polycystic disease in the mouse model.","method":"CRISPR/Cas9 Ganab knockout mice; genotyping, western blot, histological analysis of kidneys and liver","journal":"BioMed research international","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo genetic model with multiple readouts (protein expression, histology, phenotype), single lab; partially negative result (no cysts in haploinsufficient mice)","pmids":["32550232"],"is_preprint":false},{"year":2020,"finding":"Novel GANAB variants (frameshift, nonsense, splice) predicted and partially confirmed to cause loss of glucosidase II enzymatic activity; cells bearing c.687delT or c.2002+1G>C variants show incomplete colocalization of GIIα and GIIβ subunits, indicating disrupted α/β subunit interaction as a mechanism of pathogenicity.","method":"Cell line expression of variant proteins, immunofluorescence colocalization of GIIα and GIIβ subunits, in silico active-site modeling","journal":"Orphanet journal of rare diseases","confidence":"Low","confidence_rationale":"Tier 3 / Weak — colocalization assay in cell lines with in silico support, no enzymatic activity directly measured, single lab","pmids":["33097077"],"is_preprint":false},{"year":2023,"finding":"ERVW-1 (endogenous retrovirus envelope protein) decreases GANAB expression in vitro, leading to ER stress activation via the ATF6/XBP1 arm of the unfolded protein response; confocal microscopy showed ERVW-1 alters ER morphology, and GANAB was found to participate in ERVW-1-regulated ER stress.","method":"In vitro overexpression of ERVW-1, ELISA, western blot, confocal microscopy of ER morphology","journal":"Viruses","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, limited mechanistic dissection of GANAB's specific role; ER morphology and UPR markers measured but causality of GANAB reduction not formally rescued","pmids":["37376599"],"is_preprint":false},{"year":2023,"finding":"YTHDC1 suppresses GANAB expression via the STAT3 signaling pathway in ovarian cancer cells; YTHDC1 stabilizes PIK3R1 mRNA in an m6A-dependent manner, which inhibits STAT3 activation, which in turn reduces GANAB expression in the N-glycan biosynthesis pathway.","method":"RNA sequencing, RNA immunoprecipitation sequencing, m6A-modified RNA immunoprecipitation, actinomycin-D mRNA stability assay, chromatin immunoprecipitation, western blot; in vitro and in vivo models","journal":"International journal of biological sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (RIP-seq, m6A-RIP, ChIP, mRNA stability) in a single lab establishing a regulatory axis upstream of GANAB","pmids":["37781028"],"is_preprint":false}],"current_model":"GANAB encodes GIIα, the catalytic α-subunit of the endoplasmic reticulum glucosidase II complex, which is absolutely required for proper N-glycan trimming and thereby for the maturation, surface localization, and ciliary trafficking of polycystin-1 (PC1) and polycystin-2 (PC2); loss of GIIα activity leads to failure of PC1 maturation and cystogenesis in polycystic kidney/liver disease, while complete (homozygous) loss is embryonic lethal and haploinsufficiency alone does not cause cysts in mice, suggesting a threshold or second-hit requirement for disease."},"narrative":{"mechanistic_narrative":"GANAB encodes GIIα, the catalytic α-subunit of the endoplasmic reticulum glucosidase II complex, where it functions partnered with the GIIβ subunit and is required for N-glycan processing that drives maturation of the polycystins [PMID:27259053, PMID:33097077]. Loss of GIIα activity causes complete failure of polycystin-1 (PC1) and polycystin-2 (PC2) to reach the cell surface and primary cilium, and only wild-type — not disease-mutant — GIIα rescues PC1 surface localization, placing GANAB upstream of PC1/PC2 maturation and identifying defective PC1 maturation as the driver of cystogenesis in polycystic kidney and liver disease [PMID:27259053]. Pathogenic GANAB variants act through several routes: coding frameshift, nonsense, and splice variants disrupt the GIIα/GIIβ subunit interaction [PMID:33097077], a noncoding intronic deletion near the exon 24 splice donor causes exon skipping and polycystic liver disease [PMID:29243290], and homozygous loss is embryonic lethal in mice while heterozygous loss preserves PC1, PC2, and ciliary tubulin and produces no cysts — indicating haploinsufficiency alone is insufficient for disease [PMID:32550232]. GANAB expression is itself controlled by upstream regulatory inputs, being suppressed through a YTHDC1–PIK3R1–STAT3 axis in ovarian cancer cells [PMID:37781028].","teleology":[{"year":2016,"claim":"Established that GANAB/GIIα is required for polycystin maturation, defining the molecular link between glucosidase II and cystogenesis.","evidence":"GANAB-null cell lines with reciprocal rescue by wild-type vs. disease-mutant GIIα, surface and ciliary localization assays, western blot for mature PC1","pmids":["27259053"],"confidence":"High","gaps":["Direct enzymatic glucan-trimming activity of GIIα on polycystin glycans not measured biochemically","Threshold of GIIα loss required for PC1 maturation failure not quantified"]},{"year":2018,"claim":"Showed that noncoding GANAB variants can be pathogenic by disrupting splicing, broadening the mutational spectrum beyond coding changes.","evidence":"Minigene splicing assay in cell lines and primary human cholangiocytes","pmids":["29243290"],"confidence":"Medium","gaps":["Functional consequence of exon 24 skipping on GIIα protein and enzymatic activity not assessed","Patient-tissue confirmation of aberrant transcript not shown"]},{"year":2020,"claim":"Defined the in vivo dosage requirement for GANAB, distinguishing essential developmental function from disease-causing haploinsufficiency.","evidence":"CRISPR/Cas9 Ganab knockout mice with genotyping, western blot, and kidney/liver histology","pmids":["32550232"],"confidence":"Medium","gaps":["Mechanism by which homozygous loss causes embryonic lethality not defined","Whether a second-hit cooperates with heterozygous loss to produce cysts not tested","Single laboratory model"]},{"year":2020,"claim":"Proposed disrupted GIIα/GIIβ subunit assembly as a pathogenic mechanism for several GANAB variants.","evidence":"Cell-line expression of variant proteins, immunofluorescence colocalization of GIIα and GIIβ, in silico active-site modeling","pmids":["33097077"],"confidence":"Low","gaps":["No direct measurement of glucosidase II enzymatic activity for the variants","Colocalization is a proxy and was not validated by co-immunoprecipitation","Effect on PC1 maturation not tested for these variants"]},{"year":2023,"claim":"Implicated GANAB in viral envelope-triggered ER stress, linking glucosidase II level to the unfolded protein response.","evidence":"In vitro ERVW-1 overexpression, ELISA, western blot, confocal ER morphology imaging","pmids":["37376599"],"confidence":"Low","gaps":["Causality of GANAB reduction in the UPR phenotype not established by rescue","Direct mechanism connecting GANAB to ATF6/XBP1 not defined"]},{"year":2023,"claim":"Identified an upstream regulatory axis controlling GANAB transcription in cancer cells.","evidence":"RNA-seq, RIP-seq, m6A-RIP, mRNA stability assay, ChIP, western blot in vitro and in vivo","pmids":["37781028"],"confidence":"Medium","gaps":["Functional consequence of GANAB suppression on N-glycan biosynthesis in this context not measured","Generality of the YTHDC1-STAT3-GANAB axis beyond ovarian cancer unknown"]},{"year":null,"claim":"How partial GANAB loss cooperates with additional genetic or environmental insults to cross the threshold for cystogenesis remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No second-hit model defining the trigger for cyst formation under heterozygous loss","No direct biochemical reconstitution of GIIα trimming of polycystin N-glycans"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[0,3]}],"localization":[{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[4]}],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0]}],"complexes":["glucosidase II complex"],"partners":["PRKCSH"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q14697","full_name":"Neutral alpha-glucosidase AB","aliases":["Alpha-glucosidase 2","Glucosidase II subunit alpha"],"length_aa":944,"mass_kda":106.9,"function":"Catalytic subunit of glucosidase II that cleaves sequentially the 2 innermost alpha-1,3-linked glucose residues from the Glc(2)Man(9)GlcNAc(2) oligosaccharide precursor of immature glycoproteins (PubMed:10929008). Required for PKD1/Polycystin-1 and PKD2/Polycystin-2 maturation and localization to the cell surface and cilia (PubMed:27259053)","subcellular_location":"Endoplasmic reticulum; Golgi apparatus; Melanosome","url":"https://www.uniprot.org/uniprotkb/Q14697/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/GANAB","classification":"Not Classified","n_dependent_lines":161,"n_total_lines":1208,"dependency_fraction":0.13327814569536423},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"CANX","stoichiometry":0.2},{"gene":"COPA","stoichiometry":0.2},{"gene":"COPE","stoichiometry":0.2},{"gene":"SAR1B","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/GANAB","total_profiled":1310},"omim":[{"mim_id":"600666","title":"POLYCYSTIC KIDNEY DISEASE 3 WITH OR WITHOUT POLYCYSTIC LIVER DISEASE; PKD3","url":"https://www.omim.org/entry/600666"},{"mim_id":"173900","title":"POLYCYSTIC KIDNEY DISEASE 1 WITH OR WITHOUT POLYCYSTIC LIVER DISEASE; PKD1","url":"https://www.omim.org/entry/173900"},{"mim_id":"104160","title":"GLUCOSIDASE, ALPHA, NEUTRAL AB; GANAB","url":"https://www.omim.org/entry/104160"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Endoplasmic reticulum","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/GANAB"},"hgnc":{"alias_symbol":["GluII","G2AN","KIAA0088","GIIA","GIIalpha"],"prev_symbol":[]},"alphafold":{"accession":"Q14697","domains":[{"cath_id":"2.60.40.1760","chopping":"49-180_238-382","consensus_level":"medium","plddt":94.0455,"start":49,"end":382}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q14697","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q14697-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q14697-F1-predicted_aligned_error_v6.png","plddt_mean":92.94},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=GANAB","jax_strain_url":"https://www.jax.org/strain/search?query=GANAB"},"sequence":{"accession":"Q14697","fasta_url":"https://rest.uniprot.org/uniprotkb/Q14697.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q14697/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q14697"}},"corpus_meta":[{"pmid":"27259053","id":"PMC_27259053","title":"Mutations in GANAB, Encoding the Glucosidase IIα Subunit, Cause Autosomal-Dominant Polycystic Kidney and Liver Disease.","date":"2016","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/27259053","citation_count":361,"is_preprint":false},{"pmid":"30859476","id":"PMC_30859476","title":"Biological characterization and pathogenicity of a newly isolated Chinese highly virulent genotype GIIa porcine epidemic diarrhea virus strain.","date":"2019","source":"Archives of virology","url":"https://pubmed.ncbi.nlm.nih.gov/30859476","citation_count":28,"is_preprint":false},{"pmid":"30827401","id":"PMC_30827401","title":"Evaluation and comparison of immunogenicity and cross-protective efficacy of two inactivated cell culture-derived GIIa- and GIIb-genotype porcine epidemic diarrhea virus vaccines in suckling piglets.","date":"2019","source":"Veterinary microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/30827401","citation_count":26,"is_preprint":false},{"pmid":"20795712","id":"PMC_20795712","title":"Molecular docking and 3D-QSAR CoMFA studies on indole inhibitors of GIIA secreted phospholipase A(2).","date":"2010","source":"Journal of chemical information and modeling","url":"https://pubmed.ncbi.nlm.nih.gov/20795712","citation_count":26,"is_preprint":false},{"pmid":"20067579","id":"PMC_20067579","title":"Group IIA secretory phospholipase A2 (GIIA) mediates apoptotic death during NMDA receptor activation in rat primary cortical neurons.","date":"2010","source":"Journal of neurochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/20067579","citation_count":22,"is_preprint":false},{"pmid":"29243290","id":"PMC_29243290","title":"A noncoding variant in GANAB explains isolated polycystic liver disease (PCLD) in a large family.","date":"2018","source":"Human mutation","url":"https://pubmed.ncbi.nlm.nih.gov/29243290","citation_count":20,"is_preprint":false},{"pmid":"37781028","id":"PMC_37781028","title":"Low expression of m6A reader YTHDC1 promotes progression of ovarian cancer via PIK3R1/STAT3/GANAB axis.","date":"2023","source":"International journal of biological sciences","url":"https://pubmed.ncbi.nlm.nih.gov/37781028","citation_count":18,"is_preprint":false},{"pmid":"33097077","id":"PMC_33097077","title":"Novel GANAB variants associated with polycystic liver disease.","date":"2020","source":"Orphanet journal of rare diseases","url":"https://pubmed.ncbi.nlm.nih.gov/33097077","citation_count":17,"is_preprint":false},{"pmid":"35806376","id":"PMC_35806376","title":"GANAB and N-Glycans Substrates Are Relevant in Human Physiology, Polycystic Pathology and Multiple Sclerosis: A Review.","date":"2022","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/35806376","citation_count":16,"is_preprint":false},{"pmid":"37376599","id":"PMC_37376599","title":"ERVW-1 Activates ATF6-Mediated Unfolded Protein Response by Decreasing GANAB in Recent-Onset Schizophrenia.","date":"2023","source":"Viruses","url":"https://pubmed.ncbi.nlm.nih.gov/37376599","citation_count":13,"is_preprint":false},{"pmid":"33255269","id":"PMC_33255269","title":"A Representative GIIA Phospholipase A2 Activates Preadipocytes to Produce Inflammatory Mediators Implicated in Obesity Development.","date":"2020","source":"Biomolecules","url":"https://pubmed.ncbi.nlm.nih.gov/33255269","citation_count":13,"is_preprint":false},{"pmid":"37201320","id":"PMC_37201320","title":"Recombinant human adenovirus type 5 based vaccine candidates against GIIa- and GIIb-genotype porcine epidemic diarrhea virus induce robust humoral and cellular response in mice.","date":"2023","source":"Virology","url":"https://pubmed.ncbi.nlm.nih.gov/37201320","citation_count":12,"is_preprint":false},{"pmid":"30792735","id":"PMC_30792735","title":"GANAB and PKD1 Variations in a 12 Years Old Female Patient With Early Onset of Autosomal Dominant Polycystic Kidney Disease.","date":"2019","source":"Frontiers in genetics","url":"https://pubmed.ncbi.nlm.nih.gov/30792735","citation_count":12,"is_preprint":false},{"pmid":"31037987","id":"PMC_31037987","title":"Adipocyte abundances of CES1, CRYAB, ENO1 and GANAB are modified in-vitro by glucose restriction and are associated with cellular remodelling during weight regain.","date":"2019","source":"Adipocyte","url":"https://pubmed.ncbi.nlm.nih.gov/31037987","citation_count":9,"is_preprint":false},{"pmid":"34357571","id":"PMC_34357571","title":"Expanding the variability of the ADPKD-GANAB clinical phenotype in a family of Italian ancestry.","date":"2021","source":"Journal of nephrology","url":"https://pubmed.ncbi.nlm.nih.gov/34357571","citation_count":7,"is_preprint":false},{"pmid":"24657378","id":"PMC_24657378","title":"Renaturation and one step purification of the chicken GIIA secreted phospholipase A2 from inclusion bodies.","date":"2014","source":"International journal of biological macromolecules","url":"https://pubmed.ncbi.nlm.nih.gov/24657378","citation_count":6,"is_preprint":false},{"pmid":"34832977","id":"PMC_34832977","title":"GANAB as a Novel Biomarker in Multiple Sclerosis: Correlation with Neuroinflammation and IFI35.","date":"2021","source":"Pharmaceuticals (Basel, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/34832977","citation_count":6,"is_preprint":false},{"pmid":"31669635","id":"PMC_31669635","title":"The in silico characterization of neutral alpha-glucosidase C (GANC) and its evolution from GANAB.","date":"2019","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/31669635","citation_count":4,"is_preprint":false},{"pmid":"36015109","id":"PMC_36015109","title":"Identification of a Dual Inhibitor of Secreted Phospholipase A2 (GIIA sPLA2) and SARS-CoV-2 Main Protease.","date":"2022","source":"Pharmaceuticals (Basel, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/36015109","citation_count":3,"is_preprint":false},{"pmid":"40134995","id":"PMC_40134995","title":"GANAB-Associated Severe Autosomal Dominant Polycystic Kidney Disease in an 18-Year-Old Female: A Case Report.","date":"2025","source":"Cureus","url":"https://pubmed.ncbi.nlm.nih.gov/40134995","citation_count":2,"is_preprint":false},{"pmid":"32550232","id":"PMC_32550232","title":"Ganab Haploinsufficiency Does Not Cause Polycystic Kidney Disease or Polycystic Liver Disease in Mice.","date":"2020","source":"BioMed research international","url":"https://pubmed.ncbi.nlm.nih.gov/32550232","citation_count":1,"is_preprint":false},{"pmid":"39862751","id":"PMC_39862751","title":"Characterization of a cell-adapted completely attenuated genotype GIIa porcine epidemic diarrhea virus strain.","date":"2025","source":"Virology","url":"https://pubmed.ncbi.nlm.nih.gov/39862751","citation_count":0,"is_preprint":false},{"pmid":"23688417","id":"PMC_23688417","title":"Renaturation and one step purification of the chicken GIIA secreted phospholipase A2 from inclusion bodies.","date":"2013","source":"International journal of biological macromolecules","url":"https://pubmed.ncbi.nlm.nih.gov/23688417","citation_count":0,"is_preprint":false},{"pmid":"39961537","id":"PMC_39961537","title":"GANAB c.1118C > T is a novel variant in patients with polycystic liver disease / polycystic kidney disease.","date":"2025","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/39961537","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":13888,"output_tokens":1723,"usd":0.033754,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8562,"output_tokens":2245,"usd":0.049467,"stage2_stop_reason":"end_turn"},"total_usd":0.083221,"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\": 2016,\n      \"finding\": \"GANAB (GIIα, the α-subunit of glucosidase II) is absolutely required for maturation and surface/ciliary localization of the ADPKD proteins polycystin-1 (PC1) and polycystin-2 (PC2); GANAB-null cells show complete failure of PC1 and PC2 to reach the cell surface and cilia, and reduced mature PC1 is seen in GANAB(+/-) cells. Wild-type but not disease-mutant GIIα rescues PC1 surface localization in GANAB(-/-) cells, placing GANAB in the PC1/PC2 maturation pathway and establishing that cystogenesis is driven by defects in PC1 maturation.\",\n      \"method\": \"GANAB-null cell lines, rescue with wild-type vs. mutant GIIα constructs, surface and ciliary localization assays, western blot for mature PC1\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal rescue experiment with null cells and wild-type vs. mutant constructs, multiple orthogonal readouts (surface localization, ciliary localization, protein maturation), single lab but rigorous controls\",\n      \"pmids\": [\"27259053\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"A noncoding intronic 9 bp deletion near the GANAB exon 24 splice donor causes skipping of exon 24, establishing that non-coding variants in GANAB can disrupt pre-mRNA splicing and cause polycystic liver disease.\",\n      \"method\": \"Minigene splicing assay in cell lines and primary human cholangiocytes\",\n      \"journal\": \"Human mutation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — minigene assay in two independent cell systems (cell lines and primary cholangiocytes), single lab\",\n      \"pmids\": [\"29243290\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Homozygous loss of Ganab in mice results in early embryonic lethality, demonstrating an essential developmental role for GIIα. Heterozygous (Ganab+/-) mice show at least 50% reduction in Ganab protein but no reduction in PC1, PC2, or acetylated tubulin expression, and develop no kidney or liver cysts, indicating that Ganab haploinsufficiency alone is not sufficient to cause polycystic disease in the mouse model.\",\n      \"method\": \"CRISPR/Cas9 Ganab knockout mice; genotyping, western blot, histological analysis of kidneys and liver\",\n      \"journal\": \"BioMed research international\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo genetic model with multiple readouts (protein expression, histology, phenotype), single lab; partially negative result (no cysts in haploinsufficient mice)\",\n      \"pmids\": [\"32550232\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Novel GANAB variants (frameshift, nonsense, splice) predicted and partially confirmed to cause loss of glucosidase II enzymatic activity; cells bearing c.687delT or c.2002+1G>C variants show incomplete colocalization of GIIα and GIIβ subunits, indicating disrupted α/β subunit interaction as a mechanism of pathogenicity.\",\n      \"method\": \"Cell line expression of variant proteins, immunofluorescence colocalization of GIIα and GIIβ subunits, in silico active-site modeling\",\n      \"journal\": \"Orphanet journal of rare diseases\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — colocalization assay in cell lines with in silico support, no enzymatic activity directly measured, single lab\",\n      \"pmids\": [\"33097077\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"ERVW-1 (endogenous retrovirus envelope protein) decreases GANAB expression in vitro, leading to ER stress activation via the ATF6/XBP1 arm of the unfolded protein response; confocal microscopy showed ERVW-1 alters ER morphology, and GANAB was found to participate in ERVW-1-regulated ER stress.\",\n      \"method\": \"In vitro overexpression of ERVW-1, ELISA, western blot, confocal microscopy of ER morphology\",\n      \"journal\": \"Viruses\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, limited mechanistic dissection of GANAB's specific role; ER morphology and UPR markers measured but causality of GANAB reduction not formally rescued\",\n      \"pmids\": [\"37376599\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"YTHDC1 suppresses GANAB expression via the STAT3 signaling pathway in ovarian cancer cells; YTHDC1 stabilizes PIK3R1 mRNA in an m6A-dependent manner, which inhibits STAT3 activation, which in turn reduces GANAB expression in the N-glycan biosynthesis pathway.\",\n      \"method\": \"RNA sequencing, RNA immunoprecipitation sequencing, m6A-modified RNA immunoprecipitation, actinomycin-D mRNA stability assay, chromatin immunoprecipitation, western blot; in vitro and in vivo models\",\n      \"journal\": \"International journal of biological sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (RIP-seq, m6A-RIP, ChIP, mRNA stability) in a single lab establishing a regulatory axis upstream of GANAB\",\n      \"pmids\": [\"37781028\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"GANAB encodes GIIα, the catalytic α-subunit of the endoplasmic reticulum glucosidase II complex, which is absolutely required for proper N-glycan trimming and thereby for the maturation, surface localization, and ciliary trafficking of polycystin-1 (PC1) and polycystin-2 (PC2); loss of GIIα activity leads to failure of PC1 maturation and cystogenesis in polycystic kidney/liver disease, while complete (homozygous) loss is embryonic lethal and haploinsufficiency alone does not cause cysts in mice, suggesting a threshold or second-hit requirement for disease.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"GANAB encodes GIIα, the catalytic α-subunit of the endoplasmic reticulum glucosidase II complex, where it functions partnered with the GIIβ subunit and is required for N-glycan processing that drives maturation of the polycystins [#0, #3]. Loss of GIIα activity causes complete failure of polycystin-1 (PC1) and polycystin-2 (PC2) to reach the cell surface and primary cilium, and only wild-type — not disease-mutant — GIIα rescues PC1 surface localization, placing GANAB upstream of PC1/PC2 maturation and identifying defective PC1 maturation as the driver of cystogenesis in polycystic kidney and liver disease [#0]. Pathogenic GANAB variants act through several routes: coding frameshift, nonsense, and splice variants disrupt the GIIα/GIIβ subunit interaction [#3], a noncoding intronic deletion near the exon 24 splice donor causes exon skipping and polycystic liver disease [#1], and homozygous loss is embryonic lethal in mice while heterozygous loss preserves PC1, PC2, and ciliary tubulin and produces no cysts — indicating haploinsufficiency alone is insufficient for disease [#2]. GANAB expression is itself controlled by upstream regulatory inputs, being suppressed through a YTHDC1–PIK3R1–STAT3 axis in ovarian cancer cells [#5].\",\n  \"teleology\": [\n    {\n      \"year\": 2016,\n      \"claim\": \"Established that GANAB/GIIα is required for polycystin maturation, defining the molecular link between glucosidase II and cystogenesis.\",\n      \"evidence\": \"GANAB-null cell lines with reciprocal rescue by wild-type vs. disease-mutant GIIα, surface and ciliary localization assays, western blot for mature PC1\",\n      \"pmids\": [\"27259053\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Direct enzymatic glucan-trimming activity of GIIα on polycystin glycans not measured biochemically\",\n        \"Threshold of GIIα loss required for PC1 maturation failure not quantified\"\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Showed that noncoding GANAB variants can be pathogenic by disrupting splicing, broadening the mutational spectrum beyond coding changes.\",\n      \"evidence\": \"Minigene splicing assay in cell lines and primary human cholangiocytes\",\n      \"pmids\": [\"29243290\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Functional consequence of exon 24 skipping on GIIα protein and enzymatic activity not assessed\",\n        \"Patient-tissue confirmation of aberrant transcript not shown\"\n      ]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Defined the in vivo dosage requirement for GANAB, distinguishing essential developmental function from disease-causing haploinsufficiency.\",\n      \"evidence\": \"CRISPR/Cas9 Ganab knockout mice with genotyping, western blot, and kidney/liver histology\",\n      \"pmids\": [\"32550232\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Mechanism by which homozygous loss causes embryonic lethality not defined\",\n        \"Whether a second-hit cooperates with heterozygous loss to produce cysts not tested\",\n        \"Single laboratory model\"\n      ]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Proposed disrupted GIIα/GIIβ subunit assembly as a pathogenic mechanism for several GANAB variants.\",\n      \"evidence\": \"Cell-line expression of variant proteins, immunofluorescence colocalization of GIIα and GIIβ, in silico active-site modeling\",\n      \"pmids\": [\"33097077\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No direct measurement of glucosidase II enzymatic activity for the variants\",\n        \"Colocalization is a proxy and was not validated by co-immunoprecipitation\",\n        \"Effect on PC1 maturation not tested for these variants\"\n      ]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Implicated GANAB in viral envelope-triggered ER stress, linking glucosidase II level to the unfolded protein response.\",\n      \"evidence\": \"In vitro ERVW-1 overexpression, ELISA, western blot, confocal ER morphology imaging\",\n      \"pmids\": [\"37376599\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"Causality of GANAB reduction in the UPR phenotype not established by rescue\",\n        \"Direct mechanism connecting GANAB to ATF6/XBP1 not defined\"\n      ]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Identified an upstream regulatory axis controlling GANAB transcription in cancer cells.\",\n      \"evidence\": \"RNA-seq, RIP-seq, m6A-RIP, mRNA stability assay, ChIP, western blot in vitro and in vivo\",\n      \"pmids\": [\"37781028\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Functional consequence of GANAB suppression on N-glycan biosynthesis in this context not measured\",\n        \"Generality of the YTHDC1-STAT3-GANAB axis beyond ovarian cancer unknown\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How partial GANAB loss cooperates with additional genetic or environmental insults to cross the threshold for cystogenesis remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No second-hit model defining the trigger for cyst formation under heterozygous loss\",\n        \"No direct biochemical reconstitution of GIIα trimming of polycystin N-glycans\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [0, 3]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"complexes\": [\"glucosidase II complex\"],\n    \"partners\": [\"PRKCSH\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":4,"faith_total":4,"faith_pct":100.0}}