{"gene":"GYG2","run_date":"2026-06-10T01:55:21","timeline":{"discoveries":[{"year":1997,"finding":"GYG2 (glycogenin-2/GN-2) is a self-glucosylating protein that initiates glycogen biosynthesis. When expressed in E. coli or COS cells, GYG2 is enzymatically active in self-glucosylation assays, and the self-glucosylated GYG2 product can be elongated by skeletal muscle glycogen synthase. In H4IIEC3 hepatoma cells, most GYG2 is present as free protein but some is covalently associated with glycogen fractions, released only by alpha-amylase treatment. GYG2 is expressed preferentially in liver, heart, and pancreas, and multiple isoforms (GN-2alpha, GN-2beta, GN-2gamma) arise from alternative splicing.","method":"Expression in E. coli and COS cells; in vitro self-glucosylation assay; elongation assay with skeletal muscle glycogen synthase; immunoblotting with anti-GN-2 antibodies; subcellular fractionation with alpha-amylase treatment in H4IIEC3 hepatoma cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro enzymatic reconstitution (self-glucosylation) in two expression systems plus functional elongation assay, replicated across cell-based and biochemical contexts in a single rigorous study","pmids":["9346895"],"is_preprint":false},{"year":2000,"finding":"The human GYG2 gene spans more than 46 kb, contains 11 exons, and alternative exon usage explains the observed diversity in GYG2 cDNA sequences. The gene was localized to Xp22.3 by fluorescence in situ hybridization (FISH), outside pseudoautosomal region PAR1 but in a region of X-Y shared genes. An inactive remnant of GYG2 consisting of exons 1–3 may be present on the Y chromosome.","method":"Genomic cloning; exon structure analysis; FISH mapping; STS mapping","journal":"Gene","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct chromosomal localization by FISH with genomic clone, supported by STS mapping; gene structure determined by cloning and sequencing","pmids":["10721716"],"is_preprint":false},{"year":2001,"finding":"Evidence strongly suggests that a second glycogenin gene (GYG2 ortholog) does not exist in rodents, indicating that GYG2 is likely primate-specific. Attempts to generate rodent reagents were unsuccessful and no rodent GYG2 sequence could be identified, suggesting differential regulation of glycogen initiation between rodents and primates.","method":"Sequence database searches; failure to generate rodent-reactive GYG2 reagents (negative result)","journal":"IUBMB life","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — negative finding supported by multiple failed experimental approaches across a focused study; relevant mechanistic implication for species-specificity of GYG2","pmids":["11463169"],"is_preprint":false},{"year":2009,"finding":"GYG2 is subject to X chromosome inactivation (XCI) in normal human fibroblasts, as determined by allele-specific expression analysis and DNA methylation profiling of its 5' end. This contrasts with reports in rodent/human somatic cell hybrids where it appeared to escape XCI, indicating that hybrid cell systems are not adequate for studying GYG2 epigenotype.","method":"Allele-specific expression analysis using human fibroblasts with skewed XCI; DNA methylation profiling of the 5' end of GYG2","journal":"Epigenetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — two orthogonal methods (allele-specific expression and methylation profiling), single lab, direct epigenetic mechanism established","pmids":["19684479"],"is_preprint":false},{"year":2013,"finding":"A hemizygous missense mutation in GYG2 (c.665G>C, p.W222S) abolishes the self-glucosylation activity of GYG2 in vitro. Structural modeling indicated the mutation destabilizes the protein. The mutation was identified in male siblings with Leigh syndrome, suggesting a possible link between GYG2 dysfunction and this neurodegenerative disorder.","method":"Whole exome sequencing; in vitro self-glucosylation assay of wild-type vs. mutant GYG2; structural modeling","journal":"Human genetics","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro enzymatic assay directly demonstrating loss of self-glucosylation activity for the mutant, combined with structural modeling; single lab but two orthogonal approaches (biochemical assay + structural analysis)","pmids":["24100632"],"is_preprint":false},{"year":2015,"finding":"Complete deletion of GYG2 in hemizygous males does not result in overt impairment of liver glycogen synthesis or glucagon-stimulated glucose release. Liver biopsies from GYG2-deletion carriers showed the presence of both alpha- and beta-glycogen by electron microscopy, and GYG1 (glycogenin-1) mRNA was detected in liver. This indicates GYG2 is dispensable for liver glycogen synthesis, likely because GYG1 compensates.","method":"Identification of 102-kb GYG2 deletion by copy number variation analysis; glucagon stimulation tests in deletion carriers vs. controls; liver biopsy with light and electron microscopy; RT-PCR for GYG1 and GYG2 mRNA in liver","journal":"The Journal of clinical endocrinology and metabolism","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal approaches (genetic, physiological, histological, molecular) in human loss-of-function subjects; finding independently supported across two families","pmids":["25751106"],"is_preprint":false},{"year":2025,"finding":"GYG2 exhibits minimal autoglycosylation activity compared to GYG1 and acts as a suppressor of glycogen formation rather than an initiator. GYG2 coordinates with GYG1 to regulate glycogen synthase activity and glycogen assembly in a cell-type-dependent manner, modulating glucose metabolic pathways to maintain cellular glucose homeostasis.","method":"Cellular models; structural biology; biochemical analyses including autoglycosylation assays comparing GYG1 and GYG2","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Strong — multiple orthogonal methods (structural biology, biochemical assays, cellular models) in a single rigorous study establishing a mechanistically distinct role for GYG2","pmids":["40670355"],"is_preprint":false},{"year":2019,"finding":"A 114-kb deletion on the X chromosome spanning XG exons 4–10 and the downstream GYG2 gene was identified in anti-Xga makers, defining this deletion as the genetic basis of the Xgnull phenotype. Males were hemizygous and the female likely homozygous for this deletion. The deletion breakpoint involves a heterogeneous LTR6B sequence.","method":"Exon sequencing; PCR with deletion-specific primers; Sanger sequencing of recombination junctions; bioinformatics; analysis of genomic and cell-free DNA","journal":"Transfusion","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct PCR and sequencing demonstrated deletion spanning GYG2; mechanistic implication for GYG2's chromosomal context, single lab","pmids":["30938838"],"is_preprint":false},{"year":2025,"finding":"In VSV-M51-infected glioma cells, GYG2 expression is downregulated after oncolytic virus infection. Loss-of-function experiments showed that downregulating GYG2 inhibits glioma cell growth and facilitates tumor cell apoptosis, while GYG2 gain-of-function promotes cell survival. VSV-M51 infection promotes glioma cell apoptosis by downregulating GYG2, identifying an anti-apoptotic role for GYG2 in glioma.","method":"siRNA knockdown and overexpression (loss- and gain-of-function); rescue studies; qRT-PCR; analysis of glioma datasets (GSE136330, GSE166914, TCGA); apoptosis assays in VSV-M51-infected cells","journal":"BMC cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss- and gain-of-function with rescue experiments establishing GYG2's anti-apoptotic role, single lab, two orthogonal functional approaches","pmids":["41350820"],"is_preprint":false}],"current_model":"GYG2 (glycogenin-2) is an X-linked, primate-specific self-glucosylating protein that initiates glycogen biosynthesis preferentially in liver, heart, and pancreas; it exhibits minimal autoglycosylation activity compared to GYG1 and acts as a suppressor of glycogen formation, coordinating with GYG1 to regulate glycogen synthase activity and cellular glucose homeostasis in a cell-type-dependent manner, while a missense mutation (p.W222S) abolishes its self-glucosylation activity and complete gene deletion in humans is compensated by GYG1 in liver."},"narrative":{"mechanistic_narrative":"GYG2 (glycogenin-2) is a self-glucosylating protein originally characterized as an initiator of glycogen biosynthesis, expressed preferentially in liver, heart, and pancreas, with multiple isoforms arising from alternative splicing [PMID:9346895]. In vitro it autoglucosylates and the resulting product serves as a primer that is elongated by glycogen synthase [PMID:9346895]. The gene maps to Xp22.3, is subject to X chromosome inactivation, and appears to be primate-specific, with no functional ortholog in rodents [PMID:10721716, PMID:11463169, PMID:19684479]. More recent structural and biochemical work revises the simple initiator model: GYG2 exhibits minimal autoglycosylation activity relative to GYG1 and acts as a suppressor of glycogen formation, coordinating with GYG1 to modulate glycogen synthase activity and glycogen assembly in a cell-type-dependent manner to maintain cellular glucose homeostasis [PMID:40670355]. Consistent with a functional redundancy with GYG1, complete GYG2 deletion in hemizygous human males does not impair liver glycogen synthesis, as GYG1 compensates [PMID:25751106]. A hemizygous missense mutation (p.W222S) abolishes GYG2 self-glucosylation activity in vitro and destabilizes the protein, and was identified in male siblings with Leigh syndrome [PMID:24100632]. In glioma cells, GYG2 has a separable anti-apoptotic, pro-survival role: its downregulation upon oncolytic VSV-M51 infection promotes tumor cell apoptosis [PMID:41350820].","teleology":[{"year":1997,"claim":"Established that GYG2 is an enzymatically active self-glucosylating protein capable of initiating glycogen synthesis, defining its core biochemical activity and tissue distribution.","evidence":"Expression in E. coli and COS cells with in vitro self-glucosylation and glycogen synthase elongation assays; fractionation in H4IIEC3 hepatoma cells","pmids":["9346895"],"confidence":"High","gaps":["Did not establish physiological contribution relative to GYG1","Functional role of distinct splice isoforms unresolved"]},{"year":2000,"claim":"Defined the genomic structure and X-linked chromosomal location of GYG2, placing it in an X-Y shared gene region at Xp22.3.","evidence":"Genomic cloning, exon structure analysis, and FISH/STS mapping","pmids":["10721716"],"confidence":"High","gaps":["Functional consequence of X-Y shared context not addressed","Y-chromosome remnant activity not tested"]},{"year":2001,"claim":"Indicated GYG2 is primate-specific with no rodent ortholog, implying species differences in glycogen initiation regulation.","evidence":"Sequence database searches and failed generation of rodent-reactive reagents (negative result)","pmids":["11463169"],"confidence":"Medium","gaps":["Negative finding limited by database completeness at the time","Does not explain functional consequence of primate-specificity"]},{"year":2009,"claim":"Determined that GYG2 undergoes X chromosome inactivation in normal fibroblasts, correcting prior hybrid-cell reports of XCI escape.","evidence":"Allele-specific expression analysis in skewed-XCI fibroblasts and 5' DNA methylation profiling","pmids":["19684479"],"confidence":"Medium","gaps":["Tissue-specificity of XCI status not assessed","Dosage consequences for glycogen metabolism unexplored"]},{"year":2013,"claim":"Linked a specific missense mutation to loss of GYG2 catalytic activity and a human neurodegenerative phenotype.","evidence":"Whole exome sequencing of Leigh syndrome siblings, in vitro self-glucosylation assay of WT vs. p.W222S mutant, and structural modeling","pmids":["24100632"],"confidence":"High","gaps":["Causal link between GYG2 loss and Leigh syndrome not proven by rescue or animal model","Single family"]},{"year":2015,"claim":"Showed GYG2 is dispensable for liver glycogen synthesis in humans, demonstrating GYG1 compensation in vivo.","evidence":"CNV-identified 102-kb GYG2 deletion carriers analyzed by glucagon stimulation tests, liver biopsy EM, and RT-PCR for GYG1/GYG2","pmids":["25751106"],"confidence":"High","gaps":["Does not address GYG2 function in heart or pancreas","Compensation mechanism beyond GYG1 presence not dissected"]},{"year":2019,"claim":"Characterized the genomic deletion context of GYG2 within the XG-region Xgnull phenotype, clarifying its chromosomal neighborhood.","evidence":"Exon sequencing, deletion-specific PCR, and Sanger sequencing of recombination junctions","pmids":["30938838"],"confidence":"Medium","gaps":["Metabolic consequence of the GYG2-spanning deletion not assessed","Single lab"]},{"year":2025,"claim":"Revised the functional model: GYG2 has minimal autoglycosylation and acts as a suppressor rather than initiator of glycogen formation, coordinating with GYG1 to regulate glycogen synthase and glucose homeostasis.","evidence":"Structural biology, biochemical autoglycosylation assays comparing GYG1 and GYG2, and cellular models","pmids":["40670355"],"confidence":"High","gaps":["Molecular basis of suppression versus initiation not fully mapped","Cell-type determinants of coordination with GYG1 unresolved"]},{"year":2025,"claim":"Identified a context-specific anti-apoptotic role for GYG2 in glioma, separable from its glycogen-metabolic function.","evidence":"siRNA knockdown/overexpression with rescue, qRT-PCR, apoptosis assays in VSV-M51-infected glioma cells, and tumor dataset analysis","pmids":["41350820"],"confidence":"Medium","gaps":["Molecular pathway linking GYG2 to apoptosis suppression not defined","Single lab; in vivo tumor relevance untested"]},{"year":null,"claim":"How GYG2's suppressor activity and its catalytic/structural features mechanistically reconcile with its earlier-described initiator activity and its anti-apoptotic role in cancer remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified mechanism connecting glycogen suppression to apoptosis regulation","Tissue-specific physiological role in heart and pancreas uncharacterized","No structural explanation for switch between initiation and suppression"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[0,4,6]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[0,5,6]}],"complexes":[],"partners":["GYG1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O15488","full_name":"Glycogenin-2","aliases":[],"length_aa":501,"mass_kda":55.2,"function":"Glycogenin participates in the glycogen biosynthetic process along with glycogen synthase and glycogen branching enzyme. It catalyzes the formation of a short alpha (1,4)-glucosyl chain covalently attached via a glucose 1-O-tyrosyl linkage to internal tyrosine residues and these chains act as primers for the elongation reaction catalyzed by glycogen synthase","subcellular_location":"Cytoplasm; Nucleus","url":"https://www.uniprot.org/uniprotkb/O15488/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/GYG2","classification":"Not Classified","n_dependent_lines":4,"n_total_lines":1208,"dependency_fraction":0.0033112582781456954},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000056998","cell_line_id":"CID001594","localizations":[{"compartment":"cytoplasmic","grade":3}],"interactors":[{"gene":"GYG1","stoichiometry":10.0},{"gene":"GYS1","stoichiometry":10.0}],"url":"https://opencell.sf.czbiohub.org/target/CID001594","total_profiled":1310},"omim":[{"mim_id":"603942","title":"GLYCOGENIN 1; GYG1","url":"https://www.omim.org/entry/603942"},{"mim_id":"300198","title":"GLYCOGENIN 2; GYG2","url":"https://www.omim.org/entry/300198"},{"mim_id":"256000","title":"LEIGH SYNDROME, NUCLEAR; NULS","url":"https://www.omim.org/entry/256000"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoli","reliability":"Approved"},{"location":"Cytosol","reliability":"Approved"},{"location":"Nucleoplasm","reliability":"Additional"},{"location":"Mitotic spindle","reliability":"Additional"},{"location":"Centrosome","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"adipose tissue","ntpm":146.8},{"tissue":"breast","ntpm":40.4}],"url":"https://www.proteinatlas.org/search/GYG2"},"hgnc":{"alias_symbol":["GN-2"],"prev_symbol":[]},"alphafold":{"accession":"O15488","domains":[{"cath_id":"3.90.550.10","chopping":"38-300","consensus_level":"high","plddt":93.4114,"start":38,"end":300}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O15488","model_url":"https://alphafold.ebi.ac.uk/files/AF-O15488-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O15488-F1-predicted_aligned_error_v6.png","plddt_mean":70.94},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=GYG2","jax_strain_url":"https://www.jax.org/strain/search?query=GYG2"},"sequence":{"accession":"O15488","fasta_url":"https://rest.uniprot.org/uniprotkb/O15488.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O15488/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O15488"}},"corpus_meta":[{"pmid":"2650538","id":"PMC_2650538","title":"Clinical outcome of three discrete histologic patterns of injury in severe lupus glomerulonephritis.","date":"1989","source":"American journal of kidney diseases : the official journal of the National Kidney Foundation","url":"https://pubmed.ncbi.nlm.nih.gov/2650538","citation_count":66,"is_preprint":false},{"pmid":"11602789","id":"PMC_11602789","title":"gpUL73 (gN) genomic variants of human cytomegalovirus isolates are clustered into four distinct genotypes.","date":"2001","source":"The Journal of general virology","url":"https://pubmed.ncbi.nlm.nih.gov/11602789","citation_count":62,"is_preprint":false},{"pmid":"11058123","id":"PMC_11058123","title":"Formation of cis-diamminedichloroplatinum(II) 1,2-intrastrand cross-links on DNA is flanking-sequence independent.","date":"2000","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/11058123","citation_count":56,"is_preprint":false},{"pmid":"11792756","id":"PMC_11792756","title":"Urine macrophage migration inhibitory factor reflects the severity of renal injury in human glomerulonephritis.","date":"2002","source":"Journal of the American Society of Nephrology : JASN","url":"https://pubmed.ncbi.nlm.nih.gov/11792756","citation_count":55,"is_preprint":false},{"pmid":"9346895","id":"PMC_9346895","title":"Glycogenin-2, a novel self-glucosylating protein involved in liver glycogen biosynthesis.","date":"1997","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/9346895","citation_count":50,"is_preprint":false},{"pmid":"17498742","id":"PMC_17498742","title":"The role of high affinity non-specific DNA binding by Lrp in transcriptional regulation and DNA organization.","date":"2007","source":"Journal of molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/17498742","citation_count":38,"is_preprint":false},{"pmid":"17325203","id":"PMC_17325203","title":"Translation attenuation by PERK balances ER glycoprotein synthesis with lipid-linked oligosaccharide flux.","date":"2007","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/17325203","citation_count":37,"is_preprint":false},{"pmid":"12927749","id":"PMC_12927749","title":"Intrauterine cytomegalovirus infection and glycoprotein N (gN) genotypes.","date":"2003","source":"Journal of clinical virology : the official publication of the Pan American Society for Clinical Virology","url":"https://pubmed.ncbi.nlm.nih.gov/12927749","citation_count":36,"is_preprint":false},{"pmid":"31031182","id":"PMC_31031182","title":"Epigenetic regulation of diabetogenic adipose morphology.","date":"2019","source":"Molecular metabolism","url":"https://pubmed.ncbi.nlm.nih.gov/31031182","citation_count":34,"is_preprint":false},{"pmid":"2459395","id":"PMC_2459395","title":"Non-enzymatic template-directed synthesis on RNA random copolymers. 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Transplant.","date":"2019","source":"Transplantation proceedings","url":"https://pubmed.ncbi.nlm.nih.gov/31256873","citation_count":5,"is_preprint":false},{"pmid":"28745689","id":"PMC_28745689","title":"[Kidney injury molecules (KIM-1, MCP-1) and type IV collagen in the assessment of activity of antineutrophil cytoplasmic antibody-associated glomerulonephritis].","date":"2017","source":"Terapevticheskii arkhiv","url":"https://pubmed.ncbi.nlm.nih.gov/28745689","citation_count":5,"is_preprint":false},{"pmid":"40670355","id":"PMC_40670355","title":"Human glycogenins maintain glucose homeostasis by regulating glycogen metabolism.","date":"2025","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/40670355","citation_count":4,"is_preprint":false},{"pmid":"37185710","id":"PMC_37185710","title":"Distribution of Exonic Variants in Glycogen Synthesis and Catabolism Genes in Late Onset Pompe Disease (LOPD).","date":"2023","source":"Current issues in molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/37185710","citation_count":4,"is_preprint":false},{"pmid":"15631346","id":"PMC_15631346","title":"Can von Willebrand factor, platelet-endothelial cell adhesion molecule-1 and thrombomodulin be used as alternative markers of endothelial cell injury in human glomerulonephritis?","date":"2004","source":"Roczniki Akademii Medycznej w Bialymstoku (1995)","url":"https://pubmed.ncbi.nlm.nih.gov/15631346","citation_count":4,"is_preprint":false},{"pmid":"27356476","id":"PMC_27356476","title":"[Expression of mRNA and protein of Klotho gene in placental tissue of macrosomia and its relationship with birth weight of neonates].","date":"2016","source":"Zhonghua fu chan ke za zhi","url":"https://pubmed.ncbi.nlm.nih.gov/27356476","citation_count":3,"is_preprint":false},{"pmid":"6978404","id":"PMC_6978404","title":"Lymphocytotoxic activity in primary glomerulonephritis: evidence for immune complex-mediated cytotoxicity.","date":"1981","source":"Journal of clinical & laboratory immunology","url":"https://pubmed.ncbi.nlm.nih.gov/6978404","citation_count":2,"is_preprint":false},{"pmid":"41007959","id":"PMC_41007959","title":"Multi-Omics Insights into Postnatal Skeletal Muscle Development in Duroc Pigs.","date":"2025","source":"Animals : an open access journal from MDPI","url":"https://pubmed.ncbi.nlm.nih.gov/41007959","citation_count":1,"is_preprint":false},{"pmid":"39925213","id":"PMC_39925213","title":"Genetic background of anti-CD99 producers in Japan and analysis of hemolytic transfusion reactions due to anti-CD99.","date":"2025","source":"Transfusion","url":"https://pubmed.ncbi.nlm.nih.gov/39925213","citation_count":1,"is_preprint":false},{"pmid":"18209455","id":"PMC_18209455","title":"Mycophenolate Mofetil (MMF) Efficacy in Glomerulonephritis (GN), a Retrospective Analysis.","date":"2005","source":"Saudi journal of kidney diseases and transplantation : an official publication of the Saudi Center for Organ Transplantation, Saudi Arabia","url":"https://pubmed.ncbi.nlm.nih.gov/18209455","citation_count":1,"is_preprint":false},{"pmid":"41350820","id":"PMC_41350820","title":"Functional analysis and verification of GYG2 in oncolytic virus-infected glioma.","date":"2025","source":"BMC cancer","url":"https://pubmed.ncbi.nlm.nih.gov/41350820","citation_count":0,"is_preprint":false},{"pmid":"41350704","id":"PMC_41350704","title":"Ferroptosis-induced remodeling of glycosylation the immune microenvironment and improves survival in pancreatic cancer.","date":"2025","source":"World journal of surgical oncology","url":"https://pubmed.ncbi.nlm.nih.gov/41350704","citation_count":0,"is_preprint":false},{"pmid":"36533986","id":"PMC_36533986","title":"Long-term kidney outcome of patients with rheumatological diseases and antineutrophil cytoplasmic antibody-glomerulonephritis: comparison with a primitive ANCA-glomerulonephritis cohort.","date":"2022","source":"Clinical and experimental rheumatology","url":"https://pubmed.ncbi.nlm.nih.gov/36533986","citation_count":0,"is_preprint":false},{"pmid":"41003840","id":"PMC_41003840","title":"Ruderal Tithonia diversifolia inclusion in sheep diets: impacts on digestibility and greenhouse gas emissions.","date":"2025","source":"Tropical animal health and production","url":"https://pubmed.ncbi.nlm.nih.gov/41003840","citation_count":0,"is_preprint":false},{"pmid":"6264424","id":"PMC_6264424","title":"Human glomerulonephritis and persistent non-polio enterovirus infection.","date":"1980","source":"Proceedings of the European Dialysis and Transplant Association. European Dialysis and Transplant Association","url":"https://pubmed.ncbi.nlm.nih.gov/6264424","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":31539,"output_tokens":2596,"usd":0.066779,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9807,"output_tokens":2776,"usd":0.059217,"stage2_stop_reason":"end_turn"},"total_usd":0.125996,"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\": 1997,\n      \"finding\": \"GYG2 (glycogenin-2/GN-2) is a self-glucosylating protein that initiates glycogen biosynthesis. When expressed in E. coli or COS cells, GYG2 is enzymatically active in self-glucosylation assays, and the self-glucosylated GYG2 product can be elongated by skeletal muscle glycogen synthase. In H4IIEC3 hepatoma cells, most GYG2 is present as free protein but some is covalently associated with glycogen fractions, released only by alpha-amylase treatment. GYG2 is expressed preferentially in liver, heart, and pancreas, and multiple isoforms (GN-2alpha, GN-2beta, GN-2gamma) arise from alternative splicing.\",\n      \"method\": \"Expression in E. coli and COS cells; in vitro self-glucosylation assay; elongation assay with skeletal muscle glycogen synthase; immunoblotting with anti-GN-2 antibodies; subcellular fractionation with alpha-amylase treatment in H4IIEC3 hepatoma cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro enzymatic reconstitution (self-glucosylation) in two expression systems plus functional elongation assay, replicated across cell-based and biochemical contexts in a single rigorous study\",\n      \"pmids\": [\"9346895\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"The human GYG2 gene spans more than 46 kb, contains 11 exons, and alternative exon usage explains the observed diversity in GYG2 cDNA sequences. The gene was localized to Xp22.3 by fluorescence in situ hybridization (FISH), outside pseudoautosomal region PAR1 but in a region of X-Y shared genes. An inactive remnant of GYG2 consisting of exons 1–3 may be present on the Y chromosome.\",\n      \"method\": \"Genomic cloning; exon structure analysis; FISH mapping; STS mapping\",\n      \"journal\": \"Gene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct chromosomal localization by FISH with genomic clone, supported by STS mapping; gene structure determined by cloning and sequencing\",\n      \"pmids\": [\"10721716\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Evidence strongly suggests that a second glycogenin gene (GYG2 ortholog) does not exist in rodents, indicating that GYG2 is likely primate-specific. Attempts to generate rodent reagents were unsuccessful and no rodent GYG2 sequence could be identified, suggesting differential regulation of glycogen initiation between rodents and primates.\",\n      \"method\": \"Sequence database searches; failure to generate rodent-reactive GYG2 reagents (negative result)\",\n      \"journal\": \"IUBMB life\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — negative finding supported by multiple failed experimental approaches across a focused study; relevant mechanistic implication for species-specificity of GYG2\",\n      \"pmids\": [\"11463169\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"GYG2 is subject to X chromosome inactivation (XCI) in normal human fibroblasts, as determined by allele-specific expression analysis and DNA methylation profiling of its 5' end. This contrasts with reports in rodent/human somatic cell hybrids where it appeared to escape XCI, indicating that hybrid cell systems are not adequate for studying GYG2 epigenotype.\",\n      \"method\": \"Allele-specific expression analysis using human fibroblasts with skewed XCI; DNA methylation profiling of the 5' end of GYG2\",\n      \"journal\": \"Epigenetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — two orthogonal methods (allele-specific expression and methylation profiling), single lab, direct epigenetic mechanism established\",\n      \"pmids\": [\"19684479\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"A hemizygous missense mutation in GYG2 (c.665G>C, p.W222S) abolishes the self-glucosylation activity of GYG2 in vitro. Structural modeling indicated the mutation destabilizes the protein. The mutation was identified in male siblings with Leigh syndrome, suggesting a possible link between GYG2 dysfunction and this neurodegenerative disorder.\",\n      \"method\": \"Whole exome sequencing; in vitro self-glucosylation assay of wild-type vs. mutant GYG2; structural modeling\",\n      \"journal\": \"Human genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro enzymatic assay directly demonstrating loss of self-glucosylation activity for the mutant, combined with structural modeling; single lab but two orthogonal approaches (biochemical assay + structural analysis)\",\n      \"pmids\": [\"24100632\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Complete deletion of GYG2 in hemizygous males does not result in overt impairment of liver glycogen synthesis or glucagon-stimulated glucose release. Liver biopsies from GYG2-deletion carriers showed the presence of both alpha- and beta-glycogen by electron microscopy, and GYG1 (glycogenin-1) mRNA was detected in liver. This indicates GYG2 is dispensable for liver glycogen synthesis, likely because GYG1 compensates.\",\n      \"method\": \"Identification of 102-kb GYG2 deletion by copy number variation analysis; glucagon stimulation tests in deletion carriers vs. controls; liver biopsy with light and electron microscopy; RT-PCR for GYG1 and GYG2 mRNA in liver\",\n      \"journal\": \"The Journal of clinical endocrinology and metabolism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal approaches (genetic, physiological, histological, molecular) in human loss-of-function subjects; finding independently supported across two families\",\n      \"pmids\": [\"25751106\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"GYG2 exhibits minimal autoglycosylation activity compared to GYG1 and acts as a suppressor of glycogen formation rather than an initiator. GYG2 coordinates with GYG1 to regulate glycogen synthase activity and glycogen assembly in a cell-type-dependent manner, modulating glucose metabolic pathways to maintain cellular glucose homeostasis.\",\n      \"method\": \"Cellular models; structural biology; biochemical analyses including autoglycosylation assays comparing GYG1 and GYG2\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — multiple orthogonal methods (structural biology, biochemical assays, cellular models) in a single rigorous study establishing a mechanistically distinct role for GYG2\",\n      \"pmids\": [\"40670355\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"A 114-kb deletion on the X chromosome spanning XG exons 4–10 and the downstream GYG2 gene was identified in anti-Xga makers, defining this deletion as the genetic basis of the Xgnull phenotype. Males were hemizygous and the female likely homozygous for this deletion. The deletion breakpoint involves a heterogeneous LTR6B sequence.\",\n      \"method\": \"Exon sequencing; PCR with deletion-specific primers; Sanger sequencing of recombination junctions; bioinformatics; analysis of genomic and cell-free DNA\",\n      \"journal\": \"Transfusion\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct PCR and sequencing demonstrated deletion spanning GYG2; mechanistic implication for GYG2's chromosomal context, single lab\",\n      \"pmids\": [\"30938838\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In VSV-M51-infected glioma cells, GYG2 expression is downregulated after oncolytic virus infection. Loss-of-function experiments showed that downregulating GYG2 inhibits glioma cell growth and facilitates tumor cell apoptosis, while GYG2 gain-of-function promotes cell survival. VSV-M51 infection promotes glioma cell apoptosis by downregulating GYG2, identifying an anti-apoptotic role for GYG2 in glioma.\",\n      \"method\": \"siRNA knockdown and overexpression (loss- and gain-of-function); rescue studies; qRT-PCR; analysis of glioma datasets (GSE136330, GSE166914, TCGA); apoptosis assays in VSV-M51-infected cells\",\n      \"journal\": \"BMC cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss- and gain-of-function with rescue experiments establishing GYG2's anti-apoptotic role, single lab, two orthogonal functional approaches\",\n      \"pmids\": [\"41350820\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"GYG2 (glycogenin-2) is an X-linked, primate-specific self-glucosylating protein that initiates glycogen biosynthesis preferentially in liver, heart, and pancreas; it exhibits minimal autoglycosylation activity compared to GYG1 and acts as a suppressor of glycogen formation, coordinating with GYG1 to regulate glycogen synthase activity and cellular glucose homeostasis in a cell-type-dependent manner, while a missense mutation (p.W222S) abolishes its self-glucosylation activity and complete gene deletion in humans is compensated by GYG1 in liver.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"GYG2 (glycogenin-2) is a self-glucosylating protein originally characterized as an initiator of glycogen biosynthesis, expressed preferentially in liver, heart, and pancreas, with multiple isoforms arising from alternative splicing [#0]. In vitro it autoglucosylates and the resulting product serves as a primer that is elongated by glycogen synthase [#0]. The gene maps to Xp22.3, is subject to X chromosome inactivation, and appears to be primate-specific, with no functional ortholog in rodents [#1, #2, #3]. More recent structural and biochemical work revises the simple initiator model: GYG2 exhibits minimal autoglycosylation activity relative to GYG1 and acts as a suppressor of glycogen formation, coordinating with GYG1 to modulate glycogen synthase activity and glycogen assembly in a cell-type-dependent manner to maintain cellular glucose homeostasis [#6]. Consistent with a functional redundancy with GYG1, complete GYG2 deletion in hemizygous human males does not impair liver glycogen synthesis, as GYG1 compensates [#5]. A hemizygous missense mutation (p.W222S) abolishes GYG2 self-glucosylation activity in vitro and destabilizes the protein, and was identified in male siblings with Leigh syndrome [#4]. In glioma cells, GYG2 has a separable anti-apoptotic, pro-survival role: its downregulation upon oncolytic VSV-M51 infection promotes tumor cell apoptosis [#8].\",\n  \"teleology\": [\n    {\n      \"year\": 1997,\n      \"claim\": \"Established that GYG2 is an enzymatically active self-glucosylating protein capable of initiating glycogen synthesis, defining its core biochemical activity and tissue distribution.\",\n      \"evidence\": \"Expression in E. coli and COS cells with in vitro self-glucosylation and glycogen synthase elongation assays; fractionation in H4IIEC3 hepatoma cells\",\n      \"pmids\": [\"9346895\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not establish physiological contribution relative to GYG1\", \"Functional role of distinct splice isoforms unresolved\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Defined the genomic structure and X-linked chromosomal location of GYG2, placing it in an X-Y shared gene region at Xp22.3.\",\n      \"evidence\": \"Genomic cloning, exon structure analysis, and FISH/STS mapping\",\n      \"pmids\": [\"10721716\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of X-Y shared context not addressed\", \"Y-chromosome remnant activity not tested\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Indicated GYG2 is primate-specific with no rodent ortholog, implying species differences in glycogen initiation regulation.\",\n      \"evidence\": \"Sequence database searches and failed generation of rodent-reactive reagents (negative result)\",\n      \"pmids\": [\"11463169\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Negative finding limited by database completeness at the time\", \"Does not explain functional consequence of primate-specificity\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Determined that GYG2 undergoes X chromosome inactivation in normal fibroblasts, correcting prior hybrid-cell reports of XCI escape.\",\n      \"evidence\": \"Allele-specific expression analysis in skewed-XCI fibroblasts and 5' DNA methylation profiling\",\n      \"pmids\": [\"19684479\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Tissue-specificity of XCI status not assessed\", \"Dosage consequences for glycogen metabolism unexplored\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Linked a specific missense mutation to loss of GYG2 catalytic activity and a human neurodegenerative phenotype.\",\n      \"evidence\": \"Whole exome sequencing of Leigh syndrome siblings, in vitro self-glucosylation assay of WT vs. p.W222S mutant, and structural modeling\",\n      \"pmids\": [\"24100632\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Causal link between GYG2 loss and Leigh syndrome not proven by rescue or animal model\", \"Single family\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Showed GYG2 is dispensable for liver glycogen synthesis in humans, demonstrating GYG1 compensation in vivo.\",\n      \"evidence\": \"CNV-identified 102-kb GYG2 deletion carriers analyzed by glucagon stimulation tests, liver biopsy EM, and RT-PCR for GYG1/GYG2\",\n      \"pmids\": [\"25751106\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not address GYG2 function in heart or pancreas\", \"Compensation mechanism beyond GYG1 presence not dissected\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Characterized the genomic deletion context of GYG2 within the XG-region Xgnull phenotype, clarifying its chromosomal neighborhood.\",\n      \"evidence\": \"Exon sequencing, deletion-specific PCR, and Sanger sequencing of recombination junctions\",\n      \"pmids\": [\"30938838\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Metabolic consequence of the GYG2-spanning deletion not assessed\", \"Single lab\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Revised the functional model: GYG2 has minimal autoglycosylation and acts as a suppressor rather than initiator of glycogen formation, coordinating with GYG1 to regulate glycogen synthase and glucose homeostasis.\",\n      \"evidence\": \"Structural biology, biochemical autoglycosylation assays comparing GYG1 and GYG2, and cellular models\",\n      \"pmids\": [\"40670355\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis of suppression versus initiation not fully mapped\", \"Cell-type determinants of coordination with GYG1 unresolved\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identified a context-specific anti-apoptotic role for GYG2 in glioma, separable from its glycogen-metabolic function.\",\n      \"evidence\": \"siRNA knockdown/overexpression with rescue, qRT-PCR, apoptosis assays in VSV-M51-infected glioma cells, and tumor dataset analysis\",\n      \"pmids\": [\"41350820\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular pathway linking GYG2 to apoptosis suppression not defined\", \"Single lab; in vivo tumor relevance untested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How GYG2's suppressor activity and its catalytic/structural features mechanistically reconcile with its earlier-described initiator activity and its anti-apoptotic role in cancer remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified mechanism connecting glycogen suppression to apoptosis regulation\", \"Tissue-specific physiological role in heart and pancreas uncharacterized\", \"No structural explanation for switch between initiation and suppression\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [0, 4, 6]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [0, 5, 6]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"GYG1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}