{"gene":"COL6A3","run_date":"2026-04-28T17:28:53","timeline":{"discoveries":[{"year":2002,"finding":"The C5 domain of the COL6A3-encoded α3(VI) collagen chain is cleaved off from type VI collagen fibrils immediately after secretion; immunostaining and immunoelectron microscopy in human articular cartilage showed C5 domain localization in the cytoplasm and immediate pericellular matrix but not in the mature pericellular type VI collagen matrix, demonstrating post-secretion proteolytic processing.","method":"Immunostaining, confocal laser-scanning microscopy, immunoelectron microscopy, double-labeling experiments in human articular cartilage","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 2 — direct localization experiment with functional consequence, multiple orthogonal imaging methods, single lab","pmids":["11785962"],"is_preprint":false},{"year":2002,"finding":"Homozygous loss-of-function and splice-site mutations in COL6A3 cause Ullrich congenital muscular dystrophy (UCMD) with absence or partial reduction of collagen VI in muscle and fibroblasts, establishing COL6A3 as a disease-causing gene for UCMD via collagen VI deficiency.","method":"Genome-wide linkage mapping, mutation analysis, muscle biopsy immunostaining, mRNA transcript analysis","journal":"American journal of human genetics","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis plus functional protein analysis in patient tissue, replicated across three families","pmids":["11992252"],"is_preprint":false},{"year":1998,"finding":"A missense mutation (Gly→Glu) in the N2 von Willebrand factor type A domain of the COL6A3-encoded α3(VI) collagen chain causes autosomal dominant Bethlem myopathy, demonstrating that the N-terminal globular domain of α3(VI) is functionally critical for collagen VI integrity in muscle.","method":"Genetic linkage, Sanger sequencing, segregation analysis in a large pedigree (19 affected members)","journal":"Human molecular genetics","confidence":"Medium","confidence_rationale":"Tier 2 — mutation segregation with functional domain assignment, single lab","pmids":["9536084"],"is_preprint":false},{"year":1999,"finding":"A de novo Gly→Arg substitution in the triple-helical domain of the COL6A3-encoded α3(VI) chain disrupts the collagen VI triple helix structure and causes Bethlem myopathy, establishing that glycine substitutions in the triple helix are pathogenic dominant-negative mutations.","method":"Clinical characterization, molecular mutation identification, Sanger sequencing in a two-generation family","journal":"Neuromuscular disorders","confidence":"Medium","confidence_rationale":"Tier 3 — mutation identification with structural inference, single lab","pmids":["10399756"],"is_preprint":false},{"year":2008,"finding":"The chromosomal translocation t(1;2)(p13;q37) generates COL6A3-CSF1 fusion transcripts in tenosynovial giant cell tumors, where the strong COL6A3 promoter drives overexpression of CSF1; RT-PCR identified in-frame and out-of-frame fusion transcripts, though the pathogenetic mechanism remains incompletely defined.","method":"RT-PCR on six TGCT cases with t(1;2) translocation","journal":"Genes, chromosomes & cancer","confidence":"Medium","confidence_rationale":"Tier 2 — direct detection of fusion transcripts with molecular characterization, single lab","pmids":["17918257"],"is_preprint":false},{"year":2013,"finding":"Mice expressing a very low level of non-functional α3(VI) collagen chain (Col6a3 mutant) are deficient in extracellular collagen VI microfibrils, exhibit decreased muscle mass and contractile force, and display ultrastructurally abnormal collagen fibrils in tendon but not cornea, demonstrating a tissue-specific role of α3(VI) in collagen I fibrillogenesis and muscle function.","method":"Mouse knockout model characterization: ultrastructural analysis, muscle contractile force measurement, immunofluorescence, electron microscopy","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — clean KO with multiple defined cellular/ultrastructural phenotypes, multiple orthogonal methods","pmids":["23564457"],"is_preprint":false},{"year":2014,"finding":"Heterozygous deletion of exon 16 in Col6a3 produces a mutant α3(VI) chain with an in-frame 54 bp triple-helical deletion that exerts a dominant-negative effect on collagen VI microfibrillar assembly in fibroblast biosynthetic studies, causing histopathologic myopathy, mitochondrial and sarcoplasmic reticulum ultrastructural alterations in muscle, and abnormal collagen fibrils in tendons.","method":"Mouse knock-in model, biosynthetic studies in mutant fibroblasts, histopathology, electron microscopy, muscle contractile function assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 — reconstitution-level biosynthetic assay demonstrating dominant-negative mechanism, multiple orthogonal phenotypic analyses","pmids":["24563484"],"is_preprint":false},{"year":2015,"finding":"Recessive loss-of-function mutations in COL6A3, particularly affecting exon 41, cause early-onset isolated dystonia (DYT27) with neurodevelopmental deficits; suppression of the exon 41 ortholog in zebrafish caused deficits in axonal outgrowth, whereas suppression of other exons phenocopied collagen deposition mutants, indicating an exon 41-specific neuronal function of α3(VI) collagen.","method":"Whole-exome sequencing, genetic screening of dystonia cohort, zebrafish morpholino-based in-frame deletion experiments, mRNA expression analysis in mouse brain","journal":"American journal of human genetics","confidence":"High","confidence_rationale":"Tier 2 — epistasis via zebrafish model with specific phenotypic readout, replicated across three pedigrees with orthogonal human genetics","pmids":["26004199"],"is_preprint":false},{"year":2011,"finding":"COL6A3 undergoes tumor-specific alternative splicing in pancreatic ductal adenocarcinoma, with consistent inclusion of exons 3 and 6 in tumor versus adjacent tissue, and exclusive tumor-specific inclusion of exon 4; COL6A3 protein is upregulated in the desmoplastic stroma surrounding malignant ducts.","method":"RT-PCR with exon-specific primers on paired PDA-normal tissue (n=18), Western blot, immunohistochemistry, xenograft and transgenic PDA animal models","journal":"Surgery","confidence":"Medium","confidence_rationale":"Tier 2 — multiple orthogonal methods confirming tumor-specific splicing and protein localization, single lab","pmids":["21719059"],"is_preprint":false},{"year":2017,"finding":"Gapmer antisense oligonucleotides selectively suppress the mutant COL6A3 allele (heterozygous 18-nt deletion in exon 15) at both pre-mRNA and mRNA levels via RNase H-mediated cleavage, and silencing the mutant allele increases deposition of collagen VI protein into the extracellular matrix in UCMD patient-derived fibroblasts, restoring functional protein production.","method":"Gapmer AON allele-specific silencing, RT-PCR transcript analysis, immunofluorescence of collagen VI matrix in patient fibroblasts","journal":"Molecular therapy. Nucleic acids","confidence":"High","confidence_rationale":"Tier 2 — clean allele-specific knockdown with direct matrix deposition readout, multiple methods","pmids":["28918041"],"is_preprint":false},{"year":2014,"finding":"siRNA targeting a dominant COL6A3 exon 16-skipping mutation selectively suppresses mutant allele expression and protein from a reporter construct without affecting the wild-type allele, and treatment of UCMD fibroblasts with these siRNAs considerably improved the quantity and quality of the collagen VI matrix.","method":"siRNA allele-specific silencing, semi-quantitative and quantitative RT-PCR, reporter assay in HEK293T cells, confocal microscopy of collagen VI matrix in patient fibroblasts","journal":"Molecular therapy. Nucleic acids","confidence":"High","confidence_rationale":"Tier 2 — allele-specific mechanism validated in reporter assay and patient cells with multiple methods","pmids":["24518369"],"is_preprint":false},{"year":2018,"finding":"COL6A3-derived endotrophin (ETP, cleavage product of the C5 domain) induces JNK-dependent hepatocyte apoptosis and activates nonparenchymal cells to drive hepatic inflammation and fibrosis in chronic liver disease; neutralizing antibodies against ETP suppressed these pathological consequences.","method":"In vitro ETP treatment of hepatocytes, JNK pathway analysis, neutralizing antibody treatment in chronic liver disease models","journal":"The Journal of pathology","confidence":"Medium","confidence_rationale":"Tier 2 — loss-of-function (neutralizing antibody) with defined signaling pathway readout, single lab","pmids":["30246318"],"is_preprint":false},{"year":2014,"finding":"COL6A3 expression in adipocytes is regulated by PPARγ: PPARG knockdown in developing adipocytes increased COL6A3 mRNA 1.5-fold, and COL6A3 mRNA was 2.8-fold higher in small compared to large adipocytes, linking PPARγ-mediated adipocyte development to COL6A3 transcriptional control.","method":"PPARG knockdown in primary human adipocytes, qPCR, euglycemic-hyperinsulinemic clamp for insulin resistance phenotyping","journal":"Obesity (Silver Spring, Md.)","confidence":"Medium","confidence_rationale":"Tier 2 — direct knockdown experiment with transcriptional readout, single lab","pmids":["24719315"],"is_preprint":false},{"year":2015,"finding":"Leptin treatment causes a dose-dependent decrease in COL6A3 expression in human adipose tissue, identifying a direct paracrine leptin signaling pathway that regulates extracellular matrix composition; insulin and glucose had no effect on COL6A3 expression.","method":"Leptin/insulin/glucose treatment of human adipose tissue explants, qPCR, comparison across depots and weight-loss conditions","journal":"Endocrinology","confidence":"Medium","confidence_rationale":"Tier 2 — direct pharmacological regulation experiment with dose-response, single lab","pmids":["25337653"],"is_preprint":false},{"year":2016,"finding":"COL6A3 knockdown in immortalized human preadipocytes increased triglyceride content, lipolysis, insulin-induced Akt phosphorylation, and adipogenic gene expression, while also decreasing basal MCP1 (CCL2) expression and abrogating TNF-α- and LPS-induced MCP1 induction; matrix metalloproteinase-11 treatment reduced COL6A3 protein and phenocopied MCP1 suppression, placing COL6A3 upstream of MCP1 inflammatory signaling in adipocytes.","method":"Stable shRNA knockdown in human adipocyte cell lines, MMP-11 treatment, flow cytometry, ELISA, THP1 macrophage co-culture assay","journal":"Obesity (Silver Spring, Md.)","confidence":"Medium","confidence_rationale":"Tier 2 — stable KD with multiple functional readouts and pharmacological validation, single lab","pmids":["27312141"],"is_preprint":false},{"year":2020,"finding":"The homeobox transcription factor PRRX1 directly transactivates the endogenous human COL6A3 promoter; PRRX1 knockdown reduced COL6A3 mRNA in human and mouse adipose cells, and stable PRRX1 overexpression in 3T3-L1 cells induced Col6a3 mRNA threefold after adipogenic induction, while TNF-α decreased PRRX1-mediated Col6a3 transactivation.","method":"PRRX1 knockdown and overexpression in adipose cells, reporter construct with endogenous COL6A3 promoter, qPCR, transcriptome correlation across multiple clinical cohorts","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 2 — direct promoter transactivation assay combined with KD and OE with orthogonal methods, replicated across cohorts","pmids":["33214660"],"is_preprint":false},{"year":2023,"finding":"COL6A3 knockdown induces transcriptional changes overlapping the majority of experimental senescence models, with cell-cycle arrest linked to modulation of DREAM complex-targeted genes, identifying COL6A3 as a candidate SASP factor and potential driver of senescence in human tissues.","method":"COL6A3 knockdown followed by transcriptomic analysis, integration with 10 senescence cell models and 224 multi-tissue gene co-expression network from ~600 CAD patients","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 — KD with transcriptomic readout integrated across multiple models, single experimental perturbation","pmids":["37938972"],"is_preprint":false},{"year":2024,"finding":"A damaging COL6A3 variant introduced by CRISPR-Cas9 into human iPSC-derived neocartilage organoids results in significantly lower binding between the pericellular matrix proteins collagen VI and fibronectin, provokes an osteoarthritic chondrocyte state, and abolishes the characteristic inflammatory signaling response (PTGS2, PECAM1, ADAMTS5) to hyperphysiological mechanical loading; the lncRNA MIR31HG was identified as a key regulator of this response.","method":"CRISPR-Cas9 genome engineering in iPSC-derived neocartilage organoids, multi-omics (mRNA and lncRNA), mechanical loading assay, protein binding assay (COLVI–FN interaction)","journal":"Advanced science","confidence":"High","confidence_rationale":"Tier 1–2 — CRISPR engineering with reconstituted organoid model, multi-omics and protein binding assay, mechanically defined functional readout","pmids":["39021299"],"is_preprint":false},{"year":2020,"finding":"Mutations in COL6A3 p.Val86Ala and p.Arg689Cys cause abnormal intracellular retention of the mutant COL6A3 protein and decrease cellular resistance to oxidative stress through an enhanced endoplasmic reticulum stress response, establishing a disease mechanism for COL6A3 mutation-associated Peters' anomaly.","method":"Panel and whole-exome sequencing, immunofluorescence of mutant protein localization, ER stress assay, oxidative stress resistance assay in patient-derived and transfected cells","journal":"Frontiers in cell and developmental biology","confidence":"Medium","confidence_rationale":"Tier 2 — direct functional assay of mutant protein with defined cellular phenotypes, single lab","pmids":["33304895"],"is_preprint":false},{"year":2025,"finding":"ETP-specific knockout (ETPKO) mice, which selectively ablate the endotrophin cleavage product of COL6A3 while preserving Col6a3 expression, show significantly attenuated kidney fibrosis following ischemia-reperfusion injury, establishing endotrophin as a key driver of fibrosis independent of full-length COL6A3.","method":"CRISPR-based conditional ETP knockout mouse model with Cre-mediated recombination, unilateral/bilateral renal ischemia-reperfusion injury, mRNA quantification, fibrosis histopathology","journal":"bioRxiv","confidence":"High","confidence_rationale":"Tier 1–2 — novel conditional KO model with specific ablation of cleavage product and defined disease phenotype, rigorous genetic controls","pmids":[],"is_preprint":true},{"year":2025,"finding":"COL6A3 exon 4 alternative splicing is specifically induced by TGF-β in skin fibroblasts undergoing myofibroblast differentiation, constituting part of a 5-ASE signature validated by ddPCR/AS-PCR and retrieved in multiple independent TGF-β-stimulated lung and skin fibroblast RNA-seq datasets.","method":"RNA-seq, ddPCR, AS-PCR validation in primary skin fibroblasts with TGF-β treatment, replicated in publicly available datasets","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 — TGF-β-regulated splicing event validated by multiple methods and replicated in independent datasets; preprint","pmids":[],"is_preprint":true},{"year":2025,"finding":"Mendelian randomization and colocalization analyses show that genetically elevated COL6A3 (particularly its endotrophin product) causally increases coronary artery disease risk, and that an aortic eQTL for COL6A3 colocalizes with plasma pQTL and AAA risk signals, suggesting a causal pathway from genetic variation in aortic wall COL6A3 expression to extracellular matrix remodeling and vascular disease.","method":"Two-step proteome-wide Mendelian randomization, Bayesian colocalization, epigenomics, single-cell RNA sequencing, plasma endotrophin measurement after fat reduction","journal":"Nature genetics","confidence":"Medium","confidence_rationale":"Tier 2 — multi-method causal inference with colocalization and functional endpoint, but primarily genetic/epidemiologic rather than direct mechanistic experiment","pmids":["39856218"],"is_preprint":false},{"year":2026,"finding":"A damaging COL6A3 variant in human iPSC-derived chondrocytes results in lower pericellular matrix elastic modulus, reduced key matrix protein expression, heightened osmotically-induced calcium signaling (consistent with reduced PCM modulus), reduced anabolic response to TRPV4 activation, disrupted circadian rhythms with increased BMAL1 expression, and exacerbated catabolic response to IL-1, demonstrating that COL6A3 is required for normal chondrocyte mechanotransduction via the pericellular matrix.","method":"CRISPR-Cas9 genome editing in hiPSC-derived chondrocytes, AFM for PCM elastic modulus, calcium imaging, RNA-sequencing, matrix biosynthesis assay, circadian rhythm analysis","journal":"Stem cell research & therapy","confidence":"High","confidence_rationale":"Tier 1–2 — isogenic CRISPR model with reconstitution-level mechanobiological assays and multi-omics, single lab","pmids":["41692747"],"is_preprint":false}],"current_model":"COL6A3 encodes the α3(VI) chain of type VI collagen, which is required for assembly and extracellular deposition of collagen VI microfibrils; its C-terminal C5 domain is proteolytically cleaved after secretion to generate endotrophin, a bioactive peptide that drives fibrosis and cancer progression via TGF-β-like signaling; loss-of-function mutations cause collagen VI-deficient myopathies (Ullrich/Bethlem spectrum), while exon 41-specific mutations cause recessive isolated dystonia (DYT27) through a distinct neuronal mechanism involving axonal outgrowth deficits; α3(VI) is also essential for pericellular matrix integrity and mechanotransduction in chondrocytes, and its expression is transcriptionally regulated by PPARγ, PRRX1, leptin, and TGF-β-induced alternative splicing."},"narrative":{"teleology":[{"year":1998,"claim":"Establishing that mutations in the α3(VI) globular domains cause Bethlem myopathy answered whether COL6A3 itself could be a disease gene for heritable myopathies and implicated the N-terminal vWFA domain as functionally critical.","evidence":"Missense mutation segregation in a large Bethlem myopathy pedigree","pmids":["9536084"],"confidence":"Medium","gaps":["No biochemical demonstration of how the N2 domain mutation disrupts assembly","Single pedigree"]},{"year":2002,"claim":"Demonstrating that the C5 domain is proteolytically cleaved immediately after collagen VI secretion revealed a previously unknown post-secretion processing step and identified a bioactive fragment later termed endotrophin.","evidence":"Immunoelectron microscopy and double-label immunostaining in human articular cartilage","pmids":["11785962"],"confidence":"High","gaps":["Protease responsible for C5 cleavage not identified","Biological function of the released C5 fragment not yet tested"]},{"year":2002,"claim":"Identifying homozygous loss-of-function COL6A3 mutations in Ullrich congenital muscular dystrophy families established the causal link between α3(VI) chain deficiency and severe congenital myopathy.","evidence":"Genome-wide linkage, mutation analysis, and collagen VI immunostaining in muscle biopsies from three UCMD families","pmids":["11992252"],"confidence":"High","gaps":["Molecular mechanism by which collagen VI absence damages muscle fibers not defined","Genotype-phenotype correlation across mutation types incomplete"]},{"year":2013,"claim":"Characterization of a Col6a3-deficient mouse model demonstrated that α3(VI) is required for collagen VI microfibril deposition in vivo and revealed tissue-specific roles in muscle contractile function and tendon collagen I fibrillogenesis.","evidence":"Mouse knockout with ultrastructural analysis, immunofluorescence, and muscle contractile force measurement","pmids":["23564457"],"confidence":"High","gaps":["Why corneal collagen fibrils are unaffected despite collagen VI expression not explained","Downstream signaling consequences of microfibril loss not characterized"]},{"year":2014,"claim":"A knock-in mouse carrying an in-frame triple-helical deletion in Col6a3 proved the dominant-negative mechanism of Bethlem myopathy mutations and showed that mutant α3(VI) chains are incorporated into defective trimers that poison microfibril assembly.","evidence":"Mouse knock-in model with fibroblast biosynthetic studies, histopathology, and electron microscopy","pmids":["24563484"],"confidence":"High","gaps":["Stoichiometric threshold for dominant-negative poisoning not quantified","Whether all triple-helical glycine mutations act identically is unknown"]},{"year":2014,"claim":"Allele-specific siRNA silencing of a dominant COL6A3 mutation restored collagen VI matrix deposition in UCMD patient fibroblasts, providing proof-of-concept that selective knockdown of the mutant allele is a viable therapeutic strategy.","evidence":"siRNA targeting mutation-specific sequence in patient fibroblasts and HEK293T reporter assay","pmids":["24518369"],"confidence":"High","gaps":["In vivo delivery and efficacy not tested","Long-term matrix quality restoration not assessed"]},{"year":2015,"claim":"Discovery that exon 41-specific COL6A3 mutations cause recessive isolated dystonia (DYT27) with axonal outgrowth deficits in zebrafish revealed a neuronal function of α3(VI) distinct from its structural role in the extracellular matrix.","evidence":"Whole-exome sequencing in dystonia pedigrees plus zebrafish morpholino knockdown of exon 41 versus other exons","pmids":["26004199"],"confidence":"High","gaps":["Molecular mechanism linking exon 41 to axonal outgrowth unknown","Whether collagen VI is assembled in neurons or acts cell-non-autonomously not resolved"]},{"year":2018,"claim":"Showing that endotrophin (the C5 cleavage product) induces JNK-dependent hepatocyte apoptosis and drives hepatic fibrosis, suppressible by neutralizing antibodies, established endotrophin as an independent signaling molecule with pro-fibrotic and pro-inflammatory activity.","evidence":"In vitro endotrophin treatment of hepatocytes and neutralizing antibody intervention in chronic liver disease models","pmids":["30246318"],"confidence":"Medium","gaps":["Receptor for endotrophin not identified","Whether endotrophin signals through TGF-β pathway components or an independent pathway not fully resolved"]},{"year":2020,"claim":"Identification of PRRX1 as a direct transcriptional activator of COL6A3 established a transcription factor–extracellular matrix axis controlling collagen VI levels in adipose tissue, modulated by inflammatory signals such as TNF-α.","evidence":"PRRX1 knockdown and overexpression with endogenous COL6A3 promoter reporter assay in human and mouse adipose cells","pmids":["33214660"],"confidence":"High","gaps":["PRRX1 binding site on COL6A3 promoter not mapped at base-pair resolution","Whether PRRX1 regulation extends beyond adipose tissue not tested"]},{"year":2024,"claim":"CRISPR-engineered COL6A3 loss in iPSC-derived neocartilage organoids showed that collagen VI is required for fibronectin binding, mechanical load sensing, and suppression of an osteoarthritic chondrocyte state, placing COL6A3 as a central node in cartilage mechanotransduction.","evidence":"CRISPR-Cas9 in iPSC-derived organoids with multi-omics, protein binding assay, and mechanical loading","pmids":["39021299"],"confidence":"High","gaps":["Whether COL6A3 loss-of-function is sufficient to initiate osteoarthritis in vivo not shown","Signaling intermediates between pericellular matrix disruption and inflammatory gene induction not fully mapped"]},{"year":2025,"claim":"Mendelian randomization provided causal genetic evidence that elevated COL6A3/endotrophin increases coronary artery disease risk through aortic wall expression, linking the pro-fibrotic endotrophin pathway to cardiovascular disease at the population level.","evidence":"Proteome-wide Mendelian randomization, Bayesian colocalization, plasma pQTL, and aortic eQTL analyses","pmids":["39856218"],"confidence":"Medium","gaps":["No direct experimental intervention confirming the causal chain in vascular tissue","Endotrophin receptor and downstream vascular signaling cascade remain unidentified"]},{"year":2026,"claim":"Isogenic COL6A3-mutant iPSC-derived chondrocytes showed that α3(VI) is required for pericellular matrix stiffness, TRPV4-mediated anabolic responses, and circadian clock regulation, deepening the mechanotransduction model to include ion channel function and temporal gene regulation.","evidence":"CRISPR-edited hiPSC chondrocytes with AFM, calcium imaging, RNA-seq, and circadian rhythm analysis","pmids":["41692747"],"confidence":"High","gaps":["Whether circadian disruption is primary or secondary to matrix softening not resolved","TRPV4 interaction with collagen VI pericellular matrix not structurally characterized"]},{"year":null,"claim":"The receptor and direct signaling pathway by which endotrophin exerts its pro-fibrotic and pro-apoptotic effects remain unidentified, and the molecular basis of the exon 41-specific neuronal function of α3(VI) is unexplained.","evidence":"","pmids":[],"confidence":"Low","gaps":["Endotrophin receptor unknown","Exon 41-encoded domain's neuronal interactors not identified","Protease responsible for C5 domain cleavage not identified"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[5,6,17,22]},{"term_id":"GO:0098631","term_label":"cell adhesion mediator activity","supporting_discovery_ids":[17,22]}],"localization":[{"term_id":"GO:0031012","term_label":"extracellular matrix","supporting_discovery_ids":[0,5,6,9,10,17,22]},{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[0,11,19]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[18]}],"pathway":[{"term_id":"R-HSA-1474244","term_label":"Extracellular matrix organization","supporting_discovery_ids":[0,5,6,9,10,17,22]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[11,14,21]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[1,2,7,18]}],"complexes":["type VI collagen heterotrimer (α1/α2/α3)"],"partners":["COL6A1","COL6A2","FN1","PRRX1","MIR31HG"],"other_free_text":[]},"mechanistic_narrative":"COL6A3 encodes the α3(VI) chain of type VI collagen, a major structural component of pericellular and extracellular matrices whose assembly, secretion, and post-secretion proteolytic processing are essential for tissue integrity across muscle, tendon, cartilage, adipose, and vascular compartments. The α3(VI) chain is required for collagen VI microfibril formation; loss-of-function mutations cause Ullrich congenital muscular dystrophy and Bethlem myopathy through deficient or dominant-negatively disrupted collagen VI deposition [PMID:11992252, PMID:24563484], while exon 41-specific mutations cause recessive isolated dystonia (DYT27) via a distinct neuronal mechanism involving axonal outgrowth deficits [PMID:26004199]. The C-terminal C5 domain is proteolytically cleaved after secretion to release endotrophin, a bioactive fragment that drives organ fibrosis through JNK-dependent apoptosis and inflammatory cell activation and contributes causally to cardiovascular disease risk [PMID:11785962, PMID:30246318, PMID:39856218]. In chondrocytes, COL6A3 maintains pericellular matrix mechanical properties and is required for normal mechanotransduction, TRPV4-mediated anabolic signaling, and circadian rhythm regulation; its loss provokes an osteoarthritic cellular state with exaggerated catabolic and inflammatory responses to mechanical and cytokine stimuli [PMID:39021299, PMID:41692747]."},"prefetch_data":{"uniprot":{"accession":"P12111","full_name":"Collagen alpha-3(VI) chain","aliases":[],"length_aa":3177,"mass_kda":343.7,"function":"Collagen VI acts as a cell-binding protein","subcellular_location":"Secreted, extracellular space, extracellular matrix","url":"https://www.uniprot.org/uniprotkb/P12111/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/COL6A3","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":[],"url":"https://opencell.sf.czbiohub.org/search/COL6A3","total_profiled":1310},"omim":[{"mim_id":"620728","title":"ULLRICH CONGENITAL MUSCULAR DYSTROPHY 1C; UCMD1C","url":"https://www.omim.org/entry/620728"},{"mim_id":"620726","title":"BETHLEM MYOPATHY 1C; BTHLM1C","url":"https://www.omim.org/entry/620726"},{"mim_id":"620725","title":"BETHLEM MYOPATHY 1B; BTHLM1B","url":"https://www.omim.org/entry/620725"},{"mim_id":"616471","title":"BETHLEM MYOPATHY 2; BTHLM2","url":"https://www.omim.org/entry/616471"},{"mim_id":"616411","title":"DYSTONIA 27; DYT27","url":"https://www.omim.org/entry/616411"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Endoplasmic reticulum","reliability":"Approved"},{"location":"Vesicles","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"smooth muscle","ntpm":391.7}],"url":"https://www.proteinatlas.org/search/COL6A3"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"P12111","domains":[],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P12111","model_url":"https://alphafold.ebi.ac.uk/files/AF-P12111-5-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P12111-5-F1-predicted_aligned_error_v6.png","plddt_mean":84.38},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=COL6A3","jax_strain_url":"https://www.jax.org/strain/search?query=COL6A3"},"sequence":{"accession":"P12111","fasta_url":"https://rest.uniprot.org/uniprotkb/P12111.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P12111/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P12111"}},"corpus_meta":[{"pmid":"11992252","id":"PMC_11992252","title":"Mutations in COL6A3 cause severe and mild phenotypes of Ullrich congenital muscular dystrophy.","date":"2002","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/11992252","citation_count":125,"is_preprint":false},{"pmid":"29143985","id":"PMC_29143985","title":"Silencing of COL1A2, COL6A3, and THBS2 inhibits gastric cancer cell proliferation, migration, and invasion while promoting apoptosis through the PI3k-Akt signaling pathway.","date":"2018","source":"Journal of cellular biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/29143985","citation_count":103,"is_preprint":false},{"pmid":"17918257","id":"PMC_17918257","title":"Molecular identification of COL6A3-CSF1 fusion transcripts in tenosynovial giant cell tumors.","date":"2008","source":"Genes, chromosomes & cancer","url":"https://pubmed.ncbi.nlm.nih.gov/17918257","citation_count":82,"is_preprint":false},{"pmid":"1981051","id":"PMC_1981051","title":"Mapping of Col3a1 and Col6a3 to proximal murine chromosome 1 identifies conserved linkage of structural protein genes between murine chromosome 1 and human chromosome 2q.","date":"1990","source":"Genomics","url":"https://pubmed.ncbi.nlm.nih.gov/1981051","citation_count":78,"is_preprint":false},{"pmid":"11785962","id":"PMC_11785962","title":"The C5 domain of Col6A3 is cleaved off from the Col6 fibrils immediately after secretion.","date":"2002","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/11785962","citation_count":75,"is_preprint":false},{"pmid":"30014607","id":"PMC_30014607","title":"Dermatofibrosarcoma protuberans with a novel COL6A3-PDGFD fusion gene and apparent predilection for breast.","date":"2018","source":"Genes, chromosomes & cancer","url":"https://pubmed.ncbi.nlm.nih.gov/30014607","citation_count":73,"is_preprint":false},{"pmid":"9536084","id":"PMC_9536084","title":"Missense mutation in a von Willebrand factor type A domain of the alpha 3(VI) collagen gene (COL6A3) in a family with Bethlem myopathy.","date":"1998","source":"Human molecular 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collagen fibrils immediately after secretion; immunostaining and immunoelectron microscopy in human articular cartilage showed C5 domain localization in the cytoplasm and immediate pericellular matrix but not in the mature pericellular type VI collagen matrix, demonstrating post-secretion proteolytic processing.\",\n      \"method\": \"Immunostaining, confocal laser-scanning microscopy, immunoelectron microscopy, double-labeling experiments in human articular cartilage\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct localization experiment with functional consequence, multiple orthogonal imaging methods, single lab\",\n      \"pmids\": [\"11785962\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Homozygous loss-of-function and splice-site mutations in COL6A3 cause Ullrich congenital muscular dystrophy (UCMD) with absence or partial reduction of collagen VI in muscle and fibroblasts, establishing COL6A3 as a disease-causing gene for UCMD via collagen VI deficiency.\",\n      \"method\": \"Genome-wide linkage mapping, mutation analysis, muscle biopsy immunostaining, mRNA transcript analysis\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis plus functional protein analysis in patient tissue, replicated across three families\",\n      \"pmids\": [\"11992252\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"A missense mutation (Gly→Glu) in the N2 von Willebrand factor type A domain of the COL6A3-encoded α3(VI) collagen chain causes autosomal dominant Bethlem myopathy, demonstrating that the N-terminal globular domain of α3(VI) is functionally critical for collagen VI integrity in muscle.\",\n      \"method\": \"Genetic linkage, Sanger sequencing, segregation analysis in a large pedigree (19 affected members)\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — mutation segregation with functional domain assignment, single lab\",\n      \"pmids\": [\"9536084\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"A de novo Gly→Arg substitution in the triple-helical domain of the COL6A3-encoded α3(VI) chain disrupts the collagen VI triple helix structure and causes Bethlem myopathy, establishing that glycine substitutions in the triple helix are pathogenic dominant-negative mutations.\",\n      \"method\": \"Clinical characterization, molecular mutation identification, Sanger sequencing in a two-generation family\",\n      \"journal\": \"Neuromuscular disorders\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — mutation identification with structural inference, single lab\",\n      \"pmids\": [\"10399756\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"The chromosomal translocation t(1;2)(p13;q37) generates COL6A3-CSF1 fusion transcripts in tenosynovial giant cell tumors, where the strong COL6A3 promoter drives overexpression of CSF1; RT-PCR identified in-frame and out-of-frame fusion transcripts, though the pathogenetic mechanism remains incompletely defined.\",\n      \"method\": \"RT-PCR on six TGCT cases with t(1;2) translocation\",\n      \"journal\": \"Genes, chromosomes & cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct detection of fusion transcripts with molecular characterization, single lab\",\n      \"pmids\": [\"17918257\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Mice expressing a very low level of non-functional α3(VI) collagen chain (Col6a3 mutant) are deficient in extracellular collagen VI microfibrils, exhibit decreased muscle mass and contractile force, and display ultrastructurally abnormal collagen fibrils in tendon but not cornea, demonstrating a tissue-specific role of α3(VI) in collagen I fibrillogenesis and muscle function.\",\n      \"method\": \"Mouse knockout model characterization: ultrastructural analysis, muscle contractile force measurement, immunofluorescence, electron microscopy\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with multiple defined cellular/ultrastructural phenotypes, multiple orthogonal methods\",\n      \"pmids\": [\"23564457\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Heterozygous deletion of exon 16 in Col6a3 produces a mutant α3(VI) chain with an in-frame 54 bp triple-helical deletion that exerts a dominant-negative effect on collagen VI microfibrillar assembly in fibroblast biosynthetic studies, causing histopathologic myopathy, mitochondrial and sarcoplasmic reticulum ultrastructural alterations in muscle, and abnormal collagen fibrils in tendons.\",\n      \"method\": \"Mouse knock-in model, biosynthetic studies in mutant fibroblasts, histopathology, electron microscopy, muscle contractile function assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — reconstitution-level biosynthetic assay demonstrating dominant-negative mechanism, multiple orthogonal phenotypic analyses\",\n      \"pmids\": [\"24563484\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Recessive loss-of-function mutations in COL6A3, particularly affecting exon 41, cause early-onset isolated dystonia (DYT27) with neurodevelopmental deficits; suppression of the exon 41 ortholog in zebrafish caused deficits in axonal outgrowth, whereas suppression of other exons phenocopied collagen deposition mutants, indicating an exon 41-specific neuronal function of α3(VI) collagen.\",\n      \"method\": \"Whole-exome sequencing, genetic screening of dystonia cohort, zebrafish morpholino-based in-frame deletion experiments, mRNA expression analysis in mouse brain\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — epistasis via zebrafish model with specific phenotypic readout, replicated across three pedigrees with orthogonal human genetics\",\n      \"pmids\": [\"26004199\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"COL6A3 undergoes tumor-specific alternative splicing in pancreatic ductal adenocarcinoma, with consistent inclusion of exons 3 and 6 in tumor versus adjacent tissue, and exclusive tumor-specific inclusion of exon 4; COL6A3 protein is upregulated in the desmoplastic stroma surrounding malignant ducts.\",\n      \"method\": \"RT-PCR with exon-specific primers on paired PDA-normal tissue (n=18), Western blot, immunohistochemistry, xenograft and transgenic PDA animal models\",\n      \"journal\": \"Surgery\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods confirming tumor-specific splicing and protein localization, single lab\",\n      \"pmids\": [\"21719059\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Gapmer antisense oligonucleotides selectively suppress the mutant COL6A3 allele (heterozygous 18-nt deletion in exon 15) at both pre-mRNA and mRNA levels via RNase H-mediated cleavage, and silencing the mutant allele increases deposition of collagen VI protein into the extracellular matrix in UCMD patient-derived fibroblasts, restoring functional protein production.\",\n      \"method\": \"Gapmer AON allele-specific silencing, RT-PCR transcript analysis, immunofluorescence of collagen VI matrix in patient fibroblasts\",\n      \"journal\": \"Molecular therapy. Nucleic acids\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean allele-specific knockdown with direct matrix deposition readout, multiple methods\",\n      \"pmids\": [\"28918041\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"siRNA targeting a dominant COL6A3 exon 16-skipping mutation selectively suppresses mutant allele expression and protein from a reporter construct without affecting the wild-type allele, and treatment of UCMD fibroblasts with these siRNAs considerably improved the quantity and quality of the collagen VI matrix.\",\n      \"method\": \"siRNA allele-specific silencing, semi-quantitative and quantitative RT-PCR, reporter assay in HEK293T cells, confocal microscopy of collagen VI matrix in patient fibroblasts\",\n      \"journal\": \"Molecular therapy. Nucleic acids\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — allele-specific mechanism validated in reporter assay and patient cells with multiple methods\",\n      \"pmids\": [\"24518369\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"COL6A3-derived endotrophin (ETP, cleavage product of the C5 domain) induces JNK-dependent hepatocyte apoptosis and activates nonparenchymal cells to drive hepatic inflammation and fibrosis in chronic liver disease; neutralizing antibodies against ETP suppressed these pathological consequences.\",\n      \"method\": \"In vitro ETP treatment of hepatocytes, JNK pathway analysis, neutralizing antibody treatment in chronic liver disease models\",\n      \"journal\": \"The Journal of pathology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — loss-of-function (neutralizing antibody) with defined signaling pathway readout, single lab\",\n      \"pmids\": [\"30246318\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"COL6A3 expression in adipocytes is regulated by PPARγ: PPARG knockdown in developing adipocytes increased COL6A3 mRNA 1.5-fold, and COL6A3 mRNA was 2.8-fold higher in small compared to large adipocytes, linking PPARγ-mediated adipocyte development to COL6A3 transcriptional control.\",\n      \"method\": \"PPARG knockdown in primary human adipocytes, qPCR, euglycemic-hyperinsulinemic clamp for insulin resistance phenotyping\",\n      \"journal\": \"Obesity (Silver Spring, Md.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct knockdown experiment with transcriptional readout, single lab\",\n      \"pmids\": [\"24719315\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Leptin treatment causes a dose-dependent decrease in COL6A3 expression in human adipose tissue, identifying a direct paracrine leptin signaling pathway that regulates extracellular matrix composition; insulin and glucose had no effect on COL6A3 expression.\",\n      \"method\": \"Leptin/insulin/glucose treatment of human adipose tissue explants, qPCR, comparison across depots and weight-loss conditions\",\n      \"journal\": \"Endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct pharmacological regulation experiment with dose-response, single lab\",\n      \"pmids\": [\"25337653\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"COL6A3 knockdown in immortalized human preadipocytes increased triglyceride content, lipolysis, insulin-induced Akt phosphorylation, and adipogenic gene expression, while also decreasing basal MCP1 (CCL2) expression and abrogating TNF-α- and LPS-induced MCP1 induction; matrix metalloproteinase-11 treatment reduced COL6A3 protein and phenocopied MCP1 suppression, placing COL6A3 upstream of MCP1 inflammatory signaling in adipocytes.\",\n      \"method\": \"Stable shRNA knockdown in human adipocyte cell lines, MMP-11 treatment, flow cytometry, ELISA, THP1 macrophage co-culture assay\",\n      \"journal\": \"Obesity (Silver Spring, Md.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — stable KD with multiple functional readouts and pharmacological validation, single lab\",\n      \"pmids\": [\"27312141\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"The homeobox transcription factor PRRX1 directly transactivates the endogenous human COL6A3 promoter; PRRX1 knockdown reduced COL6A3 mRNA in human and mouse adipose cells, and stable PRRX1 overexpression in 3T3-L1 cells induced Col6a3 mRNA threefold after adipogenic induction, while TNF-α decreased PRRX1-mediated Col6a3 transactivation.\",\n      \"method\": \"PRRX1 knockdown and overexpression in adipose cells, reporter construct with endogenous COL6A3 promoter, qPCR, transcriptome correlation across multiple clinical cohorts\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct promoter transactivation assay combined with KD and OE with orthogonal methods, replicated across cohorts\",\n      \"pmids\": [\"33214660\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"COL6A3 knockdown induces transcriptional changes overlapping the majority of experimental senescence models, with cell-cycle arrest linked to modulation of DREAM complex-targeted genes, identifying COL6A3 as a candidate SASP factor and potential driver of senescence in human tissues.\",\n      \"method\": \"COL6A3 knockdown followed by transcriptomic analysis, integration with 10 senescence cell models and 224 multi-tissue gene co-expression network from ~600 CAD patients\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — KD with transcriptomic readout integrated across multiple models, single experimental perturbation\",\n      \"pmids\": [\"37938972\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"A damaging COL6A3 variant introduced by CRISPR-Cas9 into human iPSC-derived neocartilage organoids results in significantly lower binding between the pericellular matrix proteins collagen VI and fibronectin, provokes an osteoarthritic chondrocyte state, and abolishes the characteristic inflammatory signaling response (PTGS2, PECAM1, ADAMTS5) to hyperphysiological mechanical loading; the lncRNA MIR31HG was identified as a key regulator of this response.\",\n      \"method\": \"CRISPR-Cas9 genome engineering in iPSC-derived neocartilage organoids, multi-omics (mRNA and lncRNA), mechanical loading assay, protein binding assay (COLVI–FN interaction)\",\n      \"journal\": \"Advanced science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — CRISPR engineering with reconstituted organoid model, multi-omics and protein binding assay, mechanically defined functional readout\",\n      \"pmids\": [\"39021299\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Mutations in COL6A3 p.Val86Ala and p.Arg689Cys cause abnormal intracellular retention of the mutant COL6A3 protein and decrease cellular resistance to oxidative stress through an enhanced endoplasmic reticulum stress response, establishing a disease mechanism for COL6A3 mutation-associated Peters' anomaly.\",\n      \"method\": \"Panel and whole-exome sequencing, immunofluorescence of mutant protein localization, ER stress assay, oxidative stress resistance assay in patient-derived and transfected cells\",\n      \"journal\": \"Frontiers in cell and developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct functional assay of mutant protein with defined cellular phenotypes, single lab\",\n      \"pmids\": [\"33304895\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"ETP-specific knockout (ETPKO) mice, which selectively ablate the endotrophin cleavage product of COL6A3 while preserving Col6a3 expression, show significantly attenuated kidney fibrosis following ischemia-reperfusion injury, establishing endotrophin as a key driver of fibrosis independent of full-length COL6A3.\",\n      \"method\": \"CRISPR-based conditional ETP knockout mouse model with Cre-mediated recombination, unilateral/bilateral renal ischemia-reperfusion injury, mRNA quantification, fibrosis histopathology\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — novel conditional KO model with specific ablation of cleavage product and defined disease phenotype, rigorous genetic controls\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"COL6A3 exon 4 alternative splicing is specifically induced by TGF-β in skin fibroblasts undergoing myofibroblast differentiation, constituting part of a 5-ASE signature validated by ddPCR/AS-PCR and retrieved in multiple independent TGF-β-stimulated lung and skin fibroblast RNA-seq datasets.\",\n      \"method\": \"RNA-seq, ddPCR, AS-PCR validation in primary skin fibroblasts with TGF-β treatment, replicated in publicly available datasets\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — TGF-β-regulated splicing event validated by multiple methods and replicated in independent datasets; preprint\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Mendelian randomization and colocalization analyses show that genetically elevated COL6A3 (particularly its endotrophin product) causally increases coronary artery disease risk, and that an aortic eQTL for COL6A3 colocalizes with plasma pQTL and AAA risk signals, suggesting a causal pathway from genetic variation in aortic wall COL6A3 expression to extracellular matrix remodeling and vascular disease.\",\n      \"method\": \"Two-step proteome-wide Mendelian randomization, Bayesian colocalization, epigenomics, single-cell RNA sequencing, plasma endotrophin measurement after fat reduction\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multi-method causal inference with colocalization and functional endpoint, but primarily genetic/epidemiologic rather than direct mechanistic experiment\",\n      \"pmids\": [\"39856218\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"A damaging COL6A3 variant in human iPSC-derived chondrocytes results in lower pericellular matrix elastic modulus, reduced key matrix protein expression, heightened osmotically-induced calcium signaling (consistent with reduced PCM modulus), reduced anabolic response to TRPV4 activation, disrupted circadian rhythms with increased BMAL1 expression, and exacerbated catabolic response to IL-1, demonstrating that COL6A3 is required for normal chondrocyte mechanotransduction via the pericellular matrix.\",\n      \"method\": \"CRISPR-Cas9 genome editing in hiPSC-derived chondrocytes, AFM for PCM elastic modulus, calcium imaging, RNA-sequencing, matrix biosynthesis assay, circadian rhythm analysis\",\n      \"journal\": \"Stem cell research & therapy\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — isogenic CRISPR model with reconstitution-level mechanobiological assays and multi-omics, single lab\",\n      \"pmids\": [\"41692747\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"COL6A3 encodes the α3(VI) chain of type VI collagen, which is required for assembly and extracellular deposition of collagen VI microfibrils; its C-terminal C5 domain is proteolytically cleaved after secretion to generate endotrophin, a bioactive peptide that drives fibrosis and cancer progression via TGF-β-like signaling; loss-of-function mutations cause collagen VI-deficient myopathies (Ullrich/Bethlem spectrum), while exon 41-specific mutations cause recessive isolated dystonia (DYT27) through a distinct neuronal mechanism involving axonal outgrowth deficits; α3(VI) is also essential for pericellular matrix integrity and mechanotransduction in chondrocytes, and its expression is transcriptionally regulated by PPARγ, PRRX1, leptin, and TGF-β-induced alternative splicing.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"COL6A3 encodes the α3(VI) chain of type VI collagen, a major structural component of pericellular and extracellular matrices whose assembly, secretion, and post-secretion proteolytic processing are essential for tissue integrity across muscle, tendon, cartilage, adipose, and vascular compartments. The α3(VI) chain is required for collagen VI microfibril formation; loss-of-function mutations cause Ullrich congenital muscular dystrophy and Bethlem myopathy through deficient or dominant-negatively disrupted collagen VI deposition [PMID:11992252, PMID:24563484], while exon 41-specific mutations cause recessive isolated dystonia (DYT27) via a distinct neuronal mechanism involving axonal outgrowth deficits [PMID:26004199]. The C-terminal C5 domain is proteolytically cleaved after secretion to release endotrophin, a bioactive fragment that drives organ fibrosis through JNK-dependent apoptosis and inflammatory cell activation and contributes causally to cardiovascular disease risk [PMID:11785962, PMID:30246318, PMID:39856218]. In chondrocytes, COL6A3 maintains pericellular matrix mechanical properties and is required for normal mechanotransduction, TRPV4-mediated anabolic signaling, and circadian rhythm regulation; its loss provokes an osteoarthritic cellular state with exaggerated catabolic and inflammatory responses to mechanical and cytokine stimuli [PMID:39021299, PMID:41692747].\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"Establishing that mutations in the α3(VI) globular domains cause Bethlem myopathy answered whether COL6A3 itself could be a disease gene for heritable myopathies and implicated the N-terminal vWFA domain as functionally critical.\",\n      \"evidence\": \"Missense mutation segregation in a large Bethlem myopathy pedigree\",\n      \"pmids\": [\"9536084\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No biochemical demonstration of how the N2 domain mutation disrupts assembly\", \"Single pedigree\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Demonstrating that the C5 domain is proteolytically cleaved immediately after collagen VI secretion revealed a previously unknown post-secretion processing step and identified a bioactive fragment later termed endotrophin.\",\n      \"evidence\": \"Immunoelectron microscopy and double-label immunostaining in human articular cartilage\",\n      \"pmids\": [\"11785962\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Protease responsible for C5 cleavage not identified\", \"Biological function of the released C5 fragment not yet tested\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Identifying homozygous loss-of-function COL6A3 mutations in Ullrich congenital muscular dystrophy families established the causal link between α3(VI) chain deficiency and severe congenital myopathy.\",\n      \"evidence\": \"Genome-wide linkage, mutation analysis, and collagen VI immunostaining in muscle biopsies from three UCMD families\",\n      \"pmids\": [\"11992252\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular mechanism by which collagen VI absence damages muscle fibers not defined\", \"Genotype-phenotype correlation across mutation types incomplete\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Characterization of a Col6a3-deficient mouse model demonstrated that α3(VI) is required for collagen VI microfibril deposition in vivo and revealed tissue-specific roles in muscle contractile function and tendon collagen I fibrillogenesis.\",\n      \"evidence\": \"Mouse knockout with ultrastructural analysis, immunofluorescence, and muscle contractile force measurement\",\n      \"pmids\": [\"23564457\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Why corneal collagen fibrils are unaffected despite collagen VI expression not explained\", \"Downstream signaling consequences of microfibril loss not characterized\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"A knock-in mouse carrying an in-frame triple-helical deletion in Col6a3 proved the dominant-negative mechanism of Bethlem myopathy mutations and showed that mutant α3(VI) chains are incorporated into defective trimers that poison microfibril assembly.\",\n      \"evidence\": \"Mouse knock-in model with fibroblast biosynthetic studies, histopathology, and electron microscopy\",\n      \"pmids\": [\"24563484\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometric threshold for dominant-negative poisoning not quantified\", \"Whether all triple-helical glycine mutations act identically is unknown\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Allele-specific siRNA silencing of a dominant COL6A3 mutation restored collagen VI matrix deposition in UCMD patient fibroblasts, providing proof-of-concept that selective knockdown of the mutant allele is a viable therapeutic strategy.\",\n      \"evidence\": \"siRNA targeting mutation-specific sequence in patient fibroblasts and HEK293T reporter assay\",\n      \"pmids\": [\"24518369\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo delivery and efficacy not tested\", \"Long-term matrix quality restoration not assessed\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Discovery that exon 41-specific COL6A3 mutations cause recessive isolated dystonia (DYT27) with axonal outgrowth deficits in zebrafish revealed a neuronal function of α3(VI) distinct from its structural role in the extracellular matrix.\",\n      \"evidence\": \"Whole-exome sequencing in dystonia pedigrees plus zebrafish morpholino knockdown of exon 41 versus other exons\",\n      \"pmids\": [\"26004199\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular mechanism linking exon 41 to axonal outgrowth unknown\", \"Whether collagen VI is assembled in neurons or acts cell-non-autonomously not resolved\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Showing that endotrophin (the C5 cleavage product) induces JNK-dependent hepatocyte apoptosis and drives hepatic fibrosis, suppressible by neutralizing antibodies, established endotrophin as an independent signaling molecule with pro-fibrotic and pro-inflammatory activity.\",\n      \"evidence\": \"In vitro endotrophin treatment of hepatocytes and neutralizing antibody intervention in chronic liver disease models\",\n      \"pmids\": [\"30246318\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Receptor for endotrophin not identified\", \"Whether endotrophin signals through TGF-β pathway components or an independent pathway not fully resolved\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identification of PRRX1 as a direct transcriptional activator of COL6A3 established a transcription factor–extracellular matrix axis controlling collagen VI levels in adipose tissue, modulated by inflammatory signals such as TNF-α.\",\n      \"evidence\": \"PRRX1 knockdown and overexpression with endogenous COL6A3 promoter reporter assay in human and mouse adipose cells\",\n      \"pmids\": [\"33214660\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"PRRX1 binding site on COL6A3 promoter not mapped at base-pair resolution\", \"Whether PRRX1 regulation extends beyond adipose tissue not tested\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"CRISPR-engineered COL6A3 loss in iPSC-derived neocartilage organoids showed that collagen VI is required for fibronectin binding, mechanical load sensing, and suppression of an osteoarthritic chondrocyte state, placing COL6A3 as a central node in cartilage mechanotransduction.\",\n      \"evidence\": \"CRISPR-Cas9 in iPSC-derived organoids with multi-omics, protein binding assay, and mechanical loading\",\n      \"pmids\": [\"39021299\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether COL6A3 loss-of-function is sufficient to initiate osteoarthritis in vivo not shown\", \"Signaling intermediates between pericellular matrix disruption and inflammatory gene induction not fully mapped\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Mendelian randomization provided causal genetic evidence that elevated COL6A3/endotrophin increases coronary artery disease risk through aortic wall expression, linking the pro-fibrotic endotrophin pathway to cardiovascular disease at the population level.\",\n      \"evidence\": \"Proteome-wide Mendelian randomization, Bayesian colocalization, plasma pQTL, and aortic eQTL analyses\",\n      \"pmids\": [\"39856218\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No direct experimental intervention confirming the causal chain in vascular tissue\", \"Endotrophin receptor and downstream vascular signaling cascade remain unidentified\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Isogenic COL6A3-mutant iPSC-derived chondrocytes showed that α3(VI) is required for pericellular matrix stiffness, TRPV4-mediated anabolic responses, and circadian clock regulation, deepening the mechanotransduction model to include ion channel function and temporal gene regulation.\",\n      \"evidence\": \"CRISPR-edited hiPSC chondrocytes with AFM, calcium imaging, RNA-seq, and circadian rhythm analysis\",\n      \"pmids\": [\"41692747\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether circadian disruption is primary or secondary to matrix softening not resolved\", \"TRPV4 interaction with collagen VI pericellular matrix not structurally characterized\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The receptor and direct signaling pathway by which endotrophin exerts its pro-fibrotic and pro-apoptotic effects remain unidentified, and the molecular basis of the exon 41-specific neuronal function of α3(VI) is unexplained.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Endotrophin receptor unknown\", \"Exon 41-encoded domain's neuronal interactors not identified\", \"Protease responsible for C5 domain cleavage not identified\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [5, 6, 17, 22]},\n      {\"term_id\": \"GO:0098631\", \"supporting_discovery_ids\": [17, 22]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0031012\", \"supporting_discovery_ids\": [0, 5, 6, 9, 10, 17, 22]},\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [0, 11, 19]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [18]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1474244\", \"supporting_discovery_ids\": [0, 5, 6, 9, 10, 17, 22]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [11, 14, 21]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [1, 2, 7, 18]}\n    ],\n    \"complexes\": [\n      \"type VI collagen heterotrimer (α1/α2/α3)\"\n    ],\n    \"partners\": [\n      \"COL6A1\",\n      \"COL6A2\",\n      \"FN1\",\n      \"PRRX1\",\n      \"MIR31HG\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}