{"gene":"COL6A1","run_date":"2026-04-28T17:28:53","timeline":{"discoveries":[{"year":2003,"finding":"A heterozygous in-frame deletion near the amino-terminus of the COL6A1 triple-helical domain that preserves a unique cysteine required for dimer formation allows secretion of abnormal tetramers that exert a dominant-negative effect on microfibrillar assembly, causing loss of normal collagen VI localization in the basement membrane surrounding muscle fibers. In contrast, a deletion that removes this cysteine prevents dimer formation and secretion of the mutant chain, abrogating the dominant-negative effect and resulting in a milder phenotype.","method":"In vitro fibroblast analysis of mutant chain synthesis, secretion, and extracellular matrix deposition; genotype-phenotype correlation with active-site residue (cysteine) mutagenesis context","journal":"American journal of human genetics","confidence":"High","confidence_rationale":"Tier 1/2 — biochemical dissection of secretion and assembly with functional residue identification, replicated across two different deletion mutations with contrasting phenotypes","pmids":["12840783"],"is_preprint":false},{"year":1998,"finding":"A heterozygous nonsense mutation in COL6A1 generates unstable mRNA subject to nonsense-mediated decay, causing haploinsufficiency of the α1(VI) subunit and reduced production of structurally normal collagen VI, leading to Bethlem myopathy.","method":"RT-PCR, mRNA stability analysis in patient fibroblasts and skeletal muscle, western blot of collagen VI production","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (mRNA decay assay, protein quantification) in patient-derived cells; first demonstration of haploinsufficiency as mechanism","pmids":["9580662"],"is_preprint":false},{"year":2009,"finding":"Loss of COL6A1/type VI collagen in Col6a1−/− mice causes structurally intact but mechanically deficient pericellular matrix (PCM) in articular cartilage, altering the biomechanical environment of chondrocytes and accelerating osteoarthritis development.","method":"Col6a1 knockout mouse model; micropipette aspiration of PCM mechanical properties; histomorphometry; bone mineral density measurement","journal":"Arthritis and rheumatism","confidence":"High","confidence_rationale":"Tier 2 — direct mechanical measurement in knockout mice with multiple orthogonal readouts (biomechanics, histology, BMD); highly cited","pmids":["19248115"],"is_preprint":false},{"year":2009,"finding":"Collagen VI deficiency in Col6a1−/− myopathic mice leads to mitochondrial dysfunction and increased apoptosis in skeletal muscle via sensitization of the mitochondrial permeability transition pore (mPTP); pharmacological inhibition of cyclophilin D with Debio 025 desensitizes the mPTP and normalizes mitochondrial function and ultrastructural defects without affecting calcineurin.","method":"Col6a1−/− mouse model; mitochondrial Ca2+ retention assay; membrane potential measurement; TUNEL apoptosis assay; electron microscopy; NFAT translocation assay for calcineurin activity","journal":"British journal of pharmacology","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal functional assays in knockout mice with pharmacological rescue; establishes mPTP as the downstream mechanism of COL6A1 deficiency in muscle","pmids":["19519726"],"is_preprint":false},{"year":1999,"finding":"A splice site mutation in COL6A1 intron 14 causes skipping of exon 14 and in-frame deletion of 18 amino acids including a cysteine residue in the triple-helical domain. The shortened α1(VI) chain is synthesized but not secreted by fibroblasts, resulting in reduced collagen VI microfibril deposition in the extracellular matrix.","method":"RT-PCR of patient fibroblast RNA; western blot; immunofluorescence of ECM","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 2 — direct molecular analysis in patient fibroblasts with protein secretion and matrix deposition assays; mechanistically linked to cysteine required for dimer formation","pmids":["10329467"],"is_preprint":false},{"year":2019,"finding":"A deep intronic c.930+189C>T variant in COL6A1 creates a cryptic donor splice site, inserting an in-frame 72-nt pseudoexon into COL6A1 mRNA. The encoded mutant α1(VI) chain exerts a dominant-negative effect on collagen VI matrix assembly. Antisense oligomers (ASOs) targeting the pseudoexon efficiently skip it in patient-derived fibroblasts, restoring wild-type matrix. CRISPR/Cas9 deletion of the intronic sequence containing the pseudoexon also abolishes its inclusion.","method":"Muscle RNA sequencing; patient fibroblast culture; ASO splice-switching; CRISPR/Cas9 deletion; western blot; immunofluorescence of collagen VI matrix","journal":"JCI insight","confidence":"High","confidence_rationale":"Tier 1/2 — multiple orthogonal therapeutic correction methods (ASO and CRISPR) with protein-level readout; splice mechanism precisely defined","pmids":["30895940"],"is_preprint":false},{"year":2020,"finding":"ASOs targeting the pseudoexon created by the COL6A1 c.930+189C>T deep intronic variant efficiently induce pseudoexon exclusion from mature transcripts in patient fibroblasts, restoring functional collagen VI microfibrillar matrix as assessed at RNA, protein, and structural levels.","method":"ASO transfection in patient-derived fibroblasts; qRT-PCR; western blot; immunofluorescence","journal":"Molecular therapy. Nucleic acids","confidence":"High","confidence_rationale":"Tier 2 — systematic ASO tiling with functional readout at multiple levels; replicates and extends PMID 30895940","pmids":["32585628"],"is_preprint":false},{"year":2008,"finding":"The Col6a1 gene enhancer region (−5.4 to −3.9 kb from transcription start) is required for activation of transcription in connective tissue cells associated with skeletal muscle. Using lacZ transgenic mice crossed with metD/D mutant mice (lacking myogenic cells in limb buds), the presence of myogenic-lineage cells was shown to be necessary for enhancer activation in mesenchymal cells, demonstrating that muscle cells signal to connective tissue cells to drive COL6A1 expression.","method":"Promoter-lacZ transgenic mice; genetic cross with metD/D (myogenic cell-deficient) mice; lacZ reporter expression analysis; collagen VI immunostaining","journal":"Experimental cell research","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis via double-mutant cross with functional reporter readout; strong mechanistic evidence for muscle-to-connective-tissue paracrine regulation of COL6A1 transcription","pmids":["18761340"],"is_preprint":false},{"year":2000,"finding":"The 383-bp E-L fragment (within the −5.4/−3.9 kb Col6a1 enhancer region) is the most active sequence for tissue-specific transcription; integrity of the entire E-J subfragment is required for enhancer activity in articular cartilage. EMSA showed at least 22 ubiquitous transcription factors bind this region, and their relative proportions (not tissue-specific factors) determine tissue-specific expression.","method":"Transgenic mice with deletion constructs; linker-scanning mutagenesis; electrophoretic mobility shift assay (EMSA) with nuclear extracts","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — in vivo mutagenesis + protein–DNA binding assays; defines enhancer mechanism for tissue-specific Col6a1 transcription","pmids":["10747869"],"is_preprint":false},{"year":2001,"finding":"Activation of Col6a1 gene transcription in Schwann cells is part of their differentiation program induced by neuregulins from the neural crest; once competence to transcribe Col6a1 is established, transcriptional regulation becomes neuregulin-independent and is modulated by cell cycle status, correlating with myelination onset after birth.","method":"lacZ transgenic mouse reporter; developmental expression analysis; neuregulin-deficient genetic background","journal":"Mechanisms of development","confidence":"Medium","confidence_rationale":"Tier 2 — transgenic reporter in vivo, but mechanistic pathway not fully dissected biochemically","pmids":["11287188"],"is_preprint":false},{"year":2013,"finding":"Truncating mutations within the COL6A1 C-terminal C2 subdomain result in intracellular retention of mutant collagen VI protein and severely decreased collagen VI matrix deposition; the absence of the α1(VI) C2 domain also leads to abnormal fibronectin network interactions, revealing a role for this domain in ECM organization.","method":"Patient fibroblast immunofluorescence; western blot; RNA analysis for NMD; fibronectin network staining","journal":"BMC medical genetics","confidence":"Medium","confidence_rationale":"Tier 3 — single patient case with protein-level analysis; provides domain-specific mechanistic insight into C2 domain function in secretion and ECM interactions","pmids":["23738969"],"is_preprint":false},{"year":2004,"finding":"Dominant glycine substitutions in the triple-helical domain of COL6A1 cause disease via a dominant-negative mechanism, whereas recessive mutations (nonsense, frameshift) cause more severe phenotypes via loss of function, establishing that glycine substitutions in the triple helix act dominantly and missense/truncating mutations outside this region act recessively.","method":"Patient cell analysis; RT-PCR; western blot; immunofluorescence; parental DNA sequencing to confirm de novo status","journal":"Annals of neurology","confidence":"Medium","confidence_rationale":"Tier 2 — protein secretion and matrix assays in patient fibroblasts; multiple patients with different mutation types compared","pmids":["16130093"],"is_preprint":false},{"year":2021,"finding":"Upregulation of COL6A1 in osteosarcoma cells promotes migration and invasion by interacting with SOCS5 to suppress STAT1 expression via ubiquitination and proteasomal degradation. Exosomal COL6A1 derived from osteosarcoma cells converts normal fibroblasts to cancer-associated fibroblasts that secrete IL-6 and IL-8, promoting further invasion via TGF-β/COL6A1 signaling.","method":"Co-immunoprecipitation; ubiquitination assay; RNA sequencing; in vitro migration/invasion assays; exosome tracing; co-culture experiments; in vivo xenograft","journal":"Theranostics","confidence":"Medium","confidence_rationale":"Tier 2 — Co-IP and ubiquitination assays with functional rescue experiments; single lab but multiple orthogonal methods","pmids":["33391546"],"is_preprint":false},{"year":2023,"finding":"The COL6A1 c.930+189C>T mutation leads to secretion of the mutant α1(VI) chain as a single chain (not incorporated into tetramers) that forms large extracellular aggregates, while wild-type α1(VI) is assembled normally into tetramers. Expression of the mutant chain in α1-chain-deficient WI-26 VA4 cells confirms it cannot support tetramer assembly.","method":"Mutation-specific antibody; patient fibroblast cell culture; co-localization immunofluorescence; transfection of mutant/wild-type chains into WI-26 VA4 cells; protein secretion analysis","journal":"Human mutation","confidence":"High","confidence_rationale":"Tier 1/2 — reconstitution in deficient cell line + patient-derived fibroblast analysis + mutation-specific detection; defines precise assembly failure mechanism","pmids":["40225172"],"is_preprint":false},{"year":2024,"finding":"COL6A1 interacts with ITGA5 (integrin alpha-5) and activates the FAK/Paxillin/AKT focal adhesion pathway in glioblastoma cells; tumor electric field therapy downregulates COL6A1, hindering its interaction with ITGA5 and suppressing this pathway.","method":"Co-immunoprecipitation; immunofluorescence co-localization; western blot of FAK/Paxillin/AKT pathway","journal":"CNS neuroscience & therapeutics","confidence":"Low","confidence_rationale":"Tier 3 — single Co-IP in a cancer cell line context; no mutagenesis or reconstitution","pmids":["38887185"],"is_preprint":false},{"year":2019,"finding":"COL6A1 knockdown in PDGF-BB-stimulated vascular smooth muscle cells attenuates cell viability and invasive ability, partially reverses increased expression of fibronectin, MMP-2 and MMP-9, and inhibits AKT/mTOR pathway activation, placing COL6A1 upstream of AKT/mTOR signaling in VSMC migration.","method":"siRNA knockdown; CCK-8 viability assay; wound healing and Transwell invasion assay; western blot of pathway components","journal":"Experimental and therapeutic medicine","confidence":"Low","confidence_rationale":"Tier 3 — single lab, knockdown with pathway readout but no direct binding or epistasis confirmation","pmids":["31410158"],"is_preprint":false},{"year":2025,"finding":"COL6A1 promotes osteoclast differentiation and formation in osteoarthritis by activating the EPAC/RAP1 signaling axis; COL6A1 knockdown in vivo reduces osteoclast-mediated subchondral bone remodeling and slows OA progression in DMM mouse models.","method":"WGCNA; in vitro perturbation and rescue experiments; in vivo DMM mouse model with COL6A1 knockdown; molecular docking","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 2 — in vitro and in vivo perturbation with rescue; identifies specific signaling axis, though binding mechanism not directly demonstrated","pmids":["40143596"],"is_preprint":false},{"year":2022,"finding":"CRISPR/Cas9 allele-specific disruption of the dominant-negative COL6A1 c.877G>A (p.Gly293Arg) mutation in patient fibroblasts reduces mutant allele expression in >40% of reads with no effect on the wild-type allele, rescuing collagen VI extracellular matrix assembly.","method":"CRISPR/Cas9 genome editing; next-generation sequencing; droplet digital PCR with allele-specific probes; immunofluorescence of collagen VI matrix","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2 — allele-specific editing with quantitative allele discrimination and functional matrix readout; establishes dominant-negative mechanism for this specific variant","pmids":["35457228"],"is_preprint":false},{"year":2024,"finding":"An allele-specific siRNA with an intentional additional mismatch selectively silences the dominant-negative COL6A1 G293R (c.877G>A) mutant transcript while preserving wild-type transcript levels in patient fibroblasts, rescuing secretion and assembly of collagen VI matrix.","method":"siRNA transfection; allele-specific RT-qPCR; western blot; immunofluorescence of collagen VI matrix in patient fibroblasts","journal":"Molecular therapy. Nucleic acids","confidence":"High","confidence_rationale":"Tier 2 — systematic allele-specific silencing with multiple molecular and functional readouts; mechanistically validates dominant-negative nature of G293R variant","pmids":["38617974"],"is_preprint":false},{"year":2018,"finding":"A non-triple-helical polypeptide of type VI collagen α1 chain (NTH α1(VI), ~140 kDa) is encoded by COL6A1 and represents an alternative gene product with distinct glycosylation from the triple-helical form, detected in supernatants of several human cancer cell lines.","method":"Antibody characterization; western blot; lectin reactivity assays; expression in cancer cell supernatants","journal":"Journal of biochemistry","confidence":"Low","confidence_rationale":"Tier 3 — identification of novel protein product by antibody detection; function not established; single lab","pmids":["29659864"],"is_preprint":false},{"year":2025,"finding":"ANTXR2 (anthrax toxin receptor 2) expressed by fibro-adipogenic precursors controls COL6A1/collagen VI turnover via receptor-mediated endocytosis; Antxr2−/− mice accumulate collagen VI in intramuscular connective tissue, leading to tissue stiffening and myopathy, which is rescued in Antxr2−/−Col6a1−/− double knockout mice.","method":"Antxr2−/− and Antxr2−/−Col6a1−/− double knockout mouse models; proteomics; muscle histology; biomechanical testing; locomotion analysis","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 — double knockout genetic epistasis rescues phenotype, establishing ANTXR2 as regulator of COL6A1 turnover; preprint not yet peer-reviewed","pmids":["bio_10.1101_2025.09.11.675515"],"is_preprint":true},{"year":2025,"finding":"In a zebrafish col6a1 Δex14 model of Bethlem myopathy, Col6a1 deficiency leads to reduced dihydropyridine receptor (DHPR) charge movement density, a negative shift in DHPR voltage-dependence, elevated resting Ca2+ sparks (SR Ca2+ leak), and reduced twitch force, suggesting COL6A1 is required for proper DHPR function and Ca2+ homeostasis in skeletal muscle fibers.","method":"Zebrafish knockout model; electrophysiology (charge movement measurement); intracellular Ca2+ transient imaging; Ca2+ spark measurement; immunofluorescence of DHPR localization; muscle force measurement; swimming performance","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 — multiple electrophysiological and Ca2+ imaging methods in zebrafish ortholog model; preprint not yet peer-reviewed","pmids":["bio_10.1101_2025.06.02.657388"],"is_preprint":true},{"year":2025,"finding":"In Col6a1−/− rats, absence of collagen VI reduces cardiac systolic function and paradoxically increases Ca2+ transient amplitude and SR Ca2+ load in isolated cardiomyocytes; β-adrenergic stimulation triggers diastolic Ca2+ release events in knockout cardiomyocytes, suggesting collagen VI contributes to cardiac Ca2+ regulation, potentially via linkage to the dystrophin-glycoprotein complex.","method":"Global Col6a1 knockout rat; echocardiography; cardiomyocyte Ca2+ transient imaging; SR Ca2+ load measurement; β-adrenergic stimulation protocol","journal":"bioRxiv","confidence":"Low","confidence_rationale":"Tier 2 method but preprint, single study; proposed mechanism (DGC linkage) is speculative","pmids":["bio_10.1101_2025.03.21.644665"],"is_preprint":true},{"year":2025,"finding":"Thyroid hormone receptor α (TRα) directly binds the Col6a1 promoter region (identified by ChIP-seq) and positively regulates Col6a1 transcription; TRα knockdown in C2C12 myoblasts reduces Col6a1 expression and inhibits myoblast proliferation and differentiation.","method":"ChIP-seq; RNA-seq; ChIP-qPCR; siRNA knockdown of TRα; RT-qPCR; C2C12 proliferation/differentiation assays","journal":"Journal of muscle research and cell motility","confidence":"Medium","confidence_rationale":"Tier 2 — ChIP-seq identifies direct TRα binding at Col6a1 locus; functional knockdown confirms transcriptional regulation; peer-reviewed","pmids":["40317420"],"is_preprint":false}],"current_model":"COL6A1 encodes the α1(VI) chain of type VI collagen, which assembles intracellularly into anti-parallel dimers (requiring a specific triple-helical cysteine residue), then tetramers with the α2(VI) and α3(VI) chains, and is secreted as microfibrillar networks into the pericellular and extracellular matrix of skeletal muscle, cartilage, and connective tissue; loss of function causes mechanically deficient pericellular matrix and mitochondrial permeability transition pore sensitization leading to muscle apoptosis, while dominant-negative glycine substitutions or pseudoexon insertions in the triple-helical domain disrupt tetramer assembly and produce pathological aggregates, collectively causing the spectrum from Bethlem myopathy to Ullrich congenital muscular dystrophy, with transcription regulated by an upstream tissue-specific enhancer activated by signals from myogenic cells and directly by thyroid hormone receptor α."},"narrative":{"teleology":[{"year":1998,"claim":"Establishing that COL6A1 haploinsufficiency—via nonsense-mediated mRNA decay of a premature stop codon allele—is sufficient to cause Bethlem myopathy resolved the question of whether quantitative reduction alone (without a structurally abnormal protein) can be pathogenic.","evidence":"RT-PCR and mRNA stability assays in patient fibroblasts and muscle, plus western blot of collagen VI output","pmids":["9580662"],"confidence":"High","gaps":["Threshold of α1(VI) reduction needed for disease not defined","No rescue experiment to confirm causality"]},{"year":1999,"claim":"Demonstrating that deletion of a triple-helical cysteine prevents dimer formation and blocks mutant chain secretion established this residue as the gatekeeper for collagen VI assembly quality control.","evidence":"RT-PCR, western blot, and immunofluorescence of ECM in patient fibroblasts carrying a splice-site mutation deleting exon 14","pmids":["10329467"],"confidence":"High","gaps":["Identity of the chaperone/ER retention machinery that detects misfolded chains unknown","Only one mutation analyzed"]},{"year":2000,"claim":"Mapping the minimal Col6a1 enhancer (E-L fragment) and showing that combinatorial binding of ubiquitous transcription factors—not tissue-restricted factors—drives tissue-specific expression answered how a widely expressed gene achieves restricted transcription in connective tissue and cartilage.","evidence":"Transgenic mice with deletion constructs and linker-scanning mutagenesis; EMSA with nuclear extracts from multiple tissues","pmids":["10747869"],"confidence":"High","gaps":["Identity of the 22 ubiquitous factors not fully resolved","Chromatin context and epigenetic regulation not addressed"]},{"year":2001,"claim":"Showing that neuregulin signaling from neural crest cells initiates Col6a1 transcriptional competence in Schwann cells, which then becomes neuregulin-independent and cell-cycle-regulated, revealed a developmental switch coupling Col6a1 to myelination onset.","evidence":"lacZ transgenic reporter mice analyzed across development and in neuregulin-deficient backgrounds","pmids":["11287188"],"confidence":"Medium","gaps":["Direct transcription factor mediating neuregulin-to-Col6a1 activation not identified","Biochemical pathway not dissected"]},{"year":2003,"claim":"By comparing two in-frame deletions—one preserving and one removing the dimerization cysteine—this study resolved why some triple-helical domain mutations exert dominant-negative effects while others do not, establishing that secretion competence of the mutant chain is the key determinant of phenotypic severity.","evidence":"In vitro fibroblast analysis of mutant chain synthesis, secretion, and ECM deposition across two contrasting mutations","pmids":["12840783"],"confidence":"High","gaps":["Stoichiometry of mutant-to-wild-type chains in secreted tetramers not quantified","Fate of intracellularly retained chains not tracked"]},{"year":2004,"claim":"Systematic comparison of dominant glycine substitutions versus recessive truncating mutations across multiple patients established the general rule that triple-helical glycine substitutions act via dominant-negative poisoning of assembly while loss-of-function alleles cause the more severe Ullrich phenotype through biallelic depletion.","evidence":"Patient fibroblast analysis with RT-PCR, western blot, immunofluorescence, and parental genotyping","pmids":["16130093"],"confidence":"Medium","gaps":["Some glycine substitutions produce intermediate phenotypes not explained by simple dominant-negative model","Modifier genes not explored"]},{"year":2008,"claim":"Genetic ablation of myogenic cells in limb buds (metD/D cross) abolished Col6a1 enhancer activation in mesenchymal cells, proving that muscle-derived paracrine signals are required for Col6a1 transcription in connective tissue.","evidence":"lacZ transgenic reporter crossed with metD/D myogenic-cell-deficient mice; reporter expression and collagen VI immunostaining","pmids":["18761340"],"confidence":"High","gaps":["Identity of the paracrine signal from myogenic cells unknown","Whether this regulation operates in adult muscle homeostasis not tested"]},{"year":2009,"claim":"Two concurrent studies using Col6a1−/− mice established that collagen VI deficiency causes both mechanically deficient pericellular matrix in cartilage (accelerating osteoarthritis) and mitochondrial permeability transition pore sensitization in skeletal muscle (driving apoptosis rescuable by cyclophilin D inhibition), defining the two major downstream pathological axes of COL6A1 loss.","evidence":"Col6a1 knockout mice; micropipette aspiration of PCM; mitochondrial Ca2+ retention and membrane potential assays; TUNEL; Debio 025 pharmacological rescue","pmids":["19248115","19519726"],"confidence":"High","gaps":["Molecular link between absent pericellular collagen VI and mPTP sensitization not identified","Whether mPTP mechanism also operates in cartilage chondrocytes unknown"]},{"year":2013,"claim":"Identifying that truncations in the C-terminal C2 subdomain cause intracellular retention and also disrupt fibronectin network organization revealed a dual role for the C2 domain in both secretion competence and ECM network interactions.","evidence":"Patient fibroblast immunofluorescence, western blot, fibronectin staining","pmids":["23738969"],"confidence":"Medium","gaps":["Only one patient studied","Direct binding interface between C2 domain and fibronectin not characterized"]},{"year":2019,"claim":"Discovery that a deep intronic variant (c.930+189C>T) creates a pseudoexon encoding an assembly-incompetent α1(VI) chain, correctable by ASO splice-switching and CRISPR deletion, established a new class of COL6A1 pathogenic mechanism and a therapeutic paradigm.","evidence":"Muscle RNA-seq; patient fibroblast culture; ASO and CRISPR/Cas9 correction with protein and matrix readouts","pmids":["30895940"],"confidence":"High","gaps":["In vivo delivery and efficacy of ASOs not demonstrated","Long-term stability of correction unknown"]},{"year":2021,"claim":"Demonstration that COL6A1 interacts with SOCS5 to promote ubiquitin-dependent STAT1 degradation and that exosomal COL6A1 converts fibroblasts to cancer-associated fibroblasts revealed a non-structural signaling role for COL6A1 in osteosarcoma invasion.","evidence":"Co-immunoprecipitation; ubiquitination assay; exosome tracing; co-culture; in vivo xenograft","pmids":["33391546"],"confidence":"Medium","gaps":["Structural basis of COL6A1–SOCS5 interaction unknown","Relevance outside osteosarcoma context not tested","Whether full-length or processed collagen VI mediates this effect unclear"]},{"year":2022,"claim":"Allele-specific CRISPR disruption of the dominant-negative G293R allele rescued collagen VI matrix assembly, providing proof-of-concept that selectively silencing the mutant allele is sufficient for phenotypic correction.","evidence":"CRISPR/Cas9 editing in patient fibroblasts; ddPCR allele quantification; immunofluorescence of matrix","pmids":["35457228"],"confidence":"Medium","gaps":["Efficiency of editing (~40%) may be insufficient in vivo","Off-target analysis limited"]},{"year":2023,"claim":"Showing that the pseudoexon-containing mutant α1(VI) chain is secreted as a single chain (not incorporated into tetramers) and forms extracellular aggregates precisely defined why this mutation is dominant-negative: the mutant chain bypasses intracellular quality control but poisons the extracellular matrix.","evidence":"Mutation-specific antibody; patient fibroblasts; reconstitution of mutant chain in α1-deficient WI-26 VA4 cells","pmids":["40225172"],"confidence":"High","gaps":["Nature and composition of extracellular aggregates not characterized at ultrastructural level","Whether aggregates actively damage surrounding matrix not tested"]},{"year":2024,"claim":"Allele-specific siRNA with an engineered mismatch selectively silenced the G293R mutant transcript and rescued collagen VI matrix, advancing therapeutic strategy beyond CRISPR by demonstrating reversible, tunable allele-selective knockdown.","evidence":"siRNA transfection in patient fibroblasts; allele-specific RT-qPCR; western blot; immunofluorescence","pmids":["38617974"],"confidence":"High","gaps":["In vivo delivery to muscle not demonstrated","Duration of effect and dosing not established"]},{"year":2025,"claim":"ChIP-seq identification of direct thyroid hormone receptor α binding at the Col6a1 promoter, with functional validation by TRα knockdown, established a hormonal transcriptional input for COL6A1 expression relevant to myoblast proliferation and differentiation.","evidence":"ChIP-seq and ChIP-qPCR in C2C12 myoblasts; siRNA knockdown of TRα; RT-qPCR; proliferation/differentiation assays","pmids":["40317420"],"confidence":"Medium","gaps":["Whether TRα regulation operates in vivo in adult muscle not confirmed","Relationship to the upstream −5.4 kb enhancer not examined"]},{"year":null,"claim":"The molecular link between absence of pericellular collagen VI and sensitization of the mitochondrial permeability transition pore—the central pathogenic mechanism in collagen VI myopathies—remains undefined, as does the identity of the muscle-derived paracrine signal that activates COL6A1 transcription in connective tissue.","evidence":"","pmids":[],"confidence":"High","gaps":["Transmembrane receptor mediating collagen VI signal to mitochondria unknown","Identity of muscle paracrine factor unknown","No structural model of collagen VI tetramer at atomic resolution"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[0,1,2,4,13]}],"localization":[{"term_id":"GO:0031012","term_label":"extracellular matrix","supporting_discovery_ids":[0,2,4,5,10,13]},{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[0,13,19]}],"pathway":[{"term_id":"R-HSA-1474244","term_label":"Extracellular matrix organization","supporting_discovery_ids":[0,2,4,10,13]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[3]}],"complexes":["Collagen VI tetramer (α1/α2/α3)"],"partners":["COL6A2","COL6A3","SOCS5","ITGA5","THRA"],"other_free_text":[]},"mechanistic_narrative":"COL6A1 encodes the α1(VI) chain of type VI collagen, a structural extracellular matrix protein that assembles into microfibrils critical for the biomechanical integrity of pericellular matrices in skeletal muscle, cartilage, and connective tissue. Intracellularly, the α1(VI) chain forms anti-parallel dimers via a triple-helical cysteine residue and then tetramers with α2(VI) and α3(VI) chains; mutations that preserve this cysteine permit secretion of abnormal tetramers exerting dominant-negative effects on microfibrillar assembly, whereas mutations that remove it or truncate the C2 domain prevent secretion entirely [PMID:12840783, PMID:10329467, PMID:23738969]. Loss of collagen VI in knockout mice causes mechanically deficient pericellular matrix in cartilage, sensitization of the mitochondrial permeability transition pore leading to muscle fiber apoptosis, and accelerated osteoarthritis [PMID:19248115, PMID:19519726]. Dominant glycine substitutions and pseudoexon insertions in the triple-helical domain, as well as recessive loss-of-function mutations, cause the Bethlem myopathy–Ullrich congenital muscular dystrophy spectrum [PMID:9580662, PMID:16130093, PMID:30895940]."},"prefetch_data":{"uniprot":{"accession":"P12109","full_name":"Collagen alpha-1(VI) chain","aliases":[],"length_aa":1028,"mass_kda":108.5,"function":"Collagen VI acts as a cell-binding protein","subcellular_location":"Secreted, extracellular space, extracellular matrix","url":"https://www.uniprot.org/uniprotkb/P12109/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/COL6A1","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/COL6A1","total_profiled":1310},"omim":[{"mim_id":"620728","title":"ULLRICH CONGENITAL MUSCULAR DYSTROPHY 1C; UCMD1C","url":"https://www.omim.org/entry/620728"},{"mim_id":"620727","title":"ULLRICH CONGENITAL MUSCULAR DYSTROPHY 1B; UCMD1B","url":"https://www.omim.org/entry/620727"},{"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":"616613","title":"COLLAGEN, TYPE VI, ALPHA-6; COL6A6","url":"https://www.omim.org/entry/616613"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Cytosol","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in 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patient.","date":"2025","source":"Stem cell research","url":"https://pubmed.ncbi.nlm.nih.gov/39954549","citation_count":0,"is_preprint":false},{"pmid":"41276784","id":"PMC_41276784","title":"Synergistic Anticancer Effects of COL6A1 Downregulation and the PD1 Inhibitor Pembrolizumab in Bladder Cancer.","date":"2025","source":"Journal of biochemical and molecular toxicology","url":"https://pubmed.ncbi.nlm.nih.gov/41276784","citation_count":0,"is_preprint":false},{"pmid":"38585878","id":"PMC_38585878","title":"A humanized knock-in Col6a1 mouse recapitulates a deep-intronic splice-activating variant.","date":"2024","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/38585878","citation_count":0,"is_preprint":false},{"pmid":"37315421","id":"PMC_37315421","title":"Homozygous splice variant (c.1741-6G>A) of the COL6A1 gene in three patients with Ullrich congenital muscular dystrophy.","date":"2023","source":"Neuromuscular disorders : NMD","url":"https://pubmed.ncbi.nlm.nih.gov/37315421","citation_count":0,"is_preprint":false},{"pmid":"40626679","id":"PMC_40626679","title":"Multimodal Evaluation of Bethlem Myopathy with the c.788G > A Variant in the COL6A1 Gene: a case report with genetic, ultrasonographic, and structural-functional discordance correlations.","date":"2025","source":"Acta myologica : myopathies and cardiomyopathies : official journal of the Mediterranean Society of Myology","url":"https://pubmed.ncbi.nlm.nih.gov/40626679","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.09.11.675515","title":"Antxr2-mediated fine-tuning of Collagen VI ensures skeletal muscle function","date":"2025-09-19","source":"bioRxiv","url":"https://doi.org/10.1101/2025.09.11.675515","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.06.02.657388","title":"Col6 deficiency in a zebrafish model of Bethlem myopathy leads to dysfunction of the muscle dihydropyridine receptor","date":"2025-06-04","source":"bioRxiv","url":"https://doi.org/10.1101/2025.06.02.657388","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.09.02.673624","title":"Bioengineered iPSC Vessels Recapitulate Human Vascular Physiological Function and Aging Phenotypes","date":"2025-09-05","source":"bioRxiv","url":"https://doi.org/10.1101/2025.09.02.673624","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.03.11.642560","title":"Generation and Characterization of <i>Col6a1</i> knock-in mice: A Promising Pre-Clinical Model for Collagen VI-Related Dystrophies","date":"2025-03-13","source":"bioRxiv","url":"https://doi.org/10.1101/2025.03.11.642560","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.03.21.644665","title":"The absence of collagen VI reduces systolic function but paradoxically increases Ca<sup>2+</sup>release in the rat heart","date":"2025-03-25","source":"bioRxiv","url":"https://doi.org/10.1101/2025.03.21.644665","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.02.14.638307","title":"Targeting of the nuclear RNA exosome to chromatin by HP1 affects the transcriptional programs of liver cells","date":"2025-02-19","source":"bioRxiv","url":"https://doi.org/10.1101/2025.02.14.638307","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":45949,"output_tokens":6053,"usd":0.114321},"stage2":{"model":"claude-opus-4-6","input_tokens":9761,"output_tokens":3489,"usd":0.204045},"total_usd":0.318366,"stage1_batch_id":"msgbatch_011kfMfE81o6CTcyhVUqumuW","stage2_batch_id":"msgbatch_01DTputS6WNkH745x1nVSoBo","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2003,\n      \"finding\": \"A heterozygous in-frame deletion near the amino-terminus of the COL6A1 triple-helical domain that preserves a unique cysteine required for dimer formation allows secretion of abnormal tetramers that exert a dominant-negative effect on microfibrillar assembly, causing loss of normal collagen VI localization in the basement membrane surrounding muscle fibers. In contrast, a deletion that removes this cysteine prevents dimer formation and secretion of the mutant chain, abrogating the dominant-negative effect and resulting in a milder phenotype.\",\n      \"method\": \"In vitro fibroblast analysis of mutant chain synthesis, secretion, and extracellular matrix deposition; genotype-phenotype correlation with active-site residue (cysteine) mutagenesis context\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1/2 — biochemical dissection of secretion and assembly with functional residue identification, replicated across two different deletion mutations with contrasting phenotypes\",\n      \"pmids\": [\"12840783\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"A heterozygous nonsense mutation in COL6A1 generates unstable mRNA subject to nonsense-mediated decay, causing haploinsufficiency of the α1(VI) subunit and reduced production of structurally normal collagen VI, leading to Bethlem myopathy.\",\n      \"method\": \"RT-PCR, mRNA stability analysis in patient fibroblasts and skeletal muscle, western blot of collagen VI production\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (mRNA decay assay, protein quantification) in patient-derived cells; first demonstration of haploinsufficiency as mechanism\",\n      \"pmids\": [\"9580662\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Loss of COL6A1/type VI collagen in Col6a1−/− mice causes structurally intact but mechanically deficient pericellular matrix (PCM) in articular cartilage, altering the biomechanical environment of chondrocytes and accelerating osteoarthritis development.\",\n      \"method\": \"Col6a1 knockout mouse model; micropipette aspiration of PCM mechanical properties; histomorphometry; bone mineral density measurement\",\n      \"journal\": \"Arthritis and rheumatism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct mechanical measurement in knockout mice with multiple orthogonal readouts (biomechanics, histology, BMD); highly cited\",\n      \"pmids\": [\"19248115\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Collagen VI deficiency in Col6a1−/− myopathic mice leads to mitochondrial dysfunction and increased apoptosis in skeletal muscle via sensitization of the mitochondrial permeability transition pore (mPTP); pharmacological inhibition of cyclophilin D with Debio 025 desensitizes the mPTP and normalizes mitochondrial function and ultrastructural defects without affecting calcineurin.\",\n      \"method\": \"Col6a1−/− mouse model; mitochondrial Ca2+ retention assay; membrane potential measurement; TUNEL apoptosis assay; electron microscopy; NFAT translocation assay for calcineurin activity\",\n      \"journal\": \"British journal of pharmacology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal functional assays in knockout mice with pharmacological rescue; establishes mPTP as the downstream mechanism of COL6A1 deficiency in muscle\",\n      \"pmids\": [\"19519726\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"A splice site mutation in COL6A1 intron 14 causes skipping of exon 14 and in-frame deletion of 18 amino acids including a cysteine residue in the triple-helical domain. The shortened α1(VI) chain is synthesized but not secreted by fibroblasts, resulting in reduced collagen VI microfibril deposition in the extracellular matrix.\",\n      \"method\": \"RT-PCR of patient fibroblast RNA; western blot; immunofluorescence of ECM\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct molecular analysis in patient fibroblasts with protein secretion and matrix deposition assays; mechanistically linked to cysteine required for dimer formation\",\n      \"pmids\": [\"10329467\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"A deep intronic c.930+189C>T variant in COL6A1 creates a cryptic donor splice site, inserting an in-frame 72-nt pseudoexon into COL6A1 mRNA. The encoded mutant α1(VI) chain exerts a dominant-negative effect on collagen VI matrix assembly. Antisense oligomers (ASOs) targeting the pseudoexon efficiently skip it in patient-derived fibroblasts, restoring wild-type matrix. CRISPR/Cas9 deletion of the intronic sequence containing the pseudoexon also abolishes its inclusion.\",\n      \"method\": \"Muscle RNA sequencing; patient fibroblast culture; ASO splice-switching; CRISPR/Cas9 deletion; western blot; immunofluorescence of collagen VI matrix\",\n      \"journal\": \"JCI insight\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1/2 — multiple orthogonal therapeutic correction methods (ASO and CRISPR) with protein-level readout; splice mechanism precisely defined\",\n      \"pmids\": [\"30895940\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"ASOs targeting the pseudoexon created by the COL6A1 c.930+189C>T deep intronic variant efficiently induce pseudoexon exclusion from mature transcripts in patient fibroblasts, restoring functional collagen VI microfibrillar matrix as assessed at RNA, protein, and structural levels.\",\n      \"method\": \"ASO transfection in patient-derived fibroblasts; qRT-PCR; western blot; immunofluorescence\",\n      \"journal\": \"Molecular therapy. Nucleic acids\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — systematic ASO tiling with functional readout at multiple levels; replicates and extends PMID 30895940\",\n      \"pmids\": [\"32585628\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"The Col6a1 gene enhancer region (−5.4 to −3.9 kb from transcription start) is required for activation of transcription in connective tissue cells associated with skeletal muscle. Using lacZ transgenic mice crossed with metD/D mutant mice (lacking myogenic cells in limb buds), the presence of myogenic-lineage cells was shown to be necessary for enhancer activation in mesenchymal cells, demonstrating that muscle cells signal to connective tissue cells to drive COL6A1 expression.\",\n      \"method\": \"Promoter-lacZ transgenic mice; genetic cross with metD/D (myogenic cell-deficient) mice; lacZ reporter expression analysis; collagen VI immunostaining\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis via double-mutant cross with functional reporter readout; strong mechanistic evidence for muscle-to-connective-tissue paracrine regulation of COL6A1 transcription\",\n      \"pmids\": [\"18761340\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"The 383-bp E-L fragment (within the −5.4/−3.9 kb Col6a1 enhancer region) is the most active sequence for tissue-specific transcription; integrity of the entire E-J subfragment is required for enhancer activity in articular cartilage. EMSA showed at least 22 ubiquitous transcription factors bind this region, and their relative proportions (not tissue-specific factors) determine tissue-specific expression.\",\n      \"method\": \"Transgenic mice with deletion constructs; linker-scanning mutagenesis; electrophoretic mobility shift assay (EMSA) with nuclear extracts\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vivo mutagenesis + protein–DNA binding assays; defines enhancer mechanism for tissue-specific Col6a1 transcription\",\n      \"pmids\": [\"10747869\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Activation of Col6a1 gene transcription in Schwann cells is part of their differentiation program induced by neuregulins from the neural crest; once competence to transcribe Col6a1 is established, transcriptional regulation becomes neuregulin-independent and is modulated by cell cycle status, correlating with myelination onset after birth.\",\n      \"method\": \"lacZ transgenic mouse reporter; developmental expression analysis; neuregulin-deficient genetic background\",\n      \"journal\": \"Mechanisms of development\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — transgenic reporter in vivo, but mechanistic pathway not fully dissected biochemically\",\n      \"pmids\": [\"11287188\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Truncating mutations within the COL6A1 C-terminal C2 subdomain result in intracellular retention of mutant collagen VI protein and severely decreased collagen VI matrix deposition; the absence of the α1(VI) C2 domain also leads to abnormal fibronectin network interactions, revealing a role for this domain in ECM organization.\",\n      \"method\": \"Patient fibroblast immunofluorescence; western blot; RNA analysis for NMD; fibronectin network staining\",\n      \"journal\": \"BMC medical genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — single patient case with protein-level analysis; provides domain-specific mechanistic insight into C2 domain function in secretion and ECM interactions\",\n      \"pmids\": [\"23738969\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Dominant glycine substitutions in the triple-helical domain of COL6A1 cause disease via a dominant-negative mechanism, whereas recessive mutations (nonsense, frameshift) cause more severe phenotypes via loss of function, establishing that glycine substitutions in the triple helix act dominantly and missense/truncating mutations outside this region act recessively.\",\n      \"method\": \"Patient cell analysis; RT-PCR; western blot; immunofluorescence; parental DNA sequencing to confirm de novo status\",\n      \"journal\": \"Annals of neurology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — protein secretion and matrix assays in patient fibroblasts; multiple patients with different mutation types compared\",\n      \"pmids\": [\"16130093\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Upregulation of COL6A1 in osteosarcoma cells promotes migration and invasion by interacting with SOCS5 to suppress STAT1 expression via ubiquitination and proteasomal degradation. Exosomal COL6A1 derived from osteosarcoma cells converts normal fibroblasts to cancer-associated fibroblasts that secrete IL-6 and IL-8, promoting further invasion via TGF-β/COL6A1 signaling.\",\n      \"method\": \"Co-immunoprecipitation; ubiquitination assay; RNA sequencing; in vitro migration/invasion assays; exosome tracing; co-culture experiments; in vivo xenograft\",\n      \"journal\": \"Theranostics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP and ubiquitination assays with functional rescue experiments; single lab but multiple orthogonal methods\",\n      \"pmids\": [\"33391546\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"The COL6A1 c.930+189C>T mutation leads to secretion of the mutant α1(VI) chain as a single chain (not incorporated into tetramers) that forms large extracellular aggregates, while wild-type α1(VI) is assembled normally into tetramers. Expression of the mutant chain in α1-chain-deficient WI-26 VA4 cells confirms it cannot support tetramer assembly.\",\n      \"method\": \"Mutation-specific antibody; patient fibroblast cell culture; co-localization immunofluorescence; transfection of mutant/wild-type chains into WI-26 VA4 cells; protein secretion analysis\",\n      \"journal\": \"Human mutation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1/2 — reconstitution in deficient cell line + patient-derived fibroblast analysis + mutation-specific detection; defines precise assembly failure mechanism\",\n      \"pmids\": [\"40225172\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"COL6A1 interacts with ITGA5 (integrin alpha-5) and activates the FAK/Paxillin/AKT focal adhesion pathway in glioblastoma cells; tumor electric field therapy downregulates COL6A1, hindering its interaction with ITGA5 and suppressing this pathway.\",\n      \"method\": \"Co-immunoprecipitation; immunofluorescence co-localization; western blot of FAK/Paxillin/AKT pathway\",\n      \"journal\": \"CNS neuroscience & therapeutics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single Co-IP in a cancer cell line context; no mutagenesis or reconstitution\",\n      \"pmids\": [\"38887185\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"COL6A1 knockdown in PDGF-BB-stimulated vascular smooth muscle cells attenuates cell viability and invasive ability, partially reverses increased expression of fibronectin, MMP-2 and MMP-9, and inhibits AKT/mTOR pathway activation, placing COL6A1 upstream of AKT/mTOR signaling in VSMC migration.\",\n      \"method\": \"siRNA knockdown; CCK-8 viability assay; wound healing and Transwell invasion assay; western blot of pathway components\",\n      \"journal\": \"Experimental and therapeutic medicine\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single lab, knockdown with pathway readout but no direct binding or epistasis confirmation\",\n      \"pmids\": [\"31410158\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"COL6A1 promotes osteoclast differentiation and formation in osteoarthritis by activating the EPAC/RAP1 signaling axis; COL6A1 knockdown in vivo reduces osteoclast-mediated subchondral bone remodeling and slows OA progression in DMM mouse models.\",\n      \"method\": \"WGCNA; in vitro perturbation and rescue experiments; in vivo DMM mouse model with COL6A1 knockdown; molecular docking\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vitro and in vivo perturbation with rescue; identifies specific signaling axis, though binding mechanism not directly demonstrated\",\n      \"pmids\": [\"40143596\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"CRISPR/Cas9 allele-specific disruption of the dominant-negative COL6A1 c.877G>A (p.Gly293Arg) mutation in patient fibroblasts reduces mutant allele expression in >40% of reads with no effect on the wild-type allele, rescuing collagen VI extracellular matrix assembly.\",\n      \"method\": \"CRISPR/Cas9 genome editing; next-generation sequencing; droplet digital PCR with allele-specific probes; immunofluorescence of collagen VI matrix\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — allele-specific editing with quantitative allele discrimination and functional matrix readout; establishes dominant-negative mechanism for this specific variant\",\n      \"pmids\": [\"35457228\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"An allele-specific siRNA with an intentional additional mismatch selectively silences the dominant-negative COL6A1 G293R (c.877G>A) mutant transcript while preserving wild-type transcript levels in patient fibroblasts, rescuing secretion and assembly of collagen VI matrix.\",\n      \"method\": \"siRNA transfection; allele-specific RT-qPCR; western blot; immunofluorescence of collagen VI matrix in patient fibroblasts\",\n      \"journal\": \"Molecular therapy. Nucleic acids\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — systematic allele-specific silencing with multiple molecular and functional readouts; mechanistically validates dominant-negative nature of G293R variant\",\n      \"pmids\": [\"38617974\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"A non-triple-helical polypeptide of type VI collagen α1 chain (NTH α1(VI), ~140 kDa) is encoded by COL6A1 and represents an alternative gene product with distinct glycosylation from the triple-helical form, detected in supernatants of several human cancer cell lines.\",\n      \"method\": \"Antibody characterization; western blot; lectin reactivity assays; expression in cancer cell supernatants\",\n      \"journal\": \"Journal of biochemistry\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — identification of novel protein product by antibody detection; function not established; single lab\",\n      \"pmids\": [\"29659864\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"ANTXR2 (anthrax toxin receptor 2) expressed by fibro-adipogenic precursors controls COL6A1/collagen VI turnover via receptor-mediated endocytosis; Antxr2−/− mice accumulate collagen VI in intramuscular connective tissue, leading to tissue stiffening and myopathy, which is rescued in Antxr2−/−Col6a1−/− double knockout mice.\",\n      \"method\": \"Antxr2−/− and Antxr2−/−Col6a1−/− double knockout mouse models; proteomics; muscle histology; biomechanical testing; locomotion analysis\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — double knockout genetic epistasis rescues phenotype, establishing ANTXR2 as regulator of COL6A1 turnover; preprint not yet peer-reviewed\",\n      \"pmids\": [\"bio_10.1101_2025.09.11.675515\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In a zebrafish col6a1 Δex14 model of Bethlem myopathy, Col6a1 deficiency leads to reduced dihydropyridine receptor (DHPR) charge movement density, a negative shift in DHPR voltage-dependence, elevated resting Ca2+ sparks (SR Ca2+ leak), and reduced twitch force, suggesting COL6A1 is required for proper DHPR function and Ca2+ homeostasis in skeletal muscle fibers.\",\n      \"method\": \"Zebrafish knockout model; electrophysiology (charge movement measurement); intracellular Ca2+ transient imaging; Ca2+ spark measurement; immunofluorescence of DHPR localization; muscle force measurement; swimming performance\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple electrophysiological and Ca2+ imaging methods in zebrafish ortholog model; preprint not yet peer-reviewed\",\n      \"pmids\": [\"bio_10.1101_2025.06.02.657388\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In Col6a1−/− rats, absence of collagen VI reduces cardiac systolic function and paradoxically increases Ca2+ transient amplitude and SR Ca2+ load in isolated cardiomyocytes; β-adrenergic stimulation triggers diastolic Ca2+ release events in knockout cardiomyocytes, suggesting collagen VI contributes to cardiac Ca2+ regulation, potentially via linkage to the dystrophin-glycoprotein complex.\",\n      \"method\": \"Global Col6a1 knockout rat; echocardiography; cardiomyocyte Ca2+ transient imaging; SR Ca2+ load measurement; β-adrenergic stimulation protocol\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 2 method but preprint, single study; proposed mechanism (DGC linkage) is speculative\",\n      \"pmids\": [\"bio_10.1101_2025.03.21.644665\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Thyroid hormone receptor α (TRα) directly binds the Col6a1 promoter region (identified by ChIP-seq) and positively regulates Col6a1 transcription; TRα knockdown in C2C12 myoblasts reduces Col6a1 expression and inhibits myoblast proliferation and differentiation.\",\n      \"method\": \"ChIP-seq; RNA-seq; ChIP-qPCR; siRNA knockdown of TRα; RT-qPCR; C2C12 proliferation/differentiation assays\",\n      \"journal\": \"Journal of muscle research and cell motility\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — ChIP-seq identifies direct TRα binding at Col6a1 locus; functional knockdown confirms transcriptional regulation; peer-reviewed\",\n      \"pmids\": [\"40317420\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"COL6A1 encodes the α1(VI) chain of type VI collagen, which assembles intracellularly into anti-parallel dimers (requiring a specific triple-helical cysteine residue), then tetramers with the α2(VI) and α3(VI) chains, and is secreted as microfibrillar networks into the pericellular and extracellular matrix of skeletal muscle, cartilage, and connective tissue; loss of function causes mechanically deficient pericellular matrix and mitochondrial permeability transition pore sensitization leading to muscle apoptosis, while dominant-negative glycine substitutions or pseudoexon insertions in the triple-helical domain disrupt tetramer assembly and produce pathological aggregates, collectively causing the spectrum from Bethlem myopathy to Ullrich congenital muscular dystrophy, with transcription regulated by an upstream tissue-specific enhancer activated by signals from myogenic cells and directly by thyroid hormone receptor α.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"COL6A1 encodes the α1(VI) chain of type VI collagen, a structural extracellular matrix protein that assembles into microfibrils critical for the biomechanical integrity of pericellular matrices in skeletal muscle, cartilage, and connective tissue. Intracellularly, the α1(VI) chain forms anti-parallel dimers via a triple-helical cysteine residue and then tetramers with α2(VI) and α3(VI) chains; mutations that preserve this cysteine permit secretion of abnormal tetramers exerting dominant-negative effects on microfibrillar assembly, whereas mutations that remove it or truncate the C2 domain prevent secretion entirely [PMID:12840783, PMID:10329467, PMID:23738969]. Loss of collagen VI in knockout mice causes mechanically deficient pericellular matrix in cartilage, sensitization of the mitochondrial permeability transition pore leading to muscle fiber apoptosis, and accelerated osteoarthritis [PMID:19248115, PMID:19519726]. Dominant glycine substitutions and pseudoexon insertions in the triple-helical domain, as well as recessive loss-of-function mutations, cause the Bethlem myopathy–Ullrich congenital muscular dystrophy spectrum [PMID:9580662, PMID:16130093, PMID:30895940].\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"Establishing that COL6A1 haploinsufficiency—via nonsense-mediated mRNA decay of a premature stop codon allele—is sufficient to cause Bethlem myopathy resolved the question of whether quantitative reduction alone (without a structurally abnormal protein) can be pathogenic.\",\n      \"evidence\": \"RT-PCR and mRNA stability assays in patient fibroblasts and muscle, plus western blot of collagen VI output\",\n      \"pmids\": [\"9580662\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Threshold of α1(VI) reduction needed for disease not defined\", \"No rescue experiment to confirm causality\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Demonstrating that deletion of a triple-helical cysteine prevents dimer formation and blocks mutant chain secretion established this residue as the gatekeeper for collagen VI assembly quality control.\",\n      \"evidence\": \"RT-PCR, western blot, and immunofluorescence of ECM in patient fibroblasts carrying a splice-site mutation deleting exon 14\",\n      \"pmids\": [\"10329467\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the chaperone/ER retention machinery that detects misfolded chains unknown\", \"Only one mutation analyzed\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Mapping the minimal Col6a1 enhancer (E-L fragment) and showing that combinatorial binding of ubiquitous transcription factors—not tissue-restricted factors—drives tissue-specific expression answered how a widely expressed gene achieves restricted transcription in connective tissue and cartilage.\",\n      \"evidence\": \"Transgenic mice with deletion constructs and linker-scanning mutagenesis; EMSA with nuclear extracts from multiple tissues\",\n      \"pmids\": [\"10747869\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the 22 ubiquitous factors not fully resolved\", \"Chromatin context and epigenetic regulation not addressed\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Showing that neuregulin signaling from neural crest cells initiates Col6a1 transcriptional competence in Schwann cells, which then becomes neuregulin-independent and cell-cycle-regulated, revealed a developmental switch coupling Col6a1 to myelination onset.\",\n      \"evidence\": \"lacZ transgenic reporter mice analyzed across development and in neuregulin-deficient backgrounds\",\n      \"pmids\": [\"11287188\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct transcription factor mediating neuregulin-to-Col6a1 activation not identified\", \"Biochemical pathway not dissected\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"By comparing two in-frame deletions—one preserving and one removing the dimerization cysteine—this study resolved why some triple-helical domain mutations exert dominant-negative effects while others do not, establishing that secretion competence of the mutant chain is the key determinant of phenotypic severity.\",\n      \"evidence\": \"In vitro fibroblast analysis of mutant chain synthesis, secretion, and ECM deposition across two contrasting mutations\",\n      \"pmids\": [\"12840783\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry of mutant-to-wild-type chains in secreted tetramers not quantified\", \"Fate of intracellularly retained chains not tracked\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Systematic comparison of dominant glycine substitutions versus recessive truncating mutations across multiple patients established the general rule that triple-helical glycine substitutions act via dominant-negative poisoning of assembly while loss-of-function alleles cause the more severe Ullrich phenotype through biallelic depletion.\",\n      \"evidence\": \"Patient fibroblast analysis with RT-PCR, western blot, immunofluorescence, and parental genotyping\",\n      \"pmids\": [\"16130093\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Some glycine substitutions produce intermediate phenotypes not explained by simple dominant-negative model\", \"Modifier genes not explored\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Genetic ablation of myogenic cells in limb buds (metD/D cross) abolished Col6a1 enhancer activation in mesenchymal cells, proving that muscle-derived paracrine signals are required for Col6a1 transcription in connective tissue.\",\n      \"evidence\": \"lacZ transgenic reporter crossed with metD/D myogenic-cell-deficient mice; reporter expression and collagen VI immunostaining\",\n      \"pmids\": [\"18761340\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the paracrine signal from myogenic cells unknown\", \"Whether this regulation operates in adult muscle homeostasis not tested\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Two concurrent studies using Col6a1−/− mice established that collagen VI deficiency causes both mechanically deficient pericellular matrix in cartilage (accelerating osteoarthritis) and mitochondrial permeability transition pore sensitization in skeletal muscle (driving apoptosis rescuable by cyclophilin D inhibition), defining the two major downstream pathological axes of COL6A1 loss.\",\n      \"evidence\": \"Col6a1 knockout mice; micropipette aspiration of PCM; mitochondrial Ca2+ retention and membrane potential assays; TUNEL; Debio 025 pharmacological rescue\",\n      \"pmids\": [\"19248115\", \"19519726\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular link between absent pericellular collagen VI and mPTP sensitization not identified\", \"Whether mPTP mechanism also operates in cartilage chondrocytes unknown\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Identifying that truncations in the C-terminal C2 subdomain cause intracellular retention and also disrupt fibronectin network organization revealed a dual role for the C2 domain in both secretion competence and ECM network interactions.\",\n      \"evidence\": \"Patient fibroblast immunofluorescence, western blot, fibronectin staining\",\n      \"pmids\": [\"23738969\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Only one patient studied\", \"Direct binding interface between C2 domain and fibronectin not characterized\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Discovery that a deep intronic variant (c.930+189C>T) creates a pseudoexon encoding an assembly-incompetent α1(VI) chain, correctable by ASO splice-switching and CRISPR deletion, established a new class of COL6A1 pathogenic mechanism and a therapeutic paradigm.\",\n      \"evidence\": \"Muscle RNA-seq; patient fibroblast culture; ASO and CRISPR/Cas9 correction with protein and matrix readouts\",\n      \"pmids\": [\"30895940\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo delivery and efficacy of ASOs not demonstrated\", \"Long-term stability of correction unknown\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Demonstration that COL6A1 interacts with SOCS5 to promote ubiquitin-dependent STAT1 degradation and that exosomal COL6A1 converts fibroblasts to cancer-associated fibroblasts revealed a non-structural signaling role for COL6A1 in osteosarcoma invasion.\",\n      \"evidence\": \"Co-immunoprecipitation; ubiquitination assay; exosome tracing; co-culture; in vivo xenograft\",\n      \"pmids\": [\"33391546\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural basis of COL6A1–SOCS5 interaction unknown\", \"Relevance outside osteosarcoma context not tested\", \"Whether full-length or processed collagen VI mediates this effect unclear\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Allele-specific CRISPR disruption of the dominant-negative G293R allele rescued collagen VI matrix assembly, providing proof-of-concept that selectively silencing the mutant allele is sufficient for phenotypic correction.\",\n      \"evidence\": \"CRISPR/Cas9 editing in patient fibroblasts; ddPCR allele quantification; immunofluorescence of matrix\",\n      \"pmids\": [\"35457228\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Efficiency of editing (~40%) may be insufficient in vivo\", \"Off-target analysis limited\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Showing that the pseudoexon-containing mutant α1(VI) chain is secreted as a single chain (not incorporated into tetramers) and forms extracellular aggregates precisely defined why this mutation is dominant-negative: the mutant chain bypasses intracellular quality control but poisons the extracellular matrix.\",\n      \"evidence\": \"Mutation-specific antibody; patient fibroblasts; reconstitution of mutant chain in α1-deficient WI-26 VA4 cells\",\n      \"pmids\": [\"40225172\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Nature and composition of extracellular aggregates not characterized at ultrastructural level\", \"Whether aggregates actively damage surrounding matrix not tested\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Allele-specific siRNA with an engineered mismatch selectively silenced the G293R mutant transcript and rescued collagen VI matrix, advancing therapeutic strategy beyond CRISPR by demonstrating reversible, tunable allele-selective knockdown.\",\n      \"evidence\": \"siRNA transfection in patient fibroblasts; allele-specific RT-qPCR; western blot; immunofluorescence\",\n      \"pmids\": [\"38617974\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo delivery to muscle not demonstrated\", \"Duration of effect and dosing not established\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"ChIP-seq identification of direct thyroid hormone receptor α binding at the Col6a1 promoter, with functional validation by TRα knockdown, established a hormonal transcriptional input for COL6A1 expression relevant to myoblast proliferation and differentiation.\",\n      \"evidence\": \"ChIP-seq and ChIP-qPCR in C2C12 myoblasts; siRNA knockdown of TRα; RT-qPCR; proliferation/differentiation assays\",\n      \"pmids\": [\"40317420\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether TRα regulation operates in vivo in adult muscle not confirmed\", \"Relationship to the upstream −5.4 kb enhancer not examined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The molecular link between absence of pericellular collagen VI and sensitization of the mitochondrial permeability transition pore—the central pathogenic mechanism in collagen VI myopathies—remains undefined, as does the identity of the muscle-derived paracrine signal that activates COL6A1 transcription in connective tissue.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Transmembrane receptor mediating collagen VI signal to mitochondria unknown\", \"Identity of muscle paracrine factor unknown\", \"No structural model of collagen VI tetramer at atomic resolution\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 1, 2, 4, 13]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0031012\", \"supporting_discovery_ids\": [0, 2, 4, 5, 10, 13]},\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [0, 13, 19]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1474244\", \"supporting_discovery_ids\": [0, 2, 4, 10, 13]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"complexes\": [\n      \"Collagen VI tetramer (α1/α2/α3)\"\n    ],\n    \"partners\": [\n      \"COL6A2\",\n      \"COL6A3\",\n      \"SOCS5\",\n      \"ITGA5\",\n      \"THRA\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}