{"gene":"COL5A1","run_date":"2026-06-09T22:57:19","timeline":{"discoveries":[{"year":2011,"finding":"Conditional knockout of Col5a1 in corneal stroma (using Kera-Cre) results in severely increased and heterogeneous fibril diameters, abnormal fibril structure, decreased fibril number, disorganized lamellae, decreased stroma thickness, and corneal opacity, demonstrating that collagen V is a dominant regulator of collagen fibrillogenesis and matrix assembly during tissue development.","method":"Conditional knockout mouse model (Cre-loxP), electron microscopy, corneal haze quantification","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 1/2 / Strong — direct loss-of-function in vivo with multiple orthogonal structural and functional readouts in a dedicated study","pmids":["22159420"],"is_preprint":false},{"year":2006,"finding":"Col5a1 heterozygous mice (haploinsufficient, 50% reduction in collagen V) exhibit two fibril subpopulations: relatively normal fibrils with periodic collagen V immunoreactivity (where type I/V interactions regulate nucleation) and abnormal fibrils lacking collagen V formed by unregulated type I collagen sequestration. This disrupts normal linear and lateral fibril growth via fusion, revealing that collagen V regulates fibril nucleation and growth.","method":"Targeted gene inactivation in mice, immunoelectron microscopy, tensile strength testing, skin extensibility measurement","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1/2 / Strong — in vivo loss-of-function with mechanistic dissection of fibril subpopulations using multiple orthogonal methods","pmids":["16492673"],"is_preprint":false},{"year":1997,"finding":"A missense mutation substituting the most 5' cysteine in the COL5A1 C-propeptide domain prevents incorporation of mutant pro-α1(V) chains into collagen V trimers, reducing collagen V levels and causing EDS type I. Additionally, splice-site mutations in COL5A1 were identified in EDS I and II patients, confirming COL5A1 haploinsufficiency as a causal mechanism.","method":"Mutation analysis, fibroblast collagen biochemistry, segregation analysis in a four-generation family","journal":"American journal of human genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct mutation characterization with biochemical demonstration of reduced collagen V incorporation, replicated across multiple families","pmids":["9042913"],"is_preprint":false},{"year":2000,"finding":"In eight of 28 classical EDS probands, one COL5A1 allele was completely or nearly completely absent from mRNA due to nonsense-mediated mRNA decay caused by small insertions/deletions or splice-site mutations, establishing COL5A1 haploinsufficiency as a common (~one-third of cases) molecular mechanism in classical EDS.","method":"RT-PCR allele expression analysis, cycloheximide treatment to block nonsense-mediated decay, heteroduplex analysis, genomic sequencing","journal":"American journal of human genetics","confidence":"High","confidence_rationale":"Tier 1/2 / Strong — two orthogonal molecular methods (allele expression + cycloheximide rescue) across 16 individuals, replicated in a parallel study (PMID:10777716)","pmids":["10796876","10777716"],"is_preprint":false},{"year":2004,"finding":"COL5A1-mutant fibroblasts from EDS type I patients fail to organize collagens and fibronectin in the ECM, downregulate α2β1 integrin, and recruit αvβ3 instead of α5β1 integrin. Treatment with purified collagen V (but not fibronectin) restores the control phenotype, and blocking α2β1 integrin in control fibroblasts recapitulates the EDS phenotype, demonstrating that collagen V controls α2β1 integrin organization which in turn regulates fibronectin integrin receptor recruitment.","method":"EDS patient-derived fibroblasts, purified collagen V rescue experiment, function-blocking antibodies, immunofluorescence, ECM organization assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal approaches (rescue, antibody blocking, patient cells) establishing a mechanistic pathway in a single rigorous study","pmids":["14970208"],"is_preprint":false},{"year":2004,"finding":"COL5A1 haploinsufficient EDS fibroblasts deposit less than half the hydroxyproline of controls and assemble significantly fewer collagen fibrils despite near-normal total collagen synthesis rates, and fibril diameter is inversely proportional to type V/type I collagen ratio. This demonstrates that the quantity of fibrils deposited is highly sensitive to type V collagen reduction, far out of proportion to its contribution to collagen mass.","method":"Long-term dermal fibroblast cultures, hydroxyproline assay, electron microscopy of fibril morphology, comparison with OI (COL1A1 haploinsufficient) cells","journal":"Journal of cellular biochemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — quantitative biochemical and ultrastructural analysis with isogenic comparison groups establishing a dose-response relationship","pmids":["15095409"],"is_preprint":false},{"year":2001,"finding":"A COL5A1 exon 14 splice acceptor mutation (A(-2)→G) creates a cryptic acceptor site that causes a +1 frameshift leading to a premature stop codon in exon 17; the mutant transcript undergoes nonsense-mediated mRNA decay (only 8% of normal level in untreated fibroblasts, equimolar in cycloheximide-treated cells), yielding α1(V) haploinsufficiency and heterogeneous dermal collagen fibril diameters including 'cauliflower' fibrils.","method":"RT-PCR, RNase protection, cycloheximide treatment, transmission electron microscopy of dermal biopsy","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1/2 / Strong — mechanistic dissection of NMD with cycloheximide rescue and ultrastructural confirmation in a single rigorous study","pmids":["11278977"],"is_preprint":false},{"year":2009,"finding":"Missense mutations (p.L25R and p.L25P) in the signal peptide hydrophobic core of pre-pro-α1(V) collagen prevent translocation of the mutant protein into the endoplasmic reticulum, causing intracellular retention and reduced collagen V in the ECM, demonstrating that signal peptide integrity is required for proper secretion and fibrillogenesis.","method":"Patient-derived fibroblast analysis, immunofluorescence for intracellular retention, collagen electrophoresis, mutation characterization","journal":"Human mutation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional demonstration of ER retention in patient cells with two independent mutations, single lab","pmids":["18972565"],"is_preprint":false},{"year":2002,"finding":"A COL5A1 splice-acceptor mutation (IVS4-2A→G) causes complex splicing outcomes dependent on the order of intron removal: when intron 5 is removed rapidly, exons 5 and 6 are jointly skipped producing the major product; when intron 6 is removed first, only exon 5 is skipped; when intron 4 is removed last, cryptic exon 5 acceptors are used. The resulting mutant pro-α1(V) chains with abnormal N-propeptides are secreted, incorporated into ECM, and cause dramatic alterations in collagen fibril structure.","method":"RT-PCR characterization of splice products, genomic sequencing, intron removal order analysis, electron microscopy of fibril structure","journal":"American journal of human genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple splice products characterized mechanistically with order-of-removal model validated and fibril structure confirmed, single lab","pmids":["12145749"],"is_preprint":false},{"year":2011,"finding":"Two major forms of the COL5A1 3'-UTR (C-allele and T-allele) differ in mRNA stability: the T-allele shows significantly higher luciferase reporter activity (90.6%) than the C-allele (69.0%), indicating greater mRNA stability; a functional miR-608 binding site was identified within the 3'-UTR; deletion constructs revealed additional elements regulating COL5A1 mRNA stability.","method":"Luciferase reporter assay with cloned 3'-UTR variants, deletion constructs, sequence analysis","journal":"Matrix biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional reporter assay with multiple construct variants demonstrating differential mRNA stability, single lab","pmids":["21609763"],"is_preprint":false},{"year":2004,"finding":"TGF-β1 upregulates COL5A1 expression during the proliferation and differentiation phases of osteoblast development in MC3T3-E1 cells, and COL5A1 mRNA is expressed in developing mouse bone at E17.5, establishing COL5A1 as a TGF-β target gene in osteoblasts.","method":"cDNA microarray, Northern blotting, RNA in situ hybridization, immunohistochemistry in mouse embryos","journal":"Matrix biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — microarray finding validated by Northern blotting and in situ hybridization, single lab with in vivo confirmation","pmids":["15579311"],"is_preprint":false},{"year":2010,"finding":"Sp7/Osterix transcription factor binds to a Sp1-binding site in the Col5a1 core promoter and activates its transcription specifically in osteoblastic cells: overexpression of Sp7 increases Col5a1 promoter activity and endogenous mRNA; siRNA knockdown of Sp7 decreases both; mutation of the Sp1-binding site abolishes the effect; and Sp7 and Col5a1 expression co-increase during osteoblast differentiation.","method":"Promoter-reporter transfection assays, mutagenesis of Sp1 binding site, siRNA knockdown, overexpression, osteoblast differentiation model","journal":"Matrix biology","confidence":"High","confidence_rationale":"Tier 1/2 / Strong — multiple orthogonal approaches (gain-of-function, loss-of-function, mutagenesis, differentiation model) establishing the Sp7-Col5a1 regulatory axis in a single rigorous study","pmids":["20888414"],"is_preprint":false},{"year":2004,"finding":"The Col5a1 core promoter lacks a TATA motif and has high GC content; three nuclear factor binding sites were identified: BS1 binds Sp1, BS2 binds CBF (at a CAAAT motif), and BS3 binds an Sp1-related protein. CBF activates the Col5a1 promoter and overexpression of CBF-B subunit modulates this activity, suggesting coordinated regulation of type I and V collagen genes by CBF.","method":"Transient transfection promoter-reporter assays, electrophoretic mobility shift assay (EMSA), oligonucleotide competition and supershift assays, CBF-B overexpression","journal":"Matrix biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — EMSA with competition/supershift plus functional promoter assays, single lab","pmids":["15246108"],"is_preprint":false},{"year":1995,"finding":"The COL5A1 promoter lacks TATA and CAAT boxes, has multiple transcription start sites, high GC content, lies within a CpG island, and contains multiple Sp1 binding sites. Stepwise deletion analysis shows gradual decrease in promoter activity, indicating an array of cis-acting elements; gel mobility shift assays confirm Sp1 binding at multiple sites within the minimal promoter.","method":"5' deletion reporter assays, gel mobility shift assay (EMSA), S1 nuclease mapping, multiple transcription start site mapping","journal":"The Biochemical journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional promoter deletion analysis combined with EMSA in a single dedicated study","pmids":["7646438"],"is_preprint":false},{"year":1996,"finding":"A translocation breakpoint within COL5A1 intron 24 produces a fusion mRNA between COL5A1 and an Alu sequence but no aberrant protein; instead, type V collagen is reduced in patient fibroblasts, demonstrating haploinsufficiency as the mechanism causing EDS type I.","method":"Chromosomal translocation mapping, RT-PCR fusion transcript analysis, fibroblast collagen biochemistry","journal":"Nature genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct demonstration of haploinsufficiency mechanism via molecular analysis and biochemical quantification of collagen V in patient cells","pmids":["8673139"],"is_preprint":false},{"year":2018,"finding":"miR-29b directly binds to the 3'-UTR of Col5a1 and represses its expression at the mRNA and protein levels; miR-29b overexpression decreases Col5a1 luciferase reporter activity, endogenous mRNA, and protein; CRISPR/Cas9 knockout or RNAi knockdown of miR-29b increases Col5a1 expression, establishing miR-29b as a post-transcriptional repressor of Col5a1.","method":"Luciferase reporter assay with 3'-UTR constructs and binding-site mutants, miRNA overexpression, RNAi knockdown, CRISPR/Cas9 knockout, RT-PCR, Western blotting","journal":"Connective tissue research","confidence":"High","confidence_rationale":"Tier 1/2 / Strong — multiple orthogonal methods (reporter assay with mutagenesis, gain-of-function, loss-of-function including CRISPR) in a single study","pmids":["28829698"],"is_preprint":false},{"year":2022,"finding":"Col5a1 haploinsufficient mice show dysregulation of ECM components including thrombospondin-1, lysyl oxidase, and lumican in skin, and upregulation of TGF-β1 in serum with increased pSmad2 in skin, suggesting that altered matrix-to-cell TGF-β signaling contributes to abnormal wound healing and atrophic scarring in classic EDS.","method":"Transcriptome analysis of skin and Achilles tendons, serum TGF-β1 ELISA, pSmad2 immunohistochemistry in Col5a1+/- mice","journal":"Human molecular genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — transcriptome plus targeted protein validation in a mouse model, single lab","pmids":["34740257"],"is_preprint":false},{"year":2021,"finding":"Col5a1 knockout rats (CRISPR/Cas9) show fracture of elastic fibers and disarray of collagenous fibers by electron microscopy at 6 weeks. After β-aminopropionitrile and angiotensin II treatment to induce aortic dissection, Col5a1 knockout rats have significantly higher aortic dissection incidence than wild-type (93.3% vs 0%), and the TGF-β signaling pathway is significantly activated in Col5a1 knockout rats.","method":"CRISPR/Cas9 Col5a1 knockout rats, electron microscopy, aortic dissection induction model, TGF-β pathway analysis","journal":"Journal of the American Heart Association","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo knockout model with mechanistic pathway analysis, single lab","pmids":["34041919"],"is_preprint":false},{"year":1996,"finding":"A 4 bp deletion at positions +3 to +6 of COL5A1 intron 65 removes exon 65 from processed mRNAs; since exon 65 encodes 78 residues of the carboxyl propeptide, the mutation reduces efficiency of incorporating mutant pro-α1(V) chains into type V collagen trimers and reduces total type V collagen synthesis, causing EDS type I.","method":"Linkage analysis, genomic sequencing identifying splice-site deletion, mRNA analysis by RT-PCR","journal":"Human molecular genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — molecular characterization of splice-site mutation with predicted mechanistic consequence for chain assembly, single family","pmids":["8923000"],"is_preprint":false},{"year":2024,"finding":"COL5A1 interacts with TGM2 and inhibits its K48-linked ubiquitination-mediated degradation, thereby stabilizing TGM2 and enhancing chemoresistance and IL-6 secretion in triple-negative breast cancer cells. Additionally, TGF-β from M2 macrophages drives COL5A1 expression through a TGFβ/Smad3/COL5A1 signaling pathway, establishing a feedback loop.","method":"Co-immunoprecipitation, ubiquitination assay, in vitro and in vivo functional assays, cytokine profiling","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP and ubiquitination assay establishing protein-protein interaction and post-translational mechanism, single lab","pmids":["38609499"],"is_preprint":false}],"current_model":"COL5A1 encodes the pro-α1(V) chain of type V collagen, which co-assembles with type I collagen into heterotypic fibrils and acts as a dominant regulator of collagen fibril nucleation, diameter, and organization; haploinsufficiency (caused by null alleles, splice mutations, signal peptide mutations, or nonsense-mediated mRNA decay) leads to classical Ehlers-Danlos syndrome by reducing the number and increasing the heterogeneity of collagen fibrils, while its 3'-UTR regulates mRNA stability (modulated by miR-29b and miR-608 binding sites), its promoter is controlled by Sp1/CBF and Sp7/Osterix transcription factors in a cell-type-specific manner, and loss of COL5A1 activates TGF-β/Smad signaling as a downstream pathogenic mechanism in connective tissue disease."},"narrative":{"mechanistic_narrative":"COL5A1 encodes the pro-α1(V) chain of type V collagen, a quantitatively minor fibrillar collagen that acts as a dominant regulator of collagen fibrillogenesis: it nucleates heterotypic fibrils and controls their number, diameter, and organization during connective tissue assembly [PMID:22159420, PMID:16492673]. In vivo loss-of-function and haploinsufficiency reveal that fibril nucleation is exquisitely sensitive to collagen V dose — a ~50% reduction yields fewer fibrils, two abnormal fibril subpopulations, increased diameter heterogeneity, and tissue-level defects in cornea, skin, and tendon, with fibril diameter inversely proportional to the type V/type I ratio [PMID:22159420, PMID:16492673, PMID:15095409]. At the cell-matrix interface, collagen V controls α2β1 integrin organization, which in turn governs fibronectin receptor recruitment and ECM assembly [PMID:14970208]. COL5A1 haploinsufficiency — caused by null and translocation alleles, splice-site mutations producing premature stop codons subject to nonsense-mediated mRNA decay, signal-peptide mutations blocking ER translocation, and C-propeptide mutations preventing chain incorporation — is the principal molecular mechanism of classical Ehlers-Danlos syndrome [PMID:9042913, PMID:10796876, PMID:10777716, PMID:11278977, PMID:18972565, PMID:8673139]. Reduced collagen V also dysregulates matrix-to-cell TGF-β/Smad signaling, contributing to abnormal wound healing and predisposition to aortic dissection in animal models [PMID:34740257, PMID:34041919]. Expression is governed by a TATA-less, GC-rich promoter bound by Sp1, CBF, and the osteoblast-specific factor Sp7/Osterix, and post-transcriptionally by 3'-UTR elements including miR-29b and miR-608 binding sites that tune mRNA stability [PMID:21609763, PMID:20888414, PMID:15246108, PMID:28829698].","teleology":[{"year":1995,"claim":"Established the architecture of the COL5A1 promoter, defining how the gene's transcription is controlled at the cis level.","evidence":"5' deletion reporter assays, EMSA, and transcription start site mapping","pmids":["7646438"],"confidence":"Medium","gaps":["TATA-less GC-rich promoter with multiple Sp1 sites mapped but cell-type-specific factors not yet identified","no link to differentiation-stage regulation"]},{"year":1996,"claim":"Demonstrated that COL5A1 loss-of-function causes EDS through haploinsufficiency rather than dominant-negative protein, resolving the disease mechanism.","evidence":"translocation breakpoint mapping in COL5A1 intron 24 and fibroblast collagen biochemistry; plus splice-site deletion analysis affecting the C-propeptide","pmids":["8673139","8923000"],"confidence":"Medium","gaps":["single family/patient per mutation","downstream tissue consequences of reduced collagen V not yet characterized"]},{"year":1997,"claim":"Pinpointed the C-propeptide cysteine and splice-site mutations that prevent pro-α1(V) incorporation into trimers, biochemically anchoring the haploinsufficiency model.","evidence":"mutation analysis, fibroblast collagen biochemistry, four-generation family segregation","pmids":["9042913"],"confidence":"High","gaps":["mechanism of intracellular handling of mutant chains not detailed","fibril-level consequences inferred not imaged in this study"]},{"year":2000,"claim":"Quantified nonsense-mediated mRNA decay of mutant alleles as a common (~one-third) molecular route to classical EDS, generalizing the haploinsufficiency mechanism across patients.","evidence":"RT-PCR allele expression analysis with cycloheximide NMD rescue, replicated in a parallel cohort","pmids":["10796876","10777716"],"confidence":"High","gaps":["does not account for the remaining two-thirds of EDS cases","no genotype-phenotype severity correlation"]},{"year":2001,"claim":"Connected a specific splice mutation through NMD to α1(V) haploinsufficiency and abnormal dermal fibril ultrastructure, linking the molecular lesion to the structural phenotype.","evidence":"RT-PCR, RNase protection, cycloheximide rescue, and TEM of dermal biopsy","pmids":["11278977"],"confidence":"High","gaps":["single mutation","quantitative relationship between transcript level and fibril defect not established"]},{"year":2002,"claim":"Showed that some splice mutations yield secreted mutant chains with abnormal N-propeptides that incorporate into matrix and disrupt fibril structure, defining a non-NMD pathogenic route.","evidence":"RT-PCR characterization of order-dependent splice products and EM of fibril structure","pmids":["12145749"],"confidence":"Medium","gaps":["single lab","relative contribution of secreted-mutant vs haploinsufficiency mechanisms unquantified"]},{"year":2004,"claim":"Defined the cellular consequence of collagen V loss — failure to organize ECM via control of α2β1 integrin and fibronectin receptor recruitment — and confirmed dose-sensitivity of fibril deposition.","evidence":"patient fibroblasts, purified collagen V rescue, function-blocking antibodies; hydroxyproline and fibril morphology quantification with OI comparison; plus identification of COL5A1 as a TGF-β1-induced osteoblast gene","pmids":["14970208","15095409","15579311"],"confidence":"High","gaps":["integrin signaling pathway downstream of α2β1 not traced","fibril count sensitivity mechanism not molecularly resolved"]},{"year":2004,"claim":"Mapped trans-acting factors at the promoter (Sp1, CBF), advancing the model of coordinated regulation of type I and V collagen genes.","evidence":"promoter-reporter assays, EMSA with competition/supershift, CBF-B overexpression","pmids":["15246108"],"confidence":"Medium","gaps":["single lab","in vivo relevance of CBF binding not tested"]},{"year":2006,"claim":"Dissected how haploinsufficiency produces two distinct fibril subpopulations, establishing collagen V's role in regulating both nucleation and growth.","evidence":"targeted gene inactivation in mice, immunoelectron microscopy, tensile and skin extensibility testing","pmids":["16492673"],"confidence":"High","gaps":["molecular basis of unregulated type I sequestration in collagen-V-deficient fibrils not resolved"]},{"year":2009,"claim":"Showed signal-peptide mutations block ER translocation, adding a secretion-failure mechanism that reduces matrix collagen V.","evidence":"patient fibroblasts, immunofluorescence for intracellular retention, collagen electrophoresis","pmids":["18972565"],"confidence":"Medium","gaps":["single lab, two mutations","fate of retained protein (degradation vs ER stress) unaddressed"]},{"year":2010,"claim":"Identified Sp7/Osterix as a cell-type-specific activator of Col5a1 in osteoblasts, explaining tissue-restricted regulation.","evidence":"promoter-reporter assays, Sp1-site mutagenesis, Sp7 overexpression and siRNA knockdown, osteoblast differentiation model","pmids":["20888414"],"confidence":"High","gaps":["interplay between Sp7 and Sp1/CBF at the same site not resolved","in vivo osteoblast requirement not tested"]},{"year":2011,"claim":"Established conditional Col5a1 deletion in cornea as causing dominant fibrillogenesis failure, and defined 3'-UTR allelic variants and a miR-608 site controlling mRNA stability.","evidence":"corneal conditional knockout with EM; luciferase reporter assays of 3'-UTR allele variants and deletion constructs","pmids":["22159420","21609763"],"confidence":"High","gaps":["miR-608 functional repression in cells not directly tested","tissue specificity of 3'-UTR allelic effect unknown"]},{"year":2018,"claim":"Validated miR-29b as a direct post-transcriptional repressor of Col5a1, adding a defined miRNA layer to expression control.","evidence":"3'-UTR luciferase reporter with binding-site mutants, miR-29b overexpression, RNAi and CRISPR/Cas9 knockout, RT-PCR and Western blot","pmids":["28829698"],"confidence":"High","gaps":["physiological context where miR-29b regulates Col5a1 in tissue not defined"]},{"year":2022,"claim":"Linked collagen V haploinsufficiency to dysregulated matrix-to-cell TGF-β/Smad signaling as a downstream pathogenic axis in EDS skin and tendon.","evidence":"skin/tendon transcriptomics, serum TGF-β1 ELISA, pSmad2 IHC in Col5a1+/- mice","pmids":["34740257"],"confidence":"Medium","gaps":["causality of TGF-β activation in scarring not tested by intervention","single lab"]},{"year":2024,"claim":"Extended COL5A1 biology beyond matrix structure, showing it stabilizes TGM2 against ubiquitin-mediated degradation and participates in a TGF-β/Smad3 feedback loop driving chemoresistance in breast cancer.","evidence":"Co-immunoprecipitation, ubiquitination assay, in vitro/in vivo functional assays, cytokine profiling","pmids":["38609499"],"confidence":"Medium","gaps":["interaction domain and direct vs indirect binding not mapped","relevance of intracellular COL5A1 functions to connective tissue biology unclear","single lab"]},{"year":null,"claim":"How collagen V dose is mechanistically transduced into fibril number control, and how matrix-derived TGF-β dysregulation feeds back on connective tissue and disease phenotypes, remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["molecular link between type V/I ratio and fibril nucleation rate not defined","whether TGF-β activation is cause or consequence of matrix disorganization untested by rescue","genotype-phenotype determinants of EDS severity unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[0,1,5]}],"localization":[{"term_id":"GO:0031012","term_label":"extracellular matrix","supporting_discovery_ids":[0,1,4]},{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[4,5]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[7]}],"pathway":[{"term_id":"R-HSA-1474244","term_label":"Extracellular matrix organization","supporting_discovery_ids":[0,1,4,5]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[2,3,6]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[16,17,19]}],"complexes":["type V collagen heterotrimer","type I/V heterotypic collagen fibril"],"partners":["COL1A1","ITGA2","TGM2"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P20908","full_name":"Collagen alpha-1(V) chain","aliases":[],"length_aa":1838,"mass_kda":183.6,"function":"Type V collagen is a member of group I collagen (fibrillar forming collagen). It is a minor connective tissue component of nearly ubiquitous distribution. Type V collagen binds to DNA, heparan sulfate, thrombospondin, heparin, and insulin","subcellular_location":"Secreted, extracellular space, extracellular matrix","url":"https://www.uniprot.org/uniprotkb/P20908/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/COL5A1","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/COL5A1","total_profiled":1310},"omim":[{"mim_id":"619329","title":"FIBROMUSCULAR DYSPLASIA, MULTIFOCAL; FMDMF","url":"https://www.omim.org/entry/619329"},{"mim_id":"610025","title":"COLLAGEN, TYPE XXIV, ALPHA-1; COL24A1","url":"https://www.omim.org/entry/610025"},{"mim_id":"605101","title":"TAK1-BINDING PROTEIN 2; TAB2","url":"https://www.omim.org/entry/605101"},{"mim_id":"604539","title":"A DISINTEGRIN-LIKE AND METALLOPROTEINASE WITH THROMBOSPONDIN TYPE 1 MOTIF, 2; ADAMTS2","url":"https://www.omim.org/entry/604539"},{"mim_id":"602575","title":"LIM HOMEOBOX TRANSCRIPTION FACTOR 1, BETA; LMX1B","url":"https://www.omim.org/entry/602575"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Vesicles","reliability":"Approved"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"cervix","ntpm":144.7}],"url":"https://www.proteinatlas.org/search/COL5A1"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"P20908","domains":[{"cath_id":"2.60.120.200","chopping":"37-248","consensus_level":"medium","plddt":89.3933,"start":37,"end":248},{"cath_id":"2.60.120.1000","chopping":"1617-1838","consensus_level":"medium","plddt":92.6136,"start":1617,"end":1838}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P20908","model_url":"https://alphafold.ebi.ac.uk/files/AF-P20908-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P20908-F1-predicted_aligned_error_v6.png","plddt_mean":51.25},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=COL5A1","jax_strain_url":"https://www.jax.org/strain/search?query=COL5A1"},"sequence":{"accession":"P20908","fasta_url":"https://rest.uniprot.org/uniprotkb/P20908.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P20908/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P20908"}},"corpus_meta":[{"pmid":"16430677","id":"PMC_16430677","title":"The COL5A1 gene and Achilles tendon pathology.","date":"2006","source":"Scandinavian journal of medicine & science in sports","url":"https://pubmed.ncbi.nlm.nih.gov/16430677","citation_count":208,"is_preprint":false},{"pmid":"19654427","id":"PMC_19654427","title":"The COL5A1 gene is associated with increased risk of anterior cruciate ligament ruptures in female participants.","date":"2009","source":"The American journal of sports medicine","url":"https://pubmed.ncbi.nlm.nih.gov/19654427","citation_count":171,"is_preprint":false},{"pmid":"22159420","id":"PMC_22159420","title":"Collagen V is a dominant regulator of collagen fibrillogenesis: dysfunctional regulation of structure and function in a corneal-stroma-specific Col5a1-null mouse model.","date":"2011","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/22159420","citation_count":153,"is_preprint":false},{"pmid":"18443036","id":"PMC_18443036","title":"Variants within the COL5A1 gene are associated with Achilles 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Associated with Temporomandibular Joint Anterior Disc Displacement without Reduction in Polish Caucasians.","date":"2021","source":"Cells","url":"https://pubmed.ncbi.nlm.nih.gov/34572072","citation_count":10,"is_preprint":false},{"pmid":"31239369","id":"PMC_31239369","title":"Compound phenotype of osteogenesis imperfecta and Ehlers-Danlos syndrome caused by combined mutations in COL1A1 and COL5A1.","date":"2019","source":"Bioscience reports","url":"https://pubmed.ncbi.nlm.nih.gov/31239369","citation_count":10,"is_preprint":false},{"pmid":"35241120","id":"PMC_35241120","title":"Association of COL5A1 gene polymorphisms and musculoskeletal soft tissue injuries: a meta-analysis based on 21 observational studies.","date":"2022","source":"Journal of orthopaedic surgery and research","url":"https://pubmed.ncbi.nlm.nih.gov/35241120","citation_count":9,"is_preprint":false},{"pmid":"35627182","id":"PMC_35627182","title":"Independent COL5A1 Variants in Cats with Ehlers-Danlos Syndrome.","date":"2022","source":"Genes","url":"https://pubmed.ncbi.nlm.nih.gov/35627182","citation_count":9,"is_preprint":false},{"pmid":"34740257","id":"PMC_34740257","title":"Molecular alterations due to Col5a1 haploinsufficiency in a mouse model of classic Ehlers-Danlos syndrome.","date":"2022","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/34740257","citation_count":9,"is_preprint":false},{"pmid":"31772763","id":"PMC_31772763","title":"A Novel Splice-Site Variation in COL5A1 Causes Keratoconus in an Indian Family.","date":"2019","source":"Journal of ophthalmology","url":"https://pubmed.ncbi.nlm.nih.gov/31772763","citation_count":9,"is_preprint":false},{"pmid":"9582436","id":"PMC_9582436","title":"cDNA sequence and expression of the mouse alpha1(V) collagen gene (Col5a1).","date":"1998","source":"Biochimica et biophysica acta","url":"https://pubmed.ncbi.nlm.nih.gov/9582436","citation_count":9,"is_preprint":false},{"pmid":"26244122","id":"PMC_26244122","title":"The COL5A1 genotype is associated with range of motion.","date":"2015","source":"Journal of exercise nutrition & biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/26244122","citation_count":8,"is_preprint":false},{"pmid":"28829698","id":"PMC_28829698","title":"The pro-α1(V) collagen gene (Col5a1) is coordinately regulated by miR-29b with core promoter in cultured cells.","date":"2018","source":"Connective tissue research","url":"https://pubmed.ncbi.nlm.nih.gov/28829698","citation_count":8,"is_preprint":false},{"pmid":"8462976","id":"PMC_8462976","title":"Are the nail-patella syndrome and the autosomal Goltz-like syndrome the phenotypic expressions of different alleles at the COL5A1 locus?","date":"1993","source":"Human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/8462976","citation_count":8,"is_preprint":false},{"pmid":"31660461","id":"PMC_31660461","title":"Coil embolization of bilateral internal mammary artery aneurysms in the setting of a heterozygous missense variant of unknown significance in COL5A1 and fibromuscular dysplasia.","date":"2019","source":"Journal of vascular surgery cases and innovative techniques","url":"https://pubmed.ncbi.nlm.nih.gov/31660461","citation_count":8,"is_preprint":false},{"pmid":"27717059","id":"PMC_27717059","title":"Human COL5A1 polymorphisms and quadriceps muscle-tendon mechanical stiffness in vivo.","date":"2016","source":"Experimental physiology","url":"https://pubmed.ncbi.nlm.nih.gov/27717059","citation_count":7,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":54466,"output_tokens":5224,"usd":0.120879,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":13683,"output_tokens":4481,"usd":0.09022,"stage2_stop_reason":"end_turn"},"total_usd":0.211099,"stage1_batch_id":"msgbatch_01ACAxJQabDsht39JXeWG22d","stage2_batch_id":"msgbatch_01QEU22A9U5sbPTgsMzTmvSf","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2011,\n      \"finding\": \"Conditional knockout of Col5a1 in corneal stroma (using Kera-Cre) results in severely increased and heterogeneous fibril diameters, abnormal fibril structure, decreased fibril number, disorganized lamellae, decreased stroma thickness, and corneal opacity, demonstrating that collagen V is a dominant regulator of collagen fibrillogenesis and matrix assembly during tissue development.\",\n      \"method\": \"Conditional knockout mouse model (Cre-loxP), electron microscopy, corneal haze quantification\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1/2 / Strong — direct loss-of-function in vivo with multiple orthogonal structural and functional readouts in a dedicated study\",\n      \"pmids\": [\"22159420\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Col5a1 heterozygous mice (haploinsufficient, 50% reduction in collagen V) exhibit two fibril subpopulations: relatively normal fibrils with periodic collagen V immunoreactivity (where type I/V interactions regulate nucleation) and abnormal fibrils lacking collagen V formed by unregulated type I collagen sequestration. This disrupts normal linear and lateral fibril growth via fusion, revealing that collagen V regulates fibril nucleation and growth.\",\n      \"method\": \"Targeted gene inactivation in mice, immunoelectron microscopy, tensile strength testing, skin extensibility measurement\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1/2 / Strong — in vivo loss-of-function with mechanistic dissection of fibril subpopulations using multiple orthogonal methods\",\n      \"pmids\": [\"16492673\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"A missense mutation substituting the most 5' cysteine in the COL5A1 C-propeptide domain prevents incorporation of mutant pro-α1(V) chains into collagen V trimers, reducing collagen V levels and causing EDS type I. Additionally, splice-site mutations in COL5A1 were identified in EDS I and II patients, confirming COL5A1 haploinsufficiency as a causal mechanism.\",\n      \"method\": \"Mutation analysis, fibroblast collagen biochemistry, segregation analysis in a four-generation family\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct mutation characterization with biochemical demonstration of reduced collagen V incorporation, replicated across multiple families\",\n      \"pmids\": [\"9042913\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"In eight of 28 classical EDS probands, one COL5A1 allele was completely or nearly completely absent from mRNA due to nonsense-mediated mRNA decay caused by small insertions/deletions or splice-site mutations, establishing COL5A1 haploinsufficiency as a common (~one-third of cases) molecular mechanism in classical EDS.\",\n      \"method\": \"RT-PCR allele expression analysis, cycloheximide treatment to block nonsense-mediated decay, heteroduplex analysis, genomic sequencing\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1/2 / Strong — two orthogonal molecular methods (allele expression + cycloheximide rescue) across 16 individuals, replicated in a parallel study (PMID:10777716)\",\n      \"pmids\": [\"10796876\", \"10777716\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"COL5A1-mutant fibroblasts from EDS type I patients fail to organize collagens and fibronectin in the ECM, downregulate α2β1 integrin, and recruit αvβ3 instead of α5β1 integrin. Treatment with purified collagen V (but not fibronectin) restores the control phenotype, and blocking α2β1 integrin in control fibroblasts recapitulates the EDS phenotype, demonstrating that collagen V controls α2β1 integrin organization which in turn regulates fibronectin integrin receptor recruitment.\",\n      \"method\": \"EDS patient-derived fibroblasts, purified collagen V rescue experiment, function-blocking antibodies, immunofluorescence, ECM organization assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal approaches (rescue, antibody blocking, patient cells) establishing a mechanistic pathway in a single rigorous study\",\n      \"pmids\": [\"14970208\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"COL5A1 haploinsufficient EDS fibroblasts deposit less than half the hydroxyproline of controls and assemble significantly fewer collagen fibrils despite near-normal total collagen synthesis rates, and fibril diameter is inversely proportional to type V/type I collagen ratio. This demonstrates that the quantity of fibrils deposited is highly sensitive to type V collagen reduction, far out of proportion to its contribution to collagen mass.\",\n      \"method\": \"Long-term dermal fibroblast cultures, hydroxyproline assay, electron microscopy of fibril morphology, comparison with OI (COL1A1 haploinsufficient) cells\",\n      \"journal\": \"Journal of cellular biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — quantitative biochemical and ultrastructural analysis with isogenic comparison groups establishing a dose-response relationship\",\n      \"pmids\": [\"15095409\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"A COL5A1 exon 14 splice acceptor mutation (A(-2)→G) creates a cryptic acceptor site that causes a +1 frameshift leading to a premature stop codon in exon 17; the mutant transcript undergoes nonsense-mediated mRNA decay (only 8% of normal level in untreated fibroblasts, equimolar in cycloheximide-treated cells), yielding α1(V) haploinsufficiency and heterogeneous dermal collagen fibril diameters including 'cauliflower' fibrils.\",\n      \"method\": \"RT-PCR, RNase protection, cycloheximide treatment, transmission electron microscopy of dermal biopsy\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1/2 / Strong — mechanistic dissection of NMD with cycloheximide rescue and ultrastructural confirmation in a single rigorous study\",\n      \"pmids\": [\"11278977\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Missense mutations (p.L25R and p.L25P) in the signal peptide hydrophobic core of pre-pro-α1(V) collagen prevent translocation of the mutant protein into the endoplasmic reticulum, causing intracellular retention and reduced collagen V in the ECM, demonstrating that signal peptide integrity is required for proper secretion and fibrillogenesis.\",\n      \"method\": \"Patient-derived fibroblast analysis, immunofluorescence for intracellular retention, collagen electrophoresis, mutation characterization\",\n      \"journal\": \"Human mutation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional demonstration of ER retention in patient cells with two independent mutations, single lab\",\n      \"pmids\": [\"18972565\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"A COL5A1 splice-acceptor mutation (IVS4-2A→G) causes complex splicing outcomes dependent on the order of intron removal: when intron 5 is removed rapidly, exons 5 and 6 are jointly skipped producing the major product; when intron 6 is removed first, only exon 5 is skipped; when intron 4 is removed last, cryptic exon 5 acceptors are used. The resulting mutant pro-α1(V) chains with abnormal N-propeptides are secreted, incorporated into ECM, and cause dramatic alterations in collagen fibril structure.\",\n      \"method\": \"RT-PCR characterization of splice products, genomic sequencing, intron removal order analysis, electron microscopy of fibril structure\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple splice products characterized mechanistically with order-of-removal model validated and fibril structure confirmed, single lab\",\n      \"pmids\": [\"12145749\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Two major forms of the COL5A1 3'-UTR (C-allele and T-allele) differ in mRNA stability: the T-allele shows significantly higher luciferase reporter activity (90.6%) than the C-allele (69.0%), indicating greater mRNA stability; a functional miR-608 binding site was identified within the 3'-UTR; deletion constructs revealed additional elements regulating COL5A1 mRNA stability.\",\n      \"method\": \"Luciferase reporter assay with cloned 3'-UTR variants, deletion constructs, sequence analysis\",\n      \"journal\": \"Matrix biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional reporter assay with multiple construct variants demonstrating differential mRNA stability, single lab\",\n      \"pmids\": [\"21609763\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"TGF-β1 upregulates COL5A1 expression during the proliferation and differentiation phases of osteoblast development in MC3T3-E1 cells, and COL5A1 mRNA is expressed in developing mouse bone at E17.5, establishing COL5A1 as a TGF-β target gene in osteoblasts.\",\n      \"method\": \"cDNA microarray, Northern blotting, RNA in situ hybridization, immunohistochemistry in mouse embryos\",\n      \"journal\": \"Matrix biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — microarray finding validated by Northern blotting and in situ hybridization, single lab with in vivo confirmation\",\n      \"pmids\": [\"15579311\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Sp7/Osterix transcription factor binds to a Sp1-binding site in the Col5a1 core promoter and activates its transcription specifically in osteoblastic cells: overexpression of Sp7 increases Col5a1 promoter activity and endogenous mRNA; siRNA knockdown of Sp7 decreases both; mutation of the Sp1-binding site abolishes the effect; and Sp7 and Col5a1 expression co-increase during osteoblast differentiation.\",\n      \"method\": \"Promoter-reporter transfection assays, mutagenesis of Sp1 binding site, siRNA knockdown, overexpression, osteoblast differentiation model\",\n      \"journal\": \"Matrix biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1/2 / Strong — multiple orthogonal approaches (gain-of-function, loss-of-function, mutagenesis, differentiation model) establishing the Sp7-Col5a1 regulatory axis in a single rigorous study\",\n      \"pmids\": [\"20888414\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"The Col5a1 core promoter lacks a TATA motif and has high GC content; three nuclear factor binding sites were identified: BS1 binds Sp1, BS2 binds CBF (at a CAAAT motif), and BS3 binds an Sp1-related protein. CBF activates the Col5a1 promoter and overexpression of CBF-B subunit modulates this activity, suggesting coordinated regulation of type I and V collagen genes by CBF.\",\n      \"method\": \"Transient transfection promoter-reporter assays, electrophoretic mobility shift assay (EMSA), oligonucleotide competition and supershift assays, CBF-B overexpression\",\n      \"journal\": \"Matrix biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — EMSA with competition/supershift plus functional promoter assays, single lab\",\n      \"pmids\": [\"15246108\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"The COL5A1 promoter lacks TATA and CAAT boxes, has multiple transcription start sites, high GC content, lies within a CpG island, and contains multiple Sp1 binding sites. Stepwise deletion analysis shows gradual decrease in promoter activity, indicating an array of cis-acting elements; gel mobility shift assays confirm Sp1 binding at multiple sites within the minimal promoter.\",\n      \"method\": \"5' deletion reporter assays, gel mobility shift assay (EMSA), S1 nuclease mapping, multiple transcription start site mapping\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional promoter deletion analysis combined with EMSA in a single dedicated study\",\n      \"pmids\": [\"7646438\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"A translocation breakpoint within COL5A1 intron 24 produces a fusion mRNA between COL5A1 and an Alu sequence but no aberrant protein; instead, type V collagen is reduced in patient fibroblasts, demonstrating haploinsufficiency as the mechanism causing EDS type I.\",\n      \"method\": \"Chromosomal translocation mapping, RT-PCR fusion transcript analysis, fibroblast collagen biochemistry\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct demonstration of haploinsufficiency mechanism via molecular analysis and biochemical quantification of collagen V in patient cells\",\n      \"pmids\": [\"8673139\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"miR-29b directly binds to the 3'-UTR of Col5a1 and represses its expression at the mRNA and protein levels; miR-29b overexpression decreases Col5a1 luciferase reporter activity, endogenous mRNA, and protein; CRISPR/Cas9 knockout or RNAi knockdown of miR-29b increases Col5a1 expression, establishing miR-29b as a post-transcriptional repressor of Col5a1.\",\n      \"method\": \"Luciferase reporter assay with 3'-UTR constructs and binding-site mutants, miRNA overexpression, RNAi knockdown, CRISPR/Cas9 knockout, RT-PCR, Western blotting\",\n      \"journal\": \"Connective tissue research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1/2 / Strong — multiple orthogonal methods (reporter assay with mutagenesis, gain-of-function, loss-of-function including CRISPR) in a single study\",\n      \"pmids\": [\"28829698\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Col5a1 haploinsufficient mice show dysregulation of ECM components including thrombospondin-1, lysyl oxidase, and lumican in skin, and upregulation of TGF-β1 in serum with increased pSmad2 in skin, suggesting that altered matrix-to-cell TGF-β signaling contributes to abnormal wound healing and atrophic scarring in classic EDS.\",\n      \"method\": \"Transcriptome analysis of skin and Achilles tendons, serum TGF-β1 ELISA, pSmad2 immunohistochemistry in Col5a1+/- mice\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — transcriptome plus targeted protein validation in a mouse model, single lab\",\n      \"pmids\": [\"34740257\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Col5a1 knockout rats (CRISPR/Cas9) show fracture of elastic fibers and disarray of collagenous fibers by electron microscopy at 6 weeks. After β-aminopropionitrile and angiotensin II treatment to induce aortic dissection, Col5a1 knockout rats have significantly higher aortic dissection incidence than wild-type (93.3% vs 0%), and the TGF-β signaling pathway is significantly activated in Col5a1 knockout rats.\",\n      \"method\": \"CRISPR/Cas9 Col5a1 knockout rats, electron microscopy, aortic dissection induction model, TGF-β pathway analysis\",\n      \"journal\": \"Journal of the American Heart Association\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo knockout model with mechanistic pathway analysis, single lab\",\n      \"pmids\": [\"34041919\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"A 4 bp deletion at positions +3 to +6 of COL5A1 intron 65 removes exon 65 from processed mRNAs; since exon 65 encodes 78 residues of the carboxyl propeptide, the mutation reduces efficiency of incorporating mutant pro-α1(V) chains into type V collagen trimers and reduces total type V collagen synthesis, causing EDS type I.\",\n      \"method\": \"Linkage analysis, genomic sequencing identifying splice-site deletion, mRNA analysis by RT-PCR\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — molecular characterization of splice-site mutation with predicted mechanistic consequence for chain assembly, single family\",\n      \"pmids\": [\"8923000\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"COL5A1 interacts with TGM2 and inhibits its K48-linked ubiquitination-mediated degradation, thereby stabilizing TGM2 and enhancing chemoresistance and IL-6 secretion in triple-negative breast cancer cells. Additionally, TGF-β from M2 macrophages drives COL5A1 expression through a TGFβ/Smad3/COL5A1 signaling pathway, establishing a feedback loop.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, in vitro and in vivo functional assays, cytokine profiling\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP and ubiquitination assay establishing protein-protein interaction and post-translational mechanism, single lab\",\n      \"pmids\": [\"38609499\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"COL5A1 encodes the pro-α1(V) chain of type V collagen, which co-assembles with type I collagen into heterotypic fibrils and acts as a dominant regulator of collagen fibril nucleation, diameter, and organization; haploinsufficiency (caused by null alleles, splice mutations, signal peptide mutations, or nonsense-mediated mRNA decay) leads to classical Ehlers-Danlos syndrome by reducing the number and increasing the heterogeneity of collagen fibrils, while its 3'-UTR regulates mRNA stability (modulated by miR-29b and miR-608 binding sites), its promoter is controlled by Sp1/CBF and Sp7/Osterix transcription factors in a cell-type-specific manner, and loss of COL5A1 activates TGF-β/Smad signaling as a downstream pathogenic mechanism in connective tissue disease.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"COL5A1 encodes the pro-\\u03b11(V) chain of type V collagen, a quantitatively minor fibrillar collagen that acts as a dominant regulator of collagen fibrillogenesis: it nucleates heterotypic fibrils and controls their number, diameter, and organization during connective tissue assembly [#0, #1]. In vivo loss-of-function and haploinsufficiency reveal that fibril nucleation is exquisitely sensitive to collagen V dose \\u2014 a ~50% reduction yields fewer fibrils, two abnormal fibril subpopulations, increased diameter heterogeneity, and tissue-level defects in cornea, skin, and tendon, with fibril diameter inversely proportional to the type V/type I ratio [#0, #1, #5]. At the cell-matrix interface, collagen V controls \\u03b12\\u03b21 integrin organization, which in turn governs fibronectin receptor recruitment and ECM assembly [#4]. COL5A1 haploinsufficiency \\u2014 caused by null and translocation alleles, splice-site mutations producing premature stop codons subject to nonsense-mediated mRNA decay, signal-peptide mutations blocking ER translocation, and C-propeptide mutations preventing chain incorporation \\u2014 is the principal molecular mechanism of classical Ehlers-Danlos syndrome [#2, #3, #6, #7, #14]. Reduced collagen V also dysregulates matrix-to-cell TGF-\\u03b2/Smad signaling, contributing to abnormal wound healing and predisposition to aortic dissection in animal models [#16, #17]. Expression is governed by a TATA-less, GC-rich promoter bound by Sp1, CBF, and the osteoblast-specific factor Sp7/Osterix, and post-transcriptionally by 3'-UTR elements including miR-29b and miR-608 binding sites that tune mRNA stability [#9, #11, #12, #15].\",\n  \"teleology\": [\n    {\n      \"year\": 1995,\n      \"claim\": \"Established the architecture of the COL5A1 promoter, defining how the gene's transcription is controlled at the cis level.\",\n      \"evidence\": \"5' deletion reporter assays, EMSA, and transcription start site mapping\",\n      \"pmids\": [\"7646438\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"TATA-less GC-rich promoter with multiple Sp1 sites mapped but cell-type-specific factors not yet identified\", \"no link to differentiation-stage regulation\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Demonstrated that COL5A1 loss-of-function causes EDS through haploinsufficiency rather than dominant-negative protein, resolving the disease mechanism.\",\n      \"evidence\": \"translocation breakpoint mapping in COL5A1 intron 24 and fibroblast collagen biochemistry; plus splice-site deletion analysis affecting the C-propeptide\",\n      \"pmids\": [\"8673139\", \"8923000\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"single family/patient per mutation\", \"downstream tissue consequences of reduced collagen V not yet characterized\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Pinpointed the C-propeptide cysteine and splice-site mutations that prevent pro-\\u03b11(V) incorporation into trimers, biochemically anchoring the haploinsufficiency model.\",\n      \"evidence\": \"mutation analysis, fibroblast collagen biochemistry, four-generation family segregation\",\n      \"pmids\": [\"9042913\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"mechanism of intracellular handling of mutant chains not detailed\", \"fibril-level consequences inferred not imaged in this study\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Quantified nonsense-mediated mRNA decay of mutant alleles as a common (~one-third) molecular route to classical EDS, generalizing the haploinsufficiency mechanism across patients.\",\n      \"evidence\": \"RT-PCR allele expression analysis with cycloheximide NMD rescue, replicated in a parallel cohort\",\n      \"pmids\": [\"10796876\", \"10777716\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"does not account for the remaining two-thirds of EDS cases\", \"no genotype-phenotype severity correlation\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Connected a specific splice mutation through NMD to \\u03b11(V) haploinsufficiency and abnormal dermal fibril ultrastructure, linking the molecular lesion to the structural phenotype.\",\n      \"evidence\": \"RT-PCR, RNase protection, cycloheximide rescue, and TEM of dermal biopsy\",\n      \"pmids\": [\"11278977\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"single mutation\", \"quantitative relationship between transcript level and fibril defect not established\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Showed that some splice mutations yield secreted mutant chains with abnormal N-propeptides that incorporate into matrix and disrupt fibril structure, defining a non-NMD pathogenic route.\",\n      \"evidence\": \"RT-PCR characterization of order-dependent splice products and EM of fibril structure\",\n      \"pmids\": [\"12145749\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"single lab\", \"relative contribution of secreted-mutant vs haploinsufficiency mechanisms unquantified\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Defined the cellular consequence of collagen V loss \\u2014 failure to organize ECM via control of \\u03b12\\u03b21 integrin and fibronectin receptor recruitment \\u2014 and confirmed dose-sensitivity of fibril deposition.\",\n      \"evidence\": \"patient fibroblasts, purified collagen V rescue, function-blocking antibodies; hydroxyproline and fibril morphology quantification with OI comparison; plus identification of COL5A1 as a TGF-\\u03b21-induced osteoblast gene\",\n      \"pmids\": [\"14970208\", \"15095409\", \"15579311\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"integrin signaling pathway downstream of \\u03b12\\u03b21 not traced\", \"fibril count sensitivity mechanism not molecularly resolved\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Mapped trans-acting factors at the promoter (Sp1, CBF), advancing the model of coordinated regulation of type I and V collagen genes.\",\n      \"evidence\": \"promoter-reporter assays, EMSA with competition/supershift, CBF-B overexpression\",\n      \"pmids\": [\"15246108\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"single lab\", \"in vivo relevance of CBF binding not tested\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Dissected how haploinsufficiency produces two distinct fibril subpopulations, establishing collagen V's role in regulating both nucleation and growth.\",\n      \"evidence\": \"targeted gene inactivation in mice, immunoelectron microscopy, tensile and skin extensibility testing\",\n      \"pmids\": [\"16492673\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"molecular basis of unregulated type I sequestration in collagen-V-deficient fibrils not resolved\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Showed signal-peptide mutations block ER translocation, adding a secretion-failure mechanism that reduces matrix collagen V.\",\n      \"evidence\": \"patient fibroblasts, immunofluorescence for intracellular retention, collagen electrophoresis\",\n      \"pmids\": [\"18972565\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"single lab, two mutations\", \"fate of retained protein (degradation vs ER stress) unaddressed\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Identified Sp7/Osterix as a cell-type-specific activator of Col5a1 in osteoblasts, explaining tissue-restricted regulation.\",\n      \"evidence\": \"promoter-reporter assays, Sp1-site mutagenesis, Sp7 overexpression and siRNA knockdown, osteoblast differentiation model\",\n      \"pmids\": [\"20888414\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"interplay between Sp7 and Sp1/CBF at the same site not resolved\", \"in vivo osteoblast requirement not tested\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Established conditional Col5a1 deletion in cornea as causing dominant fibrillogenesis failure, and defined 3'-UTR allelic variants and a miR-608 site controlling mRNA stability.\",\n      \"evidence\": \"corneal conditional knockout with EM; luciferase reporter assays of 3'-UTR allele variants and deletion constructs\",\n      \"pmids\": [\"22159420\", \"21609763\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"miR-608 functional repression in cells not directly tested\", \"tissue specificity of 3'-UTR allelic effect unknown\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Validated miR-29b as a direct post-transcriptional repressor of Col5a1, adding a defined miRNA layer to expression control.\",\n      \"evidence\": \"3'-UTR luciferase reporter with binding-site mutants, miR-29b overexpression, RNAi and CRISPR/Cas9 knockout, RT-PCR and Western blot\",\n      \"pmids\": [\"28829698\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"physiological context where miR-29b regulates Col5a1 in tissue not defined\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Linked collagen V haploinsufficiency to dysregulated matrix-to-cell TGF-\\u03b2/Smad signaling as a downstream pathogenic axis in EDS skin and tendon.\",\n      \"evidence\": \"skin/tendon transcriptomics, serum TGF-\\u03b21 ELISA, pSmad2 IHC in Col5a1+/- mice\",\n      \"pmids\": [\"34740257\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"causality of TGF-\\u03b2 activation in scarring not tested by intervention\", \"single lab\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Extended COL5A1 biology beyond matrix structure, showing it stabilizes TGM2 against ubiquitin-mediated degradation and participates in a TGF-\\u03b2/Smad3 feedback loop driving chemoresistance in breast cancer.\",\n      \"evidence\": \"Co-immunoprecipitation, ubiquitination assay, in vitro/in vivo functional assays, cytokine profiling\",\n      \"pmids\": [\"38609499\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"interaction domain and direct vs indirect binding not mapped\", \"relevance of intracellular COL5A1 functions to connective tissue biology unclear\", \"single lab\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How collagen V dose is mechanistically transduced into fibril number control, and how matrix-derived TGF-\\u03b2 dysregulation feeds back on connective tissue and disease phenotypes, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"molecular link between type V/I ratio and fibril nucleation rate not defined\", \"whether TGF-\\u03b2 activation is cause or consequence of matrix disorganization untested by rescue\", \"genotype-phenotype determinants of EDS severity unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 1, 5]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0031012\", \"supporting_discovery_ids\": [0, 1, 4]},\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [4, 5]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [7]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1474244\", \"supporting_discovery_ids\": [0, 1, 4, 5]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [2, 3, 6]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [16, 17, 19]}\n    ],\n    \"complexes\": [\"type V collagen heterotrimer\", \"type I/V heterotypic collagen fibril\"],\n    \"partners\": [\"COL1A1\", \"ITGA2\", \"TGM2\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":6,"faith_pct":83.33333333333333}}