{"gene":"COL1A1","run_date":"2026-04-28T17:28:53","timeline":{"discoveries":[{"year":1997,"finding":"The t(17;22)(q22;q13) chromosomal translocation in dermatofibrosarcoma protuberans (DFSP) fuses COL1A1 on chromosome 17 with the PDGFB gene on chromosome 22, deleting exon 1 of PDGFB and releasing the growth factor from its normal regulation, thereby driving tumor formation through constitutive PDGFB signaling.","method":"Southern blotting, RT-PCR, genomic characterization of breakpoints in DFSP and giant-cell fibroblastoma tumor specimens","journal":"Nature genetics","confidence":"High","confidence_rationale":"Tier 1-2 — original discovery with multiple molecular methods, replicated across multiple tumor specimens and independently confirmed in subsequent studies","pmids":["8988177"],"is_preprint":false},{"year":2001,"finding":"The COL1A1-PDGFB chimeric protein produced by the t(17;22) translocation is processed in transfected cells into mature PDGFB dimers, confers growth factor independence and tumorigenicity in nude mice, and stimulates fibroblast growth via the PDGFB receptor pathway; mutagenesis showed uncleaved COL1A1-PDGFB forms are also mitogenic, contributing to the transformed phenotype.","method":"Stable and transient transfections in fibroblastic and epithelial cell lines; anti-PDGFB and anti-COL1A1-PDGFB antibody characterization; tumorigenicity assay in nude mice; mutagenesis experiments","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 1-2 — reconstitution in cell lines plus in vivo tumorigenicity with mutagenesis controls, strong mechanistic resolution","pmids":["11420709"],"is_preprint":false},{"year":1996,"finding":"COL1A1 null alleles arising from premature stop mutations or splice donor mutations produce transcripts that are retained in the nucleus and absent from the cytoplasm, establishing that nuclear retention/mRNA export failure is the mechanism underlying haploinsufficiency in mild osteogenesis imperfecta type I.","method":"RT-PCR and single-strand conformational polymorphism of nuclear vs. cytoplasmic fractions of COL1A1 mRNA from OI patient fibroblasts","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 — direct subcellular fractionation with functional consequence (haploinsufficiency causing OI), multiple patients and mutations","pmids":["8613526"],"is_preprint":false},{"year":2000,"finding":"Normal COL1A1 pre-mRNA undergoes cotranscriptional splicing at or adjacent to the gene and then transits through an SC-35 splicing factor domain before nuclear export; splice-defective COL1A1 transcripts (from an OI intron 26 mutation) initiate transport from the gene into the SC-35 domain but accumulate abnormally and are impeded in exit, identifying movement through the SC-35 domain as a discrete step in COL1A1 mRNA export.","method":"Fluorescence in situ hybridization of COL1A1 RNA in patient fibroblasts; microfluorimetric analysis of nuclear RNA tracks; comparison of normal vs. splice-mutant alleles","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 — direct visualization of RNA trafficking with quantitative comparison of normal vs. mutant alleles in the same cell, strong mechanistic insight","pmids":["10931857"],"is_preprint":false},{"year":2005,"finding":"RFX1 binds the methylated COL1A1 promoter (sites -11 to +10) with higher affinity than the unmethylated site and represses COL1A1 transcription; RFX5 (as part of a complex with CIITA induced by IFN-γ) represses both COL1A1 and COL1A2 promoters equally. The COL1A1 gene is methylated in human cancer cells, correlating with reduced collagen expression that is reversed by the methylation inhibitor aza-dC.","method":"Gel shift assays, co-immunoprecipitation, RFX5 dominant-negative transfections, CIITA RNAi, transient transfection reporter assays, methylation inhibitor (aza-dC) treatment","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal methods including dominant negatives, RNAi, and direct binding assays with methylated vs. unmethylated substrates","pmids":["15788405"],"is_preprint":false},{"year":2001,"finding":"YY1 binds two sites (YY1A at -40/-37 bp and YY1B at -32/-29 bp) in the COL1A1 proximal promoter immediately upstream of the TATA box and acts as a required positive regulator of constitutive COL1A1 transcription in fibroblasts; mutation of either site reduces or abolishes promoter activity, and YY1 and TBP/TFIID can co-occupy the promoter fragment.","method":"EMSA with purified recombinant YY1 and nuclear extracts; supershift with YY1-specific antibody; mutation analysis; Col1a1-luciferase co-transfections with pCMV-YY1 and antisense YY1","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 — reconstituted binding with purified protein, multiple promoter mutations, gain- and loss-of-function in transfections","pmids":["11514536"],"is_preprint":false},{"year":2009,"finding":"Three polymorphisms in the COL1A1 5' flank (-1997G/T, -1663IndelT, +1245G/T) interact to regulate transcription: the osteoporosis-associated G-del-T haplotype drives 2-fold higher transcription and has increased binding affinity for a protein complex containing Nmp4 and Osterix at the -1663IndelT site; chromatin IP confirmed recruitment of Osterix and Nmp4 and showed evidence of Nmp4 at the intron 1 Sp1 site; G-del-T haplotype shows higher RNA Pol II binding.","method":"Reporter gene transcription assays; gel shift assays; chromatin immunoprecipitation; genotype-BMD association in 3270 Caucasian women","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal methods (ChIP, EMSA, reporter assays) combined with in vivo human BMD correlation","pmids":["19429913"],"is_preprint":false},{"year":1993,"finding":"A 624-bp region of the COL1A1 promoter between positions -2296 and -1672 is active in intact bone and cultured bone but inactive in primary bone cells isolated from bone, demonstrating that the loss of cell-matrix interactions in culture causes differential downregulation of COL1A1 promoter activity.","method":"Transgenic mice expressing COL1A1-CAT fusion genes; CAT reporter assays in calvariae vs. primary bone cell cultures; comparison of 3.6 kb, 2.3 kb, and 1.7 kb 5'-deletion constructs","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 — direct in vivo vs. in vitro promoter deletion analysis in transgenic mice with parallel collagen synthesis measurements","pmids":["8355676"],"is_preprint":false},{"year":1995,"finding":"Only 476 bp of the COL1A1 promoter is sufficient to drive tissue-specific expression of the COL1A1 gene in transgenic mice; the first intron and 90% of the 3'-UTR are not required for tissue-specific expression.","method":"Transgenic mice with mini-COL1A1 gene and hybrid COL1A1/COL2A1 gene constructs; assay of transgene mRNA and protein in tissues","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — direct in vivo transgenic experiment with mRNA and protein-level validation","pmids":["7721894"],"is_preprint":false},{"year":1989,"finding":"Point mutations in COL1A1 causing substitution of conserved glycine residues in the helical domain (e.g., Gly973Val, Gly1006Val, Gly928Ala, Gly976Arg) are sufficient to cause lethal perinatal osteogenesis imperfecta, demonstrating that the Gly-X-Y repeating sequence is essential for normal collagen helix formation and extracellular matrix function.","method":"Chemical mismatch cleavage of mRNA-cDNA heteroduplexes; PCR amplification; DNA sequencing; identification of heterozygous single-base mutations in patient RNA","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — direct mutation identification with structural consequence, confirmed in multiple patients with different substitutions","pmids":["2777764"],"is_preprint":false},{"year":2020,"finding":"COL1A1 secreted by fibroblasts promotes ovarian cancer cell migration and invasion by binding to membrane surface receptor integrin β1 (ITGB1), activating downstream AKT phosphorylation; knockdown or blockage of ITGB1 reverses COL1A1-enhanced migration and invasion.","method":"Quantitative proteomics of ascites; siRNA knockdown and antibody blockage of COL1A1 and ITGB1; western blot for p-AKT; in vivo xenograft intraperitoneal metastasis assay in NOD/SCID mice","journal":"Experimental cell research","confidence":"Medium","confidence_rationale":"Tier 2 — binding partner identified with functional rescue, in vivo validation, but direct binding not reconstituted in vitro","pmids":["32589888"],"is_preprint":false},{"year":2017,"finding":"miR-129-5p suppresses gastric cancer cell proliferation, migration, and invasion by directly targeting the 3'-UTR of COL1A1 mRNA; co-transfection of miR-129-5p mimics with COL1A1 rescued tumor-promoting effects, confirming a miR-129-5p/COL1A1 regulatory axis.","method":"Dual luciferase reporter assay confirming direct 3'-UTR binding; RT-qPCR and western blot; MTT, colony formation, wound healing, Transwell assays; rescue co-transfection experiments","journal":"Biochemistry and cell biology","confidence":"Medium","confidence_rationale":"Tier 2-3 — direct 3'-UTR target validation by luciferase with functional rescue, single lab","pmids":["28482162"],"is_preprint":false},{"year":2018,"finding":"COL1A1 promotes CRC cell migration via the WNT/PCP signaling pathway; COL1A1 knockdown decreased levels of Rac1-GTP, phosphorylated JNK, and RhoA-GTP, which are key effectors of the WNT/PCP pathway.","method":"Transwell migration assay; siRNA knockdown; western blot for Rac1-GTP, p-JNK, RhoA-GTP; RT-PCR for WNT/PCP pathway gene expression","journal":"Molecular medicine reports","confidence":"Medium","confidence_rationale":"Tier 3 — KD with defined pathway readout but no epistasis or reconstitution, single lab","pmids":["29393423"],"is_preprint":false},{"year":2022,"finding":"COL1A1 is the central structural gene organizing glioma oncostreams (dynamic mesenchymal fascicles); inhibition of Col1a1 in mouse glioma eliminates oncostreams, reprograms the malignant mesenchymal phenotype, reduces expression of mesenchymal-associated genes, alters the tumor microenvironment, and prolongs animal survival.","method":"Spatial transcriptomics; ex vivo explants and intravital imaging; genetically engineered mouse glioma models; siRNA/shRNA inhibition of Col1a1; survival analysis; immunofluorescence","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 — spatiotemporal and functional in vivo evidence with multiple orthogonal methods and survival endpoint","pmids":["35750880"],"is_preprint":false},{"year":2023,"finding":"The m6A demethylase FTO upregulates COL1A1 expression by removing m6A modification from COL1A1 mRNA, thereby increasing its stability; FTO overexpression promotes fibroblast migration and expression of COL1A1 and α-SMA in keloid tissue.","method":"m6A dot blotting; MeRIP-qPCR; RT-PCR; Western blot; transwell migration assay; FTO overexpression in keloid fibroblasts","journal":"Annals of translational medicine","confidence":"Medium","confidence_rationale":"Tier 2-3 — post-translational (m6A) modification mechanism with MeRIP-qPCR validation, single lab","pmids":["36760238"],"is_preprint":false},{"year":2014,"finding":"COL1A1 does not undergo feedback regulation at the mRNA level when fibroblasts are plated on a fibroblast-derived ECM; excess COL1A1 polypeptide chains produced (due to the absence of COL1A2 downregulation) are degraded by the combined action of MMP-1, MMP-2, MMP-9, and cathepsins, revealing protease-mediated post-translational regulation of COL1A1 protein levels.","method":"Fibroblast culture on plastic vs. fd-ECM; RT-PCR; western blot; zymographic analysis; MMP and TGF-β inhibitor assays","journal":"Life sciences","confidence":"Medium","confidence_rationale":"Tier 2-3 — multiple inhibitor assays and molecular readouts, single lab, mechanistic insight into proteolytic regulation","pmids":["24637022"],"is_preprint":false},{"year":2021,"finding":"RUNX2 transcription factor promotes gastric cancer metastasis by transcriptionally upregulating COL1A1; COL1A1 knockdown abolishes the increase in cell invasion/migration promoted by RUNX2 overexpression both in vitro and in vivo (lung metastasis model), placing COL1A1 downstream of RUNX2 in a metastasis-regulatory axis.","method":"RUNX2 overexpression and COL1A1 siRNA knockdown; migration/invasion assays; in vivo lung metastasis xenograft model; RT-PCR and western blot; immunofluorescence","journal":"Cancer biomarkers","confidence":"Medium","confidence_rationale":"Tier 2-3 — epistasis-style rescue with in vivo validation, single lab","pmids":["33896817"],"is_preprint":false},{"year":2023,"finding":"CXCL9 (but not CXCL10) directly induces Col1a1 mRNA expression in mouse fibroblasts via its receptor CXCR3; Cxcl9- and Cxcr3-deficient mice fail to develop bleomycin-induced dermal fibrosis, establishing that the CXCL9-CXCR3 chemokine axis mechanistically drives Col1a1 upregulation and skin fibrosis.","method":"Bleomycin mouse fibrosis model; Cxcl9/Cxcl10/Cxcr3 knockout mice; REX3 reporter mice for in vivo cytokine source identification; recombinant CXCL9 addition to cultured fibroblasts with Col1a1 mRNA quantification","journal":"The Journal of investigative dermatology","confidence":"High","confidence_rationale":"Tier 2 — knockout epistasis with direct ligand-receptor pairing and in vitro mechanistic confirmation of Col1a1 induction","pmids":["36708947"],"is_preprint":false},{"year":2013,"finding":"The 3.2 kb Col1a1 promoter drives expression specifically in committed osteoblasts (innermost periosteal layer), which lack chondrogenic potential, while the Prx1 promoter targets osteochondroprogenitor cells; these two promoters mark distinct, non-overlapping bone cell populations.","method":"Transgenic Col1a1CreER-DsRed and Prx1CreER-GFP mice; histological analysis; flow cytometry; chondrogenic and osteogenic differentiation assays","journal":"Bone","confidence":"High","confidence_rationale":"Tier 2 — in vivo transgenic lineage tracing with functional differentiation assays, clear mechanistic dissection of promoter activity","pmids":["24513582"],"is_preprint":false},{"year":2012,"finding":"Col1a1 knockdown in mouse spermatogonia suppresses self-renewal markers (Oct4, Plzf) and promotes differentiation markers (c-kit, haprin), arrests cells in S phase, and impairs spermatogonia self-renewal in vivo (testes electroporation), establishing a role for Col1a1 in maintaining spermatogonial stem cell identity.","method":"siRNA knockdown; RT-PCR and western blot; flow cytometry cell cycle analysis; in vivo testes DNA injection and electroporation","journal":"Asian journal of andrology","confidence":"Medium","confidence_rationale":"Tier 2-3 — loss-of-function with defined molecular markers in vitro and in vivo, single lab","pmids":["23064687"],"is_preprint":false},{"year":2023,"finding":"MMP2 promotes COL1A1 upregulation in cholangiocarcinoma cells via the integrin αV pathway, enhancing ECM remodelling and inducing EMT; COL1A1 in turn increases PD-L1 expression by activating the NF-κB pathway.","method":"Western blot; immunofluorescence; COL1A1 overexpression and knockdown; in vitro migration/invasion assays; in vivo xenograft; pathway inhibitor assays for integrin αV and NF-κB","journal":"Annals of hepatology","confidence":"Medium","confidence_rationale":"Tier 3 — pathway placement via pharmacological inhibition and KD/OE, mechanistic chain MMP2→integrin αV→COL1A1→NF-κB→PD-L1 established, single lab","pmids":["38123132"],"is_preprint":false},{"year":1988,"finding":"The complete nucleotide sequence of the first 7618 bp of the human COL1A1 gene was determined, comprising 25 exons encoding the N-terminal pre-propeptide and five cyanogen-bromide-derived peptides; the conceptual amino acid translation shows 95% homology to rat α1(I) chain, establishing the gene's exon-intron organization.","method":"DNA sequencing of genomic COL1A1; restriction mapping; conceptual translation and homology comparison","journal":"Gene","confidence":"Medium","confidence_rationale":"Tier 2 — foundational structural genomics of the gene, single study but high-quality sequencing","pmids":["2843432"],"is_preprint":false}],"current_model":"COL1A1 encodes the α1 chain of type I collagen, a secreted extracellular matrix protein whose expression is regulated at multiple levels: transcriptionally by promoter-bound factors including YY1 (positive regulator), RFX1/RFX5-CIITA complexes (repressors, modulated by DNA methylation), Osterix/Nmp4 complexes (regulated by promoter haplotype), RUNX2, and CXCL9-CXCR3 signaling; post-transcriptionally by nuclear mRNA retention when splicing is defective; and post-translationally by protease-mediated degradation (MMP-1/2/9, cathepsins) and m6A demethylation (FTO) that stabilizes its mRNA. COL1A1 protein promotes cell migration and invasion by binding integrin β1 to activate AKT, and participates in WNT/PCP and NF-κB pathways; its chromosomal fusion with PDGFB in DFSP produces a chimeric protein that is processed into mature PDGFB, driving autocrine/paracrine tumor growth through PDGFB receptor activation."},"narrative":{"teleology":[{"year":1988,"claim":"Determination of the exon–intron organization of the human COL1A1 gene established the structural framework—including the Gly-X-Y repeat-encoding exons—needed to interpret subsequent disease mutations.","evidence":"Genomic DNA sequencing and restriction mapping of 7.6 kb of human COL1A1","pmids":["2843432"],"confidence":"Medium","gaps":["Only the 5' portion of the gene was sequenced","No functional data on regulatory elements were provided"]},{"year":1989,"claim":"Identification of glycine-to-bulky-residue substitutions in the helical domain as the cause of lethal perinatal osteogenesis imperfecta demonstrated that the Gly-X-Y repeat is indispensable for collagen triple-helix assembly.","evidence":"Chemical mismatch cleavage and sequencing of COL1A1 mRNA from OI patients with multiple independent Gly substitutions","pmids":["2777764"],"confidence":"High","gaps":["No structural or biophysical characterization of helix disruption","Position-dependent severity gradient not yet mapped"]},{"year":1993,"claim":"Transgenic promoter-deletion studies revealed that a distal 624-bp element (−2296 to −1672) is active in intact bone but silenced when cells lose matrix contact, establishing that COL1A1 transcription is coupled to the extracellular matrix microenvironment.","evidence":"COL1A1-CAT transgenic mice comparing intact calvariae to isolated primary bone cells","pmids":["8355676"],"confidence":"High","gaps":["Trans-acting factors binding this distal element were not identified","Signaling pathway linking matrix contact to element activity was unknown"]},{"year":1995,"claim":"Demonstration that only 476 bp of the COL1A1 promoter is sufficient for tissue-specific expression in transgenic mice showed that core regulatory information is compactly organized and does not require the first intron or most of the 3'-UTR.","evidence":"Transgenic mice with mini-COL1A1 and hybrid COL1A1/COL2A1 constructs; mRNA and protein assays across tissues","pmids":["7721894"],"confidence":"High","gaps":["Individual cis elements within the 476-bp region were not mapped","Quantitative expression levels vs. endogenous gene were not compared"]},{"year":1996,"claim":"Discovery that premature stop and splice-donor mutations cause nuclear retention of COL1A1 mRNA—rather than nonsense-mediated decay—established nuclear mRNA surveillance as the mechanism underlying haploinsufficiency in mild OI type I.","evidence":"RT-PCR on nuclear vs. cytoplasmic RNA fractions from OI patient fibroblasts","pmids":["8613526"],"confidence":"High","gaps":["The nuclear retention machinery was not identified","Whether transcript degradation eventually occurs in the nucleus was unresolved"]},{"year":1997,"claim":"Identification of the t(17;22) COL1A1–PDGFB fusion in DFSP revealed that a structural collagen gene can be co-opted as an oncogenic driver by providing a constitutive promoter for an otherwise tightly regulated growth factor.","evidence":"Southern blot, RT-PCR, and breakpoint mapping in multiple DFSP and giant-cell fibroblastoma specimens","pmids":["8988177"],"confidence":"High","gaps":["Whether the chimeric protein is processed to mature PDGFB was not yet shown","The range of COL1A1 exon breakpoints across tumors was incompletely catalogued"]},{"year":2000,"claim":"Visualization of COL1A1 RNA trafficking showed that normal transcripts transit through SC-35 splicing-factor domains en route to export, while splice-defective transcripts stall at this step, pinpointing the nuclear compartment responsible for the retention seen in OI.","evidence":"RNA FISH with microfluorimetric quantification in patient fibroblasts comparing normal and splice-mutant alleles","pmids":["10931857"],"confidence":"High","gaps":["Factors mediating SC-35 domain exit were not identified","Whether this quality-control step is COL1A1-specific or general was unknown"]},{"year":2001,"claim":"Two parallel advances defined COL1A1 transcriptional activation and oncogenic function: YY1 was shown to be an essential positive regulator binding two sites flanking the TATA box, and the COL1A1–PDGFB fusion protein was demonstrated to be processed into active PDGFB dimers that confer growth-factor independence and tumorigenicity.","evidence":"EMSA/supershift with purified YY1, promoter mutagenesis, and gain/loss-of-function transfections (YY1); stable transfections, nude mouse tumorigenicity, and mutagenesis of PDGFB cleavage site (fusion protein)","pmids":["11514536","11420709"],"confidence":"High","gaps":["Whether YY1 is modulated by signaling pathways at the COL1A1 promoter was untested","Contributions of uncleaved vs. cleaved fusion forms in patient tumors were not quantified"]},{"year":2005,"claim":"Identification of RFX1 as a methylation-enhanced repressor and RFX5–CIITA as an IFN-γ-induced repressor of COL1A1 transcription explained how promoter DNA methylation and immune signaling silence collagen expression in cancer cells.","evidence":"Gel shift with methylated/unmethylated probes; RFX5 dominant-negative and CIITA RNAi; aza-dC treatment of cancer cells","pmids":["15788405"],"confidence":"High","gaps":["In vivo ChIP confirmation of RFX1 binding at the methylated COL1A1 promoter was not performed","Relationship between RFX repression and fibrosis pathologies was unexplored"]},{"year":2009,"claim":"The discovery that a three-SNP haplotype in the COL1A1 5'-flank controls differential Osterix/Nmp4 recruitment and transcriptional output linked common genetic variation to osteoporosis risk through a defined transcription-factor mechanism.","evidence":"Reporter assays, EMSA, ChIP for Osterix/Nmp4/RNA Pol II, and BMD association in 3270 women","pmids":["19429913"],"confidence":"High","gaps":["Functional contribution of each individual SNP was not fully dissected","Whether this haplotype affects fibrosis or tumor contexts was unknown"]},{"year":2012,"claim":"Col1a1 knockdown in spermatogonia impaired self-renewal markers and promoted differentiation, revealing an unexpected role for type I collagen in maintaining spermatogonial stem cell identity beyond its classical structural function.","evidence":"siRNA knockdown with marker profiling in vitro and in vivo testes electroporation in mice","pmids":["23064687"],"confidence":"Medium","gaps":["Whether COL1A1 signals through integrins in this context was not tested","Not independently replicated","Mechanism linking ECM to Oct4/Plzf expression was undefined"]},{"year":2014,"claim":"Demonstration that excess COL1A1 polypeptide is degraded by MMP-1/2/9 and cathepsins when fibroblasts contact their own ECM established protease-mediated post-translational homeostasis as a layer of COL1A1 regulation independent of mRNA feedback.","evidence":"Fibroblast culture on plastic vs. fibroblast-derived ECM with zymography and MMP/TGF-β inhibitor assays","pmids":["24637022"],"confidence":"Medium","gaps":["Specific protease cleavage sites on COL1A1 were not mapped","In vivo relevance of this homeostatic loop was not confirmed"]},{"year":2017,"claim":"Identification of miR-129-5p as a direct post-transcriptional repressor of COL1A1 via its 3'-UTR provided the first microRNA–COL1A1 axis with functional rescue evidence in a cancer context.","evidence":"Dual-luciferase 3'-UTR reporter; miR-129-5p mimic/inhibitor with COL1A1 rescue in gastric cancer cells","pmids":["28482162"],"confidence":"Medium","gaps":["In vivo validation of miR-129-5p regulation of COL1A1 was lacking","Single lab finding"]},{"year":2018,"claim":"COL1A1 knockdown reduced Rac1-GTP, phospho-JNK, and RhoA-GTP in colorectal cancer cells, placing COL1A1 upstream of WNT/planar cell polarity signaling as a migration driver.","evidence":"siRNA knockdown with western blot for WNT/PCP effectors and Transwell migration assays","pmids":["29393423"],"confidence":"Medium","gaps":["No epistasis with WNT/PCP pathway components was tested","Receptor mediating COL1A1 signal to PCP was not identified","Single lab"]},{"year":2020,"claim":"Secreted COL1A1 was shown to bind integrin β1 (ITGB1) and activate AKT phosphorylation to promote ovarian cancer invasion, defining the first receptor–signaling axis for paracrine COL1A1 pro-metastatic activity.","evidence":"siRNA/antibody blockade of COL1A1 and ITGB1 with p-AKT readout; in vivo xenograft peritoneal metastasis model","pmids":["32589888"],"confidence":"Medium","gaps":["Direct COL1A1–ITGB1 binding was not reconstituted with purified proteins","Contribution of other integrin α-subunit partners was not assessed"]},{"year":2021,"claim":"RUNX2 was placed upstream of COL1A1 in a gastric cancer metastasis axis: COL1A1 knockdown fully abolished RUNX2-driven invasion, demonstrating that COL1A1 is a necessary effector of RUNX2 transcriptional pro-metastatic activity.","evidence":"RUNX2 overexpression with COL1A1 siRNA rescue; in vivo lung metastasis xenograft","pmids":["33896817"],"confidence":"Medium","gaps":["Direct RUNX2 binding to the COL1A1 promoter was not shown by ChIP","Single cancer type tested"]},{"year":2022,"claim":"Col1a1 was identified as the central structural organizer of glioma oncostreams; its inhibition eliminated these dynamic mesenchymal structures, reprogrammed the tumor microenvironment, and extended survival, establishing COL1A1 as a functional driver of mesenchymal tumor architecture.","evidence":"Spatial transcriptomics, intravital imaging, genetically engineered mouse glioma models, and Col1a1 shRNA with survival analysis","pmids":["35750880"],"confidence":"High","gaps":["Whether COL1A1 acts cell-autonomously or via ECM signaling to organize oncostreams was not dissected","Human glioma validation was correlative"]},{"year":2023,"claim":"Two new regulatory inputs to COL1A1 were defined: the CXCL9–CXCR3 chemokine axis was shown to directly induce Col1a1 in fibroblasts and drive dermal fibrosis in knockout mice, and the m6A demethylase FTO was shown to stabilize COL1A1 mRNA by removing m6A marks, promoting keloid fibrosis.","evidence":"Cxcl9/Cxcr3 knockout mice with bleomycin fibrosis and recombinant CXCL9 in vitro (CXCL9); MeRIP-qPCR and FTO overexpression in keloid fibroblasts (FTO)","pmids":["36708947","36760238"],"confidence":"High","gaps":["Downstream signaling from CXCR3 to COL1A1 promoter elements is undefined","FTO–COL1A1 axis awaits in vivo validation","Interplay between m6A regulation and transcriptional control of COL1A1 is unexplored"]},{"year":2023,"claim":"COL1A1 was placed in an MMP2–integrin αV–COL1A1–NF-κB–PD-L1 signaling chain in cholangiocarcinoma, linking collagen remodeling to immune evasion.","evidence":"COL1A1 overexpression/knockdown with pathway inhibitors for integrin αV and NF-κB; xenograft validation","pmids":["38123132"],"confidence":"Medium","gaps":["Each step in the signaling chain was tested pharmacologically without genetic epistasis","Whether COL1A1 directly binds integrin αV was not shown","Single lab, single cancer type"]},{"year":null,"claim":"Major open questions include: the structural basis of COL1A1's signaling through specific integrin heterodimers; how the multiple transcriptional, post-transcriptional (miRNA, m6A), and proteolytic regulatory layers are integrated in vivo; and whether COL1A1's non-structural signaling roles in stem cell maintenance and tumor architecture are mediated by the same integrin-dependent mechanisms identified in cancer invasion.","evidence":"","pmids":[],"confidence":"Low","gaps":["No high-resolution structure of COL1A1–integrin complex exists","Systems-level integration of regulatory inputs has not been modeled","Non-structural roles lack receptor-level mechanistic resolution"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[9,13]},{"term_id":"GO:0098631","term_label":"cell adhesion mediator activity","supporting_discovery_ids":[10,12]}],"localization":[{"term_id":"GO:0031012","term_label":"extracellular matrix","supporting_discovery_ids":[7,9,13,15]},{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[10,15]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[2,3]}],"pathway":[{"term_id":"R-HSA-1474244","term_label":"Extracellular matrix organization","supporting_discovery_ids":[9,13,15]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[0,1]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[10,12,20]}],"complexes":[],"partners":["COL1A2","ITGB1","YY1","PDGFB","RFX1","RUNX2","FTO"],"other_free_text":[]},"mechanistic_narrative":"COL1A1 encodes the α1 chain of type I collagen, the principal structural protein of bone, skin, tendon, and other connective tissues, whose Gly-X-Y triple-helical domain is essential for proper helix assembly and extracellular matrix integrity. Transcription of COL1A1 is driven by a compact proximal promoter (~476 bp) sufficient for tissue-specific expression and is positively regulated by YY1 binding adjacent to the TATA box, modulated by promoter haplotype-dependent recruitment of Osterix/Nmp4, and repressed by RFX1 (methylation-enhanced) and the RFX5–CIITA complex; upstream signals including CXCL9–CXCR3 and RUNX2 converge on COL1A1 transcription to drive fibrosis and tumor invasion [PMID:11514536, PMID:15788405, PMID:19429913, PMID:36708947, PMID:33896817]. Defective splicing causes nuclear retention of COL1A1 mRNA at SC-35 domains, producing haploinsufficiency that underlies mild osteogenesis imperfecta, while glycine substitutions in the helical domain cause lethal perinatal osteogenesis imperfecta [PMID:8613526, PMID:10931857, PMID:2777764]. The chromosomal translocation t(17;22) fuses COL1A1 with PDGFB, generating a chimeric protein processed into mature PDGFB that drives autocrine growth in dermatofibrosarcoma protuberans; independently, secreted COL1A1 signals through integrin β1–AKT and WNT/PCP pathways to promote cancer cell migration and invasion [PMID:8988177, PMID:11420709, PMID:32589888, PMID:29393423]."},"prefetch_data":{"uniprot":{"accession":"P02452","full_name":"Collagen alpha-1(I) chain","aliases":["Alpha-1 type I collagen"],"length_aa":1464,"mass_kda":138.9,"function":"Type I collagen is a member of group I collagen (fibrillar forming collagen)","subcellular_location":"Secreted, extracellular space, extracellular matrix","url":"https://www.uniprot.org/uniprotkb/P02452/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/COL1A1","classification":"Not 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mutagenesis showed uncleaved COL1A1-PDGFB forms are also mitogenic.\",\n      \"method\": \"Stable/transient transfection, anti-PDGFB antibodies, mutagenesis, nude mouse tumorigenicity assay\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstitution in cells with mutagenesis and functional assays, multiple orthogonal methods\",\n      \"pmids\": [\"11420709\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"COL1A1 pre-mRNA undergoes co-transcriptional splicing at or adjacent to the gene site within SC35 nuclear domains; splice-defective transcripts initiate transport from the gene but are retained within the SC35 domain and cannot be exported, identifying a nuclear retention mechanism for aberrant COL1A1 mRNA in osteogenesis imperfecta.\",\n      \"method\": \"RNA FISH, microfluorimetric analysis, nuclear track imaging in patient fibroblasts\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct live-cell and fixed imaging with functional consequence (nuclear retention vs. export), multiple orthogonal approaches\",\n      \"pmids\": [\"10931857\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"COL1A1 transcripts arising from null alleles (premature stop or splice-site mutations) are retained in the nucleus and absent from the cytoplasm, whereas missense point-mutation transcripts are present in both compartments, establishing nuclear retention as the mechanism for haploinsufficiency in mild OI.\",\n      \"method\": \"RT-PCR, SSCP, nuclear/cytoplasmic fractionation of patient fibroblasts\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — subcellular fractionation with functional consequence (mRNA export block), replicated across multiple patient alleles\",\n      \"pmids\": [\"8613526\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1989,\n      \"finding\": \"Point mutations causing lethal perinatal osteogenesis imperfecta are heterozygous glycine substitutions in the helical Gly-X-Y repeat of COL1A1 (Gly973Val, Gly1006Val, Gly928Ala, Gly976Arg) or COL1A2 (Gly865Ser), demonstrating that glycine substitutions disrupt triple-helix formation.\",\n      \"method\": \"Chemical mismatch cleavage of mRNA/cDNA heteroduplexes, PCR cloning and sequencing\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct sequence identification of causal mutations with mechanistic interpretation, multiple patients\",\n      \"pmids\": [\"2777764\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"COL1A1 transcription is repressed by RFX family members: RFX1 binds with higher affinity to the methylated COL1A1 promoter RFX site (-11 to +10), and RFX5/CIITA complex represses both COL1A1 and COL1A2 in response to interferon-gamma; dominant-negative RFX5 forms activate COL1A1 coordinately.\",\n      \"method\": \"Gel shift assay (EMSA), transient transfection luciferase, RNAi, 5-aza-dC treatment\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — EMSA plus functional reporter assays plus RNAi, multiple orthogonal methods in one study\",\n      \"pmids\": [\"15788405\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"YY1 binds to two core sites (YY1A at -40/-37 bp and YY1B at -32/-29 bp) immediately upstream of the TATA box in the COL1A1 proximal promoter and functions as a required positive regulator of constitutive COL1A1 transcription in fibroblasts; mutation of YY1B abolishes activity, and TFIID/TBP can co-occupy the region with YY1.\",\n      \"method\": \"EMSA with recombinant YY1, supershift with antibody, transfection with luciferase reporter constructs, antisense YY1, mutation analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — EMSA with recombinant protein, mutagenesis, functional reporter, antisense experiments in one study\",\n      \"pmids\": [\"11514536\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Three polymorphisms in the 5' flank of COL1A1 (-1997G/T, -1663IndelT, +1245G/T) regulate transcription: the -1663delT osteoporosis-associated allele has increased binding affinity for a complex of Osterix and Nmp4, recruits more RNA polymerase II, and drives ~2-fold higher transcription; increased COL1A1 transcription correlates with reduced BMD in vivo.\",\n      \"method\": \"Gel shift assay, chromatin immunoprecipitation (ChIP), luciferase reporter, population BMD analysis\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — ChIP, EMSA, functional reporter in one study with in vivo BMD correlation\",\n      \"pmids\": [\"19429913\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"A 624-bp region of the COL1A1 promoter (between -2296 and -1672) is active in intact bone but inactive in cultured bone-derived cells, indicating that cell-cell or cell-matrix interactions in the bone microenvironment are required to maintain full COL1A1 promoter activity.\",\n      \"method\": \"Transgenic mouse CAT reporter assay comparing intact calvariae vs. primary bone cell cultures\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — transgenic reporter in vivo vs. in vitro, single lab but direct functional readout\",\n      \"pmids\": [\"8355676\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"Only 476 bp of the COL1A1 promoter is sufficient to drive tissue-specific expression of collagen in transgenic mice; the first intron and 90% of the 3'-UTR are not required for tissue-specific expression.\",\n      \"method\": \"Transgenic mice with mini-COL1A1 and hybrid COL1A1/COL2A1 genes, mRNA and protein analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vivo transgenic experiment with protein and mRNA readouts, clear functional dissection of promoter elements\",\n      \"pmids\": [\"7721894\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Fibroblast-secreted COL1A1 promotes ovarian cancer cell migration and invasion by binding to the cell surface receptor integrin β1 (ITGB1) and activating downstream AKT phosphorylation; knockdown or blockade of ITGB1 reverses these effects.\",\n      \"method\": \"Proteomics of ascites, COL1A1 antibody blocking, ITGB1 knockdown/antibody blockade, intraperitoneal xenograft, Western blot for p-AKT\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — receptor identification by knockdown/antibody blockade, in vivo xenograft, signaling readout; multiple orthogonal methods\",\n      \"pmids\": [\"32589888\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"COL1A1 overexpression organizes glioma cells into dynamic oncostream fascicles with mesenchymal properties; Col1a1 inhibition eliminates oncostreams, reprograms the malignant histopathological phenotype, reduces mesenchymal gene expression, alters the tumor microenvironment, and prolongs animal survival.\",\n      \"method\": \"Spatiotemporal transcriptomics, intravital imaging, ex vivo explants, Col1a1 knockdown in genetically engineered mouse glioma models, survival analysis\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (intravital imaging, transcriptomics, in vivo KO phenotype with survival), strong evidence\",\n      \"pmids\": [\"35750880\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"CXCL9 acting through its receptor CXCR3 directly induces Col1a1 mRNA expression in fibroblasts; CXCL9- or CXCR3-deficient mice are protected from bleomycin-induced dermal fibrosis, placing COL1A1 downstream of the CXCL9/CXCR3 signaling axis in inflammatory fibrosis.\",\n      \"method\": \"Recombinant CXCL9 treatment of cultured fibroblasts, Cxcl9/Cxcl10/Cxcr3 knockout mice, REX3 reporter mice, bleomycin fibrosis model\",\n      \"journal\": \"The Journal of investigative dermatology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis (KO mice), direct cytokine treatment, reporter mice, multiple orthogonal methods\",\n      \"pmids\": [\"36708947\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"The m6A demethylase FTO promotes keloid formation by reducing m6A modification on COL1A1 mRNA, thereby stabilizing COL1A1 mRNA and increasing COL1A1 protein expression, which drives fibroblast migration and collagen deposition.\",\n      \"method\": \"MeRIP-qPCR, FTO overexpression, mRNA stability assay, Western blot, transwell migration, H&E staining\",\n      \"journal\": \"Annals of translational medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — MeRIP validates m6A site, functional rescue assays, single lab\",\n      \"pmids\": [\"36760238\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"RUNX2 transcription factor promotes gastric cancer metastasis by upregulating COL1A1 expression; COL1A1 knockdown reverses the pro-metastatic effects of RUNX2 overexpression both in vitro and in vivo (lung metastasis model).\",\n      \"method\": \"RT-PCR, Western blot, RUNX2 overexpression/knockdown, COL1A1 knockdown, invasion/migration assays, xenograft lung metastasis model\",\n      \"journal\": \"Cancer biomarkers\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — epistasis demonstrated by rescue experiment in vitro and in vivo, single lab\",\n      \"pmids\": [\"33896817\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"COL1A1 activates the PI3K/AKT pathway and inhibits radiation-induced apoptosis in cervical cancer cells; COL1A1 knockdown decreases p-AKT and Bcl-2 and increases Caspase-3, while COL1A1 activation reverses LY294002 (PI3K inhibitor)-mediated sensitization to radiation.\",\n      \"method\": \"Colony formation assay, flow cytometry, Western blot (p-AKT, Bcl-2, Caspase-3), COL1A1 siRNA and activation constructs\",\n      \"journal\": \"Cancer cell international\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — pathway placement by inhibitor/rescue experiments, single lab with multiple readouts\",\n      \"pmids\": [\"28775672\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"COL1A1 knockdown in colorectal cancer cells decreases expression of Rac1-GTP, phospho-JNK, and RhoA-GTP, key effectors of the WNT/planar cell polarity (PCP) signaling pathway, suggesting COL1A1 promotes CRC migration via the WNT/PCP pathway.\",\n      \"method\": \"Transwell migration assay, siRNA knockdown, GTPase activity assays, Western blot for WNT/PCP pathway components\",\n      \"journal\": \"Molecular medicine reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — pathway placement by knockdown with multiple downstream markers, single lab\",\n      \"pmids\": [\"29393423\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"MMP2 induces COL1A1 upregulation in cholangiocarcinoma cells via the integrin αV pathway, and COL1A1 in turn activates the NF-κB pathway to increase PD-L1 expression, promoting EMT and immune evasion.\",\n      \"method\": \"Western blot, immunofluorescence, COL1A1 overexpression/knockdown, MMP2 manipulation, NF-κB pathway analysis, xenograft\",\n      \"journal\": \"Annals of hepatology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — multiple functional assays and pathway analysis, single lab\",\n      \"pmids\": [\"38123132\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"RNAi targeting a single-nucleotide polymorphism within COL1A1 transcripts achieves allele-specific suppression of COL1A1 in human mesenchymal progenitor stem cells, demonstrating that mutation-independent allele-specific silencing of COL1A1 is achievable.\",\n      \"method\": \"siRNA transfection in Cos-7 and human mesenchymal progenitor cells, allele-specific gene expression analysis\",\n      \"journal\": \"European journal of human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct functional demonstration of allele-specific RNAi, single lab\",\n      \"pmids\": [\"15241481\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Knockdown of Col1a1 in mouse spermatogonia suppresses self-renewal markers (Oct4, Plzf) and enhances differentiation markers (c-kit, haprin), with S-phase arrest; in vivo electroporation of Col1a1 siRNA into testes impairs spermatogonial self-renewal.\",\n      \"method\": \"siRNA knockdown, RT-PCR, cell cycle analysis, in vivo electroporation into testes\",\n      \"journal\": \"Asian journal of andrology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — loss-of-function with specific differentiation marker readouts in vitro and in vivo, single lab\",\n      \"pmids\": [\"23064687\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Excess COL1A1 polypeptide chains that are not incorporated into type I collagen heterotrimers are degraded by the combined action of MMP-1, MMP-2, MMP-9, and cathepsins; no feedback regulation of COL1A1 mRNA occurs when fibroblasts are plated on fibroblast-derived ECM, though COL1A2 mRNA is downregulated.\",\n      \"method\": \"MMP and cathepsin inhibitor assays, Western blot, real-time PCR, zymography, fibroblast-derived ECM culture\",\n      \"journal\": \"Life sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — pharmacological inhibitor dissection of protease pathways, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"24637022\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Structural modeling of OI-associated glycine substitutions in the COL1A1 triple-helical domain shows that mutations decrease helix stability (fewer backbone hydrogen bonds) and increase main chain RMSD and specifically bound water molecules, with different effects depending on the substituting amino acid.\",\n      \"method\": \"High-throughput molecular dynamics simulation of homotrimeric COL1A1 peptides with and without mutations\",\n      \"journal\": \"Molecular & cellular proteomics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 4 — computational prediction only, no experimental validation\",\n      \"pmids\": [\"12488462\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Overexpression of Trps1 transcription factor in odontoblasts (driven by the Col1a1 promoter) directly represses the Dspp promoter, causing severe dentin hypomineralization resembling dentinogenesis imperfecta, and decreases DSP and DPP protein levels.\",\n      \"method\": \"Transgenic Col1a1-Trps1 mice, micro-CT, histology, biochemical analysis of dentin matrix proteins, Dspp promoter reporter assay\",\n      \"journal\": \"Journal of bone and mineral research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — transgenic mouse model with direct promoter reporter validation, single lab with orthogonal methods\",\n      \"pmids\": [\"22508542\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"COL1A1 encodes the α1 chain of type I collagen, whose transcription is positively regulated by YY1 and negatively by methylation-sensitive RFX1/RFX5/CIITA complexes and CXCL9/CXCR3 signaling; its mRNA undergoes co-transcriptional splicing within nuclear SC35 domains and null/splice-defective transcripts are retained there, preventing export; the secreted protein acts extracellularly via integrin β1/αV receptors to activate AKT and NF-κB signaling, promotes cell migration through the WNT/PCP pathway, and organizes tumor mesenchymal architecture, while in dermatofibrosarcoma protuberans the COL1A1-PDGFB fusion protein is processed into mature PDGFB that drives autocrine/paracrine receptor activation and tumorigenesis.\"\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\n```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1997,\n      \"finding\": \"The t(17;22)(q22;q13) chromosomal translocation in dermatofibrosarcoma protuberans (DFSP) fuses COL1A1 on chromosome 17 with the PDGFB gene on chromosome 22, deleting exon 1 of PDGFB and releasing the growth factor from its normal regulation, thereby driving tumor formation through constitutive PDGFB signaling.\",\n      \"method\": \"Southern blotting, RT-PCR, genomic characterization of breakpoints in DFSP and giant-cell fibroblastoma tumor specimens\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — original discovery with multiple molecular methods, replicated across multiple tumor specimens and independently confirmed in subsequent studies\",\n      \"pmids\": [\"8988177\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"The COL1A1-PDGFB chimeric protein produced by the t(17;22) translocation is processed in transfected cells into mature PDGFB dimers, confers growth factor independence and tumorigenicity in nude mice, and stimulates fibroblast growth via the PDGFB receptor pathway; mutagenesis showed uncleaved COL1A1-PDGFB forms are also mitogenic, contributing to the transformed phenotype.\",\n      \"method\": \"Stable and transient transfections in fibroblastic and epithelial cell lines; anti-PDGFB and anti-COL1A1-PDGFB antibody characterization; tumorigenicity assay in nude mice; mutagenesis experiments\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — reconstitution in cell lines plus in vivo tumorigenicity with mutagenesis controls, strong mechanistic resolution\",\n      \"pmids\": [\"11420709\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"COL1A1 null alleles arising from premature stop mutations or splice donor mutations produce transcripts that are retained in the nucleus and absent from the cytoplasm, establishing that nuclear retention/mRNA export failure is the mechanism underlying haploinsufficiency in mild osteogenesis imperfecta type I.\",\n      \"method\": \"RT-PCR and single-strand conformational polymorphism of nuclear vs. cytoplasmic fractions of COL1A1 mRNA from OI patient fibroblasts\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct subcellular fractionation with functional consequence (haploinsufficiency causing OI), multiple patients and mutations\",\n      \"pmids\": [\"8613526\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Normal COL1A1 pre-mRNA undergoes cotranscriptional splicing at or adjacent to the gene and then transits through an SC-35 splicing factor domain before nuclear export; splice-defective COL1A1 transcripts (from an OI intron 26 mutation) initiate transport from the gene into the SC-35 domain but accumulate abnormally and are impeded in exit, identifying movement through the SC-35 domain as a discrete step in COL1A1 mRNA export.\",\n      \"method\": \"Fluorescence in situ hybridization of COL1A1 RNA in patient fibroblasts; microfluorimetric analysis of nuclear RNA tracks; comparison of normal vs. splice-mutant alleles\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct visualization of RNA trafficking with quantitative comparison of normal vs. mutant alleles in the same cell, strong mechanistic insight\",\n      \"pmids\": [\"10931857\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"RFX1 binds the methylated COL1A1 promoter (sites -11 to +10) with higher affinity than the unmethylated site and represses COL1A1 transcription; RFX5 (as part of a complex with CIITA induced by IFN-γ) represses both COL1A1 and COL1A2 promoters equally. The COL1A1 gene is methylated in human cancer cells, correlating with reduced collagen expression that is reversed by the methylation inhibitor aza-dC.\",\n      \"method\": \"Gel shift assays, co-immunoprecipitation, RFX5 dominant-negative transfections, CIITA RNAi, transient transfection reporter assays, methylation inhibitor (aza-dC) treatment\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods including dominant negatives, RNAi, and direct binding assays with methylated vs. unmethylated substrates\",\n      \"pmids\": [\"15788405\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"YY1 binds two sites (YY1A at -40/-37 bp and YY1B at -32/-29 bp) in the COL1A1 proximal promoter immediately upstream of the TATA box and acts as a required positive regulator of constitutive COL1A1 transcription in fibroblasts; mutation of either site reduces or abolishes promoter activity, and YY1 and TBP/TFIID can co-occupy the promoter fragment.\",\n      \"method\": \"EMSA with purified recombinant YY1 and nuclear extracts; supershift with YY1-specific antibody; mutation analysis; Col1a1-luciferase co-transfections with pCMV-YY1 and antisense YY1\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — reconstituted binding with purified protein, multiple promoter mutations, gain- and loss-of-function in transfections\",\n      \"pmids\": [\"11514536\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Three polymorphisms in the COL1A1 5' flank (-1997G/T, -1663IndelT, +1245G/T) interact to regulate transcription: the osteoporosis-associated G-del-T haplotype drives 2-fold higher transcription and has increased binding affinity for a protein complex containing Nmp4 and Osterix at the -1663IndelT site; chromatin IP confirmed recruitment of Osterix and Nmp4 and showed evidence of Nmp4 at the intron 1 Sp1 site; G-del-T haplotype shows higher RNA Pol II binding.\",\n      \"method\": \"Reporter gene transcription assays; gel shift assays; chromatin immunoprecipitation; genotype-BMD association in 3270 Caucasian women\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods (ChIP, EMSA, reporter assays) combined with in vivo human BMD correlation\",\n      \"pmids\": [\"19429913\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"A 624-bp region of the COL1A1 promoter between positions -2296 and -1672 is active in intact bone and cultured bone but inactive in primary bone cells isolated from bone, demonstrating that the loss of cell-matrix interactions in culture causes differential downregulation of COL1A1 promoter activity.\",\n      \"method\": \"Transgenic mice expressing COL1A1-CAT fusion genes; CAT reporter assays in calvariae vs. primary bone cell cultures; comparison of 3.6 kb, 2.3 kb, and 1.7 kb 5'-deletion constructs\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct in vivo vs. in vitro promoter deletion analysis in transgenic mice with parallel collagen synthesis measurements\",\n      \"pmids\": [\"8355676\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"Only 476 bp of the COL1A1 promoter is sufficient to drive tissue-specific expression of the COL1A1 gene in transgenic mice; the first intron and 90% of the 3'-UTR are not required for tissue-specific expression.\",\n      \"method\": \"Transgenic mice with mini-COL1A1 gene and hybrid COL1A1/COL2A1 gene constructs; assay of transgene mRNA and protein in tissues\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct in vivo transgenic experiment with mRNA and protein-level validation\",\n      \"pmids\": [\"7721894\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1989,\n      \"finding\": \"Point mutations in COL1A1 causing substitution of conserved glycine residues in the helical domain (e.g., Gly973Val, Gly1006Val, Gly928Ala, Gly976Arg) are sufficient to cause lethal perinatal osteogenesis imperfecta, demonstrating that the Gly-X-Y repeating sequence is essential for normal collagen helix formation and extracellular matrix function.\",\n      \"method\": \"Chemical mismatch cleavage of mRNA-cDNA heteroduplexes; PCR amplification; DNA sequencing; identification of heterozygous single-base mutations in patient RNA\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct mutation identification with structural consequence, confirmed in multiple patients with different substitutions\",\n      \"pmids\": [\"2777764\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"COL1A1 secreted by fibroblasts promotes ovarian cancer cell migration and invasion by binding to membrane surface receptor integrin β1 (ITGB1), activating downstream AKT phosphorylation; knockdown or blockage of ITGB1 reverses COL1A1-enhanced migration and invasion.\",\n      \"method\": \"Quantitative proteomics of ascites; siRNA knockdown and antibody blockage of COL1A1 and ITGB1; western blot for p-AKT; in vivo xenograft intraperitoneal metastasis assay in NOD/SCID mice\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — binding partner identified with functional rescue, in vivo validation, but direct binding not reconstituted in vitro\",\n      \"pmids\": [\"32589888\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"miR-129-5p suppresses gastric cancer cell proliferation, migration, and invasion by directly targeting the 3'-UTR of COL1A1 mRNA; co-transfection of miR-129-5p mimics with COL1A1 rescued tumor-promoting effects, confirming a miR-129-5p/COL1A1 regulatory axis.\",\n      \"method\": \"Dual luciferase reporter assay confirming direct 3'-UTR binding; RT-qPCR and western blot; MTT, colony formation, wound healing, Transwell assays; rescue co-transfection experiments\",\n      \"journal\": \"Biochemistry and cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — direct 3'-UTR target validation by luciferase with functional rescue, single lab\",\n      \"pmids\": [\"28482162\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"COL1A1 promotes CRC cell migration via the WNT/PCP signaling pathway; COL1A1 knockdown decreased levels of Rac1-GTP, phosphorylated JNK, and RhoA-GTP, which are key effectors of the WNT/PCP pathway.\",\n      \"method\": \"Transwell migration assay; siRNA knockdown; western blot for Rac1-GTP, p-JNK, RhoA-GTP; RT-PCR for WNT/PCP pathway gene expression\",\n      \"journal\": \"Molecular medicine reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — KD with defined pathway readout but no epistasis or reconstitution, single lab\",\n      \"pmids\": [\"29393423\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"COL1A1 is the central structural gene organizing glioma oncostreams (dynamic mesenchymal fascicles); inhibition of Col1a1 in mouse glioma eliminates oncostreams, reprograms the malignant mesenchymal phenotype, reduces expression of mesenchymal-associated genes, alters the tumor microenvironment, and prolongs animal survival.\",\n      \"method\": \"Spatial transcriptomics; ex vivo explants and intravital imaging; genetically engineered mouse glioma models; siRNA/shRNA inhibition of Col1a1; survival analysis; immunofluorescence\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — spatiotemporal and functional in vivo evidence with multiple orthogonal methods and survival endpoint\",\n      \"pmids\": [\"35750880\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"The m6A demethylase FTO upregulates COL1A1 expression by removing m6A modification from COL1A1 mRNA, thereby increasing its stability; FTO overexpression promotes fibroblast migration and expression of COL1A1 and α-SMA in keloid tissue.\",\n      \"method\": \"m6A dot blotting; MeRIP-qPCR; RT-PCR; Western blot; transwell migration assay; FTO overexpression in keloid fibroblasts\",\n      \"journal\": \"Annals of translational medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — post-translational (m6A) modification mechanism with MeRIP-qPCR validation, single lab\",\n      \"pmids\": [\"36760238\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"COL1A1 does not undergo feedback regulation at the mRNA level when fibroblasts are plated on a fibroblast-derived ECM; excess COL1A1 polypeptide chains produced (due to the absence of COL1A2 downregulation) are degraded by the combined action of MMP-1, MMP-2, MMP-9, and cathepsins, revealing protease-mediated post-translational regulation of COL1A1 protein levels.\",\n      \"method\": \"Fibroblast culture on plastic vs. fd-ECM; RT-PCR; western blot; zymographic analysis; MMP and TGF-β inhibitor assays\",\n      \"journal\": \"Life sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — multiple inhibitor assays and molecular readouts, single lab, mechanistic insight into proteolytic regulation\",\n      \"pmids\": [\"24637022\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"RUNX2 transcription factor promotes gastric cancer metastasis by transcriptionally upregulating COL1A1; COL1A1 knockdown abolishes the increase in cell invasion/migration promoted by RUNX2 overexpression both in vitro and in vivo (lung metastasis model), placing COL1A1 downstream of RUNX2 in a metastasis-regulatory axis.\",\n      \"method\": \"RUNX2 overexpression and COL1A1 siRNA knockdown; migration/invasion assays; in vivo lung metastasis xenograft model; RT-PCR and western blot; immunofluorescence\",\n      \"journal\": \"Cancer biomarkers\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — epistasis-style rescue with in vivo validation, single lab\",\n      \"pmids\": [\"33896817\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"CXCL9 (but not CXCL10) directly induces Col1a1 mRNA expression in mouse fibroblasts via its receptor CXCR3; Cxcl9- and Cxcr3-deficient mice fail to develop bleomycin-induced dermal fibrosis, establishing that the CXCL9-CXCR3 chemokine axis mechanistically drives Col1a1 upregulation and skin fibrosis.\",\n      \"method\": \"Bleomycin mouse fibrosis model; Cxcl9/Cxcl10/Cxcr3 knockout mice; REX3 reporter mice for in vivo cytokine source identification; recombinant CXCL9 addition to cultured fibroblasts with Col1a1 mRNA quantification\",\n      \"journal\": \"The Journal of investigative dermatology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — knockout epistasis with direct ligand-receptor pairing and in vitro mechanistic confirmation of Col1a1 induction\",\n      \"pmids\": [\"36708947\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"The 3.2 kb Col1a1 promoter drives expression specifically in committed osteoblasts (innermost periosteal layer), which lack chondrogenic potential, while the Prx1 promoter targets osteochondroprogenitor cells; these two promoters mark distinct, non-overlapping bone cell populations.\",\n      \"method\": \"Transgenic Col1a1CreER-DsRed and Prx1CreER-GFP mice; histological analysis; flow cytometry; chondrogenic and osteogenic differentiation assays\",\n      \"journal\": \"Bone\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo transgenic lineage tracing with functional differentiation assays, clear mechanistic dissection of promoter activity\",\n      \"pmids\": [\"24513582\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Col1a1 knockdown in mouse spermatogonia suppresses self-renewal markers (Oct4, Plzf) and promotes differentiation markers (c-kit, haprin), arrests cells in S phase, and impairs spermatogonia self-renewal in vivo (testes electroporation), establishing a role for Col1a1 in maintaining spermatogonial stem cell identity.\",\n      \"method\": \"siRNA knockdown; RT-PCR and western blot; flow cytometry cell cycle analysis; in vivo testes DNA injection and electroporation\",\n      \"journal\": \"Asian journal of andrology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — loss-of-function with defined molecular markers in vitro and in vivo, single lab\",\n      \"pmids\": [\"23064687\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"MMP2 promotes COL1A1 upregulation in cholangiocarcinoma cells via the integrin αV pathway, enhancing ECM remodelling and inducing EMT; COL1A1 in turn increases PD-L1 expression by activating the NF-κB pathway.\",\n      \"method\": \"Western blot; immunofluorescence; COL1A1 overexpression and knockdown; in vitro migration/invasion assays; in vivo xenograft; pathway inhibitor assays for integrin αV and NF-κB\",\n      \"journal\": \"Annals of hepatology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — pathway placement via pharmacological inhibition and KD/OE, mechanistic chain MMP2→integrin αV→COL1A1→NF-κB→PD-L1 established, single lab\",\n      \"pmids\": [\"38123132\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1988,\n      \"finding\": \"The complete nucleotide sequence of the first 7618 bp of the human COL1A1 gene was determined, comprising 25 exons encoding the N-terminal pre-propeptide and five cyanogen-bromide-derived peptides; the conceptual amino acid translation shows 95% homology to rat α1(I) chain, establishing the gene's exon-intron organization.\",\n      \"method\": \"DNA sequencing of genomic COL1A1; restriction mapping; conceptual translation and homology comparison\",\n      \"journal\": \"Gene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — foundational structural genomics of the gene, single study but high-quality sequencing\",\n      \"pmids\": [\"2843432\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"COL1A1 encodes the α1 chain of type I collagen, a secreted extracellular matrix protein whose expression is regulated at multiple levels: transcriptionally by promoter-bound factors including YY1 (positive regulator), RFX1/RFX5-CIITA complexes (repressors, modulated by DNA methylation), Osterix/Nmp4 complexes (regulated by promoter haplotype), RUNX2, and CXCL9-CXCR3 signaling; post-transcriptionally by nuclear mRNA retention when splicing is defective; and post-translationally by protease-mediated degradation (MMP-1/2/9, cathepsins) and m6A demethylation (FTO) that stabilizes its mRNA. COL1A1 protein promotes cell migration and invasion by binding integrin β1 to activate AKT, and participates in WNT/PCP and NF-κB pathways; its chromosomal fusion with PDGFB in DFSP produces a chimeric protein that is processed into mature PDGFB, driving autocrine/paracrine tumor growth through PDGFB receptor activation.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"COL1A1 encodes the pro-α1 chain of type I collagen, the principal structural protein of bone, skin, and connective tissues, whose production is regulated at transcriptional, post-transcriptional, and post-translational levels. Constitutive transcription requires YY1 binding near the TATA box and is modulated by Osterix/Nmp4 at upstream regulatory polymorphisms, while IFN-γ-induced RFX5/CIITA complexes and methylation-sensitive RFX1 repress the promoter; CXCL9/CXCR3 signaling and FTO-mediated m6A demethylation further upregulate COL1A1 mRNA levels in fibrotic and keloid contexts [PMID:11514536, PMID:15788405, PMID:19429913, PMID:36708947, PMID:36760238]. Pre-mRNA is co-transcriptionally spliced within SC35 nuclear domains, and transcripts from null or splice-defective alleles are retained in the nucleus rather than exported, providing the molecular basis for haploinsufficiency in mild osteogenesis imperfecta, while glycine-to-bulky-residue substitutions in the Gly-X-Y helical repeat cause lethal forms by disrupting triple-helix assembly [PMID:10931857, PMID:8613526, PMID:2777764]. Extracellularly, COL1A1 signals through integrin β1 and αV receptors to activate PI3K/AKT and NF-κB pathways, promotes cell migration via WNT/PCP effectors, and organizes mesenchymal tumor architecture including glioma oncostreams; the COL1A1–PDGFB fusion arising from t(17;22) in dermatofibrosarcoma protuberans is processed into mature PDGFB dimers that drive autocrine/paracrine receptor activation [PMID:32589888, PMID:38123132, PMID:29393423, PMID:35750880, PMID:11420709].\",\n  \"teleology\": [\n    {\n      \"year\": 1989,\n      \"claim\": \"Identifying the molecular basis of lethal osteogenesis imperfecta: heterozygous glycine substitutions in the Gly-X-Y helical repeat of COL1A1 disrupt triple-helix formation, establishing the genotype-phenotype relationship for dominant-negative OI mutations.\",\n      \"evidence\": \"Chemical mismatch cleavage and sequencing of mRNA/cDNA heteroduplexes from multiple OI patients\",\n      \"pmids\": [\"2777764\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No direct biophysical measurement of helix stability for each substitution\", \"Position-dependent severity gradient along the helix not systematically mapped\"]\n    },\n    {\n      \"year\": 1995,\n      \"claim\": \"Defining minimal cis-regulatory requirements: only 476 bp of the COL1A1 promoter is sufficient for tissue-specific expression in transgenic mice, showing that intronic and 3′-UTR elements are dispensable for basic tissue specificity.\",\n      \"evidence\": \"Transgenic mice carrying mini-COL1A1 and hybrid COL1A1/COL2A1 genes with mRNA and protein analysis\",\n      \"pmids\": [\"7721894\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Bone microenvironment-dependent upstream enhancer (~-2296 to -1672) activity not captured by this minimal promoter\", \"Chromatin context effects in transgenic insertion sites not controlled\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Solving the mechanism of haploinsufficiency in mild OI: null-allele COL1A1 transcripts are retained in the nucleus and excluded from the cytoplasm, whereas missense transcripts are exported normally, explaining why null mutations cause mild rather than lethal disease.\",\n      \"evidence\": \"Nuclear/cytoplasmic fractionation and RT-PCR/SSCP across multiple patient fibroblast lines\",\n      \"pmids\": [\"8613526\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the nuclear surveillance factor responsible for retention unknown\", \"Whether this mechanism operates in non-fibroblast cell types not tested\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Localizing the nuclear retention mechanism: COL1A1 pre-mRNA is co-transcriptionally spliced within SC35 nuclear speckle domains, and splice-defective transcripts initiate transport but are trapped within the speckle, pinpointing the compartment of quality control.\",\n      \"evidence\": \"RNA FISH and microfluorimetric track imaging in patient fibroblasts\",\n      \"pmids\": [\"10931857\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular identity of retention factors within SC35 domains not determined\", \"Whether retained transcripts are eventually degraded or stably sequestered not resolved\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Identifying key transcriptional regulators: YY1 binds two sites near the TATA box and is required for constitutive COL1A1 transcription, while the COL1A1-PDGFB fusion protein from dermatofibrosarcoma protuberans is processed into mitogenic PDGFB dimers, establishing both normal transcriptional control and a disease-linked gain-of-function mechanism.\",\n      \"evidence\": \"EMSA with recombinant YY1, antisense YY1, reporter mutagenesis (transcription); stable transfection, anti-PDGFB antibodies, mutagenesis, nude mouse assay (fusion protein)\",\n      \"pmids\": [\"11514536\", \"11420709\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether YY1 interacts with tissue-specific cofactors to confer cell-type selectivity unknown\", \"In vivo processing site of COL1A1-PDGFB fusion not mapped\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Establishing interferon-γ-mediated repression: RFX1 binds with higher affinity to the methylated COL1A1 promoter, and the RFX5/CIITA complex represses both COL1A1 and COL1A2 in response to IFN-γ, linking immune signaling to coordinated collagen silencing.\",\n      \"evidence\": \"EMSA, transient transfection luciferase reporters, RNAi, 5-aza-dC demethylation treatment\",\n      \"pmids\": [\"15788405\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether RFX-mediated repression operates in vivo during inflammation or fibrosis resolution not tested\", \"Chromatin-level mechanism (histone marks) not examined\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Connecting genetic variation to bone density: the -1663delT polymorphism increases Osterix/Nmp4 binding affinity and RNA Pol II recruitment, driving ~2-fold higher COL1A1 transcription that correlates with reduced BMD, providing a mechanistic link between regulatory SNPs and osteoporosis risk.\",\n      \"evidence\": \"ChIP, EMSA, luciferase reporter, population BMD analysis\",\n      \"pmids\": [\"19429913\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Causal relationship between elevated COL1A1 and reduced BMD not formally demonstrated by genetic rescue\", \"Interaction with other osteoporosis risk loci not explored\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Defining post-translational fate of excess α1 chains: unincorporated COL1A1 polypeptides are degraded by MMP-1, -2, -9 and cathepsins, with no feedback on COL1A1 mRNA levels, distinguishing protein-level quality control from transcriptional autoregulation.\",\n      \"evidence\": \"Pharmacological MMP and cathepsin inhibitor assays, zymography, real-time PCR in fibroblast-derived ECM cultures\",\n      \"pmids\": [\"24637022\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"ER-associated degradation contribution not assessed\", \"Whether the same proteases operate in vivo in bone not confirmed\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Placing extracellular COL1A1 in signaling cascades: COL1A1 knockdown reduces Rac1-GTP, p-JNK, and RhoA-GTP in colorectal cancer cells, implicating COL1A1 as an upstream activator of the WNT/PCP pathway to promote migration.\",\n      \"evidence\": \"siRNA knockdown, GTPase activity assays, transwell migration, Western blot\",\n      \"pmids\": [\"29393423\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct receptor through which COL1A1 activates WNT/PCP not identified in this study\", \"Autocrine vs. paracrine signaling mode not distinguished\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identifying the COL1A1 receptor for pro-tumorigenic signaling: fibroblast-secreted COL1A1 binds integrin β1 (ITGB1) on ovarian cancer cells and activates AKT phosphorylation to promote migration and invasion; ITGB1 blockade reverses these effects.\",\n      \"evidence\": \"COL1A1 antibody blocking, ITGB1 knockdown/antibody blockade, intraperitoneal xenograft, p-AKT Western blot\",\n      \"pmids\": [\"32589888\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether other integrin heterodimer partners contribute not fully resolved\", \"Downstream AKT substrate specificity in this context unknown\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Demonstrating COL1A1 as an organizer of tumor mesenchymal architecture: COL1A1 overexpression drives formation of dynamic oncostream fascicles in glioma, and its inhibition eliminates oncostreams, reprograms the malignant phenotype, and extends survival.\",\n      \"evidence\": \"Spatiotemporal transcriptomics, intravital imaging, ex vivo explants, Col1a1 knockdown in genetically engineered mouse glioma models\",\n      \"pmids\": [\"35750880\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular mechanism by which COL1A1 nucleates fascicle formation not dissected\", \"Whether this architectural role generalizes to non-CNS tumors not tested\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Expanding upstream signals: CXCL9/CXCR3 signaling directly induces Col1a1 mRNA in fibroblasts and is required for bleomycin-induced dermal fibrosis; separately, FTO-mediated m6A demethylation stabilizes COL1A1 mRNA in keloid fibroblasts, and MMP2 induces COL1A1 via integrin αV to activate NF-κB and PD-L1 in cholangiocarcinoma.\",\n      \"evidence\": \"CXCL9 treatment/CXCR3 KO mice/bleomycin model; MeRIP-qPCR/FTO overexpression/mRNA stability assay; MMP2 manipulation/NF-κB analysis/xenograft\",\n      \"pmids\": [\"36708947\", \"36760238\", \"38123132\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Transcription factor downstream of CXCR3 that directly binds COL1A1 promoter not identified\", \"Specific m6A site on COL1A1 mRNA responsible for stabilization not mapped at nucleotide resolution\", \"NF-κB activation mechanism by COL1A1 (direct vs. indirect) not resolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The nuclear surveillance machinery that retains defective COL1A1 transcripts in SC35 domains remains molecularly unidentified, the structural basis for position-dependent severity of glycine substitutions along the triple helix is incompletely understood, and the receptor complexes and downstream signaling cascades through which extracellular COL1A1 modulates tumor architecture and immune evasion require further mechanistic dissection.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Identity of nuclear retention factors for aberrant COL1A1 mRNA unknown\", \"No comprehensive structure-function map relating glycine substitution position to clinical severity\", \"Integrin heterodimer specificity for COL1A1 signaling in different tumor types not systematically compared\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [3, 10, 19]},\n      {\"term_id\": \"GO:0098631\", \"supporting_discovery_ids\": [9, 16]},\n      {\"term_id\": \"GO:0048018\", \"supporting_discovery_ids\": [9, 14, 16]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [9, 10, 16, 19]},\n      {\"term_id\": \"GO:0031012\", \"supporting_discovery_ids\": [9, 10, 19]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [1, 2]},\n      {\"term_id\": \"GO:0005654\", \"supporting_discovery_ids\": [1, 2]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1474244\", \"supporting_discovery_ids\": [3, 9, 10, 19]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [9, 14, 15, 16]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [4, 5, 6]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [1, 2, 19]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [0, 3]}\n    ],\n    \"complexes\": [\n      \"type I collagen heterotrimer (α1₂α2₁)\"\n    ],\n    \"partners\": [\n      \"COL1A2\",\n      \"YY1\",\n      \"RFX5\",\n      \"CIITA\",\n      \"ITGB1\",\n      \"PDGFB\",\n      \"RUNX2\",\n      \"FTO\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\n```json\n{\n  \"mechanistic_narrative\": \"COL1A1 encodes the α1 chain of type I collagen, the principal structural protein of bone, skin, tendon, and other connective tissues, whose Gly-X-Y triple-helical domain is essential for proper helix assembly and extracellular matrix integrity. Transcription of COL1A1 is driven by a compact proximal promoter (~476 bp) sufficient for tissue-specific expression and is positively regulated by YY1 binding adjacent to the TATA box, modulated by promoter haplotype-dependent recruitment of Osterix/Nmp4, and repressed by RFX1 (methylation-enhanced) and the RFX5–CIITA complex; upstream signals including CXCL9–CXCR3 and RUNX2 converge on COL1A1 transcription to drive fibrosis and tumor invasion [PMID:11514536, PMID:15788405, PMID:19429913, PMID:36708947, PMID:33896817]. Defective splicing causes nuclear retention of COL1A1 mRNA at SC-35 domains, producing haploinsufficiency that underlies mild osteogenesis imperfecta, while glycine substitutions in the helical domain cause lethal perinatal osteogenesis imperfecta [PMID:8613526, PMID:10931857, PMID:2777764]. The chromosomal translocation t(17;22) fuses COL1A1 with PDGFB, generating a chimeric protein processed into mature PDGFB that drives autocrine growth in dermatofibrosarcoma protuberans; independently, secreted COL1A1 signals through integrin β1–AKT and WNT/PCP pathways to promote cancer cell migration and invasion [PMID:8988177, PMID:11420709, PMID:32589888, PMID:29393423].\",\n  \"teleology\": [\n    {\n      \"year\": 1988,\n      \"claim\": \"Determination of the exon–intron organization of the human COL1A1 gene established the structural framework—including the Gly-X-Y repeat-encoding exons—needed to interpret subsequent disease mutations.\",\n      \"evidence\": \"Genomic DNA sequencing and restriction mapping of 7.6 kb of human COL1A1\",\n      \"pmids\": [\"2843432\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Only the 5' portion of the gene was sequenced\", \"No functional data on regulatory elements were provided\"]\n    },\n    {\n      \"year\": 1989,\n      \"claim\": \"Identification of glycine-to-bulky-residue substitutions in the helical domain as the cause of lethal perinatal osteogenesis imperfecta demonstrated that the Gly-X-Y repeat is indispensable for collagen triple-helix assembly.\",\n      \"evidence\": \"Chemical mismatch cleavage and sequencing of COL1A1 mRNA from OI patients with multiple independent Gly substitutions\",\n      \"pmids\": [\"2777764\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No structural or biophysical characterization of helix disruption\", \"Position-dependent severity gradient not yet mapped\"]\n    },\n    {\n      \"year\": 1993,\n      \"claim\": \"Transgenic promoter-deletion studies revealed that a distal 624-bp element (−2296 to −1672) is active in intact bone but silenced when cells lose matrix contact, establishing that COL1A1 transcription is coupled to the extracellular matrix microenvironment.\",\n      \"evidence\": \"COL1A1-CAT transgenic mice comparing intact calvariae to isolated primary bone cells\",\n      \"pmids\": [\"8355676\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Trans-acting factors binding this distal element were not identified\", \"Signaling pathway linking matrix contact to element activity was unknown\"]\n    },\n    {\n      \"year\": 1995,\n      \"claim\": \"Demonstration that only 476 bp of the COL1A1 promoter is sufficient for tissue-specific expression in transgenic mice showed that core regulatory information is compactly organized and does not require the first intron or most of the 3'-UTR.\",\n      \"evidence\": \"Transgenic mice with mini-COL1A1 and hybrid COL1A1/COL2A1 constructs; mRNA and protein assays across tissues\",\n      \"pmids\": [\"7721894\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Individual cis elements within the 476-bp region were not mapped\", \"Quantitative expression levels vs. endogenous gene were not compared\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Discovery that premature stop and splice-donor mutations cause nuclear retention of COL1A1 mRNA—rather than nonsense-mediated decay—established nuclear mRNA surveillance as the mechanism underlying haploinsufficiency in mild OI type I.\",\n      \"evidence\": \"RT-PCR on nuclear vs. cytoplasmic RNA fractions from OI patient fibroblasts\",\n      \"pmids\": [\"8613526\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The nuclear retention machinery was not identified\", \"Whether transcript degradation eventually occurs in the nucleus was unresolved\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Identification of the t(17;22) COL1A1–PDGFB fusion in DFSP revealed that a structural collagen gene can be co-opted as an oncogenic driver by providing a constitutive promoter for an otherwise tightly regulated growth factor.\",\n      \"evidence\": \"Southern blot, RT-PCR, and breakpoint mapping in multiple DFSP and giant-cell fibroblastoma specimens\",\n      \"pmids\": [\"8988177\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether the chimeric protein is processed to mature PDGFB was not yet shown\", \"The range of COL1A1 exon breakpoints across tumors was incompletely catalogued\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Visualization of COL1A1 RNA trafficking showed that normal transcripts transit through SC-35 splicing-factor domains en route to export, while splice-defective transcripts stall at this step, pinpointing the nuclear compartment responsible for the retention seen in OI.\",\n      \"evidence\": \"RNA FISH with microfluorimetric quantification in patient fibroblasts comparing normal and splice-mutant alleles\",\n      \"pmids\": [\"10931857\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Factors mediating SC-35 domain exit were not identified\", \"Whether this quality-control step is COL1A1-specific or general was unknown\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Two parallel advances defined COL1A1 transcriptional activation and oncogenic function: YY1 was shown to be an essential positive regulator binding two sites flanking the TATA box, and the COL1A1–PDGFB fusion protein was demonstrated to be processed into active PDGFB dimers that confer growth-factor independence and tumorigenicity.\",\n      \"evidence\": \"EMSA/supershift with purified YY1, promoter mutagenesis, and gain/loss-of-function transfections (YY1); stable transfections, nude mouse tumorigenicity, and mutagenesis of PDGFB cleavage site (fusion protein)\",\n      \"pmids\": [\"11514536\", \"11420709\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether YY1 is modulated by signaling pathways at the COL1A1 promoter was untested\", \"Contributions of uncleaved vs. cleaved fusion forms in patient tumors were not quantified\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Identification of RFX1 as a methylation-enhanced repressor and RFX5–CIITA as an IFN-γ-induced repressor of COL1A1 transcription explained how promoter DNA methylation and immune signaling silence collagen expression in cancer cells.\",\n      \"evidence\": \"Gel shift with methylated/unmethylated probes; RFX5 dominant-negative and CIITA RNAi; aza-dC treatment of cancer cells\",\n      \"pmids\": [\"15788405\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo ChIP confirmation of RFX1 binding at the methylated COL1A1 promoter was not performed\", \"Relationship between RFX repression and fibrosis pathologies was unexplored\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"The discovery that a three-SNP haplotype in the COL1A1 5'-flank controls differential Osterix/Nmp4 recruitment and transcriptional output linked common genetic variation to osteoporosis risk through a defined transcription-factor mechanism.\",\n      \"evidence\": \"Reporter assays, EMSA, ChIP for Osterix/Nmp4/RNA Pol II, and BMD association in 3270 women\",\n      \"pmids\": [\"19429913\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional contribution of each individual SNP was not fully dissected\", \"Whether this haplotype affects fibrosis or tumor contexts was unknown\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Col1a1 knockdown in spermatogonia impaired self-renewal markers and promoted differentiation, revealing an unexpected role for type I collagen in maintaining spermatogonial stem cell identity beyond its classical structural function.\",\n      \"evidence\": \"siRNA knockdown with marker profiling in vitro and in vivo testes electroporation in mice\",\n      \"pmids\": [\"23064687\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether COL1A1 signals through integrins in this context was not tested\", \"Not independently replicated\", \"Mechanism linking ECM to Oct4/Plzf expression was undefined\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Demonstration that excess COL1A1 polypeptide is degraded by MMP-1/2/9 and cathepsins when fibroblasts contact their own ECM established protease-mediated post-translational homeostasis as a layer of COL1A1 regulation independent of mRNA feedback.\",\n      \"evidence\": \"Fibroblast culture on plastic vs. fibroblast-derived ECM with zymography and MMP/TGF-β inhibitor assays\",\n      \"pmids\": [\"24637022\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Specific protease cleavage sites on COL1A1 were not mapped\", \"In vivo relevance of this homeostatic loop was not confirmed\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Identification of miR-129-5p as a direct post-transcriptional repressor of COL1A1 via its 3'-UTR provided the first microRNA–COL1A1 axis with functional rescue evidence in a cancer context.\",\n      \"evidence\": \"Dual-luciferase 3'-UTR reporter; miR-129-5p mimic/inhibitor with COL1A1 rescue in gastric cancer cells\",\n      \"pmids\": [\"28482162\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"In vivo validation of miR-129-5p regulation of COL1A1 was lacking\", \"Single lab finding\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"COL1A1 knockdown reduced Rac1-GTP, phospho-JNK, and RhoA-GTP in colorectal cancer cells, placing COL1A1 upstream of WNT/planar cell polarity signaling as a migration driver.\",\n      \"evidence\": \"siRNA knockdown with western blot for WNT/PCP effectors and Transwell migration assays\",\n      \"pmids\": [\"29393423\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No epistasis with WNT/PCP pathway components was tested\", \"Receptor mediating COL1A1 signal to PCP was not identified\", \"Single lab\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Secreted COL1A1 was shown to bind integrin β1 (ITGB1) and activate AKT phosphorylation to promote ovarian cancer invasion, defining the first receptor–signaling axis for paracrine COL1A1 pro-metastatic activity.\",\n      \"evidence\": \"siRNA/antibody blockade of COL1A1 and ITGB1 with p-AKT readout; in vivo xenograft peritoneal metastasis model\",\n      \"pmids\": [\"32589888\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct COL1A1–ITGB1 binding was not reconstituted with purified proteins\", \"Contribution of other integrin α-subunit partners was not assessed\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"RUNX2 was placed upstream of COL1A1 in a gastric cancer metastasis axis: COL1A1 knockdown fully abolished RUNX2-driven invasion, demonstrating that COL1A1 is a necessary effector of RUNX2 transcriptional pro-metastatic activity.\",\n      \"evidence\": \"RUNX2 overexpression with COL1A1 siRNA rescue; in vivo lung metastasis xenograft\",\n      \"pmids\": [\"33896817\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct RUNX2 binding to the COL1A1 promoter was not shown by ChIP\", \"Single cancer type tested\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Col1a1 was identified as the central structural organizer of glioma oncostreams; its inhibition eliminated these dynamic mesenchymal structures, reprogrammed the tumor microenvironment, and extended survival, establishing COL1A1 as a functional driver of mesenchymal tumor architecture.\",\n      \"evidence\": \"Spatial transcriptomics, intravital imaging, genetically engineered mouse glioma models, and Col1a1 shRNA with survival analysis\",\n      \"pmids\": [\"35750880\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether COL1A1 acts cell-autonomously or via ECM signaling to organize oncostreams was not dissected\", \"Human glioma validation was correlative\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Two new regulatory inputs to COL1A1 were defined: the CXCL9–CXCR3 chemokine axis was shown to directly induce Col1a1 in fibroblasts and drive dermal fibrosis in knockout mice, and the m6A demethylase FTO was shown to stabilize COL1A1 mRNA by removing m6A marks, promoting keloid fibrosis.\",\n      \"evidence\": \"Cxcl9/Cxcr3 knockout mice with bleomycin fibrosis and recombinant CXCL9 in vitro (CXCL9); MeRIP-qPCR and FTO overexpression in keloid fibroblasts (FTO)\",\n      \"pmids\": [\"36708947\", \"36760238\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Downstream signaling from CXCR3 to COL1A1 promoter elements is undefined\", \"FTO–COL1A1 axis awaits in vivo validation\", \"Interplay between m6A regulation and transcriptional control of COL1A1 is unexplored\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"COL1A1 was placed in an MMP2–integrin αV–COL1A1–NF-κB–PD-L1 signaling chain in cholangiocarcinoma, linking collagen remodeling to immune evasion.\",\n      \"evidence\": \"COL1A1 overexpression/knockdown with pathway inhibitors for integrin αV and NF-κB; xenograft validation\",\n      \"pmids\": [\"38123132\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Each step in the signaling chain was tested pharmacologically without genetic epistasis\", \"Whether COL1A1 directly binds integrin αV was not shown\", \"Single lab, single cancer type\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Major open questions include: the structural basis of COL1A1's signaling through specific integrin heterodimers; how the multiple transcriptional, post-transcriptional (miRNA, m6A), and proteolytic regulatory layers are integrated in vivo; and whether COL1A1's non-structural signaling roles in stem cell maintenance and tumor architecture are mediated by the same integrin-dependent mechanisms identified in cancer invasion.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No high-resolution structure of COL1A1–integrin complex exists\", \"Systems-level integration of regulatory inputs has not been modeled\", \"Non-structural roles lack receptor-level mechanistic resolution\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [9, 13]},\n      {\"term_id\": \"GO:0098631\", \"supporting_discovery_ids\": [10, 12]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0031012\", \"supporting_discovery_ids\": [7, 9, 13, 15]},\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [10, 15]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [2, 3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1474244\", \"supporting_discovery_ids\": [9, 13, 15]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [10, 12, 20]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"COL1A2\",\n      \"ITGB1\",\n      \"YY1\",\n      \"PDGFB\",\n      \"RFX1\",\n      \"RUNX2\",\n      \"FTO\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}