{"gene":"CHRD","run_date":"2026-04-28T17:28:52","timeline":{"discoveries":[{"year":1998,"finding":"Mouse chordin (Chrd) encodes a secreted protein that dorsalizes early vertebrate embryonic tissues by binding to ventralizing TGF-β-like bone morphogenetic proteins and sequestering them in latent complexes; Chrd is expressed at high levels in 7-day post-coitum mouse embryos and at lower levels in adult tissues including liver and cerebellum.","method":"RNA blot analysis, cDNA sequencing, radiation hybrid mapping","journal":"Genomics","confidence":"High","confidence_rationale":"Tier 2 — direct characterization of mammalian chordin cDNA and expression; foundational paper replicated across species","pmids":["9782094"],"is_preprint":false},{"year":2001,"finding":"Human CHRD encodes alternatively spliced C-truncated variants that can antagonize BMP activity in a Xenopus axis-duplication assay, demonstrating that alternative splicing generates sub-products capable of influencing BMP activity in addition to metalloprotease-mediated cleavage.","method":"cDNA cloning, Xenopus axis-duplication functional assay","journal":"Mechanisms of development","confidence":"High","confidence_rationale":"Tier 1 — functional in vivo assay (Xenopus axis duplication) directly demonstrates BMP-antagonist activity of splice variants","pmids":["11472837"],"is_preprint":false},{"year":2002,"finding":"Chordin and Noggin function as dedicated BMP antagonists in the mouse organizer (node) and its mesendodermal derivatives; loss of Chrd in combination with reduced Nog causes loss of SHH and FGF8 expression at rostral organizing centers due to elevated BMP activity, demonstrating that CHRD promotes inductive activities of rostral organizing centers by limiting BMP signaling.","method":"Chrd/Nog compound mutant mouse analysis, in situ hybridization, ectopic BMP2 application to cephalic explants","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 2 — genetic loss-of-function with defined molecular phenotypes and rescue experiments in multiple mutant contexts","pmids":["12397106"],"is_preprint":false},{"year":2006,"finding":"Chordin and Noggin function as BMP antagonists in vivo to promote mammalian neural crest development; reduced BMP antagonism expands the early neural crest domain, perturbs neural crest cell emigration, and increases apoptosis in neural crest cells, placing Chordin upstream of BMP signaling in neural crest generation and survival.","method":"Chrd/Nog single and compound mutant mouse analysis, immunostaining for BMP signaling, apoptosis assays","journal":"Developmental dynamics","confidence":"High","confidence_rationale":"Tier 2 — clean genetic loss-of-function with defined molecular and cellular phenotypes, replicated across multiple mutant combinations","pmids":["16894609"],"is_preprint":false},{"year":2006,"finding":"CHRD (chordin) is underexpressed in ovarian epithelial cancer cell lines compared to normal OSE; ectopic expression of CHRD in cancer cell lines (BG1, PEO14) reduces migratory and invasive properties and enhances cell adhesion, consistent with CHRD regulating BMP activity in normal OSE physiology.","method":"RT-PCR expression analysis, wound-healing/invasion assays, cell adhesion assays in cancer cell lines","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 3 — single lab, functional overexpression assay without full pathway placement","pmids":["16449796"],"is_preprint":false},{"year":2008,"finding":"Chordin and Noggin (BMP antagonists) are expressed at higher levels in the left lateral plate mesoderm (LPM) and limit BMP signaling there; in Chrd;Nog double mutants, BMP signaling is elevated bilaterally and Nodal expression is absent; ectopic Nog in the left LPM of double mutants restores Nodal expression, demonstrating that CHRD functions in the left LPM to derepress Nodal transcription for left-right axis establishment.","method":"Chrd/Nog compound mutant mouse analysis, in situ hybridization, ectopic gene expression via electroporation","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis with multiple orthogonal methods including rescue experiment","pmids":["18550712"],"is_preprint":false},{"year":2007,"finding":"Genetic inactivation of mouse Chordin (Chrd-/-) results in neural crest defects that cause persistent truncus arteriosus and multiple venous patterning defects including absence of anterior cardinal vein segments, looping, and midline defects, establishing that BMP pathway activity regulated by CHRD is required for cephalic vascular patterning.","method":"Chrd-/- mouse analysis, resin injection/vascular casting in fixed transparent embryos","journal":"Developmental dynamics","confidence":"Medium","confidence_rationale":"Tier 2 — clean genetic KO with novel anatomical phenotype readout; single lab","pmids":["17685487"],"is_preprint":false},{"year":2017,"finding":"Ectopic Shh expression in the interdigital region of Hm mice upregulates Chrd, which antagonizes BMP signaling; Chrd-overexpressing transgenic mice recapitulate syndactyly with webbing, establishing CHRD as a downstream effector of Shh-mediated BMP antagonism in interdigital cell death.","method":"Transcriptome analysis of Hm mutant mice, generation and phenotyping of Chrd-overexpressing transgenic mice","journal":"PNAS","confidence":"High","confidence_rationale":"Tier 2 — transgenic overexpression directly recapitulates phenotype, mechanistic pathway placement via epistasis","pmids":["29255029"],"is_preprint":false},{"year":2021,"finding":"Smad2 and Smad3 directly bind to two activin response elements (ARE1 and ARE2) in the distal region of the chordin (chrd) promoter to regulate transcription; Smad2 acts on both ARE1 and ARE2 while Smad3 acts only on ARE2, demonstrating differential transcriptional regulation of chrd by TGFβ/activin signaling.","method":"Reporter gene assay, site-directed mutagenesis of chrd promoter, chromatin immunoprecipitation in Xenopus gastrula embryos","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 1 — direct binding confirmed by ChIP, functional validation by mutagenesis and reporter assays","pmids":["33945994"],"is_preprint":false},{"year":2021,"finding":"Foxd4l1.1 negatively regulates chrd transcription in two ways: by directly binding Foxd4l1.1 response elements (FRE) in the chrd promoter, and by physically interacting with Smad2/Smad3 to block their binding to activin response elements in the chrd promoter.","method":"Reporter gene assay, site-directed mutagenesis of chrd promoter FRE, ChIP-PCR, co-immunoprecipitation in Xenopus embryos","journal":"Cells","confidence":"High","confidence_rationale":"Tier 1 — dual mechanism validated by mutagenesis, ChIP, and co-IP; orthogonal methods in same study","pmids":["34685759"],"is_preprint":false},{"year":2023,"finding":"Goosecoid (Gsc) activates chrd transcription by binding Gsc response elements (GRE) adjacent to a TCF7/Wnt response element (WRE) in the chrd promoter; Ventx1.1 represses chrd transcription by binding a Ventx1.1 response element (VRE) in the same promoter region; both activities confirmed by ChIP-PCR and mutagenesis.","method":"Reporter gene assay, site-directed mutagenesis, ChIP-PCR in Xenopus gastrula embryos","journal":"Cells","confidence":"High","confidence_rationale":"Tier 1 — direct binding confirmed by ChIP, functional validation by mutagenesis with multiple cis-elements tested","pmids":["36980215"],"is_preprint":false},{"year":2023,"finding":"O-fucosylation of BMP1 by poFUT1 promotes BMP1 secretion and enhances its binding to CHRD in the extracellular matrix; the BMP1-CHRD interaction releases CHRD-bound BMP4, activating the BMP/Smad signaling pathway and accelerating endometrial stromal cell decidualization.","method":"Co-immunoprecipitation, ELISA, overexpression/knockdown in human endometrial stromal cells, BMP/Smad pathway readouts","journal":"Biology of reproduction","confidence":"Medium","confidence_rationale":"Tier 3 — binding interaction shown by Co-IP, functional consequence demonstrated; single lab","pmids":["37338142"],"is_preprint":false},{"year":2021,"finding":"TWSG1 (Twisted gastrulation 1) can enhance CHRD's antagonism of BMP2, BMP4, BMP7, and GDF5, demonstrating a synergistic functional interaction between TWSG1 and the chordin subfamily in modulating BMP signaling in the ovary.","method":"Bioactivity assays (BMP signaling inhibition), quantitative PCR expression profiling in rat/mouse/human ovaries","journal":"Molecular and cellular endocrinology","confidence":"Medium","confidence_rationale":"Tier 3 — functional bioactivity assay demonstrates synergy; single lab, no direct binding confirmed","pmids":["34517078"],"is_preprint":false},{"year":2019,"finding":"Among four BMP-binding proteins tested (gremlin, noggin, chordin, follistatin), chordin had no effect on BMP2-, BMP4-, BMP6-, or BMP7-induced suppression of androstenedione secretion by bovine theca cells, suggesting CHRD does not functionally antagonize these BMPs in the thecal steroidogenesis context despite being expressed there.","method":"Primary bovine theca cell culture, androstenedione secretion assay with recombinant proteins","journal":"Journal of molecular endocrinology","confidence":"Medium","confidence_rationale":"Tier 2 — direct functional assay with recombinant protein in primary cells; unexpected negative result contrasting with known CHRD BMP antagonism","pmids":["30400042"],"is_preprint":false}],"current_model":"CHRD (chordin) is a secreted BMP antagonist that binds BMP ligands (particularly BMP2, BMP4, BMP7) in the extracellular space to prevent receptor engagement; its transcription is directly activated by Smad2/3 (downstream of activin/TGFβ) and Goosecoid at defined promoter elements, and repressed by Foxd4l1.1 and Ventx1.1, while in vivo it functions in the gastrula organizer and lateral plate mesoderm to establish dorsoventral and left-right axes by limiting BMP signaling, and in neural crest, vascular, and limb development; BMP1 cleavage of CHRD releases bound BMP ligands to activate BMP signaling, and alternatively spliced truncated isoforms retain BMP-antagonist activity."},"narrative":{"teleology":[{"year":1998,"claim":"Establishing that mammalian chordin is a secreted dorsalizing factor that binds BMPs answered the fundamental question of whether the Xenopus/Drosophila-discovered BMP antagonist mechanism is conserved in mammals.","evidence":"cDNA cloning, RNA blot analysis, and radiation hybrid mapping of mouse Chrd","pmids":["9782094"],"confidence":"High","gaps":["Binding affinities for individual BMP ligands not quantified","No loss-of-function data in mammals yet"]},{"year":2001,"claim":"Demonstrating that alternatively spliced C-truncated CHRD variants retain BMP-antagonist activity revealed that post-transcriptional processing, not just BMP1-mediated cleavage, generates biologically active sub-products.","evidence":"cDNA cloning of human splice variants and Xenopus axis-duplication functional assay","pmids":["11472837"],"confidence":"High","gaps":["Relative abundance of splice variants in vivo unknown","Whether splice variants have distinct BMP-binding specificities untested"]},{"year":2002,"claim":"Compound Chrd/Nog mutant analysis established that CHRD and Noggin act redundantly in the mouse organizer to limit BMP signaling, which is required for SHH and FGF8 expression at rostral organizing centers — answering how BMP antagonism links to downstream patterning genes.","evidence":"Chrd/Nog compound mutant mouse embryos with in situ hybridization and ectopic BMP2 application","pmids":["12397106"],"confidence":"High","gaps":["Individual contributions of CHRD versus Noggin to each organizer function not fully resolved","Downstream transcriptional targets beyond SHH and FGF8 uncharacterized"]},{"year":2006,"claim":"Loss-of-function studies extended CHRD's developmental role beyond axial patterning to neural crest generation, emigration, and survival, and to cephalic vascular morphogenesis, showing that BMP antagonism by CHRD is required in multiple tissue contexts.","evidence":"Chrd single and Chrd/Nog compound mutant mice with immunostaining, apoptosis assays, and vascular casting","pmids":["16894609","17685487"],"confidence":"High","gaps":["Cell-autonomous versus non-autonomous requirement for CHRD in neural crest not distinguished","Molecular basis of vascular patterning defect beyond elevated BMP signaling unclear"]},{"year":2008,"claim":"Demonstrating that CHRD limits BMP signaling in the left lateral plate mesoderm to permit Nodal expression resolved how BMP antagonism feeds into left-right axis determination.","evidence":"Chrd/Nog double-mutant mice with in situ hybridization and electroporation rescue of Nog in left LPM","pmids":["18550712"],"confidence":"High","gaps":["Whether CHRD acts by direct BMP4/7 sequestration versus indirect signaling in LPM not resolved","How CHRD asymmetry in LPM is initially established is unknown"]},{"year":2017,"claim":"Placing CHRD as a downstream effector of Shh that antagonizes BMP signaling during interdigital cell death established a Shh→Chrd→BMP inhibition axis in limb morphogenesis.","evidence":"Transcriptome analysis of Hm mutant limbs and phenotypic recapitulation in Chrd-overexpressing transgenic mice","pmids":["29255029"],"confidence":"High","gaps":["Whether CHRD is the sole mediator of Shh-dependent BMP antagonism in limb unclear","Direct Shh-responsive cis-elements in Chrd promoter not identified"]},{"year":2021,"claim":"Identification of Smad2/3 binding to discrete activin response elements (ARE1, ARE2) in the chrd promoter answered how TGF-β/activin signaling directly activates CHRD transcription, with Smad2 and Smad3 showing differential element usage.","evidence":"ChIP, reporter assays, and site-directed mutagenesis of chrd promoter in Xenopus gastrula embryos","pmids":["33945994"],"confidence":"High","gaps":["Whether mammalian CHRD promoter has equivalent AREs not confirmed","Cofactors recruited by Smad2/3 to the chrd promoter unidentified"]},{"year":2021,"claim":"Foxd4l1.1 was shown to repress chrd both by direct promoter binding and by sequestering Smad2/3 away from AREs, revealing a dual-mechanism transcriptional repressor that links neuroectodermal specification to CHRD downregulation.","evidence":"ChIP-PCR, co-immunoprecipitation, reporter assays, and FRE mutagenesis in Xenopus embryos","pmids":["34685759"],"confidence":"High","gaps":["Whether Foxd4l1.1 homologs in mammals repress CHRD similarly untested","Stoichiometric relationship between Foxd4l1.1 and Smad2/3 not quantified"]},{"year":2021,"claim":"TWSG1 was shown to synergistically enhance CHRD antagonism of BMP2, BMP4, BMP7, and GDF5, expanding the functional BMP-binding repertoire of the CHRD system beyond its solo activity.","evidence":"BMP bioactivity assays with recombinant proteins and expression profiling in ovarian tissues","pmids":["34517078"],"confidence":"Medium","gaps":["Direct physical complex between TWSG1 and CHRD not confirmed","Physiological relevance of CHRD-TWSG1 synergy in non-ovarian tissues untested"]},{"year":2023,"claim":"Mapping of Goosecoid (GRE) and Ventx1.1 (VRE) response elements in the chrd promoter completed a cis-regulatory logic integrating organizer-specific activation and ventral repression of CHRD transcription.","evidence":"ChIP-PCR, reporter assays, and site-directed mutagenesis in Xenopus gastrula embryos","pmids":["36980215"],"confidence":"High","gaps":["Whether GRE and VRE are conserved in the mammalian CHRD promoter is unknown","How TCF7/Wnt signaling at the adjacent WRE integrates with Gsc activation not fully resolved"]},{"year":2023,"claim":"O-fucosylation of BMP1 by poFUT1 was shown to enhance BMP1 secretion and its binding to CHRD, releasing CHRD-bound BMP4 to activate Smad signaling in endometrial decidualization — extending the BMP1-CHRD axis to a new physiological context.","evidence":"Co-immunoprecipitation, ELISA, overexpression/knockdown in human endometrial stromal cells","pmids":["37338142"],"confidence":"Medium","gaps":["BMP1-CHRD binding stoichiometry and cleavage site usage in this context not defined","Whether other tolloid-family proteases substitute for BMP1 in the endometrium untested"]},{"year":null,"claim":"A structural model of the full-length CHRD-BMP complex, quantitative binding affinities for individual BMP ligands, and the in vivo relevance of individual CHRD splice variants remain unresolved.","evidence":"","pmids":[],"confidence":"High","gaps":["No crystal or cryo-EM structure of full-length CHRD bound to BMPs","Relative contributions of individual cysteine-rich domains to BMP specificity not mapped","Functional significance of each CHRD splice variant in mammalian tissues undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,1,2,3,5,7,12]},{"term_id":"GO:0140313","term_label":"molecular sequestering activity","supporting_discovery_ids":[0,1,5,12]}],"localization":[{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[0,1,11]},{"term_id":"GO:0031012","term_label":"extracellular matrix","supporting_discovery_ids":[11]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,2,5,7,11]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[2,3,5,6,7]}],"complexes":[],"partners":["BMP1","BMP2","BMP4","BMP7","NOG","TWSG1","SMAD2","SMAD3"],"other_free_text":[]},"mechanistic_narrative":"CHRD (chordin) is a secreted BMP antagonist that establishes tissue polarity during embryonic development by sequestering BMP ligands in latent extracellular complexes, thereby restricting BMP receptor activation across dorsoventral, left-right, and limb axes. CHRD binds BMP2, BMP4, and BMP7, and this antagonism is potentiated by TWSG1; BMP1 metalloprotease cleaves CHRD to release bound BMPs and restore signaling [PMID:9782094, PMID:37338142, PMID:34517078]. Genetic loss of Chrd, alone or with Nog, disrupts gastrula organizer function, neural crest development, cephalic vascular patterning, and left-right axis establishment by derepressing BMP signaling in the lateral plate mesoderm, where CHRD is required for Nodal transcription [PMID:12397106, PMID:16894609, PMID:17685487, PMID:18550712]. Transcription of chrd is directly activated by Smad2/3 at activin response elements and by Goosecoid at GRE sites in the promoter, and repressed by Foxd4l1.1 and Ventx1.1, integrating TGF-β/activin, Wnt, and ventral homeobox inputs into a tightly regulated BMP-antagonist output [PMID:33945994, PMID:34685759, PMID:36980215]."},"prefetch_data":{"uniprot":{"accession":"Q9H2X0","full_name":"Chordin","aliases":[],"length_aa":955,"mass_kda":102.0,"function":"Dorsalizing factor. Key developmental protein that dorsalizes early vertebrate embryonic tissues by binding to ventralizing TGF-beta family bone morphogenetic proteins (BMPs) and sequestering them in latent complexes (By similarity)","subcellular_location":"Secreted","url":"https://www.uniprot.org/uniprotkb/Q9H2X0/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CHRD","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/CHRD","total_profiled":1310},"omim":[{"mim_id":"619695","title":"RAUCH-STEINDL SYNDROME; RAUST","url":"https://www.omim.org/entry/619695"},{"mim_id":"618640","title":"ZINC FINGER CCCH DOMAIN-CONTAINING PROTEIN 3; ZC3H3","url":"https://www.omim.org/entry/618640"},{"mim_id":"613127","title":"CHORDIN-LIKE 2; CHRDL2","url":"https://www.omim.org/entry/613127"},{"mim_id":"603475","title":"CHORDIN; CHRD","url":"https://www.omim.org/entry/603475"},{"mim_id":"602054","title":"T-BOX TRANSCRIPTION FACTOR 1; TBX1","url":"https://www.omim.org/entry/602054"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"brain","ntpm":71.0},{"tissue":"liver","ntpm":124.3}],"url":"https://www.proteinatlas.org/search/CHRD"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"Q9H2X0","domains":[{"cath_id":"-","chopping":"170-400","consensus_level":"medium","plddt":86.9838,"start":170,"end":400},{"cath_id":"-","chopping":"406-646","consensus_level":"medium","plddt":86.2246,"start":406,"end":646},{"cath_id":"-","chopping":"712-741","consensus_level":"high","plddt":86.5973,"start":712,"end":741},{"cath_id":"-","chopping":"794-828","consensus_level":"medium","plddt":81.9409,"start":794,"end":828}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9H2X0","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9H2X0-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9H2X0-F1-predicted_aligned_error_v6.png","plddt_mean":73.5},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CHRD","jax_strain_url":"https://www.jax.org/strain/search?query=CHRD"},"sequence":{"accession":"Q9H2X0","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9H2X0.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9H2X0/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9H2X0"}},"corpus_meta":[{"pmid":"11566865","id":"PMC_11566865","title":"The organizer of the mouse gastrula is composed of a dynamic population of progenitor cells for the axial mesoderm.","date":"2001","source":"Development (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/11566865","citation_count":194,"is_preprint":false},{"pmid":"12397106","id":"PMC_12397106","title":"Chordin and noggin promote organizing centers of forebrain development in the mouse.","date":"2002","source":"Development (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/12397106","citation_count":157,"is_preprint":false},{"pmid":"19063703","id":"PMC_19063703","title":"PCSK9 as a therapeutic target of dyslipidemia.","date":"2009","source":"Expert opinion on therapeutic targets","url":"https://pubmed.ncbi.nlm.nih.gov/19063703","citation_count":112,"is_preprint":false},{"pmid":"27058611","id":"PMC_27058611","title":"De Novo and Rare Variants at Multiple Loci Support the Oligogenic Origins of Atrioventricular Septal Heart Defects.","date":"2016","source":"PLoS genetics","url":"https://pubmed.ncbi.nlm.nih.gov/27058611","citation_count":93,"is_preprint":false},{"pmid":"12805376","id":"PMC_12805376","title":"CRIM1 regulates the rate of processing and delivery of bone morphogenetic proteins to the cell surface.","date":"2003","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/12805376","citation_count":90,"is_preprint":false},{"pmid":"27848974","id":"PMC_27848974","title":"Differential expression of TGF-β superfamily members and role of Smad1/5/9-signalling in chondral versus endochondral chondrocyte differentiation.","date":"2016","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/27848974","citation_count":65,"is_preprint":false},{"pmid":"23105118","id":"PMC_23105118","title":"The M2 module of the Cys-His-rich domain (CHRD) of PCSK9 protein is needed for the extracellular low-density lipoprotein receptor (LDLR) degradation pathway.","date":"2012","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/23105118","citation_count":64,"is_preprint":false},{"pmid":"18550712","id":"PMC_18550712","title":"BMP antagonism is required in both the node and lateral plate mesoderm for mammalian left-right axis establishment.","date":"2008","source":"Development (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/18550712","citation_count":55,"is_preprint":false},{"pmid":"28316143","id":"PMC_28316143","title":"Endothelial microparticles act as novel diagnostic and therapeutic biomarkers of circulatory hypoxia-related diseases: a literature review.","date":"2017","source":"Journal of cellular and molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/28316143","citation_count":52,"is_preprint":false},{"pmid":"22387305","id":"PMC_22387305","title":"Microarray expression analysis of genes and pathways involved in growth plate cartilage injury responses and bony repair.","date":"2012","source":"Bone","url":"https://pubmed.ncbi.nlm.nih.gov/22387305","citation_count":50,"is_preprint":false},{"pmid":"16894609","id":"PMC_16894609","title":"Endogenous bone morphogenetic protein antagonists regulate mammalian neural crest generation and survival.","date":"2006","source":"Developmental dynamics : an official publication of the American Association of Anatomists","url":"https://pubmed.ncbi.nlm.nih.gov/16894609","citation_count":50,"is_preprint":false},{"pmid":"18434745","id":"PMC_18434745","title":"Altered transforming growth factor-beta signaling in a murine model of thoracic aortic aneurysm.","date":"2008","source":"Journal of vascular research","url":"https://pubmed.ncbi.nlm.nih.gov/18434745","citation_count":38,"is_preprint":false},{"pmid":"11291865","id":"PMC_11291865","title":"Defects of the body plan of mutant embryos lacking Lim1, Otx2 or Hnf3beta activity.","date":"2001","source":"The International journal of developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/11291865","citation_count":36,"is_preprint":false},{"pmid":"21791559","id":"PMC_21791559","title":"Identification and regulation of bone morphogenetic protein antagonists associated with preantral follicle development in the ovary.","date":"2011","source":"Endocrinology","url":"https://pubmed.ncbi.nlm.nih.gov/21791559","citation_count":35,"is_preprint":false},{"pmid":"16845531","id":"PMC_16845531","title":"CHRD, a plant member of the evolutionarily conserved YjgF family, influences photosynthesis and chromoplastogenesis.","date":"2006","source":"Planta","url":"https://pubmed.ncbi.nlm.nih.gov/16845531","citation_count":32,"is_preprint":false},{"pmid":"16449796","id":"PMC_16449796","title":"Chordin is underexpressed in ovarian tumors and reduces tumor cell motility.","date":"2006","source":"FASEB journal : official publication of the Federation of American Societies for Experimental Biology","url":"https://pubmed.ncbi.nlm.nih.gov/16449796","citation_count":31,"is_preprint":false},{"pmid":"20298438","id":"PMC_20298438","title":"Distinct functionalities of bone morphogenetic protein antagonists during fracture healing in mice.","date":"2010","source":"Journal of anatomy","url":"https://pubmed.ncbi.nlm.nih.gov/20298438","citation_count":30,"is_preprint":false},{"pmid":"9782094","id":"PMC_9782094","title":"Coding sequence and expression patterns of mouse chordin and mapping of the cognate mouse chrd and human CHRD genes.","date":"1998","source":"Genomics","url":"https://pubmed.ncbi.nlm.nih.gov/9782094","citation_count":29,"is_preprint":false},{"pmid":"35346191","id":"PMC_35346191","title":"Integrative analyses of biomarkers and pathways for heart failure.","date":"2022","source":"BMC medical genomics","url":"https://pubmed.ncbi.nlm.nih.gov/35346191","citation_count":29,"is_preprint":false},{"pmid":"27284008","id":"PMC_27284008","title":"Proprotein Convertase Subtilisin/Kexin Type 9 (PCSK9) Single Domain Antibodies Are Potent Inhibitors of Low Density Lipoprotein Receptor Degradation.","date":"2016","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/27284008","citation_count":29,"is_preprint":false},{"pmid":"27385727","id":"PMC_27385727","title":"BMP signalling in human fetal ovary somatic cells is modulated in a gene-specific fashion by GREM1 and GREM2.","date":"2016","source":"Molecular human reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/27385727","citation_count":28,"is_preprint":false},{"pmid":"35115727","id":"PMC_35115727","title":"The landscape of promoter-centred RNA-DNA interactions in rice.","date":"2022","source":"Nature plants","url":"https://pubmed.ncbi.nlm.nih.gov/35115727","citation_count":26,"is_preprint":false},{"pmid":"28256631","id":"PMC_28256631","title":"Spore surface proteins of Brevibacillus laterosporus are involved in insect pathogenesis.","date":"2017","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/28256631","citation_count":26,"is_preprint":false},{"pmid":"11472837","id":"PMC_11472837","title":"The human chordin gene encodes several differentially expressed spliced variants with distinct BMP opposing activities.","date":"2001","source":"Mechanisms of development","url":"https://pubmed.ncbi.nlm.nih.gov/11472837","citation_count":25,"is_preprint":false},{"pmid":"10607295","id":"PMC_10607295","title":"Molecular mechanisms underlying carotenogenesis in the chromoplast: multilevel regulation of carotenoid-associated genes.","date":"1999","source":"The Plant journal : for cell and molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/10607295","citation_count":25,"is_preprint":false},{"pmid":"34435185","id":"PMC_34435185","title":"BMP antagonists in tissue development and disease.","date":"2021","source":"Matrix biology plus","url":"https://pubmed.ncbi.nlm.nih.gov/34435185","citation_count":24,"is_preprint":false},{"pmid":"18573151","id":"PMC_18573151","title":"PerioGlas regulates osteoblast RNA interfering.","date":"2008","source":"Journal of prosthodontics : official journal of the American College of Prosthodontists","url":"https://pubmed.ncbi.nlm.nih.gov/18573151","citation_count":24,"is_preprint":false},{"pmid":"30400042","id":"PMC_30400042","title":"Gremlin, noggin, chordin and follistatin differentially modulate BMP-induced suppression of androgen secretion by bovine ovarian theca cells.","date":"2019","source":"Journal of molecular endocrinology","url":"https://pubmed.ncbi.nlm.nih.gov/30400042","citation_count":23,"is_preprint":false},{"pmid":"22886456","id":"PMC_22886456","title":"Chromatin dynamics in living cells: identification of oscillatory motion.","date":"2013","source":"Journal of cellular physiology","url":"https://pubmed.ncbi.nlm.nih.gov/22886456","citation_count":22,"is_preprint":false},{"pmid":"25770357","id":"PMC_25770357","title":"A semi-automated mass spectrometric immunoassay coupled to selected reaction monitoring (MSIA-SRM) reveals novel relationships between circulating PCSK9 and metabolic phenotypes in patient cohorts.","date":"2015","source":"Methods (San Diego, Calif.)","url":"https://pubmed.ncbi.nlm.nih.gov/25770357","citation_count":22,"is_preprint":false},{"pmid":"19296120","id":"PMC_19296120","title":"Chromatin dynamics is correlated with replication timing.","date":"2009","source":"Chromosoma","url":"https://pubmed.ncbi.nlm.nih.gov/19296120","citation_count":22,"is_preprint":false},{"pmid":"29670507","id":"PMC_29670507","title":"Evaluation of Gene-Based Family-Based Methods to Detect Novel Genes Associated With Familial Late Onset Alzheimer Disease.","date":"2018","source":"Frontiers in neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/29670507","citation_count":21,"is_preprint":false},{"pmid":"26809343","id":"PMC_26809343","title":"Osteogenic differentiation of bone marrow stromal cells is hindered by the presence of intervertebral disc cells.","date":"2015","source":"Arthritis research & therapy","url":"https://pubmed.ncbi.nlm.nih.gov/26809343","citation_count":21,"is_preprint":false},{"pmid":"28266688","id":"PMC_28266688","title":"The BMP2 variant L51P restores the osteogenic differentiation of human mesenchymal stromal cells in the presence of intervertebral disc cells.","date":"2017","source":"European cells & materials","url":"https://pubmed.ncbi.nlm.nih.gov/28266688","citation_count":19,"is_preprint":false},{"pmid":"20493240","id":"PMC_20493240","title":"The expression of twisted gastrulation in postnatal mouse brain and functional implications.","date":"2010","source":"Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/20493240","citation_count":18,"is_preprint":false},{"pmid":"29802913","id":"PMC_29802913","title":"Effects of acute and chronic methamphetamine administration on cynomolgus monkey hippocampus structure and cellular transcriptome.","date":"2018","source":"Toxicology and applied pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/29802913","citation_count":18,"is_preprint":false},{"pmid":"10480362","id":"PMC_10480362","title":"Genomic organisation of the human chordin gene and mutation screening of candidate Cornelia de Lange syndrome genes.","date":"1999","source":"Human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/10480362","citation_count":17,"is_preprint":false},{"pmid":"36566984","id":"PMC_36566984","title":"Molecular interactions of PCSK9 with an inhibitory nanobody, CAP1 and HLA-C: Functional regulation of LDLR levels.","date":"2022","source":"Molecular metabolism","url":"https://pubmed.ncbi.nlm.nih.gov/36566984","citation_count":14,"is_preprint":false},{"pmid":"34739847","id":"PMC_34739847","title":"PCSK9 regulates the NODAL signaling pathway and cellular proliferation in hiPSCs.","date":"2021","source":"Stem cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/34739847","citation_count":13,"is_preprint":false},{"pmid":"29255029","id":"PMC_29255029","title":"Enhancer adoption caused by genomic insertion elicits interdigital Shh expression and syndactyly in mouse.","date":"2017","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/29255029","citation_count":13,"is_preprint":false},{"pmid":"33945994","id":"PMC_33945994","title":"Smad2 and Smad3 differentially modulate chordin transcription via direct binding on the distal elements in gastrula Xenopus embryos.","date":"2021","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/33945994","citation_count":13,"is_preprint":false},{"pmid":"36851576","id":"PMC_36851576","title":"SKI-1/S1P Facilitates SARS-CoV-2 Spike Induced Cell-to-Cell Fusion via Activation of SREBP-2 and Metalloproteases, Whereas PCSK9 Enhances the Degradation of ACE2.","date":"2023","source":"Viruses","url":"https://pubmed.ncbi.nlm.nih.gov/36851576","citation_count":10,"is_preprint":false},{"pmid":"9008387","id":"PMC_9008387","title":"Isolation and regulation of accumulation of a minor chromoplast-specific protein from cucumber corollas.","date":"1997","source":"Plant physiology","url":"https://pubmed.ncbi.nlm.nih.gov/9008387","citation_count":9,"is_preprint":false},{"pmid":"33980237","id":"PMC_33980237","title":"The culture microenvironment of juvenile idiopathic arthritis synovial fibroblasts is favorable for endochondral bone formation through BMP4 and repressed by chondrocytes.","date":"2021","source":"Pediatric rheumatology online journal","url":"https://pubmed.ncbi.nlm.nih.gov/33980237","citation_count":8,"is_preprint":false},{"pmid":"34685759","id":"PMC_34685759","title":"Foxd4l1.1 Negatively Regulates Chordin Transcription in Neuroectoderm of Xenopus Gastrula.","date":"2021","source":"Cells","url":"https://pubmed.ncbi.nlm.nih.gov/34685759","citation_count":7,"is_preprint":false},{"pmid":"36980215","id":"PMC_36980215","title":"Two Homeobox Transcription Factors, Goosecoid and Ventx1.1, Oppositely Regulate Chordin Transcription in Xenopus Gastrula Embryos.","date":"2023","source":"Cells","url":"https://pubmed.ncbi.nlm.nih.gov/36980215","citation_count":6,"is_preprint":false},{"pmid":"32218218","id":"PMC_32218218","title":"Thymosin β4 Identified by Transcriptomic Analysis from HF Anagen to Telogen Promotes Proliferation of SHF-DPCs in Albas Cashmere Goat.","date":"2020","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/32218218","citation_count":6,"is_preprint":false},{"pmid":"37338142","id":"PMC_37338142","title":"O-Fucosylation of BMP1 promotes endometrial decidualization by activating BMP/Smad signaling pathway.","date":"2023","source":"Biology of reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/37338142","citation_count":5,"is_preprint":false},{"pmid":"17685487","id":"PMC_17685487","title":"Abnormal venous and arterial patterning in Chordin mutants.","date":"2007","source":"Developmental dynamics : an official publication of the American Association of Anatomists","url":"https://pubmed.ncbi.nlm.nih.gov/17685487","citation_count":5,"is_preprint":false},{"pmid":"37260544","id":"PMC_37260544","title":"The developmental gene Chordin is amplified and expressed in human cancers.","date":"2023","source":"Molecular & cellular oncology","url":"https://pubmed.ncbi.nlm.nih.gov/37260544","citation_count":4,"is_preprint":false},{"pmid":"34517078","id":"PMC_34517078","title":"Expression profiling of ovarian BMP antagonists reveals the potential interaction between TWSG1 and the chordin subfamily in the ovary.","date":"2021","source":"Molecular and cellular endocrinology","url":"https://pubmed.ncbi.nlm.nih.gov/34517078","citation_count":4,"is_preprint":false},{"pmid":"35581152","id":"PMC_35581152","title":"ccr7 affects both morphogenesis and differentiation during early Xenopus embryogenesis.","date":"2022","source":"Development, growth & differentiation","url":"https://pubmed.ncbi.nlm.nih.gov/35581152","citation_count":3,"is_preprint":false},{"pmid":"39938772","id":"PMC_39938772","title":"PRDM14 is essential for vertebrate gastrulation and safeguards avian germ cell identity.","date":"2025","source":"Developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/39938772","citation_count":3,"is_preprint":false},{"pmid":"38698265","id":"PMC_38698265","title":"Suppression of lysosome metabolism-meditated GARP/TGF-β1 complexes specifically depletes regulatory T cells to inhibit breast cancer metastasis.","date":"2024","source":"Oncogene","url":"https://pubmed.ncbi.nlm.nih.gov/38698265","citation_count":3,"is_preprint":false},{"pmid":"39462339","id":"PMC_39462339","title":"Exploration of transcriptional regulation network between buffalo oocytes and granulosa cells and its impact on different diameter follicles.","date":"2024","source":"BMC genomics","url":"https://pubmed.ncbi.nlm.nih.gov/39462339","citation_count":3,"is_preprint":false},{"pmid":"36861303","id":"PMC_36861303","title":"ccl19 and ccl21 affect cell movements and differentiation in early Xenopus development.","date":"2023","source":"Development, growth & differentiation","url":"https://pubmed.ncbi.nlm.nih.gov/36861303","citation_count":2,"is_preprint":false},{"pmid":"35494490","id":"PMC_35494490","title":"RNA sequence analysis identified bone morphogenetic protein-2 (BMP2) as a biomarker underlying form deprivation myopia.","date":"2022","source":"Biochemistry and biophysics reports","url":"https://pubmed.ncbi.nlm.nih.gov/35494490","citation_count":2,"is_preprint":false},{"pmid":"29017964","id":"PMC_29017964","title":"Isolation and characterization of a stress-responsive gene encoding a CHRD domain-containing protein from a halotolerant green alga.","date":"2017","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/29017964","citation_count":1,"is_preprint":false},{"pmid":"41649655","id":"PMC_41649655","title":"The secreted protein FonCHRD is essential for vegetative growth, asexual reproduction, and pathogenicity in watermelon Fusarium wilt fungus.","date":"2024","source":"Crop health","url":"https://pubmed.ncbi.nlm.nih.gov/41649655","citation_count":1,"is_preprint":false},{"pmid":"41445585","id":"PMC_41445585","title":"Maternal provisioning and zygotic activation: transcriptomic dynamics of early atlantic halibut (Hippoglossus hippoglossus) embryogenesis.","date":"2025","source":"Frontiers in cell and developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/41445585","citation_count":1,"is_preprint":false},{"pmid":"41174197","id":"PMC_41174197","title":"ChRD-PET: A Method for Mapping RNA-DNA Interactions.","date":"2026","source":"Methods in molecular biology (Clifton, N.J.)","url":"https://pubmed.ncbi.nlm.nih.gov/41174197","citation_count":0,"is_preprint":false},{"pmid":"40948898","id":"PMC_40948898","title":"Simultaneous Capture of Chromatin-Associated RNA and Global RNA-RNA Interactions With Reduced Input Requirements.","date":"2025","source":"Bio-protocol","url":"https://pubmed.ncbi.nlm.nih.gov/40948898","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":32568,"output_tokens":3262,"usd":0.073317},"stage2":{"model":"claude-opus-4-6","input_tokens":6650,"output_tokens":2874,"usd":0.15765},"total_usd":0.230967,"stage1_batch_id":"msgbatch_011kfMfE81o6CTcyhVUqumuW","stage2_batch_id":"msgbatch_01DTputS6WNkH745x1nVSoBo","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1998,\n      \"finding\": \"Mouse chordin (Chrd) encodes a secreted protein that dorsalizes early vertebrate embryonic tissues by binding to ventralizing TGF-β-like bone morphogenetic proteins and sequestering them in latent complexes; Chrd is expressed at high levels in 7-day post-coitum mouse embryos and at lower levels in adult tissues including liver and cerebellum.\",\n      \"method\": \"RNA blot analysis, cDNA sequencing, radiation hybrid mapping\",\n      \"journal\": \"Genomics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct characterization of mammalian chordin cDNA and expression; foundational paper replicated across species\",\n      \"pmids\": [\"9782094\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Human CHRD encodes alternatively spliced C-truncated variants that can antagonize BMP activity in a Xenopus axis-duplication assay, demonstrating that alternative splicing generates sub-products capable of influencing BMP activity in addition to metalloprotease-mediated cleavage.\",\n      \"method\": \"cDNA cloning, Xenopus axis-duplication functional assay\",\n      \"journal\": \"Mechanisms of development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — functional in vivo assay (Xenopus axis duplication) directly demonstrates BMP-antagonist activity of splice variants\",\n      \"pmids\": [\"11472837\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Chordin and Noggin function as dedicated BMP antagonists in the mouse organizer (node) and its mesendodermal derivatives; loss of Chrd in combination with reduced Nog causes loss of SHH and FGF8 expression at rostral organizing centers due to elevated BMP activity, demonstrating that CHRD promotes inductive activities of rostral organizing centers by limiting BMP signaling.\",\n      \"method\": \"Chrd/Nog compound mutant mouse analysis, in situ hybridization, ectopic BMP2 application to cephalic explants\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic loss-of-function with defined molecular phenotypes and rescue experiments in multiple mutant contexts\",\n      \"pmids\": [\"12397106\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Chordin and Noggin function as BMP antagonists in vivo to promote mammalian neural crest development; reduced BMP antagonism expands the early neural crest domain, perturbs neural crest cell emigration, and increases apoptosis in neural crest cells, placing Chordin upstream of BMP signaling in neural crest generation and survival.\",\n      \"method\": \"Chrd/Nog single and compound mutant mouse analysis, immunostaining for BMP signaling, apoptosis assays\",\n      \"journal\": \"Developmental dynamics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean genetic loss-of-function with defined molecular and cellular phenotypes, replicated across multiple mutant combinations\",\n      \"pmids\": [\"16894609\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"CHRD (chordin) is underexpressed in ovarian epithelial cancer cell lines compared to normal OSE; ectopic expression of CHRD in cancer cell lines (BG1, PEO14) reduces migratory and invasive properties and enhances cell adhesion, consistent with CHRD regulating BMP activity in normal OSE physiology.\",\n      \"method\": \"RT-PCR expression analysis, wound-healing/invasion assays, cell adhesion assays in cancer cell lines\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — single lab, functional overexpression assay without full pathway placement\",\n      \"pmids\": [\"16449796\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Chordin and Noggin (BMP antagonists) are expressed at higher levels in the left lateral plate mesoderm (LPM) and limit BMP signaling there; in Chrd;Nog double mutants, BMP signaling is elevated bilaterally and Nodal expression is absent; ectopic Nog in the left LPM of double mutants restores Nodal expression, demonstrating that CHRD functions in the left LPM to derepress Nodal transcription for left-right axis establishment.\",\n      \"method\": \"Chrd/Nog compound mutant mouse analysis, in situ hybridization, ectopic gene expression via electroporation\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis with multiple orthogonal methods including rescue experiment\",\n      \"pmids\": [\"18550712\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Genetic inactivation of mouse Chordin (Chrd-/-) results in neural crest defects that cause persistent truncus arteriosus and multiple venous patterning defects including absence of anterior cardinal vein segments, looping, and midline defects, establishing that BMP pathway activity regulated by CHRD is required for cephalic vascular patterning.\",\n      \"method\": \"Chrd-/- mouse analysis, resin injection/vascular casting in fixed transparent embryos\",\n      \"journal\": \"Developmental dynamics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean genetic KO with novel anatomical phenotype readout; single lab\",\n      \"pmids\": [\"17685487\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Ectopic Shh expression in the interdigital region of Hm mice upregulates Chrd, which antagonizes BMP signaling; Chrd-overexpressing transgenic mice recapitulate syndactyly with webbing, establishing CHRD as a downstream effector of Shh-mediated BMP antagonism in interdigital cell death.\",\n      \"method\": \"Transcriptome analysis of Hm mutant mice, generation and phenotyping of Chrd-overexpressing transgenic mice\",\n      \"journal\": \"PNAS\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — transgenic overexpression directly recapitulates phenotype, mechanistic pathway placement via epistasis\",\n      \"pmids\": [\"29255029\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Smad2 and Smad3 directly bind to two activin response elements (ARE1 and ARE2) in the distal region of the chordin (chrd) promoter to regulate transcription; Smad2 acts on both ARE1 and ARE2 while Smad3 acts only on ARE2, demonstrating differential transcriptional regulation of chrd by TGFβ/activin signaling.\",\n      \"method\": \"Reporter gene assay, site-directed mutagenesis of chrd promoter, chromatin immunoprecipitation in Xenopus gastrula embryos\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct binding confirmed by ChIP, functional validation by mutagenesis and reporter assays\",\n      \"pmids\": [\"33945994\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Foxd4l1.1 negatively regulates chrd transcription in two ways: by directly binding Foxd4l1.1 response elements (FRE) in the chrd promoter, and by physically interacting with Smad2/Smad3 to block their binding to activin response elements in the chrd promoter.\",\n      \"method\": \"Reporter gene assay, site-directed mutagenesis of chrd promoter FRE, ChIP-PCR, co-immunoprecipitation in Xenopus embryos\",\n      \"journal\": \"Cells\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — dual mechanism validated by mutagenesis, ChIP, and co-IP; orthogonal methods in same study\",\n      \"pmids\": [\"34685759\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Goosecoid (Gsc) activates chrd transcription by binding Gsc response elements (GRE) adjacent to a TCF7/Wnt response element (WRE) in the chrd promoter; Ventx1.1 represses chrd transcription by binding a Ventx1.1 response element (VRE) in the same promoter region; both activities confirmed by ChIP-PCR and mutagenesis.\",\n      \"method\": \"Reporter gene assay, site-directed mutagenesis, ChIP-PCR in Xenopus gastrula embryos\",\n      \"journal\": \"Cells\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct binding confirmed by ChIP, functional validation by mutagenesis with multiple cis-elements tested\",\n      \"pmids\": [\"36980215\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"O-fucosylation of BMP1 by poFUT1 promotes BMP1 secretion and enhances its binding to CHRD in the extracellular matrix; the BMP1-CHRD interaction releases CHRD-bound BMP4, activating the BMP/Smad signaling pathway and accelerating endometrial stromal cell decidualization.\",\n      \"method\": \"Co-immunoprecipitation, ELISA, overexpression/knockdown in human endometrial stromal cells, BMP/Smad pathway readouts\",\n      \"journal\": \"Biology of reproduction\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — binding interaction shown by Co-IP, functional consequence demonstrated; single lab\",\n      \"pmids\": [\"37338142\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"TWSG1 (Twisted gastrulation 1) can enhance CHRD's antagonism of BMP2, BMP4, BMP7, and GDF5, demonstrating a synergistic functional interaction between TWSG1 and the chordin subfamily in modulating BMP signaling in the ovary.\",\n      \"method\": \"Bioactivity assays (BMP signaling inhibition), quantitative PCR expression profiling in rat/mouse/human ovaries\",\n      \"journal\": \"Molecular and cellular endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — functional bioactivity assay demonstrates synergy; single lab, no direct binding confirmed\",\n      \"pmids\": [\"34517078\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Among four BMP-binding proteins tested (gremlin, noggin, chordin, follistatin), chordin had no effect on BMP2-, BMP4-, BMP6-, or BMP7-induced suppression of androstenedione secretion by bovine theca cells, suggesting CHRD does not functionally antagonize these BMPs in the thecal steroidogenesis context despite being expressed there.\",\n      \"method\": \"Primary bovine theca cell culture, androstenedione secretion assay with recombinant proteins\",\n      \"journal\": \"Journal of molecular endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct functional assay with recombinant protein in primary cells; unexpected negative result contrasting with known CHRD BMP antagonism\",\n      \"pmids\": [\"30400042\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CHRD (chordin) is a secreted BMP antagonist that binds BMP ligands (particularly BMP2, BMP4, BMP7) in the extracellular space to prevent receptor engagement; its transcription is directly activated by Smad2/3 (downstream of activin/TGFβ) and Goosecoid at defined promoter elements, and repressed by Foxd4l1.1 and Ventx1.1, while in vivo it functions in the gastrula organizer and lateral plate mesoderm to establish dorsoventral and left-right axes by limiting BMP signaling, and in neural crest, vascular, and limb development; BMP1 cleavage of CHRD releases bound BMP ligands to activate BMP signaling, and alternatively spliced truncated isoforms retain BMP-antagonist activity.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"CHRD (chordin) is a secreted BMP antagonist that establishes tissue polarity during embryonic development by sequestering BMP ligands in latent extracellular complexes, thereby restricting BMP receptor activation across dorsoventral, left-right, and limb axes. CHRD binds BMP2, BMP4, and BMP7, and this antagonism is potentiated by TWSG1; BMP1 metalloprotease cleaves CHRD to release bound BMPs and restore signaling [PMID:9782094, PMID:37338142, PMID:34517078]. Genetic loss of Chrd, alone or with Nog, disrupts gastrula organizer function, neural crest development, cephalic vascular patterning, and left-right axis establishment by derepressing BMP signaling in the lateral plate mesoderm, where CHRD is required for Nodal transcription [PMID:12397106, PMID:16894609, PMID:17685487, PMID:18550712]. Transcription of chrd is directly activated by Smad2/3 at activin response elements and by Goosecoid at GRE sites in the promoter, and repressed by Foxd4l1.1 and Ventx1.1, integrating TGF-β/activin, Wnt, and ventral homeobox inputs into a tightly regulated BMP-antagonist output [PMID:33945994, PMID:34685759, PMID:36980215].\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"Establishing that mammalian chordin is a secreted dorsalizing factor that binds BMPs answered the fundamental question of whether the Xenopus/Drosophila-discovered BMP antagonist mechanism is conserved in mammals.\",\n      \"evidence\": \"cDNA cloning, RNA blot analysis, and radiation hybrid mapping of mouse Chrd\",\n      \"pmids\": [\"9782094\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Binding affinities for individual BMP ligands not quantified\", \"No loss-of-function data in mammals yet\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Demonstrating that alternatively spliced C-truncated CHRD variants retain BMP-antagonist activity revealed that post-transcriptional processing, not just BMP1-mediated cleavage, generates biologically active sub-products.\",\n      \"evidence\": \"cDNA cloning of human splice variants and Xenopus axis-duplication functional assay\",\n      \"pmids\": [\"11472837\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative abundance of splice variants in vivo unknown\", \"Whether splice variants have distinct BMP-binding specificities untested\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Compound Chrd/Nog mutant analysis established that CHRD and Noggin act redundantly in the mouse organizer to limit BMP signaling, which is required for SHH and FGF8 expression at rostral organizing centers — answering how BMP antagonism links to downstream patterning genes.\",\n      \"evidence\": \"Chrd/Nog compound mutant mouse embryos with in situ hybridization and ectopic BMP2 application\",\n      \"pmids\": [\"12397106\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Individual contributions of CHRD versus Noggin to each organizer function not fully resolved\", \"Downstream transcriptional targets beyond SHH and FGF8 uncharacterized\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Loss-of-function studies extended CHRD's developmental role beyond axial patterning to neural crest generation, emigration, and survival, and to cephalic vascular morphogenesis, showing that BMP antagonism by CHRD is required in multiple tissue contexts.\",\n      \"evidence\": \"Chrd single and Chrd/Nog compound mutant mice with immunostaining, apoptosis assays, and vascular casting\",\n      \"pmids\": [\"16894609\", \"17685487\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cell-autonomous versus non-autonomous requirement for CHRD in neural crest not distinguished\", \"Molecular basis of vascular patterning defect beyond elevated BMP signaling unclear\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Demonstrating that CHRD limits BMP signaling in the left lateral plate mesoderm to permit Nodal expression resolved how BMP antagonism feeds into left-right axis determination.\",\n      \"evidence\": \"Chrd/Nog double-mutant mice with in situ hybridization and electroporation rescue of Nog in left LPM\",\n      \"pmids\": [\"18550712\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether CHRD acts by direct BMP4/7 sequestration versus indirect signaling in LPM not resolved\", \"How CHRD asymmetry in LPM is initially established is unknown\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Placing CHRD as a downstream effector of Shh that antagonizes BMP signaling during interdigital cell death established a Shh→Chrd→BMP inhibition axis in limb morphogenesis.\",\n      \"evidence\": \"Transcriptome analysis of Hm mutant limbs and phenotypic recapitulation in Chrd-overexpressing transgenic mice\",\n      \"pmids\": [\"29255029\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether CHRD is the sole mediator of Shh-dependent BMP antagonism in limb unclear\", \"Direct Shh-responsive cis-elements in Chrd promoter not identified\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Identification of Smad2/3 binding to discrete activin response elements (ARE1, ARE2) in the chrd promoter answered how TGF-β/activin signaling directly activates CHRD transcription, with Smad2 and Smad3 showing differential element usage.\",\n      \"evidence\": \"ChIP, reporter assays, and site-directed mutagenesis of chrd promoter in Xenopus gastrula embryos\",\n      \"pmids\": [\"33945994\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether mammalian CHRD promoter has equivalent AREs not confirmed\", \"Cofactors recruited by Smad2/3 to the chrd promoter unidentified\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Foxd4l1.1 was shown to repress chrd both by direct promoter binding and by sequestering Smad2/3 away from AREs, revealing a dual-mechanism transcriptional repressor that links neuroectodermal specification to CHRD downregulation.\",\n      \"evidence\": \"ChIP-PCR, co-immunoprecipitation, reporter assays, and FRE mutagenesis in Xenopus embryos\",\n      \"pmids\": [\"34685759\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether Foxd4l1.1 homologs in mammals repress CHRD similarly untested\", \"Stoichiometric relationship between Foxd4l1.1 and Smad2/3 not quantified\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"TWSG1 was shown to synergistically enhance CHRD antagonism of BMP2, BMP4, BMP7, and GDF5, expanding the functional BMP-binding repertoire of the CHRD system beyond its solo activity.\",\n      \"evidence\": \"BMP bioactivity assays with recombinant proteins and expression profiling in ovarian tissues\",\n      \"pmids\": [\"34517078\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct physical complex between TWSG1 and CHRD not confirmed\", \"Physiological relevance of CHRD-TWSG1 synergy in non-ovarian tissues untested\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Mapping of Goosecoid (GRE) and Ventx1.1 (VRE) response elements in the chrd promoter completed a cis-regulatory logic integrating organizer-specific activation and ventral repression of CHRD transcription.\",\n      \"evidence\": \"ChIP-PCR, reporter assays, and site-directed mutagenesis in Xenopus gastrula embryos\",\n      \"pmids\": [\"36980215\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether GRE and VRE are conserved in the mammalian CHRD promoter is unknown\", \"How TCF7/Wnt signaling at the adjacent WRE integrates with Gsc activation not fully resolved\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"O-fucosylation of BMP1 by poFUT1 was shown to enhance BMP1 secretion and its binding to CHRD, releasing CHRD-bound BMP4 to activate Smad signaling in endometrial decidualization — extending the BMP1-CHRD axis to a new physiological context.\",\n      \"evidence\": \"Co-immunoprecipitation, ELISA, overexpression/knockdown in human endometrial stromal cells\",\n      \"pmids\": [\"37338142\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"BMP1-CHRD binding stoichiometry and cleavage site usage in this context not defined\", \"Whether other tolloid-family proteases substitute for BMP1 in the endometrium untested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"A structural model of the full-length CHRD-BMP complex, quantitative binding affinities for individual BMP ligands, and the in vivo relevance of individual CHRD splice variants remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No crystal or cryo-EM structure of full-length CHRD bound to BMPs\", \"Relative contributions of individual cysteine-rich domains to BMP specificity not mapped\", \"Functional significance of each CHRD splice variant in mammalian tissues undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 1, 2, 3, 5, 7, 12]},\n      {\"term_id\": \"GO:0140313\", \"supporting_discovery_ids\": [0, 1, 5, 12]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [0, 1, 11]},\n      {\"term_id\": \"GO:0031012\", \"supporting_discovery_ids\": [11]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 2, 5, 7, 11]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [2, 3, 5, 6, 7]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"BMP1\",\n      \"BMP2\",\n      \"BMP4\",\n      \"BMP7\",\n      \"NOG\",\n      \"TWSG1\",\n      \"SMAD2\",\n      \"SMAD3\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}