{"gene":"FGA","run_date":"2026-06-09T23:54:43","timeline":{"discoveries":[{"year":1999,"finding":"Homozygous deletion of ~11 kb of the FGA gene causes congenital afibrinogenemia by eliminating the capacity to synthesize the fibrinogen Aα-chain, demonstrating that the FGA locus is required for functional fibrinogen production.","method":"Southern blotting, genetic analysis, haplotype analysis of affected patients","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct molecular identification of causative deletion with haplotype confirmation, replicated across multiple independent chromosomes and patients","pmids":["9916133"],"is_preprint":false},{"year":1999,"finding":"The ~11 kb FGA deletion is mediated by a 7 bp direct repeat (AACTTTT) in FGA intron 1 and the FGA-FGB intergenic region via non-homologous (illegitimate) recombination, and all three independent deletion junctions are identical to the base-pair.","method":"Nucleotide sequence analysis of deletion junctions compared to normal sequences","journal":"European journal of human genetics","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct sequencing of all three deletion junctions with base-pair resolution, multiple independent chromosomes analyzed","pmids":["10602365"],"is_preprint":false},{"year":2001,"finding":"The most common afibrinogenemia mutation FGA IVS4+1 G→T causes aberrant mRNA splicing through activation of multiple cryptic donor splice sites in exon 4 and intron 4; the predominant cryptic site (85% of transcripts) is 4 bp downstream of the normal site, causing a frameshift and premature Aα-chain truncation.","method":"Transfection of normal and mutant constructs into COS-7 cells, RT-PCR analysis of aberrant mRNAs","journal":"Blood","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct functional demonstration in transfected cells with 100% specificity of normal vs mutant constructs, multiple aberrant products characterized","pmids":["11238133"],"is_preprint":false},{"year":2001,"finding":"The majority of congenital afibrinogenemia cases are caused by truncating mutations in FGA (particularly IVS4+1 G→T), with FGA mutations more frequent than FGG or FGB mutations as a cause of afibrinogenemia.","method":"Molecular genetic analysis (sequencing) of 16 unrelated afibrinogenemia patients","journal":"Human genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — systematic sequencing of all fibrinogen genes in 16 patients, single lab but consistent with prior findings","pmids":["11354637"],"is_preprint":false},{"year":2002,"finding":"The outcome of FGA donor splice mutations (exon skipping vs. intron retention/cryptic splice-site use) follows the order of intron removal: FGA intron 3 is spliced first, followed by intron 2, intron 4, and intron 1. Mutations in early-spliced introns cause exon skipping, while mutations in later-spliced introns cause intron inclusion or cryptic splice-site use.","method":"Minigene transfection in COS-7 cells, RT-PCR analysis of splice products from IVS3delGTAA and other FGA splice mutations","journal":"Blood","confidence":"High","confidence_rationale":"Tier 1 / Moderate — direct functional splicing assay with transfected constructs, multiple mutations tested, mechanistic model validated","pmids":["12406899"],"is_preprint":false},{"year":2010,"finding":"A nonsense mutation in FGA exon 5 (p.Q240X) produces a truncated Aα-chain that is expressed but less efficiently secreted compared to wild-type Aα-chain when co-expressed with wild-type Bβ and γ chains in COS-7 cells.","method":"Expression of mutant Aα-chain cDNA in combination with wild-type Bβ and γ-chain cDNAs in COS-7 cells, detection of secreted protein in media","journal":"Blood coagulation & fibrinolysis","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro reconstitution assay in transfected cells, single lab, single method","pmids":["20051841"],"is_preprint":false},{"year":2012,"finding":"A mutation at the FGA translation initiation codon (c.1 A>T, M1L) in compound heterozygosity with a nonsense mutation (R129X) causes complete absence of fibrinogen, demonstrating that the canonical ATG start codon is essential for FGA Aα-chain synthesis.","method":"Sequencing of FGA gene in patient, compound heterozygosity confirmed","journal":"Blood coagulation & fibrinolysis","confidence":"Low","confidence_rationale":"Tier 3 / Weak — genetic identification only, no functional reconstitution or expression assay performed","pmids":["22732251"],"is_preprint":false},{"year":2012,"finding":"A novel regulatory element (PFE2) located between FGA and FGG genes functions as a hepatocyte enhancer in vitro and in vivo, driving FGA promoter-driven gene expression in hepatoma cells and in zebrafish larval livers regardless of orientation, with a short conserved nucleotide sequence maintaining enhancer activity.","method":"Luciferase reporter gene assay in hepatoma cells, transgenic zebrafish in vivo enhancer assay, ChIP-seq data integration","journal":"Thrombosis and haemostasis","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro luciferase assay combined with in vivo transgenic zebrafish validation, multiple orientations tested","pmids":["22836734"],"is_preprint":false},{"year":2013,"finding":"siRNA-mediated 50% reduction of FGA mRNA in HepG2 cells reduces secreted fibrinogen concentration to only ~78% of control (compared to ~49% for FGB and ~57% for FGG knockdown), indicating that FGA mRNA level is not the limiting factor for fibrinogen expression in normal liver, whereas FGG mRNA is limiting.","method":"siRNA knockdown of FGA, FGB, or FGG in HepG2 cells, quantitative RT-PCR for mRNA levels, ELISA for secreted fibrinogen concentration","journal":"Thrombosis research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional knockdown experiment with quantitative mRNA and protein measurements, multiple fibrinogen subunits compared in parallel","pmids":["23414568"],"is_preprint":false},{"year":2014,"finding":"Targeted frameshift mutations in zebrafish fga using zinc finger nucleases result in undetectable plasma fibrinogen and cause hemorrhage and reduced survival in homozygous mutant fish, demonstrating that fga/FGA is essential for circulating fibrinogen production.","method":"Zinc finger nuclease-mediated targeted mutagenesis in zebrafish, anti-fibrinogen antibody Western blot/ELISA of plasma, phenotypic analysis","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 / Strong — three independent frameshift mutations tested, functional fibrinogen absence confirmed by multiple antibodies, clear bleeding phenotype with homozygous mutants","pmids":["24553182"],"is_preprint":false},{"year":2014,"finding":"FGA-deficient hepatocytes transduced with lentiviral vectors encoding the fibrinogen Aα-chain produce fully functional fibrinogen in vitro, demonstrating that the hepatocyte is the cell type responsible for fibrinogen Aα-chain synthesis and secretion.","method":"Lentiviral transduction of patient hepatocytes with FGA construct, functional fibrinogen assay in vitro","journal":"Journal of thrombosis and haemostasis","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — direct functional gene rescue in primary patient hepatocytes, single experiment, single lab","pmids":["25163824"],"is_preprint":false},{"year":2016,"finding":"Familial mutations in the C-terminal region of FGA (E540V and R554L) increase in vitro amyloidogenicity of the FGA(496-581) fragment: E540V forms amyloid-like fibrils while R554L forms globular β-sheet-rich aggregates, whereas wild-type FGA(496-581) remains monomeric at physiological pH.","method":"In vitro aggregation assay, atomic force microscopy (AFM), assessment of β-sheet content","journal":"Biochimie","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — direct in vitro reconstitution with mutant vs wild-type peptides, AFM validation, single lab","pmids":["27126074"],"is_preprint":false},{"year":2016,"finding":"FGA variant fibrinogen Shanghai (c.169_180+2 del) causes exon 2 skipping via aberrant mRNA splicing, producing an Aα-chain with 42 N-terminal amino acid truncation that impairs fibrinopeptide A release and fibrin polymerization (prolonged lag time, slower maximum slope, reduced final turbidity) without affecting fibrinogen synthesis, assembly, or secretion.","method":"Minigene transfection assay, turbidity-based fibrin polymerization assay, HPLC fibrinopeptide release analysis, scanning electron microscopy of fibrin clot ultrastructure","journal":"Journal of clinical pathology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — multiple orthogonal methods (minigene splicing, fibrinopeptide release by HPLC, polymerization kinetics, SEM), single lab but rigorous characterization","pmids":["27555433"],"is_preprint":false},{"year":2017,"finding":"FGA Arg104Cys (g.3057 C>T) mutation impairs fibrinogen secretion: the variant Aα chain is underrepresented in plasma (making up only ~25% of total Aα chains) as determined by TOF-MS, causing hypodysfibrinogenemia despite near-normal clot structure.","method":"DNA sequencing, reverse phase electrospray TOF-MS of plasma fibrinogen chains, turbidity-based polymerization assay, confocal microscopy of fibrin structure","journal":"BMC hematology","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — direct mass spectrometry quantification of mutant vs wild-type chain ratio in plasma, multiple functional assays, single lab","pmids":["29299315"],"is_preprint":false},{"year":2012,"finding":"FGA FGAΔ1238 deletion generates two aberrant mRNAs (both frameshift/premature termination); FGA c.54+3A>C generates two aberrant mRNAs, one causing frameshift and one using a cryptic 5' splice site in exon 1 that deletes six signal peptide amino acids. Both variants result in lack of mature Aα-chain and impaired fibrinogen assembly/secretion.","method":"Minigene cloning and transfection into CHO cells, RT-PCR and cDNA sequencing of aberrant transcripts","journal":"International journal of hematology","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — direct functional splicing assay in transfected cells with cDNA sequencing, two distinct mutations tested, single lab","pmids":["22639050"],"is_preprint":false},{"year":2005,"finding":"FGA functional polymorphisms (-1051G, -3A, TaqI duplication alleles) significantly enhance FGA transcription in vitro, though carriers without elevated fibrinogen suggest post-transcriptional regulation also contributes to plasma fibrinogen levels.","method":"In vitro transcription/reporter assay for FGA promoter polymorphisms","journal":"Human genetics","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — direct in vitro functional transcription assay, single lab, discordance with in vivo fibrinogen levels noted","pmids":["16362348"],"is_preprint":false},{"year":2022,"finding":"Mice carrying a premature termination codon at Fga residue 271 (Fga270 mice) have ~90% reduction in hepatic Fga mRNA due to nonsense-mediated mRNA decay, resulting in ~10% plasma fibrinogen levels. Despite minimal circulating fibrinogen, hemostasis is preserved, but thrombosis in the inferior vena cava stasis model is completely abolished. Fga270/270 platelet fibrinogen is ~30% of wild-type with compensatory increase in fibronectin.","method":"Knock-in mouse model, NMD analysis, tail bleeding assay, laser-induced saphenous vein injury, IVC stasis thrombosis model, platelet aggregation, siRNA fibrinogen reduction experiment","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal in vivo and in vitro assays, knock-in mouse model plus siRNA replication, multiple labs implied by author list","pmids":["34905618"],"is_preprint":false},{"year":2022,"finding":"FGA knockdown in endometrial stromal cells reduces VEGFA, PDGF, FGF-B, MMP-2, and MMP-9 expression, and conditioned medium from FGA-knockdown cells inhibits HUVEC migration and tube formation by reducing VEGFR2 and FAK signaling pathway activity, establishing a FGA→VEGFA→VEGFR2→FAK axis promoting angiogenesis.","method":"siRNA knockdown, conditioned medium experiments, tube formation assay, wound assay, transwell assay, western blotting, matrigel plug assay in vivo, immunofluorescence for F-actin and VE-cadherin","journal":"Frontiers in endocrinology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple functional assays in vitro and in vivo, pathway validated by western blot, single lab","pmids":["35498401"],"is_preprint":false},{"year":2022,"finding":"FGA overexpression in gastric cancer cells inhibits migration, invasion, and EMT, and suppresses ITGA5 (integrin α5) transcription (confirmed by luciferase and ChIP assay), thereby inhibiting the FAK/ERK pathway and inducing autophagic cell death.","method":"CCK-8, colony formation, wound healing, transwell, immunofluorescence, luciferase reporter assay, ChIP assay, western blotting, double-label RFP-GFP-LC3 immunofluorescence, in vivo xenograft in nude mice","journal":"Tissue & cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP assay and luciferase assay confirm transcriptional regulation of ITGA5 by FGA, multiple functional readouts, single lab","pmids":["35257941"],"is_preprint":false},{"year":2024,"finding":"FGA knockout in hepatocellular carcinoma cells activates the PI3K/AKT pathway and increases N-cadherin and slug (EMT markers) while decreasing E-cadherin, promoting invasion and metastasis; FGA overexpression reverses these effects and restricts tumor spread in a mouse metastasis model.","method":"FGA KO and overexpression cell models, transwell migration/invasion assay, wound healing, western blotting for EMT markers and PI3K/AKT pathway components, in vivo metastasis mouse model","journal":"Aging","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal KO and overexpression experiments, pathway validated by western blot, in vivo confirmation, single lab","pmids":["39227068"],"is_preprint":false},{"year":2025,"finding":"HDAC2 regulates FGA transcription by controlling chromatin accessibility and H3K9ac enrichment at the FGA promoter (−1350/−1454 bp region); HDAC2 knockdown reduces FGA protein levels by decreasing H3K9ac binding at the FGA promoter. FGA promotes granulosa cell proliferation by upregulating PCNA and CCNE1, and inhibits apoptosis by suppressing Caspase3 and Caspase9, thereby promoting follicular development in vitro and in vivo.","method":"siRNA knockdown of HDAC1/2/3, chromatin accessibility assay, ChIP assay for H3K9ac at FGA promoter, proliferation/apoptosis assays, western blotting for PCNA/CCNE1/Caspase3/Caspase9, in vivo mouse experiments (corpora lutea counting, estradiol measurement)","journal":"Biological research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP assay identifies specific histone mark at FGA promoter, combined in vitro and in vivo validation, single lab","pmids":["40605115"],"is_preprint":false}],"current_model":"FGA encodes the fibrinogen Aα-chain, which is synthesized in hepatocytes under transcriptional control of a liver enhancer (PFE2) and HDAC2-regulated H3K9 acetylation at its promoter; loss-of-function mutations (deletions, nonsense, frameshift, splice-site) cause afibrinogenemia via nonsense-mediated mRNA decay or production of truncated Aα-chains that fail to assemble or secrete, while missense mutations in the αC-domain increase amyloidogenic propensity or impair fibrinopeptide A release and fibrin polymerization; beyond coagulation, FGA regulates angiogenesis via a VEGFA→VEGFR2→FAK signaling axis, and suppresses tumor invasion/metastasis through transcriptional repression of ITGA5 and inhibition of PI3K/AKT and FAK/ERK pathways, and promotes granulosa cell survival by suppressing Caspase3/9-mediated apoptosis."},"narrative":{"mechanistic_narrative":"FGA encodes the fibrinogen Aα-chain, a hepatocyte-synthesized, secreted subunit that is essential for production of circulating functional fibrinogen [PMID:9916133, PMID:24553182, PMID:25163824]. The locus is required for fibrinogen synthesis: homozygous deletion of FGA, and targeted frameshift mutagenesis of zebrafish fga, both eliminate plasma fibrinogen and cause a bleeding phenotype [PMID:9916133, PMID:24553182], while lentiviral re-expression of the Aα-chain in deficient patient hepatocytes restores functional fibrinogen, establishing the hepatocyte as the synthetic source [PMID:25163824]. Transcription is driven by a hepatocyte enhancer (PFE2) located between FGA and FGG and is modulated at the chromatin level by HDAC2, which controls H3K9 acetylation at the FGA promoter [PMID:22836734, PMID:40605115]; promoter polymorphisms further tune transcriptional output [PMID:16362348]. The major mechanism of congenital afibrinogenemia is truncating mutations — large deletions, splice-site mutations activating cryptic donor sites or causing exon skipping, and initiation-codon loss — that yield no mature Aα-chain through nonsense-mediated decay or assembly/secretion failure [PMID:10602365, PMID:11238133, PMID:12406899, PMID:22639050, PMID:34905618]. The ordered removal of FGA introns dictates whether a donor-site mutation causes exon skipping versus cryptic-site use [PMID:12406899]. Distinct missense and in-frame variants produce dysfibrinogenemia or hypodysfibrinogenemia: N-terminal truncation impairs fibrinopeptide A release and fibrin polymerization [PMID:27555433], Arg104Cys reduces secretion of the variant chain into plasma [PMID:29299315], and C-terminal αC-domain variants (E540V, R554L) increase amyloidogenic propensity in vitro [PMID:27126074]. A knock-in mouse with ~10% residual fibrinogen retains hemostasis but loses venous thrombosis, dissociating the threshold requirements for the two processes [PMID:34905618]. Beyond coagulation, FGA acts in cell signaling and tissue contexts: it promotes angiogenesis through a VEGFA→VEGFR2→FAK axis in endometrial stromal cells [PMID:35498401], suppresses tumor invasion and EMT by transcriptionally repressing ITGA5 and restraining FAK/ERK and PI3K/AKT signaling while inducing autophagic death [PMID:35257941, PMID:39227068], and supports granulosa cell proliferation and survival by upregulating PCNA/CCNE1 and suppressing Caspase3/9 [PMID:40605115].","teleology":[{"year":1999,"claim":"Established that the FGA locus is genetically required for fibrinogen production, defining loss of the Aα-chain as a cause of human afibrinogenemia.","evidence":"Southern blotting and haplotype analysis identifying a homozygous ~11 kb FGA deletion in patients, with junction sequencing revealing a 7 bp direct-repeat-mediated illegitimate recombination","pmids":["9916133","10602365"],"confidence":"High","gaps":["Did not address how partial or truncating lesions are processed at the mRNA/protein level","No mechanism for the residual hemostatic consequences in heterozygotes"]},{"year":2002,"claim":"Defined the molecular basis by which splice-site mutations cause afibrinogenemia, showing that the order of intron removal dictates exon skipping versus cryptic-site use or intron retention.","evidence":"Minigene transfection in COS-7/CHO cells with RT-PCR of aberrant transcripts for IVS4+1 G>T, IVS3delGTAA and other variants","pmids":["11238133","12406899","22639050"],"confidence":"High","gaps":["Did not quantify the contribution of NMD versus protein truncation for each transcript","Splicing assays in heterologous cell lines may not fully recapitulate hepatocyte splicing"]},{"year":2010,"claim":"Distinguished assembly/secretion failure from transcript loss as a cause of fibrinogen deficiency by showing truncated and missense Aα-chains can be expressed yet poorly secreted.","evidence":"Co-expression of mutant Aα with wild-type Bβ and γ chains in COS-7 cells (Q240X) and TOF-MS quantification of plasma chain ratios (Arg104Cys)","pmids":["20051841","29299315"],"confidence":"Medium","gaps":["Mechanism of intracellular retention or degradation not resolved","Single-lab in vitro reconstitution for the secretion defect"]},{"year":2012,"claim":"Identified the cis-regulatory architecture controlling FGA expression, locating a hepatocyte-specific enhancer and demonstrating transcription-modulating promoter polymorphisms.","evidence":"Luciferase reporter assays in hepatoma cells and transgenic zebrafish enhancer assays for PFE2; reporter assays for -1051G/-3A/TaqI promoter alleles","pmids":["22836734","16362348"],"confidence":"Medium","gaps":["Transcription factors binding PFE2 not identified","Discordance between in vitro transcription gain and in vivo plasma fibrinogen implicates uncharacterized post-transcriptional control"]},{"year":2013,"claim":"Tested whether FGA mRNA abundance limits fibrinogen output, finding FGA is not rate-limiting whereas FGG is.","evidence":"Parallel siRNA knockdown of FGA, FGB, FGG in HepG2 cells with qRT-PCR and ELISA for secreted fibrinogen","pmids":["23414568"],"confidence":"Medium","gaps":["Does not identify the step that becomes limiting when FGA is reduced","Single cell-line context"]},{"year":2014,"claim":"Confirmed in vivo that FGA is essential for circulating fibrinogen and that hepatocytes are the productive cell type, providing a gene-rescue proof of principle.","evidence":"Zinc finger nuclease frameshift mutagenesis in zebrafish with plasma fibrinogen and bleeding phenotyping; lentiviral FGA rescue of patient hepatocytes with functional fibrinogen assay","pmids":["24553182","25163824"],"confidence":"High","gaps":["Rescue performed in vitro only","Extrahepatic contributions not quantified"]},{"year":2016,"claim":"Linked specific FGA variant classes to dysfunction beyond deficiency: N-terminal truncation impairing fibrin polymerization and C-terminal αC variants driving amyloidogenicity.","evidence":"Minigene splicing, HPLC fibrinopeptide release, turbidity and SEM clot analysis (fibrinogen Shanghai); in vitro aggregation assays with AFM on FGA(496-581) E540V/R554L peptides","pmids":["27555433","27126074"],"confidence":"High","gaps":["Amyloidogenicity shown for isolated peptides, not full-length plasma fibrinogen in vivo","Structural basis of impaired fibrinopeptide A release not resolved"]},{"year":2022,"claim":"Dissociated the fibrinogen thresholds for hemostasis versus thrombosis using a low-fibrinogen mouse model, and defined NMD as the mechanism reducing transcript from a premature termination codon.","evidence":"Fga270 knock-in mouse with NMD analysis, tail-bleeding, laser injury, IVC stasis thrombosis model, platelet aggregation and siRNA replication","pmids":["34905618"],"confidence":"High","gaps":["Molecular basis of preserved hemostasis at ~10% fibrinogen not fully explained","Compensatory fibronectin role only correlative"]},{"year":2022,"claim":"Extended FGA function beyond coagulation into angiogenesis and tumor biology, implicating it in VEGFA/VEGFR2/FAK signaling and in transcriptional repression of ITGA5.","evidence":"siRNA knockdown with conditioned-medium HUVEC tube/migration assays and matrigel plug (endometrial stromal cells); overexpression with luciferase and ChIP assays plus xenograft (gastric cancer)","pmids":["35498401","35257941"],"confidence":"Medium","gaps":["Direct physical mechanism by which intracellular/secreted FGA modulates these pathways unresolved","Single-lab, single-tissue contexts"]},{"year":2024,"claim":"Reinforced a tumor-suppressive role for FGA via reciprocal knockout/overexpression, linking it to PI3K/AKT-driven EMT and metastasis.","evidence":"FGA KO and overexpression HCC cell models, migration/invasion assays, EMT and PI3K/AKT western blots, in vivo metastasis model","pmids":["39227068"],"confidence":"Medium","gaps":["Whether effect is mediated by secreted versus intracellular FGA not addressed","Direct effectors connecting FGA to PI3K/AKT not identified"]},{"year":2025,"claim":"Identified an epigenetic regulator of FGA and a survival/proliferation function in granulosa cells.","evidence":"siRNA HDAC1/2/3 knockdown with chromatin accessibility and H3K9ac ChIP at the FGA promoter; proliferation/apoptosis assays with PCNA/CCNE1/Caspase3/9 westerns and in vivo ovarian readouts","pmids":["40605115"],"confidence":"Medium","gaps":["How HDAC2-controlled H3K9ac integrates with PFE2 enhancer activity unknown","Mechanism by which FGA suppresses caspases not defined"]},{"year":null,"claim":"The molecular mechanism by which intracellular or secreted FGA controls signaling pathways (VEGFR2/FAK, ITGA5, PI3K/AKT, caspases) in non-hepatic cells remains undefined, as does the identity of the transcription factors operating at PFE2.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No direct receptor or binding partner established for the signaling functions","PFE2-binding transcription factors unidentified","Post-transcriptional regulators implicated by polymorphism studies not characterized"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[0,9,12]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[18]}],"localization":[{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[9,10,16]}],"pathway":[{"term_id":"R-HSA-109582","term_label":"Hemostasis","supporting_discovery_ids":[0,9,16]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[7,20]}],"complexes":["fibrinogen"],"partners":["FGB","FGG"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P02671","full_name":"Fibrinogen alpha chain","aliases":[],"length_aa":866,"mass_kda":95.0,"function":"Cleaved by the protease thrombin to yield monomers which, together with fibrinogen beta (FGB) and fibrinogen gamma (FGG), polymerize to form an insoluble fibrin matrix. Fibrin has a major function in hemostasis as one of the primary components of blood clots. In addition, functions during the early stages of wound repair to stabilize the lesion and guide cell migration during re-epithelialization. Was originally thought to be essential for platelet aggregation, based on in vitro studies using anticoagulated blood. However, subsequent studies have shown that it is not absolutely required for thrombus formation in vivo. Enhances expression of SELP in activated platelets via an ITGB3-dependent pathway. Maternal fibrinogen is essential for successful pregnancy. Fibrin deposition is also associated with infection, where it protects against IFNG-mediated hemorrhage. May also facilitate the immune response via both innate and T-cell mediated pathways","subcellular_location":"Secreted","url":"https://www.uniprot.org/uniprotkb/P02671/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/FGA","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"SRP14","stoichiometry":0.2},{"gene":"WIPF2","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/FGA","total_profiled":1310},"omim":[{"mim_id":"616004","title":"DYSFIBRINOGENEMIA, CONGENITAL","url":"https://www.omim.org/entry/616004"},{"mim_id":"613378","title":"AIG2-LIKE DOMAIN-CONTAINING PROTEIN 1; A2LD1","url":"https://www.omim.org/entry/613378"},{"mim_id":"610784","title":"MICRO RNA 29C; MIR29C","url":"https://www.omim.org/entry/610784"},{"mim_id":"610783","title":"MICRO RNA 29B1; MIR29B1","url":"https://www.omim.org/entry/610783"},{"mim_id":"610782","title":"MICRO RNA 29A; MIR29A","url":"https://www.omim.org/entry/610782"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Enhanced","locations":[{"location":"Endoplasmic reticulum","reliability":"Enhanced"}],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"liver","ntpm":17201.5}],"url":"https://www.proteinatlas.org/search/FGA"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"P02671","domains":[{"cath_id":"3.90.215.10","chopping":"633-863","consensus_level":"high","plddt":91.6616,"start":633,"end":863},{"cath_id":"1.20.5","chopping":"71-180_194-213","consensus_level":"high","plddt":80.7542,"start":71,"end":213}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P02671","model_url":"https://alphafold.ebi.ac.uk/files/AF-P02671-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P02671-F1-predicted_aligned_error_v6.png","plddt_mean":60.34},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=FGA","jax_strain_url":"https://www.jax.org/strain/search?query=FGA"},"sequence":{"accession":"P02671","fasta_url":"https://rest.uniprot.org/uniprotkb/P02671.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P02671/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P02671"}},"corpus_meta":[{"pmid":"9916133","id":"PMC_9916133","title":"Deletion of the fibrinogen [correction of fibrogen] alpha-chain gene (FGA) causes congenital afibrogenemia.","date":"1999","source":"The Journal of clinical investigation","url":"https://pubmed.ncbi.nlm.nih.gov/9916133","citation_count":85,"is_preprint":false},{"pmid":"11354637","id":"PMC_11354637","title":"Molecular analysis of the fibrinogen gene cluster in 16 patients with congenital afibrinogenemia: novel truncating mutations in the FGA and FGG genes.","date":"2001","source":"Human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/11354637","citation_count":62,"is_preprint":false},{"pmid":"29719494","id":"PMC_29719494","title":"Identification of serum proteins AHSG, FGA and APOA-I as diagnostic biomarkers for gastric cancer.","date":"2018","source":"Clinical proteomics","url":"https://pubmed.ncbi.nlm.nih.gov/29719494","citation_count":41,"is_preprint":false},{"pmid":"12406899","id":"PMC_12406899","title":"Outcome of donor splice site mutations accounting for congenital afibrinogenemia 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Bericht uber die biologisch-anthropologische Literatur","url":"https://pubmed.ncbi.nlm.nih.gov/11591050","citation_count":0,"is_preprint":false},{"pmid":"29070135","id":"PMC_29070135","title":"[Genetic Analysis of A Case of Congenital Dysfibrinogenemia Caused by Arg16His Mutation in Exon 2 of FGA].","date":"2017","source":"Zhongguo shi yan xue ye xue za zhi","url":"https://pubmed.ncbi.nlm.nih.gov/29070135","citation_count":0,"is_preprint":false},{"pmid":"10646230","id":"PMC_10646230","title":"DNA-PCR system FGA (FIBRA)--genotype and allele frequencies in a sample of western Germany (Düsseldorf region).","date":"1999","source":"Collegium antropologicum","url":"https://pubmed.ncbi.nlm.nih.gov/10646230","citation_count":0,"is_preprint":false},{"pmid":"19065534","id":"PMC_19065534","title":"[Identification of a rare allele of FGA-13].","date":"2008","source":"Zhonghua yi xue yi chuan xue za zhi = Zhonghua yixue yichuanxue zazhi = Chinese journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/19065534","citation_count":0,"is_preprint":false},{"pmid":"24327161","id":"PMC_24327161","title":"[Identification of a rare allele FGA-13 in Guangdong Han population].","date":"2013","source":"Zhonghua yi xue yi chuan xue za zhi = Zhonghua yixue yichuanxue zazhi = Chinese journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/24327161","citation_count":0,"is_preprint":false},{"pmid":"12536389","id":"PMC_12536389","title":"[Study of the high polymorphism STR locus-FGA in Chinese population].","date":"1999","source":"Fa yi xue za zhi","url":"https://pubmed.ncbi.nlm.nih.gov/12536389","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":37884,"output_tokens":5104,"usd":0.095106,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":13580,"output_tokens":4143,"usd":0.085737,"stage2_stop_reason":"end_turn"},"total_usd":0.180843,"stage1_batch_id":"msgbatch_01AsR7g8dGTEiEw9U83bJeWn","stage2_batch_id":"msgbatch_01YV5ZyxtFNUZEjxRcpd9jzb","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1999,\n      \"finding\": \"Homozygous deletion of ~11 kb of the FGA gene causes congenital afibrinogenemia by eliminating the capacity to synthesize the fibrinogen Aα-chain, demonstrating that the FGA locus is required for functional fibrinogen production.\",\n      \"method\": \"Southern blotting, genetic analysis, haplotype analysis of affected patients\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct molecular identification of causative deletion with haplotype confirmation, replicated across multiple independent chromosomes and patients\",\n      \"pmids\": [\"9916133\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"The ~11 kb FGA deletion is mediated by a 7 bp direct repeat (AACTTTT) in FGA intron 1 and the FGA-FGB intergenic region via non-homologous (illegitimate) recombination, and all three independent deletion junctions are identical to the base-pair.\",\n      \"method\": \"Nucleotide sequence analysis of deletion junctions compared to normal sequences\",\n      \"journal\": \"European journal of human genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct sequencing of all three deletion junctions with base-pair resolution, multiple independent chromosomes analyzed\",\n      \"pmids\": [\"10602365\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"The most common afibrinogenemia mutation FGA IVS4+1 G→T causes aberrant mRNA splicing through activation of multiple cryptic donor splice sites in exon 4 and intron 4; the predominant cryptic site (85% of transcripts) is 4 bp downstream of the normal site, causing a frameshift and premature Aα-chain truncation.\",\n      \"method\": \"Transfection of normal and mutant constructs into COS-7 cells, RT-PCR analysis of aberrant mRNAs\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct functional demonstration in transfected cells with 100% specificity of normal vs mutant constructs, multiple aberrant products characterized\",\n      \"pmids\": [\"11238133\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"The majority of congenital afibrinogenemia cases are caused by truncating mutations in FGA (particularly IVS4+1 G→T), with FGA mutations more frequent than FGG or FGB mutations as a cause of afibrinogenemia.\",\n      \"method\": \"Molecular genetic analysis (sequencing) of 16 unrelated afibrinogenemia patients\",\n      \"journal\": \"Human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — systematic sequencing of all fibrinogen genes in 16 patients, single lab but consistent with prior findings\",\n      \"pmids\": [\"11354637\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"The outcome of FGA donor splice mutations (exon skipping vs. intron retention/cryptic splice-site use) follows the order of intron removal: FGA intron 3 is spliced first, followed by intron 2, intron 4, and intron 1. Mutations in early-spliced introns cause exon skipping, while mutations in later-spliced introns cause intron inclusion or cryptic splice-site use.\",\n      \"method\": \"Minigene transfection in COS-7 cells, RT-PCR analysis of splice products from IVS3delGTAA and other FGA splice mutations\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct functional splicing assay with transfected constructs, multiple mutations tested, mechanistic model validated\",\n      \"pmids\": [\"12406899\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"A nonsense mutation in FGA exon 5 (p.Q240X) produces a truncated Aα-chain that is expressed but less efficiently secreted compared to wild-type Aα-chain when co-expressed with wild-type Bβ and γ chains in COS-7 cells.\",\n      \"method\": \"Expression of mutant Aα-chain cDNA in combination with wild-type Bβ and γ-chain cDNAs in COS-7 cells, detection of secreted protein in media\",\n      \"journal\": \"Blood coagulation & fibrinolysis\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro reconstitution assay in transfected cells, single lab, single method\",\n      \"pmids\": [\"20051841\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"A mutation at the FGA translation initiation codon (c.1 A>T, M1L) in compound heterozygosity with a nonsense mutation (R129X) causes complete absence of fibrinogen, demonstrating that the canonical ATG start codon is essential for FGA Aα-chain synthesis.\",\n      \"method\": \"Sequencing of FGA gene in patient, compound heterozygosity confirmed\",\n      \"journal\": \"Blood coagulation & fibrinolysis\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — genetic identification only, no functional reconstitution or expression assay performed\",\n      \"pmids\": [\"22732251\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"A novel regulatory element (PFE2) located between FGA and FGG genes functions as a hepatocyte enhancer in vitro and in vivo, driving FGA promoter-driven gene expression in hepatoma cells and in zebrafish larval livers regardless of orientation, with a short conserved nucleotide sequence maintaining enhancer activity.\",\n      \"method\": \"Luciferase reporter gene assay in hepatoma cells, transgenic zebrafish in vivo enhancer assay, ChIP-seq data integration\",\n      \"journal\": \"Thrombosis and haemostasis\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro luciferase assay combined with in vivo transgenic zebrafish validation, multiple orientations tested\",\n      \"pmids\": [\"22836734\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"siRNA-mediated 50% reduction of FGA mRNA in HepG2 cells reduces secreted fibrinogen concentration to only ~78% of control (compared to ~49% for FGB and ~57% for FGG knockdown), indicating that FGA mRNA level is not the limiting factor for fibrinogen expression in normal liver, whereas FGG mRNA is limiting.\",\n      \"method\": \"siRNA knockdown of FGA, FGB, or FGG in HepG2 cells, quantitative RT-PCR for mRNA levels, ELISA for secreted fibrinogen concentration\",\n      \"journal\": \"Thrombosis research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional knockdown experiment with quantitative mRNA and protein measurements, multiple fibrinogen subunits compared in parallel\",\n      \"pmids\": [\"23414568\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Targeted frameshift mutations in zebrafish fga using zinc finger nucleases result in undetectable plasma fibrinogen and cause hemorrhage and reduced survival in homozygous mutant fish, demonstrating that fga/FGA is essential for circulating fibrinogen production.\",\n      \"method\": \"Zinc finger nuclease-mediated targeted mutagenesis in zebrafish, anti-fibrinogen antibody Western blot/ELISA of plasma, phenotypic analysis\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — three independent frameshift mutations tested, functional fibrinogen absence confirmed by multiple antibodies, clear bleeding phenotype with homozygous mutants\",\n      \"pmids\": [\"24553182\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"FGA-deficient hepatocytes transduced with lentiviral vectors encoding the fibrinogen Aα-chain produce fully functional fibrinogen in vitro, demonstrating that the hepatocyte is the cell type responsible for fibrinogen Aα-chain synthesis and secretion.\",\n      \"method\": \"Lentiviral transduction of patient hepatocytes with FGA construct, functional fibrinogen assay in vitro\",\n      \"journal\": \"Journal of thrombosis and haemostasis\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — direct functional gene rescue in primary patient hepatocytes, single experiment, single lab\",\n      \"pmids\": [\"25163824\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Familial mutations in the C-terminal region of FGA (E540V and R554L) increase in vitro amyloidogenicity of the FGA(496-581) fragment: E540V forms amyloid-like fibrils while R554L forms globular β-sheet-rich aggregates, whereas wild-type FGA(496-581) remains monomeric at physiological pH.\",\n      \"method\": \"In vitro aggregation assay, atomic force microscopy (AFM), assessment of β-sheet content\",\n      \"journal\": \"Biochimie\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — direct in vitro reconstitution with mutant vs wild-type peptides, AFM validation, single lab\",\n      \"pmids\": [\"27126074\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"FGA variant fibrinogen Shanghai (c.169_180+2 del) causes exon 2 skipping via aberrant mRNA splicing, producing an Aα-chain with 42 N-terminal amino acid truncation that impairs fibrinopeptide A release and fibrin polymerization (prolonged lag time, slower maximum slope, reduced final turbidity) without affecting fibrinogen synthesis, assembly, or secretion.\",\n      \"method\": \"Minigene transfection assay, turbidity-based fibrin polymerization assay, HPLC fibrinopeptide release analysis, scanning electron microscopy of fibrin clot ultrastructure\",\n      \"journal\": \"Journal of clinical pathology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — multiple orthogonal methods (minigene splicing, fibrinopeptide release by HPLC, polymerization kinetics, SEM), single lab but rigorous characterization\",\n      \"pmids\": [\"27555433\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"FGA Arg104Cys (g.3057 C>T) mutation impairs fibrinogen secretion: the variant Aα chain is underrepresented in plasma (making up only ~25% of total Aα chains) as determined by TOF-MS, causing hypodysfibrinogenemia despite near-normal clot structure.\",\n      \"method\": \"DNA sequencing, reverse phase electrospray TOF-MS of plasma fibrinogen chains, turbidity-based polymerization assay, confocal microscopy of fibrin structure\",\n      \"journal\": \"BMC hematology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct mass spectrometry quantification of mutant vs wild-type chain ratio in plasma, multiple functional assays, single lab\",\n      \"pmids\": [\"29299315\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"FGA FGAΔ1238 deletion generates two aberrant mRNAs (both frameshift/premature termination); FGA c.54+3A>C generates two aberrant mRNAs, one causing frameshift and one using a cryptic 5' splice site in exon 1 that deletes six signal peptide amino acids. Both variants result in lack of mature Aα-chain and impaired fibrinogen assembly/secretion.\",\n      \"method\": \"Minigene cloning and transfection into CHO cells, RT-PCR and cDNA sequencing of aberrant transcripts\",\n      \"journal\": \"International journal of hematology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — direct functional splicing assay in transfected cells with cDNA sequencing, two distinct mutations tested, single lab\",\n      \"pmids\": [\"22639050\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"FGA functional polymorphisms (-1051G, -3A, TaqI duplication alleles) significantly enhance FGA transcription in vitro, though carriers without elevated fibrinogen suggest post-transcriptional regulation also contributes to plasma fibrinogen levels.\",\n      \"method\": \"In vitro transcription/reporter assay for FGA promoter polymorphisms\",\n      \"journal\": \"Human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — direct in vitro functional transcription assay, single lab, discordance with in vivo fibrinogen levels noted\",\n      \"pmids\": [\"16362348\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Mice carrying a premature termination codon at Fga residue 271 (Fga270 mice) have ~90% reduction in hepatic Fga mRNA due to nonsense-mediated mRNA decay, resulting in ~10% plasma fibrinogen levels. Despite minimal circulating fibrinogen, hemostasis is preserved, but thrombosis in the inferior vena cava stasis model is completely abolished. Fga270/270 platelet fibrinogen is ~30% of wild-type with compensatory increase in fibronectin.\",\n      \"method\": \"Knock-in mouse model, NMD analysis, tail bleeding assay, laser-induced saphenous vein injury, IVC stasis thrombosis model, platelet aggregation, siRNA fibrinogen reduction experiment\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal in vivo and in vitro assays, knock-in mouse model plus siRNA replication, multiple labs implied by author list\",\n      \"pmids\": [\"34905618\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"FGA knockdown in endometrial stromal cells reduces VEGFA, PDGF, FGF-B, MMP-2, and MMP-9 expression, and conditioned medium from FGA-knockdown cells inhibits HUVEC migration and tube formation by reducing VEGFR2 and FAK signaling pathway activity, establishing a FGA→VEGFA→VEGFR2→FAK axis promoting angiogenesis.\",\n      \"method\": \"siRNA knockdown, conditioned medium experiments, tube formation assay, wound assay, transwell assay, western blotting, matrigel plug assay in vivo, immunofluorescence for F-actin and VE-cadherin\",\n      \"journal\": \"Frontiers in endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple functional assays in vitro and in vivo, pathway validated by western blot, single lab\",\n      \"pmids\": [\"35498401\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"FGA overexpression in gastric cancer cells inhibits migration, invasion, and EMT, and suppresses ITGA5 (integrin α5) transcription (confirmed by luciferase and ChIP assay), thereby inhibiting the FAK/ERK pathway and inducing autophagic cell death.\",\n      \"method\": \"CCK-8, colony formation, wound healing, transwell, immunofluorescence, luciferase reporter assay, ChIP assay, western blotting, double-label RFP-GFP-LC3 immunofluorescence, in vivo xenograft in nude mice\",\n      \"journal\": \"Tissue & cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP assay and luciferase assay confirm transcriptional regulation of ITGA5 by FGA, multiple functional readouts, single lab\",\n      \"pmids\": [\"35257941\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"FGA knockout in hepatocellular carcinoma cells activates the PI3K/AKT pathway and increases N-cadherin and slug (EMT markers) while decreasing E-cadherin, promoting invasion and metastasis; FGA overexpression reverses these effects and restricts tumor spread in a mouse metastasis model.\",\n      \"method\": \"FGA KO and overexpression cell models, transwell migration/invasion assay, wound healing, western blotting for EMT markers and PI3K/AKT pathway components, in vivo metastasis mouse model\",\n      \"journal\": \"Aging\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal KO and overexpression experiments, pathway validated by western blot, in vivo confirmation, single lab\",\n      \"pmids\": [\"39227068\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"HDAC2 regulates FGA transcription by controlling chromatin accessibility and H3K9ac enrichment at the FGA promoter (−1350/−1454 bp region); HDAC2 knockdown reduces FGA protein levels by decreasing H3K9ac binding at the FGA promoter. FGA promotes granulosa cell proliferation by upregulating PCNA and CCNE1, and inhibits apoptosis by suppressing Caspase3 and Caspase9, thereby promoting follicular development in vitro and in vivo.\",\n      \"method\": \"siRNA knockdown of HDAC1/2/3, chromatin accessibility assay, ChIP assay for H3K9ac at FGA promoter, proliferation/apoptosis assays, western blotting for PCNA/CCNE1/Caspase3/Caspase9, in vivo mouse experiments (corpora lutea counting, estradiol measurement)\",\n      \"journal\": \"Biological research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP assay identifies specific histone mark at FGA promoter, combined in vitro and in vivo validation, single lab\",\n      \"pmids\": [\"40605115\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"FGA encodes the fibrinogen Aα-chain, which is synthesized in hepatocytes under transcriptional control of a liver enhancer (PFE2) and HDAC2-regulated H3K9 acetylation at its promoter; loss-of-function mutations (deletions, nonsense, frameshift, splice-site) cause afibrinogenemia via nonsense-mediated mRNA decay or production of truncated Aα-chains that fail to assemble or secrete, while missense mutations in the αC-domain increase amyloidogenic propensity or impair fibrinopeptide A release and fibrin polymerization; beyond coagulation, FGA regulates angiogenesis via a VEGFA→VEGFR2→FAK signaling axis, and suppresses tumor invasion/metastasis through transcriptional repression of ITGA5 and inhibition of PI3K/AKT and FAK/ERK pathways, and promotes granulosa cell survival by suppressing Caspase3/9-mediated apoptosis.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"FGA encodes the fibrinogen Aα-chain, a hepatocyte-synthesized, secreted subunit that is essential for production of circulating functional fibrinogen [#0, #9, #10]. The locus is required for fibrinogen synthesis: homozygous deletion of FGA, and targeted frameshift mutagenesis of zebrafish fga, both eliminate plasma fibrinogen and cause a bleeding phenotype [#0, #9], while lentiviral re-expression of the Aα-chain in deficient patient hepatocytes restores functional fibrinogen, establishing the hepatocyte as the synthetic source [#10]. Transcription is driven by a hepatocyte enhancer (PFE2) located between FGA and FGG and is modulated at the chromatin level by HDAC2, which controls H3K9 acetylation at the FGA promoter [#7, #20]; promoter polymorphisms further tune transcriptional output [#15]. The major mechanism of congenital afibrinogenemia is truncating mutations — large deletions, splice-site mutations activating cryptic donor sites or causing exon skipping, and initiation-codon loss — that yield no mature Aα-chain through nonsense-mediated decay or assembly/secretion failure [#1, #2, #4, #14, #16]. The ordered removal of FGA introns dictates whether a donor-site mutation causes exon skipping versus cryptic-site use [#4]. Distinct missense and in-frame variants produce dysfibrinogenemia or hypodysfibrinogenemia: N-terminal truncation impairs fibrinopeptide A release and fibrin polymerization [#12], Arg104Cys reduces secretion of the variant chain into plasma [#13], and C-terminal αC-domain variants (E540V, R554L) increase amyloidogenic propensity in vitro [#11]. A knock-in mouse with ~10% residual fibrinogen retains hemostasis but loses venous thrombosis, dissociating the threshold requirements for the two processes [#16]. Beyond coagulation, FGA acts in cell signaling and tissue contexts: it promotes angiogenesis through a VEGFA→VEGFR2→FAK axis in endometrial stromal cells [#17], suppresses tumor invasion and EMT by transcriptionally repressing ITGA5 and restraining FAK/ERK and PI3K/AKT signaling while inducing autophagic death [#18, #19], and supports granulosa cell proliferation and survival by upregulating PCNA/CCNE1 and suppressing Caspase3/9 [#20].\",\n  \"teleology\": [\n    {\n      \"year\": 1999,\n      \"claim\": \"Established that the FGA locus is genetically required for fibrinogen production, defining loss of the Aα-chain as a cause of human afibrinogenemia.\",\n      \"evidence\": \"Southern blotting and haplotype analysis identifying a homozygous ~11 kb FGA deletion in patients, with junction sequencing revealing a 7 bp direct-repeat-mediated illegitimate recombination\",\n      \"pmids\": [\"9916133\", \"10602365\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not address how partial or truncating lesions are processed at the mRNA/protein level\", \"No mechanism for the residual hemostatic consequences in heterozygotes\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Defined the molecular basis by which splice-site mutations cause afibrinogenemia, showing that the order of intron removal dictates exon skipping versus cryptic-site use or intron retention.\",\n      \"evidence\": \"Minigene transfection in COS-7/CHO cells with RT-PCR of aberrant transcripts for IVS4+1 G>T, IVS3delGTAA and other variants\",\n      \"pmids\": [\"11238133\", \"12406899\", \"22639050\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not quantify the contribution of NMD versus protein truncation for each transcript\", \"Splicing assays in heterologous cell lines may not fully recapitulate hepatocyte splicing\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Distinguished assembly/secretion failure from transcript loss as a cause of fibrinogen deficiency by showing truncated and missense Aα-chains can be expressed yet poorly secreted.\",\n      \"evidence\": \"Co-expression of mutant Aα with wild-type Bβ and γ chains in COS-7 cells (Q240X) and TOF-MS quantification of plasma chain ratios (Arg104Cys)\",\n      \"pmids\": [\"20051841\", \"29299315\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of intracellular retention or degradation not resolved\", \"Single-lab in vitro reconstitution for the secretion defect\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Identified the cis-regulatory architecture controlling FGA expression, locating a hepatocyte-specific enhancer and demonstrating transcription-modulating promoter polymorphisms.\",\n      \"evidence\": \"Luciferase reporter assays in hepatoma cells and transgenic zebrafish enhancer assays for PFE2; reporter assays for -1051G/-3A/TaqI promoter alleles\",\n      \"pmids\": [\"22836734\", \"16362348\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Transcription factors binding PFE2 not identified\", \"Discordance between in vitro transcription gain and in vivo plasma fibrinogen implicates uncharacterized post-transcriptional control\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Tested whether FGA mRNA abundance limits fibrinogen output, finding FGA is not rate-limiting whereas FGG is.\",\n      \"evidence\": \"Parallel siRNA knockdown of FGA, FGB, FGG in HepG2 cells with qRT-PCR and ELISA for secreted fibrinogen\",\n      \"pmids\": [\"23414568\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Does not identify the step that becomes limiting when FGA is reduced\", \"Single cell-line context\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Confirmed in vivo that FGA is essential for circulating fibrinogen and that hepatocytes are the productive cell type, providing a gene-rescue proof of principle.\",\n      \"evidence\": \"Zinc finger nuclease frameshift mutagenesis in zebrafish with plasma fibrinogen and bleeding phenotyping; lentiviral FGA rescue of patient hepatocytes with functional fibrinogen assay\",\n      \"pmids\": [\"24553182\", \"25163824\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Rescue performed in vitro only\", \"Extrahepatic contributions not quantified\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Linked specific FGA variant classes to dysfunction beyond deficiency: N-terminal truncation impairing fibrin polymerization and C-terminal αC variants driving amyloidogenicity.\",\n      \"evidence\": \"Minigene splicing, HPLC fibrinopeptide release, turbidity and SEM clot analysis (fibrinogen Shanghai); in vitro aggregation assays with AFM on FGA(496-581) E540V/R554L peptides\",\n      \"pmids\": [\"27555433\", \"27126074\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Amyloidogenicity shown for isolated peptides, not full-length plasma fibrinogen in vivo\", \"Structural basis of impaired fibrinopeptide A release not resolved\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Dissociated the fibrinogen thresholds for hemostasis versus thrombosis using a low-fibrinogen mouse model, and defined NMD as the mechanism reducing transcript from a premature termination codon.\",\n      \"evidence\": \"Fga270 knock-in mouse with NMD analysis, tail-bleeding, laser injury, IVC stasis thrombosis model, platelet aggregation and siRNA replication\",\n      \"pmids\": [\"34905618\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis of preserved hemostasis at ~10% fibrinogen not fully explained\", \"Compensatory fibronectin role only correlative\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Extended FGA function beyond coagulation into angiogenesis and tumor biology, implicating it in VEGFA/VEGFR2/FAK signaling and in transcriptional repression of ITGA5.\",\n      \"evidence\": \"siRNA knockdown with conditioned-medium HUVEC tube/migration assays and matrigel plug (endometrial stromal cells); overexpression with luciferase and ChIP assays plus xenograft (gastric cancer)\",\n      \"pmids\": [\"35498401\", \"35257941\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct physical mechanism by which intracellular/secreted FGA modulates these pathways unresolved\", \"Single-lab, single-tissue contexts\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Reinforced a tumor-suppressive role for FGA via reciprocal knockout/overexpression, linking it to PI3K/AKT-driven EMT and metastasis.\",\n      \"evidence\": \"FGA KO and overexpression HCC cell models, migration/invasion assays, EMT and PI3K/AKT western blots, in vivo metastasis model\",\n      \"pmids\": [\"39227068\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether effect is mediated by secreted versus intracellular FGA not addressed\", \"Direct effectors connecting FGA to PI3K/AKT not identified\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identified an epigenetic regulator of FGA and a survival/proliferation function in granulosa cells.\",\n      \"evidence\": \"siRNA HDAC1/2/3 knockdown with chromatin accessibility and H3K9ac ChIP at the FGA promoter; proliferation/apoptosis assays with PCNA/CCNE1/Caspase3/9 westerns and in vivo ovarian readouts\",\n      \"pmids\": [\"40605115\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How HDAC2-controlled H3K9ac integrates with PFE2 enhancer activity unknown\", \"Mechanism by which FGA suppresses caspases not defined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The molecular mechanism by which intracellular or secreted FGA controls signaling pathways (VEGFR2/FAK, ITGA5, PI3K/AKT, caspases) in non-hepatic cells remains undefined, as does the identity of the transcription factors operating at PFE2.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No direct receptor or binding partner established for the signaling functions\", \"PFE2-binding transcription factors unidentified\", \"Post-transcriptional regulators implicated by polymorphism studies not characterized\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 9, 12]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [18]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [9, 10, 16]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-109582\", \"supporting_discovery_ids\": [0, 9, 16]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [7, 20]}\n    ],\n    \"complexes\": [\"fibrinogen\"],\n    \"partners\": [\"FGB\", \"FGG\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}