{"gene":"SMAD5","run_date":"2026-06-10T07:46:35","timeline":{"discoveries":[{"year":1998,"finding":"BMP-2 causes serine phosphorylation of SMAD5 via direct physical association with BMP type Ia or Ib receptors; following phosphorylation, SMAD5 binds to DPC4 (SMAD4) and the complex translocates to the nucleus. A point mutant SMAD5 (G419S) or C-terminal deletion of DPC4 blocked BMP-2-induced osteoblastic differentiation of C2C12 cells.","method":"Co-immunoprecipitation, serine phosphorylation assays, dominant-negative mutagenesis, alkaline phosphatase/osteocalcin differentiation assays in C2C12 cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal co-IP and mutagenesis in a single lab with multiple orthogonal methods (phosphorylation assay, complex formation, functional differentiation readout)","pmids":["9442019"],"is_preprint":false},{"year":1997,"finding":"Overexpression of SMAD5 (or SMAD1) in C2C12 myoblasts induces alkaline phosphatase activity and decreases myogenin promoter activity without exogenous BMP-2, mimicking BMP signaling; C-terminal truncated SMAD5 blocks BMP signals from constitutively active BMPR-IB, establishing SMAD5 as a downstream mediator of BMP-induced osteoblast conversion and myogenic inhibition.","method":"Transient transfection of wild-type and dominant-negative SMAD5 constructs, CAT reporter assays, alkaline phosphatase activity assays in C2C12 cells","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional loss/gain-of-function with constitutively active receptor, single lab, two orthogonal readouts","pmids":["9299554"],"is_preprint":false},{"year":1997,"finding":"SMAD5 misexpression in Xenopus embryos causes ventralization, induces ventral mesoderm and epidermis; these activities require SMAD4 (DPC4) activity, placing SMAD5 downstream of BMP4 signaling.","method":"mRNA injection into Xenopus embryos, epistasis with dominant-negative SMAD4","journal":"Developmental biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo gain-of-function with genetic epistasis, single lab, replicated by zebrafish studies","pmids":["9133445"],"is_preprint":false},{"year":1998,"finding":"OP-1 (BMP-7) stimulates phosphorylation of SMAD5 in ROB-C26 osteoprogenitor cells; SMAD1, SMAD5, and SMAD8 (but not SMAD2/3) stably interact with kinase-deficient BMPR-IB after phosphorylation by BMPR-II kinase; a SMAD5-2SA (C-terminal serine-to-alanine) mutant acts as a dominant negative inhibitor of OP-1 signaling.","method":"In vitro kinase/phosphorylation assays, co-immunoprecipitation with BMPR-IB, dominant-negative transfection assays","journal":"Journal of cellular physiology","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — in vitro phosphorylation assay, co-IP, and dominant-negative mutagenesis in a single study","pmids":["9766532"],"is_preprint":false},{"year":1998,"finding":"Antisense oligonucleotides to SMAD5 in human CD34+ hematopoietic progenitor cells reversed the inhibitory effects of TGF-β on myeloid, erythroid, megakaryocyte, and multilineage colony formation, demonstrating SMAD5 is required in the TGF-β inhibitory signaling pathway in primitive human hematopoiesis.","method":"Antisense oligonucleotide knockdown in primary CD34+ cells, semisolid colony formation assays","journal":"Blood","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function in primary human cells with defined functional readout, single lab, two antisense sequences used","pmids":["9490674"],"is_preprint":false},{"year":1999,"finding":"The zebrafish smad5 mutant somitabun (sbntc24) carries a single amino-acid change in the L3 loop that converts SMAD5 into an antimorphic form inhibiting wild-type SMAD5 and related Smads; double mutant analyses place smad5 genetically downstream of bmp2b in dorsoventral patterning.","method":"ENU mutagenesis screen, double mutant analysis, RNA injection rescue experiments in zebrafish","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis confirmed by multiple alleles, double mutant, and rescue experiments","pmids":["10207140"],"is_preprint":false},{"year":1999,"finding":"Smad5 knockout (homozygous null) mice die between E9.5–E11.5 with defects in amnion, gut, heart, turning, craniofacial structures, and yolk sac vasculature, demonstrating essential in vivo roles for SMAD5 in embryonic and extraembryonic development downstream of BMP signaling.","method":"Homologous recombination gene targeting in ES cells; whole-mount in situ hybridization, histology","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 2 / Strong — two independent Smad5 knockout studies (PMID 10079226, 10079220) with overlapping phenotypes","pmids":["10079226","10079220"],"is_preprint":false},{"year":1999,"finding":"Loss of SMAD5 in mice causes enlarged blood vessels with decreased vascular smooth muscle cells and massive mesenchymal apoptosis, establishing SMAD5 as required for endothelium-mesenchyme interactions during angiogenesis.","method":"Homologous recombination knockout, histology, in vitro angiogenesis assay","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic loss-of-function with defined cellular phenotype, replicated across two independent knockout studies","pmids":["10079220"],"is_preprint":false},{"year":2000,"finding":"Smad5-deficient mouse embryos show defects in heart looping and embryonic turning (first signs of L-R asymmetry); lefty-1 expression is absent or very low, while nodal, lefty-2, and Pitx2 are expressed bilaterally, placing SMAD5 upstream of lefty-1 and the L-R axis determination cascade.","method":"Smad5 knockout mouse analysis, whole-mount in situ hybridization for lefty-1, lefty-2, nodal, Pitx2","journal":"Developmental biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic loss-of-function with molecular marker analysis establishing pathway position","pmids":["10677256"],"is_preprint":false},{"year":2001,"finding":"SMAD5 null embryos have greatly reduced or absent primordial germ cells (PGCs), with some ectopic PGC-like cells in the amnion, phenocopying Bmp4 and Bmp8b mutants and establishing SMAD5 as a downstream mediator of BMP signaling in PGC generation and localization.","method":"Oct4 whole-mount in situ hybridization, alkaline phosphatase staining in Smad5-/- mice","journal":"Mechanisms of development","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic loss-of-function with two orthogonal PGC markers, single lab","pmids":["11404080"],"is_preprint":false},{"year":2001,"finding":"The MH1 domain of SMAD5 binds a consensus sequence TGTGC; unlike SMAD1 and SMAD8, SMAD5 also binds the canonical Smad-binding element (SBE: GTCTAGAC) at a level similar to SMAD3 and SMAD4, revealing unique DNA-binding properties among BMP-R-Smads.","method":"SELEX (random oligonucleotide selection) with GST-Smad5 MH1 fusion protein; mutational analysis of SBE binding","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro binding assay with mutagenesis, single lab","pmids":["11527422"],"is_preprint":false},{"year":2002,"finding":"BMP4 directs SMAD5 phosphorylation, nuclear translocation, and specific transcriptional responses in human hematopoietic CD34+ cells; antisense inhibition of SMAD5 significantly reduces BMP4-induced erythroid differentiation (BFU-E expansion and glycophorin-A+ cells) without affecting granulocyte-macrophage lineages.","method":"Protein phosphorylation assays, nuclear translocation assays, antisense oligonucleotide knockdown, colony formation assays in primary human CD34+ cells","journal":"Blood cells, molecules & diseases","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (phosphorylation, translocation, functional colony assay) in primary human cells, single lab","pmids":["12064918"],"is_preprint":false},{"year":2002,"finding":"SMAD5-deficient yolk sacs contain elevated high-proliferative potential colony-forming cells (HPP-CFCs) with enhanced self-renewal and decreased sensitivity to TGF-β1 inhibition; Smad5-/- embryoid bodies show increased HPP-CFCs in a gene-dosage dependent manner, establishing SMAD5 as a negative regulator of primitive hematopoietic progenitors.","method":"Smad5 knockout mouse yolk sac colony assays, ES cell differentiation/embryoid body assays, gene dosage analysis","journal":"Blood","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic loss-of-function in two in vivo/in vitro systems, single lab","pmids":["12393578"],"is_preprint":false},{"year":2002,"finding":"H. pylori cagPAI-positive strains upregulate SMAD5 mRNA in gastric epithelial cells; RNAi knockdown of SMAD5 completely inhibits H. pylori-induced apoptosis, establishing SMAD5 as a required mediator of H. pylori-induced apoptosis.","method":"cDNA microarray, RT-PCR, Northern blot, siRNA knockdown with apoptosis assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — siRNA loss-of-function with defined apoptosis phenotype, multiple expression methods, single lab","pmids":["12473652"],"is_preprint":false},{"year":2002,"finding":"Cbfa1 (RUNX2) induces osteoblastic differentiation in C2C12 cells without forming a complex with SMAD1 or SMAD5; however, interactions with SMAD1/SMAD5 enhance Cbfa1 osteogenic actions. Smad6 overexpression (preventing Cbfa1-Smad1/5 interaction) did not block Cbfa1-induced osteocalcin promoter transactivation.","method":"Co-immunoprecipitation, reporter gene assays, dominant-negative Cbfa1 and Smad6 overexpression in C2C12 cells","journal":"Bone","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP and functional reporter assays with multiple constructs, single lab","pmids":["12151083"],"is_preprint":false},{"year":2002,"finding":"The 5' UTR of human SMAD5 mRNA contains an internal ribosome entry site (IRES) located within 100 nt of the 3' end of the 5'UTR, which shows cell-type specificity (more active in C2C12 than 293T) and requires a nuclear event for efficient translation initiation.","method":"Dicistronic reporter assays in cell lines, transfection of in vitro transcripts vs. DNA constructs","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro and cell-based IRES assays with multiple constructs, single lab","pmids":["12087169"],"is_preprint":false},{"year":2003,"finding":"Smurf1 promotes ubiquitin-mediated degradation of endogenous SMAD5 (selectively over SMAD2, SMAD3, SMAD7); elevated Smurf1 reduces SMAD5 protein levels and blocks BMP-induced osteogenic conversion of C2C12 cells; re-expression of SMAD5 from an exogenous source restores BMP osteogenic response. Smurf1 depletion by siRNA confirms its requirement for myogenic differentiation.","method":"Smurf1 overexpression, siRNA knockdown, SMAD5 rescue experiments, Western blot for protein levels in C2C12 cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal approaches (OE, KD, rescue), selectivity demonstrated across multiple Smads, single lab with strong controls","pmids":["12871975"],"is_preprint":false},{"year":2003,"finding":"BMP4 stimulation of cultured spermatogonia induces SMAD4/5 nuclear translocation and formation of a DNA-binding complex with transcriptional coactivator p300/CBP; BMP4 also induces Kit expression and mitogenic/differentiative effects, with SMAD5 expressed specifically in spermatogonia downstream of Sertoli cell-derived BMP4.","method":"Immunofluorescence for SMAD4/5 nuclear translocation, p300/CBP co-IP, in vitro BMP4 stimulation of spermatogonia","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP and nuclear translocation assays with functional differentiation readout, single lab","pmids":["12857787"],"is_preprint":false},{"year":2004,"finding":"BMP4/SMAD5-dependent signaling, regulated by hypoxia, initiates differentiation and expansion of stress erythroid progenitors in the adult spleen in response to acute anemia; flexed-tail (f) mutant mice carrying a Smad5 mutation cannot mount this stress erythropoiesis response.","method":"Genetic mapping identifying f mutation in Madh5/Smad5, in vivo anemia model, progenitor colony assays","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic identification of Smad5 as the f locus, in vivo functional assays, replicated by multiple subsequent studies","pmids":["15591122"],"is_preprint":false},{"year":2004,"finding":"In developing cerebellum, Bmp2 signals through SMAD5 (not SMAD1) specifically in newly differentiated granule neurons; only SMAD5 is phosphorylated in vivo by Bmp2 in granule cells, and SMAD5 overexpression alone is sufficient to induce granule cell differentiation even in the presence of Shh, antagonizing Shh-mediated proliferation.","method":"In vivo phosphorylation assays, SMAD5 overexpression in cerebellar granule cell cultures, Shh proliferation assay","journal":"Development (Cambridge, England)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo phosphorylation and gain-of-function with defined cellular phenotype, single lab","pmids":["15197161"],"is_preprint":false},{"year":2004,"finding":"An Id1 promoter-derived BRE (Smad1/5-specific response element) drives reporter activity in mouse ES cells and embryos where BMP/Smad1/5 signaling is active; used to map spatio-temporal transcriptional activity of SMAD1/5 in vivo, demonstrating autocrine BMP signaling in ES cells.","method":"Transgenic reporter mouse lines, luciferase/β-galactosidase assays in ES cells and chimeric embryos","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo reporter assay with multiple independent transgenic lines, single lab","pmids":["15331632"],"is_preprint":false},{"year":2005,"finding":"Loss of SMAD5 in cardiomyocytes (from ES cell differentiation) causes abnormal swollen mitochondria, reduced mitochondrial membrane potential (ΔΨm), cytochrome c leakage, and elevated p53, p21, and caspase-3, indicating SMAD5 protects cardiomyocytes from mitochondria-dependent apoptosis.","method":"ES cell differentiation from Smad5 null cells, electron microscopy, JC-1 mitochondrial potential assay, cytochrome c fractionation, Western blot","journal":"Experimental cell research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple mechanistic assays in defined genetic system, single lab","pmids":["15878335"],"is_preprint":false},{"year":2006,"finding":"Smad5 deletion in cardiomyocytes (via Sm22-Cre) results in decreased cardiac contractility (enlarged LV internal diameter, reduced fractional shortening) without cardiac hypertrophy, establishing a cell-autonomous requirement for SMAD5 in cardiac homeostasis; deletion in endothelial or vascular smooth muscle cells alone does not affect vasculature.","method":"Cre-loxP conditional knockout, echocardiography, isolated cardiomyocyte fractional shortening, treadmill test","journal":"The American journal of pathology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — conditional KO with multiple functional readouts, single lab","pmids":["17456754"],"is_preprint":false},{"year":2007,"finding":"In zebrafish, Smad1 and Smad5 have distinct and even opposite roles in embryonic hematopoiesis: Smad5 depletion causes defects in primitive erythropoiesis but normal macrophage numbers, while Smad1 depletion increases erythrocytes but impairs macrophages; Smad5 cannot rescue Smad1 loss-of-function, indicating inherently distinct activities. Microarray shows Smad5 uniquely regulates the BMP signaling pathway itself.","method":"Morpholino knockdown in zebrafish, rescue experiments, microarray analysis","journal":"Blood","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal loss-of-function with cross-rescue experiments, microarray, single lab","pmids":["17761518"],"is_preprint":false},{"year":2007,"finding":"The WW2 domain of Smurf1 physically interacts with the PPXY motif in the linker region of SMAD5 (and SMAD1, SMAD6); deletion of the WW2 domain abolishes Smurf1 binding to Smads and its ubiquitination activity on Smad1 in an in vitro ubiquitination assay.","method":"Pull-down with purified recombinant proteins, WW2 domain deletion mutants, in vitro ubiquitination assay","journal":"Journal of biomolecular structure & dynamics","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with recombinant proteins and ubiquitination assay, single lab","pmids":["17676934"],"is_preprint":false},{"year":2008,"finding":"Smad5 and Gata2 cooperate to induce Eklf (KLF1) expression in hematopoietic progenitors prior to erythroid commitment; upon erythroid commitment, Gata1 takes over regulation of Eklf, establishing a stage-dependent switch involving SMAD5 in lineage fate decisions.","method":"Transgenic reporter assays in ES cell differentiation and fetal liver, in vivo Smad5 loss-of-function in embryoid bodies, ChIP-based binding studies","journal":"Development (Cambridge, England)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (reporter, ChIP, loss-of-function), single lab","pmids":["18448565"],"is_preprint":false},{"year":2009,"finding":"BMP4/Smad5-dependent stress erythropoiesis pathway expands stress erythroid progenitors in the fetal liver; defects in BMP4/Smad5 signaling preferentially impair expansion of stress (not steady-state) erythroid progenitors, causing fetal anemia in flexed-tail mutants.","method":"f/f mutant (Smad5 mutation) analysis, fetal liver progenitor assays, BFU-E colony assays","journal":"Developmental biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic model with defined progenitor phenotype, single lab, consistent with prior stress erythropoiesis work","pmids":["18374325"],"is_preprint":false},{"year":2010,"finding":"In DLBCL, a non-canonical TGF-β1/SMAD5 signaling module is active; miR-155 directly targets SMAD5 3'UTR; miR-155 overexpression renders cells resistant to TGF-β1 and BMP growth inhibition via defective p21 induction and impaired cell cycle arrest; RNAi-based SMAD5 knockdown recapitulates these effects in vitro and in vivo.","method":"miR-155 overexpression and RNAi knockdown of SMAD5, luciferase reporter assay, cell cycle assays, in vivo xenograft","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — genome-wide identification plus multiple functional validation methods (luciferase, RNAi, in vivo), single lab with comprehensive mechanistic follow-up","pmids":["20133617"],"is_preprint":false},{"year":2011,"finding":"Loss of SMAD5 in intestinal epithelial cells (Smad5ΔIEC) causes hypermigration, loss of E-cadherin from the apical junctional complex (displaced to cytoplasm), and deregulated claudin-1/claudin-2 expression, leading to increased susceptibility to DSS-induced colitis and impaired wound healing.","method":"Intestinal epithelium-specific Cre-loxP knockout, immunofluorescence, Western blot, DSS colitis model","journal":"American journal of physiology. Gastrointestinal and liver physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — conditional KO with multiple molecular and functional readouts, single lab","pmids":["21212325"],"is_preprint":false},{"year":2012,"finding":"BMP-activated SMAD5 antagonizes Nodal signaling by interfering with the Nodal-Smad2/4-Foxh1 autoregulatory pathway through formation of an unusual BMP4-induced Smad complex containing Smad2 and Smad5; loss of Smad5 in mouse embryos results in ectopic Nodal expression and ectopic primitive streak formation in the amnion.","method":"Smad5 knockout mouse analysis, cell culture BMP4 stimulation with co-immunoprecipitation of Smad2/Smad5 complex, quantitative gene expression analysis","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic loss-of-function combined with co-IP demonstrating novel Smad2/Smad5 complex and mechanistic pathway interference","pmids":["22912414"],"is_preprint":false},{"year":2013,"finding":"miR-155 expression in DLBCL blocks TGF-β1-mediated activation of retinoblastoma protein (RB) by suppressing SMAD5, which reduces TGF-β1-induced transcription of p15 and p21, sustaining RB phosphorylation and inactivity; miR-155 KO mice show elevated SMAD5 in mature B cells with heightened TGF-β1 sensitivity and G0/G1 arrest.","method":"miR-155 KO mouse analysis, DLBCL cell lines with ectopic miR-155 expression, genetic knockdown of SMAD5/p15/p21, cell cycle analysis","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo KO plus DLBCL cell genetic dissection, multiple orthogonal methods establishing the miR-155/SMAD5/p15/p21/RB circuit","pmids":["24136167"],"is_preprint":false},{"year":2014,"finding":"In zebrafish, smad1 and smad9 act redundantly downstream of smad5 to mediate ventral specification: smad5 knockdown can be rescued by smad1 or smad9 overexpression, but smad5 overexpression cannot rescue smad1+smad9 double knockdown; smad1 and smad9 are direct transcriptional targets of Smad5.","method":"Morpholino knockdown in zebrafish, rescue experiments with mRNA injection, transcriptional target analysis","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis by reciprocal rescue experiments, single lab","pmids":["24488494"],"is_preprint":false},{"year":2015,"finding":"Crystal structure of the SMAD5 MH1 domain in complex with the GC-rich sequence reveals that the same β-hairpin contacts both GC-rich and SBE DNA but with different interaction modes; a composite DNA sequence structure shows modular binding, with spacer length affecting MH1 assembly.","method":"X-ray crystallography of SMAD5 MH1 domain–DNA complexes (GC-rich, SBE, and composite sequences)","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structures providing atomic resolution of DNA recognition mechanism with multiple DNA sequence contexts","pmids":["26304548"],"is_preprint":false},{"year":2017,"finding":"SMAD5 responds to intracellular pH (pHi) changes: increased pHi (cold, basic, hypertonic conditions) promotes proton dissociation from charged clusters in the MH1 domain, driving nuclear-to-cytoplasmic relocalization; decreased pHi blocks nuclear export causing nuclear accumulation. This nucleocytoplasmic shuttling is independent of BMP signaling, C-terminal phosphorylation, and Smad4. Cytoplasmic SMAD5 physically interacts with hexokinase 1 and accelerates glycolysis; ablation of SMAD5 causes dysregulation of bioenergetic homeostasis.","method":"Live-cell imaging of SMAD5 localization under pH/osmotic perturbations, co-IP with hexokinase 1, rescue experiments with cytoplasmic-only SMAD5, metabolic assays in human pluripotent stem cell differentiation model","journal":"Cell research","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (live imaging, co-IP, functional metabolic rescue, domain mutagenesis) in a single comprehensive study","pmids":["28675158"],"is_preprint":false},{"year":2019,"finding":"Hepatocyte-specific deletion of SMAD1/5 (and SMAD1/5/8) causes severe hepcidin deficiency and iron overload; EGF fails to suppress hepcidin in SMAD1/5 knockout hepatocytes, establishing a requirement for SMAD1/5 in EGF-mediated hepcidin regulation; inflammatory hepcidin induction is preserved, demonstrating pathway specificity.","method":"Hepatocyte-specific Cre-loxP knockout, serum hepcidin and iron measurements, EGF/LPS challenge","journal":"Hepatology (Baltimore, Md.)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — conditional KO with specific ligand challenges distinguishing pathway requirements, single lab","pmids":["31127639"],"is_preprint":false},{"year":2019,"finding":"LncRNA TUG1 directly binds the 50–90 aa region of SMAD5 (MH1 domain) and blocks nuclear translocation of phosphorylated SMAD5 after irradiation, suppressing osteogenic signaling in bone marrow MSCs despite increased SMAD5 phosphorylation.","method":"RNA immunoprecipitation (RIP), serial SMAD5 deletion constructs identifying binding region, immunofluorescence for p-SMAD5 nuclear translocation, osteogenic differentiation assays","journal":"Theranostics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RIP with domain-mapping deletions and functional nuclear translocation assay, single lab","pmids":["31149038"],"is_preprint":false},{"year":2021,"finding":"BMP signaling through a conserved ACVR2A/SMAD1/5 axis in the uterine endometrium is required for endometrial receptivity; SMAD1/5 conditional knockout (PR-cre) causes cystic endometrial glands, hyperproliferative epithelium during the implantation window, and impaired apicobasal transformation preventing embryo implantation. ACVR2B is dispensable.","method":"Conditional knockout (PR-Cre) for SMAD1/5, ACVR2A, and ACVR2B; histology, fertility assays in mice","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple conditional knockouts with specific receptor identification (ACVR2A vs ACVR2B), defined cellular and functional phenotypes","pmids":["34099644"],"is_preprint":false},{"year":2006,"finding":"BMP9 causes phosphorylation of SMAD1 and SMAD5, formation of a SMAD4/SMAD1/SMAD5 complex, and nuclear translocation of this complex in cultured basal forebrain cells, establishing the canonical BMP signaling pathway for BMP9 in cholinergic neuron differentiation.","method":"Phosphorylation assays, co-immunoprecipitation, nuclear translocation assays in primary basal forebrain cultures","journal":"Brain research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple biochemical assays in primary cells, single lab","pmids":["16626664"],"is_preprint":false},{"year":2007,"finding":"An intronic poly(T) element in intron 4 of Smad5 is mutated in flexed-tail (f/f) mice; loss of 1–2 T residues causes tissue-specific (spleen-predominant) splicing defects throughout Smad5, generating misspliced mRNAs including one encoding a truncated inhibitory Smad5 protein.","method":"Sequencing of f/f mouse Smad5 intron 4, RT-PCR analysis of misspliced isoforms, tissue-specific splicing analysis","journal":"Mammalian genome","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic identification of the regulatory mutation with functional consequences on splicing, single lab","pmids":["18060457"],"is_preprint":false},{"year":2010,"finding":"SMAD5 knockdown in L6 myotubes decreases Akt2 expression and serine phosphorylation and reduces insulin-induced glucose uptake while increasing Ship2 expression; ChIP demonstrates SMAD5 binding to the Akt2 gene, which is decreased by dexamethasone treatment.","method":"siRNA knockdown of SMAD5, glucose uptake assays, Western blot, chromatin immunoprecipitation (ChIP) for Akt2 gene","journal":"Molecular and cellular endocrinology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP plus loss-of-function with functional metabolic readout, single lab","pmids":["20079400"],"is_preprint":false},{"year":2014,"finding":"BMP-2-induced Dlx3 expression in osteoblasts requires both SMAD5 and p38; SMAD5 binds to two TGTCT Smad-binding elements in the Dlx3 promoter region (−698 to −368) as shown by EMSA and ChIP; p38 activation is necessary for BMP-2-induced SMAD5 phosphorylation and nuclear translocation.","method":"EMSA, ChIP assay, promoter deletions/mutagenesis, Smad5 knockdown, p38 inhibitor, Western blot in MC3T3-E1 cells","journal":"Journal of cellular physiology","confidence":"Medium","confidence_rationale":"Tier 1–2 / Moderate — EMSA/ChIP plus functional mutagenesis defining binding sites, single lab","pmids":["24647893"],"is_preprint":false},{"year":2006,"finding":"Jun activation domain-binding protein 1 (Jab1) physically interacts with SMAD5 in chondrocytes (identified by yeast 2-hybrid, confirmed by co-IP); Jab1 overexpression attenuates BMP-dependent transcriptional responses, acting as a negative modulator of BMP signaling.","method":"Yeast 2-hybrid screen of cartilage cDNA library, co-immunoprecipitation, BMP-responsive transcriptional reporter assay","journal":"Arthritis and rheumatism","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — y2h discovery confirmed by co-IP with functional transcriptional assay, single lab","pmids":["17133595"],"is_preprint":false}],"current_model":"SMAD5 is a receptor-regulated (R-Smad) intracellular signal transducer that is directly phosphorylated on C-terminal serines by BMP type I receptors (BMPR-IA/IB) upon ligand stimulation, whereupon it heterodimerizes with SMAD4 and translocates to the nucleus to regulate transcription via its MH1 domain (which binds GC-rich elements and the canonical SBE); it is targeted for ubiquitin-mediated proteasomal degradation by Smurf1 via a PPXY-WW2 domain interaction; in addition to canonical BMP signaling, SMAD5 participates in a non-canonical TGF-β1 module, responds to intracellular pH changes through charge-dependent nucleocytoplasmic shuttling (independent of phosphorylation and SMAD4) to regulate glycolysis via hexokinase 1, and is essential in vivo for embryonic angiogenesis, primordial germ cell specification, left-right axis determination, stress erythropoiesis, endometrial receptivity, intestinal epithelial integrity, and cardiac homeostasis."},"narrative":{"mechanistic_narrative":"SMAD5 is a receptor-regulated R-Smad that transduces BMP signals from the cell surface to the nucleus to control developmental cell-fate decisions and tissue homeostasis [PMID:9442019, PMID:10079226, PMID:10079220]. Upon BMP-2/BMP-7/BMP-9 ligand stimulation, SMAD5 is serine-phosphorylated at its C-terminus through direct association with BMP type I receptors (BMPR-IA/IB), an event dependent on BMPR-II kinase, after which it binds SMAD4 (DPC4) and the complex translocates to the nucleus; C-terminal serine-to-alanine or G419S point mutants act as dominant negatives that block BMP responses [PMID:9442019, PMID:9766532, PMID:16626664]. In the nucleus, the SMAD5 MH1 domain recognizes GC-rich elements (consensus TGTGC) and, uniquely among BMP R-Smads, also the canonical SBE; crystal structures show a single β-hairpin engages both DNA modes, and SMAD5 directly occupies target promoters such as Dlx3 and Akt2 and recruits the p300/CBP coactivator [PMID:11527422, PMID:26304548, PMID:24647893, PMID:12857787]. SMAD5 output is constrained by multiple negative regulators: Smurf1 binds the SMAD5 linker PPXY motif via its WW2 domain and targets SMAD5 for ubiquitin-mediated proteasomal degradation [PMID:12871975, PMID:17676934]; miR-155 represses the SMAD5 3'UTR to disable TGF-β1/BMP growth arrest in DLBCL through the p15/p21/RB axis [PMID:20133617, PMID:24136167]; and Jab1 and lncRNA TUG1 antagonize nuclear SMAD5 activity [PMID:17133595, PMID:31149038]. Genetically, SMAD5 acts downstream of BMP2b/BMP4 in dorsoventral and left-right patterning, and is essential in vivo for yolk-sac angiogenesis, primordial germ cell specification, lefty-1-dependent L-R axis determination, stress erythropoiesis, endometrial receptivity, intestinal epithelial integrity, and cardiac homeostasis [PMID:10207140, PMID:10079226, PMID:10079220, PMID:10677256, PMID:11404080, PMID:15591122, PMID:34099644, PMID:21212325, PMID:17456754]. Beyond canonical signaling, SMAD5 forms an unusual BMP4-induced SMAD2/SMAD5 complex that antagonizes Nodal signaling [PMID:22912414], and undergoes phosphorylation-, SMAD4-independent nucleocytoplasmic shuttling driven by intracellular pH, with cytoplasmic SMAD5 binding hexokinase 1 to accelerate glycolysis [PMID:28675158].","teleology":[{"year":1997,"claim":"Established SMAD5 as a downstream intracellular mediator of BMP signaling, resolving whether overexpression alone could mimic ligand-driven osteoblast conversion and myogenic suppression.","evidence":"Wild-type and dominant-negative SMAD5 transfection with reporter and alkaline phosphatase assays in C2C12 cells, and mRNA injection epistasis in Xenopus","pmids":["9299554","9133445"],"confidence":"Medium","gaps":["Did not show direct receptor phosphorylation of endogenous SMAD5","SMAD4 requirement inferred from epistasis rather than biochemistry"]},{"year":1998,"claim":"Defined the biochemical activation step: BMP type I receptors directly phosphorylate SMAD5 on C-terminal serines, triggering SMAD4 binding and nuclear translocation.","evidence":"Co-IP with BMPR-Ia/Ib, serine phosphorylation and in vitro kinase assays, and C-terminal serine/G419S dominant-negative mutants in C2C12 and ROB-C26 cells","pmids":["9442019","9766532"],"confidence":"High","gaps":["Exact phosphoacceptor residues not enumerated at this stage","Stoichiometry and selectivity of receptor-Smad pairing not fully resolved"]},{"year":1998,"claim":"Demonstrated SMAD5 is functionally required in primary human hematopoiesis as a transducer of TGF-β inhibitory signaling.","evidence":"Antisense oligonucleotide knockdown of SMAD5 in CD34+ progenitors with colony formation assays","pmids":["9490674"],"confidence":"Medium","gaps":["Antisense specificity vs other R-Smads not excluded","Direct transcriptional targets in hematopoietic cells not identified"]},{"year":1999,"claim":"Placed SMAD5 genetically downstream of BMP2b/BMP4 in dorsoventral patterning and established its essential in vivo developmental roles.","evidence":"Zebrafish somitabun antimorph genetics and double-mutant epistasis, plus two independent Smad5 knockout mouse studies with histology and in situ hybridization","pmids":["10207140","10079226","10079220"],"confidence":"High","gaps":["Tissue-specific contributions not separable in global null","Molecular targets driving each phenotype not defined"]},{"year":1999,"claim":"Identified SMAD5 as required for endothelium-mesenchyme interactions in angiogenesis, explaining the vascular component of the null phenotype.","evidence":"Knockout mouse histology showing enlarged vessels, reduced VSMCs, and mesenchymal apoptosis, plus in vitro angiogenesis assay","pmids":["10079220"],"confidence":"High","gaps":["Cell-autonomy of the vascular defect not resolved here","Downstream effectors of mesenchymal survival unknown"]},{"year":2000,"claim":"Positioned SMAD5 upstream of lefty-1 in the left-right axis determination cascade.","evidence":"Whole-mount in situ hybridization for lefty-1, lefty-2, nodal, and Pitx2 in Smad5 knockout embryos","pmids":["10677256"],"confidence":"High","gaps":["Direct vs indirect regulation of lefty-1 not established","Mechanism linking SMAD5 to asymmetric gene expression unknown"]},{"year":2001,"claim":"Established SMAD5 as a BMP-pathway mediator of primordial germ cell generation and localization.","evidence":"Oct4 in situ and alkaline phosphatase staining in Smad5-null embryos, phenocopying Bmp4/Bmp8b mutants","pmids":["11404080"],"confidence":"Medium","gaps":["Cell-intrinsic vs extrinsic requirement in PGC precursors unresolved","Target genes in PGC specification not defined"]},{"year":2001,"claim":"Defined the DNA-binding specificity of the SMAD5 MH1 domain, distinguishing it from other BMP R-Smads.","evidence":"SELEX with GST-SMAD5 MH1 fusion and mutational SBE binding analysis","pmids":["11527422"],"confidence":"Medium","gaps":["In vitro binding not linked to specific endogenous promoters","Structural basis of dual recognition not yet known"]},{"year":2002,"claim":"Extended SMAD5 function into lineage-specific hematopoietic differentiation and progenitor self-renewal control.","evidence":"BMP4-induced phosphorylation/translocation with antisense knockdown in CD34+ cells, and Smad5-null yolk-sac/embryoid-body colony assays with gene-dosage analysis","pmids":["12064918","12393578"],"confidence":"Medium","gaps":["Mechanism of erythroid vs myeloid selectivity unclear","Direct targets controlling progenitor self-renewal unidentified"]},{"year":2002,"claim":"Uncovered translational and apoptotic dimensions of SMAD5 regulation, including a cell-type-specific 5'UTR IRES and a requirement in H. pylori-induced apoptosis.","evidence":"Dicistronic IRES reporter assays in cell lines, and cDNA microarray with siRNA knockdown and apoptosis assays in gastric epithelial cells","pmids":["12087169","12473652"],"confidence":"Medium","gaps":["IRES trans-acting factors not identified","Apoptotic effectors downstream of SMAD5 in H. pylori response unknown"]},{"year":2003,"claim":"Defined the degradation mechanism controlling SMAD5 protein levels via Smurf1-mediated ubiquitination.","evidence":"Smurf1 overexpression, siRNA, and SMAD5 rescue with Western blot of endogenous SMAD5 in C2C12 cells, plus p300/CBP co-IP showing coactivator recruitment in spermatogonia","pmids":["12871975","12857787"],"confidence":"High","gaps":["Ubiquitin chain linkage and acceptor lysines not mapped","Regulation of Smurf1-SMAD5 engagement not defined"]},{"year":2004,"claim":"Identified the flexed-tail Smad5 locus as the genetic basis of stress erythropoiesis and revealed SMAD5-specific functions in neuronal differentiation and BMP-responsive transcription in vivo.","evidence":"Genetic mapping of the f mutation to Smad5 with in vivo anemia and progenitor assays, in vivo phosphorylation in cerebellar granule cells, and Id1-BRE transgenic reporters","pmids":["15591122","15197161","15331632"],"confidence":"High","gaps":["Why stress but not steady-state erythropoiesis requires SMAD5 not mechanistically resolved","SMAD1/SMAD5 functional divergence basis unclear"]},{"year":2005,"claim":"Linked SMAD5 to protection of cardiomyocytes from mitochondria-dependent apoptosis, foreshadowing a cardiac homeostatic role.","evidence":"Smad5-null ES-derived cardiomyocytes analyzed by EM, JC-1 potential, cytochrome c fractionation, and p53/p21/caspase-3 Western blot","pmids":["15878335"],"confidence":"Medium","gaps":["Transcriptional targets controlling mitochondrial integrity unidentified","In vitro model not yet validated in vivo at this step"]},{"year":2006,"claim":"Established cell-autonomous requirement of SMAD5 in cardiac contractility and identified Jab1 as a negative modulator of SMAD5-dependent BMP transcription.","evidence":"Sm22-Cre conditional knockout with echocardiography and cardiomyocyte fractional shortening, and yeast-2-hybrid/co-IP identifying Jab1 with reporter assays","pmids":["17456754","17133595"],"confidence":"Medium","gaps":["Molecular basis of contractility defect undefined","Mechanism of Jab1 antagonism not resolved"]},{"year":2007,"claim":"Resolved the physical basis of Smurf1 recognition and demonstrated non-redundant SMAD5 functions distinct from SMAD1.","evidence":"Recombinant pull-downs mapping Smurf1 WW2 to the SMAD5 linker PPXY with in vitro ubiquitination, and reciprocal morpholino knockdown/cross-rescue plus microarray in zebrafish","pmids":["17676934","17761518"],"confidence":"Medium","gaps":["Structural detail of WW2-PPXY interface absent","Sequence determinants of SMAD5-specific output unknown"]},{"year":2007,"claim":"Identified the flexed-tail intronic regulatory mutation causing tissue-specific Smad5 missplicing.","evidence":"Sequencing of Smad5 intron 4 poly(T) and RT-PCR of misspliced isoforms in f/f mice","pmids":["18060457"],"confidence":"Medium","gaps":["Splicing factor reading the poly(T) element unidentified","Functional contribution of the truncated inhibitory isoform not quantified"]},{"year":2008,"claim":"Placed SMAD5 within a transcriptional network controlling erythroid lineage commitment through cooperative regulation of Eklf/KLF1.","evidence":"Transgenic reporters, embryoid-body loss-of-function, and ChIP-based binding in hematopoietic differentiation","pmids":["18448565"],"confidence":"Medium","gaps":["Direct SMAD5 occupancy at Eklf vs cooperative effects not fully separated","Stage switch from Gata2 to Gata1 mechanism incomplete"]},{"year":2010,"claim":"Established a tumor-suppressive SMAD5 circuit silenced by miR-155 in DLBCL and a metabolic transcriptional role at the Akt2 gene.","evidence":"miR-155 overexpression/RNAi with 3'UTR luciferase, cell cycle and xenograft assays in DLBCL, and SMAD5 knockdown with ChIP at Akt2 and glucose uptake in L6 myotubes","pmids":["20133617","20079400"],"confidence":"High","gaps":["Direct SMAD5 transcriptional targets mediating p21 induction not enumerated","Metabolic Akt2 regulation not validated in vivo"]},{"year":2012,"claim":"Revealed a non-canonical SMAD5 mechanism: a BMP4-induced SMAD2/SMAD5 complex that antagonizes Nodal signaling to restrain ectopic primitive streak formation.","evidence":"Smad5 knockout embryo analysis with co-IP of the Smad2/Smad5 complex and quantitative gene expression","pmids":["22912414"],"confidence":"High","gaps":["Structural arrangement of the atypical complex unknown","Promoter-level interference with Foxh1 not mapped"]},{"year":2013,"claim":"Detailed the miR-155/SMAD5/p15/p21/RB circuit controlling B-cell cycle arrest in vivo.","evidence":"miR-155 knockout mice and DLBCL lines with genetic SMAD5/p15/p21 knockdown and cell cycle analysis","pmids":["24136167"],"confidence":"High","gaps":["Direct vs indirect SMAD5 control of p15/p21 promoters not fully dissected","Contribution to lymphomagenesis in patients not addressed"]},{"year":2014,"claim":"Clarified the genetic architecture downstream of SMAD5 and the cooperating signals required for its transcriptional targets.","evidence":"Zebrafish reciprocal rescue placing smad1/smad9 as redundant SMAD5 targets, and EMSA/ChIP plus p38 inhibition defining SMAD5 binding at the Dlx3 promoter in MC3T3-E1 cells","pmids":["24488494","24647893"],"confidence":"Medium","gaps":["Mechanism of p38-dependent SMAD5 phosphorylation not detailed","Generality of the SMAD5-driven feed-forward loop beyond fish unknown"]},{"year":2015,"claim":"Provided the atomic-resolution basis for SMAD5 MH1 recognition of both GC-rich and SBE DNA.","evidence":"X-ray crystallography of SMAD5 MH1–DNA complexes across GC-rich, SBE, and composite sequences","pmids":["26304548"],"confidence":"High","gaps":["Full-length SMAD5 trimer assembly on chromatin not resolved","Coactivator engagement in the structural context not captured"]},{"year":2017,"claim":"Uncovered a phosphorylation- and SMAD4-independent SMAD5 function: pH-driven nucleocytoplasmic shuttling that couples cytoplasmic SMAD5 to hexokinase 1 and glycolysis.","evidence":"Live-cell imaging under pH/osmotic perturbation, hexokinase 1 co-IP, cytoplasmic-only rescue, and metabolic assays in human pluripotent stem cells","pmids":["28675158"],"confidence":"High","gaps":["Physiological triggers of pHi shifts in vivo not defined","How cytoplasmic SMAD5 modulates HK1 catalysis mechanistically unknown"]},{"year":2019,"claim":"Extended SMAD1/5 function to iron homeostasis and additional layers of SMAD5 regulation via lncRNA TUG1.","evidence":"Hepatocyte-specific SMAD1/5 knockout with hepcidin/iron measurements and EGF/LPS challenge, and RIP plus domain mapping showing TUG1 blocks p-SMAD5 nuclear translocation","pmids":["31127639","31149038"],"confidence":"Medium","gaps":["SMAD5-specific vs SMAD1 contribution to hepcidin not isolated","Structural basis of TUG1 binding to the MH1 region not resolved"]},{"year":2021,"claim":"Identified a conserved ACVR2A/SMAD1/5 axis required for endometrial receptivity and embryo implantation.","evidence":"PR-Cre conditional knockouts of SMAD1/5, ACVR2A, and ACVR2B with histology and fertility assays in mice","pmids":["34099644"],"confidence":"High","gaps":["SMAD5-specific role separate from SMAD1 not isolated","Transcriptional targets driving apicobasal transformation undefined"]},{"year":null,"claim":"How SMAD5's canonical transcriptional output, its degradation and RNA-mediated regulation, and its non-canonical pH-sensing/metabolic and Nodal-antagonizing functions are integrated within a single cell remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model linking nuclear transcriptional and cytoplasmic metabolic SMAD5 pools","Direct genome-wide SMAD5 target set in mammalian tissues not defined","Determinants of SMAD5 vs SMAD1 functional specialization unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[10,32,40,39]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[0,17,40,25]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[0,3,37]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0,17,33,35]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[33]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,3,29,37]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[5,6,8,9,36]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[27,30]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[16,24]}],"complexes":["SMAD5–SMAD4 complex","BMP4-induced SMAD2–SMAD5 complex"],"partners":["SMAD4","BMPR1A","BMPR1B","SMURF1","HK1","SMAD2","EP300","JAB1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q99717","full_name":"SMAD family member 5","aliases":["JV5-1","Mothers against decapentaplegic homolog 5","MAD homolog 5","Mothers against DPP homolog 5"],"length_aa":465,"mass_kda":52.3,"function":"Transcriptional regulator that plays a role in various cellular processes including embryonic development, cell differentiation, angiogenesis and tissue homeostasis (PubMed:12064918, PubMed:16516194). Upon BMP ligand binding to their receptors at the cell surface, is phosphorylated by activated type I BMP receptors (BMPRIs) and associates with SMAD4 to form a heteromeric complex which translocates into the nucleus acting as transcription factor (PubMed:9442019). In turn, the hetero-trimeric complex recognizes cis-regulatory elements containing Smad Binding Elements (SBEs) to modulate the outcome of the signaling network (PubMed:33510867). Non-phosphorylated SMAD5 has a cytoplasmic role in energy metabolism regulation by promoting mitochondrial respiration and glycolysis in response to cytoplasmic pH changes (PubMed:28675158). Mechanistically, interacts with hexokinase 1/HK1 and thereby accelerates glycolysis (PubMed:28675158)","subcellular_location":"Cytoplasm; Nucleus; Mitochondrion","url":"https://www.uniprot.org/uniprotkb/Q99717/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/SMAD5","classification":"Not Classified","n_dependent_lines":3,"n_total_lines":74,"dependency_fraction":0.04054054054054054},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/SMAD5","total_profiled":1310},"omim":[{"mim_id":"620997","title":"SEMAPHORIN 3G; SEMA3G","url":"https://www.omim.org/entry/620997"},{"mim_id":"620847","title":"BONE MORPHOGENETIC PROTEIN 8A; BMP8A","url":"https://www.omim.org/entry/620847"},{"mim_id":"620121","title":"IRON OVERLOAD, SUSCEPTIBILITY TO; IO","url":"https://www.omim.org/entry/620121"},{"mim_id":"620035","title":"SMAD5 ANTISENSE RNA 1, NONCODING; SMAD5AS1","url":"https://www.omim.org/entry/620035"},{"mim_id":"619560","title":"MICRO RNA 135B; MIR135B","url":"https://www.omim.org/entry/619560"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/SMAD5"},"hgnc":{"alias_symbol":["Dwfc","JV5-1"],"prev_symbol":["MADH5"]},"alphafold":{"accession":"Q99717","domains":[{"cath_id":"3.90.520.10","chopping":"13-129","consensus_level":"high","plddt":93.7456,"start":13,"end":129},{"cath_id":"2.60.200.10","chopping":"261-453","consensus_level":"high","plddt":95.4435,"start":261,"end":453}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q99717","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q99717-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q99717-F1-predicted_aligned_error_v6.png","plddt_mean":80.88},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=SMAD5","jax_strain_url":"https://www.jax.org/strain/search?query=SMAD5"},"sequence":{"accession":"Q99717","fasta_url":"https://rest.uniprot.org/uniprotkb/Q99717.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q99717/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q99717"}},"corpus_meta":[{"pmid":"10079226","id":"PMC_10079226","title":"Smad5 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SMAD5 via direct physical association with BMP type Ia or Ib receptors; following phosphorylation, SMAD5 binds to DPC4 (SMAD4) and the complex translocates to the nucleus. A point mutant SMAD5 (G419S) or C-terminal deletion of DPC4 blocked BMP-2-induced osteoblastic differentiation of C2C12 cells.\",\n      \"method\": \"Co-immunoprecipitation, serine phosphorylation assays, dominant-negative mutagenesis, alkaline phosphatase/osteocalcin differentiation assays in C2C12 cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal co-IP and mutagenesis in a single lab with multiple orthogonal methods (phosphorylation assay, complex formation, functional differentiation readout)\",\n      \"pmids\": [\"9442019\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"Overexpression of SMAD5 (or SMAD1) in C2C12 myoblasts induces alkaline phosphatase activity and decreases myogenin promoter activity without exogenous BMP-2, mimicking BMP signaling; C-terminal truncated SMAD5 blocks BMP signals from constitutively active BMPR-IB, establishing SMAD5 as a downstream mediator of BMP-induced osteoblast conversion and myogenic inhibition.\",\n      \"method\": \"Transient transfection of wild-type and dominant-negative SMAD5 constructs, CAT reporter assays, alkaline phosphatase activity assays in C2C12 cells\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional loss/gain-of-function with constitutively active receptor, single lab, two orthogonal readouts\",\n      \"pmids\": [\"9299554\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"SMAD5 misexpression in Xenopus embryos causes ventralization, induces ventral mesoderm and epidermis; these activities require SMAD4 (DPC4) activity, placing SMAD5 downstream of BMP4 signaling.\",\n      \"method\": \"mRNA injection into Xenopus embryos, epistasis with dominant-negative SMAD4\",\n      \"journal\": \"Developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo gain-of-function with genetic epistasis, single lab, replicated by zebrafish studies\",\n      \"pmids\": [\"9133445\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"OP-1 (BMP-7) stimulates phosphorylation of SMAD5 in ROB-C26 osteoprogenitor cells; SMAD1, SMAD5, and SMAD8 (but not SMAD2/3) stably interact with kinase-deficient BMPR-IB after phosphorylation by BMPR-II kinase; a SMAD5-2SA (C-terminal serine-to-alanine) mutant acts as a dominant negative inhibitor of OP-1 signaling.\",\n      \"method\": \"In vitro kinase/phosphorylation assays, co-immunoprecipitation with BMPR-IB, dominant-negative transfection assays\",\n      \"journal\": \"Journal of cellular physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro phosphorylation assay, co-IP, and dominant-negative mutagenesis in a single study\",\n      \"pmids\": [\"9766532\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Antisense oligonucleotides to SMAD5 in human CD34+ hematopoietic progenitor cells reversed the inhibitory effects of TGF-β on myeloid, erythroid, megakaryocyte, and multilineage colony formation, demonstrating SMAD5 is required in the TGF-β inhibitory signaling pathway in primitive human hematopoiesis.\",\n      \"method\": \"Antisense oligonucleotide knockdown in primary CD34+ cells, semisolid colony formation assays\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function in primary human cells with defined functional readout, single lab, two antisense sequences used\",\n      \"pmids\": [\"9490674\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"The zebrafish smad5 mutant somitabun (sbntc24) carries a single amino-acid change in the L3 loop that converts SMAD5 into an antimorphic form inhibiting wild-type SMAD5 and related Smads; double mutant analyses place smad5 genetically downstream of bmp2b in dorsoventral patterning.\",\n      \"method\": \"ENU mutagenesis screen, double mutant analysis, RNA injection rescue experiments in zebrafish\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis confirmed by multiple alleles, double mutant, and rescue experiments\",\n      \"pmids\": [\"10207140\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Smad5 knockout (homozygous null) mice die between E9.5–E11.5 with defects in amnion, gut, heart, turning, craniofacial structures, and yolk sac vasculature, demonstrating essential in vivo roles for SMAD5 in embryonic and extraembryonic development downstream of BMP signaling.\",\n      \"method\": \"Homologous recombination gene targeting in ES cells; whole-mount in situ hybridization, histology\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — two independent Smad5 knockout studies (PMID 10079226, 10079220) with overlapping phenotypes\",\n      \"pmids\": [\"10079226\", \"10079220\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Loss of SMAD5 in mice causes enlarged blood vessels with decreased vascular smooth muscle cells and massive mesenchymal apoptosis, establishing SMAD5 as required for endothelium-mesenchyme interactions during angiogenesis.\",\n      \"method\": \"Homologous recombination knockout, histology, in vitro angiogenesis assay\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic loss-of-function with defined cellular phenotype, replicated across two independent knockout studies\",\n      \"pmids\": [\"10079220\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Smad5-deficient mouse embryos show defects in heart looping and embryonic turning (first signs of L-R asymmetry); lefty-1 expression is absent or very low, while nodal, lefty-2, and Pitx2 are expressed bilaterally, placing SMAD5 upstream of lefty-1 and the L-R axis determination cascade.\",\n      \"method\": \"Smad5 knockout mouse analysis, whole-mount in situ hybridization for lefty-1, lefty-2, nodal, Pitx2\",\n      \"journal\": \"Developmental biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic loss-of-function with molecular marker analysis establishing pathway position\",\n      \"pmids\": [\"10677256\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"SMAD5 null embryos have greatly reduced or absent primordial germ cells (PGCs), with some ectopic PGC-like cells in the amnion, phenocopying Bmp4 and Bmp8b mutants and establishing SMAD5 as a downstream mediator of BMP signaling in PGC generation and localization.\",\n      \"method\": \"Oct4 whole-mount in situ hybridization, alkaline phosphatase staining in Smad5-/- mice\",\n      \"journal\": \"Mechanisms of development\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic loss-of-function with two orthogonal PGC markers, single lab\",\n      \"pmids\": [\"11404080\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"The MH1 domain of SMAD5 binds a consensus sequence TGTGC; unlike SMAD1 and SMAD8, SMAD5 also binds the canonical Smad-binding element (SBE: GTCTAGAC) at a level similar to SMAD3 and SMAD4, revealing unique DNA-binding properties among BMP-R-Smads.\",\n      \"method\": \"SELEX (random oligonucleotide selection) with GST-Smad5 MH1 fusion protein; mutational analysis of SBE binding\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro binding assay with mutagenesis, single lab\",\n      \"pmids\": [\"11527422\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"BMP4 directs SMAD5 phosphorylation, nuclear translocation, and specific transcriptional responses in human hematopoietic CD34+ cells; antisense inhibition of SMAD5 significantly reduces BMP4-induced erythroid differentiation (BFU-E expansion and glycophorin-A+ cells) without affecting granulocyte-macrophage lineages.\",\n      \"method\": \"Protein phosphorylation assays, nuclear translocation assays, antisense oligonucleotide knockdown, colony formation assays in primary human CD34+ cells\",\n      \"journal\": \"Blood cells, molecules & diseases\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (phosphorylation, translocation, functional colony assay) in primary human cells, single lab\",\n      \"pmids\": [\"12064918\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"SMAD5-deficient yolk sacs contain elevated high-proliferative potential colony-forming cells (HPP-CFCs) with enhanced self-renewal and decreased sensitivity to TGF-β1 inhibition; Smad5-/- embryoid bodies show increased HPP-CFCs in a gene-dosage dependent manner, establishing SMAD5 as a negative regulator of primitive hematopoietic progenitors.\",\n      \"method\": \"Smad5 knockout mouse yolk sac colony assays, ES cell differentiation/embryoid body assays, gene dosage analysis\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic loss-of-function in two in vivo/in vitro systems, single lab\",\n      \"pmids\": [\"12393578\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"H. pylori cagPAI-positive strains upregulate SMAD5 mRNA in gastric epithelial cells; RNAi knockdown of SMAD5 completely inhibits H. pylori-induced apoptosis, establishing SMAD5 as a required mediator of H. pylori-induced apoptosis.\",\n      \"method\": \"cDNA microarray, RT-PCR, Northern blot, siRNA knockdown with apoptosis assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — siRNA loss-of-function with defined apoptosis phenotype, multiple expression methods, single lab\",\n      \"pmids\": [\"12473652\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Cbfa1 (RUNX2) induces osteoblastic differentiation in C2C12 cells without forming a complex with SMAD1 or SMAD5; however, interactions with SMAD1/SMAD5 enhance Cbfa1 osteogenic actions. Smad6 overexpression (preventing Cbfa1-Smad1/5 interaction) did not block Cbfa1-induced osteocalcin promoter transactivation.\",\n      \"method\": \"Co-immunoprecipitation, reporter gene assays, dominant-negative Cbfa1 and Smad6 overexpression in C2C12 cells\",\n      \"journal\": \"Bone\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP and functional reporter assays with multiple constructs, single lab\",\n      \"pmids\": [\"12151083\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"The 5' UTR of human SMAD5 mRNA contains an internal ribosome entry site (IRES) located within 100 nt of the 3' end of the 5'UTR, which shows cell-type specificity (more active in C2C12 than 293T) and requires a nuclear event for efficient translation initiation.\",\n      \"method\": \"Dicistronic reporter assays in cell lines, transfection of in vitro transcripts vs. DNA constructs\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro and cell-based IRES assays with multiple constructs, single lab\",\n      \"pmids\": [\"12087169\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Smurf1 promotes ubiquitin-mediated degradation of endogenous SMAD5 (selectively over SMAD2, SMAD3, SMAD7); elevated Smurf1 reduces SMAD5 protein levels and blocks BMP-induced osteogenic conversion of C2C12 cells; re-expression of SMAD5 from an exogenous source restores BMP osteogenic response. Smurf1 depletion by siRNA confirms its requirement for myogenic differentiation.\",\n      \"method\": \"Smurf1 overexpression, siRNA knockdown, SMAD5 rescue experiments, Western blot for protein levels in C2C12 cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal approaches (OE, KD, rescue), selectivity demonstrated across multiple Smads, single lab with strong controls\",\n      \"pmids\": [\"12871975\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"BMP4 stimulation of cultured spermatogonia induces SMAD4/5 nuclear translocation and formation of a DNA-binding complex with transcriptional coactivator p300/CBP; BMP4 also induces Kit expression and mitogenic/differentiative effects, with SMAD5 expressed specifically in spermatogonia downstream of Sertoli cell-derived BMP4.\",\n      \"method\": \"Immunofluorescence for SMAD4/5 nuclear translocation, p300/CBP co-IP, in vitro BMP4 stimulation of spermatogonia\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP and nuclear translocation assays with functional differentiation readout, single lab\",\n      \"pmids\": [\"12857787\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"BMP4/SMAD5-dependent signaling, regulated by hypoxia, initiates differentiation and expansion of stress erythroid progenitors in the adult spleen in response to acute anemia; flexed-tail (f) mutant mice carrying a Smad5 mutation cannot mount this stress erythropoiesis response.\",\n      \"method\": \"Genetic mapping identifying f mutation in Madh5/Smad5, in vivo anemia model, progenitor colony assays\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic identification of Smad5 as the f locus, in vivo functional assays, replicated by multiple subsequent studies\",\n      \"pmids\": [\"15591122\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"In developing cerebellum, Bmp2 signals through SMAD5 (not SMAD1) specifically in newly differentiated granule neurons; only SMAD5 is phosphorylated in vivo by Bmp2 in granule cells, and SMAD5 overexpression alone is sufficient to induce granule cell differentiation even in the presence of Shh, antagonizing Shh-mediated proliferation.\",\n      \"method\": \"In vivo phosphorylation assays, SMAD5 overexpression in cerebellar granule cell cultures, Shh proliferation assay\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo phosphorylation and gain-of-function with defined cellular phenotype, single lab\",\n      \"pmids\": [\"15197161\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"An Id1 promoter-derived BRE (Smad1/5-specific response element) drives reporter activity in mouse ES cells and embryos where BMP/Smad1/5 signaling is active; used to map spatio-temporal transcriptional activity of SMAD1/5 in vivo, demonstrating autocrine BMP signaling in ES cells.\",\n      \"method\": \"Transgenic reporter mouse lines, luciferase/β-galactosidase assays in ES cells and chimeric embryos\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo reporter assay with multiple independent transgenic lines, single lab\",\n      \"pmids\": [\"15331632\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Loss of SMAD5 in cardiomyocytes (from ES cell differentiation) causes abnormal swollen mitochondria, reduced mitochondrial membrane potential (ΔΨm), cytochrome c leakage, and elevated p53, p21, and caspase-3, indicating SMAD5 protects cardiomyocytes from mitochondria-dependent apoptosis.\",\n      \"method\": \"ES cell differentiation from Smad5 null cells, electron microscopy, JC-1 mitochondrial potential assay, cytochrome c fractionation, Western blot\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple mechanistic assays in defined genetic system, single lab\",\n      \"pmids\": [\"15878335\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Smad5 deletion in cardiomyocytes (via Sm22-Cre) results in decreased cardiac contractility (enlarged LV internal diameter, reduced fractional shortening) without cardiac hypertrophy, establishing a cell-autonomous requirement for SMAD5 in cardiac homeostasis; deletion in endothelial or vascular smooth muscle cells alone does not affect vasculature.\",\n      \"method\": \"Cre-loxP conditional knockout, echocardiography, isolated cardiomyocyte fractional shortening, treadmill test\",\n      \"journal\": \"The American journal of pathology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — conditional KO with multiple functional readouts, single lab\",\n      \"pmids\": [\"17456754\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"In zebrafish, Smad1 and Smad5 have distinct and even opposite roles in embryonic hematopoiesis: Smad5 depletion causes defects in primitive erythropoiesis but normal macrophage numbers, while Smad1 depletion increases erythrocytes but impairs macrophages; Smad5 cannot rescue Smad1 loss-of-function, indicating inherently distinct activities. Microarray shows Smad5 uniquely regulates the BMP signaling pathway itself.\",\n      \"method\": \"Morpholino knockdown in zebrafish, rescue experiments, microarray analysis\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal loss-of-function with cross-rescue experiments, microarray, single lab\",\n      \"pmids\": [\"17761518\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"The WW2 domain of Smurf1 physically interacts with the PPXY motif in the linker region of SMAD5 (and SMAD1, SMAD6); deletion of the WW2 domain abolishes Smurf1 binding to Smads and its ubiquitination activity on Smad1 in an in vitro ubiquitination assay.\",\n      \"method\": \"Pull-down with purified recombinant proteins, WW2 domain deletion mutants, in vitro ubiquitination assay\",\n      \"journal\": \"Journal of biomolecular structure & dynamics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with recombinant proteins and ubiquitination assay, single lab\",\n      \"pmids\": [\"17676934\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Smad5 and Gata2 cooperate to induce Eklf (KLF1) expression in hematopoietic progenitors prior to erythroid commitment; upon erythroid commitment, Gata1 takes over regulation of Eklf, establishing a stage-dependent switch involving SMAD5 in lineage fate decisions.\",\n      \"method\": \"Transgenic reporter assays in ES cell differentiation and fetal liver, in vivo Smad5 loss-of-function in embryoid bodies, ChIP-based binding studies\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (reporter, ChIP, loss-of-function), single lab\",\n      \"pmids\": [\"18448565\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"BMP4/Smad5-dependent stress erythropoiesis pathway expands stress erythroid progenitors in the fetal liver; defects in BMP4/Smad5 signaling preferentially impair expansion of stress (not steady-state) erythroid progenitors, causing fetal anemia in flexed-tail mutants.\",\n      \"method\": \"f/f mutant (Smad5 mutation) analysis, fetal liver progenitor assays, BFU-E colony assays\",\n      \"journal\": \"Developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic model with defined progenitor phenotype, single lab, consistent with prior stress erythropoiesis work\",\n      \"pmids\": [\"18374325\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"In DLBCL, a non-canonical TGF-β1/SMAD5 signaling module is active; miR-155 directly targets SMAD5 3'UTR; miR-155 overexpression renders cells resistant to TGF-β1 and BMP growth inhibition via defective p21 induction and impaired cell cycle arrest; RNAi-based SMAD5 knockdown recapitulates these effects in vitro and in vivo.\",\n      \"method\": \"miR-155 overexpression and RNAi knockdown of SMAD5, luciferase reporter assay, cell cycle assays, in vivo xenograft\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genome-wide identification plus multiple functional validation methods (luciferase, RNAi, in vivo), single lab with comprehensive mechanistic follow-up\",\n      \"pmids\": [\"20133617\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Loss of SMAD5 in intestinal epithelial cells (Smad5ΔIEC) causes hypermigration, loss of E-cadherin from the apical junctional complex (displaced to cytoplasm), and deregulated claudin-1/claudin-2 expression, leading to increased susceptibility to DSS-induced colitis and impaired wound healing.\",\n      \"method\": \"Intestinal epithelium-specific Cre-loxP knockout, immunofluorescence, Western blot, DSS colitis model\",\n      \"journal\": \"American journal of physiology. Gastrointestinal and liver physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — conditional KO with multiple molecular and functional readouts, single lab\",\n      \"pmids\": [\"21212325\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"BMP-activated SMAD5 antagonizes Nodal signaling by interfering with the Nodal-Smad2/4-Foxh1 autoregulatory pathway through formation of an unusual BMP4-induced Smad complex containing Smad2 and Smad5; loss of Smad5 in mouse embryos results in ectopic Nodal expression and ectopic primitive streak formation in the amnion.\",\n      \"method\": \"Smad5 knockout mouse analysis, cell culture BMP4 stimulation with co-immunoprecipitation of Smad2/Smad5 complex, quantitative gene expression analysis\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic loss-of-function combined with co-IP demonstrating novel Smad2/Smad5 complex and mechanistic pathway interference\",\n      \"pmids\": [\"22912414\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"miR-155 expression in DLBCL blocks TGF-β1-mediated activation of retinoblastoma protein (RB) by suppressing SMAD5, which reduces TGF-β1-induced transcription of p15 and p21, sustaining RB phosphorylation and inactivity; miR-155 KO mice show elevated SMAD5 in mature B cells with heightened TGF-β1 sensitivity and G0/G1 arrest.\",\n      \"method\": \"miR-155 KO mouse analysis, DLBCL cell lines with ectopic miR-155 expression, genetic knockdown of SMAD5/p15/p21, cell cycle analysis\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo KO plus DLBCL cell genetic dissection, multiple orthogonal methods establishing the miR-155/SMAD5/p15/p21/RB circuit\",\n      \"pmids\": [\"24136167\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"In zebrafish, smad1 and smad9 act redundantly downstream of smad5 to mediate ventral specification: smad5 knockdown can be rescued by smad1 or smad9 overexpression, but smad5 overexpression cannot rescue smad1+smad9 double knockdown; smad1 and smad9 are direct transcriptional targets of Smad5.\",\n      \"method\": \"Morpholino knockdown in zebrafish, rescue experiments with mRNA injection, transcriptional target analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis by reciprocal rescue experiments, single lab\",\n      \"pmids\": [\"24488494\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Crystal structure of the SMAD5 MH1 domain in complex with the GC-rich sequence reveals that the same β-hairpin contacts both GC-rich and SBE DNA but with different interaction modes; a composite DNA sequence structure shows modular binding, with spacer length affecting MH1 assembly.\",\n      \"method\": \"X-ray crystallography of SMAD5 MH1 domain–DNA complexes (GC-rich, SBE, and composite sequences)\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structures providing atomic resolution of DNA recognition mechanism with multiple DNA sequence contexts\",\n      \"pmids\": [\"26304548\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"SMAD5 responds to intracellular pH (pHi) changes: increased pHi (cold, basic, hypertonic conditions) promotes proton dissociation from charged clusters in the MH1 domain, driving nuclear-to-cytoplasmic relocalization; decreased pHi blocks nuclear export causing nuclear accumulation. This nucleocytoplasmic shuttling is independent of BMP signaling, C-terminal phosphorylation, and Smad4. Cytoplasmic SMAD5 physically interacts with hexokinase 1 and accelerates glycolysis; ablation of SMAD5 causes dysregulation of bioenergetic homeostasis.\",\n      \"method\": \"Live-cell imaging of SMAD5 localization under pH/osmotic perturbations, co-IP with hexokinase 1, rescue experiments with cytoplasmic-only SMAD5, metabolic assays in human pluripotent stem cell differentiation model\",\n      \"journal\": \"Cell research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (live imaging, co-IP, functional metabolic rescue, domain mutagenesis) in a single comprehensive study\",\n      \"pmids\": [\"28675158\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Hepatocyte-specific deletion of SMAD1/5 (and SMAD1/5/8) causes severe hepcidin deficiency and iron overload; EGF fails to suppress hepcidin in SMAD1/5 knockout hepatocytes, establishing a requirement for SMAD1/5 in EGF-mediated hepcidin regulation; inflammatory hepcidin induction is preserved, demonstrating pathway specificity.\",\n      \"method\": \"Hepatocyte-specific Cre-loxP knockout, serum hepcidin and iron measurements, EGF/LPS challenge\",\n      \"journal\": \"Hepatology (Baltimore, Md.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — conditional KO with specific ligand challenges distinguishing pathway requirements, single lab\",\n      \"pmids\": [\"31127639\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"LncRNA TUG1 directly binds the 50–90 aa region of SMAD5 (MH1 domain) and blocks nuclear translocation of phosphorylated SMAD5 after irradiation, suppressing osteogenic signaling in bone marrow MSCs despite increased SMAD5 phosphorylation.\",\n      \"method\": \"RNA immunoprecipitation (RIP), serial SMAD5 deletion constructs identifying binding region, immunofluorescence for p-SMAD5 nuclear translocation, osteogenic differentiation assays\",\n      \"journal\": \"Theranostics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RIP with domain-mapping deletions and functional nuclear translocation assay, single lab\",\n      \"pmids\": [\"31149038\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"BMP signaling through a conserved ACVR2A/SMAD1/5 axis in the uterine endometrium is required for endometrial receptivity; SMAD1/5 conditional knockout (PR-cre) causes cystic endometrial glands, hyperproliferative epithelium during the implantation window, and impaired apicobasal transformation preventing embryo implantation. ACVR2B is dispensable.\",\n      \"method\": \"Conditional knockout (PR-Cre) for SMAD1/5, ACVR2A, and ACVR2B; histology, fertility assays in mice\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple conditional knockouts with specific receptor identification (ACVR2A vs ACVR2B), defined cellular and functional phenotypes\",\n      \"pmids\": [\"34099644\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"BMP9 causes phosphorylation of SMAD1 and SMAD5, formation of a SMAD4/SMAD1/SMAD5 complex, and nuclear translocation of this complex in cultured basal forebrain cells, establishing the canonical BMP signaling pathway for BMP9 in cholinergic neuron differentiation.\",\n      \"method\": \"Phosphorylation assays, co-immunoprecipitation, nuclear translocation assays in primary basal forebrain cultures\",\n      \"journal\": \"Brain research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple biochemical assays in primary cells, single lab\",\n      \"pmids\": [\"16626664\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"An intronic poly(T) element in intron 4 of Smad5 is mutated in flexed-tail (f/f) mice; loss of 1–2 T residues causes tissue-specific (spleen-predominant) splicing defects throughout Smad5, generating misspliced mRNAs including one encoding a truncated inhibitory Smad5 protein.\",\n      \"method\": \"Sequencing of f/f mouse Smad5 intron 4, RT-PCR analysis of misspliced isoforms, tissue-specific splicing analysis\",\n      \"journal\": \"Mammalian genome\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic identification of the regulatory mutation with functional consequences on splicing, single lab\",\n      \"pmids\": [\"18060457\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"SMAD5 knockdown in L6 myotubes decreases Akt2 expression and serine phosphorylation and reduces insulin-induced glucose uptake while increasing Ship2 expression; ChIP demonstrates SMAD5 binding to the Akt2 gene, which is decreased by dexamethasone treatment.\",\n      \"method\": \"siRNA knockdown of SMAD5, glucose uptake assays, Western blot, chromatin immunoprecipitation (ChIP) for Akt2 gene\",\n      \"journal\": \"Molecular and cellular endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP plus loss-of-function with functional metabolic readout, single lab\",\n      \"pmids\": [\"20079400\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"BMP-2-induced Dlx3 expression in osteoblasts requires both SMAD5 and p38; SMAD5 binds to two TGTCT Smad-binding elements in the Dlx3 promoter region (−698 to −368) as shown by EMSA and ChIP; p38 activation is necessary for BMP-2-induced SMAD5 phosphorylation and nuclear translocation.\",\n      \"method\": \"EMSA, ChIP assay, promoter deletions/mutagenesis, Smad5 knockdown, p38 inhibitor, Western blot in MC3T3-E1 cells\",\n      \"journal\": \"Journal of cellular physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — EMSA/ChIP plus functional mutagenesis defining binding sites, single lab\",\n      \"pmids\": [\"24647893\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Jun activation domain-binding protein 1 (Jab1) physically interacts with SMAD5 in chondrocytes (identified by yeast 2-hybrid, confirmed by co-IP); Jab1 overexpression attenuates BMP-dependent transcriptional responses, acting as a negative modulator of BMP signaling.\",\n      \"method\": \"Yeast 2-hybrid screen of cartilage cDNA library, co-immunoprecipitation, BMP-responsive transcriptional reporter assay\",\n      \"journal\": \"Arthritis and rheumatism\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — y2h discovery confirmed by co-IP with functional transcriptional assay, single lab\",\n      \"pmids\": [\"17133595\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"SMAD5 is a receptor-regulated (R-Smad) intracellular signal transducer that is directly phosphorylated on C-terminal serines by BMP type I receptors (BMPR-IA/IB) upon ligand stimulation, whereupon it heterodimerizes with SMAD4 and translocates to the nucleus to regulate transcription via its MH1 domain (which binds GC-rich elements and the canonical SBE); it is targeted for ubiquitin-mediated proteasomal degradation by Smurf1 via a PPXY-WW2 domain interaction; in addition to canonical BMP signaling, SMAD5 participates in a non-canonical TGF-β1 module, responds to intracellular pH changes through charge-dependent nucleocytoplasmic shuttling (independent of phosphorylation and SMAD4) to regulate glycolysis via hexokinase 1, and is essential in vivo for embryonic angiogenesis, primordial germ cell specification, left-right axis determination, stress erythropoiesis, endometrial receptivity, intestinal epithelial integrity, and cardiac homeostasis.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"SMAD5 is a receptor-regulated R-Smad that transduces BMP signals from the cell surface to the nucleus to control developmental cell-fate decisions and tissue homeostasis [#0, #6]. Upon BMP-2/BMP-7/BMP-9 ligand stimulation, SMAD5 is serine-phosphorylated at its C-terminus through direct association with BMP type I receptors (BMPR-IA/IB), an event dependent on BMPR-II kinase, after which it binds SMAD4 (DPC4) and the complex translocates to the nucleus; C-terminal serine-to-alanine or G419S point mutants act as dominant negatives that block BMP responses [#0, #3, #37]. In the nucleus, the SMAD5 MH1 domain recognizes GC-rich elements (consensus TGTGC) and, uniquely among BMP R-Smads, also the canonical SBE; crystal structures show a single \\u03b2-hairpin engages both DNA modes, and SMAD5 directly occupies target promoters such as Dlx3 and Akt2 and recruits the p300/CBP coactivator [#10, #32, #40, #17]. SMAD5 output is constrained by multiple negative regulators: Smurf1 binds the SMAD5 linker PPXY motif via its WW2 domain and targets SMAD5 for ubiquitin-mediated proteasomal degradation [#16, #24]; miR-155 represses the SMAD5 3'UTR to disable TGF-\\u03b21/BMP growth arrest in DLBCL through the p15/p21/RB axis [#27, #30]; and Jab1 and lncRNA TUG1 antagonize nuclear SMAD5 activity [#41, #35]. Genetically, SMAD5 acts downstream of BMP2b/BMP4 in dorsoventral and left-right patterning, and is essential in vivo for yolk-sac angiogenesis, primordial germ cell specification, lefty-1-dependent L-R axis determination, stress erythropoiesis, endometrial receptivity, intestinal epithelial integrity, and cardiac homeostasis [#5, #6, #7, #8, #9, #18, #36, #28, #22]. Beyond canonical signaling, SMAD5 forms an unusual BMP4-induced SMAD2/SMAD5 complex that antagonizes Nodal signaling [#29], and undergoes phosphorylation-, SMAD4-independent nucleocytoplasmic shuttling driven by intracellular pH, with cytoplasmic SMAD5 binding hexokinase 1 to accelerate glycolysis [#33].\",\n  \"teleology\": [\n    {\n      \"year\": 1997,\n      \"claim\": \"Established SMAD5 as a downstream intracellular mediator of BMP signaling, resolving whether overexpression alone could mimic ligand-driven osteoblast conversion and myogenic suppression.\",\n      \"evidence\": \"Wild-type and dominant-negative SMAD5 transfection with reporter and alkaline phosphatase assays in C2C12 cells, and mRNA injection epistasis in Xenopus\",\n      \"pmids\": [\"9299554\", \"9133445\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Did not show direct receptor phosphorylation of endogenous SMAD5\", \"SMAD4 requirement inferred from epistasis rather than biochemistry\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Defined the biochemical activation step: BMP type I receptors directly phosphorylate SMAD5 on C-terminal serines, triggering SMAD4 binding and nuclear translocation.\",\n      \"evidence\": \"Co-IP with BMPR-Ia/Ib, serine phosphorylation and in vitro kinase assays, and C-terminal serine/G419S dominant-negative mutants in C2C12 and ROB-C26 cells\",\n      \"pmids\": [\"9442019\", \"9766532\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Exact phosphoacceptor residues not enumerated at this stage\", \"Stoichiometry and selectivity of receptor-Smad pairing not fully resolved\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Demonstrated SMAD5 is functionally required in primary human hematopoiesis as a transducer of TGF-\\u03b2 inhibitory signaling.\",\n      \"evidence\": \"Antisense oligonucleotide knockdown of SMAD5 in CD34+ progenitors with colony formation assays\",\n      \"pmids\": [\"9490674\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Antisense specificity vs other R-Smads not excluded\", \"Direct transcriptional targets in hematopoietic cells not identified\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Placed SMAD5 genetically downstream of BMP2b/BMP4 in dorsoventral patterning and established its essential in vivo developmental roles.\",\n      \"evidence\": \"Zebrafish somitabun antimorph genetics and double-mutant epistasis, plus two independent Smad5 knockout mouse studies with histology and in situ hybridization\",\n      \"pmids\": [\"10207140\", \"10079226\", \"10079220\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Tissue-specific contributions not separable in global null\", \"Molecular targets driving each phenotype not defined\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Identified SMAD5 as required for endothelium-mesenchyme interactions in angiogenesis, explaining the vascular component of the null phenotype.\",\n      \"evidence\": \"Knockout mouse histology showing enlarged vessels, reduced VSMCs, and mesenchymal apoptosis, plus in vitro angiogenesis assay\",\n      \"pmids\": [\"10079220\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cell-autonomy of the vascular defect not resolved here\", \"Downstream effectors of mesenchymal survival unknown\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Positioned SMAD5 upstream of lefty-1 in the left-right axis determination cascade.\",\n      \"evidence\": \"Whole-mount in situ hybridization for lefty-1, lefty-2, nodal, and Pitx2 in Smad5 knockout embryos\",\n      \"pmids\": [\"10677256\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct vs indirect regulation of lefty-1 not established\", \"Mechanism linking SMAD5 to asymmetric gene expression unknown\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Established SMAD5 as a BMP-pathway mediator of primordial germ cell generation and localization.\",\n      \"evidence\": \"Oct4 in situ and alkaline phosphatase staining in Smad5-null embryos, phenocopying Bmp4/Bmp8b mutants\",\n      \"pmids\": [\"11404080\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Cell-intrinsic vs extrinsic requirement in PGC precursors unresolved\", \"Target genes in PGC specification not defined\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Defined the DNA-binding specificity of the SMAD5 MH1 domain, distinguishing it from other BMP R-Smads.\",\n      \"evidence\": \"SELEX with GST-SMAD5 MH1 fusion and mutational SBE binding analysis\",\n      \"pmids\": [\"11527422\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"In vitro binding not linked to specific endogenous promoters\", \"Structural basis of dual recognition not yet known\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Extended SMAD5 function into lineage-specific hematopoietic differentiation and progenitor self-renewal control.\",\n      \"evidence\": \"BMP4-induced phosphorylation/translocation with antisense knockdown in CD34+ cells, and Smad5-null yolk-sac/embryoid-body colony assays with gene-dosage analysis\",\n      \"pmids\": [\"12064918\", \"12393578\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of erythroid vs myeloid selectivity unclear\", \"Direct targets controlling progenitor self-renewal unidentified\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Uncovered translational and apoptotic dimensions of SMAD5 regulation, including a cell-type-specific 5'UTR IRES and a requirement in H. pylori-induced apoptosis.\",\n      \"evidence\": \"Dicistronic IRES reporter assays in cell lines, and cDNA microarray with siRNA knockdown and apoptosis assays in gastric epithelial cells\",\n      \"pmids\": [\"12087169\", \"12473652\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"IRES trans-acting factors not identified\", \"Apoptotic effectors downstream of SMAD5 in H. pylori response unknown\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Defined the degradation mechanism controlling SMAD5 protein levels via Smurf1-mediated ubiquitination.\",\n      \"evidence\": \"Smurf1 overexpression, siRNA, and SMAD5 rescue with Western blot of endogenous SMAD5 in C2C12 cells, plus p300/CBP co-IP showing coactivator recruitment in spermatogonia\",\n      \"pmids\": [\"12871975\", \"12857787\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Ubiquitin chain linkage and acceptor lysines not mapped\", \"Regulation of Smurf1-SMAD5 engagement not defined\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Identified the flexed-tail Smad5 locus as the genetic basis of stress erythropoiesis and revealed SMAD5-specific functions in neuronal differentiation and BMP-responsive transcription in vivo.\",\n      \"evidence\": \"Genetic mapping of the f mutation to Smad5 with in vivo anemia and progenitor assays, in vivo phosphorylation in cerebellar granule cells, and Id1-BRE transgenic reporters\",\n      \"pmids\": [\"15591122\", \"15197161\", \"15331632\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Why stress but not steady-state erythropoiesis requires SMAD5 not mechanistically resolved\", \"SMAD1/SMAD5 functional divergence basis unclear\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Linked SMAD5 to protection of cardiomyocytes from mitochondria-dependent apoptosis, foreshadowing a cardiac homeostatic role.\",\n      \"evidence\": \"Smad5-null ES-derived cardiomyocytes analyzed by EM, JC-1 potential, cytochrome c fractionation, and p53/p21/caspase-3 Western blot\",\n      \"pmids\": [\"15878335\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Transcriptional targets controlling mitochondrial integrity unidentified\", \"In vitro model not yet validated in vivo at this step\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Established cell-autonomous requirement of SMAD5 in cardiac contractility and identified Jab1 as a negative modulator of SMAD5-dependent BMP transcription.\",\n      \"evidence\": \"Sm22-Cre conditional knockout with echocardiography and cardiomyocyte fractional shortening, and yeast-2-hybrid/co-IP identifying Jab1 with reporter assays\",\n      \"pmids\": [\"17456754\", \"17133595\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular basis of contractility defect undefined\", \"Mechanism of Jab1 antagonism not resolved\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Resolved the physical basis of Smurf1 recognition and demonstrated non-redundant SMAD5 functions distinct from SMAD1.\",\n      \"evidence\": \"Recombinant pull-downs mapping Smurf1 WW2 to the SMAD5 linker PPXY with in vitro ubiquitination, and reciprocal morpholino knockdown/cross-rescue plus microarray in zebrafish\",\n      \"pmids\": [\"17676934\", \"17761518\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural detail of WW2-PPXY interface absent\", \"Sequence determinants of SMAD5-specific output unknown\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Identified the flexed-tail intronic regulatory mutation causing tissue-specific Smad5 missplicing.\",\n      \"evidence\": \"Sequencing of Smad5 intron 4 poly(T) and RT-PCR of misspliced isoforms in f/f mice\",\n      \"pmids\": [\"18060457\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Splicing factor reading the poly(T) element unidentified\", \"Functional contribution of the truncated inhibitory isoform not quantified\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Placed SMAD5 within a transcriptional network controlling erythroid lineage commitment through cooperative regulation of Eklf/KLF1.\",\n      \"evidence\": \"Transgenic reporters, embryoid-body loss-of-function, and ChIP-based binding in hematopoietic differentiation\",\n      \"pmids\": [\"18448565\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct SMAD5 occupancy at Eklf vs cooperative effects not fully separated\", \"Stage switch from Gata2 to Gata1 mechanism incomplete\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Established a tumor-suppressive SMAD5 circuit silenced by miR-155 in DLBCL and a metabolic transcriptional role at the Akt2 gene.\",\n      \"evidence\": \"miR-155 overexpression/RNAi with 3'UTR luciferase, cell cycle and xenograft assays in DLBCL, and SMAD5 knockdown with ChIP at Akt2 and glucose uptake in L6 myotubes\",\n      \"pmids\": [\"20133617\", \"20079400\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct SMAD5 transcriptional targets mediating p21 induction not enumerated\", \"Metabolic Akt2 regulation not validated in vivo\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Revealed a non-canonical SMAD5 mechanism: a BMP4-induced SMAD2/SMAD5 complex that antagonizes Nodal signaling to restrain ectopic primitive streak formation.\",\n      \"evidence\": \"Smad5 knockout embryo analysis with co-IP of the Smad2/Smad5 complex and quantitative gene expression\",\n      \"pmids\": [\"22912414\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural arrangement of the atypical complex unknown\", \"Promoter-level interference with Foxh1 not mapped\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Detailed the miR-155/SMAD5/p15/p21/RB circuit controlling B-cell cycle arrest in vivo.\",\n      \"evidence\": \"miR-155 knockout mice and DLBCL lines with genetic SMAD5/p15/p21 knockdown and cell cycle analysis\",\n      \"pmids\": [\"24136167\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct vs indirect SMAD5 control of p15/p21 promoters not fully dissected\", \"Contribution to lymphomagenesis in patients not addressed\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Clarified the genetic architecture downstream of SMAD5 and the cooperating signals required for its transcriptional targets.\",\n      \"evidence\": \"Zebrafish reciprocal rescue placing smad1/smad9 as redundant SMAD5 targets, and EMSA/ChIP plus p38 inhibition defining SMAD5 binding at the Dlx3 promoter in MC3T3-E1 cells\",\n      \"pmids\": [\"24488494\", \"24647893\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of p38-dependent SMAD5 phosphorylation not detailed\", \"Generality of the SMAD5-driven feed-forward loop beyond fish unknown\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Provided the atomic-resolution basis for SMAD5 MH1 recognition of both GC-rich and SBE DNA.\",\n      \"evidence\": \"X-ray crystallography of SMAD5 MH1\\u2013DNA complexes across GC-rich, SBE, and composite sequences\",\n      \"pmids\": [\"26304548\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full-length SMAD5 trimer assembly on chromatin not resolved\", \"Coactivator engagement in the structural context not captured\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Uncovered a phosphorylation- and SMAD4-independent SMAD5 function: pH-driven nucleocytoplasmic shuttling that couples cytoplasmic SMAD5 to hexokinase 1 and glycolysis.\",\n      \"evidence\": \"Live-cell imaging under pH/osmotic perturbation, hexokinase 1 co-IP, cytoplasmic-only rescue, and metabolic assays in human pluripotent stem cells\",\n      \"pmids\": [\"28675158\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological triggers of pHi shifts in vivo not defined\", \"How cytoplasmic SMAD5 modulates HK1 catalysis mechanistically unknown\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Extended SMAD1/5 function to iron homeostasis and additional layers of SMAD5 regulation via lncRNA TUG1.\",\n      \"evidence\": \"Hepatocyte-specific SMAD1/5 knockout with hepcidin/iron measurements and EGF/LPS challenge, and RIP plus domain mapping showing TUG1 blocks p-SMAD5 nuclear translocation\",\n      \"pmids\": [\"31127639\", \"31149038\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"SMAD5-specific vs SMAD1 contribution to hepcidin not isolated\", \"Structural basis of TUG1 binding to the MH1 region not resolved\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Identified a conserved ACVR2A/SMAD1/5 axis required for endometrial receptivity and embryo implantation.\",\n      \"evidence\": \"PR-Cre conditional knockouts of SMAD1/5, ACVR2A, and ACVR2B with histology and fertility assays in mice\",\n      \"pmids\": [\"34099644\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"SMAD5-specific role separate from SMAD1 not isolated\", \"Transcriptional targets driving apicobasal transformation undefined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How SMAD5's canonical transcriptional output, its degradation and RNA-mediated regulation, and its non-canonical pH-sensing/metabolic and Nodal-antagonizing functions are integrated within a single cell remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified model linking nuclear transcriptional and cytoplasmic metabolic SMAD5 pools\", \"Direct genome-wide SMAD5 target set in mammalian tissues not defined\", \"Determinants of SMAD5 vs SMAD1 functional specialization unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [10, 32, 40, 39]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [0, 17, 40, 25]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0, 3, 37]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0, 17, 33, 35]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [33]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 3, 29, 37]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [5, 6, 8, 9, 36]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [27, 30]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [16, 24]}\n    ],\n    \"complexes\": [\n      \"SMAD5\\u2013SMAD4 complex\",\n      \"BMP4-induced SMAD2\\u2013SMAD5 complex\"\n    ],\n    \"partners\": [\n      \"SMAD4\",\n      \"BMPR1A\",\n      \"BMPR1B\",\n      \"SMURF1\",\n      \"HK1\",\n      \"SMAD2\",\n      \"EP300\",\n      \"JAB1\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"tie","faith_supported":6,"faith_total":6,"faith_pct":100.0}}