{"gene":"INHBB","run_date":"2026-06-10T01:55:23","timeline":{"discoveries":[{"year":2000,"finding":"The INHBB-encoded βB subunit can functionally substitute for the βA subunit (INHBA) in vivo: knock-in of Inhbb into the Inhba locus rescued craniofacial defects of Inhba-null mice, demonstrating functional interchangeability of activin A and activin B when expressed from the same locus. Novel phenotypes (somatic, testicular, genital, hair growth) emerged in a dosage-dependent manner, revealing distinct bioactivities of activin B.","method":"Genetic knock-in (insertion of Inhbb coding sequence into the Inhba locus); phenotypic rescue analysis in mice","journal":"Nature genetics","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vivo genetic rescue with defined phenotypic readouts, replicated across multiple allele dosages in a rigorous mouse genetics study","pmids":["10932194"],"is_preprint":false},{"year":2015,"finding":"RNAi-mediated knockdown of INHBB in mouse granulosa cells arrested cells in G1 phase, increased apoptosis (downregulating Cyclin D1, Cyclin E, Bcl2; upregulating Bax), and decreased estradiol and progesterone concentrations via reduced CYP19A1 and CYP11A1 expression, establishing a role for INHBB in granulosa cell cycle progression, survival, and steroidogenesis.","method":"RNAi knockdown with shRNA vectors; Western blot, flow cytometry, ELISA, qRT-PCR","journal":"The Journal of reproduction and development","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean KD with defined cellular phenotypes using multiple orthogonal methods (flow cytometry, ELISA, Western blot), single lab","pmids":["26063610"],"is_preprint":false},{"year":2017,"finding":"Menin represses Inhbb transcription by recruiting Ezh2 to the Inhbb promoter via an indirect mechanism involving Akt phosphorylation, promoting H3K27me3 repressive marks at the Inhbb locus. Loss of Menin results in de-repression of Inhbb/activin B expression in vivo and in vitro.","method":"Animal models (Men1 KO), cell lines, ChIP (Menin binding to Inhbb promoter), H3K27me3 chromatin analysis, pharmacological modulation of Akt","journal":"Biochimica et biophysica acta. Gene regulatory mechanisms","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP and H3K27me3 analysis with in vivo and in vitro validation, single lab, multiple orthogonal approaches","pmids":["28215965"],"is_preprint":false},{"year":2020,"finding":"Sox9 induces INHBB expression by directly binding to its enhancer, leading to secretion of activin B from hepatoma cells, which activates surrounding hepatic stellate cells through activin B/Smad signaling, promoting liver fibrosis and tumor metastasis.","method":"Gain- and loss-of-function experiments; Sox9 enhancer binding assays; activin B/Smad signaling inhibition; orthotopic HCC mouse model","journal":"Cancer letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct enhancer binding demonstrated, in vivo and in vitro validation with gain/loss-of-function, single lab","pmids":["33246092"],"is_preprint":false},{"year":2021,"finding":"In tubular epithelial cells (TECs), Sox9 upregulates INHBB expression; secreted activin B then activates interstitial fibroblasts in a paracrine manner through activin B/Smad signaling, driving renal fibrosis. Inhibiting INHBB blocked fibroblast activation and ameliorated renal fibrosis in UUO and IRI mouse models.","method":"In vivo mouse models (UUO, IRI); ectopic INHBB overexpression in TECs; in vitro overexpression; Smad signaling inhibition; histology and fibrosis markers","journal":"The Journal of pathology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo and in vitro validation with gain/loss-of-function and defined signaling readout (Smad), single lab","pmids":["34543458"],"is_preprint":false},{"year":2022,"finding":"A human INHBB missense variant (p.Met360Thr), modeled in mice (InhbbM364T), significantly reduced circulating activin B levels without affecting inhibin B or FSH, demonstrating that this residue is required for activin B biosynthesis/secretion but not inhibin B. The variant also caused enlarged testes with increased Sertoli cell and spermatid numbers. Two INHBB human variants (p.Met360Thr and p.Thr105Met) each significantly disrupted activin B in vitro biosynthesis.","method":"CRISPR/Cas9 knock-in mouse model; serum hormone assays; testis histomorphometry; in vitro biosynthesis assays for activin B and inhibin B","journal":"Endocrinology","confidence":"High","confidence_rationale":"Tier 1 / Strong — CRISPR knock-in mouse with defined hormonal and histomorphometric phenotypes, plus independent in vitro biosynthesis assays for two variants, single rigorous study with multiple orthogonal methods","pmids":["35022746"],"is_preprint":false},{"year":2023,"finding":"INHBB knockdown in HESCs suppressed ADCY1 expression and cAMP production, attenuating decidualization of human endometrial stromal cells. RNA-seq identified the INHBB-ADCY1-cAMP signaling axis as the mechanistic pathway, and a positive correlation between INHBB and ADCY1 expression was confirmed in RIF patient endometria.","method":"siRNA knockdown; RNA-seq; RT-qPCR; immunofluorescence; cAMP analogue (forskolin) rescue; Pearson correlation analysis","journal":"Journal of assisted reproduction and genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — siRNA KD with RNA-seq pathway identification and forskolin rescue, single lab, multiple methods","pmids":["36913138"],"is_preprint":false},{"year":2025,"finding":"INHBB knockdown in CRC cells reduced migration, invasion, and hepatic metastasis formation by attenuating TGF-β/Smad2/3/Smad4 signaling (reduced Smad2/3 phosphorylation), reversing EMT (E-cadherin upregulation, N-cadherin/vimentin downregulation), and increasing anoikis sensitivity. In vivo INHBB silencing inhibited liver metastasis in a xenograft spleen injection model.","method":"siRNA knockdown in HCT116/Caco-2 cells; transwell migration/invasion assays; anoikis detection (calcein AM/EthD-1); Western blot for Smad phosphorylation and EMT markers; in vivo xenograft mouse model","journal":"Tissue & cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KD with defined signaling readout (Smad2/3 phosphorylation), EMT markers, and in vivo validation, single lab, multiple orthogonal methods","pmids":["41380489"],"is_preprint":false}],"current_model":"INHBB encodes the inhibin βB subunit, which homodimerizes to form activin B (or heterodimerizes with the α-subunit to form inhibin B); it is transcriptionally regulated by Sox9 (via direct enhancer binding) and repressed by Menin through Akt/Ezh2-mediated H3K27 trimethylation, and signals primarily through activin B/Smad pathways to regulate granulosa cell survival and steroidogenesis, endometrial decidualization via ADCY1/cAMP, paracrine fibroblast/stellate cell activation in renal and hepatic fibrosis, and tumor cell migration/invasion/anoikis resistance via TGF-β/Smad and EMT mechanisms."},"narrative":{"mechanistic_narrative":"INHBB encodes the inhibin βB subunit, the building block of activin B, a secreted TGF-β-family ligand that signals through Smad pathways to control reproductive tissue homeostasis and to drive paracrine fibrosis and tumor progression [PMID:10932194, PMID:33246092]. The βB subunit is functionally interchangeable with the βA subunit (activin A) when expressed from the same locus, yet confers distinct dosage-dependent bioactivities affecting somatic, testicular, genital, and hair phenotypes [PMID:10932194]; a conserved residue (Met360/Met364) is specifically required for activin B biosynthesis and secretion without affecting inhibin B production, and its disruption enlarges testes with increased Sertoli cell and spermatid numbers [PMID:35022746]. In the ovary, INHBB sustains granulosa cell cycle progression and survival and supports estradiol/progesterone synthesis via CYP19A1 and CYP11A1 [PMID:26063610], while in the endometrium it promotes decidualization through an INHBB–ADCY1–cAMP axis [PMID:36913138]. INHBB transcription is activated by direct Sox9 enhancer binding [PMID:33246092] and repressed by Menin, which recruits Ezh2 to deposit H3K27me3 at the locus through an Akt-dependent mechanism [PMID:28215965]. In disease, Sox9-driven INHBB induction in hepatoma and tubular epithelial cells secretes activin B that activates hepatic stellate cells and interstitial fibroblasts through activin B/Smad signaling, driving liver and renal fibrosis and metastasis [PMID:33246092, PMID:34543458]; in colorectal cancer cells INHBB promotes migration, invasion, EMT, and anoikis resistance via TGF-β/Smad2/3/Smad4 signaling [PMID:41380489].","teleology":[{"year":2000,"claim":"Established whether the βB and βA subunits encode functionally equivalent ligands, resolving whether activin B has activities distinct from activin A.","evidence":"Genetic knock-in of Inhbb coding sequence into the Inhba locus with phenotypic rescue analysis in mice","pmids":["10932194"],"confidence":"High","gaps":["Did not define the molecular signaling differences underlying the distinct activin B phenotypes","Interchangeability tested only from the Inhba locus, not at endogenous expression contexts"]},{"year":2015,"claim":"Defined the cell-autonomous role of INHBB in the ovary, linking it to granulosa cell cycle progression, survival, and steroidogenesis.","evidence":"shRNA knockdown in mouse granulosa cells with flow cytometry, ELISA, Western blot, and qRT-PCR","pmids":["26063610"],"confidence":"Medium","gaps":["Did not establish whether effects are mediated by activin B autocrine signaling or by inhibin B","Signaling pathway downstream of INHBB not mapped"]},{"year":2017,"claim":"Identified an epigenetic mechanism controlling INHBB transcription, showing Menin represses the locus to limit activin B output.","evidence":"Men1 KO mice and cell lines with ChIP for Menin promoter binding, H3K27me3 analysis, and pharmacological Akt modulation","pmids":["28215965"],"confidence":"Medium","gaps":["Ezh2 recruitment shown to be indirect but the bridging factor not identified","Physiological contexts where this repression operates not fully defined"]},{"year":2020,"claim":"Demonstrated transcriptional activation of INHBB by Sox9 and established activin B as a paracrine driver of hepatic stellate cell activation in liver fibrosis and HCC metastasis.","evidence":"Sox9 enhancer binding assays, gain/loss-of-function, activin B/Smad inhibition, and orthotopic HCC mouse model","pmids":["33246092"],"confidence":"Medium","gaps":["Direct receptor engagement on stellate cells not characterized","Single-lab study"]},{"year":2021,"claim":"Generalized the Sox9–INHBB–activin B/Smad paracrine fibrotic axis to the kidney, showing tubular epithelial INHBB activates interstitial fibroblasts.","evidence":"UUO and IRI mouse models, ectopic INHBB overexpression in TECs, Smad inhibition, histology and fibrosis markers","pmids":["34543458"],"confidence":"Medium","gaps":["Receptor and downstream effectors in fibroblasts not defined","Single-lab study"]},{"year":2022,"claim":"Resolved which structural determinant separates activin B from inhibin B biosynthesis and linked an INHBB variant to testicular phenotypes.","evidence":"CRISPR/Cas9 knock-in mouse modeling a human missense variant, serum hormone assays, testis histomorphometry, and in vitro biosynthesis assays for two variants","pmids":["35022746"],"confidence":"High","gaps":["Mechanism by which the residue selectively impairs activin B but not inhibin B assembly not structurally resolved","Human clinical consequences of the variants not established"]},{"year":2023,"claim":"Defined INHBB function in human endometrium, identifying the INHBB–ADCY1–cAMP axis as required for decidualization.","evidence":"siRNA knockdown in HESCs, RNA-seq, forskolin rescue, immunofluorescence, and correlation analysis in RIF patient endometria","pmids":["36913138"],"confidence":"Medium","gaps":["How INHBB connects to ADCY1 transcriptionally not mechanistically resolved","Correlative human data not causal"]},{"year":2025,"claim":"Extended the pro-metastatic role of INHBB to colorectal cancer via TGF-β/Smad-driven EMT and anoikis resistance.","evidence":"siRNA knockdown in HCT116/Caco-2, transwell and anoikis assays, Western blot for Smad phosphorylation and EMT markers, and xenograft spleen-injection metastasis model","pmids":["41380489"],"confidence":"Medium","gaps":["Whether effect is autocrine activin B signaling versus intracellular role not distinguished","Receptor complex engaged not identified"]},{"year":null,"claim":"The activin B receptor complexes and the structural basis for βB dimerization choice (activin B versus inhibin B) across the diverse reproductive, fibrotic, and oncogenic contexts remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No receptor identified for activin B in any of the characterized tissues","No structural model of the βB dimerization interface","Tissue-specific determinants of dimer partner choice unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0048018","term_label":"receptor ligand activity","supporting_discovery_ids":[0,3,4]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[3,4,7]}],"localization":[{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[3,4,5]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[3,4,7]},{"term_id":"R-HSA-1474244","term_label":"Extracellular matrix organization","supporting_discovery_ids":[3,4]},{"term_id":"R-HSA-1474165","term_label":"Reproduction","supporting_discovery_ids":[1,5,6]}],"complexes":["activin B","inhibin B"],"partners":["INHBA","SOX9","MEN1","EZH2","ADCY1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P09529","full_name":"Inhibin beta B chain","aliases":["Activin beta-B chain"],"length_aa":407,"mass_kda":45.1,"function":"Inhibins and activins inhibit and activate, respectively, the secretion of follitropin by the pituitary gland. Inhibins/activins are involved in regulating a number of diverse functions such as hypothalamic and pituitary hormone secretion, gonadal hormone secretion, germ cell development and maturation, erythroid differentiation, insulin secretion, nerve cell survival, embryonic axial development or bone growth, depending on their subunit composition. Inhibins appear to oppose the functions of activins Activin B is a dimer of alpha and beta-B that plays a role in several essential biological processes including embryonic development, stem cell maintenance and differentiation, haematopoiesis, cell proliferation and wound healing (PubMed:22611157, PubMed:15196700). Signals through type I receptor ACVR1C, abundantly expressed in pancreatic beta cells, and type II receptors like ACVR2A or BMPR2 (PubMed:35643319). Upon ligand binding, these receptors phosphorylate intracellular signaling mediators SMAD2 and SMAD3, which form a complex with SMAD4, translocate to the nucleus, and regulate gene expression (PubMed:15196700). Plays a crucial role in the induction of hepcidin by inflammation through activation of ACVR1C and subsequent phosphorylation of SMAD1/5/8 (PubMed:22611157). Regulates adipocyte lipid metabolism by decreasing non-esterified fatty acids and glycerol release and increases intracellular triglyceride content (By similarity). Stimulates wound healing by promoting cell migration and hair follicle regeneration through the JNK and ERK signaling pathways downstream of RHOA (By similarity) Inhibin B is a dimer of alpha and beta-B that plays a crucial role in the regulation of the reproductive system by inhibiting the secretion of follicle-stimulating hormone (FSH) from the anterior pituitary gland. Thereby, maintains reproductive homeostasis in both males and females. Acts as a more potent suppressor of FSH release than inhibin A (By similarity). Functions as competitive receptor antagonist binding activin type II receptors with high affinity in the presence of the TGF-beta type III coreceptor/TGFBR3L (By similarity)","subcellular_location":"Secreted","url":"https://www.uniprot.org/uniprotkb/P09529/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/INHBB","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/INHBB","total_profiled":1310},"omim":[{"mim_id":"612031","title":"INHIBIN, BETA E; INHBE","url":"https://www.omim.org/entry/612031"},{"mim_id":"601788","title":"MYOSTATIN; MSTN","url":"https://www.omim.org/entry/601788"},{"mim_id":"600963","title":"SIX HOMEOBOX 5; SIX5","url":"https://www.omim.org/entry/600963"},{"mim_id":"276400","title":"TWINNING, DIZYGOTIC","url":"https://www.omim.org/entry/276400"},{"mim_id":"228300","title":"HYPOGONADOTROPIC HYPOGONADISM 23 WITH OR WITHOUT ANOSMIA; HH23","url":"https://www.omim.org/entry/228300"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Vesicles","reliability":"Approved"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"adipose tissue","ntpm":49.6},{"tissue":"breast","ntpm":42.2}],"url":"https://www.proteinatlas.org/search/INHBB"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"P09529","domains":[{"cath_id":"2.10.90.10","chopping":"76-84_291-407","consensus_level":"high","plddt":81.1727,"start":76,"end":407},{"cath_id":"2.60.120.970","chopping":"141-283","consensus_level":"high","plddt":82.8344,"start":141,"end":283}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P09529","model_url":"https://alphafold.ebi.ac.uk/files/AF-P09529-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P09529-F1-predicted_aligned_error_v6.png","plddt_mean":73.81},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=INHBB","jax_strain_url":"https://www.jax.org/strain/search?query=INHBB"},"sequence":{"accession":"P09529","fasta_url":"https://rest.uniprot.org/uniprotkb/P09529.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P09529/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P09529"}},"corpus_meta":[{"pmid":"10932194","id":"PMC_10932194","title":"Insertion of Inhbb into the Inhba locus rescues the Inhba-null phenotype and reveals new activin functions.","date":"2000","source":"Nature genetics","url":"https://pubmed.ncbi.nlm.nih.gov/10932194","citation_count":162,"is_preprint":false},{"pmid":"26063610","id":"PMC_26063610","title":"RNAi-mediated knockdown of INHBB increases apoptosis and inhibits steroidogenesis in mouse granulosa cells.","date":"2015","source":"The Journal of reproduction and development","url":"https://pubmed.ncbi.nlm.nih.gov/26063610","citation_count":44,"is_preprint":false},{"pmid":"33246092","id":"PMC_33246092","title":"Sox9/INHBB axis-mediated crosstalk between the hepatoma and hepatic stellate cells promotes the metastasis of hepatocellular carcinoma.","date":"2020","source":"Cancer letters","url":"https://pubmed.ncbi.nlm.nih.gov/33246092","citation_count":41,"is_preprint":false},{"pmid":"34543458","id":"PMC_34543458","title":"Tubule-derived INHBB promotes interstitial fibroblast activation and renal fibrosis.","date":"2021","source":"The Journal of pathology","url":"https://pubmed.ncbi.nlm.nih.gov/34543458","citation_count":27,"is_preprint":false},{"pmid":"28215965","id":"PMC_28215965","title":"Menin regulates Inhbb expression through an Akt/Ezh2-mediated H3K27 histone modification.","date":"2017","source":"Biochimica et biophysica acta. Gene regulatory mechanisms","url":"https://pubmed.ncbi.nlm.nih.gov/28215965","citation_count":16,"is_preprint":false},{"pmid":"32156482","id":"PMC_32156482","title":"KLF10 is upregulated in osteoarthritis and inhibits chondrocyte proliferation and migration by upregulating Acvr1 and suppressing inhbb expression.","date":"2020","source":"Acta histochemica","url":"https://pubmed.ncbi.nlm.nih.gov/32156482","citation_count":13,"is_preprint":false},{"pmid":"35022746","id":"PMC_35022746","title":"Human INHBB Gene Variant (c.1079T>C:p.Met360Thr) Alters Testis Germ Cell Content, but Does Not Impact Fertility in Mice.","date":"2022","source":"Endocrinology","url":"https://pubmed.ncbi.nlm.nih.gov/35022746","citation_count":7,"is_preprint":false},{"pmid":"38422566","id":"PMC_38422566","title":"Circular RNA circRPS19 promotes chicken granulosa cell proliferation and steroid hormone synthesis by interrupting the miR-218-5p/INHBB axis.","date":"2024","source":"Theriogenology","url":"https://pubmed.ncbi.nlm.nih.gov/38422566","citation_count":7,"is_preprint":false},{"pmid":"39183219","id":"PMC_39183219","title":"Inhibin subunit beta B (INHBB): an emerging role in tumor progression.","date":"2024","source":"Journal of physiology and biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/39183219","citation_count":6,"is_preprint":false},{"pmid":"37116368","id":"PMC_37116368","title":"INHBB promotes tumor aggressiveness and stemness of glioblastoma via activating EGFR signaling.","date":"2023","source":"Pathology, research and practice","url":"https://pubmed.ncbi.nlm.nih.gov/37116368","citation_count":5,"is_preprint":false},{"pmid":"36913138","id":"PMC_36913138","title":"Downregulated INHBB in endometrial tissue of recurrent implantation failure patients impeded decidualization through the ADCY1/cAMP signalling pathway.","date":"2023","source":"Journal of assisted reproduction and genetics","url":"https://pubmed.ncbi.nlm.nih.gov/36913138","citation_count":5,"is_preprint":false},{"pmid":"33970982","id":"PMC_33970982","title":"Effect of Mouse Ovarian Vitrification on Promoter Methylation of Inhba and Inhbb in Granulosa Cells of Follicles.","date":"2021","source":"Cryo letters","url":"https://pubmed.ncbi.nlm.nih.gov/33970982","citation_count":5,"is_preprint":false},{"pmid":"10912684","id":"PMC_10912684","title":"Linkage mapping of the ovine alpha-inhibin (INHA) beta(A)-inhibin/activin (INHBA) and beta(B)-inhibin/activin (INHBB) genes.","date":"2000","source":"The Journal of heredity","url":"https://pubmed.ncbi.nlm.nih.gov/10912684","citation_count":4,"is_preprint":false},{"pmid":"1979678","id":"PMC_1979678","title":"BamHI RFLP of the inhibin beta B (INHBB) chain gene on chromosome 2.","date":"1990","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/1979678","citation_count":2,"is_preprint":false},{"pmid":"34987992","id":"PMC_34987992","title":"Identification of Novel Nucleotide Changes in INHBB Gene by Mutation Screening in Females with Ovarian Dysgenesis: A Case Report.","date":"2021","source":"Journal of reproduction & infertility","url":"https://pubmed.ncbi.nlm.nih.gov/34987992","citation_count":1,"is_preprint":false},{"pmid":"41380489","id":"PMC_41380489","title":"INHBB promotes liver metastasis of colorectal cancer via regulation of TGF-β/Smad signaling, EMT and anoikis resistance.","date":"2025","source":"Tissue & cell","url":"https://pubmed.ncbi.nlm.nih.gov/41380489","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.09.12.675858","title":"Transcriptomic and proteomic dynamics of ovarian follicle group culture resemble  <i>in vivo</i>  folliculogenesis","date":"2025-09-15","source":"bioRxiv","url":"https://doi.org/10.1101/2025.09.12.675858","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.08.20.608775","title":"Minipuberty regulates reproductive lifespan and ovarian follicular loss in a mouse model with reduced minipubertal gonadotropin levels","date":"2024-08-21","source":"bioRxiv","url":"https://doi.org/10.1101/2024.08.20.608775","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":11934,"output_tokens":2283,"usd":0.035023,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9364,"output_tokens":2896,"usd":0.05961,"stage2_stop_reason":"end_turn"},"total_usd":0.094633,"stage1_batch_id":"msgbatch_01DUPACZi7AAWwuZiUjseQF4","stage2_batch_id":"msgbatch_018yt7chE3f48PEFtDwtj6AE","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2000,\n      \"finding\": \"The INHBB-encoded βB subunit can functionally substitute for the βA subunit (INHBA) in vivo: knock-in of Inhbb into the Inhba locus rescued craniofacial defects of Inhba-null mice, demonstrating functional interchangeability of activin A and activin B when expressed from the same locus. Novel phenotypes (somatic, testicular, genital, hair growth) emerged in a dosage-dependent manner, revealing distinct bioactivities of activin B.\",\n      \"method\": \"Genetic knock-in (insertion of Inhbb coding sequence into the Inhba locus); phenotypic rescue analysis in mice\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vivo genetic rescue with defined phenotypic readouts, replicated across multiple allele dosages in a rigorous mouse genetics study\",\n      \"pmids\": [\"10932194\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"RNAi-mediated knockdown of INHBB in mouse granulosa cells arrested cells in G1 phase, increased apoptosis (downregulating Cyclin D1, Cyclin E, Bcl2; upregulating Bax), and decreased estradiol and progesterone concentrations via reduced CYP19A1 and CYP11A1 expression, establishing a role for INHBB in granulosa cell cycle progression, survival, and steroidogenesis.\",\n      \"method\": \"RNAi knockdown with shRNA vectors; Western blot, flow cytometry, ELISA, qRT-PCR\",\n      \"journal\": \"The Journal of reproduction and development\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean KD with defined cellular phenotypes using multiple orthogonal methods (flow cytometry, ELISA, Western blot), single lab\",\n      \"pmids\": [\"26063610\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Menin represses Inhbb transcription by recruiting Ezh2 to the Inhbb promoter via an indirect mechanism involving Akt phosphorylation, promoting H3K27me3 repressive marks at the Inhbb locus. Loss of Menin results in de-repression of Inhbb/activin B expression in vivo and in vitro.\",\n      \"method\": \"Animal models (Men1 KO), cell lines, ChIP (Menin binding to Inhbb promoter), H3K27me3 chromatin analysis, pharmacological modulation of Akt\",\n      \"journal\": \"Biochimica et biophysica acta. Gene regulatory mechanisms\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP and H3K27me3 analysis with in vivo and in vitro validation, single lab, multiple orthogonal approaches\",\n      \"pmids\": [\"28215965\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Sox9 induces INHBB expression by directly binding to its enhancer, leading to secretion of activin B from hepatoma cells, which activates surrounding hepatic stellate cells through activin B/Smad signaling, promoting liver fibrosis and tumor metastasis.\",\n      \"method\": \"Gain- and loss-of-function experiments; Sox9 enhancer binding assays; activin B/Smad signaling inhibition; orthotopic HCC mouse model\",\n      \"journal\": \"Cancer letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct enhancer binding demonstrated, in vivo and in vitro validation with gain/loss-of-function, single lab\",\n      \"pmids\": [\"33246092\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"In tubular epithelial cells (TECs), Sox9 upregulates INHBB expression; secreted activin B then activates interstitial fibroblasts in a paracrine manner through activin B/Smad signaling, driving renal fibrosis. Inhibiting INHBB blocked fibroblast activation and ameliorated renal fibrosis in UUO and IRI mouse models.\",\n      \"method\": \"In vivo mouse models (UUO, IRI); ectopic INHBB overexpression in TECs; in vitro overexpression; Smad signaling inhibition; histology and fibrosis markers\",\n      \"journal\": \"The Journal of pathology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo and in vitro validation with gain/loss-of-function and defined signaling readout (Smad), single lab\",\n      \"pmids\": [\"34543458\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"A human INHBB missense variant (p.Met360Thr), modeled in mice (InhbbM364T), significantly reduced circulating activin B levels without affecting inhibin B or FSH, demonstrating that this residue is required for activin B biosynthesis/secretion but not inhibin B. The variant also caused enlarged testes with increased Sertoli cell and spermatid numbers. Two INHBB human variants (p.Met360Thr and p.Thr105Met) each significantly disrupted activin B in vitro biosynthesis.\",\n      \"method\": \"CRISPR/Cas9 knock-in mouse model; serum hormone assays; testis histomorphometry; in vitro biosynthesis assays for activin B and inhibin B\",\n      \"journal\": \"Endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — CRISPR knock-in mouse with defined hormonal and histomorphometric phenotypes, plus independent in vitro biosynthesis assays for two variants, single rigorous study with multiple orthogonal methods\",\n      \"pmids\": [\"35022746\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"INHBB knockdown in HESCs suppressed ADCY1 expression and cAMP production, attenuating decidualization of human endometrial stromal cells. RNA-seq identified the INHBB-ADCY1-cAMP signaling axis as the mechanistic pathway, and a positive correlation between INHBB and ADCY1 expression was confirmed in RIF patient endometria.\",\n      \"method\": \"siRNA knockdown; RNA-seq; RT-qPCR; immunofluorescence; cAMP analogue (forskolin) rescue; Pearson correlation analysis\",\n      \"journal\": \"Journal of assisted reproduction and genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — siRNA KD with RNA-seq pathway identification and forskolin rescue, single lab, multiple methods\",\n      \"pmids\": [\"36913138\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"INHBB knockdown in CRC cells reduced migration, invasion, and hepatic metastasis formation by attenuating TGF-β/Smad2/3/Smad4 signaling (reduced Smad2/3 phosphorylation), reversing EMT (E-cadherin upregulation, N-cadherin/vimentin downregulation), and increasing anoikis sensitivity. In vivo INHBB silencing inhibited liver metastasis in a xenograft spleen injection model.\",\n      \"method\": \"siRNA knockdown in HCT116/Caco-2 cells; transwell migration/invasion assays; anoikis detection (calcein AM/EthD-1); Western blot for Smad phosphorylation and EMT markers; in vivo xenograft mouse model\",\n      \"journal\": \"Tissue & cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KD with defined signaling readout (Smad2/3 phosphorylation), EMT markers, and in vivo validation, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"41380489\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"INHBB encodes the inhibin βB subunit, which homodimerizes to form activin B (or heterodimerizes with the α-subunit to form inhibin B); it is transcriptionally regulated by Sox9 (via direct enhancer binding) and repressed by Menin through Akt/Ezh2-mediated H3K27 trimethylation, and signals primarily through activin B/Smad pathways to regulate granulosa cell survival and steroidogenesis, endometrial decidualization via ADCY1/cAMP, paracrine fibroblast/stellate cell activation in renal and hepatic fibrosis, and tumor cell migration/invasion/anoikis resistance via TGF-β/Smad and EMT mechanisms.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"INHBB encodes the inhibin βB subunit, the building block of activin B, a secreted TGF-β-family ligand that signals through Smad pathways to control reproductive tissue homeostasis and to drive paracrine fibrosis and tumor progression [#0, #3]. The βB subunit is functionally interchangeable with the βA subunit (activin A) when expressed from the same locus, yet confers distinct dosage-dependent bioactivities affecting somatic, testicular, genital, and hair phenotypes [#0]; a conserved residue (Met360/Met364) is specifically required for activin B biosynthesis and secretion without affecting inhibin B production, and its disruption enlarges testes with increased Sertoli cell and spermatid numbers [#5]. In the ovary, INHBB sustains granulosa cell cycle progression and survival and supports estradiol/progesterone synthesis via CYP19A1 and CYP11A1 [#1], while in the endometrium it promotes decidualization through an INHBB–ADCY1–cAMP axis [#6]. INHBB transcription is activated by direct Sox9 enhancer binding [#3] and repressed by Menin, which recruits Ezh2 to deposit H3K27me3 at the locus through an Akt-dependent mechanism [#2]. In disease, Sox9-driven INHBB induction in hepatoma and tubular epithelial cells secretes activin B that activates hepatic stellate cells and interstitial fibroblasts through activin B/Smad signaling, driving liver and renal fibrosis and metastasis [#3, #4]; in colorectal cancer cells INHBB promotes migration, invasion, EMT, and anoikis resistance via TGF-β/Smad2/3/Smad4 signaling [#7].\",\n  \"teleology\": [\n    {\n      \"year\": 2000,\n      \"claim\": \"Established whether the βB and βA subunits encode functionally equivalent ligands, resolving whether activin B has activities distinct from activin A.\",\n      \"evidence\": \"Genetic knock-in of Inhbb coding sequence into the Inhba locus with phenotypic rescue analysis in mice\",\n      \"pmids\": [\"10932194\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the molecular signaling differences underlying the distinct activin B phenotypes\", \"Interchangeability tested only from the Inhba locus, not at endogenous expression contexts\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Defined the cell-autonomous role of INHBB in the ovary, linking it to granulosa cell cycle progression, survival, and steroidogenesis.\",\n      \"evidence\": \"shRNA knockdown in mouse granulosa cells with flow cytometry, ELISA, Western blot, and qRT-PCR\",\n      \"pmids\": [\"26063610\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Did not establish whether effects are mediated by activin B autocrine signaling or by inhibin B\", \"Signaling pathway downstream of INHBB not mapped\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Identified an epigenetic mechanism controlling INHBB transcription, showing Menin represses the locus to limit activin B output.\",\n      \"evidence\": \"Men1 KO mice and cell lines with ChIP for Menin promoter binding, H3K27me3 analysis, and pharmacological Akt modulation\",\n      \"pmids\": [\"28215965\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Ezh2 recruitment shown to be indirect but the bridging factor not identified\", \"Physiological contexts where this repression operates not fully defined\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Demonstrated transcriptional activation of INHBB by Sox9 and established activin B as a paracrine driver of hepatic stellate cell activation in liver fibrosis and HCC metastasis.\",\n      \"evidence\": \"Sox9 enhancer binding assays, gain/loss-of-function, activin B/Smad inhibition, and orthotopic HCC mouse model\",\n      \"pmids\": [\"33246092\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct receptor engagement on stellate cells not characterized\", \"Single-lab study\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Generalized the Sox9–INHBB–activin B/Smad paracrine fibrotic axis to the kidney, showing tubular epithelial INHBB activates interstitial fibroblasts.\",\n      \"evidence\": \"UUO and IRI mouse models, ectopic INHBB overexpression in TECs, Smad inhibition, histology and fibrosis markers\",\n      \"pmids\": [\"34543458\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Receptor and downstream effectors in fibroblasts not defined\", \"Single-lab study\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Resolved which structural determinant separates activin B from inhibin B biosynthesis and linked an INHBB variant to testicular phenotypes.\",\n      \"evidence\": \"CRISPR/Cas9 knock-in mouse modeling a human missense variant, serum hormone assays, testis histomorphometry, and in vitro biosynthesis assays for two variants\",\n      \"pmids\": [\"35022746\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which the residue selectively impairs activin B but not inhibin B assembly not structurally resolved\", \"Human clinical consequences of the variants not established\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Defined INHBB function in human endometrium, identifying the INHBB–ADCY1–cAMP axis as required for decidualization.\",\n      \"evidence\": \"siRNA knockdown in HESCs, RNA-seq, forskolin rescue, immunofluorescence, and correlation analysis in RIF patient endometria\",\n      \"pmids\": [\"36913138\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How INHBB connects to ADCY1 transcriptionally not mechanistically resolved\", \"Correlative human data not causal\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Extended the pro-metastatic role of INHBB to colorectal cancer via TGF-β/Smad-driven EMT and anoikis resistance.\",\n      \"evidence\": \"siRNA knockdown in HCT116/Caco-2, transwell and anoikis assays, Western blot for Smad phosphorylation and EMT markers, and xenograft spleen-injection metastasis model\",\n      \"pmids\": [\"41380489\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether effect is autocrine activin B signaling versus intracellular role not distinguished\", \"Receptor complex engaged not identified\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The activin B receptor complexes and the structural basis for βB dimerization choice (activin B versus inhibin B) across the diverse reproductive, fibrotic, and oncogenic contexts remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No receptor identified for activin B in any of the characterized tissues\", \"No structural model of the βB dimerization interface\", \"Tissue-specific determinants of dimer partner choice unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0048018\", \"supporting_discovery_ids\": [0, 3, 4]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [3, 4, 7]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [3, 4, 5]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [3, 4, 7]},\n      {\"term_id\": \"R-HSA-1474244\", \"supporting_discovery_ids\": [3, 4]},\n      {\"term_id\": \"R-HSA-1474165\", \"supporting_discovery_ids\": [1, 5, 6]}\n    ],\n    \"complexes\": [\"activin B\", \"inhibin B\"],\n    \"partners\": [\"INHBA\", \"SOX9\", \"MEN1\", \"EZH2\", \"ADCY1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}