{"gene":"THPO","run_date":"2026-06-10T10:51:55","timeline":{"discoveries":[{"year":1995,"finding":"MGDF (THPO) is the ligand for the c-mpl receptor; chronic overexpression via retroviral gene transfer in mice leads to lineage-specific megakaryocyte expansion, elevated platelets (4-8 fold above normal), myelofibrosis, and osteosclerosis, with no significant effect on other hematopoietic lineages, establishing THPO's stimulatory effect in vivo is restricted to the megakaryocyte lineage.","method":"Retroviral-mediated gene transfer / overexpression in mice with histological and hematological analysis","journal":"Blood","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo loss/gain-of-function with defined cellular phenotype, single lab, multiple readouts","pmids":["7492757"],"is_preprint":false},{"year":1995,"finding":"The human MGDF (THPO) gene consists of seven exons and six introns spanning 8 kilobases; the protein-coding sequence is encoded by exons 3–7; the gene maps to chromosome 3q26.3; two cDNA splice variants arise from differential splicing in fetal liver.","method":"Genomic cloning, cDNA sequencing, chromosomal mapping, comparison of cDNA variants with genomic sequence","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct genomic characterization with sequencing and chromosomal mapping; replicated in multiple molecular analyses","pmids":["7822271"],"is_preprint":false},{"year":1995,"finding":"MGDF (THPO) enhances in vitro platelet aggregation in a dose-dependent manner in response to epinephrine and ADP; this effect is partially blocked by the soluble extracellular domain of c-mpl, and MGDF induces tyrosine phosphorylation of platelet proteins at ~85 kDa and ~130 kDa, indicating signaling through the c-mpl receptor.","method":"In vitro platelet aggregometry, soluble receptor blocking experiment, tyrosine phosphorylation assay (Western blot)","journal":"Thrombosis research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro functional assay with receptor-blocking control and biochemical readout, single lab","pmids":["8578535"],"is_preprint":false},{"year":1996,"finding":"Recombinant human MGDF (THPO) administered subcutaneously to baboons specifically stimulates thrombopoiesis in a dose-dependent manner, increasing platelet counts up to 5-fold and markedly enlarging marrow megakaryocytes with increased nuclear lobes, with no effect on red cell mass or white blood cell counts; heat-inactivated MGDF had no effect, confirming the requirement for native protein structure.","method":"In vivo primate administration of recombinant MGDF and heat-inactivated control, platelet counting, marrow biopsy","journal":"Stem cells (Dayton, Ohio)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo primate model with dose-response and negative control, single lab","pmids":["8948024"],"is_preprint":false},{"year":1997,"finding":"MGDF (THPO) stimulates proliferation and survival of human megakaryocyte progenitors (CD34+CD61+) and also promotes survival of BFU-E and granulocyte-macrophage CFC, demonstrating a broader progenitor survival role beyond megakaryocyte lineage; MGDF acts additively with SCF and IL-3.","method":"Single-cell clonogenic assay with timed cytokine delay, immunoenzymatic colony labeling","journal":"Stem cells (Dayton, Ohio)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — single-cell assay with delayed-addition survival design, single lab, multiple lineage readouts","pmids":["9007220"],"is_preprint":false},{"year":1997,"finding":"MGDF (THPO) stimulates proliferation of a human megakaryocyte/erythroid progenitor cell line (B1647) expressing c-mpl, and increases gamma-globin chain synthesis, but does not induce megakaryocytic differentiation, demonstrating that THPO signaling through c-mpl can modulate erythroid gene expression in a bipotent progenitor.","method":"Cell proliferation assay in serum-free culture, cytofluorimetric analysis, S1 protection analysis of globin mRNA","journal":"British journal of haematology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cell line with c-mpl expression confirmed, multiple molecular readouts, single lab","pmids":["9332307"],"is_preprint":false},{"year":1997,"finding":"MGDF (THPO) stimulates proliferation and colony formation in AML blast cells that express functional c-mpl, and induces tyrosine phosphorylation of an ~90 kDa protein upon stimulation; AML cases unresponsive to MGDF show no such phosphorylation, linking THPO signaling to c-mpl-dependent tyrosine kinase activation.","method":"Blast cell proliferation assay, clonogenic colony assay, tyrosine phosphorylation Western blot on primary AML cells","journal":"Leukemia","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — primary patient cells, functional and biochemical readouts correlated, single lab","pmids":["9096694"],"is_preprint":false},{"year":1998,"finding":"rHuMGDF (THPO) sensitizes platelets to aggregating agents in vitro and ex vivo, and is associated with clear increases in tyrosine phosphorylation of JAK2 and the c-mpl receptor both in vitro and ex vivo; however, platelet-sensitizing doses of rHuMGDF did not enhance platelet-dependent thrombosis in a rabbit carotid artery cyclic flow reduction model.","method":"In vitro platelet aggregation, ex vivo platelet analysis, JAK2/c-mpl phosphorylation assay, rabbit carotid artery thrombosis model","journal":"Stem cells (Dayton, Ohio)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro and in vivo models with biochemical readouts, single lab, includes negative in vivo thrombosis result","pmids":["11012184"],"is_preprint":false},{"year":2023,"finding":"A homozygous c.-323C>T substitution in the THPO promoter prevents binding of transcription factors ETS1 and STAT4 to the putative THPO promoter, impairing THPO expression and causing congenital amegakaryocytic thrombocytopenia (CAMT); treatment with the THPO-mimetic eltrombopag rescued platelet counts, confirming THPO pathway dependence.","method":"Bioinformatics prediction, in vitro transcription factor binding assay, serum THPO measurement, clinical therapeutic response to THPO-mimetic","journal":"Haematologica","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro binding assay plus clinical functional validation, single lab/case","pmids":["36226497"],"is_preprint":false},{"year":2023,"finding":"A splicing donor site mutation (THPO c.13+1G>A) causes exon 3 skipping, abrogating a suppressive upstream open reading frame (ORF) in the 5'-UTR; mutated transcripts are more efficiently translated, resulting in significantly higher THPO protein expression compared to wild-type, explaining hereditary thrombocythemia.","method":"Cloning of mutated and wild-type THPO expression vectors, RT-PCR transcript analysis, THPO protein expression comparison","journal":"Annals of hematology","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — molecular cloning with expression vectors and direct protein quantification, single lab","pmids":["37962621"],"is_preprint":false},{"year":2024,"finding":"All six known hereditary thrombocythemia THPO mutations (c.-47delG, c.-31G>T, c.13G>A, c.13+1G>A, c.13+2T>C, c.13+5G>A) result in increased THPO protein production via two distinct molecular mechanisms: (1) exon 3 skipping that deletes upstream suppressive ORF7, or (2) a single base deletion that shifts ORF7 in-frame with the THPO start codon; in both cases, translation of THPO is normally suppressed by out-of-frame ORF7 and mutations relieve this suppression.","method":"Cloning of six distinct THPO mutant expression vectors, transcript analysis by RT-PCR, protein expression quantification","journal":"Experimental hematology","confidence":"High","confidence_rationale":"Tier 1 / Strong — systematic molecular cloning and expression analysis of all known mutations across multiple sites, single lab with multiple orthogonal methods","pmids":["38548144"],"is_preprint":false}],"current_model":"THPO (thrombopoietin/MGDF) is the ligand for the c-mpl receptor that primarily drives megakaryocyte proliferation, differentiation, and platelet production by activating c-mpl-dependent JAK2 tyrosine phosphorylation; its translation is normally suppressed by an upstream out-of-frame ORF7 in the 5'-UTR, and hereditary thrombocythemia mutations relieve this suppression via exon 3 skipping or ORF7 frameshift; transcription of THPO itself is regulated by ETS1 and STAT4 binding to its promoter, and loss-of-function promoter or coding mutations cause congenital amegakaryocytic thrombocytopenia."},"narrative":{"mechanistic_narrative":"THPO (thrombopoietin/MGDF) is the lineage-specifying cytokine for megakaryopoiesis, acting as the ligand for the c-mpl receptor to drive megakaryocyte proliferation, maturation, and platelet production [PMID:7492757]. In vivo, chronic THPO overexpression in mice produces lineage-restricted megakaryocyte expansion with 4–8-fold elevated platelets, myelofibrosis, and osteosclerosis without perturbing other hematopoietic lineages [PMID:7492757], and recombinant THPO selectively stimulates dose-dependent thrombopoiesis and megakaryocyte enlargement in primates [PMID:8948024]. At the receptor level, THPO binding to c-mpl triggers tyrosine phosphorylation of JAK2 and the c-mpl receptor, the proximal signaling event underlying its effects on platelets and progenitors [PMID:11012184, PMID:8578535, PMID:9096694]. Beyond mature megakaryocytes, THPO supports proliferation and survival of CD34+CD61+ megakaryocyte progenitors and broader progenitor populations including BFU-E and granulocyte-macrophage CFC, and can modulate erythroid gene expression in bipotent c-mpl-expressing progenitors [PMID:9007220, PMID:9332307]. THPO expression is tightly controlled at both transcriptional and translational levels: transcription depends on ETS1 and STAT4 binding to the promoter, and its mRNA carries a suppressive out-of-frame upstream ORF7 in the 5'-UTR that normally restrains translation [PMID:36226497, PMID:38548144]. This regulatory architecture is the basis of two opposing Mendelian disorders: a homozygous promoter mutation (c.-323C>T) that abolishes ETS1/STAT4 binding and impairs THPO expression causes congenital amegakaryocytic thrombocytopenia [PMID:36226497], while hereditary thrombocythemia mutations relieve ORF7-mediated translational suppression—either through exon 3 skipping that deletes ORF7 or a frameshift that brings ORF7 in-frame with the THPO start codon—yielding increased THPO protein [PMID:37962621, PMID:38548144].","teleology":[{"year":1995,"claim":"Establishing that THPO is the physiological c-mpl ligand and defining the lineage scope of its action answered whether a single cytokine specifies megakaryopoiesis in vivo.","evidence":"Retroviral overexpression of MGDF in mice with hematological and histological readout","pmids":["7492757"],"confidence":"Medium","gaps":["Overexpression phenotype does not establish endogenous requirement","Myelofibrosis/osteosclerosis as secondary consequences not mechanistically dissected"]},{"year":1995,"claim":"Genomic characterization defined the THPO locus architecture, mapping it to 3q26.3 and assigning the coding sequence to exons 3–7, providing the structural framework later needed to interpret regulatory and disease mutations.","evidence":"Genomic cloning, cDNA sequencing, and chromosomal mapping","pmids":["7822271"],"confidence":"High","gaps":["Functional significance of the two fetal-liver splice variants not determined","5'-UTR regulatory ORF not yet recognized at this stage"]},{"year":1995,"claim":"Demonstrating that THPO sensitizes platelets to aggregating agents and induces platelet protein tyrosine phosphorylation extended its role from megakaryocyte production to direct modulation of mature platelet function.","evidence":"In vitro platelet aggregometry with soluble c-mpl blocking and phosphorylation Western blot","pmids":["8578535"],"confidence":"Medium","gaps":["Identity of the ~85/130 kDa phosphoproteins not established","Physiological relevance of platelet sensitization unclear"]},{"year":1996,"claim":"Primate dosing with native versus heat-inactivated recombinant THPO confirmed lineage-specific, structure-dependent thrombopoietic activity in a clinically relevant model.","evidence":"Subcutaneous recombinant MGDF administration in baboons with platelet counting and marrow biopsy","pmids":["8948024"],"confidence":"Medium","gaps":["Receptor-level mechanism not addressed in this model","Long-term effects and marrow fibrosis not assessed"]},{"year":1997,"claim":"Progenitor clonogenic assays revealed THPO supports survival and proliferation beyond the megakaryocyte lineage, including erythroid and granulocyte-macrophage progenitors and modulation of erythroid gene expression in bipotent progenitors.","evidence":"Single-cell clonogenic assays, c-mpl-expressing progenitor cell lines, and globin mRNA analysis","pmids":["9007220","9332307"],"confidence":"Medium","gaps":["In vivo significance of broader progenitor survival not established","Mechanism of erythroid gene modulation not defined"]},{"year":1997,"claim":"Correlating THPO responsiveness with c-mpl-dependent tyrosine phosphorylation in primary AML blasts tied functional output to receptor signaling competence.","evidence":"Proliferation and clonogenic assays with phosphorylation Western blot on primary AML cells","pmids":["9096694"],"confidence":"Medium","gaps":["Identity of the ~90 kDa phosphoprotein not determined","Relevance to leukemogenesis not addressed"]},{"year":1998,"claim":"Identifying JAK2 and c-mpl tyrosine phosphorylation as the proximal signal clarified the kinase axis transducing THPO action, while the absence of enhanced arterial thrombosis bounded its in vivo prothrombotic effect.","evidence":"In vitro/ex vivo platelet phosphorylation assays plus a rabbit carotid artery thrombosis model","pmids":["11012184"],"confidence":"Medium","gaps":["Downstream effectors of JAK2 in platelets not mapped","Discrepancy between platelet sensitization and lack of thrombosis unexplained"]},{"year":2023,"claim":"Linking a THPO promoter mutation to loss of ETS1/STAT4 binding established the transcriptional control of THPO and its loss-of-function disease mechanism, validated by therapeutic rescue.","evidence":"Promoter bioinformatics, in vitro transcription factor binding assays, serum THPO measurement, and eltrombopag clinical response in CAMT","pmids":["36226497"],"confidence":"Medium","gaps":["Single case/family limits generality","Direct in vivo confirmation of ETS1/STAT4 occupancy at the endogenous locus not shown"]},{"year":2023,"claim":"Defining a splice-donor mutation that triggers exon 3 skipping and removes a suppressive 5'-UTR upstream ORF revealed translational repression as the normal restraint on THPO, whose relief causes hereditary thrombocythemia.","evidence":"Mutant versus wild-type expression vectors with RT-PCR and protein quantification","pmids":["37962621"],"confidence":"Medium","gaps":["Endogenous translational regulation in megakaryocytes not directly measured","Single-mutation analysis"]},{"year":2024,"claim":"Systematic analysis of all six known hereditary thrombocythemia mutations consolidated two convergent mechanisms—ORF7 deletion via exon 3 skipping or ORF7 frameshift—both relieving translational suppression of THPO, unifying the gain-of-function disease class.","evidence":"Cloning of six mutant expression vectors with transcript and protein expression quantification","pmids":["38548144"],"confidence":"High","gaps":["Quantitative contribution of ORF7 derepression to clinical platelet levels not modeled","Mechanism of ORF7-mediated suppression on ribosome scanning not detailed"]},{"year":null,"claim":"How THPO transcriptional control, ORF7-mediated translational repression, and c-mpl/JAK2 signaling are integrated to set physiological platelet set-point remains incompletely defined.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of THPO–c-mpl engagement in the timeline","Downstream JAK2 effectors and transcriptional outputs in megakaryocytes not mapped","Identity of THPO-induced platelet phosphoproteins unresolved"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0048018","term_label":"receptor ligand activity","supporting_discovery_ids":[0,2,3]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[7,6]}],"localization":[{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[3,8]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[7,2,6]},{"term_id":"R-HSA-109582","term_label":"Hemostasis","supporting_discovery_ids":[2,7]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[8,9,10]}],"complexes":[],"partners":["MPL","JAK2","ETS1","STAT4"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P40225","full_name":"Thrombopoietin","aliases":["C-mpl ligand","ML","Megakaryocyte colony-stimulating factor","Megakaryocyte growth and development factor","MGDF","Myeloproliferative leukemia virus oncogene ligand"],"length_aa":353,"mass_kda":37.8,"function":"Lineage-specific cytokine affecting the proliferation and maturation of megakaryocytes from their committed progenitor cells. It acts at a late stage of megakaryocyte development. It may be the major physiological regulator of circulating platelets","subcellular_location":"Secreted","url":"https://www.uniprot.org/uniprotkb/P40225/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/THPO","classification":"Not Classified","n_dependent_lines":2,"n_total_lines":1208,"dependency_fraction":0.0016556291390728477},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/THPO","total_profiled":1310},"omim":[{"mim_id":"620481","title":"AMEGAKARYOCYTIC THROMBOCYTOPENIA, CONGENITAL, 2; CAMT2","url":"https://www.omim.org/entry/620481"},{"mim_id":"620478","title":"THROMBOCYTOPENIA 9; THC9","url":"https://www.omim.org/entry/620478"},{"mim_id":"616604","title":"CHROMOSOME 14q32 DUPLICATION SYNDROME, 700-KB","url":"https://www.omim.org/entry/616604"},{"mim_id":"616046","title":"PROLINE/SERINE/THREONINE PHOSPHATASE-INTERACTING PROTEIN 2; PSTPIP2","url":"https://www.omim.org/entry/616046"},{"mim_id":"610049","title":"SAP DOMAIN-CONTAINING RIBONUCLEOPROTEIN; SARNP","url":"https://www.omim.org/entry/610049"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"liver","ntpm":33.7}],"url":"https://www.proteinatlas.org/search/THPO"},"hgnc":{"alias_symbol":["TPO","MPLLG"],"prev_symbol":["MGDF"]},"alphafold":{"accession":"P40225","domains":[{"cath_id":"1.20.1250.10","chopping":"39-50_57-175","consensus_level":"medium","plddt":86.9422,"start":39,"end":175}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P40225","model_url":"https://alphafold.ebi.ac.uk/files/AF-P40225-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P40225-F1-predicted_aligned_error_v6.png","plddt_mean":61.44},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=THPO","jax_strain_url":"https://www.jax.org/strain/search?query=THPO"},"sequence":{"accession":"P40225","fasta_url":"https://rest.uniprot.org/uniprotkb/P40225.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P40225/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P40225"}},"corpus_meta":[{"pmid":"7492757","id":"PMC_7492757","title":"Chronic exposure to retroviral vector encoded MGDF (mpl-ligand) induces lineage-specific growth and differentiation of megakaryocytes in mice.","date":"1995","source":"Blood","url":"https://pubmed.ncbi.nlm.nih.gov/7492757","citation_count":135,"is_preprint":false},{"pmid":"7822271","id":"PMC_7822271","title":"Cloning and characterization of the human megakaryocyte growth and development factor (MGDF) gene.","date":"1995","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/7822271","citation_count":89,"is_preprint":false},{"pmid":"11071622","id":"PMC_11071622","title":"Hypersensitivity of circulating progenitor cells to megakaryocyte growth and development factor (PEG-rHu MGDF) in essential thrombocythemia.","date":"2000","source":"Blood","url":"https://pubmed.ncbi.nlm.nih.gov/11071622","citation_count":79,"is_preprint":false},{"pmid":"10866797","id":"PMC_10866797","title":"Structure and expression of mGDF, a new member of the transforming growth factor-beta superfamily in the bivalve mollusc Crassostrea gigas.","date":"2000","source":"European journal of biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/10866797","citation_count":43,"is_preprint":false},{"pmid":"8578535","id":"PMC_8578535","title":"Megakaryocyte growth and development factor (MGDF) moderately enhances in-vitro platelet aggregation.","date":"1995","source":"Thrombosis research","url":"https://pubmed.ncbi.nlm.nih.gov/8578535","citation_count":43,"is_preprint":false},{"pmid":"9603398","id":"PMC_9603398","title":"Flt 3 ligand, MGDF, Epo and G-CSF enhance ex vivo expansion of hematopoietic cell compartments in the presence of SCF, IL-3 and IL-6.","date":"1998","source":"Bone marrow transplantation","url":"https://pubmed.ncbi.nlm.nih.gov/9603398","citation_count":41,"is_preprint":false},{"pmid":"9007220","id":"PMC_9007220","title":"Mpl ligand (MGDF) alone and in combination with stem cell factor (SCF) promotes proliferation and survival of human megakaryocyte, erythroid and granulocyte/macrophage progenitors.","date":"1997","source":"Stem cells (Dayton, Ohio)","url":"https://pubmed.ncbi.nlm.nih.gov/9007220","citation_count":37,"is_preprint":false},{"pmid":"10437984","id":"PMC_10437984","title":"Engraftment of primates with G-CSF mobilized peripheral blood CD34+ progenitor cells expanded in G-CSF, SCF and MGDF decreases the duration and severity of neutropenia.","date":"1999","source":"Stem cells (Dayton, Ohio)","url":"https://pubmed.ncbi.nlm.nih.gov/10437984","citation_count":25,"is_preprint":false},{"pmid":"8948024","id":"PMC_8948024","title":"Recombinant human ligand for MPL, megakaryocyte growth and development factor (MGDF), stimulates thrombopoiesis in vivo in normal and myelosuppressed baboons.","date":"1996","source":"Stem cells (Dayton, Ohio)","url":"https://pubmed.ncbi.nlm.nih.gov/8948024","citation_count":25,"is_preprint":false},{"pmid":"9332307","id":"PMC_9332307","title":"An erythroid and megakaryocytic common precursor cell line (B1647) expressing both c-mpl and erythropoietin receptor (Epo-R) proliferates and modifies globin chain synthesis in response to megakaryocyte growth and development factor (MGDF) but not to erythropoietin (Epo).","date":"1997","source":"British journal of haematology","url":"https://pubmed.ncbi.nlm.nih.gov/9332307","citation_count":19,"is_preprint":false},{"pmid":"10976539","id":"PMC_10976539","title":"Megakaryocyte growth and development factor (MGDF): an Mpl ligand and cytokine that regulates thrombopoiesis.","date":"2000","source":"Cytokines, cellular & molecular therapy","url":"https://pubmed.ncbi.nlm.nih.gov/10976539","citation_count":17,"is_preprint":false},{"pmid":"9096694","id":"PMC_9096694","title":"Megakaryocyte growth and development factor (MGDF)-induced acute leukemia cell proliferation and clonal growth is associated with functional c-mpl.","date":"1997","source":"Leukemia","url":"https://pubmed.ncbi.nlm.nih.gov/9096694","citation_count":13,"is_preprint":false},{"pmid":"22453305","id":"PMC_22453305","title":"Hereditary thrombocythemia caused by a thrombopoietin (THPO) gain-of-function mutation associated with multiple myeloma and congenital limb defects.","date":"2012","source":"Annals of hematology","url":"https://pubmed.ncbi.nlm.nih.gov/22453305","citation_count":11,"is_preprint":false},{"pmid":"36226497","id":"PMC_36226497","title":"Defective binding of ETS1 and STAT4 due to a mutation in the promoter region of THPO as a novel mechanism of congenital amegakaryocytic thrombocytopenia.","date":"2023","source":"Haematologica","url":"https://pubmed.ncbi.nlm.nih.gov/36226497","citation_count":10,"is_preprint":false},{"pmid":"1397027","id":"PMC_1397027","title":"Discriminative stimulus properties of the muscarinic receptor agonists Lu 26-046 and O-Me-THPO in rats: evidence for involvement of different muscarinic receptor subtypes.","date":"1992","source":"European journal of pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/1397027","citation_count":10,"is_preprint":false},{"pmid":"12483365","id":"PMC_12483365","title":"In vitro response of myelodysplastic megakaryocytopoiesis to megakaryocyte growth and development factor (MGDF).","date":"2002","source":"Annals of hematology","url":"https://pubmed.ncbi.nlm.nih.gov/12483365","citation_count":5,"is_preprint":false},{"pmid":"25482588","id":"PMC_25482588","title":"THPO-MPL pathway and bone marrow failure.","date":"2014","source":"Hematology/oncology and stem cell therapy","url":"https://pubmed.ncbi.nlm.nih.gov/25482588","citation_count":4,"is_preprint":false},{"pmid":"25728710","id":"PMC_25728710","title":"Somatic thrombopoietin (THPO) gene mutations in childhood myeloid leukemias.","date":"2015","source":"International journal of hematology","url":"https://pubmed.ncbi.nlm.nih.gov/25728710","citation_count":3,"is_preprint":false},{"pmid":"37962621","id":"PMC_37962621","title":"Hereditary thrombocythemia due to splicing donor site mutation of THPO in a Japanese family.","date":"2023","source":"Annals of hematology","url":"https://pubmed.ncbi.nlm.nih.gov/37962621","citation_count":1,"is_preprint":false},{"pmid":"39479124","id":"PMC_39479124","title":"A Rare THPO Gene Mutation in a Saudi Female Child: A Case Report and Literature Review.","date":"2024","source":"Cureus","url":"https://pubmed.ncbi.nlm.nih.gov/39479124","citation_count":1,"is_preprint":false},{"pmid":"38548144","id":"PMC_38548144","title":"Relative impact of THPO mutation causing hereditary thrombocythemia.","date":"2024","source":"Experimental hematology","url":"https://pubmed.ncbi.nlm.nih.gov/38548144","citation_count":0,"is_preprint":false},{"pmid":"11012184","id":"PMC_11012184","title":"The effect of MGDF on platelet function and thrombosis in animal models.","date":"1998","source":"Stem cells (Dayton, Ohio)","url":"https://pubmed.ncbi.nlm.nih.gov/11012184","citation_count":0,"is_preprint":false},{"pmid":"40386912","id":"PMC_40386912","title":"THPO promoter mutation: a familial study on congenital amegakaryocytic thrombocytopenia.","date":"2025","source":"Journal of genetics","url":"https://pubmed.ncbi.nlm.nih.gov/40386912","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":13341,"output_tokens":2785,"usd":0.040899,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":10038,"output_tokens":3499,"usd":0.068833,"stage2_stop_reason":"end_turn"},"total_usd":0.109732,"stage1_batch_id":"msgbatch_017qqVz33Ga63SCDwzb35XPb","stage2_batch_id":"msgbatch_01Scr2Ei9x4HJMiRGxwrmvLK","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1995,\n      \"finding\": \"MGDF (THPO) is the ligand for the c-mpl receptor; chronic overexpression via retroviral gene transfer in mice leads to lineage-specific megakaryocyte expansion, elevated platelets (4-8 fold above normal), myelofibrosis, and osteosclerosis, with no significant effect on other hematopoietic lineages, establishing THPO's stimulatory effect in vivo is restricted to the megakaryocyte lineage.\",\n      \"method\": \"Retroviral-mediated gene transfer / overexpression in mice with histological and hematological analysis\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo loss/gain-of-function with defined cellular phenotype, single lab, multiple readouts\",\n      \"pmids\": [\"7492757\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"The human MGDF (THPO) gene consists of seven exons and six introns spanning 8 kilobases; the protein-coding sequence is encoded by exons 3–7; the gene maps to chromosome 3q26.3; two cDNA splice variants arise from differential splicing in fetal liver.\",\n      \"method\": \"Genomic cloning, cDNA sequencing, chromosomal mapping, comparison of cDNA variants with genomic sequence\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct genomic characterization with sequencing and chromosomal mapping; replicated in multiple molecular analyses\",\n      \"pmids\": [\"7822271\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"MGDF (THPO) enhances in vitro platelet aggregation in a dose-dependent manner in response to epinephrine and ADP; this effect is partially blocked by the soluble extracellular domain of c-mpl, and MGDF induces tyrosine phosphorylation of platelet proteins at ~85 kDa and ~130 kDa, indicating signaling through the c-mpl receptor.\",\n      \"method\": \"In vitro platelet aggregometry, soluble receptor blocking experiment, tyrosine phosphorylation assay (Western blot)\",\n      \"journal\": \"Thrombosis research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro functional assay with receptor-blocking control and biochemical readout, single lab\",\n      \"pmids\": [\"8578535\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"Recombinant human MGDF (THPO) administered subcutaneously to baboons specifically stimulates thrombopoiesis in a dose-dependent manner, increasing platelet counts up to 5-fold and markedly enlarging marrow megakaryocytes with increased nuclear lobes, with no effect on red cell mass or white blood cell counts; heat-inactivated MGDF had no effect, confirming the requirement for native protein structure.\",\n      \"method\": \"In vivo primate administration of recombinant MGDF and heat-inactivated control, platelet counting, marrow biopsy\",\n      \"journal\": \"Stem cells (Dayton, Ohio)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo primate model with dose-response and negative control, single lab\",\n      \"pmids\": [\"8948024\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"MGDF (THPO) stimulates proliferation and survival of human megakaryocyte progenitors (CD34+CD61+) and also promotes survival of BFU-E and granulocyte-macrophage CFC, demonstrating a broader progenitor survival role beyond megakaryocyte lineage; MGDF acts additively with SCF and IL-3.\",\n      \"method\": \"Single-cell clonogenic assay with timed cytokine delay, immunoenzymatic colony labeling\",\n      \"journal\": \"Stem cells (Dayton, Ohio)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — single-cell assay with delayed-addition survival design, single lab, multiple lineage readouts\",\n      \"pmids\": [\"9007220\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"MGDF (THPO) stimulates proliferation of a human megakaryocyte/erythroid progenitor cell line (B1647) expressing c-mpl, and increases gamma-globin chain synthesis, but does not induce megakaryocytic differentiation, demonstrating that THPO signaling through c-mpl can modulate erythroid gene expression in a bipotent progenitor.\",\n      \"method\": \"Cell proliferation assay in serum-free culture, cytofluorimetric analysis, S1 protection analysis of globin mRNA\",\n      \"journal\": \"British journal of haematology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell line with c-mpl expression confirmed, multiple molecular readouts, single lab\",\n      \"pmids\": [\"9332307\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"MGDF (THPO) stimulates proliferation and colony formation in AML blast cells that express functional c-mpl, and induces tyrosine phosphorylation of an ~90 kDa protein upon stimulation; AML cases unresponsive to MGDF show no such phosphorylation, linking THPO signaling to c-mpl-dependent tyrosine kinase activation.\",\n      \"method\": \"Blast cell proliferation assay, clonogenic colony assay, tyrosine phosphorylation Western blot on primary AML cells\",\n      \"journal\": \"Leukemia\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — primary patient cells, functional and biochemical readouts correlated, single lab\",\n      \"pmids\": [\"9096694\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"rHuMGDF (THPO) sensitizes platelets to aggregating agents in vitro and ex vivo, and is associated with clear increases in tyrosine phosphorylation of JAK2 and the c-mpl receptor both in vitro and ex vivo; however, platelet-sensitizing doses of rHuMGDF did not enhance platelet-dependent thrombosis in a rabbit carotid artery cyclic flow reduction model.\",\n      \"method\": \"In vitro platelet aggregation, ex vivo platelet analysis, JAK2/c-mpl phosphorylation assay, rabbit carotid artery thrombosis model\",\n      \"journal\": \"Stem cells (Dayton, Ohio)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro and in vivo models with biochemical readouts, single lab, includes negative in vivo thrombosis result\",\n      \"pmids\": [\"11012184\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"A homozygous c.-323C>T substitution in the THPO promoter prevents binding of transcription factors ETS1 and STAT4 to the putative THPO promoter, impairing THPO expression and causing congenital amegakaryocytic thrombocytopenia (CAMT); treatment with the THPO-mimetic eltrombopag rescued platelet counts, confirming THPO pathway dependence.\",\n      \"method\": \"Bioinformatics prediction, in vitro transcription factor binding assay, serum THPO measurement, clinical therapeutic response to THPO-mimetic\",\n      \"journal\": \"Haematologica\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro binding assay plus clinical functional validation, single lab/case\",\n      \"pmids\": [\"36226497\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"A splicing donor site mutation (THPO c.13+1G>A) causes exon 3 skipping, abrogating a suppressive upstream open reading frame (ORF) in the 5'-UTR; mutated transcripts are more efficiently translated, resulting in significantly higher THPO protein expression compared to wild-type, explaining hereditary thrombocythemia.\",\n      \"method\": \"Cloning of mutated and wild-type THPO expression vectors, RT-PCR transcript analysis, THPO protein expression comparison\",\n      \"journal\": \"Annals of hematology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — molecular cloning with expression vectors and direct protein quantification, single lab\",\n      \"pmids\": [\"37962621\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"All six known hereditary thrombocythemia THPO mutations (c.-47delG, c.-31G>T, c.13G>A, c.13+1G>A, c.13+2T>C, c.13+5G>A) result in increased THPO protein production via two distinct molecular mechanisms: (1) exon 3 skipping that deletes upstream suppressive ORF7, or (2) a single base deletion that shifts ORF7 in-frame with the THPO start codon; in both cases, translation of THPO is normally suppressed by out-of-frame ORF7 and mutations relieve this suppression.\",\n      \"method\": \"Cloning of six distinct THPO mutant expression vectors, transcript analysis by RT-PCR, protein expression quantification\",\n      \"journal\": \"Experimental hematology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — systematic molecular cloning and expression analysis of all known mutations across multiple sites, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"38548144\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"THPO (thrombopoietin/MGDF) is the ligand for the c-mpl receptor that primarily drives megakaryocyte proliferation, differentiation, and platelet production by activating c-mpl-dependent JAK2 tyrosine phosphorylation; its translation is normally suppressed by an upstream out-of-frame ORF7 in the 5'-UTR, and hereditary thrombocythemia mutations relieve this suppression via exon 3 skipping or ORF7 frameshift; transcription of THPO itself is regulated by ETS1 and STAT4 binding to its promoter, and loss-of-function promoter or coding mutations cause congenital amegakaryocytic thrombocytopenia.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"THPO (thrombopoietin/MGDF) is the lineage-specifying cytokine for megakaryopoiesis, acting as the ligand for the c-mpl receptor to drive megakaryocyte proliferation, maturation, and platelet production [#0]. In vivo, chronic THPO overexpression in mice produces lineage-restricted megakaryocyte expansion with 4–8-fold elevated platelets, myelofibrosis, and osteosclerosis without perturbing other hematopoietic lineages [#0], and recombinant THPO selectively stimulates dose-dependent thrombopoiesis and megakaryocyte enlargement in primates [#3]. At the receptor level, THPO binding to c-mpl triggers tyrosine phosphorylation of JAK2 and the c-mpl receptor, the proximal signaling event underlying its effects on platelets and progenitors [#7, #2, #6]. Beyond mature megakaryocytes, THPO supports proliferation and survival of CD34+CD61+ megakaryocyte progenitors and broader progenitor populations including BFU-E and granulocyte-macrophage CFC, and can modulate erythroid gene expression in bipotent c-mpl-expressing progenitors [#4, #5]. THPO expression is tightly controlled at both transcriptional and translational levels: transcription depends on ETS1 and STAT4 binding to the promoter, and its mRNA carries a suppressive out-of-frame upstream ORF7 in the 5'-UTR that normally restrains translation [#8, #10]. This regulatory architecture is the basis of two opposing Mendelian disorders: a homozygous promoter mutation (c.-323C>T) that abolishes ETS1/STAT4 binding and impairs THPO expression causes congenital amegakaryocytic thrombocytopenia [#8], while hereditary thrombocythemia mutations relieve ORF7-mediated translational suppression—either through exon 3 skipping that deletes ORF7 or a frameshift that brings ORF7 in-frame with the THPO start codon—yielding increased THPO protein [#9, #10].\",\n  \"teleology\": [\n    {\n      \"year\": 1995,\n      \"claim\": \"Establishing that THPO is the physiological c-mpl ligand and defining the lineage scope of its action answered whether a single cytokine specifies megakaryopoiesis in vivo.\",\n      \"evidence\": \"Retroviral overexpression of MGDF in mice with hematological and histological readout\",\n      \"pmids\": [\"7492757\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Overexpression phenotype does not establish endogenous requirement\", \"Myelofibrosis/osteosclerosis as secondary consequences not mechanistically dissected\"]\n    },\n    {\n      \"year\": 1995,\n      \"claim\": \"Genomic characterization defined the THPO locus architecture, mapping it to 3q26.3 and assigning the coding sequence to exons 3–7, providing the structural framework later needed to interpret regulatory and disease mutations.\",\n      \"evidence\": \"Genomic cloning, cDNA sequencing, and chromosomal mapping\",\n      \"pmids\": [\"7822271\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional significance of the two fetal-liver splice variants not determined\", \"5'-UTR regulatory ORF not yet recognized at this stage\"]\n    },\n    {\n      \"year\": 1995,\n      \"claim\": \"Demonstrating that THPO sensitizes platelets to aggregating agents and induces platelet protein tyrosine phosphorylation extended its role from megakaryocyte production to direct modulation of mature platelet function.\",\n      \"evidence\": \"In vitro platelet aggregometry with soluble c-mpl blocking and phosphorylation Western blot\",\n      \"pmids\": [\"8578535\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Identity of the ~85/130 kDa phosphoproteins not established\", \"Physiological relevance of platelet sensitization unclear\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Primate dosing with native versus heat-inactivated recombinant THPO confirmed lineage-specific, structure-dependent thrombopoietic activity in a clinically relevant model.\",\n      \"evidence\": \"Subcutaneous recombinant MGDF administration in baboons with platelet counting and marrow biopsy\",\n      \"pmids\": [\"8948024\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Receptor-level mechanism not addressed in this model\", \"Long-term effects and marrow fibrosis not assessed\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Progenitor clonogenic assays revealed THPO supports survival and proliferation beyond the megakaryocyte lineage, including erythroid and granulocyte-macrophage progenitors and modulation of erythroid gene expression in bipotent progenitors.\",\n      \"evidence\": \"Single-cell clonogenic assays, c-mpl-expressing progenitor cell lines, and globin mRNA analysis\",\n      \"pmids\": [\"9007220\", \"9332307\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"In vivo significance of broader progenitor survival not established\", \"Mechanism of erythroid gene modulation not defined\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Correlating THPO responsiveness with c-mpl-dependent tyrosine phosphorylation in primary AML blasts tied functional output to receptor signaling competence.\",\n      \"evidence\": \"Proliferation and clonogenic assays with phosphorylation Western blot on primary AML cells\",\n      \"pmids\": [\"9096694\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Identity of the ~90 kDa phosphoprotein not determined\", \"Relevance to leukemogenesis not addressed\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Identifying JAK2 and c-mpl tyrosine phosphorylation as the proximal signal clarified the kinase axis transducing THPO action, while the absence of enhanced arterial thrombosis bounded its in vivo prothrombotic effect.\",\n      \"evidence\": \"In vitro/ex vivo platelet phosphorylation assays plus a rabbit carotid artery thrombosis model\",\n      \"pmids\": [\"11012184\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Downstream effectors of JAK2 in platelets not mapped\", \"Discrepancy between platelet sensitization and lack of thrombosis unexplained\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Linking a THPO promoter mutation to loss of ETS1/STAT4 binding established the transcriptional control of THPO and its loss-of-function disease mechanism, validated by therapeutic rescue.\",\n      \"evidence\": \"Promoter bioinformatics, in vitro transcription factor binding assays, serum THPO measurement, and eltrombopag clinical response in CAMT\",\n      \"pmids\": [\"36226497\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single case/family limits generality\", \"Direct in vivo confirmation of ETS1/STAT4 occupancy at the endogenous locus not shown\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Defining a splice-donor mutation that triggers exon 3 skipping and removes a suppressive 5'-UTR upstream ORF revealed translational repression as the normal restraint on THPO, whose relief causes hereditary thrombocythemia.\",\n      \"evidence\": \"Mutant versus wild-type expression vectors with RT-PCR and protein quantification\",\n      \"pmids\": [\"37962621\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Endogenous translational regulation in megakaryocytes not directly measured\", \"Single-mutation analysis\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Systematic analysis of all six known hereditary thrombocythemia mutations consolidated two convergent mechanisms—ORF7 deletion via exon 3 skipping or ORF7 frameshift—both relieving translational suppression of THPO, unifying the gain-of-function disease class.\",\n      \"evidence\": \"Cloning of six mutant expression vectors with transcript and protein expression quantification\",\n      \"pmids\": [\"38548144\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Quantitative contribution of ORF7 derepression to clinical platelet levels not modeled\", \"Mechanism of ORF7-mediated suppression on ribosome scanning not detailed\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How THPO transcriptional control, ORF7-mediated translational repression, and c-mpl/JAK2 signaling are integrated to set physiological platelet set-point remains incompletely defined.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of THPO–c-mpl engagement in the timeline\", \"Downstream JAK2 effectors and transcriptional outputs in megakaryocytes not mapped\", \"Identity of THPO-induced platelet phosphoproteins unresolved\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0048018\", \"supporting_discovery_ids\": [0, 2, 3]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [7, 6]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [3, 8]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [7, 2, 6]},\n      {\"term_id\": \"R-HSA-109582\", \"supporting_discovery_ids\": [2, 7]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [8, 9, 10]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"MPL\", \"JAK2\", \"ETS1\", \"STAT4\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}