title: Inhibition of Smad5 in human hematopoietic progenitors blocks erythroid differentiation induced by BMP4.
abstract: Patients with secondary myelodysplasias and acute myeloid leukemias (MDS/AML) frequently exhibit interstitial deletions of the chromosome-5q resulting in hemizygous loss of the transcription transactivator Smad5. Smad5 is a member of the signal transducer family conveying the pleiotropic TGF-gb/BMP cytokine signals with roles in development, cell growth control, and tumor progression. Here we present a study of the Smad5 expression and its functional role in leukemia cell lines as well as in primary CD34+ progenitors of MDS/AML patients and healthy individuals. Consistent Smad5 gene expression in these cell types and the gradual increase in its mRNA and protein levels in a model of induced erythroid differentiation of murine erythroleukemia (MEL) cells suggest a role of the gene in hematopoiesis. We show that bone morphogenetic protein 4 (BMP4) directs Smad5 activation in human hematopoietic cells, as monitored at the levels of protein phosphorylation, nuclear translocation, and specific transcription response. In vitro induction of normal human CD34+ cells by BMP4 results in significantly increased proliferation of erythroid progenitors (BFU-E) and formation of glycophorin-A+ cells, whereas perturbation of Smad5 expression by antisense oligonucleotides causes significantly decreased rates of BMP4-induced erythroid differentiation. We have not detected any effects of Smad5 inhibition on BMP4-stimulated progenitors of the granulocyteNmacrophage lineage. We propose that the BMP4/Smad5 signal transduction pathway activates hematopoietic differentiation programs that may be impaired in anemia manifestations in MDS and AML patients with Smad5 haploinsufficiency.
authors.affiliation: Institute of Hematology and Blood Transfusion, Prague, Czech Republic. fuchs@uhkt.cz
authors.forename: Ota
authors.initials: O
authors.lastname: Fuchs
authors.forename: Olga
authors.initials: O
authors.lastname: Simakova
authors.forename: Pavel
authors.initials: P
authors.lastname: Klener
authors.forename: Jana
authors.initials: J
authors.lastname: Cmejlova
authors.forename: Jan
authors.initials: J
authors.lastname: Zivny
authors.forename: Jiri
authors.initials: J
authors.lastname: Zavadil
authors.forename: Tomas
authors.initials: T
authors.lastname: Stopka
mesh_terms: D021581:Active Transport, Cell Nucleus; D000818:Animals; D018952:Antigens, CD34; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins / Q000502:physiology*; D016022:Case-Control Studies; D002454:Cell Differentiation; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D015672:Erythroid Precursor Cells / Q000166:cytology*; D005786:Gene Expression Regulation; D006021:Glycophorins / Q000096:biosynthesis; D006412:Hematopoietic Stem Cells / Q000166:cytology*; D006801:Humans; D007951:Leukemia, Myeloid / Q000209:etiology / Q000378:metabolism / Q000473:pathology; D051379:Mice; D009190:Myelodysplastic Syndromes / Q000209:etiology / Q000378:metabolism / Q000473:pathology; D020411:Oligonucleotide Array Sequence Analysis; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D010750:Phosphoproteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction; D051902:Smad5 Protein; D015534:Trans-Activators / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D014407:Tumor Cells, Cultured
chemical_list: D018952:Antigens, CD34; C525809:BMP4 protein, human; C525810:Bmp4 protein, mouse; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins; D004268:DNA-Binding Proteins; D006021:Glycophorins; D016376:Oligonucleotides, Antisense; D010750:Phosphoproteins; C497797:SMAD5 protein, human; D051902:Smad5 Protein; C497798:Smad5 protein, mouse; D015534:Trans-Activators